Loss of Id3 Increases VCAM-1 Expression, Macrophage Accumulation, and Atherogenesis in Ldlr–/– Mice
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Objective—Inhibitor of differention-3 (Id3) promotes B cells homing to the aorta and atheroprotection in Apoe−/− mice. We sought to determine the impact of loss of Id3 in the Ldlr−/− mouse model of diet-induced atherosclerosis and identify novel Id3 targets in the vessel wall.
Methods and Results—Ex vivo optical imaging confirmed that Id3−/− Ldlr−/− mice have significantly fewer aortic B cells than Id3+/+ Ldlr−/− mice. After 8 and 16 weeks of Western diet, Id3−/− Ldlr−/− mice developed significantly more atherosclerosis than Id3+/+ Ldlr−/− mice, with Id3+/− Ldlr−/− mice demonstrating an intermediate phenotype. There were no differences in serum lipid levels between genotypes. Immunostaining demonstrated that aortas from Id3−/− Ldlr−/− mice had greater intimal macrophage density and C-C chemokine ligand 20 and vascular cell adhesion molecule 1 (VCAM-1) expression compared with Id3+/+ Ldlr−/− mice. Real-time polymerase chain reaction demonstrated increased VCAM-1 mRNA levels in the aortas of Id3−/− Ldlr−/− mice. Primary vascular smooth muscle cells from Id3−/− mice expressed greater amounts of VCAM-1 protein compared with control. Gain and loss of function studies in primary vascular smooth muscle cells identified a role for Id3 in repressing VCAM-1 promoter activation. Chromatin immunoprecipitation demonstrated interaction of E12 with the VCAM-1 promoter, which is inhibited by Id3.
Conclusion—Id3 is an atheroprotective transcription regulator with targets in both B cells and vessel wall cells leading to reduced macrophage accumulation and reduced atherosclerosis formation.
- Received March 30, 2012.
- Accepted September 7, 2012.
- © 2012 American Heart Association, Inc.