Protective Effects Of Helix B Surface Peptide Against Myocardial Ischemia/Reperfusion Injur

Background:Thrombolysis or PCI is an effective method to restore myocardium blood perfusion,for limiting myocardial infarct size,preserving left-ventricular contractile function and reducing the onset of heart failure on STAMIpatients.However,reperfusion itself could give rise to myocardial ischemia/ reperfusion injury(I/RI).It could cause fatal arrhythmia,aggravating heart failure,lead to higher mortality.The mechanism of I/RI is complex and still unclear.Autophagy is an evolutionarily conserved intracellular self-degestion biological process,which removes the internal damaged organelles,misfolded proteins and the invasion of pathogens under the influence of external environment factors.It is a common physical phenomenon.Recent studies showed that autophagy participate in the process of myocardial ischemia/reperfusion.the excessive activation of autophagy can cause myocardial reperfusion injury.Erythropoietin(EPO)is one of the common medicines for anemia.Brines et al.compount helix B surface peptide(HBSP),analyzing EPO space structure.Previous experiments in this study showed that HBSP can reduce the damage of myocardial cells and endothelial cells induced by ischemia/reperfusion injury.However,it is still unclear whether autophagy is connect with the protection from HBSP for myocardial ischemia/reperfusion injury.Objective:1.To observe the activity enhancement of autophagy induced by myocardial ischemia/ reperfusion injury.2.To observe HBSP inhibit autophagy induced by myocardial ischemia / reperfusion injury.3.To investigate the mechanism of HBSP against myocardial ischemia / reperfusion injury induced by inhibiting autophagy.Methods:1.The left anterior descending artery of male mice(20±2g)were ligatured for 30 min,were injected saline,HBSP and Wortmannin after 25 min to preparated ischemia /reperfusion model.2.Male mice were Randomly divided into four groups: Sham(Sham),ischemia /reperfusion group(I/R),ischemia/reperfusion +HBSP(I/R+ HBSP),ischemia/reperfusion+HBSP+Wortmannin group(I/R+HBSP+Wort).3.The heart function of mice was detected by Vevo770 animal ultrasound system.4.The myocardial infarction area of the mice was detected by Evans blue/TTC staining.5.The number of autophagosomes were observed by electron microscopy.6.Expression of protien of myocardial cells in mice were detected by Western blotting.7.The primary myocardial cells were randomly divided into 4 groups: Control group,Hypoxia/Reoxygenation group(H/R),Hypoxia/Reoxygenation+ HBSP group(H/R+HBSP),Hypoxia /Reoxygenation +HBSP+Wortmannin groug(H/R + HBSP + Wort).8.Apoptosis of primary myocardial cells were detect by TUNEL.9.The autophagosome of cardiomyocyte was observed by transmission electron microscope.10.Expression of protien of primary myocardial cells in mice were detected by Western blotting.Results:1.Compared with sham group,the values of LVEF and FS in I/R+HBSP group were lower(P<0.05)after reperfusion 24 houres and 7 days.Compared with I/R group,the values of LVEF and FS in I/R+HBSP group were higher(P<0.05)after reperfusion 24 houres and 7 days.2.The myocardial infarct size in I/R+HBSP group was reduced compared with I/R group(P<0.05).The myocardial infarct size in I/R+HBSP+Wortmannin group were reduced compared with I/R+HBSP group(P<0.05).3.Compared with those in sham group,the proportion of LC3-II/LC3-I in I/R group was higher.Compared with those in I/R group,the proportion of LC3-II/LC3-I in I/R+HBSP group was higher.4.Compared with those in sham group,the numbers of autophosome in I/R group were higher.Compared with those in I/R group,the numbers of autophosome in I/R+HBSP group were reduced.5.Compared with those in Control group,apoptosis of cardiomyocytes in H/R group were higher by TUNEL.Compared with those in H/R group,apoptosis of cardiomyocytes in H/R+HBSP group were detected by TUNEL.6.Compared with those in Control group,LC3 dots in H/R group were higher.Compared with those in H/R group,LC3 dots in H/R+HBSP group were reduced.7.Compared with those in Control group,expression phosphor-Akt or phosphor-mTOR in H/R+HBSP group was higher(P<0.05),the proportion of LC3-II/LC3-I was higher,expression of P62 was reduced.Compared with those in H/R group,expressionphosphor-Akt or phosphor-mTOR in H/R+HBSP group was lower(P<0.05),the proportion of LC3-II/LC3-I was lower,expression of P62 was highter.Conclusion:Helix B Surface Peptide attenuated myocardial ischemia/ reperfusion injury by inhibiting autophagy.Its protective effect may related with the activation of PI3K/Akt/mTOR signal pathway.