STING介导的循环mtDNA调控肠黏膜免疫屏障的机制研究

Gut is the origin and center of MODS (multiple organ dysfunction syndrome). Intestinal hypoxia and ischemia result in the injury to intestinal epithelial cell (IEC) and its mitochondrion, which release various DAMPs (damage-associated molecular patterns), among which mitochondrial DNA (mtDNA) causes the strongest immune responses. STING (stimulator of interferon genes) distributed within lamina propria is newly recognized as the specific sensor for mtDNA. We hypothesized that circulating mtDNA initiates SIRS (systemic inflammatory response syndrome), and causes extensive damage to intestinal mucosal membrane via circulatory system. Amelioration of SIRS could be achieved by blocking STING-mediated mtDNA signaling. We will discover that mtDNA originates from damaged IEC and becomes critical for subsequent SIRS. We will develop STING-deficient mice, and demonstrate that circulating mtDNA initiates TH17 differentiation by STING signaling in lamina propria. We will establish Salmonella infection model, and reveal that enteral nutrition could inhibit the release of mtDNA and the phosphorylation of STING signaling, and therefore prevent bacteria translocation, ameliorate inflammation and eventually reverse organ dysfunctions. We will also evaluate the clearance of circulating mtDNA by CVVH (continuous veno-venous hemofiltration), which could provide potential guidance for the development of new CVVH filter. This study will uncover the pivotal role of STING-mediated circulating mtDNA in the regulation of systemic and intestinal immune responses, and thereby promote the development of clinical prophylactic and therapeutic strategies.

肠道是MODS的始动与中心器官。肠缺血缺氧可导致黏膜细胞线粒体损伤，释放出以线粒体DNA（mtDNA）为主的损伤相关分子模式。肠黏膜内存在以STING为主的mtDNA识别系统。本项目提出mtDNA可引起SIRS，通过血液循环介导肠黏膜广泛损伤；阻断该炎性机制，可有效减轻SIRS。本研究拟证实损伤的肠黏膜细胞可释放mtDNA，进入血液循环引发SIRS；构建STING基因敲除小鼠，论证循环mtDNA经STING可激活肠黏膜TH17应答，破坏肠屏障功能；建立肠道沙门氏菌感染模型，证实黏膜营养可减少mtDNA释放并下调STING信号通路，抑制肠道菌群易位，减轻炎性反应并逆转MODS；观察CVVH滤柱前后血液及滤液中循环mtDNA的变化，评价CVVH清除mtDNA的效应，为新型滤器开发提供理论依据。此研究将阐述STING介导的mtDNA调控全身及肠黏膜免疫应答的机制，指导临床探索新的预防与治疗手段。

肠道是多脏器功能障碍（MODS）的始动与中心器官。肠缺血缺氧可导致肠上皮细胞线粒体损伤，释放出以线粒体DNA（mtDNA）为代表的损伤相关分子模式。肠黏膜内存在以STING通路为主的mtDNA识别系统。本课题揭示在创伤及感染等应激时，mtDNA激活的STING通路发挥调控肠黏膜及全身炎性反应的始动与放大作用并阐明其机制，揭示mtDNA诱导的STING信号通路是肠道成为MODS始动和中心器官的重要途径。通过临床试验证实，黏膜营养/肠内营养通过促进受损肠黏膜上皮细胞的修复与再生，抑制mtDNA的释放与后续STING信号通路，减轻肠道及全身炎性反应，改善MODS的分子生物学基础。基础结合临床研究评价持续性静脉-静脉血液滤过(CVVH)对包括循环mtDNA在内的多种致炎介质的清除效应，探讨此机制在阻断全身过度炎性反应及继发性肠黏膜免疫屏障损伤中的作用，为针对此机制改善CVVH 的治疗方式与效果提供理论依据与指导。.本课题紧紧围绕“创伤与感染状态下，mtDNA 调控全身炎性反应及肠黏膜免疫屏障的机制及其临床意义”这一论题，深入探讨STING 介导的循环mtDNA引发全身炎性反应及肠黏膜广泛炎症的机制，为肠黏膜“一处打击、多处受损”的级联效应提供理论解释。本课题揭示黏膜营养通过促进肠黏膜修复，抑制mtDNA 的释放，阻断肠道菌群易位的机制，进一步肯定CVVH 可有效清除循环mtDNA。