ascorbic-acid and 4-hydroperoxy-2-nonenal

The lack of suitable biomarkers of oxidative stress is a common problem for antioxidant intervention studies in humans. We evaluated the efficacy of vitamin C supplementation in decreasing biomarkers of lipid peroxidation in nonsmokers and in cigarette smokers, a commonly studied, free-living human model of chronic oxidative stress. Participants received ascorbic acid (500mg twice per day) or placebo for 17 days in a double-blind, placebo-controlled, randomized crossover design study. The urinary biomarkers assessed and reported herein are derived from 4-hydroperoxy-2-nonenal (HPNE) and include the mercapturic acid (MA) conjugates of 4-hydroxy-2(E)-nonenal (HNE), 1,4-dihydroxy-2(E)-nonene (DHN), and 4-oxo-2(E)-nonenol(ONO). Vitamin C supplementation decreased the urinary concentrations of both ONO-MA (p=0.0013) and HNE-MA (p=0.0213) by ~30%; however, neither cigarette smoking nor sex affected these biomarkers. In contrast, vitamin C supplementation decreased urinary concentrations of DHN-MA (three-way interaction p=0.0304) in nonsmoking men compared with nonsmoking women (p<0.05), as well as in nonsmoking men compared with smoking men (p<0.05). Vitamin C supplementation also decreased (p=0.0092) urinary total of metabolites by ~20%. Thus, HPNE metabolites can be reduced favorably in response to improved plasma ascorbic acid concentrations, an effect due to ascorbic acid antioxidant function.

Topics: Acetylcysteine; Administration, Oral; Adolescent; Adult; Aldehydes; Alkenes; Antioxidants; Ascorbic Acid; Biomarkers; Cross-Over Studies; Double-Blind Method; Female; Humans; Lipid Peroxidation; Male; Oxidation-Reduction; Oxidative Stress; Sex Factors; Smoking; Young Adult

Polyunsaturated fatty acids are highly susceptible to oxidation induced by reactive oxygen species and enzymes, leading to the formation of lipid hydroperoxides. The linoleic acid (LA)-derived hydroperoxide, 13-hydroperoxyoctadecadienoic acid (HPODE) undergoes homolytic decomposition to reactive aldehydes, 4-oxo-2(E)-nonenal (ONE), 4-hydroxy-2(E)-nonenal, trans-4,5-epoxy-2(E)-decenal (EDE), and 4-hydroperoxy-2(E)-nonenal (HPNE), which can covalently modify peptides and proteins. ONE and HNE have been shown to react with angiotensin (Ang) II (DRVYIHPF) and modify the N-terminus, Arg(2), and His(6). ONE-derived pyruvamide-Ang II (Ang P) alters the biological activities of Ang II considerably. The present study revealed that EDE and HPNE preferentially modified the N-terminus and His(6) of Ang II. In addition to the N-substituted pyrrole of [N-C4H2]-Ang II and Michael addition products of [His(6)(EDE)]-Ang II, hydrated forms were detected as major products, suggesting considerable involvement of the vicinal dihydrodiol (formed by epoxide hydration) in EDE-derived protein modification in vivo. Substantial amounts of [N-(EDE-H2O)]-Ang II isomers were also formed and their synthetic pathway might involve the tautomerization of a carbinolamine intermediate, followed by intramolecular cyclization and dehydration. The main HPNE-derived products were [His(6)(HPNE)]-Ang II and [N-(HPNE-H2O)]-Ang II. However, ONE, HNE, and malondialdehyde-derived modifications were dominant, because HPNE is a precursor of these aldehydes. A mixture of 13-HPODE and [(13)C18]-13-HPODE (1:1) was then used to determine the major modifications derived from LA peroxidation. The characteristic doublet (1:1) observed in the mass spectrum and the mass difference of the [M+H](+) doublet aided the identification of Ang P (N-terminal α-ketoamide), [N-ONE]-Ang II (4-ketoamide), [Arg(2)(ONE-H2O)]-Ang II, [His(6)(HNE)]-Ang II (Michael addition product), [N-C4H2]-Ang II (EDE-derived N-substituted pyrrole), [His(6)(HPNE)]-Ang II, [N-(9,12-dioxo-10(E)-dodecenoic acid)]-Ang II, and [His(6)(9-hydroxy-12-oxo-10(E)-decenoic acid)]-Ang II as the predominant LA-derived modifications. These modifications could represent the majority of lipid-derived modifications to peptides and proteins in biological systems.

Topics: Aldehydes; Angiotensin II; Ascorbic Acid; Aspartame; Carbon Isotopes; Epoxy Compounds; Isomerism; Linoleic Acids; Lipid Peroxides; Malondialdehyde; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry