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Karkisaval AG, Hassan R, Nguyen A, Balster B, Abedin F, Lal R, Tatulian SA. The structure of tyrosine-10 favors ionic conductance of Alzheimer's disease-associated full-length amyloid-β channels. Nat Commun 2024; 15:1296. [PMID: 38351257 PMCID: PMC10864385 DOI: 10.1038/s41467-023-43821-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Accepted: 11/21/2023] [Indexed: 02/16/2024] Open
Abstract
Amyloid β (Aβ) ion channels destabilize cellular ionic homeostasis, which contributes to neurotoxicity in Alzheimer's disease. The relative roles of various Aβ isoforms are poorly understood. We use bilayer electrophysiology, AFM imaging, circular dichroism, FTIR and fluorescence spectroscopy to characterize channel activities of four most prevalent Aβ peptides, Aβ1-42, Aβ1-40, and their pyroglutamylated forms (AβpE3-42, AβpE3-40) and correlate them with the peptides' structural features. Solvent-induced fluorescence splitting of tyrosine-10 is discovered and used to assess the sequestration from the solvent and membrane insertion. Aβ1-42 effectively embeds in lipid membranes, contains large fraction of β-sheet in a β-barrel-like structure, forms multi-subunit pores in membranes, and displays well-defined ion channel features. In contrast, the other peptides are partially solvent-exposed, contain minimal β-sheet structure, form less-ordered assemblies, and produce irregular ionic currents. These findings illuminate the structural basis of Aβ neurotoxicity through membrane permeabilization and may help develop therapies that target Aβ-membrane interactions.
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Affiliation(s)
- Abhijith G Karkisaval
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, USA
| | - Rowan Hassan
- Department of Physics, University of Central Florida, Orlando, FL, USA
| | - Andrew Nguyen
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA
| | - Benjamin Balster
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA
| | - Faisal Abedin
- Department of Physics, University of Central Florida, Orlando, FL, USA
- Department of Biology, Xavier University of Louisiana, New Orleans, LA, USA
| | - Ratnesh Lal
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, USA.
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA.
| | - Suren A Tatulian
- Department of Physics, University of Central Florida, Orlando, FL, USA.
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2
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Zambrano P, Jemiola-Rzeminska M, Muñoz-Torrero D, Suwalsky M, Strzalka K. A rhein-huprine hybrid protects erythrocyte membrane integrity against Alzheimer's disease related Aβ(1-42) peptide. Biophys Chem 2023; 300:107061. [PMID: 37307659 DOI: 10.1016/j.bpc.2023.107061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 05/26/2023] [Accepted: 06/02/2023] [Indexed: 06/14/2023]
Abstract
Alzheimer's disease remains largely unknown, and currently there is no complete cure for the disease. New synthetic approaches have been developed to create multi-target agents, such as RHE-HUP, a rhein-huprine hybrid which can modulate several biological targets that are relevant to the development of the disease. While RHE-HUP has shown in vitro and in vivo beneficial effects, the molecular mechanisms by which it exerts its protective effect on cell membranes have not been fully clarified. To better understand RHE-HUP interactions with cell membranes, we used synthetic membrane models and natural models of human membranes. For this purpose, human erythrocytes and molecular model of its membrane built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were used. The latter correspond to classes of phospholipids present in the outer and inner monolayers of the human erythrocyte membrane, respectively. X-ray diffraction and differential scanning calorimetry (DSC) results indicated that RHE-HUP was able to interact mainly with DMPC. In addition, scanning electron microscopy (SEM) analysis showed that RHE-HUP modified the normal biconcave shape of erythrocytes inducing the formation of echinocytes. Moreover, the protective effect of RHE-HUP against the disruptive effect of Aβ(1-42) on the studied membrane models was tested. X-ray diffraction experiments showed that RHE-HUP induced a recovery in the ordering of DMPC multilayers after the disruptive effect of Aβ(1-42), confirming the protective role of the hybrid.
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Affiliation(s)
- Pablo Zambrano
- Facultad de Ciencias Químicas, Universidad de Concepción, Concepción, Chile.
| | - Malgorzata Jemiola-Rzeminska
- Malopolska Centre of Biotechnology, Jagiellonian University, Kraków, Poland; Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland
| | - Diego Muñoz-Torrero
- Laboratory of Medicinal Chemistry (CSIC Associated Unit), Faculty of Pharmacy and Food Sciences, University of Barcelona, Barcelona, Spain; Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain
| | - Mario Suwalsky
- Facultad de Medicina, Universidad Católica de la Santísima Concepción, Concepción, Chile
| | - Kazimierz Strzalka
- Malopolska Centre of Biotechnology, Jagiellonian University, Kraków, Poland; Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland
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3
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Basli A, Bounaas J. Pathophysiological mechanism and natural preventive and therapeutic strategies of Alzheimer's disease. Nutr Health 2023; 29:403-413. [PMID: 36377316 DOI: 10.1177/02601060221137104] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Alzheimer's disease (AD) is characterized by the presence of two types of protein deposits in the brain, amyloid plaques and neurofibrillary tangles. The first one are dense deposits of beta amyloid protein, the second one are dense deposits of the protein tau. These proteins are present in all of our brains, but in AD they act unusually, leading to neuronal degeneration. This review will provide an overview of the AD, including the role of amyloid beta and tau, and mechanisms that lead to the formation of plaques and tangles. The review will also cover the existing researches that have focused on the inhibition of amyloid beta formation, cholinesterase, tau hyperphosphorylation, the pathogenic mechanisms of apoE4, and GSK-3 as a solution that could be used to slow or prevent the disease.
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Affiliation(s)
- Abdelkader Basli
- Laboratory of Interaction Research, Biodiversity, Ecosystems and Biotechnology, Faculty of Sciences, University of Skikda, Skikda, Algeria
| | - Jihane Bounaas
- Laboratory of Interaction Research, Biodiversity, Ecosystems and Biotechnology, Faculty of Sciences, University of Skikda, Skikda, Algeria
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4
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Li S, Ji X, Gao M, Huang B, Peng S, Wu J. Endogenous Amyloid-formed Ca 2+-permeable Channels in Aged 3xTg AD Mice. FUNCTION 2023; 4:zqad025. [PMID: 37342418 PMCID: PMC10278988 DOI: 10.1093/function/zqad025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 05/13/2023] [Accepted: 05/25/2023] [Indexed: 06/22/2023] Open
Abstract
Alzheimer's disease (AD), the leading cause of dementia, is characterized by the accumulation of beta-amyloid peptides (Aβ). However, whether Aβ itself is a key toxic agent in AD pathogenesis and the precise mechanism of Aβ-elicited neurotoxicity are still debated. Emerging evidence demonstrates that the Aβ channel/pore hypothesis could explain Aβ toxicity, because Aβ oligomers are able to disrupt membranes and cause edge-conductivity pores that may disrupt cell Ca2+ homeostasis and drive neurotoxicity in AD. However, all available data to support this hypothesis have been collected from "in vitro" experiments using high concentrations of exogenous Aβ. It is still unknown whether Aβ channels can be formed by endogenous Aβ in AD animal models. Here, we report an unexpected finding of the spontaneous Ca2+ oscillations in aged 3xTg AD mice but not in age-matched wild-type mice. These spontaneous Ca2+ oscillations are sensitive to extracellular Ca2+, ZnCl2, and the Aβ channel blocker Anle138b, suggesting that these spontaneous Ca2+ oscillations in aged 3xTg AD mice are mediated by endogenous Aβ-formed channels.
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Affiliation(s)
- Shuangtao Li
- Brain Function and Disease Laboratory, Shantou University Medical College, Shantou, Guangdong 515041, China
| | - Xiaoyu Ji
- Brain Function and Disease Laboratory, Shantou University Medical College, Shantou, Guangdong 515041, China
- Department of Neurosurgery, First Affiliated Hospital, Shantou University Medical College, Shantou, Guangdong 515041, China
| | - Ming Gao
- Department of Neurobiology, Barrow Neurological Institute and St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA
| | - Bing Huang
- Brain Function and Disease Laboratory, Shantou University Medical College, Shantou, Guangdong 515041, China
- Department of Neurosurgery, First Affiliated Hospital, Shantou University Medical College, Shantou, Guangdong 515041, China
| | - Shuang Peng
- School of Sport and Health Sciences, Guangzhou Sport University, Guangzhou 510500, China
- Key Laboratory of Sports Technique, Tactics and Physical Function of General Administration of Sport of China, Scientific Research Center, Guangzhou Sport University, Guangzhou 510500, China
| | - Jie Wu
- Brain Function and Disease Laboratory, Shantou University Medical College, Shantou, Guangdong 515041, China
- Department of Neurosurgery, First Affiliated Hospital, Shantou University Medical College, Shantou, Guangdong 515041, China
- Department of Neurobiology, Barrow Neurological Institute and St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA
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5
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Ma C, Hong F, Yang S. Amyloidosis in Alzheimer's Disease: Pathogeny, Etiology, and Related Therapeutic Directions. Molecules 2022; 27:1210. [PMID: 35209007 PMCID: PMC8876037 DOI: 10.3390/molecules27041210] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 01/25/2022] [Accepted: 02/01/2022] [Indexed: 11/23/2022] Open
Abstract
The amyloid hypothesis of Alzheimer's disease has long been the predominant theory, suggesting that Alzheimer's disease is caused by the accumulation of amyloid beta protein (Aβ) in the brain, leading to neuronal toxicity in the central nervous system (CNS). Because of breakthroughs in molecular medicine, the amyloid pathway is thought to be central to the pathophysiology of Alzheimer's disease (AD). Currently, it is believed that altered biochemistry of the Aβ cycle remains a central biological feature of AD and is a promising target for treatment. This review provides an overview of the process of amyloid formation, explaining the transition from amyloid precursor protein to amyloid beta protein. Moreover, we also reveal the relationship between autophagy, cerebral blood flow, ACHE, expression of LRP1, and amyloidosis. In addition, we discuss the detailed pathogenesis of amyloidosis, including oxidative damage, tau protein, NFTs, and neuronal damage. Finally, we list some ways to treat AD in terms of decreasing the accumulation of Aβ in the brain.
