Alzheimer Disease: Takashima A

Takashima A. · Laboratory for Alzheimer's Disease, RIKEN Brain Science Institute, Japan. · J Pharmacol Sci. · Pubmed #19179803 links to  free full text

Abstract: Glycogen synthase kinase-3beta (GSK-3beta) is a constitutively active kinase. Since its activation results in neurofibrillary tangle (NFT) deposits in aged and Alzheimer's disease (AD) brains, GSK-3beta may be inhibited under normal conditions but activated under pathological conditions. Given its link to NFT formation, we sought to determine whether GSK-3beta exists in the brain as a "pathological time bomb" that promotes disease development. To address this hypothesis, we analyzed GSK-3beta heterozygote (GSK+/-) mice, which express GSK-3beta at 50% wild-type levels. When tested in the Morris water maze test, GSK+/- mice surprisingly exhibited retrograde amnesia. Further analysis indicated that GSK+/- mice had impaired memory reconsolidation but normal memory consolidation. Therefore, we concluded that GSK-3beta activation is required for memory reconsolidation in the adult brain.

Sahara N, Maeda S, Takashima A. · Laboratory for Alzheimer's Disease, RIKEN Brain Science Institute, Wako-shi, Saitama 351-0198, Japan. · Curr Alzheimer Res. · Pubmed #19075586 No free full text.

Abstract: Intracellular accumulation of filamentous tau proteins is a defining feature of neurodegenerative diseases, including Alzheimer's disease, progressive supranuclear palsy, corticobasal degeneration, Pick's disease, and frontotemporal dementia with Parkinsonism linked to chromosome 17, all known collectively as tauopathies. Tau protein is a member of microtubule (MT)-associated proteins. Tau is a highly soluble and natively unfolded protein dominated by a random coil structure in solution. It is believed that aberrant modifications of tau, including phosphorylation, truncation, and conformational changes, induce filamentous aggregation. However, the mechanism underlying the conversion of tau protein from a soluble state to one of insoluble aggregates still remains elusive. The importance of tau aggregation intermediates (e.g. tau dimer, tau multimer, and granular tau oligomer) in disease pathogenesis was suggested by recent studies. Here, we review the latest developments in tracking the structural changes of tau protein and discuss the utility improving our understanding of tau aggregation pathway leading to human tauopathies.

Sotiropoulos I, Cerqueira JJ, Catania C, Takashima A, Sousa N, Almeida OF. · Max Planck Institute of Psychiatry, Kraepelinstrasse 2-10, 80804 Munich, Germany. · Neurosci Biobehav Rev. · Pubmed #18573532 No free full text.

Abstract: Increasingly, stress is recognized as a trigger of depressive episodes and recent evidence suggests a causal role of stress in the onset and progression of Alzheimer's disease (AD) pathology. Besides aging, sex is an important determinant of prevalence rates for both AD and mood disorders. In light of a recent meta-analysis indicating that depressed subjects have a higher likelihood of developing AD, a key message in this article will be that both depression and AD are stress-related disorders and may represent a continuum that should receive more attention in future neurobiological studies. Accordingly, this review considers some of the cellular mechanisms that may be involved in regulating this transition threshold. In addition, it highlights the importance of addressing the question of how aging and sex interplay with stress to influence mood and cognition, with a bias towards consideration of neuroplastic events in particular brain regions, as the basis of AD and depressive disorders.

Takashima A. · Laboratory for Alzheimer's Disease, Riken, Brain Science Institute, 2-1 Hirosawa, Wako-si, Saitama 351-0198, Japan. · J Alzheimers Dis. · Pubmed #16914869 No free full text.

Abstract: Glycogen synthase kinase-3 (GSK-3) is a pivotal molecule in the development of Alzheimer's disease (AD). GSK-3beta is involved in the formation of paired helical filament (PHF)-tau, which is an integral component of the neurofibrillary tangle (NFT) deposits that disrupt neuronal function, and a marker of neurodegeneration in AD. GSK-3beta has exactly the same oligonucleotide sequence as tau-protein kinase I (TPKI), which was first purified from the microtubule fraction of bovine brain. Initially, we discovered that GSK-3beta was involved in amyloid-beta (Abeta)-induced neuronal death in rat hippocampal cultures. In the present review, we discuss our initial in vitro results and additional investigations showing that Abeta activates GSK-3beta through impairment of phosphatidylinositol-3 (PI3)/Akt signaling; that Abeta-activated GSK-3beta induces hyperphosphorylation of tau, NFT formation, neuronal death, and synaptic loss (all found in the AD brain); that GSK-3beta can induce memory deficits in vivo; and that inhibition of GSK-3alpha (an isoform of GSK-3beta) reduces Abeta production. These combined results strongly suggest that GSK-3 activation is a critical step in brain aging and the cascade of detrimental events in AD, preceding both the NFT and neuronal death pathways. Therefore, therapeutics targeted to inhibiting GSK-3 may be beneficial in the treatment of this devastating disease.

