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Background & Aims: Countries endemic for parasitic infestations have a lower incidence of Crohn's disease (CD) than nonendemic countries, and there have been anecdotal reports of the beneficial effects of helminths in CD patients. Tuft cells in the small intestine sense and direct the immune response against eukaryotic parasites. We investigated the activities of tuft cells in patients with CD and mouse models of intestinal inflammation., Methods: We used microscopy to quantify tuft cells in intestinal specimens from patients with ileal CD (n = 19), healthy individuals (n = 14), and TNF ΔARE /+ mice, which develop Crohn's-like ileitis. We performed single-cell RNA sequencing, mass spectrometry, and microbiome profiling of intestinal tissues from wild-type and Atoh1-knockout mice, which have expansion of tuft cells, to study interactions between microbes and tuft cell populations. We assessed microbe dependence of tuft cell populations using microbiome depletion, organoids, and microbe transplant experiments. We used multiplex imaging and cytokine assays to assess alterations in inflammatory response following expansion of tuft cells with succinate administration in TNF ΔARE/+ and anti-CD3E CD mouse models., Results: Inflamed ileal tissues from patients and mice had reduced numbers of tuft cells, compared with healthy individuals or wild-type mice. Expansion of tuft cells was associated with increased expression of genes that regulate the tricarboxylic acid cycle, which resulted from microbe production of the metabolite succinate. Experiments in which we manipulated the intestinal microbiota of mice revealed the existence of an ATOH1-independent population of tuft cells that was sensitive to metabolites produced by microbes. Administration of succinate to mice expanded tuft cells and reduced intestinal inflammation in TNF ΔARE/+ mice and anti-CD3E-treated mice, increased GATA3 + cells and type 2 cytokines (IL22, IL25, IL13), and decreased RORGT + cells and type 17 cytokines (IL23) in a tuft cell-dependent manner., Conclusions: We found that tuft cell expansion reduced chronic intestinal inflammation in mice. Strategies to expand tuft cells might be developed for treatment of CD., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Background & Aims: Levels of microRNAs are altered in intestinal tissues of patients with Crohn's disease (CD). The adherent-invasive Escherichia coli (AIEC), which colonize the ileal mucosa of patients with CD, adhere to and invade intestinal epithelial cells. We investigated the mechanism by which AIEC infection alters the expression of microRNAs and the host immune response., Methods: Levels of microRNAs in human intestinal epithelial T84 cells and in mouse enterocytes were measured using quantitative reverse-transcription polymerase chain reaction. Luciferase assays were used to measure binding of microRNAs to the 3'-untranslated region of messenger RNA targets. Binding of nuclear factor-κB to promoters of genes encoding microRNAs was assessed by chromatin immunoprecipitation assays. Autophagy was measured by immunoblot analyses and immunofluorescent labeling of LC3. Anti-microRNAs were transferred to mice using ileal loops. Biopsy specimens from the terminal ileum of patients with ulcerative colitis (n = 20), CD (n = 20), or individuals without inflammatory bowel disease undergoing surveillance colonoscopies (controls, n = 13) were collected during endoscopic examination., Results: AIEC infection up-regulated levels of microRNA (MIR) 30C and MIR130A in T84 cells and in mouse enterocytes by activating nuclear factor-κB. Up-regulation of these microRNAs reduced the levels of ATG5 and ATG16L1 and inhibited autophagy, leading to increased numbers of intracellular AIEC and an increased inflammatory response. In ileal biopsy samples of patients with CD, there was an inverse correlation between levels of MIR30C and MIR130A and those of ATG5 and ATG16L1, supporting in vitro findings. Inhibition of MIR30C and MIR130A in cultured intestinal epithelial cells and in mouse enterocytes blocked AIEC-induced inhibition of ATG5 and ATG16L1 expression and restored functional autophagy. This resulted in more effective clearance of intracellular AIEC and reduced AIEC-induced inflammation., Conclusions: Infection with AIEC up-regulates microRNAs to reduce expression of proteins required for autophagy and autophagy response in