Abraha, A., N. Ghoshal, et al. (2000). "C-terminal inhibition of tau assembly in vitro and in Alzheimer's disease." J Cell Sci 113 Pt 21: 3737-45.
Alzheimer's disease (AD) is, in part, defined by the polymerization of tau into paired helical and straight filaments (PHF/SFs) which together comprise the fibrillar pathology in degenerating brain regions. Much of the tau in these filaments is modified by phosphorylation. Additionally, a subset also appears to be proteolytically truncated, resulting in the removal of its C terminus. Antibodies that recognize tau phosphorylated at S(396/404 )or truncated at E(391) do not stain control brains but do stain brain sections very early in the disease process. We modeled these phosphorylation and truncation events by creating pseudo-phosphorylation and deletion mutants derived from a full-length recombinant human tau protein isoform (ht40) that contains N-terminal exons 2 and 3 and all four microtubule-binding repeats. In vitro assembly experiments demonstrate that both modifications greatly enhance the rates of tau filament formation and that truncation increases the mass of polymer formed, as well. Removal of as few as 12 or as many as 121 amino acids from the C terminus of tau greatly increases the rate and extent of tau polymerization. However, deletion of an additional 7 amino acids, (314)DLSKVTS(320), from the third microtubule-binding repeat results in the loss of tau's ability to form filaments in vitro. These results suggest that only part of the microtubule-binding domain (repeats 1, 2 and a small portion of 3) is crucial for tau polymerization. Moreover, the C terminus of tau clearly inhibits the assembly process; this inhibition can be partially reversed by site-specific phosphorylation and completely removed by truncation events at various sites from S(320) to the end of the molecule.

Ackmann, M., H. Wiech, et al. (2000). "Nonsaturable binding indicates clustering of tau on the microtubule surface in a paired helical filament-like conformation." J Biol Chem 275(39): 30335-43.
Tau protein modulates microtubule dynamics and forms insoluble aggregates in Alzheimer's disease. Because there is a discrepancy between reported affinities of Tau to microtubules, we determined the interaction over a wide concentration range using a sensitive enzyme-linked immunosorbent assay. We found that the interaction is biphasic and not monophasic as assumed earlier. The first binding phase is typical for identical and noninteracting binding sites, with dissociation constants around 0.1 micrometer and stoichiometries around 0.2 Tau/tubulin dimer. Surprisingly, the second phase is nonsaturable and shows a nearly linear increase in bound Tau versus free Tau for free Tau concentrations higher than 2 micrometer. The slope is proportional to the microtubule concentration. From this we define an overloading parameter with values around 50 micrometer. The influence of Tau isoform, phosphorylation, and dimerization on both phases was investigated. Remarkably the overloading of Tau on microtubules leads to a thioflavin S fluorescence increase reminiscent of that seen with Tau aggregated into Alzheimer paired helical filaments. Because polyanions stimulate Tau aggregation and because the C-terminal domain of tubulin is polyanionic, we suggest that an early conformational change in Tau leading to paired helical filament aggregation occurs right on the microtubule surface.

Ahlijanian, M. K., N. X. Barrezueta, et al. (2000). "Hyperphosphorylated tau and neurofilament and cytoskeletal disruptions in mice overexpressing human p25, an activator of cdk5." Proc Natl Acad Sci U S A 97(6): 2910-5.
Hyperphosphorylation of microtubule-associated proteins such as tau and neurofilament may underlie the cytoskeletal abnormalities and neuronal death seen in several neurodegenerative diseases including Alzheimer's disease. One potential mechanism of microtubule-associated protein hyperphosphorylation is augmented activity of protein kinases known to associate with microtubules, such as cdk5 or GSK3beta. Here we show that tau and neurofilament are hyperphosphorylated in transgenic mice that overexpress human p25, an activator of cdk5. The p25 transgenic mice display silver-positive neurons using the Bielschowsky stain. Disturbances in neuronal cytoskeletal organization are apparent at the ultrastructural level. These changes are localized predominantly to the amygdala, thalamus/hypothalamus, and cortex. The p25 transgenic mice display increased spontaneous locomotor activity and differences from control in the elevated plus-maze test. The overexpression of an activator of cdk5 in transgenic mice results in increased cdk5 activity that is sufficient to produce hyperphosphorylation of tau and neurofilament as well as cytoskeletal disruptions reminiscent of Alzheimer's disease and other neurodegenerative diseases.

Alafuzoff, I., S. Helisalmi, et al. (2000). "Severity of cardiovascular disease, apolipoprotein E genotype, and brain pathology in aging and dementia." Ann N Y Acad Sci 903: 244-51.
Neuropathological lesions, essential for the diagnosis of Alzheimer's disease (AD), such as senile-neuritic plaques (SP/NPs), neurofibrillary tangles (NFTs), the beta-amyloid load (A beta 4) and the load of PHF-tau did not increase with increased severity of cardiovascular disease in 126 clinically demented and 303 nondemented aged individuals. In contrast, the extent of AD lesions was greater in nondemented and demented individuals with the ApoE epsilon 4 allele compared to those without this allele. On the other hand, the extent of vascular lesions currently used for the diagnosis of vascular dementia (VaD) showed correlation with the cardiovascular index, whereas ApoE epsilon 4 allele did not seem to influence the extent of vascular lesions. The calculated CVI showed significant correlation with premortem estimated Hachinski score, and both the CVI and Hachinski score were higher in demented patients with extensive vascular lesions. Our results demonstrate that ApoE epsilon 4 allele, a known risk factor for dementia, indeed influences the extent of Alzheimer's lesions seen in the brain tissue of demented patients and asymptomatic controls. The cardiovascular disease again seems to influence the extent of vascular lesions.

Alafuzoff, I., S. Helisalmi, et al. (2000). "Selegiline treatment and the extent of degenerative changes in brain tissue of patients with Alzheimer's disease." Eur J Clin Pharmacol 55(11-12): 815-9.
BACKGROUND: A beneficial effect of selegiline (L-deprenyl) in Alzheimer's disease (AD) has been reported in several clinical studies. METHODS: The brain tissue from 17 deceased patients, members of a double-blind clinical trial to assess the potential benefit of selegiline in AD, were analysed. FINDINGS: In our study, the decrease in the Mini-Mental State Examination (MMSE) scores during the progress of the disease had been significantly influenced by selegiline treatment. Prior to death, the MMSE scores were significantly higher in those patients receiving selegiline than in those receiving placebo. However, according to our results, none of the lesions critical for AD diagnosis, such as counts of senile/neuritic plaques, neurofibrillary tangles or beta-A4 load, were influenced by the selegiline treatment. INTERPRETATION: In conclusion, according to our study, mechanisms other than neuronal degeneration seen as lesions critical for AD diagnosis are influenced by selegiline treatment, leading to the functional benefit found in AD.

Andersen, C., S. Froelich Fabre, et al. (2000). "Tau protein in cerebrospinal fluid from semantic dementia patients." Neurosci Lett 294(3): 155-8.
Apolipoprotein E (APOE) genotypes and cerebrospinal fluid (CSF) tau protein concentration were evaluated in patients suffering from semantic dementia, with the aim of determining whether these markers could help to differentiate this condition from Alzheimer's disease (AD) in early stages. By strictly following diagnostic criteria for semantic dementia, we found a clinically homogeneous group comprising eight patients from a total population of 621 subjects referred for dementia investigation. CSF tau protein concentrations were moderately increased with a small intraindividual variation 437+/-36 pg/ml (mean+/-SD) compared to healthy control individuals. APOE genotype distribution showed an over representation of the epsilon4 allele (69% epsilon3, 31% epsilon4 and no epsilon2), a pattern similar to that found in AD. These results indicate that semantic dementia is a rather uncommon but clinically distinct condition which shows a moderate increase of CSF tau protein levels and for which the epsilon4 allele is a risk factor.

Anderson, A. J., W. W. Ruehl, et al. (2000). "DNA damage and apoptosis in the aged canine brain: relationship to Abeta deposition in the absence of neuritic pathology." Prog Neuropsychopharmacol Biol Psychiatry 24(5): 787-99.
1. In addition to beta-amyloid (Abeta) deposition and cytoskeletal neuropathology, both the Alzheimer's disease (AD) and Down's syndrome (DS) human brain exhibit marked evidence of DNA damage, however, it is difficult to separate events that occur in conjunction with neurofibrillary pathology versus Abeta pathology in these systems. 2. In contrast, the aged canine brain exhibits the accumulation of Abeta into diffuse deposits similar to those found in early AD and DS in the absence of neurofibrillary pathology. Furthermore, Abeta deposition in canine brain is correlated with cognitive deficits. 3. In order to test the hypothesis that TUNEL labeling for DNA damage in AD is not simply a consequence of agonal artifacts, postmortem artifacts, or neurofibrillary pathology, and may be directly related to Abeta deposition, we examined Abeta immunoreactivity, PHF-1 immunoreactivity, and TUNEL labeling in this animal model. 4. These experiments reveal a relationship between the amount of DNA damage detected by TUNEL labeling and levels of Abeta deposition. Further, in animals with no TUNEL labeling, we detected no Abeta immunoreactivity. 5. These data support the hypothesis that TUNEL labeling in AD ans DS is not a consequence of agonal artifact, postmortem artifact, or tau pathology, and may be directly related to Abeta deposition and perhaps AD pathogenesis.

Anderton, B. H., R. Dayanandan, et al. (2000). "Does dysregulation of the Notch and wingless/Wnt pathways underlie the pathogenesis of Alzheimer's disease?" Mol Med Today 6(2): 54-9.
Alzheimer's disease is characterized by the presence of neurofibrillary tangles and senile neuritic plaques in the brain. Tangles are aggregates of paired helical filaments composed of the microtubule-associated protein, tau, in a hyperphosphorylated state. Senile plaques have a core of amyloid beta-peptide derived by proteolysis of the amyloid precursor protein. A major hurdle in defining the pathogenic mechanisms in Alzheimer's disease is to understand how both amyloid beta-peptide deposition and paired helical filament formation are biochemically linked. Recent genetic discoveries provide some clues, suggesting that components of two developmentally important signalling pathways, Notch and wingless, or the vertebrate homologue of wingless, Wnt, are involved.

Andorfer, C. A. and P. Davies (2000). "PKA phosphorylations on tau: developmental studies in the mouse." Dev Neurosci 22(4): 303-9.
PKA phosphorylations of tau may be an early event in the development of neurofibrillary pathology in Alzheimer's disease. Serines 214 and 409 of tau are highly phosphorylated in PHF-tau, but are not phosphorylated to any significant extent in normal adult human brain; both of these sites are phosphorylated in human fetal tissue. To further study this phenomenon, a developmental characterization of these phosphorylation sites relative to PKA, cAMP-dependent response binding element (CREB) and phosphorylated CREB was performed using samples from mouse brain. Immunoblot analysis using antibodies specific for phospho-serine 214 (CP-3) and phospho-serine 409 (PG-5) revealed a marked decrease in phosphorylation occurring at each of these sites between postnatal day 11 (P11) and P20. Immunoblots with TG-5, a pan-tau antibody, revealed uniform expression of tau during postnatal development, as well as a switch in isoform composition that is evident between P7 and P11. This switch in isoform composition just precedes the change in the extent of phosphorylation at serines 214 and 409, and occurs at a time when PKA phosphorylation of CREB is increasing.

Arai, H., K. Ishiguro, et al. (2000). "CSF phosphorylated tau protein and mild cognitive impairment: a prospective study." Exp Neurol 166(1): 201-3.
Cerebrospinal fluid (CSF) tau protein phosphorylated at both Thr231 and Ser235 sites (CSF/phospho-tau(231-235)) and total tau (CSF/total-tau) were quantified by sandwich ELISA in 20 patients with mild cognitive impairment (MCI) who eventually developed AD on follow-up as well as seven memory complainers with no objective memory loss. 13/20 (65%) of the MCI patients had high CSF/total-tau and detectable levels of CSF/phospho-tau(231-235), whereas these markers were low and under a detectable level in all of the memory complainers. Although either a total-tau, phospho-tau measurement or a combination of these can help in predicting if MCI will develop AD, our results suggest that the pathogenic steps of AD may be at the stage that finally leads to an accumulation of abnormally phosphorylated tau and neuron death, at least in some brain areas, when MCI patients present with the earliest detectable clinical symptoms of dementia.

Arai, H., T. Suzuki, et al. (2000). "[A new interventional strategy for Alzheimer's disease by Japanese herbal medicine]." Nippon Ronen Igakkai Zasshi 37(3): 212-5.
A Japanese herbal medicine termed "Kami-Umtan-To (KUT)" was first described in Japanese literature in 1626, KUT consists of 13 different herbs, and it has been used for a long time in the treatment of a variety of neuropsychiatric problems including neurosis and insomnia. Recently, Yabe et al. have demonstrated that KUT increased both choline acetyltransferase (ChAT) and nerve growth factor at the protein and mRNA levels in cultured rat brain cells. Moreover, the same research group has reported that KUT improved mean latency on passive avoidance test in both basal for brain lesioned and aged rats. KUT significantly improved the survival rate, and increased the number of ChAT-positive neurons in aged rats. Here, we report a 12-month open clinical trial of KUT and combination of estrogen, vitamin E and NSAID to aim at slowing down the progression of Alzheimer's disease (AD). Twenty AD patients (MMSE score: 18.6 +/- 5.8) received extracts from original KUT herbs, and 7AD patients (MMSE score: 21.3 +/- 2.8) were placed on the combination therapy. Rate of cognitive decline as measured by change in MMSE score per year was significantly slower (p = 0.04, ANOVA) in the KUT group (1.4 points) and the combination group (0.4 points) as compared to 4.1 points in 32 control AD patients (MMSE score: 20.8 +/- 5.6) who received no medicines for AD. Any of CSF measures including tau. and A beta 1-42 did not differ significantly after KUT therapy. The efficacy of the KUT therapy was most obvious at 3 months. Our results suggest that traditional Japanese herbal medicine(s) may serve a new interventional strategy for AD.

