Role of Aryl Hydrocarbon Receptor in Microbiota-Colon Stem Cell Interactions

 描述(申请人提供)：这个项目的总体目标是更好地了解成人结肠干细胞群体如何响应芳香烃受体(AhR)活性毒物，包括干细胞相关表型、能量代谢以及体内暴露于AhR配体后结肠癌的发生和发展。结肠的“成体”体细胞干细胞特别令人感兴趣，因为它们维持自我更新，是癌症启动突变的靶细胞。结肠干细胞分化/可塑性、干细胞定位/增殖和Wnt/β-catenin信号的紊乱通常被认为是结肠肿瘤发生的最早一步。鉴于AhR及其配体已知可影响造血干细胞和胃肠道生物学，我们建议研究AhR信号在结肠干细胞动力学和功能中的作用。我们将特别关注AhR活性毒物、典型的膳食AhR配体和微生物群从膳食色氨酸产生的代谢物(AhR的外源和内源配体)。由于大多数AhR配体是组织和浓度特异性的AhR的激动剂和/或拮抗剂，我们假设AhR配体的联合激动剂和拮抗剂作用是结肠干细胞动力学和反应的重要决定因素。这得到了我们的初步研究的支持，该研究首次表明AhR配体显著影响结肠干细胞的动态平衡和基因表达。拟议的实验是新颖和相关的，因为暴露于外源性AhR配体及其与具有AhR活性的肠道内源性AhR配体的相互作用对成人肠道干细胞生物学的影响尚未确定。具体目标如下：(1)利用结肠癌细胞系和体外有机物培养系统，确定AhR活性毒剂和膳食AhR配体对肠道干细胞反应的激动剂和/或拮抗剂活性；(2)研究微生物来源的AhR配体及其与环境毒物和膳食配体在体内和体外对肠道干细胞反应的相互作用；(3)定量检测体内暴露AhR配体后，干细胞的数量和时空位置、DNA损伤和结肠隐窝中的靶向缺失。利用体内和体外模型将使我们能够剖析在存在或不存在AhR的情况下AhR配体的作用。

 DESCRIPTION (provided by applicant): The overall goal of this project is to better understand how the adult colonic stem cell population responds to Aryl hydrocarbon receptor (AhR)-active toxicants in terms of stem cell-related phenotypes, energy metabolism, and the initiation and progression of colon cancer following exposure to AhR ligands in vivo. "Adult" somatic stem cells of the colon are of particular interest because they sustain self-renewal and are target cell for cancer initiating mutations. Perturbations in colon stem cell differentiation/plasticity, stem ell location/proliferation, and Wnt/beta-catenin signaling are generally believed to represent the earliest step towards colon tumorigenesis. Since the AhR and its ligands are known to affect hematopoietic stem cells and gastrointestinal biology, we propose to investigate the role of signaling through the AhR on colon stem cell dynamics and function. We will specifically focus on AhR-active toxicants, prototypical dietary AhR ligands and metabolites generated from dietary tryptophan by the microbiota (exogenous and endogenous ligands for the AhR, respectively). Since a majority of the AhR ligands are agonists and/or antagonists for the AhR in a tissue- and concentration- specific manner, we hypothesize that the combined agonist and antagonistic role of AhR ligands are important determinants in colon stem cell dynamics and responses. This is supported by our preliminary studies, which demonstrate for the first time that AhR ligands significantly influence colonic stem cell homeostasis and gene expression. The proposed experiments are novel and relevant because the impact of exposures to exogenous AhR ligands and their interactions with AhR-active intestinal endogenous AhR ligands on adult intestinal stem cell biology has not been determined. The following specific aims will be addressed: (1) Determine the agonist and/or antagonist activity of AhR-active toxicants and dietary AhR ligands on intestinal stem cell responses using colon cancer cell lines and an ex vivo organoid culture system; (2) Investigate the effect of microbiota-derived AhR ligands and their interactions with environmental toxicants and dietary ligands on intestinal stem cell responses in vivo and ex vivo; and (3) Quantify the number and spatio-temporal location of stem cells, DNA damage and targeted deletion in the colonic crypt at the initiation and progression stages of colon carcinogenesis following exposure to AhR ligands in vivo. Utilization of both in vivo and ex vivo models will allow us to dissect the effects of AhR ligands in the presence or absence of the AhR.