Occurrence Of Neurofibrillary Tangles Research Articles

Cyanobacterial neurotoxin BMAA and brain pathology in stranded dolphins.

Dolphin stranding events occur frequently in Florida and Massachusetts. Dolphins are an excellent sentinel species for toxin exposures in the marine environment. In this report we examine whether cyanobacterial neurotoxin, β-methylamino-L-alanine (BMAA), is present in stranded dolphins. BMAA has been shown to bioaccumulate in the marine food web, including in the muscles and fins of sharks. Dietary exposure to BMAA is associated with the occurrence of neurofibrillary tangles and β-amyloid plaques in nonhuman primates. The findings of protein-bound BMAA in brain tissues from patients with Alzheimer’s disease has advanced the hypothesis that BMAA may be linked to dementia. Since dolphins are apex predators and consume prey containing high amounts of BMAA, we examined necropsy specimens to determine if dietary and environmental exposures may result in the accumulation of BMAA in the brains of dolphins. To test this hypothesis, we measured BMAA in a series of brains collected from dolphins stranded in Florida and Massachusetts using two orthogonal analytical methods: 1) high performance liquid chromatography, and 2) ultra-performance liquid chromatography with tandem mass spectrometry. We detected high levels of BMAA (20–748 μg/g) in the brains of 13 of 14 dolphins. To correlate neuropathological changes with toxin exposure, gross and microscopic examinations were performed on cortical brain regions responsible for acoustico-motor navigation. We observed increased numbers of β-amyloid+ plaques and dystrophic neurites in the auditory cortex compared to the visual cortex and brainstem. The presence of BMAA and neuropathological changes in the stranded dolphin brain may help to further our understanding of cyanotoxin exposure and its potential impact on human health.

Phosphorylation of different tau sites during progression of Alzheimer\u2019s disease

Alzheimer’s disease is characterized by accumulation of amyloid plaques and tau aggregates in several cortical brain regions. Tau phosphorylation causes formation of neurofibrillary tangles and neuropil threads. Phosphorylation at tau Ser202/Thr205 is well characterized since labeling of this site is used to assign Braak stage based on occurrence of neurofibrillary tangles. Only little is known about the spatial and temporal phosphorylation profile of other phosphorylated tau (ptau) sites. Here, we investigate total tau and ptau at residues Tyr18, Ser199, Ser202/Thr205, Thr231, Ser262, Ser396, Ser422 as well as amyloid-β plaques in human brain tissue of AD patients and controls. Allo- and isocortical brain regions were evaluated applying rater-independent automated quantification based on digital image analysis. We found that the level of ptau at several residues, like Ser199, Ser202/Thr205, and Ser422 was similar in healthy controls and Braak stages I to IV but was increased in Braak stage V/VI throughout the entire isocortex and transentorhinal cortex. Quantification of ThioS-stained plaques showed a similar pattern. Only tau phosphorylation at Tyr18 and Thr231 was already significantly increased in the transentorhinal region at Braak stage III/IV and hence showed a progressive increase with increasing Braak stages. Additionally, the increase in phosphorylation relative to controls was highest at Tyr18, Thr231 and Ser199. By contrast, Ser396 tau and Ser262 tau showed only a weak phosphorylation in all analyzed brain regions and only minor progression. Our results suggest that the ptau burden in the isocortex is comparable between all analyzed ptau sites when using a quantitative approach while levels of ptau at Tyr18 or Thr231 in the transentorhinal region are different between all Braak stages. Hence these sites could be crucial in the pathogenesis of AD already at early stages and therefore represent putative novel therapeutic targets.

Drosophila melanogaster: Deciphering Alzheimer's Disease.

Alzheimer's disease (AD) is the most widespread neurodegenerative disorder worldwide. Its pathogenesis involves two hallmarks: aggregation of amyloid beta (Aβ) and occurrence of neurofibrillary tangles (NFTs). The mechanism behind the disease is still unknown. This has prompted the use of animal models to mirror the disease. The fruit fly, Drosophila melanogaster has garnered considerable attention as an organism to recapitulate human disorders. With the ability to monopolise a multitude of traditional and novel genetic tools, Drosophila is ideal for studying not only cellular aspects but also physiological and behavioural traits of human neurodegenerative diseases. Here, we discuss the use of the Drosophila model in understanding AD pathology and the insights gained in discovering drug therapies for AD.