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Affiliation(s)
- Chen Ma
- Experimental Center of Pathogen Biology, Nanchang University, Nanchang 330006, China;
- Queen Marry College, School of Medicine, Nanchang University, Nanchang 330036, China
| | - Fenfang Hong
- Experimental Center of Pathogen Biology, Nanchang University, Nanchang 330006, China;
| | - Shulong Yang
- Department of Physiology, College of Medicine, Nanchang University, Nanchang 330006, China
- Department of Physiology, Fuzhou Medical College, Nanchang University, Nanchang 344099, China
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6
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Sanchez-Varo R, Sanchez-Mejias E, Fernandez-Valenzuela JJ, De Castro V, Mejias-Ortega M, Gomez-Arboledas A, Jimenez S, Sanchez-Mico MV, Trujillo-Estrada L, Moreno-Gonzalez I, Baglietto-Vargas D, Vizuete M, Davila JC, Vitorica J, Gutierrez A. Plaque-Associated Oligomeric Amyloid-Beta Drives Early Synaptotoxicity in APP/PS1 Mice Hippocampus: Ultrastructural Pathology Analysis. Front Neurosci 2021; 15:752594. [PMID: 34803589 PMCID: PMC8600261 DOI: 10.3389/fnins.2021.752594] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 10/04/2021] [Indexed: 01/14/2023] Open
Abstract
Alzheimer’s disease (AD) is a devastating neurodegenerative disorder characterized by initial memory impairments that progress to dementia. In this sense, synaptic dysfunction and loss have been established as the pathological features that best correlate with the typical early cognitive decline in this disease. At the histopathological level, post mortem AD brains typically exhibit intraneuronal neurofibrillary tangles (NFTs) along with the accumulation of amyloid-beta (Abeta) peptides in the form of extracellular deposits. Specifically, the oligomeric soluble forms of Abeta are considered the most synaptotoxic species. In addition, neuritic plaques are Abeta deposits surrounded by activated microglia and astroglia cells together with abnormal swellings of neuronal processes named dystrophic neurites. These periplaque aberrant neurites are mostly presynaptic elements and represent the first pathological indicator of synaptic dysfunction. In terms of losing synaptic proteins, the hippocampus is one of the brain regions most affected in AD patients. In this work, we report an early decline in spatial memory, along with hippocampal synaptic changes, in an amyloidogenic APP/PS1 transgenic model. Quantitative electron microscopy revealed a spatial synaptotoxic pattern around neuritic plaques with significant loss of periplaque synaptic terminals, showing rising synapse loss close to the border, especially in larger plaques. Moreover, dystrophic presynapses were filled with autophagic vesicles in detriment of the presynaptic vesicular density, probably interfering with synaptic function at very early synaptopathological disease stages. Electron immunogold labeling showed that the periphery of amyloid plaques, and the associated dystrophic neurites, was enriched in Abeta oligomers supporting an extracellular location of the synaptotoxins. Finally, the incubation of primary neurons with soluble fractions derived from 6-month-old APP/PS1 hippocampus induced significant loss of synaptic proteins, but not neuronal death. Indeed, this preclinical transgenic model could serve to investigate therapies targeted at initial stages of synaptic dysfunction relevant to the prodromal and early AD.
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Affiliation(s)
- Raquel Sanchez-Varo
- Departamento Biologia Celular, Genetica y Fisiologia, Instituto de Investigacion Biomedica de Malaga-IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.,Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento Fisiologia Humana, Histologia Humana, Anatomia Patologica y Educacion Fisica y Deportiva, Facultad de Medicina, Universidad de Málaga, Málaga, Spain
| | - Elisabeth Sanchez-Mejias
- Departamento Biologia Celular, Genetica y Fisiologia, Instituto de Investigacion Biomedica de Malaga-IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.,Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Juan Jose Fernandez-Valenzuela
- Departamento Biologia Celular, Genetica y Fisiologia, Instituto de Investigacion Biomedica de Malaga-IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.,Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Vanessa De Castro
- Departamento Biologia Celular, Genetica y Fisiologia, Instituto de Investigacion Biomedica de Malaga-IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
| | - Marina Mejias-Ortega
- Departamento Biologia Celular, Genetica y Fisiologia, Instituto de Investigacion Biomedica de Malaga-IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.,Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Angela Gomez-Arboledas
- Departamento Biologia Celular, Genetica y Fisiologia, Instituto de Investigacion Biomedica de Malaga-IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.,Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Sebastian Jimenez
- Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento Bioquimica y Biologia Molecular, Facultad de Farmacia, Universidad de Sevilla, Seville, Spain.,Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocio CSIC/Universidad de Sevilla, Seville, Spain
| | - Maria Virtudes Sanchez-Mico
- Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento Bioquimica y Biologia Molecular, Facultad de Farmacia, Universidad de Sevilla, Seville, Spain.,Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocio CSIC/Universidad de Sevilla, Seville, Spain
| | - Laura Trujillo-Estrada
- Departamento Biologia Celular, Genetica y Fisiologia, Instituto de Investigacion Biomedica de Malaga-IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.,Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Ines Moreno-Gonzalez
- Departamento Biologia Celular, Genetica y Fisiologia, Instituto de Investigacion Biomedica de Malaga-IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.,Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Department of Neurology, McGovern Medical School, UTHealth Science Center at Houston, Houston, TX, United States
| | - David Baglietto-Vargas
- Departamento Biologia Celular, Genetica y Fisiologia, Instituto de Investigacion Biomedica de Malaga-IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.,Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Marisa Vizuete
- Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento Bioquimica y Biologia Molecular, Facultad de Farmacia, Universidad de Sevilla, Seville, Spain.,Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocio CSIC/Universidad de Sevilla, Seville, Spain
| | - Jose Carlos Davila
- Departamento Biologia Celular, Genetica y Fisiologia, Instituto de Investigacion Biomedica de Malaga-IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.,Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Javier Vitorica
- Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento Bioquimica y Biologia Molecular, Facultad de Farmacia, Universidad de Sevilla, Seville, Spain.,Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocio CSIC/Universidad de Sevilla, Seville, Spain
| | - Antonia Gutierrez
- Departamento Biologia Celular, Genetica y Fisiologia, Instituto de Investigacion Biomedica de Malaga-IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.,Centro de Investigación Biomedica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
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7
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Boopathi S, Poma AB, Garduño-Juárez R. An Overview of Several Inhibitors for Alzheimer's Disease: Characterization and Failure. Int J Mol Sci 2021; 22:10798. [PMID: 34639140 PMCID: PMC8509255 DOI: 10.3390/ijms221910798] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 10/01/2021] [Accepted: 10/03/2021] [Indexed: 01/04/2023] Open
Abstract
Amyloid beta (Aβ) oligomers are the most neurotoxic aggregates causing neuronal death and cognitive damage. A detailed elucidation of the aggregation pathways from oligomers to fibril formation is crucial to develop therapeutic strategies for Alzheimer's disease (AD). Although experimental techniques rely on the measure of time- and space-average properties, they face severe difficulties in the investigation of Aβ peptide aggregation due to their intrinsically disorder character. Computer simulation is a tool that allows tracing the molecular motion of molecules; hence it complements Aβ experiments, as it allows to explore the binding mechanism between metal ions and Aβ oligomers close to the cellular membrane at the atomic resolution. In this context, integrated studies of experiments and computer simulations can assist in mapping the complete pathways of aggregation and toxicity of Aβ peptides. Aβ oligomers are disordered proteins, and due to a rapid exploration of their intrinsic conformational space in real-time, they are challenging therapeutic targets. Therefore, no good drug candidate could have been identified for clinical use. Our previous investigations identified two small molecules, M30 (2-Octahydroisoquinolin-2(1H)-ylethanamine) and Gabapentin, capable of Aβ binding and inhibiting molecular aggregation, synaptotoxicity, intracellular calcium signaling, cellular toxicity and memory losses induced by Aβ. Thus, we recommend these molecules as novel candidates to assist anti-AD drug discovery in the near future. This review discusses the most recent research investigations about the Aβ dynamics in water, close contact with cell membranes, and several therapeutic strategies to remove plaque formation.
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Affiliation(s)
- Subramanian Boopathi
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca 62210, Mexico;
| | - Adolfo B. Poma
- Department of Biosystems and Soft Matter, Institute of Fundamental Technological Research Polish Academy of Science, Pawińskiego 5B, 02-106 Warsaw, Poland
- International Center for Research on Innovative Biobased Materials (ICRI-BioM)—International Research Agenda, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland;
| | - Ramón Garduño-Juárez
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca 62210, Mexico;
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8
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Effects of Aβ-derived peptide fragments on fibrillogenesis of Aβ. Sci Rep 2021; 11:19262. [PMID: 34584131 PMCID: PMC8479085 DOI: 10.1038/s41598-021-98644-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 09/13/2021] [Indexed: 11/08/2022] Open
Abstract
Amyloid β (Aβ) peptide aggregation plays a central role in Alzheimer's disease (AD) etiology. AD drug candidates have included small molecules or peptides directed towards inhibition of Aβ fibrillogenesis. Although some Aβ-derived peptide fragments suppress Aβ fibril growth, comprehensive analysis of inhibitory potencies of peptide fragments along the whole Aβ sequence has not been reported. The aim of this work is (a) to identify the region(s) of Aβ with highest propensities for aggregation and (b) to use those fragments to inhibit Aβ fibrillogenesis. Structural and aggregation properties of the parent Aβ1-42 peptide and seven overlapping peptide fragments have been studied, i.e. Aβ1-10 (P1), Aβ6-15 (P2), Aβ11-20 (P3), Aβ16-25 (P4), Aβ21-30 (P5), Aβ26-36 (P6), and Aβ31-42 (P7). Structural transitions of the peptides in aqueous buffer have been monitored by circular dichroism and Fourier transform infrared spectroscopy. Aggregation and fibrillogenesis were analyzed by light scattering and thioflavin-T fluorescence. The mode of peptide-peptide interactions was characterized by fluorescence resonance energy transfer. Three peptide fragments, P3, P6, and P7, exhibited exceptionally high propensity for β-sheet formation and aggregation. Remarkably, only P3 and P6 exerted strong inhibitory effect on the aggregation of Aβ1-42, whereas P7 and P2 displayed moderate inhibitory potency. It is proposed that P3 and P6 intercalate between Aβ1-42 molecules and thereby inhibit Aβ1-42 aggregation. These findings may facilitate therapeutic strategies of inhibition of Aβ fibrillogenesis by Aβ-derived peptides.
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9
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Fernandez‐Perez EJ, Muñoz B, Bascuñan DA, Peters C, Riffo‐Lepe NO, Espinoza MP, Morgan PJ, Filippi C, Bourboulou R, Sengupta U, Kayed R, Epsztein J, Aguayo LG. Synaptic dysregulation and hyperexcitability induced by intracellular amyloid beta oligomers. Aging Cell 2021; 20:e13455. [PMID: 34409748 PMCID: PMC8441418 DOI: 10.1111/acel.13455] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 07/21/2021] [Accepted: 08/05/2021] [Indexed: 12/19/2022] Open
Abstract
Intracellular amyloid beta oligomer (iAβo) accumulation and neuronal hyperexcitability are two crucial events at early stages of Alzheimer's disease (AD). However, to date, no mechanism linking iAβo with an increase in neuronal excitability has been reported. Here, the effects of human AD brain-derived (h-iAβo) and synthetic (iAβo) peptides on synaptic currents and action potential firing were investigated in hippocampal neurons. Starting from 500 pM, iAβo rapidly increased the frequency of synaptic currents and higher concentrations potentiated the AMPA receptor-mediated current. Both effects were PKC-dependent. Parallel recordings of synaptic currents and nitric oxide (NO)-associated fluorescence showed that the increased frequency, related to pre-synaptic release, was dependent on a NO-mediated retrograde signaling. Moreover, increased synchronization in NO production was also observed in neurons neighboring those dialyzed with iAβo, indicating that iAβo can increase network excitability at a distance. Current-clamp recordings suggested that iAβo increased neuronal excitability via AMPA-driven synaptic activity without altering membrane intrinsic properties. These results strongly indicate that iAβo causes functional spreading of hyperexcitability through a synaptic-driven mechanism and offers an important neuropathological significance to intracellular species in the initial stages of AD, which include brain hyperexcitability and seizures.
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Affiliation(s)
| | - Braulio Muñoz
- Laboratory of NeurophysiologyDepartment of PhysiologyUniversidad de ConcepciónConcepciónChile
| | - Denisse A. Bascuñan
- Laboratory of NeurophysiologyDepartment of PhysiologyUniversidad de ConcepciónConcepciónChile
| | - Christian Peters
- Laboratory of NeurophysiologyDepartment of PhysiologyUniversidad de ConcepciónConcepciónChile
| | - Nicolas O. Riffo‐Lepe
- Laboratory of NeurophysiologyDepartment of PhysiologyUniversidad de ConcepciónConcepciónChile
| | - Maria P. Espinoza
- Laboratory of NeurophysiologyDepartment of PhysiologyUniversidad de ConcepciónConcepciónChile
| | - Peter J. Morgan
- Institute of Neurobiology of the Mediterranean Sea (INMED)Institut National de la Santé et de la Recherche Médicale (INSERM) U901, Aix-Marseille UniversitéMarseilleFrance
| | - Caroline Filippi
- Institute of Neurobiology of the Mediterranean Sea (INMED)Institut National de la Santé et de la Recherche Médicale (INSERM) U901, Aix-Marseille UniversitéMarseilleFrance
| | - Romain Bourboulou
- Institute of Neurobiology of the Mediterranean Sea (INMED)Institut National de la Santé et de la Recherche Médicale (INSERM) U901, Aix-Marseille UniversitéMarseilleFrance
| | - Urmi Sengupta
- Mitchell Center for Neurodegenerative DiseasesUniversity of Texas Medical BranchGalvestonTexasUSA
- Department of Neurology, Neuroscience and Cell BiologyUniversity of Texas Medical BranchGalvestonTexasUSA
| | - Rakez Kayed
- Mitchell Center for Neurodegenerative DiseasesUniversity of Texas Medical BranchGalvestonTexasUSA
- Department of Neurology, Neuroscience and Cell BiologyUniversity of Texas Medical BranchGalvestonTexasUSA
| | - Jérôme Epsztein
- Institute of Neurobiology of the Mediterranean Sea (INMED)Institut National de la Santé et de la Recherche Médicale (INSERM) U901, Aix-Marseille UniversitéMarseilleFrance
| | - Luis G. Aguayo
- Laboratory of NeurophysiologyDepartment of PhysiologyUniversidad de ConcepciónConcepciónChile
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10
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Zhang S, Asghar S, Zhu C, Ye J, Lin L, Xu L, Hu Z, Chen Z, Shao F, Xiao Y. Multifunctional nanorods based on self-assembly of biomimetic apolipoprotein E peptide for the treatment of Alzheimer's disease. J Control Release 2021; 335:637-649. [PMID: 34087249 DOI: 10.1016/j.jconrel.2021.05.044] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 05/25/2021] [Accepted: 05/30/2021] [Indexed: 12/18/2022]
Abstract
Targeting a single molecule or a single pathway and poor drug delivery to the brain hamper the therapy of Alzheimer's disease (AD) based on abnormal metabolism of amyloid-β (Aβ). To solve these problems, we designed and synthesized a multi - strategy peptide (MOP), an ingenious apolipoprotein E mimetic peptide, which could reduce Aβ deposition via inhibiting Aβ aggregation and at the same time accelerate Aβ clearance. Meanwhile, MOP could be self-assembled into different nanostructure, thus we constructed a multifunctional delivery system (APND-3) based on MOP self-assembled nanorods (aspect ratios of 3) that was a favorable morphology to enhance the permeation across the blood brain barrier (BBB) to address the poor delivery to brain issues. Besides, the drug delivery system introduces polydopamine (PDA) and COG1410 ligand as a shell to keep the favorable morphology of core and enhance the BBB targeting efficiency. As a result, the delivery system significantly enhances the delivery of MOP to the brain, thus reducing Aβ deposition, mitigating the memory deficits, and ameliorating neurologic damage in AD model mice. Our findings suggest that our drug and carrier integrated multifunctional delivery system has the potential for AD treatment.
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Affiliation(s)
- Shanshan Zhang
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 210009, PR China; School of Basic Medical Sciences, Zhejiang Chinese Medical University, Hangzhou 310053, China
| | - Sajid Asghar
- Faculty of Pharmaceutical Sciences, Government College University Faisalabad, Faisalabad, Pakistan
| | - Chenqi Zhu
- Department of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210023, PR China; Department of Pharmacy, The Affiliated Suzhou Hospital of Nanjing Medical University, Suzhou 215002, PR China
| | - Junxiu Ye
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 210009, PR China
| | - Ling Lin
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 210009, PR China
| | - Liu Xu
- Department of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210023, PR China
| | - Ziyi Hu
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 210009, PR China
| | - Zhipeng Chen
- Department of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210023, PR China.
| | - Feng Shao
- Phase I Clinical Trial Unit, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, PR China.
| | - Yanyu Xiao
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 210009, PR China.
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11
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Toledo JP, Fernández-Pérez EJ, Ferreira IL, Marinho D, Riffo-Lepe NO, Pineda-Cuevas BN, Pinochet-Pino LF, Burgos CF, Rego AC, Aguayo LG. Boldine Attenuates Synaptic Failure and Mitochondrial Deregulation in Cellular Models of Alzheimer's Disease. Front Neurosci 2021; 15:617821. [PMID: 33679301 PMCID: PMC7933475 DOI: 10.3389/fnins.2021.617821] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 01/25/2021] [Indexed: 11/18/2022] Open
Abstract
Alzheimer’s disease (AD) is the most common cause of senile dementia worldwide, characterized by both cognitive and behavioral deficits. Amyloid beta peptide (Aβ) oligomers (AβO) have been found to be responsible for several pathological mechanisms during the development of AD, including altered cellular homeostasis and synaptic function, inevitably leading to cell death. Such AβO deleterious effects provide a way for identifying new molecules with potential anti-AD properties. Available treatments minimally improve AD symptoms and do not extensively target intracellular pathways affected by AβO. Naturally-derived compounds have been proposed as potential modifiers of Aβ-induced neurodysfunction and cytotoxicity based on their availability and chemical diversity. Thus, the aim of this study was to evaluate boldine, an alkaloid derived from the bark and leaves of the Chilean tree Peumus boldus, and its capacity to block some dysfunctional processes caused by AβO. We examined the protective effect of boldine (1–10 μM) in primary hippocampal neurons and HT22 hippocampal-derived cell line treated with AβO (24–48 h). We found that boldine interacts with Aβ in silico affecting its aggregation and protecting hippocampal neurons from synaptic failure induced by AβO. Boldine also normalized changes in intracellular Ca2+ levels associated to mitochondria or endoplasmic reticulum in HT22 cells treated with AβO. In addition, boldine completely rescued the decrease in mitochondrial membrane potential (ΔΨm) and the increase in mitochondrial reactive oxygen species, and attenuated AβO-induced decrease in mitochondrial respiration in HT22 hippocampal cells. We conclude that boldine provides neuroprotection in AD models by both direct interactions with Aβ and by preventing oxidative stress and mitochondrial dysfunction. Additional studies are required to evaluate the effect of boldine on cognitive and behavioral deficits induced by Aβ in vivo.
