Role of STIM1 in E. coli Pneumonia

简介(申请人提供)：大肠埃希氏菌是院内肺炎的主要原因之一。此外，患有糖尿病、酒精中毒和慢性阻塞性肺病等基础疾病的患者也可能是社区获得性肺炎。虽然不适当的炎性宿主反应在肺炎的发病机制中起着核心作用，但这种疾病发展的确切分子机制仍然知之甚少。钙稳态的改变被认为在炎症中起着重要作用。虽然大多数免疫细胞使用的升高细胞内钙的主要机制是存储操作的钙内流(SOCE)，即内质网(ER)钙库的耗尽触发细胞外钙的内流，但SOCE激活的直接分子基础直到最近被确定为关键的内质网钙感受器(STIM1)才被发现。然而，STIM1和SOCE在体内炎症反应、感染免疫和其他免疫相关疾病中的意义仍然很大程度上尚不清楚。利用Cre重组酶-loxP系统，我们最近在髓系细胞中产生了编码STIM1基因的特异性缺失的小鼠(STIM1-/-)。我们的初步数据表明，与WT小鼠(STIM1+/+)相比，STIM1缺乏显著降低了大肠杆菌诱导的支气管肺泡灌洗液(BAL)中IL-6、KC、IL-1b和MCP-1的水平以及中性粒细胞在肺中的聚集。此外，大肠杆菌刺激的STIM1-/-小鼠表现出肺转录因子CCAAT/增强子结合蛋白(C/EBPS)活性显著降低(主要是C/EBP�)。我们进一步证明STIM1与免疫细胞中SOCE的重要钙通道Orai1和TRPC1相互作用。基于这些研究，我们推测STIM1通过与Orai1、TRPC1和其他信号分子相互作用，在肺部对大肠杆菌的炎症反应和宿主对大肠杆菌肺炎的防御中发挥重要的调节作用。因此，本探索性研究旨在明确STIM1在大肠杆菌诱导的肺泡炎中的作用及其潜在的分子机制。为了检验我们的假设，本文提出了两个具体目标。在第一个目标中，我们将确定STIM1在肺部对抗大肠杆菌感染中的作用。在第二个目标中，我们将阐明STIM1在大肠杆菌肺炎中发挥作用的分子机制。我们的研究结果有望为STIM1在肺部对细菌的炎症反应中的调节作用提供重要的新信息。这一知识将代表一种新的范例，用于探讨肺炎治疗的新治疗目标的开发。

DESCRIPTION (provided by applicant): Escherichia coli (E. coli) is one of the major causes of nosocomial pneumonia. Moreover, E. coli pneumonia may also be community-acquired in patients who have underlying disease such as diabetes mellitus, alcoholism, and chronic obstructive pulmonary disease. Although inappropriate inflammatory host responses play a central role in the pathogenesis of pneumonia, the precise molecular mechanisms underlying the development of this disorder remain poorly understood. Altered calcium homeostasis is considered to play an important role in inflammation. Although the predominant mechanisms to raise intracellular calcium used by most immune cells is store-operated Ca2+ entry (SOCE) whereby the depletion of endoplasmic reticulum (ER) Ca2+ stores triggers the influx of extracellular Ca2+, the direct molecular basis of SOCE activation was unknown until the recent identification of stromal interaction molecule 1 (STIM1) as the critical ER Ca2+ sensor. However, the significance of STIM1 and SOCE in in vivo inflammatory responses, immunity to infection, and other immune-related diseases remains largely unknown. Using the Cre recombinase-loxP system, we recently generated mice with specific deletion of the gene encoding STIM1 in myeloid cells (STIM1-/-). Our preliminary data indicate that STIM1 deficiency significantly reduced E. coli-induced IL-6, KC, IL-1b, and MCP-1 levels in bronchoalveolar lavage (BAL) fluids and neutrophil accumulation in the lung compared to WT mice (STIM1+/+). Furthermore, E. coli-stimulated STIM1-/- mice showed significantly reduced lung transcription factors CCAAT/enhancer-binding proteins (C/EBPs) activation (mainly C/EBP�). We further show that STIM1 interacts with Orai1 and TRPC1, important Ca2+ channels for SOCE in immune cells. Based on these studies, we hypothesize that STIM1 plays an important regulatory role in lung inflammatory responses to E. coli and host defense against E. coli pneumonia by interacting with Orai1, TRPC1, and other signaling molecules. Therefore, this exploratory study is designed to define the roles of STIM1 in E. coli- induced pulmonary alveolitis and the underlying molecular mechanisms. Two specific aims are proposed to test our hypothesis. In the first aim, we will determine the role of STIM1 in the lungs against E. coli infection. In the second aim, we will elucidate the molecular mechanisms of STIM1 function in the E. coli pneumonia. The results of our studies are expected to provide important novel information on the regulatory roles of STIM1 in the lung inflammatory responses to bacteria. This knowledge will represent a new paradigm for approaching the development of novel therapeutic targets for treatment of pneumonia.