Alzheimer's Tangles Research Articles

Apolipoprotein E Is Present in Hippocampal Neurons without Neurofibrillary Tangles in Alzheimer's Disease and in Age-Matched Controls

Apolipoprotein E (apoE, protein; APOE, gene) is a susceptibility gene for late-onset familial and sporadic Alzheimer's disease (AD). To examine the role of apoE in the pathogenesis of AD, we used immunocytochemistry to compare apoE localization in the hippocampus of histologically confirmed cases of AD, Parkinson's disease (PD), and normal controls. We confirmed apoE immunoreactivity in astrocytes, senile plaques, blood vessels, and some neurons containing neurofibrillary tangles (NFTs). In addition, we observed apoE immunoreactivity in hippocampal neurons without NFTs in AD and PD patients as well as in some nondemented aged controls. In AD cases, apoE-immunoreactive neurites were closely associated with β-amyloid (Aβ) containing senile plaques and intraneuronal apoE was sometimes associated with immunoreactive tau protein accumulation. Thus, apoE is localized where it may affect the biological expression of two characteristic AD pathological correlates: extracellular Aβ deposition and intraneuronal tau metabolism and NFT formation.

Stable intrachain and interchain complexes of neurofilament peptides: a putative link between Al3+ and Alzheimer disease.

The etiologic role of Al3+ in Alzheimer disease has been controversial. Circular dichroism (CD) spectroscopic studies on two synthetic fragments of human neurofilament protein mid-sized subunit (NF-M), NF-M13 (KSPVPKSPVEEKG) and NF-M17 (EEKGKSPVPKSPVEEKG), and their alanine-substituted and/or serine-phosphorylated derivatives were carried out in an attempt to find a molecular mechanism for the effect of Al3+ to induce aggregation of neuronal proteins or their catabolic fragments. Al3+ and Ca2+ ions were found to induce beta-pleated sheet formation in the phosphorylated fragments. The cation sensitivity depended on the length and charge distribution of the sequence and site of phosphorylation. Al3+-induced conformational changes were irreversible to citric acid chelation, whereas Ca(2+)-induced conformational changes were reversible with citric acid. Studies of the alanine derivatives demonstrated which residues affected Al3+ or Ca2+ binding. Peptides containing at least one free (nonphosphorylated) serine residue were shown to form an intramolecular Al3+ complex, rather than an intermolecular one. In the intramolecular (intrachain) complex, the ligand function of the deprotonated serine hydroxyl was delineated [(Al.pepH-1)-type complex]. Ca2+ ions did not show a tendency for intramolecular complexing. The potential role of Al3+ in Alzheimer disease tangle and plaque formation is strongly suggested.

Neuronal cytoskeletal abnormalities in human cerebral cortical dysplasia.

The cytoskeletal abnormalities of cortical neurons in human cerebral cortical dysplasia were compared by immunohistochemical methods to the neurofibrillary tangles of Alzheimer's disease (AD). Surgical specimens from cortical resections performed for the treatment of intractable childhood seizures as well as autopsied samples from AD patients were analyzed with different antibodies directed against high- or medium-molecular mass neurofilament epitopes, phosphorylated or non-phosphorylated forms of neurofilaments, ubiquitin, the microtubule-associated protein tau, and paired helical filaments (PHF), a defining feature of AD tangles. A strong abnormal increase in immunoreactivity to the high and medium molecular mass neurofilament epitopes was seen in hypertrophic neurons of cortical dysplasia. These neurofilamentous accumulations of cortical dysplasia as well as AD tangles also displayed immunoreactivity with antibodies against phosphorylated and non-phosphorylated neuro-filament epitopes, tau and ubiquitin. Only the AD tangles, however, were immunoreactive to the antiserum to PHF. These results replicate and extend our previous findings that the neurofibrillary accumulations in cerebral cortical dysplasia share some common antigens with the neurofibrillary tangles of AD but do not demonstrate immunoreactivity to PHF antiserum. The results also suggest that the cytoskeletal abnormalities observed in neurons of cortical dysplasia may result in part from alterations in the level of expression, in phosphorylation state or in transport of cytoskeletal components.

Differential distribution of amyloid protein precursor immunoreactivity in the rat brain studied by using five different antibodies.

The beta-amyloid or A4 protein is found deposited in neuritic plaques and neurofibrillary tangles in Alzheimer's disease (AD) affected brains and in the brains of adults with Down's Syndrome. The precursor to this 42 amino acid protein is the 695 amino acid long amyloid protein precursor (APP-695). Two additional APP species, APP-751 and APP-770, each contain a 56-amino-acid insert sequence that is analogous to Kunitz protease inhibitors. APP mRNA is widely distributed in both the human and rat brain, although the adult rat does not develop mature amyloid pathology. In this study we used antibodies against the N-terminus, junction site (unique to APP-695) insert sequence (unique to APP-751,-770), A4 region, and C-terminus of APP to immunolabel sections from throughout the young adult rat brain. From these results we constructed maps of the staining pattern of each antibody. We found that APP is widely distributed throughout the brain, that labelling is predominantly neuronal in character, and that there is marked variation among the antibodies in the extent of labelling, the particular cell populations stained, and the structures labelled within individual cells. The differential staining patterns observed with the five different antibodies suggest that the way APP is processed differs from one region to another and within different compartments in the cell. The specificity of the antibodies was established by Western blot analysis, in which APP species of approximately 95 and 110 kD were found. Our findings on the distribution of APP provide a foundation for further investigations into the normal role of APP and the pathogenesis of AD.

Alzheimer's-disease-like changes in tau protein processing: association with aluminium accumulation in brains of renal dialysis patients

Tau protein is a major structural protein of the paired helical filaments (PHFs) found in both neuritic senile plaques and neurofibrillary tangles in Alzheimer's disease (AD). Senile plaques also contain amyloid β protein (Aβ). We did an immunochemical analysis of frontal cortex from 15 dialysis cases, 5 Alzheimer's disease patients, and 6 control cases to see whether AD-like changes in Aβ deposition and tau protein were linked to aluminium accumulation. Dialysis patients were used because they are frequently exposed to increased levels of aluminium. 8 of the 15 dialysis cases had insoluble Aβ, but there was no association between its presence and the accumulation of aluminium. However, we found AD-like changes in the processing of tau protein. In white matter, truncated tau protein in the PHF-core fraction and endogenously truncated tau in the supernatant fraction were both increased in association with aluminium accumulation in the brain. In grey matter, normal tau protein was depleted and insoluble hyperphosphorylated tau increased in association with aluminium concentration. Protease-resistant PHFs were present in grey matter in 2 dialysis cases, a frequency above that expected for AD in this age group. PHF-core tau in both grey and white matter correlated with decreased levels of normal tau protein in white matter. These findings are consistent with a role for aluminium in the development of AD-like pathology in patients subjected to prolonged aluminium exposure.

Immunohistochemical staging of neurofibrillary degeneration in Alzheimer's disease.

Antibodies to different phosphorylated and non-phosphorylated tau epitopes have been used to identify three histologically distinct types of neurofibrillary tangles in Alzheimer's disease. Intracellular tangles (Type 1) were identified by antibodies recognizing epitopes throughout the tau molecule, including the NH2-terminus. Compact extracellular tangles (Type 2) were characterized by the loss of NH2-terminal immunoreactivity and retention of other tau epitopes. Dispersed extracellular tangles (Type 3) were characterized by the presence of epitopes associated with the microtubule binding region and the COOH-terminus. These three types of tangles, found in situ in hippocampus, could be created experimentally by proteolytic treatment of brain sections. These findings suggest that three stages of neurofibrillary degeneration can be understood as a sequential stripping of paired helical filaments in which the loss of amino-terminus epitopes, followed by loss of phosphorylated epitopes, results in the appearance of dispersed extracellular tangles containing PHF-core epitopes.

Quantitative neuropathologic analysis of Pick's disease cases: cortical distribution of Pick bodies and coexistence with Alzheimer's disease.

Pick's disease is characterized morphologically by severe atrophy of the frontal and temporal lobes and the presence in the cerebral cortex of degenerative neuronal lesions referred to as Pick bodies. In the present study, we analyzed the regional and laminar distribution of Pick bodies in a series of 16 Pick's disease cases. These distribution and density patterns were compared with those observed for neurofibrillary tangles in Alzheimer's disease. Very high densities of Pick bodies were observed Ammon's horn, subiculum, entorhinal cortex, and in the granule cell layer of the dentate gyrus. In the frontal and temporal neocortex, they were preferentially distributed in layers II and VI. All of the Pick's disease cases also exhibited neurofibrillary tangles in the frontal and temporal areas and in the hippocampal formation, with higher densities in layers II-III than in layers V-VI of the neocortical regions. Interestingly, this laminar distribution of neurofibrillary tangles was strikingly different from that observed in Alzheimer's disease cases, where they were more numerous in the infragranular layers than in the supragranular layers. In addition, a few Pick's disease cases also had cortical senile plaques. These results suggest that the presence of neurofibrillary tangles in Pick's disease may be more frequent than previously reported, and that Pick's disease and Alzheimer's disease may coexist in certain cases. The lesion distribution patterns suggest that different populations of cortical neurons are affected in Pick's and Alzheimer's disease, and that alterations of select corticocortical and corticosubcortical projections may distinguish these forms of dementia. It is also possible that these two disorders share certain pathogenetic mechanisms, even though both display specific patterns of regional and neuronal vulnerability to the degenerative processes.

Cerebral ischemia induces alterations in tau and ubiquitin proteins.

Excessive stimulation of glutamate receptors and elevation of intracellular calcium levels initiate the neurodegenerative process resulting from cerebral ischemia. However, the subsequent cascade of molecular changes which are of pathogenic significance is less well understood. Breakdown of the cytoskeleton may be involved in the progression from compromise of neuronal viability to irreversible damage. Alteration of the microtubule-associated protein tau, as reflected by increased Alz-50 immunoreactivity, was induced by permanent focal cerebral ischemia in vivo but only in a proportion of neurones. Alz-50 immunoreactive neurones did not exhibit the characteristics of irreversible ischemic cell damage. Increased immunoreactivity to the stress response protein ubiquitin was also induced by ischemia in a proportion of neurones. Both proteins are components of neurofibrillary tangles in Alzheimer's disease. Alterations of the microtubule-associated protein tau may be a feature of the early stages of the ischemia-induced degeneration and the ubiquitin response may be an attempt by compromised neurones to deal with the presence of abnormal proteins.

Immunoreactivity to ubiquitin-activating enzyme (E1) of neurofibrillary tangles in Alzheimer's disease : M. Landon, D. Rog, J. Arnold, J. Lowe ∗, R.J. Mayer and R. Layfield. Departments of Biochemistry and Pathology ∗, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, NG7 2UH, UK

Immunoreactivity to ubiquitin-activating enzyme (E1) of neurofibrillary tangles in Alzheimer's disease : M. Landon, D. Rog, J. Arnold, J. Lowe ∗, R.J. Mayer and R. Layfield. Departments of Biochemistry and Pathology ∗, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, NG7 2UH, UK

Effects of intrahippocampal colchicine administration on the levels and localization of microtubule-associated proteins, tau and MAP2

Colchicine, a microtubule disrupting agent, has been used to model several aspects of Alzheimer's disease-related neuropathology. The formation of neurofibrillary tangles, one of the pathological hallmarks of Alzheimer's disease, involves the loss of tau (a low mol. wt. microtubule-associated protein) from axons and accumulation of abnormally phosphorylated tau in somatodendritic compartments. Other cytoskeletal proteins, such as microtubule-associated protein 2 (MAP2), disappear as tau accumulates. The present study was directed at evaluating the effects of colchicine on tau and MAP2, to determine if changes in their levels or distribution might be similar to those which precede the formation of neurofibrillary tangles in Alzheimer's disease. Six hours following intrahippocampal colchicine injection (3.5 μg injected into two rostro-caudal locations) tau-1 immunostaining was enhanced in CA1 s. radiatum and decreased in the outer molecular layer of the dentate gyrus. In addition, a shift in the relative abundance of tau isoforms was observed in Western blots. Both the immunocytochemical and immunoblot results are consistent with a dephosphorylation of tau. Loss of MAP2 was evident 3 days postinjection which coincided with a loss of Cresyl violet staining in granule cell, CA3, subicular and entorhinal neurons. Accumulation of tau or MAP2 in neuronal perikarya was not observed at any postinjection time points. Thus, intrahippocampal colchicine administration does not model the shift in tau localization, excessive tau phosphorylation, or other cytoskeletal alterations that are suggested to precede or accompany the formation of neurofibrillary pathology in Alzheimer's disease.