Inhibition of Glycogen Synthase Kinase-3 Reverses Tau Hyperphosphorylation Induced by Pin1 Down-Regulation

One of the neuropathological hallmarks of Alzheimer's disease (AD) is the occurrence of neurofibrillary tangles (NFTs) that are composed of abnormally hyperphosphorylated microtubule-associated protein tau. Abnormal tau hyperphosphorylation is mainly induced due to the imbalance between protein kinases and phosphatases. In the tanglerich subregions of the hippocampus and parietal cortex in the brain of AD patients, the levels of the phosphorylationdependent protein peptidyl-prolyl cis-trans isomerase (Pin1) were found to be low. Although Pin1 can regulate tau phosphorylation, it is not clear whether the inhibition of glycogen synthase kinase 3 (GSK-3), the primary mediator of tau phosphorylation in AD, could reverse tau hyperphosphorylation induced due to the down-regulation of Pin1. We found that while suppression of Pin1, either by using its inhibitor Juglone or a shRNA plasmid against Pin1, induces tau hyperphosphorylation and GSK-3β activation both in vivo and in vitro, inhibition of GSK-3β by SB216763 or LiCl reverses tau hyperphosphorylation. Our data suggest that GSK-3β activation plays an important role in tau hyperphosphorylation induced by the down-regulation of Pin1, and the inhibition of GSK-3β might be a potential therapeutic approach for AD pathology.

Phosphorylation of tau and α-synuclein in synaptic-enriched fractions of the frontal cortex in Alzheimer’s disease, and in Parkinson’s disease and related α-synucleinopathies

Phosphorylation of tau and phosphorylation of α-synuclein are crucial abnormalities in Alzheimer’s disease (AD) and α-synucleinopathies (Parkinson’s disease: PD, and dementia with Lewy bodies: DLB), respectively. The presence and distribution of phospho-tau were examined by sub-fractionation, gel electrophoresis and Western blotting in the frontal cortex of cases with AD at different stages of disease progression, PD, DLB pure form and common form, and in age-matched controls. Phospho-tauSer396 has been found in synaptic-enriched fractions in AD frontal cortex at entorhinal/transentorhinal, limbic and neocortical stages, thus indicating early tau phosphorylation at the synapses in AD before the occurrence of neurofibrillary tangles in the frontal cortex. Phospho-tauSer396 is also found in synaptic-enriched fractions in the frontal cortex in PD and DLB pure and common forms, thus indicating increased tau phosphorylation at the synapses in these α-synucleinopathies. Densitometric studies show between 20% and 40% phospho-tauSer396, in relation with tau-13, in synaptic-enriched fractions of the frontal cortex in AD stages I–III, and in PD and DLB. The percentage reaches about 95% in AD stage V and DLB common form. Yet tau phosphorylation characteristic of neurofibrillary tangles, as revealed with the AT8 antibody, is found in the synaptic fractions of the frontal cortex only at advanced stages of AD. Increased phosphorylated α-synucleinSer129 levels are observed in the synaptic-enriched fractions of the frontal cortex in PD and DLB pure and common forms, and in advanced stages of AD. Since tau-hyperphosphorylation has implications in microtubule assembly, and phosphorylation of α-synuclein at Ser129 favors α-synuclein aggregation, it can be suggested that synapses are targets of abnormal tau and α-synuclein phosphorylation in both groups of diseases. Tau phosphorylation at Ser396 has also been found in synaptic-enriched fractions in 12-month-old transgenic mice bearing the A53T α-synuclein mutation.

Neuronal COX-2 expression and phosphorylation of pRb precede p38 MAPK activation and neurofibrillary changes in AD temporal cortex

In Alzheimer's disease (AD) brain, increased levels of cyclooxygenase-2 (COX-2), cell cycle markers, and p38 MAP kinase (MAPK) can be detected in neuronal cells. Besides mediating COX-2 expression, p38 MAPK is suggested to mediate cell cycle progression through phosphorylation of the retinoblastoma protein (pRb). In this study, we show that neuronal immunoreactivity for phosphorylated p38 MAPK does not correlate with COX-2 or phosphorylated pRb (ppRb) in control and AD temporal cortex. Immunoreactivity for activated p38 MAPK co-localizes with AT8 immunoreactivity and increases with the occurrence of neurofibrillary tangles and plaques. On the other hand, COX-2 immunoreactivity co-localizes and correlates with ppRb immunoreactivity in pyramidal neurons. COX-2 and ppRb do not co-localize with AT8 and decrease with increasing pathology. These results suggest that p38 MAPK does not mediate COX-2 expression and pRb inactivation, which are involved in cellular changes in pyramidal neurons early in AD pathogenesis.

Identification of an aging-related spherical inclusion in the human brain.

Inclusions, such as corpora amylacea, axonal spheroids and ubiquitin-positive granular structures, are present in aged brains. We found a phosphorylated tau-positive inclusion in brain tissues obtained from 13 non-demented subjects and five patients with Alzheimer's disease. This inclusion was spherical and 3-20 microm in size. It was most frequently detected in the hippocampal CA1 region and in the prosubiculum but was not present in the white matter. The density of this inclusion increased significantly with aging and decreased after the occurrence of neurofibrillary tangles. The presence of the inclusion was confirmed using immunoelectron microscopy. These findings show a possibility that the inclusion is a novel aging-related structure in the human brain.

P35/Cdk5 pathway mediates soluble amyloid-beta peptide-induced tau phosphorylation in vitro.

Alzheimer's disease (AD) is pathologically characterized by deposition of amyloid-beta peptides (Abeta) as senile plaques and by the occurrence of neurofibrillary tangles (NFTs) composed primarily of hyperphosphorylated tau protein. Activation of cyclin-dependent kinase 5 (Cdk5) via its potent activator p25 has recently been shown to promote phosphorylation of tau at AD-specific phosphoepitopes, and increased cleavage of p35 to p25 has been demonstrated in AD patients, suggesting that Cdk5 may represent a pathogenic tau protein kinase. We were interested in the potential effect of soluble forms of Abeta on Cdk5-mediated AD-like tau phosphorylation, insofar as previous studies of human biopsies and aged canine and primate brains have shown that dystrophic neurites appear before the formation of neuritic plaques. We transfected N2a cells with a p35 vector (N2a/p35 cells) and, after differentiation, challenged these cells with Abeta(1-42) peptide in soluble form (sAbeta(1-42)). Results show that sAbeta(1-42) at relatively low levels (1-5 microM) dose-dependently increases tau phosphorylation at AD-specific phosphoepitopes in differentiated N2a/p35 cells compared with controls, an effect that is blocked by antisense oligonucleotides against p35. sAbeta(1-42)-induced tau phosphorylation is concomitant with an increase in both p25 to p35 ratio and Cdk5 activity (but not protein levels). Additionally, blockade of L-type calcium channels or inhibition of calpain completely abolishes this effect. Taken together, these data indicate that sAbeta is a potent activator of the p25/Cdk5 pathway, resulting in promotion of AD-like tau phosphorylation in vitro.

