Total antioxidant capacity and total oxidant status in patients with major depression: Impact of antidepressant treatment

Aim:  The purpose of the present study was to investigate whether total antioxidant capacity (TAC) and total oxidant status (TOS) are associated with major depressive disorder (MDD) and to evaluate the impact of antidepressant treatment on TAC and TOS in MDD.
Methods:  Fifty-seven MDD patients and 40 healthy controls participated in the study. Serum TAC and TOS were measured both in patients and controls using Erel's methods. Patients were treated with antidepressant drugs for 12 weeks. The treatment course was evaluated using the Montgomery–Asberg Depression Rating Scale (MADRS) in all patients.
Results:  TOS and oxidative stress index (OSI) were higher ( P  = 0.0001 for both) and TAC was lower ( P  = 0.0001) in the MDD group compared with those of the controls. After 3 months of antidepressant treatment, TOS and OSI were decreased and TAC was increased compared with the pretreatment values ( P  = 0.0001, for all). Furthermore, there were significant positive correlations between the severity of the disease and serum TOS and OSI (r = 0.584, P  = 0.0001; r = 0.636, P  = 0.0001, respectively). A negative correlation was found between the severity of the disease and serum TAC (r = −0.553, P  = 0.0001) at the pre-treatment stage.
Conclusion:  Treatment administered for 3 months to MDD patients increases TAC while decreasing TOS and OSI.     

Calcitonin gene-related peptide levels during nitric oxide-induced headache in patients with chronic tension-type headache

It has been proposed that nitric oxide (NO) induced headache in primary headaches may be associated with release of calcitonin gene-related peptide (CGRP). In the present study we aimed to investigate plasma levels of CGRP during headache induced by the NO donor glyceryl trinitrate (GTN) in 16 patients with chronic tension-type headache and 16 healthy controls. The subjects were randomly allocated to receive 0.5 microg/kg/min GTN or placebo over 20 min on two headache-free days. Blood samples were collected at baseline, 10, 20 and 60 min after start of infusion. Both patients and controls developed significantly stronger immediate headache on the GTN day than on the placebo day and the headache was significantly more pronounced in patients than in controls. There was no difference between the area under the CGRP curve (AUCCGRP) on GTN vs. placebo day in either patients (P=0.65) or controls (P=0.48). The AUCCGRP recorded on the GTN day did not differ between patients and controls (P=0.36). Both in patients and controls, CGRP levels changed significantly over time, on both the GTN and placebo days (P < 0.05). The present study indicates that NO-induced immediate headache is not associated with release of CGRP.     

Evaluation of Oxidative Metabolism in Child and Adolescent Patients with Attention Deficit Hyperactivity Disorder

Objective

Oxidative metabolism is impaired in several medical conditions including psychiatric disorders, and this imbalance may be involved in the etiology of these diseases. The present study evaluated oxidative balance in pediatric and adolescent patients with attention deficit hyperactivity disorder (ADHD).

Methods

The study included 48 children and adolescents (34 male, 14 female) with ADHD who had no neurological, systemic, or comorbid psychiatric disorders, with the exception of oppositional defiant disorder (ODD), and 24 sex- and age-matched healthy controls (17 male and seven female).

Results

TAS was significantly lower, and TOS and OSI were significantly higher in patients with ADHD than in healthy controls. Total antioxidant levels were lower in patients with comorbid ODD than in those with no comorbidity. No difference was found in TOS or OSI among the ADHD subtypes; however, TAS was higher in the attention-deficient subtype.

Conclusion

Our findings demonstrated that oxidative balance is impaired and oxidative stress is increased in children and adolescents with ADHD. This results are consistent with those of previous studies.     

The prevalence and severity of insomnia in university students and their associations with migraine,tension-type headache,anxiety and depression disorders: a cross-sectional study

