Impaired neoangiogenesis in β 2 –adrenoceptor gene‐deficient mice: restoration by intravascular human β 2 –adrenoceptor gene transfer and role of NFκB and CREB transcription factors

BACKGROUND AND PURPOSE There is much evidence supporting the role of β 2 ‐adrenoceptors (β 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 β 2 AR knock‐out mice (β 2 AR−/−) in vivo and explored possible molecular mechanisms in vitro . EXPERIMENTAL APPROACH Femoral artery resection (FAR) was performed in wild‐type and β 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 β 2 AR (ADβ 2 AR) was used to reinstate β 2 ARs in β 2 AR−/− mice. Molecular mechanisms were investigated in mouse‐derived aortic endothelial cells (EC) in vitro , focusing on NFκB activation and transcriptional activity. RESULTS Angiogenesis was severely impaired in β 2 AR−/− mice subjected to FAR, but was restored by gene therapy with ADβ 2 AR. The proangiogenic responses to a variety of stimuli were impaired in β 2 AR−/− EC in vitro . Moreover, removal of β 2 ARs impaired the activation of NFκB, a transcription factor that promotes angiogenesis; neither isoprenaline (stimulates βARs) nor TNFα induced NFκB activation in β 2 AR −/− EC. Interestingly, cAMP response element binding protein (CREB), a transcription factor that counter regulates NFκB, was constitutively increased in β 2 AR −/− ECs. ADβ 2 AR administration restored β 2 AR membrane density, reduced CREB activity and reinstated the NFκB response to isoprenaline and TNFα. CONCLUSIONS AND IMPLICATIONS Our results suggest that β 2 ARs control angiogenesis through the tight regulation of nuclear transcriptional activity.