Microbial-Derived Daidzin (Eco-3) Suppresses RANKL-Induced Osteoclastogenesis by Targeting the TBK1-NFATc1 Signaling Axis.

Eco-3, a microbial-derived daidzin, has been reported to possess diverse biological activities; however, its effects on osteoclast differentiation and the underlying molecular mechanisms remain unclear. In the present study, we investigated the effects of Eco-3 on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis and explored the signaling pathways involved using RAW264.7 macrophages. Eco-3 suppressed RANKL-induced osteoclast formation at the concentrations tested without significantly affecting cell viability. Eco-3 also altered F-actin organization and reduced the expression of key osteoclastogenic markers, including tartrate-resistant acid phosphatase (TRAP), nuclear factor of activated T cells c1 (NFATc1), c-Fos, and cathepsin K (CTSK). In particular, Eco-3 attenuated NFATc1 expression during the early stage of osteoclast differentiation, suggesting interference with the transcriptional program associated with osteoclastogenesis. Furthermore, RANKL stimulation progressively increased TANK-binding kinase 1 (TBK1) phosphorylation during osteoclast differentiation, whereas Eco-3 attenuated this activation. Genetic silencing of TBK1 suppressed osteoclast formation, while pharmacological inhibition of TBK1 reduced TBK1 phosphorylation, osteoclastogenic gene expression, and osteoclast formation. Collectively, these findings suggest that Eco-3 suppresses RANKL-induced osteoclastogenesis, at least in part, through modulation of the TBK1-NFATc1 signaling axis in RAW264.7 macrophages. Our findings identify TBK1 as a potential regulatory component of osteoclast differentiation and suggest that Eco-3 warrants further investigation as a potential bioactive candidate for osteoclast-related bone disorders.