Local immune response to food antigens drives meal-induced abdominal pain.

Up to 20% of people worldwide develop gastrointestinal symptoms following a meal1, leading to decreased quality of life, substantial morbidity and high medical costs. Although the interest of both the scientific and lay communities in this issue has increased markedly in recent years, with the worldwide introduction of gluten-free and other diets, the underlying mechanisms of food-induced abdominal complaints remain largely unknown. Here we show that a bacterial infection and bacterial toxins can trigger an immune response that leads to the production of dietary-antigen-specific IgE antibodies in mice, which are limited to the intestine. Following subsequent oral ingestion of the respective dietary antigen, an IgE- and mast-cell-dependent mechanism induced increased visceral pain. This aberrant pain signalling resulted from histamine receptor H1-mediated sensitization of visceral afferents. Moreover, injection of food antigens (gluten, wheat, soy and milk) into the rectosigmoid mucosa of patients with irritable bowel syndrome induced local oedema and mast cell activation. Our results identify and characterize a peripheral mechanism that underlies food-induced abdominal pain, thereby creating new possibilities for the treatment of irritable bowel syndrome and related abdominal pain disorders.

Tofacitinib in Pregnancy: Assessing Pregnancy and Infant Outcomes, Cord Blood, and Breast Milk Concentrations.

Janus kinase (JAK) inhibitors are effective anti-inflammatory agents for treatment of ulcerative colitis (UC).1 According to drug regulatory agencies and international guidelines, JAK inhibitors should be avoided during pregnancy and lactation.2-4 The existing evidence on safety of JAK inhibitors during pregnancy is scarce and almost exclusively limited to tofacitinib.4-7.

Approaches to Account for Colon Absorption in Physiologically Based Biopharmaceutics Modeling of Extended-Release Drug Products.

The rate and extent of colon absorption are important determinants of the in vivo performance of extended-release (ER) drug products. The ability to appropriately predict this at different stages of development using mechanistic physiologically based biopharmaceutic modeling (PBBM) is highly desirable. This investigation aimed to evaluate the prediction performance of three different approaches to account for colon absorption in predictions of the in vivo performance of ER drug product variants with different in vitro release profiles. This was done by mechanistic predictions of the absorption and plasma exposure of the ER drug products using GastroPlus and GI-Sim for five drugs with different degrees of colon absorption limitations in humans. Colon absorption was accounted for in the predictions using three different approaches: (1) by an a priori approach using the default colon models, (2) by fitting the colon absorption scaling factors to the observed plasma concentration-time profiles after direct administration to the colon in humans, or (3) from the ER drug product variant with the slowest in vitro release profile. The prediction performance was evaluated based on the percentage prediction error and the average absolute prediction error (AAPE). Two levels of acceptance criteria corresponding to highly accurate (AAPE ≤ 20%) and accurate (AAPE 20-50%) predictions were defined prior to the evaluation. For the a priori approach, the relative bioavailability (Frel), AUC0-t, and Cmax of the ER drug product variants for the low to medium colon absorption limitation risk drugs was accurately predicted with an AAPE range of 11-53 and 8-59% for GastroPlus and GI-Sim, respectively. However, the prediction performance was poor for the high colon absorption limitation risk drugs. Moreover, accounting for the human regional colon absorption data in the models did not improve the prediction performance. In contrast, using the colon absorption scaling factors derived from the slowest ER variant significantly improved the prediction performance regardless of colon absorption limitation, with a majority of the predictions meeting the high accuracy criteria. For the slowest ER approach, the AAPE ranges were 5-24 and 5-32% for GastroPlus and GI-Sim, respectively, excluding the low permeability drug. In conclusion, the a priori PBBM can be used during candidate selection and early product design to predict the in vivo performance of ER drug products for low to medium colon absorption limitation risk drugs with sufficient accuracy. The results also indicate a limited value in performing human regional absorption studies in which the drug is administered to the colon as a bolus to support PBBM development for ER drug products. Instead, by performing an early streamlined relative bioavailability study with the slowest relevant ER in vitro release profile, a highly accurate PBBM suitable for ER predictions for commercial and regulatory applications can be developed, except for permeability-limited drugs.

Molecular Dynamics Simulations of Self-Assembling Colloids in Fed-State Human Intestinal Fluids and Their Solubilization of Lipophilic Drugs.

Bioavailability of oral drugs often depends on how soluble the active pharmaceutical ingredient is in the fluid present in the small intestine. For efficient drug discovery and development, computational tools are needed for estimating this drug solubility. In this paper, we examined human intestinal fluids collected in the fed state, with coarse-grained molecular dynamics simulations. The experimentally obtained concentrations in aspirated duodenal fluids from five healthy individuals were used in three simulation sets to evaluate the importance of the initial distribution of molecules and the presence of glycerides in the simulation box when simulating the colloidal environment of the human intestinal fluid. We observed self-assembly of colloidal structures of different types: prolate, elongated, and oblate micelles, and vesicles. Glycerides were important for the formation of vesicles, and their absence was shown to induce elongated micelles. We then simulated the impact of digestion and absorption on the different colloidal types. Finally, we looked at the solubilization of three model compounds of increasing lipophilicity (prednisolone, fenofibrate, and probucol) by calculating contact ratios of drug-colloid to drug-water. Our simulation results of colloidal interactions with APIs were in line with experimental solubilization data but showed a dissimilarity to solubility values when comparing fasted-/fed-state ratios between two of the APIs. This work shows that coarse-grained molecular dynamics simulation is a promising tool for investigation of the intestinal fluids, in terms of colloidal attributes and drug solubility.

Development and complications of nutritional deficiencies after bariatric surgery.

The clinical effectiveness of bariatric surgery has encouraged the use of bariatric procedures for the treatment of morbid obesity and its comorbidities, with sleeve gastrectomy and Roux-en-Y gastric bypass being the most common procedures. Notwithstanding its success, bariatric procedures are recognised to predispose the development of nutritional deficiencies. A framework is proposed that provides clarity regarding the immediate role of diet, the gastrointestinal tract and the medical state of the patient in the development of nutritional deficiencies after bariatric surgery, while highlighting different enabling resources that may contribute. Untreated, these nutritional deficiencies can progress in the short term into haematological, muscular and neurological complications and in the long term into skeletal complications. In this review, we explore the development of nutritional deficiencies after bariatric surgery through a newly developed conceptual framework. An in-depth understanding will enable the optimisation of the post-operative follow-up, including detecting clinical signs of complications, screening for laboratory abnormalities and treating nutritional deficiencies.

Favipiravir at high doses has potent antiviral activity in SARS-CoV-2-infected hamsters, whereas hydroxychloroquine lacks activity.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapidly spread around the globe after its emergence in Wuhan in December 2019. With no specific therapeutic and prophylactic options available, the virus has infected millions of people of which more than half a million succumbed to the viral disease, COVID-19. The urgent need for an effective treatment together with a lack of small animal infection models has led to clinical trials using repurposed drugs without preclinical evidence of their in vivo efficacy. We established an infection model in Syrian hamsters to evaluate the efficacy of small molecules on both infection and transmission. Treatment of SARS-CoV-2-infected hamsters with a low dose of favipiravir or hydroxychloroquine with(out) azithromycin resulted in, respectively, a mild or no reduction in virus levels. However, high doses of favipiravir significantly reduced infectious virus titers in the lungs and markedly improved lung histopathology. Moreover, a high dose of favipiravir decreased virus transmission by direct contact, whereas hydroxychloroquine failed as prophylaxis. Pharmacokinetic modeling of hydroxychloroquine suggested that the total lung exposure to the drug did not cause the failure. Our data on hydroxychloroquine (together with previous reports in macaques and ferrets) thus provide no scientific basis for the use of this drug in COVID-19 patients. In contrast, the results with favipiravir demonstrate that an antiviral drug at nontoxic doses exhibits a marked protective effect against SARS-CoV-2 in a small animal model. Clinical studies are required to assess whether a similar antiviral effect is achievable in humans without toxic effects.

Change in carbohydrate intake one year after Roux-en-Y gastric bypass: A prospective study.

