Ether lipid content and fatty acid distribution in rabbit polymorphonuclear neutrophil phospholipids

Abstract

This study was undertaken to determine if rabbit neutrophils contain sufficient ether-linked precursor for the synthesis of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activating factor) by a deacylation-reacylation pathway. The phospholipids from rabbit peritoneal polymorphonuclear neutrophils were purified and quantitated, and the choline-containing and ethanolamine-containing phosphoglycerides were analyzed for ether lipid content. Choline-containing phosphoglycerides (37%), ethanolamine-containing phosphoglycerides (30%), and sphingomyelin (28%) were the predominant phospholipid classes, with smaller amounts of phosphatidylserine (5%) and phosphatidylinositol (less than 1%). The choline-linked fraction contained high amounts of 1-O-alkyl-2-acyl-(46%) and 1,2-diacyl-sn-glycero-3-phosphocholine (54%), with a trace of the 1-O-alk-1'-enyl-2-acyl species. The ethanolamine-linked fraction contained high amounts of 1-O-alk-1'-enyl-2-acyl-(63%) and 1,2-diacyl-sn-glycero-3-phosphoethanolamine (34%), and a low quantity of the 1-O-alkyl-2-acyl species (3%). The predominant 1-O-alkyl ether chains found in the sn-1 position of the choline-linked fraction were 16:0 (35%), 18:0 (14%), 18:1 (26%), 20:0 (16%), and 22:0 (9%). The major 1-O-alk-1'-enyl ether chains found in the sn-1 position of the ethanolamine-linked fraction were 14:0 (13%), 16:0 (44%), 18:0 (27%), 18:1 (12%) and 18:2 (3%). The major acyl groups in the sn-1 position of 1,2-diacyl-sn-glycero-3-phosphocholine and 1,2-diacyl-sn-glycero-3-phosphoethanolamine were 16:0, 18:0 and 18:1. The most abundant acyl group in the sn-2 position of all classes of choline- and ethanolamine-linked phosphoglycerides was 18:2. Although this work does not define the biosynthetic pathway for platelet activating factor, it does show that there is ample precursor present to support its synthesis by a deacylation-reacylation pathway.

Endotoxins Stimulate Neutrophil Adhesion Followed by Synthesis and Release of Platelet-activating Factor in Microparticles

“…Some of the fragmented phospholipids formed by an uncontrolled oxidative attack on polyunsaturated alkyl phospholipids (17,18) activate the PAF receptor (19). These precursor polyunsaturated alkyl phospholipids are abundant in leukocytes, and LPS primes the oxidative burst of leukocytes that generates oxidizing free radicals.…”

“…PMNs in Response to Endotoxin-Endotoxins stimulate an oxidative burst in leukocytes and oxidative fragmentation of polyunsaturated alkyl phosphatidylcholines, and PMNs are a rich source of this class of phospholipids (17), creating reaction products that stimulate the PAF receptor (36). We analyzed the structure of the active lipid fraction of endotoxin-treated PMNs by tandem mass spectrometry after inclusion of a deuterated PAF internal standard.…”

Mobilization of arachidonic acid between diacyl and ether phospholipids in rabbit alveolar macrophages

“…It seems a distinctive feature of various types of leukocytes such as macrophages [l-3], polymorphonuclear leukocytes [2,4] and lymphocytes [2,5], that they contain high amounts of alkylacyl GPC which are utilized for the synthesis of PAF by a deacylation-reacetylation reaction [3].…”

Fluoride activates diradylglycerol and Superoxide generation in human neutrophils via PLD/PA phosphohydrolase‐dependent and ‐independent pathways

“…The occurrence of the latter implies an origin from phospholipid sources other than phosphoinositides which are comprised almost exclusively of diacyl linkages [49]. Ethanol reduced the production of both species to basal levels.…”