Abstract P2012: GRK2-Induced Cardiomyocyte AdipoR1 Phosphorylation Blocks Adipocytes-Derived Exosomes Cardioprotection Against Ischemic Heart Failure

Abstract

Background: Despite significant reduction in acute MI death, ischemic heart failure (IHF) and resultant death continually escalate with incompletely understood mechanism. We recently reported that adipocyte-derived exosomes (ADp-Exo) protect heart from acute MI/R injury. However, it remains unknown whether and how cardiomyocytes (CM) response to ADp-Exo is altered during the chronic phase of MI, negatively impacting IHF development. Methods and Results: Intramyocardial injection of ADp-Exo (isolated from epididymal fat pad) immediately after MI (90 min MI/4 weeks reperfusion) significantly attenuated post-MI remodeling. However, the protective effects were completely lost when ADp-Exo were administered 1 week after MI. To identify the molecular mechanisms responsible for ADp-Exo cardioprotection and its alteration during chronic MI, a series of in vitro experiments were performed. Adiponectin (APN), a potent cardioprotective adipokine, was detected on the surface of ADp-Exo (Exo-flow kit). Treatment of CM with ADp-Exo activated multiple cell salvage kinases (e.g., ACC, ERK and AMPK). These effects were lost in APN neutralization antibody pre-incubated ADp-Exo or ADp-Exo from APNKO mice, suggesting Exo surface APN may mediate ADp-Exo cardioprotection. Moreover, ADp-Exo cell salvage kinase activation effect was absent in CM from AdipoR1KO mice or GRK2 transfected CM, suggesting GRK2-induced AdipoR1 phosphorylation at Ser 205 (as we demonstrated in Circulation, 2015 and Circ Res, 2022) is likely responsible for incapability of ADp-Exo protection during post-MI remodeling. To obtain direct evidence supporting this novel hypothesis, AdipoR1 S205A or AdipoR1 S205E (pseudo-phosphorylation) mice were generated. ADp-Exo cardioprotection was restored in AdipoR1 S205A mice, even when they were administered 1 week after MI. In contrast, ADp-Exo cardioprotection was lost in AdipoR1 S205E mice, even when they were administered immediately after MI. Conclusions: We demonstrate for the first time that, APN located on the surface of ADp-Exo acts as the critical executor of ADp-CM communication, mediating ADp-Exo cardioprotection. GRK2-induced CM AdipoR1 phosphorylation blocks ADp-Exo protective action, contributing to IHF progression.