BackgroundThere is possibly an association between migraine, tension-type headache, anxiety, depression and insomnia. These conditions are prevalent among university students. Our primary objective was to verify whether students with primary headaches (migraine and tension-type headache) have a higher prevalence of insomnia. Our secondary objective was to assess whether the impact of headaches was associated with greater severity of insomnia.MethodsCross-sectional study. 440 students out of 3030 were randomly selected. A semi-structured questionnaire containing information about the characteristics of the headaches, including their frequencies in the last 3 months; the Headache Impact Test (HIT-6); the Hospital Anxiety Depression Scale; and the Insomnia Severity Index were used.Results420 students (95.5%) agreed to participate; 51.4% men; median age of 21 (19, 23); 95 (22.6%) had insomnia; 265 (63.1%), migraine; 152 (36.2%), tension-type headache; 201 (47.9%) suffered from anxiety and 108 (25.7%), from depression. The severe impact of headache (HIT-6>55 points; OR = 3.9; p = 0.003) and anxiety (OR = 3.6; p = 0.003) were associated with insomnia (logistic regression). The severity of insomnia was positively and significantly correlated with the impact (HIT-6 score), with frequency of headache, and with having anxiety (multiple linear regression).ConclusionsThe diagnoses of migraine and tension-type headache are not associated with the presence of insomnia. The severity of insomnia is associated with the impact and the frequency of the headaches.     

Inflammation and oxidative stress as biomarkers of premature aging in persons with intellectual disability

The decline in cognitive ability and physical performance in older adults with intellectual disabilities (ID) is accompanied by less participation in social activities and a sedentary lifestyle; however the pathogenesis is not clear yet. It was recently suggested that chronic disease, adverse drug reactions, and aging create a cascade of events that can be best characterized as an asymptomatic inflammatory process. This cascade of events is mediated by cytokine interleukins 1 and 6 (IL-1α, and IL-6), nitric oxide (NO) and total oxidative stress (OS). Our hypothesis was that chronic inflammation in the bloodstream of persons with ID contributes to their “premature aging”. To test this hypothesis, we measured and compared the levels of inflammatory molecules in persons with and without ID. Fifteen adults with, and 15 adults without ID (control group) participated in this study. The levels of NO metabolites (NOx), IL-1α, and IL-6 were obtained from participants’ serum. OS markers were drawn from participants’ capillary. Western blot, RT-PCR and specific chemical analysis were used as measurement tools. The levels of inflammatory molecules and OS were significantly higher in persons with ID compared to the control group. Asymptomatic inflammation in the bloodstream of the older adults with ID might explain the “premature aging” of these individuals. Monitoring the levels of inflammatory molecules could serve as biomarkers of “premature aging” which may allow early diagnosis and intervention, and improve the quality of care for persons with ID.     

3-Hydroxyglutaric acid induces oxidative stress and decreases the antioxidant defenses in cerebral cortex of young rats

Glutaryl-CoA dehydrogenase deficiency (GDD) is an inherited neurometabolic disorder biochemically characterized by tissue accumulation of glutaric, 3-hydroxyglutaric (3-OHGA) and glutaconic acids and clinically by severe neurological symptoms and cerebral atrophy whose pathophysiology is poorly known. In the present study we investigated the effect of 3-OHGA, considered the main neurotoxin in GDD, on the lipoperoxidation parameters chemiluminescence and thiobarbituric acid-reactive species (TBA-RS), and on the amount of nitric oxide metabolites in cerebral cortex of young rats. Total radical-trapping antioxidant potential (TRAP), which reflects the tissue antioxidant defenses, was also examined. We observed that 3-OHGA significantly increased chemiluminescence, TBA-RS and nitric oxide metabolites, in contrast to TRAP, which was decreased by the metabolite. The data indicate a stimulation of lipid peroxidation and free radical production, and a reduction of the tissue antioxidant defenses caused by the metabolite. In case these findings also occur in the human condition, it may be presumed that oxidative stress is involved in the brain damage observed in GDD.     

Oxidative imbalance in child and adolescent patients with obsessive compulsive disorder

Various psychological, social, genetic and biochemical factors are thought to be involved in etiology of obsessive–compulsive disorder (OCD). To the best of our knowledge there are no studies investigating the effects of free radicals in children and adolescents with OCD. This study evaluated total oxidant and antioxidant status, oxidative stress index, and arylesterase and paraoxonase activity in children and adolescents with OCD. The study included 28 patients diagnosed with OCD and 36 healthy children as an age- and sex-matched control group. Their serum total oxidant status (TOS) and total antioxidant status (TAS) were measured and the oxidative stress index (OSI) was calculated. Although serum TOS and OSI values in the OCD patients were significantly higher than those in the control group (p = 0.008, p < 0.001, respectively), TAS and paraxonase activity were significantly lower ( p < 0.001 for both). However, no statistically significant difference in arylesterase activity was found (p > 0.05). The increase in oxidative status and decrease in antioxidants in patients with OCD demonstrate that oxidative stress may have an important role in the pathophysiology of the disease. It has been suggested that drugs that contain antioxidants should be added to conventional pharmacotherapy during follow-up.     

