Arsenite promotes apoptosis and dysfunction in microvascular endothelial cells via an alteration of intracellular calcium homeostasis.Suriyo, T., Watcharasit, P., Thiantanawat, A. and Satayavivad, J.
Toxicology in Vitro, 26(3): 386-395.
Vascular endothelium has been considered as a target for arsenic-induced cardiovascular toxicity. The present study demonstrated that arsenite caused slow and sustained elevation of intracellular free calcium levels ([Ca(2+)](i)) in HMEC-1, a human microvessel-derived endothelial cell line, in a concentration-dependent manner. Pretreatment with U-73122 (a specific PLC inhibitor) or 2-APB (a specific IP(3) receptor antagonist) attenuated this effect, suggesting that PLC/IP(3) signaling cascade is involved in arsenite-induced elevation of [Ca(2+)](i). Cytotoxic concentrations of arsenite (5 and 10μM) significantly enhanced endothelial nitric oxide synthase (eNOS) phosphorylation, nitric oxide (NO) production and apoptosis after 24-h exposure. Additionally, 2-APB attenuated eNOS phosphorylation and apoptosis induced by arsenite, indicating that Ca(2+)-mediated eNOS activation participates in arsenite-induced endothelial cell apoptosis. Moreover, we also found that non-apoptotic concentrations of arsenite (0.5 and 1μM) dramatically mitigated thrombin-induced rapid transient rise of [Ca(2+)](i), eNOS phosphorylation and NO production, suggesting functional disruption of endothelial by arsenite, and these effects occurred without an alteration of PLC-β(1) and thrombin receptor levels. Altogether, the results reveal that arsenite induces apoptotic cell death and endothelial dysfunction as indicated by the reduction of thrombin responses, particularly related to an alteration of intracellular Ca(2+) homeostasis.