1
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Hernandez-Espinosa DR, Gale JR, Scrabis MG, Aizenman E. Microglial reprogramming by Hv1 antagonism protects neurons from inflammatory and glutamate toxicity. J Neurochem 2023; 165:29-54. [PMID: 36625847 PMCID: PMC10106429 DOI: 10.1111/jnc.15760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 12/28/2022] [Accepted: 01/02/2023] [Indexed: 01/11/2023]
Abstract
Although the precise mechanisms determining the neurotoxic or neuroprotective activation phenotypes in microglia remain poorly characterized, metabolic changes in these cells appear critical for these processes. As cellular metabolism can be tightly regulated by changes in intracellular pH, we tested whether pharmacological targeting of the microglial voltage-gated proton channel 1 (Hv1), an important regulator of intracellular pH, is critical for activated microglial reprogramming. Using a mouse microglial cell line and mouse primary microglia cultures, either alone, or co-cultured with rat cerebrocortical neurons, we characterized in detail the microglial activation profile in the absence and presence of Hv1 inhibition. We observed that activated microglia neurotoxicity was mainly attributable to the release of tumor necrosis factor alpha, reactive oxygen species, and zinc. Strikingly, pharmacological inhibition of Hv1 largely abrogated inflammatory neurotoxicity not only by reducing the production of cytotoxic mediators but also by promoting neurotrophic molecule production and restraining excessive phagocytic activity. Importantly, the Hv1-sensitive change from a pro-inflammatory to a neuroprotective phenotype was associated with metabolic reprogramming, particularly via a boost in NADH availability and a reduction in lactate. Most critically, Hv1 antagonism not only reduced inflammatory neurotoxicity but also promoted microglia-dependent neuroprotection against a separate excitotoxic injury. Our results strongly suggest that Hv1 blockers may provide an important therapeutic tool against a wide range of inflammatory neurodegenerative disorders.
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Affiliation(s)
- Diego R Hernandez-Espinosa
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Jenna R Gale
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Mia G Scrabis
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Elias Aizenman
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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2
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Effects of Marginal Zn Excess and Thiamine Deficiency on Microglial N9 Cell Metabolism and Their Interactions with Septal SN56 Cholinergic Cells. Int J Mol Sci 2023; 24:ijms24054465. [PMID: 36901896 PMCID: PMC10002586 DOI: 10.3390/ijms24054465] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 02/10/2023] [Accepted: 02/21/2023] [Indexed: 03/12/2023] Open
Abstract
Mild thiamine deficiency aggravates Zn accumulation in cholinergic neurons. It leads to the augmentation of Zn toxicity by its interaction with the enzymes of energy metabolism. Within this study, we tested the effect of Zn on microglial cells cultivated in a thiamine-deficient medium, containing 0.003 mmol/L of thiamine vs. 0.009 mmol/L in a control medium. In such conditions, a subtoxic 0.10 mmol/L Zn concentration caused non-significant alterations in the survival and energy metabolism of N9 microglial cells. Both activities of the tricarboxylic acid cycle and the acetyl-CoA level were not decreased in these culture conditions. Amprolium augmented thiamine pyrophosphate deficits in N9 cells. This led to an increase in the intracellular accumulation of free Zn and partially aggravated its toxicity. There was differential sensitivity of neuronal and glial cells to thiamine-deficiency-Zn-evoked toxicity. The co-culture of neuronal SN56 with microglial N9 cells reduced the thiamine-deficiency-Zn-evoked inhibition of acetyl-CoA metabolism and restored the viability of the former. The differential sensitivity of SN56 and N9 cells to borderline thiamine deficiency combined with marginal Zn excess may result from the strong inhibition of pyruvate dehydrogenase in neuronal cells and no inhibition of this enzyme in the glial ones. Therefore, ThDP supplementation can make any brain cell more resistant to Zn excess.
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3
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Hussain A, Jiang W, Wang X, Shahid S, Saba N, Ahmad M, Dar A, Masood SU, Imran M, Mustafa A. Mechanistic Impact of Zinc Deficiency in Human Development. Front Nutr 2022; 9:717064. [PMID: 35356730 PMCID: PMC8959901 DOI: 10.3389/fnut.2022.717064] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Accepted: 01/31/2022] [Indexed: 12/15/2022] Open
Abstract
Zinc (Zn) deficiency in humans is an emerging global health issue affecting approximately two billion people across the globe. The situation prevails due to the intake of Zn deficient grains and vegetables worldwide. Clinical identification of Zn deficiency in humans remains problematic because the symptoms do not appear until impair the vital organs, such as the gastrointestinal track, central nervous system, immune system, skeletal, and nervous system. Lower Zn body levels are also responsible for multiple physiological disorders, such as apoptosis, organs destruction, DNA injuries, and oxidative damage to the cellular components through reactive oxygen species (ROS). The oxidative damage causes chronic inflammation lead toward several chronic diseases, such as heart diseases, cancers, alcohol-related malady, muscular contraction, and neuro-pathogenesis. The present review focused on the physiological and growth-related changes in humans under Zn deficient conditions, mechanisms adopted by the human body under Zn deficiency for the proper functioning of the body systems, and the importance of nutritional and nutraceutical approaches to overcome Zn deficiency in humans and concluded that the biofortified food is the best source of Zn as compared to the chemical supplementation to avoid their negative impacts on human.
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Affiliation(s)
- Azhar Hussain
- Department of Soil Science, The Islamia Diversity of Bahawalpur, Bahawalpur, Pakistan
| | - Wenting Jiang
- College of Life Sciences, Yan'an University, Yan'an, China
| | - Xiukang Wang
- College of Life Sciences, Yan'an University, Yan'an, China
| | - Shumaila Shahid
- Department of Soil Science, The Islamia Diversity of Bahawalpur, Bahawalpur, Pakistan
| | - Noreena Saba
- Qaid-e-Azam Medical College, Bahawal Victoria Hospital, Bahawalpur, Pakistan
| | - Maqshoof Ahmad
- Department of Soil Science, The Islamia Diversity of Bahawalpur, Bahawalpur, Pakistan
| | - Abubakar Dar
- Department of Soil Science, The Islamia Diversity of Bahawalpur, Bahawalpur, Pakistan
| | - Syed Usama Masood
- Clinical Fellow Pediatric Nephrology, Children Hospital and Institute of Child Health Multan, Multan, Pakistan
| | | | - Adnan Mustafa
- Faculty of Chemistry, Institute of Chemistry and Technology of Environmental Protection, Brno University of Technology, Brno, Czechia
- Department of Agrochemistry, Soil Science, Microbiology and Plant Nutrition (FA), Mendel University, Brno, Czechia
- Institute of Environmental Studies, Charles University Prague, Prague, Czechia
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4
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Yarim GF, Yarim M, Sozmen M, Gokceoglu A, Ertekin A, Kabak YB, Karaca E. Nobiletin attenuates inflammation via modulating proinflammatory and antiinflammatory cytokine expressions in an autoimmune encephalomyelitis mouse model. Fitoterapia 2021; 156:105099. [PMID: 34896483 DOI: 10.1016/j.fitote.2021.105099] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 12/03/2021] [Accepted: 12/03/2021] [Indexed: 11/17/2022]
Abstract
The aim of this study is to investigate the potential preventive and therapeutic effects of nobiletin by evaluating the expression of cytokines associated with inflammatory reactions in an autoimmune encephalomyelitis mouse model. A total of 60 male C57BL/6 mice aged between 8 and 10 weeks were used. Mice were divided into six groups (n = 10 mice per group): control, EAE, low-prophylaxis, high-prophylaxis, low-treatment and high-treatment. Experimental autoimmune encephalomyelitis (EAE) was induced by myelin oligodendrocyte glycoprotein (MOG) and pertussis toxin. Nobiletin was administered in low (25 mg/kg) and high (50 mg/kg) doses, intraperitoneally. The prophylactic and therapeutic effects of nobiletin on brain tissue and spinal cord were evaluated by expression of interleukin-1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), interferon gamma (IFNγ), IL-6, IL-10 and transforming growth factor-beta (TGF-β) using immunohistochemistry and real-time polymerase chain reaction (RT-PCR). Prophylactic and therapeutic use of nobiletin inhibited EAE-induced increase of TNF-α, IL-1β and IL-6 activities to alleviate inflammatory response in brain and spinal cord. Moreover, nobiletin supplement dramatically increased the IL-10, TGF-β and IFNγ expressions in prophylaxis and treatment groups compared with the EAE group in the brain and spinal cord. The results obtained from this study show that prophylactic and therapeutic nobiletin modulates expressions of proinflammatory and antiinflammatory cytokines in brain and spinal cord dose-dependent manner in EAE model. These data demonstrates that nobiletin has a potential to attenuate inflammation in EAE mouse model. These experimental findings need to be supported by clinical studies.
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MESH Headings
- Animals
- Antioxidants/pharmacology
- Antioxidants/therapeutic use
- Brain/drug effects
- Brain/immunology
- Brain/pathology
- Cytokines/drug effects
- Cytokines/metabolism
- DNA, Complementary/biosynthesis
- Disease Models, Animal
- Encephalomyelitis, Autoimmune, Experimental/drug therapy
- Encephalomyelitis, Autoimmune, Experimental/immunology
- Encephalomyelitis, Autoimmune, Experimental/pathology
- Encephalomyelitis, Autoimmune, Experimental/prevention & control
- Flavones/pharmacology
- Flavones/therapeutic use
- Immunohistochemistry
- Inflammation/drug therapy
- Inflammation/immunology
- Inflammation/prevention & control
- Male
- Mice
- Mice, Inbred C57BL
- Multiple Sclerosis/drug therapy
- Multiple Sclerosis/immunology
- Multiple Sclerosis/pathology
- Multiple Sclerosis/prevention & control
- RNA/genetics
- RNA/isolation & purification
- Real-Time Polymerase Chain Reaction
- Spinal Cord/drug effects
- Spinal Cord/immunology
- Spinal Cord/pathology
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Affiliation(s)
- Gul Fatma Yarim
- Department of Biochemistry, Faculty of Veterinary Medicine, Ondokuz Mayis University, Atakum, 55200 Samsun, Turkey.
| | - Murat Yarim
- Department of Pathology, Faculty of Veterinary Medicine, Ondokuz Mayis University, Atakum, 55200 Samsun, Turkey
| | - Mahmut Sozmen
- Department of Pathology, Faculty of Veterinary Medicine, Ondokuz Mayis University, Atakum, 55200 Samsun, Turkey
| | - Ayris Gokceoglu
- Department of Biochemistry, Faculty of Veterinary Medicine, Ondokuz Mayis University, Atakum, 55200 Samsun, Turkey
| | - Ali Ertekin
- Department of Biochemistry, Faculty of Veterinary Medicine, Ondokuz Mayis University, Atakum, 55200 Samsun, Turkey
| | - Yonca Betil Kabak
- Department of Pathology, Faculty of Veterinary Medicine, Ondokuz Mayis University, Atakum, 55200 Samsun, Turkey
| | - Efe Karaca
- Department of Pathology, Faculty of Veterinary Medicine, Ondokuz Mayis University, Atakum, 55200 Samsun, Turkey
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5
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Zinc Signaling in the Mammary Gland: For Better and for Worse. Biomedicines 2021; 9:biomedicines9091204. [PMID: 34572390 PMCID: PMC8469023 DOI: 10.3390/biomedicines9091204] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 09/06/2021] [Accepted: 09/06/2021] [Indexed: 02/07/2023] Open
Abstract
Zinc (Zn2+) plays an essential role in epithelial physiology. Among its many effects, most prominent is its action to accelerate cell proliferation, thereby modulating wound healing. It also mediates affects in the gastrointestinal system, in the testes, and in secretory organs, including the pancreas, salivary, and prostate glands. On the cellular level, Zn2+ is involved in protein folding, DNA, and RNA synthesis, and in the function of numerous enzymes. In the mammary gland, Zn2+ accumulation in maternal milk is essential for supporting infant growth during the neonatal period. Importantly, Zn2+ signaling also has direct roles in controlling mammary gland development or, alternatively, involution. During breast cancer progression, accumulation or redistribution of Zn2+ occurs in the mammary gland, with aberrant Zn2+ signaling observed in the malignant cells. Here, we review the current understanding of the role of in Zn2+ the mammary gland, and the proteins controlling cellular Zn2+ homeostasis and signaling, including Zn2+ transporters and the Gq-coupled Zn2+ sensing receptor, ZnR/GPR39. Significant advances in our understanding of Zn2+ signaling in the normal mammary gland as well as in the context of breast cancer provides new avenues for identification of specific targets for breast cancer therapy.
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6
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Bachmann M, Li W, Edwards MJ, Ahmad SA, Patel S, Szabo I, Gulbins E. Voltage-Gated Potassium Channels as Regulators of Cell Death. Front Cell Dev Biol 2020; 8:611853. [PMID: 33381507 PMCID: PMC7767978 DOI: 10.3389/fcell.2020.611853] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 11/23/2020] [Indexed: 12/11/2022] Open
Abstract
Ion channels allow the flux of specific ions across biological membranes, thereby determining ion homeostasis within the cells. Voltage-gated potassium-selective ion channels crucially contribute to the setting of the plasma membrane potential, to volume regulation and to the physiologically relevant modulation of intracellular potassium concentration. In turn, these factors affect cell cycle progression, proliferation and apoptosis. The present review summarizes our current knowledge about the involvement of various voltage-gated channels of the Kv family in the above processes and discusses the possibility of their pharmacological targeting in the context of cancer with special emphasis on Kv1.1, Kv1.3, Kv1.5, Kv2.1, Kv10.1, and Kv11.1.
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Affiliation(s)
- Magdalena Bachmann
- Department of Biology, University of Padova, Padua, Italy.,Department of Surgery, Medical School, University of Cincinnati, Cincinnati, OH, United States
| | - Weiwei Li
- Department of Surgery, Medical School, University of Cincinnati, Cincinnati, OH, United States
| | - Michael J Edwards
- Department of Surgery, Medical School, University of Cincinnati, Cincinnati, OH, United States
| | - Syed A Ahmad
- Department of Surgery, Medical School, University of Cincinnati, Cincinnati, OH, United States
| | - Sameer Patel
- Department of Surgery, Medical School, University of Cincinnati, Cincinnati, OH, United States
| | - Ildiko Szabo
- Department of Biology, University of Padova, Padua, Italy.,Consiglio Nazionale delle Ricerche Institute of Neuroscience, Padua, Italy
| | - Erich Gulbins
- Department of Surgery, Medical School, University of Cincinnati, Cincinnati, OH, United States.,Department of Molecular Biology, University of Duisburg-Essen, Essen, Germany
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7
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Ijomone OM, Ifenatuoha CW, Aluko OM, Ijomone OK, Aschner M. The aging brain: impact of heavy metal neurotoxicity. Crit Rev Toxicol 2020; 50:801-814. [PMID: 33210961 DOI: 10.1080/10408444.2020.1838441] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The aging process is accompanied by critical changes in cellular and molecular functions, which upset the homeostatic balance in the central nervous system. Accumulation of metals renders the brain susceptible to neurotoxic insults by mechanisms such as mitochondrial dysfunction, neuronal calcium-ion dyshomeostasis, buildup of damaged molecules, compromised DNA repair, reduction in neurogenesis, and impaired energy metabolism. These hallmarks have been identified to be responsible for neuronal injuries, resulting in several neurological disorders. Various studies have shown solid associations between metal accumulation, abnormal protein expressions, and pathogenesis of neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, Huntington's disease, and Amyotrophic lateral sclerosis. This review highlights metals (such as manganese, zinc, iron, copper, and nickel) for their accumulation, and consequences in the development of neurological disorders, in relation to the aging brain.
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Affiliation(s)
- Omamuyovwi M Ijomone
- The Neuro-Lab, School of Health and Health Technology, Federal University of Technology, Akure, Nigeria.,Department of Human Anatomy, School of Health and Health Technology, Federal University of Technology, Akure, Nigeria
| | - Chibuzor W Ifenatuoha
- The Neuro-Lab, School of Health and Health Technology, Federal University of Technology, Akure, Nigeria
| | - Oritoke M Aluko
- The Neuro-Lab, School of Health and Health Technology, Federal University of Technology, Akure, Nigeria.,Department of Physiology, School of Health and Health Technology, Federal University of Technology, Akure, Nigeria
| | - Olayemi K Ijomone
- The Neuro-Lab, School of Health and Health Technology, Federal University of Technology, Akure, Nigeria.,Department of Anatomy, University of Medical Sciences, Ondo, Nigeria
| | - Michael Aschner
- Departments of Molecular Pharmacology, Pediatrics and Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA
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8
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Aizenman E, Loring RH, Reynolds IJ, Rosenberg PA. The Redox Biology of Excitotoxic Processes: The NMDA Receptor, TOPA Quinone, and the Oxidative Liberation of Intracellular Zinc. Front Neurosci 2020; 14:778. [PMID: 32792905 PMCID: PMC7393236 DOI: 10.3389/fnins.2020.00778] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Accepted: 07/02/2020] [Indexed: 12/14/2022] Open
Abstract
This special issue of Frontiers in Neuroscience-Neurodegeneration celebrates the 50th anniversary of John Olney's seminal work introducing the concept of excitotoxicity as a mechanism for neuronal cell death. Since that time, fundamental research on the pathophysiological activation of glutamate receptors has played a central role in our understanding of excitotoxic cellular signaling pathways, leading to the discovery of many potential therapeutic targets in the treatment of acute or chronic/progressive neurodegenerative disorders. Importantly, excitotoxic signaling processes have been found repeatedly to be closely intertwined with oxidative cellular cascades. With this in mind, this review looks back at long-standing collaborative efforts by the authors linking cellular redox status and glutamate neurotoxicity, focusing first on the discovery of the redox modulatory site of the N-methyl-D-aspartate (NMDA) receptor, followed by the study of the oxidative conversion of 3,4-dihydroxyphenylalanine (DOPA) to the non-NMDA receptor agonist and neurotoxin 2,4,5-trihydroxyphenylalanine (TOPA) quinone. Finally, we summarize our work linking oxidative injury to the liberation of zinc from intracellular metal binding proteins, leading to the uncovering of a signaling mechanism connecting excitotoxicity with zinc-activated cell death-signaling cascades.
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Affiliation(s)
- Elias Aizenman
- Department of Neurobiology, Pittsburgh Institute for Neurodegenerative Diseases, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
| | - Ralph H. Loring
- Department of Pharmaceutical Sciences, School of Pharmacy, Northeastern University, Boston, MA, United States
| | | | - Paul A. Rosenberg
- Program in Neuroscience, F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States
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9
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Hara H, Kobayashi M, Shiiba M, Kamiya T, Adachi T. Sublethal treatment with plasma-activated medium induces senescence-like growth arrest of A549 cells: involvement of intracellular mobile zinc. J Clin Biochem Nutr 2019; 65:16-22. [PMID: 31379409 PMCID: PMC6667388 DOI: 10.3164/jcbn.19-17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 03/13/2019] [Indexed: 11/29/2022] Open
Abstract
Plasma-activated medium (PAM) is a solution produced by exposing a liquid medium to non-thermal atmospheric pressure plasma (NTAPP). A number of reactive molecules, such as reactive oxygen species and reactive nitrogen species, are contained in PAM. Therefore, exposure to high doses of PAM results in cell death. We previously demonstrated that intracellular zinc (Zn2+) serves as an important mediator in PAM-induced cell death; however, the effects of sublethal treatment with PAM on cell functions are not fully understood. In the present study, we found that sublethal PAM treatment suppressed cell proliferation and induced senescence-like changes in lung adenocarcinoma A549 cells. Cell cycle analysis revealed that PAM induced cell cycle arrest at the G2/M phase. PAM increased the level of intracellular free Zn2+ and the Zn2+ chelator TPEN counteracted PAM-induced growth suppression, suggesting that Zn2+ functions in PAM-induced growth suppression. In addition, sublethal treatment with PAM induced phosphorylation of ATM kinase, accumulation of p53 protein, and expression of p21 and GADD45A, which are known p53 target genes, in a Zn2+-dependent manner. These results suggest that the induction of growth arrest and cellular senescence by sublethal PAM treatment is mediated by Zn2+-dependent activation of the ATM/p53 pathway.
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Affiliation(s)
- Hirokazu Hara
- Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan
| | - Mari Kobayashi
- Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan
| | - Moe Shiiba
- Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan
| | - Tetsuro Kamiya
- Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan
| | - Tetsuo Adachi
- Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan
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10
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Spinal cord injury: pathophysiology, treatment strategies, associated challenges, and future implications. Cell Tissue Res 2019; 377:125-151. [PMID: 31065801 DOI: 10.1007/s00441-019-03039-1] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 04/01/2019] [Indexed: 12/16/2022]
Abstract
Axonal regeneration and formation of tripartite (axo-glial) junctions at damaged sites is a prerequisite for early repair of injured spinal cord. Transplantation of stem cells at such sites of damage which can generate both neuronal and glial population has gained impact in terms of recuperation upon infliction with spinal cord injury. In spite of the fact that a copious number of pre-clinical studies using different stem/progenitor cells have shown promising results at acute and subacute stages, at the chronic stages of injury their recovery rates have shown a drastic decline. Therefore, developing novel therapeutic strategies are the need of the hour in order to assuage secondary morbidity and effectuate improvement of the spinal cord injury (SCI)-afflicted patients' quality of life. The present review aims at providing an overview of the current treatment strategies and also gives an insight into the potential cell-based therapies for the treatment of SCI.
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11
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Justice JA, Manjooran DT, Yeh CY, Hartnett-Scott KA, Schulien AJ, Kosobucki GJ, Mammen S, Palladino MJ, Aizenman E. Molecular Neuroprotection Induced by Zinc-Dependent Expression of Hepatitis C-Derived Protein NS5A Targeting Kv2.1 Potassium Channels. J Pharmacol Exp Ther 2018; 367:348-355. [PMID: 30190339 PMCID: PMC6193254 DOI: 10.1124/jpet.118.252338] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 09/06/2018] [Indexed: 12/20/2022] Open
Abstract
We present the design of an innovative molecular neuroprotective strategy and provide proof-of-concept for its implementation, relying on the injury-mediated activation of an ectopic gene construct. As oxidative injury leads to the intracellular liberation of zinc, we hypothesize that tapping onto the zinc-activated metal regulatory element (MRE) transcription factor 1 system to drive expression of the Kv2.1-targeted hepatitis C protein NS5A (hepatitis C nonstructural protein 5A) will provide neuroprotection by preventing cell death-enabling cellular potassium loss in rat cortical neurons in vitro. Indeed, using biochemical and morphologic assays, we demonstrate rapid expression of MRE-driven products in neurons. Further, we report that MRE-driven NS5A expression, induced by a slowly evolving excitotoxic stimulus, functionally blocks injurious, enhanced Kv2.1 potassium whole-cell currents and improves neuronal viability. We suggest this form of "on-demand" neuroprotection could provide the basis for a tenable therapeutic strategy to prevent neuronal cell death in neurodegeneration.
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Affiliation(s)
- Jason A Justice
- Departments of Neurobiology (J.A.J., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., E.A.) and Pharmacology and Chemical Biology (D.T.M., M.J.P.) and Pittsburgh Institute for Neurodegenerative Diseases (J.A.J., D.T.M., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., M.J.P., E.A.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Daniel T Manjooran
- Departments of Neurobiology (J.A.J., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., E.A.) and Pharmacology and Chemical Biology (D.T.M., M.J.P.) and Pittsburgh Institute for Neurodegenerative Diseases (J.A.J., D.T.M., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., M.J.P., E.A.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Chung-Yang Yeh
- Departments of Neurobiology (J.A.J., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., E.A.) and Pharmacology and Chemical Biology (D.T.M., M.J.P.) and Pittsburgh Institute for Neurodegenerative Diseases (J.A.J., D.T.M., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., M.J.P., E.A.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Karen A Hartnett-Scott
- Departments of Neurobiology (J.A.J., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., E.A.) and Pharmacology and Chemical Biology (D.T.M., M.J.P.) and Pittsburgh Institute for Neurodegenerative Diseases (J.A.J., D.T.M., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., M.J.P., E.A.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Anthony J Schulien
- Departments of Neurobiology (J.A.J., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., E.A.) and Pharmacology and Chemical Biology (D.T.M., M.J.P.) and Pittsburgh Institute for Neurodegenerative Diseases (J.A.J., D.T.M., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., M.J.P., E.A.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Gabrielle J Kosobucki
- Departments of Neurobiology (J.A.J., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., E.A.) and Pharmacology and Chemical Biology (D.T.M., M.J.P.) and Pittsburgh Institute for Neurodegenerative Diseases (J.A.J., D.T.M., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., M.J.P., E.A.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Shalom Mammen
- Departments of Neurobiology (J.A.J., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., E.A.) and Pharmacology and Chemical Biology (D.T.M., M.J.P.) and Pittsburgh Institute for Neurodegenerative Diseases (J.A.J., D.T.M., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., M.J.P., E.A.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Michael J Palladino
- Departments of Neurobiology (J.A.J., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., E.A.) and Pharmacology and Chemical Biology (D.T.M., M.J.P.) and Pittsburgh Institute for Neurodegenerative Diseases (J.A.J., D.T.M., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., M.J.P., E.A.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Elias Aizenman
- Departments of Neurobiology (J.A.J., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., E.A.) and Pharmacology and Chemical Biology (D.T.M., M.J.P.) and Pittsburgh Institute for Neurodegenerative Diseases (J.A.J., D.T.M., C.-Y.Y., K.A.H.-S., A.J.S., G.J.K., S.M., M.J.P., E.A.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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Li JW, Zong Y, Cao XP, Tan L, Tan L. Microglial priming in Alzheimer's disease. ANNALS OF TRANSLATIONAL MEDICINE 2018; 6:176. [PMID: 29951498 DOI: 10.21037/atm.2018.04.22] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Alzheimer's disease (AD) is a chronic and progressive neurodegenerative disease of central nervous system (CNS). Nowadays, increasing evidence suggests that immune system plays a significant role in the mechanisms of AD's onset and progression. Microglia, the main participator in the immune system of CNS, is always regarded as a protector of our brain in a healthy state and also has a beneficial role in maintaining the homeostasis of CNS microenvironment. However, chronic and sustained stimulation can push microglia into the state termed priming. Primed microglia can induce the production of amyloid β (Aβ), tau pathology, neuroinflammation and reduce the release of neurotrophic factors, resulting in loss of normal neurons in quantity and function that has immense relationship with AD. The therapeutic strategies mainly aimed at modulating the microenvironment and microglial activity in CNS to delay progression and alleviate pathogenesis of AD. Overall, in this review, we highlight the mechanism of microglial priming, and discuss the profound relationship between microglial priming and AD. Besides, we also pay attention to the therapeutic strategies targeting at microglial priming.
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Affiliation(s)
- Jun-Wei Li
- Department of Neurology, Qingdao Municipal Hospital, Dalian Medical University, Qingdao 266000, China
| | - Yu Zong
- Department of Neurology, Qingdao Municipal Hospital, Qingdao University, Qingdao 266071, China
| | - Xi-Peng Cao
- Clinical Research Center, Qingdao Municipal Hospital, Qingdao University, Qingdao 266071, China
| | - Lin Tan
- Department of Neurology, Qingdao Municipal Hospital, Qingdao University, Qingdao 266071, China
| | - Lan Tan
- Department of Neurology, Qingdao Municipal Hospital, Dalian Medical University, Qingdao 266000, China.,Department of Neurology, Qingdao Municipal Hospital, Qingdao University, Qingdao 266071, China
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Hu B, Wu Y, Tong F, Liu J, Shen X, Shen R, Xu G. Apocynin Alleviates Renal Ischemia/Reperfusion Injury Through Regulating the Level of Zinc and Metallothionen. Biol Trace Elem Res 2017; 178:71-78. [PMID: 27909865 DOI: 10.1007/s12011-016-0904-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 11/23/2016] [Indexed: 02/07/2023]
Abstract
The purpose of this research was to evaluate the protective effects of apocynin on renal ischemia/reperfusion (I/R) injury (RI/RI) in rats. Rats preconditioned with apocynin were subjected to renal I/R. Zinc levels in serum and renal tissues, blood urea nitrogen (BUN), and serum creatinine (Scr) were detected. We further measured the activity of superoxide dismutase (SOD); the content of malondialdehyde (MDA), IL-4, IL-6, IL-10, and TNF-α; and the expression of metallothionein (MT) in the renal tissues. Results indicated that the levels of MDA, IL-4, IL-6, IL-10, TNF-α, and MT in the kidney tissue and serum BUN and Scr levels in RI/RI group were significantly higher than those in sham-operated group, while the levels of serum Zn and kidney Zn and SOD were reduced in RI/RI group. Apocynin treatment further decreased the levels of MDA, IL-6, TNF-α, and serum BUN and Scr, whereas it significantly increased the levels of Zn, SOD, IL-4, IL-10, and MT in the kidney tissue and serum Zn. These findings suggest that apocynin might play a protective role against RI/RI in rats through regulating zinc level and MT expression involving in oxidative stress.
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Affiliation(s)
- Bo Hu
- Department of Pathology and Nephrology, Jiaxing Hospital of Traditional Chinese Medicine, Zhejiang Chinese Medical University, 314001, Jiaxing, Zhejiang Province, People's Republic of China
| | - Yuhong Wu
- Department of Pathology and Nephrology, Jiaxing Hospital of Traditional Chinese Medicine, Zhejiang Chinese Medical University, 314001, Jiaxing, Zhejiang Province, People's Republic of China
| | - Fei Tong
- Department of Pathology, Provincial Key Discipline of Pharmacology, Jiaxing University Medical College, 314001, Jiaxing, Zhejiang Province, People's Republic of China
| | - Jie Liu
- Department of Pathology and Nephrology, Jiaxing Hospital of Traditional Chinese Medicine, Zhejiang Chinese Medical University, 314001, Jiaxing, Zhejiang Province, People's Republic of China
| | - Xiaohua Shen
- Department of Pathology and Nephrology, Jiaxing Hospital of Traditional Chinese Medicine, Zhejiang Chinese Medical University, 314001, Jiaxing, Zhejiang Province, People's Republic of China
| | - Ruilin Shen
- Department of Pathology and Nephrology, Jiaxing Hospital of Traditional Chinese Medicine, Zhejiang Chinese Medical University, 314001, Jiaxing, Zhejiang Province, People's Republic of China
| | - Guangtao Xu
- Department of Pathology, Provincial Key Discipline of Pharmacology, Jiaxing University Medical College, 314001, Jiaxing, Zhejiang Province, People's Republic of China.
