Translational Regulation in Bronchial Epithelial Cells

支气管呼吸道的上皮细胞直接暴露在环境中，是第一个 防止空气中的颗粒物、过敏原和传染病的防线。在过敏期间 呼吸道炎症上皮细胞既是产生介质的来源，也是 重塑过程。因此，支气管上皮细胞不仅在维持肺功能方面起着关键作用。 呼吸道的理化动态平衡，但也在呼吸道疾病的发病机制中。然而， 对介体、效应和重塑基因的转录后调控知之甚少 炎症反应过程中这些细胞的表达。使用两种体外细胞模型和一种 对于过敏性呼吸道炎症的活体小鼠模型，我们的初步研究支持以下模型： 在IL-4/肿瘤坏死因子的刺激下，转录激活导致炎症介质的流入 MRNA进入细胞质，在那里释放microRNA(MiRNA)介导的翻译抑制， 整体翻译增加，P-小体(用于储存和/或降解的细胞质结构域 翻译抑制的mRNAs)分解。这些协同的转录后活动有助于 该细胞处理将炎症介质mRNAs转换为蛋白质的快速需求。在.之后 持续暴露于IL-4/肿瘤坏死因子，Hur易位，一种富含AU的元素(ARE)结合蛋白， 从细胞核到细胞质是在激活的支气管上皮细胞中被激发的。然后，HUR将 通过细胞质中含有ARE的mRNAs编码炎症介质来下调其 翻译，从而抑制炎症反应。以下具体目标旨在 测试这个模型：1)阐明改变细胞功能的分子和生化机制 MiR-155，一种与免疫密切相关的miRNA，在激活的支气管上皮细胞中表达，并定义 MiR-155在调节支气管上皮细胞炎症介质基因表达中的作用；2) 确定P小体减少是否是激活的支气管上皮细胞的标志，以及如何 P小体组装和拆解改变对支气管炎性反应的影响 3)确定HUR如何下调炎症介质的表达 活化的支气管上皮细胞中单核细胞趋化蛋白-1等分子及其对HUR表达的影响 支气管上皮调节过敏性呼吸道炎症。拟议的研究将提供 对支气管上皮转录后机制的重要机械学见解 调节其炎症反应的细胞，从而导致开发新的治疗方法 减轻与哮喘等慢性呼吸道疾病相关的呼吸道炎症的方法 和慢性阻塞性肺疾病(COPD)。

Epithelial cells of the bronchial airways are directly exposed to the environment and are the first line of defense against airborne particulate matter, allergens and infectious agents. During allergic airway inflammation the epithelium is both a source of mediator production as well as a target of remodeling processes. Thus, bronchial epithelial cells play a critical role not only in the maintenance of physico-chemical homoeostasis of the airways but also in the pathogenesis of airway diseases. Yet, little is known about the post-transcriptional regulation of mediator, effector and remodeling gene expression in these cells during the inflammatory response. Using two in vitro cell models and an in vivo mouse model for allergic airway inflammation, our preliminary studies support the following model: Upon IL-4/TNF-α stimulation, transcriptional activation results in an influx of inflammatory mediator mRNAs into the cytoplasm, where microRNA (miRNA)-mediated translation repression is released, global translation increases, and P-bodies (cytoplasmic domains for storage and/or degradation of translationally repressed mRNAs) disassembled. These concerted post-transcriptional activities help the cell deal with a rapid demand for translating inflammatory mediator mRNAs into proteins. After a persistent exposure to IL-4/TNF-α, translocation of HuR, an AU-rich element (ARE) binding protein, from the nucleus to the cytoplasm is elicited in activated bronchial epithelial cells. HuR then associates with cytoplasmic ARE-containing mRNAs coding for inflammatory mediators to down-regulate their translation, thereby dampening the inflammatory response. The following specific aims are designed to test this model: 1) To elucidate the molecular and biochemical mechanisms that alter the function of miR-155, an miRNA closely linked to immunity, in activated bronchial epithelial cells and to define the role of miR-155 in regulating inflammatory mediator gene expression in bronchial epithelial cells; 2) To determine whether a reduction in P-bodies is a hallmark of activated bronchial epithelial cells and how alteration of P-body assembly and disassembly influences the inflammatory responses in bronchial epithelial cells; and 3) To determine how HuR down-regulates the expression of inflammatory mediator molecules such as MCP-1 in activated bronchial epithelial cells and how altering HuR expression in bronchial epithelium modulates allergic airway inflammation. The proposed studies will provide important mechanistic insights into the post-transcriptional mechanisms operating in bronchial epithelial cells to regulate their inflammatory responses, thereby leading to the development of new therapeutic approaches to alleviate airway inflammation associated with chronic airway diseases such as asthma and chronic obstructive pulmonary diseases (COPD).