Reduction of plasma glutathione in psychosis associated with schizophrenia and bipolar disorder in translational psychiatry

Schizophrenia and Glutathione: A Challenging Story

Schizophrenia (SZ) is a devastating mental illness with a complex and heterogeneous clinical state. Several conditions like symptoms, stage and severity of the disease are only some of the variables that have to be considered to define the disorder and its phenotypes. SZ pathophysiology is still unclear, and the diagnosis is currently relegated to the analysis of clinical symptoms; therefore, the search for biomarkers with diagnostic relevance is a major challenge in the field, especially in the era of personalized medicine. Though the mechanisms implicated in SZ are not fully understood, some processes are beginning to be elucidated. Oxidative stress, and in particular glutathione (GSH) dysregulation, has been demonstrated to play a crucial role in SZ pathophysiology. In fact, glutathione is a leading actor of oxidative-stress-mediated damage in SZ and appears to reflect the heterogeneity of the disease. The literature reports differing results regarding the levels of glutathione in SZ patients. However, each GSH state may be a sign of specific symptoms or groups of symptoms, candidating glutathione as a biomarker useful for discriminating SZ phenotypes. Here, we summarize the literature about the levels of glutathione in SZ and analyze the role of this molecule and its potential use as a biomarker.

Potential Role of Glutathione Antioxidant Pathways in the Pathophysiology and Adjunct Treatment of Psychiatric Disorders

Oxidative stress is defined as the imbalance between the production of free radicals and their removal by antioxidants, leading to accumulation and subsequent organ and tissue damage. Antioxidant status and its role in the accumulation of free radicals has been observed in a number of psychological disorders. Glutathione is commonly referred to as the principal antioxidant of the brain and, therefore, plays a critical role in maintaining redox homeostasis. Reduced levels of glutathione in the brain increase its vulnerability to oxidative stress, and may be associated with the development and progression of several psychiatric disorders. Within this review, we focus on analyzing potential associations between the glutathione antioxidant pathway and psychiatric disorders: major depressive disorder, schizophrenia, bipolar disorder, and generalized anxiety disorder. Our research suggests that studies regarding these four disorders have shown decreased levels of GSH in association with diseased states; however, conflicting results note no significant variance in glutathione pathway enzymes and/or metabolites based on diseased state. In studying the potential of NAC administration as an adjunct therapy, various studies have shown NAC to augment therapy and/or aid in symptomatic management for psychiatric disorders, while contrasting results exist within the literature. Based on the conflicting findings throughout this review, there is room for study regarding the potential role of glutathione in the development and progression of psychiatric disorders. Our findings further suggest a need to study such pathways with consideration of the interactions with first-line pharmacotherapy, and the potential use of antioxidants as supplemental therapy.

Identification of late-life depression and mild cognitive impairment via serum surface-enhanced Raman spectroscopy and multivariate statistical analysis

Identification of age-related neuropsychiatric disorders, i.e., late-life depression (LDD) and mild cognitive impairment (MCI) is of imperative clinical value considering the large probability of misdiagnosis and current lack of sensitive, non-invasive and low-cost diagnostic approaches. Here, the serum surface-enhanced Raman spectroscopy (SERS) technique is proposed to identify healthy controls, LDD and MCI patients. Based on SERS peaks analysis, abnormal levels of ascorbic acid, saccharide, cell-free DNA and amino acids in serum are found to be potential biomarkers for identifying LDD and MCI. These biomarkers might be related to oxidative stress, nutritional status, lipid peroxidation and metabolic abnormalities. Moreover, partial least square analysis-linear discriminant analysis (PLS-LDA) is applied to those collected SERS spectra. Finally, the overall identification accuracy is 83.2%, and accuracies are 91.6% and 85.7% for differentiating healthy versus neuropsychiatric disorders and LDD versus MCI, respectively. Thus, the serum SERS combined with multivariate statistical analysis has proved its successful potential for rapid, sensitive and non-invasive identification of healthy, LDD and MCI, which may open new avenues for early diagnosis and timely intervention for age-related neuropsychiatric disorders.

Therapeutic Strategies to Ameliorate Neuronal Damage in Epilepsy by Regulating Oxidative Stress, Mitochondrial Dysfunction, and Neuroinflammation

Epilepsy is a central nervous system disorder involving spontaneous and recurring seizures that affects 50 million individuals globally. Because approximately one-third of patients with epilepsy do not respond to drug therapy, the development of new therapeutic strategies against epilepsy could be beneficial. Oxidative stress and mitochondrial dysfunction are frequently observed in epilepsy. Additionally, neuroinflammation is increasingly understood to contribute to the pathogenesis of epilepsy. Mitochondrial dysfunction is also recognized for its contributions to neuronal excitability and apoptosis, which can lead to neuronal loss in epilepsy. This review focuses on the roles of oxidative damage, mitochondrial dysfunction, NAPDH oxidase, the blood-brain barrier, excitotoxicity, and neuroinflammation in the development of epilepsy. We also review the therapies used to treat epilepsy and prevent seizures, including anti-seizure medications, anti-epileptic drugs, anti-inflammatory therapies, and antioxidant therapies. In addition, we review the use of neuromodulation and surgery in the treatment of epilepsy. Finally, we present the role of dietary and nutritional strategies in the management of epilepsy, including the ketogenic diet and the intake of vitamins, polyphenols, and flavonoids. By reviewing available interventions and research on the pathophysiology of epilepsy, this review points to areas of further development for therapies that can manage epilepsy.

Comparative Analysis of the Pre- and Post-Medication Effects of Antipsychotic Agents on the Blood-Based Oxidative Stress Biomarkers in Patients with Schizophrenia: A Meta-Analysis

OBJECTIVE

Studies have shown that oxidative stress (OS) is related to the pathophysiology of schizophrenia (SCZ), but whether antipsychotics can induce OS has not been investigated well. Moreover, antipsychotics have differential effects on the OS level modulation, i.e., different types of antipsychotics have different effects on the cellular antioxidants or pro-oxidants.

METHODS

We followed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines and investigated the OS indicators including both enzymatic and nonenzymatic markers, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), malondialdehyde (MDA), glutathione (GSH), vitamin C, etc., of SCZ patients at baseline and follow-up of mono-medication.

RESULTS

Twenty studies met the inclusion criteria, with a total of 1162 patients enrolled at baseline, and 1105 patients completed the follow-up. OS markers were changed after a period of antipsychotic treatment in SCZ patients. The GPx activity and MDA level decreased in the whole blood (P<0.05), also the serum MDA level decreased (P<0.05). For the first-episode SCZ patients, the activity of GPx and the level of MDA decreased, while the level of vitamin C increased (all P<0.05). The levels of MDA in patients receiving atypical antipsychotics decreased (P<0.05), while the level of GSH in patients with typical antipsychotics decreased (P=0.05).

CONCLUSION

Antipsychotic medication may cause changes in the levels of OS markers in different blood samples of SCZ patients. However, the available studies might not be sufficient to reveal the underlying facts accurately due to the poor quality of experimental designs in the published literature.

The Role of Equilibrium between Free Radicals and Antioxidants in Depression and Bipolar Disorder

Background: Increasing evidence suggests that the presence of oxidative stress and disorders of the antioxidant defense system are involved in a wide range of neuropsychiatric disorders, such as bipolar disorder, schizophrenia and major depression, but the exact mechanism remains unknown. This review focuses on a better appreciation of the contribution of oxidative stress to depression and bipolar disorder. Methods: This review was conducted by extracting information from other research and review studies, as well as other meta-analyses, using two search engines, PubMed and Google Scholar. Results: As far as depression is concerned, there is agreement among researchers on the association between oxidative stress and antioxidants. In bipolar disorder, however, most of them observe strong lipid peroxidation in patients, while regarding antioxidant levels, opinions are divided. Nevertheless, in recent years, it seems that on depression, there are mainly meta-analyses and reviews, rather than research studies, unlike on bipolar disorder. Conclusions: Undoubtedly, this review shows that there is an association among oxidative stress, free radicals and antioxidants in both mental disorders, but further research should be performed on the exact role of oxidative stress in the pathophysiology of these diseases.

Targeting D-Amino Acid Oxidase (DAAO) for the Treatment of Schizophrenia: Rationale and Current Status of Research

In the brain, D-amino acid oxidase (DAAO) is a peroxisomal flavoenzyme. Through oxidative deamination by DAAO, D-serine, the main coagonist of synaptic N-methyl-D-aspartate receptors (NMDARs), is degraded into α-keto acids and ammonia; flavin adenine dinucleotide (FAD) is simultaneously reduced to dihydroflavine-adenine dinucleotide (FADH2), which is subsequently reoxidized to FAD, with hydrogen peroxide produced as a byproduct. NMDAR hypofunction is implicated in the pathogenesis of schizophrenia. In previous studies, compared with control subjects, patients with schizophrenia had lower D-serine levels in peripheral blood and cerebrospinal fluid but higher DAAO expression and activity in the brain. Inhibiting DAAO activity and slowing D-serine degradation by using DAAO inhibitors to enhance NMDAR function may be a new strategy for use in the treatment of schizophrenia. The aim of this leading article is to review the current research in DAAO inhibitors.

