title: Tumor necrosis factor alpha induces a caspase-independent death pathway in human neutrophils.
abstract: Tumor necrosis factor alpha (TNF-alpha) is a cytokine with multiple roles in the immune system, including the induction and potentiation of cellular functions in neutrophils (PMNs). TNF-alpha also induces apoptotic signals leading to the activation of several caspases, which are involved in different steps of the process of cell death. Inhibition of caspases usually increases cell survival. Here, we found that inhibition of caspases by the general caspase inhibitor zVAD-fmk did not prevent TNF-alpha-induced PMN death. After 6 hours of incubation, TNF-alpha alone caused PMN death with characteristic apoptotic features (typical morphologic changes, DNA laddering, external phosphatidyl serine [PS] exposure in the plasma membrane, Bax clustering and translocation to the mitochondria, and degradation of mitochondria), which coincided with activation of caspase-8 and caspase-3. However, in the presence of TNF-alpha, PMNs died even when caspases were completely inhibited. This type of cell death lacked nuclear features of apoptosis (ie, no DNA laddering but aberrant hyperlobulated nuclei without typical chromatin condensation) and demonstrated no Bax redistribution, but it did show mitochondria clustering and plasma membrane PS exposure. In contrast, Fas-triggered PMN apoptosis was completely blocked by zVAD-fmk. Experiments with scavengers of reactive oxygen species (ROS) and with inhibitors of mitochondrial respiration, with PMN-derived cytoplasts (which lack mitochondria) and with PMNs from patients with chronic granulomatous disease (which have impaired nicotinamide adenine dinucleotide phosphate [NADPH] oxidase) indicated that TNF-alpha/zVAD-fmk-induced cell death depends on mitochondria-derived ROS. Thus, TNF-alpha can induce a "classical," caspase-dependent and a "nonclassical" caspase-independent cell death.
authors.affiliation: Sanquin Research at Central Laboratory of the Netherlands Blood Transfusion Service, Landsteiner Laboratory, and Emma Children's Hospital, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Nikolai A
authors.initials: NA
authors.lastname: Maianski
authors.forename: Dirk
authors.initials: D
authors.lastname: Roos
authors.forename: Taco W
authors.initials: TW
authors.lastname: Kuijpers
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017304:Annexin A5 / Q000032:analysis; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D002478:Cells, Cultured / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D053938:DNA Fragmentation; D004789:Enzyme Activation; D016166:Free Radical Scavengers / Q000494:pharmacology; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019255:NADPH Oxidases / Q000502:physiology; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects*; D018384:Oxidative Stress; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein; D019014:fas Receptor / Q000276:immunology / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D017304:Annexin A5; D000911:Antibodies, Monoclonal; C494826:BAX protein, human; D015853:Cysteine Proteinase Inhibitors; D016166:Free Radical Scavengers; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D051028:bcl-2-Associated X Protein; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; D019255:NADPH Oxidases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases