Mechanism of endoplasmic reticulum stress-induced vascular endothelial dysfunction

Background: We recently reported that ER stress plays a key role in vascular endothelial dysfunction during hypertension. In this study we aimed to elucidate the mechanisms by which ER stress induction and oxidative stress impair vascular endothelial function. Methodology/principal findings: We conducted in vitro studies with primary endothelial cells from coronary arteries stimulated with tunicamycin, 1 mu g/mL, in the presence or absence of two ER stress inhibitors: tauroursodeoxycholic acid (Tudca), 500 mu g/mL, and 4-phenylbutyric acid (PBA), 5 mM. ER stress induction was assessed by enhanced phosphorylation of PERK and eIF2 alpha, and increased expression of CHOP, ATF6 and Grp78/Bip. The ER stress induction increased p38 MAPK phosphorylation, Nox2/4 mRNA levels and NADPH oxidase activity, and decreased eNOS promoter activity, eNOS expression and phosphorylation, and nitrite levels. Interestingly, the inhibition of p38 MAPK pathway reduced CHOP and Bip expressions enhanced by tunicamycin and restored eNOS promoter activation as well as phosphorylation. To study the effects of ER stress induction in vivo, we used C57BL/6J mice and p47phox(-/-) mice injected with tunicamycin or saline. The ER stress induction in mice significantly impaired vascular endothelium-dependent and independent relaxation in C57BL/6J mice compared with p47phox(-/-) mice indicating NADPH oxidase activity as an intermediate for ER stress in vascular endothelial dysfunction. Conclusion/significance: We conclude that chemically induced ER stress leads to a downstream enhancement of p38 MAPK and oxidative stress causing vascular endothelial dysfunction. Our results indicate that inhibition of ER stress could be a novel therapeutic strategy to attenuate vascular dysfunction during cardiovascular diseases. (C) 2014 Elsevier B.V. All rights reserved.