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Farfara D, Sooliman M, Avrahami L, Royal TG, Amram S, Rozenstein-Tsalkovich L, Trudler D, Blanga-Kanfi S, Eldar-Finkelman H, Pahnke J, Rosenmann H, Frenkel D. Physiological expression of mutated TAU impaired astrocyte activity and exacerbates β-amyloid pathology in 5xFAD mice. J Neuroinflammation 2023; 20:174. [PMID: 37496076 PMCID: PMC10369740 DOI: 10.1186/s12974-023-02823-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 06/04/2023] [Indexed: 07/28/2023] Open
Abstract
BACKGROUND Alzheimer's disease (AD) is the leading cause of dementia in the world. The pathology of AD is affiliated with the elevation of both tau (τ) and β-amyloid (Aβ) pathologies. Yet, the direct link between natural τ expression on glia cell activity and Aβ remains unclear. While experiments in mouse models suggest that an increase in Aβ exacerbates τ pathology when expressed under a neuronal promoter, brain pathology from AD patients suggests an appearance of τ pathology in regions without Aβ. METHODS Here, we aimed to assess the link between τ and Aβ using a new mouse model that was generated by crossing a mouse model that expresses two human mutations of the human MAPT under a mouse Tau natural promoter with 5xFAD mice that express human mutated APP and PS1 in neurons. RESULTS The new mouse model, called 5xFAD TAU, shows accelerated cognitive impairment at 2 months of age, increased number of Aβ depositions at 4 months and neuritic plaques at 6 months of age. An expression of human mutated TAU in astrocytes leads to a dystrophic appearance and reduces their ability to engulf Aβ, which leads to an increased brain Aβ load. Astrocytes expressing mutated human TAU showed an impairment in the expression of vascular endothelial growth factor (VEGF) that has previously been suggested to play an important role in supporting neurons. CONCLUSIONS Our results suggest the role of τ in exacerbating Aβ pathology in addition to pointing out the potential role of astrocytes in disease progression. Further research of the crosstalk between τ and Aβ in astrocytes may increase our understanding of the role glia cells have in the pathology of AD with the aim of identifying novel therapeutic interventions to an otherwise currently incurable disease.
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Affiliation(s)
- Dorit Farfara
- Department of Neurobiology, School of Neurobiology, Biochemistry and Biophysics, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Meital Sooliman
- Department of Neurobiology, School of Neurobiology, Biochemistry and Biophysics, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Limor Avrahami
- Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978, Tel Aviv, Israel
| | - Tabitha Grace Royal
- Department of Neurobiology, School of Neurobiology, Biochemistry and Biophysics, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Shoshik Amram
- Department of Neurobiology, School of Neurobiology, Biochemistry and Biophysics, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Lea Rozenstein-Tsalkovich
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Dorit Trudler
- Department of Neurobiology, School of Neurobiology, Biochemistry and Biophysics, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Shani Blanga-Kanfi
- Department of Neurobiology, School of Neurobiology, Biochemistry and Biophysics, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Hagit Eldar-Finkelman
- Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978, Tel Aviv, Israel
| | - Jens Pahnke
- Department of Neurobiology, School of Neurobiology, Biochemistry and Biophysics, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
- Section of Neuropathology, Translational Neurodegeneration Research and Neuropathology Lab, Department of Pathology, University of Oslo (UiO) and Oslo University Hospital (OUS), Oslo, Norway.
- Drug Development and Chemical Biology, Lübeck Institute of Dermatology (LIED), University Medical Center Schleswig Holstein (UKSH), LIED, Lübeck, Germany.
