Protective effects of hydrogen sulfide against angiotensin II-induced endoplasmic reticulum stress in HUVECs.

The inhibitory effects of hydrogen sulfide (H2S) on angiotensin II (AngII)-stimulated human umbilical vein endothelial cell (HUVEC) dysfunction remain to be elucidated. Endoplasmic reticulum (ER) stress has been detected in endothelial dysfunction (ED). The present study aimed to determine whether H2S may exert an inhibitory effect on AngII‑induced ER stress. Using HUVECs as a model system, the present study used western blotting to detect protein expression, intracellular reactive oxygen species (ROS) levels were determined by oxidative conversion of cell permeable DCFH‑DA to fluorescent dichlorofluorescein, CCK‑8 assay was used to investigate the cell viability, methylene blue was used to investigate the CSE activity, TUNEL was used to investigate the cells apoptosis. The present study demonstrated that AngII not only upregulated the expression levels of inducible nitric oxide synthase (iNOS), stimulated ROS production and increased cell apoptosis, but also downregulated the expression levels of phosphorylated‑endothelial nitric oxide synthase, decreased the expression and activity of cystathionine‑c‑lyase (CSE) and decreased cell viability. Furthermore, hydrogen peroxide (H2O2; an exogenous ROS) downregulated the expression and activity of CSE, and had similar effects as AngII, whereas the inhibitory effects of AngII were completely suppressed by N-acetyl-L-cysteine (a ROS scavenger). In addition, AngII induced the expression of glucose‑regulated protein 78 (GRPP78) and C/EBP homologous protein (CHOP), which are markers of ER stress. Conversely, the stimulatory effects of AngII were completely inhibited by sodium hydrosulfide (NaHS; a H2S donor). Treatment with NaHS attenuated ROS production, inhibited CHOP and GRP78 expression, and decreased cell apoptosis. The present study indicated that AngII induced ED via the activation of ER stress in HUVECs. In addition, the effects of AngII on ER stress could be suppressed by H2S.