Beta-site amyloid precursor protein cleaving enzyme 1 levels become elevated in neurons around amyloid plaques: implications for Alzheimer's disease pathogenesis

Rhei Undulati Rhizoma attenuates memory decline and reduces amyloid-β induced neuritic dystrophy in 5xFAD mouse

BACKGROUND

Alzheimer's disease (AD) is a common type of dementia characterized by amyloid-β (Aβ) accumulation, lysosomal dysfunction, and tau hyperphosphorylation, leading to neurite dystrophy and memory loss. This study aimed to investigate whether Rhei Undulati Rhizoma (RUR), which has been reported to have anti-neuroinflammatory effect, attenuates Aβ-induced memory impairment, neuritic dystrophy, and tau hyperphosphorylation, and to reveal its mode of action.

METHODS

Five-month-old 5xFAD mice received RUR (50 mg/kg) orally for 2 months. The Y-maze test was used to assess working memory. After behavioral testing, brain tissue was analyzed using thioflavin S staining, western blotting, and immunofluorescence staining to investigate the mode of action of RUR. To confirm whether RUR directly reduces Aβ aggregation, a thioflavin T assay and dot blot were performed after incubating Aβ with RUR.

RESULTS

RUR administration attenuated the Aβ-induced memory impairment in 5xFAD mice. Furthermore, decreased accumulation of Aβ was observed in the hippocampus of the RUR-treated 5xFAD group compare to the vehicle-treated 5xFAD group. Moreover, RUR reduced the dystrophic neurites (DNs) that accumulate impaired endolysosomal organelles around Aβ. In particular, RUR treatment downregulated the expression of β-site amyloid precursor protein cleaving enzyme 1 and the hyperphosphorylation of tau within DNs. Additionally, RUR directly suppressed the aggregation of Aβ, and eliminated Aβ oligomers in vitro.

CONCLUSIONS

This study showed that RUR could attenuate Aβ-induced pathology and directly regulate the aggregation of Aβ. These results suggest that RUR could be an efficient material for AD treatment through Aβ regulation.

Multicolor, Cell-Impermeable, and High Affinity BACE1 Inhibitor Probes Enable Superior Endogenous Staining and Imaging of Single Molecules

The prevailing but not undisputed amyloid cascade hypothesis places the β-site of APP cleaving enzyme 1 (BACE1) center stage in Alzheimer's Disease pathogenesis. Here, we investigated functional properties of BACE1 with novel tag- and antibody-free labeling tools, which are conjugates of the BACE1-inhibitor IV (also referred to as C3) linked to different impermeable Alexa Fluor dyes. We show that these fluorescent small molecules bind specifically to BACE1, with a 1:1 labeling stoichiometry at their orthosteric site. This is a crucial property especially for single-molecule and super-resolution microscopy approaches, allowing characterization of the dyes' labeling capabilities in overexpressing cell systems and in native neuronal tissue. With multiple colors at hand, we evaluated BACE1-multimerization by Förster resonance energy transfer (FRET) acceptor-photobleaching and single-particle imaging of native BACE1. In summary, our novel fluorescent inhibitors, termed Alexa-C3, offer unprecedented insights into protein-protein interactions and diffusion behavior of BACE1 down to the single molecule level.

BACE1 Inhibitors for Alzheimer's Disease: Current Challenges and Future Perspectives

Disease-modifying therapies (DMT) for Alzheimer's disease (AD) are highly longed-for. In this quest, anti-amyloid therapies take center stage supported by genetic facts that highlight an imbalance between production and clearance of amyloid-β peptide (Aβ) in AD patients. Indeed, evidence from basic research, human genetic and biomarker studies, suggests the accumulation of Aβ as a driver of AD pathogenesis and progression. The aspartic protease β-site AβPP cleaving enzyme (BACE1) is the initiator for Aβ production. Underpinning a critical role for BACE1 in AD pathophysiology are the elevated BACE1 concentration and activity observed in the brain and body fluids of AD patients. Therefore, BACE1 is a prime drug target for reducing Aβ levels in early AD. Small-molecule BACE1 inhibitors have been extensively developed for the last 20 years. However, clinical trials with these molecules have been discontinued for futility or safety reasons. Most of the observed adverse side effects were due to other aspartic proteases cross-inhibition, including the homologue BACE2, and to mechanism-based toxicity since BACE1 has substrates with important roles for synaptic plasticity and synaptic homeostasis besides amyloid-β protein precursor (AβPP). Despite these setbacks, BACE1 persists as a well-validated therapeutic target for which a specific inhibitor with high substrate selectivity may yet to be found. In this review we provide an overview of the evolution in BACE1 inhibitors design pinpointing the molecules that reached advanced phases of clinical trials and the liabilities that precluded adequate trial effects. Finally, we ponder on the challenges that anti-amyloid therapies must overcome to achieve clinical success.

Quercetin-3-O-glc-1-3-rham-1-6-glucoside decreases Aβ production, inhibits Aβ aggregation and neurotoxicity, and prohibits the production of inflammatory cytokines

Alzheimer's disease (AD) is a progressive neurodegenerative disease with the hallmark of aggregation of beta-amyloid (Aβ) into extracellular fibrillar deposition. Accumulating evidence suggests that soluble toxic Aβ oligomers exert diverse roles in neuronal cell death, oxidative stress, neuroinflammation, and the eventual pathogenesis of AD. Aβ is derived from the sequential cleavage of amyloid-β precursor protein (APP) by β-secretase (BACE1) and γ-secretase. The current effect of single targeting is not ideal for the treatment of AD. Therefore, developing multipotent agents with multiple properties, including anti-Aβ generation and anti-Aβ aggregation, is attracting more attention for AD treatment. Previous studies indicated that Quercetin was able to attenuate the effects of several pathogenetic factors in AD. Here, we showed that naturally synthesized Quercetin-3-O-glc-1-3-rham-1-6-glucoside (YCC31) could inhibit Aβ production by reducing β-secretase activity. Further investigations indicated that YCC31 could suppress toxic Aβ oligomer formation by directly binding to Aβ. Moreover, YCC31 could attenuate Aβ-mediated neuronal death, ROS and NO production, and pro-inflammatory cytokines release. Taken together, YCC31 targeting multiple pathogenetic factors deserves further investigation for drug development of AD.

Current Insights of Nanocarrier-Mediated Gene Therapeutics to Treat Potential Impairment of Amyloid Beta Protein and Tau Protein in Alzheimer's Disease

Alzheimer's disease (AD), is the major type of dementia and most progressive, irreversible widespread neurodegenerative disorder affecting the elderly worldwide. The prime hallmarks of Alzheimer's disease (AD) are beta-amyloid plaques (Aβ) and neurofibrillary tangles (NFT). In spite of recent advances and developments in targeting the hallmarks of AD, symptomatic medications that promise neuroprotective activity against AD are currently unable to treat degenerating brain clinically or therapeutically and show little efficacy. The extensive progress of AD therapies over time has resulted in the advent of disease-modifying medications with the potential to alleviate AD. However, due to the presence of a defensive connection between the vascular system and the neural tissues known as the blood-brain barrier (BBB), directing these medications to the site of action in the degenerating brain is the key problem. BBB acts as a highly selective semipermeable membrane that prevents any type of foreign substance from entering the microenvironment of neurons. To overcome this limitation, the revolutionary approach of nanoparticle(NP)/nanocarrier-mediated drug delivery system has marked the era with its unique property to cross, avoid, or disrupt the defensive BBB efficiently and release the modified drug at the target site of action. After comprehensive data mining, this review focuses on the detailed understanding of different types of nanoparticle(NP)/nanocarrier-mediated drug delivery system like liposomes, micelles, gold nanoparticles(NP), polymeric NPs, etc. which have promising potential in carrying the desired drug(cargo) to the location in the degenerated brain thus mitigating the Alzheimer's disease.

Axonal organelle buildup from loss of AP-4 complex function causes exacerbation of amyloid plaque pathology and gliosis in Alzheimer's disease mouse model

Lysosomes and related precursor organelles robustly build up in swollen axons that surround amyloid plaques and disrupted axonal lysosome transport has been implicated in worsening Alzheimer's pathology. Our prior studies have revealed that loss of Adaptor protein-4 (AP-4) complex function, linked primarily to Spastic Paraplegia (HSP), leads to a similar build of lysosomes in structures we term "AP-4 dystrophies". Surprisingly, these AP-4 dystrophies were also characterized by enrichment of components of APP processing machinery, β-site cleaving enzyme 1 (BACE1) and Presenilin 2. Our studies examining whether the abnormal axonal lysosome build up resulting from AP-4 loss could lead to amyloidogenesis revealed that the loss of AP-4 complex function in an Alzheimer's disease model resulted in a strong increase in size and abundance of amyloid plaques in the hippocampus and corpus callosum as well as increased microglial association with the plaques. Interestingly, we found a further increase in enrichment of the secretase, BACE1, in the axonal swellings of the plaques of Alzheimer model mice lacking AP-4 complex compared to those having normal AP-4 complex function, suggestive of increased amyloidogenic processing under this condition. Additionally, the exacerbation of plaque pathology was region-specific as it did not increase in the cortex. The burden of the AP-4 linked axonal dystrophies/AP-4 dystrophies was higher in the corpus callosum and hippocampus compared to the cortex, establishing the critical role of AP-4 -dependent axonal lysosome transport and maturation in regulating amyloidogenic amyloid precursor protein processing.

Single-Cell RNA-seq reveals transcriptomic modulation of Alzheimer's disease by activated protein C

Single-Cell RNA sequencing reveals changes in cell population in Alzheimer's disease (AD) model 5xFAD (5x Familial AD mutation) versus wild type (WT) mice. The returned sequencing data was processed through the 10x Genomics CellRanger platform to perform alignment and form corresponding matrix to perform bioinformatic analysis. Alterations in glial cells occurred in 5xFAD versus WT, especially increases in microglia proliferation were profound in 5xFAD. Differential expression testing of glial cells in 5xFAD versus WT revealed gene regulation. Globally, the critical genes implicated in AD progression are upregulated such as Apoe, Ctsb, Trem2, and Tyrobp. Using this differential expression data, GO term enrichment was completed to observe possible biological processes impacted by AD progression. Utilizing anti-inflammatory and cyto-protective recombinant Activated Protein C (APC), we uncover inflammatory processes to be downregulated by APC treatment in addition to recuperation of nervous system processes. Moreover, animal studies demonstrated that administration of recombinant APC significantly attenuated Aβ burden and improved cognitive function of 5xFAD mice. The downregulation of highly expressed AD biomarkers in 5xFAD could provide insight into the mechanisms by which APC administration benefits AD.

Design, synthesis, and biological evaluation of novel capsaicin-tacrine hybrids as multi-target agents for the treatment of Alzheimer's disease

A series of novel hybrid compounds were designed, synthesized, and utilized as multi-target drugs to treat Alzheimer's disease (AD) by connecting capsaicin and tacrine moieties. The biological assays indicated that most of these compounds demonstrated strong inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities with IC50 values in the nanomolar, as well as good blood-brain barrier permeability. Among the synthesized hybrids, compound 5s displayed the most balanced inhibitory effect on hAChE (IC50 = 69.8 nM) and hBuChE (IC50 = 68.0 nM), and exhibited promising inhibitory activity against β-secretase-1 (BACE-1) (IC50 = 3.6 µM). Combining inhibition kinetics and molecular model analysis, compound 5s was shown to be a mixed inhibitor affecting both the catalytic active site (CAS) and peripheral anionic site (PAS) of hAChE. Additionally, compound 5s showed low toxicity in PC12 and BV2 cell assays. Moreover, compound 5s demonstrated good tolerance at the dose of up to 2500 mg/kg and exhibited no hepatotoxicity at the dose of 3 mg/kg in mice, and it could effectively improve memory ability in mice. Taken together, these findings suggest that compound 5s is a promising and effective multi-target agent for the potential treatment of AD.

Effects of DHA (omega-3 fatty acid) and estradiol on amyloid β-peptide regulation in the brain

In the early stages of sporadic Alzheimer's disease (SAD), there is a strong correlation between memory impairment and cortical levels of soluble amyloid-β peptide oligomers (Aβ). It has become clear that Aβ disrupt glutamatergic synaptic function, which can in turn lead to the characteristic cognitive deficits of SAD, but the actual pathways are still not well understood. This opinion article describes the pathogenic mechanisms underlying cerebral amyloidosis. These mechanisms are dependent on the amyloid precursor protein and concern the synthesis of Aβ peptides with competition between the non-amyloidogenic pathway and the amyloidogenic pathway (i.e. a competition between the ADAM10 and BACE1 enzymes), on the one hand, and the various processes of Aβ residue clearance, on the other hand. This clearance mobilizes both endopeptidases (NEP, and IDE) and removal transporters across the blood-brain barrier (LRP1, ABCB1, and RAGE). Lipidated ApoE also plays a major role in all processes. The disturbance of these pathways induces an accumulation of Aβ. The description of the mechanisms reveals two key molecules in particular: (i) free estradiol, which has genomic and non-genomic action, and (ii) free DHA as a preferential ligand of PPARα-RXRα and PPARɣ-RXRα heterodimers. DHA and free estradiol are also self-regulating, and act in synergy. When a certain level of chronic DHA and free estradiol deficiency is reached, a permanent imbalance is established in the central nervous system. The consequences of these deficits are revealed in particular by the presence of Aβ peptide deposits, as well as other markers of the etiology of SAD.

The Ratio of Plasma Amyloid-β 1-42 over Serum Albumin Can Be a Novel Biomarker Signature for Diagnosing End-Stage Renal Disease-Associated Cognitive Impairment

BACKGROUND

Cognitive impairment (CI) is one of the major complications in chronic kidney disease patients, especially those with end-stage renal disease (ESRD). Limited biomarkers have been found that can significantly predict ESRD-associated cognitive decline.

OBJECTIVE

This cohort study aimed to investigate de novo biomarkers for diagnosis of the ESRD-associated CI.

METHODS

In this cohort study, qualified samples were divided into control (with an estimated glomerular filtration rate (eGFR) of≥60 mL/min and a Mini-Mental State Examination (MMSE) score of > 27), ESRD without CI (eGFR < 15 and MMSE > 27), and ESRD with CI (eGFR < 15 and MMSE < 27) groups. Levels of plasma amyloid-β (Aβ)1 - 42, serum indoxyl sulfate, and hematologic and biochemical parameters were measured.

RESULTS

Compared to the control group, levels of blood urea nitrogen, creatinine, and indoxyl sulfate were elevated in ESRD patients both without and with CI. Interestingly, ESRD patients with CI had the lowest levels of serum albumin. In contrast, levels of plasma Aβ1 - 42 were significantly higher in the ESRD with CI group than in the control and ESRD without CI groups. In addition, the ratio of plasma Aβ1 - 42 over serum albumin was significantly higher in the ESRD with CI group than in the control or ESRD without CI groups. Importantly, the area under the receiver operating characteristic curve (AUROC) for CI in the total population by the ratio of Aβ1 - 42 over albumin was 0.785 and significant (p < 0.05).

CONCLUSIONS

This cohort study has shown that the ratio of plasma Aβ1 - 42 over serum albumin can be a de novo biomarker for the diagnosis and prognosis of ESRD-associated cognitive decline.

miR-29c-3p Attenuates beta-Amyloid-Induced Neurotoxicity in Alzheimer's Disease Through Regulating beta-Site Amyloid Precursor Protein-Cleaving Enzyme 1

The aberrantly expressed microRNAs (miRNAs) including miR-29c-3p have been reported in the brains of Alzheimer's disease (AD) patients in recent researches. Nevertheless, the functional role and underlying molecular mechanism of miR-29c-3p in AD pathogenesis are still not well elucidated. The purpose of this study was to examine whether miR-29c-3p regulated beta-Ameyloid (Abeta)-induced neurotoxicity by targeting beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1). The expressions of miR 29c 3p and BACE1 mRNA and protein levels in Abeta-treated PC12 cellular AD model were examined by qRT-PCR and western blot analyses. Luciferase reporter assay verified the potential target of miR 29c 3p. Cell viability, apoptosis, and caspase-3 activity in PC12 cells were detected by the MTT assay, flow cytometry, and caspase-3 activity assay, respectively. Our results indicated that miR-29c-3p downregulation and BACE1 upregulation existed in the cellular AD model of PC12 cells. Moreover, miR-29c-3p directly inhibited BACE1 expression. miR-29c-3p overexpression and BACE1 knockdown strengthened Abeta-induced cell apoptosis, and caspase-3 activity in PC12 cells, which was partially eliminated by over-expression of BACE1. Conversely, BACE1 knockdown reversed the miR-29c-3p inhibition- mediated inhibitory effect on Abeta-induced cell toxicity, apoptosis, and caspase-3 activity in PC12 cells. Considering, miR-29c-3p attenuated Abeta-induced neurotoxicity through targeting BACE1 in an cellular AD model of PC12, providing a potential therapeutic target for AD treatment.

Insight into the emerging and common experimental in-vivo models of Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial, rapidly progressing neurodegenerative disorder. As the exact cause of the disease is still unclear, the drug development is very challenging. This review encompasses the commonly used AD models involving various chemicals, heavy metals and endogenous substances induced models and the transgenic models. It also provides insight into the reliable emerging models of AD that may overcome the shortcomings associated with available models. Chemicals like streptozotocin, scopolamine, colchicine and okadaic acid render the animal susceptible to neuroinflammation and oxidative stress induced neurodegeneration along with amyloid-β deposition and tau hyperphosphorylation. Similarly, endogenous substances like acrolein and amyloid-β 1-42 are efficient in inducing the major pathologies of AD. Heavy metals like aluminum and fluoride and mixture of these have been reported to induce neurotoxicity therefore are used as animal models for AD. Transgenic models developed as a result of knock-in or knock-out of certain genes associated with AD including PDAPP, APP23, Tg2576, APP/PS1, 3 × Tg and 5 × FAD have also been incorporated in this study. Further, emerging and advanced pathomimetic models of AD are provided particular interest here which will add on to the current knowledge of animal models and may aid in the drug development process and deepen our understanding related to AD pathogenesis. These newly discovered models include oAβ25-35 model, transgenic model expressing 82-kDa ChAT, oDGal mouse and APP knock-in rat. This study may aid in the selection of suitable model for development of novel potent therapeutics and for exploring detailed pathogenic mechanism of AD.

Hypometabolism, Alzheimer's Disease, and Possible Therapeutic Targets: An Overview

The brain is a highly dynamic organ that requires a constant energy source to function normally. This energy is mostly supplied by glucose, a simple sugar that serves as the brain's principal fuel source. Glucose transport across the blood-brain barrier (BBB) is primarily controlled via sodium-independent facilitated glucose transport, such as by glucose transporter 1 (GLUT1) and 3 (GLUT3). However, other glucose transporters, including GLUT4 and the sodium-dependent transporters SGLT1 and SGLT6, have been reported in vitro and in vivo. When the BBB endothelial layer is crossed, neurons and astrocytes can absorb the glucose using their GLUT1 and GLUT3 transporters. Glucose then enters the glycolytic pathway and is metabolized into adenosine triphosphate (ATP), which supplies the energy to support cellular functions. The transport and metabolism of glucose in the brain are impacted by several medical conditions, which can cause neurological and neuropsychiatric symptoms. Alzheimer's disease (AD), Parkinson's disease (PD), epilepsy, traumatic brain injury (TBI), schizophrenia, etc., are a few of the most prevalent disorders, characterized by a decline in brain metabolism or hypometabolism early in the course of the disease. Indeed, AD is considered a metabolic disorder related to decreased brain glucose metabolism, involving brain insulin resistance and age-dependent mitochondrial dysfunction. Although the conventional view is that reduced cerebral metabolism is an effect of neuronal loss and consequent brain atrophy, a growing body of evidence points to the opposite, where hypometabolism is prodromal or at least precedes the onset of brain atrophy and the manifestation of clinical symptoms. The underlying processes responsible for these glucose transport and metabolic abnormalities are complicated and remain poorly understood. This review article provides a comprehensive overview of the current understanding of hypometabolism in AD and potential therapeutic targets.

Spotlight on Coenzyme Q10 in scopolamine-induced Alzheimer's disease: oxidative stress/PI3K/AKT/GSK 3ß/CREB/BDNF/TrKB

OBJECTIVES

Excess amyloid beta (Aβ) and oxidative stress (OS) are inextricable hallmarks of the neuronal damage associated Alzheimer's disease. Aβ-induced cognitive and memory dysfunctions are mediated through different signalling pathways as phosphatidylinositol-3-kinase (PI3K) and their downstream intermediates including protein-kinase-B, known as Akt, glycogen-synthase-kinase-3β (GSK-3β), cAMP-response-element-binding-protein (CREB), brain-derived-neurotrophic factor (BDNF) and tropomyosin-related-kinase receptor-B (TrKB). The current work aims to investigate the protective potentials of CoQ10 against scopolamine (Scop)-induced cognitive disability and the contribution of PI3K/Akt/GSK-3β/CREB/BDNF/TrKB in the neuroprotection effects.

METHODS

The chronic co-administration of CQ10 (50, 100 and 200 mg/kg/day i.p.) with Scop in Wistar rats for 6 weeks were assayed both behaviourally and biochemically.

KEY FINDINGS

CoQ10 ameliorated the Scop-induced cognitive and memory defects by restoring alterations in novel object recognition and Morris water maze behavioural tests. CoQ10 favourably changed the Scop-induced deleterious effects in hippocampal malondialdehyde, 8-hydroxy-2' deoxyguanosine, antioxidants and PI3K/Akt/GSK-3β/CREB/BDNF/TrKB levels.

CONCLUSIONS

These results exhibited the neuroprotective effects of CoQ10 on Scop-induced AD and revealed its ability to inhibit oxidative stress, amyloid deposition and to modulate PI3K/Akt/GSK-3β/CREB/BDNF/TrKB pathway.

Metabolic response of microglia to amyloid deposition during Alzheimer's disease progression in a mouse model

Alzheimer's disease (AD) drives metabolic changes in the central nervous system (CNS). In AD microglia are activated and proliferate in response to amyloid β plaques. To further characterize the metabolic changes in microglia associated with plaque deposition in situ, we examined cortical tissue from 2, 4, and 8-month-old wild type and 5XFAD mice, a mouse model of plaque deposition. 5XFAD mice exhibited progressive microgliosis and plaque deposition as well as changes in microglial morphology and neuronal dystrophy. Multiphoton-based fluorescent lifetime imaging microscopy (FLIM) metabolic measurements showed that older mice had an increased amount of free NAD(P)H, indicative of a shift towards glycolysis. Interestingly in 5XFAD mice, we also found an abundant previously undescribed third fluorescence component that suggests an alternate NAD(P)H binding partner associated with pathology. This work demonstrates that FLIM in combination with other quantitative imaging methods, is a promising label-free tool for understanding the mechanisms of AD pathology.

INPP5D modulates TREM2 loss-of-function phenotypes in a β-amyloidosis mouse model

The genetic associations of TREM2 loss-of-function variants with Alzheimer disease (AD) indicate the protective roles of microglia in AD pathogenesis. Functional deficiencies of TREM2 disrupt microglial clustering around amyloid β (Aβ) plaques, impair their transcriptional response to Aβ, and worsen neuritic dystrophy. However, the molecular mechanism underlying these phenotypes remains unclear. In this study, we investigated the pathological role of another AD risk gene, INPP5D, encoding a phosphoinositide PI(3,4,5)P3 phosphatase expressed in microglia. In a Tyrobp-deficient TREM2 loss-of-function mouse model, Inpp5d haplodeficiency restored the association of microglia with Aβ plaques, partially restored plaque compaction, and astrogliosis, and reduced phosphorylated tau+ dystrophic neurites. Mechanistic analyses suggest that TREM2/TYROBP and INPP5D exert opposing effects on PI(3,4,5)P3 signaling pathways as well as on phosphoproteins involved in the actin assembly. Our results suggest that INPP5D acts downstream of TREM2/TYROBP to regulate the microglial barrier against Aβ toxicity, thereby modulates Aβ-dependent pathological conversion of tau.

The Alzheimer's disease-linked protease BACE1 modulates neuronal IL-6 signaling through shedding of the receptor gp130

BACKGROUND

The protease BACE1 is a major drug target for Alzheimer's disease, but chronic BACE1 inhibition is associated with non-progressive cognitive worsening that may be caused by modulation of unknown physiological BACE1 substrates.

METHODS

To identify in vivo-relevant BACE1 substrates, we applied pharmacoproteomics to non-human-primate cerebrospinal fluid (CSF) after acute treatment with BACE inhibitors.

RESULTS

Besides SEZ6, the strongest, dose-dependent reduction was observed for the pro-inflammatory cytokine receptor gp130/IL6ST, which we establish as an in vivo BACE1 substrate. Gp130 was also reduced in human CSF from a clinical trial with a BACE inhibitor and in plasma of BACE1-deficient mice. Mechanistically, we demonstrate that BACE1 directly cleaves gp130, thereby attenuating membrane-bound gp130 and increasing soluble gp130 abundance and controlling gp130 function in neuronal IL-6 signaling and neuronal survival upon growth-factor withdrawal.

CONCLUSION

BACE1 is a new modulator of gp130 function. The BACE1-cleaved, soluble gp130 may serve as a pharmacodynamic BACE1 activity marker to reduce the occurrence of side effects of chronic BACE1 inhibition in humans.

Honey and Alzheimer's Disease-Current Understanding and Future Prospects

Alzheimer's disease (AD), a leading cause of dementia, has been a global concern. AD is associated with the involvement of the central nervous system that causes the characteristic impaired memory, cognitive deficits, and behavioral abnormalities. These abnormalities caused by AD is known to be attributed by extracellular aggregates of amyloid beta plaques and intracellular neurofibrillary tangles. Additionally, genetic factors such as abnormality in the expression of APOE, APP, BACE1, PSEN-1, and PSEN-2 play a role in the disease. As the current treatment aims to treat the symptoms and to slow the disease progression, there has been a continuous search for new nutraceutical agent or medicine to help prevent and cure AD pathology. In this quest, honey has emerged as a powerful nootropic agent. Numerous studies have demonstrated that the high flavonoids and phenolic acids content in honey exerts its antioxidant, anti-inflammatory, and neuroprotective properties. This review summarizes the effect of main flavonoid compounds found in honey on the physiological functioning of the central nervous system, and the effect of honey intake on memory and cognition in various animal model. This review provides a new insight on the potential of honey to prevent AD pathology, as well as to ameliorate the damage in the developed AD.

Phenolic-protein interactions: insight from in-silico analyses – a review

Phenolic compounds are ubiquitous plant secondary metabolites that possess various biological activities and are known to interact with proteins, altering their structure and properties. Therefore, interactions between these compounds and proteins has gained increasing attention due to their potential benefits to human health and for exploitation by the food industry. Phenolic compounds and proteins can form complexes via covalent linkages and/or non-covalent interactions through hydrophobic, electrostatic, van der Waals forces and hydrogen bonding. This review describes possible mechanisms of phenol-protein complex formation, their physiological action and activities that are important in the food industry, and possible outcomes in the terms of molecular docking and simulation analysis. The conformational changes of the protein upon binding with polyphenols can lead to the folding or unfolding of the protein molecules, forming insoluble or soluble complexes. The concentration of polyphenols, their molecular weight and structure, ions/cofactors and conditions of the system determine the precipitation or solubilization of the complex, affecting their nutritional and functional properties as well as their bioactivities. In this regard, molecular docking and simulation studies of phenolic-protein interactions allows comprehensive virtual screening of competitive/non-competitive and site-specific/non-specific conjugation of phenolics with different protein targets and facilitates understanding the observed effects. The docking analysis of flavonoids with enzymes and milk proteins has indicated their potential application in producing nutraceuticals and functional foods. Thus, combining molecular docking and simulation studies with experimental techniques is vital for better understanding the reactions that take place during digestion to engineer and manufacture novel food ingredients with desirable pharmacological properties and as potential food additives.

Graphical Abstract

Biological Mechanism-based Neurology and Psychiatry: A BACE1/2 and Downstream Pathway Model

In oncology, comprehensive omics and functional enrichment studies have led to an extensive profiling of (epi)genetic and neurobiological alterations that can be mapped onto a single tumor's clinical phenotype and divergent clinical phenotypes expressing common pathophysiological pathways. Consequently, molecular pathway-based therapeutic interventions for different cancer typologies, namely tumor type- and site-agnostic treatments, have been developed, encouraging the real-world implementation of a paradigm shift in medicine. Given the breakthrough nature of the new-generation translational research and drug development in oncology, there is an increasing rationale to transfertilize this blueprint to other medical fields, including psychiatry and neurology. In order to illustrate the emerging paradigm shift in neuroscience, we provide a state-of-the-art review of translational studies on the β-site amyloid precursor protein cleaving enzyme (BACE) and its most studied downstream effector, neuregulin, which are molecular orchestrators of distinct biological pathways involved in several neurological and psychiatric diseases. This body of data aligns with the evidence of a shared genetic/biological architecture among Alzheimer's disease, schizoaffective disorder, and autism spectrum disorders. To facilitate a forward-looking discussion about a potential first step towards the adoption of biological pathway-based, clinical symptom-agnostic, categorization models in clinical neurology and psychiatry for precision medicine solutions, we engage in a speculative intellectual exercise gravitating around BACE-related science, which is used as a paradigmatic case here. We draw a perspective whereby pathway-based therapeutic strategies could be catalyzed by highthroughput techniques embedded in systems-scaled biology, neuroscience, and pharmacology approaches that will help overcome the constraints of traditional descriptive clinical symptom and syndrome-focused constructs in neurology and psychiatry.

Bilateral Hippocampal Volume Mediated the Relationship Between Plasma BACE1 Concentration and Memory Function in the Early Stage of Alzheimer's Disease: A Cross-Sectional Study

BACKGROUND

β-site amyloid precursor protein cleaving enzyme 1 (BACE1) is a key enzyme in the formation of amyloid-β (Aβ) protein. Increasing evidence suggests that BACE1 concentration is a potential biomarker for Alzheimer's disease (AD).

OBJECTIVE

To evaluate the correlations between plasma BACE1 concentration, cognition, and hippocampal volume at different stages of the AD continuum.

METHODS

Plasma BACE1 concentrations were measured in 32 patients with probable dementia due to AD (ADD), 48 patients with mild cognitive impairment (MCI) due to AD, and 40 cognitively unimpaired (CU) individuals. Memory function was evaluated using the auditory verbal learning test (AVLT), and voxel-based morphometry was used to analyze bilateral hippocampal volumes. Correlation and mediation analyses were performed to investigate the associations between plasma BACE1 concentration, cognition, and hippocampal atrophy.

RESULTS

The MCI and ADD groups exhibited elevated BACE1 concentrations compared with the CU group after adjusting for age, sex, and apolipoprotein E (APOE) genotype. Increased BACE1 concentration was found in AD continuum patients who were APOE ɛ4 carriers (p < 0.05). BACE1 concentration was negatively associated with the scores of the subitems of the AVLT and hippocampal volume (p < 0.05, false discovery rate correction) in the MCI group. Moreover, bilateral hippocampal volume mediated the relationship between BACE1 concentration and recognition in the MCI group.

CONCLUSION

BACE1 expression increased in the AD continuum, and bilateral hippocampal volume mediated the effect of BACE1 concentration on memory function in patients with MCI. Research has indicated that the plasma BACE1 concentration might be a biomarker at the early stage of AD.

Krüppel-like factor 5 accelerates the pathogenesis of Alzheimer’s disease via BACE1-mediated APP processing

Background

The deposition of β-amyloid (Aβ) in the brain plays a major role in the pathogenesis of Alzheimer’s disease (AD). Aβ is generated via amyloid precursor protein (APP) cleavage through the amyloidogenic pathway. In this pathway, β-secretase (BACE1) is the first and rate-limiting enzyme. Its expression increases through an unknown mechanism in patients with AD. Thus, the key regulatory mechanism of BACE1 in the AD process should be revealed to understand the pathogenesis of AD and explore the key treatment targets of AD.

Methods

Here, APPswe/PS1dE9 (APP/PS1) mice were employed to observe the Krüppel-like factor 5 (KLF5) and BACE1 levels in the serum and brain tissues. HT22 cells were used to explore the relationship between KLF5 and BACE1.

Results

In this study, KLF5 was found to be a novel transcription factor that positively regulated BACE1 by binding to the BACE1 promoter. The KLF5 levels significantly increased not only in the CSF and serum of patients with AD but also in the brain tissue of APP/PS1 mice. They were closely related to cognitive capacity. KLF5 accelerated APP amyloidogenic metabolism and promoted Aβ synthesis through BACE1. Silencing BACE1 could block the KLF5-induced amyloidogenic process of APP. ML264 ameliorated the cognitive deficits and slowed down APP amyloidogenic cleavage in APP/PS1 mice.

Conclusion

The findings above suggest that upregulation of KLF5 might be a critical element in AD progression by accelerating BACE1-mediated APP amyloidogenic cleavage. The inhibition of KLF5 or the combined inhibitory effect of KLF5 and the BACE1 promoter might be a potential strategy to prevent AD pathogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-022-01050-3.

Multitargeted Molecular Docking and Dynamic Simulation Studies of Bioactive Compounds from Rosmarinus officinalis against Alzheimer’s Disease

Alzheimer’s disease (AD) has been associated with the hallmark features of cholinergic dysfunction, amyloid beta (Aβ) aggregation and impaired synaptic transmission, which makes the associated proteins, such as β-site amyloid precursor protein cleaving enzyme 1 (BACE I), acetylcholine esterase (AChE) and synapsin I, II and III, major targets for therapeutic intervention. The present study investigated the therapeutic potential of three major phytochemicals of Rosmarinus officinalis, ursolic acid (UA), rosmarinic acid (RA) and carnosic acid (CA), based on their binding affinity with AD-associated proteins. Detailed docking studies were conducted using AutoDock vina followed by molecular dynamic (MD) simulations using Amber 20. The docking analysis of the selected molecules showed the binding energies of their interaction with the target proteins, while MD simulations comprising root mean square deviation (RMSD), root mean square fluctuation (RMSF) and molecular mechanics/generalized born surface area (MM/GBSA) binding free energy calculations were carried out to check the stability of bound complexes. The drug likeness and the pharmacokinetic properties of the selected molecules were also checked through the Lipinski filter and ADMETSAR analysis. All these bioactive compounds demonstrated strong binding affinity with AChE, BACE1 and synapsin I, II and III. The results showed UA and RA to be potential inhibitors of AChE and BACE1, exhibiting binding energies comparable to those of donepezil, used as a positive control. The drug likeness and pharmacokinetic properties of these compounds also demonstrated drug-like characteristics, indicating the need for further in vitro and in vivo investigations to ascertain their therapeutic potential for AD.

