The role of contact pathway factors in mechanical circulation

摘要 体外膜肺氧合(ECMO)和体外循环(CPB)与 毁灭性但鲜为人知的血栓性炎症状态。标准的抗凝策略会导致 由于危及生命的血栓仍然很常见，因此存在显著的出血风险，但还不够。没有 有效策略缓解机械循环启动后数分钟内引发的炎性风暴 支持。PIS实验室的数据表明，凝血因子XII(FXII)既促进血栓形成，又促进炎症 体外循环术中介导的器官损伤。人们对FXII作为机械循环的目标非常感兴趣， 但FXII与机械循环相关的血栓炎症的耦合机制尚不清楚- 学习。FXII是一种多功能的蛋白酶，连接止血和炎症系统。FXII激活 凝血因子XI(FXI)，导致凝血酶生成。FXII介导的FXI激活在环境中的重要性 从未对机械循环进行过评估。来自PIS实验室的数据表明，机械循环 组分可以促进凝血酶介导的FXI激活，显著限制FXII在某些情况下的相关性 上下文。此外，在体外循环心脏直视手术期间，靶向FXII似乎不够 胸骨切开和心脏操作可提高循环组织因子水平。FXII也激活前激肽释放酶 (PKK)到活性蛋白激肽释放酶(Kal)。Kal与多种炎症途径有关，包括 补体激活和缓激肽生成。Kal也被提出用来促进血栓形成 独立于FXI。FXII介导的PKK激活被认为是在 ECMO，但目前尚无研究直接评价PKK在机械循环中的作用 血栓性炎症。来自PIS实验室的数据表明，靶向PKK显著限制了血栓形成和 体外循环中的器官损伤。拟议的研究将使用专门为此而开发的新型基因靶标大鼠。 提议，并用尖端药理学药物检验以下假设：1)FXII促进ECMO 与FXI激活相关的独立机制与CPB相关的血栓性炎症病理 和库尔德工人党。2)FXI在机械循环环境中是一个优越的抗血栓靶点，其相对较高的 循环转铁蛋白水平，例如在体外循环期间存在的水平。3)FXII介导的PKK激活促进关键炎症反应 在ECMO/CPB期间导致器官损害的事件，以及血栓栓塞性并发症。4)合并 针对FXI和FXII或FXI和PKK的策略可提供更好的预防血栓形成和炎症的保护 器官损伤比单独针对这些因素之一更好，而不会招致重大出血风险。建议数 研究将为FXII与相关机械循环的耦合机制提供必要的见解 血栓性炎症病理学。所获得的知识将为未来可用的临床试验提供关键信息 以及针对FXII和FXI的新兴药物。拟议的研究还可能确定更多的小说 靶点(例如，PKK)，以限制机械循环中血栓炎症引起的发病率。

SUMMARY Extracorporeal membrane oxygenation (ECMO) and cardiopulmonary bypass (CPB) are associated with a devastating but poorly understood thromboinflammatory state. Standard anticoagulation strategies result in significant bleeding risk, yet are inadequate as life-threatening thromboses remain common. There are no effective strategies to mitigate the inflammatory storm initiated within minutes of starting mechanical circulatory support. Data from the PIs lab suggests that factor XII (FXII) promotes both thrombosis and inflammatory mediated organ damage during ECMO. There is significant interest in FXII as a target in mechanical circulation, but the mechanisms coupling FXII to mechanical circulation associated thromboinflammation are under- studied. FXII is a multifunctional protease that bridges the hemostatic and inflammatory systems. FXII activates factor XI (FXI), leading to thrombin generation. The importance of FXII-mediated FXI activation in the setting of mechanical circulation has never been evaluated. Data from the PIs lab suggests mechanical circulation components can promote thrombin-mediated FXI activation, significantly limiting the relevance of FXII in some contexts. Moreover, targeting FXII appears inadequate during CPB with open heart operations where sternotomy and cardiac manipulation increase circulating tissue factor levels. FXII also activates prekallikrein (PKK) to the active protease kallikrein (Kal). Kal is linked to multiple inflammatory pathways, including complement activation and bradykinin generation. Kal has also been proposed to promote thrombosis independently of FXI. FXII-mediated PKK activation has been proposed to drive inflammatory events during ECMO, but there are no studies directly evaluating the role of PKK in mechanical circulation associated thromboinflammation. Data from the PIs lab suggests that targeting PKK significantly limits thrombosis and organ damage in ECMO. The proposed studies will use novel gene-targeted rats developed specifically for this proposal, and cutting-edge pharmacological agents to test the following hypotheses: 1) FXII promotes ECMO and CPB related thromboinflammatory pathologies by independent mechanisms related to activation of FXI and PKK. 2) FXI is a superior antithrombotic target in mechanical circulation contexts with relatively high circulating TF levels, such as exist during CPB. 3) FXII-mediated PKK activation promotes key inflammatory events that lead to organ damage during ECMO/CPB, as well as thromboembolic complications. 4) Combined strategies targeting FXI and FXII, or FXI and PKK, provide better protection from thrombosis and inflammatory organ damage than targeting one of these factors alone, without incurring a major bleeding risk. The proposed studies will provide needed insights into the mechanisms coupling FXII to mechanical circulation associated thromboinflammatory pathologies. The knowledge gained will critically inform future clinical trials of available and emerging agents targeting FXII and FXI. The proposed studies are also likely to identify additional novel targets (e.g., PKK) to limit thromboinflammatory driven morbidity in mechanical circulation.