Advances in the therapy of Alzheimer's disease: targeting amyloid beta and tau and perspectives for the future

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.

Decoding the best automated segmentation tools for vascular white matter hyperintensities in the aging brain: a clinician's guide to precision and purpose

White matter hyperintensities of vascular origin (WMH) are commonly found in individuals over 60 and increase in prevalence with age. The significance of WMH is well-documented, with strong associations with cognitive impairment, risk of stroke, mental health, and brain structure deterioration. Consequently, careful monitoring is crucial for the early identification and management of individuals at risk. Luckily, WMH are detectable and quantifiable on standard MRI through visual assessment scales, but it is time-consuming and has high rater variability. Addressing this issue, the main aim of our study is to decipher the utility of quantitative measures of WMH, assessed with automatic tools, in establishing risk profiles for cerebrovascular deterioration. For this purpose, first, we work to determine the most precise WMH segmentation open access tool compared to clinician manual segmentations (LST-LPA, LST-LGA, SAMSEG, and BIANCA), offering insights into methodology and usability to balance clinical precision with practical application. The results indicated that supervised algorithms (LST-LPA and BIANCA) were superior, particularly in detecting small WMH, and can improve their consistency when used in parallel with unsupervised tools (LST-LGA and SAMSEG). Additionally, to investigate the behavior and real clinical utility of these tools, we tested them in a real-world scenario (N = 300; age > 50 y.o. and MMSE > 26), proposing an imaging biomarker for moderate vascular damage. The results confirmed its capacity to effectively identify individuals at risk comparing the cognitive and brain structural profiles of cognitively healthy adults above and below the resulted threshold.

The Effect of the Optogenetic Stimulation of Astrocytes on Neural Network Activity in an In Vitro Model of Alzheimer's Disease

Optogenetics is a combination of optical and genetic technologies used to activate or, conversely, inhibit specific cells in living tissues. The possibilities of using optogenetics approaches for the treatment of epilepsy, Parkinson's and Alzheimer's disease (AD) are being actively researched. In recent years, it has become clear that one of the most important players in the development of AD is astrocytes. Astrocytes affect amyloid clearance, participate in the development of neuroinflammation, and regulate the functioning of neural networks. We used an adeno-associated virus carrying the glial fibrillary acidic protein (GFAP) promoter driving the optogenetic channelrhodopsin-2 (ChR2) gene to transduce astrocytes in primary mouse hippocampal cultures. We recorded the bioelectrical activity of neural networks from day 14 to day 21 of cultivation using multielectrode arrays. A single optogenetic stimulation of astrocytes at 14 day of cultivation (DIV14) did not cause significant changes in neural network bioelectrical activity. Chronic optogenetic stimulation from DIV14 to DIV21 exerts a stimulatory effect on the bioelectrical activity of primary hippocampal cultures (the proportion of spikes included in network bursts significantly increased since DIV19). Moreover, chronic optogenetic stimulation over seven days partially preserved the activity and functional architecture of neuronal network in amyloidosis modeling. These results suggest that the selective optogenetic activation of astrocytes may represent a promising novel therapeutic strategy for combating AD.

New Insights into the Development of Donepezil-Based Hybrid and Natural Molecules as Multi-Target Drug Agents for Alzheimer's Disease Treatment

Alzheimer's disease (AD) involves a complex pathophysiology with multiple interconnected subpathologies, including protein aggregation, impaired neurotransmission, oxidative stress, and microglia-mediated neuroinflammation. Current treatments, which generally target a single subpathology, have failed to modify the disease's progression, providing only temporary symptom relief. Multi-target drugs (MTDs) address several subpathologies, including impaired aggregation of pathological proteins. In this review, we cover hybrid molecules published between 2014 and 2024. We offer an overview of the strategies employed in drug design and approaches that have led to notable improvements and reduced hepatotoxicity. Our aim is to offer insights into the potential development of new Alzheimer's disease drugs. This overview highlights the potential of multi-target drugs featuring heterocycles with N-benzylpiperidine fragments and natural compounds in improving Alzheimer's disease treatment.

Decoding the Best Automated Segmentation Tools for Vascular White Matter Hyperintensities in the Aging Brain: A Clinician's Guide to Precision and Purpose

Cerebrovascular damage from small vessel disease (SVD) occurs in healthy and pathological aging. SVD markers, such as white matter hyperintensities (WMH), are commonly found in individuals over 60 and increase in prevalence with age. WMHs are detectable on standard MRI by adhering to the STRIVE criteria. Currently, visual assessment scales are used in clinical and research scenarios but is time-consuming and has rater variability, limiting its practicality. Addressing this issue, our study aimed to determine the most precise WMH segmentation software, offering insights into methodology and usability to balance clinical precision with practical application. This study employed a dataset comprising T1, FLAIR, and DWI images from 300 cognitively healthy older adults. WMHs in this cohort were evaluated using four automated neuroimaging tools: Lesion Prediction Algorithm (LPA) and Lesion Growth Algorithm (LGA) from Lesion Segmentation Tool (LST), Sequence Adaptive Multimodal Segmentation (SAMSEG), and Brain Intensity Abnormalities Classification Algorithm (BIANCA). Additionally, clinicians manually segmented WMHs in a subsample of 45 participants to establish a gold standard. The study assessed correlations with the Fazekas scale, algorithm performance, and the influence of WMH volume on reliability. Results indicated that supervised algorithms were superior, particularly in detecting small WMHs, and can improve their consistency when used in parallel with unsupervised tools. The research also proposed a biomarker for moderate vascular damage, derived from the top 95th percentile of WMH volume in healthy individuals aged 50 to 60. This biomarker effectively differentiated subgroups within the cohort, correlating with variations in brain structure and behavior.

Interaction of Tau with G-Protein-Coupled Purinergic P2Y12 Receptor by Molecular Docking and Molecular Dynamic Simulation

Alzheimer's disease, a progressive neurological disorder, is characterized by the accumulation of neurofibrillary tangles and senile plaques by Tau and amyloid-β, respectively, in the brain microenvironment. The misfolded protein aggregates interact with several components of neuronal and glial cells such as membrane lipids, receptors, transporters, enzymes, cytoskeletal proteins, etc. Under pathological conditions, Tau interacts with several G-protein-coupled receptors (GPCRs), which undergoes either receptor signaling or desensitization followed by internalization of the protein complex. The purinergic GPCR, P2Y12 which is expressed in microglial cells, plays a key role in its activation and migration. Microglial cells sense and migrate to the site of injury aided by P2Y12 receptor that interacts with ADP released from damaged cells. P2Y12 receptor also interacts with misfolded Tau accumulated at the extracellular space and promotes receptor-mediated internalization. Immunocolocalization and co-immunoprecipitation studies demonstrated the interaction of Tau species with the P2Y12 receptor. Later, in-silico analyses were carried out with the repeat domain of Tau (TauRD), which has been identified as the interacting partner of P2Y12 receptor by in-vitro studies. Molecular docking and molecular dynamics simulation studies show the stability and the type of interaction in TauRD-receptor complex. Tau interaction with P2Y12 receptor plays a significant role in maintaining the active state of microglia which could lead to neuroinflammation and neuronal damage in AD brain. Hence, blocking P2Y12-Tau interaction and P2Y12-mediated Tau internalization in microglial cells could be possible therapeutic strategies in downregulating the severity of neuroinflammation in AD.

