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Low Glucose Utilization and Neurodegenerative Changes Caused by Sodium Fluoride Exposure in Rat’s Developmental Brain
Abstract
Fluorine, a toxic and reactive element, is widely prevalent throughout the environment and can induce toxicity when absorbed into the body. This study was to explore the possible mechanisms of developmental neurotoxicity in rats treated with different levels of sodium fluoride (NaF). The rats' intelligence, as well as changes in neuronal morphology, glucose absorption, and functional gene expression within the brain were determined using the Morris water maze test, transmission electron microscopy, small-animal magnetic resonance imaging and Positron emission tomography and computed tomography, and Western blotting techniques. We found that NaF treatment-impaired learning and memory in these rats. Furthermore, NaF caused neuronal degeneration, decreased brain glucose utilization, decreased the protein expression of glucose transporter 1 and glial fibrillary acidic protein, and increased levels of brain-derived neurotrophic factor in the rat brains. The developmental neurotoxicity of fluoride may be closely associated with low glucose utilization and neurodegenerative changes.
... F decreases the risk of dental caries by increasing the formation of fluorapatite or fluorohydroxyapatite, decreasing acid production by bacteria found in the mouth, and improving remineralization after acidogenic challenge [11,12]. Fluoridation of water is deemed one of the most important public health policies of the 20th century for its role in reducing dental caries [12], however, excessive F intake has been reported to adversely affect neurodevelopment [13][14][15], although other studies do not find an association between F and childhood and adult intelligence quotient (IQ) or learning disabilities [16,17]. ...
... In attempting to explain the relationship between F exposure during pregnancy and IQ, preclinical studies of F exposure during pregnancy have focused on the effects of high levels of F exposure on offspring growth and neurodevelopment. Excessive F exposure decreases the food consumption and weight gain in the mother whereas in the offspring, growth (in utero and postnatal) [117], brain weight [15], and hippocampal [15,[118][119][120][121][122][123] as well as cerebellum [124] neurons are adversely affected. Attention, sensory and motor development were also reported to be affected in the study by Bartos et al. but not in the study by Flace et al. [125,126]. ...
... In attempting to explain the relationship between F exposure during pregnancy and IQ, preclinical studies of F exposure during pregnancy have focused on the effects of high levels of F exposure on offspring growth and neurodevelopment. Excessive F exposure decreases the food consumption and weight gain in the mother whereas in the offspring, growth (in utero and postnatal) [117], brain weight [15], and hippocampal [15,[118][119][120][121][122][123] as well as cerebellum [124] neurons are adversely affected. Attention, sensory and motor development were also reported to be affected in the study by Bartos et al. but not in the study by Flace et al. [125,126]. ...
Iodine (I), an essential nutrient, is important for thyroid function and therefore growth and development. Fluoride (F), also an essential nutrient, strengthens bones and teeth, and prevents childhood dental caries. Both severe and mild-to-moderate I deficiency and high F exposure during development are associated to decreased intelligence quotient with recent reports associating high levels of F exposure during pregnancy and infancy to low intelligence quotient. Both F and I are halogens, and it has been suggested that F may interfere with the role of I in thyroid function. We provide a scoping review of the literature on I and F exposure dur pregnancy and their individual effects on thyroid function and offspring neurodevelopment. We first discuss I intake and status in pregnancy and the relationship to thyroid function and offspring neurodevelopment. We follow with the F in pregnancy and offspring neurodevelopment. We then review the interaction between I and F on thyroid function. We searched for, and found only one study that assessed both I and F in pregnancy. We conclude more studies are needed.
... In fluorosis-endemic areas, a certain high dose of fluoride intake is a potential risk factor for cognitive impairment in elderly people [7]. Moreover, structural changes in nerve cells and brain functions in experimental animals subjected to chronic fluorosis have been described such as nuclear shrinkage, mitochondrial swelling, neurodegeneration, and deterioration of learning and memory [8][9][10]. These findings suggest a direct link between excessive exposure to fluoride and brain function impairment, but little is known about mechanisms underlying these phenomena. ...
... Reactive oxygen species (ROS) and free radicals can be generated when the fluoride content is high in the brain and cause oxidative damage and cell apoptosis in neurons [12], which may be controlled by apoptosis-related genes [13][14][15]. The literature suggests that increased ROS and lipid peroxidation (LPO) and decreased antioxidant enzyme activity occur in the brains of fluoride-intoxicated rats and that histopathological changes can be observed, especially swelling of mitochondria and endoplasmic reticulum dilation in neurons [9,16]. Also, some studies confirm that specific antioxidants may protect against this damage [17]. ...
... Chronic fluorosis can cause brain structural and functional changes via oxidative stress after fluoride exposure [8][9][10], and we noted histological changes in the brains of fluoride-treated rats characterized by cell nucleus deformation, chromatin condensation, and swollen mitochondria and typical morphological manifestations of apoptosis. Similar observations were made by others who reported cytomorphosis, intranuclear heterochromatin margination condensation, and shrinkage of the nucleus in the brains of fluorideintoxicated mice [37]. ...
In fluorosis-endemic areas, exposure to high levels of fluoride causes
neurotoxicity such as lowered intelligence and cognitive impairment. Oxidative
damage is critical to pathophysiologic processes of fluoride intoxication, and
neurotoxicity of fluoride may be associated with oxidative stress. In previous
studies, maize purple plant pigment (MPPP), which was rich in anthocyanins,
showed a strong scavenging activity in vitro and in
vivo. The present study aimed to determine whether treatment with
MPPP can alleviate fluoride-induced oxidative damage in rat brain. After 3
months of experiment, brain tissues were assayed for oxidative stress variables,
histological and Western blotting examinations. Our results showed that MPPP
reduced the elevated malondialdehyde levels, increased superoxide dismutase
activity, and further attenuated histopathological alterations and mitigated
neuronal apoptosis. Importantly, MPPP also reversed changes in Bax and Bcl-2.
Therefore, it was speculated that MPPP protects brain tissue from fluoride
toxicity through its antioxidant capacity.
... Rat pups born from the mothers exposed to F À during pregnancy and lactation exhibited delayed sensory development (eye opening) and decreased locomotor activity (Bartos et al. 2015). Further treatment of offspring with the same F À doses as their mothers (25-200 mg/L NaF) after birth caused a variety of behavioral and cognitive defects such as hyperactivity, aggressive behavior, decreased pain sensitivity, longer reaction to auditory stimuli, spontaneous locomotor activity, marked impairment in coordination, habituation, grooming and sexual behavior, decrease in learning ability, reduced degree of memory retention (Mullenix et al. 1995;Bera et al. 2007;Niu et al. 2009;El-Lethey et al. 2010;Jiang et al. 2014aJiang et al. , 2014bDong et al. 2015;Zhu et al. 2017;Adedara et al. 2017). Similar disturbances in spatial memory and learning ability were observed in rat pups born from mothers with chronic coal burning fluorosis (Gui et al. 2010). ...
... Prolonged intoxication with high F À doses (up to 125-200 ppm) started at adult stage of life also led to disturbances in grooming, motor coordination, increase in spontaneous locomotor activity, longer latency of pain and auditory reactions, reduced anxiety, impairment of conditioned reflexes, difficulties with habituation, deleterious learning ability, poor acquisition and retention of memory, deficit of long-term memory in rats (Mullenix et al. 1995;Wu et al. 2006;Chioca et al. 2008;Wu et al. 2008;Gao et al. 2009;Liu et al. 2010;Pereira et al. 2011;Basha et al. 2011a;Zhang et al. 2013;Jiang et al. 2014b;Zheng et al. 2016) and mice Liu et al. 2014;Han et al. 2014;Lu et al. 2019;Yuan et al. 2019). Shashi (2003) reported that the rabbits given 20-50 mg NaF/kg BW/day for 15 weeks developed tremors, seizure, and various types of paralysis (hemiplenia, paraplenia, and quadriplenia). ...
... Another mechanism at least partially contributing to Finduced memory impairment is a deficit or disturbed metabolism of glutamate, the most abundant neurotransmitter in the CNS responsible for attention, alertness, and learning (Meldrum 2000). The level of glutamate declined in hippocampus of rat pups born from mothers with fluorosis and exposed to 150 mg/L NaF for 12 weeks after birth (Niu et al. 2009), in brain tissues of adult rats injected with 20 mg NaF/kg BW for 14 days (Vani and Reddy 2000) or exposed to 120 ppm NaF for 3 months (Jiang et al. 2014b), and in the cultured Neuro-2A cell line (Chen et al. 2017a). In contrast, Reddy et al. (2014) described an increased level of glutamate in rat brain. ...
Although actively disputed and questioned, it has been proposed that chronic exposure to inorganic fluoride (F⁻) is toxic for brain. The major question for this review was whether an excessive F⁻ intake is causally related to adverse neurological and cognitive health conditions in human beings and animals. The paper systematically and critically summarizes the findings of the studies showing positive associations between F⁻ intoxication and various intellectual defects, as well as of those which attempted to clarify the nature of F⁻ neurotoxicity. Many works provide support for a link between pre- and postnatal F⁻ exposure and structural and functional changes in the central nervous system responsible for neurological and cognitive disorders. The mechanisms suggested to underlie F⁻ neurotoxicity include the disturbances in synaptic transmission and synaptic plasticity, premature death of neurons, altered activities of components of intracellular signaling cascades, impaired protein synthesis, deficit of neurotrophic and transcriptional factors, oxidative stress, metabolic changes, inflammatory processes. However, the majority of works have been performed on laboratory rodents using such F⁻ doses which are never exist in the nature even in the regions of endemic fluorosis. Thus, this kind of treatment is hardly comparable with human exposure even taking into account the higher rate of F⁻ clearance in animals. Of special importance are the data collected on humans chronically consuming excessive F⁻ doses in the regions of endemic fluorosis or contacting with toxic F⁻ compounds at industrial sites, but those works are scarce and often criticized due to low quality. New, expertly performed studies with repeated exposure assessment in independent populations are needed to prove an ability of F⁻ to impair neurological and intellectual development of human beings and to understand the molecular mechanisms implicated in F⁻-induced neurotoxicity.
... Translation of findings from these studies to human exposures is often difficult because of the high levels of fluoride (F − , > 100 ppm) administered or routes of exposure not representative of drinking water. The majority of rat studies have focused on exposure to adult males with only a limited number examining developmental exposure (Wang et al. 2004;Niu et al. 2009;El-lethey et al. 2010;Banji et al. 2013;Jiang et al. 2014b;Wei et al. 2014). At drinking water concentrations of ≥ 100 ppm F − , various studies suggested performance deficits in rats on learning and memory tasks (Basha et al. 2011;Basha and Sujitha 2012;Jiang et al. 2014a;Zhu et al. 2017). ...
... Studies examining F − exposures ≤ 100 ppm present an inconsistent pattern of neurobehavioral effects. A number of studies reported effects on motor or learning performance in rats at drinking water concentrations of~2 to 50 ppm F − (Bera et al. 2007;Gao et al. 2008;Liu et al. 2009;El-lethey et al. 2010;Jiang et al. 2014b;Wang et al. 2004;Wu et al. 2006;Wei et al. 2014; Bartos et al. 2015;Dong et al. 2015a). Many of these studies had limitations in experimental design and often utilized latency measures of learning that were dependent on a motor response (NTP 2016). ...
... Many of these studies had limitations in experimental design and often utilized latency measures of learning that were dependent on a motor response (NTP 2016). Rather than examining improvement in performance with training (acquisition), many studies relied on a single assessment of learning and a single latency measure at the end of training (Gao et al. , 2009aJiang et al. 2014b;Wei et al. 2014;Dong et al. 2015a), not taking into consideration the initial latency differences. In studies that reported acquisition data, longer latencies were often observed; yet, performance improved with training (Gui et al. 2010;Basha et al. 2011;Basha and Sujitha 2012;Zhu et al. 2017). ...
At elevated levels, fluoride (F⁻) exposure has been associated with adverse human health effects. In rodents, F⁻ exposure has been reported to induce deficits in motor performance and learning and memory. In this study, we examined Long-Evans hooded male rats maintained on a standard diet (20.5 ppm F⁻) or a low F⁻ diet (3.24 ppm F⁻) with drinking water exposure to 0, 10, or 20 ppm F⁻ from gestational day 6 through adulthood. At postnatal day 25, brain F⁻ levels were 0.048 or 0.081 μg/g and femur 235 or 379.8 μg/g for 10 and 20 ppm F⁻, respectively. Levels increase with age and in adults, levels for plasma were 0.036 or 0.025 μg/ml; for the brain 0.266 or 0.850 μg/g; and for the femur, 681.2 or 993.4 μg/g. At these exposure levels, we observed no exposure-related differences in motor, sensory, or learning and memory performance on running wheel, open-field activity, light/dark place preference, elevated plus maze, pre-pulse startle inhibition, passive avoidance, hot-plate latency, Morris water maze acquisition, probe test, reversal learning, and Y-maze. Serum triiodothyronine (T3), thyroxine (T4), and thyroid stimulating hormone (TSH) levels were not altered as a function of 10 or 20 ppm F⁻ in the drinking water. No exposure-related pathology was observed in the heart, liver, kidney, testes, seminal vesicles, or epididymides. Mild inflammation in the prostate gland was observed at 20 ppm F⁻. No evidence of neuronal death or glial activation was observed in the hippocampus at 20 ppm F⁻.
Electronic supplementary material
The online version of this article (10.1007/s12640-018-9870-x) contains supplementary material, which is available to authorized users.
... Fluorine compounds impair energy metabolism of the brain, dependent primarily on the burning of glucose. Fluoride exposure may be associated with changes in the profile of proteins involved in energy metabolism [64], and researchers have suggested that impaired glucose metabolism in neurons is correlated with decreased expression of the GLUT-1 transporter [65]. On the other hand, increased glucose transport into brain cells has also been documented, although without changes in transporter expression, suggesting a compensatory mechanism in response to damage [66]. ...
... Studies in rats have shown that NaF decreases the expression of GLUT1, a glucose transporter in the brain, but the results of the few existing studies are conflicting. Some point to decreased expression of the GLUT1 glucose transporter and reduced glucose uptake into the brain [65], while others report compensatory increases in glucose uptake in the brain and peripheral tissues without significant changes in GLUT1 and GLUT3 expression [66]. Due to the paucity of data on the molecular mechanism underlying the effects of fluoride on brain glucose uptake, transport, and metabolism, it is difficult to clearly assess its role in glioma progression and invasiveness. ...
The purpose of this review is to attempt to outline the potential role of fluoride in the pathogenesis of brain tumours, including glioblastoma (GBM). In this paper, we show for the first time that fluoride can potentially affect the generally accepted signalling pathways implicated in the formation and clinical course of GBM. Fluorine compounds easily cross the blood–brain barrier. Enhanced oxidative stress, disruption of multiple cellular pathways, and microglial activation are just a few examples of recent reports on the role of fluoride in the central nervous system (CNS). We sought to present the key mechanisms underlying the development and invasiveness of GBM, as well as evidence on the current state of knowledge about the pleiotropic, direct, or indirect involvement of fluoride in the regulation of these mechanisms in various tissues, including neural and tumour tissue. The effects of fluoride on the human body are still a matter of controversy. However, given the growing incidence of brain tumours, especially in children, and numerous reports on the effects of fluoride on the CNS, it is worth taking a closer look at these mechanisms in the context of brain tumours, including gliomas.
... Se sabe poco acerca de su trasporte y metabolismo a nivel cerebral. Se ha reportado que ratas expuestas a 25, 50 y 100 ppm de flúor desde la gestación y edad adulta (60 días), muestran alteraciones en el metabolismo energético cerebral al disminuir la expresión del trasportador a glucosa tipo 1 (GLUT1) en la corteza cerebral e hipocampo (Jiang et al., 2014). Sin embargo, en ratas adultas tras la exposición al flúor durante 30 días a concentraciones de 10 o 50 ppm, la expresión de las proteínas transportadoras a glucosa GLUT 1 y GLUT 3 en la corteza frontal y el cuerpo estriado no se modifican, mientras que la recaptura de glucosa incrementa, probablemente como mecanismo compensatorio en la absorción y utilización (Rogalska et al., 2017). ...
... Sin embargo, en ratas adultas tras la exposición al flúor durante 30 días a concentraciones de 10 o 50 ppm, la expresión de las proteínas transportadoras a glucosa GLUT 1 y GLUT 3 en la corteza frontal y el cuerpo estriado no se modifican, mientras que la recaptura de glucosa incrementa, probablemente como mecanismo compensatorio en la absorción y utilización (Rogalska et al., 2017). Aunado a esto, la exposición crónica al flúor altera los cofactores para el metabolismo de lípidos (Jiang et al., 2014) y disminuye proteínas totales y la fracción de lípidos en el cerebro. En este sentido, dichas modificaciones podrían inducir la progresión de enfermedades neurodegenerativas (Guan et al., 1998). ...
Investigaciones en el campo de la Salud Ambiental que abordan temáticas tales como los determinantes de la salud, los agroquímicos utilizados en el estado de Jalisco y las afectaciones al ecosistema en general y a la salud humana específicamente, impactos de la contaminación del aire en la salud, el efecto de la contaminación ambiental por fluoruros sobre los estados afectivos de distintos organismos y los parques como espacios de oportunidades socio-culturales para la salud y bienestar de las personas en las ciudades.
... Se sabe poco acerca de su trasporte y metabolismo a nivel cerebral. Se ha reportado que ratas expuestas a 25, 50 y 100 ppm de flúor desde la gestación y edad adulta (60 días), muestran alteraciones en el metabolismo energético cerebral al disminuir la expresión del trasportador a glucosa tipo 1 (GLUT1) en la corteza cerebral e hipocampo (Jiang et al., 2014). Sin embargo, en ratas adultas tras la exposición al flúor durante 30 días a concentraciones de 10 o 50 ppm, la expresión de las proteínas transportadoras a glucosa GLUT 1 y GLUT 3 en la corteza frontal y el cuerpo estriado no se modifican, mientras que la recaptura de glucosa incrementa, probablemente como mecanismo compensatorio en la absorción y utilización (Rogalska et al., 2017). ...
... Sin embargo, en ratas adultas tras la exposición al flúor durante 30 días a concentraciones de 10 o 50 ppm, la expresión de las proteínas transportadoras a glucosa GLUT 1 y GLUT 3 en la corteza frontal y el cuerpo estriado no se modifican, mientras que la recaptura de glucosa incrementa, probablemente como mecanismo compensatorio en la absorción y utilización (Rogalska et al., 2017). Aunado a esto, la exposición crónica al flúor altera los cofactores para el metabolismo de lípidos (Jiang et al., 2014) y disminuye proteínas totales y la fracción de lípidos en el cerebro. En este sentido, dichas modificaciones podrían inducir la progresión de enfermedades neurodegenerativas (Guan et al., 1998). ...
