IL-13 Regulation of Mucus Production

哮喘是一种慢性衰弱性疾病，尽管目前可用的治疗方法广泛使用，但近几十年来一直呈上升趋势。虽然哮喘的病因是未知的，我们已经表明，Th 2细胞衍生的细胞因子，IL-13，是哮喘发病机制的重要介质。尽管认识到这一点，但它诱导哮喘症状的机制仍然难以捉摸。为了阐明IL-13诱导细胞凋亡的机制， 哮喘表型，我们进行了小鼠肺中IL-13调节基因的微阵列分析。值得注意的是，我们发现IL-13显著抑制称为NKCC 1（Sc 112 a2）的Na+/K+/2Cl-共转运蛋白家族的成员的表达。NKCC 1以电中性方式将Na+、K+和Cl-离子移入和移出细胞。在其他系统中，NKCC 1已被证明在调节细胞体积、增殖和血管平滑肌收缩中是重要的。为了更好地了解NKCC 1的生理功能，我们 在NKCC 1缺陷型和野生型小鼠中检测对IL-13的应答。有趣的是，NKCC 1的遗传缺陷导致对IL-13给药的气道反应显著增强，特别是IL-13驱动的气道高反应性（AHR）和粘液产生。因此，我们假设IL-13至少部分通过调节肺中NKCC 1的表达诱导粘液细胞化生和AHR。因此，这一总体目标 该研究的目的是确定IL-13调节这种协同转运蛋白表达的机制，并确定其在粘液化生和AHR发展中的作用。具体目标是：1）为了明确IL-13调节NKCC 1表达的机制，我们将进行一系列研究，旨在确定IL-13对NKCC 1在气道中的时空表达的影响，并确定受体信号通路 2）为了确定IL-13抑制NKCC 1活性导致体外粘液产生的机制，我们将比较NKCC 1缺陷对粘液细胞变化的影响，（即杯状细胞数目、粘蛋白基因表达、粘液积累、粘液分泌）; 3）为了确定IL-13抑制NKCC 1表达导致体内AHR发展的机制，我们将检验仅上皮中的NKCC 1基因调控赋予哮喘易感性的假设。为此，我们将检查以下鼠品系中的过敏性表型：上皮特异性IL-4 Ra过表达转基因（Tgs）;诱导型上皮特异性NKCC 1 Tgs）。更好地了解这个家族的离子转运蛋白在哮喘病理生理学中的作用，应该指导开发新的策略来治疗这种使人衰弱的疾病。

Asthma is a chronic debilitating condition which has been on the rise in recent decades, despite widespread use of currently available therapies. Although the etiology of asthma is unknown, we have shown that the Th2 cell-derived cytokine, IL-13, is an important mediator of asthma pathogenesis. Despite this recognition, the mechanisms by which it induces the symptoms of asthma remain elusive. In an effort to elucidate the mechanisms by which IL-13 induces the asthma phenotype, we conducted a microarray analysis of IL-13-regulated genes in the murine lung. Notably, we found that IL-13 dramatically inhibits the expression of a member of a family of Na+/K+/2CI- co-transporters known as NKCC1 (Sc112a2). NKCC1 moves Na+, K+, and Cl- ions into and out of cells in an electrically neutral manner. In other systems, NKCC1 has been shown to be important in the regulation of cell volume, proliferation and vascular smooth muscle contraction. To gain a better understanding of the physiological functions of NKCC1, we have examined responses to IL-13 in NKCC1 deficient and wildtype mice. Interestingly, genetic deficiency in NKCC1 results in marked enhancement of airway responses to IL-13 administration, particularly IL-13 driven airway hyperresponsiveness (AHR) and mucus production. Thus, we hypothesize that IL-13 induces mucus cell metaplasia and AHR, at least in part, through its regulation of NKCC1 expression in the lung. Thus the overall goal of this proposal is to determine the mechanisms by which IL-13 regulates expression of this cotransporter and to determine its role in the development of mucus metaplasia and AHR. The specific aims are: 1) To determine the mechanisms by which IL-13 regulates NKCC1 expression, we will conduct a series of studies designed to determine the effects of IL-13 on the temporal and spatial expression of NKCC1 in the airways and to define the receptor signaling pathways mediating IL-13 suppression of NKCC1 expression in vivo and in vitro; 2) To determine the mechanisms by which IL-13 suppression of NKCC1 activity leads to mucus production in vitro, we will compare the consequences of NKCC1 deficiency on mucus cell changes (i.e. goblet cell numbers, mucin gene expression, mucus accumulation, mucus secretion) in primary epithelial cells derived from NKCC1 KO and wildtype mice; 3) To determine the mechanisms by which IL-13 suppression of NKCC1 expression leads to development of AHR in vivo, we will test the hypothesis that NKCC1 gene regulation in the epithelium alone confers susceptibility to asthma. To this end, we will examine the allergic phenotype in the following murine strains epithelial-specific IL-4Ra overexpressing transgenic (Tgs); an inducible epithelial specific NKCC1 Tgs). A better understanding of the role of this family of ion cotransporters in asthma pathophysiology should guide development of novel strategies for the treatment of this debilitating disease.