Sevanian A, Hodis H N, Hwang J, McLeod L L, Peterson H
Department of Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California, Los Angeles 90033, USA.
J Lipid Res. 1995 Sep;36(9):1971-86.
The present study describes the toxicity of oxidized LDL towards rabbit aortic endothelial cells in terms of its lipid components with specific attention to the cholesterol oxidation products (ChOx) found in oxidized LDL isolated from human plasma. Measurements of the major ChOx associated with freshly isolated unmodified LDL, those found in oxidized LDL isolated from human plasma and LDL subjected to oxidation in vitro are described. We have confirmed previous findings that most of the cytotoxicity of freshly isolated human LDL may be attributable to a minor fraction that appears to be oxidatively modified by several criteria. Moreover, this plasma-derived oxidized LDL (referred to as LDL) is highly enriched in ChOx, whereas the content of lipid peroxides or derived products (measured as conjugated dienes and thiobarbituric acid reacting products) are much lower, particularly when compared to copper-induced LDL oxidation. Much of the ChOx found in plasma are associated with LDL, however, the levels and proportions of the various ChOx found in LDL differ from those produced after extensive copper-induced oxidation but resemble those produced after moderate oxidation with copper. The species and concentrations of ChOx found in LDL when applied as a mixture exhibit considerably more toxicity than any individual ChOx alone. At non-toxic levels this ChOx mixture causes an increased influx of several ions, including calcium, an effect not seen with individual ChOx at comparable doses. Perturbations in ionic homeostasis, and particularly the sustained increase in intracellular calcium concentrations, are associated with much of the cytotoxicity, an effect attributable to the membrane disruptive action of ChOx leading to altered ion transporter activity. The effect of the ChOx mixture (but not any individual ChOx) on sodium and potassium flux appears to be due to enhanced Na+/K(+)-ATPase activity based on the complete inhibition produced by ouabain under all treatment conditions. These findings also show that the levels of cholesterol oxidation products found in normal LDL are not cytotoxic whereas those present in oxidized LDL exceed the toxic threshold for endothelial cells and account for most of the cytotoxicity produced by this modified lipoprotein.
本研究从氧化型低密度脂蛋白（LDL）的脂质成分方面描述了其对兔主动脉内皮细胞的毒性，特别关注了从人血浆中分离出的氧化型LDL中发现的胆固醇氧化产物（ChOx）。描述了与新鲜分离的未修饰LDL相关的主要ChOx的测量结果，以及从人血浆中分离出的氧化型LDL和体外氧化的LDL中发现的ChOx的测量结果。我们已经证实了先前的发现，即新鲜分离的人LDL的大部分细胞毒性可能归因于一小部分似乎在几个标准下被氧化修饰的部分。此外，这种源自血浆的氧化型LDL（称为LDL）富含ChOx，而脂质过氧化物或衍生产物的含量（以共轭二烯和硫代巴比妥酸反应产物测量）要低得多，特别是与铜诱导的LDL氧化相比。血浆中发现的大部分ChOx与LDL相关，然而，LDL中发现的各种ChOx的水平和比例与广泛铜诱导氧化后产生的不同，但类似于适度铜氧化后产生的。当作为混合物应用时，LDL中发现的ChOx的种类和浓度表现出比任何单独的ChOx更大的毒性。在无毒水平下，这种ChOx混合物会导致几种离子（包括钙）的流入增加，在可比剂量下单独的ChOx不会出现这种效果。离子稳态的扰动，特别是细胞内钙浓度的持续增加，与大部分细胞毒性相关，这种效果归因于ChOx的膜破坏作用导致离子转运体活性改变。ChOx混合物（但不是任何单独的ChOx）对钠和钾通量的影响似乎是由于基于哇巴因在所有处理条件下产生的完全抑制作用而增强的Na+/K(+)-ATP酶活性。这些发现还表明，正常LDL中发现的胆固醇氧化产物水平没有细胞毒性，而氧化型LDL中存在的那些超过了内皮细胞的毒性阈值，并占这种修饰脂蛋白产生的大部分细胞毒性。
