胆道梗阻导致肠道机械屏障损伤及其分子机制研究

Intestinal barrier is the basis of safeguarding the normal physiological function of intestinal tract. Intestinal mechanical barrier is the vital part of intestinal barrier. Biliary obstruction always leads to the alterations in intestinal barrier function and intestinal permeability. However, the relevant studies are quite limited. Recent researches have shown that bile acids and inflammatory factors could activate multiple signaling pathways in the liver and intestine, regulating various functions of tissues and cells. Our previous study has demonstrated that biliary obstruction could impair intestinal mechanical barrier, increase intestinal permeability, alter the expression of bile acid receptors, tight junction related genes and stemness related genes of intestinal stem cells, increase the level of intestinal secretion protein Zonulin and serum inflammatory factors. In this project, we will establish mice bile duct ligation, bile duct drainage and other models to study the changes of intestinal mechanical barrier function after biliary obstruction. In addition, we will clarify the functional role and potential mechanism of bile acids and inflammatory factors in the regulation of Zonulin, intestinal tight junctions and stemness of intestinal stem cells through in vivo and in vitro experiments. Moreover, further studies will be carried out to identify relevant receptors and signaling pathways in this process, and analyze the correlation between clinical characteristics of biliary obstruction and levels of Zonulin, inflammatory factors, intestinal tight junction related proteins and stemness related proteins of intestinal stem cells. Collectively, our study will not only shed lights on the role and underlying mechanism of biliary obstruction in intestinal barrier impairment, but also provide novel insights and therapeutic targets for the prevention of complications related to biliary obstruction.

肠道屏障是保障肠道发挥正常生理功能的基础。机械屏障是肠道屏障的重要组成部分。胆道梗阻往往会影响肠道机械屏障功能和通透性，而相关研究甚少。近年研究表明，胆汁酸和炎症因子可激活肝脏和肠道多条信号通路，调节组织和细胞众多功能。我们前期研究发现胆道梗阻引起肠道机械屏障功能损伤、通透性增高，胆汁酸受体、紧密连接和小肠干细胞干性相关基因表达显著改变，肠道分泌蛋白Zonulin及血清中炎症因子水平增高。本项目将建立小鼠胆道梗阻、胆道外引流等模型，系统研究胆道梗阻后肠道机械屏障功能变化，通过进一步体内外实验阐明胆汁酸和炎症因子对肠道Zonulin、紧密连接和小肠干细胞干性的调节作用及机制，明确其中涉及的相关受体及信号通路，分析Zonulin、紧密连接和小肠干细胞干性相关蛋白、炎症因子水平与胆道梗阻临床特征相关性，阐明胆道梗阻导致肠道机械屏障损伤的机制，为胆道梗阻后肠道并发症防治提供新的理论依据及治疗靶点。

胆道梗阻是由炎症、结石、肿瘤等多种原因引起的临床常见病症，可导致肠道内胆汁酸缺乏，引起肠道并发症。然而，胆道梗阻后肠道机械屏障与肠道干性的改变及其细胞分子机制鲜有研究。本项目围绕胆道梗阻及胆汁酸缺乏对肠道机械屏障与肠道干性的影响及其作用机制开展研究，获得以下结果：（1）胆道梗阻可导致肠道机械屏障受损、干性破坏、隐窝增殖受到抑制，这主要是由于肠道胆汁酸缺乏；（2）胆道梗阻可导致肠道胆汁酸受体FXR表达下降，而FXR在维持肠道屏障和干性中发挥重要作用，胆道梗阻后激活FXR可修复肠道屏障、恢复干性；（3）转录组学结果显示，胆道梗阻导致肠道脂代谢相关通路显著变化，进一步研究发现，激活FXR可能通过上调皮质酮合成限速酶CYP11A1的表达，增加肠道皮质酮合成水平，进而发挥维持肠道屏障和干性的作用；（4）胆道梗阻后给予皮质酮治疗能显著修复肠道机械屏障、降低通透性、恢复干性、促进隐窝增殖，减轻菌群易位，同时还能减轻胆道梗阻引起的肝脏炎症和肝纤维化；（5）激活FXR或给予皮质酮治疗可能通过上调肠上皮细胞内c-Myc表达以及抑制c-Myc降解，从而维持肠道干性。本研究揭示了胆汁酸受体FXR在胆道梗阻后维持肠道屏障功能和干性的作用及其分子机制，发现了皮质酮作为胆道梗阻后肠道并发症治疗药物的应用潜力，为胆道梗阻后肠道屏障的变化以及相关肠道并发症的防治提供新的理论基础和治疗策略。