Polyphenols suppress inducible oxidative stress in human osteoarthritic and bovine chondrocytes

Reactive oxygen species (ROS) and nitric oxide (NO) have been implicated in chondrocyte senescence and cartilage aging, pathogenesis of osteoarthritis (OA), and rheumatoid arthritis. Naturally occurring polyphenolic compounds (PPCs), such as curcumin (turmeric), resveratrol (grape), and epigallocatechin-3-gallate (EGCG) (green tea), have been known for their anti-inflammatory and chondroprotective effects. However, the potential protective effects of these PPCs against oxidative stress in chondrocytes are unclear. To investigate this, bovine articular chondrocytes and human osteoarthritic chondrocytes were pre-treated with PPCs at varying concentrations, and then exposed to hydrogen peroxide (H₂O₂) as an ROS inducer or S-nitroso-N-acetylpenicillamine (SNAP) as a NO donor. Alternatively, chondrocytes were co-treated with polyphenols and H₂O₂. Intracellular ROS/NO were measured using a fluorescent dye technique (H₂DCF-DA for ROS; DAF-FM for NO). Our findings showed that PPC pre-/co-treatment inhibited both H₂O₂-induced ROS and SNAP-induced NO at different concentrations in both bovine chondrocytes and human osteoarthritic chondrocytes. Curcumin also increased glutathione peroxidase activity in the presence of H₂O₂ in bovine chondrocytes. Taken together, these findings indicate that PPCs are capable of suppressing oxidative stress- induced responses in chondrocytes, which may have potential therapeutic value for OA clinical application.