The role of oxidative stress in the dysregulation of gene expression and protein metabolism in neurodegenerative disease

Therapeutic Potential of Antioxidants and Hybrid TEMPOL Derivatives in Ocular Neurodegenerative Diseases: A Glimpse into the Future

Reactive oxygen species play a significant role in the pathogenesis of various ocular neurodegenerative diseases especially glaucoma, age-related macular degeneration (AMD), and ocular ischemic stroke. Increased oxidative stress and the accumulation of ROS have been implicated in the progression of these diseases. As a result, there has been growing interest in exploring potential therapeutic and prophylactic strategies involving exogenous antioxidants. In recent years, there have been significant advancements in the development of synthetic therapeutic antioxidants for targeting reactive oxygen species (ROS) in neurodegenerative diseases. One area of focus has been the development of hybrid TEMPOL derivatives. In the context of ocular diseases, the application of next-generation hybrid TEMPOL antioxidants may offer new avenues for neuroprotection. By targeting ROS and reducing oxidative stress in the retina and optic nerve, these compounds have the potential to preserve retinal ganglion cells and trabecular meshwork and protect against optic nerve damage, mitigating irreversible blindness associated with these diseases. This review seeks to highlight the potential impact of hybrid TEMPOL antioxidants and their derivatives on ocular neurodegenerative disorders.

Oxytocin Prevents the Development of 3-NP-Induced Anxiety and Depression in Male and Female Rats: Possible Interaction of OXTR and mGluR2

Huntington disease (HD) is a progressive neurological disorder with dominant motor symptoms. It also has psychiatric manifestations, like anxiety and depression, that can emerge themselves before motor symptoms and impose a major burden on patients. Oxytocin (OXT) is a newly emerged treatment for disorders like autism and schizophrenia and recently is using to alleviate depression and anxiety. In the current study, we investigated the behavioral and molecular effects of OXT on the development of anxiety and depression in 3-nitropropionic acid (3-NP)-induced model of HD. Anxiety- and depression-like behaviors as well as the levels of oxytocin receptor (OXTR), metabotropic glutamate receptor (mGluR) 2, mGluR5, and glutathione (GSH) were measured in striatum, hippocampus, prefrontal cortex, and amygdala. Also, we questioned if sex had any modulatory effect. We found that 3-NP increased anxiety and depression compared to controls. It also reduced the levels of OXTR and mGluR2, increased mGluR5, and reduced GSH in studied brain regions. Pretreatment with OXT before the injection of 3-NP ameliorated anxiety and depression. Additionally, it protected the brain from developing low levels of OXTR, mGluR2, and GSH and high levels of mGluR5 in studied regions. The protective effects of OXT were similar between male and female animals. These data suggest that OXTR, mGluR2, mGluR5, and GSH may contribute to psychiatric manifestations of HD. In addition, pretreatment with OXT could prevent the mood changes in male and female rats.

Oxytocin, a Novel Treatment for Methamphetamine Use Disorder

The treatment of substance abuse with oxytocin is a novel approach to a challenging public health issue that continues to contribute to a growing economic cost for societies worldwide. Methamphetamine addiction is one of the leading causes of mortality worldwide, and despite advances in understanding the neurobiology of methamphetamine addiction, treatment options are limited. There are no medications that the Food and Drug Administration currently approves for stimulant use disorder. Off-label use of therapies for stimulant misuse include antidepressants, anxiolytics, and milder stimulants as replacement agents. Due to the shortcomings of these attempts to treat a complicated psychiatric disorder, recent attention to oxytocin therapy (OT) has gained momentum in clinical studies as a possible therapy in the context of social stress, social anxiety, social cognition, and psychosis. Oxytocin produces enhanced connectivity between cortical regions. The results from studies in rodents with OT suggest that central neuromodulation of oxytocin may be beneficial across transition states of stimulant dependence and may alleviate intense withdrawal symptoms. Studies of oxytocin in the context of other drugs of abuse, including cocaine, cannabis, and alcohol, also support the potential of oxytocin to treat stimulant use disorder, methamphetamine type. Methamphetamine abuse continues to be a significant cause of distress and dysfunction throughout the world. The effects of oxytocin on methamphetamine use outlined in this review should act as a catalyst for further investigation into the efficacy of treating stimulant use disorder, methamphetamine type with oxytocin in humans. More human-based research should initiate studies involving the long-term efficacy, side effects, and patient selection.

Natural Products in Modulating Methamphetamine-Induced Neuronal Apoptosis

Methamphetamine (METH), an amphetamine-type psychostimulant, is highly abused worldwide. Chronic abuse of METH causes neurodegenerative changes in central dopaminergic neurons with numerous neuropsychiatric consequences. Neuronal apoptosis plays a critical role in METH-induced neurotoxicity and may provide promising pharmacological targets for preventing and treating METH addiction. In recent years, accumulating evidence has revealed that natural products may possess significant potentials to inhibit METH-evoked neuronal apoptosis. In this review, we summarized and analyzed the improvement effect of natural products on METH-induced neuronal apoptosis and their potential molecular mechanisms on modulating dopamine release, oxidative stress, mitochondrial-dependent apoptotic pathway, endoplasmic reticulum stress-mediated apoptotic pathway, and neuroinflammation. Hopefully, this review may highlight the potential value of natural products in modulating METH-caused neuronal apoptosis and provide useful information for future research and developments of novel and efficacious pharmacotherapies in this field.

Pre-mRNA splicing defects and RNA binding protein involvement in Niemann Pick type C disease

Niemann-Pick type C (NPC) is an autosomal recessive lysosomal storage disorder due to mutations in NPC1 (95 % cases) or NPC2 genes, encoding NPC1 and NPC2 proteins, respectively. Both NPC1 and NPC2 proteins are involved in transport of intracellular cholesterol and their alteration leads to the accumulation of unesterified cholesterol and other lipids within the lysosomes. The disease is characterized by visceral, neurological and psychiatric symptoms. However, the pathogenic mechanisms that lead to the fatal neurodegeneration are still unclear. To date, several mutations leading to the generation of aberrant splicing variants or mRNA degradation in NPC1 and NPC2 genes have been reported. In addition, different lines of experimental evidence have highlighted the possible role of RNA-binding proteins and RNA-metabolism, in the onset and progression of many neurodegenerative disorders, that could explain NPC neurological features and in general, the disease pathogenesis. In this review, we will provide an overview of the impact of mRNA processing and metabolism on NPC disease pathology.

