The Key Laboratory of Geriatrics, Beijing Institute of Geriatrics, Beijing Hospital, National Center of Gerontology, National Health Commission, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China.
Peking University Fifth School of Clinical Medicine (Beijing Hospital), Beijing, China.
FEBS J. 2020 Dec;287(23):5080-5095. doi: 10.1111/febs.15310. Epub 2020 Apr 14.
Cholesterol efflux from macrophages is the initial step of reverse cholesterol transport, an important process for high-density lipoprotein-mediated atheroprotection. G protein-coupled receptor (GPR) 120, which functions as long-chain fatty acid receptor, is well known for its anti-inflammatory and insulin-sensitizing function in macrophages. However, the role of GPR120 on macrophage foam cell formation, the hallmark of atherosclerotic plaques, has not been verified. In this study, we found for the first time that stimulation of GPR120 by its agonist GW9508 elevated the expression of ATP-binding cassette transporters (ABC) A1 and ABCG1 in THP-1 macrophage-derived foam cells and Raw264.7 macrophages, and promoted ABCA1- and ABCG1-mediated cholesterol efflux and reduced cellular cholesteryl ester (CE) content as well. In addition, GPR120 activation was accompanied with the stimulation of AMPK pathway in macrophages; however, the effect of GPR120 on macrophage cholesterol efflux was largely abolished by AMPK inhibition. Moreover, the AMPK activity and the expression of ABCA1 and ABCG1 were markedly abrogated by knockdown of GPR120, or application of phospholipase C (PLC) inhibitor, calcium chelator, or CaMKK inhibitor. Because only free cholesterol can be effluxed from macrophages, we found that activation of AMPK could lead to increase both neutral CEs hydrolysis by upregulation of neutral cholesterol ester hydrolase expression and acid CEs hydrolysis by activation of ULK1. In conclusion, these results demonstrated that GPR120 facilitated ABCA1- and ABCG1-mediated cholesterol efflux through activation of PLC/Ca /CaMKK/AMPK signaling pathway, which induced CE hydrolysis and elevated the expression of ABCA1 and ABCG1 in macrophages.
胆固醇从巨噬细胞中流出是胆固醇逆转运的初始步骤，这是高密度脂蛋白介导的动脉粥样硬化保护的一个重要过程。G 蛋白偶联受体（GPR）120 作为长链脂肪酸受体，其在巨噬细胞中的抗炎和胰岛素增敏作用是众所周知的。然而，GPR120 对巨噬细胞泡沫细胞形成的作用，即动脉粥样硬化斑块的标志，尚未得到验证。在这项研究中，我们首次发现，其激动剂 GW9508 刺激 GPR120 可上调 THP-1 巨噬细胞源性泡沫细胞和 Raw264.7 巨噬细胞中 ABC 转运蛋白（ABC）A1 和 ABCG1 的表达，并促进 ABCA1 和 ABCG1 介导的胆固醇流出，同时减少细胞内胆固醇酯（CE）含量。此外，GPR120 的激活伴随着巨噬细胞中 AMPK 通路的刺激；然而，AMPK 抑制在很大程度上消除了 GPR120 对巨噬细胞胆固醇流出的影响。此外，GPR120 的敲低或应用 PLC 抑制剂、钙螯合剂或 CaMKK 抑制剂显著削弱了 AMPK 的活性和 ABCA1 和 ABCG1 的表达。由于只有游离胆固醇才能从巨噬细胞中流出，我们发现 AMPK 的激活可以通过上调中性胆固醇酯水解酶的表达来增加中性 CE 的水解，通过激活 ULK1 来增加酸性 CE 的水解。总之，这些结果表明，GPR120 通过激活 PLC/Ca/CaMKK/AMPK 信号通路促进 ABCA1 和 ABCG1 介导的胆固醇流出，从而诱导 CE 水解并上调巨噬细胞中 ABCA1 和 ABCG1 的表达。
