Response Variability to Drug Testing in Two Models of Chemically Induced Colitis.

The lack of knowledge regarding the pathogenesis of IBD is a challenge for the development of more effective and safer therapies. Although in vivo preclinical approaches are critical for drug testing, none of the existing models accurately reproduce human IBD. Factors that influence the intra-individual response to drugs have barely been described. With this in mind, our aim was to compare the anti-inflammatory efficacy of a new molecule (MTADV) to that of corticosteroids in TNBS and DSS-induced colitis mice of both sexes in order to clarify further the response mechanism involved and the variability between sexes. The drugs were administered preventively and therapeutically, and real-time bioluminescence was performed for the in vivo time-course colitis monitoring. Morphometric data were also collected, and colonic cytokines and acute plasma phase proteins were analyzed by qRT-PCR and ELISA, respectively-bioluminescence images correlated with inflammatory markers. In the TNBS model, dexamethasone worked better in females, while MTADV improved inflammation in males. In DSS-colitis, both therapies worked similarly. Based on the molecular profiles, interaction networks were constructed to pinpoint the drivers of therapeutic response that were highly dependent on the sex. In conclusion, our results suggest the importance of considering sex in IBD preclinical drug screening.

Transcriptomic identification of TMIGD1 and its relationship with the ileal epithelial cell differentiation in Crohn's disease.

Crohn's disease (CD) is a complex and multifactorial illness. There are still considerable gaps in our knowledge regarding its pathophysiology. A transcriptomic approach could shed some light on little-known biological alterations of the disease. We therefore aimed to explore the ileal transcriptome to gain knowledge about CD. We performed whole transcriptome gene expression analysis on ileocecal resections from CD patients and inflammatory bowel disease-free controls, as well as on a CD-independent cohort to replicate selected results. Normalized data were hierarchically clustered, and gene ontology and the molecular network were studied. Cell cultures and molecular methods were used for further evaluations. Genome-wide expression data analysis identified a robust transmembrane immunoglobulin domain-containing 1 (TMIGD1) gene underexpression in CD tissue, which was even more marked in inflamed ileum, and which was replicated in the validation cohort. Immunofluorescence showed TMIGD1 to be located in the apical microvilli of well-differentiated enterocytes but not in intestinal crypt. This apical TMIGD1 was lower in the noninflamed tissue and almost disappeared in the inflamed mucosa of surgical resections. In vitro studies showed hypoxic-dependent TMIGD1 decreased its expression in enterocyte-like cells. The gene enrichment analysis linked TMIGD1 with cell recovery and tissue remodeling in CD settings, involving guanylate cyclase activities. Transcriptomics may be useful for finding new targets that facilitate studies of the CD pathology. This is how TMIGD1 was identified in CD patients, which was related to multiciliate ileal epithelial cell differentiation.NEW & NOTEWORTHY This is a single-center translational research study that aimed to look for key targets involved in Crohn's disease and define molecular pathways through different functional analysis strategies. With this approach, we have identified and described a novel target, the almost unknown TMIGD1 gene, which may be key in the recovery of injured mucosa involving intestinal epithelial cell differentiation.

The Complex Relationship Between Microbiota, Immune Response and Creeping Fat in Crohn's Disease.

In the last decade, there has been growing interest in the pathological involvement of hypertrophic mesenteric fat attached to the serosa of the inflamed intestinal segments involved in Crohn's disease [CD], known as creeping fat. In spite of its protective nature, creeping fat harbours an aberrant inflammatory activity which, in an already inflamed intestine, may explain why creeping fat is associated with a greater severity of CD. The transmural inflammation of CD facilitates the interaction of mesenteric fat with translocated intestinal microorganisms, contributing to activation of the immune response. This may be not the only way in which microorganisms alter the homeostasis of this fatty tissue: intestinal dysbiosis may also impair xenobiotic metabolism. All these CD-related alterations have a functional impact on nuclear receptors such as the farnesoid X receptor or the peroxisome proliferator-activated receptor γ, which are implicated in regulation of the immune response, adipogenesis and the maintenance of barrier function, as well as on creeping fat production of inflammatory-associated cells such as adipokines. The dysfunction of creeping fat worsens the inflammatory course of CD and may favour intestinal fibrosis and fistulizing complications. However, our current knowledge of the pathophysiology and pathogenic role of creeping fat is controversial and a better understanding might provide new therapeutic targets for CD. Here we aim to review and update the key cellular and molecular alterations involved in this inflammatory process that link the pathological components of CD with the development of creeping fat.