- Department of Pharmacology, Faculty of Medicine, University of Latvia, Riga, Latvia.
| | - Hanna Rosenmann
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew University Medical Center, Jerusalem, Israel.
| | - Dan Frenkel
- Department of Neurobiology, School of Neurobiology, Biochemistry and Biophysics, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
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Sweetat S, Nitzan K, Suissa N, Haimovich Y, Lichtenstein M, Zabit S, Benhamron S, Akarieh K, Mishra K, Barasch D, Saada A, Ziv T, Kakhlon O, Lorberboum-Galski H, Rosenmann H. The Beneficial Effect of Mitochondrial Transfer Therapy in 5XFAD Mice via Liver–Serum–Brain Response. Cells 2023; 12:cells12071006. [PMID: 37048079 PMCID: PMC10093713 DOI: 10.3390/cells12071006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 03/15/2023] [Accepted: 03/21/2023] [Indexed: 03/29/2023] Open
Abstract
We recently reported the benefit of the IV transferring of active exogenous mitochondria in a short-term pharmacological AD (Alzheimer’s disease) model. We have now explored the efficacy of mitochondrial transfer in 5XFAD transgenic mice, aiming to explore the underlying mechanism by which the IV-injected mitochondria affect the diseased brain. Mitochondrial transfer in 5XFAD ameliorated cognitive impairment, amyloid burden, and mitochondrial dysfunction. Exogenously injected mitochondria were detected in the liver but not in the brain. We detected alterations in brain proteome, implicating synapse-related processes, ubiquitination/proteasome-related processes, phagocytosis, and mitochondria-related factors, which may lead to the amelioration of disease. These changes were accompanied by proteome/metabolome alterations in the liver, including pathways of glucose, glutathione, amino acids, biogenic amines, and sphingolipids. Altered liver metabolites were also detected in the serum of the treated mice, particularly metabolites that are known to affect neurodegenerative processes, such as carnosine, putrescine, C24:1-OH sphingomyelin, and amino acids, which serve as neurotransmitters or their precursors. Our results suggest that the beneficial effect of mitochondrial transfer in the 5XFAD mice is mediated by metabolic signaling from the liver via the serum to the brain, where it induces protective effects. The high efficacy of the mitochondrial transfer may offer a novel AD therapy.
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Parrocha CMT, Nowick JS. Current Peptide Vaccine and Immunotherapy Approaches Against Alzheimer's Disease. Pept Sci (Hoboken) 2023; 115:e24289. [PMID: 36778914 PMCID: PMC9916509 DOI: 10.1002/pep2.24289] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Peptide vaccines and immunotherapies against aggregating proteins involved in the pathogenesis and progression of Alzheimer's disease (AD) - the β-amyloid peptide (Aβ) and tau - are promising therapeutic avenues against AD. Two decades of effort has led to the controversial FDA approval of the monoclonal antibody Aducanumab (Aduhelm), which has subsequentially sparked the revival and expedited review of promising monoclonal antibody immunotherapies that target Aβ. In this review, we explore the development of Aβ and tau peptide vaccines and immunotherapies with monoclonal antibodies in clinical trials against AD.
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Affiliation(s)
| | - James S. Nowick
- Department of Chemistry, University of California Irvine, Irvine, CA 92697,Department of Pharmaceutical Sciences, University of California Irvine, Irvine, CA 92697
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4
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Peptide-Based Vaccines for Neurodegenerative Diseases: Recent Endeavors and Future Perspectives. Vaccines (Basel) 2021; 9:vaccines9111278. [PMID: 34835209 PMCID: PMC8622585 DOI: 10.3390/vaccines9111278] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 10/25/2021] [Accepted: 10/30/2021] [Indexed: 02/06/2023] Open
Abstract
The development of peptide-based vaccines for treating human neurodegenerative diseases has been the eventual aim of many research endeavors, although no active immunotherapies have been approved for clinical use till now. A typical example of such endeavors is the effort to develop vaccines for Alzheimer’s disease based on the beta-amyloid peptide, which continues to be intensively investigated despite previous setbacks. In this paper, recent developments in peptide-based vaccines which target beta-amyloid as well as tau protein and α-synuclein are presented. Particular focus has been directed toward peptide epitopes and formulation systems selected/developed and employed to enhance vaccine efficacy and safety. Results from both, human clinical trials and animal preclinical studies conducted mainly in transgenic mice have been included. Future perspectives on the topic are also briefly discussed.
