Mediation of Electronegative Low-Density Lipoprotein Signaling by LOX-1 A Possible Mechanism of Endothelial Apoptosis
Mediation of Electronegative Low-Density Lipoprotein Signaling by LOX-1 A Possible Mechanism of Endothelial Apoptosis
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DOI：
10.1161/circresaha.108.190116
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发表时间：
2009-03-13
影响因子：
20.1
通讯作者：
Chen, Chu-Huang
中科院分区：
文献类型：
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作者：
Lu, Jonathan;Yang, Jun-Hai;Chen, Chu-Huang
凝集素样氧化低密度脂蛋白受体LOX-1介导内皮细胞（EC）摄取实验制备的铜氧化低密度脂蛋白（oxLDL）。为了证实抗铜氧化低密度脂蛋白克隆的这种受体的致动脉粥样硬化作用，我们研究了它是否介导EC摄取L5，一种在血脂异常但血脂正常的人血浆中丰富的负电性低密度脂蛋白。通过离子交换色谱法将高胆固醇血症（LDL-胆固醇，> 160 mg/dL）的人LDL分级分离成L1-L5，其电负性逐渐增加。在培养的牛主动脉内皮细胞（BAECs），L5上调LOX-1和诱导凋亡。用LOX-1特异性小干扰RNA（siLOX-1）转染BAEC使基线LOX-1产生最小化并抑制L5诱导的LOX-1上调。通过荧光显微镜监测标记的L1-L5在BAEC和人脐静脉EC中的内化。用siLOX-1敲低LOX-1抑制L5的内吞作用，但不抑制L1-L4。相反，用RAP（LDL受体相关蛋白）阻断LDL受体可以阻止L1-L4的内化，但不能阻止L5的内化。虽然化学性质不同，L5和oxLDL竞争通过LOX-1进入EC。通过LOX-1，L5信号传导阻碍Akt磷酸化并抑制成纤维细胞生长因子-2和Bcl-2的EC表达。L5还选择性抑制Bcl-xL表达和内皮型一氧化氮合酶磷酸化，但增加Bax、Bad和肿瘤坏死因子-α的合成。用渥曼青霉素阻断Akt磷酸化增加LOX-1表达，表明Akt在LOX-1合成中的调节作用; L5通过使Akt去磷酸化上调LOX-1。由于内皮型一氧化氮合酶和Bcl-2活性是Akt依赖性的，L5通过LOX-1损害血管EC中Akt介导的生长和存活信号。因此，L5/LOX-1复合物可能在动脉粥样硬化形成中发挥关键作用，并阐明疾病干预的重要靶点。(Circ Res. 2009; 104：619-627）。
The lectin-like oxidized LDL receptor LOX-1 mediates endothelial cell (EC) uptake of experimentally prepared copper-oxidized LDL (oxLDL). To confirm the atherogenic role of this receptor cloned against copper-oxLDL, we examined whether it mediates EC uptake of L5, an electronegative LDL abundant in dyslipidemic but not normolipidemic human plasma. Hypercholesterolemic (LDL-cholesterol, > 160 mg/dL) human LDL was fractionated into L1-L5, increasingly electronegative, by ion-exchange chromatography. In cultured bovine aortic ECs (BAECs), L5 upregulated LOX-1 and induced apoptosis. Transfection of BAECs with LOX-1-specific small interfering RNAs (siLOX-1) minimized baseline LOX-1 production and restrained L5-induced LOX-1 upregulation. Internalization of labeled L1-L5 was monitored in BAECs and human umbilical venous ECs by fluorescence microscopy. LOX-1 knockdown with siLOX-1 impeded the endocytosis of L5 but not L1-L4. In contrast, blocking LDL receptor with RAP (LDL receptor-associated protein) stopped the internalization of L1-L4 but not L5. Although chemically different, L5 and oxLDL competed for EC entry through LOX-1. Via LOX-1, L5 signaling hampered Akt phosphorylation and suppressed EC expression of fibroblast growth factor-2 and Bcl-2. L5 also selectively inhibited Bcl-xL expression and endothelial nitric oxide synthase phosphorylation but increased synthesis of Bax, Bad, and tumor necrosis factor-alpha. Blocking Akt phosphorylation with wortmannin increased LOX-1 expression, suggesting a modulatory role of Akt in LOX-1 synthesis; L5 upregulated LOX-1 by dephosphorylating Akt. Because endothelial nitric oxide synthase and Bcl-2 activities are Akt-dependent, L5 impairs Akt-mediated growth and survival signals in vascular ECs by way of LOX-1. Thus, the L5/LOX-1 complex may play a critical role in atherogenesis and illuminate important targets for disease intervention. (Circ Res. 2009; 104: 619-627.)