Zheng Lemin, Nukuna Benedicta, Brennan Marie-Luise, Sun Mingjiang, Goormastic Marlene, Settle Megan, Schmitt Dave, Fu Xiaoming, Thomson Leonor, Fox Paul L, Ischiropoulos Harry, Smith Jonathan D, Kinter Michael, Hazen Stanley L
Department of Cell Biology, Center for Cardiovascular Diagnostics and Prevention, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
J Clin Invest. 2004 Aug;114(4):529-41. doi: 10.1172/JCI21109.
In recent studies we demonstrated that systemic levels of protein-bound nitrotyrosine (NO(2)Tyr) and myeloperoxidase (MPO), a protein that catalyzes generation of nitrating oxidants, serve as independent predictors of atherosclerotic risk, burden, and incident cardiac events. We now show both that apolipoprotein A-I (apoA-I), the primary protein constituent of HDL, is a selective target for MPO-catalyzed nitration and chlorination in vivo and that MPO-catalyzed oxidation of HDL and apoA-I results in selective inhibition in ABCA1-dependent cholesterol efflux from macrophages. Dramatic selective enrichment in NO(2)Tyr and chlorotyrosine (ClTyr) content within apoA-I recovered from serum and human atherosclerotic lesions is noted, and analysis of serum from sequential subjects demonstrates that the NO(2)Tyr and ClTyr contents of apoA-I are markedly higher in individuals with cardiovascular disease (CVD). Analysis of circulating HDL further reveals that higher NO(2)Tyr and ClTyr contents of the lipoprotein are each significantly associated with diminished ABCA1-dependent cholesterol efflux capacity of the lipoprotein. MPO as a likely mechanism for oxidative modification of apoA-I in vivo is apparently facilitated by MPO binding to apoA-I, as revealed by cross-immunoprecipitation studies in plasma, recovery of MPO within HDL-like particles isolated from human atheroma, and identification of a probable contact site between the apoA-I moiety of HDL and MPO. To our knowledge, the present results provide the first direct evidence for apoA-I as a selective target for MPO-catalyzed oxidative modification in human atheroma. They also suggest a potential mechanism for MPO-dependent generation of a proatherogenic dysfunctional form of HDL in vivo.
在最近的研究中，我们证明，蛋白结合硝基酪氨酸（NO₂Tyr）的全身水平以及髓过氧化物酶（MPO，一种催化硝化氧化剂生成的蛋白质）可作为动脉粥样硬化风险、负担及心脏事件发生率的独立预测指标。我们现在发现，高密度脂蛋白（HDL）的主要蛋白质成分载脂蛋白A-I（apoA-I）在体内是MPO催化硝化和氯化的选择性靶点，并且MPO催化的HDL和apoA-I氧化会导致巨噬细胞中ABCA1依赖的胆固醇流出受到选择性抑制。我们注意到，从血清和人类动脉粥样硬化病变中回收的apoA-I内的NO₂Tyr和氯酪氨酸（ClTyr）含量显著选择性富集，对连续受试者的血清分析表明，心血管疾病（CVD）患者的apoA-I的NO₂Tyr和ClTyr含量明显更高。对循环HDL的分析进一步显示，脂蛋白中较高的NO₂Tyr和ClTyr含量均与脂蛋白ABCA1依赖的胆固醇流出能力降低显著相关。血浆中的交叉免疫沉淀研究、从人类动脉粥样硬化斑块中分离出的HDL样颗粒中MPO的回收以及HDL的apoA-I部分与MPO之间可能接触位点的鉴定表明，MPO与apoA-I的结合显然促进了MPO作为体内apoA-I氧化修饰的可能机制。据我们所知，目前的结果为apoA-I作为人类动脉粥样硬化斑块中MPO催化氧化修饰的选择性靶点提供了首个直接证据。它们还提示了体内MPO依赖生成促动脉粥样硬化功能失调形式HDL的潜在机制。
