Group V secretory phospholipase A2-modified low density lipoprotein promotes foam cell formation by a SR-A- and CD36-independent process that involves cellular proteoglycans
Group V secretory phospholipase A2-modified low density lipoprotein promotes foam cell formation by a SR-A- and CD36-independent process that involves cellular proteoglycans
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DOI：
10.1074/jbc.m502067200
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发表时间：
2005-09-23
影响因子：
4.8
通讯作者：
Webb, NR
中科院分区：
文献类型：
--
作者：
Boyanovsky, BB;van der Westhuyzen, DR;Webb, NR
越来越多的证据表明，分泌型磷脂酶A(2)(Spla(2))促进动脉粥样硬化的形成。我们以前已经在人和小鼠的动脉粥样硬化病变中发现了V组Spla(2)(GV Spla(2))，其对低密度脂蛋白(LDL)颗粒的水解性，以及GV Spla(2)修饰的低密度脂蛋白(GV-LDL)在体外诱导巨噬细胞泡沫细胞形成的能力。本研究的目的是探讨巨噬细胞摄取GV-LDL的机制。用对照低密度脂蛋白、GV-低密度脂蛋白、氧化低密度脂蛋白和涡流聚集低密度脂蛋白处理C57BL/6小鼠(野生型)、低密度脂蛋白受体缺陷小鼠(LDLR-/-)、SR-A和CD36(DKO)小鼠的腹腔巨噬细胞。不出所料，与DKO巨噬细胞相比，氧化低密度脂蛋白在WT和LDLR-/-中诱导了更多的胆固醇酯蓄积。相反，GV-LDL和VX-LDL在三种细胞类型中的积聚没有差异。I-125-OX-LDL显示出与WT细胞的高亲和力、可饱和结合，而在DKO细胞中这一结合显著减少。VX-低密度脂蛋白和GV-低密度脂蛋白表现出低亲和力、非饱和结合，这两种细胞类型相似，但显著高于对照低密度脂蛋白。WT和DKO细胞对GV-LDL的降解相似。共聚焦显微镜分析表明，Alexa-568标记的GV-LDL和Alexa-488标记的ox-LDL在细胞内有明显的分布。在预先用肝素或NaClO_3孵育的细胞中，对GV-LDL的摄取显著减少(而不是OX-LDL或VX-LDL)，这表明蛋白多糖在GV-LDL摄取中起作用。我们的数据表明，低密度脂蛋白的生理修饰有可能促进巨噬细胞泡沫细胞的形成，而不依赖于清道夫受体。
Accumulating evidence indicates that secretory phospholipase A(2) (sPLA(2)) enzymes promote atherogenic processes. We have previously showed the presence of Group V sPLA(2) (GV sPLA(2)) in human and mouse atherosclerotic lesions, its hydrolysis of low density lipoprotein (LDL) particles, and the ability of GV sPLA(2)-modified LDL (GV- LDL) to induce macrophage foam cell formation in vitro. The goal of this study was to investigate the mechanisms involved in macrophage uptake of GV-LDL. Peritoneal macrophages from C57BL/6 mice (wild type (WT)), C57BL/6 mice deficient in LDL receptor (LDLR-/-), or SR-A and CD36 (DKO) were treated with control LDL, GV-LDL, oxidized LDL (ox-LDL) or LDL aggregated by vortexing (vx-LDL). As expected, ox- LDL induced significantly more cholesterol ester accumulation in WT and LDLR-/- compared with DKO macrophages. In contrast, there was no difference in the accumulation of GV-LDL or vx-LDL in the three cell types. I-125-ox-LDL exhibited high affinity, saturable binding to WT cells that was significantly reduced in DKO cells. Vx-LDL and GV-LDL showed low affinity, non-saturable binding that was similar for both cell types, and significantly higher compared with control LDL. GV-LDL degradation in WT and DKO cells was similar. Analyses by confocal microscopy indicated a distinct intracellular distribution of Alexa-568-labeled GV-LDL and Alexa-488-labeled ox-LDL. Uptake of GV-LDL (but not ox-LDL or vx-LDL) was significantly reduced in cells preincubated with heparin or NaClO3, suggesting a role for proteoglycans in GV-LDL uptake. Our data point to a physiological modification of LDL that has the potential to promote macrophage foam cell formation independent of scavenger receptors.