Interaction of GAG trinucleotide repeat and C-129T polymorphisms impairs expression of the glutamate-cysteine ligase catalytic subunit gene

Polymorphisms of the GCLC Gene Are Novel Genetic Markers for Susceptibility to Psoriasis Associated with Alcohol Abuse and Cigarette Smoking

The aim of this pilot study was to investigate whether single nucleotide polymorphisms (SNP) in the gene encoding the catalytic subunit of glutamate cysteine ligase (GCLC) are associated with the risk and clinical features of psoriasis. A total of 944 unrelated individuals, including 474 patients with a diagnosis of psoriasis and 470 healthy controls, were recruited for the study. Six common SNPs in the GCLC gene were genotyped using the MassArray-4 system. Polymorphisms rs648595 (OR = 0.56, 95% CI 0.35-0.90; P_perm = 0.017) and rs2397147 (OR = 0.54, 95% CI 0.30-0.98; P_perm = 0.05) were associated with susceptibility to psoriasis in males. In the male group, diplotype rs2397147-C/C × rs17883901-G/G was associated with a decreased risk of psoriasis (FDR-adjusted p = 0.014), whereas diplotype rs6933870-G/G × rs17883901-G/G (FDR-adjusted p = 0.045) showed an association with an increased disease risk in females. The joint effects of SNPs with tobacco smoking (rs648595 and rs17883901) and alcohol abuse (rs648595 and rs542914) on psoriasis risk were observed (P_perm ≤ 0.05). We also found multiple sex-independent associations between GCLC gene polymorphisms and various clinical features such as earlier disease onset, the psoriatic triad, and specific localizations of skin lesions. The present study is the first to show that polymorphisms of the GCLC gene are significantly associated with the risk of psoriasis and related to its clinical features.

Association of Polymorphisms of Glutamate Cysteine Ligase Genes GCLC C-129 T and GCLM C-588 T with Risk of Polycystic Ovary Syndrome in Chinese Women

Polycystic ovary syndrome (PCOS) is generally considered a multifactorial disease caused by interactions between multiple susceptible genes and environmental factors. Glutamate cysteine ligase (GCL) is the rate-limiting enzyme in glutathione biosynthesis. This study examined the relationship between single nucleotide polymorphisms (SNPs) in the GCL catalytic subunit (GCLC C-129 T) and the modifier subunit (GCLM C-588 T) and PCOS. The two SNPs were genotyped in 1017 PCOS patients and 793 control women. Clinical, metabolic, hormonal, and oxidative stress parameters were also assessed. The frequencies of the CT + TT genotypes (21.6% vs. 27.7%) and T allele (11.5% vs. 14.7%) of SNP GCLC C-129 T were significantly lower in hyperandrogenism (HA)-PCOS patients than in control women. Logistic regression analysis revealed that the relative hazard of HA-PCOS was lower in individuals with the -129 T allele (CT + TT genotypes) than in those with the CC genotype (OR = 0.723, 95% CI: 0.571-0.915, P = 0.007). When using the GCLC-CC/GCLM-CC combined genotype as the reference category, the GCLC-CT + TT/GCLM-CC combined genotype was a protective factor for PCOS with HA (OR = 0.743, 95% CI: 0.566-0.976, P = 0.033). HA-PCOS patients with the -129 T allele had lower waist circumference, waist-to-hip ratio, and body mass index (BMI) and lower fasting insulin concentration and homeostatic model assessment of insulin resistance after correcting for age and BMI (P < 0.05). The T allele of SNP GCLC C-129 T and its combination with the CC genotype of SNP GCLM C-588 T are associated with decreased risk of HA-PCOS in Chinese women.

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.

Association of GCLM -588C/T and GCLC -129T/C Promoter Polymorphisms of Genes Coding the Subunits of Glutamate Cysteine Ligase with Ischemic Heart Disease Development in Kazakhstan Population

BACKGROUND

Glutamate cysteine ligase (GCL) is a rate-limiting enzyme in synthesis of glutathione. Evidence suggests that genetic variations in the promoter region of genes coding a catalytic subunit (GCLC -129T/C) and a modifier subunit (GCLM -588C/T) of GCL have a functional impact on their transcriptional activity and were associated with various disorders. Hence, we hypothesize whether these two polymorphic variants of GCLM and GCLC genes are associated with the risk of ischemic heart disease (IHD) development in the population of Kazakhstan.

METHODS

We evaluated 360 patients with IHD and 341 control subjects. Allele frequencies of studied promoters' polymorphisms were detected by PCR-RFLP analysis. Multiple logistic regression analysis was applied to assess the risk for different genotypes obtained.

RESULTS

The presence of -588T allele in GCLM and -129T allele in GCLC gene genotypes was associated with an increased risk of IHD (GCLM -588T: OR = 3.92, p = 0.003; GCLC -129T: OR = 3.22, p = 0.03) for general ethnically mixed group. Analysis of each ethnical groups separately showed the higher risk tendency for Kazakhs as for GCLM -588T (OR = 4.79; p = 0.03) and as for GCLC -129T (OR = 4.79, p = 0.03). For Russians, statistically differences for two polymorphisms were not observed.

