Rosavin derived from Rhodiola alleviates colitis in mice through modulation of Th17 differentiation.

Background: Rosavin (RSV) is a naturally occurring compound isolated from Rhodiola species. While RSV has been reported with pharmacological activities of anti-oxidation, anti-inflammation, anti-stress and immunomodulation, its effect on colitis and the underlying mechanisms remain unclear.

Purpose: This study aims to investigate whether and how RSV alleviated colitis in mice.

Study design and methods: The protective effect of RSV (50, 100, 200 mg/kg, p.o.) was investigated in dextran sulfate sodium (DSS) mediated mouse models of acute and chronic colitis. Alterations in fecal microbiota were evaluated by 16S rRNA sequencing. Pseudo germ-free mice achieved by antibiotics treatment were applied to assess the RSV-mediated functional role of gut microbiota in colitis. RNA sequencing was performed to determine RSV-induced colonic response. Primary T cell culture was conducted to examine the effect of RSV on Th17 and Treg differentiation. Whole blood assay, dual luciferase reporter assay, and molecular docking methods were applied to investigate the mechanisms and targets of RSV in Th17 regulation.

Results: Oral RSV significantly relieved DSS-mediated acute and chronic colitis in mice, which recovered body weight loss, reduced disease activity index, alleviated colon injury, inhibited inflammation, suppressed the apoptosis of intestinal epithelia, and maintained intestinal barrier function. Moreover, RSV specifically regulated intestinal microbiota by recovering DSS-mediated microbial changes and elevating beneficial microbes such as Lactobacillus and Akkermansia. Antibiotics treatment experiment showed that the protective role of RSV was at least partially dependent on gut microbiota; however, in vitro incubation showed that RSV did not directly promote the growth of Lactobacillus and Akkermansia strains. Further analysis showed that RSV-mediated genetic alterations in colon were enriched in pathways related to lymphocyte regulation. Additionally, RSV regulated the balance of Th17/Treg in colitis mice. Importantly, RSV inhibited the differentiation of Th17 cell in vitro, suppressed the production of IL-17 by Th17 cells, and downregulated Rorc encoding RORγt and its downstream Il17. RSV significantly inhibited the RORγt transcription activity and bound to its ligand binding domain.

Conclusion: RSV alleviates murine colitis through regulating intestinal immunity. Notably, RSV is identified as a novel regulator of Th17 cells that inhibits RORγt-mediated Th17 differentiation. These findings potentiate the Rhodiola-derived natural chemicals as novel anti-colitis agents.