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Abstract
Degeneration of dopaminergicrgic neurons in the substantia nigra of the brain is a hallmark of Parkinson's disease and inflammation and oxidative stress are closely associated with the pathogenesis of degenerative neurological disorders. Treatment of rat mesencephalic mixed neuron-glia cultures with lipopolysaccharide (LPS)-activated microglia, resident immune cells of the brain, to release proinflammatory and neurotoxic factors tumor necrosis factor-alpha, interleukin-1beta, nitric oxide, and superoxide and subsequently caused damage to midbrain neurons, including dopaminergic neurons. The LPS-induced degeneration of the midbrain neurons was significantly reduced by cotreatment with naloxone, an opioid receptor antagonist. This study focused on understanding the mechanism of action for the protective effect of naloxone on dopaminergic neurons because of relevance to Parkinson's disease. Both naloxone and its opioid receptor inactive stereoisomer (+)-naloxone protected the dopaminergic neurons with equal potency. Naloxone inhibited LPS-induced activation of microglia and release of proinflammatory factors, and inhibition of microglia generation of superoxide free radical best correlated with the neuroprotective effect of naloxone isomers. To further delineate the site of action, naloxone was found to partially inhibit the binding of [(3)H]LPS to cell membranes, whereas it failed to prevent damage to dopaminergic neurons by peroxynitrite, a product of nitric oxide and superoxide. These results suggest that naloxone at least in part interferes with the binding of LPS to cell membranes to inhibit microglia activation and protect dopaminergic neurons as well as other neurons in the midbrain cultures from inflammatory damage.
... The mu-opioid receptors' (MORs) tolerance is not only agonist-dependent, but it also depends on the opioid dose, the route of administration, the duration of the receptors' exposure and the cellular environment in which receptors are expressed [28,30]. Finally, prolonged opioid treatment activates glial cells in the central nervous system, leading to tolerance development [31][32][33]. Recent studies consider toll-like receptor 4 (TLR4) to play a critical role in mediating opioidinduced glial activation and pro-inflammatory cytokine release [34][35][36]. ...
... Opioid antagonists, such as naloxone and naltrexone, used at ultra-low doses in combination with opioid agonists, can decrease or block the development of opioid tolerance in rodents [21,37,38]. Animal models suggest that naloxone has a biphasic dose-dependent effect on pain and that low doses of opioid antagonist could paradoxically produce analgesia [33]. Although clinical experiences with opioid antagonists combined with opioid agonists in humans show that ultra-low doses of naloxone or naltrexone have some analgesic properties and may reduce opioid tolerance [35][36][37][38], there are no specific studies demonstrating that such drugs can reduce the long-term development of opioid tolerance. ...
... The exact mechanism of the analgesic effect of ultra-low doses of naloxone is not fully understood; however, some suggestions have arisen. In animal models, naloxone was reported to inhibit microglia activation and superoxide generation and thus protect neurons from injuries [33]. Because neuronal apoptosis is a pathological process occurring in opioid tolerance, the neuroprotective effect of naloxone may inhibit opioid tolerance development. ...
Chronic low back pain (CLBP) due to osteoarthritis represents a therapeutic challenge worldwide. Opioids are extensively used to treat such pain, but the development of tolerance, i.e., less susceptibility to the effects of the opioid, which can result in a need for higher doses to achieve the same analgesic effect, may limit their use. Animal models suggest that ultra-low doses of opioid antagonists combined with opioid agonists can decrease or block the development of opioid tolerance. In this retrospective study, we tested this hypothesis in humans. In 2019, 53 patients suffering from CLBP were treated with either Oxycodone and Naloxone Prolonged Release (27 patients, OXN patients) or Oxycodone Controlled Release (26 patients, OXY patients). The follow-up period lasted 2 years, during which 10 patients discontinued the treatment, 5 out of each group. The remaining 43 patients reached and maintained the targeted pain relief, but at 18 and 24 months, the OXY patients showed a significantly higher oxycodone consumption than OXN patients to reach the same level of pain relief. No cases of respiratory depression or opioid abuse were reported. There were no significant differences in the incidence of adverse effects between the two treatments, except for
constipation, more common in OXY patients. From our results, we can affirm that a long-term
opioid treatment with oxycodone-naloxone combination, when compared with oxycodone only,
may significantly hinder the development of opioid tolerance. We were also able to confirm, in our
cohort, the well known positive effect of naloxone in terms of opioid-induced bowel dysfunction
incidence reduction.
... Mounting evidence shows that LPS promotes apoptotic neurodegeneration in adult mice by triggering mitochondrial apoptotic and neuroinflammatory pathways via the upregulation of several apoptotic markers such as Bax, cytochrome C release, caspase-9, and caspase-3 cleavage. Western blot analyses of the hippocampi extracts showed increased protein levels of cytochrome C, cleaved caspase-9, caspase-3, apoptotic protease activating factor 1, and poly (ADP-ribose) polymerase-1, indicating LPS-mediated neural damage in adult mice [49]. Fluoro-Jade B and Nissl staining results revealed that LPS-treated rodents showed increased numbers of damaged, shrunken, and degenerative neuronal cells in the cortex as well as CA1, CA3, and dentate gyrus regions of the hippocampus. ...
... LPS administered into rats was shown to up-regulate cell surface receptor CD14 expression within a specific cellular population including microglial cells by binding to CD14/TLR4 complex [84]. It causes microglial activation and the release of proinflammatory cytokines and neurotoxic factors such as IL-1β, TNF-α, prostaglandins, superoxide, and NO that damage dopaminergic neurons [49] via mitochondrial dysfunction and apoptosis [85,86]. In an in vitro study, intestinal epithelial IEC-6 cells exposed to LPS down-regulated the expression of tight junction proteins ZO-1, occludin, and epithelialcadherin (e-cadherin) [87]. ...
Lipopolysaccharide (LPS) is a cell-wall immunostimulatory endotoxin component of Gram-negative bacteria. A growing body of evidence reveals that alterations in the bacterial composition of the intestinal microbiota (gut dysbiosis) disrupt host immune homeostasis and the intestinal barrier function. Microbial dysbiosis leads to a proinflammatory milieu and systemic endotoxemia, which contribute to the development of neurodegenerative diseases and metabolic disorders. Two important pathophysiological hallmarks of neurodegenerative diseases (NDDs) are oxidative/nitrative stress and inflammation, which can be initiated by elevated intestinal permeability, with increased abundance of pathobionts. These changes lead to excessive release of LPS and other bacterial products into blood, which in turn induce chronic systemic inflammation, which damages the blood–brain barrier (BBB). An impaired BBB allows the translocation of potentially harmful bacterial products, including LPS, and activated neutrophils/leucocytes into the brain, which results in neuroinflammation and apoptosis. Chronic neuroinflammation causes neuronal damage and synaptic loss, leading to memory impairment. LPS-induced inflammation causes inappropriate activation of microglia, astrocytes, and dendritic cells. Consequently, these alterations negatively affect mitochondrial function and lead to increases in oxidative/nitrative stress and neuronal senescence. These cellular changes in the brain give rise to specific clinical symptoms, such as impairment of locomotor function, muscle weakness, paralysis, learning deficits, and dementia. This review summarizes the contributing role of LPS in the development of neuroinflammation and neuronal cell death in various neurodegenerative diseases.
... W. Liu et al., 2013), it could be suggested that naloxone inhibits this process. It has been found that in addition to the effect of naloxone on MOR, naloxone inhibits the binding of lipopolysaccharide (LPS) to the membrane and consequently prevents microglial activation, hence protecting dopaminergic neurons (Liu et al., 2000). Additionally, naloxone prevents the release of proinflammatory factors and superoxide free radicals from microglia F I G U R E 5 The effect of tramadol on synaptophysin and stathmin levels in cultured hippocampal neurons. ...
... loxone for 1 h. The protein levels of synaptophysin (a) and stathmin (b) were evaluated with western blot analysis. Data are presented as means ± SEM (n = 3). **p < .01 versus control, #p < .05, ##p < .01 versus tramadol. p-values were determined with one-way analysis of variance followed by Tukey's post hoc test. and induces its protective effect (B. Liu et al., 2000). Moreover, naloxone could decrease the level of caspase-3 in LPS-induced apoptosis in cultured microglia (Cheng et al., 2014). Our results also revealed that caspase-3, as a crucial protein of the apoptosis pathway, was augmented after tramadol exposure, and naloxone could attenuate it. Thus, it could be concluded that naloxone could pr ...
Tramadol is a synthetic opioid with centrally acting analgesic activity that alleviates moderate to severe pain and treats withdrawal symptoms of the other opioids. Like other opioid drugs, tramadol abuse has adverse effects on central nervous system components. Chronic administration of tramadol induces maladaptive plasticity in brain structures responsible for cognitive function, such as the hippocampus. However, the mechanisms by which tramadol induces these alternations are not entirely understood. Here, we examine the effect of tramadol on apoptosis and synaptogenesis of hippocampal neuronal in vitro. First, the primary culture of hippocampal neurons from neonatal rats was established, and the purity of the neuronal cells was verified by immunofluorescent staining. To evaluate the effect of tramadol on neuronal cell viability MTT assay was carried out. The western blot analysis technique was performed for the assessment of apoptosis and synaptogenesis markers. Results show that chronic exposure to tramadol reduces cell viability of neuronal cells and naloxone reverses this effect. Also, the level of caspase‐3 significantly increased in tramadol‐exposed hippocampal neurons. Moreover, tramadol downregulates protein levels of synaptophysin and stathmin as synaptogenesis markers. Interestingly, the effects of tramadol were abrogated by naloxone treatment. These findings suggest that tramadol can induce neurotoxicity in hippocampal neuronal cells, and this effect was partly mediated through opioid receptors.
... Three days later, 0.5 mL/well of fresh medium was replenished into the cultures. Seven days after seeding, the neuron-glia cultures made up of about 10% microglia, 50% astrocytes, and 40% neurons based on the visual counting of immunostained cells with antibodies against cell-type specific markers: neurons (Neu-N), microglia (OX-42), and astrocytes (GFAP) [28]. The NG cultures were ready for further endotoxin tolerance treatment regimen ( Figure 1A). ...
... Moreover, treated NG cells with cycloheximide, an inhibitor for protein synthesis, was performed to determine involvement of de novo protein synthesis in PGE 2 tolerance of microglia. cytes (GFAP) [28]. The NG cultures were ready for further endotoxin tolerance trea regimen ( Figure 1A). ...
Cellular and molecular mechanisms of the peripheral immune system (e.g., macrophage and monocyte) in programming endotoxin tolerance (ET) have been well studied. However, regulatory mechanism in development of brain immune tolerance remains unclear. The inducible COX-2/PGE2 axis in microglia, the primary innate immune cells of the brain, is a pivotal feature in causing inflammation and neuronal injury, both in acute excitotoxic insults and chronic neurodegenerative diseases. This present study investigated the regulatory mechanism of PGE2 tolerance in microglia. Multiple reconstituted primary brain cells cultures, including neuron–glial (NG), mixed glial (MG), neuron-enriched, and microglia-enriched cultures, were performed and consequently applied to a treatment regimen for ET induction. Our results revealed that the levels of COX-2 mRNA and supernatant PGE2 in NG cultures, but not in microglia-enriched and MG cultures, were drastically reduced in response to the ET challenge, suggesting that the presence of neurons, rather than astroglia, is required for PGE2 tolerance in microglia. Furthermore, our data showed that neural contact, instead of its soluble factors, is sufficient for developing microglial PGE2 tolerance. Simultaneously, this finding determined how neurons regulated microglial PGE2 tolerance. Moreover, by inhibiting TLR4 activation and de novo protein synthesis by LPS-binding protein (LBP) manipulation and cycloheximide, our data showed that the TLR4 signal and de novo protein synthesis are necessary for microglia to develop PGE2 tolerance in NG cells under the ET challenge. Altogether, our findings demonstrated that neuron–microglia contacts are indispensable in emerging PGE2 tolerance through the regulation of TLR4-mediated de novo protein synthesis.
... Evidence of a possible in vitro connection between opioids and TLR4 originates from studies that examined the effects of LPS, the classical TLR4 agonist, on cultured primary brain cells, as well as the ability of opioids to inhibit these effects [21][22][23][24]. Das et al. reported a concentration-dependent increase in the secretion of IL-lβ, upon treating the mixed brain cell cultures of embryonic mice with either LPS or with the endogenous opioid peptide [Met 5 ]-enkephalin [21]. ...
... The non-stereoselective effect of opioids at TLR4 refers to the ability of (+) opioid isomers to interact with TLR4, while opioid receptors are selective for (−) isomers. The inhibitory effects of naloxone isomers on microglial activation, and the inflammatory damage of dopaminergic neurons induced by LPS, have been reported [23]. Treatment of rat mesencephalic neuron-glia cultures with LPS (0.1-100 ng/mL) induced microglial activation, as evidenced by nitrite accumulation and a rise in levels of the pro-inflammatory cytokines TNF-α and IL-1β, and resulted in inflammatory damage, as reflected by a reduction in high affinity dopamine uptake and a decrease in the number of healthy neurons. ...
The innate immune receptor toll-like receptor 4 (TLR4) is known as a sensor for the gram-negative bacterial cell wall component lipopolysaccharide (LPS). TLR4 activation leads to a strong pro-inflammatory response in macrophages; however, it is also recognised to play a key role in cancer. Recent studies of the opioid receptor (OR)-independent actions of opioids have identified that TLR4 can respond to opioids. Opioids are reported to weakly activate TLR4, but to significantly inhibit LPS-induced TLR4 activation. The action of opioids at TLR4 is suggested to be non-stereoselective, this is because OR-inactive (+)-isomers of opioids have been shown to activate or to inhibit TLR4 signalling, although there is some controversy in the literature. While some opioids can bind to the lipopolysaccharide (LPS)-binding cleft of the Myeloid Differentiation factor 2 (MD-2) co-receptor, pharmacological characterisation of the inhibition of opioids on LPS activation of TLR4 indicates a noncompetitive mechanism. In addition to a direct interaction at the receptor, opioids affect NF-κB activation downstream of both TLR4 and opioid receptors and modulate TLR4 expression, leading to a range of in vivo outcomes. Here, we review the literature reporting the activity of opioids at TLR4, its proposed mechanism(s), and the complex functional consequences of this interaction.
... Concomitantly, the mean lengths of TH + neurites or neuronal processes in MPP + -treated Fyn KO neurons were significantly longer than those of MPP + -treated WT neurons ( Figure 3C). We further performed [ 3 H]-DA uptake assays since the functional capacity of DAergic neurons is well correlated with the DA reuptake capacity of their neurites (Liu et al., 2000). For this, we treated WT and Fyn KO primary neurons with 3 and 5 μM MPP + for 48 h. ...
... In agreement with the neuroprotective abilities of SFK inhibition in primary neurons, we observed that primary DAergic neurons derived from Fyn KO mice are protected from MPP + -induced TH + neurite shortening and neuron loss. The health of DAergic neurons is also exemplified by their ability to reuptake DA from the synapse (Liu et al., 2000;Bilsland et al., 2002;Zhang et al., 2007a). We additionally demonstrate that the primary DAergic neurons from Fyn KO mice still retain DA reuptake capacity following MPP + treatment, suggesting that DA transporter proteins also may be functionally intact in the Fyn KO mice. ...
