IL-33调控的肠神经胶质细胞在炎症性肠病中的作用及机制研究

The inscidence of inflammatory bowel disease (IBD) has increased gradually in recent years，while there’s no effective and safty treatment for IBD so far. Therefore, researches about novel effective theraputics of IBD become more and more popular. Studies show that IL-33 may play a role in the occurrence and development of IBD, since its level in the intestinal mucosa of IBD patients are significantly elevated. Our previous studies have shown that ST2 (the receptor of IL-33) can be expressed on astrocytes, and its expression is significantly increased after brain cells damage. It is shown that IL-33 can induce astrocytes to produce CCL2, and CCL2 is reported to be closely related to the destruction of the blood-brain barrier. Enteric glia cells(EGC) is an important cell in the enteric nervous system that resembles astrocytes of the central nervous system. Some studies have indicate that EGC has an important role in the animal model of colitis with its regulation of intestinal mucosal barrier . Therefore, we propose that IL-33 can destroy the intestinal mucosal barrier by inducing EGC to produce CCL2 and play an important role in the pathogenesis of IBD. This research will use DSS-induced experimental colitis and Caco-2 cells and EGC co-culture system to explore the role and mechanism of IL-33-dependent EGC in IBD, and seek for new therapeutic targets and directions for the treatment of IBD.

炎症性肠病在我国发病率逐渐上升，而目前尚缺乏有效安全的治疗手段。因此研究治疗IBD的新型靶点成为了目前的研究热门。研究表明，IBD患者的肠粘膜中IL-33水平显著升高，这提示IL-33可能在IBD发病机制中发挥某种重要作用。本项目组前期研究发现ST2（IL-33的受体）可在星形胶质细胞上表达且于脑损伤后表达显著升高。另有研究表明IL-33可诱导星形胶质细胞产生CCL2，而CCL2被报道与血脑屏障的破坏密切相关。肠神经胶质细胞（EGC）是肠神经系统中一种类似于星形胶质细胞的重要细胞。研究表明在实验性肠炎中EGC可参与调节肠粘膜屏障。因此我们提出IL-33可通过诱导EGC产生CCL2破坏肠粘膜屏障，在IBD的发病中发挥重要作用。本项目拟用DSS诱导实验性肠炎和Caco-2细胞和EGC共培养系统，探索IL-33调控的EGC在IBD中的作用及其机制，为治疗IBD寻求新的治疗靶点和方向。

炎症性肠病(Inflammatory bowel disease,IBD)是一种慢性肠道炎症性疾病包括溃疡性结肠炎和克罗恩病。在我国IBD的发病率逐渐上升，而目前尚缺乏安全有效的治疗手段。研究IBD发病机制及潜在的新靶点是目前的研究热门。肠神经胶质细胞（Enteric glial cells, EGC）与中枢神经系统中的星形胶质细胞具有类似的形态和功能，参与了肠道的炎症和免疫反应。白细胞介素 33（interleukin-33，IL-33）可应对周围环境的应激启动炎症反应；同时也是一种细胞损伤后释放的“警戒”物质。ST2是IL-33的特异性受体。与正常人相比，IBD 患者的肠粘膜中 IL-33 水平要显著升高。而目前IL-33/ST2信号通路在 IBD 中的作用仍存在争议。本研究旨在探索IL-33调控EGC在IBD中的作用及其机制。1）我们的研究发现ST2敲除小鼠对DSS诱导的结肠炎更敏感，外源性给予IL-33能改善DSS诱导的小鼠结肠炎。炎症性肠病患者肠道损伤的动态RNAseq数据支持IL33的早期升高和后续分泌不足，而炎症因子持续高水平释放。因此IL-33/ST2信号通路在IBD中发挥保护性作用。2）在DSS诱导的小鼠结肠炎中IL-33表达升高，EGC也被激活，且EGC表达ST2，可接受IL-33调控。3）L-33干预的肠神经胶质细胞系RNASeq测序结果显示：IL33与肠神经胶质细胞的ST2结合后可以激活下游信号，促进cxcl1、mmp9、cxcl6等基因的表达。在IBDMDB数据库中进行患者真实样本相关性分析提示在IBD患者中前述RNAseq结果中IL33最相关的基因是MMP9。在进一步的动物实验中抑制MMP9可抵消外源性IL-33对DSS诱导的小鼠结肠炎的保护作用。因此MMP9是IL-33在IBD中发挥保护作用的关键分子。从而在IBD中发挥保护作用。因此我们的结论是：IL-33/ST2信号通路可以通过上调肠神经胶质细胞中MMP9的表达，从而在IBD中发挥保护作用。因此，IL-33/ST2信号通路的激活可成为潜在的IBD的有效免疫治疗方式。