title: IPF2alpha-I: an index of lipid peroxidation in humans.
abstract: Isoprostanes are prostaglandin isomers produced from arachidonic acid by a free radical-catalyzed mechanism. Urinary excretion of 8-iso-prostaglandin F2alpha, an isomer of the PGG/H synthase (cyclooxygenase or COX) enzyme product, prostaglandin F2alpha (PGF2alpha), has exhibited promise as an index of oxidant stress in vivo. We have developed a quantitative method to measure isoprostane F2alpha-I, (IPF2alpha-I) a class I isomer (8-iso-PGF2alpha is class IV), using gas chromatography/mass spectrometry. IPF2alpha-I is severalfold as abundant in human urine as 8-iso-PGF2alpha, with mean values of 737 +/- 20.6 pg/mg creatinine. Both isoprostanes are formed in a free radical-dependent manner in low density lipoprotein oxidized by copper in vitro. However, IPF2alpha-I, unlike 8-iso-PGF2alpha, is not formed in a COX-dependent manner by platelets activated by thrombin or collagen in vitro. Similarly, COX inhibition in vivo has no effect on IPF2alpha-I. Neither serum IPF2alpha-I, an index of cellular capacity to generate the isoprostane, nor urinary excretion of IPF2alpha-I, an index of actual generation in vivo, is depressed by aspirin or indomethacin. In contrast, both serum thromboxane B2 and urinary excretion of its 11-dehydro metabolite are depressed by the COX inhibitors. Although serum 8-iso-PGF2alpha formation is substantially depressed by COX inhibitors, urinary excretion of the compound is unaffected. Urinary IPF2alpha-I is elevated in cigarette smokers compared with controls (1525 +/- 180 versus 740 +/- 40 pg/mg creatinine; P < 0.01) and is highly correlated with urinary 8-iso-PGF2alpha (r = 0.9; P < 0.001). Urinary IPF2alpha-I is a novel index of lipid peroxidation in vivo, which can be measured with precision and sensitivity. It is an abundant F2-isoprostane formed in a free radical- but not COX-dependent manner. Although 8-iso-PGF2alpha may be formed as a minor product of COX, this pathway contributes trivially, if at all, to levels in urine. Urinary excretion of both isoprostanes is elevated in cigarette smokers.
authors.affiliation: Center for Experimental Therapeutics, University of Pennsylvania, Philadelphia, PA 19104-6100, USA.
authors.forename: D
authors.initials: D
authors.lastname: Praticò
authors.forename: O P
authors.initials: OP
authors.lastname: Barry
authors.forename: J A
authors.initials: JA
authors.lastname: Lawson
authors.forename: M
authors.initials: M
authors.lastname: Adiyaman
authors.forename: S W
authors.initials: SW
authors.lastname: Hwang
authors.forename: S P
authors.initials: SP
authors.lastname: Khanapure
authors.forename: L
authors.initials: L
authors.lastname: Iuliano
authors.forename: J
authors.initials: J
authors.lastname: Rokach
authors.forename: G A
authors.initials: GA
authors.lastname: FitzGerald
mesh_terms: D015415:Biomarkers; D015237:Dinoprost / Q000737:chemistry / Q000652:urine*; D006801:Humans; D007536:Isomerism; D015227:Lipid Peroxidation; D018384:Oxidative Stress
chemical_list: D015415:Biomarkers; D015237:Dinoprost