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.