Abstract 465: The CB2 Cannabinoid Receptor Mediates the Anti-Proliferative Actions of Angiotensin-(1-7) in Vascular Smooth Muscle Cells

Abstract

Therapeutic interventions to reduce vascular proliferation are critical for the effective treatment of hypertension-induced end-organ damage, restenosis and atherosclerosis. We showed that angiotensin-(1-7) [Ang-(1-7)] reduces neointimal formation following vascular injury and inhibits vascular growth, through activation of the AT7 receptor mas and production of arachidonic acid derivatives. Endocannaboids (ECs) derived from membrane phospholipids also inhibit vascular proliferation and reduce growth following vascular injury, by stimulation of the CB2 receptor. The impact of CB2 receptor blockade on the anti-proliferative actions of Ang-(1-7) was investigated to assess a potential interaction between the EC and Ang-(1-7)/mas receptor systems. Rat thoracic aortic vascular smooth muscle cells (VSMCs) were treated with platelet-derived growth factor (PDGF) to stimulate growth and incubated with Ang-(1-7), the AT7 receptor antagonist [D-alanine7]-angiotensin-(1-7) [Dala], the CB2 receptor agonist HU308 and/or the CB2 receptor antagonist AM630. PDGF-stimulated VSMC growth was markedly reduced by Ang-(1-7) (74 ± 6% of control, n = 10, p<0.0001) and this effect was blocked by Dala (116 ± 14% of control, n = 4; n.s.). The Ang-(1-7)-mediated reduction in growth was abolished by the CB2 receptor antagonist AM630 (136 ± 16% of control, n = 4; n.s.); AM630 alone had no effect. In contrast, the CB1 receptor antagonist AM281 did not prevent the inhibitory actions of Ang-(1-7) on VSMC growth. CB2 receptor activation by the agonist HU308 also reduced PDGF-stimulated VSMC proliferation to a similar extent as Ang-(1-7) (67 ± 4% of control, n = 5, p<0.001); Dala did not influence the response to HU308 (50 ± 10% of control, n = 5, p<0.005). Ang-(1-7) significantly increased the endogenous cannabinoid 2-arachidonoylglycerol (2-AG) by 48% in VSMC by 24 h (p<0.05, n = 4). We conclude that the growth inhibitory properties of Ang-(1-7) involve a novel pathway culminating in the downstream formation of 2-AG and subsequent activation of the CB2 receptor in VSMC. Thus, Ang-(1-7) and/or CB2 receptor activation may constitute a new and beneficial therapeutic strategy for the prevention of vascular proliferation that is prevalent in cardiovascular disease.