Genetic Polymorphisms in Metabolizing Enzymes and Susceptibility of Chromosomal Damage Induced by Vinyl Chloride Monomer in a Chinese Worker Population

Plasma cholinesterase activity is influenced by interactive effect between omethoate exposure and CYP2E1 polymorphisms

The aim of this study was to explore the association between metabolizing enzyme gene polymorphisms and the decrease in cholinesterase activity induced by omethoate exposure. A total of 180 workers exposed to omethoate over an extended period were recruited along with 115 healthy controls. Cholinesterase activity in whole blood, erythrocyte, and plasma was detected using acetylthiocholine and the dithio-bis-(nitrobenzoic acid) method. Six polymorphic loci of GSTT1(+/-), GSTM1(+/-), GSTP1 rs1695, CYP2E1 rs6413432, CYP2E1 rs3813867, and PON2 rs12026 were detected by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). The gene-environment interactions were analyzed using the generalized linear model method. The cholinesterase activity of erythrocyte and plasma in the exposure group was significantly lower than that in the control group (P < 0.001) in general. The plasma cholinesterase activity in the TT + AT genotype in CYP2E1 rs6413432 was lower than that in the AA genotype in the exposure group (P = 0.016). Interaction between the AA genotype in CYP2E1 rs6413432 and omethoate exposure had a significant effect on plasma cholinesterase activity (P = 0.079). The decrease in plasma cholinesterase activity was associated with interaction between the AA genotypes in rs6413432 and omethoate exposure.

Genetic polymorphisms of metabolic enzyme genes associated with leukocyte mitochondrial DNA copy number in PAHs exposure workers

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) exposure had been reported to be a risk factor of mtDNAcn in our early study. However, the effect of metabolic enzymes' genetic polymorphisms on mtDNAcn in PAHs-Exposure workers has not been fully evaluated.

AIM

The aim of the study was to explore the effect of metabolic enzymes' genetic polymorphisms on mtDNAcn in PAHs-Exposure.

METHODS AND RESULTS

We investigated the effects of metabolic enzymes' genetic polymorphisms on mtDNAcn among 544 coke oven workers and 238 office staffs. The mtDNAcn of peripheral blood leukocytes was measured using the Real-time quantitative polymerase chain reaction (PCR) method. PCR and restriction fragment length was used to detect five polymorphisms in GSTT1, GSTM1, GSTP1 rs1695, CYP2E1 rs6413432, and CYP2E1 rs3813867. The mtDNAcn in peripheral blood leukocytes was significantly lower in the exposure group than that in the control group (p < .001). The 1-OHPYR had an increasing trend with the genotypes AA→AG → GG of GSTP1 rs1695 in the control group. Generalized linear model indicated that the influencing factors of mtDNAcn were PAHs-exposure [β (95% CI) = -0.420 (-0.469, -0.372), p < .001], male [β (95% CI) = -0.058 (-0.103, -0.012), p = .013], and AA genotype for GSTP1 rs1695 [β (95% CI) = -0.051 (-0.095, -0.008), p = .020].

CONCLUSION

The individuals carrying the AA genotype of GSTP1 rs1695 may have a lower mtDNAcn due to their weaker detoxification of PAHs.

The interaction effects of coke oven emissions exposure and metabolic enzyme Gene variants on total antioxidant capacity of workers

OBJECTIVES

The aim of this study was to investigate the association between coke oven emissions (COEs) exposure and total antioxidant capacity (T-AOC), and to explore whether genetic variations in metabolic enzyme genes GSTT1, GSTM1, GSTP1, and CYP2E1 can affect these associations in coke oven workers.

METHODS

536 coke oven workers and 238 healthy controls were recruited. T-AOC of plasma was determined with kit. Five polymorphic loci of GSTT1 (+/-), GSTM1 (+/-), GSTP1 rs1695, CYP2E1 rs6413432 and CYP2E1 rs3813867 were detected by polymerase chain reaction and restriction fragment length polymorphism.

