Nodosin alleviates cholestatic liver injury by activation of SIRT1/FXR signaling pathway and inhibition of hepatic inflammation.

Cholestatic liver injury is characterized by abnormal synthesis and excretion of bile acids, which often deteriorates into liver fibrosis, liver cancer and other diseases. Nodosin (Nod), a natural active compound derived from Chinese herb Isodon serra (Maxim.) Kudo, has been reported with valuable bioactivity for anti-cancer and anti-inflammation. However, the mechanism of Nod on cholestatic liver injury has not yet been explored. This research was to investigate the anti-cholestatic effectiveness of Nod and elucidate underlying mechanisms. CYP7A1-promoter-luciferase reporter assay was employed to screen the potential anti-cholestatic compounds. The anti-cholestatic as well as hepatoprotective effects of Nod were validated in AML12 and HepG2 cells, as well as bile duct ligation (BDL) and MDR2-/- mice. Cellular thermal shift assay (CETSA), drug affinity responsive target stability (DARTS), RNA-sequencing, co-immunoprecipitation, and immunofluorescence were employed to explore the targeting activation of SIRT1/FXR signaling. The results demonstrated that Nod significantly decreased CYP7A1 gene expression and increased FXR protein, but did not affect Fxr/FXR mRNA expression in vivo and in vitro. Nod alleviated cholestasis by maintaining bile acid homeostasis and inhibiting incipient fibrosis in two cholestatic models. Transcriptomics revealed that Nod activated FXR pathway, while restrained inflammation and fibrosis. Mechanistically, Nod stabilized SIRT1 and promoted the deacetylation and phosphorylation of FXR, which activated FXR downstream signaling. In addition, Nod curbed the NF-κB expression and inflammatory response. These findings demonstrate that Nod alleviates cholestasis by activating SIRT1/FXR signaling and down-regulating the NF-κB signaling. Therefore, Nod might be a hopeful therapeutic medicine for cholestasis.