Role of endogenous calcitonin gene related peptide in stress-induced retinal cell apoptosis

Abstract

Background Acute stress can provoke the apoptosis of retina cells and induce increasing expression of calcitonin gene related peptide(CGRP)in retina.However,the role of CGRP in pathology of the stressinduced apoptosis of the retina ceils is still elusive.Objective The aim of this study was to investigate the effects of endogenous CGRP on retinal cell apoptosis induced by stress of acute myocardial ischemia after coronary artery occlusion in rats. Methods The acute myocardial ischemia model was established by ligating the left anterior descending branch of coronary artery in 12 male Sprague-Dawley rats.The rats were randomized into CGRP8-37 injection group and normal saline injection group,6 rats 12 eyes for every group.CGRP8-37(10-7 mol/L),a specific antagonist of CGRP receptor,was intravenously injected in CGRP8-37 group by caudal vine at 15 minutes prior to the coronary artery occlusion,and the equivalent amount of normal saline was used at the same fashion in normal saline group.The retinal samples of the rats were collected at 3 hours after coronary artery occlusion for TUNEL staining and caspase-3 activity detection respectively. Results The cellular displacement was observed in inner and outer nuclear layer,and vacuolar degeneration of retinal ganglion cells was found in the coronary artery occlusion animals.The total apoptosis index of retinal cells in CGRP8-37 group was significantly higher than that in normal saline group (42.8％±2.8％ vs 37.5％±2.9％,t=-3.244,P<0.01).The retinal capase-3 activity was significantly enhanced in the CGRP8-37 group compared with saline group(11.3±3.1 fold vs 4.9±1.2 fold,t=-4.603,P<0.01)at 3 hours of coronary artery occlusion.Conclusion The results suggest that the endogenous CGRP may play an anti-apoptotic role in the stress.induced retinal cell injury. Key words: Retina cell apoptosis; Calcitonin gene related peptide; Stress response; Acute myocardial ischemia