In vivo involvement of cytochrome P450 4A family in the oxidative metabolism of the lipid peroxidation product trans-4-hydroxy-2-nonenal, using PPAR alpha-deficient mice

Trans-4-hydroxy-2-nonenal (HNE) is a potent cytotoxic and genotoxic compoun d originating from the peroxidation of n-6 polyunsaturated fatty acids. Its metabolism has been previously studied in the rat (Alary et al, 1995, Chem . Res. Toxicol., 8: 35-39), In addition to major urinary mercapturic deriva tives, some polar urinary metabolites were isolated and could correspond to hydroxylated compounds. 4-Hydroxynonenoic acid (HNA), resulting from the o xidation of the HNE carbonyl group, is a medium chain fatty acid and its om ega-hydroxylation might be hypothesized. Therefore, the involvement of the CYP 4A family isoenzymes in the metabolism of [H-3]HNE has been investigate d in vivo, using inducer treatments (fibrates) in wild-type or in peroxisom e proliferator-activated receptor alpha (PPAR alpha)-deficient mice. In wil d-type mice, but not in PPAR alpha (-/-) mice, fibrate treatments resulted in an increase of two urinary metabolites characterized, after HPLC purific ations and mass spectrometry analyses, as the omega-hydroxylated metabolite of HNA, i.e., 4,9-dihydroxy-2-nonenoic acid, and its oxidized form, 4-hydr oxy-2-nonene-1,9-dicarboxylic acid. The formation of the latter is correlat ed accurately to laurate hydroxylase activity studied concurrently in micro somes prepared from the liver of these animals. Basal levels of these two m etabolites were measured in urine of normal and PPAR alpha-deficient mice. These results are in accord with an implication of the P450 4A family in th e extended oxidative metabolism of 4-HNE.