Null genotypes of GSTM1 and GSTT1 contribute to increased risk of diabetes mellitus: A meta-analysis

Diabetes mellitus (DM) is a common disease which results from various causes including genetic and environmental factors. Glutathione S-Transferase M1 (GSTM1) and Glutathione S-Transferase T1 (GSTT1) genes are polymorphic in human and the null genotypes lead to the absence of enzyme function. Many studies assessed the associations between GSTM1/GSTT1 null genotypes and DM risk but reported conflicting results. In order to get a more precise estimate of the associations of GSTM1/GSTT1 null genotypes with DM risk, we performed this meta-analysis. Published literature from PubMed, Embase and China Biology Medicine (CBM) databases was searched for eligible studies. Pooled odds ratios (OR) and corresponding 95% confidence intervals (95%CI) were calculated using a fixed- or random-effects model. 11 publications (a total of 2577 cases and 4572 controls) were finally included into this meta-analysis. Meta-analyses indicated that null genotypes of GSTM1/GSTT1 and dual null genotype of GSTM1–GSTT1 were all associated with increased risk of DM (GSTM1: OR _{random-effects} = 1.60, 95%CI 1.10–2.34, P_OR = 0.014; GSTT1: OR _{random-effects} = 1.47, 95%CI 1.12–1.92, P_OR = 0.005; GSTM1–GSTT1: OR _{fixed-effects} = 1.83, 95%CI 1.30–2.59, P_OR = 0.001). Subgroup by ethnicity suggested significant associations between null genotypes of GSTM1 and GSTT1 and DM risk among Asians (GSTM1: OR _{random-effects} = 1.77, 95%CI 1.24–2.53, P_OR = 0.002; GSTT1: OR _{random-effects} = 1.58, 95%CI 1.09–2.27, P_OR = 0.015). This meta-analysis suggests null genotypes of GSTM1/GSTT1 and dual null genotype of GSTM1–GSTT1 are all associated with increased risk of DM, and null genotypes of GSTM1/GSTT1 and dual null genotype of GSTM1–GSTT1 are potential biomarkers of DM.     

GSTM1 null genotype as a risk factor for anti-BPDE-DNA adduct formation in mononuclear white blood cells of coke-oven workers

The influence of the genetic deletion polymorphism of glutathione S-transferase micro 1 (GSTM1 *0/*0) on levels of anti (+/-)-r-7,t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE-DNA) adduct in the peripheral blood lymphocyte plus monocyte fraction (LMF) of coke-oven workers was investigated. A total of 95 male Polish coke-oven workers (60% current smokers) from two different plants comprised the sample population. Polycyclic aromatic hydrocarbons (PAH) exposure was assessed by means of the individual post-shift urinary excretion of 1-pyrenol (mean +/- S.D.: 6.93 +/- 7.20 micromol/mol creatinine; 70% of the subjects exceeded the proposed biological exposure index (BEI) 2.28 micromol/mol creatinine). Anti-BPDE-DNA adduct levels were detected by high performance liquid chromatography (HPLC)/fluorescence analysis of the anti-BPDE tetrol I-1 released after acid hydrolysis of DNA samples. Genotypes were determined by polymerase chain reaction (PCR) on the genomic DNA of each subject. Coke-oven workers without active GSTM1 (GSTM1 *0/*0, 33%) had significantly higher adduct levels than those with active GSTM1 (GSTM1*1/*1 and *1/*0) (5.90 +/- 5.59 versus 3.25 +/- 2.01 adducts/10(8) bases, Mann-Whitney U-test, z = 2.53, P = 0.011), PAH exposure in the two subgroups being similar (7.06 +/- 6.83 versus 6.67 +/- 8.00 1-pyrenol micromol/mol creatinine). The highest number of GSTM1 null subjects (12/23, 39%) belonged to the quartile with the highest adduct levels (i.e., >4.67 adducts/10(8) nucleotides). That is, coke-oven workers with GSTM1 *0/*0 genotype had a significantly higher risk of having high adduct levels than individuals with active GSTM1 genotype (Fisher exact test P = 0.0355; odds ratio (OR) = 4.145, 95% CI 1.0-18.8). Multiple linear regression analysis showed that the increase in anti-BPDE-DNA adduct levels in LMF was significantly related to the high occupational exposure to PAHs (benzo[a]pyrene (BaP)) of coke-oven workers (t = 3.087, P < 0.01) and to the lack of GSTM1 activity (t = 3.512, P < 0.001), rather than to the two other confounding factors of PAH intake, i.e. charcoal-broiled meat consumption and smoking habits. In conclusion, our results indicate the clear influence of the GSTM1 detoxifying genotype on anti-BPDE-DNA adduct formation in the LMF of coke-oven workers. This is invaluable for future environmental-occupational studies using this biomarker of PAH exposure.     

