Role of AHR, OVOL1, and SPINK7 in Eosinophilic Esophagitis

摘要 本研究的长期目标是阐明嗜酸性食管炎(EoE)的免疫学特征。这 是一个重要的课题，因为EoE是一种新出现的慢性疾病，通常从儿童时期开始并持续到 成年期与相当高的发病率有关，特别是本研究中正在研究的其他特应性疾病。 U19提议，但还没有FDA批准的治疗方法。理解这个主题具有重要的意义，因为 阐明其基本免疫学特征有可能为改进诊断奠定基础。 和治疗。我们的中心假设是芳烃受体(AHR)起食道的作用 并通过转录因子OVOL1介导其作用，OVOL1诱导抗蛋白酶的转录 而IL-4和IL-13抑制这一途径。这一假设的基本原理是基于以下研究结果 我们目前的U19资助已经为丝氨酸肽酶抑制剂Kazal 7型的核心作用提供了证据 (SPINK7)在EoE发病机制中的作用。获得性SPINK7丢失足以释放失控的食道 蛋白酶活性，进而导致上皮细胞分化丧失，桥粒蛋白丢失 表达和屏障功能受损，以及促炎介质的过度生产，包括 TSLP。然而，关于SPINK7表达的分子调控几乎一无所知，这是 这笔拨款续期的标的。我们已经发现，食道上皮富含转录因子， OVO样转录抑制因子1(OVOL1)调节SPINK7启动子的活性和表达。此外， OVOL1的过表达增加了SPINK7的表达，而OVOL1的缺失则降低了SPINK7的表达 上皮屏障，重要的是增加了TSLP的产生。从机制上讲，AHR的配体诱导 OVOL1核转位，进而促进SPINK7的表达；相反，AHR拮抗剂抑制 SPINK7表达。IL-4和IL-13可减少AHR诱导的OVOL1核转位和OVOL1诱导的SPINK7的表达，这与2型免疫有关。此外，过度表达 CAPN14由一个主要的EoE遗传易感基因编码，可降低OVOL1的表达。 翻译研究显示EoE患者食道OVOL1蛋白表达降低 阻断丝氨酸蛋白酶活性可减弱小鼠实验性EoE。这些指标的临床意义 数据被质子泵抑制剂奥美拉唑强调，奥美拉唑是一种AHR配体，用于治疗EoE 这就引出了SPINK7。我们将使用创新的方法，通过3个互补的目标来检验中心假设 它结合了分子、基因组和生物学研究。在目标1中，我们将测试OVOL1在食道中的作用 通过调节分化基因的表达，包括SPINK7，检验假设 OVOL1在上皮分化和屏障功能中起关键作用。在目标2中，我们将研究AHR对 SPINK7，检验AHR是食道感受器及其机制依赖于OVOL1的假设 和SPINK7。在目标3中，我们将测试IL-4和IL-13是否对抗SPINK7，以及这是否通过CAPN14发生。

Summary The long-term goal of this study is to elucidate the immunologic features of Eosinophilic Esophagitis (EoE). This is an important subject as EoE is an emerging, chronic disease that often starts in childhood and continues into adulthood and is associated with substantial morbidity, especially the other atopic diseases being studied in this U19 proposal, yet has no FDA-approved therapies. Understanding this subject has significant implications as elucidating its fundamental immunologic features has potential to lay the foundation for improved diagnostics and therapies. Our central hypothesis is that the aryl hydrocarbon receptor (AHR) serves as an esophageal sensor and mediates its action via the transcription factor OVOL1, which induces transcription of the antiprotease SPINK7, and that IL-4 and IL-13 repress this pathway. The rationale for this hypothesis is based on findings from our current U19 grant that have provided evidence for a central role of serine peptidase inhibitor Kazal type 7 (SPINK7) in EoE pathogenesis. Acquired loss of SPINK7 is sufficient to unleash uncontrolled esophageal protease activity, which in turn induces loss of epithelial cell differentiation, loss of desmosomal protein expression, and impaired barrier function, as well as overproduction of proinflammatory mediators, including TSLP. Yet, there is virtually nothing known about the molecular regulation of SPINK7 expression, which is the subject of this grant renewal. We have uncovered that the esophageal epithelial enriched transcription factor, Ovo-like transcriptional repressor 1 (OVOL1) regulates SPINK7 promoter activity and expression. Furthermore, OVOL1 overexpression increases SPINK7 expression, whereas OVOL1 depletion decreases SPINK7, impairs the epithelial barrier, and importantly increases TSLP production. Mechanistically, ligands of the AHR induce OVOL1 nuclear translocation, which in turn promotes SPINK7 expression; conversely, AHR antagonists inhibit SPINK7 expression. A link with type 2 immunity is revealed by the finding that IL-4 and IL-13 reduce AHRinduced OVOL1 nuclear translocation and OVOL1-induced SPINK7 expression. Furthermore, overexpression of CAPN14, which is encoded for by a chief EoE genetic susceptibility locus, decreases OVOL1 expression. Translational studies demonstrate a decrease in esophageal expression of OVOL1 protein in patients with EoE and blockade of serine protease activity attenuates murine experimental EoE. The clinical significance of these data are underscored by the proton pump inhibitor omeprazole, which is used to treat EoE, being an AHR ligand that induces SPINK7. We will test the central hypothesis via 3 complementary aims using innovative approaches that combine molecular, genomic, and biological studies. In Aim 1, we will test the role of OVOL1 in esophageal epithelium by regulating the expression of differentiation genes, including SPINK7, testing the hypothesis that OVOL1 is critical for epithelial differentiation and barrier function. In Aim 2, we will examine AHR regulation of SPINK7, testing the hypothesis that AHR is an esophageal sensor and that its mechanism depends upon OVOL1 and SPINK7. In Aim 3, we will test whether IL-4 and IL-13 oppose SPINK7 and whether this occurs via CAPN14.