The Effect Of Intestinal Barrier On The Pathogenesis Of Autoimmune Hepatitis

Background and objectsAutoimmune hepatitis(AIH)is a chronic liver-specific autoimmune disease.Because of its unclear pathogenesis,the diagnostic criteria and treatment strategies of AIH are currently lacking in key points and need to be continuously explored.Intestines and the liver are closely related in anatomy and physiology.The role of intestinal mucosal barriers in the development of various liver diseases has been studied,but it still requires extensive research evidence in AIH.In this study,the serum D-Lactate(D-LA)and diamine oxidase(DAO)in patients with AIH but without cirrhosis were measured by enzyme linked immunosorbent assay(ELISA)to assess the changes in intestinal permeability.In mice study,the damaged intestinal mucosal barrier model was established with a 1%concentration of dextran sulfate sodium(DSS)solution.The concanavalin A(ConA)was used to establish acute ConA liver injury model and 1%DSS-ConA sequential model.Based on the sequential model,we used Bifidobacterium triple viable capsules to protect and repair the damaged intestinal mucosa.Observe and analyze the role of intestinal mucosal intervention in the pathogenesis of acute ConA liver injury to provide a direction for explaining the pathogenesis of AIH and exploring new treatment strategies.Methods1.Changes in intestinal permeability of AIH patients:From January 2016 to November 2017,48 patients with AIH but without cirrhosis who were admitted to the Department of Gastroenterology at the Tianjin General Hospital of Tianjin Medical University were screened.And 23 healthy controls were collected.Peripheral blood samples were tested for the concentration of D-LA and DAO in the serum by ELISA to assess the differences in intestinal permeability between the groups.2.The role of intestinal barrier in the pathogenesis of acute liver injury induced by ConA in mice:Female BALB/c mice were divided into blank group,DSS group,ConA group,DSS+ConA group,and DSS+intragastric bacterial suspension administration+ConA(DSS+IG+ConA)group.Each group of mice were fed for 7days.Groups with DSS consumed 1%DSS daily,while others consumed distilled water.The DSS+IG+ConA group began to administer Bifidobacterium triple viable capsules’suspension(Based on Bifidobacterium:5.6×10~4 CFU/10g)24 hours after first drinking,once every 24 hours for 6 times,and the rest were administered with normal saline intragastrically.Groups with ConA received ConA(10 mg/kg)intravenously 12 hours before the end of the 7th day,and the rest were injected with saline.Serum alanine transaminase(ALT)and aspartate aminotransferase(AST)levels were measured to evaluate liver injury.Liver hematoxylin and eosin(HE)staining was observed.Hepatic inflammatory activity was assessed using the Knodell histological activity index scoring system.Colonic HE staining was used to observe histological changes,and quantitative real-time RT-PCR(RT-qPCR)was used to detect the relative expression of zonula occludens-1(ZO-1)and Occludin to evaluate the intestinal barrier.Results1.Changes in intestinal permeability of AIH patients:Compared with healthycontrols,the levels of serum D-LA and DAO in AIH group were significantly higher(P<0.05).2.The role of intestinal barrier in the pathogenesis of acute liver injury induced by ConA in mice:(1)There was no significant difference in the final body weight and colon length among groups(P=0.817,0.257 respectively).(2)ALT and AST levels:There was no significant difference between the DSS group and the blank group(P=0.999,0.922 respectively).The ConA group had higher levels than the blank group(P<0.05).The DSS+ConA group had higher levels than the ConA group(P<0.05).The DSS+IG+ConA group was lower than the DSS+ConA group(P<0.05).(3)The hepatic HE staining of ConA-injected mice showed inflammatory cell infiltration and parenchymal necrosis.The inflammatory activity score showed that the DSS+ConA group was higher than the ConA group(P<0.05).And the DSS+IG+ConA group was relatively lower than the DSS+ConA group but without statistical significance(P=0.139).There was no abnormity found in liver HE staining of the blank and DSS groups.(4)The infiltration of inflammatory cells and damaged epithelium were found in colonic HE staining of mice in DSS and DSS+ConA groups.Although there was sporadic inflammatory infiltration found in the DSS+IG+ConA group,the cell structure of colonic epithelium was almost complete,and the gland arrangement and glandular cavity were regular.There was no abnormity found in colonic HE staining of the blank and ConA groups.(5)ZO-1 and Occludin in the colon:Compared with the blank group,both of them in the DSS group were decreased(P<0.05),and both of them in the ConA group were not statistically significant(P=0.734,1.000 respectively).Compared with the ConA group,both of them in the DSS+ConA group were decreased(P<0.05).Both of them in the DSS+IG+ConA group were relatively higher than those of the DSS+ConA group(P<0.05).Conclusions1.Serum levels of D-LA and DAO in patients with AIH but without cirrhosis were higher than those in healthy controls,indicating an increased intestinal permeability in patients with AIH but without cirrhosis.2.The 1%DSS for 7 days can cause injury in distal colon but has no effect on the liver in mice.Acute ConA modelling can cause significant hepatic injury but has no effect on the colonic mucosal barrier.DSS can cause injury in intestinal mucosa and can further worsen ConA-induced liver inflammation.Based on the 1%DSS-ConA sequential model,Bifidobacterium triple viable capsules’suspension can protect and repair DSS-induced intestinal mucosal injury,relatively ameliorating the liver inflammation.