Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00492 (hypoxanthine-guanine phosphoribosyltransferase)
 2,385 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies of mutation at the hypoxanthine phosphoribosyl transferase (hrpt) locus in human T-cells have the potential to elucidate the molecular basis of in vivo mutagenesis, reveal exposure dependent changes in ther background frequency of mutation, and provide knowledge on individual sensitivity. Styrene exposed lamination workers in Bohemia showed a significantly higher frequency of hprt mutant cells than Swedish control populations studied simultaneously. In a study of 47 healthy, non-smoking male bus maintenance workers exposed to diesel exhausts, soot and oil, and 22 unexposed controls, a significant correlation (P = 0.008) was obtained between the levels of aromatic DNA adducts and frequencies of hprt-mutant T-cells. In the group of workers with the highest exposure, subjects with glutathione S-transferase (GSTM1) deficiency showed significantly higher (P < 0.05) frequency of hprt mutant T-cells than GSTM1-positive subjects. The highest adduct levels were found in subjects with the combined genotype of GSTM1 and NAT2 deficiency (GSTM1-negative slow acetylators). These results indicate that GSTM1 and NAT2 genotypes may play a role in determining the individual levels of hprt mutation and DNA adducts. Using PCR-based screening methods, hprt mutations have been classified in 462 T-cell clones from 43 subjects in this study population. Deletions were found in 3% of the mutants, coding errors in 81% and splice mutations in 17%. Transitions and transversions were equally common, and all types of base substitutions were detected.
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PMID:Analysis of mutation at the hprt locus in human T lymphocytes. 859 72

While 1,3-butadiene is carcinogenic in rodents, cancer causation in humans is less certain. We examined a spectrum of genotoxic outcomes in 41 butadiene polymer production workers and 38 non-exposed controls, in China, to explore the role of butadiene in human carcinogenesis. Because in vitro studies suggest that genetic polymorphisms in glutathione S-transferase enzymes influence genotoxic effects of butadiene, we also related genotoxicity to genetic polymorphisms in GSTT1 and GSTM1. Among butadiene-exposed workers, median air exposure was 2 p.p.m. (6 h time-weighted average), due largely to intermittent high level exposures. Compared with unexposed subjects, butadiene-exposed workers had greater levels of hemoglobin N-(2,3,4-trihydroxybutyl)valine (THBVal) adducts (P < 0.0001) and adduct levels tended to correlate, among butadiene-exposed workers, with air measures (P = 0.03). Butadiene-exposed workers did not differ, however, from unexposed workers with respect to frequency of uninduced or diepoxybutane-induced sister chromatid exchanges, aneuploidy as measured by fluorescence in situ hybridization of chromosomes 1, 7, 8 and 12, glycophorin A variants or lymphocyte hprt somatic mutation. Also among the exposed, greater THBVal levels were not associated with increases in uninduced sister chromatid exchanges, aneuploidy, glycophorin A or hprt mutations. Butadiene-exposed workers had greater lymphocyte (P = 0.002) and platelet counts (P = 0.07) and lymphocytes as a percentage of white blood cells were moderately correlated with greater THBVal levels (Spearman's phi = 0.32, P = 0.07). Among butadiene-exposed workers, neither GSTM1 nor GSTT1 genotype status predicted urinary mercapturic acid butanediol formation, THBVal adducts, uninduced sister chromatid exchanges, aneuploidy or mutations in the glycophorin A or hprt genes. Overall, the study demonstrated exposure to butadiene in these workers, by a variety of short-term and long-term measures, but did not show specific genotoxic effects, at the chromosomal or gene levels, related to that exposure.
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PMID:Genotoxic markers among butadiene polymer workers in China. 1060 34

Molecular epidemiology is a new and evolving area of research, combining laboratory measurement of internal dose, biologically effective dose, biologic effects, and influence of individual susceptibility with epidemiologic methodologies. Biomarkers evaluated were selected according to basic scheme: biomarkers of exposure--metabolites in urine, DNA adducts, protein adducts, and Comet assay parameters; biomarkers of effect--chromosomal aberrations, sister chromatid exchanges, micronuclei, mutations in the hypoxanthine-guanine phosphoribosyltransferase gene, and the activation of oncogenes coding for p53 or p21 proteins as measured on protein levels; biomarkers of susceptibility--genetic polymorphisms of genes CYP1A1, GSTM1, GSTT1, NAT2. DNA adducts measured by 32P-postlabeling are the biomarker of choice for the evaluation of exposure to polycyclic aromatic hydrocarbons. Protein adducts are useful as a biomarker for exposure to tobacco smoke (4-aminobiphenyl) or to smaller molecules such as acrylonitrile or 1,3-butadiene. Of the biomarkers of effect, the most common are cytogenetic end points. Epidemiologic studies support the use of chromosomal breakage as a relevant biomarker of cancer risk. The use of the Comet assay and methods analyzing oxidative DNA damage needs reliable validation for human biomonitoring. Until now there have not been sufficient data to interpret the relationship between genotypes, biomarkers of exposure, and biomarkers of effect for assessing the risk of human exposure to mutagens and carcinogens.
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PMID:Molecular epidemiology studies on occupational and environmental exposure to mutagens and carcinogens, 1997-1999. 1069 23

