The Effect Of CCR6 Knock-out On Atherogenesis In ApoE^-/-Mice

Background Cardiovascular disease is an important public health problem in the world, and atherosclerosis is the important pathological basis of this kind of disease. Studies have shown that chemokines and their receptors were the crucial factors to progression of atherosclerosis. They play the very important role in the activation and migration of inflammatory cells, and the plaque formation. CCR6 is a kind of chemokine receptor which has the function of inflammation and steady-state. CCR6 is expressed in a variety of subtypes of leukocytes including monocytes/macrophages, neutrophil leukocytes and so on. A large number of macrophages could transform into macrophage-derived foam cells after oxidized LDL were phagocytized, and promote the formation of plaques. Several studies showed that MCP-1 expressed by monocyte /macrophages was also involved in the inflammatory process and progress of atherosclerosis. Though the expression level of CCR6 is low in static monocytes/macrophages and neutrophil leukocytes, CCR6 expression can quickly increase under the atherosclerosis-related cytokines stimulation. Therefore, we speculate that CCR6 will play an important role in the formation and development of atherosclerosis.Objective To further explore the effect of CCR6 on atherogenesis in ApoE-/- mice and its mechanism.Methods (1) Experiment in vitro:RAW264.7 macrophages from mice were cultivated, and CCR6 siRNA was used to interfere with the expression of CCR6. MTT and Transwell tests were conducted to confirm the effect of CCR6 on the proliferative and migratory ability of macrophages; western blotting was applied to detect the expression of MCP-1. (2) Experiment in vivo:20 CCR6-/- ApoE-/- mice were cultured as experimental group, while 20 ordinary ApoE-/- mice were cultured as control group.After a high-fat diet for 12 weeks, mice were executed. Roots of aorta were collected and made into frozen sections. HE staining was used to observe the plaque area. Oil red O staining was applied to observe the lipid deposition in the plaque. The expression levels of macrophage marker (MOMA-2) and MCP-1 were detected, with the help of immunohistochemisty staining.Results (1) The proliferative and migratory abilities of RAW264.7 cells were significant suppressed, after the expression of CCR6 was interfered with by CCR6 siRNA (p<0.05). (2) Compared with ordinary ApoE-/- mice (control group), the plaques areas of CCR6-/- ApoE-/- mice were significantly decreased (16.1±2.0% vs 8.3±1.9%, P<0.05), and the lipid deposition were significantly reduced (28.5±3.4% vs 14.4±2.1%, P<0.05). The expression of MOMA-2 and MCP-1 in the plaques were all significantly different between CCR6+/+ApoE-/- and CCR6-/- ApoE-/- mice (P<0.05).Conclusions (1) The proliferative and migratory abilities of macrophages can be significantly suppressed, with the blocking of CCR6. (2) Blocking CCR6 can reduce the MCP-1 expressed by macrophages. (3)CCR6 promotes atherogenesis through affecting lipid deposition and aggregation of macrophages.