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Targeting a Potassium Channel/Syntaxin Interaction Ameliorates Cell Death in Ischemic Stroke. J Neurosci 2017; 37:5648-5658. [PMID: 28483976 DOI: 10.1523/jneurosci.3811-16.2017] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 04/25/2017] [Accepted: 05/01/2017] [Indexed: 12/12/2022] Open
Abstract
The voltage-gated K+ channel Kv2.1 has been intimately linked with neuronal apoptosis. After ischemic, oxidative, or inflammatory insults, Kv2.1 mediates a pronounced, delayed enhancement of K+ efflux, generating an optimal intracellular environment for caspase and nuclease activity, key components of programmed cell death. This apoptosis-enabling mechanism is initiated via Zn2+-dependent dual phosphorylation of Kv2.1, increasing the interaction between the channel's intracellular C-terminus domain and the SNARE (soluble N-ethylmaleimide-sensitive factor activating protein receptor) protein syntaxin 1A. Subsequently, an upregulation of de novo channel insertion into the plasma membrane leads to the critical enhancement of K+ efflux in damaged neurons. Here, we investigated whether a strategy designed to interfere with the cell death-facilitating properties of Kv2.1, specifically its interaction with syntaxin 1A, could lead to neuroprotection following ischemic injury in vivo The minimal syntaxin 1A-binding sequence of Kv2.1 C terminus (C1aB) was first identified via a far-Western peptide screen and used to create a protherapeutic product by conjugating C1aB to a cell-penetrating domain. The resulting peptide (TAT-C1aB) suppressed enhanced whole-cell K+ currents produced by a mutated form of Kv2.1 mimicking apoptosis in a mammalian expression system, and protected cortical neurons from slow excitotoxic injury in vitro, without influencing NMDA-induced intracellular calcium responses. Importantly, intraperitoneal administration of TAT-C1aB in mice following transient middle cerebral artery occlusion significantly reduced ischemic stroke damage and improved neurological outcome. These results provide strong evidence that targeting the proapoptotic function of Kv2.1 is an effective and highly promising neuroprotective strategy.SIGNIFICANCE STATEMENT Kv2.1 is a critical regulator of apoptosis in central neurons. It has not been determined, however, whether the cell death-enabling function of this K+ channel can be selectively targeted to improve neuronal survival following injury in vivo The experiments presented here demonstrate that the cell death-specific role of Kv2.1 can be uniquely modulated to provide neuroprotection in an animal model of acute ischemic stroke. We thus reveal a novel therapeutic strategy for neurological disorders that are accompanied by Kv2.1-facilitated forms of cell death.
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Justice JA, Schulien AJ, He K, Hartnett KA, Aizenman E, Shah NH. Disruption of K V2.1 somato-dendritic clusters prevents the apoptogenic increase of potassium currents. Neuroscience 2017; 354:158-167. [PMID: 28461216 DOI: 10.1016/j.neuroscience.2017.04.034] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 03/01/2017] [Accepted: 04/21/2017] [Indexed: 12/27/2022]
Abstract
As the predominant mediator of the delayed rectifier current, KV2.1 is an important regulator of neuronal excitability. KV2.1, however, also plays a well-established role in apoptotic cell death. Apoptogenic stimuli induce syntaxin-dependent trafficking of KV2.1, resulting in an augmented delayed rectifier current that acts as a conduit for K+ efflux required for pro-apoptotic protease/nuclease activation. Recent evidence suggests that KV2.1 somato-dendritic clusters regulate the formation of endoplasmic reticulum-plasma membrane junctions that function as scaffolding sites for plasma membrane trafficking of ion channels, including KV2.1. However, it is unknown whether KV2.1 somato-dendritic clusters are required for apoptogenic trafficking of KV2.1. By overexpression of a protein derived from the C-terminus of the cognate channel KV2.2 (KV2.2CT), we induced calcineurin-independent disruption of KV2.1 somato-dendritic clusters in rat cortical neurons, without altering the electrophysiological properties of the channel. We observed that KV2.2CT-expressing neurons are less susceptible to oxidative stress-induced cell death. Critically, expression of KV2.2CT effectively blocked the increased current density of the delayed rectifier current associated with oxidative injury, supporting a vital role of KV2.1-somato-dendritic clusters in apoptogenic increases in KV2.1-mediated currents.
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Affiliation(s)
- Jason A Justice
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.
| | - Anthony J Schulien
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Kai He
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Karen A Hartnett
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Elias Aizenman
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Niyathi H Shah
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
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Hara H, Kimoto D, Kajita M, Takada C, Kamiya T, Adachi T. Apomorphine prevents LPS-induced IL-23 p19 mRNA expression via inhibition of JNK and ATF4 in HAPI cells. Eur J Pharmacol 2017; 795:108-114. [DOI: 10.1016/j.ejphar.2016.12.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 11/14/2016] [Accepted: 12/08/2016] [Indexed: 01/14/2023]
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Malaiyandi LM, Sharthiya H, Dineley KE. Fluorescence detection of intracellular cadmium with Leadmium Green. Biometals 2016; 29:625-35. [PMID: 27260023 DOI: 10.1007/s10534-016-9939-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 05/15/2016] [Indexed: 12/18/2022]
Abstract
Leadmium Green is a commercially available, small molecule, fluorescent probe advertised as a detector of free intracellular cadmium (Cd(2+)) and lead (Pb(2+)). Leadmium Green has been used in various paradigms, such as tracking Cd(2+) sequestration in plant cells, heavy metal export in protozoa, and Pb(2+) absorption by vascular endothelial cells. However very little information is available regarding its affinity and selectivity for Cd(2+), Pb(2+), and other metals. We evaluated the in vitro selectivity of Leadmium Green using spectrofluorimetry. Consistent with manufacturer's claims, Leadmium Green was sensitive to Cd(2+) (KD ~600 nM) and also Pb(2+) (KD ~9.0 nM) in a concentration-dependent manner, and furthermore proved insensitive to Ca(2+), Co(2+), Mn(2+) and Ni(2+). Leadmium Green also responded to Zn(2+) with a KD of ~82 nM. Using fluorescence microscopy, we evaluated Leadmium Green in live mouse hippocampal HT22 cells. We demonstrated that Leadmium Green detected ionophore-mediated acute elevations of Cd(2+) or Zn(2+) in a concentration-dependent manner. However, the maximum fluorescence produced by ionophore-delivered Zn(2+) was much less than that produced by Cd(2+). When tested in a model of oxidant-induced liberation of endogenous Zn(2+), Leadmium Green responded weakly. We conclude that Leadmium Green is an effective probe for monitoring intracellular Cd(2+), particularly in models where Cd(2+) accumulates rapidly, and when concomitant fluctuations of intracellular Zn(2+) are minimal.
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Affiliation(s)
- Latha M Malaiyandi
- Department of Anatomy, Chicago College of Osteopathic Medicine, Midwestern University, 555 31st Street, Downers Grove, IL, 60515, USA
| | - Harsh Sharthiya
- Department of Anatomy, Chicago College of Osteopathic Medicine, Midwestern University, 555 31st Street, Downers Grove, IL, 60515, USA
| | - Kirk E Dineley
- Department of Pharmacology, Chicago College of Osteopathic Medicine, Midwestern University, 555 31st Street, Downers Grove, IL, 60515, USA.
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Hara H, Taniguchi M, Kobayashi M, Kamiya T, Adachi T. Plasma-activated medium-induced intracellular zinc liberation causes death of SH-SY5Y cells. Arch Biochem Biophys 2015; 584:51-60. [DOI: 10.1016/j.abb.2015.08.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 08/21/2015] [Accepted: 08/23/2015] [Indexed: 01/29/2023]
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Zinc regulates expression of IL-23 p19 mRNA via activation of eIF2α/ATF4 axis in HAPI cells. Biometals 2015; 28:891-902. [PMID: 26174742 DOI: 10.1007/s10534-015-9874-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 07/03/2015] [Indexed: 12/22/2022]
Abstract
Zinc (Zn(2+)) is considered to be one of the factors aggravating brain damage after cerebral ischemia. Since Zn(2+) activates microglia, immune cells in the brain, this metal is proposed to modulate neuroinflammatory responses in the post-ischemic brain. Interleukin (IL)-23 is a heterodimeric cytokine composed of the p19 subunit unique to IL-23 and the p40 subunit common to IL-12. IL-23 has been shown to play a critical role in the progression of ischemic brain injury. However, whether Zn(2+) participates in the expression of IL-23 in microglia remains unknown. In this study, we examined the effect of Zn(2+) on IL-23 p19 mRNA expression using rat immortalized microglia HAPI cells. Exposure to Zn(2+) dose- and time-dependently induced the expression of IL-23 p19 mRNA in HAPI cells. Inhibitors of MAPK and NF-κB pathways failed to suppress this induction. Interestingly, we found that Zn(2+) stimulated the phosphorylation of eIF2α and promoted the nuclear accumulation of activating transcription factor 4 (ATF4). Treatment with salubrinal, an eIF2α dephosphorylation inhibitor, enhanced Zn(2+)-induced ATF4 accumulation and IL-23 p19 mRNA expression. In addition, reporter assay using the IL-23 p19 promoter region revealed that ATF4 directly transactivated IL-23 p19 promoter and that dominant-negative ATF4 suppressed Zn(2+)-induced activation of IL-23 p19 promoter. Taken together, these findings suggest that Zn(2+) up-regulates expression of the IL-23 p19 gene via the eIF2α/ATF4 axis in HAPI cells.
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He K, McCord MC, Hartnett KA, Aizenman E. Regulation of Pro-Apoptotic Phosphorylation of Kv2.1 K+ Channels. PLoS One 2015; 10:e0129498. [PMID: 26115091 PMCID: PMC4482604 DOI: 10.1371/journal.pone.0129498] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 05/08/2015] [Indexed: 12/12/2022] Open
Abstract
Caspase activity during apoptosis is inhibited by physiological concentrations of intracellular K+. To enable apoptosis in injured cortical and hippocampal neurons, cellular loss of this cation is facilitated by the insertion of Kv2.1 K+ channels into the plasma membrane via a Zn2+/CaMKII/SNARE-dependent process. Pro-apoptotic membrane insertion of Kv2.1 requires the dual phosphorylation of the channel by Src and p38 at cytoplasmic N- and C-terminal residues Y124 and S800, respectively. In this study, we investigate if these phosphorylation sites are mutually co-regulated, and whether putative N- and C-terminal interactions, possibly enabled by Kv2.1 intracellular cysteine residues C73 and C710, influence the phosphorylation process itself. Studies were performed with recombinant wild type and mutant Kv2.1 expressed in Chinese hamster ovary (CHO) cells. Using immunoprecipitated Kv2.1 protein and phospho-specific antibodies, we found that an intact Y124 is required for p38 phosphorylation of S800, and, importantly, that Src phosphorylation of Y124 facilitates the action of the p38 at the S800 residue. Moreover, the actions of Src on Kv2.1 are substantially decreased in the non-phosphorylatable S800A channel mutant. We also observed that mutations of either C73 or C710 residues decreased the p38 phosphorylation at S800 without influencing the actions of Src on tyrosine phosphorylation of Kv2.1. Surprisingly, however, apoptotic K+ currents were suppressed only in cells expressing the Kv2.1(C73A) mutant but not in those transfected with Kv2.1(C710A), suggesting a possible structural alteration in the C-terminal mutant that facilitates membrane insertion. These results show that intracellular N-terminal domains critically regulate phosphorylation of the C-terminal of Kv2.1, and vice versa, suggesting possible new avenues for modifying the apoptotic insertion of these channels during neurodegenerative processes.
