title: p-Hydroxyphenylacetaldehyde, the major product of tyrosine oxidation by the activated myeloperoxidase system can act as an antioxidant in LDL.
abstract: The oxidative modification of low density lipoprotein (LDL) may play a significant role in atherogenesis. HOCl generated by the myeloperoxidase/H2O2/Cl- system of activated neutrophils may be operative in vivo making LDL atherogenic. Tyrosine has been found to be oxidized by HOCl to p-hydroxyphenylacetaldehyde (p-HA) capable of modifying phospholipid amino groups in LDL. As an amphiphatic phenolic compound, p-HA may have the potential to act as an antioxidant in the lipid phase of LDL. The present results show that (a) tyrosine exerts a protective effect on LDL modification by HOCl, (b) p-HA could act as antioxidant associated with the lipoprotein preventing cell- and transition metal ion-mediated LDL oxidation and (c) p-HA was able to scavenge free radicals.
authors.affiliation: Department of Laboratory Medicine, University of Vienna, Vienna, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Exner
authors.forename: E
authors.initials: E
authors.lastname: Alt
authors.forename: M
authors.initials: M
authors.lastname: Hermann
authors.forename: R
authors.initials: R
authors.lastname: Hofbauer
authors.forename: S
authors.initials: S
authors.lastname: Kapiotis
authors.forename: P
authors.initials: P
authors.lastname: Quehenberger
authors.forename: W
authors.initials: W
authors.lastname: Speiser
authors.forename: E
authors.initials: E
authors.lastname: Minar
authors.forename: B
authors.initials: B
authors.lastname: Gmeiner
mesh_terms: D000079:Acetaldehyde / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004587:Electrophoresis, Agar Gel; D004730:Endothelium, Vascular / Q000166:cytology; D016166:Free Radical Scavengers / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006997:Hypochlorous Acid / Q000378:metabolism; D007477:Ions; D050356:Lipid Metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism*; D009504:Neutrophils / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism*; D019800:Phenol; D011485:Protein Binding; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism*; D014471:Umbilical Veins / Q000166:cytology
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D007477:Ions; D008077:Lipoproteins, LDL; D017392:Thiobarbituric Acid Reactive Substances; D019800:Phenol; D014443:Tyrosine; D006997:Hypochlorous Acid; C097891:4-hydroxyphenylacetaldehyde; D009195:Peroxidase; D000079:Acetaldehyde; D010100:Oxygen