Aβ Secretion Research Articles

A Lipid-Raft Theory of Alzheimer's Disease.

I present a theory of Alzheimer's disease (AD) that explains its symptoms, pathology, and risk factors. To do this, I introduce a new theory of brain plasticity that elucidates the physiological roles of AD-related agents. New events generate synaptic and branching candidates competing for long-term enhancement. Competition resolution crucially depends on the formation of membrane lipid rafts, which requires astrocyte-produced cholesterol. Sporadic AD is caused by impaired formation of plasma-membrane lipid rafts, preventing the conversion of short- to long-term memory and yielding excessive tau phosphorylation, intracellular cholesterol accumulation, synaptic dysfunction, and neurodegeneration. Amyloid β (Aβ) production is promoted by cholesterol during the switch to competition resolution, and cholesterol accumulation stimulates chronic Aβ production, secretion, and aggregation. The theory addresses all of the major established facts known about the disease and is supported by strong evidence.

Effect of bioactive extracts from Eucalyptus globulus leaves in experimental models of Alzheimer's disease.

Current therapies for Alzheimer's disease (AD) do not delay its progression, therefore, novel disease-modifying strategies are urgently needed. Recently, an increasing number of compounds from natural origin with protective properties against AD have been identified. Mixtures or extracts obtained from natural products containing several bioactive compounds have multifunctional properties and have drawn the attention because multiple AD pathways can be simultaneously modulated. This study evaluated the in vitro and in vivo effect of the essential oil (EO) obtained from the hydrodistillation of Eucalyptus globulus leaves, and an extract obtained from the hydrodistillation residual water (HRW). It was observed that EO and HRW have anti-inflammatory effect in brain immune cells modeling AD, namely lipopolysaccharide (LPS)- and amyloid-beta (Aβ)-stimulated microglia. In cell models that mimic AD-related neuronal dysfunction, HRW attenuated Aβ secretion and Aβ-induced mitochondrial dysfunction. Since the HRW's major components did not cross the blood-brain barrier, both EO and HRW were administered to the APP/PS1 transgenic AD mouse model by an intranasal route, which reduced cortical and hippocampal Aβ levels, and to rescue memory deficits and anxiety-like behaviors. Finally, HRW and EO were found to regulate cholesterol levels in aged mice after intranasal administration, suggesting that these extracts can reduce hypercholesterolemia and avoid risk for AD development. Overall, findings support a protective role of E. globulus extracts against AD‑like pathology and cognitive impairment highlighting the underlying mechanisms. These extracts obtained from underused forest biomass could be useful to develop nutraceutical supplements helpful to avoid AD risk and to prevent its progression.

Propionate Decreases Microglial Activation but Impairs Phagocytic Capacity in Response to Aggregated Fibrillar Amyloid Beta Protein.

Microglia, the innate immune cell of the brain, are a principal player in Alzheimer's disease (AD) pathogenesis. Their surveillance of the brain leads to interaction with the protein aggregates that drive AD pathogenesis, most notably Amyloid Beta (Aβ). Microglia attempt to clear and degrade Aβ using phagocytic machinery, spurring damaging neuroinflammation in the process. Thus, modulation of the microglial response to Aβ is crucial in mitigating AD pathophysiology. SCFAs, microbial byproducts of dietary fiber fermentation, are blood-brain barrier permeable molecules that have recently been shown to modulate microglial function. It is unclear whether propionate, one representative SCFA, has beneficial or detrimental effects on microglia in AD. Thus, we investigated its impact on microglial Aβ response in vitro. Using a multiomics approach, we characterized the transcriptomic, metabolomic, and lipidomic responses of immortalized murine microglia following 1 h of Aβ stimulation, as well as characterizing Aβ phagocytosis and secretion of reactive nitrogen species. Propionate blunted the early inflammatory response driven by Aβ, downregulating the expression of many Aβ-stimulated immune genes, including those regulating inflammation, the immune complement system, and chemotaxis. Further, it reduced the expression of Apoe and inflammation-promoting Aβ-binding scavenger receptors such as Cd36 and Msr1 in favor of inflammation-dampening Lpl, although this led to impaired phagocytosis. Finally, propionate shifted microglial metabolism, altering phospholipid composition and diverting arginine metabolism, resulting in decreased nitric oxide production. Altogether, our data demonstrate a modulatory role of propionate on microglia that may dampen immune activation in response to Aβ, although at the expense of phagocytic capacity.

