The molecular mechanism of osteoclastogenesis: ODF/RANKL-dependent and independent pathways

Egg-Derived Tripeptide IRW Attenuates LPS-Induced Osteoclastogenesis in RAW 264.7 Macrophages via Inhibition of Inflammatory Responses and NF-κB/MAPK Activation

Excessive bone resorption, because of increased osteoclastic activity, is a key underlying cause of osteolytic disorders. Lipopolysaccharide (LPS) is a potent factor to stimulate osteoclastic activity by inducing inflammatory stress. An egg-derived tripeptide IRW (Ile-Arg-Trp) was previously shown to exert anti-inflammatory activity. The overall objective of this study was to investigate the effect of IRW on inhibiting LPS-induced osteoclastogenesis and inflammatory bone resorption in the mouse macrophage RAW 264.7 cells. IRW (25 and 50 μM) significantly inhibited the LPS-induced osteoclast formation and resorptive activity. Meanwhile, IRW significantly suppressed the LPS-induced expression of TNF-α, IL-6, iNOS, COXII, NO, and PGE2. Furthermore, IRW regulated a group of osteoclastogenesis-associated factors (TRAF6, c-Fos, NFATc1, and cathepsin K) because of the inhibition of LPS-activated NF-κB and MAPK pathways. In conclusion, our study suggested the ability of IRW to prevent LPS-induced inflammatory bone resorption activity via the inhibition of inflammatory responses and the activation of osteoclastogenesis-associated signaling pathways.

Neohesperidin suppresses osteoclast differentiation, bone resorption and ovariectomised-induced osteoporosis in mice

Excessive bone resorption by osteoclasts plays an important role in osteoporosis. Bone loss occurs in ovariectomised (OVX) mice in a similar manner to that in humans, so this model is suitable for evaluating potential new therapies for osteoporosis. Neohesperidin (NE) is a flavonoid compound isolated from citrus fruits. Its role in bone metabolism is unknown. In this study we found that neohesperidin inhibits osteoclast differentiation, bone resorption and the expression of osteoclast marker genes, tartrate-resistant acid phosphatase and cathepsin K. In addition, neohesperidin inhibited receptor activator of NF-κB ligand (RANKL)-induced activation of NF-κB, and the degradation of inhibitor of kappa B-alpha (IκBα). Furthermore, neohesperidin inhibited RANKL induction of nuclear factor of activated T-cells (NFAT) and calcium oscillations. In vivo treatment of ovariectomised mice with neohesperidin protected against bone loss in mice. The results suggest neohesperidin has anti-osteoclastic effects in vitro and in vivo and possesses therapeutic potential as a natural anti-catabolic treatment in osteoporosis.