GSTM1, GSTT1, and GSTP1 polymorphism in north Indian population and its influence on the hydroquinone-induced in vitro genotoxicity

A field-based investigation of simple phenol variation in Australian Agaricus xanthodermus

Agaricus xanthodermus and other species of the yellow-staining section Xanthodermatei are responsible for mushroom-related poisoning cases that require treatment. However, longstanding anecdotal evidence indicates that this species appears to exhibit considerable variation in toxicity, resulting in gastrointestinal irritation of varying severity in most cases. We quantified the amount of phenol, hydroquinone, and catechol in mushrooms using a novel protocol for gas chromatography-mass spectrometry (GC-MS) and investigated their levels in different basidiomatal structures, different developmental stages, and on different nutritional substrates. Phenol concentration was greater in the pileus than the stipe, in mature compared with immature basidiomata, and in basidiomata occurring in woody mulch versus lawns. Variation in toxicity is suggested to be due in part to variation in phenol concentration, developmental stage and tissue type consumed, and substrate. Variation in human sensitivity to simple phenols may also play a role but was not formally investigated in this study.

Shielding effect of anethole against arsenic induced genotoxicity in cultured human peripheral blood lymphocytes and effect of GSTO1 polymorphism

Chronic exposure of inorganic arsenic compounds is responsible for the manifestation of various tumours as well as other diseases. The principal mechanism behind arsenic toxicity is the induction of a strong oxidative stress with production of free radicals in cells. The present study was aimed to explore the shielding effect of anethole against oxidative damage induced by arsenic in cultured human peripheral blood lymphocytes and the effect of GSTO1 polymorphism. Sister chromatid exchange (SCE) frequency, comet tail moment and lipid peroxidation levels were used as biomarkers to assess the oxidative damage. Heparinised venous blood was collected from healthy individuals and treated with sodium arsenite (50 µM) in the presence of anethole (25 and 50 µM) for the analysis of shielding effect of anethole. For the genotyping of GSTO1, PCR RFLP method was adopted. A significant dose-dependent increase in the frequency of SCEs, tail moment and lipid peroxidation levels, was observed when lymphocytes were treated with sodium arsenite. Anethole in combination with sodium arsenite has shown a dose-dependent significant decrease in the frequency of SCEs, tail moment and lipid peroxidation levels. Genetic polymorphism of GSTO1 was found to effect individual susceptibility towards arsenic-mediated genotoxicity and was found insignificant when antigenotoxic effect of anethole was considered. GSTO1 mutant genotypes were found to have significant higher genotoxicity of sodium arsenite as compared to wild-type genotype. The results of the present study suggest ameliorative effects of anethole against arsenic-mediated genotoxic damage in cultured human peripheral blood lymphocytes. A significant effect of GSTO1 polymorphism was observed on genotoxicity of sodium arsenite.

Glutathione S-Transferase Gene Polymorphisms: Modulator of Genetic Damage in Gasoline Pump Workers

This study investigated genetic damage in gasoline pump workers using the cytokinesis blocked micronucleus (CBMN) assay. Blood and urine samples were collected from 50 gasoline pump workers and 50 control participants matched with respect to age and other confounding factors except for exposure to benzene through gasoline vapors. To determine the benzene exposure, phenol was analyzed in urinary samples of exposed and control participants. Urinary mean phenol level was found to be significantly high (P < 0.05) in exposed workers. The CBMN frequency was found to be significantly higher in gasoline pump workers (6.70 ± 1.78) when compared to control individuals (2.20 ± 0.63; P < 0.05). We also investigated influence of polymorphisms of GSTM1, GSTT1, and GSTP1 genes on CBMN frequency. The individuals having GSTM1 and GSTT1 null genotypes had significantly higher frequency of CBMN (P < 0.05). Our study indicates that chronic and long-term exposure of gasoline vapors can increase genotoxic risk in gasoline pump workers.