Early blood immune molecular alterations in cynomolgus monkeys with a PSEN1 mutation causing familial Alzheimer's disease.

More robust non-human primate models of Alzheimer's disease (AD) will provide new opportunities to better understand the pathogenesis and progression of AD. We designed a CRISPR/Cas9 system to achieve precise genomic deletion of exon 9 in cynomolgus monkeys using two guide RNAs targeting the 3' and 5' intron sequences of PSEN1 exon 9. We performed biochemical, transcriptome, proteome, and biomarker analyses to characterize the cellular and molecular dysregulations of this non-human primate model. We observed early changes of AD-related pathological proteins (cerebrospinal fluid Aβ42 and phosphorylated tau) in PSEN1 mutant (ie, PSEN1-ΔE9) monkeys. Blood transcriptome and proteome profiling revealed early changes in inflammatory and immune molecules in juvenile PSEN1-ΔE9 cynomolgus monkeys. PSEN1 mutant cynomolgus monkeys recapitulate AD-related pathological protein changes, and reveal early alterations in blood immune signaling. Thus, this model might mimic AD-associated pathogenesis and has potential utility for developing early diagnostic and therapeutic interventions. A dual-guide CRISPR/Cas9 system successfully mimics AD PSEN1-ΔE9 mutation by genomic excision of exon 9. PSEN1 mutant cynomolgus monkey-derived fibroblasts exhibit disrupted PSEN1 endoproteolysis and increased Aβ secretion. Blood transcriptome and proteome profiling implicate early inflammatory and immune molecular dysregulation in juvenile PSEN1 mutant cynomolgus monkeys. Cerebrospinal fluid from juvenile PSEN1 mutant monkeys recapitulates early changes of AD-related pathological proteins (increased Aβ42 and phosphorylated tau).

Pyrogallol intermediates elicit beta-amyloid secretion via radical formation and alterations in intracellular trafficking, distinct from pyrogallol-generated superoxide

This study unveils a novel role of pyrogallol (PG), a recognized superoxide generator, in inducing beta-amyloid (Aβ) secretion in an Alzheimer's disease (AD) cellular model. Contrary to expectations, the analysis of dihydroethidium fluorescence and UV-VIS spectrum scanning reveals that Aβ secretion arises from PG reaction intermediates rather than superoxide or other by-products. Investigation into Aβ secretion mechanisms identifies dynasore-dependent endocytosis and BFA-dependent exocytosis as independent pathways, regulated by tiron, tempol, and superoxide dismutase. Cell-type specificity is observed, with 293sw cells showing both pathways, while H4sw cells and primary astrocytes from an AD animal model exclusively exhibit the Aβ exocytosis pathway. This exploration contributes to understanding PG's chemical reactions and provides insights into the interplay between environmental factors, free radicals, and AD, linking occupational PG exposure to AD risk as reported in the literature.

Histone deacetylase-3 regulates the expression of the amyloid precursor protein and its inhibition promotes neuroregenerative pathways in Alzheimer's disease models.

HDAC3 inhibition has been shown to improve memory and reduce amyloid-β (Aβ) in Alzheimer's disease (AD) models, but the underlying mechanisms are unclear. We investigated the molecular effects of HDAC3 inhibition on AD pathology, using invitro and exvivo models of AD, based on our finding that HDAC3 expression is increased in AD brains. For this purpose, N2a mouse neuroblastoma cells as well as organotypic brain cultures (OBCSs) of 5XFAD and wild-type mice were incubated with various concentrations of the HDAC3 selective inhibitor RGFP966 (0.1-10 μM) for 24 h. Treatment with RGFP966 or HDAC3 knockdown in N2a cells was associated with an increase on amyloid precursor protein (APP) and mRNA expressions, without alterations in Aβ42 secretion. Invitro chromatin immunoprecipitation analysis revealed enriched HDAC3 binding at APP promoter regions. The increase in APP expression was also detected in OBCSs from 5XFAD mice incubated with 1 μM RGFP966, without changes in Aβ. In addition, HDAC3 inhibition resulted in a reduction of activated Iba-1-positive microglia and astrocytes in 5XFAD slices, which was not observed in OBCSs from wild-type mice. mRNA sequencing analysis revealed that HDAC3 inhibition modulated neuronal regenerative pathways related to neurogenesis, differentiation, axonogenesis, and dendritic spine density in OBCSs. Our findings highlight the complexity and diversity of the effects of HDAC3 inhibition on AD models and suggest that HDAC3 may have multiple roles in the regulation of APP expression and processing, as well as in the modulation of neuroinflammatory and neuroprotective genes.

