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Cheng S, Mao X, Lin X, Wehn A, Hu S, Mamrak U, Khalin I, Wostrack M, Ringel F, Plesnila N, Terpolilli NA. Acid-Ion Sensing Channel 1a Deletion Reduces Chronic Brain Damage and Neurological Deficits after Experimental Traumatic Brain Injury. J Neurotrauma 2021; 38:1572-1584. [PMID: 33779289 DOI: 10.1089/neu.2020.7568] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Traumatic brain injury (TBI) causes long-lasting neurodegeneration and cognitive impairments; however, the underlying mechanisms of these processes are not fully understood. Acid-sensing ion channels 1a (ASIC1a) are voltage-gated Na+- and Ca2+-channels shown to be involved in neuronal cell death; however, their role for chronic post-traumatic brain damage is largely unknown. To address this issue, we used ASIC1a-deficient mice and investigated their outcome up to 6 months after TBI. ASIC1a-deficient mice and their wild-type (WT) littermates were subjected to controlled cortical impact (CCI) or sham surgery. Brain water content was analyzed 24 h and behavioral outcome up to 6 months after CCI. Lesion volume was assessed longitudinally by magnetic resonance imaging and 6 months after injury by histology. Brain water content was significantly reduced in ASIC1a-/- animals compared to WT controls. Over time, ASIC1a-/- mice showed significantly reduced lesion volume and reduced hippocampal damage. This translated into improved cognitive function and reduced depression-like behavior. Microglial activation was significantly reduced in ASIC1a-/- mice. In conclusion, ASIC1a deficiency resulted in reduced edema formation acutely after TBI and less brain damage, functional impairments, and neuroinflammation up to 6 months after injury. Hence, ASIC1a seems to be involved in chronic neurodegeneration after TBI.
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Affiliation(s)
- Shiqi Cheng
- Institute for Stroke and Dementia Research, Munich University Hospital, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Xiang Mao
- Institute for Stroke and Dementia Research, Munich University Hospital, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Xiangjiang Lin
- Institute for Stroke and Dementia Research, Munich University Hospital, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Antonia Wehn
- Institute for Stroke and Dementia Research, Munich University Hospital, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Senbin Hu
- Institute for Stroke and Dementia Research, Munich University Hospital, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Uta Mamrak
- Institute for Stroke and Dementia Research, Munich University Hospital, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Igor Khalin
- Institute for Stroke and Dementia Research, Munich University Hospital, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Maria Wostrack
- Department of Neurosurgery, Technical University Munich, Munich, Germany
| | - Florian Ringel
- Department of Neurosurgery, University Medical Center Mainz, Mainz, Germany
| | - Nikolaus Plesnila
- Institute for Stroke and Dementia Research, Munich University Hospital, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Nicole A Terpolilli
- Institute for Stroke and Dementia Research, Munich University Hospital, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany.,Department of Neurosurgery, Munich University Hospital, Munich, Germany
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2
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Bertalan G, Klein C, Schreyer S, Steiner B, Kreft B, Tzschätzsch H, de Schellenberger AA, Nieminen-Kelhä M, Braun J, Guo J, Sack I. Biomechanical properties of the hypoxic and dying brain quantified by magnetic resonance elastography. Acta Biomater 2020; 101:395-402. [PMID: 31726251 DOI: 10.1016/j.actbio.2019.11.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 11/01/2019] [Accepted: 11/06/2019] [Indexed: 12/24/2022]
Abstract
Respiratory arrest is a major life-threatening condition leading to cessation of vital functions and hypoxic-anoxic injury of the brain. The progressive structural tissue changes characterizing the dying brain biophysically are unknown. Here we use noninvasive magnetic resonance elastography to show that biomechanical tissue properties are highly sensitive to alterations in the brain in the critical period before death. Our findings demonstrate that brain stiffness increases after respiratory arrest even when cardiac function is still preserved. Within 5 min of cardiac arrest, cerebral stiffness further increases by up to 30%. This early mechanical signature of the dying brain can be explained by water accumulation and redistribution from extracellular spaces into cells. These processes, together, increase interstitial and intracellular pressure as revealed by magnetic resonance spectroscopy and diffusion-weighted imaging. Our data suggest that the fast response of cerebral stiffness to respiratory arrest enables the monitoring of life-threatening brain pathology using noninvasive in vivo imaging. STATEMENT OF SIGNIFICANCE: Hypoxia-anoxia is a life-threatening condition eventually leading to brain death. Therefore, monitoring vital brain functions in patients at risk is urgently required during emergency care or treatment of acute brain damage due to insufficient oxygen supply. In mouse model of hypoxia-anoxia, we have shown for the first time that biophysical tissue parameters such as brain stiffness changed markedly during the process of death.
