Potentiation of β-adrenergic signaling by adenoviral-mediated gene transfer in adult rabbit ventricular myocytes

Our laboratory has been testing the hypothesis that genetic modulation of the β-adrenergic signaling cascade can enhance cardiac function. We have previously shown that transgenic mice with cardiac overexpression of either the human β₂-adrenergic receptor (β₂AR) or an inhibitor of the β- adrenergic receptor kinase (βARK), an enzyme that phosphorylates and uncouples agonist-bound receptors, have increased myocardial inotropy. We now have created recombinant adenoviruses encoding either the β₂AR (Adeno- β₂AR) or a peptide βARK inhibitor (consisting of the carboxyl terminus of βARK1, Adeno-βARKct) and tested their ability to potentiate β-adrenergic signaling in cultured adult rabbit ventricular myocytes. As assessed by radioligand binding, Adeno-β₂AR infection led to ~20-fold over-expression of β-adrenergic receptors. Protein immunoblots demonstrated the presence of the Adeno-βARKct transgene. Both transgenes significantly increased isoproterenol-stimulated cAMP as compared to myocytes infected with an adenovirus encoding β-galactosidase (Adeno-βGal) but did not affect the sarcolemmal adenylyl cyclase response to Forskolin or NaF. β-Adrenergic agonist-induced desensitization was significantly inhibited in Adeno-βARKct- infected myocytes (16±2%) as compared to Adeno-βGal-infected myocytes (37±1%, P < 0.001). We conclude that recombinant adenoviral gene transfer of the β₂AR or an inhibitor of βARK-mediated desensitization can potentiate β-adrenergic signaling.