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5
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Roda AR, Montoliu-Gaya L, Serra-Mir G, Villegas S. Both Amyloid-β Peptide and Tau Protein Are Affected by an Anti-Amyloid-β Antibody Fragment in Elderly 3xTg-AD Mice. Int J Mol Sci 2020; 21:E6630. [PMID: 32927795 PMCID: PMC7554787 DOI: 10.3390/ijms21186630] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 09/02/2020] [Accepted: 09/04/2020] [Indexed: 12/15/2022] Open
Abstract
Alzheimer's disease (AD) is the most common dementia worldwide. According to the amyloid hypothesis, the early accumulation of the Aβ-peptide triggers tau phosphorylation, synaptic dysfunction, and eventually neuronal death leading to cognitive impairment, as well as behavioral and psychological symptoms of dementia. ScFv-h3D6 is a single-chain variable fragment that has already shown its ability to diminish the amyloid burden in 5-month-old 3xTg-AD mice. However, tau pathology is not evident at this early stage of the disease in this mouse model. In this study, the effects of scFv-h3D6 on Aβ and tau pathologies have been assessed in 22-month-old 3xTg-AD mice. Briefly, 3xTg-AD female mice were treated for 2 weeks with scFv-h3D6 and compared with 3xTg-AD and non-transgenic (NTg) mice treated with PBS. The treatment with scFv-h3D6 was unequivocally effective in reducing the area of Aβ staining. Furthermore, a tendency for a reduction in tau levels was also observed after treatment that points to the interplay between Aβ and tau pathologies. The pro-inflammatory state observed in the 3xTg-AD mice did not progress after scFv-h3D6 treatment. In addition, the treatment did not alter the levels of apolipoprotein E or apolipoprotein J. Thus, a 2-week treatment with scFv-h3D6 was able to reduce AD-like pathology in elderly 3xTg-AD female mice.
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Affiliation(s)
- Alejandro R. Roda
- Protein Design and Immunotherapy Group, Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain; (A.R.R.); (L.M.-G.); (G.S.-M.)
| | - Laia Montoliu-Gaya
- Protein Design and Immunotherapy Group, Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain; (A.R.R.); (L.M.-G.); (G.S.-M.)
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, 431 41 Mölndal, Sweden
| | - Gabriel Serra-Mir
- Protein Design and Immunotherapy Group, Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain; (A.R.R.); (L.M.-G.); (G.S.-M.)
| | - Sandra Villegas
- Protein Design and Immunotherapy Group, Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain; (A.R.R.); (L.M.-G.); (G.S.-M.)
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6
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Maron R, Armony G, Tsoory M, Wilchek M, Frenkel D, Arnon R. Peptide Interference with APP and Tau Association: Relevance to Alzheimer's Disease Amelioration. Int J Mol Sci 2020; 21:E3270. [PMID: 32380752 PMCID: PMC7246762 DOI: 10.3390/ijms21093270] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Revised: 04/27/2020] [Accepted: 04/29/2020] [Indexed: 01/02/2023] Open
Abstract
The two major proteins involved in Alzheimer's disease (AD) are the amyloid precursor protein (APP) and Tau. Here, we demonstrate that these two proteins can bind to each other. Four possible peptides APP1 (390-412), APP2 (713-730), Tau1 (19-34) and Tau2 (331-348), were predicted to be involved in this interaction, with actual binding confirmed for APP1 and Tau1. In vivo studies were performed in an Alzheimer Disease animal model-APP double transgenic (Tg) 5xFAD-as well as in 5xFAD crossed with Tau transgenic 5xFADXTau (FT), which exhibit declined cognitive reduction at four months of age. Nasal administration of APP1 and Tau1 mixture, three times a week for four or five months, reduced amyloid plaque burden as well as the level of soluble Aβ 1-42 in the brain. The treatment prevented the deterioration of cognitive functions when initiated at the age of three months, before cognitive deficiency was evident, and also at the age of six months, when such deficiencies are already observed, leading to a full regain of cognitive function.
