The GSTM1 genetic polymorphism in healthy Saudi Arabians and Filipinos, and Saudi Arabians with coronary atherosclerosis

Glutathione S-transferases and their implications in the lung diseases asthma and chronic obstructive pulmonary disease: Early life susceptibility?

Our lungs are exposed daily to airborne pollutants, particulate matter, pathogens as well as lung allergens and irritants. Exposure to these substances can lead to inflammatory responses and may induce endogenous oxidant production, which can cause chronic inflammation, tissue damage and remodeling. Notably, the development of asthma and Chronic Obstructive Pulmonary Disease (COPD) is linked to the aforementioned irritants. Some inhaled foreign chemical compounds are rapidly absorbed and processed by phase I and II enzyme systems critical in the detoxification of xenobiotics including the glutathione-conjugating enzymes Glutathione S-transferases (GSTs). GSTs, and in particular genetic variants of GSTs that alter their activities, have been found to be implicated in the susceptibility to and progression of these lung diseases. Beyond their roles in phase II metabolism, evidence suggests that GSTs are also important mediators of normal lung growth. Therefore, the contribution of GSTs to the development of lung diseases in adults may already start in utero, and continues through infancy, childhood, and adult life. GSTs are also known to scavenge oxidants and affect signaling pathways by protein-protein interaction. Moreover, GSTs regulate reversible oxidative post-translational modifications of proteins, known as protein S-glutathionylation. Therefore, GSTs display an array of functions that impact the pathogenesis of asthma and COPD.

In this review we will provide an overview of the specific functions of each class of mammalian cytosolic GSTs. This is followed by a comprehensive analysis of their expression profiles in the lung in healthy subjects, as well as alterations that have been described in (epithelial cells of) asthmatics and COPD patients. Particular emphasis is placed on the emerging evidence of the regulatory properties of GSTs beyond detoxification and their contribution to (un)healthy lungs throughout life. By providing a more thorough understanding, tailored therapeutic strategies can be designed to affect specific functions of particular GSTs.

An updated meta-analysis showed smoking modify the association of GSTM1 null genotype on the risk of coronary heart disease

Background Oxidative stress is considered to be involved in the pathogenesis of coronary heart disease (CHD). Glutathione-S-transferase (GST) enzymes play important roles in antioxidant defenses and may influence CHD risk. The present meta-analysis was performed to investigate the link between glutathione S-transferase M1 (GSTM1) null genotype and CHD and to get a precise evaluation of interaction between GSTM1 null genotype and smoking by the case-only design.

Methods PubMed and EMBASE databases were searched through 15 December 2020 to retrieve articles. Odds ratios (ORs) were pooled using either fixed-effects or random-effects models.

Results Thirty-seven studies showed that GSTM1 null genotype was associated with risk of CHD in total population, Caucasians and Asians (for total population, OR = 1.38, 95% confidence interval (CI): 1.15, 1.65; for Caucasians, OR = 1.34, 95% CI: 1.04, 1.72; for Asians, OR = 1.40, 95% CI: 1.11, 1.77). After adjustment for heterogeneity, these relationships were still significant. After adjustment for heterogeneity, case-only analysis of 11 studies showed a positive multiplicative interaction between GSTM1 null genotype and smoking (ever smoking vs. never smoking) (OR = 1.27, 95% CI: 1.08, 1.50; I² = 0%, P=0.553).

Conclusions The overall results indicated that GSTM1 null genotype was associated with a higher risk of CHD, and the association may be affected by smoking status. This is the first meta-analysis to prove a positive effect of the interaction between GSTM1 null genotype and smoking status on the risk of CHD. Well-designed studies are needed to investigate the possible gene–gene or gene–environment interactions.

Glutathione S-transferase M1 polymorphism and coronary heart disease susceptibility: a meta-analysis involving 47,596 subjects

BACKGROUND

Many studies have investigated the association between glutathione S-transferase M1 (GSTM1) null genotype and the risk of coronary heart disease (CHD). However, the effect of the GSTM1 null genotype on CHD is still unclear because of apparent inconsistencies among those studies. A meta-analysis was performed to characterise the relationship more accurately.

