Immunohistological study on brains of Alzheimer's disease using antibodies to fetal antigens, C-series gangliosides and microtubule-associated protein 5

Alzheimer's disease and related tauopathies: disorders of disrupted neuronal identity

Postmitotic neurons require persistently active controls to maintain terminal differentiation. Unlike dividing cells, aberrant cell cycle activation in mature neurons causes apoptosis rather than transformation. In Alzheimer's disease (AD) and related tauopathies, evidence suggests that pathogenic forms of tau drive neurodegeneration via neuronal cell cycle re-entry. Multiple interconnected mechanisms linking tau to cell cycle activation have been identified, including, but not limited to, tau-induced overstabilization of the actin cytoskeleton, consequent changes to nuclear architecture, and disruption of heterochromatin-mediated gene silencing. Cancer- and development-associated pathways are upregulated in human and cellular models of tauopathy, and many tau-induced cellular phenotypes are also present in various cancers and progenitor/stem cells. In this review, I delve into mechanistic parallels between tauopathies, cancer, and development, and highlight the role of tau in cancer and in the developing brain. Based on these studies, I put forth a model by which pathogenic forms of tau disrupt the program that maintains terminal neuronal differentiation, driving cell cycle re-entry and consequent neuronal death. This framework presents tauopathies as conditions involving the profound toxic disruption of neuronal identity.

Gangliosides as Biomarkers of Human Brain Diseases: Trends in Discovery and Characterization by High-Performance Mass Spectrometry

Gangliosides are effective biochemical markers of brain pathologies, being also in the focus of research as potential therapeutic targets. Accurate brain ganglioside mapping is an essential requirement for correlating the specificity of their composition with a certain pathological state and establishing a well-defined set of biomarkers. Among all bioanalytical methods conceived for this purpose, mass spectrometry (MS) has developed into one of the most valuable, due to the wealth and consistency of structural information provided. In this context, the present article reviews the achievements of MS in discovery and structural analysis of gangliosides associated with severe brain pathologies. The first part is dedicated to the contributions of MS in the assessment of ganglioside composition and role in the specific neurodegenerative disorders: Alzheimer’s and Parkinson’s diseases. A large subsequent section is devoted to cephalic disorders (CD), with an emphasis on the MS of gangliosides in anencephaly, the most common and severe disease in the CD spectrum. The last part is focused on the major accomplishments of MS-based methods in the discovery of ganglioside species, which are associated with primary and secondary brain tumors and may either facilitate an early diagnosis or represent target molecules for immunotherapy oriented against brain cancers.

Tau Protein Interaction Partners and Their Roles in Alzheimer's Disease and Other Tauopathies

Tau protein plays a critical role in the assembly, stabilization, and modulation of microtubules, which are important for the normal function of neurons and the brain. In diseased conditions, several pathological modifications of tau protein manifest. These changes lead to tau protein aggregation and the formation of paired helical filaments (PHF) and neurofibrillary tangles (NFT), which are common hallmarks of Alzheimer's disease and other tauopathies. The accumulation of PHFs and NFTs results in impairment of physiological functions, apoptosis, and neuronal loss, which is reflected as cognitive impairment, and in the late stages of the disease, leads to death. The causes of this pathological transformation of tau protein haven't been fully understood yet. In both physiological and pathological conditions, tau interacts with several proteins which maintain their proper function or can participate in their pathological modifications. Interaction partners of tau protein and associated molecular pathways can either initiate and drive the tau pathology or can act neuroprotective, by reducing pathological tau proteins or inflammation. In this review, we focus on the tau as a multifunctional protein and its known interacting partners active in regulations of different processes and the roles of these proteins in Alzheimer's disease and tauopathies.

