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11β-Hydroxysteroid dehydrogenase type 2 protects the neonatal cerebellum from deleterious effects of glucocorticoids
Abstract
11beta-Hydroxysteroid dehydrogenase type 2 is a glucocorticoid metabolizing enzyme that catalyzes rapid inactivation of corticosterone and cortisol to inert 11-keto derivatives. As 11beta-hydroxysteroid dehydrogenase type 2 is highly expressed in the developing brain, but not in the adult CNS, we hypothesized that it may represent a protective barrier to the deleterious actions of corticosteroids on proliferating cells. To test this hypothesis we have investigated the development and growth of the cerebellum in neonatal C57BL/6 mice and mice lacking 11beta-hydroxysteroid dehydrogenase type 2 (-/-). 11beta-Hydroxysteroid dehydrogenase type 2-/- mice had consistently lower body weight throughout the neonatal period, coupled with a smaller brain size although this was normalized when corrected for body weight. The cerebellar size was smaller in 11beta-hydroxysteroid dehydrogenase type 2-/- mice, due to decreases in size of both the molecular and internal granule layers. When exogenous corticosterone was administered to the pups between postnatal days 4 and 13, 11beta-hydroxysteroid dehydrogenase type 2(-/-) mice were more sensitive, showing further inhibition of cerebellar growth while the wildtype mice were not affected. Upon withdrawal of exogenous steroid, there was a rebound growth spurt so that at day 21 postnatally, the cerebellar size in 11beta-hydroxysteroid dehydrogenase type 2-/- mice was similar to untreated mice of the same genotype. Furthermore, 11beta-hydroxysteroid dehydrogenase type 2-/- mice had a delay in the attainment of neurodevelopmental landmarks such as negative geotaxis and eye opening. We therefore suggest that 11beta-hydroxysteroid dehydrogenase type 2 acts as to protect the developing nervous system from the deleterious consequences of glucocorticoid overexposure.
... Outside the NTS, no other brain region contains HSD2-immunoreactive cells (Supplementary Figure A1), as reported previously for Hsd11b2 expression in adult mice (Holmes et al. 2006). Specifically, and in contrast to some reports in rats (Robson et al. 1998;Haque et al. 2015), we do not find any HSD2-immunoreactivity above background levels in the paraventricular hypothalamic nucleus, supraoptic hypothalamic nucleus, or amygdala (Supplementary Figure A2). ...
... Hsd11b2-Cre;R26-LSL-L10GFP mice express L10GFP prominently in the cerebellar granule cell layer (Fig. 5a). This is consistent with the initial report of a beta-galactosidase reporter for this Cre strain (Naray-Fejes-Toth and Fejes-Toth 2007), and is expected from reports of abundant Hsd11b2 expression by proliferating granule cells in the lateembryonic and early-postnatal period (Diaz et al. 1998;Robson et al. 1998;Holmes et al. 2006). In the NTS, despite a normal distribution of HSD2-immunoreactive neurons, we found GFP in just few neurons in most mice. ...
... In rats, we and others found HSD2 protein and Hsd11b2 mRNA in three consistent locations: the NTS, the subcommissural organ (SCO), the ventrolateral subdivision of the ventromedial nucleus of the hypothalamus (VMHvL) (Roland et al. 1995;Robson et al. 1998;Askew et al. 2015). Yet in mice, radioactive in situ hybridization identified Hsd11b2 mRNA in the NTS exclusively (Holmes et al. 2006). Here we confirm this observation, and add that Hsd11b2 mRNA and HSD2 protein Fig. 11 Sagittal diagram summarizing the axonal projections of HSD2 neurons and genes and proteins that identify or distinguish them from surrounding NTS neurons immunoreactivity co-localize in the same NTS neurons. ...
Sodium deficiency elevates aldosterone, which in addition to epithelial tissues acts on the brain to promote dysphoric symptoms and salt intake. Aldosterone boosts the activity of neurons that express 11-beta-hydroxysteroid dehydrogenase type 2 (HSD2), a hallmark of aldosterone-sensitive cells. To better characterize these neurons, we combine immunolabeling and in situ hybridization with fate mapping and Cre-conditional axon tracing in mice. Many cells throughout the brain have a developmental history of Hsd11b2 expression, but in the adult brain one small brainstem region with a leaky blood–brain barrier contains HSD2 neurons. These neurons express Hsd11b2, Nr3c2 (mineralocorticoid receptor), Agtr1a (angiotensin receptor), Slc17a6 (vesicular glutamate transporter 2), Phox2b, and Nxph4; many also express Cartpt or Lmx1b. No HSD2 neurons express cholinergic, monoaminergic, or several other neuropeptidergic markers. Their axons project to the parabrachial complex (PB), where they intermingle with AgRP-immunoreactive axons to form dense terminal fields overlapping FoxP2 neurons in the central lateral subnucleus (PBcL) and pre-locus coeruleus (pLC). Their axons also extend to the forebrain, intermingling with AgRP- and CGRP-immunoreactive axons to form dense terminals surrounding GABAergic neurons in the ventrolateral bed nucleus of the stria terminalis (BSTvL). Sparse axons target the periaqueductal gray, ventral tegmental area, lateral hypothalamic area, paraventricular hypothalamic nucleus, and central nucleus of the amygdala. Dual retrograde tracing revealed that largely separate HSD2 neurons project to pLC/PB or BSTvL. This projection pattern raises the possibility that a subset of HSD2 neurons promotes the dysphoric, anorexic, and anhedonic symptoms of hyperaldosteronism via AgRP-inhibited relay neurons in PB.
... However, there is also substantial fetal expression of 11β-HSD2, notably in the human, rat, mouse and pig fetal brain ( Brown et al., 1996a;Brown et al., 1996b). This shows locus-specific patterns of late developmental inactivation that appear to correlate with the entry of brain regions into terminal differentiation pathways that are induced by glucocorticoids ( Brown et al., 1996a;Holmes et al., 2006b). Moreover, at least in rodents, though fetal programming by maternal malnutrition is associated with elevated fetal glucocorticoid levels, these appear of fetal adrenal rather than maternal circulation origins ( Cottrell et al., 2012). ...
... Prenatal tissue collections were taken at E12.5, E15.5 or E17.5 to assess 11β-HSD2 activity (Brown et al., 1993), corticosterone levels, and/or gene expression in CON and HSD2BKO fetal and placental tissues (see SI Methods). At postnatal day (P) 21, cerebellum were dissected and assessed for morphological changes as described by Holmes et al., (2006b). Adult brains and adrenals were collected and processed as described in SI Methods. ...
... To determine the rate of development of postnatal functional neural maturation, negative geotaxis and timing of eye opening were assessed at P7 and P14 respectively ( Holmes et al., 2006b). For negative geotaxis, pups were removed from their mothers and placed on an inclined plane of approx 30° with their head facing downwards. ...
Stress or elevated glucocorticoids during sensitive windows of fetal development increase the risk of neuropsychiatric disorders in adult rodents and humans, a phenomenon known as glucocorticoid programming. 11β-Hydroxysteroid dehydrogenase type 2 (11β-HSD2), which catalyses rapid inactivation of glucocorticoids in the placenta, controls access of maternal glucocorticoids to the fetal compartment, placing it in a key position to modulate glucocorticoid programming of behavior. However, the importance of the high expression of 11β-HSD2 within the midgestational fetal brain is unknown. To examine this, a brain-specific knockout of 11β-HSD2 (HSD2BKO) was generated and compared to wild-type littermates. HSD2BKO have markedly diminished fetal brain 11β-HSD2, but intact fetal body and placental 11β-HSD2 and normal fetal and placental growth. Despite normal fetal plasma corticosterone, HSD2BKO exhibit elevated fetal brain corticosterone levels at midgestation. As adults, HSD2BKO show depressive-like behavior and have cognitive impairments. However, unlike complete feto-placental deficiency, HSD2BKO show no anxiety-like behavioral deficits. The clear mechanistic separation of the programmed components of depression and cognition from anxiety implies distinct mechanisms of pathogenesis, affording potential opportunities for stratified interventions.
Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.
... This rodent "stress hyporesponsive period" begins before EGL NPCs become vulnerable to GC induced NPC apoptosis. After the neonate becomes susceptible to this toxicity, endogenous corticosterone levels only rise to adult levels around the same time the EGL decreases proliferation and begins to disappear [49,50,[52][53][54]. In order to test what effect this rise might have on apoptosis, we increased corticosterone levels during the stress hyporesponsive period to levels normally seen in the adult. ...
... A final way the body can regulate endogenous GC stimulation is through the expression of the enzyme 11β-Hydroxysteroid Dehydrogenase Type II (HSD2), which selectively protects tissue from GC stimulation by rapidly inactivating endogenous GCs before they can stimulate GC receptors [52,53]. This enzyme is thought to be involved in neurodevelopment due to its high expression throughout the rodent brain in early gestation [55]. ...
... Around mid-gestation, levels in the brain decrease rapidly until HSD2 is almost exclusively isolated to the EGL at birth. As the neonate ages, high HSD2 levels are maintained until disappearing as the EGL is naturally eliminated from the cerebellum [52]. In order to test whether this natural decrease in HSD2 might contribute to the disintegration of the EGL, this enzyme was inhibited in neonatal mouse pups and the cerebella were screened for apoptosis. ...
Prematurely born infants commonly suffer respiratory dysfunction due to the immature state of their lungs. As a result, clinicians often administer glucocorticoid (GC) therapy to accelerate lung maturation and reduce inflammation. Unfortunately, several studies have found GC therapy can also produce neuromotor/cognitive deficits and selectively stunt the cerebellum. However, despite its continued use, relatively little is known about how exposure to this hormone might produce neurodevelopmental deficits. In this review, we use rodent and human research to provide evidence that GC therapy may disrupt cerebellar development through the rapid induction of apoptosis in the cerebellar external granule layer (EGL). The EGL is a transient proliferative region responsible for the production of over 90% of the neurons in the cerebellum. During normal development, endogenous GC stimulation is thought to selectively signal the elimination of the EGL once production of new neurons is complete. As a result, GC therapy may precociously eliminate the EGL before it can produce enough neurons for normal cerebellar function. It is hoped that this review may provide information for future clinical research in addition to translational guidance for the safer use of GC therapy.
... Several other genes have been found imperative for the regulation of HPA-axis function, including the FKBP5 gene, which exerts an inhibitory role on GR signaling by modulating hormone-binding affinity (i.e., the strength of binding interaction) (202,203), and the 11beta-hydroxysteroid dehydrogenase type 1 and 2 (11β-HSD), functions as a dehydrogenase which degrades cortisol to cortisone (11β-HSD2), and catalyzing the conversion of inactive cortisone to active cortisol (11β-HSD1) [for a review see (204)]. So far, only one study investigated FKBP5 gene transcription in relation to prematurity. ...
... Studies indeed showed that prenatal stress was associated with downregulation of placental 11β-HSD2 gene encoding (212,213), as well as lower and greater methylation of 11β-HSD2, respectively (214,215). In turn, in rodents, 11β-HSD2 −/− selectively determined programming of anxiety and depressive-like adult behavior (204,211,216). Similarly, 11β-HSD1 −/− mice showed elevated basal corticosterone levels and exaggerated responses to stress (207,208,217). ...
The third trimester of pregnancy represents a sensitive phase for infant brain plasticity when a series of fast-developing cellular events (synaptogenesis, neuronal migration, and myelination) regulates the development of neural circuits. Throughout this dynamic period of growth and development, the human brain is susceptible to stress. Preterm infants are born with an immature brain and are, while admitted to the neonatal intensive care unit, precociously exposed to stressful procedures. Postnatal stress may contribute to altered programming of the brain, including key systems such as the hypothalamic–pituitary–adrenal axis and the autonomic nervous system. These neurobiological systems are promising markers for the etiology of several affective and social psychopathologies. As preterm birth interferes with early development of stress-regulatory systems, early interventions might strengthen resilience factors and might help reduce the detrimental effects of chronic stress exposure. Here we will review the impact of stress following premature birth on the programming of neurobiological systems and discuss possible stress-related neural circuits and pathways involved in resilience and vulnerability. Finally, we discuss opportunities for early intervention and future studies.
... This protection lasts through the first few weeks of neonatal life. This is clearly seen in the external granule cell layer of the cerebellum, where 11β-HSD2 reportedly protects neural progenitor cells from CORT-induced apoptosis, cerebellar atrophy, and developmental deficits (45,(60)(61)(62). These patterns in the developing mammal brain raise the question of whether 11β-HSD2 plays a similar role in the adult songbird brain, especially in the CER, cNp and NCM, regions where 11β-HSD2 transcript levels were highest. ...
... GCs can impair hippocampal neurogenesis, depending on dose and context (23,(66)(67)(68). As 11β-HSD2 protects neurogenesis during mammalian fetal development (60,69), it is plausible that the enzyme serves a similar function in adult songbirds, and potentially in fish, where 11β-HSD2 is also widely expressed in the adult brain (70). ...
Glucocorticoid (GC) hormones act on the brain to regulate diverse functions, from behavior and homeostasis to the activity of the hypothalamic–pituitary–adrenal axis. Local regeneration and metabolism of GCs can occur in target tissues through the actions of the 11β-hydroxysteroid dehydrogenases [11 beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and 11 beta-hydroxysteroid dehydrogenase type 2 (11β-HSD2), respectively] to regulate access to GC receptors. Songbirds have become especially important model organisms for studies of stress hormone action; however, there has been little focus on neural GC metabolism. Therefore, we tested the hypothesis that 11β-HSD1 and 11β-HSD2 are expressed in GC-sensitive regions of the songbird brain. Localization of 11β-HSD expression in these regions could provide precise temporal and spatial control over GC actions. We quantified GC sensitivity in zebra finch (Taeniopygia guttata) brain by measuring glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) expression across six regions, followed by quantification of 11β-HSD1 and 11β-HSD2 expression. We detected GR, MR, and 11β-HSD2 mRNA expression throughout the adult brain. Whereas 11β-HSD1 expression was undetectable in the adult brain, we detected low levels of expression in the brain of developing finches. Across several adult brain regions, expression of 11β-HSD2 covaried with GR and MR, with the exception of the cerebellum and hippocampus. It is possible that receptors in these latter two regions require direct access to systemic GC levels. Overall, these results suggest that 11β-HSD2 expression protects the adult songbird brain by rapid metabolism of GCs in a context and region-specific manner.
... This barrier has key roles in the metabolism of cortisol to its inactive form via the enzyme 11bHSD2. Increasing cortisol exposure in primates and rodents (via prenatal stress [41], using 11bHSD2 knockout mice [42], blocking placental 11bHSD2 activity [43], or direct glucocorticoid administration [44]) alters neurodevelopment. These include motor and cognitive deficits (attention, neuromotor capabilities and learning), increased anxiety and stress-like behaviours and structural alterations (reduced hippocampal and dentate gyrus volumes), observed in the neonatal period [42], during infancy [41,44] and in adult offspring [43]. ...
... Increasing cortisol exposure in primates and rodents (via prenatal stress [41], using 11bHSD2 knockout mice [42], blocking placental 11bHSD2 activity [43], or direct glucocorticoid administration [44]) alters neurodevelopment. These include motor and cognitive deficits (attention, neuromotor capabilities and learning), increased anxiety and stress-like behaviours and structural alterations (reduced hippocampal and dentate gyrus volumes), observed in the neonatal period [42], during infancy [41,44] and in adult offspring [43]. ...
