Selective cytotoxicity of intracellular amyloid beta peptide1-42 through p53 and Bax in cultured primary human neurons

West Nile virus non-structural protein 1 promotes amyloid Beta deposition and neurodegeneration

Recent observations highlight a notable surge in West Nile Virus (WNV) infections in Europe that can lead to neuroinvasive consequences associated with neurodegeneration, mainly triggered by WNV Non-Structural protein 1 (NS1). During viral replication, various protein-protein interactions take place, allowing viral proteins to interact with host factors. NS1 is actively secreted in the bloodstream by infected cells and is known to affect endothelial permeability and host immune response. Focusing on the recently discovered antimicrobial roles of Amyloid-Beta (Aβ) in the context Central Nervous System (CNS), we connected WNV late pathology to overlapping features encountered in neurodegenerative diseases. In fact, CNS viral infections, or presence of specific viral components, activate glial cells, which in turn increase Aβ expression as an antiviral mechanism, leading to Aβ accumulation and neuronal damage. Considering West Nile neuroinvasive disease (WNND) as a possible complication of WNV infection, we investigated the impact of soluble WNV (s)NS1 on glial and neuronal cells, in 2D and 3D in vitro models. We reported an increased Aβ deposition after WNV sNS1 treatment, particularly of Aβ-142 isoform, and increased glial activation with a subsequent neurotoxicity. These findings underscore the crucial role of sNS1 in CNS-related effects during WNV infection, suggesting a novel pathogenetic role.

Small-Molecule Inhibitors of Amyloid Beta: Insights from Molecular Dynamics-Part A: Endogenous Compounds and Repurposed Drugs

The amyloid hypothesis is the predominant model of Alzheimer's disease (AD) pathogenesis, suggesting that amyloid beta (Aβ) peptide is the primary driver of neurotoxicity and a cascade of pathological events in the central nervous system. Aβ aggregation into oligomers and deposits triggers various processes, such as vascular damage, inflammation-induced astrocyte and microglia activation, disrupted neuronal ionic homeostasis, oxidative stress, abnormal kinase and phosphatase activity, tau phosphorylation, neurofibrillary tangle formation, cognitive dysfunction, synaptic loss, cell death, and, ultimately, dementia. Molecular dynamics (MD) is a powerful structure-based drug design (SBDD) approach that aids in understanding the properties, functions, and mechanisms of action or inhibition of biomolecules. As the only method capable of simulating atomic-level internal motions, MD provides unique insights that cannot be obtained through other techniques. Integrating experimental data with MD simulations allows for a more comprehensive understanding of biological processes and molecular interactions. This review summarizes and evaluates MD studies from the past decade on small molecules, including endogenous compounds and repurposed drugs, that inhibit amyloid beta. Furthermore, it outlines key considerations for future MD simulations of amyloid inhibitors, offering a potential framework for studies aimed at elucidating the mechanisms of amyloid beta inhibition by small molecules.

Expression of Neuronal Nicotinic Acetylcholine Receptor and Early Oxidative DNA Damage in Aging Rat Brain-The Effects of Memantine

Aging and age-related neurodegenerative disorders are characterized by the dysfunction or loss of brain nicotinic acetylcholine receptors (nAChRs), and these changes may be related to other senescence markers, such as oxidative stress and DNA repair dysfunction. However, the mechanism of nAChR loss in the aging brain and the modification of this process by drugs (e.g., memantine, Mem) are not yet fully understood. To study whether the differences in nAChR expression in the rat brain occur due to aging or oxidative stress and are modulated by Mem, we analyzed nAChR subunits (at RNA and protein levels) and other biomarkers by real-time quantitative polymerase chain reaction (RQ-PCR) and Western blot validation. Twenty-one female Wistar rats were divided into four groups, depending on age, and the oldest group received injections of Mem or water with the use of intragastric catheters. We studied the cerebral grey matter (CGM), subcortical white matter (SCWM), and cerebellum (Ce). Results showed an age-related decrease of α7 nAChR mRNA level in SCWM. The α7 nAChR mRNA loss was accompanied by reduced expression of 8-oxoguanine DNA glycosylase 1 (OGG1) and an increased tumor necrosis factor alpha (TNFα) level. In the water group, we observed a higher level of α7 nAChR protein in the SCWM and Ce. Biomarker levels changed, but to a different extent depending on the brain area. Importantly, the dysfunction in antioxidative status was stopped and even regressed under Mem treatment. After two weeks of treatment, an increase in TP53 protein level and a decrease in 8-oxo-2'deoxyguanosine (8-oxo-2'dG) level were observed. We conclude that Mem administration may be protective against the senescence process by antioxidative mechanisms.

Non-canonical pathways associated to Amyloid beta and tau protein dyshomeostasis in Alzheimer's disease: A narrative review

Alzheimer's Disease (AD) is the most common form of dementia among elderly people. This disease imposes a significant burden on the healthcare system, society, and economy due to the increasing global aging population. Current trials with drugs or bioactive compounds aimed at reducing cerebral Amyloid beta (Aβ) plaques and tau protein neurofibrillary tangles, which are the two main hallmarks of this devastating neurodegenerative disease, have not provided significant results in terms of their neuropathological outcomes nor met the expected clinical end-points. Ageing, genetic and environmental risk factors, along with different clinical symptoms suggest that AD is a complex and heterogeneous disorder with multiple interconnected pathological pathways rather than a single disease entity. In the present review, we highlight and discuss various non-canonical, Aβ-independent mechanisms, like gliosis, unhealthy dietary intake, lipid and sugar signaling, and cerebrovascular damage that contribute to the onset and development of AD. We emphasize that challenging the traditional "amyloid cascade hypothesis" may improve our understanding of this age-related complex syndrome and help fight the progressive cognitive decline in AD.

A Recent Update on the Role of Estrogen and Progesterone in Alzheimer's Disease

Alzheimer's disease (AD), one of the most prevalent neurodegenerative disease responsible for 60%-80% dementia cases globally. The disease is more prevalent among elder females. Female reproductive hormones are found to be essential for cellular activities in brain. The physiological role of neurotrophins and sex hormones in hippocampal region during neurogenesis and neuron differentiation was studied as well. In addition to triggering cellular pathways, estrogen and progesterone carry out a number of biological processes that lead to neuroprotection. They might have an impact on learning and memory. One of estrogen's modest antioxidant properties is its direct scavenging of free radicals. The neurotrophic effect of estrogen and progesterone can be explained by their ability to rise the expression of the brain-derived neurotrophic factor (BDNF) mRNA. Additionally, they have the ability to degrade beta-amyloid and stop inflammation, apoptotic neuronal cell death, and tau protein phosphorylation. To enhance their neuroprotective action, various cross-talking pathways in cells that are mediated by estrogen, progesterone, and BDNF receptors. This include signaling by mitogen-activated protein kinase/extracellular regulated kinase, phosphatidylinositol 3-kinase/protein kinase B, and phospholipase/protein kinase C. Clinical research to establish the significance of these substances are fragmented, despite publications claiming a lower prevalence of AD when medication is started before menopause. This review article emphasizes an update on the role of estrogen, and progesterone in AD.

Islet amyloid polypeptide fibril catalyzes amyloid-β aggregation by promoting fibril nucleation rather than direct axial growth

Aberrant aggregation of amyloid-β (Aβ) and islet amyloid polypeptide (IAPP) into amyloid fibrils underlies the pathogenesis of Alzheimer's disease (AD) and type 2 diabetes (T2D), respectively. T2D significantly increases AD risk, with evidence suggesting that IAPP and Aβ co-aggregation and cross-seeding might contribute to the cross-talk between two diseases. Experimentally, preformed IAPP fibril seeds can accelerate Aβ aggregation, though the cross-seeding mechanism remains elusive. Here, we computationally demonstrated that Aβ monomer preferred to bind to the elongation ends of preformed IAPP fibrils. However, due to sequence mismatch, the Aβ monomer could not directly grow onto IAPP fibrils by forming multiple stable β-sheets with the exposed IAPP peptides. Conversely, in our control simulations of self-seeding, the Aβ monomer could axially grow on the Aβ fibril, forming parallel in-register β-sheets. Additionally, we showed that the IAPP fibril could catalyze Aβ fibril nucleation by promoting the formation of parallel in-register β-sheets in the C-terminus between bound Aβ peptides. This study enhances our understanding of the molecular interplay between Aβ and IAPP, shedding light on the cross-seeding mechanisms potentially linking T2D and AD. Our findings also underscore the importance of clearing IAPP deposits in T2D patients to mitigate AD risk.

Autophagy-lysosomal pathway impairment and cathepsin dysregulation in Alzheimer's disease

Alzheimer's disease (AD) is characterized by neuronal loss, attributed to amyloid-beta (Aβ) aggregation and accumulation. The autophagy-lysosomal pathway, including cathepsins B and D, is crucial for protein degradation and clearance, but it is impaired in some diseases. This review summarizes current knowledge on the dysregulation of this pathway in AD. Accumulating evidence suggests that Aβ overload impairs autophagy-lysosomal function and cathepsin activity, exacerbating Aβ accumulation and neurodegeneration. However, the precise mechanisms underlying these interactions remain elusive. Despite these challenges, targeting the lysosomal pathway emerges as a promising therapeutic strategy, and a comprehensive understanding of the autophagy-lysosomal system is essential to develop effective interventions for AD.

Significance of Programmed Cell Death Pathways in Neurodegenerative Diseases

Programmed cell death (PCD) is a form of cell death distinct from accidental cell death (ACD) and is also referred to as regulated cell death (RCD). Typically, PCD signaling events are precisely regulated by various biomolecules in both spatial and temporal contexts to promote neuronal development, establish neural architecture, and shape the central nervous system (CNS), although the role of PCD extends beyond the CNS. Abnormalities in PCD signaling cascades contribute to the irreversible loss of neuronal cells and function, leading to the onset and progression of neurodegenerative diseases. In this review, we summarize the molecular processes and features of different modalities of PCD, including apoptosis, necroptosis, pyroptosis, ferroptosis, cuproptosis, and other novel forms of PCD, and their effects on the pathogenesis of neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), multiple sclerosis (MS), traumatic brain injury (TBI), and stroke. Additionally, we examine the key factors involved in these PCD signaling pathways and discuss the potential for their development as therapeutic targets and strategies. Therefore, therapeutic strategies targeting the inhibition or facilitation of PCD signaling pathways offer a promising approach for clinical applications in treating neurodegenerative diseases.

Glyceraldehyde-3-phosphate dehydrogenase is involved in the pathogenesis of Alzheimer's disease

One of important characteristics of Alzheimer's disease is a persistent oxidative/nitrosative stress caused by pro-oxidant properties of amyloid-beta peptide (Aβ) and chronic inflammation in the brain. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is easily oxidized under oxidative stress. Numerous data indicate that oxidative modifications of GAPDH in vitro and in cell cultures stimulate GAPDH denaturation and aggregation, and the catalytic cysteine residue Cys152 is important for these processes. Both intracellular and extracellular GAPDH aggregates are toxic for the cells. Interaction of denatured GAPDH with soluble Aβ results in mixed insoluble aggregates with increased toxicity. The above-described properties of GAPDH (sensitivity to oxidation and propensity to form aggregates, including mixed aggregates with Aβ) determine its role in the pathogenesis of Alzheimer's disease.

Heparan sulfate proteoglycans: Mediators of cellular and molecular Alzheimer's disease pathogenic factors via tunnelling nanotubes?

Neurological disorders impact around one billion individuals globally (15 % approx.), with significant implications for disability and mortality with their impact in Australia currently amounts to 6.8 million deaths annually. Heparan sulfate proteoglycans (HSPGs) are complex extracellular molecules implicated in promoting Tau fibril formation resulting in Tau tangles, a hallmark of Alzheimer's disease (AD). HSPG-Tau protein interactions contribute to various AD stages via aggregation, toxicity, and clearance, largely via interactions with the glypican 1 and syndecan 3 core proteins. The tunnelling nanotubes (TNTs) pathway is emerging as a facilitator of intercellular molecule transport, including Tau and Amyloid β proteins, across extensive distances. While current TNT-associated evidence primarily stems from cancer models, their role in Tau propagation and its effects on recipient cells remain unclear. This review explores the interplay of TNTs, HSPGs, and AD-related factors and proposes that HSPGs influence TNT formation in neurodegenerative conditions such as AD.

Serotonergic dysfunction may mediate the relationship between alcohol consumption and Alzheimer's disease

The impact of Alzheimer's disease (AD) and its related dementias is rapidly expanding, and its mitigation remains an urgent social and technical challenge. To date there are no effective treatments or interventions for AD, but recent studies suggest that alcohol consumption is correlated with the risk of developing dementia. In this review, we synthesize data from preclinical, clinical, and epidemiological models to evaluate the combined role of alcohol consumption and serotonergic dysfunction in AD, underscoring the need for further research on this topic. We first discuss the limitations inherent to current data-collection methods, and how neuropsychiatric symptoms common among AD, alcohol use disorder, and serotonergic dysfunction may mask their co-occurrence. We additionally describe how excess alcohol consumption may accelerate the development of AD via direct effects on serotonergic function, and we explore the roles of neuroinflammation and proteostasis in mediating the relationship between serotonin, alcohol consumption, and AD. Lastly, we argue for a shift in current research to disentangle the pathogenic effects of alcohol on early-affected brainstem structures in AD.

Multi-target potential of newly designed tacrine-derived cholinesterase inhibitors: Synthesis, computational and pharmacological study

Simple and scalable synthetic approach was used for the preparation of thirteen novel tacrine derivatives consisting of tacrine and N-aryl-piperidine-4-carboxamide moiety connected by a five-methylene group linker. An anti-Alzheimer disease (AD) potential of newly designed tacrine derivatives was evaluated against two important AD targets, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). In vitro pharmacological evaluation showed strong ChE inhibitory activity of all compounds, with IC50 values ranging from 117.5 to 455 nM for AChE and 34 to 324 nM for BuChE. As a representative of the series with the best cytotoxicity / ChE inhibitory activity ratio, expressed as the selectivity index (SI), 2-chlorobenzoyl derivative demonstrated mixed-type inhibition on AChE and BuChE, suggesting binding to both CAS and PAS of the enzymes. It also exhibited antioxidant capacity and neuroprotective potential against amyloid-β (Aβ) toxicity in the culture of neuron-like cells. In-depth computational analysis corroborated well with in vitro ChE inhibition, illuminating that all compounds exhibit significant potential in targeting both enzymes. Molecular dynamics (MD) simulations revealed that 2-chlorobenzoyl derivative, created complexes with AChE and BuChE that demonstrated sufficient stability throughout the observed MD simulation. Computationally predicted ADME properties indicated that these compounds should have good blood-brain barrier (BBB) permeability, an important factor for CNS-targeting drugs. Overall, all tested compounds showed promising pharmacological behavior, highlighting the multi-target potential of 2-chlorobenzoyl derivative which should be further investigated as a new lead in the drug development process.

Identifying potential genetic epistasis implicated in Alzheimer's disease via detection of SNP-SNP interaction on quantitative trait CSF Aβ42

Although genome-wide association studies have identified multiple Alzheimer's disease (AD)-associated loci by selecting the main effects of individual single-nucleotide polymorphisms (SNPs), the interpretation of genetic variance in AD is limited. Based on the linear regression method, we performed genome-wide SNP-SNP interaction on cerebrospinal fluid Aβ42 to identify potential genetic epistasis implicated in AD, with age, gender, and diagnosis as covariates. A GPU-based method was used to address the computational challenges posed by the analysis of epistasis. We found 368 SNP pairs to be statistically significant, and highly significant SNP-SNP interactions were identified between the marginal main effects of SNP pairs, which explained a relatively high variance at the Aβ42 level. Our results replicated 100 previously reported AD-related genes and 5 gene-gene interaction pairs of the protein-protein interaction network. Our bioinformatics analyses provided preliminary evidence that the 5-overlapping gene-gene interaction pairs play critical roles in inducing synaptic loss and dysfunction, thereby leading to memory decline and cognitive impairment in AD-affected brains.

