Fungal Exposure and the Respiratory Tract Microbiome

描述（由申请人提供）：呼吸系统是宿主-环境的中心界面，每天暴露于数十亿颗粒和病原体。气道粘液对于消除沉积的环境因子和通过粘液纤毛清除（MCC）限制病原体积累至关重要。在许多肺部疾病中，粘液的产生和组成发生了巨大的变化。最近的研究已经确定了哮喘和COPD患者肺微生物组的变化，但MCC功能改变与呼吸微生物组变化之间的直接联系尚未得到测试。在这项探索性拨款提案中，将确定真菌毒物暴露引起上呼吸道和下呼吸道微生物组变化的机制以及这些变化的功能后果。本研究的重点是气道粘液的主要大分子成分- MUC5AC和MUC5B基因编码的粘蛋白糖蛋白。最近对哮喘和COPD患者的研究表明，粘液产生的改变与MUC5AC（上升）和MUC5B（保持稳定表达或下降）的差异调节有关。为了研究粘蛋白是否决定了呼吸道微生物的多样性，我们最近培育了Muc5ac和Muc5b敲除小鼠。在没有炎症挑战的情况下，Muc5b（但不是Muc5ac）缺乏导致自发性致命感染，其特征是获得肺部金黄色葡萄球菌感染。因此，Muc5b对于控制肺内的稳态和病理微生物群至关重要。在这里，目的是实现RFA的主要目的-测试“环境暴露如何影响微生物组的组成和/或功能”-在呼吸道炎症的小鼠模型中。曲霉真菌暴露是哮喘加重和几种类型的过敏性肺炎（一种相关的职业性肺病）的主要原因。在初步研究中，暴露于气溶胶米曲霉提取物（AOE）的野生型小鼠表现出炎症，Muc5ac增加，Muc5b表达减少，与哮喘患者相似。因此，假设aoe诱导的呼吸道微生物组组成的变化依赖于Muc5b表达水平，这些变化影响疾病病理和对机会致病菌感染的易感性。为了验证这一点，野生型小鼠将暴露于

DESCRIPTION (provided by applicant): The respiratory system is a central host-environment interface that is exposed to billions of particles and pathogens daily. Airway mucus is critical fo eliminating deposited environmental agents and limiting pathogen accumulation through a process called mucociliary clearance (MCC). Mucus production and composition are dramatically altered in numerous lung diseases. Recent studies have identified changes in the lung microbiome in asthma and COPD, but direct links between altered MCC function and changes in the respiratory microbiome have not been tested. In this exploratory grant proposal, mechanisms by which fungal toxicant exposure elicits changes will be identified in the upper and lower respiratory tract microbiomes along with the functional consequences of these changes. This work focuses on the major macromolecular components of airway mucus - mucin glycoproteins encoded by the MUC5AC and MUC5B genes. Recent studies in patients with asthma and COPD show that alterations in mucus production are related to differential regulation of MUC5AC (which goes up) and MUC5B (which remains stably expressed or goes down). To address whether mucins determine respiratory microbial diversity, Muc5ac and Muc5b knockout mice were recently generated. In the absence of an inflammatory challenge, Muc5b (but not Muc5ac) deficiency causes spontaneous lethal infections marked by acquisition of pulmonary Staphylococcus aureus infection. Thus, Muc5b is essential for controlling homeostatic and pathological microbial populations in the lungs. Here, the intent is to accomplish the primary purpose of this RFA - to test "how environmental exposures impact the composition and/or function of the microbiome" - in mouse models of respiratory inflammation. Aspergillus fungal exposure is a major cause of asthma exacerbations and several types of hypersensitivity pneumonitis, a related occupational lung disease. In preliminary studies, wild type mice exposed to an aerosol Aspergillus oryzae extract (AOE) show inflammation, increased Muc5ac, and reduced Muc5b expression similar to that seen in humans with asthma. Thus, it is hypothesized that AOE-induced changes in respiratory microbiome composition are dependent upon Muc5b expression levels and that these changes affect disease pathology and susceptibility to opportunistic pathogen infection. To test this, wild type mice will be exposed to aerosolized AOE. Changes will be measured in the upper and lower airway microbiota, and we will assess changes in inflammation, histopathology, and susceptibility to S. aureus. These data will be compared to that seen in Muc5b deficient and Muc5b overexpressing mice. Collectively, these studies will be used to develop a framework for designing and analyzing subsequent investigations in mice and in humans. MUC5B expression varies significantly in humans, and common genetic polymorphisms significantly regulate its expression. In addition treatments such as inhaled hypertonic saline enhance MCC effectively. Thus, successful completion of the proposed studies may significantly impact human health in the near-term.