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Affiliation(s)
- Juan P Toledo
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Barrio Universitario, Concepción, Chile
| | - Eduardo J Fernández-Pérez
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Barrio Universitario, Concepción, Chile
| | - Ildete L Ferreira
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,IIIUC-Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Daniela Marinho
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,IIIUC-Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Nicolas O Riffo-Lepe
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Barrio Universitario, Concepción, Chile
| | - Benjamin N Pineda-Cuevas
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Barrio Universitario, Concepción, Chile
| | - Luis F Pinochet-Pino
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Barrio Universitario, Concepción, Chile
| | - Carlos F Burgos
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Barrio Universitario, Concepción, Chile
| | - A Cristina Rego
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,FMUC-Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Luis G Aguayo
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Barrio Universitario, Concepción, Chile
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12
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Jarero-Basulto JJ, Rivera-Cervantes MC, Gasca-Martínez D, García-Sierra F, Gasca-Martínez Y, Beas-Zárate C. Current Evidence on the Protective Effects of Recombinant Human Erythropoietin and Its Molecular Variants against Pathological Hallmarks of Alzheimer's Disease. Pharmaceuticals (Basel) 2020; 13:ph13120424. [PMID: 33255969 PMCID: PMC7760199 DOI: 10.3390/ph13120424] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 11/04/2020] [Accepted: 11/10/2020] [Indexed: 12/13/2022] Open
Abstract
Substantial evidence in the literature demonstrates the pleiotropic effects of the administration of recombinant human erythropoietin (rhEPO) and its molecular variants in different tissues and organs, including the brain. Some of these reports suggest that the chemical properties of this molecule by itself or in combination with other agents (e.g., growth factors) could provide the necessary pharmacological characteristics to be considered a potential protective agent in neurological disorders such as Alzheimer’s disease (AD). AD is a degenerative disorder of the brain, characterized by an aberrant accumulation of amyloid β (Aβ) and hyperphosphorylated tau (tau-p) proteins in the extracellular and intracellular space, respectively, leading to inflammation, oxidative stress, excitotoxicity, and other neuronal alterations that compromise cell viability, causing neurodegeneration in the hippocampus and the cerebral cortex. Unfortunately, to date, it lacks an effective therapeutic strategy for its treatment. Therefore, in this review, we analyze the evidence regarding the effects of exogenous EPOs (rhEPO and its molecular variants) in several in vivo and in vitro Aβ and tau-p models of AD-type neurodegeneration, to be considered as an alternative protective treatment to this condition. Particularly, we focus on analyzing the differential effect of molecular variants of rhEPO when changes in doses, route of administration, duration of treatment or application times, are evaluated for the improved cellular alterations generated in this disease. This narrative review shows the evidence of the effectiveness of the exogenous EPOs as potential therapeutic molecules, focused on the mechanisms that establish cellular damage and clinical manifestation in the AD.
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Affiliation(s)
- José J. Jarero-Basulto
- Cellular Neurobiology Laboratory, Cell and Molecular Biology Department, CUCBA, University of Guadalajara, Zapopan 45220, Mexico
- Correspondence: (J.J.J.-B.); (M.C.R.-C.); Tel.: +52-33-37771150 ((J.J.J.-B. & M.C.R.-C.)
| | - Martha C. Rivera-Cervantes
- Cellular Neurobiology Laboratory, Cell and Molecular Biology Department, CUCBA, University of Guadalajara, Zapopan 45220, Mexico
- Correspondence: (J.J.J.-B.); (M.C.R.-C.); Tel.: +52-33-37771150 ((J.J.J.-B. & M.C.R.-C.)
| | - Deisy Gasca-Martínez
- Behavioral Analysis Unit, Neurobiology Institute, Campus UNAM-Juriquilla, Querétaro 76230, Mexico;
| | - Francisco García-Sierra
- Department of Cell Biology, Center of Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV), Ciudad de Mexico 07360, Mexico;
| | - Yadira Gasca-Martínez
- Development and Neural Regeneration Laboratory, Cell and Molecular Biology Department, CUCBA, University of Guadalajara, Zapopan 45220, Mexico; (Y.G.-M.); (C.B.-Z.)
| | - Carlos Beas-Zárate
- Development and Neural Regeneration Laboratory, Cell and Molecular Biology Department, CUCBA, University of Guadalajara, Zapopan 45220, Mexico; (Y.G.-M.); (C.B.-Z.)
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13
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González-Sanmiguel J, Schuh CMAP, Muñoz-Montesino C, Contreras-Kallens P, Aguayo LG, Aguayo S. Complex Interaction between Resident Microbiota and Misfolded Proteins: Role in Neuroinflammation and Neurodegeneration. Cells 2020; 9:E2476. [PMID: 33203002 PMCID: PMC7697492 DOI: 10.3390/cells9112476] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 11/02/2020] [Accepted: 11/10/2020] [Indexed: 12/13/2022] Open
Abstract
Neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD) and Creutzfeldt-Jakob disease (CJD) are brain conditions affecting millions of people worldwide. These diseases are associated with the presence of amyloid-β (Aβ), alpha synuclein (α-Syn) and prion protein (PrP) depositions in the brain, respectively, which lead to synaptic disconnection and subsequent progressive neuronal death. Although considerable progress has been made in elucidating the pathogenesis of these diseases, the specific mechanisms of their origins remain largely unknown. A body of research suggests a potential association between host microbiota, neuroinflammation and dementia, either directly due to bacterial brain invasion because of barrier leakage and production of toxins and inflammation, or indirectly by modulating the immune response. In the present review, we focus on the emerging topics of neuroinflammation and the association between components of the human microbiota and the deposition of Aβ, α-Syn and PrP in the brain. Special focus is given to gut and oral bacteria and biofilms and to the potential mechanisms associating microbiome dysbiosis and toxin production with neurodegeneration. The roles of neuroinflammation, protein misfolding and cellular mediators in membrane damage and increased permeability are also discussed.
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Affiliation(s)
| | - Christina M. A. P. Schuh
- Centro de Medicina Regenerativa, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago 7710162, Chile; (C.M.A.P.S.); (P.C.-K.)
| | - Carola Muñoz-Montesino
- Department of Physiology, Universidad de Concepción, Concepción 4070386, Chile; (J.G.-S.); (C.M.-M.)
| | - Pamina Contreras-Kallens
- Centro de Medicina Regenerativa, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago 7710162, Chile; (C.M.A.P.S.); (P.C.-K.)
| | - Luis G. Aguayo
- Department of Physiology, Universidad de Concepción, Concepción 4070386, Chile; (J.G.-S.); (C.M.-M.)
- Program on Neuroscience, Psychiatry and Mental Health, Universidad de Concepción, Concepción 4070386, Chile
| | - Sebastian Aguayo
- School of Dentistry, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile
- Institute for Biological and Medical Engineering, Schools of Engineering, Medicine and Biological Sciences, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
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14
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González-Sanmiguel J, Burgos CF, Bascuñán D, Fernández-Pérez EJ, Riffo-Lepe N, Boopathi S, Fernández-Pérez A, Bobadilla-Azócar C, González W, Figueroa M, Vicente B, Aguayo LG. Gabapentin Inhibits Multiple Steps in the Amyloid Beta Toxicity Cascade. ACS Chem Neurosci 2020; 11:3064-3076. [PMID: 32886489 DOI: 10.1021/acschemneuro.0c00414] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Oligomeric β-amyloid peptide (Aβ) is one of the main neurotoxic agents of Alzheimer's disease (AD). Oligomers associate to neuronal membranes, forming "pore-like" structures that cause intracellular calcium and neurotransmitter dyshomeostasis, leading to synaptic failure and death. Through molecular screening targeting the C terminal region of Aβ, a region involved in the toxic properties of the peptide, we detected an FDA approved compound, gabapentin (GBP), with neuroprotective effects against Aβ toxicity. At micromolar concentrations, GBP antagonized peptide aggregation over time and reduced the Aβ absorbance plateau to 28% of control. In addition, GBP decreased Aβ association to membranes by almost half, and the effects of Aβ on intracellular calcium in hippocampal neurons were antagonized without causing effects on its own. Finally, we found that GBP was able to block the synaptotoxicity induced by Aβ in hippocampal neurons, increasing post-synaptic currents from 1.7 ± 0.9 to 4.2 ± 0.7 fC and mean relative fluorescence intensity values of SV2, a synaptic protein, from 0.7 ± 0.09 to 1.00 ± 0.08. The results show that GBP can interfere with Aβ-induced toxicity by blocking multiple steps, resulting in neuroprotection, which justifies advancing toward additional animal and human studies.
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Affiliation(s)
- Juliana González-Sanmiguel
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción 4030000, Chile
| | - Carlos F. Burgos
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción 4030000, Chile
| | - Denisse Bascuñán
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción 4030000, Chile
| | - Eduardo J. Fernández-Pérez
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción 4030000, Chile
| | - Nicolás Riffo-Lepe
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción 4030000, Chile
| | - Subramanian Boopathi
- The Center for Bioinformatics and Molecular Simulations (CBSM), Universidad de Talca, Talca 3460000, Chile
| | | | - Catalina Bobadilla-Azócar
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción 4030000, Chile
| | - Wendy González
- The Center for Bioinformatics and Molecular Simulations (CBSM), Universidad de Talca, Talca 3460000, Chile
- Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Talca, Talca 3460000, Chile
| | - Maximiliano Figueroa
- Laboratory of Molecular Biophysics, Department of Biochemistry and Molecular Biology, Universidad de Concepción, Concepción 4030000, Chile
| | - Benjamín Vicente
- Department of Psychiatry and Mental Health, Universidad de Concepcion, Concepción 4030000, Chile
- Program on Neuroscience, Psychiatry and Mental Health, Universidad de Concepcion, Concepción 4030000, Chile
| | - Luis G. Aguayo
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción 4030000, Chile
- Program on Neuroscience, Psychiatry and Mental Health, Universidad de Concepcion, Concepción 4030000, Chile
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15
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Peters C, Bascuñán D, Burgos CF, Bobadilla C, González-Sanmiguel J, Boopathi S, Riffo N, Fernández-Pérez EJ, Tarnok ME, Aguilar LF, Gonzalez W, Aguayo LG. Characterization of a new molecule capable of inhibiting several steps of the amyloid cascade in Alzheimer's disease. Neurobiol Dis 2020; 141:104938. [PMID: 32434047 DOI: 10.1016/j.nbd.2020.104938] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 05/04/2020] [Indexed: 11/16/2022] Open
Abstract
INTRODUCTION Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder in elderly people. Existent therapies are directed at alleviating some symptoms, but are not effective in altering the course of the disease. METHODS Based on our previous study that showed that an Aβ-interacting small peptide protected against the toxic effects of amyloid-beta peptide (Aβ), we carried out an array of in silico, in vitro, and in vivo assays to identify a molecule having neuroprotective properties. RESULTS In silico studies showed that the molecule, referred to as M30 (2-Octahydroisoquinolin-2(1H)-ylethanamine), was able to interact with the Aβ peptide. Additionally, in vitro assays showed that M30 blocked Aβ aggregation, association to the plasma membrane, synaptotoxicity, intracellular calcium, and cellular toxicity, while in vivo experiments demonstrated that M30 induced a neuroprotective effect by decreasing the toxicity of Aβ in the dentate gyrus of the hippocampus and improving the alteration in spatial memory in behavior assays. DISCUSSION Therefore, we propose that this new small molecule could be a useful candidate for the additional development of a treatment against AD since it appears to block multiple steps in the amyloid cascade. Overall, since there are no drugs that effectively block the progression of AD, this approach represents an innovative strategy. SIGNIFICANCE Currently, there is no effective treatment for AD and the expectations to develop an effective therapy are low. Using in silico, in vitro, and in vivo experiments, we identified a new compound that is able to inhibit Aβ-induced neurotoxicity, specifically aggregation, association to neurons, synaptic toxicity, calcium dyshomeostasis and memory impairment induced by Aβ. Because Aβ toxicity is central to AD progression, the inhibition mediated by this new molecule might be useful as a therapeutic tool.
