Frequency and Predictors of Dysplasia in Pseudopolyp-like Colorectal Lesions in Patients with Long-Standing Inflammatory Bowel Disease.

Current endoscopic surveillance programs do not consider inflammatory bowel disease (IBD)-associated post-inflammatory polyps (pseudopolyps) per se clinically relevant, even though their presence seems to increase the risk of colorectal cancer (CRC). However, it remains unclear whether the link between pseudopolyps and CRC is indirect or whether some subsets of pseudopolyp-like lesions might eventually undergo neoplastic transformation. This study aimed to assess the frequency and predictors of dysplasia in pseudopolyp-like lesions in a population with long-standing colonic IBD. This was a retrospective, single-center study including patients with a colonic IBD (median disease duration of 192 months) and at least a pseudopolyp-like lesion biopsied or resected in the period from April 2021 to November 2022. One hundred and five pseudopolyps were identified in 105 patients (80 with ulcerative colitis and 25 with Crohn's disease). Twenty-three out of 105 pseudopolyp samples (22%) had dysplastic foci, and half of the dysplastic lesions were hyperplastic. Multivariate analysis showed that the age of the patients (odds ratio (OR) 1.1; p = 0.0012), size (OR 1.39; p = 0.0005), and right colonic location (OR 5.32; p = 0.04) were independent predictors of dysplasia, while previous exposure to immunosuppressors/biologics and left colonic location of the lesions were inversely correlated to dysplasia (OR 0.11; p = 0.005, and OR 0.09; p = 0.0008, respectively). No differences were seen between ulcerative colitis and Crohn's disease patients. Lesions with a size greater than 5 mm had a sensitivity of 87% and a specificity of 63% to be dysplastic. These data show that one-fourth of pseudopolyp-like lesions evident during surveillance colonoscopy in patients with longstanding IBD bear dysplastic foci and suggest treating such lesions properly.

Echopattern parameter as an aid to profile Crohn's disease patients.

BACKGROUND: Intestinal ultrasonography (US) allows for the characterization of the intestinal lesions and provides information on transmural inflammation. The aim of the study was to assess the clinical relevance of echopattern and correlation with Crohn's disease (CD) behavior and activity. METHODS: We performed a prospective study including CD patients assessed by intestinal US. The echopattern was classified as hypoechoic, hyperechoic and stratified. Color-doppler US was also performed in the thickest segment. RESULTS: One hundred CD patients were enrolled. The hypoechoic echopattern was significantly correlated with penetrating behavior (r = 0.44, p<0.0001), active disease (r = 0.21, p = 0.034), C-reactive protein/Fecal Calprotectin (r = 0.31, p = 0.004; r = 0.34, p = 0.031, respectively) and steroids (r = 0.33, p = 0.0008). Hypoechoic echopattern was associated with younger age than stratified (p = 0.046) and hyperechoic (p = 0.018) echopatterns. Bowel wall thickness was greater in the hypoechoic group than in the hyperechoic/stratified groups (p = 0.011 and p<0.0001, respectively). Hypoechoic echopattern was associated with fistulas (r = 0.52, p<0.0001) and increased vascularization (r = 0.32, p = 0.001). The hyperechoic echopattern showed a significant correlation with stricturing disease and an inverse correlation with fistulas. During a follow up period of 6 months, patients with hypoechoic echopattern had an increased risk of biological therapy need or surgery. CONCLUSIONS: The characterization of bowel wall echopattern allows for the identification of different CD behaviors.

Ultrasonographic Transmural Healing in Crohn's Disease.

Therapeutic targets in Crohn's disease (CD) have evolved greatly over the past several decades to include endoscopic improvement along with clinical remission. Yet CD is characterized by transmural damage, and there is increasing evidence of improved outcomes associated with transmural healing. Intestinal ultrasonography is a noninvasive, highly accurate imaging modality that provides real-time results and can assess for transmural healing in CD. In this review, we present the definition of transmural healing by ultrasonography, its comparison with other imaging modalities and with endoscopy, the efficacy of diverse therapies on achieving transmural healing, and data on patient outcomes in those achieving transmural healing. This review can guide clinicians who care for patients with inflammatory bowel disease on the added value of achieving transmural healing and its eventual incorporation as a target of therapy.

