Alzheimer Neurofibrillary Tangles Research Articles

Estrogen receptor-α is localized to neurofibrillary tangles in Alzheimer's disease.

The female predominance for developing Alzheimer disease (AD) suggests the involvement of gender specific factor(s) such as a reduced estrogen-estrogen receptor signaling in the pathogenesis of AD. The potential role of ERα in AD pathogenesis has been explored by several groups with mixed results. We revisited this issue of expression and distribution of ERα in AD brain using a specific ERα antibody. Interestingly, we found that ERα co-localized with neurofibrillary pathology in AD brain and further demonstrated that ERα interacts with tau protein in vivo. Immunoprecipitaion experiments found increased ERα-tau interaction in the AD cases, which may account for ERα being sequestered in neuronal tau pathology. Indeed, tau overexpression in M17 cells leads to interruption of estrogen signaling. Our data support the idea that sequestration of ERα by tau pathology underlies the loss of estrogen neuroprotection during the course of AD.

Commentary on Ubiquitin is Associated with Early Truncation of Tau Protein at Aspartic Acid421 during the Maturation of Neurofibrillary Tangles in Alzheimer Disease

Commentary on Ubiquitin is Associated with Early Truncation of Tau Protein at Aspartic Acid421 during the Maturation of Neurofibrillary Tangles in Alzheimer Disease

Neurofibrillary tangles in Alzheimer's disease: elucidation of the molecular mechanism by immunohistochemistry and tau protein phospho-proteomics.

Neurofibrillary tangles in Alzheimer's disease: elucidation of the molecular mechanism by immunohistochemistry and tau protein phospho-proteomics.

Neuronal network activity in the hippocampus of tau transgenic (Tg4510) mice

Development of neurofibrillary tangles in Alzheimer's disease correlates with neuronal loss and dementia. Transgenic Tg4510 mice model the tauopathy of the disease, with these mice exhibiting progressive, region-specific neuronal loss, and behavioral deficits. In the present study, neuronal network activity in the hippocampus of 7-month-old Tg4510 mice was investigated and compared with age-matched wild-type (WT) mice. Multisite field potentials were recorded using 16-site silicon probes, inserted across the hippocampus in urethane anesthetized mice. The hippocampal network theta oscillation was evaluated in these mice by stimulating the brainstem nucleus pontis oralis. Subsequently, population spikes in the dentate gyrus were identified in response to perforant path stimulation, and long-term potentiation was elicited by theta burst stimulation. Tg4510 mice showed dramatically reduced dentate gyrus population spike amplitude; however, the magnitude of theta burst stimulation-induced long-term potentiation was identical in WT and transgenic mice. WT and Tg4510 mice showed identical increase in frequency to nucleus pontis oralis stimulation, whereas absolute theta power was severely reduced in the Tg4510 animals. Because total signal power over the entire frequency band range was reduced, there was no difference in relative theta power between WT and Tg4510 mice. These presently described electrophysiological findings can be directly attributed to the drastic reduction of pyramidal/granule neurons in Tg4510 mice, which could be the main contributing factor to their impaired behavior and cognitive function. However, the remaining synapses and neuronal circuitry seem to function properly in these assays.

α1B-Adrenoceptor signaling molecule expression in Alzheimer’s disease brain tissue / Alzeimer hastalığı olan beyin dokusunda α1B-Adrenoseptör Sinyal Molekülü Ekspresyonu

AbstractObjective: Gαh (tissue transglutaminase; TGII), known as the α1B-adrenoceptor signal mediator, is a bifunctional enzyme possessing transglutaminase and guanosine triphosphatase activities. The microtubule-associated protein tau plays a role in formation of neurofibrillary tangles in Alzheimer’s disease (AD) brain. Tau is also known as a substrate of transglutaminase. We aimed to better understand the correlation between α1B-adrenoceptor signaling and AD.Methods: We examined not only the cross-linking ability of TGII for tau, but also the expression level of tau as well as α1B-adrenoceptor signaling molecules, TGII and phospholipase C-δ1, in the human brain.Results: When the tau protein was assayed as a transglutaminase substrate of TGII, tau proteins formed cross-linked products. However, phospholipase C-δ1 inhibited transglutaminase activity in TGII to cross-link with tau in vitro. The amount of expressed mRNA in AD brain tissue was elevated 2~10 fold for tau and 3~20 fold for TGII. Consistent with these observations, the densities of expressed proteins in AD brain tissue also increased 9 fold for tau and 15 fold for TGII. Moreover, phospholipase C-δ1, which is a negative regulator for transglutaminase activity of TGII, also increased 2~25 fold for mRNA as well as 8 fold for protein in AD brain tissue. In contrast, expressed mRNA and protein activity for α1B-adrenoceptor were almost the same between AD and normal brains.Conclusion: These results suggest that the α1B-adrenoceptor signal mediator, TGII and tau, as a substrate of TGII might have a pathophysiological role in AD, but this correlation may be independent of the α1B-adrenoceptor signaling system, including α1B-adrenoceptor and phospholipase C-δ1.

Structure-Activity Relationship Study of Heterocyclic Phenylethenyl and Pyridinylethenyl Derivatives as Tau-Imaging Agents That Selectively Detect Neurofibrillary Tangles in Alzheimer's Disease Brains.

In order to explore novel tau-imaging agents that can selectively detect neurofibrillary tangles in Alzheimer's disease (AD) brains, we designed and synthesized a series of heterocyclic phenylethenyl and (3-pyridinyl)ethenyl derivatives with or without a dimethyl amino group. In in vitro autoradiography using AD brain sections, all radioiodinated ligands with a dimethyl amino group bound to Aβ deposits in the sections. In contrast, the ligands without a dimethyl amino group showed different patterns of radioactivity accumulation in the sections depending on the kind of heterocycle contained in their molecules. Particularly, a phenylethenyl benzimidazole derivative ([(125)I]64) showed marked radioactivity accumulation in the temporal lobe which corresponded with the distribution of tau deposits. [(125)I]64 also showed the most favorable pharmacokinetics in normal mouse brains (3.69 and 0.06% ID/g at 2 and 60 min postinjection, respectively) among all ligands in this study. Taken together, these results suggest that [(123)I]64 may be a new candidate tau-imaging agent.

ELISA measurement of specific antibodies to phosphorylated tau in intravenous immunoglobulin products

The therapeutic effects of intravenous immunoglobulin (IVIG) products were recently studied in Alzheimer's disease (AD) patients. Pilot studies produced encouraging results but phase II and III trials gave disappointing results; a further study is in progress. IVIG products contain antibodies to tau protein, the main component of neurofibrillary tangles (NFTs). The tau used to detect IVIG's anti-tau antibodies in previous studies was non-phosphorylated recombinant human tau-441, but NFT-associated tau is extensively phosphorylated. The objective of this study was to determine if various IVIG products contain specific antibodies to phosphorylated tau (anti-pTau antibodies). ELISAs were used to evaluate binding of six IVIG products to a 12 amino acid peptide, tau 196–207, which was phosphorylated (“pTau peptide”) or non-phosphorylated (“non-pTau peptide”) at Serine-199 and Serine-202. Both amino acid residues are phosphorylated in AD NFTs. Each IVIG's “anti-pTau antibody ratio” was calculated by dividing its binding to the pTau peptide by its binding to the non-pTau peptide. Seven experiments were performed and data were pooled, with each experiment contributing one data point from each IVIG product. Mean anti-pTau antibody ratios greater than 1.0, suggesting specific antibodies to phosphorylated tau, were found for three IVIG products. Because administration of antibodies to phosphorylated tau has been found to reduce tau-associated pathology in transgenic mouse models of tauopathy, increasing the levels of anti-pTau antibodies, together with other selected antibodies such as anti-Aβ, in IVIG might increase its ability to slow AD's progression.

PFTAA: a high affinity oligothiophene probe that detects filamentous tau in vivo and in cultured neurons.

Tauopathies describe a group of neurodegenerative diseases in which the protein tau, encoded by the gene MAPT, is aberrantly misfolded, leading to tau aggregation, neural dysfunction, and cell death (Spillantini and Goedert, 2013). In Alzheimer's disease (AD), tau forms the characteristic intracellular neurofibrillary tangles (NFTs), which are thought to be the major cause of neurodegeneration (Bloom, 2014). In other tauopathies, including frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17T), corticobasal degeneration and progressive supranuclear palsy, there are specific forms of tau aggregates and filaments without any amyloid pathology, demonstrating tau's potent disease-causing potential (Spillantini and Goedert, 2013). Tau is a microtubule (MT) binding protein, which becomes abnormally hyperphosphorylated on several residues prior/during the process of aggregation, thereby causing loss of its MT binding activity (Mandelkow and Mandelkow, 2012). The importance of tau as a single cause of disease is reinforced by the identification of numerous (> 55) mutations in autosomal-dominant forms of familial tauopathies, many of which occur in the MT binding domain. Indeed, more and more diseases are being uncovered in which aberrant phosphorylation and folding of tau is implicated, not least in Huntington's disease (HD), while MAPT is a genetic risk factor for Parkinson's disease (PD), so it is of major interest to understand how it leads to cell dysfunction and death.

Quantitative phosphoproteomics of Alzheimer's disease reveals cross-talk between kinases and small heat shock proteins.

Abnormal phosphorylation contributes to the formation of neurofibrillary tangles in Alzheimer's disease (AD), but may play other signaling roles during AD pathogenesis. In this study, we employed IMAC followed by LC-MS/MS to identify phosphopeptides from eight individual AD and eight age-matched control postmortem human brain tissues. Using this approach, we identified 5569 phosphopeptides in frontal cortex across all 16 cases in which phosphopeptides represented 80% of all peptide spectral counts collected following IMAC enrichment. Marker selection identified 253 significantly altered phosphopeptides by precursor intensity, changed by at least 1.75-fold relative to controls, with an empirical false discovery rate below 7%. Approximately 21% of all significantly altered phosphopeptides in AD tissue were derived from tau. Of the other 142 proteins hyperphosphorylated in AD, membrane, synapse, cell junction, and alternatively spliced proteins were overrepresented. Of these, we validated differential phosphorylation of HSP 27 (HSPB1) and crystallin-alpha-B (CRYAB) as hyperphosphorylated by Western blotting. We further identified a network of phosphorylated kinases, which coenriched with phosphorylated small HSPs. This supports a hypothesis that a number of kinases are regulating and/or regulated by the small HSP folding network.

Asparagine endopeptidase cleaves tau and promotes neurodegeneration.

Truncation of tau contributes to the formation of neurofibrillary tangles in Alzheimer's disease. A new study finds a direct role for a lysosomal cysteine protease, asparagine endopeptidase, in cleaving tau into neurotoxic fragments.

Frequent and symmetric deposition of misfolded tau oligomers within presynaptic and postsynaptic terminals in Alzheimer's disease.

The accumulation of neurofibrillary tangles in Alzheimer’s disease (AD) propagates with characteristic spatiotemporal patterns which follow brain network connections, implying trans-synaptic transmission of tauopathy. Since misfolded tau has been shown to transmit across synapses in AD animal models, we hypothesized that synapses in AD patients may contain misfolded tau. By immunofluorescence imaging of bipartite synapses from AD subjects, we detected tau protein in 38.4% of presynaptic and 50.9% of postsynaptic terminals. The pre/post distribution for hyperphosphorylated tau was 26.9%/30.7%, and for misfolded tau 18.3%/19.3%. In the temporal cortex, microscopic aggregates of tau, containing ultra-stable oligomers, were estimated to accumulate within trillions of synapses, outnumbering macroscopic tau aggregates such as tangles by 10000 fold. Non-demented elderly also showed considerable synaptic tau hyperphosphorylation and some misfolding, implicating the synapse as one of the first subcellular compartments affected by tauopathy. Misfolding of tau protein appeared to occur in situ inside synaptic terminals, without mislocalizing or mistrafficking. Misfolded tau at synapses may represent early signs of neuronal degeneration, mediators of synaptotoxicity, and anatomical substrates for transmitting tauopathy, but its actual role in these processes remain to be elucidated.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-014-0146-2) contains supplementary material, which is available to authorized users.

Preventing Dementia in Older Cardiovascular Patients

Cardiovascular disease (CVD) contributes to risk of dementia by either enhancing the development and progression of brain vascular disease and subsequent neurodegeneration and Alzheimer's disease (AD) pathology, ie, amyloid plaques and neurofibrillary tangles, acts as a precipitant of dementia in older individuals with preexisting subclinical neuropathology of dementia. Atrial fibrillation, congestive heart failure (CHF), stroke, and myocardial infarction are associated with increased risk of dementia. All older individuals age 65–70+ can be considered to be at very high risk of vascular disease and dementia and candidates for aggressive CV preventive therapies, such as lipid lowering, antihypertensive therapy, increased physical activity, antidiabetic therapies, smoking cessation, etc to prevent heart attacks subsequent CHF, atrial fibrillation, stroke, frailty, and dementia. Furthermore, preventing or delaying dementia should be a primary outcome of all CV trials in older individuals.

Genes associated with the progression of neurofibrillary tangles in Alzheimer's disease.

The spreading of neurofibrillary tangles (NFTs), intraneuronal aggregates of highly phosphorylated microtubule-associated protein tau, across the human brain is correlated with the cognitive severity of Alzheimer's disease (AD). To identify genes relevant to NFT expansion defined by the Braak stage, we conducted whole-genome exon array analysis with an exploratory sample set consisting of 213 human post-mortem brain tissue specimens from the entorinal, temporal and frontal cortices of 71 brain-donor subjects: Braak NFT stages 0 (N=13), I–II (N=20), III–IV (N=19) and V–VI (N=19). We identified eight genes, RELN, PTGS2, MYO5C, TRIL, DCHS2, GRB14, NPAS4 and PHYHD1, associated with the Braak stage. The expression levels of three genes, PHYHD1, MYO5C and GRB14, exhibited reproducible association on real-time quantitative PCR analysis. In another sample set, including control subjects (N=30), and in patients with late-onset AD (N=37), dementia with Lewy bodies (N=17) and Parkinson disease (N=36), the expression levels of two genes, PHYHD1 and MYO5C, were obviously associated with late-onset AD. Protein–protein interaction network analysis with a public database revealed that PHYHD1 interacts with MYO5C via POT1, and PHYHD1 directly interacts with amyloid beta-peptide 42. It is thus likely that functional failure of PHYHD1 and MYO5C could lead to AD development.

Time for tau.

It is almost exactly 10 years since the first report of a PET ligand that specifically bound to a pathological protein in the brain was published (Klunk et al. , 2004). This tracer, 11C-Pittsburgh compound B (PIB), detected fibrillar aggregated forms of amyloid-β, the major constituent of the Alzheimer’s disease plaque and, according to many, the initiating event in Alzheimer’s disease pathogenesis. This report was soon followed by several amyloid imaging tracers that were radiolabelled with the longer half-life positron-emitting nuclide 18F, opening the door to commercial manufacture and clinical application. Several of these tracers are now approved by worldwide regulatory agencies including the US Food and Drug Administration and the European Medicines Agency, although reimbursement for clinical use remains problematic. In this issue of Brain , Okamura and colleagues report the first human PET studies with a new tracer for tau, 18F-THK5105, and reveal that retention of this tracer correlates with dementia severity and brain atrophy in Alzheimer’s disease (Okamura et al. , 2014). Because it is difficult to develop, test and validate a new PET imaging agent, it may have seemed overly optimistic 10 years ago to conclude that a new era in human brain imaging had begun, but it had. The latest developments are a series of PET tracers that bind to the microtubule-associated protein tau that is aggregated as neurofibrillary tangles in Alzheimer’s disease. Tau-related diseases also include the group of tauopathies often referred to as frontotemporal lobar degenerations, and the highly publicized chronic traumatic encephalopathy. Tau would seem to be a difficult target for PET imaging: it may be intracellular thus requiring tracer passage across both the blood–brain barrier and cell membranes; it is found in the brain at lower concentrations than amyloid-β; and it is characterized by different …

Frequent and symmetric deposition of misfolded tau oligomers within presynaptic and postsynaptic terminals in Alzheimer¿s disease

