Center for Biomedical Research and The Texas Lung Injury Institute, The University of Texas Health Science Center at Tyler, Tyler, TX 75708, USA.
J Thromb Haemost. 2011 Mar;9(3):531-9. doi: 10.1111/j.1538-7836.2010.04167.x.
A growing body of experimental evidence supports broad inhibitory and regulatory activity of plasminogen activator inhibitor 1 (PAI-1). The present study was designed to investigate whether PAI-1 inhibits factor (F) VIIa complexed with tissue factor (TF), a well-known procoagulant risk factor.
The ability of PAI-1 to inhibit FVIIa-TF activity was evaluated in both clotting and factor X (FX) activation assays. PAI-1 and its complex with vitronectin inhibit: (i) clotting activity of FVIIa-TF (PAI-1(IC50) , 817 and 125 nm, respectively); (ii) FVIIa-TF-mediated FX activation (PAI-1(IC50) , 260 and 50 nm, respectively); and (iii) FVIIa bound to TF expressed on the surface of stimulated endothelial cells (PAI-1(IC50) , 260 and 120 nm, respectively). The association rate constant (k(a)) for PAI-1 inhibition of FVIIa-TF was determined using a chromogenic assay. K(a) for PAI-1 inhibition of FVIIa bound to relipidated TF is 3.3-fold higher than that for FVIIa bound to soluble TF (k(a) = 0.09 ± 0.01 and 0.027 ± 0.03 μm(-1) min(-1), respectively). Vitronectin increases k(a) for both soluble and relipidated TF by 3.5- and 30-fold, respectively (to 0.094 ± 0.020 and 2.7 ± 0.2 μm(-1) min(-1)). However, only a 3.5- to 5.0-fold increase in the acylated FVIIa was observed on SDS PAGE in the presence of vitronectin for both relipidated and soluble TF, indicating fast formation of PAI-1/vitronectin/FVIIa/relipidated TF non-covalent complex.
Our results demonstrate potential anticoagulant activity of PAI-1 in the presence of vitronectin, which could contribute to regulation of hemostasis under pathological conditions such as severe sepsis, acute lung injury and pleural injury, where PAI-1 and TF are overexpressed.
越来越多的实验证据表明纤溶酶原激活物抑制剂 1（PAI-1）具有广泛的抑制和调节活性。本研究旨在探讨 PAI-1 是否抑制与组织因子（TF）结合的因子（F）VIIa，TF 是众所周知的促凝风险因子。
在凝血和因子 X（FX）激活测定中评估了 PAI-1 抑制 FVIIa-TF 活性的能力。PAI-1 及其与 vitronectin 的复合物抑制：（i）FVIIa-TF 的凝血活性（PAI-1（IC50）分别为 817 和 125nm）；（ii）FVIIa-TF 介导的 FX 激活（PAI-1（IC50）分别为 260 和 50nm）；（iii）结合到刺激的内皮细胞表面表达的 TF 的 FVIIa（PAI-1（IC50）分别为 260 和 120nm）。使用比色法测定 PAI-1 抑制 FVIIa-TF 的关联速率常数（k(a)）。与 relipidated TF 结合的 PAI-1 抑制 FVIIa 的 k(a)是与可溶性 TF 结合的 FVIIa 的 3.3 倍（k(a)=0.09±0.01 和 0.027±0.03μm(-1) min(-1)）。vitronectin 分别将可溶性和 relipidated TF 的 k(a)提高 3.5-和 30 倍，分别为 0.094±0.020 和 2.7±0.2μm(-1) min(-1)）。然而，在存在 vitronectin 的情况下，仅在 relipidated 和可溶性 TF 中观察到 SDS PAGE 上酰化 FVIIa 增加 3.5-至 5.0 倍，表明 PAI-1/vitronectin/FVIIa/relipidated TF 非共价复合物的快速形成。
我们的结果表明 PAI-1 在 vitronectin 存在下具有潜在的抗凝活性，这可能有助于调节严重败血症、急性肺损伤和胸腔损伤等病理条件下的止血，这些条件下 PAI-1 和 TF 过度表达。
