Identification of Two Major F2 Isoprostanes, 8,12-Iso- and 5-epi-8,12-Iso-isoprostane F2α-VI, in Human Urine

Abstract

Isoprostanes (iPs) are nonenzymatic, free radical-derived compounds isomeric with enzymatically formed eicosanoids such as prostaglandins, leukotrienes, and thromboxanes. One group formed by the auto-oxidation of arachidonic acid, the F 2 -iPs, consists of four classes of isomers of prostaglandin F 2␣ (PGF 2␣ ). They are relatively abundant in human urine. This fact, along with their chemical stability and excellent characteristics for quantitation by gas chromatography/mass spectrometry, has made them attractive indices of oxidative stress in humans. We developed a specific assay using gas chromatography/mass spectrometry for the first identified F 2 -iP, iPF 2␣ -III (previously called 8-iso-PGF 2␣ or 8-epi-PGF 2␣ ), which demonstrated the utility of monitoring a specific isomer. Recently, we described an assay for another isomer, iPF 2␣ -VI, which is present in urine in greater concentration than iPF 2␣ -III and which is particularly amenable to quantitation. We now describe the identification in human urine of two more isomers, 8,12-iso-iPF 2␣ -VI and 5-epi-8,12-iso-iPF 2␣ -VI, using high performance liquid chromatography/tandem mass spectrometry and gas chromatography/mass spectrometry. These compounds are each present in ϳ5-fold greater concentrations than iPF 2␣ -VI (ϳ20-fold greater than iPF 2␣ -III). They share the unique chemical characteristics of class VI compounds, which make them attractive targets for quantitation by gas chromatography/mass spectrometry and immunoassay development.

Oxidized derivatives of ω-3 fatty acids: identification of IPF3α-VI in human urine

“…Although nPs can be measured in brain tissue, an attempt to measure F 4 -nPs by GC/MS in the urine of patients suffering from AD found them to be undetectable (20). We selected Group VI F 3 -iPs and F 4 -nPs as our initial targets for detection in biological fluids because we had previously observed that among AA-derived iPs, Group VI iPs such as iPF 2a -VI 2 and 8,12-iso-iPF 2a -VI are the most abundant in human urine (2,8). Because of the close structural analogy of iPF 3a -VI 3 and nPF 4a -VI to iPF 2a -VI 2 ( Fig.…”

“…These synthetic markers have been used to discover and characterize four classes of iPs in biological fluids (2,8,9). The availability of these standards permitted the development of gas chromatography/mass spectrometry (GC/MS) and liquid chromatography tandem mass spectrometry (LC/MS/MS) methodologies to examine the distribution of iPs within each of these classes (10,11).…”

Unorthodox routes to prostanoid formation: new twists in cyclooxygenase-initiated pathways

“…Isoprostane F 2α -III (iPF 2α -III, previously designated 8-iso-PGF 2α ) was first discovered in human urine. This compound serves as a marker of in vivo lipid peroxidation (33,34), as do several other isoprostanes, particularly iPF 2α -I, iPF 2α -IV, and isomers of 8,12-isoiPF 2α -IV (35)(36)(37). The isoprostane indices of lipid peroxidation increase following bolus injection of LPSs in humans (38), and they are elevated in cigarette smokers compared with controls and in patients with acute alcoholic hepatitis (39).…”

Effect of regulated expression of human cyclooxygenase isoforms on eicosanoid and isoeicosanoid production in inflammation

“…30) iPF 2α -VI (formerly known as IPF 2α -I; ref. 29) and 8,12-iso-iPF 2α -V1 (32), the most abundant urinary F 2 -iP (33).…”

“…Given the evidence that urinary iPs reflect alterations in lipid peroxidation in vivo (32), it seems likely that they will also reflect the oxidant component of inflammatory responses in humans. Although the present results pertain to experimental endotoxemia, we have previously reported that urinary iPF 2α -III is increased in patients with the adult respiratory distress syndrome and that alterations in iP excretion reflect the clinical course of this disease (74).…”