DNA methyltransferase expression and DNA hypomethylation status in human hepatocytes following trichloroacetic acid exposure.

Trichloroacetic acid (TCA) is one of the major metabolites of trichloroethylene (TCE) as the significant factor of environmental and occupational pollution. TCA has been shown to induce a series of epigenetic mutation in mouse liver. However, the epigenetic cytotoxicity of TCA is still in infancy. In this study, we explored the cellular biological characteristics, the genome DNA methylation status and the expression profile of DNA methyltransferases in human hepatic L-02 cells treated with TCA with certain time and dose effects. The cell cycle measured by flow cytometry revealed an increasing S + G2 (M) phase of TCA (0.9 mM 24 h, 48 h and 72 h) treated cells after a recovery day, and sub-G1 phase was not appeared. The levels of 5 -mC were decreased in TCA (0.9 mM 24 h and 72 h) treated cells by 5-mC immunolocalization process and HPCE (decreased from 27.2% to 50.1% respectively). Meanwhile, the mCpG% in normal L-02 cells and TCA (0.9 mM 48 h) treated cells was 79.6% ± 6.5% and 50.8% ± 3.8%, respectively (P < 0.05). It also revealed that treatment of L-02 cells with TCA induced decreased in DNMT1 and DNMT3a mRNA and protein levels with a time-dependent manner and a dose-response relationship, while DNMT3b had no obvious change. These results establish a link between DNA methyltransferases and Genome DNA hypomethylation, which is associated with TCA exposure.