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de Paula Arrifano G, Crespo-Lopez ME, Lopes-Araújo A, Santos-Sacramento L, Barthelemy JL, de Nazaré CGL, Freitas LGR, Augusto-Oliveira M. Neurotoxicity and the Global Worst Pollutants: Astroglial Involvement in Arsenic, Lead, and Mercury Intoxication. Neurochem Res 2023; 48:1047-1065. [PMID: 35997862 DOI: 10.1007/s11064-022-03725-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 07/01/2022] [Accepted: 08/09/2022] [Indexed: 10/15/2022]
Abstract
Environmental pollution is a global threat and represents a strong risk factor for human health. It is estimated that pollution causes about 9 million premature deaths every year. Pollutants that can cross the blood-brain barrier and reach the central nervous system are of special concern, because of their potential to cause neurological and development disorders. Arsenic, lead and mercury are usually ranked as the top three in priority lists of regulatory agencies. Against xenobiotics, astrocytes are recognised as the first line of defence in the CNS, being involved in virtually all brain functions, contributing to homeostasis maintenance. Here, we discuss the current knowledge on the astroglial involvement in the neurotoxicity induced by these pollutants. Beginning by the main toxicokinetic characteristics, this review also highlights the several astrocytic mechanisms affected by these pollutants, involving redox system, neurotransmitter and glucose metabolism, and cytokine production/release, among others. Understanding how these alterations lead to neurological disturbances (including impaired memory, deficits in executive functions, and motor and visual disfunctions), by revisiting the current knowledge is essential for future research and development of therapies and prevention strategies.
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Affiliation(s)
- Gabriela de Paula Arrifano
- Laboratory of Molecular Pharmacology, Institute of Biological Sciences, Federal University of Pará, Av. Augusto Corrêa, 01, Belém, PA, 66075-110, Brazil
| | - Maria Elena Crespo-Lopez
- Laboratory of Molecular Pharmacology, Institute of Biological Sciences, Federal University of Pará, Av. Augusto Corrêa, 01, Belém, PA, 66075-110, Brazil
| | - Amanda Lopes-Araújo
- Laboratory of Molecular Pharmacology, Institute of Biological Sciences, Federal University of Pará, Av. Augusto Corrêa, 01, Belém, PA, 66075-110, Brazil
| | - Letícia Santos-Sacramento
- Laboratory of Molecular Pharmacology, Institute of Biological Sciences, Federal University of Pará, Av. Augusto Corrêa, 01, Belém, PA, 66075-110, Brazil
| | - Jean L Barthelemy
- Laboratory of Molecular Pharmacology, Institute of Biological Sciences, Federal University of Pará, Av. Augusto Corrêa, 01, Belém, PA, 66075-110, Brazil
| | - Caio Gustavo Leal de Nazaré
- Laboratory of Molecular Pharmacology, Institute of Biological Sciences, Federal University of Pará, Av. Augusto Corrêa, 01, Belém, PA, 66075-110, Brazil
| | - Luiz Gustavo R Freitas
- Laboratory of Molecular Pharmacology, Institute of Biological Sciences, Federal University of Pará, Av. Augusto Corrêa, 01, Belém, PA, 66075-110, Brazil
| | - Marcus Augusto-Oliveira
- Laboratory of Molecular Pharmacology, Institute of Biological Sciences, Federal University of Pará, Av. Augusto Corrêa, 01, Belém, PA, 66075-110, Brazil.
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Emerging Role of Neuron-Glia in Neurological Disorders: At a Glance. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2022; 2022:3201644. [PMID: 36046684 PMCID: PMC9423989 DOI: 10.1155/2022/3201644] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 08/05/2022] [Indexed: 11/18/2022]
Abstract
Based on the diverse physiological influence, the impact of glial cells has become much more evident on neurological illnesses, resulting in the origins of many diseases appearing to be more convoluted than previously happened. Since neurological disorders are often random and unknown, hence the construction of animal models is difficult to build, representing a small fraction of people with a gene mutation. As a result, an immediate necessity is grown to work within in vitro techniques for examining these illnesses. As the scientific community recognizes cell-autonomous contributions to a variety of central nervous system illnesses, therapeutic techniques involving stem cells for treating neurological diseases are gaining traction. The use of stem cells derived from a variety of sources is increasingly being used to replace both neuronal and glial tissue. The brain's energy demands necessitate the reliance of neurons on glial cells in order for it to function properly. Furthermore, glial cells have diverse functions in terms of regulating their own metabolic activities, as well as collaborating with neurons via secreted signaling or guidance molecules, forming a complex network of neuron-glial connections in health and sickness. Emerging data reveals that metabolic changes in glial cells can cause morphological and functional changes in conjunction with neuronal dysfunction under disease situations, highlighting the importance of neuron-glia interactions in the pathophysiology of neurological illnesses. In this context, it is required to improve our understanding of disease mechanisms and create potential novel therapeutics. According to research, synaptic malfunction is one of the features of various mental diseases, and glial cells are acting as key ingredients not only in synapse formation, growth, and plasticity but also in neuroinflammation and synaptic homeostasis which creates critical physiological capacity in the focused sensory system. The goal of this review article is to elaborate state-of-the-art information on a few glial cell types situated in the central nervous system (CNS) and highlight their role in the onset and progression of neurological disorders.
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Dong L, Yang B, Zhang Y, Wang S, Li F, Xing G, Farina M, Zhang Y, Appiah-Kubi K, Tinkov AA, Aschner M, Shi H, Liu T, Lu R. Ferroptosis contributes to methylmercury-induced cytotoxicity in rat primary astrocytes and Buffalo rat liver cells. Neurotoxicology 2022; 90:228-236. [DOI: 10.1016/j.neuro.2022.04.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 03/27/2022] [Accepted: 04/14/2022] [Indexed: 01/18/2023]
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Revisiting Astrocytic Roles in Methylmercury Intoxication. Mol Neurobiol 2021; 58:4293-4308. [PMID: 33990914 DOI: 10.1007/s12035-021-02420-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 05/04/2021] [Indexed: 02/06/2023]
Abstract
Intoxication by heavy metals such as methylmercury (MeHg) is recognized as a global health problem, with strong implications in central nervous system pathologies. Most of these neuropathological conditions involve vascular, neurotransmitter recycling, and oxidative balance disruption leading to accelerated decline in fine balance, and learning, memory, and visual processes as main outcomes. Besides neurons, astrocytes are involved in virtually all the brain processes and perform important roles in neurological response following injuries. Due to astrocytes' strategic functions in brain homeostasis, these cells became the subject of several studies on MeHg intoxication. The most heterogenous glial cells, astrocytes, are composed of plenty of receptors and transporters to dialogue with neurons and other cells and to monitor extracellular environment responding tightly through fluctuation of cytosolic ions. The overall toxicity of MeHg might be determined on the basis of the balance between MeHg-mediated injury to neurons and protective responses from astrocytes. Although the role of neurons in MeHg intoxication is relatively well-established, the role of the astrocytes is only beginning to be understood. In this review, we update the information on astroglial modulation of the MeHg-induced neurotoxicity, providing remarks on their protective and deleterious roles and insights for future studies.
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Liao Y, Peng S, He L, Wang Y, Li Y, Ma D, Wang Y, Sun L, Zheng H, Yang W, Dai F, Zhao J. Methylmercury cytotoxicity and possible mechanisms in human trophoblastic HTR-8/SVneo cells. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2021; 207:111520. [PMID: 33254395 DOI: 10.1016/j.ecoenv.2020.111520] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 09/22/2020] [Accepted: 10/13/2020] [Indexed: 06/12/2023]
Abstract
Methylmercury (MeHg) exposure during pregnancy can lead to adverse outcomes, including miscarriage and intrauterine growth retardation. In this study, MeHg cytotoxicity and its mechanisms in HTR-8/SVneo cells were investigated. MeHg inhibited HTR-8/SVneo cell viability and severely disrupted the cellular submicrostructure, showing a time-dose effect relationship. After MeHg treatment, the reactive oxygen species levels, malondialdehyde content, and superoxide dismutase (SOD) and catalase activities in the HTR-8/SVneo cells increased significantly with increased MeHg concentration (P<0.05). Similarly, MeHg also induced HTR-8/SVneo cell apoptosis in a dose-dependent manner. The proportion of cells in G1 phase decreased with increasing MeHg concentration, while that in the S and G2/M phases gradually increased. Moreover, cell migration and invasion capacities gradually decreased with increasing MeHg concentration, showing a significant difference between the MeHg-treated and control groups. Genes related to oxidative stress (HSPA6, HSPA1A, Nrf2, SOD1, HO-1, NQO1, OSGIN1, and gPX1), cell cycle (P21 and CDC25A), apoptosis (CYCS and AIFM2), and migration and invasion (CXCL8, CXCL3, CLU, IL24, COL3A1, MAPT, and ITGA7) were differentially expressed in the MeHg-treated group, indicating MeHg toxicity and mechanism of action. This study will provide insights into the prevention and treatment of pregnancy-related diseases caused by MeHg.
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Affiliation(s)
- Ying Liao
- College of Life Science, Sichuan Normal University, Chengdu, 610101 Sichuan, PR China
| | - Shiqin Peng
- College of Life Science, Sichuan Normal University, Chengdu, 610101 Sichuan, PR China
| | - Lei He
- College of Life Science, Sichuan Normal University, Chengdu, 610101 Sichuan, PR China
| | - Yu Wang
- College of Life Science, Sichuan Normal University, Chengdu, 610101 Sichuan, PR China
| | - Yang Li
- College of Life Science, Sichuan Normal University, Chengdu, 610101 Sichuan, PR China
| | - Danwei Ma
- College of Life Science, Sichuan Normal University, Chengdu, 610101 Sichuan, PR China
| | - Yanan Wang
- College of Life Science, Sichuan Normal University, Chengdu, 610101 Sichuan, PR China
| | - Liang Sun
- Department of Pathology, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, PR China; Key Laboratory of Birth Defects and Related Diseases of Women and Children, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, PR China
| | - Hong Zheng
- College of Life Science, Sichuan Normal University, Chengdu, 610101 Sichuan, PR China
| | - Wenke Yang
- College of Life Science, Sichuan Normal University, Chengdu, 610101 Sichuan, PR China
| | - Fengyan Dai
- College of Life Science, Sichuan Normal University, Chengdu, 610101 Sichuan, PR China
| | - Jiayuan Zhao
- College of Life Science, Sichuan Normal University, Chengdu, 610101 Sichuan, PR China.
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Ben Bacha A, Norah AO, Al-Osaimi M, Harrath AH, Mansour L, El-Ansary A. The therapeutic and protective effects of bee pollen against prenatal methylmercury induced neurotoxicity in rat pups. Metab Brain Dis 2020; 35:215-224. [PMID: 31625070 DOI: 10.1007/s11011-019-00496-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Accepted: 09/12/2019] [Indexed: 12/14/2022]
Abstract
The current study evaluated the protective and therapeutic potency of bee pollen in ameliorating the toxic effects of methylmercury (MeHg), by measuring certain biochemical parameters related to neurotransmission, neuroinflammation, apoptosis, and glutamate excitotoxicity in the male neonate brain. Healthy, pregnant female rats (N = 40) were randomly divided into 5 groups, each comprising10 male neonates, as follows: (i) neonates delivered by control mothers; (ii) neonates delivered by MeHg-treated mothers who received 0.5 mg/kg BW/day MeHg via drinking water from gestational day 7 till postnatal day 7; (iii) neonates delivered by bee pollen treated mothers who received 200-mg/kg BW bee pollen from postnatal day 0 for 4 weeks; (iv) protective group of neonates delivered by MeHg and bee pollen-treated mothers, who continued to receive bee pollen until day 21 at the same dose, and (v) therapeutic group of neonates delivered by MeHg- treated mothers followed by bee pollen treatment, wherein they received 200-mg/kg BW bee pollen from postnatal day 0 for 4 weeks. Selected biochemical parameters in brain homogenates from each group were measured. MeHg-treated groups exhibited various signs of brain toxicity, such as a marked reduction in neurotransmitters (serotonin (5-HT), nor-adrenalin (NA), dopamine (DA)) and gamma aminobutyric acid (GABA) and elevated levels of interferon gamma (IFN-γ), caspase-3, and glutamate (Glu). Bee pollen effectively reduced the neurotoxic effects of MeHg. Minimal changes in all measured parameters were observed in MeHg-treated animals compared to the control group. Therefore, bee pollen may safely improve neurotransmitter defects, inflammation, apoptosis, and glutamate excitotoxicity.
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Affiliation(s)
- Abir Ben Bacha
- Biochemistry Department, Science College, King Saud University, P.O Box 22452, Riyadh, 11495, Saudi Arabia.
- Laboratory of Plant Biotechnology Applied to Crop Improvement, Faculty of Science of Sfax, University of Sfax, Sfax, Tunisia.
| | - Al-Orf Norah
- Biochemistry Department, Science College, King Saud University, P.O Box 22452, Riyadh, 11495, Saudi Arabia
- The Materials Science Research Institute, King Abdulaziz City for Science and Technology, Riyadh, Saudi Arabia
| | - May Al-Osaimi
- Biochemistry Department, Science College, King Saud University, P.O Box 22452, Riyadh, 11495, Saudi Arabia
| | - Abdel Halim Harrath
- Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Lamjed Mansour
- Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Afaf El-Ansary
- Central Laboratory, King Saud University, Riyadh, Saudi Arabia
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Watson WH, Ritzenthaler JD, Peyrani P, Wiemken TL, Furmanek S, Reyes Vega AM, Burke TJ, Zheng Y, Ramirez JA, Roman J. Plasma cysteine/cystine and glutathione/glutathione disulfide redox potentials in HIV and COPD patients. Free Radic Biol Med 2019; 143:55-61. [PMID: 31369840 PMCID: PMC6848776 DOI: 10.1016/j.freeradbiomed.2019.07.031] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 06/10/2019] [Accepted: 07/28/2019] [Indexed: 12/16/2022]
Abstract
Chronic obstructive pulmonary disease (COPD) is prevalent in patients infected with HIV. The purpose of this study was to test the hypothesis that systemic oxidation correlates with loss of lung function in subjects with COPD, and that HIV infection can contribute to creating such an environment. Subjects were recruited at the University of Louisville in the following groups: HIV-infected (n = 36), COPD (n = 32), HIV and COPD (n = 28), and uninfected controls with normal lung function (n = 34). HIV infection was assessed by viral load and CD4 cell counts. Pulmonary function was determined by spirometry, and plasma was collected for measurement of cysteine (Cys), cystine (CySS), glutathione (GSH) and GSH disulfide (GSSG) by HPLC followed by estimation of redox potentials (Eh) using the Nernst equation. Results showed that patients with COPD had more oxidized plasma Eh Cys/CySS than patients with normal lung function, but plasma Eh GSH/GSSG was unaltered. In addition, there was a correlation between the extent of plasma Eh Cys/CySS oxidation and loss of lung function, and this correlation remained even after correcting for age, sex, race and body mass index. HIV infection per se was not associated with increased oxidation of plasma Eh Cys/CySS, but plasma Eh Cys/CySS was more oxidized in patients with lower CD4-positve T cell counts. In patients with both HIV infection and COPD, there was a significant correlation between CD4 cell counts and lung function. Thus, systemic oxidation correlated with decreased lung function in subjects with COPD and decreased CD4 counts in subjects infected with HIV. Thus, factors contributing to plasma Eh Cys/CySS may represent novel mechanisms underlying the increased prevalence of COPD in people living with HIV.
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Affiliation(s)
- Walter H Watson
- Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition, University of Louisville School of Medicine, USA; Department of Pharmacology & Toxicology, University of Louisville School of Medicine, USA.
| | - Jeffrey D Ritzenthaler
- Department of Medicine, Division of Pulmonary, Critical Care, and Sleep Medicine, University of Louisville School of Medicine, USA
| | - Paula Peyrani
- Department of Medicine, Division of Infectious Diseases, University of Louisville School of Medicine, USA
| | - Timothy L Wiemken
- Department of Medicine, Division of Infectious Diseases, University of Louisville School of Medicine, USA
| | - Stephen Furmanek
- Department of Medicine, Division of Infectious Diseases, University of Louisville School of Medicine, USA
| | - Andrea M Reyes Vega
- Department of Medicine, Division of Infectious Diseases, University of Louisville School of Medicine, USA
| | - Tom J Burke
- Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition, University of Louisville School of Medicine, USA
| | - Yuxuan Zheng
- Department of Pharmacology & Toxicology, University of Louisville School of Medicine, USA
| | - Julio A Ramirez
- Department of Medicine, Division of Infectious Diseases, University of Louisville School of Medicine, USA; Robley Rex VA Medical Center, Louisville, KY, USA
| | - Jesse Roman
- Department of Medicine, Division of Pulmonary, Critical Care, and Sleep Medicine, University of Louisville School of Medicine, USA; Robley Rex VA Medical Center, Louisville, KY, USA
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Verkhratsky A, Parpura V, Vardjan N, Zorec R. Physiology of Astroglia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1175:45-91. [PMID: 31583584 DOI: 10.1007/978-981-13-9913-8_3] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Astrocytes are principal cells responsible for maintaining the brain homeostasis. Additionally, these glial cells are also involved in homocellular (astrocyte-astrocyte) and heterocellular (astrocyte-other cell types) signalling and metabolism. These astroglial functions require an expression of the assortment of molecules, be that transporters or pumps, to maintain ion concentration gradients across the plasmalemma and the membrane of the endoplasmic reticulum. Astrocytes sense and balance their neurochemical environment via variety of transmitter receptors and transporters. As they are electrically non-excitable, astrocytes display intracellular calcium and sodium fluctuations, which are not only used for operative signalling but can also affect metabolism. In this chapter we discuss the molecules that achieve ionic gradients and underlie astrocyte signalling.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK. .,Faculty of Health and Medical Sciences, Center for Basic and Translational Neuroscience, University of Copenhagen, 2200, Copenhagen, Denmark. .,Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, 48011, Bilbao, Spain.
| | - Vladimir Parpura
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Nina Vardjan
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia
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Yang B, Yin C, Zhou Y, Wang Q, Jiang Y, Bai Y, Qian H, Xing G, Wang S, Li F, Feng Y, Zhang Y, Cai J, Aschner M, Lu R. Curcumin protects against methylmercury-induced cytotoxicity in primary rat astrocytes by activating the Nrf2/ARE pathway independently of PKCδ. Toxicology 2019; 425:152248. [PMID: 31330227 PMCID: PMC6710134 DOI: 10.1016/j.tox.2019.152248] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 07/07/2019] [Accepted: 07/18/2019] [Indexed: 12/11/2022]
Abstract
Methylmercury (MeHg) is a ubiquitous environmental toxicant that leads to long-lasting neurological deficits in animals and humans. Curcumin, a polyphenol obtained from the rhizome of turmeric, has well-known antioxidant functions. Here, we evaluated curcumin's efficacy in mitigating MeHg-induced cytotoxicity and further investigated the underlying mechanism of this neuroprotection in primary rat astrocytes. Pretreatment with curcumin (2, 5, 10 and 20 μM for 3, 6, 12 or 24 h) protected against MeHg-induced (5 μM for 6 h) cell death in a time and dose-dependent manner. Curcumin (2, 5, 10 or 20 μM) pretreatment for 12 h significantly ameliorated the MeHg-induced astrocyte injury and oxidative stress, as evidenced by morphological alterations, lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) generation, and glutathione (GSH) and catalase (CAT) levels. Moreover, curcumin pretreatment increased Nrf2 nuclear translocation and downstream enzyme expression, heme oxygenase-1 (HO-1) and NADPH quinone reductase-1 (NQO1). Knockdown of Nrf2 with siRNA attenuated the protective effect of curcumin against MeHg-induced cell death. However, both the pan-protein kinase C (PKC) inhibitor, Ro 31-8220, and the selective PKCδ inhibitor, rottlerin, failed to suppress the curcumin-activated Nrf2/Antioxidant Response Element(ARE) pathway and attenuate the protection exerted by curcumin. Taken together, these findings confirm that curcumin protects against MeHg-induced neurotoxicity by activating the Nrf2/ARE pathway and this protection is independent of PKCδ activation. More studies are needed to understand the mechanisms of curcumin cytoprotection.
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Affiliation(s)
- Bobo Yang
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Changsheng Yin
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu 212013, China; Institute of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Yun Zhou
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Qiang Wang
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Yuanyue Jiang
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Yu Bai
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Hai Qian
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Guangwei Xing
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Suhua Wang
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Fang Li
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Yun Feng
- Department of Pharmacology, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Yubin Zhang
- Department of Occupational Health and Toxicology, School of Public Health, Fudan University, Shanghai 200032, China
| | - Jiyang Cai
- Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, TX 77550-1106, USA
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Rongzhu Lu
- Department of Preventive Medicine and Public Health Laboratory Sciences, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu 212013, China; Center for Experimental Research, Kunshan Hospital Affiliated to Jiangsu University, Kunshan, Jiangsu 215132, China.
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Zhou Z, Ikegaya Y, Koyama R. The Astrocytic cAMP Pathway in Health and Disease. Int J Mol Sci 2019; 20:E779. [PMID: 30759771 PMCID: PMC6386894 DOI: 10.3390/ijms20030779] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 02/06/2019] [Accepted: 02/08/2019] [Indexed: 12/11/2022] Open
Abstract
Astrocytes are major glial cells that play critical roles in brain homeostasis. Abnormalities in astrocytic functions can lead to brain disorders. Astrocytes also respond to injury and disease through gliosis and immune activation, which can be both protective and detrimental. Thus, it is essential to elucidate the function of astrocytes in order to understand the physiology of the brain to develop therapeutic strategies against brain diseases. Cyclic adenosine monophosphate (cAMP) is a major second messenger that triggers various downstream cellular machinery in a wide variety of cells. The functions of astrocytes have also been suggested as being regulated by cAMP. Here, we summarize the possible roles of cAMP signaling in regulating the functions of astrocytes. Specifically, we introduce the ways in which cAMP pathways are involved in astrocyte functions, including (1) energy supply, (2) maintenance of the extracellular environment, (3) immune response, and (4) a potential role as a provider of trophic factors, and we discuss how these cAMP-regulated processes can affect brain functions in health and disease.
