Accumulation Of Neurofibrillary Tangles Research Articles

Recent Advances in Drug Delivery Systems Targeting Insulin Signalling for the Treatment of Alzheimer's Disease.

Alzheimer's disease (AD) is a complex neurodegenerative disorder characterized by the accumulation of neurofibrillary tangles and amyloid-β plaques. Recent research has unveiled the pivotal role of insulin signaling dysfunction in the pathogenesis of AD. Insulin, once thought to be unrelated to brain function, has emerged as a crucial factor in neuronal survival, synaptic plasticity, and cognitive processes. Insulin and the downstream insulin signaling molecules are found mainly in the hippocampus and cortex. Some molecules responsible for dysfunction in insulin signaling are GSK-3β, Akt, PI3K, and IRS. Irregularities in insulin signaling or insulin resistance may arise from changes in the phosphorylation levels of key molecules, which can be influenced by both stimulation and inactivity. This, in turn, is believed to be a crucial factor contributing to the development of AD, which is characterized by oxidative stress, neuroinflammation, and other pathological hallmarks. Furthermore, this route is known to be indirectly influenced by Nrf2, NF-κB, and the caspases. This mini-review delves into the intricate relationship between insulin signaling and AD, exploring how disruptions in this pathway contribute to disease progression. Moreover, we examine recent advances in drug delivery systems designed to target insulin signaling for AD treatment. From oral insulin delivery to innovative nanoparticle approaches and intranasal administration, these strategies hold promise in mitigating the impact of insulin resistance on AD. This review consolidates current knowledge to shed light on the potential of these interventions as targeted therapeutic options for AD.

Role of Cytoskeletal Elements in Regulation of Synaptic Functions: Implications Toward Alzheimer's Disease and Phytochemicals-Based Interventions.

Alzheimer's disease (AD), a multifactorial disease, is characterized by the accumulation of neurofibrillary tangles (NFTs) and amyloid beta (Aβ) plaques. AD is triggered via several factors like alteration in cytoskeletal proteins, a mutation in presenilin 1 (PSEN1), presenilin 2 (PSEN2), amyloid precursor protein (APP), and post-translational modifications (PTMs) in the cytoskeletal elements. Owing to the major structural and functional role of cytoskeletal elements, like the organization of axon initial segmentation, dendritic spines, synaptic regulation, and delivery of cargo at the synapse; modulation of these elements plays an important role in AD pathogenesis; like Tau is a microtubule-associated protein that stabilizes the microtubules, and it also causes inhibition of nucleo-cytoplasmic transportation by disrupting the integrity of nuclear pore complex. One of the major cytoskeletal elements, actin and its dynamics, regulate the dendritic spine structure and functions; impairments have been documented towards learning and memory defects. The second major constituent of these cytoskeletal elements, microtubules, are necessary for the delivery of the cargo, like ion channels and receptors at the synaptic membranes, whereas actin-binding protein, i.e., Cofilin's activation form rod-like structures, is involved in the formation of paired helical filaments (PHFs) observed in AD. Also, the glial cells rely on their cytoskeleton to maintain synaptic functionality. Thus, making cytoskeletal elements and their regulation in synaptic structure and function as an important aspect to be focused for better management and targeting AD pathology. This review advocates exploring phytochemicals and Ayurvedic plant extracts against AD by elucidating their neuroprotective mechanisms involving cytoskeletal modulation and enhancing synaptic plasticity. However, challenges include their limited bioavailability due to the poor solubility and the limited potential to cross the blood-brain barrier (BBB), emphasizing the need for targeted strategies to improve therapeuticefficacy.

Saffron (Crocus sativus L.) extract attenuates chronic scopolamine-induced cognitive impairment, amyloid beta, and neurofibrillary tangles accumulation in rats

