Effect of selenium on human phospholipid hydroperoxide glutathione peroxidase expression and host cell susceptibility to lipid hydroperoxide-mediated injury.

We recently isolated stable transfectants expressing human phospholipid hydroperoxide glutathione peroxidase (PHGPx) from the cells of guinea pig cell line 104C1 (Biochem. Biophys. Res. Commun. 219, 486-491, 1996). Among them, one transfectant, designated 104C1/O4C, expressed high glutathione peroxidase activity toward dilinoleoyl phosphatidylcholine hydroperoxide (PCOOH); and another one, 104C1/O2D, moderate activity. In the present study, we investigated the effect of selenium on the PHGPx activity and on the lipid hydroperoxide-mediated cell injury in the transfectants to clarify further the action of PHGPx in preventing oxidative injury of the cells. When transfectant 104C1/O2D cells were cultured in the medium added with 250 nM selenium, glutathione peroxidase activity toward PCOOH increased 8-fold. Western blot analysis also revealed an increase in the amount of protein immunoreactive against anti-rat PHGPx antibody in this transfectant. Lipid hydroperoxide-mediated cell injury to the transfectant 104C1/O2D was significantly suppressed in accordance with the increase in the enzyme activity when the cells were cultured in the medium added with selenium. On the contrary, neither glutathione peroxidase activity toward PCOOH nor susceptibility to the injury was affected by selenium addition to the medium of the parental 104C1 cells, which have no selenium-dependent glutathione peroxidase. These results clearly support our previous conclusion that expression of PHGPx is responsible for the protection of host cells from lipid hydroperoxide-mediated injury.