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OKUBO YOHEI. Investigation of Brain Functions with Fluorescence Imaging Techniques. JUNTENDO IJI ZASSHI = JUNTENDO MEDICAL JOURNAL 2022; 68:157-162. [PMID: 38912284 PMCID: PMC11189797 DOI: 10.14789/jmj.jmj21-0051-ot] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 01/05/2022] [Indexed: 06/25/2024]
Abstract
An intricate interplay of complex spatio-temporal events underlies brain functions. Therefore, clarifying these dynamic processes is indispensable for revealing the mechanisms of brain functions. Fluorescence imaging is a powerful technique for visualizing cellular and molecular dynamics in the brain. Recent developments in fluorescent indicators and specialized optics have advanced research in the field of neuroscience. In this review, I will exemplify the power and beauty of fluorescence imaging by discussing my work focusing on the molecular dynamics of metabotropic glutamate receptor (mGluR) signaling at the synapse. By developing novel fluorescent indicators for glutamate, inositol 1,4,5-trisphosphate and Ca2+ within the endoplasmic reticulum, I succeeded in imaging the spatio-temporal dynamics of synaptic mGluR signaling, which led to the identification of novel mechanisms of mGluR-mediated glutamatergic neurotransmission. These discoveries highlight the importance of the development and application of novel fluorescence imaging techniques for the investigation of brain functions.
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Affiliation(s)
- YOHEI OKUBO
- Corresponding author: Yohei Okubo (ORCiD: 0000-0001-7611-3237), Department of Cellular and Molecular Pharmacology, Juntendo University Graduate School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo 113-8421, Japan, TEL: +81-3-5802-1035 E-mail:
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Zhang H, Xiao J, Hu Z, Xie M, Wang W, He D. Blocking transient receptor potential vanilloid 2 channel in astrocytes enhances astrocyte-mediated neuroprotection after oxygen-glucose deprivation and reoxygenation. Eur J Neurosci 2016; 44:2493-2503. [PMID: 27468746 DOI: 10.1111/ejn.13352] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 07/13/2016] [Accepted: 07/23/2016] [Indexed: 01/14/2023]
Abstract
Astrocytes play important roles in homeostatic regulation in the central nervous system and are reported to influence the outcome of ischemic injury. Regulating Ca2+ signaling of astrocytes is a promising strategy for stroke therapy. Herein, we report for the first time that transient receptor potential vanilloid 2 (TRPV2), a Ca2+ -permeable channel that is important in osmotic balance regulation, expresses in rat cortical astrocytes by immunofluorescence. Moreover, oxygen-glucose deprivation and reoxygenation (OGD/R) treatment enhanced the expression. The TRPV2 is functional because Ca2+ imaging showed that activating the TRPV2 channel in cultured astrocytes increased intracellular Ca2+ level and the increment of intracellular Ca2+ level expanded when astrocytes were treated with OGD/R. Staining with 5-ethynyl-2'-deoxyuridine (EdU) revealed that while blocking the TRPV2, it promoted the proliferation of astrocytes. Additionally, blocking the TRPV2 in astrocytes increased the synthesis of nerve growth factor (NGF) mRNA and the secretion of NGF by real-time PCR and enzyme-linked immunosorbent assay respectively. We further found that the increased secretion of NGF could be reversed by c-JunN-terminalkinase (JNK) inhibitor and blocking the TRPV2 caused the phosphorylation of JNK. These indicated that blocking the TRPV2 induced NGF secretion via the mitogen-activated protein kinase (MAPK)-JNK signaling pathway. As the promoted proliferation of astrocytes and secretion of NGF were reported to have neuroprotective effects in the early stage of stroke, we concluded that targeting the TRPV2 channel in astrocytes might be a potential new therapeutic strategy in ischemic stroke.
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Affiliation(s)
- Han Zhang
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Avenue, Wuhan, Hubei, 430030, China
| | - Jun Xiao
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Avenue, Wuhan, Hubei, 430030, China
| | - Zheng Hu
- Department of Obstetrics and Gynecology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Minjie Xie
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Avenue, Wuhan, Hubei, 430030, China
| | - Wei Wang
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Avenue, Wuhan, Hubei, 430030, China
| | - Dan He
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Avenue, Wuhan, Hubei, 430030, China. .,Department of Neurology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, China.
