Study On The Mechanisms Of Rhein In The Treatment Of Colitis Based On Gut Microbiota And Intestinal Barrier Integrity

Background and purposeAnthraquinones and its Chinese medicine preparations are widely used in clinic,particularly sennosides,rhein and emodin.They are commonly used for obesity and long-term constipation patients.Long-term use of anthraquinone laxatives might lead to colon inflammation and colon melanosis,thus may exert colorectal cancer risk.Although long-term use of anthraquinones is considered to be a potential cause of colonic melanosis,as well as its inflammation and carcinogenic potential,emodin,rhein and chrysophanol also exhibit strong anti-bacterial,anti-tumor and anti-inflammatory pharmacological effects.Previous study has shown that rhein could attenuate DSS induced colitis,but its mechanisms remain unknown.Further investigation we found gut microbiota participate in the transformation of anthraquinones,and rhein could affect microbiota composition in specific diseases.The purpose of this project is to clarify the possible mechanism of rhein and gut microbiota in colitis,and provide new ideas for research of Chinese medicine.Research contents and resultsIn this study,C57BL/6 male mice were selected and we used DSS-induced chronic colitis model to assess whether rhein treatment could have an impact on colitis.By assessing the hematoxylin-eosin(HE)staining score,the pro-inflammatory cytokines,body weight change and inflammatory cells infiltration in the rmesenteric lymph nodes,we found rhein treatment did not cause colitis and on the contrary,rhein alleviated DSS-induced colitis.Using 16s rRNA gene sequencing method we found compared to the model group,rhein treatment showed a significant difference in gut microbiota composition,rhein reversed the microbiota dysbiosis caused by DSS.Also,we found that that the specific micorbiota species Lactobacillus genus was significantly increased after rhein treatment by LEfSe analysis and STAMP analysis.Furthermore,rhein increased the lactate acid concentration in stool and the Lactobacillus spp.gene copies in fecal contents.Non-targeted metabolomics showed rhein altered purine metabolism and decreased the level of purine metabolite uric acid.Correlation analysis showed Lactobacillus abundance negatively correlate with the uric acid,Lactobacillus could directly decrease uric acid level of NCM-460 cells in vitro.Excessive uric acid concentration has been proved to exacerbate colitis and destroy intestinal barrier.We found uric acid could impair the tight junction of NCM-460 cells in vitro.The colon samples from animal study also showed worse intestinal permeability in model group and rhein treatment reversed this effect.Fecal microbiota transplantation could reverse the DSS-induced colitis and altered purine metabolism,demonstrating that rhein attenuated colitis through regulating gut microbiota.Conclusion and significanceBased on the above results,we found rhein treatment did not cause colitis in 8 weeks.50mg/kg and 100mg/kg treatment of rhein could alleviated colitis induced by DSS.Rhein could increase the Lactobacillus genus abundance and affect host purine metabolism,thus cause the decrease in fecal uric acid concentration and the increased the level of short chain fatty acid,protect the intestinal barrier intergrity and finally result in the remission of colitis.This study found rhein did not cause colitis or have potential carcinogenic risk,and fully elucidated the role of rhein in colitis by altering gut microbiota,provided an important reference for the discussion of Chinese medicine treatment.