Trichloroethylene (TCE) is a halogenated hydrocarbon used as a solvent in industrial settings and in house-cleaning products. Exposure to TCE has been linked to increased risk for congenital heart malformations in both human and animal models. Previous studies showed TCE exposure reduced the expression and function of the ATP-dependent calcium pump, Serca2a, which is important for regulating calcium flux in myocytes and maintaining physiological cardiac function. In this study, we investigated whether TCE reduced Serca2a expression by altering the methylation status of its proximal promoter region. Low doses of TCE exposure (10 ppb) induced DNA hyper methylation in the Serca2 promoter region in cardiac myoblast cells and rat embryonic cardiac tissue. TCE exposure induced DNA methylation in a region of the Serca2 promoter which is the target for SP1 binding site essential for regulation of Serca2a transcriptional activity. Chromatin immunoprecipitation data confirmed that TCE exposure reduced the binding of SP1 to the Serca2 promoter region adjacent to the methylated CpG dimer. Finally, low-dose TCE exposure reduced the concentration of S-adenosyl-methionine in exposed cells and embryos. These cumulative data indicate that epigenetic mechanisms, including DNA methylation, may be important in mediating the teratogenic effects of TCE in embryonic heart.

Background Previous studies show gene expression alterations in rat embryo hearts and cell lines that correspond to the cardio-teratogenic effects of trichloroethylene (TCE) in animal models. One potential mechanism of TCE teratogenicity may be through altered regulation of calcium homeostatic genes with a corresponding inhibition of cardiac function. It has been suggested that TCE may interfere with the folic acid/methylation pathway in liver and kidney and alter gene regulation by epigenetic mechanisms. According to this hypothesis, folate supplementation in the maternal diet should counteract TCE effects on gene expression in the embryonic heart. Approach To identify transcriptional targets altered in the embryonic heart after exposure to TCE, and possible protective effects of folate, we used DNA microarray technology to profile gene expression in embryonic mouse hearts with maternal TCE exposure and dietary changes in maternal folate. Results Exposure to low doses of TCE (10ppb) caused extensive alterations in transcripts encoding proteins involved in transport, ion channel, transcription, differentiation, cytoskeleton, cell cycle and apoptosis. Exogenous folate did not offset the effects of TCE exposure on normal gene expression and both high and low levels of folate produced additional significant changes in gene expression. Conclusions A mechanism where TCE induces a folate deficiency does not explain altered gene expression patterns in the embryonic mouse heart. The data further suggest that use of folate supplementation, in the presence of this toxin, may be detrimental and non-protective of the developing embryo.