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Affiliation(s)
- Ruth Maron
- Department of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Gad Armony
- Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Michael Tsoory
- Department of Veterinary Resources, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Meir Wilchek
- Department of Biomolecular Science, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Dan Frenkel
- Department of Neurobiology, School of Neurobiology, Biochemistry and Biophysics, The George S. Wise Faculty of Life Sciences, Sagol School of Neuroscience Tel Aviv University, Tel Aviv 6997801, Israel;
| | - Ruth Arnon
- Department of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel;
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Binyamin O, Nitzan K, Frid K, Ungar Y, Rosenmann H, Gabizon R. Brain targeting of 9c,11t-Conjugated Linoleic Acid, a natural calpain inhibitor, preserves memory and reduces Aβ and P25 accumulation in 5XFAD mice. Sci Rep 2019; 9:18437. [PMID: 31804596 PMCID: PMC6895090 DOI: 10.1038/s41598-019-54971-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 11/21/2019] [Indexed: 02/08/2023] Open
Abstract
Deregulation of Cyclin-dependent kinase 5 (CDK5) by binding to the activated calpain product p25, is associated with the onset of neurodegenerative diseases, such as Alzheimer's disease (AD). Conjugated Linoleic Acid (CLA), a calpain inhibitor, is a metabolite of Punicic Acid (PA), the main component of Pomegranate seed oil (PSO). We have shown recently that long-term administration of Nano-PSO, a nanodroplet formulation of PSO, delays mitochondrial damage and disease advance in a mouse model of genetic Creutzfeldt Jacob disease (CJD). In this project, we first demonstrated that treatment of mice with Nano-PSO, but not with natural PSO, results in the accumulation of CLA in their brains. Next, we tested the cognitive, biochemical and pathological effects of long-term administration of Nano-PSO to 5XFAD mice, modeling for Alzheimer's disease. We show that Nano-PSO treatment prevented age-related cognitive deterioration and mitochondrial oxidative damage in 5XFAD mice. Also, brains of the Nano-PSO treated mice presented reduced accumulation of Aβ and of p25, a calpain product, and increased expression of COX IV-1, a key mitochondrial enzyme. We conclude that administration of Nano-PSO results in the brain targeting of CLA, and suggest that this treatment may prevent/delay the onset of neurodegenerative diseases, such as AD and CJD.
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Affiliation(s)
- Orli Binyamin
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Keren Nitzan
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Kati Frid
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Yael Ungar
- Chemistry laboratory, Milouda & Migal Laboratories, Merieux Nutrisciences, Milu'ot South Industrial Zone, Akko, Israel
| | - Hanna Rosenmann
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Ruth Gabizon
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
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8
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Joly-Amado A, Davtyan H, Serraneau K, Jules P, Zitnyar A, Pressman E, Zagorski K, Antonyan T, Hovakimyan A, Paek HJ, Gordon MN, Cribbs DH, Petrovsky N, Agadjanyan MG, Ghochikyan A, Morgan D. Active immunization with tau epitope in a mouse model of tauopathy induced strong antibody response together with improvement in short memory and pSer396-tau pathology. Neurobiol Dis 2019; 134:104636. [PMID: 31629891 DOI: 10.1016/j.nbd.2019.104636] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 08/30/2019] [Accepted: 10/07/2019] [Indexed: 12/16/2022] Open
Abstract
Abnormal tau hyperphosphorylation and its aggregation into neurofibrillary tangles are a hallmark of tauopathies, neurodegenerative disorders that include Alzheimer's disease (AD). Active and passive Tau-immunotherapy has been proposed as a therapeutic approach to AD with mixed results. One of the limitations of active immunotherapy may be associated with the mediocre immunogenicity of vaccines that are not inducing therapeutically potent titers of antibodies. The aim of this study was to test the efficacy of an anti-tau vaccine, AV-1980R/A composed of N terminal peptide of this molecule fused with an immunogenic MultiTEP platform and formulated in a strong adjuvant, AdvaxCpG in a Tg4510 mouse model of tauopathy. Experimental mice were immunized with AV-1980R/A and a control group of mice were injected with adjuvant only. Nontransgenic and tetracycline transactivator (tTA) transgenic littermates were included as baseline controls to contrast with the tau phenotype. Active immunization with AV-1980R/A induced very strong anti-tau humoral immune responses in both nontransgenic and transgenic mice with evidence of IgG in brains of AV-1980R/A vaccinated mice. These experimental animals displayed an improvement in short-term memory during a novel object recognition test. However, impairments in other behavioral tasks were not prevented by AV-1980R/A vaccinations. At the same time, high titers of anti-tau antibodies reduced hyperphosphorylated pSer396 tau but did not lower the level of other phosphorylated tau species in the brains of AV-1980R/A vaccinated mice. These data indicate that active immunotherapy with an N-terminal Tau epitope was only partially effective in improving cognition and reducing pathology in the stringent Tg4510 mouse model of tauopathy.