Ethnopharmacological relevanceCrocus sativus L. known as saffron, is a popular food condiment with a high aroma, deep colour, and long and thick threads (stigmas) cultivated in Iran, Morocco, Spain, Italy, China, Japan, France, Turkey, and India. In ‘Ayurveda’, saffron is acknowledged for its immunostimulant, aphrodisiac, cardiotonic, liver tonic, nervine tonic, carminative, diaphoretic, diuretic, emmenagogue, galactagogue, febrifuge, sedative, relaxant, and anxiolytic activities. The renowned Persian physician and philosopher, Avicenna, delineated saffron as an antidepressant, hypnotic, anti-inflammatory, hepatoprotective, bronchodilator, and aphrodisiac in his book, the Canon of Medicine. Within traditional Iranian Medicine (TIM), saffron is characterized as a mood elevator and a rejuvenator for the body and senses. Further, the ethnopharmacological evidence indicates that saffron has shown an effect against neurodegenerative disorders namely, dementia, Alzheimer's, and Parkinson's with its bioactive constituents i.e., carotenoids and apocarotenoids. AimThe present study aimed to investigate the potential of standardized (Kashmir Saffron, India) Crocus sativus extract (CSE) in chronic scopolamine-induced cognitive impairment, amyloid beta (Aβ) plaque, and neurofibrillary tangles (NFT) accumulation in rat brains by targeting AChE inhibition and scopolamine mechanistic effect. MethodsThe experimental animals were divided into six groups: group 1: normal control, group 2: scopolamine, group 3,4 and 5 rivastigmine tartrate, CSE (p.o. 10 mg/kg, 15 mg/kg, and 20 mg/kg) respectively. Each treatment group received scopolamine after 20 min of dosing, till 4 weeks. The effects of different treatments on learning, acquisition, and reversal memory were performed using a Morris water maze test. In addition to behavioral assessments, biochemical parameters such as AChE, IL-6, and antioxidants were measured in isolated brains. Histological observations were also conducted to assess the presence of Aβ plaques and NFT. Furthermore, molecular docking was performed to explore the potential AChE inhibitory activity of the bioactive constituents of standardized CSE. ResultsScopolamine produces memory impairment, and its chronic administration forms Aβ plaque and NFT in rat brains. Supplementation with CSE in presence of scopolamine has shown remarkable effects on behavioural activity, special acquisition, and reversal memory. The CSE has also shown promising effects on AChE inhibition and antioxidant activity. The results of the docking study also indicate that trans-crocetin, i.e., a biologically active metabolite of Crocins, has strong AChE inhibitory activity, supported by an in vivo animal experiment. ConclusionSupplementation with CSE significantly attenuates the formation of Aβ plaque and NFT in the hippocampus at a dose of 20 mg/kg per day. In addition, CSE also counters scopolamine-induced neuroinflammation.

Non-coding RNAs in Regulation of Protein Aggregation and Clearance Pathways: Current Perspectives Towards Alzheimer's Research and Therapy.

Alzheimer's disease (AD) is the leading cause of dementia, affecting approximately 45.0 million people worldwide and ranking as the fifth leading cause of mortality. AD is identified by neurofibrillary tangles (NFTs), which include abnormally phosphorylated tau-protein and amyloid protein (amyloid plaques). Peptide dysregulation is caused by an imbalance between the production and clearance of the amyloid-beta (Aβ) and NFT. AD begins to develop when these peptides are not cleared from the body. As a result, understanding the processes that control both normal and pathological protein recycling in neuronal cells is critical. Insufficient Aβ and NFT clearance are important factors in the development of AD. Autophagy, lysosomal dysfunction, and ubiquitin-proteasome dysfunction have potential roles in the pathogenesis of many neurodegenerative disorders, particularly in AD. Modulation of these pathways may provide a novel treatment strategy for AD. Non-coding RNAs (ncRNAs) have recently emerged as important biological regulators, with particular relevance to the emergence and development of neurodegenerative disorders such as AD. ncRNAs can be used as potential therapeutic targets and diagnostic biomarkers due to their critical regulatory functions in several biological processes involved in disease development, such as the aggregation and accumulation of Aβ and NFT. It is evident that ncRNAs play a role in the pathophysiology of AD. In this communication, we explored the link between ncRNAs and AD and their regulatory mechanisms that may help in finding new therapeutic targets and AD medications.

Neuroprotective Effect of Solid Lipid Nanoparticles Loaded with Lepidium sativum (L.) Seed Bioactive Components Enhance Bioavailability and Wnt/β-Catenin/Camk-II Signaling Cascade in SH-SY5Y Neuroblastoma Cells.

The primary pathological hallmark of Alzheimer's disease (AD) is the formation and accumulation of neurofibrillary tangles and plaques, which result from the aggregation of amyloid-β (Aβ) induced by oxidative stress. The effectiveness of Alzheimer's disease (AD) therapeutics significantly hinges on the drug's bioavailability and its ability to penetrate neuronal cells. The current investigation was designed as a first attempt to examine bio-fabricated Lepidium sativum (LS) seed-extract-loaded solid lipid nanoparticles (SLNps) to increase bioavailability and bioefficacy for the prevention of undifferentiated SH-SY5Y neuronal cells from oxidative stress induced by H2O2 and amyloid-β peptide (Aβ,1-42). The SLNps were fabricated using LS extract as a water phase and hyaluronic acid and chia seed fatty acids as a lipid phase, then confirmed and characterized using UV, Zeta size, and SEM methods. The biological safety of synthesized LS-SLNps has been determined using MTT assay and PI staining (nuclear damage) in hMSCs. LS-SLNp-pretreated neuronal cells were induced with oxidative stress and 2 µM of beta-amyloid (Aβ,1-42) fibrils; furthermore, the neuroprotective potential of LS-SLNps was determined through the quenching of oxidative stress, enhancing mitochondrial oxidative capacity, and immunoregulatory potential. Observations found that cells treated with both H2O2 and beta-amyloid (Aβ,1-42) fibrils showed decreased neuronal cell growth, nuclear damage, and mitochondrial membrane potential due to oxidative stress. However, SH-SY5Y cells pretreated with LS-SLNps for 24 h showed an increase in cell proliferation with uniform morphology and increased mitochondrial membrane potential compared to cells pretreated with LS alone. Gene expression analysis found that LS-SLNps increased the expression of Wnt 3a and 5a, which stimulated the canonical, β-catenin, and non-canonical Camk-II expressions of nerve cell growth factors, confirming the molecular-level reversal of neurodegenerative diseases.

