Insights for Oxidative Stress and mTOR Signaling in Myocardial Ischemia/Reperfusion Injury under Diabetes
Ischemic postconditioning (IPC) represents one of the most effective cardioprotective strategies against myocardial ischemia/reperfusion. Depression is commonly present in patients with coronary heart disease. However, whether depression interferes with the cardioprotection of IPC during myocardial ischemia/reperfusion and their underlying mechanisms remain largely unknown. Isolated hearts from chronic mild stress induced-depressed rats and non-depressed rats were subjected to 30 min of regional ischemia followed by 120 min of reperfusion in the presence or absence of IPC (consisting of 6 cycles of 10 s of reperfusion and 10 s of ischemia immediately after the sustained ischemia). Myocardial infarct size, creatine kinase (CK) and cardiac troponin T (cTnT) release, cardiac function and phosphorylated AKT and signal transducer and activator of transcription-3 (STAT-3) were measured. IPC significantly prevented the hearts from myocardial ischemia/reperfusion injury by decreasing infarct size, and CK and cTnT release in coronary effluent, and improving cardiac functional recovery in non-depressed rats. However, these cardioprotective effects of IPC were not observed in depressed rats. In addition, IPC had no effects on the phosphorylation of AKT and STAT-3 at reperfusion in depressed hearts, although it markedly increased the phosphorylation of AKT and STAT-3 at reperfusion in non-depressed hearts. In conclusion, these data indicate that cardioprotection by IPC is abolished during myocardial ischemia/reperfusion in depressed rats, and the underlying mechanisms are probably related to the impaired activation of AKT and STAT-3 at reperfusion.