Broad-spectrum caspase inhibition paradoxically augments cell death in TNF-α–stimulated neutrophils

CY Liu, A Takemasa, WC Liles… - Blood, The Journal …, 2003 - ashpublications.org
CY Liu, A Takemasa, WC Liles, RB Goodman, M Jonas, H Rosen, E Chi, RK Winn…
Blood, The Journal of the American Society of Hematology, 2003ashpublications.org
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 …
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-α (TNF-α) and cycloheximide ex vivo. In contrast, the same caspase inhibitors could augment cell death upon stimulation by TNF-α alone during the 6-hour time course examined. Caspase inhibitor–sensitized, TNF-α–stimulated, dying neutrophils exhibit apoptoticlike and necroticlike features. This occurred without apparent alteration in nuclear factor–κB (NF-κB) activation. Nevertheless, intracellular oxidant production was enhanced and sustained in caspase inhibitor-sensitized, TNF-α–stimulated neutrophils obtained from healthy subjects. However, despite reduced or absent intracellular oxidant production following TNF-α stimulation, cell death was also augmented in neutrophils isolated from patients with chronic granulomatous disease incubated with a caspase inhibitor and TNF-α. These results demonstrate that, in human neutrophils, TNF-α induces a caspase-independent but protein synthesis–dependent cell death signal. Furthermore, they suggest that TNF-α activates a caspase-dependent pathway that negatively regulates reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity.
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