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Balkaya M, Dohare P, Chen S, Schober AL, Fidaleo AM, Nalwalk JW, Sah R, Mongin AA. Conditional deletion of LRRC8A in the brain reduces stroke damage independently of swelling-activated glutamate release. iScience 2023; 26:106669. [PMID: 37182109 PMCID: PMC10173736 DOI: 10.1016/j.isci.2023.106669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 03/03/2023] [Accepted: 04/11/2023] [Indexed: 05/16/2023] Open
Abstract
The ubiquitous volume-regulated anion channels (VRACs) facilitate cell volume control and contribute to many other physiological processes. Treatment with non-specific VRAC blockers or brain-specific deletion of the essential VRAC subunit LRRC8A is highly protective in rodent models of stroke. Here, we tested the widely accepted idea that the harmful effects of VRACs are mediated by release of the excitatory neurotransmitter glutamate. We produced conditional LRRC8A knockout either exclusively in astrocytes or in the majority of brain cells. Genetically modified mice were subjected to an experimental stroke (middle cerebral artery occlusion). The astrocytic LRRC8A knockout yielded no protection. Conversely, the brain-wide LRRC8A deletion strongly reduced cerebral infarction in both heterozygous (Het) and full KO mice. Yet, despite identical protection, Het mice had full swelling-activated glutamate release, whereas KO animals showed its virtual absence. These findings suggest that LRRC8A contributes to ischemic brain injury via a mechanism other than VRAC-mediated glutamate release.
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Affiliation(s)
- Mustafa Balkaya
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Preeti Dohare
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Sophie Chen
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Alexandra L. Schober
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Antonio M. Fidaleo
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Julia W. Nalwalk
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Rajan Sah
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Alexander A. Mongin
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
- Corresponding author
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2
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Finney CA, Shvetcov A, Westbrook RF, Morris MJ, Jones NM. The selective estrogen receptor modulator tamoxifen protects against subtle cognitive decline and early markers of injury 24 h after hippocampal silent infarct in male Sprague-Dawley rats. Horm Behav 2021; 134:105016. [PMID: 34242875 DOI: 10.1016/j.yhbeh.2021.105016] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 06/03/2021] [Accepted: 06/05/2021] [Indexed: 02/07/2023]
Abstract
Silent infarcts (SI) are subcortical cerebral infarcts occurring in the absence of typical ischemia symptoms and are linked to cognitive decline and dementia development. There are no approved treatments for SI. One potential treatment is tamoxifen, a selective estrogen receptor modulator. It is critical to establish whether treatments effectively target the early consequences of SI to avoid progression to complete injury. We induced SI in the dorsal hippocampal CA1 of rats and assessed whether tamoxifen is protective 24 h later against cognitive deficits and injury responses including gliosis, apoptosis, inflammation and changes in estrogen receptors (ERs). SI led to subtle cognitive impairment on the object place task, an effect ameliorated by tamoxifen administration. SI did not lead to detectable hippocampal cell loss but increased apoptosis, astrogliosis, microgliosis and inflammation. Tamoxifen protected against the effects of SI on all measures except microgliosis. SI increased ERα and decreased ERβ in the hippocampus, which were mitigated by tamoxifen. Exploratory data analyses using scatterplot matrices and principal component analysis indicated that SI rats given tamoxifen were indistinguishable from controls. Further, SI rats were significantly different from all other groups, an effect associated with low levels of ERα and increased apoptosis, gliosis, inflammation, ERβ, and time spent with the unmoved object. The results demonstrate that tamoxifen is protective against the early cellular and cognitive consequences of hippocampal SI 24 h after injury. Tamoxifen mitigates apoptosis, gliosis, and inflammation and normalization of ER levels in the CA1, leading to improved cognitive outcomes after hippocampal SI.
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Vahidinia Z, Karimian M, Joghataei MT. Neurosteroids and their receptors in ischemic stroke: From molecular mechanisms to therapeutic opportunities. Pharmacol Res 2020; 160:105163. [DOI: 10.1016/j.phrs.2020.105163] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 08/17/2020] [Accepted: 08/17/2020] [Indexed: 01/09/2023]
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Wang M, Theis T, Kabat M, Loers G, Agre LA, Schachner M. Functions of Small Organic Compounds that Mimic the HNK-1 Glycan. Int J Mol Sci 2020; 21:ijms21197018. [PMID: 32987628 PMCID: PMC7582369 DOI: 10.3390/ijms21197018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 09/15/2020] [Accepted: 09/22/2020] [Indexed: 12/27/2022] Open
Abstract
Because of the importance of the HNK-1 carbohydrate for preferential motor reinnervation after injury of the femoral nerve in mammals, we screened NIH Clinical Collection 1 and 2 Libraries and a Natural Product library comprising small organic compounds for identification of pharmacologically useful reagents. The reason for this attempt was to obviate the difficult chemical synthesis of the HNK-1 carbohydrate and its isolation from natural sources, with the hope to render such compounds clinically useful. We identified six compounds that enhanced neurite outgrowth from cultured spinal motor neurons at nM concentrations and increased their neurite diameter, but not their neurite branch points. Axons of dorsal root ganglion neurons did not respond to these compounds, a feature that is in agreement with their biological role after injury. We refer to the positive functions of some of these compounds in animal models of injury and delineate the intracellular signaling responses elicited by application of compounds to cultured murine central nervous system neurons. Altogether, these results point to the potential of the HNK-1 carbohydrate mimetics in clinically-oriented settings.
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Affiliation(s)
- Minjuan Wang
- Keck Center for Collaborative Neuroscience and Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08554, USA; (M.W.); (T.T.); (M.K.)
| | - Thomas Theis
- Keck Center for Collaborative Neuroscience and Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08554, USA; (M.W.); (T.T.); (M.K.)
| | - Maciej Kabat
- Keck Center for Collaborative Neuroscience and Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08554, USA; (M.W.); (T.T.); (M.K.)
| | - Gabriele Loers
- Zentrum für Molekulare Neurobiologie Hamburg, Universitätsklinikum Hamburg-Eppendorf, 20251 Hamburg, Germany;
| | - Lynn A. Agre
- Rutgers School of Arts and Sciences, Department of Statistics and Rutgers Business School, Rutgers University, Piscataway, NJ 08854, USA;
| | - Melitta Schachner
- Keck Center for Collaborative Neuroscience and Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08554, USA; (M.W.); (T.T.); (M.K.)
- Correspondence: ; Tel.: +1-848-445-1780
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Tamoxifen promotes white matter recovery and cognitive functions in male mice after chronic hypoperfusion. Neurochem Int 2019; 131:104566. [PMID: 31593788 DOI: 10.1016/j.neuint.2019.104566] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 09/30/2019] [Accepted: 10/02/2019] [Indexed: 12/18/2022]
Abstract
Cerebral white matter lesions (WMLs) induced by chronic cerebral hypoperfusion are one of the major components of stroke pathology and closely associated with cognitive impairment. However, the repair and related pathophysiology of white matter after brain injury remains relatively elusive and underexplored. Successful neuroregeneration is a method for the potential treatment of central nervous system (CNS) disorders. A non-steroidal estrogen receptor modulator, Tamoxifen, is an effective inhibitor of cell-swelling-activated anion channels and can mimic neuroprotective effects of estrogen in experimental ischemic stroke. However, its remains unclear whether Tamoxifen has beneficial effects in the pathological process after WMLs. In the present study, we investigated the efficacy of Tamoxifen on multiple elements of oligovascular niche of the male C57BL/6 mice brain after bilateral carotid artery stenosis (BCAS) - induced WMLs. Tamoxifen was injected intraperitoneally once daily from 1 day after BCAS until 1 day before sacrificed. Following chronic hypoperfusion, BCAS mice presented white matter demyelination, loss of axon-glia integrity, activated inflammatory response, and cognitive impairments. Tamoxifen treatment significantly facilitated functional restoration of working memory impairment in mice after white matter injury, thus indicating a translational potential for this estrogen receptor modulator given its clinical safety and applicability for WMLs, which lack of currently available treatments. Furthermore, Tamoxifen treatment reduced microglia activation and inflammatory response, favored microglial polarization toward to the M2 phenotype, enhanced oligodendrocyte precursor cells proliferation and differentiation, and promoted remyelination after chronic hypoperfusion. Together, our data indicate that Tamoxifen could alleviate white matter injury and play multiple targets protective effects following chronic hypoperfusion, which is a promising candidate for the therapeutic target for ischemic WMLs and other demyelination diseases associated cognitive impairment.
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Wilson CS, Bach MD, Ashkavand Z, Norman KR, Martino N, Adam AP, Mongin AA. Metabolic constraints of swelling-activated glutamate release in astrocytes and their implication for ischemic tissue damage. J Neurochem 2019; 151:255-272. [PMID: 31032919 DOI: 10.1111/jnc.14711] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Revised: 03/01/2019] [Accepted: 04/10/2019] [Indexed: 12/20/2022]
Abstract
Volume-regulated anion channel (VRAC) is a glutamate-permeable channel that is activated by physiological and pathological cell swelling and promotes ischemic brain damage. However, because VRAC opening requires cytosolic ATP, it is not clear if and how its activity is sustained in the metabolically compromised CNS. In the present study, we used cultured astrocytes - the cell type which shows prominent swelling in stroke - to model how metabolic stress and changes in gene expression may impact VRAC function in the ischemic and post-ischemic brain. The metabolic state of primary rat astrocytes was modified with chemical inhibitors and examined using luciferin-luciferase ATP assays and a Seahorse analyzer. Swelling-activated glutamate release was quantified with the radiotracer D-[3 H]aspartate. The specific contribution of VRAC to swelling-activated glutamate efflux was validated by RNAi knockdown of the essential subunit, leucine-rich repeat-containing 8A (LRRC8A); expression levels of VRAC components were measured with qRT-PCR. Using this methodology, we found that complete metabolic inhibition with the glycolysis blocker 2-deoxy-D-glucose and the mitochondrial poison sodium cyanide reduced astrocytic ATP levels by > 90% and abolished glutamate release from swollen cells (via VRAC). When only mitochondrial respiration was inhibited by cyanide or rotenone, the intracellular ATP levels and VRAC activity were largely preserved. Bypassing glycolysis by providing the mitochondrial substrates pyruvate and/or glutamine led to partial recovery of ATP levels and VRAC activity. Unexpectedly, the metabolic block of VRAC was overridden when ATP-depleted cells were exposed to extreme cell swelling (≥ 50% reduction in medium osmolarity). Twenty-four hour anoxic adaptation caused a moderate reduction in the expression levels of the VRAC component LRRC8A, but no significant changes in VRAC activity. Overall, our findings suggest that (i) astrocytic VRAC activity and metabolism can be sustained by low levels of glucose and (ii) the inhibitory influence of diminishing ATP levels and the stimulatory effect of cellular swelling are the two major factors that govern VRAC activity in the ischemic brain.
