Role of p38MAPK signaling pathway in reduction of myocardial ischemia-reperfusion injury by morphine preconditioning in rats with chronic heart failure in vitro

Abstract

Objective To investigate the role of p38 mitogen-activated protein kinase (p38MAPK) signaling pathway in reduction of myocardial ischemia-reperfusion (I/R) injury by morphine preconditioning in the rats with chronic heart failure in vitro. Methods Adult male Sprague-Dawley rats, weighing 200-230 g, aged 6-7 weeks, in which doxorubicin 2 mg/kg was injected via the tail vein once a week for 6 consecutive weeks to induce chronic heart failure, were studied.At the end of 8th week, 30 rats with chronic heart failure were randomly divided into 5 groups (n=6 each) using a random number table: sham operation group (group Sham), I/R group, morphine preconditioning group (group MPC), SB203580 (p38MAPK inhibitor) + morphine preconditioning group (group SBM), and SB203580 group (group SB). The hearts were quickly excised and passively perfused in a Langendorff apparatus and subjected to 30 min of occlusion of the anterior descending branch of the left coronary artery followed by 120 min of reperfusion to establish the model of myocardial I/R injury.After equilibration, the hearts were subjected to 3 cycles of 5 min perfusion with K-H solution containing morphine 1 μmol/L at 5-min intervals before ischemia in group MPC.In group SBM, the hearts were perfused with K-H solution containing SB203580 (5 μmol/L) for 45 min starting from 10 min before morphine preconditioning until 5 min of ischemia.In group SB, morphine preconditioning was not performed, and the hearts were only perfused with K-H solution containing SB203580 (5 μmol/L) starting from 40 min before ischemia until 5 min of ischemia.At 15 min of equilibration (baseline), 5 and 10 min of reperfusion, the coronary effluent was collected to detect the activity of lactate dehydrogenase (LDH) using the chemical colorimetry.At 10 min of reperfusion, the expression of phosphor-p38MAPK (p-p38MAPK) in the myocardium was determined by Western blot in Sham, I/R and MPC groups.At 120 min of reperfusion, the area at risk (AAR), total areas of right and left ventricles (LV+ RV), and infarct size (IS) were measured, and the IS/AAR ratio was calculated. Results Compared with group Sham, the LDH activity in coronary effluent during reperfusion and IS/AAR ratio were significantly increased in the other groups, and the expression of p-p38MAPK was significantly up-regulated in I/R and MPC groups (P 0.05). Compared with group MPC, the LDH activity in coronary effluent during reperfusion was significantly increased, and the IS and IS/AAR ratio were significantly increased in group SBM (P<0.05). Conclusion The mechanism by which morphine preconditioning reduces myocardial I/R injury is related to activation of p38MAPK signaling pathway in the rats with chronic heart failure in vitro. Key words: p38 Mitogen-activated protein kinases; Heart failure; Myocardial reperfusion injury; Morphine; Ischemic preconditioning