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

Background and purpose: Gusuibu (Drynaria fortunei) is a traditional Chines e herb that has been claimed to have therapeutic effects on bone healing; h owever, a clinical mechanism responsible for this effect has not been ident ified. This study evaluated the cytotoxic and antioxidant effects of the wa ter extract of gusuibu (WEGSB) on rat osteoblasts. Materials and methods: Osteoblasts were prepared from neonatal Wistar rat c alvarias osteoblasts and treated with WEGSB. Cell viability and alkaline ph osphatase activity were determined Intracellular reactive oxygen species we re detected using the dye 2',7'-dichlorofluorescin, and mitochondrial membr ane potential was deterred using the dye 3,3 '-dihexyloxacarbocyanine iodid e and flow cytometry. Results: WEGSB at 1 and 10 mug/mL was not cytotoxic to rat osteoblasts, but WEGSB at 100 mug/mL reduced cell viability and alkaline phosphatase activi ty in a time-dependent manner. Although WEGSB and hydrogen peroxide did not affect the mitochondrial membrane potential of rat osteoblasts, combined t reatment with WEGSB (100 mug/mL) and hydrogen peroxide lowered the membrane potential of mitochondria and resulted in cell death. The basal level of i ntracellular reactive oxygen species in rat osteoblasts was significantly s uppressed hy WEGSB at 10 to 100 mug/mL. WEGSB (10 mug/mL)specifically inhib ited hydrogen peroxide-induced oxidative stress without an effect on nitric oxide-induced stress. Hydrogen peroxide caused concentration-dependent dea th of rat osteoblasts. but WEGSB significantly protected cells from hydroge n peroxide-induced death. Conclusion: This study has shown that WEGSB at 10 mug/mL is not cytotoxic t o rat osteoblasts in vitro, and also that the extract at 10 mug/muL has an antioxidant effect on these cells. The antioxidant activity of WEGSB can pr otect rat osteoblasts from hydrogen peroxide-induced death and may promote bone recovery under similar pathologic conditions.