Study On The Effect And Mechanism Of Tryptophan Combined With Lactobacillus Acidophilus On UC Mice

Ulcerative colitis(UC)is a common disease of the digestive system that occurs repeatedly and for a long time.However,the clinically used therapeutic drugs are expensive and have many side effects,which have great limitations.The interaction and interaction between the intestinal flora,its metabolites,and the host are critical to maintaining intestinal health.In recent years,the tryptophan metabolic pathway has received more and more attention in the study of intestinal homeostasis.Lactobacillus plays an important role in the intestinal tryptophan metabolism pathway.After this type of flora degrades tryptophan,it can produce a variety of tryptophan metabolites,among which indole derivatives can activate aryl hydrocarbon receptor(AHR),which in turn promotes the secretion of Interleukin 22(IL-22)from lymphocytes in the lamina propria,and relieves UC.Lactobacillus acidophilus is one of the common Lactobacillus,but the therapeutic effect and mechanism of Lactobacillus acidophilus for UC are not yet fully understood.This project proposes a combined treatment method of Lactobacillus acidophilus and high tryptophan diet,and explores whether it can act on the AHR/IL-22 pathway to reduce ulcerative colitis in mice,in order to provide a new way for the prevention and treatment of UC.The main results are as follows:(1)The combination method can alleviate the symptoms of colitis in mice.The dextran sodium sulfate method(DSS)was used to construct a mouse model of acute colitis,mainly using ELISA,RT-q PCR,and HE staining methods,from the mouse disease activity index(DAI),colon length,histopathological score,weight change,changes in inflammatory factors to evaluate the effect of tryptophan diet combined with Lactobacillus acidophilus treatment group(TDL)on the improvement of colitis in mice.The results showed that the TDL group can alleviate the shortening of the colon length(P<0.01),the decrease of disease activity index(P<0.01),the decrease of the histological score(P<0.05),the decrease of weight,and the decrease of inflammatory factors in colon tissue caused by DSS.TDL group reduced the expression of the inflammatory factors IL-6(P<0.001),IL-1β(P<0.05),and TNF-α(P<0.01)in colon tissue;it reduced the levels of IL-6(P<0.001)and TNF-α(P<0.01)in the serum of mice.(2)The combination method promotes the tryptophan metabolism pathway and activates AHR/IL-22 and downstream pathways.HPLC,ELISA,and RT-q PCR techniques were used to evaluate the effect of the combined method on the AHR/IL-22 pathway.The results showed that,compared with the DSS model group,the combined method can promote the content of tryptamine and indole-3-acetaldehyde in mouse feces(P<0.01),and promote the levels of AHR,IL-22 and downstream signaling molecules STAT3 and Reg3γ expression(P<0.05).(3)High tryptophan diet combined with Lactobacillus acidophilus treatment to improve the intestinal barrier function.Using RT-q PCR technology,explore the effect on the mouse intestinal barrier.The results showed that,compared with the DSS model group,the combination method can promote the expression of tight junction proteins Occludin and Claudin-3(P<0.05);it can improve the decrease of MUC2 protein transcription level caused by modeling(P<0.001).(4)High tryptophan diet combined with Lactobacillus acidophilus treatment can improve the imbalance of intestinal flora caused by DSS.Based on 16 S r DNA high-throughput sequencing method,analyze each group of intestinal flora.The results showed that the combined method increased the abundance of butyric acid-producing bacteria Clostridium(P<0.05),Faecalibacterium,Roseburia(P<0.01)in small feces,and improved the changes of IBD-related bacteria Lachnospiraceae and Enterobacteriaceae caused by DSS.The above results indicate that the combination method can activate the AHR/IL-22 pathway,reduce the content of plasma inflammatory factors,promote the expression of intestinal mucin,and improve the reduction of intestinal microbial diversity caused by colitis,and the reduction of short-chain fatty acid-producing bacteria.There are better treatment advantages in such aspects.