Aβ Oligomers Research Articles

Magnetic stirring with iron oxide nanospinners accretes neurotoxic Aβ42 oligomers into phagocytic clearable plaques for Alzheimer's disease treatment

An increasing number of medications have been explored to treat the progressive and irreversible Alzheimer's disease (AD) that stands as the predominant form of dementia among neurodegenerative ailments. However, assertions about toxic side effects of these drugs are a significant hurdle to overcome, calling for drug-free nanotherapeutics. Herein, a new therapeutic strategy devoid of conventional drugs or other cytotoxic species was developed. The constructed superparamagnetic iron oxide nanoparticles (SPIONs) nanospinners can accrete neurotoxic β-amyloid 42 oligomers (oAβ42) into aggregated magnetic plaques (mpAβ) by mechanical rotating force via remote interaction between nanoparticles and the applied magnetic field. While the cellular uptake of mpAβ attained from the magnetic stirring treatment by neuronal cells is severely limited, the facile phagocytic uptake of mpAβ by microglial cells leads to the polarization of the brain macrophages to M2 phenotype and thus the increased anti-inflammatory responses to the treatment. The SPION stirring treatment protects the AD mice from memory deterioration and maintain cognitive ability as evidenced from both nesting and Barnes maze tests. The examination of the oAβ42 injected brain tissues with the stirring treatment showed significant amelioration of functional impairment of neurons, microglia, astrocytes and oligodendrocytes alongside no obvious tissue damage caused by stirring meanwhile complete degradation of SPION was observed at day 7 after the treatment. The in vitro and animal data of this work strongly corroborate that this new modality of undruggable stirring treatment with SPIONs provides a new feasible strategy for developing novel AD treatments.

Disrupted mitochondrial response to nutrients is a presymptomatic event in the cortex of the APPSAA knock-in mouse model of Alzheimer's disease.

Reduced brain energy metabolism, mammalian target of rapamycin (mTOR) dysregulation, and extracellular amyloid beta (Aβ) oligomer (xcAβO) buildup are some well-known Alzheimer's disease (AD) features; how they promote neurodegeneration is poorly understood. We previously reported that xcAβOs inhibit nutrient-induced mitochondrial activity (NiMA) in cultured neurons. We now report NiMA disruption in vivo. Brain energy metabolism and oxygen consumption were recorded in heterozygous amyloid precursor protein knock-in (APPSAA) mice using two-photon fluorescence lifetime imaging and multiparametric photoacoustic microscopy. NiMA is inhibited in APPSAA mice before other defects are detected in these Aβ-producing animals that do not overexpress APP or contain foreign DNA inserts into genomic DNA. Glycogen synthase kinase 3 (GSK3β) signals through mTORC1 to regulate NiMA independently of mitochondrial biogenesis. Inhibition of GSK3β with TWS119 stimulates NiMA in cultured human neurons, and mitochondrial activity and oxygen consumption in APPSAA mice. NiMA disruption in vivo occurs before plaques, neuroinflammation, and cognitive decline in APPSAA mice, and may represent an early stage in human AD. Amyloid beta blocks communication between lysosomes and mitochondria in vivo. Nutrient-induced mitochondrial activity (NiMA) is disrupted long before the appearance of Alzheimer's disease (AD) histopathology in heterozygous amyloid precursor protein knock-in (APPSAA/+) mice. NiMA is disrupted long before learning and memory deficits in APPSAA/+ mice. Pharmacological interventions can rescue AD-related NiMA disruption in vivo.

The KEAP1/PGAM5/AIFM1-Mediated oxeiptosis pathway in Alzheimer’s disease

BackgroundAlzheimer’s Disease (AD) is a neurodegenerative disease with mitochondrial dysfunction and oxidative stress. Oxeiptosis is a cell death pathway sensitive to reactive oxygen species (ROS). This study investigates the role of oxeiptosis pathway and mitochondrial damage in AD. MethodsAn AD model was developed in C57BL/6 mice by injecting Aβ1-42 oligomers into the brain. Cognitive function was tested using the Morris water maze. Exposure of HT22 mouse hippocampal neurons to H2O2 induces oxidative stress. Protein levels of KEAP1, PGAM5 and AIFM1 were analyzed by western blot, and mitochondrial damage was observed with electron microscopy. Cell survival rates were using the CCK8 assay and flow cytometry after knocking down KEAP1, PGAM5 and AIFM1. ResultsThe protein concentrations of KEAP1, PGAM5 and AIFM1 were found to be elevated in the hippocampal tissues of AD mice compared to control group, accompanied by mitochondrial damage in the hippocampal neurons of the AD group. Similarly, in the HT22 oxidative stress model, there was an increase in the protein levels of KEAP1, PGAM5 and AIFM1, along with observed mitochondrial damage. Following individual and combined knockdown of KEAP1, PGAM5 and AIFM1, cell survival rates under oxidative stress conditions were higher compared to H2O2 group, with no significant difference in cell survival rates among the knockdown groups. ConclusionThis research underscores the critical role of the KEAP1/PGAM5/AIFM1-mediated oxeiptosis pathway in neuronal cell death, offering insights into potential therapeutic targets for mitigating neurodegeneration in AD.

