B- and T-lymphocyte micronuclei in chimney sweeps with respect to genetic polymorphism for CYP1A1 and GST1 (class Mu)

Cytogenetic evaluation and the association with polymorphisms of the CPY1A1 and NR1I3 genes in individuals exposed to BTEX

The gas station attendants are exposed daily to chemical agents that compose gasoline, such as BTEX (benzene, toluene, ethylbenzene, and xylene), and the exposure to these agents can cause a variety of effects on the human health. Among the various possible cell alterations associated with these exposures are the formation of micronuclei and of binucleated cells which are used as indicators of clastogenic action. Benzene, the main carcinogenic agent, is metabolized to more soluble forms and easily excreted by isoenzymes of cytochrome P450, such as CYP1A1. The CYP1A1 gene is highly polymorphic and one of its allele variations can be detected by the use of restriction endonucleasis MspI and is originated by the transition of a thymine by a cytosine (3798T>C), resulting in the polymorphic allele CYP1A1*2A. The objective of this study was to evaluate the cytogenetic damage induced by the exposure to BTEX and to associate it with the polymorphisms of the CYP1A1 and NR1I3 genes. Samples of exfoliated cells from the oral mucosa of 27 gas station attendants and from a control group were collected. The results found show that the group exposed to BTEX presents significantly higher alterations than those in the control group for micronuclei (MN; 6.85 ± 1.33 vs. 2.96 ± 1.91, P < 0.001) and for the total of nuclear alterations observed (MN + binucleated cells (BNC); 9.59 ± 4.73 vs. 5.07 ± 2.21, P < 0.001). When comparing the cytological alterations and the genotypes among the exposed individuals for the polymorphism 3798T>C of the CYP1A1 gene, homozygotes TT present MN + BNC significantly higher than carriers of the allele C (10.88 ± 5.36 vs. 5.33 ± 2.52, P = 0.028). No association was observed in the control group or for the NR1I3 gene. These results show that molecular and cytogenetic data can be used in the future as tools to monitor individuals exposed to such compounds.

Population analysis of xenobiotic metabolizing genes in South Brazilian Euro and Afro-descendants

Individual variability in xenobiotic metabolism has been associated with susceptibility to developing complex diseases. Genes involved in xenobiotic metabolism have been evaluated in association studies; the difficulty of obtaining accurate gene frequencies in mixed populations makes interpretation of the results difficult. We sought to estimate population parameters for the cytochrome P450 and glutathione S-transferase gene families, thus contributing to studies using these genes as markers. We describe the frequencies of six genes (CYP1A1, CYP2D6, CYP2E1, GSTM1, GSTT1, and GSTP1) and estimate population parameters in 115 Euro-descendants and 196 Afro-descendants from Curitiba, South of Brazil. PCR-based methods were used for genotyping, and statistical analysis were performed by AMOVA with ARLEQUIN software. The mutant allele frequencies in the Afro-descendants and Euro-descendants, respectively, were: CYP1A1*2A = 30.1% and 15.2%; CYP2D6*4 = 14.5% and 21.5%; CYP2E1*5B = 7.9% and 5%; GSTP1*B = 37.8% and 28.3%. The null genotype frequencies were: GSTM1*0 = 36.8% and 46.1%; GSTT1*0 = 24.2% and 17.4%.

Genetic polymorphisms in oestrogen metabolic pathway and breast cancer: a positive association with combined CYP/GST genotypes

The cytochrome P450 family (CYPs) and the glutathione S-transferase (GSTs) enzymes play an important role in the metabolism of environmental carcinogens and of oestrogen and can affect breast cancer risk. In this study we examine the role of the genes CYP1A1, CYP17, CYP2D6, GSTM1, GSTP1 and GSTT1 in breast cancer risk in Brazilian women. The study population consisted of 102 incident breast cancer cases and 102 healthy controls. Genotyping analyses were performed by PCR-based methods. A significant finding was observed between GSTP1 Ile-Val polymorphism and breast cancer risk (OR = 1.81; CI 95% = 1.04-3.16). A significant association was observed between women with 0-2 risk genotypes and those with 4 or more risk genotypes (OR = 2.42; CI 95% = 1.13-5.18) when the potential combined effects of the risk genotypes were examined. No significant differences between cases and controls were found correlating the genotypes and the clinical-histopathological parameters. In conclusion, in our population only GSTP1 was associated with breast cancer risk. However, when the genes were tested in combination, a significant association in the breast cancer risk was observed.

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.

Phase I/II enzyme gene polymorphisms and esophageal cancer risk: A meta-analysis of the literature

AIM: Phase I/II enzymes metabolize environmental carcin-ogens and several functional polymorphisms have been reported in their encoding genes. Although their significance with regard to esophageal carcinogenicity has been examined epidemiologically, it remains controversial. The present systematic review of the literature was performed to clarify associations.

METHODS: Eligible studies were case-control or cohort studies published until September 2004 that were written in any language. From PubMed and a manual review of refe-rence lists in relevant review articles, we obtained 16 studies related to the CYP1A1 Ile-Val substitution in exon 7, CYP1A1 MspI polymorphisms, CYP2E1 RsaI polymorphisms, GSTM1 null type, GSTT1 null type and GSTP1 Ile104Val. All were of case-control design. Summary statistics were odds ratios (ORs) comparing heterozygous-, homozygous-non-wild type or these two in combination with the homozygous wild type, or the null type with the non-null type for GSTM1 and GSTT1. A random effect model was used to estimate the summary ORs. A meta-regression analysis was applied to explore sources of heterogeneity.

RESULTS: Individuals with the Ile-Val substitution in CYP1A1 exon 7 had increased esophageal cancer risk, with ORs (95%CI) compared with Ile/Ile of 1.37 (1.09-1.71), 2.52 (1.62-3.91) and 1.44 (1.17-1.78) for Ile-Val, Val/Val genotype and the combined group. No significant association was found between esophageal cancer risk and the other genetic parameters.

CONCLUSION: A significant association exists between the CYP1A1 Ile-Val polymorphism and risk of esophageal cancer. Polymorphisms that increase the internal exposure to activated carcinogens may increase the risk of esophageal cancer.

Effects of Genetic Polymorphisms of Metabolic Enzymes on Cytokinesis-Block Micronucleus in Peripheral Blood Lymphocyte among Coke-Oven Workers

Exploring the associations between genetic polymorphisms of metabolic enzymes and susceptibility to polycyclic aromatic hydrocarbon (PAH)–induced chromosomal damage is of great significance for understanding PAH carcinogenesis. Cytochrome P450, glutathione S-transferase, microsomal epoxide hydrolase, NAD(P)H:quinone oxidoreductase, and N-acetyltransferase are PAH-metabolizing enzymes. In this study, we genotyped for the polymorphisms of these genes and assessed their effects on cytokinesis-block micronucleus (CBMN) frequencies in peripheral blood lymphocytes among 141 coke-oven workers and 66 non–coke-oven worker controls. The geometric means of urinary 1-hydroxypyrene levels in coke-oven workers and the controls were 12.0 and 0.7 μmol/mol creatinine, respectively (P &lt; 0.01). The CBMN frequency (number of micronuclei per 1,000 binucleated lymphocytes) was significantly higher in coke-oven workers (9.5 ± 6.6‰) than in the controls (4.0 ± 3.6‰; P &lt; 0.01). Among the coke-oven workers, age was positively associated with CBMN frequency; the mEH His113 variant genotype exhibited significantly lower CBMN frequency (8.5 ± 6.5‰) than did the Tyr113/Tyr113 genotype (11.3 ± 6.4‰; P &lt; 0.01); the low mEH activity phenotype exhibited a lower CBMN frequency (8.6 ± 6.8‰) than did the high mEH activity phenotype (13.2 ± 6.7‰; P = 0.01); the GSTP1 Val105/Val105 genotype exhibited a higher CBMN frequency (15.0 ± 5.8‰) than did the GSTP1 Ile105/Ile105 or Ile105/Val105 genotypes (9.3 ± 6.5‰; P &lt; 0.01); the joint effect of high mEH activity phenotype and GSTM1 null genotype on CBMN frequencies was also found. Gene-environment interactions between occupational PAH exposure and polymorphisms of mEH and/or GSTM1 were also evident. These results indicate that the mEH, GSTP1, and GSTM1 polymorphisms may play a role in sensitivity or genetic susceptibility to the genotoxic effects of PAH exposure in the coke-oven workers.

Chromosome and DNA damage analysis in individuals occupationally exposed to pesticides with relation to genetic polymorphism for CYP 1A1gene in Ecuador

DNA damage was measured by using the alkaline comet assay and the chromosomal aberration (CA) test using peripheral blood samples from 45 pesticide sprayers from Cayambe, Ecuador. From a total of approximately 200 nuclei scored for each donor with the comet assay, a highly significant increase in DNA migration was observed when compared with a similar unexposed control population. Additionally, in the CA test, the exposed individuals were found to be significantly different when compared to the control population. Polymorphisms for the CYP 1A1 (Msp I and Ile/Val) in exposed individuals were analyzed by PCR-RFLP and allele-specific PCR techniques. No association was found between the polymorphisms and higher levels of DNA damage as assessed by the comet assay.

Influence of CYP1A1, GSTM1, GSTT1, and NQO1 Genotypes and Cumulative Smoking Dose on Lung Cancer Risk in a Swedish Population

The major identified risk factor for lung cancer is tobacco smoking. We identified previously the possible modifying influence of CYP1A1 and GSTM1 polymorphisms on lung cancer risk in a Swedish population. The present study, extended by several study subjects and with analyses for polymorphisms in GSTT1 and NQO1, includes 524 lung cancer cases and 530 control subjects. No evidence for an influence of genetic polymorphisms in CYP1A1, GSTM1, GSTT1, and NQO1 on lung cancer risk overall was found. In smokers, there was, however, a suggestion that the variant CYP1A1 and NQO1 genotypes may confer an increased risk for squamous cell carcinoma. In ever smokers, the homozygously deleted GSTM1 (GSTM1*O/*O) genotype was significantly associated with increased risk of small cell carcinoma (adjusted odds ratio 2.72, 95% confidence interval 1.32-5.90). The risks noted for the variant CYP1A1 genotypes and the GSTM1*O/*O genotype seemed to be restricted to light smokers. The GSTT1*O/*O genotype also appeared to be a possible risk factor in light smokers, whereas, in heavy smokers, this genotype was associated with decreased risk for lung cancer overall (odds ratio 0.36, 95% confidence interval 0.13-0.99). Due to the multiple comparisons made, we cannot exclude the possibility that some of these associations may represent chance findings.

Genetic polymorphisms and susceptibility to childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most common form of pediatric cancer. Although exposure to environmental agents appears to predispose individuals to this disease, little attention has been paid to the role of genetic susceptibility to environmental exposures in the etiology of childhood ALL. The enzymes GSTM1, GSTT1, GSTP1, CYP1A1, and CYP2E1 are involved in the bioactivation and detoxification of a variety of xenobiotics present in food, organic solvents, tobacco smoke, drugs, alcoholic drinks, pesticides, and environmental pollutants. Polymorphisms in the genes coding for these enzymes have been associated with increased susceptibility to different cancers, including hematologic malignancies. To investigate whether these polymorphisms represent risk-modifying factors for childhood ALL, a study was conducted involving 113 Brazilian patients of childhood ALL and 221 controls with similar ethnic backgrounds. The data revealed that carriers of the rare GSTP1 Val allele were at higher risk of ALL (odds ratio [OR] = 2.7; 95% confidence interval [CI] = 1.1-6.8; P = 0.04). No difference was found in the prevalence of the GSTM1 and GSTT1 null genotypes between ALL patients and the controls, and no association was found between CYP1A1*2 and CYP2E1*3 variants and ALL. However, when the mutant CYP1A1 and CYP2E1 alleles were considered together with the GSTM1 and GSTP1 risk-elevating genotypes, the risk of ALL was increased further (OR = 10.3; 95% CI = 1.0-111.8; P = 0.05), suggesting a combined effect. These results imply that genetic variants of xenobiotic metabolizing genes influence the risk of developing childhood ALL.

Metabolic polymorphisms and the micronucleus frequency in buccal epithelium of adolescents living in an urban environment

Micronuclei and other biomarkers were evaluated in oral cells from 11- to 16-year-old girls living in a foster home in the central area of México City. Variables analyzed for possible association with these biomarkers include smoking habits, body mass index, metabolic polymorphisms for NAT1 and GSTM1 and whether the cells were obtained from the cheek or pharynx. The results indicated that individuals having the NAT1*10 homozygous genotype showed a significant increase in chromatin buds and binucleated cells. When the damage in the cheek was compared with damage in the pharynx, a significant increase in micronuclei and binucleated cells was found for the latter tissue in all the individuals analyzed.