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Affiliation(s)
- Christian Peters
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Denisse Bascuñán
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Carlos F Burgos
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Catalina Bobadilla
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | | | - Subramanian Boopathi
- The Center for Bioinformatics and Molecular Simulations (CBSM), Universidad de Talca, Talca, Chile
| | - Nicolás Riffo
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Eduardo J Fernández-Pérez
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - María Elena Tarnok
- Laboratory of Photophysics and Molecular Spectroscopy, Chemistry, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Luis Felipe Aguilar
- Laboratory of Photophysics and Molecular Spectroscopy, Chemistry, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Wendy Gonzalez
- The Center for Bioinformatics and Molecular Simulations (CBSM), Universidad de Talca, Talca, Chile; Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Talca, Talca, Chile
| | - Luis G Aguayo
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile.
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16
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Muñoz B, Gallegos S, Peters C, Murath P, Lovinger DM, Homanics GE, Aguayo LG. Influence of nonsynaptic α1 glycine receptors on ethanol consumption and place preference. Addict Biol 2020; 25:e12726. [PMID: 30884072 DOI: 10.1111/adb.12726] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 11/23/2018] [Accepted: 01/17/2019] [Indexed: 12/21/2022]
Abstract
Here, we used knock-in (KI) mice that have ethanol-insensitive alpha 1 glycine receptors (GlyRs) (KK385/386AA) to examine how alpha 1 GlyRs might affect binge drinking and conditioned place preference. Data show that tonic alpha 1 GlyR-mediated currents were exclusively sensitive to ethanol only in wild-type mice. Behavioral studies showed that the KI mice have a higher intake of ethanol upon first exposure to drinking and greater conditioned place preference to ethanol. This study suggests that nonsynaptic alpha 1-containing GlyRs have a role in motivational and early reinforcing effects of ethanol.
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Affiliation(s)
- Braulio Muñoz
- Laboratory of Neurophysiology, Department of PhysiologyUniversidad de Concepcion Concepcion Chile
| | - Scarlet Gallegos
- Laboratory of Neurophysiology, Department of PhysiologyUniversidad de Concepcion Concepcion Chile
| | - Christian Peters
- Laboratory of Neurophysiology, Department of PhysiologyUniversidad de Concepcion Concepcion Chile
| | - Pablo Murath
- Laboratory of Neurophysiology, Department of PhysiologyUniversidad de Concepcion Concepcion Chile
| | - David M. Lovinger
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and AlcoholismNational Institutes of Health Bethesda Maryland USA
| | - Gregg E. Homanics
- Department of AnesthesiologyUniversity of Pittsburgh Pittsburgh Pennsylvania USA
- Department Pharmacology and Chemical BiologyUniversity of Pittsburgh Pittsburgh Pennsylvania USA
| | - Luis G. Aguayo
- Laboratory of Neurophysiology, Department of PhysiologyUniversidad de Concepcion Concepcion Chile
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17
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Aguayo S, Schuh CMAP, Vicente B, Aguayo LG. Association between Alzheimer's Disease and Oral and Gut Microbiota: Are Pore Forming Proteins the Missing Link? J Alzheimers Dis 2019; 65:29-46. [PMID: 30040725 DOI: 10.3233/jad-180319] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Alzheimer's disease (AD) is a neurodegenerative condition affecting millions of people worldwide. It is associated with cerebral amyloid-β (Aβ) plaque deposition in the brain, synaptic disconnection, and subsequent progressive neuronal death. Although considerable progress has been made to elucidate the pathogenesis of AD, the specific causes of the disease remain highly unknown. Recent research has suggested a potential association between certain infectious diseases and dementia, either directly due to bacterial brain invasion and toxin production, or indirectly by modulating the immune response. Therefore, in the present review we focus on the emerging issues of bacterial infection and AD, including the existence of antimicrobial peptides having pore-forming properties that act in a similar way to pores formed by Aβ in a variety of cell membranes. Special focus is placed on oral bacteria and biofilms, and on the potential mechanisms associating bacterial infection and toxin production in AD. The role of bacterial outer membrane vesicles on the transport and delivery of toxins as well as porins to the brain is also discussed. Aβ has shown to possess antimicrobial activity against several bacteria, and therefore could be upregulated as a response to bacteria and bacterial toxins in the brain. Although further research is needed, we believe that the control of biofilm-mediated diseases could be an important potential prevention mechanism for AD development.
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18
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Cline EN, Bicca MA, Viola KL, Klein WL. The Amyloid-β Oligomer Hypothesis: Beginning of the Third Decade. J Alzheimers Dis 2019; 64:S567-S610. [PMID: 29843241 PMCID: PMC6004937 DOI: 10.3233/jad-179941] [Citation(s) in RCA: 535] [Impact Index Per Article: 107.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The amyloid-β oligomer (AβO) hypothesis was introduced in 1998. It proposed that the brain damage leading to Alzheimer’s disease (AD) was instigated by soluble, ligand-like AβOs. This hypothesis was based on the discovery that fibril-free synthetic preparations of AβOs were potent CNS neurotoxins that rapidly inhibited long-term potentiation and, with time, caused selective nerve cell death (Lambert et al., 1998). The mechanism was attributed to disrupted signaling involving the tyrosine-protein kinase Fyn, mediated by an unknown toxin receptor. Over 4,000 articles concerning AβOs have been published since then, including more than 400 reviews. AβOs have been shown to accumulate in an AD-dependent manner in human and animal model brain tissue and, experimentally, to impair learning and memory and instigate major facets of AD neuropathology, including tau pathology, synapse deterioration and loss, inflammation, and oxidative damage. As reviewed by Hayden and Teplow in 2013, the AβO hypothesis “has all but supplanted the amyloid cascade.” Despite the emerging understanding of the role played by AβOs in AD pathogenesis, AβOs have not yet received the clinical attention given to amyloid plaques, which have been at the core of major attempts at therapeutics and diagnostics but are no longer regarded as the most pathogenic form of Aβ. However, if the momentum of AβO research continues, particularly efforts to elucidate key aspects of structure, a clear path to a successful disease modifying therapy can be envisioned. Ensuring that lessons learned from recent, late-stage clinical failures are applied appropriately throughout therapeutic development will further enable the likelihood of a successful therapy in the near-term.
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Affiliation(s)
- Erika N Cline
- Department of Neurobiology, Cognitive Neurology and Alzheimer's Disease Center, International Institute for Nanotechnology, and Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, USA
| | - Maíra Assunção Bicca
- Department of Neurobiology, Cognitive Neurology and Alzheimer's Disease Center, International Institute for Nanotechnology, and Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, USA
| | - Kirsten L Viola
- Department of Neurobiology, Cognitive Neurology and Alzheimer's Disease Center, International Institute for Nanotechnology, and Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, USA
| | - William L Klein
- Department of Neurobiology, Cognitive Neurology and Alzheimer's Disease Center, International Institute for Nanotechnology, and Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, USA
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19
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Castillo C, Fernández-Mendívil C, Buendia I, Saavedra P, Meza C, Parra NC, Lopez MG, Toledo JR, Fuentealba J. Neuroprotective effects of EpoL against oxidative stress induced by soluble oligomers of Aβ peptide. Redox Biol 2019; 24:101187. [PMID: 30965198 PMCID: PMC6454060 DOI: 10.1016/j.redox.2019.101187] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/26/2019] [Accepted: 03/28/2019] [Indexed: 12/22/2022] Open
Abstract
Erythropoietin is a glycoproteic hormone that regulates hematopoiesis by acting on its specific receptor (EpoR). The expression of EpoR in the central nervous system (CNS) suggests a role for this hormone in the brain. Recently, we developed a new Epo variant without hematopoietic activity called EpoL, which showed marked neuroprotective effects against oxidative stress in brain ischemia related models. In this study, we have evaluated the neuroprotective effects of EpoL against oxidative stress induced by chronic treatment with Aβ. Our results show that EpoL was neuroprotective against Aβ-induced toxicity by a mechanism that implicates EpoR, reduction in reactive oxygen species, and reduction in astrogliosis. Furthermore, EpoL treatment improved calcium handling and SV2 levels. Interestingly, the neuroprotective effect of EpoL against oxidative stress induced by chronic Aβ treatment was achieved at a concentration 10 times lower than that of Epo. In conclusion, EpoL, a new variant of Epo without hematopoietic activity, is of potential interest for the treatment of diseases related to oxidative stress in the CNS such as Alzheimer disease.
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Affiliation(s)
- C Castillo
- Laboratorio de Biotecnología y Biofarmacos, Departamento de Fisiopatologia, Facultad de Ciencias Biológicas, Universidad de Concepcion, Chile
| | - C Fernández-Mendívil
- Departamento de Farmacología y Terapéutica, Instituto Teófilo Hernando, Universidad Autónoma de Madrid, Spain
| | - I Buendia
- Departamento de Farmacología y Terapéutica, Instituto Teófilo Hernando, Universidad Autónoma de Madrid, Spain
| | - P Saavedra
- Laboratorio de Biotecnología y Biofarmacos, Departamento de Fisiopatologia, Facultad de Ciencias Biológicas, Universidad de Concepcion, Chile
| | - C Meza
- Laboratorio de Biotecnología y Biofarmacos, Departamento de Fisiopatologia, Facultad de Ciencias Biológicas, Universidad de Concepcion, Chile
| | - N C Parra
- Laboratorio de Biotecnología y Biofarmacos, Departamento de Fisiopatologia, Facultad de Ciencias Biológicas, Universidad de Concepcion, Chile
| | - M G Lopez
- Departamento de Farmacología y Terapéutica, Instituto Teófilo Hernando, Universidad Autónoma de Madrid, Spain
| | - J R Toledo
- Laboratorio de Biotecnología y Biofarmacos, Departamento de Fisiopatologia, Facultad de Ciencias Biológicas, Universidad de Concepcion, Chile.
| | - J Fuentealba
- Laboratorio de Screening de Compuestos Neuroactivos, Departamento de Fisiología, Facultad de Ciencias Biológicas, Universidad de Concepcion, Chile; Centro de Investigaciones Avanzadas en Biomedicina (CIAB-UdeC), Facultad de Ciencias Biológicas, Universidad de Concepcion, Chile.
