RESUMO
Proteasome inhibitors represent a promising therapy for the treatment of relapsed and/or refractory multiple myeloma, a disease that is concomitant with osteolysis and enhanced osteoclast formation. While blockade of the proteosome pathway has been recently shown to influence osteoclast formation and function, the precise molecular cascade underlying these effects is presently unclear. Here, we provide evidence that proteasome inhibitors directly impair osteoclast formation and function via the disruption of key RANK-mediated signaling cascades. Disruption of the proteosome pathway using selective inhibitors (MG-132, MG-115, and epoxomicin) resulted in the accumulation of p62 and CYLD, and altered the subcellular targeting and distribution of p62 and TRAF6 in osteoclast-like cells. Proteosome inhibition also blocked RANKL-induced NF-kappaB activation, IkappaBalpha degradation and nuclear translocation of p65. The disruption in RANK-signaling correlated dose-dependently with an impairment in osteoclastogenesis, with relative potency epoxomicin > MG-132 > MG-115 based on equimolar concentrations. In addition, these inhibitors were found to impact osteoclastic microtubule organization and attenuate bone resorption. Based on these data we propose that deregulation of key RANK-mediated signaling cascades (p62, TRAF6, CYLD, and IkappaBalpha) underscores proteasome-mediated inhibition of osteolytic bone conditions.
Assuntos
Cisteína Endopeptidases/metabolismo , Proteínas I-kappa B/metabolismo , NF-kappa B/metabolismo , Osteoclastos/fisiologia , Inibidores de Proteassoma , Ligante RANK/metabolismo , Fator 6 Associado a Receptor de TNF/metabolismo , Fatores de Transcrição/metabolismo , Actinas/metabolismo , Animais , Reabsorção Óssea , Linhagem Celular , Cisteína , Cisteína Endopeptidases/genética , Inibidores de Cisteína Proteinase/farmacologia , Enzima Desubiquitinante CYLD , Eritropoetina/metabolismo , Humanos , Proteínas I-kappa B/genética , Leupeptinas/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Microtúbulos/metabolismo , Inibidor de NF-kappaB alfa , NF-kappa B/genética , Oligopeptídeos/farmacologia , Osteoclastos/citologia , Osteoclastos/efeitos dos fármacos , Complexo de Endopeptidases do Proteassoma/metabolismo , Ligante RANK/genética , Transdução de Sinais/fisiologia , Sinaptotagmina I/genética , Sinaptotagmina I/metabolismo , Fator 6 Associado a Receptor de TNF/genética , Fator de Transcrição TFIIH , Fatores de Transcrição/genéticaRESUMO
BACKGROUND: In Singapore, an outbreak of fungal keratitis caused by members of the Fusarium solani species complex (FSSC) was identified in March 2005 to May 2006 involving 66 patients. Epidemiological investigations have indicated that improper contact lens wear and the use of specific contact lens solutions were risk factors. METHODS: We assessed the genetic diversity of the isolates using AFLP, Rep-PCR, and ERIC-PCR and compared the usefulness of these typing schemes to characterize the isolates. RESULTS: AFLP was the most discriminative typing scheme and appears to group FSSC from eye infections and from other infections differently. CONCLUSION: There was a high genomic heterogeneity among the isolates confirming that this was not a point source outbreak.