猕猴肠缺血再灌注后肠道菌群变化与肠黏膜屏障损伤的关系

Relevance of Intestinal Mucosal Barrier Damage and Alteration of Luminal Microflora after Intestinal Ischemia Reperfusion Injury in Macaque

肠道菌群移位是多器官功能障碍的重要机制之一,但其与肠黏膜天然免疫有何关系?细菌移位究竟发生在大肠还是小肠?目前尚不清楚。目的:探讨肠缺血再灌注后猕猴肠道菌群的变化及其对机体的影响。方法:通过肠系膜上动脉钳闭——松开造成猕猴肠缺血再灌注损伤;细菌培养分析回肠和结肠菌群的变化;免疫组化SP法检测回肠组织中Toll样受体(TLR)2和TLR4的表达;HE染色观察猕猴肠道组织学改变;取门静脉血行血培养,观察菌血症发生情况。结果:猕猴肠缺血再灌注损伤后,回肠和结肠腔内细菌较对照组分别增加约2×106倍和1×102倍,均以大肠杆菌等需氧菌为优势菌群;回肠黏膜出血坏死损伤明显,结肠病变轻微;回肠黏膜中普遍表达TLR2和TLR4,以上皮细胞膜表达最为明显。IIR组大肠杆菌菌血症发生率为100.0%。结论:猕猴肠缺血再灌注后,回肠中大肠杆菌等需氧菌过生长,启动天然免疫,导致肠黏膜屏障受损和肠道菌群移位。

Background： Bacterial translocation is considered as one of the important mechanisms of muhiorgan dysfunction syndrome. However, whether it is relevant to innate intestinal immunity or is originated from large or small intestine remains unclear. Aims： To investigate the alteration of the intestinal microflora and its effects on the host after intestinal ischemia reperfusion （IIR） in macaque. Methods： IIR injury was induced by clamping and unclamping of superior mesenteric artery. Intestinal histopathologic changes were studied under light microscope and changes of microflora in the colon and the ileum were studied by bacterial culture. The expressions of Toll-like receptor （TLR） 2 and TLR4 in the ileum were detected by immunohistoehemistry. In addition, blood samples from portal vein were cultured for detection of bacteremia. Results： The amount of bacteria in the ileum and the colon after IIR was 2×10^6 and 1×10^2 folds higher than that in the normal control, respectively, where Escherichia coli was the predominant bacteria flora. Severe inflammatory lesions including necrosis and bleeding were observed in small intestinal mucosa subsequent to IIR, whereas only mild lesions were seen in the colonic mucosa, furthermore, 100% Escherichia coli bacteremia was present in IIR group. Diffuse expressions of Toll-like receptor 2 or 4 were seen in the ileal mucosal epithelium. Conclusions： IIR injury in the macaque may initiate the sequential events in the intestinal tract： overgrowth of Escherichia coil and other aerobic bacilli, initiation of innate immunity, and a result of mucosal barrier damage and bacterial translocation.