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

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.

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.