Genomic damages in peripheral blood lymphocytes and association with polymorphisms of three glutathione S-transferases in workers exposed to formaldehyde

DNA and chromosome damages in peripheral blood lymphocytes were evaluated in 151 workers occupationally exposed to formaldehyde (FA) and 112 non-FA exposed controls. The effects of polymorphisms in three glutathione-S-transferase (GSTs) genes on the DNA and chromosome damages were assessed as well. Alkaline comet assay and cytokinesis-block micronucleus (CBMN) assay were used to determine DNA and chromosome damages, respectively. The genotypes of GSTP1 (Ile105Val), GSTT1, and GSTM1 were assayed. The mean 8-h time-weighted average (TWA) concentrations of FA in two plywood factories were 0.83 ppm (range: 0.08–6.30 ppm). FA-exposed workers had higher olive tail moment (TM) and CBMN frequency compared with controls (Olive TM, 3.54, 95%CI = 3.19–3.93 vs. 0.93, 95%CI = 0.78–1.10, P < 0.01; CBMN frequency, 5.51 ± 3.37 vs. 2.67 ± 1.32, P < 0.01). Olive TM and the CBMN frequency also had a dose-dependent relation with the personal FA exposure. Significant association between FA exposure history and olive TM and CBMN frequency were also identified. The level of olive TM was slightly higher in FA-exposed workers with GSTM1 null genotype than those with non-null genotype (3.86, 95%CI = 3.31–4.50 vs. 3.27, 95%CI = 2.83–3.78, P = 0.07) with adjustment of covariates. We also found that FA-exposed workers carrying GSTP1 Val allele had a slightly higher CBMN frequency compared with workers carrying only the wild-type allele (6.32 ± 3.78 vs. 5.01 ± 2.98, P = 0.05). Our results suggest that the FA exposure in this occupational population increased DNA and chromosome damages and polymorphisms in GSTs genes may modulate the genotoxic effects of FA exposure.     

Micronuclei in peripheral blood lymphocytes of workers exposed to lead

Lead plays an important role in many industrial processes. Although highly useful to man, lead has various types of toxic effects. There is constantly growing evidence of a relationship between the induction of chromosome breaks and an increased risk of onset of cancer. However, available data about the possible genotoxic and carcinogenic action of lead are conflicting. In this report we present the results of studies on lead concentrations in blood and the respective micronucleus frequencies in peripheral blood lymphocytes from workers employed in the recycling of automotive batteries in the surroundings of Porto Alegre, Brazil. We observed that in the occupationally exposed group, both lead concentration in peripheral blood and micronucleus frequency in lymphocytes were significantly higher compared to control (Z=6.35, P<0.0001 and Z=4.47, P<0.0001). The nuclear division index (NDI) values were significantly higher in the control group than in the exposed group (Z=2.13, P=0.0330), indicating a possible effect of Pb on nuclear proliferation. We also detected a negative correlation between micronuclei and progression of nuclear division (tau=-0.312, P=0.0129). There were no changes in micronucleus frequency between smoking and non-smoking workers exposed to lead (Z=0.03, P=0.9790). The only difference found between the groups of smokers and non-smokers was with respect to NDI, whose values were significantly higher among non-smokers (Z=1.98, P=0.0481).     

Association between heat-shock protein 70 gene polymorphisms and DNA damage in peripheral blood lymphocytes among coke-oven workers

Hsp70 has been shown to act as a chaperone and be associated with cytoprotection against DNA damage caused by environmental stresses. However, it is unknown whether genetic variation in HSP70 plays a role in stress tolerance and cytoprotection against DNA damage. We determined the frequencies of three polymorphisms, HSP70-1 G190C, HSP70-2 G1267A, and HSP70-hom T2437C from 251 steel-plant workers exposed to coke-oven emission and 130 controls. We estimated the association between the HSP70variants/haplotypes and the levels of DNA damage in their peripheral blood lymphocytes detected by single-cell gel electrophoresis assay. Our results showed that overall coke-oven workers had higher levels of the Olive tail moment (Olive TM) (1.27+/-1.12) than that of the controls (0.56+/-0.99, P<0.001). Coke-oven workers with the HSP70-1 C/C genotype had higher levels of Olive TM (2.19+/-0.65), compared with HSP70-1 G/C and G/G carriers (Olive TM=1.34+/-1.09 and 1.14+/-1.08, respectively, P=0.022 and 0.003, respectively). However, the HSP70-2 G1267A and HSP70-hom T2437C polymorphisms were not associated with the levels of Olive TM (P=0.929 and 0.795, respectively). Haplotype analysis showed that carriers of TCG/TCG haplotype pairs had the highest levels of Olive TM among both the exposed subjects (2.04+/-0.59) and the controls (0.81+/-0.59). Our results suggest that the individuals with the homozygous HSP70-1 C/C genotype among the coke-oven workers may be susceptible to DNA damage.     

Cytogenetic analysis of peripheral blood lymphocytes in workers exposed to benzene

In the present study, the method of cytogenetic analysis of peripheral blood lymphocytes was used to investigate 66 workers exposed to benzene, and 20 individuals selected from general population from the same locality, not exposed to particular mutagenic or carcinogenic agents (control group). Altogether, 8,600 metaphases were analysed. Frequencies of aberrant cells, including chromatide and chromosomal breaks, and chromatide and chromosomal exchanges, were scored in both groups. A very slight increase in aberrant cell frequencies (2.152% aberrant cells) was observed in the professional exposure group as compared to the control group (1.6% aberrant cells). Increased frequencies of aberrant cells were found in smokers of both the benzene-exposed and the control group. The differences were however not significant. In addition to cytogenetic examination, the workers underwent a general examination of their health condition (preventive examination). Benzene exposure seemed to have no injurious effect on the state of health of exposed workers. Biochemical and haematological tests gave normal values.     

Cytogenetic analysis of peripheral blood lymphocytes in workers exposed to vinyl chloride

In the present study, the method of cytogenetic analysis of peripheral blood lymphocytes was used to examine 43 workers exposed to vinyl chloride monomer (average exposure 11.2 years) and 22 subjects selected from the same locality (control group). A total number of 8650 metaphases were analysed. All cytogenetic parameters examined were increased in the exposed group as compared to the control group and 3 parameters, chromatid breaks, percentage of aberrant cells and breaks per cell, were significantly increased (P less than 0.001).     

Cytogenetic analysis of peripheral blood lymphocytes of workers occupationally exposed to styrene

The genetic risk run by workers occupationally exposed to styrene vapors was assessed in two different plants A and B, using the cytogenetic analysis of peripheral blood lymphocytes. In plant A engaged in the manufacture of polystyrene vessels the mean styrene exposure level was found to range between 70 and 150 mg . m-3, in plant B manufacturing sports boats, plastic slides for children and plastic guard-stones it reached the level of about 200 mg . m-3. The rate of aberrant cells (AB.C.) found in plant A workers (N = 36) at the time of first sampling was 1.38% and the value of break/cell (B/C) ratio was 0.015; at the second sampling the rate of AB.C. was 1.41% and the B/C ratio was 0.014. The group of matched controls (N = 19) was found to have 1.26% of AB.C. and 0.014 breaks per cell. Plant B workers (N = 22) exhibited at the first sampling 1.72% of AB.C. and their value of B/C ratio was 0.018, the group of matched controls (N = 22) had 1.36% of AB.C and the B/C ratio 0.015; the respective values at the time of second sampling were 2.81% for AB.C. rate and 0.029 for B/C ratio in the exposed and 1.89% for AB.C. rate and 0.021 for B/C ratio in the control group. It is concluded that styrene exposure levels below 100 mg . m-3 do not pose any serious genetic risk for the exposed population groups. The variations found in the degree of chromosome injury by smoking habits, drug intake pattern, or sex were not statistically significant.     

