Prevention and management of perioperative pulmonary embolism

描述(由申请人提供)：肺栓塞(PE)是一种常见的手术后并发症，治疗方法不够理想。纤溶酶原激活剂(PA)在术后期间的使用仅限于次大块或大块PE的患者，否则有资格进行栓子切除，因为其缺乏已证实的临床有效性和出血风险。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绕过这个问题的新方法。我们最近的研究有助于解释我们所说的“肺纤溶悖论”。我们的发现暗示脂蛋白受体相关的激活 蛋白受体(LRP1)和N-甲基-D-天冬氨酸(NMDAR)受体(NMDAR)通过uPA(和tPA)破坏肺血管内皮细胞屏障功能，放松对血管张力的调节，抵消纤溶的有益益处。我们假设uPA信号通过LRP1在部分闭塞的缺氧血管中诱导血管收缩，同时在充分灌流的节段激活NMDAR，从而产生导致血管扩张的压倒一切的信号。这会将血液从未充分灌流的缺血节段分流，并加剧通风/灌流不匹配。幸运的是，我们已经成功地将有害的非纤溶血管活性与有益的纤溶活性分离开来，每个都是由不同的结构域介导的，这些结构域可以被特定的多肽和受体拮抗剂阻断，并被特定的uPA突变体所绕过。我们将阐明uPA激活的受体介导的破坏肺内皮屏障功能和增加血管紧张性的途径，并利用这些见解开发新的纤溶药物和递送系统，通过三个相互关联的目标用于在围手术期预防和管理PE：在目标1中，我们将通过评估体外和体内低氧和常氧条件下LRP和NMDAR的贡献来阐明uPA诱导的跨内皮自运输和肺血管收缩的机制，并评估新型“血管中性粒细胞”uPA变体的疗效。在目标2中，我们将评估亚大面积PE模型中血管活性、纤溶和临床结果之间的关系，以及“血管中性粒细胞”uPA变体的拟议增强疗效。在目标3中，我们将探索以RBC为靶点的血管中和物形成纤维蛋白通道的血栓预防潜力，这种通道允许红细胞在完全溶解血栓之前快速运输到挽救缺血组织，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、受体和抑制剂削弱了PAS的临床疗效；2)重新设计uPA可以绕过这个过程；3)描述了一种安全有效的血栓预防的新方法，我们希望这将改善PE的围术期预防和治疗。

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.