Genetic polymorphisms of XRCC1, HOGG1 and MGMT and micronucleus occurrence in Chinese vinyl chloride-exposed workers

Regular Sport Activity Is Able to Reduce the Level of Genomic Damage

Regular physical activity is considered one of the most valid tools capable of reducing the risk of onset of many diseases in humans. However, it is known that intense physical activity can induce high levels of genomic damage, while moderate exercise can elicit a favorable adaptive response by the organism. We evaluated, by the buccal micronuclei assay, the frequencies of micronuclei, nuclear buds and binucleated cells in a sample of amateur athletes practicing different disciplines, comparing the obtained data with those of subjects who practiced sports just occasionally and subjects that did not practice sport at all. The aim was to evaluate whether physical activity affects background levels of genomic damage and whether the different sports disciplines, as well as some gene polymorphisms, differentially affect these levels. A total of 206 subjects, 125 athletes and 81 controls, were recruited. Athletes showed significantly lower values of micronuclei, nuclear buds and binucleated cells with respect to controls. Sprinters and Martial Artists displayed significantly higher frequencies of micronuclei than other categories of athletes. Finally, neither sex nor gene polymorphisms seemed to influence the levels of genomic damage, confirming that the observed genomic damage is probably due to the nature of the sport activity.

Genotoxic evaluation of occupational exposure to antineoplastic drugs

During the last years, several reports have provided evidence about adverse health effects on personal involved in Antineoplastic Drugs (ANPD) handling. ANPD has the ability to bind DNA, thus produce genotoxic damage. In this way, XRCC1 and XRCC3 proteins are necessary for efficient DNA repair and polymorphisms in this genes can be associated with an individual response to ANPD exposure. Therefore, the aim of this study was to evaluate genetic damage of occupational exposure to antineoplastic drugs and the possible effect of XRCC1 and XRCC3 polymorphisms in oncology employees from Bogotá, Colombia. Peripheral blood samples were obtained from 80 individuals, among exposed workers and healthy controls. The comet assay and Cytokinesis-block micronucleus cytome assay was performed to determinate genetic damage. From every sample DNA was isolated and genotyping for XRCC1 (Arg194Trp, Arg280His and Arg399Gln) and XRCC3 (Thr241Met) SNPs by PCR-RFLP. The exposed group showed a significant increase of comet assay results and micronucleus frequency, compared with unexposed group. It was observed a gender, exposure time and workplace effect on comet assay results. Our results showed no significant associations of comet assay results and micronucleus frequency with either genotype, allele, nor haplotype of XRCC1 and XRCC3 SNPs. The results suggest that occupational exposure to ANPD may lead to genotoxic damage and even be a risk to human health. To our knowledge, this is the first study to assess the genotoxic damage of occupational exposure to APND in South America.

Investigation of pesticide exposure by genotoxicological, biochemical, genetic polymorphic and in silico analysis

Soybean farmers are exposed to various types of pesticides that contain in their formulations a combination of chemicals with genotoxic and mutagenic potential. Therefore, the objective of this paper was to evaluate the genetic damages caused by this pesticide exposure to soybean producers in the state of Mato Grosso (Brazil), regarding biochemical, genetic polymorphic and in silico analyses. A total of 148 individuals were evaluated, 76 of which were occupationally exposed and 72 were not exposed at all. The buccal micronucleus cytome assay (BMCyt) detected in the exposed group an increase on DNA damage and cell death. No inhibition of butyrylcholinesterase (BchE) was observed within the exposed group. The detection of inorganic elements was made through the particle-induced X-ray emission technique (PIXE), which revealed higher concentrations of Bromine (Br), Rubidium (Rb) and Lead (Pb) in rural workers. A molecular model using in silico analysis suggests how metal ions can cause both DNA damage and apoptosis in the exposed cells. Analysis of the compared effect of X-ray Repair Cross-complement Protein 1 (XRCC1) and Paraoxonase 1 (PON1) genotypes in the groups demonstrated an increase of binucleated cells (exposed group) and nuclear bud (non-exposed group) in individuals with the XRCC1 Trip/- and PON1 Arg/- genes. There was no significant difference in the telomere (TL) mean value in the exposed group in contrast to the non-exposed group. Our results showed that soybean producers showed genotoxic effect and cell death, which may have been induced by exposure to complex mixtures of agrochemicals and fertilizers. In addition, XRCC1 Arg/Arg could, in some respects, provide protection to individuals.

