title: Apoptotic sphingolipid signaling by ceramides in lung endothelial cells.
abstract: The de novo pathway of ceramide synthesis has been implicated in the pathogenesis of excessive lung apoptosis and murine emphysema. Intracellular and paracellular-generated ceramides may trigger apoptosis and propagate the death signals to neighboring cells, respectively. In this study we compared the sphingolipid signaling pathways triggered by the paracellular- versus intracellular-generated ceramides as they induce lung endothelial cell apoptosis, a process important in emphysema development. Intermediate-chain length (C(8:0)) extracellular ceramides, used as a surrogate of paracellular ceramides, triggered caspase-3 activation in primary mouse lung endothelial cells, similar to TNF-alpha-generated endogenous ceramides. Inhibitory siRNA against serine palmitoyl transferase subunit 1 but not acid sphingomyelinase inhibited both C(8:0) ceramide- and TNF-alpha (plus cycloheximide)-induced apoptosis, consistent with the requirement for activation of the de novo pathway of sphingolipid synthesis. Tandem mass spectrometry analysis detected increases in both relative and absolute levels of C(16:0) ceramide in response to C(8:0) and TNF-alpha treatments. These results implicate the de novo pathway of ceramide synthesis in the apoptotic effects of both paracellular ceramides and TNF-alpha-stimulated intracellular ceramides in primary lung endothelial cells. The serine palmitoyl synthase-regulated ceramides synthesis may contribute to the amplification of pulmonary vascular injury induced by excessive ceramides.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Terry R
authors.initials: TR
authors.lastname: Medler
authors.forename: Daniela N
authors.initials: DN
authors.lastname: Petrusca
authors.forename: Patty J
authors.initials: PJ
authors.lastname: Lee
authors.forename: Walter C
authors.initials: WC
authors.lastname: Hubbard
authors.forename: Evgeny V
authors.initials: EV
authors.lastname: Berdyshev
authors.forename: Jarrett
authors.initials: J
authors.lastname: Skirball
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Kamocki
authors.forename: Edward
authors.initials: E
authors.lastname: Schuchman
authors.forename: Rubin M
authors.initials: RM
authors.lastname: Tuder
authors.forename: Irina
authors.initials: I
authors.lastname: Petrache
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism; D002478:Cells, Cultured; D002518:Ceramides / Q000737:chemistry / Q000378:metabolism*; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D008168:Lung / Q000166:cytology*; D051379:Mice; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051102:Serine C-Palmitoyltransferase / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013107:Sphingolipids / Q000378:metabolism*; D013108:Sphingomyelin Phosphodiesterase / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D002518:Ceramides; D034741:RNA, Small Interfering; D013107:Sphingolipids; D014409:Tumor Necrosis Factor-alpha; D051102:Serine C-Palmitoyltransferase; D013108:Sphingomyelin Phosphodiesterase; D053148:Caspase 3