Immune Regulation of Cysteinyl Leukotriene Biosynthesis

描述(申请人提供)：肥大细胞(MC)通过产生二十烷基类化合物，特别是半胱氨酰白三烯(CysLts)和前列腺素(PG)D2，对天然刺激或高亲和力IgE受体(FceRI)的激活做出反应，与哮喘的炎症过程直接相关。除了激活MC的能力外，我们的初步研究表明，肽聚糖(PGN)是一种激活Toll样受体(TLR)-2的先天免疫刺激，它还可以诱导小鼠骨髓来源的MC表达LTC4合成酶(LTC4S)。用PGN启动mBMMCs，可增加其在离子载体刺激和FceRI交联时产生LTC4的能力。LTC4S的表达也被适应性免疫刺激白介素4上调。此外，在IL-4存在下，PGN启动对LTC4S表达的影响是相加/协同增强的。由于CysLTs在哮喘的发病机制中起着重要作用，我们的结果可能解释了观察到的由微生物或病毒感染导致的哮喘恶化。由于TLR激活了NF-β，而IL-4激活了信号转导转录激活子(STAT)6，我们假设：1)转录因子STAT6和NF-β通过重叠的STAT6/NF-βB位点共同调控LTC4S基因的转录(S)；2)微生物或病毒感染通过TLR信号通路激活固有免疫系统，使细胞LTC4S的表达高于IL-4的获得性免疫激活的最大效应，从而加重哮喘。因此，我们提出以下具体目标：1)检测不同的TLR激动剂对其增加LTC4S表达能力的影响，以及它们与IL-4的联合作用以及核因子-B转录因子的作用；2)确定IL-4和PGN激活MBMMC共同增强LTC4S表达的机制；3)阐明IL-4和TLR信号在抗原激发的肺部炎症反应和对乙酰甲胆碱的气道反应性中的协同作用。

DESCRIPTION (provided by applicant): Mast cells (MCs) respond to activation by innate stimuli or cross linking of the high-affinity receptor for IgE (FceRI) by generating eicosanoids, particularly the cysteinyl leukotrienes (cysLTs) and prostaglandin (PG) D2, providing a direct link to the inflammatory processes in bronchial asthma. In addition to its ability to activate MC, our preliminary studies have now revealed that peptidoglycan (PGN), an innate immune stimulus which activates toll-like receptor (TLR)-2, can also induce the expression of LTC4 synthase (LTC4S) by mouse bone marrow-derived MCs (mBMMCs). Priming of mBMMCs with PGN increases their capacity to generate LTC4 upon ionophore stimulation and upon cross-linking of FceRI. LTC4S expression is also upregulated by an adaptive immune stimulus, interleukin (IL)-4. Moreover, the effect of PGN priming on LTC4S expression is additively/synergistically increased in the presence of IL-4. Because cysLTs play an important role in the pathogenesis of bronchial asthma, our results may explain the observed exacerbation of asthma by microbial or viral infection. Because TLR activates NF-?B and IL-4 activates signal transducer activator of transcription (STAT) 6, we hypothesize that 1) there is cooperation between the transcription factors STAT6 and NF-?B in regulating the transcription of LTC4S gene through the overlapping STAT6/NF-?B site(s), and 2) that activation of innate immune system by microbial or viral infections by TLR signaling pathways, aggravates bronchial asthma through an increase in cellular LTC4S expression above the maximal effect of adaptive immune activation by IL-4. We therefore propose the following Specific Aims: 1) To examine the effect of various TLR agonists on their ability to increase LTC4S expression, their effect in combination with IL-4 and the role of NF-?B transcription factor; 2) To determine the mechanism of additive enhancement of LTC4S expression by IL-4 and PGN priming of mBMMC; and 3) To elucidate synergistic effects of IL-4 and TLR signaling in vivo on the pulmonary inflammatory response to antigen challenge and on airway reactivity to methacholine in surrogate mouse models of allergen induced airway disease.