title: Decreased akt activity is associated with activation of forkhead transcription factor after transient forebrain ischemia in gerbil hippocampus.
abstract: The authors recently reported that sodium orthovanadate rescues cells from delayed neuronal death in gerbil hippocampus after transient forebrain ischemia through phosphatidylinositol 3-kinase-protein kinase B (Akt) pathway (Kawano et al., 2001). In the current study, they demonstrated that the activation of FKHR, a Forkhead transcription factor and a substrate for Akt, preceded delayed neuronal death in CA1 regions after transient forebrain ischemia. Adult Mongolian gerbils were subjected to 5-minute forebrain ischemia. Immunoblotting analysis with anti-phospho-FKHR antibody showed that phosphorylation of FKHR at serine-256 in the CA1 region decreased immediately after and 0.5 and 1 hour after reperfusion. The dephosphorylation of FKHR was correlated with the decreased Akt activity. Intracerebroventricular injection of orthovanadate 30 minutes before ischemia inhibited dephosphorylation of FKHR after reperfusion, and blocked delayed neuronal death in the CA1 region. Gel mobility shift analysis using nuclear extracts from the CA1 region prepared immediately after reperfusion revealed increases in DNA binding activity for the FKHR-responsive element on the Fas ligand promoter. The orthovanadate injection administered before ischemia inhibited its binding activity. Two days after reperfusion, expression of Fas ligand increased in the CA1 region and the orthovanadate injection inhibited this increased expression. These results suggest that the inactivation of Akt results in the activation of FKHR and, in turn, relates to the expression of Fas ligand in the CA1 region after transient forebrain ischemia.
authors.affiliation: Department of Pharmacology, Kumamoto University School of Medicine, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kawano
authors.forename: Motohiro
authors.initials: M
authors.lastname: Morioka
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Yano
authors.forename: Jun-Ichiro
authors.initials: J
authors.lastname: Hamada
authors.forename: Yukitaka
authors.initials: Y
authors.lastname: Ushio
authors.forename: Eishichi
authors.initials: E
authors.lastname: Miyamoto
authors.forename: Kohji
authors.initials: K
authors.lastname: Fukunaga
mesh_terms: D000818:Animals; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D053222:Fas Ligand Protein; D005849:Gerbillinae; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D002546:Ischemic Attack, Transient / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D015424:Reperfusion; D014157:Transcription Factors / Q000378:metabolism*; D014638:Vanadates / Q000494:pharmacology
chemical_list: D004268:DNA-Binding Proteins; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D014638:Vanadates; D004247:DNA; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt