Magnetic resonance colonography in rats with TNBS-induced colitis: a feasibility and validation study

SPH7854, a gut-limited RORγt antagonist, ameliorates TNBS-induced experimental colitis in rat

Multiple lines of evidence suggest that Retinoic Acid Related Orphan Nuclear Receptor gamma t (RORγt) is a potent therapeutic target for inflammatory bowel disease (IBD). However, systemic blockade of RORγt easily leads to thymic lymphoma and aberrant liver function. Therefore, the development of gut-limited RORγt antagonists may lead to the development of innovative IBD therapeutics that improve safety and retain effectiveness. We discovered SPH7854, a potent and selective RORγt antagonist. The effect of SPH7854 on the differentiation of T helper 1 (Th1)/Th17/regulatory T (Treg) cells was evaluated in mouse and human primary cells. SPH7854 (2-(4-(ethylsulfonyl)phenyl)-N- (6-(2-methyl-2-(pyridin-2-yl) propanoyl)pyridin-3-yl)acetamide) dose-dependently inhibited interleukin-17A (IL-17A) secretion from mouse CD4 + T cells and human peripheral blood mononuclear cells (PBMC). Additionally, SPH7854 strongly suppressed Th17 cell differentiation and considerably promoted Treg cell differentiation while slightly affected Th1 cell differentiation from mouse CD4 + T cells. The pharmacokinetic (PK) studies indicated that SPH7854 was restricted to the gut: the bioavailability and maximal plasma concentration of SPH7854 after oral administration (6 mg/kg) were 1.24 ± 0.33 % and 4.92 ± 11.81 nM, respectively, in rats. Strikingly, oral administration of SPH7854 (5 mg/kg and 15 mg/kg) twice daily significantly alleviated 2, 4, 6-trinitrobenzensulfonic acid (TNBS)-induced colitis in rats. SPH7854, especially at 15 mg/kg, significantly alleviated symptoms and improved macroscopic signs and microscopic structure in rat colitis, with decreased colonic mucosal levels of IL-17A, IL-6, tumor necrosis factor α (TNFα), monocyte chemoattractant protein-1 (MCP-1) and myeloperoxidase (MPO). These evidences indicated that blockade of RORγt activity via a gut-limited antagonist may be an effective and safe therapeutic strategy for IBD treatment.

Magnetic resonance colonography assessment of acute trinitrobenzene sulfonic acid colitis in pre-pubertal rats

Pre-pubertal murine models of acute colitis are lacking. Magnetic resonance colonography (MRC) is a promising minimally invasive tool to assess colitis. We aimed to: 1/ Adapt a model of acute experimental colitis to pre-pubertal rats and determine whether MRC characteristics correlate with histological inflammation. 2/ Test this model by administering a diet supplemented in transforming growth factor β2 to reverse inflammation. Twenty-four rats were randomized at weaning to one of 3 groups: Trinitrobenzene Sulfonic Acid (TNBS) group (n = 8) fed a standard diet, that received an intra-rectal 60 mg/kg dose of TNBS-ethanol; Control group (n = 8) fed standard diet, that received a dose of intra-rectal PBS; TNBS+MODULEN group (n = 8) that received a dose of TNBS and were exclusively fed MODULEN-IBD® after induction of colitis. One week after induction of colitis, rats were assessed by MRC, colon histopathology and inflammation markers (Interleukin 1β, Tumor necrosis factor α, Nitric Oxide Synthase 2 and Cyclooxygenase 2). TNBS induced typical features of acute colitis on histopathology and MRC (increased colon wall thickness, increased colon intensity on T2-weighted images, target sign, ulcers). Treatment with MODULEN-IBD® did not reduce signs of colitis on MRC. Inflammatory marker expression did not differ among study groups.

Dietary salt exacerbates intestinal fibrosis in chronic TNBS colitis via fibroblasts activation

Intestinal fibrosis is a frequent complication in inflammatory bowel diseases (IBD). It is a challenge to identify environmental factors such as diet that may be driving this risk. Intestinal fibrosis result from accumulation of extracellular matrix (ECM) proteins secreted by myofibroblasts. Factors promoting intestinal fibrosis are unknown, but diet appears to be a critical component in its development. Consumption of salt above nutritional recommendations can exacerbate chronic inflammation. So far, high salt diet (HSD) have not been thoroughly investigated in the context of intestinal fibrosis associated to IBD. In the present study, we analyze the role of dietary salt in TNBS chronic colitis induced in rat, an intestinal fibrosis model, or in human colon fibroblast cells. Here, we have shown that high-salt diet exacerbates undernutrition and promoted ECM-associated proteins in fibroblasts. Taken together, our results suggested that dietary salt can activate intestinal fibroblasts, thereby contributing to exacerbation of intestinal fibrosis. Dietary salt may be considered as a putative environmental factor that drives intestinal fibrosis risk.

