内毒素耐受对脓毒症大鼠肠道功能的保护作用

目的：动态观察内毒素耐受大鼠在内毒素血症时肠道炎症反应和免疫功能的变化,探讨内毒素耐受对内毒素血症大鼠肠道的保护作用及其机制。方法：选择健康成年雄性SD大鼠70只,随机分成3组：正常对照组（10只）、内毒素（LPS）组（30只）和内毒素耐受组（30只）。内毒素耐受组大鼠于实验第1日经腹腔注射LPS 0.25 mg/kg,24h后经腹腔注射LPS 0.5 mg/kg,LPS组在上述时间均给予等量生理盐水;实验第5日上述两组大鼠均腹腔注射大剂量LPS 10 mg/kg,于注射大剂量LPS前（0h）和注射后2、4、6、12h取大鼠肠组织制备肠黏膜上清液,用双抗体夹心法测定肠黏膜组织中分泌型免疫球蛋白A（sIgA）的含量,用免疫组化技术检测肠组织细胞间黏附分子-1（ICAM-1）的表达,并与正常对照组进行比较;光学显微镜下观察3组大鼠肠组织病理学变化,并进行病理学评分。结果：内毒素耐受组在给予小剂量LPS后没有出现体重下降。内毒素耐受组肠黏膜中slgA的含量较正常对照组明显升高,6 h最为明显（P〈0.05）,LPS组sIgA含量2 h明显升高（P〈0.05）,从6 h开始下降（P〈0.05）。内毒素耐受组给予大剂量LPS后肠黏膜ICAM-1的表达没有呈上升趋势,各时间点ICAM-1的表达与正常对照组比较差异有显著性,以6h ICAM-1的表达最低,而LPS组肠黏膜ICAM-1的表达随时间的延长逐渐升高,明显高于内毒素耐受组。肠组织病理学观察可见：LPS组肠黏膜水肿,绒毛脱落,并伴有大量炎性细胞浸润;内毒素耐受组上述表现较LPS组减轻。两组肠黏膜炎症损伤病理学评分LPS组（3.89±0.45）分;内毒素耐受组（2.65±0.36）分]差异有显著性（P〈0.01）。结论：内毒素耐受可减轻内毒素血症导致的肠道黏膜屏障的损害,升高sIgA水平,减少ICAM-1表达,从而起到肠保护作用。

Protective effect of endotoxin tolerance on intestinal function in rat

Objective:To observe the changes in inflammation and immune function of intestine after endotoxin challenge in endotoxin tolerant rats,and investigate the protective effect as well as its mechanism of endotoxin tol- erance of intestine.Methods:Seventy male SD rats were randomly divided into three groups:normal control group (n=10),lipopolysaecharide(LPS)group(n=30)and endotoxin tolerant group(n=30).On the first day of the experiment,rats of endotoxin tolerant group received intraperitoneal injection of 0.25 mg/kg of LPS,and 24 hours later 0.5 mg/kg of LPS was again injected intraperitoneatly.Rats of LPS group received an equivalent amount of normal saline.After 72 hours,to rats of both LPS and endotoxin tolerant groups LPS 10 mg/kg was intraperito- neally injected.The levels of sIgA in intestinal mucosa were measured by radioimmunoassay in LPS and endotoxin tolerant rats at 0,2,4,6 and 12 hours after intraperitoneal injection of 10 mg/kg LPS,and the levels of intercel- lular adhesion molecule 1(ICAM-1)in the intestine was determined by immunohistochemistry.They were all compared with those of the normal controls.The pathological changes in intestinal tissues in rats of three groups were observed under optical microscope,and the pathological changes were recorded.Results:Body weight of en- dotoxic tolerance rats was not reduced after injection of 0.25 mg/kg LPS.The levels of sIgA in intestinal mucosa of endotoxin tolerant rats were higher than those of normal controls,especially at 6 hours(P<0.05).The sIgA levels in LPS group raised at 2 hours and began to decrease from 6 hours(P<0.05)on.The expression of ICAM- 1 of endotoxin tolerant rats was higher at 0 hours,and then began to decrease(P<0.05),and the expression of ICAM-1 was lowest at 6 hours(P<0.05).But in LPS group,the expression of ICAM-1 gradually increased,and they were higher than those of endotoxin tolerant rats.There was more obvious mucosal congestion and edema in the intestinal mucosa,with infiltration of inflammatory cells in LPS group compared with endotoxin tolerant group. Chiu pathologic grade was lower in endotoxin tolerant group compared with the LPS group.Conclusion:Endotoxin tolerance can reduce intestinal mucosal injury and the expression of ICAM-1 induced by endotoxemia.