Bacterial metabolites controlling Th17 and Treg cells

摘要 维持炎症Th17细胞和抗炎Treg细胞之间的平衡对于 支持肠道屏障功能和组织动态平衡。核激素受体(NHRs)一直是 被证明在关键免疫细胞的发育和功能中发挥关键作用，包括Th17和Treg细胞。 基于我们之前的工作，我们假设宿主产生的、经细菌修饰的类固醇与宿主NHR结合 调节T细胞分化和功能。具体地说，我们假设次级胆汁酸(微生物 宿主产生的初级胆汁酸的代谢产物)与宿主NHR结合并调节T细胞分化和 功能。 我们先前证明了两种胆汁酸代谢物调节T细胞分化：3-oxo- 石胆酸(3oxoLCA)可抑制幼稚T细胞向炎性Th17细胞分化，并可抑制Th17细胞向炎性T细胞分化。 石胆酸可促进幼稚T细胞分化为抗炎Treg细胞。 尽管我们确定3oxoLCA通过作为RORγt(维甲酸)的配体来抑制Th17细胞 受体相关的孤儿核受体γt)，目前尚不清楚异基因LCA是否发挥其Treg细胞的调节作用 通过国家人力资源中心开展活动(S)。此外，可能还有额外的胆汁酸可以调节T细胞 回应。在初步工作中，我们鉴定了一种丰富的胆汁酸代谢物，异石胆酸。 抑制Th17细胞分化和功能的IsoLCA，以及产生IsoLCA的人类肠道细菌 和等异体LCA。我们发现，这些代谢物的水平在粪便中显著降低。 人类克罗恩病患者与健康对照组的比较。我们建议(1)识别人类的内脏 细菌和负责产生等LCA和等同源LCA的细菌基因，(2)决定 这些化合物影响Th17和Treg分化和功能的分子机制以及(3) 研究肠道细菌是否在体内影响宿主免疫反应，产生等LCA和等同LCA。 免疫调节性胆汁酸的产生途径及其作用机制 将开辟令人兴奋的途径来研究寄居在肠道的微生物和 宿主免疫细胞。这项研究将为开发新的治疗方法奠定基础。 自身免疫性疾病，包括炎症性肠病。

Abstract Maintaining an equilibrium between inflammatory Th17 cells and anti-inflammatory Treg cells is critical to support intestinal barrier function and tissue homeostasis. Nuclear hormone receptors (NhRs) have been shown to play crucial roles in the development and function of key immune cells, including Th17 and Treg cells. Based on our prior work, we hypothesize that host-produced, bacterially modified steroids bind to host NhRs and modulate T cell differentiation and function. Specifically, we posit that secondary bile acids (microbial metabolites of host-produced primary bile acids) bind to host NhRs and modulate T cell differentiation and function. We previously demonstrated that two bile acid metabolites modulate T cell differentiation: 3-oxo- lithocholic acid (3oxoLCA) inhibits the differentiation of naïve T cells into inflammatory Th17 cells, and isoallo- lithocholic acid (isoalloLCA) enhances the differentiation of naïve T cells into anti-inflammatory Treg cells. Although we determined that 3oxoLCA inhibited Th17 cells by acting as a ligand for RORγt (retinoic acid receptor-related orphan nuclear receptor γ t), it is unknown whether isoalloLCA exerts its Treg cell-modulating activity by acting through NhR(s). In addition, it is likely that there are additional bile acids that modulate T cell responses. In preliminary work, we have identified an abundant bile acid metabolite, iso-lithocholic acid (isoLCA) that inhibits Th17 cell differentiation and function, as well as human gut bacteria that produce isoLCA and isoalloLCA. We have found that the levels of these metabolites are significantly decreased in the feces of human patients with Crohn’s disease compared to healthy controls. We propose to (1) identify human gut bacteria and bacterial genes responsible for the production of isoLCA and isoalloLCA, (2) determine the molecular mechanisms by which these compounds influence Th17 and Treg differentiation and function, and (3) investigate whether gut bacteria producing isoLCA and isoalloLCA affect host immune responses in vivo. Elucidating the pathways that produce immunomodulatory bile acids and their mechanisms of action will open up exciting avenues to study unique regulatory interactions between gut-residing microorganisms and host immune cells. This research will lay the groundwork for the development of new therapies to treat autoimmune diseases, including inflammatory bowel disease.