Enhancement of bacterial mutagenicity of bifunctional alkylating agents by expression of mammalian glutathione s-transferase

Thier, Ricarda, Muller, Michael, Taylor, John B., Pemble, Sally E., Ketterer, Brian, & Guengerich, F. Peter (1995) Enhancement of bacterial mutagenicity of bifunctional alkylating agents by expression of mammalian glutathione s-transferase. Chemical Research in Toxicology, 8(3), pp. 465-472.

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Abstract

Recently, we inserted the plasmid vector pKK233-2 containing rat GSH S-transferase (GST) 5-5 cDNA into Salmonella typhimurium TA1535 and found that these bacteria [GST 5-5(+)] expressed the protein and produced mutations when ethylene or methylene dihalides were added [Thier, R., Taylor, J. B., Pemble, S. E., Ketterer, B., Persmark, M., Humphreys, W. G., and Guengerich, F. P. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 8576-8580]. After exposure to the known GST 5-5 substrate 1,2-epoxy-3-(4′-nitrophenoxy)propane, the GST 5-5(+) strain showed fewer mutants than the bacteria transfected with the cDNA clone in a reverse orientation [GST 5-5(-)], suggesting a protective role of GST 5-5. However, mutations were considerably enhanced in the GST 5-5(+) strain [as compared to GST 5-5(-)] when 1,2,3,4-diepoxybutane (butadiene diepoxide) or 1,2-epoxy-4-bromobutane was added. The GST 5-5(+) and GST 5-5(-) bacterial stains showed similar responses to 1,2-epoxypropane, 3,4-epoxy-1-butene, and 1,4-dibromobutane. The results suggest that some bifunctional activated butanes are transformed to mutagenic products through GSH conjugation. We also found that the GST 5-5(+) strain showed enhanced mutagenicity with 1,4-dibromo-2,3-epoxybutane, 1,2-epoxy-3-bromopropane (epibromohydrin), and (±)-1,4-dibromo-2,3-dihydroxybutane. The possibility was considered that a 5-membered thialonium ion may be involved in the mutagenicity. Model thialonium compounds were rather stable to hydrolysis in aqueous solution at pH 7.4 and slowly alkylated 4-(4-nitrobenzyl)pyridine. The presence of a hydroxyl group β to the sulfur did not enhance reactivity. Mechanisms involving episulfonium ions are considered more likely. Potential oxidation products of the toxic pesticide 1,2-dibromo-3-chloropropane (DBCP) were also considered in this system. DBCP itself gave rather similar results in the two strains. Others have reported that oxidation of DBCP is required for mutagenicity, along with GST-catalyzed GSH conjugation [Simula, T. P., Glancey, M. J., Söderlund, E. J., Dybing, E., and Wolf, C. R. (1993) Carcinogenesis 14, 2303-2307]. The putative oxidation product 1,2-dibromopropional did not show a difference between the two strains. However, 1,3-dichloroacetone, a model for the putative oxidation product 1-bromo-3-chloroacetone, was considerably more mutagenic in the GST 5-5(+) strain.

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ID Code: 77491
Item Type: Journal Article
Refereed: Yes
Keywords: 1 bromo 3 chloroacetone, 1, 4 dibromo 2, 3 dihydroxybutane, 4 (4 nitrobenzyl)pyridine, alkylating agent, butadiene diepoxide, epibromohydrin, glutathione transferase, unclassified drug, article, bacterial mutation, mutagen testing, mutagenicity, nonhuman, salmonella typhimurium, Alkylating Agents, Animal, Drug Synergism, Glutathione, Insecticides, Organochlorine, Mutagenicity Tests, Mutagens, Propane, Rats, Support, Non-U.S. Gov't, Support, U.S. Gov't, P.H.S.
DOI: 10.1021/tx00045a019
ISSN: 0893-228X
Divisions: Current > Schools > School of Clinical Sciences
Current > QUT Faculties and Divisions > Faculty of Health
Copyright Owner: Copyright 1995 American Chemical Society
Deposited On: 16 Oct 2014 02:10
Last Modified: 16 Oct 2014 02:10

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