Mechanisms of IL-17A-mediated enhancement of asthma severity

描述（由申请人提供）：哮喘是一种慢性肺部炎症性疾病，目前全球有超过3亿人患有哮喘。虽然哮喘是由对过敏原的过度Th2免疫反应介导的，但最近的证据表明，Th17细胞因子IL-17A的产生与更严重疾病的发展有关。虽然严重哮喘患者在急性发作后发病或死亡的风险最大，并且对轻度疾病患者非常有效的治疗可能难以治愈，但IL-17A促进严重过敏性哮喘发展的分子机制尚不明确。更深入地了解IL-17A促进严重哮喘的分子机制，将为目前治疗不足的人群提供额外的治疗靶点。通过小鼠模型，我们提供了证据，证明严重哮喘与IL-17A产生增加有关，并与il - 17ra表达增强和IL-17A反应性升高相结合。这些IL-17A产生和反应性的改变加剧了il -13驱动的STAT6激活、基因表达和气道反应。我们的初步数据表明，在小鼠细胞中，il - 17a介导的il -13驱动反应的增强通过两种非相互独立的机制发生；1)通过引起IL-13R -1和TRAF3复合物的解解，这通常会限制IL-13驱动的STAT6磷酸化；2)通过激活转录因子（NF- B、C/EBP和C/EBP），从而增强IL-13/STAT6驱动基因的表达。虽然本文提出的初步研究也表明，类似的机制可能在人类细胞系中起作用，但我们在小鼠模型中观察到的结果在多大程度上适用于患有严重哮喘的人类尚不清楚。提出了三个特定的目标来确定IL-17A通过分子机制提高小鼠和人类哮喘的严重程度。特异性Aim 1将确定在IL- 17a存在下观察到的IL-13驱动的STAT6磷酸化和AHR的增加是否是IL- 13R α 1:TRAF3复合物在IL- 17a信号启动后解解的结果。特异性目标2将分析IL- 17a驱动的NF- B（典型的与非典型的）、C/EBP和C/EBP在体外和体内IL-13/IL- 17a协同作用中的重要性。特异性Aim 3将直接测试IL-13和IL-17A之间是否在哮喘相关的原代人细胞中观察到类似的协同相互作用。此外，我们将确定儿童的严重哮喘是否与IL-17A产生、il - 17ra表达和IL-17A反应性增加有关，就像在小鼠中一样。总的来说，本申请中提出的研究将使我们超越过敏性哮喘的“Th2范式”，开始表征th17产品引发严重过敏性哮喘发展的机制，并确定类似的机制是否可能在小鼠和人类中起作用。更好地了解这些机制将使我们能够为严重哮喘患者确定新的治疗干预目标，这是目前治疗方法不足的人群。

DESCRIPTION (provided by applicant): Asthma is a chronic, inflammatory disease of the lung that currently afflicts more than 300 million people worldwide. While asthma is mediated by an excessive Th2 immune response to allergens, recent evidence suggests that production of the Th17 cytokine, IL-17A, is associated with the development of more severe disease. While severe asthmatics are at greatest risk for morbidity or death following acute exacerbations, and can be refractory to therapies that are highly effective in individuals with mild disease, the molecular mechanisms whereby IL-17A contributes to the development of severe allergic asthma are ill-defined. A greater understanding of the molecular mechanisms through which IL-17A facilitates severe asthma would provide additional therapeutic targets for populations underserved by current therapies. Using a mouse model we provide evidence that severe asthma is associated with increased IL-17A production, and is compounded by enhanced Il17ra expression and elevated responsiveness to IL-17A. These alterations in IL-17A production and responsiveness exacerbate IL-13-driven STAT6 activation, gene expression, and airway responses. Our preliminary data suggests that IL-17A-mediated enhancement of IL-13-driven responses occur through two, non-mutually independent mechanisms in mouse cells; 1) by causing the dissociation of a complex including IL-13R�1 and TRAF3, which normally limits IL-13-driven STAT6 phosphorylation, and 2) by activating transcription factors (NF-�B, C/EBP� and C/EBP�) which can enhance IL-13/STAT6 driven gene expression. While preliminary studies presented here also suggest that similar mechanisms may operate in human cell lines, the extent to which the observations made in our mouse model apply to humans with severe asthma is unclear. Three specific aims are proposed to identify the molecular mechanisms through which IL-17A enhances asthma severity in mice, and humans. Specific Aim 1 will determine if the increased IL-13-driven STAT6 phosphorylation and AHR observed in the presence of IL-17A is the result of the dissociation of the IL- 13R�1:TRAF3 complex following initiation of IL-17A signaling. Specific Aim 2 will dissect the importance of IL- 17A-driven activation of NF-�B (canonical versus non-canonical), C/EBP� and C/EBP� in IL-13/IL-17A synergy in vitro and in vivo. Specific Aim 3 will directly test whether similar synergistic interactions between IL-13 and IL-17A are observed in asthma relevant, primary human cells. Additionally, we will determine whether severe asthma in children is associated, as it is in the mouse, with increased IL-17A production, IL17RA expression, and IL-17A responsiveness. Collectively, the studies proposed in this application will move us beyond the "Th2 paradigm" of allergic asthma, begin to characterize the mechanisms whereby Th17-products trigger the development of severe allergic asthma, and determine whether similar mechanisms may be at play in mice and humans. A better understanding of these mechanisms will enable us to identify novel targets for therapeutic interventions in individuals with severe asthma, a population underserved by current therapies.