Polyphyllin VII attenuated RANKL-induced osteoclast differentiation via inhibiting of TRAF6/c-Src/PI3K pathway and ROS production

Osteoporosis is a worldwide severe bone disease. This study aimed to evaluate the effect of polyphyllin VII on the genesis of osteoclasts from bone marrow macrophages (BMMs) and its potentiality as a therapeutic drug for osteoporosis.

BMMs were induced to differentiate into osteoclasts by RANKL and M-CSF. The cells were then treated with various concentrations of polyphyllin VII. Intracellular reactive oxygen species (ROS) measurement assay, resorption pit formation assay, tartrate-resistant acid phosphatase (TRAP) staining and TRAP activity assessment, cell viability assay, active GTPase pull-down assay, immunofluorescent staining, immunoblotting, and RT-PCR were performed.

RANKL + M-CSF significantly increased TRAP activity, number of osteoclasts, number and area of lacunae, intracellular content of ROS, protein levels of Nox1, TRAF6, c-Src and p-PI3K, as well as the content of activated GTP-Rac1, which were significantly blocked by polyphyllin VII in a concentration-dependent manner.

These findings suggested that polyphyllin VII inhibited differentiation of BMMs into osteoclasts through suppressing ROS synthesis, which was modulated by TRAF6-cSrc-PI3k signal transduction pathway including GTP-Rac1 and Nox1. Polyphyllin VII could be a therapeutic drug for osteoporosis.