Arends, Y. M., C. Duyckaerts, et al. (2000). "Microglia, amyloid and dementia in alzheimer disease. A correlative study." Neurobiol Aging 21(1): 39-47.
To elucidate the role of microglia in Alzheimer's disease, a clinicopathological study was performed involving 26 cases, the mental status of which had been studied pre mortem by the Blessed test score (BTS). We measured the volume density of CD 68 immunoreactive (IR) microglia, congophilic plaques and Abeta deposits, and the numerical density of neurofibrillary tangles (NFT) in a sample of Area 9 (middle frontal gyrus). Dementia was significantly correlated only with the volume density of Abeta deposits and the numerical density of NFT. The volume densities of microglia and congophilic plaques were strongly correlated. With the intellectual status used as a time scale, IR microglia and amyloid deposits appeared almost simultaneously at an early stage in the pathological cascade and decreased, whereas Abeta and NFT were still accumulating. The intellectual deficit seemed to be more significantly related to the latter two lesions than to the microglia-amyloid complex, that was visible at an earlier stage (around BTS = 15).

Arnold, S. E., L. Y. Han, et al. (2000). "Quantitative neurohistological features of frontotemporal degeneration." Neurobiol Aging 21(6): 913-9.
Frontotemporal degeneration (FTD) is a neurodegenerative condition that has been principally associated with frontal lobe dementia. In this study, we compared neuropathological abnormalities in frontal, hippocampal, and calcarine cortices from patients assigned a diagnosis of FTD, normal elderly and Alzheimer's disease (AD). Densities of Nissl-stained neurons and lesions which were immunolabeled for tau, beta-amyloid (Abeta), alpha- and beta-synuclein, ubiquitin, glial fibrillary acidic protein (GFAP) and CD68 antigen were determined using computer-assisted, non-biased quantitative microscopy. We found that FTD frontal and hippocampal regions exhibited marked neuron loss, abundant ubiquitin-immunoreactive (ir) dystrophic neurites, GFAP-ir astrocytes, and CD68-ir microglia, while calcarine cortex was spared. No alpha- or beta-synuclein-ir lesions were observed, and neither the density of tau-ir neurofibrillary tangles nor that of Abeta-ir plaques in FTD exceeded normal controls. In addition, there were no neuropathological differences between FTD subjects who presented clinically with a frontal lobe dementia versus an AD-like dementia. These findings indicate that FTD is a category of neurodegnerative dementias with varying clinical presentations that is characterized by the progressive degeneration of select populations of cortical neurons. The molecular neurodegenerative mechanisms that lead to FTD remain to be elucidated.

Askanas, V., W. K. Engel, et al. (2000). "Novel immunolocalization of alpha-synuclein in human muscle of inclusion-body myositis, regenerating and necrotic muscle fibers, and at neuromuscular junctions." J Neuropathol Exp Neurol 59(7): 592-8.
Alpha-synuclein (alpha-syn) is an important component of neuronal and glial inclusions in brains of patients with several neurodegenerative disorders. Sporadic inclusion-body myositis (s-IBM) is the most common progressive muscle disease of older patients. Its muscle phenotype shows several similarities with Alzheimer disease brain. A distinct feature of s-IBM pathology is specific vacuolar degeneration of muscle fibers characterized by intracellular amyloid inclusions formed by both amyloid-beta (Abeta) and paired-helical filaments composed of phosphorylated tau. We immunostained alpha-syn in muscle biopsies of s-IBM, disease-control, and normal patients. Approximately 60% of Abeta-positive vacuolated muscle fibers (VMF) contained well-defined inclusions immunoreactive with antibodies against alpha-syn. In those fibers. alpha-syn co-localized with Abeta, both by light microscopy, and ultrastructurally. Paired-helical filaments did not contain alpha-syn immunoreactivity. In all muscle biopsies, alpha-syn was strongly immunoreactive at the postsynaptic region of the neuromuscular junctions. alpha-syn immunoreactivity also occurred diffusely in regenerating and necrotic muscle fibers. In cultured human muscle fibers, alpha-syn and its mRNA were expressed by immunocytochemistry, immunoblots, and Northern blots. Our study provides the first demonstration that alpha-syn participates in normal and pathologic processes of human muscle. Therefore. its function is not exclusive to the brain and neurodegenerative diseases.

Averback, P. (2000). "Combined assessment of tau and neuronal thread protein in Alzheimer's disease CSF." Neurology 55(7): 1068-9.

Avila, J. (2000). "Tau aggregation into fibrillar polymers: taupathies." FEBS Lett 476(1-2): 89-92.
Different neurological disorders, known as taupathies have been recently described. In these disorders it has been suggested that modifications in the microtubule-associated protein tau could cause neural degeneration in specific regions. Although these regions are different in the different taupathies, some common features appear to occur in all of them: abnormal hyperphosphorylation of tau and aberrant tau aggregation. These two features are commented upon in this review.

Baker, M., D. Graff-Radford, et al. (2000). "No association between TAU haplotype and Alzheimer's disease in population or clinic based series or in familial disease." Neurosci Lett 285(2): 147-9.
We and others have previously identified two distinct haplotypes of the TAU gene in Caucasian populations. In this study, we have assessed whether these haplotypes show an association with Alzheimer's disease in a variety of populations. They do not. These data are consistent with the view that the involvement of TAU in Alzheimer's disease is a downstream event.

Barghorn, S., Q. Zheng-Fischhofer, et al. (2000). "Structure, microtubule interactions, and paired helical filament aggregation by tau mutants of frontotemporal dementias." Biochemistry 39(38): 11714-21.
We have studied biochemical and structural parameters of several missense and deletion mutants of tau protein (G272V, N279K, DeltaK280, P301L, V337M, R406W) found in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). The mutant proteins were expressed on the basis of both full-length tau (htau40) and constructs derived from the repeat domain. They were analyzed with respect to the capacity to enhance microtubule assembly, binding of tau to microtubules, secondary structure content, and aggregation into Alzheimer-like paired helical or straight filaments. We find that the mutations cause a moderate decrease in microtubule interactions and stabilization, and they show no gross structural changes compared with the natively unfolded conformation of the wild-type protein, but the aggregation into PHFs is strongly enhanced, particularly for the mutants DeltaK280 and P301L. This gain of pathological aggregation would be consistent with the autosomal dominant nature of the disease.

Bennecib, M., C. X. Gong, et al. (2000). "Role of protein phosphatase-2A and -1 in the regulation of GSK-3, cdk5 and cdc2 and the phosphorylation of tau in rat forebrain." FEBS Lett 485(1): 87-93.
In Alzheimer disease brain the activities of protein phosphatase (PP)-2A and PP-1 are decreased and the microtubule-associated protein tau is abnormally hyperphosphorylated at several sites at serine/threonine. Employing rat forebrain slices kept metabolically active in oxygenated artificial CSF as a model system, we investigated the role of PP-2A/PP-1 in the regulation of some of the major abnormally hyperphosphorylated sites of tau and the protein kinases involved. Treatment of the brain slices with 1.0 microM okadaic acid inhibited approximately 65% of PP-2A and produced hyperphosphorylation of tau at Ser 198/199/202, Ser 396/404 and Ser 422. No significant changes in the activities of glycogen synthase kinase-3 (GSK-3) and cyclin dependent protein kinases cdk5 and cdc2 were observed. Calyculin A (0.1 microM) inhibited approximately 50% PP-1, approximately 20% PP-2A, 50% GSK-3 and approximately 30% cdk5 but neither inhibited the activity of cyclin AMP dependent protein kinase A (PKA) nor resulted in the hyperphosphorylation of tau at any of the above sites. Treatment of brain slices with 1 microM okadaic acid plus 0.1 microM calyculin A inhibited approximately 100% of both PP-2A and PP-1, approximately 80% of GSK-3, approximately 50% of cdk5 and approximately 30% of cdc2 but neither inhibited PKA nor resulted in the hyperphosphorylation of tau at any of the above sites. These studies suggest (i) that PP-1 upregulates the phosphorylation of tau at Ser 198/199/202 and Ser 396/404 indirectly by regulating the activities of GSK-3, cdk5 and cdc2 whereas PP-2A regulates the phosphorylation of tau directly by dephosphorylation at the above sites, and (ii) that a decrease in the PP-2A activity leads to abnormal hyperphosphorylation of tau at Ser 198/199/202, Ser 396/404 and Ser 422.

Bi, X., T. S. Haque, et al. (2000). "Novel cathepsin D inhibitors block the formation of hyperphosphorylated tau fragments in hippocampus." J Neurochem 74(4): 1469-77.
Lysosomal disturbances may be a contributing factor to Alzheimer's disease. We used novel compounds to test if suppression of the lysosomal protease cathepsin D blocks production of known precursors to neurofibrillary tangles. Partial lysosomal dysfunction was induced in cultured hippocampal slices with a selective inhibitor of cathepsins B and L. This led within 48 h to hyperphosphorylated tau protein fragments recognized by antibodies against human tangles. Potent nonpeptidic cathepsin D inhibitors developed using combinatorial chemistry and structure-based design blocked production of the fragments in a dose-dependent fashion. Threshold was in the submicromolar range, with higher concentrations producing complete suppression. The effects were selective and not accompanied by pathophysiology. Comparable results were obtained with three structurally distinct inhibitors. These results support the hypothesis that cathepsin D links lysosomal dysfunction to the etiology of Alzheimer's disease and suggest a new approach to treating the disease.

Bornemann, K. D. and M. Staufenbiel (2000). "Transgenic mouse models of Alzheimer's disease." Ann N Y Acad Sci 908: 260-6.
Alzheimer's disease (AD) pathology is characterized by A beta peptide-containing plaques, neurofibrillary tangles consisting of hyperphosphorylated tau, extensive neuritic degeneration, and distinct neuron loss. We generated several transgenic mouse lines expressing the human amyloid precursor protein (APP751) containing the AD-linked KM670/671NL double mutation (Swedish mutation) under the control of a neuron-specific Thy-1 promoter fragment. In the best APP-expressing line (APP23), compact A beta deposits can be detected at 6 months of age. These plaques dramatically increase with age, are mostly Congo Red positive, and accumulate typical plaque-associated proteins such as heparansulfate proteoglycan and apolipoprotein E. Activated astrocytes and microglia indicative of inflammatory processes reminiscent of AD accumulate around the deposits. Furthermore, plaques are surrounded by enlarged dystrophic neurites as visualized by neurofilament or Holmes-Luxol staining. Strong staining for acetylcholinesterase activity is found throughout the plaques and is accompanied by local distortion of the cholinergic fiber network. All congophilic plaques contain hyperphosphorylated tau reminiscent of early tau pathology. Modern stereologic methods demonstrate a significant loss of neurons in the hippocampal CA1 region, correlating with an increasing A beta plaque load. Interestingly, APP23 mice develop cerebral amyloid angiopathy in addition to amyloid plaques even though the APP transgene is only expressed in neurons. Crossbreeding of APP23 mice with transgenic mice carrying AD-linked presenilin mutations but not wild-type presenilin resulted in enhanced formation of pathology. In conclusion, our APP transgenic mice present many pathologic features, similar to those observed in AD and therefore offer excellent tools for studying the contribution of A beta to AD pathogenesis.

Boss, M. A. (2000). "Diagnostic approaches to Alzheimer's disease." Biochim Biophys Acta 1502(1): 188-200.
The importance of obtaining an accurate and early diagnosis for Alzheimer's disease is now becoming recognized. Nonpharmacological as well as pharmacological therapies can be best initiated once a diagnosis is obtained. Biochemical markers to identify Alzheimer's disease have been sought for many years, with many candidates proposed. Recently criteria were established to evaluate putative diagnostic tests. Several biomarkers now show utility in identifying those with Alzheimer's disease. The ApoE e4 allele, while a risk factor rather than a deterministic gene, in the context of an individual with suspicion of AD has a positive predictive value of 94-98% and may come to have utility in predicting response to certain classes of pharmacological agents. Independent groups have shown that the markers in cerebrospinal fluid tau and Ab42 are, respectively, elevated and reduced in patients with AD versus other patient groups and that the lumbar puncture itself is usually well tolerated. For early-onset AD, sequencing presenilin 1 has come into use and the positive frequency is similar to that found in other genetic-based laboratory tests.

Botez, G., C. Schultz, et al. (2000). "[Clinical aspects of "argyrophilic grain disease"]." Nervenarzt 71(1): 38-43.
Argyrophilic grain disease (AGD) is a frequently occurring degenerative illness of the aging human brain. It is accompanied by progressive pathological alterations of the cytsokeleton which are traceable to an abnormal phosphorylation of the microtubule associated tau protein. Histologically, it is possible with the help of suitable staining techniques to identify pathognomonic spindle-shaped cellular inclusions (argyrophilic grains). These cellular inclusions display a typical cortical as well as subcortical distribution pattern. The goal of the present study is the retrospective evaluation of the clinical findings from 53 individuals with neuropathologically demonstrable AGD-related changes of the brain. Nearly one-half of the cases (49%) was classifiable as demented in accordance with DSM IV-criteria. Moreover, the frequency of the dementia increased significantly in relation to the growing severity of the AGD-associated pathological cytoskeletal degeneration. These results confirm the assumption that AGD can cause degenerative changes ranging from cognitive impairment all the way to dementia. They also underscore the necessity of further prospective studies pertaining to the clinical aspects of this still enigmatic disease.

Broccolini, A., W. K. Engel, et al. (2000). "Paired helical filaments of inclusion-body myositis muscle contain RNA and survival motor neuron protein." Am J Pathol 156(4): 1151-5.
Sporadic inclusion-body myositis (s-IBM) is the most common progressive muscle disease of older persons. Pathologically, the muscle biopsy manifests various degrees of inflammation and specific vacuolar degeneration of muscle fibers characterized by paired helical filaments (PHFs) composed of phosphorylated tau. IBM vacuolated fibers also contain accumulations of several other Alzheimer-characteristic proteins. Molecular mechanisms leading to formation of the PHFs and accumulations of proteins in IBM muscle are not known. We report that the abnormal muscle fibers of IBM contained (i) acridine-orange-positive RNA inclusions that colocalized with the immunoreactivity of phosphorylated tau and (ii) survival motor neuron protein immunoreactive inclusions, which by immuno-electron microscopy were confined to paired helical filaments. This study demonstrates two novel components of the IBM paired helical filaments, which may lead to better understanding of their pathogenesis.

Buee, L., T. Bussiere, et al. (2000). "Tau protein isoforms, phosphorylation and role in neurodegenerative disorders." Brain Res Brain Res Rev 33(1): 95-130.
Tau proteins belong to the family of microtubule-associated proteins. They are mainly expressed in neurons where they play an important role in the assembly of tubulin monomers into microtubules to constitute the neuronal microtubules network. Microtubules are involved in maintaining the cell shape and serve as tracks for axonal transport. Tau proteins also establish some links between microtubules and other cytoskeletal elements or proteins. Tau proteins are translated from a single gene located on chromosome 17. Their expression is developmentally regulated by an alternative splicing mechanism and six different isoforms exist in the human adult brain. Tau proteins are the major constituents of intraneuronal and glial fibrillar lesions described in Alzheimer's disease and numerous neurodegenerative disorders referred to as 'tauopathies'. Molecular analysis has revealed that an abnormal phosphorylation might be one of the important events in the process leading to their aggregation. Moreover, a specific set of pathological tau proteins exhibiting a typical biochemical pattern, and a different regional and laminar distribution could characterize each of these disorders. Finally, a direct correlation has been established between the progressive involvement of the neocortical areas and the increasing severity of dementia, suggesting that pathological tau proteins are reliable marker of the neurodegenerative process. The recent discovery of tau gene mutations in frontotemporal dementia with parkinsonism linked to chromosome 17 has reinforced the predominant role attributed to tau proteins in the pathogenesis of neurodegenerative disorders, and underlined the fact that distinct sets of tau isoforms expressed in different neuronal populations could lead to different pathologies.

Bullido, M. J., J. Aldudo, et al. (2000). "A polymorphism in the tau gene associated with risk for Alzheimer's disease." Neurosci Lett 278(1-2): 49-52.
Searching for tau genetic variations which could be associated with risk for Alzheimer's disease (AD), we have performed a mutational analysis of a region containing the whole exon 11 of the tau gene, which encodes a microtubule binding region critical for tau self-assembly, and we have found a biallelic polymorphism at position +34 of intron 11 (IVS11 + 34G/A). We have analyzed the allelic frequencies of this polymorphism in a case-control sample (167 clinically diagnosed AD and 194 controls) and found that the presence of any G allele (genotypes AG + GG) is associated with a five-fold AD risk in individuals carrying the apolipoprotein E4 allele, strongly suggesting that the combined effect of tau and apoE is relevant in relation with AD pathogenesis.

Capsoni, S., G. Ugolini, et al. (2000). "Alzheimer-like neurodegeneration in aged antinerve growth factor transgenic mice." Proc Natl Acad Sci U S A 97(12): 6826-31.
Neurotrophin nerve growth factor (NGF) has been suggested to be involved in age-related neurodegenerative diseases, but no transgenic model is currently available to study this concept. We have obtained transgenic mice expressing a neutralizing anti-NGF recombinant antibody, in which the levels of antibodies are three orders of magnitude higher in adult than in newborn mice [F.R., S. C. , A.C., E. Di Daniel, J. Franzot, S. Gonfloni, G. Rossi, N. B. & A. C. (2000) J. Neurosci., 20, 2589-2601]. In this paper, we analyze the phenotype of aged anti-NGF transgenic mice and demonstrate that these mice acquire an age-dependent neurodegenerative pathology including amyloid plaques, insoluble and hyperphosphorylated tau, and neurofibrillary tangles in cortical and hippocampal neurons. Aged anti-NGF mice also display extensive neuronal loss throughout the cortex, cholinergic deficit in the basal forebrain, and behavioral deficits. The overall picture is strikingly reminiscent of human Alzheimer's disease. Aged anti-NGF mice represent, to our knowledge, the most comprehensive animal model for this severe neurodegenerative disease. Also, these results demonstrate that, in mice, a deficit in the signaling and/or transport of NGF leads to neurodegeneration.

Celsis, P. (2000). "Age-related cognitive decline, mild cognitive impairment or preclinical Alzheimer's disease?" Ann Med 32(1): 6-14.
With the promising development of effective treatment, significant improvement in the very early diagnosis of Alzheimer's disease (AD) is required. There is vast agreement that a decline in memory, especially in verbal episodic memory, is the earliest and perhaps the most sensitive sign of incipient AD at the preclinical stage. However, this review offers evidence that impairment in episodic memory can be observed in normal elderly people as well as in aged subjects with mild cognitive impairment (MCI), a large proportion of whom will, however, not convert to dementia. Quantitative measurement of atrophy and brain activation in the hippocampal-parahippocampal formation by using structural and functional magnetic resonance imaging may help to distinguish the MCI decliners from the nondecliners. Cerebrospinal fluid levels of tau protein and Abet1-42 peptide, together with the presence of an apolipoprotein (apo)E epsilon4 allele may also increase our confidence in the early positive diagnosis of AD. This review concludes, however, that while adequate for constituting groups of patients in a research perspective, the extensive diagnostic procedure based on specific cognitive testing, neuroimaging and biological investigations is still out of reach for the practitioner.

Chambers, C. B., E. M. Sigurdsson, et al. (2000). "Amyloid-beta injection in rat amygdala alters tau protein but not mRNA expression." Exp Neurol 162(1): 158-70.
Previously we demonstrated local and distant changes in tau protein immunoreactivity reminiscent of those seen in Alzheimer's disease (AD) following a unilateral injection of amyloid-beta (Abeta)(25-35) into the rat amygdala. To explore the relevance of these findings to AD, we compared the effects of Abeta(1-42) to those of Abeta(25-35). Injections of both Abeta(1-42) and Abeta(25-35) into rat amygdala resulted in increased tau-2 immunolabeling in neurons. To determine whether these alterations were due to changes in the expression of tau, we measured tau protein expression by Western blotting and tau mRNA isoform expression by the reverse transcription-polymerase chain reaction in the amygdala, hippocampus, and cerebellum following a unilateral injection of Abeta(25-35) or vehicle into the amygdala. The levels of tau proteins were increased bilaterally in the amygdala of Abeta(25-35)- compared to vehicle-treated animals 8 and 16 days following treatment. The molecular weights of tau proteins were decreased in the Abeta(25-35)-treated (59-69 kDa) compared to the vehicle-treated (67-72 kDa) animals 8 days following treatment. There were no changes in tau mRNA expression in any brain region examined. In this model, just as in AD, there is an increase in tau protein levels without a change in tau mRNA expression, suggesting that Abeta peptides may influence tau protein stability in both the rat and the human brain.

Chen, C. P., S. L. Eastwood, et al. (2000). "Immunocytochemical study of the dorsal and median raphe nuclei in patients with Alzheimer's disease prospectively assessed for behavioural changes." Neuropathol Appl Neurobiol 26(4): 347-55.
The dorsal and median raphe nuclei were examined with immunocytochemistry to display the 5-HT neurones in 16 cases of post-mortem-proven Alzheimer's disease (AD) and 12 age and sex-matched controls. The AD cases had been prospectively assessed during life for expression of behavioural changes as well as for cognitive decline. A significant (P < 0.001) 41% reduction in density of dorsal raphe neurones was found along with a significant (P < 0.02) 29% reduction in density of median raphe neurones in AD. There were significantly more neurofibrillary tangles in both dorsal and median raphe nuclei in AD than in controls (P < 0.001). There was no correlation between reduction in neurone density in these nuclei and behavioural change, cognitive decline, neurofibrillary tangle counts in these nuclei or plaque and tangle pathology in frontal and temporal cortex. It was concluded from these findings that the raphe nuclei are significantly affected by the pathology of AD and that plasticity in the 5-HT system is the probable reason for the lack of correlation of reduced 5-HT neurone density and clinical disease parameters.

Cheng, L. Y., J. Z. Wang, et al. (2000). "Multiple forms of phosphatase from human brain: isolation and partial characterization of affi-gel blue binding phosphatases." Neurochem Res 25(1): 107-20.
Implication of protein phosphatases in Alzheimer disease led us to a systemic investigation of the identification of these enzyme activities in human brain. Human brain phosphatases eluted from DEAE-Sephacel with 0.22 M NaCl were resolved into two main groups by affi-gel blue chromatography, namely affi-gel blue-binding phosphatases and affi-gel blue-nonbinding phosphatases. Affi-gel blue-binding phosphatases were further separated into four different phosphatases, designated P1, P2, P3, and P4 by calmodulin-Sepharose 4B and poly-(L-lysine)-agarose chromatographies. These four phosphatases exhibited activities towards nonprotein phosphoester and two of them, P1 and P4, could dephosphorylate phosphoproteins. The activities of the four phosphatases differed in pH optimum, divalent metal ion requirements, sensitivities to various inhibitors and substrate affinities. The apparent molecular masses as estimated by gel-filtration for P1, P2, P3, and P4 were 97, 45, 42, and 125 kDa, respectively. P1 is markedly similar to PP2B from bovine brain and rabbit skeletal muscle. P4 was labeled with anti-PP2A antibody and may represent a new subtype of PP2A. P1 and P4 were also effective in dephosphorylating Alzheimer disease abnormally hyperphosphorylated tau (AD P-tau). The resulting dephosphorylated AD P-tau had its activity restored in promoting assembly of microtubules in vitro. These results suggest that P1 and P4 might be involved in the regulation of phosphorylation of tau in human brain, especially in neurodegenerative conditions like Alzheimer's disease which are characterized by the abnormal hyperphosphorylation of this protein.

Chin, J. Y., R. B. Knowles, et al. (2000). "Microtubule-affinity regulating kinase (MARK) is tightly associated with neurofibrillary tangles in Alzheimer brain: a fluorescence resonance energy transfer study." J Neuropathol Exp Neurol 59(11): 966-71.
Paired helical filaments, the main structural components of the neurofibrillary tangles in Alzheimer disease, consist of phosphorylated tau protein. Because the levels and degree of phosphorylation are significantly higher in paired helical filament (PHF)-derived tau than in normal adult tau, and because phosphorylation of tau severely disrupts microtubule stability, it is postulated that tau phosphorylation is an important step in PHF formation. The kinases and/or phosphatases that act in vivo to help induce such a pathological state of tau, however, are not yet known. In this study we implicate the non-proline directed kinase MARK in PHF-tau phosphorylation, by virtue of its close intermolecular association with the phosphorylated Ser262 epitope on PHF-tau as assessed by fluorescence resonance energy transfer. Moreover, because this tight enzyme-substrate association is observed in neurofibrillary tangles in Alzheimer tissue, we suggest that PHF-tau phosphorylation may occur to some extent on assembled PHF filaments.

Colle, M. A., J. J. Hauw, et al. (2000). "Vascular and parenchymal Abeta deposition in the aging dog: correlation with behavior." Neurobiol Aging 21(5): 695-704.
The behavior of 25 dogs was indirectly assessed by a formal questionnaire (evaluation of Age-Related Cognitive and Affective Disorders-ARCAD), filled out by the owner. The density of diffuse and vascular deposits was evaluated using four anti-Abeta peptide antibodies, in four temporal areas. Parenchymal, diffuse deposits of Abeta42 peptide were found in all aged animals but one. They were Congo red negative and were not immunostained by the anti-Abeta40 antibody, contrary to the vascular deposits. The densities of vascular and parenchymal deposits were not correlated. The ARCAD score was correlated with age, density of Abeta parenchymal and vascular deposits, and with the number of areas containing deposits (extension index). Multivariate analysis showed that the age and the extension index explained most of the variance. Congo red positivity (indicating that the Abeta peptide has the characteristics of an amyloid substance) is limited in the dog to the vascular wall and is associated, as in man, with the deposition of the Abeta 1-40 isoform. Parenchymal Abeta deposition seems to be a common correlate of behavioral problems in aging dogs.

Colle, M. A., C. Duyckaerts, et al. (2000). "Laminar specific loss of isocortical presenilin 1 immunoreactivity in Alzheimer's disease. Correlations with the amyloid load and the density of tau-positive neurofibrillary tangles." Neuropathol Appl Neurobiol 26(2): 117-23.
Presenilin 1 has been shown to be mutated in a high proportion of cases of familial Alzheimer's disease. Immunoreactive epitopes of the protein have been found mainly in neurones devoid of neurofibrillary tangles - an observation that has led to the conclusion that presenilin 1 could have a protective role. In this study, the relationship between deposits of Abeta peptide (both the 40 and 42 isoforms), tau positive neurofibrillary tangles and presenilin 1-positive neuronal profiles were analysed in three cases of presenilin 1 mutation, four cases of sporadic Alzheimer's disease and five controls. Immunohistochemistry was performed in a sample from the supramarginal gyrus. The proportion of volume occupied by the Abeta1-40 and Abeta1-42 deposits (amyloid load) was evaluated by a point-counting technique. Tau-positive neurofibrillary tangles, and presenilin 1-positive neuronal profiles were directly counted. The location of the lesions in the thickness of the cortex was recorded. The density of PS1-positive neuronal profiles in Alzheimer's disease cases was lower than in the controls. The deficit was significant only in the upper layers of the cortex. The density of presenilin 1 neuronal profiles was negatively correlated with Abeta1-40 and Abeta1-42 loads, and with the density of tau-positive neurofibrillary tangles. Multivariate analysis showed that the Abeta1-42 load was the best determinant of the decrease in presenilin 1-positive neuronal profiles. Presenilin 1-positive neurones appear to be lost rather than protected in the course of Alzheimer disease.

