Institute of Cardiovascular Research, Key Laboratory for Atherosclerology of Hunan Province, Life Science Research Center, University of South China, Hengyang, China.
J Atheroscler Thromb. 2012;19(9):823-36. doi: 10.5551/jat.12823. Epub 2012 Jul 4.
Apolipoprotein A-I (apoA-I), the major component of high-density lipoprotein (HDL), has been recently found to suppress inflammation. This study was to investigate the effects and potential mechanisms of apoA-I on the CD40/CD40 ligand (CD40L) proinflammatory signaling pathway.
Human THP-1 macrophage-derived foam cells were treated with sCD40L alone or in the presence of apoA-I. Secretion of proinflammatory cytokines was performed by enzyme-linked immunosorbent assay(ELISA). The proteins and mRNA expression were examined by western-blot and real-time PCR analysis, respectly. Cholesterol efflux was assessed by liquid scintillation counting. Cholesterol depletion of macrophages was performed with methylated β-cyclodextrin.
ApoA-I inhibits the inflammatory response stimulated by soluble CD40L (sCD40L) in macrophages. In addition, apoA-I inhibited the sCD40L-stimulated activation of nuclear factor-kB (NF-kB). The apoA-I-induced NF-kB deactivation was related to the decreased recruitment of tumor necrosis factor receptor-associated factor 6 (TRAF-6), a crucial adapter protein for CD40 in macrophages, to lipid rafts after being treated by sCD40L. When interfering the expression of ATP-binding cassette transporter A1 (ABCA1), a major cholesterol transporter for apoA-I in macrophages, it could significantly diminish the effect of apoA-I on the sCD40L-stimulated inflammatory response.
ApoA-I suppresses CD40 proinflammatory signaling in macrophages by preventing TRAF-6 translocation to lipid rafts through ABCA1-dependent regulation of free cholesterol (FC) efflux, which may present a novel mechanism of apoA-I-mediated inflammation inhibition in macrophages.
载脂蛋白 A-I（apoA-I）是高密度脂蛋白（HDL）的主要成分，最近发现其具有抑制炎症的作用。本研究旨在探讨 apoA-I 对 CD40/CD40 配体（CD40L）促炎信号通路的影响及其潜在机制。
用 sCD40L 单独或存在 apoA-I 时处理人 THP-1 巨噬细胞源性泡沫细胞。通过酶联免疫吸附试验（ELISA）测定促炎细胞因子的分泌。通过 Western blot 和实时 PCR 分析分别检测蛋白和 mRNA 的表达。通过液体闪烁计数评估胆固醇外排。用甲基-β-环糊精处理巨噬细胞以耗尽胆固醇。
apoA-I 抑制巨噬细胞中可溶性 CD40L（sCD40L）刺激的炎症反应。此外，apoA-I 抑制 sCD40L 刺激的核因子-κB（NF-κB）激活。apoA-I 诱导的 NF-κB 失活与 sCD40L 处理后肿瘤坏死因子受体相关因子 6（TRAF-6）向脂筏的募集减少有关，TRAF-6 是巨噬细胞中 CD40 的关键衔接蛋白。当干扰巨噬细胞中载脂蛋白 A-I 的主要胆固醇转运蛋白 ATP 结合盒转运蛋白 A1（ABCA1）的表达时，它可以显著减少 apoA-I 对 sCD40L 刺激的炎症反应的影响。
apoA-I 通过 ABCA1 依赖性调节游离胆固醇（FC）外排，防止 TRAF-6 向脂筏易位，从而抑制巨噬细胞中 CD40 的促炎信号，这可能为 apoA-I 介导的巨噬细胞炎症抑制提供一种新的机制。
