Ebselen protects Chinese hamster ovary cells from radiation-induced apoptosis

Radiation-induced apoptosis in chinese hamster ovary (CHO) cell lines is characterized by endonucleolytic cleavage of cellular DNA and changes of cell morphology within hours after radiation exposure. We investigated the capacity of ebselen [2-phenyl-1,2-benzisoselenazol-3(2H)-one], a seleno-organic compound with selenium-dependent glutathione peroxidase (GPx) activity, to protect cells from radiation-induced apoptosis. This phenomenon was studied by the quantitation of apoptotic cells and DNA gel electrophoresis after 6 Gy X-ray exposure. We also measured the activity of GPx and membrane lipid peroxidation. It was observed that 20 µM ebselen efficiently blocked apoptotic cell formation and DNA fragmentation 48 h post irradiation. Furthermore the data demonstrated that lipid peroxides increased significantly in irradiated cells and ebselen inhibited this process by elevating the cellular GPx activity. The results presented here indicate the requirement of free radicals for radiation-induced apoptosis and ultimately may yield insight necessary for designing protocols to modulate the process of radiation-induced apoptosis with antioxidant agents that scavenge radiation-induced free radicals.