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)

We present here the results obtained within the framework of an EU funded project aimed to develop and validate alternative metabolic activating systems to be used in short-term mutagenicity assays, in order to reduce the use of laboratory animals for toxicology testing. The activating systems studied were established cell lines (Hep G2, CHEL), genetically engineered V79 cell lines expressing specific rat cytochromes P450, erythrocyte-derived systems, CYP-mimetic chemical systems and plant homogenates. The metabolically competent cell lines were used as indicator cells for genotoxic effects as well as for the preparation of external activating systems using other indicator cells. The following endpoints were used: micronuclei, chromosomal aberrations and sister chromatid exchanges, mutations at the hprt locus, gene mutations in bacteria (Ames test), unscheduled DNA synthesis and DNA breaks detected in the comet assay. All metabolic systems employed activated some promutagens. With some of them, promutagens belonging to many different classes of chemicals were activated to genotoxicants, including carcinogens negative in liver S9-mediated assays. In other cases, the use of the new activating systems allowed the detection of mutagens at much lower substrate concentrations than in liver S9-mediated assays. Therefore, the alternative metabolizing systems, which do not require the use of laboratory animals, have a substantial potential in in vitro toxicology, in the basic genotoxicity testing as well as in the elucidation of activation mechanisms. However, since the data basis is much smaller for the new systems than for the activating systems produced from subcellular liver preparations, the overlapping use of both systems is recommended for the present and near future. For example, liver S9 preparations may be used with some indicator systems (e.g., bacterial mutagenicity), and metabolically competent mammalian cell lines may be used with other indicator systems (e.g., a cytogenetic endpoint) in a battery of basic tests.
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PMID:Development and validation of alternative metabolic systems for mutagenicity testing in short-term assays. 869 90

2-Amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC) and some metabolites were investigated for mutagenicity in mammalian cell lines and bacterial strains engineered for the expression of human enzymes. MeAalphaC induced gene mutations (studied at the hprt locus) in Chinese hamster V79-derived cells co-expressing cytochrome (CYP) 1A2 and sulphotransferase (SULT) 1A1 even at a concentration of 30 nM, but was inactive in cells co-expressing CYP1A2 and N-acetyltransferase (NAT) 1 or 2. MeAalphaC, tested in the presence of rat liver post-mitochondrial fraction, showed strongly enhanced mutagenicity in a Salmonella typhimurium strain expressing human SULT1A1 compared with the control (recipient) strain TA1538/1,8-DNP (deficient in endogenous acetyltransferase). Mutagenicity was also enhanced, although to a lesser extent, when NAT2 was expressed in the latter strain. The metabolite, 2-hydroxylamino-3-methyl-9H-pyrido[2,3-b]indole (N-OH-MeAalphaC) was a direct mutagen to strains TA1538 and TA1538/ 1,8-DNP. This mutagenicity was strongly enhanced in corresponding strains expressing SULT1A1. A moderate enhancement was observed when SULT1A2, SULT1B1, SULT1C2 or NAT2 were expressed in strain TA1538. The remaining enzymes studied (SULT1A3, 1C1, 1E1, 2A1, 2B1a, 2B1b, 4A1 and NAT1) did not indicate any activation of N-OH-MeAalphaC. Preliminary mutagenicity experiments in SULT-expressing S.typhimurium strains were conducted with other hydroxylated metabolites of MeAalphaC. The phenols, 6- and 7-hydroxy-MeAalphaC, were inactive under the conditions studied. The benzylic alcohol, 2-amino-3-hydroxymethyl-9H-pyrido[2,3-b]indole, was mutagenic in a strain expressing SULT1A1, but its activity was much weaker than that of N-OH-MeAalphaC. Thus, N-hydroxylation (e.g. mediated by CYP1A2) and sulpho conjugation (primarily mediated by SULT1A1) was the dominating activation pathway of MeAalphaC in model systems engineered for human enzymes. Some other SULT forms as well as NAT2 were also capable of activating N-OH-MeAalphaC, although with much lower efficiency than SULT1A1. Another minor activation pathway involved benzylic hydroxylation followed by sulpho conjugation by SULT1A1.
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PMID:Bioactivation of the heterocyclic aromatic amine 2-amino-3-methyl-9H-pyrido [2,3-b]indole (MeAalphaC) in recombinant test systems expressing human xenobiotic-metabolizing enzymes. 1472 82

Sudan-1 and para red are industrial dyes that have been illegally added to some foodstuffs, leading to withdrawal of the adulterated products throughout the UK since 2003. This resulted in international concern that arose because Sudan-1 is classified by International Agency for Research on Cancer as a Category 3 carcinogen. However, little is known about the dose response of this chemical at low, more biologically relevant, doses. The study therefore aimed to characterize the dose response for gene mutation and chromosomal damage induced by two azo dyes, namely Sudan-1 and para red. Gene mutations were analysed using the hypoxanthine phosphoribosyltransferase forward mutation assay and chromosomal damage was measured using the cytokinesis-blocked micronucleus assay. Two cell lines were used in these investigations. These were the AHH-1 cell line, which inducibly expresses CYP1A1, and the MCL-5 cell line derived from a subpopulation of AHH-1 cells that expresses a particularly high level of CYP1A1 activity. The MCL-5 cell line has also been transfected with two plasmids that stably express CYP1A2, CYP2A6 and CYP3A4 and all four of these CYP enzymes are known to metabolically activate Sudan-1. AHH-1 cells were used to investigate the dose response of the azo dyes, and MCL-5 cells were used to see if the dose response changed with increased metabolism. Sudan-1 induced a non-linear dose-response curve for gene mutation and chromosomal damage in AHH-1 cells. The genotoxic activity of Sudan-1 was greatly increased in MCL-5 cells. This indicated that the oxidation metabolites from Sudan-1 were both more mutagenic and more clastogenic than the parent compound. Para red also demonstrated a non-linear dose response for both gene mutation and chromosome damage in AHH-1 cells, and an increase in micronuclei induction was observed after increased oxidative metabolism in MCL-5 cells. Sudan-1 and para red are genotoxic chemicals with non-linear dose responses in AHH-1 but not in MCL-5 cells, and oxidative metabolism increases the genotoxic effect of both compounds.
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PMID:Metabolic influences for mutation induction curves after exposure to Sudan-1 and para red. 2019 15