The enantiomer and the positional isomer of platelet-activating factor

On the synthesis of platelet-activating factor via acetylation of 1-alkyl-sn-glycero-3-phosphocholine. Formation of structural isomer of PAF in the presence of bases

It has been shown that platelet-activating factor (PAF) specimens prepared via acetylation of 1-alkyl-sn-glycero-3-phosphocholine (lyso-PF) with acetic anhydride are heterogeneous. The contaminated compound was isolated and identified to be the structural isomer of PAF, 1-alkyl-3-acetyl-sn-glycero-2-phosphocholine (iso-PAF). It appeared, that iso-PAF is formed when performing the reaction in the presence of organic bases,but not under acid catalysis. The mechanism of iso-PAF formation is discussed.

Capillary gas chromatography and tandem mass spectrometry of paf-acether and analogs: absence of 1-O-alkyl-2-propionyl-sn-glycero-3-phosphocholine in human polymorphonuclear neutrophils

Fast atom bombardment-tandem mass spectrometry was used to identify molecular species of paf-acether (paf) produced by human polymorphonuclear neutrophils. Using this biological material, normal phase high performance liquid chromatography was necessary prior to the fast atom bombardment-tandem mass spectrometry step. Gas liquid chromatography/electron capture detection after hydrolysis with phospholipase C and conversion to heptafluorobutyrate derivatives was used to confirm the results. The results indicated the presence of mainly 1-O-hexadecyl/octadecyl-2-acetyl-sn-glycero-3-phosphocholine, acyl analogs of paf and only trace amounts of other alkyl analogs of paf. We did not detect the 2-propionyl analog of paf. Moreover, supplementation of human polymorphonuclear neutrophils with sodium propionate did not result in formation of the 2-propionyl analog of paf.

Effects of PAF-acether and structural analogues on platelet activation and bronchoconstriction in guinea-pigs

PAF-acether (platelet-activating factor) (1-O-alkyl-2-acetyl-sn-glycerol-3-phosphorylcholine) induces platelet-dependent bronchoconstriction in the guinea-pig which correlates with its in vivo thrombocytopenic effect. We investigated the influence of modifications of the polar head group in position 3 of the glycerol skeleton of PAF-acether on guinea-pig platelet activation and bronchoconstriction. PAF-acether itself induced concentration-dependent platelet activation (EC50 for aggregation = 0.41 nM and EC20 for secretion of ATP = 0.56 nM). The 3-phosphoryl-N-methyl-morpholino ethanol analogue was slightly more active than PAF-acether and the 3-phosphoryl-N-methyl-piperidinium ethanol, 3-phopshoryl-(N-methyl-piperidino-3') methanol and 3-phosphoryl-(N-methyl-hydroxy-4') piperidine analogues were equieffective to PAF-acether in activating platelets. The 3-phosphoryl-piperidino ethanol analogue was 8 times less active than PAF-acether; the 3-phosphoryl-morpholino ethanol analogue and the 1-O-octadecyl-2-O-acetyl-3-O-[trimethyl-ammonio)-propyl) glycerol were inactive up to 1 microM. Our data show that the choline head group is not a compulsory requirement for activity. When injected i.v. to the propranolol-treated guinea-pigs, the platelet-activating analogues also induced bronchoconstriction. Two PAF-acether antagonists, compounds 48740 RP and BN 52021, inhibited PAF-acether-induced platelet activation when added to PRP at the final concentration of 0.1 mM (aggregation inhibited by 91 +/- 4 and by 94 +/- 3% respect.; secretion inhibited by 80 +/- 12 and 79 +/- 10% respectively, mean +/- S.E.M., n = 4). Both antagonists also suppressed platelet activation and in vivo bronchoconstriction, thrombocytopenia, leukopenia and hypotension induced by PAF-acether and the various analogues. Our results indicate that PAF-acether and the analogues studied trigger platelet activation and the consequent bronchoconstriction through mechanisms which share sensitivity to same antagonists.

Inflammation and mediators of lung injury

This article covers the major pathways involved in acute inflammation in mammals with a particular emphasis on their relevance to the bovine species. It focuses on the potential and proven contributions of these systems to pulmonary defense mechanisms and lung pathology. The article also points out what is known and where gaps in our information exist as well as promising areas for research in the coming years.

Synthesis and characterization of a radioiodinated, photoreactive and physiologically active analogue of platelet activating factor

The multistep synthesis of a photoreactive, radioactive and aggregating analogue of platelet-activating factor (PAF)-acether is described. The photoreactive and radioactive moiety was added at the last step; the specific radioactivity was higher than 1000 Ci/mmol. The concentration of this new analogue which causes 50% of aggregation of platelets were of the same order of magnitude as for synthetic snPAF-acether, so as for two other analogues having a bulky group at the omega end of the fatty ether chain. The photoreactivity was proved by the covalent binding of the analogue to protein (BSA) after 10-min irradiation times at 300 nm. The binding was largely prevented by prior (not by later) addition of a high concentration of lyso phosphatidyl choline.

Paf-acether generates chemiluminescence in human neutrophils in the absence of cytochalasin B

In the absence of cytochalasin B, synthetic Paf-acether (0.1-10 microM) induced oxygen radical production in polymorphonuclear neutrophils as measured by the luminol-dependent chemiluminescence ( LDCL ) test. This effect was observed after a lag period of 10 s and was maximal between 5 and 15 min. In the presence of cytochalasin B, the kinetics were shortened, but the lag period was not modified and the same concentrations of the agonist had to be used to induce LDCL . None of the structural analogs tested (2-lyso Paf-acether, Paf-acether enantiomer, 1 ester analog of Paf-acether, lyso-phosphatidylcholine) were active, irrespective of the presence of cytochalasin B. Paf-acether (10 microM) shortened the kinetics of opsonized zymosan (10 micrograms/ml)-induced LDCL and enhanced it by 550% and 250% at 5 min and 10 min respectively, without affecting the peak value. Similar results were obtained using non-opsonized zymosan (100 micrograms/ml). Lower concentrations of Paf-acether (0.1 microM) were also able to increase oxygen radical production induced by low doses of zymosan and opsonized zymosan. The triggering and enhancing effects of Paf-acether on oxygen radical production by resting and stimulated polymorphonuclear neutrophils support the role of Paf-acether in inflammation.