BIOTRANSFORMATION OF PLATELET ACTIVATING FACTOR

嗜中性粒细胞和巨噬细胞的流入是炎症的特征。 过程 这些细胞通过以下方式对吞噬和可溶性刺激作出反应： 产生包括花生四烯酸代谢物的炎症介质 和血小板活化因子（PAF）。 PAF的生产和 花生四烯酸衍生的介质被认为与 1-O-烷基-2-花生四烯酰基-sn-甘油-3-磷酸胆碱的可用性。 本研究讨论了醚磷脂催化剂的贡献 PAF前体的调节。 本提案的长期目标是确定：1）如果 醚磷脂的组成和水平是受管制的，2） 这类磷脂的功能意义可能是和3） 阐明醚磷脂调节的机制，如果这种调节 本文综述了1-O-[3 H]烷基-2-乙酰基-N-（2-乙酰基）-N-（2-乙酰基 GPC已经确定了PAF代谢的两种替代途径。 发现了一条通路 在几种细胞类型中，但在本提案中， 骨髓来源的巨噬细胞或克隆巨噬细胞样细胞系，其中 乙醇胺磷脂是PAF的代谢产物。 第二路径 发现于PC-12细胞（源自大鼠嗜铬细胞瘤的克隆系）， 脾T细胞，其特征在于1-O-烷基-2-酰基-sn-甘油-3-基， 磷酸甘油（1-O-烷基-2-酰基-GPG）作为主要代谢产物。 令人惊讶的是，1- 0-烷基-2-酰基-GPG的醚键不被取代。 易水解。 血小板活化因子在巨噬细胞中代谢的研究 证明了来源于1-O-的烷基部分的标记物 [3 H]烷基-2-乙酰基-GPC出现在以下种类中：1-O-[3 H]烷基-2-乙酰基-GPC。 乙酰基-GPC、1-O-[3 H]烷基-2-酰基-GPC、1-O-[3 H]烷基-2-酰基-GPE和1-O-烷氧基-GPC。 在孵育1小时或更短时间后，1 '-烯基-2-酰基-GPE。 孵育期（2至6小时），标签的显著部分 存在于二酰基磷脂的酰基键和 中性脂质表明醚键已经断裂。 一 提出了一种用磷脂碱交换反应合成1-O- 烷基-2-酰基-GPE来自1-O-烷基-2-酰基-GPC。 alk-1 '-的裂解 乙醇胺缩醛磷脂的烯基被认为是 释放醚脂质的Sn-1基团。

An influx of neutrophils and macrophages characterizes the inflammatory process. These cells respond to phagocytic and soluble stimuli by producing inflammatory mediators including the arachidonic acid metabolites and platelet activating factor (PAF). The production of PAF and the arachidonic acid derived mediators is thought to be very closely related to the availability of 1-O-alkyl-2-arachidonoyl-sn-glycerol-3-phosphocholine. This study addresses the contribution made by ether phospholipid catabolism in the regulation of PAF precursors. The long term objectives of this proposal are to determine: 1) If the composition and level of ether phospholipids is regulated, 2) what the functional significance of this class of phospholipids might be and 3) elucidate the mechanism of ether phospholipid regulation if such regulation is found. The current studies on the metabolism of 1-O-[3H]alkyl-2-acety- GPC has defined two alternate pathways of PAF metabolism. A pathway found in several cell types but represented in this proposal by either bone marrow derived macrophages or a clonal macrophage-like cell line in which ethanolamine phospholipids are metabolites of PAF. The second pathway found in PC-12 cells (a clonal line derived from rat pheochromocytoma) and splenic T cells, is characterized by 1-O-alkyl-2-acyl-sn-glycero-3- phosphoglycerol (1-O-alkyl-2-acyl-GPG) as the primary metabolite. Surprisingly, the ether linkage of 1-O-alkyl-2-acyl-GPG does not to be susceptible to hydrolysis. Studies of PAF metabolism in macrophages demonstrated that label which originated in the alkyl moiety of 1-O- [3H]alkyl-2-acetyl-GPC appeared in the following species; 1-O-[3H]alkyl-2- acetyl-GPC, 1-O-[3H]alkyl-2-acyl-GPC, 1-O-[3H]alkyl-2-acyl-GPE and 1-O-alk- 1'-enyl-2-acyl-GPE after incubations of one hour or less. After extended incubation periods (2 to 6 hours) a significant portion of the label was present in the acyl linkage of diacyl phospholipids and acyl linkage of neutral lipids indicating then the ether linkage had been cleaved. A phsopholilpid base exchange reaction is proposed for the synthesis of 1-O- alkyl-2-acyl-GPE from 1-O-alkyl-2-acyl-GPC. The cleavage of the alk-1'- enyl group of ethanolamine plasmalogen is considered as the means of releasing the sn-1 group of the ether lipid.