Dual mechanism of Fas-induced cell death in neuroglioma cells: a role for reactive oxygen species.

ApoI/Fas belongs to the tumor necrosis factor receptor (TNFR) superfamily and mediates cell death in various cell types. A dual mode of Fas-triggered cell death has been reported depending on cell types used in the experiments. The present study was carried out to test the possible role of reactive oxygen species in this dual mechanism in neuroglioma cells. Anti-Fas antibody caused dose-dependent and time-dependent increase in cell death measured by lactate dehydrogenase (LDH) release in control neuroglioma cells and in cells that were transfected with catalase cDNA. However, cells transfected with copper/zinc superoxide dismutase (Cu/ZnSOD) cDNA showed marked attenuation of Fas-induced LDH release. Moreover, flow cytometry and confocal microscopy revealed that Fas-induced cell death in control cells occur mostly through an apoptotic process. This process was also completely abrogated in cells overexpressing catalase or copper/zinc superoxide dismutase (Cu/ZnSOD). Further experiments revealed that Fas-induced cell death was associated with increased formation of superoxide anions in control neuroglioma cells and in cells overexpressing catalase. These increases were significantly suppressed by Cu/ZnSOD overexpression. These data indicate that Fas-mediated cell death in neuroglioma cells occur, in part, through the production of reactive oxygen species (ROS). These observations also suggest that Fas-induced cell death in these cells occur through apoptosis and necrosis. Thus overexpression of Cu/ZnSOD caused the suppression of both types of Fas-induced cell death whereas catalase prevented apoptotic but not necrotic cell death. These observations are discussed in terms of their support for a role for both peroxides and superoxide radicals in Fas-induced cell death.