Background and objectives: To investigate the effect of carbohydrate intake before laparoscopic Roux-en-Y gastric bypass (LRYGB) on body weight, body composition and glycaemic status after surgery. Methods: In a tertiary centre cohort study, dietary habits, body composition and glycaemic status were evaluated before and 3, 6 and 12 months after LRYGB. Detailed dietary food records were processed by specialized dietitians on the basis of a standard protocol. The study population was subdivided according to relative carbohydrate intake before surgery. Results: Before surgery, 30 patients had a moderate relative carbohydrate intake (26%-45%, M-CHO), a mean body mass index (BMI) of 40.4 ± 3.9 kg/m² and a mean glycated haemoglobin A1c (A1C) of 6.5 ± 1.2% compared to 20 patients with a high relative carbohydrate intake (> 45%, H-CHO), mean BMI of 40.9 ± 3.7 kg/m² (non-significant, NS) and a mean A1C of 6.2% (NS). One year after surgery, body weight, body composition and glycaemic status were similar in the M-CHO (n = 25) and H-CHO groups (n = 16), despite less caloric intake in the H-CHO group (1317 ± 285 g vs. 1646 ± 345 g in M-CHO, p < 0.01). Their relative carbohydrate intake converged to 46% in both groups, but the H-CHO group reduced the absolute total carbohydrate consumption more than the M-CHO group (190 ± 50 g in M-CHO vs. 153 ± 39 g in H-CHO, p < 0.05), and this was especially pronounced for the mono- and disaccharides (86 ± 30 g in M-CHO vs. 65 ± 27 g in H-CHO, p < 0.05). Conclusion: A high relative carbohydrate intake before LRYGB, did not influence the change in body composition or diabetes status after surgery, despite a significantly lower total energy intake and less mono- and disaccharide consumption after surgery.

Proton Pump Inhibitors Reduce Duodenal Eosinophilia, Mast Cells, and Permeability in Patients With Functional Dyspepsia.

BACKGROUND & AIMS: Despite the growing recognition of duodenal alterations in the pathophysiology of functional dyspepsia (FD), the effect and mechanism of proton pump inhibitors (PPIs) or first-line therapy remain unclear. We studied duodenal and systemic alterations in relation to PPI therapy in patients with FD and healthy volunteers (HVs). METHODS: We performed a prospective interventional study assessing symptoms (Patient Assessment of Gastrointestinal Symptom Severity Index), duodenal alterations, and systemic factors in patients with FD ("FD-starters") and HVs before and after PPI therapy (pantoprazole 40 mg once daily for 4 weeks). Duodenal mucosal eosinophils, mast cells and permeability were quantified. Luminal pH and bile salts were determined in duodenal aspirates. Procedures were also performed in PPI-refractory patients with FD ("FD-stoppers") before and 8 weeks after PPI withdrawal. Between- and within-group changes from baseline and associations with duodenal or systemic factors were analyzed using linear mixed models. RESULTS: The study was completed by 30 HV, 27 FD-starters, and 18 FD-stoppers. Symptoms and duodenal eosinophils, mast cells (all, P < .0001), and paracellular passage (P = .02) were significantly higher in FD-starters vs HVs and reduced with PPI therapy. Symptoms and duodenal immune cells also decreased in FD-stoppers off PPIs. In contrast, immune cells and permeability increased in HVs on PPIs. Dyspeptic symptoms correlated with eosinophils before and during PPI therapy, and increased eosinophils and permeability in HVs on PPIs were associated with changes in bile salts. CONCLUSIONS: We provide the first prospective evidence for eosinophil-reducing effects as a therapeutic mechanism of PPIs in FD, with differential effects in HVs pointing to a role of luminal changes. ClinicalTrials.gov, Number: NCT03545243.

Duodenal Dysbiosis and Relation to the Efficacy of Proton Pump Inhibitors in Functional Dyspepsia.

Proton pump inhibitors (PPI) may improve symptoms in functional dyspepsia (FD) through duodenal eosinophil-reducing effects. However, the contribution of the microbiome to FD symptoms and its interaction with PPI remains elusive. Aseptic duodenal brushings and biopsies were performed before and after PPI intake (4 weeks Pantoprazole 40 mg daily, FD-starters and controls) or withdrawal (2 months, FD-stoppers) for 16S-rRNA sequencing. Between- and within-group changes in genera or diversity and associations with symptoms or duodenal factors were analyzed. In total, 30 controls, 28 FD-starters and 19 FD-stoppers were followed. Mucus-associated Porphyromonas was lower in FD-starters vs. controls and correlated with symptoms in FD and duodenal eosinophils in both groups, while Streptococcus correlated with eosinophils in controls. Although clinical and eosinophil-reducing effects of PPI therapy were unrelated to microbiota changes in FD-starters, increased Streptococcus was associated with duodenal PPI effects in controls and remained higher despite withdrawal of long-term PPI therapy in FD-stoppers. Thus, duodenal microbiome analysis demonstrated differential mucus-associated genera, with a potential role of Porphyromonas in FD pathophysiology. While beneficial effects of short-term PPI therapy were not associated with microbial changes in FD-starters, increased Streptococcus and its association with PPIeffects in controls suggest a role for duodenal dysbiosis after long-term PPI therapy.

