Effect Of Urocortin-Postconditioning On Mitochondria-Dependent Apoptotic Pathway In Ischemia Rat Hearts

Objectives : To investigate the effect of Urocortin ( UCN )-postconditioning on mitochondria-dependent apoptotic pathway in ischemia rat hearts.Methods : 24 Wistar rats were randomly divided into 3 groups(n=8), named Control group(CON), I/R group(I/R), and UCN group(UCN). The left ventricular samples in CON group were collected as pre-ischemia control through thoracotomy. After isolated heart Langendoff and Neely models were established, the rat hearts in I/R group and UCN group were continuously perfused with Krebs-Henseleit buffer solution(K-H) for 30 min, then the rat hearts were arrested by cardioplegia St.Thomas-2 solution(STH-2) for 30 min. After that, the rat hearts in the I/R group were reperfused with K-H buffer solution for 90 min. The rat hearts in the UCN group were reperfused with K-H containing 10-8 mol/L Urocortin for 90 min. The release of Cyto C protein was detected by Western blot. The expressions of Bcl-2 and Caspase-3 protein were detected by immunohistochemical assay in cardiomyocyte. The apoptosis index(AI) of cardiomyocyte was detected by TUNEL. Results : CytoC protein in CON group,I/R group and UCN group was 56.7±2.63%,129.4±2.79%and88.1±2.25% by Western blot. Compared with CON group, the expression of CytoC protein in I/R and UCN group was significantly increased (P<0.05);the expression of CytoC protein in UCN group was lower than that in I/R group(P<0.05).Caspase-3 protein expressinon in CON group , I/R group and UCN group was 0.15±0.05, 0.36±0.07 and 0.24±0.06 by immunohistochemical assay. The expression of Caspase-3 protein in I/R and UCN group was higher than that in CON group (P<0.05), while Caspase-3 protein in UCN group was lower than that in I/R group (P<0.05).The expression of Bcl-2 protein in I/R group(0.12±0.06)and in UCN group (0.20±0.05)was higher than that in CON group(0.077±0.05)(P<0.05);Bcl-2 protein expressinon in UCN group was higher than that in I/R group( P<0.05).More apoptotic cardiomytocytes were found in both I/R and UCN group than that in CON group. The apoptosis index(AI) of cardiomyocyte was 12.81±0.62% in I/R group and 6.77±1.12% in UCN group, much higher than that in CON group(2.29±0.67%,P<0.05); AI in UCN group was lower than that in I/R group(P<0.05).There was a positive correlation(r=0.796,P<0.05)between CytoC protein and Caspase-3 protein in three groups; and a positive correlation(r=0.956,P<0.05)between CytoC protein and AI of cardiomyocyte as well .Conclusion: Urocortin ( UCN ) -postconditioning could inhibit mitochondria-dependent apoptotic pathway. The mechanism was probably up-regulating expression of anti-apoptosis Bcl-2 protein, inhibiting the release of CytoC protein from mitochondria and Caspase-3 activation, and alleviating the apoptosis of rat cardiomyocytes.