HMGB1-NLRP3炎症体在UC肠道菌群激活粘膜免疫中的作用及机制研究

The activation of mucosal immunity by intestinal flora is the key point in the pathogenesis of UC, but how the intestinal flora on epithelial surface activate the immune cells in lamina propria is not clear. Inflammasome is the dangerous signal receptors in macrophages, which may cause abnormal activation of IL-1 beta secretion increased, mediats autoimmune disease. HMGB1 is intracellular alarmins. In sinusitis bacteria stimulate the release of HMGB1 and promote the nasal mucosa inflammation. We found that secretion of HMGB1 from intestinal epithelial cells in UC patients increased significantly, and HMGB1 in liver cancer cells can activate NLRP3 inflammasome by TLR4 and RAGE, suggesting that intestinal flora can stimulate intestinal epithelial cells to release HMGB1, which activate inflammasome and cause excessive immune response. From the intestinal flora-intestinal epithelial cells-intestinal immune homeostasis perspective, we will explore the regulation of intestinal flora on mucosal immunity. We will isolate intestinal bacteria in UC patients and stimulate the intestinal epithelial cells, establish co culture system of intestinal epithelial cells and the macrophage and do experiments in vivo and in vitro to investigate the mechanism of intestinal flora stimulation of HMGB1 release and HMGB1 activation of NLRP3 in intestinal epithelial cells in UC, providing a potential therapeutic target.

肠道菌群激活粘膜免疫是UC发生的关键，但肠上皮表面细菌通过何种途径激活粘膜固有层免疫细胞机制不清。炎症体是巨噬细胞内危险信号感受器，其异常激活可引起IL-1β分泌增加，介导自身免疫性疾病；HMGB1是细胞内警报素，鼻窦炎中细菌通过刺激鼻粘膜上皮释放HMGB1促进炎症发生。我们发现UC患者肠上皮细胞HMGB1分泌大量增加，且肝癌细胞中HMGB1可通过TLR4和RAGE激活NLRP3炎症体，提示我们肠道菌群可能通过刺激肠上皮细胞释放HMGB1激活炎症体引发过度免疫应答。我们将从肠道菌群-肠上皮细胞-肠道免疫稳态的角度,探讨肠道菌群对粘膜免疫的调控，通过分离培养UC患者肠道菌群并刺激肠上皮细胞、建立肠上皮细胞-巨噬细胞共培养体系等方法，运用体内、体外实验探讨肠道菌群刺激肠上皮细胞HMGB1释放和HMGB1激活NLRP3炎症体引发UC免疫反应的具体机制，为有效干预炎症提供治疗靶点。

肠黏膜免疫失调是溃疡性结肠炎发病机制的关键，HMGB1是细胞内警报素，我们前期研究已发现UC患者肠上皮细胞分泌HMGB1显著增加，但HMGB1在UC中作用及机制不明。我们研究发现HMGB1蛋白含量在IBD患者粪便中明显高于IBS患者和正常对照组，且可作为粪便标志物鉴别IBD和IBS，此外我们用益生菌干预TNBS灌肠诱导的小鼠急性结肠炎模型，发现益生菌干预可通过减少肠道黏膜固有层巨噬细胞浸润并抑制巨噬细胞分泌HMGB1，调节Hmgb1造成的肠黏膜屏障损害从而缓解小鼠结肠炎症程度。另外，在研究中我们还发现岩藻糖可能通过抑制NLRP3炎症体的激活来抑制巨噬细胞向M1型促炎型巨噬细胞方向极化，从而减轻小鼠急性结肠炎症程度，而抑制NLRP3炎症体的机制可能与岩藻糖增加巨噬细胞线粒体自噬，清除了过多的ROS有关。我们的研究表明HMGB1和NLRP3炎症体参与了UC炎症的发生，多种干预可通过调节HMGB1的水平和NLRP3炎症体的激活来调控肠道炎症，提示HMGB1和NLRP3炎症体可能成为新的炎症性肠病治疗靶点。此外，我们还发现IL-1家族新成员IL-38在IBD患者血清和结肠病灶中表达升高，利用IL-38重组蛋白干预可缓解DSS诱导的小鼠急性结肠炎，提示IL-38可能为IBD治疗的潜在靶点。