Increased Tau Phosphorylation Research Articles

Mouse serum albumin induces neuronal apoptosis and tauopathies

The elderly frequently present impaired blood–brain barrier which is closely associated with various neurodegenerative diseases. However, how the albumin, the most abundant protein in the plasma, leaking through the disrupted BBB, contributes to the neuropathology remains poorly understood. We here demonstrated that mouse serum albumin-activated microglia induced astrocytes to A1 phenotype to remarkably increase levels of Elovl1, an astrocytic synthase for very long-chain saturated fatty acids, significantly promoting VLSFAs secretion and causing neuronal lippoapoptosis through endoplasmic reticulum stress response pathway. Moreover, MSA-activated microglia triggered remarkable tau phosphorylation at multiple sites through NLRP3 inflammasome pathway. Intracerebroventricular injection of MSA into the brains of C57BL/6J mice to a similar concentration as in patient brains induced neuronal apoptosis, neuroinflammation, increased tau phosphorylation, and decreased the spatial learning and memory abilities, while Elovl1 knockdown significantly prevented the deleterious effect of MSA. Overall, our study here revealed that MSA induced tau phosphorylation and neuron apoptosis based on MSA-activated microglia and astrocytes, respectively, showing the critical roles of MSA in initiating the occurrence of tauopathies and cognitive decline, and providing potential therapeutic targets for MSA-induced neuropathology in multiple neurodegenerative disorders.

Phosphorylation of tau protein based on the activity of kinases and phosphatases in various forms of synaptic plasticity.

The aim of this study is to show the relationship between the change in the strengthening of synaptic plasticity and tau phosphorylation and tau-kinases and phosphatase. The averages of the field excitatory-postsynaptic potential (fEPSP) and population spike (PS) in the last 5 min were used as a measure of LTP, LTD and MP. Total and phosphorylated levels of tau, kinases and phosphatases were evaluated by western blot and mRNA levels were evaluated by RT-qPCR. The stimulation of synapses by HFS and LFS+HFS increased the phosphorylation of total-tau and phospho-tau at the Thr181, Ser202/Thr205, Ser396 and Ser416 residues, and these were accompanied by increased enzymatic activity of Akt, ERK1/2. Theincreased phosphorylation of tau may mediate maintenance of LTP. If the increase in phosphorylation of tau cannot be prevented, together with inhibition of the subsequent LTP, this may indicate that the physiological role of hyperphosphorylated tau in synaptic plasticity may extend to pathological processes.

Microtubule-affinity regulating kinase family members distinctively affect tau phosphorylation and promote its toxicity in a Drosophila model.

Accumulation of abnormally phosphorylated tau and its aggregation constitute a significant hallmark of Alzheimer's disease (AD). Tau phosphorylation at Ser262 and Ser356 in the KXGS motifs of microtubule-binding repeats plays a critical role in its physiological function and AD disease progression. Major tau kinases to phosphorylate tau at Ser262 and Ser356 belong to the Microtubule Affinity Regulating Kinase family (MARK1-4), which are considered one of the major contributors to tau abnormalities in AD. However, whether and how each member affects tau toxicity in vivo is unclear. We used transgenic Drosophila as a model to compare the effect on tau-induced neurodegeneration among MARKs in vivo. MARK4 specifically promotes tau accumulation and Ser396 phosphorylation, which yields more tau toxicity than was caused by other MARKs. Interestingly, MARK1, 2, and 4 increased tau phosphorylation at Ser262 and Ser356, but only MARK4 caused tau accumulation, indicating that these sites alone did not cause pathological tau accumulation. Our results revealed MARKs are different in their effect on tau toxicity, and also in tau phosphorylation at pathological sites other than Ser262 and Ser356. Understanding the implementation of each MARK into neurodegenerative disease helps to develop more target and safety therapies to overcome AD and related tauopathies.

Inhibition of BMP signaling delays tauopathy and cognitive deficits in P301S mouse model

AbstractBackgroundAging is the highest risk factor for sporadic Alzheimer’s disease (AD). Expression of bone morphogenic protein 4 (BMP4) increases 10‐fold with age, while expression of the BMP antagonist, noggin, decreases. We have observed that activating BMP signaling in induced human neurons increased levels of phosphorylated tau. The increase of p‐tau has been correlated with the activated non‐canonical BMP pathway leading to p38 activity. We hypothesized that modulating BMP signaling in an AD mouse model of tau would rescue disease phenotype.MethodP301S (PS19) mice were injected with lentivirus overexpressing noggin (LV‐noggin) or lentivirus mcherry (LV‐mcherry) control in the dentate gyrus. Cognitive behavioral testing was run at 7 months of age and brain tissue was collected for protein and immunofluorescent imaging.ResultWe observe that levels of BMP4, as well as BMP signaling, are increased in the brains of PS19 mice compared to littermate wildtype mice. Analysis of noggin injected PS19 brains show downregulation of BMP signaling in the DG shown by decreased pSMAD1/5/8, as well as non‐canonical signaling through p38 kinase activity. Inhibition of BMP signaling through overexpression of noggin improves cognitive ability shown through Barnes maze testing. Downregulation of BMP signaling in P301S mice led to a decrease in tau phosphorylation seen both in immunoblotting, as well as immunocytochemical analysis in the DG.ConclusionPS19 model of tauopathy show increased levels of BMP signaling. We have shown that increased levels of BMP signaling lead to increased tau phosphorylation and reduced degradation of p‐tau. We show that by inhibiting BMP signaling in vivo we can delay cognitive behavioral deficits seen in these mice by decreasing tau phosphorylation. This suggests that the age‐related increase in BMP signaling may participate in the initiation and progression of AD pathology and help to explain why age is the largest risk factor for AD.

7,8-Dihydroxyflavone ameliorates cognitive impairment induced by repeated neonatal sevoflurane exposures in mice through increasing tau O-GlcNAcylation

BackgroundSevoflurane, one of the most commonly used general anesthetics for pediatric anesthesia, has recently gained significant attention in both preclinical and clinical settings due to its potential neurotoxicity in the developing brain. Tau phosphorylation, induced by sevoflurane, is recognized as one of the major causes of neurotoxicity. 7,8-dihydroxyflavone (DHF), a TrkB receptor agonist, has been reported to exhibit potential neuroprotective effects against tauopathies. In this study, our objective was to investigate whether DHF could provide neuroprotective effects against sevoflurane-induced neurotoxicity and explore the underlying molecular mechanisms. MethodsSix-day-old mice were subjected to 2 h of anesthesia with 3 % sevoflurane, with or without pretreatment of DHF (5 mg/kg/day, i.p.) for 3 consecutive days. Autonomic motor ability was assessed by open-field test, while learning and memory abilities were evaluated by the fear conditioning test. Western blotting was conducted to measure the levels of t-TrkB, p-TrkB, tau, and phosphorylated tau. Additionally, a co-immunoprecipitation assay was performed to investigate the interaction between O-GlcNAcylation and tau. ResultsRepeated neonatal sevoflurane exposures resulted in reduced freezing time during the context and cued fear conditioning tests in adulthood. However, pretreatment with DHF restored the freezing time to the level of the control group, indicating that DHF effectively alleviated cognitive impairments induced by neonatal sevoflurane exposure. We also observed that repeated neonatal sevoflurane exposures increased tau phosphorylation while decreasing tau O-GlcNAcylation. However, DHF pretreatment rebalanced the tau O-GlcNAcylation/phosphorylation ratio by enhancing the interaction between tau and O-GlcNAcylation. ConclusionOur findings demonstrate that DHF effectively ameliorates sevoflurane-induced cognitive impairment in developing mice by restoring the balance between tau O-GlcNAcylation and phosphorylation. Therefore, this study suggests that DHF has the potential to be a therapeutic agent for treating cognitive impairment associated with anesthetics, such as sevoflurane.

Elevated 4R tau contributes to endolysosomal dysfunction and neurodegeneration in VCP-related frontotemporal dementia.

Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are two incurable neurodegenerative diseases that exist on a clinical, genetic and pathological spectrum. The VCP gene is highly relevant, being directly implicated in both FTD and ALS. Here, we investigate the effects of VCP mutations on the cellular homoeostasis of human induced pluripotent stem cell-derived cortical neurons, focusing on endolysosomal biology and tau pathology. We found that VCP mutations cause abnormal accumulation of enlarged endolysosomes accompanied by impaired interaction between two nuclear RNA binding proteins: fused in sarcoma (FUS) and splicing factor, proline- and glutamine-rich (SFPQ) in human cortical neurons. The spatial dissociation of intranuclear FUS and SFPQ correlates with alternative splicing of the MAPT pre-mRNA and increased tau phosphorylation. Importantly, we show that inducing 4R tau expression using antisense oligonucleotide technology is sufficient to drive neurodegeneration in control human neurons, which phenocopies VCP-mutant neurons. In summary, our findings demonstrate that tau hyperphosphorylation, endolysosomal dysfunction, lysosomal membrane rupture, endoplasmic reticulum stress and apoptosis are driven by a pathogenic increase in 4R tau.

Development of an accelerated cellular model for early changes in Alzheimer’s disease

Alzheimer’s Disease (AD) is a leading cause of dementia characterized by amyloid plaques and neurofibrillary tangles, and its pathogenesis remains unclear. Current cellular models for AD often require several months to exhibit phenotypic features due to the lack of an aging environment in vitro. Lamin A is a key component of the nuclear lamina. Progerin, a truncated protein resulting from specific lamin A mutations, causes Hutchinson–Gilford Progeria Syndrome (HGPS), a disease that prematurely ages individuals. Studies have reported that lamin A expression is induced in the brains of AD patients, and overlapping cellular phenotypes have been observed between HGPS and AD cells. In this study, we investigated the effects of exogenous progerin expression on neural progenitor cells carrying familial AD mutations (FAD). Within three to four weeks of differentiation, these cells exhibited robust AD phenotypes, including increased tau phosphorylation, amyloid plaque accumulation, and an elevated Aβ42 to Aβ40 ratio. Additionally, progerin expression significantly increased AD cellular phenotypes such as cell death and cell cycle re-entry. Our results suggest that progerin expression could be used to create an accelerated model for AD development and drug screening.

Age-Dependent Increase in Tau Phosphorylation at Serine 396 in Huntington's Disease Prefrontal Cortex.

To date, it is still controversial whether tau phosphorylation plays a role in Huntington's disease (HD), as previous studies demonstrated either no alterations or increases in phosphorylated tau (pTau) in HD postmortem brain and mouse models. The goal of this study was to determine whether total tau and pTau levels are altered in HD. Immunohistochemistry, cellular fractionations, and western blots were used to measure total tau and pTau levels in a large cohort of HD and control postmortem prefrontal cortex (PFC). Furthermore, western blots were performed to assess tau, and pTau levels in HD and control isogenic embryonic stem cell (ESC)-derived cortical neurons and neuronal stem cells (NSCs). Similarly, western blots were used to assess tau and pTau levels in HttQ111 and transgenic R6/2 mice. Lastly, total tau levels were assessed in HD and healthy control plasma using Quanterix Simoa assay. Our results revealed that, while there was no difference in total tau or pTau levels in HD PFC compared to controls, the levels of tau phosphorylated at S396 were increased in PFC samples from HD patients 60 years or older at time of death. Additionally, tau and pTau levels were not changed in HD ESC-derived cortical neurons and NSCs. Similarly, total tau or pTau levels were not altered in HttQ111 and transgenic R6/2 mice compared to wild-type littermates. Lastly, tau levels were not changed in plasma from a small cohort of HD patients compared to controls. Together these findings demonstrate that pTau-S396 levels increase significantly with age in HD PFC.

Phosphorylation of MAP 1A regulates hyperphosphorylation of Tau in Alzheimer's disease model.

