ox-LDL downregulates eNOS activity via LOX-1-mediated endoplasmic reticulum stress

Zhou,Jie; Abid,Morad  Dirhem Naji; Xiong,Yufang; Chen,Qing; Chen,Juan

doi:10.3892/ijmm.2013.1513

ox-LDL downregulates eNOS activity via LOX-1-mediated endoplasmic reticulum stress

Authors:
- Jie Zhou
- Morad Dirhem Naji Abid
- Yufang Xiong
- Qing Chen
- Juan Chen
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Affiliations: Department of Biochemistry and Molecular Biology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China, Department of Hepatobiliary Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
Published online on: September 30, 2013 https://doi.org/10.3892/ijmm.2013.1513
Pages: 1442-1450

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Abstract

Vascular endothelial injury induced by oxidized low-density lipoprotein (ox-LDL) has been implicated in the early stages of the pathogenesis of atherosclerosis. In this study, we incubated bovine aortic endothelial cells (BAECs) with ox-LDL (100 µg/ml) in order to induce endoplasmic reticulum (ER) stress and to investigate the regulation of endothelial nitric oxide synthase (eNOS). Within 4 h of exposure, ox-LDL rapidly induced ER stress, as demonstrated by the measurements of proline-rich extensin-like receptor kinase (PERK) and glucose-regulated protein (GRP)78. ox-LDL induced the rapid dephosphorylation of eNOS at Ser1179 and a subsequent decrease in eNOS activity. This effect appeared to be highly specific as no change was observed in the levels of phosphorylated eNOS at Thr497 or eNOS protein. Of note, a simultaneous decrease was also observed in the active (phosphorylated) form of Akt (Thr308/Ser473), which has been demonstrated to phosphorylate eNOS at Ser1179. Further analysis indicated that Brefeldin A (BFA), an ER stress-inducing reagent, induced the rapid dephosphorylation of Akt and eNOS at Ser1179. 4-Phenylbutyric acid (PBA), an inhibitor of ER stress, blocked the ox-LDL-induced dephosphorylation of Akt and eNOS. Furthermore, JTX20, a lectin-like ox-LDL receptor-1 (LOX-1) blocking antibody significantly eliminated the ability of ox-LDL to mediate the dephosphorylation of eNOS and Akt. Our results indicate that the downregulation of eNOS by ox-LDL, as driven by LOX-1-mediated ER stress, is associated with the PI3K-Akt-eNOS signaling pathway.

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