Protective Effects Of PI3K/AKT Pathway On Myocardial Function In Rats With Myocardial Ischemic Postconditioning And Intervention Of Rhepo

Objective Through the establishment of acute myocardial ischemia reperfusion model in rats, to observe the effect of myocardial ischemic postconditioning and rhEPO on myocardial function, serum biochemical markers creatine kinase (CK),lactate dehydrogenase(LDH), ischemic and infarct areas, the mRNA and protein expression of Akt and p70S6K in myocardium, to investigate the influence of PI3K/Akt pathway on myocardial function in rats with myocardial ischemic postconditioning and intervention of rhEPO.Methods 84 rats were randomly divided into①Sham operation group (Sham group)②Ischemia/Reperfusion group(I/R group )③Ischemia-Postconditioning group(I-postC group)④I-postC+Wortmannin group(I-postC+Wort group)⑤rhErythropoietin group(rhEPO group)⑥rhEPO+Wort group⑦rhEPO+I-postC group. ECG changes and LVSP,LVEDP,+dp/dtmax and–dp/dtmax were monitored during the procedure,serum biochemical markers creatine kinase (CK) , lactate dehydrogenase(LDH) of different groups were assessed and evaluated at the end of reperfusion.Ischemic and infarct areas were measured by Evans blue and TTC staining respectively .The mRNA and protein expression of Akt and p70S6K in myocardium were tested by RT-PCR and immunohistochemistry.Results (1) Systolic and diastolic function of myocardium: Systolic and diastolic function of myocardium in I/R group, I-PostC+Wort group and rhEPO+Wort group were significantly weaker than those in Sham group( P < 0.05 ), while systolic and diastolic function of myocardium in I-PostC group, rhEPO group and rhEPO+I-PostC group were much stronger than I/R group ( P<0.05) . I-Post+Wort group and rhEPO+Wort group had weaker systolic and diastolic function of myocardium compared with I-Post group ( P<0.05) . rhEPO+Wort group had weaker systolic and diastolic function of myocardium than rhEPO group ( P<0.05 ). And systolic and diastolic function of myocardium were not sifgnificantly different in I-PostC group, rhEPO group and rhEPO+I-PostC. (2) Serum levels of CK,LDH: The serum levels of CK and LDH in I/R group,I-PostC+Wort group,rhEPO+Wort group were obviously higher than those in Sham group ( P<0.05 ) . I-PostC group ,rhEPO group and rhEPO+I-PostC group had lower levels compared with I/R group( P<0.05 ), while I-PostC+Wort group and rhEPO+Wort group had higher levels than I-PostC group ( P<0.05 ), rhEPO+Wort group had higer levels than rhEPO group. There were no significant differences among I-PostC group, rhEPO group and rhEPO+I-Post group , the same as the comparation among I-Post+Wort group, rhEPO+Wort group and I/R group. (3) Areas of myocardial infarction: I-PostC group ,rhEPO group and rhEPO+I-PostC group had smaller areas of myocardial infarction compared with I/R group ( P<0.05 ), while I-PostC+Wort group and rhEPO+Wort group had bigger areas of myocardial infarction than I-PostC group ( P<0.05) , rhEPO+Wort group had bigger areas of myocardial infarction than rhEPO group. There were no significant differences among I-PostC group, rhEPO group and rhEPO+I-Post group , the same as the comparation among I-Post+Wort group, rhEPO+Wort group and I/R group. (4) The expressions of Akt,p70s6k protein in myocardium: Akt,p70s6k protein expressed in myocardium in each group, with the lowest expressions in Sham group . I-PostC group, rhEPO group and rhEPO + I-PostC group had higher expression of Akt,p70s6k protein than I/R group (P< 0.05), while I-PostC+Wort group and rhEPO+Wort group had significantly lower expressions compared with I-PostC group ( P< 0.05);the expressions of Akt,p70s6k protein in rhEPO group and rhEPO+I-PostC group were obviously higher than those in I-PostC+Wort group (P< 0.05); rhEPO+Wort group had much lower expressions of Akt,p70s6k protein than rhEPO group( P< 0.05); however, rhEPO+I-PostC group had significantly higher expressions of Akt,p70s6k protein than rhEPO+Wort group (P< 0.05). There were no significant differences in Akt,p70s6k protein expressions among I-PostC group, rhEPO group and rhEPO+ I-PostC group, the same as those among I/R group, I-PostC+Wort group and rhEPO+Wort group.(5) The expressions of Akt mRNA,p70s6k mRNA i n myocardium :Akt mRNA,p70s6k mRNA expressed in myocardium in each group, with the lowest expression in Sham group . I-PostC group, rhEPO group and rhEPO + I-PostC group had higher expression of Akt mRNA,p70s6k mRNA than I/R group( P< 0.05); I-PostC+Wort group and rhEPO+Wort group had significantly lower expressions of Akt mRNA,p70s6k mRNA compared with I-PostC group ( P< 0.05);the expressions of Akt mRNA in rhEPO group and rhEPO+I-PostC group were obviously higher than those in I-PostC+Wort group (P< 0.05); rhEPO+Wort group had much lower expressions of Akt mRNA,p70s6k mRNA compared with those in rhEPO group (P< 0.05); however, rhEPO+I-PostC group had significantly higher expressions of Akt mRNA,p70s6k mRNA than rhEPO+Wort group (P< 0.05). There were no significant differences in Akt mRNA,p70s6k mRNA expressions among I-PostC group, rhEPO group and rhEPO+ I-PostC group, the same as those among I/R group, I-PostC+Wort group and rhEPO +Wort group.Conclusion⑴Myocardial ischemia/reperfusion injury in rats can cause severe damage to myocardial systolic and diastolic function and myocardial tissues.⑵I-PostC can significantly improve the impaired myocardial systolic and diastolic function and myocardial tissue caused by myocardial ischemia/reperfusion injury in rats.⑶Wortmannin , a specific PI3K inhibitor , can lessen the protective effects of I-PoctC on myocardial systolic and diastolic function and myocardial tissue, and reduce the expressions of Akt,p70s6k mRNA and protein in myocardial tissues, suggesting that the protective effects of I-Post on myocardial systolic and diastolic function and myocardial tissues may be related to the activation of PI3-Akt signaling pathways and its downstream target p70s6k.⑷rhEPO can significantly protect the myocardial systolic and diastolic function and myocardial tissues, and exert similar protective effects on myocardial systolic and diastolic function and myocardial tissues to I-Post.⑸Wortmannin, a specific PI3K inhibitor, can impare the protective effects of I-PoctC on myocardial systolic and diastolic function and myocardial tissue and reduce the expressions of Akt,p70s6k mRNA and protein in myocardial tissue, suggesting that the protective effects of rhEPO on myocardial systolic and diastolic function and myocardial tissues caused by I/R injury may be related to the activation of PI3-Akt signaling pathways and its downstream target p70s6k. Its underlying mechanisms need to be further explored.