Phylogenetic analysis of Prevotella copri from fecal and mucosal microbiota of IBS and IBD patients.

Background: Prevotella copri is the most abundant member of the genus Prevotella that inhabits the human large intestines. Evidences correlated the increase in Prevotella abundance to inflammatory disorders, suggesting a pathobiont role. Objectives: The aim of this study was to investigate the phylogenetic dynamics of P. copri in patients with irritable bowel syndrome (IBS), inflammatory bowel diseases (IBDs) and in healthy volunteers (CTRL). Design: A phylogenetic approach was used to characterize 64 P. copri 16S rRNA sequences, selected from a metagenomic database of fecal and mucosal samples from 52 patients affected by IBD, 44 by IBS and 59 healthy. Methods: Phylogenetic reconstructions were carried out using the maximum likelihood (ML) and Bayesian methods. Results: Maximum likelihood phylogenetic tree applied onto reference and data sets, assigned all the reads to P. copri clade, in agreement with the taxonomic classification previously obtained. The longer mean genetic distances were observed for both the couples IBD and CTRL and IBD and IBS, respect to the distance between IBS and CTRL, for fecal samples. The intra-group mean genetic distance increased going from IBS to CTRLs to IBD, indicating elevated genetic variability within IBD of P. copri sequences. None clustering based on the tissue inflammation or on the disease status was evidenced, leading to infer that the variability seemed to not be influenced by concomitant diseases, disease phenotypes or tissue inflammation. Moreover, patients with IBS appeared colonized by different strains of P. copri. In IBS, a correlation between isolates and disease grading was observed. Conclusion: The characterization of P. copri phylogeny is relevant to better understand the interactions between microbiota and pathophysiology of IBD and IBS, especially for future development of therapies based on microbes (e.g. probiotics and synbiotics), to restore the microbiota in these bowel diseases.

Degradation of biogas in a simulated landfill cover soil at laboratory scale: Compositional changes of main components and volatile organic compounds.

A laboratory experiment lasting 28 days was run to simulate a typical landfill system and to investigate the compositional changes affecting the main components (CH4, CO2, and H2) and nonmethane volatile organic compounds from biogas generated by anaerobic digestion of food waste and passing through a soil column. Gas samples were periodically collected from both the digester headspace and the soil column at increasing distances from the biogas source. CH4 and H2 were efficiently degraded along the soil column. The isotopic values of δ13C measured in CH4 and CO2 from the soil column were relatively enriched in 13C compared to the biogas. Aromatics and alkanes were the most abundant groups in the biogas samples. Among these compounds, alkylated benzenes and long-chain C3+ alkanes were significantly degraded within the soil column, whereas benzene and short-chain alkanes were recalcitrant. Terpene and O-substituted compounds were relatively stable under oxidising conditions. Cyclic, alkene, S-substituted, and halogenated compounds, which exhibited minor amounts in the digester headspace, were virtually absent in the soil column. These results pointed out how many recalcitrant potentially toxic and polluting compounds tend to be relatively enriched along the soil column, claiming action to minimise diffuse landfill gas (LFG) emissions. The proposed experimental approach represents a reliable tool for investigating the attenuation capacities of landfill cover soils for LFG components and developing optimised covers by adopting proper soil treatments and operating conditions to improve their degradation efficiencies.

Endoscopic Predictors of Neoplastic Lesions in Inflammatory Bowel Diseases Patients Undergoing Chromoendoscopy.