Mucosal Interleukin-10 depletion in steroid-refractory Crohn's disease patients.

BACKGROUND: Previous studies suggested that Interleukin-10 (IL-10) depletion in Crohn's disease (CD) could predict outcome. AIM: To determine IL-10 in blood and at different intestinal locations in patients with active CD and to assess its potential prognostic capacity to identify aggressive CD. METHODS: Twenty-three patients with CD were included. Ulcerative colitis (UC), infectious colitis and healthy individuals acted as controls. Serum and mucosal samples were taken at baseline and 1 month after steroid initiation in CD patients. Patients were classified according to steroid response. Control samples were obtained from different intestinal locations. IL-10 expression was measured with real-time polymerase chain reaction, immunofluorescence (intestine) and ELISA (serum, biopsy cultures' supernatants and tissue homogenates). RESULTS: CD and UC showed an increase in IL-10 messenger RNA (mRNA) versus controls (p < .0001) in mucosa, whereas IL-10 protein secretion was increased in all types of intestinal inflammation (p < .001). No differences in IL-10 mRNA were found in CD at baseline regarding steroid response, but levels decreased in non-responders versus responders (p = .027) and were restored with rescue therapy. Serum IL-10 was increased in steroid-refractory CD at baseline and after treatment. CONCLUSIONS: Abnormal IL-10 levels in refractory patients in both mucosa and blood have physiopathological relevance and may have potential clinical applications.

Bacteria and spontaneous experimental colitis: immunological changes.

BACKGROUND: Intestinal commensal flora seems to be a requisite for both human and experimental intestinal inflammation. Our aim was to assess the immunological changes in the colon of IL-10(-/-) mice depending on the environmental conditions. MATERIALS AND METHODS: Twelve wild-type (WT) and 24 IL-10(-/-) 4-week-old mice were kept under specific pathogen-free (SPF) conditions for 4 weeks. Half of them were transferred to a conventional environment. Mice were sacrificed at 12 weeks of age, and the incidence and severity of colitis was assessed. Intraepithelial (IEL) and lamina propria (LPL) lymphocytes were assessed for phenotype and apoptosis by flow cytometry. Toll-like receptors 2 (TLR2) and TLR9 expression was assessed by real-time PCR. Immunohistochemical analyses for cell apoptosis, TLR2 and MyD88 were also performed. RESULTS: IL-10(-/-) mice shifted to conventional conditions showed a greater incidence (66% vs. 50%) and severity of colitis than animals kept under SPF conditions (P = 0·009). The number of CD3+ IEL was higher and their apoptosis rate lower in IL-10(-/-) than in their WT counterparts, regardless of the environment. In LPL, however, these differences were only observed in mice shifted to conventional conditions. TLR2 expression was significantly increased in SPF-housed IL-10(-/-) mice when compared to WT controls. Immunohistochemistry demonstrated the loss of TLR2 and MyD88 in damaged areas. CONCLUSIONS: In SPF conditions, IL-10 deficiency appears to be compensated by an increased epithelial TLR2 expression, thus resulting in a milder colonic damage. However, in conventional conditions, this compensatory mechanism would be exceeded inducing a more severe colonic damage with activation of LPL immune cells.

Therapeutic effect of antisecretory factor-rich egg yolk on the late phases of 2,4,6-trinitrobenzenesulphonic acid colitis in mice.

