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首页> 外文期刊>Biochemistry >Spontaneous Transfer of Phospholipid and Cholesterol Hydroperoxides between Cell Membranes and Low-Density Lipoprotein: Assessment of Reaction Kinetics and Prooxidant Effects.
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Spontaneous Transfer of Phospholipid and Cholesterol Hydroperoxides between Cell Membranes and Low-Density Lipoprotein: Assessment of Reaction Kinetics and Prooxidant Effects.

机译：磷脂和胆固醇氢过氧化物在细胞膜和低密度脂蛋白之间的自发转移：反应动力学和促氧化作用的评估。

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摘要

Under oxidative pressure in the vascular circulation, erythrocytes and phagocytic cells may accumulate membrane lipid hydroperoxides (LOOHs), including cholesterol- and phospholipid-derived species (ChOOHs, PLOOHs). LOOH translocation from cells to low-density lipoprotein (LDL) might sensitize the latter to free radical-mediated oxidative modification, an early event associated with atherogenesis. To test this, we examined the spontaneous transfer kinetics of various ChOOH species (5alpha-OOH, 6alpha-OOH, 6beta-OOH, 7alpha/7beta-OOH) and various PLOOH groups (PCOOH, PEOOH, PSOOH, SMOOH) using photoperoxidized erythrocyte ghosts as model donors and freshly prepared LDL as an acceptor. LOOH departure or uptake was monitored by reverse-phase HPLC with reductive electrochemical detection. Mildly peroxidized ghost membranes transferred overall ChOOH and PLOOH to LDL with apparent first-order rate constants approximately 60 and approximately 35 times greater than those of the respective parent lipids. Individual ChOOH rate constants decreased in the following order: 7alpha/7beta-OOH > 5alpha-OOH > 6alpha-OOH > 6beta-OOH. Kinetics for reverse transfer from LDL to ghosts followed the same trend, but rates were significantly higher for all species and their combined activation energy was lower (41 vs 85 kJ/mol). PLOOH transfer rate constants ranged from 4- to 15-fold lower than the composite ChOOH constant, their order being as follows: PCOOH approximately PEOOH approximately PSOOH > SMOOH. Similar PLOOH transfer kinetics were observed when LDL acceptor was replaced by unilamellar liposomes, consistent with desorption from the donor membrane being the rate-limiting step. The susceptibility of transfer LOOH-enriched LDL to Cu(2+)-induced chain peroxidative damage was assessed by monitoring the accumulation of conjugated dienes and products of free radical-mediated cholesterol oxidation. In both cases, transfer-acquired LOOHs significantly reduced the lag time for chain initiation relative to that observed using nonperoxidized ghosts. These findings are consistent with the idea that LDL can acquire significant amounts of "seeding" LOOHs via translocation from various donors in the circulation.
机译：在血管循环中的氧化压力下，红细胞和吞噬细胞可能积聚膜脂质氢过氧化物（LOOH），包括胆固醇和磷脂衍生的物种（ChOOH，PLOOH）。从细胞到低密度脂蛋白（LDL）的LOOH易位可能使后者对自由基介导的氧化修饰敏感，这是与动脉粥样硬化相关的早期事件。为了测试这一点，我们使用光过氧化的红细胞幻影检查了各种ChOOH物种（5alpha-OOH，6alpha-OOH，6beta-OOH，7alpha / 7beta-OOH）和各种PLOOH基团（PCOOH，PEOOH，PSOOH，SMOOH）的自发转移动力学作为模型捐助者，并以新鲜制备的LDL作为受体。通过具有还原电化学检测的反相HPLC监测LOOH的离开或摄取。轻度过氧化的鬼膜将整体ChOOH和PLOOH转移到LDL，其表观一级速率常数比各个亲本脂质的一级常数大约大60倍和大约35倍。各个ChOOH速率常数按以下顺序降低：7alpha / 7beta-OOH> 5alpha-OOH> 6alpha-OOH> 6beta-OOH。从低密度脂蛋白向幽灵反向转移的动力学也遵循相同的趋势，但是所有物种的反应速率均显着较高，并且它们的组合活化能较低（41 vs 85 kJ / mol）。 PLOOH转移速率常数比复合ChOOH常数低4至15倍，其顺序如下：PCOOH约PEOOH约PSOOH> SMOOH。当LDL受体被单层脂质体代替时，观察到相似的PLOOH转移动力学，这与限速步骤从供体膜上解吸一致。通过监测共轭二烯和自由基介导的胆固醇氧化产物的积累，评估了LOOH富集的LDL向Cu（2+）诱导的链过氧化损伤转移的敏感性。在这两种情况下，相对于使用非过氧化鬼影所观察到的，转移获得的LOOH均显着减少了链引发的滞后时间。这些发现与LDL可以通过从循环中各种供体的转运获得大量“播种” LOOH的想法相一致。

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