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Type: Journal article
Title: Carboxylic acid drug-induced DNA nicking in HEK293 cells expressing human UDP-glucuronosyltransferases: Role of acyl glucuronide metabolites and glycation pathways
Author: Southwood, H.
DeGraaf, Y.
MacKenzie, P.
Miners, J.
Burcham, P.
Sallustio, B.
Citation: Chemical Research in Toxicology, 2007; 20(10):1520-1527
Publisher: Amer Chemical Soc
Issue Date: 2007
ISSN: 0893-228X
Statement of
Hamish T. Southwood, Yvette C. DeGraaf, Peter I. Mackenzie, John O. Miners, Philip C. Burcham and Benedetta C. Sallustio
Abstract: Glucuronidation of carboxylic-acid-containing drugs can yield reactive acyl (ester-linked) glucuronide metabolites that are able to modify endogenous macromolecules. Previous research has shown that several carboxylic acid drugs are genotoxic in isolated mouse hepatocytes, and that DNA damage is prevented by the glucuronidation inhibitor, borneol. Whether these species induce comparable genetic damage in human cells is unknown. In this study, we investigated the mechanisms of clofibric acid-induced genotoxicity in HEK293 cells expressing the human UDP-glucuronosyltransferases UGT1A3, UGT1A9, or UGT2B7, and screened three other carboxylic acid drugs for UGT-dependent genotoxicity. DNA damage was detected using the alkaline version of the comet assay. HEK293 cells were incubated for 18 h with vehicle (2.5 mM NaOH), 0.1–2.5 mM clofibric acid or 0.1–1.0 mM benoxaprofen, bezafibrate, or probenecid. To identify mechanisms underlying any observed genotoxicity, we treated UGT2B7 transfectants with 10 mM aminoguanidine, 1 mM borneol, or 2 mM desferrioxamine mesylate prior to co-incubation with 1 mM clofibric acid for 18 h. Compared to vehicle, clofibric acid, benoxaprofen, and probenecid produced significant DNA damage in all three UGT-transfected HEK293 cell lines, detectable from the lowest concentration tested. Bezafibrate caused DNA damage only at higher concentrations (1.0 mM) in UGT2B7- and UGT1A9-, but not UGT1A3-transfected cells. No drug-induced DNA damage was detected in untransfected cells, consistent with the limited glucuronidation capacity of these cells. The glycation/glycoxidation inhibitor aminoguanidine and the glucuronidation inhibitor borneol significantly decreased clofibric-acid-mediated DNA damage in UGT2B7 transfected cells by 73.5 and 94.8%, respectively. The inhibitor of transition -metal-catalyzed oxidation, desferrioxamine mesylate, had no significant effect on DNA damage. This study demonstrates the substrate-dependent role of human UGTs in the bioactivation of carboxylic acid drugs to genotoxic acyl glucuronide metabolites that are able to damage nuclear DNA via glycation and/or glycoxidation mechanisms.
Keywords: Kidney; Cell Line; Humans; DNA Damage; Guanidines; Clofibric Acid; Glucuronides; Glucuronosyltransferase; Anticholesteremic Agents; Enzyme Inhibitors; Comet Assay; Transfection; Cell Survival; Glycosylation; Dose-Response Relationship, Drug
Description: Copyright © 2007 American Chemical Society
RMID: 0020073188
DOI: 10.1021/tx700188x
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Appears in Collections:Pharmacology publications

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