Bax deficiency extends the survival of Ku70 knockout mice that develop lung and heart diseases

Ku70 (Lupus Ku autoantigen p70) is essential in nonhomologous end joining DNA double-strand break repair, and ku70^−/− mice age prematurely because of increased genomic instability and DNA damage responses. Previously, we found that Ku70 also inhibits Bax, a key mediator of apoptosis. We hypothesized that Bax-mediated apoptosis would be enhanced in the absence of Ku70 and contribute to premature death observed in ku70^−/− mice. Here, we show that ku70^−/−bax^+/− and ku70^−/−bax^−/− mice have better survival, especially in females, than ku70^−/− mice, even though Bax deficiency did not decrease the incidence of lymphoma observed in a Ku70-null background. Moreover, we found that ku70^−/− mice develop lung diseases, like emphysema and pulmonary arterial (PA) occlusion, by 3 months of age. These lung abnormalities can trigger secondary health problems such as heart failure that may account for the poor survival of ku70^−/− mice. Importantly, Bax deficiency appeared to delay the development of emphysema. This study suggests that enhanced Bax activity exacerbates the negative impact of Ku70 deletion. Furthermore, the underlying mechanisms of emphysema and pulmonary hypertension due to PA occlusion are not well understood, and therefore ku70^−/− and Bax-deficient ku70^−/− mice may be useful models to study these diseases.

Neuronal binucleation in Alzheimer disease hippocampus

AIMS

The literature and teachings instruct that neurones in the adult brain are fully differentiated, quiescent cells that never divide. Somewhat surprisingly, and counter to such dogma, susceptible neurones in Alzheimer disease display an activated cell cycle phenotype. However, whether this leads to a coordinated procession through the cell cycle is unclear, particularly whether neurones enter anaphase and beyond. To begin to address this issue, in this study we sought to determine whether nuclear division occurs in these neurones.

METHODS

We examined a series of 101 archived, routinely stained hippocampal sections collected at post mortem for neuropathological evaluation for evidence of neuronal binucleation.

RESULTS

We report for the first time, binucleated neurones within the hippocampus in cases of Alzheimer disease but not in control cases (P < 0.05).

CONCLUSIONS

While a relatively rare event, occurring once every 20,000 neurones, this morphological evidence that neuronal cells within the cortical regions of the adult human brain in Alzheimer disease contain two nuclei supports the hypothesis that neuronal cells can re-enter into a coordinated cell cycle that culminates in nuclear division.

Neurofilament proteins in neurodegenerative diseases

The function of neurofilaments, the major component in large myelinated neurons, is not well understood even though they were discovered as structures over 100 years ago. Recent studies have suggested that neuro-filaments are closely related to many neurodegenerative diseases, such as amyotrophic lateral sclerosis, Parkinson disease Alzheimer disease, and diabetes. Using in vitro assays, cultures and transgenic mice, these studies provided new insights into neurofilament function. The function of each subunit, the relationship of neurofilaments with other cytoskeletal elements and their clinical significance are topics of increasing attention.

Oxidative stress mechanisms and potential therapeutics in Alzheimer disease

Oxidative damage of biological macromolecules is a hallmark of most neurodegenerative disorders such as Alzheimer, Parkinson and diffuse Lewy body diseases. Another important phenomenon involved in these disorders is the alteration of iron and copper homeostasis. Data from the literature support the involvement of metal homeostasis in mitochondrial dysfunction, protein alterations and nucleic acid damage which are relevant in brain function and consequently, in the development of neurodegenerative disorders. Although alterations in transition metal homeostasis, redox activity, and localization are well documented, it must be determined how alterations of specific copper- and iron-containing metalloenzymes are also involved in Alzheimer disease. The clarification of these phenomena can open a new window for understanding the mechanisms underlying neurodegeneration and, consequently, for the development of new therapeutic strategies such as gene therapy and new pharmaceutical formulations with antioxidant and chelating properties.

The mitochondrial common deletion in Parkinson's disease and related movement disorders

The mitochondrial 4977-bp common deletion has been reported in some studies to occur exclusively or with increased frequency in the midbrain of patients with Parkinson's disease (PD). Other studies could not confirm these results; rather, it was suggested that the mitochondrial common deletion is associated with aging in the midbrain and not PD. One possible explanation for these conflicting results is the difficulty in quantifying mitochondrial DNA deletions or mutations in the whole midbrain or substantia nigra (SN) while only a subset of midbrain neurons degenerate in PD. In addition, none of the studies has addressed the cell types with the common deletion within the midbrain. In this study we used in situ hybridization to detect the common deletion in sections of midbrain from patients with PD, multiple system atrophy-parkinsonian type (MSA-P), progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB), age-matched controls, and individuals of different ages. The results demonstrated that the mitochondrial common deletion accumulated primarily in neurons but not glia in both the SN and other midbrain regions. There was no significant difference in the number or distribution of neurons with the common deletion or the average of the mean densities (AMD) of staining with the common deletion in nigral neurons among patients with PD, MSA-P, PSP, DLB, or age-matched controls. In addition, there was no difference in the number or distribution of neurons with the common deletion in nigral neurons between any age group, although there was a tendency for the common deletion to increase in the non-nigral neurons in older patients. These data indicate that accumulation of the 4977-bp common deletion in mitochondrial DNA in midbrain occurred primarily in neurons, and by this cytological approach, it was not associated with nigral neurodegeneration in the common movement disorders or aging.

Mitochondrial abnormalities in Alzheimer's disease

The finding that oxidative damage, including that to nucleic acids, in Alzheimer's disease is primarily limited to the cytoplasm of susceptible neuronal populations suggests that mitochondrial abnormalities might be part of the spectrum of chronic oxidative stress of Alzheimer's disease. In this study, we used in situ hybridization to mitochondrial DNA (mtDNA), immunocytochemistry of cytochrome oxidase, and morphometry of electron micrographs of biopsy specimens to determine whether there are mitochondrial abnormalities in Alzheimer's disease and their relationship to oxidative damage marked by 8-hydroxyguanosine and nitrotyrosine. We found that the same neurons showing increased oxidative damage in Alzheimer's disease have a striking and significant increase in mtDNA and cytochrome oxidase. Surprisingly, much of the mtDNA and cytochrome oxidase is found in the neuronal cytoplasm and in the case of mtDNA, the vacuoles associated with lipofuscin. Morphometric analysis showed that mitochondria are significantly reduced in Alzheimer's disease. The relationship shown here between the site and extent of mitochondrial abnormalities and oxidative damage suggests an intimate and early association between these features in Alzheimer's disease.

Abortive apoptosis in Alzheimer's disease

Multiple studies suggest that neuronal death in Alzheimer's disease (AD) is the result of an apoptotic mechanism. However, the stereotypical manifestations that define the terminal phases of apoptosis, such as chromatin condensation, apoptotic bodies, and blebbing, are not seen in AD. In this study, we show that the caspases, such as caspase 6, which cleave amyloid-beta protein precursor (A beta PP) and presenilins, are localized to the pathological lesions associated with AD. However, while upstream caspases such as 8 and 9 are clearly found in association with the intraneuronal pathology in AD, downstream caspases such as 3, 6 and 7 are present only at control levels. Given that execution of apoptosis requires amplification of the caspase-mediated apoptotic signal, our results indicate that in AD there is a lack of effective apoptotic signal propagation to downstream caspase effectors. Therefore, while the presence of caspases, especially caspase 6, in association with extracellular deposits of amyloid-beta, could obviously have important ramifications on the proteolytic processing of A beta PP and, thereby, on disease pathogenesis, it seems that AD represents the first in vivo situation reported in which the initiation of apoptosis does not proceed to caspase-dependent cell death. This novel phenomenon of apoptotic avoidance, which we term abortive apoptosis, or abortosis, may represent an exit from the caspase-induced apoptotic program that leads to neuronal survival in AD.

Erythrocyte, plasma, and serum antioxidant activities in untreated toxic multinodular goiter patients

Erythrocyte, plasma, and serum antioxidant activities were studied in patients with newly diagnosed and untreated toxic multinodular hyperthyroid goiter and compared to healthy control subjects. Erythrocyte antioxidant enzyme activities, glutathione, malondialdehyde, and ceruloplasmin levels were significantly increased, whereas serum vitamin E, plasma vitamin C, and selenium levels were decreased in hyperthyroid patients compared to control subjects. The findings show that untreated toxic multinodular goiter causes profound alterations in components of the antioxidant system in erythrocytes indicative of increased oxidative stress. Taken together, these data suggest that hyperthyroid patients may benefit from dietary supplements of antioxidants.

In Alzheimer's disease, heme oxygenase is coincident with Alz50, an epitope of tau induced by 4-hydroxy-2-nonenal modification

In this study, we compared the neuronal induction of the antioxidant heme oxygenase-1 (HO-1) in Alzheimer's disease with abnormalities in tau marked by antibodies recognizing either phosphorylation (AT8) or conformational change (Alz50). The epitope recognized by Alz50 shows a complete overlap with HO-1-containing neurons, but AT8 recognized these neurons as well as neurons not displaying HO-1. These findings suggest that tau phosphorylation precedes the HO-1 response and that HO-1 is coincident with the Alz50 epitope. This led us to consider whether oxidative damage plays a role in forming the Alz50 epitope. We found that 4-hydroxy-2-nonenal (HNE), a highly reactive product of lipid peroxidation, reacts with normal tau and induces the Alz50 epitope in tau. It is important that the ability of HNE to create the Alz50 epitope not only is dependent on lysine residues of tau but also requires tau phosphorylation because neither methylated, recombinant, nor dephosphorylated tau reacts with HNE to create the Alz50 epitope. Supporting the in vivo relevance of this observation, endogenous paired helical filament-tau isolated from subjects with Alzheimer's disease was immunoreactive with an antibody to a stable HNE-lysine adduct, as were all vulnerable neurons in subjects with Alzheimer's disease but not in control individuals. Together, these findings support the involvement of oxidative damage early in neurofibrillary tangle formation in Alzheimer's disease and also suggest that HNE modification contributes to the generation of the tau conformation defining the Alz50 epitope. These findings provide evidence that an interplay between phosphorylation of tau and neuronal oxidative stress-induced pathology is important in the formation of neurofibrillary tangles.

Sequestration of iron by Lewy bodies in Parkinson's disease

Central to the oxidative stress hypothesis of Parkinson's disease (PD) pathogenesis is the ability of iron to generate hydroxyl radicals via the Fenton reaction, and the consistent demonstration of iron elevation in the pars compacta region of the substantia nigra. However, uncertainty exists as to whether the excess iron exists in a state suitable for redox chemistry. Here, using a method we developed that detects redox-active iron in situ, we were able to demonstrate strong labeling of Lewy bodies in substantia nigra pars compacta neurons in PD. In contrast, cortical Lewy bodies in cases of Lewy body variant of Alzheimer's disease were unstained. While the presence of elevated iron in PD substantiates the oxidative stress hypothesis, one must remember that these are viable neurons, indicating that Lewy bodies may act to sequester iron in PD brains in a protective, rather than degenerative, mechanism. The absence of redox-active iron in neocortical Lewy bodies highlights a fundamental difference between cortical and brain stem Lewy bodies.