Dye-based chromoendoscopy (DCE) with targeted biopsies is recommended for surveillance of patients with long-standing inflammatory bowel diseases (IBD), but endoscopic features that predict dysplasia are not fully clarified. We here aimed at identifying predictive factors of dysplastic/neoplastic lesions in IBD patients undergoing DCE. Two-hundred-and-nineteen patients were consecutively and prospectively enrolled from October 2019 to March 2022. One-hundred-and-forty-five out of 219 patients underwent DCE, and 148 lesions were detected in 79/145 (54%) patients. Thirty-nine lesions (26%) were dysplastic and one of them contained a CRC. Among these lesions, 7 (17.9%) had Kudo pit pattern I-II and 32 (82.1%) had a neoplastic pit pattern (Kudo III-IV). Multivariate analysis showed that neoplastic lesions Kudo III-IV (OR: 5.8, 95% CI: 2.3−14.6; p = 0.0002), lesion's size (OR 1.16, 95% CI: 1.06−1.26; p = 0.0009), and polypoid lesions according to Paris Classification (OR 7.4, 95% CI: 2.7−20.2; p = 0.0001) were independent predictors of dysplasia. A cut-off of lesion's size > 7 mm was identified as the best predictor of dysplasia. Among such features, Kudo pit pattern III-IV had the highest sensitivity and specificity to predict dysplasia (79% and 80%, respectively). Lesions with all three endoscopic features had a sensitivity of 90% and specificity of 100% to predict dysplasia. In contrast, non-polypoid lesions were inversely associated with dysplasia (OR 0.13, 95% CI: 0.05−0.36; p = 0.0001). These findings indicate that, in IBD patients, DCE-evidenced polypoid lesions with Kudo pit pattern III-IV and size > 7 mm are frequently dysplastic.

Long-Term Risk of Colectomy in Patients with Severe Ulcerative Colitis Responding to Intravenous Corticosteroids or Infliximab.

Background and aims: Intravenous corticosteroids (IVCS) and rescue therapy with infliximab (IFX) are useful for managing patients with acute severe ulcerative colitis (ASUC). However, nearly one fifth of responders undergo colectomy. Predictive factors of colectomy in this subset of patients are not fully known. We retrospectively examined the long-term risk and the predictors of colectomy in ASUC patients achieving clinical remission following treatment with IVCS or IFX. Patients and methods: Clinical and demographic characteristics were evaluated in consecutive ASUC patients who were admitted to the "Tor Vergata University" hospital between 2010 and 2020 and responded to IVCS or IFX. A multivariate logistic regression model was constructed to identify independent predictors of colectomy. Results: A total of 116 ASUC patients responding to IVCS (98 patients) or IFX (18 patients) were followed up for a median of 46 months. After discharge, 29 patients (25%) underwent colectomy. Multivariate analysis showed that a serum albumin level <3 g/dL and colonic dilation >5.5 cm on admission were independent predictors of colectomy (OR: 6.9, 95% CI: 2.08−22.8, and OR 8.5, 95% CI: 1.23−58.3, respectively). Patients with both these factors had a risk of colectomy 13 times greater than those with no risk factor. Conclusions: A low serum albumin level and colonic dilation are risk factors of long-term colectomy in ASUC patients responding to IVCS or IFX.

Ultrasonography Tight Control and Monitoring in Crohn's Disease During Different Biological Therapies: A Multicenter Study.