Brain gangliosides of a transgenic mouse model of Alzheimer's disease with deficiency in GD3-synthase: expression of elevated levels of a cholinergic-specific ganglioside, GT1aα

In order to examine the potential involvement of gangliosides in AD (Alzheimer's disease), we compared the ganglioside compositions of the brains of a double-transgenic (Tg) mouse model [APP (amyloid precursor protein)/PSEN1 (presenilin)] of AD and a triple mutant mouse model with an additional deletion of the GD3S (GD3-synthase) gene (APP/PSEN1/GD3S(-/-)). These animals were chosen since it was previously reported that APP/PSEN1/GD3S(-/-) triple-mutant mice performed as well as WT (wild-type) control and GD3S(-/-) mice on a number of reference memory tasks. Cholinergic neuron-specific gangliosides, such as GT1aα and GQ1bα, were elevated in the brains of double-Tg mice (APP/PSEN1), as compared with those of WT mice. Remarkably, in the triple mutant mouse brains (APP/PSEN1/GD3S(-/-)), the concentration of GT1aα was elevated and as expected there was no expression of GQ1bα. On the other hand, the level of c-series gangliosides, including GT3, was significantly reduced in the double-Tg mouse brain as compared with the WT. Thus, the disruption of the gene of a specific ganglioside-synthase, GD3S, altered the expression of cholinergic neuron-specific gangliosides. Our data thus suggest the intriguing possibility that the elevated cholinergic-specific ganglioside, GT1aα, in the triple mutant mouse brains (APP/PSEN1/GD3S(-/-)) may contribute to the memory retention in these mice.

The pathological roles of ganglioside metabolism in Alzheimer's disease: effects of gangliosides on neurogenesis

Conversion of the soluble, nontoxic amyloid β-protein (Aβ) into an aggregated, toxic form rich in β-sheets is a key step in the onset of Alzheimer's disease (AD). It has been suggested that Aβ induces changes in neuronal membrane fluidity as a result of its interactions with membrane components such as cholesterol, phospholipids, and gangliosides. Gangliosides are known to bind Aβ. A complex of GM1 and Aβ, termed “GAβ”, has been identified in AD brains. Abnormal ganglioside metabolism also may occur in AD brains. We have reported an increase of Chol-1α antigens, GQ1bα and GT1aα, in the brain of transgenic mouse AD model. GQ1bα and GT1aα exhibit high affinities to Aβs. The presence of Chol-1α gangliosides represents evidence for genesis of cholinergic neurons in AD brains. We evaluated the effects of GM1 and Aβ1–40 on mouse neuroepithelial cells. Treatment of these cells simultaneously with GM1 and Aβ1–40 caused a significant reduction of cell number, suggesting that Aβ1–40 and GM1 cooperatively exert a cytotoxic effect on neuroepithelial cells. An understanding of the mechanism on the interaction of GM1 and Aβs in AD may contribute to the development of new neuroregenerative therapies for this disorder.

Roles for dysfunctional sphingolipid metabolism in Alzheimer's disease neuropathogenesis

Sphingolipids in the membranes of neurons play important roles in signal transduction, either by modulating the localization and activation of membrane-associated receptors or by acting as precursors of bioactive lipid mediators. Activation of cytokine and neurotrophic factor receptors coupled to sphingomyelinases results in the generation of ceramides and gangliosides, which in turn, modify the structural and functional plasticity of neurons. In aging and neurodegenerative conditions such as Alzheimer's disease (AD), there are increased membrane-associated oxidative stress and excessive production and accumulation of ceramides. Studies of brain tissue samples from human subjects, and of experimental models of the diseases, suggest that perturbed sphingomyelin metabolism is a pivotal event in the dysfunction and degeneration of neurons that occurs in AD and HIV dementia. Dietary and pharmacological interventions that target sphingolipid metabolism should be pursued for the prevention and treatment of neurodegenerative disorders.

Role of ganglioside metabolism in the pathogenesis of Alzheimer's disease--a review

Gangliosides are expressed in the outer leaflet of the plasma membrane of the cells of all vertebrates and are particularly abundant in the nervous system. Ganglioside metabolism is closely associated with the pathology of Alzheimer's disease (AD). AD, the most common form of dementia, is a progressive degenerative disease of the brain characterized clinically by progressive loss of memory and cognitive function and eventually death. Neuropathologically, AD is characterized by amyloid deposits or "senile plaques," which consist mainly of aggregated variants of amyloid beta-protein (Abeta). Abeta undergoes a conformational transition from random coil to ordered structure rich in beta-sheets, especially after addition of lipid vesicles containing GM1 ganglioside. In AD brain, a complex of GM1 and Abeta, termed "GAbeta," has been found to accumulate. In recent years, Abeta and GM1 have been identified in microdomains or lipid rafts. The functional roles of these microdomains in cellular processes are now beginning to unfold. Several articles also have documented the involvement of these microdomains in the pathogenesis of certain neurodegenerative diseases, such as AD. A pivotal neuroprotective role of gangliosides has been reported in in vivo and in vitro models of neuronal injury, Parkinsonism, and related diseases. Here we describe the possible involvement of gangliosides in the development of AD and the therapeutic potentials of gangliosides in this disorder.