NADPH oxidase regulates paraquat and maneb-induced dopaminergic neurodegeneration through ferroptosis

The activation of NADPH oxidase contributes to dopaminergic neurodegeneration induced by paraquat and maneb, two concurrently used pesticides in agriculture. However, the mechanisms remain unclear. Ferroptosis, a recently recognized form of regulated cell death, has been implicated in the pathogenesis of multiple neurodegenerative diseases. This study is designed to investigate whether ferroptosis is involved in NADPH oxidase-regulated dopaminergic neurotoxicity. In vitro study showed that paraquat and maneb exposure induced ferroptosis in SHSY5Y dopaminergic cells, which was associated with activation of NADPH oxidase. Inhibition of NADPH oxidase by apocynin or diphenyleneiodonium (DPI), two widely used NADPH oxidase inhibitors mitigated paraquat and maneb-induced ferroptotic cell death. Consistently, stimulating activation of NADPH oxidase by phorbol myristate acetate (PMA) or supplementation of H₂O₂ exacerbated ferroptosis in paraquat and maneb-treated SHSY5Y cells. Mechanistic inquiry revealed that NADPH oxidase activation elicited lipid peroxidation, a main driving force for ferroptosis, since both apocynin and DPI greatly reduced MDA contents and simultaneously recovered levels of glutathione and glutathione peroxidase 4 (GPX4) in paraquat and maneb-treated SHSY5Y cells. The contribution of NADPH oxidase on ferroptosis of dopaminergic neurons was further verified in vivo by showing reduced iron content, lipid peroxidation, neuroinflammation and dopaminergic neurodegeneration, which are all involved in ferroptosis, in combined apocynin and paraquat and maneb-treated mice compared with paraquat and maneb alone group. Altogether, our findings showed that NADPH oxidase contributed to paraquat and maneb-induced dopaminergic neurodegeneration through ferroptosis, providing a novel mechanism for pesticide-induced dopaminergic neurotoxicity.

Epigenetic Effects Induced by Methamphetamine and Methamphetamine-Dependent Oxidative Stress

Methamphetamine is a widely abused drug, which possesses neurotoxic activity and powerful addictive effects. Understanding methamphetamine toxicity is key beyond the field of drug abuse since it allows getting an insight into the molecular mechanisms which operate in a variety of neuropsychiatric disorders. In fact, key alterations produced by methamphetamine involve dopamine neurotransmission in a way, which is reminiscent of spontaneous neurodegeneration and psychiatric schizophrenia. Thus, understanding the molecular mechanisms operated by methamphetamine represents a wide window to understand both the addicted brain and a variety of neuropsychiatric disorders. This overlapping, which is already present when looking at the molecular and cellular events promoted immediately after methamphetamine intake, becomes impressive when plastic changes induced in the brain of methamphetamine-addicted patients are considered. Thus, the present manuscript is an attempt to encompass all the molecular events starting at the presynaptic dopamine terminals to reach the nucleus of postsynaptic neurons to explain how specific neurotransmitters and signaling cascades produce persistent genetic modifications, which shift neuronal phenotype and induce behavioral alterations. A special emphasis is posed on disclosing those early and delayed molecular events, which translate an altered neurotransmitter function into epigenetic events, which are derived from the translation of postsynaptic noncanonical signaling into altered gene regulation. All epigenetic effects are considered in light of their persistent changes induced in the postsynaptic neurons including sensitization and desensitization, priming, and shift of neuronal phenotype.

The Balance between Life and Death of Cells: Roles of Metallothioneins

Metallothionein (MT) is a highly conserved, low-molecular-weight, cysteine-rich protein that occurs in 4 isoforms (MT-I to MT-IV), of which MT-I+II are the major and best characterized proteins.

This review will focus on mammalian MT-I+II and their functional impact upon cellular survival and death, as seen in two rather contrasting pathological conditions: Neurodegeneration and neoplasms. MT-I+II have analogous functions including: 1) Antioxidant scavenging of reactive oxygen species (ROS); 2) Cytoprotection against degeneration and apoptosis; 3) Stimulation of cell growth and repair including angiogenesis/revascularization, activation of stem/progenitor cells, and neuroregeneration. Thereby, MT-I+II mediate neuroprotection, CNS restoration and clinical recovery during neurodegenerative disorders. Due to the promotion of cell survival, increased MT-I+II levels have been associated with poor tumor prognosis, although the data are less clear and direct causative roles of MT-I+II in oncogenesis remain to be identified.

The MT-I+II molecular mechanisms of actions are not fully elucidated. However, their role in metal ion homeostasis might be fundamental in controlling Zn-dependent transcription factors, protein synthesis, cellular energy levels/metabolism and cell redox state.

Here, the neuroprotective and regenerative functions of MT-I+II are reviewed, and the presumed link to oncogenesis is critically perused.

The Effect of Diabetes Mellitus on Apoptosis in Hippocampus: Cellular and Molecular Aspects

Background:

Diabetes mellitus is associated with cognitive deficits in humans and animals. These deficits are paralleled by neurophysiological and structural changes in brain. In diabetic animals, impairments of spatial learning, memory, and cognition occur in association with distinct changes in hippocampus, a key brain area for many forms of learning and memory and are particularly sensitive to changes in glucose homeostasis. However, the multifactorial pathogenesis of diabetic encephalopathy is not yet completely understood. Apoptosis plays a crucial role in diabetes-induce neuronal loss in hippocampus.

Methods:

The effects of diabetes on hippocampus and cognitive/behavioral dysfunctions in experimental models of diabetes are reviewed, with a focus on the negative impact on increased neuronal apoptosis and related cellular and molecular mechanisms.

Results:

Of all articles that were assessed, most of the experimental studies clearly showed that diabetes causes neuronal apoptosis in hippocampus through multiple mechanisms, including oxidative stress, inhibition of caspases, disturbance in expression of apoptosis regulator genes, as well as deficits in mitochondrial function. The balance between pro-apoptotic and anti-apoptotic signaling may determine the neuronal apoptotic outcome in vitro and in vivo models of experimental diabetes.