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Affiliation(s)
- Zhiwen Zhou
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033, Japan.
| | - Yuji Ikegaya
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033, Japan.
- Center for Information and Neural Networks, Suita City, Osaka 565-0871, Japan.
| | - Ryuta Koyama
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033, Japan.
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Analyzing the Mechanisms Behind Macrolide Antibiotic-Induced Liver Injury Using Quantitative Systems Toxicology Modeling. Pharm Res 2019; 36:48. [PMID: 30734107 PMCID: PMC6373306 DOI: 10.1007/s11095-019-2582-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Accepted: 01/27/2019] [Indexed: 12/22/2022]
Abstract
PURPOSE Macrolide antibiotics are commonly prescribed treatments for drug-resistant bacterial infections; however, many macrolides have been shown to cause liver enzyme elevations and one macrolide, telithromycin, has been pulled from the market by its provider due to liver toxicity. This work seeks to assess the mechanisms responsible for the toxicity of macrolide antibiotics. METHODS Five macrolides were assessed in in vitro systems designed to test for bile acid transporter inhibition, mitochondrial dysfunction, and oxidative stress. The macrolides were then represented in DILIsym, a quantitative systems pharmacology (QST) model of drug-induced liver injury, placing the in vitro results in context with each compound's predicted liver exposure and known biochemistry. RESULTS DILIsym results suggest that solithromycin and clarithromycin toxicity is primarily due to inhibition of the mitochondrial electron transport chain (ETC) while erythromycin toxicity is primarily due to bile acid transporter inhibition. Telithromycin and azithromycin toxicity was not predicted by DILIsym and may be caused by mechanisms not currently incorporated into DILIsym or by unknown metabolite effects. CONCLUSIONS The mechanisms responsible for toxicity can be significantly different within a class of drugs, despite the structural similarity among the drugs. QST modeling can provide valuable insight into the nature of these mechanistic differences.
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Farina M, Aschner M. Glutathione antioxidant system and methylmercury-induced neurotoxicity: An intriguing interplay. Biochim Biophys Acta Gen Subj 2019; 1863:129285. [PMID: 30659883 DOI: 10.1016/j.bbagen.2019.01.007] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 12/09/2018] [Accepted: 01/09/2019] [Indexed: 01/20/2023]
Abstract
Methylmercury (MeHg) is a toxic chemical compound naturally produced mainly in the aquatic environment through the methylation of inorganic mercury catalyzed by aquatic microorganisms. MeHg is biomagnified in the aquatic food chain and, consequently, piscivorous fish at the top of the food chain possess huge amounts of MeHg (at the ppm level). Some populations that have fish as main protein's source can be exposed to exceedingly high levels of MeHg and develop signs of toxicity. MeHg is toxic to several organs, but the central nervous system (CNS) represents a preferential target, especially during development (prenatal and early postnatal periods). Though the biochemical events involved in MeHg-(neuro)toxicity are not yet entirely comprehended, a vast literature indicates that its pro-oxidative properties explain, at least partially, several of its neurotoxic effects. As result of its electrophilicity, MeHg interacts with (and oxidize) nucleophilic groups, such as thiols and selenols, present in proteins or low-molecular weight molecules. It is noteworthy that such interactions modify the redox state of these groups and, therefore, lead to oxidative stress and impaired function of several molecules, culminating in neurotoxicity. Among these molecules, glutathione (GSH; a major thiol antioxidant) and thiol- or selenol-containing enzymes belonging to the GSH antioxidant system represent key molecular targets involved in MeHg-neurotoxicity. In this review, we firstly present a general overview concerning the neurotoxicity of MeHg. Then, we present fundamental aspects of the GSH-antioxidant system, as well as the effects of MeHg on this system.
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Affiliation(s)
- Marcelo Farina
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, New York, USA
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Verkhratsky A, Ho MS, Vardjan N, Zorec R, Parpura V. General Pathophysiology of Astroglia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1175:149-179. [PMID: 31583588 PMCID: PMC7188602 DOI: 10.1007/978-981-13-9913-8_7] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Astroglial cells are involved in most if not in all pathologies of the brain. These cells can change the morpho-functional properties in response to pathology or innate changes of these cells can lead to pathologies. Overall pathological changes in astroglia are complex and diverse and often vary with different disease stages. We classify astrogliopathologies into reactive astrogliosis, astrodegeneration with astroglial atrophy and loss of function, and pathological remodelling of astrocytes. Such changes can occur in neurological, neurodevelopmental, metabolic and psychiatric disorders as well as in infection and toxic insults. Mutation in astrocyte-specific genes leads to specific pathologies, such as Alexander disease, which is a leukodystrophy. We discuss changes in astroglia in the pathological context and identify some molecular entities underlying pathology. These entities within astroglia may repent targets for novel therapeutic intervention in the management of brain pathologies.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester, M13 9PT, UK.
- Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
- Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, 48011, Bilbao, Spain.
| | - Margaret S Ho
- School of Life Science and Technology, ShanghaiTech University, 201210, Shanghai, China
| | - Nina Vardjan
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia
- Celica BIOMEDICAL, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia
- Celica BIOMEDICAL, Ljubljana, Slovenia
| | - Vladimir Parpura
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, USA
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Consolidating probiotic with dandelion, coriander and date palm seeds extracts against mercury neurotoxicity and for maintaining normal testosterone levels in male rats. Toxicol Rep 2018; 5:1069-1077. [PMID: 30425928 PMCID: PMC6224333 DOI: 10.1016/j.toxrep.2018.10.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 10/19/2018] [Accepted: 10/20/2018] [Indexed: 11/22/2022] Open
Abstract
Objective Heavy metals are major elements polluting our universe. The inhalation, ingestion or even contacting human body with these elements results in huge health problems. The most common pollutant in our surrounding is mercury. Therefore, the present study aimed to elucidating the protective ability of hot water extracts of dandelion (DA), coriander (CO), date palm seeds (DS), probiotic supernatant (PS) and their combined mixture against mercury-induced neurotoxicity and altered testosterone levels in male rats. Methods Fifty six male rats were randomly allotted into seven groups (n = 8 rats/group). Group1 (negative control; NC) animals were fed on the basal diet only, group2 (positive controls; PC) animals were fed on the basal diet and given an aqueous solution of mercuric chloride (25 ppm mercuric) in drinking water. Animals of the antioxidant-treated groups (3–7) were fed on the basal diet and given an aqueous solution of mercuric chloride (25 ppm mercuric) in drinking water together with the herbal antioxidant extracts and probiotics (25 ml/rat/day) throughout the experimental period. Where, group3 (Hg/CO) given coriander extract, group4 (Hg/DA) given dandelion extract, group5 (Hg/DS) given date palm seeds extract, group6 (Hg/PS) given probiotic supernatant, and group7 (Hg/Mix) given mixture of equal quantities of probiotic supernatant together with the three herbal extracts. The treatment lasted for 6 weeks, animals were sacrificed and blood samples were collected. Blood testosterone, enzyme activity and histopathological sections were performed. Results The obtained data exhibited that mercury intoxication revealed increases of lactic dehydrogenase and decreases of glutathione-s-transferase and testosterone. Light microscopic investigations of the brain cortex and cerebellum were suggestive of multiple foci of inflammation, cellular infiltration, gliosis and degeneration. Moreover, decreased glial fibrillary acidic protein (GFAP)-immunoreactivity and potential astrocyte toxicity both reflected impaired neuro-protective function of astrocytes necessary for maintaining the brain structure and function. Conclusion Administration of the herbal extracts and their mixture with probiotics enhance the body defense and contain protective factor against mercury neurotoxicity and for maintaining normal testosterone levels in male rats. Also, treatment restored the normal control levels of biochemical attributes and histological architecture.
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Antunes Dos Santos A, Ferrer B, Marques Gonçalves F, Tsatsakis AM, Renieri EA, Skalny AV, Farina M, Rocha JBT, Aschner M. Oxidative Stress in Methylmercury-Induced Cell Toxicity. TOXICS 2018; 6:toxics6030047. [PMID: 30096882 PMCID: PMC6161175 DOI: 10.3390/toxics6030047] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 08/03/2018] [Accepted: 08/07/2018] [Indexed: 02/06/2023]
Abstract
Methylmercury (MeHg) is a hazardous environmental pollutant, which elicits significant toxicity in humans. The accumulation of MeHg through the daily consumption of large predatory fish poses potential health risks, and the central nervous system (CNS) is the primary target of toxicity. Despite well-described neurobehavioral effects (i.e., motor impairment), the mechanisms of MeHg-induced toxicity are not completely understood. However, several lines of evidence point out the oxidative stress as an important molecular mechanism in MeHg-induced intoxication. Indeed, MeHg is a soft electrophile that preferentially interacts with nucleophilic groups (mainly thiols and selenols) from proteins and low-molecular-weight molecules. Such interaction contributes to the occurrence of oxidative stress, which can produce damage by several interacting mechanisms, impairing the function of various molecules (i.e., proteins, lipids, and nucleic acids), potentially resulting in modulation of different cellular signal transduction pathways. This review summarizes the general aspects regarding the interaction between MeHg with regulators of the antioxidant response system that are rich in thiol and selenol groups such as glutathione (GSH), and the selenoenzymes thioredoxin reductase (TrxR) and glutathione peroxidase (Gpx). A particular attention is directed towards the role of the PI3K/Akt signaling pathway and the nuclear transcription factor NF-E2-related factor 2 (Nrf2) in MeHg-induced redox imbalance.
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Affiliation(s)
| | - Beatriz Ferrer
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Filipe Marques Gonçalves
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Aristides M Tsatsakis
- Laboratory of Toxicology, Medical School, University of Crete, 71003 Heraklion, Greece.
| | - Elisavet A Renieri
- Laboratory of Toxicology, Medical School, University of Crete, 71003 Heraklion, Greece.
| | - Anatoly V Skalny
- Department of Medical Elementology, Peoples' Friendship University of Russia (RUDN University), Moscow 150000, Russia.
- Laboratory of Biotechnology and Applied Bioelementology, Yaroslavl State University, Yaroslavl 150014, Russia.
- All-Russian Research Institute of Medicinal and Aromatic Plants (VILAR), Moscow 150000, Russia.
| | - Marcelo Farina
- Department of Biochemistry, Federal University of Santa Catarina, Florianopolis 88040-900, Santa Catarina, Brazil.
| | - João B T Rocha
- Department of Biochemistry, Federal University of Santa Maria, Santa Maria 97105-900, Rio Grande do Sul, Brazil.
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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16
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Oxidative stress, caspase-3 activation and cleavage of ROCK-1 play an essential role in MeHg-induced cell death in primary astroglial cells. Food Chem Toxicol 2018; 113:328-336. [PMID: 29428217 DOI: 10.1016/j.fct.2018.01.057] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 01/30/2018] [Accepted: 01/31/2018] [Indexed: 12/13/2022]
Abstract
Methylmercury is a toxic environmental contaminant that elicits significant toxicity in humans. The central nervous system is the primary target of toxicity, and is particularly vulnerable during development. Rho-associated protein kinase 1 (ROCK-1) is a major downstream effector of the small GTPase RhoA and a direct substrate of caspase-3. The activation of ROCK-1 is necessary for membrane blebbing during apoptosis. In this work, we examined whether MeHg could affect the RhoA/ROCK-1 signaling pathway in primary cultures of mouse astrocytes. Exposure of cells with 10 μM MeHg decreased cellular viability after 24 h of incubation. This reduction in viability was preceded by a significant increase in intracellular and mitochondrial reactive oxygen species levels, as well as a reduced NAD+/NADH ratio. MeHg also induced an increase in mitochondrial-dependent caspase-9 and caspase-3, while the levels of RhoA protein expression were reduced or unchanged. We further found that MeHg induced ROCK-1 cleavage/activation and promoted LIMK1 and MYPT1 phosphorylation, both of which are the best characterized ROCK-1 downstream targets. Inhibiting ROCK-1 and caspases activation attenuated the MeHg-induced cell death. Collectively, these findings are the first to show that astrocytes exposed to MeHg showed increased cleavage/activation of ROCK-1, which was independent of the small GTPase RhoA.
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Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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18
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 899] [Impact Index Per Article: 149.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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19
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Banerjee M, Roy G. Cleavage of Hg–C Bonds of Organomercurials Induced by ImOHSe via Two Distinct Pathways. Inorg Chem 2017; 56:12739-12750. [DOI: 10.1021/acs.inorgchem.7b01301] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Mainak Banerjee
- Department of Chemistry, School of Natural
Sciences, Shiv Nadar University, NH91, Dadri, Gautam Buddha Nagar, Uttar Pradesh 201314, India
| | - Gouriprasanna Roy
- Department of Chemistry, School of Natural
Sciences, Shiv Nadar University, NH91, Dadri, Gautam Buddha Nagar, Uttar Pradesh 201314, India
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20
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Verkhratsky A, Zorec R, Parpura V. Stratification of astrocytes in healthy and diseased brain. Brain Pathol 2017; 27:629-644. [PMID: 28805002 PMCID: PMC5599174 DOI: 10.1111/bpa.12537] [Citation(s) in RCA: 153] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 06/03/2017] [Accepted: 06/06/2017] [Indexed: 12/11/2022] Open
Abstract
Astrocytes, a subtype of glial cells, come in variety of forms and functions. However, overarching role of these cell is in the homeostasis of the brain, be that regulation of ions, neurotransmitters, metabolism or neuronal synaptic networks. Loss of homeostasis represents the underlying cause of all brain disorders. Thus, astrocytes are likely involved in most if not all of the brain pathologies. We tabulate astroglial homeostatic functions along with pathological condition that arise from dysfunction of these glial cells. Classification of astrocytes is presented with the emphasis on evolutionary trails, morphological appearance and numerical preponderance. We note that, even though astrocytes from a variety of mammalian species share some common features, human astrocytes appear to be the largest and most complex of all astrocytes studied thus far. It is then an imperative to develop humanized models to study the role of astrocytes in brain pathologies, which is perhaps most abundantly clear in the case of glioblastoma multiforme.
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Affiliation(s)
- Alexei Verkhratsky
- Division of Neuroscience & Experimental PsychologyThe University of ManchesterManchesterUnited Kingdom
- Achúcarro Basque Center for NeuroscienceIKERBASQUE, Basque Foundation for Science48011 BilbaoSpain
- Department of NeuroscienceUniversity of the Basque Country UPV/EHU and CIBERNED48940 LeioaSpain
| | - Robert Zorec
- Laboratory of Cell EngineeringCelica BIOMEDICAL, Tehnološki park 24, Ljubljana 1000SloveniaEurope
- Laboratory of Neuroendocrinology‐Molecular Cell PhysiologyInstitute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, Ljubljana 1000SloveniaEurope
| | - Vladimir Parpura
- Department of Neurobiology, Civitan International Research Center and Center for Glial Biology in Medicine, Evelyn F. McKnight Brain Institute, Atomic Force Microscopy & Nanotechnology Laboratories, 1719 6th Avenue South, CIRC 429University of Alabama at BirminghamBirminghamAL 35294‐0021
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21
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Branco V, Caito S, Farina M, Teixeira da Rocha J, Aschner M, Carvalho C. Biomarkers of mercury toxicity: Past, present, and future trends. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2017; 20:119-154. [PMID: 28379072 PMCID: PMC6317349 DOI: 10.1080/10937404.2017.1289834] [Citation(s) in RCA: 130] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Mercury (Hg) toxicity continues to represent a global health concern. Given that human populations are mostly exposed to low chronic levels of mercurial compounds (methylmercury through fish, mercury vapor from dental amalgams, and ethylmercury from vaccines), the need for more sensitive and refined tools to assess the effects and/or susceptibility to adverse metal-mediated health risks remains. Traditional biomarkers, such as hair or blood Hg levels, are practical and provide a reliable measure of exposure, but given intra-population variability, it is difficult to establish accurate cause-effect relationships. It is therefore important to identify and validate biomarkers that are predictive of early adverse effects prior to adverse health outcomes becoming irreversible. This review describes the predominant biomarkers used by toxicologists and epidemiologists to evaluate exposure, effect and susceptibility to Hg compounds, weighing on their advantages and disadvantages. Most importantly, and in light of recent findings on the molecular mechanisms underlying Hg-mediated toxicity, potential novel biomarkers that might be predictive of toxic effect are presented, and the applicability of these parameters in risk assessment is examined.
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Affiliation(s)
- Vasco Branco
- a Research Institute for Medicines (iMed.ULisboa), Faculdade de Farmácia , Universidade de Lisboa , Lisboa , Portugal
| | - Sam Caito
- b Department of Molecular Pharmacology , Albert Einstein College of Medicine , Bronx , New York , USA
| | - Marcelo Farina
- c Departamento de Bioquímica, Centro de Ciências Biológicas , Universidade Federal de Santa Catarina , Florianópolis , Brazil
| | - João Teixeira da Rocha
- d Departamento Bioquímica e Biologia Molecular , Universidade Federal de Santa Maria , Santa Maria , RS , Brazil
| | - Michael Aschner
- b Department of Molecular Pharmacology , Albert Einstein College of Medicine , Bronx , New York , USA
| | - Cristina Carvalho
- a Research Institute for Medicines (iMed.ULisboa), Faculdade de Farmácia , Universidade de Lisboa , Lisboa , Portugal
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22
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Iwai-Shimada M, Takahashi T, Kim MS, Fujimura M, Ito H, Toyama T, Naganuma A, Hwang GW. Methylmercury induces the expression of TNF-α selectively in the brain of mice. Sci Rep 2016; 6:38294. [PMID: 27910896 PMCID: PMC5133575 DOI: 10.1038/srep38294] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 11/07/2016] [Indexed: 01/01/2023] Open
Abstract
Methylmercury selectively damages the central nervous system (CNS). The tumor necrosis factor (TNF) superfamily includes representative cytokines that participate in the inflammatory response as well as cell survival, and apoptosis. In this study, we found that administration of methylmercury selectively induced TNF-α expression in the brain of mice. Although the accumulated mercury concentration in the liver and kidneys was greater than in the brain, TNF-α expression was induced to a greater extent in brain. Thus, it is possible that there may exist a selective mechanism by which methylmercury induces TNF-α expression in the brain. We also found that TNF-α expression was induced by methylmercury in C17.2 cells (mouse neural stem cells) and NF-κB may participate as a transcription factor in that induction. Further, we showed that the addition of TNF-α antagonist (WP9QY) reduced the toxicity of methylmercury to C17.2 cells. In contrast, the addition of recombinant TNF-α to the culture medium decreased the cell viability. We suggest that TNF-α may play a part in the selective damage of the CNS by methylmercury. Furthermore, our results indicate that the higher TNF-α expression induced by methylmercury maybe the cause of cell death, as TNF-α binds to its receptor after being released extracellularly.
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Affiliation(s)
- Miyuki Iwai-Shimada
- Laboratory of Molecular and Biochemical Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan.,Center for Health and Environmental Risk Research, National Institute for Environmental Studies, Onogawa16-2, Tsukuba, Ibaraki 305-8506, Japan
| | - Tsutomu Takahashi
- Laboratory of Molecular and Biochemical Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan.,School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0232, Japan
| | - Min-Seok Kim
- Laboratory of Molecular and Biochemical Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan.,Department of Inhalation Toxicology Research, Korea Institute of Toxicology, Jeonbuk 56212, Republic of Korea
| | - Masatake Fujimura
- Department of Basic Medical Science, National Institute for Minamata Disease, Kumamoto 867-0008, Japan
| | - Hitoyasu Ito
- Department of Informative Clinical Medicine, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu 501-1194, Japan
| | - Takashi Toyama
- Laboratory of Molecular and Biochemical Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan
| | - Akira Naganuma
- Laboratory of Molecular and Biochemical Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan
| | - Gi-Wook Hwang
- Laboratory of Molecular and Biochemical Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan
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Antunes Dos Santos A, Appel Hort M, Culbreth M, López-Granero C, Farina M, Rocha JBT, Aschner M. Methylmercury and brain development: A review of recent literature. J Trace Elem Med Biol 2016; 38:99-107. [PMID: 26987277 PMCID: PMC5011031 DOI: 10.1016/j.jtemb.2016.03.001] [Citation(s) in RCA: 101] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 03/02/2016] [Indexed: 02/02/2023]
Abstract
Methylmercury (MeHg) is a potent environmental pollutant, which elicits significant toxicity in humans. The central nervous system (CNS) is the primary target of toxicity, and is particularly vulnerable during development. Maternal exposure to MeHg via consumption of fish and seafood can have irreversible effects on the neurobehavioral development of children, even in the absence of symptoms in the mother. It is well documented that developmental MeHg exposure may lead to neurological alterations, including cognitive and motor dysfunction. The neurotoxic effects of MeHg on the developing brain have been extensively studied. The mechanism of toxicity, however, is not fully understood. No single process can explain the multitude of effects observed in MeHg-induced neurotoxicity. This review summarizes the most current knowledge on the effects of MeHg during nervous system development considering both, in vitro and in vivo experimental models. Considerable attention was directed towards the role of glutamate and calcium dyshomeostasis, mitochondrial dysfunction, as well as the effects of MeHg on cytoskeletal components/regulators.
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Affiliation(s)
| | - Mariana Appel Hort
- Institute of Biological Sciences, Federal University of Rio Grande, Campus Carreiros, Rio Grande do Sul, Brazil
| | - Megan Culbreth
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Caridad López-Granero
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Marcelo Farina
- Department of Biochemistry, Federal University of Santa Catarina, Florianopolis, Santa Catarina, Brazil
| | - Joao B T Rocha
- Department of Biochemistry, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul, Brazil
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA.
