Myocardial Adeno-Associated Virus Serotype 6–βARKct Gene Therapy Improves Cardiac Function and Normalizes the Neurohormonal Axis in Chronic Heart Failure

Abstract

Background-The upregulation of G protein-coupled receptor kinase 2 in failing myocardium appears to contribute to dysfunctional ␤-adrenergic receptor (␤AR) signaling and cardiac function. The peptide ␤ARKct, which can inhibit the activation of G protein-coupled receptor kinase 2 and improve ␤AR signaling, has been shown in transgenic models and short-term gene transfer experiments to rescue heart failure (HF). This study was designed to evaluate long-term ␤ARKct expression in HF with the use of stable myocardial gene delivery with adeno-associated virus serotype 6 (AAV6). Methods and Results-In HF rats, we delivered ␤ARKct or green fluorescent protein as a control via AAV6-mediated direct intramyocardial injection. We also treated groups with concurrent administration of the ␤-blocker metoprolol. We found robust and long-term transgene expression in the left ventricle at least 12 weeks after delivery. ␤ARKct significantly improved cardiac contractility and reversed left ventricular remodeling, which was accompanied by a normalization of the neurohormonal (catecholamines and aldosterone) status of the chronic HF animals, including normalization of cardiac ␤AR signaling. Addition of metoprolol neither enhanced nor decreased ␤ARKct-mediated beneficial effects, although metoprolol alone, despite not improving contractility, prevented further deterioration of the left ventricle. Conclusions-Long-term cardiac AAV6-␤ARKct gene therapy in HF results in sustained improvement of global cardiac function and reversal of remodeling at least in part as a result of a normalization of the neurohormonal signaling axis. In addition, ␤ARKct alone improves outcomes more than a ␤-blocker alone, whereas both treatments are compatible. These findings show that ␤ARKct gene therapy can be of long-term therapeutic value in HF. (Circulation. 2009;119:89-98.)

Treatment of Chronic Heart Failure With β-Adrenergic Receptor Antagonists

“…140 Both ␤ 1 - 141 and ␤ 2 -ARs 58 undergo uncoupling in the failing heart, a process likely explained by receptor phosphorylation 142,143 and increased activity or expression of the inhibitory G protein Gi. 144,145 Strategies for using peptide 146 or small molecule 147 inhibitors of GRK2-mediated receptor phosphorylation have shown promise, and, in addition to restoring receptor function, may improve contractility and reflexively reduce neurohormonal signaling. 146…”

Targeting GRK2 by gene therapy for heart failure: benefits above β-blockade

“…Furthermore, in studies with bARKct in rat and pig models of HF, 40,46 chronic bARKct expression in failing myocardium resulted in lower circulating catecholamine levels, showing that when bARs are normalized there is feedback to the SNS to lower its stimulation. This is also a property of b-blockers.…”

“…Importantly, these molecular effects are associated with improved hemodynamics and overall cardiac performance. [36][37][38][39][40] However, the full extent of whether these molecular changes are the true therapeutic mechanisms of action of bAR antagonists in HF is not fully understood as there are some specific differences in b-blocker classes used (discussed below). 41 Three different subclasses of b-blockers were defined depending on their properties.…”

“…43,49,50 In addition, viral delivery of bARKct (adenovirus and adeno-associated virus) has demonstrated successful inhibition of GRK2 activity connected with decreased bAR desensitization without disrupting normal signaling and leading to HF prevention or reversal in rats and rabbit models of HF. 40,44,45 Taking advantage of genetic HF models, Blaxall et al 48 demonstrated that the therapeutic bARKct effect is accompanied by normalization of cardiac gene expression. 48 Importantly, Williams et al 51 could demonstrate improved single myocyte contractility on isolated failing human cardiomyocytes following adenovirus-mediated gene transfer of bARKct.…”

“…50 More recently, a study in post-MI HF in rats showed considerable synergy between bARKct expression after AAV6 gene delivery to the heart and metoprolol. 40 Therefore, molecular GRK2 inhibition appears to complement the primary current pharmacological strategy aimed at normalization of bAR signaling. bARKct and b-blockade acting synergistically appears to be a paradox as bARKct and GRK2 inhibition would act to resensitize cardiac bAR whereas bAR antagonism blocks these receptors.…”