title: Insulin neuroprotection against oxidative stress in cortical neurons--involvement of uric acid and glutathione antioxidant defenses.
abstract: In this study we investigated the effect of insulin on neuronal viability and antioxidant defense mechanisms upon ascorbate/Fe2+-induced oxidative stress, using cultured cortical neurons. Insulin (0.1 and 10 microM) prevented the decrease in neuronal viability mediated by oxidative stress, decreasing both necrotic and apoptotic cell death. Moreover, insulin inhibited ascorbate/Fe2+-mediated lipid and protein oxidation, thus decreasing neuronal oxidative stress. Increased 4-hydroxynonenal (4-HNE) adducts on GLUT3 glucose transporters upon exposure to ascorbate/Fe2+ were also prevented by insulin, suggesting that this peptide can interfere with glucose metabolism. We further analyzed the influence of insulin on antioxidant defense mechanisms in the cortical neurons. Oxidative stress-induced decreases in intracellular uric acid and GSH/GSSG levels were largely prevented upon treatment with insulin. Inhibition of phosphatidylinositol-3-kinase (PI-3K) or mitogen-induced extracellular kinase (MEK) reversed the effect of insulin on uric acid and GSH/GSSG, suggesting the activation of insulin-mediated signaling pathways. Moreover, insulin stimulated glutathione reductase (GRed) and inhibited glutathione peroxidase (GPx) activities under oxidative stress conditions, further supporting that insulin neuroprotection was related to the modulation of the glutathione redox cycle. Thus, insulin may be useful in preventing oxidative stress-mediated injury that occurs in several neurodegenerative disorders.
authors.affiliation: Department of Zoology, Faculty of Sciences and Technology, Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal.
authors.forename: Ana I
authors.initials: AI
authors.lastname: Duarte
authors.forename: Maria S
authors.initials: MS
authors.lastname: Santos
authors.forename: Catarina R
authors.initials: CR
authors.lastname: Oliveira
authors.forename: A Cristina
authors.initials: AC
authors.lastname: Rego
mesh_terms: D000447:Aldehydes / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001205:Ascorbic Acid / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D005260:Female; D005296:Ferrous Compounds / Q000494:pharmacology; D051274:Glucose Transporter Type 3 / Q000096:biosynthesis; D005978:Glutathione / Q000378:metabolism*; D007328:Insulin / Q000502:physiology*; D015227:Lipid Peroxidation / Q000187:drug effects; D009336:Necrosis / Q000517:prevention & control; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018384:Oxidative Stress / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D013268:Stimulation, Chemical; D014527:Uric Acid / Q000378:metabolism*
chemical_list: D000447:Aldehydes; D005296:Ferrous Compounds; D051274:Glucose Transporter Type 3; D007328:Insulin; C495690:Slc2a3 protein, rat; D014527:Uric Acid; C020748:ferrous sulfate; D005978:Glutathione; C027576:4-hydroxy-2-nonenal; D001205:Ascorbic Acid