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Affiliation(s)
- Corinne S Wilson
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
| | - Martin D Bach
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
| | - Zahra Ashkavand
- Department of Regenerative and Cancer Cell Biology, Albany Medical College, Albany, New York, USA
| | - Kenneth R Norman
- Department of Regenerative and Cancer Cell Biology, Albany Medical College, Albany, New York, USA
| | - Nina Martino
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York, USA
| | - Alejandro P Adam
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York, USA
| | - Alexander A Mongin
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
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Mohajeri M, Martín-Jiménez C, Barreto GE, Sahebkar A. Effects of estrogens and androgens on mitochondria under normal and pathological conditions. Prog Neurobiol 2019; 176:54-72. [DOI: 10.1016/j.pneurobio.2019.03.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 02/23/2019] [Accepted: 03/05/2019] [Indexed: 02/06/2023]
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Baez-Jurado E, Rincón-Benavides MA, Hidalgo-Lanussa O, Guio-Vega G, Ashraf GM, Sahebkar A, Echeverria V, Garcia-Segura LM, Barreto GE. Molecular mechanisms involved in the protective actions of Selective Estrogen Receptor Modulators in brain cells. Front Neuroendocrinol 2019; 52:44-64. [PMID: 30223003 DOI: 10.1016/j.yfrne.2018.09.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 09/09/2018] [Accepted: 09/12/2018] [Indexed: 02/06/2023]
Abstract
Synthetic selective modulators of the estrogen receptors (SERMs) have shown to protect neurons and glial cells against toxic insults. Among the most relevant beneficial effects attributed to these compounds are the regulation of inflammation, attenuation of astrogliosis and microglial activation, prevention of excitotoxicity and as a consequence the reduction of neuronal cell death. Under pathological conditions, the mechanism of action of the SERMs involves the activation of estrogen receptors (ERs) and G protein-coupled receptor for estrogens (GRP30). These receptors trigger neuroprotective responses such as increasing the expression of antioxidants and the activation of kinase-mediated survival signaling pathways. Despite the advances in the knowledge of the pathways activated by the SERMs, their mechanism of action is still not entirely clear, and there are several controversies. In this review, we focused on the molecular pathways activated by SERMs in brain cells, mainly astrocytes, as a response to treatment with raloxifene and tamoxifen.
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Affiliation(s)
- E Baez-Jurado
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | - M A Rincón-Benavides
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | - O Hidalgo-Lanussa
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | - G Guio-Vega
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | - G M Ashraf
- King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia
| | - A Sahebkar
- Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran; Neurogenic Inflammation Research Center, Mashhad University of Medical Sciences, Mashhad, Iran; School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran
| | - V Echeverria
- Universidad San Sebastián, Fac. Cs de la Salud, Lientur 1457, Concepción 4080871, Chile; Research & Development Service, Bay Pines VA Healthcare System, Bay Pines, FL 33744, USA
| | - L M Garcia-Segura
- Instituto Cajal, CSIC, Madrid, Spain; Centro de Investigación Biomédica en Red Fragilidad y Envejecimiento Saludable (CIBERFES), Instituto de Salud Carlos III, Madrid, Spain
| | - G E Barreto
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia; Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, Santiago, Chile.
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Colón JM, Torrado AI, Cajigas Á, Santiago JM, Salgado IK, Arroyo Y, Miranda JD. Tamoxifen Administration Immediately or 24 Hours after Spinal Cord Injury Improves Locomotor Recovery and Reduces Secondary Damage in Female Rats. J Neurotrauma 2016; 33:1696-708. [PMID: 26896212 PMCID: PMC5035917 DOI: 10.1089/neu.2015.4111] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Spinal cord injury (SCI) is a condition with no available cure. The initial physical impact triggers a cascade of molecular and cellular events that generate a nonpermissive environment for cell survival and axonal regeneration. Spinal cord injured patients often arrive at the clinic hours after the initial insult. This indicates the need to study and develop treatments with a long therapeutic window of action and multiactive properties, which target the complex set of events that arise after the initial trauma. We provide evidence that tamoxifen (TAM), a drug approved by the Food and Drug Administration, exerts neuroprotective effects in an animal model when applied up-to 24 h after SCI. We hypothesized that continuous TAM administration will improve functional locomotor recovery by favoring myelin preservation and reducing secondary damage after SCI. Adult female Sprague-Dawley rats (∼230 g) received a moderate contusion to the thoracic (T9-T10) spinal cord, using the MASCIS impactor device. To determine the therapeutic window available for TAM treatment, rats were implanted with TAM pellets (15 mg) immediately or 24 h after SCI. Locomotor function (Basso, Beattie, Bresnahan open field test, grid walk, and beam crossing tests) was assessed weekly for 35 days post-injury. TAM-treated rats showed significant functional locomotor recovery and improved fine movements when treated immediately or 24 h after SCI. Further, TAM increased white matter preservation and reduced secondary damage caused by astrogliosis, axonal degeneration, and cell death after trauma. These results provide evidence for TAM as a potential therapeutic agent to treat SCI up to 24 h after the trauma.
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Affiliation(s)
- Jennifer M. Colón
- Department of Physiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
| | - Aranza I. Torrado
- Department of Physiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
| | - Ámbar Cajigas
- Department of Biology, University of Puerto Rico Rio Piedras Campus, San Juan, Puerto Rico
| | - José M. Santiago
- Department of Natural Sciences, University of Puerto Rico Carolina Campus, Carolina, Puerto Rico
| | - Iris K. Salgado
- Department of Physiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
| | - Yaría Arroyo
- Department of Natural Sciences, University of Puerto Rico Carolina Campus, Carolina, Puerto Rico
| | - Jorge D. Miranda
- Department of Physiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
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Lucke-Wold BP, Logsdon AF, Manoranjan B, Turner RC, McConnell E, Vates GE, Huber JD, Rosen CL, Simard JM. Aneurysmal Subarachnoid Hemorrhage and Neuroinflammation: A Comprehensive Review. Int J Mol Sci 2016; 17:497. [PMID: 27049383 PMCID: PMC4848953 DOI: 10.3390/ijms17040497] [Citation(s) in RCA: 208] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 03/08/2016] [Accepted: 03/28/2016] [Indexed: 02/06/2023] Open
Abstract
Aneurysmal subarachnoid hemorrhage (SAH) can lead to devastating outcomes including vasospasm, cognitive decline, and even death. Currently, treatment options are limited for this potentially life threatening injury. Recent evidence suggests that neuroinflammation plays a critical role in injury expansion and brain damage. Red blood cell breakdown products can lead to the release of inflammatory cytokines that trigger vasospasm and tissue injury. Preclinical models have been used successfully to improve understanding about neuroinflammation following aneurysmal rupture. The focus of this review is to provide an overview of how neuroinflammation relates to secondary outcomes such as vasospasm after aneurysmal rupture and to critically discuss pharmaceutical agents that warrant further investigation for the treatment of subarachnoid hemorrhage. We provide a concise overview of the neuroinflammatory pathways that are upregulated following aneurysmal rupture and how these pathways correlate to long-term outcomes. Treatment of aneurysm rupture is limited and few pharmaceutical drugs are available. Through improved understanding of biochemical mechanisms of injury, novel treatment solutions are being developed that target neuroinflammation. In the final sections of this review, we highlight a few of these novel treatment approaches and emphasize why targeting neuroinflammation following aneurysmal subarachnoid hemorrhage may improve patient care. We encourage ongoing research into the pathophysiology of aneurysmal subarachnoid hemorrhage, especially in regards to neuroinflammatory cascades and the translation to randomized clinical trials.
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Affiliation(s)
- Brandon P Lucke-Wold
- Department of Neurosurgery, West Virginia University School of Medicine, Morgantown, WV 26505, USA.
| | - Aric F Logsdon
- Department of Basic Pharmaceutical Sciences, West Virginia University School of Pharmacy, Morgantown, WV 26505, USA.
| | - Branavan Manoranjan
- McMaster Stem Cell and Cancer Research Institute, Michael G. DeGroote School of Medicine, Hamilton, ON L8S 4K1, Canada.
| | - Ryan C Turner
- Department of Neurosurgery, West Virginia University School of Medicine, Morgantown, WV 26505, USA.
| | - Evan McConnell
- Department of Neurobiology and Anatomy, University of Rochester Medical Center, Rochester, NY 14642, USA.
| | - George Edward Vates
- Department of Neurobiology and Anatomy, University of Rochester Medical Center, Rochester, NY 14642, USA.
| | - Jason D Huber
- Department of Basic Pharmaceutical Sciences, West Virginia University School of Pharmacy, Morgantown, WV 26505, USA.
| | - Charles L Rosen
- Department of Neurosurgery, West Virginia University School of Medicine, Morgantown, WV 26505, USA.
| | - J Marc Simard
- Departments of Neurosurgery, Pathology, and Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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Mongin AA. Volume-regulated anion channel--a frenemy within the brain. Pflugers Arch 2015; 468:421-41. [PMID: 26620797 DOI: 10.1007/s00424-015-1765-6] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 11/16/2015] [Accepted: 11/20/2015] [Indexed: 10/22/2022]
Abstract
The volume-regulated anion channel (VRAC) is a ubiquitously expressed yet highly enigmatic member of the superfamily of chloride/anion channels. It is activated by cellular swelling and mediates regulatory cell volume decrease in a majority of vertebrate cells, including those in the central nervous system (CNS). In the brain, besides its crucial role in cellular volume regulation, VRAC is thought to play a part in cell proliferation, apoptosis, migration, and release of physiologically active molecules. Although these roles are not exclusive to the CNS, the relative significance of VRAC in the brain is amplified by several unique aspects of its physiology. One important example is the contribution of VRAC to the release of the excitatory amino acid neurotransmitters glutamate and aspartate. This latter process is thought to have impact on both normal brain functioning (such as astrocyte-neuron signaling) and neuropathology (via promoting the excitotoxic death of neuronal cells in stroke and traumatic brain injury). In spite of much work in the field, the molecular nature of VRAC remained unknown until less than 2 years ago. Two pioneer publications identified VRAC as the heterohexamer formed by the leucine-rich repeat-containing 8 (LRRC8) proteins. These findings galvanized the field and are likely to result in dramatic revisions to our understanding of the place and role of VRAC in the brain, as well as other organs and tissues. The present review briefly recapitulates critical findings in the CNS and focuses on anticipated impact on the LRRC8 discovery on further progress in neuroscience research.
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Affiliation(s)
- Alexander A Mongin
- Center for Neuropharmacology and Neuroscience, Albany Medical College, 47 New Scotland Ave., Albany, NY, 12208, USA.