Conclusions:

Dissecting out the mechanisms responsible for diabetes-related changes in the hippocampal cell apoptosis helps improve treatment of impaired cognitive and memory functions in diabetic individuals.

Depression, body mass index, and chronic obstructive pulmonary disease - a holistic approach

Background

Several clinical studies suggest common underlying pathogenetic mechanisms of COPD and depressive/anxiety disorders. We aim to evaluate psychopathological and physical effects of aerobic exercise, proposed in the context of pulmonary rehabilitation, in a sample of COPD patients, through the correlation of some psychopathological variables and physical/pneumological parameters.

Methods

Fifty-two consecutive subjects were enrolled. At baseline, the sample was divided into two subgroups consisting of 38 depression-positive and 14 depression-negative subjects according to the Hamilton Depression Rating Scale (HAM-D). After the rehabilitation treatment, we compared psychometric and physical examinations between the two groups.

Results

The differences after the rehabilitation program in all assessed parameters demonstrated a significant improvement in psychiatric and pneumological conditions. The reduction of BMI was significantly correlated with fat mass but only in the depression-positive patients.

Conclusion

Our results suggest that pulmonary rehabilitation improves depressive and anxiety symptoms in COPD. This improvement is significantly related to the reduction of fat mass and BMI only in depressed COPD patients, in whom these parameters were related at baseline. These findings suggest that depressed COPD patients could benefit from a rehabilitation program in the context of a multidisciplinary approach.

Stress-induced upregulation of VLDL receptor alters Wnt-signaling in neurons

Lipoprotein receptor family members hold multiple roles in the brain, and alterations in lipoprotein receptor expression and function are implicated in neuronal stress, developmental disorders and neurodegenerative diseases, such as Alzheimer's disease. Berberine (BBR), a nutraceutical shown to have both neuroprotective and neurotoxic properties, is suggested to regulate lipoprotein receptor expression. We show that subtoxic concentration of BBR regulates neuronal lipoprotein receptor expression in a receptor- and time-dependent fashion in cerebellar granule neurons (CGN). Similarly to BBR, subtoxic concentrations of neuronal stressors cobalt chloride, thapsigargin and rotenone increased very-low-density lipoprotein receptor (VLDLR) mRNA and protein expression in CGN suggesting a conserved pathway for stress-induced upregulation of VLDLR in neurons. We also show that VLDLR upregulation is accompanied by transiently increased stabilization of hypoxia-induced factor 1 alpha (HIF-1α) and decreased β-catenin levels affecting the Wnt pathway through GSK3β phosphorylation, a crucial player in neurodegenerative processes. Our results indicate that neuronal stress differentially regulates lipoprotein receptor expression in neurons, with VLDLR upregulation as a common element as a modulator of neuronal Wnt signaling.

Mangiferin Protects Retinal Ganglion Cells in Ischemic Mouse Retina via SIRT1

PURPOSE

To investigate whether mangiferin can increase the viability of retinal ganglion cells (RGCs) in ischemic mouse retina, and to determine the possible mechanism of neuroprotection.

METHODS

C57BL/6J mice underwent constant elevation of intraocular pressure for 60 min and received saline or mangiferin (30 mg/kg) intraperitoneally once daily until sacrifice. HIF-1α, GFAP and SIRT1 expression was assessed at 1, 4, and 7 days after retinal ischemia. Bax and Bcl-2 expression was also analyzed at 1 and 4 days. RGC survival was assessed by labeling flat-mounted retinas with Brn3a at 2 weeks after retinal ischemia. The effect of co-treatment with mangiferin and sirtinol (SIRT1 inhibitor) was also evaluated.

RESULTS

The expression of HIF-1α and GFAP was upregulated in saline-treated retinas within 7 days after ischemia. Mangiferin treatment suppressed this upregulation. The expression of SIRT1 was downregulated in saline-treated ischemic retinas. This downregulation was reversed by mangiferin treatment, resulting in a significant difference from saline-treated ischemic retinas. In mangiferin-treated ischemic retinas, Bax expression was downregulated, whereas Bcl-2 expression was upregulated in comparison with saline-treated ischemic retinas. Mangiferin treatment protected ischemic retinas against RGC loss. Treatment of sirtinol decreased the neuroprotective effect of mangiferin.

CONCLUSIONS

Our findings suggest that mangiferin has a neuroprotective effect on RGC through downregulation of HIF-1a and GFAP, and upregulation of SIRT1 in ischemic mouse retinas. We suggest that mangiferin might be a potential neuroprotective agent against RGC loss under oxidative stress.

Neuroprotective effect of edaravone in experimental glaucoma model in rats: a immunofluorescence and biochemical analysis

AIM

To evaluate the neuroprotective activity of systemically administered edaravone in early and late stage of experimental glaucoma in rats.

METHODS

In this study, 60 Wistar albino rats were used. Experimental glaucoma model was created by injecting hyaluronic acid to the anterior chamber once a week for 6wk in 46 of 60 subjects. Fourteen subjects without any medication were included as control group. Edaravone administered intraperitoneally 3 mg/kg/d to the 15 of 30 subjects starting at the onset of glaucoma induction and also administered intraperitoneally 3 mg/kg/d to the other 15 subjects starting at three weeks after the onset of glaucoma induction. The other 16 subjects who underwent glaucoma induction was administered any therapy. Retinal ganglion cells (RGCs) have been marked with dextran tetramethylrhodamine (DTMR) retrograde at the end of the sixth week and after 48h, subjects were sacrificed by the method of cardiac perfusion. Alive RGC density was assessed in the whole-mount retina. Whole-mount retinal tissues homogenized and nitric oxide (NO), malondialdehyde (MDA) and total antioxidant capacity (TAC) values were measured biochemically.

RESULTS

RGCs counted with Image-Pro Plus program, in the treatment group were found to be statistically significantly protected, compared to the glaucoma group (Bonferroni, P<0.05). The neuroprotective activity of edaravone was found to be more influential by administration at the start of the glaucoma process. Statistically significant lower NO levels were determined in the glaucoma group comparing treatment groups (Bonferroni, P<0.05). MDA levels were found to be highest in untreated glaucoma group, TAC levels were found to be lower in the glaucoma induction groups than the control group (Bonferroni, P<0.05).