Association between metabolic gene polymorphisms and susceptibility to peripheral nerve damage in workers exposed to n-hexane: A preliminary study

Abstract

Chronic exposure to n-hexane may result in peripheral neuropathy. 2,5-Hexanedione (2,5-HD) has been identified as a toxic metabolite of n-hexane. The CYP2E1, CYP1A1 and GST genes are involved in the formation of 2,5-hexanedione from n-hexane as well as the elimination of 2,5-HD-formed electrophile, and these genes are highly polymorphic in the general population. A nested case-control study in an industrial cohort was conducted to evaluate the associations between polymorphisms in these metabolic genes and n-hexane-induced peripheral nerve damage. The study subjects included 22 cases, who worked in a printing factory with symptoms of peripheral nerve damage, and 163 controls, who came from the same factory of cases. DNA was extracted from blood samples and genotyping was conducted for CYP2E1 Pst, CYP2E1 Dra, CYP2E1 Ins96, CYP1A1 Msp, GSTT1 null, GSTM1 null and GSTP1 105V. Unconditional logistic regression was applied to estimate the odds ratio and 95% confidence intervals. There were no significant differences between the two groups regarding age, sex, smoking and alcohol status. A significant association between Dra polymorphism and peripheral nerve damage was found. The frequency of CYP2E1 Dra homozygous mutation in the case group (18.2%) was higher than that in the control group (3.7%, p=0.015). Individuals with homozygote genotype (CC) of CYP2E1 Dra had a significantly higher risk of peripheral nerve damage compared with those with DD genotype (adjusted OR?=?5.58, 95% CI?=?1.32–23.65) after n-hexane exposure duration, sex, age, smoking and alcohol status were adjusted. No significant association was found that CYP2E1 Pst, CYP2E1 Ins96, CYP1A1 Msp, GSTT1, GSTM1, GSTP gene polymorphisms associated with the susceptibility of peripheral nerve damage. These findings suggested that CYP2E1 gene might increase the susceptibility to n-hexane-induced peripheral damage.     

Association between metabolic gene polymorphisms and susceptibility to peripheral nerve damage in workers exposed to n-hexane: A preliminary study

Chronic exposure to n-hexane may result in peripheral neuropathy. 2,5-Hexanedione (2,5-HD) has been identified as a toxic metabolite of n-hexane. The CYP2E1, CYP1A1 and GST genes are involved in the formation of 2,5-hexanedione from n-hexane as well as the elimination of 2,5-HD-formed electrophile, and these genes are highly polymorphic in the general population. A nested case-control study in an industrial cohort was conducted to evaluate the associations between polymorphisms in these metabolic genes and n-hexane-induced peripheral nerve damage. The study subjects included 22 cases, who worked in a printing factory with symptoms of peripheral nerve damage, and 163 controls, who came from the same factory of cases. DNA was extracted from blood samples and genotyping was conducted for CYP2E1 Pst, CYP2E1 Dra, CYP2E1 Ins96, CYP1A1 Msp, GSTT1 null, GSTM1 null and GSTP1 105V. Unconditional logistic regression was applied to estimate the odds ratio and 95% confidence intervals. There were no significant differences between the two groups regarding age, sex, smoking and alcohol status. A significant association between Dra polymorphism and peripheral nerve damage was found. The frequency of CYP2E1 Dra homozygous mutation in the case group (18.2%) was higher than that in the control group (3.7%, p=0.015). Individuals with homozygote genotype (CC) of CYP2E1 Dra had a significantly higher risk of peripheral nerve damage compared with those with DD genotype (adjusted OR = 5.58, 95% CI = 1.32-23.65) after n-hexane exposure duration, sex, age, smoking and alcohol status were adjusted. No significant association was found that CYP2E1 Pst, CYP2E1 Ins96, CYP1A1 Msp, GSTT1, GSTM1, GSTP gene polymorphisms associated with the susceptibility of peripheral nerve damage. These findings suggested that CYP2E1 gene might increase the susceptibility to n-hexane-induced peripheral damage.     

Association of genetic polymorphisms in glutathione S-transferases and susceptibility to head and neck cancer

