Studies of the activation of factor VII bound to tissue factor.
Studies of the activation of factor VII bound to tissue factor.
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DOI：
10.1182/blood.v87.9.3738.bloodjournal8793738
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发表时间：
1996-05
期刊：
影响因子：
20.3
通讯作者：
L. Rao;T. Williams;S. Rapaport
中科院分区：
文献类型：
--
作者：
L. Rao;T. Williams;S. Rapaport
进行实验以评价与悬浮液中的再脂化组织因子（TF）结合和与卵巢癌细胞系（OC-2008）表面上组成型表达的TF结合的因子VII的活化。通过测量125 I-因子VII的裂解和未标记的因子VII催化活化后不能反向活化因子VII的变体因子IX分子的能力来评估活化。发现因子Xa有效地激活与在酸性或中性磷脂囊泡中再脂化的TF结合的因子VII。在悬浮液中与TF结合的因子VII的自激活依赖于所用TF脱辅基蛋白的制备及其再脂化技术。这突出表明，在从悬浮液中的TF外推数据到止血过程中与细胞表面结合的因子VII的活化时需要谨慎。一致地观察到在不存在添加的蛋白酶的情况下与OC-2008单层结合的因子VII的相对缓慢的活化。在肝素存在或不存在的情况下，抗凝血酶阻止了这种基础激活，而TF途径抑制剂（TFPI/Xa因子复合物）仅具有有限的抑制作用。添加因子X的底物浓度显著增强因子VII的基础活化，但TFPI/因子Xa和抗凝血酶/肝素都消除了这种增强。总的来说，我们的数据与以下假设是一致的：在止血过程中，并非所有在组织损伤部位形成的因子VII/TF复合物都容易被激活为因子VIIa（VIIa）/TF复合物。本文对这一结果的临床意义进行了讨论。
Experiments were performed to evaluate activation of factor VII bound to relipidated tissue factor (TF) in suspension and to TF constitutively expressed on the surface of an ovarian carcinoma cell line (OC-2008). Activation was assessed by measuring cleavage of 125I-factor VII and by the ability of unlabeled factor VII to catalyze activation of a variant factor IX molecule that, after activation, cannot back-activate factor VII. Factor Xa was found to effectively activate factor VII bound to TF relipidated in either acidic or neutral phospholipid vesicles. Autoactivation of factor VII bound to TF in suspension was dependent on the preparation of TF apoprotein used and the technique of its relipidation. This highlights the need for caution in extrapolating data from TF in suspension to the activation of factor VII bound to cell surfaces during hemostasis. A relatively slow activation of factor VII bound to OC-2008 monolayers in the absence of added protease was observed consistently. Antithrombin in the presence or absence of heparin prevented this basal activation, whereas TF pathway inhibitor (TFPI/factor Xa complexes had only a limited inhibitory effect. Adding a substrate concentration of factor X markedly enhanced basal activation of factor VII, but both TFPI/factor Xa and antithrombin/heparin abolished this enhancement. Overall, our data are compatible with the hypothesis that not all factor VII/TF complexes formed at a site of tissue injury are readily activated to factor VIIa (VIIa)/TF complexes during hemostasis. The clinical significance of this is discussed.