从局部感染到MODS：细菌DNA在脓毒性腹膜炎发病机制中的关键性作用

腹腔细菌感染是脓毒症常见病因。胞外组蛋白已被证明是多种危重症时多器官功能障碍综合征（MODS）的重要介质；脓毒性腹膜炎小鼠同时存在高浓度循环组蛋白及脾与胸腺的大面积凋亡现象，但直接静脉注射外源性组蛋白却未引起明显的脾细胞凋亡；腹腔注射经DNase1消化后的细菌裂解液上清也未导致实验小鼠死亡。本研究提出脓毒性腹膜炎的级联反应发病过程：腹腔细菌感染→细菌DNA促发失控性反应→免疫细胞大量死亡→高浓度循环组蛋白→MODS，并将通过体内、外实验：1）观察细菌DNA对腹腔细菌感染小鼠的脾与胸腺凋亡、循环组蛋白水平及多脏器损伤标志物的影响；2）评价细菌DNA-TLR9信号通路对体外培养脾脏与胸腺细胞存活情况的影响，以及共培养条件下对多器官来源细胞的杀伤效应；3）通过小鼠CLP模型评价拮抗细菌DNA的保护性作用；4）初步探讨“细菌DNA+”组合模式的的脓毒症建模效果，为该病精准治疗提供关键靶标。

Intra-abdominal sepsis or septic peritonitis is the second most common form of sepsis after pulmonary sepsis and is frequently associated with high morbidity and mortality. As important damage associated molecular model patterns (DAMPs), extracellular histones have been proved to be the major mediators of MODS in sepsis and other critical illnesses. We not only detected high levels of circulating histones in septic mice induced by intraperitoneal bacterial infections, but also found large areas of apoptosis happened in spleen and thymus. However, intravenous injection of recombinant histones did not cause obvious apoptosis in the spleen; intraperitoneal injection of bacterial lysate supernatants digested with DNase1 did not cause death in the mice. Therefore, we propose a hypothesis for the pathogenesis of septic peritonitis: intraperitoneal bacterial infections → uncontrolled response primed by bacterial DNA → extensive immune cell death → high concentrations of circulating histones → MODS, and in vivo and in vitro experiments will be performed: 1) to observe the effects of bacterial DNA on apoptosis induction of spleen and thymus, circulating histone levels and multiple organ injury markers in mice receiving intraperitoneal injection of bacteria ;2) To evaluate the effect of bacterial DNA-TLR9 signaling pathway on the survival rates of splenocytes and thymocytes in vitro, and the killing effects on the co-cultivated cells derived from multiple organs; to access the protective effect of bacterial DNA blocking strategies via CLP model;4) to preliminarily explore the modelling efficiency of "bacterial DNA +" combination mode; and the study is aimed to gain a better understanding of sepsis pathophysiology and afford more effective strategies for precision therapies targeting sepsis.