Effects Of Gut Microbiota On Intestinal Barrier Function In Mice With Mycophenolic Acid-induced Colitis

Background: Chronic diarrhea is a common gastrointestinal side effect of mycophenolic acid(MPA)drugs.Stopping or reducing the dose will increase the risk of rejection.Studies have shown that regulating intestinal flora imbalance has great potential in the treatment of chronic diarrhea,but its safety and mechanism under immunosuppression need to be further studied.Objective: We established a MPA-induced colitis model in mice to explore the pathological mechanism of MPA-induced colitis and to study the effect of intestinal microorganisms on mouse MPA-associated colitis(MAC)and its related mechanism,so as to provide new ideas and theoretical basis for the treatment of immunosuppressant-associated diarrhea and improving the survival rate of patients with solid organ transplantation(SOT).Methods: 15 SPF(no specific pathogen)male C57BL/6 mice were randomly divided into three groups: Model group,Intervention group and Normal group.Mice in the Model group were gavaged with MPA solution,and mice in the Intervention group were gavaged with the same amount of probiotic preparations on the basis of gavage with MPA solution,and the Normal group received the same amount of normal saline at the same time.The mice were weighed every 3 days,the general condition was observed,and the fecal traits were scored.After 21 days,the mice were killed.After measuring the length of the colon,part of the proximal colon was taken for HE staining and pathological score;colon secretory immunoglobulin A(s Ig A)was measured by ELISA method;colonic occludin and ZO-1 proteins were detected by Western Blot;feces were collected for 16 sr DNA high-throughput sequencing to analyze intestinal flora.Results: 1.Compared with the Normal group,the Model group was poor in spirit,curled up,slow movement,severe diarrhea and even hematochezia,weight loss,higher diarrhea score and shorter colon length after dissection,indicating the success of the model.The disease progression in the Intervention group was slower than that in the Model group;2.The results of HE staining showed that the pathological damage occurred in the model group,and the degree of inflammation,lesion extent and pathological score in the model group were higher than those in the normal group,and significantly relieved in the intervention group;3.The Concentration of s Ig A protein,occludin protein and ZO-1protein in colon of the Model group was lower than that of the Normal group,and that of the Intervention group was higher than that of the Model group,and there was statistical significance;4.Compared with the Normal group,the species composition,flora structure,α diversity and βdiversity of the model group changed,while the intestinal flora of the Intervention group was similar to that of the Normal group.Conclusion: MAC is related to the damage of colonic barrier function and intestinal flora imbalance.The use of probiotics can effectively alleviate the symptoms of MAC.The mechanism may be to improve the intestinal immunity of mice and rescue the mechanical barrier function by regulating the homeostasis of intestinal flora.Ultimately repair the colon tissue structure.Through gene prediction,probiotics can improve the functional abundance of energy generation and conversion,intracellular transport,coenzyme transport and metabolism,post-transcriptional modification,extracellular structure and so on.