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Affiliation(s)
- Gergely Bertalan
- Department of Radiology, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Germany
| | - Charlotte Klein
- Department of Neurology, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Germany
| | - Stefanie Schreyer
- Department of Neurology, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Germany
| | - Barbara Steiner
- Department of Neurology, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Germany
| | - Bernhard Kreft
- Department of Radiology, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Germany
| | - Heiko Tzschätzsch
- Department of Radiology, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Germany
| | - Angela Ariza de Schellenberger
- Department of Radiology, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Germany
| | - Melina Nieminen-Kelhä
- Department of Neurosurgery, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Germany
| | - Jürgen Braun
- Institute for Medical Informatics, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Germany
| | - Jing Guo
- Department of Radiology, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Germany.
| | - Ingolf Sack
- Department of Radiology, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Germany
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3
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Roles of volume-regulatory anion channels, VSOR and Maxi-Cl, in apoptosis, cisplatin resistance, necrosis, ischemic cell death, stroke and myocardial infarction. CURRENT TOPICS IN MEMBRANES 2019; 83:205-283. [DOI: 10.1016/bs.ctm.2019.03.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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4
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Manchester LC, Lee V, Schmithorst V, Kochanek PM, Panigrahy A, Fink EL. Global and Regional Derangements of Cerebral Blood Flow and Diffusion Magnetic Resonance Imaging after Pediatric Cardiac Arrest. J Pediatr 2016; 169:28-35.e1. [PMID: 26561380 PMCID: PMC4729616 DOI: 10.1016/j.jpeds.2015.10.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 08/19/2015] [Accepted: 10/01/2015] [Indexed: 01/06/2023]
Abstract
OBJECTIVE To quantify and examine the relationship between global and regional cerebral blood flow (CBF) and water diffusion on brain magnetic resonance imaging (MRI) in children after cardiac arrest. STUDY DESIGN Children admitted to a tertiary care children's hospital from July 2011 to April 2013 who received a brain MRI within 2 weeks after cardiac arrest that included arterial spin labeling and apparent diffusion coefficient (ADC) sequences were studied. CBF and ADC values were calculated globally and in 19 regions of interest. Outcome variables included survival and favorable neurologic outcome, which was defined as Pediatric Cerebral Performance Category ≤3 at 6 months. We examined global and regional relationships between CBF and ADC and their association with outcome. RESULTS This sample included 14 pediatric patients (mean time to MRI 6 ± 4 days), 9 of whom survived and 6 who survived with favorable outcome. Global ADC was significantly decreased in patients with unfavorable outcome (P = .02). Increased CBF and decreased ADC often were colocalized in the same region, especially in children who had unfavorable outcomes. CONCLUSIONS In this exploratory study, global restricted water diffusion on ADC after pediatric cardiac arrest was associated with unfavorable outcome. MRI assessments of perfusion and diffusion may have prognostic value after pediatric cardiac arrest.
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Affiliation(s)
| | - Vince Lee
- Department of Radiology, Children’s Hospital of Pittsburgh
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5
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Rivera-Pagán AF, Rivera-Aponte DE, Melnik-Martínez KV, Zayas-Santiago A, Kucheryavykh LY, Martins AH, Cubano LA, Skatchkov SN, Eaton MJ. Up-regulation of TREK-2 potassium channels in cultured astrocytes requires de novo protein synthesis: relevance to localization of TREK-2 channels in astrocytes after transient cerebral ischemia. PLoS One 2015; 10:e0125195. [PMID: 25886567 PMCID: PMC4401746 DOI: 10.1371/journal.pone.0125195] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 03/12/2015] [Indexed: 11/19/2022] Open
Abstract
Excitotoxicity due to glutamate receptor over-activation is one of the key mediators of neuronal death after an ischemic insult. Therefore, a major function of astrocytes is to maintain low extracellular levels of glutamate. The ability of astrocytic glutamate transporters to regulate the extracellular glutamate concentration depends upon the hyperpolarized membrane potential of astrocytes conferred by the presence of K+ channels in their membranes. We have previously shown that TREK-2 potassium channels in cultured astrocytes are up-regulated by ischemia and may support glutamate clearance by astrocytes during ischemia. Thus, herein we determine the mechanism leading to this up-regulation and assess the localization of TREK-2 channels in astrocytes after transient middle cerebral artery occlusion. By using a cell surface biotinylation assay we confirmed that functional TREK-2 protein is up-regulated in the astrocytic membrane after ischemic conditions. Using real time RT-PCR, we determined that the levels of TREK-2 mRNA were not increased in response to ischemic conditions. By using Western blot and a variety of protein synthesis inhibitors, we demonstrated that the increase of TREK-2 protein expression requires De novo protein synthesis, while protein degradation pathways do not contribute to TREK-2 up-regulation after ischemic conditions. Immunohistochemical studies revealed TREK-2 localization in astrocytes together with increased expression of the selective glial marker, glial fibrillary acidic protein, in brain 24 hours after transient middle cerebral occlusion. Our data indicate that functional TREK-2 channels are up-regulated in the astrocytic membrane during ischemia through a mechanism requiring De novo protein synthesis. This study provides important information about the mechanisms underlying TREK-2 regulation, which has profound implications in neurological diseases such as ischemia where astrocytes play an important role.