A significant proportion of children born preterm will experience some level of neurodevelopmental impairment. Changes in placental function have been observed with many antenatal conditions that are risk factors for preterm birth and/or poor neurodevelopment including fetal growth restriction and in-utero inflammation. This review will highlight placental factors that have been studied to understand the underlying mechanisms and identify biomarkers that lead to poor child neurodevelopmental outcomes. These include changes in gross morphological and histopathological structure and the placental inflammatory response to prenatal infection. Further, we will describe the placenta's role as both a barrier to maternally-derived bioactive substances critical for normal fetal brain development, such as cortisol, and a source of neuroactive steroids and neurotrophins known to have critical functions in neuronal proliferation, axonal growth, myelination and the regulation of apoptosis. Finally, emerging data supporting the potential utility of novel placental biomarkers in the early prediction of poor neurodevelopmental outcome in infants born both preterm and term will be discussed. These include the assessment of genetic variants (e.g. single nucleotide polymorphisms in placental tissue) and epigenetic biomarkers (e.g. placental microRNAs and placental DNA methylation). With the placenta the key tissue regulating the fetal environment, integration of observed changes in placental function with genetic and epigenetic variations may advance our ability to predict future infant health. Ultimately, this may facilitate targeted allocation of health resources with the aim of improving lifelong neurodevelopmental capability.
... 17 Fetal 11 HSD2 expression is progressively silenced from mid-gestation and in adulthood 11 HSD2 is restricted to sub-populations of neurons in brain areas influencing blood pressure and, less certainly, salt appetite. [17][18][19] In the adult mouse, Hsd11b2 is only expressed in the nucleus of the solitary tract (NTS) 20 . However, defining the role of 11 HSD2 in these NTS neurons of the adult brain has been challenging. ...
... However, 11 HSD2 is also expressed in the brain, 17 restricted to a subset of neurons in the NTS in the adult mouse. 20 We used a Cre-Lox strategy to conditionally delete Hsd11b2 in the brain, reducing expression in the NTS by >90%. We found that 11 HSD2 ...
Background:
-The hypertensive syndrome of Apparent Mineralocorticoid Excess is caused by loss of function mutations in the gene encoding 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2), allowing inappropriate activation of the mineralocorticoid receptor (MR) by endogenous glucocorticoid. Hypertension is attributed to sodium retention in the distal nephron but 11βHSD2 is also expressed in the brain. However, the central contribution to Apparent Mineralocorticoid Excess and other hypertensive states is often overlooked and is unresolved. We therefore used a Cre-Lox strategy to generate 11βHSD2 brain-specific knockout (Hsd11b2.BKO) mice, measuring blood pressure and salt appetite in adults.
Methods and results:
-Basal blood pressure, electrolytes and circulating corticosteroids were unaffected in Hsd11b2.BKO mice. When offered saline to drink, Hsd11b2.BKO mice consumed 3-times more sodium than controls and became hypertensive. Salt appetite was inhibited by spironolactone. Control mice fed the same daily sodium intake remained normotensive, showing intrinsic salt-resistance of the background strain. Dexamethasone suppressed endogenous glucocorticoid and abolished the salt-induced blood pressure differential between genotypes. Salt-sensitivity in Hsd11b2.BKO mice was not caused by impaired renal sodium excretion or volume expansion; pressor responses to phenylephrine were enhanced and baroreflexes impaired in these animals.
Conclusions:
-Reduced 11βHSD2 activity in the brain does not intrinsically cause hypertension but promotes a hunger for salt and a transition from salt-resistance to salt-sensitivity. Our data suggest that 11βHSD2-positive neurons integrate salt-appetite and the blood pressure response to dietary sodium through an MR-dependent pathway. Therefore, central MR antagonism could increase compliance to low-sodium regimens and help blood pressure management in cardiovascular disease.
... The effect of steroids on the developing brain can be explained by their pharmacological properties; DXM is a synthetic steroid 25 times more potent than HCHS and its interaction with glucocorticoid receptors in the brain causes adverse neuronal effects on the hippocampus by activating the apoptotic pathway, while HCHS mainly interacts with mineralocorticoid receptors [30]. The 11b-hydroxysteroid dehydrogenase type 2 enzyme is widely expressed in the foetal or preterm brain and metabolises active HCHS into the inactive form, 11-dehydroxysteroid [31]; there is no equivalent enzyme for DXM metabolism in the human brain. In addition, DXM is administered with sodium bisulphite for its preservation, unlike HCHS and BTM, and this excipient is toxic to neuronal cell lines [32]. ...
The administration of dexamethasone has been associated with suboptimal neurodevelopment. We aimed to compare the development of extremely premature infants treated or not with alternatives to dexamethasone: betamethasone, hydrocortisone hemisuccinate. This retrospective cohort study included infants born before 29 weeks of gestational age, treated or not with late (day ≥ 7) postnatal steroids (betamethasone, hydrocortisone hemisuccinate). The neurodevelopment outcome was evaluated at 24 months corrected age, after adjustment on comorbidities of extreme prematurity. In order to analyse their overall development, data about growth and respiratory outcomes were collected. Among the 192 infants included, 59 (30.7%) received postnatal steroids. Suboptimal neurodevelopment concerned 37/59 (62.7%) postnatal steroid-treated and 43/133 (38.1%; p = 0.002) untreated infants. However, in multivariable analysis, only severe neonatal morbidity (p = 0.007) and male gender (p = 0.027) were associated with suboptimal neurodevelopment outcome at 24 months.
Conclusions: Betamethasone or hydrocortisone hemisuccinate treatment was not an independent risk for suboptimal neurological development, growth and respiratory outcomes assessed at 24 months corrected age in extremely premature infants.
Registration number: The study was registered on the ClinicalTrials.gov register: NCT05055193.
What is Known:
• Late postnatal steroids are used to treat bronchopulmonary dysplasia
• Meta-analyses warned against the neurological risk of dexamethasone use during neonatal period. Early or late hydrocortisone hemisuccinate has been evaluated in multiple studies, none of which have reported an adverse effect on neurodevelopment at least to 2 years. Data about the use of betamethasone are scarce.
What is New:
• The risk of suboptimal neurodevelopment was higher among extremely premature infants who received postnatal steroids when compared to those who did not.
• Betamethasone and hydrocortisone hemisuccinate treatment was not an independent risk factor for suboptimal neurodevelopment at 24 months corrected age.
... Control ( treated mice had equivalent body weights to controls. Numerous studies showed decreased body weight following CORT treatment (Claflin et al., 2017;Holmes et al., 2006;Sousa et al., 1998) and numerous others showed preserved body weight (Claflin et al., 2017;Demuyser et al., 2016;Gourley et al., 2008;Harlé et al., 2017), depending on stress levels, mouse strain, and housing conditions. The upregulation in Nr3c1 expression found in the hypothalamus of CORT-treated mice reflects elevated circulating CORT levels, as demonstrated in adult mice after repeated injections of the same dose for 6 days (Harlé et al., 2017). ...
... Toutefois, cela suggère également que le rein pourrait être un organe particulièrement sensible à la programmation foetale par les glucocorticoïdes en période périnatale, ce qui pourrait s'expliquer par l'expression très faible de la 11bHSD2 dans cet organe à la naissance (Martinerie et al. 2012a). A l'inverse, le cervelet exprime temporairement la 11bHSD2 durant la période périnatale, alors qu'elle est non détectable dans cette structures à l'âge adulte (Holmes et al. 2006;Heine et Rowitch 2009), probablement pour protéger cette structure d'une exposition trop importante aux glucocorticoïdes pendant une fenêtre développementale cruciale. Plusieurs observations avaient déjà permis de souligner que plusieurs évènements indésirables survenant au cours de la gestation, comme l'exposition à un stress, un régime restrictif hypocalorique, hypoprotidique, carencé en micronutriments, ou l'exposition à la DEX en période périnatale, pouvaient mener à la programmation de pathologies cardio-vasculaires similaires, dont l'hypertension artérielle (Woodall et al. 1996b; L. L. Woods et al. 2001;Lewis et al. 2002;Ortiz et al. 2003;Koleganova et al. 2011). ...
La prématurité et la restriction de croissance fœtale (RCF) sont deux pathologies néonatales fréquentes, qui ont en commun des difficultés d'adaptation à la naissance, avec le développement d'une tubulopathie chez le prématuré, et le développement d'une hypertension artérielle (HTA) a l'âge adulte. L’objectif de ce travail était d’évaluer l'implication des voies de signalisation corticostéroïdes rénales dans la survenue de ces complications dans un modèle murin de prématurité induite par des lipopolysaccharides, et un modèle de RCF par exposition périnatale a la dexaméthasone. Dans ce travail nous avons montré que ces deux pathologies programment la survenue d’une HTA à l’âge adulte chez les mâles, associée à des altérations franches de la signalisation corticostéroïde rénale en période périnatale et une augmentation de la sensibilité rénale aux glucocorticoïdes à l’âge adulte. Dans le modèle de prématurité, nous avons identifié la transmission transgénérationelle d’anomalies de régulation de la pression artérielle chez les mâles jusqu’à la 3ème génération de souris, associée à une hypométhylation du promoteur de GILZ et une augmentation d’expression de GILZ. Notre étude a permis l’identification de potentiels mécanismes moléculaires impliqués dans la programmation fœtale de l’HTA, sur plusieurs générations, ce qui pourrait aboutir à une meilleure prise en charge des patients nés prématurés ou avec une RCF, et de leurs descendants.
... To assess development in early postnatal life, negative geotaxis, righting reflex, snout-vent length, and timing of both eye opening and fur development were assessed at PND7 (Holmes et al. 2006b). Snout-vent length and negative geotaxis were also measured at PND14. ...
Atmospheric carbon dioxide (CO2) levels are currently at 418 parts per million (ppm), and by 2100 may exceed 900 ppm. The biological effects of lifetime exposure to CO2 at these levels is unknown. Previously we have shown that mouse lung function is altered by long‐term exposure to 890 ppm CO2. Here, we assess the broader systemic physiological responses to this exposure. Mice were exposed to either 460 or 890 ppm from preconception to 3 months of age, and assessed for effects on developmental, renal and osteological parameters. Locomotor, memory, learning and anxiety‐like behaviours of the mice were also assessed. Exposure to 890 ppm CO2 increased birthweight, decreased female body weight after weaning, and, as young adults, resulted in reduced engagement in memory/learning tasks, and hyperactivity in both sexes in comparison to controls. There were no clear anxiety, learning or memory changes. Renal and osteological parameters were minimally affected. Overall, this study shows that exposure of mice to 890 ppm CO2 from preconception to young adulthood alters growth and some behaviours, with limited evidence of compensatory changes in acid–base balance. These findings highlight the potential for a direct effect of increased atmospheric CO2 on mammalian health outcomes. image
Key points
Long‐term exposure to elevated levels of atmospheric CO2 is an uncontrolled experiment already underway.
This is the first known study to assess non‐respiratory physiological impacts of long‐term (conception to young adulthood) exposure of mice to CO2 at levels that may arise in the atmosphere due to global emissions.
Exposure to elevated CO2, in comparison to control mice, altered growth patterns in early life and resulted in hyperactive behaviours in young adulthood.
Renal and bone parameters, which are important to balance acid–base levels to compensate for increased CO2 exposure, remained relatively unaffected.
This work adds to the body of evidence regarding the effects of carbon emissions on mammalian health and highlights a potential future burden of disease.
... In humans, under normal conditions, the secretion of corticosteroids is under the regulation of the hypothalamic-pituitary-adrenal (HPA) axis, and characterized by 24-h circadian oscillations, with the lowest corticosteroid levels around midnight and an acrophasic peak around 08:00 AM [1][2][3][4]. During pregnancy, placental 11β-hydroxysteroid dehydrogenase type 2 (HSD11B2) limits fetal exposure to maternal corticosteroids from early gestation [5]. Exogenous synthetic corticosteroids, however, either betamethasone or dexamethasone, are not metabolized by HSD11B2 and therefore cross the placenta to exert their biological activity [6]. ...
Introduction:
Our objective was to evaluate whether there is a relationship between the "time during the day" of maternal betamethasone administration between 24 and 34 weeks' gestation and the risk for neonatal hypoglycemia.
Material and methods:
A retrospective study included cases between 2008 and 2018. Eligible cases were pregnant women with singleton pregnancies who received a single course of betamethasone between 24 and 34 weeks' gestation. Each woman was allocated into one of four pre-defined groups based on the time when intramuscular betamethasone was administered. Group 1 (23:00-04:59) represents the lowest daily natural corticosteroids' activity, group 2 (05:00-10:59) represents the peak daily natural corticosteroids' activity, whereas group 3 (11:00-16:59) and group 4 (17:00-22:59) present an intermediate natural state of steady corticosteroids' secretion and activity. The primary outcome of the study was the incidence of neonatal hypoglycemia (glucose level of less than 40 mg/dL).
Results:
We have identified 868 women who received a single complete course of betamethasone, of which 353 women (40.7%) had a steroid treatment latency to delivery up to 14 days. The incidence of neonatal hypoglycemia was significantly higher in group 2 (39.5%, 30/76, p = 0.0063), compared to group 1, who had the lowest incidence of neonatal hypoglycemia (16.9%, 12/71), and to group 3 and group 4.
Conclusions:
The "time during the day" when betamethasone administered is important when considering the risk for neonatal hypoglycemia. The risk was significantly higher when betamethasone was administered during the peak time and significantly lower when administered at the nadir time of maternal endogenous corticosteroid activity.
... In the mouse, HSD2 is expressed in the majority of fetal tissues until E13.5, when a rapid decline in expression is observed [20]. The expression of HSD2 in the brain declines after mid-gestation but is maintained in discreet pockets into the third trimester, after which it further declines, with early postnatal expression restricted to the thalamus and the cerebellum in the rodent [20][21][22]. In the placenta HSD2 is expressed in the syncytiotrophoblast, where maternal and fetal circulations are in apposition [18,20,23]. ...
Developmental exposure to stress hormones, glucocorticoids, is central to the process of prenatal programming of later life health. Glucocorticoid overexposure, through stress or exogenous glucocorticoids, results in reduced birthweight, as well as affective and neuropsychiatric outcomes in adults, combined with altered hypothalamus-pituitary-adrenal (HPA) axis activity. As such, glucocorticoids are tightly regulated during development through the presence of the metabolising enzyme 11β-Hydroxysteroid Dehydrogenase type 2 (HSD2). HSD2 is highly expressed in two hubs during development: the placenta and the fetus itself, protecting the fetus from inappropriate glucocorticoid exposure early in gestation. Through manipulation of HSD2 expression in the mouse placenta and fetal tissues, we are able to determine the relative contribution of glucocorticoid exposure in each compartment. Feto-placental HSD2 deletion resulted in reduced birthweight and the development of anxiety- and depression-like behaviours in adult mice. The placenta itself is altered by glucocorticoid overexposure, which causes reduced placental weight and vascular arborisation. Furthermore, altered flow and resistance in the umbilical vessels and modification of fetal heart function and development is observed. However, brain-specific HSD2 removal (HSD2BKO), also generated adult phenotypes of depressive-like behaviour and memory deficit, demonstrating the importance of fetal brain HSD2 expression in development. In this review we will discuss potential mechanisms underpinning early-life programming of adult neuropsychiatric disorders and the novel therapeutic potential of statins.
... Cortisol levels are substantially higher in maternal versus cord blood (12). Placental 11b-hydroxysteroid dehydrogenase type 2 (11b-HSD2) enzyme serves as a barrier to inactivate glucocorticoids from the maternal circulation to avoid fetal overexposure to high cortisol levels (13). Animal studies have shown that placental 11b-HSD2 insufficiency may enhance cardiometabolic risk in the offspring (14) and that overexposure to endogenous or exogenous glucocorticoids is associated with hypothalamus-pituitary-adrenal axis reprogramming and cardiometabolic dysfunction (14)(15)(16). ...
Objective:
Fetal excessive exposure to glucocorticoids may program cardiometabolic risk. Placental 11 β-hydroxysteroid dehydrogenase 2 (11β-HSD2) serves as a barrier to prevent fetal overexposure to maternal glucocorticoids. It has not been explored whether placental 11β-HSD2 levels are associated with cardiometabolic health in postnatal life.
Research design and methods:
In a prospective birth cohort study of 246 mother-infant pairs, we measured placental 11β-HSD2 expression and maternal (32-35 weeks of gestation) and cord plasma cortisol concentrations. The primary outcomes were HOMA of insulin resistance (IR) and blood pressure (BP) in infants at age 1 year. Other outcomes included fasting insulin, HOMA β-cell function, carotid intima-media thickness, weight z score, and skinfold thickness (triceps and subscapular) at age 1 year.
Results:
Placental 11β-HSD2 expression was negatively correlated with HOMA-IR (r = -0.17, P = 0.021) and fasting insulin (r = -0.18, P = 0.017) and marginally negatively correlated with systolic BP (r = -0.16, P = 0.057) but was not correlated with HOMA of β-cell function, diastolic BP, carotid intima-media thickness, and skinfold thickness (all P > 0.1) in infants at age 1 year. Cord plasma cortisol was negatively correlated to skinfold thickness (r = -0.20, P = 0007) but was not correlated with other outcomes at age 1 year. Maternal plasma cortisol was positively correlated with maximal carotid intima-media thickness (r = 0.20, P = 0.03) but was not correlated with other outcomes. Adjusting for maternal and infant characteristics, the associations were similar.
Conclusions:
The study is the first to show that higher placental 11β-HSD2 expression is associated with lower IR in infancy. Independent cohort studies are required to confirm this novel finding.
... En effet, elle est fortement exprimée après la naissance, notamment au niveau des cellules granulaires du cortex cérébelleux et dans certains noyaux thalamiques (Robson et al., 1998). Chez les souris invalidées pour le gène codant la 11β-HSD2, une perte des couches granulaires interne et moléculaire du cortex cérébelleux est observée lors du développement, entraînant la formation d'un cervelet plus petit que la normale (Holmes et al., 2006). ...
Lors d’un stress, l’activation de l’axe hypothalamo-hypophyso-surrénalien (HHS) conduit à une augmentation de la production de glucocorticoïdes (tel que la corticostérone) par les glandes surrénales. Le rôle de la corticotropin-releasing hormone (CRH), à l’origine de l’activation de l’axe HHS, est encore méconnu. En effet, les récepteurs à la CRH sont présents aussi bien au niveau du système nerveux central (SNC), notamment au niveau du cervelet, qu’au niveau du système immunitaire (SI). Cela suggère donc une action directe possible de cette hormone sur ces deux systèmes. Au cours de ce projet, nous avons étudié les régulations des SNC et SI lors d’un stress, et plus particulièrement le rôle de la CRH et de ses récepteurs dans ces régulations. Suite à des injections chroniques de corticostérone, mimant un stress, nous avons observé une altération des fonctions locomotrices qui semble être reversée lorsque le CRH-R1 est inhibé avec un antagoniste. Ces premiers résultats permettent de mettre en avant un éventuel rôle de la CRH dans la régulation des fonctions motrices au niveau du cervelet en conditions de stress. En parallèle, d’autres études in vitro réalisées sur des splénocytes murins stimulés avec de la CRH ont montré une diminution de la viabilité des lymphocytes B (LB). Suite à ces résultats, nous avons caractérisé pour la première fois la présence de récepteurs à la CRH sur cette population de LB murins. Ces résultats montrent l’importance de la CRH dans les régulations des SNC et SI en condition de stress et le rôle de cette hormone dans les interactions entre les deux systèmes
... P = 0.0275; Air-righting reflex: 12.6 ± 0.21 vs. 11.6 ± 0.32 days, U = 114, P = 0.0139; n = 20 in each group; Figures 2B,C). As previous reports have illustrated the impairment of the negative geotaxis (Holmes et al., 2006) and the air righting reflex (Wolf et al., 1996) in cerebellar developmental disorders, it is thus reasonable to speculate that prenatal VPA exposure may cause early postnatal developmental disorders of the cerebellum. ...
Autistic spectral disorder (ASD) is a prevalent neurodevelopmental disease that affects multiple brain regions. Both clinical and animal studies have revealed the possible involvement of the cerebellum in ASD pathology. In this study, we generated a rodent ASD model through a single prenatal administration of valproic acid (VPA) into pregnant mice, followed by cerebellar morphological and functional studies of the offspring. Behavioral studies showed that VPA exposure led to retardation of critical motor reflexes in juveniles and impaired learning in a tone-conditioned complex motor task in adults. These behavioral phenotypes were associated with premature migration and excess apoptosis of the granular cell (GC) precursor in the cerebellar cortex during the early postnatal period, and the decreased cell density and impaired dendritic arborization of the Purkinje neurons. On acute cerebellar slices, suppressed synaptic transmission of the Purkinje cells were reported in the VPA-treated mice. In summary, converging evidence from anatomical, electrophysiological and behavioral abnormalities in the VPA-treated mice suggest cerebellar pathology in ASD and indicate the potential values of motor dysfunction in the early diagnosis of ASD.
... In contrast, corticosterone and prednisolone are susceptible to inactivation by 11βHSD2 activity. 11βHSD2 is expressed in the developing CNS, including cerebellar granule neuron precursors (CGNPs) [32] where its function is necessary for normal cerebellar development [33]. Indeed, Shh signaling is protective against prednisolone-induced cerebellar injury through upregulation of 11βHSD2 specifically in CGNPs. ...
The cerebellum undergoes rapid growth during the third trimester and is vulnerable to injury and deficient growth in infants born prematurely. Factors associated with preterm cerebellar hypoplasia include chronic lung disease and postnatal glucocorticoid administration. We modeled chronic hypoxemia and glucocorticoid administration in neonatal mice to study whole cerebellar and cell type-specific effects of dual exposure. Chronic neonatal hypoxia resulted in permanent cerebellar hypoplasia. This was compounded by administration of prednisolone as shown by greater volume loss and Purkinje cell death. In the setting of hypoxia and prednisolone, administration of a small molecule Smoothened-Hedgehog agonist (SAG) preserved cerebellar volume and protected against Purkinje cell death. Such protective effects were observed even when SAG was given as a one-time dose after dual insult. To model complex injury and determine cell type-specific roles for the hypoxia inducible factor (HIF) pathway, we performed conditional knockout of von Hippel Lindau (VHL) to hyperactivate HIF1α in cerebellar granule neuron precursors (CGNP) or Purkinje cells. Surprisingly, HIF activation in either cell type resulted in no cerebellar deficit. However, in mice administered prednisolone, HIF overactivation in CGNPs resulted in significant cerebellar hypoplasia, whereas HIF overactivation in Purkinje cells caused cell death. Together, these findings indicate that HIF primes both cell types for injury via glucocorticoids, and that hypoxia/HIF + postnatal glucocorticoid administration act on distinct cellular pathways to cause cerebellar injury. They further suggest that SAG is neuroprotective in the setting of complex neonatal cerebellar injury.
Electronic supplementary material
The online version of this article (10.1007/s12311-017-0895-0) contains supplementary material, which is available to authorized users.
... This enzyme is also available at high levels during development in the brain and placenta to protect the body against deleterious effects of high cortisol levels (e.g. cerebellar malformation [33], high HPA activity in adult life [34] and increased incidence of diseases related to corticoids hypersensitivity [22]. ...
Information on insulin resistance/sensitivity in term-normoweight neonates is scarce. The hypothalamus-pituitary-adrenal cortex axis and pancreas are implicated in several aspects of foetal maturation and programming. This study aims to analyse the effects of a combination of hyperinsulinaemia plus hypercortisolaemia in such neonates together with their mothers℉ gestational glucose tolerance on growth hormone (GH), insulin-like growth factor-1 (IGF)-1, glucose, and insulin resistance/sensitivity markers [homeostatic model assessment-insulin resistance (HOMA-IR)/quantitative insulin sensitivity check index (QUICKI)] at birth. Furthermore, the importance of pregnancy diet quality on these markers is discussed. In a selected group of 187 term-normoweight non-distressed neonates, about 9% had increased insulin and cortisol cord-blood concentrations. In spite of normality criteria applied, the combination of hypercortisolaemia and hyperinsulinaemia at birth was associated with higher body weight, body length, glucose, HOMA-IR, GH, IGF-1 and glucose/insulin ratio values than those of neonates presenting low/normal concentrations of insulin and cortisol. Hyperinsulinaemia preferentially to hypercortisolaemia affected the markers studied. Impaired glucose tolerance prevalence was higher in mothers whose neonates were hyperinsulinaemic at birth. The hyperinsulinaemic plus hypercortisolaemic status was more prevalent in neonates whose mothers had poor Mediterranean diet adherence. Results show the importance of analysing insulin and cortisol in cord-blood even in term-normoweight neonates.
Information on insulin resistance/sensitivity in term-normoweight neonates is scarce. The hypothalamus-pituitary-adrenal cortex axis and pancreas are implicated in several aspects of foetal maturation and programming. This study aims to analyse the effects of a combination of hyperinsulinaemia plus hypercortisolaemia in such neonates together with their mothers℉ gestational glucose tolerance on growth hormone (GH), insulin-like growth factor-1 (IGF)-1, glucose, and insulin resistance/sensitivity markers [homeostatic model assessment-insulin resistance (HOMA-IR)/quantitative insulin sensitivity check index (QUICKI)] at birth. Furthermore, the importance of pregnancy diet quality on these markers is discussed. In a selected group of 187 term-normoweight non-distressed neonates, about 9% had increased insulin and cortisol cord-blood concentrations. In spite of normality criteria applied, the combination of hypercortisolaemia and hyperinsulinaemia at birth was associated with higher body weight, body length, glucose, HOMA-IR, GH, IGF-1 and glucose/insulin ratio values than those of neonates presenting low/normal concentrations of insulin and cortisol. Hyperinsulinaemia preferentially to hypercortisolaemia affected the markers studied. Impaired glucose tolerance prevalence was higher in mothers whose neonates were hyperinsulinaemic at birth. The hyperinsulinaemic plus hypercortisolaemic status was more prevalent in neonates whose mothers had poor Mediterranean diet adherence. Results show the importance of analysing insulin and cortisol in cord-blood even in term-normoweight neonates.
... Placental HSD2 inactivates corticosterone, and the enzyme plays a critical role in regulating the levels of maternal corticosterone that cross the placenta and enter fetal circulation (Michael et al., 2003;Waddel et al., 1998). If reduced gene expression results in diminished HSD2 protein or enzymatic activity, the fetus may be exposed to abnormally high levels of corticosterone, which has been shown to have deleterious effects on brain development (Holmes et al., 2006;Welberg et al., 2000;Weinstock, 2007) and longerterm consequences (see review by Seckl and Holmes, 2007). In contrast to the neuroprotective effects of placental HSD2 during development, placental iodothyronine deiodinase 2 (DIO2) is responsible for the conversion of maternal thyroxine (T 4 ) to the triiodothyronine (T 3 ), the physiologically active form of thyroid hormone. ...
... The metabolism of glucocorticoids at a neuronal level is regulated by enzymes (11-bhydroxysteroid dehydrogenases: 11b-HSD) that convert cortisol to its inactive metabolite (cortisone), or vice versa. 11b-HSD type2 protects cerebellar neurons from the damaging actions of GCs (Holmes et al., 2006) and inhibiting 11b-HSD type1 improves cognition in ageing men (55-75 yr) (Sandeep et al., 2004). A rare variant of the 11-HSD type1 gene (reducing its action) has been linked with a 6-fold increase in the risk for AD; apparently type 1 can remove potentially damaging GCs (Quervain et al., 2004). ...
... Dit enzym zou het ontwikkelende zenuwstelsel tegen de nadelige gevolgen van overexposure van glucocorticoïd, zoals bij vroege HC-behandeling, beschermen. 35,36 Deze hypothese vereist nader onderzoek. ...
The use of postnatal corticosteroids to prevent or treat chronic lung disease in newborns remains a controversial issue. Dexamethasone has many negative side effects. Hydrocortisone could be a suitable alternative if equally effective and causing fewer negative sequelae on neuromotor development. This paper describes the published studies on hydrocortisone treatment in the neonatal period in relation with long-term neurodevelopmental outcome.
... Dans des conditions normales, si une femelle gestante est stressée, l'accès aux glucocorticoïdes maternels endogènes est généralement réduit pour le foetus car une enzyme placentaire, la 11 béta-hydroxystéroïde déshydrogénase (11β-HSD) dégrade les glucocorticoïdes et protège le foetus des effets délétères des glucocorticoïdes maternels. Cette enzyme jouerait également un rôle non négligeable au niveau du cerveau du foetus pour le protéger d'éventuels excès de glucocorticoides (Holmes et al 2006). Cependant, il semblerait qu'en situation de stress chronique ou d'expositions répétées à des agents stressants, une partie du cortisol maternel traverse la barrière placentaire (Owen et al 2005). ...
Stress that occurs during pregnancy can have consequences on the behaviour of offspring such as increased emotional reactivity, impaired learning ability and feminisation of male sexual behaviour. A modification of the hypothalamo-pituitary axis is often observed, for example, an increase in basal glucocorticoid concentrations and a higher secretion rate after a stressful event. Immune responses can also be modified, and birth-weight reduced. However, there is a high level of variability in the effects of prenatal stress. This may be due to the type of stressor, its intensity and period of application during pregnancy. The effect may also differ according to the gender of the offspring, with females appearing to be more affected than males. Stress experienced by a dam during pregnancy could have consequences on neuroendocrine development in the foetus. Maternal hormones secreted during stress, which can cross the placental barrier, could be one of the mechanisms explaining these effects. Modification of maternal behaviour due to chronic stress may also be involved in the effect on the behaviour of the offspring. Most studies have been performed on rodents and primates but the few experiments involving farm animals tend to show that the consequences can be important.
... Dans des conditions normales, si une femelle gestante est stressée, l'accès aux glucocorticoïdes maternels endogènes est généralement réduit pour le foetus car une enzyme placentaire, la 11 béta-hydroxystéroïde déshydrogénase (11β-HSD) dégrade les glucocorticoïdes et protège le foetus des effets délétères des glucocorticoïdes maternels. Cette enzyme jouerait également un rôle non négligeable au niveau du cerveau du foetus pour le protéger d'éventuels excès de glucocorticoides (Holmes et al 2006). Cependant, il semblerait qu'en situation de stress chronique ou d'expositions répétées à des agents stressants, une partie du cortisol maternel traverse la barrière placentaire (Owen et al 2005). ...
Stress that occurs during pregnancy can have consequences on the behaviour of offspring such as increased emotional reactivity, impaired learning ability and feminisation of male sexual behaviour. A modification of the hypothalamo-pituitary axis is often observed, for example, an increase in basal glucocorticoid concentrations and a higher secretion rate after a stressful event. Immune responses can also be modified, and birth-weight reduced. However, there is a high level of variability in the effects of prenatal stress. This may be due to the type of stressor, its intensity and period of application during pregnancy. The effect may also differ according to the gender of the offspring, with females appearing to be more affected than males. Stress experienced by a dam during pregnancy could have consequences on neuroendocrine development in the foetus. Maternal hormones secreted during stress, which can cross the placental barrier, could be one of the mechanisms explaining these effects. Modification of maternal behaviour due to chronic stress may also be involved in the effect on the behaviour of the offspring. Most studies have been performed on rodents and primates but the few experiments involving farm animals tend to show that the consequences can be important.
