Mutagenicity of ochratoxin A and its hydroquinone metabolite in the SupF gene of the mutation reporter plasmid Ps189.

Steven A Akman,Richard A Manderville,Marissa Adams,Doug Case,Gyungse Park

doi:10.3390/toxins4040267

Steven A Akman, Richard A Manderville + Show 3 more

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https://doi.org/10.3390/toxins4040267

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Abstract

Ochratoxin A (OTA) is a mycotoxin that enhances renal tumor formation in the outer medulla of male rat kidney. Direct DNA damage and subsequent mutagenicity may contribute to these processes. In this study we have determined whether OTA in the absence or presence of activated rat liver microsomes (RLM) or redox-active transition metals (Fe(III) or Cu(II)) causes promutagenic DNA damage in the supF gene of the mutation reporter plasmid pS189 replicating in human Ad293 cells. In addition, we have assessed the mutagenicity of the hydroquinone metabolite (OTHQ) of OTA in the absence or presence of cysteine without added cofactors. Our results show that oxidation of OTA, either by RLM or by transition metal ions, activates OTA to a directly genotoxic mutagen(s). The Fe(III)/OTA system was the most potent mutagen in our experimental system, causing a 32-fold increase in mutant fraction (MF) above the spontaneous control MF. The Cu(II)/OTA system caused a 9-fold increase in MF, while a 6–10-fold increase in MF was observed for OTA in the presence of RLM. The OTHQ metabolite is also mutagenic, especially in the presence of cysteine, in which a 6-fold increase in MF was observed. Our data provide further insight into OTA bioactivation that may account for its in vivo mutagenicity in male rat kidney.

Highlights

Ochratoxin A (OTA, Figure 1) is a human toxin produced by Penicillium verrucosum and severalAspergillus species [1,2]
OTA generates the OTB-dG adduct in male rat kidney [44] demonstrates that DNA adduction and mutagenicity remains a viable mechanism of action for OTA-mediated renal carcinogenesis [46]. These results prompted us to report the current study, in which we address the mutagenicity of OTA in cell culture, using the human mutation reporter plasmid pSP189 developed by Seidman [47]
Exposure to OTA did not significantly enhance the mutant fraction (MF) of plasmid pSP189 replicated in human Ad293 cells above the background value of 3.5 × 10−6 (Table 1)

Summary

Introduction

Ochratoxin A (OTA, Figure 1) is a human toxin produced by Penicillium verrucosum and severalAspergillus species [1,2]. Ochratoxin A (OTA, Figure 1) is a human toxin produced by Penicillium verrucosum and several. OTA has been implicated as a cause of nephropathies and urothelial tract tumors in the Balkans [5,6,7] and in North African countries [8]. OTA is a substrate for photochemical [14,15,16], electrochemical [17], and transition metal ion-mediated [18,19] oxidation. The cytotoxicity of OTA shows a close correlation with the onset of oxidative DNA damage mediated by the toxin through production of reactive oxygen species (ROS) [25,27,28]

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