The USP14?NLRC5 pathway inhibits titanium particle?induced osteolysis in mice by suppressing NF-?B and PI3K/AKT activities

Total hip arthroplasty (THA) is a widely-used surgical intervention for treating patients with end-stage degenerative and inflammatory osteoarthropathy. However, wear particles from the artificial titanium joint can induce osteolysis, limiting the long-term survivorship of THA. Monocyte/macrophage lineage cells are the key players in the response to wear particles, and the proinflammatory NF-?B and phosphoinositide 3-kinase (PI3K)?AKT Ser/Thr kinase (AKT)-signaling pathways have been shown to be the most important contributors to wear particle?induced osteolysis. In contrast, ubiquitin-specific protease 14 (USP14) specifically removes the polyubiquitin chains from the nucleotide-binding and oligomerization domain (NOD)-like receptor family Caspase recruitment domain (CARD)?containing 5 (NLRC5) and thereby enhances the NLRC5-mediated inhibition of NF-?B signaling. In this study, we aimed to clarify the role of the USP14?NLRC5 pathway in wear particle?induced osteolysis in vitro and in vivo. We found that NLRC5 or USP14 overexpression inhibits titanium particle?induced proinflammatory tumor necrosis factor ? (TNF?) production and NF-?B pathway activation, and it also decreases M1 macrophage polarization and PI3K/AKT pathway activation. Of note, NLRC5 and USP14 overexpression attenuated titanium particle?induced cranial osteolysis in mice. In conclusion, the findings of our study indicate that the USP14?NLRC5 pathway inhibits titanium particle?induced osteolysis by suppressing the NF-?B and PI3K/AKT pathways both in vitro and in vivo.