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

• Published in: Blood Vol. 101; no. 1; pp. 295 - 304
• Main Authors: Liu, Chien-Ying, Takemasa, Akihiro, Liles, W. Conrad, Goodman, Richard B., Jonas, Mechthild, Rosen, Henry, Chi, Emil, Winn, Robert K., Harlan, John M., Chuang, Peter I.
• Format: Journal Article
• Language: English
• Published: Washington, DC Elsevier Inc 01.01.2003; The Americain Society of Hematology
• Subjects: Biological and medical sciences; Case-Control Studies; Caspase Inhibitors; Cell Death - drug effects; Enzyme Inhibitors - pharmacology; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Humans; Immunobiology; Kinetics; Myeloid cells: ontogeny, maturation, markers, receptors; NADPH Oxidases - metabolism; Neutrophils - cytology; Neutrophils - drug effects; Oligopeptides - pharmacology; Polynuclears; Reactive Oxygen Species - metabolism; Tumor Necrosis Factor-alpha - pharmacology; Human; Fas ligand; Fas antigen; Enzyme; Cysteine endopeptidases; Cytokine; Granulocyte; Caspase; NADPH dehydrogenase; Peptidases; Tumor necrosis factor; Cell death; Hydrolases; Oxidoreductases; Neutrophil; Apoptosis
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2001-12-0266

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.