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Goldberg JM, Lippard SJ. Mobile zinc as a modulator of sensory perception. FEBS Lett 2023; 597:151-165. [PMID: 36416529 PMCID: PMC10108044 DOI: 10.1002/1873-3468.14544] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 11/15/2022] [Accepted: 11/16/2022] [Indexed: 11/24/2022]
Abstract
Mobile zinc is an abundant transition metal ion in the central nervous system, with pools of divalent zinc accumulating in regions of the brain engaged in sensory perception and memory formation. Here, we present essential tools that we developed to interrogate the role(s) of mobile zinc in these processes. Most important are (a) fluorescent sensors that report the presence of mobile zinc and (b) fast, Zn-selective chelating agents for measuring zinc flux in animal tissue and live animals. The results of our studies, conducted in collaboration with neuroscientist experts, are presented for sensory organs involved in hearing, smell, vision, and learning and memory. A general principle emerging from these studies is that the function of mobile zinc in all cases appears to be downregulation of the amplitude of the response following overstimulation of the respective sensory organs. Possible consequences affecting human behavior are presented for future investigations in collaboration with interested behavioral scientists.
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Affiliation(s)
| | - Stephen J Lippard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
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Hu S, Anastassov IA, Kreitzer MA, Slaughter MM, Chappell RL. A dark decrement for enhanced dynamic sensitivity of retinal photoreceptors. Vision Res 2020; 180:80-86. [PMID: 33387934 DOI: 10.1016/j.visres.2020.12.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 11/06/2020] [Accepted: 12/10/2020] [Indexed: 10/22/2022]
Abstract
The skate retina provides a native all-rod retina suited for investigating a single type of photoreceptor regarding its properties and signaling to second order cells. Using the aspartate-induced isolated A-wave of the skate eyecup electroretinogram (ERG), it has been shown that adaptation in rods remains Weber-Fechner-like over a 6-log unit increase in background light intensity. Zinc, which can block calcium channels, has been found in the rod synaptic terminal and the synaptic cleft. Histidine is a zinc chelator. Voltage signals from neurons post-synaptic to rods indicate that histidine increases the dark release of glutamate and increases the horizontal cell light response. In histidine, the A-wave response to various light intensities in the dark-adapted retina increased more than fifty percent, corresponding to the effect on horizontal cells. In the presence of background light, although histidine-treated rod light responses remained Weber-Fechner-like, their increment threshold was raised significantly. This indicates that endogenous zinc feedback serves to increase rod sensitivity in a light-adapted retina, despite a corresponding reduction of threshold sensitivity in the dark. We propose that the increase in A-wave amplitude is a result of the increased conductance at the synaptic terminal and that the A-wave can be used to monitor changes in rod transmitter release. Furthermore, endogenous zinc may also provide the benefit of reducing metabolic stress and the risk of glutamate toxicity in the dark.
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Affiliation(s)
- Shen Hu
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, United States
| | - Ivan A Anastassov
- Department of Biology, San Francisco State University, San Francisco, CA, United States; Marine Biological Laboratory, Woods Hole, MA, United States
| | - Matthew A Kreitzer
- Marine Biological Laboratory, Woods Hole, MA, United States; Department of Biology, Indiana Wesleyan University, Marion, IN, United States
| | - Malcolm M Slaughter
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, United States
| | - Richard L Chappell
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, United States; Marine Biological Laboratory, Woods Hole, MA, United States.
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Gilbert R, Peto T, Lengyel I, Emri E. Zinc Nutrition and Inflammation in the Aging Retina. Mol Nutr Food Res 2019; 63:e1801049. [PMID: 31148351 DOI: 10.1002/mnfr.201801049] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 04/18/2019] [Indexed: 12/16/2022]
Abstract
Zinc is an essential nutrient for human health. It plays key roles in maintaining protein structure and stability, serves as catalytic factor for many enzymes, and regulates diverse fundamental cellular processes. Zinc is important in affecting signal transduction and, in particular, in the development and integrity of the immune system, where it affects both innate and adaptive immune responses. The eye, especially the retina-choroid complex, has an unusually high concentration of zinc compared to other tissues. The highest amount of zinc is concentrated in the retinal pigment epithelium (RPE) (RPE-choroid, 292 ± 98.5 µg g-1 dry tissue), followed by the retina (123 ± 62.2 µg g-1 dry tissue). The interplay between zinc and inflammation has been explored in other parts of the body but, so far, has not been extensively researched in the eye. Several lines of evidence suggest that ocular zinc concentration decreases with age, especially in the context of age-related disease. Thus, a hypothesis that retinal function could be modulated by zinc nutrition is proposed, and subsequently trialled clinically. In this review, the distribution and the potential role of zinc in the retina-choroid complex is outlined, especially in relation to inflammation and immunity, and the clinical studies to date are summarized.
