Zhao Y, Sparks D L, Marcel Y L
Lipoprotein and Atherosclerosis Group, University of Ottawa Heart Institute, Ontario, Canada.
Biochemistry. 1996 Dec 24;35(51):16510-8. doi: 10.1021/bi961622t.
Five series of reconstituted discoidal HDL (LpA-I) particles have been prepared, and their constituents, apolipoprotein A-I (apoA-I), 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), unesterified cholesterol (UC), phosphatidylinositol (PI), or sphingomyelin (SM), have been systematically varied to elucidate the relationship between HDL composition and cholesterol efflux from non-cholesterol-loaded human skin fibroblasts. The physical properties, such as hydrodynamic diameters, alpha-helix contents, and surface potentials, of these LpA-I have been measured and related to the ability of the LpA-I to accept cellular cholesterol. The results show that for LpA-I particles containing 2, 3, or 4 apoA-I per particle, Lp4A-I are the best acceptors of cellular cholesterol, followed by Lp3A-I and then Lp2A-I particles. Discoidal Lp2A-I with variations in POPC content, from 121 to 266 mol/particle; show no difference in their abilities to promote cholesterol efflux. Similarly, inclusion of 7 and 15 mol of free cholesterol to Lp2A-I also does not affect their ability to accept cellular cholesterol. However, increasing the content of either PI or SM, up to 20 mol/particle, is associated with significantly increased abilities of the LpA-I to promote cholesterol efflux. The efflux of cellular cholesterol to discoidal LpA-I particles is independent of specific changes in apoA-I conformation and charge, but appears to be positively related to major changes in the size of the lipoprotein particle. The study suggests that in contrast to interlipoprotein cholesterol transfers, the efflux of cholesterol from cultured fibroblasts is less sensitive to factors that affect the frequency of molecular collisions and more dependent on the ability of an HDL particle to absorb and retain cholesterol molecules. Since SM and PI appear to modulate this adsorption/desorption of cholesterol to HDL, variations in the concentration of these lipids within HDL would be expected to affect plasma cholesterol homeostasis.
已制备了五组重构盘状高密度脂蛋白（LpA-I）颗粒，并系统地改变了它们的成分，即载脂蛋白A-I（apoA-I）、1-棕榈酰-2-油酰磷脂酰胆碱（POPC）、未酯化胆固醇（UC）、磷脂酰肌醇（PI）或鞘磷脂（SM），以阐明高密度脂蛋白组成与非胆固醇负载的人皮肤成纤维细胞胆固醇流出之间的关系。已测量了这些LpA-I的物理性质，如流体动力学直径、α-螺旋含量和表面电位，并将其与LpA-I接受细胞胆固醇的能力相关联。结果表明，对于每个颗粒含有2、3或4个apoA-I的LpA-I颗粒，Lp4A-I是细胞胆固醇的最佳接受者，其次是Lp3A-I，然后是Lp2A-I颗粒。POPC含量从121到266 mol/颗粒变化的盘状Lp2A-I，在促进胆固醇流出的能力上没有差异。同样，向Lp2A-I中加入7和15 mol游离胆固醇也不会影响它们接受细胞胆固醇的能力。然而，将PI或SM的含量增加至20 mol/颗粒，会使LpA-I促进胆固醇流出的能力显著增加。细胞胆固醇向盘状LpA-I颗粒的流出与apoA-I构象和电荷的特定变化无关，但似乎与脂蛋白颗粒大小的主要变化呈正相关。该研究表明，与脂蛋白间胆固醇转移不同，培养的成纤维细胞中胆固醇的流出对影响分子碰撞频率的因素不太敏感，而更依赖于高密度脂蛋白颗粒吸收和保留胆固醇分子的能力。由于SM和PI似乎调节胆固醇与高密度脂蛋白的这种吸附/解吸，因此预计高密度脂蛋白中这些脂质浓度的变化会影响血浆胆固醇稳态。