CONCLUSION

Systemic administration of Edaravone in experimental glaucoma showed potent neuroprotective activity. The role of oxidative stress causing RGC damage in glaucoma was supported by this study results.

Diazinon and diazoxon impair the ability of astrocytes to foster neurite outgrowth in primary hippocampal neurons

Evidence from in vivo and epidemiological studies suggests that organophosphorus insecticides (OPs) are developmental neurotoxicants, but possible underlying mechanisms are still unclear. Astrocytes are increasingly recognized for their active role in normal neuronal development. This study sought to investigate whether the widely-used OP diazinon (DZ), and its oxygen metabolite diazoxon (DZO), would affect glial-neuronal interactions as a potential mechanism of developmental neurotoxicity. Specifically, we investigated the effects of DZ and DZO on the ability of astrocytes to foster neurite outgrowth in primary hippocampal neurons. The results show that both DZ and DZO adversely affect astrocyte function, resulting in inhibited neurite outgrowth in hippocampal neurons. This effect appears to be mediated by oxidative stress, as indicated by OP-induced increased reactive oxygen species production in astrocytes and prevention of neurite outgrowth inhibition by antioxidants. The concentrations of OPs were devoid of cytotoxicity, and cause limited acetylcholinesterase inhibition in astrocytes (18 and 25% for DZ and DZO, respectively). Among astrocytic neuritogenic factors, the most important one is the extracellular matrix protein fibronectin. DZ and DZO decreased levels of fibronectin in astrocytes, and this effect was also attenuated by antioxidants. Underscoring the importance of fibronectin in this context, adding exogenous fibronectin to the co-culture system successfully prevented inhibition of neurite outgrowth caused by DZ and DZO. These results indicate that DZ and DZO increase oxidative stress in astrocytes, and this in turn modulates astrocytic fibronectin, leading to impaired neurite outgrowth in hippocampal neurons.

The effects of locus coeruleus and norepinephrine in methamphetamine toxicity

The activity of locus coeruleus (LC) neurons has been extensively investigated in a variety of behavioural states. In fact this norepinephrine (NE)-containing nucleus modulates many physiological and pathological conditions including the sleep-waking cycle, movement disorders, mood alterations, convulsive seizures, and the effects of drugs such as psychostimulants and opioids. This review focuses on the modulation exerted by central NE pathways on the behavioural and neurotoxic effects produced by the psychostimulant methamphetamine, essentially the modulation of the activity of mesencephalic dopamine (DA) neurons. In fact, although NE in itself mediates some behavioural effects induced by methamphetamine, NE modulation of DA release is pivotal for methamphetamine-induced behavioural states and neurotoxicity. These interactions are discussed on the basis of the state of the art of the functional neuroanatomy of central NE- and DA systems. Emphasis is given to those brain sites possessing a remarkable overlapping of both neurotransmitters.

Somatic drugs for psychiatric diseases: aspirin or simvastatin for depression?

The evolution in the understanding of the neurobiology of most prevalent mental disorders such as major depressive disorder (MDD), bipolar disorder or schizophrenia has not gone hand in hand with the synthesis and clinical use of new drugs that would represent a therapeutic revolution such as that brought about by selective serotonin reuptake inhibitors (SSRIs) or atypical antipsychotics. Although scientists are still a long way from understanding its true aetiology, the neurobiological concept of depression has evolved from receptor regulation disorder, to a neurodegenerative disorder with a hippocampal volume decrease with the controversial reduction in neurotrophins such as BDNF, to current hypotheses that consider depression to be an inflammatory and neuroprogressive process. As regards antidepressants, although researchers are still far from knowing their true mechanism of action, they have gone from monoaminergic hypotheses, in which serotonin was the main protagonist, to emphasising the anti-inflammatory action of some of these drugs, or the participation of p11 protein in their mechanism of action.In the same way, according to the inflammatory hypothesis of depression, it has been proposed that some NSAIDS such as aspirin or drugs like simvastatin that have an anti-inflammatory action could be useful in some depressive patients. Despite the fact that there may be some data to support their clinical use, common sense and the evidence advise us to use already tested protocols and wait for the future to undertake new therapeutic strategies.

Functional and structural brain changes associated with methamphetamine abuse

Methamphetamine (MA) is a potent psychostimulant drug whose abuse has become a global epidemic in recent years. Firstly, this review article briefly discusses the epidemiology and clinical pharmacology of methamphetamine dependence. Secondly, the article reviews relevant animal literature modeling methamphetamine dependence and discusses possible mechanisms of methamphetamine-induced neurotoxicity. Thirdly, it provides a critical review of functional and structural neuroimaging studies in human MA abusers; including positron emission tomography (PET) and functional and structural magnetic resonance imaging (MRI). The effect of abstinence from methamphetamine, both short- and long-term within the context of these studies is also reviewed.

Natural toxins implicated in the development of Parkinson's disease

Experimental models of Parkinson's disease (PD) are of great importance for improving the design of future clinical trials. Various neurotoxic models are available, including 6-hydroxydopamine (6-OHDA), 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), paraquat and rotenone. However, no model is considered perfect; each has its own limitations. Based on epidemiological data, a new trend of using environmental toxins in PD modeling seems attractive and has dominated public discussions of the disease etiology. A search for new environmental toxin-based models would improve our knowledge of the pathology of the condition. Here, we discuss some toxins of natural origin (e.g. cycad-derived toxins, epoxomicin, Nocardia asteroides bacteria, Streptomyces venezuelae bacteria, annonacin and DOPAL) that possibly represent a contributory environmental component to PD.

