Protective effects of N(2)-L-alanyl-L-glutamine mediated by the JAK2/STAT3 signaling pathway on myocardial ischemia reperfusion

Abstract

To explore the protective effect of N(2)-L-alanyl-L-glutamine (NLAG) on myocardial ischemia-reperfusion injury (IRI), and observe the influence of NLAG on the Janus activated kinase signal transducer 2 and activator of transcription 3 (JAK2/STAT3) signaling pathway-associated molecules. Wistar rats were randomly divided into three groups: Sham, IRI and NLAG. In the IRI rat model, the cardiac hemodynamics, the maximum rate of left ventricular pressure (+dP/dtmax) and the left ventricular end-diastolic pressure (LVDP) were recorded. Hematoxylin-eosin and Masson staining were used to detect myocardial histological changes. The levels of plasma interleukin (IL)-1β and -6, tumor necrosis factor (TNF)-α, lactase dehydrogenase (LDH), troponin (cTn)I, creatine kinase (CK), heart type fatty acid binding protein (hFABP), malondialdehyde (MDA) and succinate dehydrogenase (SDH) were determined with ELISA. The protein expression levels of B-cell lymphoma (Bcl)-2, Bcl2-associated X protein (Bax), Caspase-3, JAK2, phosphorylated (p)-JAK2, STAT3 and p-STAT3 were detected by western blot analysis. The IRI model demonstrated notable myocardial injury; myocardial cells were arranged disorderly with some nuclei disappearing, and cardiac muscular fibers were degenerated. Following 60 min of reperfusion, LVDP, HR and +dP/dtmax were 31.3±4.53 mmHg, 239.17±8.45 beats/min and 615.17 mmHg/sec, respectively. Compared with the Sham group, the levels of LDH, cTnI, CK, hFABP release, inflammatory factors (IL-1β, IL-6 and TNF-α) and oxygen free radical (MDA and SDH) levels were increased in the IRI group. In the NLAG group, myocardial injury was improved, the concentrations of LDH, cTnI, CK, hFABP, IL-1β, IL-6, TNF-α, MDA were decreased, and SDH release was increased compared with the IRI group. In addition, NLAG significantly increased Bcl-2, JAK2, p-JAK2, STAT3 and p-STAT3 protein expression, and decreased Bax protein expression compared with the IRI group. In conclusion, myocardial ischemia-reperfusion can lead to myocardial cell apoptosis and myocardial injury and NLAG attenuates the IRI-induced mitochondrial oxidative stress injury and apoptosis by activating the JAK2/STAT3 signaling pathway, thus exerting protective effects against IRI.