Determination of glutathione S-transferase mu and theta polymorphisms in neurological disease

A meta-analysis of association between glutathione S-transferase M1 gene polymorphism and Parkinson's disease susceptibility

The aim of this meta-analysis was to evaluate whether there was an association between glutathione S-transferase M1(GSTM1)gene polymorphism and Parkinson’s disease (PD) susceptibility by pooling published data.

We performed comprehensive electronic database search for articles published between February12,2015 and April30 2016. The published case-control or cohort studies related to GSTM1 gene polymorphism and Parkinson’s disease susceptibility were screened, reviewed, and included in this meta-analysis. The correlation between GSTM1 gene polymorphism and PD susceptibility was expressed by odds ratio (OR) and its corresponding 95% confidence interval (95%CI). Publication bias was evaluated by Begg’s funnel plot and Egger’s line regression test. All analysis was done by stata11.0 software.

After searching the PubMed, EMBASE, and CNKI databases, seventeen case-control studies with 3,538 PD and 5,180 controls were included in the final meta-analysis. The data was pooled by a fixed-effect model for lack of statistical heterogeneity across the studies; the results showed GSTM1 null expression can significant increase the susceptibility of PD (OR=1.11, 95% CI:1.01-1.21, P<0.05). Subgroup analysis indicated GSTM1 gene polymorphism was associated with PD susceptibility in the Caucasian ethnic group (OR=1.15, 95% CI:1.05-1.27, P<0.05) but not in the Asian ethnic group (OR=0.89, 95% CI:0.70-1.12, P>0.05). Begg’s funnel plot and Egger’s line regression test showed no significant publication bias.

Based on the present evidence, GSTM1 null expression can significant increase the susceptibility of PD in persons of Caucasian ethnicity.

GSTM1 Null Genotype and GSTP1 Ile105Val Polymorphism Are Associated with Alzheimer's Disease: a Meta-Analysis

Published studies on the associations between glutathione S-transferase (GST) polymorphisms and Alzheimer's disease reported controversial findings. A meta-analysis of published studies was performed to assess the associations between polymorphisms of GSTM1, GSTT1 and GSTP1, and Alzheimer's disease. PubMed, Embase, and other databases were searched for case-control on the associations between polymorphisms of GSTM1, GSTT1 and GSTP1, and Alzheimer's disease. The odds ratio (OR) and 95% confidence interval (95% CI) were used to assess the associations. Eleven articles were finally included into the meta-analysis, including eight studies on GSTM1 null genotype, six studies on GSTT1 null genotype, and six studies on GSTP1 Ile105Val polymorphism. Overall, GSTM1 null genotype was associated with increased risk of Alzheimer's disease (fixed effect OR = 1.34, 95% CI 1.10-1.64, P = 0.004). GSTT1 null genotype was not associated with risk of Alzheimer's disease (random effect OR = 1.15, 95% CI 0.68-1.92, P = 0.60). Besides, GSTP1 Ile105Val polymorphism was significantly associated with increased risk of Alzheimer's disease (Val vs Ile: OR = 1.45, 95% CI 1.05-1.99, P = 0.023; ValVal vs IleIle: OR = 1.87, 95% CI 1.30-2.69, P = 0.001; ValVal vs IleIle + IleVal: OR = 1.76, 95% CI 1.24-2.51, P = 0.002). No obvious risk of publication bias was observed in the meta-analysis. GSTM1 null genotype and GSTP1 Ile105Val polymorphism are associated with increased risk of Alzheimer's disease. More studies with large sample size are needed to validate the findings in the meta-analysis.