Oxidative stress, neuroinflammation and apoptosis are some of the key etiological factors responsible for dopamin(DA)ergic degeneration during Parkinson’s disease (PD), yet the downstream molecular mechanisms underlying neurodegeneration are largely unknown. Recently, a genome-wide association study revealed the FYN gene to be associated with PD, suggesting that Fyn kinase could be a pharmacological target for PD. In this study, we report that Fyn-mediated PKCδ tyrosine (Y311) phosphorylation is a key event preceding its proteolytic activation in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of Parkinsonism. MPP⁺/MPTP induced Fyn kinase activation in N27 DAergic neuronal cells and the mouse substantia nigra. PKCδ-Y311 phosphorylation by activated Fyn initiates the apoptotic caspase-signaling cascade during DAergic degeneration. Pharmacological attenuation of Fyn activity protected DAergic neurons from MPP⁺-induced degeneration in primary mesencephalic neuronal cultures. We further employed Fyn wild-type and Fyn knockout (KO) mice to confirm whether Fyn is a valid pharmacological target of DAergic neurodegeneration. Primary mesencephalic neurons from Fyn KO mice were greatly protected from MPP⁺-induced DAergic cell death, neurite loss and DA reuptake loss. Furthermore, Fyn KO mice were significantly protected from MPTP-induced PKCδ-Y311 phosphorylation, behavioral deficits and nigral DAergic degeneration. This study thus unveils a mechanism by which Fyn regulates PKCδ′s pro-apoptotic function and DAergic degeneration. Pharmacological inhibitors directed at Fyn activation could prove to be a novel therapeutic target in the delay or halting of selective DAergic degeneration during PD.
... 20 Microglial suppression may operate protectively as well by preventing downstream cascades affecting neurodegenerative diseases. 21 A study of the effect of Naltrexone on inflammation in the collagen-induced arthritis rat model 22 suggests that Naltrexone's beneficial effect on signs and symptoms of arthritis was mediated through opioid receptors on lymphocytes, suggesting the possible role of neuroimmune modulation in chronic pain states. 23,24 Interestingly, the MED of 10 mg/kg/day, was significantly superior to 5 and 20 mg/kg/day doses, once again suggesting a dose specificity being key to successful regulation of the inflammatory biochemical pathways involved, and beneficial effects overall. ...
Purpose
Despite the availability of a wide variety of analgesics, many patients with chronic pain often experience suboptimal pain relief in part related to the absence of any medication to address the nociplastic component of common pain syndromes. Low-dose naltrexone has been used for the treatment of chronic pain, typically at 4.5 mg per day, even though it is also noted that effective doses of naltrexone for chronic pain presentations range from 0.1 to 4.5 mg per day. We performed an observational analysis to determine the range of effective naltrexone daily dosing in 41 patients with chronic musculoskeletal pain.
Methods
Charts of 385 patients, 115 males, 270 females, ages 18–92, were reviewed. Two hundred and sixty patients with chronic diffuse, symmetrical pain were prescribed a titrating dose of naltrexone to determine a maximally effective dose established by self-report of 1) reduction of diffuse/generalized and/or severity level of pain and/or 2) positive effects on mood, energy, and mental clarity. Brief Pain Inventory and PROMIS scales were given pre- and post-determining a maximally effective naltrexone dose.
Results
Forty-one patients met all criteria for inclusion, successfully attained a maximally effective dose, and completed a pre- and post-outcome questionnaire. Hormesis was demonstrated during the determination of the maximally effective dosing, which varied over a wide range, with statistically significant improvement in BPI.
Conclusion
The maximally effective dose of low-dose naltrexone for the treatment of chronic pain is idiosyncratic, suggesting the need for 1) dosage titration to establish a maximally effective dose and 2) the possibility of re-introduction of low-dose naltrexone to patients who had failed initial trials on a fixed dose of naltrexone.
... Clinical and preclinical studies have reported that food reward responses are sensitive to inflammatory mediators, suggesting an influence of pro-inflammatory cytokine profiles in reward perception. A positive correlation between increased proinflamatrory profile such as IL-6, TNF-a and IL-1b and defective reward responses has been previously reported in the context of monetary reward tasks (Eisenberger et al., 2010), pain related inflammation (Elvemo et al., 2015;Taylor et al., 2015), depression and aging (Felger et al., 2016;White et al., 2017), Crohn's disease, psoriasis, complex regional pain syndrome (Kappelmann et al., 2018) Parkinson's disease (Liu et al., 2000;Jiang et al., 2022), drug (Brown et al., 2018), alcohol exposure (Boyadjieva and Sarkar, 2010;Lacagnina et al., 2017) and psychostimulants abuse (Beardsley and Hauser; and also maternal motivation (Aubert et al., 1997). Notably, subjects diagnosed with a reduced reward responsiveness experience pain-related inflammation showed a reduced volume in the NAc (Elvemo et al., 2015; Taylor et al., 2015). ...
Accumulation of white adipose tissue (WAT) during obesity is associated with the development of chronic low-grade inflammation, a biological process known as lipoinflammation. Systemic and central lipoinflammation accumulates pro-inflammatory cytokines including IL-6, IL-1β and TNF-α in plasma and also in brain, disrupting neurometabolism and cognitive behavior. Obesity-mediated lipoinflammation has been reported in brain regions of the mesocorticolimbic reward circuit leading to alterations in the perception and consumption of ultra-processed foods. While still under investigation, lipoinflammation targets two major outcomes of the mesocorticolimbic circuit during food reward: perception and motivation ("Wanting") and the pleasurable feeling of feeding ("Liking"). This review will provide experimental and clinical evidence supporting the contribution of obesity- or overnutrition-related lipoinflammation affecting the mesocorticolimbic reward circuit and enhancing food reward responses. We will also address neuroanatomical targets of inflammatory profiles that modulate food reward responses during obesity and describe potential cellular and molecular mechanisms of overnutrition linked to addiction-like behavior favored by brain lipoinflammation.
... In consequence, when activated, microglia and astrocytes release pro-inflammatory cytokines in PD, and degeneration of dopaminergic neurons can occur [172]. Recent preclinical research has focused on preventing microglia activation to delay the progression of the disease [172,173], although the use of these drugs in clinical practice is far from being a reality. PD patients accumulate α-synuclein in the form of Lewy bodies [174]. ...
The cholinergic system plays an essential role in brain development, physiology, and pathophysiology. Herein, we review how specific alterations in this system, through genetic mutations or abnormal receptor function, can lead to aberrant neural circuitry that triggers disease. The review focuses on the nicotinic acetylcholine receptor (nAChR) and its role in addiction and in neurodegenerative and neuropsychiatric diseases and epilepsy. Cholinergic dysfunction is associated with inflammatory processes mainly through the involvement of α7 nAChRs expressed in brain and in peripheral immune cells. Evidence suggests that these neuroinflammatory processes trigger and aggravate pathological states. We discuss the preclinical evidence demonstrating the therapeutic potential of nAChR ligands in Alzheimer disease, Parkinson disease, schizophrenia spectrum disorders, and in autosomal dominant sleep-related hypermotor epilepsy. PubMed and Google Scholar bibliographic databases were searched with the keywords indicated below.
... Alternative drugs with anti-inflammatory properties, including dexamethasone, minocycline, naloxone, are going to be or have already been tested in preclinical and clinical trials. [560][561][562] Given the vital role of the NLRP3 inflammasome in the pathogenesis of PD, researchers have suggested targeting NLRP3 signaling as a potential therapeutic strategy. Inhibiting the expression of NLRP3 by microRNA can ameliorate α-synuclein aggregation and protect dopaminergic neurons against degeneration in a mouse model of PD. 360 MCC950, a specific NLRP3 inhibitor, exerted neuroprotective effects and improved behavioral dysfunctions in an MPTP-induced PD mouse model. ...
Studies in neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease and Amyotrophic lateral sclerosis, Huntington’s disease, and so on, have suggested that inflammation is not only a result of neurodegeneration but also a crucial player in this process. Protein aggregates which are very common pathological phenomenon in neurodegeneration can induce neuroinflammation which further aggravates protein aggregation and neurodegeneration. Actually, inflammation even happens earlier than protein aggregation. Neuroinflammation induced by genetic variations in CNS cells or by peripheral immune cells may induce protein deposition in some susceptible population. Numerous signaling pathways and a range of CNS cells have been suggested to be involved in the pathogenesis of neurodegeneration, although they are still far from being completely understood. Due to the limited success of traditional treatment methods, blocking or enhancing inflammatory signaling pathways involved in neurodegeneration are considered to be promising strategies for the therapy of neurodegenerative diseases, and many of them have got exciting results in animal models or clinical trials. Some of them, although very few, have been approved by FDA for clinical usage. Here we comprehensively review the factors affecting neuroinflammation and the major inflammatory signaling pathways involved in the pathogenicity of neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, and Amyotrophic lateral sclerosis. We also summarize the current strategies, both in animal models and in the clinic, for the treatment of neurodegenerative diseases.
... Subsequently, 3 days after seeding, the NG cultures were replenished with fresh medium (0.5 ml/well). At the 7 th day after seeding, the composition of NG cultures was found to be 11% microglia, 50% astrocytes, and 39% neurons as determined by the visual counting of immunostained cells with antibodies against cell-type specific markers: neurons (neuronal nuclear protein or Neu -N), microglia (OX-42), and astrocytes (glial fibrillary acidic protein or GFAP) [6,15,24]. Microglia-enriched cultures were prepared from the whole brains of 1-day-old C57BL/6 J mouse pups as described in previous reports [6,15]. After removal of the meninges and blood vessels, brain tissues were dissociated by mild mechanical trituration to isolate cells. ...
The development of microglial endotoxin tolerance (ET) is a critical event in protecting neurons against excessive immune responses when microglia are administered two consecutive lipopolysaccharide (LPS) challenges. However, the intrinsic mechanisms of microglia shape ET programs and protect neurons remain unclear. This study aimed to determine whether extracellular autocrine cascades or intracellular signaling pathways are involved in ET microglia-mediated tumor necrosis factor-alpha (TNF-α) reduction and neuroprotection. Neuron-glia cultures composed of astroglia, neurons, and microglia were performed in different conditions: with or without serum or LPS-binding proteins (LBP), along with an induction approach of ET. Enzyme-linked immunosorbent assay results revealed that LPS induced TNF-α tolerance of microglia in an LBP-dependent manner. Furthermore, we determined whether the early pro-inflammatory cytokines induced by LPS might contribute to the development of microglial ET. Our data showed that the neutralization of TNF-α using an anti-TNF-α antibody had no change in the TNF-α tolerance of microglia during the ET challenge. Furthermore, pre-incubation of TNF-α, interleukin-1 beta, and prostaglandin E2 failed to induce any TNF-α tolerance in microglia after LPS treatment. Moreover, using three specific chemical inhibitors that respectively blocked the activities of the mitogen-activated protein kinases (MAPKs) namely p38, c-Jun N-terminal kinase and extracellular signal-related kinases revealed that inhibition of p38 MAPK by SB203580 disrupted the tolerated microglia-mediated TNF-α reduction and neuroprotection. In summary, our findings demonstrated that the LPS pre-treatment immediately programmed the microglial ET to prevent endotoxin-induced TNF-α production and neuronal damage through the intracellular p38 MAPK signaling pathway.
... Studies conducted in vitro have demonstrated that NLX can exert lipid antioxidant activities [1]. Additionally, several studies have showed that NLX reduces oxidative stress in motor neurons [2][3][4]as well as in microglial cells and can attenuate the degeneration of dopaminergic neurons by inhibiting superoxide production in microglia [5,6]. Moreover, NLX has demonstrated efficacy in different experimental in vivo models of stroke, brain injury, myocardial ischemia, and spinal cord injuries [3,4], in which oxidative stress also plays a significant role [7]. ...
Background:
Experimental evidence indicates that Naloxone (NLX) holds antioxidant properties. The present study aims at verifying the hypothesis that NLX could prevent oxidative stress induced by hydrogen peroxide (H2O2) in PC12 cells.
Methods:
To investigate the antioxidant effect of NLX, initially, we performed electrochemical experiments by means of platinum-based sensors in a cell-free system. Subsequently, NLX was tested in PC12 cells on H2O2-induced overproduction of intracellular levels of reactive-oxygen-species (ROS), apoptosis, modification of cells' cycle distribution and damage of cells' plasma membrane.
Results:
This study reveals that NLX counteracts intracellular ROS production, reduces H2O2-induced apoptosis levels, and prevents the oxidative damage-dependent increases of the percentage of cells in G2/M phase. Likewise, NLX protects PC12 cells from H2O2- induced oxidative damage, by preventing the lactate dehydrogenase (LDH) release. Moreover, electrochemical experiments confirmed the antioxidant properties of NLX.
Conclusion:
Overall, these findings provide a starting point for studying further the protective effects of NLX on oxidative stress.
... Furthermore, LPS-activated microglia can trigger the death of growing oligodendrocytes [10]. The release of ROS by LPS-activated microglia is a key step in the generation of neurotoxicity [11], which can be principally abrogated by neutralizing extracellular hydrogen peroxide and superoxide by catalase and superoxide dismutase treatment, respectively [12,13]. This underlines the key antioxidant function of peroxisomal antioxidant enzymes. ...
Oxidative stress and inflammation are the key players in neuroinflammation, in which microglia dysfunction plays a central role. Previous studies suggest that argan oil attenuates oxidative stress, inflammation, and peroxisome dysfunction in mouse brains. In this study, we explored the effects of two major argan oil (AO) phytosterols, Schottenol (Schot) and Spinasterol (Spina), on oxidative stress, inflammation, and peroxisomal dysfunction in two murine microglial BV-2 cell lines, wild-ype (Wt) and Acyl-CoA oxidase 1 (Acox1)-deficient cells challenged with LPS treatment. Herein, we used an MTT test to reveal no cytotoxicity for both phytosterols with concentrations up to 5 µM. In the LPS-activated microglial cells, cotreatment with each of these phytosterols caused a significant decrease in intracellular ROS production and the NO level released in the culture medium. Additionally, Schot and Spina were able to attenuate the LPS-dependent strong induction of Il-1β and Tnf-α mRNA levels, as well as the iNos gene and protein expression in both Wt and Acox1−/− microglial cells. On the other hand, LPS treatment impacted both the peroxisomal antioxidant capacity and the fatty acid oxidation pathway. However, both Schot and Spina treatments enhanced ACOX1 activity in the Wt BV-2 cells and normalized the catalase activity in both Wt and Acox1−/− microglial cells. These data suggest that Schot and Spina can protect cells from oxidative stress and inflammation and their harmful consequences for peroxisomal functions and the homeostasis of microglial cells. Collectively, our work provides a compelling argument for the protective mechanisms of two major argan oil phytosterols against LPS-induced brain neuroinflammation.