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24
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Liu W, Xu Z, Yang T, Deng Y, Xu B, Feng S. Tea Polyphenols Protect Against Methylmercury-Induced Cell Injury in Rat Primary Cultured Astrocytes, Involvement of Oxidative Stress and Glutamate Uptake/Metabolism Disorders. Mol Neurobiol 2016; 53:2995-3009. [PMID: 25952541 DOI: 10.1007/s12035-015-9161-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 03/25/2015] [Indexed: 02/06/2023]
Abstract
Methylmercury (MeHg) is an extremely dangerous environmental contaminant, accumulating preferentially in CNS and causing a series of cytotoxic effects. However, the precise mechanisms are still incompletely understood. The current study explored the mechanisms that contribute to MeHg-induced cell injury focusing on the oxidative stress and Glu uptake/metabolism disorders in rat primary cultured astrocytes. Moreover, the neuroprotective effects of tea polyphenols (TP), a natural antioxidant, against MeHg cytotoxicity were also investigated. Astrocytes were exposed to 0, 2.5, 5, 10, and 20 μM MeHgCl for 6-30 h, or pretreated with 50, 100, 200, and 400 μM TP for 1-12 h; cell viability and LDH release were then determined. For further experiments, 50, 100, and 200 μM of TP pretreatment for 6 h followed by 10 μM MeHgCl for 24 h were performed for the examination of the responses of astrocytes, specifically addressing NPSH levels, ROS generation, ATPase activity, the expressions of Nrf2 pathway as well as Glu metabolism enzyme GS and Glu transporters (GLAST and GLT-1). Exposure of MeHg resulted in damages of astrocytes, which were shown by a loss of cell viability, and supported by high levels of LDH release, morphological changes, apoptosis rates, and NPSH depletion. In addition, astrocytes were sensitive to MeHg-mediated oxidative stress, a finding that is consistent with ROS overproduction; Nrf2 as well as its downstream genes HO-1 and γ-GCSh were markedly upregulated. Moreover, MeHg significantly inhibited GS activity, as well as expressions of GS, GLAST, and GLT-1. On the contrary, pretreatment with TP presented a concentration-dependent prevention against MeHg-mediated cytotoxic effects of astrocytes. In conclusion, the findings clearly indicated that MeHg aggravated oxidative stress and Glu uptake/metabolism dysfunction in astrocytes. TP possesses some abilities to prevent MeHg cytotoxicity through its antioxidative properties.
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Affiliation(s)
- Wei Liu
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122, Liaoning province, China
| | - Zhaofa Xu
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122, Liaoning province, China.
| | - Tianyao Yang
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122, Liaoning province, China
| | - Yu Deng
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122, Liaoning province, China
| | - Bin Xu
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122, Liaoning province, China
| | - Shu Feng
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122, Liaoning province, China
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Sulforaphane Prevents Methylmercury-Induced Oxidative Damage and Excitotoxicity Through Activation of the Nrf2-ARE Pathway. Mol Neurobiol 2016; 54:375-391. [PMID: 26742517 DOI: 10.1007/s12035-015-9643-y] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 12/16/2015] [Indexed: 12/29/2022]
Abstract
Methylmercury (MeHg) is a prominent environmental neurotoxicant, which induces oxidative damage and an indirect excitotoxicity caused by altered glutamate (Glu) metabolism. However, the interaction between oxidative damage and excitotoxicity in MeHg-exposed rats has not been fully recognized. Here, we explored the interaction between oxidative damage and excitotoxicity and evaluated the preventive effects of sulforaphane (SFN) on MeHg-induced neurotoxicity in rat cerebral cortex. Seventy-two rats were randomly assigned to four groups: control group, MeHg-treated groups (4 and 12 μmol/kg), and SFN pretreatment group. After treatment (28 days), the rats were killed and the cerebral cortex was analyzed. Then, Hg, glutathione (GSH), malondialdehyde (MDA), protein sulfhydryl, protein carbonyl, 8-hydroxy-2-deoxyguanosine (8-OHdG), and the levels of reactive oxygen species (ROS) and apoptosis were examined. Glu and glutamine (Gln) levels, glutamine synthetase (GS), phosphate-activated glutaminase (PAG), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), Na+-K+-ATPase and Ca2+-ATPase activities, intracellular Ca2+ levels, and the mRNA and protein expressions of Nrf2, Nrf2-regulated gene products, and N-methyl-D-aspartate receptors (NMDARs) were investigated in rat cerebral cortex. In our study, MeHg exposure not only induced Hg accumulation, apoptosis, ROS formation, GSH depletion, inhibition of antioxidant enzyme activities, and activation of Nrf2-ARE pathway signaling but also caused lipid, protein, and DNA peroxidative damage in a dose-dependent manner in rat cerebral cortex. Moreover, MeHg treatment significantly altered Gln/Glu cycling and NMDAR expression and resulted in calcium overloading. Furthermore, the present study also indicated that SFN pretreatment significantly reinforced the activation of the Nrf2-ARE pathway, which could prevent the toxic effects of MeHg exposure. Collectively, MeHg initiates multiple additive or synergistic disruptive mechanisms that lead to oxidative damage and excitotoxicity in rat cerebral cortex; pretreatment with SFN might prevent the MeHg-induced neurotoxicity by reinforcing the activation of the Nrf2-ARE pathway and then downregulating the interaction between oxidative damage and excitotoxicity pathways.
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Dysregulation of Glutamate Cycling Mediates Methylmercury-Induced Neurotoxicity. ADVANCES IN NEUROBIOLOGY 2016; 13:295-305. [PMID: 27885634 DOI: 10.1007/978-3-319-45096-4_11] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
To examine the toxicological implications of glutamate, this chapter will focus specifically on its impact in the brain. More explicitly, it will illustrate the role glutamate plays in mediating methylmercury (MeHg)-induced neurotoxicity. In this chapter, one intends to highlight the processes that occur prior to glutamate-stimulated excitotoxicity and subsequent neurodegeneration. As such, it will emphasize three main routes by which MeHg alters glutamate homeostasis. It is essential to recognize that these effects are not mutually exclusive, and that they synergistically influence glutamate dysregulation. Furthermore, the consequences of MeHg exposure will be presented here as a direct pathway; however, it must be noted these effects occur simultaneously. First, glutamate uptake will be reviewed emphasizing the function of astrocytes. Next, the induction of oxidative stress by MeHg exposure will be discussed. This process has a two-fold effect on glutamate homeostasis by (1) inhibiting extracellular glutamate uptake and (2) altering transcription of genes vital to glutamate cycling. Finally, the impact glutamate dysregulation has on glutathione synthesis will be examined. Although this chapter centers on the link between glutamate and MeHg toxicity, it is imperative that the reader acknowledges the processes discussed here can be extended to any pro-oxidant.
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Patel D, Kharkar PS, Nandave M. Emerging roles of system antiporter and its inhibition in CNS disorders. Mol Membr Biol 2015; 32:89-116. [PMID: 26508554 DOI: 10.3109/09687688.2015.1096972] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
| | - Prashant S. Kharkar
- Department of Pharmaceutical Chemistry, SPP School of Pharmacy and Technology Management, SVKM’s NMIMS University, Mumbai, India
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Puttachary S, Sharma S, Stark S, Thippeswamy T. Seizure-induced oxidative stress in temporal lobe epilepsy. BIOMED RESEARCH INTERNATIONAL 2015; 2015:745613. [PMID: 25650148 PMCID: PMC4306378 DOI: 10.1155/2015/745613] [Citation(s) in RCA: 142] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 09/11/2014] [Accepted: 09/11/2014] [Indexed: 01/08/2023]
Abstract
An insult to the brain (such as the first seizure) causes excitotoxicity, neuroinflammation, and production of reactive oxygen/nitrogen species (ROS/RNS). ROS and RNS produced during status epilepticus (SE) overwhelm the mitochondrial natural antioxidant defense mechanism. This leads to mitochondrial dysfunction and damage to the mitochondrial DNA. This in turn affects synthesis of various enzyme complexes that are involved in electron transport chain. Resultant effects that occur during epileptogenesis include lipid peroxidation, reactive gliosis, hippocampal neurodegeneration, reorganization of neural networks, and hypersynchronicity. These factors predispose the brain to spontaneous recurrent seizures (SRS), which ultimately establish into temporal lobe epilepsy (TLE). This review discusses some of these issues. Though antiepileptic drugs (AEDs) are beneficial to control/suppress seizures, their long term usage has been shown to increase ROS/RNS in animal models and human patients. In established TLE, ROS/RNS are shown to be harmful as they can increase the susceptibility to SRS. Further, in this paper, we review briefly the data from animal models and human TLE patients on the adverse effects of antiepileptic medications and the plausible ameliorating effects of antioxidants as an adjunct therapy.
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Affiliation(s)
- Sreekanth Puttachary
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA
| | - Shaunik Sharma
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA
| | - Sara Stark
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA
| | - Thimmasettappa Thippeswamy
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA
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Feng S, Xu Z, Liu W, Li Y, Deng Y, Xu B. Preventive effects of dextromethorphan on methylmercury-induced glutamate dyshomeostasis and oxidative damage in rat cerebral cortex. Biol Trace Elem Res 2014; 159:332-45. [PMID: 24819089 DOI: 10.1007/s12011-014-9977-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Accepted: 04/10/2014] [Indexed: 12/29/2022]
Abstract
Methylmercury (MeHg) is a well-known environmental pollutant leading to neurotoxicant associated with aberrant central nervous system (CNS) functions, but its toxic mechanisms have not yet been fully recognized. In the present study, we tested the hypothesis that MeHg induces neuronal injury via glutamate (Glu) dyshomeostasis and oxidative damage mechanisms and that these effects are attenuated by dextromethorphan (DM), a low-affinity and noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist. Seventy-two rats were randomly divided into four groups of 18 animals in each group: control group, MeHg-treated group (4 and 12 μmol/kg), and DM-pretreated group. After the 4-week treatment, we observed that the administration of MeHg at a dose of 12 μmol/kg significantly increased in total mercury (Hg) levels, disrupted Glu metabolism, overexcited NMDARs, and led to intracellular calcium overload in the cerebral cortex. We also found that MeHg reduced nonenzymatic and enzymatic antioxidants, enhanced neurocyte apoptosis, induced reactive oxygen species (ROS), and caused lipid, protein, and DNA peroxidative damage in the cerebral cortex. Moreover, glutamate/aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) appeared to be inhibited by MeHg exposure. These alterations were significantly prevented by the pretreatment with DM at a dose of 13.5 μmol/kg. In conclusion, these findings strongly implicate that DM has potential to protect the brain from Glu dyshomeostasis and oxidative damage resulting from MeHg-induced neurotoxicity in rat.
