Ethyl acetate extract of the Musa nana flower inhibits osteoclastogenesis and suppresses NF-κB and MAPK pathways

Tereticornate A suppresses RANKL-induced osteoclastogenesis via the downregulation of c-Src and TRAF6 and the inhibition of RANK signaling pathways

Excessive osteoclast differentiation and activation are closely associated with the development and progression of osteoporosis. Natural plant-derived compounds that can inhibit osteoclastogenesis are an efficient strategy for the prevention and treatment of osteoporosis. Tereticornate A (TA) is a natural terpene ester compound extracted from the leaves and branches of Eucalyptus gracilis, with antiviral, antibacterial, and anti-inflammatory activities. However, the effect of TA on osteoclastogenesis and the underlying molecular mechanism remain unclear. Based on the key role of the NF-κB pathway in the regulation of osteoclastogenesis and the observation that TA exhibits an anti-inflammatory effect by inhibiting NF-κB activity, we speculated that TA could exert anti-osteoclastogenesis activity. Herein, TA could inhibit the RANKL-induced osteoclast differentiation and formation of F-actin rings in RAW 264.7 cells. Mechanistically, TA downregulated the expression of c-Src and TRAF6, and also suppressed the RANKL-stimulated canonical RANK signaling pathways, including AKT, MAPK (p38, JNK, and ERK), and NF-κB; ultimately, downregulating the expression of NFATc1 and c-Fos, the key transcriptional factors required for the expression of genes (e.g., TRAP, cathepsin K, β-Integrin, MMP-9, ATP6V0D2, and DC-STAMP) that govern osteoclastogenesis. Our findings demonstrated that TA could effectively inhibit RANKL-induced osteoclastogenesis via the downregulation of c-Src and TRAF6 and the inhibition of RANK signaling pathways. Thus, TA could serve as a novel osteoclastogenesis inhibitor and might have beneficial effects on bone health.

Niloticin inhibits osteoclastogenesis by blocking RANKL-RANK interaction and suppressing the AKT, MAPK, and NF-κB signaling pathways

Dysregulation of osteoclasts or excessive osteoclastogenesis significantly -contributes to the occurrence and development of osteolytic diseases, including osteoporosis, inflammatory bone erosion, and tumor-induced osteolysis. The protein-protein interaction between the receptor activator of nuclear factor (NF)-κB (RANK) and its ligand (RANKL) mediates the differentiation and activation of osteoclasts, making it a key therapeutic target for osteoclastogenesis inhibition. However, very few natural compounds exerting anti-osteoclastogenesis activity by inhibiting the RANKL-RANK interaction have been found. Niloticin is a natural tetracyclic triterpenoid compound with anti-viral, antioxidative, and mosquitocidal activities. However, its role in osteoclastogenesis remains unknown. The present study found that niloticin directly binds to RANK with an equilibrium dissociation constant of 5.8 μM, blocking RANKL-RANK interaction, thereby inhibiting RANKL-induced AKT, MAPK (p38, JNK, and ERK1/2), and NF-κB (IKKα/β, IκBα, and p65) pathways activation, and reducing the expression of key osteoclast differentiation-related regulatory factors (NFATc1, c-Fos, TRAP, c-Src, β3-Integrin, and cathepsin K) in osteoclast precursors, ultimately negatively regulating osteoclastogenesis. These findings suggest that niloticin could serve as a novel osteoclastogenesis inhibitor and might have beneficial effects on bone health.

Inhibitory effects of Atlantic cod (Gadus morhua) peptides on RANKL-induced osteoclastogenesis in vitro and osteoporosis in ovariectomized mice

Atlantic cod (Gadus morhua) is one of the most important fishes in the world with high nutritional value and economic value. However, the impact and underlying mechanism of the G....