Institute of Diagnostics, Department of Medical Microbiology and Immunology, University of Oulu, 90014 Oulu, Finland.
Free Radic Biol Med. 2011 Aug 15;51(4):834-43. doi: 10.1016/j.freeradbiomed.2011.05.029. Epub 2011 Jun 6.
Oxidatively modified low-density lipoproteins (Ox-LDL) and complement anaphylatoxins C3a and C5a are colocalized in atherosclerotic lesions. Anaphylatoxin C3a also binds and breaks bacterial lipid membranes and phosphatidylcholine liposomes. The role of oxidized lipid adducts in C3a binding to Ox-LDL and apoptotic cells was investigated. Recombinant human C3a bound specifically to low-density lipoprotein and bovine serum albumin modified with malondialdehyde (MDA) and malondialdehyde acetaldehyde (MAA) in chemiluminescence immunoassays. No binding was observed to native proteins, LDL oxidized with copper ions (CuOx-LDL), or phosphocholine. C3a binding to MAA-LDL was inhibited by two monoclonal antibodies specific for MAA-LDL. On agarose gel electrophoresis, C3a comigrated with MDA-LDL and MAA-LDL, but not with native LDL or CuOx-LDL. C3a bound to apoptotic cells in flow cytometry. C3a opsonized MAA-LDL and was taken up by J774A.1 macrophages in immunofluorescence analysis. Complement-activated human serum samples (n=30) showed increased C3a binding to MAA-LDL (P<0.001) and MDA-LDL (P<0.001) compared to nonactivated samples. The amount of C3a bound to MAA-LDL was associated with total complement activity, C3a desArg concentration, and IgG antibody levels to MAA-LDL. Proteins containing MDA adducts or MAA adducts may bind C3a in vivo and contribute to inflammatory processes involving activation of the complement system in atherosclerosis.
氧化修饰的低密度脂蛋白（Ox-LDL）和补体过敏毒素 C3a 和 C5a 共同定位于动脉粥样硬化病变中。过敏毒素 C3a 还结合并破坏细菌脂质膜和磷脂酰胆碱脂质体。本研究旨在探讨氧化脂质加合物在 C3a 与 Ox-LDL 和凋亡细胞结合中的作用。在化学发光免疫分析中，重组人 C3a 特异性结合到经丙二醛（MDA）和丙二醛乙醛（MAA）修饰的低密度脂蛋白和牛血清白蛋白上。在天然蛋白、铜离子氧化的 LDL（CuOx-LDL）或磷酸胆碱上未观察到结合。两种针对 MAA-LDL 的单克隆抗体可抑制 C3a 与 MAA-LDL 的结合。在琼脂糖凝胶电泳上，C3a 与 MDA-LDL 和 MAA-LDL 共迁移，但与天然 LDL 或 CuOx-LDL 不迁移。在流式细胞术上，C3a 结合凋亡细胞。在免疫荧光分析中，C3a 调理 MAA-LDL 并被 J774A.1 巨噬细胞摄取。与非激活样本相比，补体激活的人血清样本（n=30）显示出对 MAA-LDL（P<0.001）和 MDA-LDL（P<0.001）的 C3a 结合增加。与 MAA-LDL 结合的 C3a 量与总补体活性、C3a desArg 浓度和针对 MAA-LDL 的 IgG 抗体水平相关。含有 MDA 加合物或 MAA 加合物的蛋白质可能在体内结合 C3a，并有助于涉及补体系统在动脉粥样硬化中激活的炎症过程。
