肠道共生梭菌通过抑制β-catenin表达维持肠黏膜Treg功能稳定的机制研究

Dysfunction of regulatory T cells occured in intestinal lamina propria in Crohn’s disease patients, and Clostridium spp. can induce the differentiation and proliferation of regulatory T cell. Our previous study has shown that the proportion and number of Clostridium leptum group and Clostridium coccoides group decreased in CD patients, and Clostridium spp. has been isolated and cultured from feces in healthy populations, and spontaneous inflammation in mouse intestinal tract was abrogated administrated with Clostridium spp. isolated from healthy populations. Additionally, our preliminary experiment found that expression of β-catenin increased in mucosa of CD patients, and no significant decrease of Foxp3 expression was observed in mucosa of CD, and expression of β-catenin increased in peripheral Foxp3+ regulatory T cells. Thus, we hypothesize that Clostridium spp. can maintain the functional stability of regulatory T cell. We are going to demonstrate that Clostridium spp. can regulate the expression of β-catenin and Foxp3 and inhibit β-catenin binding to the target gene promoter site, and explore the CD4+ T cell commitment and functional change of regulatory T cell administrated with Clostridium spp., and validate the effect of Clostridium spp. on changes of phenotypes and immunosuppressive function of the regulatory T cell. These will clarify the pathogenesis of dysfunction of regulatory T cells involved in Crohn’s disease. This study may explore new target for management of mucosa inflammation in CD.

克罗恩病（Crohn’s disease, CD）患者肠黏膜调节性T细胞(regulatory T cell, Treg)功能存在异常，已知共生梭菌能诱导Treg分化增殖。我们前期研究发现：①IBD患者黏膜和粪便中共生梭菌群减少，②从健康人粪便中分离出多株共生梭菌，③分离的共生梭菌株能减轻小鼠自发性肠炎。此外，我们在预实验中发现：①CD患者黏膜中β-catenin表达增加，②CD患者黏膜Foxp3表达无明显异常，③CD患者外周血Foxp3+Treg内β-catenin表达增加。我们推测肠道共生梭菌能抑制Treg内β-catenin的表达维持其效应表型。我们拟进一步研究共生梭菌对：①调节性T细胞内β-catenin、Foxp3表达的调节作用，②CD4+T淋巴细胞亚群分布及Treg免疫抑制功能影响，③炎性环境下Treg效应表型及功能影响。进一步明确Treg功能异常机制，为IBD治疗提供新靶点。

研究背景：目前研究发现多种自体免疫疾病中Treg功能存在异常，可能有Foxp3转录异常导致局部炎性组织中Treg功能被抑制；在Treg中 -Catenin 能与Foxp3共享基因组结合位点，通过TCF1转录因子依赖方式Wnt信号通路负性调节Treg功能，但是有研究表明，-Catenin 可不通过PI 3k-AKT and Wnt-TCF1 信号通路与FOXO相互作用对抗氧化应激并抑制细胞周期活动。.主要研究内容：①验证目标基因及其上游调控因子mRNA在IBD患者中的表达情况；②验证目标基因及其上游调控因子蛋白在IBD患者中的表达情况；③验证β-catenin是否在IBD患者黏膜组织中Treg淋巴细胞内有表达；④确认在β-catenin+Treg淋巴细胞中其对Foxp3基因下游序列调控的影响.重要结果：①克罗恩病患者中 -catenin表达与健康对照不同；②CD患者肠黏膜中 -catenin上游的信号分子mRNA表达无差异；③CD患者小肠组织中Foxp3表达与健康对照无差；④CD患者肠黏膜中 -catenin蛋白表达水平明显升高；⑤ -catenin和Foxp3在Treg淋巴细胞中存在共定位：.以上研究提示在特定炎症组织中Treg淋巴细胞功能可能存在异常。