A novel TGR5 agonist Sauchinone ameliorates IMQ induced murine psoriasis by regulating macrophage polarization

G-protein-coupled bile acid receptor (TGR5) is a member of G-protein-coupled receptor (GPCR) superfamily that participates in regulating macrophage polarization and resolving inflammatory diseases. Sauchinone is Saururus chinensis derived natural product with anti-inflammatory activity. Still, whether Sauchinone could regulate macrophage polarization and its direct target remain to explore. This study aims to demonstrate the direct target of Sauchinone, its influences on macrophage polarization and its pharmacological actions on imiquimod (IMQ) induced mouse psoriasis model. We detected the TGR5 agonistic activity of Sauchinone in mouse/human TGR5/ cAMP response elements (CRE)/HEK293 stable cell lines and verified its direct effect on mouse/human macrophages by Cellular thermal shift assay (CETSA) and by examining downstream CREB phosphorylation. Afterwards, we discovered the activity of Sauchinone on regulating macrophage M1/M2 polarization in Bone marrow-derived macrophages (BMDM) by detecting M1/M2 markers through Enzyme-linked immunosorbent assay (ELISA), Real-time polymerase chain reaction (RT-qPCR), Western blot and Fluorescence-activated cell sorting (FACS). We further utilized macrophages derived from Tgr5-/- mice or introduce TGR5 specific inhibitor, TGR5 si-RNA and PKA inhibitor to determine whether Sauchinone regulate macrophage polarization through TGR5. We then prepared Sauchinone cream formulation to disclose its pharmacological action in IMQ induced mouse psoriasis model and use FACS and immunofluorescence to verified its action on macrophage polarization in psoriatic skin. Moreover, we tested the protective actions of Sauchinone cream in IMQ treated Tgr5-/- mice to verify that Sauchinone alleviated psoriasis in TGR5 dependent manner. Sauchinone is a novel TGR5 agonist without human/mouse species selectivity. Sauchinone rectified macrophage M1 polarization through activating TGR5. Topical use of Sauchinone cream ameliorates IMQ induced psoriasis and regulates macrophage polarization in psoriatic skins. Sauchinone cream alleviated psoriasis in TGR5 dependent manner. Our work identified Sauchinone as a novel TGR5 agonist that could ameliorate IMQ induced murine psoriasis by regulating macrophage polarization.