... In the neonatal brain, systemic administration of the Smoothened analog (SAG) and transgenic Smoothened activation resulted in improved granule neuron generation and cerebellar granule neuron progenitor proliferation in a glucocorticoid injury model, in which chronic glucocorticoid treatment in the first postnatal week inhibits cerebellar growth (Heine et al., 2011). The antagonism of glucocorticoid effects was mediated by the induction of 11betahydroxysteroid dehydrogenase type 2 (11beta-HSD2) (Holmes et al., 2006) by Smoothened activation (Heine et al., 2011;Heine and Rowitch, 2009). It is, however presently unknown whether a similar approach with SAG would attenuate WM changes in the developing corpus callosum following perinatal hypoxic injury, although caution is warranted due to the documented effect of Hh in tumorigenesis (Gulino et al., 2007) and surprising decreased functional outcome in stem cell therapy for hypoxiaeischemia (van Velthoven et al., 2014). ...
White matter disease afflicts both developing and mature central nervous systems. Both cell intrinsic and extrinsic dysregulation result in profound changes in cell survival, axonal metabolism and functional performance. Experimental models of developmental white matter (WM) injury and demyelination have not only delineated mechanisms of signaling and inflammation, but have also paved the way for the discovery of pharmacological approaches to intervention. These reagents have been shown to enhance protection of the mature oligodendrocyte cell, accelerate progenitor cell recruitment and/or differentiation, or attenuate pathological stimuli arising from the inflammatory response to injury. Here we highlight reports of studies in the CNS in which compounds, namely peptides, hormones, and small molecule agonists/antagonists, have been used in experimental animal models of demyelination and neonatal brain injury that affect aspects of excitotoxicity, oligodendrocyte development and survival, and progenitor cell function, and which have been demonstrated to attenuate damage and improve WM protection in experimental models of injury. The molecular targets of these agents include growth factor and neurotransmitter receptors, morphogens and their signaling components, nuclear receptors, as well as the processes of iron transport and actin binding. By surveying the current evidence in non-immune targets of both the immature and mature WM, we aim to better understand pharmacological approaches modulating endogenous oligodendroglia that show potential for success in the contexts of developmental and adult WM pathology.
Copyright © 2015. Published by Elsevier Ltd.
... Glucocorticoids are lipophilic and readily cross placenta barriers. In fact, fetoplacental 11β-hydroxy steroid dehydrogenase type 2 (11β-HSD2), which catalyses the rapid metabolism of active cortisol and corticosterone to physiologically inert 11-keto forms (cortisone, 11-dehydro corticosterone), forms a barrier to transport of maternal glucocorticoids [5]. However, this barrier is not complete, as a minor proportion of maternal gluco-corticoid crosses intact to the fetus; thus, maternal stress elevates fetal glucocorticoid levels. ...
The aim of this study was to investigate the relationship between serum 11β-HSD2 mRNA level and insulin sensitivity in term small-for-gestational age (SGA) neonates after birth. The 38 infants were divided into two groups, the SGA group and the appropriate-for-gestational age (AGA) group. The placental 11β-HSD2 mRNA abundance and concentration of cortisol, fasting glucose, fasting insulin, adiponectin, visfatin and insulin-like growth factor-I (IGF-1) in the umbilical vein plasma were measured. The results showed that in the SGA group, neonates had lower levels of placental 11β-HSD2 mRNA and serum cortisol, and higher fasting insulin and HOMA-IR compared to AGA group. For some insulin sensitivity relative factor, levels of serum adiponectin and IGF-1 were lower while visfatin was higher in the SGA group than AGA group. Correlation analyses revealed that 11β-HSD2 mRNA level had a negative correlation with fasting insulin, HOMA-IR and visfatin.
... Expression of HSD2 has been detected in blood vessel walls and in epithelial cells of the distal nephron, colon, and sweat glands, i.e. in organs of high aldosterone sensitivity. HSD2 expression has been detected in the brain of rats and mice including the nucleus tractus solitarius (NTS) [80][81][82]. Potential candidates for mediating the induction of sodium appetite include the neurons in the NTS that co-express MR and HSD2 ( Figure 1) and are activated (increase in nuclear c-Fos) by chronic salt deprivation and inactivated following salt repletion [83]. These neurons, like sodium appetite, can still be activated by dietary sodium deprivation after adrenalectomy, indicating that they integrate other signals in addition to aldosterone [84]. ...
An increase in renal sodium chloride (salt) retention and an increase in sodium appetite are the body's responses to salt restriction or depletion in order to restore salt balance. Renal salt retention and increased sodium appetite can also be maladaptive and sustain the pathophysiology in conditions like salt-sensitive hypertension and chronic heart failure. Here we review the central role of the mineralocorticoid aldosterone in both the increase in renal salt reabsorption and sodium appetite. We discuss the working hypothesis that aldosterone activates similar signaling and effector mechanisms in the kidney and brain, including the mineralocorticoid receptor, the serum- and glucocorticoid-induced kinase SGK1, the ubiquitin ligase NEDD4-2, and the epithelial sodium channel ENaC. The latter also mediates the gustatory salt sensing in the tongue, which is required for the manifestation of increased salt intake. Effects of aldosterone on both the brain and kidney synergize with the effects of angiotensin II. Thus, mineralocorticoids appear to induce similar molecular pathways in the kidney, brain, and possibly tongue, which could provide opportunities for more effective therapeutic interventions. Inhibition of renal salt reabsorption is compensated by stimulation of salt appetite and vice versa; targeting both mechanisms should be more effective. Inhibiting the arousal to consume salty food may improve a patient's compliance to reducing salt intake. While a better understanding of the molecular mechanisms is needed and will provide new therapeutic options, current pharmacological interventions that target both salt retention and sodium appetite include mineralocorticoid receptor antagonists and potentially inhibitors of angiotensin II and ENaC. © 2014 S. Karger AG, Basel.
... This results in inactivation of cortisol by oxidation to the inactive cortisone. The tissue distribution of the type 2 enzyme is restricted to mineralocorticoid target tissues, notably the renal tubule 11,12,13 . ...
Glucocorticosteroids (GCs) are commonly used for long-term medication in immunosuppressive and anti-inflammatory therapy, but prolonged use of GCs produce number of systemic side effects. To further improve the therapeutic index, that is the ratio of the toxic to the therapeutic dose of a drug, it is at least theoretically possible by changing both pharmacokinetics and pharmacodynamic parameters. Pharmacokinetics can deliberately be altered by using the "inactive metabolite approach" in which one can design a soft analog of a drug that is active at the site of action (e.g.,in the lung in case of inhaled medications) but undergoes a one-step predicted metabolism in the circulation and will be transformed to the very inactive metabolite from which its creation had been started. This process happens after the drug achieves its therapeutic role at the site of action and thus prevents the rest of the body to be exposed to the active drug or to various active or reactive metabolic products. Pharmacodynamic possibility to separate beneficial and deleterious effects of steroids is to try to dissociate the two main activities of glucocorticoids, which are transactivation and transrepression. INTRODUCTION: Endogenous glucocorticoids (GC) play an essential role in maintaining body homeostasis and preventing excessive immune responses to antigenic challenges 1, 2 . Supraphysiological doses of synthetic GC are used to treat patients with inflammatory or autoimmune diseases 3 .
... 42 HSD2 significantly attenuates the actions of natural glucocorticoids on the brain. 43,44 HSD2 expression decreases with advancing gestation from fetal to newborn, and up to adulthood, concomitantly as endogenous glucocorticoid production increases. Consequently, a larger portion of endogenous cortisol or exogenous hydrocortisone that enters the brain at more mature postmenstrual ages will remain active to bind more receptors and augment their biologic actions. ...
Deleterious effects result from both glucocorticoid insufficiency and excess glucocorticoid tissue exposure in the developing brain. Accumulating evidence suggests a net benefit of postnatal glucocorticoid therapy when administered shortly after the first week of life to premature infants with early and persistent pulmonary dysfunction, particularly in those with evidence of relative adrenal insufficiency. The decision to treat with steroids should ensure maximum respiratory benefit at the lowest possible neurologic risk, while avoiding serious systemic complications. Ongoing clinical trials must validate this approach.
... The prenatal period is a time where offspring undergo massive ontogenetic changes, particularly brain development, and, consequently, offspring phenotypes are exceptionally vulnerable to changes in the maternal uterine environment (Charil, Laplante, Vaillancourt, & King, 2010). Cortisol concentrations naturally rise during pregnancy in both nonhuman primates and humans (Mustoe, Birnie, Korgan, Santo, & French, 2012;Sandman et al., 2006), and alterations in metabolism, efficacy of 11b-hydroxysteroid dehydrogenase type 2 (11b-HSD2), or increases in maternal stress, anxiety, or depression can affect the fetus' exposure to glucocorticoids and later-life outcomes (Field, Diego, & Hernandez-Reif, 2006;Holmes et al., 2006). Given that glucocorticoids vary considerably among mothers during gestation, it appears that the effects of prenatal stress and other alterations in glucocorticoid exposure during pregnancy may alert fetuses to demands in their imminent environment (Glover, 2011). ...
Both gestational cortisol exposure (GCE) and variability in postnatal environments can shape the later-life behavioral and endocrine outcomes of the hypothalamic-pituitary-adrenal (HPA) axis. We examined the influence of GCE and social play on HPA functioning in developing marmosets. Maternal urinary cortisol samples were collected across pregnancy to determine GCE for 28 marmoset offspring (19 litters). We administered a social separation stressor to offspring at 6, 12, and 18 months of age, during which we collected urinary cortisol samples and behavioral observations. Increased GCE was associated with increased basal cortisol levels and cortisol reactivity, but the strength of this relationship decreased across age. Increased social play was associated with decreased basal cortisol levels and a marginally greater reduction in cortisol reactivity as offspring aged, regardless of offspring GCE. Thus, GCE is associated with HPA functioning, but socially enriching postnatal environments can alter the effects associated with increased fetal exposure to glucocorticoids. © 2014 Wiley Periodicals, Inc. Dev Psychobiol.
Exposure to stress during early life may alter the developmental trajectory of an animal by a mechanism known as adaptive plasticity. For example, to enhance reproductive success in an adverse environment, it is known that animals accelerate their growth during development. However, these short-term fitness benefits are often associated with reduced longevity, a phenomenon known as the growth rate–lifespan trade-off. In humans, early life stress exposure compromises health later in life and increases disease susceptibility. Glucocorticoids (GCs) are major stress hormones implicated in these processes. This Review discusses the evidence for GC-mediated adaptive plasticity in development, leading to allostatic overload in later life. We focus on GC-induced effects on brain structure and function, including neurogenesis; highlight the need for longitudinal studies; and discuss approaches to identify molecular mechanisms mediating GC-induced alteration of the brain developmental trajectory leading to adult dysfunctions. Further understanding of how stress and GC exposure can alter developmental trajectories at the molecular and cellular level is of critical importance to reduce the burden of mental and physical ill health across the life course.
11‐beta‐hydroxysteroid dehydrogenases (11β‐HSDs) catalyse the conversion of active 11‐hydroxy glucocorticoids (cortisol, corticosterone) and their inert 11‐keto forms (cortisone, 11‐dehydrocorticosterone). They were first reported in the body and brain 70 years ago, but only recently have they become of interest. 11β‐HSD2 is a dehydrogenase, potently inactivating glucocorticoids. In the kidney, 11β‐HSD2 generates the aldosterone‐specificity of intrinsically non‐selective mineralocorticoid receptors. 11β‐HSD2 also protects the developing foetal brain and body from premature glucocorticoid exposure, which otherwise engenders the programming of neuropsychiatric and cardio‐metabolic disease risks. In the adult CNS, 11β‐HSD2 is confined to a part of the brain stem where it generates aldosterone‐specific central control of salt appetite and perhaps blood pressure. 11β‐HSD1 is a reductase, amplifying active glucocorticoid levels within brain cells, notably in the cortex, hippocampus and amygdala, paralleling its metabolic functions in peripheral tissues. 11β‐HSD1 is elevated in the ageing rodent and, less certainly, human forebrain. Transgenic models show this rise contributes to age‐related cognitive decline, at least in mice. 11β‐HSD1 inhibition robustly improves memory in healthy and pathological ageing rodent models and is showing initial promising results in phase II studies of healthy elderly people. Larger trials are needed to confirm and clarify the magnitude of effect and define target populations. The next decade will be crucial in determining how this tale ends – in new treatments or disappointment.
Regulation of glucocorticoids (GCs), important mediators of physiology and behavior at rest and during stress, is multi-faceted and dynamic. The 11ß hydroxysteroid dehydrogenases 11ß-HSD1 and 11ß-HSD2 catalyze the regeneration and inactivation of GCs, respectively, and provide peripheral and central control over GC actions in mammals. While these enzymes have only recently been investigated in just two songbird species, central expression patterns suggest that they may function differently in birds and mammals, and little is known about how peripheral expression regulates circulating GCs. In this study, we utilized the 11ß-HSD inhibitor carbenoxolone (CBX) to probe the functional effects of 11ß-HSD activity on circulating GCs and central GC-dependent gene expression in the adult zebra finch (Taeniopygia guttata). Peripheral CBX injection produced a marked increase in baseline GCs 60min after injection, suggestive of a dominant role for 11ß-HSD2 in regulating circulating GCs. In the adult zebra finch brain, where 11ß-HSD2 but not 11ß-HSD1 is expressed, co-incubation of micro-dissected brain regions with CBX and stress-level GCs had no impact on expression of several GC-dependent genes. These results suggest that peripheral 11ß-HSD2 attenuates circulating GCs, whereas central 11ß-HSD2 has little impact on gene expression. Instead, rapid 11ß-HSD2-based regulation of local GC levels might fine-tune membrane GC actions in brain. These results provide new insights into the dynamics of GC secretion and action in this important model organism.
Background
Preterm infants with severe bronchopulmonary dysplasia require rescue therapy with glucocorticoids, and hydrocortisone is increasingly replacing dexamethasone. The standard for rescue therapy is unclear.
Aim
To quantify the short-term effects of respiratory rescue hydrocortisone of 4 mg/kg/day for 3 days.
Study design
Retrospective single-center study.
Subjects
Ventilator-dependent infants born at <28 weeks of gestation with an increased oxygen demand to maintain the target oxygen saturation at 88% to 95% >1 week after birth.
Outcome measures
Ventilator settings, SpO2/FiO2 ratio, heart rate, and blood parameters within 24 hours before and 228 hours after starting hydrocortisone.
Results
Twenty-five infants (median gestational age, 25.1 weeks) received hydrocortisone at a median age of 16 days. The median pre-therapy SpO2/FiO2 was 297 (interquartile range, 265–320) and began to rise after 12 hours of administration, reaching 307 (interquartile range, 278–335). The increase in SpO2/FiO2 peaked from the third day to 3 days after therapy (median range, 341–356). SpO2/FiO2 decreased thereafter and remained unchanged from 6 and 7 days after therapy (median range, 304–314). The pCO2 level (median range, 49–53 mmHg) did not change significantly. The heart rate significantly decreased from −4 to −6 beats/min from the first day to 1 day after therapy. Systolic blood pressure increased by a median of 4 to 8 mmHg after therapy. Blood electrolytes and glucose were similar after therapy.
Conclusion
Rescue hydrocortisone administration improved oxygenation without particular adverse effects but did not affect ventilation at the stage of respiratory deterioration in preterm infants.
