Cannabinoid receptor CB2 protects against balloon-induced neointima formation

Molica F, Matter CM, Burger F, Pelli G, Lenglet S, Zimmer A, Pacher P, Steffens S. Cannabinoid receptor CB2 protects against balloon-induced neointima formation. Am J Physiol Heart Circ Physiol 302: H1064-H1074, 2012. First published January 6, 2012; doi:10.1152/ajpheart.00444.2011.-Cannabinoid receptor CB2 activation inhibits inflammatory proliferation and migration of vascular smooth muscle cells in vitro. The potential in vivo relevance of these findings is unclear. We performed carotid balloon distension injury in hypercholesterolemic apolipoprotein E knockout (ApoE(-/-)) mice receiving daily intraperitoneal injection of the CB2 agonist JWH133 (5 mg/kg) or vehicle, with the first injection given 30 min before injury. Alternatively, we subjected CB2-/- and wild-type (WT) mice to balloon injury. We determined CB2 mRNA and protein expression in dilated arteries of ApoE(-/-) mice. Neointima formation was assessed histologically. We used bone marrow-derived murine CB2-/- and WT macrophages to study adhesion to plastic, fibronectin, or collagen, and migration was assayed by modified Boyden chamber. Aortic smooth muscle cells were isolated to determine in vitro proliferation rates. We found increased vascular CB2 expression in ApoE(-/-) mice in response to balloon injury. Seven to twenty-one days after dilatation, injured vessels of JWH133-treated mice had less intimal nuclei numbers as well as intimal and medial areas, associated with less staining for proliferating cells, smooth muscle cells, and macrophages. Complete endothelial repair was observed after 14 days in both JWH133- and vehicle-treated mice. CB2 deficiency resulted in increased intima formation compared with WT, whereas JWH133 did not affect intimal formation in CB2-/- mice. Apoptosis rates assessed by in situ terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling staining 1 h postballooning were significantly higher in the CB2 knockouts. In vitro, bone marrow-derived CB2-/- macrophages showed enhanced adherence and migration compared with WT cells and elevated mRNA levels of adhesion molecules, chemokine receptors CCR1 and 5, and chemokine CCL2. Proliferation rates were significantly increased in CB2-/- smooth muscle cells compared with WT. In conclusion, pharmacological activation or genetic deletion of CB2 receptors modulate neointima formation via protective effects in macrophages and smooth muscle cells.