oxidants and antioxidants in biology - Oxygen Club of California

Can insulin have a neuroprotective role in cultured cortical
neurons submitted to oxidative stress?
AI. DUARTE 2 , M. S. SANTOS 2 , C. R. OLIVEIRA 1 AND A C. REGO 1
1 Institute of Biochemistry, Faculty of Medicine, and 2 Department of Zoology,
Faculty of Sciences and Technology, Center for Neuroscience and Cell Biology,
University of Coimbra, 3004-504 Coimbra, Portugal
Insulin has been suggested to have a neuroprotective role in
neurodegenerative disorders, such as Alzheimer’s disease, in which
oxidative stress was previously demonstrated. In this study, we investigated
the role of insulin under oxidative stress conditions, induced
by the oxidizing pair ascorbate/Fe 2+ , in cultured cortical neurons.
A significant decrease in cell viability, determined by the
MTT assay, was observed after the induction of oxidative stress (15
min), followed by 5 h-postincubation in Neurobasal medium. Under
these conditions, we have studied the effect of insulin (0.1, 1,
10 and 25 µM), which was added to the culture medium 96 or 48 h
prior and/or during the induction of oxidative stress. Preincubation
of cortical neurons for 96 h with increasing concentrations of insulin
induced an U-shaped curve in MTT reduction, and 25 µM insulin
prevented the effect of oxidative stress. Insulin (0.1 and 10 µM,
added 48 h prior and during the incubation with ascorbate/Fe 2+ , respectively)
protected against oxidative stress-mediated decreased in
MTT reduction. Furthermore, insulin (0.1, 10 and 25 µM, incubated
for 96 or 48 h) significantly decreased the levels of lipid peroxidation
induced by ascorbate/Fe 2+ . These results suggest that the
neuroprotective role of insulin in the brain may be associated with a
protective effect against oxidative stress-mediated cell damage.
A. I. Duarte is supported by Fundação para a Ciência e Tecnologia,
Portugal (SFRH/BD/5338/2001).
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