No association between the Pro197Leu polymorphism in the glutathione peroxidase (GPX1) gene and schizophrenia

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.

GPX1 Pro198Leu polymorphism and GSTP1 Ile105Val polymorphisms are not associated with the risk of schizophrenia in the Chinese Han population

Increasing lines of evidence show that oxidative stress plays a role in the pathophysiological mechanisms of schizophrenia (SCZ). Polymorphic variants of oxidative stress-related candidate genes GPX1 and GST1 can affect the antioxidant activities of their encoded enzymes. Therefore, this study aimed to explore the association between the single nucleotide polymorphisms (SNPs) of GPX1 and GSTP1 and susceptibility to schizophrenia in the Chinese Han population. DNA from 323 healthy controls and 210 schizophrenic patients was genotyped for SNPs rs1050450 in GPX1 and rs1695 in GSTP1 using a predesigned TaqMan SNP genotyping assay. Differences in genetic distributions between cases and controls were compared using the χ-test. No significant differences in allelic or genotypic frequencies of GPX1 rs1050450 or GSTP1 rs1695 were detected between cases and controls (GPX1 rs1050450: χ=0.370, P=0.831 by genotype, χ=0.377, P=0.539, odds ratio=1.145, 95% confidence interval=0.743-1.766 by allele; GSTP1 rs1695: χ=1.537, P=0.464 by genotype, χ=1.623, P=0.203, odds ratio=0.813, 95% confidence interval=0.592-1.118 by allele). Our results suggest that GPX1 rs1050450 and GSTP1 rs1695 SNPs are unlikely to play a major role in the pathogenesis of schizophrenia in the Chinese Han population. However, these results should be validated by replication in larger and independent samples.

Pro198Leu polymorphism in the oxidative stress gene, glutathione peroxidase-1, is associated with a gender-specific risk for panic disorder

OBJECTIVE

Panic disorder (PD) is an anxiety disorder characterized by sudden attacks of intense fear. Biochemical studies suggest that oxidative stress (OS) index is significantly higher in PD, and OS genes may participate in development of anxiety-like behavioral phenotypes. We aimed to investigate role of polymorphisms in OS gene, glutathione peroxidase-1 (GPX1), and DNA repair enzyme gene, 8-oxoguanine glycosylase-1 (OGG1), in PD patients.

METHODS

GPX1 Pro198Leu (rs1050450) and OGG1 Ser326Cys (rs1052133) polymorphisms of 127 patients with PD and 151 disease-free controls were analyzed with real-time polymerase chain reaction. Severity of PD symptoms was assessed by Panic and Agoraphobia Scale (PAS).

RESULTS

No significant relationship was found in genotype distributions of OGG1 Ser326Cys and GPX1 Pro198Leu polymorphisms between PD and control groups (p > 0.05). There was no significant relationship between OGG1 or GPX1 polymorphisms, and age of onset, agoraphobia, or PAS scores in PD group (p > 0.05). However, in GPX1 Pro198Leu polymorphism, C allele (Pro) was found to be more frequent in female subgroup of PD patients compared with that in males (p = 0.027).

CONCLUSIONS

GPX1 Pro198Leu and OGG1 Ser326Cys polymorphisms were not associated with PD risk in Turkish patients. However, a gender-specific effect of GPX1 Pro198Leu C allele may be associated with PD development.

Oxidative stress and psychological disorders

Oxidative stress is an imbalance between cellular production of reactive oxygen species and the counteracting antioxidant mechanisms. The brain with its high oxygen consumption and a lipid-rich environment is considered highly susceptible to oxidative stress or redox imbalances. Therefore, the fact that oxidative stress is implicated in several mental disorders including depression, anxiety disorders, schizophrenia and bipolar disorder, is not surprising. Although several elegant studies have established a link between oxidative stress and psychiatric disorders, the causal relationship between oxidative stress and psychiatric diseases is not fully determined. Another critical aspect that needs much attention and effort is our understanding of the association between cellular oxidative stress and emotional stress. This review examines some of the recent discoveries that link oxidative status with anxiety, depression, schizophrenia and bipolar disorder. A discussion of published results and questions that currently exist in the field regarding a causal relationship between oxidative and emotional stress is also provided.

Free radicals, antioxidant defense systems, and schizophrenia

The etiopathogenic mechanisms of schizophrenia are to date unknown, although several hypotheses have been suggested. Accumulating evidence suggests that excessive free radical production or oxidative stress may be involved in the pathophysiology of schizophrenia as evidenced by increased production of reactive oxygen or decreased antioxidant protection in schizophrenic patients. This review aims to summarize the basic molecular mechanisms of free radical metabolism, the impaired antioxidant defense system and membrane pathology in schizophrenia, their interrelationships with the characteristic clinical symptoms and the implications for antipsychotic treatments. In schizophrenia, there is accumulating evidence of altered antioxidant enzyme activities and increased levels of lipid peroxidation, as well as altered levels of plasma antioxidants. Moreover, free radical-mediated abnormalities may contribute to specific aspects of schizophrenic symptomatology and complications of its treatment with antipsychotic drugs, as well as the development of tardive dyskinesia (TD). Finally, the potential therapeutic strategies implicated by the accumulating data on oxidative stress mechanisms for the treatment of schizophrenia are discussed.