Couderc, R. (2000). "[Search of biological markers of Alzheimer's disease]." Ann Biol Clin (Paris) 58(5): 581-93.
Peripheral markers for Alzheimer's disease are of interest to confirm the diagnosis, to perform epidemiological screening, to identify distinct groups of patients, to predict the outcome of the disease, to monitor its progression and its sensibility to treatment and to give help in performing studies on the relationship between brain and behaviour and on the pathophysiology of the Alzheimer's disease. The ideal biomarker for Alzheimer's disease should detect a fundamental feature of neuropathology and be validated in neuropathologically confirmed cases and be confirmed by at least two independent studies; should be as sensitive and specific than the clinical diagnosis (about 85% and 80%), reliable, reproducible, simple to perform, inexpensive and non invasive (studies on blood, urine, saliva, or buccal scrapings) or moderately invasive (skin, rectal biopsies, bone marrow samples, or cerebrospinal fluid). Such a marker has not yet been found. In this paper we present those markers which come closest to fulfilling criteria for a useful biomarker, keeping in mind that these criteria depends on what purpose it is used (screening, prediction, diagnosis, monitoring, pathophysiological studies.) and that the finding of a good marker depends on the understanding of the disease.

Crowther, R. A. and M. Goedert (2000). "Abnormal tau-containing filaments in neurodegenerative diseases." J Struct Biol 130(2-3): 271-9.
It has been known for some time that the neurofibrillary pathology in Alzheimer's disease consists of so-called paired helical and straight filaments made up of the microtubule-associated protein tau. The degree of dementia observed in the disease correlates better with the extent of neurofibrillary pathology than with the Abeta amyloid deposits, the other characteristic defining pathological fibrous deposit in Alzheimer's disease. However, no familial cases of Alzheimer's disease have been genetically linked to the tau protein locus. Recently a group of frontotemporal dementias with parkinsonism linked to chromosome 17 has been shown to be caused by mutations in the tau gene. Some are missense mutations giving altered tau proteins, whereas others affect the splicing of the pre-mRNA and change the balance between different tau isoforms. Histologically these diseases are all characterised by various kinds of filamentous tau protein deposits, mostly in the complete absence of Abeta deposits. The abnormal tau filaments show different morphologies, depending on the nature of the tau mutation. These diseases show that tau mutations can be a prime cause of inherited dementing illness and may throw some light on the pathological process in the much larger number of sporadic cases of Alzheimer's disease.

Cruz-Sanchez, F. F., N. Durany, et al. (2000). "Correlation between Apolipoprotein-E Polymorphism and Alzheimer's Disease Pathology." J Alzheimers Dis 2(3,4): 223-229.
Alzheimer's disease (AD) and small vessel disease dementia (SVDD) are common causes of dementia. The ApoE genotype has been proposed as a risk factor for AD. The frequency of the three ApoE alleles was correlated with the neuropathological changes of AD (senile plaques, neurofibrillary tangles and amyloid angiopathy) and SVDD (status lacunaris, status cribosus, leucoencephalopathy, micronecrosis and vascular fibrohyalinosis) in order to validate previous ApoE genotyping results in AD and to identify pre-clinical AD. Representative cerebral regions (cortex, gyrus cinguli, putamen, hippocampus, white matter) from 28 AD cases, 7 SVDD and 38 non-neurological controls were studied using classical histological techniques and immunohistochemistry for tau protein and amyloid-b. The frequency of the ApoE allele 4 was significantly increased not only in AD patients but also in aged controls. However, following a detailed histopathological examination was found 62% of this group to exhibit histological changes associated with AD in limited brain areas (entorhinal region, hippocampus and adjacent temporal cortex or entorhinal region and hippocampus, or only in the entorhinal region), but 87% of these cases were found to be ApoE4 positive. The significant differences found in the distribution of ApoE allele frequencies were more marked when these cases were excluded from the control group and included as AD cases. In contrast, the frequency of the ApoE allele 2 is significantly increased in SVDD patients. Using histological techniques we confirmed the clinical diagnoses of all cases and classified the AD patients according to the severity of cortical pathology related to AD, while re-grouping from the control group those cases which had no clinical history of the disease but exhibited typical AD and SVDD histological lessions which could be considered as "pre-clinical" forms of these diseases.

Daly, N. L., R. Hoffmann, et al. (2000). "Role of phosphorylation in the conformation of tau peptides implicated in Alzheimer's disease." Biochemistry 39(30): 9039-46.
A series of peptides corresponding to isolated regions of Tau (tau) protein have been synthesized and their conformations determined by (1)H NMR spectroscopy. Immunodominant peptides corresponding to tau(224-240) and a bisphosphorylated derivative in which a single Thr and a single Ser are phosphorylated at positions 231 and 235 respectively, and which are recognized by an Alzheimer's disease-specific monoclonal antibody, were the main focus of the study. The nonphosphorylated peptide adopts essentially a random coil conformation in aqueous solution, but becomes slightly more ordered into beta-type structure as the hydrophobicity of the solvent is increased by adding up to 50% trifluoroethanol (TFE). Similar trends are observed for the bisphosphorylated peptide, with a somewhat stronger tendency to form an extended structure. There is tentative NMR evidence for a small population of species containing a turn at residues 229-231 in the phosphorylated peptide, and this is strongly supported by CD spectroscopy. A proposal that the selection of a bioactive conformation from a disordered solution ensemble may be an important step (in either tubulin binding or in the formation of PHF) is supported by kinetic data on Pro isomerization. A recent study showed that Thr231 phosphorylation affected the rate of prolyl isomerization and abolished tubulin binding. This binding was restored by the action of the prolyl isomerase Pin1. In the current study, we find evidence for the existence of both trans and cis forms of tau peptides in solution but no difference in the equilibrium distribution of cis-trans isomers upon phosphorylation. Increasing hydrophobicity decreases the prevalence of cis forms and increases the major trans conformation of each of the prolines present in these molecules. We also synthesized mutant peptides containing Tyr substitutions preceding the Pro residues and found that phosphorylation of Tyr appears to have an effect on the equilibrium ratio of cis-trans isomerization and decreases the cis content.

Davies, P. (2000). "A very incomplete comprehensive theory of Alzheimer's disease." Ann N Y Acad Sci 924: 8-16.
For this meeting, I was asked to put down some ideas toward the development of theories of the etiology and pathogenesis of Alzheimer's disease. This charge has led to a first attempt to consider the "big picture," at least as seen from my viewpoint. Many details of the schemes I propose could be discussed in much greater depth, but I have tried to avoid getting bogged down in this way. It is sometimes valuable to step back from our own little domains of research and to attempt to integrate what we have collectively discovered into a more comprehensive framework.

De Ferrari, G. V. and N. C. Inestrosa (2000). "Wnt signaling function in Alzheimer's disease." Brain Res Brain Res Rev 33(1): 1-12.
Alzheimer's disease (AD) is a neurodegenerative disease with progressive dementia accompanied by three main structural changes in the brain: diffuse loss of neurons; intracellular protein deposits termed neurofibrillary tangles (NFT) and extracellular protein deposits termed amyloid or senile plaques, surrounded by dystrophic neurites. Two major hypotheses have been proposed in order to explain the molecular hallmarks of the disease: The 'amyloid cascade' hypothesis and the 'neuronal cytoskeletal degeneration' hypothesis. While the former is supported by genetic studies of the early-onset familial forms of AD (FAD), the latter revolves around the observation in vivo that cytoskeletal changes - including the abnormal phosphorylation state of the microtubule associated protein tau - may precede the deposition of senile plaques. Recent studies have suggested that the trafficking process of membrane associated proteins is modulated by the FAD-linked presenilin (PS) proteins, and that amyloid beta-peptide deposition may be initiated intracellularly, through the secretory pathway. Current hypotheses concerning presenilin function are based upon its cellular localization and its putative interaction as macromolecular complexes with the cell-adhesion/signaling beta-catenin molecule and the glycogen synthase kinase 3beta (GSK-3beta) enzyme. Developmental studies have shown that PS proteins function as components in the Notch signal transduction cascade and that beta-catenin and GSK-3beta are transducers of the Wnt signaling pathway. Both pathways are thought to have an important role in brain development, and they have been connected through Dishevelled (Dvl) protein, a known transducer of the Wnt pathway. In addition to a review of the current state of research on the subject, we present a cell signaling model in which a sustained loss of function of Wnt signaling components would trigger a series of misrecognition events, determining the onset and development of AD.

De La Monte, S. M., N. Ganju, et al. (2000). "Oxygen Free Radical Injury Is Sufficient to Cause Some Alzheimer-Type Molecular Abnormalities in Human CNS Neuronal Cells." J Alzheimers Dis 2(3,4): 261-281.
Cell loss and neuritic/cytoskeletal lesions represent two of the major categories of dementia-associated structural abnormalities in Alzheimer's disease (AD). Cell loss is ultimately mediated by apoptosis and mitochondrial DNA damage due to enhanced sensitivity to oxidative stress, but the mechanism responsible for the neuritic/cytoskeletal lesions including the abnormal proliferation of cortical neurites is not known. This study examines the potential role of oxygen free radical injury as a factor contributing to both cell death and neuritic sprouting cascades in AD. PNET2 human neuronal cells were treated with H2O2 (8 micro M to 88 micro M) for 24 hours and then analyzed for viability, DNA damage, and pro-apoptosis, survival, and sprouting gene expression and signaling. H2O2-treatment resulted in dose-dependent increases in cell death due to genomic and mitochondrial DNA damage associated with increased levels of 8-OHdG and the p53 and CD95 pro-apoptosis genes, reduced levels of the Bcl-2 survival gene, activation of JNK and p38 stress kinases, and inhibition of PI3 kinase survival signaling. However, the H2O2-treated cells also manifested increased expression of growth and sprouting molecules, including GAP-43, nitric oxide synthase 3, neuronal thread protein (NTP; ~17 kD and ~21 kD forms), proliferating cell nuclear antigen, and phospho-Erk MAPK, and normal levels of the AD-associated ~41 kD NTP species, cyclin dependent kinase 5 (cdk-5), and phospho-tau. In addition, the H2O2-treated cells had increased levels of p25, the catalytically active and stable cleavage product of p35, which regulates cdk-5 activity. Previous studies demonstrated p25 accumulation in AD brains and p25-induced hyperphosphorylation of tau and neuronal apoptosis. The findings herein suggest that oxygen free radical injury in human CNS neuronal cells is sufficient to cause some but not all of the pro-death and pro-sprouting molecular abnormalities that occur in AD.

Delacourte, A. and L. Buee (2000). "Tau pathology: a marker of neurodegenerative disorders." Curr Opin Neurol 13(4): 371-6.
Tau is not only a basic component of neurofibrillary degeneration, but is also an aetiological factor, as demonstrated by mutations on the tau gene responsible for frontotemporal dementias with parkinsonism linked to chromosome 17. Polymorphisms on the tau gene and the hierarchical invasion of neocortical areas by tau pathology in numerous sporadic neurodegenerative diseases also suggest that tau pathology is a primary pathogenic event in non-familial dementing diseases and a lead for solid diagnostic and therapeutic approaches.

Dewachter, I., J. van Dorpe, et al. (2000). "Modeling Alzheimer's disease in transgenic mice: effect of age and of presenilin1 on amyloid biochemistry and pathology in APP/London mice." Exp Gerontol 35(6-7): 831-41.
In transgenic mice that overexpress mutant Amyloid Precursor Protein [V717I], or APP/London (APP/Lo) (1999a. Early phenotypic changes in transgenic mice that overexpress different mutants of Amyloid Precursor Protein in brain. J. Biol. Chem. 274, 6483-6492; 1999b. Premature death in transgenic mice that overexpress mutant Amyloid precursor protein is preceded by severe neurodegeneration and apoptosis. Neuroscience 91, 819-830) the AD related phenotype of plaque and vascular amyloid pathology is late (12-15 months). This typical and diagnostic pathology is thereby dissociated in time from early symptoms (3-9 months) that include disturbed behavior, neophobia, aggression, glutamate excitotoxicity, defective cognition and decreased LTP. The APP/Lo transgenic mice are therefore a very interesting model to study early as well as late pathology, including the effect of age. In ageing APP*Lo mice, brain soluble and especially "insoluble" amyloid peptides dramatically increased, while normalized levels of secreted APPsalpha and APPsbeta, as well as cell-bound beta-C-stubs, remained remarkably constant, indicating normal alpha- and beta-secretase processing of APP. In double transgenic mice, i.e. APP/LoxPS1, clinical mutant PS1[A246E] but not wild-type human PS1 increased Abeta, and plaques and vascular amyloid developed at age 6-9 months. The PS1 mutant caused increasing Abeta42 production, while ageing did not. Amyloid deposits are thus formed, not by overproduction of Abeta, but by lack of clearance and/or degradation in the brain of ageing APP/Lo transgenic mice. The clearance pathways of the cerebral amyloid peptides are therefore valuable targets for fundamental research and for therapeutic potential. Although hyper-phosphorylated protein tau was evident in swollen neurites around the amyloid plaques, neurofibrillary pathology is not observed and the "tangle" aspect of AD pathology is therefore still missing from all current transgenic "amyloid" models. Also the "ApoE4" risk for late onset AD remains a problem for modeling in transgenic mice. We have generated transgenic mice that overexpress human ApoE4 (2000. Expression of Human Apolipoprotein E4 in neurons causes hyperphosphorylation of Protein tau in the brains of transgenic mice. Am. J. Pathol. 156 (3) 951-964) or human protein tau (1999. Prominent axonopathy in the brain and spinal cord of transgenic mice overexpressing four-repeat human tau protein. Am. J. Pathol. 155, 2153-2165) in their neurons. Both develop a similar although not identical axonopathy, with progressive degeneration of nerves and with muscle wasting resulting in motoric problems. Remarkably, ApoE4 transgenic mice are, like the tau transgenic mice, characterized by progressive hyper-phosphorylation of protein tau also in motor neurons which explains the motoric defects. Further crossing with the APP/Lo transgenic mice is ongoing to yield "multiple" transgenic mouse strains to study new aspects of amyloid and tau pathology.