Altered cell-matrix associated ADAM proteins in Alzheimer disease

Alterations in cell-matrix 'contact' are often related to a disruption of cell cycle regulation and, as such, occur variously in neoplasia. Given the recent findings showing cell cycle alterations in Alzheimer disease, we undertook a study of ADAM-1 and 2 (A Disintegrin And Metalloprotease), developmentally-regulated, integrin-binding, membrane-bound metalloproteases. Our results show that whereas ADAM-1 and 2 are found in susceptible hippocampal neurons in Alzheimer disease, these proteins were not generally increased in similar neuronal populations in younger or age-matched controls except in association with age-related neurofibrillary alterations. This increase in both ADAM-1 and 2 in cases of Alzheimer disease was verified by immunoblot analysis (P < 0.05). An ADAM-induced loss of matrix integration would effectively "reset" the mitotic clock and thereby stimulate re-entry into the cell cycle in neurons in Alzheimer disease. Furthermore, given the importance of integrins in maintaining short-term memory, alterations in ADAM proteins or their proteolytic activity could also play a proximal role in the clinico-pathological manifestations of Alzheimer disease.

Protein disulfide isomerase in Alzheimer disease

There is a great deal of evidence that places oxidative stress as a proximal event in the natural history of Alzheimer disease (AD). In addition to increased damage, there are compensatory increases in the levels of free sulfhydryls, glucose-6-phosphate dehydrogenase, and NAD(P)H:quinone oxidoreductase 1. To investigate redox homeostasis further in AD, we analyzed protein disulfide isomerase (PDI), a multifunctional enzyme, which catalyzes the disruption and formation of disulfide bonds. PDI plays a pivotal role in both secreted and cell-surface-associated protein disulfide rearrangement. In this study, we show that PDI specifically localizes to neurons, where there is no substantial increase in AD compared to age-matched controls. These findings indicate that the neurons at risk of death in AD do not show a substantial change in PDI to compensate for the increased sulfhydryls and reductive state found during the disease. This suggests that, despite compensatory reductive changes in AD, the level of PDI is sufficiently high physiologically in neurons to accommodate a more reducing environment.

Increased neuronal glucose-6-phosphate dehydrogenase and sulfhydryl levels indicate reductive compensation to oxidative stress in Alzheimer disease

We analyzed glucose-6-phosphate dehydrogenase, the rate-controlling enzyme of the pentose phosphate pathway and free sulfhydryls, to study redox balance in Alzheimer disease. Glucose-6-phosphate dehydrogenase plays a pivotal role in homeostatic redox control by providing reducing equivalents to glutathione, the major nonenzymatic cellular antioxidant. There is a multitude of evidence that marks oxidative stress proximally in the natural history of Alzheimer disease. Consistent with a role for glutathione in defense against increased reactive oxygen, we found an upregulation of glucose-6-phosphate dehydrogenase together with increased sulfhydryls in Alzheimer disease. These data indicate that reductive compensation may play an important role in combating oxidative stress in Alzheimer disease.

Role of oxidative stress in frontotemporal dementia

Recent reports have established oxidative stress and damage as playing a role in the pathogenesis of a number of neurodegenerative diseases including Alzheimer disease, Parkinson disease, corticobasal degeneration, Pick's disease and Alexander's disease. Here we present evidence that oxidative damage is also one of the earliest cytopathological markers of neuronal dysfunction in frontotemporal dementia.

Activation of neuronal extracellular receptor kinase (ERK) in Alzheimer disease links oxidative stress to abnormal phosphorylation

Responses to increased oxidative stress may be the common mechanism responsible for the varied cytopathology of Alzheimer disease (AD). A possible link in support of this hypothesis is that one of the most striking features of AD, the abnormal accumulation of highly phosphorylated tau and neurofilament proteins, may be brought about by extracellular receptor kinase (ERK) whose activation is a common response to oxidative stress. In this study, we demonstrate that activated ERK is specifically increased in the same vulnerable neurons in AD that are the site of oxidative damage and abnormal phosphorylation. These findings suggest that ERK dysregulation, likley resulting from oxidative stress, could play an important role in the increased phosphorylation of cytoskeletal proteins observed in AD.

