Neuritic Senile Plaques Research Articles

Alzheimer's Disease Neuropathological Change in Aged Non-Primate Mammals.

Human brain aging is characterized by the production and deposition of β-amyloid (Aβ) in the form of senile plaques and cerebral amyloid angiopathy and the intracellular accumulation of hyper-phosphorylated tau (Hp-tau) to form neurofibrillary tangles (NFTs) and dystrophic neurites of senile plaques. The process progresses for years and eventually manifests as cognitive impairment and dementia in a subgroup of aged individuals. Aβ is produced and deposited first in the neocortex in most aged mammals, including humans; it is usually not accompanied by altered behavior and cognitive impairment. Hp-tau is less frequent than Aβ pathology, and NFTs are rare in most mammals. In contrast, NFTs are familiar from middle age onward in humans; NFTs first appear in the paleocortex and selected brain stem nuclei. NFTs precede for decades or years Aβ deposition and correlate with dementia in about 5% of individuals at the age of 65 and 25% at the age of 85. Based on these comparative data, (a) Aβ deposition is the most common Alzheimer's disease neuropathological change (ADNC) in the brain of aged mammals; (b) Hp-tau is less common, and NFTs are rare in most aged mammals; however, NFTs are the principal cytoskeletal pathology in aged humans; (c) NFT in aged humans starts in selected nuclei of the brain stem and paleocortical brain regions progressing to the most parts of the neocortex and other regions of the telencephalon; (d) human brain aging is unique among mammalian species due to the early appearance and dramatic progression of NFTs from middle age onward, matching with cognitive impairment and dementia in advanced cases; (e) neither mammalian nor human brain aging supports the concept of the amyloid cascade hypothesis.

Alzheimer Disease

Alzheimer's disease (AD) is typified by memory deficiencies that worsen with time, along with cognitive and behavioral abnormalities that eventually result in dementia. AD is one of the most difficult diseases to treat because of its prevalence, high cost of care, effects on patients and caregivers, and lack of mechanism-based therapies. The malfunction and loss of neurons in particular circuits and locations, especially in the populations of nerve cells supporting memory and cognition, causes the AD condition.The neuropathology of AD is characterized by intracellular and extracellular protein aggregation accumulations. In the neuronal perikarya and dystrophic neurites, abnormally phosphorylated tau forms paired helical filaments (PHFs) that combine to form neurofibrillary tangles (NFTs). The extracellular deposition of β-pleated assemblies of Aβ peptide, which result in widespread and neuritic senile plaques, is the second pathogenic hallmark.

Nanocarrier based drug delivery system – Future of Alzheimer disease

Alzheimer’s disease (AD) has risen to the top most cause of mortality in the world. Every twenty years, the illness rate doubles, affecting about one in every 10 households. AD is characterized by a gradual loss of neurons in the cerebral cortex, resulting in brain shrinkage. Senile neuritic plaques and neurofibrillary tangles become the disease’s primary characteristic. However, a continuous strategy is customized to cure AD effectively. However, as a result of difficulties in the medication delivery system induced by different barriers such as blood–brain barrier and cerebrospinal fluid has become the primary cause of therapeutic failure. Thus, to address these problems, nanotechnology is a potential technique for overcoming them. This study discusses the use of targeted delivery of medicament for the successful remedy and diagnosis of AD that utilizes nanocarriers as an alternative administration route, thus allowing the release of the drug into central nervous system.

Quantitative electroencephalographic evaluations of electrophysiological biomarkers and impaired functional networks of older adults diagnosed with dementia

AbstractBackgroundAlzheimer’s disease (AD) is a neurodegenerative disorder attributable to neurofibrillary tangles, senile neuritic plaques, and a reduction of neurons and synapses. Because the etiopathogenesis of AD is complex and its associated risk factors are not well understood, clinical interventions to effectively treat AD are being developed. Thus, interventional strategies to delay disease progression have been the focus of numerous pharmacologically oriented trials. Recognition of near‐infrared photobiomodulation as having disease modifying properties in the treatment of age‐related dementia has been reported by Paul Chazot PhD, Senior Lecturer in Neuropharmacology at Durham University. The utilization of electrophysiological biomarkers and dysregulated functional networks may allow for neuromodulation applications to curtail symptomatic progression and therefore non‐invasive prophylactic strategies.Methods19‐channel electroencephalographic (EEG) assessment was employed across all participants (n=96) to evaluate responsivity to intensive (twice daily), self‐administered, near‐infrared treatment (INIRT) using active or placebo devices that mimicked the photobiomodulation intervention. The EEG recordings were evaluated using a normative database and standardized weight low resonance tomography (swLORETA) analysis software. Participants were administered a comprehensive neuropsychiatric battery before, during and after 60 days to evaluate cognitive performance while undergoing the PBM intervention or sham condition. Specifically, the Alzheimer’s Disease Neuroimaging Initiative (ADNI), which includes 12 inventories such as the Mini Mental State Exam (MMSE), clock drawing test (CDT), auditory verbal learning test‐ immediate (A.V.L.T.‐1), WAIS‐R digit symbol substitution test, the auditory verbal learning test‐ delayed (A.V.L.T.‐2) were employed to evaluate working memory, word recall, visuospatial recall, comprehension, logical memory, and number recall cognitive domains.ResultsPreliminary results indicate subjects in the active PBM condition demonstrated significant improvements in cognitive functioning and activities of daily living and alterations in neural connectivity and phase lag (inter‐electrode signal transmission) in both theta (4‐7hz) and delta (.5‐4hz) frequency bands and a normalization of alpha (8‐12hz) amplitude.ConclusionsExposure to PBM interventions indicate subjects in the active PBM condition demonstrated significant alterations in neural connectivity and phase lag (inter‐electrode signal transmission) in both theta (4‐7hz) and delta (.5‐4hz) frequency bands and a normalization of alpha (8‐12hz) amplitude. Normalization of the EEG correlated with symptomatic remission of cognitive impairment, alertness, attention, and improved sleep architecture. Participants exposed to the placebo condition did not report symptomatic remission and continued to exemplify cognitive decline associated with the progression of this neurodegenerative disorder.

Amyloid Beta Immunoreactivity in the Retinal Ganglion Cell Layer of the Alzheimer's Eye.

Alzheimer’s disease (AD) is the most prevalent form of dementia, accounting for 60–70% of all dementias. AD is often under-diagnosed and recognized only at a later, more advanced stage, and this delay in diagnosis has been suggested as a contributing factor in the numerous unsuccessful AD treatment trials. Although there is no known cure for AD, early diagnosis is important for disease management and care. A hallmark of AD is the deposition of amyloid-β (Aβ)-containing senile neuritic plaques and neurofibrillary tangles composed of hyperphosporylated tau in the brain. However, current in vivo methods to quantify Aβ in the brain are invasive, requiring radioactive tracers and positron emission tomography. Toward development of alternative methods to assess AD progression, we focus on the retinal manifestation of AD pathology. The retina is an extension of the central nervous system uniquely accessible to light-based, non-invasive ophthalmic imaging. However, earlier studies in human retina indicate that the literature is divided on the presence of Aβ in the AD retina. To help resolve this disparity, this study assessed retinal tissues from neuropathologically confirmed AD cases to determine the regional distribution of Aβ in retinal wholemounts and to inform on future retinal image studies targeting Aβ. Concurrent post-mortem brain tissues were also collected. Neuropathological cortical assessments including neuritic plaque (NP) scores and cerebral amyloid angiopathy (CAA) were correlated with retinal Aβ using immunohistochemistry, confocal microscopy, and quantitative image analysis. Aβ load was compared between AD and control (non-AD) eyes. Our results indicate that levels of intracellular and extracellular Aβ retinal deposits were significantly higher in AD than controls. Mid-peripheral Aβ levels were greater than central retina in both AD and control eyes. In AD retina, higher intracellular Aβ was associated with lower NP score, while higher extracellular Aβ was associated with higher CAA score. Our data support the feasibility of using the retinal tissue to assess ocular Aβ as a surrogate measure of Aβ in the brain of individuals with AD. Specifically, mid-peripheral retina possesses more Aβ deposition than central retina, and thus may be the optimal location for future in vivo ocular imaging.

