Abstract 17251: Notch Signaling by Delta-Like 4 In Macrophages Contributes to Lesion Formation after Vascular Injury
Purpose: Monocytes/macrophages play causal roles in the neointimal hyperplasia after vascular injury through the promotion of inflammation, which associates with restenosis, a major limitation of the coronary angioplasty. The Notch pathway regulates embryonic development and contributes to physiological and pathological processes in adult tissues. We recently showed that Notch signaling triggered by Delta-like 4 (Dll4), one of the Notch ligand, promotes inflammatory responses in macrophages, leading to the development of cardiometabolic disorders. The role of Dll4 in the neointimal hyperplasia, however, remains unknown. This study tested the hypothesis that Dll4-mediated Notch signaling contributes to the lesion formation after vascular injury.
Methods and Results: We induced wire-mediated vascular injury to C57BL/6 mice. Vascular injury promotes the expression of Dll4 (N=5, P<0.05), but not Jagged 1, another major Notch ligand. Immunohistochemistry in the lesions co-localized Dll4 expression and Notch activation as gauged by accumulation of a cleaved product of Notch1 receptor. In vivo blockade of Dll4-mediated Notch signaling using well-characterized anti-Dll4 neutralizing antibody (Dll4-Ab) attenuated lesion formation compared with control IgG at four weeks after injury (N=10, P<0.01). Dll4-Ab treatment reduced MCP-1expression and macrophage accumulation in injured arteries at one week after surgery (P<0.05). Gain-of-function experiments using Dll4 expressing vector or recombinant protein stimulates MCP-1 expression in the murine macrophage cell line RAW264.7 (P<0.05 and P<0.01, respectively). On the other hand, loss-of-function experiments using Dll4 siRNA decreased MCP-1 in this cell type (P<0.05). Furthermore, trans-membrane co-culture experiments with RAW264.7 cells overexpressing or lacking Dll4 enhanced or reduced MCP-1 expression in vascular smooth muscle cells (SMCs), respectively (P<0.05).
Conclusions: Macrophage Dll4 promotes MCP-1 expression by macrophages and SMCs, suggesting homotypic and heterotypic cell communications via Notch signaling induce inflammation and lesion development after vascular injury. Dll4 can be a potential therapeutic target for neointimal hyperplasia.
- © 2012 by American Heart Association, Inc.