Water solution of onion crude powder inhibits RANKL-induced osteoclastogenesis through ERK, p38 and NF-kappa B pathways

Onion powder has been reported to decrease the ovariectomy-induced bone resorption of rats. However, the molecular mechanism of onion powder on the bone cells has not been reported. Here, we report that water solution of onion crude powder decreases the osteoclastogenesis from co-cultures of bone marrow stromal cells and macrophage cells. Additionally, water solution of onion crude powder inhibits the RANKL-induced ERK, p38 and NF-kappa B activation in macrophages. In summary, our data showed that onion powder may benefit bone through an anti-resorption effect on the osteoclasts. Introduction A nutritional approach is important for both prevention and treatment of osteoporosis. Onion has been reported to decrease the ovariectomy-induced bone resorption. However, the functional effects of onion on the cultured osteoclasts and osteoblasts remain largely unknown. Here, we found that water solution of onion crude powder markedly inhibited the receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclastogenesis through ERK, p38 and NF-kappa B pathways. Other studies were also designed to investigate the potential signaling pathways involved in onion-induced decrease in osteoclastogenesis. Methods The osteoclastogenesis was examined using the TRAP staining method. The MAPKs and NF-kappa B pathways were measured using Western blot analysis. A transfection protocol was used to examine NF-kappa B activity. Results Water solution of onion crude powder inhibited the RANKL plus M-CSF-induced osteoclastic differentiation from either bone marrow stromal cells or from RAW264.7 macrophage cells. Treatment of RAW264.7 macrophages with RANKL could induce the activation of ERK, p38 and NF-kappa B that was inhibited by water solution of onion crude powder. On the other hand, it did not affect the cell proliferation and differentiation of human cultured osteoblasts. Conclusions Our data suggest that water solution of onion crude powder inhibits osteoclastogenesis from co-cultures of bone marrow stromal cells and macrophage cells via attenuation of RANKL-induced ERK, p38 and NF-kappa B activation.