Antisecretory factor (AF) is expressed in all tissues of mammals, inhibits intestinal hypersecretion and has anti-inflammatory properties as well. Endogenous AF synthesis may be stimulated by feeding hydrothermally processed cereals. Alternatively, freeze-dried egg yolk can be used as a source of exogenous AF. Several reports have suggested that AF from freeze-dried egg yolk may be useful in inflammatory bowel disease. We assessed the effect of freeze-dried, AF-rich egg yolk intake on 2,4,6-trinitrobenzenesulphonic acid (TNBS) colitis. Balb/c mice were randomised to receive (1) AF in sterile drinking-water (4 g/l, n 38) and (2) sterile drinking-water alone (vehicle, n 38) from TNBS or saline administration onwards. Different subsets of mice were killed at weeks 1-3 after TNBS or saline administration. Macroscopic and microscopic damage was assessed in colonic specimens. Eicosanoid and cytokine production was evaluated in supernatants of 24 h-incubated colonic explants. Myeloperoxidase activity was measured in frozen colonic samples, while apoptosis was assessed in paraffined samples by the in situ oligoligation method. AF-treated mice showed a milder colonic damage compared with the vehicle group, which became statistically significant at week 3. This was accompanied by decreased IL-2, IL-1 and leukotriene B4 production at weeks 2 and 3, as well as increased interferon-γ at week 1, in AF-treated mice compared with vehicle-treated mice. AF-treated mice had significantly increased counts of apoptotic cells in the lamina propria at weeks 1 and 2 post-TNBS. In conclusion, the administration of AF-rich egg yolk has a therapeutic effect in the late phases of TNBS colitis in Balb/c mice.

Partial replacement of dietary (n-6) fatty acids with medium-chain triglycerides decreases the incidence of spontaneous colitis in interleukin-10-deficient mice.

Enteral nutrition has a primary therapeutic effect in active Crohn's disease. It is unknown which nutrient(s) account for this action, but a role for both the amount and type of dietary fat has been postulated. Some clinical and experimental data suggest that medium-chain triglycerides (MCT) may reduce intestinal inflammation. We aimed to assess the effect of replacing part of the dietary fat with MCT on the incidence and severity of colitis in interleukin (IL)-10(-/-) mice under specific pathogen-free conditions. Twenty-four IL-10(-/-) 4-wk-old mice were randomized to receive a control diet based on sunflower oil [(n-6) fatty acids (FA)] and an experimental isocaloric, isonitrogenous diet with 50% sunflower and 50% coconut oil (MCT diet). When the mice were 12 wk old, they were killed and the colon was examined for the presence of colitis, lymphocyte subpopulations and apoptosis, ex vivo cytokine production in supernatant of colon explants, toll-like receptor (TLR)-2 and TLR-9 mRNA, and FA profile in colonic tissue homogenates. Colitis incidence was lower in the IL-10(-/-) mice fed the MCT diet (1/12) than in the mice fed the control diet (8/12; P = 0.03). The histological damage score was also lower in the former (P < 0.0005). Feeding the MCT diet resulted in fewer total and apoptotic intraepithelial CD3+ and lamina propria CD3+CD4+ lymphocytes, as well as downregulated production of IL-6 and interferon-gamma, and reduced TLR-9 mRNA. We conclude that partial replacement of dietary (n-6) FA with MCT decreases the incidence of colitis in a model of spontaneous intestinal inflammation and provide experimental arguments for a possible primary therapeutic effect of MCT in human Crohn's disease.

Comparative Effect of the I3.1 Probiotic Formula in Two Animal Models of Colitis.

