Antibiotic-modulated Microbiome Suppresses Colon Inflammation In Mice By Modulating The Intestinal Bile Acids Metabolism

Backgrounds and aims Intestinal microbiota has been implicated in the pathogenesis of IBD.However,there is limited insight into how this occurs.The co-metabolite of host and intestinal microbiota,such as bile acids,may be involved in the exacerbation of colonic inflammation.It is an emerging strategy for controlling intestinal inflammation by discovering beneficial symbiotic flora and related metabolic bile acids.In this study,we compared the severity of experimental colitis in mice with/without administration of different antibiotics.We aimed to find out the key bile acids and their related metabolic bacteria that affect intestinal inflammation.Methods:Six-week C57BL/6J female mice were divided into five groups(NC group,DSS group,Ceftriaxone sodium(CRO)group,Vancomycin(VA)group,and VA +Imipenem(IPM)group).For the DSS group,experimental colitis in mice was induced using DSS 3%.For three antibiotic-treated groups,mice were treated by CRO,VA or VA + IPM respectively,and DSS 3% was used to induce experimental colitis at the same time.The DAI score was evaluated daily.The mice were sacrificed on the 8th day.The full colon was removed,one part was used to make a swiss roll,and HE staining was performed to evaluate the histological scores.The rest part was used for the molecular test including WB and q PCR.We detected microbial profiling(using16S r RNA gene sequencing),bile acid profiling(using liquid chromatography-mass spectrometry)in the fecal samples.Multivariate statistical analysis of profiling data was performed to find the key bile acid,as well as the association between microbiota and bile metabolism.Finally,we verified the effect of the key bile acid treatment on the intestinal inflammation.Results:Compared with the NC group,the other four groups developed symptoms of experimental colitis,such as weight loss,increased DAI,decreased total colon length,increased histological score and m RNA expression of inflammatory factors.The antibiotics treatment had significantly relieved the intestinal inflammation of the mice.Compared with the NC group,colitis mice with/without antibiotic treatment have different profiles in fecal microbiome and metabolome.Compared with the NC group,the levels of CA,MCA,UDCA,LCA and TLCA increased in the DSS group,and the levels of DCA and TDCA decreased.Treatment with antibiotics increased the levels of TCA,TCDCA,TUDCA but decreased the levels of CA,CDCA,MCA,TLCA and TDCA.Variable Importance for the Projection(VIP)was calculated after OPLS-DA analysis,the five key bile acids LCA,αMCA,UDCA,TDCA,and βMCA were identified by VIP value(VIP> 1),and the LCA changed most significantly between the five groups(VIP = 2.5).We determined the correlation between the fecal bile acids and the relative abundance of bacterial genus.Further animal experiments confirmed the pro-inflammatory effects of LCA in experimental colitis in mice.Conclusions:Our results determined the microbial and metabolomic signatures which were associated with the antibiotics.We found that antibiotics treatment could inhibit intestinal inflammation by changing the intestinal bile acid metabolism,suggesting that the bile acid metabolism of intestinal microbiota could be selected as a treatment target for colitis.