Peripherally Applied Synthetic Peptide isoAsp7-Aβ(1-42) Triggers Cerebral β-Amyloidosis

Post-translational modifications of beta-amyloid alter its transport in the blood-brain barrier in vitro model

One of the hallmarks of Alzheimer's disease (AD) is the accumulation of beta-amyloid peptide (Aβ) leading to formation of soluble neurotoxic Aβ oligomers and insoluble amyloid plaques in various parts of the brain. Aβ undergoes post-translational modifications that alter its pathogenic properties. Aβ is produced not only in brain, but also in the peripheral tissues. Such Aβ, including its post-translationally modified forms, can enter the brain from circulation by binding to RAGE and contribute to the pathology of AD. However, the transport of modified forms of Aβ across the blood-brain barrier (BBB) has not been investigated. Here, we used a transwell BBB model as a controlled environment for permeability studies. We found that Aβ42 containing isomerized Asp7 residue (iso-Aβ42) and Aβ42 containing phosphorylated Ser8 residue (pS8-Aβ42) crossed the BBB better than unmodified Aβ42, which correlated with different contribution of endocytosis mechanisms to the transport of these isoforms. Using microscale thermophoresis, we observed that RAGE binds to iso-Aβ42 an order of magnitude weaker than to Aβ42. Thus, post-translational modifications of Aβ increase the rate of its transport across the BBB and modify the mechanisms of the transport, which may be important for AD pathology and treatment.

Switching On/Off Amyloid Plaque Formation in Transgenic Animal Models of Alzheimer's Disease

A hallmark of Alzheimer's disease (AD) are the proteinaceous aggregates formed by the amyloid-beta peptide (Aβ) that is deposited inside the brain as amyloid plaques. The accumulation of aggregated Aβ may initiate or enhance pathologic processes in AD. According to the amyloid hypothesis, any agent that has the capability to inhibit Aβ aggregation and/or destroy amyloid plaques represents a potential disease-modifying drug. In 2023, a humanized IgG1 monoclonal antibody (lecanemab) against the Aβ-soluble protofibrils was approved by the US FDA for AD therapy, thus providing compelling support to the amyloid hypothesis. To acquire a deeper insight on the in vivo Aβ aggregation, various animal models, including aged herbivores and carnivores, non-human primates, transgenic rodents, fish and worms were widely exploited. This review is based on the recent data obtained using transgenic animal AD models and presents experimental verification of the critical role in Aβ aggregation seeding of the interactions between zinc ions, Aβ with the isomerized Asp7 (isoD7-Aβ) and the α4β2 nicotinic acetylcholine receptor.

Molecular Mechanism of Zinc-Dependent Oligomerization of Alzheimer's Amyloid-β with Taiwan (D7H) Mutation

Amyloid-β (Aβ) is a peptide formed by 39-43 amino acids, heterogenous by the length of its C-terminus. Aβ constitutes a subnanomolar monomeric component of human biological fluids; however, in sporadic variants of Alzheimer's disease (AD), it forms soluble neurotoxic oligomers and accumulates as insoluble extracellular polymeric aggregates (amyloid plaques) in the brain tissues. The plaque formation is controlled by zinc ions; therefore, abnormal interactions between the ions and Aβ seem to take part in the triggering of sporadic AD. The amyloid plaques contain various Aβ isoforms, among which the most common is Aβ with an isoaspartate in position 7 (isoD7). The spontaneous conversion of D7 to isoD7 is associated with Aβ aging. Aβ molecules with isoD7 (isoD7-Aβ) easily undergo zinc-dependent oligomerization, and upon administration to transgenic animals (mice, nematodes) used for AD modeling, act as zinc-dependent seeds of the pathological aggregation of Aβ. The formation of zinc-bound homo- and hetero-oligomers with the participation of isoD7-Aβ is based on the rigidly structured segment 11-EVHH-14, located in the Aβ metal binding domain (Aβ₁₆). Some hereditary variants of AD are associated with familial mutations within the domain. Among these, the most susceptible to zinc-dependent oligomerization is Aβ with Taiwan (D7H) mutation (D7H-Aβ). In this study, the D7H-Aβ metal binding domain (D7H-Aβ₁₆) has been used as a model to establish the molecular mechanism of zinc-induced D7H-Aβ oligomerization through turbidimetry, dynamic light scattering, isothermal titration calorimetry, mass spectrometry, and computer modelling. Additionally, the modeling data showed that a molecule of D7H-Aβ, as well as isoD7-Aβ in combination with two Aβ molecules, renders a stable zinc-induced heterotrimer. The trimers are held together by intermolecular interfaces via zinc ions, with the primary interfaces formed by 11-EVHH-14 sites of the interacting trimer subunits. In summary, the obtained results confirm the role of the 11-EVHH-14 region as a structure and function determinant for the zinc-dependent oligomerization of all known Aβ species (including various chemically modified isoforms and AD-associated mutants) and point at this region as a potent target for drugs aimed to stop amyloid plaque formation in both sporadic and hereditary variants of AD.

Alzheimer's Disease: Significant Benefit from the Yeast-Based Models

Alzheimer's disease (AD) is an age-related, multifaceted neurological disorder associated with accumulation of aggregated proteins (amyloid Aβ and hyperphosphorylated tau), loss of synapses and neurons, and alterations in microglia. AD was recognized by the World Health Organization as a global public health priority. The pursuit of a better understanding of AD forced researchers to pay attention to well-defined single-celled yeasts. Yeasts, despite obvious limitations in application to neuroscience, show high preservation of basic biological processes with all eukaryotic organisms and offer great advantages over other disease models due to the simplicity, high growth rates on low-cost substrates, relatively simple genetic manipulations, the large knowledge base and data collections, and availability of an unprecedented amount of genomic and proteomic toolboxes and high-throughput screening techniques, inaccessible to higher organisms. Research reviewed above clearly indicates that yeast models, together with other, more simple eukaryotic models including animal models, C. elegans and Drosophila, significantly contributed to understanding Aβ and tau biology. These models allowed high throughput screening of factors and drugs that interfere with Aβ oligomerization, aggregation and toxicity, and tau hyperphosphorylation. In the future, yeast models will remain relevant, with a focus on creating novel high throughput systems to facilitate the identification of the earliest AD biomarkers among different cellular networks in order to achieve the main goal-to develop new promising therapeutic strategies to treat or prevent the disease.

