Vitamin D and Innate Immunity in Respiratory Infections

描述（由申请人提供）：呼吸道上皮是抵御激发性病原微生物的第一道防线。这种防御的一个组成部分是抗菌肽的产生，如防御素和抗菌肽。我们研究的长期目标是了解宿主-病原体在气道上皮中的相互作用。鉴定一种可以通过转录机制增加气道抗菌能力的无毒药物可能对气道感染的治疗具有长远意义。为了实现这一目标，我们最近证明了一种抗菌肽，cathelicidin LL-37，可以通过激素活性形式的维生素D 1,25(OH)2D3诱导生长在气液界面（ALI）中的气道上皮细胞（AEC）。此外，我们观察到一种新的先天免疫受体，骨髓细胞触发受体（TREM-1）在AEC上的诱导。在TREM-1水平增加1.25 (OH)2D3后，该受体的激活导致先天免疫介质的刺激，包括-防御素。我们进一步确定了这些1,25(OH) 2d3调节的先天免疫基因启动子中的转录因子结合位点，这些基因可能是诱导所必需的。因此，我们发现了一种新的气道细胞先天免疫刺激方法。基于这些结果，我们假设1,25(OH)2D3可以增加气道上皮的抗菌和整体先天免疫反应。然而，为了解决这个假设，我们必须首先了解维生素D和气道先天免疫之间的关系。因此，我们在此提出一项探索性研究，以表征维生素D对先天免疫途径和气道先天免疫防御的影响。在特定的目的1中，我们将在体外描述基于tlr的先天免疫途径与调节LL-37和TREM-1表达的维生素D途径之间的交叉对话。在具体的目标2中，我们将通过表征导致气道上皮细胞中LL-37和TREM-1基因表达的途径和转录因子，确定先天免疫调节气道上皮细胞中维生素D调节途径的机制。在具体目的3中，我们将在气道感染小鼠模型中确定1,25(OH)2D3对先天免疫的影响，使用我们现有的经鼻接种肺炎链球菌的气道感染模型来量化1,25(OH)2D3对气道宿主防御的体内影响。由于小鼠cathelicidin不受维生素D的调节，我们将使用在其自身启动子控制下表达人类LL-37基因的人源化小鼠来研究1,25(OH)2D3在体内的作用。我们的三个目标的结果将为进一步深入分析它们所发挥的作用提供坚实的基础

DESCRIPTION (provided by applicant): The respiratory epithelium is the first line of defense against inspired pathogenic microorganisms. One component of this defense is the production of antimicrobial peptides such as ¿-defensins and cathelicidins. The long-range goal of our research has been to understand host-pathogen interactions in the airway epithelium. Identification of a non-toxic agent that could increase antibacterial capabilities of the airway through transcriptional mechanisms could have long-reaching implications for the treatment of airway infections. Toward this goal, we recently demonstrated that an antimicrobial peptide, the cathelicidin LL-37, can be induced in airway epithelial cells (AEC) grown in an air-liquid interfac (ALI) by the hormonally active form of vitamin D, 1,25(OH)2D3. In addition, we observed the induction of a novel innate immune receptor, Triggering Receptor Expressed on Myeloid cells (TREM-1) on AEC. After TREM-1 levels are increased by 1,25(OH)2D3, activation of this receptor results in stimulation of innate immune mediators, including ¿-defensins. We have further identified transcription factor binding sites in the promoter of these 1,25(OH)2D3-regulated innate immune genes that may be required for the induction. Thus we have uncovered a novel method for innate immune stimulation of airway cells. Based upon these results, we hypothesize that 1,25(OH)2D3 can increase the antibacterial and overall innate immune response of the airway epithelium. However, in order to address this hypothesis, we must first understand the relationship between vitamin D and innate immunity in the airway. Thus, we are proposing here an exploratory study to characterize the effect of vitamin D on innate immune pathways and on in the innate immune defense of the airway. In specific aim 1 we will characterize the cross- talk between the TLR-based innate immune pathways and the vitamin D pathways regulating LL-37 and TREM-1 expression in vitro. In specific aim 2, we will define the mechanism of innate immune regulation of the vitamin D regulatory pathway in airway epithelial cells through a characterization of the pathways and transcription factors leading to LL-37 and TREM-1 gene expression in airway epithelial cells. In specific aim 3 we will determine the effect of 1,25(OH)2D3 on innate immunity in a mouse model of airway infection, using our existing airway infection model of intranasal inoculation of Streptococcus pneumoniae to quantify the effect of 1,25(OH)2D3 on airway host defense in vivo. Since murine cathelicidin is not regulated by vitamin D, we will examine the effect of 1,25(OH)2D3 in vivo using a humanized mouse expressing the human LL-37 gene under the control of its own promoter. The results of our three aims will provide a solid foundation for further in-depth analysis of the roles played by these innate immune mediators in host defense of the airway, and of the potential for the development of 1,25(OH)2D3 treatment as a therapy for airway infections. This application is appropriate for the R21 mechanism because it involves considerable risk but may lead to a breakthrough in vitamin D and innate immunity that could have a major impact on research in the field of airway infections.