Genetic association studies of antioxidant pathway genes and schizophrenia

The importance of oxidative biomarkers in diagnosis, treatment, and monitoring schizophrenia patients

INTRODUCTION

The etiology of schizophrenia (SCZ), an incredibly complex disorder, remains multifaceted. Literature suggests the involvement of oxidative stress (OS) in the pathophysiology of SCZ.

OBJECTIVES

Determination of selected OS markers and brain-derived neurotrophic factor (BDNF) in patients with chronic SCZ and those in states predisposing to SCZ-first episode psychosis (FP) and ultra-high risk (UHR).

MATERIALS AND METHODS

Determination of OS markers and BDNF levels by spectrophotometric methods and ELISA in 150 individuals (116 patients diagnosed with SCZ or in a predisposed state, divided into four subgroups according to the type of disorder: deficit schizophrenia, non-deficit schizophrenia, FP, UHR). The control group included 34 healthy volunteers.

RESULTS

Lower activities of analyzed antioxidant enzymes and GSH and TAC concentrations were found in all individuals in the study group compared to controls (p < 0.001). BDNF concentration was also lower in all groups compared to controls except in the UHR subgroup (p = 0.01). Correlations were observed between BDNF, R-GSSG, GST, GPx activity, and disease duration (p < 0.02). A small effect of smoking on selected OS markers was also noted (rho<0.06, p < 0.03).

CONCLUSIONS

OS may play an important role in the pathophysiology of SCZ before developing the complete clinical pattern of the disorder. The redox imbalance manifests itself with such severity in individuals with SCZ and in a state predisposing to the development of this psychiatric disease that natural antioxidant systems become insufficient to compensate against it completely. The discussed OS biomarkers may support the SCZ diagnosis and predict its progression.

The Underlying Neurobiological Mechanisms of Psychosis: Focus on Neurotransmission Dysregulation, Neuroinflammation, Oxidative Stress, and Mitochondrial Dysfunction

Psychosis, defined as a set of symptoms that results in a distorted sense of reality, is observed in several psychiatric disorders in addition to schizophrenia. This paper reviews the literature relevant to the underlying neurobiology of psychosis. The dopamine hypothesis has been a major influence in the study of the neurochemistry of psychosis and in development of antipsychotic drugs. However, it became clear early on that other factors must be involved in the dysfunction involved in psychosis. In the current review, it is reported how several of these factors, namely dysregulation of neurotransmitters [dopamine, serotonin, glutamate, and γ-aminobutyric acid (GABA)], neuroinflammation, glia (microglia, astrocytes, and oligodendrocytes), the hypothalamic-pituitary-adrenal axis, the gut microbiome, oxidative stress, and mitochondrial dysfunction contribute to psychosis and interact with one another. Research on psychosis has increased knowledge of the complexity of psychotic disorders. Potential new pharmacotherapies, including combinations of drugs (with pre- and probiotics in some cases) affecting several of the factors mentioned above, have been suggested. Similarly, several putative biomarkers, particularly those related to the immune system, have been proposed. Future research on both pharmacotherapy and biomarkers will require better-designed studies conducted on an all stages of psychotic disorders and must consider confounders such as sex differences and comorbidity.

Connecting Neurobiological Features with Interregional Dysconnectivity in Social-Cognitive Impairments of Schizophrenia

Schizophrenia (SZ) is a devastating psychiatric disorder affecting about 1% of the world's population. Social-cognitive impairments in SZ prevent positive social interactions and lead to progressive social withdrawal. The neurobiological underpinnings of social-cognitive symptoms remain poorly understood, which hinders the development of novel treatments. At the whole-brain level, an abnormal activation of social brain regions and interregional dysconnectivity within social-cognitive brain networks have been identified as major contributors to these symptoms. At the cellular and subcellular levels, an interplay between oxidative stress, neuroinflammation and N-methyl-D-aspartate receptor hypofunction is thought to underly SZ pathology. However, it is not clear how these molecular processes are linked with interregional dysconnectivity in the genesis of social-cognitive symptoms. Here, we aim to bridge the gap between macroscale (connectivity analyses) and microscale (molecular and cellular mechanistic) knowledge by proposing impaired myelination and the disinhibition of local microcircuits as possible causative biological pathways leading to dysconnectivity and abnormal activity of the social brain. Furthermore, we recommend electroencephalography as a promising translational technique that can foster pre-clinical drug development and discuss attractive drug targets for the treatment of social-cognitive symptoms in SZ.

Different Directions of Effects of Polyclonal IgG Antibodies from Patients with Schizophrenia and Healthy Individuals on Cell Death In Vitro: A Pilot Study

Numerous studies indicate the involvemen of oxidative stress in the pathogenesis of schizophrenia. It has been shown that the serum pool of antibodies in patients with schizophrenia contains catalytically active antibodies (abzymes) that have a wide range of activities, including redox properties. In the present work, the effects of IgGs-having oxidoreductase activities-isolated from the serum of patients with schizophrenia and healthy individuals were studied in vitro. The IgGs were purified by affinity chromatography followed by an SDS-PAGE analysis of homogeneity in a 4-18% gradient gel. The catalase and superoxide dismutase (SOD) activities of the IgGs were measured spectrophotometrically using a kinetic module. Human neuroblastoma SH-SY5Y cells were cultured with IgG at a final concentration of 0.2 mg/mL for 24 h. In a parallel experiment, tert-butyl hydroperoxide was used as an oxidative stressor. The number of dead cells after incubation was determined with fluorescent dyes, propidium iodide and Hoechst, by high-throughput screening on the CellInsight CX7 platform. A cytotoxic effect of the IgG from the schizophrenia patients on SH-SY5Y cells was detected after 24 h incubation. A correlation was found between the SOD activity of the IgGs and IgG-induced cell death. Under the induced oxidative stress, the cytotoxic effect of the IgG from the patients with schizophrenia on the SH-SY5Y cell line was five times stronger. Meanwhile, the IgG from the healthy individuals exerted a cytoprotective effect on the cultured cells, accompanied by high catalase activity. Thus, the observed influence on cell viability depends on the catalytic properties of the abzymes.

Establishment of an assistive diagnostic model for schizophrenia with oxidative stress biomarkers

Objective: In this study, alterations in oxidative stress-related indicators were evaluated in drug-naïve, first-episode schizophrenia (SCZ) patients, and the effectiveness of blood serum glucose, superoxide dismutase (SOD), bilirubin in the objective assistive diagnosis of schizophrenia was explored. Materials and methods: We recruited 148 drug-naïve, first-episode SCZ patients and 97 healthy controls (HCs). Blood biochemical indexes including blood glucose, SOD, bilirubin and homocysteine (HCY) in participants were measured, the indexes were compared between patients with SCZ and HCs. The assistive diagnostic model for SCZ was established on the basis of the differential indexes. Results: In SCZ patients, the blood serum levels of glucose, total (TBIL), indirect bilirubin (IBIL) and homocysteine (HCY) were significantly higher than those in HCs (p < 0.05), and the serum levels of SOD were significantly lower than those in HCs (p < 0.05). There was a negative correlation between SOD with the general symptom scores and total scores of PANSS. After risperidone treatment, the levels of uric acid (UA) and SOD tended to increase in patients with SCZ (p = 0.02, 0.19), and the serum levels of TBIL and HCY tended to decrease in patients with SCZ (p = 0.78, 0.16). The diagnostic model based on blood glucose, IBIL and SOD was internally cross-validated, and the accuracy was 77%, with an area under the curve (AUC) of 0.83. Conclusion: Our study demonstrated an oxidative state imbalance in drug-naïve, first-episode SCZ patients, which might be associated with the pathogenesis of the disease. Our study proved that glucose, IBIL and SOD may be potential biological markers of schizophrenia, and the model based on these markers can assist the early objective and accurate diagnosis of schizophrenia.