乌司他丁对急性脑梗死患者氧化应激状态的影响观察

目的 观察乌司他丁对急性脑梗死患者氧化应激状态的影响.方法 回顾性分析我院收治的104例急性脑梗死患者的临床资料,根据治疗方法 不同分为治疗组和对照组各52例,其中对照组患者给予常规治疗,治疗组患者在对照组的基础上加用乌司他丁,比较2组患者的临床效果和治疗前后氧化应激指标MDA、SOD、TAO水平的变化情况.结果 治疗后治疗组患者的总有效率90.38%,对照组78.85%,2组差异具有统计学意义,P〈0.05;治疗组患者基本痊愈率为38.46%,显著高于对照组患者的26.92%,P〈0.05;治疗前2组患者的MDA、SOD、TAO水平差异均无统计学意义,P〉0.05;治疗后,治疗组患者的MDA水平显著低于对照组患者,SOD、TAO水平均显著高于对照组患者,P〈0.05.结论 乌司他丁用于治疗急性脑梗死患者,显著降低患者体内MDA,升高SOD和TAO水平,降低患者氧化应激程度,从而保护脑神经元细胞,提高临床疗效.     

Regional distribution of heme oxygenase, HSP70, and glutathione in brain: relevance for endogenous oxidant/antioxidant balance and stress tolerance

It is generally recognized that lipid peroxides play an important role in the pathogenesis of several diseases and that sulfhydryl groups are critically involved in cellular defense against endogenous or exogenous oxidants. Recent evidence indicates that lipid peroxides directly participate in induction of cytoprotective proteins, such as heat shock proteins (Hsps), which play a central role in the cellular mechanisms of stress tolerance. Heme oxygenase (HO) is a stress protein that has been implicated in defense mechanisms against agents that may induce oxidative injury, such as endotoxins, cytokines and heme and its induction represents a common feature in a number of neurodegenerative diseases. In the present report we studied regional distribution of heme oxygenase (HO) activity and protein expression, together with that of Hps70, in brain of C57BL6 mice. Endogenous lipid peroxidation was investigated on the basis of the analysis of ultra weak chemiluminescence, hydro peroxides and lipid soluble fluorescent products, and compared to the regional distribution of thiols, antioxidant enzymes and trace metals. Our results show that levels of HO activity and expression of inducible Hsp70 and the ratio of GSH/GSSG in the different brain regions examined were positively correlated with the content of peroxides. Substantia Nigra was the brain area exhibiting the highest levels of HO-2, constitutive and inducible Hsp70, GSSG, peroxides, iron, and calcium, in contrast with the lowest content in GSH, GSH/GSSG ratio and glutathione reductase activity, compared to the other cerebral regions examined. Among these, cortex showed the lowest levels of HO-2, Hsp70, GSSG and peroxides that were associated with the highest levels of GSH and GSH/GSSG ratio. These data support the hypothesis that the glutathione redox state and basal peroxides can directly participate in the signaling pathways of heat shock protein expression and hence of stress tolerance.     

Kynurenines and oxidative status are independently associated with thrombomodulin and von Willebrand factor levels in patients with end-stage renal disease

Introduction

Increased oxidative stress (SOX) is one of the most potent inductors of endothelial dysfunction in end-stage renal disease (ESRD) patients. Kynurenines are the metabolites of tryptophan (TRP) degradation in mammals. However, the role of kynurenines in the function of the endothelium is still not recognized.

Materials and methods

We determined the plasma concentrations of TRP, kynurenine (KYN), 3-hydroxykynurenine (3-HKYN), quinolinic acid (QA); markers of SOX: Cu/Zn superoxide dismutase (Cu/Zn SOD), malondialdehyde (MDA); and endothelial dysfunction markers: thrombomodulin (TM) and von Willebrand factor (vWF) levels in 148 ESRD patients and healthy controls.

