Targeted β-adrenergic receptor kinase (βARK1) inhibition by gene transfer in failing human hearts

Background - Failing human myocardium is characterized by an attenuated contractile response to beta-adrenergic receptor (betaAR) stimulation due to changes in this signaling cascade, including increased expression and activity of the beta-adrenergic receptor kinase (betaARK1). This leads to desensitization and downregulation of betaARs. Previously, expression of a peptide inhibitor of betaARK1 (betaARKct) has proven beneficial in several animal models of heart failure (HF). Methods and Results - To test the hypothesis that inhibition of betaARK1 could improve beta-adrenergic signaling and contractile function in failing human myocytes, the betaARKct was expressed via adenovirus-mediated (AdbetaARKct) gene transfer in ventricular myocytes isolated from hearts explanted from 10 patients with end-stage HF undergoing cardiac transplantation. AdbetaARKct also contained the marker gene, green fluorescent protein, and successful gene transfer was confirmed via fluorescence and immunoblotting. Compared with uninfected failing myocytes ( control), the velocities of both contraction and relaxation in the AdbetaARKct-treated cells were increased in response to the beta-agonist isoproterenol ( contraction: 57.5 +/- 6.6% versus 37.0 +/- 4.2% shortening per second, P < 0.05; relaxation: 43.8 +/- 5.5% versus 27.5 +/- 3.9% lengthening per second, P < 0.05). Fractional shortening was similarly enhanced (12.2 +/- 1.2% versus 8.0 +/- 0.9%, P < 0.05). Finally, adenylyl cyclase activity in response to isoproterenol was also increased in Ad beta ARKct-treated myocytes. Conclusions - These results demonstrate that as in animal models of HF, expression of the beta ARKct can improve contractile function and beta-adrenergic responsiveness in failing human myocytes. Thus, beta ARK1 inhibition may represent a therapeutic strategy for human HF.