MicroRNA schizophrenia: Etiology, biomarkers and therapeutic targets

The three sets of symptoms associated with schizophrenia-positive, negative, and cognitive-are burdensome and have serious effects on public health, which affects up to 1% of the population. It is now commonly believed that in addition to the traditional dopaminergic mesolimbic pathway, the etiology of schizophrenia also includes neuronal networks, such as glutamate, GABA, serotonin, BDNF, oxidative stress, inflammation and the immune system. Small noncoding RNA molecules called microRNAs (miRNAs) have come to light as possible participants in the pathophysiology of schizophrenia in recent years by having an impact on these systems. These small RNAs regulate the stability and translation of hundreds of target transcripts, which has an impact on the entire gene network. There may be improved approaches to treat and diagnose schizophrenia if it is understood how these changes in miRNAs alter the critical related signaling pathways that drive the development and progression of the illness.

Links of platelet glutamate and glutathione metabolism with attenuated positive and negative symptoms in depressed patients at clinical high risk for psychosis

Aim of the study is to reveal clinical and biological correlations in patients with adolescent depression and attenuated psychotic symptoms. Activity of platelet enzymes involved in glutamate-, glutathione- and energy metabolism was evaluated in control group and in the patients, because these systems are suspected as related to pathogenesis of psychosis. Adolescents (78 men, 16-25 years old) hospitalized with the first acute depressive state composed two groups: with prevalence of attenuated psychotic positive or negative symptoms (Gr1 and Gr2, 48 and 30 patients, respectively). Control group comprised 20 mentally healthy men of 19-25 years old. Gr1 differed significantly from Gr2 in scores by the Scale of Prodromal Symptoms (SOPS) for positive symptoms, p < 0.001, for disorganization symptoms, p < 0.003, and for total SOPS score, p < 0.001, before the treatment started. When patients from either Gr1 or Gr2 were compared with the control group, significantly decreased baseline activities of platelet glutamate dehydrogenase (GDH), glutathione reductase (GR) and glutathione S-transferase (GST) were found (p < 0.0001). Different correlations were found between baseline enzymatic activities in Gr1 and Gr2: GDH activity correlated with GR activity in Gr1 (R = 0.37), and with GST activity in Gr2 (R = 0.70). Significant correlations were found only in Gr2 between the delta of scores by SOPS negative symptoms (SOPS-N) under treatment and baseline GDH, GST, and GR activities (R = - 0.36, R = - 0.60, and R = 0.38, respectively). The found correlations of the baseline enzymatic activity levels with the value of the decrease (delta) in SOPS-N scores under the treatment represent interest for the prediction of the pharmacotherapy efficiency.

Glutathione S-Transferase M1/T1 Polymorphisms and Schizophrenia Risk: A New Method for Quality Assessment and a Systematic Review

BACKGROUND

GST genes were reported to be involved in susceptibility to mental disorder. The results between deletions of GST genes and schizophrenia were inconclusive and confusing. Therefore, we performed this updated meta-analysis to outline the association using a new method for quality assessment.

METHODS

Sixteen reported studies were selected, and the overall OR and 95% CI were calculated and analyzed by Review Manager 5.4 and STATE 12. The Newcastle-Ottawa Quality Assessment Scale (NOS) for case-control studies was rewritten to evaluate the quality of published studies, as there was no "Exposure" in these studies and other factors should be suggested to assess the quality.

RESULTS

There was no significant association between deletions of GST genes and SZ risk (p > 0.05 in Random model). We also failed to find a significant relation between null genotypes and SZ risk in East Asian population. Based on further analysis of PCR methods, GSTM1 null was weakly associated with SZ risk in 8 studies using multiplex PCR (OR = 1.17, 95% CI = 1.00-1.37, p = 0.05), but GSTT1 null was a protective factor for SZ risk (OR = 0.73, 95% CI = 0.56-0.94, p = 0.02). When stratified by rewritten NOS stars and deductions, GSTM1 null was significantly associated with SZ risk in 9 studies with high quality (OR = 1.24, 95% CI = 1.08-1.43, p = 0.002), and in 10 studies with no deductions (OR = 1.20, 95% CI = 1.05-1.38, p = 0.007).

CONCLUSION

GSTM1 null genotype may be a genetic risk factor for SZ in studies using multiplex PCR and high-quality studies. However, GSTT1 null might be a protective factor. Besides, we provided a new method for quality assessment and it was useful and should be promoted in further analysis.

Oxidative stress impairs cognitive function by affecting hippocampal fimbria volume in drug-naïve, first-episode schizophrenia

Objective

The aim of the present study was to explore influencing factors of cognitive impairments and their interrelationships in drug-naïve, first-episode schizophrenia (SCZ).

Methods

Patients with drug naïve, first episode SCZ and healthy controls (HCs) were enrolled. Cognitive function was assessed by the MATRICS Consensus Cognitive Battery (MCCB). Serum levels of oxidative stress indices, including folate, superoxide dismutase (SOD), uric acid (UA) and homocysteine (Hcy), were determined after an overnight fast. Hippocampal subfield volumes were measured using FreeSurfer. Mediation models were conducted using the SPSS PROCESS v3.4 macro. A false discovery rate (FDR) correction was applied for multiple comparisons.

Results

Sixty-seven patients with SCZ and 65 HCs were enrolled in our study. The patient group had significantly lower serum levels of folate and SOD and higher serum levels of HCY compared with the HCs (all p < 0.05). The patient group had a significantly smaller volume of the whole hippocampus than the HC group (p < 0.05). We also found significant volume differences between the two groups in the following subfields: CA1, molecular layer, GC-ML-DG and fimbria (all p < 0.05, uncorrected). The partial correlation analysis controlling for age and sex showed that the fimbria volume in the patient group was significantly positively associated with NAB scores (r = 0.382, pFDR = 0.024); serum levels of SOD in the patient group showed a significantly positive correlation with fimbria volume (r = 0.360, pFDR = 0.036). Mediation analyses controlling for age and sex showed that the serum levels of SOD in patients with SCZ had significant indirect effects on the NAB scores which were mediated by the fimbria volume [indirect effect = 0.0565, 95% CI from the bootstrap test excluding zero (0.0066 to 0.0891)].

Conclusion

Oxidative stress, a reduction in hippocampal subfield volumes and cognitive impairments occur in early SCZ. Oxidative stress impairs cognitive function by affecting hippocampal subfield volumes.