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Rayabarapu N, Patel BM. Beneficial role of tamoxifen in isoproterenol-induced myocardial infarction. Can J Physiol Pharmacol 2014; 92:849-57. [DOI: 10.1139/cjpp-2013-0348] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
ER-α and ER-β agonist 17β-estradiol is reported to attenuate cardiac hypertrophy. Tamoxifen is a selective estrogen receptor modulator. Hence, the objective of this study was to investigate the effects of tamoxifen in myocardial infarction. For this, tamoxifen was administered to Sprague–Dawley rats for 1–14 days, and isoproterenol (ISO) (100 mg·(kg body mass)−1·day−1) was administered subcutaneously on the 13th and 14th days of the study in order to induce myocardial infarction, after which, various biochemical, cardiac, and morphometric parameters were evaluated. ISO produced significant dyslipidemia, hypertension, bradycardia, oxidative stress, and an increase in serum cardiac markers. Treatment with tamoxifen significantly controlled dyslipidemia, hypertension, bradycardia, oxidative stress, and reduced serum cardiac markers. The ISO control rats exhibited significant increases in the infarct size of the left ventricle (LV), LV cavity area, cardiac and LV hypertrophic indices, LV-wall thickness, cardiomyocyte diameter, and area. Treatment with tamoxifen significantly reduced infarction as well as hypertrophic and morphometric parameters. ISO also produced significant increases in the LV collagen level, decreases in Na+K+ATPase activity, and a reduction in the rate of pressure development and decay, which were prevented by tamoxifen treatment. The protective effect of tamoxifen on myocardial infarct was further confirmed by histopathological examination. Our data thus suggest that tamoxifen exerts beneficial effects in ISO-induced myocardial infarction.
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Affiliation(s)
- Nihar Rayabarapu
- Institute of Pharmacy, Nirma University, Sarkhej-Gandhinagar Highway, Ahmedabad 382 481, Gujarat, India
| | - Bhoomika M. Patel
- Institute of Pharmacy, Nirma University, Sarkhej-Gandhinagar Highway, Ahmedabad 382 481, Gujarat, India
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13
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Tsai YT, Wang CC, Leung PO, Lin KC, Chio CC, Hu CY, Kuo JR. Extracellular signal–regulated kinase 1/2 is involved in a tamoxifen neuroprotective effect in a lateral fluid percussion injury rat model. J Surg Res 2014; 189:106-16. [DOI: 10.1016/j.jss.2014.02.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 12/20/2013] [Accepted: 02/11/2014] [Indexed: 12/13/2022]
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Wei HY, Ma X. Tamoxifen reduces infiltration of inflammatory cells, apoptosis and inhibits IKK/NF-kB pathway after spinal cord injury in rats. Neurol Sci 2014; 35:1763-8. [PMID: 24873902 DOI: 10.1007/s10072-014-1828-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Accepted: 05/08/2014] [Indexed: 11/27/2022]
Abstract
In this study, neuroprotective effect of tamoxifen has been explored in spinal cord injury (SCI) in rats by examining factors influencing IKK/NF-kB pathway in SCI in rats. It has been shown in several studies that IKK/NF-kB signaling pathway plays a key role in pathophysiology of SCI. In this study, three groups of rats (n = 17 each) were selected that included, tamoxifen group (here tamoxifen was injected after SCI in rats), SCI group (here only dimethylsulfoxide was administered after inducing SCI in rats) and sham group (here only laminectomy was performed). The effect of tamoxifen (5 mg/kg) on various factors responsible for activation of IKK/NF-kB signaling pathway including NF-kB p65, phosphorylated I-kBα was studied through Western blotting as well as densitometry. The examination of expression of active caspase-3 and myeloperoxidase activity was also carried out through Western blot analysis and densitometry. A comparison of three groups of rats showed that administration of tamoxifen significantly reduced the expression of NF-kB p65 and phosphorylated I-kBα (P < 0.05) compared to control. It also attenuated the expression of active caspase-3 resulting in the reduction of apoptosis, and infiltration of leukocytes to the injury site was also greatly reduced in the group where tamoxifen was administered. Statistical analysis through SPSS 13.0 software showed a significant decrease in the expression of inflammatory factors in groups where tamoxifen was administered. We conclude that tamoxifen possesses the potential neuroprotective effects that can be explored further for future therapeutic techniques in treating spinal cord injuries.
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Affiliation(s)
- Hong-Yu Wei
- Department of Spinal Surgery, China-Japan Friendship Hospital, Beijing, 100029, China
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15
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Karki P, Smith K, Johnson J, Lee E. Astrocyte-derived growth factors and estrogen neuroprotection: role of transforming growth factor-α in estrogen-induced upregulation of glutamate transporters in astrocytes. Mol Cell Endocrinol 2014; 389:58-64. [PMID: 24447465 PMCID: PMC4040305 DOI: 10.1016/j.mce.2014.01.010] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 01/09/2014] [Accepted: 01/09/2014] [Indexed: 01/31/2023]
Abstract
Extensive studies from the past decade have completely revolutionized our understanding about the role of astrocytes in the brain from merely supportive cells to an active role in various physiological functions including synaptic transmission via cross-talk with neurons and neuroprotection via releasing neurotrophic factors. Particularly, numerous studies have reported that astrocytes mediate the neuroprotective effects of 17β-estradiol (E2) and selective estrogen receptor modulators (SERMs) in various clinical and experimental models of neuronal injury. Astrocytes contain two main glutamate transporters, glutamate aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1), that play a key role in preventing excitotoxic neuronal death, a process associated with most neurodegenerative diseases. E2 has been shown to increase expression of both GLAST and GLT-1 mRNA and protein and glutamate uptake in astrocytes. Growth factors such as transforming growth factor-α (TGF-α) appear to mediate E2-induced enhancement of these transporters. These findings suggest that E2 exerts neuroprotection against excitotoxic neuronal injuries, at least in part, by enhancing astrocytic glutamate transporter levels and function. Therefore, the present review will discuss proposed mechanisms involved in astrocyte-mediated E2 neuroprotection, with a focus on glutamate transporters.
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Affiliation(s)
- Pratap Karki
- Department of Physiology, School of Medicine, Meharry Medical College, Nashville, TN, USA
| | - Keisha Smith
- Department of Physiology, School of Medicine, Meharry Medical College, Nashville, TN, USA
| | - James Johnson
- Department of Physiology, School of Medicine, Meharry Medical College, Nashville, TN, USA
| | - Eunsook Lee
- Department of Physiology, School of Medicine, Meharry Medical College, Nashville, TN, USA.
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16
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Mosquera L, Colón JM, Santiago JM, Torrado AI, Meléndez M, Segarra AC, Rodríguez-Orengo JF, Miranda JD. Tamoxifen and estradiol improved locomotor function and increased spared tissue in rats after spinal cord injury: their antioxidant effect and role of estrogen receptor alpha. Brain Res 2014; 1561:11-22. [PMID: 24637260 DOI: 10.1016/j.brainres.2014.03.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 02/20/2014] [Accepted: 03/05/2014] [Indexed: 12/17/2022]
Abstract
17β-Estradiol is a multi-active steroid that imparts neuroprotection via diverse mechanisms of action. However, its role as a neuroprotective agent after spinal cord injury (SCI), or the involvement of the estrogen receptor-alpha (ER-α) in locomotor recovery, is still a subject of much debate. In this study, we evaluated the effects of estradiol and of Tamoxifen (an estrogen receptor mixed agonist/antagonist) on locomotor recovery following SCI. To control estradiol cyclical variability, ovariectomized female rats received empty or estradiol filled implants, prior to a moderate contusion to the spinal cord. Estradiol improved locomotor function at 7, 14, 21, and 28 days post injury (DPI), when compared to control groups (measured with the BBB open field test). This effect was ER-α mediated, because functional recovery was blocked with an ER-α antagonist. We also observed that ER-α was up-regulated after SCI. Long-term treatment (28 DPI) with estradiol and Tamoxifen reduced the extent of the lesion cavity, an effect also mediated by ER-α. The antioxidant effects of estradiol were seen acutely at 2 DPI but not at 28 DPI, and this acute effect was not receptor mediated. Rats treated with Tamoxifen recovered some locomotor activity at 21 and 28 DPI, which could be related to the antioxidant protection seen at these time points. These results show that estradiol improves functional outcome, and these protective effects are mediated by the ER-α dependent and independent-mechanisms. Tamoxifen׳s effects during late stages of SCI support the use of this drug as a long-term alternative treatment for this condition.
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Affiliation(s)
- Laurivette Mosquera
- Department of Physiology, University of Puerto Rico-School of Medicine, San Juan, PR 00936, USA
| | - Jennifer M Colón
- Department of Physiology, University of Puerto Rico-School of Medicine, San Juan, PR 00936, USA
| | - José M Santiago
- University of Puerto Rico Carolina Campus, Department of Natural Sciences, Carolina, PR 00984, USA
| | - Aranza I Torrado
- Department of Physiology, University of Puerto Rico-School of Medicine, San Juan, PR 00936, USA
| | | | - Annabell C Segarra
- Department of Physiology, University of Puerto Rico-School of Medicine, San Juan, PR 00936, USA
| | - José F Rodríguez-Orengo
- Department of Biochemistry, University of Puerto Rico-School of Medicine, San Juan, PR 00936, USA
| | - Jorge D Miranda
- Department of Physiology, University of Puerto Rico-School of Medicine, San Juan, PR 00936, USA.
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17
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Tamoxifen as an effective neuroprotectant against early brain injury and learning deficits induced by subarachnoid hemorrhage: possible involvement of inflammatory signaling. J Neuroinflammation 2013; 10:157. [PMID: 24373431 PMCID: PMC3881500 DOI: 10.1186/1742-2094-10-157] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 12/08/2013] [Indexed: 12/26/2022] Open
Abstract
Background Tamoxifen, a selective estrogen receptor modulator, has successfully been used to treat several animal models of brain injury, but the underlying mechanisms remain unclear. This study was undertaken to evaluate the effect of tamoxifen on the toll-like receptor 4 (TLR4)- and nuclear factor-κB (NF-κB)-related inflammatory signaling pathway and secondary brain injury in rats after subarachnoid hemorrhage (SAH). Methods Adult male Sprague-Dawley rats were divided into four groups: (1) control group (n = 28); (2) SAH group (n = 28); (3) SAH + vehicle group (n = 28); and (4) SAH + tamoxifen group (n = 28). All SAH animals were subjected to injection of autologous blood into the prechiasmatic cistern once on day 0. In SAH + tamoxifen group, tamoxifen was administered intraperitoneally at a dose of 5 mg/kg at 2 h, 12 h, and 36 h after SAH. In the first set of experiments, brain samples were extracted and evaluated at 48 h after SAH. In the second set of experiments, the Morris water maze was used to investigate cognitive and memory changes. Results We found that treatment with tamoxifen markedly inhibited the protein expressions of TLR4, NF-κB and the downstream inflammatory agents, such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and intercellular adhesion molecule-1 (ICAM-1). Administration of tamoxifen following SAH significantly ameliorated the early brain injury (EBI), such as brain edema, blood-brain barrier (BBB) impairment, and clinical behavior scale. Learning deficits induced by SAH were markedly alleviated after tamoxifen treatment. Conclusions Post-SAH tamoxifen administration may attenuate TLR4/NF-kappaB-mediated inflammatory response in the rat brain and result in abatement of the development of EBI and cognitive dysfunction after SAH.
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18
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Karki P, Webb A, Smith K, Lee K, Son DS, Aschner M, Lee E. cAMP response element-binding protein (CREB) and nuclear factor κB mediate the tamoxifen-induced up-regulation of glutamate transporter 1 (GLT-1) in rat astrocytes. J Biol Chem 2013; 288:28975-86. [PMID: 23955341 DOI: 10.1074/jbc.m113.483826] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Tamoxifen (TX), a selective estrogen receptor modulator, exerts antagonistic effects on breast tissue and is used to treat breast cancer. Recent evidence also suggests that it may act as an agonist in brain tissue. We reported previously that TX enhanced the expression and function of glutamate transporter 1 (GLT-1) in rat astrocytes, an effect that was mediated by TGF-α. To gain further insight into the mechanisms that mediate TX-induced up-regulation of GLT-1 (EAAT2 in humans), we investigated its effect on GLT-1 at the transcriptional level. TX phosphorylated the cAMP response element-binding protein (CREB) and recruited CREB to the GLT-1 promoter consensus site. The effect of TX on astrocytic GLT-1 was attenuated by the inhibition of PKA, the upstream activator of the CREB pathway. In addition, the effect of TX on GLT-1 promoter activity was abolished by the inhibition of the NF-κB pathway. Furthermore, TX recruited the NF-κB subunits p65 and p50 to the NF-κB binding domain of the GLT-1 promoter. Mutation of NF-κB (triple, -583/-282/-251) or CRE (-308) sites on the GLT-1 promoter led to significant repression of the promoter activity, but neither mutant completely abolished the TX-induced GLT-1 promoter activity. Mutation of both the NF-κB (-583/-282/-251) and CRE (-308) sites led to a complete abrogation of the effect of TX on GLT-1 promoter activity. Taken together, our findings establish that TX regulates GLT-1 via the CREB and NF-κB pathways.
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Affiliation(s)
- Pratap Karki
- From the Department of Physiology, Meharry Medical College, Nashville, Tennessee 37208
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Mongin AA, Dohare P, Jourd'heuil D. Selective vulnerability of synaptic signaling and metabolism to nitrosative stress. Antioxid Redox Signal 2012; 17:992-1012. [PMID: 22339371 PMCID: PMC3411350 DOI: 10.1089/ars.2012.4559] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
SIGNIFICANCE Nitric oxide (NO) plays diverse physiological roles in the central nervous system, where it modulates neuronal communication, regulates blood flow, and contributes to the innate immune responses. In a number of brain pathologies, the excessive production of NO also leads to the formation of reactive and toxic intermediates generically termed reactive nitrogen species (RNS). RNS cause irreversible or poorly reversible damage to brain cells. RECENT ADVANCES Recent work in the field focused on the ability of NO and RNS to yield protein modifications, including the S-nitrosation of cysteine residues, which, in many instances, impact cellular functions and viability. CRITICAL ISSUES The vast majority of neuropathological studies focus on the loss of cell viability, but nitrosative stress may also strongly impair the functions of neuronal processes: axonal projections and dendritic trees. The functional integrity of axons and dendrites critically depends on local metabolism and effective delivery of metabolic enzymes and organelles. Here, we summarize the existing literature describing the effects of nitrosative stress on the major pathways of energetic metabolism: glycolysis, tricarboxylic acid cycle, and mitochondrial respiration, with the emphasis on modifications of protein thiols. FUTURE DIRECTIONS We propose that axons and dendrites are highly vulnerable to nitrosative stress because of their low glycolytic capacity and high dependence on timely delivery of metabolic enzymes and organelles from the cell body. Thus, supplementation with the end products of glycolysis, pyruvate or lactate, may help preserve metabolism in distal neuronal processes and protect or restore synaptic function in the ailing brain.
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Affiliation(s)
- Alexander A Mongin
- Center for Neuropharmacology and Neuroscience, Albany Medical College, New York 12208, USA.
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20
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Neuroprotection of hydroxysafflor yellow A in the transient focal ischemia: Inhibition of protein oxidation/nitration, 12/15-lipoxygenase and blood–brain barrier disruption. Brain Res 2012; 1473:227-35. [DOI: 10.1016/j.brainres.2012.07.047] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 07/23/2012] [Accepted: 07/24/2012] [Indexed: 01/01/2023]
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21
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Belenichev IF, Odnokoz OV, Pavlov SV, Belenicheva OI, Polyakova EN. The neuroprotective activity of tamoxifen and tibolone during glutathione depletion in vitro. NEUROCHEM J+ 2012. [DOI: 10.1134/s181971241203004x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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22
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Boulos AS, Deshaies EM, Dalfino JC, Feustel PJ, Popp AJ, Drazin D. Tamoxifen as an effective neuroprotectant in an endovascular canine model of stroke. J Neurosurg 2011; 114:1117-26. [DOI: 10.3171/2010.8.jns09352] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Object
Tamoxifen has been shown to be a potent neuroprotectant against stroke in rodents. Because other neuroprotectant medications have failed in human trials, a study of tamoxifen in a large-animal model was necessary to further assess the drug's effectiveness. For this study, the authors developed an endovascular model of anterior circulation infarction in canines to mimic the human clinical condition. They assessed the following hypotheses: 1) that they will be able to consistently produce an internal carotid artery (ICA) terminus infarction and 2) that tamoxifen is an effective neuroprotectant against stroke in canines.
Methods
In 24 male beagles (weight 9–11 kg), bilateral femoral artery cutdowns were performed, and the vertebral artery and left ICA were each selectively catheterized. Under fluoroscopic guidance, a microcatheter was introduced via the vertebral artery, guiding the catheter into the basilar artery, posterior communicating artery, and ICA terminus. A 1-ml clot was injected in the terminus, occluding the middle cerebral artery (MCA) and anterior cerebral artery (ACA) origin. In the first 12 canines, the occlusions were confirmed by angiography. A Canine Stroke Score (CSS) was assigned (score range 0–18 [0 = intact on examination, 18 = comatose]). The animals were then killed and their brains stained with 2,3,5-triphenyltetrazolium chloride (TTC). The subsequent 12 canines underwent a blinded randomized study in which the authors compared the results of tamoxifen (5 mg/kg) infused intravenously 1 hour after clot injection with an equal volume of vehicle (dimethylsulfoxide). After 3 hours, the animals underwent MR imaging, were extubated, and clinical examinations were performed. The canines were killed at 8 hours after clot injection, and TTC staining was used.
Results
In the first group, infarct volume and CSSs were consistent with the extent of the occlusion of the angiographic vessels. An occlusion of the ACA, MCA, and posterior cerebral artery resulted in larger infarcts and higher stroke scores than occlusion of the ACA and MCA. In the second group, tamoxifen significantly reduced infarct size and improved clinical outcomes. In tamoxifen-treated animals, the mean infarct volume reduction was 40% (p < 0.05) and the mean CSS was significantly less than vehicle-treated animals (p < 0.001). There were significant correlations among MR imaging-determined volume, TTC-determined volume, and neurological clinical outcome (p < 0.05).
Conclusions
Using this endovascular model of stroke, the authors were able to consistently produce an infarction in the canines that was similar in scope to a carotid terminus occlusion in humans. Also, angiography could predict subsequent clinical course and infarct size. Tamoxifen was effective at significantly improving the canine neurological deficits and reducing the size of the stroke. This study took the first step in demonstrating the effectiveness of a promising human neuroprotectant in a large animal.
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Affiliation(s)
| | | | | | - Paul J. Feustel
- 2Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York; and
| | - A. John Popp
- 1Department of Surgery, Division of Neurosurgery, and
| | - Doniel Drazin
- 3Department of Neurosurgery, Cedars-Sinai Medical Center, Los Angeles, California
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23
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Ismailoğlu O, Oral B, Görgülü A, Sütçü R, Demir N. Neuroprotective effects of tamoxifen on experimental spinal cord injury in rats. J Clin Neurosci 2010; 17:1306-10. [PMID: 20630763 DOI: 10.1016/j.jocn.2010.01.049] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 12/23/2009] [Accepted: 01/04/2010] [Indexed: 12/20/2022]
Abstract
The aim of this study was to evaluate the effects of tamoxifen on tumor necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) levels and ultrastructural changes in rats with spinal cord injury. Rats were divided into four groups: control group (laminectomy only), trauma group (laminectomy+spinal trauma), tamoxifen group (laminectomy+spinal trauma+tamoxifen), and vehicle group (laminectomy+spinal trauma+vehicle). Spinal cords were extirpated at the T(7)-T(12) level and tissue samples from the spinal cords were gathered for TNF-alpha and IL-1beta measurements at 1 and 6hours. Spinal cords harvested at 6 hours were evaluated for ultrastructural changes. TNF-alpha and IL-1beta levels at 6 hours were significantly lower in the tamoxifen group than in the trauma group. Electron microscopic examination of tissue from the trauma group revealed gross cell deformities with widespread edema of all structures as well as severe edema in the neuropil. At 6 hours after trauma, these ultrastructural changes were less marked in the tamoxifen group. Our findings support a neuroprotective and restorative role for tamoxifen in the context of secondary pathological biochemical events after SCI.
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Affiliation(s)
- Ozgür Ismailoğlu
- Department of Neurosurgery, School of Medicine, Süleyman Demirel University, Cünür, Isparta 32260, Turkey.
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24
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Tamoxifen alleviates irradiation-induced brain injury by attenuating microglial inflammatory response in vitro and in vivo. Brain Res 2010; 1316:101-11. [PMID: 20044983 DOI: 10.1016/j.brainres.2009.12.055] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2009] [Revised: 12/16/2009] [Accepted: 12/18/2009] [Indexed: 01/01/2023]
Abstract
Irradiation-induced brain injury, leading to cognitive impairment several months to years after whole brain irradiation (WBI) therapy, is a common health problem in patients with primary or metastatic brain tumor and greatly impairs quality of life for tumor survivors. Recently, it has been demonstrated that a rapid and sustained increase in activated microglia following WBI led to a chronic inflammatory response and a corresponding decrease in hippocampal neurogenesis. Tamoxifen, serving as a radiosensitizer and a useful agent in combination therapy of glioma, has been found to exert anti-inflammatory response both in cultured microglial cells and in a spinal cord injury model. In the present study, we investigated whether tamoxifen alleviated inflammatory damage seen in the irradiated microglia in vitro and in the irradiated brain. Irradiating BV-2 cells (a murine microglial cell line) with various radiation doses (2-10 Gy) led to the increase in IL-1 beta and TNF-alpha expression determined by ELISA, and the conditioned culture medium of irradiated microglia with 10 Gy radiation dose initiated astroglial activation and decreased the number of neuronal cells in vitro. Incubation BV-2 cells with tamoxifen (1 microM) for 45 min significantly inhibited the radiation-induced microglial inflammatory response. In the irradiated brain, WBI induced the breakdown of the blood-brain barrier permeability at day 1 post irradiation and tissue edema formation at day 3 post-radiation. Furthermore, WBI led to microglial activation and reactive astrogliosis in the cerebral cortex and neuronal apoptosis in the CA1 hippocampus at day 3 post-radiation. Tamoxifen administration (i.p., 5 mg/kg) immediately post radiation reduced the irradiation-induced brain damage after WBI. Taken together, these data support that tamoxifen can decrease the irradiation-induced brain damage via attenuating the microglial inflammatory response.
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25
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Armagan G, Kanit L, Terek CM, Sozmen EY, Yalcin A. The levels of glutathione and nitrite-nitrate and the expression of Bcl-2 mRNA in ovariectomized rats treated by raloxifene against kainic acid. Int J Neurosci 2009; 119:227-39. [PMID: 19125376 DOI: 10.1080/00207450802330959] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The selective estrogen receptor modulators (SERMs) are compounds that activate the estrogen receptors with different estrogenic and antiestrogenic tissue-specific effects. The similar effects of SERMs on estrogen encourage the efforts in the research of neuroprotective effects of SERMs. In our study, the potential neuroprotective effects of raloxifene were investigated on the brain cortex of ovariectomized rats after kainic acid-induced oxidative stress. To show the neuroprotective effect of raloxifene against a neurodegenerative agent, kainic acid, expression of Bcl-2, total glutathione (GSH), and nitrite-nitrate levels were investigated in the rat brain cortex. Our results demostrate that raloxifene treatment against oxidative stress significantly increases the expression of Bcl-2 and the level of GSH in the brain cortex.
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Affiliation(s)
- Guliz Armagan
- Department of Biochemistry, Faculty of Pharmacy, Ege University, Bornova, Izmir, Turkey.
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26
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Tian DS, Liu JL, Xie MJ, Zhan Y, Qu WS, Yu ZY, Tang ZP, Pan DJ, Wang W. Tamoxifen attenuates inflammatory-mediated damage and improves functional outcome after spinal cord injury in rats. J Neurochem 2009; 109:1658-67. [PMID: 19457130 DOI: 10.1111/j.1471-4159.2009.06077.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Tamoxifen has been found to be neuroprotective in both transient and permanent experimental ischemic stroke. However, it remains unknown whether this agent shows a similar beneficial effect after spinal cord injury (SCI), and what are its underlying mechanisms. In this study, we investigated the efficacy of tamoxifen treatment in attenuating SCI-induced pathology. Blood-spinal cord barrier (BSCB) permeability, tissue edema formation, microglial activation, neuronal cell death and myelin loss were determined in rats subjected to spinal cord contusion. The results showed that tamoxifen, administered at 30 min post-injury, significantly decreased interleukin-1beta (IL-1beta) production induced by microglial activation, alleviated the amount of Evans blue leakage and edema formation. In addition, tamoxifen treatment clearly reduced the number of apoptotic neurons post-SCI. The myelin loss and the increase in production of myelin-associated axonal growth inhibitors were also found to be significantly attenuated at day 3 post-injury. Furthermore, rats treated with tamoxifen scored much higher on the locomotor rating scale after SCI than did vehicle-treated rats, suggesting improved functional outcome after SCI. Together, these results demonstrate that tamoxifen provides neuroprotective effects for treatment of SCI-related pathology and disability, and is therefore a potential neuroprotectant for human spinal cord injury therapy.
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Affiliation(s)
- Dai-Shi Tian
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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27
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Deshaies EM, Boulos AS, Drazin D, Popp AJ. Evidence-based pharmacotherapy for cerebral vasospasm. Neurol Res 2008; 31:615-20. [PMID: 19108757 DOI: 10.1179/174313209x382377] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
INTRODUCTION The vast amount of literature on the pharmaceutical treatment of cerebral vasospasm after aneurysmal subarachnoid hemorrhage remains daunting. Optimal treatment regimens for patients can be obscured by studies not statistically powered to draw evidenced-based conclusions. METHODS In this chapter, we reviewed the English literature using the National Library of Medicine for studies regarding pharmacotherapies for the treatment of cerebral vasospasm. These studies were then categorized according to the US Preventative Services Task Force ranking system for evidence based medicine and reviewed each pharmacotherapy for its efficacy in the treatment of cerebral vasospasm. RESULTS Nimodipine (Nimotop), HMG Co-A reductase inhibitor (statins) and enoxaparin (Lovenox) were the only drugs with level-1 evidence available for the treatment of vasospasm from aneurysmal subarachnoid hemorrhage as defined by the US Preventative Services Task Force. CONCLUSION As the understanding of the pathophysiological mechanisms of vasospasm after aneurysmal subarachnoid hemorrhage evolves in the basic science laboratory, novel medications are being trialed in humans. However, significantly more work must be carried out in this area before we have an effective medical treatment that can prevent or reverse the devastating events of cerebral vasospasm.
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Affiliation(s)
- Eric Michael Deshaies
- Department of Surgery, Division of Neurosurgery, Albany Medical Center, Albany, NY, USA.
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28
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Zhang H, Xie M, Schools GP, Feustel PF, Wang W, Lei T, Kimelberg HK, Zhou M. Tamoxifen mediated estrogen receptor activation protects against early impairment of hippocampal neuron excitability in an oxygen/glucose deprivation brain slice ischemia model. Brain Res 2008; 1247:196-211. [PMID: 18992727 DOI: 10.1016/j.brainres.2008.10.015] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Revised: 10/02/2008] [Accepted: 10/04/2008] [Indexed: 12/18/2022]
Abstract
Pretreatment of ovarectomized rats with estrogen shows long-term protection via activation of the estrogen receptor (ER). However, it remains unknown whether activation of the ER can provide protection against early neuronal damage when given acutely. We simulated ischemic conditions by applying oxygen and glucose deprived (OGD) solution to acute male rat hippocampal slices and examined the neuronal electrophysiological changes. Pyramidal neurons and interneurons showed a time-dependent membrane potential depolarization and reduction in evoked action potential frequency and amplitude over a 10 to 15 min OGD exposure. These changes were largely suppressed by 10 microM TAM. The TAM effect was neuron-specific as the OGD-induced astrocytic membrane potential depolarization was not altered. The TAM effect was mediated through ER activation because it could be simulated by 17beta-estradiol and was completely inhibited by the ER inhibitor ICI 182, 780, and is therefore an example of TAM's selective estrogen receptor modulator (SERM) action. We further show that TAM's effects on OGD-induced impairment of neuronal excitability was largely due to activation of neuroprotective BK channels, as the TAM effect was markedly attenuated by the BK channel inhibitor paxilline at 10 microM. TAM also significantly reduced the frequency and amplitude of AMPA receptor mediated spontaneous excitatory postsynaptic currents (sEPSCs) in pyramidal neurons which is an early consequence of OGD. Altogether, this study demonstrates that both 17beta-estradiol and TAM attenuate neuronal excitability impairment early on in a simulated ischemia model via ER activation mediated potentiation of BK K(+) channels and reduction in enhanced neuronal AMPA/NMDA receptor-mediated excitotoxicity.
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Affiliation(s)
- Huaqiu Zhang
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong, University of Science and Technology, Wuhan, 430030, PR China
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29
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Kimelberg HK. Volume activated anion channel and astrocytic cellular edema in traumatic brain injury and stroke. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 559:157-67. [PMID: 18727237 DOI: 10.1007/0-387-23752-6_15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Harold K Kimelberg
- Neural and Vascular Biology Theme, Ordway Research Institute, 150 New Scotland Avenue., Albany, NY 12208, USA.
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30
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Yanagisawa D, Kitamura Y, Inden M, Takata K, Taniguchi T, Morikawa S, Morita M, Inubushi T, Tooyama I, Taira T, Iguchi-Ariga SMM, Akaike A, Ariga H. DJ-1 protects against neurodegeneration caused by focal cerebral ischemia and reperfusion in rats. J Cereb Blood Flow Metab 2008; 28:563-78. [PMID: 17882163 DOI: 10.1038/sj.jcbfm.9600553] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Reactive oxygen species (ROS) is massively produced in the brain after cerebral ischemia and reperfusion. It reacts strongly with cellular components, which has detrimental effects and leads to neuronal cell death. DJ-1, which was found to be the causative gene of familial Parkinson's disease PARK7, is a multifunction protein, which plays a key role in transcriptional regulation, and a molecular chaperone. In this study, we investigated the neuroprotective effect of DJ-1 against neurodegeneration caused by ischemia/reperfusion injury. Cerebral ischemia was induced in rats by 120 mins of middle cerebral artery occlusion (MCAO) using an intraluminal introduction method. The intrastriatal injection of recombinant glutathione S-transferase-tagged human DJ-1 (GST-DJ-1) markedly reduced infarct size in 2,3,5-triphenyltetrazolium chloride staining at 3 days after MCAO. In addition, we performed a noninvasive evaluation of ischemic size using magnetic resonance imaging and found a significant reduction of infarct size with the administration of GST-DJ-1. In GST-DJ-1-treated rats, behavioral dysfunction and nitrotyrosine formation were significantly inhibited. Furthermore, GST-DJ-1 markedly inhibited H(2)O(2)-mediated ROS production in SH-SY5Y cells. These results indicate that GST-DJ-1 exerts a neuroprotective effect by reducing ROS-mediated neuronal injury, suggesting that DJ-1 may be a useful therapeutic target for ischemic neurodegeneration.
