Substance P On Norepinephrine-induced Cultured Rat Cardiac Myocyte Apoptosis And Its Mechanism Research

Background-Myocardial sympathetic activity is increased in myocardial ischemia and infarction, indicated by increases in catecholamines in myocardium and in plasma. Previous studies revealed that such high concentration of norepinephrine (NE) induces apoptosis in cultured rat myocytes and this effect is mediated by protein kinase A (cAMP-Dependent Protein Kinase, PKA). Substance P (SP) belongs to a group of neurokinins (NKs), small peptides, which is broadly distributed in the central nervous system and peripheral nervous system, and in heart, implying the peptide may participate in physiological or/and pathology functions of heart. Plasma SP was found increased in heart failure. We tested the hypothesis that SP regulates NE induced apoptosis in cultured rat ventricular myocytes.Objective-The purpose of this study was to investigate the effect of SP on NE induced apoptosis of myocytes and explore the possible mechanism of the effect.Methods-Cultured neonatal rat cardiomyocytes were exposed to NE alone(10μmol/L), NE+H89 (a protein kinase a inhibitor,30μmol/L),NE+SP (1μmol/L), NE+SP+D-SP([D-Arg1,D-Phe5, D-Trp7.9,Leu11]-Substance P,a neurokinin-1 [NK1] receptor antagonist,sigma,10μmol/L) for 15minutes. Apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated nick end-labeling(TUNEL). PKA activity was measured by using a non-radioactive method, PepTag(?) Assay for Non-Radioactive Detection of PKA.Results-SP reduced NE induced apoptosis rate,apoptosis cells/(apoptosis cells+alive cells) from 46.3±13.1% to 23.0%±8.0%,H89 reduced NE induced apoptosis rate as SP.The PKA activity of NE group up-regulated,and the activity of SP+NE group is down-regulated. Conclusions-Substance P prevents apoptosis induced by norepinephrine in neonatal rat cardiomyocytes. This effect is mediated by PKA.Conclusion-SP inhibits NE induced apoptosis of cultured rat cardiomyocytes, via modulation of PKA activity. The effect of SP is mediated by neuokinin-1 receptor.