Up to 20% of the global population develops gastrointestinal symptoms following a meal 1 , leading to decreased quality of life, significant morbidity and high medical costs. Although the interest of both the scientific and lay community has increased dramatically with the worldwide introduction of gluten-free and other diets, the underlying mechanisms leading to food-induced abdominal complaints remain largely unknown. Here we show that a bacterial infection and bacterial toxins can trigger an immune response leading to the production of dietary antigen-specific IgE antibodies in mice, a mechanism confined to the intestine. Subsequent oral ingestion of the respective dietary antigen results in increased visceral pain via an IgE-and mast cell-dependent mechanism. This aberrant pain signaling results from histamine receptor H1 (H1R)-mediated sensitization of visceral afferents. Moreover, in patients with irritable bowel syndrome (IBS), we show that injection of food antigens (gluten, wheat, soy and milk) into the rectosigmoid induces local edema and mast cell activation. Hence, we have unveiled and characterized a novel peripheral mechanism underlying food-induced abdominal pain, which creates new opportunities for the treatment of IBS and related abdominal pain disorders. MAIN TEXT:The mucosal immune system provides a balanced response to pathogens and harmless commensal bacteria or food antigens, thereby limiting unnecessary inflammation and concomitant tissue damage 2 . This is achieved by an active suppression of cellular and humoral responses to orally administered antigens, a mechanism referred to as oral tolerance 3 . Viral and bacterial infections can, however, interfere with tolerance to dietary antigens, thereby perturbing intestinal homeostasis 4 . An infectious gastroenteritis is a significant risk factor to develop IBS, defined as a constellation of abdominal pain and altered bowel patterns. Between 3 and 36% of enteric infections lead to new onset IBS 5 , while up to 17% of IBS patients report that their symptoms started Supplementary information included as a separate pdf file and videos (Supplementary Information Video 1-4). EXTENDED DATA LEGENDS: Extended Data Fig. 1. Extended analysis of the OVA-specific immune response and VHS in postinfectious mice. a, b, diarrhea development quantification by (a) water content in feces and (b) whole-gut transit time upon gavage of carmine red dye in OVA/sham + OVA, OVA/infected + OVA (n = 10/group) mice. c, quantification of OVA-specific IgE in intestinal homogenates of OVA/sham + OVA, saline/infected + OVA,

ObjectivesVagus nerve stimulation (VNS), most likely via enteric neurons, prevents postoperative ileus (POI) by reducing activation of alpha7 nicotinic receptor (α7nAChR) positive muscularis macrophages (mMφ) and dampening surgery-induced intestinal inflammation. Here, we evaluated if 5-HT4 receptor (5-HT4R) agonist prucalopride can mimic this effect in mice and human.DesignUsing Ca2+ imaging, the effect of electrical field stimulation (EFS) and prucalopride was evaluated in situ on mMφ activation evoked by ATP in jejunal muscularis tissue. Next, preoperative and postoperative administration of prucalopride (1–5 mg/kg) was compared with that of preoperative VNS in a model of POI in wild-type and α7nAChR knockout mice. Finally, in a pilot study, patients undergoing a Whipple procedure were preoperatively treated with prucalopride (n=10), abdominal VNS (n=10) or sham/placebo (n=10) to evaluate the effect on intestinal inflammation and clinical recovery of POI.ResultsEFS reduced the ATP-induced Ca2+ response of mMφ, an effect that was dampened by neurotoxins tetrodotoxin and ω-conotoxin and mimicked by prucalopride. In vivo, prucalopride administered before, but not after abdominal surgery reduced intestinal inflammation and prevented POI in wild-type, but not in α7nAChR knockout mice. In humans, preoperative administration of prucalopride, but not of VNS, decreased Il6 and Il8 expression in the muscularis externa and improved clinical recovery.ConclusionEnteric neurons dampen mMφ activation, an effect mimicked by prucalopride. Preoperative, but not postoperative treatment with prucalopride prevents intestinal inflammation and shortens POI in both mice and human, indicating that preoperative administration of 5-HT4R agonists should be further evaluated as a treatment of POI.Trial registration numberNCT02425774.

Background The vagus nerve has emerged as an important modulator of the intestinal immune system. Its anti‐inflammatory properties have been previously shown in innate and Th1/Th17 predominant inflammatory models. To what extent the vagus nerve is of importance in Th2 inflammatory responses like food allergy is still unclear. In this study, we therefore aimed to investigate the effect of vagotomy (VGX) and vagus nerve stimulation (VNS), on the development and severity of experimental food allergy. Methods Balb/C mice were first sensitized with ovalbumin (OVA) in the presence of alum. Prior to oral challenges with OVA, mice were subjected to VGX or VNS. Disease severity was determined by assessing severity and onset of diarrhoea, OVA‐specific antibody production, mast cell number and activity, inflammatory gene expression in duodenal tissue and lamina propria immune cells by flow cytometry analysis. Results When compared to control mice, VGX did not significantly affect the development and severity of the disease in our model of food allergy. VNS, on the other hand, resulted in a significant amelioration of the different inflammatory parameters assessed. This effect was independent of α7nAChR and is possibly mediated through the dampening of mast cells and increased phagocytosis of OVA by CX3CR1hi macrophages. Conclusions These results underscore the anti‐inflammatory properties of the vagus nerve and the potential of neuro‐immune interactions in the intestine. Further insight into the underlying mechanisms could ultimately lead to novel therapeutic approaches in the treatment of not only food allergy but also other immune‐mediated diseases.

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Background Ephrin‐B2/EphB receptor signaling contributes to persistent pain states such as postinflammatory and neuropathic pain. Visceral hypersensitivity (VHS) is a major mechanism underlying abdominal pain in patients with irritable bowel syndrome (IBS) and inflammatory bowel diseases (IBD) in remission, but the underlying pathophysiology remains unclear. Here, we evaluated the spinal ephrin‐B2/EphB pathway in VHS in 2 murine models of VHS, that is, postinflammatory TNBS colitis and maternal separation (MS). Methods Wild‐type (WT) mice and mice lacking ephrin‐B2 in Nav1.8 nociceptive neurons (cKO) were studied. VHS was induced by: 1. intracolonic instillation of TNBS or 2. water avoidance stress (WAS) in mice that underwent maternal separation (MS). VHS was assessed by quantifying the visceromotor response (VMRs) during colorectal distention. Colonic tissue and spinal cord were collected for histology, gene, and protein expression evaluation. Key Results In WT mice, but not cKO mice, TNBS induced VHS at day 14 after instillation, which returned to baseline perception from day 28 onwards. In MS WT mice, WAS induced VHS for up to 4 weeks. In cKO however, visceral pain perception returned to basal level by week 4. The development of VHS in WT mice was associated with significant upregulation of spinal ephrin‐B2 and EphB1 mRNA expression or protein levels in the TNBS model and upregulation of spinal ephrin‐B2 protein in the MS model. No changes were observed in cKO mice. VHS was not associated with persistent intestinal inflammation. Conclusions and Inferences Overall, our data indicate that the ephrin‐B2/EphB1 spinal signaling pathway is involved in VHS and may represent a novel therapeutic target.

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SummaryCorrect development and maturation of the enteric nervous system (ENS) is critical for survival. Early in life, the ENS requires significant refinement in order to adapt to the evolving needs of the tissue, changing from milk to solid food at the time of weaning. Here, we demonstrate that resident macrophages of the muscularis externa, MMϕ, refine the ENS early in life by pruning synapses and phagocytosing abundant enteric neurons. After weaning, MMϕ continue to closely interact with the ENS, acquire a microglia-like phenotype and are crucial for the survival of enteric neurons. Of note, this microglia-like phenotype is instructed by TGFβ produced by the ENS, introducing a novel reciprocal cell-cell communication responsible for the maintenance of the neuron-associated MMФ niche in the gut. These findings elucidate a novel role of intestinal macrophages in ENS refinement early in life, and open new opportunities to treat intestinal neurodegenerative disorders by manipulating the ENS-macrophage niche.

Background: Methods to study gastric emptying in rodents are time consuming or terminal, preventing repetitive assessment in the same animal. Magnetic resonance imaging (MRI) is a non-invasive technique increasingly used to investigate gastrointestinal function devoid of these shortcomings. Here, we evaluated MRI to measure gastric emptying in control animals and in two different models of gastroparesis.Methods: Mice were scanned using a 9.4 Tesla MR scanner. Gastric volume was measured by delineating the stomach lumen area. Control mice were scanned every 30 min after ingestion of a 0.2 g meal and stomach volume was quantified. The ability of MRI to detect delayed gastric emptying was evaluated in models of morphine-induced gastroparesis and streptozotocin-induced diabetes.Key Results: Magnetic resonance imaging reproducibly detected increased gastric volume following ingestion of a standard meal and progressively decreased with a half emptying time of 59 ± 5 min. Morphine significantly increased gastric volume measured at t = 120 min (saline: 20 ± 2 vs morphine: 34 ± 5 mm 3 ; n = 8-10; p < 0.001) and increased half emptying time using the breath test (saline: 85 ± 22 vs morphine: 161 ± 46 min; n = 10; p < 0.001). In diabetic mice, gastric volume assessed by MRI at t = 60 min (control: 23 ± 2 mm 3 ; n = 14 vs diabetic: 26 ± 5 mm 3 ; n = 18; p = 0.014) but not at t = 120 min (control: 21 ± 3 mm 3 ; n = 13 vs diabetic: 18 ± 5 mm 3 ; n = 18; p = 0.115) was significantly increased compared to nondiabetic mice. Conclusions and Inferences:Our data indicate that MRI is a reliable and reproducible tool to assess gastric emptying in mice and represents a useful technique to study gastroparesis in disease models or for evaluation of pharmacological compounds.