RESULTS

This study shows that the T-AOC in exposure group (12.02 ± 4.72) was significantly lower than that in control group (15.32 ± 7.19) (P < 0.01), and the COEs exposure could decrease the T-AOC of coke oven workers significantly [β(95% CI) = -2.663 (-4.538,-0.787), P < 0.001]. The T-AOC of female was lower than that of male in exposed and control groups (P < 0.001). The T-AOC was higher in GSTM1 (-) individuals than in GSTM1 (+) individuals in the control group (P = 0.037). The T-AOC with the AG genotype in GSTP1 rs1695 polymorphism was higher than that of the GG genotype in the control group (P = 0.043). The generalized linear model results showed that the risk factors for the decrease of T-AOC include GSTT1 (+) (b = -0.999, P = 0.009), female (b = -2.875, P < 0.01), COEs-exposed (b = -2.712, P = 0.004), GSTM1 (+) (b = -1.814, P = 0.008), and interactions of GSTM1 (+) and COEs-exposed (b = 1.872, P=0.024).

CONCLUSIONS

The risk factors for the decrease of T-AOC include GSTT1 (+), female, COEs-exposed, GSTM1 (+), and interactions of GSTM1 (+) and COEs-exposed.

Cross-sectional associations between genetic polymorphisms in metabolic enzymes and longer leukocyte telomere length induced by omethoate

Purpose

This study aimed to explore the effects of genetic polymorphisms in metabolic enzymes on relative telomere length changes and explore the mechanism of canceration induced by omethoate.

Materials and Methods

180 long-term omethoate-exposed workers and 115 healthy controls were recruited. Real-time PCR method was applied to determine the relative telomere length in peripheral blood leukocytes DNA, and Six polymorphic loci of GSTT1(+/−), GSTM1(+/−), GSTP1 rs1695, CYP2E1 rs6413432, CYP2E1 rs3813867 and PON2 rs12026 were detected by polymerase chain reaction and restriction fragment length polymorphism method; Multiple linear regression was conducted to explore the effects of omethoate exposure and genetic polymorphisms on the telomere length.

Results

The relative telomere lengths in the control group (0.94 [0.76, 1.32]) were significantly shorter than that in the exposure group (1.50 [1.11, 2.57]) (Z = 7.910, P < 0.001). Univariate analysis showed that the relative telomere lengths of the GSTM1-deletion individuals were significantly longer than that of the non - deletion genotype in the control group (Z = 2.911, P = 0.004), and the relative telomere lengths of GSTP1 rs1695 polymorphism locus (GG+AG) genotype individuals were longer than that of AA genotype in the exposure group. The difference was statistically significant (Z = 2.262, P = 0.024). Multivariate analysis found that pesticide-exposure (b = 0.524, P < 0.001) and GSTM1 polymorphism (b = −0.136, P = 0.029) had an impact on telomere length.

Conclusions

The relative telomere lengths of omethoate-exposure workers were longer than that in the control population. Also GSTM1 genetic polymorphism may influence the changes of the telomere length induced by omethoate.

Polymorphisms in the p53 pathway genes and micronucleus occurrence in Chinese vinyl chloride-exposed workers

OBJECTIVES

To investigate the association between polymorphisms in the p53 pathway genes and chromosomal damage in vinyl chloride (VC)-exposed workers.

MATERIALS AND METHODS

Cytokinesis block micronucleus test was performed in 310 VC-exposed workers and 149 non-exposed workers to determine chromosomal damage. The polymerase chain reaction and restriction fragment length polymorphism technique were used to detect six SNPs in the p53 pathway genes involved in the cell cycle.

RESULTS

There was a highly significant dose-response relationship between VC exposure and chromosomal damage. Individuals carrying the variant genotypes were at higher risk for chromosomal damage compared with their wild type genotype: p53rs1042522, MDM2 Del1518rs3730485, MDM2rs2279744 and GADD45Ars532446. On the other hand, individuals possessing the variant genotype of CDKN2A rs3088440 had significantly decreased risk compared with the corresponding wild-type.

CONCLUSIONS

Genetic polymorphisms in P53 pathway genes may have an impact on VC-induced chromosomal damage.

Estimation of a safe level for occupational exposure to vinyl chloride using a benchmark dose method in central China

OBJECTIVES

The aim of this study was to estimate a benchmark dose (BMD) for chromosome damage induced by vinyl chloride monomer (VCM) in VCM-exposed workers in central China and validate the published results in Shanghai.

METHODS

VCM-exposed workers who had been exposed to VCM for at least one year (n=463) and matched subjects not exposed to VCM or other toxins (n=273) were asked to participate in this study. Micronucleus (MN) frequency based on the cytokinesis-block micronucleus assay (CBMN) was used as a biomarker for chromosome damage induced by VCM exposure.

RESULTS

The MN frequency in the VCM-exposed workers was significantly higher than that in the control group, and multivariate Poisson regression suggested that gender, smoking status and VCM exposure were the significant factors influencing the risk of increased MN frequency. When subjects were further stratified according to gender and smoking status, the results showed that female VCM-exposed workers were more susceptible than the males to the risk of increased MN frequency. The MN frequency of smokers was significantly higher than that of nonsmokers in the control group. Our study also suggested that there was a strong dose-response relationship between VCM CED and the increased risk of MN frequency in the total group, males and females. The BMDL(10) was found to be 630.6, 670.2 and 273.7 mg-year for all VCM-exposed workers, males and females, respectively.

CONCLUSIONS

These results invite further scrutiny of the current VCM occupational exposure limits and warrant further study of the risk of VCM genotoxicity and carcinogenicity.

Plastics and carcinogenesis: The example of vinyl chloride

The manufacture, use and disposal of various plastics can pose numerous health risks, including the risk of cancer. A model example of carcinogenic risk from plastics is provided by polyvinyl chloride, since it is composed of the known human carcinogen vinyl chloride (VC). In recent years, much has been learned about the molecular biological pathways of VC carcinogenesis. This has led to molecular epidemiologic studies of VC carcinogenesis in exposed human populations which have identified useful biomarkers of exposure, effect and susceptibility for VC. These studies have in turn provided the basis for new molecular approaches for the prevention and treatment of VC cancers. This model could have much wider applicability for many other carcinogenic exposures and many other human cancers.

Independent and combined effects of ethanol self-administration and nicotine treatment on hepatic CYP2E1 in African green monkeys

Cytochrome P450 2E1 metabolizes ethanol and also bioactivates many toxins and procarcinogens. Elevated levels of hepatic CYP2E1 are associated with an increased susceptibility to chemical toxicity and carcinogenesis. This study investigated the induction of hepatic CYP2E1 by ethanol and nicotine, alone and in combination, in a nonhuman primate model. Monkeys that self-administered ethanol and that received subcutaneous injections of nicotine (0.5 mg/kg b.i.d.), alone and in combination, were compared with control animals (four groups, n = 10/group). Chlorzoxazone (CZN) was used as a probe drug to phenotype in vivo CYP2E1 activity before and after chronic ethanol and/or nicotine exposure. CYP2E1 protein levels and in vitro chlorzoxazone metabolism were assessed in liver microsomes. Average daily ethanol consumption was ≈3.0 g/kg (blood ethanol levels ≈24 mM) and was unaffected by nicotine treatment. Ethanol self-administration and nicotine treatment, alone and in combination, significantly increased in vivo CZN disposition compared with that in control animals. The effect of ethanol was only observed at higher levels of intake. Ethanol and nicotine increased CYP2E1 protein levels and in vitro CZN metabolism, with combined exposure to both drugs resulting in the greatest increase. The effect of ethanol was also dependent on level of intake. Chronic exposure to ethanol and nicotine induced hepatic CYP2E1 activity and protein levels, particularly when both drugs were used in combination and when ethanol intake was high. These results have important implications for public health, given the association between elevated CYP2E1 and disease, and the large proportion of individuals who are exposed to ethanol and nicotine, often in combination.