Caspase-3-like activity determines the type of cell death following ionizing radiation in MOLT-4 human leukaemia cells.
Caspases, a family of cysteine proteases, play a central role in the pathways leading to apoptosis. Recently, it has been reported that a broad spectrum inhibitor of caspases, the tripeptide Z-VAD-fmk, induced a switch from apoptosis to necrosis in dexamethasone-treated B lymphocytes and thymocytes. As such a cell death conversion could increase the efficiency of radiation therapy and in order to identify the caspases involved in this cell death transition, we investigated the effects of caspase-3-related proteases inhibition in irradiated MOLT-4 cells. Cells were pretreated with Ac-DEVD-CHO, an inhibitor of caspase-3-like activity, and submitted to X-rays at doses ranging from 1 to 4 Gy. Our results show that the inhibition of caspase-3-like activity prevents completely the appearance of the classical hallmarks of apoptosis such as internucleosomal DNA fragmentation or hypodiploid particles formation and partially the externalization of phosphatidylserine. However, this was not accompanied by any persistent increase in cell survival. Instead, irradiated cells treated by this inhibitor exhibited characteristics of a necrotic cell death. Therefore, functional caspase-3-subfamily not only appears as key proteases in the execution of the apoptotic process, but their activity may also influence the type of cell death following an exposure to ionizing radiation.
Coelho
D
D
Laboratoire de Cancérologie Expérimentale et de Radiobiologie, IRCAD, Hôpitaux Universitaires, BP 426, Strasbourg Cedex, F-67091, France.
Holl
V
V
Weltin
D
D
Lacornerie
T
T
Magnenet
P
P
Dufour
P
P
Bischoff
P
P
D017304:Annexin A5 / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases / Q000378:metabolism*; D002384:Catalysis; D016923:Cell Death / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D004396:Coloring Agents / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D053938:DNA Fragmentation; D004307:Dose-Response Relationship, Radiation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000494:pharmacology; D006801:Humans; D020287:In Situ Nick-End Labeling; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D007938:Leukemia / Q000473:pathology* / Q000532:radiotherapy*; D009336:Necrosis; D009842:Oligopeptides / Q000494:pharmacology; D010078:Oxazines; D010718:Phosphatidylserines / Q000378:metabolism; D011419:Propidium / Q000494:pharmacology; D011839:Radiation, Ionizing; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014965:X-Rays; D014966:Xanthenes
D017304:Annexin A5; D004396:Coloring Agents; D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D009842:Oligopeptides; D010078:Oxazines; D010718:Phosphatidylserines; D014966:Xanthenes; C099158:acetyl-aspartyl-glutamyl-valyl-aspartal; C005843:resazurin; D011419:Propidium; D007770:L-Lactate Dehydrogenase; C505407:CASP3 protein, human; C505520:CASP7 protein, human; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases; D016650:Fluorescein-5-isothiocyanate