Striation is the characteristic neuritic abnormality in Alzheimer disease

In this study, we found that neuropil threads of Alzheimer disease, rather than being continuous filaments along cell processes, show multiple interruptions. They are segmental in nature and therefore appear as striations rather than continuous filaments along the length of the neurite. Neuritic striation is not an artifact of section thickness since the majority of abnormal filament accumulations are extremely short. The dominance of short striations demonstrates that argyrophilic grains, rather than being distinct structures, simply represent a short variant of striation and that longer striations are arbitrarily considered neuropil threads. Ultrastructural examination showed that the intervals between striations lack a cytoskeleton. We suggest that neuritic striations may interrupt the microtubule system functionally blocking fast neuritic transport as well as playing a role in loss of neuronal connectivity.

Amyloid-beta deposition in Alzheimer transgenic mice is associated with oxidative stress

Increased awareness for a role of oxidative stress in the pathogenesis of Alzheimer's disease has highlighted the issue of whether oxidative damage is a fundamental step in the pathogenesis or instead results from disease-associated pathology. In vitro experiments support both possibilities: Oxidative stress increases amyloid-beta production, and, conversely, amyloid-beta increases oxidative damage. To address the relationship between amyloid-beta and oxidative stress in vivo, we examined, using an array of oxidative markers, transgenic mice that overexpress amyloid-beta precursor protein and, as in Alzheimer's disease, develop characteristic amyloid-beta deposits within the brain parenchyma. Transgenic animals show the same type of oxidative damage that is found in Alzheimer's disease, and it is important that this damage directly correlates with the presence of amyloid-beta deposits. The significance of these studies is twofold. First, they provide evidence that amyloid-beta and oxidative damage are inextricably linked in vivo. Second, they support the use of transgenic animals for the development of antioxidant therapeutic strategies.

Cerebrovascular muscle atrophy is a feature of Alzheimer's disease

We examined vascular amyloid-beta deposition and other abnormalities in the posterior cerebral artery of consecutive cases of Alzheimer's disease (AD) compared to controls. Smooth muscle atrophy was a consistent feature in the cases of AD examined (p<0.01) and was surprisingly independent of adjacent amyloid-beta deposition. These findings suggest that vascular abnormalities are a consistent feature in AD and may be an important contributor to the pathogenesis and complications of AD.

Abnormal localization of iron regulatory protein in Alzheimer's disease

A role for altered iron metabolism in the pathogenesis of Alzheimer's disease has been suggested by several reports associating the cardinal neuropathologic lesions with markers of free radical-induced damage and redox-active iron. We hypothesized that the abnormal distribution of iron in Alzheimer brain might result from alterations in iron regulatory proteins (IRP) such as IRP-1 and IRP-2, the main control elements of cellular iron homeostasis. Here, we report that while IRP-1 is present at similar levels in both Alzheimer and control brain tissue, IRP-2 shows striking differences and is associated with intraneuronal lesions, including neurofibrillary tangles, senile plaque neurites and neuropil threads. Since IRP-2 colocalizes with redox-active iron, our results suggest that alterations in IRP-2 might be directly linked to impaired iron homeostasis in Alzheimer's disease.

Quantitative solubilization and analysis of insoluble paired helical filaments from Alzheimer disease

In this study, we evaluate the ability of several solvents to solubilize insoluble paired helical filaments (PHF) of Alzheimer disease. Specifically, we use protein extraction and reduction in the volume of insoluble material as quantitative assays to establish solvents of PHF. Using sequential categories of protein solvent to analyze insoluble PHF, only alkali or exhaustive proteolysis are effective in completely solubilizing PHF, while a variety of denaturants are ineffective. Alkali does not affect the phosphorylation state of PHF and complete dephosphorylation of PHF with hydrofluoric acid does not affect PHF solubility. These findings suggest that the 'hyperphosphorylation' of PHF proteins is not responsible for PHF insolubility. However the in vitro glycation of tau generates PHF that are insoluble in SDS and soluble in alkali. These findings suggest that protein crosslinks, including advanced glycation endproduct-derived crosslinks which were recently described in Alzheimer disease, play a major role in effecting PHF insolubility in vivo.

