Apoptosis and Activation of the Sphingomyelin-Ceramide Pathway Induced by Oxidized Low Density Lipoproteins Are Not Causally Related in ECV-304 Endothelial Cells

• DOI: 10.1074/jbc.273.42.27389
• Publication Date: 2002-07-26T15:02:22Z
• Authors: Isabelle Escargue...; Nathalie Andrieu-...; Sylvie Caspar-Bau...; Reinhard Brossmer; Thierry Levade; Anne Nègre-Salvayre; Robert Salvayre
• Keywords: 0301 basic medicine; Umbilical Veins; Serine Proteinase Inhibitors; Arteriosclerosis; Hydrolysis; Apoptosis; Ceramides; Cell Line; Sphingomyelins; 3. Good health; Lipoproteins, LDL; 03 medical and health sciences; Sphingomyelin Phosphodiesterase; Sphingosine; Humans; Calcium; Endothelium, Vascular; Cell Division; Signal Transduction

Oxidized low density lipoproteins (oxLDL) are thought to play a central role in the development of atherosclerosis. Toxic concentrations of mildly oxidized LDL elicit massive apoptosis of endothelial cells (Escargueil-Blanc, I., Meilhac, O., Pieraggi, M. T. , Arnal J. F., Salvayre, R., Nègre-Salvayre, A. (1997) Arterioscler. Thromb. Vasc. Biol. 17, 331-339). Since the lipid mediator ceramide emerged as a potent inducer of apoptosis, we aimed at investigating the occurrence of ceramide formation and its potential role in oxLDL-induced apoptosis. In ECV-304 endothelial cells, toxic concentrations of oxLDL triggered an early activation of the sphingomyelin-ceramide pathway, as shown by both sphingomyelin hydrolysis and ceramide formation. N-Tosyl-L-phenylalanyl chloromethyl ketone (TPCK) and dichloroisocoumarin (DCIC), two serine-protease inhibitors (serpins), blocked the oxLDL-induced ceramide generation but, unexpectedly, did not inhibit the oxLDL-induced apoptosis. Conversely, treatment of endothelial cells by bacterial sphingomyelinase, under conditions effectively generating ceramide, did not induce apoptosis. In contrast, short-chain permeant C2- and C6-ceramides elicited apoptosis of ECV-304. However, the mechanisms of apoptosis triggered by C2-ceramide and by oxLDL were (at least in part) different, because C2-ceramide-induced apoptosis was calcium-independent, whereas oxLDL-induced apoptosis was calcium-dependent. In conclusion, it is suggested that oxLDL-induced apoptosis is calcium-dependent but independent of the activation of the sphingomyelin-ceramide pathway and that the toxic effect of short chain permeant ceramides is calcium-independent and does not mimic the effect of natural ceramides induced by oxLDL.