Suc I, Escargueil-Blanc I, Troly M, Salvayre R, Nègre-Salvayre A
Department of Biochemistry, INSERM U.466, IFR Louis Bugnard, University Paul Sabatier, Toulouse, France.
Arterioscler Thromb Vasc Biol. 1997 Oct;17(10):2158-66. doi: 10.1161/01.atv.17.10.2158.
We have previously demonstrated that toxic doses of mildly oxidized LDL evokes in cultured cells a delayed and sustained rise of cytosolic [Ca2+], eliciting in turn irreversible cell damage and leading finally to cell death. HDL and delipidated apolipoprotein (apo). A prevented effectively the toxic effect of oxidized LDL to bovine aortic endothelial cells, in a time- and dose-dependent manner. The major part of the protective effect was mimicked by purified apoA-I, whereas purified apoA-II exhibited only very low protective activity. The protective effect was independent of the paraoxonase-linked HDL activity. The protective effect of HDL is independent of the contact of HDL with oxidized LDL, as shown by preincubation of oxidized LDL with HDL or apoA. In contrast, the protective effect was dependent on the integrity of apoA and on the contact of HDL with cells, thus suggesting that HDL acts directly on cells by enhancing their resistance against oxidized LDL. Preincubation experiments show that the protective effect is dependent on the duration of the contact of cells with HDL (maximal effect observed after 12 to 16 hours' preincubation), is also dependent on protein synthesis, and is persistent for at least 48 hours after the end of the contact of HDL with cells. Finally, effective concentrations of HDL inhibit the Ca2+ peak, which is directly involved in the cytotoxic effect of oxidized LDL, as shown by the inhibitory effect of Ca2+ chelators. All together, these results suggest that HDL, mainly apoA-I, increases the resistance of endothelial cells against oxidized LDL and prevents its toxic (apoptotic) effect by blocking the pathogenic intracellular signaling (culminating in sustained Ca2+ rise) involved in cell death.
我们之前已经证明，毒性剂量的轻度氧化低密度脂蛋白（LDL）可在培养细胞中引发胞质[Ca2+]的延迟且持续升高，进而引发不可逆的细胞损伤并最终导致细胞死亡。高密度脂蛋白（HDL）和脱脂载脂蛋白（apo）A可有效预防氧化LDL对牛主动脉内皮细胞的毒性作用，且呈时间和剂量依赖性。纯化的载脂蛋白A-I可模拟大部分保护作用，而纯化的载脂蛋白A-II仅表现出极低的保护活性。该保护作用与对氧磷酶相关的HDL活性无关。HDL的保护作用与HDL与氧化LDL的接触无关，这可通过氧化LDL与HDL或载脂蛋白A的预孵育来证明。相反，保护作用取决于载脂蛋白A的完整性以及HDL与细胞的接触，因此表明HDL通过增强细胞对氧化LDL的抗性直接作用于细胞。预孵育实验表明，保护作用取决于细胞与HDL接触的持续时间（预孵育12至16小时后观察到最大效应），也取决于蛋白质合成，并且在HDL与细胞接触结束后至少持续48小时。最后，如Ca2+螯合剂的抑制作用所示，有效浓度的HDL可抑制直接参与氧化LDL细胞毒性作用的Ca2+峰值。综上所述，这些结果表明，HDL（主要是载脂蛋白A-I）可增加内皮细胞对氧化LDL的抗性，并通过阻断参与细胞死亡的致病性细胞内信号传导（最终导致Ca2+持续升高）来预防其毒性（凋亡）作用。