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Affiliation(s)
- Aixa F. Rivera-Pagán
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
- * E-mail: (AFRP); (SNS)
| | - David E. Rivera-Aponte
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
| | - Katya V. Melnik-Martínez
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
| | - Astrid Zayas-Santiago
- Department of Physiology, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
| | - Lilia Y. Kucheryavykh
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
| | - Antonio H. Martins
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
| | - Luis A. Cubano
- Departments of Anatomy and Cell Biology, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
| | - Serguei N. Skatchkov
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
- Department of Physiology, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
- * E-mail: (AFRP); (SNS)
| | - Misty J. Eaton
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
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Qiu B, Li X, Sun X, Wang Y, Jing Z, Zhang X, Wang Y. Overexpression of aquaporin‑1 aggravates hippocampal damage in mouse traumatic brain injury models. Mol Med Rep 2014; 9:916-22. [PMID: 24430824 DOI: 10.3892/mmr.2014.1899] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 01/10/2014] [Indexed: 11/05/2022] Open
Abstract
'Secondary insult' following primary traumatic brain injury (TBI), including ischemia and edema, may aggravate brain impairments and affect the outcomes. The hippocampus is particularly sensitive to ischemia or edema due to its selective vulnerability, as neural cells of the hippocampus may be more prone to abnormal function or cell death in response to ischemia and edema. Aquaporin‑1 (AQP‑1) was reported to be associated with cerebral edema; however, the expression and role of AQP‑1 in hippocampal edema following TBI have seldom been investigated. In the current study, BALB/c mouse closed craniocerebral injury models were established and the changes of AQP‑1 expression in hippocampi of mouse models following TBI were investigated. Neurological function and edema formation of the models were evaluated and the apoptotic hippocampal cells were then stained in situ and detected, followed by determination of AQP‑1 expression in the hippocampus using immunohistochemistry and western blot analysis. As a result, the majority of mice in the TBI group were severely injured and hippocampal edema was confirmed. The apoptotic cells increased significantly in the hippocampi of mice in the TBI group compared with those in the sham group (P<0.01) and the apoptotic rate increased gradually in a time‑dependent manner. The expression levels of AQP‑1 in the hippocampi of mice were markedly higher in the TBI group than in the sham group (P<0.05) at various time points and AQP‑1 expression levels peaked one day following TBI. These results indicate that upregulation of AQP‑1 may participate in edema formation and delayed cell death of the hippocampus following TBI and may also be a novel therapeutic target to protect the hippocampus from secondary injury following TBI.
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Affiliation(s)
- Bo Qiu
- Department of Neurosurgery, First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Xinguo Li
- Department of Neurosurgery, First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Xiyang Sun
- Department of Pharmaceutics, School of Pharmacy, Fudan University, Shanghai 201203, P.R. China
| | - Yong Wang
- Department of Neurosurgery, First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Zhitao Jing
- Department of Neurosurgery, First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
| | - Xu Zhang
- Liaoning Centers for Diseases Control and Prevention, Shenyang, Liaoning 110005, P.R. China
| | - Yunjie Wang
- Department of Neurosurgery, First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China
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7
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Dynamic Change of Hydrogen Sulfide After Traumatic Brain Injury and its Effect in Mice. Neurochem Res 2013; 38:714-25. [DOI: 10.1007/s11064-013-0969-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2012] [Revised: 12/14/2012] [Accepted: 01/08/2013] [Indexed: 01/20/2023]
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8
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Na+/H+ Exchangers as Therapeutic Targets for Cerebral Ischemia. Transl Stroke Res 2012. [DOI: 10.1007/978-1-4419-9530-8_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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9
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Tran ND, Kim S, Vincent HK, Rodriguez A, Hinton DR, Bullock MR, Young HF. Aquaporin-1-mediated cerebral edema following traumatic brain injury: effects of acidosis and corticosteroid administration. J Neurosurg 2010; 112:1095-104. [PMID: 19731985 DOI: 10.3171/2009.8.jns081704] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
OBJECT Dysregulation of water homeostasis induces cerebral edema. Edema is a major cause of morbidity and mortality following traumatic brain injury (TBI). Aquaporin-1 (AQP-1), a water channel found in the brain, can function as a transporter for CO2 across the cellular membrane. Additionally, AQP-1's promoter contains a glucocorticoid response element. Thus, AQP-1 may be involved with edema-related brain injury and might be modulated by external conditions such as the pH and the presence of steroids. In this study, the authors investigated the hypotheses that: 1) AQP-1 participates in brain water homeostasis following TBI; 2) secondary injury (for example, acidosis) alters the expression of AQP-1 and exacerbates cerebral edema; and 3) corticosteroids augment brain AQP-1 expression and differentially affect cerebral edema under nonacidotic and acidotic conditions. METHODS Anesthetized Sprague-Dawley rats were subjected to moderate to severe TBI (2.5-3.5 atm) or surgery without injury, and they were randomized to receive a 3-mg/kg bolus of intravenous dexamethasone within 10 minutes after injury or surgery, a 3-mg/kg bolus of dexamethasone followed by 1-mg/kg maintenance doses every 8 hours for 24 hours, or saline boluses at similar time intervals. A second group of animals was subjected to respiratory acidosis with target arterial blood pH 6.8-7.2 for 1 hour following the surgery or injury. To evaluate selective blockage of AQP-1, some animals received a single intraperitoneal dose of HgCl2 (0.3-30.0 mmol/L) within 30 minutes of injury or surgery. At 4 or 24 hours postinjury, animals were killed and their brains were harvested for mRNA, protein, or water content analyses. RESULTS The authors demonstrated elevated cerebral edema levels at 4 and 24 hours following TBI. Dexamethasone administration within 1 hour of TBI attenuated the cerebral edema under nonacidotic conditions but worsened it under acidotic conditions. Selective blockage of AQP-1 channels with HgCl2 attenuated the edematous effects of corticosteroids and acidosis. Reverse transcriptase polymerase chain reaction and immunohistochemical analyses demonstrated a paucity of AQP-1 in the cerebral cortices of the uninjured animals. In contrast, AQP-1 mRNA and protein levels were higher in the cerebral cortices of animals that sustained a TBI. CONCLUSIONS These findings implicate an important, modifiable role for AQP-1 in water homeostasis within the CNS following TBI.
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Affiliation(s)
- Nam D Tran
- Department of Neurosurgery, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia, USA.
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10
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Structural and ultrastructural analysis of cerebral cortex, cerebellum, and hypothalamus from diabetic rats. EXPERIMENTAL DIABETES RESEARCH 2009; 2009:329632. [PMID: 19812703 PMCID: PMC2756466 DOI: 10.1155/2009/329632] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2009] [Accepted: 07/15/2009] [Indexed: 11/17/2022]
Abstract
Autonomic and peripheral neuropathies are well-described complications in diabetes. Diabetes mellitus is also associated to central nervous system damage. This little-known complication is characterized by impairment of brain functions and electrophysiological changes associated with neurochemical and structural abnormalities. The purpose of this study was to investigate brain structural and ultrastructural changes in rats with streptozotocin-induced diabetes. Cerebral cortex, hypothalamus, and cerebellum were obtained from controls and 8 weeks diabetic rats. Light and electron microscope studies showed degenerative changes of neurons and glia, perivascular and mitochondrial swelling, disarrangement of myelin sheath, increased area of myelinated axons, presynaptic vesicle dispersion in swollen axonal boutoms, fragmentation of neurofilaments, and oligodendrocyte abnormalities. In addition, depressive mood was observed in diabetic animals. The brain morphological alterations observed in diabetic animals could be related to brain pathologic process leading to abnormal function, cellular death, and depressive behavioral.
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Kucheryavykh LY, Kucheryavykh YV, Inyushin M, Shuba YM, Sanabria P, Cubano LA, Skatchkov SN, Eaton MJ. Ischemia Increases TREK-2 Channel Expression in Astrocytes: Relevance to Glutamate Clearance. ACTA ACUST UNITED AC 2009; 3:40-47. [PMID: 19890471 DOI: 10.2174/1874082000903010040] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The extent of an ischemic insult is less in brain regions enriched in astrocytes suggesting that astrocytes maintain function and buffer glutamate during ischemia. Astrocytes express a wide variety of potassium channels to support their functions including TREK-2 channels which are regulated by polyunsaturated fatty acids, intracellular acidosis and swelling; conditions that pertain to ischemia. The present study investigated the possible involvement of TREK-2 channels in cultured cortical astrocytes during experimental ischemia (anoxia/hypoglycemia) by examining TREK-2 protein levels, channel activity and ability to clear glutamate. We found that TREK-2 protein levels were increased rapidly within 2 hrs of the onset of simulated ischemia. This increase corresponded to an increase in temperature-sensitive TREK-2-like channel conductance and the ability of astrocytes to buffer extracellular glutamate even during ischemia. Together, these data suggest that up-regulation of TREK-2 channels may help rescue astrocyte function and lower extracellular glutamate during ischemia.