Evaluation of baseline frequency of sister chromatid exchanges in an Italian population according to age, sex, smoking habits, and gene polymorphisms

OBJECTIVES

Increased SCEs frequencies in human lymphocytes are an indicator of spontaneous chromosome instability and could be influenced by different exogenous and endogenous factors. In this study, we evaluated the influence of age, sex, smoking habits, and genetic polymorphisms on the background levels of SCEs in peripheral blood lymphocytes.

METHODS

Two hundred-thirty healthy Italian subjects were recruited. Data about age, sex and smoking habits were recorded. Subjects were also genotyped for GSTT1, GSTM1, GSTP1 A/G, CYP1A1 Ile/Val, CYP2C19 G/A, ERCC2/XPD Lys751Gln, XRCC1 Arg194ATrp, XRCC1 Arg399Gln, and XRCC1Arg208His gene polymorphisms.

RESULTS

The frequency of SCEs/cell was 5.15 ± 1.87, with females showing a significantly higher SCEs value with respect to males (5.36 ± 2.10 and 4.82 ± 1.39, respectively). Smokers showed significantly increased levels of SCEs with respect to nonsmokers (5.93 ± 1.75 and 4.70 ± 1.79, respectively) whereas no differences were observed between heavy and light smokers. Age correlated with the RI value (P = .01) but not with the SCEs frequency (P = 07), although the 31-40 age group showed a significantly lower SCEs frequency with respect to the other age groups. A significant association was also found between GSTP2C19-AA, GSTT1-null, GSTM1-null, ERCC2/XPD Gln751Gln, and XRCC1 His208His genotypes, and higher frequencies of SCEs.

CONCLUSION

We describe the association between some phase I, phase II, and DNA-repair gene polymorphisms with increased SCEs frequencies, reinforcing the importance of genetic analysis in biomonitoring studies. Sex and age were found to be important endogenous factors that affect the level of genomic damage and the replicative capacity of cells, respectively.

Exploring a new method for the biological monitoring of plastic workers exposed to the vinyl chloride monomer

Vinyl chloride monomer (VCM) is widely used in the production of polyvinyl chloride (PVC) plastics. VCM is recognized as a confirmed human and animal carcinogenic compound. Recent studies have reported poor health of plastic workers, even having exposure at concentrations below the permissible limit to VCM. There has not been any study regarding exposed workers to VCM in Iran. Similarly, no information exists as to the biological monitoring of such workers. The main purpose of this study was to conduct a thorough occupational and biological monitoring of Iranian plastic workers exposed to VCM.A total of 100 workers from two plastic manufacturing plants (A and B) in Tehran along with 25 unexposed workers as controls were studied. The personal monitoring of all nonsmoking workers exposed to VCM at two plastic manufacturing plants (A and B) was performed in the morning shift (8 a.m. to 4 p.m.) according to the National Institute For Occupational Safety And Health method no. 1007.Biological monitoring of workers was carried out through collection of exhaled breath of all exposed and control workers in Tedlar bags and with a subsequent analysis using gas chromatography-flame ionization detector.Not only the mean occupational exposure of workers to VCM at plant A was higher than the respective threshold limit value but also the statistical significance was higher than workers at plant B. Similarly, VCM concentration in exhaled breath of workers at plant A was also statistically significantly higher than at plant B. Correlation of occupational exposure of all workers to vinyl chloride with its concentration in exhaled breath was statistically significant.This is the first study on biological monitoring for exposed plastic workers to VCM using exhaled breath. On the basis of the results in this study, a novel method of biological monitoring of plastic workers was proposed.

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.

