Role of Gene-Microbial Interactions in the Development of Crohn's Disease-like Colitis

摘要 克罗恩病(CD)是炎症性肠病(IBD)的主要形式之一，是一种复杂的疾病 以由CD4+T辅助细胞1(TH1)细胞驱动的慢性复发性炎症为特征，该细胞可影响 胃肠道。CD被认为是对肠道的不适当的粘膜免疫反应所致 遗传易感个体的微生物区系。与这一观点一致的是，CD患者体内存在一种反生菌。 微生物区系。然而，目前尚不清楚与镉相关的生物失调是发挥着偶然的作用，还是继发于 发炎。有100多个基因座易患CD，其中NOD2基因的多态性是已知的最强的 成人和儿童起病的疾病发展的遗传危险因素。然而，绝大多数人 NOD2 CD相关变异纯合子个体不会发生CD，也不会自发肠道 类似CD的炎症发生在Nod2−/−小鼠或CD相关纯合子敲打小鼠中 L1007insC NOD2变体。这些发现表明，额外的遗传和/或环境因素 对疾病发展至关重要。我们发现，NOD2和吞噬细胞共同缺乏，但不是单一缺乏 NAPDH氧化酶活性触发早发性自发性TH1型肠炎 CD的病理和免疫特征。疾病的发展需要粘螺旋菌的存在 Shaedleri，一种革兰氏阴性厌氧细菌，是正常人结肠粘液层的居住者 老鼠。NOD2和CyBB的缺失导致粘螺旋菌在肠道中显著积累，这是 与中性粒细胞招募受损和中性粒细胞腔内杀灭细菌有关。突变型 母鼠在哺乳期间通过母体免疫球蛋白对抗粘螺旋菌来保护其免受疾病的侵袭。 这些结果表明，一种特定的肠道微生物可以在受损的人中引发类似CD的疾病 通过先天免疫清除细菌。我们假设NOD2和NAPDH氧化酶调节 通过控制特定病原体的丰度和局部入侵而对Cd的敏感性 粘螺旋菌。我们进一步假设，通过NOD2和NOD2调节的中性粒细胞对特定微生物的杀灭 NAPDH氧化酶对防止CD样病的发展具有重要作用。最后，我们假设 利用饮食靶向引起结肠炎的致病菌，如粘螺旋菌，可能是治疗CD-like的一种方法 结肠炎。在这项拨款申请中，我们提出了三个具体目标，以了解NOD2和吞噬细胞的作用 利用一种新的动物模型，NAPDH氧化酶在调节微生物区系和诱导结肠炎中的作用 表现出CD特有的病理和免疫改变。

ABSTRACT Crohn’s disease (CD), one of the major forms of Inflammatory Bowel Disease (IBD), is a complex disorder marked by chronic relapsing inflammation driven by CD4+ T helper 1 (TH1) cells that can affect any part of the gastrointestinal tract. CD is thought to result from an inappropriate mucosal immune response to the intestinal microbiota in genetically susceptible individuals. Consistent with this notion, CD patients harbor a dysbiotic microbiota. However, it remains unclear if the CD-associated dysbiosis plays a casual role or is secondary to inflammation. More than 100 loci predispose to CD of which polymorphisms in NOD2 are the strongest known genetic risk factor for disease development in adult and pediatric onset CD. However, the great majority of individuals homozygous for NOD2 CD-associated variants do not develop CD and no spontaneous intestinal inflammation mimicking CD occurs in Nod2−/− mice or knockin mice homozygous for the CD-associated L1007insC NOD2 variant. These findings suggest that additional genetic and/or environmental factors are critical for disease development. We found that combined, but not single deficiency, of NOD2 and phagocyte NAPDH oxidase activity triggers early-onset spontaneous TH1-type intestinal inflammation in mice with the pathological and immune hallmarks of CD. Development of disease required the presence of Mucispirillum schaedleri, a Gram-negative anaerobic bacterium that is an inhabitant of the colonic mucus layer of normal mice. The absence of NOD2 and CYBB led to marked accumulation of Mucispirillum in the gut which was associated with impaired recruitment of neutrophils and killing of the bacterium by luminal neutrophils. Mutant mice were protected from disease by maternal immunoglobulins against Mucispirillum during breastfeeding. These results indicate that a specific intestinal microbe can trigger CD-like disease in the presence of impaired clearance of the bacterium by innate immunity. We hypothesize that NOD2 and the NAPDH oxidase regulate the susceptibility to CD by controlling the abundance and local invasion of specific pathobionts such as Mucispirillum. We further hypothesize that killing of specific microbes by neutrophils regulated via NOD2 and NAPDH oxidase is important to prevent the development of CD-like disease. Finally, we hypothesize that targeting colitis-causing pathobionts such as Mucispirillum using diet could be an approach to treat CD-like colitis. In this grant application, we propose three specific Aims to understand the role of NOD2 and phagocyte NAPDH oxidase in the regulation of the microbiota and induction of colitis using a new animal model that exhibit pathology and immune alterations characteristic of CD.