Oxidative modification of human lipoproteins by lipoxygenases of different positional specificities

Cellular lipoxygenases have been implicated in foam cell formation during the early stages of atherogenesis. We studied the interaction of lipoxygenases of different positional specificities with human lipoproteins and found that the arachidonate 15-lipoxygenases of rabbit and humans and the arachidonate 12-lipoxygenase of porcine leukocytes oxygenate lipoproteins as indicated by the formation of oxygenated lipids and changes in electrophoretic mobility of low density lipoprotein. The arachidonate 12-lipoxygenase of human platelets, the recombinant arachidonate 5-lipoxygenase of human leukocyte, and the soybean lipoxygenase I were less effective in oxidizing human LDL. As a major oxygenation product, esterified 13S-hydro(pero)xy-9Z,11E-octadecadienoic acid was identified for both the rabbit reticulocyte 15- and the porcine leukocyte 12-lipoxygenase. In addition, esterified 15S-hydro(pero)xy-5,8,11,13(Z,Z,Z,E)-eicosatetraenoic acid (for the rabbit 15-lipoxygenase) and 12S-hydro(pero)xy-5,8,10,14(Z,Z,E,Z)-eicosatetraenoic acid (for the porcine 12-lipoxygenase) as well as small amounts of racemic 9-hydro(pero)xy-10,12-octadecadienoic acid isomers were detected. More than 90% of the oxygenated polyenoic fatty acids were found in the ester lipid fraction, particularly in the cholesteryl esters and in various phospholipid classes (phosphatidylcholine and phosphatidylethanolamine). The possible biological significance of lipoxygenase-induced oxidative modification of lipoproteins in the pathogenesis of atherosclerosis is discussed.