激活素 A 通过 Alk4-Smad 信号通路抑制 RAW 264.7 巨噬细胞泡沫细胞形成并上调 ABCA1 和 ABCG1 的表达。
Activin a inhibits foam cell formation and up-regulates ABCA1 and ABCG1 expression through Alk4-Smad signaling pathway in RAW 264.7 macrophages.
机构信息
Department of Geriatrics, Peking University First Hospital, Beijing 100034, People's Republic of China.
Department of Geriatrics, Peking University First Hospital, Beijing 100034, People's Republic of China; Division of Cardiology, Xiamen Cardiovascular Hospital, Xiamen University, Xiamen 361000, People's Republic of China.
出版信息
Steroids. 2021 Oct;174:108887. doi: 10.1016/j.steroids.2021.108887. Epub 2021 Jul 6.
BACKGROUND
Activin A has been reported to play important roles in the pathogenesis of atherosclerosis. The purpose of this study is to investigate the effects of activin A on oxidized low-density lipoprotein (ox-LDL)-induced foam cell formation and explore the underlying molecular mechanisms in murine macrophage-like cell line RAW 264.7.
METHODS
The effects of activin A on Dil-labeled ox-LDL uptake were examined by confocal microscopy and flow cytometry analysis. The mRNA and protein levels of cholesterol receptors were analyzed by RT-qPCR and western blot analysis, respectively. To investigate whether activin receptor-like kinase 4 (Alk4) is required for activin A-mediated cellular effects, cells were pre-treated with SB-431542. The involvement of Smad2, Smad3 and Smad4 was confirmed by transfection with specific small interfering RNAs (siRNAs).
RESULTS
Activin A inhibits ox-ldl-induced foam cell formation and class A scavenger receptors (SR-A) expression, while up-regulates ATP-binding cassette transporter A1 (ABCA1) and ABCG1 expression in RAW 264.7 macrophages. Pre-treatment with SB-431542 abolished activin A-mediated anti-atherogenic effect. Knockdown of Smad2 reversed activin A-induced inhibition of ox-LDL uptake and SR-A expression. However, knockdown of Smad3 or Smad4 did not have such effect. Meanwhile, knockdown of either Smad2, Smad3 or Smad4 reversed the activin A-induced up-regulation of ABCA1 and ABCG1.
CONCLUSIONS
Our study provides novel evidence that activin A may exert anti-atherogenic effects through Alk4-Smad signaling pathway in RAW 264.7 macrophages.
背景
激活素 A 已被报道在动脉粥样硬化的发病机制中发挥重要作用。本研究旨在探讨激活素 A 对氧化型低密度脂蛋白（ox-LDL）诱导的泡沫细胞形成的影响，并在鼠源巨噬细胞样细胞系 RAW 264.7 中探索其潜在的分子机制。
方法
通过共聚焦显微镜和流式细胞术分析检测激活素 A 对 Dil 标记的 ox-LDL 摄取的影响。用 RT-qPCR 和 Western blot 分析分别检测胆固醇受体的 mRNA 和蛋白水平。为了研究激活素受体样激酶 4（Alk4）是否是激活素 A 介导的细胞效应所必需的，用 SB-431542 预处理细胞。通过转染特定的小干扰 RNA（siRNA）证实了 Smad2、Smad3 和 Smad4 的参与。
结果
激活素 A 抑制 ox-ldl 诱导的泡沫细胞形成和 A 类清道夫受体（SR-A）的表达，同时上调 RAW 264.7 巨噬细胞中的 ATP 结合盒转运体 A1（ABCA1）和 ABCG1 的表达。用 SB-431542 预处理可消除激活素 A 介导的抗动脉粥样硬化作用。Smad2 的敲低逆转了激活素 A 诱导的 ox-LDL 摄取和 SR-A 表达的抑制。然而，Smad3 或 Smad4 的敲低没有这种作用。同时，Smad2、Smad3 或 Smad4 的敲低均逆转了激活素 A 诱导的 ABCA1 和 ABCG1 的上调。
结论
本研究提供了新的证据，表明激活素 A 可能通过 RAW 264.7 巨噬细胞中的 Alk4-Smad 信号通路发挥抗动脉粥样硬化作用。
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