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Affiliation(s)
- Rosie Gilbert
- Moorfields Eye Hospital NHS Foundation Trust, City Road, London, EC1V 2PD, UK.,UCL Institute of Ophthalmology, Bath Street, London, EC1V 2EL, UK
| | - Tunde Peto
- School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Ireland
| | - Imre Lengyel
- UCL Institute of Ophthalmology, Bath Street, London, EC1V 2EL, UK.,School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Ireland
| | - Eszter Emri
- School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Ireland
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Ugarte M, Osborne NN. Recent advances in the understanding of the role of zinc in ocular tissues. Metallomics 2014; 6:189-200. [DOI: 10.1039/c3mt00291h] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Anastassov I, Ripps H, Chappell RL. Cytoprotection by endogenous zinc in the vertebrate retina. J Neurochem 2013; 129:249-55. [PMID: 24286124 DOI: 10.1111/jnc.12627] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2013] [Revised: 11/16/2013] [Accepted: 11/18/2013] [Indexed: 12/26/2022]
Abstract
Our recent studies have shown that endogenous zinc, co-released with glutamate from the synaptic terminals of vertebrate retinal photoreceptors, provides a feedback mechanism that reduces calcium entry and the concomitant vesicular release of glutamate. We hypothesized that zinc feedback may serve to protect the retina from glutamate excitotoxicity, and conducted in vivo experiments on the retina of the skate (Raja erinacea) to determine the effects of removing endogenous zinc by chelation. These studies showed that removal of zinc by injecting the zinc chelator histidine results in inner retinal damage similar to that induced by the glutamate receptor agonist kainic acid. In contrast, when an equimolar quantity of zinc followed the injection of histidine, the retinal cells were unaffected. Our results are a good indication that zinc, co-released with glutamate by photoreceptors, provides an auto-feedback system that plays an important cytoprotective role in the retina.
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Affiliation(s)
- Ivan Anastassov
- Department of Biological Sciences, Hunter College and the Graduate Center, CUNY, New York, New York, USA; Marine Biological Laboratory, Woods Hole, Massachusetts, USA
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Lee SC, Zhong YM, Li RX, Yu Z, Yang XL. Localization of zinc in the outer retina of carp: A light- and electron-microscopic study. Synapse 2008; 62:352-7. [DOI: 10.1002/syn.20501] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Redenti S, Ripps H, Chappell RL. Zinc release at the synaptic terminals of rod photoreceptors. Exp Eye Res 2007; 85:580-4. [PMID: 17825289 DOI: 10.1016/j.exer.2007.07.017] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2007] [Revised: 07/20/2007] [Accepted: 07/23/2007] [Indexed: 10/23/2022]
Abstract
The presence of reactive zinc (Zn2+) within photoreceptor terminals, and evidence that exogenous zinc affects the electrophysiological activity of the distal retina, led to the suggestion that its co-release with glutamate could play an essential role in the modulation of information at the first synapse in the visual pathway. Although we had shown previously that zinc release could be visualized in the region of the outer synaptic layer of a retinal slice preparation, it could not be ascertained with certainty that the release sites were at the presynaptic terminal rather than from the mitochondria-rich inner segment or from zinc within the distal processes of photoreceptors and Müller cells. Using membrane permeant and membrane impermeant forms of a fluorescent zinc indicator (Newport green), we show both the intracellular distribution of Zn2+ and its depolarization-dependent discharge from the terminals of isolated zebrafish photoreceptors in culture. Zinc release could be detected in the dark-adapted preparation, and was further enhanced by brief exposures to black widow spider venom or high K+. Synaptically released zinc may significantly influence neural processing in the vertebrate retina by modulating the activity of excitatory and/or inhibitory receptors as well as intracellular signaling proteins.
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Hirzel K, Müller U, Latal AT, Hülsmann S, Grudzinska J, Seeliger MW, Betz H, Laube B. Hyperekplexia Phenotype of Glycine Receptor α1 Subunit Mutant Mice Identifies Zn2+ as an Essential Endogenous Modulator of Glycinergic Neurotransmission. Neuron 2006; 52:679-90. [PMID: 17114051 DOI: 10.1016/j.neuron.2006.09.035] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Revised: 08/08/2006] [Accepted: 09/18/2006] [Indexed: 01/09/2023]
Abstract
Zn(2+) is thought to modulate neurotransmission by affecting currents mediated by ligand-gated ion channels and transmitter reuptake by Na(+)-dependent transporter systems. Here, we examined the in vivo relevance of Zn(2+) neuromodulation by producing knockin mice carrying the mutation D80A in the glycine receptor (GlyR) alpha1 subunit gene (Glra1). This substitution selectively eliminates the potentiating effect of Zn(2+) on GlyR currents. Mice homozygous for Glra1(D80A) develop a severe neuromotor phenotype postnatally that resembles forms of human hyperekplexia (startle disease) caused by mutations in GlyR genes. In spinal neurons and brainstem slices from Glra1(D80A) mice, GlyR expression, synaptic localization, and basal glycinergic transmission were normal; however, potentiation of spontaneous glycinergic currents by Zn(2+) was significantly impaired. Thus, the hyperekplexia phenotype of Glra1(D80A) mice is due to the loss of Zn(2+) potentiation of alpha1 subunit containing GlyRs, indicating that synaptic Zn(2+) is essential for proper in vivo functioning of glycinergic neurotransmission.
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Affiliation(s)
- Klaus Hirzel
- Abteilung Neurochemie, Max-Planck-Institut für Hirnforschung, Deutschordenstrasse 46, 60528 Frankfurt am Main, Germany
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Redenti S, Chappell RL. Neuroimaging of zinc released by depolarization of rat retinal cells. Vision Res 2005; 45:3520-5. [PMID: 16181655 DOI: 10.1016/j.visres.2005.07.039] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Revised: 07/27/2005] [Accepted: 07/27/2005] [Indexed: 11/12/2022]
Abstract
Zinc is associated with glutamatergic pathways in brain and retina, yet its role in neuromodulation remains unknown. High concentrations of reactive zinc in vertebrate photoreceptor terminals suggest a neuromodulatory role in the outer plexiform layer but zinc release has not been demonstrated. Using the membrane-impermeable form of the Zn(2+) sensitive fluorescent dye Newport Green, we have demonstrated increased release of Zn(2+) from the rat retina in response to potassium-induced depolarization of retinal cells. This increase was greatest in the outer retina with densest bands observed in the outer plexiform layer and photoreceptor inner segment regions of rat retinal slices.
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