intestinal epithelial cells. Ileal samples from patients with CD have increased levels of these same microRNAs and reduced levels of ATG5 and ATG16L1., (Copyright © 2014 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Background & Aims: Rifaximin is used to treat patients with functional gastrointestinal disorders, but little is known about its therapeutic mechanism. We propose that rifaximin modulates the ileal bacterial community, reduces subclinical inflammation of the intestinal mucosa, and improves gut barrier function to reduce visceral hypersensitivity., Methods: We induced visceral hyperalgesia in rats, via chronic water avoidance or repeat restraint stressors, and investigated whether rifaximin altered the gut microbiota, prevented intestinal inflammation, and improved gut barrier function. Quantitative polymerase chain reaction (PCR) and 454 pyrosequencing were used to analyze bacterial 16S ribosomal RNA in ileal contents from the rats. Reverse transcription, immunoblot, and histologic analyses were used to evaluate levels of cytokines, the tight junction protein occludin, and mucosal inflammation, respectively. Intestinal permeability and rectal sensitivity were measured., Results: Water avoidance and repeat restraint stress each led to visceral hyperalgesia, accompanied by mucosal inflammation and impaired mucosal barrier function. Oral rifaximin altered the composition of bacterial communities in the ileum (Lactobacillus species became the most abundant) and prevented mucosal inflammation, impairment to intestinal barrier function, and visceral hyperalgesia in response to chronic stress. Neomycin also changed the composition of the ileal bacterial community (Proteobacteria became the most abundant species). Neomycin did not prevent intestinal inflammation or induction of visceral hyperalgesia induced by water avoidance stress., Conclusions: Rifaximin alters the bacterial population in the ileum of rats, leading to a relative abundance of Lactobacillus. These changes prevent intestinal abnormalities and visceral hyperalgesia in response to chronic psychological stress., (Copyright © 2014 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Background & Aims: Clostridium difficile-associated disease (CDAD) is the leading cause of nosocomial diarrhea in the United States. C difficile toxins TcdA and TcdB breach the intestinal barrier and trigger mucosal inflammation and intestinal damage. The inflammasome is an intracellular danger sensor of the innate immune system. In the present study, we hypothesize that TcdA and TcdB trigger inflammasome-dependent interleukin (IL)-1beta production, which contributes to the pathogenesis of CDAD., Methods: Macrophages exposed to TcdA and TcdB were assessed for IL-1beta production, an indication of inflammasome activation. Macrophages deficient in components of the inflammasome were also assessed. Truncated/mutated forms of TcdB were assessed for their ability to activate the inflammasome. The role of inflammasome signaling in vivo was assessed in ASC-deficient and IL-1 receptor antagonist-treated mice., Results: TcdA and TcdB triggered inflammasome activation and IL-1beta secretion in macrophages and human mucosal biopsy specimens. Deletion of Nlrp3 decreased, whereas deletion of ASC completely abolished, toxin-induced IL-1beta release. TcdB-induced IL-1beta release required recognition of the full-length toxin but not its enzymatic function. In vivo, deletion of ASC significantly reduced toxin-induced inflammation and damage, an effect that was mimicked by pretreatment with the IL-1 receptor antagonist anakinra., Conclusions: TcdA and TcdB trigger IL-1beta release by activating an ASC-containing inflammasome, a response that contributes to toxin-induced inflammation and damage in vivo. Pretreating mice with the IL-1 receptor antagonist anakinra afforded the same level of protection that was observed in ASC-/- mice. These data suggest that targeting inflammasome or IL-1beta signaling may represent new therapeutic targets in the treatment of CDAD., (Copyright (c) 2010 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Background & Aims: Clostridium difficile toxin A causes acute inflammation and fluid secretion in experimental animals and patients with C difficile infection. We previously reported that toxin A increased cyclooxygenase-2/prostaglandin E(2) (PGE(2)) expression and apoptosis in human colonocytes. Here, we assessed the role