Alteration on global and gene-spesific DNA methylation and global histone modifications in HepG2 cells in response to BPA

Abstract

Bisphenol A (BPA), as synthetic monomer used in industry in the production of polycarbonate plastic and epoxy resins, has endocrine disruptor properties and high risk on human health. Continuous release of free BPA into food, beverages, and the environment has resulted in a widespread human exposure to this chemical. Recent studies have showed the role of endocrine effects of environmental chemicals on the changes in gene expression may be associated with epigenetic mechanisms such as DNA methylation and histone modifications. The aim of the study was to investigate dose-related effects of BPA (0, 0.1 mu M, 1 and 10 mM for 48 and 96 h) on global and gene-spesific (p16, cyclin D2 and Rassf1 genes) DNA methylation in human hepatocarcinoma (HepG2) cells. We also investigated global histone modifications such as H3K9 trimethylation (H3K9me3), H3K9 acetylation (H3K9ac), H3K27 trimethylation (H3K27me3). The 50% inhibitory concentration (IC50) value of BPA was determined as 134 and 180 mu M in HepG2 cells for 24 h by MTT and neutral red uptake (NRU) tests, respectively. We observed decrease on the global levels of 5-methylcytosine and 5-hydroxymethylcytosine at 1 and 10 mM after 96 h BPA exposure. There is no significant alterations on the promoter-region of methylation and expression of p16, cyclin D2 and Rassf1 genes. Global levels of H3K9me3 decreased after 0.1 and 1 mu M concentration of BPA exposure for 48 h, while increased after 96 h 0.1 and 1 mu M of BPA exposure for. Hovewer, it has not been observed significantly changes for the global levels of H3K27me3 and H3K9ac. In this study we suggest that BPA may disrupt epigenetic events by altering global and gene-spesific DNA methylation and histone modifications in HepG2 cells.