Discovery of sinomenine derivatives inhibiting macrophage polarization against rheumatoid arthritis through selectively targeting heme oxygenase-1.

Sinomenine (SIN) is clinically available for the treatment of rheumatoid arthritis (RA), but the side effects of SIN limit clinical applications. In this study, we designed and synthesized SIN derivatives that incorporated a novel ring fragment and assessed bioactivities in macrophages. Among the compounds, SIN 14 exhibited significantly more potent inhibitory effects on inflammatory mediator production compared to the other derivatives, which induced macrophage polarization from M1 to M2 phenotype. Through thermal proteome profiling (TPP), we demonstrated that SIN 14 specifically targeted heme oxygenase 1 (HO-1) and induced the activation through an allosteric mechanism. In particular, SIN 14 exhibited the distal helix and the surface-exposed loop (CD-loop), which facilitates substrate binding and product release, ultimately leading to the liberation of anti-inflammatory metabolites. In vivo, SIN 14 could inhibit RA-related inflammatory edema in collagen-induced arthritis (CIA) mice. Single-cell RNA transcriptome sequencing was employed to elucidate the cellular and transcriptional landscape in CIA mice after SIN 14 treatment. These results indicated that SIN 14 reduced the M1/M2 polarization ratio of macrophages, thereby alleviating the severity of inflammation in synovial tissues. Taken together, our study identifies SIN 14 as a promising candidate for anti-RA drug discovery. Furthermore, we emphasize HO-1 as a distinctive cellular target for RA therapy.