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Julien C, Tomberlin C, Roberts CM, Akram A, Stein GH, Silverman MA, Link CD. In vivo induction of membrane damage by β-amyloid peptide oligomers. Acta Neuropathol Commun 2018; 6:131. [PMID: 30497524 PMCID: PMC6263551 DOI: 10.1186/s40478-018-0634-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Accepted: 11/13/2018] [Indexed: 01/17/2023] Open
Abstract
Exposure to the β-amyloid peptide (Aβ) is toxic to neurons and other cell types, but the mechanism(s) involved are still unresolved. Synthetic Aβ oligomers can induce ion-permeable pores in synthetic membranes, but whether this ability to damage membranes plays a role in the ability of Aβ oligomers to induce tau hyperphosphorylation, or other disease-relevant pathological changes, is unclear. To examine the cellular responses to Aβ exposure independent of possible receptor interactions, we have developed an in vivo C. elegans model that allows us to visualize these cellular responses in living animals. We find that feeding C. elegans E. coli expressing human Aβ induces a membrane repair response similar to that induced by exposure to the CRY5B, a known pore-forming toxin produced by B. thuringensis. This repair response does not occur when C. elegans is exposed to an Aβ Gly37Leu variant, which we have previously shown to be incapable of inducing tau phosphorylation in hippocampal neurons. The repair response is also blocked by loss of calpain function, and is altered by loss-of-function mutations in the C. elegans orthologs of BIN1 and PICALM, well-established risk genes for late onset Alzheimer's disease. To investigate the role of membrane repair on tau phosphorylation directly, we exposed hippocampal neurons to streptolysin O (SLO), a pore-forming toxin that induces a well-characterized membrane repair response. We find that SLO induces tau hyperphosphorylation, which is blocked by calpain inhibition. Finally, we use a novel biarsenical dye-tagging approach to show that the Gly37Leu substitution interferes with Aβ multimerization and thus the formation of potentially pore-forming oligomers. We propose that Aβ-induced tau hyperphosphorylation may be a downstream consequence of induction of a membrane repair process.
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21
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Fernández-Pérez EJ, Sepúlveda FJ, Peters C, Bascuñán D, Riffo-Lepe NO, González-Sanmiguel J, Sánchez SA, Peoples RW, Vicente B, Aguayo LG. Effect of Cholesterol on Membrane Fluidity and Association of Aβ Oligomers and Subsequent Neuronal Damage: A Double-Edged Sword. Front Aging Neurosci 2018; 10:226. [PMID: 30123122 PMCID: PMC6085471 DOI: 10.3389/fnagi.2018.00226] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 07/03/2018] [Indexed: 02/06/2023] Open
Abstract
Background: The beta-amyloid peptide (Aβ) involved in Alzheimer's disease (AD) has been described to associate/aggregate on the cell surface disrupting the membrane through pore formation and breakage. However, molecular determinants involved for this interaction (e.g., some physicochemical properties of the cell membrane) are largely unknown. Since cholesterol is an important molecule for membrane structure and fluidity, we examined the effect of varying cholesterol content with the association and membrane perforation by Aβ in cultured hippocampal neurons. Methods: To decrease or increase the levels of cholesterol in the membrane we used methyl-β-cyclodextrin (MβCD) and MβCD/cholesterol, respectively. We analyzed if membrane fluidity was affected using generalized polarization (GP) imaging and the fluorescent dye di-4-ANEPPDHQ. Additionally membrane association and perforation was assessed using immunocytochemistry and electrophysiological techniques, respectively. Results: The results showed that cholesterol removal decreased the macroscopic association of Aβ to neuronal membranes (fluorescent-puncta/20 μm: control = 18 ± 2 vs. MβCD = 10 ± 1, p < 0.05) and induced a facilitation of the membrane perforation by Aβ with respect to control cells (half-time for maximal charge transferred: control = 7.2 vs. MβCD = 4.4). Under this condition, we found an increase in membrane fluidity (46 ± 3.3% decrease in GP value, p < 0.001). On the contrary, increasing cholesterol levels incremented membrane rigidity (38 ± 2.7% increase in GP value, p < 0.001) and enhanced the association and clustering of Aβ (fluorescent-puncta/20 μm: control = 18 ± 2 vs. MβCD = 10 ± 1, p < 0.01), but inhibited membrane disruption. Conclusion: Our results strongly support the significance of plasma membrane organization in the toxic effects of Aβ in hippocampal neurons, since fluidity can regulate distribution and insertion of the Aβ peptide in the neuronal membrane.
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Affiliation(s)
- Eduardo J Fernández-Pérez
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Fernando J Sepúlveda
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Christian Peters
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Denisse Bascuñán
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Nicolás O Riffo-Lepe
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | | | - Susana A Sánchez
- Departamento de Polímeros, Facultad de Ciencias Químicas, Universidad de Concepción, Concepción, Chile
| | - Robert W Peoples
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI, United States
| | - Benjamín Vicente
- Department of Psychiatry and Mental Health, Universidad de Concepción, Concepción, Chile
| | - Luis G Aguayo
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
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22
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Peters C, Sepúlveda FJ, Fernández-Pérez EJ, Peoples RW, Aguayo LG. The Level of NMDA Receptor in the Membrane Modulates Amyloid-β Association and Perforation. J Alzheimers Dis 2018; 53:197-207. [PMID: 27163827 DOI: 10.3233/jad-160170] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Alzheimer's disease is a neurodegenerative disorder that affects mostly the elderly. The main histopathological markers are the senile plaques formed by amyloid-β peptide (Aβ) aggregates that can perforate the plasma membrane of cells, increasing the intracellular calcium levels and releasing synaptic vesicles that finally lead to a delayed synaptic failure. Several membrane proteins and lipids interact with Aβ affecting its toxicity in neurons. Here, we focus on NMDA receptors (NMDARs) as proteins that could be modulating the association and neurotoxic perforation induced by Aβ on the plasma membrane. In fact, our results showed that decreasing NMDARs, using enzymatic or siRNA approaches, increased the association of Aβ to the neurons. Furthermore, overexpression of NMDARs also resulted in an enhanced association between NMDA and Aβ. Functionally, the reduction in membrane NMDARs augmented the process of membrane perforation. On the other hand, overexpressing NMDARs had a protective effect because Aβ was now unable to cause membrane perforation, suggesting a complex relationship between Aβ and NMDARs. Because previous studies have recognized that Aβ oligomers are able to increase membrane permeability and produce amyloid pores, the present study supports the conclusion that NMDARs play a critical protective role on Aβ actions in hippocampal neurons. These results could explain the lack of correlation between brain Aβ burden and clinically observed dementia.
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Affiliation(s)
- Christian Peters
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Chile
| | - Fernando J Sepúlveda
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Chile
| | | | - Robert W Peoples
- Laboratory of Biomedical Sciences, Marquette University, Milwaukee, WI, USA
| | - Luis G Aguayo
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Chile
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23
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Fernández-Pérez EJ, Sepúlveda FJ, Peters C, Bascuñán D, Riffo-Lepe NO, González-Sanmiguel J, Sánchez SA, Peoples RW, Vicente B, Aguayo LG. Effect of Cholesterol on Membrane Fluidity and Association of Aβ Oligomers and Subsequent Neuronal Damage: A Double-Edged Sword. Front Aging Neurosci 2018. [PMID: 30123122 DOI: 10.3389/fnagi.2018.002.26] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2023] Open
Abstract
Background: The beta-amyloid peptide (Aβ) involved in Alzheimer's disease (AD) has been described to associate/aggregate on the cell surface disrupting the membrane through pore formation and breakage. However, molecular determinants involved for this interaction (e.g., some physicochemical properties of the cell membrane) are largely unknown. Since cholesterol is an important molecule for membrane structure and fluidity, we examined the effect of varying cholesterol content with the association and membrane perforation by Aβ in cultured hippocampal neurons. Methods: To decrease or increase the levels of cholesterol in the membrane we used methyl-β-cyclodextrin (MβCD) and MβCD/cholesterol, respectively. We analyzed if membrane fluidity was affected using generalized polarization (GP) imaging and the fluorescent dye di-4-ANEPPDHQ. Additionally membrane association and perforation was assessed using immunocytochemistry and electrophysiological techniques, respectively. Results: The results showed that cholesterol removal decreased the macroscopic association of Aβ to neuronal membranes (fluorescent-puncta/20 μm: control = 18 ± 2 vs. MβCD = 10 ± 1, p < 0.05) and induced a facilitation of the membrane perforation by Aβ with respect to control cells (half-time for maximal charge transferred: control = 7.2 vs. MβCD = 4.4). Under this condition, we found an increase in membrane fluidity (46 ± 3.3% decrease in GP value, p < 0.001). On the contrary, increasing cholesterol levels incremented membrane rigidity (38 ± 2.7% increase in GP value, p < 0.001) and enhanced the association and clustering of Aβ (fluorescent-puncta/20 μm: control = 18 ± 2 vs. MβCD = 10 ± 1, p < 0.01), but inhibited membrane disruption. Conclusion: Our results strongly support the significance of plasma membrane organization in the toxic effects of Aβ in hippocampal neurons, since fluidity can regulate distribution and insertion of the Aβ peptide in the neuronal membrane.
