Mechansim by which Commensal Bacteria Prevent Colitis

共生细菌预防结肠炎的机制

• 批准号: 8909913
• 负责人: Mallory Paynich
• 金额: $ 2.99万
• 依托单位: LOYOLA UNIVERSITY CHICAGO
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-05-01 至 2017-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8909913
• 关键词: Acute; Adaptor Signaling Protein; Anti-Inflammatory Agents; Anti-inflammatory; Bacillus subtilis; Bacteria; Binding; CD4 Positive T Lymphocytes; Celiac Disease; Cell Lineage; Cells; Citrobacter rodentium; Colitis; Colon; Crohn' s disease; DNA-Binding Proteins; Data; Development; Disease; Dose; Environment; Gastrointestinal tract structure; Generations; Genes; Goals; Greater sac of peritoneum; Homeostasis; Human; ITGAM gene; Immune; Immune system; In Vitro; Infection; Inflammation; Inflammatory; Interleukin-13; Interleukin-4; Intraperitoneal Injections; Knowledge; Life; MHC Class II Genes; Maintenance; Mediating; Mus; Myelogenous; Oral; PPAR gamma; Peritoneal; Peritoneal Macrophages; Population; Probiotics; Reproduction spores; Signal Transduction; Site; T cell response; T-Cell Activation; T-Cell Proliferation; TLR4 gene; Testing; Th2 Cells; Therapeutic; Therapeutic Uses; Ulcerative Colitis; YM1 doxorubicin analog; arginase; autocrine; cell type; commensal microbes; cytokine; design; enteric pathogen; enteropathogenic Escherichia coli; human disease; in vivo; intestinal homeostasis; intraperitoneal; macrophage; mouse model; pathogen; prevent; public health relevance; research study; response; trafficking

 DESCRIPTION (provided by applicant): Mechanism by which Commensal Bacteria Prevent Colitis Trillions of bacteria live in homeostasis within the gastrointestinal tract and provide a variety of benefits to the host immune system. Many of these commensal bacteria have been shown to limit colitis, however, little is known about the mechanisms by which this occurs. We utilize a mouse model in which a single dose of the commensal bacterium, Bacillus subtilis, protects mice from acute colitis induced by the enteric pathogen Citrobacter rodentium. Our goal is to elucidate the mechanism by which B. subtilis protects from inflammation caused by C. rodentium infection. We identified exopolysaccharides (EPS) to be the active molecule of B. subtilis, and a single i.p. dose of EPS protect mice from disease. EPS bind F4/80+CD11b+ peritoneal macrophages, and after i.p. injection of EPS, we identified F4/80+CD11b+ cells that are MHCII+CD206+Arg1+YM-1+, indicative of alternatively-activated macrophages (AAM) or M2 macrophages (M2 MF). We further show that peritoneal macrophages from EPS-treated mice suppress T cell proliferation in vitro, suggesting that these cells contribute to EPS-mediated protection from inflammation. We hypothesize that EPS induce M2 MF and that these cells mediate protection from acute colitis induced by C. rodentium. In aim 1, we will determine if B. subtilis spores also induce M2 MF, test if M2 MF protect mice from C. rodentium infection, and if these cells traffic to the site of inflammation during infection. M2 MF are induced in the presence of IL-4 and IL-13, usually derived from Th2 cells. Interestingly, F4/80+CD11b+ macrophages purified from EPS-treated mice expressed increased levels of these cytokines compared to untreated mice. We hypothesize that EPS bind to peritoneal macrophages, upregulating IL-4 and IL-13, which act in an autocrine fashion to upregulate MHC class II, CD206, arginase and YM-1. Since EPS-mediated protection requires TLR4 signaling, we hypothesize that this induction requires TLR4 and PPARγ, a DNA-binding protein downstream of TLR4 that induces M2 MF genes (Aim 2). CD4+ T cells drive much of the inflammation associated with C. rodentium infection. This inflammation is suppressed when mice are pretreated with EPS prior to infection. In aim 3, we will use IL-2cre EGFP mice to test if EPS suppress T cell responses during infection and if M2 MF mediate this suppression. Taken together, these experiments will determine the mechanism by which EPS suppress inflammation leading to intestinal homeostasis. Gaining knowledge of the mechanisms by which commensals protect from colitis will ultimately help to design rational therapeutics that can be used to reduce inflammation and limit human disease.

 描述（由申请人提供）：共生细菌预防结肠炎的机制数万亿细菌生活在胃肠道内的稳态，并为宿主免疫系统提供各种益处。许多这些肠道细菌已被证明可以限制结肠炎，然而，人们对这种情况发生的机制知之甚少。我们利用一种小鼠模型，其中单剂量的枯草芽孢杆菌可保护小鼠免受由肠道病原体啮齿类柠檬酸杆菌诱导的急性结肠炎。我们的目标是阐明B.枯草杆菌可防止由C.啮齿类感染我们确定胞外多糖（EPS）是B的活性分子。枯草芽孢杆菌，并且单次腹膜内剂量的EPS保护小鼠免于疾病。EPS结合F4/80+ CD 11b+腹腔巨噬细胞，并且在腹膜内注射EPS后，我们鉴定出F4/80+ CD 11b+细胞为MHCII+ CD 206 + Arg 1 +YM-1+，指示交替激活的巨噬细胞（AAM）或M2巨噬细胞（M2 MF）。我们进一步表明，经EPS处理的小鼠的腹腔巨噬细胞在体外抑制T细胞增殖，这表明这些细胞有助于EPS介导的炎症保护。我们假设EPS诱导M2 MF，并且这些细胞介导对由C.啮齿动物。在目标1中，我们将确定 B。枯草芽孢杆菌孢子也能诱导M2 MF，检测M2 MF是否能保护小鼠免受C.啮齿类感染，以及这些细胞是否在感染期间运输到炎症部位。M2 MF在IL-4和IL-13存在下诱导，通常来源于Th 2细胞。有趣的是，与未处理的小鼠相比，从EPS处理的小鼠中纯化的F4/80+ CD 11b+巨噬细胞表达这些细胞因子的水平增加。我们假设EPS与腹腔巨噬细胞结合，上调IL-4和IL-13，IL-4和IL-13以自分泌方式上调II类MHC、CD 206、β-内酰胺酶和YM-1。由于EPS介导的保护作用需要TLR 4信号传导，我们假设这种诱导作用需要TLR 4和PPARγ（一种位于TLR 4下游的DNA结合蛋白，可诱导M2 MF基因）（Aim 2）。CD 4 + T细胞驱动与C.啮齿类感染当小鼠在感染前用EPS预处理时，这种炎症被抑制。在目标3中，我们将使用IL-2cre EGFP小鼠来测试EPS在感染期间是否抑制T细胞应答以及M2 MF是否介导这种抑制。总之，这些实验将确定EPS抑制炎症导致肠道稳态的机制。获得关于益生菌预防结肠炎的机制的知识将最终有助于设计可用于减少炎症和限制人类疾病的合理疗法。