Results

TM, vWF, KYN, 3-HKYN and QA levels were significantly elevated in ESRD patients compared to controls. TRP concentrations in uremics were significantly lower than in healthy people. Both dialyzed groups showed a significant increase Cu/Zn SOD and MDA levels compared to controls. TM and vWF were positively associated with kynurenine pathway metabolites: KYN, 3-HKYN, QA (all p < 0.001), and with SOX markers: Cu/Zn SOD (both p < 0.0001) and MDA levels (p < 0.05, and p < 0.0001; respectively) in the whole ESRD group. The positive relationship were between Cu/Zn SOD and KYN (p < 0.010), 3-HKYN and QA levels (both p < 0.0001), whereas MDA was correlated with 3-HKYN and QA concentrations (both p < 0.05). Multiple stepwise regression analysis showed that KYN metabolites and oxidative status were the independent variables significantly associated with increased both TM and vWF levels in uremic patients.

Conclusions

Our study demonstrated that kynurenine metabolites and increased oxidative status are independently and significantly associated with endothelial dysfunction in ESRD patients.     

无抽搐电休克治疗与碳酸锂对双相障碍抑郁发作患者氧化应激水平的影响

目的了解无抽搐电休克治疗(modified electroconvulsive therapy,MECT)对双相障碍抑郁发作患者氧化应激水平的影响。方法选取双相障碍抑郁发作患者42例,随机分为两组,MECT组18例患者在抗抑郁药物治疗基础上行12次MECT治疗,碳酸锂组24例患者使用碳酸锂合并抗抑郁药物治疗,共治疗6周。分别在治疗前、治疗6周末采用17项汉密尔顿抑郁量表(17 items Hamilton depression scale,HAMD-17)、杨氏躁狂量表(Young mania rating scale,YMRS)、临床疗效总评量表(clinical global impression scale,CGI)、副反应量表(treatment emergent symptom scale,TESS)评估疗效和不良反应,检测外周血超氧化物歧化酶(superoxide dismutase,SOD)、过氧化氢酶(catalase,CAT)、谷胱甘肽过氧化物酶(glutathione peroxidase,GSH-Px)、丙二醛(malondialdehyde,MDA)含量,评估氧化应激水平。结果重复测量方差分析显示,SOD指标分组主效应有统计学意义(F=15.26,P0.01),碳酸锂组的水平整体高于MECT组(P0.05);MDA指标分组主效应有统计学意义(F=18.18,P0.01),MECT组的水平整体高于碳酸锂组(P0.05);GSH-Px指标分组主效应(F=6.24,P=0.02)、分组与时间交互效应(F=6.39,P=0.02)有统计学意义,碳酸锂组的水平整体高于MECT组(P0.05),治疗前两组间无统计学差异(P0.05),治疗6周末MECT组GSH-Px低于碳酸锂组(P0.05)。治疗6周末,MECT组中治疗有效者CAT水平较无效者高(P0.05)。结论 MECT能改变双相障碍抑郁发作患者氧化应激水平,其对血浆CAT的调节可能是治疗有效的作用机制之一。     

Low plasma antioxidant status in patients with epilepsy and the role of antiepileptic drugs on oxidative stress

Background:

Oxidative stress has been implicated in various disorders including epilepsy. We studied the antioxidant status in patients with epilepsy and aimed at determining whether there was any difference in the antioxidant levels between patients and controls, patients who are not on antiepileptic drugs (AEDs), and on treatment, between individual AEDs and patients on monotherapy and polytherapy.

Materials and Methods:

Antioxidant levels like catalase, glutathione peroxidase (GPx), vitamin E, glutathione (GSH), thiol group (SH), uric acid, and total antioxidant capacity (TAC) were compared between 100 patients with epilepsy and equal number of controls. Twenty-five patients who were not on AEDs were compared with patients on AEDs and the control group. Patients were divided into monotherapy and polytherapy group and antioxidant status was compared between the two groups and between individual drugs.

Results:

Catalase, SH, vitamin E, and TAC were significantly low in patients with epilepsy than those in the control group (P < 0.001). GSH and uric acid did not show any difference; GPx in patients was significantly higher than those in the control group There were no differences in the antioxidant levels between the treated and the untreated groups; however, it was lower in untreated patients than controls (P < 0.001), suggesting that AEDs do not modify the oxidative stress. Patients on Valproate (VPA) showed higher catalase and GPx levels. Catalase was higher in the monotherapy than polytherapy group (P < 0.04).