Analysis of manganese superoxide dismutase (MnSOD: Ala-9Val) and glutathione peroxidase (GSH-Px: Pro 197 Leu) gene polymorphisms in mood disorders

We investigated the etiopathogenetic role of manganese superoxide dismutase (MnSOD) (Ala-9Val) and glutathione peroxidase (GSH-Px) (Pro 197 Leu) gene polymorphisms in patients diagnosed with major depressive disorder (MDD) and bipolar I disorder (BD). Eighty patients with MDD, 82 patients with BD (total 162 patients) and 96 healthy controls were enrolled in this study and genotyped using a Real Time-Quantitative Polymer Chain Reaction (RT-qPCR)-based method. The patients with BD and MDD and the controls had a similar distribution of the genotypes and alleles in the Ala-9Val MnSOD gene polymorphism. Comparison of the MDD group and control group regarding the Pro 197 Leu GSH-Px gene polymorphism revealed similar genotype distribution but different allele distribution. The BD group and control group were similar both for genotypes and for alleles when compared regarding the Pro 197 Leu GSH-Px gene polymorphism. The combined analysis (MDD plus BD) also failed to find any association between the Ala-9Val MnSOD and Pro 197 Leu GSH-Px gene polymorphism. Although small statistical power of the current study the significant difference between patients with depression and the control group for the Pro 197 Leu GSH-Px polymorphism indicates that the distribution of these alleles may have a contribution in the physiopathogenesis of depression. One of the limitation of the current study is that the sample size is too small. Understanding of the exact role of Pro 197 Leu GSH-Px polymorphism in the development of depression needs to further studies with more sample size and high statistical power.

Association study between the genetic polymorphisms of glutathione-related enzymes and schizophrenia in a Japanese population

Several lines of evidence suggest that oxidative stress plays a role in the pathogenesis of schizophrenia, and that glutathione (GSH) plays a crucial role in antioxidant defense mechanisms. In this study, we performed association studies between GSH-related genes (GSTM1, GSTP1, GSTO1, GSTT1, GSTT2, GPX1, and GCLM) and schizophrenia in a Japanese population. The overall distributions of the genotypes and alleles of each gene were not different between schizophrenic patients and controls. Subjects with residual-type schizophrenia showed different distributions in the analysis of GSTM1 genotype and in the combination analysis of GSTs, GPX1, and GCLM genotypes although the small sample size should be considered as a limitation of this study. In addition, our findings revealed that there were large ethnic differences in the genotype distributions of those GSH-related genes. The present study suggests that GSH-related genes may not play a major role in the pathogenesis of schizophrenia in a Japanese population. However, a dysregulation of GSH metabolism may be one of the vulnerability factors contributing to the development of a certain type of schizophrenia, and it is likely that the ethnic background should be considered in further study for those GSH-related genes.

Schizophrenia and oxidative stress: glutamate cysteine ligase modifier as a susceptibility gene

Oxidative stress could be involved in the pathophysiology of schizophrenia, a major psychiatric disorder. Glutathione (GSH), a redox regulator, is decreased in patients' cerebrospinal fluid and prefrontal cortex. The gene of the key GSH-synthesizing enzyme, glutamate cysteine ligase modifier (GCLM) subunit, is strongly associated with schizophrenia in two case-control studies and in one family study. GCLM gene expression is decreased in patients' fibroblasts. Thus, GSH metabolism dysfunction is proposed as one of the vulnerability factors for schizophrenia.

Functional polymorphism of the glutathione peroxidase 1 gene is associated with personality traits in healthy subjects

BACKGROUND

Several lines of evidence suggest that a certain type of personality or temperament as well as oxidative stress may be implicated in the pathophysiology of neuropsychiatric diseases. Glutathione peroxidase 1 (GPX1) plays a role in the antioxidant defense system.

OBJECTIVES

The authors studied the association between the GPX1 gene polymorphism and personality traits in healthy subjects.

METHODS

One hundred forty-nine healthy subjects were enrolled. Analysis of the functional polymorphism (Pro198Leu) in the human GPX1 gene was performed.

RESULTS

Subjects with Pro198Pro have significantly higher scores in openness to experience on the Revised NEO Personality Inventory (NEO-PI-R) as compared with subjects with other genotypes (Pro198Leu or Leu198Leu). In contrast, we detected no association between other personality dimensions on the NEO-PI-R and scores on the Temperament and Character Inventory.

CONCLUSION

This study reports that the functional polymorphism (Pro198Leu) in the GPX1 gene might be associated with openness to experience among the personality traits.