Effect Of Substance P On Myocardial Ischemia-reperfusion Injury In Rat Heart And Its Mechanism

Background:Ischemia-reperfusion injury(IRI) is refers to further damage of myocardium and its function following restoration of blood perfusion of the ischemic area, presenting myocardial stunning, reperfusion arrhythmias, microvascular dysfunction and myocardial apoptosis. SP is an important neurotransmitter which releases from sensory nerve endings, conveys the damage signal to nerve center. It is widely distributed in the nerve center and peripheral nervous system and cardiac tissue. The study found that, in the process of myocardial ischemia and myocardial infarction, the concentration of SP in the myocardial tissue is increased, which suggests that SP may be involved in the pathophysiological process in myocardial ischemia and myocardial infarction. Previous studies of this laboratory have shown that SP can significantly reduce the incidence of arrhythmias in isolated perfused model after coronary artery occlusion. And SP inhibits cardiomyocyte apoptosis induced by norepinephrine via modulation of PKA activity.SOD, an antioxidant enzyme system, can removes oxygen radical in vivo, and the level of its content and activity can reflect the ability of lipid peroxidation. CRYAB is a small molecule of heat shock proteins, accounting for3-5%of the myocardial total proteins. As a molecular chaperone, CRYAB can interact with a variety of proteins and promote cell survival.And in the case of stress as rat cardiac ischemic, it plays a role in anti-apoptotic and myocardial protection. However, what impact does the endogenous SP acted on IRI? What is the correlation between SP induced cardioprotection and mechanisms mediated by SOD and CRYAB?Objective: The aim of this study is to investigate the the potential cardioprotective effect of SP and the underlying mechanism correlating with SOD and CRYAB in myocardial ischemia and reperfusion injury.Methods:The study was carried out in a series of experiments:1.The impact of substance P to ventricular arrhythmias and hemodynamics caused of myocardial ischemia-reperfusion:Use rat in vivo model,Healthy rats were divided into sham group(only wear lines,without ligation,continued120min)、 Ischemia-reperfusion group (intravenous give an equal volume of saline)、different concentrations of SP receptor antagonist([D-Argl,D-Phe5,D-Trp7,9, Leull]-Substance P,D-SP) group,(10-11mol/kg,10-10mol/kg and10-9mol/kg Ischemia-reperfusion group and each dose group ligation30min,reperfusion120min,1ul/g dose at5min before reperfusion.Then record and analysis changes of ventricular arrhythmias,and systolic blood pressure,diastolic blood pressure,mean arterial pressure,pulse pressure and heart rate within120minutes after reperfusion.2.The impact of substance P to cell apoptosis caused of myocardial ischemia-reperfusion:model.groups,administration method ibid.Extract myocardial tissue protein at the end of reperfusion.Use Caspase-3activity spectrophotometric assay kit to detect its activity,Using2,3,5-triphenyltetrazolium chloride staining (TTC) to calculate myocardial infarct size.3.SP on ischemia-reperfusion in the rat myocardium SOD and CRYAB: model,groups,administration method ibid.Using a protein immunoblot (Western blot) semi-quantitative measure the expression level of SOD and CRYAB in myocardium.Results:①Compared with IR,group Outbreak number of ventricular arrhythmias were lower in S group (P<0.01)and higher in D-SP10-9and D-SP10-10(P<0.01).The role of D-SP10-10is most obvious. In addition to the S group,The occurrence of ventricular contraction in the other groups distribution in the first15minutes of reperfusion, and each administered group have another peak in25min-55min after reperfusion. Compared with S group.the systolic blood pressure and mean arterial pressure of IR group were lower.Compared with IR group, the systolic blood pressure of D-SP10-9group was higher. The rest of index was not statistically different.②Compared with S group, Caspase-3activity in Group IR increased0.20-fold (P<0.05). Compared with IR group, DSP10-10increased0.24-fold (P<0.05). For TTC staining, Compared with IR group,infarct size in DSP10’10group was significantly higher (P<0.01)③Compared with S group, SOD activity in Group IR decreased (P<0.05). Compared with IR group, the SOD activity in each dose group were lower (P<0.01).The D-SP10-10group had a significant role.Compared with D-SP10-10group, D-SP10-9and D-SP-11group were increased (P<0.01), Compared with S group,The Cryab expression in IR group was significantly increased (P<0.01). Compared with IR group, Cryab expression in D-SP10-10group was lower (P<0.01).Conclusion:Ischemia-reperfusion can lead to myocardial injury,D-SP by reducing Cryab and SOD expression levels induced myocardial apoptosis,causing the occurrence of ventricular arrhythmias,suggesting that endogenous SP may have a protective effect on myocardial in ischemia reperfusion.