The accumulation of neurofibrillary tangles in Alzheimer’s disease (AD) propagates with characteristic spatiotemporal patterns which follow brain network connections, implying trans-synaptic transmission of tauopathy. Since misfolded tau has been shown to transmit across synapses in AD animal models, we hypothesized that synapses in AD patients may contain misfolded tau. By immunofluorescence imaging of bipartite synapses from AD subjects, we detected tau protein in 38.4% of presynaptic and 50.9% of postsynaptic terminals. The pre/post distribution for hyperphosphorylated tau was 26.9%/30.7%, and for misfolded tau 18.3%/19.3%. In the temporal cortex, microscopic aggregates of tau, containing ultra-stable oligomers, were estimated to accumulate within trillions of synapses, outnumbering macroscopic tau aggregates such as tangles by 10000 fold. Non-demented elderly also showed considerable synaptic tau hyperphosphorylation and some misfolding, implicating the synapse as one of the first subcellular compartments affected by tauopathy. Misfolding of tau protein appeared to occur in situ inside synaptic terminals, without mislocalizing or mistrafficking. Misfolded tau at synapses may represent early signs of neuronal degeneration, mediators of synaptotoxicity, and anatomical substrates for transmitting tauopathy, but its actual role in these processes remain to be elucidated.

Protein Disulfide Isomerase P5-Immunopositive Inclusions in Patients with Alzheimer's Disease

Amyloid plaques and neurofibrillary tangles (NFTs) are the major pathological characteristics of Alzheimer's disease (AD). NFTs are composed of tubular filaments and paired helical filaments containing polymerized hyperphosphorylated tau protein. Another feature of AD is excessive generation of nitric oxide (NO). Protein disulfide isomerase (PDI) is a chaperon protein located in the endoplasmic reticulum (ER). It was recently reported that NO-induced S-nitrosylation of PDI inhibits its enzymatic activity, leading to the accumulation of polyubiquitinated proteins, and activates the unfolded protein response. In addition, we previously reported the presence of PDI-immunopositive NFTs in AD. Here, we found that protein disulfide isomerase P5 (P5), which is a member of the PDI protein family, was co-localized with tau in NFTs. To our knowledge, this is the first report of P5-immunopositive inclusion in AD. Furthermore, we showed that S-nitrosylated P5 was present and the expression level of P5 was decreased in AD brains compared with that of control brains. We also demonstrated that the knock-down of PDI or P5 by siRNA could affect the viability of SH-SY5Y cells under ER stress. Previously, the observation of S-nitrosylated PDI in AD was reported. NO may inhibit P5 by inducing S-nitrosylation in the same manner as PDI, which inhibits its enzymatic activity allowing protein misfolding to occur in AD. The accumulation of misfolded proteins induces ER stress and may cause apoptosis of neuronal cells through S-nitrosylation and down-regulation of PDI and P5 in AD.

Novel 18F-Labeled Arylquinoline Derivatives for Noninvasive Imaging of Tau Pathology in Alzheimer Disease

Neurofibrillary tangles in Alzheimer disease (AD) brains are composed of the microtubule-associated protein tau. Noninvasive monitoring of tau protein aggregates in the living brain will provide useful information regarding tau pathophysiology in AD. However, no PET probes are currently available for selective detection of tau pathology in AD. We have previously reported (18)F-labeled THK-523 ((18)F-6-(2-fluoroethoxy)-2-(4-aminophenyl)quinoline) as a tau imaging radiotracer candidate for PET. After compound optimization, we developed novel (18)F-labeled arylquinoline derivatives, (18)F-THK-5105 and (18)F-THK-5117, for use as tau imaging PET tracers. (18)F-labeled compounds were prepared from the corresponding tosylated precursors. The binding affinity of compounds to synthetic tau aggregates and tau-rich AD brain homogenates was determined by saturation and competition binding assays. The binding selectivity of compounds to tau pathology was evaluated by autoradiography of AD brain sections. The pharmacokinetics of compounds were assessed in biodistribution studies in normal mice. A 14-d toxicity study with intravenous administration of compounds was performed using rats and mice. In vitro binding assays demonstrated higher binding affinity of THK-5105 and THK-5117 than THK-523 to tau protein aggregates and tau-rich AD brain homogenates. Autoradiographic analyses of AD brain sections showed that these radiotracers preferentially bound to neurofibrillary tangles and neuropil threads, which colocalized with Gallyas-positive and immunoreactive tau protein deposits. The distribution of this radiotracer binding in AD brain sections was completely different from that of (11)C-Pittsburgh compound B, showing preferential binding to amyloid plaques. Furthermore, these derivatives demonstrated abundant initial brain uptake and faster clearance in normal mice than (18)F-THK-523 and other reported (18)F-labeled radiotracers. THK-5105 and THK-5117 showed no toxic effects related to the administration of these compounds in mice and rats and no significant binding for various neuroreceptors, ion channels, and transporters at 1-μM concentrations. (18)F-labeled THK-5105 and THK-5117 are promising candidates as PET tau imaging radiotracers.