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Affiliation(s)
- A Joly-Amado
- USF Health Byrd Alzheimer's Institute, Tampa, FL 33613, USA.
| | - H Davtyan
- The Institute for Molecular Medicine, Huntington Beach, CA 92647, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - K Serraneau
- USF Health Byrd Alzheimer's Institute, Tampa, FL 33613, USA
| | - P Jules
- USF Health Byrd Alzheimer's Institute, Tampa, FL 33613, USA
| | - A Zitnyar
- USF Health Byrd Alzheimer's Institute, Tampa, FL 33613, USA
| | - E Pressman
- USF Health Byrd Alzheimer's Institute, Tampa, FL 33613, USA
| | - K Zagorski
- The Institute for Molecular Medicine, Huntington Beach, CA 92647, USA
| | - T Antonyan
- The Institute for Molecular Medicine, Huntington Beach, CA 92647, USA
| | - A Hovakimyan
- The Institute for Molecular Medicine, Huntington Beach, CA 92647, USA
| | - H J Paek
- Molecular Pharmacology and Physiology, College of Medicine, University of South Florida, Tampa, FL, USA
| | - M N Gordon
- USF Health Byrd Alzheimer's Institute, Tampa, FL 33613, USA
| | - D H Cribbs
- Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - N Petrovsky
- Flinders Med. Ctr., Bedford Park, Adelaide 5042, Australia
| | - M G Agadjanyan
- The Institute for Molecular Medicine, Huntington Beach, CA 92647, USA
| | - A Ghochikyan
- The Institute for Molecular Medicine, Huntington Beach, CA 92647, USA
| | - D Morgan
- USF Health Byrd Alzheimer's Institute, Tampa, FL 33613, USA
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Vogels T, Murgoci AN, Hromádka T. Intersection of pathological tau and microglia at the synapse. Acta Neuropathol Commun 2019; 7:109. [PMID: 31277708 PMCID: PMC6612163 DOI: 10.1186/s40478-019-0754-y] [Citation(s) in RCA: 112] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 06/19/2019] [Indexed: 02/07/2023] Open
Abstract
Tauopathies are a heterogenous class of diseases characterized by cellular accumulation of aggregated tau and include diseases such as Alzheimer’s disease (AD), progressive supranuclear palsy and chronic traumatic encephalopathy. Tau pathology is strongly linked to neurodegeneration and clinical symptoms in tauopathy patients. Furthermore, synapse loss is an early pathological event in tauopathies and is the strongest correlate of cognitive decline. Tau pathology is additionally associated with chronic neuroinflammatory processes, such as reactive microglia, astrocytes, and increased levels of pro-inflammatory molecules (e.g. complement proteins, cytokines). Recent studies show that as the principal immune cells of the brain, microglia play a particularly important role in the initiation and progression of tau pathology and associated neurodegeneration. Furthermore, AD risk genes such as Triggering receptor expressed on myeloid cells 2 (TREM2) and Apolipoprotein E (APOE) are enriched in the innate immune system and modulate the neuroinflammatory response of microglia to tau pathology. Microglia can play an active role in synaptic dysfunction by abnormally phagocytosing synaptic compartments of neurons with tau pathology. Furthermore, microglia are involved in synaptic spreading of tau – a process which is thought to underlie the progressive nature of tau pathology propagation through the brain. Spreading of pathological tau is also the predominant target for tau-based immunotherapy. Active tau vaccines, therapeutic tau antibodies and other approaches targeting the immune system are actively explored as treatment options for AD and other tauopathies. This review describes the role of microglia in the pathobiology of tauopathies and the mechanism of action of potential therapeutics targeting the immune system in tauopathies.
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