Cytotoxic and antioxidant effects of the water extract of the traditional Chinese herb Gusuibu (Drynaria fortunei) on rat osteoblast

Background and purpose: Gusuibu (Drynaria fortunei) is a traditional Chinese herb that has been claimed to have therapeutic effects on bone healing; however, a clinical mechanism responsible for this effect has not been identified. This study evaluated the cytotoxic and antioxidant effects of the water extract of gusuibu (WEGSB) on rat osteoblasts. Materials and methods: Osteoblasts were prepared from neonatal Wistar rat calvarias and treated with WEGSB. Cell viability and alkaline phosphate activity were determined. Intracellular reactive oxygen species were detected using the dye 2',7'-dichlorofluorescin, and mitochondrial membrane potential was detected using the dye 3,3'-dihexyloxacarbocyanine iodide and flow cytometry. Results: WEGSB at 1 and 10 μg/mL was not cytotoxic to rat osteoblasts, but WEGSB at 100 μg/mL reduced cell viability and alkaline phosphatase activity in a time-dependent manner. Although WEGSB and hydrogen peroxide did not affect the mitochondrial membrane potential of rat osteoblasts, combined treatment with WEGSB (100 μg/mL) and hydrogen peroxide lowered the membrane potential of mitochondria and resulted in cell death. The basal level of intracellular reactive oxygen species in rat osteoblasts was significantly suppressed by WEGSB at 10 to 100 μg/mL. WEGSB (10 μg/mL) specifically inhibited hydrogen peroxide-induced oxidative stress without an effect on nitric oxide-induced stress. Hydrogen peroxide caused concentration-dependent death of rat osteoblasts, but WEGSB significantly protected cells from hydrogen peroxide-induced death. Conclusion: This study has shown that WEGSB at 10 μg/mL is not cytotoxic to rat osteoblasts in vitro, and also that the extract at 10 μg/mL has an antioxidant effect on these cells. The antioxidant activity of WEGSB can protect rat osteoblasts from hydrogen peroxide-induced death and may promote bone recovery under similar pathologic conditions.