Deposition Of Amyloid Peptides Research Articles

Behaviour Hallmarks in Alzheimer's Disease 5xFAD Mouse Model.

The 5xFAD transgenic mouse model widely used in Alzheimer's disease (AD) research recapitulates many AD-related phenotypes with a relatively early onset and aggressive age-dependent progression. Besides developing amyloid peptide deposits alongside neuroinflammation by the age of 2 months, as well as exhibiting neuronal decline by the age of 4 months that intensifies by the age of 9 months, these mice manifest a broad spectrum of behavioural impairments. In this review, we present the extensive repertoire of behavioural dysfunctions in 5xFAD mice, organised into four categories: motor skills, sensory function, learning and memory abilities, and neuropsychiatric-like symptoms. The motor problems, associated with agility and reflex movements, as well as balance and coordination, and skeletal muscle function, typically arise by the time mice reach 9 months of age. The sensory function (such as taste, smell, hearing, and vision) starts to deteriorate when amyloid peptide buildups and neuroinflammation spread into related anatomical structures. The cognitive functions, encompassing learning and memory abilities, such as visual recognition, associative, spatial working, reference learning, and memory show signs of decline from 4 to 6 months of age. Concerning neuropsychiatric-like symptoms, comprising apathy, anxiety and depression, and the willingness for exploratory behaviour, it is believed that motivational changes emerge by approximately 6 months of age. Unfortunately, numerous studies from different laboratories are often contradictory on the conclusions drawn and the identification of onset age, making preclinical studies in rodent models not easily translatable to humans. This variability is likely due to a range of factors associated with animals themselves, housing and husbandry conditions, and experimental settings. In the forthcoming studies, greater clarity in experimental details when conducting behavioural testing in 5xFAD transgenic mice could minimise the inconsistencies and could ensure the reliability and the reproducibility of the results.

Whey protein powder with milk fat globule membrane attenuates Alzheimer's disease pathology in 3×Tg-AD mice by modulating neuroinflammation through the peroxisome proliferator-activated receptor γ signaling pathway

Whey protein powder (PP), which is mainly derived from bovine milk, is rich in milk fat globule membrane (MFGM). The MGFM has been shown to play a role in promoting neuronal development and cognition in the infant brain. However, its role in Alzheimer's disease (AD) has not been elucidated. Here, we showed that the cognitive ability of 3×Tg-AD mice (a triple-transgenic mouse model of AD) could be improved by feeding PP to mice for 3 mo. In addition, PP ameliorated amyloid peptide deposition and tau hyperphosphorylation in the brains of AD mice. We found that PP could alleviate AD pathology by inhibiting neuroinflammation through the peroxisome proliferator-activated receptor γ (PPARγ)-nuclear factor-κB signaling pathway in the brains of AD mice. Our study revealed an unexpected role of PP in regulating the neuroinflammatory pathology of AD in a mouse model.

Aβ and Tau Interact with Metal Ions, Lipid Membranes and Peptide-Based Amyloid Inhibitors: Are These Common Features Relevant in Alzheimer's Disease?

In the last two decades, the amyloid hypothesis, i.e., the abnormal accumulation of toxic Aβ assemblies in the brain, has been considered the mainstream concept sustaining research in Alzheimer’s Disease (AD). However, the course of cognitive decline and AD development better correlates with tau accumulation rather than amyloid peptide deposition. Moreover, all clinical trials of amyloid-targeting drug candidates have been unsuccessful, implicitly suggesting that the amyloid hypothesis needs significant amendments. Accumulating evidence supports the existence of a series of potentially dangerous relationships between Aβ oligomeric species and tau protein in AD. However, the molecular determinants underlying pathogenic Aβ/tau cross interactions are not fully understood. Here, we discuss the common features of Aβ and tau molecules, with special emphasis on: (i) the critical role played by metal dyshomeostasis in promoting both Aβ and tau aggregation and oxidative stress, in AD; (ii) the effects of lipid membranes on Aβ and tau (co)-aggregation at the membrane interface; (iii) the potential of small peptide-based inhibitors of Aβ and tau misfolding as therapeutic tools in AD. Although the molecular mechanism underlying the direct Aβ/tau interaction remains largely unknown, the arguments discussed in this review may help reinforcing the current view of a synergistic Aβ/tau molecular crosstalk in AD and stimulate further research to mechanism elucidation and next-generation AD therapeutics.

In vivo Evaluation of a Newly Synthesized Acetylcholinesterase Inhibitor in a Transgenic Drosophila Model of Alzheimer's Disease.

Alzheimer’s disease is a neurodegenerative disease characterized by disrupted memory, learning functions, reduced life expectancy, and locomotor dysfunction, as a result of the accumulation and aggregation of amyloid peptides that cause neuronal damage in neuronal circuits. In the current study, we exploited a transgenic Drosophila melanogaster line, expressing amyloid-β peptides to investigate the efficacy of a newly synthesized acetylcholinesterase inhibitor, named XJP-1, as a potential AD therapy. Behavioral assays and confocal microscopy were used to characterize the drug effect on AD symptomatology and amyloid peptide deposition. The symptomatology induced in this particular transgenic model recapitulates the scenario observed in human AD patients, showing a shortened lifespan and reduced locomotor functions, along with a significant accumulation of amyloid plaques in the brain. XJP-1 treatment resulted in a significant improvement of AD symptoms and a reduction of amyloid plaques by diminishing the amyloid aggregation rate. In comparison with clinically effective AD drugs, our results demonstrated that XJP-1 has similar effects on AD symptomatology, but at 10 times lower drug concentration than donepezil. It also showed an earlier beneficial effect on the reduction of amyloid plaques at 10 days after drug treatment, as observed for donepezil at 20 days, while the other drugs tested have no such effect. As a novel and potent AChE inhibitor, our study demonstrates that inhibition of the enzyme AChE by XJP-1 treatment improves the amyloid-induced symptomatology in Drosophila, by reducing the number of amyloid plaques within the fruit fly CNS. Thus, compound XJP-1 has the therapeutic potential to be further investigated for the treatment of AD.

Passive Aβ Immunotherapy: Current Achievements and Future Perspectives.

Passive immunotherapy has emerged as a very promising approach for the treatment of Alzheimer’s disease and other neurodegenerative disorders, which are characterized by the misfolding and deposition of amyloid peptides. On the basis of the amyloid hypothesis, the majority of antibodies in clinical development are directed against amyloid β (Aβ), the primary amyloid component in extracellular plaques. This review focuses on the current status of Aβ antibodies in clinical development, including their characteristics and challenges that came up in clinical trials with these new biological entities (NBEs). Emphasis is placed on the current view of common side effects observed with passive immunotherapy, so-called amyloid-related imaging abnormalities (ARIAs), and potential ways to overcome this issue. Among these new ideas, a special focus is placed on molecules that are directed against post-translationally modified variants of the Aβ peptide, an emerging approach for development of new antibody molecules.

The age-related slow increase in amyloid pathology in APP.V717I mice activates microglia, but does not alter hippocampal neurogenesis

In Alzheimer's disease, the hippocampus is characterized by abundant deposition of amyloid peptides (amyloid β [Aβ]) and neuroinflammation. Adult hippocampal neurogenesis (AHN) is a form of plasticity that contributes to cognition and can be influenced by either or both pathology and neuroinflammation. Their interaction has been studied before in rapidly progressing transgenic mouse models with strong overexpression of amyloid precursor protein (APP) and/or presenilin 1. So far, changes in AHN and neuroinflammation remain poorly characterized in slower progressing models at advanced age, which approach more closely sporadic Alzheimer's disease. Here, we analyzed 10- to 26-month-old APP.V717I mice for possible correlations between Aβ pathology, microglia, and AHN. The age-related increase in amyloid pathology was closely paralleled by microglial CD68 upregulation, which was largely absent in age-matched wild-type littermates. Notably, aging reduced the AHN marker doublecortin, but not calretinin, to a similar extent in wild-type and APP.V717I mice between 10 and 26 months. This demonstrates that AHN is influenced by advanced age in the APP.V717I mouse model, but not by Aβ and microglial activation.