Immunological findings in cigarette smokers

The aim of our study was to assess the effects of cigarette smoking on selected indices of immunity. The study comprised 116 men divided into three groups: 37 subjects smoking for not more than 10 yr, 39 subjects smoking for more than 10 yr, and control group consisting of 40 age-matched men who never used to smoke. The following parameters were studied: total number of lymphocytes, B-cells, T-cells subpopulations: (CD3+)T-, (CD4+)T-helper, (CD8+)T-cytotoxic and (CD16+)natural killer (NK)-cells and serum concentration of immunoglobulins A, D, G and M, C3c and C4 complement components, acute phase proteins: alpha(1)-acid glycoprotein, haptoglobin, ceruloplasmin and lysozyme. The (CD4+)/(CD8+) ratio was also calculated. The suppressive effect of tobacco smoke on human immunity was seen as decreased serum concentration of immunoglobulins and lysozyme, especially in men smoking for more than 10 yr, decreased (CD16+)NK-cells absolute number and elevated population of (CD8+)T-cytotoxic lymphocytes entailing a decrease in CD4+/CD8+ ratio.

Glutathione transferase T1 phenotype affects the toxicokinetics of inhaled methyl chloride in human volunteers

The aim of the present study was to investigate how the genetic polymorphism in glutathione transferase T1 (GSTT1) affects the metabolism and disposition of methyl chloride in humans in vivo. The 24 volunteers (13 males and 11 females) who participated in the study were recruited from a group of 208 individuals previously phenotyped for GSTT1 by measuring the glutathione transferase activity with methyl chloride in lysed erythrocytes ex vivo. Eight individuals with high (+/+), eight with medium (+/0) and eight with no (0/0) GSTT1 activity were exposed to methyl chloride gas (10 p.p.m.) in an exposure chamber for 2 h. Uptake and disposition was studied by measuring the concentration of methyl chloride in inhaled air, exhaled air and blood. A two-compartment model with two elimination pathways corresponding to exhalation and metabolism was fitted to experimental data. The average net respiratory uptake of methyl chloride was 243, 158, and 44 micromol in individuals with high, intermediate and no GSTT1 activity, respectively. Metabolic clearance was high (4.6 l/min) in the +/+ group, intermediate (2.4 l/min) in the +/0 group, and close to zero in 0/0 individuals, while the exhalation clearance was similar in the three groups. No exposure related increase in urinary S-methyl cysteine was detected. However, gender and the GSTTl phenotype seemed to affect the background levels. In conclusion, GSTT1 appears to be the sole determinant of methyl chloride metabolism in humans. Thus, individuals with nonfunctional GSTT1 entirely lack the capacity to metabolize methyl chloride.

Biological indicators of genotoxic risk and metabolic polymorphisms

International scientific publications on the influence of metabolic genotypes on biological indicators of genotoxic risk in environmental or occupational exposure are reviewed. Biomarkers of exposure (substance or its metabolites in biological fluids, urinary mutagenicity, protein and DNA adducts) and of effects (chromosome aberrations (CAs), sister chromatid exchanges (SCEs), micronuclei (Mn), COMET assay, HPRT mutants) have been evaluated according to different genotypes (or phenotypes) of several activating/detoxifying metabolic activities. In less than half the studies (43 out of 95), the influence of genotype on the examined biological indicator was found, of which four report poorly reliable results (i.e., with scarce biological plausibility, because of the inconsistency of modulated effect with the type of enzymatic activity expressed). As regards urinary metabolites, the excretion of mercapturic acids (MA) is greater in subjects with high GST activity, that of 1-pyrenol and other PAH metabolites turns out to be significantly influenced by genotypes CYP1A1 or GSTM1 null, and that of exposure indicators to aromatic amines (AA) (acetylated and non-acetylated metabolites) is modulated by NAT2. In benzene exposure, preliminary results suggest an increase in urinary t, t-muconic acid (t,t-MA) in subjects with some genotypes. On urinary mutagenicity of PAH-exposed subjects, the effects of genotype GSTM1 null, alone or combined with NAT2 slow are reported. When DNA adduct levels are clearly increased in PAH-exposed group (18 out of 22), 7 out of 18 studies report the influence of GSTM1 null on this biomarker, and of the five studies which also examined genotype CYP1A1, four report the influence of genotype CYP1A1, alone or in combination with GSTM1 null. A total of 25 out of 41 publications (61%) evaluating the influence of metabolic polymorphisms on biomarkers of effect (cytogenetic markers, COMET assay, HPRT mutants) do not record any increase in the indicator due to exposure to the genotoxic agents studied, confirming the scarce sensitivity of these indicators (mainly HPRT mutants, Mn, COMET assay) for assessing environmental or occupational exposure to genotoxic substances. Concluding, in determining urinary metabolites for monitoring exposure to genotoxic substances, there is sufficient evidence that genetically-based metabolic polymorphisms must be taken into account in the future. The unfavourable association for the activating/detoxifying metabolism of PAH is also confirmed as a risk factor due to the formation of PAH-DNA adducts. The clearly protective role played by GSTT1 on DEB (and/or related compound)-induced sister chromatid exchanges (SCEs) should be noted. The modulating effects of genotypes on protein adduct levels in environmental and occupational exposure have not yet been documented, and most studies on the influence of genotype on biological indicators of early genotoxic effects report negative results.

Role of maternal exposures and newborn genotypes on newborn chromosome aberration frequencies

Maternal exposures may induce chromosome damage and birth defects in the fetus. Polymorphic variation in genes coding for enzymes involved in metabolic activation and detoxification of environmental procarcinogens may account for some of the differences in chromosome aberration frequencies in newborns. In this study, 40 mothers completed questionnaires regarding exposures they received during their pregnancy. Umbilical cord blood samples were analyzed for chromosome aberrations. An average of 1020 metaphase cell equivalents (equal to 1020 G-banded cells) were examined from each newborn. In 26 of the newborns, genotyping analysis was performed for genes functioning in metabolic activation and detoxification (cytochrome P450 genes: CYP2D6 and CYP1A1, and phase II genes: NAT1, NAT2, GSTT1, GSTM1, GSTP1, and epoxide hydrolase). A significant association between the CYP1A1 MspI polymorphism and chromosome aberration frequencies was observed in the newborns (p=0.02), with heterozygotes showing higher aberration frequencies than the wild type homozygotes. Some large differences in chromosome aberration frequencies for other genotypes were also noted, but these were not statistically significant. Exposure to tobacco smoke in utero also appeared to increase translocation frequencies. The mean frequency of translocations per 100 cell equivalents from newborns of mothers who smoked during pregnancy was significantly higher than that of newborns whose mothers did not smoke (0.21 vs. 0.11, respectively, p=0.045).

Micronuclei in blood lymphocytes and genetic polymorphism for GSTM1, GSTT1 and NAT2 in pesticide-exposed greenhouse workers

The frequency of micronuclei (MN) in cultured peripheral lymphocytes was used as a biomarker of genotoxic effects in 34 Italian pesticide-exposed greenhouse workers and 33 unexposed referents matched with the exposed workers for age and smoking habits. The possible influence of the genetic polymorphisms of xenobiotic metabolizing enzymes glutathione S-transferase M1 (GSTM1), T1 (GSTT1), and N-acetyltransferase 2 (NAT2) was also evaluated. To restrict the analysis primarily to cells that have divided once in vitro, MN were scored only in cells showing label after a 42-h incubation with bromodeoxyuridine (BrdU), as detected by immunofluorescence (anti-BrdU technique). Two different concentrations of BrdU (0.5 and 1 microg/ml) were compared. Individual frequencies of micronucleated cells (MNCs) obtained with the two concentrations of BrdU significantly correlated with each other (r=0.55, P<0.001). Higher mean MNCs frequencies (per 1000 cells) were detected among exposed smokers (9.0 at 0.5 microg/ml BrdU and 7.8 at 1 microg/ml BrdU) than in smoking referents (6.3 and 5.9, respectively). In multiple regression analysis controlling for age, sex, smoking and genotypes, a significant elevation of MNC frequency (P=0.004 at 1 microg/ml BrdU; P=0.052 at 0.5 microg/ml BrdU) was observed in greenhouse workers with a work history of extensive pesticide spraying (n=17). Increased MNC frequencies were also associated with ageing at 0.5 microg/ml BrdU, with the GSTM1-positive genotype at both 1 (P=0.028) and 0.5 (P=0.056) microg/ml BrdU in all subjects, and with the NAT2 fast acetylator genotype in smokers at 0.5 microg/ml BrdU (P=0.043). The results indicate that MN rates are increased in greenhouse workers, especially in those involved in pesticide spraying. The GSTM1 positive and NAT2 fast genotypes appear to be associated with elevated MNC frequencies, which contradicts with earlier results on elevated chromosomal aberration rates in GSTM1 null smokers and NAT2 slow subjects.

Influence of GSTM1 and GSTT1 polymorphisms on the frequency of chromosome aberrations in lymphocytes of smokers and pesticide-exposed greenhouse workers

The influence of polymorphic glutathione S-transferases mu (GSTM1) and theta (GSTT1) on the rate of chromosome aberrations (CA) in peripheral lymphocytes of 30 pesticide-exposed floriculturists and 32 control subjects was studied. Pesticide exposure was not associated with elevated frequencies of CA. Among cigarette smokers, a statistically significant (p = 0.026) increase in baseline CA frequencies was observed in subjects with a homozygous deletion of the GSTM1 gene (GSTM1 null, n = 36) in comparison with those having at least one copy of the gene (GSTM1 positive, n = 26). This effect was mainly due to an excess of chromatid-type aberrations (p = 0.006). In addition, the few individuals (n = 5) deficient for both GSTM1 and GSTT1 showed significantly higher (p = 0.012) CA counts than GSTM1 positive GSTT1 nulls. Despite the limited number of subjects genotyped, the results seem to indicate an association between smoking induced CA frequencies and GSTM1 polymorphism, and a possible interaction between the GSTM1 and GSTT1 genotypes. The findings may be explained by the reduced detoxification capacity of GSTM1 null and GSTT1 null individuals.

Cytogenetic monitoring of occupational exposure to pesticides: characterization of GSTM1, GSTT1, and NAT2 genotypes

Occupational exposure of floriculturists is characterized by alternating periods of intense pesticide spraying and reduced or no activity. Induction of sister chromatid exchanges (SCE), structural chromosome aberrations (CA) and micronuclei (MN) was investigated in peripheral lymphocytes of a group of 23 Italian floriculturists and 22 matched controls. Blood sampling was performed during and one month after the end of intensive pesticide treatments, in order to cover a period of high and low exposure, respectively. Each donor was genotyped for glutathione S-transferase M1 (GSTM1), T1 (GSTT1), and N-acetyltransferase 2 (NAT2), three polymorphic genes involved in xenobiotic metabolism, to assess their potential role in individual genotoxic response to the pesticide exposure. No effect of the pesticide exposure on the cytogenetic parameters were detected. Smoking, however, was found to increase SCE levels. The only significant influence of phenotype composition on cytogenetic response was an increase in SCE levels in the GSTT1 positive individuals compared with the GSTT1 nulls (P=0.02). This finding was, however, based on only four GSTT1 null donors (n=41 for GSTT1 positive donors). In addition, a possible interaction was observed between smoking and GSTM1 genotype in the CA assay, GSTM1 null smokers, earlier reported to have an elevated risk for lung cancer, showing higher CA frequencies than GSTM1 positive smokers.

Diagnosis of polymorphisms in carcinogen-activating and inactivating enzymes and cancer susceptibility--a review

Up to 90% of all cancers are possibly caused by environmental factors, such as tobacco smoke, diet and occupational exposures. The majority of chemical carcinogens require metabolic activation before they interact with cellular macromolecules and can cause cancer initiation. The xenobiotic-metabolising machinery contains two main types of enzymes: the phase-I cytochromes P-450 (CYP) mediating oxidative metabolism, and phase-II conjugating enzymes. Several phase-I and phase-II genes have recently been cloned and identified in humans. Many of them show polymorphism and have been suggested to contribute to individual cancer susceptibility as genetic modifiers of cancer risk. Altered phenotypes and genotypes in the CYP subfamilies CYP1A1, CYP2D6 and CYP2E1 have been associated with tobacco smoke-induced lung cancer and other cancers. Defective glutathione S-transferase (GST) and N-acetyltransferase (NAT) enzymes have been associated with an increased risk of developing lung and bladder cancer. There are also several studies in each category in which no associations have been found. The risk of developing lung cancer is dramatically (up to 40-fold) elevated in subpopulations having simultaneously high-risk genotypes in CYP1A1 and GSTM1. There are several difficulties in this area of research. First, many of the observed restriction-fragment length polymorphisms (RFLPs) are due to mutations in introns or other silent areas of DNA, raising the possibility that any associations found between RFLPs and cancer occur only by chance. Second, biologically plausible mechanisms linking genotypes and cancer are lacking in most of the observed cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiographic changes and lung function in relation to activity of the glutathione transferases theta and mu among asbestos cement workers

Experimental data indicate that active oxygen species may be casually involved in the development of asbestos-related disease. Thus, it was hypothesized that individual differences in glutathione transferase activity, which may affect the ability to inactivate molecules formed in relation to oxidative stress, could influence the biological response to asbestos exposure. We could, however, not demonstrate an increased risk for radiographic changes or reduced lung function among asbestos cement workers deficient for glutathione transferase theta (GSTT1), glutathione transferase mu (GSTM1), or having a combined deficiency of enzyme activity.

