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Lombardi P, Karadayian AG, Guerra JI, Bustamante J, Rodríguez de Lores Arnaiz G, Lores-Arnaiz S. Mitochondrial bioenergetics and cytometric characterization of a synaptosomal preparation from mouse brain cortex. Mitochondrion 2023; 73:95-107. [PMID: 37944836 DOI: 10.1016/j.mito.2023.10.002] [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: 12/30/2022] [Revised: 09/06/2023] [Accepted: 10/28/2023] [Indexed: 11/12/2023]
Abstract
Mitochondrial function at synapses can be assessed in isolated nerve terminals. Synaptosomes are structures obtained in vitro by detaching the nerve endings from neuronal bodies under controlled homogenization conditions. Several protocols have been described for the preparation of intact synaptosomal fractions. Herein a fast and economical method to obtain synaptosomes with optimal intrasynaptic mitochondria functionality was described. Synaptosomal fractions were obtained from mouse brain cortex by differential centrifugation followed by centrifugation in a Ficoll gradient. The characteristics of the subcellular particles obtained were analyzed by flow cytometry employing specific tools. Integrity and specificity of the obtained organelles were evaluated by calcein and SNAP-25 probes. The proportion of positive events of the synaptosomal preparation was 75 ± 2 % and 48 ± 7% for calcein and Synaptosomal-Associated Protein of 25 kDa (SNAP-25), respectively. Mitochondrial integrity was evaluated by flow cytometric analysis of cardiolipin content, which indicated that 73 ± 1% of the total events were 10 N-nonylacridine orange (NAO)-positive. Oxygen consumption, ATP production and mitochondrial membrane potential determinations showed that mitochondria inside synaptosomes remained functional after the isolation procedure. Mitochondrial and synaptosomal enrichment were determined by measuring synaptosomes/ homogenate ratio of specific markers. Functionality of synaptosomes was verified by nitric oxide detection after glutamate addition. As compared with other methods, the present protocol can be performed briefly, does not imply high economic costs, and provides an useful tool for the isolation of a synaptosomal preparation with high mitochondrial respiratory capacity and an adequate integrity and function of intraterminal mitochondria.
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Affiliation(s)
- Paulina Lombardi
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Fisicoquímica, Buenos Aires, Argentina; CONICET- Universidad de Buenos Aires, Instituto de Bioquímica y Medicina Molecular "Profesor Alberto Boveris" (IBIMOL), Buenos Aires, Argentina
| | - Analía G Karadayian
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Fisicoquímica, Buenos Aires, Argentina; CONICET- Universidad de Buenos Aires, Instituto de Bioquímica y Medicina Molecular "Profesor Alberto Boveris" (IBIMOL), Buenos Aires, Argentina
| | - Juan I Guerra
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Fisicoquímica, Buenos Aires, Argentina; CONICET- Universidad de Buenos Aires, Instituto de Bioquímica y Medicina Molecular "Profesor Alberto Boveris" (IBIMOL), Buenos Aires, Argentina
| | | | - Georgina Rodríguez de Lores Arnaiz
- Universidad de Buenos Aires, Facultad de Medicina, Buenos Aires, Argentina; CONICET-Universidad de Buenos Aires, Instituto de Biología Celular y Neurociencias "Profesor Eduardo De Robertis" (IBCN), Buenos Aires, Argentina
| | - Silvia Lores-Arnaiz
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Fisicoquímica, Buenos Aires, Argentina; CONICET- Universidad de Buenos Aires, Instituto de Bioquímica y Medicina Molecular "Profesor Alberto Boveris" (IBIMOL), Buenos Aires, Argentina.
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Rodrigues MS, Ferreira SG, Quiroz C, Earley CJ, García-Borreguero D, Cunha RA, Ciruela F, Köfalvi A, Ferré S. Brain Iron Deficiency Changes the Stoichiometry of Adenosine Receptor Subtypes in Cortico-Striatal Terminals: Implications for Restless Legs Syndrome. Molecules 2022; 27:molecules27051489. [PMID: 35268590 PMCID: PMC8911604 DOI: 10.3390/molecules27051489] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 02/19/2022] [Accepted: 02/21/2022] [Indexed: 01/01/2023] Open
Abstract
Brain iron deficiency (BID) constitutes a primary pathophysiological mechanism in restless legs syndrome (RLS). BID in rodents has been widely used as an animal model of RLS, since it recapitulates key neurochemical changes reported in RLS patients and shows an RLS-like behavioral phenotype. Previous studies with the BID-rodent model of RLS demonstrated increased sensitivity of cortical pyramidal cells to release glutamate from their striatal nerve terminals driving striatal circuits, a correlative finding of the cortical motor hyperexcitability of RLS patients. It was also found that BID in rodents leads to changes in the adenosinergic system, a downregulation of the inhibitory adenosine A1 receptors (A1Rs) and upregulation of the excitatory adenosine A2A receptors (A2ARs). It was then hypothesized, but not proven, that the BID-induced increased sensitivity of cortico-striatal glutamatergic terminals could be induced by a change in A1R/A2AR stoichiometry in favor of A2ARs. Here, we used a newly developed FACS-based synaptometric analysis to compare the relative abundance on A1Rs and A2ARs in cortico-striatal and thalamo-striatal glutamatergic terminals (labeled with vesicular glutamate transporters VGLUT1 and VGLUT2, respectively) of control and BID rats. It could be demonstrated that BID (determined by measuring transferrin receptor density in the brain) is associated with a selective decrease in the A1R/A2AR ratio in VGLUT1 positive-striatal terminals.
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Affiliation(s)
- Matilde S. Rodrigues
- CNC-Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; (M.S.R.); (S.G.F.); (R.A.C.); (A.K.)
| | - Samira G. Ferreira
- CNC-Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; (M.S.R.); (S.G.F.); (R.A.C.); (A.K.)
| | - César Quiroz
- Integrative Neurobiology Section, National Institute on Drug Abuse, Baltimore, MD 21224, USA;
| | | | | | - Rodrigo A. Cunha
- CNC-Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; (M.S.R.); (S.G.F.); (R.A.C.); (A.K.)
- Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Francisco Ciruela
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, 08907 L’Hospitalet de Llobregat, Spain;
- Neuropharmacology and Pain Group, Neuroscience Program, Institut d’Investigació Biomèdica de Belvitge, Idibell, 08907 L’Hospitalet de Llobregat, Spain
| | - Attila Köfalvi
- CNC-Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; (M.S.R.); (S.G.F.); (R.A.C.); (A.K.)
| | - Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Baltimore, MD 21224, USA;
- Correspondence:
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Phongpreecha T, Gajera CR, Liu CC, Vijayaragavan K, Chang AL, Becker M, Fallahzadeh R, Fernandez R, Postupna N, Sherfield E, Tebaykin D, Latimer C, Shively CA, Register TC, Craft S, Montine KS, Fox EJ, Poston KL, Keene CD, Angelo M, Bendall SC, Aghaeepour N, Montine TJ. Single-synapse analyses of Alzheimer's disease implicate pathologic tau, DJ1, CD47, and ApoE. SCIENCE ADVANCES 2021; 7:eabk0473. [PMID: 34910503 PMCID: PMC8673771 DOI: 10.1126/sciadv.abk0473] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Synaptic molecular characterization is limited for Alzheimer’s disease (AD). Our newly invented mass cytometry–based method, synaptometry by time of flight (SynTOF), was used to measure 38 antibody probes in approximately 17 million single-synapse events from human brains without pathologic change or with pure AD or Lewy body disease (LBD), nonhuman primates (NHPs), and PS/APP mice. Synaptic molecular integrity in humans and NHP was similar. Although not detected in human synapses, Aβ was in PS/APP mice single-synapse events. Clustering and pattern identification of human synapses showed expected disease-specific differences, like increased hippocampal pathologic tau in AD and reduced caudate dopamine transporter in LBD, and revealed previously unidentified findings including increased hippocampal CD47 and lowered DJ1 in AD and higher ApoE in AD with dementia. Our results were independently supported by multiplex ion beam imaging of intact tissue. This highlights the higher depth and breadth of insight on neurodegenerative diseases obtainable through SynTOF.
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Affiliation(s)
- Thanaphong Phongpreecha
- Department of Pathology, Stanford University, Stanford, CA, USA
- Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University, Stanford, CA, USA
- Department of Biomedical Data Science, Stanford University, Stanford, CA, USA
| | | | - Candace C. Liu
- Department of Pathology, Stanford University, Stanford, CA, USA
| | | | - Alan L. Chang
- Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University, Stanford, CA, USA
- Department of Biomedical Data Science, Stanford University, Stanford, CA, USA
- Department of Pediatrics, Stanford University, Stanford, CA, USA
| | - Martin Becker
- Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University, Stanford, CA, USA
- Department of Biomedical Data Science, Stanford University, Stanford, CA, USA
- Department of Pediatrics, Stanford University, Stanford, CA, USA
| | - Ramin Fallahzadeh
- Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University, Stanford, CA, USA
- Department of Biomedical Data Science, Stanford University, Stanford, CA, USA
- Department of Pediatrics, Stanford University, Stanford, CA, USA
| | | | - Nadia Postupna
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Emily Sherfield
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Dmitry Tebaykin
- Department of Pathology, Stanford University, Stanford, CA, USA
| | - Caitlin Latimer
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Carol A. Shively
- Department of Pathology/Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Thomas C. Register
- Department of Pathology/Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Suzanne Craft
- Department of Internal Medicine–Geriatrics, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | | | - Edward J. Fox
- Department of Pathology, Stanford University, Stanford, CA, USA
| | - Kathleen L. Poston
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
- Department of Neurosurgery, Stanford University, Stanford, CA, USA
| | - C. Dirk Keene
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Michael Angelo
- Department of Pathology, Stanford University, Stanford, CA, USA
| | - Sean C. Bendall
- Department of Pathology, Stanford University, Stanford, CA, USA
| | - Nima Aghaeepour
- Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University, Stanford, CA, USA
- Department of Biomedical Data Science, Stanford University, Stanford, CA, USA
- Department of Pediatrics, Stanford University, Stanford, CA, USA
| | - Thomas J. Montine
- Department of Pathology, Stanford University, Stanford, CA, USA
- Corresponding author.