Propagation of Neuronal Damage to Embryonic Grafts Transplanted in the Hippocampus of Murine Models of Alzheimer's Disease.

Alzheimer's disease (AD) is the most common form of dementia, characterized by the presence of two principal hallmarks-amyloid plaques and neurofibrillary tangles. The primary cause of the majority of AD cases is not known. Likewise, the mechanisms underlying the propagation of the pathology from affected tissue to neighboring healthy neurons are largely unknown, but knowledge about them could be helpful to design strategies aimed at halting the progression of the disease. To throw light on the mechanisms of propagation of neuronal damage to healthy tissue, wild-type (WT) hippocampal solid tissue chunks derived from green fluorescent protein (GFP)-positive embryos were grafted into the hippocampus of 6-month-old WT and 3xTg-AD mice, a triple-transgenic mouse model that exhibits both amyloid-beta (Aβ) and tau protein pathology. The histological and morphological alterations of the grafted tissues were assessed 3 months post-transplantation. Tissues grafted in 3xTg-AD hosts, compared to those grafted in WT recipients, presented a significant decrease in neurite outgrowth (35.4%) and dendritic spine density (41.3%), mainly due to a reduction of stubby and thin-shaped spines. Moreover, some cells of the tissue transplanted in 3xTg-AD hosts accumulated intracellular amyloid peptide deposits similar to the cells of the host. Furthermore, the immunohistochemical examination of reactive astrocytes and microglia revealed the presence of more inflammation in the grafted tissues hosted in 3xTg-AD compared to WT recipients. These results show a propagation of neuronal damage to initially healthy embryonic grafts, validating this methodology for future studies on the mechanisms of the progression of AD pathology to surrounding regions.

Silymarin effect on amyloid-β plaque accumulation and gene expression of APP in an Alzheimer’s disease rat model

BackgroundThe deposition of amyloid peptides is associated with Alzheimer’s disease (AD). These amyloid peptides are derived from the amyloid protein precursor (APP). Silymarin, a standardized extract of milk thistle, which is currently used in liver diseases, may be effective in the inhibition of amyloid formation. However, its effect has not been assessed on APP expression.ResultsIn this study, first, the effect of silymarin was examined on the passive avoidance learning in a rat model of AD. This model was induced by the intracerebroventricular injection of Aβ peptide (Aβ1–42) in Wistar rats. Rats were treated with 70 and 140 mg/kgof the extract, once a day, for 4 weeks. Memory function that was evaluated in a shuttle-cage test, showed improvement upon administration of this extract. Brain amyloid plaques had also decreased upon administration of the extract. Furthermore, APP gene expression was compared in treated and untreated groups. The result showed that silymarin was able to suppress APP expression.ConclusionOur results are in accordance with the in vitro tests concerning the positive antiamyloidogenic property of the main component of silymarin, namely silibinin. We suggest that the beneficial effect of sylimarin in the AD model is related to its capacity to disaggregate amyloid plaques and to suppress APP expression. Considering the limited side effects of silymarin, this compound could be of use in AD therapy.

Xanthoceraside attenuates amyloid β peptide25–35-induced learning and memory impairments in mice

In Alzheimer's disease (AD), the deposition of amyloid peptides is invariably associated with oxidative stress and inflammatory responses. Xanthoceraside has anti-inflammatory and antioxidative activities. However, it remains unclear whether xanthoceraside improves amyloid β (Aβ)-induced neurotoxicity. The purpose of this study was to examine the effect of xanthoceraside on behavioral impairments, inflammatory responses, and oxidative stress induced by Aβ peptide(25-35) (Aβ(25-35)) in mice. The mice were treated orally with xanthoceraside (0.02, 0.08, or 0.32 mg/kg, once daily) after the intracerebroventricular injection of Aβ(25-35) (day 0). Cognitive functions were evaluated in Y-maze (day 6) and novel object recognition tests (days 7 and 8). Inducible nitric oxide synthase (iNOS) and nitrotyrosine levels in the hippocampus were examined (day 9). The mRNA expressions of iNOS and interleukin-4 (IL-4) in the hippocampus were measured 2 h and 3 days after the Aβ(25-35) injection by real-time reverse transcription-polymerase chain reaction. Xanthoceraside significantly attenuated behavioral impairments induced by Aβ(25-35) in the Y-maze and novel object recognition tests. Repeated treatment with xanthoceraside significantly inhibited the increase in the expression of iNOS and nitrotyrosine in the hippocampus induced by Aβ(25-35), which is associated with an enhanced expression of the IL-4 mRNA. These findings suggest that xanthoceraside attenuates memory impairments through amelioration of oxidative stress and inflammatory responses induced by Aβ(25-35) and is a potential candidate for an AD treatment.

