The Roles of IBD Associated Genes ATG16L1 and TNFSF15 in Gut Mucosal Inflammation

描述（由申请人提供）：炎症性肠病（IBD）由易感基因、环境和粘膜免疫系统之间的复杂相互作用引起。这些相互作用导致对肠道微生物植物群的过度免疫应答。随着高通量分子技术的出现，全基因组关联研究（GWAS）鉴定了几个IBD相关基因，包括细胞内模式识别传感器NOD 2、自噬基因（ATG 16 L1和IRGM）和肿瘤坏死因子超家族成员15（TNFSF 15）。最近的几份报告显示，ATG 16 L1和NOD 2在一个共同的途径中相互作用，以影响微生物的处理，包括将细菌隔离到自噬体中，清除细胞内细菌和抗原呈递。几项研究表明，TNFSF 15由抗原呈递细胞（APC）表达，并通过增强Th 1、Th 17和Th 2应答来决定慢性肠道炎症的严重程度。我们证明了多种细菌，包括致病性和非致病性细菌，都可以诱导APC中TNFSF 15的表达。我们未发表的数据表明，TNFSF 15的表达可以通过NOD 2激活和诱导自噬而增加，这表明细菌加工在TNFSF 15的诱导中具有重要作用。本研究计划的目的是解决自噬依赖性细菌处理在诱导TNFSF 15表达和调节肠道炎症中的机制。我们将检验以下假设：微生物的自噬处理对于通过细菌抗原的自噬处理导致增强的肠道炎症的最佳TNFSF 15表达是重要的。此外，我假设TL 1A的高水平表达将放大炎症免疫反应，并加剧慢性肠道炎症的严重程度。以下具体目标将检验这一假设。具体目标1：确定自噬途径中有助于TNFSF 15最佳表达的步骤;具体目标2：将ATG 16 L1和IRGM的遗传CD变体与人APC中的TNFSF 15表达相关联;具体目标3：确定上皮细胞、树突状细胞和巨噬细胞中自噬对小鼠慢性结肠炎的发展和严重程度的作用。这项研究的意义在于，它将使人们能够深入了解肠道微生物菌群的粘膜免疫反应，这可能导致新的IBD疗法。 公共卫生相关性：炎症性肠病（IBD）影响估计140万美国人，表现为胃肠道慢性炎症，具有显著的发病率，有时甚至是危及生命的并发症。该提案研究了微生物-宿主相互作用的作用，特别是自噬，细菌和IBD相关基因TNFSF 15之间的相互作用在肠道粘膜炎症严重程度中的作用。从这项研究中获得的信息将使人们能够深入了解对肠道细菌的免疫反应，这可能导致IBD治疗方法的开发。

DESCRIPTION (provided by applicant): Inflammatory bowel diseases (IBD) result from complex interactions between susceptibility genes, the environment, and the mucosal immune system. These interactions lead to an exaggerated immune response to the gut microbial flora. With the advent of high-throughput molecular technologies, genome wide association studies (GWAS) identified several IBD associated genes including intracellular pattern recognition sensor NOD2, autophagy genes (ATG16L1 and IRGM) and tumor necrosis factor superfamily member 15 (TNFSF15). Several recent reports show that ATG16L1 and NOD2 interact in a common pathway to affect microbial handling including sequestration of bacteria into autophagosomes, clearance of intracellular bacteria, and antigen presentation. Several studies have shown that TNFSF15 is expressed by antigen presenting cells (APC) and determines the severity of chronic gut inflammation by enhancing Th1, Th17 and Th2 responses. We demonstrated that a variety of bacteria, both pathogenic and commensal, can induce TNFSF15 expression in APC. Our unpublished data show that TNFSF15 expression can be increased by NOD2 activation and induction of autophagy, indicating an important role of bacterial processing in the induction of TNFSF15. The objective of this research proposal is to address the mechanism(s) of autophagy dependent bacterial handling in the induction of TNFSF15 expression and modulation of intestinal inflammation. We will test the hypothesis that autophagy handling of microbial organism is important for optimal TNFSF15 expression through autophagy processing of bacterial antigen leading to enhanced intestinal inflammation. Furthermore, I hypothesize that the higher level of TL1A expression will amplify inflammatory immune responses and exacerbate the severity of chronic intestinal inflammation. The following specific aims will test this hypothesis. Specific Aim 1: Determine the steps in the autophagy pathway that contribute to optimal expression of TNFSF15; Specific Aim 2: Correlate genetic CD variants of ATG16L1 and IRGM to TNFSF15 expression in human APC; Specific Aim 3: Determine the role of autophagy in epithelial cells, dendritic cells, and macrophage on the development and severity of murine chronic colitis. The significance of this research is that it will allow insight on mucosal immune responses to gut microflora that may lead to new IBD therapies. PUBLIC HEALTH RELEVANCE: Inflammatory bowel disease (IBD) affects an estimated 1.4 million Americans and is manifested by chronic inflammation of the gastrointestinal tract with significant morbidity and at times, life-threatening complications. This proposal examines the role of microbial-host interaction, specifically the interaction between autophagy, bacteria, and an IBD associated gene TNFSF15 in severity of gut mucosal inflammation. Information obtained from this study will allow insight on immune responses to gut bacteria that potentially could lead to the development of therapeutics for IBD.