of secreted PGE(2) in inflammation and enterocyte apoptosis in toxin A enteritis., Methods: Effects of PGE(2) and PGE(2) blockade on toxin A-induced apoptosis of human colonocytes (NCM460) and of PGE(2) or toxin A on the Fas ligand (FasL) induction were analyzed by flow cytometry and Western blot. Functional activity of elevated FasL on colonocytes was assessed by coculture of colonocytes with Fas bearing Jurkat T cells. The involvement of PGE(2)-dependent Fas/FasL activation in toxin A enteritis was further assessed in either scid or FasL and Fas deficient mice., Results: Inhibition of cyclooxygenase-2 by NS-398 and of PGE(2) using a blocking antibody markedly attenuated apoptosis in colonocytes exposed to toxin A. Enhanced expression and release of FasL followed PGE(2) or toxin A exposure in vivo and in vitro and also was significantly attenuated by treatment with NS-398 and PGE(2) blocking antibody. PGE(2) acting through an EP1 receptor activated nuclear factor-kappaB, which induced transcription of FasL. Toxin A enteritis was accompanied by increased cellular infiltration, fluid secretion, and mucosal damage in control mice, but this response was markedly reduced in both Fas(-/-) and FasL(-/-) mice., Conclusions: Toxin A enteritis involves release of PGE(2), which activates the Fas/FasL system, causing enterocyte apoptosis and inflammation.

We present the case of a young woman with fulminating terminal ileitis due to Yersinia pseudotuberculosis, in whom Crohn's disease was subsequently diagnosed. Serological testing was prompted by radiological, macroscopic and histological changes which were atypical of Crohn's disease. We speculate that Y. pseudotuberculosis ileitis may occasionally produce an acute exacerbation of Crohn's disease, but that its occurrence may not be diagnosed if the atypical features are not recognised. In this case, the classical features of Y. pseudotuberculosis may have been modified by pre-existing Crohn's disease. We propose that, because of defects in mucosal barrier function and immunological function, patients with Crohn's may have increased susceptibility to infection by Yersinia sp.

A 38-yr-old homosexual man developed fever, diarrhea, and weight loss. An upper gastrointestinal examination revealed terminal ileitis, and stains of stool revealed acid-fast bacilli that were subsequently identified as Mycobacterium avium-intracellulare. Antimycobacterial therapy was associated with weight gain and loss of fever and diarrhea. Several months later, cutaneous Kaposi's sarcoma was observed. When the patient developed strictures in the terminal ileum, a surgical resection was performed. Numerous granulomas and acid-fast bacilli, later identified as M. avium-intracellulare, were present in the resected terminal ileum. This report demonstrates that infection of the terminal ileum with M. avium-intracellulare in a patient with acquired immune deficiency syndrome can present with a clinical and radiologic picture resembling Crohn's disease. It also demonstrates symptomatic improvement of this infection temporally related to the administration of antimycobacterial therapy and the ability of an acquired immune deficiency syndrome patient to tolerate major abdominal surgery.

The clinical, radiological, and endoscopic aspects of Yersinia enterocolitica infections in man were studied in a group of 37 adult patients observed in a 4-year period in a single gastrointestinal unit. The diagnosis was based on isolation of the bacterium in all but 1 patient. Abdominal pain and diarrhea were the most prominent symptoms, occurring in 80% of the patients. A syndrome simulating appendicitis was observed in 40%. The duration of symptoms before diagnosis varied from 1 or 2 weeks in 32 patients to several months in 5. On radiological examination the terminal ileum was involved over a distance of 10 to 20 cm in 21 of 24 patients. A coarse, irregular, or nodular mucosal pattern and pictures suggestive of ulcerations were the most prominent and early radiological signs. Endoscopic observations in 13 patients with marked diarrhea showed signs of colitis in 6 and aphthoid ulcers in 2 patients. On pathological examination, ulcerations and a nonspecific acute inflammatory cell infiltrate were observed. Although treatment with tetracycline or chloramphenicol resulted in 4 to 6 weeks in the disappearance of most symptoms and signs, pictures of "follicular ileitis" persisted for several months.