BACKGROUND & AIMS: Bowel ultrasonography (BUS) is a noninvasive tool for evaluating bowel activity in Crohn's disease (CD) patients. Aim of our multicenter study was to assess whether BUS helps to monitor intestinal activity improvement/resolution following different biological therapies. METHODS: Adult CD patients were prospectively enrolled at 16 sites in Italy. Changes in BUS parameters [i.e. bowel wall thickening (BWT), lesion length, echo pattern, blood flow changes and transmural healing (TH: normalization of all BUS parameters)] were analyzed at baseline and after 3, 6 and 12 months of different biological therapies. RESULTS: One hundred eighty-eight out of 201 CD patients were enrolled and analyzed (116 males [62%]; median age 36 years). Fifty-five percent of patients were treated with adalimumab, 16% with infliximab, 13% with vedolizumab and 16% with ustekinumab. TH rates at 12 months were 27.5% with an NNT of 3.6. TH at 12 months after adalimumab was 26.8%, 37% after infliximab, 27.2% after vedolizumab and 20% after ustekinumab. Mean BWT improvement from baseline was statistically significant at 3 and 12 months (P < .0001). Median Harvey-Bradshaw index, C-reactive protein and fecal calprotectin decreased after 12 months from baseline (P < .0001). Logistic regression analysis showed colonic lesion was associated with a higher risk of TH at 3 months and a greater BWT at baseline was associated with a lower risk of TH at 3 months [P = .03 (OR 0.70, 95% CI 0.50-0.97)] and 12 months [P = .01 (OR 0.58, 95% CI 0.38-0.89)]. At 3 months therapy optimization during the study was the only independent factor associated with a higher risk of no ultrasonographic response [P = .02 (OR 3.34, 95% CI 1.18-9.47)] and at 12 months disease duration [P = .02 (OR 3.03, 95% CI 1.15-7.94)]. CONCLUSIONS: Data indicate that BUS is useful to monitor biologics-induced bowel activity improvement/resolution in CD.

Long-Term Outcomes and Predictive Factors of Hospitalized Patients with Severe Ulcerative Colitis Treated with Intravenous Corticosteroids.

Background and Aims: Treatment with intravenous corticosteroids (IVCS) is a mainstay in the management of acute severe ulcerative colitis (UC). Although most patients respond to IVCS, little is known about the long-term outcomes. In this study, we assessed the long-term outcomes of IVCS in a real-life cohort. Methods: Disease activity, clinical relapse (partial Mayo score >4), the need for steroids or other maintenance therapies and the rates of colectomy and re-hospitalization were evaluated in consecutive patients admitted to the Tor Vergata University hospital between 2010 and 2020 for acute severe UC who responded to IVCS. Results: Eighty-eight patients were followed up with for a median period of 46 (range 6-133) months. Of these, 56 (64%) patients were treated with 5-aminosalycilic acid and 32 (36%) with immunomodulators or biologics after discharge. A total of 60 out of 88 patients (68%) relapsed, 28 (32%) were re-hospitalized, and 15 (17%) underwent a colectomy with no difference between the two maintenance therapy groups. The multivariate analysis showed that patients in clinical remission 6 months after discharge had a lower risk of relapse during the follow-up. Conclusions: Nearly two-thirds of patients with acute UC responding to IVCS experienced relapse after a median follow-up of 4 years, and this was not influenced by the maintenance therapy.

High Smad7 in the early post-operative recurrence of Crohn's disease.

BACKGROUND: In Crohn's disease (CD), one of the major inflammatory bowel disease (IBD) in human beings, there is over-expression of Smad7, an intracellular inhibitor of the suppressive cytokine TGF-ß1. The aim of this study was to assess whether Smad7 over-expression occurs in the early and/or late phases of CD. METHODS: Mucosal samples were taken from the neo-terminal ileum of CD patients undergoing ileocolonic resection, with or without (early CD) post-operative endoscopic recurrence, and terminal ileum of CD patients with long-standing disease undergoing intestinal resection (late CD). Smad7 was examined by immunohistochemistry and cytokine expression was analysed by flow-cytometry. RESULTS: Before the appearance of endoscopic lesions, the mucosa of the neo-terminal ileum contained high number of Smad7-expressing cells in both the epithelial and lamina propria compartments. Transition from this stage to endoscopic recurrence was marked by persistence of high number of Smad7-positive cells, which reduced significantly in the late stages of the disease, where Smad7 expression remained, however, greater than that seen in normal controls. In samples with early lesions, Smad7 expression positively correlated with the number of interferon-γ-secreting cells. CONCLUSIONS: Smad7 induction is an early event in the inflammatory sequence occurring in CD, thus suggesting that knockdown of Smad7 can help prevent post-operative recurrence.