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Singh A, Allen D, Fracassi A, Tumurbaatar B, Natarajan C, Scaduto P, Woltjer R, Kayed R, Limon A, Krishnan B, Taglialatela G. Functional Integrity of Synapses in the Central Nervous System of Cognitively Intact Individuals with High Alzheimer's Disease Neuropathology Is Associated with Absence of Synaptic Tau Oligomers. J Alzheimers Dis 2021; 78:1661-1678. [PMID: 33185603 PMCID: PMC7836055 DOI: 10.3233/jad-200716] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Certain individuals, here referred to as Non-Demented with Alzheimer Neuropathology (NDAN), do not show overt neurodegeneration (N-) and remain cognitively intact despite the presence of plaques (A+) and tangles (T+) that would normally be consistent with fully symptomatic Alzheimer's disease (AD). OBJECTIVE The existence of NDAN (A + T+N-) subjects suggests that the human brain utilizes intrinsic mechanisms that can naturally evade cognitive decline normally associated with the symptomatic stages of AD (A + T+N+). Deciphering the underlying mechanisms would prove relevant to develop complementing therapeutics to prevent progression of AD-related cognitive decline. METHODS Previously, we have reported that NDAN present with preserved neurogenesis and synaptic integrity paralleled by absence of amyloid oligomers at synapses. Using postmortem brain samples from age-matched control subjects, demented AD patients and NDAN individuals, we performed immunofluorescence, western blots, micro transplantation of synaptic membranes in Xenopus oocytes followed by twin electrode voltage clamp electrophysiology and fluorescence assisted single synaptosome-long term potentiation studies. RESULTS We report decreased tau oligomers at synapses in the brains of NDAN subjects. Furthermore, using novel approaches we report, for the first time, that such absence of tau oligomers at synapses is associated with synaptic functional integrity in NDAN subjects as compared to demented AD patients. CONCLUSION Overall, these results give further credence to tau oligomers as primary actors of synaptic destruction underscoring cognitive demise in AD and support their targeting as a viable therapeutic strategy for AD and related tauopathies.
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Affiliation(s)
- Ayush Singh
- Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA
| | - Dyron Allen
- Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA
| | - Anna Fracassi
- Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA
| | - Batbayar Tumurbaatar
- Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA
| | - Chandramouli Natarajan
- Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA
| | - Pietro Scaduto
- Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA
| | - Randy Woltjer
- Department of Pathology, Oregon Health and Science University, Portland, OR, USA
| | - Rakez Kayed
- Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA
| | - Agenor Limon
- Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA
| | - Balaji Krishnan
- Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA,Correspondence to: Giulio Taglialatela, PhD, Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA. Tel.: +1 409 772 1679; Fax: +1 409 772 0015; E-mail: . and Balaji Krishnan, PhD, Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA. Tel.: +1 409 772 8069; Fax: +1 409 772 0015; E-mail:
| | - Giulio Taglialatela
- Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA,Correspondence to: Giulio Taglialatela, PhD, Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA. Tel.: +1 409 772 1679; Fax: +1 409 772 0015; E-mail: . and Balaji Krishnan, PhD, Mitchell Center for Neurodegenerative Diseases, Department of Neurology, UTMB Galveston, TX, USA. Tel.: +1 409 772 8069; Fax: +1 409 772 0015; E-mail:
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Gajera CR, Fernandez R, Montine KS, Fox EJ, Mrdjen D, Postupna NO, Keene CD, Bendall SC, Montine TJ. Mass-tag barcoding for multiplexed analysis of human synaptosomes and other anuclear events. Cytometry A 2021; 99:939-945. [PMID: 33818911 PMCID: PMC8590852 DOI: 10.1002/cyto.a.24340] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 02/27/2021] [Accepted: 03/17/2021] [Indexed: 12/17/2022]
Abstract
Mass-tag cell barcoding has increased the throughput, multiplexing, and robustness of multiple cytometry approaches. Previously, we adapted mass cytometry for cells to analyze synaptosome preparations (mass synaptometry or SynTOF), extending mass cytometry to these smaller, anuclear particles. To improve throughput and individual event resolution, we report here the application of palladium-based barcoding in human synaptosomes. Up to 20 individual samples, each with a unique combinatorial barcode, were pooled for labeling with an antibody cocktail. Our synaptosome protocol used six palladium-based barcoding reagents, and in combination with sequential gating increased the identification of presynaptic events approximately fourfold. These same parameters also efficiently resolved two other anuclear particles: human red blood cells and platelets. The addition of palladium-based mass-tag barcoding to our approach improves mass cytometry of synaptic particles.
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Affiliation(s)
| | - Rosemary Fernandez
- Department of Pathology, Stanford University, Stanford, CA, United States
| | | | - Edward J. Fox
- Department of Pathology, Stanford University, Stanford, CA, United States
| | - Dunja Mrdjen
- Department of Pathology, Stanford University, Stanford, CA, United States
| | - Nadia O. Postupna
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, United States
| | - C. Dirk Keene
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, United States
| | - Sean C. Bendall
- Department of Pathology, Stanford University, Stanford, CA, United States
| | - Thomas J. Montine
- Department of Pathology, Stanford University, Stanford, CA, United States
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Chronic Low Dose Neutron Exposure Results in Altered Neurotransmission Properties of the Hippocampus-Prefrontal Cortex Axis in Both Mice and Rats. Int J Mol Sci 2021; 22:ijms22073668. [PMID: 33915974 PMCID: PMC8036585 DOI: 10.3390/ijms22073668] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 03/29/2021] [Accepted: 03/31/2021] [Indexed: 12/18/2022] Open
Abstract
The proposed deep space exploration to the moon and later to Mars will result in astronauts receiving significant chronic exposures to space radiation (SR). SR exposure results in multiple neurocognitive impairments. Recently, our cross-species (mouse/rat) studies reported impaired associative memory formation in both species following a chronic 6-month low dose exposure to a mixed field of neutrons (1 mGy/day for a total dose pf 18 cGy). In the present study, we report neutron exposure induced synaptic plasticity in the medial prefrontal cortex, accompanied by microglial activation and significant synaptic loss in the hippocampus. In a parallel study, neutron exposure was also found to alter fluorescence assisted single synaptosome LTP (FASS-LTP) in the hippocampus of rats, that may be related to a reduced ability to insert AMPAR into the post-synaptic membrane, which may arise from increased phosphorylation of the serine 845 residue of the GluA1 subunit. Thus, we demonstrate for the first time, that low dose chronic neutron irradiation impacts homeostatic synaptic plasticity in the hippocampal-cortical circuit in two rodent species, and that the ability to successfully encode associative recognition memory is a dynamic, multicircuit process, possibly involving compensatory changes in AMPAR density on the synaptic surface.
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Exosomal tau with seeding activity is released from Alzheimer's disease synapses, and seeding potential is associated with amyloid beta. J Transl Med 2021; 101:1605-1617. [PMID: 34462532 PMCID: PMC8590975 DOI: 10.1038/s41374-021-00644-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 07/07/2021] [Accepted: 07/09/2021] [Indexed: 01/23/2023] Open
Abstract
Synaptic transfer of tau has long been hypothesized from the human pathology pattern and has been demonstrated in vitro and in vivo, but the precise mechanisms remain unclear. Extracellular vesicles such as exosomes have been suggested as a mechanism, but not all tau is exosomal. The present experiments use a novel flow cytometry assay to quantify depolarization of synaptosomes by KCl after loading with FM2-10, which induces a fluorescence reduction associated with synaptic vesicle release; the degree of reduction in cryopreserved human samples equaled that seen in fresh mouse synaptosomes. Depolarization induced the release of vesicles in the size range of exosomes, along with tetraspanin markers of extracellular vesicles. A number of tau peptides were released, including tau oligomers; released tau was primarily unphosphorylated and C-terminal truncated, with Aβ release just above background. When exosomes were immunopurified from release supernatants, a prominent tau band showed a dark smeared appearance of SDS-stable oligomers along with the exosomal marker syntenin-1, and these exosomes induced aggregation in the HEK tau biosensor assay. However, the flow-through did not seed aggregation. Size exclusion chromatography of purified released exosomes shows faint signals from tau in the same fractions that show a CD63 band, an exosomal size signal, and seeding activity. Crude synaptosomes from control, tauopathy, and AD cases demonstrated lower seeding in tauopathy compared to AD that is correlated with the measured Aβ42 level. These results show that AD synapses release exosomal tau that is C-terminal-truncated, oligomeric, and with seeding activity that is enhanced by Aβ. Taken together with previous findings, these results are consistent with a direct prion-like heterotypic seeding of tau by Aβ within synaptic terminals, with subsequent loading of aggregated tau onto exosomes that are released and competent for tau seeding activity.
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Selected microRNAs Increase Synaptic Resilience to the Damaging Binding of the Alzheimer's Disease Amyloid Beta Oligomers. Mol Neurobiol 2020; 57:2232-2243. [PMID: 31997075 PMCID: PMC7170988 DOI: 10.1007/s12035-020-01868-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Accepted: 01/06/2020] [Indexed: 01/30/2023]
Abstract
Alzheimer’s disease (AD) is marked by synaptic loss (at early stages) and neuronal death (at late stages). Amyloid beta (Aβ) and tau oligomers can target and disrupt synapses thus driving cognitive decay. Non-demented individuals with Alzheimer’s neuropathology (NDAN) are capable of withstanding Aβ and tau toxicity, thus remaining cognitively intact despite presence of AD neuropathology. Understanding the involved mechanism(s) would lead to development of novel effective therapeutic strategies aimed at promoting synaptic resilience to amyloid toxicity. NDAN have a unique hippocampal post-synaptic proteome when compared with AD and control individuals. Potential upstream modulators of such unique proteomic profile are miRNA-485, miRNA-4723 and miRNA-149, which we found differentially expressed in AD and NDAN vs. control. We thus hypothesized that these miRNAs play an important role in promoting either synaptic resistance or sensitization to Aβ oligomer binding. Using an in vivo mouse model, we found that administration of these miRNAs affected key synaptic genes and significantly decreased Aβ binding to the synapses. Our findings suggest that miRNA regulation and homeostasis are crucial for Aβ interaction with synaptic terminals and support that a unique miRNA regulation could be driving synaptic resistance to Aβ toxicity in NDAN, thus contributing to their preserved cognitive abilities.
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9
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Critical Analysis of Particle Detection Artifacts in Synaptosome Flow Cytometry. eNeuro 2019; 6:ENEURO.0009-19.2019. [PMID: 31118205 PMCID: PMC6565374 DOI: 10.1523/eneuro.0009-19.2019] [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: 01/07/2019] [Revised: 04/01/2019] [Accepted: 04/27/2019] [Indexed: 11/21/2022] Open
Abstract
Flow cytometry and fluorescence-activated sorting are powerful techniques that hold great promise for studying heterogeneous populations of submicron particles such as synaptosomes, but many technical challenges arise in these experiments. To date, most flow cytometry studies of synaptosomes have relied on particle detection using forward scatter (FSC) measurements and size estimation with polystyrene (PS) bead standards. However, these practices have serious limitations, and special care must be taken to overcome the poor sensitivity of conventional flow cytometers in the analysis of submicron particles. Technical artifacts can confound these experiments, especially the detection of multiple particles as a single event. Here, we compared analysis of P2 crude synaptosomal preparations from murine forebrain on multiple flow cytometers using both FSC-triggered and fluorescence-triggered detection. We implemented multicolor fluorescent dye-based assays to quantify coincident particle detection and aggregation, and we assessed the false colocalization of antigens in immunostaining analyses. Our results demonstrate that fluorescence triggering and proper dilution can control for coincident particle detection, but not particle aggregation. We confirmed previous studies showing that FSC-based size estimation with PS beads underestimates biological particle size, and we identified pervasive aggregation in the FSC range analyzed in most synaptosome flow cytometry studies. We found that analyzing P2 samples in sucrose/EDTA/tris (SET) buffer reduces aggregation compared to PBS, but does not completely eliminate the presence of aggregates, especially in immunostaining experiments. Our study highlights challenges and pitfalls in synaptosome flow cytometry and provides a methodological framework for future studies.
