title: Broad-spectrum caspase inhibition paradoxically augments cell death in TNF-alpha -stimulated neutrophils.
abstract: It is increasingly clear that there are caspase-dependent and -independent mechanisms for the execution of cell death and that the utilization of these mechanisms is stimulus- and cell type-dependent. Intriguingly, broad-spectrum caspase inhibition enhances death receptor agonist-induced cell death in a few transformed cell lines. Endogenously produced oxidants are causally linked to necroticlike cell death in these instances. We report here that broad-spectrum caspase inhibitors effectively attenuated apoptosis induced in human neutrophils by incubation with agonistic anti-Fas antibody or by coincubation with tumor necrosis factor-alpha (TNF-alpha) and cycloheximide ex vivo. In contrast, the same caspase inhibitors could augment cell death upon stimulation by TNF-alpha alone during the 6-hour time course examined. Caspase inhibitor-sensitized, TNF-alpha-stimulated, dying neutrophils exhibit apoptoticlike and necroticlike features. This occurred without apparent alteration in nuclear factor-kappaB (NF-kappaB) activation. Nevertheless, intracellular oxidant production was enhanced and sustained in caspase inhibitor-sensitized, TNF-alpha-stimulated neutrophils obtained from healthy subjects. However, despite reduced or absent intracellular oxidant production following TNF-alpha stimulation, cell death was also augmented in neutrophils isolated from patients with chronic granulomatous disease incubated with a caspase inhibitor and TNF-alpha. These results demonstrate that, in human neutrophils, TNF-alpha induces a caspase-independent but protein synthesis-dependent cell death signal. Furthermore, they suggest that TNF-alpha activates a caspase-dependent pathway that negatively regulates reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity.
authors.affiliation: Department of Medicine, Pathology, and Surgery, University of Washington, Seattle, USA.
authors.forename: Chien-Ying
authors.initials: CY
authors.lastname: Liu
authors.forename: Akihiro
authors.initials: A
authors.lastname: Takemasa
authors.forename: W Conrad
authors.initials: WC
authors.lastname: Liles
authors.forename: Richard B
authors.initials: RB
authors.lastname: Goodman
authors.forename: Mechthild
authors.initials: M
authors.lastname: Jonas
authors.forename: Henry
authors.initials: H
authors.lastname: Rosen
authors.forename: Emil
authors.initials: E
authors.lastname: Chi
authors.forename: Robert K
authors.initials: RK
authors.lastname: Winn
authors.forename: John M
authors.initials: JM
authors.lastname: Harlan
authors.forename: Peter I
authors.initials: PI
authors.lastname: Chuang
mesh_terms: D016022:Case-Control Studies; D061945:Caspase Inhibitors; D016923:Cell Death / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D019255:NADPH Oxidases / Q000378:metabolism; D009504:Neutrophils / Q000166:cytology* / Q000187:drug effects; D009842:Oligopeptides / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D009842:Oligopeptides; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; C103712:benzyloxycarbonyl-valyl-alanyl-aspartyl-fluoromethane; D019255:NADPH Oxidases