Genetic polymorphisms of glutathione S-transferases M1 and T1 modulate hematological changes of individuals chronically exposed to natural sour gas

Association between polymorphism of GSTP1, GSTT1, GSTM1 and CYP2E1 genes and susceptibility to benzene-induced hematotoxicity

Occupational exposure to benzene has been associated with leukemia, anemia, leukopenia, and thrombocytopenia. Genetic susceptibility to benzene toxicity in humans may be related to variations in benzene metabolizing genes. The main objective of this study was to ascertain whether polymorphism of GSTP1, GSTM1, GSTT1 and CYP2E1 genes might influence susceptibility to the adverse effects of benzene among employees of a petrochemical plant. In this cross-sectional study, 124 employees of a petrochemical plant who had been occupationally exposed to benzene and had one or more abnormal hematological parameter (cases) and 184 subjects with a similar exposure scenario, free from any abnormal hematological parameters (referent) were studied. Atmospheric concentrations of benzene were measured and GSTM1 and GSTT1 genotypes were evaluated using the multiplex polymerase chain reaction (PCR) technique. Additionally, GSTP1 and CYP2E1 genotypes were determined by PCR- restriction fragment length polymorphism (PCR–RFLP). The frequency of null GSTT1 genotype in cases was significantly higher than that of referent group (32.3 vs. 18.5%, OR 2.1, 95% CI 1.23–3.56, p = 0.004). The mean value of platelets in subjects with null GSTT1 genotype was significantly lower than that of individuals with positive GSTT1 genotype (p = 0.015). Conversely, the mean value of leukocytes was significantly higher in subjects with null GSTM1 genotype as compared to those with positive GSTM1 genotype (p = 0.026). Logistic regression analysis showed that, subjects with null GSTT1 genotype had a significantly higher risk for hematological disorders, as compared to those with positive GSTT1 genotype (OR 2.1, 95% CI 1.23–3.56). Moreover, subjects with both null GSTT1 and GSTM1 genotypes had a significantly higher risk for hematological disorders as compared to subjects with positive GSTT1 and GSTM1 genotypes (OR 2.35, 95% CI 1.14–4.8). The results of this study showed that, individuals carrying null GSTT1 or both null STT1 and GSTM1 genotypes had a higher risk and were more susceptible to benzene-induced hematological disorders.

Expression Levels of Some Detoxification Genes in Liver and Testis of Rats Exposed to a Single Dose of Methyl-Tertiary Butyl Ether

AIM

Methyl-tertiary-butyl ether (MTBE), a well-known gasoline oxygenate compound, is still used in several countries. Several studies investigated the effects of MTBE on the activity of phase II metabolism enzymes. There is no published data on the effect(s) of short-term exposure to MTBE on mRNA levels of antioxidant genes. Therefore, the present study was carried out.

METHODS

A total of 15 adults male Wistar rats were randomly divided into five equal experimental groups. They received a single dose of 0, 400, 800 and 1600 mg/Kg MTBE in peanut oil by gavages. The final group received no MTBE and peanut oil. After 24 hr animals were slaughtered then livers and testis were removed to extract the total RNA. Real-time PCR was done to detect the gene expressions of glutathione S-transferase family (Gstt1, Gstm1, and Gstp1).

RESULTS

The mRNAs levels of the examined genes neither in liver nor in testis showed a significant difference between the exposed groups and control rats.

CONCLUSIONS

The present data revealed that exposure to a single dose of MTBE has no significant effect on the mRNA levels of the Gstt1, Gstm1, and Gstp1 genes.

Alteration of serum sex hormonal profile in male gasoline filling station workers in respect to their polymorphism of glutathione S-transferase M1

Alterations in offspring sex ratio at birth and level of serum testosterone in filling-station workers have been reported. To determine the association of glutathione S-transferase M1 (GSTM1) polymorphism with serum levels of total testosterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) of male filling-station workers, the present study was carried out on 114 gasoline workers and 100 age- and sex-matched controls with no occupational exposure to gasoline. We have found no significant difference between the workers and controls for levels of sex hormones in the presence of active GSTM1 genotype. Among subjects with the GSTM1 null genotype, there was significant difference between exposed and unexposed subjects for the concentration of testosterone (t=4.37, df=97, P<0.001). To investigate whether one null genotype could be compensated by an active genotype for the other isoenzyme, the mean concentrations of sex hormones was compared between the exposed and control groups with respect to their combinations of the GSTM1 and GSTT1 genotypes. The exposed group having either "null GSTM1/positive GSTT1" (t=2.76, df=72, P=0.007) or "null GSTM1/null GSTT1" (t=4.91, df=23, P<0.001) combinations had a lower testosterone compared with the controls. It seems that GSTM1 polymorphism has more effect on serum testosterone compared to the GSTT1 polymorphism, in exposed workers.

Genetic polymorphisms of glutathione S-transferase T1 (GSTT1) and M1 (GSTM1) in selected populations of Afghanistan

Genetic polymorphisms in genes encoding glutathione S-transferase T1 (GSTT1, a member of class theta) and M1 (GSTM1, a member of class mu) have been defined. Previous studies have revealed that there was significant difference between populations for allelic frequency of several members of GSTs. In order to find the prevalence of null genotypes of GSTM1 and GSTT1 in Afghanis populations the present study was carried out. The total study subjects consisted of 656 unrelated healthy Afghanis refugees living in Fars province (southern Iran). From these 257, 217, 120, and 62 individuals were Pashtuns, Tajiks, Hazaras, and Uzbeks, respectively. Genetic polymorphisms for GSTT1 and GSTM1 were detected by multiplex PCR. The prevalence of null genotype of GSTM1 in Pashtuns, Tajiks, Hazaras, and Uzbeks was 42.4, 48.4, 52.5, and 40.3 %, respectively. There was no significant difference between these populations for the genotypic distribution of the GSTM1 polymorphism (χ(2) = 4.67, df = 3, P = 0.197). The frequency of GSTT1 null genotype in Pashtuns, Tajiks, Hazaras, and Uzbeks was 7.4, 25.3, 25.0, and 29.0 %, respectively. The observed difference between populations for prevalence of GSTT1 null genotype was statistically significant (χ(2) = 35.54, df = 3, P < 0.001). In comparison with European and Asian populations, Afghanistan populations like Iranian populations showed intermediate frequency for GSTT1 and GSTM1 null genotypes.

Glutathione S-transferase genetic polymorphisms (GSTM1, GSTT1 and GSTO2) in three Iranian populations

Genetic polymorphisms in genes encoding glutathione S-transferases M1 (GSTM1; a member of class mu), T1 (GSTT1; a member of class theta) and O2 (GSTO2; a member of class omega) have been defined previously. Studies have revealed that there were significant differences between populations for allelic frequencies of GSTT1, GSTM1 and GSTO2 N412D polymorphisms. To get more insight into the genetic structure of Iranian populations the present study was done on Iranian Georgians living in Frydoonshahr (Isfahan province) and two Persian populations who living in Shiraz (Fars province) and Frydoonshahr. Study subjects consisted of 401 unrelated healthy individuals. From these 121 were Georgians. The remaining subjects were Persians from either Frydoonshahr (n = 34) or Shiraz (n = 246). The genetic polymorphism of GSTT1, GSTM1 and GSTO2 N412D was detected by PCR-based method. The frequency of GSTT1 null genotype in Georgian and Persians of Frydoonshahr and Shiraz was 15.7, 35.2 and 24.8%, respectively. There was significant difference between these populations for the distributions of the GSTT1 genotypes (chi(2) = 7.00, df = 2, P = 0.030). No significant difference was observed between these populations for polymorphisms of GSTM1 (chi(2) = 1.682, df = 2, P = 0.431) and GSTO N142D (chi(2) = 4.622, df = 4, P = 0.328). The prevalence of GSTT1 null genotype in Iranian Georgians showed significant difference with Persians and other Asian countries, but it seems to be similar with the frequency which was reported from European populations.

Association between genetic polymorphism of GSTT1 and depression score in individuals chronically exposed to natural sour gas

In order to investigate the association between effects of genetic polymorphisms of GSTT1 and GSTM1 and depression score of individuals chronically exposed to natural sour gas containing sulfur compounds, the present cross-sectional study was done. The study was performed on 124 healthy females living in the polluted area of Masjid-i-Sulaiman (MIS; Khozestan province, southwest of Iran). The GSTT1 and GSTM1 genotypes were determined using a polymerase chain reaction (PCR)-based method. Depression and hopelessness scores were determined by means of Beck's depression inventory (BDI) and Beck's hopelessness scale (BHS), respectively. The BHS score was positively correlated to the depression score (beta=0.687, t=10.474, p<0.001). The GSTT1 active genotype decreased the BDI score (beta=-0.161, t=-2.451, p=0.016). Polymorphism of GSTM1 may not be a good predictive factor for BDI (beta=-0.056, t=-0.857, p=0.393). There is no evidence for additive effect of GSTM1 and GSTT1 polymorphisms on BDI score. It is supposed that chronic exposure to natural sour gas may positively associated with DNA strand breaks and apoptosis in brain, especially in GSTT1 null genotype persons; finally living in the contaminated areas of MIS is associated with high BDI score.

