Role of bone marrow-derived CC-chemokine receptor 5 in the development of atherosclerosis of low-density lipoprotein receptor knockout mice

Objective-CC chemokine receptor CCR5 is expressed by atheroma-associated cells and could mediate leukocyte attraction into developing lesions. We examined the role of bone marrow-derived CCR5 in the development of atherosclerotic lesions after 8, 12, or 35 weeks of high-fat diet. Methods and Results-Low-density lipoprotein-receptor (LDLr)-deficient mice were lethally irradiated and transplanted with CCR5(+/+) or CCR5(-/-) bone marrow. After 8 weeks of fat diet, CCR5 deficiency in leukocytes led to 30% decrease of macrophage accumulation within the fatty streak (P < 0.05), with no change in lesion size. After 12 weeks of fat diet, CCR5 deficiency also resulted in 30% decrease of plaque-macrophage accumulation (P < 0.005), associated with 16% reduction in lesion size in the aortic sinus (P=0.13), despite a significant increase in total cholesterol levels (P=0.03). Lesions with CCR5 deficiency showed 52% reduction in matrix metalloproteinase (MMP)-9 expression (P=0.02) and 2-fold increase in collagen accumulation (P < 0.0001). These changes were associated with a significant increase of interleukin (IL)-10 mRNA expression in spleens of CCR5(-/-) mice compared with CCR5(+/+) controls. In addition, we found enhanced IL-10 production by CCR5-deficient peritoneal macrophages and decreased tumor necrosis factor (TNF)-alpha production by CCR5(-/-) T cells in comparison with CCR5(+/+) controls. CCR5(-/-) and CCR5(+/+) reconstituted animals showed no differences in plaque size or composition after 35 weeks of high-fat diet despite the persistent absence of CCR5 in plaques of mice reconstituted with CCR5(-/-) bone marrow. Conclusion-Bone marrow-derived CCR5 favors the development of an inflammatory and collagen-poor plaque phenotype in association with decreased macrophage-derived IL-10 and enhanced T cell-derived TNF-alpha. These effects are not sustained in the very advanced stages of atherosclerosis.