APP-C31: An Intracellular Promoter of Both Metal-Free and Metal-Bound Amyloid-β40 Aggregation and Toxicity in Alzheimer's Disease

Intracellular C-terminal cleavage of the amyloid precursor protein (APP) is elevated in the brains of Alzheimer's disease (AD) patients and produces a peptide labeled APP-C31 that is suspected to be involved in the pathology of AD. But details about the role of APP-C31 in the development of the disease are not known. Here, this work reports that APP-C31 directly interacts with the N-terminal and self-recognition regions of amyloid-β40 (Aβ40 ) to form transient adducts, which facilitates the aggregation of both metal-free and metal-bound Aβ40 peptides and aggravates their toxicity. Specifically, APP-C31 increases the perinuclear and intranuclear generation of large Aβ40 deposits and, consequently, damages the nucleus leading to apoptosis. The Aβ40 -induced degeneration of neurites and inflammation are also intensified by APP-C31 in human neurons and murine brains. This study demonstrates a new function of APP-C31 as an intracellular promoter of Aβ40 amyloidogenesis in both metal-free and metal-present environments, and may offer an interesting alternative target for developing treatments for AD that have not been considered thus far.

Mechanisms of the Beneficial Effects of Exercise on Brain-Derived Neurotrophic Factor Expression in Alzheimer's Disease

Brain-derived neurotrophic factor (BDNF) is a key molecule in promoting neurogenesis, dendritic and synaptic health, neuronal survival, plasticity, and excitability, all of which are disrupted in neurological and cognitive disorders such as Alzheimer's disease (AD). Extracellular aggregates of amyloid-β (Aβ) in the form of plaques and intracellular aggregates of hyperphosphorylated tau protein have been identified as major pathological insults in the AD brain, along with immune dysfunction, oxidative stress, and other toxic stressors. Although aggregated Aβ and tau lead to decreased brain BDNF expression, early losses in BDNF prior to plaque and tangle formation may be due to other insults such as oxidative stress and contribute to early synaptic dysfunction. Physical exercise, on the other hand, protects synaptic and neuronal structure and function, with increased BDNF as a major mediator of exercise-induced enhancements in cognitive function. Here, we review recent literature on the mechanisms behind exercise-induced BDNF upregulation and its effects on improving learning and memory and on Alzheimer's disease pathology. Exercise releases into the circulation a host of hormones and factors from a variety of peripheral tissues. Mechanisms of BDNF induction discussed here are osteocalcin, FNDC5/irisin, and lactate. The fundamental mechanisms of how exercise impacts BDNF and cognition are not yet fully understood but are a prerequisite to developing new biomarkers and therapies to delay or prevent cognitive decline.

Flanking regions, amyloid cores, and polymorphism: the potential interplay underlying structural diversity

The β-sheet-rich amyloid core is the defining feature of protein aggregates associated with neurodegenerative disorders. Recent investigations have revealed that there exist multiple examples of the same protein, with the same sequence, forming a variety of amyloid cores with distinct structural characteristics. These structural variants, termed as polymorphs, are hypothesized to influence the pathological profile and the progression of different neurodegenerative diseases, giving rise to unique phenotypic differences. Thus, identifying the origin and properties of these structural variants remain a focus of studies, as a preliminary step in the development of therapeutic strategies. Here, we review the potential role of the flanking regions of amyloid cores in inducing polymorphism. These regions, adjacent to the amyloid cores, show a preponderance for being structurally disordered, imbuing them with functional promiscuity. The dynamic nature of the flanking regions can then manifest in the form of conformational polymorphism of the aggregates. We take a closer look at the sequences flanking the amyloid cores, followed by a review of the polymorphic aggregates of the well-characterized proteins amyloid-β, α-synuclein, Tau, and TDP-43. We also consider different factors that can potentially influence aggregate structure and how these regions can be viewed as novel targets for therapeutic strategies by utilizing their unique structural properties.

p53-dependent c-Fos expression is a marker but not executor for motor neuron death in spinal muscular atrophy mouse models

The activation of the p53 pathway has been associated with neuronal degeneration in different neurological disorders, including spinal muscular atrophy (SMA) where aberrant expression of p53 drives selective death of motor neurons destined to degenerate. Since direct p53 inhibition is an unsound therapeutic approach due carcinogenic effects, we investigated the expression of the cell death-associated p53 downstream targets c-fos, perp and fas in vulnerable motor neurons of SMA mice. Fluorescence in situ hybridization (FISH) of SMA motor neurons revealed c-fos RNA as a promising candidate. Accordingly, we identified p53-dependent nuclear upregulation of c-Fos protein in degenerating motor neurons from the severe SMNΔ7 and intermediate Smn2B/– SMA mouse models. Although motor neuron-specific c-fos genetic deletion in SMA mice did not improve motor neuron survival or motor behavior, p53-dependent c-Fos upregulation marks vulnerable motor neurons in different mouse models. Thus, nuclear c-Fos accumulation may serve as a readout for therapeutic approaches targeting neuronal death in SMA and possibly other p53-dependent neurodegenerative diseases.

NMDA receptors mediate synaptic plasticity impairment of hippocampal neurons due to arsenic exposure

Endemic arsenism is a worldwide health problem. Chronic arsenic exposure results in cognitive dysfunction due to arsenic and its metabolites accumulating in hippocampus. As the cellular basis of cognition, synaptic plasticity is pivotal in arsenic-induced cognitive dysfunction. N-methyl-D-aspartate receptors (NMDARs) serve physiological functions in synaptic transmission. However, excessive NMDARs activity contributes to exitotoxicity and synaptic plasticity impairment. Here, we provide an overview of the mechanisms that NMDARs and their downstream signaling pathways mediate synaptic plasticity impairment due to arsenic exposure in hippocampal neurons, ways of arsenic exerting on NMDARs, as well as the potential therapeutic targets except for water improvement.

Model scenarios for cell cycle re-entry in Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease. Aberrant production and aggregation of amyloid beta (Aβ) peptide into plaques is a frequent feature of AD, but therapeutic approaches targeting Aβ accumulation fail to inhibit disease progression. The approved cholinesterase inhibitor drugs are symptomatic treatments. During human brain development, the progenitor cells differentiate into neurons and switch to a postmitotic state. However, cell cycle re-entry often precedes loss of neurons. We developed mathematical models of multiple routes leading to cell cycle re-entry in neurons that incorporate the crosstalk between cell cycle, neuronal, and apoptotic signaling mechanisms. We show that the integration of multiple feedback loops influences disease severity making the switch to pathological state irreversible. We observe that the transcriptional changes associated with this transition are also characteristics of the AD brain. We propose that targeting multiple arms of the feedback loop may bring about disease-modifying effects in AD.

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Developed mathematical models of cell cycle re-entry in Alzheimer's disease (AD)

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Integration of multiple feedback loops drives irreversible transition to AD

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Predicted transcriptional dysregulation is validated using AD gene expression data

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Inhibition of self-amplifying feedback loops brings about disease-modifying effects

Golgi stress induces upregulation of the ER-Golgi SNARE Syntaxin-5, altered βAPP processing, and Caspase-3-dependent apoptosis in NG108-15 cells

The involvement of secretory pathways and Golgi dysfunction in neuronal cells during Alzheimer's disease progression is poorly understood. Our previous overexpression and knockdown studies revealed that the intracellular protein level of Syntaxin-5, an endoplasmic reticulum-Golgi soluble N-ethylmaleimide-sensitive factor-attachment protein receptor (SNARE), modulates beta-amyloid precursor protein processing in neuronal cells. We recently showed that changes in endogenous Syntaxin-5 protein expression occur under stress induction. Syntaxin-5 was upregulated by endoplasmic reticulum stress but was degraded by Caspase-3 during apoptosis in neuronal cells. In addition, we showed that sustained endoplasmic reticulum stress promotes Caspase-3-dependent apoptosis during the later phase of the endoplasmic reticulum stress response in NG108-15 cells. In this study, to elucidate the consequences of secretory pathway dysfunction in beta-amyloid precursor protein processing that lead to neuronal cell death, we examined the effect of various stresses on endoplasmic reticulum-Golgi SNARE expression and beta-amyloid precursor protein processing. By using compounds to disrupt Golgi function, we show that Golgi stress promotes upregulation of the endoplasmic reticulum-Golgi SNARE Syntaxin-5, and prolonged stress causes Caspase-3-dependent apoptosis. Golgi stress induced intracellular beta-amyloid precursor protein accumulation and a concomitant decrease in total amyloid-beta production. We also examined the protective effect of the chemical chaperone 4-phenylbutylate on changes in amyloid-beta production and the activation of Caspase-3 induced by endoplasmic reticulum and Golgi stress. The compound alleviated the increase in the amyloid-beta 1-42/amyloid-beta 1-40 ratio induced by endoplasmic reticulum and Golgi stress. Furthermore, 4-phenylbutylate could rescue Caspase-3-dependent apoptosis induced by prolonged organelle stress. These results suggest that organelle stress originating from the endoplasmic reticulum and Golgi has a substantial impact on the amyloidogenic processing of beta-amyloid precursor protein and Caspase-3-dependent apoptosis, leading to neuronal cell death.

Current Progress on Neuroprotection Induced by Artemisia, Ginseng, Astragalus, and Ginkgo Traditional Chinese Medicines for the Therapy of Alzheimer's Disease

Aging is associated with the occurrence of diverse degenerative changes in various tissues and organs and with an increased incidence of neurological disorders, especially neurodegenerative diseases such as Alzheimer's disease (AD). In recent years, the search for effective components derived from medicinal plants in delaying aging and preventing and treating neurodegenerative diseases has been increasing and the number of related publications shows a rising trend. Here, we present a concise, updated review on the preclinical and clinical research progress in the assessment of the therapeutic potential of different traditional Chinese medicines and derived active ingredients and their effect on the signaling pathways involved in AD neuroprotection. Recognized by their multitargeting ability, these natural compounds hold great potential in developing novel drugs for AD.

Near-Infrared Fluorescent Probes as Imaging and Theranostic Modalities for Amyloid-Beta and Tau Aggregates in Alzheimer's Disease

A person suspected of having Alzheimer's disease (AD) is clinically diagnosed for the presence of principal biomarkers, especially misfolded amyloid-beta (Aβ) and tau proteins in the brain regions. Existing radiotracer diagnostic tools, such as PET imaging, are expensive and have limited availability for primary patient screening and pre-clinical animal studies. To change the status quo, small-molecular near-infrared (NIR) probes have been rapidly developed, which may serve as an inexpensive, handy imaging tool to comprehend the dynamics of pathogenic progression in AD and assess therapeutic efficacy in vivo. This Perspective summarizes the biochemistry of Aβ and tau proteins and then focuses on structurally diverse NIR probes with coverages of their spectroscopic properties, binding affinity toward Aβ and tau species, and theranostic effectiveness. With the summarized information and perspective discussions, we hope that this paper may serve as a guiding tool for designing novel in vivo imaging fluoroprobes with theranostic capabilities in the future.

The Complex Mechanisms by Which Neurons Die Following DNA Damage in Neurodegenerative Diseases

Human cells are exposed to numerous exogenous and endogenous insults every day. Unlike other molecules, DNA cannot be replaced by resynthesis, hence damage to DNA can have major consequences for the cell. The DNA damage response contains overlapping signalling networks that repair DNA and hence maintain genomic integrity, and aberrant DNA damage responses are increasingly described in neurodegenerative diseases. Furthermore, DNA repair declines during aging, which is the biggest risk factor for these conditions. If unrepaired, the accumulation of DNA damage results in death to eliminate cells with defective genomes. This is particularly important for postmitotic neurons because they have a limited capacity to proliferate, thus they must be maintained for life. Neuronal death is thus an important process in neurodegenerative disorders. In addition, the inability of neurons to divide renders them susceptible to senescence or re-entry to the cell cycle. The field of cell death has expanded significantly in recent years, and many new mechanisms have been described in various cell types, including neurons. Several of these mechanisms are linked to DNA damage. In this review, we provide an overview of the cell death pathways induced by DNA damage that are relevant to neurons and discuss the possible involvement of these mechanisms in neurodegenerative conditions.

Structural Features of Cytochrome b5-Cytochrome b5 Reductase Complex Formation and Implications for the Intramolecular Dynamics of Cytochrome b5 Reductase

Membrane cytochrome b5 reductase is a pleiotropic oxidoreductase that uses primarily soluble reduced nicotinamide adenine dinucleotide (NADH) as an electron donor to reduce multiple biological acceptors localized in cellular membranes. Some of the biological acceptors of the reductase and coupled redox proteins might eventually transfer electrons to oxygen to form reactive oxygen species. Additionally, an inefficient electron transfer to redox acceptors can lead to electron uncoupling and superoxide anion formation by the reductase. Many efforts have been made to characterize the involved catalytic domains in the electron transfer from the reduced flavoprotein to its electron acceptors, such as cytochrome b5, through a detailed description of the flavin and NADH-binding sites. This information might help to understand better the processes and modifications involved in reactive oxygen formation by the cytochrome b5 reductase. Nevertheless, more than half a century since this enzyme was first purified, the one-electron transfer process toward potential electron acceptors of the reductase is still only partially understood. New advances in computational analysis of protein structures allow predicting the intramolecular protein dynamics, identifying potential functional sites, or evaluating the effects of microenvironment changes in protein structure and dynamics. We applied this approach to characterize further the roles of amino acid domains within cytochrome b5 reductase structure, part of the catalytic domain, and several sensors and structural domains involved in the interactions with cytochrome b5 and other electron acceptors. The computational analysis results allowed us to rationalize some of the available spectroscopic data regarding ligand-induced conformational changes leading to an increase in the flavin adenine dinucleotide (FAD) solvent-exposed surface, which has been previously correlated with the formation of complexes with electron acceptors.

Application of the Double-Mutant Cycle Strategy to Protein Aggregation Reveals Transient Interactions in Amyloid-β Oligomers

Transient oligomeric intermediates in the peptide or protein aggregation pathway are suspected to be the key toxic species in many amyloid diseases, but deciphering their molecular nature has remained a challenge. Here we show that the strategy of "double-mutant cycles", used effectively in probing protein-folding intermediates, can reveal transient interactions during protein aggregation. It does so by comparing the changes in thermodynamic parameters between the wild type, and single and double mutants. We demonstrate the strategy by probing the possible transient salt bridge partner of lysine 28 (K28) in the oligomeric states of amyloid β-40 (Aβ₄₀), the putative toxic species in Alzheimer's disease. In mature fibrils, the binding partner is aspartate 23. This interaction differentiates Aβ₄₀ from the more toxic Aβ₄₂, where K28's binding partner is the C-terminal carboxylate. We selectively acetylated K28 and amidated the C-terminus of Aβ₄₀, creating four distinct variants. Spectroscopic measurements of the kinetics and thermodynamics of aggregation show that K28 and the C-terminus interact transiently in the early phases of the Aβ₄₀ aggregation pathway. Hydrogen-deuterium exchange mass spectrometry (using a simple analysis method that we introduce here that takes into account the isotopic mass distribution) supports this interpretation. It is also supported by cellular toxicity measurements, suggesting possible similarities in the mechanisms of toxicity of Aβ₄₀ oligomers (which are more toxic than Aβ₄₀ fibrils) and Aβ₄₂. Our results show that double-mutant cycles can be a powerful tool for probing transient interactions during protein aggregation.

Molecular mechanisms of cell death in neurological diseases

Tightly orchestrated programmed cell death (PCD) signalling events occur during normal neuronal development in a spatially and temporally restricted manner to establish the neural architecture and shaping the CNS. Abnormalities in PCD signalling cascades, such as apoptosis, necroptosis, pyroptosis, ferroptosis, and cell death associated with autophagy as well as in unprogrammed necrosis can be observed in the pathogenesis of various neurological diseases. These cell deaths can be activated in response to various forms of cellular stress (exerted by intracellular or extracellular stimuli) and inflammatory processes. Aberrant activation of PCD pathways is a common feature in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease, Parkinson's disease, and Huntington's disease, resulting in unwanted loss of neuronal cells and function. Conversely, inactivation of PCD is thought to contribute to the development of brain cancers and to impact their response to therapy. For many neurodegenerative diseases and brain cancers current treatment strategies have only modest effect, engendering the need for investigations into the origins of these diseases. With many diseases of the brain displaying aberrations in PCD pathways, it appears that agents that can either inhibit or induce PCD may be critical components of future therapeutic strategies. The development of such therapies will have to be guided by preclinical studies in animal models that faithfully mimic the human disease. In this review, we briefly describe PCD and unprogrammed cell death processes and the roles they play in contributing to neurodegenerative diseases or tumorigenesis in the brain. We also discuss the interplay between distinct cell death signalling cascades and disease pathogenesis and describe pharmacological agents targeting key players in the cell death signalling pathways that have progressed through to clinical trials.

The Relevance of Amyloid β-Calmodulin Complexation in Neurons and Brain Degeneration in Alzheimer's Disease

Intraneuronal amyloid β (Aβ) oligomer accumulation precedes the appearance of amyloid plaques or neurofibrillary tangles and is neurotoxic. In Alzheimer’s disease (AD)-affected brains, intraneuronal Aβ oligomers can derive from Aβ peptide production within the neuron and, also, from vicinal neurons or reactive glial cells. Calcium homeostasis dysregulation and neuronal excitability alterations are widely accepted to play a key role in Aβ neurotoxicity in AD. However, the identification of primary Aβ-target proteins, in which functional impairment initiating cytosolic calcium homeostasis dysregulation and the critical point of no return are still pending issues. The micromolar concentration of calmodulin (CaM) in neurons and its high affinity for neurotoxic Aβ peptides (dissociation constant ≈ 1 nM) highlight a novel function of CaM, i.e., the buffering of free Aβ concentrations in the low nanomolar range. In turn, the concentration of Aβ-CaM complexes within neurons will increase as a function of time after the induction of Aβ production, and free Aβ will rise sharply when accumulated Aβ exceeds all available CaM. Thus, Aβ-CaM complexation could also play a major role in neuronal calcium signaling mediated by calmodulin-binding proteins by Aβ; a point that has been overlooked until now. In this review, we address the implications of Aβ-CaM complexation in the formation of neurotoxic Aβ oligomers, in the alteration of intracellular calcium homeostasis induced by Aβ, and of dysregulation of the calcium-dependent neuronal activity and excitability induced by Aβ.

Effects of Ecklonia cava Extract on Neuronal Damage and Apoptosis in PC-12 Cells against Oxidative Stress

Marine algae (seaweed) encompass numerous groups of multicellular organisms with various shapes, sizes, and colors, and serve as important sources of natural bioactive substances. The brown alga Ecklonia cava Kjellman, an edible seaweed, contains many bioactives such as phlorotannins and fucoidans. Here, we evaluated the antioxidative, neuroprotective, and anti-apoptotic effects of E. cava extract (ECE), E. cava phlorotannin-rich extract (ECPE), and the phlorotannin dieckol on neuronal PC-12 cells. The antioxidant capacities of ECPE and ECE were 1,711.5 and 1,050.4 mg vitamin C equivalents/g in the ABTS assay and 704.0 and 474.6 mg vitamin C equivalents/g in the DPPH assay, respectively. The dieckol content of ECPE (58.99 mg/g) was approximately 60% higher than that of ECE (36.97 mg/g). Treatment of PC-12 cells with ECPE and ECE increased cell viability in a dose-dependent manner. Intracellular oxidative stress in PC-12 cells due to ECPE and ECE decreased dose-independently by up to 63% and 47%, respectively, compared with the stress control (323%). ECPE reduced the production of the pro-apoptotic proteins Bax and caspase-3 more effectively than ECE. Early and late apoptosis in PC-12 cells were more effectively decreased by ECPE than ECE treatments. From the results obtained in this study, we concluded that ECPE, which is rich in phlorotannins, including the marker compound dieckol, may be applied to the development of functional materials for improving cognition and memory.

Tunneling nanotubes: A novel pharmacological target for neurodegenerative diseases?

Diversiform ways of intercellular communication are vital links in maintaining homeostasis and disseminating physiological states. Among intercellular bridges, tunneling nanotubes (TNTs) discovered in 2004 were recognized as potential pharmacology targets related to the pathogenesis of common or infrequent neurodegenerative disorders. The neurotoxic aggregates in neurodegenerative diseases including scrapie prion protein (PrPSc), mutant tau protein, amyloid-beta (Aβ) protein, alpha-synuclein (α-syn) as well as mutant Huntington (mHTT) protein could promote TNT formation via certain physiological mechanisms, in turn, mediating the intercellular transmission of neurotoxicity. In this review, we described in detail the skeleton, the formation, the physicochemical properties, and the functions of TNTs, while paying particular attention to the key role of TNTs in the transport of pathological proteins during neurodegeneration.

An Analysis of the Neurological and Molecular Alterations Underlying the Pathogenesis of Alzheimer's Disease

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by amyloid beta (Aβ) plaques, neurofibrillary tangles, and neuronal loss. Unfortunately, despite decades of studies being performed on these histological alterations, there is no effective treatment or cure for AD. Identifying the molecular characteristics of the disease is imperative to understanding the pathogenesis of AD. Furthermore, uncovering the key causative alterations of AD can be valuable in developing models for AD treatment. Several alterations have been implicated in driving this disease, including blood–brain barrier dysfunction, hypoxia, mitochondrial dysfunction, oxidative stress, glucose hypometabolism, and altered heme homeostasis. Although these alterations have all been associated with the progression of AD, the root cause of AD has not been identified. Intriguingly, recent studies have pinpointed dysfunctional heme metabolism as a culprit of the development of AD. Heme has been shown to be central in neuronal function, mitochondrial respiration, and oxidative stress. Therefore, dysregulation of heme homeostasis may play a pivotal role in the manifestation of AD and its various alterations. This review will discuss the most common neurological and molecular alterations associated with AD and point out the critical role heme plays in the development of this disease.

Peptidomimetic-Based Vesicles Inhibit Amyloid-β Fibrillation and Attenuate Cytotoxicity

An interruption in Aβ homeostasis leads to the deposit of neurotoxic amyloid plaques and is associated with Alzheimer's disease. A supramolecular strategy based on the assembly of peptidomimetic agents into functional vesicles has been conceived for the simultaneous inhibition of Aβ₄₂ fibrillation and expedited clearance of Aβ₄₂ aggregates. Tris-pyrrolamide peptidomimetic, ADH-353, contains one hydrophobic N-butyl and two hydrophilic N-propylamine side chains and readily forms vesicles under physiological conditions. These vesicles completely rescue both mouse neuroblastoma N2a and human neuroblastoma SH-SY5Y cells from the cytotoxicity that follows from Aβ₄₂ misfolding likely in mitochondria. Biophysical studies, including confocal imaging, demonstrate the biocompatibility and selectivity of the approach toward this aberrant protein assembly in cellular milieu.

Assessing the cellular toxicity of peptide inhibitors of intracellular protein-protein interactions by microinjection

Inhibitors of protein-protein interactions can be developed through a number of technologies to provide leads that include cell-impermeable molecules. Redesign of these impermeable leads to provide cell-permeable derivatives can be challenging and costly. We hypothesised that intracellular toxicity of leads could be assessed by microinjection prior to investing in the redesign process. We demonstrate this approach for our development of inhibitors of the protein-protein interaction between inducible nitric-oxide synthase (iNOS) and SPRY domain-containing SOCS box proteins (SPSBs). We microinjected a lead molecule into AD-293 cells and were able to perform an intracellular toxicity assessment. We also investigated the intracellular distribution and localisation of injected inhibitor using a fluorescently-labelled analogue. Our findings show that a lead peptide inhibitor, CP2, had no toxicity even at intracellular concentrations four orders of magnitude higher than its K_d for binding to SPSB2. This early toxicity assessment justifies further development of this cell-impermeable lead to confer cell permeability. Our investigation highlights the utility of microinjection as a tool for assessing toxicity during development of drugs targeting protein-protein interactions.

Restoration of BMI1 levels after the administration of early harvest extra virgin olive oil as a therapeutic strategy against Alzheimer's disease

Even though Alzheimer's disease (AD) is the most common cause of dementia, the mechanisms governing the establishment and progression of the disease remain largely unknown. Here, we investigated the implication of the neuroprotective protein BMI1 (B lymphoma Mo-MLV insertion region 1 homolog) in AD and the possibility to reverse the onset of the disease through the administration of extra virgin olive oil (EVOO) in Mild Cognitive Impairment (MCI) patients. For this purpose, we utilized a wide bank of MCI patient samples to examine the potential effects of EVOO. We found that while EVOO treatment increases BMI1 levels, p53 levels drop in MCI patient serum after EVOO treatment for 12 months. Additionally, AD-related biomarkers (p-tau, Aβ1-42 and Aβ1-42/Aβ-40 ratio) return to normal levels after administration of EVOO in MCI patients for 12 months. Moreover, we show that upon EVOO administration, BMI1-upregulation correlates with reduction of oxidative stress and inflammatory responses. In conclusion, we provide clinical trial evidence to confirm that restoration of BMI1 activity through EVOO administration in MCI patients constitutes a potential therapeutic approach against neurodegeneration leading to AD.

Dynamic changes in the brain protein interaction network correlates with progression of Aβ42 pathology in Drosophila

Alzheimer's disease (AD), the most prevalent form of dementia, is a progressive and devastating neurodegenerative condition for which there are no effective treatments. Understanding the molecular pathology of AD during disease progression may identify new ways to reduce neuronal damage. Here, we present a longitudinal study tracking dynamic proteomic alterations in the brains of an inducible Drosophila melanogaster model of AD expressing the Arctic mutant Aβ42 gene. We identified 3093 proteins from flies that were induced to express Aβ42 and age-matched healthy controls using label-free quantitative ion-mobility data independent analysis mass spectrometry. Of these, 228 proteins were significantly altered by Aβ42 accumulation and were enriched for AD-associated processes. Network analyses further revealed that these proteins have distinct hub and bottleneck properties in the brain protein interaction network, suggesting that several may have significant effects on brain function. Our unbiased analysis provides useful insights into the key processes governing the progression of amyloid toxicity and forms a basis for further functional analyses in model organisms and translation to mammalian systems.

Assessing Reproducibility in Amyloid β Research: Impact of Aβ Sources on Experimental Outcomes

The difficulty of synthesizing and purifying the amyloid β (Aβ) peptide, combined with its high aggregation propensity and low solubility under physiological conditions, leads to a wide variety of experimental results from kinetic assays to biological activity. Thus, it becomes challenging to reproduce outcomes, and this limits our ability to rely on reported results as the foundation for new research. This article examines variability of the Aβ peptide from different sources, comparing purity, and oligomer and fibril formation propensity side by side. The results highlight the importance of performing rigorous controls so that meaningful biophysical, biochemical, and neurobiological results can be obtained to improve our understanding on Aβ.

Cathepsin D regulates cerebral Aβ42/40 ratios via differential degradation of Aβ42 and Aβ40

BACKGROUND

Cathepsin D (CatD) is a lysosomal protease that degrades both the amyloid β-protein (Aβ) and the microtubule-associated protein, tau, and has been genetically linked to late-onset Alzheimer disease (AD). Here, we sought to examine the consequences of genetic deletion of CatD on Aβ proteostasis in vivo and to more completely characterize the degradation of Aβ42 and Aβ40 by CatD.

METHODS

We quantified Aβ degradation rates and levels of endogenous Aβ42 and Aβ40 in the brains of CatD-null (CatD-KO), heterozygous null (CatD-HET), and wild-type (WT) control mice. CatD-KO mice die by ~ 4 weeks of age, so tissues from younger mice, as well as embryonic neuronal cultures, were investigated. Enzymological assays and surface plasmon resonance were employed to quantify the kinetic parameters (K_M, k_cat) of CatD-mediated degradation of monomeric human Aβ42 vs. Aβ40, and the degradation of aggregated Aβ42 species was also characterized. Competitive inhibition assays were used to interrogate the relative inhibition of full-length human and mouse Aβ42 and Aβ40, as well as corresponding p3 fragments.

RESULTS

Genetic deletion of CatD resulted in 3- to 4-fold increases in insoluble, endogenous cerebral Aβ42 and Aβ40, exceeding the increases produced by deletion of an insulin-degrading enzyme, neprilysin or both, together with readily detectable intralysosomal deposits of endogenous Aβ42-all by 3 weeks of age. Quite significantly, CatD-KO mice exhibited ~ 30% increases in Aβ42/40 ratios, comparable to those induced by presenilin mutations. Mechanistically, the perturbed Aβ42/40 ratios were attributable to pronounced differences in the kinetics of degradation of Aβ42 vis-à-vis Aβ40. Specifically, Aβ42 shows a low-nanomolar affinity for CatD, along with an exceptionally slow turnover rate that, together, renders Aβ42 a highly potent competitive inhibitor of CatD. Notably, the marked differences in the processing of Aβ42 vs. Aβ40 also extend to p3 fragments ending at positions 42 vs. 40.

CONCLUSIONS

Our findings identify CatD as the principal intracellular Aβ-degrading protease identified to date, one that regulates Aβ42/40 ratios via differential degradation of Aβ42 vs. Aβ40. The finding that Aβ42 is a potent competitive inhibitor of CatD suggests a possible mechanistic link between elevations in Aβ42 and downstream pathological sequelae in AD.

A Single-Neuron: Current Trends and Future Prospects

The brain is an intricate network with complex organizational principles facilitating a concerted communication between single-neurons, distinct neuron populations, and remote brain areas. The communication, technically referred to as connectivity, between single-neurons, is the center of many investigations aimed at elucidating pathophysiology, anatomical differences, and structural and functional features. In comparison with bulk analysis, single-neuron analysis can provide precise information about neurons or even sub-neuron level electrophysiology, anatomical differences, pathophysiology, structural and functional features, in addition to their communications with other neurons, and can promote essential information to understand the brain and its activity. This review highlights various single-neuron models and their behaviors, followed by different analysis methods. Again, to elucidate cellular dynamics in terms of electrophysiology at the single-neuron level, we emphasize in detail the role of single-neuron mapping and electrophysiological recording. We also elaborate on the recent development of single-neuron isolation, manipulation, and therapeutic progress using advanced micro/nanofluidic devices, as well as microinjection, electroporation, microelectrode array, optical transfection, optogenetic techniques. Further, the development in the field of artificial intelligence in relation to single-neurons is highlighted. The review concludes with between limitations and future prospects of single-neuron analyses.

Effect of C-phycocyanin on HDAC3 and miRNA-335 in Alzheimer's disease

BACKGROUND

Amyloid-beta (Aβ) plaque deposits and neurofibrillary tangles containing tau proteins are the key pathognomonic manifestations of Alzheimer's disease (AD). Lack of holistic drugs for AD has reinvigorated enthusiasm in the natural product-based therapies. In this study, our idea to decipher the beneficial effects of C-phycocyanin (CPC) in the management of AD is buoyed by its multifaceted and holistic therapeutic effects.

METHODS

We evaluated the effect of CPC treatment on epigenetic factors and inflammatory mediators in a mouse with oligomeric Aβ1-42-induced AD. Besides, the cognitive function was evaluated by the spatial memory performance on a radial arm maze.

RESULTS

The results showed cognitive deficit in the mice with AD along with upregulated HDAC3 expression and diminished miRNA-335 and brain-derived neurotrophic factor (BDNF) expressions. In addition, inflammation was provoked (manifested by increased interleukins (IL)-6 and IL-1β) and neuronal apoptosis was accelerated (indicated by increased Bax, caspase-3, and caspase-9 along with decreased Bcl2) in the hippocampus of the mice with AD. Interestingly, CPC treatment in the mice with AD improved spatial memory performance and decreased the perturbations in the epigenetic and inflammatory biofactors.

CONCLUSION

These results underscore that mitigation of inflammation via regulation of epigenetic factors might be the key pathway underlying the ameliorative effect of CPC against the aberrations in AD. Our findings provide the rationale for considering CPC as a viable therapeutic option in the management of AD.

Nanoparticles as contrast agents for the diagnosis of Alzheimer’s disease: a systematic review

Nanoparticle (NP)-based magnetic contrast agents have opened the potential for MRI to be used for early diagnosis of Alzheimer’s disease (AD). This article aims to review the current progress of research in this field. A comprehensive literature search was performed based on PubMed, Medline, EMBASE, PsychINFO and Scopus databases using the following terms: ‘Alzheimer’s disease’ AND ‘nanoparticles’ AND ‘Magnetic Resonance Imaging.’ 33 studies were included that described the development and utility of various NPs for AD imaging, including their coating, functionalization, MRI relaxivity, toxicity and bioavailability. NPs show immense promise for neuroimaging, due to superior relaxivity and biocompatibility compared with currently available imaging agents. Consistent reporting is imperative for further progress in this field.

CIRBP Ameliorates Neuronal Amyloid Toxicity via Antioxidative and Antiapoptotic Pathways in Primary Cortical Neurons

It is generally accepted that the amyloid β (Aβ) peptide toxicity contributes to neuronal loss and is involved in the initiation and progression of Alzheimer's disease (AD). Cold-inducible RNA-binding protein (CIRBP) is reported to be a general stress-response protein, which is induced by different stress conditions. Previous reports have shown the neuroprotective effects of CIRBP through the suppression of apoptosis via the Akt and ERK pathways. The objective of this study is to examine the effect of CIRBP against Aβ-induced toxicity in cultured rat primary cortical neurons and attempt to uncover its underlying mechanism. Here, MTT, LDH release, and TUNEL assays showed that CIRBP overexpression protected against both intracellular amyloid β- (iAβ-) induced and Aβ _25-35-induced cytotoxicity in rat primary cortical neurons. Electrophysiological changes responsible for iAβ-induced neuronal toxicity, including an increase in neuronal resting membrane potentials and a decrease in K⁺ currents, were reversed by CIRBP overexpression. Western blot results further showed that Aβ _25-35 treatment significantly increased the level of proapoptotic protein Bax, cleaved caspase-3, and cleaved caspase-9 and decreased the level of antiapoptotic factor Bcl-2, but were rescued by CIRBP overexpression. Furthermore, CIRBP overexpression prevented the elevation of ROS induced by Aβ _25-35 treatment by decreasing the activities of oxidative biomarker and increasing the activities of key enzymes in antioxidant system. Taken together, our findings suggested that CIRBP exerted protective effects against neuronal amyloid toxicity via antioxidative and antiapoptotic pathways, which may provide a promising candidate for amyloid-based AD prevention or therapy.

Targeting alpha synuclein and amyloid beta by a multifunctional, brain-penetrant dopamine D2/D3 agonist D-520: Potential therapeutic application in Parkinson's disease with dementia

A significant number of people with Parkinson’s disease (PD) develop dementia in addition to cognitive dysfunction and are diagnosed as PD with dementia (PDD). This is characterized by cortical and limbic alpha synuclein (α-syn) accumulation, and high levels of diffuse amyloid beta (Aβ) plaques in the striatum and neocortical areas. In this regard, we evaluated the effect of a brain-penetrant, novel multifunctional dopamine D2/D3 agonist, D-520 on the inhibition of Aβ aggregation and disintegration of α-syn and Aβ aggregates in vitro using purified proteins and in a cell culture model that produces intracellular Aβ-induced toxicity. We further evaluated the effect of D-520 in a Drosophila model of Aβ_1-42 toxicity. We report that D-520 inhibits the formation of Aβ aggregates in vitro and promotes the disaggregation of both α-syn and Aβ aggregates. Finally, in an in vivo Drosophila model of Aβ_1-42 dependent toxicity, D-520 exhibited efficacy by rescuing fly eyes from retinal degeneration caused by Aβ toxicity. Our data indicate the potential therapeutic applicability of D-520 in addressing motor dysfunction and neuroprotection in PD and PDD, as well as attenuating dementia in people with PDD.

Spontaneous self-assembly of amyloid β (1-40) into dimers

The self-assembly and fibrillation of amyloid β (Aβ) proteins is the neuropathological hallmark of Alzheimer's disease. However, the molecular mechanism of how disordered monomers assemble into aggregates remains largely unknown. In this work, we characterize the assembly of Aβ (1-40) monomers into dimers using long-time molecular dynamics simulations. Upon interaction, the monomers undergo conformational transitions, accompanied by change of the structure, leading to the formation of a stable dimer. The dimers are stabilized by interactions in the N-terminal region (residues 5-12), in the central hydrophobic region (residues 16-23), and in the C-terminal region (residues 30-40); with inter-peptide interactions focused around the N- and C-termini. The dimers do not contain long β-strands that are usually found in fibrils.

Amyloid β oligomers inhibit growth of human cancer cells

Effects of amyloid beta (Aβ) oligomers on viability and function of cell lines such as NB4 (human acute promyelocytic leukemia), A549 (human lung cancer (adenocarcinomic alveolar basal epithelial tumor)) and MCF-7 (human breast cancer (invasive breast ductal carcinoma)) were investigated. Two types of Aβ oligomers were used in the study. The first type was produced in the presence of oligomerization inhibitor, hexafluoroisopropanol (HFIP). The second type of amyloids was assembled in the absence of the inhibitor. The first type preparation was predominantly populated with dimers and trimers, while the second type contained mostly pentadecamers. These amyloid species exhibited different secondary protein structure with considerable amount of antiparallel β sheet structural elements in HFIP oligomerized Aβ mixtures. The effect of the cell growth inhibition, which was stronger in the case of HFIP Aβ oligomers, was observed for all cell lines. Tests aiming at elucidating the effects of the amyloid species on cell cycles showed little differences between amyloid preparations. This prompts us to conclude that the effect on the cancer cell proliferation rate is less specific to the biological processes developing inside the cells during the proliferation. Therefore, cell growth inhibition may involve interactions with the peripheral parts of the cancer cells, such as a phospholipid membrane, and only in case of the NB4 cells, where accumulation of amyloid species inside the cells was detected, one may imply the opposite. In general, cancer cells were much less susceptible to the damaging effects of amyloid oligomers compared to earlier observations in mixed neuronal cell cultures.

Neuroprotective Approach of Anti-Cancer Microtubule Stabilizers Against Tauopathy Associated Dementia: Current Status of Clinical and Preclinical Findings

Neuronal microtubule (MT) tau protein provides cytoskeleton to neuronal cells and plays a vital role including maintenance of cell shape, intracellular transport, and cell division. Tau hyperphosphorylation mediates MT destabilization resulting in axonopathy and neurotransmitter deficit, and ultimately causing Alzheimer’s disease (AD), a dementing disorder affecting vast geriatric populations worldwide, characterized by the existence of extracellular amyloid plaques and intracellular neurofibrillary tangles in a hyperphosphorylated state. Pre-clinically, streptozotocin stereotaxically mimics the behavioral and biochemical alterations similar to AD associated with tau pathology resulting in MT assembly defects, which proceed neuropathological cascades. Accessible interventions like cholinesterase inhibitors and NMDA antagonist clinically provides only symptomatic relief. Involvement of microtubule stabilizers (MTS) prevents tauopathy particularly by targeting MT oriented cytoskeleton and promotes polymerization of tubulin protein. Multiple in vitro and in vivo research studies have shown that MTS can hold substantial potential for the treatment of AD-related tauopathy dementias through restoration of tau function and axonal transport. Moreover, anti-cancer taxane derivatives and epothiolones may have potential to ameliorate MT destabilization and prevent the neuronal structural and functional alterations associated with tauopathies. Therefore, this current review strictly focuses on exploration of various clinical and pre-clinical features available for AD to understand the neuropathological mechanisms as well as introduce pharmacological interventions associated with MT stabilization. MTS from diverse natural sources continue to be of value in the treatment of cancer, suggesting that these agents have potential to be of interest in the treatment of AD-related tauopathy dementia in the future.

Receptor-based pharmacophore modeling, virtual screening, and molecular docking studies for the discovery of novel GSK-3β inhibitors

Considering the emerging importance of glycogen synthase kinase 3 beta (GSK-3β) inhibitors in treatment of Alzheimer's disease, multi-protein structure receptor-based pharmacophore modeling was adopted to generate a 3D pharmacophore model for (GSK-3β) inhibitors. The generated 3D pharmacophore was then validated using a test set of 1235 compounds. The ZINCPharmer web tool was used to virtually screen the public ZINC database using the generated 3D pharmacophore. A set of 12,251 hits was produced and then filtered according to their lead-like properties, predicted central nervous system (CNS) activity, and Pan-assay interference compounds (PAINS) fragments to 630 compounds. Scaffold Hunter was then used to cluster the filtered compounds according to their chemical structure framework. From the different clusters, 123 compounds were selected to cover the whole chemical space of the obtained hits. The SwissADME online tool was then used to filter out the compounds with undesirable pharmacokinetic properties giving a set of 91 compounds with promising predicted pharmacodynamic and pharmacokinetic properties. To confirm their binding capability to the GSK-3β binding site, molecular docking simulations were performed for the final 91 compounds in the GSK-3β binding site. Twenty-five compounds showed acceptable binding poses that bind to the key amino acids in the binding site Asp133 and Val135 with good binding scores. The quinolin-2-one derivative ZINC67773573 was found to be a promising lead for designing new GSK-3β inhibitors for Alzheimer's disease treatment. Graphical abstract A 3D pharmacophore model for the discovery of novel (GSK-3β) inhibitors.

Amyloid-ß promotes neurotoxicity by Cdk5-induced p53 stabilization

Neurodegeneration in selective brain areas underlies the pathology of Alzheimer's disease (AD). Although oligomeric amyloid-β (Aβ) plays a central role in the AD pathogenesis, the mechanism of neuronal loss in response to Aβ remains elusive. The p53 tumor suppressor protein, a key regulator of cell apoptosis, has been described to accumulate in affected brain areas from AD patients. However, whether p53 plays any role in AD pathogenesis remains unknown. To address this issue, here we investigated the involvement of p53 on Aß-induced neuronal apoptosis. We found that exposure of neurons to oligomers of the amyloidogenic fragment 25-35 of the Aß peptide (Aβ_25-35) promoted p53 protein phosphorylation and stabilization, leading to mitochondrial dysfunction and neuronal apoptosis. To address the underlying mechanism, we focused on cyclin dependent kinase-5 (Cdk5), a known p53-phosphorylating kinase. The results revealed that Aβ_25-35 treatment activated Cdk5, and that inhibiting Cdk5 activity prevented p53 protein stabilization. Furthermore, Aβ_25-35-mediated mitochondrial dysfunction and neuronal apoptosis were prevented by both genetic and pharmacological inhibition of either p53 or Cdk5 activities. This effect was mimicked with the full-length peptide Aβ_1-42. To confirm the mechanism in vivo, Aβ_25-35 was stereotaxically injected in the cerebral right ventricle of mice, a treatment that caused p53 protein accumulation, dendrite disruption and neuronal death. Furthermore, these effects were prevented in p53 knockout mice or by pharmacologically inhibiting p53. Thus, Aβ_25-35 triggers Cdk5 activation to induce p53 phosphorylation and stabilization, which leads to neuronal damage. Inhibition of the Cdk5-p53 pathway may therefore represent a novel therapeutic strategy against Aβ-induced neurodegeneration.

Effect of Cell Inner Pressure on Deposition Volume in Microinjection

Microinjection is a widely used technique for introducing exogenous materials into cells. Many applications of microinjection, such as gene editing and drug testing, rely on the accurate control of the deposition volume. However, the deposition volume in microinjection is presently calibrated in an open medium without considering the cell inner pressure effect, which we experimentally show in this paper that it can induce an error as large as 30% between the actual deposition volume and the set volume. In this work, the relationship between the cell inner pressure and the deposition volume was analytically modeled and experimentally validated. On the basis of the developed model, the cell inner pressure of a given cell type can be well estimated from the injection pressure and the resulting deposition volume. The quantitated cell inner pressure is then used to reduce the error between the set volume and the actual deposition volume. Experiments conducted on human bladder cancer cells (T24 and RT4) showed that T24 cells have a higher inner pressure than RT4 cells (405 ± 45 Pa vs 341 ± 34 Pa), and after compensating for the cell inner pressure, the error between the intended set volume and the actual deposition volume into a cell became less than 3%.

A Bifunctional Anti-Amyloid Blocks Oxidative Stress and the Accumulation of Intraneuronal Amyloid-Beta

There is growing recognition regarding the role of intracellular amyloid beta (Aβ) in the Alzheimer’s disease process, which has been linked with aberrant signaling and the disruption of protein degradation mechanisms. Most notably, intraneuronal Aβ likely underlies the oxidative stress and mitochondrial dysfunction that have been identified as key elements of disease progression. In this study, we employed fluorescence imaging to explore the ability of a bifunctional small molecule to reduce aggregates of intracellular Aβ and attenuate oxidative stress. Structurally, this small molecule is comprised of a nitroxide spin label linked to an amyloidophilic fluorene and is known as spin-labeled fluorene (SLF). The effect of the SLF on intracellular Aβ accumulation and oxidative stress was measured in MC65 cells, a human neuronal cell line with inducible expression of the amyloid precursor protein and in the N2a neuronal cell line treated with exogenous Aβ. Super-resolution microscopy imaging showed SLF decreases the accumulation of intracellular Aβ. Confocal microscopy imaging of MC65 cells treated with a reactive oxygen species (ROS)-sensitive dye demonstrated SLF significantly reduces the intracellular Aβ-induced ROS signal. In order to determine the contributions of the separate SLF moieties to these protective activities, experiments were also carried out on cells with nitroxides lacking the Aβ targeting domain or fluorene derivatives lacking the nitroxide functionality. The findings support a synergistic effect of SLF in counteracting both the conformational toxicity of both endogenous and exogenous Aβ, its promotion of ROS, and Aβ metabolism. Furthermore, these studies demonstrate an intimate link between ROS production and Aβ oligomer formation.