Mechanism of Activated Protein C Action in Sepsis Therapy

描述(申请人提供)：脓毒症是一种全身炎症宿主对微生物感染的反应，严重脓毒症和感染性休克患者的死亡率分别达到30%至70%。重组活化蛋白C(APC)是第一种，也是迄今为止唯一一种可以降低严重脓毒症患者死亡率的药物，但可能导致严重出血，对儿童和轻度脓毒症患者似乎缺乏疗效。APC在患者中的治疗效果的调节机制，以及APC治疗局限性的原因大多不清楚。目前的建议使用细菌败血症的小鼠模型、重组APC的突变和转基因小鼠品系来解决APC功能在治疗脓毒症中的关键方面。初步数据表明，目前临床剂量所基于的APC的抗凝血活性可能不仅会增加严重出血的风险，而且还会损害纤维蛋白依赖的细菌病原体的清除，从而降低APC治疗的有效性。相反，APC通过受体EPCR和PAR1的细胞信号活性似乎是APC治疗降低脓毒症死亡率的主要机制。因此，与正常的APC相比，选择性减少抗凝剂但信号活性正常的重组APC变体在脓毒症小鼠模型中显示出显著的疗效。拟议的实验将(AIM 1)证明APC的抗凝血活性对抗细菌宿主防御的有害影响并揭示其潜在的分子机制；以及(AIM 2)精确定位APC信号活性靶向的关键受体和细胞成分以降低脓毒症死亡率，以及(AIM 3)首次提供证据表明侵袭剂量具有选择性降低抗凝活性的重组APC变体是否有望提高APC治疗的整体有效性和安全性。公共卫生相关性：仅在美国，微生物感染后的严重败血症每年影响超过70万名患者，占所有原因死亡的约9%。重组活化蛋白C(APC)是迄今为止唯一一种可降低严重脓毒症患者绝对死亡率(~6%)的脓毒症药物，但可能导致严重出血，对儿童和轻度脓毒症患者缺乏疗效。我们将研究选择性地结合关键分子和细胞靶点以促进生存，但没有正常APC的有害副作用的新型APC变体是否可以显著提高APC治疗的疗效。

DESCRIPTION (provided by applicant): Sepsis is a systemic inflammatory host response to microbial infection, with mortality of patients with severe sepsis and septic shock reaching 30% to 70%, respectively. Recombinant activated protein C (APC) is the first, and as yet only drug demonstrated to reduce mortality of patients with severe sepsis, but may cause severe bleeding, and appears to lack efficacy in children and in patients with less than severe sepsis. The mechanisms mediating the therapeutic efficacy of APC in patients, and the reasons for the limitations of APC therapy are largely unknown. The current proposal employs murine models of bacterial sepsis, mutagenesis of recombinant APC, and transgenic mouse strains to address critical aspects of APC function in the treatment of sepsis. Preliminary data suggest the working hypothesis that the anticoagulant activity of APC, on which current clinical dosing is based, may not only increase the risk of severe bleeding, but also impair the fibrin-dependent clearance of bacterial pathogens and thereby diminish the efficacy of APC therapy. In contrast, the cell signaling activity of APC via the receptors EPCR and PAR1 appears to be the predominant mechanism underlying sepsis mortality reduction by APC therapy. Accordingly, recombinant APC variants with selectively reduced anticoagulant, but normal signaling activity exhibit a striking gain of efficacy in murine models of sepsis, as compared to normal APC. Proposed experiments will (AIM 1) demonstrate the harmful effects of APC's anticoagulant activity on the antibacterial host defense and reveal the underlying molecular mechanism; and (AIM 2) pinpoint the critical receptors and cellular components targeted by APC's signaling activity to reduce sepsis mortality, and (AIM 3) provide first evidence whether aggressive dosing of recombinant APC variants with selectively reduced anticoagulant activity may be expected to improve the overall efficacy and safety of APC therapy. PUBLIC HEALTH RELEVANCE: Severe sepsis after microbial infection affects in excess of 700,000 patients annually in the US alone, and is responsible for ~9% of deaths from all causes. Recombinant activated protein C (APC) is the as yet only available sepsis drug shown to reduce (by ~6%) absolute mortality of patients with severe sepsis, but may cause severe bleeding, and lacks efficacy in children and in patients with less than severe sepsis. We will investigate whether novel APC variants that selectively engage the critical molecular and cellular targets to promote survival, but lack the harmful side effects of normal APC can significantly improve the efficacy of APC therapy.