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Zhao N, Ma D, Leong WY, Han J, VanDongen A, Chen T, Goh ELK. The methyl-CpG-binding domain (MBD) is crucial for MeCP2's dysfunction-induced defects in adult newborn neurons. Front Cell Neurosci 2015; 9:158. [PMID: 25964742 PMCID: PMC4408855 DOI: 10.3389/fncel.2015.00158] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 04/08/2015] [Indexed: 12/31/2022] Open
Abstract
Mutations in the human X-linked gene MECP2 are responsible for most Rett syndrome (RTT) cases, predominantly within its methyl-CpG-binding domain (MBD). To examine the role of MBD in the pathogenesis of RTT, we generated two MeCP2 mutant constructs, one with a deletion of MBD (MeCP2-ΔMBD), another mimicking a mutation of threonine 158 within the MBD (MeCP2-T158M) found in RTT patients. MeCP2 knockdown resulted in a decrease in total dendrite length, branching, synapse number, as well as altered spontaneous Ca(2+) oscillations in vitro, which could be reversed by expression of full length human MeCP2 (hMeCP2-FL). However, the expression of hMeCP2-ΔMBD in MeCP2-silenced neurons did not rescue the changes in neuronal morphology and spontaneous Ca(2+) oscillations, while expression of hMeCP2-T158M in these neurons could only rescue the decrease in dendrite length and branch number. In vivo over expression of hMeCP2-FL but not hMeCP2-ΔMBD in adult newborn neurons of the dentate gyrus also rescued the cell autonomous effect caused by MeCP2 deficiency in dendrites length and branching. Our results demonstrate that an intact and functional MBD is crucial for MeCP2 functions in cultured hippocampal neurons and adult newborn neurons.
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Affiliation(s)
- Na Zhao
- Programme in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School Singapore, Singapore ; Key Laboratory of Health Ministry for Forensic Science, Department of Forensic Medicine, Xi'an Jiaotong University School of Medicine Xi'an, Shaanxi, China
| | - Dongliang Ma
- Programme in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School Singapore, Singapore
| | - Wan Ying Leong
- Programme in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School Singapore, Singapore
| | - Ju Han
- Programme in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School Singapore, Singapore
| | - Antonius VanDongen
- Programme in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School Singapore, Singapore ; Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore Singapore, Singapore
| | - Teng Chen
- Key Laboratory of Health Ministry for Forensic Science, Department of Forensic Medicine, Xi'an Jiaotong University School of Medicine Xi'an, Shaanxi, China
| | - Eyleen L K Goh
- Programme in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School Singapore, Singapore ; Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore Singapore, Singapore ; KK Research Center, KK Women's and Children's Hospital Singapore, Singapore
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Okubo Y. [Visualization of metabotropic glutamate-receptor signaling]. Nihon Yakurigaku Zasshi 2014; 144:76-80. [PMID: 25109520 DOI: 10.1254/fpj.144.76] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Verma KD, Forgács A, Uh H, Beyerlein M, Maier ME, Petoud S, Botta M, Logothetis NK. New calcium-selective smart contrast agents for magnetic resonance imaging. Chemistry 2013; 19:18011-26. [PMID: 24353083 DOI: 10.1002/chem.201300169] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Revised: 08/25/2013] [Indexed: 11/06/2022]
Abstract
Calcium plays a vital role in the human body and especially in the central nervous system. Precise maintenance of Ca(2+) levels is very crucial for normal cell physiology and health. The deregulation of calcium homeostasis can lead to neuronal cell death and brain damage. To study this functional role played by Ca(2+) in the brain noninvasively by using magnetic resonance imaging, we have synthesized a new set of Ca(2+) -sensitive smart contrast agents (CAs). The agents were found to be highly selective to Ca(2+) in the presence of other competitive anions and cations in buffer and in physiological fluids. The structure of CAs comprises Gd(3+)-DO3A (DO3A=1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane) coupled to a Ca(2+) chelator o-amino phenol-N,N,O-triacetate (APTRA). The agents are designed to sense Ca(2+) present in extracellular fluid of the brain where its concentration is relatively high, that is, 1.2-0.8 mM. The determined dissociation constant of the CAs to Ca(2+) falls in the range required to sense and report changes in extracellular Ca(2+) levels followed by an increase in neural activity. In buffer, with the addition of Ca(2+) the increase in relaxivity ranged from 100-157%, the highest ever known for any T1-based Ca(2+)-sensitive smart CA. The CAs were analyzed extensively by the measurement of luminescence lifetime measurement on Tb(3+) analogues, nuclear magnetic relaxation dispersion (NMRD), and (17)O NMR transverse relaxation and shift experiments. The results obtained confirmed that the large relaxivity enhancement observed upon Ca(2+) addition is due to the increase of the hydration state of the complexes together with the slowing down of the molecular rotation and the retention of a significant contribution of the water molecules of the second sphere of hydration.
