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. Although RSV has been reported with pharmacological activities of anti-oxidation, anti-inflammation, anti-stress and immunomodulation, its effect on colitis relieving and the underlying mechanism remains 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 on dextran sulfate sodium (DSS) mediated mouse models of acute and chronic colitis. Alterations in fecal microbiota was evaluated by 16S rRNA sequencing. Pseudo germ-free mice by antibiotics treatment was applied to evaluate the RSV-mediated functional role of gut microbiota on colitis. RNA sequencing was performed to determine RSV-induced colonic response. Primary T cell culture was conducted to see the effect of RSV on Th17 and Treg differentiation. Whole blood assay, dual luciferase reporter assay and molecular docking method were applied to investigate the mechanism and target 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 of 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 alteration in colon was enriched in lymphocyte regulation. Moreover, RSV regulated the balance of Th17/Treg in colitis mice. Importantly, RSV inhibited the differentiation of Th17 cell in vitro, suppressed the generation of IL-17 by Th17 cells, and downregulated Rorc encoding RORγt and the downstream Il17. RSV significantly inhibited the RORγt transcription activity, and bound to the RORγt ligand binding domain. Conclusion RSV alleviates murine colitis through regulating intestinal immunity. Notably, RSV is identified as a novel Th17 regulator that inhibits RORγt-mediated Th17 differentiation. The results potentiate the Rhodiola-derived chemical as novel anti-colitis agents.