Abstract
Ceramide has recently been regarded as a potential mediator of apoptosis. In the present study, the effects of Bcl-2 and Bax on the ceramide-mediated apoptotic pathways were examined in glioma cells overexpressing Bcl-2 or Bax. Etoposide, cisplatin and tumor necrosis factor-alpha induced apoptosis of C6 rat glioma cells which was associated with ceramide formation due to activation of neutral sphingomyelinase, followed by release of mitochondrial cytochrome c into the cytosol and activation of caspases-9 and -3. The growth of C6 cells stably overexpressing either Bcl-2 or Bax was almost equal to that of the vector-transfected cells. Bax overexpression enhanced etoposide-induced apoptosis through acceleration of cytochrome c release and caspases activation. However, Bax had no effect on ceramide formation. Similar findings were obtained in C6 cells and U87-MG human glioblastoma cells which were transiently overexpressed with Bax. In contrast, Bcl-2 overexpression resulted in a retardation of the apoptotic process via prevention of cytochrome c release and caspases activation, and ceramide formation was also blocked when Bcl-2 was highly overexpressed in glioma cells. In addition, transient overexpression of Bcl-xL also exerted inhibitory effects on ceramide formation and apoptotic cell death induced by etoposide. These results indicate that Bax promotes apoptosis regardless of ceramide formation and that Bcl-2 or Bcl-xL prevents ceramide formation by repressing neutral sphingomyelinase as well as ceramide-induced cytochrome c release. Oncogene (2000) 19, 3508 - 3520
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Animals
-
Apoptosis / drug effects
-
Apoptosis / genetics*
-
Apoptosis / physiology
-
Brain Neoplasms / genetics
-
Brain Neoplasms / metabolism
-
Brain Neoplasms / pathology*
-
Caspases / metabolism
-
Ceramides / physiology*
-
Cisplatin / pharmacology
-
Culture Media, Serum-Free / pharmacology
-
Cytochrome c Group / metabolism
-
Enzyme Activation
-
Etoposide / pharmacology
-
Gene Expression Regulation, Neoplastic*
-
Genes, bcl-2
-
Glioblastoma / genetics
-
Glioblastoma / metabolism
-
Glioblastoma / pathology*
-
Glioma / genetics
-
Glioma / metabolism
-
Glioma / pathology*
-
Humans
-
Mitochondria / enzymology
-
Neoplasm Proteins / biosynthesis
-
Neoplasm Proteins / genetics
-
Neoplasm Proteins / physiology*
-
Proto-Oncogene Proteins / biosynthesis
-
Proto-Oncogene Proteins / genetics
-
Proto-Oncogene Proteins / physiology*
-
Proto-Oncogene Proteins c-bcl-2 / biosynthesis
-
Proto-Oncogene Proteins c-bcl-2 / genetics
-
Proto-Oncogene Proteins c-bcl-2 / physiology*
-
Rats
-
Recombinant Fusion Proteins / physiology
-
Sphingomyelin Phosphodiesterase / metabolism
-
Transfection
-
Tumor Cells, Cultured / drug effects
-
Tumor Cells, Cultured / metabolism
-
Tumor Cells, Cultured / pathology
-
Tumor Necrosis Factor-alpha / pharmacology
-
bcl-2-Associated X Protein
-
bcl-X Protein
Substances
-
BAX protein, human
-
BCL2L1 protein, human
-
Bax protein, rat
-
Bcl2l1 protein, rat
-
Ceramides
-
Culture Media, Serum-Free
-
Cytochrome c Group
-
Neoplasm Proteins
-
Proto-Oncogene Proteins
-
Proto-Oncogene Proteins c-bcl-2
-
Recombinant Fusion Proteins
-
Tumor Necrosis Factor-alpha
-
bcl-2-Associated X Protein
-
bcl-X Protein
-
Etoposide
-
Sphingomyelin Phosphodiesterase
-
Caspases
-
Cisplatin