Beta-amyloid plaque deposits and increased tau protein in the early diagnosis of alzheimer’s disease: the importance of physical activity in the prevention and evolution of the patient

In recent years, it has become clear that the β-amyloid (Aβ) component of senile plaques may be the key molecule in the pathology of Alzheimer's disease (AD). However, the origin and site of Aβ's neurotoxic action are still the subject of controversy. The precursor of the β-amyloid peptide is the β-amyloid precursor protein, which is predominantly neuronal. The hypothesis is that intraneuronal dysregulation of Amyloid Precursor Protein (APP) leads to the accumulation of Aβ peptides in intracellular compartments. This accumulation impairs the trafficking of APP, which initiates a cascade of pathological changes and causes the degeneration of pyramidal neurons. The increased secretion of Aβ as a function of stressed neurons and degenerated neuron remnants provides seeds for extracellular Aβ aggregates, which induce secondary degenerative events involving neighboring cells such as neurons, astroglia and macrophages/microglia. The benefits of physical exercise to reduce low-grade inflammation and improve cognitive function have become a growing field of interest. Epidemiological research has shown that a sedentary lifestyle intensifies the processes of disability and dependence, and also increases the incidence of chronic diseases. Physical exercise has been inversely associated with high levels of different inflammatory markers. It plays a neurotrophic role, capable of promoting a reduction in the accumulation of β-amyloid peptide and the hyperphosphorylation of tau protein, being an important alternative pathway for reducing the degenerative process, which does not result in the release of pro-inflammatory factors, as well as helping to reduce the levels of pro-inflammatory cytokines and improve peripheral concentrations.

Spatial-Temporal Mapping Reveals the Golgi as the Major Processing Site for the Pathogenic Swedish APP Mutation: Familial APP Mutant Shifts the Major APP Processing Site.

Alzheimer's disease is associated with increased levels of amyloid beta (Aβ) generated by sequential intracellular cleavage of amyloid precursor protein (APP) by membrane-bound secretases. However, the spatial and temporal APP cleavage events along the trafficking pathways are poorly defined. Here, we use the Retention Using Selective Hooks (RUSH) to compare in real time the anterograde trafficking and temporal cleavage events of wild-type APP (APPwt) with the pathogenic Swedish APP (APPswe) and the disease-protective Icelandic APP (APPice). The analyses revealed differences in the trafficking profiles and processing between APPwt and the APP familial mutations. While APPwt was predominantly processed by the β-secretase, BACE1, following Golgi transport to the early endosomes, the transit of APPswe through the Golgi was prolonged and associated with enhanced amyloidogenic APP processing and Aβ secretion. A 20°C block in cargo exit from the Golgi confirmed β- and γ-secretase processing of APPswe in the Golgi. Inhibition of the β-secretase, BACE1, restored APPswe anterograde trafficking profile to that of APPwt. APPice was transported rapidly through the Golgi to the early endosomes with low levels of Aβ production. This study has revealed different intracellular locations for the preferential cleavage of APPwt and APPswe and Aβ production, and the Golgi as the major processing site for APPswe, findings relevant to understand the molecular basis of Alzheimer's disease.

Role Of Lncrna In Alzheimer’s Diseases

Long noncoding RNA (lncRNA) are a family of RNA molecules with over 200 nucleotides in size. They cannot code for proteins but still have biological activities. lncRNAs are abundantly expressed in the pathogenic process of neurological diseases like Alzheimer’s. The lncRNA EBF3-AS is more expressed in the brains of older Alzheimer's disease patients called late onset Alzheimer’s disease. NAT-Rad18, a lncRNA over synthesized in specific areas of the brain in AD rats. The lncRNA n336694 targets miR-106b which increases its expression. MiR-106b leads to apoptosis markers in cells. oxidative stress-induced injury to the neurons is caused by the lncRNA SOX21-AS1. The lncRNA-ATB is involved in AD pathophysiology and reducing its expression helps with oxidative stress-induced injury. lncRNA MEG3 inhibits inflammatory injury and oxidative stress in individuals suffering from AD. The increase of lncRNA 17A in cerebral tissues of AD patients affects Aβ secretion. BACE1-AS suppression reduces Aβ and BACE1 levels and inhibits tau protein phosphorylation (3). The lncRNA BC200, also known as BCYRN1 upregulates Aβ production through BACE1 modulation which leads to AD pathogenesis. NEAT1 regulates the miR-124/BACE1 axis and plays a role in AD development. Reduced SORL1 expression increases neurotoxic Aβ formation in AD brains. LRP1-AS negatively regulates systemic Aβ clearance during AD progression. GAS5 regulates insulin signaling, neuronal survival, tau phosphorylation, and neuroinflammation. MAGI2-AS3-miR-374b-5p axis modulates neuroinflammation and neurotoxicity caused by Aβ fragment. Upregulation of WT1-AS inhibits the miR-375/SIX4 axis, OSI, and neuronal apoptosis in AD. BDNF-AS is found to be important in AD though the mechanism has yet to be determined. This review study aims to enhance comprehension of the disease progression of Alzheimer's disease (AD) in relation to various long non-coding RNAs (lncRNA).

Estradiol enhanced neuronal plasticity and ameliorated astrogliosis in human iPSC-derived neural models

Introduction17β-Estradiol (E2) is a sex hormone that has been previously demonstrated to have neurotherapeutic effects on animal models of Alzheimer's disease (AD). However, clinical trials on E2 replacement therapy for preventing AD onset yielded inconsistent results. Therefore, it is imperative to clarify the therapeutic effects of E2 on human cells. In this study, we utilized induced pluripotent stem cells (iPSCs) derived from multiple AD donors to explore the therapeutic effects of E2 on the in vitro model of human cells. MethodsWe conducted a systematic review and meta-analysis using a random-effects model of the previously reported AD clinical trials to summarize the effects of E2 replacement therapy on AD prevention. Subsequently, we induced iPSCs from the donors of the healthy control (1210B2 line (female) and 201B7 line (female)), the familial AD (APP V717L line (female) and APP KM670/671NL line (female)), and the sporadic AD (UCSD-SAD3.7 line (APOE ε3/ε3) (male), UCSD-SAD7D line (APOE ε3/ε4) (male), and TMGH-1 line (APOE ε3/ε3) (female)), then differentiated to neurons. In addition to the mono-culture model of the neurons, we also examined the effects of E2 on the co-culture model of neurons and astrocytes. ResultsThe meta-analysis of the clinical trials concluded that E2 replacement therapy reduced the risk of AD onset (OR, 0.69; 95 % confidence interval [CI], 0.53–0.91; I2 = 82 %). Neural models from the iPSCs of AD donors showed an increase in secreted amyloid-beta (Aβ) levels in the mono-culture model and an astrogliosis-like phenotype in the co-culture model. E2 treatment to the neuronal models derived from the iPSCs enhanced neuronal activity and increased neurite complexity. Furthermore, E2 treatment of the co-culture model ameliorated the astrogliosis-like phenotype. However, in contrast to the previous reports using mouse models, E2 treatment did not change AD pathogenesis, including Aβ secretion and phosphorylated tau (pTau) accumulation. ConclusionE2 treatment of the human cellular model did not impact Aβ secretion and pTau accumulation, but promoted neuronal plasticity and alleviated the astrogliosis-like phenotype. The limited effects of E2 may give a clue for the mixed results of E2 clinical trials.

IPSC-derived PSEN2 (N141I) astrocytes and microglia exhibit a primed inflammatory phenotype

BackgroundWidescale evidence points to the involvement of glia and immune pathways in the progression of Alzheimer’s disease (AD). AD-associated iPSC-derived glial cells show a diverse range of AD-related phenotypic states encompassing cytokine/chemokine release, phagocytosis and morphological profiles, but to date studies are limited to cells derived from PSEN1, APOE and APP mutations or sporadic patients. The aim of the current study was to successfully differentiate iPSC-derived microglia and astrocytes from patients harbouring an AD-causative PSEN2 (N141I) mutation and characterise the inflammatory and morphological profile of these cells.MethodsiPSCs from three healthy control individuals and three familial AD patients harbouring a heterozygous PSEN2 (N141I) mutation were used to derive astrocytes and microglia-like cells and cell identity and morphology were characterised through immunofluorescent microscopy. Cellular characterisation involved the stimulation of these cells by LPS and Aβ42 and analysis of cytokine/chemokine release was conducted through ELISAs and multi-cytokine arrays. The phagocytic capacity of these cells was then indexed by the uptake of fluorescently-labelled fibrillar Aβ42.ResultsAD-derived astrocytes and microglia-like cells exhibited an atrophied and less complex morphological appearance than healthy controls. AD-derived astrocytes showed increased basal expression of GFAP, S100β and increased secretion and phagocytosis of Aβ42 while AD-derived microglia-like cells showed decreased IL-8 secretion compared to healthy controls. Upon immunological challenge AD-derived astrocytes and microglia-like cells showed exaggerated secretion of the pro-inflammatory IL-6, CXCL1, ICAM-1 and IL-8 from astrocytes and IL-18 and MIF from microglia.ConclusionOur study showed, for the first time, the differentiation and characterisation of iPSC-derived astrocytes and microglia-like cells harbouring a PSEN2 (N141I) mutation. PSEN2 (N141I)-mutant astrocytes and microglia-like cells presented with a ‘primed’ phenotype characterised by reduced morphological complexity, exaggerated pro-inflammatory cytokine secretion and altered Aβ42 production and phagocytosis.

White Light Stimulation at Gamma Frequency to Modify the Aβ42 and tau Proteins in SH-SY5Y Cells

Background Non-invasive 40 Hz gamma frequency stimulation has shown improved cognition and memory recall in Alzheimer’s disease (AD). Purpose The present study investigates the effects of white light stimulation at gamma frequency on SH-SY5Y cells using Delta M + BrainCare Light without causing discomfort. Methods SH-SY5Y cells were exposed to The Delta M + BrainCare Light for 15, 30, 45, and 60 minutes. The secretion of amyloid-β42 (Aβ42), p-AKT (Ser473), AKT, p-mTOR (Ser2448), mTOR, p-4E-BP1 (Thr37/46), 4E-BP1, p-tau (Thr181), and tau were analyzed. Aβ42 fibril aggregation and phagocytosis of FITC-Aβ42 in BV-2 cells were also observed. Results Delta M + BrainCare Light reduced tau, AKT, and p-mTOR and increased p-4E-BP1 in SH-SY5Y cells. Further, it inhibited secretion and aggregation of Aβ42, alongside increased phagocytosis in microglial cells. Conclusion These findings underscore the potential of the Delta M + BrainCare Light in mitigating the associated proteins and pathways implicated in AD.

Investigating lysosomal exocytosis as a pathway of beta‐amyloid release from neurons

AbstractBackgroundThe endosomal‐lysosomal system has long been linked to the production of beta‐amyloid (Aβ), but the specific intracellular compartments involved in Aβ secretion remain contentious. Conventionally, lysosomes are associated with Aβ degradation, yet studies have also shown that lysosomes are a site of Aβ accumulation. Lysosomal exocytosis is a major secretory pathway in non‐neuronal cells, but few studies have investigated this pathway in neurons. This project examined the role and mechanism of lysosomal exocytosis in neurons, and we hypothesized that lysosomal exocytosis is a pathway for Aβ secretion from neurons.MethodsWe have established human iPSC‐derived neurons in culture, including cells bearing the APP Swedish mutation. Cells were transduced with pH sensitive fluorescent (pHluorin/pHmScarlet) tagged compartment markers to examine neurosecretory granules (synaptophysin), early endosomes (Rab5), late endosomes (Rab9) and lysosomes (LAMP1). Cells were loaded with fluorescent exogenous Aβ or Amytracker to label endogenous Aβ. We then stimulated secretion with ionomycin and used live cell Total Internal Reflection Fluorescence (TIRF) microscopy to examine molecular events occurring within 250 nm to the plasma membrane. shRNA against proteins known to be involved with lysosomal secretion (Rab27b, Munc13‐4 and synaptotagmin‐7) were used as controls. Imaris software was used to analyze the number and timing of lysosomal secretory events and the secretion of Aβ.ResultsAs previously reported, exogenous Aβ in wild‐type cells and endogenous Aβ in APP Swedish cells accumulates in lysosomes, but not in early endosomes. TIRF microscopy captured videos of lysosomes approaching and fusing with the plasma membrane. Fusion appears as a reduction in normal fluorescent LAMP1 signal and an increase in pH sensitive fluorescent protein marker signal (reflecting the loss of luminal acidity due to fusion). Intracellular Aβ was released from neurons as lysosomes fused with the plasma membrane, seen as a simultaneous decrease in fluorescent Aβ labelling. Silencing of Rab27b significantly reduced lysosomal exocytosis and Aβ secretion, which confirmed that this is a lysosomal process.ConclusionOur results demonstrate that lysosomal exocytosis is a novel secretion pathway for Aβ in human neurons and identify potential pharmacological targets that regulate clearance of Aβ.