Oxidative stress in MeHg-induced neurotoxicity

Methylmercury (MeHg) is an environmental toxicant that leads to long-lasting neurological and developmental deficits in animals and humans. Although the molecular mechanisms mediating MeHg-induced neurotoxicity are not completely understood, several lines of evidence indicate that oxidative stress represents a critical event related to the neurotoxic effects elicited by this toxicant. The objective of this review is to summarize and discuss data from experimental and epidemiological studies that have been important in clarifying the molecular events which mediate MeHg-induced oxidative damage and, consequently, toxicity. Although unanswered questions remain, the electrophilic properties of MeHg and its ability to oxidize thiols have been reported to play decisive roles to the oxidative consequences observed after MeHg exposure. However, a close examination of the relationship between low levels of MeHg necessary to induce oxidative stress and the high amounts of sulfhydryl-containing antioxidants in mammalian cells (e.g., glutathione) have led to the hypothesis that nucleophilic groups with extremely high affinities for MeHg (e.g., selenols) might represent primary targets in MeHg-induced oxidative stress. Indeed, the inhibition of antioxidant selenoproteins during MeHg poisoning in experimental animals has corroborated this hypothesis. The levels of different reactive species (superoxide anion, hydrogen peroxide and nitric oxide) have been reported to be increased in MeHg-exposed systems, and the mechanisms concerning these increments seem to involve a complex sequence of cascading molecular events, such as mitochondrial dysfunction, excitotoxicity, intracellular calcium dyshomeostasis and decreased antioxidant capacity. This review also discusses potential therapeutic strategies to counteract MeHg-induced toxicity and oxidative stress, emphasizing the use of organic selenocompounds, which generally present higher affinity for MeHg when compared to the classically studied agents.

Geniposide induces the expression of heme oxygenase-1 via PI3K/Nrf2-signaling to enhance the antioxidant capacity in primary hippocampal neurons

Oxidative stress in brain is emerging as a potential causal factor in aging and age-related neurodegenerative disorders. A large body of evidence shows that induction of endogenous antioxidative proteins seems to be a reasonable strategy for delaying the progression of cell injury. In this study, geniposide upregulates the expression of heme oxygenase-1 (HO-1) to attenuate the cell apoptosis induced by 3-morpholinosydnonimine hydrochloride (SIN-1) in primary cultured hippocampal neurons. Furthermore, geniposide induces the nuclear translocation of nuclear factor-E2-related factor 2 (Nrf2) and activation of phosphatidylinositol 3'-kinase (PI3K) in the presence of oxidative stress, and both LY294002 (a specific inhibitor of PI3K) and Zinc protoporphyrin (ZnPP, an inhibitor of HO-1) decrease the cytoprotective action of geniposide in hippocampal neurons. Taken together, the novel cytoprotective mechanism of geniposide to antagonize oxidative stress may be involved in PI3K- and Nrf2-mediated upregulation of the antioxidative enzyme HO-1.

Cytokines mediated inflammation and decreased neurogenesis in animal models of depression

In patients with major depression or in animal models of depression, significantly increases in the concentrations of pro-inflammatory cytokines have been consistently reported. Proinflammatory cytokines can stimulate the hypothalamic-pituitary-adrenal (HPA) axis to release stress hormone, glucocorticoids. As a consequence of excessive inflammatory response triggered by pro-inflammatory cytokines in the periphery, free radicals, oxidants and glucocorticoids are over-produced, which can affect glial cell functions and damage neurons in the brain. Indeed, decreased neurogenesis and the dysfunction of neurotrophic system (up- or down-regulations of neurotrophins and their receptors) have been recently found. Effective treatments for depressive symptoms, such as antidepressants and omega-3 fatty acids can increase or modulate neurotrophic system and enhance neurogenesis. However, the relationship between glial cells; microglia (mostly involved in neuroinflammation) and astrocytes (producing neurotrophins), and the contribution of inflammation to decreased neurogenesis and dysfunction of neurotrophic system are almost unknown. This review first introduces changes in behavior, neurotransmitter, cytokine and neurogenesis aspects in depressed patients and several animal models of depression, secondly explores the possible relationship between pro- and anti-inflammatory cytokines and neurogenesis in these models, then discusses the effects of current treatments on inflammation, neurotrophic system and neurogenesis, and finally pointes out the limitations and future research directions.

SECIS-binding protein 2 promotes cell survival by protecting against oxidative stress

Reactive oxygen species (ROS) are a primary cause of cellular damage that leads to cell death. In cells, protection from ROS-induced damage and maintenance of the redox balance is mediated to a large extent by selenoproteins, a distinct family of proteins that contain selenium in form of selenocysteine (Sec) within their active site. Incorporation of Sec requires the Sec-insertion sequence element (SECIS) in the 3'-untranslated region of selenoproteins mRNAs and the SECIS-binding protein 2 (SBP2). Previous studies have shown that SBP2 is required for the Sec-incorporation mechanism; however, additional roles of SBP2 in the cell have remained undefined. We herein show that depletion of SBP2 by using antisense oligonucleotides (ASOs) causes oxidative stress and induction of caspase- and cytochrome c-dependent apoptosis. Cells depleted of SBP2 have increased levels of ROS, which lead to cellular stress manifested as 8-oxo-7,8-dihydroguanine (8-oxo-dG) DNA lesions, stress granules, and lipid peroxidation. Small-molecule antioxidants N-acetylcysteine, glutathione, and alpha-tocopherol only marginally reduced ROS and were unable to rescue cells fully from apoptosis, indicating that apoptosis might be directly mediated by selenoproteins. Our results demonstrate that SBP2 is required for protection against ROS-induced cellular damage and cell survival.

delta-Opioid receptor activation attenuates oxidative injury in the ischemic rat brain

BACKGROUND

We have recently shown that delta-opioid receptors (DORs) play an important role in neuroprotection from hypoxic injury via the regulation of extracellular signaling-regulated kinase (ERK) and cytochrome c release. Since ERK and cytochrome c are differentially involved in caspase signaling of oxidative injury that significantly contributes to neuronal damage in ischemia/reperfusion, we considered if DOR activation protects the ischemic brain by attenuating oxidative injury.

RESULTS

We observed that, in a model of cerebral ischemia with middle cerebral artery occlusion, DOR activation increased the activity of major antioxidant enzymes, glutathione peroxidase and superoxide dismutase, and decreased malondialdehyde and nitric oxide levels in the cortex exposed to cerebral ischemia/reperfusion. In addition, DOR activation reduced caspase 3 expression, though it did not significantly affect the increase in interleukin (IL)1beta and tumor necrosis factor (TNF)alpha expression at the same timepoint. PD98059, an inhibitor of mitogen-activated protein kinase (MAPK) extracellular signaling-regulated kinase kinase, accelerated animal death during ischemia/reperfusion.

