Shuhei Hosomi

Paneth cells as a site of origin for intestinal inflammation

The recognition of autophagy related 16-like 1 (ATG16L1) as a genetic risk factor has exposed the critical role of autophagy in Crohn’s disease. Homozygosity for the highly prevalent ATG16L1 risk allele, or murine hypomorphic (HM) activity, causes Paneth cell dysfunction. As Atg16l1HM mice do not develop spontaneous intestinal inflammation, the mechanism(s) by which ATG16L1 contributes to disease remains obscure. Deletion of the unfolded protein response (UPR) transcription factor X-box binding protein-1 (Xbp1) in intestinal epithelial cells, the human orthologue of which harbours rare inflammatory bowel disease risk variants, results in endoplasmic reticulum (ER) stress, Paneth cell impairment and spontaneous enteritis. Unresolved ER stress is a common feature of inflammatory bowel disease epithelium, and several genetic risk factors of Crohn’s disease affect Paneth cells. Here we show that impairment in either UPR (Xbp1ΔIEC) or autophagy function (Atg16l1ΔIEC or Atg7ΔIEC) in intestinal epithelial cells results in each other’s compensatory engagement, and severe spontaneous Crohn’s-disease-like transmural ileitis if both mechanisms are compromised. Xbp1ΔIEC mice show autophagosome formation in hypomorphic Paneth cells, which is linked to ER stress via protein kinase RNA-like endoplasmic reticulum kinase (PERK), elongation initiation factor 2α (eIF2α) and activating transcription factor 4 (ATF4). Ileitis is dependent on commensal microbiota and derives from increased intestinal epithelial cell death, inositol requiring enzyme 1α (IRE1α)-regulated NF-κB activation and tumour-necrosis factor signalling, which are synergistically increased when autophagy is deficient. ATG16L1 restrains IRE1α activity, and augmentation of autophagy in intestinal epithelial cells ameliorates ER stress-induced intestinal inflammation and eases NF-κB overactivation and intestinal epithelial cell death. ER stress, autophagy induction and spontaneous ileitis emerge from Paneth-cell-specific deletion of Xbp1. Genetically and environmentally controlled UPR function within Paneth cells may therefore set the threshold for the development of intestinal inflammation upon hypomorphic ATG16L1 function and implicate ileal Crohn’s disease as a specific disorder of Paneth cells.

ER stress transcription factor Xbp1 suppresses intestinal tumorigenesis and directs intestinal stem cells

X-box–binding protein 1 suppresses tumor formation in the gut by regulating Ire1α and Stat3-mediated regenerative responses in the epithelium as a consequence of ER stress.

Phenotypical and functional study of ghrelin and its receptor in the pathogenesis of Crohn's disease

Background: Ghrelin, a novel endogenous ligand for the growth hormone secretagogue receptor (GHSR), has been demonstrated to possess multiple functions including antiinflammatory effects. The aim of this study was to investigate the expression of ghrelin and GHSR and the function of ghrelin in inflammatory bowel disease (IBD). Methods: The expression of ghrelin and GHSR mRNA was quantified in mucosal biopsy specimens from 9 controls, 15 patients with Crohns disease (CD), and 15 patients with ulcerative colitis (UC) using quantitative reverse‐transcriptase polymerase chain reaction (RT‐PCR). The locations of ghrelin and GHSR were investigated immunohistochemically in surgically resected specimens. We also evaluated the percentage of GHSR‐positive peripheral blood mononuclear cells (PBMCs) in healthy controls and patients with CD by flow cytometry. In addition, we investigated the immunoregulatory function of ghrelin in peripheral blood T cells. Results: Ghrelin mRNA levels in colonic mucosa of IBD were higher than control level. The GHSR‐1a mRNA level in active CD was also significantly higher than the control level. Ghrelin and GHSR‐1a were expressed on CD3‐ and CD68‐positive cells. The percentage of GHSR‐1a‐positive peripheral blood T cells in patients with CD was significantly higher than the control level. Stimulation of human T cells with ghrelin increased levels of IL‐4 and IL‐13 proteins and decreased levels of IFN‐gamma protein. Reactivity to ghrelin was low in CD compared with the control level. Conclusions: Our findings demonstrate that ghrelin may play an important role in the immune system in CD. The dysregulation of reactivity of T cells induced by ghrelin suggests that ghrelin might participate in the pathogenesis of CD.