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Gajera CR, Fernandez R, Postupna N, Montine KS, Fox EJ, Tebaykin D, Angelo M, Bendall SC, Keene CD, Montine TJ. Mass synaptometry: High-dimensional multi parametric assay for single synapses. J Neurosci Methods 2018; 312:73-83. [PMID: 30465796 DOI: 10.1016/j.jneumeth.2018.11.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 11/09/2018] [Accepted: 11/10/2018] [Indexed: 01/19/2023]
Abstract
BACKGROUND Synaptic alterations, especially presynaptic changes, are cardinal features of neurodegenerative diseases and strongly correlate with cognitive decline. NEW METHOD We report "Mass Synaptometry" for the high-dimensional analysis of individual human synaptosomes, enriched nerve terminals from brain. This method was adapted from cytometry by time-of-flight mass spectrometry (CyTOF), which is commonly used for single-cell analysis of immune and blood cells. RESULT Here we overcome challenges for single synapse analysis by optimizing synaptosome preparations, generating a 'SynTOF panel,' recalibrating acquisition settings, and applying computational analyses. Through the analysis of 390,000 individual synaptosomes, we also provide proof-of principle validation by characterizing changes in synaptic diversity in Lewy Body Disease (LBD), Alzheimer's disease and normal brain. COMPARISON WITH EXISTING METHOD(S) Current imaging methods to study synapses in humans are capable of analyzing a limited number of synapses, and conventional flow cytometric techniques are typically restricted to fewer than 6 parameters. Our method allows for the simultaneous detection of 34 parameters from tens of thousands of individual synapses. CONCLUSION We applied Mass Synaptometry to analyze 34 parameters simultaneously on more than 390,000 synaptosomes from 13 human brain samples. This new approach revealed regional and disease-specific changes in synaptic phenotypes, including validation of this method with the expected changes in the molecular composition of striatal dopaminergic synapses in Lewy body disease and Alzheimer's disease. Mass synaptometry enables highly parallel molecular profiling of individual synaptic terminals.
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Affiliation(s)
- Chandresh R Gajera
- Department of Pathology, Stanford University Medical Center, Stanford, CA, United States
| | - Rosemary Fernandez
- Department of Pathology, Stanford University Medical Center, Stanford, CA, United States
| | - Nadia Postupna
- Department of Pathology, University of Washington, Seattle, WA, United States
| | - Kathleen S Montine
- Department of Pathology, Stanford University Medical Center, Stanford, CA, United States
| | - Edward J Fox
- Department of Pathology, Stanford University Medical Center, Stanford, CA, United States
| | - Dmitry Tebaykin
- Department of Pathology, Stanford University Medical Center, Stanford, CA, United States
| | - Michael Angelo
- Department of Pathology, Stanford University Medical Center, Stanford, CA, United States
| | - Sean C Bendall
- Department of Pathology, Stanford University Medical Center, Stanford, CA, United States
| | - C Dirk Keene
- Department of Pathology, University of Washington, Seattle, WA, United States
| | - Thomas J Montine
- Department of Pathology, Stanford University Medical Center, Stanford, CA, United States.
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11
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Blokhina S, Sharapova A, Ol'khovich M, Ustinov A, Perlovich G. New derivatives of hydrogenated pyrido[4,3-b]indoles as potential neuroprotectors: Synthesis, biological testing and solubility in pharmaceutically relevant solvents. Saudi Pharm J 2018; 26:801-809. [PMID: 30202220 PMCID: PMC6128713 DOI: 10.1016/j.jsps.2018.04.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 04/02/2018] [Indexed: 02/05/2023] Open
Abstract
The derivatives of hydrogenated pyrido[4,3-b]indoles as potential neuroprotectors have been synthesized. The different substituents were introduced into position 8 of the carboline fragment of the molecule: methyl-, methoxy-, fluorine- and chlorine-. Biological tests have shown that all the studied compounds can modulate glutamate-dependent uptake of calcium ions in rats’ cerebral cortex synaptosomes. The shake-flask method was used to measure the solubility of the compounds in the buffer solution (pH 7.4), hexane and 1-octanol within the temperature interval of 293.15–313.15 К. All the derivatives have been found to have low solubility (not exceeding 8 ∙ 10−4 mole fractions) in the mentioned solvents. The effect of thermophysical and protolytic properties of the compounds on the solubility have been studied and the thermodynamic functions of compounds dissolution in the solvents used have been calculated.
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Affiliation(s)
- Svetlana Blokhina
- Institute of Solution Chemistry, Russian Academy of Sciences, 1 Akademicheskaya Street, 153045 Ivanovo, Russia
| | - Angelica Sharapova
- Institute of Solution Chemistry, Russian Academy of Sciences, 1 Akademicheskaya Street, 153045 Ivanovo, Russia
| | - Marina Ol'khovich
- Institute of Solution Chemistry, Russian Academy of Sciences, 1 Akademicheskaya Street, 153045 Ivanovo, Russia
| | - Anatoly Ustinov
- Institute of Physiologically Active Compounds, Russian Academy of Sciences, 142432 Chernogolovka, Russia
| | - German Perlovich
- Institute of Solution Chemistry, Russian Academy of Sciences, 1 Akademicheskaya Street, 153045 Ivanovo, Russia
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Abstract
Synaptic pruning is dominant in early ontogenesis when a large number of unnecessary synapses are eliminated, and it maintains synaptic plasticity in the mature healthy brain, e.g., in memory processes. Its malfunction is involved in degenerative diseases such as Alzheimer’s disease. C1q, a member of the immune complement system, plays a central role in the selective pruning of synapses by microglial phagocytosis. Understanding the molecular aspects of complement-mediated synapse elimination is of high importance for developing effective therapeutic interventions in the future. Our analysis on C1q-tagged synaptosomes revealed that C1q label-based synaptic pruning is linked to local apoptotic-like processes in synapses. C1q, a member of the immune complement cascade, is implicated in the selective pruning of synapses by microglial phagocytosis. C1q-mediated synapse elimination has been shown to occur during brain development, while increased activation and complement-dependent synapse loss is observed in neurodegenerative diseases. However, the molecular mechanisms underlying C1q-controlled synaptic pruning are mostly unknown. This study addresses distortions in the synaptic proteome leading to C1q-tagged synapses. Our data demonstrated the preferential localization of C1q to the presynapse. Proteomic investigation and pathway analysis of C1q-tagged synaptosomes revealed the presence of apoptotic-like processes in C1q-tagged synapses, which was confirmed experimentally with apoptosis markers. Moreover, the induction of synaptic apoptotic-like mechanisms in a model of sensory deprivation-induced synaptic depression led to elevated C1q levels. Our results unveiled that C1q label-based synaptic pruning is triggered by and directly linked to apoptotic-like processes in the synaptic compartment.
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Gylys KH, Bilousova T. Flow Cytometry Analysis and Quantitative Characterization of Tau in Synaptosomes from Alzheimer's Disease Brains. Methods Mol Biol 2018; 1523:273-284. [PMID: 27975256 DOI: 10.1007/978-1-4939-6598-4_16] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Abstract
Synaptosomes, resealed nerve terminals that form when tissue is homogenized in isotonic medium, are a model system that has been a key source of knowledge about neurotransmission. Synaptosomes contain mitochondria, cytoskeletal proteins, and release neurotransmitters; many have postsynaptic elements. Cryopreservation at the time of autopsy makes it possible to prepare synaptosomes from human samples. Flow cytometry is a powerful analytic technique that precisely measures fluorescence on a cell-by-cell basis, and also indicates particle size and complexity with a routine parameter that measures light scattering. We describe here a procedure for flow cytometry analysis of tau in synaptosomes, a procedure that enables (1) "purification" of synaptosomes from the P-2 fraction (crude synaptosomes) by gating on particle size, and (2) quantitative measure of tau immunofluorescence in individual terminals. Application of flow cytometry to study of synaptosomes has yielded important information, not possible with routine biochemistry, about synaptic pathology in Alzheimer's disease.
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Affiliation(s)
- Karen Hoppens Gylys
- UCLA School of Nursing and Mary S. Easton Center for Alzheimer's Research at UCLA, Box 956919, Factor Building, Los Angeles, CA, 90095-6919, USA.
| | - Tina Bilousova
- UCLA School of Nursing and Mary S. Easton Center for Alzheimer's Research at UCLA, Box 956919, Factor Building, Los Angeles, CA, 90095-6919, USA
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14
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15
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Abud EM, Ramirez RN, Martinez ES, Healy LM, Nguyen CHH, Newman SA, Yeromin AV, Scarfone VM, Marsh SE, Fimbres C, Caraway CA, Fote GM, Madany AM, Agrawal A, Kayed R, Gylys KH, Cahalan MD, Cummings BJ, Antel JP, Mortazavi A, Carson MJ, Poon WW, Blurton-Jones M. iPSC-Derived Human Microglia-like Cells to Study Neurological Diseases. Neuron 2017; 94:278-293.e9. [PMID: 28426964 DOI: 10.1016/j.neuron.2017.03.042] [Citation(s) in RCA: 617] [Impact Index Per Article: 88.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 02/16/2017] [Accepted: 03/28/2017] [Indexed: 12/15/2022]
Abstract
Microglia play critical roles in brain development, homeostasis, and neurological disorders. Here, we report that human microglial-like cells (iMGLs) can be differentiated from iPSCs to study their function in neurological diseases, like Alzheimer's disease (AD). We find that iMGLs develop in vitro similarly to microglia in vivo, and whole-transcriptome analysis demonstrates that they are highly similar to cultured adult and fetal human microglia. Functional assessment of iMGLs reveals that they secrete cytokines in response to inflammatory stimuli, migrate and undergo calcium transients, and robustly phagocytose CNS substrates. iMGLs were used to examine the effects of Aβ fibrils and brain-derived tau oligomers on AD-related gene expression and to interrogate mechanisms involved in synaptic pruning. Furthermore, iMGLs transplanted into transgenic mice and human brain organoids resemble microglia in vivo. Together, these findings demonstrate that iMGLs can be used to study microglial function, providing important new insight into human neurological disease.
