Abstract 250: Differential Role of Autophagy in Idiopathic versus Ischemic Heart Failure in Humans

Abstract

Background: Autophagy is an evolutionary conserved process that plays a key role in a variety of physiological and pathological processes. Despite its beneficial role, excessive/insufficient autophagic activity is known to contribute to the pathogenesis of cardiovascular disorders, including ischemia/reperfusion injury and heart failure. However, the differential role of autophagy in idiopathic versus ischemic heart failure remains unknown. Methods: To investigate the role of autophagy and associated apoptosis in idiopathic versus ischemic heart failure, we obtained LV myocardium biopsies from healthy controls (via 3 commercial sources), and from 10 patients with idiopathic and ischemic end-stage heart failure before the insertion of a left ventricular assist devise. The expression of inducers/markers of autophagy (mTOR, phospho-mTOR, LC3-I/II, p62, Beclin-1, autophagy-related genes ATG4B/ATG5) and apoptosis (Bcl-2 and caspase-3) were assessed at the transcript and protein level using quantitative RT-PCR and Western blotting. Results: Autophagy was activated in both idiopathic and ischemic heart failure in comparison to control, as confirmed by a significant reduction in mTOR expression/activation and a 3.4-fold and 2.2-fold increase in LC3 II/I ratio, respectively. An increase in apoptosis, marked by increased caspase3 and Bcl2 expression, was also observed in both groups in comparison to control. Interestingly, autophagy activity—marked by decreased mTOR expression/activation, increased ATG4B, ATG5, and Beclin-1—was significantly higher in idiopathic heart failure, when compared to ischemic heart failure. While we observed increased autophagic activity in idiopathic heart failure, p62 expression was also significantly increased in this group (2.8-fold increase; p<0.05), demonstrating an impairment of autophagic flux in idiopathic versus ischemic heart failure. Conclusions: For the first time, we provide a direct comparision of autophagy and apoptosis in idiopathic versus ischemic heart failure. Our data, demonstrating an excessive yet insufficient autophagic activity in idiopathic heart failure, suggests a differential role of autophagy apoptosis in idiopathic versus ischemia-related heart failure.