Effect of trivalent arsenicals on cell proliferation in mouse and human microvascular endothelial cells

Chronic exposure to high levels of inorganic arsenic (iAs) has been associated with cancerous and non-cancerous health effects, including cardiovascular effects. However, the mechanism for a presumed toxic effect of arsenic on vascular tissue is not clear. Our working hypothesis is that inorganic trivalent arsenic and its methylated metabolites react with cysteine-containing cellular proteins and alter their function leading to adverse events such as cytotoxicity or proliferation. In this study, human microvascular endothelial cells (HMEC1) and mouse microvascular endothelial cells (MFP-MVEC) were exposed to arsenite (iAs^III), monomethylarsonous acid (MMA^III), or dimethylarsinous acid (DMA^III) for 72h to evaluate cytotoxicity, and for 24, 48 or 72h to evaluate cell proliferation. Both cell lines showed similar LC₅₀ values, from 0.1 to 2.4μM, for all three trivalent arsenicals. The endothelial cells treated with1nM to 1μM concentrations of the three trivalent arsenicals did not show increased cell proliferation at 24, 48 or 72h or increased rate of proliferation at 72h of exposure. Overall, cytotoxicity of trivalent arsenicals to microvascular endothelial cells is similar to their cytotoxicity to epithelial cells, and that these compounds are not mitogenic.