... Microglia activation results in sickness behaviors due to the release of inflammatory factors. By blocking TLR-4, the microglia may be prevented from assuming an inflammatory state, thus stopping the release of proinflammatory cytokines and neurotoxic superoxides [33]. Furthermore, naltrexone causes a continuous blockade of the opioid growth factor receptor axis (OGFr), resulting in the proliferation of immune cells [34,35]. ...
Background
Major depressive disorder (MDD) is a leading cause of disability worldwide. The current treatments are ineffective in approximately one-third of patients, resulting in a large economic burden and reduced quality of life for a significant proportion of the global population. There is considerable evidence that increased inflammation may distinguish a sub-type of MDD, and there are no validated diagnostic tools or treatments for neuroinflammation in MDD patients. The current study aims to explore the potential role of low-dose naltrexone (LDN), a drug with purported anti-inflammatory properties in the central nervous system, as an adjunctive treatment in patients with MDD.
Methods/design
This double-blind placebo-controlled hybrid parallel arm study enables the exploration of peripheral and central inflammatory markers with LDN as an approach to investigate inflammation as a pathophysiological contributor to MDD. Eligible participants with MDD (n = 48) will be stratified into the high and low inflammatory groups according to the levels of high-sensitivity C-reactive protein (hs-CRP) and then randomized to receive LDN or placebo for an initial 12 weeks, followed by a further 12 weeks during which all participants will receive LDN. The primary outcome measure will be the Montgomery-Åsberg Depression Rating Scale (MADRS) administered at baseline, 2 weeks, 4 weeks, 8 weeks, 12 weeks, 14 weeks, 16 weeks, 20 weeks, and 24 weeks, to assess the effectiveness of the anti-depressant response. The secondary outcomes include the use of MRI techniques including quantitative magnetization transfer (qMT), echo-planar spectroscopic imaging (EPSI), and diffusion-weighted imaging (DWI) to help to elucidate the neurobiological mechanism of LDN, and the inflammatory mechanisms in action in MDD. Electroencephalography, blood samples, cognitive tasks, and additional questionnaires will also be used to determine if there is a specific profile of symptoms in individuals with inflammatory MDD. Healthy participants (n = 24) will be recruited for baseline outcome measures only, to enable comparison with patients with MDD.
Discussion
This trial contributes to the literature on inflammation in MDD, including the understanding of the pathophysiology and efficacy of anti-inflammatory treatments. The investigation of inflammatory mechanisms in MDD is an important first step in the development of biomarkers to classify patient sub-groups, increase the accuracy of diagnosis, and tailor the approach to patients in clinical practice. This study may provide evidence of the benefit of LDN for the groups in whom conventional anti-depressants are ineffective and lead the way for translation into clinical practice.
Trial registration
Australian New Zealand Clinical Trials Registry ACTRN12622000881730. Registered on 21 June 2022
... Overactivation of microglia cells in the cerebral cortex of FM patients was demonstrated by Albrecht et al. using PET [217]. Inhibition of microglial activation by naltrexone or naloxone therefore has an anti-inflammatory effect through the decrease in production of neurotoxic chemicals [218,219], which is suggested to contribute to its analgesic effect [216]. ...
Neuropathic pain is a complex and challenging secondary pain condition. It is a sequela of central nervous or peripheral nervous system lesions and pathologies. It can be debilitating and affects approximately 7% of the general population. Many factors contribute to the development of this chronic neuropathic pain. It can originate from the central part of the nervous system as a result of brain or spinal cord injury, stroke, or multiple sclerosis. Peripheral neuropathic pain manifests in the peripheral nervous system, and includes large fiber and small fiber polyneuropathy, radiculopathy, and mononeuropathy. Pharmacological options include tricyclic antidepressants (TCA), serotonin and norepinephrine reuptake inhibitors (SNRI), and gabapentinoids. For more severe cases, interventional pain management techniques such as peripheral nerve blocks, spinal cord, or peripheral nerve stimulation may be reasonable options.
... Microglia activation results in sickness behaviors due to the release of in ammatory factors. By blocking TLR-4, microglia may be prevented from assuming an in ammatory state, thus stopping the release of pro-in ammatory cytokines and neurotoxic superoxides (34). Furthermore, naltrexone causes a continuous blockade of the opioid growth factor receptor axis (OGFr), resulting in the proliferation of immune cells (35,36). ...
Background
Major Depressive Disorder (MDD) is a leading cause of disability worldwide. Current treatments are ineffective in approximately one-third of patients, resulting in a large economic burden and reduced quality of life for a significant proportion of the global population. There is considerable evidence that increased inflammation may distinguish a sub-type of MDD, there are no validated diagnostic tools or treatments for neuroinflammation in MDD patients. The current study aims to explore the potential role of low-dose naltrexone (LDN), a drug with purported anti-inflammatory properties in the central nervous system, as an adjunctive treatment in patients with MDD.
Methods/Design
This double-blind placebo-controlled hybrid parallel arm study enables exploration of peripheral and central inflammatory markers with LDN as an approach to investigate inflammation as a pathophysiological contributor to MDD. Eligible participants with MDD (n = 48) will be stratified into high and low inflammatory groups according to levels of high sensitivity C-reactive protein (hs-CRP), and then randomized to receive LDN or placebo for an initial 12 weeks, followed by a further 12 weeks during which all participants will receive LDN. The primary outcome measure will be the Montgomery-Åsberg Depression Rating Scale (MADRS) administered at baseline, 2 weeks, 4 weeks, 8 weeks, 12 weeks, 14 weeks, 16 weeks, 20 weeks, and 24 weeks, to assess effectiveness of the anti-depressant response. Secondary outcomes include the use of MRI techniques including quantitative magnetization transfer (qMT), echo-planar spectroscopic imaging (EPSI), and diffusion-weighted imaging (DWI) to help to elucidate the neurobiological mechanism of LDN, and the inflammatory mechanisms in action in MDD. Electroencephalography, blood samples, cognitive tasks, and additional questionnaires, will also be used to determine if there is a specific profile of symptoms in individuals with inflammatory MDD. Healthy participants (n = 24) will be recruited for baseline outcome measures only, to enable comparison with patients with MDD.
Discussion
This trial contributes to the literature on inflammation in MDD, including understanding of the pathophysiology and efficacy of anti-inflammatory treatments. The investigation of inflammatory mechanisms in MDD is an important first step in the development of biomarkers to classify patient sub-groups, increase the accuracy of diagnosis, and tailor the approach to patients in clinical practice. This study may provide evidence of the benefit of LDN for groups in whom conventional anti-depressants are ineffective and lead the way for translation into clinical practice.
Trial registration
The trial was registered in the Australian New Zealand Clinical Trials Registry (registration number ACTRN12622000881730). Registered on 21 June 2022 (https://anzctr.org.au/Trial/Registration/TrialReview.aspx?id=383741&isReview=true).
... Previous results show that the anti-inflammatory drug dexamethasone prevents glial cell activation and exerts a protective effect against dopaminergic degenerative processes [141]. Similarly, naloxone inhibits microglia activation and pro-inflammatory cytokine production to protect dopaminergic neurons as well as other neurons [142]. In addition, non-steroidal antiinflammatory drugs (NSAIDS) also have protective effects against neuronal damage. ...
Parkinson’s disease (PD) is the second most common neurodegenerative disorder which affects 6.1 million people worldwide. The neuropathological hallmarks include the loss of dopaminergic neurons in the substantia nigra, the presence of Lewy bodies and Lewy neurites caused by α-synuclein aggregation, and neuroinflammation in the brain. The prodromal phase happens years before the onset of PD during which time many patients show gastro-intestinal symptoms. These symptoms are in support of Braak’s theory and model where pathological α‐synuclein propagates from the gut to the brain. Importantly, immune responses play a determinant role in the pathogenesis of Parkinson’s disease. The innate immune responses triggered by microglia can cause neuronal death and disease progression. In addition, T cells infiltrate into the brains of PD patients and become involved in the adaptive immune responses. Interestingly, α‐synuclein is associated with both innate and adaptive immune responses by directly interacting with microglia and T cells. Here, we give a detailed review of the immunobiology of Parkinson’s disease, focusing on the role α-synuclein in the gut-brain axis hypothesis, the innate and adaptive immune responses involved in the disease, and current treatments.
... Several products protect dopaminergic neurons against inflammatory damage by inhibiting microglia activation, such as naloxone (a nonselective opioid receptor antagonist) (Liu et al., 2000) and miR-let-7a , in models of PD. A phase II randomised study showed that AZD3241 treatment, an inhibitor of myeloperoxidase, decreased microglia activity in PD patients . ...
Parkinson’s disease (PD) is the second most common age-associated neurodegenerative disorder and is characterized by progressive loss of dopamine neurons in the substantia nigra. Peripheral immune cell infiltration and activation of microglia and astrocytes are observed in PD, a process called neuroinflammation. Neuroinflammation is a fundamental response to protect the brain but, when chronic, it triggers neuronal damage. In the last decade, central and peripheral inflammation were suggested to occur at the prodromal stage of PD, sustained throughout disease progression, and may play a significant role in the pathology. Understanding the pathological mechanisms of PD has been a high priority in research, primarily to find effective treatments once symptoms are present. Evidence indicates that early life exposure to neuroinflammation as a consequence of life events, environmental or behaviour factors such as exposure to infections, pollution or a high fat diet increase the risk of developing PD. Many studies show healthy habits and products that decrease neuroinflammation also reduce the risk of PD. Here, we aim to stimulate discussion about the role of neuroinflammation in PD onset and progression. We highlight that reducing neuroinflammation throughout the lifespan is critical for preventing idiopathic PD, and present epidemiological studies that detail risk and protective factors. It is possible that introducing lifestyle changes that reduce neuroinflammation at the time of PD diagnosis may slow symptom progression. Finally, we discuss compounds and therapeutics to treat the neuroinflammation associated with PD.
... Further analysis determined whether modification of classical opioid receptor binding occurred in the absence of TLR4. The ligands [ 3 H] (-)-naloxone and [ 3 H]diprenorphine were chosen for the binding experiments as they are of the 4,5-epoxymorphinan structure, a class which has previously been shown to interact with TLR4 (Liu et al., 2000;Hutchinson et al., 2010;Wang et al., 2012). ...
Toll-like receptors (TLR) have been proposed as a site of action that alters opioid pharmacodynamics. However, a comprehensive assessment of acute opioid antinociception, tolerance and withdrawal behaviours in genetic null mutant strains with altered innate immune signalling has not been performed. Nor has the impact of genetic deletion of TLR2/4 on high-affinity opioid receptor binding. Here we show that diminished TLR signalling potentiates acute morphine antinociception equally in male and female mice. However, only male TIR8 null mutant mice showed reduced morphine analgesia. Analgesic tolerance was prevented in TLR2 and TLR4 null mutants, but not MyD88 animals. Withdrawal behaviours were only protected in TLR2-/- mice. In silico docking simulations revealed opioid ligands bound preferentially to the LPS binding pocket of MD-2 rather than TLR4. There was no binding of [³H](-)-naloxone or [³H]diprenorphine to TLR4 in the concentrations explored. These data confirm that opioids have high efficacy activity at innate immune pattern recognition binding sites but do not bind to TLR4 and identify critical pathway and sex-specific effects of the complex innate immune signalling contributions to opioid pharmacodynamics. These data further support the behavioural importance of the TLR-opioid interaction but fail to demonstrate direct evidence for high-affinity binding of the TLR4 signalling complex to ligands.
... Therefore, accumulating studies have focused on the inhibition of MG activation to delay the progression of PD. For example, a number of studies in PD mouse models have shown that naloxone has neuroprotective effects by inhibiting MG activation and reducing the release of inflammatory factors (Liu et al., 2000(Liu et al., , 2002Lu et al., 2000). However, there are still many hurdles to overcome in applying these drugs to clinical practice. ...
Parkinson’s disease (PD) is a clinically common neurodegenerative disease of the central nervous system (CNS) characterized by loss of dopamine neurons in the substantia nigra. Microglia (MG), as an innate immune cell in the CNS, are involved in a variety of immunity and inflammatory responses in the CNS. A number of studies have shown that the overactivation of MG is one of the critical pathophysiological mechanisms underlying PD. MicroRNAs (miRNAs) are considered to be an important class of gene expression regulators and are involved in a variety of physiological and pathological mechanisms, including immunity and inflammation. In addition, miRNAs can affect the progress of PD by regulating the expression of various MG genes and the polarization state of the MG. Here, we summarize recent articles and describe the important role of MG pathological polarization in the progression of PD, the diverse mechanisms responsible for how miRNAs regulate MG, and the potential therapeutic prospects of miRNAs for PD. We also propose that the regulation of miRNAs may be a novel protective approach against the pathogenesis of PD.
... LPS is a gram-negative bacterial endotoxin that activates microglia through the toll-like receptor-4, leading to the production of inflammatory cytokines and chemokines (9,10). Microglia are the major players in the inflammatory process that mediate inflammation lipopolysaccharide (LPS)-induced neurotoxicity (11)(12)(13)(14)(15). Activated microglia produce a variety of pro-inflammatory factors, including nitric oxide (NO) (12,(16)(17)(18)(19)(20)(21), tumor necrosis factor α (TNFα) (20,22,23), interleukin-1β (IL-1β) (20,24,25), prostaglandin E₂ (PGE₂) (26-28) and reactive oxygen species (ROS) (29-31), all of which serve immune surveillance functions by removing foreign microorganisms (32). ...
... LPS is a gram-negative bacterial endotoxin that activates microglia through the toll-like receptor-4, leading to the production of inflammatory cytokines and chemokines (9,10). Microglia are the major players in the inflammatory process that mediate inflammation lipopolysaccharide (LPS)-induced neurotoxicity (11)(12)(13)(14)(15). Activated microglia produce a variety of pro-inflammatory factors, including nitric oxide (NO) (12,(16)(17)(18)(19)(20)(21), tumor necrosis factor α (TNFα) (20,22,23), interleukin-1β (IL-1β) (20,24,25), prostaglandin E₂ (PGE₂) (26-28) and reactive oxygen species (ROS) (29-31), all of which serve immune surveillance functions by removing foreign microorganisms (32). ...
... An unanswered question remains as to the impact of such drug-induced inflammatory changes to perpetuate fentanyl selfadministration; if this is the case, there may be the potential anti-inflammatory therapeutics to help mitigate J o u r n a l P r e -p r o o f continuing opioid abuse. For instance, opiate antagonists which are used to treat alcohol and opiate use disorders also block induction of innate immune cytokine and chemokine generation, and prevent LPS-induced immune responses (Liu et al., 2000a;Liu et al., 2000b). Perhaps, prevention of inflammatory cytokine and chemokine cascades may reduce alcohol and opiate use. ...
The coronavirus disease 2019 (Covid-19) pandemic intensified the already catastrophic drug overdose and substance use disorder (SUD) epidemic, signaling a syndemic as social isolation, economic and mental health distress, and disrupted treatment services disproportionally impacted this vulnerable population. Along with these social and societal factors, biological factors triggered by intense stress intertwined with incumbent overactivity of the immune system and resulting inflammatory outcomes may impact the functional status the central nervous system (CNS). We review the literature concerning SARS-CoV2 infiltration and infection in the CNS and the prospects of synergy between stress, inflammation, and kynurenine pathway function during illness and recovery from Covid-19. Taken together, inflammation and neuroimmune signaling, a consequence of Covid-19 infection, may dysregulate critical pathways and underlie maladaptive changes in the CNS, to exacerbate the development of neuropsychiatric symptoms and in the vulnerability to develop SUD.
