The role of oxidative stress in zearalenone-mediated toxicity in Hep G2 cells: Oxidative DNA damage, gluthatione depletion and stress proteins induction

Zearalenone (ZEN) is a fusarial mycotoxin with several adverse effects in laboratory and domestic animals including mainly estrogenicity. While most ZEN toxic effects have been quite well investigated, little is known regarding its mechanism of toxicity. Our previous investigations have shown the involvement of cytotoxicity, inhibition of macromolecules synthesis as well as genotoxicity. However, there are no available data regarding the involvement of the oxidative stress pathway in ZEN toxicity. In this context, the aim of this study was to find out whether ZEN induces oxidative cell damage. Using human hepatocytes Hep G2 cells, ZEN-induced stress response is monitored at several levels in these cells. ZEN mediated induction of oxidative DNA damage (comet assay using the repair enzymes), modulation of gluthatione (GSH), cytotoxicity (growth inhibition) and the oxidative stress responsive gene Hsp 70 and Hsp 90 were investigated with respect to concentration and time dependency.Hep G2 cells respond to ZEN exposure by loss of cell viability, induction of oxidative DNA damage, GSH depletion and Hsp 70 and Hsp 90 induction already at concentrations, which are not yet cytotoxic. The perturbation of the oxidative status was further confirmed by the significant reduction of the induced oxidative DNA damage as well as stress protein induction when cells were pre-treated with Vitamin E prior to exposure to ZEN. Our study clearly demonstrates that oxidative damage is likely to be evoked as one of the main pathway of ZEN toxicity. This oxidative damage may therefore be an initiating event and contribute, at least in part, to the mechanism of ZEN different genotoxic and cytotoxic effects.