RÉSUMÉ
Epidemiological and preclinical studies have indicated a factual association between gut microbiota dysbiosis and high incidence of colitis. Dietary polysaccharides can specifically shift the composition of gut microbiome response to colitis. Here we validated the preventive role of polysaccharides from Pericarpium Citri Reticulatae 'Chachiensis' (PCRCP), a well-known traditional Chinese medicine, in colitis induced by dextrose sodium sulfate (DSS) in both rats and mice. We found that treatment with PCRCP not only significantly reduced DSS-induced colitis via down-regulating colonic inflammatory signaling pathways including PI3K-Akt, NLRs and NF-κB, but also enhanced colonic barrier integrity in rats. These protective activities of PCRCP against DSS-induced injuries in rats were in part due to the modulation of the gut microbiota revealed by both broad-spectrum antibiotic (ABX)-deleted bacterial and non-oral treatments. Furthermore, the improvement of PCRCP on colitis was impaired by intestinal neomycin-sensitive bacteria in DSS-exposed mice. Specifically, in vivo and in vitro treatment with PCRCP led to a highly sensible enrichment in the gut commensal Parabacteroides goldsteinii. Administration of Parabacteroides goldsteinii significantly alleviated typical symptoms of colitis and suppressed the activation of PI3K-Akt-involved inflammatory response in DSS-exposed mice. The anti-colitic effects of Parabacteroides goldsteinii were abolished after the activation of PI3K-Akt signaling pathway by lipopolysaccharide treatment in mice exposed to DSS. This study provides new insights into an anti-colitic mechanism driven by PCRCP and highlights the potential prebiotic of Parabacteroides goldsteinii for the prevention of ulcerative colitis.