Aromatic DNA adduct levels in coke oven workers: correlation with polymorphisms in genes GSTP1, GSTM1, GSTT1 and CYP1A1

The aim of this study was to use DNA adducts levels, detected by 32P-postlabelling, as a biomarker to assess human exposure to polycyclic aromatic hydrocarbons (PAHs) from a coke oven plant and explore the possible association between CYP1A1 MspI, GSTP1, GSTM1 and GSTT1 genotypes, and smoking status on bulky DNA adduct formation. A large amount of inter-individual variation in adduct level was observed among workers with the same job and the same smoking habits. No significant differences were observed in DNA adduct levels between the coke oven workers and control group. Smokers in the control group had significantly higher DNA adducts than the non-smokers in the same group (35.13+/-21.11 versus 11.18+/-8.00, per 10(8) nucleotides, P=0.003). In this group, the correlation between the level of DNA adducts and the cigarettes smoked was strongly significant (r=0.70, P<0.0005), but no correlation was found among the coke oven workers. Among non-smokers there was a significant difference between the control group and the coke oven workers (11.18+/-8.00 versus 24.62+/-15.20, per 10(8) nucleotides, P=0.03). These results suggests that tobacco smoke could behave as a confounding factor for evaluation of DNA adducts arising from occupational exposure. The levels of DNA adducts in smokers not occupationally exposed to PAHs is dependent on the polymorphisms CYP1A1 MspI in the 3' non-coding region (49.04+/-22.18 versus 25.85+/-15.87, per 10(8) nucleotides, P<0.05), but no effect was observed for the GST genotypes studied.     

Benzo(a)pyrene diolepoxide adducts to albumin in workers exposed to polycyclic aromatic hydrocarbons: association with specific CYP1A1, GSTM1, GSTP1 and EHPX genotypes

We investigated whether the presence of (+)-anti-benzo(a)pyrene diolepoxide adducts to serum albumin (BPDE-SA) among workers exposed to benzo(a)pyrene (BaP) and unexposed reference controls was influenced by genetic polymorphisms of cytochrome P4501A1 (CYP1A1), microsomal epoxide hydrolase (EHPX), glutathione S-transferases M1 (GSTM1) and P1 (GSTP1), all involved in BaP metabolism. Exposed workers had significantly higher levels of adducts (0.124 ± 0.02 fmol BPTmg^?1 SA, mean ± SE) and a higher proportion of detectable adducts (40.3%) than controls (0.051 ± 0.01 fmol BPT mg^?1 SA; 16.1%) (p = 0:014 and p = 0:012). Smoking increased adduct levels only in occupationally exposed workers with the GSTM1 deletion (GSTM1 null) (p = 0:034). Smokers from the exposed group had higher adduct levels when they were CYP1A1 *1/*1 wild-type rather than heterozygous and homozygous for the variant alleles (CYP1A1 *1/*2 plus *2/*2) (p = 0:01). The dependence of BPDE-SA adduct levels and frequency on the CYP1A1 *1/*1 genotype was most pronounced in GSTM1-deficient smokers. Exposed workers with GSTM1 null/GSTP1 variant alleles had fewer detectable adducts than those with the GSTM1 null/GSTP1*A wild-type allele, supporting for the first time the recent in vitro finding that GSTP1 variants may be more effective in the detoxification of BPDE than the wild-type allele. Logistic regression analysis indicated that occupational exposure, wild-type CYP1A1*1/*1 allele and the combination of GSTM1 null genotype+EHPX genotypes associated with predicted low enzyme activity were significant predictors of BPDE-SA adducts. Though our findings should be viewed with caution because of the relatively limited size of the population analysed, the interaction between these polymorphic enzymes and BPDE-SA adducts seems to be specific for high exposure and might have an impact on the quantitative risk estimates for exposure to polycyclic aromatic hydrocarbons.     

Are glutathione S-transferase polymorphisms (GSTM1, GSTT1) associated with primary open angle glaucoma? A meta-analysis

Background

Glutathione S-transferase (GST) variants have been considered as risk factors for the pathogenesis of primary open angle glaucoma (POAG). However, the results have been inconsistent. In this study, we performed a meta-analysis to assess the association between GSTM1 and GSTT1 null genotypes and the risk for POAG.

Methods

Published literature from PubMed and EMBASE databases was retrieved. All studies evaluating the association between GSTM1/GSTT1 variants and POAG were included. Pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using fixed- or random-effects model.