Effect of β-amyloid on blood-brain barrier properties and function

The deposition of beta-amyloid (Aβ) aggregates in the brain, accompanied by impaired cognitive function, is a characteristic feature of Alzheimer's disease (AD). An important role in this process is played by vascular disorders, in particular, a disturbance of the blood-brain barrier (BBB). The BBB controls the entry of Aβ from plasma to the brain via the receptor for advanced glycation end products (RAGE) and the removal of brain-derived Aβ via the low-density lipoprotein receptor-related protein (LRP1). The balance between the input of Aβ to the brain from the periphery and its output is disturbed during AD. Aβ changes the redox-status of BBB cells, which in turn changes the functioning of mitochondria and disrupts the barrier function of endothelial cells by affecting tight junction proteins. Aβ oligomers have the greatest toxic effect on BBB cells, and oligomers are most rapidly transferred by transcytosis from the brain side of the BBB to the blood side. Both the cytotoxic effect of Aβ and the impairment of barrier function are partly due to the interaction of Aβ monomers and oligomers with membrane-bound RAGE. AD therapies based on the disruption of this interaction or the creation of decoys for Aβ are being developed. The question of the transfer of various Aβ isoforms through the BBB is important, since it can influence the development of AD. It is shown that the rate of input of Aβ40 and Aβ42 from the blood into the brain is different. The actual question of the transfer of pathogenic Aβ isoforms with post-translational modifications or mutations through the BBB still remains open.

The Amyloid-Beta Clearance: From Molecular Targets to Glial and Neural Cells

The deposition of amyloid-beta (Aβ) plaques in the brain is one of the primary pathological characteristics of Alzheimer's disease (AD). It can take place 20-30 years before the onset of clinical symptoms. The imbalance between the production and the clearance of Aβ is one of the major causes of AD. Enhancing Aβ clearance at an early stage is an attractive preventive and therapeutic strategy of AD. Direct inhibition of Aβ production and aggregation using small molecules, peptides, and monoclonal antibody drugs has not yielded satisfactory efficacy in clinical trials for decades. Novel approaches are required to understand and combat Aβ deposition. Neurological dysfunction is a complex process that integrates the functions of different types of cells in the brain. The role of non-neurons in AD has not been fully elucidated. An in-depth understanding of the interactions between neurons and non-neurons can contribute to the elucidation of Aβ formation and the identification of effective drug targets. AD patient-derived pluripotent stem cells (PSCs) contain complete disease background information and have the potential to differentiate into various types of neurons and non-neurons in vitro, which may bring new insight into the treatment of AD. Here, we systematically review the latest studies on Aβ clearance and clarify the roles of cell interactions among microglia, astroglia and neurons in response to Aβ plaques, which will be beneficial to explore methods for reconstructing AD disease models using inducible PSCs (iPSCs) through cell differentiation techniques and validating the applications of models in understanding the formation of Aβ plaques. This review may provide the most promising directions of finding the clues for preventing and delaying the development of AD.

Role of Interaction between Zinc and Amyloid Beta in Pathogenesis of Alzheimer’s Disease

Progression of Alzheimer's disease is accompanied by the appearance of extracellular deposits in the brain tissues of patients with characteristic supramolecular morphology (amyloid plaques) the main components of which are β-amyloid isoforms (Aβ) and biometal ions (zinc, copper, iron). For nearly 40 years and up to the present time, the vast majority of experimental data indicate critical role of formation and accumulation of amyloid plaques (cerebral amyloidogenesis) in pathogenesis of Alzheimer's disease, however, nature of the molecular agents that initiate cerebral amyloidogenesis, as well as causes of aggregation of the native Aβ molecules in vivo remained unknown for a long time. This review discusses the current level of fundamental knowledge about the molecular mechanisms of interactions of zinc ions with a number of Aβ isoforms present in amyloid plaques of the patients with Alzheimer's disease, and also shows how this knowledge made it possible to identify driving forces of the cerebral amyloidogenesis in Alzheimer's disease and made it possible to determine fundamentally new biomarkers and drug targets as part of development of innovative strategy for diagnosis and treatment of Alzheimer's disease.

Distinct Effects of Beta-Amyloid, Its Isomerized and Phosphorylated Forms on the Redox Status and Mitochondrial Functioning of the Blood-Brain Barrier Endothelium

The Alzheimer's disease (AD)-associated breakdown of the blood-brain barrier (BBB) promotes the accumulation of beta-amyloid peptide (Aβ) in the brain as the BBB cells provide Aβ transport from the brain parenchyma to the blood, and vice versa. The breakdown of the BBB during AD may be caused by the emergence of blood-borne Aβ pathogenic forms, such as structurally and chemically modified Aβ species; their effect on the BBB cells has not yet been studied. Here, we report that the effects of Aβ₄₂, Aβ₄₂, containing isomerized Asp7 residue (iso-Aβ₄₂) or phosphorylated Ser8 residue (p-Aβ₄₂) on the mitochondrial potential and respiration are closely related to the redox status changes in the mouse brain endothelial cells bEnd.3. Aβ₄₂ and iso-Aβ₄₂ cause a significant increase in nitric oxide, reactive oxygen species, glutathione, cytosolic calcium and the mitochondrial potential after 4 h of incubation. P-Aβ₄₂ either does not affect or its effect develops after 24 h of incubation. Aβ₄₂ and iso-Aβ₄₂ activate mitochondrial respiration compared to p-Aβ₄₂. The isomerized form promotes a greater cytotoxicity and mitochondrial dysfunction, causing maximum oxidative stress. Thus, Aβ₄₂, p-Aβ₄₂ and iso-Aβ₄₂ isoforms differently affect the BBBs' cell redox parameters, significantly modulating the functioning of the mitochondria. The changes in the level of modified Aβ forms can contribute to the BBBs' breakdown during AD.

Synthetic, Cell-Derived, Brain-Derived, and Recombinant β-Amyloid: Modelling Alzheimer's Disease for Research and Drug Development

Alzheimer's disease (AD) is the most common cause of dementia in the elderly, characterised by the accumulation of senile plaques and tau tangles, neurodegeneration, and neuroinflammation in the brain. The development of AD is a pathological cascade starting according to the amyloid hypothesis with the accumulation and aggregation of the β-amyloid peptide (Aβ), which induces hyperphosphorylation of tau and promotes the pro-inflammatory activation of microglia leading to synaptic loss and, ultimately, neuronal death. Modelling AD-related processes is important for both studying the molecular basis of the disease and the development of novel therapeutics. The replication of these processes is often achieved with the use of a purified Aβ peptide. However, Aβ preparations obtained from different sources can have strikingly different properties. This review aims to compare the structure and biological effects of Aβ oligomers and aggregates of a higher order: synthetic, recombinant, purified from cell culture, or extracted from brain tissue. The authors summarise the applicability of Aβ preparations for modelling Aβ aggregation, neurotoxicity, cytoskeleton damage, receptor toxicity in vitro and cerebral amyloidosis, synaptic plasticity disruption, and cognitive impairment in vivo and ex vivo. Further, the paper discusses the causes of the reported differences in the effect of Aβ obtained from the sources mentioned above. This review points to the importance of the source of Aβ for AD modelling and could help researchers to choose the optimal way to model the Aβ-induced abnormalities.

Mass spectrometric studies of the variety of beta-amyloid proteoforms in Alzheimer's disease

This review covers the results of the application of mass spectrometric (MS) techniques to study the diversity of beta-amyloid (Aβ) peptides in human samples. Since Aβ is an important hallmark of Alzheimer's disease (AD), which is a socially significant neurodegenerative disorder of the elderly worldwide, analysis of its endogenous variations is of particular importance for elucidating the pathogenesis of AD, predicting increased risks of the disease onset, and developing effective therapy. MS approaches have no alternative for the study of complex samples, including a wide variety of Aβ proteoforms, differing in length and modifications. Approaches based on matrix-assisted laser desorption/ionization time-of-flight and liquid chromatography with electrospray ionization tandem MS are most common in Aβ studies. However, Aβ forms with isomerized and/or racemized Asp and Ser residues require the use of special methods for separation and extra sensitive and selective methods for detection. Overall, this review summarizes current knowledge of Aβ species found in human brain, cerebrospinal fluid, and blood plasma; focuses on application of different MS approaches for Aβ studies; and considers the potential of MS techniques for further studies of Aβ-peptides.

Zn-dependent β-amyloid Aggregation and its Reversal by the Tetrapeptide HAEE

The pathogenesis of Alzheimer's disease (AD) is associated with the formation of cerebral amyloid plaques, the main components of which are the modified Aβ molecules as well as the metal ions. Aβ isomerized at Asp7 residue (isoD7-Aβ) is the most abundant isoform in amyloid plaques. We hypothesized that the pathogenic effect of isoD7-Aβ is due to the formation of zinc-dependent oligomers, and that this interaction can be disrupted by the rationally designed tetrapeptide (HAEE). Here, we utilized surface plasmon resonance, nuclear magnetic resonance, and molecular dynamics simulation to demonstrate Zn²⁺-dependent oligomerization of isoD7-Aβ and the formation of a stable isoD7-Aβ:Zn²⁺:HAEE complex incapable of forming oligomers. To demonstrate the physiological importance of zinc-dependent isoD7-Aβ oligomerization and the ability of HAEE to interfere with this process at the organismal level, we employed transgenic nematodes overexpressing human Aβ. We show that the presence of isoD7-Aβ in the medium triggers extensive amyloidosis that occurs in a Zn²⁺-dependent manner, enhances paralysis, and shortens the animals' lifespan. Exogenous HAEE completely reverses these pathological effects of isoD7-Aβ. We conclude that the synergistic action of isoD7-Aβ and Zn²⁺ promotes Aβ aggregation and that the selected small molecules capable of interrupting this process, such as HAEE, can potentially serve as anti-amyloid therapeutics.

The Dynamics of β-Amyloid Proteoforms Accumulation in the Brain of a 5xFAD Mouse Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is the leading cause of dementia among the elderly. Neuropathologically, AD is characterized by the deposition of a 39- to 42-amino acid long β-amyloid (Aβ) peptide in the form of senile plaques. Several post-translational modifications (PTMs) in the N-terminal domain have been shown to increase the aggregation and cytotoxicity of Aβ, and specific Aβ proteoforms (e.g., Aβ with isomerized D7 (isoD7-Aβ)) are abundant in the senile plaques of AD patients. Animal models are indispensable tools for the study of disease pathogenesis, as well as preclinical testing. In the presented work, the accumulation dynamics of Aβ proteoforms in the brain of one of the most widely used amyloid-based mouse models (the 5xFAD line) was monitored. Mass spectrometry (MS) approaches, based on ion mobility separation and the characteristic fragment ion formation, were applied. The results indicated a gradual increase in the Aβ fraction of isoD7-Aβ, starting from approximately 8% at 7 months to approximately 30% by 23 months of age. Other specific PTMs, in particular, pyroglutamylation, deamidation, and oxidation, as well as phosphorylation, were also monitored. The results for mice of different ages demonstrated that the accumulation of Aβ proteoforms correlate with the formation of Aβ deposits. Although the mouse model cannot be a complete analogue of the processes occurring in the human brain in AD, and several of the observed parameters differ significantly from human values supposedly due to the limited lifespan of the model animals, this dynamic study provides evidence on at least one of the possible mechanisms that can trigger amyloidosis in AD, i.e., the hypothesis on the relationship between the accumulation of isoD7-Aβ and the progression of AD-like pathology.

First Immunoassay for Measuring Isoaspartate in Human Serum Albumin

Isoaspartate (isoAsp) is a damaging amino acid residue formed in proteins mostly as a result of spontaneous deamidation of asparaginyl residues. An association has been found between isoAsp in human serum albumin (HSA) and Alzheimer’s disease (AD). Here we report on a novel monoclonal antibody (mAb) 1A3 with excellent specificity to isoAsp in the functionally important domain of HSA. Based on 1A3 mAb, an indirect enzyme-linked immunosorbent assay (ELISA) was developed, and the isoAsp occupancy in 100 healthy plasma samples was quantified for the first time, providing the average value of (0.74 ± 0.13)%. These results suggest potential of isoAsp measurements for supplementary AD diagnostics as well as for assessing the freshness of stored donor blood and its suitability for transfusion.