Anti-Inflammatory Therapy for Alzheimers Disease from Epidemiological Fact to New Mechanisms of Action

While the exact causes or mechanisms of Alzheimer’s disease (AD) are still not known, the most critical risk factor is aging. Cellular oxidative stress is known to occur in the brain during aging and some pathology of AD could be explained by the oxidative stress, including senile plaques, deposition of amyloid peptide (Aβ) and tangles (deposition of an abnormally phosphorylated tau). Also gliosis, which may release inflammatory molecules and cause oxidative stress, is a feature of aging and AD. Epidemiological analysis indicates that people with severe arthritis and who are subjected to leprosy therapy have significantly lower rates of AD. Since both arthritis and leprosy therapy involves high doses of nonsteroidal anti-inflammatory drugs (NSAIDs), and the fact that inflammation is involved in AD pathology, NSAID-therapy might prevent or delay the onset of AD. More recently NSAIDs were found to reduce production of Aβ peptide. Therefore, we should revisit NSAIDs as potential treatment for AD therapy. There are clinical studies showing the beneficial effects of NSAIDs treatments in AD patients, in contrast, other studies show a lack of benefit. This article discusses the role of inflammation and oxidative stress in AD and the role of drugs preventing them.

Amyloid-Beta Peptide, Oxidative Stress and Inflammation in Alzheimer's Disease: Potential Neuroprotective Effects of Omega-3 Polyunsaturated Fatty Acids

Alzheimer's disease is the most common form of dementia in the elderly and is a progressive neurodegenerative disorder characterised by a decline in cognitive function and also profound alterations in mood and behaviour. The pathology of the disease is characterised by the presence of extracellular amyloid peptide deposits and intracellular neurofibrillary tangles in the brain. Although many hypotheses have been put forward for the aetiology of the disease, increased inflammation and oxidative stress appear key to be features contributing to the pathology. The omega-3 polyunsaturated fats, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) have well-characterised effects on inflammation and may have neuroprotective effects in a number of neurodegenerative conditions including Alzheimer's disease. The aims of this paper are to review the neuroprotective effects of EPA and DHA in Alzheimer's disease, with special emphasis on their role in modulating oxidative stress and inflammation and also examine their potential as therapeutic agents.

