title: Biochemical and kinetic characterization of the glucocorticoid-induced apoptosis of immature CD4+CD8+ thymocytes.
abstract: We characterized kinetic and biochemical changes during glucocorticoid (GC)-induced apoptosis of immature CD8+CD4+ double-positive (DP) thymocytes. A GC analog dexamethasone (Dex) induced rapid apoptotic commitment and a transient up-regulation of the NF-kappaB/RelA-p50-binding activity in DP cells. This required an early activation of proteasome, as judged by the ability of a specific proteasomal inhibitor, lactacystine, to delay apoptosis and to suppress Dex-dependent NF-kappaB activation. Dex-induced apoptotic commitment was preceded by the rapid (3 h) cleavage of both a typical caspase substrate, poly(ADP-ribose) polymerase (PARP), and of nuclear transcription factors AP-1, NF-kappaB p50-p50 and NUR-77. By contrast, phorbol myristate acetate (PMA) and/or ionomycin-induced apoptosis had much slower kinetics, were preceded by an early increase of NF-kappaB/RelA-p50, AP-1 and NUR-77 activities, and were insensitive to proteasome inhibition. Both the transgenic Bcl-2 and zVAD-fmk, an inhibitor of caspases, affected all features of Dex-induced apoptosis in a similar fashion, by inhibiting cell death and PARP cleavage, and by stabilizing AP-1, NF-kappaB p50-p50 and NUR-77 levels. Furthermore, Bcl-2 prevented Dex-induced RelA-p50 activation. However, a higher gene dosage of the transgenic Bcl-2 was required for protection against Dex, compared to the PMA and/or ionomycin-induced apoptosis. These findings highlight the unique mechanistic features of GC-induced apoptosis.
authors.affiliation: Laboratory of T Cell Development, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
authors.forename: V N
authors.initials: VN
authors.lastname: Ivanov
authors.forename: J
authors.initials: J
authors.lastname: Nikolić-Zugić
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology* / Q000187:drug effects; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology* / Q000187:drug effects; D061945:Caspase Inhibitors; D003546:Cysteine Endopeptidases / Q000187:drug effects / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003907:Dexamethasone / Q000493:pharmacokinetics* / Q000494:pharmacology*; D005260:Female; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D009097:Multienzyme Complexes / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D051996:Transcription Factor RelA; D014157:Transcription Factors / Q000378:metabolism; D019076:Transgenes; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D007476:Ionophores; D009097:Multienzyme Complexes; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D051996:Transcription Factor RelA; D014157:Transcription Factors; C067713:lactacystin; D015759:Ionomycin; D003907:Dexamethasone; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D013755:Tetradecanoylphorbol Acetate; D000111:Acetylcysteine