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Affiliation(s)
- Edsel M Abud
- Department of Neurobiology & Behavior, University of California Irvine, Irvine, CA 92697, USA; Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Ricardo N Ramirez
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA 92697, USA
| | - Eric S Martinez
- Department of Neurobiology & Behavior, University of California Irvine, Irvine, CA 92697, USA; Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Luke M Healy
- Neuroimmunology Unit, Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University, Montreal, QC H3A 2B4, Canada
| | - Cecilia H H Nguyen
- Department of Neurobiology & Behavior, University of California Irvine, Irvine, CA 92697, USA; Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Sean A Newman
- Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA
| | - Andriy V Yeromin
- Department of Physiology and Biophysics, University of California Irvine, Irvine, CA 92697, USA
| | - Vanessa M Scarfone
- Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA
| | - Samuel E Marsh
- Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Cristhian Fimbres
- Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Chad A Caraway
- Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Gianna M Fote
- Department of Neurobiology & Behavior, University of California Irvine, Irvine, CA 92697, USA; Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Abdullah M Madany
- Division of Biomedical Sciences, Center for Glia-Neuronal Interactions, University of California, Riverside, Riverside, CA 92521, USA
| | - Anshu Agrawal
- Department of Medicine, School of Medicine, University of California Irvine, Irvine, CA 92697, USA
| | - Rakez Kayed
- Department of Neurology, George P. and Cynthia Woods Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Karen H Gylys
- UCLA School of Nursing, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Michael D Cahalan
- Department of Physiology and Biophysics, University of California Irvine, Irvine, CA 92697, USA
| | - Brian J Cummings
- Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA; Anatomy and Neurobiology, University of California Irvine, Irvine, CA 92697, USA
| | - Jack P Antel
- Neuroimmunology Unit, Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University, Montreal, QC H3A 2B4, Canada
| | - Ali Mortazavi
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA 92697, USA
| | - Monica J Carson
- Division of Biomedical Sciences, Center for Glia-Neuronal Interactions, University of California, Riverside, Riverside, CA 92521, USA
| | - Wayne W Poon
- Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA.
| | - Mathew Blurton-Jones
- Department of Neurobiology & Behavior, University of California Irvine, Irvine, CA 92697, USA; Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA.
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16
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Postupna N, Latimer CS, Larson EB, Sherfield E, Paladin J, Shively CA, Jorgensen MJ, Andrews RN, Kaplan JR, Crane PK, Montine KS, Craft S, Keene CD, Montine TJ. Human Striatal Dopaminergic and Regional Serotonergic Synaptic Degeneration with Lewy Body Disease and Inheritance of APOE ε4. THE AMERICAN JOURNAL OF PATHOLOGY 2017; 187:884-895. [PMID: 28212814 DOI: 10.1016/j.ajpath.2016.12.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Revised: 12/10/2016] [Accepted: 12/20/2016] [Indexed: 01/22/2023]
Abstract
Cognitive impairment in older individuals is a complex trait that in population-based studies most commonly derives from an individually varying mixture of Alzheimer disease, Lewy body disease, and vascular brain injury. We investigated the molecular composition of synaptic particles from three sources: consecutive rapid autopsy brains from the Adult Changes in Thought Study, a population-based cohort; four aged nonhuman primate brains optimally processed for molecular investigation; and targeted replacement transgenic mice homozygous for APOE ε4. Our major goal was to characterize the molecular composition of human synaptic particles in regions of striatum and prefrontal cortex. We performed flow cytometry to measure six markers of synaptic subtypes, as well as amyloid β 42 and paired helical filament tau. Our results showed selective degeneration of dopaminergic terminals throughout the striatum in individuals with Lewy body disease, and serotonergic degeneration in human ventromedial caudate nucleus from individuals with an APOE ε4 allele. Similar results were seen in mouse caudate nucleus homozygous for APOE ε4 via targeted replacement. Together, extension of these clinical, pathologic, and genetic associations from tissue to the synaptic compartment of cerebral cortex and striatum strongly supports our approach for accurately observing the molecular composition of human synapses by flow cytometry.
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Affiliation(s)
- Nadia Postupna
- Department of Pathology, University of Washington, Seattle, Washington
| | - Caitlin S Latimer
- Department of Pathology, University of Washington, Seattle, Washington
| | - Eric B Larson
- Group Health Research Institute, Seattle, Washington
| | - Emily Sherfield
- Department of Pathology, University of Washington, Seattle, Washington
| | - Julie Paladin
- Department of Pathology, University of Washington, Seattle, Washington
| | - Carol A Shively
- Department of Pathology, Section on Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Matthew J Jorgensen
- Department of Pathology, Section on Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Rachel N Andrews
- Department of Pathology, Section on Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Jay R Kaplan
- Department of Pathology, Section on Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Paul K Crane
- Department of Medicine, University of Washington, Seattle, Washington
| | | | - Suzanne Craft
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - C Dirk Keene
- Department of Pathology, University of Washington, Seattle, Washington
| | - Thomas J Montine
- Department of Pathology, University of Washington, Seattle, Washington.
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17
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Lores-Arnaiz S, Lombardi P, Karadayian AG, Orgambide F, Cicerchia D, Bustamante J. Brain cortex mitochondrial bioenergetics in synaptosomes and non-synaptic mitochondria during aging. Neurochem Res 2016; 41:353-63. [DOI: 10.1007/s11064-015-1817-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 12/23/2015] [Accepted: 12/25/2015] [Indexed: 10/22/2022]
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18
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Anastasio NC, Stutz SJ, Fink LHL, Swinford-Jackson SE, Sears RM, DiLeone RJ, Rice KC, Moeller FG, Cunningham KA. Serotonin (5-HT) 5-HT2A Receptor (5-HT2AR):5-HT2CR Imbalance in Medial Prefrontal Cortex Associates with Motor Impulsivity. ACS Chem Neurosci 2015; 6:1248-58. [PMID: 26120876 DOI: 10.1021/acschemneuro.5b00094] [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] [Indexed: 02/07/2023] Open
Abstract
A feature of multiple neuropsychiatric disorders is motor impulsivity. Recent studies have implicated serotonin (5-HT) systems in medial prefrontal cortex (mPFC) in mediating individual differences in motor impulsivity, notably the 5-HT2AR receptor (5-HT2AR) and 5-HT2CR. We investigated the hypothesis that differences in the ratio of 5-HT2AR:5-HT2CR protein expression in mPFC would predict the individual level of motor impulsivity and that the engineered loss of the 5-HT2CR would result in high motor impulsivity concomitant with elevated 5-HT2AR expression and pharmacological sensitivity to the selective 5-HT2AR antagonist M100907. High and low impulsive rats were identified in a 1-choice serial reaction time task. Native protein levels of the 5-HT2AR and the 5-HT2CR predicted the intensity of motor impulsivity and the 5-HT2AR:5-HT2CR ratio in mPFC positively correlated with levels of premature responses in individual outbred rats. The possibility that the 5-HT2AR and 5-HT2CR act in concert to control motor impulsivity is supported by the observation that high phenotypic motor impulsivity associated with a diminished mPFC synaptosomal 5-HT2AR:5-HT2CR protein:protein interaction. Knockdown of mPFC 5-HT2CR resulted in increased motor impulsivity and triggered a functional disruption of the local 5-HT2AR:5-HT2CR balance as evidenced by a compensatory upregulation of 5-HT2AR protein expression and a leftward shift in the potency of M100907 to suppress impulsive behavior. We infer that there is an interactive relationship between the mPFC 5-HT2AR and 5-HT2CR, and that a 5-HT2AR:5-HT2CR imbalance may be a functionally relevant mechanism underlying motor impulsivity.
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Affiliation(s)
| | | | | | | | - Robert M. Sears
- Department
of Psychiatry, Yale University, New Haven, Connecticut 06520, United States
| | - Ralph J. DiLeone
- Department
of Psychiatry, Yale University, New Haven, Connecticut 06520, United States
| | - Kenner C. Rice
- Chemical
Biology Research Branch, National Institute on Drug Abuse, DHHS/NIH/NIDA, Bethesda, Maryland 20892, United States
| | - F. Gerard Moeller
- Department
of Psychiatry, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298, United States
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19
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Individual Differences in Impulsive Action Reflect Variation in the Cortical Serotonin 5-HT2A Receptor System. Neuropsychopharmacology 2015; 40:1957-68. [PMID: 25666313 PMCID: PMC4839520 DOI: 10.1038/npp.2015.46] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 01/05/2015] [Accepted: 01/26/2015] [Indexed: 11/08/2022]
Abstract
Impulsivity is an important feature of multiple neuropsychiatric disorders, and individual variation in the degree of inherent impulsivity could play a role in the generation or exacerbation of problematic behaviors. Serotonin (5-HT) actions at the 5-HT2AR receptor (5-HT2AR) promote and 5-HT2AR antagonists suppress impulsive action (the inability to withhold premature responses; motor impulsivity) upon systemic administration or microinfusion directly into the medial prefrontal cortex (mPFC), a node in the corticostriatal circuit that is thought to play a role in the regulation of impulsive action. We hypothesized that the functional capacity of the 5-HT2AR, which is governed by its expression, localization, and protein/protein interactions (eg, postsynaptic density 95 (PSD95)), may drive the predisposition to inherent impulsive action. Stable high-impulsive (HI) and low-impulsive (LI) phenotypes were identified from an outbred rodent population with the 1-choice serial reaction time (1-CSRT) task. HI rats exhibited a greater head-twitch response following administration of the preferential 5-HT2AR agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) and were more sensitive to the effects of the selective 5-HT2AR antagonist M100907 to suppress impulsive action relative to LI rats. A positive correlation was observed between levels of premature responses and 5-HT2AR binding density in frontal cortex ([(3)H]-ketanserin radioligand binding). Elevated mPFC 5-HT2AR protein expression concomitant with augmented association of the 5-HT2AR with PSD95 differentiated HI from LI rats. The observed differential sensitivity of HI and LI rats to 5-HT2AR ligands and associated distinct 5-HT2AR protein profiles provide evidence that spontaneously occurring individual differences in impulsive action reflect variation in the cortical 5-HT2AR system.