A comprehensive analysis of plausible genotoxic covariates among workers of a polyvinyl chloride plant exposed to vinyl chloride monomer

The aim of this study was to assess the frequency of chromosomal aberrations-including chromatid type aberrations (CTAs), chromosomal type aberrations, micronucleus (MN) comet assay, and XRCC1 399 Arg/Gln polymorphism-in peripheral blood lymphocytes of workers occupationally exposed to vinyl chloride monomer (VCM). A total of 52 workers and an equal number of controls were recruited into the study to explore the potential cytogenetic risk of occupational exposure to VCM. Questionnaires were administered to obtain details of habitual cigarette-smoking, alcohol-consumption pattern, and occupation, etc. The exposed subjects and controls were classified into two groups based on age (group I <40 years; group II ≥40 years), and exposed subjects were further classified based on exposure duration (>8 and ≥8 years). CTA, MN, and comet assay frequency were significantly greater in polyvinyl chloride (PVC) factory workers (p < 0.05) with long-duration work. CTA, MN, and comet assay values were found to be increased with age in exposed subjects as well as in controls, with exposed subjects showing a statistically greater degree. An extensively greater MN frequency was observed in smokers exposed to VCM than in the control group (P < 0.05). The mean tail length of exposed subjects was greater compared with controls. The study on XRCC1 399 Arg/gln polymorphism in PVC factory workers showed less significant difference in allele frequency compared with controls. In conclusion, this results of work provides evidence for an apparent genotoxic effect associated with VCM exposure. Our results reinforce the greater sensitivity of cytogenetic assays for biomonitoring of occupationally exposed populations. Statistics indicate that workers exposed to VCM are at carcinogenic risk and should be monitored for long-term adverse effects from their exposure.

Estimation of benchmark dose for micronucleus occurrence in Chinese vinyl chloride-exposed workers

In this study, we estimated the possibility of using benchmark dose (BMD) to assess the dose-response relationship between vinyl chloride monomer (VCM) exposure and chromosome damage. A group of 317 workers occupationally exposed to vinyl chloride monomer and 166 normal, unexposed control in Shandong Province northern China were examined for chromosomal damage in peripheral blood lymphocytes (PBL) using the cytokinesis-blocked micronucleus (CB-MN) assay of DNA damage. The exposed group (3.47 ± 2.65)‰ showed higher micronucleus frequency than the control (1.60 ± 1.30)‰ (P < 0.01). Occupational exposure level based on micronucleus occurrence in all individuals was analyzed with benchmark dose (BMD) methods. The benchmark dose lower limit of a one-sided 95% confidence interval (BMDL) for 10% excess risk was also determined. Results showed a dose-response relationship between cumulative exposure and MN frequency, and a BMDL of 0.54 mg/m3 and 0.23 mg/m3 for males and females, respectively. Female workers were more susceptible to MN damage than male workers.

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.

Polymorphism in the DNA repair enzyme XRCC1: utility of current database and implications for human health risk assessment

Genetic polymorphisms are increasingly recognized as sources of variability not only in toxicokinetic but also in toxicodynamic response to environmental agents. XRCC1 is involved in base excision repair (BER) of DNA; it has variant genotypes that are associated with modified repair function. This analysis focuses on four polymorphisms: three in the coding region that affect protein structure and one in an upstream regulatory sequence that affects gene expression. The Arg399Gln variant is the most widely studied with evidence supporting a quantitative effect of genotype on phenotype. The homozygous variant (Gln/Gln) can have 3-4-fold diminished capacity to remove DNA adducts and oxidized DNA damage. This variant is relatively common in Caucasians and Asians where approximately 10% are homozygous variant. In contrast, the Arg194Trp variant appears to protect against genotoxic effects although the degree to which DNA repair is enhanced by this polymorphism is uncertain. The homozygous variant is rare in Caucasians and African Americans but it is present at 7% in Asians. A third coding region polymorphism at codon 280 appears to decrease repair function but additional quantitative information is needed and the homozygous variant is rare across populations studied. A polymorphism in an upstream promoter binding sequence (-77T>C) appears to lower XRCC1 levels by decreasing gene expression. Based upon genotype effect on phenotype and allele frequency, the current analysis finds that the codon 399 and upstream (-77) polymorphisms have the greatest potential to affect the toxicodynamic response to DNA damaging agents. However, the implications for risk assessment are limited by the likelihood that polymorphisms in multiple BER genes interact to modulate DNA repair.