感染后肠易激综合征小鼠模型建立过程中肠道细胞因子表达的变化

目的 观察旋毛虫急性感染美国国立卫生院(NIH)小鼠建立感染后肠易激综合征模型的不同阶段,肠道组织中Th1类细胞因子白细胞介素(IL)-12和Th2类细胞因子IL-4表达的变化.方法 旋毛虫幼虫囊胞(350～400条)感染成年NIH小鼠,分别于感染后0、2、4、8、12周测量小鼠体重,并于每个观察时间点测最腹壁回撤反应(AWR)以评估感染后小鼠对结直肠扩张的内脏敏感性,于不同时间点处死小鼠取末端回肠行病理切片HE染色观察肠道炎症情况.应用反转录-聚合酶链反应(RT-PCR)和Western印迹检测不同时间点小鼠末端回肠IL-12、IL-4的mRNA和蛋白的表达量.结果 感染后2、4周小鼠体重均低于对照组[(31.1±3.7)g比(35.6±2.7)g,(36.1±3.4)g比(39.8±2.7)g,均P<0.05],感染后8、12周小鼠体重与对照组差异均无统计学意义(均P>0.05).感染后2周肠道急性炎症明显,4周炎症开始恢复,感染后8周至12周肠道无明显炎症表现.在结直肠扩张压力为30、45、60 mm Hg(1 mm Hg=0.133 kPa)时,感染后各时间点小鼠AWR评分均高于对照组,其中以2周时为最高(2.60±0.55比1.00±0.35,2.90±0.20比1.50±0.70,3.30±0.50比2.00±0.35,均P<0.05).感染后8周可作为感染后肠易激综合征的成功模型.感染后小鼠末端回肠组织中IL-12 mRNA及蛋白表达量均高于对照组(均P<0.05),其中以2周时为最高(0.77±0.04,0.40±0.05),4周(0.45±0.04,0.30±0.07)、8周(0.42±0.03,0.25±0.05)、12周(0.39±0.02,0.24±0.04)时依次降低但仍均高于对照(0.34±0.04,0.15±0.07,均P<0.05);IL-4 mRNA及蛋白表达在2周时升高(0.42±0.04,0.33±0.05),4周时(0.20±0.02,0.14±0.02)接近对照组(0.19±0.04,0.13±0.06),8周(0.10±0.03,0.08±0.03)至12周(0.08±0.03,0.06±0.03)时降低(均P<0.05).结论 感染后肠易激综合征模型小鼠肠道组织中Th类细胞因子在模型发展的不同阶段处于不同的表达水平,急性期均表达增强,模型建立成功后Th1表达持续增强而Th2表达持续降低.

Altered expression of intestinal cytokines in development of postinfectious irritable bowel syndrome mouse model

Objective To observe the expression of Th1 type cytokine IL-12 and Th2 type cytokine IL-4 in different development phases of postinfectious irritable bowel syndrome in mouse model.Methods Mice were infected by Trichinella spiralis (350-400 Trichinella) and weighted weekly after infection.Visceral sensitivity of colorectal distention in mice was assessed by abdominal withdrawal reflex (AWR) at Weeks 0,2,4,8,12 post-infection.Tissues of terminal ileum were collected.Histological pathology and inflammation were evaluated by HE staining.Results The weights of mice in 2 and 4-week groups were lower than those in the control group[(31.1±3.7) g vs (35.6±2.7) g,(36.1±3.4) g vs (39.8±2.7) g,all P < 0.05)].The weights of 8,12-week groups had no statistical difference with the control group (all P > 0.05).Severe intestinal inflammation was observed at Week 2 during acute infectious period,but after a 4-week infection it recovered from intestinal inflammation,until Weeks 8-12,there was no difference with the control group.At 30,45,60 mm Hg,the AWR scores of the infectious group was higher than those in the control group.The 2-week group was the highest (2.60 ±0.55 vs 1.00 ±0.35,2.90 ±0.20 vs 1.50 ±0.70,3.30±0.50 vs 2.00±0.35,all P < 0.05).Mice infected at Week 8 could serve as a successful model of postinfectious irritable bowel syndrome.An elevated expression of IL-12,IL-4 mRNA and protein was observed in ileocecum at Week 2 during acute phase (0.77±0.04 and 0.40±0.05,0.42±0.04 and 0.33 ±0.05),decreased expression of IL-4 mRNA and protein was observed in ileocecum at Weeks 8,12(0.10±0.03 and 0.08 ±0.03,0.08 ±0.03 and 0.06 ±0.03).However a prolonged high expression of IL-12 mRNA and protein was observed in ileocecum at Weeks 8,12 (0.42±0.03 and 0.25±0.05,0.39±0.02 and 0.24±0.04),but lower than those in the 2-week group (all P < 0.05).Conclusion A differential expression of Th type cytokines is observed in different development phases of postinfectious irritable bowel syndrome in a mouse model.All cytokines increase during acute infection stage; However Th1type cytokine increases continuously while Th2 type cytokine decreases in the established model.