Understanding Severe Asthma Using an Experimental Model

描述(由申请人提供)：严重哮喘是一种难以通过皮质类固醇(CS)控制的疾病，它仍然是哮喘治疗的主要药物。这种对CS治疗反应的不同结果，即使是在高剂量口服或非肠道使用时，也表明这两类哮喘患者的炎症反应性质存在根本差异。为了了解促进CS难治性哮喘的机制和介质，我们开发了一种小鼠疾病模型，在该模型中，呼吸道炎症和CS无反应都模拟了人类严重哮喘的表型，包括高干扰素-γ/Th1、IL-27和IL-17反应。我们的模型包括将小鼠暴露于含有黏膜佐剂环二GMP(c-di-GMP)的过敏原(屋尘螨-hdm)，以促进混合粒细胞在呼吸道中的渗透，并诱导显著更高的干扰素-γ和IL-17反应。 小鼠肺引流淋巴结和肺组织的IL-13/IL-5反应低于HDM单独诱导的小鼠。在HDM+c-di-GMP暴露的小鼠中，给予CS地塞米松(Dex)，不能抑制干扰素-γ/IL-17/IL-13的反应或气道中性粒细胞的增多，但部分地减轻了嗜酸性粒细胞的增多。CS对这些小鼠的气道高反应性也只有部分减弱作用。总而言之，我们的数据引导我们假设：1)CS难治性哮喘是由高Th1反应引起的，通常伴随着促进呼吸道中性粒细胞增多的Th17反应。2)树突状细胞(DC)等天然细胞分泌的IL-27和IL-12(Th1)、IL-6和IL-23(Th17)等Th1和Th17细胞因子的增加是Th1和Th17应答增强的基础。3)转录因子IRF5参与M1巨噬细胞产生IL-6、IL-12和IL-23，转录因子STAT1位于IFN和IL-27下游，参与Th1和Th17的发育。CS难治性重症哮喘可能涉及干扰素-γ、IL-27和Th17型细胞因子在重症哮喘中的协同作用，这一观点在以往的研究中尚未得到认可或调查。为了解决我们的假设，我们将：目的1.研究Th1和Th17通路在促进以混合粒细胞呼吸道炎症为特征的CS难治性重症哮喘表型中的作用。目的2.探讨HDM和c-di-GMP通过对天然细胞的作用，诱导Th1和Th17细胞高应答的机制。目的3.明确IL-27的细胞来源及其在CS难治性重症哮喘表型发生和延续中的作用。小鼠模型与基因工程小鼠相结合，将使我们能够研究关键介质在促进严重哮喘表型中的作用。当新的治疗方法可用时，该模型将有助于测试它们。此外，这项研究产生的RNA测序数据将识别SA中的新网络，以便将来在实验模型和翻译研究中进行询问。

DESCRIPTION (provided by applicant): Severe asthma is a difficult disease to control by corticosteroids (CSs), which remain the mainstay of asthma therapy. This differential outcome in response to CS therapy, even when used at a high dose orally or parenterally, suggests a fundamental difference in the nature of the inflammatory response in the two subclasses of asthmatics. To understand the mechanisms and mediators that promote CS-refractory asthma, we have developed a mouse model of disease in which both airway inflammation and CS-unresponsiveness mimic the severe asthma phenotype in humans including high IFN-γ/Th1, IL-27 and IL-17 responses. Our model involves exposure of mice to an allergen (house dust mite-HDM) with a mucosal adjuvant, cyclic-di- GMP (c-di-GMP), to promote a mixed granulocytic infiltration in the airways with induction of significantly higher IFN-γ and IL-17 responses in the lung-draining lymph nodes and the lungs of the mice but a lower IL-13/IL-5 response compared to that induced by HDM alone. Administration of the CS, dexamethasone (Dex), in HDM+c-di-GMP-exposed mice did not subdue the IFN-γ/IL-17/IL-13 response or the airway neutrophilia but partially attenuated the eosinophilia. Airway hyperreactivity in these mice was also only partially attenuated by CS. Collectively, our data lead us to hypothesize that 1) CS-refractory asthma is orchestrated by a high Th1 response often accompanied by a Th17 response that promotes airway neutrophilia. 2) Increased production of key Th1- and Th17-skewing cytokines such as IL-27 and IL-12 (Th1) and IL-6 and IL-23 (Th17) from innate cells such as dendritic cells (DCs) underlies the heightened Th1 and Th17 response. 3) The transcription factors IRF5, recently implicated in IL-6, IL-12 and IL-23 production from M1 macrophages, and STAT1, downstream of IFNs and IL-27, are involved in driving Th1 and Th17 development. The idea that CS refractory severe asthma might involve collaboration between IFN-γ, IL-27 and Th17 cytokines in severe asthma has not been appreciated or investigated in prior studies. To address our hypotheses we will: Aim 1. Investigate the role of the Th1 and Th17 pathways in promoting the CS-refractory severe asthma phenotype characterized by mixed granulocytic airway inflammation. Aim 2. Determine the mechanisms by which high Th1 and Th17 responses are induced by exposure to HDM and c-di-GMP via effects on innate cells. Aim 3. Identify the cellular source and role of IL-27 in initiation and perpetuation of CS-refractory severe asthma phenotype. The mouse model in conjunction with genetically engineered mice will allow us to investigate the role of key mediators in promoting the severe asthma phenotype. The model will be useful to test novel therapeutic modalities as and when they become available. Additionally, RNA sequencing data generated from this study will identify novel networks in SA for future interrogation in the experimental model and in translational studies.