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Affiliation(s)
- Shu Feng
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, People's Republic of China
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The Glutathione System: A New Drug Target in Neuroimmune Disorders. Mol Neurobiol 2014; 50:1059-84. [DOI: 10.1007/s12035-014-8705-x] [Citation(s) in RCA: 119] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Accepted: 03/31/2014] [Indexed: 01/17/2023]
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Krzyżanowska W, Pomierny B, Filip M, Pera J. Glutamate transporters in brain ischemia: to modulate or not? Acta Pharmacol Sin 2014; 35:444-62. [PMID: 24681894 DOI: 10.1038/aps.2014.1] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 01/03/2014] [Indexed: 01/18/2023] Open
Abstract
In this review, we briefly describe glutamate (Glu) metabolism and its specific transports and receptors in the central nervous system (CNS). Thereafter, we focus on excitatory amino acid transporters, cystine/glutamate antiporters (system xc-) and vesicular glutamate transporters, specifically addressing their location and roles in CNS and the molecular mechanisms underlying the regulation of Glu transporters. We provide evidence from in vitro or in vivo studies concerning alterations in Glu transporter expression in response to hypoxia or ischemia, including limited human data that supports the role of Glu transporters in stroke patients. Moreover, the potential to induce brain tolerance to ischemia through modulation of the expression and/or activities of Glu transporters is also discussed. Finally we present strategies involving the application of ischemic preconditioning and pharmacological agents, eg β-lactam antibiotics, amitriptyline, riluzole and N-acetylcysteine, which result in the significant protection of nervous tissues against ischemia.
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In vitro to in vivo extrapolation and species response comparisons for drug-induced liver injury (DILI) using DILIsym™: a mechanistic, mathematical model of DILI. J Pharmacokinet Pharmacodyn 2012; 39:527-41. [DOI: 10.1007/s10928-012-9266-0] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 07/25/2012] [Indexed: 12/16/2022]
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Santello M, Calì C, Bezzi P. Gliotransmission and the tripartite synapse. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 970:307-31. [PMID: 22351062 DOI: 10.1007/978-3-7091-0932-8_14] [Citation(s) in RCA: 145] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
In the last years, the classical view of glial cells (in particular of astrocytes) as a simple supportive cell for neurons has been replaced by a new vision in which glial cells are active elements of the brain. Such a new vision is based on the existence of a bidirectional communication between astrocytes and neurons at synaptic level. Indeed, perisynaptic processes of astrocytes express active G-protein-coupled receptors that are able (1) to sense neurotransmitters released from the synapse during synaptic activity, (2) to increase cytosolic levels of calcium, and (3) to stimulate the release of gliotransmitters that in turn can interact with the synaptic elements. The mechanism(s) by which astrocytes can release gliotransmitter has been extensively studied during the last years. Many evidences have suggested that a fraction of astrocytes in situ release neuroactive substances both with calcium-dependent and calcium-independent mechanism(s); whether these mechanisms coexist and under what physiological or pathological conditions they occur, it remains unclear. However, the calcium-dependent exocytotic vesicular release has received considerable attention due to its potential to occur under physiological conditions via a finely regulated way. By releasing gliotransmitters in millisecond time scale with a specific vesicular apparatus, astrocytes can integrate and process synaptic information and control or modulate synaptic transmission and plasticity.
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Affiliation(s)
- Mirko Santello
- DBCM, Department of Physiology, University of Bern, Bühlplatz 5, 3012 Bern, Switzerland
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Bridges RJ, Natale NR, Patel SA. System xc⁻ cystine/glutamate antiporter: an update on molecular pharmacology and roles within the CNS. Br J Pharmacol 2012; 165:20-34. [PMID: 21564084 DOI: 10.1111/j.1476-5381.2011.01480.x] [Citation(s) in RCA: 353] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
System x(c)(-) is an amino acid antiporter that typically mediates the exchange of extracellular l-cystine and intracellular L-glutamate across the cellular plasma membrane. Studied in a variety of cell types, the import of L-cystine through this transporter is critical to glutathione production and oxidative protection. The exchange-mediated export of L-glutamate takes on added significance within the CNS, as it represents a non-vesicular route of release through which this excitatory neurotransmitter can participate in either neuronal signalling or excitotoxic pathology. When both the import of L-cystine and the export of L-glutamate are taken into consideration, system x(c)(-) has now been linked to a wide range of CNS functions, including oxidative protection, the operation of the blood-brain barrier, neurotransmitter release, synaptic organization, viral pathology, drug addiction, chemosensitivity and chemoresistance, and brain tumour growth. The ability to selectively manipulate system x(c)(-), delineate its function, probe its structure and evaluate it as a therapeutic target is closely linked to understanding its pharmacology and the subsequent development of selective inhibitors and substrates. Towards that goal, this review will examine the current status of our understanding of system x(c)(-) pharmacology and the structure-activity relationships that have guided the development of an initial pharmacophore model, including the presence of lipophilic domains adjacent to the substrate binding site. A special emphasis is placed on the roles of system x(c)(-) within the CNS, as it is these actions that are among the most exciting as potential long-range therapeutic targets.
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Affiliation(s)
- Richard J Bridges
- Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, USA.
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Yang H, Xu Z, Liu W, Wei Y, Deng Y, Xu B. Effect of grape seed proanthocyanidin extracts on methylmercury-induced neurotoxicity in rats. Biol Trace Elem Res 2012; 147:156-64. [PMID: 22116679 DOI: 10.1007/s12011-011-9272-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 11/13/2011] [Indexed: 10/15/2022]
Abstract
As a highly toxic environmental pollutant, methylmercury (MeHg) can cause neurotoxicity in animals and humans. Considering the antioxidant property of grape seed proanthocyanidin extracts (GSPE), this study was aimed to evaluate the effect of GSPE on MeHg-induced neurotoxicity in rats. Rats were exposed to MeHg by intraperitoneal injection (4, 12 μmol/kg, respectively) and GSPE was administered by gavage (250 mg/kg) 2 h later. After a 4-week treatment, phosphate-activated glutaminase, glutamine synthetase, glutathione peroxidase and superoxide dismutase activities, glutamate, glutamine, malondialdehyde and glutathione contents in cerebral cortex were measured. Reactive oxygen species (ROS) and apoptosis were also estimated in cells. The results showed that the MeHg-induced neurotoxicity was significantly attenuated. GSPE significantly decreased the production of ROS, counteracted oxidative damage and increased the antioxidants and antioxidant enzymes activities in rats prior to MeHg exposure. Moreover, the effects on the rate of apoptotic cells and the disturbance of glutamate homeostasis were correspondingly modulated. These observations highlighted the potential of GSPE in offering protection against MeHg-induced neurotoxicity.
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Affiliation(s)
- Haibo Yang
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, China
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Blossom SJ, Melnyk S, Cooney CA, Gilbert KM, James SJ. Postnatal exposure to trichloroethylene alters glutathione redox homeostasis, methylation potential, and neurotrophin expression in the mouse hippocampus. Neurotoxicology 2012; 33:1518-1527. [PMID: 22421312 DOI: 10.1016/j.neuro.2012.02.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 02/27/2012] [Accepted: 02/27/2012] [Indexed: 12/23/2022]
Abstract
Previous studies have shown that continuous exposure throughout gestation until the juvenile period to environmentally relevant doses of trichloroethylene (TCE) in the drinking water of MRL+/+ mice promoted adverse behavior associated with glutathione depletion in the cerebellum indicating increased sensitivity to oxidative stress. The purpose of this study was to extend our findings and further characterize the impact of TCE exposure on redox homeostasis and biomarkers of oxidative stress in the hippocampus, a brain region prone to oxidative stress. Instead of a continuous exposure, the mice were exposed to water only or two environmentally relevant doses of TCE in the drinking water postnatally from birth until 6 weeks of age. Biomarkers of plasma metabolites in the transsulfuration pathway and the transmethylation pathway of the methionine cycle were also examined. Gene expression of neurotrophins was examined to investigate a possible relationship between oxidative stress, redox imbalance and neurotrophic factor expression with TCE exposure. Our results show that hippocampi isolated from male mice exposed to TCE showed altered glutathione redox homeostasis indicating a more oxidized state. Also observed was a significant, dose dependent increase in glutathione precursors. Plasma from the TCE treated mice showed alterations in metabolites in the transsulfuration and transmethylation pathways indicating redox imbalance and altered methylation capacity. 3-Nitrotyrosine, a biomarker of protein oxidative stress, was also significantly higher in plasma and hippocampus of TCE-exposed mice compared to controls. In contrast, expression of key neurotrophic factors in the hippocampus (BDNF, NGF, and NT-3) was significantly reduced compared to controls. Our results demonstrate that low-level postnatal and early life TCE exposure modulates neurotrophin gene expression in the mouse hippocampus and may provide a mechanism for TCE-mediated neurotoxicity.
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Affiliation(s)
- Sarah J Blossom
- Department of Pediatrics, University of Arkansas for Medical Sciences, College of Medicine, Arkansas Children's Hospital Research Institute, 13 Children's Way, Little Rock, AR 72202, United States.
| | - Stepan Melnyk
- Department of Pediatrics, University of Arkansas for Medical Sciences, College of Medicine, Arkansas Children's Hospital Research Institute, 13 Children's Way, Little Rock, AR 72202, United States
| | - Craig A Cooney
- Department of Research and Development, Central Arkansas Veterans Healthcare System, Little Rock, AR 72205, United States
| | - Kathleen M Gilbert
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, College of Medicine, Arkansas Children's Hospital Research Institute, 13 Children's Way, Little Rock, AR 72202, United States
| | - S Jill James
- Department of Pediatrics, University of Arkansas for Medical Sciences, College of Medicine, Arkansas Children's Hospital Research Institute, 13 Children's Way, Little Rock, AR 72202, United States
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Giraudi PJ, Bellarosa C, Coda-Zabetta CD, Peruzzo P, Tiribelli C. Functional induction of the cystine-glutamate exchanger system Xc(-) activity in SH-SY5Y cells by unconjugated bilirubin. PLoS One 2011; 6:e29078. [PMID: 22216172 PMCID: PMC3246462 DOI: 10.1371/journal.pone.0029078] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Accepted: 11/21/2011] [Indexed: 12/18/2022] Open
Abstract
We have previously reported that exposure of SH-SY5Y neuroblastoma cells to unconjugated bilirubin (UCB) resulted in a marked up-regulation of the mRNA encoding for the Na+ -independent cystine∶glutamate exchanger System Xc− (SLC7A11 and SLC3A2 genes). In this study we demonstrate that SH-SY5Y cells treated with UCB showed a higher cystine uptake due to a significant and specific increase in the activity of System Xc−, without the contribution of the others two cystine transporters (XAG− and GGT) reported in neurons. The total intracellular glutathione content was 2 folds higher in the cells exposed to bilirubin as compared to controls, suggesting that the internalized cystine is used for gluthathione synthesis. Interestingly, these cells were significantly less sensitive to an oxidative insult induced by hydrogen peroxide. If System Xc− is silenced the protection is lost. In conclusion, these results suggest that bilirubin can modulate the gluthathione levels in neuroblastoma cells through the induction of the System Xc−, and this renders the cell less prone to oxidative damage.
