MENADIONE-INDUCED CYTOTOXICITY TO RAT OSTEOBLASTS

Oxygen-derived free radical injury has been associated with several cy topathic conditions. Oxygen radicals produced by chondrocytes is an im portant mechanism by which chondrocytes induce matrix degradation. In the present study, we extend these observations by studying oxidative processes against osteoblasts. Osteoblasts were mixed in in vitro cult ure with 200 mu M menadione. The cytotoxic effect of menadione-induced oxidative stress was monitored by lucigenin-or luminol-amplified chem iluminescence,tetrazolium assay and immunocytochemical study. Results showed that adding menadione induces an oxidative stress on osteoblast s, via superoxide and hydrogen peroxide production, that call be eradi cated by superoxide dismutase (SOD) and catalase in a dose-dependent m anner. Catalase and the appropriate concentration of dimethyl sulfoxid e have a protective effect on cytotoxicity induced by menadione, where as SOD does not. Menadione-treated osteoblasts have a strong affinity for annexin V, and the nuclei are strongly stained by TUNEL (TdT-media ted dUTP nick-end labelling). The results suggest that menadione-trigg ered production of reactive oxygen species leads to apoptosis of osteo blasts.