Diamandis, E. P., G. M. Yousef, et al. (2000). "Human kallikrein 6 as a biomarker of alzheimer's disease." Clin Biochem 33(8): 663-7.
OBJECTIVES: Alzheimer's disease (AD) is a major cause of dementia in the elderly. It is generally difficult to diagnose accurately early AD. A few biomarkers, including tau protein and amyloid beta-42, are now used as aids for diagnosis and monitoring of AD. Our aim was to examine the possible use of cerebrospinal fluid, blood and tissue, and human kallikrein 6 (hK6) concentration as a marker of AD. METHODS: We have used a highly sensitive and specific immunofluorometric procedure for measuring hK6. We measured hK6 in tissue extracts from AD brain or normal individuals, in cerebrospinal fluids of AD patients or normals and in whole blood of AD patients and normals and compared the findings. We have used ten pairs of AD/normal controls in all cases. RESULTS: We found that hK6 concentration is tissue extracts from AD brain were approximately twofold lower than extracts from normal controls. Further, we found that cerebrospinal fluid hK6 concentration is approximately a threefold increase, in comparison to cerebrospinal fluid controls (p = 0.001). We have also found that the whole blood hK6 concentration in AD patients is about ten times higher than hK6 concentration in normal controls (p = 0.002). We have immunohistochemically localized the expression of hK6 in epithelial cells of the chorioid plexus. CONCLUSIONS: This is the first report describing significant elevations of cerebrospinal fluid and plasma and whole blood hK6 concentration in AD patients, in comparison to controls. These data suggest that hK6 may constitute a new biomarker for diagnosis and monitoring of AD.

Dore, S., S. Kar, et al. (2000). "Rediscovering good old friend IGF-I in the new millenium: possible usefulness in Alzheimer's disease and stroke." Pharm Acta Helv 74(2-3): 273-80.
Much research has been done over the past two decades on the role of insulin-like growth factors I and II (IGF) in the maintenance of normal body homeostasis, especially in regard to various endocrine functions, growth and aging. For example, IGF-I is a well established promoter of tissue growth and has been used in the clinics for the treatment of growth related disorders, even being abused by athletes to enhance performance in competitions. In contrast, comparatively limited attention has been given to the potential significance of the IGFs in the central nervous system. Over the past few years, we have studied the trophic as well as neuromodulatory roles of the IGFs in the brain. IGF-I and IGF-II are potent modulators of acetylcholine release, IGF-I inhibiting release while IGF-II is a potent stimulant. Moreover, only the internalization of the IGF-I receptor complex was blocked by an inhibitor of phosphotyrosylation. This is in accordance with the differential nature of the IGF-I and IGF-II receptors, the former being a tyrosine kinase receptor while the later is a single transmembrane domain protein bearing binding sites for 6-mannose phosphate containing residues. The activation of IGF-I receptors protected neurons against cell death induced by amyloidogenic derivatives likely by an intracellular mechanism distinct from those involved in the regulation of acetylcholine release and neuronal growth. The stimulation of IGF-I receptors can activate intracellular pathways implicating a PI3/Akt kinase and CREB phosphorylation or modulate the production of free radicals. The effects, particularly those of IGF-I on key markers of the Alzheimer's (AD) brains namely cholinergic dysfunction, neuronal amyloid toxicity, tau phosphorylation and glucose metabolism suggest the potential usefulness of this growth factor in the treatment of neurodegenerative diseases. However, the poor bioavailability, enzymatic stability and brain penetration of IGF-I hamper progress in this regard. The recent development of a small, non-peptidyl mimetic of insulin able to directly activate the insulin receptor [Zhang, B., Salituro, G., Szalkowski, D., Li, Z., Zhang, Y., Royo, I., Vilella, D., Diez, M.T., Pelaez, F., Ruby, C., Kendall, R.L., Mao, X., Griffin, P., Calaycay, J., Zierath, J.R., Heck, J. V., Smith, R.G., Moller, D.E., 1999. Science, 284, 974-977] suggests that a similar strategy could be used for IGF-I and the IGF-I receptor leading to the characterization of IGF-I mimics of potential clinical usefulness.

Drouet, B., M. Pincon-Raymond, et al. (2000). "Molecular basis of Alzheimer's disease." Cell Mol Life Sci 57(5): 705-15.
Despite an exponential production of data, Alzheimer's disease (AD) remains an enigma. Unresolved questions persist in the face of the heterogeneity of this neuropathology. Recent progress in understanding mechanisms for AD results from the study of amyloid precursor protein (APP) metabolism and the involvement of senile plaque-associated proteins. In addition to the amyloid cascade hypothesis, alternative schemes emerge, in which the amyloid peptide is not the primary effector of the disease. Perturbations of vesicular trafficking, the cytoskeletal network, and membrane cholesterol distribution could be central events. Furthermore, since the physiological role of APP, presenilins, and apolipoprotein E in the central nervous system are not completely understood, their involvement in AD etiology remains speculative. New actors have to be found to try to explain sporadic cases and non-elucidated familial cases.

Duff, K., H. Knight, et al. (2000). "Characterization of pathology in transgenic mice over-expressing human genomic and cDNA tau transgenes." Neurobiol Dis 7(2): 87-98.
To examine the normal cellular function of tau and its role in pathogenesis, we have created transgenic mice that overexpress a tau transgene derived from a human PAC that contains the coding sequence, intronic regions, and regulatory regions of the human gene. All six isoforms of human tau are represented in the transgenic mouse brain at the mRNA and protein level and the human tau is distributed in neurites and at synapses, but is absent from cell bodies. A comparison between the genomic tau mice and mice that overexpress a tau cDNA transgene shows that overall, the distribution of tau is similar in the two lines, but human tau is located in the somatodendritic compartment of many neurons in the cDNA mice. Tau-immunoreactive axonal swellings were found in the spinal cords of the cDNA mice, which correlated with a hind-limb abnormality, whereas neuropathology was essentially normal in the genomic mice up to 8 months of age.

Durany, N., R. Ravid, et al. (2000). "Increased frequency of the alpha-1-antichymotrypsin T allele in cerebral amyloid angiopathy." Neuropathology 20(3): 184-9.
Cerebral amyloid angiopathy (CAA) is a process of unknown etiology characterized by amyloid deposition in the wall of small cerebral and meningeal blood vessels. CAA is also a feature of Alzheimer's disease (AD) and of a subgroup of elderly people. Alpha-1-Antichymotrypsin (ACT) is a serum glycoprotein frequently associated with vascular and senile plaque amyloid. The ACT gene is known to have a bi-allele polymorphism that causes a simple amino acid substitution. In an attempt to clarify the possible role of ACT polymorphism in AD and in cases of CAA, the ACT genotype was investigated in AD, CAA, and intellectually intact controls. Representative brain areas (cerebral cortex, hippocampus, putamen, white matter, and gyrus cinguli) from all cases were studied using classical histologic staining techniques (hematoxylin-eosin (HE), Mallory's thrichromic or alkaline congo red stain), and immunohistochemistry for tau and beta-amyloid proteins. There was a significantly increased T allele and TT genotype frequency in the CAA group, but not in the AD group, suggesting a role for the ACT genotype in the development of vascular lesions. The presence of the apolipoprotein E4 allele (ApoE4) did not correlate with the ACT-A allele, as previously reported, and appeared to be independent of the risk for developing AD.

Eidenmuller, J., T. Fath, et al. (2000). "Structural and functional implications of tau hyperphosphorylation: information from phosphorylation-mimicking mutated tau proteins." Biochemistry 39(43): 13166-75.
Abnormal tau-immunoreactive filaments are a hallmark of tauopathies, including Alzheimer's disease (AD). A higher phosphorylation ("hyperphosphorylation") state of tau protein may represent a critical event. To determine the potential role of tau hyperphosphorylation in these disorders, mutated tau proteins were produced where serine/threonine residues known to be highly phosphorylated in tau filaments isolated from AD patients were substituted for glutamate to simulate a paired helical filament (PHF)-like tau hyperphosphorylation. We demonstrate that, like hyperphosphorylation, glutamate substitutions induce compact structure elements and SDS-resistant conformational domains in tau protein. Hyperphosphorylation-mimicking glutamate-mutated tau proteins display a complete functional loss in its ability to promote microtubule nucleation which can partially be overcome by addition of the osmolyte trimethylamine N-oxide (TMAO), which is similar to phosphorylated tau. In addition, glutamate-mutated tau proteins fail to interact with the dominant brain protein phosphatase 2A isoform ABalphaC, and exhibit a reduced ability to assemble into filaments. Interestingly, wild-type tau and phosphorylation-mimicking tau similarly bind to microtubules when added alone, but the mutated tau is almost completely displaced from the microtubule surface by equimolar concentrations of wild-type tau. The data indicate that glutamate-mutated tau proteins provide a useful model for analyzing the functional consequences of tau hyperphosphorylation. They suggest that several mechanisms contribute to the abnormal tau accumulation observed during tauopathies, in particular a selective displacement of hyperphosphorylated tau from microtubules, a functional loss in promoting microtubule nucleation, and a failure to interact with phosphatases.

Ekinci, F. J. and T. B. Shea (2000). "Phosphorylation of tau alters its association with the plasma membrane." Cell Mol Neurobiol 20(4): 497-508.
1. The potential functions of the microtubule-associated protein tau have been expanded by the recent demonstration of its interaction with the plasma membrane. Since the association of tau with microtubules is regulated by phosphorylation, herein we examine whether or not the association of tau with the plasma membrane is also regulated by phosphorylation. 2. A range of tau isoforms migrating from 46 to 64 kDa was associated with crude particulate fractions derived from SH-SY-5Y human neuroblastoma cells, and were retained during the initial stages of plasma membrane purification. During the extensive washing utilized in purification of the plasma membrane, portions of each of these isoforms were depleted from the resultant purified membrane. Immunoblot analysis with phospho-dependent and -independent antibodies revealed selective depletion of phospho isoforms during membrane washing. This effect was more pronounced for the slowest-migrating (64-kDa) tau isoform. 3. This putative influence of phosphorylation on the association of tau with the plasma membrane was further probed by transfection of SH-SY-5Y human neuroblastoma cells with a tau construct that could associate with the plasma membrane but not with microtubules. Treatment with phorbol ester or calcium ionophore, both of which increased phospho-tau levels within the cytosol and plasma membrane, was accompanied by the dissociation of this tau construct from the membrane. 4. These data indicate that phosphorylation regulates the association with the plasma membrane. Dissociation from the membrane by phosphorylation may place tau at risk for hyperphosphorylation and ultimate PHF formation in a manner previously considered for tau dissociated from microtubules.

Emmerling, M. R., M. C. Morganti-Kossmann, et al. (2000). "Traumatic brain injury elevates the Alzheimer's amyloid peptide A beta 42 in human CSF. A possible role for nerve cell injury." Ann N Y Acad Sci 903: 118-22.
The increased risk for Alzheimer's Disease (AD) associated with traumatic brain injury (TBI) suggests that environmental insults may influence the development of this age-related dementia. Recently, we have shown that the levels of the beta-amyloid peptide (A beta 1-42) increase in the cerebrospinal fluid (CSF) of patients after severe brain injury and remain elevated for some time after the initial event. The relationships of elevated A beta with markers of blood-brain barrier (BBB) disruption, inflammation, and nerve cell or axonal injury were evaluated in CSF samples taken daily from TBI patients. This analysis reveals that the rise in A beta 1-42 is best correlated with possible markers of neuronal or axonal injury, the cytoskeletal protein tau, neuron-specific enolase (NSE), and apolipoprotein E (ApoE). Similar or better correlations were observed between A beta 1-40 and the three aforementioned markers. These results imply that the degree of brain injury may play a decisive role in determining the levels of A beta 1-42 and A beta 1-40 in the CSF of TBI patients. Inflammation and alterations in BBB may play lesser, but nonetheless significant, roles in determining the A beta level in CSF after brain injury.

Esposito, G., P. Viglino, et al. (2000). "The solution structure of the C-terminal segment of tau protein." J Pept Sci 6(11): 550-9.
Pathological changes in the microtubule associated protein tau, leading to tau-containing filamentous lesions, are a major hallmark common to many types of human neurodegenerative diseases, including Alzheimer's disease (AD). No structural data are available which could rationalize the extensive conformational changes that occur when tau protein is converted to Alzheimer's paired helical filaments (PHF). The C-terminal portion of tau plays a crucial role in the aggregation of tau into PHF and in the truncation process that generates cytotoxic segments of tau. Therefore, we investigated the solution structure of the hydrophobic C-terminal segment 423-441 of tau protein (PQLATLADEVSASLAKQGL) by 1H 2D NMR spectroscopy. The peptide displays the typical NMR evidence consistent with a alpha-helix geometry with a stabilizing C-capping motif. The reported data represent the first piece of structural information on an important portion of the molecule and can have implications towards the understanding of its pathophysiology.

