Tyrosine: an inhibitor of LDL oxidation and endothelial cell cytotoxicity initiated by superoxide/nitric oxide radicals.
Tyrosyl radicals can catalyze LDL oxidation. In addition to their LDL oxidizing ability, superoxide (O2.-)/nitric oxide (NO.) generate phenoxyl radicals when reacting with tyrosine. Therefore we tested if tyrosine can act as a pro-oxidant in O2.-/NO.-initiated LDL oxidation. When LDL was exposed to O2.-/NO., tyrosine exerted a strong inhibitory effect on O2.-/ NO.-initiated LDL oxidation as measured by TBARS formation and alteration in electrophoretic mobility of LDL. Tyrosine was also able to protect human endothelial cells from the cytotoxic effect of O2.-/NO.. Because O2.-/NO. can occur in vivo, the results may indicate that serum-free tyrosine could act as an efficacious physiological antioxidant in case of O2.-/NO.-initiated LDL oxidation and endothelial cell cytotoxicity.
Kapiotis
S
S
Clinical Institute of Medical and Chemical Laboratory Diagnostics, University of Vienna, Austria.
Hermann
M
M
Held
I
I
Mühl
A
A
Gmeiner
B
B
D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism* / Q000633:toxicity; D015227:Lipid Peroxidation / Q000187:drug effects*; D008077:Lipoproteins, LDL / Q000037:antagonists & inhibitors*; D008563:Membrane Lipids / Q000378:metabolism; D009569:Nitric Oxide / Q000494:pharmacology*; D017382:Reactive Oxygen Species; D013481:Superoxides / Q000494:pharmacology*; D014443:Tyrosine / Q000494:pharmacology*; D014471:Umbilical Veins
D008077:Lipoproteins, LDL; D008563:Membrane Lipids; D017382:Reactive Oxygen Species; D013481:Superoxides; D009569:Nitric Oxide; D014443:Tyrosine; D007770:L-Lactate Dehydrogenase