Identification of linear polyubiquitin chain immunoreactivity in tau pathology of Alzheimer’s disease

Characteristic neuropathological structures observed in Alzheimer’s disease, such as neurofibrillary tangles and dystrophic neurites of senile plaques, are universally ubiquitinated. Eight linkage types of polyubiquitin chains are known, and each type of chain exerts different intracellular action. Among them, linear polyubiquitin chain was recently reported to be associated with the pathomechanism of neuronal cell death. We therefore generated a novel antibody that specifically recognizes linear polyubiquitin chain. We immunohistochemically examined the brains of patients with Alzheimer’s disease. A subset of neurofibrillary tangles, dystrophic neurites of senile plaques, and neuropil threads were evident to be immunopositive for linear polyubiquitin chains, but their number was fewer than those recognized by the antibody against K48-linked polyubiquitin chains. Double immunofluorescence investigation showed that in certain neurofibrillary tangles, a part of K48-linked polyubiquitin-immunopositive structures were immunolabeled for linear polyubiquitin chains. Our results imply that linear polyubiquitination follows K48-linked polyubiquitination in abnormally accumulated tau proteins in Alzheimer’s disease, and imply involvement in its neurodegeneration.

Chlamydia pneumoniae: An Etiologic Agent for Late-Onset Dementia.

The disease known as late-onset Alzheimer’s disease is a neurodegenerative condition recognized as the single most commonform of senile dementia. The condition is sporadic and has been attributed to neuronal damage and loss, both of which have been linked to the accumulation of protein deposits in the brain. Significant progress has been made over the past two decades regarding our overall understanding of the apparently pathogenic entities that arise in the affected brain, both for early-onset disease, which constitutes approximately 5% of all cases, as well as late-onset disease, which constitutes the remainder of cases. Observable neuropathology includes: neurofibrillary tangles, neuropil threads, neuritic senile plaques and often deposits of amyloid around the cerebrovasculature. Although many studies have provided a relatively detailed knowledge of these putatively pathogenic entities, understanding of the events that initiate and support the biological processes generating them and the subsequent observable neuropathology and neurodegeneration remain limited. This is especially true in the case of late-onset disease. Although early-onset Alzheimer’s disease has been shown conclusively to have genetic roots, the detailed etiologic initiation of late-onset disease without such genetic origins has remained elusive. Over the last 15 years, current and ongoing work has implicated infection in the etiology and pathogenesis of late-onset dementia. Infectious agents reported to be associated with disease initiation are various, including several viruses and pathogenic bacterial species. We have reported extensively regarding an association between late-onset disease and infection with the intracellular bacterial pathogen Chlamydia pneumoniae. In this article, we review previously published data and recent results that support involvement of this unusual respiratory pathogen in disease induction and development. We further suggest several areas for future research that should elucidate details relating to those processes, and we argue for a change in the designation of the disease based on increased understanding of its clinical attributes.

Association of adipocyte enhancer-binding protein 1 with Alzheimer's disease pathology in human hippocampi.

Adipocyte enhancer binding protein 1 (AEBP1) activates inflammatory responses via the NF-κB pathway in macrophages and regulates adipogenesis in preadipocytes. Up-regulation of AEBP1 in the hippocampi of patients with Alzheimer's disease (AD) has been revealed by microarray analyses of autopsied brains from the Japanese general population (the Hisayama study). In this study, we compared the expression patterns of AEBP1 in normal and AD brains, including in the hippocampus, using immunohistochemistry. The subjects were 24 AD cases and 52 non-AD cases. Brain specimens were immunostained with antibodies against AEBP1, tau protein, amyloid β protein, NF-κB, GFAP and Iba-1. In normal brains, AEBP1 immunoreactivity mainly localized to the perikarya of hippocampal pyramidal neurons, and its expression was elevated in the pyramidal neurons and some astrocytes in AD hippocampi. Although AEBP1 immunoreactivity was almost absent in neurons containing neurofibrillary tangles, AEBP1 was highly expressed in neurons with pretangles and in the tau-immunopositive, dystrophic neurites of senile plaques. Nuclear localization of NF-κB was also observed in certain AEBP1-positive neurons in AD cases. Comparison of AD and non-AD cases suggested a positive correlation between the expression level of AEBP1 and the degree of amyloid β pathology. These findings imply that AEBP1 protein has a role in the progression of AD pathology.

