基于肠道菌群调控肠道NLRP3炎症小体激活探讨重症急性胰腺炎肠黏膜屏障损伤机制

Intestinal mucosal barrier dysfunction is an important factor involved in the development of severe acute pancreatitis(SAP), the incidence of multiple organ failure and pancreatic necrosis. Intestinal microbiota dysbiosis plays an important role in this processes. However, it remains unclear regarding the specific and core mechanisms of intestinal microbiota dysbiosis-induced intestinal mucosal barrier dysfunction. Nucleotide binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) can recognize the majority of pathogenic microorganisms, leading to the incidence of the intestinal inflammation and immune responses. Our preliminary data indicates that the amount of the beneficial bacteria was significantly decreased while the amount of conditioned pathogenic bacteria was significantly increased in the early stage of AP patients. Moreover, the alteration of intestinal flora was significantly associated with the intestinal mucosal barrier function. In addition, our animal experiments demonstrated that NLRP3 inflammasome was activated which is in coincidence with intestinal microbiota dysbiosis. Therefore, we propose here that intestinal microbiota dysbiosis may lead to SAP intestinal mucosal barrier damage by regulating the activation of intestinal mucosa NLRP3 inflammasome. We will systematically study the role of intestinal microbiota dysbiosis during the development of SAP and its effects on intestinal barrier function by using wild type, sterile and NLRP3-knockout SAP mice models. We will further explore the effects and mechanism of NLRP3 inflammasome during the pathogenesis, to illustrate the novel mechanism of SAP intestinal dysfunction. Additionally, we will find out whether fecal bacteria transplantation could reverse the intestinal microbiota dysbiosis, reduce intestinal barrier damage and improve prognosis of SAP. The implementation of this project will provide a novel therapy approach for intestinal mucosal barrier dysfunction of SAP.

肠黏膜屏障功能障碍是促进重症急性胰腺炎（SAP）病情发展甚至诱发多脏器功能障碍和胰腺坏死感染的重要原因，SAP患者肠道菌群失衡在其中发挥了重要作用，但其具体机制不明。NLRP3可识别大部分病原微生物，引起肠道炎症免疫反应。我们前期研究显示AP患者肠道有益菌明显减少及条件致病菌明显增加，这与患者肠黏膜屏障功能损伤呈显著相关性；且SAP小鼠肠道菌群失衡的同时NLRP3炎症小体出现活化。因此，推测肠道菌群失衡可能调控肠道NLRP3炎症小体激活导致SAP肠黏膜屏障损伤。本课题拟通过应用野生型、无菌型及NLRP3基因敲除小鼠SAP模型系统研究肠道菌群失衡对SAP肠黏膜屏障功能的影响，探讨肠道NLRP3炎症小体激活在其中的作用及机制, 明确SAP肠功能障碍发生新机制；明确粪菌移植能否纠正SAP肠道菌群失衡、减轻肠黏膜屏障功能损害从而改善预后，对探索SAP肠功能障碍治疗新方法具有实际意义。

肠黏膜屏障功能障碍是促进重症急性胰腺炎（SAP）病情发展甚至诱发多脏器功能障碍和胰腺坏死感染的重要原因，SAP患者肠道菌群失衡在其中发挥了重要作用，但其具体机制不明。NLRP3可识别大部分病原微生物，引起肠道炎症免疫反应。我们前期研究显示AP患者肠道有益菌明显减少及条件致病菌明显增加，这与患者肠黏膜屏障功能损伤呈显著相关性。本项目我们首先通过野生型SAP⼩⿏模型探讨SAP小⿏肠道菌群、肠黏膜屏障功能的变化，确定肠道细菌移位情况，结果发现SAP过程中肠道菌群发生明显改变且存在肠道细菌移位，肠道NLRP3表达明显上调；其次，我们选择了无菌和假无菌两种小鼠模型验证肠道菌群在SAP过程中的作用，结果发现无菌和假无菌小鼠SAP胰腺炎明显减轻，胰腺组织炎症细胞浸润明显减少，无菌及假无菌SAP小鼠血清炎症因子水平明显降低，肠道NLRP3表达明显下调，说明无菌状态下小鼠胰腺炎可明显减轻；最后，我们选择NLRP3敲除小鼠进行后一步研究，结果发现，与野生型相比，NLRP3 KO小鼠经SAP诱导后水肿、炎症浸润及胰腺腺泡细胞坏死均减轻，WT和NLRP3 KO小鼠在基线时存在显著的微生物群落差异。因此我们得出肠道菌群和NLRP3炎症小体在SAP进程中的双向调节作用，提示宿主和微生物群在SAP进程中相互作用，调节肠道菌群失衡和炎症免疫纠正肠黏膜屏障功能障碍减少肠道菌群移位对预防AP继发胰腺坏死感染、改善患者预后具有现实指导意义。

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