Interaction of Tau with G-Protein-Coupled Purinergic P2Y12 Receptor by Molecular Docking and Molecular Dynamic Simulation.

Alzheimer's disease, a progressive neurological disorder, is characterized by the accumulation of neurofibrillary tangles and senile plaques by Tau and amyloid-β, respectively, in the brain microenvironment. The misfolded protein aggregates interact with several components of neuronal and glial cells such as membrane lipids, receptors, transporters, enzymes, cytoskeletal proteins, etc. Under pathological conditions, Tau interacts with several G-protein-coupled receptors (GPCRs), which undergoes either receptor signaling or desensitization followed by internalization of the protein complex. The purinergic GPCR, P2Y12 which is expressed in microglial cells, plays a key role in its activation and migration. Microglial cells sense and migrate to the site of injury aided by P2Y12 receptor that interacts with ADP released from damaged cells. P2Y12 receptor also interacts with misfolded Tau accumulated at the extracellular space and promotes receptor-mediated internalization. Immunocolocalization and co-immunoprecipitation studies demonstrated the interaction of Tau species with the P2Y12 receptor. Later, in-silico analyses were carried out with the repeat domain of Tau (TauRD), which has been identified as the interacting partner of P2Y12 receptor by in-vitro studies. Molecular docking and molecular dynamics simulation studies show the stability and the type of interaction in TauRD-receptor complex. Tau interaction with P2Y12 receptor plays a significant role in maintaining the active state of microglia which could lead to neuroinflammation and neuronal damage in AD brain. Hence, blocking P2Y12-Tau interaction and P2Y12-mediated Tau internalization in microglial cells could be possible therapeutic strategies in downregulating the severity of neuroinflammation in AD.

Tau Imaging in Late Traumatic Brain Injury: A [18F]MK-6240 Positron Emission Tomography Study.

Epidemiological studies have identified prior traumatic brain injury (TBI) as a risk factor for developing Alzheimer's disease (AD). Neurofibrillary tangles (NFTs) are common to AD and chronic traumatic encephalopathy following repetitive mild TBI. However, it is unclear if a single TBI is sufficient to cause accumulation of NFTs. We performed a [18F]MK-6240 positron emission tomography (PET) imaging study to assess NFTs in patients who had sustained a single TBI at least 2 years prior to study inclusion. Fourteen TBI patients (49 ± 20 years; 5 M/9 F; 8 moderate-severe, 1 mild-probable, 5 symptomatic-possible TBI) and 40 demographically similar controls (57 ± 19 years; 19 M/21 F) underwent simultaneous [18F]MK-6240 PET and magnetic resonance imaging (MRI) as well as neuropsychological assessment including the Cambridge Neuropsychological Test Automated Battery (CANTAB). A region-based voxelwise partial volume correction was applied, using parcels obtained by FreeSurfer v6.0, and standardized uptake value ratios (SUVR) were calculated relative to the cerebellar gray matter. Group differences were assessed on both a voxel- and a volume-of-interest-based level and correlations of [18F]MK-6240 SUVR with time since injury as well as with clinical outcomes were calculated. Visual assessment of TBI images did not show global or focal increases in tracer uptake in any subject. On a group level, [18F]MK-6240 SUVR was not significantly different in patients versus controls or between subgroups of moderate-severe TBI versus less severe TBI. Within the TBI group, One Touch Stockings problem solving and spatial working memory (executive function), reaction time (attention), and Mini-Mental State Examination (MMSE) (global cognition) were associated with [18F]MK-6240 SUVR. We found no group-based increase of [18F]MK-6240 brain uptake in patients scanned at least 2 years after a single TBI compared with healthy volunteers, which suggests that no NFTs are building up in the first years after a single TBI. Nonetheless, correlations with cognitive outcomes were found that warrant further investigation.

