Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, USA.
J Physiol Pharmacol. 2013 Oct;64(5):557-64.
Sustained endoplasmic reticulum (ER) stress and thus activation of the unfolded protein response is now thought to be the foundation of various chronic disorders including whole-body insulin resistance and cardiovascular disease. The purpose of the present study was to test the hypothesis that ER stress impairs insulin-stimulated vasomotor reactivity. We report that experimental induction of ER stress in isolated aortic rings with tunicamycin (20 μg/mL), a well-established inducer of ER stress, resulted in insulin-stimulated vascular contraction (-78±21% at 1000 μIU/mL; -100±27% at 10,000 μIU/mL; all p<0.05) rather than relaxation (+23±7% at 1000 μIU/mL; +43±8% at 10,000 μIU/mL; all p<0.05). Importantly, we found that insulin-stimulated vascular contraction as a result of ER stress was largely eliminated in the presence of tezosentan (3 μM), a nonselective endothelin-1 (ET-1) receptor blocker (+1±14% at 1000 μIU/mL; +8±17% at 10,000 μIU/mL). Similarly, inhibition of ET-1 receptors fully restored the impairment of acetylcholine-mediated relaxation induced by ER stress (maximal relaxation: control = 94±2%, tunicamycin = 76±5%, tunicamycin + tezosentan = 90±3). Furthermore, we demonstrate that ER stress caused a ≈20-fold greater release of ET-1 from aortic endothelial cells under basal conditions as well as a ≈15-fold increase under insulin-stimulated conditions (p<0.05). This ER stress-mediated up-regulation in ET-1 release from endothelial cells was accompanied by a ≈3-fold increase in phosphorylation of p44/22 MAPK (p<0.05), a known pathway by which insulin signaling activates ET-1. Together, these findings support the hypothesis that vascular ER stress-mediated activation of ET-1 may be an underlying cause of impaired vasomotor responsiveness to insulin and endothelial dysfunction.
持续的内质网 (ER) 应激，进而激活未折叠蛋白反应，现在被认为是包括全身胰岛素抵抗和心血管疾病在内的各种慢性疾病的基础。本研究的目的是检验内质网应激损伤胰岛素刺激血管舒缩反应的假说。我们报告说，用衣霉素（20μg/mL）在分离的主动脉环中实验性诱导内质网应激，导致胰岛素刺激的血管收缩（在 1000μIU/mL 时为-78±21%；在 10,000μIU/mL 时为-100±27%；所有 p<0.05），而不是舒张（在 1000μIU/mL 时为+23±7%；在 10,000μIU/mL 时为+43±8%；所有 p<0.05）。重要的是，我们发现，在非选择性内皮素-1（ET-1）受体阻滞剂 tezosentan（3μM）存在的情况下，内质网应激引起的胰岛素刺激血管收缩大部分被消除（在 1000μIU/mL 时为+1±14%；在 10,000μIU/mL 时为+8±17%）。同样，抑制 ET-1 受体完全恢复了内质网应激引起的乙酰胆碱介导舒张的损伤（最大舒张：对照=94±2%，衣霉素=76±5%，衣霉素+tezosentan=90±3%）。此外，我们证明内质网应激导致基础状态下内皮细胞释放 ET-1 增加约 20 倍，胰岛素刺激状态下增加约 15 倍（p<0.05）。这种内质网应激介导的内皮细胞 ET-1 释放的上调伴随着 p44/22 MAPK 磷酸化增加约 3 倍（p<0.05），这是胰岛素信号激活 ET-1 的已知途径。综上所述，这些发现支持了这样一种假说，即血管内质网应激介导的 ET-1 激活可能是胰岛素引起的血管舒缩反应受损和内皮功能障碍的一个潜在原因。
