Abstract 11773: N-3 Polyunsaturated Fatty Acids Inhibit Inflammatory Responses in Macrophages by the Reduction of Toll-like Receptor 4 Expression in Lipid Rafts, Leading to the Suppression of Atherogenesis in Apolipoprotein E Deficient Mice
Introduction: Macrophages promote inflammatory responses, contributing to the development of atherosclerosis. Lipid rafts in macrophages facilitate inflammatory responses by gathering inflammatory molecules such as toll-like receptor 4 (TLR4). Whereas, n-3 polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), incorporated into the plasma membrane cause functional alteration of lipid rafts. Here, we tested the hypothesis that n-3 PUFAs decrease macrophage activation by the reduction of TLR4 expression in lipid rafts and attenuate atherogenesis in apolipoprotein E knockout (ApoE KO) mice.
Methods and Results: ApoE KO mice were fed western-type diets supplemented with 2.5% EPA, 5% omega-3-acid ethyl esters which include 2.3% EPA and 1.9% DHA (EPA+DHA), or none of n-3 PUFAs (control group) from 8-week-old for 20 weeks. Blood pressure and plasma total cholesterol level did not differ in these groups. En face Sudan IV staining of the aorta revealed that n-3 PUFAs treatment significantly attenuated atherogenesis compared with control group, and the effect was enhanced in EPA+DHA group (P< 0.05). Histological or quantitative RT-PCR analyses demonstrated that EPA+DHA treatment decreased lipid deposition, MMP-9 expression, and macrophage accumulation in atherosclerotic lesions in the aorta compared with control group (P<0.05, P<0.01 and P<0.01, respectively). In vitro experiment using RAW264.7, a murine macrophage cell line, demonstrated that n-3 PUFAs attenuated the up-regulation of MMP-9 and MCP-1 induced by LPS. Isolation of lipid rafts from RAW264.7 by sucrose gradient ultracentrifugation demonstrated that n-3 PUFAs suppressed LPS-induced TLR4 expression in lipid rafts. Lipid raft disruption by methyl-β-cyclodextrin, the membrane cholesterol depleting agent, suppressed LPS-induced up-regulation of MMP-9 and MCP-1 in this cell type.
Conclusions: N-3 PUFAs inhibited inflammatory responses in macrophages by the reduction of TLR4 expression in lipid rafts, leading to the suppression of atherogenesis in ApoE KO mice. Our results suggested that lipid rafts in macrophages may serve as a potential therapeutic target for atherosclerosis.
Author Disclosures: A. Takashima: None. D. Fukuda: None. K. Tanaka: None. Y. Higashikuni: None. Y. Hirata: None. H. Yamada: None. T. Soeki: None. T. Wakatsuki: None. M. Shimabukuro: None. M. Sata: None.
- © 2015 by American Heart Association, Inc.