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Affiliation(s)
- Kai He
- Department of Neurobiology, University of Pittsburgh School of Medicine, E1456 BST, 3500 Terrace St., Pittsburgh, PA, 15261, United States of America
| | - Meghan C. McCord
- Department of Neurobiology, University of Pittsburgh School of Medicine, E1456 BST, 3500 Terrace St., Pittsburgh, PA, 15261, United States of America
| | - Karen A. Hartnett
- Department of Neurobiology, University of Pittsburgh School of Medicine, E1456 BST, 3500 Terrace St., Pittsburgh, PA, 15261, United States of America
| | - Elias Aizenman
- Department of Neurobiology, University of Pittsburgh School of Medicine, E1456 BST, 3500 Terrace St., Pittsburgh, PA, 15261, United States of America
- * E-mail:
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Hancock SM, Finkelstein DI, Adlard PA. Glia and zinc in ageing and Alzheimer's disease: a mechanism for cognitive decline? Front Aging Neurosci 2014; 6:137. [PMID: 25009495 PMCID: PMC4069481 DOI: 10.3389/fnagi.2014.00137] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 06/09/2014] [Indexed: 11/13/2022] Open
Abstract
Normal ageing is characterized by cognitive decline across a range of neurological functions, which are further impaired in Alzheimer’s disease (AD). Recently, alterations in zinc (Zn) concentrations, particularly at the synapse, have emerged as a potential mechanism underlying the cognitive changes that occur in both ageing and AD. Zn is now accepted as a potent neuromodulator, affecting a variety of signaling pathways at the synapse that are critical to normal cognition. While the focus has principally been on the neuron: Zn interaction, there is a growing literature suggesting that glia may also play a modulatory role in maintaining both Zn ion homeostasis and the normal function of the synapse. Indeed, zinc transporters (ZnT’s) have been demonstrated in glial cells where Zn has also been shown to have a role in signaling. Furthermore, there is increasing evidence that the pathogenesis of AD critically involves glial cells (such as astrocytes), which have been reported to contribute to amyloid-beta (Aβ) neurotoxicity. This review discusses the current evidence supporting a complex interplay of glia, Zn dyshomeostasis and synaptic function in ageing and AD.
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Affiliation(s)
- Sara M Hancock
- Synaptic Neurobiology Laboratory, Florey Institute of Neuroscience and Mental Health Parkville, VIC, Australia
| | - David I Finkelstein
- Parkinson's Disease Laboratory, Florey Institute of Neuroscience and Mental Health Parkville, VIC, Australia
| | - Paul A Adlard
- Synaptic Neurobiology Laboratory, Florey Institute of Neuroscience and Mental Health Parkville, VIC, Australia
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22
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McCord MC, Kullmann PH, He K, Hartnett KA, Horn JP, Lotan I, Aizenman E. Syntaxin-binding domain of Kv2.1 is essential for the expression of apoptotic K+ currents. J Physiol 2014; 592:3511-21. [PMID: 24928958 DOI: 10.1113/jphysiol.2014.276964] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Intracellular signalling cascades triggered by oxidative injury can lead to upregulation of Kv2.1 K(+) channels at the plasma membrane of dying neurons. Membrane incorporation of new channels is necessary for enhanced K(+) efflux and a consequent reduction of intracellular K(+) that facilitates apoptosis. We showed previously that the observed increase in K(+) currents is a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-mediated process, and that the SNARE protein syntaxin binds directly to Kv2.1 channels. In the present study, we tested whether disrupting the interaction of Kv2.1 and syntaxin promoted the survival of cortical neurons following injury. Syntaxin is known to bind to Kv2.1 in a domain comprising amino acids 411-522 of the channel's cytoplasmic C terminus (C1a). Here we show that this domain is required for the apoptotic K(+) current enhancement. Moreover, expression of an isolated, Kv2.1-derived C1a peptide is sufficient to suppress the injury-induced increase in currents by interfering with Kv2.1/syntaxin binding. By subdividing the C1a peptide, we were able to localize the syntaxin binding site on Kv2.1 to the most plasma membrane-distal residues of C1a. Importantly, expression of this peptide segment in neurons prevented the apoptotic K(+) current enhancement and cell death following an oxidative insult, without greatly impairing baseline K(+) currents or normal electrical profiles of neurons. These results establish that binding of syntaxin to Kv2.1 is crucial for the manifestation of oxidant-induced apoptosis, and thereby reveal a potential new direction for therapeutic intervention in the treatment of neurodegenerative disorders.
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Affiliation(s)
- Meghan C McCord
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Paul H Kullmann
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Kai He
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Karen A Hartnett
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - John P Horn
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Ilana Lotan
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Ramat Aviv, 69978, Israel
| | - Elias Aizenman
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
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23
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McCord MC, Aizenman E. The role of intracellular zinc release in aging, oxidative stress, and Alzheimer's disease. Front Aging Neurosci 2014; 6:77. [PMID: 24860495 PMCID: PMC4028997 DOI: 10.3389/fnagi.2014.00077] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 04/02/2014] [Indexed: 01/26/2023] Open
Abstract
Brain aging is marked by structural, chemical, and genetic changes leading to cognitive decline and impaired neural functioning. Further, aging itself is also a risk factor for a number of neurodegenerative disorders, most notably Alzheimer’s disease (AD). Many of the pathological changes associated with aging and aging-related disorders have been attributed in part to increased and unregulated production of reactive oxygen species (ROS) in the brain. ROS are produced as a physiological byproduct of various cellular processes, and are normally detoxified by enzymes and antioxidants to help maintain neuronal homeostasis. However, cellular injury can cause excessive ROS production, triggering a state of oxidative stress that can lead to neuronal cell death. ROS and intracellular zinc are intimately related, as ROS production can lead to oxidation of proteins that normally bind the metal, thereby causing the liberation of zinc in cytoplasmic compartments. Similarly, not only can zinc impair mitochondrial function, leading to excess ROS production, but it can also activate a variety of extra-mitochondrial ROS-generating signaling cascades. As such, numerous accounts of oxidative neuronal injury by ROS-producing sources appear to also require zinc. We suggest that zinc deregulation is a common, perhaps ubiquitous component of injurious oxidative processes in neurons. This review summarizes current findings on zinc dyshomeostasis-driven signaling cascades in oxidative stress and age-related neurodegeneration, with a focus on AD, in order to highlight the critical role of the intracellular liberation of the metal during oxidative neuronal injury.
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Affiliation(s)
- Meghan C McCord
- Department of Neurobiology, University of Pittsburgh School of Medicine Pittsburgh, PA, USA
| | - Elias Aizenman
- Department of Neurobiology, University of Pittsburgh School of Medicine Pittsburgh, PA, USA
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24
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Significance of metallothioneins in aging brain. Neurochem Int 2014; 65:40-8. [DOI: 10.1016/j.neuint.2013.12.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 12/01/2013] [Accepted: 12/26/2013] [Indexed: 12/14/2022]
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El Hachmane MF, Rees KA, Veale EL, Sumbayev VV, Mathie A. Enhancement of TWIK-related acid-sensitive potassium channel 3 (TASK3) two-pore domain potassium channel activity by tumor necrosis factor α. J Biol Chem 2013; 289:1388-401. [PMID: 24307172 DOI: 10.1074/jbc.m113.500033] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TASK3 two-pore domain potassium (K2P) channels are responsible for native leak K channels in many cell types which regulate cell resting membrane potential and excitability. In addition, TASK3 channels contribute to the regulation of cellular potassium homeostasis. Because TASK3 channels are important for cell viability, having putative roles in both neuronal apoptosis and oncogenesis, we sought to determine their behavior under inflammatory conditions by investigating the effect of TNFα on TASK3 channel current. TASK3 channels were expressed in tsA-201 cells, and the current through them was measured using whole cell voltage clamp recordings. We show that THP-1 human myeloid leukemia monocytes, co-cultured with hTASK3-transfected tsA-201 cells, can be activated by the specific Toll-like receptor 7/8 activator, R848, to release TNFα that subsequently enhances hTASK3 current. Both hTASK3 and mTASK3 channel activity is increased by incubation with recombinant TNFα (10 ng/ml for 2-15 h), but other K2P channels (hTASK1, hTASK2, hTREK1, and hTRESK) are unaffected. This enhancement by TNFα is not due to alterations in levels of channel expression at the membrane but rather to an alteration in channel gating. The enhancement by TNFα can be blocked by extracellular acidification but persists for mutated TASK3 (H98A) channels that are no longer acid-sensitive even in an acidic extracellular environment. TNFα action on TASK3 channels is mediated through the intracellular C terminus of the channel. Furthermore, it occurs through the ASK1 pathway and is JNK- and p38-dependent. In combination, TNFα activation and TASK3 channel activity can promote cellular apoptosis.
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Affiliation(s)
- Mickael-F El Hachmane
- From the Medway School of Pharmacy, University of Kent, Central Avenue, Chatham Maritime, ME4 4TB Kent, United Kingdom
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Shah NH, Aizenman E. Voltage-gated potassium channels at the crossroads of neuronal function, ischemic tolerance, and neurodegeneration. Transl Stroke Res 2013; 5:38-58. [PMID: 24323720 DOI: 10.1007/s12975-013-0297-7] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 09/14/2013] [Accepted: 10/14/2013] [Indexed: 11/29/2022]
Abstract
Voltage-gated potassium (Kv) channels are widely expressed in the central and peripheral nervous system and are crucial mediators of neuronal excitability. Importantly, these channels also actively participate in cellular and molecular signaling pathways that regulate the life and death of neurons. Injury-mediated increased K(+) efflux through Kv2.1 channels promotes neuronal apoptosis, contributing to widespread neuronal loss in neurodegenerative disorders such as Alzheimer's disease and stroke. In contrast, some forms of neuronal activity can dramatically alter Kv2.1 channel phosphorylation levels and influence their localization. These changes are normally accompanied by modifications in channel voltage dependence, which may be neuroprotective within the context of ischemic injury. Kv1 and Kv7 channel dysfunction leads to neuronal hyperexcitability that critically contributes to the pathophysiology of human clinical disorders such as episodic ataxia and epilepsy. This review summarizes the neurotoxic, neuroprotective, and neuroregulatory roles of Kv channels and highlights the consequences of Kv channel dysfunction on neuronal physiology. The studies described in this review thus underscore the importance of normal Kv channel function in neurons and emphasize the therapeutic potential of targeting Kv channels in the treatment of a wide range of neurological diseases.
