RESUMEN
BACKGROUND AND PURPOSE: Osteoclasts play a pivotal role in diseases such as osteoporosis, rheumatoid arthritis and tumour bone metastasis. Thus, searching for natural compounds that may suppress osteoclast formation and/or function is promising for the treatment of osteoclast-related diseases. Here, we examined changes in osteoclastogenesis and LPS-induced osteolysis in response to andrographolide (AP), a diterpenoid lactone isolated from the traditional Chinese and Indian medicinal plant Andrographis paniculata. EXPERIMENTAL APPROACH: Effects of AP on osteoclast differentiation and bone resorption were measured in vitro. Western blots and RT-PCR techniques were used to examine the underlying molecular mechanisms. The bone protective activity of APâ in vivo was assessed in a mouse model of osteolysis. KEY RESULTS: AP concentration-dependently suppressed RANKL-mediated osteoclast differentiation and bone resorption in vitro and reduced the expression of osteoclast-specific markers, including tartrate-resistant acid phosphatase, calcitonin receptors and cathepsin K. Further molecular analysis revealed that AP impaired RANKL-induced NF-κB signalling by inhibiting the phosphorylation of TGF-ß-activated kinase 1, suppressing the phosphorylation and degradation of IκBα, and subsequently preventing the nuclear translocation of the NF-κB p65 subunit. AP also inhibited the ERK/MAPK signalling pathway without affecting p38 or JNK signalling. CONCLUSIONS AND IMPLICATIONS: AP suppressed RANKL-induced osteoclastogenesis through attenuating NF-κB and ERK/MAPK signalling pathways in vitro, thus preventing bone loss in vivo. These data indicated that AP is a promising natural compound for the treatment of osteoclast-related bone diseases.
Asunto(s)
Conservadores de la Densidad Ósea/uso terapéutico , Modelos Animales de Enfermedad , Diterpenos/uso terapéutico , Osteoclastos/efectos de los fármacos , Osteogénesis/efectos de los fármacos , Osteólisis/prevención & control , Ligando RANK/antagonistas & inhibidores , Animales , Antiinflamatorios no Esteroideos/farmacología , Antiinflamatorios no Esteroideos/uso terapéutico , Biomarcadores/metabolismo , Densidad Ósea/efectos de los fármacos , Conservadores de la Densidad Ósea/farmacología , Células de la Médula Ósea/citología , Huesos/efectos de los fármacos , Huesos/inmunología , Huesos/patología , Células Cultivadas , Diterpenos/farmacología , Regulación hacia Abajo/efectos de los fármacos , Femenino , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Macrófagos/citología , Ratones , Ratones Endogámicos C57BL , FN-kappa B/antagonistas & inhibidores , FN-kappa B/metabolismo , Osteoclastos/inmunología , Osteoclastos/metabolismo , Osteoclastos/patología , Osteólisis/inducido químicamente , Osteólisis/inmunología , Osteólisis/patología , Ligando RANK/genética , Ligando RANK/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismoRESUMEN
The vacuolar-type H(+)-ATPase (V-ATPase) proton pump is a macromolecular complex composed of at least 14 subunits organized into two functional domains, V(1) and V(0). The complex is located on the ruffled border plasma membrane of bone-resorbing osteoclasts, mediating extracellular acidification for bone demineralization during bone resorption. Genetic studies from mice to man implicate a critical role for V-ATPase subunits in osteoclast-related diseases including osteopetrosis and osteoporosis. Thus, the V-ATPase complex is a potential molecular target for the development of novel anti-resorptive agents useful for the treatment of osteolytic diseases. Here, we review the current structure and function of V-ATPase subunits, emphasizing their exquisite roles in osteoclastic function. In addition, we compare several distinct classes of V-ATPase inhibitors with specific inhibitory effects on osteoclasts. Understanding the structure-function relationship of the osteoclast V-ATPase may lead to the development of osteoclast-specific V-ATPase inhibitors that may serve as alternative therapies for the treatment of osteolytic diseases.