Microbiota-mediated fibrotic remodeling in the inflamed intestine

摘要 纤维化疾病与估计45%的人类死亡相关。慢性炎症相关 肠纤维化是约40%的克罗恩病（CD）患者的显著并发症。这种情况导致 严重的肠增厚和堵塞，是CD患者肠切除术的最常见原因。 尽管存在这一公共卫生问题，但对CD的疾病过程仍知之甚少- 相关纤维化。微生物群提供了一个假定的因果关系，以CD和其他炎症性肠道 疾病，但仍不清楚哪些特定的微生物产品诱导不同的细胞反应和宿主 表型我们假设，从微生物群中分泌的一类微生物小分子 破坏局部宿主金属稳态，并通过改变巨噬细胞 功能营养金属是生物体所必需的，肠道是宿主和 常驻微生物为获得金属而斗争。宿主金属清除和隔离防御感染性疾病 疾病，但其对慢性炎症相关疾病的贡献还不清楚。这里我们 揭示了一种新的炎症相关的纤维化模型，该模型使用单定殖的gnotobiotic Il 10-/-小鼠， 粘附侵袭性大肠杆菌（AIEC）NC 101。纤维化需要细菌产生一种特定的小 在AIEC菌株中过度表达并在CD的宏基因组中丰富的分子金属载体 患者令人惊讶的是，纤维化不需要细菌摄取和利用金属载体，这表明 它的目标是宿主事实上，这种金属载体诱导巨噬细胞中的金属饥饿基因。金属载体 在肠道微生物群中丰富，在人类微生物组的宏基因组中预测有数百种 项目（HMP）。因此，我们的项目具有广泛的影响，并支持一个模型，其中过量的金属 螯合作用可以表征有利于纤维化相对于非纤维化CD的生态失调微生物群。铁和锌 缺乏与CD相关，并促进肠外纤维化动物模型中的纤维化。 因此，本项目的目标是确定微生物金属载体促进 纤维化，并将微生物金属清除和改变的宿主金属稳态与CD相关的 纤维化我们已经产生了许多AIEC菌株，其消除了AIEC的合成和/或转运。 金属载体我们将利用这些菌株和纯化的金属载体在我们的新的炎症相关 纤维化小鼠模型，一个重要的工具，概括了CD- 相关纤维化。我们将使用NC 101定义促纤维化体内效应的金属特异性 和临床菌株。我们还将鉴定促纤维化结肠单核细胞/巨噬细胞群体，并探索 改变的金属可用性促进这种巨噬细胞表型的机制。理解 具体的细菌产物如何影响不同的宿主疾病表型对于发展 用于炎症性肠病的基于微生物群的诊断和治疗。

ABSTRACT Fibrotic disorders are associated with an estimated 45% of human deaths. Chronic inflammation-associated intestinal fibrosis is a significant complication in ~40% of Crohn’s disease (CD) patients. This condition causes severe intestinal thickening and blockage, and is the most common reason for bowel resection in CD patients. Despite this public health problem, there is minimal understanding behind the disease process of CD- associated fibrogenesis. The microbiota provides a putative causal link to CD and other inflammatory bowel diseases, but it remains unknown which specific microbial products induce distinct cellular responses and host phenotypes. We hypothesize that a class of secreted microbial small molecules from a dysbiotic microbiota disrupts local host metal homeostasis and promotes inflammation-associated fibrosis by altering macrophage function. Nutrient metals are essential for living organisms, and the intestine is a battleground where host and resident microbes fight to acquire metal. Host metal scavenging and sequestration defends against infectious diseases, but its contribution to chronic inflammation-associated disease is not well understood. Here we reveal a novel inflammation-associated fibrosis model using gnotobiotic Il10-/- mice mono-colonized with adherent-invasive Escherichia coli (AIEC) NC101. Fibrosis requires bacterial production of a specific small molecule metallophore that is over-represented in AIEC strains and abundant in the metagenomes of CD patients. Surprisingly, fibrosis does not require bacterial uptake and utilization of the metallophore, suggesting it targets the host. Indeed, this metallophore induces metal-starvation genes in macrophages. Metallophores are abundant in the gut microbiota, with hundreds predicted in the metagenomes of the Human Microbiome Project (HMP). Therefore, our project has broad implications and supports a model in which excessive metal chelation may characterize a dysbiotic microbiota that favors fibrotic vs. non-fibrotic CD. Iron and zinc deficiency are associated with CD and promote fibrosis in animal models of extra-intestinal fibrosis. Accordingly, the objective of this project is to define mechanisms by which microbial metallophores promote fibrogenesis, and link microbial metal scavenging and altered host metal homeostasis with CD-associated fibrosis. We have generated numerous AIEC strains that abolish the synthesis and/or transport of metallophores. We will utilize these strains and purified metallophores in our novel inflammation-associated fibrosis mouse model, an essential tool that recapitulates the histologic and molecular features of CD- associated fibrosis. We will define the metal specificity underlying the pro-fibrotic in vivo effects using NC101 and clinical strains. We will also identify the pro-fibrotic colonic monocyte/macrophage population and explore mechanisms by which altered metal availability promotes this macrophage phenotype. Understanding precisely how specific bacterial products impact distinct host disease phenotypes is essential for developing microbiota-based diagnostics and therapeutics for inflammatory bowel diseases.