粪肠球菌MG 2108对小鼠结肠炎症的缓解作用及机制研究

【目的】为了筛选能抑制鼠类柠檬酸杆菌(Citrobacter rodentium)诱发的小鼠结肠炎的益生菌，并研究其干预机制。【方法】对4株筛选的菌株进行人工模拟胃肠液耐受试验，并体外测试它们对鼠类柠檬酸杆菌的抑制能力，最终筛选出粪肠球菌(Enterococcus faecalis)MG 2108。72只雄性7周龄ICR小鼠经过适应性饲养7d后，被随机分为2组：正常对照组(MC组，24只，生理盐水)和炎症对照组(IC组，48只，1×10¹⁰CFU/mL灌胃鼠类柠檬酸杆菌)，7d后各采12只小鼠，通过结肠组织HE染色和炎症因子检测实验，判断炎症模型建成。原MC组(剩下12只小鼠)更名为NC组，用以区别建模前后的正常对照组，IC组随机分成3组：自然恢复组(IR组，12只，生理盐水)、环丙沙星组(CF组，12只，4mg/mL环丙沙星)和粪肠球菌MG 2108组(EF组，12只，1×10⁸CFU/mL粪肠球菌MG 2108)。18d后结束灌胃，所有小鼠麻醉后眼球取血，解剖。【结果】粪肠球菌MG 2108可以缓解和修复鼠类柠檬酸杆菌引发的小鼠结肠和肝脏损伤，并且通过降低炎症细胞因子的表达水平和增加紧密连接蛋白的表达水平，促进了结肠炎症组织的修复。它改变了肠道微生物菌群结构，EF组的肠杆菌属(Enterorhabdus)和阿克曼菌属(Akkermansia)等有益菌群的丰度增加，同时短链脂肪酸也显著增加(P<0.05)，并且优于CF组和IR组。【结论】粪肠球菌MG2108是一株有利于肠道健康的益生菌，治疗鼠类柠檬酸杆菌诱导的小鼠结肠炎效果优于环丙沙星，自然恢复组效果明显差于EF组。

Mechanism of Enterococcus faecalis MG 2108 against mouse colitis

[Objective] To screen probiotics with inhibitory effect on murine colitis induced by Citrobacter rodentium and to investigate the mechanism. [Methods] The tolerance of the four screened strains was tested with simulated gastrointestinal fluid, and their inhibitory ability against C. rodentium was examined in vitro. Finally, Enterococcus faecalis MG 2108 was screened out. A total of 72 male 7-week-old ICR mice were randomized into two groups after 7-day adaptive feeding:normal control group (MC, 24 mice, normal saline) and inflammation control group (IC, 48 mice, 1×10¹⁰ CFU/mL C. rodentium). After 7 days, 12 mice were respectively selected from the two groups and the inflammation was examined based on hematoxylin and eosin (HE) staining of colonic tissues and detection of inflammatory factors. The remaining 12 mice from the MC were renamed as NC to distinguish the normal control group before and after modeling. The mice of IC group were randomly divided into three groups:natural recovery group (IR, 12 mice, normal saline), ciprofloxacin group (CF, 12 mice, 4 mg/mL ciprofloxacin), and E. faecalis MG 2108 group (EF, 12 mice, 1×10⁸ CFU/mL E. faecalis MG 2108). After 18 days of gavage, all mice were anesthetized and dissected and blood was taken from the eyes. [Results] E. faecalisMG 2108 alleviated the injury of colon and liver induced by C. rodentium. E. faecalis MG 2108 promoted the repair of colon tissue via decreasing the expression of inflammatory cytokines and increasing the expression of tight junction protein.E. faecalisMG 2108 induced structural changes in gut microbiota, as the abundance of beneficial flora such as Enterorhabdus and Akkermansia increased in EF group, and the content of short-chain fatty acids (SCFAs) in EF group was higher than that in CF and IR groups (P<0.05). [Conclusion] E. faecalisMG 2108, an intestinal probiotic strain, shows better effect on the C. rodentium-induced colitis than ciprofloxacin, and the effect of IR group was significantly inferior to that of EF group.