Sufactant Protein-A and Lung Defense

描述(由申请人提供)：细菌性肺炎引起的肺部炎症过程在美国和其他国家造成了相当大的发病率和死亡率的临床负担。一些被认为是潜在的生物恐怖威胁的微生物会导致严重的肺部炎症。在之前的资助期间，使用转基因小鼠的研究表明，表面活性蛋白-A(SP-A)可以减少微生物和微生物产品引起的炎症。来自肺炎或囊性纤维化(CF)患者的研究表明，SP-A浓度降低，表明SP-A调节微生物引起的肺部炎症的程度。本申请的目的是确定SP-A调节肺炎性反应的机制。最近的研究表明，Toll样受体在诱导炎症反应中具有重要作用。TLR4是内毒素和革兰氏阴性菌的主要受体。内毒素与CD14结合，内毒素/CD14与MD-2/TLR4相互作用，形成细胞表面三组分受体复合体，传递细胞内信号，激活细胞因子和其他炎症调节因子。SP-A不与光滑形式的内毒素结合，但在体内和体外阻断光滑形式的内毒素诱导的细胞因子的产生。缺乏对平滑内毒素的结合表明，SP-A不能简单地隔离内毒素与TLR复合体的相互作用。TLR4、CD14和MD-2RNA存在于肺泡巨噬细胞和小鼠肺上皮细胞中，支持SP-A通过TLR-4成分减少平滑的内毒素信号而改变肺部炎症反应的中心假说。这一假说将通过在细胞转染中顺利诱导NF-kappaB的诱导或在小鼠的内毒素和革兰氏阴性菌感染模型中进行验证，以完成下列目标：(1)在体外将确定SP-A的结构和内毒素受体组分，它们在功能上相互作用而导致SP-A抑制内毒素介导的信号转导；(2)通过检测SP-A是否改变体外内毒素信号转导所需的TLR4组分之间的相互作用来确定SP-A抑制内毒素介导的信号转导的机制；以及(3)将确定体内SP-A抑制内毒素或革兰氏阴性细菌介导的信号转导所需的SP-A结构域。本申请旨在确定SP-A调节肺部炎症反应的新机制，目的是确定减轻肺部炎症的新方法。

DESCRIPTION (provided by applicant): Pulmonary inflammatory processes due to bacterial pneumonia impose a considerable clinical burden of morbidity and mortality in the US and other countries. A number of microbes considered as potential bioterrorist threats cause severe pulmonary inflammation. During the previous funding period, studies using transgenic mice, demonstrated that surfactant protein-A (SP-A) reduces inflammation caused by microbes and microbial products. Studies from patients with pneumonia or cystic fibrosis (CF) demonstrated reduced concentrations of SP-A suggesting that SP-A modulates the extent of microbial induced pulmonary inflammation. The goal of the present application is to determine mechanisms whereby SP-A regulates pulmonary inflammatory responses. Recent studies have demonstrated important roles for toll-like receptors (TLR) in inducing inflammatory responses. TLR4 is a major receptor for LPS and gram-negative bacteria. LPS binds to CD14 and LPS/CD14 interacts with MD-2/TLR4 forming a cell surface tripartite receptor complex that transduces intracellular signals leading to activation of cytokines and other inflammatory modulators. SP-A does not bind smooth forms of LPS but SP-A blocks smooth LPS induced cytokine production in vivo and in vitro. The lack of binding to smooth LPS suggests that SP-A cannot simply be sequestering LPS from interactions with the TLR complex. TLR4, CD14, and MD-2 RNA are present in alveolar macrophages and mouse lung epithelial cells supporting the central hypothesis that SP-A alters inflammatory responses in the lung by reducing smooth LPS signaling through TLR-4 components. This hypothesis will be tested using smooth LPS mediated induction of NF-kappaB in cell transfections or LPS and gram-negative infection in mouse models to complete the following aims: (1) The SP-A structures and LPS receptor components that functionally interact to cause SP-A inhibition of LPS mediated signaling will be identified in vitro; (2) Mechanisms by which SP-A inhibits LPS mediated signaling will be determined by testing if SP-A alters interactions between TLR4 components necessary for LPS signaling in vitro; and (3) Structural domains of SP-A required for SP-A inhibition of LPS or gram-negative bacterial mediated signaling in vivo will be identified. The present application seeks to identify novel mechanisms of SP-A regulation of pulmonary inflammatory responses with the goal of identifying novel approaches to reducing pulmonary inflammation.