Review of Alzheimer's disease drugs and their relationship with neuron-glia interaction

Alzheimer's disease (AD) is the most common cause of dementia worldwide. Because Alzheimer's disease has no known treatment, sufferers and their caregivers must concentrate on symptom management. Astrocytes and microglia are now known to play distinct physiological roles in synaptic function, the blood-brain barrier, and neurovascular coupling. Consequently, the search for drugs that can slow the degenerative process in dementia sufferers continues because existing drugs are designed to alleviate the symptoms of Alzheimer's disease. Drugs that address pathological changes without interfering with the normal function of glia, such as eliminating amyloid-beta deposits, are prospective treatments for neuroinflammatory illnesses. Because neuron-astrocytes-microglia interactions are so complex, developing effective, preventive, and therapeutic medications for AD will necessitate novel methodologies and strategic targets. This review focused on existing medications used in treating AD amongst which include Donepezil, Choline Alphoscerate, Galantamine, Dextromethorphan, palmitoylethanolamide, citalopram, resveratrol, and solanezumab. This review summarizes the effects of these drugs on neurons, astrocytes, and microglia interactions based on their pharmacokinetic properties, mechanism of action, dosing, and clinical presentations.

Melanocortin receptor agonist NDP-α-MSH improves cognitive deficits and microgliosis but not amyloidosis in advanced stages of AD progression in 5XFAD and 3xTg mice

Introduction

Alzheimer's disease (AD) is the most frequent cause of dementia and still lacks effective therapy. Clinical signs of AD include low levels of endogenous melanocortins (MCs) and previous studies have shown that treatment with MC analogs induces neuroprotection in the early stages of AD.

Methods

We investigated the neuroprotective role of MCs in two transgenic mouse models of severe AD using 5 and 7 month-old (mo) 5XFAD mice and 9 and 12 mo 3xTg mice. These mice were subjected to a chronic stimulation of MC receptors (MCRs) with MC analogue Nle4-D-Phe7-α-melanocyte stimulating hormone (NDP-α-MSH, 340 μg/kg, i.p.). Mouse behavior and ex-vivo histological and biochemical analyses were performed after 50 days of treatment.

Results

Our analysis demonstrated an improvement in cognitive abilities of AD mice at late stage of AD progression. We also showed that these protective effects are associated with decreased levels of hyperphosphorylated Tau but not with Aβ burden, that was unaffected in the hippocampus and in the cortex of AD mice. In addition, an age-dependent NDP effect on glial reactivity was observed only in 3xTg mice whereas a global downregulation of p38 mitogen-activated protein kinase was selectively observed in 7 mo 5XFAD and 14 mo 3xTg mice.

Conclusion

Our results suggest that MCR stimulation by NDP-α-MSH could represent a promising therapeutic strategy in managing cognitive decline also at late stage of AD, whereas the effects on neuroinflammation may be restricted to specific stages of AD progression.

Novel Algorithm of Network Calcium Dynamics Analysis for Studying the Role of Astrocytes in Neuronal Activity in Alzheimer's Disease Models

Accumulated experimental data strongly suggest that astrocytes play an important role in the pathogenesis of neurodegeneration, including Alzheimer's disease (AD). The effect of astrocytes on the calcium activity of neuron-astroglia networks in AD modelling was the object of the present study. We have expanded and improved our approach's capabilities to analyze calcium activity. We have developed a novel algorithm to construct dynamic directed graphs of both astrocytic and neuronal networks. The proposed algorithm allows us not only to identify functional relationships between cells and determine the presence of network activity, but also to characterize the spread of the calcium signal from cell to cell. Our study showed that Alzheimer's astrocytes can change the functional pattern of the calcium activity of healthy nerve cells. When healthy nerve cells were cocultivated with astrocytes treated with Aβ42, activation of calcium signaling was found. When healthy nerve cells were cocultivated with 5xFAD astrocytes, inhibition of calcium signaling was observed. In this regard, it seems relevant to further study astrocytic-neuronal interactions as an important factor in the regulation of the functional activity of brain cells during neurodegenerative processes. The approach to the analysis of streaming imaging data developed by the authors is a promising tool for studying the collective calcium dynamics of nerve cells.

Advances in fucoxanthin chemistry and management of neurodegenerative diseases

BACKGROUND

Neurodegenerative diseases are chronic, currently incurable, diseases of the elderly, which are characterized by protein misfolding and neuronal damage. Fucoxanthin, derived from marine brown algae, presents a promising candidate for the development of effective therapeutic strategies.

HYPOTHESIS AND PURPOSE

The relationship between neurodegenerative disease management and fucoxanthin has not yet been clarified. This study focuses on the fundamental mechanisms and targets of fucoxanthin in Alzheimer's and Parkinson's disease management, showing that communication between the brain and the gut contributes to neurodegenerative diseases and early diagnosis of ophthalmic diseases. This paper also presents, new insights for future therapeutic directions based on the integrated application of artificial intelligence.

CONCLUSION

Fucoxanthin primarily binds to amyloid fibrils with spreading properties such as Aβ, tau, and α-synuclein to reduce their accumulation levels, alleviate inflammatory factors, and restore mitochondrial membranes to prevent oxidative stress via Nrf2 and Akt signaling pathways, involving reduction of specific secretases. In addition, fucoxanthin may serve as a preventive diagnosis for neurodegenerative diseases through ophthalmic disorders. It can modulate gut microbes and has potential for the alleviation and treatment of neurodegenerative diseases.

Clinical relevance of biomarkers, new therapeutic approaches, and role of post-translational modifications in the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder that causes progressive loss of cognitive functions like thinking, memory, reasoning, behavioral abilities, and social skills thus affecting the ability of a person to perform normal daily functions independently. There is no definitive cure for this disease, and treatment options available for the management of the disease are not very effective as well. Based on histopathology, AD is characterized by the accumulation of insoluble deposits of amyloid beta (Aβ) plaques and neurofibrillary tangles (NFTs). Although several molecular events contribute to the formation of these insoluble deposits, the aberrant post-translational modifications (PTMs) of AD-related proteins (like APP, Aβ, tau, and BACE1) are also known to be involved in the onset and progression of this disease. However, early diagnosis of the disease as well as the development of effective therapeutic approaches is impeded by lack of proper clinical biomarkers. In this review, we summarized the current status and clinical relevance of biomarkers from cerebrospinal fluid (CSF), blood and extracellular vesicles involved in onset and progression of AD. Moreover, we highlight the effects of several PTMs on the AD-related proteins, and provide an insight how these modifications impact the structure and function of proteins leading to AD pathology. Finally, for disease-modifying therapeutics, novel approaches, and targets are discussed for the successful treatment and management of AD.