Beta Amyloid, Tau Protein, and Neuroinflammation: An Attempt to Integrate Different Hypotheses of Alzheimer’s Disease Pathogenesis

Abstract

Alzheimer’s disease (AD) is a neurodegenerative disease that inevitably results in dementia and death. Currently, there are no pathogenetically grounded methods for the prevention and treatment of AD, and all current treatment regimens are symptomatic and unable to significantly delay the development of dementia. The accumulation of β-amyloid peptide (Aβ), which is a spontaneous, aggregation-prone, and neurotoxic product of the processing of signaling protein APP (Amyloid Precursor Protein), in brain tissues, primarily in the hippocampus and the frontal cortex, was for a long time considered the main cause of neurodegenerative changes in AD. However, attempts to treat AD based on decreasing Aβ production and aggregation did not bring significant clinical results. More and more arguments are arising in favor of the fact that the overproduction of Aβ in most cases of AD is not the initial cause, but a concomitant event of pathological processes in the course of the development of sporadic AD. The concept of neuroinflammation has come to the fore, suggesting that inflammatory responses play the leading role in the initiation and development of AD, both in brain tissue and in the periphery. The hypothesis about the key role of neuroinflammation in the pathogenesis of AD opens up new opportunities in the search for ways to treat and prevent this socially significant disease.

Blood cell-produced amyloid-β induces cerebral Alzheimer-type pathologies and behavioral deficits

It is traditionally believed that cerebral amyloid-beta (Aβ) deposits are derived from the brain itself in Alzheimer's disease (AD). Peripheral cells such as blood cells also produce Aβ. The role of peripherally produced Aβ in the pathogenesis of AD remains unknown. In this study, we established a bone marrow transplantation model to investigate the contribution of blood cell-produced Aβ to AD pathogenesis. We found that bone marrow cells (BMCs) transplanted from APPswe/PS1dE9 transgenic mice into wild-type (Wt) mice at 3 months of age continuously expressed human Aβ in the blood, and caused AD phenotypes including Aβ plaques, cerebral amyloid angiopathy (CAA), tau hyperphosphorylation, neuronal degeneration, neuroinflammation, and behavioral deficits in the Wt recipient mice at 12 months after transplantation. Bone marrow reconstitution in APPswe/PS1dE9 mice with Wt-BMCs at 3 months of age reduced blood Aβ levels, and alleviated brain Aβ burden, neuronal degeneration, neuroinflammation, and behavioral deficits in the AD model mice at 12 months after transplantation. Our study demonstrated that blood cell-produced Aβ plays a significant role in AD pathogenesis, and the elimination of peripheral production of Aβ can decrease brain Aβ deposition and represents a novel therapeutic approach for AD.

Quantification of N-terminal amyloid-β isoforms reveals isomers are the most abundant form of the amyloid-β peptide in sporadic Alzheimer's disease

Plaques that characterize Alzheimer's disease accumulate over 20 years as a result of decreased clearance of amyloid-β peptides. Such long-lived peptides are subjected to multiple post-translational modifications, in particular isomerization. Using liquid chromatography ion mobility separations mass spectrometry, we characterized the most common isomerized amyloid-β peptides present in the temporal cortex of sporadic Alzheimer's disease brains. Quantitative assessment of amyloid-β N-terminus revealed that > 80% of aspartates (Asp-1 and Asp-7) in the N-terminus was isomerized, making isomerization the most dominant post-translational modification of amyloid-β in Alzheimer's disease brain. Total amyloid-β1-15 was ∼85% isomerized at Asp-1 and/or Asp-7 residues, with only 15% unmodified amyloid-β1-15 left in Alzheimer's disease. While amyloid-β4-15 the next most abundant N-terminus found in Alzheimer's disease brain, was only ∼50% isomerized at Asp-7 in Alzheimer's disease. Further investigations into different biochemically defined amyloid-β-pools indicated a distinct pattern of accumulation of extensively isomerized amyloid-β in the insoluble fibrillar plaque and membrane-associated pools, while the extent of isomerization was lower in peripheral membrane/vesicular and soluble pools. This pattern correlated with the accumulation of aggregation-prone amyloid-β42 in Alzheimer's disease brains. Isomerization significantly alters the structure of the amyloid-β peptide, which not only has implications for its degradation, but also for oligomer assembly, and the binding of therapeutic antibodies that directly target the N-terminus, where these modifications are located.

Infusion of blood from mice displaying cerebral amyloidosis accelerates amyloid pathology in animal models of Alzheimer's disease

Previous studies showed that injection of tissue extracts containing amyloid-β (Aβ) aggregates accelerate amyloid deposition in the brain of mouse models of Alzheimer’s disease (AD) through prion-like mechanisms. In this study, we evaluated whether brain amyloidosis could be accelerated by blood infusions, procedures that have been shown to transmit prion diseases in animals and humans. Young transgenic mice infused with whole blood or plasma from old animals with extensive Aβ deposition in their brains developed significantly higher levels brain amyloidosis and neuroinflammation compared to untreated animals or mice infused with wild type blood. Similarly, intra-venous injection of purified Aβ aggregates accelerated amyloid pathology, supporting the concept that Aβ seeds present in blood can reach the brain to promote neuropathological alterations in the brain of treated animals. However, an amyloid-enhancing effect of other factors present in the blood of donors cannot be discarded. Our results may help to understand the role of peripheral (amyloid-dependent or -independent) factors implicated in the development of AD and uncover new strategies for disease intervention.

Targeting isoaspartate-modified Aβ rescues behavioral deficits in transgenic mice with Alzheimer's disease-like pathology

Background

Amyloid β (Aβ)-directed immunotherapy has shown promising results in preclinical and early clinical Alzheimer’s disease (AD) trials, but successful translation to late clinics has failed so far. Compelling evidence suggests that post-translationally modified Aβ peptides might play a decisive role in onset and progression of AD and first clinical trials targeting such Aβ variants have been initiated. Modified Aβ represents a small fraction of deposited material in plaques compared to pan-Aβ epitopes, opening up pathways for tailored approaches of immunotherapy. Here, we generated the first monoclonal antibodies that recognize l-isoaspartate-modified Aβ (isoD7-Aβ) and tested a lead antibody molecule in 5xFAD mice.

Methods

This work comprises a combination of chemical and biochemical techniques as well as behavioral analyses. Aβ peptides, containing l-isoaspartate at position 7, were chemically synthesized and used for immunization of mice and antibody screening methods. Biochemical methods included anti-isoD7-Aβ monoclonal antibody characterization by surface plasmon resonance, immunohistochemical staining of human and transgenic mouse brain, and the development and application of isoD7-Aβ ELISA as well as different non-modified Aβ ELISA. For antibody treatment studies, 12 mg/kg anti-isoD7-Aβ antibody K11_IgG2a was applied intraperitoneally to 5xFAD mice for 38 weeks. Treatment controls implemented were IgG2a isotype as negative and 3D6_IgG2a, the parent molecule of bapineuzumab, as positive control antibodies. Behavioral studies included elevated plus maze, pole test, and Morris water maze.

