However, the role of chloride channel or chloride/proton exchanger ClC-3 in the vascular endothelium and its relationship with endothelium-dependent relaxation remains unclear.<h4>Methods</h4>This study aims to explore the role and mechanism of ClC-3 in endothelial dysfunction during hypertension, by using primary cultured human umbilical vein endothelial cells (HUVECs) and ClC-3 knockout mice.<h4>Results</h4>We found that AngiotensinII (AngII) treatment significantly upregulated ClC-3 expression and reduced NO levels, while ClC-3 interference increased eNOS phosphorylation. Here, CLCN3 is linked to endothelial dysfunction.