Shigetoshi Yano

Activation of Akt/Protein Kinase B Contributes to Induction of Ischemic Tolerance in the CA1 Subfield of Gerbil Hippocampus

Apoptosis plays an important role in delayed neuronal cell death after cerebral ischemia. Activation of Akt/protein kinase B has been recently reported to prevent apoptosis in several cell types. In this article the authors examine whether induction of ischemic tolerance resulting from a sublethal ischemic insult requires Akt activation. Sublethal ischemia gradually and persistently stimulated phosphorylation of Akt-Ser-473 in the hippocampal CA1 region after reperfusion. After lethal ischemia, phosphorylation of Akt-Ser-473 showed no obvious decrease in preconditioned gerbils but a marked decrease in nonconditioned gerbils. Changes in Akt-Ser-473 phosphorylation were correlated with changes in Akt activities, as measured by an in vitro kinase assay. Intracerebral ventricular infusion of wortmannin before preconditioning blocked both the increase in Akt-Ser-473 phosphorylation in a dose-dependent manner and the neuroprotective action of preconditioning. These results suggest that Akt activation is induced by a sublethal ischemic insult in gerbil hippocampus and contributes to neuroprotective ischemic tolerance in CA1 pyramidal neurons.

Neuroprotective effect of sodium orthovanadate on delayed neuronal death after transient forebrain ischemia in gerbil hippocampus

In transient forebrain ischemia, sodium orthovanadate as well as insulinlike growth factor-1 (IGF-1) rescued cells from delayed neuronal death in the hippocampal CA1 region. Adult Mongolian gerbils were subjected to 5-minute forebrain ischemia. Immunoblotting analysis with anti–phospho-Akt/PKB (Akt) antibody showed that phosphorylation of Akt at serine-473 (Akt-Ser-473) in the CA1 region decreased immediately after reperfusion, and in turn transiently increased 6 hours after reperfusion. The decreased phosphorylation of Akt-Ser-473 was not observed in the CA3 region. The authors then tested effects of intraventricular injection of orthovanadate and IGF-1, which are known to activate Akt. Treatment with orthovanadate or IGF-1 30 minutes before ischemia blocked delayed neuronal death in the CA1 region. The neuroprotective effects of orthovanadate and IGF-1 were associated with preventing decreased Akt-Ser-473 phosphorylation in the CA1 region observed immediately after reperfusion. Immunohistochemical studies with the anti–phospho-Akt-Ser-473 antibody also demonstrated that Akt was predominantly in the nucleus and was moderately activated in the cell bodies and dendrites of pyramidal neurons after orthovanadate treatment. The orthovanadate treatment also prevented the decrease in phosphorylation of mitogen-activated protein kinase (MAPK). Pretreatment with combined blockade of phosphatidylinositol 3-kinase and MAPK pathways totally abolished the orthovanadate-induced neuroprotective effect. These results suggest that the activation of both Akt and MAPK activities underlie the neuroprotective effects of orthovanadate on the delayed neuronal death in the CA1 region after transient forebrain ischemia.

Angiographic Dilatation and Branch Extension of the Anterior Choroidal and Posterior Communicating Arteries Are Predictors of Hemorrhage in Adult Moyamoya Patients

Background and Purpose— The cause of intracranial bleeding in moyamoya disease patients is still unknown. To identify factors that contribute to bleeding, we assessed the angiographic findings of moyamoya disease patients. Methods— We examined angiograms obtained from 107 moyamoya patients; 70 manifested ischemic and 37 had hemorrhagic lesions. Patients with intracerebral aneurysms or both hemorrhagic and ischemic lesions in the same cerebral hemisphere were not included. Patients were divided into those <20 years of age (n=47) and those ≥20 years of age (n=60). The right and left hemispheres in each patient were individually classified as hemorrhagic, ischemic, or asymptomatic. Each hemisphere was assessed for dilatation and branch extension of the anterior choroidal artery (AChA) and posterior communicating artery (P-CoM) and for the degree of proliferation of basal moyamoya vessels. These data were then statistically analyzed for correlation with intracranial bleeding events. Results— The degree of proliferation of basal moyamoya vessels was not statistically correlated with hemorrhagic events. On the other hand, there was a correlation between hemorrhage and dilatation and abnormal branching of the AChA. In 27 of 37 hemorrhagic hemispheres (73.0%), this artery was dilated, and its abnormal branches served as collateral supply vessels to other regions. This phenomenon was observed in 4 of 5 hemorrhagic hemispheres from young patients; it was noted in fewer than one third of ischemic and asymptomatic hemispheres from this age group. Similarly, 71.9% of hemorrhagic hemispheres from adult patients manifested AChA dilatation and branching, and the difference between hemorrhagic hemispheres and those that were ischemic or asymptomatic was statistically significant (P <0.01). Although the incidence of dilatation and abnormal branching of the P-CoM was relatively low in hemorrhagic hemispheres from adult patients (18.8%), it was significantly higher than in the ischemic and asymptomatic hemispheres from this age group. Using dilatation and abnormal branching of the AChA and/or P-CoM as assessment criteria, we obtained high specificity (86.4%) and sensitivity (84.4%) for hemorrhagic events in adult moyamoya patients. Conclusions— In adult moyamoya patients, dilatation and abnormal branching of the AChA and/or P-CoM are strong predictors of hemorrhagic events.

