School of Biomedical Sciences and Li Ka Shing Institute of Health Science, The Chinese University of Hong Kong, Hong Kong SAR, China.
Heart and Vascular Institute and Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR, China.
Acta Pharmacol Sin. 2021 Oct;42(10):1598-1609. doi: 10.1038/s41401-020-00589-x. Epub 2021 Jan 25.
Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular diseases and increases mortality in type 2 diabetic patients. HHcy induces endoplasmic reticulum (ER) stress and oxidative stress to impair endothelial function. The glucagon-like peptide 1 (GLP-1) analog exendin-4 attenuates endothelial ER stress, but the detailed vasoprotective mechanism remains elusive. The present study investigated the beneficial effects of exendin-4 against HHcy-induced endothelial dysfunction. Exendin-4 pretreatment reversed homocysteine-induced impairment of endothelium-dependent relaxations in C57BL/6 mouse aortae ex vivo. Four weeks subcutaneous injection of exendin-4 restored the impaired endothelial function in both aortae and mesenteric arteries isolated from mice with diet-induced HHcy. Exendin-4 treatment lowered superoxide anion accumulation in the mouse aortae both ex vivo and in vivo. Exendin-4 decreased the expression of ER stress markers (e.g., ATF4, spliced XBP1, and phosphorylated eIF2α) in human umbilical vein endothelial cells (HUVECs), and this change was reversed by cotreatment with compound C (CC) (AMPK inhibitor). Exendin-4 induced phosphorylation of AMPK and endothelial nitric oxide synthase in HUVECs and arteries. Exendin-4 increased the expression of endoplasmic reticulum oxidoreductase (ERO1α), an important ER chaperone in endothelial cells, and this effect was mediated by AMPK activation. Experiments using siRNA-mediated knockdown or adenoviral overexpression revealed that ERO1α mediated the inhibitory effects of exendin-4 on ER stress and superoxide anion production, thus ameliorating HHcy-induced endothelial dysfunction. The present results demonstrate that exendin-4 reduces HHcy-induced ER stress and improves endothelial function through AMPK-dependent ERO1α upregulation in endothelial cells and arteries. AMPK activation promotes the protein folding machinery in endothelial cells to suppress ER stress.
高同型半胱氨酸血症（HHcy）是心血管疾病的独立危险因素，并增加 2 型糖尿病患者的死亡率。HHcy 诱导内质网（ER）应激和氧化应激，损害内皮功能。胰高血糖素样肽 1（GLP-1）类似物 exendin-4 减轻内皮 ER 应激，但详细的血管保护机制仍不清楚。本研究探讨了 exendin-4 对 HHcy 诱导的内皮功能障碍的有益作用。exendin-4 预处理逆转了同型半胱氨酸诱导的 C57BL/6 小鼠离体主动脉依赖性舒张受损。四周皮下注射 exendin-4 恢复了饮食诱导 HHcy 小鼠离体主动脉和肠系膜动脉受损的内皮功能。exendin-4 治疗降低了离体和体内小鼠主动脉中超氧阴离子的积累。exendin-4 降低了人脐静脉内皮细胞（HUVEC）中 ER 应激标志物（如 ATF4、剪接 XBP1 和磷酸化 eIF2α）的表达，这种变化被 CC（AMPK 抑制剂）共同处理所逆转。exendin-4 在 HUVEC 和动脉中诱导 AMPK 和内皮型一氧化氮合酶的磷酸化。exendin-4 增加了内质网氧化还原酶 1α（ERO1α）的表达，ERO1α 是内皮细胞中重要的 ER 伴侣，这种作用是通过 AMPK 激活介导的。使用 siRNA 介导的敲低或腺病毒过表达的实验表明，ERO1α 介导了 exendin-4 对 ER 应激和超氧阴离子产生的抑制作用，从而改善 HHcy 诱导的内皮功能障碍。本研究结果表明，exendin-4 通过 AMPK 依赖性 ERO1α 在内皮细胞和动脉中的上调，降低 HHcy 诱导的 ER 应激，改善内皮功能。AMPK 激活促进内皮细胞中的蛋白质折叠机制，抑制 ER 应激。