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Affiliation(s)
- Pablo J Giraudi
- Centro Studi Fegato, Fondazione Italiana Fegato, Trieste, Italy
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Wormser U, Brodsky B, Milatovic D, Finkelstein Y, Farina M, Rocha JB, Aschner M. Protective effect of a novel peptide against methylmercury-induced toxicity in rat primary astrocytes. Neurotoxicology 2011; 33:763-8. [PMID: 22186600 DOI: 10.1016/j.neuro.2011.12.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 12/02/2011] [Accepted: 12/06/2011] [Indexed: 10/14/2022]
Abstract
Methylmercury (MeHg) is an environmental neurotoxicant associated with aberrant central nervous system (CNS) functions. In this study, we examined the protective effect of a novel anti-inflammatory and cytoprotective nonapeptide, termed IIIM1, against MeHg-induced toxicity in cultured rat neonatal primary astrocytes. Astrocytes were pretreated for 66 h with 5 μg/ml IIIM1 (4.95 μM) followed by 6 h exposure to MeHg (5 μM). MeHg significantly increased F(2)-isoprostane generation, a lipid peroxidation biomarker of oxidative injury and this effect was significantly reduced upon pre-treatment with IIIM1. The MeHg-induced increase in levels of prostaglandin E(2) (PGE(2)), biomarkers of inflammatory responses, was also decreased in the peptide-treated cells. Mass spectrometry analysis revealed no chemical or binding interaction between MeHg and IIIM1, indicating that intracellular cytoprotective mechanism of action accounts for the neuroprotection rather than direct intracellular neutralization of the neurotoxicant with the peptide. These findings point to therapeutic potential for IIIM1 in a plethora of conditions associated with reactive oxygen species (ROS) generation. The implication of these findings may prove beneficial in designing new treatment modalities that efficiently suppress neurotoxicity, triggered not only by MeHg, but also by other metals and environmental agents, as well as chronic disease conditions that inherently increase reactive radical production and inflammatory signaling.
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Affiliation(s)
- Uri Wormser
- Institute of Drug Research, School of Pharmacy, the Hebrew University, 91120 Jerusalem, Israel
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Seib TM, Patel SA, Bridges RJ. Regulation of the system x(C)- cystine/glutamate exchanger by intracellular glutathione levels in rat astrocyte primary cultures. Glia 2011; 59:1387-401. [PMID: 21590811 DOI: 10.1002/glia.21176] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Accepted: 03/18/2011] [Indexed: 12/31/2022]
Abstract
The system x(C)- (Sx(C)-) transporter functions to mediate the exchange of extracellular cystine (L-Cys(2)) and intracellular glutamate (L-Glu). Internalized L-Cys(2) serves as a rate-limiting precursor for the biosynthesis of glutathione (GSH), while the externalized L-Glu can contribute to either excitatory signaling or excitotoxicity. In the present study the influence of culture conditions (with and without dibutyryl-cAMP) and GSH levels on the expression of Sx(C)- were investigated in primary rat astrocyte cultures. Sx(C)- activity in dbcAMP-treated cells was nearly sevenfold greater than in untreated astrocytes and increased further (∼threefold) following the depletion of intracellular GSH with buthionine sulfoximine. This increase in Sx(C)- triggered by GSH depletion was only observed in the dbcAMP-treated phenotype and was distinct from the Nrf2-mediated response initiated by exposure to electrophiles. Changes in Sx(C)- activity correlated with increases in both protein and mRNA levels of the xCT subunit of the Sx(C)- heterodimer, an increase in the V(max) for L-Glu uptake and was linked temporally to GSH levels. This induction of Sx(C)- was not mimicked by hydrogen peroxide nor attenuated by nonspecific antioxidants but was partially prevented by the co-administration of the cell-permeant thiols GSH-ethyl ester and N-acetylcysteine. These findings demonstrate that the expression of Sx(C)- on astrocytes is dynamically regulated by intracellular GSH levels in a cell- and phenotype-dependent manner. The presence of this pathway likely reflects the inherent vulnerability of the CNS to oxidative damage and raises interesting questions as to the functional consequences of changes in Sx(C)- activity in CNS injury and disease.
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Affiliation(s)
- Todd Michael Seib
- CSFN, Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, USA
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Garrecht M, Austin DW. The plausibility of a role for mercury in the etiology of autism: a cellular perspective. TOXICOLOGICAL AND ENVIRONMENTAL CHEMISTRY 2011; 93:1251-1273. [PMID: 22163375 PMCID: PMC3173748 DOI: 10.1080/02772248.2011.580588] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 04/10/2011] [Indexed: 05/23/2023]
Abstract
Autism is defined by a behavioral set of stereotypic and repetitious behavioral patterns in combination with social and communication deficits. There is emerging evidence supporting the hypothesis that autism may result from a combination of genetic susceptibility and exposure to environmental toxins at critical moments in development. Mercury (Hg) is recognized as a ubiquitous environmental neurotoxin and there is mounting evidence linking it to neurodevelopmental disorders, including autism. Of course, the evidence is not derived from experimental trials with humans but rather from methods focusing on biomarkers of Hg damage, measurements of Hg exposure, epidemiological data, and animal studies. For ethical reasons, controlled Hg exposure in humans will never be conducted. Therefore, to properly evaluate the Hg-autism etiological hypothesis, it is essential to first establish the biological plausibility of the hypothesis. This review examines the plausibility of Hg as the primary etiological agent driving the cellular mechanisms by which Hg-induced neurotoxicity may result in the physiological attributes of autism. Key areas of focus include: (1) route and cellular mechanisms of Hg exposure in autism; (2) current research and examples of possible genetic variables that are linked to both Hg sensitivity and autism; (3) the role Hg may play as an environmental toxin fueling the oxidative stress found in autism; (4) role of mitochondrial dysfunction; and (5) possible role of Hg in abnormal neuroexcitory and excitotoxity that may play a role in the immune dysregulation found in autism. Future research directions that would assist in addressing the gaps in our knowledge are proposed.
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Affiliation(s)
- Matthew Garrecht
- Swinburne Autism Bio-Research Initiative, Faculty of Life and Social Sciences, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
| | - David W. Austin
- Swinburne Autism Bio-Research Initiative, Faculty of Life and Social Sciences, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
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Had-Aissouni L. Toward a new role for plasma membrane sodium-dependent glutamate transporters of astrocytes: maintenance of antioxidant defenses beyond extracellular glutamate clearance. Amino Acids 2011; 42:181-97. [DOI: 10.1007/s00726-011-0863-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 02/17/2011] [Indexed: 01/17/2023]
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Roos DH, Puntel RL, Lugokenski TH, Ineu RP, Bohrer D, Burger ME, Franco JL, Farina M, Aschner M, Rocha JBT, de Vargas Barbosa NB. Complex methylmercury-cysteine alters mercury accumulation in different tissues of mice. Basic Clin Pharmacol Toxicol 2011; 107:789-92. [PMID: 20486922 DOI: 10.1111/j.1742-7843.2010.00577.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Methylmercury (MeHg) can cause deleterious effects in vertebrate tissues, particularly in the central nervous system. MeHg interacts with sulfhydryl groups from low and high molecular weight thiols in the blood, which can facilitate MeHg uptake into different tissues. The purpose of this study was to examine the effect of MeHg-Cysteine (MeHg-Cys) complex administration on Hg-uptake in cerebral areas (cortex and cerebellum), liver and kidney of adult mice. Animals were divided into four groups: control (1 mL/kg distilled water), MeHg (2 mg/kg), Cys (2 mg/kg) and MeHg-Cys complex (0.8 molar ratio). Mice received one intraperitoneal injection per day for 60 consecutive days. Treatment with MeHg significantly increased mercury concentrations in all tissues analysed when compared with the control group. The accumulation of mercury in brain and in liver was further increased in animals that received MeHg-Cys complex when compared with the MeHg alone group. However, renal Hg decreased in MeHg-Cys treated mice, when compared with the group treated only with MeHg. In summary, the transport of MeHg-Cys complex was tissue-specific, and we observed an increase in its uptake by liver and brain as well as a decrease in kidney.
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Affiliation(s)
- Daniel Henrique Roos
- Departamento de Química, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil
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Oliveira KRM, Herculano AM, Crespo-López ME, do Nascimento JLM. Pharmacological characterization of glutamate Na+-independent transport in retinal cell cultures: Implications in the glutathione metabolism. Neurochem Int 2010; 56:59-66. [DOI: 10.1016/j.neuint.2009.09.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Revised: 09/03/2009] [Accepted: 09/07/2009] [Indexed: 11/30/2022]
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Yin Z, Albrecht J, Syversen T, Jiang H, Summar M, Rocha JBT, Farina M, Aschner M. Comparison of alterations in amino acids content in cultured astrocytes or neurons exposed to methylmercury separately or in co-culture. Neurochem Int 2009; 55:136-42. [PMID: 19428818 DOI: 10.1016/j.neuint.2009.01.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Revised: 01/20/2009] [Accepted: 01/21/2009] [Indexed: 10/21/2022]
Abstract
Methylmercury (MeHg) is an environmental toxicant that induces enduring neuropsychological deficits in humans. Although the mechanisms associated with MeHg-induced neurotoxicity have not yet been fully elucidated, some lines of evidence point out to excitatory amino acids dyshomeostasis as an important outcome of MeHg exposure. The present study was designed to characterize the effects of MeHg on amino acid content in co-cultured astrocytes and neurons or in each cell type under solitary conditions. The results showed that glutamate concentrations significantly decreased in neurons, but not in astrocyte cultures exposed to 10 microM MeHg. The decrease in neurons was fully reversed when these cells were co-cultured with astrocytes. The content of other amino acids (aspartate, alanine, glycine and serine) decreased upon exposure to 10 microM MeHg in both neurons and astrocytes cultured in solitary conditions, although the effect was generally smaller in astrocytes than in neurons. However, the content of these amino acids in each of the cell types was indistinguishable from controls when co-cultures were treated with MeHg. Overall, the results indicate that astrocytes, which are more resistant to amino acid modulation by MeHg, can (i) mitigate the effects of MeHg that occur in neurons cultured in solitary conditions and (ii) become themselves more MeHg resistant in the presence of neurons. Delineating the mechanisms underlying the mutual neuroprotective effects of astrocytes and neurons in co-culture to MeHg-induced amino acid imbalance requires further investigation.
