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Mizuno D, Kawahara M, Konoha-Mizuno K, Hama R, Ogawara T. The Role of Zinc in the Development of Vascular Dementia and Parkinson's Disease and the Potential of Carnosine as Their Therapeutic Agent. Biomedicines 2024; 12:1296. [PMID: 38927502 PMCID: PMC11201809 DOI: 10.3390/biomedicines12061296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Revised: 05/10/2024] [Accepted: 06/07/2024] [Indexed: 06/28/2024] Open
Abstract
Synaptic zinc ions (Zn2+) play an important role in the development of vascular dementia (VD) and Parkinson's disease (PD). In this article, we reviewed the current comprehension of the Zn2+-induced neurotoxicity that leads to the pathogenesis of these neuronal diseases. Zn2+-induced neurotoxicity was investigated by using immortalised hypothalamic neurons (GT1-7 cells). This cell line is useful for the development of a rapid and convenient screening system for investigating Zn2+-induced neurotoxicity. GT1-7 cells were also used to search for substances that prevent Zn2+-induced neurotoxicity. Among the tested substances was a protective substance in the extract of Japanese eel (Anguilla japonica), and we determined its structure to be like carnosine (β-alanylhistidine). Carnosine may be a therapeutic drug for VD and PD. Furthermore, we reviewed the molecular mechanisms that involve the role of carnosine as an endogenous protector and its protective effect against Zn2+-induced cytotoxicity and discussed the prospects for the future therapeutic applications of this dipeptide for neurodegenerative diseases and dementia.
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Affiliation(s)
- Dai Mizuno
- Department of Forensic Medicine, Faculty of Medicine, Yamagata University, 2-2-2 Iida-Nishi, Yamagata-shi 990-9585, Yamagata, Japan; (K.K.-M.); (R.H.); (T.O.)
| | - Masahiro Kawahara
- Research Institute of Pharmaceutical Sciences, Faculty of Pharmacy, Musashino University, 1-1-20 Shin-machi, Nishitokyo-shi 202-8585, Tokyo, Japan;
| | - Keiko Konoha-Mizuno
- Department of Forensic Medicine, Faculty of Medicine, Yamagata University, 2-2-2 Iida-Nishi, Yamagata-shi 990-9585, Yamagata, Japan; (K.K.-M.); (R.H.); (T.O.)
| | - Ryoji Hama
- Department of Forensic Medicine, Faculty of Medicine, Yamagata University, 2-2-2 Iida-Nishi, Yamagata-shi 990-9585, Yamagata, Japan; (K.K.-M.); (R.H.); (T.O.)
| | - Terumasa Ogawara
- Department of Forensic Medicine, Faculty of Medicine, Yamagata University, 2-2-2 Iida-Nishi, Yamagata-shi 990-9585, Yamagata, Japan; (K.K.-M.); (R.H.); (T.O.)
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Tseng HC, Pan CY. Dopamine Activates the D1R-Zn 2+ Signaling Pathway to Trigger Inflammatory Response in Primary-Cultured Rat Embryonic Cortical Neurons. Cell Mol Neurobiol 2023; 43:3593-3604. [PMID: 37289255 DOI: 10.1007/s10571-023-01367-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 05/24/2023] [Indexed: 06/09/2023]
Abstract
Neuroinflammation is an early event during the pathogenesis of neurodegenerative disorders. Most studies focus on how the factors derived from pathogens or tissue damage activate the inflammation-pyroptosis cell death pathway. It is unclear whether endogenous neurotransmitters could induce inflammatory responses in neurons. Our previous reports have shown that dopamine-induced elevation of intracellular Zn2+ concentration via the D1-like receptor (D1R) is a prerequisite for autophagy and cell death in primary cultured rat embryonic neurons. Here we further examined that this D1R-Zn2+ signaling initiates the transient inflammatory response leading to cell death in cultured cortical neurons. Pretreating the cultured neurons with Zn2+ chelator and inhibitors against inflammation could enhance the cell viability in neurons treated with dopamine and dihydrexidine, an agonist of D1R. Both dopamine and dihydrexidine greatly enhanced inflammasome formation; a Zn2+ chelator, N,N,N',N'-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine, suppressed this increment. Dopamine and dihydrexidine increased the expression levels of NOD-like receptor pyrin domain-containing protein 3 and enhanced the maturation of caspase-1, gasdermin D, and IL-1β; these changes were all Zn2+-dependent. Dopamine treatment did not recruit the N-terminal of the gasdermin D to the plasma membrane but enhanced its localization to the autophagosomes. Pretreating the neurons with IL-1β could increase the viability of neurons challenged with dopamine. These results demonstrate a novel D1R-Zn2+ signaling cascade activating neuroinflammation and cell death. Therefore, maintaining a balance between dopamine homeostasis and inflammatory responses is an important therapeutic target for neurodegeneration. Dopamine elicits transient inflammatory responses in cultured cortical neurons via the D1R-Zn2+ signaling pathway. Dopamine elevates [Zn2+]i to induce the formation of inflammasomes, which activates caspase-1, resulting in the maturation of IL-1β and gasdermin D (GSDMD). Therefore, the homeostasis of dopamine and Zn2+ are critical therapeutic targets for inflammation-derived neurodegeneration.
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Affiliation(s)
- Hui-Chiun Tseng
- Department of Life Science, National Taiwan University, 1 Roosevelt Rd. Sec 4, Taipei, 106, Taiwan
| | - Chien-Yuan Pan
- Department of Life Science, National Taiwan University, 1 Roosevelt Rd. Sec 4, Taipei, 106, Taiwan.
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Tamura H, Sasaki M, Nakajima S, Nishio R, Saeki N, Katahira M, Tamano H, Takeda A. Reactive oxygen species produced by Zn 2+ influx after exposure to AMPA, but not NMDA and their capturing effect on nigral dopaminergic protection. Neurotoxicology 2023; 95:173-180. [PMID: 36775207 DOI: 10.1016/j.neuro.2023.02.003] [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: 06/22/2022] [Revised: 12/14/2022] [Accepted: 02/08/2023] [Indexed: 02/12/2023]
Abstract
Glutamate excitotoxicity is involved in dopaminergic degeneration in the substantia nigra pars compacta (SNpc). Here we compared vulnerability to neurodegeneration after exposure to NMDA and AMPA. Apomorphine-induced movement disorder and dopaminergic degeneration in the SNpc, which are associated with Parkinson's syndrome, were induced after injection of AMPA into the SNpc of rats, but not after injection of NMDA. Co-injection of 1-naphthyl acetyl spermine (NASPM), a selective blocker of Ca2+- and Zn2+-permeable GluR2-lacking AMPA receptors rescued dopaminergic degeneration and increase in intracellular Zn2+ by AMPA. Furthermore, we tested the effect of capturing reactive oxygen species (ROS) produced by Zn2+ on neuroprotection in vivo. The levels of ROS, which were determined by HYDROP, a membrane-permeable H2O2 fluorescence probe and Aminophenyl Fluorescein (APF), a fluorescence probe for hydroxyl radical and peroxynitrite, were increased after injection of AMPA, but not after co-injection of CaEDTA, an extracellular Zn2+ chelator, suggesting that increase in Zn2+ influx by AMPA elevates the levels of intracellular ROS. AMPA-mediated dopaminergic degeneration was completely rescued by co-injection of either HYDROP or APF. The present study indicates that neurotoxic signaling of the influx of extracellular Zn2+ through Zn2+-permeable GluR2-lacking AMPA receptors is converted to ROS production and that capturing the ROS completely protects dopaminergic degeneration after exposure to AMPA, but not NMDA. It is likely that regulation of the conversion from Zn2+ influx into ROS production plays a key role to preventing Parkinson's syndrome.
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Affiliation(s)
- Haruna Tamura
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Miki Sasaki
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Satoko Nakajima
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Ryusuke Nishio
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Nana Saeki
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Misa Katahira
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
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Liaquat H, Imran M, Latif S, Hussain N, Bilal M. Multifunctional nanomaterials and nanocomposites for sensing and monitoring of environmentally hazardous heavy metal contaminants. ENVIRONMENTAL RESEARCH 2022; 214:113795. [PMID: 35803339 DOI: 10.1016/j.envres.2022.113795] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 05/25/2022] [Accepted: 06/27/2022] [Indexed: 06/15/2023]
Abstract
The applications of conventional sensors are limited by the long response time, high cost, large detection limit, low sensitivity, complicated usage and low selectivity. These sensors are nowadays replaced by Nanocomposite-based modalities and nanomaterials which are known for their high selectivity and physical and chemical properties. These nanosensors effectively detect heavy metal contaminants in the environment as the discharge of heavy metals into natural water as a result of human activity has become a global epidemic. Exposure to these toxic metals might induce many health-related complications, including kidney failure, brain injury, immune disorders, muscle paleness, cardiac damage, nervous system impairment and limb paralysis. Therefore, designing and developing novel sensing systems for the detection and recognition of these harmful metals in various environmental matrices, particularly water, is of extremely important. Emerging nanotechnological approaches in the past two decades have played a key role in overcoming environmentally-related problems. Nanomaterial-based fabrication of chemical nanosensors has widely been applied as a powerful analytical tool for sensing heavy metals. Portability, high sensitivity, on-site detection capability, better device performance and selectivity are all advantages of these nanosensors. The detection and selectivity have been improved using molecular recognition probes for selective binding on different nanostructures. This study aims to evaluate the sensing properties of various nanomaterials such as metal-organic frameworks, fluorescent materials, metal-based nanoparticles, carbon-based nanomaterials and quantum dots and graphene-based nanomaterials and quantum dots for heavy metal ions recognition. All these nano-architectures are frequently served as effective fluorescence probes to directly (or by modification with some large or small biomolecules) sense heavy metal ions for improved selectivity. However, efforts are still needed for the simultaneous designing of multiple metal ion-based detection systems, exclusively in colorimetric or optical fluorescence nanosensors for heavy metal cations.
