Reassessing the amyloid cascade hypothesis of Alzheimer's disease

Protein aggregation and its affecting mechanisms in neurodegenerative diseases

Protein aggregation serves as a critical pathological marker in a spectrum of neurodegenerative diseases (NDs), including the formation of amyloid β (Aβ) and Tau neurofibrillary tangles in Alzheimer's disease, as well as α-Synuclein (α-Syn) aggregates in Parkinson's disease, Parkinson's disease-related dementia (PDD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). A significant proportion of patients with amyotrophic lateral sclerosis (ALS) exhibit TDP-43 aggregates. Moreover, a confluence of brain protein pathologies, such as Aβ, Tau, α-Syn, and TDP-43, has been identified in individual NDs cases, highlighting the intricate interplay among these proteins that is garnering heightened scrutiny. Importantly, protein aggregation is modulated by an array of factors, with burgeoning evidence suggesting that it frequently results from perturbations in protein homeostasis, influenced by the cellular membrane milieu, metal ion concentrations, post-translational modifications, and genetic mutations. This review delves into the pathological underpinnings of protein aggregation across various NDs and elucidates the intercommunication among disparate proteins within the same disease context. Additionally, we examine the pathogenic mechanisms by which diverse factors impinge upon protein aggregation, offering fresh perspectives for the future therapeutic intervention of NDs.

Edaravone N-benzyl pyridinium derivatives: BACE-1 inhibition, kinetics and in silico binding pose determination

BACE-1 plays a pivotal role in the production of β-amyloid (Aβ) peptides, implicated in Alzheimer's Disease (AD) pathology. We previously described edaravone N-benzyl pyridinium derivatives (EBPDs) that exhibited multifunctional activity against multiple AD targets. In this study we explored the EBPDs BACE-1 inhibitory activity to potentially enhance the compounds therapeutic profile. The EBPDs exhibited moderate BACE-1 inhibitory activity (IC50 = 44.10 µM - 123.70 µM) and obtained IC50 values between 2.0 and 5.8-fold greater than resveratrol, a known BACE-1 inhibitor (IC50 = 253.20 µM), in this assay. Compound 3 was the most potent inhibitor with an IC50 of 44.10 µM and a Ki of 19.96 µM and a mixed-type mode of inhibition that favored binding in a competitive manner. Molecular docking identified crucial interactions with BACE-1 active site residues, supported by 100 ns MD simulations. The study highlighted the EBPDs therapeutic potential as BACE-1 inhibitors and multifunctional anti-AD therapeutic agents.

BACE1 inhibitor drugs for the treatment of Alzheimer's disease: Lessons learned, challenges to overcome, and future prospects†

Alzheimer's disease (AD), first diagnosed over a century ago, remains one of the major healthcare crises around the globe. Currently, there is no cure or effective treatment. The majority of drug development efforts to date have targeted reduction of amyloid-β peptide (Aβ). Drug development through inhibition of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), resulted in promising early clinical studies. However, nearly all small molecule BACE1 inhibitor drugs failed to live up to expectations in later phase clinical trials, due to toxicity and efficacy issues. This commentary aims to provide a brief review of over two decades of BACE1 inhibitor drug development challenges and efforts for treatment of AD and prospects of future BACE1-based drugs.

Cytotoxic Effect of Amyloid-β1-42 Oligomers on Endoplasmic Reticulum and Golgi Apparatus Arrangement in SH-SY5Y Neuroblastoma Cells

Amyloid-β oligomers are a cytotoxic structure that is key for the establishment of the beginning stages of Alzheimer's disease (AD). These structures promote subcellular alterations that cause synaptic dysfunction, loss of cell communication, and even cell death, generating cognitive deficits. The aim of this study was to investigate the cytotoxic effects of amyloid-β1-42 oligomers (AβOs) on the membranous organelles involved in protein processing: the endoplasmic reticulum (ER) and Golgi apparatus (GA). The results obtained with 10 μM AβOs in SH-SY5Y neuroblastoma cells showed that oligomeric structures are more toxic than monomers because they cause cell viability to decrease as exposure time increases. Survivor cells were analyzed to further understand the toxic effects of AβOs on intracellular organelles. Survivor cells showed morphological alterations associated with abnormal cytoskeleton modification 72-96 h after exposure to AβOs. Moreover, the ER and GA presented rearrangement throughout the cytoplasmic space, which could be attributed to a lack of constitutive protein processing or to previous abnormal cytoskeleton modification. Interestingly, the disorganization of both ER and GA organelles exposed to AβOs is likely an early pathological alteration that could be related to aberrant protein processing and accumulation in AD.

The need for systems thinking to advance Alzheimer's disease research

Despite extensive research efforts to mechanistically understand late-onset Alzheimer's disease (LOAD) and other complex mental health disorders, curative treatments remain elusive. We emphasize the multiscale multicausality inherent to LOAD, highlighting the interplay between interconnected pathophysiological processes and risk factors. Systems thinking methods, such as causal loop diagrams and systems dynamic models, offer powerful means to capture and study this complexity. Recent studies developed and validated a causal loop diagram and system dynamics model using multiple longitudinal data sets, enabling the simulation of personalized interventions on various modifiable risk factors in LOAD. The results indicate that targeting factors like sleep disturbance and depressive symptoms could be promising and yield synergistic benefits. Furthermore, personalized interventions showed significant potential, with top-ranked intervention strategies differing significantly across individuals. We argue that systems thinking approaches can open new prospects for multifactorial precision medicine. In future research, systems thinking may also guide structured, model-driven data collection on the multiple interactions in LOAD's complex multicausality, facilitating theory development and possibly resulting in effective prevention and treatment options.

Astragaloside IV against Alzheimer's disease via microglia-mediated neuroinflammation using network pharmacology and experimental validation

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases in the world. The effective therapeutic methods and drugs are still not clear. Astragaloside IV (AS-IV), a triterpenoid saponin isolated from the root of Huangqi, has a beneficial effect in the treatment of AD. However, whether AS-IV alters microglia in the inflammation of AD is still ambiguous. In our study, 99 common targets were collected between AS-IV and AD. BCL2 apoptosis regulator (Bcl-2), pro-apoptotic BCL-2 protein BAX, epidermal growth factor receptor (EGFR), and receptor tyrosine phosphatase type C (PTPRC) were screened for inflammation and microglia in the above targets by network pharmacology. Interleukin-1β (IL-1β) and EGFR both interact with signal transducer and activator of transcription 3 (STAT3) by a protein interaction network, and IL-1β had a higher affinity for AS-IV based on molecular docking. Enrichment revealed targets involved in the regulation of neuronal cell bodies, growth factor receptor binding, EGFR tyrosine kinase inhibitor resistance., etc. Besides, AS-IV alleviated the reduced cell proliferation in amyloid-beta (Aβ)-treated microglial BV2 cells. AS-IV affected BV2 cell morphological changes and decreased cluster of differentiation 11b (CD11b) gene, IL-1β, and EGFR mRNA levels increment during lipopolysaccharide (LPS) injury in BV2 cell activation. Therefore, AS-IV may regulate microglial activation and inflammation via EGFR-dependent pathways in AD. EGFR and IL-1β are vital targets that may relate to each other to coregulate downstream molecular functions in the cure of AD. Our study provides a candidate drug and disease target for the treatment of neurodegenerative diseases in the clinic.

