Myocardial β₂-adrenoceptor gene delivery promotes coordinated cardiac adaptive remodelling and angiogenesis in heart failure

Background and purpose We investigated whether β₂- adrenoceptor overexpression could promote angiogenesis and improve blood perfusion and left ventricular (LV) remodeling of the failing heart. Experimental Approach We explored the angiogenic effects of β₂- adrenoceptor overexpression in a rat model of post-myocardial infarction (MI) heart failure (HF). Cardiac adenoviral-mediated β₂-adrenoceptor overexpression was obtained via direct intramyocardial injection 4-weeks post-MI. Adenovirus(Ad)-GFP and saline injected rats served as controls. Furthermore, we extended our observation to β₂-adrenoceptor -/- mice undergoing MI. KEy Results Transgenes were robustly expressed in the LV at 2 weeks post-gene therapy, whereas their expression was minimal at 4-weeks post-gene delivery. In HF rats, cardiac β₂-adrenoceptor overexpression resulted in enhanced basal and isoprenaline-stimulated cardiac contractility at 2-weeks post-gene delivery. At 4 weeks post-gene transfer, Ad-β₂-adrenoceptor HF rats showed improved LV remodeling and cardiac function. Importantly, β₂-adrenoceptor overexpression was associated with a markedly increased capillary and arteriolar length density and enhanced in vivo myocardial blood flow and coronary reserve. At the molecular level, cardiac β₂-adrenoceptor gene transfer induced the activation of the VEGF/PKB/eNOS pro-angiogenic pathway. In β₂-adrenoceptor-/- mice, we found a a 25% reduction in cardiac capillary density compared with β₂-adrenoceptor+/+ mice. The lack of β₂-adrenoceptors was associated with a higher mortality rate at 30 days and LV dilatation, and a worse global cardiac contractility compared with controls. CONCLUSIONS AND IMPLICATION β₂- Adrenoceptors play an important role in the regulation of the angiogenic response in HF. The activation of VEGF/PKB/eNOS pathway seems to be strongly involved in this mechanism.