Use of probiotic therapy is an active area of investigation to treat intestinal disorders. The clinical benefits of the I3.1 probiotic formula (Lactobacillus plantarum (CECT7484, CECT7485) and P. acidilactici (CECT7483)) were demonstrated in irritable bowel syndrome (IBS) patients in a randomized, double-blind, placebo-controlled clinical trial. The aim of this study was to evaluate the therapeutic effects of I3.1 in two experimental models of colitis, a dextran sulfate sodium (DSS)-induced colitis model and an interleukin (IL)-10-deficient mice model. Colitis was induced in 32 8-week-old Balb/c mice by administering 3% (w/v) DSS in drinking water for 5 days. Probiotics were administered orally (I3.1 or VSL#3, 1 × 109 CFU daily) for 10 days before the administration of DSS. Also, probiotics (I3.1 or VSL#3, 1 × 109 CFU daily) were administered orally to 36 6-week-old C57B6J IL-10(-/-) mice for 10 weeks. Body weight was recorded daily. Colon samples were harvested for histological examination and cytokine measurements. Body weight after DSS administration did not change in the I3.1 group, whereas the VSL#3 group had weight loss. Also, I3.1 normalized IL-6 to levels similar to that of healthy controls and significantly increased the reparative histologic score. In the IL-10-deficient model, both VSL#3 and I3.1 reduced the severity of colitis compared to untreated controls, and I3.1 significantly reduced the levels of IFN-γ compared to the other two groups. In conclusion, I3.1 displays a protective effect on two murine models of experimental colitis. Results suggest that the mechanism of action could be different from VSL#3.

Interleukin-10 Enhances the Intestinal Epithelial Barrier in the Presence of Corticosteroids through p38 MAPK Activity in Caco-2 Monolayers: A Possible Mechanism for Steroid Responsiveness in Ulcerative Colitis.

Glucocorticosteroids are the first line therapy for moderate-severe flare-ups of ulcerative colitis. Despite that, up to 60% of patients do not respond adequately to steroid treatment. Previously, we reported that low IL-10 mRNA levels in intestine are associated with a poor response to glucocorticoids in active Crohn's disease. Here, we test whether IL-10 can favour the response to glucocorticoids by improving the TNFα-induced intestinal barrier damage (assessed by transepithelial electrical resistance) in Caco-2 monolayers, and their possible implications on glucocorticoid responsiveness in active ulcerative colitis. We show that the association of IL-10 and glucocorticoids improves the integrity of TNFα-treated Caco-2 cells and that p38 MAPK plays a key role. In vitro, IL-10 facilitates the nuclear translocation of p38 MAPK-phosphorylated thereby modulating glucocorticoids-receptor-α, IL-10-receptor-α and desmoglein-2 expression. In glucocorticoids-refractory patients, p38 MAPK phosphorylation and membrane desmoglein-2 expression are reduced in colonic epithelial cells. These results suggest that p38 MAPK-mediated synergism between IL-10 and glucocorticoids improves desmosome straightness contributing to the recovery of intestinal epithelium and reducing luminal antigens contact with lamina propria in ulcerative colitis. This study highlights the link between the intestinal epithelium in glucocorticoids-response in ulcerative colitis.

Comparison of lymphocyte isolation methods for endoscopic biopsy specimens from the colonic mucosa.

An ideal method of immune cell isolation should provide maximum cell yield without disturbing functional properties. Intestinal endoscopic biopsies, in contrast to surgical samples, allow the study of all disease stages but have the drawback of a minimum amount of tissue available, making protocol optimization mandatory. We compared for the first time two methods of separation of colonic epithelium and five methods of lamina propria cell isolation for colonic biopsy specimens (mechanical, enzymatic and organ culture protocols). Lymphocyte number, viability and phenotype (CD45+, CD103+, CD3+, CD4+, CD8+, CD19+, CD16-56+) were analyzed by flow cytometry. Neither of the two epithelial detachment protocols achieved proper epithelial separation, though the high intensity ion chelation method was more accurate. Maximum cell yield of lamina propria lymphocytes without phenotypic modification was obtained with overnight smooth enzymatic digestion. High dose collagenase incubation caused a marked decrease in CD4+ lymphocytes of the lamina propria as compared to low enzymatic method (p=0.004). Mechanical and biopsy culture are not advisable methods because of the low cell yield, and phenotypic alterations and high contamination rate, respectively.