The brain is the most cholesterol rich organ in the body containing about 25% of the body's free cholesterol. Cholesterol cannot pass the blood–brain barrier and be imported or exported; instead, it is synthesised in situ and metabolised to oxysterols, oxidised forms of cholesterol, which can pass the blood–brain barrier. 24S‐Hydroxycholesterol is the dominant oxysterol in the brain after parturition, but during development, a myriad of other oxysterols are produced, which persist as minor oxysterols after birth. During both development and in later life, sterols and oxysterols interact with a variety of different receptors, including nuclear receptors, membrane bound GPCRs, the oxysterol/sterol sensing proteins INSIG and SCAP, and the ligand‐gated ion channel NMDA receptors found in nerve cells. In this review, we summarise the different oxysterols and sterols found in the CNS whose biological activity is transmitted via these different classes of protein receptors.
LINKED ARTICLES
This article is part of a themed issue on Oxysterols, Lifelong Health and Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.16/issuetoc
Early life vitamin D plays a prominent role in neurodevelopment and subsequent brain function, including schizophrenic-like outcomes and increasing evidence for an association with autism spectrum disorder (ASD). Here, we investigate how early life vitamin D deficiency during rat pregnancy and lactation alters maternal care and influences neurodevelopment and affective, cognitive and social behaviours in male adult offspring. Sprague-Dawley rats were placed on either a vitamin D control (2195 IU/kg) or deficient diet (0 IU/kg) for five weeks before timed mating, and diet exposure was maintained until weaning of offspring on postnatal day (PND) 23. MRI scans were conducted to assess brain morphology, and plasma corticosterone levels and neural expression of genes associated with language, dopamine and glucocorticoid exposure were characterised at PND1, PND12 and 4 months of age. Compared to controls, vitamin D-deficient dams exhibited decreased licking and grooming of their pups but no differences in pup retrieval. Offspring neurodevelopmental markers were unaltered, but vitamin D-deficient pup ultrasonic vocalisations were atypical. As adults, males that had been exposed to vitamin D deficiency in early life exhibited decreased social behaviour, impaired learning and memory outcomes and increased grooming behaviour, but unaltered affective behaviours. Accompanying these behavioural changes was an increase in lateral ventricle volume, decreased cortical FOXP2 (a protein implicated in language and communication) and altered neural expression of genes involved in dopamine and glucocorticoid-related pathways. These data highlight that early life levels of vitamin D are an important consideration for maternal behavioural adaptations as well as offspring neuropsychiatry.
A recent multicentre, double-blind, randomised, placebo-controlled trial has demonstrated that administration of betamethasone to women with threatened preterm delivery at 34–36 weeks of gestational age reduces the risk of neonatal respiratory morbidity. There is, however, no long-term outcome data on the children, and we believe that it is biologically plausible that this treatment may cause long-term harm through effects on the infant’s brain. Given this, we argue that steroids should not be used in the context of late preterm delivery until evidence of long-term safety is available. This example illustrates some strengths and weaknesses of using ‘levels of evidence’ to grade the empirical support for making clinical decisions.
One of the major advances in perinatal medicine in the last 30 years has been the administration of synthetic glucocorticoids to mothers who are likely to deliver at extreme preterm gestational ages, and this intervention clearly reduces perinatal mortality and severe morbidity.1 A recent multicentre, double-blind, randomised controlled trial (RCT) compared the effects of betamethasone versus placebo among women presenting between 34 and 36 weeks of gestational age with a high probability of delivery.2 The primary outcome was need for respiratory support 3 days after delivery. The rate was 11.6% in steroid-treated children and 14.4% with placebo, yielding a number needed to treat of 35 (95% CI 19 to 259). In addressing the question of whether this trial justifies immediate incorporation of glucocorticoids into the management of threatened delivery at 34–36 weeks, we need to consider both the science of glucocorticoids in pregnancy and the science of clinical trials.
Physiologically, the fetus prepares for birth near term by an increased production of cortisol from the fetal adrenal. The glucocorticoids employed therapeutically to accelerate fetal lung maturation are betamethasone and dexamethasone. The choice is purposeful as both are resistant to 11β-hydroxysteroid dehydrogenase-2 …
11?-Hydroxysteroid dehydrogenase (11?-HSD), which interconverts hormonally active cortisol and inactive cortisone in multiple human tissues, has two distinct isoforms named 11?-hydroxysteroid dehydrogenase 1 (11?-HSD1) and 11?-hydroxysteroid dehydrogenase 2 (11?-HSD2). 11?-HSD2 is an NAD(+)-dependent oxidase which lowers cortisol by converting it to cortisone while 11?-HSD1 mainly catalyzes the reduction which converts cortisone into cortisol. Selective inhibition of 11?-HSD2 is generally detrimental to health because the accumulation of cortisol can cause metabolic symptoms such as apparent mineralocorticoid excess (AME), fetal developmental defects and lower testosterone levels in males. There has been some advances on the study of 11?-HSD2 inhibitors and we think it necessary to make a summary of the characteristics and inhibiting properties of latest 11?-HSD2 inhibitors. As another review on 11?-HSD2 inhibitors has been issued on 2011 (see review (Ma et al., 2011)), this mini-review concerns advances during the last 5 years.
The early life environment is crucial for later life health including mental health and cognitive function. Exposure to glucocorticoids in utero is thought to be a key underlying mechanism. Here we review the evidence from both animal and human studies that alterations in fetal exposure to glucocorticoids impact on fetal brain development with implications for neurodevelopment and life-long mental health and cognitive function.
Background and Objectives
This study aims to investigate the significance of changes in the expression 11β-hydroxysteroid dehydrogenase (11β-HSD) and glucocorticoid receptor (GR) for the development of Kawasaki disease (KD).
Subjects and Methods
Real-time polymerase chain reaction was performed to determine the mRNA expression levels of GR and 11β-HSD in peripheral blood monocytes, both in the acute phase of the disease and after treatment. Western blotting was performed to determine the protein expression levels of GR and 11β-HSD.
Results
The expression levels of GRβ, GRβ, and 11β-HSD1 mRNA in the acute phase were significantly higher than levels at baseline (p<0.01) and after treatment (p<0.05). The 11β-HSD2 mRNA levels were lower in the acute phase than in the normal group (p<0.01), and they were significantly higher after treatment than before (p<0.01). Western blot results were consistent with the real-time PCR results. The coronary artery lesion group exhibited significantly different 11β-HSD2 expression levels from that of the group with normal coronary arteries (p<0.01).
Conclusion
GR and 11β-HSD expression changes in the acute phase of KD are important factors for regulating inflammatory responses in KD.
Fetal glucocorticoid exposure is a key mechanism proposed to underlie prenatal ‘programming’ of adult cardiometabolic and neuropsychiatric disorders. Regulation of fetal glucocorticoid exposure is achieved by the placental glucocorticoid barrier, which involves glucocorticoid inactivation within the labyrinth zone of the murine placenta by 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2). In this chapter the work to determine the role of 11β-HSD2 in the developmental programming of adult behaviour is described. Modeling developmental programming has frequently highlighted changes in feto-placental 11β-HSD2 as a hub for eliciting effects. To explore this concept in detail 11β-HSD2 has been removed globally from mice and the ramifications of this removal has been assessed for neurodevelopment, affective behaviours in adult life, as well as placental development and function. Here the authors highlight the molecular, physiological, behavioural, and imaging techniques used in their research and how this work has led to a refinement of the global 11β-HSD2 knock-out mouse model. Ultimately, this research highlights the importance of 11β-HSD2 as a mediator for eliciting programmed adult health outcomes and will pave the way for generating human impact, such as using placental 11β-HSD2 levels as a biomarker for novel treatments to improve long-term health.
Ziram is a widely used fungicide for crops. Its endocrine disrupting action is largely unknown. 11β-hydroxysteroid dehydrogenases, isoforms 1 (HSD11B1) and 2 (HSD11B2), have been demonstrated to be the regulators of the local levels of active glucocorticoids, which have a broad of physiological actions. In the present study, the potency of ziram was tested for its inhibition of rat and human HSD11B1 and HSD11B2. Ziram showed the inhibition of rat HSD11B1 reductase with IC50 of 87.07 µM but no inhibition of human enzyme at 100 M. Ziram showed the inhibition of both rat and human HSD11B2 with IC50 of 90.26 and 34.93 µM, respectively. Ziram exerted a competitive inhibition of rat HSD11B1 when 11-dehydrocorticosterone was used and a mixed inhibition when NADPH was supplied. Ziram exerted a noncompetitive inhibition of both rat and human HSD11B2 when steroid substrates were used and an uncompetitive inhibition when NAD+ was supplied. Increased DDT concentrations antagonized rat and human HSD11B2 activities, suggesting the cysteine residues are associated with the inhibition of ziram. In conclusion, for human, ziram is a selective inhibitor of HSD11B2, implying that this agent may cause excessive glucocorticoid action in local tissues such as kidney, brain, and placenta.
This study tested whether maternal responsiveness may buffer the child to the effects of maternal depressive symptoms on DNA methylation of NR3C1, 11β-HSD2, and neuroendocrine functioning. DNA was derived from buccal epithelial cells and prestress cortisol was obtained from the saliva of 128 infants. Mothers with depressive symptoms who were more responsive and who engaged in more appropriate touch during face-to-face play had infants with less DNA methylation of NR3C1 and 11β-HSD2 compared to mothers with depressive symptoms who were also insensitive. The combination of exposure to maternal depressive symptoms and maternal sensitivity was related to the highest prestress cortisol levels, whereas exposure to maternal depressive symptoms and maternal insensitivity was related to the lowest prestress cortisol levels.
Epidemiological evidence suggests that early life adversity, as marked by lower birth weight, associates with a substantially increased risk of cardiometabolic and neuropsychiatric disorders in later life, so called “fetal programming.” Fetal overexposure to glucocorticoids is a possible basis for this association. Indeed glucocorticoid treatment or maternal stress may reproduce programmed phenotypes in inbred models where genetic differences are minimised.
The placenta and developing fetal organs highly express 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) which catalyses rapid inactivation of cortisol and corticosterone thus forming a functional barrier to cellular glucocorticoid action. By pass, gene deletion or inhibition of 11β-HSD2 reduces birth weight and programmes lasting changes in cardiometabolic and behavioural parameters in the offspring in mammals including humans. In contrast, whilst maternal malnutrition similarly programmes the offspring and also reduces placental 11β-HSD2 levels, the effects appear to be mediated more by premature activation of the fetal hypothalamic-pituitary-adrenal axis than trans-placental passage of maternal glucocorticoids.
At a molecular level, epigenetic alterations, notably in methylation of specific cytosine deoxynucleotide residues in the promoters of target genes, may underpin persisting alterations in cellular gene expression. However, the inconsistency of patterns of methylation and related gene expression, notably in phenotypically similar progeny of a second programmed generation, imply understanding of such processes is far from complete. This emerging biology and its pathophysiological implications is a ripe avenue for future study.
Aim:
To determine predictors for decision-making on a differential approach to choosing glucocorticosteroids (GCS) for children and adolescents with acute lymphoblastic leukemia (ALL).
Subjects and methods:
The analysis covered 1064 primary patients aged to 1 to 18 years with ALL who had been registered at the clinics of Russia and Belorussia in April 2002 to November 2006. Before induction therapy, the patients were randomized into a dexamethasone (DEXA) 6 mg/m2 group (n=539) and a methylprednisolone (MePRED) 60 mg/m2 one (n=525).
Results:
The entire group showed no statistically significant differences in survival rates between the patients receiving DEXA or MePRED. However, an analysis of age groups revealed the benefits of DEXA in children younger than 14 years (the event-free survival (EFS) was 76±2 and 71±2%, respectively (p=0.048); the overall survival (OS) was 81±2 and 77±2%, respectively (p=0.046); therapy-induced mortality was 6.4% (DEXA) andl 1.1% (MePRED) (p=0.01 4); the rate of isolated extramedullary relapses was 1.5% (DEXA) and 4.4% (MePRED) (p=0.009). At the same time, EFS and OS in 14-to-18-year-old adolescents were statistically significantly higher than in those who used MePRED (EFS, 65±6 and 52±6%, respectively (p=0.087); OS, 72±6 and 61±6%, respectively; (p=0.l 7).
Conclusion:
The findings suggest that it is possible that the choice of a GCS for ALL therapy must be also based on a patient's age. There is a need for further studies of this matter in prospective randomized multicenter trials in children and adolescents.
Circulating glucocorticoid (GC) levels are controlled by the Hypothalamo-Pituitary-Adrenal (HPA) axis, but within tissues, GC availability is controlled by the isoforms of 11β (Beta)-Hydroxysteroid Dehydrogenase 11β (Beta)-HSD that interconvert inactive cortisone and active cortisol. Two isoforms have been identified; in key metabolic target tissues (including liver and adipose), expression of 11β (Beta)-HSD1 predominates that in vivo converts cortisone to cortisol and thus amplifies local GC action. In contrast, in mineralocorticoid target tissues 11β (Beta)-HSD2 is the isoform that is most abundantly expressed. This inactivates cortisol to cortisone and offers protection for the mineralocorticoid receptor form occupation and activation by cortisol. Dysregulated 11β (Beta)-HSD1 activity has been implicated in many metabolic diseases such as obesity and diabetes and inhibition of 11β (Beta)-HSD1 represents a promising therapeutic target. Mutations within the gene encoding 11β (Beta)-HSD2 cause the Syndrome of Apparent Mineralocorticoid Excess and decreases in activity are linked to hypertension as well as impairment in placental function and neonatal growth. We will discuss the molecular biology and enzymology of 11β (Beta)-HSD and its role in normal physiology and discuss altered 11β (Beta)-HSD activity in pathological states and the potential for therapeutic targeting.
Although a strong connection between chronic pain and mental health disorders has long been recognized by clinicians, by researchers, and even by many patients themselves, the specific nature of this relationship has been poorly understood. Clinicians’ assumptions about the direction of causality between psychiatric syndromes and physical symptoms can greatly impact quality of patient evaluation and perhaps lead to suboptimal treatment of the patient presenting with pain. Patients’ concerns about the clinician’s assumptions with regard to these issues may lead to underreporting of important and relevant history or symptoms, which in turn may also promote suboptimal care. The common copresentation of chronic pain syndromes and mental health conditions may leave the clinician struggling with a which came first? mindset. Do mental illnesses cause the onset of physical pains or impair one’s ability to cope with physical symptoms? Or, alternatively, does unrelenting physical discomfort lead to the onset of psychological symptoms and the development of psychiatric disorders such as major depression? A clinician’s approach to the patient and choice of interventions may be dramatically altered when working with the understanding that a shared biological etiopathology can produce either a chronic pain syndrome or a psychiatric disorder or, perhaps more commonly, a presentation with features of both these conditions.
Despite the tremendous interest in understanding the effects of prenatal stress on fetal health and the programming of adult disease risk, the adaptive functions of hypothalamic–pituitary–adrenal (HPA) axis activity in healthy pregnancies and during lactation have been less widely considered. Existing research has addressed the influence of glucocorticoids on altered patterns of fetal growth and development in humans (Kuzawa and Sweet 2009; Seckl and Holmes 2007; Sloboda et al. 2005; 2009a, b) and the effects of prenatal stress in animal models, particularly with respect to offspring birth weight and stress reactivity (Drake et al. 2005; Neumann 2001; Seckl and Meaney 2004). With several important exceptions, the majority of this research has invoked the concept of “maternal stress” to encapsulate the premise that maternal activation of the HPA axis is associated with adverse birth outcomes, without the simultaneous acknowledgment that progressive elevation of the maternal HPA activity across the course of pregnancy is part of an anthropoid-typical pattern of neuroendocrine activity (Bowman et al. 2001; Smith et al. 1999). Even less is known about the HPA dynamics of pregnancy in non-Western populations with distinct infectious disease ecologies and marginal energetic status (Nyberg 2012). Given the human reproductive strategy of giving birth to secondarily altricial infants (Martin 2007), basal glucocorticoids may play a pivotal role in facilitating parturition and accelerating fetal tissue maturation in coordination with the timing of birth (Power and Schulkin 2006; Pike 2005; Smith et al. 2001). These constraints on the duration of gestation may be imposed, in part, by the metabolic demands of pregnancy (Ellison 2001, 2003; Martin 1996) and are further impacted by the obstetrical dilemma, imposed by the “tight fit” between fetal head circumference and the maternal pelvis that occurred as a result our hominin transition to obligate bipedalism (Rosenberg 2001; Rosenberg and Trevathan 1996). As a result, human birth is physiologically stressful, even by primate standards (Leigh 2004; Martin 1996; Rosenberg 2001; Rosenberg and Trevathan 1996).