METHODS

Pubmed, Embase, and Web of Science were searched. We estimated the summary odds ratio (OR) with a 95% confidence interval (95% CI) to assess the association.

RESULTS

Up to 26 case-control studies with 13,929 CHD cases and 33,667 control cases were included into this meta-analysis. Meta-analysis of the 26 studies showed that GSTM1 null genotype was associated with the risk of CHD (random effects OR=1.35, 95% CI 1.00 to 1.83). After adjustment for heterogeneity, meta-analysis showed that GSTM1 null genotype was not associated with increased risk of CHD in the total population (fixed effects OR=1.01, 95% CI 0.95 to 1.07). In the subgroup analysis by ethnicity, increased risks were not found for either Caucasians (OR=1.36, 95% CI=0.96-1.92) or Asians (OR=1.28, 95% CI=0.91-1.80). When stratified by smoking status, in the subgroup of smokers, GSTM1 null genotype was significantly associated with increased CHD risk (random effects OR=1.64, 95% CI 1.02 to 2.64). No evidence of publication bias was observed.

CONCLUSION

In conclusion, this meta-analysis suggested that there is overall lack of association between GSTM1 genotypes and CHD risk, however, GSTM1 null genotype when combining with smoking history may contribute to CHD susceptibility.

Role of GSTM1 in resistance to lung inflammation

Lung inflammation resulting from oxidant/antioxidant imbalance is a common feature of many lung diseases. In particular, the role of enzymes regulated by the NF-E2-related factor 2 transcription factor has recently received increased attention. Among these antioxidant genes, glutathione S-transferase Mu 1 (GSTM1) has been most extensively characterized because it has a null polymorphism that is highly prevalent in the population and associated with increased risk of inflammatory lung diseases. Present evidence suggests that GSTM1 acts through interactions with other genes and environmental factors, especially air pollutants. Here, we review GSTM1 gene expression and regulation and summarize the findings from epidemiological, clinical, animal, and in vitro studies on the role played by GSTM1 in lung inflammation. We discuss limitations in the existing knowledge base and future perspectives and evaluate the potential of pharmacologic and genetic manipulation of the GSTM1 gene to modulate pulmonary inflammatory responses.

Copy Number Variation in Glutathione S-Transferases M1 and T1 and Ischemic Vascular Disease

Background—

Glutathione S-transferases (GSTs) M1 and T1 detoxify products of oxidative stress and may protect against atherosclerosis and ischemic vascular disease (IVD). We tested the hypothesis that copy number variation (CNV) in GSTM1 and GSTT1 genes, known to be associated with stepwise decreases in catalytic activity, predict risk of IVD.

Methods and Results—

We included 23 059 Danes from 2 general population studies and 2 case-control studies, of whom 4930 had ischemic heart disease (IHD) and 2086 had ischemic cerebrovascular disease. A real-time polymerase chain reaction method genotyped for the exact number of GSTM1 and GST T1 gene copies. We also performed meta-analyses, including our own and former studies, totaling 13 196 IHD cases and 33 228 controls. CNV in GSTM1 or GSTT1 or genotype combinations were not associated with an increased risk of IHD, myocardial infarction, ischemic cerebrovascular disease, ischemic stroke, or any ischemic vascular event in studies individually or combined or in the meta-analyses. Furthermore, genotypes did not interact with smoking on risk of disease end points. Finally, GST genotypes did not associate with markers of inflammation and oxidation or interact with smoking on markers of inflammation in the general population. In contrast, we observed the well-established association between CNV in GSTM1 and risk of bladder cancer.

Conclusions—

In studies including 6557 IVD cases and 16 502 controls and in meta-analyses of 13 196 cases and 33 228 controls, CNV in GSTM1 and GST T1 genes did not associate with risk of IVD or with markers of inflammation. These observations were independent of smoking exposure.

