TGR5激动剂对炎症性肠病的治疗作用及其机制研究

Inflammatory bowel disease (IBD) is a group of disorders associated with chronic inflammation of the gastrointestinal tract. The pathogenesis of IBD remains unclear. IBD is hard to cure and easy to relapse, so patients need long term medications. The drugs for treating IBD were really insufficient, and with the defects of low efficacy and varying side effects. It is of great urgency for us to do related research and develop new strategies for the treatment of IBD. TGR5 is a Gαs coupled GPCR. Activation of TGR5 in enteroendocrine L cells increases the secretion of GLP-1, GLP-2 and PYY. A great deal of researches were carried out based on its anti-diabetic effects, while, only a few of researches focused on its linking with other diseases. Based on intestinal-targeted strategy, we synthesized OM8, which was a specific TGR5 agonist with the properties of good potency, high exposure to intestine and low absorption to the plasma. Our previous research indicated that OM8 alleviated DSS induced colitis in mice significantly, elevated GLP-2 levels in plasma of the mice, and increased the phosphorylation of Akt in fetal rat intestinal cells (FRIC). We will take advantage of these results, using OM8 as a powerful ligand tool to verify the therapeutic potential of TGR5 agonist on colitis model mice, and to investigate its dual modulation mechanism on both the intestinal mucosal barrier and the mucosal immune system. The aim of this research is to estimate the possibility of targeting TGR5 for the treatment of IBD, clarify the molecular mechanisms underlying the biological functions and provide new strategies for the treatment of IBD.

炎症性肠病（IBD）是一种发病机制尚不明确的慢性肠道炎症性疾病，病程长，难治愈，易复发，患者需长期用药，但现有药物种类有限、药效不足且副作用较大，研发IBD治疗新药和开展相关基础研究刻不容缓。TGR5是Gs型GPCR，激活后可促进肠内分泌L细胞GLP-1、GLP-2和PYY的分泌，是抗糖尿病新药研究领域的热门靶点，但对其他疾病的研究报道很少。我们前期研究发现，基于靶向肠道策略设计合成的非体循环类高活性选择性TGR5激动剂OM8对DSS诱导的小鼠溃疡性结肠炎具有显著治疗作用，可增加血浆中GLP-2水平和原代培养胎鼠肠细胞中Akt蛋白磷酸化。本项目将在此基础上，以OM8为探针系统研究TGR5激动剂对IBD的治疗作用，并深入研究其对肠黏膜屏障和肠黏膜免疫系统的调控机理，揭示TGR5激动剂的新型药理作用，明确其作为IBD药物治疗新靶标的可能性及其分子机制，为抗IBD新药研发提供新思路。

炎症性肠病（IBD）是一种发病机制复杂的慢性肠道炎症性疾病，主要包括溃疡性结肠炎（UC）和克罗恩病（CD）两种类型，研发IBD治疗新药和开展相关基础研究具有重要意义。TGR5是抗糖尿病新药研发的热门靶点，但对其他疾病的研究报道很少。本课题以靶向肠道的高活性选择性TGR5激动剂OM8为探针，开展TGR5激动剂对溃疡性结肠炎的治疗作用及机制研究。研究发现，OM8对DSS诱导UC小鼠具有显著治疗作用，可明显缓解小鼠疾病症状，增加结肠长度，改善结肠组织病理性受损，抑制结肠组织炎症因子表达。OM8可增加DSS诱导UC小鼠血浆GLP-2水平，并维持结肠组织GLP-2R信号通路，DPP-4抑制剂西格列汀与OM8联用可显著增强OM8对UC的改善效应，提示OM8对UC治疗作用可能与其促进GLP-2分泌相关。OM8对DSS诱导UC小鼠肠上皮屏障具有保护作用，可显著改善UC小鼠结肠组织紧密连接蛋白表达受损，并可促进肠干细胞增殖和分化，抑制肠上皮细胞凋亡。OM8可显著抑制TNF-α诱导的HT-29和Caco-2细胞凋亡，且该作用依赖于TGR5。OM8激活TGR5后通过cAMP/PKA信号通路增加c-FLIP蛋白表达，抑制JNK磷酸化，进而抑制肠上皮细胞凋亡，维持肠上皮完整性。综上，本课题明确了TGR5激动剂OM8对DSS诱导UC小鼠的治疗作用，该作用与OM8促进GLP-2分泌、促进结肠组织肠干细胞增殖和分化、抑制肠上皮细胞凋亡、进而维护肠上皮屏障相关。同时，本课题发现OM8对肠上皮细胞凋亡具有直接抑制作用，并阐明了TGR5激活后通过cAMP/PKA/CREB/c-FLIP/JNK信号通路抑制肠上皮细胞凋亡的新机制。本课题明确了TGR5激动剂作为溃疡性结肠炎药物治疗新靶标的可能性及其分子机制，为新药研发提供了新思路。