Unbiased screen reveals ubiquilin-1 and -2 highly associated with huntingtin inclusions

Recently mutations in ubiquilin-2 were identified in patients with amyotrophic lateral sclerosis (ALS) and ALS/dementia providing direct evidence for the importance of this protein in neurodegenerative diseases. Histological studies have suggested that ubiquilin-1/-2 are associated with various pathological inclusions including Lewy bodies in Parkinson's disease, neurofibrillary tangles in Alzheimer's disease, polyQ inclusions in expansion repeat diseases and various proteinopathies associated with ALS and frontotemporal dementia. Using specific ubiquilin-2 antibodies and a series of transgenic mouse models of proteinopathies associated with neurodegenerative disease, we show that ubiquilin-2 preferentially associates with huntingtin polyQ expansion aggregates compared to α-synuclein, tau and several other types of protein inclusions. These results were confirmed by similar findings for ubiquilin-1 and -2 in human brain tissue sections, where accumulation was observed in huntingtin inclusions, but only infrequently in other types of protein inclusions. In cultured cells, ubiquilin-2 associates with huntingtin/polyQ aggregates, but this is not compromised by disease-causing mutations. Although ubiquilin proteins can function as chaperones to shuttle proteins for degradation, there is persistent co-localization between ubiquilin-2 and polyQ aggregated proteins during disease progression in the N586-82Q-C63 Huntington's disease mouse model. Thus, the co-localization of ubiquilin-2 with the huntingtin aggregates does not appear to facilitate aggregate removal.

Role of Individual MARK Isoforms in Phosphorylation of Tau at Ser262 in Alzheimer’s Disease

The microtubule-affinity regulating kinase (MARK) family consists of four highly conserved members that have been implicated in phosphorylation of tau protein, causing formation of neurofibrillary tangles in Alzheimer's disease (AD). Understanding of roles by individual MARK isoform in phosphorylating tau has been limited due to lack of antibodies selective for each MARK isoform. In this study, we first applied the proximity ligation assay on cells to select antibodies specific for each MARK isoform. In cells, a CagA peptide specifically and significantly inhibited tau phosphorylation at Ser²⁶² mediated by MARK4 but not other MARK isoforms. We then used these antibodies to study expression levels of MARK isoforms and interactions between tau and individual MARK isoforms in postmortem human brains. We found a strong and significant elevation of MARK4 expression and MARK4-tau interactions in AD brains, correlating with the Braak stages of the disease. These results suggest the MARK4-tau interactions are of functional importance in the progression of AD and the results also identify MARK4 as a promising target for AD therapy.

NAP (davunetide) rescues neuronal dysfunction in a Drosophila model of tauopathy

Alzheimer's disease (AD) is a devastating neurodegenerative disease causing irreversible cognitive decline in the elderly. There is no disease-modifying therapy for this condition and the mechanisms underpinning neuronal dysfunction and neurodegeneration are unclear. Compromised cytoskeletal integrity within neurons is reported in AD. This is believed to result from loss-of-function of the microtubule-associated protein tau, which becomes hyper-phosphorylated and deposits into neurofibrillary tangles in AD. We have developed a Drosophila model of tauopathy in which abnormal human tau mediates neuronal dysfunction characterised by microtubule destabilisation, axonal transport disruption, synaptic defects and behavioural impairments. Here we show that a microtubule-stabilising drug, NAPVSIPQ (NAP), prevents as well as reverses these phenotypes even after they have become established. Moreover, it does not alter abnormal tau levels indicating that it by-passes toxic tau altogether. Thus, microtubule stabilisation is a disease-modifying therapeutic strategy protecting against tau-mediated neuronal dysfunction, which holds great promise for tauopathies like AD.