Results

14 studies (1711 POAG cases and 1537 controls) were included in the meta-analysis of GSTM1 genotypes and 10 studies (1306 POAG cases and 1114 controls) were included in the meta-analysis of GSTT1 genotypes. The overall result showed that the association between GSTM1 and GSTT1 null genotypes and risk for POAG was not statistically significant (GSTM1: OR = 1.19, 95% CI = 0.82–1.73, p = 0.361; GSTT1: OR = 1.26, 95% CI = 0.77–2.06, p = 0.365). The results by ethnicity showed that the association between the GSTM1 null genotype and risk for POAG is statistically significant in East Asians (OR = 1.41, 95% CI = 1.04–1.90, p = 0.026), but not in Caucasians (OR = 1.13, 95% CI = 0.69–1.84, p = 0.638) and Latin-American (OR = 1.09, 95% CI = 0.62–1.92, p = 0.767). In addition, there was no significant association of GSTT1 null genotype with risk for POAG in either ethnic population.

Conclusions

The present meta-analysis suggested that there might be a significant association of GSTM1 null genotype with POAG risk in East Asians.     

The effect of the genetic polymorphisms of CYP1A1,CYP2D6, GSTM1 and GSTP1 on aromatic DNA adduct levels in the population of healthy women

Aromatic DNA adduct levels and polymorphisms of two phase I enzymes - CYP1A1 and CYP2D6 and two phase II enzymes - GSTM1 and GSTP1 were analyzed in a group of 133 nonsmoking healthy women 35-45 years old and holding jobs not connected with the exposure to the combustion products of organic matter. They were office workers from the south and north-eastern parts of Poland. Blood samples were collected in winter and in summer. Aromatic DNA adduct levels were measured in all winter and summer samples. The frequencies of CYP1A1, CYP2D6, GSTM1 and GSTP1 polymorphisms in samples from the studied women did not show any differences when compared with other Caucasian populations and the Polish male population studied previously. The differences in the levels of DNA adducts among the carriers of different genotypes were statistically non-significant. Analysis of combined genotypes selected the groups of volunteers with the highest and the lowest DNA adduct levels. The highest levels of DNA adducts were observed in the carriers of GSTM1(null)/CYP1A1Ile/Val (8.00+/-13.00 adducts/10(8) nucleotides in summer samples) and GSTP1-AA/CYP1A1Ile/Val genotypes (7.00+/-4.32 in winter and 7.30+/-7. 27/10(8) nucleotides in summer). The lowest levels of DNA adducts (3. 00+/-2.30 in winter and 2.00+/-3.16/10(8) nucleotides in summer) were found in the carriers of the genotype GSTP1-AG+GG/CYP1A1Ile/Val. The levels of DNA adducts in these groups were determined by the polymorphisms of GSTM1 and GSTP1 phase II detoxifying enzymes.     

Genetic polymorphisms of GSTM1, GSTT1 and GSTP1 and susceptibility to DNA damage in workers occupationally exposed to organophosphate pesticides

GSTM1, T1 and P1 are important enzymes of glutathione S-transferases (GSTs), involved in the metabolism of many endogenous and exogenous compounds. Individual genetic variation in these metabolizing enzymes may influence the metabolism of their substrates. The present study was designed to determine the genotoxic effects using DNA damage and its association with GSTM1, GSTT1, and GSTP1 (Ile105Val) genetic polymorphisms in workers occupationally exposed to organophosphate pesticides (OPs). We examined 230 subjects including 115 workers occupationally exposed to OPs and an equal number of normal healthy controls. The DNA damage was evaluated using the alkaline comet assay and genotyping was done using individual PCR or PCR-RFLP. Significantly higher DNA tail moment (TM) was observed in workers as compared to control subjects (14.41 ± 2.25 vs. 6.36 ± 1.41 tail % DNA, p<0.001). The results revealed significantly higher DNA TM in workers with GSTM1 null genotype than those with GSTM1 positive (15.18 vs. 14.15 tail % DNA, p=0.03). A significantly higher DNA TM was also observed in workers with homozygous Ile-Ile GSTP1 genotype than heterozygous (Ile-Val) and mutant (Val-Val) GSTP1 genotype (p=0.02). In conclusion, the results show that null deletion of GSTM1 and homozygote wild GSTP1 genotype could be related to inter-individual differences in DNA damage arises from the gene-environment interactions in workers occupationally exposed to OPs.     

Influence of GSTM1 genotype on association between aromatic DNA adducts and urinary PAH metabolites in incineration workers

Waste incinerating workers are exposed to various pyrolysis products including polycyclic aromatic hydrocarbons (PAHs). We examined their PAH exposure by assessing urinary 1-hydroxypyrene glucuronide (1-OHPG), as a measure of internal dose, and aromatic DNA adducts in peripheral white blood cells (WBCs), as a measure of biological effect dose. The potential effect of genetic polymorphisms of three enzymes involved in PAH metabolisms (i.e., CYP1A1, GSTM1, and GSTT1) on these exposure markers was also investigated.Twenty-nine employees including workers incinerating industrial wastes and 21 non-exposed on-site controls were recruited from a company handling industrial wastes in South Korea. Sixteen ambient PAHs were determined by GC/MSD (NIOSH method) from personal breathing zone samples of nine subjects working near incinerators. Urinary 1-OHPG was assayed by synchronous fluorescence spectroscopy (SFS) after immunoaffinity purification using monoclonal antibody 8E11. Aromatic DNA adducts in peripheral WBC were measured by the nuclease P1-enhanced post-labelling assay. Genotypes were assessed by PCR-based methods. Information on smoking habits and use of personal protective equipment were collected by self-administered questionnaire.Urinary 1-OHPG levels were significantly higher in workers handling industrial wastes than in those with presumed lower exposure to PAHs (P=0.006, by Kruskal-Wallis test). A statistically significant dose-response increase in 1-OHPG levels was seen with the number of cigarettes consumed per day (r=0.686, P<0.001). Smoking and GSTM1 genotype were significant predictors for log-transformed 1-OHPG by multiple regression analysis (overall model R(2)=0.565, P<0.001), whereas smoking was the only significant predictor for log-transformed aromatic DNA adducts (overall model R(2)=0.249, P=0.201). Aromatic DNA adducts were significantly correlated with log-transformed urinary 1-OHPG level (r=0.31, P=0.04). However, the partial correlation coefficient adjusting for age, sex, and cigarette consumption was not significant (r=0.15, P=0.17). The significant association exists only in individuals with the GSTM1 null genotype (Pearson's correlation coefficient, r=0.52, P=0.01; partial correlation coefficient adjusting for age, sex, and cigarette consumption, r=0.36, P=0.04).Our results suggest that the significant increase in urinary 1-OHPG in the exposed workers is due to higher prevalence of smokers among them, and that the association between urinary PAH metabolites and aromatic DNA adducts in workers of industrial waste handling may be modulated by GSTM1 genotype. These results remain to be confirmed in future larger studies.     

Evaluation of glutathione S-transferase genetic variants affecting type 2 diabetes susceptibility: A meta-analysis

Genetic polymorphisms of glutathione S-transferases (GSTs) and type 2 diabetes mellitus (T2DM) risk have been widely studied, however, the results were somewhat conflicting. To evaluate the association of GSTs (GSTM1, GSTT1 and GSTP1) gene polymorphisms with T2DM, a meta-analysis was performed before October, 2012. ORs were pooled according to random-effects model. There were a total of 1354/1666 (n = 9) cases/controls (studies) for GSTM1, 1271/1470 (n = 8) for GSTT1, and 1205/1250 (n = 7) for GSTM1. There were significant associations between GSTM1 polymorphism, GSTT1 polymorphism and T2DM in the contrast of present genotype vs. null genotype, with pooled OR = 1.99 (95%CI = 1.46–2.71) and OR = 1.61 (95%CI = 1.19–2.17), respectively. Yet no significant association of GSTP1 polymorphism and T2DM was showed. When stratified by ethnicity, the significant associations were also existed in Asians for GSTM1 and GSTT1, but not GSTP1. No publication bias but some extent of heterogeneity was observed. Finally, the accumulated evidence proved the obvious associations of GSTM1 and GSTT1 polymorphisms with an increased risk of T2DM.     

Impact of metabolic genotypes on levels of biomarkers of genotoxic exposure

Phase I and Phase II xenobiotic-metabolising enzyme families are involved in the metabolic activation and detoxification of various classes of environmental carcinogens. Particular genetic polymorphisms of these enzymes have been shown to influence individual cancer risk. A brief overview is presented about recent research of the relationship between metabolic genotypes and internal dose, biologically effective dose and cytogenetic effects of complex and specific genotoxic exposures of human study populations, and we report our new results from two molecular epidemiological studies. We investigated the effects of multiple interactions among CYP1A1 Ile462Val, CYP1A1 MspI, CYP1B1 Leu432Val, CYP2C9 Arg144Cys, CYP2C9 Ile359Leu, NQO1 Pro189Ser, GSTM1 gene deletion and GSTP1 Ile105Val genotypes on the levels of carcinogen-DNA adducts determined by (32)P-postlabelling and PAH-DNA immunoassay in peripheral blood lymphocytes from workers occupationally exposed to polycyclic aromatic hydrocarbons in aluminium plants, and in bronchial tissue from smoking lung patients. A statistically significant positive linear correlation was observed between white blood cell aromatic DNA adduct and urinary 1-hydroxypyrene (1-OHPY) levels from potroom workers with GSTM1 null genotype (P=0.011). Our results suggest interactions between GSTM1 and GSTP1 alleles in modulation of urinary 1-OHPY levels and white blood cell DNA adduct levels in the PAH-exposed workers. Interactions between GSTM1 and GSTP1 alleles, in association with particular genotype combinations of CYPs, were also recognised in bronchial aromatic DNA adduct levels of smoking lung patients. The impact of single metabolic genotypes and their combinations on biomarkers of exposure was usually weak, if any, in both our studies and reports of the literature. The effect of special metabolic gene interactions may be better recognised if the compared groups of individuals are stratified for multiple potential modulators of the observable biomarker end-point, and/or if chemical structure-specific biomarker methods are applied.     

Association of glutathione S-transferase M1/T1 polymorphisms with susceptibility to vitiligo

Background

Some studies suggested that Glutathione S-transferases M1/T1(GSTM1/T1) null polymorphisms may be associated with the risk of vitiligo.

Aims

The purpose of this study is to further evaluate the association between GSTM1/T1 null polymorphisms and the susceptibility to vitiligo.

Methods

We carried out a retrieval of studies in the databases. Odds ratios (OR) and 95% confidence intervals (95% CIs) were used to assess the strength of this association. We analyzed the data using Stata 11.0.

Results

Six case–control studies including 1358 cases and 1673 controls were included in this meta-analysis. Our overall results showed the GSTM1 or GSTT1 null polymorphism was associated with vitiligo (GSTM1:OR = 1.59, 95% CI: 1.21–2.08, P = 0.001; GSTT1: OR = 1.30, 95% CI: 1.12–1.51, P = 0.001). In the subgroup analysis, the GSTM1 null polymorphism might be a genetic risk factor to vitiligo in East Asian (OR = 1.71, 95% CI: 1.12–2.63, P = 0.014) but not in the Mediterranean, however individuals with the GSTT1 null polymorphism in the Mediterranean (OR = 1.76, 95% CI: 1.15–2.71, P = 0.010) but not in East Asian have a greater predisposition to vitiligo. In addition there was also a significant trend toward an association with the combination of the GSTM1 null and GSTT1 null in either East Asians or Mediterraneans.

Conclusion

The GSTM1/T1 null polymorphisms may be associated with vitiligo. More studies are needed to confirm this conclusion.     

Influence of CYP2C9, GSTM1, GSTT1 and NAT2 genetic polymorphisms on DNA damage in workers occupationally exposed to organophosphate pesticides

Previous studies have revealed that organophosphate pesticides (OPs) are primarily metabolized by xenobiotic metabolizing enzymes (XMEs). Very few studies have explored genetic polymorphisms of XMEs and their association with DNA damage in pesticides-exposed workers. Present study was designed to determine the influence of CYP2C9, GSTM1, GSTT1 and NAT2 genetic polymorphisms on DNA damage in workers occupationally exposed to OPs. We examined 268 subjects including 134 workers occupationally exposed to OPs and an equal number of normal healthy controls. The DNA damage was evaluated using alkaline comet assay and genotyping was done using individual polymerase chain reaction (PCR) or polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Acetylcholinesterase and paraoxonase activity were found to be significantly lowered in workers as compared to control subjects which were analyzed as biomarkers of toxicity due to OPs exposure (p<0.001). Workers showed significantly higher DNA tail moment (TM) compared to control subjects (14.32±2.17 vs. 6.24±1.37 tail % DNA, p<0.001). GSTM1 null genotype was found to influence DNA TM in workers (p<0.05). DNA TM was also found to be increased with concomitant presence of NAT2 slow acetylation and CYP2C9*3/*3 or GSTM1 null genotypes (p<0.05). DNA TM was found increased in NAT2 slow acetylators with mild and heavy smoking habits in control subjects and workers, respectively (p<0.05). The results of this study suggest that GSTM1 null genotypes, and an association of NAT2 slow acetylation genotypes with CYP2C9*3/*3 or GSTM1 null genotypes may modulate DNA damage in workers occupationally exposed to OPs.     

GSTM1 and GSTT1 gene polymorphisms as major risk factors for bronchopulmonary dysplasia in a Chinese Han population

Bronchopulmonary dysphasia (BPD) is a complex multifactorial disease with an obvious genetic predisposition. Oxidative stress plays an important role in its pathogenesis. Glutathione S-transferases (GSTs) detoxify metabolites produced by oxidative stress within the cell and protect the cells against injury. In the present study, the hypothesis that polymorphisms in the GSTM1 and GSTT1 genes are associated with BPD in Chinese Han infants was examined. Sixty infants with BPD and 100 gestational age and birth weight-matched preterm infants without BPD were recruited. Genotyping for GSTM1 and GSTT1 was performed by multiplex polymerase chain reaction (PCR). The GSTM1 null genotype was more prevalent in BPD infants (65.0%) than in the control subjects (48.0%), which yielded higher risk towards BPD (odds ratio (OR): 2.012, 95% confidence interval (CI) = 1.040–3.892, p = 0.037). There was no statistically significant association of GSTT1 genotype with BPD (OR: 1.691, 95% CI = 0.884–3.236, p = 0.111), although the frequency of GSTT1 null genotype was higher among the BPD subjects (60.0%) than in the control patients (47.0%). GSTM1 and GSTT1 double null genotype was also higher in BPD group (38.3%) than in controls (21.0%) with a higher risk towards BPD (OR: 2.338, 95%CI = 1.151–4.751, p = 0.017). The results suggest that null genotypes of GSTM1 and GSTT1 genes may contribute to the development of BPD in our Chinese Han population.     

PAH-DNA adducts in a Chinese population: relationship to PAH exposure, smoking and polymorphisms of metabolic and DNA repair genes.

The present study was conducted in a Chinese population to evaluate the usefulness and sensitivity of PAH-DNA adduct as a biomarker of PAH exposure, and to examine the potential effects of smoking and polymorphisms of responsive genes on DNA adduct formation induced by PAH exposure. The polymorphisms of genes examined include GSTM1, GSTT1, CYP1A1, microsomal epoxide hydrolase (mEH) and excision repair cross-complementary group 2 (ERCC2). A total of 194 subjects with a broad range of PAH exposures were recruited, including 116 occupationally exposed workers, 49 metropolitan residents and 29 suburban gardeners. A significant exposure-response relationship was observed between PAH exposure and DNA adducts in leukocytes across the entire group of subjects (p < 0.0001). The levels of PAH-DNA adducts in the subgroup with lowest occupational exposure to PAHs (< 0.1 microg BaP m(-3)) was significantly higher than that in metropolitan residents and suburban gardeners. However, no significant difference was detected between residents and gardeners, with mean BaP concentrations of 0.028 and 0.011 microg m(-3), respectively. The polymorphisms of genes examined failed to show significant effects on PAH-induced adduct formation except ERCC2 Lys751Gln genotypes. A significantly higher level of PAH-DNA adduct was found in subjects with wild-type ERCC2 than those who have either heterozygous or homozygous variant alleles (p < 0.01). Smoking, age and gender did not substantially contribute to PAH-induced DNA adduct formation in this study. The study suggests that PAH-DNA adducts may serve as a reliable biomarker of PAH exposure in occupational settings but may not be sensitive enough to be used in populations with environmental exposures to PAHs.     

PAH-DNA adducts in environmentally exposed population in relation to metabolic and DNA repair gene polymorphisms

Epidemiologic studies indicate that prolonged exposure to particulate air pollution may be associated with increased risk of cardiovascular diseases and cancer in general population. These effects may be attributable to polycyclic aromatic hydrocarbons (PAHs) adsorbed to respirable air particles. It is expected that metabolic and DNA repair gene polymorphisms may modulate individual susceptibility to PAH exposure. This study investigates relationships between exposure to PAHs, polymorphisms of these genes and DNA adducts in group of occupationally exposed policemen (EXP, N = 53, males, aged 22–50 years) working outdoors in the downtown area of Prague and in matched “unexposed” controls (CON, N = 52). Personal exposure to eight carcinogenic PAHs (c-PAHs) was evaluated by personal samplers during working shift prior to collection of biological samples. Bulky-aromatic DNA adducts were analyzed in lymphocytes by ³²P-postlabeling assay. Polymorphisms of metabolizing (GSTM1, GSTP1, GSTT1, EPHX1, CYP1A1-MspI) and DNA repair (XRCC1, XPD) genes were determined by PCR-based RFLP assays. As potential modifiers and/or cofounders, urinary cotinine levels were analyzed by radioimmunoassay, plasma levels of vitamins A, C, E and folates by HPLC, cholesterol and triglycerides using commercial kits. During the sampling period ambient particulate air pollution was as follows: PM10 32–55 μg/m³, PM2.5 27–38 μg/m³, c-PAHs 18–22 ng/m³; personal exposure to c-PAHs: 9.7 ng/m³ versus 5.8 ng/m³ (P < 0.01) for EXP and CON groups, respectively. The total DNA adduct levels did not significantly differ between EXP and CON groups (0.92 ± 0.28 adducts/10⁸ nucleotides versus 0.82 ± 0.23 adducts/10⁸ nucleotides, P = 0.065), whereas the level of the B[a]P-“like” adduct was significantly higher in exposed group (0.122 ± 0.036 adducts/10⁸ nucleotides versus 0.099 ± 0.035 adducts/10⁸ nucleotides, P = 0.003). A significant difference in both the total (P < 0.05) and the B[a]P-“like” DNA adducts (P < 0.01) between smokers and nonsmokers within both groups was observed. A significant positive association between DNA adduct and cotinine levels (r = 0.368, P < 0.001) and negative association between DNA adduct and vitamin C levels (r = −0.290, P = 0.004) was found. The results of multivariate regression analysis showed smoking, vitamin C, polymorphisms of XPD repair gene in exon 23 and GSTM1 gene as significant predictors for total DNA adduct levels. Exposure to ambient air pollution, smoking, and polymorphisms of XPD repair gene in exon 6 were significant predictors for B[a]P-“like” DNA adduct. To sum up, this study suggests that polymorphisms of DNA repair genes involved in nucleotide excision repair may modify aromatic DNA adduct levels and may be useful biomarkers to identify individuals susceptible to DNA damage resulting from c-PAHs exposure.     