Apoptosis resistance of mucosal lymphocytes and IL-10 deficiency in patients with steroid-refractory Crohn's disease.

BACKGROUND: Apoptosis resistance of T-cells is considered an abnormality of immune pathways in Crohn's disease (CD). It has been previously shown that corticosteroids induce apoptosis of cells involved in inflammation. Thus, our aim was to assess the apoptosis of mononuclear cells and pro/antiinflammatory cytokines in the intestinal mucosa of patients with active CD, related to steroid response, and identify cellular and molecular factors that may predict this response to therapy. METHODS: Patients with CD (n = 26), ulcerative colitis (UC) (n = 32), and controls (n = 10) were prospectively studied with mucosal biopsies before and 7-10 days after corticosteroid treatment. Immunophenotype and apoptosis of T and B lymphocytes, plasma cells, and macrophages were assessed by flow cytometry, immunohistochemistry, and immunofluorescence. The cytokine expression pattern was evaluated by quantitative polymerase chain reaction (PCR). RESULTS: Apoptosis resistance of T and B lymphocytes was observed only in steroid-refractory and -dependent CD patients as compared to responsive patients (P = 0.032; P = 0.004, respectively), being evident after steroid treatment. Interleukin (IL)-10 was markedly increased at baseline in steroid-responsive patients compared to the nonresponders (P = 0.006; sensitivity: 88.8%; specificity: 66.6% to predict steroid response). CONCLUSIONS: Apoptosis resistance of mucosal T and B cells in steroid-refractory and -dependent CD patients appears during the evolution of the acute phase, limiting its clinical application as a predictor marker. In contrast, increased expression of IL-10 at an early stage of active steroid-sensitive CD patients supports its usefulness at predicting a good steroid response. Steroid-dependent and -refractory CD patients share similar molecular and cellular pathophysiological mechanisms.

Lactobacillus fermentum CECT 5716 prevents and reverts intestinal damage on TNBS-induced colitis in mice.

BACKGROUND: Probiotics attenuate gut inflammation when administered before experimental colitis, but data on their effect after colitis induction are scarce. We aimed to evaluate the effects of Lactobacillus fermentum CECT 5716 on gut injury when administered either before or after trinitrobencene sulfonic acid (TNBS) colitis in Balb/c mice. METHODS: In a preventive study, probiotic or vehicle was administered for 2 weeks before colitis. Then mice were allocated to: probiotic + TNBS, probiotic + sham, vehicle + TNBS, or vehicle + sham, and sacrificed 72 hours later. In a therapeutic study, mice were allocated into the same groups as before. Probiotic or vehicle were administered for 3 weeks. Mice were sacrificed at weeks 1, 2, and 3 after TNBS. Histological score, myeloperoxidase activity, and eicosanoid and cytokine production in colonic explant cultures were measured. Immunohistochemistry for nitrotyrosine and MyD88 was also performed. RESULTS: In the preventive study, colitis was milder with probiotic than with vehicle (P = 0.041). This was associated with increased PGE(2), IL-2, and IL-4 production, as well as attenuated nitrotyrosine staining in the former. In the therapeutic study, histological score at week 1 post-TNBS was higher in probiotic than in vehicle fed mice (P = 0.018). However, at weeks 2 and 3 the histological score was significantly lower-with decreased IL-6 production and increased MyD88 staining-in mice receiving the probiotic. CONCLUSIONS: Pretreatment with L. fermentum CECT 5716 attenuates TNBS colitis, an effect that seems to be due to its antioxidant abilities. When administered after TNBS, this probiotic is also effective in accelerating colitis recovery, and this is associated with an enhanced Toll-like receptor function.