Protective effects of ugonin K on hydrogen peroxide-induced osteoblast cell damage

• Ugonin K suppressed H2O2-induced ROS production and apoptosis.
• Protective effects of ugonin K are stronger than Vit C, α-tocopherol and probucol.
• Ugonin K suppressed cytochrome c, active forms of PARP, caspases-9 and 3 expression.
• Activation of ER/Src signaling participates in the protective mechanism of ugonin K.
• Post-treatment of ugonin K after H2O2 treatment recovered H2O2-induced cell death.

Oxidative stress is a risk factor in the pathogenesis of osteoporosis. The present results showed that ugonin K, an osteogenic constituent presented in Helminthostachys zeylanica, was more potent than ascorbic acid, α-tocopherol and probucol, in protecting osteoblasts against hydrogen peroxide (H2O2)-induced oxidative injury in murine osteoblast MC3T3-E1 cells. Ugonin K suppressed H2O2-induced reactive oxygen species (ROS) production and the Annexin V/propidium iodide assay confirmed that decrease in cell viability by H2O2 was due to apoptosis. Suppression by Ugonin K of H2O2-induced activation of apoptotic signaling was evidenced by a decrease in expressions of cytosolic cytochrome c, active forms of caspase-9, caspase-3 and poly(ADP-ribose)polymerase (PARP). Treatment of cells with caspase inhibitor Ac-DEVD-cho recovered apoptosis and ugonin K decreased H2O2-triggered caspase 3 activity. Ugonin K-induced alleviation of cell viability was concentration-dependently attenuated by the estrogen receptor (ER) antagonist and the Src inhibitor, suggesting that activation of ER/Src signaling might also participate in the protective mechanisms. Furthermore, post-treatment with ugonin K after H2O2 challenge also rescued H2O2-induced osteoblast cell death. Our results showed that ugonin K protected osteoblasts from oxidative stress through regulation of ROS production and suppression of caspase cascade. These results suggest that ugonin K may be an alternative remedy for osteoporosis.