Endothelin‐1 (ET‐1), an endothelium‐derived vasoactive peptide, participates in the regulation of endothelial function through mechanisms that are not fully elucidated. This study examined the impact of ET‐1 on oxidative stress, apoptosis and cell proliferation in human umbilical vein endothelial cells (HUVEC). HUVECs were challenged for 24 h with ET‐1 (10 pM–10 nM) in the absence or presence of the ET_B receptor antagonist BQ788 (1 μM) or the NADPH oxidase inhibitor apocynin (1 μM). Reactive oxygen species (ROS) were detected using chloromethyl‐2′,7′‐dichlorodihydrofluorescein diacetate. Apoptosis was evaluated with 4′,6′‐diamidino‐2′‐phenylindoladihydrochloride staining and by the caspase‐3 assay. Cell proliferation was measured by a colorimetric assay. Expression of NADPH oxidase, Akt, pAkt, Bcl‐2, Bax, IκB, caveolin‐1 and eNOS was evaluated by Western blot analysis.

ET‐1 significantly enhanced ROS generation and cell proliferation following 24‐h incubation, both of which were prevented by BQ788 or apocynin, consistent with the ability of ET‐1 to directly upregulate NADPH oxidase. ET‐1 itself did not affect apoptosis but attenuated homocysteine‐induced apoptosis through an ET_B receptor‐mediated mechanism. Western blot analysis indicated that ET‐1 alleviated homocysteine (Hcy)‐induced apoptosis, likely acting by antagonizing the Hcy‐induced decreases in Akt, pAkt, pAkt‐to‐Akt, Bcl‐2‐to‐Bax ratios and increases in Bax and caveolin‐1 expression. Furthermore, ET‐1 downregulated expression of caveolin‐1 and eNOS, which was attenuated by BQ788 or apocynin.

In summary, our results suggest that ET‐1 affects oxidative stress, proliferation and apoptosis possibly through ET_B, NADPH oxidase, Akt, Bax and caveolin‐1‐mediated mechanisms.