Homocysteine-induced brain lipid peroxidation: effects of NMDA receptor blockade, antioxidant treatment, and nitric oxide synthase inhibition.
The effect of homocysteine (HCY) on lipid peroxidation (LP), a current mechanism of oxidative neurotoxicity, was investigated in rat brain synaptosomes. LP was assessed by measuring the amount of thiobarbituric acid-reactive substances (TBARS) formed from synaptosomal fractions following HCY treatment. Increasing HCY concentrations (5-1000 micro M) enhanced the TBARS formation in brain synaptosomes in a concentration-dependent manner. When compared at equimolar concentrations (100 micro M), the oxidative potency of HCY was lower than that of the oxidant ferrous sulfate, similar to that produced by glutamate (Glu) and the mitochondrial toxin 3-nitropropionic acid, and higher than that of the Glu agonists, kainate and quinolinate. The N-methyl-D-aspartate receptor (NMDAr) antagonist dizocilpine (MK-801) completely blocked the HCY-induced LP at concentrations between 5 to 1000 micro M, whereas the well-known antioxidant N-acetylcysteine (NAC) was less effective, but still protective against the HCY oxidative toxicity at higher concentrations (400 and 1000 micro M). Three nitric oxide synthase (NOS) inhibitors, 7-nitroindazole (7-NI), Nomega-nitro-L-arginine (L-NARG) and Nomega-nitro-L-arginine methyl ester (L-NAME), were also tested on HCY-induced LP at increasing concentrations. Both nonspecific NOS inhibitors (L-NARG and L-NAME) decreased more effectively the HCY-induced LP than did the selective neuronal NOS inhibitor, 7-NI. These results show that submillimolar concentrations of HCY can induce oxidative injury to nerve terminals, and this effect involves NMDAr stimulation, NOS activation, and associated free radicals formation.
Jara-Prado
Aurelio
A
Departamento de Genetica, Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez, S.S.A. Insurgentes Sur # 3877, México D.F., 14269, México.
Ortega-Vazquez
Alberto
A
Martinez-Ruano
Leticia
L
Rios
Camilo
C
Santamaria
Abel
A
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001921:Brain / Q000378:metabolism*; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006710:Homocysteine / Q000378:metabolism / Q000633:toxicity*; D007191:Indazoles / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects / Q000502:physiology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019335:Nitroarginine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism
D000975:Antioxidants; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D016166:Free Radical Scavengers; D007191:Indazoles; D016194:Receptors, N-Methyl-D-Aspartate; D017392:Thiobarbituric Acid Reactive Substances; D006710:Homocysteine; D019335:Nitroarginine; D016291:Dizocilpine Maleate; D019001:Nitric Oxide Synthase; C080122:7-nitroindazole; D019331:NG-Nitroarginine Methyl Ester; D000111:Acetylcysteine