IL-22在结肠生理性炎症向溃疡性结肠炎转化中的作用及黄芩汤干预机制研究

The term intestinal physiological inflammation refers to the sustained mild inflammation state stimulated by antigen derived from enteric flora. One of the pathogenesis of ulcerative colitis (UC) is abnormal immune response in mucosal induced by the change of intestinal physiological inflammation. By maintaining balance of normal flora, promoting the restoration of intestinal mucosa barrier function and epithelial cell proliferation, IL-22 is essential in the transformation of intestinal physiological inflammation to UC. But the molecular mechanisms are not well defined. UC is a chronic refractory gastrointestinal diseases and studies showed that the classic prescription of Huangqin-Tang has definite curative effect of UC. Our recent studies suggested that Huangqin-Tang could enhance the production of IL-22 in UC. However, little is known about the mechanism of the actions of Huangqin-Tang on the generation, receptor binding and signal transduction of IL-22. Therefore in the present study, we chose UC patients, animal model and intestinal epithelial cells as the research objects and Huangqin-Tang as the intervention drug. We observed the differences among the key indexes of intestinal mucosal barrier function, intestinal epithelial cell proliferation, inflammatory reaction and the changes of the expression of IL-22 by changing the intestinal physiological inflammatory status. The aim of our study was to clarify the mechanism of the actions of IL-22 in the transformation of colonic physiological inflammation to UC and the intervention mechanism of Huangqin-Tang. An in-depth study of this project is of great significance for further elucidating the pathogenesis of UC, searching for new therapeutic targets and drug development.

肠道生理性炎症是指以肠道菌群为主的抗原所激发的持续轻度炎症状态，生理性炎症改变所诱发的肠黏膜异常免疫损伤是溃疡性结肠炎（UC）的发病机制之一。在肠道中，IL-22通过调节菌群平衡、促进肠黏膜屏障功能修复和上皮细胞的增殖，在生理性炎症向UC转化中发挥重要作用，但具体机制未明。UC是一种顽固难治的消化道疾病，经方黄芩汤疗效确切。我们近期研究发现，在UC中，黄芩汤能够促进IL-22的表达，但对IL-22的生成、受体结合、信号传导的作用机制尚不清楚。因此，本项目以UC患者、动物模型和肠上皮细胞为研究对象，以黄芩汤作为干预药物，通过改变肠道生理性炎症状态，观察肠黏膜屏障功能、肠上皮细胞增殖和炎症反应中关键指标的差异以及IL-22表达的变化，明确IL-22在结肠生理性炎症向UC转化中的机制及黄芩汤的干预机理。本项目的深入研究，对进一步阐明UC的发病机制、寻找新的药物治疗靶点以及新药开发，具有重要意义。

由于肠粘膜屏障功能障碍，肠道细菌或有害物质会侵入肠粘膜，诱导宿主免疫细胞的过度免疫反应，并引发肠道炎症。黄芩汤在中国被广泛用于各种胃肠道腹泻和炎症，然而其在修复受损粘膜屏障的功能尚不明确。本项目旨在探讨黄芩汤对DSS诱导小鼠UC黏膜屏障功能的保护作用。结果表明黄芩汤修复DSS诱导的肠粘膜损伤，调节肠道结构紊乱和减少炎性细胞浸润，促进肠上皮细胞增殖，且体重下降幅度减少，体重恢复明显；DAI评分显著降低；抑制结肠缩短，降低结肠MPO值。黄芩汤能显著降低UC体内调节肠道屏障中免疫屏障功能关键因子—IL-22的分泌水平，包括CD3-IL-22+和CD3+IL-22+百分比。CD3+IL-22+细胞可能主要来源于CD4+T细胞亚群中的Th17及Th22细胞分泌。有趣地是，黄芩汤抑制IL-22分泌是以减少LPL和mLN分泌CD3-IL-22+水平为著。此外，我们证明这群CD3-IL-22+主要来源于ILC3s。黄芩汤能显著抑制ILC3s水平，且导致其分泌的特异性IL-17、IL-22细胞因子和转录因子RORγt表达减少。我们进一步发现，黄芩汤通过减少肠道IL-22的分泌，抑制UC IL-22与IL-22BP结合并诱导STAT3磷酸化的信号通路活化，同时增强肠道屏障中的物理和化学屏障，包括促进IL-22介导的粘液蛋白（Muc1和Muc3）和抗菌肽（Reg3b和Reg3g）分泌，增强紧密蛋白（ZO-1, Occludin和Claudin-1）与上皮细胞之间的连接，改善肠道屏障功能。这些实验均表明黄芩汤可作为IL-22活性的内源性抑制剂，且通过IL-22/IL-22BP/STAT3信号通路来改善UC的肠道屏障功能障碍。