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Affiliation(s)
- Lilia Y Kucheryavykh
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico
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12
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Benesova J, Hock M, Butenko O, Prajerova I, Anderova M, Chvatal A. Quantification of astrocyte volume changes during ischemia in situ reveals two populations of astrocytes in the cortex of GFAP/EGFP mice. J Neurosci Res 2009; 87:96-111. [PMID: 18752295 DOI: 10.1002/jnr.21828] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Energy depletion during ischemia leads to disturbed ionic homeostasis and accumulation of neuroactive substances in the extracellular space, subsequently leading to volume changes in astrocytes. Confocal microscopy combined with 3D reconstruction was used to quantify ischemia-induced astrocyte volume changes in cortical slices of GFAP/EGFP transgenic mice. Twenty-minutes of oxygen-glucose deprivation (OGD) or oxygen-glucose deprivation combined with acidification (OGD(pH 6.8)) revealed the presence of two distinct astrocytic populations, the first showing a large volume increase (HR astrocytes) and the second displaying a small volume increase (LR astrocytes). In addition, changes in resting membrane potential (V(m)), measured by the patch-clamp technique, supported the existence of two astrocytic populations responding differently to ischemia. Although one group markedly depolarized during OGD or OGD(pH 6.8), only small changes in V(m) toward more negative values were observed in the second group. Conversely, acidification (ACF(pH 6.8)) led to a uniform volume decrease in all astrocytes, accompanied by only a small depolarization. Interestingly, two differently responding populations were not detected during acidification. Differences in the expression of inwardly rectifying potassium channels (Kir4.1), glial fibrillary acidic protein (GFAP), and taurine levels in cortical astrocytes were detected using immunohistochemical methods. We conclude that two distinct populations of astrocytes are present in the cortex of GFAP/EGFP mice, based on volume and V(m) changes during exposure to OGD or OGD(pH 6.8). Immunohistochemical analysis suggests that the diverse expression of Kir4.1 channels and GFAP as well as differences in the accumulation of taurine might contribute to the distinct ability of astrocytes to regulate their volume.
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Affiliation(s)
- Jana Benesova
- Laboratory of Neurobiology, Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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Lactate Contributes to Ammonia-Mediated Astroglial Dysfunction During Hyperammonemia. Neurochem Res 2008; 34:556-65. [DOI: 10.1007/s11064-008-9819-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Accepted: 07/31/2008] [Indexed: 10/21/2022]
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14
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Miller KL, Bulte DP, Devlin H, Robson MD, Wise RG, Woolrich MW, Jezzard P, Behrens TEJ. Evidence for a vascular contribution to diffusion FMRI at high b value. Proc Natl Acad Sci U S A 2007; 104:20967-72. [PMID: 18093924 PMCID: PMC2409250 DOI: 10.1073/pnas.0707257105] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Indexed: 11/18/2022] Open
Abstract
Recent work has suggested that diffusion-weighted functional magnetic resonance imaging (FMRI) with strong diffusion weighting (high b value) detects neuronal swelling that is directly related to neuronal firing. This would constitute a much more direct measure of brain activity than current methods and represent a major advance in neuroimaging. However, it has not been firmly established that the observed signal changes do not reflect residual vascular effects, which are known to exist at low b value. This study measures the vascular component of diffusion FMRI directly by using hypercapnia, which induces blood flow changes in the absence of a change in neuronal firing. Hypercapnia elicits a similar diffusion FMRI response to a visual stimulus including a rise in percent signal change with increasing b value, which was reported for visual activation. Analysis of the response timing found no evidence for an early response at high b value, which has been reported as evidence for a nonhemodynamic response. These results suggest that a large component of the diffusion FMRI signal at high b value is vascular rather than neuronal.
