title: A role for the de novo sphingolipids in apoptosis of photosensitized cells.
abstract: Sphingolipids have been implicated in apoptosis after various stress inducers. To assess the involvement of the de novo sphingolipid pathway in apoptosis, photodynamic therapy (PDT) with the photosensitizer Pc 4 was used as a novel stress inducer. Here we provide biochemical and genetic evidence of the role of the de novo sphingolipids in apoptosis post-Pc 4-PDT. In Jurkat cells PDT-induced intracellular sphinganine accumulation, DEVDase activation, PARP cleavage, and apoptosis were suppressed by the de novo sphingolipid synthesis inhibitor ISP-1 (Myriocin). Coincubation with sphinganine, sphingosine, or C16-ceramide specifically reversed the antiapoptotic actions of ISP-1 or the singlet oxygen scavenger L-histidine. PDT-induced cytochrome c release from mitochondria into the cytosol was inhibited by L-histidine, but not by ISP-1. Cotreatment with sphinganine did not reverse the inhibitory effect of L-histidine. In addition, PDT-induced sphinganine accumulation and apoptosis were ISP-1-sensitive in A431 human epidermoid and HT29 human carcinoma cells. Furthermore, in LY-B cells, CHO-derived mutants deficient in the de novo sphingolipid synthesis enzyme serine palmitoyltransferase (SPT) activity, DEVDase activation and apoptosis were delayed and suppressed post-PDT. Hence, the data are consistent with the partial involvement of the de novo sphingolipid pathway in apoptosis via DEVDase activation downstream of mitochondrial cytochrome c release post-Pc 4-PDT.
authors.affiliation: Department of Occupational and Environmental Health Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Detroit Michigan 48201, USA.
authors.forename: Bambang
authors.initials: B
authors.lastname: Wispriyono
authors.forename: Eva
authors.initials: E
authors.lastname: Schmelz
authors.forename: Homer
authors.initials: H
authors.lastname: Pelayo
authors.forename: Kentaro
authors.initials: K
authors.lastname: Hanada
authors.forename: Duska
authors.initials: D
authors.lastname: Separovic
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000502:physiology; D000818:Animals; D017209:Apoptosis; D016466:CHO Cells; D002264:Carboxylic Acids / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D006224:Cricetinae; D003574:Cytochrome c Group / Q000378:metabolism; D005229:Fatty Acids, Monounsaturated / Q000037:antagonists & inhibitors / Q000494:pharmacology; D037341:Fumonisins; D006639:Histidine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D019169:Jurkat Cells; D007700:Kinetics; D008928:Mitochondria / Q000378:metabolism; D008956:Models, Chemical; D009369:Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051102:Serine C-Palmitoyltransferase; D013107:Sphingolipids / Q000494:pharmacology / Q000502:physiology*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D002264:Carboxylic Acids; D003574:Cytochrome c Group; D005229:Fatty Acids, Monounsaturated; D037341:Fumonisins; D007211:Indoles; D017319:Photosensitizing Agents; D013107:Sphingolipids; C107448:phthalocyanine Pc 4; C056933:fumonisin B1; D006639:Histidine; D000217:Acyltransferases; C495089:SPTLC2 protein, human; D051102:Serine C-Palmitoyltransferase; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases; D013110:Sphingosine; C005682:safingol; C001996:thermozymocidin