Substance P Activates Akt Signaling Pathway To Alleviate Hypoxia-reoxygenation-induced Cardiomyocyte Apoptosis

Background Myocardial ischemia reperfusion injury(IRI)is a common injury in the treatment of ischemic heart disease,and it is also one of the main causes of aggravation and death in ischemic heart disease.There are many pathophysiological mechanisms of IRI,among which cardiomyocyte apoptosis may be one of the most important factor.Substance P(SP)is a small molecule neurotransmitter released from sensory nerve endings and involved in neurogenic inflammation.More and more evidences show that SP has cardioprotective effect after IRI,mainly because it has strong coronary artery dilation and can improve myocardial ischemia.However,its direct effect on cardiomyocytes is still controversial.SP can activate Akt signaling pathway.Akt signaling pathway is an important pathway of membrane receptor signal transduction,which plays a role in regulating cell growth,apoptosis and the expression of some other important genes.Can SP reduce IRI induced cardiomyocyte apoptosis by activating Akt signaling pathway? In this experiment,we observed whether SP has direct anti-cardiomyocyte apoptosis effect and its molecular mechanism through animal and cell experiments.Objective1.To investigate the protective effect of SP on cardiomyocyte apoptosis in mice with myocardial ischemia reperfusion injury.2.In cell model,it was proved that SP combined with NK-1 receptor and activated Akt signaling pathway to alleviate H9C2 apoptosis induced by Hypoxia/Reoxygenation(H/R).Method1.Myocardial IRI model of mice was established and divided into sham group and I/R group.Then the mice were divided into sham group,I/R group,I/R + SP group and I/R + NK-1R antagonist group.The expression of Bax m RNA was detected by RT-PCR;Western blot was used to detect the expression of Bax and Cleaved Caspase-3.2.H9C2 H/R model was used to simulate IRI of cardiomyocytes.SP,Akt agonist insulin-like growth factor-1(IGF-1),Akt antagonist(LY294002)and NK-1R antagonist(RP 67580)were given to H9C2 cells respectively.Lactate dehydrogenase(LDH)was used to determine the necrosis.The apoptosis rate of H9C2 cardiomyocytes was determined by TUNEL staining;Western blot was used to detect the expression of Bax,cleaved Caspase-3,NK-1R and Akt/p-Akt.Result1.SP significantly reduced the increase of Bax and cleaved caspase-3 induced by I/R.2.SP reduce H/R-induced H9C2 cell apoptosis and the expression of Bax and cleaved caspase-3;Akt antagonist(LY294002)eliminated the above effects of SP;Akt agonist(IGF-1)did not further enhance the above effects of SP.NK-1R antagonist(RP67580)attenuated the anti-apoptotic effect of SP.Conclusion1.SP can reduce IRI induced apoptosis.2.SP binds to NK-1 receptor and activates Akt signaling pathway to alleviate H/R induced apoptosis of H9C2 cells...