Schizophrenia: a disorder of broken brain bioenergetics

A substantial and diverse body of literature suggests that the pathophysiology of schizophrenia is related to deficits of bioenergetic function. While antipsychotics are an effective therapy for the management of positive psychotic symptoms, they are not efficacious for the complete schizophrenia symptom profile, such as the negative and cognitive symptoms. In this review, we discuss the relationship between dysfunction of various metabolic pathways across different brain regions in relation to schizophrenia. We contend that several bioenergetic subprocesses are affected across the brain and such deficits are a core feature of the illness. We provide an overview of central perturbations of insulin signaling, glycolysis, pentose-phosphate pathway, tricarboxylic acid cycle, and oxidative phosphorylation in schizophrenia. Importantly, we discuss pharmacologic and nonpharmacologic interventions that target these pathways and how such interventions may be exploited to improve the symptoms of schizophrenia.

The Effects of Probiotic and Selenium Co-supplementation on Clinical and Metabolic Scales in Chronic Schizophrenia: a Randomized, Double-blind, Placebo-Controlled Trial

This study evaluated the effects of probiotic and selenium co-supplementation on clinical and metabolic symptoms in patients with chronic schizophrenia. A randomized, double-blind, placebo-controlled trial was conducted among 60 people with chronic schizophrenia to receive either 8 × 10⁹ CFU/day probiotic plus 200 μg/day selenium (n = 30) or placebo (n = 30) for 12 weeks. Probiotic and selenium co-supplementation resulted in a significant improvement in the general Positive and Negative Syndrome Scale (PANSS) score (β - 1.29; 95% CI, - 2.48, - 0.10; P = 0.03) compared with the placebo. Compared with the placebo, probiotic and selenium co-supplementation resulted in a significant elevation in total antioxidant capacity (β 91.09 mmol/L; 95% CI, 35.89, 146.30; P = 0.002) and total glutathione (β 96.50 μmol/L; 95% CI, 26.13, 166.87; P = 0.008) and a significant reduction in high-sensitivity C-reactive protein levels (β - 1.44 mg/L; 95% CI, - 2.22, - 0.66; P = 0.001). Additionally, co-supplementation significantly decreased fasting glucose (β - 7.40 mg/dL; 95% CI, - 10.15, - 4.64; P < 0.001), insulin levels (β - 1.46 μIU/mL; 95% CI, - 2.35, - 0.57; P = 0.002), and homeostasis model of assessment-insulin resistance (β - 0.51; 95% CI, - 0.72, - 0.29; P < 0.001) and a significant increase in quantitative insulin sensitivity check index (β 0.01; 95% CI, 0.006, 0.01; P < 0.001) compared with the placebo. Probiotic and selenium co-supplementation for 12 weeks to patients with chronic schizophrenia had beneficial effects on the general PANSS score and some metabolic profiles. http://www.irct.ir , identifier IRCT20170513033941N41.

[Oxidative stress in schizophrenia as a promising target for psychopharmacotherapy]

Until now, only dopamine receptor blockers are used for psychopharmacotherapy of schizophrenia, despite the active search for alternative pharmacological agents and a lot of research. However, most of these studies concerned molecules that somehow affect various neurotransmitter receptors. In addition, various anti-inflammatory drugs have been studied quite actively. At the same time, attempts to correct oxidative stress are given significantly less attention, although the emergence of the latter is facilitated by completely different pathophysiological processes and environmental factors associated with the development of schizophrenia. NMDA receptor blockage, vitamin D deficiency, social isolation, chronic stress in adolescence, inflammation, perinatal infection etc. - all this can ultimately lead to the occurrence of oxidative stress. However, there is a significant difference in the severity of this process depending on the stage of the course of schizophrenia, which probably partially explains the heterogeneity of results of the studies on the oxidative stress biomarkers in this disorder. In order to overcome these methodological problems, it seems promising to conduct double-blind studies of the effectiveness of antioxidants in schizophrenia with the selection of groups of patients taking into account the stage of the disorder and the level of certain biomarkers of oxidative stress (F2-isoprostanes, 8-oxodG, 8-oxoGuo). The optimal pharmacological agents for such studies are N-acetylcysteine due to the positive results of previous studies, and melatonin as an antioxidant with a unique activity profile.

Cystine/Glutamate Antiporter in Schizophrenia: From Molecular Mechanism to Novel Biomarker and Treatment

Glutamate, a crucial excitatory neurotransmitter, plays a major role in the modulation of schizophrenia’s pathogenesis. New drug developments for schizophrenia have been prompted by the hypoglutamatergic hypothesis of schizophrenia. The cystine/glutamate antiporter system x_c⁻ is related to glutamate-release regulation. Patients with schizophrenia were recently discovered to exhibit downregulation of x_c⁻ subunits—the solute carrier (SLC) family 3 member 2 and the SLC family 7 member 11. We searched for relevant studies from 1980, when Bannai and Kitamura first identified the protein subunit system x_c⁻ in lung fibroblasts, with the aim of compiling the biological, functional, and pharmacological characteristics of antiporter x_c⁻, which consists of several subunits. Some of them can significantly stimulate the human brain through the glutamate pathway. Initially, extracellular cysteine activates neuronal x_c⁻, causing glutamate efflux. Next, excitatory amino acid transporters enhance the unidirectional transportation of glutamate and sodium. These two biochemical pathways are also crucial to the production of glutathione, a protective agent for neural and glial cells and astrocytes. Investigation of the expression of system x_c⁻ genes in the peripheral white blood cells of patients with schizophrenia can facilitate better understanding of the mental disorder and future development of novel biomarkers and treatments for schizophrenia. In addition, the findings further support the hypoglutamatergic hypothesis of schizophrenia.

Oxidative Stress and the Pathophysiology and Symptom Profile of Schizophrenia Spectrum Disorders

Schizophrenia is associated with increased levels of oxidative stress, as reflected by an increase in the concentrations of damaging reactive species and a reduction in anti-oxidant defences to combat them. Evidence has suggested that whilst not the likely primary cause of schizophrenia, increased oxidative stress may contribute to declining course and poor outcomes associated with schizophrenia. Here we discuss how oxidative stress may be implicated in the aetiology of schizophrenia and examine how current understanding relates associations with symptoms, potentially via lipid peroxidation induced neuronal damage. We argue that oxidative stress may be a good target for future pharmacotherapy in schizophrenia and suggest a multi-step model of illness progression with oxidative stress involved at each stage.

A variant in the 3'-untranslated region of the MC2R gene decreases the risk of schizophrenia in a female Han Chinese population

Objective

Schizophrenia is a complex mental disorder with high heritability. The hypothalamic–pituitary–adrenal (HPA) axis, which is the stress system of the neuroendocrine system, is considered to impact psychotic disorders. We hypothesized that polymorphisms of HPA axis genes might be involved in the development of schizophrenia.

Methods

A case–control study comprising 234 patients with schizophrenia and 399 matched healthy controls was conducted to investigate the association between the human melanocortin 2 receptor (MC2R) gene and schizophrenia risk. Seven tag single nucleotide polymorphisms (SNPs) (rs16941303, rs16941314, rs2186944, rs28926188, rs7230126, rs948322, and rs948331) of MC2R were genotyped by direct sequencing.