Structural Reorganization Mechanism of the Aβ42 Fibril Mediated by N-Substituted Oligopyrrolamide ADH-353.

The inhibition of amyloid-β (Aβ) fibrillation and clearance of Aβ aggregates have emerged as a potential pharmacological strategy to alleviate Aβ aggregate-induced neurotoxicity in Alzheimer's disease (AD). Maity et al. shortlisted ADH-353 from a small library of positively charged N-substituted oligopyrrolamides for its notable ability to inhibit Aβ fibrillation, disintegrate intracellular cytotoxic Aβ oligomers, and alleviate Aβ-induced cytotoxicity in the SH-SY5Y and N2a cells. However, the molecular mechanism through which ADH-353 interacts with the Aβ42 fibrils, leading to their disruption and subsequent clearance, remains unclear. Thus, a detailed molecular mechanism underlying the disruption of neurotoxic Aβ42 fibrils (PDB ID 2NAO) by ADH-353 has been illuminated in this work using molecular dynamics simulations. Interestingly, conformational snapshots during simulation depicted the shortening and disappearance of β-strands and the emergence of a helix conformation, indicating a loss of the well-organized β-sheet-rich structure of the disease-relevant Aβ42 fibril on the incorporation of ADH-353. ADH-353 binds strongly to the Aβ42 fibril (ΔGbinding= -142.91 ± 1.61 kcal/mol) with a notable contribution from the electrostatic interactions between positively charged N-propylamine side chains of ADH-353 with the glutamic (Glu3, Glu11, and Glu22) and aspartic (Asp7 and Asp23) acid residues of the Aβ42 fibril. This aligns well with heteronuclear single quantum coherence NMR studies, which depict that the binding of ADH-353 with the Aβ peptide is driven by electrostatic and hydrophobic contacts. Furthermore, a noteworthy decrease in the binding affinity of Aβ42 fibril chains on the incorporation of ADH-353 indicates the weakening of interchain interactions leading to the disruption of the double-horseshoe conformation of the Aβ42 fibril. The illumination of key interactions responsible for the destabilization of the Aβ42 fibril by ADH-353 in this work will greatly aid in designing new chemical scaffolds with enhanced efficacy for the clearance of Aβ aggregates in AD.

Relationship between the response to donepezil and plasma amyloid beta oligomers in patients with Alzheimer's disease.

To date, there is no reported effective biomarker that can predict which Alzheimer's disease (AD) patients will respond to donepezil and which will not. This study aimed to investigate whether baseline values of Aβ oligomers (AβOs), measured by the Multimer Detection System-Oligomeric Aβ (MDS-OAβ), can be used to predict responders after 6 months of donepezil medication. The study enrolled 104 patients diagnosed with probable AD. After 6 months of donepezil medication, the response to treatment was evaluated by re-assessing the Korean version of the Mini-Mental State Examination (K-MMSE) and Clinical Dementia Rating scale-Sum of Box (CDR-SB) scales conducted at baseline. The patients were categorized into two groups according to the baseline MDS-OAβ values known as the cut-off for AD diagnosis: a group with values below 0.78 and another group with values equal to or above 0.78. After 6 months of medication, the number of responders was 50 (49.5%). Responders exhibited significantly worse baseline CDR, CDR-SB, K-MMSE, and Barthel index compared with non-responders. There was a significantly higher number of responders among patients with MDS-OAβ values below the cut-off of 0.78 compared with those with values equal to or above this threshold. Furthermore, there was a significant improvement in the K-MMSE and CDR-SB after 6 months of donepezil medication in patients with MDS-OAβ values below 0.78 compared with those with values equal to or above 0.78. Baseline MDS-OAβ values might constitute a novel biochemical marker for the efficacy of 6 months of donepezil treatment in AD. Geriatr Gerontol Int 2024; ••: ••-••.

Repeated exposure to novelty promotes resilience against the amyloid-beta effect through dopaminergic stimulation.

