The role of contact pathway factors in mechanical circulation

总结 体外膜肺氧合（ECMO）和体外循环（CPB）与 破坏性的但知之甚少的血栓炎性状态。标准抗凝策略导致 显著出血风险，但由于危及生命的血栓形成仍然很常见，因此还不够。没有 有效的策略，以减轻在开始机械循环后几分钟内引发的炎症风暴 支持.来自PI实验室的数据表明，因子XII（FXII）促进血栓形成和炎症反应。 介导的器官损伤FXII作为机械循环中的靶点有很大的兴趣， 但FXII与机械循环相关血栓炎症的耦合机制尚不清楚， 研究了FXII是连接止血和炎症系统的多功能蛋白酶。FXII激活 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 机械循环的影响从未被评估过PI实验室的数据表明机械循环 成分可以促进凝血酶介导的FXI激活，从而显着限制FXII在某些情况下的相关性 contexts.此外，在CPB心脏直视手术期间，靶向FXII似乎不足， 胸骨切开术和心脏操作增加循环组织因子水平。FXII还激活前激肽释放酶 (PKK)活性蛋白酶激肽释放酶（Kal）。Kal与多种炎症途径有关，包括 补体激活和缓激肽生成。Kal也被提议促进血栓形成 独立于FXI。已经提出FXII介导的PKK活化在治疗期间驱动炎症事件。 ECMO，但没有研究直接评估PKK在机械循环相关的作用 血栓炎来自PI实验室的数据表明，靶向PKK可以显著限制血栓形成， 体外膜肺氧合中的器官损伤拟议的研究将使用专门为此开发的新型基因靶向大鼠 建议，和尖端的药理学试剂，以测试以下假设：1）FXII促进ECMO 通过与FXI激活相关的独立机制， PKK的。2)FXI是机械循环环境中的一种上级抗血栓靶点， 循环TF水平，例如CPB期间存在的水平。3)FXII介导的PKK活化促进关键炎症反应 ECMO/CPB期间导致器官损伤的事件以及血栓栓塞并发症。4)组合 靶向FXI和FXII或FXI和PKK的策略提供了更好的保护， 器官损伤，而不是单独针对这些因素之一，而不会导致重大出血风险。拟议 研究将提供必要的见解耦合FXII的机械循环相关的机制 血栓炎性病理学所获得的知识将为未来的临床试验提供重要的信息， 以及靶向FXII和FXI的新兴药剂。拟议的研究也可能发现其他新的 目标（例如，PKK），以限制机械循环中血栓炎症驱动的发病率。

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.