Lack of association between glutathione S-transferase T1 gene polymorphism and laryngeal cancer susceptibility: a meta-analysis based on 2,124 cases and 2,059 controls

Studies investigating the association between glutathione S-transferase T1 (GSTT1) gene polymorphism and laryngeal cancer susceptibility have reported conflicting results. The aim of the present study was to conduct a meta-analysis assessing the possible association of GSTT1 gene polymorphism with laryngeal cancer risk. The relevant studies were identified through a search of PubMed, Embase, ISI Web of Knowledge and Chinese National Knowledge Infrastructure until May 2011. Twelve studies were included in the present meta-analysis, which described a total of 2124 laryngeal cancer cases and 2059 controls. The overall odds ratio (OR) for GSTT1 null genotype was 1.40 (95% CI = 0.90-2.16). When stratifying for race, the pooled ORs for GSTT1 null genotype were 1.07 (95% CI = 0.81-1.41) in Caucasians and 5.63 (95% CI = 1.00-31.83) in Asians. The pooled ORs for GSTT1 null genotype were 1.03 (95% CI = 0.71-1.49) in population-based studies and 2.39 (95% CI = 0.73-7.86) in hospital-based studies, stratifying for study design. This meta-analysis suggested that there was lack of association between GSTT1 gene polymorphism and laryngeal cancer risk. However, larger scale primary studies are still required to further evaluate the interaction of GSTT1 gene polymorphism with laryngeal cancer risk.     

Lymphocytes,DNA adducts and genetic polymorphism for metabolic enzymes in low dose cigarette smokers

The aim of this study was to investigate the relationship between genetic polymorphism of metabolic enzymes and DNA adduct levels in lymphocytes of low dose cigarette smokers (less than 20 cigarettes per day). We previously reported the effects of cytochrome P4501A1 (CYP1A1) and glutathione S-transferase M1 (GSTM1) on lymphocyte DNA adducts. This time we considered not only CYP1A1 and GSTM1 but also cytochrome P4502E1 (CYP2E1) and glutathione S-transferase T1 (GSTT1). DNA adducts in lymphocytes obtained from low dose cigarette smokers (n = 41) and nonsmokers (n = 56) were measured by the 32P-postlabelling method. The adduct levels were compared regarding smoking status and polymorphic genotypes of these four enzymes. The mean SD of DNA adduct levels in all low dose cigarette smokers and non-smokers was 1 05 0 83 per 108 nucleotidesand 0 85 0 35 per 108 nucleotides, respectively. In low dose cigarette smokers, adduct levels were higher in the rare homozygous (MM) for CYP1A1-exon 7 polymorphism compared with the other types such as common homozygous (WW) and heterozygous (WM). CYP1A1-WM, MM in combination with GSTM1 null showed highest adduct levelamong low smokers. The low smokers with rare homozygous for CYP2E1 Dra1 polymorphism tended to have lower adduct levels than wild types. Low dose cigarette smokers with combined GSTM1 null and T1 null had a higher tendency for adduct levels than others. However none of the differences reached statistical significance.     

Benzo(a)pyrene diolepoxide adducts to albumin in workers exposed to polycyclic aromatic hydrocarbons: association with specific CYP1A1, GSTM1, GSTP1 and EHPX genotypes

We investigated whether the presence of (+)-anti-benzo(a)pyrene diolepoxide adducts to serum albumin (BPDE-SA) among workers exposed to benzo(a)pyrene (BaP) and unexposed reference controls was influenced by genetic polymorphisms of cytochrome P4501A1 (CYP1A1), microsomal epoxide hydrolase (EHPX), glutathione S-transferases M1 (GSTM1) and P1 (GSTP1), all involved in BaP metabolism. Exposed workers had significantly higher levels of adducts (0.124 ± 0.02 fmol BPTmg^-1 SA, mean ± SE) and a higher proportion of detectable adducts (40.3%) than controls (0.051 ± 0.01 fmol BPT mg^-1 SA; 16.1%) (p = 0:014 and p = 0:012). Smoking increased adduct levels only in occupationally exposed workers with the GSTM1 deletion (GSTM1 null) (p = 0:034).

