Chemokine receptor CCR1 disruption in bone marrow cells enhances atherosclerotic lesion development and inflammation in mice.

Several chemokines or chemokine receptors are involved in atherogenesis. CCR1 is expressed by macrophages and lymphocytes, two major cell types involved in the progression of atherosclerosis, and binds to lesion-expressed ligands. We examined the direct role of the blood-borne chemokine receptor CCR1 in atherosclerosis by transplanting bone marrow cells from either CCR1+/+ or CCR1-/- mice into low-density lipoprotein-receptor (LDLr)-deficient mice. After exposure to an atherogenic diet for 8 weeks, no differences in fatty streak size or composition were detected between the 2 groups. After 12 weeks of atherogenic diet, however, an unexpected 70% increase in atherosclerotic lesion size in the thoracic aorta was detected in the CCR1-/- mice, accompanied by a 37% increase in the aortic sinus lesion area. CCR1-/- mice showed enhanced basal and concanavalin A-stimulated IFN-gamma production by spleen T cells and enhanced plaque inflammation. In conclusion, blood-borne CCR1 alters the immuno-inflammatory response in atherosclerosis and prevents excessive plaque growth and inflammation.

Decreased atherosclerotic lesion formation in CX3CR1/apolipoprotein E double knockout mice.

BACKGROUND: Fractalkine (CX3CL1), a CX3C chemokine, is expressed in the vessel wall and mediates the firm adhesion and chemotaxis of leukocytes expressing its receptor, CX3CR1. A polymorphism in the CX3CR1 gene is associated with low CX3CR1 expression and reduced risk of acute coronary disease in humans. METHODS AND RESULTS: We generated CX3CR1-deficient mice (CX3CR1(-/-)) by targeted gene disruption and crossed them with the proatherogenic apolipoprotein E-deficient mice (apoE(-/-)). Here we show that the extent of lipid-stained lesions in the thoracic aorta was reduced by 59% in CX3CR1/apoE double knockout mice compared with their CX3CR1(+/+)/apoE(-/-) littermates. The development of atherosclerosis in the aortic sinus was also markedly altered in the double knockout mice, with 50% reduction in macrophage accumulation. Although lesions of CX3CR1(-/-) mice were smaller in size, they retained a substantial accumulation of smooth muscle cells and collagen, features consistent with a stable plaque phenotype. Finally, CX3CR1(+/-)/apoE(-/-) mice showed the same reduction in atherosclerosis as the CX3CR1(-/-)/apoE(-/-) mice. CONCLUSIONS: The CX3CR1-CX3CL1 pathway seems to play a direct and critical role in monocyte recruitment and atherosclerotic lesion development in a mouse model of human atherosclerosis.