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Affiliation(s)
- Niyathi Hegde Shah
- Department of Neurobiology, University of Pittsburgh School of Medicine, 3500 Terrace Street, E1456 BST, Pittsburgh, PA, 15261, USA,
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Tsay HJ, Huang YC, Huang FL, Chen CP, Tsai YC, Wang YH, Wu MF, Chiang FY, Shiao YJ. Amyloid β peptide-mediated neurotoxicity is attenuated by the proliferating microglia more potently than by the quiescent phenotype. J Biomed Sci 2013; 20:78. [PMID: 24152138 PMCID: PMC3870991 DOI: 10.1186/1423-0127-20-78] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Accepted: 10/20/2013] [Indexed: 12/12/2022] Open
Abstract
Background The specific role of microglia on Aβ-mediated neurotoxicity is difficult to assign in vivo due to their complicated environment in the brain. Therefore, most of the current microglia-related studies employed the isolated microglia. However, the previous in vitro studies have suggested either beneficial or destructive function in microglia. Therefore, to investigate the phenotypes of the isolated microglia which exert activity of neuroprotective or destructive is required. Results The present study investigates the phenotypes of isolated microglia on protecting neuron against Aβ-mediated neurotoxicity. Primary microglia were isolated from the mixed glia culture, and were further cultured to distinct phenotypes, designated as proliferating amoeboid microglia (PAM) and differentiated process-bearing microglia (DPM). Their inflammatory phenotypes, response to amyloid β (Aβ), and the beneficial or destructive effects on neurons were investigated. DPM may induce both direct neurotoxicity without exogenous stimulation and indirect neurotoxicity after Aβ activation. On the other hand, PAM attenuates Aβ-mediated neurotoxicity through Aβ phagocytosis and/or Aβ degradation. Conclusions Our results suggest that the proliferating microglia, but not the differentiated microglia, protect neurons against Aβ-mediated neurotoxicity. This discovery may be helpful on the therapeutic investigation of Alzheimer’s disease.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Young-Ji Shiao
- Institute of Biopharmaceutical Science, National Yang-Ming University, Taipei 11221, Taiwan.
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Convergent Ca2+ and Zn2+ signaling regulates apoptotic Kv2.1 K+ currents. Proc Natl Acad Sci U S A 2013; 110:13988-93. [PMID: 23918396 DOI: 10.1073/pnas.1306238110] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
A simultaneous increase in cytosolic Zn(2+) and Ca(2+) accompanies the initiation of neuronal cell death signaling cascades. However, the molecular convergence points of cellular processes activated by these cations are poorly understood. Here, we show that Ca(2+)-dependent activation of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is required for a cell death-enabling process previously shown to also depend on Zn(2+). We have reported that oxidant-induced intraneuronal Zn(2+) liberation triggers a syntaxin-dependent incorporation of Kv2.1 voltage-gated potassium channels into the plasma membrane. This channel insertion can be detected as a marked enhancement of delayed rectifier K(+) currents in voltage clamp measurements observed at least 3 h following a short exposure to an apoptogenic stimulus. This current increase is the process responsible for the cytoplasmic loss of K(+) that enables protease and nuclease activation during apoptosis. In the present study, we demonstrate that an oxidative stimulus also promotes intracellular Ca(2+) release and activation of CaMKII, which, in turn, modulates the ability of syntaxin to interact with Kv2.1. Pharmacological or molecular inhibition of CaMKII prevents the K(+) current enhancement observed following oxidative injury and, importantly, significantly increases neuronal viability. These findings reveal a previously unrecognized cooperative convergence of Ca(2+)- and Zn(2+)-mediated injurious signaling pathways, providing a potentially unique target for therapeutic intervention in neurodegenerative conditions associated with oxidative stress.
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Regulation of neuronal proapoptotic potassium currents by the hepatitis C virus nonstructural protein 5A. J Neurosci 2012; 32:8865-70. [PMID: 22745487 DOI: 10.1523/jneurosci.0937-12.2012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Apoptosis-enabling neuronal potassium efflux is mediated by an enhancement of K+ currents. In cortical neurons, increased currents are triggered by dual phosphorylation of Kv2.1 by Src and p38 at channel residues Y124 and S800. It was recently shown that a K+ current surge is also present in hepatocytes undergoing apoptosis, and that the hepatitis C virus (HCV) nonstructural protein 5A (NS5A) could inhibit Kv2.1-mediated currents and block cell death. Here, we show that NS5A1b (from HCV genotype 1b) expression in rat neurons depresses delayed rectifier potassium currents, limits the magnitude of the K+ current surge following exposure to activated microglia, and is neuroprotective. In a non-neuronal recombinant expression system, cells expressing Kv2.1 mutated at residue Y124, but not S800 mutants, are insensitive to NS5A1b-mediated current inhibition. Accordingly, NS5A1b coexpression prevents phosphorylation of wild-type Kv2.1 by Src at Y124, but is unable to inhibit p38 phosphorylation of the channel at S800. The actions of the viral protein are genotype-selective, as NS5A1a does not depress neuronal potassium currents nor inhibit Src phosphorylation of Kv2.1. Our results indicate that NS5A1b limits K+ currents following injury, leading to increased neuronal viability. NS5A1b may thus serve as a model for a new generation of neuroprotective agents.
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Luo XG, Chen SD. The changing phenotype of microglia from homeostasis to disease. Transl Neurodegener 2012; 1:9. [PMID: 23210447 PMCID: PMC3514090 DOI: 10.1186/2047-9158-1-9] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2012] [Accepted: 04/24/2012] [Indexed: 12/20/2022] Open
Abstract
It has been nearly a century since the early description of microglia by Rio-Hortega; since then many more biological and pathological features of microglia have been recognized. Today, microglia are generally considered to be beneficial to homeostasis at the resting state through their abilities to survey the environment and phagocytose debris. However, when activated microglia assume diverse phenotypes ranging from fully inflamed, which involves the release of many pro-inflammatory cytokines, to alternatively activated, releasing anti-inflammatory cytokines or neurotrophins, the consequences to neurons can range from detrimental to supportive. Due to the different experimental sets and conditions, contradictory results have been obtained regarding the controversial question of whether microglia are “good” or “bad.” While it is well understood that the dual roles of activated microglia depend on specific situations, the underlying mechanisms have remained largely unclear, and the interpretation of certain findings related to diverse microglial phenotypes continues to be problematic. In this review we discuss the functions of microglia in neuronal survival and neurogenesis, the crosstalk between microglia and surrounding cells, and the potential factors that could influence the eventual manifestation of microglia.
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Affiliation(s)
- Xiao-Guang Luo
- Department of Neurology & Institute of Neurology, Ruijin Hospital affiliated to Shanghai Jiao Tong University, Shanghai, 200025, China.
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31
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Filipiak M, Tylko G, Pyza E. Zinc induces caspase-dependent mitochondrial pathway of the programmed cell death in haemocytes of Drosophila melanogaster. Biometals 2012; 25:507-16. [PMID: 22367497 PMCID: PMC3349848 DOI: 10.1007/s10534-012-9530-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 02/09/2012] [Indexed: 01/11/2023]
Abstract
Zinc is an essential trace element in cells. However, its high level in cytoplasm promotes activation of stress signaling pathways and may lead to cell death. In the present study we used Drosophila melanogaster blood cells (haemocytes), obtained from the third instar larvae, to study the effects of high concentrations of Zn(2+) on programmed cell death (PCD). We analyzed the activity of caspases, the level of caspase inhibitor protein DIAP1 and metallothioneins, as well as calcium concentrations and activity of mitochondria in haemocytes exposed to 0.35 and 1.7 mM concentrations of Zn. The obtained results showed that rapid increase of [Zn(2+)]( i ) in the cytoplasm up-regulates metallothionein MtnB but not MtnA gene expression in cells treated with Zn(2+) in both concentrations. Excess of Zn(2+) also induced activation of the initiator caspase Dronc, associated with the mitochondrial pathway of PCD, and the effector caspase DrICE. In turn, the activity of receptor-regulated Dredd caspase was not changed. The level of DIAP1 decreased significantly in haemocytes in the presence of high Zn(2+) concentration in comparison to untreated cells. Moreover, mitochondrial membrane potential was significantly decreased after exposure to Zn ions. These results indicate that high concentration of Zn(2+) in the cytoplasm of haemocytes induces PCD via a mitochondrial pathway and that caspases play a pivotal role in this process.
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Affiliation(s)
- Marta Filipiak
- Department of Cell Biology and Imaging, Institute of Zoology, Jagiellonian University, Gronostajowa 9, 30-387 Kraków, Poland
| | - Grzegorz Tylko
- Department of Cell Biology and Imaging, Institute of Zoology, Jagiellonian University, Gronostajowa 9, 30-387 Kraków, Poland
| | - Elzbieta Pyza
- Department of Cell Biology and Imaging, Institute of Zoology, Jagiellonian University, Gronostajowa 9, 30-387 Kraków, Poland
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Sekler I, Silverman WF. Zinc homeostasis and signaling in glia. Glia 2012; 60:843-50. [DOI: 10.1002/glia.22286] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 12/02/2011] [Indexed: 11/08/2022]
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Aras MA, Aizenman E. Redox regulation of intracellular zinc: molecular signaling in the life and death of neurons. Antioxid Redox Signal 2011; 15:2249-63. [PMID: 20849376 PMCID: PMC3166180 DOI: 10.1089/ars.2010.3607] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Zn(2+) has emerged as a major regulator of neuronal physiology, as well as an important signaling agent in neural injury. The intracellular concentration of this metal is tightly regulated through the actions of Zn(2+) transporters and the thiol-rich metal binding protein metallothionein, closely linking the redox status of the cell to cellular availability of Zn(2+). Accordingly, oxidative and nitrosative stress during ischemic injury leads to an accumulation of neuronal free Zn(2+) and the activation of several downstream cell death processes. While this Zn(2+) rise is an established signaling event in neuronal cell death, recent evidence suggests that a transient, sublethal accumulation of free Zn(2+) can also play a critical role in neuroprotective pathways activated during ischemic preconditioning. Thus, redox-sensitive proteins, like metallothioneins, may play a critical role in determining neuronal cell fate by regulating the localization and concentration of intracellular free Zn(2+).
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Affiliation(s)
- Mandar A Aras
- Department of Neurobiology, University of Pittsburgh School of Medicine, 3500 Terrace St., Pittsburgh, PA 15261, USA.
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Higashi Y, Segawa S, Matsuo T, Nakamura S, Kikkawa Y, Nishida K, Nagasawa K. Microglial zinc uptake via zinc transporters induces ATP release and the activation of microglia. Glia 2011; 59:1933-45. [PMID: 22253048 DOI: 10.1002/glia.21235] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 07/27/2011] [Indexed: 01/14/2023]
Abstract
Previously, we demonstrated that extracellular zinc plays a key role in transient global ischemia-induced microglial activation through sequential activation of NADPH oxidase and poly(ADP-ribose) polymerase (PARP)-1. However, it remains unclear how zinc causes the sequential activation of microglia. Here, we examined whether transporter-mediated zinc uptake is necessary for microglial activation. Administration of zinc to microglia activated them through reactive oxygen species (ROS) generation and poly(ADP-ribose) (PAR) formation, which were suppressed by intracellular zinc chelation with 25 μM TPEN (N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine) or 2 μM BAPTA-AM (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester). The (65)Zn uptake by microglia was temperature- and dose-dependent, and it was blocked by metal cations, but not by L-type calcium channel blockers nifedipine and nimodipine. Expression of Zrt-Irt-like protein (ZIP)1, a plasma membrane-type zinc transporter, was detected in microglia, and nickel, a relatively sensitive substrate/inhibitor of ZIP1, showed cis- and trans-inhibitory effects on the (65)Zn uptake. Exposure of microglia to zinc increased the extracellular ATP concentration, which was suppressed by intracellular zinc chelation and inhibition of hemichannels. mRNA expression of several types of P2 receptors was detected in microglia, and periodate-oxidized ATP, a selective P2×7 receptor antagonist, attenuated the zinc-induced microglial activation via NADPH oxidase and PARP-1. Exogenous ATP and 2'(3')-O-(4-benzoyl-benzoyl) ATP also caused microglial activation through ROS generation and PAR formation. These findings demonstrate that ZIP1-mediated uptake of zinc induces ATP release and autocrine/paracrine activation of P2X(7) receptors, and then activates microglia, suggesting that zinc transporter-mediated uptake of zinc is a trigger for microglial activation via the NADPH oxidase and PARP-1 pathway. © 2011 Wiley-Liss, Inc.
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Affiliation(s)
- Youichirou Higashi
- Department of Environmental Biochemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto, Japan
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35
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Hara H, Nakamura Y, Ninomiya M, Mochizuki R, Kamiya T, Aizenman E, Koketsu M, Adachi T. Inhibitory effects of chalcone glycosides isolated from Brassica rapa L. 'hidabeni' and their synthetic derivatives on LPS-induced NO production in microglia. Bioorg Med Chem 2011; 19:5559-68. [PMID: 21856162 DOI: 10.1016/j.bmc.2011.07.036] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 07/19/2011] [Accepted: 07/20/2011] [Indexed: 01/17/2023]
Abstract
Activation of microglia induces the production of various inflammatory mediators including nitric oxide (NO), leading to neurodegeneration in many central nervous system diseases. In this study, we examined the effects of chalcone glycosides isolated from Brassica rapa L. 'hidabeni' on lipopolysaccharide (LPS)-induced NO production using rat immortalized microglia HAPI cells. 4'-O-β-D-Glucopyranosyl-3',4-dimethoxychalcone (A2) inhibited LPS-induced inducible NO synthase (iNOS) expression and NO production. However, A2 did not affect nuclear factor-κB and mitogen-activated protein kinase pathways. The signal transduction and activator of transcription 1 (STAT1), which is activated via production of IFN-β by LPS, is an important transcription factor responsible for LPS-induced iNOS expression. A2 suppressed LPS-induced phosphorylation and nuclear translocation of STAT1, although it had no effects on LPS-induced IFN-β expression. These results indicate that the inhibitory effect of A2 is due to the prevention of STAT signaling. Moreover, structure-activity relationship studies on newly synthesized 'hidabeni' chalcone derivatives showed that 4'-O-β-D-glucopyranosyl-3'-methoxychalcone (A11), which has no functional groups in the B-ring, inhibits LPS-induced NO production more potently than A2.
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Affiliation(s)
- Hirokazu Hara
- Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan.
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36
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Steinert JR, Chernova T, Forsythe ID. Nitric oxide signaling in brain function, dysfunction, and dementia. Neuroscientist 2011; 16:435-52. [PMID: 20817920 DOI: 10.1177/1073858410366481] [Citation(s) in RCA: 315] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Nitric oxide (NO) is an important signaling molecule that is widely used in the nervous system. With recognition of its roles in synaptic plasticity (long-term potentiation, LTP; long-term depression, LTD) and elucidation of calcium-dependent, NMDAR-mediated activation of neuronal nitric oxide synthase (nNOS), numerous molecular and pharmacological tools have been used to explore the physiology and pathological consequences for nitrergic signaling. In this review, the authors summarize the current understanding of this subtle signaling pathway, discuss the evidence for nitrergic modulation of ion channels and homeostatic modulation of intrinsic excitability, and speculate about the pathological consequences of spillover between different nitrergic compartments in contributing to aberrant signaling in neurodegenerative disorders. Accumulating evidence points to various ion channels and particularly voltage-gated potassium channels as signaling targets, whereby NO mediates activity-dependent control of intrinsic neuronal excitability; such changes could underlie broader mechanisms of synaptic plasticity across neuronal networks. In addition, the inability to constrain NO diffusion suggests that spillover from endothelium (eNOS) and/or immune compartments (iNOS) into the nervous system provides potential pathological sources of NO and where control failure in these other systems could have broader neurological implications. Abnormal NO signaling could therefore contribute to a variety of neurodegenerative pathologies such as stroke/excitotoxicity, Alzheimer's disease, multiple sclerosis, and Parkinson's disease.
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Affiliation(s)
- Joern R Steinert
- Neurotoxicity at the Synaptic Interface, MRC Toxicology Unit, University of Leicester, Leicester, UK
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Aizenman E, McCord MC, Saadi RA, Hartnett KA, He K. Complex role of zinc in methamphetamine toxicity in vitro. Neuroscience 2010; 171:31-9. [PMID: 20801194 PMCID: PMC2956874 DOI: 10.1016/j.neuroscience.2010.08.049] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Revised: 08/19/2010] [Accepted: 08/22/2010] [Indexed: 11/21/2022]
Abstract
Methamphetamine is a drug of abuse that can induce oxidative stress and neurotoxicity to dopaminergic neurons. We have previously reported that oxidative stress promotes the liberation of intracellular Zn(2+) from metal-binding proteins, which, in turn, can initiate neuronal injurious signaling processes. Here, we report that methamphetamine mobilizes Zn(2+) in catecholaminergic rat pheochromocytoma (PC12) cells, as measured by an increase in Zn(2+)-regulated gene expression driven by the metal response element transcription factor-1. Moreover, methamphetamine-liberated Zn(2+) was responsible for a pronounced enhancement in voltage-dependent K(+) currents in these cells, a process that normally accompanies Zn(2+)-dependent cell injury. Overnight exposure to methamphetamine induced PC12 cell death. This toxicity could be prevented by the cell-permeant zinc chelator N,N,N', N'-tetrakis(2-pyridylmethyl)-ethylenediamine (TPEN), and by over-expression of the Zn(2+)-binding protein metallothionein 3 (MT3), but not by tricine, an extracellular Zn(2+) chelator. The toxicity of methamphetamine to PC12 cells was enhanced by the presence of co-cultured microglia. Remarkably, under these conditions, TPEN no longer protected but, in fact, dramatically exacerbated methamphetamine toxicity, tricine again being without effect. Over-expression of MT3 in PC12 cells did not mimic these toxicity-enhancing actions of TPEN, suggesting that the chelator affected microglial function. Interestingly, P2X receptor antagonists reversed the toxicity-enhancing effect of TPEN. As such, endogenous levels of intracellular Zn(2+) may normally interfere with the activation of P2X channels in microglia. We conclude that Zn(2+) plays a significant but complex role in modulating the cellular response of PC12 cells to methamphetamine exposure in both the absence and presence of microglia.
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Affiliation(s)
- E Aizenman
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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Loane DJ, Byrnes KR. Role of microglia in neurotrauma. Neurotherapeutics 2010; 7:366-77. [PMID: 20880501 PMCID: PMC2948548 DOI: 10.1016/j.nurt.2010.07.002] [Citation(s) in RCA: 465] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Revised: 05/26/2010] [Accepted: 07/01/2010] [Indexed: 01/12/2023] Open
Abstract
Microglia are the primary mediators of the immune defense system of the CNS and are integral to the subsequent inflammatory response. The role of microglia in the injured CNS is under scrutiny, as research has begun to fully explore how postinjury inflammation contributes to secondary damage and recovery of function. Whether microglia are good or bad is under debate, with strong support for a dual role or differential activation of microglia. Microglia release a number of factors that modulate secondary injury and recovery after injury, including pro- and anti-inflammatory cytokines, chemokines, nitric oxide, prostaglandins, growth factors, and superoxide species. Here we review experimental work on the complex and varied responses of microglia in terms of both detrimental and beneficial effects. Addressed in addition are the effects of microglial activation in two examples of CNS injury: spinal cord and traumatic brain injury. Microglial activation is integral to the response of CNS tissue to injury. In that light, future research is needed to focus on clarifying the signals and mechanisms by which microglia can be guided to promote optimal functional recovery.
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Affiliation(s)
- David J. Loane
- Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research (STAR), National Study Center for Trauma and EMS, University of Maryland School of Medicine, 21201 Baltimore, Maryland
| | - Kimberly R. Byrnes
- grid.265436.00000000104215525Room B2048, Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, 20814 Bethesda, MD
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Aras MA, Saadi RA, Aizenman E. Zn2+ regulates Kv2.1 voltage-dependent gating and localization following ischemia. Eur J Neurosci 2009; 30:2250-7. [PMID: 20092568 DOI: 10.1111/j.1460-9568.2009.07026.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The delayed-rectifier K(+) channel Kv2.1 exists in highly phosphorylated somatodendritic clusters. Ischemia induces rapid Kv2.1 dephosphorylation and a dispersal of these clusters, accompanied by a hyperpolarizing shift in their voltage-dependent activation kinetics. Transient modulation of Kv2.1 activity and localization following ischemia is dependent on a rise in intracellular Ca(2+)and the protein phosphatase calcineurin. Here, we show that neuronal free Zn(2+)also plays a critical role in the ischemic modulation of Kv2.1. We found that sub-lethal ischemia in cultured rat cortical neurons led to characteristic hyperpolarizing shifts in K(+) current voltage dependency and pronounced dephosphorylation of Kv2.1. Zn(2+)chelation, similar to calcineurin inhibition, attenuated ischemic induced changes in K(+) channel activation kinetics. Zn(2+)chelation during ischemia also blocked Kv2.1 declustering. Surprisingly, we found that the Zn(2+)rise following ischemia occurred in spite of calcineurin inhibition. Therefore, a calcineurin-independent rise in neuronal free Zn(2+) is critical in altering Kv2.1 channel activity and localization following ischemia. The identification of Zn(2+) in mediating ischemic modulation of Kv2.1 may lead to a better understanding of cellular adaptive responses to injury.
