Escargueil-Blanc I, Andrieu-Abadie N, Caspar-Bauguil S, Brossmer R, Levade T, Nègre-Salvayre A, Salvayre R
INSERM U-466 and the Biochemistry Department, Institut Louis Bugnard, CHU Rangueil, 31054 Toulouse Cedex, France.
J Biol Chem. 1998 Oct 16;273(42):27389-95. doi: 10.1074/jbc.273.42.27389.
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.
氧化型低密度脂蛋白（oxLDL）被认为在动脉粥样硬化的发展过程中起核心作用。轻度氧化的低密度脂蛋白的毒性浓度会引发内皮细胞的大量凋亡（埃斯卡尔吉尔 - 布朗克，I.，梅亚克，O.，皮耶拉吉，M. T.，阿尔纳尔，J. F.，萨尔韦尔，R.，内格雷 - 萨尔韦尔，A.（1997年）《动脉硬化、血栓形成和血管生物学》17卷，331 - 339页）。由于脂质介质神经酰胺成为一种有效的凋亡诱导剂，我们旨在研究神经酰胺形成的情况及其在oxLDL诱导的凋亡中的潜在作用。在ECV - 304内皮细胞中，oxLDL的毒性浓度触发了鞘磷脂 - 神经酰胺途径的早期激活，这通过鞘磷脂水解和神经酰胺形成得以证明。N - 甲苯磺酰 - L - 苯丙氨酰氯甲基酮（TPCK）和二氯异香豆素（DCIC）这两种丝氨酸蛋白酶抑制剂（丝氨酸蛋白酶抑制剂）阻断了oxLDL诱导的神经酰胺生成，但出乎意料的是，并未抑制oxLDL诱导的凋亡。相反，在有效生成神经酰胺的条件下，用细菌鞘磷脂酶处理内皮细胞并未诱导凋亡。相比之下，短链可渗透的C2 - 和C6 - 神经酰胺引发了ECV - 304的凋亡。然而，C2 - 神经酰胺和oxLDL触发凋亡的机制（至少部分）不同，因为C2 - 神经酰胺诱导的凋亡不依赖于钙，而oxLDL诱导的凋亡依赖于钙。总之，提示oxLDL诱导的凋亡依赖于钙，但独立于鞘磷脂 - 神经酰胺途径的激活，并且短链可渗透神经酰胺的毒性作用不依赖于钙，也不模拟oxLDL诱导的天然神经酰胺的作用。
