Ginsenoside Rg1 Ameliorated Colitis by Regulating the Homeostasis of M1/M2 Macrophage Polarization and Intestinal Flora

Background: Aberrant M1/M2 macrophage polarization and intestinal flora disruption are involved in the pathological processes associated with ulcerative colitis (UC). Ginsenoside Rg1 has good immunomodulatory and anti-inflammatory effects and is effective in treating UC of humans and animals. However, it is unclear how ginsenoside Rg1 regulate the homeostasis of M1/M2 macrophage polarization and intestinal flora.Methods: BALB/c mice were randomly divided into 4 groups: Control, DSS, DSS+Rg1, DSS+Y27632 groups. In this study, experiment colitis was induced in BALB/c mice using sodium dextran sulfate (DSS). Mice of DSS+Rg1, DSS+Y27632 groups were treated respectively with ginsenoside Rg1 and Rock inhibitor Y27632 for 14 consecutive days. On day 21, all mice were sacrificed. Histopathological analysis of the colon tissues was performed by Hematoxylin Eosin sinning. Cytokines (IL-6, IL-33, CCL-2, TNF-α, IL-4 and IL-10) were detected by Elisa. Flow cytometry was used to analyse macrophage activation and M1/M2 macrophage polarisation. Western blotting were applied to detect the levels of Macrophage polarization-associated protein (Arg-1, MIF-1, PIM-1, TLR2) and Nogo-B/RhoA signaling molecules (Rock1, RhoA and Nogo-B). The fecal microbial populations were analyzed using 16S gene sequencing. Results: After ginsenoside Rg1 and Y27632 treatment, the changes of body weight, colon length, colonic weight index and colonic mucosal injury of colitis mice were effectively improved, accompanied by less ulcer formation and inflammatory cell infiltration, lower levels of pro-inflammatory cytokines (IL-6, IL-33, CCL-2, TNF-α) and higher anti-inflammatory cytokines (IL-4 and IL-10). Importantly, the percentage of CD11b+F4/80+, CD11b+F4/80+Tim-1+, CD11b+F4/80+TLR4+, and CD11b+F4/80+iNOS+ cells and the expression levels of MIF-1 and PIM-1 proteins were down-regulated significantly after ginsenoside Rg1 and Y27632 treatment, and CD11b+F4/80+CD206+ and CD11b+F4/80+CD163+ cells and Arg-1 up-regulated significantly. Intestinal flora composition were effectively improved after administration of ginsenoside Rg1. The Nogo-B/RchoA signaling pathway were obviously inhibited after ginsenoside Rg1 and Y27632 treatment, and the levels of Rock1, RhoA and Nogo-B proteins were significantly reduced. Conclusions: Ginsenoside Rg1 has the protective effect on UC by inhibiting macrophage activation, restoring the balance of M1/M2 macrophage polarization, and improving intestinal flora composition, associated with inhibition of the Nogo-B/RhoA signaling pathway.