Activation of NF-κB signalling and TNFα-expression in THP-1 macrophages by TiAlV- and polyethylene-wear particles

Wear particles are believed to induce periprosthetic inflammation which contributes to periprosthetic osteolysis. TNFα plays a pivotal role in the pathogenesis of this process. The molecular mechanisms leading to the development of periprosthetic inflammation with upregulated TNFα expression in monocytic cells in response to different wear particles have yet to be defined. In this study we evaluated the effects of polyethylene- and TiAlV-particles on activation of NF-κB signalling pathways and TNFα biosynthesis and release in monocytic cells with respect to periprosthetic osteoclastogenesis. THP-1 monocytic cells were differentiated to macrophage-like cells and exposed to LPS-detoxified polyethylene and prosthesis-derived TiAlV-particles. TNFα release was analyzed in culture supernatant by ELISA. NF-κB activation was examined by electrophoretic mobility shift assay (EMSA), and NF-κB target promoter activities including transactivation of the TNFα promoter were determined by luciferase reporter gene assays. Differentiated THP-1 macrophages were exposed to increasing numbers of particles for 0, 60, 180 and 360 min. Both, polyethylene- and TiAlV-particles induced a significant activation of both NF-κB and TNFα promoters at 180 min. A significant TNFα release was detected after 360 min exposure to polyethylene- and TiAlV-particles in a dose dependent manner. In comparison, LPS induced a much greater activation of NF-κB and TNFα promoters, and TNFα secretion into the supernatant was strongly induced. These results provide evidence that induction of the NF-κB signal transduction pathway in macrophages plays a major role in initiating and mediating the inflammatory response leading to periprosthetic osteolysis.