Microtubule-associated protein MAP1A, MAP1B, and MAP2 proteolysis during soluble amyloid beta-peptide-induced neuronal apoptosis. Synergistic involvement of calpain and caspase-3

A growing body of evidence supports the notion that soluble oligomeric forms of the amyloid beta-peptide (Abeta) may be the proximate effectors of neuronal injuries and death in the early stages of Alzheimer disease. However, the molecular mechanisms associated with neuronal apoptosis induced by soluble Abeta remain to be elucidated. We recently demonstrated the involvement of an early reactive oxygen species-dependent perturbation of the microtubule network (Sponne, I., Fifre, A., Drouet, B., Klein, C., Koziel, V., Pincon-Raymond, M., Olivier, J.-L., Chambaz, J., and Pillot, T. (2003) J. Biol. Chem. 278, 3437-3445). Because microtubule-associated proteins (MAPs) are responsible for the polymerization, stabilization, and dynamics of the microtubule network, we investigated whether MAPs might represent the intracellular targets that would enable us to explain the microtubule perturbation involved in soluble Abeta-mediated neuronal apoptosis. The data presented here show that soluble Abeta oligomers induce a time-dependent degradation of MAP1A, MAP1B, and MAP2 involving a perturbation of Ca2+ homeostasis with subsequent calpain activation that, on its own, is sufficient to induce the proteolysis of isoforms MAP2a, MAP2b, and MAP2c. In contrast, MAP1A and MAP1B sequential proteolysis results from the Abeta-mediated activation of caspase-3 and calpain. The prevention of MAP1A, MAP1B, and MAP2 proteolysis by antioxidants highlights the early reactive oxygen species generation in the perturbation of the microtubule network induced by soluble Abeta. These data clearly demonstrate the impact of cytoskeletal perturbations on soluble Abeta-mediated cell death and support the notion of microtubule-stabilizing agents as effective Alzheimer disease drugs.

Overexpression of full-length but not N-terminal truncated isoform of microtubule-associated protein (MAP) 1B accelerates apoptosis of cultured cortical neurons

beta-amyloid (Abeta) is presumed to play a pathogenic role in Alzheimer's disease (AD). However, there is an imperfect correlation between Abeta deposition and neuronal loss or dementia. To clarify neuronal responses to Abeta, Abeta-induced gene expression in cultured cortical neurons was analyzed by differential display followed by Northern blotting. Here we report that nonaggregated or aggregated Abeta induced microtubule-associated protein 1B (MAP1B) mRNA, especially the alternative transcript containing exon 3U, before disruption of the cell membrane by Abeta. An alternative transcript containing exon 3U is translated into an N-terminal truncated shorter isoform of MAP1B. Transfection experiments reveal that overexpression of this isoform does not accelerate neurite outgrowth or apoptosis of cortical neurons. In contrast, overexpression of MAP1B fragments containing the N-terminal 126 amino acids promoted neurite outgrowth and neuronal apoptosis. These results suggest that Abeta does not induce deleterious full-length MAP1B directly, but overexpression of full-length MAP1B might act as an effector of cell death in neurodegenerative disorders related to cytoskeletal abnormalities.

Neuropeptides interact with glycolipid receptors: a surface plasmon resonance study

Using Surface Plasmon Resonance (SPR) we investigated the interaction of seven neuropeptides with different characteristics and beta-amyloid (Abeta42) peptide, with membranes containing gangliosides. A wide range of affinities characterized the bindings (K(D) = 10(-3)- 10(-7) M), following the scheme: for GM1, Abeta42 > DYN > SP = GAL = SOM = BRD > OXY = ENK; for GD1a, Abeta42 = DYN = GAL > SP = SOM = BRD = OXY > ENK and for GT1b, Abeta42 > DYN > SP = GAL > SOM = BRD = OXY > ENK. The ganglioside sugar moiety, specifically the sialic acid, had an important role in the interactions. In general the affinities were higher with polysialo, than with monosialo gangliosides. The sensorgrams describing the interactions of Abeta42 and SP with gangliosides differed from the interactions of the other studied peptides. Ca(2+) promoted changes in peptide-glycolipid interactions.

Alzheimer's disease as a disorder of mechanisms underlying structural brain self-organization

Mental function has as its cerebral basis a specific dynamic structure. In particular, cortical and limbic areas involved in "higher brain functions" such as learning, memory, perception, self-awareness and consciousness continuously need to be self-adjusted even after development is completed. By this lifelong self-optimization process, the cognitive, behavioural and emotional reactivity of an individual is stepwise remodelled to meet the environmental demands. While the presence of rigid synaptic connections ensures the stability of the principal characteristics of function, the variable configuration of the flexible synaptic connections determines the unique, non-repeatable character of an experienced mental act. With the increasing need during evolution to organize brain structures of increasing complexity, this process of selective dynamic stabilization and destabilization of synaptic connections becomes more and more important. These mechanisms of structural stabilization and labilization underlying a lifelong synaptic remodelling according to experience, are accompanied, however, by increasing inherent possibilities of failure and may, thus, not only allow for the evolutionary acquisition of "higher brain function" but at the same time provide the basis for a variety of neuropsychiatric disorders. It is the objective of the present paper to outline the hypothesis that it might be the disturbance of structural brain self-organization which, based on both genetic and epigenetic information, constantly "creates" and "re-creates" the brain throughout life, that is the defect that underlies Alzheimer's disease (AD). This hypothesis is, in particular, based on the following lines of evidence. (1) AD is a synaptic disorder. (2) AD is associated with aberrant sprouting at both the presynaptic (axonal) and postsynaptic (dendritic) site. (3) The spatial and temporal distribution of AD pathology follows the pattern of structural neuroplasticity in adulthood, which is a developmental pattern. (4) AD pathology preferentially involves molecules critical for the regulation of modifications of synaptic connections, i.e. "morphoregulatory" molecules that are developmentally controlled, such as growth-inducing and growth-associated molecules, synaptic molecules, adhesion molecules, molecules involved in membrane turnover, cytoskeletal proteins, etc. (5) Life events that place an additional burden on the plastic capacity of the brain or that require a particularly high plastic capacity of the brain might trigger the onset of the disease or might stimulate a more rapid progression of the disease. In other words, they might increase the risk for AD in the sense that they determine when, not whether, one gets AD. (6) AD is associated with a reactivation of developmental programmes that are incompatible with a differentiated cellular background and, therefore, lead to neuronal death. From this hypothesis, it can be predicted that a therapeutic intervention into these pathogenetic mechanisms is a particular challenge as it potentially interferes with those mechanisms that at the same time provide the basis for "higher brain function".

Molecular insights into neurodevelopmental and neurodegenerative diseases

Magnetic resonance spectroscopy (MRS) is a non-invasive physical technique that is routinely used to determine the quantity and structure of organic molecules in solution. Technical advances that have expanded the usefulness of this technique include: (1) high resolution MRS to identify and quantify individual molecules present in complex mixtures of tissue extracts; (2) in vivo MRS techniques to non-invasively monitor metabolites in humans; (3) structure determination of proteins of moderate size; and (4) improved structure characterization of solids and liquid crystals, such as the detection of phase changes in membranes. The focus of this review is on the first two technical advances mentioned above. The strengths of MRS as a research tool to investigate molecular alterations in disease states include ease of sample preparation, minimum sample manipulation, avoidance of the preparation of derivatives, and the ability to analyze an unfractionated sample. The strengths of MRS in the clinic are its ability to measure neuronal metabolite levels non-invasively in humans and its potential for disease diagnosis, monitoring disease progression, and assessing the efficacy of experimental therapies.

GM1 inhibits amyloid beta-protein-induced cytokine release

The ganglioside GM1 is known to play a pivotal role in neuronal survival and/or regeneration. Recently it has been shown that GM1 binds tightly with membrane-bound amyloid beta protein (A beta) and prevents its conversion from a helical to a beta-sheet structure. To examine the potential physiological consequences of this binding, we studied the effect of GM1 on A beta-stimulated release of proinflammatory cytokines, such as interleukin (IL)-1beta, IL-6 and TNF-alpha, using the human monocytic cell line, THP-1, as a model system. Treatment of THP-1 cells with A beta 1-40 or A beta 25-35 resulted in an increased cytokine release from these cells. However, treatment of A beta-activated THP-1 cells with GM1 and several other complex gangliosides, but not hematosides and neutral glycosphingolipids such as asialo-GM1 (GA1), lactosylceramide, and globoside, significantly decreased the cytokine release. In contrast, this effect was not observed for lipopolysaccharide (LPS)-activated and thrombin-activated THP-1 cells, indicating that the ganglioside effect is specific for A beta-induced cytokine release. A direct interaction between GM1 and A beta was demonstrated using the surface plasmon resonance technique. We found that GM1 ganglioside exhibited higher affinity for A beta 1-40 than GA1, suggesting that the sialic acid moiety of GM1 is necessary for its interaction with A beta. We conclude that the inhibitory effect of GM1 on A beta-induced cytokine release may reflect pre-existing abnormalities in membrane transport at the stage of amyloid formation and that GM1 may induce conformational changes in A beta, resulting in diminished fibrillogenesis and prevention of the inflammatory response of neuronal cells in Alzheimer's disease.

C-series polysialogangliosides are expressed on stellate neurons of adult human cerebellum

Until now 'c-series' polysialogangliosides were known to exist in human brain only during development and in some pathological conditions like Alzheimer's disease. Using thin-layer chromatography (TLC) and immunostaining with Q211 antibody (TLC-overlay technique) we have analysed 'c-series' gangliosides in four human cerebella (age 20, 47, 52 and 54 years). Four distinct ganglioside bands, most probably corresponding to GT1c, GQ1c, GP1c and GH1c were found to exist in the analysed brains, which is convincing demonstration of the existence of 'c-series' gangliosides in normal adult human brain. Immunohistochemical analysis was performed to locate polysialogangliosides in the analysed tissue. Q211 antibody was found to bind specifically to a single subpopulation of neurons in the molecular layer of adult cerebellum. According to their position and morphology these cells correspond to stellate neurons.

Magnetic resonance spectroscopic changes in Alzheimer's disease

In vitro and in vivo 31P magnetic resonance (MR) spectroscopy studies of Alzheimer's disease (AD) brain have revealed alterations in membrane phospholipid metabolism and high-energy phosphate metabolism. Mildly demented AD patients compared with control subjects have increased levels of phosphomonoesters, decreased levels of phosphocreatine and probably adenosine diphosphate and an increased oxidative metabolic rate. As the dementia worsens, levels of phosphomonoesters decrease and levels of phosphocreatine and adenosine di-phosphate increase. The changes in oxidative metabolic rate suggest that the AD brain is under energetic stress. The phosphomonoester findings support our in vitro findings and implicate basic defects in membrane metabolism in AD brain. MR spectroscopy provides new diagnostic insights and a noninvasive method to follow the progression of the disease and the metabolic response to therapeutic interventions.

Synaptic plasticity is preserved in the temporal cortex of 20-month-old rats

The molecular mechanisms associated with age-related alterations in the plasticity of the cortical neurons in response to chemically-induced seizure are largely unknown. Administration of pentylenetetrazole (PTZ) (50 mg/kg body weight) to rats of various ages evoked tonic-clonic seizures. Using immunoblotting and in situ hybridization analysis we found that 72 h after the onset of seizure, the mRNA for microtubule-associated protein 1B (MAP1B), a marker of synaptic plasticity, was increased in the cortex of 3-month-old rats. The levels of MAP1B mRNA in the cortex of 3-month-old rats returned to control levels by 10 days after PTZ administration. The levels of MAP1B mRNA in the hippocampus and cortex of 20 months at later times (10 days) and returned nearly to basal levels by 20 days following PTZ treatment. Immunohistochemical analysis revealed that MAP1B-like immunoreactivity was confined to layer II and neuronal processes extending into layer I. In contrast, the staining of MAP1B in the temporal cortex of 20-month-old animals was restricted to neuronal cell bodies of layer II. Since synaptic plasticity is associated mainly with neuronal processes we conclude that synaptic plasticity is reduced in the temporal cortex of 20-month-old rats. Remarkably, the induction of MAP1B in neuronal extensions was not impaired in the temporal cortex of older animals following intense neuronal activity. However, the aged rat brain responded more slowly to chemically-induced seizure although the levels of MAP1B induction are not decreased as compared to the levels expressed by 3-month-old rats.

Embryonic genes expressed in Alzheimer's disease brains

Alzheimer's disease (AD)-specific or characteristic gene expression was explored by the identification of cDNA clones by means of differential screening for embryonic brain cDNA library with 32P-labeled cDNA probes prepared from mRNA of AD and normal human brains. To isolate neuronal genes in degenerating neurons, we used rat embryonic cDNA library at stage day 15 when glial cells developed poorly in the brain. Seventeen embryonic genes were identified as embryonic alpha-tubulin, embryonic beta-tubulin, hnRNP, protein L-isoaspartyl methyltransferase (PIMT), ferritin heavy chain, type IV collagen, actin-binding protein cofilin, profilin and nine novel sequences designated as A1-9. We characterized these genes by Northern blot analysis, RNase protection assay and immunohistochemical studies, showing that PIMT and a novel gene designated as A5 showed the transcriptional up-regulation in AD brains. In addition, the immunohistochemical studies showed PIMT, type IV collagen, and cofilin were associated with neurofibrillary tangles in degenerating neurons, brain vessels in affected regions, and synaptosomal structures in AD brains, respectively. The catalogue presented here also showed the involvement of cytoskeletal proteins, cytoskeleton-associated proteins, and an iron-storage protein, suggesting the presence of regenerating activity and the abnormal metabolisms in affected neurons of AD brains.

Alzheimer neurofibrillary lesions: molecular nature and potential roles of different components

Neurofibrillary lesions found in Alzheimer disease (AD) are known to react with antibodies raised against different molecules. At least 20 components have been detected in neurofibrillary tangles. These components can be roughly categorized into five groups, which include structural proteins, kinases and other cytosolic enzymes, stress-related molecules, amyloid and amyloid binding proteins, and others. Among them, an abnormal form of microtubule associated protein tau, PHF-tau, is a major component of Alzheimer NFT. Kinases associated with NFT, especially those belonging to the family of proline-directed Ser/Thr kinases, are considered to be important for PHF-tau hyperphosphorylation. A potentially significant kinase is a Cdc2-related kinase, which is associated tightly with paired helical filaments, has a molecular weight of 33kDa and is different from other known Cdc2-related kinases. The possibility that some of the NFT-associated elements may play an active role in the pathogenesis of Alzheimer's disease was supported by recent studies, in which advanced glycated products and markers of oxidant stress were located in NFT. In addition, PHF-tau was found to be glycated, and in vitro glycated tau was capable of inducing oxidant stress. Further characterization of different components of NFT by biochemical and other approaches will be important for understanding the mechanisms involved in the supramolecular aggregation of PHF within NFT.

Brain-specific expression of human microtubule-associated protein 1A (MAP1A) gene and its assignment to human chromosome 15

We isolated several cDNA fragments by immunoscreening a human cDNA library with our monoclonal antibody, BG5, that showed neuronal staining on human and rat brain sections. A 1,570 bp sequence of one cDNA fragment showed 75% homology to the rat microtubule-associated protein 1A (MAP1A) cDNA sequence. This rat MAP1A-like human cDNA was highly specific to the adult brain among human tissues tested, and was expressed in various brain regions including white matter. The size of the mRNA detected with Northern blot analysis in adult human brain equaled 10 kb. The gene of this cDNA was assigned to human chromosome 15 that has a syntenic region of mouse chromosome 2, where the mouse MAP1A gene has been assigned. These results indicate that this rat MAP1A-like cDNA is a portion of human MAP1A and is a conserved molecular species among humans and rodents.

Microtubule-associated protein MAP1B showing a fetal phosphorylation pattern is present in sites of neurofibrillary degeneration in brains of Alzheimer's disease patients

Alzheimer's disease results in the appearance of cytoskeletal disorders yielding pathological structures such a neurofibrillary tangles or dystrophic neurites. It has been previously described that the microtubule-associated protein, tau, modified by phosphorylation in serines adjacent to prolines, is a major component of these structures. Here, we show that another microtubule associated protein, MAP1B, aberrantly phosphorylated by a proline-dependent protein kinase, is a component of these previously mentioned structures. Thus, a possible common phosphorylation of axonal MAPs such as tau or MAP1B may correlate with their association with those aberrant cytoskeletal structures present in AD.

Ultrastructural localization of butyrylcholinesterase on neurofibrillary degeneration sites in the brains of aged and Alzheimer's disease patients

Butyrylcholinesterase histochemical techniques were applied to vibratome sections of several cortical areas from the brains of non-demented aged and of Alzheimer's disease patients. At the light microscope level, all the senile plaque types and all the structures with neurofibrillary degeneration showed butyrylcholinesterase reaction product, whereas nearby neuronal perikarya and axons on the same slides remained unstained. Areas containing stained elements were selected, re-sectioned, and finally observed under the electron microscope. Focusing on the sites of neurofibrillary degeneration, butyrylcholinesterase reaction product was found in both intra- and extracellular neurofibrillary tangles, in neurites associated with plaques, and in neuropil threads that were either axons or dendrites. This reaction product was exclusively located over filament bundles, and sometimes covered them so completely that they could not be identified. When the filaments were only partially covered, it was possible to identify them as either paired helical filaments or straight filaments. Occasionally, neurofibrillary tangles, neuropil threads and plaque-associated neurites, all of them containing either paired helical filaments or straight filaments, were found to be completely free of butyrylcholinesterase reaction product. The origin and possible role of butyrylcholinesterase, which is ultrastructurally localized over elements presenting neurofibrillary degeneration, is discussed.

Immunohistochemical expression of microtubule-associated protein 5 (MAP5) in glial cells in multiple system atrophy

An immunohistochemical study focusing on glial cells was performed using monoclonal antibodies against microtubule-associated proteins (MAP1, MAP2 and MAP5), transferrin, leukocyte common antigen (LCA) and glial fibrillary acidic protein (GFAP) in 5 cases of multiple system atrophy (MSA) exhibiting olivopontocerebellar atrophy and striatonigral degeneration. An antibody to MAP5, a fetal antigen in developing brain, was strongly demonstrated in the glial cytoplasmic inclusions (GCIs) which have recently drawn a great deal of attention and were observed in all 5 cases of MSA. Moreover, MAP5-positive glial cells (MAP5-Gs) were present in significantly higher number than in the controls in various regions where GCIs were found, predominantly in putamen, substantia nigra, cerebellar white matter and internal capsule. LCA and transferrin, markers of microglia and oligodendroglia, respectively, were immunohistochemically detected in some MAP5-Gs. GFAP, on the other hand, was not expressed in MAP5-Gs at all. These findings suggest that MAP5-Gs consist of reactive microglia and oligodendroglia. Our study is the first to demonstrate immunohistochemical detection of MAP5 in glial pathological changes in MSA.

Alzheimer disease paired helical filament core structures contain glycolipid

The core structures of sodium dodecyl sulfate extracted, pronase digested paired helical filaments of Alzheimer disease were solubilized by heating in dimethyl sulfoxide. Electron microscopy revealed that after heating in dimethyl sulfoxide, intact paired helical filaments were no longer present in the dimethyl sulfoxide soluble fractions or in the insoluble lipofuscin-containing fractions. Enzyme-linked immunosorbent assays of the various fractions with the monospecific antibody A128 to paired helical filaments demonstrated 96% of the immunoreactivity to be in the dimethyl sulfoxide soluble fraction, and only 4% in the dimethyl sulfoxide insoluble fractions. Lyophilization of the dimethyl sulfoxide soluble supernatant and resuspension in water failed to reassociate the paired helical filaments, but did result in an insoluble precipitate. Analysis of the dimethyl sulfoxide solubilized paired helical filament fraction by nuclear magnetic resonance revealed it to be composed of glycolipid in a form that was distinct from similar fractions isolated from normal aged control brains. The aggregation of an altered glycolipid to form paired helical filaments in Alzheimer disease could explain their insolubility.