Molecular Dynamics Simulations on Interindividual Variability of Intestinal Fluids: Impact on Drug Solubilization.

Efficient delivery of oral drugs is dependent on their solubility in human intestinal fluid, a complex and dynamic fluid that contains colloidal structures composed of small molecules. These structures solubilize poorly water-soluble compounds, increasing their apparent solubility, and possibly their bioavailability. In this study, we conducted coarse-grained molecular dynamics simulations with data from duodenal fluid samples previously acquired from five healthy volunteers. In these simulations, we observed the self-assembly of mixed micelles of bile salts, phospholipids, and free fatty acids. The micelles were ellipsoids with a size range of 4-7 nm. Next, we investigated micelle affinities of three model drugs. The affinities in our simulation showed the same trend as literature values for the solubility enhancement of drugs in human intestinal fluids. This type of simulations is useful for studies of events and interactions taking place in the small intestinal fluid.

Preoperative administration of the 5-HT4 receptor agonist prucalopride reduces intestinal inflammation and shortens postoperative ileus via cholinergic enteric neurons.

OBJECTIVES: Vagus 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. DESIGN: Using 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. RESULTS: EFS 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. CONCLUSION: Enteric 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 NUMBER: NCT02425774.

Immobilizing sulfotransferase 1A1 on magnetic microparticles and their evaluation using capillary electrophoresis.

Sulfotransferases are categorized as phase II metabolic enzymes. Human sulfotransferase 1A1 (SULT1A1) is involved in the sulfonation of xenobiotics with aid from the cofactor 3'-phosphoadenosine-5'-phosphosulfate that acts as a sulfonate donor. In this study, we have attempted to immobilize SULT1A1 on magnetic microparticles (MMs). Different functionalized MMs were used to immobilize SULT1A1 and their enzyme activity was compared to the control (enzyme in solution). Paracetamol was used as model substrate. Separation of paracetamol and paracetamol sulfate by CE-UV was optimized and validated. MMs with epoxy based immobilization of SULT1A1 showed better enzyme activity. Hence, they were tested for repeated usage to allow their implementation for the development of a CE immobilized micro enzyme reactor.

Gastric and Duodenal Diclofenac Concentrations in Healthy Volunteers after Intake of the FDA Standard Meal: In Vivo Observations and in Vitro Explorations.

This study investigated gastrointestinal drug concentrations of the weakly acidic drug diclofenac when dosed to healthy volunteers after intake of the FDA standard meal. In gastrointestinal aspiration studies, postprandial conditions are usually achieved using liquid or homogenized meals. However, these liquid meals may have a substantially different impact on the gastrointestinal physiology compared to a solid meal. To evaluate the effect of a solid meal on the gastrointestinal behavior of diclofenac, five healthy volunteers were recruited into a clinical study. Twenty minutes prior to diclofenac ingestion (Cataflam, 50 mg of potassium diclofenac), the volunteers were asked to eat a solid meal with the following composition corresponding to the FDA standard meal: 2 eggs, 2 bacon strips, 2 toasts, 4 ounces of hash brown potatoes, and 8 ounces of milk. Gastric and duodenal fluids were collected as a function of time, and blood samples were collected to link the gastrointestinal behavior to systemic exposure. In vivo observations were complemented with in vitro research to obtain a mechanistic understanding of diclofenac's intraluminal behavior. Ingestion of the solid meal resulted in intraluminal pH-profiles similar to earlier studies with a liquid meal. However, intraluminal drug disposition differed. In the stomach, a substantial fraction of diclofenac appeared dissolved, despite an unfavorable acidic pH. Successive in vitro tests suggested that the dissolution of diclofenac is higher in the complex gastric medium resulting from FDA standard meal ingestion compared to liquid meal ingestion. Despite the favorable pH and in contrast to a previous study with a liquid meal, significant amounts of non-dissolved diclofenac were observed in the intestine. Further in vitro tests revealed adsorption of dissolved diclofenac molecules to bacon fragments present in the FDA standard meal. This adsorption negatively affected the permeation of diclofenac across a physical barrier, suggesting that in vivo absorption is affected as well. Being the first time a gastrointestinal aspiration study is combined with the administration of a solid meal, the present study demonstrates that the intraluminal behavior of diclofenac (and possibly other drugs) heavily depends on the consistency and composition of the accompanied meal.