Reactive Sulfur Species Omics Analysis in the Brain Tissue of the 5xFAD Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder whereby oxidative stress augmentation results in mitochondrial dysfunction and cell death by apoptosis. Emerging evidence indicates that reactive sulfur species (RSS), such as glutathione hydropersulfide (GSSH), is endogenously produced, functions as potent antioxidants, and regulate redox signaling through the formation of protein polysulfides. However, the relationship between RSS and AD pathogenesis is not fully understood. In this study, we analyzed endogenous RSS production in the brain tissue of a familial AD model (5xFAD) mouse using multiple RSS-omics approaches. Memory impairment, increased amyloid plaques, and neuroinflammation have been confirmed in 5xFAD mice. Quantitative RSS omics analysis revealed that the total polysulfide content was significantly decreased in the brains of 5xFAD mice, whereas there was no significant difference in the levels of glutathione, GSSH, or hydrogen sulfide between wild-type and 5xFAD mice. In contrast, a significant decline in the protein polysulfide status was observed in the brains of 5xFAD mice, suggesting that RSS production and subsequent redox signaling might be altered during the onset and progression of AD. Our findings have important implications for understanding the significance of RSS in the development of preventive and therapeutic strategies for AD.

Oxidative Stress and Aging as Risk Factors for Alzheimer's Disease and Parkinson's Disease: The Role of the Antioxidant Melatonin

Aging and neurodegenerative diseases share common hallmarks, including mitochondrial dysfunction and protein aggregation. Moreover, one of the major issues of the demographic crisis today is related to the progressive rise in costs for care and maintenance of the standard living condition of aged patients with neurodegenerative diseases. There is a divergence in the etiology of neurodegenerative diseases. Still, a disturbed endogenous pro-oxidants/antioxidants balance is considered the crucial detrimental factor that makes the brain vulnerable to aging and progressive neurodegeneration. The present review focuses on the complex relationships between oxidative stress, autophagy, and the two of the most frequent neurodegenerative diseases associated with aging, Alzheimer's disease (AD) and Parkinson's disease (PD). Most of the available data support the hypothesis that a disturbed antioxidant defense system is a prerequisite for developing pathogenesis and clinical symptoms of ADs and PD. Furthermore, the release of the endogenous hormone melatonin from the pineal gland progressively diminishes with aging, and people's susceptibility to these diseases increases with age. Elucidation of the underlying mechanisms involved in deleterious conditions predisposing to neurodegeneration in aging, including the diminished role of melatonin, is important for elaborating precise treatment strategies for the pathogenesis of AD and PD.

It's Groundhog Day! What Can the History of Science Say About the Crisis in Alzheimer's Disease Research?

For years now, Alzheimer's disease (AD) research has been stuck in a Groundhog-Day scenario: an endless time loop with no breakthrough in sight. Disagreement about the validity of the field's dominant approach, based on the Amyloid Cascade Hypothesis, has led to a seemingly unresolvable trench war between proponents and critics. Our paper evaluates the recent scientific literature on AD from a historical and philosophical perspective. We show that AD research is a classic example of the boundary work at play in a field in crisis: both parties deploy historical and philosophical references to illustrate what counts as good and bad science, as proper scientific method and appropriate scientific conduct. We also show that boundary work has proved unable to point a way out of the deadlock and argue that the science system's tools for establishing scientific quality, such as peer review and the grant system, are unlikely to resolve the crisis. Rather, they consolidate the dominant model's position even more. In conclusion, we suggest that some kind of reverse boundary-work is needed that reopens the discussion on the nature of AD, an issue that has never been settled scientifically. Drawing on historical and philosophical work, we make clear that the definition of AD as a biomedical disease for which a cure can be found has consequences, not only for funding opportunities, but also for patients and their lives. A reconsideration of the desirability of these consequences may lead to different choices with respect to research priorities and patient care.

Kaempferol as a potential neuroprotector in Alzheimer's disease

Alzheimer's disease (AD), the most prevalent neurodegenerative disorder, is largely associated with cognitive disability, amnesia, and abnormal behavior, which accounts for about two third of people with dementia worldwide. A growing body of research demonstrates that AD is connected to several factors, such as aberrant accumulation of amyloid-beta (Aβ), increase in the hyperphosphorylation of Tau protein, and the formation of neurofibrillary tangles, mitochondrial dysfunction, and inordinate production of reactive oxygen species (ROS). Despite remarkable efforts to realize the etiology and pathophysiology of AD, until now, scientists have not developed and introduced medications that can permanently cease the progression of AD. Thus, nowadays, research on the role of natural products in the treatment and prevention of AD has attracted great attention. Kaempferol (KMP), one of the prominent members of flavonols, exerts its ameliorative actions via attenuating oxidative stress and inflammation, reducing Aβ-induced neurotoxicity, and regulating the cholinergic system. Therefore, in this review article, we outlined the possible effects of KMP in the prevention and treatment of AD. PRACTICAL APPLICATIONS: Kaempferol (KMP) exerts its ameliorative actions against AD via attenuating oxidative stress and inflammation, reducing Aβ-induced neurotoxicity, and regulating the cholinergic system. The beneficial effects of KMP were addressed in both in vitro and in vivo studies; however, conducting further research can warrant its long-term effects as a safe agent. Therefore, after confirming its favorable functions in the prevention and treatment of AD, it could be used as a safe and effective agent.

Molecular mechanism of Epimedium in the treatment of vascular dementia based on network pharmacology and molecular docking

Backgroud: Vascular dementia is the second most common cause of dementia after Alzheimer’s disease, accounting for an estimated 15% of cases. Recently, Epimedium has attracted great attention for its potential neuroprotective benefit. However, the direct role and mechanism of Epimedium on vascular dementia still lack systematic research. To systematically explore the possible pharmacological mechanism of Epimedium for the treatment of vascular dementia, network pharmacology, molecular docking, combined with experiment validation were conducted.

Methods: The bioactive compounds and targets of Epimedium were obtained from the TCMSP database. The potential targets of vascular dementia were identified from the DrugBank, OMIM, Genecards, Therapeutic Target Database, and DisGeNET databases. GO and KEGG pathway analyses were performed. Molecular docking was applied to validate the interaction between active components and hub targets. The bilateral common carotid artery occlusion (BCCAO) method was used for construction of a vascular dementia model in mice. The effects of Epimedium on learning and memory ability were examined by behavioral tests. The mechanisms of the cerebral protective effects of Epimedium were evaluated by WB, RT-PCR, and immunofluorescence.

Results: A total of 23 Epimedium active ingredients, and 71 intersecting targets of Epimedium against vascular dementia were obtained. The top five hub targets AKT1, TNF, IL1β, IL6, and MMP9 were identified, and molecular docking showed good binding. GO enrichment showed a total of 602 enrichment results, with 458 (80.56%) key targets mainly focused on biological processes (BP). The response to hypoxia, positive regulation of nitric oxide biosynthetic process, aging, inflammatory response, cellular response to lipopolysaccharide, negative regulation of apoptotic process were well ranked. KEGG pathway enrichment analysis identified the TNF signaling pathway as an important pathway, with the MAPK/extracellular signal-regulated kinase (ERK) and NF-κB signaling pathways as the key pathways involved. Consistently, in vivo experiments showed that Epimedium treatment improved learning and memory functions in mice with vascular dementia. In addition, Epimedium attenuated the activation of microglia and astrocytes in the hippocampal region after BCCAO. RT-qPCR and Western blot analysis showed that Epimedium not only affected the expression of AKT, TNF, IL1β, IL6, and MMP9, but also suppressed the TNF signaling pathway.

Conclusion: Epimedium may exert a protective effect against vascular dementia through the alleviation of oxidative stress, neuroinflammation, BBB dysfunction, apoptosis through TNF signaling pathway. This study explored the mechanism of Epimedium on vascular dementia systematically through network pharmacological and in vivo experiment approach, which provides insight into the treatment of vascular dementia.