... Of the six studies, four reported a male-specific effect of fluoride, including slower performance time [26], worse learning/memory [28], and reduced sensorymotor function [29] and spontaneous behaviours [31]. One study did not report a sex-specific effect [30], and one demonstrated lower anxiety behaviour in female rats (measured by more time spent in the maze) compared with controls, whereas treated males did not differ from controls [27]. Fluoride exposure concentrations varied considerably across the animal studies reflecting differences in between-species pharmacokinetics, diets, and age at dosing [32]. ...
... We identified six studies that evaluated sex differences in animals treated with fluoride during the gestational period. The majority of these studies (four out of six [26,28,29,31]) suggested a male vulnerability to prenatal exposure to fluoride, whereas one suggested a female vulnerability [27], and one suggested no differences by sex [30]. Further research is needed to confirm whether there is a vulnerability by sex as three of the four studies showing a male-specific finding were considered to pose an overall high risk of bias, primarily due to no randomization, lack of information on exposure, lack of blinding for outcome assessment [26,28], and one lacked adequate exposure information and control for litter effects [31]. ...
Purpose of review:
A growing body of evidence suggests adverse neurodevelopmental effects of early-life exposure to fluoride that may differ depending on timing of exposure and sex of the exposed. We conducted a literature search to identify the animal and human epidemiologic studies that examined sex-specific neurodevelopmental differences in response to prenatal and postnatal exposure to fluoride.
Recent findings:
Six of 138 animal studies and 15 of 106 human epidemiologic studies tested for sex-specific effects. Prenatal exposure to fluoride was associated with a male susceptibility to adverse behavioural effects in four of six animal studies and lower IQ in one of three prospective cohort studies. The body of evidence examining sex-effects associated with postnatal fluoride exposure was scarce, and many animal and cross-sectional human studies were considered to have a high risk of bias.
Summary:
Compared to females, male offspring appear to be more sensitive to prenatal, but not postnatal, exposure to fluoride. We discuss several sex-specific mechanisms and emphasize the need for future research.
... Multiple epidemiological studies of developmental fluoride neurotoxicity exhibited an inverse correlation between high fluoride exposure and children's intelligence [5]. Laboratory studies further demonstrated developmental exposure to fluoride adversely affects neuron function including learning and memory impairment [6,7]. However, additional research is still warranted to reveal mechanisms underlying developmental fluoride neurotoxicity. ...
... Also, to practically simulate the real children exposure in drinking-water-type fluorosis areas, a rat model of developmental fluoride exposure from pre-pregnancy until 2 months of delivery was constructed. As displayed in our recent study [9], learning and memory abilities of offspring rats were significantly impaired by developmental fluoride exposure, which is in line with previous studies [7,39]. In particular, our study further demonstrated fluoride caused abnormal mitochondrial ultrastructure and dysfunction. ...
Rationale: Potential adverse effects of fluoride on neurodevelopment has been extensively explored and mitochondria have been recognized as critical targets. Mitochondrial biogenesis serves a crucial role in maintaining mitochondrial homeostasis and salubrious properties of resveratrol (RSV) has been well-defined. However, the molecular mechanisms governing mitochondrial biogenesis in developmental fluoride neurotoxicity remain unclear and the related therapeutic dietary agent is lacking.
Methods: In vitro neuroblastoma SH-SY5Y cells and in vivo Sprague-Dawley rat model of developmental fluoride exposure were adopted. A total population of 60 children under long-term stable fluoride exposure were also recruited. This work used a combination of biochemical and behavioral techniques. Biochemical methods included analysis of mitochondrial function and mitochondrial biogenesis, as well as mRNA and protein expression of mitochondrial biogenesis signaling molecules, including silent information regulator 1 (SIRT1), peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM). Behavioral studies investigated spatial learning and memory ability of rats.
Results: Both in vivo and in vitro experiments showed that sodium fluoride (NaF) caused mitochondrial dysfunction and impaired mitochondrial biogenesis. Also, NaF elevated SIRT1 levels and suppressed SIRT1 deacetylase activity along with decreased levels of PGC-1α, NRF1 and TFAM, suggestive of dysregulation of mitochondrial biogenesis signaling molecules. Moreover, enhancement of mitochondrial biogenesis by TFAM overexpression alleviated NaF-induced neuronal death through improving mitochondrial function in vitro. Further in vivo and in vitro studies identified RSV, the strongest specific SIRT1 activator, improved mitochondrial biogenesis and subsequent mitochondrial function to protect against developmental fluoride neurotoxicity via activating SIRT1-dependent PGC-1α/NRF1/TFAM signaling pathway. Noteworthy, epidemiological data indicated intimate correlations between disturbed circulating levels of mitochondrial biogenesis signaling molecules and fluoride-caused intellectual loss in children.
Conclusions: Our data suggest the pivotal role of impaired mitochondrial biogenesis in developmental fluoride neurotoxicity and the underlying SIRT1 signaling dysfunction in such neurotoxic process, which emphasizes RSV as a potential therapeutic dietary agent for relieving developmental fluoride neurotoxicity.
... Declined ability to discriminate between familiar and new object was reported for mice subjected to short (4 weeks) intoxication with 5-10 mg NaF/L [30] and for female rats born from mothers intragastrically administered with a daily dose of 5 mg NaF/kg BW from gestational day 0 to day 9 after parturition [31]. Morris water test was used to confirm decreased ability to spatial learning of adult rats after both short-term (3 months) and long-term (10 months) exposure to 50-120 mg NaF/L, as well as of their offspring [32,33]. Fig. 4 Translocation of GTPase RhoA from cytosol to membranes in hippocampus of rats following excessive F − intake. ...
... Altered activity of BDNF and CREB following F − intoxication was shown earlier, but the data are controversial. Thus, BDNF expression was upregulated in hippocampus and cortex of rats exposed to 50-100 mg/L NaF prenatally and during 2-6 months after birth [33,47], in hippocampus of mice consumed 50-100 mg/L NaF until 64 days of age [54], and in SH-SY5Y cells treated with 20-60 mg/L NaF for 24 h [47]. In rat hippocampus and SH-SY5Y cells, an increase in BDNF activity was accompanied by downregulation of TrkB (tyrosine receptor kinase B), receptor for BDNF, suggesting the disturbance in BDNF-TrkB signaling [47]. ...
The study was designed to evaluate an influence of excessive fluoride (F-) intake on cognitive capacities of adult rats and on proteins of memory-related calpain signaling in hippocampus. Control animals were given water with natural F- content of 0.4 ppm; rats from other groups consumed the same water supplemented with 5, 20, and 50 ppm F- (as NaF) for 12 months. The efficiency of learning and memory formation was evaluated by novel object recognition (NOR) and Morris water maze tests. The expression of enzymes of calpain-1 and calpain-2 signaling in hippocampus was detected by Western blotting. Excessive F- consumption had moderate impact on short-term memory, but impaired spatial learning and long-term memory of animals. Intoxication of rats with 5-50 ppm F- led to stimulation of calpain-1 in hippocampal cells and its translocation from cytosol to membranes, accompanied by activation of GTPase RhoA. Exposure to 20-50 ppm F- resulted in proteolytic cleavage of phosphatase PHLPP1 and increased expression of phospho-ERK1/2 kinase with insignificant decline of total ERK1/2 activity. In contrast, F- did not change the expression of calpain-2 and its substrates-phosphatase PTEN and kinase mTOR. However, F- intake led to downregulation of cAMP-response element binding protein (CREB) and brain-derived neurotrophic factor (BDNF). Thus, altered expression of calpain-1 and its downstream effectors at a background of stable activity of calpain-2 indicates overstimulation of signaling pathways of early LTP phase and disrupted link between early and late LTP phases, most probably due to altered activity of transcriptional and neurotrophic factors.
... Remarkably, our results demonstrated that chronic developmental exposure of rats to fluoride resulted in cognitive defects along with neuronal dysfunction and loss in offspring. These findings are consistent with previous studies (Bartos et al. 2015;Jiang et al. 2014) and suggest that our rat model for developmental fluoride neurotoxicity is successfully established. In this context, we also showed that fluoride exposure resulted in mitochondrial structural alterations, such as swelling and cristae disorders in hippocampal neurons. ...
... In this context, we also showed that fluoride exposure resulted in mitochondrial structural alterations, such as swelling and cristae disorders in hippocampal neurons. This is in agreement with previous researches showing that exposure of rats to high fluoride exhibited a series of histopathological changes in neuronal mitochondria (Jiang et al. 2014;Yan et al. 2016). In support of these, our results further demonstrated that NaF treatment reduced SH-SY5Y cells' survival in vitro, accompanied by similar mitochondrial structural damages and, even mitochondrial malfunction including △Ψm dissipation and mitoROS overproduction. ...
Fluoride neurotoxicity is associated with mitochondrial disruption. Mitochondrial fission/fusion dynamics is crucial to maintain functional mitochondria, yet little is known about how fluoride perturbs this dynamics and whether such perturbation contributes to impaired neurodevelopment. Here in human neuroblastoma SH-SY5Y cells treated with sodium fluoride (NaF, 20, 40 and 60 mg/L), mitochondrial fission suppression exerted a central role in NaF-induced mitochondrial abnormalities and the resulting autophagy deficiency, apoptosis augmentation, and compromised neuronal survival. Mechanically, pharmacological inhibition of mitochondrial fission exacerbated NaF-induced mitochondrial defects and cell death through promoting apoptosis despite partial autophagy restoration. Conversely, genetic enhancement of mitochondrial fission alleviated NaF-produced detrimental mitochondrial and cellular outcomes by elevating autophagy and inhibiting apoptosis. Further suppressing autophagy was harmful, while blocking apoptosis was beneficial for cellular survival in this context. Consistently, using Sprague–Dawley rats developmentally exposed to NaF (10, 50, and 100 mg/L) from pre-pregnancy until 2 months of delivery to mimic human exposure, we showed that perinatal exposure to environmentally relevant levels of fluoride caused learning and memory impairments, accompanied by hippocampal mitochondrial morphological alterations manifested as fission suppression and fusion acceleration, along with defective autophagy, excessive apoptosis and neuronal loss. Intriguingly, the disturbed circulating levels of identified mitochondrial fission/fusion molecules were closely associated with intellectual loss in children under long-term environmental drinking water fluoride exposure. Collectively, our results suggest that mitochondrial fission inhibition induces mitochondrial abnormalities, triggering abnormal autophagy and apoptosis, thus contributing to neuronal death, and that the mitochondrial dynamics molecules may act as promising indicators for developmental fluoride neurotoxicity.
... These high data may be explained by the different sources of fluoride exposure that contribute to increasing the daily ingestion dose (water and table salt, toothpastes, mouthwash and food and drinks, as well as application of dental fluoride) (35)(36)(37)(38)(39)(40)(41). Similarly, the presence of other factors can increase the individual susceptibility to the toxic effects of fluoride, such as altitude and environmental temperature, malnutrition, diet components, gastric and urinary pH, kidney failure and genetic predisposition (10,42,43,20). ...
Background
Natural water sources are considered as the major environmental exposure of fluoride, resulting in increased prevalence of enamel fluorosis. This type of natural exposure should be permanently monitored to avoid the interactions with other non-natural fluoride sources. We evaluated the prevalence of enamel fluorosis in Colombian schoolchildren and its relationship with fluoride-containing water ingestion exposure dose and urinary fluoride excretion.
Material and Methods
We included 923 schoolchildren aged 7–12 years residing in eight municipalities in Colombia. Sampling of consumption water was performed in major aquifers used for daily supply. Samples were collected in 98 polyethylene containers and refrigerated until analysis. Water and urine fluoride concentrations were measured using the fluoride selective electrode method. Enamel fluorosis was evaluated using Thylstrup and Ferjerskov Index (TFI). Demographic and anthropometric characteristics were assessed. Besides, other exposures to non-natural fluoride were also evaluated. Logistic regression was applied for multiple analyses.
Results
The median fluoride concentration in water and urine samples was 10.5 mg/L and 0.63 mg/L respectively, with the highest value found in Algarrobo-Magdalena, and the lowest value found in Manzanares-Caldas. The overall prevalence of enamel fluorosis was 86.1%, being more frequent the mild codes with TFI-1 to TFI-2. The highest prevalence was found in Margarita-Bolívar and Manzanares-Caldas, and the most severe codes (TFI-5 to TFI-9) were detected in Manzanares-Caldas. The multiple analysis revealed water ingestion exposure dose, urinary excretion, involuntary intake of toothpaste, amount of table salt consumption and sex as significant factors (p< 0.001).
Conclusions
The fluoride ingestion exposure dose and its subsequent urinary excretion could be used as estimators of past fluoride exposure, explaining the current prevalence of enamel fluorosis in Colombian schoolchildren.
Key words:Fluoride, groundwater ingestion, enamel fluorosis, prevalence, severity.
... Prenatal exposure to high concentrations of fluoride has also been reported as a critical stage in the development of this deficiency, mainly among male individuals [24,29]. The stage of embryogenesis is the stage of major brain development and growth, during which the proper functioning of glutamate transporter proteins, which are affected by high fluoride exposure, is crucial, and inhibition of the thyroid during this process alters early neuronal migration in the developing foetus [31]. ...
High fluoride exposures can lead to adverse effects such as dental and bone fluorosis, as well as endocrine and cognitive developmental problems. Water is the main dietary source of this ion, although significant concentrations have also been detected in other beverages widely consumed by the population such as soft drinks. A total of 200 soft drink samples (60 flavoured, 70 extracts, 60 fruit juice and 10 soft drinks) were analysed by fluoride ion selective potentiometry. A consumption of 330 mL was estimated for exposure assessment and subsequent F-risk assessment by soft drink consumption. The highest average concentration was found in extract soft drinks (2.45 ± 1.15 mg/L), followed by flavoured (1.71 ± 2.29 mg/L) and carbonated soft drinks (1.38 ± 0.40 mg/L), while the lowest was found in fruit juice soft drinks (1.09 ± 0.62 mg/L). The flavours with the highest concentration were tea-melon and tea-passion fruit with 3.66 ± 0.40 and 3.17 ± 0.56 mg/L respectively and the lowest was lemon flavour with 0.69 mg/L. The contribution of these beverages, considering the UL (Upper level) reference values set by EFSA (European Food Safety Authority) are between 3.28–41.78%, depending on age group and sex.
... These studies have shown that F crosses the placenta and blood brain barriers (Niu et al., 2018;Sharma et al., 2017; Agency for Toxic Substances and Disease Registry (ATSDR), 2003; Mullenix et al., 1995;Ron et al., 1986) and F related histopathological changes in various brain regions, including the hippocampus (critical for learning and memory), the prefrontal cortex (executive function), and the cerebellum (motor control) (Ge et al., 2018;Lee et al., 2016;Liu et al., 2014;Jiang et al., 2014a;Whitford et al., 2009;Shivarajashankara et al., 2002;Mullenix et al., 1995). Fluoride can also impair the function of myelin and neurotransmitters, increase lipid peroxidation, and inhibit several key neuronal enzymes, suggesting potential direct impairments to brain function (Niu et al., 2018;Shivarajashankara et al., 2002;Jiang et al., 2014b). The neurotoxic effect of high levels of F exposure is frequently referenced to the hippocampus, which is involved in learning, memory, and attention (Bittencourt et al., 2023;Grandjean, 2019 and reference therein; Pereira et al., 2011;Valdez-Jimenez et al., 2011, Bhatnagar et al., 2002Mullenix et al., 1995). ...
Fluoride (F) exposure in drinking water may lead to reduced cognitive function among children; however, findings largely remain inconclusive. In this pilot study, we examined associations between a range of chronic F exposures (low to high: 0.4 to 15.5 mg/L) in drinking water and cognition in school-aged children (5-14 years) in rural Ethiopia. Fluoride exposure was determined from samples of community-based drinking water wells and urine. Cognitive performance was measured using: 1) assessments of ability to draw familiar objects (donkey, house, and person), and 2) a validated Cambridge Neuropsychological Test Automated Battery's (CANTAB) Paired Associate Learning (PAL), which examines working memory and new learning and is closely associated with hippocampus function of the brain. Associations between F and cognitive outcomes were evaluated using regression analysis, adjusting for demographic, health status, and other covariates. The median (range) of water and urine F levels was 7.6 (0.4-15.5 mg/L) and 5.3 (0.5-15.7 mg/L), respectively; these measures were strongly correlated (r = 0.74), indicating that water is the primary source of F exposure. Fluoride in drinking water was negatively associated with cognitive function, measured by both drawing and CANTAB test performance. Inverse relationships were also found between F and drawing objects task scores, after adjusting for covariates (p < 0.05). Further analysis using CANTAB PAL tasks in the children confirmed that F level in drinking water was positively associated with the number of errors made by children (p < 0.01), also after adjusting for covariates (p < 0.05). This association between water F and total errors made became markedly stronger as PAL task difficulty increased. Fluoride exposure was also inversely associated with other PAL tasksthe number of patterns reached, first attempt memory score and mean errors to success. These findings provide supportive evidence that high F exposures may be associated with cognitive deficits in children. Additional well-designed studies are critically needed to establish the neurotoxicity of F in children and adults exposed to both low levels known to protect dental decay, as well as excess F levels in drinking water.
... In a study investigating the possible developmental neurotoxicity mechanisms of NaF, rats were exposed to NaF at concentrations of 25, 50, and 100 mg/L for 10 days. The results showed that NaF impairs cognitive functions, causes neuronal degeneration and increases BDNF protein levels in rats (Jiang et al., 2014). In a similar study, it was determined that in adult mice exposed to 25, 50 and 100 mg/L NaF for 60 days, high Fexposure caused myelin damage and also decreased protein and mRNA levels of BDNF. ...
Fluoride exposure through drinking water, foods, cosmetics, and drugs causes genotoxic effects, oxidative damage, and impaired cognitive abilities. In our study, the effects of fluoride on anxiety caused by the circadian clock and circadian clock changes in a zebrafish model were investigated at the molecular level on parents and the next generations. For this purpose, adult zebrafish were exposed to 1.5 ppm, 5 ppm, and 100 ppm fluoride for 6 weeks. At the end of exposure, anxiety-like behaviors and sleep/wake behaviors of the parent fish were evaluated with the circadian rhythm test and the novel tank test. In addition, antioxidant enzyme activities and melatonin levels in brain tissues were measured. In addition, morphological, physiological, molecular and behavioral analyzes of offspring taken from zebrafish exposed to fluoride were performed. In addition, histopathological analyzes were made in the brain tissues of both adult zebrafish and offspring, and the damage caused by fluoride was determined. The levels of BMAL1, CLOCK, PER2, GNAT2, BDNF and CRH proteins were measured by immunohistochemical analysis and significant changes in their levels were determined in the F- treated groups. The data obtained as a result of behavioral and molecular analyzes showed that parental fluoride exposure disrupts the circadian rhythm, causes anxiety-like behaviors, and decreases the levels of brain antioxidant enzymes and melatonin in parents. In addition, delay in hatching, increase in death and body malformations, and decrease in blood flow velocity, and locomotor activity was observed in parallel with dose increase in offspring. On the other hand, an increase in offspring apoptosis rate, ROS level, and lipid accumulation was detected. As a result, negative effects of fluoride exposure on both parents and next generations have been identified.