The accumulation of beta-amyloid peptide (Aβ) in the forebrain leads to cognitive dysfunction and neurodegeneration in Alzheimer's disease. Studies have shown that individuals with a consistently cognitively active lifestyle are less vulnerable to Aβ toxicity. Recent research has demonstrated that intrahippocampal Aβ can impact catecholaminergic release and spatial memory. Interestingly, exposure to novelty stimuli has been found to stimulate the release of catecholamines in the hippocampus. However, it remains uncertain whether repeated enhancing catecholamine activity can effectively alleviate cognitive impairment in individuals with Alzheimer's disease. Our primary aim was to investigate whether repeated exposure to novelty could enable cognitive resilience against Aβ. This protection could be achieved by modulating catecholaminergic activity within the hippocampus. To investigate this hypothesis, we subjected mice to three different conditions-standard housing (SH), repeated novelty (Nov), or daily social interaction (Soc) for one month. We then infused saline solution (SS) or Aβ (Aβ1-42) oligomers intrahippocampally and measured spatial memory retrieval in a Morris Water Maze (MWM). Stereological analysis and extracellular baseline dopamine levels using in vivo microdialysis were assessed in independent groups of mice. The mice that received Aβ1-42 intrahippocampal infusions and remained in SH or Soc conditions showed impaired spatial memory retrieval. In contrast, animals subjected to the Nov protocol demonstrated remarkable resilience, showing strong spatial memory expression even after Aβ1-42 intrahippocampal infusion. The stereological analysis indicated that the Aβ1-42 infusion reduced the tyrosine hydroxylase axonal length in SH or Soc mice compared to the Nov group. Accordingly, the hippocampal extracellular dopamine levels increased significantly in the Nov groups. These compelling results demonstrate the potential for repeated novelty exposure to strengthen the dopaminergic system and mitigate the toxic effects of Aβ1-42. They also highlight new and promising therapeutic avenues for treating and preventing AD, especially in its early stages.

Human brain organoids containing microglia that have arisen innately adapt to a β-amyloid challenge better than those in which microglia are integrated by co-culture

BackgroundAlzheimer disease (AD) is a heterogenous and multifactorial disease, and its pathology is partly driven by microglia and their activated phenotype. Brain organoids (BOs) are gaining prominence as a relevant model of the human brain for the study of AD; however, BOs are commonly devoid of microglia. To overcome this limitation, current protocols incorporate microglia through either (1) co-culture (BO co-culture), or (2) molecular manipulation at critical windows of BO development to have microglia arise innately (BO innate cultures). It is currently unclear whether the microglia incorporated into BOs by either of these two protocols differ in function.MethodsAt in vitro day 90, BO innate cultures and BO-co-cultures were challenged with the AD-related β-amyloid peptide (Aβ) for up to 72 h. After Aβ challenge, BOs were collected for immunoblotting. Immunoblots compared immunodensity and protein banding of Aβ and ionized calcium-binding adapter molecule 1 (IBA1, a marker of microglial activation) in BOs. The translational potential of these observations was supported using 56 human cortical samples from neurocognitively normal donors and patients with early-onset AD and late-onset AD. Statistical analyses were conducted using the Kruskal–Wallis test, a two-way ANOVA, or a simple linear regression, and where applicable, followed by Dunn’s or Sidak’s test.ResultsWe show that BO co-cultures promote Aβ oligomerization as early as 24 h and this coincides with a significant increase in IBA1 levels. In contrast, the Aβs do not oligomerize in BO innate cultures and the IBA1 response was modest and only emerged after 48 h. In human cortical samples, we found IBA1 levels correlated with age at onset, age at death, and the putative diagnostic Aβ(1–42)/Aβ(1–40) ratio (particularly in their oligomeric forms) in a sex-dependent manner.ConclusionsOur unique observations suggest that BOs with innate microglia model the response of a healthy brain to Aβ, and by extension the initial stages of Aβ challenge. It would be impossible to model these early stages of pathogenesis in BOs where microglia are already compromised, such as those with microglia incorporated by co-culture.

Alternate-day fasting improves cognitive and brain energy deficits by promoting ketone metabolism in the 3xTg mouse model of Alzheimer's disease

Alzheimer's disease (AD) is characterized by disorders in brain energy. The lack of sufficient energy for nerve function leads to cognitive dysfunction and massive neuronal loss in AD. Ketone bodies are an alternative to glucose as a source of energy in the brain, and alternate-day fasting (ADF) promotes the production of the ketone body β-hydroxybutyric acid (βOHB). In this study, 7-month-old male WT mice and 3xTg mice underwent dietary control for 20 weeks. We found that ADF increased circulating βOHB concentrations in 3xTg mice, improved cognitive function, reduced anxiety-like behaviors, improved hippocampal synaptic plasticity, and reduced neuronal loss, Aβ oligomers and tau hyperphosphorylation. In addition, ADF improved mitochondrial bioenergetic function by promoting brain ketone metabolism and rescued brain energy deficits in 3xTg mice. A safety evaluation showed that ADF improved exercise endurance and liver and kidney function in 3xTg mice without negatively affecting muscle motor and heart functions. This study provides a theoretical basis and strong support for the application of ADF as a non-drug strategy for preventing and treating brain energy defects in the early stage of AD.