Amidst an amygdala renaissance in Alzheimer's disease.

The amygdala was highlighted as an early site for neurofibrillary tau tangle pathology in Alzheimer's disease in the seminal 1991 article by Braak and Braak. This knowledge has, however, only received traction recently with advances in imaging and image analysis techniques. Here, we provide a cross-disciplinary overview of pathology and neuroimaging studies on the amygdala. These studies provide strong support for an early role of the amygdala in Alzheimer's disease and the utility of imaging biomarkers of the amygdala in detecting early changes and predicting decline in cognitive functions and neuropsychiatric symptoms in early stages. We summarize the animal literature on connectivity of the amygdala, demonstrating that amygdala nuclei that show the earliest and strongest accumulation of neurofibrillary tangle pathology are those that are connected to brain regions that also show early neurofibrillary tangle accumulation. Additionally, we propose an alternative pathway of neurofibrillary tangle spreading within the medial temporal lobe between the amygdala and the anterior hippocampus. The proposed existence of this pathway is strengthened by novel experimental data on human functional connectivity. Finally, we summarize the functional roles of the amygdala, highlighting the correspondence between neurofibrillary tangle accumulation and symptomatic profiles in Alzheimer's disease. In summary, these findings provide a new impetus for studying the amygdala in Alzheimer's disease and a unique perspective to guide further study on neurofibrillary tangle spreading and the occurrence of neuropsychiatric symptoms in Alzheimer's disease.

Uncovering Novel Modifiers of Tau Aggregation and Pathology using a Proximity Proteomics Approach (BioID)

AbstractBackgroundAlzheimer’s disease (AD) is characterized by the accumulation of neurofibrillary tangles (NFTs), comprised primarily of microtubule‐associated protein tau. NFTs are defining hallmarks of AD and its accumulation into pathological oligomers and fibrils has been associated with cognitive decline in AD and other tauopathies. Despite its pivotal role in the disease process, we still have a poor understanding of how their formation, toxicity, and spread across brain regions is regulated via tau‐associated proteins that regulate the oligomerization, pathological accumulation, and seeding of tau in affected cell types and vulnerable brain regions.MethodWe have established two proximity‐dependent biotin‐identification (BioID) models as novel approaches to identify the composition and proximal molecular environment of tau aggregates. Using an in vitro and ex vivo model approach coupled with mass spectrometry, we have identified proteins that were primarily associated with mutant tau aggregates vs. soluble wildtype tau and stratified them based on significance, molecular pathway and druggability. Immunoblotting and immunofluorescence were performed to assess the interaction of endogenous and overexpressed top candidates with tau, along with visualization with NFTs in the context of human AD pathology to assess their impact on tau‐aggregate formation and toxicity.ResultTo determine the physiological and aggregate specific interacting partners of tau, we are comparing wild type tau (TauWT) with mutant tau (Tau3xMUT) carrying three tauopathy‐associated mutations (A152T/P301L/S320F). The proteomic analysis from our combined proteomic datasets revealed that significantly changed proteins included candidates involved in RNA processing, as well as protein ubiquitination and proteasome degradation. We have begun validating proteins that are enriched in mutant tau in human tissue of AD, as well as primary tauopathies, that may be druggable targets for tauopathies.ConclusionThis study provides novel insights into cellular pathways and molecular mechanisms of neurodegeneration, by identifying in the context of living neurons and brain tissue different functional classes of tau‐associated proteins with relevance for AD pathophysiology. These are expected to include proteins that may mediate the toxic effect of NFTs, facilitate the formation or degradation of pathological tau aggregates, and catalyze posttranslational modifications of tau oligomers and associated proteins.

New melatonin derivatives with donepezil fragment in Alzheimer’s disease as neuroprotectors

AbstractBackgroundAlzheimer’s disease is characterized by progressive, irreversible degeneration of acetylcholine‐producing neurons, cognitive impairment, and the accumulation of neurofibrillary tangles and amyloid plaques. The natural decline in melatonin levels with aging has been associated with insomnia and depression as well as the development of neurodegenerative disorders such as AD. Furthermore, the complexity of AD pathology has encouraged the design of molecules that are able to interact with two or more complementary targets, with the expectation that these multitarget ligands (MTL) may represent important advantages in the treatment of the disease. This study aimed to find new ChE inhibitors with improved toxicity.Method In vitro toxicity screening of the newly compounds on human neuroblastoma SH‐SY5Y, mouse neuroblastoma cell line Neuro‐2a and mouse fibroblast cells CCL‐1. The viability of the cells was assessed by MTT assay. The neuroprotective properties of the compounds were determined in a model of H2O2‐induced oxidative damage in SH‐SY5Y cells. For comparison, effects donepezil, melatonin and galanthamine were determined.ResultMost of the compounds have IC50 values over 100 µM. Compound 3f possess statistically significant protective effects. It should be noted that the neuroprotective effects were more pronounced than those of donepezil and similar to melatonin and rasagiline.ConclusionThe new series of melatonin derivatives with donepezil fragment exhibit low toxicity and a good in vitro safety profile. Further, in vitro protection study proved efficient prevention against oxidative stress in H2O2‐induced injury in SH‐SY5Ycells, especially by compound 3f and was proven as the most perspective for further investigations.Acknowledgments: The financial support by the National Science Fund of Bulgaria (Grant KP‐06‐Н63/11 14.12.2022) is gratefully acknowledged.

Amyloid‐dependent tau phosphorylation drives faster accumulation of tau aggregates in female

AbstractBackgroundThe high prevalence of Alzheimer’s dementia in females have long puzzled researchers in the field. Despite similar amyloid levels, females show higher load of neurofibrillary tangles (NFTs). Previous literature proposed that amyloid‐β (Aβ) and phosphorylated tau (p‐tau) synergism accelerates biomarker abnormalities. However, it remains to be answered whether this synergism is the driving force behind faster tau progression in females. The overarching goal of the study wa to investigate whether amyloid‐β aggregates differentially impose tau hyperphosphorylation and neurofibrillary tangles formation in a sex‐specific manner.MethodIn this longitudinal study, we assessed 287 participants from TRIAD cohort at McGill University Research Centre for Studies in Aging. Cerebral Aβ and tau deposition were assessed with positron emission tomography (PET) radiotracers [18F]AZD4694 ([18F]NAV4694) and [18F]MK6240, respectively. Cerebrospinal fluid (CSF) p‐tau181 and p‐tau217 were also measured (analysed at the Clinical Neurochemistry Laboratory at the University of Gothenburg, Sweden). Regression and voxel‐based models with interaction terms were used to evaluate baseline tau load and NFT accumulation rate as a function of sex and baseline biomarkers (Aβ and p‐tau).ResultWe identified sex difference in the relationships between CSF p‐tau, Aβ and NFT (Fig 1). Specifically, voxelwise analyses demonstrated that female presented stronger positive correlations between CSF p‐tau and AD core biomarkers (Aβ and NFT). Furthermore, we discovered that Aβ and CSF ptau181 interactively potentiated tau accumulation in females but not males (Fig 2, Table 1). Together, the present results support that Aβ load imposes higher tau aggregation in females.ConclusionAβ‐dependent tau phosphorylation was the key driver for faster NFT accumulation observed in female.

The limbic‐predominant hypometabolic subtype of AD is not enriched for comorbid TDP‐43 pathology or hippocampal sclerosis

AbstractBackgroundPrevious research has identified distinct subtypes of AD that differed with respect to the distribution of neurofibrillary tangles (NFT). One of them, a limbic‐predominant subtype, was enriched for comorbid TDP‐43 pathology. Our previous data‐driven analysis used FDG‐PET to identify a limbic‐predominant subtype of AD that may correspond to the limbic‐predominant NFT subtype. In the current study, we tested the expected associations between measures of neuropathology such as TDP‐43 pathology, hippocampal sclerosis, and Braak stages of NFT accumulation, and the limbic‐predominant hypometabolic subtype.MethodWe analyzed ante‐mortem FDG‐PET and neuropathological data of 74 individuals from the autopsy cohort of the Alzheimer’s Disease Neuroimaging Initiative (ADNI), including 7 cognitively normal participants, 12 participants with MCI, and 55 with dementia (as assessed at the last available clinical evaluation). Severity of TDP‐43 pathology was operationalized as the number of brain areas with TDP‐43 immunoreactive inclusions (including amygdala, hippocampus, entorhinal/inferior temporal cortex and neocortex). Hippocampal sclerosis was operationalized as a binary variable. We measured similarity of individual FDG‐PET profiles to the limbic‐predominant subtype. For that, we used Euclidean distances from each individual profile to the mean profile of the limbic‐predominant AD subtype identified previously in a larger ADNI sample using a data‐driven hierarchical clustering approach (Fig.1). Lower Euclidean distances indicated higher similarity to the subtype. Bayesian linear regressions in JASP were used to assess associations between neuropathological markers and similarity to the limbic‐predominant FDG‐PET pattern, controlling for Thal phase of amyloid accumulation, age, sex, and time delay between the FDG‐PET scan and death in the null model. We assessed Bayes factors representing evidence for a given model in comparison to the null model (BF10).ResultOur results suggest that similarity of individual FDG‐PET profiles to the limbic‐predominant FDG‐PET pattern was not related to severity of TDP‐43 pathology (BF10 = 0.449), presence of hippocampal sclerosis (BF10 = 0.544), or Braak NFT stages (BF10 = 0.525).ConclusionContrary to the expected effects, our current analysis indicates a lack of reliable associations between neuropathological markers such as TDP‐43 pathology, hippocampal sclerosis, or global NFT accumulation and the limbic‐predominant hypometabolic subtype. Future analyses will assess potential alternative contributors, such as region‐specific patterns of NFT distribution.

