title: Regulation of apoptosis in S49 cells.
abstract: Apoptosis, or programmed cell death, is a highly regulated physiological process by which individual cells die and are removed from a given population. This process, defined by both morphological and biochemical characteristics, has been extensively studied in the glucocorticoid-induced immature thymocyte model. In the present study we explore the effects of glucocorticoids on variants of the S49.1 thymocyte without (S49-NEO) or with (S49-bcl-2) the bcl-2 proto-oncogene. In S49-NEO cells dexamethasone induced a time- and dose-dependent loss of viability and increase in DNA internucleosomal fragmentation (a biochemical hallmark of apoptosis). Glucocorticoid treatment was also associated with an apoptotic morphology (cell shrinkage, chromatin condensation) and the effects of this steroid could be reversed by the glucocorticoid antagonist RU486. In contrast, S49-bcl-2 cells showed no change in viability, DNA fragmentation or apoptotic morphology. Interestingly, the apoptotic effects of glucocorticoid in S49-NEO cells were mimicked by the translation inhibitor cycloheximide and the zinc chelator 1,10-phenanthroline, suggesting that zinc and translational events are necessary to maintain the nonapoptotic state. Finally, nuclease activity was extracted from glucocorticoid-treated S49-NEO cells but not control cells. Together the results further define the effects of glucocorticoids on these cells and provide insight into the mechanisms controlling apoptosis.
authors.affiliation: Laboratories for Reproductive Biology, University of North Carolina at Chapel Hill 27599.
authors.forename: F M
authors.initials: FM
authors.lastname: Hughes
authors.forename: J A
authors.initials: JA
authors.lastname: Cidlowski
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D002461:Cell Line, Transformed; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000187:drug effects / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D009355:Neomycin / Q000494:pharmacology; D010618:Phenanthrolines / Q000494:pharmacology; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2; D013950:Thymus Gland / Q000166:cytology / Q000187:drug effects
chemical_list: C000715470:MAS1 protein, human; D010618:Phenanthrolines; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D003907:Dexamethasone; D004247:DNA; D003513:Cycloheximide; D009355:Neomycin; C025205:1,10-phenanthroline