1,3-Butadiene (BD) is a major commodity chemical used in the manufacture of synthetic rubber and various plastics and has been shown to be a potent animal carcinogen and a probable human carcinogen. The bioactivation of BD to reactive epoxides, and the balance between activation and detoxication of these reactive metabolites, is thought to play a critical role in the genotoxic and carcinogenic effects of BD. The detoxication of reactive BD metabolites involves enzymatic conjugation with glutathione by glutathione S-transferases (GSTs) and by hydrolysis, a reaction mediated by microsomal epoxide hydrolase (mEH). Since polymorphisms in genes of xenobiotic-metabolizing enzymes such as mEH may influence individual susceptibility to adverse health effects from BD exposure, we tested the hypothesis that the mEH Tyr113His polymorphism increases sensitivity to the genotoxic effects of BD in exposed workers. We used the autoradiographic hprt mutant lymphocyte assay as a biomarker of effect to identify genotoxicity associated with BD exposure in 49 workers from two styrene/butadiene polymer plants in Southeast Texas. Exposure to BD was assessed by collecting breathing zone air samples using passive badge dosimeters for three full 12 h work shifts 25, 20 and 14 days before blood was collected for genotyping and for the hprt assay. We genotyped the study participants for the Tyr113His polymorphism in the mEH gene and also for deletion polymorphisms in the glutathione S-transferase genes, GSTM1 and GSTT1, as potential biomarkers of susceptibility to BD. Our data indicate that the majority of the study subjects (67%) were exposed to very low levels of BD of <150 parts per billion (p.p.b.) time-weighted average (TWA). In some workers, however, we found levels of BD exposures that exceeded a TWA of 2000 p.p.b. Our data indicate a significant (P < 0.05) 2-fold increase in frequencies of hprt variant (mutant) lymphocytes (Vf) in workers exposed to >150 p.p.b. BD, compared with workers exposed to <150 p.p.b. There was no significant effect from individual GSTM1, GSTT1 or mEH genotypes in workers exposed to <150 p.p.b. BD. In workers exposed to >150 p.p.b., individuals with at least one polymorphic mEH His allele (His/His or His/Tyr genotypes) had a significant (P < 0.001) 3-fold increase in Vf (mean Vf x 10(-6) +/- SE = 13.25 +/- 1.78) compared with individuals with the Tyr/Tyr genotype (mean Vf x 10(-6) +/- SE = 4.02 +/- 0.72). There was no significant effect from individual GSTM1 or GSTT1 polymorphisms, but combined polymorphism analysis showed that the genetic damage was highest in individuals who had at least one mEH His allele and either the GSTM1 and/or GSTT1 null genotypes (hprt Vf = 14.19 +/- 2.30 x10(-6)). In contrast, this response was not observed in individuals exposed to levels of BD < 150 p.p.b. These results indicate that polymorphisms in the mEH gene may play a significant role in human sensitivity to the genotoxic effects of BD exposure, and that the hprt mutant lymphocyte assay can serve as a sensitive biomarker of genotoxicity for monitoring occupational exposure to BD in industrial settings. Additional investigations in larger populations of workers are needed to confirm our results and to characterize the possible role of additional mEH polymorphisms in the induction of genetic damage associated with occupational exposure to butadiene.
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PMID:Human sensitivity to 1,3-butadiene: role of microsomal epoxide hydrolase polymorphisms. 1123 81

In the human glutathione S-transferase (GST) mu gene family, homozygous deletion of GSTM1 is the null phenotype (frequency of approximately 50% in Caucasians). In the current study, GSTM1 status was determined in human cell lines using reverse transcriptase, polymerase chain reaction, and immunochemistry. Cell lines were challenged with a range of doses of styrene-7,8-oxide (SO) and then toxicity and genotoxicity were monitored. Toxicity was determined by growth in flasks and genotoxicity by cloning in microplates in the presence/absence of 6-thioguanine, to detect mutations at the hypoxanthine phosphoribosyltransferase (hprt) locus. A SO concentration-dependent decrease in survival was observed for all cell lines, with GSTM1-deficient lines being more sensitive. The IC(50)s of deficient and proficient cell lines were 0.45 and 0.55 mM SO, respectively. The difference between survival of GSTM1-deficient and -proficient cell lines approached statistical significance. The background mutation frequency of GSTM1-deficient cell lines was 2 x 10(-5), and that of GSTM1-proficient cell lines was 3 x 10(-6). GSTM1-deficient cell lines were significantly more sensitive than GSTM1-proficient cell lines to mutation induction for concentrations up to 2.5 mM SO (P < 0.001, regression analysis). These results suggest that cell lines containing metabolically competent GSTM1 are able to efficiently use GSTM1 to conjugate SO and reduce its hazard. This supports the epidemiological evidence that GSTM1 influences sensitivity to chemical carcinogenesis and subsequent risk of cancer induction.
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PMID:Role of glutathione S-transferase mu (GSTM1) in styrene-7,8-oxide toxicity and mutagenicity. 1142 77