Molecular Magnetic Resonance Imaging with Contrast Agents for Assessment of Inflammatory Bowel Disease: A Systematic Review

Background and Aims

Magnetic resonance imaging (MRI) has taken an important role in the diagnosis of inflammatory bowel diseases (IBD). In the wake of current advances in nanotechnology, the drug delivery industry has seen a surge of nanoparticles advertising high specificity in target imaging. Given the rapid development of the field, this review has assembled related articles to explore whether molecular contrast agents can improve the diagnostic capability on gastrointestinal imaging, especially for IBD.

Methods

Relevant articles published between 1998 and 2018 from a literature search of PubMed and EMBASE were reviewed. Data extraction was performed on the studies' characteristics, experimental animals, modelling methods, nanoparticles type, magnetic resonance methods, and means of quantitative analysis.

Results

A total of 8 studies were identified wherein the subjects were animals, and all studies employed MR equipment. One group utilized a perfluorocarbon solution and the other 7 groups used either magnetic nanoparticles or gadolinium- (Gd-) related nanoparticles for molecular contrast. With ultrasmall superparamagnetic iron oxide (USPIO) particles and Gd-related nanoparticles, signal enhancements were found in the mucosa or with focal lesion of IBD-related model in T1-weighted images (T1WI), whereas superparamagnetic iron oxide (SPIO) particles showed a signal decrease in the intestinal wall of the model in T1WI or T2-weighted images. The signal-to-noise ratio (SNR) was employed to analyze bowel intensity in 3 studies. And the percentage of normalized enhancement was used in 1 study for assessing the severity of inflammation.

Conclusion

Molecular MRI with contrast agents can improve the early diagnosis of IBD and quantitate the severity of inflammation in experimental studies.

Chickpea supplementation prior to colitis onset reduces inflammation in dextran sodium sulfate-treated C57Bl/6 male mice

The potential for a chickpea-supplemented diet (rich in fermentable nondigestible carbohydrates and phenolic compounds) to modify the colonic microenvironment and attenuate the severity of acute colonic inflammation was investigated. C57Bl/6 male mice were fed a control basal diet or basal diet supplemented with 20% cooked chickpea flour for 3 weeks prior to acute colitis onset induced by 7-day exposure to dextran sodium sulfate (DSS; 2% w/v in drinking water) and colon and serum levels of inflammatory mediators were assessed. Despite an equal degree of DSS-induced epithelial barrier histological damage and clinical symptoms between dietary groups, biomarkers of the ensuing inflammatory response were attenuated by chickpea pre-feeding, including reduced colon tissue activation of nuclear factor kappa B and inflammatory cytokine production (tumor necrosis factor alpha and interleukin (IL)-18). Additionally, colon protein expression of anti-inflammatory (IL-10) and epithelial repair (IL-22 and IL-27) cytokines were increased by chickpea pre-feeding. Furthermore, during acute colitis, chickpea pre-feeding increased markers of enhanced colonic function, including Relmβ and IgA gene expression. Collectively, chickpea pre-feeding modulated the baseline function of the colonic microenvironment, whereby upon induction of acute colitis, the severity of the inflammatory response was attenuated.

Longitudinal PET/CT evaluation of TNBS-induced inflammatory bowel disease rat model

Inflammatory bowel disease (IBD) is a group of chronic disorders of the gastrointestinal tract, which two main types are Crohn's disease and ulcerative colitis. It has multifactorial etiologies, being essential the use of animal models and disease activity measures to develop new therapies. With this aim, the use of animal models in combination with non-invasive molecular imaging can play an important role in the development of new treatments. In this study, IBD was induced in rats using 2,4,6-trinitrobenzenesulfonic acid (TNBS) and longitudinal [¹⁸F]FDG PET/CT scans were conducted to assess disease progression post-TNBS administration. Afterwards, [¹⁸F]FDG PET/CT scans were carried out after treatment with methylprednisolone to validate the model. In non-treated rats, SUV_max (Standardized Uptake Value) rapidly increased after IBD induction, being particularly significant (p < 0.01) on days 7-13 after induction. There were no significant differences between non-treated and treated IBD rats from days 0-3. Nevertheless, treated IBD rats showed a significant decrease in SUV_max between days 7-13 (p < 0.01). Histological examination showed descending and transverse colon as the most affected regions. There was a moderate (R² = 0.61) and strong (R² = 0.82) correlation of SUV_max with Nancy grade (parameter for histological assessment of disease activity) and weight changes, respectively. In this study, we have performed the first longitudinal [¹⁸F]FDG PET/CT assessment of TNBS-induced IBD in rats, demonstrating the potential role of preclinical molecular imaging for the evaluation of new therapies in combination with IBD rat models.

Quantitative MRI in murine radiation-induced rectocolitis: comparison with histopathological inflammation score

Murine radiation-induced rectocolitis is considered to be a relevant animal model of gastrointestinal inflammation. The purpose of our study was to compare quantitative MRI and histopathological features in this gastrointestinal inflammation model. Radiation rectocolitis was induced by localized single-dose radiation (27 Gy) in Sprague-Dawley rats. T₂ -weighted, T₁ -weighted and diffusion-weighted MRI was performed at 7 T in 16 rats between 2 and 4 weeks after irradiation and in 10 control rats. Rats were sacrificed and the histopathological inflammation score of the colorectal samples was assessed. The irradiated rats showed significant increase in colorectal wall thickness (2.1 ± 0.3 mm versus 0.8 ± 0.3 mm in control rats, P < 0.0001), normalized T₂ signal intensity (4 ± 0.8 versus 2 ± 0.4 AU, P < 0.0001), normalized T₁ signal intensity (1.4 ± 0.1 versus 1.1 ± 0.2 AU, P = 0.0009) and apparent and pure diffusion coefficients (ADC and D) (2.06 × 10^-3 ± 0.34 versus 1.51 × 10^-3 ± 0.23 mm² /s, P = 0.0004, and 1.97 × 10^-3 ± 0.43 mm² /s versus 1.48 × 10^-3 ± 0.29 mm² /s, P = 0.008, respectively). Colorectal wall thickness (r = 0.84, P < 0.0001), normalized T₂ signal intensity (r = 0.85, P < 0.0001) and ADC (r = 0.80, P < 0.0001) were strongly correlated with the histopathological inflammation score, whereas normalized T₁ signal intensity and D were moderately correlated (r = 0.64, P = 0.0006, and r = 0.65, P = 0.0003, respectively). High-field MRI features of single-dose radiation-induced rectocolitis in rats differ significantly from those of control rats. Quantitative MRI characteristics, especially wall thickness, normalized T₂ signal intensity, ADC and D, are potential markers of the histopathological inflammation score.

Navy and black bean supplementation attenuates colitis-associated inflammation and colonic epithelial damage

The enriched levels of nondigestible fermentable carbohydrates and phenolic compounds found in common beans can exert immunomodulatory effects within the colon that improve gut health and mitigate the severity of colitis-associated inflammatory pathology. Prior to acute colitis onset, C57Bl/6 mice were prefed isocaloric 20% cooked navy bean (NB) or black bean (BB) diets for 3 weeks and switched to control basal diet (BD) 24 h prior to colitis induction via 5-day exposure to dextran sodium sulfate (2% w/v in drinking water)+3 days of fresh water. The severity of the acute colitis phenotype was attenuated by bean prefeeding, evidenced by reduced colon tissue inflammatory transcription factor activation (NFκB, STAT3) and inflammatory mediator levels in the colon (IL-1β, IL-6, IL-18 and MCP-1) and serum (TNFα, IL-6, IL-1β, MCP-1) versus BD (P≤.05). Additionally, biomarkers of enhanced wound repair responses were increased by bean prefeeding including colon tissue protein levels of IL-22, IL-27 and activated (i.e., GTP-bound) Cdc42 and Rac1 versus BD (P≤.05). mRNA expressions of genes involved in normal colonic epithelial function and the promotion of epithelial barrier integrity, defense and/or restitution and wound closure including MUC1, RELMβ, IgA and REG3γ were all increased in NB and BB prefed mice versus BD (P≤.05). Collectively, bean supplementation prior to colitis induction (i.e., mimicking disease relapse) primes the colonic microenvironment to attenuate the severity of the colitis inflammatory phenotype and maintain aspects of epithelial barrier function.

Selective targeting of pro-inflammatory Th1 cells by microRNA-148a-specific antagomirs in vivo

In T lymphocytes, expression of miR-148a is induced by T-bet and Twist1, and is specific for pro-inflammatory Th1 cells. In these cells, miR-148a inhibits the expression of the pro-apoptotic protein Bim and promotes their survival. Here we use sequence-specific cholesterol-modified oligonucleotides against miR-148a (antagomir-148a) for the selective elimination of pro-inflammatory Th1 cells in vivo. In the murine model of transfer colitis, antagomir-148a treatment reduced the number of pro-inflammatory Th1 cells in the colon of colitic mice by 50% and inhibited miR-148a expression by 71% in the remaining Th1 cells. Expression of Bim protein in colonic Th1 cells was increased. Antagomir-148a-mediated reduction of Th1 cells resulted in a significant amelioration of colitis. The effect of antagomir-148a was selective for chronic inflammation. Antigen-specific memory Th cells that were generated by an acute immune reaction to nitrophenylacetyl-coupled chicken gamma globulin (NP-CGG) were not affected by treatment with antagomir-148a, both during the effector and the memory phase. In addition, antibody titers to NP-CGG were not altered. Thus, antagomir-148a might qualify as an effective drug to selectively deplete pro-inflammatory Th1 cells of chronic inflammation without affecting the protective immunological memory.

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Th1 cells expressing miR-148a mediate colitis in a murine model of IBD.

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Antagomir-148a inhibits colitis by selectively depleting Th1 cells from the colon.

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Antagomir-148a does not affect the protective immunological memory.

SPECT-computed tomography in rats with TNBS-induced colitis: A first step toward functional imaging

AIM

To assess the feasibility of SPECT-computed tomography (CT) in rats with trinitrobenzene sulfonic acid (TNBS)-induced acute colitis and confront it with model inflammatory characteristics.

METHODS

Colitis was induced in Sprague-Dawley rats by intrarectal injection of TNBS (n = 10) while controls received vehicle (n = 10). SPECT-CT with intravenous injection of 10 MBq of 67Ga-Citrate was performed at day 2. SPECT-CT criteria were colon wall thickness and maximal wall signal intensity. Laboratory parameters were assessed: colon weight:length ratio, colon cyclooxygenase-2 expression by western blot and histological inflammatory score.

RESULTS

Colon weight/length ratio, colon COX-2 expression and histological inflammatory score were significantly higher in the TNBS group than in the control group (P = 0.0296, P < 0.0001, P = 0.0007 respectively). Pixel max tend to be higher in the TNBS group than in the control group but did not reach statistical significance (P = 0.0662). Maximal thickness is significantly increased in the TNBS group compared to the control group (P = 0.0016) while colon diameter is not (P = 0.1904). Maximal thickness and colon diameter were correlated to colon COX-2 expression (P = 0.0093, P = 0.009 respectively) while pixel max was not (P = 0.22). Maximal thickness was significantly increased when inflammation was histologically observed (P = 0.0043) while pixel max and colon diameter did not (P = 0.2452, P = 0.3541, respectively).

CONCLUSION

SPECT-CT is feasible and easily distinguished control from colitic rats.

The TNBS-induced colitis animal model: An overview

Background

Despite recent advances the pathogenesis of Crohn's disease remains incompletely understood. A variety of animal models have been utilized in an effort to provide further insights and develop more therapeutic options. In order to simulate, to an extent, the pathogenesis and the clinical course of the disease, TNBS induced colitis is often used. Various approaches for inducing TNBS -colitis have been described in the literature.

Methods/results

In this review, we sought to present the animal model of TNBS induced colitis and outline the pathogenesis, pathophysiology, clinical course and pathological characteristics of the model. Furthermore, we describe the differences among those protocols regarding types of animals and colitis induction.

Data sources

The MEDLINE database was thoroughly searched using the keywords: TNBS, colitis, Crohn's disease, animal model. Two investigators independently reviewed the abstracts and appropriate articles were included in this review. Additional articles were gathered and evaluated.

Conclusion

The aim of this study was to thoroughly present an updated review of the TNBS-induced colitis protocols that are implemented by researchers.

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We sought to present the animal model of TNBS induced colitis and outline the pathogenesis, pathophysiology, clinical course and pathological characteristics of the model.

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Furthermore, we describe the differences among those protocols regarding types of animals and colitis induction.

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The MEDLINE database was thoroughly searched using the keywords: TNBS, colitis, Crohn's disease, animal model.

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Two investigators independently reviewed the abstracts and appropriate articles were included in this review.

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The aim of this study was to thoroughly present an updated review of the TNBS-induced colitis protocols that are implemented by researchers.