CONCLUSION

DOR activation attenuates oxidative injury in the brain exposed to ischemia/reperfusion by enhancing antioxidant ability and inhibiting caspase activity, which provides novel insights into the mechanism of DOR neuroprotection.

Functional role for senataxin, defective in ataxia oculomotor apraxia type 2, in transcriptional regulation

Ataxia oculomotor apraxia type 2 (AOA2) is an autosomal recessive neurodegenerative disorder characterized by cerebellar ataxia and oculomotor apraxia. The gene mutated in AOA2, SETX, encodes senataxin, a putative DNA/RNA helicase which shares high homology to the yeast Sen1p protein and has been shown to play a role in the response to oxidative stress. To investigate further the function of senataxin, we identified novel senataxin-interacting proteins, the majority of which are involved in transcription and RNA processing, including RNA polymerase II. Binding of RNA polymerase II to candidate genes was significantly reduced in senataxin deficient cells and this was accompanied by decreased transcription of these genes, suggesting a role for senataxin in the regulation/modulation of transcription. RNA polymerase II-dependent transcription termination was defective in cells depleted of senataxin in keeping with the observed interaction of senataxin with poly(A) binding proteins 1 and 2. Splicing efficiency of specific mRNAs and alternate splice-site selection of both endogenous genes and artificial minigenes were altered in senataxin depleted cells. These data suggest that senataxin, similar to its yeast homolog Sen1p, plays a role in coordinating transcriptional events, in addition to its role in DNA repair.

Methamphetamine toxicity and messengers of death

Methamphetamine (METH) is an illicit psychostimulant that is widely abused in the world. Several lines of evidence suggest that chronic METH abuse leads to neurodegenerative changes in the human brain. These include damage to dopamine and serotonin axons, loss of gray matter accompanied by hypertrophy of the white matter and microgliosis in different brain areas. In the present review, we summarize data on the animal models of METH neurotoxicity which include degeneration of monoaminergic terminals and neuronal apoptosis. In addition, we discuss molecular and cellular bases of METH-induced neuropathologies. The accumulated evidence indicates that multiple events, including oxidative stress, excitotoxicity, hyperthermia, neuroinflammatory responses, mitochondrial dysfunction, and endoplasmic reticulum stress converge to mediate METH-induced terminal degeneration and neuronal apoptosis. When taken together, these findings suggest that pharmacological strategies geared towards the prevention and treatment of the deleterious effects of this drug will need to attack the various pathways that form the substrates of METH toxicity.

The inflammatory & neurodegenerative (I&ND) hypothesis of depression: leads for future research and new drug developments in depression

Despite extensive research, the current theories on serotonergic dysfunctions and cortisol hypersecretion do not provide sufficient explanations for the nature of depression. Rational treatments aimed at causal factors of depression are not available yet. With the currently available antidepressant drugs, which mainly target serotonin, less than two thirds of depressed patients achieve remission. There is now evidence that inflammatory and neurodegenerative (I&ND) processes play an important role in depression and that enhanced neurodegeneration in depression may-at least partly-be caused by inflammatory processes. Multiple inflammatory-cytokines, oxygen radical damage, tryptophan catabolites-and neurodegenerative biomarkers have been established in patients with depression and these findings are corroborated by animal models of depression. A number of vulnerability factors may predispose towards depression by enhancing inflammatory reactions, e.g. lower peptidase activities (dipeptidyl-peptidase IV, DPP IV), lower omega-3 polyunsaturated levels and an increased gut permeability (leaky gut). The cytokine hypothesis considers that external, e.g. psychosocial stressors, and internal stressors, e.g. organic inflammatory disorders or conditions, such as the postpartum period, may trigger depression via inflammatory processes. Most if not all antidepressants have specific anti-inflammatory effects, while restoration of decreased neurogenesis, which may be induced by inflammatory processes, may be related to the therapeutic efficacy of antidepressant treatments. Future research to disentangle the complex etiology of depression calls for a powerful paradigm shift, i.e. by means of a high throughput-high quality screening, including functional genetics and genotyping microarrays; established and novel animal and ex vivo-in vitro models for depression, such as new transgenic mouse models and endophenotype-based animal models, specific cell lines, in vivo and ex vivo electroporation, and organotypic brain slice culture models. This screening will allow to: 1) discover new I&ND biomarkers, both at the level of gene expression and the phenotype; and elucidate the underlying molecular I&ND pathways causing depression; and 2) identify new therapeutic targets in the I&ND pathways; develop new anti-I&ND drugs for these targets; select existing anti-I&ND drugs or substances that could augment the efficacy of antidepressants; and predict therapeutic response by genetic I&ND profiles.

Neuroprotection of geniposide against hydrogen peroxide induced PC12 cells injury: involvement of PI3 kinase signal pathway

AIM

Oxidative stress plays a critical role in the pathogenic cascade leading to neuronal degeneration in AD. Consequently, the induction of endogenous antioxidative proteins by antioxidants seems to be a very reasonable strategy for delaying the disease's progression. In previous work, we identified the neurotrophic and neuroprotective effects of geniposide, which result from the activation of glucagon-like peptide 1 receptor (GLP-1R). In this study, we explore the role of PI3 kinase signaling pathway in the neuroprotection of geniposide in PC12 cells.

METHODS

Cell viability was determined by MTT assay. Apoptosis was detected by Hoechst and PI double staining. The protein expression of Bcl-2 and phosphorylation of Akt308, Akt473, GSK-3beta, and PDK1 was measured by Western blot.

RESULTS

Geniposide induced the expression of the antiapoptotic protein Bcl-2, which inhibited apoptosis in PC12 cells induced by H(2)O(2), and this effect could be inhibited by preincubation with LY294002, a selective inhibitor of PI3K. Furthermore, geniposide enhanced the phosphorylation of Akt308, Akt473, GSK-3beta and PDK1 under conditions of oxidative stress.

CONCLUSION

These results demonstrate that the PI3K signaling pathway is involved in the neuroprotection of geniposide in PC12 cells against the oxidative damage induced by H(2)O(2) in PC12 cells.