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Affiliation(s)
- Hina Liaquat
- Centre for Inorganic Chemistry, School of Chemistry, University of the Punjab, Lahore, 54000, Pakistan
| | - Muhammad Imran
- Centre for Inorganic Chemistry, School of Chemistry, University of the Punjab, Lahore, 54000, Pakistan
| | - Shoomaila Latif
- School of Physical Sciences, University of the Punjab, Lahore, 54000, Pakistan
| | - Nazim Hussain
- Center for Applied Molecular Biology (CAMB), University of the Punjab, Lahore, 54000, Pakistan
| | - Muhammad Bilal
- School of Life Science and Food Engineering, Huaiyin Institute of Technology, Huaian, 223003, China.
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Takeda A. [Brain Function and Pathophysiology Focused on Zn 2+ Dynamics]. YAKUGAKU ZASSHI 2022; 142:855-866. [PMID: 35908946 DOI: 10.1248/yakushi.22-00074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The basal levels of intracellular Zn2+ and extracellular Zn2+ are in the range of ~100 pM and ~10 nM, respectively, in the brain. Extracellular Zn2+ dynamics is involved in both cognitive performance and neurodegeneration. The bidirectional actions are linked with extracellular glutamate and amyloid-β1-42 (Aβ1-42). Intracellular Zn2+ signaling via extracellular glutamate is required for learning and memory, while intracellular Zn2+ dysregulation induces cognitive decline. Furthermore, human Aβ1-42, a causative peptide in Alzheimer's disease pathogenesis captures extracellular Zn2+ and readily taken up into hippocampal neurons followed by intracellular Zn2+ dysregulation. Aβ1-42-mediated intracellular Zn2+ dysregulation is accelerated with aging, because extracellular Zn2+ is age-relatedly increased, resulting in Aβ1-42-induced cognitive decline and neurodegeneration with aging. On the other hand, metallothioneins, zinc-binding proteins can capture Zn2+ released from intracellular Zn-Aβ1-42 complexes and serve for intracellular Zn2+-buffering to maintain intracellular Zn2+ homeostasis. This review summarizes Zn2+ function and its neurotoxicity in the brain, and also the potential defense strategy via metallothioneins against Aβ1-42-induced pathogenesis.
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Affiliation(s)
- Atsushi Takeda
- School of Pharmaceutical Sciences, University of Shizuoka
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Tamura H, Nishio R, Saeki N, Katahira M, Morioka H, Tamano H, Takeda A. Paraquat-induced intracellular Zn 2+ dysregulation causes dopaminergic degeneration in the substantia nigra, but not in the striatum. Neurotoxicology 2022; 90:136-144. [PMID: 35339517 DOI: 10.1016/j.neuro.2022.03.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 03/08/2022] [Accepted: 03/19/2022] [Indexed: 11/15/2022]
Abstract
Parkinson's disease is characterized by a selective death of nigrostriatal dopaminergic neurons, while the difference in the vulnerability to the death between the substantia nigra pars compacta (SNpc) and the striatum is poorly understood. Here we tested the difference focused on paraquat (PQ)-induced intracellular Zn2+ toxicity via extracellular glutamate accumulation. When PQ was locally injected into the SNpc and the striatum, dopaminergic degeneration was observed in the SNpc, but not in the striatum. Intracellular hydrogen peroxide (H2O2) produced by PQ was increased in both the SNpc and the striatum. In contrast, extracellular glutamate accumulation was observed only in the SNpc and rescued in the presence of N-(p-amylcinnamoyl)anthranilic acid (ACA), a blocker of the transient receptor potential melastatin 2 (TRPM2) cation channels. PQ increased intracellular Zn2+ level in the SNpc, but not in the striatum. The increase was rescued by 1-naphthyl acetyl spermine (NASPM), a selective blocker of Ca2+- and Zn2+-permeable GluR2-lacking AMPA receptors. PQ-induced dopaminergic degeneration in the SNpc was rescued by ACA, NASPM, and GBR, a dopamine reuptake inhibitor. The present study indicates intracellular H2O2 produced by PQ, which is taken up through dopamine transporters, is retrogradely transported to presynaptic glutamatergic terminals, activates TRPM2 channels, accumulates glutamate in the extracellular compartment, and induces intracellular Zn2+ dysregulation via Ca2+- and Zn2+-permeable GluR2-lacking AMPA receptor activation, resulting in dopaminergic degeneration in the SNpc. However, H2O2 signaling is not the case in the striatum. Paraquat-induced Zn2+ dysregulation plays a key role for neurodegeneration in the SNpc, but not in the striatum.