Generation of hiPSC-derived brain microvascular endothelial cells using a combination of directed differentiation and transcriptional reprogramming strategies.

The blood-brain barrier (BBB), formed by specialized brain microvascular endothelial cells (BMECs), regulates brain function in health and disease. In vitro modeling of the human BBB is limited by the lack of robust hiPSC protocols to generate BMECs. Here, we report generation, transcriptomic and functional characterization of reprogrammed BMECs (rBMECs) by combining hiPSC differentiation into BBB-primed endothelial cells and reprogramming with two BBB transcription factors FOXF2 and ZIC3. rBMECs express a subset of the BBB gene repertoire including tight junctions and transporters, exhibit stronger paracellular barrier properties, lower caveolar-mediated transcytosis, and similar p-Glycoprotein activity compared to primary HBMECs. They can acquire an inflammatory phenotype when treated with oligomeric Aβ42. rBMECs integrate with hiPSC-derived pericytes and astrocytes to form a 3D neurovascular system using the MIMETAS microfluidics platform. This novel 3D system resembles the in vivo BBB at structural and functional levels to enable investigation of pathogenic mechanisms of neurological diseases.

Enhanced phagocytosis associated with multinucleated microglia via Pyk2 inhibition in an acute β-amyloid infusion model

Multinucleated microglia have been observed in contexts associated with infection, inflammation, and aging. Though commonly linked to pathological conditions, the larger cell size of multinucleated microglia might enhance their phagocytic functions, potentially aiding in the clearance of brain debris and suggesting a reassessment of their pathological significance. To assess the phagocytic capacity of multinucleated microglia and its implications for brain debris clearance, we induced their formation by inhibiting Pyk2 activity using the pharmacological inhibitor PF-431396, which triggers cytokinesis regression. Multinucleated microglia demonstrate enhanced phagocytic function, as evidenced by their increased capacity to engulf β-amyloid (Aβ) oligomers. Concurrently, the phosphorylation of Pyk2, induced by Aβ peptide, was diminished upon treatment with a Pyk2 inhibitor (Pyk2-Inh, PF-431396). Furthermore, the increased expression of Lamp1, a lysosomal marker, with Pyk2-inh treatment, suggests an enhancement in proteolytic activity. In vivo, we generated an acute Alzheimer’s disease (AD) model by infusing Aβ into the brains of Iba-1 EGFP transgenic (Tg) mice. The administration of the Pyk2-Inh led to an increased migration of microglia toward amyloid deposits in the brains of Iba-1 EGFP Tg mice, accompanied by morphological activation, suggesting a heightened affinity for Aβ. In human microglia, lipopolysaccharide (LPS)-induced inflammatory responses showed that inhibition of Pyk2 signaling significantly reduced the transcription and protein expression of pro-inflammatory markers. These results suggest that Pyk2 inhibition can modulate microglial functions, potentially reducing neuroinflammation and aiding in the clearance of neurodegenerative disease markers. This highlights Pyk2 as a promising target for therapeutic intervention in neurodegenerative diseases.

Repurposing Anidulafungin for Alzheimer's Disease via Fragment-Based Drug Discovery.

The misfolding and aggregation of beta-amyloid (Aβ) peptides have been implicated as key pathogenic events in the early stages of Alzheimer's disease (AD). Inhibiting Aβ aggregation represents a potential disease-modifying therapeutic approach to AD treatment. Previous studies have identified various molecules that inhibit Aβ aggregation, some of which share common chemical substructures (fragments) that may be key to their inhibitory activity. Employing fragment-based drug discovery (FBDD) methods may facilitate the identification of these fragments, which can subsequently be used to screen new inhibitors and provide leads for further drug development. In this study, we used an in silico FBDD approach to identify 17 fragment clusters that are significantly enriched among Aβ aggregation inhibitors. These fragments were then used to screen anti-infective agents, a promising drug class for repurposing against amyloid aggregation. This screening process identified 16 anti-infective drugs, 5 of which were chosen for further investigation. Among the 5 candidates, anidulafungin, an antifungal compound, showed high efficacy in inhibiting Aβ aggregation in vitro. Kinetic analysis revealed that anidulafungin selectively blocks the primary nucleation step of Aβ aggregation, substantially delaying Aβ fibril formation. Cell viability assays demonstrated that anidulafungin can reduce the toxicity of oligomeric Aβ on BV2 microglia cells. Molecular docking simulations predicted that anidulafungin interacted with various Aβ species, including monomers, oligomers, and fibrils, potentially explaining its activity against Aβ aggregation and toxicity. This study suggests that anidulafungin is a potential drug to be repurposed for AD, and FBDD is a promising approach for discovering drugs to combat Aβ aggregation.