Polymorphism in glutathione S-transferase (GST) genes (GSTM1, GSTT1 and GSTP1) and interaction with environmental factors such as tobacco (smoking or chewing) and alcohol on susceptibility to head and neck squamous cell carcinoma (HNSCC) was studied in a case-control study. The study group consisted of 175 patients suffering from HNSCC and 200 age matched healthy controls. Statistical analysis showed an increase in risk to HNSCC in the patients with null genotype of GSTM1 (OR: 2.02; 95% CI: 1.32-3.10; P=0.001) or GSTT1 (OR: 1.66; 95% CI: 1.02-2.69; P=0.04), though the risk was not found to be significant when adjusted for age, sex, smoking, tobacco chewing or alcohol use by multivariate logistic regression model. Our data further showed that combination of deletion genotypes of GST (GSTM1 and GSTT1) confer an even higher risk of HNSCC. Interestingly, GSTP1 wild type genotype in combination with GSTM1 null or GSTT1 null genotype increased susceptibility for HNSCC (OR: 2.49 and 2.75, respectively). Likewise a much greater risk for HNSCC was observed in the patients carrying a genotype combination of GSTM1 null, GSTT1 null and GSTP1 (Ile/Ile) (OR: 4.47; 95% CI: 1.62-12.31; P=0.002). Our data have further provided evidence that tobacco chewing and alcohol consumption are the important risk factors for HNSCC. The interaction between tobacco chewing and null genotype of GSTM1 or GSTT1 resulted in about 3.5- and 2.2-fold increase in the risk respectively in the patients when compared to those not chewing tobacco. Alcohol use resulted in more than 4-fold increase in the risk in the patients with null genotype of GSTM1 as compared to those who are non-drinkers. Alcohol consumption also increased the risk (approx. 3-fold) in the cases with null genotype of GSTT1, though the association was not found to be significant when compared to non-drinkers. Our data have provided evidence that GST polymorphism modifies the susceptibility to HNSCC and have further demonstrated importance of gene-environment interaction in modulating the risk to HNSCC.     

Cytogenetic analysis of peripheral blood lymphocytes in glass workers occupationally exposed to mineral oils

Chromosome aberration tests were carried out in a group of 31 pressed glass makers operating an automatic line of press-and-blow machines known to release mineral oil mists containing relatively high concentrations of the mutagenic chemicals belonging to a class of polycyclic aromatic hydrocarbons (PAH). The workers were exposed to the mineral oil aerosol levels that did not exceed the Czechoslovak maximum allowable concentration limit of 5 mg . m-1 of air. The tests revealed that the frequency of aberrant cells (% AB.C.) and the value of breaks per cell (B/C) ratio found in mineral oil-exposed workers were increased significantly, accounting for 4.65 +/- 0.29% AB.C. (0.0532 B/C) vs. 1.13 +/- 0.19% AB.C. (0.0113 B/C) seen in matching controls. Also, a higher rate of dicentrics, reciprocal translocations and cells with pulverization was observed in this group of glass workers. These finding are considered as evidence suggesting that these workers might experience an increased risk of genetic injury due to exposure to mineral oil mists.     

Associations between XRCC1 and ERCC2 polymorphisms and DNA damage in peripheral blood lymphocyte among coke oven workers

A wide variety of base damages and single-strand breaks formed by reactive oxygen species during metabolic activation of polycyclic aromatic hydrocarbons (PAHs) have been recognized to be involved in PAH carcinogenesis. In this study, alkaline comet assay was used to detect the DNA damage in peripheral blood lymphocytes among 143 coke-oven workers and 50 non-coke-oven workers, and the effects of genetic polymorphisms of XRCC1 and ERCC2 genes on DNA damage were evaluated. The olive tail moment was significantly higher in coke-oven workers than in non-coke-oven workers (2.6, 95% CI=2.1–3.3 versus 1.0, 95% CI=0.8–1.2, p<0.01), and significant correlation between ln-transformed urinary 1-OHP and ln-transformed olive tail moment was found in total population (n=193, Pearson's r=0.393, p<0.001) and in coke-oven workers (n=143, Pearson's r=0.224, p=0.007). The olive tail moment was significantly higher in coke-oven workers with GA genotype of G27466A polymorphism of XRCC1 than those with GG genotype (4.6, 95% CI=2.5–8.7 versus 2.4, 95% CI=1.9–2.9, p<0.01 with adjustment for covariates). No significant associations between C26304T, G28152A and G36189A polymorphisms of XRCC1 and G23591A and A35931C polymorphisms of ERCC2 and olive tail moment were found in both groups. The study showed that the alkaline comet assay is a suitable biomarker in the detection of DNA damage among coke-oven workers and it suggested that the A allele of G27466A polymorphism of XRCC1 may be associated with decreased DNA repair capacity toward PAH-induced base damage and strand breaks.     

Cytogenetic analysis of peripheral blood lymphocytes of occupational workers exposed to low levels of ionising radiation.

The incidence of chromosomal aberrations was analysed in peripheral blood lymphocytes of occupationally exposed people having cumulative doses of 500 mSv. The exposed individuals showed higher frequencies of dicentrics as well as acentrics than normal controls. Absorbed radiation dose was calculated by using in vitro dose response curve established for Cobalt-60 gamma rays. In the control constituting 17 healthy individuals, two dicentrics were detected among 3700 metaphases analysed. In the exposed group 27 dicentrics and one centric ring was detected among 8400 metaphases analysed. Due to small number of dicentrics scored in each individual, the dose estimate suffers from a large statistical uncertainty. The collective dose was found to be 1.89 Gy. This is in good agreement with the corrected physical doses, assuming a mean life of 10 years for the disappearance of lymphocytes. The physical doses accumulated during the last 10 years of occupation were also in good agreement with the biological dose estimate.     

Associations between XRCC1 and ERCC2 polymorphisms and DNA damage in peripheral blood lymphocyte among coke oven workers.

A wide variety of base damages and single-strand breaks formed by reactive oxygen species during metabolic activation of polycyclic aromatic hydrocarbons (PAHs) have been recognized to be involved in PAH carcinogenesis. In this study, alkaline comet assay was used to detect the DNA damage in peripheral blood lymphocytes among 143 coke-oven workers and 50 non-coke-oven workers, and the effects of genetic polymorphisms of XRCC1 and ERCC2 genes on DNA damage were evaluated. The olive tail moment was significantly higher in coke-oven workers than in non-coke-oven workers (2.6, 95% CI=2.1-3.3 versus 1.0, 95% CI=0.8-1.2, p<0.01), and significant correlation between ln-transformed urinary 1-OHP and ln-transformed olive tail moment was found in total population (n=193, Pearson's r=0.393, p<0.001) and in coke-oven workers (n=143, Pearson's r=0.224, p=0.007). The olive tail moment was significantly higher in coke-oven workers with GA genotype of G27466A polymorphism of XRCC1 than those with GG genotype (4.6, 95% CI=2.5-8.7 versus 2.4, 95% CI=1.9-2.9, p<0.01 with adjustment for covariates). No significant associations between C26304T, G28152A and G36189A polymorphisms of XRCC1 and G23591A and A35931C polymorphisms of ERCC2 and olive tail moment were found in both groups. The study showed that the alkaline comet assay is a suitable biomarker in the detection of DNA damage among coke-oven workers and it suggested that the A allele of G27466A polymorphism of XRCC1 may be associated with decreased DNA repair capacity toward PAH-induced base damage and strand breaks.     

The genetic association between osteoprotegerin gene polymorphisms and fracture risk in Chinese Han population

This article put the genetic association exploration of osteoprotegerin (OPG) gene polymorphisms in promoter region (A-163G, T-245G) and fracture risk first and hoped to explain the ethology of fracture. The genotyping of OPG gene polymorphisms was conducted with the method of polymerase chain reaction-restriction fragment length polymorphism in 125 fracture patients and 138 relative controls. The genotype frequencies of selected controls based on OPG gene polymorphisms were checked by the χ² test whether conformed to Hardy–Weinberg equilibrium (HWE). The relative risk was represented with odds ratio (OR) and 95% confidence interval (95% CI) between gene polymorphism and disease. The linkage disequilibrium (LD) and haplotype were also analyzed. The genotypes distributions of selected controls in OPG polymorphisms conformed to HWE. The G allele of A-163G polymorphism carriers had the tendency to suffer from fracture in the same condition, compared with A allele carriers (OR = 1.63, 95% CI = 1.04–2.55). TG and TG/GG genotypes of OPG T-245G polymorphism also showed the increased risk of fracture development, but not TT genotype (OR = 2.22, 95% CI = 1.15–4.28; OR = 2.45, 95% CI = 1.28–4.68). Likely, the mutant allele G had an abnormally higher frequency in cases than controls (14.00% and 6.16%). These two polymorphisms existed the LD and the haplotype G _-163–G _-245 obviously increased the risk of fracture. OPG A-163G, T-245G polymorphisms were associated with the onset of fracture and both the independent risk factors.     