Evans, D. B., K. B. Rank, et al. (2000). "Tau phosphorylation at serine 396 and serine 404 by human recombinant tau protein kinase II inhibits tau's ability to promote microtubule assembly." J Biol Chem 275(32): 24977-83.
In Alzheimer's disease, hyperphosphorylated tau is an integral part of the neurofibrillary tangles that form within neuronal cell bodies and fails to promote microtubule assembly. Dysregulation of the brain-specific tau protein kinase II is reported to play an important role in the pathogenesis of Alzheimer's disease (Patrick, G. N., Zukerberg, L., Nikolic, M., De La Monte, S., Dikkes, P., and Tsai, L.-H. (1999) Nature 402, 615-622). We report here that in vitro phosphorylation of human tau by human recombinant tau protein kinase II severely inhibits the ability of tau to promote microtubule assembly as monitored by tubulin polymerization. The ultrastructure of tau-mediated polymerized tubulin was visualized by electron microscopy and compared with phosphorylated tau. Consistent with the observed slower kinetics of tubulin polymerization, phosphorylated tau is compromised in its ability to generate microtubules. Moreover, we show that phosphorylation of microtubule-associated tau results in tau's dissociation from the microtubules and tubulin depolymerization. Mutational studies with human tau indicate that phosphorylation by tau protein kinase II at serine 396 and serine 404 is primarily responsible for the functional loss of tau-mediated tubulin polymerization. These in vitro results suggest a possible role for tau protein kinase II-mediated tau phosphorylation in initiating the destabilization of microtubules.

Fagan, A. M. and D. M. Holtzman (2000). "Astrocyte lipoproteins, effects of apoE on neuronal function, and role of apoE in amyloid-beta deposition in vivo." Microsc Res Tech 50(4): 297-304.
The genetic association between the E4 isoform of apolipoprotein E (apoE) and increased risk for Alzheimer's disease (AD) has prompted interest in the neurobiology of apoE and the possible relationship between lipoprotein metabolism in the brain and neurodegenerative disease. ApoE, a product of astrocytes, is abundant in brain and in cerebrospinal fluid (CSF) where it is found in lipoproteins the size of large plasma high-density lipoproteins (HDL). Cultured astrocytes also secrete apoE/HDL, although the lipid and apoprotein composition of these nascent particles differs from that found in CSF, suggesting possible functional differences. In vitro studies have demonstrated isoform-specific effects of apoE on neurite outgrowth, neuronal plasticity, neurotoxicity, lipid peroxidation, oxidative injury, binding to cytoskeletal proteins, and interactions with amyloid-beta (Abeta), a primary component of senile plaques in AD. A number of these proposed functions have also been assessed in apoE -/- mice and transgenic mice expressing human apoE3 or apoE4. Importantly, analysis of transgenic mice overexpressing a mutant form of the human amyloid precursor protein (APP(V717F)) in the presence of mouse apoE, no apoE, or human apoE3 or E4 has demonstrated a critical and isoform-specific role for apoE in neuritic plaque formation, a pathologic hallmark of AD. Together, these data have provided important clues as to possible mechanism(s) by which apoE genotype modifies AD risk.

Fergusson, J., M. Landon, et al. (2000). "Neurofibrillary tangles in progressive supranuclear palsy brains exhibit immunoreactivity to frameshift mutant ubiquitin-B protein." Neurosci Lett 279(2): 69-72.
In Alzheimer's disease (AD) neurofibrillary tangles (NFT) are strongly tau and ubiquitin immunopositive, and contain an aberrant form of ubiquitin derived from the ubiquitin-B gene denoted as UBB+1. We explored whether the tau-related NFT seen in another neurodegenerative disease, progressive supranuclear palsy (PSP), also showed an accumulation of UBB+1. Three cases of PSP were examined immunohistochemically for tau protein, ubiquitin-protein conjugates and UBB+1 using single and double labelling. We conclude that UBB+1 is associated with compact globose tangles rather than dispersed accumulations of tau in PSP, showing that its presence is not unique to AD. We propose that aggregation of ubiquitinated proteins into compact inclusions in PSP might be due to inhibition of the degradation of multiubiquitinated proteins by ubiquitin chains containing proximal UBB+1 rather than normal ubiquitin.

Ferrer, I. and R. Blanco (2000). "N-myc and c-myc expression in Alzheimer disease, Huntington disease and Parkinson disease." Brain Res Mol Brain Res 77(2): 270-6.
The present study examines N-myc and c-myc protein expression with Western blotting and single and double-labeling immunohistochemistry in the hippocampus in Alzheimer disease (AD), the striatum in Huntington disease (HD) and the substantia nigra in Parkinson disease (PD). No modifications in the N-myc and c-myc expression are found in hippocampal neurons in AD, striatal neurons in HD, and pigmented neurons of the substantia nigra in PD. Yet punctate synaptic-like N-myc immunoreactivity, matching enhanced synaptophysin expression, occurs in diffuse plaques, but not in dystrophic neurites of neuritic plaques. In contrast, c-myc immunoreactivity is found in dystrophic neurites, but not in aberrant sproutings of neuritic plaques, as shown by double-labeling immunohistochemistry to c-myc and phosphorylated tau or phosphorylated neurofilament epitopes, and to c-myc and GAP-43, respectively. Strong N-myc and c-myc are observed in reactive astrocytes in AD, HD and PD, as revealed by double-labeling with N-myc or c-myc and GFAP. Finally, no relationship is found between nuclear DNA fragmentation and increased N-myc or c-myc expression in individual cells. These results demonstrate that neuron death in AD, HD and PD is not associated with modifications in the steady-state expression of N-myc and c-myc in individual neurons, and that neurofibrillary degeneration and Lewy body formation are not accompanied by increased immunoreactivity to these transcription factors. Increased N-myc and c-myc expression in reactive astrocytes probably plays a role in reactive astrocytosis in human neurodegenerative disorders.

Fisher, A., D. M. Michaelson, et al. (2000). "M1 muscarinic agonists as potential disease-modifying agents in Alzheimer's disease. Rationale and perspectives." Ann N Y Acad Sci 920: 315-20.
A cholinergic hypofunction in Alzheimer's disease (AD) may lead to formation of beta-amyloids that might impair the coupling of M1 muscarinic ACh receptors (mAChRs) with G proteins. This disruption in coupling can lead to decreased signal transduction, to a reduction in levels of trophic amyloid precursor proteins (APPs), and to generation of more beta-amyloids that can also suppress ACh synthesis and release, aggravating further the cholinergic deficiency. These "vicious cycles," a presynaptic and a postsynaptic one, may be inhibited, in principle, by M1 selective agonists. Such properties can be detected in the functionally selective M1 agonists from the AF series [e.g., project drugs, AF102B, AF150(S)]. These M1 agonists promote the nonamyloidogenic APP processing pathways and decrease tau protein phosphorylation. The effects on tau proteins suggest a link between M1 mAChR-mediated signal transduction system(s) and the neuronal cytoskeleton via regulation of phosphorylation of tau microtubule-associated protein. This may indicate a dual role for M1 agonists: as inhibitors of two "vicious cycles," one induced by beta-amyloids, and the other due to overactivation of certain kinases (e.g., glycogen synthase kinase-3, GSK-3) or downregulation of phosphatases, respectively. Prolonged administration of AF150(S) in apolipoprotein E-knockout mice restored cognitive impairments, cholinergic hypofunction, and tau hyperphosphorylation, and unveiled a high-affinity binding site to M1 mAChRs. Except M1 agonists, there are no reports of compounds having such combined effects, for example, amelioration of cognition dysfunction and beneficial modulation of APPs together with tau phosphorylation. This unique property of M1 agonists to alter different aspects of AD pathogenesis could represent the most remarkable, yet unexplored, clinical value of such compounds.

Fisher, A. (2000). "Therapeutic strategies in Alzheimer's disease: M1 muscarinic agonists." Jpn J Pharmacol 84(2): 101-12.
The cholinergic hypofunction in Alzheimer's disease (AD) appears to be linked with two other major hallmarks of this disease, beta-amyloid and hyperphosphorylated tau protein. Formation of beta-amyloids might impair the coupling of M1 muscarinic acetylcholine receptors (mAChR) with G-proteins. This can lead to decreased signal transduction, a decrease of trophic and non-amyloidogenic amyloid precursor protein (APPs) and generation of more beta-amyloids, aggravating further the cholinergic deficiency. This review is an attempt to explore the M1 mAChR regulation of beta-amyloid metabolism, tau hyperphosphorylation and cognitive functions. The therapeutic potential of M1-selective muscarinic agonists including AF102B, AF150(S), AF267B (the AF series) is evaluated and compared, when possible, with several FDA-approved acetylcholinesterase inhibitors. These M1 agonists can elevate APPs, decrease tau protein phosphorylation/hyperphosphorylation in vitro and in vivo and restore cognitive impairments in several animal models for AD. Except for the M1 agonists, no other compounds were reported yet with combined effects; e.g., amelioration of cognition dysfunction and beneficial modulation of APPs/beta-amyloid together with tau hyperphosphorylation/phosphorylation. This property of M1 agonists to alter different aspects associated with AD pathogenesis could represent the most remarkable clinical value of such drugs.

Flaherty, D. B., J. P. Soria, et al. (2000). "Phosphorylation of human tau protein by microtubule-associated kinases: GSK3beta and cdk5 are key participants." J Neurosci Res 62(3): 463-72.
Microtubules (MTs), primarily composed of alpha and beta tubulin polymers, must often work in concert with microtubule-associated proteins (MAPs) in order to modulate their functional demands. In a mature brain neuron, one of the key MAPs that resides primarily in the axonal compartment is the tau protein. Tau, in the adult human brain, is a set of six protein isoforms, whose binding affinity to MTs can be modulated by phosphorylation. In addition to the role that phosphorylation of tau plays in the "normal" physiology of neurons, hyperphosphorylated tau is the primary component of the fibrillary pathology in Alzheimer's disease (AD). Although many protein kinases are known to phosphorylate tau in vitro, the in vivo players contributing to the hyperphosphorylation of tau remain elusive. The experiments in this study attempt to define which protein kinases and protein phosphatases reside in the associated network of microtubules, thereby being strategically positioned to influence the phosphorylation of tau. Microtubule fractions are utilized to determine which of the microtubule-associated kinases most readily impacts the phosphorylation of tau at "AD-like" sites. Results from this study indicate that PKA, CK1, GSK3beta, and cdk5 associate with microtubules. Among the MT-associated kinases, GSK3beta and cdk5 most readily contribute to the ATP-induced "AD-like" phosphorylation of tau.

Forlenza, O. V., J. M. Spink, et al. (2000). "Muscarinic agonists reduce tau phosphorylation in non-neuronal cells via GSK-3beta inhibition and in neurons." J Neural Transm 107(10): 1201-12.
Muscarinic agonists alter the metabolism of amyloid precursor protein, leading to an increase in alpha-secretase cleavage and a decreased production of amyloidogenic peptides; suggesting that these compounds might modify the Alzheimer's disease process. A second therapeutic target in AD is the accumulation of stably phosphorylated tau into neurofibrillary tangles; an early event correlating with cognitive impairment. Glycogen synthase kinase-3 (GSK-3beta) phosphorylates tau and is inhibited via protein kinase C (PKC). As certain muscarinic receptors are linked to PKC, we examined the effect of a range of agonists on GSK-3beta phosphorylation of tau. In neurons a nonspecific muscarinic agonist, carbachol, reduced tau phosphorylation. In nonneuronal cells expressing the ml receptor a range of ml agonists reduced transiently-expressed tau phosphorylation and altered its microtubulebinding properties. These findings link the two pathological process of AD-APP metabolism and tau phosphorylation - and suggest that muscarinic and other cholinergic compounds might have disease-modifying properties.

Forman, M. S., V. M. Lee, et al. (2000). "New insights into genetic and molecular mechanisms of brain degeneration in tauopathies." J Chem Neuroanat 20(3-4): 225-44.
Abundant neurofibrillary lesions consisting of the microtubule associated protein tau and amyloid beta peptide deposits are the defining lesions of Alzheimer's disease. Prominent filamentous tau pathology and brain degeneration in the absence of extracellular amyloid deposition characterize a number of other neurodegenerative disorders (i.e. progressive supranuclear palsy, corticobasal degeneration, Pick's disease) collectively referred to as tauopathies. The discovery of multiple tau gene mutations that are pathogenic for hereditary frontotemporal dementia and parkinsonism linked to chromosome 17 in many kindreds, as well as the demonstration that tau polymorphisms are genetic risk factors for sporadic tauopathies, directly implicate tau abnormalities in the onset/progression of neurodegenerative disease. Different tau gene mutations may be pathogenic by impairing the functions of tau or by perturbing the splicing of the tau gene, thereby resulting in biochemically and structurally distinct tau aggregates. However, since specific polymorphisms and mutations in the tau gene lead to diverse phenotypes, it is plausible that additional genetic or epigenetic factors influence the clinical and pathological manifestations of both familial and sporadic tauopathies. Thus, efforts to develop animal models of tau-mediated neurodegeneration should provide further insights into the onset and progression of tauopathies as well as Alzheimer's disease, and they could accelerate research to discover more effective therapies for these disorders.

Friedhoff, P., M. von Bergen, et al. (2000). "Structure of tau protein and assembly into paired helical filaments." Biochim Biophys Acta 1502(1): 122-32.
Over the past few years the systematic investigation of paired helical filament assembly from tau protein in vitro has become feasible. We review our current understanding of the structure and conformations of tau protein and how this affects tau's assembly into the pathological paired helical filaments in Alzheimer's disease.

Gamblin, T. C., M. E. King, et al. (2000). "Oxidative regulation of fatty acid-induced tau polymerization." Biochemistry 39(46): 14203-10.
Alzheimer's disease (AD) is characterized by the presence of amyloid-positive senile plaques and tau-positive neurofibrillary tangles. Aside from these two pathological hallmarks, a growing body of evidence indicates that the amount of oxidative alteration of vulnerable molecules such as proteins, DNA, and fatty acids is elevated in the brains of AD patients. It has been hypothesized that the elevated amounts of protein oxidation could lead directly to the formation of neurofibrillary tangles through a cysteine-dependent mechanism. We have tested this hypothesis in an in vitro system in which tau assembly is induced by fatty acids. Using sulfhydryl protective agents and site-directed mutagenesis, we found that cysteine-dependent oxidation of the tau molecule is not required for its polymerization and may even be inhibitory. However, by adjusting the oxidative environment of the polymerization reaction through the addition of a strong antioxidant or through the addition of an oxidizing system consisting of iron, adenosine diphosphate, and ascorbate, we found that oxidation does play a major role in our in vitro paradigm. The results indicated that fatty acid oxidation, the amount of which is found to be elevated in AD patients, can facilitate the polymerization of tau. However, "overoxidation" of the fatty acids can inhibit the process. Therefore, we postulate that specific fatty acid oxidative products could provide a direct link between oxidative stress mechanisms and the formation of neurofibrillary tangles in AD.

Gantier, R., D. Gilbert, et al. (2000). "The pathogenic L392V mutation of presenilin 1 decreases the affinity to glycogen synthase kinase-3 beta." Neurosci Lett 283(3): 217-20.
Determination of the effects of presenilin 1 (PSEN1) mutations, involved in autosomal dominant early-onset Alzheimer's disease (ADEOAD), on the interaction between PSEN1 and binding proteins is essential to determine which interactions are involved in Alzheimer's disease (AD) pathogenesis. The PSEN1 binding protein glycogen synthase kinase-3 beta (GSK-3 beta) has been considered as a key protein in AD pathogenesis since GSK-3 beta phosphorylates tau and hyperphosphorylated tau is a main component of neurofibrillary tangles associated to AD. We show here, using surface plasmonic resonance, that the pathogenic L392V mutation, identified in a large French ADEOAD pedigree including 39 affected members, leads to a decreased affinity to GSK-3 beta. We conclude therefore that the increase of affinity of PSEN1 to GSK-3 beta reported in previous studies is not a common effect of pathogenic mutations associated to ADEOAD.

Garcia-Sierra, F., J. J. Hauw, et al. (2000). "The extent of neurofibrillary pathology in perforant pathway neurons is the key determinant of dementia in the very old." Acta Neuropathol (Berl) 100(1): 29-35.
Neurofibrillary pathology as found in Alzheimer's disease (AD) is also found in the normal elderly, suggesting that these changes may be part of the aging process. In this study, we assessed the densities and distribution of structures recognized by the monoclonal antibody (mAb) to phosphorylated tau (AT8) in the hippocampal formation and medial temporal isocortex of 19 centenarians. Of these, 4 cases were demented and 15 non-demented. AT8 immunoreactivity correlated with the global deterioration scale (GDS). The density of both intraneuronal neurofibrillary tangles (I-NFTs) and neuritic clusters (NCs) significantly correlated with the GDS in the layer II of the entorhinal cortex (r = 0.66, P = 0.005 and r= 0.611, P = 0.01, respectively). Density of I-NFTs in the subiculum (r = 0.491; P = 0.034) also correlated significantly. No other area was found to be statistically significant. Importantly, no correlation was found when demented and non-demented centenarian cases were analyzed separately, suggesting that the difference marks a fundamental shift between AD and non-demented individuals. This assertion is supported by the significantly higher densities of I-NFTs and NCs in the transentorhinal (P = 0.043 and P = 0.011, respectively) and layer II of the entorhinal cortex (P = 0.02 and P = 0.007, respectively), and I-NFTs in the subiculum (P < 0.001) and CAI (P = 0.011) in the demented group when compared with the non-demented cases. Granular diffuse deposits, an early stage parameter of the neurofibrillary pathology involving accumulation of non-fibrillar abnormally phosphorylated tau protein did not correlate with the GDS or between the two groups studied. This study, combining morphometric and confocal analyses, not only provides further evidence that, in the brains of patients with AD, the perforant pathway is highly sensitive to tau pathology but also that involvement is distinct from the changes of normal aging, even of the oldest old.

Giannetti, A. M., G. Lindwall, et al. (2000). "Fibers of tau fragments, but not full length tau, exhibit a cross beta-structure: implications for the formation of paired helical filaments." Protein Sci 9(12): 2427-35.
We have used X-ray fiber diffraction to probe the structure of fibers of tau and tau fragments. Fibers of fragments from the microtubule binding domain had a cross beta-structure that closely resembles that reported both for neurofibrillary tangles found in Alzheimer's disease brain and for fibrous lesions from other protein folding diseases. In contrast, fibers of full-length tau had a different, more complex structure. Despite major differences at the molecular level, all fiber types exhibited very similar morphology by electron microscopy. These results have a number of implications for understanding the etiology of Alzheimer's and other tauopathic diseases. The morphology of the peptide fibers suggests that the region in tau corresponding to the peptides plays a critical role in the nucleation of fiber assembly. The dramatically different structure of the full length tau fibers suggests that some region in tau has enough inherent structure to interfere with the formation of cross beta-fibers. Additionally, the similar appearance by electron microscopy of fibrils with varying molecular structure suggests that different molecular arrangements may exist in other samples of fibers formed from tau.

Goedert, M., B. Ghetti, et al. (2000). "Tau gene mutations in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). Their relevance for understanding the neurogenerative process." Ann N Y Acad Sci 920: 74-83.
Tau is a microtubule-associated protein that binds to microtubules and promotes microtubule assembly. Six tau isoforms are produced in adult human brain by alternative mRNA splicing from a single gene. Inclusion of a 31 amino acid repeat encoded by exon 10 of the tau gene gives rise to the three isoforms with four microtubule-binding repeats each. The other three tau isoforms have three repeats each. Abundant neurofibrillary lesions made of tau protein constitute a defining neuropathological characteristic of Alzheimer's disease. Filamentous tau protein deposits are also the defining characteristic of other neurodegenerative diseases, many of which are frontotemporal dementias or movement disorders, such as Pick's disease, progressive supranuclear palsy, and corticobasal degeneration. It is well established that the distribution of tau pathology correlates with the presence of symptoms of disease. However, until recently, there was no genetic evidence linking tau to neurodegeneration. This has now changed with the discovery of more than 15 mutations in the tau gene in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). The new work has shown that dysfunction of tau protein causes neurodegeneration.

Goedert, M. and M. G. Spillantini (2000). "Tau mutations in frontotemporal dementia FTDP-17 and their relevance for Alzheimer's disease." Biochim Biophys Acta 1502(1): 110-21.
Alzheimer's disease is characterised by the degeneration of selected populations of nerve cells that develop filamentous inclusions prior to degeneration. The neuronal inclusions of Alzheimer's disease are made of the microtubule-associated protein tau, in a hyperphosphorylated state. Abundant filamentous tau inclusions are not limited to Alzheimer's disease. They are the defining neuropathological characteristic of frontotemporal dementias, such as Pick's disease, and of progressive supranuclear palsy and corticobasal degeneration. The discovery of mutations in the tau gene in familial frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) has provided a direct link between tau dysfunction and dementing disease. Known mutations produce either a reduced ability of tau to interact with microtubules, or an overproduction of tau isoforms with four microtubule-binding repeats. This leads in turn to the assembly of tau into filaments similar or identical to those found in Alzheimer's disease brain. Several missense mutations also have a stimulatory effect on heparin-induced tau filament formation. Assembly of tau into filaments may be the gain of toxic function that is believed to underlie the demise of affected brain cells.

Gong, C. X., T. Lidsky, et al. (2000). "Phosphorylation of microtubule-associated protein tau is regulated by protein phosphatase 2A in mammalian brain. Implications for neurofibrillary degeneration in Alzheimer's disease." J Biol Chem 275(8): 5535-44.
Hyperphosphorylated tau, which is the major protein of the neurofibrillary tangles in Alzheimer's disease brain, is most probably the result of an imbalance of tau kinase and phosphatase activities in the affected neurons. By using metabolically competent rat brain slices as a model, we found that selective inhibition of protein phosphatase 2A by okadaic acid induced an Alzheimer-like hyperphosphorylation and accumulation of tau. The hyperphosphorylated tau had a reduced ability to bind to microtubules and to promote microtubule assembly in vitro. Immunocytochemical staining revealed hyperphosphorylated tau accumulation in pyramidal neurons in cornu ammonis and in neocortical neurons. The topography of these changes recalls the distribution of neurofibrillary tangles in Alzheimer's disease brain. Selective inhibition of protein phosphatase 2B with cyclosporin A did not have any significant effect on tau phosphorylation, accumulation, or function. These studies suggest that protein phosphatase 2A participates in regulation of tau phosphorylation, processing, and function in vivo. A down-regulation of protein phosphatase 2A activity can lead to Alzheimer-like abnormal hyperphosphorylation of tau.

Gordon-Krajcer, W., L. Yang, et al. (2000). "Conformation of paired helical filaments blocks dephosphorylation of epitopes shared with fetal tau except Ser199/202 and Ser202/Thr205." Brain Res 856(1-2): 163-75.
To determine if the high phosphate content of paired helical filaments (PHFs) in Alzheimer's disease (AD) is a result of limited access to filament phosphorylation sites, we studied in vitro dephosphorylation of intact PHFs, PHFs with filamentous structure abolished by formic acid treatment (PHF(FA)) and fetal human tau protein. Samples were treated with alkaline phosphatase for up to 24 h at 37 degrees C and then immunoblotted with eight well characterized tau antibodies, that recognize two phosphorylation-insensitive sites and six phosphorylation-sensitive epitopes at Thr181, Ser199/202, Ser202/Thr205, Thr231, Ser262/356 and Ser396/404. Intact PHFs were effectively dephosphorylated only at the two N-terminal epitopes Ser199/202 and Ser202/Thr205, with little change in electrophoretic mobility. In contrast, PHF(FA) were dephosphorylated at all epitopes, with particular effectiveness at those in the C-terminus and with significant increase in electrophoretic mobility. The fetal tau epitopes were effectively dephosphorylated except at Thr181 and Thr231 with marked increase in mobility. The extent of dephosphorylation of PHF(FA) was equal or more effective than in fetal tau, except for Thr181 that was minimally dephosphorylated in both proteins. The results indicate that intact PHFs, but not PHF(FA) or fetal tau display differential dephosphorylation of the N- and C-terminal epitopes. The results confirm that the filamentous conformation may significantly contribute to hyperphosphorylation of PHFs in the C-terminus. The filamentous conformation, however, does not limit access to two N-terminal epitopes Ser199/202 and Ser202/Thr205. The access to these sites in AD may be limited by other factors, e.g., inhibition of phosphatase binding.

Gozes, I. and D. E. Brenneman (2000). "A new concept in the pharmacology of neuroprotection." J Mol Neurosci 14(1-2): 61-8.
Vasoactive intestinal peptide (VIP), originally discovered in the intestine as a peptide of 28 amino acids, was later found to be a major brain peptide having neuroprotective activities. To exert neuroprotective activity, VIP requires glial cells secreting neuroprotective proteins. Activity-dependent neurotrophic factor (ADNF) is a recently isolated factor secreted by glial cells under the action of VIP. This protein, isolated by sequential chromatographic methods, was named activity-dependent neurotrophic factor since it protected neurons from death associated with blockade of electrical activity. A fourteen-amino-acid fragment of ADNF (ADNF-14) and the more potent, nine-amino-acid derivative (ADNF-9), exhibit activity that surpasses that of the parent protein with regard to potency and a broader range of effective concentration. Furthermore, the peptides exhibit protective activity in Alzheimer's disease-related systems (e.g., beta-amyloid toxicity and apolipoprotein E deficiencies, genes that have been associated with Alzheimer's disease onset and progression). ADNP is another glial mediator of VIP-associated neuroprotection. NAP, an eight-amino-acid peptide derived from ADNP (sharing structural and functional similarities with ADNF-9), was identified as the most potent neuroprotectant described to-date in an animal model of apolipoprotein E-deficiency (knock-out mice). These femtomolar-acting peptides form a basis for a new concept in pharmacology: femtomolar neuroprotection.

Gurwitz, D. (2000). "New imaging techniques for early diagnosis of Alzheimer's disease." Mol Med Today 6(9): 340.