Conclusion:

Our study found significantly low levels of antioxidant in patients as compared to controls. AED did not influence the antioxidant status suggesting that seizures induce oxidative stress.     

Reduced plasma total antioxidant status in first-episode drug-naive patients with schizophrenia

Excessive free radical production leading to oxidative stress may be involved in the pathophysiology of schizophrenia. Determination of total antioxidant status (TAS) provides an index of the sum of activities of all antioxidants. However, there have been few systematic studies to examine the relationship between TAS levels and psychopathology in first-episode and drug-naive patients with schizophrenia.TAS levels were determined in the plasma of 60 never-medicated first-episode patients with schizophrenia and 68 healthy control subjects. The schizophrenia symptomatology and the depressive symptoms were assessed by the positive and negative syndrome scale (PANSS) and the Hamilton rating scale for depression (HAMD). The results showed that TAS levels were significantly lower in first-episode patients with schizophrenia than in healthy control subjects (159.8 ± 45.8 U/ml vs 211.4 ± 46.8 U/ml, F = 39.5, df = 1, 126, p < 0.001). A trend toward significant inverse correlation between TAS levels and PANSS negative subscore was observed (r = 0.25, df = 60, p = 0.06). Our results suggest that oxidative stress occurs in an early course of schizophrenia and may have an important role in pathogenesis and perhaps, negative symptomatology of schizophrenia.     

Markedly elevated nitrate/nitrite levels in the cerebrospinal fluid of children with progressive encephalopathy with edema, hypsarrhythmia, and optic atrophy (PEHO syndrome)

SUMMARY: PURPOSE: To compare the levels of brain nitric oxide production in patients with PEHO or PEHO-like syndrome and in controls with other neurologic disease. METHODS: Nitric oxide metabolites, nitrates, and nitrites (NNx), were measured in the cerebrospinal fluid (CSF) of children with PEHO syndrome or PEHO-like syndrome, and in controls with other neurologic diseases. RESULTS: The NNx levels were markedly higher in both PEHO (mean, 48 microM; p < 0.001) and PEHO-like (22 microM; p < 0.003) patients as compared with the controls (6 microM), but did not correlate with age or with brain atrophy or CSF levels of insulin-like growth factor-1 (IGF-1). CONCLUSIONS: Our findings suggest that in PEHO syndrome, production of nitric oxide is markedly increased, suggesting that nitric oxide is involved in the pathologic phenomena (i.e., seizures and neurodegeneration) of the disease.     

海洛因依赖者认知功能状况与一氧化氮等的关系

目的探讨海洛因依赖者认知功能受损与血清一氧化氮(NO)等的关系。方法运用韦氏记忆量表(WMS)、数字划销测验(NCT)、威斯康星卡片分类测验(WCST)对140例男性海洛因依赖者(MPHD)及75例正常对照进行认知功能评估,用化学比色法检测受试血清NO等氧化应激指标水平。结果(1)MPHD组记忆商(MQ)、注意力及执行功能均差于对照组;(2)血清丙二醛水平高于对照组,总抗氧化能力、维生素C、超氧化物歧化酶水平低于对照组(P<0.05或P<0.01);(3)MPHD血清NO水平与记忆商(MQ)及WCST正确数呈负相关(P<0.05或P<0.01);MDA水平与MQ及NCT总净分均呈显著负相关(P<0.01);VC水平与MQ呈正相关(P<0.05);SOD水平与MQ、NCT总净分、WCST正确数均呈正相关(P<0.01)。结论海洛因依赖者存在明显的认知功能损害与氧化抗氧化反应失衡;血清NO、MDA、SOD、VC可能是与认知功能密切相关的氧化应激指标。     

Nitrite or sildenafil, but not BAY 41-2272, blunt acute pulmonary embolism-induced increases in circulating matrix metalloproteinase-9 and oxidative stress

