Paeoniflorin modulates gut microbial production of indole-3-lactate and epithelial autophagy to alleviate colitis in mice

Background: Total glucosides of peony (TGP), extracted from the root and rhizome of Paeonia lactiflora Pall, has well-confirmed immunomodulatory efficacy in the clinic. However, the mechanism and active ingredients remain largely unclear. Hypothesis/Purpose: Our previous study revealed a low systemic exposure but predominant gut distribution of TGP components. The aim of this study was to investigate involvement of the gut microbiota in the immunoregulatory effects and identify the active component. Methods: Mice received 3% DSS to establish a model of colitis. The treatment group received TGP or single paeoniflorin (PF) or albiflorin (AF). Body weight, colon length, inflammatory and histological changes were assessed. Gut microbiota structure was profiled by 16s rRNA sequencing. Antibiotic treatment and fecal transplantation were used to explore the involvement of gut microbiota. Metabolomic assay of host and microbial metabolites in colon was performed. Results: TGP improved colonic injury and gut microbial dysbiosis in colitis mice, and PF was responsible for the protective effects. Fecal microbiota transfer from TGP-treated mice conferred resilience to colitis, while antibiotic treatment abrogated the protective effects. Both TGP and PF decreased colonic indole-3-lactate (ILA), a microbial tryptophan metabolite. ILA was further identified as an inhibitor of epithelial autophagy and ILA supplementation compromised the benefits of TGP. Conclusion: Our findings suggest that TGP acts in part through a gut microbiota-ILA-epithelial autophagy axis to alleviate colitis.