Development of new donepezil analogs: synthesis, biological screening and in silico study rational

Fifteen new benzothiophene-based compounds were designed, synthesized, and evaluated as potential anti-Alzheimer agents. Most of the synthesized compounds exhibited remarkable AChE inhibitory activity and effectively inhibited self-mediated β-amyloid protein in vitro. Compound 3g (IC50 = 72.488 ± 3.69 μM) showed a significant β-amyloid inhibitory effect exceeding that of donepezil (IC50 = 87.414 ± 4.46 μM). Furthermore, compound 3j (IC50 = 0.498 ± 0.02 μM) showed the best inhibitory activity comparable to that of donepezil (IC50 = 0.404 ± 0.03 μM). The in vivo evaluation of the promising compounds (3g and 3j) confirmed a significant memory improvement in scopolamine-induced memory impairment model in mice. The molecular docking simulation of compounds 3g and 3j in Torpedo californica-AChE (TcAChE) active site showed a good agreement with the obtained screening results. The in silico ADMET and other physicochemical parameters were also reported.

Clinical Knowledge Mining Based on Image Enhancement Algorithm: Endoscopic Clinical Analysis of Peptic Ulcer in Children

The incidence rate of peptic ulcer is increasing gradually. Medical images can meet the needs of patients as an auxiliary diagnosis and treatment method for peptic ulcer. However, in the long-term treatment, the actual effect is average, and the diagnosis effect of gastrointestinal diseases will gradually deteriorate. In this paper, we use an image enhancement algorithm to study the mechanism of peptic ulcer from the perspective of a medical image. In this paper, 56 images of children with peptic ulcer were selected, and the gastroscopy based on the image enhancement algorithm provided technical support for the rapid diagnosis of patients with peptic ulcer. Experimental results show that the clinical features of peptic ulcer have different characteristics according to the age difference of patients, which can play a positive role in promoting the treatment of patients of different ages.

Carnosic acid ameliorated Aβ-mediated (amyloid-β peptide) toxicity, cholinergic dysfunction and mitochondrial defect in Caenorhabditis elegans of Alzheimer's Model

Amyloid-β peptide (Aβ)-induced cholinergic system and mitochondrial dysfunction are major risk factors for Alzheimer's disease (AD). Our previous studies found that carnosic acid (CA), an important polyphenol antioxidant, could significantly delay Aβ_1-42-mediated acute paralysis. However, many details and underlying mechanisms of CA's neuroprotection against Aβ-induced cholinergic system defects and mitochondrial dysfunction remain unclear. Herein, we deeply investigated the effects and the possible mechanisms of CA-mediated protection against Aβ toxicity in vivo through several AD Caenorhabditis elegans strains. The results showed CA delayed age-related paralysis and Aβ deposition, and significantly protected neurons from Aβ-induced toxicity. CA might downgrade the expression of ace-1 and ace-2 genes, and upregulate cha-1 and unc-17 genes to inhibit acetylcholinesterase activity and relieve Aβ-caused cholinergic system defects. Furthermore, CA might also ameliorate Aβ-induced mitochondrial imbalance and oxidative stress through up-regulating the expression of phb-1, phb-2, eat-3, and drp-1 genes. The enhancements of the cholinergic system and mitochondrial function might be the reasons for the amelioration of Aβ-mediated toxicity and Aβ aggregation mediated by CA. These findings have helped us to understand the CA anti-Aβ activity in C. elegans and the potential mechanism of action.

A New Hypothesis for Alzheimer's Disease: The Lipid Invasion Model

This paper proposes a new hypothesis for Alzheimer's disease (AD)-the lipid invasion model. It argues that AD results from external influx of free fatty acids (FFAs) and lipid-rich lipoproteins into the brain, following disruption of the blood-brain barrier (BBB). The lipid invasion model explains how the influx of albumin-bound FFAs via a disrupted BBB induces bioenergetic changes and oxidative stress, stimulates microglia-driven neuroinflammation, and causes anterograde amnesia. It also explains how the influx of external lipoproteins, which are much larger and more lipid-rich, especially more cholesterol-rich, than those normally present in the brain, causes endosomal-lysosomal abnormalities and overproduction of the peptide amyloid-β (Aβ). This leads to the formation of amyloid plaques and neurofibrillary tangles, the most well-known hallmarks of AD. The lipid invasion model argues that a key role of the BBB is protecting the brain from external lipid access. It shows how the BBB can be damaged by excess Aβ, as well as by most other known risk factors for AD, including aging, apolipoprotein E4 (APOE4), and lifestyle factors such as hypertension, smoking, obesity, diabetes, chronic sleep deprivation, stress, and head injury. The lipid invasion model gives a new rationale for what we already know about AD, explaining its many associated risk factors and neuropathologies, including some that are less well-accounted for in other explanations of AD. It offers new insights and suggests new ways to prevent, detect, and treat this destructive disease and potentially other neurodegenerative diseases.

Decoding Conformational Imprint of Convoluted Molecular Interactions Between Prenylflavonoids and Aggregated Amyloid-Beta42 Peptide Causing Alzheimer's Disease

Protein misfolding occurs due to the loss of native protein structure and adopts an abnormal structure, wherein the misfolded proteins accumulate and form aggregates, which result in the formation of amyloid fibrils that are associated with neurodegenerative diseases. Amyloid beta (Aβ42) aggregation or amyloidosis is contemplated as a unique hallmark characteristic of Alzheimer’s disease (AD). Due to aberrant accrual and aggregation of Aβ42 in extracellular space, the formation of senile plaques is found in AD patients. These senile plaques occur usually in the cognitive and memory region of the brain, enfeebles neurodegeneration, hinders the signaling between synapse, and disrupts neuronal functioning. In recent years, herbal compounds are identified and characterized for their potential as Aβ42 inhibitors. Thus, understanding their structure and molecular mechanics can provide an incredible finding in AD therapeutics. To describe the structure-based molecular studies in the rational designing of drugs against amyloid fibrils, we examined various herbal compounds that belong to prenylflavonoids. The present study characterizes the trends we identified at molecular docking studies and dynamics simulation where we observed stronger binding orientation of bavachalcone, bavachin, and neobavaisoflavone with the amyloid-beta (Aβ42) fibril structure. Hence, we could postulate that these herbal compounds could be potential inhibitors of Aβ42 fibrils; these anti-aggregation agents need to be considered in treating AD.

OAB-14 Effectively Ameliorates the Dysfunction of the Endosomal-Autophagic-Lysosomal Pathway in APP/PS1 Transgenic Mice

In Alzheimer's disease (AD), damaged Aβ clearance contributes to elevated levels of Aβ that cause a series of cytotoxic cascade reactions. Thus, targeting Aβ clearance has now been considered a valid therapeutic approach for AD. Cellular uptake and degradation are important mechanisms for Aβ clearance, which are mainly performed by the endosomal-autophagic-lysosomal (EAL) pathway. Our previous study showed that OAB-14, a novel small molecule designed with bexarotene as the lead compound, treatment for 3 months significantly alleviated cognitive disorders and remarkably reduced the deposition of Aβ without affecting its production in APP/PS1 transgenic mice. Here, we further revealed that enhancement of the EAL activity is one of the mechanisms that increases Aβ clearance after OAB-14 administration for 3 months. OAB-14 facilitates receptor-mediated endocytosis and restores autophagy flux via the AMPK/mTOR pathway. Meanwhile, OAB-14 enhances the lysosomal activity, and reduced Aβ accumulation in lysosomes was observed in OAB-14-treated AD mice. These results suggest that OAB-14 may promote Aβ clearance in lysosomes by alleviating the EAL dysfunction in AD mice.

Chemical analysis of the human brain by imaging mass spectrometry

Analysis of the chemical makeup of the brain enables a deeper understanding of several neurological processes. Molecular imaging that deciphers the spatial distribution of neurochemicals with high specificity and sensitivity is an exciting avenue in this aspect. The past two decades have witnessed a significant surge of mass spectrometry imaging (MSI) that can simultaneously map the distribution of hundreds to thousands of biomolecules in the tissue specimen at a fairly high resolution, which is otherwise beyond the scope of other molecular imaging techniques. In this review, we have documented the evolution of MSI technologies in imaging the anatomical distribution of neurochemicals in the human brain in the context of several neuro diseases. This review also addresses the potential of MSI to be a next-generation molecular imaging technique with its promising applications in neuropathology.

miR-29a/b1 Regulates BACE1 in Aluminum-Induced Aβ Deposition in Vitro

Aluminum is an environmental neurotoxin that comes extensively in contact with human beings. Animal and human studies demonstrated that aluminum exposure increases the deposition of beta amyloid proteins in the brain as it was observed in Alzheimer's disease. The purpose of this study was to investigate whether miR-29a/b1 affected the expression of beta-secrete enzymes (BACE1) in the process of amyloid β-protein (Aβ) deposition caused by aluminum exposure. The study was performed using two different cell lines. Our results showed that after rat primary cortical neurons were exposed to aluminum, BACE1 gene and protein levels increased to different degrees, and the expression level of Aβ1-42 increased. In aluminum-exposed groups, the expression of miR-29a and miR-29b1 decreased, while the expression of amyloid protein Aβ1-42 and BACE1 increased. In miRs transfection groups, the expression of amyloid protein Aβ1-42 and BACE1 decreased. Aluminum may affect the expression of BACE1 by lowering miR-29a and miR-29b1. AEK293 cells were utilized in this research since they present elevated levels of miR-29a and miR-29b1. After HEK293 cells were exposed to aluminum alone, BACE1 mRNA and BACE1 protein expression levels increased with the increase of aluminum exposure dose (p < 0.05), and the level of Aβ1-42 also increased (p < 0.05). Compared with the group exposed to aluminum alone at the same doses, the expression levels of BACE1 mRNA and BACE1 protein in the miRs transfected plus aluminum-exposed groups significantly decreased (p < 0.05), and the level of Aβ1-42 also decreased (p < 0.05). This result is consistent with the investigation in rat primary neurons. The results of two types of cells showed that aluminum may cause abnormal down-regulation of the expressions of miR-29a and miR-29b1, thus negatively regulating the increase of BACE1 expression and finally leading to the increase of Aβ.

Amyloid Beta-Mediated Changes in Synaptic Function and Spine Number of Neocortical Neurons Depend on NMDA Receptors

Onset and progression of Alzheimer's disease (AD) pathophysiology differs between brain regions. The neocortex, for example, is a brain region that is affected very early during AD. NMDA receptors (NMDARs) are involved in mediating amyloid beta (Aβ) toxicity. NMDAR expression, on the other hand, can be affected by Aβ. We tested whether the high vulnerability of neocortical neurons for Aβ-toxicity may result from specific NMDAR expression profiles or from a particular regulation of NMDAR expression by Aβ. Electrophysiological analyses suggested that pyramidal cells of 6-months-old wildtype mice express mostly GluN1/GluN2A NMDARs. While synaptic NMDAR-mediated currents are unaltered in 5xFAD mice, extrasynaptic NMDARs seem to contain GluN1/GluN2A and GluN1/GluN2A/GluN2B. We used conditional GluN1 and GluN2B knockout mice to investigate whether NMDARs contribute to Aβ-toxicity. Spine number was decreased in pyramidal cells of 5xFAD mice and increased in neurons with 3-week virus-mediated Aβ-overexpression. NMDARs were required for both Aβ-mediated changes in spine number and functional synapses. Thus, our study gives novel insights into the Aβ-mediated regulation of NMDAR expression and the role of NMDARs in Aβ pathophysiology in the somatosensory cortex.

Genetic Variability in Molecular Pathways Implicated in Alzheimer's Disease: A Comprehensive Review

Alzheimer's disease (AD) is a complex neurodegenerative disease, affecting a significant part of the population. The majority of AD cases occur in the elderly with a typical age of onset of the disease above 65 years. AD presents a major burden for the healthcare system and since population is rapidly aging, the burden of the disease will increase in the future. However, no effective drug treatment for a full-blown disease has been developed to date. The genetic background of AD is extensively studied; numerous genome-wide association studies (GWAS) identified significant genes associated with increased risk of AD development. This review summarizes more than 100 risk loci. Many of them may serve as biomarkers of AD progression, even in the preclinical stage of the disease. Furthermore, we used GWAS data to identify key pathways of AD pathogenesis: cellular processes, metabolic processes, biological regulation, localization, transport, regulation of cellular processes, and neurological system processes. Gene clustering into molecular pathways can provide background for identification of novel molecular targets and may support the development of tailored and personalized treatment of AD.

Biological Features of Reversion from Mild Cognitive Impairment to Normal Cognition: A Study of Cerebrospinal Fluid Markers and Brain Volume

BACKGROUND

Mild cognitive impairment (MCI) is a transitional condition between normal cognition and dementia. Although a significant proportion of the population with MCI experience reversion to normal cognition, it is still poorly understood.

OBJECTIVE

This study was designed to extend the present evidence regarding the difference between stable and reverting MCI by including whole brain atrophy measures as possible parameters involved.

METHODS

405 patients diagnosed with MCI at baseline were selected. After one-year follow-up period, 337 patients (83.2%) were categorized as stable MCI and 68 patients (16.8%) reverted to cognitively normal status (reversion group). Several baseline biomarkers including cerebrospinal fluid (CSF) biomarkers of AD, including Aβ42, t-tau, and p-tau and MRI-based atrophy measurements were compared.

RESULTS

Participants with stable MCI demonstrated greater brain atrophy as well as lower Aβ and higher tau proteins in the CSF. The atrophy rate was found to be associated with CSF biomarkers merely in the stable group, after adjustment for confounding variables.

CONCLUSION

These findings provide novel evidence regarding the biological perspective of the reversion phenomenon in individuals with MCI.

Recent developments in geriatric psychopharmacology

INTRODUCTION

There is a tremendous growing need to address the burden of geriatric psychiatric disorders. Recent developments relevant to geriatric psychiatry have focused on Alzheimer's disease (AD), severe/refractory depression, and cancer/end of life care.

AREAS COVERED

This is a non-systematic, narrative review (databases and websites for search: PubMed, Google Scholar, Medscape, ClinicalTrials.gov; focusing on the last 6 years), and covers developments in disease-modifying therapies for AD, diagnostic radiotracers for AD, medications for neuropsychiatric symptoms of dementia, ketamine/esketamine, psychedelics, and cannabinoids.

EXPERT OPINION

The focus of on-going trials of anti-amyloid agents has been on individuals with very early stage AD; several agents are under phase 3 investigation, and aducanumab is under FDA review. Amyloid and tau PET scans have been approved by the FDA to assist in the diagnoses of AD. Promising pharmaceuticals for neuropsychiatric symptoms of dementia include pimavanserin, brexpiprazole, escitalopram, dextromethorphan/quinidine, and lithium. Esketamine, although approved for treatment-resistant depression in general adults, failed to demonstrate efficacy in elderly patients in a phase 3 trial. There is preliminary evidence for benefit of psychedelic-assisted psychotherapy in end-of-life and cancer-related depression/anxiety. Evidence for the use of cannabinoids is currently lacking.

The complexity of Alzheimer's disease: an evolving puzzle

The history of Alzheimer's disease (AD) started in 1907, but we needed to wait until the end of the century to identify the components of pathological hallmarks and genetic subtypes and to formulate the first pathogenic hypothesis. Thanks to biomarkers and new technologies, the concept of AD then rapidly changed from a static view of an amnestic dementia of the presenium to a biological entity that could be clinically manifested as normal cognition or dementia of different types. What is clearly emerging from studies is that AD is heterogeneous in each aspect, such as amyloid composition, tau distribution, relation between amyloid and tau, clinical symptoms, and genetic background, and thus it is probably impossible to explain AD with a single pathological process. The scientific approach to AD suffers from chronological mismatches between clinical, pathological, and technological data, causing difficulty in conceiving diagnostic gold standards and in creating models for drug discovery and screening. A recent mathematical computer-based approach offers the opportunity to study AD in real life and to provide a new point of view and the final missing pieces of the AD puzzle.

The Prion-like Properties of Amyloid-beta Peptide and Tau: Is there Any Risk of Transmitting Alzheimer's Disease During Neurosurgical Interventions?

Recent studies have recognized similarities between the peptides involved in the neuropathology of Alzheimer's disease and prions. The Tau protein and the Amyloid β peptide represent the theoretical pillars of Alzheimer's disease development. It is probable that there is a shared mechanism for the transmission of these substances and the prion diseases development; this presumption is based on the presentation of several cases of individuals without risk factors who developed dementia decades after a neurosurgical procedure. This article aims to present the role of Aβ and Tau, which underlie the pathophysiologic mechanisms involved in the AD and their similarities with the prion diseases infective mechanisms by means of the presentation of the available evidence at molecular (in-vitro), animal, and human levels that support the controversy on whether these diseases might be transmitted in neurosurgical interventions, which may constitute a wide public health issue.

Discovery of a Potent Dual Inhibitor of Acetylcholinesterase and Butyrylcholinesterase with Antioxidant Activity that Alleviates Alzheimer-like Pathology in Old APP/PS1 Mice

The combination of the scaffolds of the cholinesterase inhibitor huprine Y and the antioxidant capsaicin results in compounds with nanomolar potencies toward human acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) that retain or improve the antioxidant properties of capsaicin. Crystal structures of their complexes with AChE and BChE revealed the molecular basis for their high potency. Brain penetration was confirmed by biodistribution studies in C57BL6 mice, with one compound (5i) displaying better brain/plasma ratio than donepezil. Chronic treatment of 10 month-old APP/PS1 mice with 5i (2 mg/kg, i.p., 3 times per week, 4 weeks) rescued learning and memory impairments, as measured by three different behavioral tests, delayed the Alzheimer-like pathology progression, as suggested by a significantly reduced Aβ42/Aβ40 ratio in the hippocampus, improved basal synaptic efficacy, and significantly reduced hippocampal oxidative stress and neuroinflammation. Compound 5i emerges as an interesting anti-Alzheimer lead with beneficial effects on cognitive symptoms and on some underlying disease mechanisms.

Extracellular Amyloid Deposits in Alzheimer's and Creutzfeldt-Jakob Disease: Similar Behavior of Different Proteins?

Neurodegenerative diseases are characterized by the deposition of specific protein aggregates, both intracellularly and/or extracellularly, depending on the type of disease. The extracellular occurrence of tridimensional structures formed by amyloidogenic proteins defines Alzheimer's disease, in which plaques are composed of amyloid β-protein, while in prionoses, the same term "amyloid" refers to the amyloid prion protein. In this review, we focused on providing a detailed didactic description and differentiation of diffuse, neuritic, and burnt-out plaques found in Alzheimer's disease and kuru-like, florid, multicentric, and neuritic plaques in human transmissible spongiform encephalopathies, followed by a systematic classification of the morphological similarities and differences between the extracellular amyloid deposits in these disorders. Both conditions are accompanied by the extracellular deposits that share certain signs, including neuritic degeneration, suggesting a particular role for amyloid protein toxicity.

Neuroprotective Effect of Spice Oleoresins on Memory and Cognitive Impairment Associated with Scopolamine-Induced Alzheimer's Disease in Rats

Oleoresins are a mixture of volatile and nonvolatile components of concentrated forms of wholesome products. Even though there are several reports on the effect of spice or spice components on Alzheimer's disease, there are no studies on the effect of spice oleoresins. Hence, this study investigates the effect of pepper, chili, and turmeric oleoresins in Alzheimer's type of cognitive impairment in the rat model. The animals were grouped into six groups with six animals in each. They were (i) normal, (ii) scopolamine, (iii) scopolamine + pepper oleoresin, (iv) scopolamine + turmeric oleoresin, (v) scopolamine + chili oleoresin and (vi) scopolamine + donepezil for 13 days. Learning memory and acquisition memory were evaluated by a Morris water maze, and the locomotor activity was assessed by an actophotometer. Biochemical parameters such as AChE, malondialdehyde, reduced glutathione, glutathione peroxidase, superoxide dismutase, and catalase were studied. The brain histology was also studied. The scopolamine treatment significantly (P < 0.05) elevated the locomotor activity and escape latency time and reduced the time spent in the target quadrant, which was reversed in the case of the oleoresin treatment. Scopolamine-mediated changes in AChE, malondialdehyde, reduced glutathione, glutathione peroxidase, superoxide dismutase, and catalase were improved after the treatment with oleoresins. Among the three oleoresins, chili oleoresin were the most effective in behavioral activity, brain biomarkers, and recovery of antioxidant capacities when compared to the drug treatment. Chili and pepper oleoresins improved the protection against hippocampal damage. These oleoresins can be potent preventive/therapeutic agents against Alzheimer's disease. This study confirms the effect of spice oleoresins in Alzheimer's disease condition.

Design, synthesis and biological evaluation of edaravone derivatives bearing the N-benzyl pyridinium moiety as multifunctional anti-Alzheimer's agents

A series of multi-target directed edaravone derivatives bearing N-benzyl pyridinium moieties were designed and synthesised. Edaravone is a potent antioxidant with significant neuroprotective effects and N-benzyl pyridinium has previously exhibited positive results as part of a dual-site binding, peripheral anionic site (PAS) and catalytic anionic site (CAS), acetylcholinesterase (AChE) inhibitor. The designed edaravone-N-benzyl pyridinium hybrid compounds were docked within the AChE active site. The results indicated interactions with conserved amino acids (Trp279 in PAS and Trp84 in CAS), suggesting good dual-site inhibitory activity. Significant in vitro AChE inhibitory activities were observed for selected compounds (IC50: 1.2-4.6 µM) with limited butyrylcholinesterase inhibitory activity (IC50's >160 µM), indicating excellent selectivity towards AChE (SI: 46 - >278). The compounds also showed considerable antioxidant ability, similar to edaravone. In silico studies indicated that these compounds should cross the blood-brain barrier, making them promising lead molecules in the development of anti-Alzheimer's agents.

Genetic variants beyond amyloid and tau associated with cognitive decline: A cohort study

OBJECTIVE

To identify single nucleotide polymorphisms (SNPs) associated with cognitive decline independent of β-amyloid (Aβ) and tau pathology in Alzheimer disease (AD).