The effect of levetiracetam on depression and anti-oxidant activity in patients with epilepsy

Background: Levetiracetam (LEV) is approved for treating epilepsy. The current evidence shows that LEV can cause behavioral problems such as depression. It is well-known that depression is associated with oxidative stress. Therefore, we conducted this study to assess the influence of LEV on depression severity and anti-oxidant status. Methods: In this prospective longitudinal study, 50 patients with diagnosis of epilepsy on LEV were included. We used Beck Depression Inventory-II (BDI-II) to assess depression severity. The serum levels of zinc and glutathione were measured as anti-oxidant markers. These variables were evaluated at the baseline and 3 months after the commencement of LEV. Results: A total of 30 patients finished the follow-up. Among them, 21 patients were women. The mean age at baseline was 28.76 ± 11.37 (range: 16-68 years). The severity of depression at the last follow-up was significantly higher than the baseline. We observed a decrease in the serum levels of zinc and glutathione, though they were not statistically significant. Conclusion: Our results suggest that LEV can increase the risk of depression in patients with epilepsy. This study also suggests that zinc depletion can be induced through act of LEV. Further studies are needed to validate these findings.

Predictive value of oxidative stress biomarkers in drug-free patients with bipolar disorder

OBJECTIVE

Oxidative stress is one of the primary etiological mechanisms of bipolar disorder (BD).

METHODS

The present study was conducted over a period of 24 months on Tunisian on 34 drug‑free male patients with BD (mean age: 34.5 years) and 101 age and gender matched controls (mean age: 34.20 years) were enrolled in the study.

RESULTS

Plasma reduced glutathione (GSH) and total thiols levels were significantly decreased in patients compared to controls (respectively p < .001; p = .009). In addition, malondialdehyde (MDA), advanced oxidation protein products (AOPP), protein carbonyls (PC) and homocysteine (Hcys) concentrations and glutathione peroxidase (GSH-Px) activity were significantly increased in patients compared to controls (p = .002; p < .001; p = .001; p < .001 and p = .016, respectively). The binary logistic regression analysis revealed that MDA, AOPP and Hcys could be considered as independent risk factors for BD. When using CombiROC analysis, a remarkable increase in the area under the curve (AUC) with higher sensitivity (Se) and specificity (Sp) for MDA, AOPP, PC, GSH-Px and Hcys combined markers was observed.

CONCLUSIONS

Overall, the identification of the predictive value of these five selected biomarkers related to oxidative stress in drug free patients should lead to a better identification of the etiological mechanism of BD.

Oxidative Stress and Emergence of Psychosis

Treatment and prevention strategies for schizophrenia require knowledge about the mechanisms involved in the psychotic transition. Increasing evidence suggests a redox imbalance in schizophrenia patients. This narrative review presents an overview of the scientific literature regarding blood oxidative stress markers’ evolution in the early stages of psychosis and chronic patients. Studies investigating peripheral levels of oxidative stress in schizophrenia patients, first episode of psychosis or UHR individuals were considered. A total of 76 peer-reviewed articles published from 1991 to 2022 on PubMed and EMBASE were included. Schizophrenia patients present with increased levels of oxidative damage to lipids in the blood, and decreased levels of non-enzymatic antioxidants. Genetic studies provide evidence for altered antioxidant functions in patients. Antioxidant blood levels are decreased before psychosis onset and blood levels of oxidative stress correlate with symptoms severity in patients. Finally, adjunct treatment of antipsychotics with the antioxidant N-acetyl cysteine appears to be effective in schizophrenia patients. Further studies are required to assess its efficacy as a prevention strategy. Redox imbalance might contribute to the pathophysiology of emerging psychosis and could serve as a therapeutic target for preventive or adjunctive therapies, as well as biomarkers of disease progression.

Tetrahydrobiopterin deficiency in schizophrenia: Biochemical and clinical aspects

It was reported that the levels of tetrahydrobiopterin (BH4) are reduced in schizophrenia. However, mechanisms of BH4 deficiency in schizophrenia had not been studied precisely.

OBJECTIVE

the search of the association between BH4 deficiency in schizophrenia and a range of biochemical and clinical parameters for the evaluation of the possible mechanisms of BH4 loss and its role in the development of the symptoms.

METHODS

93 patients with schizophrenia and 60 healthy volunteers were randomly selected and evaluated with a biochemical examination of BH4, folate, cobalamin (B12), homocysteine, C-reactive protein (CRP), reduced glutathione (GSH) levels in the blood serum.Patients underwent standardized psychopathological examination.

RESULTS

In patients, the levels of BH4 and folate were lower (p = 0.001 and p = 0.054, respectively), and the levels of homocysteine were higher (p = 0.012) compared to the control group. BH4 levels directly moderately correlated with folate (ρ = 0.43; p = 0.0029) and B12 levels (ρ = 0.43; p = 0.0020) and inversely moderately correlated with homocysteine levels (ρ = -0.54; p = 0.00015) in patients. Cluster analysis identified schizophrenia biotype characterized by a deficiency of BH4, folate, B12, and hyperhomocysteinemia. The clinical characteristics of this biotype were not specific. CRP and GSH were higher in patients compared to controls, but their association with serum BH4 was not confirmed.

Sex-Specific Association between Antioxidant Defense System and Therapeutic Response to Risperidone in Schizophrenia: A Prospective Longitudinal Study

BACKGROUND

There are various differences in response to different antipsychotics and antioxidant defense systems (ADS) by sex. Previous studies have shown that several ADS enzymes are closely related to the treatment response of patients with antipsychotics-naïve first-episode (ANFE) schizophrenia.

OBJECTIVE

Therefore, the main goal of this study was to assess the sex difference in the relationship between changes in ADS enzyme activities and risperidone response.

METHODS

The plasma activities of glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), and total antioxidant status (TAS) were measured in 218 patients and 125 healthy controls. Patients were treated with risperidone for 3 months, and we measured PANSS for psychopathological symptoms and ADS biomarkers at baseline and at the end of 3 months of treatment. We compared sex-specific group differences between 50 non-responders and 168 responders at baseline and at the end of the three months of treatment.

RESULTS

We found that female patients responded better to risperidone treatment than male patients. At baseline and 3-month follow-up, there were no significant sex differences in TAS levels and three ADS enzyme activities. Interestingly, only in female patients, after 12 weeks of risperidone treatment, the GPx activity of responders was higher than that of non-responders.

CONCLUSION

These results indicate that after treatment with risperidone, changes in GPx activity were associated with treatment response, suggesting that changes in GPx may be a predictor of response to risperidone treatment in female patients with ANFE schizophrenia.

Folic Acid as the Adjuvant Therapy for Chronic Schizophrenia: A Comprehensive Study on Glutathione Reductase

Abstract

Neuroprotective effect of hesperidin and its combination with coenzyme Q10 on an animal model of ketamine-induced psychosis: behavioral changes, mitochondrial dysfunctions, and oxidative stress

Background

Psychosis is a complex mental illness divided by positive symptoms, negative symptoms, and cognitive decline. Clinically available medicines are associated with some serious side effects which limit their use. Treatment with flavonoids has been associated with delayed onset and development, decreased risk, or increased improvement of various neuropsychiatric disorders including psychosis with negligible side effects. Therefore, the present study was aimed to investigate the protective effects of hesperidin (flavonoid) alone or its combination with coenzyme Q10 against ketamine-induced psychotic symptoms in mice.

Results

Ketamine (50 mg/kg, i.p.) was given for 21 days to induce psychosis in Laca mice of either sex. Locomotor activity and stereotypic behaviors, immobility duration (forced swim test), and increased transfer latency (elevated plus maze) were performed to test the effect of hesperidin (50 mg/kg, 100 mg/kg, 200 mg/kg, p.o.) and coenzyme Q10 (20 mg/kg, 40 mg/kg, p.o.) and combination of hesperidin + coenzyme Q10 followed by biochemical and mitochondrial complexes assays. For 21 days, ketamine (50 mg/kg, i.p.) administration significantly produced increased locomotor activity and stereotypic behaviors (positive symptoms), increased immobility duration (negative symptoms) and cognitive deficits (increases transfer latency) weakens oxidative defense and mitochondrial function. Further, 21 days’ administration of hesperidin and coenzyme Q10 significantly reversed the ketamine-induced psychotic behavioral changes and biochemical alterations and mitochondrial dysfunction in the discrete areas (prefrontal cortex and hippocampus) of mice brains. The potential effect of these drugs was comparable to olanzapine treatment. Moreover, the combination of hesperidin with coenzyme Q10 and or a combination of hesperidin + coenzyme Q10 + olanzapine treatment did not produce a significant effect compared to their per se effect in ketamine-treated animals.