Cytogenetic biomonitoring of Spanish greenhouse workers exposed to pesticides: micronuclei analysis in peripheral blood lymphocytes and buccal epithelial cells

In the present study, we evaluate whether or not occupational exposure to a complex mixture of pesticides results in a significant increase of micronuclei (MN) in both peripheral blood lymphocytes and buccal cells. Sixty four greenhouse workers from Almería (Southeastern Spain), together with 50 men from the same area, without indication of exposure to pesticides, that served as controls were used in this investigation. The results obtained indicate that there are no statistically significant differences in the MN frequencies between the two groups. Each donor was assessed for the presence or absence of glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1), to look for relationships between the genotypes and the cytogenetic reponses. According to the GSTT1 genotype, there is a difference between both groups only for the cytokinesis-block proliferation index (CBPI). Neither GSTM1 nor smoking habit and age showed any effect in the overall analysis.     

Lack of increased genetic damage in 1,3-butadiene-exposed Chinese workers studied in relation to EPHX1 and GST genotypes

1,3-Butadiene (BD) is an important industrial chemical and pollutant. Its ability to induce genetic damage and cause hematological malignancies in humans is controversial. We have examined chromosome damage by fluorescence in situ hybridization (FISH) and mutations in the HPRT gene in the blood of Chinese workers exposed to BD. Peripheral blood samples were collected and cultured from 39 workers exposed to BD (median level 2 ppm, 6 h time-weighted average) and 38 matched controls in Yanshan, China. No difference in the level of aneuploidy or structural changes in chromosomes 1, 7, 8, and 12 was detected in metaphase cells from exposed subjects in comparison with matched controls, nor was there an increase in the frequency of HPRT mutations in the BD-exposed workers. Because genetic polymorphisms in glutathione S-transferase (GST) enzymes and microsomal epoxide hydrolase (EPHX1) may affect the genotoxic effects of BD and its metabolites, we also related chromosome alterations and gene mutations to GSTT1, GSTM1 and EPHX1 genotypes. Overall, there was no effect of variants in these genotypes on numerical or structural changes in chromosomes 1, 7, 8 and 12 or on HPRT mutant frequency in relation to BD exposure, but the GST genotypes did influence background levels of both hyperdiploidy and HPRT mutant frequency. In conclusion, our data show no increase in chromosomal aberrations or HPRT mutations among workers exposed to BD, even in potentially susceptible genetic subgroups. The study is, however, quite small and the levels of BD exposure are not extremely high, but our findings in China do support those from a similar study conducted in the Czech Republic. Together, these studies suggest that low levels of occupational BD exposure do not pose a significant risk of genetic damage.     

Association of HSP70 and genotoxic damage in lymphocytes of workers exposed to coke-oven emission

Heat shock proteins (Hsps) have been reported to protect cells, tissues, and organisms against damage from a wide variety of stressful stimuli. Whether they protect against deoxyribonucleic acid (DNA) damage in individuals exposed to environmental stresses and chemical carcinogens is unknown. In the study, we investigated the association between Hsp70 levels (the most abundant mammalian Hsp) and genotoxic damage in lymphocytes of workers exposed to coke-oven emission using Western dot blot and 2 DNA damage assays, the comet assay and the micronucleus test. The data show that there is a significant increase in Hsp70 levels, DNA damage score, and micronucleus rates in lymphocytes of workers exposed to coke-oven emission as compared with the control subjects. Furthermore, there was a significant negative correlation of Hsp70 levels with DNA damage scores in the comet assay (r = -0.663, P < 0.01) and with micronucleus rates (r = -0.461, P < 0.01) in the exposed group. In the control group, there was also a light negative correlation between Hsp70 with DNA damage and micronuclei rate (r = -0.236 and r = 0.242, respectively), but it did not reach a statistically significant level (P > 0.05). Our results show that individuals who had high Hsp70 levels generally showed lower genotoxic damage than others. These results suggest a role of Hsp70 in the protection of DNA from genotoxic damage induced by coke-oven emission.