Protein adducts of iso[4]levuglandin E-2, a product of the isoprostane pathway, in oxidized low density lipoprotein

Levuglandin (LG) E-2, a cytotoxic seco prostanoic acid co-generated with pr ostaglandins by nonenzymatic rearrangements of the cyclooxygenase-derived e ndoperoxide, prostaglandin H-2, avidly binds to proteins. That LGE(2)-prote in adducts can also be generated nonenzymatically is demonstrated by their production during free radical-induced oxidation of low density lipoprotein (LDL). Like oxidized LDL, LGE(2)-LDL, but not native LDL, undergoes recept or-mediated uptake and impaired processing by macrophage cells. Since radic al-induced lipid oxidation produces isomers of prostaglandins, isoprostanes (isoPs), via endoperoxide intermediates, we postulated previously that a s imilar family of LG isomers, isoLGs, is cogenerated with isoPs. Now iso[4]L GE(2)-protein epitopes produced by radical-induced oxidation of arachidonic acid in the presence of protein were detected with an enzyme-linked immuno sorbent assay. Iso[4]LGE(2)-protein epitopes are also generated during free radical-induced oxidation of LDL. All of the LGE(2) isomers generated upon oxidation of LDL are efficiently sequestered by covalent adduction with LD L-based amino groups. The potent electrophilic reactivity of iso-LGs can be anticipated to have biological consequences beyond their obvious potential as markers for specific arachidonate derived protein modifications that ma y be of value for the quantitative assessment of oxidative injury.