溃疡性结肠炎中介导短链脂肪酸激活自噬抗炎的作用机理研究

Impaired intestinal mucosa and excessive inflammatory response are typical features of refractory disease-ulcerative colitis (UC). Currently, anti-inflammatory is one of the main ways to treat UC. Short-chain fatty acids as the　metabolites of intestinal flora can reduce intestinal inflammation and protect intestinal mucosal barrier system, but the specific mechanism is unclear. Scavenger-autophagy suppresses inflammatory signals by removing inflammatory stimuli and is an important regulatory target for inflammatory response. Our study found that after the UC mice treatment by short chain fatty acid butyrate, a larger of autophagosomes were able to induce, also the expression of ATG7, ULK1 and LC3-II genes were up-regulated and the expression of cytokines including TNF-α, IL-6, IL-1β, CCL5 and inflammatory gene NLRP3 were reduced. At the same time, inflammatory injury was relieved in the colon. However, after intraperitoneal injection autophagy inhibitor CQ, there was no change in proinflammatory cytokines and inflammatory pathological analysis, which showed that autophagy inhibitor CQ significantly weakened the anti-inflammatory effect of sodium butyrate. We hypothesize that autophagy may mediate the anti-inflammatory process of short chain fatty acids in ulcerative colitis. In this project, UC mice were studied to explore how the short chain fatty acids activate autophagy to reduce inflammatory response and to clarify a novel signaling pathway. The current study will reveal the molecular mechanism of the anti-inflammatory of the short chain fatty acids mediated by autophagy in UC, which will provides a new perspective for the treatment of UC.

肠道黏膜受损引起过度的炎症反应是难治疾病--溃疡性结肠炎（UC）的典型特征，目前抗炎是治疗UC的主要方式之一。肠道菌群的代谢产物短链脂肪酸能够下调肠道炎症，保护肠黏膜屏障系统，但具体机制尚不明确。细胞内的清道夫--自噬通过清除促炎介质来抑制炎症信号，是炎症反应的一个重要调节靶点。我们的研究发现：UC模型小鼠，经短链脂肪酸丁酸钠处理后，能够显著诱导自噬小体的形成和ATG7、ULK1、LC3-II基因的表达，同时下调促炎细胞因子TNF-α、IL-6、IL-1β、CCL5和炎性小体基因NLRP3的表达，缓解炎性损伤；然而，自噬抑制剂CQ处理后，促炎细胞因子和炎症病理分析均无变化，表明抑制自噬显著地削弱丁酸钠的抗炎作用。我们设想，自噬可能介导短链脂肪酸在溃疡性结肠炎中的抗炎过程。本项目以UC小鼠为对象，研究短链脂肪酸如何激活自噬下调炎症反应的分子机制，为溃疡性结肠炎的治疗提供一个全新的视角。

肠道黏膜受损和炎症反应是肠炎的主要特征，肠道菌群的代谢产物短链脂肪酸（SCFAs）能够下调肠道炎症，保护肠黏膜屏障系统，但具体机制尚不明确。自噬通过清除炎性介质来抑制炎症反应，是抗炎的一个重要调节靶点。我们的研究发现：UC模型小鼠中SCFAs显著降低，通过补充短链脂肪酸可改善结肠炎症状，通过肠屏障检测发现短链脂肪酸可促进ZO-1、Claudin-1和Occludin的表达增加修复肠道屏障，削弱炎症损伤；在UC动物和细胞中发现SCFAs能够激活自噬基因的表达，促进自噬过程。并且肠道特异性敲除自噬基因Beclin-1对DSS诱导的肠炎更加敏感， SCFAs的治疗效果被减弱，SCFAs受体减少同样引起自噬功能受损。通过蛋白组数据显示Hippo信号通路可能及自噬、UC相关；SCFAs促进YAP进入细胞核进行转录调节，我们构建了肠道特异性敲除YAP的转基因小鼠，证明YAP可以调控自噬，并且SCFAs是依赖YAP来抑制DSS引起的小鼠炎症和肠道屏障损伤。综上所述，项目明确了 YAP信号参与SCFAs诱导自噬缓解UC的过程，为抗炎治疗和缓解UC提供了潜在靶点。