title: Redistribution of cytochrome c is not an essential requirement in C2-ceramide induced apoptosis in HL-60 cells.
abstract: bcl-2 has been shown to enhance cell survival by inhibiting apoptosis. The present study investigates the potential role of bcl-2 on apoptosis in HL-60 cells induced by different agents. HL-60/bcl-2 and control HL-60/neo cells were obtained by transfection of bcl-2 cDNA or the neomycin-resistant gene, respectively. Staurosporine (STS) promoted DNA fragmentation dose-dependently in the 6 h exposure assay while C2-ceramide was relatively slow in the induction of apoptosis (approximately 40% after 24 h) and required higher concentrations (> 20 microM). Caspases inhibitors, Ac-YVAD-cmk (100 microM) and zVAD-fmk (20 microM) had no effect on DNA fragmentation themselves. However, they blocked C2-ceramide-induced caspase-3 cleavage and apoptosis, but not the release of cytochrome c from the mitochondria. In addition, we found that both Ac-YVAD-cmk and zVAD-fmk failed to protect STS-induced apoptosis in HL-60 cells. Overexpression of bcl-2 inhibited STS and C2-ceramide induced cytochrome c redistribution, caspase-3 activation and apoptosis. These results suggest a protective role of bcl-2 in the regulation of apoptosis and cytochrome c release is unlikely to be involved in the final common pathway in apoptosis.
authors.affiliation: Department of Physiology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, PR China.
authors.forename: Q H
authors.initials: QH
authors.lastname: Zhang
authors.forename: H P
authors.initials: HP
authors.lastname: Sheng
authors.forename: T T
authors.initials: TT
authors.lastname: Loh
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D003574:Cytochrome c Group / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018922:HL-60 Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D006801:Humans; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000633:toxicity
chemical_list: D061945:Caspase Inhibitors; D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; C064769:N-acetylsphingosine; D019253:Proto-Oncogene Proteins c-bcl-2; D012967:Sodium Dodecyl Sulfate; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D013110:Sphingosine