The association between GSTT1, M1, and P1 polymorphisms with coronary artery disease in Western Iran

DNA damage which occurred by the effect of oxidant and mutant agents has an essential role in the development of atherosclerosis. To investigate the possible association between GSTs polymorphism with coronary artery disease (CAD), we investigated the frequency of GSTT1, M1, and P1 genotypes in patients with CAD compared to controls. The genotypes of GSTT1, M1, and P1 were determined in 209 angiographically documented CAD patients and 108 normal coronary artery cases (as controls) by Multiplex Polymerase Chain Reaction and PCR-RFLP. In CAD patients, the frequency of GSTT1-null genotype was significantly (P = 0.025) lower than that in control. The presence of this genotype was associated with 2.2-fold increased risk of CAD. However, the frequency of GSTM1 and GSTP1 genotypes were not significantly different comparing both groups (P = 0.405 and P = 0.521, respectively). Moreover, non smokers patients had a lower frequency of GSTM1-null genotype (29.2%) compared to non smoker controls (43.5%, P = 0.043). Also, the frequency of both GSTT1-null and GSTM1-null genotypes in patients (3.8%) was significantly lower compared to controls with the same genotypes (10.2%, P = 0.014). Our results indicated that a reduction in the frequency of GSTT1-null and GSTM1-null genotypes that observed in our study might be involved in the pathogenesis of CAD in our population.

Nrf2-ARE stress response mechanism: a control point in oxidative stress-mediated dysfunctions and chronic inflammatory diseases

Nrf2, a redox sensitive transcription factor, plays a pivotal role in redox homeostasis during oxidative stress. Nrf2 is sequestered in cytosol by an inhibitory protein Keap1 which causes its proteasomal degradation. In response to electrophilic and oxidative stress, Nrf2 is activated, translocates to nucleus, binds to antioxidant response element (ARE), thus upregulates a battery of antioxidant and detoxifying genes. This function of Nrf2 can be significant in the treatment of diseases, such as cancer, neurodegenerative, cardiovascular and pulmonary complications, where oxidative stress causes Nrf2 derangement. Nrf2 upregulating potential of phytochemicals has been explored, in facilitating cure for various ailments while, in cancer cells, Nrf2 upregulation causes chemoresistance. Therefore, Nrf2 emerges as a key regulator in oxidative stress-mediated diseases and Nrf2 silencing can open avenues in cancer treatment. This review summarizes Nrf2-ARE stress response mechanism and its role as a control point in oxidative stress-induced cellular dysfunctions including chronic inflammatory diseases.

Genetic polymorphisms of glutathione S-transferase genes GSTM1, GSTT1 and risk of coronary heart disease

To clarify the role of glutathione S-transferases (GSTs; GSTM1 and GSTT1) status in susceptibility to coronary heart disease (CHD), a meta-analysis of published studies was performed. A total of 19 studies including 8020 cases and 11 501 controls were included in this meta-analysis. In a combined analysis, the relative risks for CHD of the GSTM1 null and GSTT1 null polymorphisms were 1.47 [95% confidence interval (CI): 1.08-2.01] and 1.26 (95% CI: 0.90-1.75), respectively. Three potential sources of heterogeneity including ethnicity, source of control and sample size of study were also assessed. However, no significant association was found in stratified analyses. By pooling data from eight studies (2909 cases and 3745 controls) that considered combinations of GSTT1 and GSTM1 genotypes, a statistically significant increased risk for CHD [odds ratio (OR = 2.38, 95% CI: 1.03-5.48)] was detected for individuals with combined deletion mutations in both genes compared with positive genotypes. Results from the meta-analysis of five studies on GSTs stratified according to smoking status showed an increased risk for individuals with null genotype (OR = 2.21, 95% CI: 1.24-3.92 for GSTM1 and OR = 3.29, 95% CI: 1.49-7.26 for GSTT1) versus non-null genotypes. This meta-analysis suggests that the GSTM1 null genotype may slightly increase the risk of CHD and that interaction between unfavourable GSTs genotypes may exist.

