Abstract 144: Cardiac Expression of Mitochondrial Acetyltransferase Gcn5l1 Contributes to Ischemia-Reperfusion Injury and Alters Mitochondrial Energetics After Injury

Abstract

Introduction: The increasing global burden of ischemic heart disease demands a closer examination of the mechanisms by which myocardial reperfusion produces injury to initiate long-term heart failure. Reactive oxygen species (ROS) generated after ischemia reperfusion (IR), in conjunction with the dysfunction of mitochondrial metabolic enzymes, have been identified as a primary mediator of cardiac reperfusion injury. The acetylation of mitochondrial proteins, regulated by opposing actions of NAD + -dependent sirtuin deacetylases and the recently identified mitochondrial acetyltransferase GCN5L1, has emerged as a key point of intersection between nutrient status and mitochondrial protein function in cardiomyoctyes. This makes the association between acetylation and ROS production an important topic of investigation. Intriguingly, global protein acetylation was recently reported to be upregulated in the hearts of human patients with ischemic heart failure. Despite this, it remains unknown whether GCN5L1 acetyltransferase activity plays a role in the regulation of metabolic proteins during IR injury. Hypothesis: Cardiac deletion of the acetyltransferase GCN5L1 reduces the acetylation of mitochondrial proteins during IR, reducing aberrant activity and preventing ROS production. Methods: Isolated work-performing hearts from cardiac-specific inducible GCN5L1 knockout mice were subjected to global ischemia and reperfusion. Contractility (+/- dP/dT) of the left ventricle was measured throughout as an index of post IR functional recovery. Tissue damage was assessed by measuring the release of lactate dehydrogenase and post-reperfusion staining of viable tissue with triphenyltetrazolium chloride. Acetylation levels of mitochondrial proteins were measured during IR using immunoblotting of homogenized hearts, which were also used to evaluate ROS production. Results and Conclusions: Mitochondrial acetylation was decreased in GCN5L1 hearts compared to WT, coinciding with improved post-IR recovery. We therefore conclude that acetylation of mitochondrial proteins by the acetyltransferase GCN5L1 is an important regulatory mechanism of IR-induced, ROS-mediated damage.