Effects And Mechanism Of Calcitonin Gene Related Peptide On Cardiomyocyte Apoptosis Induced By Hypoxia/reoxygenation

Objective:To investigate the effect of calcitonin gene-related peptide on neonatal rat cardiomyocytes apoptosis induced by hypoxia/reoxygenation as well as to explore the underlying possible signaling pathway.Methods:Thirty wells of primary neonatal rat cardiomyocytes were cultured in six-well plates.The hypoxia/reoxygenation model was established,Cardiomyocytes were cultured in high purity nitrogen prefilled hypoxic solution for 180 min.After rinsing,cardiomyocytes were cultured with reoxygenate for 120 min.Primary cultured neonatal rat cardiomyocytes were randomly divided into 10 groups（n=3）:control group;hypoxia/reoxygenation group（H/R group）;CGRP+H/R group（CGRP group）;CGRP receptor antagonist CGRP_8-37+CGRP+H/R group(CGRP_8-37 group);mitochondrial K_ATPTP channel agonist diazoxide+H/R group（DZ group）;mitochondrial K_ATP channel inhibitor5-hydroxydecanoate+CGRP+H/R group（5-HD group）;sarcolemmal K_ATP channel inhibitor HMR1098+CGRP+H/R group（HMR1098 group）;K_ATP channel inhibitor glibenclamide+CGRP+H/R group（GLI group）;PKC inhibitor chelerythine+CGRP+H/R group（CHE group）;PKA inhibitor H-89+CGRP+H/R group（group H-89）.Apoptotic cardiomyocytes were labeled with TUNEL method and all cardiomyocytes were labeled with DAPI to calculate the rate of cardiomyocyte apoptosis.Results:Compared with the control group,the apoptosis rate of cardiomyocytes in H/R group was significantly increased（P<0.01）.Compared with H/R group,the apoptosis rate of cardiomyocytes in DZ group and CGRP group was significantly decreased（P<0.01）.The apoptosis rate of cardiomyocytes in CGRP_8-37 group,5-HD group,GLI group,H-89 group and CHE group were all significantly increased（P<0.01）,but there was no significant difference in HMR1098 group（P>0.05）.Compared with GLI group,the apoptosis rate of cardiomyocytes in HMR1098 group was decreased（P<0.01）.Conclusion:CGRP pretreatment can significantly reduce the apoptosis of cardiomyocytes induced by hypoxia/reoxygenation.The activation of PKA,PKC and K_ATP channels were all involved in the role of CGRP in reducing the rate of cardiomyocyte apoptosis after H/R.As in K_ATP channels,mitoK_ATP channels played a more significant role.