Hypersialylation is a common feature of neurofibrillary tangles and granulovacuolar degenerations in Alzheimer's disease and tauopathy brains.

Glycosylation is one of the major post-translational modifications of proteins. The status of sialylation of the neuropathological hallmarks of various neurodegenerative disorders was investigated in this study. Here, we report the novel findings that two phosphorylated tau (p-tau)-containing structures associated with Alzheimer's disease (AD), that is, neurofibrillary tangles (NFTs) and granulovacuolar degenerations (GVDs), were hypersialylated. The NFTs, GVDs and dystrophic neurites of senile plaques (SPs) in AD hippocampi were clearly visualized by immunohistochemistry using an anti-sialic acid (SA) antibody. In contrast, the amyloid core of SPs was not sialylated at all. Interestingly, other p-tau-containing structures, that is, globose-type NFTs in progressive supranuclear palsy and Pick bodies and ballooned neurons in frontotemporal lobar degeneration with Pick bodies, were also hypersialylated. Unlike the p-tau-containing structures observed in tauopathies, the hallmarks of other neurodegenerative disorders, such as Lewy bodies in Parkinson's disease, glial cytoplasmic inclusions in multiple system atrophy, Bunina bodies, skein-like inclusions and round inclusions in amyotrophic lateral sclerosis, intranuclear inclusions in neuronal intranuclear inclusion disease and physiological bodies or granules (lipofuscin granules, corpora amylacea and melanin granules), were not immunolabeled by the anti-SA antibody. Because this antibody specifically identified NFTs and GVDs, immunostaining for sialylation represents a useful tool to screen these structures in a diagnostic setting. These results clearly indicate that the pathological hallmarks of various tauopathies are commonly hypersialylated, and that sialylation plays an important role in the process of p-tau accumulation in AD and other tauopathies.

A cellular model of amyloid precursor protein processing and amyloid-β peptide production

BackgroundA hallmark pathologic feature of Alzheimer's disease (AD) is accumulation of neuritic senile plaques in the brain parenchyma. Neurotoxic plaque cores are composed predominantly of amyloid-β (Aβ) peptides of 40 and 42 amino acids in length, formed by sequential cleavage of amyloid precursor protein (APP) by β-, and γ-secretases. There is a great interest in approaches to modulate Aβ peptide production and develop therapeutic interventions to reduce Aβ levels to halt or slow the progression of neurodegeneration. New methodWe characterized and present the BE(2)-M17 human neuroblastoma cell line as a novel in vitro model of the APP-cleavage cascade to support future (1) functional studies of molecular regulators in Aβ production, and (2) high-throughput screening assays of new pharmacotherapeutics. ResultsIn BE(2)-M17 cells, both RNA (i.e., RT-PCR, RNA sequencing) and protein analyses (i.e., Western blots, ELISA), show endogenous expression of critical components of the amyloidogenic pathway, APP-cleavage intermediates CTF83 and CTF99, and final cleavage products Aβ40 and Aβ42. We further report effects of retinoic acid-mediated differentiation on morphology and gene expression in this cell line. Comparison with existing method(s)In contrast to primary isolates or other cell lines reported in current literature, BE(2)-M17 not only sustains baseline expression of the full contingent of APP-processing components, but also remains stably adherent during culture, facilitating experimental manipulations. ConclusionsOur evidence supports the use of BE(2)-M17 as a novel, human, cell-based model of the APP processing pathway that offers a potential streamlined approach to dissect molecular functions of endogenous regulatory pathways, and perform mechanistic studies to identify modulators of Aβ production.

S4‐03‐02: Discovery of novel [18F]‐PET agents for imaging neurofibrillary tangles (NFTs)

There are two main neuropathologic hallmarks in AD, senile neuritic plaques (SP) around an amyloid beta core and neurofibrillar protein aggregates containing tau protein. In AD patients tau is abnormally phosphorylated and loses its normal function. Unlike ß-amyloid plaque deposition, human post-mortem studies indicate that neurofibrillary tangle density correlates with neurodegeneration and cognitive impairment. Furthermore, abundant neurofibrillary tangles are not observed in cognitively unimpaired individuals, in contrast to ß-amyloid plaques that can be present also in cognitively normal people. Therefore, a tau PET tracer might be a good diagnostic tool for Alzheimer's disease that can be correlated with the progression of clinical symptoms. In order to screen many compounds as potential tau binders, we developed a competitive autoradiography screening method utilizing human AD brain sections. Brain sections from over 40 human AD brains were immunostained for tau and Aß and quantified by area measurements. Selectivity of tau binding compounds was determined by competition experiments in tau rich or Aß rich brain sections. Grey and white matter binding was measured for each candidate. Double staining of fluorescent analogs confirms binding of these compounds to tau tangles in AD brains. Brain uptake of [F18]-labeled tracers was measured in rodents and monkeys. Metabolism and pharmacokinetic studies were performed in mice. We have discovered several novel, small molecule tau binding compounds that show high selectivity for native tau aggregates in human AD brain sections over ß-amyloid. Several of these candidates were further optimized to show a high brain uptake/fast clearance in mice, rats, and monkeys. White matter distribution in monkeys is very low. Metabolism studies of our lead candidates show very good stability in plasma and no metabolite presence in mouse brains. We have identified several novel small heterocyclic tau binders. Our in vitro and in vivo studies confirm that our lead candidate [F18]-T808 binds to tau selectively over ß-amyloid, shows good PK and metabolic properties, and exhibits excellent brain uptake/washout kinetics in rodent and monkey brains.

New Thinking on the Etiology and Pathogenesis of Late‐Onset Alzheimer′s Disease

New Thinking on the Etiology and Pathogenesis of Late‐Onset Alzheimer′s Disease

VDAC and ERα interaction in caveolae from human cortex is altered in Alzheimer's disease

Voltage-dependent anion channel (VDAC) is a mitochondrial porin also found in the neuronal membrane (pl-VDAC), where its function may be related to redox homeostasis and apoptosis. Murine models have evidenced pl-VDAC into caveolae in a complex with estrogen receptor alpha (mERα), which participates in neuroprotection against amyloid beta (Aβ), and whose integration into this hydrophobic domain remains unclear. Here, we have demonstrated in caveolae of human cortex and hippocampus the presence of pl-VDAC and mERα, in a complex with scaffolding caveolin-1 which likely provides mERα stability at the plasma membrane. In Alzheimer's disease (AD) brains, VDAC was accumulated in caveolae, and it was observed in dystrophic neurites of senile plaques, whereas ERα was expressed in astrocytes surrounding the plaques. Together with previous data in murine neurons demonstrating the participation of pl-VDAC in Aβ-induced neurotoxicity, these data suggest that the channel may be involved in membrane dysfunctioning observed in AD neuropathology.

Minocycline prevents Aβ(25–35)-induced reduction of somatostatin and neprilysin content in rat temporal cortex

