Abstract 445: Autophagy is Essential for Remote Preconditioning Induced Cardioprotection and May Involve JAK-STAT Pathway for Autophagy Activation

Abstract

Autophagy is a cellular process by which mammalian cells degrade and recycle damaged organelles and proteins. Remote ischemic preconditioning (RIPC) protects the myocardium from ischemia-reperfusion (I/R) injury and is thought to involve upregulation of autophagy. In this study we aim to ascertain the role of autophagy in RIPC induced cardioprotection. Sprague Dawley rats were subjected to transient blockade of left anterior descending coronary artery to simulate I/R injury, with or without prior RIPC at the hind limb. RIPC prior I/R decreased myocardial infarct size (51.5 ± 3.5% vs. 30.2 ± 5.16%; n=7, p<0.05), PARP cleavage and upregulated autophagy in the myocardium compared to I/R alone (p<0.05). RIPC alone increased autophagy in a time dependent manner in the myocardium. To further examine the effect of autophagy, H9C2 rat cardiomyoblast cells were exposed to RIPC following I/R simulation. 3-methyladenine (10mM) was used to inhibit autophagy, which ameliorated the cardioprotective effect of RIPC in H9C2 cells, producing significant increases in apoptosis and Bax protein expression, and decreasing cell viability compared to the untreated cells (p<0.05). In contrast, autophagy stimulation with rapamycin (1000nm) significantly reduced apoptosis and Bax protein expression, and improved cell viability in H9C2 cells compared to H/R group mimicking the preconditioning effect (p<0.05). In addition, RIPC of H9C2 cells upregulated IL-6 protein release into the preconditioned media. H9C2 cells exposed to this preconditioned media prior I/R were protected against apoptosis and upregulated autophagy. Recombinant IL-6 treatment prior I/R upregulated autophagy in H9C2 cells in a dose dependent manner, activating JAK-STAT pathway (p<0.05 vs. I/R) without affecting the other kinase pathways including p38 MAPK, GSK-3β pathways. Blocking JAK-STAT pathway with AG-490 (50 μM) prior I/R reduced autophagy upregulation despite recombinant IL-6 treatment (p<0.05 vs. IL-6 treated I/R control). These results suggest that, autophagy is essential for RIPC induced cardioprotection and RIPC may upregulate autophagy through IL-6/JAK-STAT dependent mechanism, thus identifying a potentially new therapeutic option for the treatment of ischemic heart disease.