Abstract 10254: HDAC Inhibition Regulates Cardiac Function via Myofilament Acetylation

Abstract

Introduction: Heart failure (HF) is a global issue and approximately 50% of patients are classified as having HF with preserved Ejection Fraction (HFpEF), with no FDA approved therapies available. We previously characterized a large animal model that recapitulates key features of HFpEF and tested the effects of suberanilohydroxamic acid (SAHA, pan-HDAC inhibitor), which reversed and prevented the development of cardiopulmonary dysfunction. Parallel studies in cardiac tissue from humans and large mammals were designed to evaluate the effects of SAHA at the cellular level. Hypothesis: SAHA treatment will improve cardiomyocyte function. Methods: Adult feline ventricular cardiomyocytes (AFVM) were isolated from male domestic short hair cats and treated with 2.5μM SAHA or vehicle (DMSO) for 90 minutes, then incubated with a calcium (Ca 2+ ) indicator (Fluo-4AM) and electrically stimulated (0.5Hz) to record Ca 2+ transients and contractions. Human left ventricle (LV) trabeculae isolated from non-failing donor hearts were treated with 10μM SAHA or vehicle for 120 minutes while being electrically stimulated (1Hz) to record developed force and relaxation parameters. Skinned myocytes were isolated from treated AFVM and human trabeculae to assess myofilament Ca 2+ sensitivity and passive stiffness. Mass spectrometry (MS) was performed on AFVM skinned myocytes to identify novel acetylation sites. Results: There was no difference in AFVM peak Ca 2+ transients with SAHA treatment, but calcium removal was increased (tau, time to 30% baseline). There was a significant increase in contractility (fractional shortening) and relaxation kinetics (time to 50% baseline, return velocity). Trabeculae treated with SAHA had decreased diastolic tension and an increase in developed force. Skinned myocytes were isolated from treated AFVMs and trabeculae and both had a significant improvement in myofilament Ca 2+ sensitivity and significant decrease in passive stiffness with SAHA. MS of AFVM skinned myocytes revealed increased acetylation of the myosin regulatory light chain, driven by lysine 115. Conclusions: These findings suggest that SAHA may have an important role in regulating cardiac function via the cardiomyocyte and myofilament in feline and human myocardium.