METHODS

Discovery and replication datasets consisting of 414 individuals (94 cognitively normal control [CN], 185 with mild cognitive impairment [MCI], and 135 with AD) and 72 individuals (22 CN, 39 with MCI, and 11 with AD), respectively, were obtained from the Alzheimer's Disease Neuroimaging Initiative database. Genome-wide association analysis was conducted to identify SNPs associated with individual cognitive function (measured with the Mini-Mental State Examination and Alzheimer's Disease Assessment Scale-Cognitive Subscale ) while controlling for the level of Aβ and tau (measured as CSF phosphorylated-tau/Aβ_1-42). Gene ontology analysis was performed on SNP-associated genes.

RESULTS

We identified 1 significant (rs55906536, β = -1.91, standard error 0.34, p = 4.07 × 10^-8) and 4 suggestive variants on chromosome 6 that were associated with poorer cognitive function. Congruent results were found in the replication data. A structural equation model showed that the identified SNP deteriorated cognitive function partially through cortical thinning of the brain in a region-specific manner. Furthermore, a bioinformatics analysis showed that the identified SNPs were associated with genes related to glutathione metabolism.

CONCLUSIONS

In this study, we identified SNPs related to cognitive decline in a manner that could not be explained by Aβ and tau levels. Our findings provide insight into the complexity of AD pathogenesis and support the growing literature on the role of glutathione in AD.

Mapping the multicausality of Alzheimer's disease through group model building

Alzheimer’s disease (AD) is a complex, multicausal disorder involving several spatiotemporal scales and scientific domains. While many studies focus on specific parts of this system, the complexity of AD is rarely studied as a whole. In this work, we apply systems thinking to map out known causal mechanisms and risk factors ranging from intracellular to psychosocial scales in sporadic AD. We report on the first systemic causal loop diagram (CLD) for AD, which is the result of an interdisciplinary group model building (GMB) process. The GMB was based on the input of experts from multiple domains and all proposed mechanisms were supported by scientific literature. The CLD elucidates interaction and feedback mechanisms that contribute to cognitive decline from midlife onward as described by the experts. As an immediate outcome, we observed several non-trivial reinforcing feedback loops involving factors at multiple spatial scales, which are rarely considered within the same theoretical framework. We also observed high centrality for modifiable risk factors such as social relationships and physical activity, which suggests they may be promising leverage points for interventions. This illustrates how a CLD from an interdisciplinary GMB process may lead to novel insights into complex disorders. Furthermore, the CLD is the first step in the development of a computational model for simulating the effects of risk factors on AD.

Astragaloside IV prevents Aβ1-42 oligomers-induced memory impairment and hippocampal cell apoptosis by promoting PPARγ/BDNF signaling pathway

Astragaloside IV (AS-IV), a natural product derived from Radix Astragali (Astragalus membranaceus), is beneficial for the treatment of Alzheimer's disease (AD), but the mechanisms underlying this benefit are not completely understood. Peroxisome proliferator-activated receptor gamma (PPARγ) and brain-derived neurotrophic factor (BDNF) are potential therapeutic targets for AD. In this study, we found that amyloid β protein fragment 1-42 oligomers (AβO) suppressed BDNF and PPARγ expression, and inhibited tyrosine receptor kinase B (TrkB) phosphorylation in cultured hippocampal neurons; these changes were ameliorated by treatment with AS-IV. Inhibition of PPARγ by genetic and pharmacological methods also blocked the effect of AS-IV on BDNF expression in AβO-treated cells. Importantly, exogenous BDNF protected against neurotoxicity and apoptosis induced by AβO, whereas inhibition of PPARγ reversed protective effects of AS-IV against these outcomes. In vivo data further revealed that AS-IV improved AβO-induced memory impairment and reduced apoptosis of hippocampal neurons. Moreover, AS-IV suppressed the AβO-induced reduction in BDNF by promoting PPARγ activation in the hippocampus. Taken together, these results indicate that AS-IV prevents AβO-induced memory impairment and hippocampal neuronal apoptosis, probably by promoting the PPARγ/BDNF signaling pathway.

Understanding the Amyloid Hypothesis in Alzheimer's Disease

The amyloid hypothesis (AH) is still the most accepted model to explain the pathogenesis of inherited Alzheimer's disease (IAD). However, despite the neuropathological overlapping with the non-inherited form (NIAD), AH waver in explaining NIAD. Thus, 30 years after its first statement several questions are still open, mainly regarding the role of amyloid plaques (AP) and apolipoprotein E (APOE). Accordingly, a pathogenetic model including the role of AP and APOE unifying IAD and NIAD pathogenesis is still missing. In the present understanding of the AH, we suggested that amyloid-β (Aβ) peptides production and AP formation is a physiological aging process resulting from a systemic age-related decrease in the efficiency of the proteins catabolism/clearance machinery. In this pathogenetic model Aβ peptides act as neurotoxic molecules, but only above a critical concentration [Aβ]c. A threshold mechanism triggers IAD/NIAD onset only when [Aβ]≥[Aβ]c. In this process, APOE modifies [Aβ]c threshold in an isoform-specific way. Consequently, all factors influencing Aβ anabolism, such as amyloid beta precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2) gene mutations, and/or Aβ catabolism/clearance could contribute to exceed the threshold [Aβ]c, being characteristic of each individual. In this model, AP formation does not depend on [Aβ]c. The present interpretation of the AH, unifying the pathogenetic theories for IAD and NIAD, will explain why AP and APOE4 may be observed in healthy aging and why they are not the cause of AD. It is clear that further studies are needed to confirm our pathogenetic model. Nevertheless, our suggestion may be useful to better understand the pathogenesis of AD.

Chemical Modulation of Mitochondria-Endoplasmic Reticulum Contact Sites

Contact sites between mitochondria and endoplasmic reticulum (ER) are points in which the two organelles are in close proximity. Due to their structural and functional complexity, their exploitation as pharmacological targets has never been considered so far. Notwithstanding, the number of compounds described to target proteins residing at these interfaces either directly or indirectly is rising. Here we provide original insight into mitochondria–ER contact sites (MERCs), with a comprehensive overview of the current MERCs pharmacology. Importantly, we discuss the considerable potential of MERCs to become a druggable target for the development of novel therapeutic strategies.

Cyclin-dependent Kinase 5 Regulates Cortical Neurotransmission and Neural Circuits Associated with Motor Control in the Secondary Motor Cortex in the Mouse

Cyclin-dependent kinase 5 (Cdk5) is a regulator of axon growth and radial neuronal migration in the developing mouse brain, and it plays critical roles in cortical structure formation and brain function. However, the function of Cdk5 in cortico-cortical and cortico-sensorimotor networks in the adult remains largely unknown. In this study, we investigated the function of Cdk5 in the rostral secondary motor cortex (M2) in the male mouse using CRISPR/Cas9 gene editing and somatic brain transgenesis, to produce M2-specific knockdown of Cdk5 in neurons in the male mouse. Mouse deficient in Cdk5 in the M2 exhibited a reduction in both the number of functional synapses and the total basal dendritic length, as well as motor dysfunction. Furthermore, whole-cell patch-clamp recordings in layer V green fluorescent protein (GFP)-tag pyramidal neurons revealed a decrease in the frequency and amplitude of miniature EPSCs and miniature IPSCs, as well as a reduction in the population synaptic responses (fEPSPs) in these mice. Specifically, retrograde labeling showed that Cdk5 knockdown in the M2 caused a reduction in long-range projections to the M2 from the thalamus/prefrontal cortex and claustrum. Collectively, our findings show a new regulatory role of Cdk5 in neural circuit maintenance, and that the changes in neural transmission and circuits in the mice with Cdk5 knockdown in the M2 likely contribute to the motor dysfunction in these animals.

Utility of Animal Models to Understand Human Alzheimer's Disease, Using the Mastermind Research Approach to Avoid Unnecessary Further Sacrifices of Animals

To diagnose and treat early-stage (preclinical) Alzheimer’s disease (AD) patients, we need body-fluid-based biomarkers that reflect the processes that occur in this stage, but current knowledge on associated processes is lacking. As human studies on (possible) onset and early-stage AD would be extremely expensive and time-consuming, we investigate the potential value of animal AD models to help to fill this knowledge gap. We provide a comprehensive overview of processes associated with AD pathogenesis and biomarkers, current knowledge on AD-related biomarkers derived from on human and animal brains and body fluids, comparisons of biomarkers obtained in human AD and frequently used animal AD models, and emerging body-fluid-based biomarkers. In human studies, amyloid beta (Aβ), hyperphosphorylated tau (P-tau), total tau (T-tau), neurogranin, SNAP-25, glial fibrillary acidic protein (GFAP), YKL-40, and especially neurofilament light (NfL) are frequently measured. In animal studies, the emphasis has been mostly on Aβ. Although a direct comparison between human (familial and sporadic) AD and (mostly genetic) animal AD models cannot be made, still, in brain, cerebrospinal fluid (CSF), and blood, a majority of similar trends are observed for human AD stage and animal AD model life stage. This indicates the potential value of animal AD models in understanding of the onset and early stage of AD. Moreover, animal studies can be smartly designed to provide mechanistic information on the interrelationships between the different AD processes in a longitudinal fashion and may also include the combinations of different conditions that may reflect comorbidities in human AD, according to the Mastermind Research approach.

An agent-based model to investigate microbial initiation of Alzheimer's via the olfactory system

BACKGROUND

Alzheimer's disease (AD) is a degenerative brain disease. A novel agent-based modelling framework was developed in NetLogo 3D to provide fundamental insights into the potential mechanisms by which a microbe (eg. Chlamydia pneumoniae) may play a role in late-onset AD. The objective of our initial model is to simulate one possible spatial and temporal pathway of bacterial propagation via the olfactory system, which may then lead to AD symptoms. The model maps the bacteria infecting cells from the nasal cavity and the olfactory epithelium, through the olfactory bulb and into the olfactory cortex and hippocampus regions of the brain.

RESULTS

Based on the set of biological rules, simulated randomized infection by the microbe led to the formation of beta-amyloid (Aβ) plaque and neurofibrillary (NF) tangles as well as caused immune responses. Our initial simulations demonstrated that breathing in C. pneumoniae can result in infection propagation and significant buildup of Aβ plaque and NF tangles in the olfactory cortex and hippocampus. Our model also indicated how mucosal and neural immunity can play a significant role in the pathway considered. Lower immunities, correlated with elderly individuals, had quicker and more Aβ plaque and NF tangle formation counts. In contrast, higher immunities, correlated with younger individuals, demonstrated little to no such formation.

CONCLUSION

The modelling framework provides an organized visual representation of how AD progression may occur via the olfactory system to better understand disease pathogenesis. The model confirms current conclusions in available research but can be easily adjusted to match future evidence and be used by researchers for their own individual purposes. The goal of our initial model is to ultimately guide further hypothesis refinement and experimental testing to better understand the dynamic system interactions present in the etiology and pathogenesis of AD.

Multiview learning for understanding functional multiomics

The molecular mechanisms and functions in complex biological systems currently remain elusive. Recent high-throughput techniques, such as next-generation sequencing, have generated a wide variety of multiomics datasets that enable the identification of biological functions and mechanisms via multiple facets. However, integrating these large-scale multiomics data and discovering functional insights are, nevertheless, challenging tasks. To address these challenges, machine learning has been broadly applied to analyze multiomics. This review introduces multiview learning-an emerging machine learning field-and envisions its potentially powerful applications to multiomics. In particular, multiview learning is more effective than previous integrative methods for learning data's heterogeneity and revealing cross-talk patterns. Although it has been applied to various contexts, such as computer vision and speech recognition, multiview learning has not yet been widely applied to biological data-specifically, multiomics data. Therefore, this paper firstly reviews recent multiview learning methods and unifies them in a framework called multiview empirical risk minimization (MV-ERM). We further discuss the potential applications of each method to multiomics, including genomics, transcriptomics, and epigenomics, in an aim to discover the functional and mechanistic interpretations across omics. Secondly, we explore possible applications to different biological systems, including human diseases (e.g., brain disorders and cancers), plants, and single-cell analysis, and discuss both the benefits and caveats of using multiview learning to discover the molecular mechanisms and functions of these systems.

Alzheimer's disease pathology in APOE transgenic mouse models: The Who, What, When, Where, Why, and How

The focus on amyloid plaques and neurofibrillary tangles has yielded no Alzheimer's disease (AD) modifying treatments in the past several decades, despite successful studies in preclinical mouse models. This inconsistency has caused a renewed focus on improving the fidelity and reliability of AD mouse models, with disparate views on how this improvement can be accomplished. However, the interactive effects of the universal biological variables of AD, which include age, APOE genotype, and sex, are often overlooked. Age is the greatest risk factor for AD, while the ε4 allele of the human APOE gene, encoding apolipoprotein E, is the greatest genetic risk factor. Sex is the final universal biological variable of AD, as females develop AD at almost twice the rate of males and, importantly, female sex exacerbates the effects of APOE4 on AD risk and rate of cognitive decline. Therefore, this review evaluates the importance of context for understanding the role of APOE in preclinical mouse models. Specifically, we detail how human AD pathology is mirrored in current transgenic mouse models ("What") and describe the critical need for introducing human APOE into these mouse models ("Who"). We next outline different methods for introducing human APOE into mice ("How") and highlight efforts to develop temporally defined and location-specific human apoE expression models ("When" and "Where"). We conclude with the importance of choosing the human APOE mouse model relevant to the question being addressed, using the selection of transgenic models for testing apoE-targeted therapeutics as an example ("Why").

Emerging signal regulating potential of small molecule biflavonoids to combat neuropathological insults of Alzheimer's disease

Alzheimer's disease (AD) is a progressive, chronic and severe neurodegenerative disorder linked with cognitive and memory impairment that eventually lead to death. There are several processes which can cause AD, including mitochondrial dysfunction-mediated oxidative stress (OS), intracellular buildup of hyper-phosphorylated tau as neurofibrillary tangles (NFTs) and excessive buildup of extracellular amyloid beta (Aβ) plaques, and/or genetic as well as the environmental factors. Existing treatments can only provide symptomatic relief via providing temporary palliative therapy which can weaken the rate of AD-associated cognitive decline. Plants are the fundamental building blocks for the environment and produce various secondary metabolites. Biflavonoids are one among such secondary metabolite that possesses the potential to mediate noticeable change in the aggregation of tau, Aβ and also efficiently can decrease the toxic effects of Aβ oligomers in comparison with the monoflavonoid moieties. Nevertheless, the molecular processes remain to be exposed, flavonoids are found to cause a change in the Aβ and tau aggregation pathway to generate non-toxic aggregates. In this review, we discuss the neuroprotective action of small molecule biflavonoid to reduce the neurodegenerative events of AD. Furthermore, this appraisal advances our knowledge to develop potential new targets for the treatment of AD.

The Erythrocytic Hypothesis of Brain Energy Crisis in Sporadic Alzheimer Disease: Possible Consequences and Supporting Evidence

Alzheimer’s disease (AD) is a fatal form of dementia of unknown etiology. Although amyloid plaque accumulation in the brain has been the subject of intensive research in disease pathogenesis and anti-amyloid drug development; the continued failures of the clinical trials suggest that amyloids are not a key cause of AD and new approaches to AD investigation and treatment are needed. We propose a new hypothesis of AD development based on metabolic abnormalities in circulating red blood cells (RBCs) that slow down oxygen release from RBCs into brain tissue which in turn leads to hypoxia-induced brain energy crisis; loss of neurons; and progressive atrophy preceding cognitive dysfunction. This review summarizes current evidence for the erythrocytic hypothesis of AD development and provides new insights into the causes of neurodegeneration offering an innovative way to diagnose and treat this systemic disease.

"Olfactory Three-Needle" Enhances Spatial Learning and Memory Ability in SAMP8 Mice

As one of the most important therapies in complementary and alternative medicine, acupuncture has been used in the treatment of Alzheimer's disease (AD). Acupuncture of “olfactory three-needle” manipulation can improve the cognitive ability of AD patients. However, the mechanism of “olfactory three-needle” in AD remains largely unknown. Here, we identified that the “olfactory three-needle” therapy and eugenol olfactory stimulation both reduced the deposition of β-amyloid (Aβ) protein and increased the expression of synaptophysin (SYP), but only the “olfactory three-needle” enhanced the spatial learning and memory ability of SAMP8. Remarkably, the “olfactory three-needle” inhibited the phosphorylation of p38MAPK and the excessive activation of microglia (MG) in the hippocampus. Our study demonstrates that the “olfactory three-needle” enhances spatial learning and memory ability by inhibiting the phosphorylation of p38MAPK and the excessive activation of MG to reduce the neuroinflammatory response and neurotoxicity of Aβ and promote synaptic regeneration, but it was not completely consistent with the stimulation of the olfactory system.

Amyloid β-protein oligomers promote the uptake of tau fibril seeds potentiating intracellular tau aggregation

BACKGROUND

Repeated failure of drug candidates targeting Alzheimer's disease (AD) in clinical trials likely stems from a lack of understanding of the molecular mechanisms underlying AD pathogenesis. Recent research has highlighted synergistic interactions between aggregated amyloid-β (Aβ) and tau proteins in AD, but the molecular details of how these interactions drive AD pathology remain elusive and speculative.

METHODS

Here, we test the hypothesis that Aβ potentiates intracellular tau aggregation, and show that oligomeric Aβ specifically exacerbates proteopathic seeding by tau. Using tau-biosensor cells, we show that treatment with sub-toxic concentrations of Aβ oligomers, but not monomers or fibrils, "primes" cells, making them more susceptible to tau seeding. The treatment with Aβ oligomers enhances intracellular tau aggregation in a dose-dependent manner when the cells are seeded with either recombinant or brain-derived tau fibrils, whereas little or no aggregation is observed in the absence of Aβ-oligomer priming.

RESULTS

Priming by Aβ oligomers appears to be specific to tau, as α-synuclein seeding is unaffected by this treatment. Aβ oligomer-enhanced tau seeding also occurs in primary mouse neurons and human neuroblastoma cells. Using fluorescently labeled tau seeds, we find that treatment with Aβ oligomers significantly enhances the cellular uptake of tau seeds, whereas a known tau-uptake inhibitor blocks the effect of Aβ on tau uptake.

CONCLUSION

The ability of Aβ to promote tau seeding suggests a specific and plausible mechanism by which extracellular Aβ initiates a deleterious cascade that is unique to AD. These data suggest that the Aβ-mediated potentiation of tau uptake into cells should also be taken into account when designing Aβ-targeted therapeutics.

Age-Dependent Decrease of Mitochondrial Complex II Activity in a Familial Mouse Model for Alzheimer's Disease

Alzheimer's disease (AD) is a severe neurodegenerative disorder for which the exact etiology is largely unknown. An increasingly recognized and investigated notion is the pathogenic role of mitochondrial dysfunction in AD. We assessed mitochondrial oxidative-phosphorylation (OXPHOS) enzyme activities in the APPswe/PS1ΔE9 mouse model from 4.5 to 14 months of age. We show an age-dependent decrease in mitochondrial complex-II activity starting at 9 months in APP/PS1 mice. Other enzymes of the OXPHOS do not show any alterations. Since amyloid-β (Aβ) plaques are already present from 4 months of age, mitochondrial dysfunction likely occurs downstream of Aβ pathology in this mouse model.

The involvement of microglia in Alzheimer's disease: a new dog in the fight

First described clinically in 1906, Alzheimer's disease (AD) is the most common neurodegenerative disease and form of dementia worldwide. Despite its prevalence, only five therapies are currently approved for AD, all dealing with the symptoms rather than the underlying causes of the disease. A multitude of experimental evidence has suggested that the once thought inconsequential process of neuroinflammation does, in fact, contribute to the AD pathogenesis. One such CNS cell type critical to this process are microglia. Plastic in nature with varied roles, microglia are emerging as key contributors to AD pathology. This review will focus on the role of microglia in the neuroinflammatory response in AD, highlighting recent studies implicating aberrant changes in microglial function in disease progression. Of critical note is that with these advances, a reconceptualization of the framework in which we view microglia is required. LINKED ARTICLES: This article is part of a themed section on Therapeutics for Dementia and Alzheimer's Disease: New Directions for Precision Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.18/issuetoc.

Unequivocal imaging of aluminium in human cells and tissues by an improved method using morin

Aluminium is biologically reactive and its ability to potentiate the immune response has driven its inclusion in both veterinary and human vaccines. Consequently, the need for unequivocal visualisation of aluminium in vivo has created a focused research effort to establish fluorescent molecular probes for this purpose. The most commonly used direct fluorescent labels for the detection of aluminium are morin (2',3,4',5,7-pentahydroxyflavone) and lumogallion [4-chloro-3-(2,4-dihydroxyphenylazo)-2-hydroxybenzene-1-sulphonic acid]. While the former has gained popularity in the detection of aluminium in plants and predominantly within root tips, the latter boasts greater sensitivity and selectivity for the detection of aluminium in human cells and tissues. Herein, we have developed a simplified morin staining protocol using the autofluorescence quenching agent, Sudan Black B. This modified protocol improves tissue morphology and increases analytical sensitivity, which allows intracellular aluminium to be detected in monocytes and when co-localised with senile plaques in human brain tissue of donors diagnosed with familial Alzheimer's disease. Overall, our results demonstrate a simple approach to minimise false positives in the use of morin to unequivocally detect aluminium in vivo.

Cytotoxic species in amyloid-associated diseases: Oligomers or mature fibrils

Amyloid diseases especially, Alzheimer's disease (AD), is characterized by an imbalance between the production and clearance of amyloid-β (Aβ) species. Amyloidogenic proteins or peptides can transform structurally from monomers into β-stranded fibrils via multiple oligomeric states. Among various amyloid species, structured oligomers are proposed to be more toxic than fibrils; however, the identification of amyloid oligomers has been challenging due to their heterogeneous and metastable nature. Multiple techniques have recently helped in better understanding of oligomer's assembly details and structural properties. Moreover, some progress on elucidating the mechanisms of oligomer-triggered toxicity has been made. Based on the collection of current findings, there is growing consensus that control of toxic amyloid oligomers could be a valid approach to regulate amyloid-associated toxicity, which could advance development of new diagnostics and therapeutics for amyloid-related diseases. In this review, we have described the recent scenario of amyloid diseases with a great deal of information about the recent understanding of oligomers' assembly, structural properties, and toxicity. Also comprehensive details have been provided to differentiate the degree of toxicity associated with prefibrillar aggregates.