Noninvasive Longitudinal Study of a Magnetic Resonance Imaging Biomarker for the Quantification of Colon Inflammation in a Mouse Model of Colitis

BACKGROUND

Colonoscopy is the gold standard to diagnose and follow up the evolution of inflammatory bowel diseases. However, this technique can still present a risk of severe complications, a general discomfort in patients, and its diagnostic value is limited to the visualization of the colon mucosal changes. Magnetic resonance imaging (MRI) is emerging as a noninvasive imaging technique of choice to overcome these limitations. The aim of this work was to evaluate the potential of colon wall thickness measured using MRI as an in vivo imaging biomarker of inflammation for inflammatory bowel disease in an animal model of this disease.

METHODS

On day 0, 2% or 3% Dextran sodium sulfate was added to the drinking water of mice (n = 10/group) for 5 days. Six mice were left as controls. Animals were imaged with colonoscopy and MRI on days 7, 11, and 21 to study the colitis progression. Histology was performed at the end of the protocol.

RESULTS

The colon wall thickness measured in Dextran sodium sulfate-treated animals was shown to be significantly and dose dependently increased compared to controls. Colonoscopy showed similar results and excellently correlated with MRI measurements and histology. The proposed protocol showed high robustness, with negligible interoperator and intraoperator variability.

CONCLUSIONS

The findings of this investigation suggest the feasibility of using MRI for the noninvasive assessment of colon wall thickness as a robust surrogate biomarker for colon inflammation detection and follow-up. The data presented show the potential of MRI in in vivo preclinical longitudinal studies, including testing of new drugs or investigation of inflammatory bowel disease development mechanisms.

Diagnostic imaging advances in murine models of colitis

Inflammatory bowel diseases (IBD) such as Crohn’s disease and ulcerative colitis are chronic-remittent inflammatory disorders of the gastrointestinal tract still evoking challenging clinical diagnostic and therapeutic situations. Murine models of experimental colitis are a vital component of research into human IBD concerning questions of its complex pathogenesis or the evaluation of potential new drugs. To monitor the course of colitis, to the present day, classical parameters like histological tissue alterations or analysis of mucosal cytokine/chemokine expression often require euthanasia of animals. Recent advances mean revolutionary non-invasive imaging techniques for in vivo murine colitis diagnostics are increasingly available. These novel and emerging imaging techniques not only allow direct visualization of intestinal inflammation, but also enable molecular imaging and targeting of specific alterations of the inflamed murine mucosa. For the first time, in vivo imaging techniques allow for longitudinal examinations and evaluation of intra-individual therapeutic response. This review discusses the latest developments in the different fields of ultrasound, molecularly targeted contrast agent ultrasound, fluorescence endoscopy, confocal laser endomicroscopy as well as tomographic imaging with magnetic resonance imaging, computed tomography and fluorescence-mediated tomography, discussing their individual limitations and potential future diagnostic applications in the management of human patients with IBD.

Diets enriched with cranberry beans alter the microbiota and mitigate colitis severity and associated inflammation

Common beans are rich in phenolic compounds and nondigestible fermentable components, which may help alleviate intestinal diseases. We assessed the gut health priming effect of a 20% cranberry bean flour diet from two bean varieties with differing profiles of phenolic compounds [darkening (DC) and nondarkening (NDC) cranberry beans vs. basal diet control (BD)] on critical aspects of gut health in unchallenged mice, and during dextran sodium sulfate (DSS)-induced colitis (2% DSS wt/vol, 7 days). In unchallenged mice, NDC and DC increased (i) cecal short-chain fatty acids, (ii) colon crypt height, (iii) crypt goblet cell number and mucus content and (iv) Muc1, Klf4, Relmβ and Reg3γ gene expression vs. BD, indicative of enhanced microbial activity and gut barrier function. Fecal 16S rRNA sequencing determined that beans reduced abundance of the Lactobacillaceae (Ruminococcus gnavus), Clostridiaceae (Clostridium perfringens), Peptococcaceae, Peptostreptococcaceae, Rikenellaceae and Pophyromonadaceae families, and increased abundance of S24-7 and Prevotellaceae. During colitis, beans reduced (i) disease severity and colonic histological damage, (ii) increased gene expression of barrier function promoting genes (Muc1-3, Relmβ, and Reg3γ) and (iii) reduced colonic and circulating inflammatory cytokines (IL-1β, IL-6, IFNγ and TNFα). Therefore, prior to disease induction, bean supplementation enhanced multiple concurrent gut health promoting parameters that translated into reduced colitis severity. Moreover, both bean diets exerted similar effects, indicating that differing phenolic content did not influence the endpoints assessed. These data demonstrate a proof-of-concept regarding the gut-priming potential of beans in colitis, which could be extended to mitigate the severity of other gut barrier-associated pathologies.