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Affiliation(s)
| | | | | | | | - Richard G. Wise
- Cardiff University Brain Research Imaging Centre (CUBRIC), Cardiff University, Cardiff CF10 3AT, United Kingdom
| | | | | | - Timothy E. J. Behrens
- Centre for Functional MRI of the Brain (FMRIB)
- Department of Experimental Psychology, University of Oxford, Oxford, Oxon OX3 9DU, United Kingdom; and
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15
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Obara M, Szeliga M, Albrecht J. Regulation of pH in the mammalian central nervous system under normal and pathological conditions: facts and hypotheses. Neurochem Int 2007; 52:905-19. [PMID: 18061308 DOI: 10.1016/j.neuint.2007.10.015] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Revised: 10/17/2007] [Accepted: 10/22/2007] [Indexed: 11/27/2022]
Abstract
The maintenance of pH homeostasis in the CNS is of key importance for proper execution and regulation of neurotransmission, and deviations from this homeostasis are a crucial factor in the mechanism underlying a spectrum of pathological conditions. The first few sections of the review are devoted to the brain operating under normal conditions. The article commences with an overview of how extrinsic factors modelling the brain at work: neurotransmitters, depolarising stimuli (potassium and voltage changes) and cyclic nucleotides as major signal transducing vehicles affect pH in the CNS. Further, consequences of pH alterations on the major aspects of CNS function and metabolism are outlined. Next, the major cellular events involved in the transport, sequestration, metabolic production and buffering of protons that are common to all the mammalian cells, including the CNS cells. Since CNS function reflects tight interaction between astrocytes and neurons, the pH regulatory events pertinent to either cell type are discussed: overwhelming evidence implicates astrocytes as a key player in pH homeostasis in the brain. The different classes of membrane proteins involved in proton shuttling are listed and their mechanisms of action are given. These include: the Na+/H+ exchanger, different classes of bicarbonate transporters acting in a sodium-dependent- or -independent mode, monocarboxylic acid transporters and the vacuolar-type proton ATPase. A separate section is devoted to carbonic anhydrase, which is represented by multiple isoenzymes capable of pH buffering both in the cell interior and in the extracellular space. Next, impairment of pH regulation and compensatory responses occurring in brain affected by different pathologies: hypoxia/ischemia, epilepsy, hyperammonemic encephalopathies, cerebral tumours and HIV will be described. The review is limited to facts and plausible hypotheses pertaining to phenomena directly involved in pH regulation: changes in pH that accompany metabolic stress but have no distinct implications for the pH regulatory mechanisms are not dealt with. In most cases, the vast body of knowledge derived from in vitro studies remains to be verified in in vivo settings.
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Affiliation(s)
- Marta Obara
- Department of Neurotoxicology, Medical Research Centre, Polish Academy of Sciences, 5 Pawińskiego Street, 02-106 Warsaw, Poland
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16
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Floyd CL, Lyeth BG. Astroglia: important mediators of traumatic brain injury. PROGRESS IN BRAIN RESEARCH 2007; 161:61-79. [PMID: 17618970 DOI: 10.1016/s0079-6123(06)61005-4] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Traumatic brain injury (TBI) research to date has focused almost exclusively on the pathophysiology of injured neurons with very little attention paid to non-neuronal cells. However in the past decade, exciting discoveries have challenged this century-old view of passive glial cells and have led to a reinterpretation of the role of glial cells in central nervous system (CNS) biology and pathology. In this chapter we review several lines of evidence, indicating that glial cells, particularly astrocytes, are active partners to neurons in the brain, and summarize recent findings that detail the significance of astrocyte pathology in traumatic brain injury.
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Affiliation(s)
- Candace L Floyd
- Department of Physical Medicine and Rehabilitation, Center for Glial Biology in Medicine, 547 Spain Rehabilitation Center, University of Alabama at Birmingham, Birmingham, AL 35249, USA.
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17
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Ringel F, Bieringer F, Baethmann A, Plesnila N. Effect of Oxidative Stress on Glial Cell Volume. J Neurotrauma 2006; 23:1693-704. [PMID: 17115914 DOI: 10.1089/neu.2006.23.1693] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Cytotoxic brain edema is a major contributor of tissue damage following cerebral ischemia and traumatic brain injury. The pathophysiology of cytotoxic edema formation is still not well understood. Although it is widely believed that oxidative stress causes cytotoxic brain edema, experimental proof is lacking. The aim of the present study was therefore to examine the effect of oxidative stress on cell volume of glial cells. C6 glial cells were exposed to hydrogen peroxide and the superoxide forming complex hypoxanthine/xanthine oxidase (HX/XO). Exposure to hydrogen peroxide (0.5-5 mM) resulted in initial cell shrinkage by 5.7 +/- 1.5% (mean +/- SEM; p < 0.05) and was followed by a dose-dependent recovery to baseline. Exposure to superoxide anions generated by HX/XO provoked a delayed, but sustained decrease of cell volume by 11.8 +/- 0.9% (p < 0.05). Cell volume showed no tendency to recover upon sustained exposure to superoxide. Neither hydrogen peroxide nor HX/XO exposure was associated with a decrease of cell viability. Thereby, the present study demonstrates that oxidative stress by hydrogen peroxide and superoxide anions does not induce cytotoxic cell swelling and suggests that free radicals are not directly involved in the formation of cytotoxic brain edema.
