| Objective:Postresuscitation myocardial ischemia reperfusion injury(IRI)after cardiac arrest/cardiopulmonary resuscitation(CA/CPR)is an important factor affecting survival status.Studies have shown that the survival and proliferation of cells are regulated by extracellular regulatory kinase 1/2(ERK1/2).In the model of focal ischemia reperfusion injury of the heart,activation of ERK pathway can alleviate myocardial IRI,while in the model of multiple organ dysfunction,inhibition of ERK pathway can alleviate organ dysfunction.Previous studies of our research group have found that PD98059(PD),as an inhibitor of ERK pathway,can alleviate cerebral IRI after CA/CPR,but its effect on myocardial IRI after resuscitation is still unclear.Therefore,this study investigated the effect of ERK inhibitor PD98059 on myocardial IRI after resuscitation and its possible mechanism in the model of CA/CPR in rats.Methods:The CA/CPR model of ventricular fibrillation in SD rats was established by the method of esophageal pacing electrical stimulation,and the rats after restoration of spontaneous circulation(ROSC)were randomly divided into three groups:low-dose PD group(PD0.15 group,n=20),high-dose PD group(PD0.3 group,n=20),and model group(CA group,n=20).Immediately after resuscitation,0.15 mg/ml of PD98059,0.3 mg/ml of PD98059 and equal volume of saline were injected into the femoral vein in the PD0.15 group,PD0.3 group and CA group,respectively.Then the Sham operation group(Sham,n=20)was randomly selected.The Sham group was only performed with anesthesia,tissue and blood vessel separation and intubation,and no electrical stimulation was performed.Blood pressure changes within 1 h after resuscitation and survival status within 24 h after resuscitation were monitored,and left ventricular tissue and blood samples were extracted at 24 h after ROSC for the following experiments.Serum troponin I,blood lactic acid level and ATP content in myocardial tissue were determined by chemiluminescence.The degree of myocardial cell injury and apoptosis index were confirmed by HE staining and TUNEL assay.The ultrastructure of mitochondria in the left ventricle was observed by transmission electron microscopy.Protein western blot assay(WB)detected the expression levels of p-ERK1/2,ERK1/2,p-DRP1,DRP1,cytochrome c and apoptosis-related proteins BCL-2,BAX,Cleaved caspase-3 and caspase-3.Results:1.MAP and SBP were significantly lower in the CA and PD0.3 groups compared with those in the sham group at 5,10,20 and 60 min after ROSC(P<0.05).However,MAP and SBP in the PD0.3 group was significantly higher compared with those in the CA group at 5 and 10 min(P<0.05).Similarly,DBP was significantly lower in the CA and PD0.3 groups compared with those in the sham group at 5,10,20 and 60 min after ROSC(P<0.05),but significantly higher in the PD0.3 group compared with that in the CA group at 10 min(P<0.05).There was no difference between the CA and PD0.15 groups in blood pressure after ROSC(P>0.05).2.The survival conditions of each group at ROSC 24 h were all Sham group survival(20/20),CA group 9/20,PD0.3 group 18/20,and PD0.15 group 16/20,respecti-vely.The ROSC 24 h cumulative survival rates of PD groups were significantly higher than that of CA group(Log rank ?2=18.166,P<0.05).There was no statistically significant difference in the cumulative survival between PD0.3 and PD0.15 groups.3.Compared with Sham group,HE staining showed severe myocardial pathological damage in CA group.Compared with the CA group,the degree of myocardial pathological damage was less in PD group and more obvious in PD0.3 group.4.Compared with Sham group,mitochondrial ultrastructure of myocardium in CA group was more obviously damaged.However,the damage of mitochondrial structure was generally mitigated in a dose-dependent manner with PD treatment.The improvement of mitochondrial ultrastructure in cardiac tissue in PD0.3 group was more obvious than that in PD0.15 group.5.While heart ATP content decreased,serum cTnI and whole blood lactate levels increased significantly(P<0.05 for all)in the CA group compared with those in the Sham group,heart ATP content increased and lactate levels decreased significantly(P<0.05)both in PD0.15 group and PD0.3 group,but the cTnI level decreased significantly(P<0.05)only in PD0.3 group compared with those in the CA group(P<0.05)at 24 h after ROSC.6.While the percentage of TUNEL positive myocytes in the CA and PD groups was significantly higher than that in the sham group(P<0.05),the percentage of TUNEL positive myocytes in PD0.3 group was significantly lower than that in the CA group(P<0.05).7.While the expression of myocardial phosphorylation of ERK1/2 in CA group was significantly higher than that in Sham group(P<0.05),the expression of myocardial phosphorylation of ERK1/2 in PD-treated groups was significantly lower than that in CA group at 24 h of ROSC(P<0.05),suggesting that PD reduce the myocardial expression of phosphorylation of ERK1/2 in the setting of CA/CPR.8.While the expression of myocardial DRP1 phosphorylation and cytochrome c in CA group was significantly higher than that in Sham group(P<0.05),the expression of myocardial DRP1 phosphorylation and cytochrome c in PD-treated groups was significantly lower than that in CA group at 24 h of ROSC(P<0.05),suggesting that PD reduce the myocardial expression of DRP1 phosphorylation and cytochrome c in the setting of CA/CPR.9.The CA group showed a higher myocardial cleaved caspase-3 and BAX,and a lower BCL-2 level than the Sham group does(P<0.05).PD-treated group resulted in a significant up-regulation in BCL-2 expression(P<0.05)and a down-regulation in cleaved caspase-3 and BAX expression than the CA group does(P<0.05).Conclusion:These findings suggest that PD98059 does mitigate myocardial IRI,improve postresuscitation myocardial energy metabolism and tissue perfusion,which may be associated with mitochondrial protection and antiapoptosis in a rat CA/CPR model. |
PDF Full Text Request