mtDNA介导的树突状细胞激活在腹腔感染所致肠屏障损伤中的角色

The intestinal barrier injury is the key pathophysiological change during the process from intra-abdominal infections to multiple organ dysfunction syndrome. But the mechanisms of intestinal barrier injury still remain unknown. Our previous study showed that mitochondrial DNA (mtDNA) released by intestinal epithelial cells (IEC) under the condition of intra-abdominal infections could induce “secondary strike”, which require further research. Recent studies indicate that mtDNA as endogenous antigen are involved in inflammatory responses and organ dysfunction by activating dendritic cells (DC). Therefore, we hypothesized that mtDNA might aggravate intra-abdominal infection induced intestinal barrier injury by activating DC. Our preliminary experiment indicated that the level of mtDNA was elevated in intestinal DC of animal models of intra-abdominal infections, and it was associated with high expression of pro-inflammatory mediators. Based on these studies, we aimed to establish animal models of intra-abdominal infections and the culture model of DC. With the help of flow cytometry and molecular biological techniques, etc., we will investigate the effects of mtDNA on DC activation and intestinal barrier by the combination of both in vivo and in vitro study. Further, we will explicit the mechanisms of the DC activation and intestinal barrier injury mediated by mtDNA. This study will provide theoretical basis for the pathophysiological changes of intra-abdominal infection induced intestinal dysfunction, and widen our horizon on the treatment for intra-abdominal infections.

肠屏障损伤是腹腔感染向多脏器功能障碍进展过程中的枢纽性病理生理改变，但肠屏障损伤机制尚未完全阐明。我们前期研究发现腹腔感染过程中肠上皮细胞(IEC)受损所释放的线粒体DNA(mtDNA)对肠屏障具有“二次打击”作用，但机制未明。新近的研究显示mtDNA作为内源性抗原主要通过激活树突状细胞(DC)参与炎症应答和器官损伤。受此启发，我们推测mtDNA可能通过激活DC途径加重腹腔感染所致肠屏障损伤。预实验发现腹腔感染模型小鼠肠DC中mtDNA水平显著升高并过表达促炎介质。在既往研究基础上，本项目拟以腹腔感染模型小鼠及肠DC细胞为研究对象，在体与离体实验相结合，采用流式细胞及分子生物学等技术，明确腹腔感染中mtDNA对肠DC的激活作用及对肠屏障的影响，深入分析mtDNA激活DC并进一步损伤肠屏障的分子机制，以期为揭示腹腔感染中肠屏障损伤的病理生理过程提供理论依据，为腹腔感染的临床诊疗拓展视角。

腹腔感染致肠屏障损伤过程中，由于黏膜过度的炎症反应和肠上皮细胞的死亡，显著增加肠黏膜的通透性，加重系统性炎症反应和多器官功能障碍。在肠损伤中，树突状细胞释放以线粒体DNA（mtDNA）为代表的损伤相关分子模式，在肠黏膜炎症与损伤中发挥关键作用。肠黏膜内广泛存在以STING为主的DNA识别受体，可参与mtDNA释放所致的肠屏障损伤。本项目揭示在创伤与感染等应激时，mtDNA激活的STING信号通路在肠黏膜炎症及损伤中发挥始动与放大作用。从临床病例出发，以临床样本揭示腹腔感染合并肠损伤患者循环mtDNA水平与坏死性凋亡、肠道损伤以及炎症的相关性，发现STING通路和坏死性凋亡参与肠屏障损伤。构建小鼠mtDNA腹腔注射和腹腔感染模型，证明STING通路是mtDNA介导肠屏障损伤的关键信号通路。以体内与体外实验相结合，发现mtDNA介导的STING通路的激活与肠道炎症、肠上皮细胞坏死性凋亡高度相关，阐明mtDNA在创伤或感染所致肠屏障损伤中的关键作用。本项目紧紧围绕“创伤与感染条件下，mtDNA介导STING通路调控肠黏膜免疫屏障的机制及其临床意义”这一论题，深入探究mtDNA介导肠道炎症与损伤的机制，为腹腔感染肠屏障损伤提供理论解释。本项目揭示mtDNA介导STING信号通路放大肠道炎症效应，促进肠上皮细胞坏死性凋亡，加重腹腔感染肠屏障损伤；并发现循环mtDNA和RIPK3蛋白可作为肠道损伤的生物学标志物，为临床治疗提供潜在靶点。