ascorbic-acid and 4-oxo-2-nonenal

Angiotensin (Ang) II is a major bioactive peptide of the renin/angiotensin system and is involved in various cardiovascular functions and diseases. Ang II type 1 (AT

Topics: Aldehydes; Angiotensin II; Ascorbic Acid; Carbon Isotopes; Cell Line; Copper Sulfate; Endothelial Cells; Humans; Isotope Labeling; Linoleic Acid; Lipid Peroxidation; Oxidative Stress; Receptor, Angiotensin, Type 1

alpha,beta-Unsaturated aldehydes such as 4-hydroxy-2-nonenal (HNE) and other electrophilic lipid peroxidation (LPO) products may contribute to the pathogenesis of cancer, cardiovascular diseases, and other age-related diseases by cytotoxic, genotoxic, and proinflammatory mechanisms. The notion that vitamin C (ascorbic acid) acts as a biological antioxidant has been challenged recently by an in vitro study showing that ascorbic acid promotes, rather than inhibits, the formation of genotoxic LPO products from the lipid hydroperoxide, hydroperoxy octadecadienoic acid [Lee, S. H., Oe, T. & Blair, I. A. (2001) Science 292, 2083-2086]. Here, we demonstrate that ascorbic acid acts as a nucleophile and forms Michael-type conjugates with electrophilic LPO products. Several ascorbyl-LPO product conjugates, resulting from the interaction of ascorbic acid with hydroperoxy octadecadienoic acid in vitro, were identified by tandem MS, including ascorbyl conjugates of HNE, 4-oxo-2-nonenal, and presumably, 12-oxo-9-hydroxy-10-dodecenoic acid. The same ascorbyl-LPO product conjugates were detected in human plasma. The concentration of the ascorbyl-HNE conjugate in plasma from 11 healthy subjects was found to be 1.30 +/- 0.74 microM (mean +/- SD). Our data identify ascorbylation (vitamin C conjugation) as a previously unrecognized, biologically relevant pathway for the elimination of electrophilic LPO products, and have implications for the prevention and treatment of chronic inflammatory diseases, as well as the development of novel biomarkers of oxidative stress.

Topics: Aldehydes; Ascorbic Acid; Calibration; Chromatography, Liquid; Electrons; Fatty Acids, Monounsaturated; Glutathione; Humans; Inflammation; Linoleic Acids; Lipid Metabolism; Lipid Peroxidation; Lipoxygenase Inhibitors; Magnetic Resonance Spectroscopy; Mass Spectrometry; Models, Chemical; Mutagens; Oxidative Stress; Plasma; Protein Conformation; Protein Structure, Tertiary; Spectrometry, Mass, Electrospray Ionization; Time Factors

Epidemiological data suggest that dietary antioxidants play a protective role against cancer. This has led to the proposal that dietary supplementation with antioxidants such as vitamin C (vit C) may be useful in disease prevention. However, vit C has proved to be ineffective in cancer chemoprevention studies. In addition, concerns have been raised over potentially deleterious transition metal ion-mediated pro-oxidant effects. We have now determined that vit C induces lipid hydroperoxide decomposition to the DNA-reactive bifunctional electrophiles 4-oxo-2-nonenal, 4,5-epoxy-2(E)-decenal, and 4-hydroxy-2-nonenal. The compound 4,5-Epoxy-2(E)-decenal is a precursor of etheno-2'-deoxyadenosine, a highly mutagenic lesion found in human DNA. Vitamin C-mediated formation of genotoxins from lipid hydroperoxides in the absence of transition metal ions could help explain its lack of efficacy as a cancer chemoprevention agent.

Topics: Aldehydes; Antioxidants; Ascorbic Acid; Buffers; Copper; Cyclooxygenase 1; Cyclooxygenase 2; DNA Adducts; DNA Damage; Epoxy Compounds; Ferrous Compounds; Humans; Isoenzymes; Linoleic Acids; Lipid Peroxides; Membrane Proteins; Metals; Mutagens; Oxidants; Oxidation-Reduction; Prostaglandin-Endoperoxide Synthases