title: Ceramide mediates caspase-independent programmed cell death.
abstract: Although numerous studies have implicated the sphingolipid ceramide in the induction of cell death, a causative function of ceramide in caspase-dependent apoptosis remains a highly debated issue. Here, we show that ceramide is a key mediator of a distinct route to programmed cell death (PCD), i.e., caspase-independent PCD. Under conditions where apoptosis is either not initiated or actively inhibited, TNF induces caspase-independent PCD in L929 fibrosarcoma cells, NIH3T3 fibroblasts, human leukemic Jurkat T cells, and lung fibroblasts by increasing intracellular ceramide levels prior to the onset of cell death. Survival is significantly enhanced when ceramide accumulation is prevented, as demonstrated in fibroblasts genetically deficient for acid sphingomyelinase, in L929 cells overexpressing acid ceramidase, by pharmacological intervention, or by RNA interference. Jurkat cells deficient for receptor-interacting protein 1 (RIP1) do not accumulate ceramide and therefore are fully resistant to caspase-independent PCD whereas Jurkat cells overexpressing the mitochondrial protein Bcl-2 are partially protected, implicating RIP1 and mitochondria as components of the ceramide death pathway. Our data point to a role of caspases (but not cathepsins) in suppressing the ceramide death pathway under physiological conditions. Moreover, clonogenic survival of tumor cells is clearly reduced by induction of the ceramide death pathway, promising additional options for the development of novel tumor therapies.
authors.affiliation: Institut für Immunologie, Universitätsklinikum Schleswig-Holstein Campus Kiel, Kiel, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Thon
authors.forename: Heike
authors.initials: H
authors.lastname: Möhlig
authors.forename: Sabine
authors.initials: S
authors.lastname: Mathieu
authors.forename: Arne
authors.initials: A
authors.lastname: Lange
authors.forename: Elena
authors.initials: E
authors.lastname: Bulanova
authors.forename: Supandi
authors.initials: S
authors.lastname: Winoto-Morbach
authors.forename: Stefan
authors.initials: S
authors.lastname: Schütze
authors.forename: Silvia
authors.initials: S
authors.lastname: Bulfone-Paus
authors.forename: Dieter
authors.initials: D
authors.lastname: Adam
mesh_terms: D000818:Animals; D017209:Apoptosis; D016227:Benzoquinones; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D002518:Ceramides / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D019169:Jurkat Cells; D047029:Lactams, Macrocyclic; D008168:Lung / Q000378:metabolism; D008564:Membrane Potentials; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D041681:NIH 3T3 Cells; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011809:Quinones / Q000494:pharmacology; D034622:RNA Interference; D017382:Reactive Oxygen Species; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D016227:Benzoquinones; D002518:Ceramides; D047029:Lactams, Macrocyclic; D011809:Quinones; D017382:Reactive Oxygen Species; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins; D014409:Tumor Necrosis Factor-alpha; D017346:Protein Serine-Threonine Kinases; C506249:RIPK1 protein, human; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C506251:Ripk1 protein, mouse; C112980:acid sphingomyelinase-1; D013108:Sphingomyelin Phosphodiesterase; D020169:Caspases; C001277:geldanamycin