Phenotype-dependent differences in apolipoprotein E metabolism and in cholesterol homeostasis in human monocyte-derived macrophages
Phenotype-dependent differences in apolipoprotein E metabolism and in cholesterol homeostasis in human monocyte-derived macrophages
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DOI：
10.1172/jci119887
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发表时间：
1998-04-15
影响因子：
15.9
通讯作者：
von Eckardstein, A
中科院分区：
文献类型：
--
作者：
Cullen, P;Cignarella, A;von Eckardstein, A
在这项研究中，我们研究了从E2/2、E3/3和E4/4受试者分离的单核细胞来源的巨噬细胞中共同的载脂蛋白E基因多态性对载脂蛋白E代谢和胆固醇稳态的影响。所有基因类型的未加载细胞含有相似数量的游离胆固醇、胆固醇酯和载脂蛋白E mRNA。E3/3细胞分泌的载脂蛋白E分别比E2/2和E4/4细胞多77%和30%。脉冲追赶实验证实，在E3/3细胞中apoE的分泌速率最大，而在E2/2细胞中apoE的分泌速率最小，并且apoE2的一部分在细胞内降解，而apoE3或apoE4则没有。肝素酶处理显示载脂蛋白E在E4/4细胞的表面结合力最强。在乙酰化低密度脂蛋白的胆固醇负荷中，载脂蛋白E的mRNA水平和蛋白分泌在E4/4细胞中升高最多，在E2/2细胞中最低。然而，胆固醇和胆固醇酯含量在E2/2细胞中上升最多，在E3/3细胞中上升最少。与H-3-胆固醇标记的乙酰化低密度脂蛋白孵育显示，E2/2细胞分泌胆固醇的效率最高。富含H-3胆固醇的颗粒重摄取最多的是E4/4巨噬细胞条件培养液。因此，尽管E2/2巨噬细胞的载脂蛋白E分泌率很低，但通过载脂蛋白E介导的胆固醇外流来保护其免受胆固醇储存的影响。在E3/3巨噬细胞中，较高的基础载脂蛋白E分泌率可以减少胆固醇的积聚。E4/4巨噬细胞分泌最多的载脂蛋白E，但由于表面结合增强和富含胆固醇颗粒的再摄取而缺乏有效的净胆固醇外流。
In this study, we investigated the impact of the common apoE polymorphism on apoE metabolism and cholesterol homeostasis in monocyte-derived macrophages isolated from E2/2, E3/3, and E4/4 subjects. Unloaded cells of all genotypes contained similar amounts of free cholesterol, cholesteryl ester, and apoE mRNA. E3/3 cells secreted 77 and 30% more apoE than E2/2 or E4/4 cells, respectively. Pulse-chase studies confirmed that the apoE secretion rate was greatest in E3/3 and least in E2/2 cells and showed that a portion of apoE2, but not apoE3 or apoE4, was degraded intracellulary. Surface binding of apoE was greatest in E4/4 cells, as revealed by heparinase treatment. On cholesterol loading with acetylated LDL, apoE mRNA levels and protein secretion rose most in E4/4 and least in E2/2 cells. Cholesterol and cholesteryl ester content, however, rose most in E2/2 and least in E3/3 cells. Incubations with H-3-cholesterol-labeled acetylated LDL revealed that E2/2 cells were most efficient at secreting cholesterol. The greatest reuptake of H-3-cholesterol-rich particles was from E4/4 macrophage-conditioned media. Thus, E2/2 macrophages, despite a low apoE secretion rate, are protected from cholesterol storage by apoE-mediated cholesterol efflux. In E3/3 macrophages, cholesterol accumulation is lessened by a high basal apoE secretion rate. E4/4 macrophages secrete the most apoE but lack effective net cholesterol efflux due to enhanced surface binding and reuptake of cholesterol-rich particles.