Journal Article

The contribution of UDP-glucuronosyltransferase 1A9 on CYP1A2-mediated genotoxicity by aromatic and heterocyclic amines

Mei-Fei Yueh, Nghia Nguyen, Maryam Famourzadeh, Christian P. Strassburg, Yoshimitsu Oda, F.Peter Guengerich and Robert H. Tukey

in Carcinogenesis

Volume 22, issue 6, pages 943-950
Published in print June 2001 | ISSN: 0143-3334
Published online June 2001 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/22.6.943
The contribution of UDP-glucuronosyltransferase 1A9 on CYP1A2-mediated genotoxicity by aromatic and heterocyclic amines

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The importance of environmental and dietary arylamines, and heterocyclic amines in the etiology of human cancer is of growing interest. These pre-carcinogens are known to undergo bioactivation by cytochrome P450 (CYP)-directed oxidation, which then become substrates for the UDP-glucuronosyltransferases (UGTs). Thus, glucuronidation may contribute to the elimination of CYP-mediated reactive intermediate metabolites, preventing a toxic event. In this study, human UGTs were analyzed for their ability to modulate the mutagenic actions of N-hydroxy-arylamines formed by CYP1A2. Studies with recombinant human UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B4, UGT2B7 and UGT2B15 expressed in heterologous cell culture confirmed that UGT1A9 glucuronidated the mutagenic arylamines N-hydroxy-2-acetylaminofluorene (N-hydroxy-2AAF) and 2-hydroxyamino-1-methyl-6-phenylimidazo(4,5-b)pyridine (N-hydroxy-PhIP). To examine the mutagenic potential of these agents, a genotoxicity assay was employed using Salmonella typhimurium NM2009, a bacterial strain expressing the umuC SOS response gene fused to a β-galactosidase reporter lacZ gene. DNA modification results in the induction of the umuC gene and subsequent enhancement of β-galactosidase activity. Both N-hydroxy-2AAF and N-hydroxy-PhIP stimulated a dose-dependent increase in bacterial β-galactosidase activity. In addition, the procarcinogens 2AAF and PhIP were efficiently bioactivated to bacterial mutagens when incubated with Escherichia coli membranes expressing CYP1A2 and NADPH reductase. CYP1A2 generated 2AAF- and PhIP-mediated DNA damage, but only the action of N-hydroxy-2AAF was blocked by expressed UGT1A9. These results indicate that UGT1A9 can control the outcome of a genotoxic response. The results also indicate that while a potential toxicant such as N-hydroxy-PhIP can serve as substrate for glucuronidation, its biological actions can exceed the capacity of the detoxification pathway to prevent the mutagenic episode.

Keywords: 2AAF, 2-acetylaminofluorene; CYP, cytochrome P450, S. typhyimurium, Salmonella typhimurium; N-hydroxy-2AAF, N-hydroxy-2-acetylaminofluorene; N-hydroxy-PhIP, 2-hydroxy-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine; β-NAPD, β-nicotinamide adenine dinucleotide phosphate; ONGP, O-nitrophenyl-β-d-galactophranoside; PhIP, 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine; Sf9, Spodoptera frugiperda insect cells; UDPGlcA, uridine 5′-diphosphoglucuronic acid; UGT, UDP-glucuronosyl-transferase.

Journal Article.  6578 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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