IntroductionInhibition of matrix metalloproteinases (MMPs) improves the hemodynamics during acute pulmonary embolism (APE) and oxidative stress upregulates MMPs. We compared the effects of different NO-cGMP pathway activators on APE-induced increases in MMPs.Materials and MethodsHemodynamic and biochemical evaluations were performed in non-embolized dogs treated with saline (N = 5), and in microspheres embolized dogs receiving saline (n = 9), or nitrite (6.75 µmol/kg i.v. over 15 min followed by 0.28 µmol/kg/min; n = 5), or sildenafil (0.25 mg/kg; n = 5), or BAY 41-2272 (0.03, 0.1, 0.3, and 1 mg/kg/h; n = 5). Plasma thiobarbituric acid reactive substances (TBARS) concentrations were determined. Zymograms of plasma samples were performed, and in vitro antioxidant effects or inhibition of MMPs by these drugs were examined.ResultsAPE increased mean pulmonary artery pressure by ~ 25 mmHg. Nitrite, BAY 41-2272, or sildenafil reversed this increase by ~ 40% (P < 0.05). Similar effects were seen on the pulmonary vascular resistance. While both nitrite and sildenafil produced no systemic effects, the highest dose of BAY 41-2272 produced systemic hypotension (P < 0.05). While nitrite and sildenafil blunted the increases in plasma pro-MMP-9 levels and TBARS (all P < 0.05), BAY 41-2272 produced no such effects. Nitrite and sildenafil produced in vitro antioxidant effects and inhibited MMPs only at high concentrations. BAY 41-2272 produced no such effects.ConclusionsActivation of the NO-cGMP pathway with nitrite or sildenafil, but not with BAY 41-2272, attenuates APE-induced oxidative stress and increased MMP-9 levels. These findings are consistent with the idea that NO-cGMP pathway activators with antioxidant effects prevent the release of MMP-9 during APE.     

静脉溶栓治疗急性脑梗死患者的临床疗效及对氧化应激指标水平与神经功能的影响

目的 探讨静脉溶栓治疗急性脑梗死患者的临床疗效及对氧化应激指标水平、神经功能的影响。方法 用抽签法将于本院2016年2月-2017年10月就诊的81例急性脑梗死患者分为2组,对照组(n=40)采用常规治疗,观察组(n=41)应用静脉溶栓治疗,观察2组的治疗效果及氧化应激指标水平、神经功能变化情况。结果 观察组总有效率为95.4%,明显高于对照组62.5%(P<0.05); 治疗后观察组各项氧化应激指标水平、NIHSS(美国国立卫生研究院卒中量表)评分、S100B蛋白及BDNF(脑源性神经营养因子)表达水平均明显优于对照组(P<0.05)。结论 应用静脉溶栓治疗急性脑梗死患者的临床疗效显著,可有效改善氧化应激指标水平、神经功能。     

No changes in cerebrospinal fluid levels of nitrite, nitrate and cyclic GMP with aging

Summary Nitric oxide (NO) is a free radical gas that plays a role in various signal transduction processes. NO has been proposed to have a function in the mechanism of synaptic plasticity, including long-term potentiation and memory formation in vivo. Because a failure in synaptic plasticity is considered to be involved in aging-associated brain dysfunction, NO production in the brain may be altered by aging. In the present study, we measured the levels of NO metabolites, nitrite and nitrate, and cyclic GMP in the cerebrospinal fluid (CSF) of human subjects without neurological or psychiatric disorders. There were no age-related changes in the CSF levels of either nitrite, nitrate or cyclic GMP. These results suggest that NO production in the brain may be maintained during the aging process.     

Decreased endothelial cell glutathione and increased sensitivity to oxidative stress in an in vitro blood–brain barrier model system

Using a cell culture model of the blood–brain barrier (BBB) we have evaluated the role of endothelial cell glutathione in protecting barrier integrity against nitric oxide (NO)-induced oxidative stress. The co-culture of human umbilical vein endothelial cells (ECV304) with rat (C6) glioma cells, or incubation with glioma cell or primary astrocytic conditioned medium, resulted in a decline in endothelial cell glutathione. Exposure to a single addition of NO gas induced a rapid breakdown in model barrier integrity in endothelial/glioma co-cultures. Addition of NO gas or tumour necrosis factor-α (TNF-α) also resulted in a loss of membrane integrity, as measured by an enhanced release of lactate dehydrogenase, only from endothelial cells treated with glioma conditioned medium. Furthermore, assessment of viability in endothelial cells grown alone or treated with glioma conditioned medium, by propidium iodide labelled flow cytometry, demonstrated no difference in the number of positively stained cells after NO exposure. These results indicate that when enhanced endothelial monolayer barrier formation occurs via astrocytic–endothelial interactions, cellular glutathione levels are decreased. This renders the barrier cells, under these conditions, more susceptible to oxidative stress but does not necessarily lead to greater cell death.