Bone marrow-specific deficiency of nuclear receptor Nur77 enhances atherosclerosis

Abstract

Rationale: Nuclear receptor Nur77, also known as NR4A1, TR3, or NGFI-B, is expressed in human atherosclerotic lesions in macrophages, endothelial cells, T cells and smooth muscle cells. Macrophages play a critical role in atherosclerosis and the function of Nur77 in lesion macrophages has not yet been investigated. Objective: This study aims to delineate the function of Nur77 in macrophages and to assess the effect of bone marrow-specific deficiency of Nur77 on atherosclerosis. Methods and Results: We investigated Nur77 in macrophage polarization using bone marrow-derived macrophages (BMM) from wild-type and Nur77-knockout (Nur77 -/-) mice. Nur77 -/- BMM exhibit changed expression of M2-specific markers and an inflammatory M1-phenotype with enhanced expression of interleukin-12, IFNγ, and SDF-1α and increased NO synthesis in (non)-stimulated Nur77 -/- BMM cells. SDF-1α expression in nonstimulated Nur77 -/- BMM is repressed by Nur77 -/- and the chemoattractive activity of Nur77 -/- BMM is abolished by SDF-1α inhibiting antibodies. Furthermore, Nur77 -/- mice show enhanced thioglycollate-elicited migration of macrophages and B cells. The effect of bone marrow-specific deficiency of Nur77 -/- on atherosclerosis was studied in low density lipoprotein receptor-deficient (Ldlr) mice. Ldlr mice with a Nur77-deficient bone marrow transplant developed 2.1-fold larger atherosclerotic lesions than wild-type bone marrow-transplanted mice. These lesions contain more macrophages, T cells, smooth muscle cells and larger necrotic cores. SDF-1α expression is higher in lesions of Nur77-transplanted mice, which may explain the observed aggravation of lesion formation. Conclusions: In conclusion, in bone marrow-derived cells the nuclear receptor Nur77 -/- has an anti-inflammatory function, represses SDF-1α expression and inhibits atherosclerosis. © 2011 American Heart Association, Inc.