Autophagy gene fingerprint in human ischemia and reperfusion

Abstract

Autophagy is an evolutionary conserved adaptive response that is believed to promote cell survival in response to stressful stimuli via recycling of precursors derived from the degradation of endogenous cellular components. The autophagic molecular machinery is controlled by a large family of autophagy-related genes (ATGs) and downstream regulators. We sought to define the autophagy gene fingerprint associated with human ischemia and reperfusion (IR) injury using an intraoperative model developed by Sellke and colleagues. Right atrial appendages, collected from human hearts before and after cardioplegic arrest and after reperfusion, were submitted for polymerase chain reaction (PCR) array, quantitative real-time PCR, and immunoblot analysis for autophagy proteins and their associated upstream regulators. Perioperative IR significantly upregulated 11 (13.1%) and downregulated 3 (3.6%) of 84 ATGs. Specifically, there were increases in the autophagy machinery components ATG4A, ATG4C, and ATG4D; tumor necrosis factor-related apoptosis-inducing ligand, MAPK8 and BCL2L1; and chaperone-mediated autophagy activity with increased heat shock protein (HSP) A8, HSP90AA1, and a-synuclein. Autophagy activity was confirmed through observations of higher LC3-I levels and an increase in the LC3-II/LC3-I ratio. Autophagy activation coincided with increased AMPK activation and decreased protein levels of the mammalian target of rapamycin, the latter a key negative regulator of autophagy. We provide the first human cardiac fingerprint of autophagy gene expression in response to IR. These findings may inform on appropriate cell- and gene-based therapeutic approaches to limit aberrant cardiac injury.