Analogues Rescues Tau Pathologies and Memory Deficits Inhibiting GSK‐3 Signaling using Scaffold morphing and in silico approaches

AbstractBackgroundAlzheimer’s disease (AD is caused by plaque agglomeration and entanglement in several areas of the neural cells, which leads to apoptosis. The main etiology of AD is senile dementia, which is linked to amyloid‐beta (Aβ) deregulation and tau perivascular pathogeny. Hyperphosphorylated tau has propensity for microtubules, which elevates the instability and tau‐protein congregates, leading to accumulation of neurofibrillary tangles (NFTs). Tau hyperphosphorylation is susceptible to GSK‐3 and is an emerging hypothesis for AD. As a result, attempts are made to conduct investigations and further advancements on new analogues capable of inhibiting the GSK‐3 protein, which are currently in the clinical trials.MethodIn this analysis, we have evaluated certain GSK‐3 inhibitor variants utilizing scaffolding and framework devise technique with pharmacological characteristics, accompanied by computational screenings (pharmacokinetics and docking).ResultThe structure‐based designed analogues interacted effectively with the active amino acids of GSK‐3β target protein. The in silico pharmacokinetic studies revealed their drug‐like properties.ConclusionThe analogues with best interactions and binding scores will be considered in the future to completely demonstrate their potential relevance as viable GSK ‐ 3 inhibitors.

To Assess Mediation Effects of BIN1 Risk Variant rs6733839 and APOE4 on Alzheimer’s disease Pathology

AbstractBackgroundAlzheimer’s disease (AD) patients carrying T‐allele in the single nucleotide polymorphism rs744373 show higher levels of misfolded tau protein levels, as well as faster accumulation of neurofibrillary tangles (Franzmeier‐2019; Franzmeier‐2022), in addition to established risk gene apolipoprotein E (APOE4). Here we conduct pathway analysis to understand the direct and indirect effects, mediated through amyloid levels, of the rs6733839 T‐allele and APOE e4‐allele on tau.MethodAmyloid‐positive (florbetapir PET) placebo‐arm patients with a clinical diagnosis of AD dementia from four clinical trials (NCT01900665, NCT02791191, NCT02245737, NCT02016560, Table.1) underwent baseline (N = 547) and follow‐up (N = 230) flortaucipir PET scans. Tau burden was assessed using standardized uptake value ratio (SUVr) in AD‐specific region (MUBADA; Devous‐2018) with respect to cerebellum‐crus. We tested direct and indirect effects of BIN1 (rs6733839) and APOE4 on baseline SUVr and change‐from baseline (CFB) in tau‐PET mediated by baseline florbetapir signal. Unstandardized indirect effects were computed for each of 1,000 bootstrapped samples, and the 95% confidence interval was computed by determining the indirect effects at the 2.5th and 97.5th percentiles.ResultBIN1 and age showed significant association with the baseline tau‐PET level (BIN1: ßeta = 0.05, P = 0.05; Age: ßeta = ‐0.03, P<0.001), whereas APOE4 association with the baseline tau‐PET levels was not statistically significant (ßeta = 0.006, P = 0.81). The bootstrapped unstandardized indirect effect of BIN1, age, and APOE4 mediated via baseline amyloid levels was insignificant (BIN1: ßeta = 0.0002, P = 0.92; Age: ßeta = 3.82e−05, P = 0.74; APOE4: ßeta = ‐0.0003, P = 0.86). When evaluated on longitudinal tau measures, the direct effect of APOE4 on CFB in tau‐PET SUVr was significant (ßeta = 0.02; P = 0.01). The direct and indirect effects (mediated via baseline amyloid levels) of BIN1 (Direct: ßeta = ‐0.007, P = 0.215; Indirect: ßeta = ‐0.0007, P = 0.58) and Age (Direct: ßeta = ‐0.0009, P = 0.26; Indirect: ßeta = 0.0001, P = 0.32) were insignificant.ConclusionBIN1 showed significant association with the baseline tau‐PET level whereas APOE‐e4 allele directly affected longitudinal tau buildup independent of amyloid levels. These observations require additional validation using larger datasets and further optimization of the applied methodology is warranted.

In Silico Approaches to Developing Novel Glycogen Synthase Kinase 3β (GSK-3β).

Alzheimer's disease (AD) is caused by plaque agglomeration and entanglement in several areas of the neural cells, which leads to apoptosis. The main etiology of AD is senile dementia, which is linked to amyloid-beta (Aβ) deregulation and tau perivascular pathogeny. Hyperphosphorylated tau has a propensity for microtubules, which elevate the instability and tau-protein congregates, leading to accumulation of neurofibrillary tangles (NFTs). Tau hyperphosphorylation is susceptible to GSK-3, which has led to an emerging hypothesis regarding the pathogenesis of AD. Accordingly, attempts have been made to conduct investigations and achieve further advancements on new analogues capable of inhibiting the GSK-3 protein, which are currently in the clinical trials. In this analysis, we have evaluated certain GSK-3 inhibitor variants utilising scaffolding and framework devised techniques with pharmacological characteristics, accompanied by computational screenings (pharmacokinetics and docking). The structure-based designed analogues interacted effectively with the active amino acids of GSK-3β target protein. The in silico pharmacokinetic studies revealed their drug-like properties. The analogues with best interactions and binding scores will be considered in the future to completely demonstrate their potential relevance as viable GSK-3 inhibitors.

Targeting tau in Alzheimer's disease: from mechanisms to clinical therapy.

Alzheimer's disease is the most prevalent neurodegenerative disease affecting older adults. Primary features of Alzheimer's disease include extracellular aggregation of amyloid-β plaques and the accumulation of neurofibrillary tangles, formed by tau protein, in the cells. While there are amyloid-β-targeting therapies for the treatment of Alzheimer's disease, these therapies are costly and exhibit potential negative side effects. Mounting evidence suggests significant involvement of tau protein in Alzheimer's disease-related neurodegeneration. As an important microtubule-associated protein, tau plays an important role in maintaining the stability of neuronal microtubules and promoting axonal growth. In fact, clinical studies have shown that abnormal phosphorylation of tau protein occurs before accumulation of amyloid-β in the brain. Various therapeutic strategies targeting tau protein have begun to emerge, and are considered possible methods to prevent and treat Alzheimer's disease. Specifically, abnormalities in post-translational modifications of the tau protein, including aberrant phosphorylation, ubiquitination, small ubiquitin-like modifier (SUMO)ylation, acetylation, and truncation, contribute to its microtubule dissociation, misfolding, and subcellular missorting. This causes mitochondrial damage, synaptic impairments, gliosis, and neuroinflammation, eventually leading to neurodegeneration and cognitive deficits. This review summarizes the recent findings on the underlying mechanisms of tau protein in the onset and progression of Alzheimer's disease and discusses tau-targeted treatment of Alzheimer's disease.

MTOR signaling and Alzheimer's disease: What we know and where we are?

Despite the great body of research done on Alzheimer's disease, the underlying mechanisms have not been vividly investigated. To date, the accumulation of amyloid-beta plaques and tau tangles constitutes the hallmark of the disease; however, dysregulation of the mammalian target of rapamycin (mTOR) seems to be significantly involved in the pathogenesis of the disease as well. mTOR, as a serine-threonine protein kinase, was previously known for controlling many cellular functions such as cell size, autophagy, and metabolism. In this regard, mammalian target of rapamycin complex 1 (mTORC1) may leave anti-aging impacts by robustly inhibiting autophagy, a mechanism that inhibits the accumulation of damaged protein aggregate and dysfunctional organelles. Formation and aggregation of neurofibrillary tangles and amyloid-beta plaques seem to be significantly regulated by mTOR signaling. Understanding the underlying mechanisms and connection between mTOR signaling and AD may suggest conducting clinical trials assessing the efficacy of rapamycin, as an mTOR inhibitor drug, in managing AD or may help develop other medications. In this literature review, we aim to elaborate mTOR signaling network mainly in the brain, point to gaps of knowledge, and define how and in which ways mTOR signaling can be connected with AD pathogenesis and symptoms.

N-Acetyltransferase 9 ameliorates Aβ42-mediated neurodegeneration in the Drosophila eye