Aims Tetracyclines have been demonstrated to inhibit formation of β-amyloid (Aβ) aggregates and to disassemble preformed fibrils. Minocycline, a semi-synthetic second-generation tetracycline, can reverse Aβ-induced impairment of cognitive functions. Since somatostatin is involved in cognition and we recently showed that Aβ(25–35) lowers somatostatin expression in the rat temporal cortex, our aim here was to analyze the effects of minocycline on somatostatin immunoreactivity and mRNA levels in the temporal cortex of Aβ(25–35)-infused and healthy rats. Moreover, since brain levels of neprilysin, an Aβ-degrading enzyme, decrease with age, favoring the appearance of senile neuritic plaques, we tested whether minocyline could affect neprilysin expression. Main methods Wistar rats were thus injected with minocycline twice on the first day of treatment. On the following day, and during 14 days, Aβ(25–35) or vehicle were administered. Minocycline was injected once again on days 13 and 14. All animals were sacrificed 24 h after the last drug injection. Key findings Minocycline abrogated the Aβ(25–35)-induced decrease of somatostatin-like immunoreactive content, somatostatin mRNA levels, phosphorylated-CREB content and neprilysin levels. Minocycline alone enhanced these targets. Significance Our findings indicate that minocycline prevents the deleterious effects of Aβ(25–35) on SRIF and neprilysin expression in the rat temporal cortex and that it has protective effects per se on these parameters.

Dystrophic neurites of senile plaques in Alzheimer’s disease are deficient in cytochrome c oxidase

Double-labeling immunofluorescence and confocal microscopy have been used to learn about the local relationship between amyloid, mitochondria, and cytochrome c oxidase (COX) in dystrophic neurites of senile plaques in the frontal cortex in Alzheimer's disease (AD). Dystrophic neurites surrounding amyloid plaques are filled with mitochondrial porin-immunoreactive structures. In contrast with tangle-bearing and non-tangle-bearing neurons, which express mitochondrial porin and COX subunit 4, porin-immunoreactive neurites of senile plaques lack COX subunit 4. Parallel western blot studies in mitochondria-enriched fractions of the frontal cortex in the same cases disclosed reduced expression levels of COX, but not of prohibitin, in AD stages VB/C of Braak. Co-localization of porin and lysosomal associated protein 1, as revealed by double-labeling immunofluorescence and confocal microscopy, suggests that mitochondria may be engulfed by lysosomes in dystrophic neurites. These findings support a local link between amyloid deposition, abnormal mitochondria and impaired respiratory chain function (resulting from decrease of COX expression) in dystrophic neurites of senile plaques in AD.

Chlamydophila Pneumoniae and the Etiology of Late-Onset Alzheimer's Disease

Sporadic, late-onset Alzheimer's disease (LOAD) is a non-familial, progressive neurodegenerative disease that is now the most common and severe form of dementia in the elderly. That dementia is a direct result of neuronal damage and loss associated with accumulations of abnormal protein deposits in the brain. Great strides have been made in the past 20 years with regard to understanding the pathological entities that arise in the AD brain, both for familial AD ( approximately 5% of all cases) and LOAD ( approximately 95% of all cases). The neuropathology observed includes: neuritic senile plaques (NSPs), neurofibrillary tangles (NFTs), neuropil threads (NPs), and often deposits of cerebrovascular amyloid. Genetic, biochemical, and immunological analyses have provided a relatively detailed knowledge of these entities, but our understanding of the "trigger" events leading to the many cascades resulting in this pathology and neurodegeneration is still quite limited. For this reason, the etiology of AD, in particular LOAD, has remained elusive. However, a number of recent and ongoing studies have implicated infection in the etiology and pathogenesis of LOAD. This review focuses specifically on infection with Chlamydophila (Chlamydia) pneumoniae in LOAD and how this infection may function as a "trigger or initiator" in the pathogenesis of this disease.

Mitochondrial degeneration in dystrophic neurites of senile plaques may lead to extracellular deposition of fine filaments

Recent data show that amyloid precursor protein accumulates inside axons after disruption of fast axonal transport, but how this leads to mature plaques with extracellular amyloid remains unclear. To investigate this issue, primitive plaques in prefrontal cortex of aged rhesus monkeys were reconstructed using serial section electron microscopy. The swollen profiles of dystrophic neurites were found to be diverticula from the main axis of otherwise normal neurites. Microtubules extended from the main neurite axis into the diverticulum to form circular loops or coils, providing a transport pathway for trapping organelles. The quantity and morphology of organelles contained within diverticula suggested a progression of degeneration. Primitive diverticula contained microtubules and normal mitochondria, while larger, presumably older, diverticula contained large numbers of degenerating mitochondria. In advanced stages of degeneration, apparent autophagosomes derived from mitochondria exhibited a loose lamellar to filamentous internal structure. Similar filamentous material and remnants of mitochondria were visible in the extracellular spaces of plaques. This progression of degeneration suggests that extracellular filaments originate inside degenerating mitochondria of neuritic diverticula, which may be a common process in diverse diseases.

