Impaired neoangiogenesis in β2-adrenoceptor gene-deficient mice: restoration by intravascular human β2-adrenoceptor gene transfer and role of NFκB and CREB transcription factors

BACKGROUND AND PURPOSE There is much evidence supporting the role of beta(2)-adrenoceptors (beta(2)AR) in angiogenesis but the mechanisms underlying their effects have not been elucidated. Hence, we studied post-ischaemic angiogenesis in the hindlimb (HL) of beta(2)AR knock-out mice (beta(2)AR-/-) in vivo and explored possible molecular mechanisms in vitro. EXPERIMENTAL APPROACH Femoral artery resection (FAR) was performed in wild-type and beta(2)AR-/- mice and adaptive responses to chronic HL ischaemia were explored; blood flow was measured by ultrasound and perfusion of dyed beads, bone rarefaction, muscle fibrosis and skin thickness were evaluated by immunoflourescence and morphometric analysis. Intrafemoral delivery of an adenovirus encoding the human beta(2)AR (AD beta(2)AR) was used to reinstate beta(2)ARs in beta(2)AR-/- mice. Molecular mechanisms were investigated in mouse-derived aortic endothelial cells (EC) in vitro, focusing on NF kappa B activation and transcriptional activity. RESULTS Angiogenesis was severely impaired in beta(2)AR-/- mice subjected to FAR, but was restored by gene therapy with AD beta(2)AR. The proangiogenic responses to a variety of stimuli were impaired in beta(2)AR-/- EC in vitro. Moreover, removal of beta(2)ARs impaired the activation of NF kappa B, a transcription factor that promotes angiogenesis; neither isoprenaline (stimulates beta ARs) nor TNF alpha induced NF kappa B activation in beta(2)AR-/- EC. Interestingly, cAMP response element binding protein (CREB), a transcription factor that counter regulates NF kappa B, was constitutively increased in beta(2)AR-/- ECs. AD beta(2)AR administration restored beta(2)AR membrane density, reduced CREB activity and reinstated the NF kappa B response to isoprenaline and TNF alpha. CONCLUSIONS AND IMPLICATIONS Our results suggest that beta(2)ARs control angiogenesis through the tight regulation of nuclear transcriptional activity.