RESUMO
Objective:To evaluate the role of adenosine monophosphate-dependent protein kinase/p38 mitogen-activated protein kinase/nuclear factor E2-associated factor 2 (AMPK/p38 MAPK/Nrf2) pathway in myocardial ischemia-reperfusion (I/R) injury in diabetic rats.Methods:Clean-grade healthy Sprague-Dawley male rats, aged 2-3 months, weighing 220-280 g, were fed with a high fat diet, and 1% streptozotocin 50 mg/kg was intraperitoneally injected for 4 consecutive days to develop the model of diabetes mellitus.Thirty diabetic rats were divided into 3 groups ( n=10 each) using the random number table method: sham operation group (sham group), myocardial I/R group (I/R group), and AMPK inhibitor compound C+ myocardial I/R group (C+ I/R group). The model of myocardial I/R injury was developed by ligation of the left anterior descending coronary artery for 30 min followed by 120 min reperfusion.Compound C 0.5 mg/kg was injected via the caudal vein at 30 min before ischemia in C+ I/R group, while the equal volume of normal saline was given instead in Sham group and I/R group.At 120 min of reperfusion, the percentage of myocardial infarct size was calculated, the serum concentrations of creatine kinase isoenzymes (CK-MB) and lactic dehydrogenase (LDH) were determined by enzyme-linked immunosorbent assay, the levels of glutathione (GSH), superoxide dismutase (SOD) and reactive oxygen species (ROS) in myocardial tissues were measured by enzyme-linked immunosorbent assay, and the expression of AMPK, phosphorylated AMPK (p-AMPK), phosphorylated p38 MAPK (p-p38 MAPK), Nrf2 and heme oxygenase-1 (HO-1) in myocardium was determined by Western blot. Results:Compared with Sham group, the percentage of myocardial infarct size and serum CK-MB and LDH levels were significantly increased, the levels of GSH and SOD in myocardial tissues were decreased, ROS level was increased, and the expression of AMPK, p-AMPK, p-p38 MAPK, Nrf2 and HO-1 was up-regulated in I/R group ( P<0.05). Compared with I/R group, the percentage of myocardial infarct size and serum CK-MB and LDH levels were significantly increased, the levels of GSH and SOD in myocardial tissues were decreased, ROS level was increased, and the expression of AMPK, Nrf2 and HO-1 was down-regulated in C+ I/R group ( P<0.05). Conclusions:AMPK/p38 MAPK/Nrf2 signaling pathway is involved in the mechanism of endogenous antioxidant stress during myocardial I/R in diabetic rats.
