HAT-Dependent Control of Cardiac Fibrosis

University Of Colorado Denver, Aurora CO

Investigators

Abstract

Project Summary/Abstract Fibrosis is defined as excess deposition of extracellular matrix (ECM), resulting in tissue scarring and organ dysfunction. In the heart, fibrotic remodeling in the context of chronic comorbidities such as hypertension and metabolic disease is associated with increased passive myocardial stiffness and the development of diastolic dysfunction (DD), a contributor to the pathogenesis of a multitude of cardiac disorders, including heart failure with preserved ejection fraction (HFpEF). The adult heart contains resident cardiac fibroblasts (CFs), which, in response to stress, undergo a cell state transition to become activated fibroblasts, sometimes referred to as myofibroblasts. Activated CFs are characterized by transcriptional reprogramming that results in enhanced production and secretion of fibrotic ECM proteins. Despite the well-recognized roles of CFs in fibrotic remodeling of the heart, there are no targeted therapies to prevent or reverse the phenotypic conversion of these cells into an activated state. Epigenetic regulatory proteins, including those that ‘erase’ (histone deacetylases [HDACs]) and ‘read’ (bromodomain-containing protein 4 [BRD4]) acetyl-histones, have clearly been shown to control of CF activation. Acetyl-histone ‘writers’ (histone acetyltransferases [HATs]) have also been suggested to regulate ECM production by CFs, but much of the prior work with HATs in the context of cardiac fibrosis was performed with pharmacological tool compounds with suboptimal selectivity and potency profiles. Following up on a recent phenotypic high-throughput screening campaign, our unpublished data reveal that highly optimized, drug-like inhibitors of the p300 and CREB-binding protein (CBP) HATs profoundly and dose-dependently suppress agonist-induced CF activation. Inhibition of p300/CBP catalytic activity with A-485, or neutralization of the acetyl- histone binding bromodomain in these HATs using PF-CBP1, blocked transforming growth factor- (TGF-)- mediated activation of cultured murine CFs through a SMAD-independent, non-canonical mechanism. Additionally, inhibition of p300/CBP catalytic activity blocked CF activation and cardiac fibrosis in a mouse model. Remarkably, A-485 and PF-CBP1 are also able to dramatically reverse constitutive activation of failing human CFs, highlighting the translational potential of our findings. Mechanistically, we provide evidence to suggest that p300/CBP inhibition squelches formation of activating acetyl-histone marks on gene regulatory elements and results in transcriptional rewiring in CFs, at least in part, through inhibition of the forkhead box protein M1 (FOXM1) transcription factor. Three specific aims are designed to extend this new field of cardiac research and test the overall hypothesis that inhibition of p300/CBP prevents and reverses the epigenomic and transcriptional reprogramming that culminates in CF activation and pathological fibrosis of the heart.