Response Assessed by Ultrasonography as Target of Biological Treatment for Crohn's Disease.

BACKGROUND & AIMS: Mucosal healing, determined by ileocolonoscopy, is a goal for treatment of Crohn's disease (CD), but this is an invasive assessment procedure. We investigated whether response to tumor necrosis factor (TNF) antagonists, determined by small-intestine contrast ultrasonography, associates with long-term outcomes. METHODS: We performed observational study of 80 patients with CD treated with anti-TNF agents for at least 1 year who underwent serial small intestine contrast ultrasonography (SICUS) at the University of Rome, in Italy. SICUS was used to evaluate disease site (based on bowel wall thickness), extent of lesions, and presence of complications. Inclusion criteria required pre-therapy SICUS with follow-up SICUS after 18 months. At second SICUS, patients were assigned to categories of complete or partial responder or non-responder. CD-related outcomes (corticosteroid need, hospitalization, and surgery) were assessed at 1 year from the second SICUS, using multivariate models, and were analyzed after long term follow up (5 years) using Kaplan-Meier survival analysis. RESULTS: Based on SICUS, after a median of 18 months, 36 patients (51%) were complete responders, 30 were partial responders (34%), and 13 were non-responders (15%). At 1 year from the second SICUS, no patients with a complete response, based on ultrasonography, underwent surgery, in comparison to partial responders (P = .0003) or non-responders (P = .001). Complete responders used smaller amounts of corticosteroids than partial responders (P = .0001) or non-responders (P < .0001). Complete responders required fewer hospitalizations than non-responders (P = .001). Kaplan-Meier survival analysis of long-term follow up data demonstrated a lower cumulative probability of need for surgery, hospitalization, and need for steroids among SICUS-categorized complete responders (P < .0001, P = .003 and P = .0001 respectively) than SICUS-categorized non-responders. CONCLUSIONS: In patients with CD, response to anti-TNF agents, determined by SICUS, is associated with better long-term outcomes than partial or no response. Ultrasonographic assessment therefore provides a relatively non-invasive method for monitoring response to treatment in patients with CD.

Exploring the genetic diversity of the 16S rRNA gene of Akkermansia muciniphila in IBD and IBS.

Aim: The human gastrointestinal tract harbors diverse, abundant microbiota and Akkermansia muciniphila is involved in this community. The aim of this study is to characterize 16 new A. muciniphila 16S ribosomal RNA sequences selected from a metagenomic database from stools of patients with irritable bowel syndrome (IBS), inflammatory bowel diseases and control (CTRLs) subjects by a phylogenetic approach. Materials & methods: A phylogenetic approach was used to study the genetic diversity and SNPs in 16 A. muciniphila 16S ribosomal RNA sequences from stools of 107 individuals, 36 of which were patients affected by IBS, 30 by inflammatory bowel disease and 41 were CTRLs. Results: Phylogenetic analysis confirmed the subdivision into different supported clusters. An increase of variability in IBS has been identified. Conclusion: The genetic variation combined to the relative abundance, contribute to the protective role of A. muciniphila. Phylogenesis represent an additional approach to investigate genetic variability.

Fecal and Mucosal Microbiota Profiling in Irritable Bowel Syndrome and Inflammatory Bowel Disease.

