Ceramide apoptosis

A variety of studies demonstrate a central role for ASM and ceramide in several forms of apoptosis. Ceramide seems to regulate the activity of certain proteins and, thus, may function, in some circumstances, as a second messenger. In addition, the concept of raft modification hy ceramide provides a comprehensive model for cellular effects of ceramide, and perhaps a biophysical explanation for the diverse functions of this lipid. 

Gamard, C.J.L., Dbaibo, G.S., Liu, B., Obeid, L.M. and Hannun, Y.A., 1997, Selective involvement of ceramide in cytoMne-induced apoptosis. Ceramide irrhibits phorbol ester activation of nuclear factor kappaB. J. Biol Chem., 272 16474-16481. 

Keywords Apoptosis ceramide drug resistance cancer therapeutics sphingolipids... 

Gulbins, E. Regulation of death receptor signaling and apoptosis by ceramide. Pharmacol. Res. 47 393-399,2003. 

Once apoptosis is triggered, a stereotyped sequence of premitochondrial events occurs that executes the cell death process. In many cases proteins and/or lipid mediators that induce changes in mitochondrial membrane permeability and calcium regulation are produced or activated. For example, the pro-apoptotic Bcl-2 family members Bax, Bad and Bid may associate with the mitochondrial membrane and modify its permeability. Membrane-derived lipid mediators such as ceramide and 4-hydroxynonenal can also induce mitochondrial membrane alterations that are critical for the execution of apoptosis. 

Tepper, A.D., Ruurs, P., Wiedmer, T, Sims, PJ., Borst, J. and van Bhtterswijk, W.J., 2000, Sphingomyelin hydrolysis to ceramide during the execution phase of apoptosis results from phospholipid scrambling and alters cell-surface morphology. J. Cell Biol., 150 F5-7. 

This ceramide-mediated apoptosis was shown to be inhibited by the simultaneous addition of PKC activators (Ni et at, 1994 Obeid et al, 1993), implying that PS may activate the ceramide-mediated apoptotic pathway. However, the inhibitors of interleukin-1 converting enzyme (ICE)-like proteases (Caspase), such as tosyl-L-lysine chloromethyl ketone (TLCK), and tosyl-L-phenylalanine chloromethyl ketone (TPCK) which inhibit ceramide-mediated apoptosis, had no effect on PS-induced apoptosis (Figure 4). Thus, PS-induced apoptotic pathway appears to be distinct from that mediated by ceramide. Further studies are required to clarify the molecular mechanisms underlying the PS-induced apoptosis. 

Bose, R., Verheij, M., Haimovitz-Friedman, A., Scotto, K., Fuks, Z., and Kolesnick, R., 1995, Ceramide synthase mediates daunombicin-induced apoptosis an alternative mechanism for generating death signals. Cell 82 405-414. 

EscargueU-Blanc, 1., Andrieu-Abadie, N., Caspar-BauguU, S., Brossmer, R., Levade, T, Negre-Salvayre, A., and Salvayre, R., 1998, Apoptosis and activation of the sphingomyehn-ceramide pathway induced by oxidizedLDL are not causally related in ECV-304 endothelial ceUs, J. Biol. Chem. 273 27389-27395. 

Monney, L., Ohvier, R., Otter, 1., Jansen, B., Poirier, GG., and Bomer, C., 1998, Role ofan acidic compartment in tumor-necrosis-factor-a-induced production of ceramide, activation of caspase-3 and apoptosis. Eur. J. Biochem. 251 295-303 Morrison, H., Jemstrom, B., Nordenskjdld, M., Thor, H., and Orrenius, S., 1984, Induction of DNA damage by menadione (2-methyl-l,4-naphthoquinone) in primary cultures of rat hepatocytes. Biochem. Pharmacol. 33 1763-1769 Neuzil, J., Svensson, 1., Weber, T, Weber, C., and Brunk, U.T., 1999, alpha-tocopheryl succinate-induced apoptosis in Jurkat T cells involves caspase-3 activation, and both lysosomal and mitochondrial destabilisation. FEES Lett. 445 295-300 Ngo, E.O., Nutter, L.M., Sura, T., and Gutierrez, P. L., 1998, Induction ofp53 by the... 

Ceramide has been shown to activate serine/threonine protein phosphatase termed CAPP (Dobrowsky and Hannun, 1992), and multiple lines of evidence point to an important role for these phosphatases in mediating apoptosis in response to ceramide in mammalian cells (Dobrowsky et al., 1993 Wolff et al., 1994 Reyes et al. 1996) and in... 

Kroesen, B., Pettus, B., Luberto, C., Busman, M., Sietsma, H., De Leij, L., and Hannun, Y.A., 2001, Induction of apoptosis through B-ceU receptor crosslinking occurs via de novo generated C16 ceramide and involves mitochondria. J. Biol. Chem. pubhshed January 17, 2001 as 10.1074/jbc.M009517200. 

Mizushima, N., Koike, R., Kohsaka, H., Kushi, Y., Handa S., Yagita, H., Miyasaka, N., 1996, Ceramide induces apoptosis via CPP32 activation. FEES Lett. 395 267-271. 

Perry, D.K., Carton, J., Shah, A.K., Meredith, F., Uhlinger, D.J., and Hannun, Y.A., 2000, Serine palmitoyltransferase regulates de novo ceramide generation during etoposide-induced apoptosis. J. Biol. Chem. 275 9078-9084. 

Wiesner, D.A., Kilkus, J.P., Gottschalk, A.R., Quint j ns, J. and Dawson, G., 1997, Antiimmunoglobulin-induced apoptosis in WEHI231 cells involves the slow formation of ceramide from sphingomyelin and is blocked by bcl-XL. J. Biol. Chem. 272 9868-9876. 

Effect of Ceramides on Phospholipid Biosynthesis and Its Implication for Apoptosis... 

It should be noted here that the synthesis of sphingomyelin, the lipid whose synthesis and breakdown are most intricately involved in the process of apoptosis, is dependent on the presence of PC, since the final step in SM synthesis involves the exchange of the phosphocholine head group from PC to ceramide (see Eigure 1). Theoretically, therefore, inhibition of PC synthesis may lead to an inhibition of SM generation and an accumulation of pro-apoptotic ceramides. On the other hand, an increased breakdown of SM by SMases as frequently observed in apoptotic cells, was shown to increase the conversion of PC to anti-apoptotic DAG (Sillence and Allan, 1998, for anti-apoptotic action of DAG see below). 

Recently, it has been shown that cell-permeable cerantides dramatically inhibited the synthesis of the two major membrane phospholipids, PC and PE (Bladergroen et al, 1999b Allan, 2000). The inhibition of phospholipid synthesis was rapid, within 2 h, and resulted in massive apoptosis after 16-24 h. The mechanism by which short-chain cerantides exert their effect on phospholipid synthesis is possibly cell type dependent. In baby-hamster kidney (BHK) fibroblasts rc synthesis was reduced at the level of CT, the putative rate-determining enzyme in the CDP-choline pathway (Allan, 2000). This conclusion was based solely on radio-label studies in combination with an earlier published observation (Wieder et al, 1995) showing that C2-SM (the SM generated from C2-ceramide by SM synthase, which was actively synthesized in the BHK-cells) inhibited CT activity in vitro. On the other hand, data obtained from studies with rat-2 fibroblasts clearly showed that short-chain cerantides regulate the synthesis of PC and PE mainly at the final step of the CDP-pathways. This conclusion was based on the following observations (a) incorporation of [ H]-choline into PC and... 

Deaeased PC and PE synthesis by ceramides in combination with the observations that inhibition of PC synthesis induces apoptosis, suggests that in some cell types the effect of ceramides on apoptosis may be exerted at least in part via a disturbance in PC synthesis (see also Section 3). 

Treatment of Rat-2 fibroblasts with various cell-permeable ceramides resulted, as discussed above, in a rapid inhibition of phospholipid synthesis. An intriguing observation was that C2-ceramides inhibited PC biosynthesis without affecting the synthesis of PE via the CDP-ethanolamine route. C2-ceramide are well known inducers of apoptosis and inhibit DNA- and protein synthesis (Obeid et al, 1993 Jayadev et al, 1995). C2-ceramide induced apoptosis in the rat-2 fibroblasts (Houweling et al, unpublished data), suggesting that inhibition of PE biosynthesis is not a prerequisite for apoptosis. 

A recent report suggests that inhibition of PC synthesis constitutes one of the primary events by which C2-ceramide triggers apoptosis (Ramos et al, 2000). Treatment of cerebral granule neurons with C2-ceramide resulted in a rapid (within 1 hour) reduction in PC biosynthesis, whereas only 6 h after exposure to the agonists the first significant drop in cell viability was observed. The authors further showed that addition of exogenous PC resulted in a dose-dependent full prevention of neuronal death. This was specific for PC, because addition of other glycerohpids Uke, PE, PS, phosphatidylinositol and phosphatidic acid had no effect on C2-ceramide-induced apoptosis. 

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