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Normoyle KP, Lillis KP, Staley KJ. Synthesis and Characterization of a Novel Concentration-Independent Fluorescent Chloride Indicator, ABP-Dextran, Optimized for Extracellular Chloride Measurement. Biomolecules 2024; 14:77. [PMID: 38254677 PMCID: PMC10813347 DOI: 10.3390/biom14010077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 12/20/2023] [Accepted: 12/22/2023] [Indexed: 01/24/2024] Open
Abstract
GABA, the primary inhibitory neurotransmitter, stimulates GABAA receptors (GABAARs) to increase the chloride conductance of the cytosolic membrane. The driving forces for membrane chloride currents are determined by the local differences between intracellular and extracellular chloride concentrations (Cli and Clo, respectively). While several strategies exist for the measurement of Cli, the field lacks tools for non-invasive measurement of Clo. We present the design and development of a fluorescent lifetime imaging (FLIM)-compatible small molecule, N(4-aminobutyl)phenanthridiunium (ABP) with the brightness, spectral features, sensitivity to chloride, and selectivity versus other anions to serve as a useful probe of Clo. ABP can be conjugated to dextran to ensure extracellular compartmentalization, and a second chloride-insensitive counter-label can be added for ratiometric imaging. We validate the utility of this novel sensor series in two sensor concentration-independent modes: FLIM or ratiometric intensity-based imaging.
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Affiliation(s)
- Kieran P. Normoyle
- Massachusetts General Hospital, Department of Neurology, 55 Fruit Street, Boston, MA 02114, USA; (K.P.N.); (K.P.L.)
- Harvard Medical School, Department of Neurology, 77 Louis Pasteur Avenue, Boston, MA 02115, USA
| | - Kyle P. Lillis
- Massachusetts General Hospital, Department of Neurology, 55 Fruit Street, Boston, MA 02114, USA; (K.P.N.); (K.P.L.)
- Harvard Medical School, Department of Neurology, 77 Louis Pasteur Avenue, Boston, MA 02115, USA
| | - Kevin J. Staley
- Massachusetts General Hospital, Department of Neurology, 55 Fruit Street, Boston, MA 02114, USA; (K.P.N.); (K.P.L.)
- Harvard Medical School, Department of Neurology, 77 Louis Pasteur Avenue, Boston, MA 02115, USA
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Rahmati N, Normoyle KP, Glykys J, Dzhala VI, Lillis KP, Kahle KT, Raiyyani R, Jacob T, Staley KJ. Unique Actions of GABA Arising from Cytoplasmic Chloride Microdomains. J Neurosci 2021; 41:4957-4975. [PMID: 33903223 PMCID: PMC8197632 DOI: 10.1523/jneurosci.3175-20.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 03/10/2021] [Accepted: 04/10/2021] [Indexed: 12/21/2022] Open
Abstract
Developmental, cellular, and subcellular variations in the direction of neuronal Cl- currents elicited by GABAA receptor activation have been frequently reported. We found a corresponding variance in the GABAA receptor reversal potential (EGABA) for synapses originating from individual interneurons onto a single pyramidal cell. These findings suggest a similar heterogeneity in the cytoplasmic intracellular concentration of chloride ([Cl-]i) in individual dendrites. We determined [Cl-]i in the murine hippocampus and cerebral cortex of both sexes by (1) two-photon imaging of the Cl--sensitive, ratiometric fluorescent protein SuperClomeleon; (2) Fluorescence Lifetime IMaging (FLIM) of the Cl--sensitive fluorophore MEQ (6-methoxy-N-ethylquinolinium); and (3) electrophysiological measurements of EGABA by pressure application of GABA and RuBi-GABA uncaging. Fluorometric and electrophysiological estimates of local [Cl-]i were highly correlated. [Cl-]i microdomains persisted after pharmacological inhibition of cation-chloride cotransporters, but were progressively modified after inhibiting the polymerization of the anionic biopolymer actin. These methods collectively demonstrated stable [Cl-]i microdomains in individual neurons in vitro and in vivo and the role of immobile anions in its stability. Our results highlight the existence of functionally significant neuronal Cl- microdomains that modify the impact of GABAergic inputs.SIGNIFICANCE STATEMENT Microdomains of varying chloride concentrations in the neuronal cytoplasm are a predictable consequence of the inhomogeneous distribution of anionic polymers such as actin, tubulin, and nucleic acids. Here, we demonstrate the existence and stability of these microdomains, as well as the consequence for GABAergic synaptic signaling: each interneuron produces a postsynaptic GABAA response with a unique reversal potential. In individual hippocampal pyramidal cells, the range of GABAA reversal potentials evoked by stimulating different interneurons was >20 mV. Some interneurons generated postsynaptic responses in pyramidal cells that reversed at potentials beyond what would be considered purely inhibitory. Cytoplasmic chloride microdomains enable each pyramidal cell to maintain a compendium of unique postsynaptic responses to the activity of individual interneurons.
