Yasushi Mandai

The Epithelia-Specific Membrane Trafficking Factor AP-1B Controls Gut Immune Homeostasis in Mice

BACKGROUND & AIMS Epithelial cells that cover the intestinal mucosal surface maintain immune homeostasis and tolerance in the gastrointestinal tract. However, little is known about the molecular mechanisms that regulate epithelial immune functions. Epithelial cells are distinct in that they are highly polarized; this polarity is, at least in part, established by the epithelium-specific polarized sorting factor adaptor protein (AP)-1B. We investigated the role of AP-1B-mediated protein sorting in the maintenance of gastrointestinal immune homeostasis. METHODS The role of AP-1B in intestinal immunity was examined in AP-1B-deficient mice (Ap1m2(-/-)) by monitoring their phenotypes, intestinal morphology, and epithelial barrier functions. AP-1B-mediated protein sorting was examined in polarized epithelial cells from AP-1B knockdown and Ap1m2(-/-) mice. RESULTS Ap1m2(-/-) mice developed spontaneous chronic colitis, characterized by accumulation of interleukin-17A-producing, T-helper 17 cells. Deficiency of AP-1B caused epithelial immune dysfunction, such as reduced expression of antimicrobial proteins and impaired secretion of immunoglobulin A. These defects promoted intestinal dysbiosis and increased bacterial translocation within the mucosa. Importantly, AP-1B deficiency led to mistargeting of a subset of basolateral cytokine receptors to the apical plasma membrane in a polarized epithelial cell line and in colonic epithelial cells from mice. AP1M2 expression was reduced significantly in colonic epithelium samples from patients with Crohns disease. CONCLUSIONS AP-1B is required for proper localization of a subset of cytokine receptors in polarized epithelial cells, which allows them to respond to cytokine signals from underlying lamina propria cells. The AP-1B-mediated protein sorting machinery is required for maintenance of immune homeostasis and prevention of excessive inflammation.

Distinct Roles for CXCR6(+) and CXCR6(-) CD4(+) T Cells in the Pathogenesis of Chronic Colitis.

CD4+ T cells play a central role in the development of inflammatory bowel disease (IBD) via high-level production of effector cytokines such as IFN-γ and TNF-α. To better characterize the colitogenic CD4+ T cells, we examined their expression of CXCR6, a chemokine receptor that is expressed by T cells upon activation and is upregulated in several inflammatory diseases. We found that 80% of colonic lamina propria CD4+ T cells expressed CXCR6 in the CD45RBhigh T cell-transferred colitis model. CXCR6 expression was similarly upregulated in inflamed mucosa of patients with Crohn’s disease. Although surface marker analysis demonstrated that both CXCR6+ and CXCR6− CD4+ T-cell subsets consist of the cells with effector and effector-memory cells, the more cells in the CXCR6+ subset produced IFN-γ and TNF-α compared to CXCR6− subset, and only the CXCR6+ subset produced IL-17A. Nevertheless, adoptive retransfer of lamina propria CXCR6+ T cells into Rag1 −/− recipients failed to induce the disease due to limited expansion of the transferred cells. By contrast, retransfer of CXCR6− cells evoked colitis similar to that observed in CD4+CD45RBhigh T cell-transferred mice, and resulted in their conversion into CXCR6+ cells. Collectively, these observations suggest that the CXCR6+CD4+ T-cell subset consists of terminally differentiated effector cells that serve as the major source of effector cytokines in the inflamed tissue, whereas CXCR6−CD4+ T-cell subset serves as a colitogenic memory compartment that retains the ability to proliferate and differentiate into CXCR6+CD4+ T cells.

Ectopic Ileal Varices Associated with Recurrent Bleeding: Report of a Case

Bleeding from ectopic varices of the ileum associated with portal hypertension is occasionally life-threatening. However, it is not easy to make an accurate preoperative diagnosis. A 62-year-old woman presented with hematochezia and anemia. Conventional examinations could not locate the bleeding point, but subsequent capsule endoscopy indicated gastrointestinal bleeding from hemorrhaging ileal varices. Contrast-enhanced abdominal computed tomography, three-dimensioned abdominal computed tomography, and mesenteric angiography demonstrated the presence of ileal and right ovarian varices. The patient then underwent an exploratory laparotomy which confirmed these findings, and resection of the affected ileum and right ovary was performed safely. Capsule endoscopy should be a diagnostic option for patients with obscure gastrointestinal bleeding, and ileal varices should be considered as one of the differential diagnoses.

Irsogladine Maleate Prevents Colitis in Interleukin-10 Gene-Deficient Mice by Reducing Interleukin-12 and -23 Production.

Irsogladine maleate (2,4-diamino-6-[2,5-dichlorophenyl]-s-triazine maleate; IM), an anti-peptic ulcer drug, may have a protective effect on the gastrointestinal mucosa. This study investigated the effects of IM on spontaneous colitis in interleukin-10 gene-deficient (IL-10(-/-)) mice. Five-week-old IL-10(-/-) mice were fed a control diet or one containing 100 ppm of IM for 10 weeks. Colonic tissues were evaluated morphologically and histologically. J774A.1 murine monocyte/macrophage cells were incubated with IM after lipopolysaccharide stimulation. mRNA expression was assessed by quantitative polymerase chain reaction (PCR) and protein concentration by enzyme-linked immunosorbent assay (ELISA). Colonic length, weight, and histological scores clearly demonstrated that spontaneous colitis was prevented in IL-10(-/-) mice fed a diet containing IM compared with those fed control diet. Levels of tumor necrosis factor-alpha (TNF-α) (-2.5-fold), IL-1β (-5.4), interferon-gamma (IFN-γ) (-4.5), IL-17 (-113.0), IL-12p35 (-21.0), IL-12p40 (-3.4), and IL-23p19 (-4.2) mRNA expression were significantly decreased in the colonic tissues of IM-treated animals, suggesting that oral treatment with IM suppressed the T-helper (Th)1/Th17 immune response in the colonic mucosa. An in vitro study using monocyte/macrophage cells to clarify the pharmacological action of IM indicated that IL-12p40 and IL-23p19 mRNA expression levels were dose-dependently decreased by IM treatment. ELISA showed that IL-12p40 and IL-23 protein secretion were significantly decreased by IM in a dose-dependent manner. Oral treatment with IM prevented spontaneous colitis in IL-10(-/-) mice by suppressing the colonic mucosal Th1/Th17 immune response through inhibition of IL-12 and -23 production in monocyte/macrophage cells.

A Case of Blind Loop Syndrome Caused by Infection with Giardia duodenalis Diagnosed with Double Balloon Enteroscopy

A 75-year-old man who had undergone partial gastrectomy was referred to our hospital due to worsening leg edema, loose stools and malnutrition. Double balloon enteroscopy followed by insertion of an indwelling ileus tube was performed to investigate the microbial flora and for washing inside the blind loop. Trophozoites of Giardia were detected in the sampled fluid from the blind loop and DNA analysis disclosed an assemblage of genotype A-II of Giardia duodenalis. Treatment with oral metronidazole was effective. This case emphasizes the importance of a correct diagnosis when treating patients with blind loop syndrome in the digestive tract.