Role of Heparin Induced Tissue Factor Pathway Inhibitor Release in Attenuation of Tissue Factor-Dependent Thrombin Generation During Cardiopulmonary Bypass

背景：大剂量肝素可引起血管内皮细胞大量释放组织因子通路抑制剂（TFPI）。然而，目前尚不清楚TFPI是否足以减弱体外循环（CPB）期间由组织因子（TF）触发的凝血酶生成。在这项研究中，我们的目的是提供证据来阐明TFPI在模拟CPB和灵长类CPB期间和之后抑制tf依赖性凝血酶生成的作用，这些实验使用食环猴（Macaca fascicularis），它们可能通过各种药理设置提供高或正常的血浆TEPI水平。方法：取250 mL供血，在氧合器和滚柱泵中循环120 min，建立模拟CPB。评估了三种方案：对照（肝素3）；75 U /毫升);TF（肝素+重组人TF 1000 pg/mL）；TF +诱导的TFPI（肝素+ TF，使用肝素化前供血，每组n=7）。第三组在捐献前5分钟静脉滴注50 U/kg肝素，使TFPI释放。采用酶免疫法测定CPB前后血浆总TEPI、凝血酶抗凝血酶复合物及F_（1+2）。对于灵长类动物CPB模型，我们使用食蟹猴（Macaca fascicularis）进行120分钟的恒温CPB。预肝素化可提高猴子血浆TFPI，并与对照动物进行凝血酶生成水平的比较。采用酶免疫法测定CPB前后血浆可溶性TF、总TFPI、凝血酶抗凝血酶复合物及F_（1+2）。结果：在模拟CPB中，3组均有明显凝血酶生成，TF增强了F_（1+ 2）的生成。在TF +诱导的TFPI组中，肝素化预处理导致总TFPI增加3倍，尽管给予TF，但CPB期间凝血酶的生成明显降低到对照水平。在灵长类CPB模型中，与对照组相比，预肝素化可提高猴子血浆TFPI，抑制外源性途径可降低凝血酶生成水平。结论：虽然TF增强了CPB中凝血酶的生成，但接触途径和内在途径可能在凝血酶的生成中仍起着相当大的作用。早期肝素治疗引起的血浆TFPI的大量释放可能会减弱临床CPB中tf依赖性凝血酶的产生。少

Background: Administration of high doses of heparin causes massive release of tissue factor pathway inhibitor (TFPI) from vascular endothelial cells. However, it is unclear whether TFPI sufficiently attenuates thrombin generation triggered by tissue factor (TF) during cardiopulmonary bypass (CPB). In this study, we purposed to provide evidence to clarify the role of TFPI in attenuation of TF-dependent thrombin generation during and after simulated CPB and primate CPB using Cynomolgus monkeys (Macaca fascicularis) which may provide high or normal plasma level of TEPI by various pharmacological settings.Methods: Simulated CPB was established by recirculating 250 mL of donor blood for 120 minutes in an oxygenator and a roller pump. Three protocols were evaluated: control (heparin 3. 75 U/mL); TF (heparin + recombinant human TF 1000 pg/mL); and TF plus induced TFPI (heparin + TF, using pre-heparinized donor blood, n=7 fot each group). In the third group, 50 U/kg of heparin was administered … More intravenously five minutes before donation to cause TFPI release. Total plasma TEPI, thrombin antithrombin complex and F_ (1+2) were measured using enzyme immunoassay before and during CPB. For a primate CPB model, we used Cynomolgus monkeys (Macaca fascicularis) for 120 minutes of normothermic CPB. Plasma TFPI was enhanced by pre-heparinization for monkeys, and levels of thrombin generation were compared with control animals. Soluble TF, total plasma TFPI, thrombin antithrombin complex and F_ (1+2) were measured using enzyme immunoassay before and during CPB.Results: In the simulated CPB, significant thrombin generation was observed in all three groups and TF enhanced the generation of F_ (1+ 2). In the TF plus induced TFPI group, pre-heparinization resulted in a 3-fold increase in total TFPI, and thrombin generation was significantly reduced to the control levels during CPB despite the administration of TF. In the primate CPB model, plasma TFPI was enhanced by pre-heparinization for monkeys, and levels of thrombin generation were reduced by inhibition of extrinsic pathway when compared with control group.Conclusions: Although TF enhances thrombin generation in CPB, it is likely that contact and intrinsic pathways still play a considerable role in the thrombin generation. Massive release of plasma TFPI induced by early heparin administration may attenuate TF-dependent thrombin generation during clinical CPB. Less