Microbiota-mediated fibrotic remodeling in the inflamed intestine

摘要 纤维性疾病与大约45%的人类死亡有关。慢性炎症相关 在约40%的克罗恩病(CD)患者中，肠纤维化是一个重要的并发症。这种情况会导致 严重的肠道增厚和阻塞，是CD患者进行肠切除的最常见原因。 尽管存在这一公共卫生问题，但人们对CD疾病过程的了解很少。 伴发纤维化。微生物区系为CD和其他炎症性肠炎提供了可能的因果联系 疾病，但目前尚不清楚哪些特定的微生物产品会诱导不同的细胞反应和宿主 表型。我们假设一类从非生物微生物群中分泌出来的微生物小分子 通过改变巨噬细胞破坏局部宿主金属动态平衡并促进炎症相关纤维化 功能。营养金属对生物体来说是必不可少的，而肠道是宿主和 栖息的微生物争先恐后地获取金属。宿主金属清除和隔离防御传染性 但其在慢性炎症相关疾病中的作用尚不清楚。在这里我们 揭示一种新的炎症相关纤维化模型，使用GnotoBiotic IL10-/-小鼠单一定植于 黏附性侵袭性大肠杆菌(AIEC)NC101。纤维化需要细菌产生一种特定的小分子 在AIEC菌株中过度表达，并在CD的元基因组中大量存在的分子金属载体 病人。令人惊讶的是，纤维化并不需要细菌对金属载体的吸收和利用，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 在肠道微生物区系中含量丰富，预计在人类微生物组的元基因组中有数百种 项目(HMP)。因此，我们的项目具有广泛的影响，并支持一个模型，在该模型中，过量的金属 螯合作用可能是有利于纤维性CD而不是非纤维性CD的微生物区系的特征。铁和锌 在肠外纤维化的动物模型中，缺乏与CD相关，并促进纤维化。 因此，该项目的目标是确定微生物金属载体促进 纤维化发生，并将微生物清除金属和改变宿主金属动态平衡与镉相关 纤维化症。我们已经产生了许多AIEC菌株，它们取消了合成和/或运输 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型炎症相关药物中 纤维化小鼠模型，是概括CD-1的组织学和分子特征的重要工具 伴发纤维化。我们将使用NC101来确定体内促纤维化效应背后的金属特异性 和临床菌株。我们还将鉴定促纤维化的结肠单核/巨噬细胞群，并探索 金属可获得性改变促进巨噬细胞表型的机制。理解 确切地说，特定的细菌产品如何影响不同的宿主疾病表型，对于开发 基于微生物区系的炎症性肠病的诊断和治疗。

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.