Cell Priming, Receptor Cross-Talk, and Acute Lung Injury

描述(由申请人提供)： 严重的创伤和出血使患者更容易受到第二种炎症刺激的影响，即所谓的“两击”模型。创伤后炎症可导致严重的多器官功能衰竭(MOF)和死亡。研究表明，由第一次撞击引起的细胞启动是细胞对第二次撞击增强反应的机制。急性肺损伤(ALL)是MOF的重要组成部分，常常是导致死亡的直接原因。中性粒细胞(PMN)在肺血管、间质和肺泡腔的聚集被认为是ALI的关键事件，并已成为各种预防策略的靶点。然而，启动PMN迁移的机制仍不清楚。内皮细胞通过表达细胞因子、趋化因子和黏附分子直接与PMN相互作用，从而在启动PMN迁移过程中发挥关键作用。我们已报道内皮细胞低水平表达Toll样受体(TLR)2，该受体是多种微生物产物的受体，UPS可通过TLR4信号上调TLR 2的表达，这提示了一种可诱导细胞对感染敏感的受体串扰机制。我们进一步证明，氧化剂可以放大内毒素诱导的内皮细胞中TLR2的表达，这在功能上与TLR2激动剂增加ICAM-1的表达和促进PMN的迁移有关。基于这些发现，我们假设：(I)肺内皮细胞启动导致创伤后PMN在肺内的迁移增强，(Ii)TLR2上调通过增加细胞对病原体的易感性而在内皮细胞启动中发挥作用，以及(Iii)失血/复苏诱导的氧化剂的产生有助于增强内皮细胞中TLR2的上调。我们将在三个相互关联的目标下进行这些假设：1)确定失血性休克对内毒素/TLR4调节肺和肺内皮细胞TLR2的影响；2)确定TLR2在失血性休克诱导的内皮细胞启动中的作用；以及3)确定TLR2在失血性休克后肺炎症启动中的作用。我们将使用体内、体外和体外模型来充分研究TLR2在休克诱导的细胞启动和肺损伤中的作用。从这些研究中获得的见解应该会显著提高我们对创伤后多器官功能衰竭中细胞启动的理解。

DESCRIPTION (provided by applicant): Severe trauma and hemorrhage renders the patient more susceptible to a second inflammatory stimulus, the so-called "two-hit" model. The post-trauma inflammation can lead to severe multi-organ failure (MOF) and death. Studies have suggested that cell priming caused by a first hit is the mechanism for enhanced response of the cell to a second hit. Acute lung injury (ALl) is an important part of the MOF, and often serves as a direct cause of death. The accumulation of polymorphonuclear neutrophils (PMN) in the lung vasculature, interstitium, and alveolar space is considered a critical event in ALI and has been the target of various preventative strategies. However, the mechanisms that prime PMN migration remain unclear. Endothelial cells play a critical role in initiating PMN migration through directly interacting with PMN by expression of cytokines, chemokines, and adhesion molecules. We have reported that endothelial cells express a low level of Toll-like receptor (TLR) 2, the receptor for a variety of microbial products, which could be up-regulated by UPS through TLR4 signaling, suggesting a receptor cross-talk mechanism of inducible cell sensitivity to infection. We have further shown that oxidants amplify LPS-induced TLR2 expression in endothelial cells and which are functionally associated with an increased ICAM-1 expression and enhanced PMN migration in response to TLR2 agonist. Based on the findings we hypothesize that: (I) pulmonary endothelial cell priming is responsible for the enhanced post-trauma PMN migration in the lungs, (II) TLR2 up-regulation serves a role in the endothelial cell priming through increasing cell susceptibility to pathogens, and (III) hemorrhage/ resuscitation-induced generation of oxidants contributes to enhanced TLR2 upregulation in the endothelial cells. We will pursue these hypotheses in three interrelated Aims: 1) to determine the effect of hemorrhagic shock on LPS/TLR4 regulation of TLR2 in the lung and pulmonary endothelial cells; 2) to determine the role of TLR2 in hemorrhagic shock-induced endothelial cell priming; and 3) to determine the role of TLR2 in priming for lung inflammation following hemorrhage shock. We will use in vivo, ex vivo, and in vitro models to fully address the role of TLR2 in shock-induced cell priming and lung injury. Insights gained from these studies should significantly enhance our understanding of cell priming in post-trauma MOF.