Baldus S, Eiserich J P, Mani A, Castro L, Figueroa M, Chumley P, Ma W, Tousson A, White C R, Bullard D C, Brennan M L, Lusis A J, Moore K P, Freeman B A
Department of Anesthesiology, and. The Center for Free Radical Biology, University of Alabama at Birmingham, 35233, USA.
J Clin Invest. 2001 Dec;108(12):1759-70. doi: 10.1172/JCI12617.
Nitrotyrosine formation is a hallmark of vascular inflammation, with polymorphonuclear neutrophil-derived (PMN-derived) and monocyte-derived myeloperoxidase (MPO) being shown to catalyze this posttranslational protein modification via oxidation of nitrite (NO(2)(-)) to nitrogen dioxide (NO(2)(*)). Herein, we show that MPO concentrates in the subendothelial matrix of vascular tissues by a transcytotic mechanism and serves as a catalyst of ECM protein tyrosine nitration. Purified MPO and MPO released by intraluminal degranulation of activated human PMNs avidly bound to aortic endothelial cell glycosaminoglycans in both cell monolayer and isolated vessel models. Cell-bound MPO rapidly transcytosed intact endothelium and colocalized abluminally with the ECM protein fibronectin. In the presence of the substrates hydrogen peroxide (H(2)O(2)) and NO(2)(-), cell and vessel wall-associated MPO catalyzed nitration of ECM protein tyrosine residues, with fibronectin identified as a major target protein. Both heparin and the low-molecular weight heparin enoxaparin significantly inhibited MPO binding and protein nitrotyrosine (NO(2)Tyr) formation in both cultured endothelial cells and rat aortic tissues. MPO(-/-) mice treated with intraperitoneal zymosan had lower hepatic NO(2)Tyr/tyrosine ratios than did zymosan-treated wild-type mice. These data indicate that MPO significantly contributes to NO(2)Tyr formation in vivo. Moreover, transcytosis of MPO, occurring independently of leukocyte emigration, confers specificity to nitration of vascular matrix proteins.
硝基酪氨酸的形成是血管炎症的一个标志，已表明多形核中性粒细胞（PMN）衍生的和单核细胞衍生的髓过氧化物酶（MPO）可通过将亚硝酸盐（NO₂⁻）氧化为二氧化氮（NO₂*）来催化这种翻译后蛋白质修饰。在此，我们表明MPO通过一种转胞吞机制集中在血管组织的内皮下基质中，并作为细胞外基质（ECM）蛋白酪氨酸硝化的催化剂。在细胞单层和离体血管模型中，纯化的MPO以及活化的人PMN腔内脱颗粒释放的MPO都能与主动脉内皮细胞糖胺聚糖紧密结合。与细胞结合的MPO迅速穿越完整的内皮，并在管腔外与ECM蛋白纤连蛋白共定位。在存在底物过氧化氢（H₂O₂）和NO₂⁻的情况下，与细胞和血管壁相关的MPO催化ECM蛋白酪氨酸残基的硝化，纤连蛋白被确定为主要的靶蛋白。肝素和低分子量肝素依诺肝素在培养的内皮细胞和大鼠主动脉组织中均显著抑制MPO结合和蛋白硝基酪氨酸（NO₂Tyr）的形成。用腹腔注射酵母聚糖处理的MPO基因敲除（MPO⁻/⁻）小鼠的肝脏NO₂Tyr/酪氨酸比值低于用酵母聚糖处理的野生型小鼠。这些数据表明MPO在体内对NO₂Tyr的形成有显著贡献。此外，MPO的转胞吞作用独立于白细胞迁移发生，赋予血管基质蛋白硝化作用特异性。
