Li Jingda, Chi Yan, Liu Shuqian, Wang Le, Wang Renjun, Han Xiaofei, Matsuura Eiji, Liu Qingping
Key Laboratory of Carbohydrate and Lipid Metabolism Research, College of Life Science and Technology, Dalian University, 10-Xuefu Avenue, Dalian Economical and Technological Development Zone, Dalian, Liaoning, 116622, China.
J Clin Immunol. 2014 Aug;34(6):669-76. doi: 10.1007/s10875-014-0063-y. Epub 2014 Jun 27.
β2-glycoprotein I (β2-GPI) is a plasma protein that interacts with oxidized low-density lipoproteins (oxLDL) via β2-GPI domain V to form oxLDL/β2-GPI complexes, potential autoantigens promoting atherogenesis in patients with antiphospholipid syndrome (APS). Such a interaction would expose β2-GPI domain I or/and IV, structures recognized by anti-β2-GPI autoantibodies. IgG immune complexes with oxLDL/β2-GPI complexes can interact with macrophages via Fcγ receptor, causing oxLDL/β2-GPI endocytosis and foam cell formation, contributing to atherosclerosis. Here, we use recombinant domain V to study the interaction between oxLDL and β2-GPI and hypothesized that domain V would interfere with this interaction thereby reducing oxLDL macrophage uptake and foam cell formation. The β2-GPI domain V sequence was expressed by using the Pichia pastoris expression system to obtain recombinant domain V of β2-GPI (P.rβ2-GPI DV). ELISA tests demonstrated that P.rβ2-GPI DV interacted with oxLDL via 7-ketocholesteryl-9-carboxynonanoate (oxLig-1), a negatively charged lipid moiety of oxLDL. The ω-carboxyl residue of oxLig-1 is required for the interaction. Serologic tests showed a significant increase in oxLDL and oxLDL/β2-GPI levels in patients with APS (p < 0.05 compared to controls). P.rβ2-GPI DV was able to bind oxLDL in high affinity and competitively inhibited native β2-GPI (nβ2-GPI) binding to free oxLDL as well as to oxLDL from the oxLDL/β2-GPI complexes. These observations suggest that P.rβ2-GPI DV may be used to inhibit the formation of the oxLDL/β2-GPI complexes, a potential approach for reducing foam cell development and mitigating atherogenesis in patients with APS. The present work provides a new effective strategy to prevent the progression of atherothrombotic vascular complications in APS patients.
β2糖蛋白I（β2-GPI）是一种血浆蛋白，它通过β2-GPI结构域V与氧化型低密度脂蛋白（oxLDL）相互作用，形成oxLDL/β2-GPI复合物，这是抗磷脂综合征（APS）患者中促进动脉粥样硬化形成的潜在自身抗原。这种相互作用会暴露β2-GPI结构域I或/和IV，这是抗β2-GPI自身抗体识别的结构。与oxLDL/β2-GPI复合物形成的IgG免疫复合物可通过Fcγ受体与巨噬细胞相互作用，导致oxLDL/β2-GPI内吞和泡沫细胞形成，从而促进动脉粥样硬化。在此，我们使用重组结构域V来研究oxLDL与β2-GPI之间的相互作用，并假设结构域V会干扰这种相互作用，从而减少oxLDL巨噬细胞摄取和泡沫细胞形成。通过毕赤酵母表达系统表达β2-GPI结构域V序列，以获得β2-GPI的重组结构域V（P.rβ2-GPI DV）。ELISA试验表明，P.rβ2-GPI DV通过7-酮胆甾醇-9-羧基壬酸（oxLig-1）与oxLDL相互作用，oxLig-1是oxLDL的带负电荷的脂质部分。oxLig-1的ω-羧基残基是这种相互作用所必需的。血清学检测显示，APS患者的oxLDL和oxLDL/β2-GPI水平显著升高（与对照组相比，p < 0.05）。P.rβ2-GPI DV能够以高亲和力结合oxLDL，并竞争性抑制天然β2-GPI（nβ2-GPI）与游离oxLDL以及与oxLDL/β2-GPI复合物中的oxLDL的结合。这些观察结果表明，P.rβ2-GPI DV可用于抑制oxLDL/β2-GPI复合物的形成，这是减少APS患者泡沫细胞形成和减轻动脉粥样硬化的一种潜在方法。目前的工作为预防APS患者动脉粥样硬化血栓性血管并发症的进展提供了一种新的有效策略。