Results

Our advanced antibody K11 showed a K_D in the low nM range and > 400fold selectivity for isoD7-Aβ compared to other Aβ variants. By using this antibody, we demonstrated that formation of isoD7-Aβ may occur after formation of aggregates; hence, the presence of the isoD7-modification differentiates aged Aβ from newly formed peptides. Importantly, we also show that the Tottori mutation responsible for early-onset AD in a Japanese pedigree is characterized by massively accelerated formation of isoD7-Aβ in cell culture. The presence of isoD7-Aβ was verified by K11 in post mortem human cortex and 5xFAD mouse brain tissue. Passive immunization of 5xFAD mice resulted in a significant reduction of isoD7-Aβ and total Aβ in brain. Amelioration of cognitive impairment was demonstrated by Morris water maze, elevated plus maze, pole, and contextual fear conditioning tests. Interestingly, despite the lower abundance of the isoD7-Aβ epitope, the application of anti-isoD7-Aβ antibodies showed comparable treatment efficacy in terms of reduction of brain amyloid and spatial learning but did not result in an increase of plasma Aβ concentration as observed with 3D6 treatment.

Conclusions

The present study demonstrates, for the first time, that the antibody-mediated targeting of isoD7-modified Aβ peptides leads to attenuation of AD-like amyloid pathology. In conjunction with previously published data on antibodies directed against pGlu-modified Aβ, the results highlight the crucial role of modified Aβ peptides in AD pathophysiology. Hence, the results also underscore the therapeutic potential of targeting modified amyloid species for defining tailored approaches in AD therapy.

Supplementary information

The online version contains supplementary material available at 10.1186/s13195-020-00719-x.

Side-chain conformers to allow conversion from normal to isoaspartate in age-related proteins and peptides

Dβ (or D-iso)- and Lβ- (or iso)- aspartyl (Asp) residues are accumulated in aged lens crystallins and amyloid beta (Aβ) proteins, respectively, as a result of spontaneous, nonenzymatic isomerization of normal Lα-Asp. To explore why such uncommon Asp isomers are accumulated, the stability of Lα-, Lβ-, and Dβ-Asp was compared in view of the staggered side-chain conformers. By using cylindrin (KVKVLGD⁷VIEV) from αB-crystallin and Aβ17-25 (L¹⁷VFF²⁰AED²³)VG²⁵) containing Asp isomers, the vicinal spin-spin coupling constants of Asp H_α-H_β1 and H_α-H_β2 were quantified by high-resolution solution ¹H NMR. It was found that the trans conformer was extremely preferred in Dβ-Asp7 side-chain of cylindrin. In Aβ17-25, the side chain of Lβ-Asp23 was likely to adopt trans conformer, while gauche conformers were rather rich in Lα-Asp23. In gauche conformers, the close distance between Asp carboxylate carbon (C_COO-) and backbone nitrogen (N) next to Asp is advantageous to the intramolecular cyclization to form succinimide intermediate, followed by the conversion from α- to β-Asp. The cyclization is limited in the trans conformer because of the long distance between C_COO- and N, to keep Dβ- or Lβ-Asp stable. This would be the reason for the site specificity of Asp isomerization in proteins. The higher population of trans conformer in Asp side chain, the less isomerization of Asp as shown as Asp76 in αA-crystallin. The stability and less reactivity of normal Asp and its isomers are the potential factors to determine whether or not the abnormal accumulation is permitted in aged crystallins and Aβ.

Revisiting the role of brain and peripheral Aβ in the pathogenesis of Alzheimer's disease

Amyloid beta (Aβ) is an intricate molecule that interacts with several biomolecules and/or produces insoluble assemblies and eventually the nonphysiological depositions of its alternate with normal neuronal conditions leading to Alzheimer's disease (AD). Aβ is formed through the proteolytic cleavage of the amyloid precursor protein (APP). Significant efforts are being made to explore the exact role of Aβ in AD pathogenesis. It is believed that the deposition of Aβ in the brain takes place from Aβ components which are derived from the brain itself. However, recent evidence suggests that Aβ derived also from the periphery and hence the Aβ circulating in the blood is capable of penetrating the blood-brain barrier (BBB) and the role of Aβ derived from the periphery is largely unknown so far. Therefore, Aβ origin determination and the underlying mechanisms of its pathological effects are of considerable interest in exploring effective therapeutic strategies. The purpose of this review is to provide a novel insight into AD pathogenesis based on Aβ in both the brain and periphery and highlight new therapeutic avenues to combat AD pathogenesis.

Aberrant interactions between amyloid-beta and alpha5 laminins as possible driver of neuronal disfunction in Alzheimer's disease

It has been widely accepted that laminins are involved in pathogenesis of Alzheimer's disease (AD). Amyloid plaques in AD patients are associated with immunostaining using antibodies raised against laminin-111, and laminin-111 has been shown to prevent aggregation of amyloid peptides. Although numerous articles describe small peptides from laminin-111 that are capable to disaggregate amyloid buildups and reduce neurotoxicity in in vitro and in vivo models, there is no approved laminin-111-based therapeutic approaches for treatment of AD. Also, it has been shown that immunoreactivity to laminin-111 appears late in development of cerebral amyloidosis. Based on the published data, we hypothesize that aberrant interaction between amyloid-beta and α5-laminins such as laminin-511 prevents the necessary laminin signaling into neurons leading to neurodegeneration and contributing to the early development of AD. Laminin-511 is the key extracellular protein that protects neurons from anoikis, inhibits excitoxicity and provides signaling that stabilizes dendritic spines and synapses in the developed brain. Absence of the signaling from laminin-511 leads to behavioral defects in mice. Laminin-511 and hippocampal neurons are in direct contact and accumulation of amyloid-beta that has been shown to avidly bind laminin-511 may physically decouple the interaction between α5-laminins and the neuronal membrane receptors inhibiting the signaling. Under this hypothesis, protein domains and peptides from laminin α5 chain may have a therapeutic potential in treatment of AD and the appearance of laminin-111 in the amyloid plaques is simply a consequence of the disease.

Effect of Post-Translational Modifications and Mutations on Amyloid-β Fibrils Dynamics at N Terminus

We investigate the variability in the dynamics of the disordered N-terminal domain of amyloid-β fibrils (Aβ), comprising residues 1-16 of Aβ1-40, due to post-translational modifications and mutations in the β-bend regions known to modulate aggregation properties. Using 2H static solid-state NMR approaches, we compare the dynamics in the wild-type Aβ fibrils in the threefold symmetric polymorph with the fibrils from three post-translational modification sequences: isoaspartate-D7, the phosphorylation of S8, and an N-terminal truncation ΔE3. Additional comparisons are made with the mutants in the β-bend region (residues 21-23) corresponding to the familial Osaka E22Δ deletion and D23N Iowa mutation. We also include the aggregates induced by Zn2+ ions. The dynamics are probed at the F4 and G9 positions. The main motional model involves two free states undergoing diffusion and conformational exchanges with the bound state in which the diffusion is quenched because of transient interactions involving fibril core and other intrastrand contacts. The fraction of the bound state increases in a sigmoidal fashion with a decrease in temperature. There is clear variability in the dynamics: the phosphorylation of S8 variant is the most rigid at the G9 site in line with structural studies, the ΔE3 fibrils are more flexible at the G9 site in line with the morphological fragmentation pattern, the Zn-induced aggregates are the most mobile, and the two β-bend mutants have the strongest changes at the F4 site toward higher rigidity. Overall, the changes underlie the potential role of conformational ensembles in setting the stage for aggregation-prone states.

Spontaneous Isomerization of Long-Lived Proteins Provides a Molecular Mechanism for the Lysosomal Failure Observed in Alzheimer's Disease

Proteinaceous aggregation is a well-known observable in Alzheimer's disease (AD), but failure and storage of lysosomal bodies within neurons is equally ubiquitous and actually precedes bulk accumulation of extracellular amyloid plaque. In fact, AD shares many similarities with certain lysosomal storage disorders though establishing a biochemical connection has proven difficult. Herein, we demonstrate that isomerization and epimerization, which are spontaneous chemical modifications that occur in long-lived proteins, prevent digestion by the proteases in the lysosome (namely, the cathepsins). For example, isomerization of aspartic acid into l-isoAsp prevents digestion of the N-terminal portion of Aβ by cathepsin L, one of the most aggressive lysosomal proteases. Similar results were obtained after examination of various target peptides with a full series of cathepsins, including endo-, amino-, and carboxy-peptidases. In all cases peptide fragments too long for transporter recognition or release from the lysosome persisted after treatment, providing a mechanism for eventual lysosomal storage and bridging the gap between AD and lysosomal storage disorders. Additional experiments with microglial cells confirmed that isomerization disrupts proteolysis in active lysosomes. These results are easily rationalized in terms of protease active sites, which are engineered to precisely orient the peptide backbone and cannot accommodate the backbone shift caused by isoaspartic acid or side chain dislocation resulting from epimerization. Although Aβ is known to be isomerized and epimerized in plaques present in AD brains, we further establish that the rates of modification for aspartic acid in positions 1 and 7 are fast and could accrue prior to plaque formation. Spontaneous chemistry can therefore provide modified substrates capable of inducing gradual lysosomal failure, which may play an important role in the cascade of events leading to the disrupted proteostasis, amyloid formation, and tauopathies associated with AD.

Isomerization of Asp7 in Beta-Amyloid Enhances Inhibition of the α7 Nicotinic Receptor and Promotes Neurotoxicity

Cholinergic dysfunction in Alzheimer’s disease (AD) can be mediated by the neuronal α7 nicotinic acetylcholine receptor (α7nAChR). Beta-amyloid peptide (Aβ) binds to the α7nAChR, disrupting the receptor’s function and causing neurotoxicity. In vivo not only Aβ but also its modified forms can drive AD pathogenesis. One of these forms, iso-Aβ (containing an isomerized Asp7 residue), shows an increased neurotoxicity in vitro and stimulates amyloidogenesis in vivo. We suggested that such effects of iso-Aβ are α7nAChR-dependent. Here, using calcium imaging and electrophysiology, we found that iso-Aβ is a more potent inhibitor of the α7nAChR-mediated calcium current than unmodified Aβ. However, Asp7 isomerization eliminated the ability of Aβ to decrease the α7nAChR levels. These data indicate differences in the interaction of the peptides with the α7nAChR, which we demonstrated using computer modeling. Neither Aβ nor iso-Aβ competed with ¹²⁵I-α-bungarotoxin for binding to the orthosteric site of the receptor, suggesting the allosteric binging mode of the peptides. Further we found that increased neurotoxicity of iso-Aβ was mediated by the α7nAChR. Thus, the isomerization of Asp7 enhances the inhibitory effect of Aβ on the functional activity of the α7nAChR, which may be an important factor in the disruption of the cholinergic system in AD.

Anti-amyloid Therapy of Alzheimer's Disease: Current State and Prospects

Drug development for the treatment of Alzheimer's disease (AD) has been for a long time focused on agents that were expected to support endogenous β-amyloid (Aβ) in a monomeric state and destroy soluble Aβ oligomers and insoluble Aβ aggregates. However, this strategy has failed over the last 20 years and was eventually abandoned. In this review, we propose a new approach to the anti-amyloid AD therapy based on the latest achievements in understanding molecular causes of cerebral amyloidosis in AD animal models.

Fluid-based proteomics targeted on pathophysiological processes and pathologies in neurodegenerative diseases

Neurodegenerative dementias constitute a broad group of diseases in which abnormally folded proteins accumulate in specific brain regions and result in tissue reactions that eventually cause neuronal dysfunction and degeneration. Depending on where in the brain this happens, symptoms appear which may be used to classify the disorders on clinical grounds. However, brain changes in neurodegenerative dementias start to accumulate many years prior to symptom onset and there is a poor correlation between the clinical picture and what pathology that is the most likely to cause it. Thus, novel drug candidates having disease-modifying effects that is targeting the underlying pathology and changes the course of the disease needs to be defined using objective biomarker-based measures since the clinical symptoms are often non-specific and overlap between different disorders. Furthermore, the treatment should ideally be initiated as soon as symptoms are evident or when biomarkers confirm an underlying pathology (pre-clinical phase of the disease) to reduce irreversible damage to, for example, neurons, synapses and axons. Clinical trials in the pre-clinical phase bring a greater importance to biomarkers since by definition the clinical effects are difficult or slow to discern in a population that is not yet clinically affected. Here, we discuss neuropathological changes that may underlie neurodegenerative dementias, including how they can be detected and quantified using currently available biofluid-based biomarkers and how more of them could be identified using targeted proteomics approaches. This article is part of the special issue "Proteomics".

