Kritharides L, Kus M, Brown A J, Jessup W, Dean R T
Cell Biology Unit, The Heart Research Institute, Camperdown, Sydney, New South Wales, Australia.
J Biol Chem. 1996 Nov 1;271(44):27450-5. doi: 10.1074/jbc.271.44.27450.
Atherosclerosis involves the arterial accumulation of lipid-laden "foam cells" containing oxidized and unoxidized sterols and their esters (Mattsson-Hulten, L., Lindmark, H., Diczfalusy, U., Bjorkhem, I., Ottosson, M., Liu, Y., Bondjers, G., and Wiklund, O. (1996) J. Clin. Invest. 97, 461-8). Oxidized sterols are probably critical to atherogenesis because they inhibit cholesterol removal from cells and are cytotoxic. We recently reported that there is deficient induction of cellular cholesterol efflux by apolipoprotein A-I, the main initial acceptor of cellular cholesterol from macrophages loaded in vitro with oxidized low density lipoprotein (Kritharides, L., Jessup, W., Mander, E., and Dean, R. T. (1995) Arterioscler. Thromb. 15, 276-289). There was an even more marked impairment of the release of 7-ketocholesterol which is a major oxysterol in these cells and in human atherosclerotic lesions. Here we show that hydroxypropyl-beta-cyclodextrin can induce selective efflux of 7-ketocholesterol. Efflux of 7-ketocholesterol was time and concentration dependent, and the rate of its removal was 50-fold greater for hydroxypropyl-beta-cyclodextrin than for apolipoprotein A-I. Over a defined range of concentrations (0-5 mg/ml), efflux of 7-ketocholesterol was preferred over that of cholesterol and occurred without cell toxicity. Efflux of free 7-ketocholesterol was associated with decreased intracellular free and esterified 7-ketocholesterol. Hydroxypropyl-beta-cyclodextrin also enhanced efflux of other oxysterols. The physical solubilization of 7-ketocholesterol by the cyclodextrin was much greater than that of cholesterol, in accordance with its differential effects on efflux. These data highlight the importance of extracellular sterol solubilization in the efflux of cellular oxysterols and the mobilization of intracellular free and esterified oxysterol pools in macrophages loaded with oxidized low density lipoprotein. Synthetic sterol-solubilizing agents such as hydroxypropyl-beta-cyclodextrin are thus potential prototypes for the further development of oxysterol-removing agents.
动脉粥样硬化涉及富含脂质的“泡沫细胞”在动脉中的积聚，这些细胞含有氧化和未氧化的固醇及其酯类（马特松 - 胡尔滕，L.，林德马克，H.，迪茨法卢西，U.，比约克赫姆，I.，奥托松，M.，刘，Y.，邦德耶斯，G.，和维克隆德，O.（1996年）《临床研究杂志》97，461 - 468）。氧化固醇可能对动脉粥样硬化的发生至关重要，因为它们抑制细胞内胆固醇的清除且具有细胞毒性。我们最近报道，载脂蛋白A - I对细胞胆固醇流出的诱导不足，载脂蛋白A - I是体外加载氧化低密度脂蛋白的巨噬细胞中细胞胆固醇的主要初始受体（克里萨里德斯，L.，杰瑟普，W.，曼德，E.，和迪恩，R.T.（1995年）《动脉硬化血栓形成》15，276 - 289）。在这些细胞和人类动脉粥样硬化病变中，作为主要氧化固醇的7 - 酮胆固醇的释放受损更为明显。在此我们表明，羟丙基 - β - 环糊精可诱导7 - 酮胆固醇的选择性流出。7 - 酮胆固醇的流出具有时间和浓度依赖性，其清除速率对于羟丙基 - β - 环糊精而言比对载脂蛋白A - I高50倍。在特定浓度范围（0 - 5毫克/毫升）内，7 - 酮胆固醇的流出优于胆固醇，且不产生细胞毒性。游离7 - 酮胆固醇的流出与细胞内游离和酯化7 - 酮胆固醇的减少相关。羟丙基 - β - 环糊精还增强了其他氧化固醇的流出。环糊精对7 - 酮胆固醇的物理增溶作用远大于对胆固醇的增溶作用，这与其对流出的不同影响一致。这些数据突出了细胞外固醇增溶在细胞氧化固醇流出以及加载氧化低密度脂蛋白的巨噬细胞内游离和酯化氧化固醇池动员中的重要性。因此，诸如羟丙基 - β - 环糊精之类的合成固醇增溶剂是进一步开发氧化固醇清除剂的潜在原型。