Assessment of colon and bladder crosstalk in an experimental colitis model using contrast-enhanced magnetic resonance imaging

BACKGROUND

Inflammatory bowel disease (IBD) consists of two chronic remitting-relapsing inflammatory disorders in the colon referred to as ulcerative colitis and Crohn's disease (CD). Inflammatory bowel disease affects about 1.4 million Americans. 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis is a widely used model of experimental intestinal inflammation with characteristic transmural and segmental lesions that are similar to CD.

METHODS

Here, we report on the use of contrast-enhanced magnetic resonance imaging (CE-MRI) to monitor in vivo bladder permeability changes resulting from bladder crosstalk following colon TNBS exposure, and TNBS-induced colitis. Changes in MRI signal intensities and histology were evaluated for both colon and bladder regions.

KEY RESULTS

Uptake of contrast agent in the colon demonstrated a significant increase in signal intensity (SI) for TNBS-exposed rats (p < 0.01) compared to controls. In addition, a significant increase in bladder SI for colon TNBS-exposed rats (p < 0.001) was observed compared to saline controls. Histological damage within the colon was observed, however, bladder histology indicated a normal urothelium in rats with TNBS-induced colitis, despite increased permeability seen by CE-MRI.

CONCLUSIONS & INFERENCES

Contrast-enhanced MRI was able to quantitatively measure inflammation associated with TNBS-induced colitis, and assess bladder crosstalk measured as an increase in urothelial permeability. Although CE-MRI is routinely used to assess inflammation with IBD, currently there is no diagnostic test to assess bladder crosstalk with this disease, and our developed method may be useful in providing crosstalk information between organ and tissue systems in IBD patients, in addition to colitis.

In-vivo monitoring of acute DSS-Colitis using Colonoscopy, high resolution Ultrasound and bench-top Magnetic Resonance Imaging in Mice

OBJECTIVE

The aim of this study was to establish and evaluate (colour Doppler-) high-resolution-ultrasound (hrUS) and bench-top magnetic resonance imaging (btMRI) as new methods to monitor experimental colitis.

MATERIALS AND METHODS

hrUS, btMRI and endoscopy were performed in mice without colitis (n = 15), in mice with acute colitis (n = 14) and in mice with acute colitis and simultaneous treatment with infliximab (n = 19).

RESULTS

Determination of colon wall thickness using hrUS (32 MHz) and measurement of the cross-sectional colonic areas by btMRI allowed discrimination between the treatment groups (mean a vs. b vs. c - btMRI: 922 vs. 2051 vs. 1472 pixel, hrUS: 0.26 vs. 0.45 vs. 0.31 mm). btMRI, endoscopy, hrUS and colour Doppler-hrUS correlated to histological scoring (p < 0.05), while endoscopy and btMRI correlated to post-mortem colon length (p < 0.05).

CONCLUSIONS

The innovative in vivo techniques btMRI and hrUS are safe and technically feasible. They differentiate between distinct grades of colitis in an experimental setting, and correlate with established post-mortem parameters. In addition to endoscopic procedures, these techniques provide information regarding colon wall thickness and perfusion. Depending on the availability of these techniques, their application increases the value of in vivo monitoring in experimental acute colitis in small rodents.

KEY POINTS

• Improved in vivo monitoring might balance interindividual differences in murine colitis. • In monitoring murine colitis, btMRI and hrUS are safe and technically feasible. • Very short examination times underline the usefulness especially of hrUS. • Results of btMRI and hrUS correlate with endoscopic and post-mortem findings.

White and dark kidney beans reduce colonic mucosal damage and inflammation in response to dextran sodium sulfate

