Des-aspartate-angiotensin Ⅰ Protects Cardiac Microvascular Endothelial Cell Against Ischemia/reperfusion Injury By Attenuating Endoplasmic Reticulum Stress

Background:Ischemic/reperfusion(I/R) could result in certain harmful events of myocardium. Reactive oxygen species and other injuries increased during ischemia/reperfusion. These factors could trigger apoptotic signaling, which was initiated by endoplasmic reticulum stress(ERS). The endoplasmic reticulum stress has been associated with pathophysiology of the heart during ischemia/reperfusion. Endoplasmic reticulum stress has been considered as a potential target for therapies.Des-aspartate-angiotensin I(DAA-I) has been shown to be a biologically active peptide, which could reduce myocardial infarct size of ischemia/reperfusion model of small animal. Our previous studies suggested that administration of DAA-I might protect cardiac microvascular endothelial cells(CMECs) against I/R injury,and endoplasmic reticulum(ER) stress could be involved, but the mechanism is uncertain. The present study investigated the actions and possible mechanism of DAA-I against ischemia/reperfusion injury of CMECs, and the possible role of endoplasmic reticulum stress.Methods:1. The cardiac microvascular endothelial cells were obtained from the adult Sprague-Dawley rats. The cells were exposed to hypoxia(94%N2, 5%CO2, 1% O2) and ischemia buffer for 2h followed by 4h reoxygenation(95% air, 5%CO2). CMECs was divided randomly into control, SI/R, SI/R + 4-PBA(inhibitor of ER stress), SI/R + DAA-I, and SI/R + DAA-I+ Compound C(AMPK specific inhibitor) groups.2. The cell viability of CMECs was measured by MTT assay. And TUNEL method was applied to detect the apoptosis of CMECs.3. The expression of GRP78, CHOP and the lever of phosphorylation of AMPK were delected by western blot.Results:1. The cardiac microvascular endothelial cells were obtained successfully. And the CMECs were divided into groups randomly.2. The cell viability was impaired(P < 0.05) and the apoptosis of CMECs was obviously increased(P< 0.05) after SI/R. While treatment with sodium 4-phenylbutyrate(4-PBA, inhibitor of ER stress) during reperfusion increased the cells’ s viability(P < 0.05). Administration of DAA-I during reperfusion decreased the apoptosis index(26.21%±2.97% vs16.18%±2.93%,P<0.05).3. DAA-I and 4-PBA down-regulated the expression of GRP78 and CHOP, and DAA-I increased the lever of p-AMPK. Compound C(AMPK specific inhibitor) reduced DAA-I-induced cytoprotection.Conclusion:Des-aspartate-angiotensin I could reduce ischemia/reperfusion injury of the cardiac microvascular endothelial cells, which was related to suppressing of excessive endoplasmic reticulum stress. And furthermore, the activation of AMPK signal was also involved.