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Clinical trials suggest that vagus nerve stimulation presents an alternative approach to classical immune suppression in Crohn's disease. T cells capable of producing acetylcholine (ChAT+ T cells) in the spleen are essential mediators of the anti-inflammatory effect of vagus nerve stimulation. Besides the spleen, ChAT+ T cells are found abundantly in Peyer’s patches of the small intestine. However, the role of ChAT+ T cells in colitis pathogenesis is unknown. Here, we made use of CD4creChATfl/fl mice (CD4ChAT−/− mice) lacking ChAT expression specifically in CD4+ T cells. Littermates (ChATfl/fl mice) served as controls. In acute dextran sulfate sodium (DSS)-induced colitis (7 days of 2% DSS in drinking water), CD4ChAT−/− mice showed attenuated colitis and lower intestinal inflammatory cytokine levels compared with ChATfl/fl mice. In contrast, in a resolution model of DSS-induced colitis (5 days of 2% DSS followed by 7 days without DSS), CD4ChAT−/− mice demonstrated a worsened colitis recovery and augmented colonic histological inflammation scores and inflammatory cytokine levels as compared with ChATfl/fl mice. In a transfer colitis model using CD4+CD45RBhigh T cells, T cells from CD4ChAT−/− mice induced a similar level of colitis compared with ChATfl/fl T cells. Together, our results indicate that ChAT+ T cells aggravate the acute innate immune response upon mucosal barrier disruption in an acute DSS-induced colitis model, whereas they are supporting the later resolution process of this innate immune-driven colitis. Surprisingly, ChAT expression in T cells seems redundant in the context of T cell-driven colitis. NEW & NOTEWORTHY By using different mouse models of experimental colitis, we provide evidence that in dextran sulfate sodium-induced colitis, ChAT+ T cells capable of producing acetylcholine worsen the acute immune response, whereas they support the later healing phase of this innate immune-driven colitis.

Background & Aims Visceral hypersensitivity is one feature of irritable bowel syndrome (IBS). Bacterial dysbiosis might be involved in the activation of nociceptive sensory pathways, but there have been few studies of the role of the mycobiome (the fungal microbiome) in the development of IBS. We analyzed intestinal mycobiomes of patients with IBS and a rat model of visceral hypersensitivity. Methods We used internal transcribed spacer 1-based metabarcoding to compare fecal mycobiomes of 18 healthy volunteers with those of 39 patients with IBS (with visceral hypersensitivity or normal levels of sensitivity). We also compared the mycobiomes of Long-Evans rats separated from their mothers (hypersensitive) with non-handled (normally sensitive) rats. We investigated whether fungi can cause visceral hypersensitivity using rats exposed to fungicide (fluconazole and nystatin). The functional relevance of the gut mycobiome was confirmed in fecal transplantation experiments: adult maternally separated rats were subjected to water avoidance stress (to induce visceral hypersensitivity), then given fungicide and donor cecum content via oral gavage. Other rats subjected to water avoidance stress were given soluble β-glucans, which antagonize C-type lectin domain family 7 member A (CLEC7A or DECTIN1) signaling via spleen-associated tyrosine kinase (SYK), a SYK inhibitor to reduce visceral hypersensitivity, or vehicle (control). The sensitivity of mast cells to fungi was tested with mesenteric windows (ex vivo) and the human mast cell line HMC-1. Results α diversity (Shannon index) and mycobiome signature (stability selection) of both groups of IBS patients differed from healthy volunteers, and the mycobiome signature of hypersensitive patients differed from that of normally sensitive patients. We observed mycobiome dysbiosis in rats that had been separated from their mothers compared with non-handled rats. Administration of fungicide to hypersensitive rats reduced their visceral hypersensitivity to normal levels of sensitivity. Administration of cecal mycobiomes from rats that had been separated from their mothers (but not non-handled mycobiome) restored hypersensitivity to distension. Administration of soluble β-glucans or a SYK inhibitor reduced visceral hypersensitivity, compared with controls. Particulate β-glucan (a DECTIN-1 agonist) induced mast cell degranulation in mesenteric windows and HMC-1 cells responded to fungal antigens by release of histamine. Conclusions In an analysis of patients with IBS and controls, we associated fungal dysbiosis with IBS. In studies of rats, we found fungi to promote visceral hypersensitivity, which could be reduced by administration of fungicides, soluble β-glucans, or a SYK inhibitor. The intestinal fungi might therefore be manipulated for treatment of IBS-related visceral hypersensitivity. © 2017 AGA Institute. Chemicals/CAS: protein kinase Syk, 138674-26-7; Antifungal Agents; beta-Glucans; Protein Kinase Inhibitors; Syk Kinase; Syk protein, rat

BACKGROUND: We previously showed that the mast cell stabilizer ketotifen reduces IBS symptoms and increases the threshold of discomfort in hypersensitive IBS-patients. However, as ketotifen also has Histamine 1-receptor antagonistic properties and is known to penetrate the blood-brain barrier, its beneficial effect observed in this trial could also result from H1 receptor blockade, either at the peripheral or central level. AIM: To establish whether fexofenadine, a peripherally restricted 2nd generation Histamine 1-receptor antagonist, can mimic the effect of ketotifen and A) reverse stress-induced, mast cell dependent visceral hypersensitivity in a rat model of maternal separation (MS), and B) modulate gastrointestinal transit in MS and non-handled (NH) rats. METHODS: Adult MS and NH rats (n=9 in all groups) were subjected to acute stress (1 hr water avoidance,WA). The visceromotor response (VMR) to colorectal distension (1, 11⁄2, 2ml) was established preand 24 hours post-WA and expressed as area-under-curve (AUC, volume-vs-response, significant difference when P