Abstract 13372: Blockade of Delta-Like 4 Prevents Lesion Formation After Vascular Injury
Background: Excessive neointimal hyperplasia after vascular injury contributes to restenosis, which remains as a major limitation of the coronary angioplasty. Monocyte/macrophage-dependent inflammation plays causal roles in this disease process through multiple cellular and molecular events. The Notch pathway regulates embryonic development and contributes to physiological homeostasis and pathological processes in adult tissues. We previously showed that Notch signaling triggered by delta-like 4 (Dll4), one of the Notch ligand, promotes inflammatory responses in human macrophages in vitro. The role of Dll4 in the lesion development, however, remains obscure. This study tested the hypothesis that inhibition of Dll4 prevents lesion formation after wire-mediated vascular injury.
Methods and Results: Dll4 RNA expression in femoral arteries increased (2.3-folds, P<0.05) at 28 days after vascular injury. Immunohistochemistry in the lesions co-localized Dll4 expression and Notch activation as gauged by accumulation of a cleaved product of Notch1 receptor. To block Dll4-mediated Notch signaling in vivo we administered anti-Dll4 antibody (Dll4-Ab) to C57BL/6 mice for 4 weeks (n=5~7). Dll4-Ab treatment significantly attenuated lesion formation after vascular injury compared with control IgG (P<0.05). Reduction of neointima area was accompanied by diminished expression of MCP-1 in the lesions (P<0.05). Overexpression experiments using the plasmid encoding Dll4 and stimulation with recombinant Dll4 significantly promoted MCP-1 expression via NF-κB in murine macrophage like cell line, RAW264.7 in vitro (P<0.05 and P<0.01, respectively). On the other hand, Dll4 suppression using RNAi significantly decreased MCP-1 in this cell type (P<0.05). Furthermore, these loss-of-function and gain-of-function experiments demonstrated that Dll4 induces polarization shift of macrophages towards pro-inflammatory state as determined by promotion of IL-1β, iNOS, and MMP-9 and reduction of IL-10.
Conclusions: These results suggest that the Dll4-Notch axis contributes to lesion formation after vascular injury through the promotion of inflammatory responses in macrophages. Dll4 can be a potential therapeutic target for neointimal hyperplasia.
- © 2011 by American Heart Association, Inc.