Decreased Akt activity is associated with activation of Forkhead transcription factor after transient forebrain ischemia in gerbil hippocampus

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.

Surgical indications to maintain quality of life in elderly patients with ruptured intracranial aneurysms.

OBJECTIVEWe performed a retrospective study to assess long-term outcomes in very old patients with ruptured intracranial aneurysms. The aim of the study was to develop guidelines for choosing surgical or conservative treatment with the goal of maintaining patients’ quality of life. METHODSBetween 1996 and 1999, 76 consecutive patients, aged 80 to 89 years, with ruptured intracranial aneurysms were treated at 18 participating centers. They were divided retrospectively into operated and nonoperated groups, and their preoperative characteristics and treatment outcomes were analyzed. Their Glasgow Outcome Scale and Barthel Index scores at least 2 years after the insult were recorded and analyzed from the perspective of their admission Hunt and Hess grade. RESULTSOur retrospective review encompassed 5.9 years. Of the original 76 patients, 54 (71.1%) died, 13 (17.1%) had a good outcome (Barthel Index ≥60), and 9 (11.8%) had a poor outcome (Barthel Index <60). All patients with Hunt and Hess grades of III or higher at admission had poor outcomes irrespective of treatment. Of 32 patients with an initial Hunt and Hess grade of I or II, 19 (59.4%) underwent surgery; 9 of these patients (47.4%) had good outcomes. Conversely, of 13 nonoperated patients (40.6%), only 2 (15.4%) experienced good outcomes. In seven of the nine operated patients with good outcomes, the aneurysm was small (<12 mm) and located at the internal carotid artery-posterior communicating artery junction. CONCLUSIONOur results suggest that patients in the 9th decade of life with ruptured intracranial aneurysms can be considered for surgical treatment if they have a Hunt and Hess grade of I or II. The highest rate of favorable results was achieved in patients with small internal carotid artery-posterior communicating artery aneurysms.

Expression of neuron specific phosphatase, striatal enriched phosphatase (STEP) in reactive astrocytes after transient forebrain ischemia

We studied the distribution and change of striatal enriched phosphatase (STEP) in the gerbil hippocampus after transient forebrain ischemia. STEP was expressed in the perikarya and in neuronal processes; it was not detected in non‐neuronal cells of control animals. After 5‐min forebrain ischemia, STEP immunoreactivity (STEP‐IR) was preserved for 2 days; it disappeared 4 and more days after ischemia with completion of delayed neuronal death (DND) in the CA1 subfield. Furthermore, only in the CA1 after ischemia, STEP was expressed in reactive astrocytes for 4 to 28 days, showing different patterns of glial fibrillary acidic protein (GFAP)‐positive reactive astrocytes. After non‐or less‐than lethal ischemia, STEP expression in reactive astrocytes corresponded with the degree of neuronal degeneration. Immunoblot analysis of the CA1 subfield revealed the expression of three isoforms, STEP45, ‐56 and ‐61; their expression patterns changed with time after ischemia. These data suggest that neuronal STEP is preserved until cell degeneration after ischemia and that STEP is expressed in reactive astrocytes only after lethal ischemia, with different expression patterns for its isoforms. Of STEP45, ‐56 and ‐61, STEP61 was the most strongly expressed in the reactive astrocytes; both STEP45 and ‐61 were expressed in neurons and the expression of STEP56 was weak. STEP may play an important role not only in neurons but also in reactive astrocytes after ischemia, depending on neuronal degeneration. GLIA 29:316–329, 2000.