γ-irradiation induced apoptosis in peritoneal macrophages by oxidative stress. Implications of antioxidants in caspase mitochondrial pathway

The in vivo and in vitro development of apoptosis induced by γ-irradiation was studied in mouse peritoneal macrophages. The apoptosis index was measured by fluorescence microscopy and DNA electrophoresis. In vivo apoptosis was greatest eight days after 8 Gy total body γ-irradiation. A DNA ladder electrophoretic pattern was only observed in the γ-irradiated group. The participation of reactive oxygen species in apoptosis induction was investigated by pretreating mice with the antioxidants superoxide dismutase, catalase, vitamin E or lipopolysaccharide before γ-irradiation. Measurement of serum lipoperoxides showed oxidative stress in the γ-irradiated mice and the protection given by the antioxidants. These results were confirmed using in vitro cultures of peritoneal macrophages: γ-irradiated groups and antioxidant-pretreated γ-irradiation groups showed results similar to those observed with in vivo irradiation. A loss of mitochondrial membrane potential (Δψm) was also observed by microscopy in the γ-irradiated cell cultures. Experiments with caspase inhibitors confirmed the participation of caspase 3 and caspase 9