Cardioprotection Of Glycine On Ischemia Reperfusion Injury And Its Mechanisms

Objectives:The aims of this study were to determine whether glycine could prevent heart from ischemia reperfusion injury in a rat model, to clarify wheathr rat myocardium and cardiomyocyte express glycine receptor. Furthermore, the possible downstream pathways of glycine protective effects were investigated. These studies are useful to further explore the clinical value of glycine and to provide theorecical reasons and new ideas to prevent myocardial ischemia-reperfusion injury.Methods:(1) This study used ischemia-reperfusion injury rat model by ligating left anterior descending coronary artery. Anesthetized male Sprague-Dawley rats were subjected to 30 min of myocardium ischemia followed by 20 min-6 hours reperfusion. Animals were divided into three groups, control animals received normal saline solution by intraperitoneal injection and treated animals received glycine at 500mg/kg of body weight, which dissolved in saline solution. Then measured the cardiac function by cardiac ultrasound, myocardial infarct size was determined by means of a double-staining technique and a digital imaging system, serum creatine kinase (CK) activity changes were determined. In addition, myocardial cell apoptosis were analyzed by TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay using an in situ cell death detection kit.(2) Hearts were harvested and cellular proteins and RNA were isolated for immunoprecipitation and.RT-PCR, western detected p38MAPK, JNK / SAPK activity and RT-PCR detected FasL, p53 expression changes between different groups. The purpose of these studies were to clarify the possible downstream pathways of glycine protective effects.(3) Used RT-PCR and western blot to detect the expression of GlyR on myocardium and cardiomyocyte. Isolated and cultured neonatal rat primary cadiocyte were isolated, using RT-PCR and indirect immunofluorescence to confirm the GlyR subunit expression on these cells.Results:Glycine administration significantly decreased infarct size by 21.74%, and the serum creatine kinase (CK) activity were decreased 31.42%, compared with the untreated MI/R group. Ejection fraction and fractional shortening in Glycine treated rat were also significantly increased by 19.11% and 30.98%, respectively, compared with the untreated MI/R group. Glycine administration significantly decreased MI/R-increased myocardial cell apoptosis as evidenced by TUNEL and attenuated MI/R-increased p38MAPK and JNK/SAPK activity, and reduced levels of FasL in the myocardium compared with the untreated MI/R group. In addition, western blot,RT-PCR, and immunofluorescence methods had confirmed that myocardium and myocardial cell exist GlyR and this submit may be GlyRα2.Conclusions:The results demonstrated that glycine could reduce ischemia/reperfusion-induced p38MAPK and JNK/SAPK activitiy, decreases FasL production and cardiomyocytes apoptosis ,which brings about reduction of infarct size and improvement of cardiac function in MI/R-induced injury and these glycine cardioprotective effects maybe mediated by GlyRα2.