Post-infectious Irritable Bowel Syndrome Mouse Research Articles

APETx2 regulates intestinal motility and visceral sensitivity in post-infectious irritable bowel syndrome mice through 5-HT signalling pathway

To investigate whether APETx2, a potent and selective inhibitor of ASIC3, regulates intestinal motility and visceral sensitivity in post-infectious irritable bowel syndrome (PI-IBS) mice through the 5-HT signalling pathway. The PI-IBS model was established by Trichinella spiralis infection of NIH mice. APETx2(120 µg/kg) was administrated to PI-IBS mice by intraperitoneal injection once a day, lasting for 7 days. The gastrointestinal function of mice was assessed by the time of the first dark stool and the number of pellets defecated within 2 h. The visceral sensitivity was tested via abdominal withdrawal reflex. The protein levels of 5-HT and CRF in colon tissues were detected by immunohistochemistry. The changes in serum 5-HT and colon CRF contents were detected by ELISA. The mRNA levels of colon 5-HT4R and CRF were detected by RT-qPCR. The protein levels of colon 5-HT4R and dorsal root ganglion (DRG) ASIC3 were detected by Western blotting. The results indicated that APETx2 could markedly improve gastrointestinal function and visceral sensitivity in mice. Moreover, APETx2 could reduce the expression level of ASIC3 protein in the DRG of PI-IBS mice. APETx2 could increase the expression levels of 5-HT in serum and colon, CRF and 5-HT4R in the colon, and 5-HT4R in brain tissue in PI-IBS mice. APETx2 can improve visceral sensitivity and intestinal motility in PI-IBS through 5-HT signalling pathway.

Modulation of the microbiota across different intestinal segments by Rifaximin in PI-IBS mice

BackgroundRifaximin has been increasingly applied in irritable bowel syndrome (IBS) treatment. Whether there were differences in the effects of rifaximin on microbiota from different intestinal segments, especially the small intestine where rifaximin predominantly acted, has not been confirmed.MethodsIn this study, we used Trichinella spiralis infection to induce post infectious irritable bowel syndrome (PI-IBS) and measured visceral sensitivity of mice by means of abdominal withdrawal reflex (AWR) tests to colorectal distention (CRD). We compared the effects of rifaximin on the composition of ileal, colonic mucosal and fecal microbiota in PI-IBS mice.ResultsRifaximin significantly reduced AWR scores and increased pain threshold in PI-IBS mice, and this effect was associated with the change in the relative abundance of ileal mucosal microbiota. Rifaximin could obviously decrease ileum mucosal microbiota alpha diversity assessed by Shannon microbial diversity index. Meanwhile, the analysis of beta diversity and relative abundance of microbiota at phylum, family and genus levels showed that rifaximin could improve the microbiota structure of ileal mucosa. However, for colonic mucosal and fecal microbiota, this effect of rifaximin was not obvious. Rifaximin could reshape the correlation of genera between different intestinal segments.ConclusionRifaximin improved visceral hypersensitivity in PI-IBS mice. Rifaximin mainly affected ileal mucosal microbiota, and its improvement effect on IBS might be closely related to the improvement of ileal microbiota structure.

Effect of altered gut microbiota on visceral hypersensitivity of postinfectious irritable bowel syndrome mice.

Irritable bowel syndrome (IBS) is a common functional bowel disorder characterized with visceral hypersensitivity. Previous studies indicated gut microbiota alteration associated short-chain fatty acids (SCFAs) dysregulation is associated with IBS development. The aim of the study is to explore the potential role of microbiota dysbiosis mediated visceral hypersensitivity in postinfectious-IBS (PI-IBS) mouse model. Four-week-old NIH mice were randomly allocated into four groups: control mice, PI-IBS mice, PI-IBS mice co-housing with normal mice, and PI-IBS mice were administrated with a cocktail of antibiotics. Trichinella spiralis infection established PI-IBS mouse model. Microbiota in cecal contents and feces were analyzed by 16S rDNA sequencing. SCFAs were detected by gas chromatography. 5-hydroxytryptamine (5-HT) was evaluated by ELISA, and N-methyl-D-aspartate receptors (NMDARs) were examined by western blot. Visceral sensitivity was determined by abdominal withdrawal reflex in response to colorectal distention. Increased SCFAs were observed in cecal contents and feces in PI-IBS mice accompanied with higher 5-HT and NMDAR subunits expressions in ileum and colon. Visceral hypersensitivity was observed in PI-IBS mice compared to control mice. When administrated with antibiotics cocktails and co-housing with normal mice, PI-IBS mice showed decreased SCFAs, 5-HT, NMDAR subunits expressions, and improved visceral hypersensitivity. Gut microbiota alteration induced increased SCFAs, 5-HT and NMDAR subunits expressions were associated with visceral hypersensitivity in PI-IBS mice. The critical role of gut microbiota in improving visceral hypersensitivity was further identified by treatment of antibiotics cocktail and co-housing.

Effect of Lactobacillus rhamnosus on Intestinal Mucosal Barrier Function in Mice with Post-Infectious Irritable Bowel Syndrome

To explore the effect of Lactobacillus rhamnosus on intestinal mucosal barrier function in post-infectious irritable bowel syndrome mice. Fifty-four 8 w old Specific-pathogen free male sprague dawley mice were randomly divided into the control group (n=18), model group (n=18), and experimental group (n=18). The post-infectious irritable bowel syndrome model was established by the Trichinella spiralis infection. The experimental group was treated with Lactobacillus rhamnosus (1.0×107 CFU/kg, 0.5 ml), twice a day for 1 w, while the control group and model group were given the same dose of normal saline for 1 w. The changes in body weight, fecal water content, intestinal motility, and D-lactic acid levels of mice in each group were compared. The body weight of mice in the model group and the experimental group was lower than that in the control group, while that in the experimental group was higher than that in the model group (p<0.05). The fecal water content of mice in the model group and the experimental group was higher than that in the control group, while that in the experimental group was lower than that in the model group (p<0.05). The Bristoli score of the model group and the experimental group was higher than that of the control group, and the Bristoli score of the experimental group was lower than that of the model group (p<0.05). The level of D-lactic acid in the model group and the experimental group was higher than that in the control group, while that in the experimental group was lower than that in the model group (p<0.05). Lactobacillus rhamnosus can improve the intestinal motility and intestinal mucosal barrier function in post-infectious irritable bowel syndrome mice.

Protease Activated Receptor-2 Induces Immune Activation and Visceral Hypersensitivity in Post-infectious Irritable Bowel Syndrome Mice.

The role of protease activated receptor-2 (PAR-2) in the pathogenesis of abdominal pain in irritable bowel syndrome (IBS) is not well defined. To investigate the role of PAR-2-mediated visceral hypersensitivity in a post-infectious IBS (PI-IBS) mouse model. T. spiralis-infected PI-IBS mouse model was used. Fecal serine protease activity and intestinal mast cells were evaluated. Intestinal permeability was assessed by urine lactulose/mannitol ratio, and colonic expressions of PAR-2 and tight junction (TJ) proteins were examined by Western blot. Intestinal immune profile was assessed by measuring Th (T helper) 1/Th2 cytokine expression. Visceral sensitivity was evaluated by abdominal withdrawal reflex in response to colorectal distention. Colonic PAR-2 expression as well as fecal serine protease activity and intestinal mast cell counts were elevated in PI-IBS compared to the control mice. Decreased colonic TJ proteins expression, increased lactulose/mannitol ratio, elevated colonic Th1/Th2 cytokine ratio, and visceral hypersensitivity were observed in PI-IBS compared to the control mice. Administration of PAR-2 agonist in control mice demonstrated similar changes observed in PI-IBS mice, while PAR-2 antagonist normalized the increased intestinal permeability and reduced visceral hypersensitivity observed in PI-IBS mice. PAR-2 activation increases intestinal permeability leading to immune activation and visceral hypersensitivity in PI-IBS mouse model.

Reduced interstitial cells of Cajal and increased intraepithelial lymphocytes are associated with development of small intestinal bacterial overgrowth in post-infectious IBS mouse model

Objective: Intestinal dysmotility and immune activation are likely involved in the pathogenesis of small intestinal bacteria overgrowth (SIBO) in irritable bowel syndrome (IBS). We aimed at investigating the role of interstitial cells of Cajal (ICC) and intestinal inflammation in the development of SIBO using a post-infectious IBS (PI-IBS) mouse model.Materials and methods: NIH mice were randomly infected with Trichinella spiralis. Visceral sensitivity and stool pattern were assessed at 8-weeks post-infection (PI). Intestinal bacteria counts from jejunum and ileum were measured by quantitative real-time PCR to evaluate the presence of SIBO. ICC density, intraepithelial lymphocytes (IELs) counts, and intestinal cytokine levels (IL1-β, IL-6, toll-like receptor-4 (TLR-4), IL-10) in the ileum were examined.Results: PI-IBS mice demonstrated increased visceral sensitivity compared with the control group. One-third of the PI-IBS mice developed SIBO (SIBO+/PI-IBS) and was more likely to have abnormal stool form compared with SIBO negative PI-IBS (SIBO−/PI-IBS) mice but without difference in visceral sensitivity. SIBO+/PI-IBS mice had decreased ICC density and increased IELs counts in the ileum compared with SIBO−/PI-IBS mice. No difference in inflammatory cytokine expression levels were detected among the groups except for increased TLR-4 in PI-IBS mice compared with the control group.Conclusions: Development of SIBO in PI-IBS mice was associated with reduced ICC density and increased IELs counts in the ileum. Our findings support the role of intestinal dysmotility and inflammation in the pathogenesis of SIBO in IBS and may provide potential therapeutic targets.

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

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.

Effectiveness of trimebutine maleate on modulating intestinal hypercontractility in a mouse model of postinfectious irritable bowel syndrome

Trimebutine maleate, which modulates the calcium and potassium channels, relieves abdominal pain in patients with irritable bowel syndrome. However, its effect on postinfectious irritable bowel syndrome is not clarified. The aim of this study was to investigate the effectiveness of trimebutine maleate on modulating colonic hypercontractility in a mouse model of postinfectious irritable bowel syndrome. Mice infected up to 8 weeks with T. spiralis underwent abdominal withdrawal reflex to colorectal distention to evaluate the visceral sensitivity at different time points. Tissues were examined for histopathology scores. Colonic longitudinal muscle strips were prepared in the organ bath under basal condition or to be stimulated by acetylcholine and potassium chloride, and consecutive concentrations of trimebutine maleate were added to the bath to record the strip responses. Significant inflammation was observed in the intestines of the mice infected 2 weeks, and it resolved in 8 weeks after infection. Visceral hyperalgesia and colonic muscle hypercontractility emerged after infection, and trimebutine maleate could effectively reduce the colonic hyperreactivity. Hypercontractility of the colonic muscle stimulated by acetylcholine and high K(+) could be inhibited by trimebutine maleate in solution with Ca(2+), but not in Ca(2+) free solution. Compared with 8-week postinfectious irritable bowel syndrome group, 2-week acute infected strips were much more sensitive to the stimulators and the drug trimebutine maleate. Trimebutine maleate was effective in reducing the colonic muscle hypercontractility of postinfectious irritable bowel syndrome mice. The findings may provide evidence for trimebutine maleate to treat postinfectious irritable bowel syndrome patients effectively.