Myocardial Ischemic Postconditioning Promotes Autophagy against Ischemia Reperfusion Injury via the Activation of the nNOS/AMPK/mTOR Pathway.

Autophagy participates in the progression of many diseases, comprising ischemia/ reperfusion (I/R). It is reported that it is involved in the protective mechanism of ischemic postconditioning (IPostC). According to research, neuronal nitric oxide synthase (nNOS) is also involved in the condition of I/R and IPostC. However, the relationship between nNOS, autophagy and IPostC has not been previously investigated. We hypothesize that IPostC promotes autophagy activity against I/R injury partially through nNOS-mediated pathways. Mouse hearts were subjected to I/R injury through the ligation of the left anterior descending coronary artery. H9c2 cells were subjected to hypoxia/reoxygenation (H/R) in vitro. IPostC, compared with I/R, restored nNOS activity, increased the formation of autophagosome and restored the impaired autophagic flux, thus autophagic activity was raised markedly. IPostC increased adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and suppressed mammalian target of rapamycin (mTOR), but a selective nNOS inhibitor abolished those effects. Similar effects of IPostC were demonstrated in H9c2 cells in vitro. IPostC decreased infarct size and preserved most of the normal structure. The level of reactive oxygen species (ROS) and cell apoptosis were reduced by IPostC with improved cell viability and mitochondrial membrane potential. However, an autophagy inhibitor suppressed the protective effects. These results suggest that IPostC promoted autophagy against I/R injury at least partially via the activation of nNOS/AMPK/mTOR pathway.