BACKGROUND: The up-regulation of G protein-coupled receptor kinase-2 (GRK2) that is present in compromised myocardium contributes to dysfunctional β-adrenergic receptor (βAR) signaling and cardiac function in heart failure (HF). The peptide βARKct, which inhibits the activation of GRK2, has been shown in acute gene transfer experiments to rescue HF. This study was designed to evaluate chronic βARKct expression in post-myocardial infarction (MI) induced HF using stable myocardial gene delivery with adeno-associated virus serotype-6 (AAV6).
METHODS AND RESULTS: In 12 week post-MI HF rats, we delivered βARKct or as a control, Green Fluorescent Protein, via direct intramyocardial injection. We also treated groups with concurrent administration of metoprolol. We found robust and long-lasting (up to 12 weeks post-delivery) transgene expression in the left ventricle (LV) and βARKct expression resulted in significantly improved global heart function as LV ejection fraction and ±dP/dt were increased, whereas LV end diastolic diameter and pressure were decreased. At the molecular level, cardiac βAR density and cAMP accumulation significantly improved over control groups. Fibrotic and hypertrophy markers, as well as heart-to-body weight ratio were markedly decreased by βARKct gene therapy indicating active reversal of adverse LV remodeling. For the first time, we found that chronic βARKct expression and normalization of cardiac βAR signaling led to a reduction of circulating levels of cardiotoxic neurohormones (catecholamines and aldosterone) demonstrating a potential additive mechanism of GRK2 inhibition. Concomitant metoprolol administration preserved the gain in inotropy achieved by βARKct, suggesting compatibility of these two therapeutic modalities, however, metoprolol alone only prevented the deterioration of cardiac function in HF.
CONCLUSIONS
: Chronic cardiac βARKct gene therapy for HF treatment via AAV6-mediated intracardiac gene delivery is feasible and results in improved cardiac function accompanied by restoration of βAR molecular abnormalities and amelioration of neurohormonal status of HF. These findings suggest βARKct gene therapy might be clinically applicable and of significant value for human HF treatment.
This research has received full or partial funding support from the American Heart Association, AHA Great Rivers Affiliate (Delaware, Kentucky, Ohio, Pennsylvania & West Virginia).
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