Genetic polymorphisms of genes involved in DNA repair and metabolism influence micronucleus frequencies in human peripheral blood lymphocytes.

The cytokinesis-block micronucleus cytome (CBMNCyt) assay is a widely used technique for measuring DNA damage in human populations. The formation of micronuclei (MN) in dividing cells can result from chromosome breakage due to unrepaired or mis-repaired DNA lesions or chromosome malsegregation due to mitotic malfunction. The sensitivity of the MN assay to polymorphisms in various genes involved in DNA repair, activation/deactivation of carcinogens/chemicals/drugs/alcohol, folate metabolism pathway and micronutrient transport has been extensively reported in the literature. MN frequency is also an important index for determining DNA repair efficiency phenotype (including mis-repair), response to environmental exposure and identifying various dietary factors required for optimal genome stability. The aim of the present study is to review the reported in vivo associations between genotype and MN frequency in humans taking into considerations the presence of interactions with nutrients levels and/or exposure to genotoxins. One hundred and eleven publications linking MN frequency in peripheral blood lymphocytes to gene polymorphism were retrieved from PubMed. After applying exclusion criteria, only 37 studies were evaluated in the present review. Polymorphisms in XRCC1 (Arg280His), ERCC2 (Lys751Gln), CYP2E1 (c1/c2) and MTR (A2756G) were consistently associated with the MN formation. These results contribute substantial evidence to the hypothesis that genotype may influence MN frequency in human cells.

General practitioners and patients with psychological stress at work.

INTRODUCTION: Identifying patients with psychological stress at work (PSW) and managing them are complex tasks. We studied the frequency of PSW as perceived by general practitioners (GPs), their practices in such situations, and the factors associated with these perceptions and practices, especially drug prescription. METHODS: Cross-sectional telephone study of GPs in southeastern France with a questionnaire about knowledge, attitudes, behavior, and practices in occupational health. We explored the management of PSW with a case-vignette of a 45-year-old supermarket cashier consulting for psychological stress that he or she attributes to the job. RESULTS: In all, 391 GPs participated; 87.2% reported that they encountered PSW often in their practice. GPs reported that they would treat the case-vignette patient by prescribing anxiolytics (66.5%) or sick leaves (65.7%) or referral to an occupational physician (80.3%) or a mental health specialist (44.8%). A multiple logistic regression showed that GPs reported prescribing an anxiolytic most frequently for the vignette-patient when they saw a high number of patients daily, asked patients about working conditions, suggested a sick leave or a referral to a specialist to the case-vignette patient and perceived more obstacles to reporting an occupational disease. CONCLUSION: Our study suggests that PSW is perceived by GPs as one of the principal work-related health problems and that in such situations, most GPs say they would prescribe drugs and sick leave and refer the patient to an occupational physician. Initial and continuing education programs and good practice guidelines would be useful to help them deal with these problems.

Inequities in reporting asbestos-related lung cancer: influence of smoking stigma and physician's specialty, workload and role perception.

OBJECTIVES: To study physician barriers to workers' compensation claims for asbestos-related cancers, focusing on smokers' stigma and physicians' speciality and role perception. METHODS: Cross-sectional telephone study of 486 randomly-selected general practitioners (GPs) and pulmonologists in south-eastern France. Standardised questionnaires explored their behaviour, attitudes and practices in the field of occupational health and their responses to a case vignette of a lung cancer patient with long-term occupational asbestos exposure. Randomised subgroups of GPs and pulmonologists heard alternative versions varying only as regards the worker's smoking status. We studied factors associated with the recommendation that the case vignette patient file a compensation claim with simple and multiple logistic regressions. RESULTS: The response rate was 64.4% among GPs and 62.5% among pulmonologists. Recommending the filing of an occupational disease claim was significantly associated in multiple logistic regressions with speciality (OR 4.46; 95% CI 2.38 to 8.37, for pulmonologists vs GPs), patient's smoking status (OR 3.15; 95% CI 2.11 to 4.70, for non-smokers vs smokers), physician's workload (OR 1.83; 95% CI 1.17 to 2.88, for 25) and role perception (OR 2.00; 95% CI 1.22 to 3.27, for those who considered completing occupational disease medical certificates to be part of their role vs those who did not). CONCLUSIONS: The results of this French study appear applicable to various countries and contexts. To make physicians and especially GPs more aware of occupational health and smoking stigma, officials and educators must give these topics higher priority during initial training and continuing medical education. Tools and equipment that take time constraints into account should be developed and disseminated to help physicians manage occupational diseases.

Genetic polymorphisms and micronucleus formation: a review of the literature.

The formation of micronuclei (MN) is extensively used in molecular epidemiology as a biomarker of chromosomal damage, genome instability, and eventually of cancer risk. The occurrence of MN represents an integrated response to chromosome-instability phenotypes and altered cellular viabilities caused by genetic defects and/or exogenous exposures to genotoxic agents. The present article reviews human population studies addressing the relationship between genetic polymorphisms and MN formation, and provides insight into how genetic variants could modulate the effect of environmental exposures to genotoxic agents, host factors (gender, age), lifestyle characteristics (smoking, alcohol, folate), and diseases (coronary artery disease, cancer). Seventy-two studies measuring MN frequency either in peripheral blood lymphocytes or exfoliated cells were retrieved after an extensive search of the MedLine/PubMed database. The effect of genetic polymorphisms on MN formation is complex, influenced to a different extent by several polymorphisms of proteins or enzymes involved in xenobiotic metabolism, DNA repair proteins, and folate-metabolism enzymes. This heterogeneity reflects the presence of multiple external and internal exposures, and the large number of chromosomal alterations eventually resulting in MN formation. Polymorphisms of EPHX, GSTT1, and GSTM1 are of special importance in modulating the frequency of chromosomal damage in individuals exposed to genotoxic agents and in unexposed populations. Variants of ALDH2 genes are consistently associated with MN formation induced by alcohol drinking. Carriers of BRCA1 and BRCA2 mutations (with or without breast cancer) show enhanced sensitivity to clastogens. Some evidence further suggests that DNA repair (XRCC1 and XRCC3) and folate-metabolism genes (MTHFR) also influence MN formation. As some of the findings are based on relatively small numbers of subjects, larger scale studies are required that include scoring of additional endpoints (e.g., MN in combination with fluorescent in situ hybridization, analysis of nucleoplasmic bridges and nuclear buds), and address gene-gene interactions.

Micronuclei frequency in peripheral blood lymphocytes of cancer patients: a meta-analysis.

Micronuclei (MN) frequency is a biomarker of chromosomal damage, genome instability, and cancer risk that integrates acquired mutations and genetic susceptibility. To evaluate and summarize the evidence reporting association between cancer and MN formation, we performed a meta-analysis assessing the frequency of this biomarker in cancer patients. Findings from 37 publications were retrieved through an extensive search of the MedLine/PubMed database. Given the heterogeneity of the study design, all studies were re-classified into three groups: (i) baseline MN frequency of untreated cancer patients (25 studies), (ii) induced MN frequency in thyroid cancer patients undergoing radioiodine treatment (9 studies), and (iii) radiosensitivity of lymphocytes (12 studies) in untreated cancer patients. A meta-estimate of the frequency ratio (meta-FR) was computed in each group. A significant increase of MN frequency was found in untreated cancer patients (meta-FR=1.45; 95% Confidence Interval (95% CI): 1.28-1.64) and in thyroid cancer patients after radioiodine treatment (meta-FR=2.26; 95% CI: 1.90-2.68). The third meta-analysis showed a negative trend of meta-FR's when plotted vs. the dose used to study patients' radiosensitivity, possibly associated to a high rate of apoptosis. The results of this review substantiate the existing evidence about a role of MN in various steps of carcinogenesis. The relatively small numbers of papers suitable for the meta-analysis call for new and larger studies, possibly based on high-throughput techniques, to further understand the role of MN formation in the occurrence of genetic instability and cancer.

Exposure to genotoxic agents, host factors, and lifestyle influence the number of centromeric signals in micronuclei: a pooled re-analysis.

We pooled data from three biomonitoring studies using the cytokinesis-block micronucleus assay in peripheral blood lymphocytes in combination with fluorescence in situ hybridization. Centromere-positive micronuclei (C+MN) were classified in two groups: those containing one centromere (C1+MN) and those with two or more (Cx+MN). The three studies evaluated untreated cancer patients, welders, and pathologists/anatomists exposed to formaldehyde. The total number of subjects included in the pooled re-analysis was 113. A higher frequency of C+MN was observed in cancer patients and exposed workers, who showed significant differences from controls in all studies. C1+MN were particularly increased in the group of pathologists/anatomists, who showed a 3.29 times higher frequency than controls (95% CI: 2.04-5.30). A borderline increase in Cx+MN was observed in welders when compared to the corresponding control group (FR: 1.31; 95% CI: 0.99-1.74). An evident effect of gender was found, with significantly increased frequencies of all endpoints measuring aneuploidy in females (C+MN, C1+MN, and Cx+MN). Alcohol consumption had a significant effect on total MN frequency and particularly on C+MN and C1+MN. In conclusion, scoring the number of centromeric signals in the micronucleus assay provides additional information about the mechanism of action of various genotoxic agents, and the role of confounding factors may be more specifically accounted for. Indeed, C+MN could be efficiently used in biomonitoring studies as an independent biomarker of exposure and early biological effect. The use of centromeric signals allows the identification of two further endpoints, representing two alternative pathways of chromosome loss, i.e., impaired chromosome migration, leading to increased C1+MN frequency, and centrosome amplification, possibly leading to Cx+MN with two or more centromeric signals.

[Physicians and occupational health: a qualitative study in south-eastern France]. / Les médecins face à la santé au travail: une étude qualitative dans le sud-est de la France.

BACKGROUND: Occupational health is a major public health problem in France. However, the level of investment of general practitioners and specialist physicians in this field is not well documented. We aimed at studying elements moving closer or differentiating groups of professionals (notably physicians) in the field of occupational health in terms of conceptions of their roles (prevention and care) and of practices (in particular detection and notification of occupational diseases and perceived barriers). METHODS: We conducted a qualitative study in south-eastern France which consisted of in-depth interviews of physicians and actors involved in the prevention of occupational hazards or in their indemnification. Then discourse analysis was carried out on the corpus collected. Content analysis grouped the data into themes. RESULTS: Several reasons could explain the low investment of physicians in the field of occupational health: insufficient detection of occupational causes of diseases, complexity of administrative procedures of declaration and bias of causal interpretation for the patients exposed to other risk factors such as smoking. The fear that notifying an occupational disease might have repercussions on patients' socio-professional situations places physicians in a situation of ethical dilemma: inducing a social risk on one side, ignoring his rights on the other. Physicians are not sufficiently prepared to deal with these situations, because they lack appropriate knowledge and support from specialists in the field, due to an important bulk-heading of actors and their practices. CONCLUSION: To sensitize and train physicians to occupational health and to support multi-field practices are essential.

[Micronuclei and genetic polymorphisms: from exposure to susceptibility]. / Micronoyaux et polymorphismes génétiques : de l'exposition à la susceptibilité.

The concept of genetic susceptibility and interactions between genetic and environmental factors of risk is a new trend in molecular epidemiology studies of cancers. Micronuclei are biomarkers of chromosome damage due to genetic instability or exposure to environmental mutagens or carcinogens. The micronucleus assay in combination with fluorescent in situ hybridization discriminates between micronuclei containing acentric chromosome fragments (chromosome breakage) and micronuclei containing whole chromosomes (chromosome loss). A recent approach is to associate the biomarkers of genetic susceptibility, which take into account cancer susceptibility and interindividual differences in the response to a genotoxic exposure, and the micronucleus assay, which serves as a biomarker of interactions between the environment and the genetic material of the cell. Information is being gathered on how DNA damage and more particularly the frequency and centromeric content of micronuclei depend on the polymorphisms of genes implicated in xenobiotic metabolism (activation or detoxication), DNA lesion repair, or folate metabolism. For biomonitoring purposes, numerous confounding factors (age, sex, tobacco consumption) influence the micronucleus biomarker, and thus associating genetic polymorphisms to micronuclei would be useful to better define the prevention and prediction of cancer risk.

Number of centromeric signals in micronuclei and mechanisms of aneuploidy.

Genome instability or changes in chromosome structure and number are important facets of oncogenesis. Aneuploidy is a major cause of human reproductive failure and plays a large role in cancer. It is therefore important that any increase in its frequency due to occupational exposure to mutagens and carcinogens should be recognized and controlled. In recent years, the cytokinesis-block micronucleus assay has emerged as a biomarker of chromosome/genome damage relevant to cancer. Fluorescent in situ hybridisation using human pancentromeric DNA probes discriminates between the presence of acentric chromosomal fragments and whole chromosomes in binucleated micronucleated lymphocytes. The separated analysis of centromeric micronuclei may improve the sensitivity of the micronucleus assay in detecting genotoxic effects and chromosome instability. Our previous findings suggest that aneugenic events leading to micronuclei (MN) containing a single centromere (C1+MN) and two or more centromeres (Cx+MN) may arise through different pathways. Chromosome migration impairment would lead to increased C1+MN frequency whereas centrosome amplification would induce Cx+MN with three or more centromeric signals. Additional studies that target cellular defects on the centrosome (microtubule nucleation, organization of the spindle poles, cell cycle progression) are required to better understand aneuploid cell production.

Genotoxic risk assessment of pathology and anatomy laboratory workers exposed to formaldehyde by use of personal air sampling and analysis of DNA damage in peripheral lymphocytes.