Phosphorylation of the Amyloid-Beta Peptide Inhibits Zinc-Dependent Aggregation, Prevents Na,K-ATPase Inhibition, and Reduces Cerebral Plaque Deposition

The triggers of late-onset sporadic Alzheimer's disease (AD) are still poorly understood. Impairment of protein phosphorylation with age is well-known; however, the role of the phosphorylation in β-amyloid peptide (Aβ) is not studied sufficiently. Zinc-induced oligomerization of Aβ represents a potential seeding mechanism for the formation of neurotoxic Aβ oligomers and aggregates. Phosphorylation of Aβ by Ser8 (pS8-Aβ), localized inside the zinc-binding domain of the peptide, may significantly alter its zinc-induced oligomerization. Indeed, using dynamic light scattering, we have shown that phosphorylation by Ser8 dramatically reduces zinc-induced aggregation of Aβ, and moreover pS8-Aβ suppresses zinc-driven aggregation of non-modified Aβ in an equimolar mixture. We have further analyzed the effect of pS8-Aβ on the progression of cerebral amyloidosis with serial retro-orbital injections of the peptide in APPSwe/PSEN1dE9 murine model of AD, followed by histological analysis of amyloid burden in hippocampus. Unlike the non-modified Aβ that has no influence on the amyloidosis progression in murine models of AD, pS8-Aβ injections reduced the number of amyloid plaques in the hippocampus of mice by one-third. Recently shown inhibition of Na+,K+-ATPase activity by Aβ, which is thought to be a major contributor to neuronal dysfunction in AD, is completely reversed by phosphorylation of the peptide. Thus, several AD-associated pathogenic properties of Aβ are neutralized by its phosphorylation.

Intravenously Injected Amyloid-β Peptide With Isomerized Asp7 and Phosphorylated Ser8 Residues Inhibits Cerebral β-Amyloidosis in AβPP/PS1 Transgenic Mice Model of Alzheimer's Disease

Cerebral β-amyloidosis, an accumulation in the patient's brain of aggregated amyloid-β (Aβ) peptides abnormally saturated by divalent biometal ions, is one of the hallmarks of Alzheimer's disease (AD). Earlier, we found that exogenously administrated synthetic Aβ with isomerized Asp7 (isoD7-Aβ) induces Aβ fibrillar aggregation in the transgenic mice model of AD. IsoD7-Aβ molecules have been implied to act as seeds enforcing endogenous Aβ to undergo pathological aggregation through zinc-mediated interactions. On the basis of our findings on zinc-induced oligomerization of the metal-binding domain of various Aβ species, we hypothesize that upon phosphorylation of Ser8, isoD7-Aβ loses its ability to form zinc-bound oligomeric seeds. In this work, we found that (i) in vitro isoD7-Aβ with phosphorylated Ser8 (isoD7-pS8-Aβ) is less prone to spontaneous and zinc-induced aggregation in comparison with isoD7-Aβ and intact Aβ as shown by thioflavin T fluorimetry and dynamic light scattering data, and (ii) intravenous injections of isoD7-pS8-Aβ significantly slow down the progression of institutional β-amyloidosis in AβPP/PS1 transgenic mice as shown by the reduction of the congophilic amyloid plaques' number in the hippocampus. The results support the role of the zinc-mediated oligomerization of Aβ species in the modulation of cerebral β-amyloidosis and demonstrate that isoD7-pS8-Aβ can serve as a potential molecular tool to block the aggregation of endogenous Aβ in AD.

Implications of Metal Binding and Asparagine Deamidation for Amyloid Formation

Increasing evidence suggests that amyloid formation, i.e., self-assembly of proteins and the resulting conformational changes, is linked with the pathogenesis of various neurodegenerative disorders such as Alzheimer’s disease, prion diseases, and Lewy body diseases. Among the factors that accelerate or inhibit oligomerization, we focus here on two non-genetic and common characteristics of many amyloidogenic proteins: metal binding and asparagine deamidation. Both reflect the aging process and occur in most amyloidogenic proteins. All of the amyloidogenic proteins, such as Alzheimer’s β-amyloid protein, prion protein, and α-synuclein, are metal-binding proteins and are involved in the regulation of metal homeostasis. It is widely accepted that these proteins are susceptible to non-enzymatic posttranslational modifications, and many asparagine residues of these proteins are deamidated. Moreover, these two factors can combine because asparagine residues can bind metals. We review the current understanding of these two common properties and their implications in the pathogenesis of these neurodegenerative diseases.

Intravenous injection of beta-amyloid seeds promotes cerebral amyloid angiopathy (CAA)

Seeding and spread of beta-amyloid (Aβ) pathologies have been considered to be based on prion-like mechanisms. However, limited transmissibility of Aβ seeding activity upon peripheral exposure would represent a key difference to prions, not only in terms of pathogenesis but also in terms of potential transmission of disease. We partially characterized the seeded Aβ amyloidosis after intracerebral injection of various brain homogenates in APP/PS1 mice. One particularly seed-laden homogenate was selected to investigate the development of Aβ pathologies after intravenous exposure. We report here that a single intravenous injection of an Alzheimer disease patient's-brain extract into APP/PS1 recipient mice led to cerebral amyloid angiopathy within 180 days post injection. Thus, vascular proteinopathies such as CAA are transmissible in mice via the intravenous route of peripheral exposure.

Amyloid-β with isomerized Asp7 cytotoxicity is coupled to protein phosphorylation

Neuronal dysfunction and loss associated with the accumulation of amyloid-β (Aβ) in the form of extracellular amyloid plaques and hyperphosphorylated tau in the form of intraneuronal neurofibrillary tangles represent key features of Alzheimer's disease (AD). Amyloid plaques found in the brains of AD patients are predominantly composed of Aβ42 and its multiple chemically or structurally modified isoforms. Recently, we demonstrated that Aβ42 with isomerised Asp7 (isoAβ42) which is one of the most abundant Aβ isoform in plaques, exhibited high neurotoxicity in human neuronal cells. Here, we show that, in SH-SY5Y neuroblastoma cells, the administration of synthetic isoAβ42 rather than intact Aβ42 resulted in a significantly higher level of protein phosphorylation, especially the phosphorylation of tau, tubulins, and matrin 3. IsoAβ42 induced a drastic reduction of tau protein levels. Our data demonstrate, for the first time, that isoAβ42, being to date the only known synthetic Aβ species to cause AD-like amyloidogenesis in an animal AD model, induced cell death by disabling structural proteins in a manner characteristic of that observed in the neurons of AD patients. The data emphasize an important role of isoAβ42 in AD progression and provide possible neurotoxicity paths for this particular isoform.