Increased frequencies of micronuclei in T8 lymphocytes of smokers

Micronucleus frequencies and mitotic indices were analyzed in B, T4, and T8 lymphocytes from 40 smokers and 42 non-smoking referents. The highest level of micronuclei was found in T4 cells followed by T8 and B cells. These differences were statistically significant. There were statistically significant linear correlations between the micronucleus frequencies of all three subsets. There was a statistically significant effect of smoking only in the T8 cells. Smoking also increased the number of neutrophilic granulocytes and lymphocytes in the peripheral blood. There was a statistically significant effect of age on the micronucleus frequencies in T4 and T8 lymphocytes. The mitotic indices did not have any effect on the micronucleus frequencies and they were not influenced by smoking, age or sex.

Genetic polymorphism for glutathione-S-transferase mu in asbestos cement workers

OBJECTIVE

To investigate whether a lack of glutathione-S-transferase mu (GSTM1) activity was related to an increased risk for adverse outcome after asbestos exposure.

METHODS

A study was made of 78 male former asbestos cement workers, with retrospective cohort data on exposure, radiographical findings, and lung function. Venous blood samples were obtained for the analysis of GSTM1 polymorphism by the polymerase chain reaction technique. Chest x ray films were classified according to the International Labour Organisation (ILO) 1980 classification. Vital capacity (VC) and forced expiratory volume during 1 s (FEV1) were determined. Individual estimates of asbestos exposure were calculated, and expressed as duration of exposure, average exposure intensity, and cumulative dose. Data on smoking were obtained from interviews.

RESULTS

The lung function in the study group was reduced, compared with reference equations. 23% of the workers had small opacities > or = 1/0, 29% circumscribed pleural thickenings, 14% diffuse thickenings, and 12% obliterated costophrenic angles. 54% of the workers were GSTM1 deficient. They were comparable with the other workers in age, follow up time (median 30 years), and duration of exposure (median 18 years), but had a slightly higher cumulated dose (median 18 v 10 fibre-years) than the others. Neither in radiographical changes nor lung function variables were there any differences between the different GSTM1 groups. The findings were similar when smoking habits and estimated asbestos exposure were taken into account.

CONCLUSIONS

We could not show that lack of GSTM1 activity was related to an increased risk for radiographical or lung function changes in a group of asbestos cement workers, followed up for a long period after the end of exposure.

Increased frequency of micronuclei in lymphocytes of Swedish chimney sweeps

Forty-five Swedish chimney sweeps and 49 controls were investigated with micronuclei stimulated by phytohemagglutinin and pokeweed mitogen and by analysis of lymphocyte subgroups and neutrophilic leukocytes. There was a statistically significant effect among sweeps with respect to both micronuclei variables and neutrophilic leukocytes. The effect on lymphocyte micronuclei was most prominent in pokeweed mitogen-stimulated cells, which may imply that the T4 lymphocytes were preferentially damaged by the occupational exposure.

Micronuclei and mitotic index in B-, T4- and T8-cells treated with mitomycin C and gamma-irradiation

Lymphocytes were treated in vitro with mitomycin C and gamma-radiation at different doses (0-250 nmol/l and 0-2 Gy, respectively). After incubation in RPMI 1640 medium and stimulation with phytohemagglutinin for 72 h, the lymphocyte subgroups T4 (CD4), T8 (CD8) and B (CD19) were separated by an immunomagnetic method and analyzed for the presence of micronuclei. With mitomycin C the highest levels were found in T4- and B-cells. When micronuclei were induced by irradiation the T4-cells showed the highest frequencies and the B-cells the lowest. The outcome of B-cells with gamma-irradiation was probably due to a pronounced cytotoxic reaction in this cell type, which could be measured as a decrease in mitotic index.