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Affiliation(s)
- Haruna Tamura
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Ryusuke Nishio
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Nana Saeki
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Misa Katahira
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Hiroki Morioka
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Haruna Tamano
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Atsushi Takeda
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
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Thirugnanam T, Santhakumar K. Chemically induced models of Parkinson's disease. Comp Biochem Physiol C Toxicol Pharmacol 2022; 252:109213. [PMID: 34673252 DOI: 10.1016/j.cbpc.2021.109213] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 09/30/2021] [Accepted: 10/14/2021] [Indexed: 12/12/2022]
Abstract
Environmental toxins are harmful substances detrimental to humans. Constant exposure to these fatal neurotoxins can cause various neurodegenerative disorders. Although poisonous, specific neurotoxins at optimal concentrations mimic the clinical features of neurodegenerative diseases in several animal models. Such chemically-induced model systems are beneficial in deciphering the molecular mechanisms of neurodegeneration and drug screening for these disorders. One such neurotoxin is 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a widely used chemical that recapitulates Parkinsonian features in various animal models. Apart from MPTP, other neurotoxins like 6-hydroxydopamine (6-OHDA), paraquat, rotenone also induce specific clinical features of Parkinson's disease in animal models. These chemically-induced Parkinson's disease models are playing a crucial role in understanding Parkinson's disease onset, pathology, and novel therapeutics. In this review, we provide a concise overview of various neurotoxins that can recapitulate Parkinsonian features in different in vivo and in vitro model systems specifically focusing on the different treatment methodologies of neurotoxins.
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Affiliation(s)
- Thilaga Thirugnanam
- Zebrafish Genetics Laboratory, Department of Genetic Engineering, SRM Institute of Science and Technology, Kattankulathur 603 203, Tamil Nadu, India
| | - Kirankumar Santhakumar
- Zebrafish Genetics Laboratory, Department of Genetic Engineering, SRM Institute of Science and Technology, Kattankulathur 603 203, Tamil Nadu, India.
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Nishio R, Morioka H, Takeuchi A, Saeki N, Furuhata R, Katahira M, Chinenn T, Tamura H, Tamano H, Takeda A. Intracellular hydrogen peroxide produced by 6-hydroxydopamine is a trigger for nigral dopaminergic degeneration of rats via rapid influx of extracellular Zn 2. Neurotoxicology 2021; 89:1-8. [PMID: 34958835 DOI: 10.1016/j.neuro.2021.12.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 12/08/2021] [Accepted: 12/22/2021] [Indexed: 01/06/2023]
Abstract
To elucidate the mechanism and significance of 6-hydroxydopamine (6-OHDA)-induced Zn2+ toxicity, which is involved in neurodegeneration in the substantia nigra pars compacta (SNpc) of rats, we postulated that intracellular hydrogen peroxide (H2O2) produced by 6-OHDA is a trigger for intracellular Zn2+ dysregulation in the SNpc. Intracellular H2O2 level elevated by 6-OHDA in the SNpc was completely inhibited by co-injection of GBR 13069 dihydrochloride (GBR), a dopamine reuptake inhibitor, suggesting that 6-OHDA taken up through dopamine transporters produces H2O2 in the intercellular compartment of dopaminergic neurons. When the SNpc was perfused with H2O2, glutamate accumulated in the extracellular compartment and the accumulation was inhibited in the presence of N-(p-amylcinnamoyl)anthranilic acid (ACA), a blocker of the transient receptor potential melastatin 2 (TRPM2) channels. In addition to 6-OHDA, H2O2 also induced intracellular Zn2+ dysregulation via AMPA receptor activation followed by nigral dopaminergic degeneration. Furthermore, 6-OHDA-induced nigral dopaminergic degeneration was completely inhibited by co-injection of either HYDROP, an intracellular H2O2 scavenger or GBR into the SNpc. The present study indicates that H2O2 is produced by 6-OHDA taken up through dopamine transporters in the SNpc, is retrogradely transported to presynaptic glutamatergic terminals, activates TRPM2 channels, accumulates glutamate in the extracellular compartment, and induces intracellular Zn2+ dysregulation via AMPA receptor activation, resulting in nigral dopaminergic degeneration prior to movement disorder. It is likely that intracellular H2O2, but not extracellular H2O2, is a key trigger for nigral dopaminergic degeneration via intracellular Zn2+ dysregulation.
