title: Ceramide accumulation precedes caspase-3 activation during apoptosis of A549 human lung adenocarcinoma cells.
abstract: Ceramide, the basic structural unit of sphingolipids, controls the balance between cell growth and death by inducing apoptosis. We have previously shown that accumulation of ceramide, triggered by hydrogen peroxide (H(2)O(2)) or by short-chain ceramide analogs, induces apoptosis of lung epithelial cells. Here we elucidate the link between caspase-3 activation, at the execution phase, and ceramide accumulation, at the commitment phase of apoptosis in A549 human lung adenocarcinoma cells. The induction of ceramide accumulation by various triggers of ceramide generation, such as H(2)O(2), C(6)-ceramide, or UDP-glucose-ceramide glucosyltransferase inhibitor dl-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol, triggered the activation of caspase-3. This ceramide elevation also induced the cleavage of the death substrate poly(ADP-ribose) polymerase and was followed by apoptotic cell death. Ceramide-mediated apoptosis was blocked by a general caspase inhibitor, Boc-d-fluoromethylketone, and by overexpression of the antiapoptotic protein Bcl-2. Notably, overexpression of Bcl-2 reduced the basal cellular levels of ceramide and prevented the induction of ceramide generation by C(6)-ceramide, which implies ceramide generation as a possible target for the antiapoptotic effects of Bcl-2.
authors.affiliation: Center for Comparative Respiratory Biology and Medicine, Department of Internal Medicine, University of California, Davis, California 95616, USA. ttgoldkorn@ucdavis.edu
authors.forename: Tommer
authors.initials: T
authors.lastname: Ravid
authors.forename: Adili
authors.initials: A
authors.lastname: Tsaba
authors.forename: Peter
authors.initials: P
authors.lastname: Gee
authors.forename: Reuven
authors.initials: R
authors.lastname: Rasooly
authors.forename: Edward A
authors.initials: EA
authors.lastname: Medina
authors.forename: Tzipora
authors.initials: T
authors.lastname: Goldkorn
mesh_terms: D000230:Adenocarcinoma; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D002518:Ceramides / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008175:Lung Neoplasms; D009025:Morpholines / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D002518:Ceramides; D004791:Enzyme Inhibitors; D009025:Morpholines; D016877:Oxidants; D019253:Proto-Oncogene Proteins c-bcl-2; C101954:N-caproylsphingosine; C033110:RV 538; D006861:Hydrogen Peroxide; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases