title: Caspase-8 mediates caspase-3 activation and cytochrome c release during singlet oxygen-induced apoptosis of HL-60 cells.
abstract: We reported previously that singlet oxygen, generated by irradiation of rose bengal with visible light, induced apoptosis in human promyelocytic leukemia HL-60 cells. However, the mechanism of apoptosis caused by this reactive oxygen species is unclear. In this study, we demonstrate that singlet oxygen induced caspase-3 activation and Z-DEVD-FMK, a caspase-3 inhibitor, blocked apoptosis induction, while caspase-1 activity was not detectable and the caspase-1 inhibitor Z-YVAD-FMK had a very limited effect on apoptosis. This suggests that the activation of caspase-3 by singlet oxygen is essential for the commitment of cells to undergo apoptosis. Further studies showed that singlet oxygen induced an increase in caspase-8 activity and a reduction in mitochondrial cytochrome c. Time course analysis indicated that the cleavage of caspase-8 precedes that of caspase-3. In addition, blockade of caspase-8 by Z-IETD-FMK inhibited cleavage of pro-caspase-3 and prevented loss of mitochondrial cytochrome c. These results suggest that caspase-8 mediates caspase-3 activation and cytochrome c release during singlet oxygen-induced apoptosis in HL-60 cells.
authors.affiliation: Wellman Laboratories of Photomedicine, Massachusetts General Hospital, Boston, Massachusetts, 02114, USA.
authors.forename: S
authors.initials: S
authors.lastname: Zhuang
authors.forename: M C
authors.initials: MC
authors.lastname: Lynch
authors.forename: I E
authors.initials: IE
authors.lastname: Kochevar
mesh_terms: D017209:Apoptosis; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism*; D004789:Enzyme Activation; D018922:HL-60 Cells; D006801:Humans; D008928:Mitochondria / Q000378:metabolism; D010100:Oxygen / Q000494:pharmacology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D026082:Singlet Oxygen
chemical_list: D061945:Caspase Inhibitors; D003574:Cytochrome c Group; D026082:Singlet Oxygen; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D010100:Oxygen