Effect of platelet activating factor on the kinetics of LDL oxidation in vitro

Oxidatively modified low-density-lipoprotein (LDL) might contribute to the atherosclerotic process. This study was performed to examine an effect of platelet-activating factor (PAF) and of synthetic PAF analogs on Cu(II) induced oxidation of LDL in vitro: The D- and L-isomers of PAF and analogs with short-chain sn-2-substituents, 1-O-alkyl-2-butyryl-sn-glycero-3-phosphocholine and 1-O-alkyl-2-heptanoyl-sn-glycero-3-phosphocholine, were found to be the most effective inhibitors of LDL oxidation. Oxidation was inhibited completely at PAF concentrations above 100 microM. Lyso-PAF and analogs carrying longer chains at the sn-2 position were less effective. These results thus provide evidence for the involvement of other parameters in LDL oxidation beyond the content of natural antioxidants like vitamin E and beta-carotene.