Daucosterol alleviates osteoarthritis by targeting chondrocyte senescence via inhibiting of the JNK pathway

Osteoarthritis (OA) is a degenerative joint disorder for which no effective disease-modifying treatments currently exist. Chondrocyte senescence is recognized as a major contributor to OA progression. Daucosterol (DAU), a naturally derived phytosterol with anti-inflammatory and antioxidant effects, has not been investigated for its therapeutic effects in OA. Murine chondrocytes stimulated with interleukin-1β (IL-1β) were treated with DAU in vitro. Senescence, matrix metabolism, inflammation, and mitochondrial function were assessed. Network pharmacology and pathway inhibition were used for mechanistic studies. In vivo, the efficacy of DAU was assessed using a mouse destabilized medial meniscus (DMM) model. DAU inhibited IL-1β-induced senescence, inflammation, and matrix degradation in chondrocytes, and simultaneously enhanced extracellular matrix (ECM) production. Mechanistically, DAU selectively inhibited the c-Jun N-terminal kinase (JNK) pathway. This JNK inhibition was crucial, as the JNK inhibitor SP600125 phenocopied DAU's effects. Furthermore, DAU restored mitochondrial membrane potential, reduced reactive oxygen species (ROS) production, and activated the NRF2 antioxidant pathway. In the mouse DMM models, intra-articular DAU administration alleviated cartilage degradation and reduced senescence marker P16 expression. This work characterizes DAU as a new senomorphic agent that alleviates OA development by selectively suppressing JNK signaling, thereby restoring mitochondrial function and mitigating cellular senescence. Overall, DAU may provide a novel therapeutic strategy for OA treatment. Graphical abstract • Daucosterol is identified as a novel senomorphic agent, effectively suppressing IL-1β-induced chondrocyte senescence, inflammation, and extracellular matrix degradation. • The chondroprotective effect of Daucosterol is mechanistically driven by the selective suppression of the JNK signaling within the MAPK cascade, distinct from its effects on ERK or p38. • JNK inhibition by Daucosterol restores mitochondrial function and reduces oxidative stress, thereby disrupting the vicious cycle linking mitochondrial dysfunction to cellular senescence in osteoarthritis.