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Affiliation(s)
- Daijiro Yanagisawa
- Department of Neurobiology, 21st Century COE Program, Kyoto Pharmaceutical University, Kyoto, Japan
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Wakade C, Khan MM, De Sevilla LM, Zhang QG, Mahesh VB, Brann DW. Tamoxifen neuroprotection in cerebral ischemia involves attenuation of kinase activation and superoxide production and potentiation of mitochondrial superoxide dismutase. Endocrinology 2008; 149:367-79. [PMID: 17901229 PMCID: PMC2194601 DOI: 10.1210/en.2007-0899] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The purpose of this study was to enhance our understanding of the mechanisms of neuronal death after focal cerebral ischemia and the neuroprotective effects of tamoxifen (TMX). The phosphorylation state of 31 protein kinases/signaling proteins and superoxide anion (O(2)(-)) production in the contralateral and ipsilateral cortex was measured after permanent middle cerebral artery occlusion (pMCAO) in ovariectomized rats treated with placebo or TMX. The study revealed that pMCAO modulated the phosphorylation of a number of kinases/proteins in the penumbra at 2 h after pMCAO. Of significant interest, phospho-ERK1/2 (pERK1/2) was elevated significantly after pMCAO. TMX attenuated the elevation of pERK1/2, an effect correlated with reduced infarct size. In situ detection of O(2)(-) production showed a significant elevation at 1-2 h after pMCAO in the ischemic cortex with enhanced oxidative damage detected at 24 h. ERK activation may be downstream of free radicals, a suggestion supported by the findings that cells positive for O(2)(-) had high pERK activation and that a superoxide dismutase (SOD) mimetic, tempol, significantly attenuated pERK activation after MCAO. TMX treatment significantly reduced the MCAO-induced elevation of O(2)(-) production, oxidative damage, and proapoptotic caspase-3 activation. Additionally, pMCAO induced a significant reduction in the levels of manganese SOD (MnSOD), which scavenge O(2)(-), an effect largely prevented by TMX treatment, thus providing a potential mechanistic basis for the antioxidant effects of TMX. As a whole, these studies suggest that TMX neuroprotection may be achieved via an antioxidant mechanism that involves enhancement of primarily MnSOD levels, with a corresponding reduction of O(2)(-) production, and downstream kinase and caspase-3 activation.
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Affiliation(s)
- Chandramohan Wakade
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th Street, Augusta, Georgia 30912, USA
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DCPIB, a specific inhibitor of volume regulated anion channels (VRACs), reduces infarct size in MCAo and the release of glutamate in the ischemic cortical penumbra. Exp Neurol 2007; 210:514-20. [PMID: 18206872 DOI: 10.1016/j.expneurol.2007.11.027] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2007] [Revised: 11/14/2007] [Accepted: 11/27/2007] [Indexed: 11/20/2022]
Abstract
Previous studies have indicated that volume regulated anion channels (VRACs) may be involved in the pathology of the ischemic brain cortical penumbra due to activation of VRAC-mediated excitatory amino-acid (EAA) release. To assess this we had studied neuroprotection and EAA release inhibition by a potent VRAC inhibitor, tamoxifen. However, tamoxifen inhibits several other neurodamaging processes. In the present study we use an ethacrynic acid derivative, 4-(2-butyl-6,7-dichloro-2-cyclopentyl-indan-1-on-5-yl) oxobutyric acid (DCPIB), that has recently been shown to be a specific antagonist of volume regulated anion channels (VRAC), to measure the extent of neuroprotection provided and thus to better assess the role of VRAC-mediated release of excitatory amino acids in an intraluminal suture, reversible middle cerebral artery occlusion (rMCAO) model in adult rats. Rats given DCPIB intracisternally had significantly better neurobehavioral scores after 24 h and showed significantly reduced infarct volumes. Mean infarct volumes were 208.0 (SD=38.3) mm3 for the vehicle groups, compared with 68.5 (SD=22.7) mm3 for intracisternally DCPIB-treated groups (p=0.02, Mann-Whitney test), a reduction of around 75%. However, a 500-fold higher dose of DCPIB given intravenously did not reduce infarct volume or improve behavior. The microdialysis study demonstrated statistically significant reduced brain extracellular fluid glutamate when DCPIB was present in the probe. Thus DCPIB, a specific inhibitor of VRACs, given i.c., provides strong neuroprotection in brain ischemia, but it appears to not cross the blood brain barrier as it is not effective when given i.v. These experiments support the hypothesis that EAA released via VRACs contributes to later ischemic-induced damage.
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33
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Blood micromolar concentrations of kaempferol afford protection against ischemia/reperfusion-induced damage in rat brain. Brain Res 2007; 1182:123-37. [DOI: 10.1016/j.brainres.2007.08.087] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Revised: 08/28/2007] [Accepted: 08/30/2007] [Indexed: 11/19/2022]
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Mongin AA. Disruption of ionic and cell volume homeostasis in cerebral ischemia: The perfect storm. ACTA ACUST UNITED AC 2007; 14:183-93. [PMID: 17961999 DOI: 10.1016/j.pathophys.2007.09.009] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The mechanisms of brain tissue damage in stroke are strongly linked to the phenomenon of excitotoxicity, which is defined as damage or death of neural cells due to excessive activation of receptors for the excitatory neurotransmitters glutamate and aspartate. Under physiological conditions, ionotropic glutamate receptors mediate the processes of excitatory neurotransmission and synaptic plasticity. In ischemia, sustained pathological release of glutamate from neurons and glial cells causes prolonged activation of these receptors, resulting in massive depolarization and cytoplasmic Ca(2+) overload. High cytoplasmic levels of Ca(2+) activate many degradative processes that, depending on the metabolic status, cause immediate or delayed death of neural cells. This traditional view has been expanded by a number of observations that implicate Cl(-) channels and several types of non-channel transporter proteins, such as the Na(+),K(+),2Cl(-) cotransporter, Na(+)/H(+) exchanger, and Na(+)/Ca(2+) exchanger, in the development of glutamate toxicity. Some of these ion transporters increase tissue damage by promoting pathological cell swelling and necrotic cell death, while others contribute to a long-term accumulation of cytoplasmic Ca(2+). This brief review is aimed at illustrating how the dysregulation of various ion transport processes combine in a 'perfect storm' that disrupts neural ionic homeostasis and culminates in the irreversible damage and death of neural cells. The clinical relevance of individual transporters as targets for therapeutic intervention in stroke is also briefly discussed.
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Affiliation(s)
- Alexander A Mongin
- Center for Neuropharmacology and Neuroscience, Albany Medical College, 47 New Scotland Avenue (MC-136), Albany, NY 12208, USA
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Brann DW, Dhandapani K, Wakade C, Mahesh VB, Khan MM. Neurotrophic and neuroprotective actions of estrogen: basic mechanisms and clinical implications. Steroids 2007; 72:381-405. [PMID: 17379265 PMCID: PMC2048656 DOI: 10.1016/j.steroids.2007.02.003] [Citation(s) in RCA: 442] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2006] [Revised: 02/07/2007] [Accepted: 02/09/2007] [Indexed: 12/16/2022]
Abstract
Estrogen is an important hormone signal that regulates multiple tissues and functions in the body. This review focuses on the neurotrophic and neuroprotective actions of estrogen in the brain, with particular emphasis on estrogen actions in the hippocampus, cerebral cortex and striatum. Sex differences in the risk, onset and severity of neurodegenerative disease such as Alzheimer's disease, Parkinson's disease and stroke are well known, and the potential role of estrogen as a neuroprotective factor is discussed in this context. The review assimilates a complex literature that spans research in humans, non-human primates and rodent animal models and attempts to contrast and compare the findings across species where possible. Current controversies regarding the Women's Health Initiative (WHI) study, its ramifications, concerns and the new studies needed to address these concerns are also addressed. Signaling mechanisms underlying estrogen-induced neuroprotection and synaptic plasticity are reviewed, including the important concepts of genomic versus nongenomic mechanisms, types of estrogen receptor involved and their subcellular targeting, and implicated downstream signaling pathways and mediators. Finally, a multicellular mode of estrogen action in the regulation of neuronal survival and neurotrophism is discussed, as are potential future directions for the field.
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Affiliation(s)
- Darrell W Brann
- Institute of Molecular Medicine and Genetics, School of Medicine, Medical College of Georgia, Augusta, GA 30912, United States.
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36
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Zhang Y, Milatovic D, Aschner M, Feustel PJ, Kimelberg HK. Neuroprotection by tamoxifen in focal cerebral ischemia is not mediated by an agonist action at estrogen receptors but is associated with antioxidant activity. Exp Neurol 2007; 204:819-27. [PMID: 17321521 PMCID: PMC1913768 DOI: 10.1016/j.expneurol.2007.01.015] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2006] [Revised: 12/14/2006] [Accepted: 01/12/2007] [Indexed: 01/22/2023]
Abstract
We have previously shown that tamoxifen can induce marked neuroprotection after middle cerebral artery occlusion (MCAo) in rats and have described two possible mechanisms of action: namely, inhibition of EAA release and inhibition of nNOS activity. In this study we tested other potential mechanisms. Namely, agonist action at estrogen receptors and an antioxidative action. Tamoxifen-treated rats had significantly improved neurobehavioral deficit scores after 24 h and showed approximately 75% reduced infarct volumes. These were unaffected by ICI 182,780 (a high affinity and pure receptor antagonist) administered intravenously, or intracisternally to avoid possible lack of brain penetration, 15 min before intravenous administration of tamoxifen. In rats subjected to 2 h MCAo followed by 22 h reperfusion, 1.8-fold and 2.9-fold increases of F(2)-IsoPs and F(4) neuroprostanes, respectively, as relatively stable markers of oxidative damage, were measured in the ischemic hemisphere compared with the corresponding contralateral hemisphere or sham controls. Tamoxifen given at 3 h after the start of ischemia reduced the IsoPs and NeuroPs to sham control levels, and also inhibited their production by chemically induced lipid peroxidation in brain homogenates. These data are consistent with at least part of tamoxifen's marked neuroprotection in focal cerebral ischemic injury being due to its antioxidant activity but not by an acute action on estrogen receptors (212 words).
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Affiliation(s)
- Yonghua Zhang
- Neural and Vascular Biology Theme, Ordway Research Institute, 150 New Scotland Avenue, Albany, NY 12208, USA
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37
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Abstract
The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.
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Affiliation(s)
- Pál Pacher
- Section on Oxidative Stress Tissue Injury, Laboratory of Physiologic Studies, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, Bethesda, Maryland, USA.
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Seifert G, Schilling K, Steinhäuser C. Astrocyte dysfunction in neurological disorders: a molecular perspective. Nat Rev Neurosci 2006; 7:194-206. [PMID: 16495941 DOI: 10.1038/nrn1870] [Citation(s) in RCA: 564] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent work on glial cell physiology has revealed that glial cells, and astrocytes in particular, are much more actively involved in brain information processing than previously thought. This finding has stimulated the view that the active brain should no longer be regarded solely as a network of neuronal contacts, but instead as a circuit of integrated, interactive neurons and glial cells. Consequently, glial cells could also have as yet unexpected roles in the diseased brain. An improved understanding of astrocyte biology and heterogeneity and the involvement of these cells in pathogenesis offers the potential for developing novel strategies to treat neurological disorders.
