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.
Department of Immunology and Rheumatology, Sydney Children's Hospital and School of Paediatrics, The University of New South Wales, Randwick, Australia.
X W
XW
Meng
M J
MJ
Fraser
J M
JM
Feller
J B
JB
Ziegler
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