Hyperphosphorylation of Tau is one of the important pathological features of Alzheimer's disease (AD). Therefore, studying the mechanisms behind Tau hyperphosphorylation is crucial in exploring the pathogenesis of neurological damage in AD. In this study, after the establishment of rat models of AD, quantitative phosphoproteomics and proteomics were performed to identify proteins, showing that phosphorylation of microtubule associated protein 1A (MAP 1A) was lower in the model group. Western blot confirmed the changes of MAP 1A in the SD rats, APP/PS1 transgenic mice and cell AD models. To further study the molecular mechanism of recombinant MAP 1A phosphorylation affecting Tau phosphorylation, interfering siRNA-MAP 1A and protein immunoprecipitation reaction analysis were performed in AD cell models. Cyclin-dependent kinase 5 (CDK5) showed reduced binding to MAP 1A and increased binding to Tau, resulting in a decrease in phosphorylated MAP 1A (p-MAP 1A) and an increase in phosphorylated Tau (p-Tau), and MAP 1A silencing promoted binding of CDK5-Tau and increased Tau phosphorylation, thereby reducing the cell survival rate. In summary, we found that p-MAP 1A downregulation associated with p-Tau upregulation was due to their altered binding forces to CDK5, and MAP 1A could enhance autophosphorylation by competitive binding to CDK5 and antagonise Tau phosphorylation. This leads to neuronal protection and reducing tissue damage levels in AD, which can help better understand the mechanisms of AD pathogenesis.

Anesthesia-induced hippocampal-cortical hyperactivity and tau hyperphosphorylation impair remote memory retrieval in Alzheimer's disease.

Anesthesia often exacerbates memory recall difficulties in individuals with Alzheimer's disease (AD), but the underlying mechanisms remain unclear. We used in vivo Ca2+ imaging, viral-based circuit tracing, and chemogenetic approaches to investigate anesthesia-induced remote memory impairment in mouse models of presymptomatic AD. Our study identified pyramidal neuron hyperactivity in the anterior cingulate cortex (ACC) as a significant contributor to anesthesia-induced remote memory impairment. This ACC hyperactivation arises from the disinhibition of local inhibitory circuits and increased excitatory inputs from the hippocampal CA1 region. Inhibiting hyperactivity in the CA1-ACC circuit improved memory recall after anesthesia. Moreover, anesthesia led to increased tau phosphorylation in the hippocampus, and inhibiting this hyperphosphorylation prevented ACC hyperactivity and subsequent memory impairment. Hippocampal-cortical hyperactivity plays a role in anesthesia-induced remote memory impairment. Targeting tau hyperphosphorylation shows promise as a therapeutic strategy to mitigate anesthesia-induced neural network dysfunction and retrograde amnesia in AD.

Stochastic formal model of PI3K/mTOR pathway in Alzheimer's disease for drug repurposing: An evaluation of rapamycin, LY294002, and NVP-BEZ235

Alzheimer's disease is the most common form of dementia characterized by the gradual loss of memory and cognition of patients. There is no drug capable of curing or preventing the disease, being the discovery of an efficient treatment for the disease is of vital importance. An approach that can contribute to this purpose of reducing time and costs of new discoveries is drug repositioning and in silico techniques. Statistical Model Checking is a formal verification technique that can aid in analyzing protein and drugs interactions and test pharmacological strategies, contributing to drug discovery and repurposing. In this work, we present a stochastic formal model that allows us to test different drugs, or combination of drugs, that target the PI3K/mTOR pathway and to evaluate the effect on tau protein and A β peptide, which are two important components that contribute to the progression of Alzheimer's disease. We have analyzed the effect of rapamycin, LY294002, and NVP-BEZ235 on those proteins. Our results have shown that rapamycin has the potential to slow down one of the biological processes that cause neuronal death. Moreover, we have identified the ideal dose of rapamycin to obtain such results. However, our findings have unveiled that LY294002 and NVP-BEZ235 can increase tau phosphorylation in all scenarios tested. This is an alert to the scientific community, as this deleterious effect can be caused by other PI3K inhibitor drugs used to treat different diseases. These results suggest the inhibition of some proteins of the pathway can trigger an unexpected pathology. Besides that, rapamycin has not reduced this side effect when administered together with LY294002. The proposed methodology has been able to model both the disease and drug interactions. We have analyzed three drugs and our model is flexible to test other drugs and pharmacological strategies and efficient to analyze the properties of the model generating new insights.

