Abstract 580: A β-arrestin-Biased β2-Adrenergic Receptor-Specific Pepducin Confers Cardioprotection

Reperfusion as a therapeutic intervention for acute myocardial infarction-induced cardiac injury itself induces further cardiomyocyte death. We recently demonstrated that the pepducin ICL1-9, a small lipidated peptide fragment designed from the first intracellular loop of β2AR, allosterically engaged pro-survival signaling cascades and enhanced cardiomyocyte contractile function in a βarr-dependent manner in vitro. Thus, in this study we tested whether ICL1-9 relays cardioprotection against ischemia/reperfusion (I/R)-induced injury in vivo. Wild-type (WT) C57BL/6 mice received intracardiac injections of either ICL1-9 or a scrambled control pepducin (Scr) at the time of ischemia (30 min) followed by reperfusion for either 24 hours, to assess infarct size and cardiomyocyte death, or 4 weeks, to monitor the impact of ICL1-9 on long-term cardiac structure and function. Intramyocardial injection of ICL1-9 at the time of I/R reduced infarct size, cardiomyocyte death and improved cardiac function in a β2AR- and βarr-dependent manner, which led to less cardiac fibrosis and improved cardiac function over time. Neonatal rat ventricular myocytes (NRVM) were used in conjunction with serum deprivation or hypoxia/reoxygenation (H/R) models to assess the mechanism by which ICL1-9 promotes cardiomyocyte survival. Notably, ICL1-9 attenuated mitochondrial superoxide production and promoted cardiomyocyte survival in a RhoA-dependent manner. ICL1-9 did not alter β2AR density in NRVM or whole heart even up to 24 hr post-treatment, at which timepoint both ICL1-9 localization in cardiomyocytes and RhoA activation were detected, indicating long-lasting presence and effects of ICL1-9 on βarr-dependent β2AR signaling. Thus, βarr-biased β2AR-selective allosteric modulation represents a novel therapeutic approach to reduce reperfusion-induced cardiac injury and relay long-term structural and functional benefits.