Vaccaria hypaphorine impairs RANKL-induced osteoclastogenesis by inhibition of ERK, p38, JNK and NF-κB pathway and prevents inflammatory bone loss in mice

Osteoclasts are sole bone-resorbing cells which exert a profound effect on skeletal metabolism. The search for medicines that affect the differentiation and function of osteoclasts is crucial in developing therapies for osteoclast-based diseases. Vaccaria hypaphorine, the main active compound of the traditionally used Chinese herb Vaccaria segetalis, has anti-inflammatory activity. The present study demonstrated for the first time that vaccaria hypaphorine could significantly inhibit the receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclastic differentiation in vitro and alleviate lipopolysaccharide (LPS)-induced bone loss in vivo. Further study showed that vaccaria hypaphorine decreased osteoclastogenesis in a dose-dependent manner. Furthermore, vaccaria hypaphorine was confirmed to inhibit osteoclasts differentiation at early stage but not at later stage. Pit formation assay and F-actin ring staining showed that vaccaria hypaphorine inhibited the bone-resorbing activity of osteoclasts. Mechanistically, vaccaria hypaphorine impaired RANKL-induced osteoclastogenesis through reduction of extracellular signal-regulated kinases (ERK), p38, c-Jun N-terminal kinase (JNK) and NF-κB p65 phosphorylation. Taken together, our results provided evidences that vaccaria hypaphorine might be considered as potential therapeutic agent for treating osteoclast-based bone loss.