Conclusions

The study revealed that hesperidin alone or in combination with coenzyme Q10 could reduce psychotic symptoms and improve mitochondrial functions and antioxidant systems in mice, suggesting neuroprotective effects against psychosis.

Thalamic reticular nucleus impairments and abnormal prefrontal control of dopamine system in a developmental model of schizophrenia: prevention by N-acetylcysteine

Recent evidence showed thalamic abnormalities in schizophrenia involving disruptions to the parvalbumin neurons in the thalamic reticular nucleus (TRN). However, their functional consequences, as well as a potential linkage to oxidative stress, are unclear. The TRN is posited to gate prefrontal control of dopamine neuron activity in the ventral tegmental area (VTA). Thus, we hypothesized that schizophrenia-related TRN abnormalities might contribute to dopamine dysregulation, a well-known feature of the disorder. To test this, in adult rats exposed prenatally to methylazoxymethanol acetate (MAM rats), oxidative impairments to the parvalbumin neurons in the anterior TRN were assessed by immunohistochemistry. Using in vivo electrophysiology, we investigated whether inactivation of the prefrontal cortex would produce differential effects on VTA dopamine neurons in MAM rats. We show that MAM rats displayed reduced markers of parvalbumin and wisteria floribunda agglutinin-labeled perineuronal nets, correlating with increased markers of oxidative stress (8-oxo-7, 8-dihydro-20-deoxyguanosine, and 3-nitrotyrosine). Moreover, MAM rats displayed heightened baseline and abnormal prefrontal control of VTA dopamine neuron activity, as tetrodotoxin-induced inactivation of the infralimbic prefrontal cortex decreased the dopamine population activity, contrary to the normal increase in controls. Such dopamine neuron dysregulation was recapitulated by enzymatic perineuronal net digestion in the TRN of normal rats. Furthermore, juvenile (postnatal day 11-25) antioxidant treatment (N-acetyl-cysteine, 900 mg/L drinking water) prevented all these impairments in MAM rats. Our findings suggest that early accumulation of oxidative stress in the TRN may shape the later onset of schizophrenia pathophysiology, highlighting redox regulation as a potential target for early intervention.

High-sucrose diets contribute to brain angiopathy with impaired glucose uptake and psychosis-related higher brain dysfunctions in mice

Metabolic dysfunction is thought to contribute to the severity of psychiatric disorders; however, it has been unclear whether current high–simple sugar diets contribute to pathogenesis of these diseases. Here, we demonstrate that a high-sucrose diet during adolescence induces psychosis-related behavioral endophenotypes, including hyperactivity, poor working memory, impaired sensory gating, and disrupted interneuron function in mice deficient for glyoxalase-1 (GLO1), an enzyme involved in detoxification of sucrose metabolites. Furthermore, the high-sucrose diet induced microcapillary impairments and reduced brain glucose uptake in brains of Glo1-deficient mice. Aspirin protected against this angiopathy, enhancing brain glucose uptake and preventing abnormal behavioral phenotypes. Similar vascular damage to our model mice was found in the brains of randomly collected schizophrenia and bipolar disorder patients, suggesting that psychiatric disorders are associated with angiopathy in the brain caused by various environmental stresses, including metabolic stress.

Treatment-resistant schizophrenia: focus on the transsulfuration pathway

Treatment-resistant schizophrenia (TRS) is a severe form of schizophrenia. The severity of illness is positively related to homocysteine levels, with high homocysteine levels due to the low activity of the transsulfuration pathway, which metabolizes homocysteine in synthesizing L-cysteine. Glutathione levels are low in schizophrenia, which indicates shortages of L-cysteine and low activity of the transsulfuration pathway. Hydrogen sulfide (H2S) levels are low in schizophrenia. H2S is synthesized by cystathionine β-synthase and cystathionine γ-lyase, which are the two enzymes in the transsulfuration pathway. Iron-sulfur proteins obtain sulfur from L-cysteine. The oxidative phosphorylation (OXPHOS) pathway has various iron-sulfur proteins. With low levels of L-cysteine, iron-sulfur cluster formation will be dysregulated leading to deficits in OXPHOS in schizophrenia. Molybdenum cofactor (MoCo) synthesis requires sulfur, which is obtained from L-cysteine. With low levels of MoCo synthesis, molybdenum-dependent sulfite oxidase (SUOX) will not be synthesized at appropriate levels. SUOX detoxifies sulfite from sulfur-containing amino acids. If sulfites are not detoxified, there can be sulfite toxicity. The transsulfuration pathway metabolizes selenomethionine, whereby selenium from selenomethionine can be used for selenoprotein synthesis. The low activity of the transsulfuration pathway decreases selenoprotein synthesis. Glutathione peroxidase (GPX), with various GPXs being selenoprotein, is low in schizophrenia. The dysregulations of selenoproteins would lead to oxidant stress, which would increase the methylation of genes and histones leading to epigenetic changes in TRS. An add-on treatment to mainline antipsychotics is proposed for TRS that targets the dysregulations of the transsulfuration pathway and the dysregulations of other pathways stemming from the transsulfuration pathway being dysregulated.

Polyphenols as adjunctive treatments in psychiatric and neurodegenerative disorders: Efficacy, mechanisms of action, and factors influencing inter-individual response

The pathophysiology of psychiatric and neurodegenerative disorders is complex and multifactorial. Polyphenols possess a range of potentially beneficial mechanisms of action that relate to the implicated pathways in psychiatric and neurodegenerative disorders. The aim of this review is to highlight the emerging clinical trial and preclinical efficacy data regarding the role of polyphenols in mental and brain health, elucidate novel mechanisms of action including the gut microbiome and gene expression, and discuss the factors that may be responsible for the mixed clinical results; namely, the role of interindividual differences in treatment response and the potentially pro-oxidant effects of some polyphenols. Further clarification as part of larger, well conducted randomized controlled trials that incorporate precision medicine methods are required to inform clinical efficacy and optimal dosing regimens.

Association of antioxidant deficiency and the level of products of protein and lipid peroxidation in patients with the first episode of schizophrenia

Schizophrenia is considered a multifactorial disease, where one of the pathogenetic links is oxidative stress; however, the results of studies are often contradictory, largely due to significant heterogeneity among study methods. The present study was undertaken to compare the levels of oxidative stress markers in the peripheral blood of patients with a first episode of schizophrenia (FES) and in healthy volunteers (HV). The study included 50 patients with FES and 37 HV. Blood samples were collected for spectrophotometric assessment of reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), aldehyde-2,4-dinitrophenylhydrazone (ADNPH), and ketone-2,4-dinitrophenylhydrazone (KDNPH) in blood plasma. Results showed that in patients with FES compared with HV, a significant decrease in CAT activity and an increase in oxidative modification of proteins (OMP) were found. In both groups, a significant increase in the level of MDA with age was revealed. In patients, the GSH plasma level was inversely proportional to the ADNPH level, and SOD activity was directly proportional to the KDNPH level. In volunteers there was no such correlation; however, there was a direct correlation between CAT activity and the levels of OMP and MDA. In both groups, a moderate direct correlation between peroxidation products was observed. The results confirm that a redox imbalance (a deficiency of antioxidants, in particular CAT, and excess OMP) may be a pathogenetic link in schizophrenia, which is manifested already at an early stage of the disease.

Potential Novel Therapies for Neurodevelopmental Diseases Targeting Oxidative Stress

Neurodevelopmental disorders are a category of diseases that is not yet fully understood. Due to their common traits and pathways, often it is difficult to differentiate between them based on their symptoms only. A series of hypotheses are trying to define their etiology, such as neuroinflammation, neurodegeneration, and immunology, but none have managed to explain their multifactorial manifestation. One feature that may link all theories is that of oxidative stress, with a redox imbalance as well as several other markers of oxidative damage (on lipids, proteins, and nucleic acids) being observed in both postmortem samples of the brain of patients with schizophrenia and autism spectrum disorders. However, the implication of oxidative stress in pathology is still distrustfully looked upon. For this purpose, in the current paper, we were interested in reviewing the implications of oxidative stress in these disorders as well as the impact of N-acetylcysteine on the oxidative status with a focus on the glutathione level and N-methyl-D-aspartate receptor. We were also interested in finding papers targeting the use of antioxidant properties of different plant extracts.

A multimodal approach to studying the relationship between peripheral glutathione, brain glutamate, and cognition in health and in schizophrenia

Involvement of oxidative stress in the pathophysiology of schizophrenia (SZ) is suggested by studies of peripheral tissue. Nonetheless, it is unclear how such biological changes are linked to relevant, pathological neurochemistry, and brain function. We designed a multi-faceted study by combining biochemistry, neuroimaging, and neuropsychology to test how peripheral changes in a key marker for oxidative stress, glutathione (GSH), may associate with central neurochemicals or neuropsychological performance in health and in SZ. GSH in dorsal anterior cingulate cortex (dACC) was acquired as a secondary 3T ¹H-MRS outcome using a MEGA-PRESS sequence. Fifty healthy controls and 46 patients with SZ were studied cross-sectionally, and analyses were adjusted for effects of confounding variables. We observed lower peripheral total GSH in SZ compared to controls in extracellular (plasma) and intracellular (lymphoblast) pools. Total GSH levels in plasma positively correlated with composite neuropsychological performance across the total population and within patients. Total plasma GSH levels were also positively correlated with the levels of Glx in the dACC across the total population, as well as within each individual group (controls, patients). Furthermore, the levels of dACC Glx and dACC GSH positively correlated with composite neuropsychological performance in the patient group. Exploring the relationship between systemic oxidative stress (in particular GSH), central glutamate, and cognition in SZ will benefit further from assessment of patients with more varied neuropsychological performance.

Investigating potential associations between neurocognition/social cognition and oxidative stress in schizophrenia

INTRODUCTION

Deficits in neurocognition and social cognition play a critical role in the functional impairment of patients with schizophrenia. Increased oxidative stress has been evidenced in schizophrenia. Increased oxidative stress can affect neuronal function and lead to impairments in neurocognitive functions (especially working memory) and social cognition.

OBJECTIVE

To investigate deficits in neurocognition and social cognition and their potential association with oxidative stress biomarkers in schizophrenia.

MATERIAL AND METHODS

Eight-five clinically stable patients with schizophrenia and 75 controls were enrolled in this study. Neurocognition was evaluated through the Brief Assessment of Cognition in Schizophrenia (BACS). Social cognition was assessed through the Hinting Task - a test of theory of mind - and an emotion processing test, Facial Emotion Recognition Test (FERT-100). Oxidative stress was assessed by measuring serum levels of glutathione (GSH) and thiobarbituric acid reactive substances (TBARS).

RESULTS

Patients had decreased serum levels of GSH (Z=3.56; p<0.001) and increased TBARS (Z=5.51; P<0.001) when compared with controls. TBARS levels are higher in patients using first generation antipsychotics. Higher serum levels of TBARS in patients were associated with poor performance in working memory test (r=-0.39; p=0.002), even when controlling for age and negative symptoms (Standard Beta: -0.36; CI= -2.52 a -13.71).

DISCUSSION

The association between greater lipid peroxidation, as assessed by TBARS, and worse performance in working memory corroborates theoretical models of greater vulnerability of schizophrenia to oxidative stress.

Extracellular free water and glutathione in first-episode psychosis-a multimodal investigation of an inflammatory model for psychosis

Evidence has been accumulating for an immune-based component to the etiology of psychotic disorders. Advancements in diffusion magnetic resonance imaging (MRI) have enabled estimation of extracellular free water (FW), a putative biomarker of neuroinflammation. Furthermore, inflammatory processes may be associated with altered brain levels of metabolites, such as glutathione (GSH). Consequently, we sought to test the hypotheses that FW is increased and associated with decreased GSH in patients with first-episode schizophrenia (SZ) compared with healthy controls (HC). SZ (n = 36) and HC (n = 40) subjects underwent a multi-shell diffusion MRI scan on a Siemens 3T scanner. ¹H-MR spectroscopy data were acquired using a GSH-optimized MEGA-PRESS editing sequence and GSH/creatine ratios were calculated for DLPFC (SZ: n = 33, HC: n = 37) and visual cortex (SZ: n = 29, HC: n = 35) voxels. Symptoms and functioning were measured using the SANS, SAPS, BPRS, and GSF/GRF. SZ demonstrated significantly elevated FW in whole-brain gray (p = .001) but not white matter (p = .060). There was no significant difference between groups in GSH in either voxel. However, there was a significant negative correlation between DLPFC GSH and both whole-brain and DLPFC-specific gray matter FW in SZ (r = -.48 and -.47, respectively; both p < .05), while this relationship was nonsignificant in HC and in both groups in the visual cortex. These data illustrate an important relationship between a metabolite known to be important for immune function-GSH-and the diffusion extracellular FW measure, which provides additional support for these measures as neuroinflammatory biomarkers that could potentially provide tractable treatment targets to guide pharmacological intervention.

Glutathione peroxidase-1 and neuromodulation: Novel potentials of an old enzyme

Glutathione peroxidase (GPx) acts in co-ordination with other signaling molecules to exert its own antioxidant role. We have demonstrated the protective effects of GPx,/GPx-1, a selenium-dependent enzyme, on various neurodegenerative disorders (i.e., Parkinson's disease, Alzheimer's disease, cerebral ischemia, and convulsive disorders). In addition, we summarized the recent findings indicating that GPx-1 might play a role as a neuromodulator in neuropsychiatric conditions, such as, stress, bipolar disorder, schizophrenia, and drug intoxication. In this review, we attempted to highlight the mechanistic scenarios mediated by the GPx/GPx-1 gene in impacting these neurodegenerative and neuropsychiatric disorders, and hope to provide new insights on the therapeutic interventions against these disorders.

Increasing Nrf2 Activity as a Treatment Approach in Neuropsychiatry

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor encoded by NFE2L2. Under oxidative stress, Nrf2 does not undergo its normal cytoplasmic degradation but instead travels to the nucleus, where it binds to a DNA promoter and initiates transcription of anti-oxidative genes. Nrf2 upregulation is associated with increased cellular levels of glutathione disulfide, glutathione peroxidase, glutathione transferases, thioredoxin and thioredoxin reductase. Given its key role in governing the cellular antioxidant response, upregulation of Nrf2 has been suggested as a common therapeutic target in neuropsychiatric illnesses such as major depressive disorder, bipolar disorder and schizophrenia, which are associated with chronic oxidative and nitrosative stress, characterised by elevated levels of reactive oxygen species, nitric oxide and peroxynitrite. These processes lead to extensive lipid peroxidation, protein oxidation and carbonylation, and oxidative damage to nuclear and mitochondrial DNA. Intake of N-acetylcysteine, coenzyme Q₁₀ and melatonin is accompanied by increased Nrf2 activity. N-acetylcysteine intake is associated with improved cerebral mitochondrial function, decreased central oxidative and nitrosative stress, reduced neuroinflammation, alleviation of endoplasmic reticular stress and suppression of the unfolded protein response. Coenzyme Q₁₀, which acts as a superoxide scavenger in neuroglial mitochondria, instigates mitohormesis, ameliorates lipid peroxidation in the inner mitochondrial membrane, activates uncoupling proteins, promotes mitochondrial biogenesis and has positive effects on the plasma membrane redox system. Melatonin, which scavenges mitochondrial free radicals, inhibits mitochondrial nitric oxide synthase, restores mitochondrial calcium homeostasis, deacetylates and activates mitochondrial SIRT3, ameliorates increased permeability of the blood-brain barrier and intestine and counters neuroinflammation and glutamate excitotoxicity.

Homocysteine in Schizophrenia: Independent Pathogenetic Factor with Prooxidant Activity or Integral Marker of Other Biochemical Disturbances?

A wide range of studies have demonstrated that hyperhomocysteinemia is associated with the risk of schizophrenia, but currently available assumptions about the direct involvement of homocysteine (Hcy) in the pathogenesis of schizophrenia are hypothetical. It is possible that in vivo Hcy is only a marker of folate metabolism disturbances (which are involved in methylation processes) and is not a pathogenetic factor per se. Only one study has been conducted in which associations of hyperhomocysteinemia with oxidative stress in schizophrenia (oxidative damage to protein and lipids) have been found, and it has been suggested that the oxidative stress may be induced by the elevated Hcy in schizophrenic patients. But the authors did not study the level of reduced glutathione (GSH), as well as possible causes of hyperhomocysteinemia-disturbances of folate metabolism. The aim of this work is to analyze the association of Hcy levels with the following: (1) redox markers in schizophrenia GSH, markers of oxidative damage of proteins and lipids, and the activity of antioxidant enzymes in blood serum; (2) with the level of folate and cobalamin (В12); and (3) with clinical features of schizophrenia measured using the Positive and Negative Syndrome Scale (PANSS). 50 patients with schizophrenia and 36 healthy volunteers, matched by sex and age, were examined. Hcy in patients is higher than in healthy subjects (p = 0.0041), and this may be due to the lower folate level in patients (p = 0.0072). In patients, negative correlation was found between the level of Hcy both with the level of folate (ρ = -0.38, p = 0.0063) and with the level of B12 (ρ = -0.36, p = 0.0082). At the same time, patients showed higher levels of oxidative modification of serum proteins (p = 0.00046) and lower catalase (CAT) activity (p = 0.014). However, Hcy is not associated with the studied markers of oxidative stress in patients. In the group of patients with an increased level of Hcy (>10 μmol/l, n = 42) compared with other patients (n = 8), some negative symptoms (PANSS) were statistically significantly more pronounced: difficulty in abstract thinking (N5, p = 0.019), lack of spontaneity and flow in conversation (N6, p = 0.022), stereotyped thinking (N7, p = 0.013), and motor retardation (G7, p = 0.050). Thus, in patients with schizophrenia, hyperhomocysteinemia caused by deficiency of folate and B12 is confirmed and can be considered a marker of disturbances of vitamin metabolism. The redox imbalance is probably not directly related to hyperhomocysteinemia and is hypothetically caused by other pathological processes or by an indirect effect of Hcy, for example, on the enzymatic antioxidant defence system (CAT activity), which requires further exploration. Further study of the role of Hcy in the pathogenesis of schizophrenia is relevant, since the proportion of patients with hyperhomocysteinemia is high and correlations of its level with negative symptoms of schizophrenia are noted.

[Plasmatic glutathione levels and their relationships with clinical and therapeutic features in patients with schizophrenia]

INTRODUCTION

Altered glutathione systems (GSH) are suggested to participate in the pathophysiology of schizophrenia. The purpose of this study was to determine the plasmatic glutathione levels of patients with schizophrenia compared to healthy controls and to examine their relationships with clinical and therapeutic features.

METHODS

It was a case-control study carried out on 100 patients with schizophrenia according to DSM-IV-TR criteria and 95 healthy controls. All patients were assessed by Clinical Global Impressions-severity (CGI-severity) and Global Assessment of Functioning (EGF). Most of the patients (55%) were under first-generation antipsychotics. Plasmatic glutathione levels (total glutathione GSHt, reduced glutathione GSHr, oxidized glutathione GSSG) were determined by spectrophotometry.

RESULTS

The levels of GSHt and GSHr were significantly decreased in schizophrenic patients in comparison with the healthy controls. These reductions were noted to be more pronounced in the untreated patients. No correlation was observed between the GSH levels and the clinical subtypes of schizophrenia and EGF scores. Depending on the therapeutic status, there were no significant differences in the GSH levels. In addition, there was no correlation between the GSH levels and the daily dosage of the antipsychotic treatment.

CONCLUSION

Our results suggest that the observed changes are related to the physiopathology of schizophrenia rather than to the presence of neuroleptic treatment. These results provide support for further studies of the possible role of antioxidants as neuroprotective therapeutic strategies.

Antioxidant Properties of Second-Generation Antipsychotics: Focus on Microglia

Recent studies suggest a primary role of oxidative stress in an early phase of the pathogenesis of schizophrenia and a strong neurobiological link has been found between dopaminergic system dysfunction, microglia overactivation, and oxidative stress. Different risk factors for schizophrenia increase oxidative stress phenomena raising the risk of developing psychosis. Oxidative stress induced by first-generation antipsychotics such as haloperidol significantly contributes to the development of extrapyramidal side effects. Haloperidol also exerts neurotoxic effects by decreasing antioxidant enzyme levels then worsening pro-oxidant events. Opposite to haloperidol, second-generation antipsychotics (or atypical antipsychotics) such as risperidone, clozapine, and olanzapine exert a strong antioxidant activity in experimental models of schizophrenia by rescuing the antioxidant system, with an increase in superoxide dismutase and glutathione (GSH) serum levels. Second-generation antipsychotics also improve the antioxidant status and reduce lipid peroxidation in schizophrenic patients. Interestingly, second-generation antipsychotics, such as risperidone, paliperidone, and in particular clozapine, reduce oxidative stress induced by microglia overactivation, decreasing the production of microglia-derived free radicals, finally protecting neurons against microglia-induced oxidative stress. Further, long-term clinical studies are needed to better understand the link between oxidative stress and the clinical response to antipsychotic drugs and the therapeutic potential of antioxidants to increase the response to antipsychotics.

Stable solid dispersion of lurasidone hydrochloride with augmented physicochemical properties for the treatment of schizophrenia and bipolar disorder

Crystalline solid dispersion of lurasidone hydrochloride (LH) was made with various polar and non-polar small molecules to overcome the poor aqueous solubility issue. LH-Glutathione (GSH) solid dispersion in 1:1 ratio was prepared by co-grinding method and characterized by using differential scanning calorimetry (DSC), powder X-ray diffraction, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. GSH acts as antioxidant and reported for anti-schizophrenic activity may provide synergistic action with LH or reduce the side effects. LH in LH-GSH solid dispersion (SD) has shown improvement in solubility by 7.9 folds than plain drug which translated in terms of improved dissolution rate by two-folds. The in vitro dissolution results showed maximum dissolution rate with LH-GSH SD (97.85 ± 2.40%) compared to plain drug (50.5 ± 3.02%) at 15 min (t₁₅ min, %) and thus, satisfying criteria of immediate release dosage form. DSC and FTIR data confirmed the stability of LH-GSH SD for 3 months at accelerated stability condition (40 ± 2°C and 75 ± 5% RH). The prepared LH-GSH SD can be used as a tool to target dual problems that is, enhanced physicochemical properties along with possible management of disorder which could be due to synergism with co-administered GSH. This approach is thought to be efficiently providing the relief to the psychological patients.

Predictive value of oxidative stress biomarkers in drug‑free patients with schizophrenia and schizo-affective disorder

Several studies have suggested that oxidative stress may represent one of the primary etiological mechanisms of schizophrenia (SZ) and schizoaffective disorder (SAD) which can be targeted by therapeutic intervention. The present study was conducted over a period of 24 months, between June 2016 and June 2018. All enrolled subjects were Tunisian, forty five drug‑free male patients with SZ (mean age: 37.6 years), twenty one drug‑free male patients with SAD (mean age: 28.8 years) and hundred and one age and gender matched controls (mean age: 34.2 years) were enrolled in the study. Plasma reduced glutathione (GSH) and Total thiols levels were significantly decreased in patients compared to controls (respectively p<0.001; p=0.050). In addition, malondialdehyde (MDA), advanced oxidation protein products (AOPP) and protein carbonyls (PC) concentrations and glutathione peroxidase (GSH-Px) activity were significantly increased in patients compared to controls (p<0.001; p<0.001; p<0.001 and p=0.003 respectively). The binary logistic regression analysis revealed that MDA, AOPP, PC and GSH-Px could be considered as independent risk factors for SZ and SAD. When using ROC analysis, a remarkable increase in the area under the curve (AUC) with higher sensitivity (Se) and specificity (Sp) for MDA, AOPP, PC and GSH-Px combined markers was observed. The present study indicated that the identification of the predictive value of this four-selected biomarkers related to oxidative stress in drug free patients should lead to a better identification of the etiological mechanism of SZ or SAD.

[The double-blind randomized placebo-controlled trial of N-acetylcysteine use in schizophrenia: preliminary results]

BACKGROUND

Currently, oxidative stress as part of the pathogenesis of schizophrenia attracts much attention. In this regard, it becomes relevant to assess the level of redox imbalance in patients with schizophrenia, its impact on existing symptoms and the possibility of its treatment. The antioxidant N-acetylcysteine is one of the potential drugs that affects oxidative stress.

OBJECTIVE

To study the possibilities of the use of N-acetylcysteine in patients with schizophrenia.

MATERIAL AND METHODS

The study included 20 patients diagnosed with paranoid schizophrenia with the disease duration of less than 3 years, randomly assigned to the main group (taking N-acetylcysteine at a dose of 2000 mg per day for 60 days) and a comparison group (placebo) in a double-blinded manner. At the beginning and end of the study, cognitive functions were evaluated using the specialized instrument BACS, the severity of psychopathological symptoms was evaluated using PANSS, and blood was collected to determine the level of glutathione (GSH), which is a metabolite of N-acetylcysteine.

RESULTS

There was a significant decrease in positive PANSS score (p=0.013), negative PANSS score (p=0.002) and the general pathology PANSS score (p=0.004) in the main group. Compared with the comparison group, the dynamics of the negative PANSS score (p=0.005) and the general psychopathology PANSS score (p=0.004) was significantly different. When assessing the dynamics of cognitive functions in the main group, a significant improvement in indicators was established in the task for a sequence of numbers that characterizes working memory (p=0.037). The level of GSH significantly increased in the main group (p=0.01), however, there were no statistically significant differences between groups at the final visit.

CONCLUSION

N-acetylcysteine has a positive effect on the negative, general psychopathology PANSS scores, some cognitive functions, in particular, working memory, that allows considering this drug as a promising method of augmentation of schizophrenia therapy and requires further attentive study.

Regulation of Reactive Oxygen Species-Mediated Damage in the Pathogenesis of Schizophrenia

The biochemical integrity of the brain is paramount to the function of the central nervous system, and oxidative stress is a key contributor to cerebral biochemical impairment. Oxidative stress, which occurs when an imbalance arises between the production of reactive oxygen species (ROS) and the efficacy of the antioxidant defense mechanism, is believed to play a role in the pathophysiology of various brain disorders. One such disorder, schizophrenia, not only causes lifelong disability but also induces severe emotional distress; however, because of its onset in early adolescence or adulthood and its progressive development, consuming natural antioxidant products may help regulate the pathogenesis of schizophrenia. Therefore, elucidating the functions of ROS and dietary antioxidants in the pathogenesis of schizophrenia could help formulate improved therapeutic strategies for its prevention and treatment. This review focuses specifically on the roles of ROS and oxidative damage in the pathophysiology of schizophrenia, as well as the effects of nutrition, antipsychotic use, cognitive therapies, and quality of life on patients with schizophrenia. By improving our understanding of the effects of various nutrients on schizophrenia, it may become possible to develop nutritional strategies and supplements to treat the disorder, alleviate its symptoms, and facilitate long-term recovery.

Assessing the Causal Effects of Human Serum Metabolites on 5 Major Psychiatric Disorders

Psychiatric disorders are the leading cause of disability worldwide while the pathogenesis remains unclear. Genome-wide association studies (GWASs) have made great achievements in detecting disease-related genetic variants. However, functional information on the underlying biological processes is often lacking. Current reports propose the use of metabolic traits as functional intermediate phenotypes (the so-called genetically determined metabotypes or GDMs) to reveal the biological mechanisms of genetics in human diseases. Here we conducted a two-sample Mendelian randomization analysis that uses GDMs to assess the causal effects of 486 human serum metabolites on 5 major psychiatric disorders, which respectively were schizophrenia (SCZ), major depression (MDD), bipolar disorder (BIP), autism spectrum disorder (ASD), and attention-deficit/hyperactivity disorder (ADHD). Using genetic variants as proxies, our study has identified 137 metabolites linked to the risk of psychiatric disorders, including 2-methoxyacetaminophen sulfate, which affects SCZ (P = 1.7 × 10-5) and 1-docosahexaenoylglycerophosphocholine, which affects ADHD (P = 5.6 × 10-5). Fourteen significant metabolic pathways involved in the 5 psychiatric disorders assessed were also detected, such as glycine, serine, and threonine metabolism for SCZ (P = .0238), Aminoacyl-tRNA biosynthesis for both MDD (P = .0144) and ADHD (P = .0029). Our study provided novel insights into integrating metabolomics with genomics in order to understand the mechanisms underlying the pathogenesis of human diseases.

The interplay between oxidative stress and bioenergetic failure in neuropsychiatric illnesses: can we explain it and can we treat it?

Nitro-oxidative stress and lowered antioxidant defences play a key role in neuropsychiatric disorders such as major depression, bipolar disorder and schizophrenia. The first part of this paper details mitochondrial antioxidant mechanisms and their importance in reactive oxygen species (ROS) detoxification, including details of NO networks, the roles of H₂O₂ and the thioredoxin/peroxiredoxin system, and the relationship between mitochondrial respiration and NADPH production. The second part highlights and identifies the causes of the multiple pathological sequelae arising from self-amplifying increases in mitochondrial ROS production and bioenergetic failure. Particular attention is paid to NAD⁺ depletion as a core cause of pathology; detrimental effects of raised ROS and reactive nitrogen species on ATP and NADPH generation; detrimental effects of oxidative and nitrosative stress on the glutathione and thioredoxin systems; and the NAD⁺-induced signalling cascade, including the roles of SIRT1, SIRT3, PGC-1α, the FOXO family of transcription factors, Nrf1 and Nrf2. The third part discusses proposed therapeutic interventions aimed at mitigating such pathology, including the use of the NAD⁺ precursors nicotinamide mononucleotide and nicotinamide riboside, both of which rapidly elevate levels of NAD⁺ in the brain and periphery following oral administration; coenzyme Q₁₀ which, when given with the aim of improving mitochondrial function and reducing nitro-oxidative stress in the brain, may be administered via the use of mitoquinone, which is in essence ubiquinone with an attached triphenylphosphonium cation; and N-acetylcysteine, which is associated with improved mitochondrial function in the brain and produces significant decreases in oxidative and nitrosative stress in a dose-dependent manner.

SKINREMS-A New Method for Assessment of the Niacin Skin Flush Test Response in Schizophrenia

Schizophrenia has been considered a disorder linked with faulty lipid homeostasis, and the proposed tool for assessment of these disruptions is the niacin skin flush test. The aims of the study were: 1. Create a new tool to analyze results of the niacin skin flush test more precisely and objectively. 2. Verify the utility of a self-created tool for differentiating between schizophrenia (SZ; n = 56), bipolar disorder (BD; n = 29) and healthy control (HC; n = 45) individuals. The proposed developed method, based on the Skin Reaction Measurement Computer System (SKINREMS), allows one to evaluate the response to the niacin skin flush test quickly and objectively. SKINREMS showed good accuracy in discriminating SZ from BD (with sensitivity 91% and specificity 72%), and SZ from HC (71% and 66%, respectively), and sufficient but not excellent accuracy in discriminating BD from HC (55% and 54%, respectively). The pathophysiological pathways and features shared by schizophrenia and bipolar disorder may be the reason for difficulties in fully discriminating between these two mental disorders using the niacin challenge test. The management of disruptions in the phospholipid metabolism and the inflammatory process could potentially become an individualized form of therapy in a subgroup of psychiatric patients.

Clinical Validation of a Multi-Biomarker Assay for the Evaluation of Chronic Pain Patients in a Cross-Sectional, Observational Study

Introduction

Chronic pain assessment and post-treatment evaluation continues to be challenging due to a lack of validated, objective tools to measure patient outcomes. Validation of mechanistic pain biomarkers would allow clinicians to objectively identify abnormal biochemistry contributing to painful symptoms.

Methods

We describe the clinical validation of a multi-biomarker assay with algorithmic analysis known as the Foundation Pain Index (FPI) in diverse cohorts of chronic pain patients in a prospective, cross-sectional, observational validation study. Levels of 11 urinary pain biomarkers were measured and tabulated using a proprietary algorithm to generate FPI scores for chronic pain subjects (N = 153) and age- and sex-matched pain-free controls (N = 334).

Results

FPI scores were significantly correlated with the 36-Item Short Form Health Survey (SF-36) scores among chronic pain subjects (P value < 0.015) and specific components of SF-36, including emotional well-being, limitations due to emotional problems, and general health (P value < 0.05). Area under ROC analysis (AUROC) revealed FPI to accurately distinguish biomarker profiles between pain-free and chronic pain cohorts (AUROC: 0.7490, P value < 0.0001) as well as the SF-36 scores between chronic pain subjects with low vs. high FPI scores (AUROC: 0.7715, P value < 0.01).

Conclusions

Our findings establish the validity and discriminatory power of a novel multi-biomarker test that evaluates the role of biochemistry in chronic pain and correlates with clinical assessments of patients. This test provides novel, reproducible, objective data which may pave the way for non-opioid therapeutic strategies to treat chronic pain.

Clinical implications of oxidative stress in schizophrenia: Acute relapse and chronic stable phase

Several studies have suggested a higher oxidative stress in schizophrenia. However, the implications of oxidative stress on clinical symptoms remain unclear. This study aimed to investigate the platelet oxidative stress in different stages of schizophrenia (i.e., chronic stable and acute relapse) in order to clarify the clinical implications of oxidative stress and the treatment effects. We recruited 43 chronic stable patients with schizophrenia and 48 non-psychiatric controls. Platelets were collected for measuring the levels of nitric oxide (NO), lipid peroxidation (LPO), and glutathione (GSH) and the activity of GSH peroxidase (GPx) and superoxide dismutase (SOD). The levels and activity were compared between patients and controls and were examined for their relationship with clinical severity. Further, we evaluated the changes of levels and activity before and after treatment in an independent sample with acute relapse (N = 19). Patients with chronic stable schizophrenia had lower SOD activity compared to non-psychiatric controls. In chronic stable patients, NO level was positively correlated with positive and disorganized symptoms, while the GPx activity were negatively correlated with excitement. In patients with acute relapse, the levels and activity were not different before and after four weeks of antipsychotic treatment, but LPO level was negatively correlated with pretreatment disorganized symptoms. The change of LPO can also predict the change of disorganized symptoms and negative symptoms. Our findings suggest that platelet SOD was lower in chronic stable schizophrenia. Platelet LPO may be associated with less disorganized symptoms in acute relapse patients and better treatment response.

Disturbance of Oxidative Stress Parameters in Treatment-Resistant Bipolar Disorder and Their Association With Electroconvulsive Therapy Response

OBJECTIVE

Electroconvulsive therapy (ECT) is an effective option for treatment-resistant bipolar disorder (trBD). However, the mechanisms of its effect are unknown. Oxidative stress is thought to be involved in the underpinnings of BD. Our study is the first, to our knowledge, to report the association between notable oxidative stress parameters (superoxide dismutase [SOD], glutathione peroxidase [GSH-Px], catalase [CAT], and malondialdehyde [MDA]) levels and ECT response in trBD patients.

METHODS

A total 28 trBD patients and 49 controls were recruited. Six-week ECT and naturalistic follow-up were conducted. SOD, GSH-Px, CAT, and MDA levels were measured by enzyme-linked immunosorbent assay, and the 17-item Hamilton Depression Rating Scale and Young Mania Rating Scale were administered at baseline and the end of the 6th week. MANCOVA, ANCOVA, 2 × 2 ANCOVA, and a multiple regression model were conducted.

RESULTS

SOD levels were lower in both trBD mania and depression (P = .001; P = .001), while GSH-Px (P = .01; P = .001) and MDA (P = .001; P = .001) were higher in both trBD mania and depression compared with controls. CAT levels were positively associated with 17-item Hamilton Depression Rating Scale scores in trBD depression (radjusted  = 0.83, P = .005). MDA levels in trBD decreased after 6 weeks of ECT (P = .001). Interestingly, MDA levels decreased in responders (P = .001) but not in nonresponders (P > .05).

CONCLUSIONS

Our study indicates that decreased SOD could be a trait rather than a state in trBD. Oxidative stress levels are associated with illness severity and ECT response. This suggests that the mechanism of oxidative stress plays a crucial role in the pathophysiology of trBD.

Sex influences in the preventive effects of N-acetylcysteine in a two-hit animal model of schizophrenia

BACKGROUND

Schizophrenia (SCZ) is a neurodevelopmental disorder influenced by patient sex. Mechanisms underlying sex differences in SCZ remain unknown. A two-hit model of SCZ combines the exposure to perinatal infection (first-hit) with peripubertal unpredictable stress (PUS, second-hit). N-acetylcysteine (NAC) has been tested in SCZ because of the involvement of glutathione mechanisms in its neurobiology.

AIMS

We aim to investigate whether NAC administration to peripubertal rats of both sexes could prevent behavioral and neurochemical changes induced by the two-hit model.

METHODS

Wistar rats were exposed to polyinosinic:polycytidylic acid (a viral mimetic) or saline on postnatal days (PND) 5-7. On PND30-59 they received saline or NAC 220 mg/kg and between PND40-48 were subjected to PUS or left undisturbed. On PND60 behavioral and oxidative alterations were evaluated in the prefrontal cortex (PFC) and striatum. Mechanisms of hippocampal memory regulation such as immune expression of G protein-coupled estrogen receptor 1 (GPER), α7-nAChR and parvalbumin were also evaluated.

RESULTS

NAC prevented sensorimotor gating deficits only in females, while it prevented alterations in social interaction, working memory and locomotor activity in both sexes. Again, in rats of both sexes, NAC prevented the following neurochemical alterations: glutathione (GSH) and nitrite levels in the PFC and lipid peroxidation in the PFC and striatum. Striatal oxidative alterations in GSH and nitrite were observed in females and prevented by NAC. Two-hit induced hippocampal alterations in females, namely expression of GPER-1, α7-nAChR and parvalbumin, were prevented by NAC.

CONCLUSION

Our results highlights the influences of sex in NAC preventive effects in rats exposed to a two-hit schizophrenia model.

Predicting individual responses to lithium with oxidative stress markers in drug-free bipolar disorder

Objectives: This is the first study to investigate the oxidative stress (OxS) levels in drug-free bipolar disorder (BD) patients and their association with lithium response.Methods: A total of 61 drug-free BD patients and 49 controls were included. Patients treated with lithium were followed-up for 6 weeks. The levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) and malondialdehyde (MDA) were measured at baseline and at the end of the sixth week.Results: Compared to controls, the SOD levels were lower, whereas the MDA were higher in the BD-depression (BD-D) group (both P < 0.001). GSH-Px levels were higher in both the BD-D and the BD-mania (BD-M) group (both P < 0.001). Both GSH-Px and MDA levels in the BD (P = 0.009, P < 0.001) and the BD-D subgroup (P = 0.006, P = 0.001) decreased significantly after the 6-week treatment with lithium. Interestingly, both GSH-Px and MDA levels decreased in responders (P = 0.03, P = 0.002) but not in the non-responders of BD-D (both p > 0.05). Moreover, the reduction in the MDA levels were associated with lithium response (B = 1.47, Wald statistic = 5.94, P = 0.015, odds ratio = 4.35, 95% confidence interval 1.33-14.20).Conclusions: Our study demonstrates an imbalance of OxS in drug-free BD, especially BD-D. Lithium reduces the GSH-Px and MDA levels in BD patients. The reduction in MDA levels may predict individual responsiveness to lithium.

DNA damage and repair in neuropsychiatric disorders. What do we know and what are the future perspectives?

Over the past two decades, extensive research has been done to elucidate the molecular etiology and pathophysiology of neuropsychiatric disorders. In majority of them, including Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), bipolar disorder (BD), schizophrenia and major depressive disorder, increased oxidative and nitrosative stress was found. This stress is known to induce oxidative damage to biomolecules, including DNA. Accordingly, increased mitochondrial and nuclear DNA, as well as RNA damage, were observed in patients suffering from these diseases. However, recent findings indicate that the patients are characterised by impaired DNA repair pathways, which may suggest that these DNA lesions could be also a result of their insufficient repair. In the current systematic, critical review, we aim to sum up, using available literature, the knowledge about the involvement of nuclear and mitochondrial DNA damage and repair, as well as about damage to RNA in pathoetiology of neuropsychiatric disorders, i.e., AD, PD, ALS, BD, schizophrenia and major depressive disorder, as well as the usefulness of the discussed factors as being diagnostic markers and targets for new therapies. Moreover, we also underline the new directions to which future studies should head to elucidate these phenomena.

The origin of NMDA receptor hypofunction in schizophrenia

N-methyl-d-aspartate (NMDA) receptor (NMDAR) hypofunction plays a key role in pathophysiology of schizophrenia. Since NMDAR hypofunction has also been reported in autism, Alzheimer's disease and cognitive dementia, it is crucial to identify the location, timing, and mechanism of NMDAR hypofunction for schizophrenia for better understanding of disease etiology and for novel therapeutic intervention. In this review, we first discuss the shared underlying mechanisms of NMDAR hypofunction in NMDAR antagonist models and the anti-NMDAR autoantibody model of schizophrenia and suggest that NMDAR hypofunction could occur in GABAergic neurons in both models. Preclinical models using transgenic mice have shown that NMDAR hypofunction in cortical GABAergic neurons, in particular parvalbumin-positive fast-spiking interneurons, in the early postnatal period confers schizophrenia-related phenotypes. Recent studies suggest that NMDAR hypofunction can also occur in PV-positive GABAergic neurons with alterations of NMDAR-associated proteins, such as neuregulin/ErbB4, α7nAChR, and serine racemase. Furthermore, several environmental factors, such as oxidative stress, kynurenic acid and hypoxia, may also potentially elicit NMDAR hypofunction in GABAergic neurons in early postnatal period. Altogether, the studies discussed here support a central role for GABAergic abnormalities in the context of NMDAR hypofunction. We conclude by suggesting potential therapeutic strategies to improve the function of fast-spiking neurons.

Putative neuroprotective pharmacotherapies to target the staged progression of mental illness

AIM

Neuropsychiatric disorders including depression, bipolar and schizophrenia frequently exhibit a neuroprogressive course from prodrome to chronicity. There are a range of agents exhibiting capacity to attenuate biological mechanisms associated with neuroprogression. This review will update the evidence for putative neuroprotective agents including clinical efficacy, mechanisms of action and limitations in current assessment tools, and identify novel agents with neuroprotective potential.

METHOD

Data for this review were sourced from online databases PUBMED, Embase and Web of Science. Only data published since 2012 were included in this review, no data were excluded based on language or publication origin.