314 FECAL STEROID HORMONES IN 3 × TG-AD AND WILD-TYPE MICE AND THEIR RELATION WITH FERTILITY

Extracellular deposition of amyloid peptides in plaques and neurofibrillary tangles are 2 characteristic pathological features of Alzheimer’s disease (AD). These models show the neuropathological symptoms and the hormonal changes. It has been observed that the pathology appears with age and gets worse progressively. Several studies have proved the neuroprotective action of the androgens and estrogens related to age. The aim of this study was reveal if aging in 3 × TG-AD transgenic mice produces a change in the androgen and estrogen levels, compared with the wild type (WT), and if these changes could influence fertility. In this experiment, we have used male and female WT (n = 40) and 3 × TG-AD transgenic (n = 40) mice for gene PS1 (involved in the acceleration of the amyloid plaque formation), tau (involved in neurodegeneration), and APP (involved in the extracellular accumulation of fi-amyloid protein). We have studied mice of different ages: 3, 4, 7, and 8 months old. Fecal samples were collected 5 days every week (between 0900-1000 h). The technique used for the hormone quantification was ELISA. Results were calculated in ngg-1 of feces. The statistical analysis was done with the Origin 8 program (Software Cientifico, Castellana, Madrid, Spain), through a 1-way ANOVA. Results were represented with the mean ± standard error (P < 0.05 values were considered statistically significant). The pregnancy rate in transgenic mice before 4 months old was 0%, whereas in WT mice, the fertility rate was 82%. At 8 months, the pregnancy rate in transgenic mice was 65% and in WT 88%. In males, although androstenedione (A4) concentrations were not significant through age, testosterone levels increased significantly in transgenic mice, but not in WT mice. Estrogens presented the biggest differences between groups. The 3-month-old transgenic mice showed significantly higher values, and this elevation of the estrogens could be the cause of infertility in transgenic mice. At 8 months, the values decreased significantly in WT mice, whereas in transgenic mice, the concentrations were higher, and this could be the reason for the differences in the fertility rate. In females, A4 concentrations were higher in WT mice, showing a significant increase with age in both groups. Testosterone concentrations were significantly higher with age in transgenic mice. These mice showed the higher estrogen concentrations, showing a decrease with age in both groups that was significant in transgenic mice. Increase of testosterone in 3-month-old transgenic mice could be the reason for the infertility in the females. In conclusion, the fecal analysis is a noninvasive method, appropriate for androgen and estrogen determination in the different types of mice. There are several differences in the androgen and estrogen levels between the 2 groups of studied mice; the levels are generally more elevated in transgenic mice. Gene modification in 3 × TG-AD transgenic mice could cause a delay in the onset of puberty.

Silibinin Attenuates Amyloid β25–35Peptide-Induced Memory Impairments: Implication of Inducible Nitric-Oxide Synthase and Tumor Necrosis Factor-α in Mice

In Alzheimer's disease (AD), the deposition of amyloid peptides is invariably associated with oxidative stress and inflammatory responses. Silibinin (silybin), a flavonoid derived from the herb milk thistle, has potent anti-inflammatory and antioxidant activities. However, it remains unclear whether silibinin improves amyloid beta (Abeta) peptide-induced neurotoxicity. In this study, we examined the effect of silibinin on the fear-conditioning memory deficits, inflammatory response, and oxidative stress induced by the intracerebroventricular injection of Abeta peptide(25-35) (Abeta(25-35)) in mice. Mice were treated with silibinin (2, 20, and 200 mg/kg p.o., once a day for 8 days) from the day of the Abeta(25-35) injection (day 0). Memory function was evaluated in cued and contextual fear-conditioning tests (day 6). Nitrotyrosine levels in the hippocampus and amygdala were examined (day 8). The mRNA expression of inducible nitric-oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-alpha) in the hippocampus and amygdala was measured 2 h after the Abeta(25-35) injection. We found that silibinin significantly attenuated memory deficits caused by Abeta(25-35) in the cued and contextual fear-conditioning test. Silibinin significantly inhibited the increase in nitrotyrosine levels in the hippocampus and amygdala induced by Abeta(25-35). Nitrotyrosine levels in these regions were negatively correlated with memory performance. Moreover, real-time RT-PCR revealed that silibinin inhibited the overexpression of iNOS and TNF-alpha mRNA in the hippocampus and amygdala induced by Abeta(25-35). These findings suggest that silibinin (i) attenuates memory impairment through amelioration of oxidative stress and inflammatory response induced by Abeta(25-35) and (ii) may be a potential candidate for an AD medication.

Effects of β‐amyloid peptide on the density of M2 muscarinic acetylcholine receptor protein in the hippocampus of the rat: relationship with GABA‐, calcium‐binding protein and somatostatin‐containing cells

The deposition of amyloid peptides (A beta) in the cortex and hippocampus is the primary trigger of Alzheimer's disease (AD). Recent studies also indicated that the M2 subtype of muscarinic acetylcholine receptors (M2mAChR) may be a key molecule involved in cognitive dysfunction. Thus, the purpose of this study was to determine the effects of extracellular deposition of A beta on the density of M2mAChR in the hippocampus of the rat by M2mAChR-immunohistochemistry. Special attention was paid to discerning any interaction between A beta and M2mAChR in GABA-, and calcium-binding protein containing cells by double-labelling immunohistochemistry. Densitometric analysis of M2mAChR-immunoreactivity was performed using Scion Image Beta Software. Quantitative analysis of GABA-, and calcium-binding protein interneurones containing M2mAChR protein was performed using a NeuroLucida morphometric system. Injections of A beta into the retrosplenial cortex resulted in a significant reduction in M2mAChR-immunoreactivity in the CA1 ipsilateral to the A beta-injected side as compared with the corresponding hemisphere of non-treated control animals and with that in the corresponding region of the CA1 in the phosphate-buffered saline-injected side. Co-localization studies showed that the M2mAChR is localized in a subset of GABA-positive cells of the hippocampus, in cells that contain calcium-binding proteins, and in a subpopulation of cells that contain the neuropeptide somatostatin. Our findings suggest that A beta induces a significant reduction in M2mAChR-immunoreactivity in the CA1 of the hippocampus and a reduction in GABAergic interneurones containing M2mAChR, which may contribute to impairment of GABAergic synaptic transmission in area CA1 of hippocampus.

Time-resolved grazing-incidence small-angle X-ray scattering studies of lipid multibilayers with the insertion of amyloid peptide during the swelling process

The β-amyloid peptide (Aβ) (1–40) is one of the major components that form Alzheimer's amyloid deposits. Studies of the membrane insertion of amyloid showed that amyloid is surface active and can insert into lipid monolayers [Ji et al. (2002). Biochemistry (Moscow), 67, 1283–1288; Ege & Lee (2004). Biophys. J. 87, 1732–1740]. The interaction between the peptide and a lipid monolayer or bilayer is critical to the understanding of the formation of amyloid peptide deposits on the membrane. In this paper, we have studied the structural transition of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) multibilayers with the insertion of amyloid peptide 1–40 by grazing-incidence small-angle X-ray scattering at different bilayer hydration levels (changing the relatively humidity). We mixed the DPPC and amyloid peptide in an organic solvent at a 10 to 1 weight ratio, then cast it onto a silicon wafer to form the mixed lipid multibilayer film. In this study of the pure DPPC multibilayer film and the DPPC multibilayer film inserted with amyloid peptide, it was found that the hydration process was bimodal with a better-hydrated top layer and a less-hydrated bottom layer. The gel-to-ripple phase transition suffers a strong confinement effect due to the presence of the solid substrate. With the insertion of the amyloid peptide, the ripple phase of the membrane bilayers was suppressed at high humidity and the whole film can be swollen more uniformly at lower incubation time than the pure DPPC film supported on a silicon wafer. This means water vapor can penetrate more easily into the DPPC bilayers inserted with Aβ than into the pure DPPC bilayers. Amyloid peptides were found to form clusters in the bilayer and possess in-plane correlation. From analyzing the diffuse scattering around the Bragg peak in the lateral direction, the amyloid peptides are found to form clusters in the bilayer with a radius of about 9 nm. It is also estimated that the number of Aβ molecules in one cluster is about 12 and on average each Aβ molecule occupies an interface area of about 22 nm2. As the relative humidity exceeds about 94%, the Aβ clusters seem to develop an ordered structure with a spacing of about 300 Å.

TAT-BH4 counteracts Aβ toxicity on capillary endothelium

Oxidative stress is one of the factor contributing to blood brain barrier degeneration. This phenomenon is observed during pathological conditions such as Alzheimer’s disease or cerebral amyloid angiopathy in which brain haemorrhages are very frequent. Both diseases are characterized by beta amyloid peptide deposition either in neurons or in vessels. Oxidative stress leads to impairment of mitochondrial functions and apoptotic cell death subsequent to caspases activation. In this paper we demonstrate that BH4 domain of Bcl-xl administrated to endothelial cells as the conjugated form with TAT peptide, reverts Aβ-induced apoptotic cell death by activating a survival programme which is Akt/endothelial nitric oxide synthase dependent.