Null genotype of GSTT1 contributes to increased Parkinson's disease risk in Caucasians: evidence from a meta-analysis

Conflicting results in previous case-control studies on the association between Glutathione S-transferase T1 (GSTT1) gene polymorphism and Parkinson's disease (PD) risk have been reported, so we conducted this meta-analysis. We searched and extracted data from 3 Chinese and 3 English web-based electronic databases to evaluate the associations by odds ratio (OR) and its 95% confidence interval (CI) under the recessive genetic comparison model (null genotype vs. present genotype). We also conducted subgroup analyses by ethnicity and adjusted status of OR, respectively. Meta-analyses and subgroup analyses of larger studies (sample size ≥300) were also reanalyzed. When 18 eligible studies (3,963 PD cases and 5,472 controls) were pooled to analyze the association, we found no statistically significant result (OR 1.24, 95% CI 0.96-1.60). In the subgroup analyses by ethnicity, there was statistically significant association between the null genotype of GSTT1 and PD risk among Caucasians, while the associations were not found among Asians and Latinos. In the subgroup analyses by adjusted status of OR, there were no significant associations both in studies with crude OR and adjusted OR. Meta-analyses and subgroup analyses of larger studies (sample size ≥300) were also confirmed the associations mentioned above. Power analysis indicated only meta-analysis of Caucasians had enough evidence to claim the association. In conclusion, the meta-analysis suggests that the null genotype of GSTT1 contributes to PD risk in Caucasians, and no association in Asians is needed more studies to confirm.

Modifying roles of glutathione S-transferase polymorphisms on the association between cumulative lead exposure and cognitive function

BACKGROUND

Glutathione-S-transferase gene (GST) polymorphisms can result in variable ability of these enzymes to remove electrophilic substrates. We investigated whether the GSTP1 Val105 and GSTM1 deletion polymorphisms modify the lead-cognitive function association.

METHODS

We used repeated measures analysis to compare the association between cumulative lead biomarkers-bone lead measured using K-shell X-Ray Fluorescence-and Mini-Mental State Exam (MMSE) score by GST variants, adjusted for covariates, among Normative Aging Study participants, a Boston-based prospective cohort of men. We had complete data for 698 men (providing 1292 observations) for GSTM1 analyses and 595 men (providing 1142 observations) for GSTP1 analyses.

RESULTS

A 15μg/g higher tibia lead concentration (interquartile range of tibia lead) was associated with a 0.24 point decrement in MMSE score among GSTP1 Val105 variant carriers, which was significantly stronger than the association among men with only wild-type alleles (p=0.01). The association among GSTP1 Val105 carriers was comparable to that of 3 years of age in baseline MMSE scores. The association between tibia lead and MMSE score appeared progressively steeper in participants with increasingly more GSTP1 Val105 alleles. A modest association between tibia lead and lower MMSE score was seen among participants with the GSTM1 deletion polymorphism. Neither of the glutathione S-transferase variants was independently associated with cognitive function, nor with lead biomarker measures. The results pertaining to patella lead were similar to those observed for tibia lead.

CONCLUSION

Our results suggest that the GSTP1 Val105 polymorphism confers excess susceptibility to the cognitive effects of cumulative lead exposure.

Genetic modification of the association of paraquat and Parkinson's disease

Paraquat is one of the most widely used herbicides worldwide. It produces a Parkinson's disease (PD) model in rodents through redox cycling and oxidative stress (OS) and is associated with PD risk in humans. Glutathione transferases provide cellular protection against OS and could potentially modulate paraquat toxicity. We investigated PD risk associated with paraquat use in individuals with homozygous deletions of the genes encoding glutathione S-transferase M1 (GSTM1) or T1 (GSTT1). Eighty-seven PD subjects and 343 matched controls were recruited from the Agricultural Health Study, a study of licensed pesticide applicators and spouses in Iowa and North Carolina. PD was confirmed by in-person examination. Paraquat use and covariates were determined by interview. We genotyped subjects for homozygous deletions of GSTM1 (GSTM1*0) and GSTT1 (GSTT1*0) and tested interaction between paraquat use and genotype using logistic regression. Two hundred and twenty-three (52%) subjects had GSTM1*0, 95 (22%) had GSTT1*0, and 73 (17%; all men) used paraquat. After adjustment for potential confounders, there was no interaction with GSTM1. In contrast, GSTT1 genotype significantly modified the association between paraquat and PD. In men with functional GSTT1, the odds ratio (OR) for association of PD with paraquat use was 1.5 (95% confidence interval [CI]: 0.6-3.6); in men with GSTT1*0, the OR was 11.1 (95% CI: 3.0-44.6; P interaction: 0.027). Although replication is needed, our results suggest that PD risk from paraquat exposure might be particularly high in individuals lacking GSTT1. GSTT1*0 is common and could potentially identify a large subpopulation at high risk of PD from oxidative stressors such as paraquat.