Abstract Tu047: Carbonic anhydrase inhibitors (CAIs) mitigate cardiac amyloid β pathology, attenuating neuro-signaling adverse remodeling and improving cardiac function in the Tg2676- AD mouse model.

FDA-approved carbonic anhydrase inhibitors (CAIs) have been shown to attenuate Aβ pathology, neurodegeneration, and cerebrovascular dysfunction in models of Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA), suggesting a key role for CAs as a novel and previously unexplored target for AD therapy. Amyloid-β accumulation severely impairs the cerebral neuro-signaling pathway with a progressive loss in neurotrophic factors (like BDNF), potentially also affecting the cardiac nervous system and culminating in lethal heart dysfunction. Yet, no studies have proposed the use of CAIs for treating and preventing the systemic and cardiac effects of amyloidosis and AD. Here, we explored for the first time, the protective effects of a chronic CAIs therapeutic regimen against cardiac amyloid pathology, neuronal fibers’ loss, and heart neurotrophic dysregulation in Tg2576 mice, a widely used model of AD and cerebral amyloidosis. Cardiac fibrosis enhancement along with progressive Aβ deposition in the heart seriously affected the cardiac neuro-signaling pathway culminating in a robust decline of BDNF expression associated with myocardial adrenergic nerve fibers and regenerated nerve endings impoverishment (stained with TH and GAP-43 respectively) in 13-month-old Tg2576 mice compared to age-matched WT littermates. These degenerative mechanisms severely compromised heart function, evidenced by a decline of both ejection fraction and fraction shortening percentage in Tg2576 animals. Accordingly, we observed that human Aβ40 or Aβ42 oligomers’ treatment drastically reduced BDNF and GAP-43 expression in human neuronal cells and human cardiomyocytes. Notably, long-term CAIs treatment in Tg2576 mice reduced Aβ accumulation in the heart tissue and reverted cardiac neuro-signaling pathway adverse remodeling, thus ameliorating heart function, as evidenced through speckle tracking-based strain echocardiography analysis. These in vivo results were validated by in vitro experiments both in neuronal and cardiac cells. These findings suggest a new beneficial role of CAIs in preventing the Aβ induced cardiovascular remodeling and neuro-signaling deregulation for the first time in the Tg2576 model of AD. Taken together with the positive effects of CAIs on cerebrovascular function and cognition, this study paves the way for future clinical trials aimed at repurposing FDA-approved CAIs to prevent and correct both central and peripheral pathologies induced by AD and amyloidosis.

A small TAT-TrkB peptide prevents BDNF receptor cleavage and restores synaptic physiology in Alzheimer's disease

In Alzheimer’s disease (AD), amyloid β (Aβ)-triggered cleavage of TrkB-FL impairs Brain-derived neurotrophic factor (BDNF) signaling, thereby compromising neuronal survival, differentiation, as well as synaptic transmission and plasticity. Using cerebrospinal fluid and post-mortem human brain samples, we show that TrkB-FL cleavage occurs from the early stages of the disease and increases as function of pathology severity. To explore the therapeutic potential of this disease mechanism, we designed small TAT-fused peptides and screened their ability to prevent TrkB-FL receptor cleavage. Among these, a TAT-TrkB peptide with a lysine-lysine linker prevented TrkB-FL cleavage both in vitro and in vivo and rescued synaptic deficits induced by oligomeric Aβ in hippocampal slices. Furthermore, this TAT-TrkB peptide improved the cognitive performance, ameliorated synaptic plasticity deficits and prevented Tau pathology progression in vivo in the 5XFAD mouse model of AD. No evidence of liver or kidney toxicity was found. We provide proof-of-concept evidence for the efficacy and safety of this therapeutic strategy and anticipate that this TAT-TrkB peptide has the potential of a disease-modifying drug that can prevent and/or reverse cognitive deficits in patients with AD.

Honokiol relieves hippocampal neuronal damage in Alzheimer's disease by activating the SIRT3-mediated mitochondrial autophagy.

