Oxidation of human low density lipoprotein (LDL) generates proinflammatory mediators and underlies early events in atherogenesis. We identified mediators in oxidized LDL that induced an inflammatory reaction in vivo, ...
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Oxidation of human low density lipoprotein (LDL) generates proinflammatory mediators and underlies early events in atherogenesis. We identified mediators in oxidized LDL that induced an inflammatory reaction in vivo, and activated polymorphonuclear leukocytes and cells ectopically expressing human platelet-activating factor (PAF) receptors, Oxidation of a synthetic phosphatidylcholine showed that an sn-l ether bond confers an 800-fold increase in potency. This suggests that rare ether-linked phospholipids in LDL are the likely source of PAF-like activity in oxidized LDL, Accordingly, treatment of oxidized LDL with phospholipase A, greatly reduced phospholipid mass, but did not decrease its PAF-like activity. Tandem mass spectrometry identified traces of PAF, and more abundant levels of 1-O-hexadecyl-2-(butanoyl or butenoyl)-sn-glycero-3-phosphocholines (C-4-PAF analogs) in oxidized LDL that comigrated with PAF-like activity. Synthesis showed that either C-4-PAF was just 10-fold less potent than PAF as a PAF receptor ligand and agonist. Quantitation by gas chromatography-mass spectrometry of pentafluorobenzoyl derivatives shows the C-4-PAF analogs were 100-fold more abundant in oxidized LDL than PAF, Oxidation of synthetic alkyl arachidonoyl phosphatidylcholine generated these C-4-PAFs in abundance. These results show that quite minor constituents of the LDL phosphatidylcholine pool are the exclusive precursors for PAF-like bioactivity in oxidized LDL.
Platelet-activating factor is the term used to denote a class of extremely patent lipid mediators that consist predominantly of 1-O-alkyl- and 1-O-acyl-2-acetyl-sn-glycero-3-phosphocholines. A method has been devised ...
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Platelet-activating factor is the term used to denote a class of extremely patent lipid mediators that consist predominantly of 1-O-alkyl- and 1-O-acyl-2-acetyl-sn-glycero-3-phosphocholines. A method has been devised for rapid isolation of these acetylated phospholipids by solid-phase extraction prior to direct derivatization with pentafluorobenzoic anhydride and analysis by gas chromatography (GC)/electron-capture mass spectrometry. Recovery through the entire method (lipid isolation, derivatization, and purification) typically ranged from 70% to 85%. Using the direct derivatization procedure described here, the practical limit of detection for each of the standard alkyl- and acyl-platelet-activating factor homologs was 1 fmol injected into the GC. Results from the application of the method to the analysis of alkyl and acyl homologs of platelet-activating factor isolated from stimulated human umbilical vein endothelial cells are presented, exhibiting excellent accuracy and precision for a wide range of tissue levels of this class of potent autacoids. (C) 2000 American Society for Mass Spectrometry.
To clarify the behavior of the novel platelet-activating factor (PAF) receptor antagonist E5880 in aqueous solution, electric conductivity was measured at different temperatures (every 5 degrees C), ranging from 15 de...
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To clarify the behavior of the novel platelet-activating factor (PAF) receptor antagonist E5880 in aqueous solution, electric conductivity was measured at different temperatures (every 5 degrees C), ranging from 15 degrees C to 50 degrees C: Critical micellization concentration (CMC) of E5880 was dependent on the temperature;at 30 degrees C, the CMC value was smallest (0.143 mM). Below that temperature, the enthalpy for formation of the micelle (Delta H-m(0)) was positive, and the formation of micelles was endothermic;above that temperature, Delta H-m(0), was negative, and the formation of micelles was exothermic.
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