Artifactual strain-specific signs of incipient brain amyloidosis in APP transgenic mice

In an attempt to generate transgenic mice modeling Alzheimer-type amyloidogenesis, the COOH-terminal 103 residue human APP segment was expressed in brain regions known to be vulnerable in AD. Transfected cells overexpressing this transgene were previously shown to develop intracytoplasmic inclusions that were immunoreactive with antibodies to the APP COOH-terminus. Transgenic C57B6/SJL mice produced transgene-coded mRNA in their brains at levels up to sixfold above endogenous APP, most abundantly within cortical and hippocampal pyramidal neurons. Immunocytochemistry with anti-A beta antibodies revealed occasional structures that resembled diffuse amyloid, but which could not be detected on serial sections. Immunolabeling with antibodies to APP regions NH2-terminal to the transgene-coded domain revealed elevated immunoreactivity within perikarya and neurites in regions expressing the highest transgene and endogenous APP mRNA levels, similar to observations previously reported within vulnerable neurons in AD brain. However, subsequent breeding revealed that this phenotype segregated with the B6/SJL background rather than the transgene, thus emphasizing the importance of genetic background to observations of putative AD-type pathology in transgenic animals.

Extracellular neurofibrillary tangles reflect neuronal loss and provide further evidence of extensive protein cross-linking in Alzheimer disease

In this report we quantitatively assess the numbers of intracellular and extracellular neurofibrillary tangles (NFT) in the brains of a series of individuals with Alzheimer's disease and of controls and correlate these with neuronal loss. Our data indicate that in some cases, NFT are not removed from the brain throughout the disease process. This finding, together with our previous demonstration of carbonyl-related modifications in NFT, provides additional evidence that the protein constituents of NFT are resistant to proteolytic removal, possibly as a result of extensive cross-links. Additionally, correlation between the number of NFT and neuronal loss indicates that there are at least two distinct mechanisms responsible for neuronal death in Alzheimer's disease that are directly and indirectly related to the presence of neurofibrillary pathology.

Tau protein directly interacts with the amyloid beta-protein precursor: implications for Alzheimer's disease

The simultaneous presence of intracellular neurofibrillary tangles (NFT) and extracellular senile plaques in Alzheimer's disease (AD) suggests that the two lesions could be synergistically interrelated. However, although the main protein components of NFT and senile plaques, tau (tau) and amyloid beta-protein, respectively, are well characterized, the molecular mechanisms responsible for their deposition in lesions are unknown. We demonstrate, using four independent techniques, that tau directly interacts with a conformation-dependent domain of the amyloid beta-protein precursor (beta PP) encompassing residues beta PP714-723. The putative tau-binding domain includes beta PP717 mutation sites that are associated with familial forms of AD. Our findings strongly suggest that NFT and senile plaques, often thought of as independent structures, may play a role in each other's formation during the pathogenesis of AD.

Apolipoprotein E interaction with the neurofibrillary tangles and senile plaques in Alzheimer disease: implications for disease pathogenesis

Apolipoprotein E (ApoE) genotype is a significant risk factor for the development of Alzheimer disease (AD) and the ApoE protein is associated with senile plaques (SP) and neurofibrillary tangles (NFT), the pathological lesions of AD. Despite this data, the relevance of ApoE to the disease pathogenesis is unknown. In this study we sought to understand the role that ApoE protein could play in the pathogenesis of AD. Using an in situ binding technique, we showed that ApoE bound avidly to SP and NFT in diseased brain. Molecular characterization of ApoE binding suggested that binding to NFT was mediated by tau, the main protein component of NFT, and that ApoE binding to SP was mediated by amyloid-beta, the main protein component of SP. There was no significant difference in binding or binding characteristics between the different ApoE isoforms, ApoE3 and ApoE4. These findings suggest that the interaction of ApoE with tau and amyloid-beta proteins in AD could play a important role in the formation of NFT and SP, respectively, contributing to the pathogenesis of AD.

Immunocytochemical evidence that the beta-protein precursor is an integral component of neurofibrillary tangles of Alzheimer's disease

Amyloid beta (A beta) immunoreactivity has been demonstrated in all extracellular neurofibrillary tangles (E-NFT) and most intraneuronal neurofibrillary tangles (I-NFT). We undertook this immunocytochemical study to understand the relationship between A beta immunoreactivity localized in NFT and beta-protein precursor (beta PP). We found epitopes of amino-, mid-, and carboxyl-terminal domains of beta PP in I-NFT and the majority of E-NFT. NFT retained beta PP after ionic detergent extraction, demonstrating that beta PP is an integral component of NFT. Finding beta PP in regions of A beta immunoreactivity raises the possibility that beta PP or its fragments associate with amyloid, and that the stability of A beta is responsible for its dominance in amyloid deposits.

Degeneration of vascular muscle cells in cerebral amyloid angiopathy of Alzheimer disease

In cerebral amyloid angiopathy, the amyloid-beta (A beta) deposits lie primarily in the tunica media suggesting that smooth muscle cells play an important role in A beta deposition. To define this role, we conducted an immunocytochemical study of brain tissue from cases of Alzheimer disease with extensive cerebral amyloid angiopathy and cerebral hemorrhage. Antibodies specific to recombinant beta protein precursor (beta PP) and synthetic peptides homologous to various beta PP sequences from residue 18 to 689 of beta PP695 were used. Antibodies to actin, tropomyosin, alpha-actinin or desmin were used to label muscle cells. Antibodies to A beta sequences intensely recognized the extracellular amyloid deposit. Antibodies raised against beta PP sequences other than the A beta domain recognized smooth muscle cells. beta PP-immunoreactivity was reduced in regions of A beta deposits, since no muscle cells were recognized by cytoskeletal markers or observed ultrastructurally. In order to assess why A beta is deposited in the tunica media, we used biotin-labelled beta PP to determine if beta PP can be locally retained. We found beta PP bound to the tunica media of vessels but not other brain elements. These findings suggest A beta in blood vessels derives from degenerating beta PP-containing smooth muscle cells.

Basic fibroblast growth factor binds to filamentous inclusions of neurodegenerative diseases

The extracellular matrix protein heparin sulfate proteoglycans (HSPG) has been found in the neurofibrillary pathology of Alzheimer disease. This study was performed to determine if similar proteoglycans might be present in the fibrillary inclusions of other neurodegenerative diseases. Basic fibroblast growth factor (bFGF) binding to heparinase sensitive sites was used as an assay for HSPGs. We found that the inclusions of Pick and Parkinson diseases as well as progressive supranuclear palsy contained heparinase sensitive bFGF binding sites while the inclusions of diffuse Lewy body disease lacked bFGF binding sites. These findings indicate that HSPG's interactions and possible role in the formation of intraneuronal inclusions are not limited to Alzheimer disease.

Beta protein immunoreactivity is found in the majority of neurofibrillary tangles of Alzheimer's disease

The presence of dystrophic neurites in most extracellular neurofibrillary tangles (E-NFT) suggests a factor promoting neurite growth in E-NFT. Although the beta-protein detected in E-NFT may fill that role, reports that only 2-10% of E-NFT contain beta-protein whereas 80-100% contain dystrophic neurites suggested that beta-protein does not play an important role. In this study, the authors used two antisera and one monoclonal antibody to beta-protein to establish the effects of tissue preparation and formic acid enhancement on the detection of beta-protein in E-NFT. We found that beta-protein epitopes in E-NFT are sensitive to formaldehyde fixation and are best enhanced by 50% formic acid, whereas beta-protein in senile plaques is best enhanced at higher formic acid concentrations. After treatment with 50% formic acid, beta-protein was found in all E-NFT. Interestingly, after treatment with 10% formic acid, half of intraneuronal-NFT (I-NFT) also contained beta-protein immunoreactivity. The finding that beta-protein immunoreactivity in senile plaques, E-NFT and I-NFT is increased at different formic acid concentrations suggests that beta-protein in each location is in a different conformation. In contrast, no beta-protein immunoreactivity could be found in E-NFT of the brain stem, an area in which dystrophic neurites do not infiltrate E-NFT. These findings indicate a correlation between neuritic infiltration and presence of beta-protein in E-NFT and suggests the two are linked in Alzheimer's disease for E-NFT as well as senile plaques.

Association of heparan sulfate proteoglycan with the neurofibrillary tangles of Alzheimer's disease

The major intracytoplasmic lesion of Alzheimer's disease is the neurofibrillary tangle (NFT), which is primarily composed of paired helical filaments (PHFs). The mechanism responsible for the formation of PHFs, as well as their insolubility and apparent heterogeneity, is unknown. We found that basic fibroblast growth factor (bFGF) binds to heparinase-sensitive sites in NFTs. bFGF binding is due to a heparan sulfate proteoglycan (HSPG) immunocytochemically identified in NFTs. In the presence of polycations (e.g., Ca2+), HSPG will bind to free carboxyl groups in NFT proteins. HSPG binding may play a role in transforming normal soluble proteins into insoluble PHFs.

Dystrophic neurites infiltrate extracellular neurofibrillary tangles in Alzheimer disease

The neurotrophic activity of beta-amyloid protein (beta-AP) has been suggested to be responsible for the dystrophic neurites that surround beta-AP deposits in senile plaques of Alzheimer disease. The recent finding that neurofibrillary tangles (NFT) that remain as remnants in the extracellular space (E-NFT) after the death of the neuron contain beta-AP, suggested that dystrophic neurites might also be associated with E-NFT. In this study, we use a probe for E-NFT, basic fibroblast growth factor (bFGF)-binding to show that E-NFT do contain dystrophic neurites. Since these neurites contain the amyloid precursor protein whose cleavage can lead to beta-AP, they may also play a role in further beta-AP deposition in the E-NFT.

Basic fibroblast growth factor binding is a marker for extracellular neurofibrillary tangles in Alzheimer disease

Neurofibrillary tangles (NFT) are abnormal filamentous inclusions that develop in neurons in Alzheimer disease and other disorders. When neurons die, the neurofibrillary tangles that persist in the extracellular space show ultrastructural and antigenic changes. Both intra- and extracellular NFT have recently been shown to contain heparan sulfate proteoglycans (HSPGs). HSPGs are also present in other amyloid deposits in the brain and in systemic amyloidoses. Basic fibroblast growth factor (bFGF) is a heparin binding growth factor which is involved in angiogenesis and also has neurite promoting activity. We now report that bFGF binds avidly to extracellular NFT. Alz-50, a monoclonal antibody (MAb) to an abnormal form of tau and bFGF binding label mutually exclusive subpopulations of neurofibrillary tangles. bFGF binding is abolished by heparinase or heparitinase treatment and therefore is most likely based on the presence of HSPG. Binding of bFGF is a specific and sensitive morphological method to distinguish intra- from extracellular NFT. As intracellular NFT, which also contain HSPGs, are not labeled by bFGF binding, this finding also suggests that HSPGs are modified when the NFT become extracellular.

Soluble derivatives of the beta amyloid protein precursor of Alzheimer's disease are labeled by antisera to the beta amyloid protein

The amyloid deposited in Alzheimer's disease (AD) is composed primarily of a 39-42 residue polypeptide (beta AP) that is derived from a larger beta amyloid protein precursor (beta APP). In previous studies, we and others identified full-length, membrane-associated forms of the beta APP and showed that these forms are processed into soluble derivatives that lack the carboxyl-terminus of the full-length forms. In this report, we demonstrate that the soluble approximately 125 and approximately 105 kDa forms of the beta APP found in human cerebrospinal fluid are specifically labeled by several different antisera to the beta AP. This finding indicates that both soluble derivatives contain all or part of the beta AP sequence, and it suggests that one or both of these forms may be the immediate precursor of the amyloid deposited in AD.