This work elucidated the effect of honokiol (HKL) on hippocampal neuronal mitochondrial function in Alzheimer's disease (AD). APP/PS1 mice were used as AD mice models and exposed to HKL and 3-TYP. Morris water maze experiment was performed to appraise cognitive performance of mice. Hippocampal Aβ+ plaque deposition and neuronal survival was evaluated by immunohistochemistry and Nissl staining. Hippocampal neurons were dissociated from C57BL/6 mouse embryos. Hippocampal neuronal AD model was constructed by Aβ oligomers induction and treated with HKL, CsA and 3-TYP. Neuronal viability and apoptosis were detected by cell counting kit-8 assay and TUNEL staining. mRFP-eGFP-LC3 assay, MitoSOX Red, dichlorodihydrofluorescein diacetate, and JC-1 staining were performed to monitor neuronal autophagosomes, mitochondrial reactive oxygen species (ROS), neuronal ROS, and mitochondrial membrane potential. Autophagy-related proteins were detected by Western blot. In AD mice, HKL improved cognitive function, relieved hippocampal Aβ1-42 plaque deposition, promoted hippocampal neuron survival, and activated hippocampal SIRT3 expression and mitochondrial autophagy. These effects of HKL on AD mice were abolished by 3-TYP treatment. In hippocampal neuronal AD model, HKL increased neuronal activity, attenuated neuronal apoptosis and Aβ aggregation, activated SIRT3 and mitochondrial autophagy, reduced mitochondrial and neuronal ROS, and elevated mitochondrial membrane potential. CsA treatment and 3-TYP treatment abrogated the protection of HKL on hippocampal neuronal AD model. The promotion of mitochondrial autophagy by HKL in hippocampal neuronal AD model was counteracted by 3-TYP. HKL activates SIRT3-mediated mitochondrial autophagy to mitigate hippocampal neuronal damage in AD. HKL may be effective in treating AD.

Monomeric Amyloid Peptide-induced Toxicity in Human Oligodendrocyte Cell Line and Mouse Brain Primary Mixed-glial Cell Cultures: Evidence for a Neuroprotective Effect of Neurosteroid 3α-O-allyl-allopregnanolone.

Amyloid-peptide (Aβ) monomeric forms (ABM) occurring in presymptomatic Alzheimer's disease (AD) brain are thought to be devoid of neurotoxicity while the transition/aggregation of ABM into oligomers is determinant for Aβ-induced toxicity since Aβ is predominantly monomeric up to 3µM and aggregates over this concentration. However, recent imaging and/or histopathological investigations revealed alterations of myelin in prodromal AD brain in absence of aggregated Aβ oligomers, suggesting that ABM may induce toxicity in myelin-producing cells in early AD-stages. To check this hypothesis, here we studied ABM effects on the viability of the Human oligodendrocyte cell line (HOG), a reliable oligodendrocyte model producing myelin proteins. Furthermore, to mimic closely interactions between oligodendrocytes and other glial cells regulating myelination, we investigated also ABM effects on mouse brain primary mixed-glial cell cultures. Various methods were combined to show that ABM concentrations (600nM-1µM), extremely lower than 3µM, significantly decreased HOG cell and mouse brain primary mixed-glial cell survival. Interestingly, flow-cytometry studies using specific cell-type markers demonstrated that oligodendrocytes represent the most vulnerable glial cell population affected by ABM toxicity. Our work also shows that the neurosteroid 3α-O-allyl-allopregnanolone BR351 (250 and 500nM) efficiently prevented ABM-induced HOG and brain primary glial cell toxicity. Bicuculline (50-100nM), the GABA-A-receptor antagonist, was unable to block/reduce BR351 effect against ABM-induced HOG and primary glial cell toxicity, suggesting that BR351-evoked neuroprotection of these cells may not depend on GABA-A-receptor allosterically modulated by neurosteroids. Altogether, our results suggest that further exploration of BR351 therapeutic potential may offer interesting perspectives to develop effective neuroprotective strategies.

Aggregation Dynamics of a 150 kDa Aβ42 Oligomer: Insights from Cryo Electron Microscopy and Multimodal Analysis.

I.Protein misfolding is a widespread phenomenon that can result in the formation of protein aggregates, which are markers of various disease states, including Alzheimer's disease (AD). In AD, amyloid beta (Aβ) peptides, particularly Aβ40 and Aβ42, are key players in the disease's progression, as they aggregate to form amyloid plaques and contribute to neuronal toxicity. Recent research has shifted attention from solely Aβ fibrils to also include Aβ protofibrils and oligomers as potentially critical pathogenic agents. Particularly, oligomers demonstrate greater toxicity compared to other Aβ specie. Hence, there is an increased interest in studying the correlation between toxicity and their structure and aggregation pathway. The present study investigates the aggregation of a 150 kDa Aβ42 oligomer that does not lead to fibril formation over time. Using negative stain transmission electron microscopy (TEM), size exclusion chromatography (SEC), dynamic light scattering (DLS), and cryo-electron microscopy (cryo-EM), we demonstrate that 150 kDa Aβ42 oligomers form higher-order string-like assemblies over time. The strings are unique from the classical Aβ fibril structures. The significance of our work lies in elucidating molecular behavior of a novel non-fibrillar form of Aβ42 aggregate.

Correlation of brain tissue volume loss with inflammatory biomarkers IL1β, P-tau, T-tau, and NLPR3 in the aging cognitively impaired population.

Blood inflammatory biomarkers have emerged as important tools for diagnosing, assessing treatment responses, and predicting neurodegenerative diseases. This study evaluated the associations between blood inflammatory biomarkers and brain tissue volume loss in elderly people. This study included 111 participants (age 67.86 ± 8.29 years; 32 men and 79 women). A battery of the following blood inflammatory biomarkers was measured, including interleukin 1-beta (IL1β), NACHT, LRR, and PYD domains-containing protein 3 (NLRP3), monomer Aβ42 (mAβ), oligomeric Aβ42 (oAβ), miR155, neurite outgrowth inhibitor A (nogo-A), phosphorylated tau (P-tau), and total tau (T-tau). Three-dimensional T1-weight images (3D T1WI) of all participants were prospectively obtained and segmented into gray matter and white matter to measure the gray matter volume (GMV), white matter volume (WMV), and gray-white matter boundary tissue volume (gwBTV). The association between blood biomarkers and tissue volumes was assessed using voxel-based and region-of-interest analyses. GMV and gwBTV significantly decreased as the levels of IL1β and T-tau increased, while no significant association was found between the level of P-tau and the three brain tissue volumes. Three brain tissue volumes were negatively correlated with the levels of IL1β, P-tau, and T-tau in the hippocampus. Specifically, IL1β and T-tau levels showed a distinct negative association with the three brain tissue volume losses in the hippocampus. In addition, gwBTV was negatively associated with the level of NLRP3. The observed association between brain tissue volume loss and elevated levels of IL1β and T-tau suggests that these biomarkers in the blood may serve as potential biomarkers of cognitive impairment in elderly people. Thus, IL1β and T-tau could be used to assess disease severity and monitor treatment response after diagnosis in elderly people who are at risk of cognitive decline.

Characterization of Olive Oil Phenolic Extracts and Their Effects on the Aggregation of the Alzheimer's Amyloid-β Peptide and Tau.

The dietary consumption of extra virgin olive oil (EVOO) is believed to slow the progression of Alzheimer's disease (AD) symptoms. Its protective mechanisms are unclear, but specific EVOO phenolic compounds can individually impede the aggregation of amyloid-β (Aβ) peptides and the microtubule-associated protein tau, two important pathological manifestations of AD. It is unknown, however, whether the numerous and variable phenolic compounds that are consumed in dietary EVOO can collectively alter tau and Aβ aggregation as effectively as the individual compounds. The activity of these complex mixtures against Aβ and tau may be moderated by competition between active and nonactive phenolic components and by extensive derivatizations and isomerization. Here, phenolic mixtures extracted from two different EVOO sources are characterized and tested for how they modulate the aggregation of Aβ40 peptide and tau peptides in vitro. The chromatographic and NMR analysis of Greek and Saudi Arabian EVOO phenolic extracts reveals that they have different concentration profiles, and over 30 compounds are identified. Thioflavin T fluorescence and circular dichroism measurements show that relatively low concentrations (<20 μg/mL) of the Greek and Saudi extracts reduce the rate of Aβ40 aggregation and fibril mass, despite the extracts having different phenolic profiles. By contrast, the Greek extract reduces the rate of tau aggregation only at very high phenolic concentrations (>100 μg/mL). Most compounds in the extracts bind to preformed Aβ40 fibrils and release soluble Aβ oligomers that are mildly toxic to SH-SY5Y cells. Much higher (500 μg/mL) extract concentrations are required to remodel tau filaments into oligomers, and a minimal binding of phenolic compounds to the preformed filaments is observed. It is concluded that EVOO extracts having different phenol profiles are similarly capable of modulating Aβ40 aggregation and fibril morphology in vitro at relatively low concentrations but are less efficient at modulating tau aggregation. Over 2 M tonnes of EVOO are consumed globally each year as part of the Mediterranean diet, and the results here provide motivation for further clinical interrogation of the antiaggregation properties of EVOO as a potential protective mechanism against AD.

