Cytolethal distending toxin induces caspase-dependent and -independent cell death in MOLT-4 cells.
Cytolethal distending toxin (CDT) induces apoptosis using the caspase-dependent classical pathway in the majority of human leukemic T cells (MOLT-4). However, we found the process to cell death is only partially inhibited by pretreatment of the cells with a general caspase inhibitor, z-VAD-fmk. Flow cytometric analysis using annexin V and propidium iodide showed that a 48-h CDT treatment decreased the living cell population by 35% even in the presence of z-VAD-fmk. z-VAD-fmk completely inhibited caspase activity in 24 h CDT-intoxicated cells. Further, CDT with z-VAD-fmk treatment clearly increased the cell population that had a low level of intracellular reactive oxygen. This is a characteristic opposite to that of caspase-dependent apoptosis. Overexpression of bcl2 almost completely inhibited cell death using CDT treatment in the presence of z-VAD-fmk. The data suggest there are at least two different pathways used in CDT-induced cell death: conventional caspase-dependent (early) apoptotic cell death and caspase-independent (late) death. Both occur via the mitochondrial membrane disruption pathway.
Ohara
Masaru
M
Department of Bacteriology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan. mohara@hiroshima-u.ac.jp
Hayashi
Tomonori
T
Kusunoki
Yoichiro
Y
Nakachi
Kei
K
Fujiwara
Tamaki
T
Komatsuzawa
Hitoshi
H
Sugai
Motoyuki
M
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis; D001427:Bacterial Toxins / Q000633:toxicity*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death; D045744:Cell Line, Tumor; D002470:Cell Survival; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003593:Cytoplasm / Q000737:chemistry; D005434:Flow Cytometry; D006801:Humans; D011419:Propidium / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000032:analysis; D013194:Staining and Labeling / Q000379:methods
D000590:Amino Acid Chloromethyl Ketones; D017304:Annexin A5; D001427:Bacterial Toxins; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D017382:Reactive Oxygen Species; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C067044:cytolethal distending toxin; D011419:Propidium; D020169:Caspases