Takashima A. · · Nippon Yakurigaku Zasshi. · Pubmed #15855731 No free full text.

This publication has no abstract.

Takashima A, Chui D. · Laboratory for Alzheimer's Disease, Brain Science Institute, RIKEN. · Nippon Rinsho. · Pubmed #15174678 No free full text.

This publication has no abstract.

Miyasaka T, Takashima A. · Laboratory for Alzheimer's Disease, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan. · No To Shinkei. · Pubmed #12428362 No free full text.

This publication has no abstract.

Takashima A. · Laboratory for Alzheimer's disease, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 358-0198. · Seikagaku. · Pubmed #12138707 No free full text.

This publication has no abstract.

Takashima A. · Laboratory for Alzheimer's Disease, Institute of Physical and Chemical Research (RIKEN), Saitama. · Seikagaku. · Pubmed #10614181 No free full text.

This publication has no abstract.

Fujiwara H, Tabuchi M, Yamaguchi T, Iwasaki K, Furukawa K, Sekiguchi K, Ikarashi Y, Kudo Y, Higuchi M, Saido TC, Maeda S, Takashima A, Hara M, Yaegashi N, Kase Y, Arai H. · Center for Asian Traditional Medicine, Tohoku University Graduate School of Medicine, Sendai, Aoba-ku, Japan. · J Neurochem. · Pubmed #19457098 No free full text.

Abstract: The deposition of amyloid beta (Abeta) protein is a consistent pathological hallmark of Alzheimer's disease (AD) brains; therefore, inhibition of Abeta fibril formation and destabilization of pre-formed Abeta fibrils is an attractive therapeutic and preventive strategy in the development of disease-modifying drugs for AD. This study demonstrated that Paeonia suffruticosa, a traditional medicinal herb, not only inhibited fibril formation of both Abeta(1-40) and Abeta(1-42) but it also destabilized pre-formed Abeta fibrils in a concentration-dependent manner. Memory function was examined using the passive-avoidance task followed by measurement of Abeta burden in the brains of Tg2576 transgenic mice. The herb improved long-term memory impairment in the transgenic mice and inhibited the accumulation of Abeta in the brain. Three-dimensional HPLC analysis revealed that a water extract of the herb contained several different chemical compounds including 1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranose (PGG). No obvious adverse/toxic were found following treatment with PGG. As was observed with Paeonia suffruticosa, PGG alone inhibited Abeta fibril formation and destabilized pre-formed Abeta fibrils in vitro and in vivo. Our results suggest that both Paeonia suffruticosa and its active constituent PGG have strong inhibitory effects on formation of Abeta fibrils in vitro and in vivo. PGG is likely to be a safe and promising lead compound in the development of disease-modifying drugs to prevent and/or cure AD.

Planel E, Krishnamurthy P, Miyasaka T, Liu L, Herman M, Kumar A, Bretteville A, Figueroa HY, Yu WH, Whittington RA, Davies P, Takashima A, Nixon RA, Duff KE. · Taub Institute for Alzheimer's Disease Research, Department of Pathology, Columbia University Medical Center, New York, New York 10032, USA. · J Neurosci. · Pubmed #19036972 links to  free full text

Abstract: In Alzheimer's disease, tau is hyperphosphorylated, which is thought to detach it from microtubules (MTs), induce MT destabilization, and promote aggregation. Using a previously described in vivo model, we investigated whether hyperphosphorylation impacts tau function in wild-type and transgenic mice. We found that after anesthesia-induced hypothermia, MT-free tau was hyperphosphorylated, which impaired its ability to bind MTs and promote MT assembly. MT-bound tau was more resistant to hyperphosphorylation compared with free tau and tau did not dissociate from MTs in wild-type mice. However, 3-repeat tau detached from MT in the transgenic mice. Surprisingly, dissociation of tau from MTs did not lead to overt depolymerization of tubulin, and there was no collapse, or disturbance of axonal MT networks. These results indicate that, in vivo, a subpopulation of tau bound to MTs does not easily dissociate under conditions that extensively phosphorylate tau. Tau remaining on the MTs under these conditions is sufficient to maintain MT network integrity.

