NF‐kB signaling blockade abolishes implant particle‐induced osteoclastogenesis

<jats:title>Abstract</jats:title><jats:p>In this study we investigated the effect of NF‐kB signaling blockade on polymethylmethacrylate (PMMA) particle‐induced osteoclastogenesis in vitro. We first established effective blockade of NF‐kB activity as tested by electrophoretic mobility shift assays (EMSA). Particle‐induced NF‐kB activation in murine osteoclast precursor cells (CSF‐1‐dependent bone marrow macrophages) was markedly reduced by co‐treatment of the cells with the NF‐kB inhibitors <jats:italic>N</jats:italic>‐tosyl‐<jats:sc>L</jats:sc>‐phenylalanine chloromethyl ketone (TPCK) and Calpain Inhibitor I (CPI). This inhibition of NF‐kB activity was associated with blockade of p50 NF‐kB subunit nuclear trans‐location. We then established a direct NF‐kB inhibition approach by utilizing a TAT‐bound, mutant IkB (TAT:IkB<jats:sup>46‐317</jats:sup>), and demonstrated an inhibitory effect evidenced by decreased NF‐kB DNA binding activity. Having established that these strategies (TPCK, CPI, TAT: IkB<jats:sup>46‐317</jats:sup>) effectively block NF‐kB activation, we next investigated the effect of these agents on particle‐stimulated osteoclast formation. PMMA particle stimulation of mature osteoclast formation from RANKL‐primed osteoclast precursor cells was blocked by all three inhibitors. To further test the efficacy of NF‐kB blockade, experiments were performed with the TAT:IkB<jats:sup>46‐317</jats:sup> mutant peptide in whole bone marrow cultures that contain supporting stromal cells. Again, this inhibitor efficiently blocked particle‐induced osteoclastogenesis. Thus, we have shown that pharmaceutical and molecular blockade of NF‐kB activation inhibits PMMA particle‐directed osteoclastogenesis in vitro. © 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.</jats:p>