Results

No significant associations were observed between any of the alleles, genotypes, or haplotypes examined within the MC2R gene and the risk of schizophrenia in the total group or in subgroups stratified by smoking or alcoholism. However, a subgroup analysis stratified by sex revealed that under the additive model, the C allele of the MC2R rs948331 SNP significantly decreased the risk of schizophrenia in females (odds ratio=0.18).

Conclusion

The C allele of the MC2R rs948331 locus may be a protective factor, reducing the risk of schizophrenia in the female Han Chinese population.

Oxidative Stress-Related Mechanisms in Schizophrenia Pathogenesis and New Treatment Perspectives

Schizophrenia is recognized to be a highly heterogeneous disease at various levels, from genetics to clinical manifestations and treatment sensitivity. This heterogeneity is also reflected in the variety of oxidative stress-related mechanisms contributing to the phenotypic realization and manifestation of schizophrenia. At the molecular level, these mechanisms are supposed to include genetic causes that increase the susceptibility of individuals to oxidative stress and lead to gene expression dysregulation caused by abnormal regulation of redox-sensitive transcriptional factors, noncoding RNAs, and epigenetic mechanisms favored by environmental insults. These changes form the basis of the prooxidant state and lead to altered redox signaling related to glutathione deficiency and impaired expression and function of redox-sensitive transcriptional factors (Nrf2, NF-κB, FoxO, etc.). At the cellular level, these changes lead to mitochondrial dysfunction and metabolic abnormalities that contribute to aberrant neuronal development, abnormal myelination, neurotransmitter anomalies, and dysfunction of parvalbumin-positive interneurons. Immune dysfunction also contributes to redox imbalance. At the whole-organism level, all these mechanisms ultimately contribute to the manifestation and development of schizophrenia. In this review, we consider oxidative stress-related mechanisms and new treatment perspectives associated with the correction of redox imbalance in schizophrenia. We suggest that not only antioxidants but also redox-regulated transcription factor-targeting drugs (including Nrf2 and FoxO activators or NF-κB inhibitors) have great promise in schizophrenia. But it is necessary to develop the stratification criteria of schizophrenia patients based on oxidative stress-related markers for the administration of redox-correcting treatment.

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.

Oxidation-reduction mechanisms in psychiatric disorders: A novel target for pharmacological intervention

While neurotransmitter dysfunction represents a key component in mental illnesses, there is now a wide agreement for a central pathophysiological hub that includes hormones, neuroinflammation, redox mechanisms as well as oxidative stress. With respect to oxidation-reduction (redox) mechanisms, preclinical and clinical evidence suggests that an imbalance in the pro/anti-oxidative homeostasis toward the increased production of substances with oxidizing potential may contribute to the etiology and manifestation of different psychiatric disorders. The substantial and continous demand for energy renders the brain highly susceptible to disturbances in its energy supply, especially following exposure to stressful events, which may lead to overproduction of reactive oxygen and nitrogen species under conditions of perturbed antioxidant defenses. This will eventually induce different molecular alterations, including extensive protein and lipid peroxidation, increased blood-brain barrier permeability and neuroinflammation, which may contribute to the changes in brain function and morphology observed in mental illnesses. This view may also reconcile different key concepts for psychiatric disorders, such as the neurodevelopmental origin of these diseases, as well as the vulnerability of selective cellular populations that are critical for specific functional abnormalities. The possibility to pharmacologically modulate the redox system is receiving increasing interest as a novel therapeutic strategy to counteract the detrimental effects of the unbalance in brain oxidative mechanisms. This review will describe the main mechanisms and mediators of the redox system and will examine the alterations of oxidative stress found in animal models of psychiatric disorders as well as in patients suffering from mental illnesses, such as schizophrenia and major depressive disorder. In addition, it will discuss studies that examined the effects of psychotropic drugs, including antipsychotics and antidepressants, on the oxidative balance as well as studies that investigated the effectiveness of a direct modulation of oxidative mechanisms in counteracting the behavioral and functional alterations associated with psychiatric disorders, which supports the promising role of the redox system as a novel therapeutic target for the improved treatment of brain disorders.

Association Between Glutathione S-Transferase (GST) Polymorphisms and Schizophrenia in a Chinese Han Population

BACKGROUND

Glutathione S-transferase (GST) is an important antioxidant enzyme in the body. The weakening of the antioxidant system causes damage to the cells and tissues that make up the organism, adversely affects the function of the nervous system, and ultimately leads to schizophrenia (SCZ). Previous studies have yielded inconsistent results across different ethnic populations.

PURPOSE

This case-control study was carried out to investigate whether genetic polymorphisms in GST could be associated with SCZ in the Chinese Han population.

PATIENTS AND METHODS

A total of 794 participants, including 379 SCZ patients (case group) and 415 healthy individuals (control group), were genotyped by polymerase chain reaction-restriction fragment length for polymorphisms in GST genes.

RESULTS

The study found that the frequency of the GSTM1 null genotype was higher in case group than control group (p=0.003). The frequency of the GSTM1 and GSTT1 double null genotype was also higher in case group than control group (p=0.008).

CONCLUSION

We conclude that the GSTM1 null genotype and the GSTM1 and GSTT1 double null genotype may be related to the onset of SCZ in Chinese Han population.

ENACT: a protocol for a randomised placebo-controlled trial investigating the efficacy and mechanisms of action of adjunctive N-acetylcysteine for first-episode psychosis

BACKGROUND

First-episode psychosis (FEP) may lead to a progressive, potentially disabling and lifelong chronic illness; however, evidence suggests that the illness course can be improved if appropriate treatments are given at the early stages. Nonetheless, the efficacy of antipsychotic medications is suboptimal, particularly for negative and cognitive symptoms, and more efficacious and benign treatments are needed. Previous studies have shown that the antioxidant amino acid N-acetylcysteine (NAC) reduces negative symptoms and improves functioning in chronic schizophrenia and bipolar disorder. Research is scarce as to whether NAC is beneficial earlier in the course of illness. The primary aim of this study is to determine the efficacy of treatment with adjunctive NAC (2 g/day for 26 weeks) compared with placebo to improve psychiatric symptoms in young people experiencing FEP. Secondary aims are to explore the neurobiological mechanisms underpinning NAC and how they relate to various clinical and functional outcomes at 26- and 52-week follow-ups.

METHODS/DESIGN

ENACT is a 26-week, randomised controlled trial of adjunctive NAC versus placebo, with a 26-week non-treatment follow-up period, for FEP. We will be recruiting 162 young people aged 15-25 years who have recently presented to, and are being treated at, the Early Psychosis Prevention and Intervention Centre, Melbourne, Australia. The primary outcome is the Total Score on the Positive and Negative Syndrome Scale which will be administered at baseline, and weeks 4, 8, 12, 26 (primary endpoint), and 52 (end of study). Secondary outcomes include: symptomatology, functioning, quality of life, neurocognition, blood-derived measures of: inflammation, oxidative and nitrosative stress, and magnetic resonance spectroscopy measures of glutathione concentration.