... It is neurotoxic [15,16] and increases oxygen free radicals and its resultant oxidative stress [17]. More recently, low glucose utilization [18], cognitive deficits and anxiety-depression-like behaviors have been described in mice treated with NaF [19]. ...
Objective: Renal and hepato-protective effects of Irvingia gabonensis juice on sodium fluoride-induced toxicity was assessed in twenty-four male Wistar albino rats. Methodology: The rats were divided into 4 groups of 6 animals each. All except normal control (NC), were intoxicated with 20 mg.Kg-1 body weight of sodium fluoride (NaF) daily by gavage for 35 days. Sodium fluoride control group (NaFC) received only the toxicant. Test group (IG) received I. gabonensis juice concurrently with the toxicant, while the standard control (Q+Vit. E) received concurrently, 15 mg.Kg-1 body weight of Quercetin+100 mg.Kg-1 body weight of α-tocopherol throughout the 35 days. Normal control (NC) group received only standard pelletized diet and water. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), total protein, albumin, total cholesterol, serum creatinine and electrolyte levels were assessed among test, standard and control animals. Result: Irvingia gabonensis significantly (p<0.05) reduced AST activity in the IG group (137.68 ± 12.66 U/L) compared to NaFC group (175.12 ± 10.63 U/L). This compares to the reduction in the AST activity in standard (Q +Vit. E) group (135.69 ± 10.66 U/L). ALT activity was also reduced in the IG group. Effects of I. gabonensis on albumin and cholesterol levels were similar to that of the standard group. Administration of I. gabonensis also significantly (p<0.002) reduced elevated creatinine and Cl-concentrations, while significantly (p<0.05) elevating serum Ca 2+ and Mg 2+ ion levels. Conclusion: Irvingia gabonensis fruit juice has some renal and hepato-protective potential which may be due to the presence of secondary plant metabolites like flavonoids, tannins and alkaloids found in the plant. The fruit is also rich in Ca 2+ and Mg 2+. Increased domestication is encouraged.
... Several studies demonstrated the neurotoxicity of long-term administration of Al, Cd, and F via oxidative stress/ inflammatory mechanism, which triggers cognitive disability and AD (Chen et al. 2008;Pogue and Lukiw 2016;Halder et al. 2018;Wang et al. 2018). In addition, fluoride has the capacity to induce CNS oxidative stress/neuroinflammation and disrupt enzymes associated with energy metabolism inducing brain cells starvation (Jiang et al. 2014). ...
Long-term exposure to environmental neurotoxic metals is implicated in the induction of dementia and cognitive decline. The present study aims to illustrate the therapeutic role of ipriflavone as a synthetic isoflavone against environmental metal–induced cognitive impairment in rats. Dementia was induced by a mixture of aluminum, cadmium, and fluoride for 90 days followed by ipriflavone for a further 30 days. Metal-treated animals exhibited abnormal behaviors in the Morris water maze task. Neuropathological biomarkers including oxidative stress (TBARS, NO, SOD, GPX, GST, and GSH), inflammation (TNF- α, IL-6, and IL-1β), neurotransmission (AChE and MAO), and insulin resistance (insulin, insulin receptor, and insulin-degrading enzyme) were altered, which consequently elevated the level of amyloid-β42 and tau protein in the hippocampus tissues inducing neuronal injury. Ipriflavone significantly (P < 0.05) ameliorated the neurobehavioral abnormalities and the cognitive dysfunction biomarkers via antioxidant/anti-inflammatory mechanism. Moreover, ipriflavone downregulated the mRNA expression level of amyloid precursor protein and tau protein, preventing amyloid plaques and neurofibrillary tangle aggregation at P < 0.05. A molecular docking study revealed that ipriflavone has a potent binding affinity towards AChE more than donepezil and acts as a strong AChE inhibitor. Our data concluded that the therapeutic potential of ipriflavone against dementia could provide a new strategy in AD treatment.
... TIMP3, on the other hand, is involved in inducing apoptosis by modulating the FAS death receptor [95], a mechanism that has been confirmed for a variety of cell types [96][97][98]. F in higher concentrations was demonstrated to trigger apoptosis in brain cells [99]. Our findings suggest that this correlation may be linked to the amounts and activity of TIMP2 and TIMP3. ...
Fluoride (F) exposure decreases brain receptor activity and neurotransmitter production. A recent study has shown that chronic fluoride exposure during childhood can affect cognitive function and decrease intelligence quotient, but the mechanism of this phenomenon is still incomplete. Extracellular matrix (ECM) and its enzymes are one of the key players of neuroplasticity which is essential for cognitive function development. Changes in the structure and the functioning of synapses are caused, among others, by ECM enzymes. These enzymes, especially matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs), are involved in both physiological processes, such as learning or memory, and pathological processes like glia scare formation, brain tissue regeneration, brain-blood barrier damage and inflammation. Therefore, in this study, we examined the changes in gene and protein expression of MMP2, MMP9, TIMP2 and TIMP3 in the prefrontal cortex, hippocampus, striatum and cerebellum of rats (Wistar) exposed to relatively low F doses (50 mg/L in drinking water) during the pre- and neonatal period. We found that exposure to F during pre- and postnatal period causes a change in the mRNA and protein level of MMP2, MMP9, TIMP2 and TIMP3 in the prefrontal cortex, striatum, hippocampus and cerebellum. These changes may be associated with many disorders that are observed during F intoxication. MMPs/TIMPs imbalance may contribute to cognitive impairments. Moreover, our results suggest that a chronic inflammatory process and blood-brain barrier (BBB) damage occur in rats’ brains exposed to F.
... The effects of fluoride on the nervous system have been manifested in intellectual development of rats [7]. Chronic high fluoride exposure of maternal mice in drinking water during pregnancy and lactation may have harmful influences on learning and memory of young mice [8]. ...
Abstract Background The intellectual loss induced by fluoride exposure has been extensively studied, but the association between fluoride exposure in different susceptibility windows and children’s intelligence is rarely reported. Hence, we conducted a cross-sectional study to explore the association between fluoride exposure in prenatal and childhood periods and intelligence quotient (IQ). Methods We recruited 633 local children aged 7–13 years old randomly from four primary schools in Kaifeng, China in 2017. The children were divided into four groups, of which included: control group (CG, n = 228), only prenatal excessive fluoride exposure group (PFG, n = 107), only childhood excessive fluoride exposure group (CFG, n = 157), both prenatal and childhood excessive fluoride exposure group (BFG, n = 141). The concentrations of urinary fluoride (UF) and urinary creatinine (UCr) were determined by fluoride ion-selective electrode assay and a creatinine assay kit (picric acid method), respectively. The concentration of UCr-adjusted urinary fluoride (CUF) was calculated. IQ score was assessed using the second revision of the Combined Raven’s Test-The Rural in China (CRT-RC2). Threshold and saturation effects analysis, multiple linear regression analysis and logistic regression analysis were conducted to analyze the association between fluoride exposure and IQ. Results The mean IQ score in PFG was respectively lower than those in CG, CFG and BFG (P
... Recent animal studies have evidenced that F can cross the blood-brain barrier and modify neural circuits of several areas such as the cerebellum, motor cortex, and hippocampus (Dec et al., 2017(Dec et al., , 2019, triggering functional deficits in learning and memory and anxietydepression behaviors (Jiang et al., 2014a;Li et al., 2019;Liu et al., 2014;Zhu et al., 2017). The hippocampus integrates the projections of other structures, such as the entorhinal, perirhinal, and parahippocampal cortices (Squire, 1992) and plays important roles in the formation of spatial, visual, and recognition memories (Barker and Warburton, 2015;Broadbent et al., 2004;Clark et al., 2000). ...
Long-term exposure to high concentrations of fluoride (F) can damage mineralized and soft tissues such as bones, liver, kidney, intestine, and nervous system of adult rats. The high permeability of the blood-brain barrier and placenta to F during pregnancy and lactation may be critical to neurological development. Therefore, this study aimed to investigate the effects of F exposure during pregnancy and lactation on molecular processes and oxidative biochemistry of offspring rats' hippocampus. Pregnant Wistar rats were randomly assigned into 3 groups in accordance with the drinking water received: G1 - deionized water (control); G2 - 10 mg/L of F and G3 - 50 mg/L of F. The exposure to fluoridated water began on the first day of pregnancy and lasted until the 21st day of breastfeeding (when the offspring rats were weaned). Blood plasma samples of the offspring rats were collected to determine F levels. Hippocampi samples were collected for oxidative biochemistry analyses through antioxidant capacity against peroxyl (ACAP), lipid peroxidation (LPO), and nitrite (NO2-) levels. Also, brain-derived neurotrophic factor (BDNF) gene expression (RT-qPCR) and proteomic profile analyses were performed. The results showed that exposure to both F concentrations during pregnancy and lactation increased the F bioavailability, triggered redox imbalance featured by a decrease of ACAP, increase of LPO and NO2- levels, BDNF overexpression and changes in the hippocampus proteome. These findings raise novel questions regarding potential repercussions on the hippocampus structure and functioning in the different cognitive domains.
... Western blotting and MTT assay were performed as described in our previous studies (18,19). ...
This study aims to explore the role and mechanism of specific lncRNA in brain metastasis (BM) from lung adenocarcinoma (LADC), providing an effective biomarker for early diagnosis and targeted therapy of BM from LADC. Based on the gene expression profiles of lncRNA and mRNA in LADC and BM tissues detected by Gene Chip, lnc-REG3G-3-1 was selected, and the related genes, including miR-215-3p, leptin, and SLC2A5, were identified by data analysis. Human LADC cell lines A549 and H1299 were cultured. Dual-luciferase and endogenous validation experiments were used to confirm the regulation between these genes. Real-time quantitative reverse transcription–polymerase chain reaction and Western blotting were used to detect gene expression. The tumor metastasis-related gene function of lnc-REG3G-3-1 and miR-215-3p in H1299 cells was verified by Transwell invasion, migration assays, and scratch testing. Nude mice xenograft tumors constructed with decreased lnc-REG3G-3-1 confirmed the influences on gene expression in vivo. lnc-REG3G-3-1 was highly expressed in BM tissues that originated from LADC compared with that in primary cancer tissues. lnc-REG3G-3-1 reduced miR-215-3p expression, thereby regulating the target genes leptin and SLC2A5 and the signaling pathways, taking part in the lnc-REG3G-3-1/miR-215-3p axis in the process of BM from LADC. lnc-REG3G-3-1, leptin, and SLC2A5 through regulating signaling pathways may be jointly involved in the regulation of the biological process of BM in patients with LADC.
... Причиной истощения нейронального слоя зон СА3 и СА1 гиппокампа у крыс, получавших избыток F -, вероятно, являются многочисленные патоморфологические изменения нейронов, типичные для гибнущих клеток -нарушение ядерной и плазматической мембран, различная степень патологии вещества Ниссля, набухание или сморщивание клеток, появление нейронов с винтообразными отростками (рис. 1, 3). Литературные данные [4,5,11,13,14,16,18,21,25,26,[28][29][30] также показали, что потребление животными избыточных доз Fприводило к сморщиванию, атрофии, хроматолизу, глиозу, некрозу или нейронофагии нейрональных клеток, пикнозу и смещению ядер к периферии, исчезновению дендритов, частичной демиелинизации. ...
... At last, there seems to be great interest in the importance of pediatric and general oral health due to the crisis that poor oral health is bringing upon us [105]. We should be concerned that research studies from several countries have all reported neurotoxicity effects from relatively low levels of fluoride in children [106][107][108][109][110][111]. Our over reliance on fluoride to create fluorapatite to inhibit decay seems inadequate at best. ...
... It is well known that glucose is the main metabolite for neuronal cells of the brain. Although, the molecular aspects involved in glucose transportation and metabolism in neural brain tissue is not very comprehensible yet it has been reported that fluoride diminishes the expression of GLUT1 responsible for the glucose uptake in the cerebral cortex and hippocampus 15 which may cause a distortion in brain energy metabolism and synthesis of precursors for nucleoside and cofactors for lipid metabolism. However Rogalska et al., 2017 has reported that glucose transporters proteins 1 (GLUT 1) or 3 (GLUT 3) remained unaltered in frontal cortex and striatum in fluoride exposed rats in spite of increased brain glucose uptake in these animals compared to control revealing that a compensatory increase in glucose uptake and utilization in brain may work out to manage fluoride-induced neurodegeneration and glial renewal 16 . ...
... [12][13][14] The involvement of oxidative stress and free radical generation has been linked to the pathophysiology of NaF-induced neurodegeneration. 15 Previous research reports have documented neuronal apoptosis, developmental neurotoxicity in rat offspring, cytoskeleton damage and decreased signal, excessive endoplasmic reticulum stress and autophagic dysfunction, synaptic impairment, and developmental neurotoxicity following exposure to NaF. 5,7,8,16,17 Furthermore, fragmentation and redistribution of mitochondria away from the axons of the cortical neurons 18 decreased the expressions of glucose transporter 1 (GLUT1) and glial fibrillary acidic protein (GFAP), 19 induction of S-phase cell-cycle arrest, upregulation of NFkappa B and DNA damage in primary rat hippocampal neurons, 20 behavioral deficit, 9 alteration of cognition, emotion, and synaptic plasticity in rat hippocampus. 21,22 Clofibrate is a peroxisome proliferator-activated receptor alpha (PPAR-α) agonist. ...
Fluoride is an environmental contaminant that is ubiquitously present in air, water, and soil. It is commonly added in minute quantity to drinking water, toothpaste, and mouth rinses to prevent tooth decay. Epidemiological findings have demonstrated that exposure to fluoride induced neurodevelopmental toxicity, developmental neurotoxicity, and motor disorders. The neuroprotective effect of clofibrate, a peroxisome proliferator‐activated receptor alpha agonist, was investigated in the present study. Forty male Wistar rats were used for this study and randomly grouped into 10 rats per group as control, sodium fluoride (NaF) alone (300 ppm), NaF plus clofibrate (250 mg/kg), and NaF plus lisinopril (10 mg/kg), respectively, for 7 days. NaF was administered in drinking water while clofibrate and lisinopril were administered by oral gavage. Markers of neuronal inflammation and oxidative stress, acetylcholinesterase activity, and neurobehavioral (hanging wire and open field) tests were performed. Immunohistochemistry was performed on brain tissues, and they were probed with glial fibrillary acidic protein, ionized calcium‐binding adaptor molecule 1, and cerebellar Ca2+‐binding protein calbindin‐D28k. The results showed that NaF significantly increased of oxidative stress and neuroinflammation and inhibited AChE activity. Immunostaining showed reactive astrocytes, microgliosis, loss of dendritic spines, and arborization in Purkinje cells in rats administered only NaF. Neurobehavioral results showed that cotreatment of NaF with clofibrate improved muscular strength and locomotion, reduced anxiety, and significantly reduced astrocytic count. Overall, cotreatment of NaF with either clofibrate or lisinopril showed neuroprotective effects by mitigating neuronal inflammation and oxidative and motor incoordination. Hence, clofibrate could be seen as a novel drug candidate against neurodegeneration and motor disorders.
... 2 Fluoride crosses the placenta, 3 and laboratory studies show that it accumulates in brain regions involved in learning and memory 4 and alters proteins and neurotransmitters in the central nervous system. 5 Higher fluoride exposure from drinking water has been associated with lower children's intelligence in a meta-analysis 6 of 27 epidemiologic studies and in studies 7,8 including biomarkers of fluoride exposure. However, most prior studies were cross-sectional and conducted in regions with higher water fluoride concentrations (0.88-31.6 mg/L; to convert to millimoles per liter, multiply by 0.05263) than levels considered optimal (ie, 0.7 mg/L) in North America. ...
Importance
The potential neurotoxicity associated with exposure to fluoride, which has generated controversy about community water fluoridation, remains unclear.
Objective
To examine the association between fluoride exposure during pregnancy and IQ scores in a prospective birth cohort.
Design, Setting, and Participants
This prospective, multicenter birth cohort study used information from the Maternal-Infant Research on Environmental Chemicals cohort. Children were born between 2008 and 2012; 41% lived in communities supplied with fluoridated municipal water. The study sample included 601 mother-child pairs recruited from 6 major cities in Canada; children were between ages 3 and 4 years at testing. Data were analyzed between March 2017 and January 2019.
Exposures
Maternal urinary fluoride (MUFSG), adjusted for specific gravity and averaged across 3 trimesters available for 512 pregnant women, as well as self-reported maternal daily fluoride intake from water and beverage consumption available for 400 pregnant women.
Main Outcomes and Measures
Children’s IQ was assessed at ages 3 to 4 years using the Wechsler Primary and Preschool Scale of Intelligence-III. Multiple linear regression analyses were used to examine covariate-adjusted associations between each fluoride exposure measure and IQ score.
Results
Of 512 mother-child pairs, the mean (SD) age for enrollment for mothers was 32.3 (5.1) years, 463 (90%) were white, and 264 children (52%) were female. Data on MUFSG concentrations, IQ scores, and complete covariates were available for 512 mother-child pairs; data on maternal fluoride intake and children’s IQ were available for 400 of 601 mother-child pairs. Women living in areas with fluoridated tap water (n = 141) compared with nonfluoridated water (n = 228) had significantly higher mean (SD) MUFSG concentrations (0.69 [0.42] mg/L vs 0.40 [0.27] mg/L; P = .001; to convert to millimoles per liter, multiply by 0.05263) and fluoride intake levels (0.93 [0.43] vs 0.30 [0.26] mg of fluoride per day; P = .001). Children had mean (SD) Full Scale IQ scores of 107.16 (13.26), range 52-143, with girls showing significantly higher mean (SD) scores than boys: 109.56 (11.96) vs 104.61 (14.09); P = .001. There was a significant interaction (P = .02) between child sex and MUFSG (6.89; 95% CI, 0.96-12.82) indicating a differential association between boys and girls. A 1-mg/L increase in MUFSG was associated with a 4.49-point lower IQ score (95% CI, −8.38 to −0.60) in boys, but there was no statistically significant association with IQ scores in girls (B = 2.40; 95% CI, −2.53 to 7.33). A 1-mg higher daily intake of fluoride among pregnant women was associated with a 3.66 lower IQ score (95% CI, −7.16 to −0.14) in boys and girls.
Conclusions and Relevance
In this study, maternal exposure to higher levels of fluoride during pregnancy was associated with lower IQ scores in children aged 3 to 4 years. These findings indicate the possible need to reduce fluoride intake during pregnancy.