Extracellular Vesicles from hiPSC-derived NSCs Protect Human Neurons against Aβ-42 Oligomers Induced Neurodegeneration, Mitochondrial Dysfunction and Tau Phosphorylation.

One of the hallmarks of Alzheimer's disease (AD) is the buildup of amyloid beta-42 (Aβ-42) in the brain, which leads to various adverse effects. Therefore, therapeutic interventions proficient in reducing Aβ-42-induced toxicity in AD are of great interest. One promising approach is to use extracellular vesicles from human induced pluripotent stem cell-derived neural stem cells (hiPSC-NSC-EVs) because they carry multiple therapeutic miRNAs and proteins capable of protecting neurons against Aβ-42-induced pathological changes. Therefore, this in vitro study investigated the proficiency of hiPSC-NSC-EVs to protect human neurons derived from two distinct hiPSC lines from Aβ-42o-induced neurodegeneration. We isolated hiPSC-NSC-EVs using chromatographic methods and characterized their size, ultrastructure, expression of EV-specific markers and proficiency in getting incorporated into mature human neurons. Next, mature human neurons differentiated from two different hiPSC lines were exposed to 1 µM Aβ-42 oligomers (Aβ-42o) alone or with varying concentrations of hiPSC-NSC-EVs. The protective effects of hiPSC-NSC-EVs against Aβ-42o-induced neurodegeneration, increased oxidative stress, mitochondrial dysfunction, impaired autophagy, and tau phosphorylation were ascertained using multiple measures and one-way ANOVA with Newman-Keuls multiple comparisons post hoc tests. Significant neurodegeneration was observed when human neurons were exposed to Aβ-42o alone. Notably, neurodegeneration was associated with elevated levels of oxidative stress markers malondialdehyde (MDA) and protein carbonyls (PCs), increased expression of proapoptotic Bax and Bad genes and proteins, reduced expression of the antiapoptotic gene and protein Bcl-2, increased expression of genes encoding mitochondrial complex proteins, decreased expression of autophagy-related proteins Beclin-1 and microtubule-associated protein 1 light chain 3B, and increased phosphorylation of tau. However, the addition of an optimal dose of hiPSC-NSC-EVs (6 x 10 9 EVs) to human neuronal cultures exposed to Aβ-42o significantly reduced the extent of neurodegeneration, along with diminished levels of MDA and PCs, normalized expressions of Bax, Bad, and Bcl-2, and genes linked to mitochondrial complex proteins, and reduced tau phosphorylation. The findings demonstrate that an optimal dose of hiPSC-NSC-EVs could significantly decrease the degeneration of human neurons induced by Aβ-42o. The results also support further research into the effectiveness of hiPSC-NSC-EVs in AD, particularly their proficiency in preserving neurons and slowing disease progression.

Embelin Mitigates Amyloid-β-Induced Neurotoxicity and Cognitive Impairment in Rats: Potential Therapeutic Implications for Alzheimer's Disease.

Alzheimer's disease (AD) is a significant form of dementia. Embelin (EMB) is a natural compound with varied actions that could help prevent AD pathology. Herein, we have investigated the neuroprotective potential of EMB against Aβ1-42-induced neurotoxicity in rats. In this experiment, Alzheimer-like dementia was induced in rats by infusing Aβ1-42 oligomers directly into the brain's ventricles. Subsequently, the Aβ1-42-intoxicated rats received treatment with varying doses of EMB (2.5, 5, and 10mg/kg, administered intraperitoneally) over 2weeks. The spatial and non-spatial memory of animals was assessed at different time intervals, and various biochemical, neurochemical, and neuroinflammatory parameters in the hippocampal brain tissue of the rats were analyzed. Infusion of Aβ1-42 in rat brain caused cognitive impairment and was accompanied by increased acetylcholinesterase activity, oxidative stress, and elevated levels of pro-inflammatory cytokines (such as TNF-α, IL-1β, and IL-6) in the hippocampal tissue. Moreover, a significant decline in the levels of monoamines and an imbalance of GABA and glutamate levels were also observed. EMB treatment significantly mitigated Aβ1-42-induced cognitive deficit and other biochemical changes, including Aβ levels. The EMB-treated rats showed improved learning and consolidation of memory. EMB also attenuated Aβ-induced oxidative stress and neuroinflammation and restored the levels of monoamines and the balance between GABA and glutamate. The observed cognitive benefits following EMB treatment in Aβ1-42-infused rats may be attributed to its antioxidant and anti-inflammatory properties and ability to restore hippocampal neurochemistry and Aβ levels. The above findings indicate the therapeutic potential of EMB in neurodegenerative pathologies associated with cognitive decline, such as Alzheimer's disease.