On the Molecular Basis Linking Nerve Growth Factor (NGF) to Alzheimer’s Disease

1. Alzheimer's disease (AD) is pathologically defined by the deposition of amyloid peptide and neurofibrillary tangles and is characterized by a progressive loss of cognition and memory function, due to marked cortical cholinergic depletion. 2. Cholinergic cortical innervation is provided by basal forebrain cholinergic neurons. The neurotrophin Nerve Growth Factor (NGF) promotes survival and differentiation of basal forebrain cholinergic neurons. 3. This assertion has been at the basis of the hypothesis developed in the last 20 years, whereby NGF deprivation would be one of the factor involved in the etiology of sporadic forms of AD. 4. In this review, we shall summarize data that lead to the production and characterization of a mouse model for AD (AD11 anti-NGF mice), based on the expression of transgenic antibodies neutralizing NGF. The AD-like phenotype of AD11 mice will be discussed on the basis of recent studies that have posed NGF and its precursor pro-NGF back to the stage of AD-like neurodegeneration, showing the involvement of the precursor pro-NGF in one of the cascades leading to AD neurodegeneration.

Uptake of Abeta 1-40- and Abeta 1-42-coated yeast by microglial cells: a role for LRP.

Artificial diffuse and amyloid core of neuritic plaques [beta-amyloid peptide (Abeta) deposits] could be prepared using heat-killed yeast particles opsonized with Abeta 1-40 or Abeta 1-42 peptides. Interaction and fate of these artificial deposits with microglial cells could be followed using a method of staining that allows discrimination of adherent and internalized, heat-killed yeast particles. Using this system, it was possible to show that nonfibrillar or fibrillar (f)Abeta peptides, formed in solution upon heating (aggregates), could not impair the internalization of heat-killed yeast particles opsonized with fAbeta 1-40 or fAbeta 1-42. This indicated that depending on their physical state, Abeta peptide(s) do not recognize the same receptors and probably do not follow the same internalization pathway. Using competitive ligands of class A scavenger receptors (SR-A) or low-density lipoprotein-related receptor protein (LRP), it has been shown that SR-A were not involved in the recognition of amyloid peptide deposits, whereas LRP specifically recognized deposits of fAbeta 1-42 (but not fAbeta 1-40) and mediated their phagocytosis.

Interactions of Alzheimer amyloid peptides with cultured cells and brain tissue, and their biological consequences.

The Alzheimer amyloid peptides are the main constituent of the diagnostic hallmark of Alzheimer disease, the senile plaque. A halo of neurodegeneration surrounds the senile plaques observed in the brains of Alzheimer patients. Significant efforts are under way to determine whether the Alzheimer peptides are the causal agents of this neurodegeneration. We review the developments in identifying the putative interaction sites of Alzheimer amyloid peptides on cells and intact brain tissue. We focus on the specificity of this interaction and on the molecular nature of potential receptors. These studies form the bases for developing therapeutics that target potential interaction sites and inhibit Alzheimer amyloid peptide deposition.

Selection of RNA Aptamers to the Alzheimer's Disease Amyloid Peptide

Alzheimer's disease is correlated with the deposition of amyloid peptides in the brain of the patients. The amyloid is thus a major target in the search for novel diagnostic and therapeutic approaches. The present work employs in vitro selection to develop new tools for the study of the Alzheimer's disease. The selection strategy enables the design of specific nucleic acids (aptamers) against virtually any target molecule. High-affinity RNA aptamers against the βA4(1–40) were isolated from a combinatorial library of ∼1015 different molecules. The apparent dissociation constants Kd of these aptamers are 29–48 nM. The binding of the RNA to the amyloid fibrils was confirmed by electron microscopy. The chemical synthesis of these nucleic acids enables tailor-made modifications. By introduction of specific reporter groups these RNAs can become suitable tools for analytical and diagnostic purposes. Thus, this study may introduce a new approach for diagnosis of the Alzheimer's disease.