Nuclear Receptor Networks in Mucosal Immune Regulation

粘膜免疫调节中的核受体网络

• 批准号: 10591752
• 负责人: Matthew Eugene Pipkin
• 金额: --
• 依托单位: UNIVERSITY OF FLORIDA
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-30 至 2026-04-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10591752
• 关键词: Nuclear; Receptor; Networks; Mucosal; Immune

Project Summary The gut is a major immunological organ where host-microbe interactions shape both local and systemic immune tolerance. However, current views of intestinal immune regulation ignore fundamental differences in the function and metabolite composition of the two distinct organs that comprise the gut—the small and large intestine (or SI and LI). This impedes a more detailed understanding of immune regulatory mechanisms along the intestinal tract, and limits efforts to develop safer, more targeted treatments for the two major forms of human inflammatory bowel diseases (IBDs), ulcerative colitis and small bowel Crohn’s disease. We hypothesize that mucosal CD4 T cells use different sets of ligand-regulated nuclear receptors (NRs) in the SI and LI to control key regulatory functions, including IL-10 expression, to local concentration gradients of bile- and microbe-derived metabolites. On one hand, we have discovered that Foxp3– effector (Teff) subsets in the SI—including Th1 and Th17 cells— utilize the nuclear xenobiotic receptor, constitutive androstane receptor (CAR/Nr1i3), to direct a ‘hepatocyte-like’ transcriptional response to contend with high local bile acid (BA) concentrations, which are far greater in SI than in LI (millimolar vs micromolar) due to ‘enterohepatic’ circulation—where primary BAs synthesized in the liver, stored in the gallbladder, and secreted into the duodenum are actively reabsorbed by specialized enterocytes in the ileum for portal recirculation to the liver. Because BAs are lipophilic, they can be toxic and pro-inflammatory, and several nuclear receptors—including CAR—have evolved to suppress BA toxicity. These studies suggest that enterohepatic circulation establishes a unique SI microenvironment that is distinct from that in the LI and requires unique transcriptional machinery to protect T cells in the SI. Conversely, the LI harbors 103-107 times more bacteria than SI, and ~1000-fold lower BA concentrations. Accordingly, microbes and their metabolites— short chain fatty acids (SCFAs; e.g., butyrate), secondary BAs (produced via microbial metabolism of residual primary BAs)—are central to immune regulation in the LI. SCFAs inhibit histone deacetylase enzymes (HDACs) and stabilize Foxp3 gene expression in peripherally-induced T regulatory cells (iTregs), whereas secondary BAs appear to promote regulatory functions of RORgt+ Tregs in the LI through another NR, vitamin D receptor (VDR). Thus, while antigens from the enteric flora prime both pro- and anti-inflammatory T cell responses throughout the gut, marked concentration gradients of bile- and bacteria-derived metabolites in the SI vs. LI are sensed by different NRs to execute compartmentalized T cell regulatory functions. In testing this hypothesis, we will apply cutting-edge genomics and computational approaches to comprehensively map the contributions of each of the 49 mouse NRs to specialized regulatory functions in the SI and LI in vivo, using IL-10 expression as the primary screening target. We will also interrogate the regulation and molecular functions of two key NRs, CAR/Nr1i3 and VDR/Nr1i1, in SI type 1 regulatory (Tr1) and LI iTreg cells, respectively. These studies will advance understanding of lymphocyte specialization in the gut, and inform new approaches to treat IBDs.

项目摘要 肠道是一个主要的免疫器官，宿主-微生物相互作用塑造了局部和全身免疫 宽容然而，目前关于肠道免疫调节的观点忽视了功能上的根本差异， 以及组成肠的两个不同器官-小肠和大肠（或SI）的代谢物组成 和LI）。这阻碍了对沿着肠道免疫调节机制的更详细的了解。 道，并限制了努力开发更安全，更有针对性的治疗两种主要形式的人类炎症 肠道疾病（IBD）、溃疡性结肠炎和小肠克罗恩病。我们假设粘膜CD 4 T细胞 细胞在SI和LI中使用不同的配体调节的核受体（NRs）组来控制关键的调节 功能，包括IL-10的表达，局部浓度梯度的胆汁和微生物衍生的代谢物。 一方面，我们已经发现SI中的Foxp 3效应子（Teff）亚群-包括Th 1和Th 17细胞- 利用核异生素受体，组成型雄烷受体（CAR/Nr 1 i3），指导“肝细胞样” 转录反应，以抗衡高局部胆汁酸（BA）浓度，这是远远大于SI比 在由于“肠肝”循环的LI（毫摩尔对微摩尔）中-其中初级BA在肝脏中合成， 储存在胆囊中，并分泌到十二指肠，被专门的肠细胞积极重吸收， 回肠进行肝门静脉再循环。因为BA是亲脂性的，它们可能是有毒的和促炎的， 并且几种核受体-包括CAR-已经进化为抑制BA毒性。这些研究表明 肝肠循环建立了一个独特的SI微环境，与LI中的微环境不同， 需要独特的转录机制来保护SI中的T细胞。相反，LI港103-107倍 比SI更多的细菌，以及低约1000倍的BA浓度。因此，微生物及其代谢产物- 短链脂肪酸（SCFA;例如，丁酸盐）、次级BAs（通过微生物代谢残留的 初级BA）-是LI中免疫调节的中心。SCFA抑制组蛋白脱乙酰酶（HDAC） 并稳定外周诱导的T调节细胞（iT细胞）中Foxp 3基因的表达，而次级BAs 似乎通过另一种NR维生素D受体（VDR）促进LI中RORgt+ Treg的调节功能。 因此，虽然来自肠道植物群的抗原在整个过程中引发促炎性和抗炎性T细胞应答， 在肠道中，SI与LI中胆汁和细菌衍生代谢物的显著浓度梯度通过 不同的NR执行区室化的T细胞调节功能。为了验证这一假设，我们将 尖端的基因组学和计算方法，以全面绘制每个基因的贡献， 49个小鼠NR在体内SI和LI中具有专门的调节功能，使用IL-10表达作为主要的 筛选目标我们还将探讨两个关键NR（CAR/Nr 1 i3和 VDR/Nrlii，分别在SI 1型调节性（Trl）和LI iTreg细胞中。这些研究将进一步 了解肠道中淋巴细胞的特化，并为治疗IBD提供新的方法。