Sakai M, Miyazaki A, Hakamata H, Suginohara Y, Sakamoto Y I, Morikawa W, Kobori S, Schichiri M, Horiuchi S
Department of Biochemistry, Kumamoto University School of Medicine, Japan.
Atherosclerosis. 1996 Jan 26;119(2):191-202. doi: 10.1016/0021-9150(95)05646-7.
Oxidized low density lipoprotein (ox-LDL) was incubated with discoidal complexes of apolipoprotein A-I (apo A-I) and dimyristoylphosphatidylcholine (DMPC) (DMPC/apo A-I) in a cell-free system and re-isolated on Sephacryl S-400 gel filtration chromatography. Analyses of re-isolated ox-LDL showed that apo A-I was transferred from DMPC/apo A-I to ox-LDL, which accounted for 10% of the total protein of ox-LDL. Re-isolated ox-LDL also showed a 2.2-fold increase in phospholipid and a 14% decrease in cholesterol content on an apo B basis. The electrophoretic mobility of re-isolated ox-LDL was markedly reduced almost to that of native LDL. Moreover, the amounts of re-isolated ox-LDL to be degraded by mouse peritoneal macrophages as well as the capacity of re-isolated ox-LDL to accumulate cholesteryl esters (CE) in these cells were markedly reduced (60% and 80% reduction, respectively), suggesting that the ligand activity of ox-LDL for the scavenger receptor was significantly reduced upon treatment with DMPC/apo A-I. Parallel incubation of ox-LDL with free apo A-I led to a similar incorporation of apo A-I into ox-LDL. However, it had no effects on the ligand activity of ox-LDL. Thus, it is likely that the reduction in the ligand activity of ox-LDL by DMPC/apo A-I is explained by the change in the lipid moiety (mainly phospholipid) of ox-LDL. Since discoidal high density lipoprotein (HDL) is known to occur in vivo, this phenomenon might explain one of the anti-atherogenic functions of HDL.
在无细胞体系中，将氧化型低密度脂蛋白（ox-LDL）与载脂蛋白A-I（apo A-I）和二肉豆蔻酰磷脂酰胆碱（DMPC）的盘状复合物（DMPC/apo A-I）一起孵育，然后通过Sephacryl S-400凝胶过滤色谱法重新分离。对重新分离的ox-LDL的分析表明，apo A-I从DMPC/apo A-I转移到了ox-LDL，其占ox-LDL总蛋白的10%。以apo B为基础，重新分离的ox-LDL的磷脂含量增加了2.2倍，胆固醇含量降低了14%。重新分离的ox-LDL的电泳迁移率明显降低，几乎降至天然LDL的水平。此外，小鼠腹腔巨噬细胞降解重新分离的ox-LDL的量以及重新分离的ox-LDL在这些细胞中积累胆固醇酯（CE）的能力均明显降低（分别降低60%和80%），这表明用DMPC/apo A-I处理后，ox-LDL对清道夫受体的配体活性显著降低。将ox-LDL与游离的apo A-I平行孵育导致apo A-I类似地掺入到ox-LDL中。然而，这对ox-LDL的配体活性没有影响。因此，ox-LDL被DMPC/apo A-I降低的配体活性很可能是由ox-LDL脂质部分（主要是磷脂）的变化所解释的。由于盘状高密度脂蛋白（HDL）在体内是已知存在的，这种现象可能解释了HDL的抗动脉粥样硬化功能之一。