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Affiliation(s)
- Eduardo J Fernández-Pérez
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Fernando J Sepúlveda
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Christian Peters
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Denisse Bascuñán
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Nicolás O Riffo-Lepe
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | | | - Susana A Sánchez
- Departamento de Polímeros, Facultad de Ciencias Químicas, Universidad de Concepción, Concepción, Chile
| | - Robert W Peoples
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI, United States
| | - Benjamín Vicente
- Department of Psychiatry and Mental Health, Universidad de Concepción, Concepción, Chile
| | - Luis G Aguayo
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
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24
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Role of membrane GM1 on early neuronal membrane actions of Aβ during onset of Alzheimer's disease. Biochim Biophys Acta Mol Basis Dis 2017; 1863:3105-3116. [DOI: 10.1016/j.bbadis.2017.08.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 07/19/2017] [Accepted: 08/14/2017] [Indexed: 11/21/2022]
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25
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Shuaib S, Goyal B. Scrutiny of the mechanism of small molecule inhibitor preventing conformational transition of amyloid-β 42 monomer: insights from molecular dynamics simulations. J Biomol Struct Dyn 2017; 36:663-678. [PMID: 28162045 DOI: 10.1080/07391102.2017.1291363] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is characterized by loss of intellectual functioning of brain and memory loss. According to amyloid cascade hypothesis, aggregation of amyloid-β42 (Aβ42) peptide can generate toxic oligomers and their accumulation in the brain is responsible for the onset of AD. In spite of carrying out a large number of experimental studies on inhibition of Aβ42 aggregation by small molecules, the detailed inhibitory mechanism remains elusive. In the present study, comparable molecular dynamics (MD) simulations were performed to elucidate the inhibitory mechanism of a sulfonamide inhibitor C1 (2,5-dichloro-N-(4-piperidinophenyl)-3-thiophenesulfonamide), reported for its in vitro and in vivo anti-aggregation activity against Aβ42. MD simulations reveal that C1 stabilizes native α-helix conformation of Aβ42 by interacting with key residues in the central helix region (13-26) with hydrogen bonds and π-π interactions. C1 lowers the solvent-accessible surface area of the central hydrophobic core (CHC), KLVFF (16-20), that confirms burial of hydrophobic residues leading to the dominance of helical conformation in the CHC region. The binding free energy analysis with MM-PBSA demonstrates that Ala2, Phe4, Tyr10, Gln15, Lys16, Leu17, Val18, Phe19, Phe20, Glu22, and Met35 contribute maximum to binding free energy (-43.1 kcal/mol) between C1 and Aβ42 monomer. Overall, MD simulations reveal that C1 inhibits Aβ42 aggregation by stabilizing native helical conformation and inhibiting the formation of aggregation-prone β-sheet conformation. The present results will shed light on the underlying inhibitory mechanism of small molecules that show potential in vitro anti-aggregation activity against Aβ42.
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Affiliation(s)
- Suniba Shuaib
- a Department of Chemistry , School of Basic and Applied Sciences, Sri Guru Granth Sahib World University , Fatehgarh Sahib 140406 , Punjab , India
| | - Bhupesh Goyal
- a Department of Chemistry , School of Basic and Applied Sciences, Sri Guru Granth Sahib World University , Fatehgarh Sahib 140406 , Punjab , India
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26
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Peters C, Bascuñán D, Opazo C, Aguayo LG. Differential Membrane Toxicity of Amyloid-β Fragments by Pore Forming Mechanisms. J Alzheimers Dis 2016; 51:689-99. [PMID: 26890761 DOI: 10.3233/jad-150896] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A major characteristic of Alzheimer's disease (AD) is the presence of amyloid-β peptide (Aβ) oligomers and aggregates in the brain. It is known that Aβ oligomers interact with the neuronal membrane and induce perforations that cause an influx of calcium ions and enhance the release of synaptic vesicles leading to a delayed synaptic failure by vesicle depletion. To better understand the mechanism by which Aβ exerts its effect on the plasma membrane, we evaluated three Aβ fragments derived from different regions of Aβ(1-42); Aβ(1-28) from the N-terminal region, Aβ(25-35) from the central region, and Aβ(17-42) from the C-terminal region. The neuronal activities of these fragments were examined with patch clamp, immunofluorescence, transmission electron microscopy, aggregation assays, calcium imaging, and MTT reduction assays. The present results indicate that the fragment Aβ(1-28) contributes to aggregation, an increase in intracellular calcium and synaptotoxicity, but is not involved in membrane perforation; Aβ(25-35) is important for membrane perforation, calcium increase, and synaptotoxicity; and Aβ(17-42) induced mitochondrial toxicity similar to the full length Aβ(1-42), but was unable to induce membrane perforation and calcium increase, supporting the idea that it is less toxic in the non-amyloidogenic pathway.
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27
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A Novel, Multi-Target Natural Drug Candidate, Matrine, Improves Cognitive Deficits in Alzheimer's Disease Transgenic Mice by Inhibiting Aβ Aggregation and Blocking the RAGE/Aβ Axis. Mol Neurobiol 2016; 54:1939-1952. [PMID: 26899576 DOI: 10.1007/s12035-016-9783-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 02/08/2016] [Indexed: 01/08/2023]
Abstract
The treatment of AD is a topic that has puzzled researchers for many years. Current mainstream theories still consider Aβ to be the most important target for the cure of AD. In this study, we attempted to explore multiple targets for AD treatments with the aim of identifying a qualified compound that could both inhibit the aggregation of Aβ and block the RAGE/Aβ axis. We believed that a compound that targets both Aβ and RAGE may be a feasible strategy for AD treatment. A novel and small natural compound, Matrine (Mat), was identified by high-throughput screening of the main components of traditional Chinese herbs used to treat dementia. Various experimental techniques were used to evaluate the effect of Mat on these two targets both in vitro and in AD mouse model. Mat could inhibit Aβ42-induced cytotoxicity and suppress the Aβ/RAGE signaling pathway in vitro. Additionally, the results of in vivo evaluations of the effects of Mat on the two targets were consistent with the results of our in vitro studies. Furthermore, Mat reduced proinflammatory cytokines and Aβ deposition and attenuated the memory deficits of AD transgenic mice. We believe that this novel, multi-target strategy to inhibit both Aβ and RAGE, is worthy of further exploration. Therefore, our future studies will focus on identifying even more effective multi-target compounds for the treatment of AD based on the molecular structure of Mat.
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28
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Sáez-Orellana F, Godoy PA, Bastidas CY, Silva-Grecchi T, Guzmán L, Aguayo LG, Fuentealba J. ATP leakage induces P2XR activation and contributes to acute synaptic excitotoxicity induced by soluble oligomers of β-amyloid peptide in hippocampal neurons. Neuropharmacology 2015; 100:116-23. [PMID: 25896766 DOI: 10.1016/j.neuropharm.2015.04.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 03/10/2015] [Accepted: 04/07/2015] [Indexed: 01/06/2023]
Abstract
Recent studies suggest that the toxic effects of Aβ can be attributed to its capability to insert in membranes and form pore-like structures, which are permeable to cations and molecules such as ATP. Our working hypothesis is that Aβ increases extracellular ATP causing activation of P2X receptors and potentiating excitatory synaptic activity. We found that soluble oligomers of β-amyloid peptide increased cytosolic Ca(2+) 4-fold above control (415 ± 28% of control). Also, ATP leakage (157 ± 10% of control) was independent of extracellular Ca(2+), suggesting that ATP traveled from the cytosol through an Aβ pore-mediated efflux and not from exocytotic mechanisms. The subsequent activation of P2XR by ATP can contribute to the cytosolic Ca(2+) increase observed with Aβ. Additionally, we found that β-amyloid oligomers bind preferentially to excitatory neurons inducing an increase in excitatory synaptic current frequency (248.1 ± 32.7%) that was blocked by the use of P2XR antagonists such as PPADS (Aβ + PPADS: 110.9 ± 18.35%) or Apyrase plus DPCPX (Aβ + inhibitors: 98.97 ± 17.4%). Taken together, we suggest that Aβ induces excitotoxicity by binding preferentially to excitatory neuron membranes forming a non-selective pore and by increasing intracellular calcium by itself and through P2XR activation by extracellular ATP leading to an augmention in mEPSC activity. All these effects were blocked with a non-specific P2XR antagonist, indicating that part of the neurotoxicity of Aβ is mediated by P2XR activation and facilitation of excitatory neurotransmitter release. These findings suggest that P2XR can be considered as a potential new target for the development of drugs or pharmacological tools to treat Alzheimer's disease. This article is part of the Special Issue entitled 'Synaptopathy--from Biology to Therapy'.
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Affiliation(s)
- F Sáez-Orellana
- Laboratory of Screening of Neuroactive Compound, Physiology Department, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - P A Godoy
- Laboratory of Screening of Neuroactive Compound, Physiology Department, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - C Y Bastidas
- Laboratory of Screening of Neuroactive Compound, Physiology Department, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - T Silva-Grecchi
- Laboratory of Screening of Neuroactive Compound, Physiology Department, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - L Guzmán
- Neurophysiology Laboratory, Physiology Department, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - L G Aguayo
- Neurophysiology Laboratory, Physiology Department, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - J Fuentealba
- Laboratory of Screening of Neuroactive Compound, Physiology Department, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile; Center for Advanced Research on Biomedicine (CIAB-UdeC), Physiology Department, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile.
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29
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Pacheco CR, Morales CN, Ramírez AE, Muñoz FJ, Gallegos SS, Caviedes PA, Aguayo LG, Opazo CM. Extracellular α-synuclein alters synaptic transmission in brain neurons by perforating the neuronal plasma membrane. J Neurochem 2015; 132:731-41. [PMID: 25669123 DOI: 10.1111/jnc.13060] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Revised: 02/01/2015] [Accepted: 02/02/2015] [Indexed: 12/25/2022]
Abstract
It has been postulated that the accumulation of extracellular α-synuclein (α-syn) might alter the neuronal membrane by formation of 'pore-like structures' that will lead to alterations in ionic homeostasis. However, this has never been demonstrated to occur in brain neuronal plasma membranes. In this study, we show that α-syn oligomers rapidly associate with hippocampal membranes in a punctate fashion, resulting in increased membrane conductance (5 fold over control) and the influx of both calcium and a fluorescent glucose analogue. The enhancement in intracellular calcium (1.7 fold over control) caused a large increase in the frequency of synaptic transmission (2.5 fold over control), calcium transients (3 fold over control), and synaptic vesicle release. Both primary hippocampal and dissociated nigral neurons showed rapid increases in membrane conductance by α-syn oligomers. In addition, we show here that α-syn caused synaptotoxic failure associated with a decrease in SV2, a membrane protein of synaptic vesicles associated with neurotransmitter release. In conclusion, extracellular α-syn oligomers facilitate the perforation of the neuronal plasma membrane, thus explaining, in part, the synaptotoxicity observed in neurodegenerative diseases characterized by its extracellular accumulation. We propose that α-synuclein (α-syn) oligomers form pore-like structures in the plasma membrane of neurons from central nervous system (CNS). We believe that extracellular α-syn oligomers facilitate the formation of α-syn membrane pore-like structures, thus explaining, in part, the synaptotoxicity observed in neurodegenerative diseases characterized by its extracellular accumulation. We think that alterations in ionic homeostasis and synaptic vesicular depletion are key steps that lead to synaptotoxicity promoted by α -syn membrane pore-like structures.
