Corydalis decumbens and tetrahydropalmatrubin inhibit macrophages inflammation to relieve rheumatoid arthritis by targeting Fosl2

Ethnopharmacological relevance: Corydalis decumbens (Thunb.) (CD) is a traditional Chinese medicine and as a single herb or formula has been used to treat RA for decades. Rheumatoid arthritis (RA) is a persistent, systemic autoimmune inflammatory disease. However, the anti-inflammatory target, effective constituents and mechanism was unclear. Aim of the study: The purpose of this study was to identify anti-RA and anti-inflammatory targets of CD, elucidate effective constituents and molecular pharmacological mechanism. Materials and methods: Anti-RA and anti-inflammatory effect of CD were evaluated on CIA-rats and in LPSinduced RAW264.7 cells respectively. The anti-inflammatory target of CD was identified using thermal proteome profiling (TPP). The recombinant Fosl2 protein was expressed and purified and the target-based effective constituents was screened with bio-layer interferometry (BLI) analysis. Combining photoaffinity probe, LC-MS/ MS analysis, docking and point mutation, the binding site was confirmed between Fosl2 and THP. Furtherly, immunofluorescence (IF), co-immunoprecipitation (co-IP) were used to research the pharmacological mechanism of THP and the THP-influenced downstream pathways were elucidated by transcriptomics analysis. Results: CD had therapeutic effect on CIA-rats and a significant anti-inflammation on macrophages. Fosl2 was identified as a target of CD and we elucidated the target-based effective constituents was protoberberine-type alkaloids. THP can inhibit inflammation and transcription of AP-1 via targeting Fosl2 on LPS-induced RAW264.7 cells. For mechanism, THP promoted Fosl2 nuclear translocating and interacting with c-Jun. Conclusions: These findings firstly elucidated the target and effective constituents of CD treating RA, and found that "undruggable target" Fosl2 can be used as therapeutic targets for RA. Meanwhile, our research suggested that THP has a significant potential for the treatment of RA.