Regulation of Cx43 and its role in trichloroethylene-induced cardiac toxicity in H9C2 rat cardiomyocytes.

Trichloroethylene (TCE), a widespread environmental contaminant, has been linked to congenital heart defects. Abnormal regulation of Connexin 43 is closely associated with various cardiac diseases. However, it is yet to be established how Cx43 responds to environmental pollutants. Here, we aim to explore the role of Cx43 in TCE-induced cardiac toxicity using H9C2 cardiomyocytes. EdU incorporation assay and cell cycle analysis revealed that increased number of TCE-treated cells entered into the S stage, indicating that TCE exposure provoked cell proliferation. Additionally, compromised mitochondrial function was observed in TCE-treated cells, and inhibition of mitochondrial permeability transition pore (mPTP) with Cyclosporin A or eliminating mitochondrial ROS by MitoQ alleviated the TCE-induced cardiac toxicity. Importantly, TCE exposure increased the protein expression levels of Cx43 and stimulated the recruitment of Cx43 to the mitochondria. TCE exposure disrupted canonical Wnt signal pathway, resulting in downregulation of antioxidant genes and ß-catenin. The adverse effects of TCE on Wnt signal pathway activation, mitochondrial function and cell proliferation were efficiently counteracted by either Cx43 knockdown or pharmaceutical activator of Wnt signaling, CHIR-99021. Taken together, our results for the first time revealed that dysregulation of Cx43 mediates TCE-induced heart defects via mitochondrial dysfunction and Wnt signaling inhibition, suggesting that Cx43 can be a potential molecular marker or therapeutic target for cardiac diseases caused by environmental pollutants.

Cx43 overexpression is involved in the hyper-proliferation effect of trichloroethylene on human embryonic stem cells.

Trichloroethylene (TCE) is a major environmental contaminant. Maternal exposure of TCE is linked to developmental defects, but the mechanisms remain to be elucidated. Along with a strategy of 3Rs principle, human embryonic stem cells (hESCs) are regarded as most promising in vitro models for developmental toxicity studies. TCE interfered with hESCs differentiation, but no report was available for TCE effects on hESCs proliferation. Here, we aimed to explore the toxic effects and mechanisms of TCE on hESCs proliferation. Treatment with TCE, did not affect the pluripotency genes expression. However, TCE enhanced hESCs proliferation, manifested by increased cell number, PCNA expression and EdU incorporation. Moreover, TCE exposure upregulated the protein expression levels of Cx43 and cyclin-dependent kinases. Knockdown of Cx43 attenuated the TCE-induced cell hyper-proliferation and CDK2 upregulation. Furthermore, TCE increased Akt phosphorylation, and the inhibition of Akt blocked the TCE-induced Cx43 overexpression and cell proliferation. In conclusion, TCE exposure resulted in upregulation of Cx43 via Akt phosphorylation, consequently stimulated CDK2 expression, contributing to hyper-proliferation in hESCs. Our study brings to light that TCE stimulated the proliferation of hESCs via Cx43, providing a new research avenue for the causes of TCE-induced developmental toxicity.