n-caproylsphingosine and benzyloxycarbonylvalyl-alanyl-aspartyl-fluoromethyl-ketone

C(6)-pyridinium (D-erythro-2-N-[6'-(1''-pyridinium)-hexanoyl]sphingosine bromide [LCL29]) is a cationic mitochondrion-targeting ceramide analog that promotes mitochondrial permeabilization and cancer cell death. In this study, we compared the biological effects of that compound with those of D-erythro-C(6)-ceramide, its non-mitochondrion-targeting analog. In MCF7 cells it was found that C(6)-pyridinium ceramide preferentially promoted autophagosome formation and retarded cell growth more extensively than its uncharged analog. This preferential inhibition of cell growth was also observed in breast epithelial cells and other breast cancer cells. In addition, this compound could promote Bax translocation to mitochondria. This redistribution of Bax in MCF7 cells could be blocked by the pan-caspase inhibitor zVAD-fmk but via a Bid-independent signaling pathway. Moreover, C(6)-pyridinium ceramide-induced translocation of Bax to mitochondria led to mitochondrial permeabilization and cell death. Overall, we show that mitochondrial targeting of C(6)-pyridinium ceramide significantly enhances cellular response to this compound.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; Autophagy; bcl-2-Associated X Protein; Caspases; Cells, Cultured; Ceramides; Growth Inhibitors; Humans; Mitochondria; Pyridinium Compounds

Sphingolipid metabolites are important regulators of cell growth and apoptosis. To clarify the biological roles of cell surface sialylation in the effects of sphingomyelinase (SM) treatment on cell viability, the human diffuse large B cell lymphoma cell line, HBL-2 with or without treatment with Vibrio cholerae neuraminidase, was incubated with exogenous bacterial SM which is a key enzyme of ceramide production from sphingolipids in cell membranes. SM treatment enhanced viability of HBL-2 cells compared to non-treatment after 6 h of incubation. On the other hand, viability of HBL-2 cells was decreased by SM treatment with neuraminidase pre-treatment after 6 and 24 h of incubation, and ceramide production on cell surfaces of SM treated cells was enhanced by neuraminidase treatment as shown by flow cytometric analysis. Furthermore, treatment with D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol, an inhibitor which specifically reduces the activity of UDP-glucose:ceramide glucosyltransferase in combination with SM treatment, causes the viability of HBL-2 cells to be decreased more with neuraminidase pre-treatment than without it. Exogenous C6-ceramide induced HBL-2 cell death, and there was no difference in the effects of C6-ceramide after 6 h of incubation between treatment and non-treatment with neuraminidase. Together these data suggest that alteration in susceptibility of HBL-2 cells to SM by neuraminidase treatment may precede the process of ceramide production, and that cell death through the activation of SM, which induces ceramide production, is regulated by cell surface sialylation in DLBCL.

Topics: Amino Acid Chloromethyl Ketones; Biotinylation; Cell Death; Cell Line, Tumor; Cell Membrane; Cell Survival; Ceramides; Enzyme Inhibitors; Flow Cytometry; Glucose; Glucosyltransferases; Humans; Lectins; Lymphoma; Lymphoma, B-Cell; Lymphoma, Non-Hodgkin; Models, Biological; Neuraminidase; Sialic Acids; Sphingomyelin Phosphodiesterase; Temperature; Time Factors; Uridine Diphosphate

Ceramide is an important lipid messenger involved in mediating a variety of cell functions including apoptosis. In this study, we show that antisense bax inhibits cytochrome c release, poly(ADP-ribose)polymerase cleavage and cell death induced by ceramide in HL-60 cells. In addition, ceramide induces translocation of Bax to mitochondria. The addition of the broad spectrum caspase inhibitor zVAD-fmk prevented ceramide-induced apoptotic cell death but did not inhibit translocation of Bax and mitochondrial cytochrome c release. Furthermore, ceramide inhibits the expression of the antiapoptotic protein Bcl-xL with an increase in the ratio of Bax to Bcl-xL. These data provide direct evidence that Bax plays an important role in regulating ceramide-induced apoptosis.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; bcl-2-Associated X Protein; bcl-X Protein; Blotting, Western; Caspases; Cell Death; Cell Survival; Ceramides; Cytochrome c Group; DNA Fragmentation; Down-Regulation; Enzyme Inhibitors; HL-60 Cells; Humans; Mitochondria; Oligonucleotides; Poly(ADP-ribose) Polymerases; Protein Transport; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Subcellular Fractions; Time Factors