Anti-Alzheimer Activity of Combinations of Cocoa with Vinpocetine or Other Nutraceuticals in Rat Model: Modulation of Wnt3/β-Catenin/GSK-3β/Nrf2/HO-1 and PERK/CHOP/Bcl-2 Pathways.

Alzheimer's disease (AD) is a devastating illness with limited therapeutic interventions. The aim of this study is to investigate the pathophysiological mechanisms underlying AD and explore the potential neuroprotective effects of cocoa, either alone or in combination with other nutraceuticals, in an animal model of aluminum-induced AD. Rats were divided into nine groups: control, aluminum chloride (AlCl3) alone, AlCl3 with cocoa alone, AlCl3 with vinpocetine (VIN), AlCl3 with epigallocatechin-3-gallate (EGCG), AlCl3 with coenzyme Q10 (CoQ10), AlCl3 with wheatgrass (WG), AlCl3 with vitamin (Vit) B complex, and AlCl3 with a combination of Vit C, Vit E, and selenium (Se). The animals were treated for five weeks, and we assessed behavioral, histopathological, and biochemical changes, focusing on oxidative stress, inflammation, Wnt/GSK-3β/β-catenin signaling, ER stress, autophagy, and apoptosis. AlCl3 administration induced oxidative stress, as evidenced by elevated levels of malondialdehyde (MDA) and downregulation of cellular antioxidants (Nrf2, HO-1, SOD, and TAC). AlCl3 also upregulated inflammatory biomarkers (TNF-α and IL-1β) and GSK-3β, leading to increased tau phosphorylation, decreased brain-derived neurotrophic factor (BDNF) expression, and downregulation of the Wnt/β-catenin pathway. Furthermore, AlCl3 intensified C/EBP, p-PERK, GRP-78, and CHOP, indicating sustained ER stress, and decreased Beclin-1 and anti-apoptotic B-cell lymphoma 2 (Bcl-2) expressions. These alterations contributed to the observed behavioral and histological changes in the AlCl3-induced AD model. Administration of cocoa, either alone or in combination with other nutraceuticals, particularly VIN or EGCG, demonstrated remarkable amelioration of all assessed parameters. The combination of cocoa with nutraceuticals attenuated the AD-mediated deterioration by modulating interrelated pathophysiological pathways, including inflammation, antioxidant responses, GSK-3β-Wnt/β-catenin signaling, ER stress, and apoptosis. These findings provide insights into the intricate pathogenesis of AD and highlight the neuroprotective effects of nutraceuticals through multiple signaling pathways.

Mesenchymal Stem Cells and Begacestat Mitigate Amyloid-β 25-35-Induced Cognitive Decline in Rat Dams and Hippocampal Deteriorations in Offspring.

Alzheimer's disease (AD) is the most common cause of age-related neurodegeneration and cognitive decline. AD more commonly occurs in females than in males, so it is necessary to consider new treatments specifically targeting this population. The present study investigated the protective effects of Begacestat (γ-secretase inhibitor-953, GSI-953) and bone marrow-derived mesenchymal stem cells (BM-MSCs) during pregnancy on cognitive impairment in rat dams and neurodegeneration in offspring caused by the intracerebroventricular injection of Aβ 25-35 before pregnancy. The performances of dams injected with amyloid-β 25-35 (Aβ 25-35) during behavioral tests were significantly impaired. The offspring of Aβ 25-35-injected dams treated with BM-MSCs or GSI-953 showed a dramatically reduced number and size of activated microglial cells, enhancement in the processes length, and a decrease in the proinflammatory cytokine levels. Additionally, BM-MSC or GSI-953 therapy reduced Aβ 25-35-induced increases in tau phosphorylation and amyloid precursor protein levels in the neonates' hippocampus and elevated the lower levels of glycogen synthase kinase-3 and brain-derived neurotrophic factor; moreover, reversed Aβ 25-35-induced alterations in gene expression in the neonatal hippocampus. Finally, the treatments with BM-MSC or GSI-953 are globally beneficial against Aβ 25-35-induced brain alterations, particularly by suppressing neural inflammation, inhibiting microglial cell activation, restoring developmental plasticity, and increasing neurotrophic signaling.

Cell‐autonomous role of the AD susceptibility gene BIN1 in the regulation of hiPSC‐derived neurons network activity

AbstractBackgroundAlzheimer’s disease (AD) is a multifactorial disease with a strong genetic background. Recent genomic wide association studies have identified several loci linked to an increased risk of AD. However, genes regulated by these variants and the pathophysiological mechanisms regulated by those genes remain largely elusive. In this work, we studied the role of Bridging Integrator 1 (BIN1), the second most important AD risk gene after APOE, in neurons generated from human induced pluripotent stem cells (hiPSCs) in bi‐dimensional cultures and cerebral organoids.MethodWe generated isogenic BIN1 wild‐type (WT), heterozygous (HET) and knockout (KO) hiPSC lines and used these cells to generate human‐induced neurons (hiNs) in bi‐dimensional (2D) and three‐dimensional (cerebral organoids) cell cultures. Next, we used calcium imaging and multi‐electrode array electrophysiology to study the functional properties of hiNs networks. Single‐nucleus RNA‐sequencing (snRNAseq) was used to identify gene expression alterations in individual cell types/subtypes. APP processing and TAU phosphorylation was assessed by western blotting and Alphalisa.ResultWe observed that deletion of BIN1 is sufficient to cause neuronal hyperactivation and network desynchronization in a cell‐autonomous fashion. These functional changes are observed both in 2D cultures and cerebral organoids, and are correlated with increased Tau phosphorylation and transcriptional changes similar to those observed in the brains of AD patients, particularly in glutamatergic neurons.ConclusionOur results reveal a role for BIN1 in the regulation of electrical activity in human neurons and suggest that its implication in AD pathogenesis could be related to the neuronal and network dysfunctions observed in the AD brain.

Chronic Sleep Disturbances Alters Sleep Structure and Tau Phosphorylation in AβPP/PS1 AD Mice and Their Wild-Type Littermates.

Emerging evidence indicates that sleep disorders are the common non-cognitive symptoms of Alzheimer's disease (AD), and they may contribute to the pathogenesis of this disease. In this study, we aim to investigate the effect of chronic sleep deprivation (CSD) on AD-related pathologies with a focus on tau phosphorylation and the underlying DNA methylation regulation. AβPPswe/PS1ΔE9 AD mice and their wild-type (WT) littermates were subjected to a two-month CSD followed by electroencephalography and electromyography recording. The mice were examined for learning and memory evaluation, then pathological, biochemical, and epigenetic assessments including western blotting, immunofluorescence, dot blotting, and bisulfite sequencing. The results show that CSD caused sleep disturbances shown as sleep pattern change, poor sleep maintenance, and increased sleep fragmentation. CSD increased tau phosphorylation at different sites and increased the level of tau kinases in AD and WT mice. The increased expression of cyclin-dependent kinase 5 (CDK5) may result from decreased DNA methylation of CpG sites in the promoter region of CDK5 gene, which might be associated with the downregulation of DNA methyltransferase 3A and 3B. CSD altered AD-related tau phosphorylation through epigenetic modification of tau kinase gene. The findings in this study may give insights into the mechanisms underlying the effects of sleep disturbances on AD pathology and provide new therapeutic targets for the treatment of this disease.

