AIM: To explore the preventive and therapeutic effects of Faecalibacterium prausnitzii(F. prausnitzii) supernatant on dextran sulfate sodium(DSS) induced colitis in mice.METHODS: Forty C57BL/6J male mice were randomlydivided into four groups: control group, model group, treatment group, and prevention group. Mice were weighed daily. On day 10, the colon length was measured, the colorectal histopathologic damage score(HDS) was assessed, and plasma interleukin(IL)-17 A, IL-6, and IL-4 levels were detected by enzyme-linked immunosorbent assay. The expression of transcription factor retinoic acid-related orphan receptor-γt(RORγt) and IL-17 A in colon inflammatory mucosa tissue were determined by immunohistochemical assay, and the expression levels of RORγt m RNA, IL-17 A m RNA, and IL-6 m RNA were detected by real-time quantitative polymerase chain reaction(PCR). The proportion of Th17 in mononuclear cells in spleen was assayed by fluorescence activated cell sorter. RESULTS: When compared with the model group, the colon length(P < 0.05) and body weight(P < 0.01) in the treatment and prevention groups were significantly increased, and the colon HDS was decreased(P < 0.05 and P < 0.01). There was no statistical difference between the treatment group and prevention group. After treatment with F. prausnitzii supernatant, the plasma levels of IL-17 A and IL-6(P < 0.05), the protein and m RNA expression of IL-17 A and RORγt, and the Th17 cell ratio of spleen cells(P < 0.01) were significantly decreased compared to the model group. Plasma IL-4 level in the prevention group was significantly higher than that in the model group(P < 0.05), but there was no significant difference between these two groups in the expression of IL-6 in both the plasma and colon mucosa tissues.CONCLUSION: F. prausnitzii supernatant exerts protective and therapeutic effects on DSS-induced colitis in mice, probably via inhibition of Th17 differentiation and IL- 17A secretion in the plasma and colon mucosa tissues. It can also improve colitis in mice by downregulating IL-6 and prevent colitis by upregulating IL-4. AIM: To explore the preventive and therapeutic effects of Faecalibacterium prausnitzii (F. prausnitzii) supernatant on dextran sulfate sodium (DSS) induced colitis in mice. METHODS: Forty C57BL / 6J male mice were differentiated into four groups: control group, model group, Treatment group, and prevention group. Mice were weighed daily. On day 10, the colon length was measured, the colorectal histopathologic damage score (HDS) was assessed, and plasma interleukin (IL) -17A, IL- 6, and IL- 4 expression levels of transcription factor retinoic acid-related orphan receptor-γt (RORγt) and IL-17 A in colon inflammatory mucosa tissue were determined by immunohistochemical assay, and the expression levels of RORγt m RNA, IL-17 A m RNA, and IL-6 m RNA were detected by real-time quantitative polymerase chain reaction (PCR). The proportion of Th17 in mononuclear cells in spleen was assayed by fluorescence activated cell sorter. RESULTS: When compar (P <0.05) and body weight (P <0.01) in the treatment and prevention groups were significantly increased, and the colon HDS was decreased (P <0.05 and P <0.01). There was After treatment with F. prausnitzii supernatant, the plasma levels of IL-17 A and IL-6 (P <0.05), the protein and m RNA expression of IL-17 A and RORγt , and the Th17 cell ratio of spleen cells (P <0.01) were significantly decreased compared to the model group. Plasma IL-4 level in the prevention group was significantly higher than that in the model group (P <0.05), but there was no significant difference between these two groups in the expression of IL-6 in both plasma and colon mucosa tissues. CONCLUSION: F. prausnitzii supernatant exerts protective and therapeutic effects on DSS-induced colitis in mice, probably via inhibition of Th17 differentiation and IL - 17A secretion in the plasma and colon mucosa tissues. It can also improve colitis in mice by downregulating IL-6 and prevent colitis by upregulating IL-4.