Formation of F 2 -Isoprostanes During Oxidation of Human Low-Density Lipoprotein and Plasma by Peroxynitrite

Abstract

Abstract F 2 -Isoprostanes are novel bioactive prostaglandin F 2 –like compounds produced by nonenzymatic free radical–catalyzed peroxidation of arachidonic acid. F 2 -Isoprostanes are initially formed in situ on phospholipids and subsequently released. Quantification of the F 2 -isoprostanes has been found to represent a valuable and reliable marker of lipid peroxidation. Oxidative modification of low-density lipoprotein (LDL) is a key process for the recognition of LDL by the scavenger receptors on macrophages. The oxidative mechanism responsible for the modification of LDL in vivo remains unclear, but an attractive candidate is the powerful oxidant peroxynitrite, which can be formed by reaction of nitric oxide and superoxide in the vessel wall. To further explore the potential role of peroxynitrite in the oxidative modification of plasma lipids, we investigated whether incubation of LDL and plasma with peroxynitrite or SIN-1, which decomposes to form nitric oxide and superoxide, catalyzes the formation of F 2 -isoprostanes. Incubation of LDL with peroxynitrite (0.125 to 1 mmol/L) or SIN-1 (0.5 and 1 mmol/L) induced a concentration-dependent increase in the formation of F 2 -isoprostanes, reaching a maximum of 5.5±2.05-fold (SEM) and 18.2±4.0-fold above control values, respectively. The increase of F 2 -isoprostanes induced by SIN-1 was essentially completely inhibited by superoxide dismutase. Incubation of plasma with peroxynitrite or SIN-1 yielded similar results. These results indicate that peroxynitrite can induce the formation of F 2 -isoprostanes in lipoproteins. Since F 2 -isoprostanes can exert potent biological activity such as vasoconstriction, they may contribute to the vascular pathobiology associated with atherosclerosis.