RESULTS

Each of the agents reviewed inhibit one or multiple pathways of neuroprogression including: inflammatory gene expression and cytokine release, oxidative and nitrosative stress, mitochondrial dysfunction, neurotrophin dysregulation and apoptotic signalling. Some demonstrate clinical efficacy in preventing neural damage or loss, relapse or cognitive/functional decline. Agents include: the psychotropic medications lithium, second generation antipsychotics and antidepressants; other pharmacological agents such as minocycline, aspirin, cyclooxygenase-2 inhibitors, statins, ketamine and alpha-2-delta ligands; and others such as erythropoietin, oestrogen, leptin, N-acetylcysteine, curcumin, melatonin and ebselen.

CONCLUSIONS

Signals of evidence of clinical neuroprotection are evident for a number of candidate agents. Adjunctive use of multiple agents may present a viable avenue to clinical realization of neuroprotection. Definitive prospective studies of neuroprotection with multimodal assessment tools are required.

Glutathione levels and activities of glutathione metabolism enzymes in patients with schizophrenia: A systematic review and meta-analysis

BACKGROUND

Glutathione is among the important antioxidants to prevent oxidative stress. However, the relationships between abnormality in the glutathione system and pathophysiology of schizophrenia remain uncertain due to inconsistent findings on glutathione levels and/or glutathione-related enzyme activities in patients with schizophrenia.

METHODS

A systematic literature search was conducted using Embase, Medline, PsycINFO, and PubMed. Original studies, in which three metabolite levels (glutathione, glutathione disulfide, and total glutathione (glutathione+glutathione disulfide)) and five enzyme activities (glutathione peroxidase, glutathione reductase, glutamate-cysteine ligase, glutathione synthetase, and glutathione S-transferase) were measured with any techniques in both patients with schizophrenia and healthy controls, were included. Standardized mean differences were calculated to determine the group differences in the glutathione levels with a random-effects model.

RESULTS

We identified 41, 9, 15, 38, and seven studies which examined glutathione, glutathione disulfide, total glutathione, glutathione peroxidase, and glutathione reductase, respectively. Patients with schizophrenia had lower levels of both glutathione and total glutathione and decreased activity of glutathione peroxidase compared to controls. Glutathione levels were lower in unmedicated patients with schizophrenia than those in controls while glutathione levels did not differ between patients with first-episode psychosis and controls.

CONCLUSIONS

Our findings suggested that there may be glutathione deficits and abnormalities in the glutathione redox cycle in patients with schizophrenia. However, given the small number of studies examined the entire glutathione system, further studies are needed to elucidate a better understanding of disrupted glutathione function in schizophrenia, which may pave the way for the development of novel therapeutic strategies in this disorder.

The Role of Dopamine D3 Receptor Partial Agonism in Cariprazine-Induced Neurotransmitter Efflux in Rat Hippocampus and Nucleus Accumbens

Cariprazine is an approved antipsychotic and antidepressant which is a dopamine (DA) D₃-preferring D₃/D₂ receptor partial agonist, serotonin (5-HT) 5-HT_1A receptor partial agonist, and 5-HT_2B and 5-HT_2A receptor antagonist, a profile unique for atypical antipsychotic drugs. The purpose of this study was to clarify the effects of cariprazine and selective D₃ receptor ligands on neurotransmitter efflux in the rat nucleus accumbens (NAC) and ventral hippocampus (HIP), brain regions important for reality testing, rewarded behavior, and cognition. In vivo microdialysis was performed in awake, freely moving rats after administration of cariprazine; (+)-PD-128907 [(4aR,10bR)-3,4a,4,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano-[4,3-b]-1,4-oxazin-9-ol hydrochloride], a D₃ receptor-preferring agonist; and SB-277011A [trans-N-[4-[2-(6-cyano-1,2,3,4-tetrahydroisoquinolin-2-yl)ethyl]cyclohexyl]-4-quinolininecarboxamide hydrochloride], a selective D₃ receptor antagonist, alone or combined, and extracellular levels of multiple neurotransmitters and metabolites were measured in the NAC and HIP by ultraperformance liquid chromatography with tandem mass spectrometry. Cariprazine increased DA, norepinephrine (NE), and 5-HT efflux in both regions, whereas it increased glycine (Gly) and glutamate efflux only in the NAC and efflux of DA metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) only in the HIP. Similarly, SB-277011A increased DA, NE, DOPAC, and HVA, but not 5-HT, efflux in the NAC and HIP, and acetylcholine efflux in the HIP. Most of these effects of cariprazine and SB-277011A were fully or partially attenuated by the D₃ receptor agonist (+)-PD-128907, suggesting these effects of cariprazine are related to its D₃ receptor partial agonism, and that this mechanism, leading to diminished stimulation of D₃ receptors, may contribute to its efficacy in both schizophrenia and bipolar disorder. The possible role of Gly in the action of cariprazine is discussed. SIGNIFICANCE STATEMENT: The novel atypical antipsychotic drug cariprazine increased nucleus accumbens and hippocampal neurotransmitter efflux, similar to the actions of the D₃ receptor antagonist SB-277011A [trans-N-[4-[2-(6-cyano-1,2,3,4-tetrahydroisoquinolin-2-yl)ethyl]cyclohexyl]-4-quinolininecarboxamide hydrochloride]. The D₃ receptor-preferring agonist (+)-PD-128907 [(4aR, 10bR)-3,4a,4,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano-[4,3-b]-1,4-oxazin-9-ol hydrochloride], diminished the effects of both compounds on neurotransmitter efflux in both regions. These results suggested D3 receptor partial agonist activity of cariprazine, producing functional antagonism, may contribute to its efficacy in schizophrenia and bipolar disorder.

A Review of Dietary (Phyto)Nutrients for Glutathione Support

Glutathione is a tripeptide that plays a pivotal role in critical physiological processes resulting in effects relevant to diverse disease pathophysiology such as maintenance of redox balance, reduction of oxidative stress, enhancement of metabolic detoxification, and regulation of immune system function. The diverse roles of glutathione in physiology are relevant to a considerable body of evidence suggesting that glutathione status may be an important biomarker and treatment target in various chronic, age-related diseases. Yet, proper personalized balance in the individual is key as well as a better understanding of antioxidants and redox balance. Optimizing glutathione levels has been proposed as a strategy for health promotion and disease prevention, although clear, causal relationships between glutathione status and disease risk or treatment remain to be clarified. Nonetheless, human clinical research suggests that nutritional interventions, including amino acids, vitamins, minerals, phytochemicals, and foods can have important effects on circulating glutathione which may translate to clinical benefit. Importantly, genetic variation is a modifier of glutathione status and influences response to nutritional factors that impact glutathione levels. This narrative review explores clinical evidence for nutritional strategies that could be used to improve glutathione status.

Mitochondria, Metabolism, and Redox Mechanisms in Psychiatric Disorders

Significance: Our current knowledge of the pathophysiology and molecular mechanisms causing psychiatric disorders is modest, but genetic susceptibility and environmental factors are central to the etiology of these conditions. Autism, schizophrenia, bipolar disorder and major depressive disorder show genetic gene risk overlap and share symptoms and metabolic comorbidities. The identification of such common features may provide insights into the development of these disorders. Recent Advances: Multiple pieces of evidence suggest that brain energy metabolism, mitochondrial functions and redox balance are impaired to various degrees in psychiatric disorders. Since mitochondrial metabolism and redox signaling can integrate genetic and environmental environmental factors affecting the brain, it is possible that they are implicated in the etiology and progression of psychiatric disorders. Critical Issue: Evidence for direct links between cellular mitochondrial dysfunction and disease features are missing. Future Directions: A better understanding of the mitochondrial biology and its intracellular connections to the nuclear genome, the endoplasmic reticulum and signaling pathways, as well as its role in intercellular communication in the organism, is still needed. This review focuses on the findings that implicate mitochondrial dysfunction, the resultant metabolic changes and oxidative stress as important etiological factors in the context of psychiatric disorders. We also propose a model where specific pathophysiologies of psychiatric disorders depend on circuit-specific impairments of mitochondrial dysfunction and redox signaling at specific developmental stages.

Striatal Glutathione in First-episode Psychosis Patients Measured In Vivo with Proton Magnetic Resonance Spectroscopy

Deficits of brain glutathione (GSH), the most abundant and primary antioxidant in living tissue, and associated redox imbalance are postulated to be implicated in schizophrenia. This pilot clinical study compared the levels of striatal GSH, measured in vivo with proton magnetic resonance spectroscopy (1H MRS) at 3T, in 10 drug-naïve, first-episode psychosis (FEP) patients with those in 9 matched healthy control subjects. The results revealed a significant GSH deficit in FEP patients (0.92 ± 0.24 × 10-3) compared to the healthy control group (1.10 ± 0.10 × 10-3) (U = 25.00, p = 0.02), as well as a positive correlation between GSH levels and the Positive Symptoms subscale of the PANSS in the FEP group (ρ = 0.96; p <0.001). These preliminary findings suggest a possible role of striatal oxidative stress in early-stage psychosis that warrants further scrutiny and confirmation in larger studies.