CONCLUSION

The two promoter polymorphisms of GCLM (-588C/T) and GCLC (-128T/C) are associated with an increased risk of IHD in Kazakhstan population.

Glutathione defense mechanism in liver injury: insights from animal models

Glutathione (GSH) is the most abundant cellular thiol antioxidant and it exhibits numerous and versatile functions. Disturbances in GSH homeostasis have been associated with liver diseases induced by drugs, alcohol, diet and environmental pollutants. Until recently, our laboratories and others have developed mouse models with genetic deficiencies in glutamate-cysteine ligase (GCL), the rate-limiting enzyme in the GSH biosynthetic pathway. This review focuses on regulation of GSH homeostasis and, specifically, recent studies that have utilized such GSH-deficient mouse models to investigate the role of GSH in liver disease processes. These studies have revealed a differential hepatic response to distinct profiles of hepatic cellular GSH concentration. In particular, mice engineered to not express the catalytic subunit of GCL in hepatocytes [Gclc(h/h) mice] experience almostcomplete loss of hepatic GSH (to 5% of normal) and develop spontaneous liver pathologies characteristic of various clinical stages of liver injury. In contrast, mice globally engineered to not express the modifier subunit of GCL [Gclm⁻/⁻ mice] show a less severe hepatic GSH deficit (to ≈15% of normal) and exhibit overall protection against liver injuries induced by a variety of hepatic insults. Collectively, these transgenic mouse models provide interesting new insights regarding pathophysiological functions of GSH in the liver.

A functional trinucleotide repeat polymorphism in the 5'-untranslated region of the glutathione biosynthetic gene GCLC is associated with increased risk for lung and aerodigestive tract cancers

Glutathione (GSH), the major intracellular antioxidant, protects against cancer development by detoxifying carcinogens and free radicals and strengthening the immune system. Recently, a GAG-trinucleotide repeat polymorphism in the 5'-untranslated region of the gene for the rate-limiting enzyme for GSH biosynthesis, γ-glutamine cysteine ligase (GCL), was shown to be associated with lowered GCL activity and GSH levels in vitro and in vivo. We tested the hypothesis that this functional polymorphism in GCL is associated with the risk for lung and aerodigestive tract cancers. To this end, we conducted a case-control study that included 375 lung cancer cases, 200 aerodigestive tract cancer cases, and 537 controls. GAG repeat genotype (4, 7, 8, 9, and 10 repeat alleles) was determined by capillary electrophoresis of PCR products from the repeat region of the GCL catalytic subunit (GCLC). Odds ratios (OR) were calculated by logistic regression and adjusted for risk factors, including age, sex, body mass index, and smoking history. The GAG-7/7 genotype was associated with a 1.9-fold increased risk of lung cancer and 2.6-fold increased risk of aerodigestive tract cancer compared to the wild-type GAG-9/9 (P < 0.05). Similarly, the GAG-7 allele was associated with an increased risk of lung cancer (OR = 1.5, P = 0.01) and aerodigestive tract cancer (OR = 2.3, P < 0.001) compared to subjects without GAG-7 allele. These findings suggest that GSH synthesis affects the risk of lung and aerodigestive tract cancers, and further implicates a role for oxidative stress in the development of these cancers.

A GAG trinucleotide-repeat polymorphism in the gene for glutathione biosynthetic enzyme, GCLC, affects gene expression through translation

A guanine-adenine-guanine (GAG) repeat polymorphism with 5 different alleles (4, 7, 8, 9, and 10 repeats) in the 5' untranslated region (UTR) of GCLC has been associated with altered GCL activity and glutathione (GSH) levels. We investigated whether this polymorphism affects either transcription or translation using luciferase reporter constructs containing variant GCLC 5' UTRs. Higher luciferase activity was observed in HepG2 and human embryonic kidney 293 (HEK293) cells transfected with constructs containing either 8 or 9 repeats than in constructs containing 4, 7, or 10 repeats (P<0.05). In cell-free lysates, GAG repeat number had no effect on luciferase mRNA yield. In vitro translation of mRNAs from luciferase constructs resulted in differences similar to those found in cell cultures (P<0.05). A similar association of GAG repeat with GCLC phenotype was observed in vivo in healthy adults, as individuals with GAG-7/7 genotype had lower GCL activity and GSH levels in lymphocytes compared to those with GAG-9/9 (P<0.05). Higher GCL activity and GSH levels observed in red blood cells (RBCs) from individuals with GAG-7/7 compared to GAG-9/9 are likely due to differences in GCL regulation in RBCs. Altogether, these results suggest that GAG polymorphism affects GCLC expression via translation, and thus may be associated with altered risk for GSH-related diseases and toxicities.