Alzheimer’s disease (AD), a progressive neurodegenerative disorder, manifests as accumulation of amyloid-beta-42 (Aβ42) plaques and intracellular accumulation of neurofibrillary tangles (NFTs) that results in microtubule destabilization. Targeted expression of human Aβ42 (GMR > Aβ42) in developing Drosophila eye retinal neurons results in Aβ42 plaque(s) and mimics AD-like extensive neurodegeneration. However, there remains a gap in our understanding of the underlying mechanism(s) for Aβ42-mediated neurodegeneration. To address this gap in information, we conducted a forward genetic screen, and identified N-acetyltransferase 9 (Mnat9) as a genetic modifier of GMR > Aβ42 neurodegenerative phenotype. Mnat9 is known to stabilize microtubules by inhibiting c-Jun-N- terminal kinase (JNK) signaling. We found that gain-of-function of Mnat9 rescues GMR > Aβ42 mediated neurodegenerative phenotype whereas loss-of-function of Mnat9 exhibits the converse phenotype of enhanced neurodegeneration. Here, we propose a new neuroprotective function of Mnat9 in downregulating the JNK signaling pathway to ameliorate Aβ42-mediated neurodegeneration, which is independent of its acetylation activity. Transgenic flies expressing human NAT9 (hNAT9), also suppresses Aβ42-mediated neurodegeneration thereby suggesting functional conservation in the interaction of fly Mnat9 or hNAT9 with JNK-mediated neurodegeneration. These studies add to the repertoire of molecular mechanisms that mediate cell death response following accumulation of Aβ42 and may provide new avenues for targeting neurodegeneration.

Drosophila eye model to study the role of NAT9 in Alzheimer’s Disease related Dementia (ADRD)

AbstractBackgroundOne of the hallmarks of Alzheimer’s disease (AD), an age‐related progressive form of dementia, is accumulation of the amyloid beta (Aβ42) plaque, which manifests in decline in cognitive function. The accumulation of these Aβ42 plaques trigger the hyperphosphorylation of tau, a microtubule associated protein, which results in the intracellular accumulation of neurofibrillary tangles (NFTs) due to destabilization of microtubules.MethodWe employed the Gal4/UAS system in Drosophila melanogaster to misexpress human Aβ42 within the developing fly retina, exhibiting AD‐like neuropathology. Accumulation of Aβ42 plaque(s) triggers the aberrant activation of signaling pathways like the JNK pathway resulting in neuronal cell death by unknown mechanism(s). Using candidate based forward genetic screening, we identified N‐acetyltransferase 9 (NAT9) as one of the genetic modifiers of GMR>Aβ42 reduced eye phenotype. Previously NAT9 has been shown to stabilize microtubules by acetylation of tubulins, thereby inhibiting JNK signaling. This study aims to understand the role of NAT9 in Aβ42‐mediated neurodegeneration.ResultThe gain‐of‐function of NAT9 rescues Aβ42‐mediated neurodegeneration whereas loss‐of‐function of NAT9 enhances Aβ42‐mediated neurodegeneration. We have also found that the gain‐of‐function of human NAT9 also suppresses Aβ42‐mediated neurodegeneration suggesting the functional conservation. Interestingly, mutated NAT9 in the acetyl‐ CoA binding site shows similar phenotype as gain‐of‐function of NAT9 suggesting its function is independent of acetylation activity. Moreover, the eye antennal imaginal discs of loss‐of‐function of NAT9 in GMR>Aβ42 background shows the activation of JNK pathway by increased pJNK levels.ConclusionOur data suggests that NAT9 downregulates JNK signaling pathway which can ameliorate Aβ42‐mediated neurodegeneration.

Neural Differentiation of Induced Pluripotent Stem Cells for a Xenogeneic Material-Free 3D Neurological Disease Model Neurulation from Pluripotent Cells Using a Human Hydrogel.

Alzheimer's Disease (AD) is characterized by synapse and neuronal loss and the accumulation of neurofibrillary tangles and Amyloid β plaques. Despite significant research efforts to understand the late stages of the disease, its etiology remains largely unknown. This is in part because of the imprecise AD models in current use. In addition, little attention has been paid to neural stem cells (NSC), which are the cells responsible for the development and maintenance of brain tissue during an individual's lifespan. Thus, an in vitro 3D human brain tissue model using induced pluripotent stem (iPS) cell-derived neural cells in human physiological conditions may be an excellent alternative to standard models to investigate AD pathology. Following the differentiation process mimicking development, iPS cells can be turned into NSCs and, ultimately, neural cells. During differentiation, the traditionally used xenogeneic products may alter the cells' physiology and prevent accurate disease pathology modeling. Hence, establishing a xenogeneic material-free cell culture and differentiation protocol is essential. This study investigated the differentiation of iPS cells to neural cells using a novel extracellular matrix derived from human platelet lysates (PL Matrix). We compared the stemness properties and differentiation efficacies of iPS cells in a PL matrix against those in a conventional 3D scaffold made of an oncogenic murine-matrix. Using well-defined conditions without xenogeneic material, we successfully expanded and differentiated iPS cells into NSCs via dual-SMAD inhibition, which regulates the BMP and TGF signaling cascades in a manner closer to human conditions. This in vitro, 3D, xenogeneic-free scaffold will enhance the quality of disease modeling for neurodegenerative disease research, and the knowledge produced could be used in developing more effective translational medicine.