Novel Eicosapentaenoic Acid-derived F3-isoprostanes as Biomarkers of Lipid Peroxidation

Abstract

Isoprostanes (iPs) are prostaglandin (PG) isomers generated by free radical-catalyzed peroxidation of polyunsaturated fatty acids (PUFAs). Urinary F 2 -iPs, PGF 2␣ isomers derived from arachidonic acid (AA) are used as indices of lipid peroxidation in vivo. We now report the characterization of two major F 3 -iPs, 5-epi-8,12-iso-iPF 3␣ -VI and 8,12-iso-iPF 3␣ -VI, derived from the -3 fatty acid, eicosapentaenoic acid (EPA). Although the potential therapeutic benefits of EPA receive much attention, a shift toward a diet rich in -3 PUFAs may also predispose to enhanced lipid peroxidation. Urinary 5-epi-8,12-iso-iPF 3␣ -VI and 8,12-iso-iPF 3␣ -VI are highly correlated and unaltered by cyclooxygenase inhibition in humans. Fish oil dose-dependently elevates urinary F 3 -iPs in mice and a shift in dietary -3/-6 PUFAs is reflected by an increasing slope [m] of the line relating urinary 8, 12-iso-iPF 3␣ -VI and 8,12-iso-iPF 2␣ -VI. Administration of bacterial lipopolysaccharide evokes a reversible increase in both urinary 8,12-iso-iPF 3␣ -VI and 8,12-iso-iPF 2␣ -VI in humans on an ad lib diet. However, while excretion of the iPs is highly correlated (R 2 median ‫؍‬ 0.8), [m] varies by an order of magnitude, reflecting marked inter-individual variability in the relative peroxidation of -3 versus -6 substrates. Clustered analysis of F 2 -and F 3 -iPs refines assessment of the oxidant stress response to an inflammatory stimulus in vivo by integrating variability in dietary intake of -3/-6 PUFAs. Isoprostanes (iPs),2 a family of prostaglandin isomers, are generated initially in situ by free radical attack on polyunsaturated fatty acids (PUFAs) in cell membranes. There, they can be immunodetected and quantified by mass spectrometry (1). They are then cleaved by phospholipases (2), circulate in plasma, and are excreted in urine (3). F 2 -iPs, isomers of PGF 2␣ (3), derived from peroxidation of arachidonic acid (AA), are the most studied species. F 2 -iPs can be quantified in normal animal and human biological fluids and tissues, implying ongoing lipid peroxidation under physiological conditions, despite replete and diversified endogenous antioxidant defense systems (4). The measurement of urinary F 2 -isoprostanes has been used to reflect lipid peroxidation noninvasively in several human diseases (5-8). In addition to their utility as markers of oxidant stress (OS), high concentrations of some F 2 -iPs also possess biological activity in vitro, including bronchoconstriction (9), vasoconstriction (10), platelet aggregation (11, 12), and adhesion (13). These effects result from iPs acting as incidental ligands at prostaglandin receptors. It is unknown whether this capacity of individual iPs to ligate prostanoid receptors has relevance to the concentration of the multiple endogenous iP species likely to be formed simultaneously under conditions of oxidant stress in vivo.iPs analogous to the F 2 -iPs may be formed from other fatty acid substrates (14 -19), including the fish oil constituent, eicosapentaenoic acid (EPA) (20). Pote...

Role of polyunsaturated fatty acids and lipid peroxidation on colorectal cancer risk and treatments

“…A fish oilenriched diet elevates dose-dependently the excretion of F 3 and F 4 -isoprostanes in mice urine, following a decrease of F 2 -isoprostanes [28]. F 2 -isoprostanes but not F 3 -isoprotanes could increase arterial pressure and irreversible platelet aggregation in mice [28]. The result indicates that F 2 -isoprostanes have systemic proinflammatory effects in animal model, whereas F 3 -isoprotanes have no such effect.…”

“…The result indicates that F 2 -isoprostanes have systemic proinflammatory effects in animal model, whereas F 3 -isoprotanes have no such effect. And v-3 PUFA-derived F 3 -isoprostanes competitively decrease the excretion of F 2 -isoprostanes from v-6 PUFAs [28]. Different production of F 3 -isoprostanes rather than F 2 -isoprostanes with fish oilenriched diet might explain the benefits of v-3 PUFAs in healthy animals.…”

“…Compared to F 2 -isoprostanes, F 3 and F 4 -isoprostanes are mainly derived from v-3 PUFAs. A fish oilenriched diet elevates dose-dependently the excretion of F 3 and F 4 -isoprostanes in mice urine, following a decrease of F 2 -isoprostanes [28]. F 2 -isoprostanes but not F 3 -isoprotanes could increase arterial pressure and irreversible platelet aggregation in mice [28].…”

“…Isoprostanes (IsoPs) are a series of prostaglandin-like compounds produced by the free radical-catalyzed peroxidation independent of COX pathway (Fig. 3) [28]. These end products of lipid peroxidation participate in the signal transduction cascade, cell proliferation and differentiation control, as well as in apoptosis pathways.…”

“…F 2 -isoprostanes, derived from v-6 PUFAs, are the most studied species. v-3 PUFAs mainly generate F 3 and F 4 -isoprostanes [28]. F 2 -isoprostanes are considered as reliable biomarkers of lipid peroxidation in various inflammatory states, such as atherosclerosis, rheumatic diseases [48], chronic lung diseases [49], degenerative diseases, aging, obesity and cancers [50].…”