Division of Molecular Medicine, Department of Medicine, 630 W 168th St, Columbia University, New York, NY 10032, USA.
Circ Res. 2010 Jun 25;106(12):1861-9. doi: 10.1161/CIRCRESAHA.110.217281. Epub 2010 Apr 29.
RATIONALE: Antiatherogenic effects of plasma high-density lipoprotein (HDL) include the ability to inhibit apoptosis of macrophage foam cells. The ATP-binding cassette transporters ABCA1 and ABCG1 have a major role in promoting cholesterol efflux from macrophages to apolipoprotein A-1 and HDL and are upregulated during the phagocytosis of apoptotic cells (efferocytosis). OBJECTIVE: The goal of this study was to determine the roles of ABCA1 and ABCG1 in preserving the viability of macrophages during efferocytosis. METHODS AND RESULTS: We show that despite similar clearance of apoptotic cells, peritoneal macrophages from Abca1(-/-)Abcg1(-/-), Abcg1(-/-), and, to a lesser extent, Abca1(-/-) mice are much more prone to apoptosis during efferocytosis compared to wild-type cells. Similar findings were observed following incubations with oxidized phospholipids, and the ability of HDL to protect against oxidized phospholipid-induced apoptosis was markedly reduced in Abca1(-/-)Abcg1(-/-) and Abcg1(-/-) cells. These effects were independent of any role of ABCA1 and ABCG1 in mediating oxidized phospholipid efflux but were reversed by cyclodextrin-mediated cholesterol efflux. The apoptotic response observed in Abca1(-/-)Abcg1(-/-) macrophages after oxidized phospholipid exposure or engulfment of apoptotic cells was dependent on an excessive oxidative burst secondary to enhanced assembly of NADPH oxidase (NOX)2 complexes, leading to sustained Jnk activation which turned on the apoptotic cell death program. Increased NOX2 assembly required Toll-like receptors 2/4 and MyD88 signaling, which are known to be enhanced in transporter deficient cells in a lipid raft-dependent fashion. CONCLUSIONS: We identified a new beneficial role of ABCA1, ABCG1 and HDL in dampening the oxidative burst and preserving viability of macrophages following exposure to oxidized phospholipids and/or apoptotic cells.
作用机制:血浆高密度脂蛋白(HDL)的抗动脉粥样硬化作用包括抑制巨噬细胞泡沫细胞凋亡的能力。ATP 结合盒转运体 ABCA1 和 ABCG1 在促进巨噬细胞胆固醇流出至载脂蛋白 A-1 和 HDL 中起主要作用,并在吞噬凋亡细胞(胞葬作用)时上调。
目的:本研究旨在确定 ABCA1 和 ABCG1 在胞葬作用过程中维持巨噬细胞活力的作用。
方法和结果:我们发现,尽管清除凋亡细胞的情况相似,但 Abca1(-/-)Abcg1(-/-)、Abcg1(-/-)和(程度较轻的)Abca1(-/-)腹腔巨噬细胞在胞葬作用期间比野生型细胞更容易凋亡。在用氧化磷脂孵育后也观察到了类似的发现,并且 HDL 保护细胞免受氧化磷脂诱导的凋亡的能力在 Abca1(-/-)Abcg1(-/-)和 Abcg1(-/-)细胞中明显降低。这些作用独立于 ABCA1 和 ABCG1 在介导氧化磷脂流出中的任何作用,但可被环糊精介导的胆固醇流出逆转。在用氧化磷脂暴露或吞噬凋亡细胞后,Abca1(-/-)Abcg1(-/-)巨噬细胞中观察到的凋亡反应依赖于 NADPH 氧化酶(NOX)2 复合物过度组装引起的过度氧化爆发,导致持续的 Jnk 激活,从而开启凋亡细胞死亡程序。NOX2 复合物的组装增加需要 Toll 样受体 2/4 和 MyD88 信号转导,已知这些在转运体缺陷细胞中以脂质筏依赖性方式增强。
结论:我们发现 ABCA1、ABCG1 和 HDL 在暴露于氧化磷脂和/或凋亡细胞后,具有减弱氧化爆发并维持巨噬细胞活力的新的有益作用。
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