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Affiliation(s)
- Florian Ringel
- Laboratory of Experimental Neurosurgery, Institute for Surgical Research, Ludwig-Maximilians University, Munich, Germany
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18
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Pedersen SF, O'Donnell ME, Anderson SE, Cala PM. Physiology and pathophysiology of Na+/H+ exchange and Na+ -K+ -2Cl- cotransport in the heart, brain, and blood. Am J Physiol Regul Integr Comp Physiol 2006; 291:R1-25. [PMID: 16484438 DOI: 10.1152/ajpregu.00782.2005] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Maintenance of a stable cell volume and intracellular pH is critical for normal cell function. Arguably, two of the most important ion transporters involved in these processes are the Na+/H+ exchanger isoform 1 (NHE1) and Na+ -K+ -2Cl- cotransporter isoform 1 (NKCC1). Both NHE1 and NKCC1 are stimulated by cell shrinkage and by numerous other stimuli, including a wide range of hormones and growth factors, and for NHE1, intracellular acidification. Both transporters can be important regulators of cell volume, yet their activity also, directly or indirectly, affects the intracellular concentrations of Na+, Ca2+, Cl-, K+, and H+. Conversely, when either transporter responds to a stimulus other than cell shrinkage and when the driving force is directed to promote Na+ entry, one consequence may be cell swelling. Thus stimulation of NHE1 and/or NKCC1 by a deviation from homeostasis of a given parameter may regulate that parameter at the expense of compromising others, a coupling that may contribute to irreversible cell damage in a number of pathophysiological conditions. This review addresses the roles of NHE1 and NKCC1 in the cellular responses to physiological and pathophysiological stress. The aim is to provide a comprehensive overview of the mechanisms and consequences of stress-induced stimulation of these transporters with focus on the heart, brain, and blood. The physiological stressors reviewed are metabolic/exercise stress, osmotic stress, and mechanical stress, conditions in which NHE1 and NKCC1 play important physiological roles. With respect to pathophysiology, the focus is on ischemia and severe hypoxia where the roles of NHE1 and NKCC1 have been widely studied yet remain controversial and incompletely elucidated.
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Affiliation(s)
- S F Pedersen
- Department of Biochemistry, Institute of Molecular Biology and Physiology, University of Copenhagen, Copenhagen, Denmark.
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19
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Ringel F, Baethmann A, Plesnila N. Lactacidosis-induced glial cell swelling depends on extracellular Ca2+. Neurosci Lett 2006; 398:306-9. [PMID: 16469448 DOI: 10.1016/j.neulet.2006.01.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2005] [Revised: 01/09/2006] [Accepted: 01/09/2006] [Indexed: 10/25/2022]
Abstract
Cerebral tissue acidosis following ischemia or traumatic brain injury contributes to cytotoxic brain edema formation. In vitro lactacidosis induces swelling of glial cells by intracellular Na+- and Cl--accumulation by the Na+/H+-antiporter, Cl-/HCO3--antiporters and the Na+-K+-2Cl--cotransport. The present study aimed to elucidate whether mechanisms of lactacidosis-induced glial swelling are dependent on intra- or extracellular Ca2+-ions. Therefore, C6 glioma cells were exposed to a lactacidosis of pH 6.2 in standard or calcium-free medium and following intracellular calcium chelation. Cell volume and intracellular pH were assessed by flow cytometry. Lactacidosis of pH 6.2 induced a prompt and sustained swelling of suspended C6 glioma cells reaching a maximum of 128% within 60 min. Omission of Ca2+ from the suspension medium strongly attenuated cell swelling while chelation of intracellular Ca2+ had no effects. Intracellular acidosis was not affected by either treatment. The present data show a strong dependency of lactacidosis-induced glial swelling upon extracellular Ca2+ while intracellular acidosis is not affected by omission of [Ca2+]e. Therefore, our data suggest that the Na+-K+-2Cl--cotransporter, the only so far known transporter involved in cell volume regulation but not in pHi regulation during lactacidosis, is activated in a [Ca2+]e-dependent manner.
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Affiliation(s)
- Florian Ringel
- Laboratory of Experimental Neurosurgery, Walter Brendel Center for Experimental Medicine, University of Munich Medical Center - Grosshadern, Munich, Germany.