Smokers from the exposed group had higher adduct levels when they were CYP1A1 *1/*1 wild-type rather than heterozygous and homozygous for the variant alleles (CYP1A1 *1/*2 plus *2/*2) (p = 0:01). The dependence of BPDE-SA adduct levels and frequency on the CYP1A1 *1/*1 genotype was most pronounced in GSTM1-deficient smokers. Exposed workers with GSTM1 null/GSTP1 variant alleles had fewer detectable adducts than those with the GSTM1 null/GSTP1*A wild-type allele, supporting for the first time the recent in vitro finding that GSTP1 variants may be more effective in the detoxification of BPDE than the wild-type allele. Logistic regression analysis indicated that occupational exposure, wild-type CYP1A1*1/*1 allele and the combination of GSTM1 null genotype+EHPX genotypes associated with predicted low enzyme activity were significant predictors of BPDE-SA adducts. Though our findings should be viewed with caution because of the relatively limited size of the population analysed, the interaction between these polymorphic enzymes and BPDE-SA adducts seems to be specific for high exposure and might have an impact on the quantitative risk estimates for exposure to polycyclic aromatic hydrocarbons.     

Relationship between the capacity to repair 8-oxoguanine, biomarkers of genotoxicity and individual susceptibility in styrene-exposed workers

Genotoxic effects related to exposure to styrene have been a matter of investigation for many years by employing markers of exposure, effect and susceptibility. The role of individual DNA-repair capacity in response to exposure to styrene may explain the controversial results so far obtained, but it is still scarcely explored. In the present study, we measured capacity to repair oxidative DNA damage in cell extracts obtained from 24 lamination workers occupationally exposed to styrene and 15 unexposed controls. The capacity to repair oxidative DNA damage was determined by use of a modified comet assay, as follows: HeLa cells, pre-treated with photosensitizer and irradiated with a halogen lamp in order to induce 7,8-dihydroxy-8-oxoguanine, were incubated with cell extracts from mononuclear leukocytes of each subject. The level of strand breaks reflects the removal of 7,8-dihydroxy-8-oxoguanine from substrate DNA by the enzymatic extract.In styrene-exposed subjects a moderate, non-significant increase in oxidative DNA repair was observed. Stratification for sex and smoking habit showed that unexposed males (P = 0.010) and unexposed smokers (P = 0.037) exhibited higher DNA-repair rates. The repair capacity did not correlate with parameters of styrene exposure and biomarkers of genotoxic effects (DNA strand breaks, N1-styrene-adenine DNA adducts, chromosomal aberrations and mutant frequencies at the HPRT locus). Significantly higher levels of DNA-repair capacity were observed in carriers of GSTM1-plus, compared to those with a deletion in GSTM1. The DNA-repair capacity was significantly lower in individuals with variant Gln/Gln genotype in XRCC1 Arg399Gln than in those with heterozygous Arg/Gln and wild-type Arg/Arg genotypes. Significantly lower repair capacity was also found in individuals with the wild-type Lys/Lys genotype in XPC Lys939Gln as compared with those homozygous for the Gln/Gln variant genotype.     

PAH-DNA adducts in a Chinese population: relationship to PAH exposure,smoking and polymorphisms of metabolic and DNA repair genes

Abstract

The present study was conducted in a Chinese population to evaluate the usefulness and sensitivity of PAH-DNA adduct as a biomarker of PAH exposure, and to examine the potential effects of smoking and polymorphisms of responsive genes on DNA adduct formation induced by PAH exposure. The polymorphisms of genes examined include GSTM1, GSTT1, CYP1A1, microsomal epoxide hydrolase (mEH) and excision repair cross-complementary group 2 (ERCC2). A total of 194 subjects with a broad range of PAH exposures were recruited, including 116 occupationally exposed workers, 49 metropolitan residents and 29 suburban gardeners. A significant exposure–response relationship was observed between PAH exposure and DNA adducts in leukocytes across the entire group of subjects (p<0.0001). The levels of PAH-DNA adducts in the subgroup with lowest occupational exposure to PAHs (<0.1µg BaP m^?3) was significantly higher than that in metropolitan residents and suburban gardeners. However, no significant difference was detected between residents and gardeners, with mean BaP concentrations of 0.028 and 0.011µg m^?3, respectively. The polymorphisms of genes examined failed to show significant effects on PAH-induced adduct formation except ERCC2 Lys751Gln genotypes. A significantly higher level of PAH-DNA adduct was found in subjects with wild-type ERCC2 than those who have either heterozygous or homozygous variant alleles (p<0.01). Smoking, age and gender did not substantially contribute to PAH-induced DNA adduct formation in this study. The study suggests that PAH-DNA adducts may serve as a reliable biomarker of PAH exposure in occupational settings but may not be sensitive enough to be used in populations with environmental exposures to PAHs.