Metabolism of 4-hydroxynonenal, a cytotoxic product of lipid peroxidation, in rat precision-cut liver slices

4-Hydroxy-2-nonenal (HNE) is a major aldehydic product of lipid peroxidation known to exert several biological and cytotoxic effects. The in vitro metabolism of [4- 3H]-HNE by rat precision-cut liver slices was investigated. Liver slices rapidly metabolize HNE — about 85% of 0.1 μM [4- 3H]-HNE was degraded within 5 min of incubation. The main metabolites of HNE identified were 4-hydroxynonenoic acid (HNA), glutathione–HNE-conjugate (HNE–GSH), glutathione–1,4-dihydroxynonene-conjugate (DHN–GSH) and cysteine–HNE-conjugate (HNE–CYS). Whereas glutathione conjugation demonstrated saturation kinetics ( K m=412.2±152.7 μM and V max=12.3±2.5 nmol h −1 per milligram protein), HNA formation was linear up to 500 μM HNE in liver slices. In contrast to previous reports, no trace of the corresponding alcohol of the HNE, 1,4-dihydroxynon-2-ene was detected in the present study. Furthermore, the β-oxidation of HNA including the formation of tritiated water was demonstrated. The identification of 4-hydroxy-9-carboxy-2-nonenoic acid and 4,9-dihydroxynonanoic acid demonstrated that ω-oxidation significantly contributes to the biotransformation of HNE in liver slices.