... Besides these trophic effects, BDNF can also exacerbate excitotoxic insults to motor, cortical, and cerebellar neurons [19][20][21][22]. BDNF expressions markedly increase in many cell types following tissue injury, tissue insult, and aging [23,24]. Nevertheless, treating slice cultures of developmental mouse cerebellum with an antibody against BDNF or BDNF peptide did not affect the survival of Purkinje cells [25]. 2 of 9 In developing neurons, BDNF expression is facilitated by GABA A receptor activation [26]. ...
Endogenous γ-aminobutyric acid (GABA)-dependent activity induces death of developing Purkinje neurons in mouse organotypic cerebellar cultures and the synthetic steroid mifepristone blocks this effect. Here, using brain-derived neurotrophic factor (BDNF) heterozygous mice, we show that BDNF plays no role in immature Purkinje cell death. However, interestingly, BDNF haploinsufficiency impairs neuronal survival induced by mifepristone and GABAA-receptors antagonist (bicuculline) treatments, indicating that the underlying neuroprotective mechanism requires the neurotrophin full expression.
... Long-term exposure to fluoride is regarded by the World Health Organization as being beneficial, including both prevention of dental caries and treating osteoporosis, though excess intake can also cause potential health hazards, including dental and skeletal fluorosis. Fluoride is also shown to readily cross the placenta (Shen and Taves, 1974) and accumulate in fetal brain tissues (Narayanaswamy and Piler, 2009), thereby inducing toxicity (Dong et al., 1993;Jiang et al., 2014). Several animal (Chen et al., 2003;Mcpherson et al., 2018;Mullenix et al., 1995) and human studies (Bashash et al., 2017;Choi et al., 2012) have explored associations between early-life exposure to fluoride and decrements in cognitive function and attention-related behaviors. ...
Background: Epidemiologic and animal-based studies have raised concern over the potential impact of fluoride exposure on neurobehavioral development as manifested by lower IQ and deficits in attention. To date, no prospective epidemiologic studies have examined the effects of prenatal fluoride exposure on behavioral outcomes using fluoride biomarkers and sensitive measures of attention. Objective: We aimed to examine the association between prenatal fluoride exposure and symptoms associated with attention-deficit/hyperactivity disorder (ADHD). Method: 213 Mexican mother-children pairs of the Early Life Exposures to Environmental Toxicants (ELEMENT) birth cohort study had available maternal urinary samples during pregnancy and child assessments of ADHD-like behaviors at age 6–12. We measured urinary fluoride levels adjusted for creatinine (MUFcr) in spot urine samples collected during pregnancy. The Conners' Rating Scales-Revised (CRS-R) was completed by mothers, and the Conners' Continuous Performance Test (CPT-II) was administered to the children. Results: Mean MUFcr was 0.85 mg/L (SD = 0.33) and the Interquartile Range (IQR) was 0.46 mg/L. In multivariable adjusted models using gamma regression, a 0.5 mg/L higher MUFcr (approximately one IQR higher) corresponded with significantly higher scores on the CRS-R for DSM-IV Inattention (2.84 points, 95% CI: 0.84, 4.84) and DSM-IV ADHD Total Index (2.38 points, 95% CI: 0.42, 4.34), as well as the following symptom scales: Cognitive Problems and Inattention (2.54 points, 95% CI: 0.44, 4.63) and ADHD Index (2.47 points; 95% CI: 0.43, 4.50). The shape of the associations suggested a possible celling effect of the exposure. No significant associations were found with outcomes on the CPT-II or on symptom scales assessing hyperactivity. Conclusion: Higher levels of fluoride exposure during pregnancy were associated with global measures of ADHD and more symptoms of inattention as measured by the CRS-R in the offspring. Keywords: Fluoride, Pregnancy, Neurobehavioral, ADHD
... Long-term exposure to fluoride is regarded by the World Health Organization as being beneficial, including both prevention of dental caries and treating osteoporosis, though excess intake can also cause potential health hazards, including dental and skeletal fluorosis. Fluoride is also shown to readily cross the placenta (Shen and Taves, 1974) and accumulate in fetal brain tissues (Narayanaswamy and Piler, 2009), thereby inducing toxicity (Dong et al., 1993;Jiang et al., 2014). Several animal (Chen et al., 2003;Mcpherson et al., 2018;Mullenix et al., 1995) and human studies (Bashash et al., 2017;Choi et al., 2012) have explored associations between early-life exposure to fluoride and decrements in cognitive function and attention-related behaviors. ...
Background:
Epidemiologic and animal-based studies have raised concern over the potential impact of fluoride exposure on neurobehavioral development as manifested by lower IQ and deficits in attention. To date, no prospective epidemiologic studies have examined the effects of prenatal fluoride exposure on behavioral outcomes using fluoride biomarkers and sensitive measures of attention.
Objective:
We aimed to examine the association between prenatal fluoride exposure and symptoms associated with attention-deficit/hyperactivity disorder (ADHD).
Method:
213 Mexican mother-children pairs of the Early Life Exposures to Environmental Toxicants (ELEMENT) birth cohort study had available maternal urinary samples during pregnancy and child assessments of ADHD-like behaviors at age 6-12. We measured urinary fluoride levels adjusted for creatinine (MUFcr) in spot urine samples collected during pregnancy. The Conners' Rating Scales-Revised (CRS-R) was completed by mothers, and the Conners' Continuous Performance Test (CPT-II) was administered to the children.
Results:
Mean MUFcr was 0.85 mg/L (SD = 0.33) and the Interquartile Range (IQR) was 0.46 mg/L. In multivariable adjusted models using gamma regression, a 0.5 mg/L higher MUFcr (approximately one IQR higher) corresponded with significantly higher scores on the CRS-R for DSM-IV Inattention (2.84 points, 95% CI: 0.84, 4.84) and DSM-IV ADHD Total Index (2.38 points, 95% CI: 0.42, 4.34), as well as the following symptom scales: Cognitive Problems and Inattention (2.54 points, 95% CI: 0.44, 4.63) and ADHD Index (2.47 points; 95% CI: 0.43, 4.50). The shape of the associations suggested a possible celling effect of the exposure. No significant associations were found with outcomes on the CPT-II or on symptom scales assessing hyperactivity.
Conclusion:
Higher levels of fluoride exposure during pregnancy were associated with global measures of ADHD and more symptoms of inattention as measured by the CRS-R in the offspring.
... The hippocampal slices were selected and ultra-thin sections (at a thickness of 400-600 μm) were made as previously described. 17,18 These ultrathin sections were stained with lead citrate and uranyl acetate and observed under an FEI Tecnai 12 and Tecnai G2 type electron microscope (Holland). Then, photos of the hippocampus were taken at 10 000-20 000× magnification. ...
Objective: The complex components of PM2.5 including metal elements transported through the blood brain barrier could induce nervous system damage. This study discusses the relationship between rats’ learning and memory and changes in the hippocampal neuron histomorphology and neurotransmitter levels induced by PM2.5 exposure. Methods: Male rats were treated with different concentrations of PM2.5 by tracheal perfusion once per week for up to 12 weeks. After the rats were sacrificed, the main metal element contents (Al, Pb, Cu, Mn, As, Cr, Cd, and Ni) of the blood and whole hippocampus, levels of neurotransmitters released in the whole hippocampus and relative receptors, and changes in the hippocampal structure were detected. Results: The results showed that PM2.5 significantly reduced the cognitive learning abilities of rats. PM2.5 exposure increased the contents of hippocampal lead, manganese, and aluminum. The level of glutamic acid was increased in the hippocampal tissues of the 20 mg kg⁻¹ group, in combination with the decreased N-methyl-D-aspartate glutamate receptor (NMDAR) and increased metabotropic glutamate receptor type1 (mGluR1) expression. Increased clearance, a mild disorder of arrangement, and mild edema could be observed in the rat hippocampal neurons treated with PM2.5. Conclusion: PM2.5-induced defects in learning and memory may be related to the morphological abnormalities of the hippocampus and the abnormal expression of neurotransmitters and their receptors.
... The end-foot of astrocytes is an indispensable part of the blood-brain barrier (BBB), and the glucose which is transported into the brain via the blood flow will preferentially contact with an astrocyte rather than a neuron (Choeiri et al. 2005;Daneman and Prat 2015). Since the membranes of astrocytes are impermeable to glucose, the uptake of glucose mainly depends on GLUT1 on the cell membranes (Benarroch 2014; Jiang et al. 2014). In astrocytes, glucose can be synthesized into glycogen by GS. ...
Lanthanum (La) can impair learning memory and induce behavioral abnormalities in animals. However, the mechanism underlying these adverse effects of La is still elusive. It has been demonstrated that lactate derived from astrocytes is the major energy source for neurons during long-term memory (LTM) formation and the deficiency of lactate supply can result in LTM damage. However, little work has been done with respect to the impact of La on the lactate production in astrocytes and astrocyte-neuron lactate transport (ANLT). Herein, experiments were undertaken to explore if there was such an adverse effect of La. Primary culture rat cortical astrocytes and primary co-culture rat cortical astrocyte-neuron were treated with (0.125, 0.25 and 0.5 mM) lanthanum chloride (LaCl3) for 24 h. The results showed that LaCl3 treatment significantly downregulated the mRNA and protein expression of glucose transporter 1 (GLUT1), glycogen synthase (GS), glycogen phosphorylase (GP), lactate dehydrogenase A (LDHA), and monocarboxylate transporter 1, 2 and 4 (MCT 1 2 and 4); upregulated the mRNA and protein expression of lactate dehydrogenase B (LDHB); and decreased the glycogen level, total LDH and GP activity, GS/p-GS ratio and lactate contents. Moreover, rolipram (20, 40 μM) or forskolin (20, 40 μM) could increase the lactate content by upregulating GP expression and the GS/p-GS ratio, as well as antagonize the effects of La. These results suggested that La-induced learning-memory damage was probably related to its suppression of lactate production in astrocytes and ANLT. This study provides some novel clues for clarifying the mechanism underlying the neurotoxicity of La.
... Fluoride induced apoptosis in hippocampal cell line (54). Primary rat hippocampal neurons were incubated with 20, 40, and 80 mg/l sodium fluoride for 24 h in vitro (55). ...
Apoptosis is genetically programmed cell death,
an irreversible process of cell senescence with characteristic
features different from other cellular mechanisms of death
such as necrosis. In the last years, apoptosis has been
extensively studied in the scientific literature, because it has
been established that apoptosis plays a crucial role following
the time course of chronic degenerative diseases, such as
cancer. Thus, several researchers have strugged to detect
what chemical agents are able to inter fere with the apoptotic
process. Thus, the purpose of this literature review is to
assess if fluoride induces apoptosis in mammalian cells using
in vivo and in vitro test systems. Certain mammalian cell
types such as oral cells, blood and brain were exetensively
investigated; the results showed that fluoride is able to induce
apoptosis in both intrinsinc and extrinsic pathways.
Moreover, other cells types have been poorly investigated
such as bone, kidney and reproductive cells with conflicting
results so far. Therefore, this area needs further investigation
for the safety of human populations exposed to fluoride in a
chronic way, as for example in developing countries.
Fluoride is one of the abundant elements found in the Earth's crust and is a global environmental issue. The present work aimed to find the impact of chronic consumption of fluoride contained groundwater on human subjects. Five hundred and twelve volunteers from different areas of Pakistan were recruited. Cholinergic status, acetylcholinesterase and butyrylcholinesterase gene SNPs and pro-inflammatory cytokines were examined. Association analysis, regression and other standard statistical analyses were performed. Physical examination of the fluoride endemic areas' participants revealed the symptoms of dental and skeletal fluorosis. Cholinergic enzymes (AChE and BChE) were significantly increased among different exposure groups. ACHE gene 3'-UTR variant and BCHE K-variant showed a significant association with risk of fluorosis. Pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) were found to be increased and have a significant correlation in response to fluoride exposure and cholinergic enzymes. The study concludes that chronic consumption of high fluoride-contained water is a risk factor for developing low-grade systemic inflammation through the cholinergic pathway and the studied cholinergic gene SNPs were identified to be associated with the risk of flurosis.
This investigation was designed to examine the potential involvement of RAGE/NADPH oxidase signaling in the damage to the brain caused by chronic fluorosis. Sprague-Dawley rats were divided randomly into 9 groups each containing 20 animals, Controls (C); rats receiving low (i.e., 10 ppm) (LF) or high does ( i.e., 50 ppm) (HF) of fluoride in their drinking water; and these same groups injected with FPS-ZM1, an inhibitor of RAGE, (CF, LFF and HFF, respectively) or administered EGb761, an active ingredient of Ginkgo biloba extract, intragastrically (CE, LFE, and HFE). Following 3 and 6 months of such treatment, the spatial learning and memory of the animals were assessed with the Morris water maze test; the levels of malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide dismutase (SOD) assayed by biochemical methods; and the levels of proteins related to the RAGE/NADPH pathway determined by Western blot and of the corresponding mRNAs by qPCR. After 6 months, the spatial learning and memory of the LF and HF groups had declined; their brain contents of MDA and H2O2 increased and SOD activity decreased; and the levels of the RAGE, gp91, P47, phospho-P47phox and P22 proteins and corresponding mRNAs in their brains were all elevated. Interestingly, all of these pathological changes caused by fluorosis could be attenuated by both FPS-ZM1 and EGb761. These findings indicate that the brain damage induced by fluorosis may be caused, at least in part, by enhanced RAGE/NADPH oxidase signaling and that FPS-ZM1 or EGb761 might be of clinical value in connection with the treatment of this condition.
Background:
On May 19, 2011, Calgary, Canada stopped fluoridating its drinking water. This prospective ecological study examined if maternal exposure to fluoride during pregnancy from drinking water that was fluoridated at the recommended level of 0.7 mg/L was associated with children's intelligence and executive function at 3-5 years of age.
Methods:
Participants were 616 maternal-child pairs enrolled in the Calgary cohort of the Alberta Pregnancy Outcomes and Nutrition (APrON) study between 2009 and 2012. Maternal-child pairs were classified as fully exposed to fluoridated drinking water throughout pregnancy (n = 295); exposed to fluoridated drinking water for at least part of the pregnancy plus an additional 90 days (n = 220); or not exposed to fluoridated drinking water during pregnancy plus the 90 days prior to pregnancy (n = 101). Children's Full Scale IQs were assessed using the Wechsler Preschool and Primary Scale of Intelligence, Fourth Edition (WPPSI-IVCDN). Children's executive functions were also assessed: working memory (WPPSI-IVCDN Working Memory Index), inhibitory control (Gift Delay, NEPSY-II Statue subtest), and cognitive flexibility (Boy-Girl Stroop, Dimensional Change Card Sort (DCCS)).
Results:
No associations were found between exposure group and Full Scale IQ. However, compared to no exposure, full exposure to fluoridated drinking water throughout pregnancy was associated with poorer performance on the Gift Delay (B = 0.53, 95 % CI = 0.31, 0.93). Sex-specific analyses revealed that girls in the fully exposed (AOR = 0.30, 95 % CI = 0.13, 0.74) and partially exposed groups (AOR = 0.42, 95 % CI = 0.17, 1.01) performed more poorly than girls in the not exposed group. Sex effects were also found on the DCCS; girls in the fully exposed (AOR = 0.34, 95 % CI = 0.14, 0.88) and partially exposed groups (AOR = 0.29, 95 % CI = 0.12, 0.73) performed more poorly.
Conclusion:
Maternal exposure to drinking water throughout pregnancy fluoridated at the level of 0.7 mg/L was associated with poorer inhibitory control and cognitive flexibility, particularly in girls, suggesting a possible need to reduce maternal fluoride exposure during pregnancy.
Background:
Fluoride, an environmental contaminant, is ubiquitously present in air, water, and soil. It usually enters the body through drinking water and may cause structural and functional disorders in the central nervous system in humans and animals. Fluoride exposure affects cytoskeleton and neural function, but the mechanism is not clear.
Methods:
The specific neurotoxic mechanism of fluoride was explored in HT-22 cells. Cellular proliferation and toxicity detection were investigated by CCK-8, CCK-F, and cytotoxicity detection kits. The development morphology of HT-22 cells was observed under a light microscope. Cell membrane permeability and neurotransmitter content were determined using lactate dehydrogenase (LDH) and glutamate content determination kits, respectively. The ultrastructural changes were detected by transmission electron microscopy, and actin homeostasis was observed by laser confocal microscopy. ATP enzyme and ATP activity were determined using the ATP content kit and ultramicro-total ATP enzyme content kit, respectively. The expression levels of GLUT1 and 3 were assessed by Western Blot assays and qRT-PCR.
Results:
Our results showed that fluoride reduced the proliferation and survival rates of HT-22 cells. Cytomorphology showed that dendritic spines became shorter, cellular bodies became rounder, and adhesion decreased gradually after fluoride exposure. LDH results showed that fluoride exposure increased the membrane permeability of HT-22 cells. Transmission electron microscopy results showed that fluoride caused cells to swell, microvilli content decreased, cellular membrane integrity was damaged, chromatin was sparse, mitochondria ridge gap became wide, and microfilament and microtubule density decreased. Western Blot and qRT-PCR analyses showed that RhoA/ROCK/LIMK/Cofilin signaling pathway was activated by fluoride. F-actin/G-actin fluorescence intensity ratio remarkably increased in 0.125 and 0.5 mM NaF, and the mRNA expression of MAP2 was significantly decreased. Further studies showed that GLUT3 significantly increased in all fluoride groups, while GLUT1 decreased (p < 0.05). ATP contents remarkably increased, and ATP enzyme activity substantially decreased after NaF treatment with the control.
Conclusion:
Fluoride activates the RhoA/ROCK/LIMK/Cofilin signaling pathway, impairs the ultrastructure, and depresses the connection of synapses in HT-22 cells. Moreover, fluoride exposure affects the expression of glucose transporters (GLUT1 and 3) and ATP synthesis. Sum up fluoride exposure disrupts actin homeostasis, ultimately affecting structure, and function in HT-22 cells. These findings support our previous hypothesis and provide a new perspective on the neurotoxic mechanism of fluorosis.
