Abstract 422: Small Molecule and Activated Fibroblast Targeting of the Gβγ-GRK2 Interface After Myocardial Ischemia Attenuates Heart Failure Progression

Cardiac fibroblasts are a critical cell population responsible for myocardial extracellular matrix homeostasis. Upon injury or pathologic stimulation, these cells transform to an activated myofibroblast state and play a fundamental role in myocardial fibrosis and remodeling. Chronic sympathetic overstimulation, a hallmark of heart failure, induces pathologic signaling through G protein βγ subunits and their interaction with G protein-coupled receptor kinase 2 (GRK2). We hypothesized that Gβγ-GRK2 inhibition/ablation after myocardial injury would attenuate pathologic myofibroblast activation and cardiac remodeling. The therapeutic potential of small molecule Gβγ-GRK2 inhibition alone or in combination with activated fibroblast- or myocyte-specific GRK2 ablation, each initiated after myocardial ischemia/reperfusion (I/R) injury, was investigated to evaluate possible salutary effects on post-I/R fibroblast activation, pathologic remodeling and cardiac function. Small molecule Gβγ-GRK2 inhibition initiated one week post-injury was cardioprotective in the I/R model of chronic heart failure, including preservation of cardiac contractility and reduction in cardiac fibrotic remodeling. Systemic small molecule Gβγ-GRK2 inhibition initiated one week post-I/R in cardiomyocyte-restricted GRK2 ablated mice (also post-I/R) demonstrated additional cardioprotection, suggesting a potential protective role beyond the cardiomyocyte. Inducible ablation of GRK2 in activated fibroblasts (i.e. myofibroblasts) post-I/R injury demonstrated significant functional cardioprotection with reduced myofibroblast transformation and fibrosis. Systemic small molecule Gβγ-GRK2 inhibition initiated one week post-I/R provided little to no further protection in mice with ablation of GRK2 in activated fibroblasts alone. Finally, Gβγ-GRK2 inhibition significantly attenuated activation characteristics of failing human cardiac fibroblasts isolated from end stage heart failure patients. These findings suggest a potential therapeutic role for Gβγ-GRK2 inhibition in limiting pathologic myofibroblast activation, interstitial fibrosis and heart failure progression.