Demonstration of Senile Plaques and Neurofibrillary Tangles in Alzheimer's Disease with Uranyl and Silver Nitrates

Demonstration of Senile Plaques and Neurofibrillary Tangles in Alzheimer's Disease with Uranyl and Silver Nitrates

Spatial Patterns of Plaques and Tangles in Alzheimer's Disease

Spatial Patterns of Plaques and Tangles in Alzheimer's Disease

Alzheimer's paired helical filaments: Amyloid precursor protein epitope mapping

Paired helical filaments (PHF) were electro-phoretically purified and solubilized from Alzheimer's neurofibrillary tangles and consisted of a primary 66 kDa protein on SDS-PAGE analysis. A panel of antibodies raised against restricted regions of the beta-amyloid precursor protein (APP) were employed for epitope mapping studies of this 66 kDa PHF protein. Western blot studies revealed that C-terminal APP antibodies were immunoreactive with the 66 kDa PHF protein. Further analysis revealed that only antisera raised against peptides that include the beta/A4-amyloid region within the C-terminal portion of APP were immunoreactive with PHF proteins. These data complement previous immunocytochemical studies which indicated that C-terminal APP antibodies preferentially label PHF-containing neurofibrillary tangles in Alzheimer's brain. The present data suggest a similarity of secondary or tertiary structure between beta/A4-amyloid and PHF which accounts for the cross-reactivity of beta/A4-amyloid antibodies with PHF proteins.

Expression of the human groEL stress-protein homologue in the brain and spinal cord

A monoclonal antibody (ML30), previously shown to identify a human mitochondrial protein epitope homologous with the groEL heat-shock protein of bacteria (hsp60), was used in an immunohistochemical survey of the central nervous system in patients dying with no evidence of neurological disease and in tissue from patients dying with various neurological disorders. Staining was performed on frozen tissue sections and on formalin fixed, paraffin embedded tissue. Astrocytes in all areas showed a strong pattern of punctate granular staining, which was increased in astrocytes showing reactive changes. Oligodendrocytes stained lightly in a diffuse granular pattern as did most neurons. Ependymal cells showed apical granular positivity. Expression of the hsp60 epitope recognised by ML30 was not seen in ubiquitinated inclusion bodies in motor neuron disease, neurofibrillary tangles in Alzheimer's disease or Lewy bodies in Parkinson's disease. The epitope recognised by ML30 was stable after formalin fixation and in post mortem tissue up to 96 h after death. Expression of the human groEL stress-protein homologue in brain and spinal cord is consistent with a mitochondrial location and may provide a morphological indicator of the functional or metabolic state of cells, especially glial cells.

Is the clustering of neurofibrillary tangles in Alzheimer's patients related to the cells of origin of specific cortico-cortical projections?

The spatial pattern of cellular neurofibrillary tangles (NFT) was studied in the supra- and infragranular layers of various cortical regions in cases of Alzheimer's disease (AD). The objective was to test the hypothesis that NFT formation was associated with the cells of origin of specific cortico-cortical projections. The novel feature of the study was that pattern analysis enabled the dimension and spacing of NFT clusters along the cortical ribbon to be estimated. In the majority of brain regions studied, NFT occurred in clusters of neurons which were regularly spaced along the cortical strip. This pattern is consistent with the predicted distribution of the cells of origin of specific cortico-cortico projections. Mean NFT cluster size varied from 250 to > 12800 μm in different cortical tissues suggesting either variation in the size of the cell clusters or a dynamic process in the development of NFT in relation to these cell clusters. The formation of NFT in cell clusters which may give rise to the feed-forward and feed-back cortico-cortical projections suggests a possible route of spread of NFT pathology in AD between cortical regions and from the cortex to subcortical areas.

Transglutaminase catalyzes the formation of sodium dodecyl sulfate-insoluble, Alz-50-reactive polymers of tau.

Paired helical filaments, a constituent of neurofibrillary tangles in Alzheimer's disease, consist primarily of the microtubule-associated protein tau. However, the process by which the detergent-insoluble filaments of the neurofibrillary tangles are formed from soluble tau remains unknown. Here, we present a potential mechanism for the abnormal aggregation of tau in Alzheimer's disease: the covalent cross-linking of tau by the enzyme transglutaminase. Macromolecular complexes of tau, formed in the presence of transglutaminase, were found to be insoluble in ionic detergent, beta-mercaptoethanol, guanidine-HCl, and urea and, furthermore, demonstrated an increased immunoreactivity with the monoclonal antibody Alz-50. Electron microscopic studies revealed that tau cross-linked by transglutaminase has a defined filamentous structure. These results indicate that transglutaminase, the activity of which has been shown to increase during programmed cell death, may play a role in the formation of pathology associated with Alzheimer's disease.

Neurofilament Monoclonal Antibodies RT97 and 8D8 Recognize Different Modified Epitopes in Paired Helical Filament‐τ in Alzheimer's Disease

Neurofibrillary tangles in Alzheimer's disease have been previously found to be labeled by some neurofilament antibodies that also recognize tau proteins. We have studied the reactivity of two such monoclonal antibodies, RT97 and 8D8, and of an anti-ubiquitin serum with the abnormal paired helical filaments (PHF)-tau (A68) polypeptides known to be the main component of the PHFs constituting the neurofibrillary tangles. 8D8 recognized the three major PHF-tau polypeptides, but RT97 reacted only with the two larger PHF-tau species. PHF-tau polypeptides were labeled by 8D8 and RT97 much more strongly than normal human tau and this labeling was decreased after alkaline phosphatase treatment. Anti-ubiquitin and anti-phosphotyrosine antibodies did not label PHF-tau polypeptides. The immunoreactivity of proteolytic fragments of PHF-tau polypeptides was studied with RT97, 8D8, and a panel of tau antibodies. The epitope for 8D8 on PHF-tau was localized between amino acids 222 and 427 in the carboxyl half of tau. The RT97 epitope on PHF-tau was localized in the amino domain of tau, probably in the 29-amino-acid insertion (insert 1) found towards the amino terminus of some tau isoforms. These results show that the basis for the labeling of neurofibrillary tangles by antibodies 8D8 and RT97 to neurofilament is their ability to react with PHF-tau polypeptides by recognizing sites specifically modified on PHF-tau, including a site specific to some tau isoforms.

Wide third ventricle correlates with low choline acetyltransferase activity of the neocortex in Alzheimer patients.

We evaluated central, temporal, and cortical atrophy by linear measurements on brain computed tomography (CT) in 17 patients with moderate to severe histologically verified Alzheimer disease (AD) compared with findings in 84 nondemented elderly controls. Measurements were adjusted for age and head size. The AD patients had wider third and lateral ventricles as well as larger temporal horns and Sylvian fissures compared with controls. Cortical atrophy tended also to be more pronounced for AD patients relative to controls. Thus measures of central and temporal atrophy clearly distinguished AD patients from normal aged individuals. In AD patients, the width of the third ventricle was significantly correlated with the choline acetyltransferase (ChAT) activity in the post-mortem frontal cortex (r = 0.65, p = 0.005) and in the temporal cortex (r = 0.59, p = 0.006). CT measures did not correlate significantly with neurofibrillary tangle or senile plaque scores. The result suggests that the width of the third ventricle better reflects the degree of cholinergic deficit than severity of histopathological changes, scores of plaques, and tangles in AD.

The spatial patterns of plaques and tangles in Alzheimer's disease do not support the 'cascade hypothesis'.

In Alzheimer's disease (AD), the 'Cascade hypothesis' proposes that the formation of paired helical filaments (PHF) may be casually linked to the deposition of beta/A4 protein. Hence, there should be a close spatial relationship between senile plaques and cellular neurofibrillary tangles in a local region of the brain. In tissue from 6 AD patients, plaques and tangles occurred in clusters and individual clusters were often regularly spaced along the cortical strip. However, the clusters of plaques and tangles were in phase in only 4/32 cortical tissues examined. Hence, the data were not consistent with the 'Cascade hypothesis' that beta/A4 and PHF are directly linked in AD.

Thrombin accumulation in brains of patients with Alzheimer's disease

Thrombin was detected immunohistochemically in brain tissue of Alzheimer's disease (AD) patients and age-matched controls. Positive staining was restricted to vessels and residual plasma in controls but was also present in senile plaques, some diffuse amyloid deposits and neurofibrillary tangles in AD. Positive staining was abolished by absorption of antibody with purified human thrombin but not by absorption with prothrombin. The data suggest that thrombin formation from prothrombin probably takes place in AD brain.