Effect of iron and manganese on hydroxyl radical production by 6-hydroxydopamine: mediation of antioxidants.
6-Hydroxydopamine (6-OHDA) neurotoxicity has often been related to the generation of free radicals. Here we examined the effect of the presence of iron (Fe(2+) and Fe(3+)) and manganese and the mediation of ascorbate, L-cysteine (CySH), glutathione (GSH), and N-acetyl-CySH on hydroxyl radical (*OH) production during 6-OHDA autoxidation. In vitro, the presence of 800 nM iron increased (> 100%) the production of *OH by 5 microM 6-OHDA while Mn(2+) caused a significant reduction (72%). The presence of ascorbate (100 microM) induced a continuous generation of *OH while the presence of sulfhydryl reductants (100 microM) limited this production to the first minutes of the reaction. In general, the combined action of metal + antioxidant increased the *OH production, this effect being particularly significant (> 400%) with iron + ascorbate. In vivo, tyrosine hydroxylase immunohistochemistry revealed that intrastriatal injections of rats with 6-OHDA (30 nmol) + ascorbate (600 nmol), 6-OHDA + ascorbate + Fe(2+) (5 nmol), and 6-OHDA + ascorbate + Mn(2+) (5 nmol) caused large striatal lesions, which were markedly reduced (60%) by the substitution of ascorbate by CySH. Injections of Fe(2+) or Mn(2+) alone showed no significant difference to those of saline. These results clearly demonstrate the role of ascorbate as an essential element for the neurotoxicity of 6-OHDA, as well as the diminishing action of sulfhydryl reductants, and the negligible effect of iron and manganese on 6-OHDA neurotoxicity.
Méndez-Alvarez
E
E
Grupo de Neuroquímica, Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
Soto-Otero
R
R
Hermida-Ameijeiras
A
A
López-Martín
M E
ME
Labandeira-García
J L
JL
D000111:Acetylcysteine / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000378:metabolism* / Q000494:pharmacology; D001205:Ascorbic Acid / Q000378:metabolism / Q000494:pharmacology; D003342:Corpus Striatum / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D005978:Glutathione / Q000378:metabolism / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism; D017665:Hydroxyl Radical / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology; D008345:Manganese / Q000378:metabolism* / Q000494:pharmacology; D010084:Oxidation-Reduction; D016627:Oxidopamine / Q000378:metabolism* / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000975:Antioxidants; D017665:Hydroxyl Radical; D008345:Manganese; D016627:Oxidopamine; D006861:Hydrogen Peroxide; D007501:Iron; D005978:Glutathione; D003545:Cysteine; D001205:Ascorbic Acid; D000111:Acetylcysteine