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Affiliation(s)
- Mandar A Aras
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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Somera-Molina KC, Nair S, Van Eldik LJ, Watterson DM, Wainwright MS. Enhanced microglial activation and proinflammatory cytokine upregulation are linked to increased susceptibility to seizures and neurologic injury in a 'two-hit' seizure model. Brain Res 2009; 1282:162-72. [PMID: 19501063 PMCID: PMC2739829 DOI: 10.1016/j.brainres.2009.05.073] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 05/18/2009] [Accepted: 05/20/2009] [Indexed: 12/21/2022]
Abstract
Early-life seizures result in increased susceptibility to seizures and greater neurologic injury with a second insult in adulthood. The mechanisms which link seizures in early-life to increased susceptibility to neurologic injury following a 'second hit' are not known. We examined the contribution of microglial activation and increased proinflammatory cytokine production to the subsequent increase in susceptibility to neurologic injury using a kainic acid (KA)-induced, established 'two-hit' seizure model in rats. Postnatal day (P)15 rats were administered intraperitoneal KA (early-life seizures) or saline, followed on P45 with either a 'second hit' of KA, a first exposure to KA (adult seizures), or saline. We measured the levels of proinflammatory cytokines (IL-1 beta, TNF-alpha, and S100B), the chemokine CCL2, microglial activation, seizure susceptibility and neuronal outcomes in adult rats 12 h and 10 days after the second hit on P45. The 'two-hit' group exposed to KA on both P15 and P45 had higher levels of cytokines, greater microglial activation, and increased susceptibility to seizures and neurologic injury compared to the adult seizures group. Treatment after early-life seizures with Minozac, a small molecule experimental therapeutic that targets upregulated proinflammatory cytokine production, attenuated the enhanced microglial and cytokine responses, the increased susceptibility to seizures, and the greater neuronal injury in the 'two-hit' group. These results implicate microglial activation as one mechanism by which early-life seizures contribute to increased vulnerability to neurologic insults in adulthood, and indicate the potential longer term benefits of early-life intervention with therapies that target up-regulation of proinflammatory cytokines.
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Affiliation(s)
- Kathleen C. Somera-Molina
- Integrated Graduate Program, Northwestern University, Chicago, IL
- Department of Pediatrics, Division of Neurology, Northwestern University, Chicago, IL
- Center for Interdisciplinary Research in Pediatric Critical Illness and Injury, Northwestern University, Chicago, IL
- Center for Drug Discovery and Chemical Biology, Northwestern University, Chicago, IL
| | - Sangeetha Nair
- Department of Pediatrics, Division of Neurology, Northwestern University, Chicago, IL
- Center for Interdisciplinary Research in Pediatric Critical Illness and Injury, Northwestern University, Chicago, IL
| | - Linda J. Van Eldik
- Center for Drug Discovery and Chemical Biology, Northwestern University, Chicago, IL
- Department of Cell and Molecular Biology, Northwestern University, Chicago, IL
| | - D. Martin Watterson
- Center for Drug Discovery and Chemical Biology, Northwestern University, Chicago, IL
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University, Chicago, IL
| | - Mark S. Wainwright
- Department of Pediatrics, Division of Neurology, Northwestern University, Chicago, IL
- Center for Interdisciplinary Research in Pediatric Critical Illness and Injury, Northwestern University, Chicago, IL
- Center for Drug Discovery and Chemical Biology, Northwestern University, Chicago, IL
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41
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Redman PT, Hartnett KA, Aras MA, Levitan ES, Aizenman E. Regulation of apoptotic potassium currents by coordinated zinc-dependent signalling. J Physiol 2009; 587:4393-404. [PMID: 19622611 DOI: 10.1113/jphysiol.2009.176321] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Oxidant-liberated intracellular Zn(2+) regulates neuronal apoptosis via an exocytotic membrane insertion of Kv2.1-encoded ion channels, resulting in an enhancement of voltage-gated K(+) currents and a loss of intracellular K(+) that is necessary for caspase-mediated proteolysis. In the present study we show that an N-terminal tyrosine of Kv2.1 (Y124), which is a known target of Src kinase, is critical for the apoptotic current surge. Moreover, we demonstrate that Y124 works in concert with a C-terminal serine (S800) target of p38 mitogen-activated protein kinase (MAPK) to regulate Kv2.1-mediated current enhancement. While Zn(2+) was previously shown to activate p38, we show here that this metal inhibits cytoplasmic protein tyrosine phosphatase (Cyt-PTPepsilon), which specifically targets Y124. Importantly, a point mutation of Y124 to a non-phosphorylatable residue or over-expression of Cyt-PTPepsilon protects cells from injury. Kv2.1-encoded channels thus regulate neuronal survival by providing a converging input for two Zn(2+)-dependent signal transduction cascades.
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Affiliation(s)
- Patrick T Redman
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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42
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Lee JY, Son HJ, Choi JH, Cho E, Kim J, Chung SJ, Hwang O, Koh JY. Cytosolic labile zinc accumulation in degenerating dopaminergic neurons of mouse brain after MPTP treatment. Brain Res 2009; 1286:208-14. [PMID: 19559009 DOI: 10.1016/j.brainres.2009.06.046] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Revised: 06/12/2009] [Accepted: 06/16/2009] [Indexed: 01/24/2023]
Abstract
High levels of labile zinc accumulate in degenerating neurons after brain injury, such as ischemic stroke, trauma, epilepsy, and hypoglycemia. Cytosolic zinc accumulation is also found in brain neurons undergoing apoptosis during development or after neuronal target ablation. Thus, staining with zinc-specific probes can be used to identify neuronal death in the brain. In this study, mice were intraperitoneally given four 20 mg/kg doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at 2-hour intervals, and dopaminergic neurons were then evaluated for zinc accumulation and apoptosis. In the substantia nigra pars compacta, zinc-specific fluorescent dyes revealed that all degenerating neurons, identified by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL), or acid fuchsin or Fluoro-Jade C staining, contained high levels of cytosolic labile zinc. Nuclear condensation/fragmentation was noted in dopaminergic neurons with cytosolic zinc accumulation, indicating apoptotic cell death. These findings support the supposition that cytosolic labile zinc accumulation is an indicator of degenerating dopaminergic neurons in animal models of Parkinson's disease.
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Affiliation(s)
- Joo-Yong Lee
- Asan Institute for Life Sciences, Asan Medical Center, Songpagu, Seoul 138-736, Republic of Korea.
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43
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Abstract
Despite zinc ions being redox inert in biologic systems, zinc-finger structures act as redox-sensitive molecular switches controlling several crucial cellular processes. Oxidative or nitrosative stress, via modification of zinc finger cysteine thiols, leads to a release of Zn(2+) from these structures, causing not only a loss of zinc-finger function but also an increase of cytoplasmic or nuclear free Zn(2+) that may, in turn, stimulate and interfere with cellular signaling cascades. A signaling cascade stimulated by exposure of cells to zinc ions or to stressful stimuli that are reported to cause an intracellular release of zinc ions involves phosphoinositide 3'-kinases and the Ser/Thr protein kinase Akt, resulting in an inactivation of transcriptional regulators of the FoxO family. Possible modes of action of zinc ions to stimulate this signaling cascade and consequences of stimulation are discussed. Moreover, we present an overview on human diseases or disorders characterized by an intracellular Zn(2+) dyshomeostasis.
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Affiliation(s)
- Klaus-D Kröncke
- Institute of Biochemistry and Molecular Biology I, Heinrich-Heine University of Düsseldorf, Düsseldorf, Germany.
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44
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Aras MA, Hara H, Hartnett KA, Kandler K, Aizenman E. Protein kinase C regulation of neuronal zinc signaling mediates survival during preconditioning. J Neurochem 2009; 110:106-17. [PMID: 19453299 DOI: 10.1111/j.1471-4159.2009.06106.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sub-lethal activation of cell death processes initiate pro-survival signaling cascades. As intracellular Zn(2+) liberation mediates neuronal death pathways, we tested whether a sub-lethal increase in free Zn(2+) could also trigger neuroprotection. Neuronal free Zn(2+) transiently increased following preconditioning, and was both necessary and sufficient for conferring excitotoxic tolerance. Lethal exposure to NMDA led to a delayed increase in Zn(2+) that contributed significantly to excitotoxicity in non-preconditioned neurons, but not in tolerant neurons, unless preconditioning-induced free Zn(2+) was chelated. Thus, preconditioning may trigger the expression of Zn(2+)-regulating processes, which, in turn, prevent subsequent Zn(2+)-mediated toxicity. Indeed, preconditioning increased Zn(2+)-regulated gene expression in neurons. Examination of the molecular signaling mechanism leading to this early Zn(2+) signal revealed a critical role for protein kinase C (PKC) activity, suggesting that PKC may act directly on the intracellular source of Zn(2+). We identified a conserved PKC phosphorylation site at serine-32 (S32) of metallothionein (MT) that was important in modulating Zn(2+)-regulated gene expression and conferring excitotoxic tolerance. Importantly, we observed increased PKC-induced serine phosphorylation in immunopurified MT1, but not in mutant MT1(S32A). These results indicate that neuronal Zn(2+) serves as an important, highly regulated signaling component responsible for the initiation of a neuroprotective pathway.
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Affiliation(s)
- Mandar A Aras
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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45
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Ho Y, Samarasinghe R, Knoch ME, Lewis M, Aizenman E, DeFranco DB. Selective inhibition of mitogen-activated protein kinase phosphatases by zinc accounts for extracellular signal-regulated kinase 1/2-dependent oxidative neuronal cell death. Mol Pharmacol 2008; 74:1141-51. [PMID: 18635668 DOI: 10.1124/mol.108.049064] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Oxidative stress induced by glutathione depletion in the mouse HT22 neuroblastoma cell line and embryonic rat immature cortical neurons causes a delayed, sustained activation of extracellular signal-regulated kinase (ERK) 1/2, which is required for cell death. This sustained activation of ERK1/2 is mediated primarily by a selective inhibition of distinct ERK1/2-directed phosphatases either by enhanced degradation (i.e., for mitogen-activated protein kinase phosphatase-1) or as shown here by reductions in enzymatic activity (i.e., for protein phosphatase type 2A). The inhibition of ERK1/2 phosphatases in HT22 cells and immature neurons subjected to glutathione depletion results from oxidative stress because phosphatase activity is restored in cells treated with the antioxidant butylated hydroxyanisole. This leads to reduced ERK1/2 activation and neuroprotection. Furthermore, an increase in free intracellular zinc that accompanies glutathione-induced oxidative stress in HT22 cells and immature neurons contributes to selective inhibition of ERK1/2 phosphatase activity and cell death. Finally, ERK1/2 also functions to maintain elevated levels of zinc. Thus, the elevation of intracellular zinc within neurons subjected to oxidative stress can trigger a robust positive feedback loop operating through activated ERK1/2 that rapidly sets into motion a zinc-dependent pathway of cell death.
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Affiliation(s)
- Yeung Ho
- Department of Neuroscience, University of Pittsburgh School of Medicine, 7041 BST 3, 3501 Fifth Ave., Pittsburgh, PA 15261, USA
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