N-domain of angiotensin-converting enzyme hydrolyzes human and rat amyloid-β(1-16) peptides as arginine specific endopeptidase potentially enhancing risk of Alzheimer's disease

Alzheimer’s disease (AD) is a multifactorial neurodegenerative disorder. Amyloid-β (Aβ) aggregation is likely to be the major cause of AD. In contrast to humans and other mammals, that share the same Aβ sequence, rats and mice are invulnerable to AD-like neurodegenerative pathologies, and Aβ of these rodents (ratAβ) has three amino acid substitutions in the metal-binding domain 1-16 (MBD). Angiotensin-converting enzyme (ACE) cleaves Aβ-derived peptide substrates, however, there are contradictions concerning the localization of the cleavage sites within Aβ and the roles of each of the two ACE catalytically active domains in the hydrolysis. In the current study by using mass spectrometry and molecular modelling we have tested a set of peptides corresponding to MBDs of Aβ and ratAβ to get insights on the interactions between ACE and these Aβ species. It has been shown that the N-domain of ACE (N-ACE) acts as an arginine specific endopeptidase on the Aβ and ratAβ MBDs with C-amidated termini, thus assuming that full-length Aβ and ratAβ can be hydrolyzed by N-ACE in the same endopeptidase mode. Taken together with the recent data on the molecular mechanism of zinc-dependent oligomerization of Aβ, our results suggest a modulating role of N-ACE in AD pathogenesis.

[The effect of neuroprotector isatin on binding of some model proteins with beta-amyloid peptide: a biosensor study]

The amyloid-beta peptide 1-42 formed during proteolytic processing of the amyloid precursor protein (APP) plays a key role in the development or progression of Alzheimer's disease (AD) and other pathologies associated with formation of protein aggregates in the central nervous system. Recent proteomic profiling of mouse and rat brain preparations by means of beta-amyloid peptide immobilized on Affigel-10 revealed a large group of amyloid-binding proteins (n>80). Many (about 25%) of these proteins were previously identified as isatin-binding proteins. The aim of this study was to validate direct interaction between beta-amyloid peptide and highly purified intact and oxidized peroxiredoxin, M-type pyruvate kinase, alpha-enolase, and the effect of isatin on this interaction. The study performed using SPR-based Biacore 3000 and Biacore X100 biosensors has shown that all the proteins form molecular complexes with immobilized beta-amyloid peptide. The Kd values for these complexes varied from 8.36х10-8 M (peroxiredoxin) to 1.97х10-6 M (alpha-enolase). Oxidative modification of investigated proteins caused opposite effects on complexes of these peptides with beta-amyloid. The endogenous neuroprotector isatin increased dissociation of complexes formed by beta-amyloid peptide with both intact proteins (peroxiredoxin, glyceraldehyde-3-phosphate dehydrogenase) and/or oxidized proteins (peroxiredoxin, pyruvate kinase) used in this study.

Prion-like disorders and Transmissible Spongiform Encephalopathies: An overview of the mechanistic features that are shared by the various disease-related misfolded proteins

Prion diseases or Transmissible Spongiform Encephalopathies (TSEs) are a group of fatal neurodegenerative disorders affecting several mammalian species. Its causative agent, disease-associated prion protein (PrP^d), is a self-propagating β-sheet rich aberrant conformation of the cellular prion protein (PrP^C) with neurotoxic and aggregation-prone properties, capable of inducing misfolding of PrP^C molecules. PrP^d is the major constituent of prions and, most importantly, is the first known example of a protein with infectious attributes. It has been suggested that similar molecular mechanisms could be shared by other proteins implicated in diseases such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis or systemic amyloidoses. Accordingly, several terms have been proposed to collectively group all these disorders. Through the stringent evaluation of those aspects that characterise TSE-causing prions, in particular propagation and spread, strain variability or transmissibility, we will discuss whether terms such as "prion", "prion-like", "prionoid" or "propagon" can be used when referring to the aetiological agents of the above other disorders. Moreover, it will also be discussed whether the term "infectious", which defines a prion essential trait, is currently misused when referring to the other misfolded proteins.

Studies of Polymorphism of Amyloid-β42 Peptide from Different Suppliers

The aim of this study was to investigate the process of amyloidogenesis of amyloid-β (Aβ)42 peptide, by means of fluorescence spectroscopy, electron microscopy, X-ray diffraction, and mass spectrometry. It has been repeatedly reported in the literature that the process of fibril formation by Aβ42 peptide depends considerably not only upon the specific conditions (ionic conditions, pH, temperature, mixing, etc.), as well as the manufacturing route (synthetic or recombinant), but also on the methods of synthesis and purification. We have, for the first time, systematically analyzed samples of Aβ42 peptide supplied by five different companies (Anaspec, Invitrogen, Enzo, Sigma-Aldrich, and SynthAssist) and obtained evidence of significant variability, including lot to lot variations. All studied samples formed amyloid-like fibrils at pH3-6, and the fibrils contained cross-β structures. Samples from Anaspec, Invitrogen, and Enzo formed one particular type of amyloid-like fibrils, while the samples from Sigma-Aldrich and SynthAssist formed another distinct type of fibrils. The observed polymorphism emphasizes the capacity of the Aβ42 peptide to act as a prion agent with varying structural characteristics. The presented data have allowed us to propose a possible mechanism of formation of amyloid-like fibrils.

Peripherally Applied Synthetic Tetrapeptides HAEE and RADD Slow Down the Development of Cerebral β-Amyloidosis in AβPP/PS1 Transgenic Mice

Two tetrapeptides, HAEE and RADD, which are ionic-complementary to the primary zinc recognition site of amyloid-β (Aβ), have been reported to inhibit zinc-induced dimerization of the Aβ metal-binding domain and slow Aβ aggregation in vitro. In the present study, we investigate the impact of HAEE and RADD on the development of cerebral β-amyloidosis in a mouse model of Alzheimer's disease. We have found chronic intravenous administration of each peptide results in significant decrease of amyloid plaque burden in the treated mice.