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

Abstract

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. 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. 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). 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 Th1 type cytokine increases continuously while Th2 type cytokine decreases in the established model.