Identification of novel pharmacological targets to minimize excitotoxic retinal damage

Excitotoxic neuronal death is a common feature of neurodegenerative and ischemic diseases of the central nervous system (CNS) and of a variety of ocular diseases, including glaucoma. Glaucoma, one of the leading causes of blindness in the world, is characterized by a progressive degeneration of retinal ganglion cells (RGCs) and their axons and is often associated with elevated intraocular pressure (IOP). Retinal ischemia/reperfusion induced by experimental elevation of IOP leads to damage and loss of RGCs. Under these conditions, structural, functional, and biochemical changes implicate the accumulation of extracellular glutamate and activation of the excitotoxic cascade. Beside the activation of associated pathways, death of RGCs is accompanied by impaired endogenous defenses, such as the PI3K/Akt prosurvival pathway. Original neurochemical and pharmacological evidence are discussed here to strengthen the role for excitotoxicity in RGCs death occurring in experimental, angle closure, glaucoma in conjunction with the discovery of novel molecular targets to potentiate endogenous prosurvival defenses in the glaucomatous retina.

Molecular bases of methamphetamine-induced neurodegeneration

Methamphetamine (METH) is a highly addictive psychostimulant drug, whose abuse has reached epidemic proportions worldwide. The addiction to METH is a major public concern because its chronic abuse is associated with serious health complications including deficits in attention, memory, and executive functions in humans. These neuropsychiatric complications might, in part, be related to drug-induced neurotoxic effects, which include damage to dopaminergic and serotonergic terminals, neuronal apoptosis, as well as activated astroglial and microglial cells in the brain. Thus, the purpose of the present paper is to review cellular and molecular mechanisms that might be responsible for METH neurotoxicity. These include oxidative stress, activation of transcription factors, DNA damage, excitotoxicity, blood-brain barrier breakdown, microglial activation, and various apoptotic pathways. Several approaches that allow protection against METH-induced neurotoxic effects are also discussed. Better understanding of the cellular and molecular mechanisms involved in METH toxicity should help to generate modern therapeutic approaches to prevent or attenuate the long-term consequences of psychostimulant use disorders in humans.

Endothelial nitric oxide synthase overexpression by neuronal cells in neurodegeneration: a link between inflammation and neuroprotection

The roles of neuronal and inducible nitric oxide synthases in neurones have been extensively investigated; by contrast, the biological significance of endothelial nitric oxide synthase (eNOS) overexpression that occurs in several pathological conditions has not yet been studied. We have started addressing this issue in a cell model of neurodegeneration, i.e. human SKNBE neuroblastoma cells transfected with a mutant form of alsin, a protein causing an early-onset type of amyotrophic lateral sclerosis, ALS2. We found that eNOS, which is endogenously expressed by these cells, was activated by tumour necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine that plays important roles in ALS2 and several neurodegenerative diseases. The TNF-alpha-dependent eNOS activation occurred through generation, by sphingosine-kinase-1, of sphingosine-1-phosphate, stimulation of its membrane receptors and activation of Akt, as determined using small interference RNA and dominant negative constructs specific for the enzymes and receptors. eNOS activation by TNF-alpha conferred cytoprotection from excitotoxicity and neurotoxic cues such as reactive oxygen species, endoplasmic reticulum stress, DNA damage, and mutated alsin itself. Our results suggest that overexpression of eNOS by neurones is a broad-range protective mechanism activated during damage and establish a link of pathophysiological relevance between this enzyme and inflammation accompanying neurodegenerative diseases. These findings also question the concept that high NO output in the presence of oxidative stress leads always to peroxynitrite formation contributing to neurodegeneration.

Interactions of HIV and methamphetamine: cellular and molecular mechanisms of toxicity potentiation

Methamphetamine (METH) is a highly addictive psychostimulant drug, whose abuse has reached epidemic proportions worldwide. METH use is disproportionally represented among populations at high risks for developing HIV infection or who are already infected with the virus. Psychostimulant abuse has been reported to exacerbate the cognitive deficits and neurodegenerative abnormalities observed in HIV-positive patients. Thus, the purpose of the present paper is to review the clinical and basic observations that METH potentiates the adverse effects of HIV infection. An additional purpose is to provide a synthesis of the cellular and molecular mechanisms that might be responsible for the increased toxicity observed in co-morbid patients. The reviewed data indicate that METH and HIV proteins, including gp120, gp41, Tat, Vpr and Nef, converge on various caspase-dependent death pathways to cause neuronal apoptosis. The role of reactive microgliosis in METH- and in HIV-induced toxicity is also discussed.

MPTP administration in mice changes the ratio of splice isoforms of fosB and rgs9

Most cases of Parkinson's disease (PD) are sporadic, suggesting an environmental influence on individuals affected by this neurodegenerative disorder. Environmental stresses often lead to changes in the regulation of splicing of pre-mRNA transcripts and this may lead to the pathogenesis of the disease. A 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)/probenecid mouse model was used to examine the changes in the splicing of the fosB and rgs9 transcripts. The ratio of DeltafosB/fosB transcript was decreased in the substantia nigra and unchanged in the striatum after acute MPTP treatment. The DeltafosB/fosB transcript ratio decreased initially and then increased in the striatum of chronically MPTP-treated animals due to different degrees of reduction for the splice variants over time, whereas the ratio was unchanged in the substantia nigra. The ratio of rgs9-2/rgs9-1 transcript decreased in the substantia nigra of mice after acute MPTP treatment and increased temporarily in the striatum after chronic MPTP treatment. There was an increase in the DeltaFosB/FosB and RGS9-2/RGS9-1 protein ratios 3 weeks and 3 days post-treatment, respectively, in chronically treated mice. The data indicate that the pattern of splice isoforms of fosB and rgs9 reflects the brain's immediate and long-term responses to the physiological stress associated with Parkinsonism.