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Affiliation(s)
- Ryusuke Nishio
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Hiroki Morioka
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Azusa Takeuchi
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Nana Saeki
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Ryo Furuhata
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Misa Katahira
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Takato Chinenn
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Haruna Tamura
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Haruna Tamano
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Atsushi Takeda
- School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
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Abstract
Since the discovery of manifest Zn deficiency in 1961, the increasing number of studies demonstrated the association between altered Zn status and multiple diseases. In this chapter, we provide a review of the most recent advances on the role of Zn in health and disease (2010-20), with a special focus on the role of Zn in neurodegenerative and neurodevelopmental disorders, diabetes and obesity, male and female reproduction, as well as COVID-19. In parallel with the revealed tight association between ASD risk and severity and Zn status, the particular mechanisms linking Zn2+ and ASD pathogenesis like modulation of synaptic plasticity through ProSAP/Shank scaffold, neurotransmitter metabolism, and gut microbiota, have been elucidated. The increasing body of data indicate the potential involvement of Zn2+ metabolism in neurodegeneration. Systemic Zn levels in Alzheimer's and Parkinson's disease were found to be reduced, whereas its sequestration in brain may result in modulation of amyloid β and α-synuclein processing with subsequent toxic effects. Zn2+ was shown to possess adipotropic effects through the role of zinc transporters, zinc finger proteins, and Zn-α2-glycoprotein in adipose tissue physiology, underlying its particular role in pathogenesis of obesity and diabetes mellitus type 2. Recent findings also contribute to further understanding of the role of Zn2+ in spermatogenesis and sperm functioning, as well as oocyte development and fertilization. Finally, Zn2+ was shown to be the potential adjuvant therapy in management of novel coronavirus infection (COVID-19), underlining the perspectives of zinc in management of old and new threats.
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Affiliation(s)
- Anatoly V Skalny
- IM Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia; Yaroslavl State University, Yaroslavl, Russia
| | - Michael Aschner
- IM Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia; Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, United States
| | - Alexey A Tinkov
- IM Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia; Yaroslavl State University, Yaroslavl, Russia.
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Synaptic Zinc: An Emerging Player in Parkinson's Disease. Int J Mol Sci 2021; 22:ijms22094724. [PMID: 33946908 PMCID: PMC8125092 DOI: 10.3390/ijms22094724] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 04/26/2021] [Accepted: 04/26/2021] [Indexed: 02/03/2023] Open
Abstract
Alterations of zinc homeostasis have long been implicated in Parkinson's disease (PD). Zinc plays a complex role as both deficiency and excess of intracellular zinc levels have been incriminated in the pathophysiology of the disease. Besides its role in multiple cellular functions, Zn2+ also acts as a synaptic transmitter in the brain. In the forebrain, subset of glutamatergic neurons, namely cortical neurons projecting to the striatum, use Zn2+ as a messenger alongside glutamate. Overactivation of the cortico-striatal glutamatergic system is a key feature contributing to the development of PD symptoms and dopaminergic neurotoxicity. Here, we will cover recent evidence implicating synaptic Zn2+ in the pathophysiology of PD and discuss its potential mechanisms of actions. Emphasis will be placed on the functional interaction between Zn2+ and glutamatergic NMDA receptors, the most extensively studied synaptic target of Zn2+.
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Takeda A, Tamano H. [Alzheimer's disease pathogenesis focused on intracellular Zn 2+ toxicity and its defense strategy]. Nihon Yakurigaku Zasshi 2021; 156:71-75. [PMID: 33642533 DOI: 10.1254/fpj.20077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The basal levels of intracellular Zn2+ and extracellular Zn2+ are in the range of ~100 pM and ~10 nM, respectively, in the hippocampus. Extracellular Zn2+ dynamics, which serves bidirectionally and involved in cognitive activity and cognitive decline, is modified by extracellular glutamate signaling and the presence of amyloid-β1-42 (Aβ1-42), a causative peptide in Alzheimer's disease (AD) pathogenesis. When human Aβ1-42 reaches 100-500 pM in the extracellular compartment of the rat hippocampus, Zn-Aβ1-42 complexes are produced and readily taken up into dentate granule cells in a synaptic activity-independent manner. Furthermore, intracellular Zn-Aβ1-42 complexes release Zn2+ followed by intracellular Zn2+ dysregulation. Aβ1-42-mediated intracellular Zn2+ toxicity is accelerated with aging, because extracellular Zn2+ is age-relatedly increased. We have reported that Aβ1-42 released physiologically from neuron terminals disrupts intracellular Zn2+ homeostasis, resulting in age-related cognitive decline and neurodegeneration. Metallothioneins (MTs), zinc-binding proteins can capture Zn2+ released from intracellular Zn-Aβ1-42 complexes and serve for intracellular Zn2+-buffering under acute intracellular Zn2+ dysregulation. Aβ1-42-induced pathogenesis leads the AD development and its defense strategy may prevent the development. This review summarizes extracellular Zn2+-dependent Aβ1-42 neurotoxicity, which is accelerated with aging, and the potential defense strategy against AD.
