Claudin-18 deficiency in the pathogenesis of asthma

描述(由申请人提供)：呼吸道上皮物理屏障的功能障碍可能导致哮喘的发展和疾病的进展。哮喘上皮屏障功能障碍的本质和机制尚不完全清楚。这在一定程度上与目前对呼吸道上皮紧密连接的了解有限有关。最近的发现突出了紧密连接结构和功能的多样性，并明确了紧密连接claudin蛋白的组织特异性差异解释了人体不同组织中上皮屏障特性的差异。这项提案旨在为 首次发现了唯一的肺特异性紧密连接蛋白claudin-18在呼吸道功能异常和哮喘中的作用。我们发现，与健康对照组相比，哮喘患者呼吸道上皮细胞中Claudin-18的表达存在缺陷。此外，随着类固醇治疗的开始，未经治疗的哮喘患者显示出呼吸道上皮细胞claudin-18的表达增加。与此观察一致的是，我们新产生的Claudin-18基因敲除小鼠表现出对抗原致敏的显著敏感性和哮喘的许多特征。由于claudin-18基因敲除小鼠的上皮通透性增加，而claudin-18基因敲除导致培养的呼吸道细胞通透性增加，这种蛋白可能是呼吸道屏障的关键组成部分。Claudin-18的缺失可能会导致抗原暴露和免疫激活增加。对基因敲除小鼠的研究将使我们能够解决上皮屏障缺陷是哮喘严重程度的主要因素这一假设。重要的是，我们还发现 IL-13诱导原代人呼吸道上皮细胞Claudin-18的特异性降低。因此，IL-13对Claudin-18的特异性丢失可能是哮喘上皮屏障缺陷的原因之一。我们将研究Claudin-18维持呼吸道上皮屏障功能的作用，并确定Claudin-18的丢失是否足以增加气道上皮对环境抗原的渗透性，并在曲霉致敏的小鼠模型中诱导更严重的哮喘表型。在气液界面原代培养人呼吸道上皮细胞的细胞培养研究中，我们还将研究IL-13介导的Claudin-18减少的机制，以及Claudin-18对呼吸道上皮通透性屏障的特殊贡献。在使用人类样本和加州大学旧金山分校呼吸道组织库收集的临床数据进行的翻译研究中，我们将调查有更严重疾病的哮喘患者的claudin-18水平较低的假设，并确定claudin-18缺乏是否与哮喘Th2表型有关。 公共卫生相关性：拟议的工作将检查呼吸道上皮屏障功能障碍对哮喘的发展和哮喘严重程度的贡献。具体地说，哮喘患者被发现缺乏肺特异的紧密连接蛋白claudin-18.1。我们将研究炎症如何降低这种蛋白的水平，以及Claudin-18.1缺乏在哮喘发展中的后果，以确定未来针对这一途径的新疗法是否可能成功。

DESCRIPTION (provided by applicant): Dysfunction of the physical barrier of the airway epithelium may contribute to the development of asthma and to disease progression. The nature and mechanisms for epithelial barrier dysfunction in asthma are incompletely understood. This is in part related to the current limited understanding epithelial tight junctions in the airways. Recent discoveries highlight the diversity of tight junction structure and function, and it is clea that tissue-specific differences in tight junction claudin proteins account for differences in epithelial barrier properties in the various tissues of the body. This proposal seeks to define for the first time the role of claudin- 18, the only lung-specific tight junction protein, in airway barier function and asthma. We have found that asthmatics have a deficiency in claudin-18 in the airway epithelium compared with healthy controls. Moreover, untreated asthmatics show an increase in airway epithelial claudin-18 expression with the initiation of steroid treatment. Consistent with this observation, our newly generated claudin-18 knock out mice show a marked susceptibility to antigen sensitization and many features of asthma. Because claudin-18 knock out mice have increased epithelial permeability and claudin-18 knock down results in increased permeability in cultured airway cells, this protein may be a critical component of the airway barrier. Loss of claudin-18 may result in increased antigen exposure and immune activation. Studies in the knock out mouse will allow us to address the hypothesis that an epithelial barrier defect is a primary contributor asthma severity. Importantly, we have also found that IL-13 induces a specific decrease in claudin-18 in primary human airway epithelial cells. Therefore, the specific loss of claudin-18 in response to IL-13 may contribute to epithelial barrie defects in asthma. We will examine the role of claudin-18 maintaining airway epithelial barrier function and determine if the loss of claudin-18 is sufficient to increase airway epithelial permeability to environmental antigen and induce a more severe asthma phenotype in the mouse model of aspergillus sensitization. In cell culture studies using primary human airway epithelial cells grown on an air-liquid interface, we will also investigate the mechanisms for the IL-13-mediated decrease in claudin-18, and the specific contribution of claudin-18 to the airway epithelial permeability barrier. In translational studies using human samples and clinical data collected by the UCSF Airway Tissue Bank, we will investigate the hypothesis that asthmatics with more severe disease have lower levels of claudin-18 and determine if claudin-18 deficiency is associated with asthma Th2 phenotype. PUBLIC HEALTH RELEVANCE: The proposed work will examine the contribution of airway epithelial barrier dysfunction to the development of asthma and asthma severity. Specifically, asthmatic subjects have been found to be deficient in the lung- specific tight junction protein claudin-18.1. We will examine how inflammation reduces the levels of this protein and the consequences of claudin-18.1 deficiency in the development of asthma to determine if future novel therapies targeting this pathway could be successful.