Foetal growth restriction (FGR), reflective of an adverse intrauterine environment, confers a significantly increased risk of perinatal mortality and morbidity. In addition, low birthweight associates with adult diseases including hypertension, metabolic dysfunction and behavioural disorders. A key mechanism underlying FGR is exposure of the foetus to glucocorticoids which, while critical for foetal development, in excess can reduce foetal growth and permanently alter organ structure and function, predisposing to disease in later life. Foetal glucocorticoid exposure is regulated, at least in part, by the enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), which catalyses the intracellular inactivation of glucocorticoids. This enzyme is highly expressed within the placenta at the maternal-foetal interface, limiting the passage of glucocorticoids to the foetus. Expression of 11β-HSD2 is also high in foetal tissues, particularly within the developing central nervous system. Down-regulation or genetic deficiency of placental 11β-HSD2 is associated with significant reductions in foetal growth and birth weight, and programmed outcomes in adulthood. To unravel the direct significance of 11β-HSD2 for developmental programming, placental function, neurodevelopment and adult behaviour have been extensively investigated in a mouse knockout of 11β-HSD2. This review highlights the evidence obtained from this mouse model for a critical role of feto-placental 11β-HSD2 in determining the adverse programming outcomes.
The hippocampus of the rat loses neurons with age, a loss which may eventuate in some of the functional impairments typical of senescence. Cumulative exposure to corticosterone (CORT) over the lifespan may be a cause of this neuronal loss, as it is prevented by adrenalectomy at mid- age. In this study, we demonstrate that prolonged exposure to CORT accelerates the process of cell loss. Rats were injected daily with sufficient CORT to produce prolonged elevations of circulating titers within the high physiological range. Animals treated for 3 months (chronic subjects) resembled aged rats in a number of ways. First, both groups had extensive and persistent depletions of CORT receptors in the hippocampus; in the case of chronic rats, no recovery of receptor concentrations occurred 4 months after the end of steroid treatment. Second, autoradiographic analysis revealed that the receptor depletion was due, in part, to a loss of CORT-concentrating cells, especially in the CA3 cell field. Remaining cells bound significantly less [3H]corticosterone than did those of control rats. Finally, analysis of size distributions of hippocampal cell bodies indicated that chronic subjects lost neurons of the same size as those lost in the aged hippocampus. Furthermore, chronic subjects also had increased numbers of small, darkly staining cells of CA3; these corresponded in size to the dark glia whose numbers increase in the aged hippocampus, and which are thought to infiltrate in response to neuronal damage or destruction. Thus, this study supports the hypothesis that cumulative exposure to CORT over the lifespan may contribute to age-related loss of neurons in the hippocampus, and that prolonged stress or exposure to CORT accelerates this process.
Glucocorticoids (GCs) act via intracellular mineralocorticoid (MR) and glucocorticoid receptors (GR). However, it has recently been recognized that GC access to receptors is determined by the presence of tissue-specific 11beta-hydroxysteroid dehydrogenases (11beta-HSDs) that catalyze the interconversion of active corticosterone and inert 11-dehydrocorticosterone. 11beta-HSD type 1 (11beta-HSD1) is a bidirectional enzyme in vitro that acts predominantly as a reductase (regenerating corticosterone) in intact neurons. In contrast, 11beta-HSD type 2 (11beta-HSD2) is a higher affinity exclusive dehydrogenase that excludes GCs from MR in the kidney, producing aldosterone-selectivity in vivo. We have examined the ontogeny of 11beta-HSD mRNAs and enzyme activity during prenatal brain development and correlated this with GR and MR mRNA development. These data reveal that (1) 11beta-HSD2 mRNA is highly expressed in all CNS regions during midgestation, but expression is dramatically reduced during the third trimester except in the thalamus and cerebellum; (2) 11beta-HSD2-like activity parallels closely the pattern of mRNA expression; (3) 11beta-HSD1 mRNA is absent from the CNS until the the third trimester, and activity is low or undectectable; and (4) GR mRNA is highly expressed throughout the brain from midgestation, but MR gene expression is absent until the last few days of gestation. High 11beta-HSD2 at midgestation may protect the developing brain from activation of GR by GCs. Late in gestation, repression of 11beta-HSD2 gene expression may allow increasing GC activation of GR and MR, permitting key GC-dependent neuronal and glial maturational events.
This study examined the consequences of elevated corticosterone levels in lactating rats on their offspring's serotonergic 5-hydroxytryptamine (5-HT)1A receptor system and behavioral coping with stress. The mothers received normal drinking water or water with corticosterone, which, via the milk, enters the circulation and brains of the pups. In adulthood, the corticosterone-nursed offspring showed a consistently more passive way of coping with environmental challenges. However, they did not seem to be more anxious. Autoradiographic analysis of the 5-HT1A receptor system revealed a decrease in the adult 5-HT1A receptor binding in the hippocampal CA1 region. The results support the hypothesis that differences in behavioral coping with stress by adult rats are associated with differences in the serotonergic system. At the same time, it suggests that adult coping and its neuronal substrates are not solely determined by genes but depend on subtle developmental factors as well.
The hippocampus of the rat loses neurons with age, a loss which may eventuate in some of the functional impairments typical of senescence. Cumulative exposure to corticosterone (CORT) over the lifespan may be a cause of this neuronal loss, as it is prevented by adrenalectomy at mid-age. In this study, we demonstrate that prolonged exposure to CORT accelerates the process of cell loss. Rats were injected daily with sufficient CORT to produce prolonged elevations of circulating titers within the high physiological range. Animals treated for 3 months (chronic subjects) resembled aged rats in a number of ways. First, both groups had extensive and persistent depletions of CORT receptors in the hippocampus; in the case of chronic rats, no recovery of receptor concentrations occurred 4 months after the end of steroid treatment. Second, autoradiographic analysis revealed that the receptor depletion was due, in part, to a loss of CORT-concentrating cells, especially in the CA3 cell field. Remaining cells bound significantly less [3H]corticosterone than did those of control rats. Finally, analysis of size distributions of hippocampal cell bodies indicated that chronic subjects lost neurons of the same size as those lost in the aged hippocampus. Furthermore, chronic subjects also had increased numbers of small, darkly staining cells of CA3; these corresponded in size to the dark glia whose numbers increase in the aged hippocampus, and which are thought to infiltrate in response to neuronal damage or destruction. Thus, this study supports the hypothesis that cumulative exposure to CORT over the lifespan may contribute to age-related loss of neurons in the hippocampus, and that prolonged stress or exposure to CORT accelerates this process.
Both serotonergic dysfunction and glucocorticoid hypersecretion are implicated in affective and eating disorders. The adverse effects of serotonergic (5-HT)2C receptor activation on mood and food intake, the antidepressant efficacy of 5-HT2 receptor antagonists, and the hyperphagia observed in 5-HT2C receptor knockout mice all suggest a key role for increased 5-HT2C receptor-mediated neurotransmission. Glucocorticoids, however, downregulate 5-HT2C receptor mRNA in the hippocampus, and it is unclear how increased 5-HT2C receptor sensitivity is achieved in the presence of elevated glucocorticoid levels in depression. Here we show a monophasic diurnal rhythm of 5-HT2C receptor mRNA expression in the rat hippocampus that parallels time-dependent variations in 5-HT2C receptor agonist-induced behaviors in open field tests. Rats entrained to chronic food restriction show marked but intermittent corticosterone hypersecretion and maintain an unaltered 5-HT2C receptor mRNA rhythm. The 5-HT2C receptor mRNA rhythm, however, is suppressed by even modest constant elevations of corticosterone (adrenalectomy + pellet) or with elevated corticosterone during the daytime (8 A.M.), whereas a normal rhythm exists in animals that have the same dose of corticosterone in the evening (6 P.M.). Thus, animals showing even a transient daytime corticosterone nadir exhibit normal hippocampal 5-HT2C receptor mRNA rhythms, even in the presence of overt corticosterone hypersecretion. Chronic food restriction also abolishes the normal diurnal variation in hippocampal glucocorticoid receptor (GR) and mineralocorticoid receptor mRNAs and produces, unusually, both elevated corticosterone and increased GR. The mismatch between elevated glucocorticoids and maintained 5-HT2C receptor and increased GR gene expression in the hippocampus provides a new model to dissect mechanisms that may underlie affective and eating disorders.
Deficiency of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) in humans leads to the syndrome of apparent mineralocorticoid excess (SAME), in which cortisol illicitly occupies mineralocorticoid receptors, causing sodium retention, hypokalemia, and hypertension. However, the disorder is usually incompletely corrected by suppression of cortisol, suggesting additional and irreversible changes, perhaps in the kidney. To examine this further, we produced mice with targeted disruption of the 11beta-HSD2 gene. Homozygous mutant mice (11beta-HSD2(-/-)) appear normal at birth, but approximately 50% show motor weakness and die within 48 hours. Both male and female survivors are fertile but exhibit hypokalemia, hypotonic polyuria, and apparent mineralocorticoid activity of corticosterone. Young adult 11beta-HSD2(-/-) mice are markedly hypertensive, with a mean arterial blood pressure of 146 +/- 2 mmHg, compared with 121 +/- 2 mmHg in wild-type controls and 114 +/- 4 mmHg in heterozygotes. The epithelium of the distal tubule of the nephron shows striking hypertrophy and hyperplasia. These histological changes do not readily reverse with mineralocorticoid receptor antagonism in adulthood. Thus, 11beta-HSD2(-/-) mice demonstrate the major features of SAME, providing a unique rodent model to study the molecular mechanisms of kidney resetting leading to hypertension.
This review examines the risk/benefit ratio of postnatal steroid treatment in preterm infants and correlates epidemiological data with experimental evidence on the effect of glucocorticosteroids on brain development.
We studied the outcomes at school age in children who had participated in a double-blind, placebo-controlled trial of early postnatal dexamethasone therapy (initiated within 12 hours after birth) for the prevention of chronic lung disease of prematurity.
Of the 262 children included in the initial study, 159 lived to school age. Of these children, 146 (72 in the dexamethasone group and 74 in the control group) were included in our study. All the infants had had severe respiratory distress syndrome requiring mechanical ventilation shortly after birth. In the dexamethasone group, 0.25 mg of dexamethasone per kilogram of body weight was given intravenously every 12 hours for one week, and then the dose was tapered. We evaluated the children's growth, neurologic and motor function, cognition, and school performance.
Children in the dexamethasone group were significantly shorter than the controls (P=0.03 for boys, P=0.01 for girls, and P=0.03 for all children) and had a significantly smaller head circumference (P=0.04). Children in the dexamethasone group had significantly poorer motor skills (P<0.001), motor coordination (P<0.001), and visual-motor integration (P=0.02). As compared with the controls, children in the dexamethasone group also had significantly lower full IQ scores (mean [+/-SD], 78.2+/-15.0 vs. 84.4+/-12.6; P=0.008), verbal IQ scores (84.1+/-13.2 vs. 88.4+/-11.8, P=0.04), and performance IQ scores (76.5+/-14.6 vs. 84.5+/-12.7, P=0.001). The frequency of clinically significant disabilities was higher among children in the dexamethasone group than among controls (28 of 72 [39 percent] vs. 16 of 74 [22 percent], P=0.04).
Early postnatal dexamethasone therapy should not be recommended for the routine prevention or treatment of chronic lung disease, because it leads to substantial adverse effects on neuromotor and cognitive function at school age.
We examined the effect of six doses of dexamethasone (Dex) administered daily (2-7 days of age) to postnatal rats on body weight gain, food and water intake, peripheral hormonal/metabolic milieu, and hypothalamic neuropeptides that regulate food intake. We observed a Dex-induced acute (3 days of age) suppression of endogenous corticosterone and an increase in circulating leptin concentrations that were associated with a decrease in body weight in males and females. Followup during the suckling, postsuckling, and adult stages (7-120 days of age) revealed hypoleptinemia in males and females, and hypoinsulinemia, a relative increase in the glucose-to-insulin ratio, and a larger increase in skeletal muscle glucose transporter (GLUT 4) concentrations predominantly in the males, reflective of a catabolic state associated with a persistent decrease in body weight gain. The increase in the glucose-to-insulin ratio and hyperglycemia was associated with an increase in water intake. In addition, the changes in the hormonal/metabolic milieu were associated with an increase in hypothalamic neuropeptide Y content in males and females during the suckling phase, which persisted only in the 120-day-old female with a transient postnatal decline in alpha-melanocyte-stimulating hormone and corticotropin-releasing factor. This increase in neuropeptide Y (NPY) during the suckling phase in males and females was associated with a subsequent increase in adult food intake that outweighed the demands of body weight gain. In contrast to the adult hypothalamic findings, cerebral ventricular dilatation was more prominent in adult males. We conclude that postnatal Dex treatment causes permanent sex-specific changes in the adult phenotype, setting the stage for future development of diabetes (increased glucose:insulin ratio), obesity (increased NPY and food intake), and neurological impairment (loss of cerebral volume).
Prenatal maternal stress has been shown to impair birth outcome and behavioral functioning in nonhuman primate offspring. Little is known about the effects of prenatal stress on behavioral development in humans. We assessed the effect of self-reported prenatal stress on behavioral characteristics of 81 newborns using the Neonatal Behavioral Assessment Scale (NBAS). We suspected that high levels of perceived chronic stress during pregnancy may negatively affect the brain development of the fetus, reflected in poorer behavioral maturity and higher irritability. We found a poorer performance of newborns from high stressed mothers in the NBAS.
Glucocorticoids play important roles in development and 'fetal programming'. Fetal exposure to excess glucocorticoids reduces birth weight and causes later hypertension. To investigate these processes further we have determined the detailed category of 11 beta-hydroxysteroid dehydrogenase type2 (11 beta-HSD2, which potently inactivates glucocorticoids) and the mineralocorticoid receptor (MR) by in situ hybridisation from embryonic day 9.5 (E9.5, term = E19) until after birth in the mouse. Widespread abundant 11 beta-HSD2 mRNA expression from E9.5-E12.5 changes dramatically at approximately E13 to a limited tissue-specific pattern (kidney, hindgut, testis/bile ducts, lung and a few brain regions (later seen in cerebellum, thalamus, roof of midbrain, neuroepithelial regions in pons and near the subicular hippocampus)). Placenta (labyrinthine zone) and extra-embryonic membranes express abundant 11 beta-HSD2 mRNA until E15.5 but this ceases = E16.5. It is unclear to what extent rodent term placental 11 beta-HSD activity is due to persisting 11 beta-HSD2 protein. Convincing MR mRNA expression is seen from E13.5 and includes pituitary, heart, muscle and meninges with expression later in gut, kidney, thymus, discrete areas of lung and several brain regions (including hippocampus, rhinencephalon and hypothalamus). 11 beta-HSD2 and MR clearly co-localise = E18.5 in kidney and colon and might do so in discrete areas of lung (E14-15) and neuroepithelia near the subicular hippocampus. Probably elsewhere MR are non-selective and 11 beta-HSD2 is involved in protecting glucocorticoid receptors in fetal fetal tissues. Comparison with previous enzymology studies suggest the changing pattern of 11 beta-HSD2 mRNA is likely to be translated into enzyme activity and have significant parallels in human development.