Etiology and pathogenesis of Alzheimer dementia

Alzheimer's disease (AD) is the most common cause of primary dementia, characterized by a progressive process of pathophysiological restructuring of the brain over decades. The hallmark of Alzheimer's disease is the extracellular accumulation and deposition of insoluble amyloid, to be found in the parenchyma in the form of amyloid plaques and in meningeal and cerebral vessels as a congophile angiopathy. Equally conspicuous is the intraneuronal occurrence of neurofibrillary tangles, consisting mainly of hyperphosphorylated tau-protein. Amyloid plaques and neurofibrillary tangles are characteristic, but not specific to Alzheimer's disease. Similar changes can be found in healthy ageing processes and in various other neurodegenerative diseases. It is common to differentiate between an early-onset, familial Alzheimer's disease with an established genetic etiology, representing only about 5% of all cases, and the more typical late-onset, sporadic Alzheimer's disease with an age of onset above 65 years and no clear pattern of inheritance. Although there seems to be a large heterogeneity in the etiology of Alzheimer's disease, the amyloid-cascade-hypothesis has taken a central position as a model for the general etiopathogenesis. The regulation of amyloid plaques underlies a diversity of cellular and molecular factors. In addition to ageing, apolipoprotein E 4 is a firmly established risk factor. Disturbance in the cerebral glucose metabolism, especially in the hippocampal regions, is a further proposed factor in the pathogenesis of Alzheimer's disease. The wide-spread loss of cortical cholinergic neurotransmission associated with the cognitive deficits is of importance to the comprehension of the symptoms and the present pharmacotherapy of Alzheimer's disease.

Immunohistochemical investigation of the brain of aged dogs. I. Detection of neurofibrillary tangles and of 4-hydroxynonenal protein, an oxidative damage product, in senile plaques

In the aging dog brain lesions develop spontaneously. They share some morphological characteristics with those of Alzheimer's disease in man. Diffuse and primitive plaques are well known, whereas neuritic plaques rarely develop. Neurofibrillary tangles have not been seen in the canine. The aim of the present investigation was to study major age-related changes of the dog's brain using paraffin sections with respect to cross-immunoreactivity oftau, Aβ protein and other immunoreactive components including hydroxynonenal protein, which is a marker for oxidative damage. The occurrence of neurofibrillary tangles and of the protein tau therein was studied in serial brain sections of two dogs with the Gallyas stain and by immunohistochem-istry with three different antibodies against tau. Senile plaques were stained with a monoclonal anti-Aβ (residues 8-17), polyclonal anti-apolipoprotein E and a monoclonal antibody against 4-hydroxynonenal (HNE). Amyloid deposits and controls were screened by Congo red staining viewed in fluorescent light, followed by polarized light for green birefringence.With the Gallyas stain and one of the antisera against tau, neurofibrillary tangles were revealed in a similar dispersed pattern, whereas the other antitau antisera gave negative results. With the anti-HNE a positive reaction was found in cerebral amyloid deposits and in vascular wall areas where amyloid deposition was confirmed by Congo-red staining, and in perivascular cells and in some neurons. These results indicate that the canine with his tangles and plaques which show oxidative changes, forms a spontaneous model for understanding the early changes and their interrelationships in Alzheimer's disease.

Recent advances in elucidating Niemann-Pick C disease.

Lysosomal sequestration of endocytosed LDL-derived cholesterol, premature and abnormal enrichment of cholesterol in trans Golgi cisternae and accompanying anomalies in intracellular sterol trafficking are the hallmark phenotypic features of the Niemann-Pick C (NPC) lesion. A variable severity of these alterations has been observed, with only partial correlation between clinical and biochemical phenotypes. NPC also affects the metabolism of sphingolipids, and other biochemical abnormalities have been reported. Occurrence of neurofibrillary tangles in the brain of patients with a slowly progressive course is a recent intriguing observation. Genetic heterogeneity was established by cell hybridization and linkage studies. The two complementation groups could not be distinguished from each other by clinical, cellular or biochemical criteria, suggesting that the two gene products may interact or function sequentially. The major (> 90% of patients) NPC1 gene was mapped to 18q11 and recently isolated by positional cloning. The cDNA sequence predicts a 1278-amino acid protein, with 13 to 16 possible transmembrane regions and a putative cholesterol-sensing domain. Two murine models of the disease involving the same gene are known. The murine cDNA and the npc(nih) mutation have been characterized. Described homologies of the NPC1 protein are in line with its putative involvement in cellular cholesterol traffic.