A study was conducted to evaluate the genotoxic effect of occupational exposure to formaldehyde on pathology and anatomy laboratory workers. The level of exposure to formaldehyde was determined by use of passive air-monitoring badges clipped near the breathing zone of 59 workers for a total sampling time of 15 min or 8 h. To estimate DNA damage, a chemiluminescence microplate assay was performed on 57 workers before and after a 1-day exposure. Assessment of chromosomal damage was carried out by use of the cytokinesis-blocked micronucleus assay (CBMN) in peripheral lymphocytes of 59 exposed subjects in comparison with 37 controls matched for gender, age, and smoking habits. The CBMN assay was combined with fluorescent in situ hybridization with a pan-centromeric DNA probe in 18 exposed subjects and 18 control subjects randomized from the initial populations. Mean concentrations of formaldehyde were 2.0 (range <0.1-20.4 ppm) and 0.1 ppm (range <0.1-0.7 ppm) for the sampling times of 15 min and 8 h, respectively. No increase in DNA damage was detected in lymphocytes after a one-workday exposure. However, the frequency of binucleated micronucleated cells was significantly higher in pathologists/anatomists than in controls (16.9‰±9.3 versus 11.1‰±6.0, P=0.001). The frequency of centromeric micronuclei was higher in exposed subjects than in controls (17.3‰±11.5 versus 10.3‰±7.1) but the difference was not significant. The frequency of monocentromeric micronuclei was significantly higher in exposed subjects than in controls (11.0‰±6.2 versus 3.1‰±2.4, P<0.001), while that of the acentromeric micronuclei was similar in exposed subjects and controls (3.7‰±4.2 and 4.1‰±2.7, respectively). The enhanced chromosomal damage (particularly chromosome loss) in peripheral lymphocytes of pathologists/anatomists emphasizes the need to develop safety programs.

A combined analysis of XRCC1, XRCC3, GSTM1 and GSTT1 polymorphisms and centromere content of micronuclei in welders.

The aims of the present study were to assess clastogenic and aneugenic properties of welding fumes using fluorescent in situ hybridization (FISH) with a human pancentromeric DNA probe. The involvement of genetic polymorphisms in DNA repair genes (p.Arg399Gln of XRCC1 and p.Thr241Met of XRCC3) and in detoxification genes (GSTM1 and GSTT1) on the centromere content of micronuclei (MN) was also evaluated. This study included 27 male welders working without any collective protection device and a control group (n = 30). The welders showed significantly higher levels of chromosome/genome damage compared to the controls. The frequencies of MN and centromere-positive MN (C+MN) per 1,000 binucleated cells were significantly higher in the exposed group than in the control group (7.1 per thousand +/- 3.7 versus 4.9 per thousand +/- 1.8; P = 0.012 and 3.5 per thousand +/- 1.8 versus 2.4 per thousand +/- 1.2; P = 0.018, respectively, Mann-Whitney U-test). The centromere-negative MN (C-MN) frequency was higher in the exposed subjects than in the controls (3.6 per thousand +/- 3.4 versus 2.5 per thousand +/- 1.4), but the Mann-Whitney U-test did not yield a significant result. In the total population, the GSTM1 and GSTT1 polymorphisms significantly affected the frequencies of C-MN and C+MN defined by FISH. GSTM1 positive subjects showed an increased C-MN frequency and GSTT1 null subjects showed an elevated C+MN frequency. When GSTM1 and GSTT1 genotypes were included in multiple regression analysis, the effect of the occupational exposure could better be demonstrated; both C+MN and C-MN were significantly increased in the welders. Our results suggest that the combined analysis of genetic polymorphisms and centromeres in MN may improve the sensitivity of the micronucleus assay in detecting genotoxic effects.

Risk assessment of welders using analysis of eight metals by ICP-MS in blood and urine and DNA damage evaluation by the comet and micronucleus assays; influence of XRCC1 and XRCC3 polymorphisms.

The aims of the present study were to assess the occupational risk of welders using analysis of metals in biological fluids, DNA damage evaluation by complementary genotoxic endpoints and the incidence of polymorphisms in DNA repair genes. A biomonitoring study was conducted that included biometrology (blood and urinary concentrations of aluminium, cadmium, chromium, cobalt, lead, manganese, nickel, zinc by ICP-MS), comet and cytokinesis-block micronucleus assays in peripheral lymphocytes and genetic polymorphisms of XRCC1 (p.Arg399Gln) and XRCC3 (p.Thr241Met). This study included 60 male welders divided into two groups: group 1 working without any collective protection device and group 2 equipped with smoke extraction systems. A control group (n = 30) was also included in the study. Higher chromium, lead and nickel blood and urinary concentrations were detected in the two groups of welders compared to controls. Statistically differences between welders of group 1 and group 2 were found for blood concentration of cobalt and urinary concentrations of aluminium, chromium, lead and nickel. The alkaline comet assay revealed that welders had a significant increase of OTMchi2 distribution at the end of a work week compared to the beginning; a significant induction of DNA strand breaks at the end of the week was observed in 20 welders out of 30. The cytokinesis-block micronucleus assay showed that welders of group 1 had a higher frequency of chromosomal damage than controls. The XRCC1 variant allele coding Gln amino acid at position 399 was found to be associated with a higher number of DNA breaks as revealed by the comet assay. Increased metal concentrations in biological fluids, DNA breaks and chromosomal damage in lymphocytes emphasized the need to develop safety programmes for welders.