HDL stimulates the efflux of peroxidized phospholipids from foam cells and its visualization

动脉粥样硬化是冠状动脉疾病和脑血管疾病的基础过程，也是工业化国家发病率的主要原因。为了预防动脉粥样硬化，世界各国都在研究动脉粥样硬化的发生机制以及膳食食品成分对其的保护作用。在这里，我们首次证明了作为动脉粥样硬化的主要原因之一的高脂血症患者的血浆磷脂酰胆碱过氧化氢(PCOOH；位于血浆脂蛋白颗粒表面的磷脂酰胆碱的初级氧化产物)水平显著高于健康志愿者。这表明高脂血症患者体内存在大量氧化程度最低的脂蛋白，提示脂蛋白磷脂的过氧化对动脉粥样硬化病变的形成尤为重要。在使用人单核细胞系(THP-1)的情况下，巨噬细胞样THP-1细胞有效地吞噬富含PCOOH的氧化型低密度脂蛋白(OxLDL)，导致PCOOH在细胞内显著积聚。通过在oxLDL处理的THP-1细胞中加入高密度脂蛋白(HDL)，细胞内的PCOOH有效地减弱。因此，我们通过体外细胞培养实验和超灵敏LC-MS分析，研究了PCOOH从oxLDL向高密度脂蛋白的掺入机理，并证实了高密度脂蛋白具有还原PCOOH的能力。另一方面，荧光标记的PCOOH能够在实验中制备，并研究了这种PCOOH的可视化(即，对oxLDL掺入THP-1细胞的荧光监测)。本研究证实，高密度脂蛋白通过还原PCOOH而显示出抗氧化作用。

Atherosclerosis is the process underlying coronary artery disease and cerebrovascular disease, and is a leading cause of morbidity in industrialized countries. With the aim of atherosclerosis prevention, mechanisms of atherosclerosis development as well as its protection by dietary food components have been studied worldwide. Here, we demonstrated for the first time that in patient with hyperlipidemia as a major cause of atherosclerosis, the levels of plasma phosphatidylcholine hydroperoxide (PCOOH; that is a primary oxidation product of phosphatidylcholine which located on the surface of plasma lipoprotein particle) were significantly higher than in the healthy volunteers. This indicated that hyperlipidemic patients possess a substantial amount of minimally-oxidized lipoproteins, and implied that the peroxidation of lipoprotein phospholipids would be especially important for the atherosclerotic lesion formation. In the case for using the human monocyte cell line (THP-1), macrophage-like THP-1 cells effectively phagocytized PCOOH-riched oxidized low density lipoprotein (oxLDL), which resulted in the marked accumulation of PCOOH in the cells. By the addition of high density lipoprotein (HDL) to the oxLDL-treated THP-1 cells, cellular PCOOH efficiently attenuated. Thus, we investigated the incorporation mechanism of PCOOH from oxLDL to HDL, and confirmed the ability of HDL to reduce PCOOH by in vitro cell culture experiments and ultra-sensitive LC-MS analysis. On the other hand, fluorescence-labeled PCOOH was able to prepare experimently, and investigated visualization of such PCOOH (I.e., fluorometrically monitorization of the incorporation of oxLDL into THP-1 cells). The present study confirmed that HDL revealed antioxidative function via the reduction of PCOOH.