Effects of Atypical Antioxidative Agents, S-nitrosoglutathione and Manganese, on Brain Lipid Peroxidation Induced by Iron Leaking from Tissue Disruption

Authors

  • PEKKA RAUHALA,

    1. Unit on Neurodegeneration and Neuroprotection, Laboratory of Clinical Science, National Institute of Mental Health, NIH Clinical Center, Bethesda, Maryland 20892–1264, USA
    2. Institute of Biomedicine, Department of Pharmacology and Toxicology, Box 8, University of Helsinki, Helsinki, Finland
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  • CHUANG C. CHIUEH

    Corresponding author
    1. Unit on Neurodegeneration and Neuroprotection, Laboratory of Clinical Science, National Institute of Mental Health, NIH Clinical Center, Bethesda, Maryland 20892–1264, USA
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Address for correspondence: Dr. Chuang C. Chiueh, Unit on Neurodegeneration and Neuroprotection, Laboratory of Clinical Science, National Institute of Mental Health, NIH Clinical Center, 10/3D-41, Bethesda, MD 20892–1264. e-mail: chiueh@helix.nih.gov

Abstract

Abstract: A fluorescent assay of brain lipid peroxidation was used for screening new antioxidants for the prevention of neurodegeneration caused by free radicals. Incubation of rat brain homogenates led to a temperature-dependent increase in production of fluorescent adducts of peroxidized poly-unsaturated fatty acids; it was inhibited completely by lowering the incubation temperature to 4°C. This tissue disruption-induced brain lipid peroxidation at 37°C was blocked by deferoxamine (IC50= 0.3 μM) and EDTA; it was augmented by adding submicromolar iron and hemoglobin. Ferrous ion's pro-oxidative activities were five times more potent than ferric ion. Micromolar manganese completely inhibited lipid peroxidation, confirming earlier unexpected in vivo reports. Trolox and vitamin C suppressed brain lipid peroxidation with IC50 values of 20 and 500 μM, respectively. U-78517F was approximately 20 times more potent than Trolox. 17β-Estradiol, hydralazine, S-nitrosoglutathione and 3-hydroxybenzylhydrazine were as potent as Trolox. Melatonin, glutathione, α-lipoic acid and l-deprenyl were about 20 times less potent than Trolox. Surprisingly, N-tert-butyl-α-phenylnitrone was a weak antioxidant. Furthermore, this procedure can also detect pro-oxidative side effects of vitamin C, oxidized glutathione, penicillamine and Angeli's salt. The present results obtained from this selective fluorescent assay are consistent with earlier reports that iron complexes promote while manganese inhibits brain lipid peroxidation caused by cell disruption. S-Nitrosoglutathione, melatonin, 17β-estradiol, and manganese have been successfully tested in cell/animal models for their potential neuroprotective effects. In conclusion, monitoring fluorescent adducts of peroxidizing polyunsaturated fatty acids in brain homogenates is a simple, quantitative method for studying iron-dependent brain lipid peroxidation and for screening of potential neuroprotective antioxidants in both in vitro and in vivo preparations.

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