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Affiliation(s)
- Negah Rahmati
- Department of Neurology, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts 02114
| | - Kieran P Normoyle
- Department of Neurology, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts 02114
| | - Joseph Glykys
- Department of Pediatrics and Neurology, Iowa Neuroscience Institute, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Volodymyr I Dzhala
- Department of Neurology, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts 02114
| | - Kyle P Lillis
- Department of Neurology, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts 02114
| | - Kristopher T Kahle
- Departments of Neurosurgery, Pediatrics, and Cellular & Molecular Physiology, Yale School of Medicine, New Haven, Connecticut 06510
| | - Rehan Raiyyani
- Department of Neurology, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts 02114
| | - Theju Jacob
- Department of Neurology, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts 02114
| | - Kevin J Staley
- Department of Neurology, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts 02114
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Wang H, Kim M, Normoyle KP, Llano D. Thermal Regulation of the Brain-An Anatomical and Physiological Review for Clinical Neuroscientists. Front Neurosci 2016; 9:528. [PMID: 26834552 PMCID: PMC4720747 DOI: 10.3389/fnins.2015.00528] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 12/31/2015] [Indexed: 12/31/2022] Open
Abstract
Humans, like all mammals and birds, maintain a near constant core body temperature of 36–37.5°C over a broad range of environmental conditions and are thus referred to as endotherms. The evolution of the brain and its supporting structures in mammals and birds coincided with this development of endothermy. Despite the recognition that a more evolved and complicated brain with all of its temperature-dependent cerebral circuitry and neuronal processes would require more sophisticated thermal control mechanisms, the current understanding of brain temperature regulation remains limited. To optimize the development and maintenance of the brain in health and to accelerate its healing and restoration in illness, focused, and committed efforts are much needed to advance the fundamental understanding of brain temperature. To effectively study and examine brain temperature and its regulation, we must first understand relevant anatomical and physiological properties of thermoregulation in the head-neck regions.
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Affiliation(s)
- Huan Wang
- Department of Neurosurgery, Carle Foundation HospitalUrbana, IL, USA; Thermal Neuroscience Laboratory, Beckman Institute, University of Illinois at Urbana-ChampaignUrbana, IL, USA; University of Illinois College of Medicine at Urbana-ChampaignUrbana, IL, USA
| | - Miri Kim
- University of Illinois College of Medicine at Urbana-ChampaignUrbana, IL, USA; Neuroscience Program and Department of Cell and Developmental Biology, University of Illinois at Urbana-ChampaignUrbana, IL, USA
| | - Kieran P Normoyle
- University of Illinois College of Medicine at Urbana-ChampaignUrbana, IL, USA; Department of Molecular and Integrative Physiology, University of Illinois at Urbana-ChampaignUrbana, IL, USA; Department of Child Neurology, Massachusetts General HospitalBoston, MA, USA
| | - Daniel Llano
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-ChampaignUrbana, IL, USA; NeuroTech Group, Beckman Institute, University of Illinois at Urbana-ChampaignUrbana, IL, USA; Department of Neurology, Carle Foundation HospitalUrbana, IL, USA
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Normoyle KP, Kim M, Farahvar A, Llano D, Jackson K, Wang H. The emerging neuroprotective role of mitochondrial uncoupling protein-2 in traumatic brain injury. Transl Neurosci 2015; 6:179-186. [PMID: 28123803 PMCID: PMC4936626 DOI: 10.1515/tnsci-2015-0019] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 07/20/2015] [Indexed: 12/11/2022] Open
Abstract
Traumatic brain injury (TBI) is a multifaceted disease with intrinsically complex heterogeneity and remains a significant clinical challenge to manage. TBI model systems have demonstrated many mechanisms that contribute to brain parenchymal cell death, including glutamate and calcium toxicity, oxidative stress, inflammation, and mitochondrial dysfunction. Mitochondria are critically regulated by uncoupling proteins (UCP), which allow protons to leak back into the matrix and thus reduce the mitochondrial membrane potential by dissipating the proton motive force. This uncoupling of oxidative phosphorylation from adenosine triphosphate (ATP) synthesis is potentially critical for protection against cellular injury as a result of TBI and stroke. A greater understanding of the underlying mechanism or mechanisms by which uncoupling protein-2 (UCP2) functions to maintain or optimize mitochondrial function, and the conditions which precipitate the failure of these mechanisms, would inform future research and treatment strategies. We posit that UCP2-mediated function underlies the physiological response to neuronal stress associated with traumatic and ischemic injury and that clinical development of UCP2-targeted treatment would significantly impact these patient populations. With a focus on clinical relevance in TBI, we synthesize current knowledge concerning UCP2 and its potential neuroprotective role and apply this body of knowledge to current and potential treatment modalities.
