Sterol carrier protein-2-facilitated intermembrane transfer of cholesterol- and phospholipid-derived hydroperoxides.
Sterol carrier protein-2-facilitated intermembrane transfer of cholesterol- and phospholipid-derived hydroperoxides.
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DOI：
10.1021/bi0491200
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发表时间：
2004-09
期刊：
影响因子：
2.9
通讯作者：
A. Vila;V. Levchenko;W. Korytowski;A. Girotti
中科院分区：
文献类型：
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作者：
A. Vila;V. Levchenko;W. Korytowski;A. Girotti
甾醇载体蛋白-2（SCP-2）促进胆固醇（Ch）和磷脂（PL）在膜间的转移/交换，并在细胞内脂质运输中起关键作用。SCP-2是否也可以促进脂质过氧化氢（LOOH）在膜之间的转移，从而潜在地增强过氧化损伤的传播，在这项研究中进行了检查。采用HPLC和电化学检测法测定了光化学生成的胆固醇氢过氧化物（ChOOH）物质（5 α-OOH、6 α/6 β-OOH、7 α/7 β-OOH）和磷脂氢过氧化物（PLOOH）家族（PCOOH、PEOOH、PSOOH）的转移动力学。转移实验中使用的LOOH供体/受体对包括（i）所有脂质体（例如，可凝集的SUV/不可凝集的LUV）;（ii）光过氧化红细胞血影/SUV或反之亦然;和（iii）SUV/线粒体。在37 ℃的SUV/ghost系统中，总ChOOH自发转移的速率常数约为未氧化Ch的8倍。纯化牛肝和人重组SCP-2显示出相同的刺激总ChOOH转移的能力，0.5单位/mL（基于[（14）C]Ch转移）使一级速率常数（k）增加约7倍。SCP-2增强的单个ChOOH的易位随着亲水性的增加而增加，顺序如下：6 β-OOH <6 α-OOH <5 α-OOH <7 α/7 β-OOH。同样，SCP-2刺激PCOOH、PEOOH或PSOOH转移约6倍，但净k是5 α-OOH的1/5和7 α/7 β-OOH的1/10。有利于SCP-2增强LOOH转移的供体膜特性包括（i）增加PL不饱和度和（ii）增加磷脂酰丝氨酸施加的净负电荷。通过显示SCP-2加速7 α-OOH从SUV转移到分离的线粒体，并且这增强了过氧化物诱导的线粒体膜电位损失，证明了细胞毒性相关性。基于这些发现，我们推测SCP-2通过运输ChOOOH和PLOOH以及母体脂质，可能加剧氧化应激条件下的细胞损伤。
Sterol carrier protein-2 (SCP-2) facilitates cholesterol (Ch) and phospholipid (PL) transfer/exchange between membranes and appears to play a key role in intracellular lipid trafficking. Whether SCP-2 can also facilitate lipid hydroperoxide (LOOH) transfer between membranes and thereby potentially enhance dissemination of peroxidative damage was examined in this study. Transfer kinetics of photochemically generated cholesterol hydroperoxide (ChOOH) species (5alpha-OOH, 6alpha/6beta-OOH, 7alpha/7beta-OOH) and phospholipid hydroperoxide (PLOOH) families (PCOOH, PEOOH, PSOOH) were determined, using HPLC with electrochemical detection for peroxide analysis. LOOH donor/acceptor pairs employed in transfer experiments included (i) all liposomes (e.g., agglutinable SUVs/ nonagglutinable LUVs); (ii) photoperoxidized erythrocyte ghosts/SUVs or vice versa; and (iii) SUVs/mitochondria. In a SUV/ghost system at 37 degrees C, the rate constant for total ChOOH spontaneous transfer was approximately 8 times greater than that for unoxidized Ch. Purified bovine liver and human recombinant SCP-2 exhibited an identical ability to stimulate overall ChOOH transfer, 0.5 unit/mL (based on [(14)C]Ch transfer) increasing the first-order rate constant (k) approximately 7-fold. SCP-2-enhanced translocation of individual ChOOHs increased with increasing hydrophilicity in the following order: 6beta-OOH < 6alpha-OOH < 5alpha-OOH < 7alpha/7beta-OOH. Likewise, SCP-2 stimulated PCOOH, PEOOH, or PSOOH transfer approximately 6-fold, but the net k was 1/5 that of 5alpha-OOH and 1/10 that of 7alpha/7beta-OOH. Donor membrane properties favoring SCP-2-enhanced LOOH transfer included (i) increasing PL unsaturation and (ii) increasing net negative charge imposed by phosphatidylserine. Cytotoxic relevance was demonstrated by showing that SCP-2 accelerates 7alpha-OOH transfer from SUVs to isolated mitochondria and that this enhances peroxide-induced loss of the mitochondrial membrane potential. On the basis of these findings, we postulate that SCP-2, by trafficking ChOOHs and PLOOHs in addition to parent lipids, might exacerbate cell injury under oxidative stress conditions.