Common beans are a rich source of nondigestible fermentable components and phenolic compounds that have anti-inflammatory effects. We assessed the gut-health-promoting potential of kidney beans in healthy mice and their ability to attenuate colonic inflammation following dextran sodium sulphate (DSS) exposure (via drinking water, 2% DSS w/v, 7 days). C57BL/6 mice were fed one of three isocaloric diets: basal diet control (BD), or BD supplemented with 20% cooked white (WK) or dark red kidney (DK) bean flour for 3 weeks. In healthy mice, anti-inflammatory microbial-derived cecal short chain fatty acid (SCFA) levels (acetate, butyrate and propionate), colon crypt height and colonic Mucin 1 (MUC1) and Resistin-like Molecule beta (Relmβ) mRNA expression all increased in WK- and DK-fed mice compared to BD, indicative of enhanced microbial activity, gut barrier integrity and antimicrobial defense response. During colitis, both bean diets reduced (a) disease severity, (b) colonic histological damage and (c) increased mRNA expression of antimicrobial and barrier integrity-promoting genes (Toll-like Receptor 4 (TLR4), MUC1-3, Relmβ and Trefoil Factor 3 (TFF3)) and reduced proinflammatory mediator expression [interleukin (IL)-1β, IL-6, interferon (IFN)γ, tumor necrosis factor (TNF)α and monocyte chemoattractant protein-1], which correlated with reduced colon tissue protein levels. Further, bean diets exerted a systemic anti-inflammatory effect during colitis by reducing serum levels of IL-17A, IFNγ, TNFα, IL-1β and IL-6. In conclusion, both WK and DK bean-supplemented diets enhanced microbial-derived SCFA metabolite production, gut barrier integrity and the microbial defensive response in the healthy colon, which supported an anti-inflammatory phenotype during colitis. Collectively, these data demonstrate a beneficial colon-function priming effect of bean consumption that mitigates colitis severity.

2,4,6-trinitrobenzene sulfonic acid-induced chronic colitis with fibrosis and modulation of TGF-β1 signaling

AIM: To investigate whether targeting proteasome might reverse intestinal fibrosis in rats.

METHODS: Chronic colitis was induced in rats by repeated administration of increasing dose of 2,4,6-trinitrobenzene sulfonic acid (TNBS, 15, 30, 45, 60, 60, 60 mg) by rectal injection for 6 wk (from day 0 to day 35), while control rats received the vehicle. TNBS + bortezomib (BTZ) rats received intraperitoneal injections of BTZ twice weekly (from day 37 to day 44) at a dose of 25 mg/kg, whereas the control and TNBS groups received the same amount of the vehicle. Histologic scoring of inflammation and fibrosis was performed. Colonic production of transforming growth factor (TGF)-β was measured by ELISA. Colon fibrosis-related proteins such as phospho-p38, phospho-SMAD2/3, Akt and peroxisome proliferator activated receptor γ (PPARγ) were studied by western blot. Expression of the tight junction proteins, occludin and claudin-1, were assessed by Western blot. Colon proteasome activities (chymotrypsin-like and trypsin-like activities) were assessed.

RESULTS: TNBS-treated rats had a higher colon weight/length ratio compared to control rats (P < 0.01). Furthermore, fibrosis and inflammation scores were higher in TNBS-treated rats compared to control rats (P < 0.01 for both). Colonic production of TGF-β production tended to be higher in TNBS-treated rats (P < 0.06). Fibrosis-related proteins such as phospho-p38, phospho-SMAD2/3, and PPARγ were significantly higher in TNBS-treated rats compared to control rats (all P < 0.05). TNBS rats had a higher expression of Akt compared to control rats (P < 0.01). Tight junction proteins were modified by repeated TNBS challenge: colon occludin expression rose significantly (P < 0.01), whereas claudin-1 expression fell (P < 0.01). Bortezomib inhibition significantly decreased chymotrypsin-like activity (P < 0.05), but had no significant effect on trypsin-like activity (P > 0.05). In contrast, bortezomib had no effect on other studied parameters such as fibrosis score, TGF-β signaling, or tight junction expression (P > 0.05 for all).

CONCLUSION: Rats with TNBS-induced chronic colitis exhibited colon fibrosis associated with higher TGF-β signaling. Proteasome inhibition by bortezomib had no effect on fibrosis in our experimental conditions.

Magnetic resonance colonography for fibrosis assessment in rats with chronic colitis

Background

Magnetic resonance colonography (MRC) has been developed to assess inflammatory bowel diseases. We aimed to assess the feasibility of MRC in rats with TNBS-induced chronic colitis and to confront imaging results with fibrosis and stenosing features of the model.

Materials and Methods

Chronic colitis was induced in 12 rats by weekly intra-rectal injection of increasing doses of TNBS for 6 weeks, while 8 control rats received the vehicle. At week 7, MRC was performed. Fibrosis scores were assessed and fibrosis mediators measured.