Hall, G. F., B. Chu, et al. (2000). "Human tau filaments induce microtubule and synapse loss in an in vivo model of neurofibrillary degenerative disease." J Cell Sci 113 ( Pt 8): 1373-87.
The intracellular accumulation of tau protein and its aggregation into filamentous deposits is the intracellular hallmark of neurofibrillary degenerative diseases such as Alzheimer's Disease and familial tauopathies in which tau is now thought to play a critical pathogenic role. Until very recently, the lack of a cellular model in which human tau filaments can be experimentally generated has prevented direct investigation of the causes and consequences of tau filament formation in vivo. In this study, we show that human tau filaments formed in lamprey central neurons (ABCs) that chronically overexpress human tau resemble the 'straight filaments' seen in Alzheimer's Disease and other neurofibrillary conditions, and are distinguishable from neurofilaments by their ultrastructure, distribution and intracellular behavior. We also show that tau filament formation in ABCs is associated with a distinctive pattern of dendritic degeneration that closely resembles the cytopathology of human neurofibrillary degenerative disease. This pattern includes localized cytoskeletal disruption and aggregation of membranous organelles, distal dendritic beading, and the progressive loss of dendritic microtubules and synapses. These results suggest that tau filament formation may be responsible for many key cytopathological features of neurofibrillary degeneration, possibly via the loss of microtubule based intracellular transport.

Harding, A. J., J. J. Kril, et al. (2000). "Practical measures to simplify the Braak tangle staging method for routine pathological screening." Acta Neuropathol (Berl) 99(2): 199-208.
The examination of neurofibrillary tangles is now recommended for the diagnosis of Alzheimer's disease as their location and density can distinguish early, intermediate and late disease stages. While the Braak tangle staging protocol can identify these stages, it uses an uncommon silver stain and hippocampal sample. The present study evaluates the Braak protocol using commonly used methods and cases fulfilling either CERAD criteria for Alzheimer's disease, criteria for dementia with Lewy bodies or without neurological disease. Temporal and occipital cortices from 72 cases were stained using tau immunohistochemistry and the Gallyas and modified Bielschowsky silver stains. The modified Bielschowsky silver stain was equivalent to the Gallyas silver stain for tangle staging. Semiquantitative evaluation of neurofibrillary tangles in the hippocampus and the inferior temporal cortex provided equivalent information to that obtained using the original Braak tangle staging protocol (kappa statistic of 0.97). Comparison of this modification with the CERAD criteria provided moderate agreement (0.51) between diagnostic categories when cases with dementia with Lewy bodies were included, but substantially increased agreement (0.74) when they were excluded. This simplification of the Braak tangle staging protocol is easy to apply, can be readily incorporated into existing CERAD procedures, and helps to distinguish cases with neurofibrillary tangles from those with Lewy bodies.

Hartig, W., C. Klein, et al. (2000). "Abnormally phosphorylated protein tau in the cortex of aged individuals of various mammalian orders." Acta Neuropathol (Berl) 100(3): 305-12.
Aged individuals of mammalian species displaying hyperphosphorylated tau protein may be suitable natural models for investigating neurodegenerative alterations occurring, for example, in Alzheimer's disease. Therefore, autoptic tissue from the entorhinal, motor and prefrontal cortices of 14 mammalian species was screened using the monoclonal antibody AT8, which is directed against a phosphorylated epitope of human tau and applicable to the tissues of aged domestic animals, as shown in previous studies. AT8-immunoreactive neuronal processes and perikarya were revealed in Campbell's guenon, rhesus monkey, baboon, rabbit, spectacled bear, guanaco, reindeer and bison. Signs for considerable neuropathological alterations in aged bisons also included neuropil threads, whereas AT8 immunoreactivity in the other species was only sparsely scattered. Hyperphosphorylated tau in the brain of an 28-year-old rhesus monkey was also detected by AT100, PHF-1 and TG-3 antibodies, but only in the hippocampal formation and entorhinal cortex, which are known as starting point for tangle spreading in the cortex of Alzheimer patients.

Hashiguchi, M., K. Sobue, et al. (2000). "14-3-3zeta is an effector of tau protein phosphorylation." J Biol Chem 275(33): 25247-54.
Neurofibrillary tangles associated with Alzheimer's disease are composed mainly of paired helical filaments that are formed by the aggregation of abnormally phosphorylated microtubule-associated protein tau. 14-3-3, a highly conserved protein family that exists as seven isoforms and regulates diverse cellular processes is present in neurofibrillary tangles (Layfield, R., Fergusson, J., Aitken, A., Lowe, J., Landon, M., Mayer, R. J. (1996) Neurosci. Lett. 209, 57-60). The role of 14-3-3 in Alzheimer's disease pathogenesis is not known. In this study, we found that the 14-3-3zeta isoform is associated with tau in brain extract and profoundly stimulates cAMP-dependent protein kinase catalyzed in vitro phosphorylation on Ser(262)/Ser(356) located within the microtubule-binding region of tau. 14-3-3zeta binds to both phosphorylated and nonphosphorylated tau, and the binding site is located within the microtubule-binding region of tau. From brain extract, 14-3-3zeta co-purifies with microtubules, and tubulin blocks 14-3-3zeta-tau binding. Among four 14-3-3 isoforms tested, beta and zeta but not gamma and epsilon associate with tau. Our data suggest that 14-3-3zeta is a tau protein effector and may be involved in the abnormal tau phosphorylation occurring during Alzheimer's disease ontogeny.

Heicklen-Klein, A. and I. Ginzburg (2000). "Tau promoter confers neuronal specificity and binds Sp1 and AP-2." J Neurochem 75(4): 1408-18.
Tau, a microtubule-associated protein, is encoded by a single gene, whose expression is primarily neuronal. In this work, we defined an 80-bp region of the tau promoter that confers tau protein with neuronal expression. This fragment works in conjunction with an endogenous initiation region to activate neuronal precursor-specific transcription of the tau promoter and works independently of this initiation region to confer nerve growth factor inducibility. Furthermore, this 80-bp fragment binds both Sp1 and AP-2 proteins. DNase I foot-print analysis revealed a third protein binding region at the center of this 80-bp fragment in neuronal cells. Mutation within any of these three protein binding sites decreases transcriptional activation of the tau gene. Comprehension of the interactions that occur between cis- and trans-regulatory elements of the tau promoter is important to understand the regulation of tau expression during normal development and changes that may occur in many cases of dementia, including Alzheimer's disease.

Heininger, K. (2000). "A unifying hypothesis of Alzheimer's disease. IV. Causation and sequence of events." Rev Neurosci 11 Spec No: 213-328.
Contrary to common concepts, the brain in Alzheimer's disease (AD) does not follow a suicide but a rescue program. Widely shared features of metabolism in starvation, hibernation and various conditions of energy deprivation, e.g. ischemia, allow the definition of a deprivation syndrome which is a phylogenetically conserved adaptive response to energetic stress. It is characterized by hypometabolism, oxidative stress and adjustments of the glucose-fatty acid cycle. Cumulative evidence suggests that the brain in aging and AD actively adapts to the progressive fuel deprivation. The counterregulatory mechanisms aim to preserve glucose for anabolic needs and promote the oxidative utilization of ketone bodies. The agent mediating the metabolic switch is soluble Abeta which inhibits glucose utilization and stimulates ketone body utilization at various levels. These processes, which are initiated during normal aging, include inhibition of pro-glycolytic neurohormones, cholinergic transmission, and pyruvate dehydrogenase, the key transmitter and effector systems regulating glucose metabolism. Hormonal and effector systems which promote ketone body utilization, such as glucocorticosteroid and galanin activity, GABAergic transmission, nitric oxide, lipid transport, Ca2+ elevation, and ketone body metabolizing enzymes, are enhanced. A multitude of risk factors feed into this pathophysiological cascade at a variety of levels. Taking into account its pleiotropic regulatory actions in the deprivation response, a new name for Abeta is suggested: deprivin. On the other hand, cumulative evidence, taken together compelling, suggests that senile plaques are the dump rather than the driving force of AD. Moreover, the neurotoxic action of fibrillar Abeta is a likely in vitro artifact but does not contribute significantly to the in vivo pathophysiological events. This archaic program, conserved from bacteria to man, aims to ensure the survival of a deprived organism and controls such divergent processes as sporulation, hibernation, aging and aging-related diseases. In contrast to the immature brain, ketone body utilization of the aged brain is no longer sufficient to meet the energetic demands and is later supplemented by lactate, thus recapitulating in reverse order the sequential fuel utilization of the immature brain. The transduction pathways which operate to switch metabolism also convey the programming and balancing of the de-/redifferentiation/apoptosis cell cycle decisions. This encompasses the reiteration of developmental processes such as transcription factor activation, tau hyperphosphorylation, and establishment of growth factor independence by means of Ca2+ set point shift. Thus, the increasing energetic insufficiency results in the progressive centralization of metabolic activity to the neuronal soma, leading to pruning of the axonal/dendritic trees, loss of neuronal polarity, downregulation of neuronal plasticity and, eventually, depending on the Ca2+ -energy-redox homeostasis, degeneration of vulnerable neurons. Finally, it is outlined that genetic (e.g. Down's syndrome, APP and presenilin mutations and apoE4) and environmental risk factors represent progeroid factors which accelerate the aging process and precipitate the manifestation of AD as a progeroid systemic disease. Aging and AD are related to each other by threshold phenomena, corresponding to stage 2, the stage of resistance, and stage 3, exhaustion, of a metabolic stress response.

Hellstrom-Lindahl, E. (2000). "Modulation of beta-amyloid precursor protein processing and tau phosphorylation by acetylcholine receptors." Eur J Pharmacol 393(1-3): 255-63.
Neurofibrillary lesions and senile plaques that are composed mainly of hyperphosphorylated tau protein and the amyloid-beta peptide derived from the amyloid precursor protein, respectively, are classical hallmarks of Alzheimer's disease. A number of studies strongly suggests that amyloid-beta formation and amyloid depositions are linked to the pathogenesis of Alzheimer's disease. Recent findings suggest that very low concentrations of the amyloid-beta can inhibit various cholinergic neurotransmitter functions independently of apparent neurotoxicity. Many factors have been shown to influence the processing of amyloid precursor protein, including activation of muscarinic and nicotinic receptors. This review focus on some recent studies concerning the regulation of amyloid precursor protein processing and modulation of tau phosphorylation by acetylcholine receptor stimulation and how cholinergic deficits and amyloid-beta might be related to one another.

Hellstrom-Lindahl, E., H. Moore, et al. (2000). "Increased levels of tau protein in SH-SY5Y cells after treatment with cholinesterase inhibitors and nicotinic agonists." J Neurochem 74(2): 777-84.
Several cholinesterase inhibitors used in the treatment of Alzheimer's disease (AD) have been shown to interact with an allosteric site on the nicotinic acetylcholine receptor (nAChR). A possible linkage between the phosphorylation state of tau, the major component of paired helical filaments found in AD brain, and stimulation of nAChRs by cholinesterase inhibitors and nicotinic agonists was investigated. Western blot analysis showed that treatment of SH-SY5Y cells for 72 h with the cholinesterase inhibitors tacrine (10(-5) M), donepezil (10(-5) M), and galanthamine (10(-5) M), nicotine (10(-5) M), and epibatidine (10(-7) M) increased tau levels as detected with Tau-1, AT 8, and AT 270 monoclonal antibodies and binding of [3H]epibatidine. The increase in tau immunoreactivity induced by nicotine, epibatidine, and tacrine, but not the up-regulation of nAChRs, was prevented by the antagonists d-tubocurarine and mecamylamine. Both antagonists were synergistic with the nicotinic agonists in causing up-regulation, but only d-tubocurarine showed a synergistic effect with tacrine. The increased tau immunoreactivity induced by tacrine was not prevented by atropine, indicating that in terms of cholinergic receptors, tacrine modulates tau levels mainly through interactions with nAChRs and not with muscarinic receptors. Additional work is needed to determine the exact mechanism by which cholinesterase inhibitors and nicotinic agonists modulate phosphorylation and levels of tau protein.

Herz, J. and U. Beffert (2000). "Apolipoprotein E receptors: linking brain development and Alzheimer's disease." Nat Rev Neurosci 1(1): 51-8.
Alzheimer's disease is a debilitating neurodegenerative disorder that afflicts an increasing part of our ageing population. An isoform of apolipoprotein E, a protein that mediates the transport of lipids and cholesterol in the circulatory system, predisposes carriers of this allele to the common late-onset form of the disease. How this protein is related to a neurodegenerative disorder is an enigma. Mounting evidence indicates that apolipoprotein E receptors, which are abundantly expressed in most neurons in the central nervous system, also fulfill critical functions during brain development and may profoundly influence the pathogenesis of Alzheimer's disease.

Hesse, C., L. Rosengren, et al. (2000). "Cerebrospinal Fluid Markers for Alzheimer's Disease Evaluated after Acute Ischemic Stroke." J Alzheimers Dis 2(3,4): 199-206.
Potential cerebrospinal fluid (CSF) markers for Alzheimer's disease (AD) include tau protein, the 42 amino-acid form of amyloid beta (amyloid beta(1-42)) and apolipoprotein E (apoE). To study new aspects of these protein markers, we examined consecutive CSF samples from 26 patients with acute ischemic stroke. CSF samples were taken on day 0-1, day 2-3, day 7-9, 3 weeks and 3-5 months after the stroke. CSF-tau showed a marked increase day 2-3, which peaked after 1 week and returned to normal after 3-5 months. CSF-tau also showed correlation (r=0.95; p<0.01) with the size of the infarct. In contrast, CSF-amyloid beta(1-42) and CSF-apoE showed no significant changes during the period. The marked increase in CSF-tau levels after acute ischemic stroke indicate that CSF-tau reflect the degree of neuronal damage. The reason for unchanged levels of CSF-amyloid beta(1-42) and CSF-apoE after ischemic stroke remains unclear.

Heutink, P. (2000). "Untangling tau-related dementia." Hum Mol Genet 9(6): 979-86.
Abundant cytoplasmic inclusions consisting of aggregated hyperphosphorylated protein tau are a characteristic pathological observation in several neurodegenerative disorders such as Alzheimer's disease, Pick's disease, frontotemporal dementia, cortico-basal degeneratio