Genetic polymorphism and function of glutathione S-transferases in tumor drug resistance

The human glutathione S-transferase, GSTs, possess both enzymatic and non-enzymatic functions and are involved in many important cellular processes, such as, phase II metabolism, stress response, cell proliferation, apoptosis, oncogenesis, tumor progression and drug resistance. The non-enzymatic functions of GSTs involve their interactions with cellular proteins, such as, JNK, TRAF, ASK, PKC, and TGM2, during which, either the interacting protein partner undergoes functional alteration or the GST protein itself is post-translationally modified and/or functionally altered. The majority of GST genes harbor polymorphisms that influence their transcription and/or function of their encoded proteins. This overview focuses on recent insights into the biology and pharmacogenetics of GSTs as a determinant of cancer drug resistance and response of cancer patients to therapy.

Glutathione S-transferase genotype as a susceptibility factor in smoking-related coronary heart disease

Cancer studies suggest that the null polymorphisms of glutathione S-transferase M1 or T1 (GSTM1/GSTT1) may affect the ability to detoxify or activate chemicals in cigarette smoke. The potential modification of the association between smoking and coronary heart disease (CHD) by GSTM1 and GSTT1 has not been studied in humans. A case-cohort study was conducted to test the hypotheses that specific genotypes of GSTM1 or GSTT1 affect susceptibility to smoking-related CHD. CHD cases (n=400) accrued during 1987-1993 and a cohort-representative sample (n=924) were selected from a biracial cohort of 15792 middle-aged men and women in four US communities. A significantly higher frequency of GSTM1-0 and a lower frequency of GSTT1-0 were found in whites (GSTM1-0=47.1%, GSTT1-0=16.4%) than in African-Americans (AAs) (GSTM1-0=17.5%, GSTT1-0=25.9%). A smoking-GSTM1-0 interaction for the risk of CHD was statistically significant on an additive scale, with ever-smokers with GSTM1-0 at a approximately 1.5-fold higher risk relative to ever-smokers with GSTM1-1 and a approximately 2-fold higher risk relative to never-smokers with GSTM1-0, after adjustment for other CHD risk factors. The interaction between having smoked >/=20 pack-years and GSTT1-1 was statistically significant on both multiplicative and additive scales. The risk of CHD given both GSTT1-1 and >/=20 pack-years of smoking was approximately three times greater than the risk given exposure to >/=20 pack-years of smoking alone, and approximately four times greater than the risk given exposure to GSTT1-1 alone. The modification of the smoking-CHD association by GSTM1 or GSTT1 suggests that chemicals in cigarette smoke that are substrates for glutathione S-transferases may be involved in the etiology of CHD.

Characterization of a human glutathione S-transferase mu cluster containing a duplicated GSTM1 gene that causes ultrarapid enzyme activity

The mu class glutathione S-transferase gene GSTM1 is polymorphic in humans, with approximately half of the Caucasian population being homozygous deleted for this gene. GSTM1 enzyme deficiency has been suggested to predispose people to lung and bladder cancer. Some people in a Saudi Arabian population, however, have been described previously with ultrarapid GSTM1 enzyme activity. Here we have evaluated the molecular genetic basis for this observation. Genomic DNA from two Saudi Arabian subjects exhibiting ultrarapid enzyme activity and from 13 Swedish subjects having null, one, or two GSTM1 genes were subjected to restriction fragment length polymorphism analysis using the restriction enzymes EcoRI, EcoRV, and HindIII and combinations thereof. Hybridization was carried out using a full-length GSTM1 cDNA or the 5' and 3' parts of the cDNA. The restriction mapping data revealed the presence of a GST mu cluster with two GSTM1 genes in tandem situated between the GSTM2 and GSTM5 genes. A quantitative multiplex polymerase chain reaction method, which simultaneously amplified a fragment of the GSTM1 gene and the beta-globin gene, was developed, and the genomic GSTM1 copy number was determined from the GSTM1/beta-globin ratio. This method clearly separated GSTM1 +/- subjects (ratios between 0.4 and 0.7) from GSTM1 +/+ subjects (ratios between 0.8 and 1.2). The two Saudi Arabians with ultrarapid GSTM1 activities had ratios of approximately 1.5, indicating that they carried three GSTM1 genes. These results demonstrate the existence of a novel mu class GST cluster containing a duplicated active GSTM1 gene causing ultrarapid enzyme activity.