Feng Bo, Zhang Dajun, Kuriakose George, Devlin Cecillia M, Kockx Mark, Tabas Ira
Department of Medicine, Columbia University, 630 West 168th Street, New York, NY 10032, USA.
Proc Natl Acad Sci U S A. 2003 Sep 2;100(18):10423-8. doi: 10.1073/pnas.1732494100. Epub 2003 Aug 15.
Macrophage death in advanced atherosclerotic lesions leads to lesional necrosis and likely promotes plaque instability, a precursor of acute vascular events. Macrophages in advanced lesions accumulate large amounts of unesterified cholesterol, which is a potent inducer of macrophage apoptosis. We have shown recently that induction of apoptosis in cultured macrophages requires cholesterol trafficking to the endoplasmic reticulum (ER). Moreover, macrophages from mice with a heterozygous mutation in the cholesterol-trafficking protein Npc1 have a selective defect in cholesterol trafficking to the ER and are protected from cholesterol-induced apoptosis. The goal of the present study was to test the importance of intracellular cholesterol trafficking in atherosclerotic lesional macrophage death by comparing lesion morphology in Npc1+/+;Apoe-/- and Npc1+/-;Apoe-/- mice. Although advanced lesions in Npc1+/+;Apoe-/- mice had extensive acellular areas that were rich in unesterified cholesterol and macrophage debris, the lesions of Npc1+/-;Apoe-/- mice were substantially more cellular and less necrotic. Moreover, compared with Npc1+/-;Apoe-/- lesions, Npc1+/+;Apoe-/- lesions had a greater number of large, TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling)-positive areas surrounding necrotic areas, indicative of macrophage apoptosis. These differences were observed despite similar total lesion area and similar plasma lipid levels in the two groups of mice. These data provide in vivo evidence that intact intracellular cholesterol trafficking is important for macrophage apoptosis in advanced atherosclerotic lesions and that the ER-based model of cholesterol-induced cytotoxicity is physiologically relevant. Moreover, by showing that lesional necrosis can be diminished by a subtle defect in intracellular trafficking, these findings suggest therapeutic strategies to stabilize atherosclerotic plaques.
晚期动脉粥样硬化病变中的巨噬细胞死亡会导致病变坏死，并可能促进斑块不稳定，而斑块不稳定是急性血管事件的先兆。晚期病变中的巨噬细胞会积累大量未酯化胆固醇，这是巨噬细胞凋亡的强效诱导剂。我们最近发现，培养的巨噬细胞中凋亡的诱导需要胆固醇转运至内质网（ER）。此外，胆固醇转运蛋白Npc1发生杂合突变的小鼠的巨噬细胞在胆固醇转运至内质网方面存在选择性缺陷，可免受胆固醇诱导的凋亡。本研究的目的是通过比较Npc1+/+;Apoe-/-和Npc1+/-;Apoe-/-小鼠的病变形态，来测试细胞内胆固醇转运在动脉粥样硬化病变巨噬细胞死亡中的重要性。尽管Npc1+/+;Apoe-/-小鼠的晚期病变有广泛的无细胞区域，富含未酯化胆固醇和巨噬细胞碎片，但Npc1+/-;Apoe-/-小鼠的病变细胞更多且坏死更少。此外，与Npc1+/-;Apoe-/-病变相比，Npc1+/+;Apoe-/-病变在坏死区域周围有更多大的、TUNEL（末端脱氧核苷酸转移酶介导的dUTP缺口末端标记）阳性区域，表明存在巨噬细胞凋亡。尽管两组小鼠的总病变面积和血浆脂质水平相似，但仍观察到了这些差异。这些数据提供了体内证据，表明完整的细胞内胆固醇转运对于晚期动脉粥样硬化病变中的巨噬细胞凋亡很重要，且基于内质网的胆固醇诱导细胞毒性模型具有生理相关性。此外，通过表明细胞内转运的细微缺陷可减少病变坏死，这些发现提示了稳定动脉粥样硬化斑块的治疗策略。