Activation of TRPV4 induces intraneuronal tau hyperphosphorylation via cholesterol accumulation

Transient receptor potential vanilloid 4 (TRPV4) is a non-selective cation channel, whose aberrant function in neurons has been reported to participate in the progression of brain disorders, including Alzheimer's disease (AD). However, the influence of TRPV4 activation on tau hyperphosphorylation in AD has not yet been elucidated. Since disturbed brain cholesterol homeostasis is considered to be related to excessive tau phosphorylation, this study aimed to explore whether dysregulation of TRPV4 affects tau phosphorylation and whether it involves cholesterol unbalance. Our data indicated that TRPV4 activation increased tau phosphorylation in the cortex and hippocampus of P301S tauopathy mouse model and aggravated its cognitive decline. In addition, we detected that TRPV4 activation upregulated cholesterol levels in primary neurons, and the elevation of cholesterol promoted hyperphosphorylation of tau. TRPV4 knockdown improved tau hyperphosphorylation by reducing intracellular cholesterol accumulation. Our results suggest that activation of TRPV4 may take part in the pathological mechanism of AD by promoting intraneuronal tau hyperphosphorylation in a cholesterol-dependent manner.

Alzheimer's disease like neuropathology in Down syndrome cortical organoids.

Introduction: Down syndrome (DS) is a genetic disorder with an extra copy of chromosome 21 and DS remains one of the most common causes of intellectual disabilities in humans. All DS patients have Alzheimer's disease (AD)-like neuropathological changes including accumulation of plaques and tangles by their 40s, much earlier than the onset of such neuropathological changes in AD patients. Due to the lack of human samples and appropriate techniques, our understanding of DS neuropathology during brain development or before the clinical onset of the disease remains largely unexplored at the cellular and molecular levels. Methods: We used induced pluripotent stem cell (iPSC) and iPSC-derived 3D cortical organoids to model Alzheimer's disease in Down syndrome and explore the earliest cellular and molecular changes during DS fetal brain development. Results: We report that DS iPSCs have a decreased growth rate than control iPSCs due to a decreased cell proliferation. DS iPSC-derived cortical organoids have a much higher immunoreactivity of amyloid beta (Aß) antibodies and a significantly higher amount of amyloid plaques than control organoids. Although Elisa results did not detect a difference of Aß40 and Aß42 level between the two groups, the ratio of Aß42/Aß40 in the detergent-insoluble fraction of DS organoids was significantly higher than control organoids. Furthermore, an increased Tau phosphorylation (pTau S396) in DS organoids was confirmed by immunostaining and Western blot. Elisa data demonstrated that the ratio of insoluble Tau/total Tau in DS organoids was significantly higher than control organoids. Conclusion: DS iPSC-derived cortical organoids mimic AD-like pathophysiologyical phenotype in vitro, including abnormal Aß and insoluble Tau accumulation. The molecular neuropathologic signature of AD is present in DS much earlier than predicted, even in early fetal brain development, illustrating the notion that brain organoids maybe a good model to study early neurodegenerative conditions.

The presence of disease‐associated tau leads to adverse effects on the autophagy and endolysosomal pathway in a cell model of tauopathy

