Activation of intrinsic and extrinsic pathways in apoptotic signaling during UV-C-induced death of Jurkat cells: the role of caspase inhibition.
We have examined UV irradiation-induced cell death in Jurkat cells and evaluated the relationships that exist between inhibition of caspase activity and the signaling mechanisms and pathways of apoptosis. Jurkat cells were irradiated with UV-C light, either with or without pretreatment with the pan-caspase inhibitor, z-VAD-fmk (ZVAD), or the more selective caspase inhibitors z-IETD-fmk (IETD), z-LEHD-fmk (LEHD), and z-DEVD-fmk (DEVD). Flow cytometry was used to examine alterations in viability, cell size, plasma membrane potential (PMP), mitochondrial membrane potential (DeltaPsi(mito)), intracellular Na(+) and K(+) concentrations, and DNA degradation. Processing of pro-caspases 3, 8, and 9 and the pro-apoptotic protein Bid was determined by Western blotting. UV-C irradiation of Jurkat cells resulted in characteristic apoptosis within 6 h after treatment and pretreatment of cells with ZVAD blocked these features. In contrast, pretreatment of the cells with the more selective caspase inhibitors under conditions that effectively blocked DNA degradation and inhibited caspase 3 and 8 processing as well as Bid cleavage had little protective effect on the other apoptotic characteristics examined. Thus, both intrinsic and extrinsic pathways are activated during UV-induced apoptosis in Jurkat cells and this redundancy appears to assure cell death during selective caspase inhibition.
Scoltock
Alyson B
AB
Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, NC 27709, USA.
Cidlowski
John A
JA
D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects*; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D048429:Cell Size / Q000502:physiology / Q000528:radiation effects; D002470:Cell Survival / Q000502:physiology / Q000528:radiation effects; D053938:DNA Fragmentation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D019169:Jurkat Cells; D015458:Leukemia, T-Cell / Q000201:enzymology / Q000378:metabolism* / Q000532:radiotherapy*; D008564:Membrane Potentials / Q000502:physiology / Q000528:radiation effects; D008928:Mitochondria / Q000502:physiology / Q000528:radiation effects; D011188:Potassium / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000528:radiation effects; D015398:Signal Transduction / Q000502:physiology / Q000528:radiation effects*; D012964:Sodium / Q000378:metabolism; D014466:Ultraviolet Rays
D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D012964:Sodium; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D011188:Potassium