DISCUSSION

Targeted drug development for FEP to date has generally not involved the exploration of neuroprotective agents. This study has the potential to offer a new, safe, and efficacious treatment for people with FEP, leading to better treatment outcomes. Additionally, the neuroprotective dimension of this study may lead to a better long-term prognosis for people with FEP. It has the potential to uncover a novel treatment that targets the neurobiological mechanisms of FEP and, if successful, will be a major advance for psychiatry.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry, ID: ACTRN12618000413224. Registered on 21 March 2018.

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.

Glutathione Transferase P1-1 an Enzyme Useful in Biomedicine and as Biomarker in Clinical Practice and in Environmental Pollution

Glutathione transferase P1-1 (GSTP1-1) is expressed in some human tissues and is abundant in mammalian erythrocytes (here termed e-GST). This enzyme is able to detoxify the cell from endogenous and exogenous toxic compounds by using glutathione (GSH) or by acting as a ligandin. This review collects studies that propose GSTP1-1 as a useful biomarker in different fields of application. The most relevant studies are focused on GSTP1-1 as a biosensor to detect blood toxicity in patients affected by kidney diseases. In fact, this detoxifying enzyme is over-expressed in erythrocytes when unusual amounts of toxins are present in the body. Here we review articles concerning the level of GST in chronic kidney disease patients, in maintenance hemodialysis patients and to assess dialysis adequacy. GST is also over-expressed in autoimmune disease like scleroderma, and in kidney transplant patients and it may be used to check the efficiency of transplanted kidneys. The involvement of GSTP in the oxidative stress and in other human pathologies like cancer, liver and neurodegenerative diseases, and psychiatric disorders is also reported. Promising applications of e-GST discussed in the present review are its use for monitoring human subjects living in polluted areas and mammals for veterinary purpose.

Early Identification and Intervention of Schizophrenia: Insight From Hypotheses of Glutamate Dysfunction and Oxidative Stress

Schizophrenia is a severe mental disorder which leads to functional deterioration. Early detection and intervention are vital for better prognosis. However, the diagnosis of schizophrenia still depends on clinical observation to date. Without reliable biomarkers, schizophrenia is difficult to detect in its early phase. Further, there is no approved medication for prodromal schizophrenia because current antipsychotics fail to show satisfactory efficacy and safety. Therefore, to develop an effective early diagnostic and therapeutic approach for schizophrenia, especially in its prodromal phase, is crucial. Glutamate signaling dysfunction and dysregulation of oxidative stress have been considered to play important roles in schizophrenic prodrome. The N-methyl-D-aspartate receptor (NMDAR) is one of three types of ionotropic glutamate receptors. In this article, we reviewed literature regarding NMDAR hypofunction, oxidative stress, and the linkage between both in prodromal schizophrenia. The efficacy of NMDAR enhancers such as D-amino acid oxidase inhibitor was addressed. Finally, we highlighted potential biomarkers related to NMDAR and oxidative stress regulation, and therefore suggested the strategies of early detection and intervention of prodromal schizophrenia. Future larger-scale studies combining biomarkers and novel drug development for early psychosis are warranted.

Clinical and metabolic response to vitamin D plus probiotic in schizophrenia patients

BACKGROUND

This study determined the effects of a novel combination of vitamin D and probiotic on metabolic and clinical symptoms in chronic schizophrenia.

METHODS

This trial was conducted among 60 patients with chronic schizophrenia to receive either 50,000 IU vitamin D3 every 2 weeks plus 8 × 10⁹ CFU/day probiotic (n = 30) or placebo (n = 30) for 12 weeks.

RESULTS

Vitamin D and probiotic co-supplementation was associated with a significant improvement in the general (- 3.1 ± 4.7 vs. + 0.3 ± 3.9, P = 0.004) and total PANSS scores (- 7.4 ± 8.7 vs. -1.9 ± 7.5, P = 0.01). Vitamin D and probiotic co-supplementation also significantly increased total antioxidant capacity (+ 51.1 ± 129.7 vs. -20.7 ± 53.3 mmol/L, P = 0.007), and significantly decreased malondialdehyde (- 0.3 ± 0.9 vs. + 0.2 ± 0.4 μmol/L, P = 0.01) and high sensitivity C-reactive protein levels (- 2.3 ± 3.0 vs. -0.3 ± 0.8 mg/L, P = 0.001) compared with the placebo. Moreover, taking vitamin D plus probiotic significantly reduced fasting plasma glucose (- 7.0 ± 9.9 vs. -0.2 ± 9.9 mg/dL, P = 0.01), insulin concentrations (- 2.7 ± 2.3 vs. + 0.4 ± 2.0 μIU/mL, P < 0.001), homeostasis model of assessment-estimated insulin resistance (- 0.8 ± 0.7 vs. + 0.1 ± 0.7, P < 0.001), triglycerides (- 7.8 ± 25.2 vs. + 10.1 ± 30.8 mg/dL, P = 0.01) and total cholesterol levels (- 4.9 ± 15.0 vs. + 5.9 ± 19.5 mg/dL, P = 0.04) and total-/HDL-cholesterol ratio (- 0.1 ± 0.6 vs. + 0.3 ± 0.8, P = 0.04).

CONCLUSION

Probiotic and vitamin D for 12 weeks to chronic schizophrenia had beneficial effects on the general and total PANSS score, and metabolic profiles.

TRIAL REGISTRATION

This study was retrospectively registered in the Iranian website ( www.irct.ir ) for clinical trials registration ( http://www.irct.ir : IRCT2017072333551N2). 07-31-2017 2.

Effect of N-acetyl cysteine (NAC) supplementation on positive and negative syndrome scale in schizophrenia: a systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To conduct a systematic review and meta-analysis of published randomised controlled trials on the efficacy of NAC supplementation on positive and negative syndrome scale in schizophrenia.

METHODS

A meta-analysis was conducted, and studies were identified by a search of electronic databases from inception to May 2018. Combined and stratified analyses were used.

RESULTS

Seven trials were identified, and data from n = 447 participants were included. Pooled analysis showed improvement of positive and negative syndrome scale following NAC treatment compared with placebo, for total (SMB = - 0.96) [95% CI - 1.69, - 0.24; P = 0.009], general (SMB = - 1.04) [95% CI - 1.80, - 0.27; P = 0.008] and negative (SMB = - 0.73) [95% CI - 1.29, - 0.17; P = 0.01] scores, respectively. Significant heterogeneity was found, and subgroup analysis showed significant reductions in studies with a treatment duration of ≤ 24 weeks, with a considerable effect size on total, general, and negative scores (Total SMD = - 0.83; General SMD = - 0.67; Negative SMD = - 1.09) following NAC.

CONCLUSIONS

NAC improved all aspects of positive and negative syndrome scale in schizophrenic populations and may be more efficacious with treatment durations up to 24 weeks.

