title: Cell line dependent involvement of ceramide in ultraviolet light-induced apoptosis.
abstract: Ultraviolet light (UV) activates an acid sphingomyelinase (ASMase) pathway, which hydrolyzes sphingomyeline to ceramide. Ceramide has been found to be a second messenger, which activates the c-jun N-terminal kinase (JNK) that is required for apoptotic cell death. However, the role of ceramide in UV-induced JNK activation and apoptosis remains controversial. In this study, we examined the correlation among ceramide production, JNK activation and cell apoptosis after UV-irradiation in three cell lines: 293 (kidney), Jurkat (lymphocytes) and MCF-7 (breast) were used in this study. The ceramide production was analyzed using the diacylglycerol kinase assay method. The JNK activation was measured by Western blot analysis using an antibody specifically recognizing phosphorylated JNK. Cell apoptosis was determined by morphological change or flow cytometry. Our data show that UV-irradiation induces ceramide production in both 293 and Jurkat cells. Inhibition of ceramide production by desipramine (25-50 microM) reduced UV-induced JNK activation in both 293 and Jurkat cells; and protects 293 cells from UV-induced apoptosis. However, inhibition of ceramide production does not prevent Jurkat cells from UV-induced apoptosis. In addition, our data demonstrates that UV-irradiation induces JNK activation and apoptosis of MCF-7 cells without production of detectable amounts of ceramide after UV-irradiation. These results suggest that UV-induced JNK activation and apoptosis can be mediated through a ceramide dependent or an independent pathway.
authors.affiliation: Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor 48109, USA.
authors.forename: M
authors.initials: M
authors.lastname: Chatterjee
authors.forename: S
authors.initials: S
authors.lastname: Wu
mesh_terms: D017209:Apoptosis / Q000528:radiation effects*; D002460:Cell Line; D002518:Ceramides / Q000378:metabolism*; D003891:Desipramine / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D019169:Jurkat Cells; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays
chemical_list: D002518:Ceramides; D004791:Enzyme Inhibitors; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D013108:Sphingomyelin Phosphodiesterase; D003891:Desipramine