We investigated whether cell-permeable, synthetic ceramide (C6 ceramide) could induce apoptosis in Fas-resistant Hodgkin's disease (HD)-derived cell lines. Despite strongly expressing the Fas-receptor, two of three HD-derived cell lines were resistant to Fas-mediated apoptosis. This resistance to Fas could not be attributed to differential Fas isoform generation patterns between the Fas-resistant and the Fas-sensitive cell lines. The Fas-resistant cell lines did not demonstrate the presence of Fas exon 8 deletion. Bcl-2 and BclxL levels were comparable between the Fas-resistant and the Fas-sensitive cell lines. C6 ceramide could induce apoptosis in both Fas-resistant cell lines and this was associated with a decrease in BclxL level. Caspase-1, caspase-3, or pan-caspase inhibitors could not prevent ceramide-induced apoptosis. Furthur, ceramide treatment did not lead to cleavage of caspase 3 or poly(ADP-ribose) polymerase, but caused a loss in mitochondrial transmembrane potential which could not be prevented by caspase inhibitors. Thus, we conclude that ceramide-induced apoptosis in Fas-resistant HD cell lines is caspase independent.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; bcl-X Protein; Caspase 1; Caspase 3; Caspase Inhibitors; Caspases; CD40 Antigens; Cell Membrane Permeability; Ceramides; Cysteine Proteinase Inhibitors; Enzyme Inhibitors; Fas Ligand Protein; fas Receptor; Gene Expression; Hodgkin Disease; Humans; Membrane Glycoproteins; Okadaic Acid; Oligopeptides; Poly(ADP-ribose) Polymerases; Proto-Oncogene Proteins c-bcl-2; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured; Up-Regulation

It is not well appreciated that nutritional status can modulate apoptosis, a process that eliminates unwanted or damaged cells. Choline is an essential nutrient, and its absence induces apoptosis. When PC12 cells were cultivated in a choline-free medium, apoptosis was induced (27.4% of cells apoptotic at 72 h as compared to 4.4% in control medium). In choline-free medium at 72 h, there was a 49% decrease in phosphatidylcholine concentration (P<0.01) and a 34% decrease in sphingomyelin concentration (P<0.01); however, there was no change in phosphatidylethanolamine concentration. Before detecting increased apoptosis in choline-deficient cells, we measured a significant increase in ceramide (218% control) and diacyglycerol (155% control) concentrations. The addition of a cell-permeable ceramide to cells in control medium induced apoptosis; however, adding a cell-permeable diacyglycerol did not induce apoptosis. Caspase is a common mediator of apoptosis, and choline deficiency-induced apoptosis was prevented completely by replacing choline or adding a caspase inhibitor into the medium within 48 h of initial choline deprivation. In those cells rescued by replacing choline at 36 h, the concentrations of phosphatidylcholine, sphingomyelin, ceramide, and diacyglycerol returned to levels of control cells. In those cells rescued by adding a caspase inhibitor at 36 h, the concentrations of sphingomyelin and ceramide returned to control levels, but the concentrations of phosphatidylcholine and diacyglycerol did not return to normal. We propose that availability of dietary factors (choline in this model) can modulate apoptosis. Mechanisms that we identify using this model may help us to explain why dietary choline influences brain development.

Topics: Amino Acid Chloromethyl Ketones; Animals; Apoptosis; Cell Membrane; Ceramides; Choline; Cysteine Proteinase Inhibitors; Diglycerides; Enzyme Activation; PC12 Cells; Phosphatidylcholines; Rats; Sphingomyelins