title: Lethal damage to murine L1210 cells by exogenous lipid hydroperoxides: protective role of glutathione-dependent selenoperoxidases.
abstract: The effect of selenium deprivation on the viability of murine L1210 cells exposed to various exogenous lipid hydroperoxides has been investigated. Selenoperoxidase activities of cells grown for longer than 1 week in 1% serum with no added selenium [Se(-) cells] were less than 10% of the activities of selenium-satisfied controls [Se(+) cells] or selenium-repleted counterparts [Se(-/+) cells]. The enzymes measured were classical glutathione peroxidase (GPX) and phospholipid hydroperoxide glutathione peroxidase (PHGPX). Se(-) cells exhibited a compensatory increase in catalase activity. Dye exclusion and clonal survival assays indicated that Se(-) and Se(+) cells were relatively insensitive to photochemically generated phospholipid hydroperoxides in liposomal form. However, both cell types were sensitive to liposomal cholesterol hydroperoxides, e.g., 7-hydroperoxycholesterol (7-OOH), Se(-) being much more so (LD50 approximately 10 microM) than Se(+) (LD50 approximately 75 microM). By contrast, 7-hydroxycholesterol over a comparable concentration range was minimally toxic to Se(-) and Se(+) cells. Cell killing by 7-OOH was inhibited by desferrioxamine and by butylated hydroxytoluene, suggesting that iron-mediated free radical reactions are involved. The involvement of glutathione in cytoprotection was confirmed by showing that Se(+) cells were more sensitive to 7-OOH after treating with buthionine sulfoximine, an inhibitor of GSH synthesis. Cellular detoxification of 7-OOH is provisionally attributed to PHGPX rather than GPX, since 7-OOH and other cholesterol hydroperoxides were found to be good substrates for PHGPX in a cell free system, but were unreactive with GPX.
authors.affiliation: Department of Biochemistry, Medical College of Wisconsin, Milwaukee 53226.
authors.forename: P G
authors.initials: PG
authors.lastname: Geiger
authors.forename: J P
authors.initials: JP
authors.lastname: Thomas
authors.forename: A W
authors.initials: AW
authors.lastname: Girotti
mesh_terms: D000818:Animals; D002084:Butylated Hydroxytoluene / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects*; D002474:Cell-Free System; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D003676:Deferoxamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005979:Glutathione Peroxidase / Q000378:metabolism*; D007700:Kinetics; D007939:Leukemia L1210 / Q000201:enzymology / Q000473:pathology*; D008054:Lipid Peroxides / Q000494:pharmacology*; D008081:Liposomes; D051379:Mice; D010743:Phospholipids / Q000378:metabolism; D012643:Selenium / Q000494:pharmacology*
chemical_list: D008054:Lipid Peroxides; D008081:Liposomes; D010743:Phospholipids; D002084:Butylated Hydroxytoluene; C041011:cholesterol 7-hydroperoxide; D002784:Cholesterol; D005979:Glutathione Peroxidase; D012643:Selenium; D003676:Deferoxamine