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Affiliation(s)
- Gerald Seifert
- Department of Experimental Neurobiology, Clinic of Neurosurgery, University of Bonn, Germany
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39
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Obata T. Nitric oxide and MPP+-induced hydroxyl radical generation. J Neural Transm (Vienna) 2006; 113:1131-44. [PMID: 16463115 DOI: 10.1007/s00702-005-0415-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Accepted: 10/22/2005] [Indexed: 10/25/2022]
Abstract
Although neuroprotective effect of nitric oxide (NO) is discussed, NO has a role of pathogenesis of cellular injury. NO is synthesized from L-arginine by NO synthase (NOS). NO contributes to the extracellular potassium-ion concentration ([K(+)](o))-induced hydroxyl radical ((*)OH) generation. Cytotoxic free radicals such as peroxinitrite (ONOO(-)) and (*)OH may also be implicated in NO-mediated cell injury. NO activation was induced by K(+) depolarization. NO may react with superoxide anion (O(2) (-)) to form ONOO(-) and its decomposition generates (*)OH. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) metabolite 1-methyl-4-phenylpyridinium ion (MPP(+)) involve toxicity induced by NO. Intraneuronal Ca(2+) triggered by MPP(+) may be detrimental to the functioning of dopaminergic nerve terminals in the striatum. Although the [K(+)](o)-induced depolarization enhances the formation of (*)OH product due to MPP(+), the (*)OH generation via NOS activation may be unrelated the dopamine (DA)-induced (*)OH generation. Depolarization enhances the MPP(+)-induced (*)OH formation via NOS activation. NOS inhibition is associated with a protective effect due to suppression of depolarization-induced (*)OH generation. ONOO(-) has been implicated as a causative factor under conditions in which DA neurons are damaged. These findings may be useful in elucidating the actual mechanism of free radical formation in the pathogenesis of neurodegenerative brain disorders, including Parkinson's disease and traumatic brain injuries.
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Affiliation(s)
- T Obata
- Department of Analytical Chemistry, Ohu University School of Pharmaceutical Sciences, Koriyama, Fukushima, Japan.
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40
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Ciriza I, Carrero P, Azcoitia I, Lundeen SG, Garcia-Segura LM. Selective estrogen receptor modulators protect hippocampal neurons from kainic acid excitotoxicity: differences with the effect of estradiol. ACTA ACUST UNITED AC 2005; 61:209-21. [PMID: 15389604 DOI: 10.1002/neu.20043] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Neuroprotective effects of estradiol are well characterized in animal experimental models. However, in humans, the outcome of estrogen treatment for cognitive function and neurological diseases is very controversial. Selective estrogen receptor modulators (SERMs) may represent an alternative to estrogen for the treatment or the prevention of neurodegenerative disorders. SERMs interact with the estrogen receptors and have tissue-specific effects distinct from those of estradiol, acting as estrogen agonists in some tissues and as antagonists in others. In this study we have assessed the effect of tamoxifen, raloxifene, lasofoxifene (CP-336,156), bazedoxifene (TSE-424), and 17beta-estradiol on the hippocampus of adult ovariectomized rats, after the administration of the excitotoxin kainic acid. Administration of kainic acid induced the expression of vimentin in reactive astroglia and a significant neuronal loss in the hilus. SERMs did not affect vimentin immunoreactivity in the hilus, while 17beta-estradiol significantly reduced the surface density of vimentin immunoreactive profiles. Estradiol, tamoxifen (0.4-2 mg/kg), raloxifene (0.4-2 mg/kg), and bazedoxifene (2 mg/kg) prevented neuronal loss in the hilus after the administration of kainic acid. Lasofoxifene (0.4-2 mg/kg) was not neuroprotective. These findings indicate that SERMs present different dose-dependent neuroprotective effects. Furthermore, the mechanisms of neuroprotection by SERMs and estradiol are not identical, because SERMs do not significantly affect reactive gliosis while neuroprotection by estradiol is associated with a strong down-regulation of reactive astroglia.
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41
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Kimelberg HK. Astrocytic swelling in cerebral ischemia as a possible cause of injury and target for therapy. Glia 2005; 50:389-397. [PMID: 15846797 DOI: 10.1002/glia.20174] [Citation(s) in RCA: 210] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In this viewpoint article, I summarize data showing that the astrocytic swelling that occurs early after the acute CNS pathologies ischemia and traumatic brain injury is damaging. We have proposed that one reason may be the release of excitatory amino acids (EAA) via volume-activated anion channels (VRACs) that are activated by such swelling. This release could be a target for therapy, which could involve blocking the astrocytic swelling or the release mechanisms. The transport mechanisms likely causing the early astrocytic swelling are therefore summarized. In terms of targeting the release mechanisms, we have found a potent inhibitor of VRACs, tamoxifen, to be strongly neuroprotective in focal ischemia with a therapeutic window of 3 h after initiation of the ischemia. The question, however, of whether neuroprotection by tamoxifen can be solely attributed to VRAC inhibition in astrocytes has yet to be resolved.
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Affiliation(s)
- Harold K Kimelberg
- Neural and Vascular Biology, Ordway Research Institute, Albany, New York
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42
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Willett MC, Dluzen DE. Tamoxifen increases methamphetamine-evoked dopamine output from superfused striatal tissue fragments of male mice. Brain Res 2004; 1029:186-94. [PMID: 15542073 DOI: 10.1016/j.brainres.2004.09.043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2004] [Indexed: 11/16/2022]
Abstract
The antiestrogen, tamoxifen (TMX), has been shown to function as a neuroprotectant against the nigrostriatal dopaminergic (NSDA) neurotoxin, methamphetamine (MA), within male mice. In the present report, we examined the effects of a combined infusion of TMX and MA within superfused striatal tissue fragments of male mice as an approach to understand some of the bases for TMX to function as a NSDA neuroprotectant within male mice. In Experiment 1, a coinfusion of TMX at 1, 10, or 100 pg/ml were all equally effective in increasing MA-evoked dopamine (DA) output as compared with a 0 pg/ml (control) dose. In Experiment 2, we tested whether this effect of TMX was specific for MA-evoked DA output by coinfusing TMX with a depolarizing concentration of potassium chloride (K+ -30 mM). No statistically significant differences were obtained between superfusions of striatal tissue fragments stimulated with K+ in the presence or absence of TMX (100 pg/ml). In Experiment 3, we assessed whether these effects of TMX may be exerted upon the dopamine transporter (DAT) by coinfusing DA (1 microM) in the presence or absence of TMX (100 pg/ml). No differences in DA recovery rates were obtained between superfusions performed in the presence or absence of TMX. Taken together, these results show that the striatum of male mice is very sensitive to the modulatory effects of TMX upon MA-evoked DA output. These effects of TMX appear to be relatively specific for MA-evoked DA output, as K+ -stimulated DA was not altered by TMX, and do not appear to exert these effects by altering dopamine transporter function.
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Affiliation(s)
- Matthew C Willett
- Department of Anatomy, Northeastern Ohio Universities College of Medicine (NEOUCOM), 4209 State Route 44, PO Box 95, Rootstown, OH 44272-0095, USA
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43
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Schliess F, Foster N, Görg B, Reinehr R, Häussinger D. Hypoosmotic swelling increases protein tyrosine nitration in cultured rat astrocytes. Glia 2004; 47:21-9. [PMID: 15139009 DOI: 10.1002/glia.20019] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Astrocyte swelling is observed in different types of brain injury. We studied a potential contribution of swelling to protein tyrosine nitration (PTN) by using cultured rat astrocytes exposed to hypoosmotic (205 mosmol/L) medium. Hypoosmolarity (2 h) increases total PTN by about 2-fold in 2 h. The hypoosmotic PTN is significantly inhibited by the NMDA receptor antagonist MK-801, the nitric oxide synthase (NOS) inhibitor L-NMMA, the extracellular Ca2+ chelator EGTA and the calmodulin antagonist W13, suggesting the involvement of NMDA receptor activation, influx of extracellular Ca2+ and Ca2+/calmodulin-dependent NO synthesis. Further, superoxide dismutase plus catalase and uric acid strongly inhibit hypoosmotic PTN, suggesting the involvement of the toxic metabolite peroxynitrite (ONOO-) as a nitrating agent. Hypoosmotic astrocyte swelling rapidly stimulates generation of reactive oxygen intermediates; this process is prevented by MK-801 and EGTA. In addition, MK-801 inhibits the hypoosmotic elevation of [Ca2+]i. The findings support the view that astrocyte swelling as induced, for example, by toxins relevant for hepatic encephalopathy is sufficient to produce oxidative stress and PTN and thus contributes to altered astroglial and neuronal function.
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Affiliation(s)
- Freimut Schliess
- Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University, Düsseldorf, Germany.
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44
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Kimelberg HK. Increased release of excitatory amino acids by the actions of ATP and peroxynitrite on volume-regulated anion channels (VRACs) in astrocytes. Neurochem Int 2004; 45:511-9. [PMID: 15186917 DOI: 10.1016/j.neuint.2003.11.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/10/2003] [Indexed: 01/01/2023]
Abstract
Rapid swelling of astrocytes in primary culture by exposure to hyposmotic medium (or slower swelling by exposure to high K+ medium) leads to release of the excitatory amino acids (EAAs) glutamate and aspartate. One question that arises is whether these phenomena are only relevant to pathological states such as ischemia and trauma where marked astrocytic swelling occurs or whether much smaller astrocytic volume changes, that might be encountered under physiological states, will cause such release. We have recently found that extracellular ATP strongly potentiated volume-regulated anion channels (VRACs)-mediated-excitatory amino acid release in non-swollen and osmotically swollen primary astrocyte cultures. However, ATP does not seem to directly activate but instead positively modulates VRACs and we postulate that a minor fraction of these are active under isoosmotic conditions based on the finding that in hyperosmotic media the ATP-induced increase was inhibited. Agonist and inhibitor analysis suggests that the effect of ATP is mediated by several subtypes of metabotropic P2Y receptors. Thus, the concept of volume transmission may be extended to volume-mediated transmission, whereby moderate cell swelling causes release of neurotransmitter substances. The product of the superoxide oxygen radical and nitric oxide, peroxynitrite, formed under pathological conditions such as cerebral ischemia, also potentiated the release of D-[3H]aspartate from astrocyte cultures exposed to limited or marked swelling via intracellular signaling mechanisms involving tyrosine kinases (TKs). Thus, the enhancement of cell volume-dependent release of excitatory amino acids from astrocytes can be physiological or pathological and its magnitude depends on the degree of the cell volume increase.
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Affiliation(s)
- Harold K Kimelberg
- Neural and Vascular Biology Theme, Ordway Research Institute, Inc., 150 New Scotland Ave., Albany, NY 12208, USA.