The development of the cerebellar cortex was studied in rats treated neonatally (days 1–4) with hydrocortisone. Effects on the external granular layer (EGL) and development of the cerebellar laminæ in lobule VIII were determined by quantitative light-microscopic methods. The 'birthdays' and numbers of various interneurons generated from the EGL were determined autoradiographically in rats injected with 3H-thymidine on days 1,2,5,7,10,15,21 or 24, and sacrificed on day 72. The growth of the EGL and the mitotic index were reduced during the hydrocortisone treatment, but rebounded following termination of the treatment. Nevertheless, the total number of cells produced by the EGL did not recover to control values and the disappearance of the EGL was not prolonged. In treated rats sacrificed at 72 days, the cerebellar foliation pattern in sagittal sections of vermis was reproducibly changed. In lobule VIII, the total area and areas of the molecular layer and internal granular layer were decreased by 14, 17 and 12%, respectively. The total numbers of all postnatally formed interneurons were decreased by this hormonal treatment, but the number of stellate cells in the outer molecular layer was most affected. During the treatment, greater proportions of both granule cells and interneurons in the inner molecular layer (mainly basket cells) completed early final cell divisions. However, 'birthdays' for the majority of granule cells were delayed probably as a result of increased cell proliferation in the EGL following release from the HCA treatment. Stellate cell birthdays were unaffected. The developmental consequences following this hormonal manipulation are discussed with respect to possible glucocorticoid actions. The implications of these results for normal rat cerebellar development are also considered.
Unlike the majority of mammalian brain regions, the rat dentate gyrus undergoes maximal cell birth and cell death during the same developmental time period. Granule cell birth and death peak at the end of the first postnatal week. We have found that manipulations of glucocorticoid levels during the stress hyporesponsive period profoundly influence the density of pyknotic cells in the dentate gyrus while apparently not affecting the density of healthy cells. This raises the possibility that glucocorticoids are regulating processes in addition to cell death, i.e., cell birth. In order to determine whether increases in circulating glucocorticoids or mineralocorticoids affect the birth of cells in the developing dentate gyrus, 3H-thymidine autoradiography was performed on brains of rat pups treated with either corticosterone or aldosterone during the first postnatal week. Quantitative analysis of 3H-thymidine-labelled cells revealed significant decreases in the density of labelled cells in the granule cell layers with both corticosterone and aldosterone treatment. In these same brains, significant decreases in the density of pyknotic cells were also observed in the granule cell layers. However, no changes in the numbers of 3H-thymidine-labelled pyknotic cells were observed with any treatment. Increases in circulating corticosterone or aldosterone resulted in significant increases in the density of both 3H-thymidine-labelled and pyknotic cells in the hilus. These results suggest that dentate gyrus cell birth and cell death are related and that these processes are regulated by adrenal steroids.
We have used Golgi-impregnated tissue to demonstrate that exposure to excess glucocorticoids alters dendritic morphology in a specific population of neurons in the adult rat hippocampus. Daily injection of 10 mg of corticosterone for 21 days resulted in decreased numbers of apical dendritic branch points and decreased total apical dendritic length measured in a 100-μm-thick section in CA3 pyramidal cells compared to sham-injected and non-injected controls. In contrast, no changes were observed in CA3 pyramidal cell basal dendritic morphology. Furthermore, no changes were observed in the dendritic morphology of CA1 pyramidal cells or granule cells of the dentate gyrus. Cross-sectional cell body area of any of the 3 cell types examined in this study was unaffected by corticosterone treatment. Finally, qualitative analysis of Nissl-stained tissue from the same brains revealed increased numbers of darkly staining, apparently shrunken CA3 pyramidal cells in corticosterone treated compared to control brains. The changes in dendritic morphology we have observed may be indicative of neurons in the early stages of degeneration, as prolonged exposure to high levels of corticosterone has been shown by others29 to result in a loss of CA3 pyramidal cells. Additionally, these results suggest possible structural alterations which may occur under physiological conditions in which corticosterone levels are chronically elevated such as in aged animals.
Repeated stress induces atrophy, or remodeling, of apical dendrites in hippocampal CA3 pyramidal neurons. In rats, the stress effect is blocked by adrenal steroid synthesis inhibitors, and mimicked by daily injection of corticosterone. We report that non-invasive administration of corticosterone in the drinking water (400 μg/ml) also produced atrophy of apical dendrites in CA3. Unexpectedly, the combination of daily stress and oral corticosterone negated the effects of either treatment alone, and no changes in the apical dendritic length or branching pattern of CA3 pyramidal neurons were observed compared to control unstressed rats.
Thyroxine and cortisol were tested to determine their effects on the ontogenetic pattern of ornithine decarboxylase (ODC) (EC 4.1.1.17) activity in rat brain. The effects of both hormones were significant, but varied with the brain region studied and with the age of the rat. Thyroxine (1 μg/g body wt/day injected i.p. × 3) altered ODC activity in all brain regions studied, if given during the first 10 postnatal days The overall effect was to compress the time course in which ODC activity passed through its ontogenetic pattern; both the peak in activity and the drop to the characteristic low adult activity level occurred earlier and were accelerated. The magnitude of the response to thyroxine was greater in the cerebellum, followed by the cerebrum and brainstem respectively. Cortisol, when given on the first postnatal day (0.5 mg i.p. × 1), initially depressed ODC activity and subsequently prolonged the time required to reach the low level of activity found normally in adult brain. The magnitude of the response to cortisol generally was greater than that of thyroxine, except in the cerebellum. The effects of these hormones on the ontogenetic pattern of ODC activity are consistent with previously observed effects in rats both on biochemical parameters, e.g. polyamine content and nucleic acid synthesis, and behavioral parameters, e.g. development of swimming ability. Our data are consistent with the hypothesis that thyroxine and cortisol, when administered to the neonate, may exert some of their effects on nucleic acid metabolism and ultimately growth, development and behaviour via their effects on polyamine metabolism.
Short (5 days)- to long-term (4 months) corticosterone (CORT) administration by injection, pellet implantation, or in the drinking water decreased glial fibrillary acidic protein (GFAP) by 20-40% in hippocampus and cortex of intact rats. In contrast to CORT, adrenalectomy (ADX) caused elevations (50-125%) in hippocampus and cortex GFAP within 12 days of surgery that persisted for at least 4 months. CORT replacement of ADX rats decreased GFAP amount in hippocampus and cortex. The effects of long-term CORT and ADX on GFAP in hippocampus and cortex were also seen in striatum, midbrain, and cerebellum, findings suggestive of brain-wide adrenal steroid regulation of this astrocyte protein. The changes in GFAP amount due to CORT and ADX were paralleled by changes in GFAP mRNA, indicating a possible transcriptional or at least genomic effect of adrenal steroids. Glucocorticoid regulation of GFAP was relatively specific; it could not be generalized to other astrocyte proteins or other major structural proteins of neurons. The negative regulation of GFAP and GFAP mRNA by adrenal steroids suggested that increases in GFAP that result from brain injury may be attenuated by glucocorticoids. However, chronic CORT treatment of intact rats did not reverse or reduce the large increases in GFAP caused by trauma- or toxicant-induced brain damage. Thus, glucocorticoids and injury appear to regulate the expression of GFAP through different mechanisms. In contrast to the lack of effects of CORT on brain damage-induced increases in GFAP, CORT treatment begun in 2-week ADX rats, after an increase in GFAP had time to occur, did reverse the ADX-induced increase in GFAP. These results suggest that the increase in GFAP resulting from ADX is not mediated through an injury-linked mechanism.
In order to determine whether short-term glucocorticoid manipulations influence the morphology and survival of neurons in the adult mammalian hippocampal formation, we performed quantitative analyses of Golgi-impregnated and Nissl-stained tissue from the brains of sham operated male rats, adrenalectomized male rats and adrenalectomized male rats which received corticosterone replacement. Three days after adrenalectomy, massive cell death, as detected by a dramatic increase in number of pyknotic cells, was observed in the granule cell layer of the dentate gyrus. By seven days following adrenalectomy, the numbers of pyknotic cells were even greater. Moreover, significant decreases in cross-sectional cell body area and numbers of dendritic branch points of Golgi-impregnated dentate gyrus granule cells were detected at seven days after adrenalectomy. Replacement of corticosterone to adrenalectomized rats prevented the appearance of large numbers of pyknotic cells as well as the decrease in granule cell cross-sectional cell body area and the numbers of dendritic branch points. In contrast, no obvious signs of degeneration were detected in the pyramidal cell layers of the CA1 and CA3 regions of the hippocampus at either three or seven days following adrenalectomy. In addition, no significant changes in morphological characteristics were observed in CA1 or CA3 pyramidal cells with adrenalectomy. These results show that dentate gyrus granule cells require glucocorticoids for their survival and for the maintenance of normal morphology and suggest that granule cell morphology and/or survival may undergo constant fluctuation in response to diurnal rhythms or stress-induced changes in glucocorticoid levels.
In vitro the mineralocorticoid receptor is non-specific and does not distinguish between aldosterone and cortisol. In vivo certain tissues with this receptor are aldosterone selective (eg, kidney and parotid) whereas others with the same receptor are not (eg, hippocampus and heart). Experiments in rats showed that 11 beta-hydroxysteroid dehydrogenase (which converts cortisol to cortisone in man and corticosterone to 11-dehydrocorticosterone in the rat) was much more highly concentrated in aldosterone-selective tissues than in non-selective tissues. The localisation in the selective tissues was such that the enzyme could act as a paracrine or possibly an autocrine mechanism protecting the receptor from exposure to corticosterone. Autoradiographic studies showed that protection is lost when the enzyme is inhibited; 3H-corticosterone and 3H-aldosterone were bound to similar sites. These findings seem to explain why sodium retention, hypokalaemia, and hypertension develop in subjects with congenital deficiency of 11 beta-OHSD and those in whom the enzyme has been inhibited by liquorice.
The neonatal rat shows a period of decreased responsiveness to noxious stimuli during the first 3 weeks of life, but the nature of this impairment is still controversial. To test the functionality of the hypothalamus-pituitary-adrenal axis during this period, we studied pituitary and adrenal responsiveness to exogenous ovine CRF and the ability of various stressors (ether vapors, electroshocks, and hypoxia) to elicit ACTH and corticosterone secretion. We also measured hypothalamic CRF content and pituitary ACTH content as well as CRF-binding sites in the anterior pituitary. From days 3-10, small elevations in plasma ACTH and corticosterone levels were observed after a 3-min exposure to ether vapors or electroshocks. In contrast, during this period, a 20-min exposure to hypoxia (5% O2 in N2) was unable to trigger measurable ACTH secretion, while corticosterone was significantly elevated. From days 14-21, plasma ACTH and corticosterone levels increased significantly after exposure to ether stress, hypoxia, and, to a lesser extent, electroshocks. By contrast, administration of urethane (1.2 g/kg BW) caused a significant increase in ACTH secretion on days 3, 5, and 10, an effect that was partially suppressed by pretreatment with an anti-CRF serum. This suggests that endogenous CRF can be released by at least some stimuli as early as day 3. Direct stimulation of the pituitary with synthetic oCRF (10 micrograms/kg BW) caused significant elevations in plasma ACTH levels at all ages tested (days 3 through 21), though these increases were significantly (P less than or equal to 0.01) smaller on day 3 (2.7-fold) than on day 21 (4.3-fold). Hypothalamic CRF content as well as ACTH content increased gradually with age, but the values reached by the third week of life were still low compared to the values on day 45. Finally, anterior pituitary CRF-binding sites averaged 317 +/- 48 fmol/mg protein on day 5 and 158 +/- 22 fmol/mg protein on day 17. The affinity (Kd) of the receptor for CRF was not significantly different on day 5, 17, or 45. These results show that although pituitary corticotrophs appear to be functional at birth, exposure to stress does not elicit marked increases in plasma ACTH until day 14 of age.
This chapter provides an overview of the current understanding of the dynamics of the hypothalamuspituitary-adrenal (HPA) system in the adult rat. The chapter particularly emphasizes on the role of glucocorticoid receptors in this process. In the adult organism, glucocorticoids (GCs) serve a wide variety of regulatory and permissive functions, aimed basically at controlling the organism's responses to stress, and at regulating circadian-driven activities. The principal GC synthesized by the rat adrenal cortex is corticosterone (CORT). CORT levels display a pronounced circadian rhythmicity: they are highest immediately preceding the animal's active period, and lowest at the end of this period. During development, however, GCs have also been shown to produce, in experimental animals, permanent effects on growth and differentiation of a number of systems, including the central nervous system. In rats, for example, high doses of GCs administered neonatally cause a decrease in mitosis and myelination, as well as altered neural morphogenesis. In addition, the chapter also reviews some of the relevant human literature and considers the implications of animal studies for the field of human functional teratology.
Rats were injected with hydrocortisone acetate on postnatal days 1–4 and the genesis of granule cells in the dentate gyrus was followed by autoradiographic techniques using tritiated thymidine. In short-survival autoradiographic experiments, the number of cells labeled by [3H] thymidine throughout the dentate hilus and stratum granulosum was decreased during and immediately after hydrocortisone treatment, but recovered to control values during the second week. Growth of this region was retarded as indicated by a 20% reduction in volume of the stratum granulosum at 7 days and 14% deficit in de-oxyribonucleic acid content in the whole hippocampus on days 4–6. At 60 days, however, the volume of the stratum granulosum in treated rats was not significantly different from that of controls.Granule cell ‘birthdays’ at dorsal and ventral levels of the hippocampus were investigated by longsurvival autoradiography in treated and control groups. Dorsally, the pattern of granule cell birthdays over the first 3 postnatal weeks was not significantly affected. Ventrally, granule cell genesis in treated rats was significantly depressed on day 5 when that in controls was maximal. This delayed the peak of granule cell birthdays at this level by several days.These experiments demonstrate that the rate and pattern of postnatal granule cell genesis in the rat hippocampus are altered by neonatal glucocorticoid treatment. Specific effects are compared to those previously reported for cerebellar neurogenesis in the glucocorticoid-treated rat.
In the present study we performed a light microscopic anatomical comparison of adrenalectomy (ADX)-induced neurodegeneration using silver impregnation and reaction of astroglial cells using GFAP immunocytochemistry in the hippocampus of the rat. Three survival times following ADX were studied: 24 hours, 3 days, and 3 weeks. Twenty-four hours following ADX we found no degenerative changes or altered GFAP immunostaining. Three days after adrenalectomy, argyrophilic somata appeared in the granular cell layer of the dentate gyrus. Argyrophilic dendrites were seen in the molecular layer of the dentate gyrus and neuritic argyrophilia were seen in the mossy fiber layer. Induction of GFAP immunoreactivity occurred simultaneously with degeneration. Increased GFAP immunoreactivity could be observed 3 days after adrenalectomy in the molecular layer of the dentate gyrus, granular cell layer, sub and supragranular cell layer, and mossy fiber layer. Size and shape of astroglial cells were changed, and their processes in the molecular layer changed from unidirectional to randomly organized. Degeneration and astroglial reaction were more pronounced 3 weeks after adrenalectomy and both were prevented by adding corticosterone to the drinking solution. Animals that did not show degenerative changes showed no increased GFAP immunoreactivity, while both effects were confined to the dentate gyrus and mossy fiber zone. These results show that there is a close relationship between the induction of GFAP immunoreactivity in the hippocampus of the rat and neuronal degeneration in the dentate gyrus following ADX, both in time and space.
