Prevention and management of perioperative pulmonary embolism

描述（由申请人提供）：肺栓塞（PE）是一种常见的术后并发症，其治疗效果欠佳。术后使用纤溶酶原激活剂（PA）仅限于次大块或大块PE患者，否则由于其缺乏经证实的临床有效性和出血风险而适合进行栓子切除术。迫切需要更好地理解为什么PE的裂解不能产生更好的结果和新的手段来规避这个问题。我们最近的研究有助于解释我们所说的“肺纤维蛋白溶解悖论”。我们的研究结果暗示了脂蛋白受体相关的激活 蛋白受体（LRP 1）和N-甲基-D-天冬氨酸（NMDA）受体（NMDAR）在肺血管系统中通过uPA（和tPA）的作用，uPA（和tPA）破坏肺动脉EC屏障功能并使血管张力失调，抵消纤维蛋白溶解的有益益处。我们假设uPA信号通过LRP 1诱导部分闭塞缺氧血管的血管收缩，同时激活灌注良好的节段中的NMDAR，这产生了导致血管舒张的压倒性信号。这将血液从灌注不足的缺血节段转移，并加剧通气/灌注不匹配。幸运的是，我们已经成功地将uPA的有害的非纤维蛋白溶解性血管活性作用与有益的纤维蛋白溶解活性分离，因此每一种都是由不同的结构域介导的，所述结构域可以被特定的肽和受体拮抗剂阻断，并且被特定的uPA突变体绕过。我们将阐明由uPA激活的受体介导的途径，这些途径破坏肺内皮屏障功能并增加血管张力，并利用这些见解开发具有更大获益风险比的新型纤溶药物和递送系统，用于通过三个相互关联的目的预防和管理围手术期PE：在目标1中，我们将阐明uPA诱导的跨内皮自我调节的机制，通过评估LRP和NMDAR在体外和体内缺氧与常氧条件下的贡献，新型“血管中性”uPA变体的功效。在目标2中，我们将评估亚大块PE模型中血管活性、纤维蛋白溶解和临床结果之间的关系，以及“血管中性”uPA变体的拟议增强有效性。在目标3中，我们将探索RBC靶向血管中性uPA的血栓预防潜力，这些uPA形成纤维蛋白内通道，允许红细胞在完全凝块溶解之前快速转运以挽救缺血组织，而不影响术后止血凝块。因此，我们的研究具有直接的翻译相关性，因为它们：1）确定了一类新的受体、激动剂、受体和抑制剂，这些受体、激动剂、受体和抑制剂会损害PA的临床疗效，2）通过重新设计uPA可以绕过这一过程，3）描述了一种安全有效的血栓预防新方法，我们希望这将改善PE的围手术期预防和治疗。

DESCRIPTION (provided by applicant): Pulmonary embolism (PE) is a common post-surgical complication for which management is suboptimal. Use of plasminogen activators (PA) in the post-operative period is restricted to patients with submassive or massive PE otherwise eligible for embolectomy because of its lack of proven clinical effectiveness and risk of hemorrhage. There is a pressing need to better understand why lysis of PE fails to generate better outcomes and new means to circumvent this problem. Our recent studies help to explain what we term the "pulmonary fibrinolytic paradox". Our findings implicate activation of lipoprotein receptor-related protein receptor (LRP1) and N-methyl-D-aspartate (NMDA) receptors (NMDARs) in the pulmonary vasculature by uPA (and tPA) which disrupts pulmonary arterial EC barrier function and deregulates vascular tone, offsetting the salutary benefits of fibrinolysis. We hypothesize that uPA signals through LRP1 to induce vasoconstriction in partially occluded hypoxic vessels, while activating NMDARs in well-perfused segments, which generates an overriding signal that leads to vasodilation. This diverts blood from underperfused ischemic segments and exacerbates ventilation/perfusion mismatch. Fortunately, we have successfully segregated the deleterious non-fibrinolytic vasoactive effects from the salutary fibrinolytic activity of uPA, sho each is mediated by distinct domains that can be blocked by specific peptides and receptor antagonists and bypassed with specific uPA mutants. We will elucidate the receptor-mediated pathways activated by uPA that disrupt pulmonary endothelial barrier function and increase vascular tone and use these insights to develop novel fibrinolytics and delivery systems with a greater benefit to risk ratio for use to prevent and manage PE in the perioperative period through three interrelated Aims: In Aim 1, we will delineate the mechanism of uPA-induced transendothelial self-transport and pulmonary vasoconstriction by assessing of contributions of LRP and NMDAR under hypoxic vs normoxic conditions in vitro and in vivo and assess the efficacy of novel "vasoneutral" uPA variants. In Aim 2, we will assess the relationship between vasoactivity, fibrinolysis and clinical outcome in a model of sub-massive PE and the proposed enhanced effectiveness of "vasoneutral" uPA variants. In Aim 3, we will explore the thromboprophylactic potential of RBC-targeted vasoneutral uPAs that form intrafibrin channels that permit rapid transport of erythrocytes to salvage ischemic tissues prior to complete clot lysi without affecting post-operative hemostatic clots. Thus, our studies are of direct translational relevance because they: 1) identify a novel class of receptors, agonists, receptors and inhibitors that impair the clinical efficacy of PAs, 2) a process that can be bypassed by re-engineering uPA, and 3) describe a new approach to safe and effective thromboprophylaxis that we hope will improve perioperative prevention and treatment of PE.