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Affiliation(s)
- Kirti Dhingra Verma
- Max Planck Institute for Biological Cybernetics, Dept. of Physiology of Cognitive Processes, 72076 Tübingen (Germany); Present address: Case NFCR Center for Imaging Research, Dept. of Radiology, Case Western Reserve University, Cleveland, OH (USA).
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Abstract
Calcium ion is a highly versatile cellular messenger. Calcium signals-defined as transient increments in intracellular-free calcium concentration-elicit a multiplicity of responses that depend on cell type and signal properties such as their intensity, duration, cellular localization, and frequency. The vast literature available on the role of calcium signals in brain cells, chiefly centered on neuronal cells, indicates that calcium signals regulate essential neuronal functions, including synaptic transmission, gene expression, synaptic plasticity processes underlying learning and memory, and survival or death. The eight articles comprising this forum issue address different and novel aspects of calcium signaling in normal neuronal function, including how calcium signals interact with the generation of reactive species of oxygen/nitrogen with various functional consequences, and focus also on how abnormal calcium homeostasis and signaling, plus oxidative stress, affect overall brain physiology during aging and in neurodegenerative conditions such as Alzheimer's or Parkinson's disease.
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Affiliation(s)
- Cecilia Hidalgo
- Facultad de Medicina, Centro de Estudios Moleculares de la Célula and Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago, Chile.
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Riquelme D, Alvarez A, Leal N, Adasme T, Espinoza I, Valdés JA, Troncoso N, Hartel S, Hidalgo J, Hidalgo C, Carrasco MA. High-frequency field stimulation of primary neurons enhances ryanodine receptor-mediated Ca2+ release and generates hydrogen peroxide, which jointly stimulate NF-κB activity. Antioxid Redox Signal 2011; 14:1245-59. [PMID: 20836702 DOI: 10.1089/ars.2010.3238] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Neuronal electrical activity increases intracellular Ca(2+) concentration and generates reactive oxygen species. Here, we show that high frequency field stimulation of primary hippocampal neurons generated Ca(2+) signals with an early and a late component, and promoted hydrogen peroxide generation via a neuronal NADPH oxidase. Hydrogen peroxide generation required both Ca(2+) entry through N-methyl-D-aspartate receptors and Ca(2+) release mediated by ryanodine receptors (RyR). Field stimulation also enhanced nuclear translocation of the NF-κB p65 protein and NF-κB -dependent transcription, and increased c-fos mRNA and type-2 RyR protein content. Preincubation with inhibitory ryanodine or with the antioxidant N-acetyl L-cysteine abolished the increase in hydrogen peroxide generation and the late Ca(2+) signal component induced by electrical stimulation. Primary cortical cells behaved similarly as primary hippocampal cells. Exogenous hydrogen peroxide also activated NF-κB-dependent transcription in hippocampal neurons; inhibitory ryanodine prevented this effect. Selective inhibition of the NADPH oxidase or N-acetyl L-cysteine also prevented the enhanced translocation of p65 in hippocampal cells, while N-acetyl L-cysteine abolished the increase in RyR2 protein content induced by high frequency stimulation. In conclusion, the present results show that electrical stimulation induced reciprocal activation of ryanodine receptor-mediated Ca(2+) signals and hydrogen peroxide generation, which stimulated jointly NF-κB activity.
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Affiliation(s)
- Denise Riquelme
- Center of Molecular Studies of the Cell, Institute of Biomedical Sciences Programs, Universidad de Chile, Santiago, Chile
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