Association between genetic variability of neuronal nitric oxide synthase and sensorimotor gating in humans

Research increasingly suggests that nitric oxide (NO) plays a role in the pathogenesis of schizophrenia. One important line of evidence comes from genetic studies, which have repeatedly detected an association between the neuronal isoform of nitric oxide synthase (nNOS or NOS1) and schizophrenia. However, the pathogenetic pathways linking nNOS, NO, and the disorder remain poorly understood. A deficit in sensorimotor gating is considered to importantly contribute to core schizophrenia symptoms such as psychotic disorganization and thought disturbance. We selected three candidate nNOS polymorphisms (Ex1f-VNTR, rs6490121 and rs41279104), associated with schizophrenia and cognition in previous studies, and tested their association with the efficiency of sensorimotor gating in healthy human adults. We found that risk variants of Ex1f-VNTR and rs6490121 (but not rs41279104) were associated with a weaker prepulse inhibition (PPI) of the acoustic startle reflex, a standard measure of sensorimotor gating. Furthermore, the effect of presence of risk variants in Ex1f-VNTR and rs6490121 was additive: PPI linearly decreased with increasing number of risk alleles, being highest in participants with no risk allele, while lowest in individuals who carry three risk alleles. Our findings indicate that NO is involved in the regulation of sensorimotor gating, and highlight one possible pathogenetic mechanism for NO playing a role in the development of schizophrenia psychosis.

Disturbed glutathione antioxidative defense is associated with structural brain changes in neuroleptic-naïve first-episode psychosis patients

BACKGROUND

Oxidative stress and impaired antioxidant defense are reported in schizophrenia and are thought to be associated with disturbed neurodevelopment, brain structural alterations, glutamatergic imbalance, negative symptomatology, and cognitive impairment. To test some of these assumptions we investigated the glutathione (GSH) antioxidant defense system (AODS) and brain structural abnormalities in drug-naïve individuals with first acute episode of psychosis (FEP).

METHOD

The study involved 27 drug-naïve FEP patients and 31 healthy controls (HC). GSH AODS markers and TBARS (thiobarbituric acid reactive substances) were measured in blood plasma and erythrocytes. High-resolution T₁-weighted 3T MRI were acquired from all subjects. To investigate brain structural abnormalities and effects of illness on interactions between GSH metabolites or enzyme activities and local grey matter density, voxel-based morphometry (VBM) with the computational anatomy toolbox (CAT12) was used. Symptomatology was assessed using the Positive and Negative Syndrome Scale (PANSS) and the Symptom Checklist 1990 revised (SCL-90-R).

RESULTS

(i) In FEP patients, glutathione reductase activity (GSR) was lower than in the HC group. GSR activity in plasma was inversely correlated with SCL-90-R scores of depression and PANSS scores of the negative symptom subscale. (ii) A reduction of GM was observed in left inferior frontal, bilateral temporal, as well as parietal cortices of FEP patients. (iii) Interaction analyses revealed an influence of illness on GSR/GM associations in the left orbitofrontal cortex (BA 47).

CONCLUSION

Our findings support the notion of altered GSH antioxidative defense in untreated acute psychosis as a potential pathomechanism for localized brain structural abnormalities. This pathology relates to a key brain region of social cognition, affective motivation control and decision making, and is clinically accompanied by depressive and negative symptoms.

[Ultrastructural pathology of oligodendrocytes in the white matter in continuous paranoid schizophrenia: a role for microglia]

AIM

Previously the authors have reported the ultrastructural pathology and deficit of oligodendrocytes in gray and white matter of the prefrontal cortex in schizophrenia. The aim of the study was to determine of the effects of microglia on the ultrastructure of oligodendrocytes in the white matter underlying the prefrontal cortex in continuous schizophrenia.

MATERIAL AND METHODS

Postmortem morphometric electron microscopic study of oligodendrocytes in close apposition to microglia was performed in white matter underlying the prefrontal cortex (BA10). Eleven cases of chronic continuous schizophrenia and 11 normal controls were studied. Areas of oligodendrocytes, of their nuclei and cytoplasm, volume density (Vv) and the number of mitochondria, vacuoles of endoplasmic reticulum and lipofuscin granules were estimated. Group comparison was performed using ANCOVA.

RESULTS

The schizophrenia group differed from the control group by paucity of ribosomes in the cytoplasm of oligodendrocytes, a significant decrease in Vv and the number of mitochondria and increase in the number of lipofuscin granules. Significant correlations between the parameters of lipofuscin granules, mitochondria and vacuoles were found only in the schizophrenia group. The number of lipofuscin granules were correlated positively with the illness duration.

CONCLUSION

Dystrophic alterations of oligodendrocytes attached to microglial cells were found in the white matter of the prefrontal cortex in chronic paranoid schizophrenia as compared to controls. The data obtained suggest that microglia might contribute to abnormalities of energy, lipid and protein metabolism of oligodendrocytes in schizophrenia.

Oxidative stress, prefrontal cortex hypomyelination and cognitive symptoms in schizophrenia

Schizophrenia (SZ) is a neurodevelopmental disorder with a broad symptomatology, including cognitive symptoms that are thought to arise from the prefrontal cortex (PFC). The neurobiological aetiology of these symptoms remains elusive, yet both impaired redox control and PFC dysconnectivity have been recently implicated. PFC dysconnectivity has been linked to white matter, oligodendrocyte (OL) and myelin abnormalities in SZ patients. Myelin is produced by mature OLs, and OL precursor cells (OPCs) are exceptionally susceptible to oxidative stress. Here we propose a hypothesis for the aetiology of cognitive symptomatology in SZ: the redox-induced prefrontal OPC-dysfunctioning hypothesis. We pose that the combination of genetic and environmental factors causes oxidative stress marked by a build-up of reactive oxygen species that, during late adolescence, impair OPC signal transduction processes that are necessary for OPC proliferation and differentiation, and involve AMP-activated protein kinase, Akt-mTOR-P70S6K and peroxisome proliferator receptor alpha signalling. OPC dysfunctioning coincides with the relatively late onset of PFC myelination, causing hypomyelination and disruption of connectivity in this brain area. The resulting cognitive deficits arise in parallel with SZ onset. Hence, our hypothesis provides a novel neurobiological framework for the aetiology of SZ cognitive symptoms. Future research addressing our hypothesis could have important implications for the development of new (combined) antioxidant- and promyelination-based strategies to treat the cognitive symptoms in SZ.

Metabolic pathways in the periphery and brain: Contribution to mental disorders?

The association between mental disorders and diabetes has a long history. Recent large-scale, well-controlled epidemiological studies confirmed a link between diabetes and psychiatric illnesses. The scope of this review is to summarize our current understanding of this relationship from a molecular perspective. We first discuss the potential contribution of diabetes-associated metabolic impairments to the etiology of mental conditions. Then, we focus on possible shared molecular risk factors and mechanisms. Simple comorbidity, shared susceptibility loci, and common pathophysiological processes in diabetes and mental illnesses have changed our traditional way of thinking about mental illness. We conclude that schizophrenia and affective disorders are not limited to an imbalance in dopaminergic and serotoninergic neurotransmission in the brain. They are also systemic disorders that can be considered, to some extent, as metabolic disorders.

