Chilton F H
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21239.
Biochem J. 1989 Mar 1;258(2):327-33. doi: 10.1042/bj2580327.
The present study has employed two approaches to address the question of whether there are specific phospholipid sources of arachidonate used for leukotriene biosynthesis in the human neutrophil. Firstly, g.c.-m.s. analysis indicated that arachidonate was lost from all major arachidonate-containing phospholipid subclasses during cell activation with ionophore A23187. On a molar basis, the rank order of breakdown among the three major phospholipids was: 1-alk-1-enyl-2-arachidonoyl-sn-glycero-3-phosphoethanolamine greater than 1-alkyl-2-arachidonoyl-sn-3-phosphocholine greater than 1-acyl-2-arachidonyl-sn-3-phosphoinositol. Leukotrienes released into the supernatant fluid accounted for only 10-35% of the total arachidonate depletion. Phospholipid sources were also identified in labelling experiments where the specific radioactivity of arachidonate in phospholipid subclasses, as well as leukotrienes produced during cell activation, was measured. The specific radioactivity of arachidonate within 1-acyl-linked molecular species of phosphatidylcholine and phosphatidylinositol was initially high relative to the leukotrienes and decreased rapidly with stimulation. By contrast, the specific radioactivity of arachidonate in all three subclasses of phosphatidylethanolamine, 1-acyl, 1-alkyl, and 1-alk-1-enyl, was 3-5-fold below that of the leukotrienes throughout cell activation. Of the six major arachidonate-containing subclasses, only in the case of 1-O-alkyl-2-arachidonoyl-sn-glycero-3-phosphocholine did the specific radioactivity correlate well with that of leukotriene B4 and 20-hydroxyleukotriene B4. These data strongly suggest that 1-ether-linked phospholipids are an important source of arachidonate used for leukotriene biosynthesis.
本研究采用了两种方法来解决人类中性粒细胞中是否存在用于白三烯生物合成的花生四烯酸特定磷脂来源这一问题。首先，气相色谱 - 质谱分析表明，在用离子载体A23187激活细胞的过程中，花生四烯酸从所有主要的含花生四烯酸磷脂亚类中流失。以摩尔为基础，三种主要磷脂的分解顺序为：1 - 烯基 - 2 - 花生四烯酰 - sn - 甘油 - 3 - 磷酸乙醇胺大于1 - 烷基 - 2 - 花生四烯酰 - sn - 3 - 磷酸胆碱大于1 - 酰基 - 2 - 花生四烯酰 - sn - 3 - 肌醇。释放到上清液中的白三烯仅占花生四烯酸总消耗的10 - 35%。在标记实验中也确定了磷脂来源，在该实验中测量了磷脂亚类中花生四烯酸的比放射性以及细胞激活过程中产生的白三烯。相对于白三烯，磷脂酰胆碱和磷脂酰肌醇的1 - 酰基连接分子物种内花生四烯酸的比放射性最初较高，并随着刺激迅速降低。相比之下，在整个细胞激活过程中，磷脂酰乙醇胺的所有三个亚类（1 - 酰基、1 - 烷基和1 - 烯基 - 1 - 烯基）中花生四烯酸的比放射性比白三烯低3 - 5倍。在六个主要的含花生四烯酸亚类中，只有1 - O - 烷基 - 2 - 花生四烯酰 - sn - 甘油 - 3 - 磷酸胆碱的比放射性与白三烯B4和20 - 羟基白三烯B4的比放射性密切相关。这些数据有力地表明，1 - 醚连接的磷脂是用于白三烯生物合成的花生四烯酸的重要来源。
