Caspase-3-dependent and caspase-3-independent pathways leading to chromatin DNA fragmentation in HL-60 cells.
Apoptosis induced by etoposide (VP-16) in HL-60 cells was confirmed to be caspase-dependent. It was fully inhibited by the broad-spectrum caspase inhibitor Z-VAD-fmk. However, the caspase-3-specific inhibitor Z-DEVDfmk only partially inhibited apoptosis. This indicated that a second caspase is required in vivo for full activation of the apoptotic nucease CAD. Aurin tricarboxylic acid (ATA) did not inhibit VP-16-induced apoptosis. In contrast, apoptosis induced by hydroxychloroquine (HCQ) in HL-60 cells was caspase-3 independent and was fully inhibited by ATA. Thus, CAD does not appear to be involved in chromatin DNA degradation in this case. A second apoptotic nuclease is postulated to degrade the DNA, likely endo- exonuclease, an abundant nuclear enzyme that acts on both DNA and RNA and is present in latent form. HCQ, but not VP-16, stimulated DNA degradation ("laddering") in isolated nuclei. This indicates that the drug can act directly in the nuclei to trigger activation of the second latent apoptotic nuclease.
Meng
X W
XW
Department of Immunology and Rheumatology, Sydney Children's Hospital and School of Paediatrics, The University of New South Wales, Randwick, Australia.
Fraser
M J
MJ
Feller
J M
JM
Ziegler
J B
JB
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D001312:Aurintricarboxylic Acid / Q000494:pharmacology; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002467:Cell Nucleus / Q000187:drug effects; D002843:Chromatin; D053938:DNA Fragmentation; D005047:Etoposide / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D006886:Hydroxychloroquine / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000187:drug effects
D000590:Amino Acid Chloromethyl Ketones; D051017:Apoptosis Regulatory Proteins; D061945:Caspase Inhibitors; D002843:Chromatin; D009842:Oligopeptides; D011506:Proteins; C110772:benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C109664:caspase-activated DNase inhibitor; D001312:Aurintricarboxylic Acid; D006886:Hydroxychloroquine; D005047:Etoposide; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases