Dendritic Cells Mediated Mast Cells Activation Induce The Visceral Hypersensitivity In A Rat Model Of Irritable Bowel Syndrome And The Therapeutic Mechanism Of Chinese Herbal Formula TongXieYaoFang

Background and Aim:The pathophysiology of Irritable bowel syndrome(IBS)remains unclear,recent findings suggest that immunological imbalance in the intestine contributes to the development of the condition.Dendritic cells(DCs)are likely to play a pivotal role in the regulation of mucosal immune response.This study tested the hypothesis that the characteristic of intestinal DCs changed in the development of a IBS rat model,which induced the visceral hyperalgesia in IBS through the activation of mast cells.And the Chinese herbal formula TongXieYaoFang may improve the visceral hypersensitivity by regulating the mucosal immune response.Methods:IBS rat model was established by combining colorectal distention with restraint stress,which underwent abdominal withdrawal reflex(AWR)to evaluate visceral sensitivity.Rat in the TongXieYaoFang group were treated with Chinese herbal formula TongXieYaoFang 4g · kg-1 · d-1 per-day,and the saline solution group were treated with the same dose of saline solution.According to experiments,surface marker of intestinal DCs was analyzed by immunohistochemistry.Toluidine blue staining was used to determine the number of mast cells(MCs).Electron microscopy was used to observe the degranulated colonic MCs.Expression of interleukin-4 and interleukin-9 both in colonic mucosa and serum were measured by enzyme-linked immunosorbent assay(ELISA),and expression of PAR-2 was measured by western blot.Mesenteric lymph node DCs(MLNDCs),splenic CD4+/CD8+Tcells were isolated and purified by magnetic label-based technique.Cytokine production of the MLNDCs cocultured with CD4+ or CD8+T cells was determined.Results:Visceral sensitivity was significantily higher in model group(p<0.05).Surface marker CD 103 was increased in model group as well as the number of colonic MCs(p<0.05),the expression of PAR-2 in colonic mucosa,IL-4 and IL-9 both in colonic mucosa and serum were higher than that in control group(p<0.05).Cocultured MLNDCs with CD4+ T cells showed a predominant IL-4 secretion in the model group(p<0.05),the secretion of IL-9 was related with CD8+Tcells.Rat in the Treatment group had lower visceral sensitivity,smaller amount of colonic MCs(p<0.05),lower expression of the IL-4 in mucosa and IL-9 in serum(p<0.05).Conclusions:The hypothesis was supported that the increased DCs in colon stimulated CD4+T cells to secrete high level of cytokines IL-4,which lead to mast cells degranulation,resulting in the generation of visceral hypersensitivity in IBS rats.Chinese herbal formula TongXieYaoFang may improve the visceral hypersensitivity by regulating IL-4/IL-9 and MCs.