An imbalance in the bacterial species resulting in the loss of intestinal homeostasis has been described in inflammatory bowel diseases (IBD) and irritable bowel syndrome (IBS). In this prospective study, we investigated whether IBD and IBS patients exhibit specific changes in richness and distribution of fecal and mucosal-associated microbiota. Additionally, we assessed potential 16S rRNA gene amplicons biomarkers for IBD, IBS, and controls (CTRLs) by comparison of taxonomic composition. The relative abundance of bacteria, at phylum and genus/species levels, and the bacterial diversity were determined through 16S rRNA sequence-based fecal and mucosal microbiota analysis. Linear discriminant analysis effect size (LEfSe) was used for biomarker discovery associated to IBD and IBS as compared to CTRLs. In fecal and mucosal samples, the microbiota richness was characterized by a microbial diversity reduction, going from CTRLs to IBS to IBD. ß-diversity analysis showed a clear separation between IBD and CTRLs and between IBD and IBS with no significant separation between IBS and CTRLs. ß-diversity showed a clear separation between mucosa and stool samples in all the groups. In IBD, there was no difference between inflamed and not inflamed mucosa. Based upon the LEfSe data, the Anaerostipes and Ruminococcaceae were identified as the most differentially abundant bacterial taxa in CTRLs. Erysipelotrichi was identified as potential biomarker for IBS, while Gammaproteobacteria, Enterococcus, and Enterococcaceae for IBD. This study provides an overview of the alterations of microbiota and may aid in identifying potential 16S rRNA gene amplicons mucosal biomarkers for IBD and IBS.

Real-time Interobserver Agreement in Bowel Ultrasonography for Diagnostic Assessment in Patients With Crohn's Disease: An International Multicenter Study.

BACKGROUND: The unavailability of standardized parameters in bowel ultrasonography (US) commonly used in Crohn's disease (CD) and the shortage of skilled ultrasonographers are 2 limiting factors in the use of this imaging modality around the world. The aim of this study is to evaluate interobserver agreement among experienced sonographers in the evaluation of bowel US parameters in order to improve standardization in imaging reporting and interpretation. METHODS: Fifteen patients with an established diagnosis of CD underwent blinded bowel US performed by 6 experienced sonographers. Prior to the evaluation, the sonographers and clinical and radiological IBD experts met to formally define the US parameters. Interobserver agreement was tested with the Quatto method (s). RESULTS: All operators agreed on the presence/absence of CD lesions and distinguished absence of/mild activity or moderate/severe lesions in all patients. S values were moderate for bowel wall thickness (s = 0.48, P = n.s.), bowel wall pattern (s = 0.41, P = n.s.), vascularization (s = 0.52, P = n.s.), and presence of lymphnodes (s = 0.61, P = n.s.). Agreement was substantial for lesion location (s = 0.68, P = n.s.), fistula (s = 0.74, P = n.s.), phlegmon (s = 0.78, P = 0.04), and was almost perfect for abscess (s = 0.95, P = 0.02). Poor agreement was observed for mesenteric adipose tissue alteration, lesion extent, stenosis, and prestenotic dilation. CONCLUSIONS: In this study, the majority of the US parameters used in CD showed moderate/substantial agreement. The development of shared US imaging interpretation patterns among sonographers will lead to improved comparability of US results among centers and facilitate the development of multicenter studies and the spread of bowel US training, thereby allowing a wider adoption of this useful technique.

Sodium chloride-enriched Diet Enhanced Inflammatory Cytokine Production and Exacerbated Experimental Colitis in Mice.

BACKGROUND AND AIM: Environmental factors are supposed to play a decisive role in the pathogenesis of inflammatory bowel diseases [IBDs]. Increased dietary salt intake has been linked with the development of autoimmune diseases, but the impact of a salt-enriched diet on the course of IBD remains unknown. In this study, we examined whether high salt intake alters mucosal cytokine production and exacerbates colitis. METHODS: Normal intestinal lamina propria mononuclear cells [LPMCs] were activated with anti-CD3/CD28 in the presence or absence of increasing concentrations of sodium chloride [NaCl] and/or SB202190, a specific inhibitor of p38/MAP Kinase. For in vivo experiments, a high dose of NaCl was administered to mice 15 days before induction of trinitrobenzene-sulfonic acid [TNBS]-colitis or dextran sulfate sodium [DSS]-colitis. In parallel, mice were given SB202190 before induction of TNBS-colitis. Transcription factors and effector cytokines were evaluated by flow-cytometry and real-time PCR. RESULTS: IL-17A, IL-23R, TNF-α, and Ror-γT were significantly increased in human LPMCs following NaCl exposure, while there was no significant change in IFN-γ, T-bet or Foxp3. Pharmacologic inhibition of p38/MAPK abrogated the NaCl-inducing effect on LPMC-derived cytokines. Mice receiving the high-salt diet developed a more severe colitis than control mice, and this effect was preventable by SB202190. CONCLUSIONS: Our data indicated that exposure of intestinal mononuclear cells to a high-NaCl diet enhanced effector cytokine production and contributed to the exacerbation of experimental colitis in mice.