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Affiliation(s)
- Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka
| | - Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka
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Nakajima S, Saeki N, Tamano H, Nishio R, Katahira M, Takeuchi A, Takeda A. Age-related vulnerability to nigral dopaminergic degeneration in rats via Zn 2+-permeable GluR2-lacking AMPA receptor activation. Neurotoxicology 2021; 83:69-76. [PMID: 33400970 DOI: 10.1016/j.neuro.2020.12.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 12/27/2020] [Accepted: 12/28/2020] [Indexed: 11/18/2022]
Abstract
On the basis of the evidence that extracellular Zn2+ influx induced with AMPA causes Parkinson's syndrome in rats that apomorphine-induced movement disorder emerges, here we used a low dose of AMPA, which does not increase intracellular Zn2+ level in the substantia nigra pars compacta (SNpc) of young adult rats, and tested whether intracellular Zn2+ dysregulation induced with AMPA is accelerated in the SNpc of aged rats, resulting in age-related vulnerability to Parkinson's syndrome. When AMPA (1 mM) was injected at the rate of 0.05 μl/min for 20 min into the SNpc, intracellular Zn2+ level was increased in the SNpc of aged rats followed by increase in turning behavior in response to apomorphine and nigral dopaminergic degeneration. In contrast, young adult rats do not show movement disorder and nigral dopaminergic degeneration, in addition to no increase in intracellular Zn2+. In aged rats, movement disorder and nigral dopaminergic degeneration were rescued by co-injection of either extracellular (CaEDTA) or intracellular (ZnAF-2DA) Zn2+ chelators. 1-Naphthyl acetyl spermine (NASPM), a selective blocker of Ca2+- and Zn2+-permeable GluR2-lacking AMPA receptors blocked increase in intracellular Zn2+ in the SNpc of aged rats followed by rescuing nigral dopaminergic degeneration. The present study indicates that intracellular Zn2+ dysregulation is accelerated by Ca2+- and Zn2+-permeable GluR2-lacking AMPA receptor activation in the SNpc of aged rats, resulting in age-related vulnerability to Parkinson's syndrome.
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Affiliation(s)
- Satoko Nakajima
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Nana Saeki
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Ryusuke Nishio
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Misa Katahira
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Azusa Takeuchi
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan.
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Sato Y, Takiguchi M, Tamano H, Takeda A. Extracellular Zn 2+-Dependent Amyloid-β 1-42 Neurotoxicity in Alzheimer's Disease Pathogenesis. Biol Trace Elem Res 2021; 199:53-61. [PMID: 32281074 DOI: 10.1007/s12011-020-02131-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 03/23/2020] [Indexed: 02/07/2023]
Abstract
The basal level of extracellular Zn2+ is in the range of low nanomolar (~ 10 nM) in the hippocampus. However, extracellular Zn2+ dynamics plays a key role for not only cognitive activity but also cognitive decline. Extracellular Zn2+ dynamics is modified by glutamatergic synapse excitation and the presence of amyloid-β1-42 (Aβ1-42), a causative peptide in Alzheimer's disease (AD). When human Aβ1-42 reaches high picomolar (> 100 pM) in the extracellular compartment of the rat dentate gyrus, Zn-Aβ1-42 complexes are readily formed and taken up into dentate granule cells, followed by Aβ1-42-induced cognitive decline that is linked with Zn2+ released from intracellular Zn-Aβ1-42 complexes. Aβ1-42-induced intracellular Zn2+ toxicity is accelerated with aging because of age-related increase in extracellular Zn2+. The recent findings suggest that Aβ1-42 secreted continuously from neuron terminals causes age-related cognitive decline and neurodegeneration via intracellular Zn2+ dysregulation. On the other hand, metallothioneins (MTs), zinc-binding proteins, quickly serve for intracellular Zn2+-buffering under acute intracellular Zn2+ dysregulation. On the basis of the idea that the defense strategy against Aβ1-42-induced pathogenesis leads to preventing the AD development, this review deals with extracellular Zn2+-dependent Aβ1-42 neurotoxicity, which is accelerated with aging.
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Affiliation(s)
- Yuichi Sato
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Mako Takiguchi
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan.
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Krzywoszyńska K, Witkowska D, Świątek-Kozłowska J, Szebesczyk A, Kozłowski H. General Aspects of Metal Ions as Signaling Agents in Health and Disease. Biomolecules 2020; 10:biom10101417. [PMID: 33036384 PMCID: PMC7600656 DOI: 10.3390/biom10101417] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 09/30/2020] [Accepted: 10/02/2020] [Indexed: 02/07/2023] Open
Abstract
This review focuses on the current knowledge on the involvement of metal ions in signaling processes within the cell, in both physiological and pathological conditions. The first section is devoted to the recent discoveries on magnesium and calcium-dependent signal transduction-the most recognized signaling agents among metals. The following sections then describe signaling pathways where zinc, copper, and iron play a key role. There are many systems in which changes in intra- and extra-cellular zinc and copper concentrations have been linked to important downstream events, especially in nervous signal transduction. Iron signaling is mostly related with its homeostasis. However, it is also involved in a recently discovered type of programmed cell death, ferroptosis. The important differences in metal ion signaling, and its disease-leading alterations, are also discussed.
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Affiliation(s)
- Karolina Krzywoszyńska
- Institute of Health Sciences, University of Opole, 68 Katowicka St., 45-060 Opole, Poland; (J.Ś.-K.); (A.S.); (H.K.)
- Correspondence: (K.K.); (D.W.); Tel.: +48-77-44-23-549 (K.K); +48-77-44-23-548 (D.W.)
| | - Danuta Witkowska
- Institute of Health Sciences, University of Opole, 68 Katowicka St., 45-060 Opole, Poland; (J.Ś.-K.); (A.S.); (H.K.)
- Correspondence: (K.K.); (D.W.); Tel.: +48-77-44-23-549 (K.K); +48-77-44-23-548 (D.W.)
| | - Jolanta Świątek-Kozłowska
- Institute of Health Sciences, University of Opole, 68 Katowicka St., 45-060 Opole, Poland; (J.Ś.-K.); (A.S.); (H.K.)
| | - Agnieszka Szebesczyk
- Institute of Health Sciences, University of Opole, 68 Katowicka St., 45-060 Opole, Poland; (J.Ś.-K.); (A.S.); (H.K.)
| | - Henryk Kozłowski
- Institute of Health Sciences, University of Opole, 68 Katowicka St., 45-060 Opole, Poland; (J.Ś.-K.); (A.S.); (H.K.)
- Faculty of Chemistry, University of Wrocław, 14 F. Joliot-Curie St., 50-383 Wrocław, Poland
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Atsushi T, Tamano H. New insight into Parkinson's disease pathogenesis from reactive oxygen species-mediated extracellular Zn 2+ influx. J Trace Elem Med Biol 2020; 61:126545. [PMID: 32438294 DOI: 10.1016/j.jtemb.2020.126545] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 04/07/2020] [Accepted: 04/30/2020] [Indexed: 01/21/2023]
Abstract
BACKGROUND Parkinson's disease (PD) is the common neurodegenerative disorder in the elderly characterized by motor symptoms such as tremors, which is caused by selective loss of nigral dopaminergic neurons. Oxidative stress induced by the auto-oxidation of dopamine has been implicated as a key cause of the selective loss of dopaminergic neurons. METHODS To understand the selective loss of nigral dopaminergic neurons, the PD pathogenesis is reviewed focused on paraquat (PQ) and 6-hydroxydopamine (6-OHDA)-induced PD in rats. RESULTS Reactive oxygen species (ROS), which are produced by PQ and 6-OHDA, are retrogradely transported to presynaptic glutamatergic neuron terminals. ROS activate presynaptic transient receptor potential melastatin 2 (TRPM2) cation channels and induce extracellular glutamate accumulation in the substantia nigra pars compacta (SNpc), followed by age-related intracellular Zn2+ dysregulation. Loss of nigral dopaminergic neurons is accelerated by age-related intracellular Zn2+ dysregulation in the SNpc of rat PD models. The intracellular Zn2+ dysregulation in nigral dopaminergic neurons is linked with the rapid influx of extracellular Zn2+ via postsynaptic AMPA receptor activation, suggesting that PQ- and 6-OHDA-induced pathogenesis is linked with age-related intracellular Zn2+ dysregulation in the SNpc. Postsynaptic TRPM2 channels may be also involved in intracellular Zn2+ dysregulation in the SNpc. CONCLUSION A novel mechanism of nigral dopaminergic degeneration, in which ROS induce rapid intracellular Zn2+ dysregulation, figures out the PD pathogenesis induced by PQ and 6-OHDA in rats. This review deals with new insight into PD pathogenesis from ROS-mediated extracellular Zn2+ influx and its proposed defense strategy.
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Affiliation(s)
- Takeda Atsushi
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
| | - Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
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Sikora J, Kieffer BL, Paoletti P, Ouagazzal AM. Synaptic zinc contributes to motor and cognitive deficits in 6-hydroxydopamine mouse models of Parkinson's disease. Neurobiol Dis 2019; 134:104681. [PMID: 31759136 DOI: 10.1016/j.nbd.2019.104681] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 11/05/2019] [Accepted: 11/19/2019] [Indexed: 12/19/2022] Open
Abstract
Hyperactivity of glutamatergic corticostrial pathways is recognized as a key pathophysiological mechanism contributing to development of PD symptoms and dopaminergic neurotoxicity. Subset of corticostriatal projection neurons uses Zn2+ as a co-transmitter alongside glutamate, but the role of synaptically released Zn2+ in PD remains unexplored. We used genetically modified mice and pharmacological tools in combination with 6-hydroxydopamine (6-OHDA) lesion models of PD to investigate the contribution of synaptic zinc to disease associated behavioral deficits and neurodegeneration. Vesicular zinc transporter-3 (ZnT3) knockout mice lacking releasable Zn2+ were more resistant to locomotor deficit and memory impairment of nigrostriatal dopamine (DA) denervation compared to wildtype littermates. The loss of striatal dopaminergic fibers was comparable between genotypes, indicating that synaptically released Zn2+ contributes to behavioral deficits but not neurotoxic effects of 6-OHDA. To gain further insight into the mechanisms of Zn2+ actions, we used the extracellular Zn2+ chelator CaEDTA and knock-in mice lacking the high affinity Zn2+ inhibition of GluN2A-containing NMDA receptors (GluN2A-NMDARs). Acute chelation of extracellular Zn2+ in the striatum restored locomotor deficit of 6-OHDA lesion, confirming that synaptic Zn2+ suppresses locomotor behavior. Disruption of the Zn2+-GluN2A interaction had, on the other hand, no impact on locomotor deficit or neurotoxic effect of 6-OHDA. Collectively, these findings provide clear evidence for the implication of striatal synaptic Zn2+ in the pathophysiology of PD. They unveil that synaptic Zn2+ plays predominantly a detrimental role by promoting motor and cognitive deficits caused by nigrostriatal DA denervation, pointing towards new therapeutic interventions.