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Affiliation(s)
- Zhaobao Yin
- Department of Pediatrics, and the Kennedy Center for Research on Human Development, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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Amonpatumrat S, Sakurai H, Wiriyasermkul P, Khunweeraphong N, Nagamori S, Tanaka H, Piyachaturawat P, Kanai Y. L-glutamate enhances methylmercury toxicity by synergistically increasing oxidative stress. J Pharmacol Sci 2009; 108:280-9. [PMID: 19023177 DOI: 10.1254/jphs.08118fp] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Methylmercury (MeHg) is a well-known environmental toxicant. With its lipophilic nature and high reactivity to sulfhydryl groups, it is widely distributed and accumulated in the body to damage cells. Oxidative stress is proposed as a major mechanism underlying the cytotoxic action of MeHg. In the present study, we found that L-glutamate (L-Glu) concentration-dependently increased MeHg cytotoxicity in HeLa S3 cells. The enhancement of the toxicity was accompanied by enhanced apoptosis, increased production of reactive oxygen species, and decreased glutathione level. An anti-oxidant N-acetylcysteine largely alleviated the cytotoxicity, suggesting enhanced oxidative stress behind L-Glu-elicited increase of MeHg toxicity. The effect was specific to L-Glu and L-alpha-aminoadipate, whereas D-Glu, L-aspartate, and D-aspartate were not effective. In addition, the cystine uptake by the cells was mostly mediated by a L-Glu/L-alpha-aminoadipate-sensitive amino acid transport system x(-)(C). All these results suggest that the inhibition of system x(-)(C) by L-Glu underlies the enhancement of MeHg cytotoxicity. The enhancement was highly synergistic because MeHg and L-Glu alone had little toxic effect in the conditions used. This synergism was confirmed in neural cells (neuroblastoma cell lines). It is proposed that similar mechanisms may underlie the neural toxicity of MeHg, particularly in the locality of lesions characteristic of MeHg toxicity.
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Affiliation(s)
- Sirirat Amonpatumrat
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Tokyo, Japan
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Wang L, Jiang H, Yin Z, Aschner M, Cai J. Methylmercury toxicity and Nrf2-dependent detoxification in astrocytes. Toxicol Sci 2009; 107:135-43. [PMID: 18815141 PMCID: PMC2638644 DOI: 10.1093/toxsci/kfn201] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Accepted: 09/16/2008] [Indexed: 12/30/2022] Open
Abstract
Methylmercury (MeHg) is a potent neurotoxicant and preferentially induces oxidative injury in astrocytes. In neuronal tissues, nuclear factor erythroid 2-related factor 2 (Nrf2) is a key factor determining the protective antioxidant response against various environmental toxicants. Nrf2 is subjected to regulation by many other signaling pathways. The purpose of this study is to characterize its interaction with the phosphatidylinositol 3 (PI3) kinase in cultured rat neonatal primary astrocytes. The results showed that at pathologically relevant concentrations, exposure of primary astrocytes to MeHg led to Nrf2 activation and upregulation of its downstream antioxidant genes. Inhibition of the PI3 kinase resulted in decreased Nrf2 activity, decreased cellular glutathione, and increased cell death to high-dose MeHg. The functional interaction between the two signaling pathways underlined an important mechanism for astrocyte protection against MeHg toxicity. Modulation of Nrf2 by pharmacological modalities should afford a treatment to attenuate MeHg-induced neurotoxicity.
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Affiliation(s)
- Ling Wang
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, TN 37232
- EENT Hospital, Fudan University, Shanghai, China
| | - Haiyan Jiang
- Departments of Pediatrics and Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Zhaobao Yin
- Departments of Pediatrics and Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Michael Aschner
- Departments of Pediatrics and Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Jiyang Cai
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, TN 37232
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Calì C, Marchaland J, Spagnuolo P, Gremion J, Bezzi P. Regulated exocytosis from astrocytes physiological and pathological related aspects. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2009; 85:261-93. [PMID: 19607976 DOI: 10.1016/s0074-7742(09)85020-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Astrocytes have traditionally been considered ancillary, satellite cells of the nervous system. However, it is a very recent acquisition that glial cells generate signaling loops which are integral to the brain circuitry and participate, interactively with neuronal networks, in the processing of information. Such a conceptual breakthrough makes this field of investigation one of the hottest in neuroscience, as it calls for a revision of past theories of brain function as well as for new strategies of experimental exploration of brain function. Glial cells are electrically not excitable, and it was only the use of optical recording techniques together with calcium sensitive dyes, that allowed the chemical excitability of glial cells to become apparent. Studies using these new techniques have shown for the first time that glial cells are activated by surrounding synaptic activity and translate neuronal signals into their own calcium code. Intracellular calcium concentration([Ca2+]i) elevations in glial cells have then shown to underlie spatial transfer of information in the glial network, accompanied by release of chemical transmitters (gliotransmitters) such as glutamate and back-signaling to neurons. As a consequence, optical imaging techniques applied to cell cultures or intact tissue have become a state-of-the-art technology for studying glial cell signaling. The molecular mechanisms leading to release of "gliotransmitters," especially glutamate, from glia are under debate. Accumulating evidence clearly indicates that astrocytes secrete numerous transmitters by Ca(2+)-dependent exocytosis. This review will discuss the mechanisms underlying the release of chemical transmitters from astrocytes with a particular emphasis to the regulated exocytosis processes.
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Affiliation(s)
- Corrado Calì
- Department of Cellular Biology and Morphology (DBCM), Faculty of Medicine, University of Lausanne, rue du Bugnon 9, 1005 Lausanne, Switzerland
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Metallothionein in the central nervous system: Roles in protection, regeneration and cognition. Neurotoxicology 2008; 29:489-503. [PMID: 18313142 DOI: 10.1016/j.neuro.2007.12.006] [Citation(s) in RCA: 135] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 12/22/2007] [Indexed: 12/23/2022]
Abstract
Metallothionein (MT) is an enigmatic protein, and its physiological role remains a matter of intense study and debate 50 years after its discovery. This is particularly true of its function in the central nervous system (CNS), where the challenge remains to link its known biochemical properties of metal binding and free radical scavenging to the intricate workings of brain. In this compilation of four reports, first delivered at the 11th International Neurotoxicology Association (INA-11) Meeting, June 2007, the authors present the work of their laboratories, each of which gives an important insight into the actions of MT in the brain. What emerges is that MT has the potential to contribute to a variety of processes, including neuroprotection, regeneration, and even cognitive functions. In this article, the properties and CNS expression of MT are briefly reviewed before Dr Hidalgo describes his pioneering work using transgenic models of MT expression to demonstrate how this protein plays a major role in the defence of the CNS against neurodegenerative disorders and other CNS injuries. His group's work leads to two further questions, what are the mechanisms at the cellular level by which MT acts, and does this protein influence higher order issues of architecture and cognition? These topics are addressed in the second and third sections of this review by Dr West, and Dr Levin and Dr Eddins, respectively. Finally, Dr Aschner examines the ability of MT to protect against a specific toxicant, methylmercury, in the CNS.
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Napier S, Bingham M. Pharmacology of Glutamate Transport in the CNS: Substrates and Inhibitors of Excitatory Amino Acid Transporters (EAATs) and the Glutamate/Cystine Exchanger System x c −. TOPICS IN MEDICINAL CHEMISTRY 2008. [PMCID: PMC7123079 DOI: 10.1007/7355_2008_026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
As the primary excitatory neurotransmitter in the mammalian CNS, l-glutamateparticipates not only in standard fast synaptic communication, but also contributes to higher order signalprocessing, as well as neuropathology. Given this variety of functional roles, interest has been growingas to how the extracellular concentrations of l-glutamate surroundingneurons are regulated by cellular transporter proteins. This review focuses on two prominent systems, eachof which appears capable of influencing both the signaling and pathological actions of l-glutamatewithin the CNS: the sodium-dependent excitatory amino acid transporters (EAATs) and the glutamate/cystineexchanger, system xc−(Sxc−). Whilethe family of EAAT subtypes limit access to glutamate receptors by rapidly and efficiently sequesteringl-glutamate in neurons and glia, Sxc−provides a route for the export of glutamate from cells into the extracellular environment. The primaryintent of this work is to provide an overview of the inhibitors and substrates that have been developedto delineate the pharmacological specificity of these transport systems, as well as be exploited as probeswith which to selectively investigate function. Particular attention is paid to the development of smallmolecule templates that mimic the structural properties of the endogenous substrates, l-glutamate,l-aspartate and l-cystine andhow strategic control of functional group position and/or the introduction of lipophilic R-groups can impactmultiple aspects of the transport process, including: subtype selectivity, inhibitory potency, and substrateactivity.
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Stringari J, Nunes AKC, Franco JL, Bohrer D, Garcia SC, Dafre AL, Milatovic D, Souza DO, Rocha JBT, Aschner M, Farina M. Prenatal methylmercury exposure hampers glutathione antioxidant system ontogenesis and causes long-lasting oxidative stress in the mouse brain. Toxicol Appl Pharmacol 2007; 227:147-54. [PMID: 18023834 DOI: 10.1016/j.taap.2007.10.010] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Revised: 10/04/2007] [Accepted: 10/14/2007] [Indexed: 11/15/2022]
Abstract
During the perinatal period, the central nervous system (CNS) is extremely sensitive to metals, including methylmercury (MeHg). Although the mechanism(s) associated with MeHg-induced developmental neurotoxicity remains obscure, several studies point to the glutathione (GSH) antioxidant system as an important molecular target for this toxicant. To extend our recent findings of MeHg-induced GSH dyshomeostasis, the present study was designed to assess the developmental profile of the GSH antioxidant system in the mouse brain during the early postnatal period after in utero exposure to MeHg. Pregnant mice were exposed to different doses of MeHg (1, 3 and 10 mg/l, diluted in drinking water, ad libitum) during the gestational period. After delivery, pups were killed at different time points - postnatal days (PND) 1, 11 and 21 - and the whole brain was used for determining biochemical parameters related to the antioxidant GSH system, as well as mercury content and the levels of F(2)-isoprostane. In control animals, cerebral GSH levels significantly increased over time during the early postnatal period; gestational exposure to MeHg caused a dose-dependent inhibition of this developmental event. Cerebral glutathione peroxidase (GPx) and glutathione reductase (GR) activities significantly increased over time during the early postnatal period in control animals; gestational MeHg exposure induced a dose-dependent inhibitory effect on both developmental phenomena. These adverse effects of prenatal MeHg exposure were corroborated by marked increases in cerebral F(2)-isoprostanes levels at all time points. Significant negative correlations were found between F(2)-isoprostanes and GSH, as well as between F(2)-isoprostanes and GPx activity, suggesting that MeHg-induced disruption of the GSH system maturation is related to MeHg-induced increased lipid peroxidation in the pup brain. In utero MeHg exposure also caused a dose-dependent increase in the cerebral levels of mercury at birth. Even though the cerebral mercury concentration decreased to nearly basal levels at postnatal day 21, GSH levels, GPx and GR activities remained decreased in MeHg-exposed mice, indicating that prenatal exposure to MeHg affects the cerebral GSH antioxidant systems by inducing biochemical alterations that endure even when mercury tissue levels decrease and become indistinguishable from those noted in pups born to control dams. This study is the first to show that prenatal exposure to MeHg disrupts the postnatal development of the glutathione antioxidant system in the mouse brain, pointing to an additional molecular mechanism by which MeHg induces pro-oxidative damage in the developing CNS. Moreover, our experimental observation corroborates previous reports on the permanent functional deficits observed after prenatal MeHg exposure.
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Affiliation(s)
- James Stringari
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, SC, Brazil
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