The Effect And Mechanism Of Bcl-2on The Cardiac Protection From Skeletal Muscle Remote Post-conditioning In Rabbit

Objective: Previous studies showed that Bcl-2could mediate thecardiac protection effect from skeletal muscle remote post-conditioning(RPostC), this research wanted to observe whether the protective effectfrom remote post-conditioning was mediated by the opening and closingof the Mitochondrial Permeability Transition Pore (mPTP), or theMitochondrial ATP-sensitive K+Channels (mKATP), and their relativeposition between the mPTP and mKATP.Method: Thirty healthy New Zealand rabbit were randomly dividedinto5groups, the ischemia reperfusion model was induced afterthoracotomy by subjected to45minutes occlusion on left circumflexcoronary artery (LCX), followed by2hours reperfusion in allanesthetized open-chest rabbits, and skeletal muscle ischemia model wasinduced by extrinsic iliac arteries occlusion and followed by reperfusionwith artery clamps. The groups were as follow: Con, RpostC,RpostC+HA14-1+CsA, RPostC+5HD, RpostC+HA14-1+CsA+5HD.HA14-1was the selective Bcl-2inhibitor (2mg/kg). CsA was the directmPTP inhibitor (5mg/Kg).5HD,5-hydroxydecanoate, was a specificmKATP-channel-blocker. Then Evans Blue dye was infused to identify thearea at risk (AAR), and measured by area ratio of ARR/LV. Furthermore,the infarct size (AN) was measured by triphenyltetrazolium chloride(TTC) staining and measured by area ratio of AN/AAR. Otherwise,plasma creatine kinase (CK) activity and lactate dehydrogenase (LDH)activity were measured at baseline, the end of ischemia, after1hour and2hours of reperfusion respectively.Results:1. Hemodynamic parameters Before the coronary artery ischemia, the hemodynamic parametersincluding heart rate (HR) and mean arterial blood pressure (MAP) werenot different significantly between every group. But the HR in everygroups was increased after the coronary artery was performed tooperated, meanwhile, the MAP showed a downward trend, but thechanges had no significant difference (P>0.05).2. The arrhythmias observed2.1Types of arrhythmia:On the basic of state, any arrhythmias were found in all of groups.After the coronary artery ischemia, various forms of arrhythmias showedup, including premature ventricular contraction, premature ventricularbigeminy, paroxysmal ventricular tachycardia, even ventricularfibrillation (could be stopped by giving the anti-arrhythmia drugs). Butmainly they were premature ventricular contractions. The number ofpremature ventricular contractions respectively of groups were as follows:Con group:82.5±25.44, RPostC group:177.5±201.73,RpostC+HA14-1+CsA group:62.83±43.91, RPostC+5HD group:161.67±150.26, RpostC+HA14-1+CsA+5HD group:138.33±83.43, butthey had no significant difference between groups (P>0.05). Ventricularfibrillation was only found one time during the ischemia time of theRpostC+HA14-1group, and could be stopped by giving theanti-arrhythmia drugs(Lidocaine).2.2Times of arrhythmia occurrence:Before coronary artery ischemia, any arrhythmias were not found inall of groups. After the coronary artery ischemia, various forms ofarrhythmias showed up. But most of them occurred in the15min after thecoronary artery ischemia. The number of premature ventricularcontractions in the groups were as follows: the Con group：67±25.05, theRPostC group：152.33±166.92, the RpostC+HA14-1+CsA group:50.33±32.14, the RPostC+5HD group：107.5±133.56, theRpostC+HA14-1+CsA+5HD group：110±68.32, but there was no significant difference between the every group. After15min of ischemia,arrhythmias was decreased obviously, the number of prematureventricular contractions of groups respectively were15±0.84,23.4±42.79,12±12.86,52.67±85.4,16.17±12.29, and the occurrence of arrhythmiaafter15min of ischemia also had no difference. Reperfusion arrhythmiaswere mainly occurring in the10min after reperfusion. After10min ofreperfusion, arrhythmias were significantly reduced or disappeared. Inthis experiment reperfusion arrhythmias in every group was less, and hadno significant difference between the every two groups (P>0.05).3. Myocardial ischemia and infarction3.1Myocardial ischemia:From this study, the myocardial ischemia sizes of the Con, RPostCand RPostC+HA14-1group were41.04±6.44%,34.09±6.67%,40.77±2.39%, but the degree of ARR in the three groups had nosignificant difference. On the basis of that, our further study showed, theARR of the RpostC+HA14-1+CsA group was36.79±3.71%, the ARR ofthe RPostC+5HD group was35.52±4.08%, the ARR of theRpostC+HA14-1+CsA+5HD group was42.41±5.99%, the degree of ARRin the Con, RPostC, RpostC+HA14-1+CsA, RPostC+5HD,RpostC+HA14-1+CsA+5HD groups had no statistical difference.3.2Myocardial infarction:Compared with the Con group, myocardial infracted size of theRPostC group was significantly reduced (29.54%±5.38%vs66.18%±9.68%, P＜0.05).Previous studies showed that: Compared with the RPostC group,myocardial infracted size of the RPostC+HA14-1group was significantlyincreased (68.75%±10.75%vs29.54%±5.38%, P＜0.05).Compared with the RPostC+HA14-1group, myocardial infractedsize of the RpostC+HA14-1+CsA group was significantly reduced(57.44±5.71%vs68.75±10.75%, P＜0.05).Compared with the RPostC group,myocardial infracted size of the RPostC+5HD group was significantly increased (56.48±14.06%vs29.54±5.38%, P＜0.05).Compared with the RpostC+HA14-1+CsA group, myocardialinfracted size of the RpostC+HA14-1+CsA+5HD group was significantlyincreased (65.6±14.06%vs57.44±5.71%, P＜0.05).4. Creatine kinase (CK) and Lactate Dehydrogenase (LDH) observation.Previous studies showed that: Compared with the Con group, theLDH content of the RPostC group had a decreasing tendency at the60min and120min after the reperfusion. Respectively, at the60min afterthe reperfusion:312.97±116.73U/L vs421.93±168.32U/L, at the120min after the reperfusion:347.75±94.07U/L vs440.57±149.54U/L.Compared with the RPostC group, the LDH content of theRpostC+HA14-1group had a increasing trend at the120min after thereperfusion. Respectively,498.47±62.22U/L vs347.75±94.07U/L, butthe changes were not statistical difference (P>0.05). The CK and LDH inthe Con, RPostC and RpostC+HA14-1groups had no significantdifference (P>0.05).From this study, compared with the RpostC+HA14-1group, the LDHcontent of the RpostC+HA14-1+CsA group had a downward trend(344.32±105.36U/L vs433.78±103.06U/L),but the changes were notstatistically different (P>0.05); Compared with the RPostC group, theLDH content of the RPostC+5HD group at the60min and120min afterthe reperfusion showed a upward trend (322.77±94.35U/L vs312.97±116.73U/L;357.05±66.2U/L vs347.75±94.07U/L), but the changeswere not statistically different (P>0.05). The CK and LDH in the Congroup, the RPostC group, the RpostC+HA14-1+CsA group, theRPostC+5HD and RpostC+HA14-1+CsA+5HD group had no significantdifference (P>0.05).Conclusions:1. Bcl-2can mediate the cardiac protective effect from skeletalmuscle remote post-conditioning. 2. The cardiac protective effect induced by Bcl-2from skeletalmuscle remote post-conditioning was mediated by the opening andclosing of the mPTP and the mKATP, Bcl-2might be located at theupstream of the mPTP.3. mPTP and mKATPmay be in the same reaction chain.