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20
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Direct inhibition of retinoic acid catabolism by fluoxetine. J Neural Transm (Vienna) 2015; 122:1329-38. [PMID: 25981674 DOI: 10.1007/s00702-015-1407-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 05/04/2015] [Indexed: 12/31/2022]
Abstract
Recent evidence from animal and human studies suggests neuroprotective effects of the SSRI fluoxetine, e.g., in the aftermath of stroke. The underlying molecular mechanisms remain to be fully defined. Because of its effects on the cytochrome P450 system (CYP450), we hypothesized that neuroprotection by fluoxetine is related to altered metabolism of retinoic acid (RA), whose CYP450-mediated degradation in brain tissue constitutes an important step in the regulation of its site-specific auto- and paracrine actions. Using traditional pharmacological in vitro assays, the effects of fluoxetine on RA degradation were probed in crude synaptosomes from rat brain and human-derived SH-SY5Y cells, and in cultures of neuron-like SH-SY5Y cells. Furthermore, retinoid-dependent effects of fluoxetine on neuronal survival following glutamate exposure were investigated in rat primary neurons cells using specific retinoid receptor antagonists. Experiments revealed dose-dependent inhibition of synaptosomal RA degradation by fluoxetine along with dose-dependent increases in RA levels in cell cultures. Furthermore, fluoxetine's neuroprotective effects against glutamate excitotoxicity in rat primary neurons were demonstrated to partially depend on RA signaling. Taken together, these findings demonstrate for the first time that the potent, pleiotropic antidepressant fluoxetine directly interacts with RA homeostasis in brain tissue, thereby exerting its neuroprotective effects.
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21
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Sokolow S, Henkins KM, Bilousova T, Gonzalez B, Vinters HV, Miller CA, Cornwell L, Poon WW, Gylys KH. Pre-synaptic C-terminal truncated tau is released from cortical synapses in Alzheimer's disease. J Neurochem 2015; 133:368-79. [PMID: 25393609 DOI: 10.1111/jnc.12991] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 10/02/2014] [Accepted: 11/06/2014] [Indexed: 12/31/2022]
Abstract
The microtubule-associated protein tau has primarily been associated with axonal location and function; however, recent work shows tau release from neurons and suggests an important role for tau in synaptic plasticity. In our study, we measured synaptic levels of total tau using synaptosomes prepared from cryopreserved human postmortem Alzheimer's disease (AD) and control samples. Flow cytometry data show that a majority of synaptic terminals are highly immunolabeled with the total tau antibody (HT7) in both AD and control samples. Immunoblots of synaptosomal fractions reveal increases in a 20 kDa tau fragment and in tau dimers in AD synapses, and terminal-specific antibodies show that in many synaptosome samples tau lacks a C-terminus. Flow cytometry experiments to quantify the extent of C-terminal truncation reveal that only 15-25% of synaptosomes are positive for intact C-terminal tau. Potassium-induced depolarization demonstrates release of tau and tau fragments from pre-synaptic terminals, with increased release from AD compared to control samples. This study indicates that tau is normally highly localized to synaptic terminals in cortex where it is well-positioned to affect synaptic plasticity. Tau cleavage may facilitate tau aggregation as well as tau secretion and propagation of tau pathology from the pre-synaptic compartment in AD. Results demonstrate the abundance of tau, mainly C-terminal truncated tau, in synaptic terminals in aged control and in Alzheimer's disease (AD) samples. Tau fragments and dimers/oligomers are prominent in AD synapses. Following depolarization, tau release is potentiated in AD nerve terminals compared to aged controls. We hypothesize (i) endosomal release of the different tau peptides from AD synapses, and (ii) together with phosphorylation, fragmentation of synaptic tau exacerbates tau aggregation, synaptic dysfunction, and the spread of tau pathology in AD. Aβ = amyloid-beta.
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Affiliation(s)
- Sophie Sokolow
- UCLA School of Nursing, Los Angeles, California, USA; UCLA Brain Research Institute, Los Angeles, California, USA; UCLA Center for the Advancement of Gerontological Nursing Sciences, Los Angeles, California, USA; UCLA Clinical and Translational Science Institute, Los Angeles, California, USA
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22
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Ferreira SG, Gonçalves FQ, Marques JM, Tomé ÂR, Rodrigues RJ, Nunes-Correia I, Ledent C, Harkany T, Venance L, Cunha RA, Köfalvi A. Presynaptic adenosine A2A receptors dampen cannabinoid CB1 receptor-mediated inhibition of corticostriatal glutamatergic transmission. Br J Pharmacol 2015; 172:1074-86. [PMID: 25296982 DOI: 10.1111/bph.12970] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2014] [Revised: 09/30/2014] [Accepted: 10/03/2014] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND AND PURPOSE Both cannabinoid CB1 and adenosine A2A receptors (CB1 receptors and A2A receptors) control synaptic transmission at corticostriatal synapses, with great therapeutic importance for neurological and psychiatric disorders. A postsynaptic CB1 -A2A receptor interaction has already been elucidated, but the presynaptic A2A receptor-mediated control of presynaptic neuromodulation by CB1 receptors remains to be defined. Because the corticostriatal terminals provide the major input to the basal ganglia, understanding the interactive nature of converging neuromodulation on them will provide us with novel powerful tools to understand the physiology of corticostriatal synaptic transmission and interpret changes associated with pathological conditions. EXPERIMENTAL APPROACH Pharmacological manipulation of CB1 and A2A receptors was carried out in brain nerve terminals isolated from rats and mice, using flow synaptometry, immunoprecipitation, radioligand binding, ATP and glutamate release measurement. Whole-cell patch-clamp recordings were made in horizontal corticostriatal slices. KEY RESULTS Flow synaptometry showed that A2A receptors were extensively co-localized with CB1 receptor-immunopositive corticostriatal terminals and A2A receptors co-immunoprecipitated CB1 receptors in these purified terminals. A2A receptor activation decreased CB1 receptor radioligand binding and decreased the CB1 receptor-mediated inhibition of high-K(+) -evoked glutamate release in corticostriatal terminals. Accordingly, A2A receptor activation prevented CB1 receptor-mediated paired-pulse facilitation and attenuated the CB1 receptor-mediated inhibition of synaptic transmission in glutamatergic synapses of corticostriatal slices. CONCLUSIONS AND IMPLICATIONS Activation of presynaptic A2A receptors dampened CB1 receptor-mediated inhibition of corticostriatal terminals. This constitutes a thus far unrecognized mechanism to modulate the potent CB1 receptor-mediated presynaptic inhibition, allowing frequency-dependent enhancement of synaptic efficacy at corticostriatal synapses.
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Affiliation(s)
- S G Ferreira
- Neuromodulation Group, CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal; Laboratory of Neuromodulation and Metabolism, CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal; Doctoral Programme in Experimental Biology and Biomedicine, CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal; Faculty of Medicine, University of Coimbra, 3004-504, Coimbra, Portugal
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Flow cytometry analysis of synaptosomes from post-mortem human brain reveals changes specific to Lewy body and Alzheimer's disease. J Transl Med 2014; 94:1161-72. [PMID: 25068655 PMCID: PMC4184945 DOI: 10.1038/labinvest.2014.103] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 06/10/2014] [Accepted: 06/13/2014] [Indexed: 01/25/2023] Open
Abstract
Synaptic dysfunction is thought to have an important role in the pathophysiology of neurodegenerative diseases, such as Alzheimer's disease (AD) and Lewy body disease (LBD). To improve our understanding of synaptic alterations in health and disease, we investigated synaptosomes prepared from post-mortem human cerebral cortex, putamen (PT), and two regions of the caudate nucleus, dorso-lateral (DL) and ventro-medial (VM), regions commonly affected in AD and LBD. We observed that the fraction of synaptosomal particles with reactivity for dopamine transporter (DAT) was significantly reduced in the PT and VM caudate of patients with neuropathological diagnosis of LBD. As expected, these differences also were reflected in direct measurements of dopamine (DA) and its metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), in caudate and PT of LBD patients. The fraction of synaptosomal particles positive for amyloid β (Aβ) was significantly increased in frontal cortical samples of patients with the neuropathological diagnosis of severe AD, and was positively correlated with disease progression. We also prepared synaptosomes from the striatum of mice with severe loss of DA neurons (Slc6a3-DTR mice) and wild-type littermate controls. We observed markedly reduced levels of DAT-positive synaptosomes in Slc6a3-DTR mice following exposure to diphtheria toxin (DT). Striatal levels of DA and DOPAC in Slc6a3-DTR mice also were reduced significantly following DT exposure. We conclude that flow cytometric analysis of synaptosomes prepared from human or mouse brain provides an opportunity to study expression of pathology-associated proteins and also the specific loss of dopaminergic nerve terminals. Hence, we believe it is a valid method to detect pathological changes at the level of the synapse in LBD as well as AD.
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Whitelaw BS, Robinson MB. Inhibitors of glutamate dehydrogenase block sodium-dependent glutamate uptake in rat brain membranes. Front Endocrinol (Lausanne) 2013; 4:123. [PMID: 24062726 PMCID: PMC3775299 DOI: 10.3389/fendo.2013.00123] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 08/30/2013] [Indexed: 02/02/2023] Open
Abstract
We recently found evidence for anatomic and physical linkages between the astroglial Na(+)-dependent glutamate transporters (GLT-1/EAAT2 and GLAST/EAAT1) and mitochondria. In these same studies, we found that the glutamate dehydrogenase (GDH) inhibitor, epigallocatechin-monogallate (EGCG), inhibits both glutamate oxidation and Na(+)-dependent glutamate uptake in astrocytes. In the present study, we extend this finding by exploring the effects of EGCG on Na(+)-dependent l-[(3)H]-glutamate (Glu) uptake in crude membranes (P2) prepared from rat brain cortex. In this preparation, uptake is almost exclusively mediated by GLT-1. EGCG inhibited l-[(3)H]-Glu uptake in cortical membranes with an IC50 value of 230 μM. We also studied the effects of two additional inhibitors of GDH, hexachlorophene (HCP) and bithionol (BTH). Both of these compounds also caused concentration-dependent inhibition of glutamate uptake in cortical membranes. Pre-incubating with HCP for up to 15 min had no greater effect than that observed with no pre-incubation, showing that the effects occur rapidly. HCP decreased the V max for glutamate uptake without changing the K m, consistent with a non-competitive mechanism of action. EGCG, HCP, and BTH also inhibited Na(+)-dependent transport of d-[(3)H]-aspartate (Asp), a non-metabolizable transporter substrate, and [(3)H]-γ-aminobutyric acid (GABA). In contrast to the forebrain, glutamate uptake in crude cerebellar membranes (P2) is likely mediated by GLAST (EAAT1). Therefore, the effects of these compounds were examined in cerebellar membranes. In this region, none of these compounds had any effect on uptake of either l-[(3)H]-Glu or d-[(3)H]-Asp, but they all inhibited [(3)H]-GABA uptake. Together these studies suggest that GDH is preferentially required for glutamate uptake in forebrain as compared to cerebellum, and GDH may be required for GABA uptake as well. They also provide further evidence for a functional linkage between glutamate transport and mitochondria.
