The Research Of The Cardioprotective Effect Of Ischemic Postconditioning Against Myocardial Ischemia And Reperfusion Injury In Rabbit

Part one The Cardioprotective Effect of Ischemic Postconditioning Against Myocardial Ischemia and Reperfusion Injury in Rabbit.Objective To observe the Cardioprotective effect of myocardial ischemic postconditioning against ischemia and reperfusion induced injury in rabbit heart.Methods:All rabbits were randomly divided into three groups:(1)sham group;(2)I/R group;(3)myocardial ischemic postconditioning group.All groups except group 1 underwent 30min of coronary occlusion followed by 180min of reperfusion.In group3,four circles of myocardial ischemia(30s)and reperfusion(30s)followed the index ischemia/reperfusion protocol.Myocardial infarct size(IS)and area at risk(AAR)were defined by Evans and TTC staining.Blood samples were taken from artery line before occlusion,30min after occlusion,1 hour after reperfusion and 3 hour after reperfusion for determination of plasma CK and cTnI.Result:Myocardial ischemic postconditioning significantly(P＜0.05)reduced infarct size(19.0±5.2%)in group 3 compared with I/R group(28.5±4.4%).The cTnI and CK levers of group 3 were significantly lower than that of group 2(P＜0.05).The injury of group 2 was worse than that of group 3 from the change of the cellular structure under electron microscope.Conclusion:Myocardial ischemic postconditioning induced cardioprotection against ischemia reperfusion injury in rabbits.Part two The signal mechanism of the protection of Ischemic Postconditioning on myocardium during ischemia/reperfusion in rabbit.Objective To investigate the signal mechanism of the protection of Ischemic Postconditioning on myocardium during ischemia/reperfusion in rabbit.Methods:All rabbits were randomly divided into five groups: (1)sham group;(2)I/R group;(3)myocardial ischemic postconditioning group;(4)AG490+ischemic postconditioning group;(5)naloxone+ ischemic postconditioning group.In group3,four circles of myocardial ischemia(30s)and reperfusion(30s)followed the index ischemia/reperfusion protocol.Adminstration of AG490,a special JAK inhibitor(3mg/kg)in group 4,naloxone,an opioid inhibitor(6mg/kg)in group 5,15min before ischemic postconditioning.All groups except group 1 underwent 30min of coronary occlusion followed by 180min of reperfusion.At the end of the reperfusion,infarct size(IS)and area at risk (AAR)were defined by Evans and TTC staining.Cardiac myocyte apoptosis was determined by Terminal deoxynucleotidyl Transferase mediated dUTP nick-end labeling(TUNEL)methods.The levels of BCL-2 and P-stat3 activity were determined by Western Blot analysis. Result:Myocardial ischemic postconditioning significantly(P＜0.05) reduced infarct size(19.0±5.2%)in group 3 compared with I/R group (28.5±4.4%).In group 2,ischemia/reperfusion caused significant cardiac myocyte apoptotic death.Ischemic postconditioning produced a significant anti- apoptotic effect as evidenced by a marked reduction of apoptotic index.(18±7)%vs(28±7)%in I/R group(P＜0.05).The activity of BCL-2 and P-stat3 in group 3 was higher than that of the other groups(P＜0.05).Adminstration of AG490 and naloxone abolished the cardioprotective of ischemic postconditioning.Conclusion:Ischemic postconditioning can inhibit cardiac myocyte apoptotic death,and promote the activity of BCL-2 and P-stat3 in myocardium during ischemia reperfusion,which is likely activited by opioid receptor and JAK-STAT signal pathway,and maybe one of the molecular mechanisms of ischemic postconditioning on cardioprotection.Part three Proteomic analysis of ischemic postconditioning on rabbit myocardiumObjective To search for global protein changes of ischemic postconditioning on rabbit myocardium by using proteomic technology. And verified the differential expression proteins in order to illuminate the mechanisms of ischemic postconditioning on cardioprotection.Methods: Twenty-four New Zealand white rabbits were randomly assigned to sham operative group,I/R group and ischemic postconditioning group.I/R groups underwent ligation of the left anterior descending coronaryartery(LAD)for 30 minutes and reperfusion for 180 minutes. Ischemic postconditioning group,four circles of myocardial ischemia(30s) and reperfusion(30s)followed the index ischemia/reperfusion protocol. Results:Differential analysis using the Student's t-test(P＜0.05)showed that the expression of 11 protein spots changed,11 protein spots were identified by mass spectrometry.The activity of the HSP27 in ischemic postconditioning group were significantly higher than that of I/R group(P＜0.05).Conclusions:Ischemic postconditioning resulted in the changes of protein expression profiles in the myocardium.The differential proteins might function as molecular chaperone,decrease free radical and promote the energy metabolism of myocardium to confer cardioprotection.Ischemic postconditioning can promote the activity of the HSP27 in myocardium during ischemia reperfusion,which maybe one of molecular mechanisms of ischemic postconditioning on cardioprotection.