Spautin-1 inhibits osteoclast differentiation and attenuates bone loss by blocking USP10/JIP1-mediated JNK pathway.

Osteoclast hyperactivity is a key factor in the pathogenesis of several skeletal disorders, including inflammatory bone loss, periprosthetic osteolysis, and rheumatoid arthritis. The ubiquitin-proteasome system (UPS) is pivotal in bone homeostasis and disease pathogenesis, modulating critical osteogenic and osteolytic signaling cascades. Our study identified Spautin-1, an inhibitor of ubiquitin-specific protease 10 (USP10), with the capacity to suppress osteoclastogenesis and the expression of genes associated with osteoclast activity, triggered by the nuclear factor-κB (NF-κB) ligand (RANKL) in bone marrow-derived macrophages (BMMs). Spautin-1 also effectively inhibited RANKL-induced bone resorption in vitro assays. At the molecular level, Spautin-1 reduced the expression of JNK interacting protein 1 (JIP1) by impeding USP10-mediated JIP1 deubiquitination, consequently dampening the RANKL-activated c-Jun N-terminal kinase (JNK)-mitogen-activated protein kinase (MAPK) signaling axis and curbing nuclear factor of activated T cells 1 (NFATc1) activation. Consistent with this mechanism, silencing of USP10 similarly reduced the expression of osteoclast‑related genes, mirroring the effects observed with Spautin‑1 treatment, whereas overexpression of JIP1 reversed these inhibitory effects. Additionally, Spautin-1 was found to ameliorate lipopolysaccharide (LPS)-induced bone loss in murine models. Notably, a positive correlation was observed between USP10 and JIP1 expression levels in bone tissues from osteoporotic patients. Collectively, our results position Spautin-1 as a potential therapeutic agent for osteoclast-mediated bone diseases.