Interplay of Supersaturation and Solubilization: Lack of Correlation between Concentration-Based Supersaturation Measurements and Membrane Transport Rates in Simulated and Aspirated Human Fluids.

Supersaturating formulations are increasingly being used to improve the absorption of orally administered poorly water-soluble drugs. To better predict outcomes in vivo, we must be able to accurately determine the degree of supersaturation in complex media designed to provide a surrogate for the gastrointestinal environment. Herein, we demonstrate that relying on measurements based on consideration of the total dissolved concentration leads to underestimation of supersaturation and consequently membrane transport rates. Crystalline and amorphous solubilities of two compounds, atazanavir and posaconazole, were evaluated in six different media. Concurrently, diffusive flux measurements were performed in a side-by-side diffusion cell to determine the activity-based supersaturation by evaluating membrane transport rates at the crystalline and amorphous solubilities. Solubility values were found to vary in each medium because of different solubilization capacities. Concentration-based supersaturation ratios were also found to vary for the different media. Activity-based measurements, however, were largely independent of the medium, leading to relatively constant values for the estimated supersaturation. These findings have important consequences for modeling and prediction of supersaturation impact on the absorption rate as well as for better defining the thermodynamic driving force for crystallization in complex media.

Intestinal phase-II metabolism of quercetin in HT29 cells, 3D human intestinal tissues and in healthy volunteers: a qualitative comparison using LC-IMS-MS and LC-HRMS.

Flavonoids are a large class of dietary molecules, among which quercetin is the most ubiquitous, which undergo an extensive intestinal phase-II metabolism. We compared the in vivo metabolism of quercetin in healthy volunteers with two in vitro models, HT29 cells and 3 D human intestinal tissues. Supernatants of the in vitro experiments and the human intestinal fluids (HIF) were analyzed by LC-IMS-MS and LC-HRMS in a qualitative way. Quercetin glucuronides, sulfates and their methyl conjugates were detected in all three systems. The metabolic profiles were found to be different, both in terms of the metabolites produced and their relative proportions. In particular, quercetin sulfates were almost absent in supernatants from HT29 cells incubations while they were a major metabolite in HIF and also found in 3 D intestinal tissues incubations. IMS provided structural information as well as a third dimension of characterization, while HRMS brought increased sensitivity and MS/MS confirmation. HT29 cells are a useful tool to generate phase-II metabolites but do not represent the in vivo situation. 3 D intestinal tissues appear as a more relevant tool to study the intestinal phase-II metabolism of flavonoids.

Advances in Capillary Electrophoretically Mediated Microanalysis for On-line Enzymatic and Derivatization Reactions.

This review summarizes recent developments, applications, and innovations of capillary electrophoretically mediated microanalysis methods. As a follow up of an earlier review, it covers the literature from early 2015 to early 2017. This article is divided into three parts. In the first part, different types of mixing procedures and applications of enzyme mediated microanalysis are discussed; the second part summarizes immobilized enzyme reactors (IMERs), while the third part deals with recent advances in on-line derivatization reactions.

An improved design to capture magnetic microparticles for capillary electrophoresis based immobilized microenzyme reactors.

In this paper, we demonstrate the effectiveness of a new 3D printed magnet holder that enables capture of magnetic microparticles in commercially available capillary electrophoresis equipment with a liquid or air based coolant system. The design as well as the method to capture magnetic microparticles inside the capillary are discussed. This setup was tested at temperature and pH values suitable for performing enzymatic reactions. To demonstrate its applicability in CE- immobilized microenzyme reactors (IMER) development, human flavin-containing monooxygenase 3 and bovine serum albumin were immobilized on amino functionalized magnetic microparticles using glutaraldehyde. These microparticles were subsequently used to perform in-line capillary electrophoresis with clozapine as a model substrate. This setup could be used further to establish CE-IMERs of other drug metabolic enzymes in a commercially available liquid based capillary coolant system. The CE-IMER setup was successful, although a subsequent decrease in enzyme activity was observed on repeated runs.

