Insulin reduces cerebral ischemia/reperfusion injury in the hippocampus of diabetic rats: a role for glycogen synthase kinase-3beta.
OBJECTIVE
There is evidence that insulin reduces brain injury evoked by ischemia/reperfusion (I/R). However, the molecular mechanisms underlying the protective effects of insulin remain unknown. Insulin is a well-known inhibitor of glycogen synthase kinase-3beta (GSK-3beta). Here, we investigate the role of GSK-3beta inhibition on I/R-induced cerebral injury in a rat model of insulinopenic diabetes.


METHODS
Rats with streptozotocin-induced diabetes were subjected to 30-min occlusion of common carotid arteries followed by 1 or 24 h of reperfusion. Insulin (2-12 IU/kg i.v.) or the selective GSK-3beta inhibitor TDZD-8 (0.2-3 mg/kg i.v.) was administered during reperfusion.


RESULTS
Insulin or TDZD-8 dramatically reduced infarct volume and levels of S100B protein, a marker of cerebral injury. Both drugs induced phosphorylation of the Ser9 residue, thereby inactivating GSK-3beta in the rat hippocampus. Insulin, but not TDZD-8, lowered blood glucose. The hippocampi of the drug-treated animals displayed reduced oxidative stress at 1 h of reperfusion as shown by the decreased generation of reactive oxygen species and lipid peroxidation. I/R-induced activation of nuclear factor-kappaB was attenuated by both drug treatments. At 24 h of reperfusion, TDZD-8 and insulin significantly reduced plasma levels of tumor necrosis factor-alpha; neutrophil infiltration, measured as myeloperoxidase activity and intercellular-adhesion-molecule-1 expression; and cyclooxygenase-2 and inducible-NO-synthase expression.


CONCLUSIONS
Acute administration of insulin or TDZD-8 reduced cerebral I/R injury in diabetic rats. We propose that the inhibitory effect on the activity of GSK-3beta contributes to the protective effect of insulin independently of any effects on blood glucose.
Department of Anatomy, Pharmacology, and Forensic Medicine, University of Turin, Turin, Italy. massimo.collino@unito.it
Massimo
M
Collino
Manuela
M
Aragno
Sara
S
Castiglia
Chiara
C
Tomasinelli
Christoph
C
Thiemermann
Giuseppe
G
Boccuzzi
Roberto
R
Fantozzi
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D015153:Blotting, Western; D001835:Body Weight / Q000187:drug effects; D002545:Brain Ischemia / Q000150:complications*; D003921:Diabetes Mellitus, Experimental / Q000097:blood / Q000503:physiopathology*; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D006728:Hormones / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D016328:NF-kappa B / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013830:Thiadiazoles / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000097:blood
C494356:4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione; D001786:Blood Glucose; D006728:Hormones; D007004:Hypoglycemic Agents; D007328:Insulin; D016328:NF-kappa B; D013830:Thiadiazoles; D014409:Tumor Necrosis Factor-alpha; D038362:Glycogen Synthase Kinase 3