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Affiliation(s)
- Brendan S. Whitelaw
- Children’s Hospital of Philadelphia Research Institute, Philadelphia, PA, USA
| | - Michael B. Robinson
- Children’s Hospital of Philadelphia Research Institute, Philadelphia, PA, USA
- Departments of Pediatrics and Pharmacology, University of Pennsylvania, Philadelphia, PA, USA
- *Correspondence: Michael B. Robinson, Department of Pediatrics, University of Pennsylvania, 502N Abramson Pediatric Research Building, 3615 Civic Center Boulevard, Philadelphia, PA 19104-4318, USA e-mail:
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VanGuilder Starkey HD, Van Kirk CA, Bixler GV, Imperio CG, Kale VP, Serfass JM, Farley JA, Yan H, Warrington JP, Han S, Mitschelen M, Sonntag WE, Freeman WM. Neuroglial expression of the MHCI pathway and PirB receptor is upregulated in the hippocampus with advanced aging. J Mol Neurosci 2012; 48:111-26. [PMID: 22562814 DOI: 10.1007/s12031-012-9783-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Accepted: 04/16/2012] [Indexed: 12/31/2022]
Abstract
The hippocampus undergoes changes with aging that impact neuronal function, such as synapse loss and altered neurotransmitter release. Nearly half of the aged population also develops deficits in spatial learning and memory. To identify age-related hippocampal changes that may contribute to cognitive decline, transcriptomic analysis of synaptosome preparations from adult (12 months) and aged (28 months) Fischer 344-Brown Norway rats assessed for spatial learning and memory was performed. Bioinformatic analysis identified the MHCI pathway as significantly upregulated with aging. Age-related increases in mRNAs encoding the MHCI genes RT1-A1, RT1-A2, and RT1-A3 were confirmed by qPCR in synaptosomes and in CA1 and CA3 dissections. Elevated levels of the MHCI cofactor (B2m), antigen-loading components (Tap1, Tap2, Tapbp), and two known MHCI receptors (PirB, Klra2) were also confirmed. Protein expression of MHCI was elevated with aging in synaptosomes, CA1, and DG, while PirB protein expression was induced in both CA1 and DG. MHCI expression was localized to microglia and neuronal excitatory postsynaptic densities, and PirB was localized to neuronal somata, axons, and dendrites. Induction of the MHCI antigen processing and presentation pathway in hippocampal neurons and glia may contribute to age-related hippocampal dysfunction by increasing neuroimmune signaling or altering synaptic homeostasis.
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Schwendt M, Reichel CM, See RE. Extinction-dependent alterations in corticostriatal mGluR2/3 and mGluR7 receptors following chronic methamphetamine self-administration in rats. PLoS One 2012; 7:e34299. [PMID: 22479593 PMCID: PMC3315516 DOI: 10.1371/journal.pone.0034299] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Accepted: 02/25/2012] [Indexed: 01/12/2023] Open
Abstract
Methamphetamine (meth) is a highly addictive and widely abused psychostimulant. Repeated use of meth can quickly lead to dependence, and may be accompanied by a variety of persistent psychiatric symptoms and cognitive impairments. The neuroadaptations underlying motivational and cognitive deficits produced by chronic meth intake remain poorly understood. Altered glutamate neurotransmission within the prefrontal cortex (PFC) and striatum has been linked to both persistent drug-seeking and cognitive dysfunction. Therefore, the current study investigated changes in presynaptic mGluR receptors within corticostriatal circuitry after extended meth self-administration. Rats self-administered meth (or received yoked-saline) in 1 hr/day sessions for 7 days (short-access) followed by 14 days of 6 hrs/day (long-access). Rats displayed a progressive escalation of daily meth intake up to 6 mg/kg per day. After cessation of meth self-administration, rats underwent daily extinction or abstinence without extinction training for 14 days before being euthanized. Synaptosomes from the medial PFC, nucleus accumbens (NAc), and the dorsal striatum (dSTR) were isolated and labeled with membrane-impermeable biotin in order to measure surface mGluR2/3 and mGluR7 receptors. Extended access to meth self-administration followed by abstinence decreased surface and total levels of mGluR2/3 receptors in the NAc and dSTR, while in the PFC, only a loss of surface mGluR2/3 and mGluR7 receptors was detected. Daily extinction trials reversed the downregulation of mGluR2/3 receptors in the NAc and dSTR and mGluR7 in the PFC, but downregulation of surface mGluR2/3 receptors in the PFC was present regardless of post-meth experience. Thus, extinction learning can selectively restore some populations of downregulated mGluRs after prolonged exposure to meth. The present findings could have implications for our understanding of the persistence (or recovery) of meth-induced motivational and cognitive deficits.
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Affiliation(s)
- Marek Schwendt
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina, United States of America.
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Sokolow S, Henkins KM, Williams IA, Vinters HV, Schmid I, Cole GM, Gylys KH. Isolation of synaptic terminals from Alzheimer's disease cortex. Cytometry A 2011; 81:248-54. [PMID: 22213704 DOI: 10.1002/cyto.a.22009] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 11/17/2011] [Accepted: 12/06/2011] [Indexed: 11/10/2022]
Abstract
Amyloid beta (Aβ) oligomers and phosphorylated tau (p-tau) aggregates are increasingly identified as potential toxic intermediates in Alzheimer's disease (AD). In cortical AD synapses, p-tau co-localizes with Aβ, but the Aβ and p-tau peptide species responsible for synaptic dysfunction and demise remains unclear. The present experiments were designed to use high-speed cell sorting techniques to purify synaptosome population based on size, and then extend the method to physically isolate Aβ-positive synaptosomes with the goal of understanding the nature of Aβ and tau pathology in AD synapses. To examine the purity of size-gated synaptosomes, samples were first gated on size; particles with sizes between 0.5 and 1.5 microns were collected. Electron microscopy documented a homogenous population of spherical particles with internal vesicles and synaptic densities. Next, size-gated synaptosomes positive for Aβ were collected by fluorescence activated sorting and then analyzed by immunoblotting techniques. Sorted Aβ-positive synaptosomes were enriched for amyloid precursor protein (APP) and for Aβ oligomers and aggregates; immunolabeling for p-tau showed a striking accumulation of p-tau aggregates compared to the original homogenate and purified synaptosomes. These results confirm co-localization of Aβ and p-tau within individual synaptic terminals and provide proof of concept for the utility of flow sorting synaptosomes.
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Affiliation(s)
- Sophie Sokolow
- UCLA School of Nursing, Los Angeles, California 90095, USA.
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Biezonski DK, Meyer JS. The Nature of 3, 4-Methylenedioxymethamphetamine (MDMA)-Induced Serotonergic Dysfunction: Evidence for and Against the Neurodegeneration Hypothesis. Curr Neuropharmacol 2011; 9:84-90. [PMID: 21886568 PMCID: PMC3137208 DOI: 10.2174/157015911795017146] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Revised: 04/17/2010] [Accepted: 05/26/2010] [Indexed: 01/18/2023] Open
Abstract
High doses of the recreational drug 3,4-methylenedioxymethamphetamine (MDMA, "Ecstasy") have been well-documented to reduce the expression of serotonergic markers in several forebrain regions of rats and nonhuman primates. Neuroimaging studies further suggest that at least one of these markers, the plasma membrane serotonin transporter (SERT), may also be reduced in heavy Ecstasy users. Such effects, particularly when observed in experimental animal models, have generally been interpreted as reflecting a loss of serotonergic fibers and terminals following MDMA exposure. This view has been challenged, however, based on the finding that MDMA usually does not elicit glial cell reactions known to occur in response to central nervous system (CNS) damage. The aim of this review is to address both sides of the MDMA-neurotoxicity controversy, including recent findings from our laboratory regarding the potential of MDMA to induce serotonergic damage in a rat binge model. Our data add to the growing literature implicating neuroregulatory mechanisms underlying MDMA-induced serotonergic dysfunction and questioning the need to invoke a degenerative response to explain such dysfunction.
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Affiliation(s)
- Dominik K Biezonski
- Neuroscience and Behavior Program, University of Massachusetts, Amherst MA 01003, USA
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Shavit E, Michaelson DM, Chapman J. Anatomical localization of protease-activated receptor-1 and protease-mediated neuroglial crosstalk on peri-synaptic astrocytic endfeet. J Neurochem 2011; 119:460-73. [PMID: 21854391 DOI: 10.1111/j.1471-4159.2011.07436.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We studied the localization, activation and function of protease-activated receptor 1 (PAR-1) at the CNS synapse utilizing rat brain synaptosomes and slices. Confocal immunofluoresence and transmission electron microscopy in brain slices with pre-embedding diaminobenzidine (DAB) immunostaining found PAR-1 predominantly localized to the peri-synaptic astrocytic endfeet. Structural confocal immunofluorescence microscopy studies of isolated synaptosomes revealed spherical structures stained with anti-PAR-1 antibody which co-stained mainly for glial-filament acidic protein compared with the neuronal markers synaptophysin and PSD-95. Immunoblot studies of synaptosomes demonstrated an appropriate major band corresponding to PAR-1 and activation of the receptor by a specific agonist peptide (SFLLRN) significantly modulated phosphorylated extracellular signal-regulated kinase. A significant membrane potential depolarization was produced by thrombin (1 U/mL) and the PAR-1 agonist (100 μM) and depolarization by high K(+) elevated extracellular thrombin-like activity in the synaptosomes preparation. The results indicate PAR-1 localized to the peri-synaptic astrocytic endfeet is most likely activated by synaptic proteases and induces cellular signaling and modulation of synaptic electrophysiology. A protease mediated neuron-glia pathway may be important in both physiological and pathological regulation of the synapse.
