Bayon Y, Croset M, Daveloose D, Guerbette F, Chirouze V, Viret J, Kader J C, Lagarde M
INSERM Unité 352, Laboratoire de Chimie biologique INSA Lyon, Villeurbanne, France.
J Lipid Res. 1995 Jan;36(1):47-56.
The incorporation of albumin-bound docosahexaenoic acid (22:6n-3), but not linoleic acid (18:2n-6), into cellular phospholipids inhibits platelet aggregation induced by the thromboxane analogue U46619. [3H]U46619 specific binding to thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptors, as well as specific binding of the antagonist [3H]SQ29548 to these sites were also decreased in these modified cells (P. G., Swann et al. 1990. J. Biol. Chem. 265: 21692-21697). More than 80% of the 22:6n-3 incorporated in these cells was esterified in the various endogenous phospholipid classes and the remaining was found in neutral lipids and in the unesterified fatty acid pool. In this study, we determined whether the effects observed could be attributed to the esterification of 22:6n-3 in phospholipids and whether the 22:6n-3 biological activity might depend on its esterification in specific phospholipid classes. Therefore, pure phosphatidylcholine (PC) and phosphatidylethanolamine (PE) molecular species were transferred to platelet membranes, using lipid transfer proteins. PC and PE containing palmitate (16:0) and 22:6n-3 or 16:0 and 18:2n-6 at position sn-1 and sn-2, respectively, were incorporated into membranes only at the expense of the corresponding endogenous phospholipid class, by an apparent exchange process. When such modified membranes were tested for specific binding of U46619 and SQ29548, a significant decrease of the receptor site affinity was only observed in membranes highly enriched with 1-palmitoyl-2-docosahexaenoyl-glycerophosphocholine (16:0/22:6-GPC). Fluidity parameters measured by electron spin resonance of 5- and 16-nitroxy-stearic acids were not significantly different in membranes enriched with 16:0/22:6-GPC relative to those enriched with 16:0/18:2n-6-GPC, arguing against a generalized perturbation of the membrane due to 22:6n-3 incorporation. We conclude that molecular species of PC with 22:6n-3 at the sn-2 position can affect TXA2/PGH2 receptors. The selectivity of the inhibitory effect of PC containing 22:6n-3 is discussed.
白蛋白结合的二十二碳六烯酸（22:6n-3）而非亚油酸（18:2n-6）掺入细胞磷脂中可抑制血栓素类似物U46619诱导的血小板聚集。在这些修饰细胞中，[3H]U46619与血栓素A2/前列腺素H2（TXA2/PGH2）受体的特异性结合以及拮抗剂[3H]SQ29548与这些位点的特异性结合也降低了（P.G.，斯旺等人，1990年。《生物化学杂志》265:21692-21697）。掺入这些细胞中的22:6n-3超过80%在各种内源性磷脂类别中被酯化，其余的则存在于中性脂质和未酯化脂肪酸池中。在本研究中，我们确定观察到的效应是否可归因于22:6n-3在磷脂中的酯化，以及22:6n-3的生物活性是否可能取决于其在特定磷脂类别中的酯化。因此，使用脂质转移蛋白将纯磷脂酰胆碱（PC）和磷脂酰乙醇胺（PE）分子种类转移到血小板膜上。分别在sn-1和sn-2位置含有棕榈酸（16:0）和22:6n-3或16:0和18:2n-6的PC和PE仅通过明显的交换过程以相应内源性磷脂类别的消耗为代价掺入膜中。当测试这种修饰膜对U46619和SQ29548的特异性结合时，仅在高度富含1-棕榈酰-2-二十二碳六烯酰甘油磷酸胆碱（16:0/22:6-GPC）的膜中观察到受体位点亲和力的显著降低。通过5-和16-硝基氧基硬脂酸的电子自旋共振测量的流动性参数在富含16:0/22:6-GPC的膜中与富含16:0/18:2n-6-GPC的膜中没有显著差异，这表明反对由于掺入22:6n-3而导致膜的普遍扰动。我们得出结论，在sn-2位置含有22:6n-3的PC分子种类可以影响TXA2/PGH2受体。讨论了含有22:6n-3的PC抑制作用的选择性。
