Background:Arsenic (As) is a well-known environmental contaminant. Chronic exposure to As is known to increase the risk of cardiovascular diseases, including atherosclerosis, hypertension, diabetes, and stroke. However, the detailed mechanisms by which As causes vascular dysfunction involving endothelial integrity and permeability is unclear.Objectives:Our goal was to investigate how exposure to As leads to endothelial dysfunction.Methods:Arsenic trioxide (ATO) was used to investigate the effects and mechanisms by which exposure to As leads to endothelial dysfunction using a mouse model and cultured endothelial cell monolayers.Results:Compared with the controls, mice exposed chronically to As (10 ppb in drinking water supplied by ATO) exhibited greater vascular permeability to Evans blue dye and fluorescein isothiocyanate–labeled bovine serum albumin (FITC-BSA). In addition, endothelial monolayers treated with ATO (0.13μM As) exhibited greater intracellular gaps and permeability to low-density lipoprotein or transmigrating THP-1 cells. Furthermore, activity and protein levels of calpain-1 (CAPN-1) were significantly higher in aortas and human umbilical vein endothelial cells (HUVECs) treated with ATO. These results were consistent with effects of ATO treatment and included a rapid increase of intracellular calcium ([normalCa2+]i) and higher levels of CAPN-1 in the plasma membrane. Endothelial cell dysfunction and the proteolytic disorganization of vascular endothelial cadherin (VE-cadherin) in HUVECs in response to ATO were partially mitigated by treatment with a CAPN-1 inhibitor (ALLM) but not a CAPN-2 inhibitor (Z-LLY-FMK).Conclusions:This study found that in mice and HUVEC models, exposure to ATO led to CAPN-1 activation by increasing [normalCa2+]i and CAPN-1 translocation to the plasma membrane. The study also suggested that inhibitor treatment may have a role in preventing the vascular endothelial dysfunction associated with As exposure. The findings presented herein suggest that As-induced endothelial dysfunction involves the hyperactivation of the CAPN proteolytic system. https://doi.org/10.1289/EHP4538

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