Glutathione s-transferase omega 1 activity is sufficient to suppress neurodegeneration in a Drosophila model of Parkinson disease

A loss-of-function mutation in the gene parkin causes a common neurodegenerative disease that may be caused by mitochondrial dysfunction. Glutathione S-transferase Omega (GSTO) is involved in cell defense mechanisms, but little is known about the role of GSTO in the progression of Parkinson disease. Here, we report that restoration of Drosophila GSTO1 (DmGSTO1), which is down-regulated in parkin mutants, alleviates some of the parkin pathogenic phenotypes and that the loss of DmGSTO1 function enhances parkin mutant phenotypes. We further identified the ATP synthase β subunit as a novel in vivo target of DmGSTO1. We found that glutathionylation of the ATP synthase β subunit is rescued by DmGSTO1 and that the expression of DmGSTO1 partially restores the activity and assembly of the mitochondrial F(1)F(0)-ATP synthase in parkin mutants. Our results suggest a novel mechanism for the protective role of DmGSTO1 in parkin mutants, through the regulation of ATP synthase activity, and provide insight into potential therapies for Parkinson disease neurodegeneration.

Polymorphism in environment responsive genes and association with Parkinson disease

Attempts were made in the present case-control study to investigate the association of polymorphism in the genes encoding proteins involved in toxication-detoxication and dopaminergic pathways and susceptibility to Parkinson's disease (PD). Seventy patients suffering from PD and one hundred healthy controls belonging to the same geographical location and same ethnicity were included in the study. PCR-RFLP and allele-specific PCR-based methodology were used to identify the genotypes. Multivariate logistic regression analysis revealed that heterozygous genotypes of cytochrome P4502D6*4(CYP2D6*4), CYP2E1*5B (RsaI) polymorphism and homozygous mutant genotypes of CYP2E1*6 (Dra1) were found to be overrepresented in PD cases when compared to the controls. Risk was also found to be increased in patients carrying glutathione S-transferase T1 (GSTT1) null or homozygous variant genotypes of GSTP1. Significant association was observed for monoamine oxidase-B(MAO-B) variant allele G and PD, whereas no difference in genotype and allele frequencies was observed for manganese-superoxide dismutase (MnSOD), dopamine receptor-D2(DRD2), and dopamine transporter (DAT) genes between controls and PD cases. Genotype combinations characterized by the presence of two variant genotypes on their corresponding loci revealed that four combinations of GSTT1 null and MnSOD(-9Val) or GST null and MAOB-G or CYP2E1*5B and MAO-B-AG or CYP2E1*5B and DRD2 (Taq1A-het) genotypes in the patients exhibited severalfold higher and significant association with risk to PD. Our data suggest that polymorphism in the genes involved in detoxification and dopamine regulation may modulate the susceptibility to PD and could be important risk factors in the pathogenesis of PD.