AbstractBackgroundDysfunctions in the autophagy and endolysosomal pathways have been reported in Alzheimer’s Disease and related tauopathies. The presence of disease‐associated tau itself may play a role in damaging these pathways leading to its altered clearance. Minimal expression of a disease‐associated truncated tau species (Tau35) in mice results in a progressive tauopathy phenotype, including increased tau phosphorylation, cognitive and behavioural abnormalities and impaired protein clearance. In this study, we sought to explore the effects of Tau35 on the autophagy and endolysosomal pathway in cultured cells expressing Tau35 and from Tau35 mice.MethodChinese hamster ovary (CHO) cells stably expressing Tau35 (CHO‐Tau35) or full‐length human 2N4R tau (CHO‐FL) were generated. Primary cortical neurons from Tau35 transgenic and wild‐type mice were isolated and cultured for 14 days in vitro (DIV). Cells were fixed for immunocytochemistry or lysed to isolate protein/RNA for western blotting and RT‐qPCR to detect the effect of Tau35 expression on autophagy and lysosomal‐related proteins and genes.ResultCHO‐Tau35 cells exhibited a marked reduction in several autophagy and lysosomal‐related markers, including LC3‐II, LAMP2 and cathepsin D. CHO‐Tau35 cells also accumulated lipid droplets and showed disruptions in mammalian target of rapamycin complex 1 (mTORC1) activity and autophagic flux. Moreover, Tau35 expression also resulted in alterations in early endocytic markers, including EEA1. Similar reductions in autophagic and endosomal markers were observed in primary cortical neurons cultured from Tau35 mice. Notably, the nuclear translocation of transcription factor EB (TFEB), a key mediator of lysosomal biogenesis, as well as the transcription of several TFEB‐target genes, was significantly reduced in both CHO‐FL and CHO‐Tau35 cells.ConclusionOur findings suggest that disease‐associated truncated tau damages the clearance of cellular proteins and reduces TFEB‐mediated lysosomal biogenesis. Investigating whether autophagy is disrupted due to tau‐induced lysosomal dysfunction may lead to the identification of novel therapeutic targets for dementia.

Nuclear Inhibitor of Protein Phosphatase 1 (NIPP1) Regulates CNS Tau Phosphorylation and Myelination During Development.

Nuclear inhibitor of protein phosphatase 1 (NIPP1) is a known regulator of gene expression and plays roles in many physiological or pathological processes such as stem cell proliferation and skin inflammation. While NIPP1 has many regulatory roles in proliferating cells, its function in the central nervous system (CNS) has not been directly investigated. In the present study, we examined NIPP1 CNS function using a conditional knockout (cKO) mouse model in which the Nipp1 gene is excised from neural precursor cells. These mice exhibited severe developmental impairments that led to premature lethality. To delineate the neurological changes occurring in these animals, we first assessed microtubule-associated protein tau, a known target of NIPP1 activity. We found that phosphorylation of tau is significantly enhanced in NIPP1 cKO mice. Consistent with this, we found altered AKT and PP1 activity in NIPP1 cKO mice, suggesting that increased tau phosphorylation likely results from a shift in kinase/phosphatase activity. Secondly, we observed tremors in the NIPP1 cKO mice which prompted us to explore the integrity of the myelin sheath, an integral structure for CNS function. We demonstrated that in NIPP1 cKO mice, there is a significant decrease in MBP protein expression in the cortex, along with deficits in both the conduction of compound action potentials (CAP) and the percentage of myelinated axons in the optic nerve. Our study suggests that NIPP1 in neural precursor cells regulates phosphorylation of tau and CNS myelination and may represent a novel therapeutic target for neurodegenerative diseases.

The 28-day repeated arsenic exposure increases tau phosphorylation in the rat brain

Herein, we examined whether prolonged arsenic exposure altered tau phosphorylation in the brain of Sprague Dawley rats expressing endogenous wild-type tau. The results showed that daily intraperitoneal injections of 2.5 mg/kg BW sodium arsenite over 28 days caused arsenic accumulation in the rat brain. Interestingly, we found an increase in tau phosphorylation at the Tau 1 region (189−207) and S202 in the hippocampus, S404 in the cerebral cortex, and S396 and S404 in the cerebellum of arsenic-treated rats. Additionally, arsenic increased active ERK1/2 phosphorylation at T202/Y204 in the hippocampus, cerebral cortex, and cerebellum. Meanwhile, we detected increasing active JNK phosphorylation at T183/Y185 in the hippocampus and cerebellum. Moreover, p35, a neuron-specific activator of CDK5, was also elevated in the cerebellum of arsenic-treated rats, suggesting that CDK5 activity may be increased by arsenic. These results suggested that arsenic may induce tau phosphorylation through the activation of tau kinases, ERK1/2, JNK, and CDK5. Together, the findings from this study demonstrated that prolonged arsenic exposure is implicated in neurodegeneration by promoting tau phosphorylation in the rat brain and points toward a possible prevention strategy against neurodegeneration induced by environmental arsenic exposure.