... The mixed glial cell culture was prepared from the brain of postnatal day (P) 1-3 inbred Lewis rats (Orientbio, Sungnam, Korea), modified as previously described [36]. Briefly, the meninges and the blood vessels of the whole brain were removed under a dissecting microscope. ...
Microglia are resident immune cells of the central nervous system that act as brain-specific macrophages and are also known to regulate the innate immune functions of astrocytes through secretory molecules. This communication plays an important role in brain functions and homeostasis as well as in neuropathologic disease. In this study, we aimed to elucidate whether astrocytes and microglia could crosstalk to induce microglial polarization and proliferation, which can be further regulated under a microenvironment mimicking that of brain stroke. Microglia in a mixed glial culture showed increased survival and proliferation and were altered to M2 microglia; CD11b−GFAP+ astrocytes resulted in an approximately tenfold increase in microglial cell proliferation after the reconstitution of astrocytes. Furthermore, GM-CSF stimulated microglial proliferation approximately tenfold and induced them to become CCR7+ M1 microglia, which have a phenotype that could be suppressed by anti-inflammatory cytokines such as IL-4, IL-10, and substance P. In addition, the astrocytes in the microglial co-culture showed an A2 phenotype; they could be activated to A1 astrocytes by TNF-α and IFN-γ under the stroke-mimicking condition. Altogether, astrocytes in the mixed glial culture stimulated the proliferation of the microglia and M2 polarization, possibly through the acquisition of the A2 phenotype; both could be converted to M1 microglia and A1 astrocytes under the inflammatory stroke-mimicking environment. This study demonstrated that microglia and astrocytes could be polarized to M2 microglia and A2 astrocytes, respectively, through crosstalk in vitro and provides a system with which to explore how microglia and astrocytes may behave in the inflammatory disease milieu after in vivo transplantation.
... There are three categories of PD animal models according to their processing methods, neurotoxic models, genetic models, and models that combine both. The neurotoxic model is the earliest and most commonly used animal model to evaluate the effect of PD treatment, in which the neurotoxins usually include 6hydroxydopamine (6-OHDA), 1-methyl-4-phenyl-1,2,3,6tetrahydropyridine (MPTP), pesticide neurotoxin, and LPS, among which LPS can activate microglia to release inflammatory and cytotoxic factors, causing degeneration of DA neurons ( 23 ). In addition, researchers used gene knockout and transgenic technologies to modify PD-related genes to create genetic animal models ( 24 ). ...
Background:
Pramipexole is the dopamine receptor agonist commonly used for treatment of PD, the effect of which on immunity played an important role in pathological process is also deserved to be further studied.
Aim of study:
We observed the effect of pramipexole on behavior and central nervous system (CNS) inflammatory cytokines of Parkinson's Disease (PD) model rats.
Methods:
We injected 3.0 μL lipopolysaccharide into the right substantia nigra compact (SNc) and ventral tegmental area (VTA) of sprague-dawley (SD) rats to establish PD models which were divided as treated group feeded with pramipexole for 14 d and untreated group feeded with saline. And SD rats were selected as control group feeded with saline. We conducted rotation test on PD model rats before and after treatment. We also performed euthanasia on all rats to obtain the striatum area and nearby tissues after treatment, measuring mRNA expression and concentration of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) by reverse transcription polymerase chain reaction test and elisa method, respectively.
Results:
It was observed that the degree of behavior improvement in treated group was greater than that in untreated group. In addition, mRNA expression and concentrations of IL-6 and TNF-α in treated group were lower than those in untreated group and higher than those in control group.
Conclusions:
Pramipexole improved behavior of PD model rat, and down regulated the mRNA expression and concentrations of IL-6 and TNF-α in their CNS.
... Apathy has been linked to more severe cognitive impairment and reduced activities of daily life, and has been found to be a predictive factor for reduction in cognition [244]. Independent determinants for the progression of apathy include memory loss at baseline, axial impairment and a more quick decline in speech [245]. This study found that apathy enhanced linearly for persons undergoing one-sided deep brain stimulation surgery to the subthalamic nucleus or internal segment of globus pallidus(GP) pre-operatively to 6 months postoperatively [246]. ...
... Besides minocycline, other compounds have been described to have a neuroprotective effect in the treatment of Parkinsonism. For instance, the synthetic steroid dexamathasone prevents dopaminergic neurons degeneration in a mouse PD model [282], and the synthetic compound naloxone blocks microglia activation thus reducing the inflammatory damage [283]. Aside from its cardiovascular application, nimodipine, a calcium channel blocker, exhibits a neuroprotective effect on dopaminergic neurons by downregulating microglial activation, thus decreasing TNF-α and IL-1β production [284]. ...
Innate immune response is one of our primary defenses against pathogens infection, although, if dysregulated, it represents the leading cause of chronic tissue inflammation. This dualism is even more present in the central nervous system, where neuroinflammation is both important for the activation of reparatory mechanisms and, at the same time, leads to the release of detrimental factors that induce neurons loss. Key players in modulating the neuroinflammatory response are mitochondria. Indeed, they are responsible for a variety of cell mechanisms that control tissue homeostasis, such as autophagy, apoptosis, energy production, and also inflammation. Accordingly, it is widely recognized that mitochondria exert a pivotal role in the development of neurodegenerative diseases, such as multiple sclerosis, Parkinson’s and Alzheimer’s diseases, as well as in acute brain damage, such in ischemic stroke and epileptic seizures. In this review, we will describe the role of mitochondria molecular signaling in regulating neuroinflammation in central nervous system (CNS) diseases, by focusing on pattern recognition receptors (PRRs) signaling, reactive oxygen species (ROS) production, and mitophagy, giving a hint on the possible therapeutic approaches targeting mitochondrial pathways involved in inflammation.
... However, other alternatives are being tested as discussed below for preclinical (Table 1) and clinical studies. (Table 2) Several preclinical and clinical studies have tried to inhibit the glial reaction and/or target proinflammatory cytokines with minocycline, dexamethasone or COX2 inhibitors [228][229][230][231] (NCT01439100, NCT00063193). A recent study has demonstrated that the NLRP3 inhibitor, MCC950, effectively suppressed microglial inflammasome activation, mitigating motor deficits, nigrostriatal dopaminergic degeneration and accumulation of α-Syn aggregates in multiple PD models [232]. ...
Parkinson’s disease (PD) is a common neurodegenerative disorder primarily characterized by the death of dopaminergic neurons that project from the substantia nigra pars compacta. Although the molecular bases for PD development are still little defined, extensive evidence from human samples and animal models support the involvement of inflammation in onset or progression. However, the exact trigger for this response remains unclear. Here, we provide a systematic review of the cellular mediators, i.e., microglia, astroglia and endothelial cells. We also discuss the genetic and transcriptional control of inflammation in PD and the immunomodulatory role of dopamine and reactive oxygen species. Finally, we summarize the preclinical and clinical approaches targeting neuroinflammation in PD.
... High levels of inflammatory cytokines are also found in the cerebrospinal fluid (CSF) and serum of epileptic patients [11]. Microglia stimulation due to SE are associated with central inflammation [12,13] and activated microglia generate various factors such as nitric oxide (NO) and both pro-and anti-inflammatory cytokines [14][15][16]. ...
Status epilepticus (SE) is a life‐threatening neurologic disorder that can be as both cause and consequence of neuroinflammation. In addition to previous reports on anti‐inflammatory property of the anti‐migraine medication sumatriptan, we have recently shown its anticonvulsive effects on pentylenetetrazole‐induced seizure in mice. In the present study, we investigated further (i) the effects of sumatriptan in the lithium‐pilocarpine SE model in rats, and (ii) the possible involvement of nitric oxide (NO), 5‐hydroxytriptamin 1B/1D (5‐HT1B/1D) receptor, and inflammatory pathways in such effects of sumatriptan. SE was induced by lithium chloride (127 mg/kg, i.p) and pilocarpine (60 mg/kg, i.p.) in Wistar rats. While SE induction increased SE scores and mortality rate, sumatriptan (0.001‐1 mg/kg, i.p.) improved it (P<0.001). Administration of the selective 5‐HT1B/1D antagonist GR‐127935 (0.01 mg/kg, i.p.) reversed the anticonvulsive effects of sumatriptan (0.01 mg/kg, i.p.). Although both tumor necrosis factor‐α (TNF‐α) and NO levels were markedly elevated in the rats’ brain tissues post SE induction, pre‐treatment with sumatriptan significantly reduced both TNF‐α (P<0.05) and NO (P<0.001) levels. Combined GR‐127935 and sumatriptan treatment inhibited these anti‐inflammatory effects of sumatriptan, whereas combined non‐specific NOS (L‐NAME) or selective neuronal NOS (7‐nitroindazole) inhibitors and sumatriptan further reduced NO levels. In conclusion, sumatriptan exerted a protective effect against the clinical manifestations and mortality rate of SE in rats which is possibly through targeting 5‐HT1B/1D receptors, neuroinflammation, and nitrergic transmission.
... Overactivation of microglia cells in the cerebral cortex of FMS patients was recently demonstrated by Albrecht et al. using PET [65]. Inhibition of microglial activation by naltrexone or naloxone therefore has an anti-inflammatory effect through the decrease in production of neurotoxic chemicals [66,67], which is suggested to contribute to its analgesic effect [25]. e ability to quantitatively assess microglial activation using nuclear methods may provide researchers and clinicians with the opportunity to use it as a biomarker for FMS activity and for measuring the effect of naltrexone. ...
Introduction. Fibromyalgia syndrome (FMS) is a pain disorder with an estimated prevalence of 1–5%. It is associated with a variety of somatic and psychological disorders. Its exact pathogenesis is still unclear but is involved with neural oversensitization and decreased conditioned pain modulation (CPM), combined with cognitive dysfunction, memory impairment, and altered information processing. Connectivity between brain areas involved in pain processing, alertness, and cognition is increased in the syndrome, making its pharmacologic therapy complex. Only three drugs, pregabalin, duloxetine, and milnacipran are currently FDA-approved for FM treatment, but many other agents have been tested over the years, with varying efficacy. Areas Covered. The purpose of this review is to summarize current clinical experience with different pharmacologic treatments used for fibromyalgia and introduce future perspectives in developing therapies. Expert Opinion. Future insights into the fields of cannabinoid and opioid research, as well as an integrative approach towards the incorporation of genetics and functional imaging combined with additional fields of research relevant towards the study of complex CNS disorders, are likely to lead to new developments of novel tailor-made treatments for FMS patients.
... Therefore, anti-inflammatory agents may be therapeutically beneficial for PD. For instance, naloxone [32] inhibits microglial activation and reduces superoxide production in the lipopolysaccharide-induced PD model, and vasoactive intestinal peptide [33] blocks microglial activation by decreasing THF-α, IL-1β, and iNOS expression in the MPTP-induced PD model. In our previous study, an anti-inflammatory agent, thiacremonone, suppressed PD progression in the MPTP-induced PD model [34]. ...
Neuroinflammation is implicated in dopaminergic neurodegeneration. We have previously demonstrated that (E)-2-methoxy-4-(3-(4-methoxyphenyl) prop-1-en-1-yl) phenol (MMPP), a selective signal transducer and activator of transcription 3 (STAT3) inhibitor, has anti-inflammatory properties in several inflammatory disease models. We investigated whether MMPP could protect against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic cell loss and behavioral impairment. Imprinting control region (ICR) mice (8 weeks old, n = 10 per group) were administered MMPP (5 mg/kg) in drinking water for 1 month, and injected with MPTP (15 mg/kg, four times with 2 h intervals) during the last 7 days of treatment. MMPP decreased MPTP-induced behavioral impairments in rotarod, pole, and gait tests. We also showed that MMPP ameliorated dopamine depletion in the striatum and inflammatory marker elevation in primary cultured neurons by high-performance liquid chromatography and immunohistochemical analysis. Increased activation of STAT3, p38, and monoamine oxidase B (MAO-B) were observed in the substantia nigra and striatum after MPTP injection, effects that were attenuated by MMPP treatment. Furthermore, MMPP inhibited STAT3 activity and expression of neuroinflammatory proteins, including ionized calcium binding adaptor molecule 1 (Iba1), inducible nitric oxide synthase (iNOS), and glial fibrillary acidic protein (GFAP) in 1-methyl-4-phenylpyridinium (MPP+; 0.5 mM)-treated primary cultured cells. However, mitogen-activated protein kinase (MAPK) inhibitors augmented the activity of MMPP. Collectively, our results suggest that MMPP may be an anti-inflammatory agent that attenuates dopaminergic neurodegeneration and neuroinflammation through MAO-B and MAPK pathway-dependent inhibition of STAT3 activation.
... During treatment, immunocytochemical staining demonstrated that primary neuron-glia co-cultures composed of 50% astrocytes, 10% microglia, 40% neurons, and 1% DA neurons. In addition, midbrain neuron-enriched cultures were prepared by adding cytosine β-D-arabinofuranoside (8 μM) in primary neuron-glia cultures to inhibit glial cells proliferation [21]. ICA treatment was performed with 7 days of cultures followed by 6-OHDA (40 μM) intervention [15]. ...
Background
Oxidative stress and neuroinflammation are considered the major central events in the process of Parkinson’s disease (PD). Nrf2 is a key regulator of endogenous defense systems. New finds have contacted activation of Nrf2 signaling with anti-inflammatory activities. Therefore, the outstanding inhibition of neuroinflammation or potent Nrf2 signaling activation holds a promising strategy for PD treatment. Icariin (ICA), a natural compound derived from Herba Epimedii, presents a number of pharmacological properties, including anti-oxidation, anti-aging and anti-inflammatory actions. Recent studies have confirmed ICA exerted neuroprotection against neurodegenerative disorders. However, the underlying mechanisms were not fully elucidated.
Methods
In the present study, mouse nigral stereotaxic injection of 6-hydroxydopamine (6-OHDA)-induced PD model was performed to investigate ICA-conferred dopamine (DA) neuroprotection. In addition, adult Nrf2 knockout mice and primary rat midbrain neuron-glia co-culture was applied to elucidate whether ICA-exerted neuroprotection was through an Nrf2-dependent mechanism.
Results
Results indicated that ICA attenuated 6-OHDA-induced DA neurotoxicity and glial cells-mediated neuroinflammatory response. Furtherly, activation of Nrf2 signaling pathway in glial cells participated in ICA-produced neuroprotection, as revealed by the following observations. First, ICA enhanced Nrf2 signaling activation in 6-OHDA-induced mouse PD model. Second, ICA failed to generate DA neuroprotection and suppress glial cells-mediated pro-inflammatory factors production in Nrf2 knockout mice. Third, ICA exhibited neuroprotection in primary neuron-glia co-cultures but not in neuron-enriched cultures (without glial cells presence). Either, ICA-mediated neuroprotection was not discerned after Nrf2 siRNA treatment in neuron-glia co-cultures.
