Identification of a Damaging Subset of Neutrophils that Arises in Septic Patients

摘要： 脓毒症是一种“由于宿主对感染的反应失调而导致的危及生命的器官功能障碍”。 中性粒细胞在脓毒症期间变得过度活跃，并在很大程度上导致了发病率和死亡率。 与这种疾病有关。然而，中性粒细胞的抗菌功能提供了好处， 败血症患者的整个中性粒细胞种群的耗尽将是免疫抑制。 中性粒细胞的异质性最近被描述为包括癌症和狼疮在内的疾病状态。我们的 实验室已经发现存在少量过度表达中性粒细胞的血液。 ICU患者和脓毒症实验动物整合素VLA3(CD49c/CD29；a3b1)的表达我们已经展示了 中性粒细胞VLA3的阻断或基因耗尽在脓毒症小鼠中具有生存优势。这些发现 表明选择性去除VLA3高亚群可改善预后，而不损害先天宿主 对感染的防御。在人类中，败血症患者的中性粒细胞表现出明显的损伤 VLA3阻断可阻断血管内皮细胞的屏障功能。这表明，主要的 VLA3高表达细胞对败血症宿主的损伤靶点是血管系统。此外，初步证据还显示， 研究表明，中性粒细胞VLA3升高的败血症患者在疾病后期死亡率增加 与血液中未显示VLA3高细胞的患者相比。最重要的假设是 在这项提议中测试的是一种独特的、高度炎症和破坏性的血液中性粒细胞亚群， 它们表达高水平的VLA3，出现在ICU脓毒症患者的循环中。它是 进一步假设，循环中的VLA3高中性粒细胞的存在预测了疾病的严重程度 由临床评分确定，并且VLA3代表了减轻炎症的可用药靶点 对败血症患者的损害，同时避免明显的免疫抑制。提出了三个具体的目标进行测试 这些假设。目标1将确定VLA3表达和外周血细胞激活之间的相关性 败血症ICU患者血液中性粒细胞与病情严重程度的关系。目标2将使用人类细胞和多光子 对脓毒症小鼠进行成像以验证VLA3高中性粒细胞构成高炎症亚群的假说 这会导致血管损伤和毛细血管渗漏。目标3将表征VLA3高水平和VLA3低水平的中性粒细胞 亚组并检查它们损害内皮屏障功能的机制。加在一起， 这项建议解决了有关失调的宿主反应如何威胁患者生存的机制 并提供了一种分子靶点，用于抑制高炎症反应的破坏性手臂，同时 保留了免疫防御的有益方面。

ABSTRACT: Sepsis is a “life-threatening organ dysfunction caused by a dysregulated host response to infection”. Neutrophils become hyperactive during sepsis and they mediate much of the morbidity and mortality associated with the disease. However the antimicrobial function of neutrophils provides benefit such that depletion of the entire population of neutrophils in the septic patient would be immunosuppressive. Heterogeneity of neutrophils has recently been described in disease states including cancer and lupus. Our laboratories have discovered the presence of a small population of bloodstream neutrophils that overexpress the integrin VLA3 (CD49c/CD29; a3b1) in ICU patients and experimental animals with sepsis. We have shown that blockade or genetic depletion of neutrophil VLA3 has a survival advantage in septic mice. These findings indicate that selective removal of the VLA3high subset improves outcome without impairment of innate host defense against infection. In humans, neutrophils from septic patients demonstrate pronounced damage to the barrier function of endothelial cells in vitro which is prevented by VLA3 blocking. This suggests that the primary target of damage to the septic host by VLA3high cells is the vasculature. In addition, preliminary evidence also shows that septic patients that have VLA3high neutrophils late into the disease have increased mortality as compared to patients who do not show VLA3high cells in their blood. The overarching hypothesis to be tested in this proposal is that a distinct, hyperinflammatory and damaging subset of blood neutrophils, which express high levels of VLA3, arises in the circulation of ICU patients with sepsis. It is hypothesized further that the presence of circulating VLA3high neutrophils predicts severity of the disease as determined by clinical scoring, and that VLA3 represents a druggable target for attenuation of inflammatory damage to the septic patient while avoiding overt immunosuppression. Three specific aims are put forth to test these hypotheses. Aim 1 will determine the correlation between VLA3 expression and activation on peripheral blood neutrophils and illness severity in septic ICU patients. Aim 2 will use human cells and multiphoton imaging of septic mice to test the hypothesis that VLA3high neutrophils comprise a hyperinflammatory subset that causes vascular damage and capillary leak. Aim 3 will characterize the VLA3high and VLA3low neutrophil subsets and examine the mechanisms through which they impair endothelial barrier function. Taken together, this proposal addresses mechanisms regarding how the dysregulated host response threatens patient survival and offers a molecular target for dampening the destructive arms of the hyperinflammatory response while preserving the beneficial aspects of immune defense.