Evaluation of the epigenetic alterations and gene expression levels of HepG2 cells exposed to zearalenone and alpha-zearalenol

Zearalenone, produced by various Fusarium species, is a non-steroidal estrogenic mycotoxin that contaminates cereals, resulting in adverse effects on human health. We investigated the effects of zearalenone and its metabolite alpha zearalenol on epigenetic modifications and its relationship with metabolic pathways in human hepatocellular carcinoma cells following 24 h of exposure. Zearalenone and alpha zearalenol at the concentrations of 1, 10 and 50 mu M significantly increased global levels of DNA methylation and global histone modifications (H3K27me3, H3K9me3, H3K9ac). Expression levels of the chromatin modifying enzymes EHMT2, ESCO1, HAT1, KAT2B, PRMT6 and SETD8 were upregulated by 50 mu M of zearalenone exposure using PCR arrays, consistent with the results of global histone modifications. Zearalenone and alpha zearalenol also changed expression levels of the AhR, LXR alpha, PPAR alpha, PPAR gamma, L-fabp, LDLR, Glut2, Akt1 and HK2 genes, which are related to nuclear receptors and metabolic pathways. PPAR gamma, a key regulator of lipid metabolism, was selected from among these genes for further analysis. The PPAR gamma promoter reduced methylation significantly following zearalenone exposure. Taken together, the epigenetic mechanisms of DNA methylation and histone modifications may be key mechanisms in zearalenone toxicity. Furthermore, effects of zearalenone in metabolic pathways could be mediated by epigenetic modifications.