The Role Of Neuro-Immuno-Endocrine Network In Patients With Irritable Bowel Syndrom

Background and aimsIrritable bowel syndrome (IBS) is a functional bowel disorder characterized by abdominal discomfort and altered bowel habits in the absence of structural or biochemical disorders to account for these symptoms. The pathogenetic mechanisms of IBS are not clear. The visceral hypersensitivity, abnormal motility, brain-gut dysfunction, abnormal epithelial function has been found to be present in IBS patients and has been proved to be some important pathophysiological characteristics of patients with IBS. However, the exact pathogenetic mechanisms of IBS are unknown. Recently, some new findings indicated that the abnormal neuro-immuno-endocrine network may play an important role in patients with IBS. The abnormal neuro-immuno-endocrine network perhaps involve supersensitive mechanoreceptors, thermal receptors, neurotransimitters (such as 5-HT), cation channels, immune factors and cytokines. It's very interesting to find which factors in this network play a role in pathogenetic mechanisms of IBS.In this study, we focus on the neuro-immuno-endocrine network in IBS patients and animal models and aimed to investigate the role of serum 5-HT, gastric mucosal thermal-receptor ANKTM1/TRPM8, serum food antigen-specific IgG/IgE antibodies and intestinal epithelial restitution in the pathogenesis of IBS, and find a sound way to prevent the occurrence of this disease, so as to provide new ideas for IBS in humans. Methods1. The plasma 5-HT/5-HIAA concentrations at 0, 30, 60, 90, 120, 150 and 180 minutes following cold or warm water intake were investigated in 32 female subjects with d-IBS (diarrhea predominant IBS) and 21 healthy female subjects. Symptomatology was assessed throughout the study.2. Fifty IBS patients and 20 healthy controls participated in this study. The IBS patients were further divided into two groups, with or without the history of cold food or drink induced symptoms. Gastroendoscopy were performed and the biopsy samples were taken from the gastric antrum with a biopsy forceps. Immuno-histological examination for ANKTM1 and EC cell were performed. Real time RT-PCR were performed to detection the ANKTM1 and TRPM8 gene expression.3. Thirty-seven IBS patients, 28 FD (functional dyspepsia) patients and 20 healthy controls participated in this study. Serum IgG and IgE antibody titers to 14 common foods including beef, chicken, codfish, corn, crab, eggs, mushroom, milk, pork, rice, shrimp, soybean, tomatoes and wheat were analyzed by enzyme linked immunosorbent assay (ELISA). Serum total IgE titers were also measured. Last, symptomatology was assessed in the study.4. The intestinal mucosal injury was induced in mice by cecal ligation and puncture (CLP), a classic septic peritonitis model. The restitution or migration of enterocytes along the crypt-villus axis was determined by assessing bromodeoxyuridine labeled cells. Milk fat globule-EGF factor 8 (MFG-E8 ) gene expressions in intestines were determined with western blot and immunofluorescence. In vitro, IEC-18 cells were examined for wound closure, lactadherin binding, and actin cytoskeleton.Results1. Under fasting conditions, the plasma 5-HT concentrations did not show significant differences between d-IBS patients and the healthy subjects. The plasma 5-HT concentrations in IBS patients were significantly higher than those of healthy subjects after cold water intake. The peak plasma 5-HT and "area under the curve" for 5-HT detection were also higher in d-IBS patients. But warm water intake did not bring such changes. Lastly, the d-IBS patients with symptoms exhibited higher 5-HT levels and there was a positive correlation between 5-HT level and the symptomatology in these patients.2. The number of EC cells with positive 5-HT staining and the ANKTM1 staining increased in IBS patients compared with controls. Furthermore, the EC cells and ANKTM1 expression were higher in the group of patients with the history of cold food induced symptoms than another group. The ANKTM1 gene expression increased in IBS patiens compared with normal controls. But the TRPM8 gene expression did not show any significant differences between the patients and normal controls.3. IBS patients had significantly higher IgG antibodies to crab (p=0.000), egg (p=0.000), shrimp (p=0.000), soybean (p=0.017), wheat (p=0.004) than controls. FD patients had significantly higher IgG antibodies to egg (p=0.000), soybean (p=0.017) than controls. The percentage of individuals with detectable positive food antigen-specific IgE antibodies of the three groups did not show any significant differences (p=0.971). There were no significant differences between IBS patients, FD patients and controls in the serum total IgE antibody titers (p=0.978). Lastly, no significant correlation was seen between symptom severity and serum food antigen-specific IgG antibody titers both in IBS and FD patients.4. MFG-E8 is expressed in intestinal lamina propria macrophages. With a wound-healing assay, we demonstrate that MFG-E8 promotes the migration of intestinal epithelial cells via a PKC dependent mechanism. MFG-E8 binds to phosphatidylserine and triggers reorientation of actin cytoskeleton in intestinal epithelial cells at the wound-edge. Depleting MFG-E8 with anti-MFGE8 antibody results in the inhibition of enterocyte migration along the crypt-villus axis and focal mucosal injury. Moreover, in septic mice, intestinal MFG-E8 expression is down-regulated, which is correlated with intestinal injury, interrupted enterocyte migration, and impaired restitution. Treatment with recombinant MFG-E8 restores the enterocyte migration, whereas administration of anti-MFG-E8 antibody impedes mucosal healing in mice with gut injury. Conclusions1. These data suggest that symptomatology following cold water intake may be associated with increased plasma 5-HT concentrations in female subjects with d-IBS.2. The ANKTM1 expression increased in IBS patiens compared with normal controls. It is higher in patients with the history of cold food induced symptoms. This maybe the reason why some IBS patients are sensitive to cold food or drink.3. Increased food antigen-specific IgG antibodies in IBS and FD patients in this study suggest that food allergy may contribute to the pathophysiology of these gastrointestinal (GI) functional diseases.4. MFG-E8 plays an important role in themaintenance of intestinal epithelial homeostasis and the promotion of mucosal healing.Recombinant MFG-E8 may be beneficial for the treatment of bowel injuries.SignificationThe study focus on some molecules such as serum 5-HT, gastric mucosal thermal-receptor ANKTM1/TRPM8, serum food antigen-specific IgG/IgE antibodies and intestinal epithelial restitution factor MFG-E8 in the neuro-immuno-endocrine network in IBS patients and animal models, and aimed to investigate the role of the above molecules in the pathogenesis of IBS. The results indicated that the abnormal neuro-immuno-endocrine network maybe play an important role in patients with IBS. This provides new ideas for IBS in human beings.