Evidence of phosphorylation of Akt and neuronal survival after transient focal cerebral ischemia in mice.
The serine-threonine kinase, Akt, prevents apoptosis by phosphorylation at serine-473 in several cell systems. After phosphorylation, activated Akt inactivates other apoptogenic factors, such as Bad or caspase-9, thereby inhibiting cell death. The present study examined phosphorylation of Akt at serine-473 and DNA fragmentation after transient focal cerebral ischemia in mice subjected to 60 minutes of focal cerebral ischemia by intraluminal blockade of the middle cerebral artery. Phospho-Akt was analyzed by immunohistochemistry and Western blot analysis. The DNA fragmentation was evaluated by terminal deoxynucleotidyl transferase-mediated uridine 5-triphosphate-biotin nick end-labeling (TUNEL). Immunohistochemistry showed the expression of phospho-Akt was markedly increased in the middle cerebral artery territory cortex at 4 hours of reperfusion compared with the control, whereas it was decreased by 24 hours. Western blot analysis showed a significant increase of phospho-Akt 4 hours after focal cerebral ischemia in the cortex, whereas phospho-Akt was decreased in the ischemic core. Double staining with phospho-Akt and TUNEL showed different cellular distributions of phospho-Akt and TUNEL-positive staining. Phosphorylation of Akt was prevented after focal cerebral ischemia by LY294002, a phosphatidylinositol 3-kinase inhibitor, which facilitated subsequent DNA fragmentation. These results suggest that phosphorylation of Akt may be involved in determining cell survival or cell death after transient focal cerebral ischemia.
Noshita
N
N
Department of Neurosurgery, Stanford University School of Medicine, Stanford, California 94305-5487, USA.
Lewén
A
A
Sugawara
T
T
Chan
P H
PH
D000818:Animals; D015153:Blotting, Western; D002470:Cell Survival / Q000502:physiology; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism; D002544:Cerebral Infarction / Q000378:metabolism; D053938:DNA Fragmentation / Q000502:physiology; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D002546:Ischemic Attack, Transient / Q000378:metabolism*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009474:Neurons / Q000166:cytology* / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000032:analysis / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt
D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt