Vasoprotective Activities of the Adrenomedullin-RAMP2 System in Endothelial Cells

Neointimal hyperplasia is the primary lesion underlying atherosclerosis and restenosis after coronary intervention. We previously described the essential angiogenic function of the adrenomedullin (AM)receptor activity-modifying protein (RAMP) 2 system. In the present study, we assessed the vasoprotective actions of the endogenous AM-RAMP2 system using a wire-induced vascular injury model. We found that neointima formation and vascular smooth muscle cell proliferation were enhanced in RAMP2(+/)male mice. The injured vessels from RAMP2(+/)mice showed greater macrophage infiltration, inflammatory cytokine expression, and oxidative stress than vessels from wild-type mice and less re-endothelialization. After endothelial cell-specific RAMP2 deletion in drug-inducible endothelial cellspecific RAMP2(-/-) (DI-E-RAMP2(-/-)) male mice, we observed markedly greater neointima formation than in control mice. In addition, neointima formation after vessel injury was enhanced in mice receiving bone marrow transplants from RAMP2(+/-) or DI-E-RAMP2(-/-) mice, indicating that bone marrow-derived cells contributed to the enhanced neointima formation. Finally, wefound that the AM-RAMP2 system augmented proliferation and migration of endothelial progenitor cells. These results demonstrate that the AM-RAMP2 system exerts crucial vasoprotective effects after vascular injury and couldbe a therapeutic target for the treatment of vascular diseases.