Bowel Ultrasonography in the Management of Crohn's Disease. A Review with Recommendations of an International Panel of Experts.

BACKGROUND: Bowel ultrasonography (US) is considered a useful technique for assessing mural inflammation and complications in Crohn's disease (CD). The aim of this review is to appraise the evidence on the accuracy of bowel US for CD. In addition, we aim to provide recommendations for its optimal use. METHODS: Publications were identified by literature search from 1992 to 2014 and selected based on predefined criteria: 15 or more patients; bowel US for diagnosing CD, complications, postoperative recurrence, activity; adequate reference standards; prospective study design; data reported to allow calculation of sensitivity, specificity, agreement, or correlation values; articles published in English. RESULTS: The search yielded 655 articles, of which 63 were found to be eligible and retrieved as full-text articles for analysis. Bowel US showed 79.7% sensitivity and 96.7% specificity for the diagnosis of suspected CD, and 89% sensitivity and 94.3% specificity for initial assessment in established patients with CD. Bowel US identified ileal CD with 92.7% sensitivity, 88.2% specificity, and colon CD with 81.8% sensitivity, 95.3% specificity, with lower accuracy for detecting proximal lesions. The oral contrast agent improves the sensitivity and specificity in determining CD lesions and in assessing sites and extent. CONCLUSIONS: Bowel US is a tool for evaluation of CD lesions in terms of complications, postoperative recurrence, and monitoring response to medical therapy; it reliably detects postoperative recurrence and complications, as well as offers the possibility of monitoring disease progression.

Smad7 Knockdown Restores Aryl Hydrocarbon Receptor-mediated Protective Signals in the Gut.

BACKGROUND AND AIM: In Crohn's disease [CD], the pathological process is driven by an excessive immune response that is poorly counterbalanced by regulatory mechanisms. One such a mechanism involves aryl hydrocarbon receptor [AhR], a transcription factor that delivers protective signals in the gut. Expression of AhR is reduced in CD lamina propria mononuclear cells [LPMC] even though factors accounting for such a defect remain unknown. Since CD LPMC express elevated levels of Smad7, an inhibitor of transforming growth factor beta 1 [TGF-ß1] activity, and TGF-ß1 regulates AhR in other systems, we examined the link between AhR and Smad7 in the gut. METHODS: AhR and interleukin [IL]-22 were evaluated in normal LPMC stimulated with TGF-ß1 and 6-formylindolo[3,2-b]carbazole [Ficz], an activator of AhR, and in CD LPMC incubated with a Smad7 antisense oligonucleotide and then stimulated with Ficz and TGF-ß1. AhR and IL-22 expression was evaluated in LPMC of Smad7-transgenic mice. Finally, we evaluated the protective effect of Ficz on colitis in RAG1 mice injected with naïve or Smad7-overexpressing T cells. RESULTS: In normal LPMC, TGF-ß1 induced AhR and this event was associated with increased production of IL-22 following stimulation with Ficz. Treatment of CD LPMC with Smad7 antisense oligonucleotide enabled TGF-ß1 to enhance AhR expression. Consistently, AhR expression and Ficz-induced IL-22 production were markedly reduced in T cells of Smad7-transgenic mice. In RAG1 mice, Ficz ameliorated colitis induced by wild type T cells but did not affect colitis induced by transfer of Smad7-overexpressing T cells. CONCLUSIONS: The inverse correlation between Smad7 and AhR expression helps to propagate inflammatory signals in the gut.