Résumé
F2-isoprostanes (F2-IsoPs) are formed from the free radicaloxidation of arachidonic acid and are widely used as biomarkers ofendogenous oxidative damage. Sixty-four F2-IsoP isomers aregenerated during lipid peroxidation; however, most studies havefocused only on one isomer, 15-F2t-IsoP (commonly referred to as8-iso-PGF2α). Immunoassay and mass spectrometric (MS)techniques have been developed to quantify 15-F2t-IsoP inbiological fluids. Even though this molecule has a short half-life ofonly a few minutes, most studies quantify 15-F2t-IsoP directlyrather than its’ urinary metabolite (2,3-dinor-5,6-dihydro-15-F2tIsoP, 15-F2t-IsoP-M). An increasing body of evidencedemonstrates the efficacy of 15-F2t-IsoP-M quantification. Forexample, 15-F2t-IsoP-M, but not 15-F2t-IsoP, was positivelyassociated with age and postmenopausal status in a largepopulation study of middle-aged and older women. Urinary 15-F2tIsoP-M also shows associations with plasma antioxidant levels,carbohydrate intake, glycemic index, and environmentalexposures while urinary 15-F2t-IsoP does not. The utility of 15-F2tIsoP measurement is further limited by the fact that this moleculecan also be generated enzymatically via the cyclooxygenases. Onthe other hand, 5-series F2-IsoPs are only generated vianonenzymatic mechanisms. And, it has been demonstrated thatthese molecules are present in greater abundance in plasma, tissue,and urine than 15-series F2-IsoPs. Yet, 5-series F2-IsoP metabolismremains unexplored. We have thus undertaken experiments toidentify and characterize metabolites of 5-epi-5-F2t-IsoP and 5-epi-5-F2c-IsoP, two abundantly produced 5-series F2-IsoPs, in humanliver microsomes. Using targeted and untargeted metabolomicapproaches, glucuronide and sulfate metabolites of F2-IsoPs havebeen identified by MS. Metabolism of these molecules by specificenzymes has also been tested. Collectively, these findings indicatethat F2-IsoP metabolism is more complex than previouslyappreciated. The presence of these metabolites in human urine isunder investigation. We anticipate that the completion of this workwill redefine F2-IsoP metabolism and outline a strategy tocomprehensively evaluate endogenous formation of theseimportant molecules