Copper-zinc superoxide dismutase affects Akt activation after transient focal cerebral ischemia in mice.
OBJECTIVE
The serine-threonine kinase Akt is activated by phosphorylation at serine-473. After phosphorylation, activated Akt inactivates BAD or caspase-9 or other apoptogenic components, thereby inhibiting cell death. In this study we examined the relationship between Akt phosphorylation and oxidative stress after transient focal cerebral ischemia (FCI) using copper-zinc superoxide dismutase (SOD1) transgenic (Tg) mice.


METHODS
The mice were subjected to 60 minutes of middle cerebral artery occlusion by intraluminal suture blockade followed by 1, 4, and 24 hours of reperfusion. Phospho-Akt expression was examined by immunohistochemistry and Western blot analysis. Production of superoxide anion was assessed by the hydroethidine method in both wild-type mice and SOD1 Tg mice. DNA fragmentation was evaluated by terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling (TUNEL).


RESULTS
Immunohistochemistry demonstrated that phospho-Akt was constitutively expressed and was decreased in the ischemic core as early as 1 hour after reperfusion, whereas it was temporally increased in the cortex at 4 hours. Phospho-Akt expression was enhanced in the SOD1 Tg mice. Western blot analysis showed that phospho-Akt was maximized 4 hours after reperfusion in the wild-type mice, whereas phospho-Akt was increased as early as 1 hour after ischemia in the SOD1 Tg mice. There was a significant decrease in TUNEL-positive cells in the SOD1 Tg mice compared with the wild-type mice.


CONCLUSIONS
The present study suggests that SOD1 may contribute to the early activation of the Akt cell survival signaling pathway and may attenuate subsequent DNA damage after transient FCI.
Department of Neurosurgery, Stanford University School of Medicine, Stanford, Calif 94305-5487, USA.
Nobuo
N
Noshita
Taku
T
Sugawara
Anders
A
Lewén
Takeshi
T
Hayashi
Pak H
PH
Chan
D000818:Animals; D030801:Animals, Genetically Modified; D000975:Antioxidants / Q000378:metabolism; D015153:Blotting, Western; D002470:Cell Survival / Q000502:physiology; D053938:DNA Fragmentation; D004195:Disease Models, Animal; D004789:Enzyme Activation / Q000235:genetics / Q000502:physiology; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D002546:Ischemic Attack, Transient / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D008297:Male; D051379:Mice; D018384:Oxidative Stress; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction / Q000502:physiology; D013482:Superoxide Dismutase / Q000235:genetics / Q000502:physiology*; D000072105:Superoxide Dismutase-1; D013481:Superoxides / Q000378:metabolism
D000975:Antioxidants; D011518:Proto-Oncogene Proteins; C000606290:SOD1 protein, human; D013481:Superoxides; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt