Mutagenesis Advance Access originally published online on November 27, 2006
Mutagenesis 2007 22(1):35-42; doi:10.1093/mutage/gel049
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Oxidative DNA damage induced by Ochratoxin A in the HK-2 human kidney cell line: evidence of the relationship with cytotoxicity
Department of Food Sciences and Toxicology, Faculty of Pharmacy, University of Navarra C/ Irunlarrea 1, 31008 Pamplona, Spain
Ochratoxin A (OTA) is a mycotoxin produced by species of the genera Aspergillus and Penicillium. The kidneys are the target organ of this mycotoxin and it is considered a potent renal carcinogen in male rats. The mechanisms of its genotoxicity and carcinogenicity have been studied thoroughly, but controversial results have been published. The aim of this study was to evaluate the ability of OTA to produce single-strand DNA breaks and oxidative DNA damage in the human renal proximal tubular epithelial cell line (HK-2), due to the fact that there is no study on human kidney cells as the toxic target. In addition, we attempted to determine if biotransformation processes mediate OTA genotoxicity. Therefore, single-cell gel electrophoresis assay (comet assay) was performed after 3h- and 6h-treatments using different OTA concentrations, both cytotoxic and non-cytotoxic, in order to be able to distinguish a genotoxic effect of the mycotoxin from an indirect effect derived from its general cellular toxicity. No effect was shown where no cytotoxicity was found, both in the presence and in the absence of metabolic activation (10% rat liver S9-mix). However, oxidative DNA damage was shown at cytotoxic concentrations when formamidopyrimidine DNA glycosylase (FPG) and endonucleaseIII (EndoIII) were introduced in the assay with or without metabolic activation. Furthermore, at these concentrations, an elevation of reactive oxygen species was measured and pre-incubation with N-acetyl-L-cysteine was able to produce a slight protective effect on OTA-induced oxidative DNA damage as well as cytotoxicity. These data suggest that OTA is not acting as a direct genotoxic carcinogen and that oxidative stress is implicated in the genotoxicity and cytotoxicity observed in these human renal cells.
*To whom correspondence should be addressed at: Department of Food Sciences and Toxicology, Faculty of Pharmacy, University of Navarra, C/ Irunlarrea 1, 31008 Pamplona, Spain. Tel: +34 948 425653; Fax: +34 948 425652; Email: acerain{at}unav.es