Amyloid-ß plaque formation and BACE1 accumulation in the brains of a 5xFAD Alzheimer's disease mouse model is associated with altered distribution and not proteolysis of BACE1 substrates Sez6 and Sez6L

The formation of amyloid-ß peptides (Aß), that accumulate in Alzheimer's disease (AD) brains, involves proteolytic processing of the amyloid precursor protein (APP) firstly by ß-secretase (BACE1). Since BACE1 cleaves a plethora of other substrates, in this work we investigated whether the proteolysis and/or distribution of other BACE1 substrates, such as seizure protein 6 (Sez6) and seizure 6-like protein (Sez6L), is altered in AD. To test this we used 5xFAD mouse model brains that show an early accumulation of Aß plaques already at 2-months of age. Here we show for the first time that accumulation of BACE1 in peri-plaque regions and its enhanced levels in AD brains does not affect proteolysis of BACE1 substrates other than APP, such as Sez6 and Sez6L. We observed altered distribution of Sez6 and Sez6L in the area of Aß plaques in 5xFAD brains which is distinct to that of APP, BACE1 and/or LAMP1, suggesting different localization and/or function of these BACE1 substrates. While it is necessary to further elucidate the potential role that this may play in the course of AD, it is likely that Aß-targeted therapies may have beneficial effects against accumulation and/or altered distribution of BACE1 and its substrates, in addition to APP.

Alzheimer’s disease: Pathophysiology and dental pulp stem cells therapeutic prospects

Alzheimer’s disease (AD) is a destructive neurodegenerative disease with the progressive dysfunction, structural disorders and decreased numbers of neurons in the brain, which leads to long-term memory impairment and cognitive decline. There is a growing consensus that the development of AD has several molecular mechanisms similar to those of other neurodegenerative diseases, including excessive accumulation of misfolded proteins and neurotoxic substances produced by hyperactivated microglia. Nonetheless, there is currently a lack of effective drug candidates to delay or prevent the progression of the disease. Based on the excellent regenerative and reparative capabilities of stem cells, the application of them to repair or replace injured neurons carries enormous promise. Dental pulp stem cells (DPSCs), originated from ectomesenchyme of the cranial neural crest, hold a remarkable potential for neuronal differentiation, and additionally express a variety of neurotrophic factors that contribute to a protective effect on injured neuronal cells. Notably, DPSCs can also express immunoregulatory factors to control neuroinflammation and potentiate the regeneration and recovery of injured neurons. These extraordinary features along with accessibility make DPSCs an attractive source of postnatal stem cells for the regeneration of neurons or protection of existing neural circuitry in the neurodegenerative diseases. The present reviews the latest research advance in the pathophysiology of AD and elaborate the neurodifferentiation and neuroprotective properties of DPSCs as well as their application prospects in AD.

Neuroprotective Effects of Resveratrol by Modifying Cholesterol Metabolism and Aβ Processing in SAMP8 Mice

Cholesterol metabolism seems dysregulated and linked to amyloid-β (Aβ) formation in neurodegeneration, but the underlying mechanisms are poorly known. Resveratrol (RSV) is a polyphenol with antioxidant activity and neuroprotective properties. Here, we analyzed the effect of age and RSV supplementation on cholesterol metabolism in the brain and blood serum, and its potential link to Aβ processing, in SAMP8 mice—an animal model of aging and Alzheimer’s disease. In the brain, our results revealed an age-related increase in ApoE and unesterified cholesterol in the plasma membrane whereas LDL receptor, HMG-CoA reductase, HMG-CoA-C1 synthase, and ABCA1 transporter remained unaltered. Furthermore, BACE-1 and APP gene expression was decreased. This dysregulation could be involved in the amyloidogenic processing pathway of APP towards Aβ formation. In turn, RSV exhibited an age-dependent effect. While levels of unesterified cholesterol in the plasma membrane were not affected by RSV, several participants in cholesterol uptake, release, and de novo synthesis differed, depending on age. Thus, RSV supplementation exhibited a different neuroprotective effect acting on Aβ processing or cholesterol metabolism in the brain at earlier or later ages, respectively. In blood serum, HDL lipoprotein and free cholesterol were increased by age, whereas VLDL and LDL lipoproteins remained unaltered. Again, the protective effect of RSV by decreasing the LDL or increasing the HDL levels also seems to depend on the intervention’s moment. In conclusion, age is a prominent factor for cholesterol metabolism dysregulation in the brain of SAMP8 mice and influences the protective effects of RSV through cholesterol metabolism and Aβ processing.

Z-Guggulsterone attenuates cognitive defects and decreases neuroinflammation in APPswe/PS1dE9 mice through inhibiting the TLR4 signaling pathway

Growing evidence indicates that inflammatory damage is implicated in the pathogenesis of Alzheimer's disease (AD). Z-Guggulsterone (Z-GS) is a natural steroid, which is extracted from Commiphora mukul and has anti-inflammatory effects in vivo and in vitro. In the present study, we investigated the disease-modifying effects of chronic Z-GS administration on the cognitive and neuropathological impairments in the transgenic mouse models of AD. We found that chronic Z-GS administration prevented learning and memory deficits in the APPswe/PS1dE9 mice. In addition, Z-GS treatment significantly decreased cerebral amyloid-β (Aβ) levels and plaque burden via inhibiting amyloid precursor protein (APP) processing by reducing beta-site APP cleaving enzyme 1 (BACE1) expression in the APPswe/PS1dE9 mice. We also found that Z-GS treatment markedly alleviated neuroinflammation and reduced synaptic defects in the APPswe/PS1dE9 mice. Furthermore, the activated TLR4/NF-κB signaling pathways in APPswe/PS1dE9 mice were remarkably inhibited by Z-GS treatment, which was achieved via suppressing the phosphorylation of JNK. Collectively, our data demonstrate that chronic Z-GS treatment restores cognitive defects and reverses multiple neuropathological impairments in the APPswe/PS1dE9 mice. This study provides novel insights into the neuroprotective effects and neurobiological mechanisms of Z-GS on AD, indicating that Z-GS is a promising disease-modifying agent for the treatment of AD.

Butyrylcholinesterase inhibitors as potential anti-Alzheimer's agents: an updated patent review (2018-present)

INTRODUCTION

Alzheimer's disease (AD) constitutes one of the most complex and devastating diseases, with an extraordinarily high increase expected for the next few years. Despite the numerous efforts accomplished so far there is still no cure but just palliative treatments.

AREAS COVERED

The main topic covered herein has been the development of butyrylcholinesterase (BuChE) inhibitors with the aim of increasing the levels of the neurotransmitter acetylcholine (ACh). Two main groups of compounds have been considered: multitarget and non-multitarget ligands, depending if the structural design is focused or not on other key targets and pathogenic factors of the disease. Seventeen patents regarding multitarget-directed ligands (MTDLs), twelve for not multitarget derivatives, and three for miscellaneous uses have been covered in the period 2018‒2021.

EXPERT OPINION

BuChE is an attractive target in the treatment of AD for many reasons. It is the most prevalent cholinesterase within more advanced stages of the disease, so drugs inhibiting it would be suitable for the treatment of mid- to severe Alzheimer's patients. Moreover, BuChE has been proved to be connected with some other key hallmarks of the disease, like amyloidogenesis; hybridization of a BuChE-targeting pharmacophore with other scaffolds designed for other therapeutic targets is quite a promising design for potential anti-Alzheimer's drugs.

Preclinical evaluation of drug treatment options for sleep-related epileptiform spiking in Alzheimer's disease

Introduction

There are no published data on prospective clinical studies on drug treatment options for sleep-related epileptiform spiking in Alzheimer's disease (AD).

Methods

Using video-EEG with hippocampal electrodes in 17 APP/PS1 transgenic male mice we assessed the effects of donepezil and memantine, anti-seizure drugs levetiracetam and lamotrigine, gamma-secretase inhibitor semagacestat, anti-inflammatory minocycline and adenosine receptor antagonist istradephylline on density of cortical and hippocampal spikes during sleep.

Results

Levetiracetam decreased the density of hippocampal giant spikes and cortical spikes. Lamotrigine reduced cortical single spikes and spike-wave discharges but dramatically increased hippocampal giant spikes. Memantine increased cortical single spikes and spike-wave discharges dose-dependently. Memantine and istradephylline decreased total sleep time while levetiracetam increased it. Lamotrigine decreased REM sleep duration. Other drugs had no significant effects.

Discussion

Levetiracetam appears promising for treating sleep-related epileptiform spiking in AD while lamotrigine should be used with caution. Donepezil at low doses appeared neutral but the memantine effects warrant further studies.

Degradation and inhibition of epigenetic regulatory protein BRD4 exacerbate Alzheimer's disease-related neuropathology in cell models

Epigenetic regulation plays substantial roles in human pathophysiology, which provides opportunities for intervention in human disorders through the targeting of epigenetic pathways. Recently, emerging evidence from preclinical studies suggested the potential in developing therapeutics of Alzheimer's disease (AD) by targeting bromodomain containing protein 4 (BRD4), an epigenetic regulatory protein. However, further characterization of AD-related pathological events is urgently required. Here, we investigated the effects of pharmacological degradation or inhibition of BRD4 on AD cell models. Interestingly, we found that both degradation and inhibition of BRD4 by ARV-825 and JQ1, respectively, robustly increased the levels of amyloid-beta (Aβ), which has been associated with the neuropathology of AD. Subsequently, we characterized the mechanisms by which downregulation of BRD4 increases Aβ levels. We found that both degradation and inhibition of BRD4 increased the levels of BACE1, the enzyme responsible for cleavage of the amyloid-beta protein precursor (APP) to generate Aβ. Consistent with Aβ increase, we also found that downregulation of BRD4 increased AD-related phosphorylated Tau (pTau) protein in our 3D-AD human neural cell culture model. Therefore, our results suggest that downregulation of BRD4 would not be a viable strategy for AD intervention. Collectively, our study not only shows that BRD4 is a novel epigenetic component that regulates BACE1 and Aβ levels, but also provides novel and translational insights into the targeting of BRD4 for potential clinical applications.

Oral nimodipine treatment has no effect on amyloid pathology or neuritic dystrophy in the 5XFAD mouse model of amyloidosis

Dysregulation of calcium homeostasis has been hypothesized to play a role in Alzheimer's disease (AD) pathogenesis. Increased calcium levels can impair axonal transport, disrupt synaptic transmission, and ultimately lead to cell death. Given the potential role of calcium dyshomeostasis in AD, there is interest in testing the ability of already approved drugs targeting various calcium channels to affect amyloid pathology and other aspects of disease. The objective of this study was to test the effects of FDA-approved L-type calcium channel antagonist nimodipine on amyloid accumulation and dystrophic neurite formation in 5XFAD mice, a mouse model of amyloid pathology. 5XFAD transgenic mice and non-transgenic littermates were treated with vehicle or nimodipine-containing chow from two to eight months of age, then brains were harvested and amyloid pathology assessed by immunoblot and immunofluorescence microscopy analyses. Nimodipine was well tolerated and crossed the blood brain barrier, as expected, but there was no effect on Aβ accumulation or on the relative amount of neuritic dystrophy, as assessed by either immunoblot, dot blot or immunofluorescence imaging of Aβ42 and dystrophic neurite marker LAMP1. While we conclude that nimodipine treatment is not likely to improve amyloid pathology or decrease neuritic dystrophy in AD, it is worth noting that nimodipine did not worsen the phenotype suggesting its use is safe in AD patients.

Exosomal microRNA Differential Expression in Plasma of Young Adults with Chronic Mild Traumatic Brain Injury and Healthy Control

Chronic mild traumatic brain injury (mTBI) has long-term consequences, such as neurological disability, but its pathophysiological mechanism is unknown. Exosomal microRNAs (exomiRNAs) may be important mediators of molecular and cellular changes involved in persistent symptoms after mTBI. We profiled exosomal microRNAs (exomiRNAs) in plasma from young adults with or without a chronic mTBI to decipher the underlying mechanisms of its long-lasting symptoms after mTBI. We identified 25 significantly dysregulated exomiRNAs in the chronic mTBI group (n = 29, with 4.48 mean years since the last injury) compared to controls (n = 11). These miRNAs are associated with pathways of neurological disease, organismal injury and abnormalities, and psychological disease. Dysregulation of these plasma exomiRNAs in chronic mTBI may indicate that neuronal inflammation can last long after the injury and result in enduring and persistent post-injury symptoms. These findings are useful for diagnosing and treating chronic mTBIs.

Serum Glycoproteomics and Identification of Potential Mechanisms Underlying Alzheimer’s Disease

Objectives. This study compares glycoproteomes in Thai Alzheimer’s disease (AD) patients with those of cognitively normal individuals. Methods. Study participants included outpatients with clinically diagnosed AD ( $N=136$ ) and healthy controls without cognitive impairment ( $N=183$ ). Blood samples were collected from all participants for biochemical analysis and for $\text{Apolipoprotein}\text{E}$ (APOE) genotyping by real-time TaqMan PCR assays. Comparative serum glycoproteomic profiling by liquid chromatography-tandem mass spectrometry was then performed to identify differentially abundant proteins with functional relevance. Results. Statistical differences in age, educational level, and APOE ɛ3/ɛ4 and ɛ4/ɛ4 haplotype frequencies were found between the AD and control groups. The frequency of the APOE ɛ4 allele was significantly higher in the AD group than in the control group. In total, 871 glycoproteins were identified, including 266 and 259 unique proteins in control and AD groups, respectively. There were 49 and 297 upregulated and downregulated glycoproteins, respectively, in AD samples compared with the controls. Unique AD glycoproteins were associated with numerous pathways, including Alzheimer’s disease-presenilin pathway (16.6%), inflammation pathway mediated by chemokine and cytokine signaling (9.2%), Wnt signaling pathway (8.2%), and apoptosis signaling pathway (6.7%). Conclusion. Functions and pathways associated with protein-protein interactions were identified in AD. Significant changes in these proteins can indicate the molecular mechanisms involved in the pathogenesis of AD, and they have the potential to serve as AD biomarkers. Such findings could allow us to better understand AD pathology.

High-Phytate Diets Increase Amyloid β Deposition and Apoptotic Neuronal Cell Death in a Rat Model

Amyloid-β (Aβ) accumulation in the hippocampus is an essential event in the pathogenesis of Alzheimer's disease. Insoluble Aβ is formed through the sequential proteolytic hydrolysis of the Aβ precursor protein, which is cleaved by proteolytic secretases. However, the pathophysiological mechanisms of Aβ accumulation remain elusive. Here, we report that rats fed high-phytate diets showed Aβ accumulation and increased apoptotic neuronal cell death in the hippocampus through the activation of the amyloidogenic pathway in the hippocampus. Immunoblotting and immunohistochemical analyses confirmed that the overexpression of BACE1 β-secretase, a critical enzyme for Aβ generation, exacerbated the hippocampal Aβ accumulation in rats fed high-phytate diets. Moreover, we identified that parathyroid hormone, a physiological hormone responding to the phytate-mediated dysregulation of calcium and phosphate homeostasis, plays an essential role in the transcriptional activation of the Aβ precursor protein and BACE1 through the vitamin D receptor and retinoid X receptor axis. Thus, our findings suggest that phytate-mediated dysregulation of calcium and phosphate is a substantial risk factor for elevated Aβ accumulation and apoptotic neuronal cell death in rats.

High Fat Diet Mediates Amyloid-β Cleaving Enzyme 1 Phosphorylation and SUMOylation, Enhancing Cognitive Impairment in APP/PS1 Mice

BACKGROUND

Alzheimer's disease (AD) is the most common form of dementia in older adults and extracellular accumulation of amyloid-β (Aβ) is one of the two characterized pathologies of AD. Obesity is significantly associated with AD developing factors. Several studies have reported that high fat diet (HFD) influenced Aβ accumulation and cognitive performance during AD pathology. However, the underlying neurobiological mechanisms have not yet been elucidated.

OBJECTIVE

The objective of this study was to explore the underlying neurobiological mechanisms of HFD influenced Aβ accumulation and cognitive performance during AD pathology.

METHODS

2.5-month-old male APP/PS1 mice were randomly separated into two groups: 1) the normal diet (ND) group, fed a standard diet (10 kcal%fat); and 2) the HFD group, fed a high fat diet (40 kcal%fat, D12492; Research Diets). After 4 months of HFD or ND feeding, mice in the two groups were subjected for further ethological, morphological, and biochemical analyses.

RESULTS

A long-term HFD diet significantly increased perirenal fat and impaired dendritic integrity and aggravated neurodegeneration, and augmented learning and memory deficits in APP/PS1 mice. Furthermore, the HFD increased beta amyloid cleaving enzyme 1 (BACE1) dephosphorylation and SUMOylation, resulting in enhanced enzyme activity and stability, which exacerbated the deposition of amyloid plaques.

CONCLUSION

Our study demonstrates that long-term HFD consumption aggravates amyloid-β accumulation and cognitive impairments, and that modifiable lifestyle factors, such as obesity, can induce BACE1 post-modifications which may contribute to AD pathogenesis.

BACE2 suppression in mice aggravates the adverse metabolic consequences of an obesogenic diet

OBJECTIVE

Pancreatic β-cell dysfunction is a central feature in the pathogenesis of type 2 diabetes (T2D). Accumulating evidence indicates that β-site APP-cleaving enzyme 2 (BACE2) inhibition exerts a beneficial effect on β-cells in different models of T2D. Thus, targeting BACE2 may represent a potential therapeutic strategy for the treatment of this disease. Here, we aimed to investigate the effects of BACE2 suppression on glucose homeostasis in a model of diet-induced obesity.

METHODS

BACE2 knock-out (BKO) and wild-type (WT) mice were fed with a high-fat diet (HFD) for 2 or 16 weeks. Body weight, food intake, respiratory exchange ratio, locomotor activity, and energy expenditure were determined. Glucose homeostasis was evaluated by glucose and insulin tolerance tests. β-cell proliferation was assessed by Ki67-positive nuclei, and β-cell function was determined by measuring glucose-stimulated insulin secretion. Leptin sensitivity was evaluated by quantifying food intake and body weight after an intraperitoneal leptin injection. Neuropeptide gene expression and insulin signaling in the mediobasal hypothalamus were determined by qPCR and Akt phosphorylation, respectively.

RESULTS

After 16 weeks of HFD feeding, BKO mice exhibited an exacerbated body weight gain and hyperphagia, in comparison to WT littermates. Glucose tolerance was similar in both groups, whereas HFD-induced hyperinsulinemia, insulin resistance, and β-cell expansion were more pronounced in BKO mice. In turn, leptin-induced food intake inhibition and hypothalamic insulin signaling were impaired in BKO mice, regardless of the diet, in accordance with deregulation of the expression of hypothalamic neuropeptide genes. Importantly, BKO mice already showed increased β-cell proliferation and glucose-stimulated insulin secretion with respect to WT littermates after two weeks of HFD feeding, before the onset of obesity.

CONCLUSIONS

Collectively, these results reveal that BACE2 suppression in an obesogenic setting leads to exacerbated body weight gain, hyperinsulinemia, and insulin resistance. Thus, we conclude that inhibition of BACE2 may aggravate the adverse metabolic effects associated with obesity.

The Amyloid-β Pathway in Alzheimer's Disease

Breakthroughs in molecular medicine have positioned the amyloid-β (Aβ) pathway at the center of Alzheimer's disease (AD) pathophysiology. While the detailed molecular mechanisms of the pathway and the spatial-temporal dynamics leading to synaptic failure, neurodegeneration, and clinical onset are still under intense investigation, the established biochemical alterations of the Aβ cycle remain the core biological hallmark of AD and are promising targets for the development of disease-modifying therapies. Here, we systematically review and update the vast state-of-the-art literature of Aβ science with evidence from basic research studies to human genetic and multi-modal biomarker investigations, which supports a crucial role of Aβ pathway dyshomeostasis in AD pathophysiological dynamics. We discuss the evidence highlighting a differentiated interaction of distinct Aβ species with other AD-related biological mechanisms, such as tau-mediated, neuroimmune and inflammatory changes, as well as a neurochemical imbalance. Through the lens of the latest development of multimodal in vivo biomarkers of AD, this cross-disciplinary review examines the compelling hypothesis- and data-driven rationale for Aβ-targeting therapeutic strategies in development for the early treatment of AD.

Green Tea Suppresses Amyloid β Levels and Alleviates Cognitive Impairment by Inhibiting APP Cleavage and Preventing Neurotoxicity in 5XFAD Mice

SCOPE

The consumption of green tea is considered to be associated with a lower incidence of neurodegenerative diseases. In the present study, it is investigated the role of amyloid precursor protein cleavage, glial cell activation, neuroinflammation, and synaptic alterations in the protective effects of green tea against the amyloid β (Aβ) accumulation and cognitive impairment.

METHODS AND RESULTS

5XFAD mice are treated with green tea extract (GTE) for 8 or 16 weeks. Barnes maze and Y maze testing demonstrated that spatial learning and memory ability are markedly improved by GTE treatment. Immunofluorescence staining, ELISA, and western blot showed GTE significantly alleviate the formation of Aβ and reduce the levels of sAPPβ and C99, as well as sAPPα and C83. Meanwhile, GTE suppressed GFAP and Iba1 levels in the glial cells, increased PSD95 and synaptophysin levels in synaptic cells. Further, the IL-1β level is decreased, RNA sequencing reveals the genes annotated in response to stimulus and immune response are regulated.

CONCLUSION

Our findings indicate GTE suppresses Aβ levels and alleviate cognitive impairment in 5XFAD mice. These beneficial effects are accompanied by inhibition of APP cleavage pathways, suppression of glial cell activation and pro-inflammatory responses, and a reduction of synapse loss.

microRNA-425 loss mediates amyloid plaque microenvironment heterogeneity and promotes neurodegenerative pathologies

Different cellular and molecular changes underlie the pathogenesis of Alzheimer's disease (AD). Among these, neuron‐specific dysregulation is a necessary event for accumulation of classic pathologies including amyloid plaques. Here, we show that AD‐associated pathophysiology including neuronal cell death, inflammatory signaling, and endolysosomal dysfunction is spatially colocalized to amyloid plaques in regions with abnormal microRNA‐425 (miR‐425) levels and this change leads to focal brain microenvironment heterogeneity, that is, an amyloid plaque‐associated microenvironment (APAM). APAM consists of multiple specific neurodegenerative signature pathologies associated with senile plaques that contribute to the heterogeneity and complexity of AD. Remarkably, miR‐425, a neuronal‐specific regulator decreased in AD brain, maintains a normal spatial transcriptome within brain neurons. We tested the hypothesis that miR‐425 loss correlates with enhanced levels of mRNA targets downstream, supporting APAM and AD progression. A miR‐425‐deficient mouse model has enhanced APP amyloidogenic processing, neuroinflammation, neuron loss, and cognitive impairment. In the APP/PS1 mouse model, intervening with miR‐425 supplementation ameliorated APAM changes and memory deficits. This study reveals a novel mechanism of dysregulation of spatial transcriptomic changes in AD brain, identifying a probable neuronal‐specific microRNA regulator capable of staving off amyloid pathogenesis. Moreover, our findings provide new insights for developing AD treatment strategies with miRNA oligonucleotide(s).

Casein Kinase 2 dependent phosphorylation of eIF4B regulates BACE1 expression in Alzheimer's disease

Alzheimer's disease (AD) is the most common age-related neurodegenerative disorder. Increased Aβ production plays a fundamental role in the pathogenesis of the disease and BACE1, the protease that triggers the amyloidogenic processing of APP, is a key protein and a pharmacological target in AD. Changes in neuronal activity have been linked to BACE1 expression and Aβ generation, but the underlying mechanisms are still unclear. We provide clear evidence for the role of Casein Kinase 2 in the control of activity-driven BACE1 expression in cultured primary neurons, organotypic brain slices, and murine AD models. More specifically, we demonstrate that neuronal activity promotes Casein Kinase 2 dependent phosphorylation of the translation initiation factor eIF4B and this, in turn, controls BACE1 expression and APP processing. Finally, we show that eIF4B expression and phosphorylation are increased in the brain of APPPS1 and APP-KI mice, as well as in AD patients. Overall, we provide a definition of a mechanism linking brain activity with amyloid production and deposition, opening new perspectives from the therapeutic standpoint.

The fluid biomarkers of Alzheimer’s disease

Alzheimer’s disease (AD) is the most common neurodegenerative disorder. However, it still has no available disease‐modifying therapies. Its pathology cascade begins decades before symptomatic presentation. For these reasons, highly sensitive and highly specific fluid biomarkers should be developed for the early diagnosis of AD. In this study, the well‐established and emerging fluid biomarkers of AD are summarized, and recent advances on their role in early diagnosis and progression monitoring as well as their correlations with AD pathology are highlighted. Future prospects and related research directions are also discussed.

Pregabalin Treatment does not Affect Amyloid Pathology in 5XFAD Mice

Background:

Calcium dysregulation has been proposed to play a causative role in the development of Alzheimer’s disease pathology. Pregabalin is a compound already approved for human use, marketed as the prescription drug Lyrica. It binds the α2-δ subunit of P/Q-type voltage-gated calcium channels, lowering calcium influx and providing effective treatment for epilepsy and neuropathic pain.

Objective:

We hypothesize that increased resting calcium in neuronal processes near amyloid plaques plays a role in the development of neuritic dystrophies and further progression of amyloid pathology.

Methods:

5XFAD mice were treated orally for 12 weeks with pregabalin, then immunoblotting and immunofluorescent imaging were used to quantify neuritic dystrophy and amyloid deposition in pregabalin compared to placebo-treated mice.

Results:

The treatment did not decrease markers of neuritic dystrophy or amyloid deposition. The image analysis of neuritic dystrophy on a plaque-by-plaque basis showed a small non-significant increase in the relative proportion of LAMP1 to Aβ42 in plaques with areas of 50-450 μm² in the cortex of pregabalin-treated mice. In addition, there was a statistically significant positive correlation between the measured cerebral concentration of pregabalin and the relative levels of BACE1 and Aβ in the cortex. This relationship was not observed in the hippocampus, and there was no increase in average Aβ levels in pregabalin treated mice compared to placebo. We confirmed previous findings that smaller amyloid plaques are associated with a greater degree of neuritic dystrophy.

Conclusion:

Pregabalin may have an effect on Aβ that merits further investigation, but our study does not suggest that pregabalin contributes substantially to amyloid pathology.

Gga3 deletion and a GGA3 rare variant associated with late onset Alzheimer's disease trigger BACE1 accumulation in axonal swellings

Axonal dystrophy, indicative of perturbed axonal transport, occurs early during Alzheimer's disease (AD) pathogenesis. Little is known about the mechanisms underlying this initial sign of the pathology. This study proves that Golgi-localized γ-ear-containing ARF binding protein 3 (GGA3) loss of function, due to Gga3 genetic deletion or a GGA3 rare variant that cosegregates with late-onset AD, disrupts the axonal trafficking of the β-site APP-cleaving enzyme 1 (BACE1) resulting in its accumulation in axonal swellings in cultured neurons and in vivo. We show that BACE pharmacological inhibition ameliorates BACE1 axonal trafficking and diminishes axonal dystrophies in Gga3 null neurons in vitro and in vivo. These data indicate that axonal accumulation of BACE1 engendered by GGA3 loss of function results in local toxicity leading to axonopathy. Gga3 deletion exacerbates axonal dystrophies in a mouse model of AD before β-amyloid (Aβ) deposition. Our study strongly supports a role for GGA3 in AD pathogenesis, where GGA3 loss of function triggers BACE1 axonal accumulation independently of extracellular Aβ, and initiates a cascade of events leading to the axonal damage distinctive of the early stage of AD.

Delta- and beta- secretases crosstalk amplifies the amyloidogenic pathway in Alzheimer's disease

Asparagine endopeptidase (AEP), a newly identified delta-secretase, simultaneously cleaves both APP and Tau, promoting Alzheimer's disease (AD) pathologies. However, its pathological role in AD remains incompletely understood. Here we show that delta-secretase cleaves BACE1, a rate-limiting protease in amyloid-β (Aβ) generation, escalating its enzymatic activity and enhancing senile plaques deposit in AD. Delta-secretase binds BACE1 and cuts it at N294 residue in an age-dependent manner and elevates its protease activity. The cleaved N-terminal motif is active even under neutral pH and associates with senile plaques in human AD brains. Subcellular fractionation reveals that delta-secretase and BACE1 reside in the endo-lysosomes. Interestingly, truncated BACE1 enzymatic domain (1-294) augments delta-secretase enzymatic activity and accelerates Aβ production, facilitating AD pathologies and cognitive impairments in APP/PS1 AD mouse model. Uncleavable BACE1 (N294A) inhibits delta-secretase activity and Aβ production and decreases AD pathologies in 5XFAD mice, ameliorating cognitive dysfunctions. Hence, delta- and beta- secretases' crosstalk aggravates each other's roles in AD pathogenesis.

The Potential Role of Protein Kinase R as a Regulator of Age-Related Neurodegeneration

There is a growing evidence describing a decline in adaptive homeostasis in aging-related diseases affecting the central nervous system (CNS), many of which are characterized by the appearance of non-native protein aggregates. One signaling pathway that allows cell adaptation is the integrated stress response (ISR), which senses stress stimuli through four kinases. ISR activation promotes translational arrest through the phosphorylation of the eukaryotic translation initiation factor 2 alpha (eIF2α) and the induction of a gene expression program to restore cellular homeostasis. However, depending on the stimulus, ISR can also induce cell death. One of the ISR sensors is the double-stranded RNA-dependent protein kinase [protein kinase R (PKR)], initially described as a viral infection sensor, and now a growing evidence supports a role for PKR on CNS physiology. PKR has been largely involved in the Alzheimer’s disease (AD) pathological process. Here, we reviewed the antecedents supporting the role of PKR on the efficiency of synaptic transmission and cognition. Then, we review PKR’s contribution to AD and discuss the possible participation of PKR as a player in the neurodegenerative process involved in aging-related pathologies affecting the CNS.

The β-Secretase BACE1 in Alzheimer's Disease

BACE1 (beta-site amyloid precursor protein cleaving enzyme 1) was initially cloned and characterized in 1999. It is required for the generation of all monomeric forms of amyloid-β (Aβ), including Aβ42, which aggregates into bioactive conformational species and likely initiates toxicity in Alzheimer's disease (AD). BACE1 concentrations and rates of activity are increased in AD brains and body fluids, thereby supporting the hypothesis that BACE1 plays a critical role in AD pathophysiology. Therefore, BACE1 is a prime drug target for slowing down Aβ production in early AD. Besides the amyloidogenic pathway, BACE1 has other substrates that may be important for synaptic plasticity and synaptic homeostasis. Indeed, germline and adult conditional BACE1 knockout mice display complex neurological phenotypes. Despite BACE1 inhibitor clinical trials conducted so far being discontinued for futility or safety reasons, BACE1 remains a well-validated therapeutic target for AD. A safe and efficacious compound with high substrate selectivity as well as a more accurate dose regimen, patient population, and disease stage may yet be found. Further research should focus on the role of Aβ and BACE1 in physiological processes and key pathophysiological mechanisms of AD. The functions of BACE1 and the homologue BACE2, as well as the biology of Aβ in neurons and glia, deserve further investigation. Cellular and molecular studies of BACE1 and BACE2 knockout mice coupled with biomarker-based human research will help elucidate the biological functions of these important enzymes and identify their substrates and downstream effects. Such studies will have critical implications for BACE1 inhibition as a therapeutic approach for AD.

Neoline Improves Memory Impairment and Reduces Amyloid-β Level and Tau Phosphorylation Through AMPK Activation in the Mouse Alzheimer's Disease Model

BACKGROUND

Alzheimer's disease (AD) is the most general, chronic, and progressive neurodegenerative senile disorder characterized clinically by progressive cognitive deterioration and memory impairment. Neoline is effective against neuropathic pain models, but the effects of neoline against AD-like phenotypes have not been investigated.

OBJECTIVE

We offer the investigation of the effects of neoline in AD.

METHODS

In this study, a Tg-APPswe/PS1dE9 AD mouse model was treated orally with neoline at a concentration of 0.5 mg/kg or 0.1 mg/kg starting at 7.5 months and administered for three months, and its anti-AD effects were evaluated.

RESULTS

Neoline improved memory and cognition impairments and reduced the number of amyloid-beta plaque and the amount of amyloid-β in the brain of AD mice. Furthermore, neoline reduced the anxiety behavior in the AD mouse model. The chronic administration of neoline also induced AMPK phosphorylation and decreased tau, amyloid-β, and BACE1 expression in the hippocampus. These findings indicate that chronic administration of neoline has therapeutic effects via AMPK activation, and BACE1 downregulation resulted in a decrease in the amyloid-β levels in the brain of Tg-APPswe/PS1dE9 AD mice.

CONCLUSION

Our results suggest that neoline is a therapeutic agent for the cure of neurodegenerative diseases like AD.

Overlapping roles of JIP3 and JIP4 in promoting axonal transport of lysosomes in human iPSC-derived neurons

The dependence of neurons on microtubule-based motors for the movement of lysosomes over long distances raises questions about adaptations that allow neurons to meet these demands. Recently, JIP3/MAPK8IP3, a neuronally enriched putative adaptor between lysosomes and motors, was identified as a critical regulator of axonal lysosome abundance. In this study, we establish a human induced pluripotent stem cell (iPSC)-derived neuron model for the investigation of axonal lysosome transport and maturation and show that loss of JIP3 results in the accumulation of axonal lysosomes and the Alzheimer’s disease–related amyloid precursor protein (APP)-derived Aβ42 peptide. We furthermore reveal an overlapping role of the homologous JIP4 gene in lysosome axonal transport. These results establish a cellular model for investigating the relationship between lysosome axonal transport and amyloidogenic APP processing and more broadly demonstrate the utility of human iPSC–derived neurons for the investigation of neuronal cell biology and pathology.

Effects of alcohol intake on cognitive function and β-amyloid protein in APP/PS1 transgenic mice

To investigate the effects of alcohol intake on cognitive function and β-amyloid protein (Aβ) in APP/PS1 double-transgenic mice with Alzheimer's disease (AD). Sixty APP/PS1 transgenic male mice were randomized into seven groups: control group, 0.5% alcohol group, 1% alcohol group, 2% alcohol group, 3% alcohol group, and 4% alcohol group, with 10 non-transgenic B6C3F1 mice of the same genetic background as the negative control group. All mice were pair-fed a liquid diet containing alcohol before assessment of learning and memory using the Y-maze test, and of Aβ content and related enzyme activity on them. Immunohistochemistry was used to detect the expression of Aβ_1-42, Aβ_1-40, and β-amyloid precursor protein (β-APP) in the cerebral cortex. 3%, and 4% alcohol intake significantly impaired the learning and memory abilities. 2%, 3%, and 4% alcohol groups indicated a remarkable change in Aβ_1-42 content, α-secretase and γ-secretase activities in the hippocampus, and β-APP in the cortex; 3% and 4% alcohol groups showed a significant increase in Aβ_1-42 content, β-site amyloid cleavage enzyme 1 (BACE1) activity, and a significant decrease in α-secretase activity in the hippocampus or cortex; 2% and 3% alcohol groups showed a significant increase in Aβ_1-40 content in the hippocampus or cortex; and 2%, 3%, and 4% alcohol groups showed an increase in the expression of Aβ_1-42, Aβ_1-40, and β-APP in the cortex; 1% alcohol groups showed a significant decline in the levels of Aβ_1-42, Aβ_1-40, β-APP, and BACE1 activity in the hippocampus, and γ-secretase activity in the hippocampus and cortex, and 1% alcohol group showed a significant increase of α-secretase activity in the hippocampus. Besides, 0.5% alcohol showed statistically significant effects on the reduction of BACE1 and γ-secretase activities in the hippocampus. Long-term intake of high-dose alcohol can induce cognitive deficits and improve the activity of β-APP decomposition-related enzymes, increase Aβ content and deposition, and initiate AD progression, while long-term intake of low-dose alcohol can antagonize excessive production of Aβ and slow down AD progression.