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Affiliation(s)
- Carla R Pacheco
- Department of Physiology, University of Concepcion, Concepcion, Chile
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30
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Brogi S, Butini S, Maramai S, Colombo R, Verga L, Lanni C, De Lorenzi E, Lamponi S, Andreassi M, Bartolini M, Andrisano V, Novellino E, Campiani G, Brindisi M, Gemma S. Disease-modifying anti-Alzheimer's drugs: inhibitors of human cholinesterases interfering with β-amyloid aggregation. CNS Neurosci Ther 2015; 20:624-32. [PMID: 24935788 DOI: 10.1111/cns.12290] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 04/18/2014] [Accepted: 04/30/2014] [Indexed: 11/26/2022] Open
Abstract
AIMS We recently described multifunctional tools (2a-c) as potent inhibitors of human Cholinesterases (ChEs) also able to modulate events correlated with Aβ aggregation. We herein propose a thorough biological and computational analysis aiming at understanding their mechanism of action at the molecular level. METHODS We determined the inhibitory potency of 2a-c on Aβ1-42 self-aggregation, the interference of 2a with the toxic Aβ oligomeric species and with the postaggregation states by capillary electrophoresis analysis and transmission electron microscopy. The modulation of Aβ toxicity was assessed for 2a and 2b on human neuroblastoma cells. The key interactions of 2a with Aβ and with the Aβ-preformed fibrils were computationally analyzed. 2a-c toxicity profile was also assessed (human hepatocytes and mouse fibroblasts). RESULTS Our prototypical pluripotent analogue 2a interferes with Aβ oligomerization process thus reducing Aβ oligomers-mediated toxicity in human neuroblastoma cells. 2a also disrupts preformed fibrils. Computational studies highlighted the bases governing the diversified activities of 2a. CONCLUSION Converging analytical, biological, and in silico data explained the mechanism of action of 2a on Aβ1-42 oligomers formation and against Aβ-preformed fibrils. This evidence, combined with toxicity data, will orient the future design of safer analogues.
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Affiliation(s)
- Simone Brogi
- European Research Centre for Drug Discovery and Development (NatSynDrugs), University of Siena, Siena, Italy; Dipartimento di Biotecnologie, Chimica e Farmacia, University of Siena, Siena, Italy
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31
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Viola KL, Klein WL. Amyloid β oligomers in Alzheimer's disease pathogenesis, treatment, and diagnosis. Acta Neuropathol 2015; 129:183-206. [PMID: 25604547 DOI: 10.1007/s00401-015-1386-3] [Citation(s) in RCA: 440] [Impact Index Per Article: 48.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 01/11/2015] [Accepted: 01/11/2015] [Indexed: 12/22/2022]
Abstract
Protein aggregation is common to dozens of diseases including prionoses, diabetes, Parkinson's and Alzheimer's. Over the past 15 years, there has been a paradigm shift in understanding the structural basis for these proteinopathies. Precedent for this shift has come from investigation of soluble Aβ oligomers (AβOs), toxins now widely regarded as instigating neuron damage leading to Alzheimer's dementia. Toxic AβOs accumulate in AD brain and constitute long-lived alternatives to the disease-defining Aβ fibrils deposited in amyloid plaques. Key experiments using fibril-free AβO solutions demonstrated that while Aβ is essential for memory loss, the fibrillar Aβ in amyloid deposits is not the agent. The AD-like cellular pathologies induced by AβOs suggest their impact provides a unifying mechanism for AD pathogenesis, explaining why early stage disease is specific for memory and accounting for major facets of AD neuropathology. Alternative ideas for triggering mechanisms are being actively investigated. Some research favors insertion of AβOs into membrane, while other evidence supports ligand-like accumulation at particular synapses. Over a dozen candidate toxin receptors have been proposed. AβO binding triggers a redistribution of critical synaptic proteins and induces hyperactivity in metabotropic and ionotropic glutamate receptors. This leads to Ca(2+) overload and instigates major facets of AD neuropathology, including tau hyperphosphorylation, insulin resistance, oxidative stress, and synapse loss. Because different species of AβOs have been identified, a remaining question is which oligomer is the major pathogenic culprit. The possibility has been raised that more than one species plays a role. Despite some key unknowns, the clinical relevance of AβOs has been established, and new studies are beginning to point to co-morbidities such as diabetes and hypercholesterolemia as etiological factors. Because pathogenic AβOs appear early in the disease, they offer appealing targets for therapeutics and diagnostics. Promising therapeutic strategies include use of CNS insulin signaling enhancers to protect against the presence of toxins and elimination of the toxins through use of highly specific AβO antibodies. An AD-dependent accumulation of AβOs in CSF suggests their potential use as biomarkers and new AβO probes are opening the door to brain imaging. Overall, current evidence indicates that Aβ oligomers provide a substantive molecular basis for the cause, treatment and diagnosis of Alzheimer's disease.
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Peters C, Espinoza MP, Gallegos S, Opazo C, Aguayo LG. Alzheimer's Aβ interacts with cellular prion protein inducing neuronal membrane damage and synaptotoxicity. Neurobiol Aging 2014; 36:1369-77. [PMID: 25599875 DOI: 10.1016/j.neurobiolaging.2014.11.019] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 11/06/2014] [Accepted: 11/25/2014] [Indexed: 12/31/2022]
Abstract
A major feature of Alzheimer's disease is the accumulation of β-amyloid (Aβ) peptide in the brain. Recent studies have indicated that Aβ oligomers (Aβo) can interact with the cellular prion protein (PrPc). Therefore, this interaction might be driving some of Aβ toxic effects in the synaptic region. In the present study, we report that Aβo binds to PrPc in the neuronal membrane playing a role on toxic effects induced by Aβ. Phospholipase C-enzymatic cleavage of PrPc from the plasma membrane attenuated the association of Aβo to the neurons. Furthermore, an anti-PrP antibody (6D11) decreased the association of Aβo to hippocampal neurons with a concomitant reduction in Aβo and PrPc co-localization. Interestingly, this antibody blocked the increase in membrane conductance and intracellular calcium induced by Aβo. Thus, the data indicate that PrPc plays a role on the membrane perforations produced by Aβo, the increase in calcium ions and the release of synaptic vesicles that subsequently leads to synaptic failure. Future studies blocking Aβo interaction with PrPc could be important for the discovery of new therapeutic strategies for Alzheimer's disease.
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Affiliation(s)
- Christian Peters
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - María Paz Espinoza
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Scarlet Gallegos
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Carlos Opazo
- Oxidation Biology Laboratory, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Melbourne, Victoria, Australia.
| | - Luis G Aguayo
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile.
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Design of non-aggregating variants of Aβ peptide. Biochem Biophys Res Commun 2014; 453:449-54. [PMID: 25281534 DOI: 10.1016/j.bbrc.2014.09.102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 09/23/2014] [Indexed: 11/22/2022]
Abstract
Self association of the amyloid-β (Aβ42) peptide into oligomers, high molecular weight forms, fibrils and ultimately neuritic plaques, has been correlated with progressive cognitive decline in Alzheimer's disease. Thus, insights into the drivers of the aggregation pathway have the capacity to significantly contribute to our understanding of disease mechanism. Functional assays and a three-dimensional crystal structure of the P3 amyloidogenic region 18-41 of Aβ were used to identify residues important in self-association and to design novel non-aggregating variants of the peptide. Biophysical studies (gel filtration, SDS-PAGE, dynamic light scattering, thioflavin T assay, and electron microscopy) demonstrate that in contrast to wild type Aβ these targeted mutations lose the ability to self-associate. Loss of aggregation also correlates with reduced neuronal toxicity. Our results highlight residues and regions of the Aβ peptide important for future targeting agents aimed at the amelioration of Alzheimer's disease.
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Rapamycin protects against Aβ-induced synaptotoxicity by increasing presynaptic activity in hippocampal neurons. Biochim Biophys Acta Mol Basis Dis 2014; 1842:1495-501. [DOI: 10.1016/j.bbadis.2014.04.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Revised: 04/21/2014] [Accepted: 04/23/2014] [Indexed: 12/19/2022]
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Sepúlveda FJ, Fierro H, Fernandez E, Castillo C, Peoples RW, Opazo C, Aguayo LG. Nature of the neurotoxic membrane actions of amyloid-β on hippocampal neurons in Alzheimer's disease. Neurobiol Aging 2013; 35:472-81. [PMID: 24112789 DOI: 10.1016/j.neurobiolaging.2013.08.035] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 08/26/2013] [Accepted: 08/30/2013] [Indexed: 10/26/2022]
Abstract
The mechanism by which amyloid-β (Aβ) produces brain dysfunction in patients with Alzheimer's disease is largely unknown. According to previous studies, Aβ might share perforating properties with gramicidin, a well-accepted membrane-disrupting peptide. Therefore, we hypothesize that the key steps leading to synaptotoxicity by Aβ and gramicidin involve peptide aggregation, pore formation, and calcium dysregulation. Here, we show that Aβ and gramicidin form aggregates enriched in β-sheet structures using electron microscopy, and Thioflavin and Congo Red staining techniques. Also, we found that Aβ and gramicidin display fairly similar actions in hippocampal cell membranes, i.e. inducing Ca(2+) entry and synaptoxicity characterized by the loss of synaptic proteins and a decrease in neuronal viability. These effects were not observed in a Ca(2+) free solution, indicating that both Aβ and gramicidin induce neurotoxicity by a Ca(2+)-dependent mechanism. Using combined perforated patch clamp and imaging recordings, we found that only Aβ produced a perforation that progressed from a small (Cl(-)-selective pore) to a larger perforation that allowed the entry of fluorescent molecules. Therefore, based on these results, we propose that the perforation at the plasma membrane by Aβ is a dynamic process that is critical in producing neurotoxicity similar to that found in the brains of AD patients.
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Affiliation(s)
- Fernando J Sepúlveda
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Concepción, Chile
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