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Osteoclasts (OCs) are multinuclear giant cells responsible for bone resorption, and an excessive bone resorption by OCs plays an important role in osteoporosis. Commonly used drugs for the treatment of osteoporosis have severe side effects. As such, identification of alternative treatments is essential. Garcinol, a polyisoprenylated benzophenone extracted from the fruit of Garcinia indica, has shown a strong antitumor effect through the nuclear factor‐κB (NF‐κB) and mitogen‐associated protein kinases (MAPK) signaling pathways. However, the role of garcinol in the osteoclastogenesis is still unclear. Here, we demonstrated that garcinol can inhibit the receptor activator of NF‐κB ligand (RANKL)‐induced osteoclastogenesis, osteoclastogenesis‐related gene expression, the f‐actin ring, and resorption pit formation. In addition, garcinol abrogated RANKL‐induced osteoclastogenesis by attenuating the degradation of the MAPK, NF‐κB, and PI3K‐AKT signaling pathway as well as downstream factors c‐jun, c‐fos, and NFATC1. In vivo, suppression of osteoclastogenesis by garcinol was evidenced by marked inhibition of lipopolysaccharide‐induced bone resorption. In conclusion, our data demonstrated that garcinol inhibited the RANKL‐induced osteoclastogenesis by suppressing the MAPK, NF‐κB, and PI3K‐AKT signaling pathways and thus has potential as a novel therapeutic option for osteolytic bone diseases. Garcinol suppresses osteoclast (OCs) formation and function in vitro. Garcinol impairs the receptor activator for the nuclear factor‐κB ligand (RANKL)‐induced mitogen‐associated protein kinases (MAPK), nuclear factor‐κB (NF‐κB), and AKT signaling pathway. Garcinol suppresses osteolysis in vivo. Garcinol may be a new therapeutic option for osteolytic bone diseases [ABSTRACT FROM AUTHOR]

Excessive bone resorption by osteoclasts (OCs) plays an important role in lytic bone diseases, such as osteoporosis. Although the pharmacological treatment of osteoporosis has been extensively developed, alternative treatments are still needed. Deguelin, a rotenoid isolated from several plant species, is a strong antitumor agent; however, its effect on OCs remains unclear. To the best of our knowledge, this is the first study to report that deguelin inhibits the receptor activator of nuclear factor‐κB (NF‐κB) ligand (RANKL)‐induced osteoclastogenesis, messenger RNA expression of osteoclastic‐specific genes, and osteoclastic bone resorption, in primary bone marrow‐derived macrophages. At the molecular level, deguelin markedly blocked RANKL‐induced osteoclastogenesis by attenuating the phosphorylation of NF‐κB p65 and inhibiting p65 nuclear translocation. In addition, deguelin suppressed the downstream expression of nuclear factor of activated T‐cell cytoplasmic 1, which is a crucial transcription factor in OC differentiation. Consistent with the in vitro results, deguelin inhibited lipopolysaccharide‐induced bone resorption by suppressing osteoclastogenesis. Taken together, our findings reveal that deguelin has antiosteoclastic effects in vitro and in vivo and possesses potential as a new therapeutic option for osteolytic bone diseases. Deguelin suppresses osteoclast formation and function in vitro. Deguelin impairs the receptor activator of nuclear factor‐κB (NF‐κB) ligand (RANKL)‐induced NF‐κB signaling pathway. Deguelin suppresses osteolysis in vivo. Deguelin may be used for treating osteoclast‐related diseases. [ABSTRACT FROM AUTHOR]

Osteosarcoma is the most common malignant bone tumor that frequently affects adolescents. Osteosarcoma cells tend to proliferate and invade other tissues such as those of the lungs. Currently, neoadjuvant chemotherapy is the primary strategy to prevent tumor progression. However, its adverse effects result in poor long-term outcomes. Previous research has shown that galangin exhibits antitumor properties on several types of cancer cells; however its effect on osteosarcoma cells is yet unknown. The aims of this study were to evaluate the effects of galangin on the proliferation, apoptosis, migration, and invasion of osteosarcoma cells and to explore the underlying mechanisms. We found that the proliferation of MG63 and U20S osteosarcoma cells decreased significantly, while the apoptosis of MG63 cells accelerated significantly after exposure to galangin. In addition, the migration and invasion of MG63 cells were significantly inhibited by galangin. Moreover, phosphoinositide 3-kinase (PI3K) and Aktp-Thr308 expression levels were found to be significantly lower in galangin-treated MG63 cells than in the control cells, and the protein expression levels of their downstream regulators cyclin D1 and matrix metalloproteinase 2/9 were also downregulated in galangin-treated groups, while those of p27Kip1, caspase-3, and caspase-8 were upregulated. These findings suggest that galangin suppresses osteosarcoma cells by inhibiting their proliferation and invasion and accelerating their apoptosis, and the mechanism may be associated with the inhibition of PI3K and its downstream signaling pathway.