Department of Traumatology, Hand-, Plastic- and Reconstructive Surgery, University Hospital of Ulm, Ulm, Germany.
J Immunol. 2010 Nov 1;185(9):5628-36. doi: 10.4049/jimmunol.0903678. Epub 2010 Sep 24.
The complement system as well as the coagulation system has fundamental clinical implications in the context of life-threatening tissue injury and inflammation. Associations between both cascades have been proposed, but the precise molecular mechanisms remain unknown. The current study reports multiple links for various factors of the coagulation and fibrinolysis cascades with the central complement components C3 and C5 in vitro and ex vivo. Thrombin, human coagulation factors (F) XIa, Xa, and IXa, and plasmin were all found to effectively cleave C3 and C5. Mass spectrometric analyses identified the cleavage products as C3a and C5a, displaying identical molecular weights as the native anaphylatoxins C3a and C5a. Cleavage products also exhibited robust chemoattraction of human mast cells and neutrophils, respectively. Enzymatic activity for C3 cleavage by the investigated clotting and fibrinolysis factors is defined in the following order: FXa > plasmin > thrombin > FIXa > FXIa > control. Furthermore, FXa-induced cleavage of C3 was significantly suppressed in the presence of the selective FXa inhibitors fondaparinux and enoxaparin in a concentration-dependent manner. Addition of FXa to human serum or plasma activated complement ex vivo, represented by the generation of C3a, C5a, and the terminal complement complex, and decreased complement hemolytic serum activity that defines exact serum concentration that results in complement-mediated lysis of 50% of sensitized sheep erythrocytes. Furthermore, in plasma from patients with multiple injuries (n = 12), a very early appearance and correlation of coagulation (thrombin-antithrombin complexes) and the complement activation product C5a was found. The present data suggest that coagulation/fibrinolysis proteases may act as natural C3 and C5 convertases, generating biologically active anaphylatoxins, linking both cascades via multiple direct interactions in terms of a complex serine protease system.
补体系统以及凝血系统在危及生命的组织损伤和炎症背景下具有重要的临床意义。已经提出了这两个级联之间的关联,但确切的分子机制尚不清楚。本研究报告了多种凝血和纤溶级联的各种因子与补体核心成分 C3 和 C5 之间的联系,包括体外和体内实验。发现凝血酶、人凝血因子(F)XIa、Xa 和 IXa 以及纤溶酶均能有效地切割 C3 和 C5。质谱分析鉴定出的切割产物为 C3a 和 C5a,其分子量与天然过敏毒素 C3a 和 C5a 相同。切割产物还分别表现出对人肥大细胞和中性粒细胞的强烈趋化作用。所研究的凝血和纤溶因子对 C3 切割的酶活性按以下顺序定义:FXa>纤溶酶>凝血酶>FIXa>FXIa>对照。此外,在存在选择性 FXa 抑制剂磺达肝素和依诺肝素的情况下,FXa 诱导的 C3 切割呈浓度依赖性方式受到显著抑制。FXa 在人血清或血浆中添加补体可激活补体,表现为 C3a、C5a 和末端补体复合物的生成,以及补体溶血血清活性的降低,该活性定义了导致 50%致敏绵羊红细胞发生补体介导溶解的确切血清浓度。此外,在多发性损伤患者的血浆(n=12)中,发现凝血(凝血酶-抗凝血酶复合物)和补体激活产物 C5a 非常早期出现且相关。这些数据表明,凝血/纤溶蛋白酶可能作为天然的 C3 和 C5 转化酶,产生具有生物活性的过敏毒素,通过复杂的丝氨酸蛋白酶系统在多个直接相互作用方面连接两个级联。