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45
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Kimelberg HK, Nestor NB, Feustel PJ. Inhibition of release of taurine and excitatory amino acids in ischemia and neuroprotection. Neurochem Res 2004; 29:267-74. [PMID: 14992286 DOI: 10.1023/b:nere.0000010455.78121.53] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Volume regulated anion channels (VRAC) have been extensively studied in purified single cell systems like cell cultures where they can be activated by cell swelling. This provides a convenient way of analyzing mechanisms and will likely lead to the holy grails of the field, namely the nature or natures of the volume sensor and the nature or natures of VRACs. Important reasons for such an understanding are that these channels are ubiquitous and have important physiological functions which under pathological conditions convert to deleterious effects. Here we summarize data showing the involvement of VRACs in ischemia-induced release of excitatory amino acids (EAAs) in a rat model of global ischemia. Using microdialysis studies we found that reversal of the astrocytic glutamate transporter and VRACs contribute about equally to the large initial release of EAAs and together account for around 80% of the total release. We used the very potent VRAC blocker, tamoxifen, to see if such inhibition of EAA release via VRACs led to significant neuroprotection. Treatment in the focal rat MCA occlusion model led to around 80% reduction in infarct size with an effective post initiation of ischemia therapeutic window of three hours. However, the common problem of other effects for even the most potent inhibitors pertains here, as tamoxifen has other, potentially neuroprotective, effects. Thus it inhibits nitrotyrosine formation, likely due to its inhibition of nNOS and reduction of peroxynitrite formation. Although tamoxifen cannot therefore be used as a test of the "VRAC-excitotxicity" hypothesis it may prove successful for translation of basic stroke research to the clinic because of its multiple targets.
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Affiliation(s)
- Harold K Kimelberg
- Center for Neuropharmacology and Neuroscience and Division of Neurosurgery Albany Medical College, Albany, New York, USA.
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46
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Feng Y, Fratkins JD, LeBlanc MH. Treatment with tamoxifen reduces hypoxic–ischemic brain injury in neonatal rats. Eur J Pharmacol 2004; 484:65-74. [PMID: 14729383 DOI: 10.1016/j.ejphar.2003.10.048] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Tamoxifen, an estrogen receptor modulator, is neuroprotective in adult rats. Does tamoxifen reduce brain injury in the rat pup? Seven-day-old rat pups had the right carotid artery permanently ligated followed by 2.5 h of hypoxia (8% oxygen). Tamoxifen (10 mg/kg) or vehicle was given i.p. 5 min prior to hypoxia, or 5 min after reoxygenation, with a second dose given 6 h after the first. Brain damage was evaluated by weight deficit of the right hemisphere 22 days following hypoxia and gross and microscopic morphology. Tamoxifen pre-treatment reduced brain weight loss from 21.5+/-4.0% in vehicle pups (n=27) to 2.6+/-2.5% in the treated pups (n=22, P<0.05). Treatment 5 min after reoxygenation reduced brain weight loss from 27.5+/-4.0% in vehicle pups (n=42) to 12.0+/-3.9% in the treated pups (n=30, P<0.05). Tamoxifen reduces brain injury in the neonatal rat.
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Affiliation(s)
- Yangzheng Feng
- Department of Pediatrics, University of Mississippi Medical Center, 2500 North State Street, 39216-4505, Jackson, MS, USA.
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47
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Hashiguchi A, Kawano T, Yano S, Morioka M, Hamada J, Sato T, Shirasaki Y, Ushio Y, Fukunaga K. The neuroprotective effect of a novel calmodulin antagonist, 3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-(4-imidazolylmethyl)-1h-indazole dihydrochloride 3.5 hydrate, in transient forebrain ischemia. Neuroscience 2003; 121:379-86. [PMID: 14521996 DOI: 10.1016/s0306-4522(03)00490-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A novel calmodulin (CaM) antagonist DY-9760e, (3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-(4-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate), with an apparent neuroprotective effect in vivo, potently inhibits CaM-dependent nitric oxide synthase in situ. In the present study, we determined whether DY-9760e inhibits nitric oxide (NO) production and protein nitration by peroxynitrite (ONOO(-)) formation in the hippocampal CA1 region of gerbils after transient forebrain ischemia. In freely moving gerbils, NO production after 10-minute forebrain ischemia was monitored consecutively with in vivo brain microdialysis. Pretreatment with DY-9760e (50 mg/kg i.p.) significantly decreased the increased levels of NO(x)(-) (NO metabolites, NO(2)(-) plus NO(3)(-)) immediately after, 24 h after cerebral ischemia-reperfusion to the control levels of sham-operated animals. Western blot and immunohistochemical analyses using an anti-nitrotyrosine antibody as a marker of ONOO(-) formation indicated a marked increase in nitrotyrosine immunoreactivity in the pyramidal neurons of the CA1 region 2 h after reperfusion, and DY-9760e significantly inhibited increased nitrotyrosine immunoreactivity. Coincident with the inhibition of the NO production and protein tyrosine nitration, pretreatment with DY-9760e rescued the delayed neuronal death in the hippocampal CA1 region. These results suggest that the inhibitory effects of DY-9760e on the NO-ONOO(-) pathway partly account for its neuroprotective effects in cerebral ischemia.
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Affiliation(s)
- A Hashiguchi
- Department of Pharmacology, Kumamoto University School of Medicine, Kumamoto-city, Kumamoto 860-0811, Japan
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Kimelberg HK, Jin Y, Charniga C, Feustel PJ. Neuroprotective activity of tamoxifen in permanent focal ischemia. J Neurosurg 2003; 99:138-42. [PMID: 12854756 DOI: 10.3171/jns.2003.99.1.0138] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT The authors have previously shown that tamoxifen is effective in protecting brain tissue from ischemic injury in a rat model of reversible focal ischemia. In this study the authors tested whether similar protective effects are found in a rat model of permanent focal ischemia (permanent middle cerebral artery [MCA] occlusion). METHODS Tamoxifen (20 mg/kg) was given either before or at 1, 3, or 6 hours after permanent MCA occlusion in rats, with sustaining doses given every 12 hours thereafter. The median infarct volume measured after 72 hours was 113 mm3 for the vehicle (dimethyl sulfoxide) groups, compared with 31 mm3 for pretreatment, and 14, 27, and 98 mm3 for treatment beginning at 1, 3, and 6 hours, respectively, after permanent MCA occlusion. The infarct reductions in the pretreated and 1- and 3-hour post-MCA occlusion treatment groups were statistically significant (p < 0.05). At 3 hours after permanent MCA occlusion, tamoxifen also significantly reduced the infarct size at a lower dose of 5 mg/kg but not at 1 mg/kg; the same sustaining doses of 5 and 1 mg/kg were given every 12 hours. CONCLUSIONS Tamoxifen is as effective in a permanent model of focal ischemia as it is in the reversible model, and the therapeutic window of 3 hours after initiation of ischemia is identical. This effectiveness is likely due to several properties of the drug, including its known ability to cross the blood-brain barrier. Because tamoxifen has been administered safely in humans for treatment of gliomas at similarly high doses to those used in this study, it may be clinically useful as a treatment for ischemic stroke.
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Affiliation(s)
- Harold K Kimelberg
- Center for Neuropharmacology and Neuroscience, and Division of Neurosurgery, Albany Medical College, Albany, New York 12208, USA.
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Murphy S, McCullough L, Littleton-Kearney M, Hurn P. Estrogen and selective estrogen receptor modulators: neuroprotection in the Women's Health Initiative era. Endocrine 2003; 21:17-26. [PMID: 12777699 DOI: 10.1385/endo:21:1:17] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2003] [Revised: 02/04/2003] [Accepted: 02/11/2003] [Indexed: 11/11/2022]
Abstract
Estrogen has been comprehensively studied as a neuroprotective agent in women, animals, and a variety of in vitro models of neural injury and degeneration. Most data suggest that estrogen can benefit the ischemic brain and reduce cell death. However, recent data from the Women's Health Initiative have raised concerns about the utility and safety of chronic estrogen use in women. While estrogen is a potent and reproducible neuroprotectant in animals and in vitro, its current administration in women has had unanticipated and paradoxical effects. Nonetheless, estrogen's diverse actions make it an ideal prototype for developing new neuroprotectants such as selective estrogen receptor modulators (SERMs). SERMs represent a class of drugs with mixed estrogen agonistic and antagonistic activity. Experimental and clinical data suggest a neuroprotective role for SERMs in normal and injured brain. The discrepancy among observational studies, preclinical data, and clinical trials emphasizes the need for further study of the mechanisms leading to the increased incidence of stroke observed in postmenopausal women. Research is still needed to optimize combined or estrogen alone hormone replacement therapy options as well as the prevention/management of cerebrovascular/ central nervous system disorders. This review critiques estrogen and SERMs' neuroprotective potential in experimental and clinical studies of stroke and cerebrovascular disease.
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Affiliation(s)
- Stephanie Murphy
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, MD, USA.
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Mehta SH, Dhandapani KM, De Sevilla LM, Webb RC, Mahesh VB, Brann DW. Tamoxifen, a selective estrogen receptor modulator, reduces ischemic damage caused by middle cerebral artery occlusion in the ovariectomized female rat. Neuroendocrinology 2003; 77:44-50. [PMID: 12624540 DOI: 10.1159/000068332] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2002] [Accepted: 11/05/2002] [Indexed: 11/19/2022]
Abstract
Previous work has demonstrated that physiological concentrations of 17beta-estradiol can protect the female rat brain against middle cerebral artery occlusion (MCAO)-induced ischemic damage. The present study examined whether therapeutic doses of the clinically relevant selective estrogen receptor modulator (SERM), tamoxifen, can similarly protect the female rat brain against ischemic stroke damage. Adult female rats were bilaterally ovariectomized and implanted subcutaneously with either a placebo or tamoxifen time-release pellet (0.1, 0.8 or 2.4 mg/kg/day). One week later, the animals underwent permanent MCAO to assess the protective ability of the different tamoxifen doses on brain infarct size. As expected, MCAO produced a large infarct ( approximately 53%) of the affected cerebral hemisphere in placebo (control) animals. The 0.1 mg/kg/day dose of tamoxifen did not exhibit any significant protective effects, however; the 0.8 and 2.4 mg/kg/day doses of tamoxifen, which are in the therapeutic range, dramatically reduced infarct of the affected cerebral hemisphere ( approximately 70% reduction) as compared to the controls. The reduction of infarct size was primarily due to protection of two major structures, the cerebral cortex and striatum. Laser Doppler analysis further revealed that tamoxifen had no significant effect on cerebral blood flow either before or after MCAO, suggesting that tamoxifen protection is independent of cerebral blood flow changes. Further studies showed that tamoxifen pellets implanted at the time of MCAO did not reduce infarct size, suggesting that pretreatment with tamoxifen is necessary to observe a protective effect. These studies suggest that clinically important SERMs may have an additional unrecognized beneficial effect of protection of the female brain.
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Affiliation(s)
- Shyamal H Mehta
- Department of Physiology, Medical College of Georgia, Augusta, Ga 30912, USA
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