Serum Amyloid A3 in Allergic Asthma: An Endogenous Mediator of Disease Severity

描述(申请人提供)：过敏性哮喘的表型受CD4T辅助细胞产生的细胞因子的影响，有严重的临床哮喘和与IL-17产生相关的严重疾病的小鼠模型，中性粒细胞和糖皮质激素抵抗。我们证明，血清淀粉样蛋白A(SAA)，一种由呼吸道上皮产生的内源性介质，诱导天然免疫细胞因子的产生，中性粒细胞，并极化Th17对无害的吸入性抗原的反应。我们已经报道，SAA刺激细胞外Toll样受体2(TLR2)和细胞内Nod样受体Nlrp3，这是分泌Th17极化细胞因子IL-1β所必需的。此外，IL-1受体的药理拮抗作用在体外阻止了IL-17的产生，IL-1受体缺陷(IL-1R-/-)小鼠不会因SAA3诱导的暴露而发生Th17极化，SAA3诱导的暴露促进了卵蛋白的过敏反应，或者SAA和卵蛋白的联合应用。最后，SAA加剧了过敏原诱导的呼吸道对乙酰甲胆碱的高反应性，并增强了过敏原致敏和挑战小鼠的气道中性粒细胞增多。我们假设，肺SAA(小鼠的SAA3)是过敏性哮喘严重程度的上皮源性内源性介质，其功能是极化IL-1依赖的Th17反应，从而导致严重疾病。在特定的目标1中，我们将确定在过敏性哮喘小鼠疾病模型发展过程中Saa3表达和SAA3产生的定量和定性模式。在特定的目标2中，我们将利用野生型和可诱导的呼吸道上皮细胞分泌SAA3的小鼠，在体外和体内建立SAA对抗原特异性的CD4T细胞适应性免疫反应的影响。我们将确定SAA3是否促进Th17极化，是否涉及受体TLR2、Nlrp3、IL-1R和FPR2(已被证明诱导白细胞对SAA趋化的甲酰蛋白受体2)，该活性是否直接作用于T细胞，以及SAA3的作用是否对糖皮质激素敏感。在特定目标3中，我们将在体内建立SAA3对于增加过敏性哮喘严重程度的必要性(使用SAA3沉默、SAA3中和和SAA3基因敲除小鼠)和充分性(使用SAA滴注和可诱导产生SAA3的转基因小鼠)，解决与先前特定目标有关的机制，即SAA3恶化肺生理性和结构性过敏性哮喘表型，包括糖皮质激素反应。了解内源性介质对Th17诱导的过敏性哮喘反应的影响，将为哮喘综合征的各种性质提供前所未有的洞察力，并可能为治疗的发展提供新的靶点。

DESCRIPTION (provided by applicant): The allergic asthma phenotype is affected by CD4+ T helper cell-produced cytokines, with severe clinical asthma and mouse models of severe disease associated with IL-17 production, neutrophilia, and glucocorticoid resistance. We demonstrate that Serum Amyloid A (SAA), an endogenous mediator produced by the airway epithelium, induces innate immune cytokine production, neutrophilia, and polarizes Th17 responses to innocuous inhaled antigens. We have reported that SAA stimulates the extracellular Toll-Like Receptor 2 (TLR2) and the intracellular NOD-like receptor, Nlrp3, which are required for the secretion of IL-1¿, a Th17- polarizing cytokine. In addition, pharmacologic antagonism of the IL-1 receptor prevents IL-17 production in vitro and IL-1 receptor-deficient (IL-1R¿-/-) mice do not undergo Th17 polarization in response to SAA3-inducing exposures that promote allergic sensitization to ovalbumin or to combined administration of SAA and ovalbumin. Finally, SAA exacerbates allergen-induced airway hyper-responsiveness to methacholine and enhances airway neutrophilia in allergen sensitized and challenged mice. We hypothesize that pulmonary SAA (SAA3 in mice) is an epithelial-derived endogenous mediator of allergic asthma severity that functions to polarize IL-1-dependent Th17 responses that contribute to severe disease. In Specific Aim 1 we will determine quantitative and qualitative patterns of Saa3 expression and SAA3 production during the development of allergic asthma in mouse models of disease. In Specific Aim 2 we will establish the effects of SAA on the antigen-specific CD4+ T cell adaptive immune response in vitro and in vivo using wildtype and inducible airway epithelial SAA3-secreting mice. We will determine whether SAA3 promotes Th17 polarization, whether the receptors TLR2, Nlrp3, IL-1R¿, and FPR2 (Formyl Protein Receptor 2, which has been shown to induce leukocyte chemotaxis to SAA) are involved, whether the activity is directly upon T cells, and whether the effect of SAA3 is glucorticoid-sensitive. In Specific Aim 3 we will establish in vivo the necessity (using Saa3 silencing, SAA3 neutralization, and SAA3 knockout mice) and sufficiency (using SAA instillation and inducible SAA3- producing transgenic mice) of SAA3 for augmentation of allergic asthma severity, addressing mechanisms implicated from the previous specific aims by which SAA3 worsens lung physiologic and structural allergic asthma phenotypes, including glucocorticoid responsiveness. Understanding the effect of endogenous mediators on Th17-inducing responses in allergic asthma will provide unprecedented insight into the varied nature of the asthma syndrome and may provide novel targets for the development of therapeutics.