Formation of Highly Reactive Cyclopentenone Isoprostane Compounds (A3/J3-Isoprostanes) in Vivo from Eicosapentaenoic Acid

Abstract

Omega-3 (-3) polyunsaturated fatty acids (PUFAs) found in marine fish oils are known to suppress inflammation associated with a wide variety of diseases. Eicosapentaenoic acid (EPA) is one of the most abundant -3 fatty acids in fish oil, but the mechanism(s) by which EPA exerts its beneficial effects is unknown. Recent studies, however, have demonstrated that oxidized EPA, rather than native EPA, possesses anti-atherosclerotic, anti-inflammatory, and anti-proliferative effects. Very few studies to date have investigated which EPA oxidation products are responsible for this bioactivity. Our research group has previously reported that anti-inflammatory prostaglandin A 2 -like and prostaglandin J 2 -like compounds, termed A 2 /J 2 -isoprostanes (IsoPs), are produced in vivo by the free radical-catalyzed peroxidation of arachidonic acid and represent one of the major products resulting from the oxidation of this PUFA. Based on these observations, we questioned whether cyclopentenoneIsoP compounds are formed from the oxidation of EPA in vivo. Herein, we report the formation of cyclopentenone-IsoP molecules, termed A 3 /J 3 -IsoPs, formed in abundance in vitro and in vivo from EPA peroxidation. Chemical approaches coupled with gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS) were used to structurally characterize these compounds as A 3 /J 3 -IsoPs. We found that levels of these molecules increase ϳ200-fold with oxidation of EPA in vitro from a basal level of 0.8 ؎ 0.4 ng/mg EPA to 196 ؎ 23 ng/mg EPA after 36 h. We also detected these compounds in significant amounts in fresh liver tissue from EPA-fed rats at basal levels of 19 ؎ 2 ng/g tissue. Amounts increased to 102 ؎ 15 ng/g tissue in vivo in settings of oxidative stress. These studies have, for the first time, definitively characterized novel, highly reactive A/J-ring IsoP compounds that form in abundance from the oxidation of EPA in vivo.

Lipid peroxidation of membrane phospholipids generates hydroxy-alkenals and oxidized phospholipids active in physiological and/or pathological conditions

“…Moreover, F(2)-IsoPs and other products of the IsoP pathway exert potent biological actions both via receptor-dependent and independent mechanisms and therefore may be pathophysiological mediators of disease. The formation of highly reactive cyclopentenone isoprostane compounds (A3/J3-isoprostanes) in vivo from eicosapentaenoic acid has been described recently (Brooks et al, 2008). Oxidation of docosahexaenoic acid, an abundant unsaturated fatty acid in the central nervous system, results in the formation of IsoP-like compounds, termed neuroprostanes.…”

Pathophysiology of isoprostanes in the cardiovascular system: implications of isoprostane‐mediated thromboxane A2 receptor activation

“…D2/E2-isoprostanes are formed in competition to F2-isoprostanes and the depletion of reducing agents such as α-tocopherol and ascorbic acid favours the formation of D2/E2-isoprostanes over that of F2-isoprostanes (Montine et al, 2003). D2/E2-isoprostanes can undergo further rearrangements generating A/J-isoprostanes, which are known as cyclopentenone isoprostanes (Chen et al, 1999a,b;Brooks et al, 2008;Hardy et al, 2011). Interestingly, degradation of A-isoprostane derivatives has been shown to occur during physiological conditions and has been demonstrated to give rise to biologically active intermediates (Benndorf et al, 2008).…”

“…Furthermore, a role of A/J isoprostanes in cell cycle regulation has been shown. These compounds can be incorporated into cells and accumulate in the nucleus, inducing a G1 cell cycle arrest (Chen et al, 1999a;Brooks et al, 2008).…”

“…Furthermore, a role of A/J isoprostanes in cell cycle regulation has been shown. These compounds can be incorporated into cells and accumulate in the nucleus, inducing a G1 cell cycle arrest (Chen et al, 1999a;Brooks et al, 2008).ROS, generated during the process of ischaemia in the mitochondria of cardiomyocytes (Becker et al, 1999) may affect the function of cardiac channel proteins. E2-isoketals, highly reactive products of the isoprostane pathway, are associated with cardiac Na + channel dysfunction indicating a role of isoprostanes in ischaemia-related conduction abnormalities and arrhythmias (Fukuda et al, 2005).…”

n-3 Fatty Acid-Derived Lipid Mediators against Neurological Oxidative Stress and Neuroinflammation

“…The enzymic lipid mediators of EPA metabolism include E-series resolvins, 3-series PGs, 5-series LTs, and 17, 18-epoxyeicosatetraenoic acid (17,. Nonenzymic mediators of EPA metabolism are cyclopentenone-isoprostanes (A 3 /J 3 -IsoPs) (Brooks et al, 2008). Similarly, the enzymic lipid mediators of DHA metabolism include D-series resolvins, neuroprotectins (NTPs), and maresins (MaRs) (Figure 7.1).…”