Evidence suggests that fluoride-induced neurodevelopment damage is linked to mitochondrial disorder, yet the detailed mechanism remains unclear. A cohort of Sprague-Dawley rats developmentally exposed to sodium fluoride (NaF) was established to simulate actual exposure of human beings. Using high-input proteomics and small RNA sequencing technology in rat hippocampus, we found mitochondrial translation as the most striking enriched biological process after NaF treatment, which involves the differentially expressed Required Meiotic Nuclear Division 1 homolog (RMND1) and neural-specific miR-221-3p. Further experiments in vivo and in vitro neuroendocrine pheochromocytoma (PC12) cells demonstrated that NaF impaired mitochondrial translation and function, as shown by declined mitochondrial membrane potential and inhibited expression of mitochondrial translation factors, mitochondrial translation products, and OXPHOS complexes, which was concomitant with decreased RMND1 and transcription factor c-Fos in mRNA and proteins as well as elevated miR-221-3p. Notably, RMND1 overexpression alleviated the NaF-elicited mitochondrial translation impairment by up-regulating translation factors, but not vice versa. Interestingly, ChIP-qPCR confirmed that c-Fos specifically controls the RMND1 transcription through direct binding with Rmnd1 promotor. Interference of gene expression verified c-Fos as an upstream positive regulator of RMND1, implicating in fluoride-caused mitochondrial translation impairment. Furthermore, dual-luciferase reporter assay evidenced that miR-221-3p targets c-Fos by binding its 3' untranslated region. By modulating the miR-221-3p expression, we identified miR-221-3p as a critical negative regulator of c-Fos. More importantly, we proved that miR-221-3p inhibitor improved mitochondrial translation and mitochondrial function to combat NaF neurotoxicity via activating the c-Fos/RMND1 axis, whereas miR-221-3p mimic tended towards opposite effects. Collectively, our data suggest fluoride impairs mitochondrial translation by dysregulating the miR-221-3p/c-Fos/RMND1 axis to trigger mitochondrial dysfunction, leading to neuronal death and neurodevelopment defects.
Dental fluorosis (DF) is a widely prevalent disease caused by excessive fluoride with limited awareness of its underlying pathogenesis. Here, a pilot population study was conducted to explore the pathogenesis of DF from the perspective of intestinal microbiome changes, and verified it in animal experiments combining intestinal microbiome and metabolomics. A total of 23 children were recruited in 2017 in China and divided into DF (n = 9) and control (n = 14) groups (DFG and CG, respectively). The SD rat model was established by drinking water containing sodium fluoride (NaF). Gut microbiome profiles of children and rats were analyzed by16S rDNA V3-V4 sequencing, and the intestinal metabolomics analysis of rats was performed by LC-MS methods. The 16 S rDNA sequencing revealed that the gut microbiome composition was significantly perturbed in children in DFG compared to that in CG. Acidobacteria and Thermi were specifically observed in DFG and CG, respectively. Besides, 15 fecal microbiotas were significantly altered at the genus level in DFG. Furthermore, only the expression of annotated genes for pentose and glucuronate interconversion pathway was significant lower in DFG than that in CG (P = 0.04). Notably, in NaF-treated rats, we also observed the changes of some key components of pentose and glucuronate interconversion pathway at the level of microorganisms and metabolites. Our findings suggested that the occurrence of DF is closely related to the alteration of intestinal microorganisms and metabolites annotated in the pentose and glucuronate interconversion pathway.
Fluoride is capable of inducing developmental neurotoxicity; regrettably, the mechanism is obscure. We aimed to probe the role of lysosomal biogenesis disorder in developmental fluoride neurotoxicity—specifically, the regulating effect of the transient receptor potential mucolipin 1 (TRPML1)/transcription factor EB (TFEB) signaling pathway on lysosomal biogenesis. Sprague-Dawley rats were given fluoridated water freely, during pregnancy to the parental rats to 2 months after delivery to the offspring. In addition, neuroblastoma SH-SY5Y cells were treated with sodium fluoride (NaF), with or without mucolipin synthetic agonist 1 (ML-SA1) or adenovirus TFEB (Ad-TFEB) intervention. Our findings revealed that NaF impaired learning and memory as well as memory retention capacities in rat offspring, induced lysosomal biogenesis disorder, and decreased lysosomal degradation capacity, autophagosome accumulation, autophagic flux blockade, apoptosis, and pyroptosis. These changes were evidenced by the decreased expression of TRPML1, nuclear TFEB, LAMP2, CTSB, and CTSD, as well as increased expression of LC3-II, p62, cleaved PARP, NLRP3, Caspase1, and IL-1β. Furthermore, TRPML1 activation and TFEB overexpression both restored TFEB nuclear protein expression and promoted lysosomal biogenesis while enhancing lysosomal degradation capacity, recovering autophagic flux, and attenuating NaF-induced apoptosis and pyroptosis. Taken together, these results show that NaF promotes the progression of developmental fluoride neurotoxicity by inhibiting TRPML1/TFEB expression and impeding lysosomal biogenesis. Notably, the activation of TRPML1/TFEB alleviated NaF-induced developmental neurotoxicity. Therefore, TRPML1/TFEB may be promising markers of developmental fluoride neurotoxicity.
Fluoride (F), an inorganic substance, is everywhere in the environment. Fluoride exposure is caused mainly by geogenic sources, such as drinking wells and deep soil water. Excess fluoride-containing water usage for many years may cause neurotoxic damage. The mechanism underlying the neurotoxicology of endemic fluorosis remains obscure. Fluoride crosses the blood-brain barrier and accumulates within neurons. In our study, chronic exposure to fluoride-induced epileptogenesis in neuroblastoma (SK-N-SH) cells was followed with tools like Brain-derived neurotrophic factor (BDNF) and Synapsin 1 (SYN 1) protein expression. SK-N-SH cells were incubated with fluoride water (1 mg/L and 6 mg/L) for 24 h in-vitro. Prolonged ingestion of fluoride causes chronic fluorosis. Fluoride exposure reduced cell viability gradually from 48 to 96 h. The standard structure of axon spines and dendritic outgrowth in high fluoride water vanished. TrkB activated MAPK/ERK downstream signaling pathway is triggered by increased BDNF protein expression and decreased SYN 1 protein levels observed in fluoride water incubation. Further 96 hours incubation with fluoride-cleared water increased viability of SK-N-SH cells and a normal expression of BDNF and SYN 1 protein levels, suggests that fluoride-blocked BDNF-TrkB pathway might have been replaced by high-levels expression of BDNF protein where incubation medium contains concomitant lowered levels of fluoride. Hypothesis is that scaffold proteins regained normal expression might have influenced conducted normal excitation and transmission could reduce neurotoxic effect or even might control seizures.
Detrimental impacts of fluoride have become a global concern for several decades. Despite its beneficial role which is restricted only in skeletal tissues, deleterious effects are also observed in soft tissues and systems. The generation of enhanced oxidative stress is the commencement of excess fluoride exposure which may lead to cell death. Fluoride causes cell death through autophagy via Beclin 1 and mTOR signaling pathways. Beside these, several organ specific anomalies through different signaling pathways have been documented. Mitochondrial dysfunction, DNA damage, autophagy and apoptosis are the damaging outcomes in case of hepatic disorders. Urinary concentration defects and cell cycle arrest have been reported in renal tissues. Abnormal immune response has been characterized in the cardiac system. Cognitive dysfunction, neurodegenerative condition and learning impairment have also been observed. Altered steroidogenesis, gametogenic abnormalities, epigenetic alterations and birth defect are the major reprotoxic conclusions. Abnormal immune responses, altered immunogenic proliferation, differentiation as well as altered ratio of immune cells are well-defined anomalies in the immune system. Though the mechanistic approach of fluoride toxicity in physiological systems is common, it follows different signaling cascades. This review emphasizes diverse signaling pathways which are the targets of overexposed fluoride.
This article reviews the effects of chronic fluorosis on the brain and possible mechanisms. We used PubMed, Medline and Cochraine databases to collect data on fluorosis, brain injury, and pathogenesis. A large number of in vivo and in vitro studies and epidemiological investigations have found that chronic fluorosis can cause brain damage, resulting in abnormal brain structure and brain function.Chronic fluorosis not only causes a decline in concentration, learning, and memory, but also has mental symptoms such as anxiety, tension, and depression. Several possible mechanisms that have been proposed: the oxidative stress and inflammation theory, neural cell apoptosis theory, neurotransmitter imbalance theory, as well as the doctrine of the interaction of fluorine with other elements. However, the specific mechanism of chronic fluorosis on brain damage is still unclear. Thus, a better understanding of the mechanisms via which chronic fluorosis causes brain damage is of great significance to protect the physical and mental health of people in developing countries, especially those living in the endemic areas of fluorosis. In brief, further investigation concerning the influence of fluoride on the brain should be conducted as the neural damage induced by it may bring about a huge problem in public health, especially considering growing environmental pollution.
Fluoride exposure has a detrimental effect on neurodevelopment, while the underlying processes remain unknown. The goal of this study was to investigate how fluoride impacts synaptogenesis, with a focus on the phosphorylation of Creb1 (p-Creb1)-brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (TrkB) pathway. We generated a sodium fluoride (NaF) model using C57 BL/6 J mice exposed to 100 mg/L NaF from gestation day 1 (GD1) to GD20. It was identified that NaF treatment impaired the learning and memory abilities of the male offspring, reduced dendritic spine density, lowered postsynaptic density protein-95 (PSD95) and synaptophysin (SYN) expression in the male offspring's hippocampus, indicating that synaptic dysfunction may contribute to the cognitive impairment in the NaF model. In addition, in vivo experiment demonstrated that the protein abundance of BDNF and the ratio of p-Creb1 to Creb1 were increased in the hippocampus of NaF offspring, while the level of TrkB was reduced. Similarly, PC12 cells treated with NaF also showed increased expression of BDNF and decreased levels of TrkB. Notably, fluoride treatment increased p-Creb1 in vitro, while inhibiting p-Creb1 by 66615 significantly alleviated the effects of NaF exposure, indicating that p-Creb1 exerts a regulatory function in the BDNF-TrkB pathway. Altogether, these results demonstrated prenatal fluoride exposure triggered neurotoxicity in the male offspring hippocampus was linked to synaptogenesis damage caused by activating p-Creb1, which disrupted the BDNF-TrkB pathway.
Aim: To compare the histomorphological changes in the precentral gyrus of cerebral cortex of albino rats by taking green tea and black tea aqueous extract. Study design: Experimental Study Duration of study: 30 days study conducted in Animal Experimental Research Laboratory of PGMI and Department of Anatomy, King Edward Medical University, Lahore. Methodology: 90 albino rats were divided into three groups of 30 animals each. Rats in the group I were given distilled water, while group II and group III received green tea and black tea aqueous extract respectively. At the end of 30 days of experiment, brains were removed and studied for histological changes. Results: When comparison among all the three groups was made at 30 days time, p-value was significant for gliosis i.e. p<0.01. However, experimental group III revealed more gliosis among all the three groups. Necrosis was absent in all the groups and was not statistically analyzed. Conclusion: Gliosis caused by black tea is highly significant as compared to green tea. Key words: Cerebral Cortex, Green tea, Black tea, Gliosis, Necrosis.
Impaired glucose utilization has been implicated in the pathophysiology of neuro-degenerative diseases. The neuroprotective effect of caffeic acid (CA) was investigated in the isolated rat brain by determining its ability to promote glucose uptake, mitigate redox imbalance, modulate purinergic and cholinergic activities, elemental distribution, and maintain tissue morphology. Isolated rat brains were incubated for 2 hours with glucose, CA and glucose, and metformin and glucose. There was an increased glucose uptake, glutathione level, superoxide dismutase, and catalase activities in brain tissues incubated with CA compared to the controls. Incubation with CA also led to significantly decreased levels of malondialdehyde, nitric oxide, acetylcholinesterase, butyrylcholinesterase, and ATPase activities. Electron microscopy (scanning electron microscopy and transmission electron mi-croscopy) analysis portrayed a maintenance of tissue ultrastructural morphology in 2CA-incubated tissues as indicated by the intact synaptic vesicles, blood vessels, dendritic and neuronal network, mitochondria, and presynaptic membrane. CA also restored altered elemental levels in brain tissues. These results indicate the stimu-latory potential of CA on brain glucose utilization with simultaneous neuroprotec-tive activities. K E Y W O R D S caffeic acid, cholinergic dysfunction, glucose uptake, neurodegenerative diseases
High fluoride exposure has been related to harmful health effects, but the impacts of low-to-moderate fluoride on child growth and obesity-related outcomes remain unclear. We performed a large-scale cross-sectional study to examine the association between low-to-moderate fluoride in drinking water and anthropometric measures among Chinese school-age children. We recruited 2430 resident children 7-13 years of age, randomly from low-to-moderate fluorosis areas of Baodi District in Tianjin, China. We analyzed the fluoride contents in drinking water and urine samples using the national standardized ion selective electrode method. Multivariable linear and logistic analyses were used to assess the relationships between fluoride exposure and age- and sex-standardized height, weight and body mass index (BMI) z-scores, and childhood overweight/obesity (BMI z-score > 1). In adjusted models, each log unit (roughly 10-fold) increase in urinary fluoride concentration was associated with a 0.136 unit increase in weight z-score (95% CI: 0.039, 0.233), a 0.186 unit increase in BMI z-score (95% CI: 0.058, 0.314), and a 1.304-fold increased odds of overweight/obesity (95% CI: 1.062, 1.602). These associations were stronger in girls than in boys (Pinteraction = 0.016), and children of fathers with lower education levels were more vulnerable to fluoride (Pinteraction = 0.056). Each log unit (roughly 10-fold) increase in water fluoride concentration was associated with a 0.129 unit increase in height z-score (95% CI: 0.005, 0.254), but not with other anthropometric measures. Our results suggest low-to-moderate fluoride exposure is associated with overweight and obesity in children. Gender and paternal education level may modify the relationship.
Autophagy and apoptosis are two important cellular processes that are crucial for neurodevelopment. Evidence shows that apoptosis is implicated in fluoride neurotoxicity. However, the biological roles of autophagy, especially its interplay with apoptosis in the neurotoxicity induced by long-term fluoride exposure remain unclear. Here we present in vivo and in vitro evidence that fluoride-induced defective autophagy elicits excessive apoptosis, thus inducing neurotoxicity. Using Sprague-Dawley rats exposed to sodium fluoride from 60 days before pregnancy until 6 months post-delivery as in vivo model, we showed that fluoride impaired the learning and memory abilities of offspring rats, with decreased neuronal number, suppressed autophagy and enhanced apoptosis in hippocampus. These results were validated in human neuroblastoma SH-SY5Y cells in vitro. Mechanistically, mTOR signaling, responsible for autophagy induction, was activated in vivo and in vitro, and targeting inhibition of mTOR with rapamycin protected SH-SY5Y cells from defective autophagy and excessive apoptosis, thereby enhancing neuronal survival. Furthermore, circulating levels of autophagy markers were low in children with higher fluoride body burden and lower intelligence quotient scores. Collectively, our results suggest that defective autophagy plays a pivotal role in fluoride neurotoxicity, and mTOR might be a promising target for the prevention and treatment of fluoride neurotoxicity.
Experts in endocrinology have shown that Fluoride causes Diabetes and Obesity. This review assembles the wealth of science that shows how Fluoride damages the organs that generate or use Insulin to control Glucose metabolism and the crucial involvement of other hormone systems.
Background:
Excessive fluoride exposure is associated with adverse health outcomes, but little is known of the effects of moderately chronic fluoride exposure on children's health.
Objectives:
We conducted a cross-sectional study to explore the health impact of moderately excessive fluoride in drinking water.
Methods:
We recruited 2886 resident children, aged 7 to 13 years, randomly from endemic and non-endemic fluorosis areas in Tianjin, China. The fluoride levels in drinking water and urine were measured using the national standardized ion selective electrode method. We examined the dose-response effects of low-to-moderate fluoride exposure on dental fluorosis (DF) and intelligence quotient (IQ), and evaluated the potential relationships between DF grades and intelligence levels using piecewise linear regression and multiple logistic regression, respectively.
Results:
The adjusted odds ratios (ORs) of DF were 2.24 (95% confidence interval [CI]: 2.02 to 2.48) for every 0.1 mg/L increment in the water fluoride concentration in the range of 0.80 to 1.50 mg/L, and 2.61 (95% CI: 2.32 to 2.93) for every 0.5 mg/L increment in the urinary fluoride level up to 1.80 mg/L. Every 0.5 mg/L increment in the water fluoride level was associated with a reduction of 4.29 in the IQ score (95% CI: -8.09 to -0.48) in the range of 3.40 to 3.90 mg/L, and a decreased probability of developing excellent intelligence (IQ ≥ 130, OR = 0.60, 95% CI: 0.47 to 0.77) in the range of 0.20-1.40 mg/L, respectively. Every 0.5 mg/L increment in the urinary fluoride level was related to a decrease of 2.67 in the IQ scores (95% CI: -4.67 to -0.68) between 1.60 mg/L to 2.50 mg/L. Excellent intelligence decreased by 51% in children with higher urinary fluoride, and by 30% with each degree increment of DF.
Conclusions:
Our study suggests threshold and saturation effects of moderately excessive fluoride exposure on DF and intelligence loss in children, and a potential association between DF and the loss of excellent intelligence.
Fluoride is capable of inducing neurotoxicity, but its mechanisms remain elusive. This study aimed to explore the roles of endoplasmic reticulum (ER) stress and autophagy in sodium fluoride (NaF)-induced neurotoxicity, focusing on the regulating role of ER stress in autophagy. The in vivo results demonstrated that NaF exposure impaired the learning and memory capabilities of rats, and resulted in histological and ultrastructural abnormalities in rat hippocampus. Moreover, NaF exposure induced excessive ER stress and associated apoptosis, as manifested by elevated IRE1α, GRP78, cleaved caspase-12 and cleaved-caspase-3, as well as defective autophagy, as shown by increased Beclin1, LC3-II and p62 expression in hippocampus. Consistently, the in vitro results further verified the findings of in vivo study that NaF induced excessive ER stress and defective autophagy in SH-SY5Y cells. Notably, inhibition of autophagy in NaF-treated SH-SY5Y cells with Wortmannin or Chloroquine decreased, while induction of autophagy by Rapamycin increased the cell viability. These results were correlated well with the immunofluorescence observations, thus confirming the pivotal role of autophagic flux dysfunction in NaF-induced cell death. Importantly, mitigation of ER stress by 4-phenylbutyrate in NaF-treated SH-SY5Y cells inhibited the expressions of autophagy markers, and decreased cell apoptosis. Taken together, these data suggest that neuronal death resulted from excessive ER stress and autophagic flux dysfunction contributes to fluoride-elicited neurotoxicity. Moreover, the autophagic flux dysfunction was mediated by excessive ER stress, which provided novel insight into a better understanding of fluoride-induced neurotoxicity.
IntroductionFluoride (F) is a toxic and reactive element, and exposure to it passes almost unnoticed, with the consumption of tea, fish, meat, fruits, etcetera and articles of common use such as: toothpaste additives; dental gels, non-stick pans and razor blades as Teflon. It has also been used with the intention of reducing the dental cares.
