Viscum coloratum (Kom.) Nakai inhibits osteoclastogenesis in RANKL-induced osteoclast differentiation through the PI3K/AKT/mTOR pathway

Viscum coloratum (Kom.) Nakai has been widely used in traditional Chinese medicine and clinical treatment mainly for rheumatoid arthritis (RA). Our latest study demonstrated that it could alleviate clinical symptoms of RA and decrease osteoclastogenesis-related gene expression in the CIA mouse model. However, whether Viscum coloratum (Kom.) Nakai could inhibit osteoclastogenesis and its underlying mechanisms need to be further elucidated. In this study, we demonstrated that extract of Viscum coloratum (Kom.) Nakai (EVC) exhibited extraordinary activity against RANKL-induced osteoclast differentiation identified by inhibiting the formation of TRAP-positive multinucleated osteoclasts, TRAP activity, and decreasing osteoclast-specific genes NFATc1 expression. The network pharmacology-based method integrating Protein-Protein interaction analysis revealed that Viscum coloratum (Kom.) Nakai could inhibit osteoclastogenesis by regulating PI3K-AKT signaling pathways. Then, the predicted signaling pathway of EVC on osteoclast differentiation was determined by Western blot. Using TRAP activity and nitric oxide assays, Viscumneoside III, which was identified as the main ingredient from Viscum coloratum (Kom.) Nakai in our previous study, was confirmed as the optimally effective ingredient. These findings reveal that EVC executed the traditional effects on strengthening muscles and bones for the treatment of RA by inhibiting osteoclastogenesis via the regulated PI3K/AKT/mTOR signaling pathway, and Viscumneoside III was its effective ingredient.