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Affiliation(s)
- Kieran P Normoyle
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, USA; College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Department of Child Neurology, Massachusetts General Hospital, Boston, MA, USA
| | - Miri Kim
- College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Arash Farahvar
- Department of Neurosurgery, Carle Foundation Hospital, Urbana, IL, USA
| | - Daniel Llano
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Department of Neurology, Carle Foundation Hospital, Urbana, IL, USA; The Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Kevin Jackson
- The Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Thermal Neuroscience Laboratory (TNL), Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Huan Wang
- Department of Neurology, Carle Foundation Hospital, Urbana, IL, USA; Thermal Neuroscience Laboratory (TNL), Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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Wang H, Wang B, Normoyle KP, Jackson K, Spitler K, Sharrock MF, Miller CM, Best C, Llano D, Du R. Brain temperature and its fundamental properties: a review for clinical neuroscientists. Front Neurosci 2014; 8:307. [PMID: 25339859 PMCID: PMC4189373 DOI: 10.3389/fnins.2014.00307] [Citation(s) in RCA: 171] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 09/12/2014] [Indexed: 01/13/2023] Open
Abstract
Brain temperature, as an independent therapeutic target variable, has received increasingly intense clinical attention. To date, brain hypothermia represents the most potent neuroprotectant in laboratory studies. Although the impact of brain temperature is prevalent in a number of common human diseases including: head trauma, stroke, multiple sclerosis, epilepsy, mood disorders, headaches, and neurodegenerative disorders, it is evident and well recognized that the therapeutic application of induced hypothermia is limited to a few highly selected clinical conditions such as cardiac arrest and hypoxic ischemic neonatal encephalopathy. Efforts to understand the fundamental aspects of brain temperature regulation are therefore critical for the development of safe, effective, and pragmatic clinical treatments for patients with brain injuries. Although centrally-mediated mechanisms to maintain a stable body temperature are relatively well established, very little is clinically known about brain temperature's spatial and temporal distribution, its physiological and pathological fluctuations, and the mechanism underlying brain thermal homeostasis. The human brain, a metabolically “expensive” organ with intense heat production, is sensitive to fluctuations in temperature with regards to its functional activity and energy efficiency. In this review, we discuss several critical aspects concerning the fundamental properties of brain temperature from a clinical perspective.
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Affiliation(s)
- Huan Wang
- Department of Neurosurgery, Carle Foundation Hospital, University of Illinois College of Medicine at Urbana-Champaign Urbana, IL, USA ; Thermal Neuroscience Laboratory, Beckman Institute, University of Illinois at Urbana-Champaign Urbana, IL, USA
| | - Bonnie Wang
- Department of Internal Medicine, Carle Foundation Hospital, University of Illinois College of Medicine at Urbana-Champaign Urbana, IL, USA
| | - Kieran P Normoyle
- Department of Internal Medicine, College of Medicine at Urbana-Champaign, University of Illinois Champaign, Urbana, IL, USA ; Department of Molecular and Integrative Physiology, University of Illinois College of Medicine at Urbana-Champaign Urbana, IL, USA
| | - Kevin Jackson
- Thermal Neuroscience Laboratory, Beckman Institute, University of Illinois at Urbana-Champaign Urbana, IL, USA
| | - Kevin Spitler
- Department of Internal Medicine, Carle Foundation Hospital, University of Illinois College of Medicine at Urbana-Champaign Urbana, IL, USA
| | - Matthew F Sharrock
- Department of Internal Medicine, College of Medicine at Urbana-Champaign, University of Illinois Champaign, Urbana, IL, USA
| | - Claire M Miller
- Department of Internal Medicine, College of Medicine at Urbana-Champaign, University of Illinois Champaign, Urbana, IL, USA ; Neuroscience Program, University of Illinois at Urbana-Champaign Urbana, IL, USA
| | - Catherine Best
- Molecular and Cellular Biology, University of Illinois at Urbana-Champaign Urbana, IL, USA
| | - Daniel Llano
- Thermal Neuroscience Laboratory, Beckman Institute, University of Illinois at Urbana-Champaign Urbana, IL, USA ; Department of Molecular and Integrative Physiology, University of Illinois College of Medicine at Urbana-Champaign Urbana, IL, USA
| | - Rose Du
- Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School Boston, MA, USA
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