The chondroprotective effect of diosmin on human articular chondrocytes under oxidative stress

Excessive oxidative stress, which can amplify inflammatory responses, is involved in the pathologic progression of knee osteoarthritis. Diosmin is known to possess a variety of biological functions such as antiinflammatory and antioxidant activities. We therefore demonstrated the chondroprotective potentials of diosmin on human articular chondrocytes under oxidative stress. The cytotoxicity of diosmin (5, 10, 50, and 100 μM) to chondrocytes was first evaluated. Subsequently, the cells were treated with diosmin (5 and 10 μM) after hydrogen peroxide (H₂O₂) exposure. We found that the cytotoxicity of diosmin occurred in a dose-dependent manner (10, 50, and 100 μM), and low-dose diosmin (5 μM) slightly impaired cell viability. Diosmin supplementations (5 and 10 μM) did not show beneficial effects on mitochondrial activity, cytotoxicity, proliferation, and survival and the cell senescence was ameliorated in H₂O₂-exposed chondrocytes. On the other hand, diosmin down-regulated the mRNA levels of iNOS, COX-2, IL-1β, COL1A1, MMP-3, and MMP-9; up-regulated TIMP-1 and SOX9; and improved COL2A1 in chondrocytes under oxidative stresses. Furthermore, diosmin also regulated glutathione reductase and glutathione peroxidase of H₂O₂-exposed chondrocytes. In conclusion, diosmin displayed a remarkable antiinflammatory effect compared with the antioxidant capacity on human chondrocytes. Diosmin can maintain the homeostasis of extracellular matrix of articular cartilage.