Incidence and Distribution of Senile Plaques and Neurofibrillary Tangles in Late‐onset Diffuse Lewy Body Disease

This report presents the results of a quantitative investigation on incidence and distribution of senile plaques (SPs) and neurofibrillary tangles (NFTs) in ten cases of late‐onset diffuse Lewy body disease (DLBD). The methenamine‐silver method was used. SP were distributed throughout the cerebral cortices of all cases. The SP stages in seven of them were compatible with those of Alzheimer‐type dementia (ATD). NFTs occurred most frequently in the transentorhinal and entorhinal pre α regions and the hippocampal CA‐1 area. The occurrence of NFTs was generally restricted to the hippocampus and parahippocampal cortex. NFTs were rarely encountered in the neocortex. The NFT stages of all ten cases were compatible with those borderline between ATD and physiological aging. When both, the SP and NFT stages are considered concurrently, the majority of our late‐onset DLBD cases had levels that corresponded to those in the very mild of ATD or the borderline between ATD and physiological aging. The occurrence of certain DLBD cases with senile changes that are insufficient for a diagnosis of ATD indicates that DLBD should not be regarded as representing part of an ATD spectrum.

Phosphorylation of Protein τ by Double-Stranded DNA-Dependent Protein Kinase

Alzheimer Disease (AD) is a distinct form of dementia characterized by the occurrence of neurofibrillary tangles, neurotic plaques and loss of certain neuronal populations. The tangles are associated with the presence of abnormal proteinaceous deposits. One such protein, referred to as tau, is found to be excessively phosphorylated in AD. We demonstrate that a double-stranded DNA-stimulated protein kinase (referred to as DNA-PK) effectively catalyzes the phosphorylation of recombinant human protein τ. Moreover, in the presence of stimulatory DNA, the hyperphosphorylation of tau is accompanied by a significant shift in its mobility on SDS polyacrylatnide gels. These results suggest that DNA-PK may contribute to the pathogenesis of AD.

Loss of large neurons and occurrence of neurofibrillary tangles in the tuberomammillary nucleus of patients with Alzheimer's disease

We studied the number of large-sized neurons and neurofibrillary tangles (NFT) in the tuberomammillary nucleus (TM) of the hypothalamus from cases with Alzheimer's disease (AD) and age-matched controls. Numerous NFT were found in TM of AD. However, NFT was never observed in this nucleus of age-matched controls. The number of large-sized neurons was significantly reduced in AD compared with that in controls. Since the majority of large neurons in TM appear to correspond to histamine neurons, the loss of large neurons observed in TM may, at least partly, cause the histaminergic dysfunction in AD brain.

Tyrosine hydroxylase-like (TH) immunoreactivity in Parkinson's disease and Alzheimer's disease.

We used tyrosine hydroxylase immunoreactivity (TH) to mark dopaminergic fibers in cerebral tissue from adult persons with Parkinson's disease (PD) or Alzheimer's disease (AD). In the PD cases we found a loss of dopaminergic neurons in the ventral tegmental area (VTA), severely reduced TH fibers in dopaminergic terminal fields (particularly in the hippocampal perforant pathway) and neurofibrillary tangles (NFT), that occurred only in the perforant pathway. In contrast, AD cases were characterized by a lack of significant neuron loss in the VTA and by mild loss of TH fibers. A decreased dopaminergic innervation of the perforant pathway in cases of PD appears to be associated with the occurrence of NFT in these structures.

Neurofibrillary degeneration of cholinergic and noncholinergic neurons of the basal forebrain in Alzheimer's disease.

Two principal features of Alzheimer's disease (AD) are (1) the occurrence of neurofibrillary tangles (NFTs) and senile plaques, and (2) the loss of cortical cholinergic activity because of dysfunction of neurons in the basal forebrain cholinergic system. The relationship of these two abnormalities is an unresolved issue in the pathology of AD. We used polyclonal antibodies specific for paired helical filaments (PHFs), combined with acetylcholinesterase (AChE) histochemistry, to assess the cytoskeletal changes of cholinergic and noncholinergic neurons in the basal forebrain in AD. In both sporadic and familial AD, the nucleus basalis of Meynert (nbM) showed a marked decrease in AChE-positive (AChE+) perikarya and abundant immunoreactive NFTs. In double-labeling studies of the nbM, PHF reactivity was found both in surviving AChE+ neurons and in many AChE- NFTs that were not associated with microscopically recognizable cell structures. Some surviving AChE+ perikarya did not contain NFTs. Numerous NFTs and senile plaques were identified by PHF immunoreactivity in other basal forebrain areas, including subnuclei of the amygdala that showed low or absent AChE activity. We conclude that the dysfunction and death of cholinergic neurons in the nbM is associated with extensive NFT formation, including apparently residual NFTs in loci where nbM neurons once existed; and many noncholinergic neurons and neurites in the basal forebrain show NFT and senile plaque formation. The cytopathology of AD involves neurons of varying transmitter specificities, including cholinergic neurons in the basal forebrain.