Conclusions
Our findings identify that ICA attenuated glial cells-mediated neuroinflammation and evoked DA neuroprotection via an Nrf2-dependent manner.
Electronic supplementary material
The online version of this article (10.1186/s12974-019-1472-x) contains supplementary material, which is available to authorized users.
... Seven days later, the neuron-enriched cultures consisted of 90% neurons, 10% astroglia, and < 0.1% microglia. Primary neuron-microglia cultures were obtained by adding primary microglia (5 × 10 4 /well) from primary microglia-enriched cultures back to neuron-enriched cultures [15]. Liquid scintillation counting was applied to detect the radioactivity. ...
Background
Microglia-mediated neuroinflammation is recognized to mainly contribute to the pathogenesis of Parkinson’s disease (PD). Tetrahydroxystilbene glucoside (TSG) has been proved to be beneficial for health with a great number of pharmacological properties. We examined the effects of TSG against dopamine (DA) neuronal loss towards development of a PD treatment strategy.
Methods
Substantia nigral stereotaxic single injection of lipopolysaccharide (LPS)-induced rat DA neuronal damage was employed to investigate TSG-produced neuroprotection. In addition, primary rat midbrain neuron-glia co-cultures were performed to explore the underlying mechanisms.
Results
Daily intraperitoneal injection of TSG for seven consecutive days significantly attenuated LPS-induced loss of DA neurons in the substantia nigra. In addition, glia-dependent mechanisms were responsible for TSG-mediated neuroprotection. First, TSG ameliorated microglia-mediated neuroinflammation and the subsequent production of various pro-inflammatory and neurotoxic factors. Second, astroglial neurotrophic factor neutralization weakened TSG-mediated neuroprotection, showing that TSG was protective in part via increasing astroglia-derived neurotrophic factor secretion.
Conclusions
TSG protects DA neurons against LPS-induced neurotoxicity through dual modulation on glial cells by attenuating microglia-mediated neuroinflammation and enhancing astroglia-derived neurotrophic effects. These findings might open new alternative avenues for PD treatment.
... Previous studies have also demonstrated that the inhibition of microglial activation or knockdown of released cytokines from microglia may be neuroprotective to DA neurons. Pharmacological blockade of microglial activation [35][36][37] or knockdown of cytokines, such as IL-1 [38], demonstrates that prevention of microglial activation attenuates some of the degeneration seen in models of PD. Furthermore, the interaction of MPTP/ MPP + with the microglial receptor TLR4, a key receptor in the microglial activation pathway, has previously been established [39,40]. ...
Background:
Parkinson's disease (PD) is characterized by selective degeneration of dopaminergic (DA) neurons of the substantia nigra pars compacta (SN) while neighboring ventral tegmental area (VTA) DA neurons are relatively spared. Mechanisms underlying the selective protection of the VTA and susceptibility of the SN are still mostly unknown. Here, we demonstrate the importance of balance between astrocytes and microglia in the susceptibility of SN DA neurons to the PD mimetic toxin 1-methyl-4-phenylpyridinium (MPP+).
Methods:
Previously established methods were used to isolate astrocytes and microglia from the cortex (CTX), SN, and VTA, as well as embryonic midbrain DA neurons from the SN and VTA. The transcriptional profile of isolated microglia was examined for 21 canonical pro- and anti-inflammatory cytokines by qRT-PCR with and without MPP+ exposure. Homo- and heterotypic co-cultures of neurons and astrocytes were established, and the effect of altering the ratio of astrocytes and microglia in vitro on the susceptibility of midbrain DA neurons to the PD mimetic toxin MPP+ was investigated.
Results:
We found that regionally isolated microglia (SN, VTA, CTX) exhibit basal differences in their cytokine profiles and that activation of these microglia with MPP+ results in differential cytokine upregulation. The addition of microglia to cultures of SN neurons and astrocytes was not sufficient to cause neurodegeneration; however, when challenged with MPP+, all regionally isolated microglia resulted in exacerbation of MPP+ toxicity which was alleviated by inhibition of microglial activation. Furthermore, we demonstrated that isolated VTA, but not SN, astrocytes were able to mediate protection of both SN and VTA DA neurons even in the presence of exacerbatory microglia; however, this protection could be reversed by increasing the numbers of microglia present.
Conclusion:
These results suggest that the balance of astrocytes and microglia within the midbrain is a key factor underlying the selective vulnerability of SN DA neurons seen in PD pathogenesis and that VTA astrocytes mediate protection of DA neurons which can be countered by greater numbers of deleterious microglia.
Studying various microglial phenotypes and their functions in neurodegenerative diseases is crucial due to the intricate nature of their phenomics and their vital immunological role. Microglia undergo substantial phenomic changes, encompassing morphological, transcriptional, and functional aspects, resulting in distinct cell types with diverse structures, functions, properties, and implications. The traditional classification of microglia as ramified, M1 (proinflammatory), or M2 (anti-inflammatory) phenotypes is overly simplistic, failing to capture the wide range of recently identified microglial phenotypes in various brain regions affected by neurodegenerative diseases. Altered and activated microglial phenotypes deviating from the typical ramified structure are significant features of many neurodegenerative conditions. Understanding the precise role of each microglial phenotype is intricate and sometimes contradictory. This review specifically focuses on elucidating recent modifications in microglial phenotypes within neurodegenerative diseases. Recognizing the heterogeneity of microglial phenotypes in diseased states can unveil novel therapeutic strategies for targeting microglia in neurodegenerative diseases. Moreover, the exploration of the use of healthy isolated microglia to mitigate disease progression has provided an innovative perspective. In conclusion, this review discusses the dynamic landscape of mysterious microglial phenotypes, emphasizing the need for a nuanced understanding to pave the way for innovative therapeutic strategies for neurodegenerative diseases.
Parkinson’s disease (PD) is an increasingly common neurodegenerative disease. It has been suggested that the etiology of idiopathic PD is complex and multifactorial involving environmental contributions, such as viral or bacterial infections and microbial dysbiosis, in genetically predisposed individuals. With advances in our understanding of the gut-brain axis, there is increasing evidence that the intestinal microbiota and the mammalian immune system functionally interact. Recent findings suggest that a shift in the gut microbiome to a pro-inflammatory phenotype may play a role in PD onset and progression. While there are links between gut bacteria, inflammation, and PD, the bacterial products involved and how they traverse the gut lumen and distribute systemically to trigger inflammation are ill-defined. Mechanisms emerging in other research fields point to a role for small, inherently stable vesicles released by Gram-negative bacteria, called outer membrane vesicles in disease pathogenesis. These vesicles facilitate communication between bacteria and the host and can shuttle bacterial toxins and virulence factors around the body to elicit an immune response in local and distant organs. In this perspective article, we hypothesize a role for bacterial outer membrane vesicles in PD pathogenesis. We present evidence suggesting that these outer membrane vesicles specifically from Gram-negative bacteria could potentially contribute to PD by traversing the gut lumen to trigger local, systemic, and neuroinflammation. This perspective aims to facilitate a discussion on outer membrane vesicles in PD and encourage research in the area, with the goal of developing strategies for the prevention and treatment of the disease.
Microglia activation is observed in various neurodegenerative diseases. Recent advances in single-cell technologies have revealed that these reactive microglia were with high spatial and temporal heterogeneity. Some identified microglia in specific states correlate with pathological hallmarks and are associated with specific functions. Microglia both exert protective function by phagocytosing and clearing pathological protein aggregates and play detrimental roles due to excessive uptake of protein aggregates, which would lead to microglial phagocytic ability impairment, neuroinflammation, and eventually neurodegeneration. In addition, peripheral immune cells infiltration shapes microglia into a pro-inflammatory phenotype and accelerates disease progression. Microglia also act as a mobile vehicle to propagate protein aggregates. Extracellular vesicles released from microglia and autophagy impairment in microglia all contribute to pathological progression and neurodegeneration. Thus, enhancing microglial phagocytosis, reducing microglial-mediated neuroinflammation, inhibiting microglial exosome synthesis and secretion, and promoting microglial conversion into a protective phenotype are considered to be promising strategies for the therapy of neurodegenerative diseases. Here we comprehensively review the biology of microglia and the roles of microglia in neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, multiple system atrophy, amyotrophic lateral sclerosis, frontotemporal dementia, progressive supranuclear palsy, corticobasal degeneration, dementia with Lewy bodies and Huntington’s disease. We also summarize the possible microglia-targeted interventions and treatments against neurodegenerative diseases with preclinical and clinical evidence in cell experiments, animal studies, and clinical trials.
In recent years, the contraposition between inflammatory and neurodegenerative processes has been increasingly challenged. Inflammation has been emphasized as a key player in the onset and progression of Parkinson disease (PD) and other neurodegenerative disorders. The strongest indicators of the involvement of the immune system derived from evidence of microglial activation, profound imbalance in phenotype and composition of peripheral immune cells, and impaired humoral immune responses. Moreover, peripheral inflammatory mechanisms (e.g., involving the gut-brain axis) and immunogenetic factors are likely to be implicated. Even though several lines of preclinical and clinical studies are supporting and defining the complex relationship between the immune system and PD, the exact mechanisms are currently unknown. Similarly, the temporal and causal connections between innate and adaptive immune responses and neurodegeneration are unsettled, challenging our ambition to define an integrated and holistic model of the disease. Despite these difficulties, current evidence is providing the unique opportunity to develop immune-targeted approaches for PD, thus enriching our therapeutic armamentarium. This chapter aims to provide an extensive overview of past and present studies that explored the implication of the immune system in neurodegeneration, thus paving the road for the concept of disease modification in PD.
There are intriguing theories regarding the biology of fibromyalgia. Whilst several researchers assume it is a psychogenic, others believe that fibromyalgia is a disease of neurological sensitization (an overactive alarm system). Fibromyalgia is a clinical entity that present with a mix of the symptoms including chronic widespread pain and other non-pain linked symptoms, such as poor sleep, fatigue and cognitive disturbances. Furthermore, fibromyalgia exhibits substantial variation not only between various patients, but also in the same patient during the disease course. Identifying a common language and classification to diagnose and treat fibromyalgia represent another challenge, as patients may seek care from different disciplines (such as rheumatology, general practice, neurology, psychology, or psychiatry and in some cases orthopedic surgery) with unique perspectives and terminologies. Furthermore, in concordance with other medically unexplained pain syndromes, fibromyalgia may be classified in several ways (such as functional somatic syndrome, chronic widespread pain syndrome, persistent somatoform pain disorder, somatic symptom disorder, affective spectrum condition, and central sensitivity syndrome). This chapter will discuss the debate of fibromyalgia as a bitterly controversial condition, the science of pain and where fibromyalgia fits in. It will then discuss fibromyalgia as a pain processing problem, different sources of pain in fibromyalgia patients and the wind-up theory. The chapter will expand to discuss Fibromyalgia associated comorbidities, fibromyalgia pain in the clinical setting, fibromyalgianess, neuroimaging, as well as pain pathways and the pharmacotherapy of Fibromyalgia.
Chronic pain is highly prevalent among patients with opioid use disorder (OUD). However, little is known about how pharmacological treatments for OUD, for example, extended-release naltrexone (XR-NTX) and buprenorphine-naloxone (BUP-NX), affect pain. To begin addressing this question, we performed a secondary analysis of pain data on a large prospective 24-week, open-label, randomized-controlled comparative effectiveness trial of XR-NTX versus BUP-NX (X:BOT trial). Participants' pain status was measured by the EuroQol (EQ-5D). Based on their responses to the pain question at baseline, participants were dichotomized into “Pain” versus “No Pain” categories. Participant's pain status was evaluated every 4 weeks. A mixed effects longitudinal logistic regression model was fitted to examine the differential effect of XR-NTX versus BUP-NX on pain, modelling pain at all available follow-up assessments, adjusted for age, sex, and baseline pain. A total of 474 individuals who were successfully inducted onto their assigned medications were included in this analysis. Among participants endorsing pain at baseline, substantial reductions in pain were observed over the course of the study in both treatment groups. Howecver reduction in pain was slightly greater in the group treated with XR-NTX than the one treated with BUP-NX (OR = 1.60 [95% CI: 1.07–2.40], P = 0.023). Future research using instruments and design specifically focused on pain could extend the present observations and evaluate their clinical significance.
Background:
Lipopolysaccharide (LPS) exerts cytotoxic effects on brain cells, especially on those belonging to the oligodendrocyte lineage, in preterm infants. The susceptibility of oligodendrocyte lineage cells to LPS-induced inflammation is dependent on the developmental stage. This study aimed to investigate the effect of LPS on oligodendrocyte lineage cells at different developmental stages in a microglial cell and oligodendrocyte co-culture model.
Methods:
The primary cultures of oligodendrocytes and microglia cells were prepared from the forebrains of 2-day-old Sprague-Dawley rats. The oligodendrocyte progenitor cells (OPCs) co-cultured with microglial cells were treated with 0 (control), 0.01, 0.1, and 1 µg/mL LPS at the D3 stage to determine the dose of LPS that impairs oligodendrocyte differentiation. The co-culture was treated with 0.01 µg/mL LPS, which was the lowest dose that did not impair oligodendrocyte differentiation, at the developmental stages D1 (early LPS group), D3 (late LPS group), or D1 and D3 (double LPS group). On day 7 of differentiation, oligodendrocytes were subjected to neural glial antigen 2 (NG2) and myelin basic protein (MBP) immunostaining to examine the number of OPCs and mature oligodendrocytes, respectively.
Results:
LPS dose-dependently decreased the proportion of mature oligodendrocytes (MBP+ cells) relative to the total number of cells. The number of MBP+ cells in the early LPS group was significantly lower than that in the late LPS group. Compared with those in the control group, the MBP+ cell numbers were significantly lower and the NG2+ cell numbers were significantly higher in the double LPS group, which exhibited impaired oligodendrocyte lineage cell development, on day 7 of differentiation.
Conclusion:
Repetitive LPS stimulation during development significantly inhibited brain cell development by impairing oligodendrocyte differentiation. In contrast, brain cell development was not affected in the late LPS group. These findings suggest that inflammation at the early developmental stage of oligodendrocytes increases the susceptibility of the preterm brain to inflammation-induced injury.
Microglia are resident immune cells of the central nervous system such as brain-specific macrophages and also known to regulate the innate immune functions of astrocytes through secretory molecules. This conversation plays an important role in brain functions and homeostasis as well as in neuropathologic disease. In this study, we aimed to elucidate whether astrocytes and microglia can cross-talk to induce microglial polarization and proliferation, which can be further regulated under the brain stroke-mimic microenvironment. Microglia in mixed glial culture increased their survival and proliferation and altered to the M2 microglia, whose role was provided by CD11b-GFAP+ astrocytes by showing approximately tenfold increase in microglia cell proliferation after the astrocyte reconstitution. Furthermore, GM-CSF stimulated microglial proliferation approximately tenfold and induced to CCR7+ M1 microglia, whose phenotype could be suppressed by anti-inflammatory cytokines such as IL-4, IL-10, and Substance-P. Also, astrocyte in the microglia co-culture revealed A2 phenotype, which could be activated to A1 astrocyte by TNFα and IFNγ under the stroke-mimic condition. Altogether, astrocyte in the mixed glial culture stimulated the microglia proliferation and M2 polarization possibly through its acquisition of A2 phenotype, both of which could be converted to M1 microglia and A1 astrocytes under the inflammatory stroke-mimic environment. This study demonstrated that microglia and astrocyte can be polarized to M2 microglia and A2 astrocytes respectively through the cross-talk in vitro and provided a system to explore how microglia and astrocyte may behave in the inflammatory disease milieu after in vivo transplantation.