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Affiliation(s)
- Efrat Shavit
- Department of Physiology and Pharmacology, Tel Aviv University, Tel Aviv, Israel
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Sokolow S, Luu SH, Nandy K, Miller CA, Vinters HV, Poon WW, Gylys KH. Preferential accumulation of amyloid-beta in presynaptic glutamatergic terminals (VGluT1 and VGluT2) in Alzheimer's disease cortex. Neurobiol Dis 2011; 45:381-7. [PMID: 21914482 DOI: 10.1016/j.nbd.2011.08.027] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 08/20/2011] [Accepted: 08/27/2011] [Indexed: 12/21/2022] Open
Abstract
Amyloid-beta (Aβ) is thought to play a central role in synaptic dysfunction (e.g. neurotransmitter release) and synapse loss. Glutamatergic dysfunction is involved in the pathology of Alzheimer's disease (AD) and perhaps plays a central role in age-related cognitive impairment. Yet, it is largely unknown whether Aβ accumulates in excitatory boutons. To assess the possibility that glutamatergic terminals are lost in AD patients, control and AD synaptosomes were immunolabeled for the most abundant vesicular glutamate transporters (VGluT1 and VGluT2) and quantified by flow cytometry and immunoblot methods. In post-mortem parietal cortex from aged control subjects, glutamatergic boutons are fairly abundant as approximately 40% were immunoreactive for VGluT1 (37%) and VGluT2 (39%). However, the levels of these specific markers of glutamatergic synapses were not significantly different among control and AD cases. To test the hypothesis that Aβ is associated with excitatory terminals, AD synaptosomes were double-labeled for Aβ and for VGluT1 and VGluT2, and analyzed by flow cytometry and confocal microscopy. Our study demonstrated that Aβ immunoreactivity (IR) was present in glutamatergic terminals of AD patients. Quantification of Aβ and VGluT1 in a large population of glutamatergic nerve terminals was performed by flow cytometry, showing that 42% of VGluT1 synaptosomes were immunoreactive for Aβ compared to 9% of VGluT1 synaptosomes lacking Aβ-IR. Percentage of VGluT2 synaptosomes immunoreactive for Aβ (21%) was significantly higher than VGluT2 synaptosomes lacking Aβ-IR (9%). Moreover, Aβ preferentially affects VGluT1 (42% positive) compared to VGluT2 terminals (21%). These data represent the first evidence of high levels of Aβ in excitatory boutons in AD cortex and support the hypothesis that Aβ may play a role in modulating glutamate transmission in AD terminals.
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Sokolow S, Luu SH, Headley AJ, Hanson AY, Kim T, Miller CA, Vinters HV, Gylys KH. High levels of synaptosomal Na(+)-Ca(2+) exchangers (NCX1, NCX2, NCX3) co-localized with amyloid-beta in human cerebral cortex affected by Alzheimer's disease. Cell Calcium 2011; 49:208-16. [PMID: 21382638 DOI: 10.1016/j.ceca.2010.12.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2010] [Revised: 11/21/2010] [Accepted: 12/30/2010] [Indexed: 12/17/2022]
Abstract
Synaptosomal expression of NCX1, NCX2, and NCX3, the three variants of the Na(+)-Ca(2+) exchanger (NCX), was investigated in Alzheimer's disease parietal cortex. Flow cytometry and immunoblotting techniques were used to analyze synaptosomes prepared from cryopreserved brain of cognitively normal aged controls and late stage Alzheimer's disease patients. Major findings that emerged from this study are: (1) NCX1 was the most abundant NCX isoform in nerve terminals of cognitively normal patients; (2) NCX2 and NCX3 protein levels were modulated in parietal cortex of late stage Alzheimer's disease: NCX2 positive terminals were increased in the Alzheimer's disease cohort while counts of NCX3 positive terminals were reduced; (3) NCX1, NCX2 and NCX3 isoforms co-localized with amyloid-beta in synaptic terminals and all three variants are up-regulated in nerve terminals containing amyloid-beta. Taken together, these data indicate that NCX isoforms are selectively regulated in pathological terminals, suggesting different roles of each NCX isoform in Alzheimer's disease terminals.
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Liu C, Wu ZZ, Shu CL, Li DF, Zeng YJ, Cui Q, Jiang WH. Experimental Investigation of HGF Inhibiting Glial Scar In Vitro. Cell Mol Neurobiol 2010; 31:259-68. [DOI: 10.1007/s10571-010-9616-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 10/07/2010] [Indexed: 10/18/2022]
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Borisova T, Krisanova N, Sivko R, Borysov A. Cholesterol depletion attenuates tonic release but increases the ambient level of glutamate in rat brain synaptosomes. Neurochem Int 2010; 56:466-78. [DOI: 10.1016/j.neuint.2009.12.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 12/07/2009] [Accepted: 12/11/2009] [Indexed: 10/20/2022]
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Castaldo P, Magi S, Cataldi M, Arcangeli S, Lariccia V, Nasti AA, Ferraro L, Tomasini MC, Antonelli T, Cassano T, Cuomo V, Amoroso S. Altered regulation of glutamate release and decreased functional activity and expression of GLT1 and GLAST glutamate transporters in the hippocampus of adolescent rats perinatally exposed to Delta(9)-THC. Pharmacol Res 2009; 61:334-41. [PMID: 19941959 DOI: 10.1016/j.phrs.2009.11.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Revised: 11/17/2009] [Accepted: 11/17/2009] [Indexed: 11/30/2022]
Abstract
The long-term effects of perinatal Delta(9)-tetrahydrocannabinol (Delta(9)-THC) exposure - from gestational day (GD) 15 to postnatal day (PND) 9 - on hippocampal glutamatergic neurotransmission were studied in slices from the 40-day-old offspring of Delta(9)-THC exposed (Delta(9)-THC-rats) and vehicle-exposed (control) dams. Basal and in K+-evoked endogenous hippocampal glutamate outflow were both significantly decreased in Delta(9)-THC-rats. The effect of short Delta(9)-THC exposure (0.1microM) on K(+)-evoked glutamate release disclosed a loss of the stimulatory effect of Delta(9)-THC on hippocampal glutamate release in Delta(9)-THC-rats, but not in controls. In addition, l-[(3)H]-glutamate uptake was significantly lower in hippocampal slices from Delta(9)-THC-rats, where a significant decrease in glutamate transporter 1 (GLT1) and glutamate/aspartate transporter (GLAST) protein was also detected. Collectively, these data demonstrate that perinatal exposure to cannabinoids induces long-term impairment in hippocampal glutamatergic neurotransmission that persist into adolescence.
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Affiliation(s)
- Pasqualina Castaldo
- Department of Neuroscience, University Politecnica delle Marche, Ancona, Italy
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Crivello NA, Rosenberg IH, Shukitt-Hale B, Bielinski D, Dallal GE, Joseph JA. Aging modifies brain region-specific vulnerability to experimental oxidative stress induced by low dose hydrogen peroxide. AGE (DORDRECHT, NETHERLANDS) 2007; 29:191-203. [PMID: 19424838 PMCID: PMC2267029 DOI: 10.1007/s11357-007-9039-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2007] [Accepted: 08/24/2007] [Indexed: 05/27/2023]
Abstract
Our previous studies demonstrated a significant decline in brain function and behavior in Fischer 344 (F344) rats with age. The present study was designed to test the hypothesis that dysregulation in calcium homeostasis (as assessed through (45)Ca flux) may contribute to the increase in age-related vulnerability to oxidative stress in brain regions, and result in a deficit in behavior-mediated signaling. Crude membrane (P-2) and more purified synaptosomal fractions were isolated from the striatum, hippocampus, and frontal cortex of young (6 months) and old (22 months) F344 rats and were assessed for calcium flux and extracellular-regulated kinase activity 1 (ERK) under control and oxidative stress conditions induced by low dose hydrogen peroxide (final concentration 5 microM). The level of oxidative stress responses was monitored by measuring reactive oxygen species (ROS) and glutathione (GSH). The results showed a significant difference in oxidative stress responses between young and old rats in evaluated brain regions. Old rats showed higher sensitivity to oxidative stress than young rats. The present findings show the differential effects of oxidative stress on calcium flux in brain regions with age that are dependent upon the brain areas examined and the fraction assessed. The accumulation of ROS and the decrease in GSH in the frontal cortex were sufficient to decrease ERK activity in old rats. This is the first study, to our knowledge, that demonstrates age-related differential sensitivity to oxidative stress expressed as a function of behavior-mediated signaling and stress levels among different fractions isolated from brain regions controlling behavior.
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Affiliation(s)
- Natalia A Crivello
- Nutrition and Neurocognition Laboratory, Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, 711 Washington Street, Boston, MA 02111, USA.
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Bayir H, Tyurin VA, Tyurina YY, Viner R, Ritov V, Amoscato AA, Zhao Q, Zhang XJ, Janesko-Feldman KL, Alexander H, Basova LV, Clark RSB, Kochanek PM, Kagan VE. Selective early cardiolipin peroxidation after traumatic brain injury: an oxidative lipidomics analysis. Ann Neurol 2007; 62:154-69. [PMID: 17685468 DOI: 10.1002/ana.21168] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Enhanced lipid peroxidation is well established in traumatic brain injury. However, its molecular targets, identity of peroxidized phospholipid species, and their signaling role have not been deciphered. METHODS Using controlled cortical impact as a model of traumatic brain injury, we employed a newly developed oxidative lipidomics approach to qualitatively and quantitatively characterize the lipid peroxidation response. RESULTS Electrospray ionization and matrix-assisted laser desorption/ionization mass spectrometry analysis of rat cortical mitochondrial/synaptosomal fractions demonstrated the presence of highly oxidizable molecular species containing C(22:6) fatty acid residues in all major classes of phospholipids. However, the pattern of phospholipid oxidation at 3 hours after injury displayed a nonrandom character independent of abundance of oxidizable species and included only one mitochondria-specific phospholipid, cardiolipin (CL). This selective CL peroxidation was followed at 24 hours by peroxidation of other phospholipids, most prominently phosphatidylserine, but also phosphatidylcholine and phosphatidylethanolamine. CL oxidation preceded appearance of biomarkers of apoptosis (caspase-3 activation, terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling-positivity) and oxidative stress (loss of glutathione and ascorbate). INTERPRETATION The temporal sequence combined with the recently demonstrated role of CL hydroperoxides (CL-OOH) in in vitro models of apoptosis suggest that CL-OOH may be both a key in vivo trigger of apoptotic cell death and a therapeutic target in experimental traumatic brain injury.
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Affiliation(s)
- Hülya Bayir
- Center for Free Radical and Antioxidant Health, University of Pittsburgh, Pittsburgh, PA, USA.
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Castaldo P, Magi S, Gaetani S, Cassano T, Ferraro L, Antonelli T, Amoroso S, Cuomo V. Prenatal exposure to the cannabinoid receptor agonist WIN 55,212-2 increases glutamate uptake through overexpression of GLT1 and EAAC1 glutamate transporter subtypes in rat frontal cerebral cortex. Neuropharmacology 2007; 53:369-78. [PMID: 17631920 DOI: 10.1016/j.neuropharm.2007.05.019] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2006] [Revised: 05/10/2007] [Accepted: 05/24/2007] [Indexed: 11/30/2022]
Abstract
Prenatal exposure to the CB1 receptor agonist (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)-pyrrolo[1,2,3-de]-1,4-benzoxazinyl]-(1-naphthalenyl)methanone) mesylate (WIN) at a daily dose of 0.5 mg/kg, and Delta9-tetrahydrocannabinol (Delta9-THC) at a daily dose of 5 mg/kg, reduced dialysate glutamate levels in frontal cerebral cortex of adolescent offspring (40-day-old) with respect to those born from vehicle-treated mothers. WIN treatment induced a statistically significant enhancement of Vmaxl-[3H]glutamate uptake, whereas it did not modify glutamate Km, in frontal cerebral cortex synaptosomes of adolescent rats. Western blotting analysis, performed either in membrane proteins derived from homogenates and in proteins extracted from synaptosomes of frontal cerebral cortex, revealed that prenatal WIN exposure enhanced the expression of glutamate transporter 1 (GLT1) and excitatory amino acid carrier 1 (EAAC1). Moreover, immunocytochemical analyses of frontal cortex area revealed a more intense GLT1 and EAAC1 immunoreactivity (ir) distribution in the WIN-treated group. Collectively these results show that prenatal exposure to the cannabinoid CB1 receptor agonist WIN increases expression and functional activity of GLT1 and EAAC1 glutamate transporters (GluTs) associated to a decrease of cortical glutamate outflow, in adolescent rats. These findings may contribute to explain the mechanism underlying the cognitive impairment observed in the offspring of mothers who used marijuana during pregnancy.
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Affiliation(s)
- Pasqualina Castaldo
- Section of Pharmacology, Department of Neuroscience, School of Medicine, Università Politecnica delle Marche, Via Tronto 10/A, 60020 Ancona, Italy
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Gylys KH, Fein JA, Yang F, Miller CA, Cole GM. Increased cholesterol in Aβ-positive nerve terminals from Alzheimer's disease cortex. Neurobiol Aging 2007; 28:8-17. [PMID: 16332401 DOI: 10.1016/j.neurobiolaging.2005.10.018] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2005] [Revised: 10/14/2005] [Accepted: 10/31/2005] [Indexed: 01/01/2023]
Abstract
Synapse loss in Alzheimer's disease (AD) is poorly understood but evidence suggests it is a key pathological event. In order to precisely detect stable synaptic changes, we have developed methods for flow cytometry analysis of synaptosomes prepared from cryopreserved AD samples, and have previously shown that amyloid-beta (Abeta) accumulates in surviving presynaptic terminals in AD cortex. In the present experiments we have examined amyloid-containing terminals in more detail, first dual labeling synaptosomes from AD cortex for Abeta and a series of markers, and then using quadrant analysis to compare amyloid-positive and amyloid-negative terminals. Amyloid-positive synaptosomes were larger in size than amyloid-negatives (p<0.007), and significant increases were observed in mean fluorescence for the lipid raft markers cholesterol (27%; p<0.0005) and GM1 ganglioside (24%; p<0.005). SNAP-25 immunofluorescence was increased by 31% (p<0.0001) in amyloid-bearing terminals, consistent with a sprouting response to amyloid accumulation. These results suggest that Abeta accumulation in synaptic terminals may underly dysfunction prior to or independent of extracellular amyloid deposition.
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Gylys KH, Fein JA, Yang F, Wiley DJ, Miller CA, Cole GM. Synaptic changes in Alzheimer's disease: increased amyloid-beta and gliosis in surviving terminals is accompanied by decreased PSD-95 fluorescence. THE AMERICAN JOURNAL OF PATHOLOGY 2004; 165:1809-17. [PMID: 15509549 PMCID: PMC1618663 DOI: 10.1016/s0002-9440(10)63436-0] [Citation(s) in RCA: 183] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In an effort to examine changes that precede synapse loss, we have measured amyloid-beta and a series of damage markers in the synaptic compartment of Alzheimer's disease (AD) cases. Because localization of events to the terminal region in neurons is problematic with conventional methods, we prepared synaptosomes from samples of cryopreserved human association cortex, and immunolabeled terminals with a procedure for intracellular antigens. Fluorescence was quantified using flow cytometry. The viability dye calcein AM was unchanged in AD terminals compared to controls, and the fraction of large synaptosome particles did not change, although a striking loss of large terminals was observed in some AD cases. The percent positive fraction for a series of pre- and postsynaptic markers was not affected by AD in this cohort. However, the amyloid-beta-positive fraction increased from 16 to 27% (P < 0.02) in terminals from AD cortex. The expression level on a per-terminal basis is indicated in this assay by fluorescence (relative fluorescence units). The fluorescence of presynaptic markers did not change in AD terminals, but PSD-95 fluorescence was decreased by 19% (P < 0.03). Amyloid-beta fluorescence was increased by 132% (P < 0.01), and glial fibrillary acidic protein labeling by 31% (P < 0.01). These results suggest that synapse-associated amyloid-beta is prominent in regions relatively unaffected by AD lesions, and that amyloid accumulation in surviving terminals is accompanied by gliosis and alteration in the postsynaptic structure.
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Affiliation(s)
- Karen Hoppens Gylys
- UCLA School of Nursing and Brain Research Institute, Box 956919 Factor Bldg., Los Angeles, CA 90095-6919, USA.
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Gylys KH, Fein JA, Yang F, Cole GM. Enrichment of presynaptic and postsynaptic markers by size-based gating analysis of synaptosome preparations from rat and human cortex. ACTA ACUST UNITED AC 2004; 60:90-6. [PMID: 15229861 DOI: 10.1002/cyto.a.20031] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND Synapse regions in the brain are difficult to isolate and study; resealed nerve terminals (synaptosomes) are a widely used in vitro system for the study of neurotransmission, but nonsynaptosomal elements in the homogenate complicate data interpretation. With the goal of quantitative analysis of pathways leading to synapse loss in neurodegenerative disease, we have developed a method that allows focus on the intact synaptosomes within a crude synaptosomal preparation by gating the largest particles based on forward angle light scatter (FSC). METHODS Crude synaptosomal fractions (P-2) were prepared and labeled with a viability dye (calcein AM), a presynaptic marker (SNAP-25), and a postsynaptic marker (PSD-95). Forward scatter gates based on size standards were drawn to identify the large population (1.4-4.5 microm), and the enrichment of each marker was quantified in preparations from fresh rat homogenates and from cryopreserved human cortex. RESULTS Gating on forward scatter resulted in an increase that was highly significant (P < 0.001) for all three markers examined. The calcein-AM-positive fraction in the large synaptosomes was 98% +/- 0.8, and 75% +/- 9.8 for rat and human, respectively. Of large particles, 90% +/- 2.7 in rat and 82% +/- 2.6 in human were positive for SNAP-25, indicating a relatively pure population of intact synaptosomes. A total of 76% +/- 2.9 of the large particles were positive for PSD-95 in rat. This compared to 36% +/- 3.0 in human tissue, and indicates that both presynaptic and postsynaptic elements may be analyzed with this methodology. CONCLUSIONS Most nonsynaptosomal elements can be excluded and the intact subpopulation of interest within the P-2 can be identified based on size. Size-based gating analysis provides a simple and cost-effective method to monitor fluorescence changes in synapse regions.
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Affiliation(s)
- Karen H Gylys
- UCLA School of Nursing and Brain Research Institute, UCLA School of Medicine, Los Angeles, California 90095, USA.
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Mattiasson G, Friberg H, Hansson M, Elmér E, Wieloch T. Flow cytometric analysis of mitochondria from CA1 and CA3 regions of rat hippocampus reveals differences in permeability transition pore activation. J Neurochem 2003; 87:532-44. [PMID: 14511130 DOI: 10.1046/j.1471-4159.2003.02026.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Mitochondria are important in the pathophysiology of several neurodegenerative diseases, and mitochondrial production of reactive oxygen species (ROS), membrane depolarization, permeability changes and release of apoptogenic proteins are involved in these processes. Following brain insults, cell death often occurs in discrete regions of the brain, such as the subregions of the hippocampus. To analyse mitochondrial structure and function in such subregions, only small amounts of mitochondria are available. We developed a protocol for flow cytometric analysis of very small samples of isolated brain mitochondria, and analysed mitochondrial swelling and formation of ROS in mitochondria from the CA1 and CA3 regions of the hippocampus. Calcium-induced mitochondrial swelling was measured, and fluorescent probes were used to selectively stain mitochondria (nonyl acridine orange), to measure membrane potential (tetramethylrhodamine-methyl-ester, 1,1',3,3,3',3'-hexamethylindodicarbocyanine-iodide) and to measure production of ROS (2',7'-dichlorodihydrofluorescein-diacetate). We found that formation of ROS and mitochondrial permeability transition pore activation were higher in mitochondria from the CA1 than from the CA3 region, and propose that differences in mitochondrial properties partly underlie the selective vulnerability of the CA1 region to brain insults. We also conclude that flow cytometry is a useful tool to analyse the role of mitochondria in cell death processes.
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Affiliation(s)
- Gustav Mattiasson
- Laboratory for Experimental Brain Research, Wallenberg Neuroscience Center, Lund University, Lund, Sweden.
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Gylys KH, Fein JA, Tan AM, Cole GM. Apolipoprotein E enhances uptake of soluble but not aggregated amyloid-beta protein into synaptic terminals. J Neurochem 2003; 84:1442-51. [PMID: 12614344 DOI: 10.1046/j.1471-4159.2003.01643.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cellular mechanism by which apolipoprotein E (apoE) affects the pathogenesis of Alzheimer's disease (AD) is not understood. We have examined the effect of apolipoprotein E on the internalization of exogenous amyloid-beta 1-40 (Abeta40) into a rat brain crude synaptosomal preparation. Abeta40 peptide in soluble (within 1 h of dilution in buffer) or aggregated (aged 4 days before dilution in buffer) form was pre-incubated with lipidated apoE then added to synaptosomes; intraterminal amyloid-beta labeling was quantified using flow cytometry following immunolabeling with the anti-Abeta (10G4) antibody. The number of Abeta-positive synaptosomes was increased ( approximately 50%) by treatment with a soluble Abeta/apoE mixture compared with treatment with soluble Abeta40 alone. However, when the Abeta was aggregated, less sodium dodecyl sulfate (SDS)-stable Abeta/apoE complex was formed and the addition of apoE decreased the number of Abeta-positive terminals. The addition of the lipoprotein-receptor related protein (LRP) antagonist receptor-associated protein (RAP) inhibited the apoE-induced increase in synaptosomal Abeta, and controls treated with trypsin and heparinase confirm intraterminal localization of the majority of the soluble Abeta. The apoE-mediated increase in Abeta labeling was confirmed in intact cells by immunocytochemistry of dorsal root ganglion (DRG) neurons. These results suggest that complex formation with apoE enhances internalization of soluble Abeta uptake into terminals.
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Affiliation(s)
- Karen H Gylys
- UCLA School of Nursing and Brain Research Institute, UCLA School of Medicine, Los Angeles, California 90095-6919, USA.
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