Astaxanthin protects against osteoarthritis via Nrf2: a guardian of cartilage homeostasis

Scope: Osteoarthritis (OA) is a progressive disease characterized by cartilage degradation. Astaxanthin (Ast), a natural compound with remarkable antioxidant activity and multiple medical applications due to its activation of Nrf2 signaling, has been studied for application to various degenerative diseases. Currently, however, little is known about its efficacy in treating OA. This study reports the effects of Ast on cartilage homeostasis in OA progression. Methods: IL-1β, TNF-α, and tert-butyl hydroperoxide (TBHP) were used to impair cartilage homeostasis. Modulating effects of Ast on the Nrf2 signaling pathway, and damage-associated events including extracellular matrix (ECM) degradation, inflammation, oxidative stress, chondrocyte apoptosis, and in vivo cartilage degradation were examined. Results: Ast attenuated ECM degradation of OA chondrocytes through the Nrf2 signaling, and ameliorated the IL-1β-induced inflammatory response and ECM degradation via blockade of MAPK signaling. Additionally, Ast alleviated TNF-α-induced ECM degradation and chondrocyte apoptosis by inhibiting the NF-κB signaling, suppressed TBHP-induced oxidative stress, and subsequently reduced chondrocyte apoptosis. In vitro results were finally corroborated in vivo by demonstrating that Ast attenuates the severity of cartilage destruction in a mouse model of OA. Conclusions: Ast could protect against osteoarthritis via the Nrf2 signaling, suggesting Ast might be a potential therapeutic supplement for OA treatment.