Results

Chronic colitis was associated with significant body weight loss (p<0.0001) and higher colon weight/length compared to controls (p = 0.0004). Fibrosis mediators and histological scores were significantly higher in rats with TNBS than in controls: α-SMA expression (0.9 versus 0.61, p = 0.0311) and fibrosis score (p = 0.0308). Colon wall thickness was higher in rats with TNBS than in controls: maximal thickness (2.38 versus 0.74 mm, p<0.0001) and minimal thickness (1.33 versus 0.48 mm, p<0.0001). Wall signal intensity on T2w images was higher in rats with TNBS than in controls (9040 versus 6192, p = 0.0101) and correlated with fibrosis score (r = 0.5214; p = 0.04). Luminal narrowing was higher in rats with TNBS (50.08 versus 10.33%, p<0.0001) and correlated with α-SMA expression (r = 0.5618; p = 0.01). Stenosis was observed in 7/9 rats with TNBS and in no controls (p = 0.0053).

Conclusions

MRC is feasible and easily distinguishes rats with colitis from controls. MRC signs correlated with fibrosis parameters. MRC evaluation may be part of a new anti-fibrosis drug assessment in experimental models of chronic colitis.

Cooked navy and black bean diets improve biomarkers of colon health and reduce inflammation during colitis

Common beans contain non-digestible fermentable components (SCFA precursors) and phenolic compounds (phenolic acids, flavonoids and anthocyanins) with demonstrated antioxidant and anti-inflammatory potential. The objective of the present study was to assess the in vivo effect of cooked whole-bean flours, with differing phenolic compound levels and profiles, in a mouse model of acute colitis. C57BL/6 mice were fed a 20 % navy bean or black bean flour-containing diet or an isoenergetic basal diet (BD) for 2 weeks before the induction of experimental colitis via 7 d dextran sodium sulphate (DSS, 2 % (w/v) in the drinking-water) exposure. Compared with the BD, both bean diets increased caecal SCFA and faecal phenolic compound concentrations (P< 0·05), which coincided with both beneficial and adverse effects on colonic and systemic inflammation. On the one hand, bean diets reduced mRNA expression of colonic inflammatory cytokines (IL-6, IL-9, IFN-γ and IL-17A) and increased anti-inflammatory IL-10 (P< 0·05), while systemically reduced circulating cytokines (IL-1β, TNFα, IFNγ, and IL-17A, P< 0·05) and DSS-induced oxidative stress. On the other hand, bean diets enhanced DSS-induced colonic damage as indicated by an increased histological injury score and apoptosis (cleaved caspase-3 and FasL mRNA expression) (P< 0·05). In conclusion, bean-containing diets exerted both beneficial and adverse effects during experimental colitis by reducing inflammatory biomarkers both locally and systemically while aggravating colonic mucosal damage. Further research is required to understand the mechanisms through which beans exert their effects on colonic inflammation and the impact on colitis severity in human subjects.

Adjunct therapy of n-3 fatty acids to 5-ASA ameliorates inflammatory score and decreases NF-κB in rats with TNBS-induced colitis

5-aminosalicylic acid (5-ASA) is widely used for the treatment of inflammatory bowel disease (IBD). Recent studies have evaluated the potential of nutritional intervention as adjunct therapy to 5-ASA in IBD. N-3 polyunsaturated fatty acids (PUFA) have shown potent anti-inflammatory properties in gut inflammation. Therefore, we aimed to evaluate the efficacy of the dual therapy (n-3 PUFA plus 5-ASA) in rats with 2, 4, 6-trinitrobenzen sulfonic acid (TNBS)-induced colitis. Colitis was induced by intrarectal injection of TNBS while control rats received the vehicle. Rats received by gavage a fish oil-rich formula (n-3 groups) or an isocaloric and isolipidic oil formula supplemented with 5-ASA for 14 days. A dose response of 5-ASA (5-75 mg. suppression mg kg(-1) d(-1)) was tested. Colitis was evaluated and several inflammatory markers were quantified in the colon. COX-2 expression (P<.05) and pro-inflammatory eicosanoids production of prostaglandin E2 (P<.001) and leukotriene B4 (P<.001) were significantly inhibited by n-3 PUFA or 5-ASA therapy. 5-ASA also reduces mRNA levels of tumor necrosis factor α (P<.05). n-3 PUFA or 5-ASA significantly inhibits nuclear factor κB (NF-κB) activation (P<.01 and P<.05, respectively). The dual therapy n-3 PUFA plus 5-ASA also inhibited inflammatory response by lowering NF-κB activation (P<.01) or inducing peroxisome proliferator-activated receptor-γ (PPARγ) expression (P<.05). These results indicate that 5-ASA plus n-3 PUFAs are more effective than a higher dose of 5-ASA alone to reduce NF-κB activation and to induce PPARγ. By contrast, the dual therapy did not improve the effects of individual treatments on eicosanoids or cytokine production. Use of n-3 PUFA in addition to 5-ASA may reduce dose of standard therapy.