Deoxynivalenol induces global DNA hypomethylation by modulating the expression of miR-29b and DNA methylation regulators in HepG2 cells.

Abstract

Deoxynivalenol (DON) is a globally distributed mycotoxin that contaminates agricultural foods. Previous studies have reported high concentrations of DON in staple foods as well as its associated toxic effects; however, there are limited studies on DNA methylation. Therefore, we investigated the effect of DON on global DNA methylation as well as the possible mechanism of DNA methylation changes by miR-29b and DNA methylation regulators in human hepatocellular carcinoma (HepG2) cells. HepG2 cells were exposed to 5, 10, and 26.17 μM of DON for 72 h. Global DNA methylation was determined using ELISA, whilst DNMT1, DNMT3a, DNMT3b, MBD2, TET1-3, and miR-29b expressions were measured using qPCR. The protein expression of DNMT1, DNMT3a, DNMT3b, and MBD2 was determined by Western blotting. At concentrations of 10 and 26.17 μM, DON induced global DNA hypomethylation. DON upregulated DNMT1 and downregulated DNMT3b; however, DNMT3a was only significantly downregulated by 5 μM DON. The protein expression of DNMT1 was upregulated and DNMT3b was downregulated at all DON concentrations, whereas DNMT3a was downregulated by 10 and 26.17 μM DON. DON upregulated MBD2 mRNA expression but downregulated its protein expression. TET2 and TET3 were upregulated, while TET1 was downregulated. miR-29b expression was significantly upregulated by 10 and 26.17 μM DON. Together, these results indicate that DON induced global DNA hypomethylation in HepG2 cells by altering miR-29b expression as well as DNMTs, MBD2, and TET expression levels, and provide insight into the potential of DON, as a DNA hypomethylation inducer, to cause genomic instability and cancer initiation and progression.