Insulin neuroprotection against oxidative stress is mediated by Akt and GSK-3beta signaling pathways and changes in protein expression.
Previously we demonstrated that insulin protects against neuronal oxidative stress by restoring antioxidants and energy metabolism. In this study, we analysed how insulin influences insulin-(IR) and insulin growth factor-1 receptor (IGF-1R) intracellular signaling pathways after oxidative stress caused by ascorbate/Fe2+ in rat cortical neurons. Insulin prevented oxidative stress-induced decrease in tyrosine phosphorylation of IR and IGF-1R and Akt inactivation. Insulin also decreased the active form of glycogen synthase kinase-3beta (GSK-3beta) upon oxidation. Since phosphatidylinositol 3-kinase (PI-3K)/Akt-mediated inhibition of GSK-3beta may stimulate protein synthesis and decrease apoptosis, we analysed mRNA and protein expression of "candidate" proteins involved in antioxidant defense, glucose metabolism and apoptosis. Insulin prevented oxidative stress-induced increase in glutathione peroxidase-1 and decrease in hexokinase-II expression, supporting previous findings of changes in glutathione redox cycle and glycolysis. Moreover, insulin precluded Bcl-2 decrease and caspase-3 increased expression. Concordantly, insulin abolished caspase-3 activity and DNA fragmentation caused by oxidative stress. Thus, insulin-mediated activation of IR/IGF-1R stimulates PI-3K/Akt and inhibits GSK-3beta signaling pathways, modifying neuronal antioxidant defense-, glucose metabolism- and anti-apoptotic-associated protein synthesis. These and previous data implicate insulin as a promising neuroprotective agent against oxidative stress associated with neurodegenerative diseases.
Duarte
Ana I
AI
Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.
Santos
Paulo
P
Oliveira
Catarina R
CR
Santos
Maria S
MS
Rego
A Cristina
AC
D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D005260:Female; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006593:Hexokinase / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D018384:Oxidative Stress; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011247:Pregnancy; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D014443:Tyrosine / Q000378:metabolism; D000094765:Glutathione Peroxidase GPX1
D007004:Hypoglycemic Agents; D007328:Insulin; D018696:Neuroprotective Agents; D019253:Proto-Oncogene Proteins c-bcl-2; D014443:Tyrosine; D005979:Glutathione Peroxidase; D019869:Phosphatidylinositol 3-Kinases; D006593:Hexokinase; D017526:Receptor, IGF Type 1; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; D053148:Caspase 3; D005978:Glutathione; D000094765:Glutathione Peroxidase GPX1; C000722069:Gpx1 protein, rat