Background Duodenal changes in functional dyspepsia (FD) might be related to the development of symptoms. However, relationships among low‐grade inflammation, Helicobacter pylori infection, and protein expression by tight junctions (TJs) in the duodenum are unclear. We therefore aimed to determine whether duodenal inflammation and genes associated with TJ proteins are associated with FD. Methods We evaluated inflammatory cell infiltration of the duodenum, H pylori infection, and genes associated with TJ proteins in duodenal biopsy specimens from 35 patients with FD according to the Rome III diagnostic questionnaire and from 31 asymptomatic controls without structural diseases. We immunohistochemically detected eosinophils and mast cells and counted them. The expression of claudins, occludin, and zonula occludens (ZO)‐1 mRNA was evaluated using quantitative RT‐PCR. Infection with H pylori was determined by measuring serum antibodies, rapid urease or urea breath tests, and endoscopic findings. Results Sex, age, and H pyloriinfection rates did not differ between patients with FD and controls. The numbers of eosinophils and mast cells were significantly increased in patients with FD compared with controls and were significantly correlated. Inflammatory cell counts in the duodenum were not associated with H pylori infection status. Claudin‐3 mRNA expression was increased in the patients with FD. Conclusions Subtle inflammation identified in the duodenum of patients with FD might be associated with the onset and persistence of dyspeptic symptoms.

Esophageal visceral hypersensitivity has been proposed to be the pathogenesis of heartburn sensation in nonerosive reflux disease. Protease-activated receptor-2 (PAR-2) is expressed in human esophageal epithelial cells and is believed to play a role in inflammation and sensation. PAR-2 activation may modulate these responses through adenosine triphosphate (ATP) release, which is involved in transduction of sensation and pain. The transient receptor potential vanilloid receptor 1 (TRPV1) and acid-sensing ion channels (ASICs) are both acid-sensitive nociceptors. However, the interaction among these molecules and the mechanisms of heartburn sensation are still not clear. We therefore examined whether ATP release in human esophageal epithelial cells in response to acid is modulated by TRPV1 and ASICs and whether PAR-2 activation influences the sensitivity of TRPV1 and ASICs. Weak acid (pH 5) stimulated the release of ATP from primary human esophageal epithelial cells (HEECs). This effect was significantly reduced after pretreatment with 5-iodoresiniferatoxin (IRTX), a TRPV1-specific antagonist, or with amiloride, a nonselective ASIC blocker. TRPV1 and ASIC3 small interfering RNA (siRNA) transfection also decreased weak acid-induced ATP release. Pretreatment of HEECs with trypsin, tryptase, or a PAR-2 agonist enhanced weak acid-induced ATP release. Trypsin treatment led to the phosphorylation of TRPV1. Acid-induced ATP release enhancement by trypsin was partially blocked by IRTX, amiloride, or a PAR-2 antagonist. Conversely, acid-induced ATP release was augmented by PAR-2 activation through TRPV1 and ASICs. These findings suggested that the pathophysiology of heartburn sensation or esophageal hypersensitivity may be associated with the activation of PAR-2, TRPV1, and ASICs.

Intestinal epithelial barrier function is impaired in irritable bowel syndrome patients. Claudins are highly expressed in cells with tight junctions and are involved in the intestinal epithelial barrier function. The expression pattern of tight junction proteins in diarrhea-predominant irritable bowel syndrome have not been fully elucidated. We therefore recruited 17 diarrhea-predominant irritable bowel syndrome patients and 20 healthy controls. The expression of the tight junction-related proteins was examined in the ileal, cecal, and rectal mucosa of diarrhea-predominant irritable bowel syndrome patients using real-time PCR and immunofluorescence. Claudin-2 expression was high in the ileum of diarrhea-predominant irritable bowel syndrome patients. Claudin-2 expression was the same in cecum and rectal mucosa of control and diarrhea-predominant irritable bowel syndrome patients. Similarly, the expression of clauidn-1, claudin-7, JAM-A, occludin, and ZO-1 in the ileal, cecal, and rectal mucosa did not change between control and diarrhea-predominant irritable bowel syndrome samples. Infiltration of eosinophil and mast cells in the mucosa of ileum, cecum and rectum was evaluated using immunohistochemical staining and was not affected by diarrhea-predominant irritable bowel syndrome. Claudin-2 was expressed on the apical side of villi and crypts of ileal mucosal epithelial cells. Clauidn-2 expression is upregulated in diarrhea-predominant irritable bowel syndrome patients and may contribute to the pathogenesis of this condition.

Acotiamide prolongs gastric accommodation and improves stress-induced impaired gastric accommodation, indicating a potential role for acotiamide in the treatment of functional dyspepsia through its effects on gastric accommodation reactions.

ONO-8539 attenuated acid-induced heartburn in healthy male subjects, suggesting that EP1 receptors play a role in generation of heartburn symptoms. ONO-8539 is a potential novel therapeutic option for controlling heartburn symptoms in GERD patients. Clinical Trials Registry No: UMIN000015753.