There is abundant literature on the role of the basolateral amygdala (BLA) and the CA1 region of the hippocampus in memory formation of inhibitory avoidance (IA) and other behaviorally arousing tasks. Here, we investigate molecular correlates of IA consolidation in the two structures and their relation to NMDA receptors (NMDArs) and β-adrenergic receptors (β-ADrs). The separate posttraining administration of antagonists of NMDAr and β-ADr to BLA and CA1 is amnesic. IA training is followed by an increase of the phosphorylation of calcium and calmodulin-dependent protein kinase II (CaMKII) and ERK2 in CA1 but only an increase of the phosphorylation of ERK2 in BLA. The changes are blocked by NMDAr antagonists but not β-ADr antagonists in CA1, and they are blocked by β-ADr but not NMDAr antagonists in BLA. In addition, the changes are accompanied by increased phosphorylation of tyrosine hydroxylase in BLA but not in CA1, suggesting that β-AD modulation results from local catecholamine synthesis in the former but not in the latter structure. NMDAr blockers in CA1 do not alter the learning-induced neurochemical changes in BLA, and β-ADr blockade in BLA does not hinder those in CA1. When put together with other data from the literature, the present findings suggest that CA1 and BLA play a role in consolidation, but they operate to an extent in parallel, suggesting that each is probably involved with different aspects of the task studied.
• consolidation
• inhibitory avoidance
• learning
Background: Although fluoride may cause neurotoxicity in animal models and acute fluoride poisoning causes neurotoxicity in adults, very little is known of its effects on children’s neurodevelopment.
Objective: We performed a systematic review and meta-analysis of published studies to investigate the effects of increased fluoride exposure and delayed neurobehavioral development.
Methods: We searched the MEDLINE, EMBASE, Water Resources Abstracts, and TOXNET databases through 2011 for eligible studies. We also searched the China National Knowledge Infrastructure (CNKI) database, because many studies on fluoride neurotoxicity have been published in Chinese journals only. In total, we identified 27 eligible epidemiological studies with high and reference exposures, end points of IQ scores, or related cognitive function measures with means and variances for the two exposure groups. Using random-effects models, we estimated the standardized mean difference between exposed and reference groups across all studies. We conducted sensitivity analyses restricted to studies using the same outcome assessment and having drinking-water fluoride as the only exposure. We performed the Cochran test for heterogeneity between studies, Begg’s funnel plot, and Egger test to assess publication bias, and conducted meta-regressions to explore sources of variation in mean differences among the studies.
Results: The standardized weighted mean difference in IQ score between exposed and reference populations was –0.45 (95% confidence interval: –0.56, –0.35) using a random-effects model. Thus, children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas. Subgroup and sensitivity analyses also indicated inverse associations, although the substantial heterogeneity did not appear to decrease.
Conclusions: The results support the possibility of an adverse effect of high fluoride exposure on children’s neurodevelopment. Future research should include detailed individual-level information on prenatal exposure, neurobehavioral performance, and covariates for adjustment.
Fluoride (F) is known to affect mineralizing tissues, but effects upon the developing brain have not been previously considered. This study in Sprague-Dawley rats compares behavior, body weight, plasma and brain F levels after sodium fluoride (NaF) exposures during late gestation, at weaning or in adults. For prenatal exposures, dams received injections (SC) of 0.13 mg/kg NaF or saline on gestational days 14–18 or 17–19. Weanlings received drinking water containing 0, 75, 100, or 125 ppm F for 6 or 20 weeks, and 3 month-old adults received water containing 100 ppm F for 6 weeks. Behavior was tested in a computer pattern recognition system that classified acts in a novel environment and quantified act initiations, total times and time structures. Fluoride exposures caused sex- and dose-specific behavioral deficits with a common pattern. Males were most sensitive to prenatal day 17–19 exposure, whereas females were more sensitive to weanling and adult exposures. After fluoride ingestion, the severity of the effect on behavior increased directly with plasma F levels and F concentrations in specific brain regions. Such association is important considering that plasma levels in this rat model (0.059 to 0.640 ppm F) are similar to those reported in humans exposed to high levels of Fluoride.
Organophosphorus (OP) nerve agents and pesticides inhibit acetylcholinesterase (AChE), and this is thought to be a primary mechanism mediating the neurotoxicity of these compounds. However, a number of observations suggest that mechanisms other than or in addition to AChE inhibition contribute to OP neurotoxicity. There is significant experimental evidence that acute OP intoxication elicits a robust inflammatory response, and emerging evidence suggests that chronic repeated low-level OP exposure also upregulates inflammatory mediators. A critical question that is just beginning to be addressed experimentally is the pathophysiologic relevance of inflammation in either acute or chronic OP intoxication. The goal of this article is to provide a brief review of the current status of our knowledge linking inflammation to OP intoxication, and to discuss the implications of these findings in the context of therapeutic and diagnostic approaches to OP neurotoxicity.
The highly toxic organophosphorus compound VX [O-ethyl S-[2-(diisopropylamino)ethyl]methylphosphonate] is an irreversible inhibitor of the enzyme acetylcholinesterase (AChE). Prolonged
inhibition of AChE increases endogenous levels of acetylcholine and is toxic at nerve synapses and neuromuscular junctions.
We hypothesized that repeated exposure to sublethal doses of VX would affect genes associated with cell survival, neuronal
plasticity, and neuronal remodeling, including brain-derived neurotrophic factor (BDNF). We examined the time course of BDNF
expression in C57BL/6 mouse brain following repeated exposure (1/day × 5 days/week × 2 weeks) to sublethal doses of VX (0.2
LD50 and 0.4 LD50). BDNF messenger RNA expression was significantly (p < 0.05) elevated in multiple brain regions, including the dentate gyrus, CA3, and CA1 regions of the hippocampal formation,
as well as the piriform cortex, hypothalamus, amygdala, and thalamus, 72 h after the last 0.4 LD50 VX exposure. BDNF protein expression, however, was only increased in the CA3 region of the hippocampus. Whether increased
BDNF in response to sublethal doses of VX exposure is an adaptive response to prevent cellular damage or a precursor to impending
brain damage remains to be determined. If elevated BDNF is an adaptive response, exogenous BDNF may be a potential therapeutic
target to reduce the toxic effects of nerve agent exposure.
Fluoride is known to cross the blood-brain barrier and alter the structure and function of neural tissue. There are few authoritative reports on neurodegenerative changes in hippocampus, neocortex, cerebellum, spinal cord and sciatic nerve in fluoride intoxication. We report the alterations in the structure of neuronal tissue after chronic administration of sodium fluoride (for 60days) to rats. Twelve male Wistar rats were divided equally into two groups: one group received 20 ppm of sodium fluoride (NaF) and the other group (which served as a control) received tap water for 60days. The body weights and organic somatic index of brain in the sodium fluoride treated animals were significantly reduced, relative to the control group. Tissue fluoride levels of hippocampus, neocortex, cerebellum, spinal cord and sciatic nerve, all increased significantly in fluoride treated rats. Electron microscopy of the hippocampus, neocortex, cerebellum, spinal cord and sciatic nerve showed neurodegenerative changes in the NaF treated group compared to controls. Axon deteri-oration, myelin sheath degeneration and dark cells with scanty cytop-lasm were observed in spinal cord and sciatic nerve in the treated group. Other distinctive morphological alterations observed were: vacuolated swollen mitochondria in neocortex, hippocampus and cerebel-lum; myelinated fibers with breaks in continuity (axon partly preserved and partly vacuolated) in hippocampus; myelin splitting and vacuolated schwann cell within the cerebellum and sciatic nerve respectively. Thus, neurodegeneration was clearly evident in the hippocampus, neocortex, cerebellum, spinal cord and sciatic nerve on fluoride exposure.
High-fluoride (100 and 200 ppm) water was administered to rats orally to study the fluoride-induced changes on the thyroid hormone status, the histopathology of discrete brain regions, the acetylcholine esterase activity, and the learning and memory abilities in multigeneration rats. Significant decrease in the serum-free thyroxine (FT4) and free triiodothyronine (FT3) levels and decrease in acetylcholine esterase activity in fluoride-treated group were observed. Presence of eosinophilic Purkinje cells, degenerating neurons, decreased granular cells, and vacuolations were noted in discrete brain regions of the fluoride-treated group. In the T-maze experiments, the fluoride-treated group showed poor acquisition and retention and higher latency when compared with the control. The alterations were more profound in the third generation when compared with the first- and second-generation fluoride-treated group. Changes in the thyroid hormone levels in the present study might have imbalanced the oxidant/antioxidant system, which further led to a reduction in learning memory ability. Hence, presence of generational or cumulative effects of fluoride on the development of the offspring when it is ingested continuously through multiple generations is evident from the present study.
The correlation between neurofibrillary tangles of tau and disease progression in the brains of Alzheimer's disease (AD) patients remains an area of contention. Innovative data are emerging from biochemical, cell-based and transgenic mouse studies that suggest that tau oligomers, a pre-filament form of tau, may be the most toxic and pathologically significant tau aggregate.
Here we report that oligomers of recombinant full-length human tau protein are neurotoxic in vivo after subcortical stereotaxic injection into mice. Tau oligomers impaired memory consolidation, whereas tau fibrils and monomers did not. Additionally, tau oligomers induced synaptic dysfunction by reducing the levels of synaptic vesicle-associated proteins synaptophysin and septin-11. Tau oligomers produced mitochondrial dysfunction by decreasing the levels of NADH-ubiquinone oxidoreductase (electron transport chain complex I), and activated caspase-9, which is related to the apoptotic mitochondrial pathway.
This study identifies tau oligomers as an acutely toxic tau species in vivo, and suggests that tau oligomers induce neurodegeneration by affecting mitochondrial and synaptic function, both of which are early hallmarks in AD and other tauopathies. These results open new avenues for neuroprotective intervention strategies of tauopathies by targeting tau oligomers.
Prenatal in utero conditions are thought to play a role in the development of adult diseases including Parkinson's disease (PD). Paraquat is
a common herbicide with chemical structure similar to 1-methyl-4-phenyl 1,2,3,6-tetrahydropyridine, a neurotoxin known to
induce parkinsonism. In order to assess the role of in utero paraquat exposure in PD, uptake in maternal and fetal brains were measured using positron emission tomography (PET)/computed
tomography (CT) imaging. Two anesthetized pregnant rhesus macaques in the late second trimester of pregnancy were given bolus
iv injections of 11C-paraquat, and whole-body PET/CT imaging was performed. Using maternal ventricular blood pool as the input function, the
unidirectional influx rate constants (Kis), a measure of the irreversible transport of paraquat from plasma to brain, were calculated for the maternal and fetal brains
using Patlak graphical analysis. Results indicate minimal uptake of paraquat by both maternal and fetal brains with average
Kis of 0.0009 and 0.0016 per minute, respectively. The highest regional cerebral uptake in the maternal brain (0.0009% injected
dose) was seen in the pineal gland, a structure known to lack a blood brain barrier. The finding of minimal paraquat uptake
in maternal and fetal brains is similar to previous findings in adult male macaques and extends the contention that a single
acute paraquat exposure, prenatally or postnatally, is unlikely to play a role in PD.
Methamphetamine (METH), an addictive psycho-stimulant drug with euphoric effect is known to cause neurotoxicity due to oxidative stress, dopamine accumulation and glial cell activation. Here we hypothesized that METH-induced interference of glucose uptake and transport at the endothelium can disrupt the energy requirement of the blood-brain barrier (BBB) function and integrity. We undertake this study because there is no report of METH effects on glucose uptake and transport across the blood-brain barrier (BBB) to date.
In this study, we demonstrate that METH-induced disruption of glucose uptake by endothelium lead to BBB dysfunction. Our data indicate that a low concentration of METH (20 μM) increased the expression of glucose transporter protein-1 (GLUT1) in primary human brain endothelial cell (hBEC, main component of BBB) without affecting the glucose uptake. A high concentration of 200 μM of METH decreased both the glucose uptake and GLUT1 protein levels in hBEC culture. Transcription process appeared to regulate the changes in METH-induced GLUT1 expression. METH-induced decrease in GLUT1 protein level was associated with reduction in BBB tight junction protein occludin and zonula occludens-1. Functional assessment of the trans-endothelial electrical resistance of the cell monolayers and permeability of dye tracers in animal model validated the pharmacokinetics and molecular findings that inhibition of glucose uptake by GLUT1 inhibitor cytochalasin B (CB) aggravated the METH-induced disruption of the BBB integrity. Application of acetyl-L-carnitine suppressed the effects of METH on glucose uptake and BBB function.
Our findings suggest that impairment of GLUT1 at the brain endothelium by METH may contribute to energy-associated disruption of tight junction assembly and loss of BBB integrity.
Alcohol consumption causes neurocognitive deficits, neuronal injury, and neurodegeneration. At the cellular level, alcohol abuse causes oxidative damage to mitochondria and cellular proteins and interlink with the progression of neuroinflammation and neurological disorders. We previously reported that alcohol inhibits glucose transport across the blood-brain barrier (BBB), leading to BBB dysfunction and neurodegeneration. In this study, we hypothesized that ethanol (EtOH)-mediated disruption in glucose uptake would deprive energy for human astrocytes and neurons inducing neurotoxicity and neuronal degeneration. EtOH may also have a direct effect on glucose uptake in neurons and astrocytes, which has not been previously described. Our results indicate that ethanol exposure decreases the uptake of D-(2-(3)H)-glucose by human astrocytes and neurons. Inhibition of glucose uptake correlates with a reduction in glucose transporter protein expression (GLUT1 in astrocytes and GLUT3 in neurons). Acetyl-L-carnitine (ALC), a neuroprotective agent, suppresses the effects of alcohol on glucose uptake and GLUT levels, thus reducing neurotoxicity and neuronal degeneration. These findings suggest that deprivation of glucose in brain cells contributes to neurotoxicity in alcohol abusers, and highlights ALC as a potential therapeutic agent to prevent the deleterious health conditions caused by alcohol abuse.
Fluoride (F) is a toxic and reactive element, and exposure to it passes almost unnoticed, with the consumption of tea, fish, meat, fruits, etcetera and articles of common use such as: toothpaste additives; dental gels, non-stick pans and razor blades as Teflon. It has also been used with the intention of reducing the dental cares.
Fluoride can accumulate in the body, and it has been shown that continuous exposure to it causes damaging effects on body tissues, particularly the nervous system directly without any previous physical malformations.
Several clinical and experimental studies have reported that the F induces changes in cerebral morphology and biochemistry that affect the neurological development of individuals as well as cognitive processes, such as learning and memory. F can be toxic by ingesting one part per million (ppm), and the effects they are not immediate, as they can take 20 years or more to become evident.
The prolonged ingestion of F may cause significant damage to health and particularly to the nervous system. Therefore, it is important to be aware of this serious problem and avoid the use of toothpaste and items that contain F, particularly in children as they are more susceptible to the toxic effects of F.
Huntington disease (HD) is caused by a polyglutamine expansion of more than 35 units in the huntingtin protein. This expanded repeat length inversely correlates with the age-at-onset (AAO), however, additional genetic factors apart from the expanded CAG repeat size are thought to influence the course and the AAO in HD. Until now, among others, the gene encoding PCG-1α (PPARGC1A) was shown to modify the AAO in two independent, however small, populations. PGC-1α is involved in the induction of various mechanisms regulating mitochondrial biogenesis and oxidative stress defence. Furthermore, several studies have linked impairment of its function and/or its expression to HD pathogenesis. As the identification of distinct modifiers in association studies is largely dependent on the size of the observed population, we investigated nine different single nucleotide polymorphisms (SNPs) in PPARGC1A in order to replicate the disease modifying effect in more than 800 European HD patients and to identify an association with AAO in HD.
Two SNPs, one in the promoter and one in the transcribed region of the gene, showed a significant effect on the AAO. While the minor allele of SNP rs7665116 (g.38570C), located in the transcribed gene region, was associated with a delay in disease onset, especially in HD patients with Italian ancestry, the minor allele of SNP rs2970870 (g.-1437C) in the promoter region leads to an earlier onset of HD in its homozygous state. Additionally, global testing of haplotype block 2, which covers the main part of the transcribed region of the gene, revealed an association between block 2 haplotypes and the disease onset.
Therefore, our results indicate opposing modifying influences of two SNPs within one gene on AAO and support the idea that PGC-1α dysfunction is involved in HD pathology.
We evaluated various forms of hippocampus-dependent learning and memory, and hippocampal synaptic plasticity in THY-Tau22 transgenic mice, a murine tauopathy model that expresses double-mutated 4-repeat human tau, and shows neuropathological tau hyperphosphorylation and aggregation throughout the brain. Focussing on hippocampus, immunohistochemical studies in aged THY-Tau22 mice revealed prominent hyper- and abnormal phosphorylation of tau in CA1 region, and an increase in glial fibrillary acidic protein (GFAP) in hippocampus, but without signs of neuronal loss. These mice displayed spatial, social, and contextual learning and memory defects that could not be reduced to subtle neuromotor disability. The behavioral defects coincided with changes in hippocampal synaptic functioning and plasticity as measured in paired-pulse and novel long-term depression protocols. These results indicate that hippocampal tauopathy without neuronal cell loss can impair neural and behavioral plasticity, and further show that transgenic mice, such as the THY-Tau22 strain, might be useful for preclinical research on tauopathy pathogenesis and possible treatment.
Lower brain glucose metabolism is present before the onset of clinically measurable cognitive decline in two groups of people at risk of Alzheimer's disease--carriers of apolipoprotein E4, and in those with a maternal family history of AD. Supported by emerging evidence from in vitro and animal studies, these reports suggest that brain hypometabolism may precede and therefore contribute to the neuropathologic cascade leading to cognitive decline in AD. The reason brain hypometabolism develops is unclear but may include defects in brain glucose transport, disrupted glycolysis, and/or impaired mitochondrial function. Methodologic issues presently preclude knowing with certainty whether or not aging in the absence of cognitive impairment is necessarily associated with lower brain glucose metabolism. Nevertheless, aging appears to increase the risk of deteriorating systemic control of glucose utilization, which, in turn, may increase the risk of declining brain glucose uptake, at least in some brain regions. A contributing role of deteriorating glucose availability to or metabolism by the brain in AD does not exclude the opposite effect, i.e., that neurodegenerative processes in AD further decrease brain glucose metabolism because of reduced synaptic functionality and hence reduced energy needs, thereby completing a vicious cycle. Strategies to reduce the risk of AD by breaking this cycle should aim to (1) improve insulin sensitivity by improving systemic glucose utilization, or (2) bypass deteriorating brain glucose metabolism using approaches that safely induce mild, sustainable ketonemia.
The brain relies upon glucose as its primary fuel. In recent years, a rich literature has developed from both human and animal studies indicating that increases in circulating blood glucose can facilitate cognitive functioning. This phenomenon has been termed the 'glucose memory facilitation effect'. The purpose of this review is to discuss a number of salient studies which have investigated the influence of glucose ingestion on neurocognitive performance in individuals with (a) compromised neurocognitive capacity, as well as (b) normally functioning individuals (with a focus on research conducted with human participants). The proposed neurocognitive mechanisms purported to underlie the modulatory effect of glucose on neurocognitive performance will also be considered. Many theories have focussed upon the hippocampus, given that this brain region is heavily implicated in learning and memory. Further, it will be suggested that glucose is a possible mechanism underlying the phenomenon that enhanced memory performance is typically observed for emotionally laden stimuli.
