Abstract 426: Stress-induced Kinase Targets of Cardioprotective 3’,4’-dihydroxyflavonol in Injured Myocardium

Abstract

3’,4’-dihydroxyflavonol (DiOHF) is a synthetic flavonol in a class of phytochemicals known as flavonoids can have beneficial biological properties. Previous studies revealed that intravenous administration of DiOHF immediately preceding myocardial reperfusion potently reduced infarct size in anaesthetised sheep that was comparable to ischemic preconditioning and the protective effects of DiOHF were recapitulated ex vivo during ischemia/reperfusion (I/R) of Langendorff-perfused rat hearts and in vitro on isolated cardiac myocytes. These studies highlight the therapeutic potential of DiOHF, with derivatives recently entering Phase II trials for the reduction of ventricular injury and contractile dysfunction following myocardial infarction (NCT02557217). In our current study, we confirmed potent cytoprotective effects of DiOHF in preventing apoptotic and necrotic death of primary rat cardiomyocytes. In addition, we revealed potent anti-hypertrophic effects in cardiomyocytes stimulated with alpha and beta-adrenergic agonists. In comparison with structurally similar compounds, fisetin, quercetin and dihydroxyflavone, DiOHF exhibited enhanced anti-hypertrophic and protective properties. The molecular targets of DiOHF that underpin it’s beneficial effects are of immense interest as they aid clinical development of derivative compounds, rational design of new compounds with biological activity and provide novel insights into the regulatory mechanisms that define the protected myocardium. In exploring the DiOHF mechanisms of action, we had previously reported DiOHF inhibited Ca2+/calmodulin dependent protein kinase II (CaMKII) activity in in vitro kinase assays and in cultured myoblasts. Here, we used resin-immobilized DiOHF for affinity purification from heart tissue lysates and confirmed direct drug-interaction with CaMKII/p-CaMKII from injured rat myocardium (I/R). In addition, we revealed DiOHF interaction and direct inhibition of apoptosis-signal regulated kinase (ASK1) from I/R rat hearts. Our ongoing studies will define whether flavonol inhibition of CaMKII and ASK1 defines protective benefits of DiOHF in the injured myocardium.