Abstract 14382: Notch Ligand Delta-like Ligand 1 Promotes Macrophage Activation and Arteriosclerosis

Abstract

Introduction: Macrophage-mediated inflammation promotes various vascular diseases, but how macrophage functions are regulated has not been fully understood. Notch signaling is a fundamental pathway regulating cell differentiation in developmental stages, but its role in adult vascular diseases are largely unknown. Aim: The aim of this study is to explore the role of Notch ligands in macrophage activation and subsequent arteriosclerosis. Methods: 1) To screen the Notch ligands, blocking antibodies of each Notch ligands (Jagged-1, Jagged-2, Dll1, and Dll4) were prepared. After pre-treatment with these antibodies, mouse peritoneal macrophages were stimulated with 10 ng/mL LPS + 10 ng/mL IFN-γ or 10 ng/mL IL-4 for 24 hours. mRNA expressions were quantified by real-time PCR. 2) C57BL/6J mice were subjected to femoral arterial wire injury and blocking antibodies (250 μg/injection) were intraperitoneally injected twice a week for 4 weeks, 3) Apolipoprotein E-deficient mice ( Apoe -/- ) at 8 weeks of age were fed a high-fat diet and blocking antibodies (250 μg/injection) were intraperitoneally injected twice a week for 12 weeks. Results: Blockade of Jagged 2, Dll1 and Dll4 decreased expression of iNOS and IL-1β in macrophages treated with LPS and IFN-γ. In contrast, blockade of Dll1 increased arginase-1 and Ym1 in IL-4 treated macrophages. Immobilized recombinant Dll1 increased prototypical Notch-target gene Hes-1 and induced subsequent IL-1β expression. Therefore, we have tested Dll1 blocking antibodies in in vivo models. After femoral arterial injury, administration of Dll1 blocking antibodies attenuated intimal hyperplasia, perivascular fibrosis, and negative remodeling of injured arteries. In Apoe -/- mice, a high-fat diet feeding increased Dll1 expression in atherosclerotic plaques, especially in Mac-3 positive macrophages. Blockade of Dll1 decreased atherosclerotic plaque area and lipid content determined by oil red O staining. In addition, blockade of Dll1 decreased accumulation of Mac-3 positive macrophages to the plaque. Conclusions: These results indicate that Dll1 promotes macrophage activation and arteriosclerosis. Dll1 may be a potential therapeutic target for vascular diseases promoted by macrophage-mediated inflammation.