Pain is common and associated with substance use among persons with HIV (PWH), yet limited management strategies exist. We assessed the feasibility, tolerability, and safety of low-dose naltrexone and standard dose nalmefene to treat chronic pain among PWH with past-year heavy alcohol use in a randomized, double-blinded, 2-arm study (planned enrollment 8 per arm). Participants were recruited in St. Petersburg, Russia between May and October 2018 and randomized to receive either nalmefene (16 mg) or low-dose naltrexone (4.5 mg) for 8 weeks. The primary outcome was tolerability of medication at eight weeks. Study visits included assessments of pain interference and severity, as well as cold-pressor testing. All participants in the nalmefene arm (N = 3) discontinued the study medication early due to side effects; nalmefene was subsequently deemed intolerable and this arm was terminated. The mean tolerability score at 8-weeks in the low-dose naltrexone arm was 90.7 (SD 22.44), median was 100 (IQR 95- 100), and median cold pain tolerance was approximately 10 s higher at the end of the 8 weeks. Low-dose naltrexone was well-tolerated, but nalmefene was not, in this sample. Further research is warranted to explore low-dose naltrexone’s potential efficacy as a non-addictive treatment for pain in this population.
Clinical trial registration
ClinicalTrials.gov identifier: NCT03278886.
Research on Parkinson's disease (PD) has mainly focused on the degeneration of the dopaminergic neurons of nigro-striatal (NS) pathway; however, post-mortem studies have demonstrated that other brain regions are significantly affected as well (Jellinger, 1999). These other regions include the locus coeruleus (LC) and raphe nuclei (RN), which are principal sites of noradrenergic and serotonergic synthesis, respectively. Degeneration of these crucial neuronal cell bodies is generally thought to occur prior to the deterioration of dopaminergic neurons in the NS pathway and hence predates the appearance of the motor symptoms that characterize PD. Many patients in the early "pre-motor" stage of PD suffer from comorbid depression, anxiety, and cognitive deficits. These deficits may be the result of a loss in noradrenergic and serotonergic innervation given the prominent role of these neurotransmitters in both emotional and cognitive function (Cummings et al., 1999). These psychiatric disturbances greatly affect the patient's quality of life. We have thus set out to create a "pre-motor" rodent model of PD which mimics the early stages of the condition. N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4), a selective noradrenergic neurotoxin, and parachloroampetamine (pCA), a selective serotonergic neurotoxin, were ultilized concomitantly with bilateral 6-hydroxydopamine (6-OHDA) injections into the striatum to produce a premotor rodent model of PD with partial deficits in the dopaminergic, noradrenergic, and serotonergic systems. Behavioral deficits were assessed using a wide array of tests including sucrose preference, open field exploration, forced swim test, and novel object recognition. Neurochemical deficiencies were assessed using in vivo microdialysis, tissue content levels, and immunohistochemistry. We then sought to evaluate the therapeutic value of Exendin-4 (EX-4) on our premotor rodent model. It has been previously demonstrated that EX-4, a glucagon-like peptide-1 receptor (GLP-1R) agonist, is neuroprotective in rodent models of PD (Bertilsson et al., 2008; Harkavyi et al., 2008). We found that EX-4 was able to reverse all neurochemical and behavioural deficits exhibited by our model and exhibits anti-depressant like properties. EX-4 preserved the functional integrity of the dopaminergic, noradrenergic, and serotonergic systems. In conclusion, we have generated a novel animal model of PD that recapitulates certain premotor symptomology. These symptoms and causative physiology are ameliorated upon treatment with EX-4 and thus it could be used as a possible therapy for the non-motor symptoms prominent in the early stages of PD.
Parkinson's disease (PD) is an irreversible neurodegenerative disorder with no cure and current treatments have limited efficacy and unpleasant side effects. The aetiology of PD is complex involving apoptotic, excitotoxic, free radical mediated and inflammatory events. This work involved studying the effect of the corticotrophin releasing factor (CRF)-like peptide urocortin (UCN) on two distinct rodent models of PD, the well established 6-OHDA rat model and the more recently introduced LPS model. UCN's effects were examined in these models immediately after the lesion was induced and also after the lesion had significantly progressed. The mechanisms of action for UCN were examined through the use of selective CRF-R2 agonists UCNII and UCNIII to determine whether they exerted the same actions as UCN. The non selective antagonist a-helical CRF was also used in conjunction with UCN to examine whether reversed the effect of UCN. Another selective CRF-R1 antagonist, NBI-27914, was also used with UCN to confirm those findings. Experiments were carried out in rats, and the effects of the different treatments used were evaluated through the use of multiple assessments. When UCN was given at the same time as 6-OHDA or LPS, this peptide reversed/restored key indicators of PD-Like damage. These included behavioral effects, loss of tissue and extracellular dopamine, loss of tyrosine hydroxylase (TH) activity and protein levels, in addition to the loss of TH immuno-reactivity in nigral sections. The effects of reversing/restoring these key indicators of PD-like damage were also observed when UCN was given seven days after 6-OHDA or LPS treatment, when the lesion had significantly progressed. When the pharmacology of the UCN phenomenon was studied using CRF receptor agonists and antagonists, it was determined that UCN was acting via CRF-R1 receptors, a finding which may prove significant for development of new medications and exploring CRF-R1 as a new target in PD treatment. It was concluded that an extension of these observations to the clinic could have potential benefits for PD patients.
Parkinson's disease (PD) is a progressive neurodegenerative disorder with no current cure and therapies that are directed towards symptomatic relief but have potentially disabling side effect profiles. The need for an alternative therapeutic approach is crucial. Not so long ago it has been demonstrated that the glucagon-like peptide-1 receptor (GLP-1R) agonist exendin-4 (EX-4) originally isolated from saliva of Heloderma suspectum lizard (Eng et al., 1992) is neurotrophic and neuroprotective in vitro leading to the suggestion that stimulation of central GLP-1 receptors could have therapeutic value in neurodegenerative disorders such as PD (Perry et al., 2002b). Here we have investigated the effects of EX-4 treatment in rats with nigrostriatal lesions following central 6-hydroxydopamine (6-OHDA) or lipopolysaccharide (LPS) injection. Both toxins were delivered stereotactically and animals were then investigated in vivo and ex vivo with a wide range of behavioural, neurochemical and histological tests to assess the integrity of the nigrostriatal dopamine (DA) system. EX-4 was administered twice daily at two different doses seven days after intracerebral toxin injection for the duration of one week. Another week thereafter the lesion severity was quantified based on contralateral circling behaviour following apomorphine injection. Circling was very pronounced in toxin only treated animals and significantly lower in rats co-treated with EX-4 at both doses (0.1 and 0.5μg/kg) while it was increased again in groups co-treated with either GLP-1R antagonist EX-9-39 or the DA D3-receptor antagonist nafadotride. This suggested that the neuroprotective effect of EX-4 involved activation of both GLP-1R and DA D3-receptors. Animals were then implanted with microdialysis probes and extracellular DA was measured using in vivo microdialysis. Both basal and potassium evoked levels of DA were markedly reduced in toxin treated animals but were comparable to control levels in EX-4 treated groups. Groups co-treated with either of the two antagonists resulted in DA levels being comparable to 6-OHDA or LPS only treated animals, which again shows the involvement of both GLP-1Rs and D3-receptors. In addition to these findings, striatal tissue DA, tyrosine hydroxylase (TH) activity and TH immunolabelling were also measured in these groups and all confirmed the behavioural and in vivo data. In conclusion, EX-4 clearly reverses the loss of extracellular DA and the integrity of the nigrostriatal system in toxin lesioned rats. The mechanism involves both the GLP-1R and D3-receptors. EX-4 readily enters the brain on peripheral administration and is already in use for type 2 diabetes for which it was FDA approved in 2005 and in our view should be clinically tested in human PD patients without further delay.
Nuclear receptor‐related 1 protein (NURR1) is essential for the development and maintenance of midbrain dopaminergic (DAergic) neurons. NURR1 also protects DAergic neurons against neuroinflammation. However, it remains to be determined to what extent does NURR1 exerts its protective function through acting autonomously in the microglia. Using Cre/lox gene targeting system, we deleted Nurr1 in the microglia of Nurr1 Cd11bcre conditional knockout (cKO) mice. The Nurr1 Cd11bcre cKO mice displayed age‐dependent motor abnormalities and increased microglial activation, but with no obvious DAergic neurodegeneration. To boost the inflammatory injury, we systemically administered endotoxin lipopolysaccharide (LPS) to Nurr1 Cd11bcre mice. As expected, LPS treatment exacerbated the motor phenotypes and inflammatory reactions in Nurr1 Cd11bcre cKO mice. More importantly, LPS administration caused DAergic neuron loss and α‐synuclein aggregation, two pathological hallmarks of Parkinson's disease (PD). Therefore, our findings provide in vivo evidence supporting a critical protective role of NURR1 in the microglia against inflammation‐induced degeneration of DAergic neurons in PD. Lipopolysaccharide treatment could exacerbate neuroinflammation and dopaminergic neuron degeneration in Nurr1 Cd11bcre conditional knockout mice.
Parkinson’s disease (PD) is the second most common neurodegenerative disorder among elderly population, characterized by the progressive degeneration of dopaminergic neurons in the midbrain. To date, exact cause remains unknown and the mechanism of neurons death uncertain. It is typically considered as a disease of central nervous system (CNS). Nevertheless, numerous evidence has been accumulated in several past years testifying undoubtedly about the principal role of neuroinflammation in progression of PD. Neuroinflammation is mainly associated with presence of activated microglia in brain and elevated levels of cytokine levels in CNS. Nevertheless, active participation of immune system as well has been noted, such as, elevated levels of cytokine levels in blood, the presence of auto antibodies, and the infiltration of T cell in CNS. Moreover, infiltration and reactivation of those T cells could exacerbate neuroinflammation to greater neurotoxic levels. Hence, peripheral inflammation is able to prime microglia into pro-inflammatory phenotype, which can trigger stronger response in CNS further perpetuating the on-going neurodegenerative process.
In the present review, the interplay between neuroinflammation and the peripheral immune response in the pathobiology of PD will be discussed. First of all, an overview of regulation of microglial activation and neuroinflammation is summarized and discussed. Afterwards, we try to collectively analyze changes that occurs in peripheral immune system of PD patients, suggesting that these peripheral immune challenges can exacerbate the process of neuroinflammation and hence the symptoms of the disease. In the end, we summarize some of proposed immunotherapies for treatment of PD.
Context:
Parkinson's disease is the second common progressive neurodegenerative disease, distressing older men and is prevalent Worldwide.
Objectives:
This paper is aimed to review the epidemiology, etiology, pathogenesis, clinical manifestation, diagnosis and management of Parkinson disease.
Methods:
A google search was performed to recognize studies that review the characteristics of Parkinson disease. Search terms included " Parkinson's disease", " epidemiology", " etiology", " pathogenesis", " clinical manifestations", " diagnosis" and " management of Parkinson disease".
Results:
Parkinson's disease is linked to factors such as environmental chemicals, aging, family history and pesticide exposure such as the use of synthetic heroin. Parkinson's disease is characterized clinically by tremors at rest, postural instability, expressionless countenance, lead pipe rigidity and less commonly cognitive impairment. After 60 years of age, Parkinson's disease is commonly prevalent in 1% to 2% of the population, no racial differences are apparent, but the prevalence of Parkinson's disease is more common in men than women. There has also been a better understanding that the disorder may be linked with major non-motor trouble in addition to the additional generally recognized motor complications. There are various management options for the timely management of Parkinson disease. As the ailment advances, further management strategies are existing; however, the management of non-motor manifestations and late stage motor complications remains mainly testing and will advantage from additional clinical studies.
Conclusion:
In this article we have discussed current progress in the understanding of the epidemiology, clinical manifestations, pathogenesis and management strategies of the disease.
Tyrosyl radicals have been detected during turnover of prostaglandin endoperoxide H synthase (PGHS), and they are speculated
to participate in cyclooxygenase catalysis. Spectroscopic approaches to elucidate the identity of the radicals have not been
definitive, so we have attempted to trap the radical(s) with nitric oxide (NO). NO quenched the EPR signal generated by reaction
of purified ram seminal vesicle PGHS with arachidonic acid, suggesting that NO coupled with a tyrosyl radical to form inter alianitrosocyclohexadienone. Subsequent formation of nitrotyrosine was detected by Western blotting of PGHS incubated with NO
and arachidonic acid or organic hydroperoxides using an antibody against nitrotyrosine. Both arachidonic acid and NO were
required to form nitrotyrosine, and tyrosine nitration was blocked by the PGHS inhibitor indomethacin. The presence of superoxide
dismutase had no effect on nitration, indicating that peroxynitrite was not the nitrating agent. To identify which tyrosines
were nitrated, PGHS was digested with trypsin, and the resulting peptides were separated by high pressure liquid chromatography
and monitored with a diode array detector. A single peptide was detected that exhibited a spectrum consistent with the presence
of nitrotyrosine. Consistent with Western blotting results, both NO and arachidonic acid were required to observe nitration
of this peptide, and its formation was blocked by the PGHS inhibitor indomethacin. Peptide sequencing indicated that the modified
residue was tyrosine 385, the source of the putative catalytically active tyrosyl radical.
Cytokines such as interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha) are produced by leukocytes and play a role in immune responses. They also function in normal brain physiology as well as in pathological conditions within the central nervous system, where they are produced by brain macrophages (microglia) and brain astrocytes. In this study, we document the ability of human immunodeficiency virus type 1 (HIV-1) to induce TNF alpha and IL-1 in primary rat brain cultures. While productive infection did not occur in these cells, it was not required for cytokine induction. Using monocyte/macrophage-tropic (JRFL) and T-cell-tropic (IIIB) strains of HIV-1, we were able to induce cytokines in both microglia and astrocytes. In addition to whole virus, recombinant envelope proteins also induced these cytokines. The induction of IL-1 and TNF alpha could be blocked by a panel of antibodies recognizing epitopes in the gp120 and gp41 areas of the envelope. Soluble recombinant CD4 did not block TNF alpha and IL-1 production. If TNF alpha and IL-1 can be induced in brain tissue by HIV-1, they may contribute to some of the neurologic disorders associated with AIDS.
A new automated system for the analysis of nitrate via reduction with a high-pressure cadmium column is described. Samples of urine, saliva, deproteinized plasma, gastric juice, and milk can be analyzed for nitrate, nitrite, or both with a lower limit of detection of 1.0 nmol NO3− or NO2−/ml. The system allows quantitative reduction of nitrate and automatically eliminates interference from other compounds normally present in urine and other biological fluids. Analysis rate is 30 samples per hour, with preparation for most samples limited to simple dilution with distilled water. The application of gas chromatography/mass spectrometry for the analysis of 15NO3− in urine after derivatization to 15NO2-benzene is also described.
The human immunodeficiency virus type 1 coat protein, gp120, kills neurons in primary cortical cultures at low picomolar concentrations. The toxicity requires external glutamate and calcium and is blocked by glutamate receptor antagonists. Nitric oxide (NO) contributes to gp120 toxicity, since nitroarginine, an inhibitor of NO synthase, prevents toxicity as does deletion of arginine from the incubation medium and hemoglobin, which binds NO. Superoxide dismutase also attenuates toxicity, implying a role for superoxide anions.
Dopaminergic neurotoxicities of 6-hydroxydopamine (6-OHDA) and the lipopolysaccharide (LPS) were compared in rat mesencephalic cultures plated on poly-L-lysine or on glial monolayers. In the neuron-enriched cultures plated on polylysine, 6-OHDA killed 89% of the tyrosine hydroxylase (TH)-immunopositive neurons, but LPS was not neurotoxic. Conversely, in mixed neuron/glial cultures, 6-OHDA killed only 27% of the TH-immunopositive neurons while LPS killed 70%. The mixed neuronal/glial mesencephalic culture offers a better in vitro model for studying possible mechanisms involved in Parkinson's disease.
Tumor necrosis factor-α (TNFα)-induced cell death involves a diverse array of mediators and regulators including proteases, reactive oxygen species, the sphingolipid ceramide, and Bcl-2. It is not known, however, if and how these components are connected. We have previously reported that GSH inhibits, in vitro, the neutral magnesium-dependent sphingomyelinase (N-SMase) from Molt-4 leukemia cells. In this study, GSH was found to reversibly inhibit the N-SMase from human mammary carcinoma MCF7 cells. Treatment of MCF7 cells with TNFα induced a marked decrease in the level of cellular GSH, which was accompanied by hydrolysis of sphingomyelin and generation of ceramide. Pretreatment of cells with GSH, GSH-methylester, or N-acetylcysteine, a precursor of GSH biosynthesis, inhibited the TNFα-induced sphingomyelin hydrolysis and ceramide generation as well as cell death. Furthermore, no significant changes in GSH levels were observed in MCF7 cells treated with either bacterial SMase or ceramide, and GSH did not protect cells from death induced by ceramide. Taken together, these results show that GSH depletion occurs upstream of activation of N-SMase in the TNFα signaling pathway.
TNFα has been shown to activate at least two groups of caspases involved in the initiation and “execution” phases of apoptosis. Therefore, additional studies were conducted to determine the relationship of GSH and the death proteases. Evidence is provided to demonstrate that depletion of GSH is dependent on activity of interleukin-1β-converting enzyme-like proteases but is upstream of the site of action of Bcl-2 and of the execution phase caspases. Taken together, these studies demonstrate a critical role for GSH in TNFα action and in connecting major components in the pathways leading to cell death.
The fundamental message emerging from immunologic and immunopathologic analyses of the brain and spinal cord in multiple sclerosis (MS) is that during inflammation, the central nervous system (CNS) is capable of interactions with the lymphoid system, mainly through induced (as opposed to constitutive) expression of immune system-specific molecules on CNS elements. CNS endothelium, astrocytes and microglial cells are the main participants, with oligodendrocytes and neurons remaining essentially inert. There appears to be nothing unique about the manner in which the CNS responds to inflammation or in the molecules expressed. The ensuing adhesion molecules, pro-inflammatory and regulatory cytokines, histocompatibility molecules, and T and B cell markers, are difficult to distinguish from those occurring in peripheral lymphoid tissue. However, differences certainly exist in the outcome of an inflammatory insult in the CNS versus other, peripheral tissues, whereby there is generally a poor reparatory response. Reasons for the latter appear to lie in the anatomical complexity of the CNS, its vulnerability to damage by soluble mediators, and in the white matter (the battlefield for the inflammatory attack in MS), the exquisite sensitivity of the oligodendrocyte and its myelin to exogenous factors. With the aid of examples drawn from experimental allergic encephalomyelitis, the prime animal model for MS, a number of approaches to prevent or downregulate CNS inflammation during immune-mediated demyelination are presented as possible therapeutic avenues for MS, some of which are already under investigation.
(C) 1994 American Association of Neuropathologists, Inc
Microglia are associated with central nervous system (CNS) pathology of both Alzheimer's disease (AD) and the acquired immunodeficiency syndrome (AIDS). In AD, microglia, especially those associated with amyloid deposits, have a phenotype that is consistent with a state of activation, including immunoreactivity with antibodies to class II major histocompatibility antigens and to inflammatory cytokines (interleukin-1-β and tumor necrosis factor-α). Evidence from other studies in rodents indicate that microglia can be activated by neuronal degeneration. These results suggest that microglial activation in AD may be secondary to neurodegeneration and that, once activated, microglia may participate in a local inflammatory cascade that promotes tissue damage and contributes to amyloid formation. In AIDS, microglia are the primary target of retroviral infection. Both ramified and ameboid microglia, in addition to multinucleated giant cells, are infected by the human immunodeficiency virus (HIV-1). The mechanism of microglial infection is not known since microglia lack CD4, the HIV-1 receptor. Microglia display high affinity receptors for immunoglobulins, which makes antibody-mediated viral uptake a possible mechanism of infection. In AIDS, the extent of active viral infection and cytokine production may be critically dependent upon other factors, such as the presence of coinfecting agents. In the latter circumstance, very severe CNS pathology may emerge, including necrotizing lesions. In other circumstances, HIV infection microglia probably leads to CNS pathology by indirect mechanisms, including release of viral proteins (gp120) and toxic cytokines. Such a mechanism is the best hypothesis for the pathogenesis of vacuolar myelopathy in adults and the diffuse gliosis that characterizes pediatric AIDS, in which very little viral antigen can be detected.
Inflammation in the brain selectively damages the myelin sheath resulting in a variety of clinical syndromes of which the
most common is multiple sclerosis. In these disorders, the areas of inflammation and demyelination can be identified in life
by magnetic resonance imaging. Events occurring at the blood-brain barrier depend on T-cell activation, which increases immune
surveillance within the central nervous system. T-cells activated against brain antigens persist to establish the conditions
needed for inflammatory demyelination and this depends on local release of cytokines, culminating in removal of oligodendrocytes
and their myelin lamellae by macrophages or microglia. These interactions involve binding between receptors present on microglia
for the Fc portion of antibody and complement components to corresponding ligands on target cells. Taken together, the evidence
from clinical and experimental studies provides a rationale for the issue of immunological treatments in patients with multiple
sclerosis.
(+)-Naloxone was prepared in 26% overall yield in eight steps from (+)-7-bromodihydrocodeinone dimethyl ketal by a synthesis which excluded enantiomeric contamination. (+)-Naloxone was examined in three assay systems and found to have no more than 1/1000(-1)/10 000th the activity of (-)-naloxone; it can, thus, serve to test the stereospecificity of the biochemical and pharmacological actions of (-)-naloxone.
Delayed biochemical changes play an important role in tissue damage resulting from traumatic injuries to the central nervous system. Identification of such 'secondary' injury factors has led to the development of various pharmacological strategies aimed at limiting this progressive tissue destruction. In this review, Alan Faden and Steven Salzman discuss the pharmacological approaches that have the most experimental support. These include corticosteroids, antioxidants and free-radical scavengers, modulators of arachidonate metabolism, gangliosides, monoamine modulators, opioid receptor antagonists, TRH and its analogs, NMDA receptor antagonists, Ca2+ channel antagonists and platelet-activating factor antagonists.
The role of inflammatory cytokines in the pathogenesis of neurological diseases is not well understood. The neurotoxic effects of cytokines could be mediated by immunostimulation of glial cells to produce toxic concentrations of nitric oxide (NO) and reactive nitrogen oxides. Cultured microglia and meningeal fibroblasts, but not Type 1 astrocytes, were induced by lipopolysaccharides and cytokines to synthesize NO and reactive nitrogen oxides from L-arginine. In co-cultures of immunostimulated microglia and cerebellar granule neurons, neurotoxicity was blocked by an inhibitor of NO synthase, NG-nitroarginine, and by oxyhemoglobin, which inactivates NO. Microglial-induced neurotoxicity was also partially attenuated by the N-methyl-D-aspartate (NMDA) receptor antagonists, MK-801 and 2-amino-5-phosphovalerate (APV). Superoxide dismutase, which stabilizes NO through inactivation of superoxide anion, augmented microglial-mediated neurotoxicity either alone or in combination with MK-801 or APV. Hence, immunostimulated microglia mediate neurotoxicity by NO, reactive nitrogen oxides, superoxide anion and NMDA-like substances. These findings suggest a novel role for microglial-produced NO and reactive nitrogen oxides as a neurotoxic agent in neurodegenerative disease states.
The effects of the stereoisomers of naloxone during myocardial ischemia were studied. (-)-Naloxone (but not the (+)-isomer naloxone) attenuated the ischemia-induced cardiac arrhythmias, hypotension, and bradycardia that result from coronary artery occlusion in anesthetized rats. From these findings, it may be inferred that endogenous opioid peptides may play a role in the pathophysiology of myocardial ischemia. It is also suggested that naloxone may have therapeutic value in the prevention and treatment of ischemic heart disease.
Epidermal growth factor (EGF) immunoreactive material has been demonstrated to be present in the basal ganglia. In this study, we investigated the effect of EGF on cells cultured from 16-day embryonic rat mesencephalon, which included dopamine neurons that project to the striatum in vivo. EGF receptors were detected in untreated cultures by [125I]-EGF binding. Treatment of the cultures with EGF resulted in up to 50-fold increases in neuronal high-affinity dopamine uptake. Scatchard analysis of uptake kinetics and counting of tyrosine hydroxylase-immunoreactive cells suggest that the effect of EGF on uptake is due to increased survival and maturation of dopaminergic neurons. By contrast, the high-affinity uptake for serotonin was increased only threefold over its controls. There was no significant effect on high-affinity gamma-aminobutyric acid (GABA) uptake. These results suggest that EGF is acting as a neurotrophic agent preferential for dopaminergic neurons in E16 mesencephalic cultures. Immunocytochemistry for glial fibrillary acidic protein demonstrated an increase in astroglia with EGF treatment. Fluorodeoxyuridine, an agent that is toxic to proliferating cells was able to eliminate the effect of EGF on dopamine uptake, suggesting that EGF may be increasing dopaminergic cell survival largely through a population of dividing cells.
Naloxone was found to prevent both opioid and non-opioid-induced migration of human granulocytes in a stereoselective way. Indeed, besides being able to inhibit morphine-induced migration, (-) but not (+), naloxone isomer proved to abolish either casein, serum of fMLP-induced chemotaxis. It is concluded that opioid-induced modulation of granulocyte migration is likely to be mediated through specific receptors, possibly of the mu type. Moreover, the antichemotactic effect of naloxone suggests an involvement of opioid receptors and/or endogenously released opioids in the mechanism of granulocyte activation by different chemoattractants.
The toxicity of MPTP to dopamine (DA) neurons was studied in dissociated cell cultures from rat embryo mesencephalon. The cultures were exposed to MPTP (from 0.1 to 200 microM) for 7 days and were analyzed by catecholamine histofluorescence after incubation with alpha-methylnorepinephrine, by tyrosine hydroxylase (T-OH) immunocytochemistry and by [3H]DA uptake. Treatment with MPTP at the lower range of concentrations (between 0.1 and 5 microM) resulted in a dose-dependent reduction of the uptake of [3H]DA, which had a maximum effect at 5 microM. Further increase in the concentration of MPTP (from 10 to 200 microM) resulted in progressive attenuation of the toxic effect. Exposure to 200 microM MPTP did not produce significant reduction in the uptake of [3H]DA. Increased survival of DA neurons at the higher concentrations of MPTP, was documented by catecholamine histofluorescence and by T-OH immunocytochemistry in cultures treated with 10 and 100 microM MPTP. MPTP was shown to be a potent inhibitor of MPP+ uptake by DA neurons in culture. In the presence of 100 or 200 microM MPTP, the uptake of MPP+ was reduced to less than 20% of control levels. Therefore, the reduction of MPTP toxicity at the high concentrations can be explained, at least in part, by the inhibition of the uptake of MPP+ (the toxic metabolite of MPTP oxidation) in the presence of high concentrations of MPTP.
Using the superoxide dismutase inhibitable reduction of cytochrome c assay, we studied, the effect of (-) naloxone on N-formyl-methionyl-leucyl-phenylalanine (FMLP) stimulated superoxide (O2-) release from human neutrophils. Neutrophils were pre-incubated with the range of concentrations of (-) naloxone that is administered in models of experimental sepsis (10(-6) - 10(-4.5) M). (-) Naloxone inhibited O2- release in a dose dependent manner. 02- produced by a cell-free xanthine-xanthine oxidase system was not inhibited by (-) naloxone, indicating that (-) naloxone was not scavanging O2-. There was no difference between the effect of (-) and (+) naloxone suggesting that the inhibition of O2- was not specific for an opiate receptor. Another opiate antagonist, nalorphine, as well as the opiate agonist, morphine, also inhibited O2- release in the same concentration range. There was no difference between the effect of naloxone and morphine.
(-)-Naloxone, 1 mM, partially reduced neuronal loss induced by exposure of murine cortical cell cultures to N-methyl-D-aspartate (NMDA) or quinolinate, but produced little or no attenuation of kainate or quisqualate neurotoxicity. Antagonism of NMDA neurotoxicity was (-)-naloxone concentration-dependent between 100 microM and 3 mM. (+)-Naloxone produced a slightly greater reduction of NMDA neurotoxicity, arguing against mediation by opioid receptors. Although this novel neuron-protective action of (-)-naloxone was weak, it may contribute to reported beneficial effects in CNS ischemia.
Naloxone has been reported to have potential benefit in the treatment of stroke. We evaluated the effect of naloxone in a double-blind trial conducted with 15 stroke patients whose deficits ranged from 8 to 60 hours in duration. All but one patient sustained a cerebral infarction. Neurologic function was assessed before and five minutes after each of two injections given to each patient in a double-blind fashion. The injections consisted of naloxone (0.4 mg in 3 patients and 4.0 mg in 12 patients) and saline. Prior to the trial, samples of plasma were obtained for determination of immunoreactive beta-endorphin for each patient. Four patients showed minimal improvement following injection of naloxone, while five patients exhibited a slightly greater improvement following saline injection. There were no significant elevations of plasma beta-endorphin among stroke patients. We conclude that naloxone may not have a significant therapeutic role for stroke in the clinical setting.
Microsurgical unilateral occlusion of the right common carotid artery in 140 adult male gerbils produced homolateral cerebral ischemia and a neurologic deficit (stroke) in 42 percent (group A); the other 58 percent did not develop signs of stroke (group B). Intraperitoneal injection of the opiate antagonist naloxone (1 milligram per kilogram of body weight) reversed the signs of stroke within 3 to 5 minutes in ten out of ten group A gerbils; the effect lasted up to 30 minutes, after which stroke returned. Repeated injections of naloxone reversed stroke, but all ten gerbils died within 48 hours of ligation. However, nine other group A gerbils implanted with 10-milligram naloxone pellets had continuous reversal of signs of stroke, and four survived for more than 2 weeks. Twenty-one out of 24 group B gerbils injected intraperitoneally with morphine sulfate (5 to 30 milligrams per kilogram) 9 hours after ligation developed stroke within 3 to 20 minutes; morphineinduced stroke lasted 4 to 24 hours and could be reversed by intraperitoneal injection of naloxone. Ten out of 11 other group B gerbils injected intraperitoneally with the stereoisomeric opiate agonist levorphanol 9 hours after ligation developed signs of mild stroke that were reversed by intraperitoneal injection of naloxone. Ten other group B gerbils injected intraperitoneally with dextrorphan, the inactive enantiomer of levorphanol, 9 hours after ligation did not develop signs of stroke. Intraperitoneal injection of an enkephalin analog (Sandoz FK33824; 15 milligrams per kilogram) 9 hours after ligation did not produce stroke in ten other group B gerbils. These findings suggest the involvement of endorphins and opiate receptors in the pathophysiology of stroke and suggest the possible clinical use of opiate antagonists in humans in the acute phase of stroke.
The relative potencies of the (+) and (-) isomers of naloxone in antagonizing electrophysiological responses to D-alanine2-methionine enkephalinamide were compared in rat frontal cortex and hippocampus. In the in vitro hippocampus, the (-) isomer was found to be at least a 100 times more potent than the (+) isomer in antagonizing opiate-induced changes in field potentials. Similar stereoselectivity was observed in vivo in both frontal cortex and hippocampus in terms of the antagonism of enkephalin-induced changes in spontaneous cell firing. The direct effects of (+) and (-)-naloxone were examined as well. In hippocampus both in vivo and in vitro, no differential effect was observed, whereas in the neocortex (-)-naloxone was considerably more potent than the (+) isomer in eliciting depressions of spontaneous activity. These direct effects of naloxone in the cortex do not appear to be due to an antagonism of the effects of endogenously released opioids. These results demonstrate that the stereoselectivity of naloxone isomers in antagonizing electrophysiological responses to opiates in the cortex and hippocampus parallels that previously observed in other brain regions and in other tissues. In addition, they suggest that naloxone may have interactions with other unknown opiate (or possibly non-opiate) receptors which are of physiological significance.
In the present study, functional interactions between [Met5]-enkephalin (ME), naloxone and lipopolysaccharide (LPS) on interleukin-1 beta (IL-1 beta) immunostaining and secretion have been assessed in mixed brain cell cultures from embryonic day 17 mice. Adding ME alone or together with LPS to the culture increased the release of IL-1 beta after 48 h in a concentration-dependent fashion. In situ hybridization studies showed that LPS, but not ME, increased the abundance of IL-1 beta mRNA. The enhanced release of IL-1 beta caused by ME or LPS was partially blocked by naloxone. LPS induced concentration-dependent morphological changes in microglia in mixed brain cell cultures, identified by a monoclonal antibody F4/80 which is specific for macrophages/microglia. Despite increasing IL-1 beta release into the media, ME (10(-8) M) did not induce morphological changes in microglia. Naloxone alone also had no effect on glial morphology; however, the LPS-induced morphological changes were blocked by naloxone. Our data indicate that both exogenous and endogenous opioids regulate IL-1 beta production by microglial cells in the mixed brain cell cultures.
The most characteristic property of microglia is their swift activation in response to neuronal stress and their capacity for site-directed phagocytosis. The transformation of microglia into intrinsic brain macrophages appears to be under strict control and takes place if neuronal and/or terminal degeneration occurs in response to nerve lesion. The differentiation of microglia into brain macrophages is accompanied by the release of several secretory products, e.g., proteinases, cytokines, reactive oxygen intermediates, and reactive nitrogen intermediates. Interference with the microglial activation or the productions of cytotoxic metabolites by microglia may thus offer new therapeutic opportunities for the prevention of neuronal cell death in CNS disease.
beta-Amyloid protein (A beta) is the major component of the senile plaques in Alzheimer's disease (AD), and microglial cells have been shown to be closely associated with these plaques. However, the roles of A beta and microglial cells in pathogenesis of AD remain unclear. Incubation of rat microglial cells with A beta(1-40) caused a significant increase in nitrite, a stable metabolite of nitric oxide (NO), in culture media, while there was no detectable increase in nitrite in astrocyte-rich glial cells or cortical neurons after incubation with A beta(1-40). Nitrite production by microglial cells was also induced by A beta(1-42), but not A beta(25-35). An inhibitor of NO synthase, NG-monomethyl-L-arginine (NMMA), as well as dexamethasone and actinomycin D, dose-dependently inhibited this nitrite production. Among the various cytokines investigated such as interleukin-1, interleukin-6, tumor necrosis factor-alpha and interferon-gamma (IFN-gamma), only IFN-gamma markedly enhanced A beta-dependent nitrite production. Cultured cortical neurons were injured by microglial cells stimulated with A beta in a dose-dependent manner in the presence of IFN-gamma. Neurotoxicity caused by the A beta plus IFN-gamma-stimulated microglial cells was significantly attenuated by NMMA. Thus, although further investigations into the effect of A beta on human microglial cells are needed, it is likely that A beta-induced NO production by microglial cells is one mechanism of the neuronal death in AD.
Dextro-naloxone [(+)-naloxone], an isomer with almost no opiate antagonist activity and no effect on spontaneous locomotor activity, can reduce cocaine-induced hyperactivity in mice. The classical opiate antagonist, levo-naloxone [(-)-naloxone], is known to counteract the excitatory motor effects of amphetamine and cocaine, but it has been tacitly assumed that this action of levo-naloxone is dependent on its ability to antagonize endogenous opioids. Our finding that a naloxone isomer with little or no opioid antagonist activity is also able to inhibit the cocaine effect on spontaneous motility, calls for a reconsideration of this assumption.
The most characteristic feature of microglial cells is their rapid activation in response to even minor pathological changes in the CNS. Microglia activation is a key factor in the defence of the neural parenchyma against infectious diseases, inflammation, trauma, ischaemia, brain tumours and neurodegeneration. Microglia activation occurs as a graded response in vivo. The transformation of microglia into potentially cytotoxic cells is under strict control and occurs mainly in response to neuronal or terminal degeneration, or both. Activated microglia are mainly scavenger cells but also perform various other functions in tissue repair and neural regeneration. They form a network of immune alert resident macrophages with a capacity for immune surveillance and control. Activated microglia can destroy invading micro-organisms, remove potentially deleterious debris, promote tissue repair by secreting growth factors and thus facilitate the return to tissue homeostasis. An understanding of intercellular signalling pathways for microglia proliferation and activation could form a rational basis for targeted intervention on glial reactions to injuries in the CNS.
Cultured brain cells are capable of generating many molecules associated with inflammatory and immune functions. They constitute the endogenous immune response system of brain. They include complement proteins and their regulators, inflammatory cytokines, acute phase reactants and many proteases and protease inhibitors. Most of the proteins are made by microglia and astrocytes, but even neurons are producers. Many appear in association with Alzheimer disease lesions, indicating a state of chronic inflammation in Alzheimer disease brain. Such a state can apparently exist without stimulation by peripheral inflammatory mediators or the peripheral immune system. A strong inflammatory response may be autotoxic to neurons, exacerbating the fundamental pathology in Alzheimer disease and perhaps other neurological disorders. Autotoxic processes may contribute to cellular death in chronic inflammatory diseases affecting other parts of the body, suggesting the general therapeutic value of anti-inflammatory agents. With respect to Alzheimer disease, multiple epidemiological studies indicate that patients taking anti-inflammatory drugs or suffering from conditions in which such drugs are routinely used, have a decreased risk of developing Alzheimer disease. In one very preliminary clinical trial, the anti-inflammatory drug indomethacin arrested progress of the disease. New agents directed against the inflammatory processes revealed in studies of Alzheimer disease lesions may have broad therapeutic applications.
Microglial cells are believed to play an active role in brain inflammatory, immune and degenerative processes. Depending on the magnitude of microglial reaction, on the type of stimulus and on the concurrence of other local factors, microglia can contribute to host defence and repair, or to the establishment and maintenance of brain damage. Many of the effects of microglial cells can be ascribed to the numerous substances that these cells can synthesize and release in response to a variety of stimuli (cytokines, pro-inflammatory substances, neurotransmitters, toxins, etc.). The present article deals with two classes of compounds that activated microglial cells can produce in large amounts: prostanoids (that derive from arachidonic acid through the cyclooxygenase pathway), and nitric oxide (that is synthesized from arginine by nitric oxide synthase). Prostanoids and nitric oxide have a number of common targets, on which they may exert similar or opposite actions, and have a crucial role in the regulation of inflammation, immune responses and cell viability. Their synthesis can massively increase when the inducible isoforms of cyclooxygenase and nitric oxide synthase are expressed. The metabolic pathways of prostanoids and nitric oxide are finely tuned by the respective end-products, by cyclic AMP and by a number of exogenous factors, such as cytokines, glucocorticoids, lipocortin-1 and others. Some of these factors (e.g. transforming growth factor-beta 1, interleukin-10, lipocortin-1) may be secreted by microglial cells themselves, and act in an autocrine-paracrine way. In view of the neuroprotective role attributed to some prostaglandins and to the cytotoxicity of excessive levels of nitric oxide or its derivatives, the balance between prostanoid and nitric oxide levels may be crucial for orienting microglial reactions towards neuroprotection or neurotoxicity.
The locomotor stimulating effect of d-amphetamine in mice was counteracted by the administration of l-naloxone [(-)-naloxone], a known opiate receptor antagonist. Mice injected with amphetamine reached a peak locomotor activity within 30 min. When treated simultaneously with amphetamine and l-naloxone, these subjects showed low motility. Furthermore, when mice were treated not with l-naloxone but with its mirror image, d-naloxone [(+)-naloxone], a compound that by itself does not antagonize opiates and does not affect spontaneous motility, they showed no amphetamine-induced hyperactivity. The finding that an enantiomer of naloxone, with no opiate antagonist activity, is able to block the excitatory action of amphetamine, suggests the existence of a hitherto unknown mechanism of counteracting some of the effects of stimulants and euphoriants like amphetamine and cocaine.
Human immunodeficiency virus (HIV)-1 neuropathogenesis can be divided into three important components: (i) virus entry into the nervous system; (ii) the role of viral proteins and/or cellular products in neural tissue damage; (iii) the mechanisms of neuronal injury/death. Both blood derived macrophages or trafficking HIV-1 infected T-lymphocytes have been implicated in viral entry to the central nervous system (CNS). The major cell type harboring productive HIV-1 infection in the nervous system is the perivascular macrophage/microglia. The HIV-1 infection of brain astrocytes, restricted to the expression of regulatory gene products, may cause astrocyte dysfunction and contribute to neuronal injury or to disruption of the blood-brain barrier (BBB). Studies of cerebrospinal fluid and postmortem tissues reveal chronic inflammation/immune activation in the nervous system during the later stages of HIV-1 infection associated with disruption of BBB integrity. Blood-brain barrier damage may underlie the white matter pallor described in HIV-1 infection and could result in further entry into the CNS of toxic viral or cellular products, or additional HIV-1 infected cells. The HIV infected and activated macrophages/microglia produce excessive amounts of pro-inflammatory cytokines, including tumor necrosis factor alpha, and platelet activating factor. These products are directly toxic to human neurons in vitro. The HIV-1 envelope glycoprotein, gp 120 may stimulate the release of toxic factors from brain macrophages. Blocking N-methyl-D-aspartate (NMDA; or AMPA) glutamate receptors can antagonize candidate toxins of both viral and cellular origin. It has been postulated that (weak) excitotoxicity leads to oxidative stress in neurons and ultimately to apoptosis. Neuronal apoptosis occurs in the brains of both children and adults with HIV-1 infection. This understanding of HIV neuropathogenesis implies that therapeutic strategies should include: (i) anti-retroviral medications to decrease systemic and CNS virus load, and possibly to prevent perinatal transmission of HIV; (ii) anti-inflammatory compounds to decrease the chronic immune activation in microglia and allow the restoration of BBB integrity; and (iii) neuroprotective compounds to reduce neuronal injury and apoptotic death.
Activation of brain glial cells with the bacterial endotoxin lipopolysaccharide (LPS), the HIV-1 coat protein gp120, or beta-amyloid-derived peptides, stimulates the expression of several cytokines, including tumor necrosis factor-alpha (TNFalpha), interleukin-1 (IL-1) and IL-6. and nitric oxide (NO) which have been proposed as causes of neurodegeneration in the brain. In the present study, the neurotoxic effects of several cytokines, alone or in various combinations, and the correlations of the release of lactate dehydrogenase, the loss of neurons, and the secretion of NO in brain neuronal cell injury were investigated in murine primary mixed neuronal/glial cell cultures. A specific combination of cytokines, i.e., IL-1 (1 ng/ml)+ TNFalpha (10 ng/ml)/interferon-gamma (IFNgamma) (200 u/ml), induced a dramatic neuronal cell injury in the neuron/glia cultures, and its cytotoxic profile was very similar to that seen with the LPS/IFNgamma-induced neuron injury. This indicates that among the many toxic immune mediators secreted in response to LPS, IL-1 and TNFalpha can mimic LPS as the triggering signals and primary mediators for glia-mediated neuron injury in the presence of IFNgamma. This study provides new insights about the cytotoxic mechanism(s) for cytokine-mediated neuron injury.
Inflammatory components play an important part in many diseases of the central nervous system (CNS). Recent evidence suggests that this may also be true of diseases which were previously considered as purely neuro-degenerative. However, it is also clear that inflammatory responses in the CNS differ in many ways from responses in non-CNS tissues. Some of these differences have been demonstrated by the use of animal models. For example, when bacteria are injected into the brain parenchyma, they induce a typical acute inflammatory response. However, unlike in other tissues, bacteria which are not cleared from the brain parenchyma remain undetected by the immune system. Some bacteria, such as bacillus Calmette-Guérin, can persist in the brain parenchyma for months sequestered in microglia and perivascular macrophages. When an animal with an intraparenchymal bacteria deposit is later sensitised peripherally, an immune response is evoked at the site of the deposits. The lesions induced in the CNS parenchyma are T-cell mediated and show characteristics typical of a delayed-type hypersensitivity response. The lesions produce a breakdown of the blood-brain barrier and demyelination. These immune responses are similar to those described for multiple sclerosis lesions. The responses to bacteria are unique to the brain parenchyma. Pathogens injected into the ventricles induce inflammatory responses similar to those in other non-CNS tissues: there is an acute inflammatory response which develops spontaneously into an immune mediated response within the first week.
The concept of innate immunity refers to the first-line host defense that serves to limit infection in the early hours after
exposure to microorganisms. Recent data have highlighted similarities between pathogen recognition, signaling pathways, and
effector mechanisms of innate immunity in Drosophila and mammals, pointing to a common ancestry of these defenses. In addition to its role in the early phase of defense, innate
immunity in mammals appears to play a key role in stimulating the subsequent, clonal response of adaptive immunity.