Inhibition of IKK activation, through sequestering NEMO, blocks PMMA-induced osteoclastogenesis and calvarial inflammatory osteolysis

Osteoclasts, the primary bone-resorbing cells, play a crucial role in periprosthetic bone loss in response to implant-derived wear debris. Differentiation and activation of osteoclasts at the implant-bone interface are fueled by elevated levels of locally secreted inflammatory cytokines that heighten the osteolytic response. Among these cytokines are members of the TNF superfamily, including TNF and RANKL, which primarily act through activation of the transcription factor NF-kappa B. Activation of NF-kappa B is required for osteoclast formation, and its inhibition hampers osteoclastogenesis and bone loss. Activation of NF-kappa B is permitted following its dissociation from the inhibitory protein I kappa B alpha, an event subsequent to phosphorylation of the latter protein by the upstream I kappa B alpha kinase (IKK) complex. Our recent findings show that attenuating IKK complex assembly, by using a short peptide termed NEMO-binding domain (NBD) peptide, that blocks binding of IKK2 and IKK1 to IKK gamma/NEMO, inhibits NF-kappa B activation, and arrests RANKL-induced osteoclastogenesis. In this study, we examined if NBD is capable of blocking inflammatory osteolysis by PMMA particles. Our findings indicate that NBD peptide inhibits PMMA-induced IKK2 and NF-kappa B activation. More importantly, this peptide potently arrests PMMA-stimulated osteoclastogenesis and alleviates PMMA-induced inflammatory and osteolytic responses in mice. Thus, NBD peptide is considered as a promising modality to regulate inflammatory osteolysis. (c) 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.