RESUMEN
BACKGROUND Osteomyelitis is one of the refractory diseases encountered in orthopedics, while Staphylococcus aureus (S. aureus) is the most common causative organism in osteomyelitis. However, the precise mechanisms underlying the bone loss caused by S. aureus infection have not been well defined. Here, we investigated the effect of S. aureus on osteoclast differentiation and the probable molecular mechanism. MATERIAL AND METHODS RAW 264.7 cells were treated for 5 days with live S. aureus, inactivated S. aureus, and S. aureus filtrate. Then, the formation of osteoclast-like cells and resorption pits was observed, and the expression of osteoclast-specific genes (TRAP, MMP-9, cathepsin K, CTR and Atp6v0d2) was detected by real-time PCR. Moreover, key proteins in the signaling pathway associated with osteoclast differentiation were detected with Western blot. RESULTS The data showed that live S. aureus, inactivated S. aureus, and S. aureus filtrate induced osteoclast formation, promoted bone resorption, and increased the expression of osteoclast-specific genes in a dose-dependent manner in the absence RANKL. In addition, we found that the S. aureus-induced osteoclastogenesis was related to the degradation of IκB-a, phosphorylation of NF-κB p65, and increased expression of NFATc1. Thus, we used JSH-23 to inhibit NF-κB transcriptional activity. The effect of the S. aureus-induced osteoclastogenesis and the expression of osteoclast-specific genes and NFATc1 were inhibited, which indicated that the NF-κB signaling pathway plays a role in S. aureus-induced osteoclastogenesis. CONCLUSIONS This study demonstrated that S. aureus induces osteoclastogenesis through its cell wall compound and secretion of small soluble molecules, and the NF-κB signaling pathway plays a role in this process.
Asunto(s)
FN-kappa B/fisiología , Osteogénesis/efectos de los fármacos , Staphylococcus aureus/patogenicidad , Animales , Resorción Ósea/metabolismo , Resorción Ósea/microbiología , Diferenciación Celular/fisiología , Regulación de la Expresión Génica/genética , Macrófagos/metabolismo , Ratones , Proteínas Quinasas Activadas por Mitógenos/metabolismo , FN-kappa B/inmunología , FN-kappa B/metabolismo , Subunidad p52 de NF-kappa B/fisiología , Factores de Transcripción NFATC , Osteoclastos/metabolismo , Osteoclastos/microbiología , Osteogénesis/inmunología , Osteogénesis/fisiología , Osteomielitis/microbiología , Células RAW 264.7 , Transducción de Señal/efectos de los fármacos , Staphylococcus aureus/metabolismo , Factor de Transcripción ReIA/metabolismoRESUMEN
Staphylococcus aureus (S. aureus) is the most common organism causing osteomyelitis, and Staphylococcus aureus protein A (SpA) is an important virulence factor anchored in its cell wall. However, the precise mechanisms underlying the bone loss caused by SpA have not been well understood. The present study aimed to investigate the effect of SpA on osteoclast differentiation, and the probable mechanism was investigated. Raw264.7 cells were treated with SpA in the absence or presence of receptoractivated (NF)κB ligand for 5 days, and morphological and biochemical assays were used to assess osteoclastogenesis and explore the underlying mechanisms. Data demonstrated that SpA induced osteoclast differentiation and promoted bone resorption in a dosedependent manner in the absence or presence of RANKL. In addition, the expression of osteoclastspecific genes, such as the tartrate resistant acid phosphatase, matrix metalloproteinase9, cathepsin K, calcitonin receptors and d2 isoform of the vacuolar ATPase Vo domain, were enhanced by SpA. Furthermore, the SpAinduced osteoclast differentiation was associated with the degradation of inhibitor of κBα, phosphorylation of NFκB p65 and increased expression of nuclear factor of activated Tcells. However, by treatment with JSH23, an NFκB inhibitor, the formation of osteoclastlike cells and resorption pits was significantly reduced, and the expression of osteoclastspecific genes was also inhibited. Collectively, in the present study SpA induced osteoclast differentiation, promoted bone resorption, and the NFκB signaling pathway was involved in this process.