The medial and lateral substantia nigra in Parkinson's disease: mRNA profiles associated with higher brain tissue vulnerability

Sporadic Parkinson's disease (PD) is characterized by progressive death of dopaminergic neurons within the substantia nigra. However, pathological cell death within this nucleus is not uniform. In PD, the lateral tier of the substantia nigra (SNl) degenerates earlier and more severely than the more medial nigral component (SNm). The cause of this brain regional vulnerability remains unknown. We have used DNA oligonucleotide microarrays to compare gene expression profiles from the SNl to those of the SNm in both PD and control cases. Genes expressed more highly in the PD SNl included the cell death gene, p53 effector related to PMP22, the tumour necrosis factor (TNF) receptor gene, TNF receptor superfamily, member 21, and the mitochondrial complex I gene, NADH dehydrogenase (ubiquinone) 1beta subcomplex, 3, 12 kDa (NDUFbeta3). Genes that were more highly expressed in PD SNm included the dopamine cell signalling gene, cyclic adenosine monophosphate-regulated phosphoprotein, 21 kDa, the activated macrophage gene, stabilin 1, and two glutathione peroxidase (GPX) genes, GPX1 and GPX3. Thus, there is increased expression of genes encoding pro-inflammatory cytokines and subunits of the mitochondrial electron transport chain, and there is a decreased expression of several glutathione-related genes in the SNl suggesting a molecular basis for pathoclisis. Importantly, some of the genes that are differentially regulated in the SNl are known to be expressed highly or predominantely in glial cells. These findings support the view that glial cells can be primarily affected in PD emphasizing the importance of using a whole tissue approach when investigating degenerative CNS disease.

Translational gene mapping of cognitive decline

The ability to maintain cognitive function during aging is a complex process subject to genetic and environmental influences. Alzheimer's disease (AD) is the most common disorder causing cognitive decline among the elderly. Among those with AD, there is broad variation in the relationship between AD neuropathology and clinical manifestations of dementia. Differences in expression of genes involved in neural processing pathways may contribute to individual differences in maintenance of cognitive function. We performed whole genome expression profiling of RNA obtained from frontal cortex of clinically non-demented and AD subjects to identify genes associated with brain aging and cognitive decline. Genetic mapping information and biological function annotation were incorporated to highlight genes of particular interest. The candidate genes identified in this study were compared with those from two other studies in different tissues to identify common underlying transcriptional profiles. In addition to confirming sweeping transcriptomal differences documented in previous studies of cognitive decline, we present new evidence for up-regulation of actin-related processes and down-regulation of translation, RNA processing and localization, and vesicle-mediated transport in individuals with cognitive decline.

Glutathione S-transferase P1 *C allelic variant increases susceptibility for late-onset Alzheimer disease: association study and relationship with apolipoprotein E epsilon4 allele

BACKGROUND

Oxidative stress and neuronal cell death have been implicated in the pathogenesis of Alzheimer disease (AD). Considering that the glutathione transferase (GST) supergene family encodes isoenzymes that appear to be critical in protection against oxidative stress, we aimed at determining the various GSTP1, GSTM1, and GSTT1 polymorphisms and ApoE genotypes to investigate their role as susceptibility genes for late-onset AD (LOAD).

METHODS

We included 210 LOAD patients and 228 healthy controls matched for age, sex, and educational level in our case-control genetic association study. GSTM1 and GSTT1 genotypes were studied by conventional PCR, whereas GSTP1 and ApoE genotypes were determined by real-time PCR on the LightCycler.

RESULTS

We found a significant association between LOAD and the GSTP1*C allelic variant [odds ratio (OR) = 1.9; P < 0.05], but no association between the GSTM1 and GSTT1 deleted genotypes and LOAD. In addition, a preliminary result suggested that carriers of both the GSTP1*C and ApoE epsilon4 allelic variants were at increased risk of LOAD (OR = 19.98; P < 0.0001).

CONCLUSION

The GSTP1*C allelic variant should be considered a candidate for LOAD, particularly in persons having the ApoE epsilon4 allelic variant, because the GSTP1 and ApoE gene products are implicated in oxidative stress and apoptosis processes leading to beta-amyloid-mediated neurodegeneration.