Caspase inhibition switches the mode of cell death induced by cyanide by enhancing reactive oxygen species generation and PARP-1 activation.
Execution of apoptosis can involve activation of the caspase family of proteases. Recent studies show that caspase inhibition can switch the morphology of cell death from apoptotic to necrotic without altering the level of death among cell populations. In the present study, the effect of caspase inhibition on cortical (CX) cell death induced by cyanide was investigated. In primary cultured CX cells exposed to cyanide (400 microM), death was primarily apoptotic as indicated by positive TUNEL staining. Reactive oxygen species (ROS) generation and subsequent caspase activation mediated the apoptosis. Inhibition of the caspase cascade with zVAD-fmk switched the apoptotic response to necrotic cell death, as assessed by increased cellular efflux of LDH and propidium iodide uptake by the cells. The change in death mode was accompanied by a marked increase in poly (ADP-ribose) polymerase-1 (PARP-1) activity, reactive oxygen species (ROS) generation, a reduction in the mitochondrial membrane potential (Delta psi(m)), and reduced cellular ATP. Prior treatment of cells with 3-aminobenzamide (3-AB), a PARP-1 inhibitor, prevented the cells from undergoing necrosis and preserved intracellular ATP levels. These findings indicate that apoptosis and necrosis share common initiation pathways and caspase inhibition can switch the apoptotic response to necrosis. Inhibition of PARP-1 preserves cellular ATP levels and in turn blocks execution of the necrotic death pathway.
Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907-1333, USA.
Krishnan
K
Prabhakaran
Li
L
Li
Joseph L
JL
Borowitz
Gary E
GE
Isom
D000255:Adenosine Triphosphate / Q000378:metabolism; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D053148:Caspase 3; D061945:Caspase Inhibitors; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000196:embryology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004789:Enzyme Activation; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D011190:Potassium Cyanide / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism*
D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D017382:Reactive Oxygen Species; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D000255:Adenosine Triphosphate; D011065:Poly(ADP-ribose) Polymerases; C505410:Casp3 protein, rat; D053148:Caspase 3; D011190:Potassium Cyanide