Long survival in Fukuyama congenital muscular dystrophy: occurrence of neurofibrillary tangles in the nucleus basalis of Meynert and locus ceruleus.

Three patients with Fukuyama congenital muscular dystrophy (FCMD), who died aged 23, 29 and 34 years, are reported. There was extensive brain malformation, but the most severe pattern of cortical dysplasia was absent in one case and in the other two localized bilaterally to small areas near the occipital poles. In two cases, numerous neurofibrillary tangles were observed in the locus ceruleus and nucleus basalis of Meynert. Electron microscopy revealed paired helical filaments, with a maximal width of about 25 nm and regular constrictions at approximately 80 nm intervals. The occurrence of neurofibrillary tangles, which is unknown in younger patients, suggests the presence of degenerative processes in the brains of the older patients with FCMD.

Chromosome studies of patients with Alzheimer disease.

Ten patients with either the familial or sporadic form of Alzheimer disease (AD) were studied cytogenetically to confirm reports of aneuploidy and "long acentric fragments" associated with the disease. Findings in leukocytes of patients were compared with those in eight unaffected relatives and seven persons of similar age. Observations from encoded slides involving 3,800 conventionally stained and 1,396 G-banded metaphases (one patient) showed no significant increase in aneuploidy. The frequency of cells with hypermodal counts, a reliable measure of aneuploidy, was 4.2% and 1.1%, respectively, in women and men with familial AD and 4.0% and 2.3%, respectively, in women and men with the sporadic form of the illness. Similar frequencies of hypermodal cells occurred in female (2.6%) and in male (2.0%) control subjects. In contrast to the lack of aneuploidy, a small but significant number of false "long acentric fragments" was found in cells of women with AD (P less than .05). These aberrations are thought to represent premature centromere division (PCD) in intact chromosomes, primarily supernumerary Xs. Often in multiple copies, PCD occurred in 2.8% of their cells and in 0.6% of cells from control women. PCD occurred in 3.6% of cells of women with the familial form and in 1.7% of cells of women with the sporadic type of dementia. Among unaffected relatives PCD increased with age. The rarity of PCD in G-banded metaphases from an affected female (3/1,396) suggests that metaphase spreading techniques also may affect observable frequency. Thus PCDs occur more frequently in, but are not unique to, AD and may represent an epiphenomenon of aging, a process also characterized by the occurrence of neurofibrillary tangles and senile plaques in the cerebral cortex.

Motor neurone disease with neurofibrillary tangles in a Brazilian woman

The occurrence of neurofibrillary tangles in both the cerebral cortex and brain stem is typically seen in the Guam type of amyotrophic lateral sclerosis, but is exceedingly rare in the classical form of the disease. Only 3 cases of sporadic amyotrophic lateral sclerosis with such histopathologic features have so far been reported, all in the United States. A 49-year-old Brazilian woman had an 18-month history of amyotrophic lateral sclerosis involving predominantly the left-sided extremities, with prominent bulbar signs. Autopsy disclosed moderate to severe loss of motor neurones in the hypoglossal nuclei and anterior spinal horns, absence of pyramidal tract demyelination, depigmentation of the substantia nigra and numerous neurofibrillary tangles in the hypothalamic region, parahippocampal gyrus, reticular substance of the mesencephalon and pons and in some brain stem nuclei. The topographical distribution of these changes was closely similar to that of Guamanian amyotrophic lateral sclerosis.