Micronucleus induction by oxidative metabolites of trichloroethylene in cultured human peripheral blood lymphocytes: a comparative genotoxicity study

The genotoxic effects of oxidative metabolites of trichloroethylene (TCE), namely chloral hydrate, trichloroacetic acid (TCA), dichloroacetic acid (DCA), and trichloroethanol (TCEOH) were examined in human peripheral blood lymphocytes. In this context, lymphocytes were exposed in vitro to 25, 50, and 100 μg/ml concentrations of these metabolites separately for a period of 48 h and examined for micronucleus (MN) induction through flow cytometer. At 50 μg/ml TCE metabolites, TCA (6.33 ± 0.56 %), DCA (5.06 ± 0.55), and TCEOH (4.70 ± 1.73) induced highly significant (p<0.001) frequency of MN in comparison to control (1.03 ± 0.40) suggestive of their genotoxic potential. However, exposure of 100 μg/ml of all the metabolites consistently declined the frequencies of MN which in some cases was equable to that of observed at 25 μg/ml. Further, cytotoxicity and cell cycle disturbances were also measured to find out the association of these endpoints with the MN induction. DNA content analysis revealed 3-4-fold elevation of S-phase at all the concentrations tested. Particularly, at 100 μg/ml, treatment elevation of S-phase was significantly (p<0.0001) higher as compared to the control. Present findings together with earlier reports indicate that TCE induces genotoxicity through its metabolites. Interaction of these metabolites with DNA, as evident by elevated S-phase, seems to be the major cause of MN induction. However, involvement of spindle disruption cannot be ruled out. This comparative study also suggests that after TCE exposure, the metabolic efficiency of human to generate oxidative metabolites determines the extent of genotoxicity.

Genetic predisposition for dermal problems in hexavalent chromium exposed population

We studied the effect of genetic susceptibility on hexavalent chromium induced dermal adversities. The health status of population was examined from the areas of Kanpur (India) having the elevated hexavalent chromium levels in groundwater. Blood samples were collected for DNA isolation to conduct polymorphic determination of genes, namely: NQO1 (C609T), hOGG1 (C1245G), GSTT1, and GSTM1 (deletion). Symptomatic exposed subjects (n = 38) were compared with asymptomatic exposed subjects (n = 108) along with asymptomatic controls (n = 148) from a non contaminated reference community. Exposed symptomatic group consisted of 36.8% subjects who were GSTM1 null genotyped as compared to asymptomatic where only 19.4% subjects were null. The exposed subjects with GSTM1 null genotype were more susceptible to dermal adversities in comparison with wild genotyped subjects (OR = 2.42; 95% CI = 1.071-5.451). Age, smoking, gender or duration of residence were not found to have any confounding effect towards this association. Association with other genes was not statistically significant, nonetheless, possible contribution by these genes cannot be ruled out. In conclusion, variation in the polymorphic status of GSTM1 gene may influence dermal outcomes among residents from Cr(VI) contaminated areas. Further studies are therefore, needed to examine these observations among different population groups.

Genome-wide functional profiling reveals genes required for tolerance to benzene metabolites in yeast

Benzene is a ubiquitous environmental contaminant and is widely used in industry. Exposure to benzene causes a number of serious health problems, including blood disorders and leukemia. Benzene undergoes complex metabolism in humans, making mechanistic determination of benzene toxicity difficult. We used a functional genomics approach to identify the genes that modulate the cellular toxicity of three of the phenolic metabolites of benzene, hydroquinone (HQ), catechol (CAT) and 1,2,4-benzenetriol (BT), in the model eukaryote Saccharomyces cerevisiae. Benzene metabolites generate oxidative and cytoskeletal stress, and tolerance requires correct regulation of iron homeostasis and the vacuolar ATPase. We have identified a conserved bZIP transcription factor, Yap3p, as important for a HQ-specific response pathway, as well as two genes that encode putative NAD(P)H:quinone oxidoreductases, PST2 and YCP4. Many of the yeast genes identified have human orthologs that may modulate human benzene toxicity in a similar manner and could play a role in benzene exposure-related disease.