Glucocorticoids play important roles in development and 'fetal programming'. Fetal exposure to excess glucocorticoids reduces birth weight and causes later hypertension. To investigate these processes further we have determined the detailed category of 11 beta-hydroxysteroid dehydrogenase type2 (11 beta-HSD2, which potently inactivates glucocorticoids) and the mineralocorticoid receptor (MR) by in situ hybridisation from embryonic day 9.5 (E9.5, term = E19) until after birth in the mouse. Widespread abundant 11 beta-HSD2 mRNA expression from E9.5-E12.5 changes dramatically at approximately E13 to a limited tissue-specific pattern (kidney, hindgut, testis/bile ducts, lung and a few brain regions (later seen in cerebellum, thalamus, roof of midbrain, neuroepithelial regions in pons and near the subicular hippocampus)). Placenta (labyrinthine zone) and extra-embryonic membranes express abundant 11 beta-HSD2 mRNA until E15.5 but this ceases = E16.5. It is unclear to what extent rodent term placental 11 beta-HSD activity is due to persisting 11 beta-HSD2 protein. Convincing MR mRNA expression is seen from E13.5 and includes pituitary, heart, muscle and meninges with expression later in gut, kidney, thymus, discrete areas of lung and several brain regions (including hippocampus, rhinencephalon and hypothalamus). 11 beta-HSD2 and MR clearly co-localise = E18.5 in kidney and colon and might do so in discrete areas of lung (E14-15) and neuroepithelia near the subicular hippocampus. Probably elsewhere MR are non-selective and 11 beta-HSD2 is involved in protecting glucocorticoid receptors in fetal fetal tissues. Comparison with previous enzymology studies suggest the changing pattern of 11 beta-HSD2 mRNA is likely to be translated into enzyme activity and have significant parallels in human development.
Pituitary-adrenal responses to stress in the neonatal rat have been reported to be substantially reduced compared to older animals (i.e. a stress hyporesponsive period). This supposed period of endocrine quiescence is characterized by reduced stress-induced increases in both plasma ACTH and corticosterone. At the same time a number of authors have noted the decreased plasma corticosteroid-binding globulin (CBG) levels of the neonate, and there is evidence for an increased percentage of free corticosterone as well as age-related changes in the volume of distribution for corticosterone. These findings suggest that the reduced CBG levels might enhance the biological significance of existing glucocorticoid levels, beyond that assumed on the basis of plasma total corticosterone levels. We examined this question by estimating hippocampal glucocorticoid receptor occupancy and ‘translocation’ in Day 6, Day 15, and adult animals under basal and stressful conditions. The results showed that: 1) plasma ACTH levels were elevated in Day 6 animals in response to acute exposure to ether, maternal separation, and maternal separation + ether, however, ACTH responses were substantially lower than in Day 15 or adult animals; 2) Plasma total corticosterone levels followed a similar pattern; most noteworthy was the potent glucocorticoid response in Day 15 animals to the combination of maternal separation + ether; 3) Plasma CBG levels in Day 6 animals were extremely low (<3% adult values); by Day 15 CBG levels were about 25% of adult levels. Interestingly, maternal separation was associated with a substantial decrease in plasma CBG levels; 4) Hippocampal glucocorticoid receptor occupancy/translocation was similar at all ages under both basal and stress conditions. The only notable exception occurred during maternal separation in Day 15 animals, where the percentage of hippocampal glucocorticoid receptor occupancy/translocation was higher than that observed at any time in either Day 6 or adult animals. This finding is likely related to the decrease in plasma CBG that occurs following separation of Day 15 pups from the dam.
Thus, despite the higher corticosterone level in the adult, the increase in glucocorticoid receptor occupancy/translocation was generally comparable across all ages either under basal conditions, or following stress. These receptor data underscore the importance of developmental changes in plasma CBG levels.
Placental 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), which converts active cortisol to inactive cortisone, has been proposed to be the mechanism guarding the fetus from the growth retarding effects of maternal glucocorticoids; however, other placental enzymes have also been implicated. Placental 11 beta-HSD is unstable in vitro, and enzyme activity thus detected may not be relevant to the proposed barrier role. We have therefore examined placental glucocorticoid metabolism in dually perfused freshly isolated intact human placentas.
Placentas were obtained from randomly selected normal term deliveries. The maternal circuit was perfused with physiological concentration of cortisol, the fetal effluent collected and steroid metabolites separated and quantified using silica columns (Sep-pak Plus) and HPLC.
Most of the maternally administered cortisol was metabolized to cortisone, and no conversion of cortisone to cortisol was detected. Cortisone was the only product of cortisol metabolism. Inhibition of 11 beta-HSD with glycyrrhetinic acid allowed cortisol to gain direct access to the fetal circulation.
We conclude that human placental 11 beta-HSD plays a crucial role in controlling glucocorticoid access to the fetus. Other enzymes are not significant contributors at physiologically relevant cortisol concentrations.
11 Beta-hydroxysteroid dehydrogenase (11 beta-HSD) catalyses the interconversion of active corticosterone and inert 11-dehydrocorticosterone. The recently discovered type 2 isozyme (11 beta-HSD-2) is a high affinity, NAD-dependent, exclusive 11 beta-dehydrogenase, which rapidly inactivates glucocorticoids. Thus the enzyme generates aldosterone-selectivity for intrinsically non-selective mineralocorticoid receptors in vivo as well as excluding glucocorticoids from glucocorticoid receptors, the latter being particularly important during development. Aldosterone exerts selective central effects upon salt appetite and blood pressure whilst glucocorticoids have potent effects upon postnatal neurogenesis and brain remodelling. We examined 11 beta-HSD-2 expression during postnatal ontogeny and in adult rat brain. High 11 beta-HSD-2 mRNA expression was found specifically in the postnatal thalamus and the external granule cell layer of the cerebellum. Expression peaked at the end of the first postnatal week and declined rapidly thereafter. Postnatal brain showed considerable activity of high affinity 11 beta-HSD-2 which paralleled expression of 11 beta-HSD-2 messenger ribonucleic acid (mRNA). Adult brain showed high 11 beta-HSD-2 mRNA expression limited to the subcommissural organ, with lower expression in the ventromedial nucleus of the hypothalamus, amygdala, locus coeruleus and nucleus tractus solitarius. These discrete areas are compatible with proposed selective central actions of aldosterone on blood pressure (subcommissural organ, nucleus tractus solitarius) and salt appetite (ventromedial nucleus, amygdala). In contrast, early postnatal 11 beta-HSD-2 coincides with glucocorticoid receptor rather than mineralocorticoid receptor expression, and areas of expression are among the regions where glucocorticoids have been demonstrated to have profound effects upon neuronal division, growth and maturation.
From postnatal day (PND) 4 to 14, neonates display a minimal pituitary-adrenal response to mild stress, the so-called 'stress hyporesponsive period' (SHRP). During the SHRP, maternal deprivation (MD) alters the pituitary-adrenal system, enabling neonates to become endocrine responsive to specific stimuli. We have previously reported that during the SHRP, mild stress enhances corticotropin-releasing hormone (CRH) messenger RNA (mRNA) expression in the paraventricular nucleus (PVN). Insofar as elevated CRH mRNA was observed both in the presence and absence of adrenocorticotropin (ACTH) release, we hypothesized that other ACTH secretagogues may participate in the pituitary stress response. During the SHRP, does arginine vasopressin (AVP) complement the actions of CRH which might be reflected centrally by the enhanced biosynthesis of both neuropeptides? To test this hypothesis we examined the time course of stress-induced CRH and AVP mRNA in the PVN at PND 6, 12, and 18. As an index of neural activity, c-fos mRNA in the PVN was also examined. Restraint was used as the stressor and MD was employed to enable an endocrine response during the SHRP. Despite the absence of stress-induced ACTH, in nondeprived pups during the SHRP, CRH mRNA was rapidly enhanced. In their maternally deprived (DEP) counterparts, ACTH levels were increased, and a significant induction of CRH mRNA was only observed at day 12. AVP mRNA levels were elevated in DEP 12-day-old pups at 15, 30 and 60 min. In rats beyond the SHRP, plasma ACTH levels, CRH and AVP mRNA were all enhanced following restraint. At PND 18, elevated CRH mRNA was not observed until 4 h after stimulus. Following restraint, c-fos mRNA was increased at all three ages, although the magnitude of c-fos response was less during the SHRP. These results demonstrate that when restraint elicits prototypical ACTH release, the neonatal central response is to enhance the biosynthesis of both AVP and CRH. If nucleic acid changes correlate with release, the increased synthesis of both neuropeptides may indicate the potential for AVP to synergize with CRH during the neonatal stress response.
The aim of this study was to determine the effects of a clinically relevant single course of prenatal betamethasone in the rat on growth parameters with particular reference to brain cell proliferation and apoptosis. We report that administration of 170 microg kg-1 betamethasone twice within 4 h to E20 pregnant rats conveys moderate somatic growth retardation. Further, using a measure of brain cell proliferation independent of blood-brain barrier (BBB) permeability, we demonstrate for the first time that betamethasone is chronically anti-proliferative to brain cells without inducing caspase-3-mediated apoptosis. More importantly we show that there is a significant and sexually divergent rebound of neural proliferation which occurs earlier in males than in females and continues until at least 21 days of postnatal life. BBB permeability to [3H]thymidine was significantly increased by steroid treatment re-iterating the fact that tracer studies not correcting for BBB permeability, such as bromodeoxyuridine (BrdU), may be questionable in this type of study. Further, prenatal steroid treatment did not alter postnatal corticosterone levels. In summary we show that prenatal betamethasone conveys significant and long-lasting side effects and that its human clinical application in preterm labour needs more careful consideration as compared to the relative ease with which it is prescribed today.
Pregnant rats were exposed to an acute or a repeated stress (presence of a cat) either at the 10th or the 14th gestational day, and the development of their offspring was studied during the first 2 weeks of life. Motor development was measured by different tests: rooting reflex, vibrissae placing response, righting reflex, negative geotaxis. Other landmarks such as eye opening and spontaneous locomotor activity were also recorded. The results showed that, except for the rooting reflex which was most often enhanced (while not significantly) in prenatally stressed rats, the development of the vibrissae placing response, the righting reflex and the negative geotaxis behavior was delayed in the offspring of dams stressed at the 10th gestational day and not (or almost not) in the offspring of dams stressed at the 14th gestational day, the delay being more severe when the prenatal stress was repeated than when it was acutely administered. The spontaneous motor activity was also altered in repeatedly prenatally stressed rats, whatever the day of pregnancy when it was administered, while it was unaffected in acutely prenatally stressed animals. The delay in motor reflexes development was interpreted as alterations in maturation of nervous structures sustaining motor skills, while permanent decrease of spontaneous motor activity was explained by emotional and motivational alterations due to prenatal stress.
Chronic stress produces deficits in cognition accompanied by alterations in neural chemistry and morphology. Medial prefrontal cortex is a target for glucocorticoids involved in the stress response. We have previously demonstrated that 3 weeks of daily corticosterone injections result in dendritic reorganization in pyramidal neurons in layer II-III of medial prefrontal cortex. To determine if similar morphological changes occur in response to chronic stress, we assessed the effects of daily restraint stress on dendritic morphology in medial prefrontal cortex. Male rats were exposed to either 3 h of restraint stress daily for 3 weeks or left unhandled except for weighing during this period. On the last day of restraint, animals were overdosed and brains were stained using a Golgi-Cox procedure. Pyramidal neurons in lamina II-III of medial prefrontal cortex were drawn in three dimensions, and the morphology of apical and basilar arbors was quantified. Sholl analyses demonstrated a significant alteration of apical dendrites in stressed animals: overall, the number and length of apical dendritic branches was reduced by 18 and 32%, respectively. The reduction in apical dendritic arbor was restricted to distal and higher-order branches, and may reflect atrophy of terminal branches: terminal branch number and length were reduced by 19 and 35%. On the other hand, basilar dendrites were not affected. This pattern of dendritic reorganization is similar to that seen after daily corticosterone injections. This reorganization likely reflects functional changes in prefrontal cortex and may contribute to stress-induced changes in cognition.
Maternal deprivation produces persistent abnormalities in behavioral and neuroendocrine functions associated with the hippocampus, a brain region that shows considerable structural change in response to experience throughout life. Here we show that adverse experience early in life affects the regulation of adult neurogenesis in the hippocampus. More specifically, a decrease in cell proliferation and immature neuron production are observed in the dentate gyrus of adult rats that are maternally separated as pups. Although maternally separated rats show normal basal levels of corticosterone, the suppression of cell proliferation in these rats can be reversed by lowering corticosterone below the control value. In addition, normal stress-induced suppression of cell proliferation and neurogenesis, despite normal activation of the hypothalamic pituitary adrenal (HPA) axis, is not observed in maternally separated rats. Our results suggest that early adverse experience inhibits structural plasticity via hypersensitivity to glucocorticoids and diminishes the ability of the hippocampus to respond to stress in adulthood.
The main characteristic of the postnatal development of the stress system in the rat is the so-called stress hypo-responsive period (SHRP). Lasting from postnatal day (pnd) 4 to pnd 14, this period is characterized by very low basal corticosterone levels and an inability of mild stressors to induce an enhanced ACTH and corticosterone release. During the last years, the mouse has become a generally used animal in stress research, also due to the wide availability of genetically modified mouse strains. However, very few data are available on the ontogeny of the stress system in the mouse. This study therefore describes the postnatal ontogeny of peripheral and central aspects of the hypothalamic-pituitary-adrenal (HPA) axis in the mouse. We measured ACTH and corticosterone in blood and CRH, urocortin 3 (UCN3), mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) transcripts in the brain at postnatal days 1, 2, 4, 6, 9, 12, 14 and 16. Our results show that we can subdivide the postnatal development of the HPA axis in the mouse in two phases. The first phase corresponds to the SHRP in the rat and lasts from right after birth (pnd 1) until pnd 12. Basal corticosterone levels were low and novelty exposure did not enhance corticosterone or ACTH levels. This period is further characterized by a high expression of CRH in the paraventricular nucleus (PVN) of the hypothalamus. Expression levels of GR in the hippocampus and UCN3 in the perifornical area are low at birth but increase significantly during the SHRP, both reaching the highest expression level at pnd 12. In the second phase, the mice have developed past the SHRP and were now exhibiting enhanced corticosterone basal levels and a response of ACTH and corticosterone to mild novelty stress. CRH expression was decreased significantly, while expression of UCN3 and GR remained high, with a small decrease at pnd 16. The expression of MR in the hippocampus was very dynamic throughout the postnatal development of the HPA axis and changed in a time and subregion specific manner. These results demonstrate for the first time the correlation between the postnatal endocrine development of the mouse and gene expression changes of central regulators of HPA axis function.
Placental 11-hydroxysteroid dehydrogenase type 2 is the placental barrier to maternal glucocorticoids: ex vivo studies
- R Benediktsson
- Edwards Aa Crw Calder
- Seckl
- Jr
Benediktsson R, Calder AA, Edwards CRW, Seckl JR (1997) Placental 11-hydroxysteroid dehydrogenase type 2 is the placental barrier to maternal glucocorticoids: ex vivo studies. Clin Endocrinol 46: 161–166.
Increased maternal corticosterone levels in rats
- Meerlo
Placental 11β-hydroxysteroid dehydrogenase type 2 is the placental barrier to maternal glucocorticoids
- Benediktsson
Ontogeny of the stress response in the rat
- Walker