Sahara N, Murayama M, Lee B, Park JM, Lagalwar S, Binder LI, Takashima A. · Laboratory for Alzheimer' Disease, RIKEN Brain Science Institute, Wako-shi, Saitama 351-0198, Japan. · Eur J Neurosci. · Pubmed #18540881 No free full text.

Abstract: Neurofibrillary tangles (NFTs), comprising human intracellular microtubule-associated protein tau, are one of the hallmarks of tauopathies, including Alzheimer's disease. Recently, a report that caspase-cleaved tau is present in NFTs has led to the hypothesis that the mechanisms underlying NFT formation may involve the apoptosis cascade. Here, we show that adenoviral infection of tau into COS-7 cells induces activation of c-jun N-terminal kinase (JNK), followed by excessive phosphorylation of tau and its cleavage by caspase. However, JNK activation alone was insufficient to induce sodium dodecyl sulfate (SDS)-insoluble tau aggregation and additional phosphorylation by GSK-3beta was required. In SH-SY5Y neuroblastoma cells, overexpression of active JNK and GSK-3beta increased caspase-3 activation and cytotoxicity more than overexpression of tau alone. Taken together, these results indicate that, although JNK activation may be a primary inducing factor, further phosphorylation of tau is required for neuronal death and NFT formation in neurodegenerative diseases, including those characterized by tauopathy.

Shimojo M, Sahara N, Mizoroki T, Funamoto S, Morishima-Kawashima M, Kudo T, Takeda M, Ihara Y, Ichinose H, Takashima A. · Laboratory for Alzheimer's Disease, RIKEN Brain Science Institute, Wako-shi, Saitama 351-0198, Japan. · J Biol Chem. · Pubmed #18430735 links to  free full text

Abstract: Presenilin (PS)/gamma-secretase-mediated intramembranous proteolysis of amyloid precursor protein produces amyloid beta (Abeta) peptides in which Abeta species of different lengths are generated through multiple cleavages at the gamma-, zeta-, and epsilon-sites. An increased Abeta42/Abeta40 ratio is a common characteristic of most cases of familial Alzheimer disease (FAD)-linked PS mutations. However, the molecular mechanisms underlying amyloid precursor protein proteolysis leading to increased Abeta42/Abeta40 ratios still remain unclear. Here, we report our findings on the enzymatic analysis of gamma-secretase derived from I213T mutant PS1-expressing PS1/PS2-deficient (PS(-/-)) cells and from the brains of I213T mutant PS1 knock-in mice. Kinetics analyses revealed that the FAD mutation reduced de novo Abeta generation, suggesting that mutation impairs the total catalytic rate of gamma-secretase. Analysis of each Abeta species revealed that the FAD mutation specifically reduced Abeta40 levels more drastically than Abeta42 levels, leading to an increased Abeta42/Abeta40 ratio. By contrast, the FAD mutation increased the generation of longer Abeta species such as Abeta43, Abeta45, and >Abeta46. These results were confirmed by analyses of gamma-secretase derived from I213T knock-in mouse brains, in which the reduction of de novo Abeta generation was mutant allele dose-dependent. Our findings clearly indicate that the mechanism underlying the increased Abeta42/Abeta40 ratio observed in cases of FAD mutations is related to the differential inhibition of gamma-site cleavage reactions, in which the reaction producing Abeta40 is subject to more inhibition than that producing Abeta42. Our results also provide novel insight into how enhancing the generation of longer Abetas may contribute to Alzheimer disease onset.

Mizoroki T, Meshitsuka S, Maeda S, Murayama M, Sahara N, Takashima A. · Laboratory for Alzheimer Disease, Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan. · J Alzheimers Dis. · Pubmed #17656819 No free full text.

Abstract: Etiological studies suggest that aluminum (Al) intake might increase an individual's risk of developing Alzheimer's disease (AD). Biochemical analysis data on the effects of Al, however, are inconsistent. Hence, the pathological involvement of Al in AD remains unclear. If Al is involved in AD, then it is reasonable to hypothesize that Al might be involved in the formation of either amyloid plaques or neurofibrillary tangles (NFTs). Here, we investigated whether Al might be involved in NFT formation by using an in vitro tau aggregation paradigm, a tau-overexpressing neuronal cell line (N2a), and a tau-overexpressing mouse model. Although Al induced tau aggregation in a heparin-induced tau assembly assay, these aggregates were neither thioflavin T positive nor did they resemble tau fibrils seen in human AD brains. With cell lysates from stable cell lines overexpressing tau, the accumulation of SDS-insoluble tau increased when the lysates were treated with at least 100 muM Al-maltolate. Yet Al-maltolate caused illness or death in transgenic mice overexpressing human tau and in non-transgenic littermates well before the Al concentration in the brain reached 100 muM. These results indicate that Al has no direct link to AD pathology.

Maeda S, Sahara N, Saito Y, Murayama M, Yoshiike Y, Kim H, Miyasaka T, Murayama S, Ikai A, Takashima A. · Lab for Alzheimer's Disease, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. · Biochemistry. · Pubmed #17338548 No free full text.

Abstract: Neurofibrillary tangles (NFTs) are pathological hallmarks of several neurodegenerative disorders, including Alzheimer's disease (AD). NFTs are composed of microtubule-binding protein tau, which assembles to form paired helical filaments (PHFs) and straight filaments. Here we show by atomic force microscopy that AD brain tissue and in vitro tau form granular and fibrillar tau aggregates. CD spectral analysis and immunostaining with conformation-dependent antibodies indicated that tau may undergo conformational changes during fibril formation. Enriched granules generated filaments, suggesting that granular tau aggregates may be an intermediate form of tau fibrils. The amount of granular tau aggregates was elevated in prefrontal cortex of Braak stage I cases compared to that of Braak stage 0 cases, suggesting that granular tau aggregation precedes PHF formation. Thus, granular tau aggregates may be a relevant marker for the early diagnosis of tauopathy. Reducing the level of these aggregates may be a promising therapy for tauopathies and for promoting healthy brain aging.

Shimojo M, Sahara N, Murayama M, Ichinose H, Takashima A. · Laboratory for Alzheimer's Disease, RIKEN Brain Science Institute, Wako-Shi, Saitama, Japan. · Neurosci Res. · Pubmed #17210196 No free full text.

Abstract: Presenilin (PS) is a catalytic subunit of the gamma-secretase complex that cleaves the intramembranous region of amyloid precursor protein (APP), producing amyloid beta (Abeta) peptide. Familial Alzheimer's disease (FAD) results from PS mutations, which may alter gamma-secretase activity to enhance the production of highly aggregable Abeta42. The precise pathogenic effects of mutant PS remain unclear. To exclude the effects of endogenous PS, we established cell lines from PS1/PS2-deficient (PS-/-) fibroblasts capable of stably expressing either wild-type (wt) PS1 or different mutant PS1s. Although both wt PS1 and mutant PS1 formed gamma-secretase complexes of the same size and containing the same components, the amount of Abeta secreted by FAD mutant PS1-expressing cells was significantly reduced. The ratio of Abeta42 to Abeta40 (Abeta42/Abeta40) secreted by these cells, however, was significantly higher than that secreted by cells expressing wt PS1, which corroborated findings from a previous report. The elevated Abeta42/Abeta40 ratio observed with mutant PS1-expressing cells may be due to reduced Abeta40 production not increased Abeta42 production.

Yamamoto N, Matsubara E, Maeda S, Minagawa H, Takashima A, Maruyama W, Michikawa M, Yanagisawa K. · Department of Alzheimer's Disease Research, National Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, Obu 474-8522, Japan. · J Biol Chem. · Pubmed #17135262 links to  free full text

Abstract: The mechanism underlying plaque-independent neuronal death in Alzheimer disease (AD), which is probably responsible for early cognitive decline in AD patients, remains unclarified. Here, we show that a toxic soluble Abeta assembly (TAbeta) is formed in the presence of liposomes containing GM1 ganglioside more rapidly and to a greater extent from a hereditary variant-type ("Arctic") Abeta than from wild-type Abeta. TAbeta is also formed from soluble Abeta through incubation with natural neuronal membranes prepared from aged mouse brains in a GM1 ganglioside-dependent manner. An oligomer-specific antibody (anti-Oligo) significantly suppresses TAbeta toxicity. Biophysical and structural analyses by atomic force microscopy and size exclusion chromatography revealed that TAbeta is spherical with diameters of 10-20 nm and molecular masses of 200-300 kDa. TAbeta induces neuronal death, which is abrogated by the small interfering RNA-mediated knockdown of nerve growth factor receptors, including TrkA and p75 neurotrophin receptor. Our results suggest that soluble Abeta assemblies, such as TAbeta, can cause plaque-independent neuronal death that favorably occurs in nerve growth factor-dependent neurons in the cholinergic basal forebrain in AD.

Fujiwara H, Iwasaki K, Furukawa K, Seki T, He M, Maruyama M, Tomita N, Kudo Y, Higuchi M, Saido TC, Maeda S, Takashima A, Hara M, Ohizumi Y, Arai H. · Department of Geriatric and Complementary Medicine, Center for Asian Traditional Medicine Research, Tohoku University School of Medicine, Sendai, Japan. · J Neurosci Res. · Pubmed #16676329 No free full text.

Abstract: Because the deposition of beta-amyloid protein (Abeta) is a consistent pathological hallmark of Alzheimer's disease (AD) brains, inhibition of Abeta generation, prevention of Abeta fibril formation, or destabilization of preformed Abeta fibrils would be attractive therapeutic strategies for the treatment of AD. We examined the effects of several medicinal herbs used in traditional Chinese medical formulae on the formation and destabilization of Abeta fibrils by using the thioflavin T binding assay, atomic force microscopic imaging, and electrophoresis. Our study demonstrates that several of these herbs have potent inhibitory effects on fibril formation of both Abeta(1-40) and Abeta(1-42) in concentration-dependent manners; in particular, Uncaria rhynchophylla inhibited Abeta aggregation most intensively. Significant destabilization of preformed Abeta(1-40) and Abeta(1-42) fibrils was also induced by Uncaria rhynchophylla as well as some other herb extracts. Three-dimensional HPLC analysis indicated that the water extract of this herb contains several different chemical compounds, including oxindole and indol alkaloids, which have been regarded as neuroprotective. Our results suggest that Uncaria rhynchophylla has remarkably inhibitory effects on the regulation of Abeta fibrils, and we conclude that this medicinal herb could have the potency to be a novel therapeutic agent to prevent and/or cure AD.

Tatebayashi Y, Planel E, Chui DH, Sato S, Miyasaka T, Sahara N, Murayama M, Kikuchi N, Yoshioka K, Rivka R, Takashima A. · Laboratory for Alzheimer's Disease, Brain Science Institute, The Institute of Physical and Chemical Research (RIKEN), Saitama, Japan. · FASEB J. · Pubmed #16478768 links to  free full text

Abstract: Tauopathies such as Alzheimer disease (AD) probably involve a type of phosphorylation imbalance causing the accumulation of abnormally hyperphosphorylated tau in neurons and/or glias. Investigation of R406W tau mutation may provide insight into such abnormal tau hyperphosphorylation, since this mutation causes AD-like dementia and tauopathy in humans and because it has the unique ability to reduce tau phosphorylation in vitro and in cultured cells. Here we show that R406W mutation primarily disrupts tau phosphorylation at Ser404, a priming phosphorylation site of glycogen synthase kinase-3beta (GSK-3beta), thereby reducing subsequent GSK-3beta-mediated phosphorylation at the PHF-1 site (mostly Ser396). In contrast, c-jun N-terminal kinase (JNK) as activated in the mitotic phase directly hyperphosphorylates R406W tau at the PHF-1 site. This was confirmed by PHF-1 hyperphosphorylation of R406W tau in mitotic cells, its association with cytoplasmic JNK activation, and its inhibition by a JNK inhibitor, SP600125. These data unveil the unknown mechanisms of physiological tau phosphorylation at the PHF-1 site and suggest that cytoplasmic JNK activation may play an important role in the abnormal tau hyperphosphorylation associated with R406W tau mutation and in AD.

Maeda S, Sahara N, Saito Y, Murayama S, Ikai A, Takashima A. · Lab for Alzheimer's Disease, Brain Science Institute, RIKEN, 2-1 Hirosaswa, Wako, Saitama 351-0198, Japan. · Neurosci Res. · Pubmed #16406150 No free full text.

Abstract: Development of neurofibrillary tangles (NFTs) is a pathological hallmark in various neurodegenerative disorders including Alzheimer's disease (AD). Recently, we identified a granular tau oligomer having a pre-filamentous structure. To determine the role of this oligomer in NFT formation, we quantified the amount of granular tau oligomer in 21 frontal cortex samples, each displaying varying degrees of Braak-staged NFT pathology. Here we report that granular tau oligomer levels in frontal cortex were significantly increased, even in brains displaying Braak-stage I neuropathology, a stage at which clinical symptoms of AD and NFTs in frontal cortex are believed to be absent. This suggests that increases in granular tau oligomer levels occur before NFTs form and before individuals manifest clinical symptoms of AD. Increased granular tau oligomer levels, therefore, may lead to NFT formation in frontal cortex, eventually leading to the development of AD. Thus, increases in granular tau oligomer levels may represent a very early sign of NFT formation and AD.

Tanemura K, Chui DH, Fukuda T, Murayama M, Park JM, Akagi T, Tatebayashi Y, Miyasaka T, Kimura T, Hashikawa T, Nakano Y, Kudo T, Takeda M, Takashima A. · Laboratory for Alzheimer Disease and Neural Architecture, Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan. · J Biol Chem. · Pubmed #16377636 links to  free full text

Abstract: Mutations in the presenilin 1 (PS1) gene are responsible for the early onset of familial Alzheimer disease (FAD). Accumulating evidence shows that PS1 is involved in gamma-secretase activity and that FAD-associated mutations of PS1 commonly accelerate Abeta(1-42) production, which causes Alzheimer disease (AD). Recent studies suggest, however, that PS1 is involved not only in Abeta production but also in other processes that lead to neurodegeneration. To better understand the causes of neurodegeneration linked to the PS1 mutation, we analyzed the development of tau pathology, another key feature of AD, in PS1 knock-in mice. Hippocampal samples taken from FAD mutant (I213T) PS1 knock-in mice contained hyperphosphorylated tau that reacted with various phosphodependent tau antibodies and with Alz50, which recognizes the conformational change of PHF tau. Some neurons exhibited Congo red birefringence and Thioflavin T reactivity, both of which are histological criteria for neurofibrillary tangles (NFTs). Biochemical analysis of the samples revealed SDS-insoluble tau, which under electron microscopy examination, resembled tau fibrils. These results indicate that our mutant PS1 knock-in mice exhibited NFT-like tau pathology in the absence of Abeta deposition, suggesting that PS1 mutations contribute to the onset of AD not only by enhancing Abeta(1-42) production but by also accelerating the formation and accumulation of filamentous tau.

Egashira N, Iwasaki K, Takashima A, Watanabe T, Kawabe H, Matsuda T, Mishima K, Chidori S, Nishimura R, Fujiwara M. · Department of Neuropharmacology, Faculty of Pharmaceutical Sciences, Fukuoka University, 8-19-1 Nanakuma, Fukuoka 814-0180, Japan. · Brain Res. · Pubmed #16182262 No free full text.

Abstract: Mutant R406W human tau was originally identified in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) and causes a hereditary tauopathy that clinically resembles Alzheimer's disease (AD). In the current study, we examined the performance of R406W transgenic (Tg) mice in the forced swimming test, a test with high predictivity of antidepressant efficacy in human depression, and found an enhancement of the immobility time. In contrast, the motor function and anxiety-related emotional response of R406W Tg mice were normal. Furthermore, a selective serotonin reuptake inhibitor (SSRI), fluvoxamine (100 mg/kg, p.o.), significantly reduced this enhancement of the immobility time, whereas a noradrenaline reuptake inhibitor, desipramine, had no effect. In an in vivo microdialysis study, R406W Tg mice exhibited a significantly decreased extracellular 5-hydroxyindoleacetic acid (5-HIAA) level in the frontal cortex and also exhibited a tendency toward a decreased extracellular 5-hydroxytryptamine (5-HT) level. Moreover, fluvoxamine, which reduced the enhancement of the immobility time, significantly increased the extracellular 5-HT level in R406W Tg mice. These results suggest that R406W Tg mice exhibit changes in depression-related behavior involving serotonergic neurons and provide an animal model for investigating AD with depression.

Sahara N, Murayama M, Mizoroki T, Urushitani M, Imai Y, Takahashi R, Murata S, Tanaka K, Takashima A. · Laboratory for Alzheimer's Disease, RIKEN Brain Science Institute, Saitama, Japan. · J Neurochem. · Pubmed #16111477 No free full text.

Abstract: The carboxyl terminus of heat-shock cognate (Hsc)70-interacting protein (CHIP) is a ubiquitin E3 ligase that can collaborate with molecular chaperones to facilitate protein folding and prevent protein aggregation. Previous studies showed that, together with heat-shock protein (Hsp)70, CHIP can regulate tau ubiquitination and degradation in a cell culture system. Ubiquitinated tau is one component in neurofibrillary tangles (NFTs), which are a major histopathological feature of Alzheimer's disease (AD). However, the precise sequence of events leading to NFT formation and the mechanisms involved remain unclear. To confirm CHIP's role in suppressing NFT formation in vivo, we performed a quantitative analysis of CHIP in human and mouse brains. We found increased levels of CHIP and Hsp70 in AD compared with normal controls. CHIP levels in both AD and controls corresponded directly to Hsp90 levels, but not to Hsp70 or Hsc70 levels. In AD samples, CHIP was inversely proportional to sarkosyl-insoluble tau accumulation. In a JNPL3 mouse brain tauopathy model, CHIP was widely distributed but weakly expressed in spinal cord, which was the most prominent region for tau inclusions and neuronal loss. Protein levels of CHIP in cerebellar regions of JNPL3 mice were significantly higher than in non-transgenic littermates. Human tau was more highly expressed in this region of mouse brains, but only moderate levels of sarkosyl-insoluble tau were detected. This was confirmed when increased insoluble tau accumulation was found in mice lacking CHIP. These findings suggest that increases in CHIP may protect against NFT formation in the early stages of AD. If confirmed, this would indicate that the quality-control machinery in a neuron might play an important role in retarding the pathogenesis of tauopathies.

Ono K, Yoshiike Y, Takashima A, Hasegawa K, Naiki H, Yamada M. · Department of Neurology and Neurobiology of Aging, Kanazawa University Graduate School of Medical Science, Kanazawa 920-8640, Japan. · Exp Neurol. · Pubmed #15380488 No free full text.

Abstract: Cerebral deposition of amyloid beta-peptide (Abeta) in the brain is an invariant feature of Alzheimer disease (AD). Plasma or cerebrospinal fluid concentrations of antioxidant vitamins and carotenoids, such as vitamins A, C, E, and beta-carotene, have been reported to be lower in AD patients, and these vitamins clinically have been demonstrated to slow the progression of dementia. In this study, we used fluorescence spectroscopy with thioflavin T (ThT) and electron microscopy to examine the effects of vitamin A (retinol, retinal, and retinoic acid), beta-carotene, and vitamins B2, B6, C, and E on the formation, extension, and destabilization of beta-amyloid fibrils (fAbeta) in vitro. Among them, vitamin A and beta-carotene dose-dependently inhibited formation of fAbeta from fresh Abeta, as well as their extension. Moreover, they dose-dependently destabilized preformed fAbetas. The overall activity of the molecules examined was in the order of retinol = retinal > beta-carotene > retinoic acid. Although the exact mechanisms are still unclear, vitamins A and beta-carotene could be key molecules for the prevention and therapy of AD.

Planel E, Miyasaka T, Launey T, Chui DH, Tanemura K, Sato S, Murayama O, Ishiguro K, Tatebayashi Y, Takashima A. · Laboratory for Alzheimer's Disease, The Institute of Physical and Chemical Research, Wako-shi, Saitama 351-0198, Japan. · J Neurosci. · Pubmed #15014115 links to  free full text

Abstract: Alzheimer's disease (AD) brains contain neurofibrillary tangles (NFTs) composed of abnormally hyperphosphorylated tau protein. Regional reductions in cerebral glucose metabolism correlating to NFT densities have been reported in AD brains. Assuming that reduced glucose metabolism might cause abnormal tau hyperphosphorylation, we induced in vivo alterations of glucose metabolism in mice by starvation or intraperitoneal injections of either insulin or deoxyglucose. We found that the treatments led to abnormal tau hyperphosphorylation with patterns resembling those in early AD brains and also resulted in hypothermia. Surprisingly, tau hyperphosphorylation could be traced down to a differential effect of low temperatures on kinase and phosphatase activities. These data indicate that abnormal tau hyperphosphorylation is associated with altered glucose metabolism through hypothermia. Our results imply that serine-threonine protein phosphatase 2A plays a major role in regulating tau phosphorylation in the adult brain and provide in vivo evidence for its crucial role in abnormal tau hyperphosphorylation in AD.