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Affiliation(s)
- Joanna Sikora
- Laboratoire de Neurosciences Cognitives, Aix-Marseille Univ, CNRS, LNC, UMR 7291, 13331 Marseille, France; Aix-marseille Université, Marseille, France
| | - Brigitte L Kieffer
- Douglas Research Center, Department of Psychiatry, McGill University, Montréal, Canada
| | - Pierre Paoletti
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, Université PSL, CNRS, INSERM, Paris, France
| | - Abdel-Mouttalib Ouagazzal
- Laboratoire de Neurosciences Cognitives, Aix-Marseille Univ, CNRS, LNC, UMR 7291, 13331 Marseille, France.
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Huang Y, Zhan H, Bhatt P, Chen S. Paraquat Degradation From Contaminated Environments: Current Achievements and Perspectives. Front Microbiol 2019; 10:1754. [PMID: 31428067 PMCID: PMC6689968 DOI: 10.3389/fmicb.2019.01754] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 07/15/2019] [Indexed: 12/26/2022] Open
Abstract
Paraquat herbicide has served over five decades to control annual and perennial weeds. Despite agricultural benefits, its toxicity to terrestrial and aquatic environments raises serious concerns. Paraquat cannot rapidly degrade in the environment and is adsorbed in clay lattices that require urgent environmental remediation. Advanced oxidation processes (AOPs) and bioaugmentation techniques have been developed for this purpose. Among various techniques, bioremediation is a cost-effective and eco-friendly approach for pesticide-polluted soils. Though several paraquat-degrading microorganisms have been isolated and characterized, studies about degradation pathways, related functional enzymes and genes are indispensable. This review encircles paraquat removal from contaminated environments through adsorption, photocatalyst degradation, AOPs and microbial degradation. To provide in-depth knowledge, the potential role of paraquat degrading microorganisms in contaminated environments is described as well.
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Affiliation(s)
- Yaohua Huang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Integrative Microbiology Research Centre, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, China
| | - Hui Zhan
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Integrative Microbiology Research Centre, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, China
| | - Pankaj Bhatt
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Integrative Microbiology Research Centre, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, China
| | - Shaohua Chen
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Integrative Microbiology Research Centre, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, China
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Paraquat as an Environmental Risk Factor in Parkinson's Disease Accelerates Age-Related Degeneration Via Rapid Influx of Extracellular Zn 2+ into Nigral Dopaminergic Neurons. Mol Neurobiol 2019; 56:7789-7799. [PMID: 31119555 DOI: 10.1007/s12035-019-01642-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 05/10/2019] [Indexed: 10/26/2022]
Abstract
On the basis of the evidence that paraquat (PQ)-induced extracellular Zn2+ influx causes PQ-induced pathogenesis in the substantia nigra pars compacta (SNpc) of rats, we postulated that the transient receptor potential melastatin 2 (TRPM2) cation channels activated with PQ-induced reactive oxygen species (ROS) are linked with extracellular glutamate accumulation in the SNpc, followed by age-related intracellular Zn2+ dysregulation. Presynaptic activity (glutamate exocytosis), which was determined with FM4-64, was enhanced in the SNpc after exposure to PQ, and the enhancement was inhibited in the presence of N-(p-amylcinnamoyl)anthranilic acid (ACA), a blocker of TRPM2 cation channels, suggesting that PQ-induced ROS enhances presynaptic activity in the SNpc, probably via TRPM2 channel activation. Extracellular glutamate concentration in the SNpc was increased almost to the same extent under the SNpc perfusion with PQ of young and aged rats, and was suppressed by co-perfusion with ACA, suggesting that PQ-induced TRPM2 cation channel activation enhances glutamate exocytosis in the SNpc. Interestingly, PQ more markedly increased intracellular Zn2+ in the aged SNpc, which was also blocked by co-injection of ACA and CaEDTA, an extracellular Zn2+ chelator. Loss of nigrostriatal dopaminergic neurons was more severely increased in aged rats and completely blocked by co-injection of PQ and CaEDTA into the SNpc. The present study indicates that rapid influx of extracellular Zn2+ into dopaminergic neurons via PQ-induced TRPM2 cation channel activation accelerates nigrostriatal dopaminergic degeneration in aged rats. It is likely that vulnerability to PQ-induced pathogenesis in the aged SNpc is due to accelerated intracellular Zn2+ dysregulation.
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