title: Down-regulation of ceramide production abrogates ionizing radiation-induced cytochrome c release and apoptosis.
abstract: Previous work has demonstrated that down-regulation of ceramide production after selection of cells with N-oleoylethanolamine (OE), an inhibitor of ceramidase, results in resistance to DNA damage-induced apoptosis. We report here that acute exposure of WEHI-231 cells (murine B-cell lymphoma) to OE activates neutral sphingomyelinase, induces ceramide production and increases intracellular reactive oxygen species. OE exposure also induces mitochondrial permeability, cytochrome c release, and apoptosis. Cells selected for resistance to OE exhibit little if any change in reactive oxygen species and cytochrome c release when exposed either to OE or to toxic doses of ceramide. Importantly, the OE resistant cells are also resistant to ionizing radiation-induced cytochrome c release and apoptosis. These findings demonstrate that down-regulation of neutral sphingomyelinase activity is associated with decreased DNA-damage-induced apoptosis. In addition, the data suggests that agents that modify extranuclear targets responsible for ceramide production select for cells resistant to ionizing radiation-induced apoptosis through alterations in mitochondrial function.
authors.affiliation: Department of Radiation and Cellular Oncology, Division of Biological Sciences, University of Chicago, Chicago, IL 60637, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Chmura
authors.forename: E
authors.initials: E
authors.lastname: Nodzenski
authors.forename: S
authors.initials: S
authors.lastname: Kharbanda
authors.forename: P
authors.initials: P
authors.lastname: Pandey
authors.forename: J
authors.initials: J
authors.lastname: Quintans
authors.forename: D W
authors.initials: DW
authors.lastname: Kufe
authors.forename: R R
authors.initials: RR
authors.lastname: Weichselbaum
mesh_terms: D000818:Animals; D017209:Apoptosis; D002518:Ceramides / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism*; D015536:Down-Regulation; D063388:Endocannabinoids; D004789:Enzyme Activation / Q000528:radiation effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004983:Ethanolamines / Q000494:pharmacology; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D009829:Oleic Acids; D010539:Permeability; D011839:Radiation, Ionizing; D013108:Sphingomyelin Phosphodiesterase / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000528:radiation effects; D014407:Tumor Cells, Cultured
chemical_list: D002518:Ceramides; D003574:Cytochrome c Group; D063388:Endocannabinoids; D004791:Enzyme Inhibitors; D004983:Ethanolamines; D009829:Oleic Acids; C033595:N-oleoylethanolamine; D013108:Sphingomyelin Phosphodiesterase