Role of endoplasmic reticulum stress and autophagy as interlinking pathways in the pathogenesis of inflammatory bowel disease.

Purpose of review The purpose of this study is to provide an overview of the role of endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) in inflammatory bowel disease (IBD). Recent findings Human genetic studies have identified several UPR-related genes and autophagy-related genes as IBD risk loci. Impairment of each branch of the UPR causes spontaneous enteritis or creates higher susceptibility for intestinal inflammation in model systems. Deficiency of either UPR or autophagy in small intestinal epithelial cells promotes each others compensatory engagement, which is especially prominent in Paneth cells such that, in the absence of both, severe spontaneous enteritis emerges. Summary Interactions between the UPR and autophagy exhibit critical synergistic interactions within the intestinal epithelium and especially Paneth cells that are of considerable importance to the maintenance of homeostasis. When dysfunctional in the Paneth cell, spontaneous inflammation can emerge that may extend beyond the epithelium providing direct experimental evidence that subsets of Crohns disease may emanate from primary Paneth cell disturbances.

The Short Isoform of the CEACAM1 Receptor in Intestinal T Cells Regulates Mucosal Immunity and Homeostasis via Tfh Cell Induction

Carcinoembryonic antigen cell adhesion molecule like I (CEACAM1) is expressed on activated T cells and signals through either a long (L) cytoplasmic tail containing immune receptor tyrosine based inhibitory motifs, which provide inhibitory function, or a short (S) cytoplasmic tail with an unknown role. Previous studies on peripheral T cells show that CEACAM1-L isoforms predominate with little to no detectable CEACAM1-S isoforms in mouse and human. We show here that this was not the case in tissue resident T cells of intestines and gut associated lymphoid tissues, which demonstrated predominant expression of CEACAM1-S isoforms relative to CEACAM1-L isoforms in human and mouse. This tissue resident predominance of CEACAM1-S expression was determined by the intestinal environment where it served a stimulatory function leading to the regulation of T cell subsets associated with the generation of secretory IgA immunity, the regulation of mucosal commensalism, and defense of the barrier against enteropathogens.

CEACAM1 on activated NK cells inhibits NKG2D-mediated cytolytic function and signaling

Carcinoembryonic antigen‐related cell adhesion molecule 1 (CEACAM1) is expressed on activated natural killer (NK) cells wherein it inhibits lysis of CEACAM1‐bearing tumor cell lines. The mechanism for this is unknown. Here, we show that interleukin‐2‐induced expression of CEACAM1 on both mouse and primary human NK cells impairs the ability of NK gene complex group 2 member D (NKG2D) to stimulate cytolysis of CEACAM1‐bearing cells. This process requires the expression of CEACAM1 on the NK cells and on the tumor cells, which is consistent with the involvement of trans‐homophilic interactions between CEACAM1. Mechanistically, co‐engagement of NKG2D and CEACAM1 results in a biochemical association between these two surface receptors and the recruitment of Src homology phosphatase 1 by CEACAM1 that leads to dephosphorylation of the guanine nucleotide exchange factor Vav1 and blockade of downstream signaling that is associated with the initiation of cytolysis. Thus, CEACAM1 on activated NK cells functions as an inhibitory receptor for NKG2D‐mediated cytolysis, which has important implications for understanding the means by which CEACAM1 expression adversely affects tumor immunity.

Usefulness of Double-Balloon Endoscopy in the Diagnosis of Malignant Small-Bowel Tumors

BACKGROUND & AIMS Double-balloon endoscopy (DBE) enables endoscopic and histopathologic diagnosis of malignant small-bowel tumors (MSBT). This study examined the clinical features of patients with MSBT and evaluated the usefulness of DBE in the diagnosis of MSBT. METHODS We retrospectively examined consecutive DBE studies of 358 patients who underwent DBE in our hospital between December 2003 and October 2007 because of suspected or established small-bowel disease. RESULTS Fourteen patients with MSBT were diagnosed by DBE. The most common type was primary adenocarcinoma (8 patients), followed by metastatic carcinoma (3 patients) and malignant lymphoma (3 patients). Half of these patients presented with obscure gastrointestinal bleeding (OGIB). Histopathologic diagnosis was obtained in 11 of 14 patients. CONCLUSIONS Of 180 patients with OGIB, MSBT accounted for only 3.9%, however, 50% of patients with MSBT presented with OGIB. OGIB is an important clinical feature of small-bowel malignancy, which can be diagnosed by DBE.

Intestinal epithelial cell endoplasmic reticulum stress promotes MULT1 up-regulation and NKG2D-mediated inflammation

Endoplasmic reticulum (ER) stress is commonly observed in intestinal epithelial cells (IECs) and can, if excessive, cause spontaneous intestinal inflammation as shown by mice with IEC-specific deletion of X-box–binding protein 1 (Xbp1), an unfolded protein response–related transcription factor. In this study, Xbp1 deletion in the epithelium (Xbp1&Dgr;IEC) is shown to cause increased expression of natural killer group 2 member D (NKG2D) ligand (NKG2DL) mouse UL16-binding protein (ULBP)–like transcript 1 and its human orthologue cytomegalovirus ULBP via ER stress–related transcription factor C/EBP homology protein. Increased NKG2DL expression on mouse IECs is associated with increased numbers of intraepithelial NKG2D-expressing group 1 innate lymphoid cells (ILCs; NK cells or ILC1). Blockade of NKG2D suppresses cytolysis against ER-stressed epithelial cells in vitro and spontaneous enteritis in vivo. Pharmacological depletion of NK1.1+ cells also significantly improved enteritis, whereas enteritis was not ameliorated in Recombinase activating gene 1−/−;Xbp1&Dgr;IEC mice. These experiments reveal innate immune sensing of ER stress in IECs as an important mechanism of intestinal inflammation.

Dysregulated upregulation of T-cell immunoglobulin and mucin domain-3 on mucosal T helper 1 cells in patients with Crohn's disease

Abstract Objective. T-cell immunoglobulin and mucin domain-3 (TIM-3) is a unique cell surface molecule expressed on T helper 1 (Th1) cells. Engagement of TIM-3 by ligand galectin-9 leads to dampened Th1 immunity. We investigated TIM-3 and galectin-9 expression in inflammatory bowel disease (IBD) patients and in healthy controls, and evaluated the immune role of the TIM-3 pathway in Crohns disease (CD) pathogenesis. Material and methods. We used flow cytometry to investigate TIM-3 expression on mononuclear cells isolated from the intestinal mucosa and peripheral blood cells of patients with IBD and healthy controls. We also evaluated galectin-9 mRNA expression on endoscopically obtained intestinal mucosal cells. Results. TIM-3 was constitutively expressed on Th cells isolated from the intestinal mucosa of IBD patients and healthy controls. While we observed low TIM-3 expression on Th cells isolated from peripheral blood mononuclear cells (PBMCs), high TIM-3 expression was induced by Th1 stimulation. The level of TIM-3 expression on Th cells isolated from intestinal mucosa and stimulated PBMCs was significantly lower in CD patients than in healthy controls. Conclusions. Our data show that TIM-3 upregulation on Th1 cells is dysregulated in patients with CD. Low TIM-3 expression on Th1 cells may provide a clue toward resolution of the inflammation associated with chronic inflammatory disease. These findings should contribute to develop understanding of CD pathogenesis.

Development of Pouchitis With Combination Therapy With Peg-Interferon α-2b and Ribavirin for Chronic Hepatitis C in a Patient With Ulcerative Colitis Who Underwent Pouch Surgery

Development of Pouchitis With Combination Therapy With Peg-Interferon α-2b and Ribavirin for Chronic Hepatitis C in a Patient With Ulcerative Colitis Who Underwent Pouch Surgery