Investigation For The Effects And Mechanism Of Glycyrrhizin On Tight Junctional Protein To Repair The Intestinal Mucosal Barrier Injury With Ulcerative Colitis

ObjectiveThe etiology of ulcerative colitis is very complicated.Anti-inflammatory therapy is the only approach against ulcerative colitis,which has little comprehensive treatment program.Ancient medical literatures reported licorice as a treatment to "chronic dysentery",and numerous researches have showed that the active ingredient diammonium glycyrrhizinate have anti-inflammatory effect in ulcerative colitis.The latest studies in pathogenesis have suggested that intestinal mucosal barrier injury is a key factor in the development and progression of ulcerative colitis and is the leading cause of high intestinal permeability and recurrent episodes of diarrhea.At present few study has shown whether licorice has a reparative effect on the intestinal mucosal barrier injury in ulcerative colitis.As the role of licorice in the treatment of "chronic dysentery ",the effect of licorice on the intestinal mucosal barrier injury of ulcerative colitis was studied by using its active components,Glycyrrhiza uralensis,as the key regulator of intestinal mucosal barrier tight junction protein,in order to clarify the pharmacological mechanism of licorice through ulcerative colitis by repairing intestinal mucosal barrier injury.MethodsIn this study,the preparation program to establish ulcerative colitis mice model was optimized.Then,the DAI score of disease activity index,histological damage and mouse mortality were evaluated by HE staining,and the control group was treated with parallel randomized control.The effects of glycyrrhizic acid and glycyrrhetinic acid on the pathological changes of intestinal mucosa in ulcerative colitis mice were studied.Finally,the effects of glycyrrhizic acid on the intestinal mucosal permeability of ulcerative colitis mice were studied based on the results of pharmacodynamics as well as the effects of the ratio of probe drug lactulose/mannitol.The expression and location of intestinal mucosal barrier tight junction protein,claudin-2,claudin-4 and occludin were studied by western blot and immunohistochemistry,and to clarify the pharmacological mechanism of licorice repairing intestinal mucosal barrier.ResultsCompared with the mice drinking DSS,the intra-group variation of DAI,histological score and MPO activity was significantly decreased in quantitative intragastric model mice.The pharmacological effects of glycyrrhizic acid and glycyrrhetinic acid on pathological changes of intestinal mucosa in model mice showed that glycyrrhizic acid could significantly inhibit the weight loss caused by intestinal mucosal barrier in model mice,And the HE staining pathology score and survival experiment showed that the colonic mucosal barrier was significantly reduced in the glycyrrhizin group,but compared with the model group,mice in glycyrrhetinic acid group with 300mg/kg by gavage have more intestinal mucosal lesions.Further lactulose/mannitol ratio experiments showed that glycyrrhizic acid was able to reduce the amount of macromolecule lactose through reducing the intestinal mucosa permeability in a dose-dependent manner,indicating that glycyrrhizic acid could reduce intestinal permeability and repair intestinal mucosal barrier damage.Immunohistochemical experiments was applied and showed that glycyrrhizin was able to correct the abnormal location of occludin in colonic epithelial cells.We also used westernblot analysis to showe that glycyrrhizin could inhibit the down-regulation of claudin-4 and occludin in a dose-dependent manner,and inhibit the upregulation of osmotic claudin-2.ConclusionsGlycyrrhizic acid in licorice has the pharmacological effect of reducing intestinal mucosal permeability and repairing intestinal mucosal barrier injury when ulcerative colitis is reduced.The mechanism of the pharmacology is that glycyrrhizic acid can inhibit the abnormal expression and misplacing of tight junction protein in ulcerative colitis.This study provides an experimental basis for the application of glycyrrhiza in the treatment of "chronic dysentery" and its application in the treatment of ulcerative colitis.