Chlamydophila (Chlamydia) pneumoniaein the Alzheimer's brain

We assessed the presence and characteristics of the intracellular pathogen Chlamydophila (Chlamydia) pneumoniae in brain-tissue samples from 25 patients with late-onset Alzheimer's disease (AD) and 27 non-AD control individuals. 20/27 AD patients, but only 3/27 controls, were PCR-positive in multiple assays targetting the Cpn1046 and Cpn0695 genes. Culture of the organism from brain-tissue homogenate from one AD patient, and assessment of various chlamydial transcripts in RNA preparations from several patients, demonstrated that the organisms were viable and metabolically active in those samples. Immunohistochemical analyses showed that astrocytes, microglia, and neurons all served as host cells for C. pneumoniae in the AD brain, and that infected cells were found in close proximity to both neuritic senile plaques and neurofibrillary tangles in the AD brain. These observations confirm and significantly extend our earlier study suggesting that this unusual pathogen may play a role in the neuropathogenesis characteristic of AD.

The Role of Calcium and Magnesium Ions in Uptake of β-Amyloid Peptides by Microglial Cells

Amyloid peptides 1-40 and 1-42 (Abeta 1-40 and Abeta 1-42) are major components of diffuse and neuritic senile plaques present in the brain of patients with Alzheimers disease. Their interaction with microglial cells was studied using a system partly mimicking these plaques, which consisted in heat-killed yeast particles coated with either Abeta 1-40 or Abeta 1-42. Using these particles, it has been shown in our laboratory that LRP is involved mainly in the elimination of Abeta 1-42-coated heat-killed yeast particles and partly in that of Abeta 1-40-coated heat-killed yeast particles by microglial cells in culture. We show here that in the presence of calcium and magnesium ions extracellular chelators, namely EDTA (for both ions) and EGTA (for calcium ions), the internalization of coated heat-killed particles was impaired. In the presence of BAPTA-AM, an intracellular chelator of calcium ions and thapsigargin, an inhibitor of the endoplasmic reticulum calcium pump, no effect was observed on the phagocytosis of Abeta 1-40-coated heat-killed yeast particles, whereas that of Abeta 1-42-coated heat-killed yeast particles was affected. These results suggest that different signaling mechanisms are involved after the internalization of Abeta 1-40 and Abeta 1-42.

Abnormal Sp1 transcription factor expression in Alzheimer disease and tauopathies

Sp1 transcription factor expression was examined by immunohistochemistry, immunofluorescence and confocal microscopy in Alzheimer disease (AD), Pick disease (PiD), progressive supranuclear palsy (PSP), Parkinson disease (PD) and Dementia with Lewy bodies (DLB). Sp1 partly co-localizes with hyper-phosphorylated tau deposits in neurofibrillary tangles, dystrophic neurites of senile plaques and neuropil threads in AD, and in neurons, astrocytes and oligodendrocytes bearing hyper-phosphorylated tau in PiD and PSP. Sp1 is not found in α-synuclein inclusions in PD and DLB. These modifications are not associated with changes in the total expression levels of Sp1, as revealed with gel electrophoresis and Western blotting of brain homogenates. Furthermore, no co-immunoprecipitation of Sp1 and phospho-tau was observed in AD and PiD cases. Since Sp1 binding sites are present in the promoters of several genes involved in amyloid and tau, and Sp1 is regulated by oxidative stress, the present findings suggest that Sp1 deposition in hyper-phosphorylated tau deposits may have functional consequences in the pathology of AD and other tauopathies.