IgE-Independent Mast Cell Activation by Food-Derived Peptides in Eosinophilic Esophagitis (EoE)

项目摘要/摘要 嗜酸性食管炎(EoE)是一种迅速出现的慢性疾病，主要由食物引起 抗原，从炎症发展到纤维化。尽管名为嗜酸性食管炎，但越来越多的人 有证据表明，在哮喘和硬皮病等疾病中导致纤维化的肥大细胞(MC)， 在EoE的发病机制中是不可或缺的。MCS经典地释放组胺和其他炎症介质 免疫球蛋白E(IgE)的交联性，但多条证据表明EoE不是 由免疫球蛋白E介导。MCS也可以被一系列阳离子物质激活，包括阿片剂，通过 新的G蛋白偶联受体，MAS相关的G蛋白偶联受体X2(MRGPRX2)。牛奶和小麦 是EoE的两个最常见的触发因素，消化这些食物会产生同源的7种氨基酸 (Aa)分别为β-酪吗啡素(BCM7)和醇溶吗啡(G7)的多肽，可与µ阿片类药物结合 受体和激活大鼠腹膜MCs。我们的团队最近发现，这两种多肽也能激活 人类LUVA MC系。利用HEK293 MRGPRX2转基因细胞株，我们的小组进一步发现 类阿片肽BCM7和G7只有在MRGPRX2存在的情况下才能激活这些细胞。这 这一发现导致了我们的中心假设，即巨噬细胞在EoE的发病机制中是不可或缺的，而非IgE MCs的介导性激活是通过食物诱导MRGPRX2的激活来实现的。麦高恩博士建议 通过检验1)BCM7和G7是否通过MRGPRX2激活MC来探索这一假设 稳定表达MRGPRX2和LUVA的HEK293细胞及其siRNA介导的LUVA细胞 沉默MRGPRX2；2)BCM7和G7刺激MC是否导致产生 已知与EoE的纤维化和嗜酸性粒细胞募集有关；以及3)食道 EoE患者的MCS表达MRGPRX2，并与纤维化特征相关。 BCM7和G7激活MC并导致炎症和纤维化的机制 EoE中的发现将对我们理解EoE的发病机制以及其他食物- 相关疾病，如肠易激综合征和非乳糜性面筋敏感，也是由 摄入牛奶和小麦。这是一个具有重大公共卫生影响的问题，就像BCM7和G7一样 在美国和其他西化国家广泛消费，在这些国家，EoE的流行率是 越来越多。展示这些食源性多肽对MC的激活可能会导致 我们看待这种疾病的发病机制和治疗方案的方式。

PROJECT SUMMARY/ABSTRACT Eosinophilic esophagitis (EoE) is a rapidly emerging chronic disease, predominantly triggered by food antigens, that progresses from inflammation to fibrosis. Despite the name eosinophilic esophagitis, increasing evidence suggests that mast cells (MC), which drive fibrosis in conditions such as asthma and scleroderma, are integral to the pathogenesis of EoE. MCs classically release histamine and other inflammatory mediators upon cross-linking of immunoglobulin E (IgE), but multiple lines of evidence have demonstrated that EoE is not mediated by IgE. MCs can also be activated by a range of cationic substances, including opiates, through a novel G-protein coupled receptor, MAS-related G protein-coupled receptor X2 (MRGPRX2). Milk and wheat are the two most common triggers of EoE, and digestion of these foods produces homologous 7 amino acid (AA) peptides, beta-casomorphin (BCM7) and gliadorphin (G7), respectively, that can engage µ opioid receptors and activate rat peritoneal MCs. Our group recently found that these two peptides also activate the human LUVA MC line. Using a HEK293 MRGPRX2 transfected cell line, our group further found that the opiate-like peptides BCM7 and G7 can activate these cells only in the presence of MRGPRX2. This finding leads to our central hypothesis that MCs are integral to the pathogenesis of EoE, and that non-IgE mediated activation of MCs occurs through food-induced activation of MRGPRX2. Dr. McGowan proposes to explore this hypothesis by examining 1) whether BCM7 and G7 activate MCs through MRGPRX2 using HEK293 cells with and without stably transfected MRGPRX2 and LUVA cells with and without siRNA-mediated silencing of MRGPRX2; 2) whether BCM7 and G7 stimulation of MCs leads to the production of mediators that are known to contribute to the fibrosis and eosinophil recruitment seen in EoE; and 3) whether esophageal MCs in patients with EoE express MRGPRX2 and correlate with fibrotic features. Elucidating the mechanism by which BCM7 and G7 activate MCs and lead to the inflammation and fibrosis seen in EoE will have broad implications for our understanding of EoE pathogenesis, as well as other food- related conditions such as irritable bowel syndrome and non-celiac gluten sensitivity that are also triggered by milk and wheat ingestion. This is a question with significant public health implications, as BCM7 and G7 are widely consumed in the United States and other westernized countries, where the prevalence of EoE is increasing. Demonstrating activation of MCs by these food-derived peptides could lead to a paradigm shift in the way that we view the pathogenesis and treatment options for this disease.