Genetic polymorphisms of glutathione S-transferase T1 (GSTT1) and alterations of sex hormones in filling-station workers

OBJECTIVE

To determine the health effects of gasoline exposure as measured by levels of sex hormones (total testosterone, follicle-stimulating hormone [FSH], and luteinizing hormone [LH]) of male filling-station workers.

DESIGN

Case-control study.

SETTING

Filling stations in Shiraz (Fars province, Iran).

PATIENT(S)

One hundred fourteen male gasoline workers and 112 age-matched (+/-5 years) and sex-matched controls with no occupational exposure to gasoline.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Serum levels of testosterone, FSH, and LH, and expression of the GSTT1 genotype.

RESULT(S)

All hormone measurements were in the normal range although subclinical changes were detected in some indexes. Men exposed to petrochemicals had lower mean serum testosterone levels compared with unexposed men, regardless of the presence of the GSTT1 genotype. However, this decrease (expressed as mean +/- standard deviation) is most pronounced in the group possessing the GSTT1-null genotype (4.26 +/- 1.44 ng/mL vs. 5.48 +/- 0.98 ng/mL) compared with the group possessing the GSTT1 genotype (4.23 +/- 1.73 ng/mL vs. 4.67 +/- 1.21 ng/mL). The LH levels varied between the two groups; the mean serum LH was lower in the exposed versus unexposed men who possessed the GSTT1 genotype (2.82 +/- 1.32 IU/L vs. 3.20 +/- 1.17 IU/L) and higher in the exposed versus unexposed men who possessed the GSTT1-null genotype (3.52 +/- 1.37 IU/L vs. 2.76 +/- 1.07 IU/L).

CONCLUSION(S)

Testosterone levels were statistically significantly decreased in male gasoline workers compared with men who had had no occupational exposure to gasoline. The relevance of the GSTT1 genotype to these differences remains to be determined.

Genetic polymorphism of GSTT1 may be under natural selection in a population chronically exposed to natural sour gas

OBJECTIVE

In order to examine whether chronic exposure to natural sour gas containing sulfur compounds act as natural selection force on genetic polymorphisms of glutathione S-transferase M1 (GSTM1) and T1 (GSTT1), the present study was done.

METHODS

The study was performed on two groups of healthy individuals of Masjid-i-Sulaiman (Khozestan province, southwest of Iran) citizens with the mean ages of 47.5 +/- 12.4 (36 male and 58 female) and 16.3 +/- 2.4 (47 male and 140 female) that were considered as first and second generation, respectively. The GSTT1 and GSTM1 genotypes were determined using a PCR-based method.

RESULTS

The genotypic frequencies of GSTM1 did not change significantly (chi(2) = 0.085, df = 1, P = 0.770). The frequency of the GSTT1 null genotype was 52.1% in the first generation and reached to 36.4% in the second generation. There was significant difference between two generations for the GSTT1 polymorphism (chi(2) = 6.397, df = 1, P = 0.011).

CONCLUSION

It was suggested that the GSTT1 polymorphism may be under natural selection because of probably favored ability of GSTT1-active genotype to survival and reproduction.

Alterations of liver function test indices of filling station workers with respect of genetic polymorphisms of GSTM1 and GSTT1

To determine the health effects of gasoline exposure on liver function test indices of filling station workers the present study was done. This case-control study was conducted in Shiraz on 56 male gasoline workers and 56 age- and sex-matched control subjects with no occupational exposure to gasoline. To elucidate the role of hepatic detoxifying enzymes, the genotypes of glutathione-S-transferases (GST) M1 and T1 were determined. Data analysis was done by multiple linear regression analysis and non-parametric Kruskal-Wallis test. The present study showed that all measurements were in normal range, although sub-clinical changes were detected in some indices. In liver function tests, exposure was associated with lower serum albumin (t=-3.88, P<0.001) and total proteins (t=-3.016, P=0.003) but higher alanine aminotransferase (t=2.856, P=0.005) and aspartate aminotransferase (t=2.11, P=0.038) levels in workers comparing to controls. Other investigators reported that GSTs involved in detoxification of several toxins including some of the compounds present in gasoline. Therefore, the possible influence of GSTT1 and GSTM1 genetic polymorphisms on alteration of liver function tests indices was investigated. The present findings showed that the genotype combinations of GSTM1 and GSTT1 did not alter the effects of exposure to gasoline in workers except for serum albumin. Serum albumin significantly decreased in workers with both active GST enzymes who had more than 5 years of employments (P=0.01). It is suggested that GSTM1 and GSTT1 are not involved in detoxification of toxicants present in gasoline which are hazardous to liver. Overall, due to detection of sub-clinical changes in hepatic test in gasoline station workers, exposure limitation and administrating safety device are recommended.