Potential role of IP3/Ca2+ signaling and phosphodiesterases: Relevance to neurodegeneration in Alzheimer's disease and possible therapeutic strategies

Despite large investments by industry and governments, no disease-modifying medications for the treatment of patients with Alzheimer's disease (AD) have been found. The failures of various clinical trials indicate the need for a more in-depth understanding of the pathophysiology of AD and for innovative therapeutic strategies for its treatment. Here, we review the rational for targeting IP3 signaling, cytosolic calcium dysregulation, phosphodiesterases (PDEs), and secondary messengers like cGMP and cAMP, as well as their correlations with the pathophysiology of AD. Various drugs targeting these signaling cascades are still in pre-clinical and clinical trials which support the ideas presented in this article. Further, we describe different molecular mechanisms and medications currently being used in various pre-clinical and clinical trials involving IP3/Ca⁺² signaling. We also highlight various isoforms, as well as the functions and pharmacology of the PDEs broadly expressed in different parts of the brain and attempt to unravel the potential benefits of PDE inhibitors for use as novel medications to alleviate the pathogenesis of AD.

Relationship Between Chronic Noise Exposure, Cognitive Impairment, and Degenerative Dementia: Update on the Experimental and Epidemiological Evidence and Prospects for Further Research

Degenerative dementia, of which Alzheimer's disease is the most common form, is characterized by the gradual deterioration of cognitive function. The events that trigger and promote degenerative dementia are not clear, and treatment options are limited. Experimental and epidemiological studies have revealed chronic noise exposure (CNE) as a potential risk factor for cognitive impairment and degenerative dementia. Experimental studies have indicated that long-term exposure to noise might accelerate cognitive dysfunction, amyloid-β deposition, and tau hyperphosphorylation in different brain regions such as the hippocampus and cortex. Epidemiological studies are increasingly examining the possible association between external noise exposure and dementia. In this review, we sought to construct a comprehensive summary of the relationship between CNE, cognitive dysfunction, and degenerative dementia. We also present the limitations of existing evidence as a guide regarding important prospects for future research.

Recent Progress on Biological Activity of Amaryllidaceae and Further Isoquinoline Alkaloids in Connection with Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive age-related neurodegenerative disease recognized as the most common form of dementia among elderly people. Due to the fact that the exact pathogenesis of AD still remains to be fully elucidated, the treatment is only symptomatic and available drugs are not able to modify AD progression. Considering the increase in life expectancy worldwide, AD rates are predicted to increase enormously, and thus the search for new AD drugs is urgently needed. Due to their complex nitrogen-containing structures, alkaloids are considered to be promising candidates for use in the treatment of AD. Since the introduction of galanthamine as an antidementia drug in 2001, Amaryllidaceae alkaloids (AAs) and further isoquinoline alkaloids (IAs) have been one of the most studied groups of alkaloids. In the last few years, several compounds of new structure types have been isolated and evaluated for their biological activity connected with AD. The present review aims to comprehensively summarize recent progress on AAs and IAs since 2010 up to June 2021 as potential drugs for the treatment of AD.

Transplantation of GABAergic Interneuron Progenitor Attenuates Cognitive Deficits of Alzheimer's Disease Model Mice

Excitatory (E) and inhibitory (I) balance of neural network activity is essential for normal brain function and of particular importance to memory. Disturbance of E/I balance contributes to various neurological disorders. The appearance of neural hyperexcitability in Alzheimer's disease (AD) is even suggested as one of predictors of accelerated cognitive decline. In this study, we found that GAD67+, Parvalbumin+, Calretinin+, and Neuropeptide Y+ interneurons were progressively lost in the brain of APP/PS1 mice. Transplanted embryonic medial ganglionic eminence derived interneuron progenitors (IPs) survived, migrated, and differentiated into GABAergic interneuron subtypes successfully at 2 months after transplantation. Transplantation of IPs hippocampally rescued impaired synaptic plasticity and cognitive deficits of APP/PS1 transgenic mice, concomitant with a suppression of neural hyperexcitability, whereas transplantation of IPs failed to attenuate amyloid-β accumulation, neuroinflammation, and synaptic loss of APP/PS1 transgenic mice. These observations indicate that transplantation of IPs improves learning and memory of APP/PS1 transgenic mice via suppressing neural hyperexcitability. This study highlights a causal contribution of GABAergic dysfunction to AD pathogenesis and the potentiality of IP transplantation in AD therapy.

Intranasal Transplantation of Human Neural Stem Cells Ameliorates Alzheimer's Disease-Like Pathology in a Mouse Model

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by memory impairments, which has no effective therapy. Stem cell transplantation shows great potential in the therapy of various disease. However, the application of stem cell therapy in neurological disorders, especially the ones with a long-term disease course such as AD, is limited by the delivery approach due to the presence of the brain blood barrier. So far, the most commonly used delivery approach in the therapy of neurological disorders with stem cells in preclinical and clinical studies are intracranial injection and intrathecal injection, both of which are invasive. In the present study, we use repetitive intranasal delivery of human neural stem cells (hNSCs) to the brains of APP/PS1 transgenic mice to investigate the effect of hNSCs on the pathology of AD. The results indicate that the intranasally transplanted hNSCs survive and exhibit extensive migration and higher neuronal differentiation, with a relatively limited glial differentiation. A proportion of intranasally transplanted hNSCs differentiate to cholinergic neurons, which rescue cholinergic dysfunction in APP/PS1 mice. In addition, intranasal transplantation of hNSCs attenuates β-amyloid accumulation by upregulating the expression of β-amyloid degrading enzymes, insulin-degrading enzymes, and neprilysin. Moreover, intranasal transplantation of hNSCs ameliorates other AD-like pathology including neuroinflammation, cholinergic dysfunction, and pericytic and synaptic loss, while enhancing adult hippocampal neurogenesis, eventually rescuing the cognitive deficits of APP/PS1 transgenic mice. Thus, our findings highlight that intranasal transplantation of hNSCs benefits cognition through multiple mechanisms, and exhibit the great potential of intranasal administration of stem cells as a non-invasive therapeutic strategy for AD.

Interaction of Tau with the chemokine receptor, CX3CR1 and its effect on microglial activation, migration and proliferation

Alzheimer's disease (AD) is a neurodegenerative disease that leads to progressive loss of memory and dementia. The pathological hallmarks of AD include extracellular accumulation of amyloid-β peptides forming senile plaques and intracellular accumulation of Tau oligomers and filamentous species. Tau is a microtubule-binding protein that stabilizes tubulin to form microtubules under physiological condition. In AD/ pathological condition, Tau detaches from microtubules and aggregates to form oligomers of different sizes and filamentous species such as paired helical filaments. Microglia are the resident brain macrophages that are involved in the phagocytosis of microbes, cellular debris, misfolded and aggregated proteins. Chemokine receptor, CX3CR1 is mostly expressed on microglia and is involved in maintaining the microglia in a quiescent state by binding to its ligand, fractalkine (CX3CL1), which is expressed in neurons as both soluble or membrane-bound state. Hence, under physiological conditions, the CX3CR1/CX3CL1 axis plays a significant role in maintaining the central nervous system (CNS) homeostasis. Further, CX3CR1/CX3CL1 signalling is involved in the synthesis of anti-inflammatory cytokines and also has a significant role in cytoskeletal rearrangement, migration, apoptosis and proliferation. In AD brain, the expression level of fractalkine is reduced, and hence Tau competes to interact with its receptor, CX3CR1. In microglia, phagocytosis and internalization of extracellular Tau species occurs in the presence of a chemokine receptor, CX3CR1 which binds directly to Tau and promotes its internalization. In this review, the pathophysiological roles of CX3CR1/fractalkine signalling in microglia and neurons at different stages of Alzheimer's disease and the possible role of CX3CR1/Tau signalling has been widely discussed.

Tryptophan-galactosylamine conjugates inhibit and disaggregate amyloid fibrils of Aβ42 and hIAPP peptides while reducing their toxicity

Self-assembly of proteins into amyloid fibrils is a hallmark of various diseases, including Alzheimer's disease (AD) and Type-2 diabetes Mellitus (T2DM). Aggregation of specific peptides, like Aβ42 in AD and hIAPP in T2DM, causes cellular dysfunction resulting in the respective pathology. While these amyloidogenic proteins lack sequence homology, they all contain aromatic amino acids in their hydrophobic core that play a major role in their self-assembly. Targeting these aromatic residues by small molecules may be an attractive approach for inhibiting amyloid aggregation. Here, various biochemical and biophysical techniques revealed that a panel of tryptophan-galactosylamine conjugates significantly inhibit fibril formation of Aβ42 and hIAPP, and disassemble their pre-formed fibrils in a dose-dependent manner. They are also not toxic to mammalian cells and can reduce the cytotoxicity induced by Aβ42 and hIAPP aggregates. These tryptophan-galactosylamine conjugates can therefore serve as a scaffold for the development of therapeutics towards AD and T2DM.

Plasma Tau Variants Detected by a Novel Anti-Tau Monoclonal Antibody: A Potential Biomarker for Alzheimer's Disease

BACKGROUND

A major drawback in Alzheimer's disease (AD) is the lack of validated biomarkers for routine clinical diagnostic. We have reported earlier a novel blood biomarker, named Alz-tau®, based on variants of platelet tau. This marker evaluates the ratio of high molecular weight tau (HMWtau) and the low molecular weight (LMWtau) tau.

OBJECTIVE

To analyze a potential novel source of antigen for Alz-tau®, plasma tau, detected by immunoreactivity with the novel monoclonal antibody, tau51.

METHODS

We evaluated tau variants in plasma precipitated with ammonium sulfate from 36 AD patients and 15 control subjects by western blot with this novel monoclonal antibody.

RESULTS

The HMW/LMWtau ratio was statistically different between AD patients and controls.

CONCLUSIONS

Plasma tau variants are suitable to be considered as a novel antigen source for the Alz-tau® biomarker for AD.

Does hearing loss lead to dementia? A review of the literature

Recent studies have revealed a correlation between aging-related hearing loss and the likelihood of developing Alzheimer Disease. However, it is not yet known if the correlation simply reflects the fact that these two disorders share common risk factors or whether there is a causal link between them. The answer to this question carries therapeutic implications. Unfortunately, it is not possible to study the question of causality between aging-related hearing loss and dementia in human subjects. Here, we evaluate the research surrounding induced-hearing loss in animal models on non-auditory cognition to help infer if there is any causal evidence linking hearing loss and a more general dementia. We find ample evidence that induction of hearing loss in animals produces cognitive decline, particularly hippocampal dysfunction. The data suggest that noise-exposure produces a toxic milieu in the hippocampus consisting of a spike in glucocorticoid levels, elevations of mediators of oxidative stress and excitotoxicity, which as a consequence induce cessation of neurogenesis, synaptic loss and tau hyperphosphorylation. These data suggest that hearing loss can lead to pathological hallmarks similar to those seen in Alzheimer's Disease and other dementias. However, the rodent data do not establish that hearing loss on its own can induce a progressive degenerative dementing illness. Therefore, we conclude that an additional "hit", such as aging, APOE genotype, microvascular disease or others, may be necessary to trigger an ongoing degenerative process such as Alzheimer Disease.

Brain-Derived Neurotrophic Factor (BDNF) Preserves the Functional Integrity of Neural Networks in the β-Amyloidopathy Model in vitro

Alzheimer’s disease (AD) is a widespread chronic neurodegenerative pathology characterized by synaptic dysfunction, partial neuronal death, cognitive decline and memory impairments. The major hallmarks of AD are extracellular senile amyloid plaques formed by various types of amyloid proteins (Aβ) and the formation and accumulation of intracellular neurofibrillary tangles. However, there is a lack of relevant experimental models for studying changes in neural network activity, the features of intercellular signaling or the effects of drugs on the functional activity of nervous cells during AD development. In this work, we examined two experimental models of amyloidopathy using primary hippocampal cultures. The first model involves the embryonic brains of 5xFAD mice; the second uses chronic application of amyloid beta 1-42 (Aβ1-42). The model based on primary hippocampal cells obtained from 5xFAD mice demonstrated changes in spontaneous network calcium activity characterized by a decrease in the number of cells exhibiting Ca²⁺ activity, a decrease in the number of Ca²⁺ oscillations and an increase in the duration of Ca²⁺ events from day 21 of culture development in vitro. Chronic application of Aβ1-42 resulted in the rapid establishment of significant neurodegenerative changes in primary hippocampal cultures, leading to marked impairments in neural network calcium activity and increased cell death. Using this model and multielectrode arrays, we studied the influence of amyloidopathy on spontaneous bioelectrical neural network activity in primary hippocampal cultures. It was shown that chronic Aβ application decreased the number of network bursts and spikes in a burst. The spatial structure of neural networks was also disturbed that characterized by reduction in both the number of key network elements (hubs) and connections between network elements. Moreover, application of brain-derived neurotrophic factor (BDNF) recombinant protein and BDNF hyperexpression by an adeno-associated virus vector partially prevented these amyloidopathy-induced neurodegenerative phenomena. BDNF maintained cell viability and spontaneous bioelectrical and calcium network activity in primary hippocampal cultures.

Plasmon-Activated Water Reduces Amyloid Burden and Improves Memory in Animals with Alzheimer's Disease

With the great extension of the human lifespan in recent times, many aging diseases have inevitably followed. Dementia is one of the most-commom neurodegenerative aging diseases, in which inflammation-related Alzheimer’s disease (AD) is the most prevalent cause of dementia. Amyloid accumulation in the brain, which occurs before any clinical presentations, might be the first and key step in the development of AD. However, many clinical trials have attempted to remove amyloid from brains of AD patients, but none has so far been successful. Negatively charged plasmon-activated water (PAW) is created by resonantly illuminated gold (Au) nanoparticles (NPs), which reduce the hydrogen-bonded (HB) structure of water. PAW was found to possess anti-oxidative and anti-inflammatory effects. Herein, we report on an innovative strategy to retard the progression of AD by the daily consumption of PAW instead of normal deionized (DI) water. APPswe/PS1dE9 transgenic mice were treated with PAW or DI water from the age of 5 months for the next 9 months. Encouragingly, compared to DI water-treated mice, mice treated with PAW presented better memory performance on a test of novel object recognition and had a significantly lower amyloid burden according to 18F-florbetapir amyloid-PET and phosphorylated (p)-tau burden according to Western blotting and immunohistochemistry measurements. There were no obvious side effects in PAW-treated mice. Collectively, our findings support that PAW was able to reduce the amyloid and p-tau burden and improve memory in an AD mouse model. However, the protein levels of molecules involved in amyloid metabolism and oligomeric amyloid did not change. We propose that the effects of PAW of reducing the amyloid burden and improving memory function cannot be attributed to synthesis/degradation of amyloid-βprotein but probably in preventing aggregation of amyloid-β proteins or other mechanisms, including anti-inflammation. Further applications of PAW in clinical trials to prevent the progression of AD are being designed.

Risk Factors for Alzheimer's Disease: Focus on Stress

In vulnerable individuals, chronic and persistent stress is an established risk factor for disorders that are comorbid with Alzheimer’s disease (AD), such as hypertension, obesity and metabolic syndrome, and psychiatric disorders. There are no disease-modifying drugs in the treatment of AD, and all phase-3 clinical trials with anti-amyloid drugs (e.g., β- or γ-secretase inhibitors and monoclonal antibodies) did not meet the primary endpoints. There are many reasons for the lack of efficacy of anti-amyloid drugs in AD, the most likely being a late start of treatment, considering that pathophysiological mechanisms underlying synaptic dysfunction and neuronal death begin several decades before the clinical onset of AD. The identification of risk factors is, therefore, an essential step for early treatment of AD with candidate disease-modifying drugs. Preclinical studies suggest that stress, and the resulting activation of the hypothalamic–pituitary–adrenal axis, can induce biochemical abnormalities reminiscent to those found in autoptic brain samples from individuals affected by AD (e.g., increases amyloid precursor protein and tau hyperphosphorylation). In this review, we will critically analyze the current knowledge supporting stress as a potential risk factor for AD.

Tau-Reactive Endogenous Antibodies: Origin, Functionality, and Implications for the Pathophysiology of Alzheimer's Disease

In Alzheimer's disease (AD), tau pathology manifested by the accumulation of intraneuronal tangles and soluble toxic oligomers emerges as a promising therapeutic target. Multiple anti-tau antibodies inhibiting the formation and propagation of cytotoxic tau or promoting its clearance and degradation have been tested in clinical trials, albeit with the inconclusive outcome. Antibodies against tau protein have been documented both in the brain circulatory system and at the periphery, but their origin and role under normal conditions and in AD remain unclear. While it is tempting to assign them a protective role in regulating tau level and removal of toxic variants, the supportive evidence remains sporadic, requiring systematic analysis and critical evaluation. Herein, we review recent data showing the occurrence of tau-reactive antibodies in the brain and peripheral circulation and discuss their origin and significance in tau clearance. Based on the emerging evidence, we cautiously propose that impairments of tau clearance at the periphery by humoral immunity might aggravate the tau pathology in the central nervous system, with implication for the neurodegenerative process of AD.

Nerve Growth Factor Pathobiology During the Progression of Alzheimer's Disease

The current review summarizes the pathobiology of nerve growth factor (NGF) and its cognate receptors during the progression of Alzheimer's disease (AD). Both transcript and protein data indicate that cholinotrophic neuronal dysfunction is related to an imbalance between TrkA-mediated survival signaling and the NGF precursor (proNGF)/p75NTR-mediated pro-apoptotic signaling, which may be related to alteration in the metabolism of NGF. Data indicate a spatiotemporal pattern of degeneration related to the evolution of tau pathology within cholinotrophic neuronal subgroups located within the nucleus basalis of Meynert (nbM). Despite these degenerative events the cholinotrophic system is capable of cellular resilience and/or plasticity during the prodromal and later stages of the disease. In addition to neurotrophin dysfunction, studies indicate alterations in epigenetically regulated proteins occur within cholinotrophic nbM neurons during the progression of AD, suggesting a mechanism that may underlie changes in transcript expression. Findings that increased cerebrospinal fluid levels of proNGF mark the onset of MCI and the transition to AD suggests that this proneurotrophin is a potential disease biomarker. Novel therapeutics to treat NGF dysfunction include NGF gene therapy and the development of small molecule agonists for the cognate prosurvival NGF receptor TrkA and antagonists against the pan-neurotrophin p75NTR death receptor for the treatment of AD.

Derivatives of the β-Crinane Amaryllidaceae Alkaloid Haemanthamine as Multi-Target Directed Ligands for Alzheimer's Disease

Twelve derivatives 1a–1m of the β-crinane-type alkaloid haemanthamine were developed. All the semisynthetic derivatives were studied for their inhibitory potential against both acetylcholinesterase and butyrylcholinesterase. In addition, glycogen synthase kinase 3β (GSK-3β) inhibition potency was evaluated in the active derivatives. In order to reveal the availability of the drugs to the CNS, we elucidated the potential of selected derivatives to penetrate through the blood-brain barrier (BBB). Two compounds, namely 11-O-(2-methylbenzoyl)-haemanthamine (1j) and 11-O-(4-nitrobenzoyl)-haemanthamine (1m), revealed the most intriguing profile, both being acetylcholinesterase (hAChE) inhibitors on a micromolar scale, with GSK-3β inhibition properties, and predicted permeation through the BBB. In vitro data were further corroborated by detailed inspection of the compounds’ plausible binding modes in the active sites of hAChE and hBuChE, which led us to provide the structural determinants responsible for the activity towards these enzymes.

The Alz-tau Biomarker for Alzheimer's Disease: Study in a Caucasian Population

The establishment of a molecular biomarker for early detection of Alzheimer's disease (AD) is critical for diagnosis and follow up of patients, and as a quantitative parameter in the evaluation of potential new drugs to control AD. A list of blood biomarkers has been reported but none has been validated for the Alzheimer's clinic. The changes in hyperphosphorylated tau and amyloid peptide in the cerebrospinal fluid is currently used as a tool in the clinics and for research purposes, but this method is highly invasive. Recently, we reported a non-invasive and reliable blood biomarker that correlates the increase in the ratio of heavy tau (HMWtau) and the low molecular weight tau (LMWtau) in human platelets and the decrease in the brain volume as measured by structural MRI. This molecular marker has been named Alz-tau®. Beyond the clinical trials developed with a Latin American population, the present study focuses on an evaluation of this biomarker in a Caucasian population. We examined 36 AD patients and 15 cognitively normal subjects recruited in Barcelona, Spain. Tau levels in platelets were determined by immunoreactivity and the cognitive status by using GDS and MMSE neuropsychological tests. The HMW/LMW tau ratio was statistically different between controls and AD patients. A high correlation was found between the increase in MMSE scores and HMW/LMW tau ratio. This study showed that this ratio is significantly higher in AD patients than controls. Moreover, this study on a peripheral marker of AD is valuable to understanding the AD pathogenesis.

In vitro studies of the neuroprotective activities of astaxanthin and fucoxanthin against amyloid beta (Aβ1-42) toxicity and aggregation

Amyloid beta (Aβ) can aggregate and form plaques, which are considered as one of the major hallmarks of Alzheimer's disease. This study aims to directly compare the neuroprotective activities in vitro of two marine-derived carotenoids astaxanthin and fucoxanthin that have shown a spectrum of biological activities, including neuroprotection. The in vitro neuroprotective activities were investigated against Aβ_1-42-mediated toxicity in pheochromocytoma (PC-12) neuronal cells using the MTT cell viability assay, anti-apoptotic, antioxidant and neurite outgrowth activities; as well as inhibition against Aβ_1-42 fibrillization in the Thioflavin T (ThT) assay of fibril kinetics and via transmission electron microscopic (TEM) evaluation of fibril morphology. The results demonstrated that both astaxanthin and fucoxanthin exhibited multi-neuroprotective effects favouring fucoxanthin over astaxanthin supporting neuroprotective roles of marine-derived carotenoids as potential novel dementia prevention or therapeutic strategies.

Blood-based biomarkers for Alzheimer disease: mapping the road to the clinic

Biomarker discovery and development for clinical research, diagnostics and therapy monitoring in clinical trials have advanced rapidly in key areas of medicine - most notably, oncology and cardiovascular diseases - allowing rapid early detection and supporting the evolution of biomarker-guided, precision-medicine-based targeted therapies. In Alzheimer disease (AD), breakthroughs in biomarker identification and validation include cerebrospinal fluid and PET markers of amyloid-β and tau proteins, which are highly accurate in detecting the presence of AD-associated pathophysiological and neuropathological changes. However, the high cost, insufficient accessibility and/or invasiveness of these assays limit their use as viable first-line tools for detecting patterns of pathophysiology. Therefore, a multistage, tiered approach is needed, prioritizing development of an initial screen to exclude from these tests the high numbers of people with cognitive deficits who do not demonstrate evidence of underlying AD pathophysiology. This Review summarizes the efforts of an international working group that aimed to survey the current landscape of blood-based AD biomarkers and outlines operational steps for an effective academic-industry co-development pathway from identification and assay development to validation for clinical use.

Rate of β-amyloid accumulation varies with baseline amyloid burden: Implications for anti-amyloid drug trials

INTRODUCTION

This study examined a longitudinal trajectory of β-amyloid (Aβ) accumulation at the predementia stage of Alzheimer's disease in the context of clinical trials.

METHODS

Analyzed were baseline (BL) and 2 years' follow-up 18F-florbetapir positron emission tomography data of 246 Aβ-positive subjects with normal cognition and mild cognitive impairment. We studied the relationship between annual accumulation rates of 18F-florbetapir and BL standard uptake value ratios in whole gray matter (SUVR_GM).

RESULTS

Subjects with BL SUVR_GM of 0.56 to 0.92 (n = 134) appeared to accumulate Aβ approximately 1.5 times faster than remaining subjects. In subjects with SUVR_GM above 0.95, most regions with the highest annual accumulation rate were outside the established set of Alzheimer's disease typical regions.

CONCLUSION

There are global and regional variations in annual accumulation rate at the predementia stage of Alzheimer's disease. When taken into account, the sample size in anti-amyloid trials can be substantially reduced. Critically, treated and placebo groups should be matched for BL SUVR_GM.

Utilizing the Centiloid scale in cross-sectional and longitudinal PiB PET studies

Amyloid imaging is a valuable tool for research and diagnosis in dementing disorders. Successful use of this tool is limited by the lack of a common standard in the quantification of amyloid imaging data. The Centiloid approach was recently proposed to address this problem and in this work, we report our implementation of this approach and evaluate the impact of differences in underlying image analysis methodologies using both cross-sectional and longitudinal datasets. The Centiloid approach successfully converts quantitative amyloid burden measurements into a common Centiloid scale (CL) and comparable dynamic range. As expected, the Centiloid values derived from different analytical approaches inherit some of the inherent benefits and drawbacks of the underlying approaches, and these differences result in statistically significant (p < 0.05) differences in the variability and group mean values. Because of these differences, even after expression in CL, the 95% specificity amyloid positivity thresholds derived from different analytic approaches varied from 5.7 CL to 11.9 CL, and the reliable worsening threshold varied from −2.0 CL to 11.0 CL. Although this difference is in part due to the dependency of the threshold determination methodology on the statistical characteristics of the measurements. When amyloid measurements obtained from different centers are combined for analysis, one should not expect Centiloid conversion to eliminate all the differences in amyloid burden measurements due to variabilities in underlying acquisition protocols and analysis techniques.

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The Centiloid approach brings amyloid burden measurements into a common scale.

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The Centiloid value inherits the characteristics of the underlying method.

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The Centiloid value derived from different analysis techniques remains different.

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The amyloid positivity thresholds in Centiloid are sensitive to implementation.

Stress as risk factor for Alzheimer's disease

Prolonged stress predisposes susceptible individuals to a number of physiological disorders including cardiovascular disease, obesity and gastrointestinal disorders, as well as psychiatric and neurodegenerative disorders. Preclinical studies have suggested that manipulation of the glucocorticoid milieu can trigger cellular, molecular and behavioral derangement resembling the hallmarks of Alzheimer's Disease (AD). For example, stress or glucocorticoid administration can increase amyloid ß precursor protein and tau phosphorylation which are involved in synaptic dysfunction and neuronal death associated with AD. Although since AD was first described in 1906 at a conference in Tubingen, Germany by Alois Alzheimer our knowledge of neuropathological and neurochemical alterations of AD has been impressively increased, at present, pharmacotherapy is symptomatic at best and has no influence on the progression of the disorder. It is generally believed that most of the drugs developed as disease modifiers have failed in clinical trials because treatment started too late, i.e., after the clinical onset of AD. Because AD pathology begins several years prior to the clinical diagnosis, it is imperative to identify subjects at high risk to develop the disorder. Consequently, the search for putative risk factors has gained importance. ApoE4, diabetes/metabolic syndrome, cardiovascular disorders, and a low cognitive reserve are established risk factors for AD. The focus of this review is on stress and glucocorticoids as potential factors increasing the risk to develop AD.

Regulatory-accepted drug development tools are needed to accelerate innovative CNS disease treatments

Central Nervous System (CNS) diseases represent one of the most challenging therapeutic areas for successful drug approvals. Developing quantitative biomarkers as Drug Development Tools (DDTs) can catalyze the path to innovative treatments, and improve the chances of drug approvals. Drug development and healthcare management requires sensitive, reliable, validated, and regulatory accepted biomarkers and endpoints. This review highlights the regulatory paths and considerations for developing DDTs required to advance biomarker and endpoint use in clinical development (e.g., consensus CDISC [Clinical Data Interchange Standards Consortium] data standards, precompetitive sharing of anonymized patient-level data, and continual alignment with regulators). Summarized is the current landscape of biomarkers in a range of CNS diseases including Alzheimer disease, Parkinson Disease, Amyotrophic Lateral Sclerosis, Autism Spectrum Disorders, Depression, Huntington's disease, Multiple Sclerosis and Traumatic Brain Injury. Advancing DDTs for these devastating diseases that are both validated and qualified will require an integrated, cross-consortium approach to accelerate the delivery of innovative CNS therapeutics.

Genetics of neurodegenerative diseases: an overview

Genetic factors are central to the etiology of neurodegeneration, both as monogenic causes of heritable disease and as modifiers of susceptibility to complex, sporadic disorders. Over the last two decades, the identification of disease genes and risk loci has led to some of the greatest advances in medicine and invaluable insights into pathogenic mechanisms and disease pathways. Large-scale research efforts, novel study designs, and advances in methodology are rapidly expanding our understanding of the genome and the genetic architecture of neurodegenerative disease. Here, we review major developments in the field to date, highlighting overarching historic trends and general insights. Monogenic neurodegenerative diseases are discussed from the perspectives of both rare Mendelian forms of common disorders, such as Alzheimer disease and Parkinson disease, and heterogeneous heritable conditions, including ataxias and spastic paraplegias. Next, we summarize the experiences from investigations of complex neurodegenerative disorders, including genomewide association studies. In the final section, we reflect upon the limitations of current findings and outline important future directions. Genetics plays an essential role in translational research, ultimately aiming to develop novel disease-modifying therapies for neurodegenerative disorders. We anticipate that individual genetic profiling will also be increasingly relevant in a clinical context, with implications for patient care in line with the proposed ideal of personalized medicine.

Polymicrobial Infections In Brain Tissue From Alzheimer's Disease Patients

Several studies have advanced the idea that the etiology of Alzheimer’s disease (AD) could be microbial in origin. In the present study, we tested the possibility that polymicrobial infections exist in tissue from the entorhinal cortex/hippocampus region of patients with AD using immunohistochemistry (confocal laser scanning microscopy) and highly sensitive (nested) PCR. We found no evidence for expression of early (ICP0) or late (ICP5) proteins of herpes simplex virus type 1 (HSV-1) in brain sections. A polyclonal antibody against Borrelia detected structures that appeared not related to spirochetes, but rather to fungi. These structures were not found with a monoclonal antibody. Also, Borrelia DNA was undetectable by nested PCR in the ten patients analyzed. By contrast, two independent Chlamydophila antibodies revealed several structures that resembled fungal cells and hyphae, and prokaryotic cells, but most probably were unrelated to Chlamydophila spp. Finally, several structures that could belong to fungi or prokaryotes were detected using peptidoglycan and Clostridium antibodies, and PCR analysis revealed the presence of several bacteria in frozen brain tissue from AD patients. Thus, our results show that polymicrobial infections consisting of fungi and bacteria can be revealed in brain tissue from AD patients.

Novel strategies for Alzheimer's disease treatment: An overview of anti-amyloid beta monoclonal antibodies

Alzheimer's disease (AD) is a multifactorial, progressive neurodegenerative disorder with a poor prognosis, and thus, novel therapies for AD are certainly needed in a growing population of elderly patients or asymptomatic individuals, who are at risk for AD, worldwide. It has been established that some AD biomarkers such as amyloid-beta load in the brain, precede the onset of the disease, by approximately 20 years. Therefore, the therapy to prevent or effectively treat AD has to be initiated before the emergence of symptoms. A goal of this review is to present the results of recent clinical trials on monoclonal antibodies against amyloid beta, used for the treatment of AD and also to address some of the current challenges and emerging strategies to prevent AD. In recent trials, a monoclonal antibody, i.e. solanezumab has shown some beneficial cognitive effects among mild AD patients. Ongoing studies with gantenerumab and crenezumab will examine when exactly the AD treatment, aimed at modifying the disease course has to be started. This review was based on Medline database search for trials on passive anti-AD immunotherapy, for which the main timeframe was set from 2012 to 2015.

Roles of tau protein in health and disease

Tau is well established as a microtubule-associated protein in neurons. However, under pathological conditions, aberrant assembly of tau into insoluble aggregates is accompanied by synaptic dysfunction and neural cell death in a range of neurodegenerative disorders, collectively referred to as tauopathies. Recent advances in our understanding of the multiple functions and different locations of tau inside and outside neurons have revealed novel insights into its importance in a diverse range of molecular pathways including cell signalling, synaptic plasticity, and regulation of genomic stability. The present review describes the physiological and pathophysiological properties of tau and how these relate to its distribution and functions in neurons. We highlight the post-translational modifications of tau, which are pivotal in defining and modulating tau localisation and its roles in health and disease. We include discussion of other pathologically relevant changes in tau, including mutation and aggregation, and how these aspects impinge on the propensity of tau to propagate, and potentially drive neuronal loss, in diseased brain. Finally, we describe the cascade of pathological events that may be driven by tau dysfunction, including impaired axonal transport, alterations in synapse and mitochondrial function, activation of the unfolded protein response and defective protein degradation. It is important to fully understand the range of neuronal functions attributed to tau, since this will provide vital information on its involvement in the development and pathogenesis of disease. Such knowledge will enable determination of which critical molecular pathways should be targeted by potential therapeutic agents developed for the treatment of tauopathies.

Potential biomarkers and novel pharmacological targets in protein aggregation-related neurodegenerative diseases

The aggregation of specific proteins plays a pivotal role in the etiopathogenesis of several neurodegenerative diseases (NDs). β-Amyloid (Aβ) peptide-containing plaques and intraneuronal neurofibrillary tangles composed of hyperphosphorylated protein tau are the two main neuropathological lesions in Alzheimer's disease. Meanwhile, Parkinson's disease is defined by the presence of intraneuronal inclusions (Lewy bodies), in which α-synuclein (α-syn) has been identified as a major protein component. The current literature provides considerable insights into the mechanisms underlying oligomeric-related neurodegeneration, as well as the relationship between protein aggregation and ND, thus facilitating the development of novel putative biomarkers and/or pharmacological targets. Recently, α-syn, tau and Aβ have been shown to interact each other or with other "pathological proteins" to form toxic heteroaggregates. These latest findings are overcoming the concept that each neurodegenerative disease is related to the misfolding of a single specific protein. In this review, potential opportunities and pharmacological approaches targeting α-syn, tau and Aβ and their oligomeric forms are highlighted with examples from recent studies. Protein aggregation as a biomarker of NDs, in both the brain and peripheral fluids, is deeply explored. Finally, the relationship between biomarker establishment and assessment and their use as diagnostics or therapeutic targets are discussed.

A modification-specific peptide-based immunization approach using CRM197 carrier protein: Development of a selective vaccine against pyroglutamate Aβ peptides

Strategies aimed at reducing cerebral accumulation of the amyloid-β (Aβ) peptides have therapeutic potential in Alzheimer's disease (AD). Aβ immunization has proven to be effective at promoting Aβ clearance in animal models but adverse effects have hampered its clinical evaluation. The first anti-Aβ immunization clinical trial, which assessed a full-length Aβ1-42 vaccine, increased the risk of encephalitis most likely because of autoimmune pro-inflammatory T helper 1 (Th1) response against all forms of Aβ. Immunization against less abundant but potentially more pathologically relevant Aβ products, such as N-terminally-truncated pyroglutamate-3 Aβ (AβpE3), could provide efficacy and improve tolerability in Aβ immunotherapy. Here, we describe a selective vaccine against AβpE3, which uses the diphtheria toxin mutant CRM197 as carrier protein for epitope presentation. CRM197 is currently used in licensed vaccines and has demonstrated excellent immunogenicity and safety in humans. In mice, our AβpE3:CRM197 vaccine triggered the production of specific anti-AβpE3 antibodies that did not cross-react with Aβ1-42, non-cyclized AβE3, or N-terminally-truncated pyroglutamate-11 Aβ (AβpE11). AβpE3:CRM197 antiserum strongly labeled AβpE3 in insoluble protein extracts and decorated cortical amyloid plaques in human AD brains. Anti-AβpE3 antibodies were almost exclusively of the IgG1 isotype, suggesting an anti-inflammatory Th2 response bias to the AβpE3:CRM197 vaccine. To the best of our knowledge, this study shows for the first time that CRM197 has potential as a safe and suitable vaccine carrier for active and selective immunization against specific protein sequence modifications or conformations, such as AβpE3.

Fungal Enolase, β-Tubulin, and Chitin Are Detected in Brain Tissue from Alzheimer's Disease Patients

Recent findings provide evidence that fungal structures can be detected in brain tissue from Alzheimer’s disease (AD) patients using rabbit polyclonal antibodies raised against whole fungal cells. In the present work, we have developed and tested specific antibodies that recognize the fungal proteins, enolase and β-tubulin, and an antibody that recognizes the fungal polysaccharide chitin. Consistent with our previous studies, a number of rounded yeast-like and hyphal structures were detected using these antibodies in brain sections from AD patients. Some of these structures were intracellular and, strikingly, some were found to be located inside nuclei from neurons, whereas other fungal structures were detected extracellularly. Corporya amylacea from AD patients also contained enolase and β-tubulin as revealed by these selective antibodies, but were devoid of fungal chitin. Importantly, brain sections from control subjects were usually negative for staining with the three antibodies. However, a few fungal structures can be observed in some control individuals. Collectively, these findings indicate the presence of two fungal proteins, enolase and β-tubulin, and the polysaccharide chitin, in CNS tissue from AD patients. These findings are consistent with our hypothesis that AD is caused by disseminated fungal infection.

Beta-Amyloid and Tau-Protein: Structure, Interaction, and Prion-Like Properties

During the last twenty years, molecular genetic investigations of Alzheimer's disease (AD) have significantly broadened our knowledge of basic mechanisms of this disorder. However, still no unambiguous concept on the molecular bases of AD pathogenesis has been elaborated, which significantly impedes the development of AD therapy. In this review, we analyze issues concerning processes of generation of two proteins (β-amyloid peptide and Tau-protein) in the cell, which are believed to play the key role in AD genesis. Until recently, these agents were considered independently of each other, but in light of the latest studies, it becomes clear that it is necessary to study their interaction and combined effects. Studies of mechanisms of toxic action of these endogenous compounds, beginning from their interaction with known receptors of main neurotransmitters to specific peculiarities of functioning of signal intracellular pathways upon development of this pathology, open the way to development of new pharmaceutical substances directed concurrently on key mechanisms of interaction of toxic proteins inside the cell and on the pathways of their propagation in the extracellular space.

Defining imaging biomarker cut points for brain aging and Alzheimer's disease

INTRODUCTION

Our goal was to develop cut points for amyloid positron emission tomography (PET), tau PET, flouro-deoxyglucose (FDG) PET, and MRI cortical thickness.

METHODS

We examined five methods for determining cut points.

RESULTS

The reliable worsening method produced a cut point only for amyloid PET. The specificity, sensitivity, and accuracy of cognitively impaired versus young clinically normal (CN) methods labeled the most people abnormal and all gave similar cut points for tau PET, FDG PET, and cortical thickness. Cut points defined using the accuracy of cognitively impaired versus age-matched CN method labeled fewer people abnormal.

DISCUSSION

In the future, we will use a single cut point for amyloid PET (standardized uptake value ratio, 1.42; centiloid, 19) based on the reliable worsening cut point method. We will base lenient cut points for tau PET, FDG PET, and cortical thickness on the accuracy of cognitively impaired versus young CN method and base conservative cut points on the accuracy of cognitively impaired versus age-matched CN method.

Molecular and cellular pathophysiology of preclinical Alzheimer's disease

Although the two pathological hallmarks of Alzheimer's disease (AD), senile plaques composed of amyloid-β (Aβ) peptides and neurofibrillary tangles (NFTs) consisting of hyperphosphorylated tau, have been studied extensively in postmortem AD and relevant animal and cellular models, the pathogenesis of AD remains unknown, particularly in the early stages of the disease where therapies presumably would be most effective. We and others have demonstrated that Aβ plaques and NFTs are present in varying degrees before the onset and throughout the progression of dementia. In this regard, aged people with no cognitive impairment (NCI), mild cognitive impairment (MCI, a presumed prodromal AD transitional state, and AD all present at autopsy with varying levels of pathological hallmarks. Cognitive decline, a requisite for the clinical diagnosis of dementia associated with AD, generally correlates better with NFTs than Aβ plaques. However, correlations are even higher between cognitive decline and synaptic loss. In this review, we illustrate relevant clinical pathological research in preclinical AD and throughout the progression of dementia in several areas including Aβ and tau pathobiology, single population expression profiling of vulnerable hippocampal and basal forebrain neurons, neuroplasticity, neuroimaging, cerebrospinal fluid (CSF) biomarker studies and their correlation with antemortem cognitive endpoints. In each of these areas, we provide evidence for the importance of studying the pathological hallmarks of AD not in isolation, but rather in conjunction with other molecular, cellular, and imaging markers to provide a more systematic and comprehensive assessment of the multiple changes that occur during the transition from NCI to MCI to frank AD.

A/T/N: An unbiased descriptive classification scheme for Alzheimer disease biomarkers

Biomarkers have become an essential component of Alzheimer disease (AD) research and because of the pervasiveness of AD pathology in the elderly, the same biomarkers are used in cognitive aging research. A number of current issues suggest that an unbiased descriptive classification scheme for these biomarkers would be useful. We propose the "A/T/N" system in which 7 major AD biomarkers are divided into 3 binary categories based on the nature of the pathophysiology that each measures. "A" refers to the value of a β-amyloid biomarker (amyloid PET or CSF Aβ42); "T," the value of a tau biomarker (CSF phospho tau, or tau PET); and "N," biomarkers of neurodegeneration or neuronal injury ([(18)F]-fluorodeoxyglucose-PET, structural MRI, or CSF total tau). Each biomarker category is rated as positive or negative. An individual score might appear as A+/T+/N-, or A+/T-/N-, etc. The A/T/N system includes the new modality tau PET. It is agnostic to the temporal ordering of mechanisms underlying AD pathogenesis. It includes all individuals in any population regardless of the mix of biomarker findings and therefore is suited to population studies of cognitive aging. It does not specify disease labels and thus is not a diagnostic classification system. It is a descriptive system for categorizing multidomain biomarker findings at the individual person level in a format that is easy to understand and use. Given the present lack of consensus among AD specialists on terminology across the clinically normal to dementia spectrum, a biomarker classification scheme will have broadest acceptance if it is independent from any one clinically defined diagnostic scheme.