Mechanistic Insights of Meglitinides Drug Repurposing and Delivery to Brain for Metabolic Syndrome Linked Neurodegenerative Disease

AbstractBackgroundMetabolic syndrome (MS) includes clusters of metabolic disorders and type 2 DM (T2DM) is most common MS which cause insulin resistance (IR). The IR mediated dysregulation of signaling cascades in brain increase the production and secretion of Aβ, p‐tau which prompt to Alzheimer’s (AD). Therefore, repaglinide (REP) a meglitinides drug is used, which act by targeting ATP binding cassette and evidence indicated that REP increase neuronal survival via upregulating ATF‐6 gene and blocking the DREAM. Thus, there is huge possibility that REP regulate and modulate the expression of pro‐apoptotic protein, anti‐apoptotic protein, calcium homeostasis and may eventually reduce the neuronal cell death.MethodsIn, in vitro studies, primarily cytotoxicity assay was performed on SHSY‐5Y cells and to mimic the neurodegenerative condition, the cells were treated with streptozotocin (STZ, 2.5mM). Further, to check the efficacy of REP in AD, in vivo studies were performed using HFD fed STZ induced murine model. The HFD was fed for 16 weeks followed by administration of STZ (30mg/kg; i.p) in wistar rats for induction of DM linked AD.ResultsIn vitro and in vivo studies were conducted to understand the neuroprotective potential of the REP. It was observed that the REP shows cellular viability of ∼80‐85% and no morphological changes in the cells were identified. Additionally, the results have shown that REP increase the cell viability of STZ treated SHSY‐5Y cells by ∼1.2‐fold and significantly (p<0.01) decreased the oxidative stress in H2O2 treated cells. After treatment of REP (4 mg/kg,p.o) for 4 weeks in DM linked AD wistar rats, a significant (p<0.01) decrement in Aβ, tau proteins, TNF‐α, IL‐6, MDA, NO and increment in BDNF, SOD, GSH level was observed compared to disease control rats. Further, in behavioral studies a significant improvement (p<0.01) in the retention memory and spatial memory was observed after the REP treatment. Additionally, a significant (p<0.05) increase in Bcl‐2, ATF‐6 expression, and decrement in Bax, Caspase‐3 expression indicates reduction in neuronal cell death then the disease rats.ConclusionIn summary, it concluded that REP act as a neuroprotective agent which might be used to treat MS linked AD.

HDAC3 inhibition increases the expression levels of the Amyloid Precursor Protein

AbstractBackgroundEpigenetic‐based interventions have recently garnered attention as potential therapies for Alzheimer’s disease (AD). Histone deacetylases (HDACs) represent an interesting target for neurodegenerative diseases therapies, since HDAC inhibitors have been shown to have the ability to reinstate memory even after neuronal loss. Particularly, HDAC3 inhibition has been shown to enhance long‐term memory and reduce amyloid‐β in AD models, although the molecular mechanisms behind these effects are unclear. The aim of this study was to characterise the effects of HDAC3 inhibition on the mechanisms of generation and degradation of Aβ using in vitro and in ex vivo models of ADMethodN2a mouse neuroblastoma cells overexpressing the Swedish mutation (N2asw) as well as organotypic brain cultures (OBCs) of 5XFAD mice were incubated with various concentrations of the HDAC3 selective inhibitor RGFP966 (0.1‐10 μM) for 24h.ResultTreatment with HDAC3 inhibitor RGFP966, led to a 4% increase on Aβ42 levels in N2a cells, associated with elevated levels carboxy‐terminus fragments (CTFs) and APP protein expressions as well as APP mRNA levels. In vitro chromatin immunoprecipitation (ChIP) analysis in N2a cells, revealed enriched HDAC3 binding at APP promoter regions. The increase in APP expression was also detected in OBCs from 5XFAD mice incubated with 1 μM RGFP966, without significant changes in Aβ secretion. In addition, mRNA sequencing in OBCs revealed that HDAC3 inhibition affects neuronal regenerative pathways, in particular linked to neurogenesis, neuronal differentiation, axonogenesis, resulting in an increase in dendritic spine density.ConclusionThese results suggest that the HDAC3 therapeutic role in AD involves the regulation of APP expression and regenerative pathways, leading to increased synaptic connectivity.

Clearance of β-amyloid mediated by autophagy is enhanced by MTORC1 inhibition but not AMPK activation in APP/PSEN1 astrocytes.

Proteostasis mechanisms mediated by macroautophagy/autophagy are altered in neurodegenerative diseases such as Alzheimer disease (AD) and their recovery/enhancement has been proposed as a therapeutic approach. From the two central nodes in the anabolism-catabolism balance, it is generally accepted that mechanistic target of rapamycin kinase complex 1 (MTORC1)_ activation leads to the inhibition of autophagy, whereas adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) has the opposite role. In AD, amyloid beta (Aβ) production disturbs the optimal neuronal/glial proteostasis. As astrocytes are essential for brain homeostasis, the purpose of this work was to analyze if the upregulation of autophagy in this cell type, either by MTORC1 inhibition or AMPK activation, could modulate the generation/degradation of β-amyloid. By using primary astrocytes from amyloid beta precursor protein (APP)/Presenilin 1 (PSEN1) mouse model of AD, we confirmed that MTORC1 inhibition reduced Aβ secretion through moderate autophagy induction. Surprisingly, pharmacologically increased activity of AMPK did not enhance autophagy but had different effects on Aβ secretion. Conversely, AMPK inhibition did not affect autophagy but reduced Aβ secretion. These puzzling data were confirmed through the overexpression of different mutant AMPK isoforms: while only the constitutively active AMPK increased autophagy, all versions augmented Aβ secretion. We conclude that AMPK has a significantly different role in primary astrocytes than in other reported cells, similar to our previous findings in neurons. Our data support that perhaps only a basal AMPK activity is needed to maintain autophagy whereas the increased activity, either physiologically or pharmacologically, has no direct effect on autophagy-dependent amyloidosis. These results shed light on the controversy about the therapeutic effect of AMPK activation on autophagy induction.

Inhibition of tau phosphorylation and Aβ accumulation by S. cerevisiae-derived vacuoles in LPS-induced SH-SY5Y cells.

Neurodegenerative diseases, such as Alzheimer's disease (AD), are characterized by the accumulation of intracellular tau and amyloid beta (Aβ) proteins, which lead to neuroinflammation and neuronal apoptosis. In this study, we investigated the potential of a bioengineered vacuoles derived from Saccharomyces cerevisiae-derived vacuoles to treat neuroinflammation and protein accumulation in AD. The yeast-derived vacuole is a small organelle that achieves efficient degradation by utilizing a diverse array of hydrolytic enzymes. These hydrolytic enzymes break down and process proteins into smaller fragments. We found that vacuoles treatment significantly reduced LPS-primed cell apoptosis and diminished Aβ42 secretion in vitro, potentially through the inhibition of the NF-kB p65 signaling pathway. Additionally, vacuole pre-treatment down-regulated NF-κB translocation and reduced phosphorylated tau levels in LPS-induced SH-SY5Y cells. Our results suggest that the vacuoles have potential as a therapeutic agent for neurodegenerative diseases. The vacuole's small size and diverse hydrolytic enzymes make it a promising drug delivery system for targeting intracellular proteins. Future studies may explore the use of vacuoles in animal models of AD to determine their therapeutic potential.

A Multisystemic Approach Revealed Aminated Polystyrene Nanoparticles-Induced Neurotoxicity.

Exposure to plastic nanoparticles has dramatically increased in the last 50 years, and there is evidence that plastic nanoparticles can be absorbed by organisms and cross the blood-brain-barrier (BBB). However, their toxic effects, especially on the nervous system, have not yet been extensively investigated, and most of the knowledge is based on studies using different conditions and systems, thus hard to compare. In this work, physicochemical properties of non-modified polystyrene (PS) and amine-functionalized PS (PS-NH2 ) nanoparticles are initially characterized. Advantage of a multisystemic approach is then taken to compare plastic nanoparticles effects in vitro, through cytotoxic readouts in mammalian cell culture, and in vivo, through behavioral readouts in the nematode Caenorhabditis elegans (C. elegans), a powerful 3R-complying model organism for toxicology studies. In vitro experiments in neuroblastoma cells indicate a specific cytotoxic effect of PS-NH2 particles, including a decreased neuronal differentiation and an increased Amyloid β (Aβ) secretion, a sensitive readout correlating with Alzheimer's disease pathology. In parallel, only in vivo treatments with PS-NH2 particles affect C. elegans development, decrease lifespan, and reveal higher sensitivity of animals expressing human Aβ compared to wild-type animals. In summary, the multisystemic approach discloses a neurotoxic effect induced by aminated polystyrene nanoparticles.

Microtubule acetylation induced by oxidative stress regulates subcellular distribution of lysosomal vesicles for amyloid-beta secretion.

Excessive production and accumulation of amyloid-beta (Aβ) in the brain are one of the hallmarks of Alzheimer's disease (AD). Although oxidative stress is known to trigger and promote the progression of AD, the molecular relationship between oxidative stress and Aβ production is not yet fully understood. In this study, we demonstrate that microtubule acetylation induced by oxidative stress plays a critical role in Aβ production and secretion by altering the subcellular distribution of Aβ precursor protein (APP)-containing lysosomal vesicles. Under oxidative stress, both H4-APPSwe/Ind and HEK293T-APPSwe/Ind cell lines showed increased microtubule acetylation and Aβ secretion. Knockdown (KD) of alpha-tubulin N-acetyltransferase 1 (ATAT1) by using a lentiviral shRNA not only inhibited the generation of intermediate APP fragments, such as β-CTF and AICD, but also suppressed Aβ secretion. Oxidative stress promoted the dispersion of LAMP1-positive vesicles to the periphery of the cell through microtubule acetylation, leading to the formation of neutralized lysosomal vesicles (NLVs), which was inhibited by ATAT1 KD. Treatment of the cells with the dynein ATPase inhibitor EHNA or downregulation of LIS1, a regulator of dynein-mediated intracellular transport, increased the peripheral localization of NLVs and promoted Aβ secretion, whereas KD of ADP ribosylation factor like GTPase 8B showed the opposite result. ATAT1 KD in the hippocampal region of the 5×FAD AD mouse model also showed significant reductions in Aβ plaque accumulation and memory loss. Taken together, these findings suggest that oxidative stress-induced microtubule acetylation promotes the peripheral localization of lysosomal vesicles to form NLVs, thereby enhancing Aβ secretion.

Protein retention in the endoplasmic reticulum rescues Aβ toxicity in Drosophila

Amyloid β (Aβ) accumulation is a hallmark of Alzheimer’s disease. In adult Drosophila brains, human Aβ overexpression harms climbing and lifespan. It’s uncertain whether Aβ is intrinsically toxic or activates downstream neurodegeneration pathways. Our study uncovers a novel protective role against Aβ toxicity: intra-endoplasmic reticulum (ER) protein accumulation with a focus on laminin and collagen subunits. Despite high Aβ, laminin B1 (LanB1) overexpression robustly counters toxicity, suggesting a potential Aβ resistance mechanism. Other laminin subunits and collagen IV also alleviate Aβ toxicity; combining them with LanB1 augments the effect. Imaging reveals ER retention of LanB1 without altering Aβ secretion. LanB1’s rescue function operates independently of the IRE1α/XBP1 ER stress response. ER-targeted GFP overexpression also mitigates Aβ toxicity, highlighting broader ER protein retention advantages. Proof-of-principle tests in murine hippocampal slices using mouse Lamb1 demonstrate ER retention in transduced cells, indicating a conserved mechanism. Though ER protein retention generally harms, it could paradoxically counter neuronal Aβ toxicity, offering a new therapeutic avenue for Alzheimer’s disease.