PI3K/AKT-NHERF4-SLC26A3在复发性溃疡性结肠炎肠黏液层屏障功能障碍中的作用及机制

The prevention of the relapse of ulcerative colitis (UC) has been a difficult issue in its clinical treatment. Previous studies suggest that intestinal mucous layer barrier dysfunction is associated with UC relapse, that the ion transporter SLC26A3 is involved in maintaining the function of the intestinal mucous layer barrier, while shows decreased expression and weakened function in UC and that the PI3K/AKT signals are highly expressed all the time in UC and promote the expression and function of SLC26A3. Analysis of the contradictions between the high expression of PI3K/AKT in UC and the low functional status of SLC26A3 may be the starting point to understanding the UC mucous layer dysfunction and the relapse mechanism of UC. Studies have shown that PDZ binding protein NHERF4 negatively regulates the expression and function of SLC26A3, and the previous experiments in this project indicated that elevated NHERF4 expression was observed during the UC activity and remission stages (see the text). Therefore, it is reasonable to assume that PI3K/AKT-NHERF4-SLC26A3 are involved in the regulation of intestinal mucous barrier function synergistically, and possibly correlated with UC relapse. This project is intended to analyze and investigate the the pathogenesis of intestinal mucous barrier dysfunction and UC relapse from two perspectives, namely the effects of NHERF4 and SLC26A3 on the intestinal mucous barrier function and their association with UC relapse and the regulation of PI3K/AKT on NHERF4 and SLC26A3 and its relationship with intestinal mucous barrier dysfunction via observation of clinical cases, animal models and cytological experiments. This study can promote our understanding of the pathogenesis of UC and the underlying correlation of diarrhea-predominant irritable bowel syndrome with mild UC, so as to provide theoretical support for seeking targets for preventing UC relapse.

预防溃疡性结肠炎（UC）复发是UC临床治疗的难点问题。既往研究提示肠黏液层屏障功能障碍可能与UC复发相关；UC中参与维持黏液层屏障功能的离子转运体SLC26A3在PI3K/AKT信号持续促进下仍处於功能减退状态。项目组前期研究提示在UC活动期及缓解期负性调控SLC26A3表达和功能的PDZ结合蛋白 NHERF4表达增高（见正文）。因此，推测PI3K/AKT-NHERF4-SLC26A3协调调控肠黏液屏障功能并与UC复发相关。项目欲利用临床病例观察、动物模型及细胞学实验从NHERF4、SLC26A3对肠黏液屏障功能影响及与UC复发的相关性和PI3K/AKT对NHERF4、SLC26A3的调控及其与肠黏液屏障功能障碍的关系两个角度分析探讨肠黏液屏障功能障碍及UC复发的发生机制。本研究可促进我们对UC发病机制及腹泻型肠易激综合征与轻度UC潜在关系的理解，为寻找预防UC复发的靶点提供理论支撑。

预防溃疡性结肠炎（UC）复发是UC临床治疗的难点问题，推测PI3K/AKT-NHERF4-SLC26A3协调调控肠黏液屏障功能并与UC复发相关。项目欲利用临床病例观察、动物模型及细胞学实验从NHERF4、SLC26A3对肠黏液屏障功能影响及与UC复发的相关性和PI3K/AKT对NHERF4、SLC26A3的调控及其与肠黏液屏障功能障碍的关系两个角度分析探讨肠黏液屏障功能障碍及UC复发的发生机制。通过本项目的实施，（1）成功在本地实验室构建了不同浓度DSS诱导的UC小鼠结肠炎模型、OXZ诱导的小鼠结肠炎模型和急性束缚实验诱导的小鼠IBS-D模型。（2）首次利用动物模型发现IBS-D与UC模型小鼠肠黏膜中均存在SLC26A3蛋白的表达量的降低和NHERF4 蛋白的表达量升高，提示，在黏膜屏障损伤方面，IBS-D与UC可能具有部分相同的机制；（3）首次在UC患者中证实UC患者的肠黏膜中NHERF4表达增高；并利用Caco-2细胞发现PI3K/AKT信号通路呈浓度依赖性双向调控SLC26A3表达，这可在一定程度上解释UC中SLC26A3的黏膜表达和功能下降与具有促进SLC26A3的黏膜表达和功能的PI3K/AKT信号通路在UC中的持续活化之间的矛盾，既往研究中未见到有类似的数据发表。（4）此外，利用本项目基金，课题组还探讨分析了轻中度UC患者的血清维生素D水平和心理状态、生活质量在治疗前后的变化，发现病情的好转可在一定程度上改善部分患者的焦虑及抑郁状态，但部分患者的心理状态和疾病的病情转归相关性不大，提示，部分UC患者的心理状态可能是和UC平行存在的，并不一定完全具有相关性。同时，我们还发现，UC患者即使疾病恢复，还可能存在维生素D的不足。（5）利用本项目基金，我们观察了PBC患者在接受UDCA治疗前后的肠道菌群的变化，发现UDCA可以部分逆转PBC患者肠道微生物的紊乱。