Identification of phase-II metabolites of flavonoids by liquid chromatography-ion-mobility spectrometry-mass spectrometry.

Flavonoids are a class of natural compounds with a broad range of potentially beneficial health properties. They are subjected to an extensive intestinal phase-II metabolism, i.e., conjugation to glucuronic acid, sulfate, and methyl groups. Flavonoids and their metabolites can interact with drug transporters and thus interfere with drug absorption, causing food-drug interactions. The site of metabolism plays a key role in the activity, but the identification of the various metabolites remains a challenge. Here, we developed an analytical method to identify the phase-II metabolites of structurally similar flavonoids. We used liquid chromatography-ion-mobility spectrometry-mass spectrometry (LC-IMS-MS) analysis to identify phase-II metabolites of flavonols, flavones, and catechins produced by HT29 cells. We showed that IMS could bring valuable structural information on the different positional isomers of the flavonols and flavones. The position of the glucuronide moiety had a strong influence on the collision cross section (CCS) of the metabolites, with only minor contribution of hydroxyl and methyl moieties. For the catechins, fragmentation data obtained from MS/MS analysis appeared more useful than IMS to determine the structure of the metabolites, mostly due to the high number of metabolites formed. Nevertheless, CCS information as a molecular fingerprint proved to be useful to identify peaks from complex mixtures. LC-IMS-MS thus appears as a valuable tool for the identification of phase-II metabolites of flavonoids. Graphical abstract Structural identification of phase-II metabolites of flavonoids using LC-IMS-MS.

Histamine Receptor H1-Mediated Sensitization of TRPV1 Mediates Visceral Hypersensitivity and Symptoms in Patients With Irritable Bowel Syndrome.

BACKGROUND & AIMS: Histamine sensitizes the nociceptor transient reporter potential channel V1 (TRPV1) and has been shown to contribute to visceral hypersensitivity in animals. We investigated the role of TRPV1 in irritable bowel syndrome (IBS) and evaluated if an antagonist of histamine receptor H1 (HRH1) could reduce symptoms of patients in a randomized placebo-controlled trial. METHODS: By using live calcium imaging, we compared activation of submucosal neurons by the TRPV1 agonist capsaicin in rectal biopsy specimens collected from 9 patients with IBS (ROME 3 criteria) and 15 healthy subjects. The sensitization of TRPV1 by histamine, its metabolite imidazole acetaldehyde, and supernatants from biopsy specimens was assessed by calcium imaging of mouse dorsal root ganglion neurons. We then performed a double-blind trial of patients with IBS (mean age, 31 y; range, 18-65 y; 34 female). After a 2-week run-in period, subjects were assigned randomly to groups given either the HRH1 antagonist ebastine (20 mg/day; n = 28) or placebo (n = 27) for 12 weeks. Rectal biopsy specimens were collected, barostat studies were performed, and symptoms were assessed (using the validated gastrointestinal symptom rating scale) before and after the 12-week period. Patients were followed up for an additional 2 weeks. Abdominal pain, symptom relief, and health-related quality of life were assessed on a weekly basis. The primary end point of the study was the effect of ebastine on the symptom score evoked by rectal distension. RESULTS: TRPV1 responses of submucosal neurons from patients with IBS were potentiated compared with those of healthy volunteers. Moreover, TRPV1 responses of submucosal neurons from healthy volunteers could be potentiated by their pre-incubation with histamine; this effect was blocked by the HRH1 antagonist pyrilamine. Supernatants from rectal biopsy specimens from patients with IBS, but not from the healthy volunteers, sensitized TRPV1 in mouse nociceptive dorsal root ganglion neurons via HRH1; this effect could be reproduced by histamine and imidazole acetaldehyde. Compared with subjects given placebo, those given ebastine had reduced visceral hypersensitivity, increased symptom relief (ebastine 46% vs placebo 13%; P = .024), and reduced abdominal pain scores (ebastine 39 ± 23 vs placebo 62 ± 22; P = .0004). CONCLUSIONS: In studies of rectal biopsy specimens from patients, we found that HRH1-mediated sensitization of TRPV1 is involved in IBS. Ebastine, an antagonist of HRH1, reduced visceral hypersensitivity, symptoms, and abdominal pain in patients with IBS. Inhibitors of this pathway might be developed as a new treatment approach for IBS. ClinicalTrials.gov no: NCT01144832.