Prenatal ethanol exposure produces severe changes in brain, liver, and kidney through mechanisms involving growth factors. These molecules regulate survival, differentiation, maintenance, and connectivity of brain, liver, and kidney cells. Despite the abundant available data on the short and mid-lasting effects of ethanol intoxication, only few data show the long-lasting damage induced by early ethanol administration. The aim of this study was to investigate changes in nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), hepatocyte growth factor (HGF), and vascular endothelial growth factor (VEGF) in brain areas, liver, and kidney of 18-mo-old male mice exposed perinatally to ethanol at 11% vol or to red wine at the same ethanol concentration. The authors found that ethanol per se elevated NGF, BDNF, HGF, and VEGF measured by ELISA in brain limbic system areas. In the liver, early exposure to ethanol solution and red wine depleted BDNF and VEGF concentrations. In the kidney, red wine exposure only decreased VEGF. In conclusion, the present study shows that, in aged mice, early administration of ethanol solution induced long-lasting damage at growth factor levels in frontal cortex, hippocampus, and liver but not in kidney. Otherwise, in mice exposed to red wine, significant changes were observed in the liver and kidney but not in the hippocampus and frontal cortex. The brain differences in ethanol-induced toxicity when ethanol is administered alone or in red wine may be related to compounds with antioxidant properties present in the red wine.
BDNF has pleiotropic effects on neuronal development and synaptic plasticity that underlie circuit formation and cognitive function. Recent breakthroughs reveal that neuronal activity regulates BDNF cell biology, including Bdnf transcription, dendritic targeting and trafficking of BDNF mRNA and protein, and secretion and extracellular conversion of proBDNF to mature BDNF. Defects in these mechanisms contribute differentially to cognitive dysfunction and anxiety-like behaviors. Here we review recent studies, presented at a symposium at Neuroscience 2009, that describe regulatory mechanisms that permit rapid and dynamic refinement of BDNF actions in neurons.
Fluorosis is a serious public health problem in many parts of the world. As in the case of many chronic degenerative diseases, increased production of reactive oxygen species has been considered to play an important role, even in the pathogenesis of chronic fluoride toxicity. Black berry is closely linked to its protective properties against free radical attack. Therefore, the aim of this study was to demonstrate the role of black berry juice (BBJ) in decreasing the hepatotoxicity and oxidative stress of sodium fluoride (NaF). Results showed that NaF caused elevation in liver TBARS and nitric oxide (NO), and reduction in superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (TAC) and glutathione (GSH). Plasma transaminases (AST and ALT), creatine kinase (CK), lactate dehydrogenase (LDH), total lipids (TL), cholesterol, triglycerides (TG), and low density lipoprotein-cholesterol (LDL-c) were increased, while high density lipoprotein-cholesterol (HDL-c) was decreased. On the other hand, BBJ reduced NaF-induced TBARS, NO, TL, cholesterol, TG, LDL-c, AST, ALT, CK and LD. Moreover, it ameliorated NaF-induced decrease in SOD, CAT, GSH, TAC and HDL-c. Therefore, the present results revealed that BBJ has a protective effect against NaF-induced hepatotoxicity by antagonizing the free radicals generation and enhancement of the antioxidant defence mechanisms.
Exposure to excessive amounts of fluoride (F(-)) causes dental fluorosis in susceptible individuals; however, the mechanism of F(-)-induced toxicity is unclear. Previously, we have shown that high-dose F(-) activates the unfolded protein response (UPR) in ameloblasts that are responsible for dental enamel formation. The UPR is a signaling pathway responsible for either alleviating endoplasmic reticulum (ER) stress or for inducing apoptosis of the stressed cells.
In this study we determined if low-dose F(-) causes ER stress and activates the UPR, and we also determined whether F(-) interferes with the secretion of proteins from the ER.
We stably transfected the ameloblast-derived LS8 cell line with secreted alkaline phosphatase (SEAP) and determined activity and localization of SEAP and F(-)-mediated induction of UPR proteins. Also, incisors from mice given drinking water containing various concentrations of F(-) were examined for eucaryotic initiation factor-2, subunit alpha (eIF2alpha) phosphorylation.
We found that F(-) decreases the extracellular secretion of SEAP in a linear, dose-dependent manner. We also found a corresponding increase in the intracellular accumulation of SEAP after exposure to F(-). These changes are associated with the induction of UPR proteins such as the molecular chaperone BiP and phosphorylation of the UPR sensor PKR-like ER kinase, and its substrate, eIF2alpha. Importantly, F(-)-induced phosphorylation of eIF2alphawas confirmed in vivo.
These data suggest that F(-) initiates an ER stress response in ameloblasts that interferes with protein synthesis and secretion. Consequently, ameloblast function during enamel development may be impaired, and this may culminate in dental fluorosis.
Sodium fluoride (NaF; Cas No. 7681-49-4) is used in fluoridating municipal water supplies, resulting in chronic exposure of millions of people worldwide. Because of a lack of pertinent developmental toxicity studies in the literature, sodium fluoride was administered ad libitum in deionized/filtered drinking water (to mimic human exposure) to Sprague-Dawley-derived rats (26/group) on Gestation Days (GD) 6 through 15 at levels of 0, 50, 150, or 300 ppm and New Zealand White rabbits (26/group) on GD 6 through 19 at levels of 0, 100, 200, or 400 ppm. Higher concentrations via drinking water were not practicable due to the poor palatability of sodium fluoride. Drinking water (vehicle) contained less than 0.6 ppm sodium fluoride (limit of detection) and sodium fluoride content of the feed was 12.4 ppm fluoride (rats) and 15.6 ppm fluoride (rabbits). Maternal food, water, body weights, and clinical signs were recorded at regular intervals throughout these studies. Animals were killed on GD 20 (rats) or 30 (rabbits) and examined for implant status, fetal weight, sex, and morphological development. In the high-dose group of both studies there was an initial decreased maternal body weight gain which recovered over time and a decreased water consumption--attributed to decreased palatability. No clear clinical signs of toxicity were observed. Maternal exposure to sodium fluoride during organogenesis did not significantly affect the frequency of postimplantation loss, mean fetal body weight/litter, or external, visceral or skeletal malformations in either the rat or the rabbit. The NOAEL for maternal toxicity was 150 ppm sodium fluoride in drinking water (approximately 18 mg/kg/day) for rats, and 200 ppm (approximately 18/mg/kg/day rabbits. The NOAEL for developmental toxicity was > or = 300 ppm sodium fluoride (approximately 27 mg/kg/day) for rats and > or = 400 ppm (approximately 29 mg/kg/day) for rabbits administered during organogenesis in drinking water. The total exposure to fluoride (mg F/kg body weight/day from food and drinking water combined) in the mid- and high-dose groups for both species was > 100-fold higher than the range at 0.014-0.08 mg F/kg/day estimated for a 70-kg person from food and fluoridated (1 ppm) drinking water.
Recent evidence indicates that fluoride produces neuronal destruction and synaptic injury by a mechanism that involves free radical production and lipid peroxidation. For a number of pathological disorders of the central nervous system (CNS), excitotoxicity plays a critical role. Various studies have shown that many of the neurotoxic metals, such as mercury, lead, aluminum, and iron also injure neural elements in the CNS by an excitotoxic mechanism. Free radical generation and lipid peroxidation, especially in the face of hypomagnesemia and low neuronal energy production, also magnify excitotoxic sensitivity of neurons and their elements. This paper reviews briefly some of the studies that point to a common mechanism for the CNS neurotoxic effects of fluoride and calls for research directed toward further elucidation of this mechanism.
Following experimental and clinical traumatic brain injury (TBI), the local cerebral metabolic rate of glucose (1CMR(G1c)) is commonly estimated using the 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG) method. The adequate estimation of 1CMR(G1c) using FDG requires a correction factor, the lumped constant (LC), to convert FDG net uptake into 1CMR(G1c). The LC, and thus 1CMR(G1c) calculations, require a steady-state that may be disrupted following TBI. In the present report, we hypothesized that [1-(14)C] glucose uptake would accurately reflect glucose dynamics early post-injury, and was compared to the regional uptake of FDG in 44 rats subjected to moderate (2.4-2.6 atm) lateral fluid percussion brain injury (FPI) or sham injury. Cortical energy state and adenylate (ATP, ADP, and AMP) levels were also measured. Early (7-42 min) after FPI, FDG uptake was increased in the ipsilateral cortex and hippocampus (p< 0.05). In contrast, no change in [1-(14)C] glucose uptake (7 and 17 min post-injury) or cortical adenylate content (42 min post-injury) was observed. At 12 h following FPI, the ipsilateral FDG and [1-(14)C] glucose uptake were decreased in the cortex and hippocampus, and the ipsilateral cortical ATP concentration was decreased in comparison to sham-injured controls (p< 0.05). Under the present experimental conditions, the rate of cerebral uptake of FDG and of [1-(14)C] glucose differed, and indicated that following TBI, regional changes in the LC may occur in the immediate, but not in the late, post-injury phase. These results should be considered when interpreting results obtained using FDG for the estimation of 1CMR(G1c) early following experimental TBI.
: To assess brain cell apoptosis induced by high fluoride and/or low iodine in their offspring, 32 one-month old Wistar albino rats were divided randomly into four equal groups, each with six females and two males. The first group of rats served as the untreated controls; the second group received high fluoride (HiF) in their drinking water (100 mg NaF/L); the third group was placed on a low iodine (LI) diet (0.0855 mg I/kg); and the fourth group was exposed to the same concentrations of HiF and LI together. After the animal model was established, the rats were allowed to breed, and 36 offspring rats in each group were randomly selected for the experiments. The treatment for these second generation rats was the same as for their parents. At 0, 10, 30, 60, and 90 days after birth, these offspring rats were anesthetized and their brain cells prepared for flow cytometry. In comparison with the controls, the percent of brain cell apoptosis in the offspring rats in the three treated groups was obviously higher, especially in the HiF+LI group. With aging, brain cell apoptosis increased gradually in every group before the 30-day mark. These results indicate that cell apoptosis may play an important role in brain function affected by exposure to HiF, LI, and HiF+LI.
Caffeic acid phenethyl ester (CAPE) is a component of honey bee propolis that can induce expression of haem oxygenase-1 (HO-1). Because HO-1 induction has been suggested to protect dopaminergic neurons in the substantia nigra, we examined the effect of CAPE in experimental models of dopaminergic neurodegeneration.
Neuroprotective effect of CAPE was investigated in rat organotypic midbrain slice cultures and in vivo, using a mouse model of dopaminergic neurodegeneration induced by intranigral injection of LPS and intrastriatal injection of 6-hydroxydopamine.
CAPE protected dopaminergic neurons in slice cultures from IFN-γ/LPS-induced injury. The effect of CAPE was inhibited by zinc protoporphyrin IX, an HO-1 inhibitor, and by neutralizing antibody against brain-derived neurotrophic factor (BDNF). A p38 MAPK inhibitor SB203580 prevented activation of NF-E2-related factor 2, attenuated increased expression of HO-1 and BDNF, and blocked the neuroprotective actions of CAPE. In the LPS-injected mouse model, daily intraperitoneal administration of CAPE protected dopaminergic neurons, up-regulated HO-1 and BDNF, and reduced the increase of activated microglia/macrophages. Neuroprotective effects of CAPE against LPS-induced injury was prevented by zinc protoporphyrin IX or anti-BDNF antibody. CAPE protected dopaminergic neurons and alleviated methamphetamine-induced rotational behaviour also in 6-hydroxydopamine hemiparkinsonian mice.
CAPE is a novel type of neuroprotective agent whose actions are mediated by both HO-1 and BDNF. These findings may provide novel clues to develop neuroprotective agents for treatment of neurodegenerative disorders.
Lead is an important heavy metal pollutant in the environment, and it induces neurodevelopmental toxicity, which is characterized by histological, ultrastructural, and neurochemical changes in the central nervous system. The aim of this study was to evaluate the effects of prenatal acute lead exposure on apoptosis, GFAP expression, and lead deposition in the developing spinal cord. Chick embryos were exposed to 150μg or 450μg doses of lead acetate via yolk sac at E3 or E5 embryonic ages and incubated for six days. Lead deposition was observed in the ependymal cells, developing dorsal, and ventral horns, and in the white matter of all the exposed embryos. TUNEL-positive cells were found in all layers of the spinal cord of the control and treated embryos, and lead exposure resulted in a significant increase in the numerical density of the apoptotic cells. Control embryos showed intense GFAP expression in the ependymal cells of the roof and floor plates, and in the gray and white matters; whereas exposure to lead reduced GFAP reactivity. In ovo lead exposure induces apoptosis, and reduces GFAP expression in the nervous system of the chick embryos, which may cause impairments during neuronal development and consequences in childhood and adulthood.
Fluoride (F) and lead (Pb) are two common environmental pollutants which are linked to the lowered intelligence, especially for children. Glutamate, a major excitatory neurotransmitter in the central nervous system, plays an important role in the process of learning and memory. However, the impact of F and Pb alone or in combination on glutamate metabolism in brain is little known. The present study was conducted to assess the glutamate level and the activities of glutamate metabolism related enzymes including asparate aminotransferase (AST), alanine aminotransferase (ALT) and glutamic acid decarboxylase (GAD) in the hippocampus, as well as learning abilities of offspring rat pups at postnatal week 6, 8, 10 and 12 exposed to F and/or Pb. During lactation, the pups ingested F and/or Pb via the maternal milk, whose mothers were exposed to sodium fluoride (150 mg/L in drinking water) and/or lead acetate (300 mg/L in drinking water) from the day of delivery. After weaning at postnatal day 21, the pups were exposed to the same treatments as their mother. Results showed that the learning abilities and hippocampus glutamate levels were significantly decreased by F and Pb individually and the combined interaction of F and Pb. The activities of AST and ALT in treatment groups were significantly inhibited, while the activities of GAD were increased, especially in rats exposed to both F and Pb together. These findings suggested that alteration of hippocampus glutamate by F and/or Pb may in part reduce learning ability in rats.
High fluoride intake may affect biological systems by increasing free radicals, which may enhance lipid peroxidation levels of the tissues, thus leading to oxidative damage. Caffeic acid phenethyl ester (CAPE), a component of honeybee propolis, protects tissues from reactive oxygen species mediated oxidative stress in ischemia-reperfusion and toxic injuries. Several studies suggest that supplementation with anti-oxidant can influence fluoride induced tissue damage. The aims of this study was to investigate the possible role of malondialdehyde (MDA) levels and activity of superoxide dismutase (SOD) and catalase (CAT), in the pathogenesis of fluoride-induced endometrial damage and to demonstrate the effect of CAPE, the potent antioxidant, in decreasing the toxicity. Twenty-four adult female rats were randomly divided into three experimental groups, as follows: control group, fluoride-treated group (F), and fluoride plus CAPE-treated group (F+CAPE). Fluoride was given orally as 30mg/L NaF solution in spring water daily for 45 days. CAPE was co-administered intraperitoneally (i.p.) with a dose of 10μM/(kgday) for 46 days. Extensive formation of DNA strand breaks, the typical biochemical feature of apoptosis, was detected with the use of the terminal deoxynucleotidyl transferase (TdT)-mediated d UTP-biotin nick and labeling (TUNEL) method. The activities of antioxidant enzymes such as SOD and CAT as well as the concentration of MDA, as an indicator of lipid peroxidation, were measured to evaluate oxidative stress in homogenates of the endometrium. Fluoride administration increased MDA levels (p<0.05), decreased SOD (p<0.05) and CAT (p<0.05) activities. CAPE co-administration with fluoride treatments caused significantly decreased MDA levels (p<0.05), increased SOD (p<0.05) and CAT (p<0.05) activities in endometrial tissue when compared with F alone. Diffuse apoptosis in glandular epithelium and stromal cells was found by TUNEL method in endometrial tissues of rats treated with fluoride. The severity of these lesions was reduced by administration of CAPE. In conclusion, our study demonstrated that MDA may play an important role in the pathogenesis of fluoride-induced oxidative endometrial damage. CAPE may have protective aspects in this process by its antioxidant and anti-inflammatory effect.
Dual medical imaging modalities, such as PET-CT, are now a routine component of clinical practice. Medical image segmentation methods, however, have generally only been applied to single modality images. In this paper, we propose the dual-modality image segmentation model to segment brain PET-CT images into gray matter, white matter and cerebrospinal fluid. This model converts PET-CT image segmentation into an optimization process controlled simultaneously by PET and CT voxel values and spatial constraints. It is innovative in the creation and application of the modality discriminatory power (MDP) coefficient as a weighting scheme to adaptively combine the functional (PET) and anatomical (CT) information on a voxel-by-voxel basis. Our approach relies upon allowing the modality with higher discriminatory power to play a more important role in the segmentation process. We compared the proposed approach to three other image segmentation strategies, including PET-only based segmentation, combination of the results of independent PET image segmentation and CT image segmentation, and simultaneous segmentation of joint PET and CT images without an adaptive weighting scheme. Our results in 21 clinical studies showed that our approach provides the most accurate and reliable segmentation for brain PET-CT images.
Oxidative stress plays a key role in pathophysiology of many neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and so on. Although Matricaria recutita L. (Asteraceae), German chamomile, is traditionally used for central nervous system (CNS)-related diseases, its antistress properties have received little attention.
The present study evaluated the neuroprotective effect of German chamomile against aluminium fluoride (AlF₄⁻)-induced oxidative stress in rats.
The Sprague-Dawley rats of either sex (200-250 g) were selected and grouped as: group I received normal saline; group II received AlF₄⁻ (negative control); groups III, IV, and V received 100, 200, and 300 mg/kg, orally, German chamomile methanol extract (GCME) along with AlF₄⁻; and group VI received quercetin (25 mg/kg, i.p.) + AlF₄⁻, respectively. After 10 days treatment with GCME, oxidative stress was induced by administering AlF₄⁻ through drinking water for 7 days. Then, the protective antioxidant enzyme levels were measured and the histopathological studies were carried out.
The GCME showed dose-dependent neuroprotective activity by significant decrease in lipid peroxidation (LPO) and increase in the superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and total thiol levels in extract-treated animals as compared with negative control group (P < 0.001). The histopathological studies also revealed the potent neuroprotective action of German chamomile against oxidative brain damage.
The present study for the first time shows potent neuroprotective activity of the methanol extract of German chamomile against AlF₄⁻-induced oxidative stress in rats.
Recognition and spatial memory are typically associated with the perirhinal cortex and hippocampal formation, respectively. Solely focusing on these structures for these specific mnemonic functions may, however, be limiting progress in the field. The distinction between these subdivisions of memory is becoming less defined as, for example, hippocampal cells traditionally considered to encode locations also encode place-object associations. There is increasing evidence for the involvement of overlapping networks of brain structures for aspects of both spatial and recognition memory. Future models of spatial and recognition memory will have to extend beyond the hippocampus and perirhinal cortex to incorporate a wider network of cortical and subcortical structures.
