Upregulation of Akt phosphorylation at the early stage of middle cerebral artery occlusion in mice.
Akt is a serine/threonine kinase that is believed to promote cell viability in many different cell types, including neurons. Here, we observed the state of Akt phosphorylation at several time points (1, 3, 6, 12, and 24 h) during permanent occlusion of the middle cerebral artery (MCA) in mice. We detected a transient upregulation of Akt phosphorylation at 1 h of MCA occlusion (MCAO) by Western blot analysis. Double immunostaining revealed that the enhanced phosphorylation of Akt occurred mainly in neurons located in the outer area of the MCA territory (ischemic penumbra). This phenomenon was accompanied by the nuclear translocation of Akt. We confirmed that Akt enzymatic activity is elevated in both the nuclear and cytosolic fractions of brain tissue subjected to 1 h of ischemia. cAMP-response-element-binding protein (CREB), an intranuclear target molecule of Akt, exhibited increased phosphorylation after 1 h of MCAO. In our ischemia model, caspase-3 was activated in the central part of the MCA territory as little as 1 h after MCAO. However, caspase-3 activation was not recognized at this time in the outer area of the MCA territory, where Akt activity was upregulated. These results suggest that prosurvival cell signaling is initiated in an active fashion before cell death pathways are activated in neurons situated in the ischemic penumbra at the early stage of ischemia.
Shibata
Mamoru
M
Division of Neuroanatomy, Osaka University Graduate School of Medicine, Osaka, Japan.
Yamawaki
Takemori
T
Sasaki
Takahiro
T
Hattori
Hidenori
H
Hamada
Junichi
J
Fukuuchi
Yasuo
Y
Okano
Hideyuki
H
Miura
Masayuki
M
D000818:Animals; D020520:Brain Infarction / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002451:Cell Compartmentation / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D002470:Cell Survival / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D020925:Hypoxia-Ischemia, Brain / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D007150:Immunohistochemistry; D020244:Infarction, Middle Cerebral Artery / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D051379:Mice; D008815:Mice, Inbred Strains; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D013687:Telencephalon / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D015854:Up-Regulation / Q000502:physiology*
D017362:Cyclic AMP Response Element-Binding Protein; D011518:Proto-Oncogene Proteins; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases