Appearance Of Neurofibrillary Tangles Research Articles

Interregional Gene Expression Analysis Identifies Signature of Cerebellar Resistance to AD Tauopathy

AbstractBackgroundThe appearance of neurofibrillary tangles (NFTs) reflects both their spatial location within affected connectivity networks and the intrinsic vulnerability of neuronal populations to their formation. Here we disaggregate human gene expression data on the basis of connectivity to identify differentially expressed genes (DEGs) associated with neuroprotection against tauopathy.MethodTranscriptomic analysis focused on prefrontal cortex (PFC) and cerebellum, which both associate with the default mode and other AD‐affected networks. However, whereas PFC is vulnerable to tauopathic neurodegeneration, the cerebellum atrophies without NFT formation or cell loss. To identify candidate mediators of selective vulnerability, gene expression patterns in both regions from AD and control brains were calculated and then subjected to cell‐type specific enrichment analysis (CSEA), gene set enrichment analysis (GSEA), and transcription factor interaction network (TFIN) analysis. To validate candidate effector genes, prioritized chaperones were incubated with tau protein to test for suppression of biochemically induced fibrillization. The resulting distribution of soluble and aggregated tau was measured by sedimentation.ResultsCSEA revealed DEGs that changed in parallel between regions originated primarily in glia and microglia. GSEA identified these as belonging to Gene Ontology (GO) categories associated with host response and ion homeostasis. Of 446 genes, 379 were linked in a TFIN, with the most central nodes including transcriptional regulators HBP1, EGR1, SERTAD1, and PER1. In contrast, DEGs changing in opposition were primarily neuronal. GSEA identified 14 heat shock genes, including nine chaperone proteins reported to regulate protein folding. Of 402 candidate vulnerability genes, 319 were linked in a TFIN, in which the most central hubs were long noncoding RNA NEAT1, and transcription factors BHLHE40, ZC3H10, and CREB3L4. Finally, aggregation and sedimentation of tau showed all nine chaperones antagonized biochemical fibrillization of 2N4R tau with octadecyl sulfate at substoichiometric ratios of chaperone to tau.ConclusionsOur study takes advantage of a selective vulnerability informed approach to gene expression and highlights the role of proteostasis and neuronal genes in protecting the cerebellum from tau lesions. This approach successfully identified biologically active effector genes and can be applied broadly to other neurodegenerative diseases featuring prion‐like pathology and will orient the field toward endogenous strategies of neuroprotection.

Amyloid protein-induced sequestration of the eukaryotic ribosome: effect of stoichiometry and polyphenolic inhibitors.

Alzheimer's disease (AD) is characterized by the appearance of neurofibrillary tangles comprising of the Tau protein and aggregation of amyloid-β peptides (Aβ 1-40 and Aβ 1-42). A concomitant loss of the ribosomal population is also observed in AD-affected neurons. Our studies demonstrate that, similarly to Tau protein aggregation, in vitro aggregation of Aβ peptides in the vicinity of the yeast 80S ribosome can induce co-aggregation of ribosomal components. The RNA-stimulated aggregation of Aβ peptides and the Tau-K18 variant is dependent on the RNA:protein stoichiometric ratio. A similar effect of stoichiometry is also observed on the ribosome-protein co-aggregation process. Polyphenolic inhibitors of amyloid aggregation, such as rosmarinic acid and myricetin, inhibit RNA-stimulated Aβ and Tau-K18 aggregation and can mitigate the co-aggregation of ribosomal components.

Reversing pathology in a preclinical model of Alzheimer's disease by hacking cerebrovascular neoangiogenesis with advanced cancer therapeutics.

BackgroundCognitive decline leading to dementia, accompanied by the accumulation of amyloid-beta (Aβ) in neuritic plaques together with the appearance of neurofibrillary tangles (NFT) composed of hyperphosphorylated tau protein (tau), are previously noted hallmarks of Alzheimer's disease (AD). We previously discovered hypervascularity in brain specimens from AD patients and consistent with this observation, we demonstrated that overexpression of Aβ drives cerebrovascular neoangiogenesis leading to hypervascularity and coincident tight-junction disruption and blood-brain barrier (BBB) leakiness in animal models of AD. We subsequently demonstrated that amyloid plaque burden and cerebrovascular pathogenesis subside when pro-angiogenic Aβ levels are reduced. Based on these data, we propose a paradigm of AD etiology where, as a compensatory response to impaired cerebral blood flow (CBF), Aβ triggers pathogenic cerebrovascular neoangiogenesis that underlies the conventional hallmarks of AD. Consequently, here we present evidence that repurposing anti-cancer drugs to modulate cerebrovascular neoangiogenesis, rather than directly targeting the amyloid cascade, may provide an effective treatment for AD and related vascular diseases of the brain.MethodsWe explored whether the anti-cancer drug, Axitinib, a small molecule tyrosine kinase inhibitor that targets vascular endothelial growth factor receptors (VEGFR) can inhibit aberrant cerebrovascular neoangiogenic changes, reduce Aβ deposits and reverse cognitive decline in an animal model of AD. One month post-treatment with Axitinib, we employed a battery of tests to assess cognition and memory in aged Tg2576 AD mice and used molecular analysis to demonstrate reduction of amyloid plaques, BBB leakage, hypervascularity and associated disease pathology.FindingsTargeting the pro-angiogenic pathway in AD using the cancer drug, Axitinib, dramatically reduced cerebrovascular neoangiogenesis, restored BBB integrity, resolved tight-junction pathogenesis, diminishes Aβ depositions in plaques and effectively restores memory and cognitive performance in a preclinical mouse model of AD.InterpretationModulation of neoangiogenesis, in an analogous approach to those used to treat aberrant vascularization in cancer and also in the wet form of age-related macular degeneration (AMD), provides an alternative therapeutic strategy for intervention in AD that warrants clinical investigation.

Human brain pathology in myotonic dystrophy type 1: A systematic review.

Brain involvement in myotonic dystrophy type 1 (DM1) is characterized by heterogeneous cognitive, behavioral, and affective symptoms and imaging alterations indicative of widespread grey and white matter involvement. The aim of the present study was to systematically review the literature on brain pathology in DM1. We conducted a structured search in EMBASE (index period 1974–2017) and MEDLINE (index period 1887–2017) on December 11, 2017, using free text and index search terms related to myotonic dystrophy type 1 and brain structures or regions. Eligible studies were full‐text studies reporting on microscopic brain pathology of DM1 patients without potentially interfering comorbidity. We discussed the findings based on the anatomical region and the nature of the anomaly. Neuropathological findings in DM1 can be classified as follows: (1) protein and nucleotide deposits; (2) changes in neurons and glial cells; and (3) white matter alterations. Most findings are unspecific to DM1 and may occur with physiological aging, albeit to a lesser degree. There are similarities and contrasts with Alzheimer's disease; both show the appearance of neurofibrillary tangles in the limbic system without plaque occurrence. Likewise, there is myelin loss and gliosis, and there are dilated perivascular spaces in the white matter resemblant of cerebral small vessel disease. However, we did not find evidence of lacunar infarction or microbleeding. The various neuropathological findings in DM1 are reflective of the heterogeneous clinical and neuroimaging features of the disease. The strength of conclusions from this study's findings is bounded by limited numbers of participants in studies, methodological constraints, and lack of assessed associations between histopathology and clinical or neuroimaging findings.

Pine Bark Polyphenolic Extract Attenuates Amyloid-β and Tau Misfolding in a Model System of Alzheimer's Disease Neuropathology.

Plant-derived polyphenolic compounds possess diverse biological activities, including strong anti-oxidant, anti-inflammatory, anti-microbial, and anti-tumorigenic activities. There is a growing interest in the development of polyphenolic compounds for preventing and treating chronic and degenerative diseases, such as cardiovascular disorders, cancer, and neurological diseases including Alzheimer's disease (AD). Two neuropathological changes of AD are the appearance of neurofibrillary tangles containing tau and extracellular amyloid deposits containing amyloid-β protein (Aβ). Our laboratory and others have found that polyphenolic preparations rich in proanthocyanidins, such as grape seed extract, are capable of attenuating cognitive deterioration and reducing brain neuropathology in animal models of AD. Oligopin is a pine bark extract composed of low molecular weight proanthocyanidins oligomers (LMW-PAOs), including flavan-3-ol units such as catechin (C) and epicatechin (EC). Based on the ability of its various components to confer resilience to the onset of AD, we tested whether oligopin can specifically prevent or attenuate the progression of AD dementia preclinically. We also explored the underlying mechanism(s) through which oligopin may exert its biological activities. Oligopin inhibited oligomer formation of not only Aβ1-40 and Aβ1-42, but also tau in vitro. Our pharmacokinetics analysis of metabolite accumulation in vivo resulted in the identification of Me-EC-O-β-Glucuronide, Me-(±)-C-O-β-glucuronide, EC-O-β-glucuronide, and (±)-C-O-β-glucuronide in the plasma of mice. These metabolites are primarily methylated and glucuronidated C and EC conjugates. The studies conducted provide the necessary impetus to design future clinical trials with bioactive oligopin to prevent both prodromal and residual forms of AD.

Allosteric Modulators of Potential Targets Related to Alzheimer's Disease: a Review.

Among neurodegenerative disorders, Alzheimer's disease (AD) is the most common type of dementia, and there is an urgent need to discover new and efficacious forms of treatment for it. Pathological patterns of AD include cholinergic dysfunction, increased β-amyloid (Aβ) peptide concentration, the appearance of neurofibrillary tangles, among others, all of which are strongly associated with specific biological targets. Interactions observed between these targets and potential drug candidates in AD most often occur by competitive mechanisms driven by orthosteric ligands that sometimes result in the production of side effects. In this context, the allosteric mechanism represents a key strategy; this can be regarded as the selective modulation of such targets by allosteric modulators in an advantageous manner, as this may decrease the likelihood of side effects. The purpose of this review is to present an overview of compounds that act as allosteric modulators of the main biological targets related to AD.

P2‐217: SUPRATHERAPEUTIC CONCENTRATIONS OF CILOSTAZOL INHIBITS β‐AMYLOID OLIGOMERIZATION IN VITRO

Alzheimer disease (AD) is the most common type of dementia, and is currently incurable. The efficacy of existing treatments for AD such as acetylcholinesterase inhibitors is limited to symptom improvement. Research on disease-modifying therapies (DMTs) has conventionally focused on amelioration of CNS pathogenesis. Two neuropathological changes correlate strongly with AD, the appearance of neurofibrillary tangles containing the microtubule-associated protein tau and extracellular amyloid deposits containing amyloid β-protein (Aβ). The aggregation of Aβ is believed to be the key pathogenic event in AD, with oligomeric assemblies thought to be the most neurotoxic form. Inhibitors of oligomer formation, therefore, could be valuable therapeutics for AD patients. The clinical phosphodiesterase type-3 inhibitor cilostazol (CSZ) was recently found to suppress the progression of cognitive decline in patients with stable AD receiving acetylcholinesterase inhibitors. We examined the effects of CSZ on in vitro aggregations of Aβ1-40 and Aβ1-42 including oligomerization, using the thioflavin T assay, photo-induced cross-linking of unmodified proteins, and electron microscopy. CSZ (25-100 μM) inhibited Aβ aggregation, especially oligomer formation. Considering that CSZ might be a key molecule for DMTs of AD, it cannot be ruled out that the low concentration of CSZ achievable in patient dosing may display some ant-oligomeric activity in synergy with its known therapeutic effects.

Processing of Mutant β-Amyloid Precursor Protein and the Clinicopathological Features of Familial Alzheimer's Disease.

Alzheimer’s disease (AD) is a complex, multifactorial disease involving many pathological mechanisms. Nonetheless, single pathogenic mutations in amyloid precursor protein (APP) or presenilin 1 or 2 can cause AD with almost all of the clinical and neuropathological features, and therefore, we believe an important mechanism of pathogenesis in AD could be revealed from examining pathogenic APP missense mutations. A comprehensive review of the literature, including clinical, neuropathological, cellular and animal model data, was conducted through PubMed and the databases of Alzforum mutations, HGMD, UniProt, and AD&FTDMDB. Pearson correlation analysis combining the clinical and neuropathological data and aspects of mutant APP processing in cellular models was performed. We find that an increase in Aβ42 has a significant positive correlation with the appearance of neurofibrillary tangles (NFTs) and tends to cause an earlier age of AD onset, while an increase in Aβ40 significantly increases the age at death. The increase in the α-carboxyl terminal fragment (CTF) has a significantly negative correlation with the age of AD onset, and β-CTF has a similar effect without statistical significance. Animal models show that intracellular Aβ is critical for memory defects. Based on these results and the fact that amyloid plaque burden correlates much less well with cognitive impairment than do NFT counts, we propose a “snowball hypothesis”: the accumulation of intraneuronal NFTs caused by extracellular Aβ42 and the increase in intraneuronal APP proteolytic products (CTFs and Aβs) could cause cellular organelle stress that leads to neurodegeneration in AD, which then resembles the formation of abnormal protein “snowballs” both inside and outside of neurons.

Supratherapeutic concentrations of cilostazol inhibits β-amyloid oligomerization in vitro

Alzheimer disease (AD) is the most common type of dementia, and is currently incurable. The efficacy of existing treatments for AD such as acetylcholinesterase inhibitors is limited to symptom improvement. Research on disease-modifying therapies (DMTs) has conventionally focused on amelioration of CNS pathogenesis. Two neuropathological changes correlate strongly with AD, the appearance of neurofibrillary tangles containing the microtubule-associated protein tau and extracellular amyloid deposits containing amyloid β-protein (Aβ). The aggregation of Aβ is believed to be the key pathogenic event in AD, with oligomeric assemblies thought to be the most neurotoxic form. Inhibitors of oligomer formation, therefore, could be valuable therapeutics for AD patients. The clinical phosphodiesterase type-3 inhibitor cilostazol (CSZ) was recently found to suppress the progression of cognitive decline in patients with stable AD receiving acetylcholinesterase inhibitors. Here we examined the effects of CSZ on in vitro aggregations of Aβ1-40 and Aβ1-42 including oligomerization, using the thioflavin T assay, photo-induced cross-linking of unmodified proteins, and electron microscopy. CSZ (25–100 μM) inhibited Aβ aggregation, especially oligomer formation. Considering that CSZ might be a key molecule for DMTs of AD, it cannot be ruled out that the low concentration of CSZ achievable in patient dosing may display some ant-oligomeric activity in synergy with its known therapeutic effects.

Neuroprotective effects of Wnt/β-catenin signaling pathway against Aβ -induced tau protein over-phosphorylation in PC12 cells

Alzheimer's disease (AD) is a progressive neurodegenerative disease, which is characterized by deposition of senile plaque (SP) and appearance of neurofibrillary tangles (NFT) in the cerebral cortex and hippocampus. SP is the accumulation of extracellular proteins/peptides, mainly consisting of the amyloid-beta protein (Aβ), and the atrophy-degraded neuritis, microglias and astrocytes. NFT could be induced by the abnormal phosphorylation of Tau protein. Aβ may interfere with certain cell signal systems, which affects the level of Tau protein phosphorylation thus resulting in the forming of NFT. The present study explored the role of Wnt/β-catenin pathway in the neurotoxic effect of Aβ25-35 on PC12 cells. Flow cytometry was employed to determine the effective sublethally dose of Aβ25-35, immunocytochemistry to decipher the intracellular distribution of microtubule associated protein-2 (MAP-2) and neurofilament H (NF–H), western blotting to assess the protein abundance of phosphorylated tau in several sites and GSK-3. As a result, the Polymerization of and MAP-2 and NF–H induced by Aβ25-35 could be significantly inhibited by Wnt3a(40 ng/ml), however enhanced by Dkk1(100 ng/ml). Meanwhile, the protein abundance of phosphorylated tau in several sites is decreased by Wnt3a, but increased by Dkk1 significantly compared with the control group. In conclusion, Wnt/β-catenin signaling pathway is involved in the neurotoxic effect of Aβ25-35 on PC12 cells.

Toxic tau oligomer formation blocked by capping of cysteine residues with 1,2-dihydroxybenzene groups.

Neurofibrillary tangles, composed of hyperphosphorylated tau fibrils, are a pathological hallmark of Alzheimer's disease; the neurofibrillary tangle load correlates strongly with clinical progression of the disease. A growing body of evidence indicates that tau oligomer formation precedes the appearance of neurofibrillary tangles and contributes to neuronal loss. Here we show that tau oligomer formation can be inhibited by compounds whose chemical backbone includes 1,2-dihydroxybenzene. Specifically, we demonstrate that 1,2-dihydroxybenzene-containing compounds bind to and cap cysteine residues of tau and prevent its aggregation by hindering interactions between tau molecules. Further, we show that orally administered DL-isoproterenol, an adrenergic receptor agonist whose skeleton includes 1,2-dihydroxybenzene and which penetrates the brain, reduces the levels of detergent-insoluble tau, neuronal loss and reverses neurofibrillary tangle-associated brain dysfunction. Thus, compounds that target the cysteine residues of tau may prove useful in halting the progression of Alzheimer's disease and other tauopathies.

Alzheimer's disease (AD) as a disorder of the plasma membrane

GENERAL COMMENTARY article Front. Physiol., 15 February 2013Sec. Membrane Physiology and Membrane Biophysics https://doi.org/10.3389/fphys.2013.00024

Elevated MARK2-Dependent Phosphorylation of Tau in Alzheimer's Disease

The appearance of neurofibrillary tangles (NFT), one of the major hallmarks of Alzheimer's disease (AD), is most likely caused by inappropriate phosphorylation and/or dephosphorylation of tau, eventually leading to the accumulation of NFTs. Enhanced phosphorylation of tau on Ser(262) is detected early in the course of the disease and may have a role in the formation of tangles. Several kinases such as microtubule-affinity regulating kinase (MARK), protein kinase A, calcium calmodulin kinase II, and checkpoint kinase 2 are known to phosphorylate tau on Ser(262) in vitro. In this study, we took advantage of the in situ proximity ligation assay to investigate the role of MARK2, one of the four MARK isoforms, in AD. We demonstrate that MARK2 interacts with tau and phosphorylates tau at Ser(262) in stably transfected NIH/3T3 cells expressing human recombinant tau. Staurosporine, a protein kinase inhibitor, significantly reduced the interaction between MARK2 and tau, and also phosphorylation of tau at Ser(262). Furthermore, we observed elevated interactions between MARK2 and tau in post-mortem human AD brains, compared to samples from non-demented elderly controls. Our results from transfected cells demonstrate a specific interaction between MARK2 and tau, as well as MARK2-dependent phosphorylation of tau at Ser(262). Furthermore, the elevated interactions between MARK2 and tau in AD brain sections suggests that MARK2 may play an important role in early phosphorylation of tau in AD, possibly qualifying as a therapeutic target for intervention to prevent disease progression.

Entropy and Complexity Analyses in Alzheimer’s Disease: An MEG Study

Alzheimer’s disease (AD) is one of the most frequent disorders among elderly population and it is considered the main cause of dementia in western countries. This irreversible brain disorder is characterized by neural loss and the appearance of neurofibrillary tangles and senile plaques. The aim of the present study was the analysis of the magnetoencephalogram (MEG) background activity from AD patients and elderly control subjects. MEG recordings from 36 AD patients and 26 controls were analyzed by means of six entropy and complexity measures: Shannon spectral entropy (SSE), approximate entropy (ApEn), sample entropy (SampEn), Higuchi’s fractal dimension (HFD), Maragos and Sun’s fractal dimension (MSFD), and Lempel-Ziv complexity (LZC). SSE is an irregularity estimator in terms of the flatness of the spectrum, whereas ApEn and SampEn are embbeding entropies that quantify the signal regularity. The complexity measures HFD and MSFD were applied to MEG signals to estimate their fractal dimension. Finally, LZC measures the number of different substrings and the rate of their recurrence along the original time series. Our results show that MEG recordings are less complex and more regular in AD patients than in control subjects. Significant differences between both groups were found in several brain regions using all these methods, with the exception of MSFD (p-value < 0.05, Welch’s t-test with Bonferroni’s correction). Using receiver operating characteristic curves with a leave-one-out cross-validation procedure, the highest accuracy was achieved with SSE: 77.42%. We conclude that entropy and complexity analyses from MEG background activity could be useful to help in AD diagnosis.

Evidence for the involvement of calbindin D28k in the presenilin 1 model of Alzheimer's disease

Pathological hallmarks of Alzheimer's disease include memory deficits, accumulation of amyloid beta (Aβ) plaques, the appearance of neurofibrillary tangles, and dysregulation of calcium homeostasis, which has been linked to mutations in the presenilin gene that code for presenilin (PS) proteins. PSs are a family of multi-pass transmembrane proteins where normal presenilins (PS1 and PS2) are highly localized in the endoplasmic reticulum (ER). Several past studies have explored alterations in long-term potentiation (LTP), a proposed molecular correlate of memory, and in behavioral tests of spatial memory in a variety of PS1 models. These reports suggest that calcium plays a role in these alterations, but mechanistic explanations for changes in LTP and in behavioral tests of memory are still lacking. To test the hypothesis that calcium-related mechanisms, such as changes in calcium buffering, are associated with alterations in LTP and memory, we utilized in vitro experimental paradigms of LTP in hippocampal slices obtained from the PS1-M146V transgenic mouse model of Alzheimer's disease (AD). We also used the in vivo Morris water maze (MWM), a test for hippocampal dependent spatial memory. In addition, we used cellular assays to explore molecular mechanisms. We confirm that PS1 mutations (M146V) enhance LTP. We also find increases in some parameters of the MWM, and alterations in other parameters, such as path length indicating impairment in cognitive functioning in PS1-M146V mice. In addition, these findings are observed in association with increased calbindin D28K expression in the CA1 hippocampus of PS1-M146V mice.

Perspectivas sobre la hipótesis de la cascada del amiloide en la enfermedad de Alzheimer

The amyloid-beta peptide cascade hypothesis has provided a useful framework for the research on Alzheimer's disease for nearly 20 years. According to this hypothesis, an increase in amyloid-beta levels triggers all of the pathological features of the disease, including tau hyperphosphorylation, appearance of neurofibrillary tangles, synaptic dysfunction and neuronal cell death. Even though amyloid-beta peptide has an important role in the neurodegenerative process, different findings, such as the presence of abundant plaques in old cognitively normal individuals or the limited success of therapeutical approaches targeting only amyloid-beta, cast some doubt on a unique role for this peptide. At present, it is rather accepted that amyloid-beta peptide acts in parallel with other factors causing Alzheimer's disease that should be also considered at the time of designing useful therapeutic strategies.

Multifunctional roles of enolase in Alzheimer’s disease brain: beyond altered glucose metabolism

Enolase enzymes are abundantly expressed, cytosolic carbon-oxygen lyases known for their role in glucose metabolism. Recently, enolase has been shown to possess a variety of different regulatory functions, beyond glycolysis and gluconeogenesis, associated with hypoxia, ischemia, and Alzheimer's disease (AD). AD is an age-associated neurodegenerative disorder characterized pathologically by elevated oxidative stress and subsequent damage to proteins, lipids, and nucleic acids, appearance of neurofibrillary tangles and senile plaques, and loss of synapse and neuronal cells. It is unclear if development of a hypometabolic environment is a consequence of or contributes to AD pathology, as there is not only a significant decline in brain glucose levels in AD, but also there is an increase in proteomics identified oxidatively modified glycolytic enzymes that are rendered inactive, including enolase. Previously, our laboratory identified alpha-enolase as one the most frequently up-regulated and oxidatively modified proteins in amnestic mild cognitive impairment (MCI), early-onset AD, and AD. However, the glycolytic conversion of 2-phosphoglycerate to phosphoenolpyruvate catalyzed by enolase does not directly produce ATP or NADH; therefore it is surprising that, among all glycolytic enzymes, alpha-enolase was one of only two glycolytic enzymes consistently up-regulated from MCI to AD. These findings suggest enolase is involved with more than glucose metabolism in AD brain, but may possess other functions, normally necessary to preserve brain function. This review examines potential altered function(s) of brain enolase in MCI, early-onset AD, and AD, alterations that may contribute to the biochemical, pathological, clinical characteristics, and progression of this dementing disorder.

Distribution of neurofibrillary tangles in diffuse neurofibrillary tangles with calcification

In this study, the appearance and distribution of neurofibrillary tangles (NFT) in diffuse neurofibrillary tangles with calcification (DNTC) were investigated neuropathologically in order to elucidate the detailed distribution pattern in this disease. The distribution of NFT in six cases neuropathologically diagnosed as DNTC (two men and four women) was studied using Gallyas-Braak silver stain. The age at death ranged from 56 to 73, with an average of 63.5 +/- 7.5 years. NFT were seen throughout the cerebral cortex, and were especially marked in the temporal and limbic cortices. The distribution pattern of NFT in the limbic lobe was similar to that in Alzheimer's disease as reported in the previous studies. In the temporal lobe, more NFT were distributed in the anterior than in the posterior area, which was confirmed in all six cases. The temporal pole showed the highest density of NFT including ghost tangles. The diffuse appearance of NFT in the cerebral cortex with the highest severity in the temporal pole was found to be a neuropathological characteristic of DNTC.

Increased level of active GSK‐3β in Alzheimer’s disease and accumulation in argyrophilic grains and in neurones at different stages of neurofibrillary degeneration

The somatodendritic accumulation of hyperphosphorylated tau proteins is an early event preceding the appearance of neurofibrillary tangles (NFT) in Alzheimer’s disease (AD) and might be necessary for their formation. Glycogen synthase kinase‐3β (GSK‐3β) is a physiological kinase for tau that generates many tau phosphorylation sites identified in NFT and in other tau‐positive inclusions. We have studied the cellular distribution and the expression of the active form of GSK‐3β (GSK‐3 pTyr216) in AD patients, in argyrophilic grain disease and in diffuse Lewy body disease. By Western blotting analysis, a significant increase in the level of GSK‐3 (pTyr216) was observed in the frontal cortex of AD patients. A population of neurones showed a somatodendritic accumulation of GSK‐3 (pTyr216) but not of the inactive form of GSK‐3β (GSK‐3 pSer9). Most of these GSK‐3 (pTyr216)‐positive cells were positive for six different phosphotau epitopes known to be generated by GSK‐3β. By using a quadruple labelling method using GSK‐3 (pTyr216) and phosphotau immunolabelling combined with Gallyas and DAPI staining, we examined neurones containing a somatodendritic GSK‐3 (pTyr216) immunoreactivity at different stages of neurodegeneration. A majority of neurones at the pretangle stage without Gallyas‐positive inclusions were GSK‐3 (pTyr216) positive and this GSK‐3 (pTyr216) immunoreactivity remained in most cells containing Gallyas and phosphotau‐positive inclusions excepted in extracellular NFT. A GSK‐3 (pTyr216) immunoreactivity was present in argyrophilic grains but not in cortical Lewy bodies. These results directly suggest that the activity of GSK‐3β is increased in AD and that somatodendritic accumulation and activation of GSK‐3β is an early event preceding and accompanying the formation of NFT and of other tau‐positive inclusions.

Trafficking of Alzheimer's Disease–Related Membrane Proteins and Its Participation in Disease Pathogenesis

Alzheimer's disease (AD) is a common neurodegenerative disorder that causes senile dementia. The pathological characteristics are the appearance of neurofibrillary tangles comprising abnormally phosphorylated tau and senile plaques composed of amyloid beta-protein depositions. Amyloid beta-protein precursor (APP) and presenilin (PS) are known to be causative genes of familial AD. Recent analyses have documented that APP functions in the axonal transport of vesicles and PS regulates intracellular protein trafficking. Dystrophic neurites, in which APP and Alcadein accumulate in swollen axons, are also observed in AD brain. These pathological characteristics and the features of AD-related proteins suggest that AD is a disease of the vesicular transport system. Here we review recent progress of research on AD pathogenesis from the viewpoint of membrane trafficking.