Protein-RNA cross-linking in the ribosomes of yeast under oxidative stress

Living systems have efficient degradative pathways for dealing with the fact that reactive oxygen species (ROS) derived from cellular metabolism and the environment oxidatively damage proteins and DNA. But aggregation and cross-linking can occur as well, leading to a series of problems including disruption of cellular regulation, mutations, and even cell death. The mechanism(s) by which protein aggregation occurs and the macromolecular species involved are poorly understood. In the study reported here, evidence is provided for a new type of aggregate between proteins and RNA in ribosomes. While studying the effect of oxidative stress induced in the yeast proteome it was noted that ribosomal proteins were widely oxidized. Eighty six percent of the proteins in yeast ribosomes were found to be carbonylated after stressing yeast cell cultures with hydrogen peroxide. Moreover, many of these proteins appeared to be cross-linked based on their coelution patterns during RPC separation. Since they were not in direct contact, it was not clear how this could occur unless it was through the RNA separating them in the ribosome. This was confirmed in a multiple-step process, the first being derivatization of all carbonylated proteins in cell lysates with biotin hydrazide through Schiff base formation. Following reduction of Schiff bases with sodium cyanoborohydride, biotinylated proteins were selected from cell lysates with avidin affinity chromatography. Oxidized proteins thus captured were then selected again using boronate affinity chromatography to capture vicinal diol-containing proteins. This would include proteins cross-linked to an RNA fragment containing a ribose residue with 2',3'-hydroxyl groups. Some glycoproteins would also be selected by this process. LC/MS/MS analyses of tryptic peptides derived from proteins captured by this process along with MASCOT searches resulted in the identification of 37 ribosomal proteins that appear to be cross-linked to RNA. Aggregation of proteins with ribosomal RNA has not been previously reported. The probable impact of this phenomenon cells is to diminish the protein synthesis capacity.

Nitric oxide and peroxynitrite in health and disease

The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.

Implication of PTEN in production of reactive oxygen species and neuronal death in in vitro models of stroke and Parkinson's disease

Oxidative stress plays crucial role in the pathogenesis of neurodegenerative diseases. However, the precise mechanism for an increased production of reactive oxygen species (ROS) under pathological conditions is not yet fully understood. We have recently demonstrated an implication of phosphatase and tensin homologue deleted on chromosome 10 (PTEN), a tumor suppressor, in ROS generation and neuronal apoptosis induced by staurosporine. These findings raised further interest whether PTEN functions as a common mediator of oxidative stress in neurodegenerative processes. To address this issue, neural cells were exposed to oxygen-glucose deprivation (OGD) and to the neurotoxin 1-methyl-4-phenylpyridinium iodide (MPP(+)), which mimic cerebral ischemia and Parkinson's disease, respectively. OGD for 4 h followed by 16 h of reoxygenation or incubation with MPP(+) (250 microM) for 48 h induced 33% and 45% neuronal death in rat hippocampal and in human dopaminergic SH-SY5Y neurons, respectively, accompanied by a gradual increase in the intracellular level of ROS. The increase in ROS by OGD and by MPP(+) did not cause oxidative inactivation of PTEN and thus, PTEN remains constitutively active. In support, the protein level of PTEN was not reduced in both cell cultures after challenging with OGD or MPP(+). Importantly, the elevated intracellular ROS levels and the neuronal death caused by OGD or by MPP(+) toxicity were significantly inhibited when PTEN was downregulated by a specific antisense oligonucleotide or by siRNA. Because SOD2 protein level is not altered either by knockdown of PTEN nor by an inhibition of the PI3K/Akt signalling, we suggest that SOD2 do not contribute to the pathomechanism of oxidative stress induced by PTEN or by inhibiting the related Akt signalling. The present study highlights PTEN as a crucial and common mediator of ROS generation and neuronal death and suggests that PTEN could become a potential therapeutic target for interfering with neurodegeneration.

Novel roles for metallothionein-I + II (MT-I + II) in defense responses, neurogenesis, and tissue restoration after traumatic brain injury: Insights from global gene expression profiling in wild-type and MT-I + II knockout mice

Traumatic injury to the brain is one of the leading causes of injury-related death or disability, especially among young people. Inflammatory processes and oxidative stress likely underlie much of the damage elicited by injury, but the full repertoire of responses involved is not well known. A genomic approach, such as the use of microarrays, provides much insight in this regard, especially if combined with the use of gene-targeted animals. We report here the results of one of these studies comparing wild-type and metallothionein-I + II knockout mice subjected to a cryolesion of the somatosensorial cortex and killed at 0, 1, 4, 8, and 16 days postlesion (dpl) using Affymetrix genechips/oligonucleotide arrays interrogating approximately 10,000 different murine genes (MG_U74Av2). Hierarchical clustering analysis of these genes readily shows an orderly pattern of gene responses at specific times consistent with the processes involved in the initial tissue injury and later regeneration of the parenchyma, as well as a prominent effect of MT-I + II deficiency. The results thoroughly confirmed the importance of the antioxidant proteins MT-I + II in the response of the brain to injury and opened new avenues that were confirmed by immunohistochemistry. Data in KO, MT-I-overexpressing, and MT-II-injected mice strongly suggest a role of these proteins in postlesional activation of neural stem cells.

Oxidative stress in glaucomatous neurodegeneration: mechanisms and consequences

Reactive oxygen species (ROS) are generated as by-products of cellular metabolism, primarily in the mitochondria. Although ROS are essential participants in cell signaling and regulation, when their cellular production overwhelms the intrinsic antioxidant capacity, damage to cellular macromolecules such as DNA, proteins, and lipids ensues. Such a state of "oxidative stress" is thought to contribute to the pathogenesis of a number of neurodegenerative diseases. Growing evidence supports the involvement of oxidative stress as a common component of glaucomatous neurodegeneration in different subcellular compartments of retinal ganglion cells (RGCs). Besides the evidence of direct cytotoxic consequences leading to RGC death, it also seems highly possible that ROS are involved in signaling RGC death by acting as a second messenger and/or modulating protein function by redox modifications of downstream effectors through enzymatic oxidation of specific amino acid residues. Different studies provide cumulating evidence, which supports the association of ROS with different aspects of the neurodegenerative process. Oxidative protein modifications during glaucomatous neurodegeneration increase neuronal susceptibility to damage and also lead to glial dysfunction. Oxidative stress-induced dysfunction of glial cells may contribute to spreading neuronal damage by secondary degeneration. Oxidative stress also promotes the accumulation of advanced glycation end products in glaucomatous tissues. In addition, oxidative stress takes part in the activation of immune response during glaucomatous neurodegeneration, as ROS stimulate the antigen presenting ability of glial cells and also function as co-stimulatory molecules during antigen presentation. By discussing current evidence, this review provides a broad perspective on cellular mechanisms and potential consequences of oxidative stress in glaucoma.