Glial fibrillary acidic protein (GFAP) is the main intermediate filament protein in mature astrocytes, but also an important component of the cytoskeleton in astrocytes during development. Major recent developments in astrocyte biology and the discovery of novel intermediate filament functions enticed the interest in the function of GFAP. The discovery of various GFAP splice variants gave an additional boost to explore this protein in more detail. The structural role of GFAP in astrocytes has been widely accepted for a long time, but over the years, GFAP has been shown to be involved in astrocyte functions, which are important during regeneration, synaptic plasticity and reactive gliosis. Moreover, different subpopulations of astrocytes have been identified, which are likely to have distinctive tasks in brain physiology and pathology, and which are not only classified by their spatial and temporal appearance, but also by their specific expression of intermediate filaments, including distinct GFAP isoforms. The presence of these isoforms enhances the complexity of the astrocyte cytoskeleton and is likely to underlie subtype specific functions. In this review we discuss the versatility of the GFAP cytoskeletal network from gene to function with a focus on astrocytes during human brain development, aging and disease.
Neurotoxicity of individual metals is well investigated but that of metal mixture (MM), an environmental reality, in the developing brain is relatively obscure. We investigated the combinatorial effect of arsenic (As), cadmium (Cd), and lead (Pb) on rat brain development, spanning in utero to postnatal development. MM was administered by gavage to pregnant and lactating rats, and to postweaning pups till 2 months. The pups exhibited behavioral disturbances characterized by hyperlocomotion, increased grip strength, and learning-memory deficit. Disruption of the blood-brain barrier (BBB) was associated with dose-dependent increase in deposition of the metals in developing brain. Astrocytes were affected by MM treatment as evident from their reduced density, area, perimeter, compactness, and number of processes, and increased apoptosis in cerebral cortex and cerebellum. The metals induced synergistic reduction in glial fibrillary acidic protein (GFAP) expression during brain development; however, postweaning withdrawal of MM partially restored the levels of GFAP in adults. To characterize the toxic mechanism, we treated rat primary astrocytes with MM at concentrations ranging from lethal concentration (LC)(10) to LC(75) of the metals. We observed synergistic downregulation in viability and increase in apoptosis of the astrocytes, which were induced by proximal activation of extra cellular signal-regulated kinase (ERK) signaling and downstream activation of Jun N-terminal kinase (JNK) pathway. Furthermore, rise in intracellular calcium ion ([Ca(2+)](i)) and reactive oxygen species generation promoted apoptosis in the astrocytes. Taken together, these observations are the first to show that mixture of As, Cd, and Pb has the capacity to induce synergistic toxicity in astrocytes that may compromise the BBB and may cause behavioral dysfunction in developing rats.
Diabetes may increase the risk of Alzheimer's disease (AD). However, a preventive strategy to combat cognitive decline in diabetic elderly with preexisting AD has remained unknown. The aim of this study was to determine the effects of metabolic perturbation on amyloid-β (Aβ) neurotoxicity and the optimal glucose range for improved neuronal survival, which is referred to as the "glucose window". Organotypic hippocampal slice cultures were incubated in either normoglycemic or hyperglycemic medium for 48 h, and subsequently treated in experimental media containing 0-30 mM glucose, with and without Aβ(25-35). Neuronal survival was evaluated by the propidium iodide method. Aβ neurotoxicity was exacerbated during hypoglycemia/hyperglycemia (≦2 mM/≧30 mM) without Aβ and ≦3 mM/≧20 mM with Aβ. ROS elevated in the respective glucose ranges and supplementation of ROS scavengers effectively improved neuronal survival. Interestingly, a sharp and sudden drop in glucose levels from preceding hyperglycemia further increased Aβ neurotoxicity. Supplementation of pyruvate protected exacerbated Aβ neurotoxicity. These results indicate that increased oxidative stress during severe hypoglycemia, hyperglycemia and fluctuation of blood glucose enhances neuronal cell death, resulting in the extremely limited glucose window, and therefore suggest that careful management of glucose avoiding hypoglycemia is needed to prevent brain degeneration in diabetic patients with AD.
The purpose of the investigation is to reveal the mechanism of the decreased ability of learning and memory induced by coal burning fluorosis. Ten offspring SD rats aged 30days, who were born from the mothers with chronic coal burning fluorosis, and ten offspring with same age from the normal mothers as controls were selected. Spatial learning and memory of the rats were evaluated by Morris Water Maze test. Cholinesterase activity was detected by photometric method. The expressions of nicotinic acetylcholine receptors (nAChRs) at protein and mRNA levels were detected by Western blotting and Real-time PCR, respectively. The results showed that in the rat offspring exposed to higher fluoride as compared to controls, the learning and memory ability declined; the cholinesterase activities in the brains were inhibited; the protein levels of alpha3, alpha4 and alpha7 nAChR subunits were decreased which showed certain significant correlations with the declined learning and memory ability; and the mRNA levels of alpha3 and alpha4 nAChRs were decreased, whereas the alpha7 mRNA increased. The data indicated that coal burning fluorosis can induce the decreased ability of learning and memory of rat offspring, in which the mechanism might be connected to the changed nAChRs and cholinesterase.
Epidemiological investigations reveal that high fluoride and low iodine have strong adverse effects on the intelligence quotient (IQ) of children. Studies also report that in some high fluoride areas, iodine deficiency also exists, especially in China. Here, with the proteomic techniques, we first report on the proteomic changes in brain proteins in offspring rats at postnatal day 20 exposed to high fluoride and/or low iodine. To investigate molecular mechanisms of central neural system injury induced by the above two elements, proteins were isolated and profiled by two-dimensional gel electrophoresis (2DE). By the analysis of Image-Master 2D Elite software, 71 protein spots in 2DE gels of treatment groups were gained and up- or down-regulated by two folds, and 5 proteins were regulated by five folds, with the comparison to the control group. The proteins changed by five folds were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The identified proteins are mainly related with cellular signaling, energy metabolism, and protein metabolism and provide a valuable clue to explore the mechanism underlining the neurotoxicity of high fluoride and low iodine. Moreover, these results could provide potential biomarkers for hazards caused by excessive fluoride and low iodine.
The study investigated the neurotoxicity of drinking water fluorosis in rat hippocampus. Just weaning male Sprague-Dawley (SD) rats were given 15, 30, 60 mg/L NaF solution and tap water for 9 months. The calcium ion concentration ([Ca(2+)]) in synaptosomes was measured by double wavelength fluorescence spectrophotometer and the expression level of nuclear transcription factor kappa-B ρ65 (NF-κB ρ65) in hippocampal CA3 region was measured by immunohistochemistry. The results showed that [Ca(2+)] significantly increased (F = 33.218, P < 0.01) in moderate fluoride group compared with the control group, and the expression level of NF-κB ρ65 in CA3 region presented an increasing trend as fluoride concentration increased. These results indicate that increase of synaptosomes [Ca(2+)] and NF-κB ρ65 expression level may be the molecular basis of central nervous system damage caused by chronic fluoride intoxication. NF-κB ρ65 in CA3 region is probably a target molecule for fluorosis.
The protein family of facilitative glucose transporters comprises 14 isoforms that share common structural features such as 12 transmembrane domains, N- and C-termini facing the cytoplasm of the cell, and a N-glycosylation side either within the first or fifth extracellular loop. Based on their sequence homology, three classes can be distinguished: class I includes GLUT1-4 and GLUT14, class II the "odd transporters" GLUT5, 7, 9, 11, and class III the "even transporters" GLUT6, 8, 10, 12 and the proton driven myoinositol transporter HMIT (or GLUT13). With the cloning and characterization of the more recent class II and III isoforms, it became apparent that despite their structural similarities, the different isoforms not only show a distinct tissue-specific expression pattern but also show distinct characteristics such as alternative splicing, specific (sub)cellular localization, and affinities for a spectrum of substrates. This review summarizes the current understanding of the physiological role for the various transport facilitators based on human genetically inherited disorders or single-nucleotide polymorphisms and knockout mice models. The emphasis of the review will be on the potential functional role of the more recent isoforms.
[(18)F]Fluorodeoxyglucose positron emission tomography ([(18)F]FDG-PET) is a valuable method for detecting focal brain dysfunction associated with epilepsy. Evidence suggests that a progressive decrease in [(18)F]FDG uptake occurs in the epileptogenic cortex with an increase in the duration of epilepsy. In this study, our aim was to use statistical parametric mapping (SPM) to test the validity of this relationship in a retrospective study of patients with temporal lobe epilepsy (TLE).
[(18)F]FDG-PET scans of 46 adult patients with pharmacoresistant unilateral TLE (25 RTLE and 21 LTLE) were subjected to SPM analysis.
Forty-six patients were diagnosed with nonlesional TLE, 16 of whom had hippocampal sclerosis (HS). The average duration of epilepsy was 17.4 +/- 12.3 years (3-46 years), <5 years in 10 patients and >or=10 years in 30 patients. Visual analysis of [(18)F]FDG-PET scans revealed hypometabolism in the epileptogenic temporal cortex in 31 (67%) patients. After SPM analysis of all [(18)F]FDG-PET images, hypometabolism was unilateral and reported in lateral and mesial structures of the epileptogenic temporal cortex in addition to the ipsilateral fusiform and middle occipital gyrus. Subsequent analysis revealed that temporal lobe hypometabolism was present only in patients with longer epilepsy duration (>or=10 years) in parahippocampal gyrus, uncus, and middle and superior temporal gyrus (P < 0.05 corrected). Epilepsy duration was inversely correlated with decreased glucose uptake in the inferior temporal gyrus, hippocampus, and parahippocampal gyrus of the epileptogenic temporal cortex (P < 0.05). Age at seizure onset did not affect the correlation between epilepsy duration and glucose uptake except in the inferior temporal gyrus (P < 0.05).
Voxel-based mapping supports the assertion that glucose hypometabolism of the epileptogenic temporal lobe cortex and other neighboring cortical regions increases with longer epilepsy duration in TLE.
In this study we investigated regional cerebral glucose metabolism abnormalities of [(18)F] fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging in traumatic brain injury (TBI). PET images of 81 TBI patients and 68 normal controls were acquired and a word list learning task was administered during the uptake period. The TBI group included 35 patients with positive structural imaging (CT or MRI) findings soon after injury, 40 patients with negative findings, and 6 cases without structural imaging. Statistical parametric mapping (SPM) analysis was applied with several levels of spatial smoothing. Cluster counting analysis was performed for each subject to identify abnormal clusters with contiguous voxel values that deviated by two standard deviations or more from the mean of the normal controls, and to count the number of clusters in 10 size categories. SPM maps demonstrated that the 81 patients had significantly lower FDG uptake than normal controls, widely across the cortex (including bilateral frontal and temporal regions), and in the thalamus. Cluster counting results indicated that TBI patients had a higher proportion of larger clusters than controls. These large low-FDG-uptake clusters of the TBI patients were closer to the brain edge than those of controls. These results suggest that deficits of cerebral metabolism in TBI are spread over multiple brain areas, that they are closer to the cortical surface than clusters in controls, and that group spatial patterns of abnormal cerebral metabolism may be similar in TBI patients with cognitive deficits with and without obvious acute abnormalities identified on structural imaging.
Monosaccharides enter cells by slow translipid bilayer diffusion by rapid, protein-mediated, cation-dependent cotransport and by rapid, protein-mediated equilibrative transport. This review addresses protein-mediated, equilibrative glucose transport catalyzed by GLUT1, the first equilibrative glucose transporter to be identified, purified, and cloned. GLUT1 is a polytopic, membrane-spanning protein that is one of 13 members of the human equilibrative glucose transport protein family. We review GLUT1 catalytic and ligand-binding properties and interpret these behaviors in the context of several putative mechanisms for protein-mediated transport. We conclude that no single model satisfactorily explains GLUT1 behavior. We then review GLUT1 topology, subunit architecture, and oligomeric structure and examine a new model for sugar transport that combines structural and kinetic analyses to satisfactorily reproduce GLUT1 behavior in human erythrocytes. We next review GLUT1 cell biology and the transcriptional and posttranscriptional regulation of GLUT1 expression in the context of development and in response to glucose perturbations and hypoxia in blood-tissue barriers. Emphasis is placed on transgenic GLUT1 overexpression and null mutant model systems, the latter serving as surrogates for the human GLUT1 deficiency syndrome. Finally, we review the role of GLUT1 in the absence or deficiency of a related isoform, GLUT3, toward establishing the physiological significance of coordination between these two isoforms.
Following experimental and clinical traumatic brain injury (TBI), the local cerebral metabolic rate of glucose (lCMR(Glc)) is commonly estimated using the 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG) method. The adequate estimation of lCMR(Glc) using FDG requires a correction factor, the lumped constant (LC), to convert FDG net uptake into lCMR(Glc). The LC, and thus lCMR(Glc) calculations, require a steady-state that may be disrupted following TBI. In the present report, we hypothesized that [1-(14)C]glucose uptake would accurately reflect glucose dynamics early post-injury, and was compared to the regional uptake of FDG in 44 rats subjected to moderate (2.4-2.6 atm) lateral fluid percussion brain injury (FPI) or sham injury. Cortical energy state and adenylate (ATP, ADP, and AMP) levels were also measured. Early (7-42 min) after FPI, FDG uptake was increased in the ipsilateral cortex and hippocampus (p < 0.05). In contrast, no change in [1-(14)C]glucose uptake (7 and 17 min post-injury) or cortical adenylate content (42 min post-injury) was observed. At 12 h following FPI, the ipsilateral FDG and [1-(14)C]glucose uptake were decreased in the cortex and hippocampus, and the ipsilateral cortical ATP concentration was decreased in comparison to sham-injured controls (p < 0.05). Under the present experimental conditions, the rate of cerebral uptake of FDG and of [1-(14)C]glucose differed, and indicated that following TBI, regional changes in the LC may occur in the immediate, but not in the late, post-injury phase. These results should be considered when interpreting results obtained using FDG for the estimation of lCMR(Glc) early following experimental TBI.
Developments of an open-field water-maze procedure in which rats learn to escape from opaque water onto a hidden platform are described. These include a procedure (A) for automatically tracking the spatial location of a hooded rat without the use of attached light-emitting diodes; (B) for studying different aspects of spatial memory (e.g. working memory); and (C) for studying non-spatial discrimination learning. The speed with which rats learn these tasks suggests that they may lend themselves to a variety of behavioural investigations, including pharmacological work and studies of cerebral function.
The developing nervous system is preferentially vulnerable to lead exposure with alterations in neuronal and glial cells of the brain. The present study examined early lead-induced alterations in the developing astrocyte population by examination of the developmentally regulated astrocyte specific protein, glial fibrillary acidic protein (GFAP). A developmental profile (Postnatal Day (PND) 6, 9, 12, 15, 20, and 25) for GFAP mRNA was generated for the cortex and hippocampus of developing Long-Evans hooded male rats under various lead exposure conditions: (1) prenatal (Gestational Day 13 to birth), (2) postnatal (Postnatal Day 1 to Postnatal Day 20), or (3) perinatal (Gestational Day 13 to Postnatal Day 20) exposure to lead acetate (0.2% in the drinking water of the dam). Control GFAP mRNA levels displayed a developmentally regulated profile of expression. In the cortex this was characterized by a transient elevation in peak level between PND 9 and PND 15 followed by a decline to within adult levels by PND 25. Under all lead acetate exposure conditions, the cortex showed an increase in the peak level of expression and extended the time of elevation of GFAP mRNA until PND 20. Levels of GFAP were elevated at PND 60 but not as early as PND 28. In the control hippocampus, levels of GFAP mRNA gradually increased until PND 20 followed by a sharp decline at PND 25. Postnatal and perinatal lead exposure followed a similar pattern; however, levels declined earlier at PND 20. Following prenatal lead exposure, levels of GFAP mRNA showed an earlier peak at PND 12 and a decrease as early as PND 15. By PND 60 protein level for GFAP was elevated in the postnatal lead exposure group only. As demonstrated by GFAP immunoreactivity, these lead-induced elevations were not associated with astrocyte hypertrophy. Following a physical injury in the cortex, astrocyte reactivity was similar between lead-exposed and control rats. These data suggest an alteration in the timing of astrocyte differentiation and maturation in the brain following developmental lead exposure.
Sodium fluoride (NaF) has been used to fluoridate drinking water in the United States since the mid 1940s. Because of the lack of reliable studies on the multigeneration effects of the compound, NaF (0, 25, 100, 175 or 250 ppm in drinking water) was given to rats continuously during three generations. Parental (F0) generation rats were treated for 10 weeks and mated within groups. At gestation day 20, caesarean sections were performed and eight F0 females per group and their litters (F1) were observed for implant status, fetal weight and length, sex and morphological development. The remaining F0 females (29-32 per group) were allowed to litter. F1 offspring (36 of each sex per group) were mated within groups, and caesarean sections were performed at gestation day 20. The F1 females and their litters (F2) were observed for implant status, fetal weight and length, sex and morphological development. In addition, F2 fetuses were evaluated for internal (soft-tissue) and skeletal development. Decreased fluid consumption for F0 and F1 dams at 175 and 250 ppm was attributed to decreased palatability of the solution. No dose-related effects in feed consumption or mean body weight gain were observed in either F0 or F1 females. Numbers of corpora lutea, implants, viable fetuses and fetal morphological development were similar in all groups. No dose-related anomalies in internal organs were observed in F2 fetuses. Ossification of the hyoid bone of F2 fetuses was significantly decreased at 250 ppm. Because of the decreased ossification of the hyoid bone, 250 ppm is considered the effect level.
The developing nervous system is susceptible to lead (Pb) exposure but less is known about the effect of this toxic agent in adult rat brain. Since astrocytes serve as a cellular Pb deposition site, it is of importance to investigate the response of astroglial cells in the adult rat brain in a model of acute lead exposure (25 mg/kg b.w. of lead acetate, i.p. for 3 days). An increased immunoreactivity of glial fibrillary acidic protein (GFAP) on Western blots was noticeable in fractions of astroglial origin-glial plasmalemmal vesicles (GPV) and in homogenates from the hippocampus and cerebral cortex but not in the cerebellum. The features of enhanced astrocytic reactivity (i.e. large accumulation of mitochondria, activated Golgi apparatus and increment of gliofilaments) were observed in electron microscopy studies in the same tissues. Total glutathione levels increased both in GPV fractions and in brain homogenates-in the cerebellum (120% above control) and in hippocampus (30% above control). The results of current studies indicate that acute lead exposure is accompanied by astrocyte activation connected with the presence of the enhanced expression of GFAP. It may indicate lead-induced neuronal injury. At the same time, a regional enhancement of detoxicative mechanisms (GSH) was noticed, suggesting activation of astrocyte-mediated neuroprotection against toxic Pb action.