Glutathione S-Transferase Deletion Polymorphisms in Early-Onset Psychotic and Bipolar Disorders: A Case-Control Study

OBJECTIVE

To examine glutathione S-transferase (GST) deletion polymorphisms in development of early-onset severe mental disorders, with the hypothesis that patients with GSTM1-null and GSTT1-null genotypes will develop psychotic disorders at a younger age.

METHODS

We identified GSTM1 and GSTT1 deletion polymorphisms by multiplex polymerase chain reaction (PCR) in 93 patients with early onset severe mental disorders and 278 control individuals. The diagnoses were confirmed by Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version and Schedule for Affective Disorders and Schizophrenia-Life-Time Version (K-SADS-PL) interviews.

RESULTS

Individuals with the GSTM1-null genotype were at 3.36-fold higher risk of developing early-onset severe mental disorders than carriers of a corresponding active genotype. The risk of those disorders was increased by 6.59-fold in patients with GSTM1-null/GSTT1-active genotype. Patients with the GSTM1-null genotype were at approximately 2-fold increased risk for developing early-onset schizophrenia-spectrum disorder (EOS), early-onset bipolar disorder (EOBD) with psychotic symptoms, or early-onset first-episode psychosis (EOFEP), compared with patients with the GSTM1-active genotype.

CONCLUSION

The GSTM1-null genotype might be associated with higher risk for early onset severe mental disorders.

Serum Glutathione in Patients with Schizophrenia in Dynamics of Antipsychotic Therapy

Serum concentrations of oxidized and reduced glutathione were measured in 73 patients with schizophrenia at admission and in dynamics of therapy with traditional and atypical antipsychotic drugs. The level of reduced glutathione in patients with schizophrenia with manifest clinical symptoms was lower than in normal subjects. Atypical neuroleptics produced virtually no effects on the glutathione system, while therapy with typical antipsychotics led to further decrease in the levels of reduced glutathione, thus aggravating the imbalance of metabolic processes typical of schizophrenia.

Effects of omega-3 PUFA on the vitamin E and glutathione antioxidant defense system in individuals at ultra-high risk of psychosis

BACKGROUND

Oxidative stress and impaired antioxidant defenses are reported in schizophrenia and are associated with disturbed neurodevelopment, brain structural alterations, glutamatergic imbalance, increased negative symptoms, and cognitive impairment. There is evidence that oxidative stress predates the onset of acute psychotic illness. Here, we investigate the effects of omega-3 PUFA on the vitamin E and glutathione antioxidant defense system (AODS).

METHOD

In 64 help-seeking UHR-individuals (13-25 years of age), vitamin E levels and glutathione were investigated before and after 12 weeks of treatment with either 1.2g/d omega-3 (PUFA-E) or saturated fatty acids (SFA-E), with each condition also containing 30.4mg/d alpha-tocopherol to ensure absorption without additional oxidative risk.

RESULTS

In multivariate tests, the effects on the AODS (alpha-tocopherol, total glutathione) were not significantly different (p=0.13, p=0.11, respectively) between treatment conditions. According to univariate findings, only PUFA-E caused a significant alpha-tocopherol increase, while PUFA-E and SFA-E caused a significant gamma- and delta-tocopherol decrease. Total glutathione (GSHt) was decreased by PUFA-E supplementation.

CONCLUSION

Effects of the PUFA-E condition on the vitamin E and glutathione AODS could be mechanisms underlying its clinical effectiveness. In terms of the vitamin E protection system, PUFA-E seems to directly support the antioxidative defense at membrane level. The effect of PUFA-E on GSHt is not yet fully understood, but could reflect antioxidative effects, resulting in decreased demand for glutathione. It is still necessary to further clarify which type of PUFA/antioxidant combination, and in which dose, is effective at each stage of psychotic illness.

Age-Related Cognitive Impairment as a Sign of Geriatric Neurocardiovascular Interactions: May Polyphenols Play a Protective Role?

It is known that endothelial dysfunction plays an important role in the development and progression of cardiovascular diseases implicated also in cognitive decline. Experimental studies pointed to the fact that the modification of NO levels via NOS activity may affect the blood pressure level as well as several higher nervous functions—for example, learning and memory. There are emerging evidences from in vitro and animal studies suggesting that polyphenols may potentially have a protective effect on the development of neurodegenerative diseases and may improve cognitive function as well as positively affecting the blood pressure regulatory mechanisms. This review accentuates the need for precisely defined clinically controlled studies as well as for use of adequate experimental procedures discriminating between the human higher brain functions and the only overall activation of the brain cortex. The physiological neurocardiovascular interactions are implicated in the increased healthy life span as well.

Accelerated aging in schizophrenia patients: the potential role of oxidative stress

Several lines of evidence suggest that schizophrenia, a severe mental illness characterized by delusions, hallucinations and thought disorder is associated with accelerated aging. The free radical (oxidative stress) theory of aging assumes that aging occurs as a result of damage to cell constituents and connective tissues by free radicals arising from oxygen-associated reactions. Schizophrenia has been associated with oxidative stress and chronic inflammation, both of which also appear to reciprocally induce each other in a positive feedback manner. The buildup of damaged macromolecules due to increased oxidative stress and failure of protein repair and maintenance systems is an indicator of aging both at the cellular and organismal level. When compared with age-matched healthy controls, schizophrenia patients have higher levels of markers of oxidative cellular damage such as protein carbonyls, products of lipid peroxidation and DNA hydroxylation. Potential confounders such as antipsychotic medication, smoking, socio-economic status and unhealthy lifestyle make it impossible to solely attribute the earlier onset of aging-related changes or oxidative stress to having a diagnosis of schizophrenia. Regardless of whether oxidative stress can be attributed solely to a diagnosis of schizophrenia or whether it is due to other factors associated with schizophrenia, the available evidence is in support of increased oxidative stress-induced cellular damage of macromolecules which may play a role in the phenomenon of accelerated aging presumed to be associated with schizophrenia.

Meta-analysis of oxidative stress in schizophrenia

BACKGROUND

Schizophrenia is associated with impaired antioxidant defense, including abnormal serum, plasma, and red blood cell (RBC) oxidative stress parameters. We performed a meta-analysis of these associations, considering the effect of clinical status and antipsychotic treatment after an acute exacerbation of psychosis.

METHODS

We identified articles by searching PubMed, PsychInfo, and Institute for Scientific Information, and the reference lists of identified studies.

RESULTS

Forty-four studies met the inclusion criteria. Total antioxidant status seemed to be a state marker, because levels were significantly decreased in cross-sectional studies of serum and plasma in first-episode psychosis (FEP) and significantly increased in longitudinal studies of antipsychotic treatment for acute exacerbations of psychosis (p < .01 for each). The RBC catalase and plasma nitrite seemed to be state-related markers, because levels in cross-sectional studies were significantly decreased in FEP (p < .01) and significantly increased in stable outpatients (p = .01). In contrast, RBC superoxide dismutase seemed to be a trait marker for schizophrenia, because levels in cross-sectional studies were significantly decreased in acutely relapsed inpatients, FEP, and stable outpatients (p < .01 for each).

CONCLUSIONS

Oxidative stress abnormalities in FEP suggest an effect that might be independent of antipsychotic medications. Although some parameters (total antioxidant status, RBC catalase, and plasma nitrite) might be state markers for acute exacerbations of psychosis, others (RBC superoxide dismutase) might be trait markers; however, more longitudinal studies are needed. Our findings suggest that oxidative stress might serve as a potential biomarker in the etiopathophysiology and clinical course of schizophrenia.

Effects of the antioxidant sulforaphane on hyperlocomotion and prepulse inhibition deficits in mice after phencyclidine administration

Objective

Accumulating evidence suggests that oxidative stress plays a role in the pathophysiology of schizophrenia and that the potent antioxidants may be potential therapeutic drugs for schizophrenia. This study was undertaken to examine the effects of the potent antioxidant sulforaphane (SFN), found in cruciferous vegetables, on behavioral abnormalities (e.g., hyperlocomotion and prepulse inhibition [PPI] deficits) in mice after a single administration of the N-methyl-D-aspartate (NMDA)-receptor antagonist phencyclidine (PCP).

Methods

Effects of SFN (3, 10, and 30 mg/kg, intraperitoneally [i.p.]) on hyperlocomotion and PPI deficits in the adult male ddY mice after administration of PCP (3.0 mg/kg, subcutaneously [s.c.]) were examined.

Results

Administration of SFN (30 mg/kg, intraperitoneally [i.p.]), but not low doses (3 and 10 mg/kg, i.p.), significantly attenuated hyperlocomotion in mice after PCP administration (3.0 mg/kg, subcutaneously [s.c.]). Furthermore, administration of SFN (3, 10, and 30 mg/kg, i.p.) attenuated the PPI deficits in mice after PCP administration (3.0 mg/kg, s.c.) in a dose-dependent manner.

Conclusion

These results suggest that SFN has antipsychotic activity in an animal model of schizophrenia. Therefore, it is likely that SFN may be a potential therapeutic drug for schizophrenia.

Cognitive impairment is related to oxidative stress and chemokine levels in first psychotic episodes

INTRODUCTION

This study measures the levels of various markers of oxidative stress and inflammation in blood samples from first-episode psychosis (FEP) patients, and examines the association between these peripheral biomarkers and cognitive performance at 6 months after treatment.

METHODS

Twenty-eight FEP patients and 28 healthy controls (matched by age, sex and educational level) had blood samples taken at admission for assessment of total antioxidant status, superoxide dismutase (SOD), total glutathione (GSH), catalase (CAT), glutathione peroxidase, lipid peroxidation, nitrites and the chemokine monocyte chemoattractant protein-1 (MCP-1). A battery of cognitive tests was also applied to the healthy controls and those FEP patients who were in remission at 6 months after the acute episode.

RESULTS

FEP patients had significantly lower levels of total antioxidant status, catalase and glutathione peroxidase, compared with the healthy controls. Regression analyses found that MCP-1 levels were negatively associated with learning and memory (verbal and working), nitrite levels were negatively associated with executive function, and glutathione levels were positively associated with executive function.

CONCLUSION

Our results suggest an association between certain peripheral markers of oxidative stress and inflammation and specific aspects of cognitive functioning in FEP patients. Further studies on the association between MCP-1 and cognition are warranted.

Oxidative stress in schizophrenia: pathogenetic and therapeutic implications

Over a century, a wide-ranging variety of pathophysiological models and causal hypotheses have been conceptualized for schizophrenia. One among these is the role for free radical-mediated pathology in schizophrenia, indicating impaired antioxidant defense system (AODS) and presence of oxidative stress in patients with schizophrenia. For the past two decades, the whole investigative domain of AODS and oxidative stress has broadened to include the wider AODS components, direct central nervous system assays of AODS, chemical imaging studies, proteomics, genetics of AODS, and, of importance to sufferers of schizophrenia, antioxidant therapeutics. These are some of the perspectives that are reviewed by several articles in this Forum. Overall, there has been growing recognition of the importance of oxidative stress in the pathophysiology of schizophrenia and in treatment-related side effects. The totality of the evidence from biochemistry, metabolomics, proteomics, genetics, and in vivo brain imaging points to the presence of multifarious abnormalities in the AODS and redox signaling in schizophrenia.

Metabolomics of oxidative stress in recent studies of endogenous and exogenously administered intermediate metabolites

Aerobic metabolism occurs in a background of oxygen radicals and reactive oxygen species (ROS) that originate from the incomplete reduction of molecular oxygen in electron transfer reactions. The essential role of aerobic metabolism, the generation and consumption of ATP and other high energy phosphates, sustains a balance of approximately 3000 essential human metabolites that serve not only as nutrients, but also as antioxidants, neurotransmitters, osmolytes, and participants in ligand-based and other cellular signaling. In hypoxia, ischemia, and oxidative stress, where pathological circumstances cause oxygen radicals to form at a rate greater than is possible for their consumption, changes in the composition of metabolite ensembles, or metabolomes, can be associated with physiological changes. Metabolomics and metabonomics are a scientific disciplines that focuse on quantifying dynamic metabolome responses, using multivariate analytical approaches derived from methods within genomics, a discipline that consolidated innovative analysis techniques for situations where the number of biomarkers (metabolites in our case) greatly exceeds the number of subjects. This review focuses on the behavior of cytosolic, mitochondrial, and redox metabolites in ameliorating or exacerbating oxidative stress. After reviewing work regarding a small number of metabolites—pyruvate, ethyl pyruvate, and fructose-1,6-bisphosphate—whose exogenous administration was found to ameliorate oxidative stress, a subsequent section reviews basic multivariate statistical methods common in metabolomics research, and their application in human and preclinical studies emphasizing oxidative stress. Particular attention is paid to new NMR spectroscopy methods in metabolomics and metabonomics. Because complex relationships connect oxidative stress to so many physiological processes, studies from different disciplines were reviewed. All, however, shared the common goal of ultimately developing “omics”-based, diagnostic tests to help influence therapies.

Oxidative stress in schizophrenia: an integrated approach

Oxidative stress has been suggested to contribute to the pathophysiology of schizophrenia. In particular, oxidative damage to lipids, proteins, and DNA as observed in schizophrenia is known to impair cell viability and function, which may subsequently account for the deteriorating course of the illness. Currently available evidence points towards an alteration in the activities of enzymatic and nonenzymatic antioxidant systems in schizophrenia. In fact, experimental models have demonstrated that oxidative stress induces behavioral and molecular anomalies strikingly similar to those observed in schizophrenia. These findings suggest that oxidative stress is intimately linked to a variety of pathophysiological processes, such as inflammation, oligodendrocyte abnormalities, mitochondrial dysfunction, hypoactive N-methyl-d-aspartate receptors and the impairment of fast-spiking gamma-aminobutyric acid interneurons. Such self-sustaining mechanisms may progressively worsen producing the functional and structural consequences associated with schizophrenia. Recent clinical studies have shown antioxidant treatment to be effective in ameliorating schizophrenic symptoms. Hence, identifying viable therapeutic strategies to tackle oxidative stress and the resulting physiological disturbances provide an exciting opportunity for the treatment and ultimately prevention of schizophrenia.