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20
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Muranyi M, Ding C, He Q, Lin Y, Li PA. Streptozotocin-induced diabetes causes astrocyte death after ischemia and reperfusion injury. Diabetes 2006; 55:349-55. [PMID: 16443767 DOI: 10.2337/diabetes.55.02.06.db05-0654] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Diabetes exacerbates neuronal cell death induced by cerebral ischemia. One contributing factor is enhanced acidosis during ischemia. Astrocytes are vulnerable to hypoxia under acidic conditions in vitro and may be targets of ischemia under diabetic conditions. The objective of this study was to determine whether diabetes would cause damage to astrocytes after an ischemic brain injury in vivo. Diabetic and nondiabetic rats were subjected to 5 min of forebrain ischemia and followed by 30 min, 6 h, or 1 or 3 days of recovery. The results showed that ischemia caused activation of astrocytes in nondiabetic rats. In contrast, diabetes caused astrocyte activation in early stage of reperfusion and astrocyte death in late stage of reperfusion. Remarkable astrocyte death was preceded by increased DNA oxidation. Further studies revealed that increased astrocyte damage coincided with enhanced production of free radicals. These data suggest that hyperglycemic ischemia worsens outcome in astrocytes, as it does in neurons.
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Affiliation(s)
- Marianna Muranyi
- Department of Complementary and Alternative Medicine, John A. Burns School of Medicine, University of Hawaii, Honolulu, 96822, USA
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21
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Willam C, Warnecke C, Schefold JC, Kügler J, Koehne P, Frei U, Wiesener M, Eckardt KU. Inconsistent effects of acidosis on HIF-alpha protein and its target genes. Pflugers Arch 2005; 451:534-43. [PMID: 16208522 DOI: 10.1007/s00424-005-1486-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2005] [Revised: 06/10/2005] [Accepted: 06/23/2005] [Indexed: 10/25/2022]
Abstract
The transcription factor HIF-1alpha has been identified as a key regulator in the cellular and systemic response to hypoxia. Because hypoxia is frequently associated with acidosis, like in ischemia or tumour growth, we studied the impact of acidosis on the expression of the HIF-1alpha and HIF-2alpha proteins and that of the three HIF target genes carbonic anhydrase-9 (CA-9), glucose transporter-1 (Glut-1) and erythropoietin (EPO). Since the HIF-prolyl hydroxylases (PHD) modulate cellular HIF-alpha protein levels we also investigated changes in PHD mRNA expression under hypoxia and acidosis. HIF-1alpha immunoblots revealed, depending on the cell line investigated, a moderate induction of HIF-alpha protein levels by acidosis in normoxia (Hep3B cells) or hypoxia (HeLa cells). Concordantly, the activity of HIF-driven luciferase reporters was slightly enhanced at pH 7.0. In contrast, HIF target genes exhibited divergent responses to acidosis: basal and hypoxia-induced CA-9 mRNA levels were further increased, whereas hypoxic EPO mRNA induction was attenuated, and Glut-1 mRNA levels were not altered by acidosis. Except from a small increase of hypoxia-induced PHD3 mRNA levels in HeLa cells, there was also no significant effect of acidosis on PHD expression. In conclusion, albeit HIF protein levels slightly induced by acidosis and the inconsistent regulation of HIF target genes under acidosis suggest additional, yet unidentified pH-sensitive factors to be involved in the regulation of these genes.
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Affiliation(s)
- Carsten Willam
- Department of Nephrology and Hypertension, Medizinische Klinik IV, University of Erlangen-Nuremberg, Germany.
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22
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Chan H, Butterworth RF, Hazell AS. Primary cultures of rat astrocytes respond to thiamine deficiency-induced swelling by downregulating aquaporin-4 levels. Neurosci Lett 2004; 366:231-4. [PMID: 15288424 DOI: 10.1016/j.neulet.2004.04.095] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2003] [Revised: 04/22/2004] [Accepted: 04/25/2004] [Indexed: 10/26/2022]
Abstract
Imaging studies indicate that cerebral edema is an important consequence of Wernicke's encephalopathy (WE), a disorder caused by thiamine deficiency (TD). We have investigated this problem using a recently developed in vitro astrocyte model of TD. Measurement of cell volume using the 3-O-methylglucose uptake method revealed a dose-dependent swelling of astrocytes during exposure to TD conditions. Time course studies indicated a progressive volume increase up to a maximum of 93% above controls after 4 days of treatment. This swelling then partially resolved, and remained stable for up to 10 days following commencement of TD treatment. Measurement of aquaporin-4 (AQP-4) levels showed a 44% loss after 10 days and a temporal profile consistent with an important role for this water channel protein in astrocyte cell volume changes during TD. Our findings of astrocyte swelling in TD are consistent with previous reports of focal brain edema in cases of WE, and indicate that AQP-4 may be an important target for ameliorating some of the clinical problems associated with this disorder.
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Affiliation(s)
- Helen Chan
- Division of Experimental Medicine, McGill University, Montreal, Que, Canada
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23
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Xiang Z, Yuan M, Hassen GW, Gampel M, Bergold PJ. Lactate induced excitotoxicity in hippocampal slice cultures. Exp Neurol 2004; 186:70-7. [PMID: 14980811 DOI: 10.1016/j.expneurol.2003.10.015] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2003] [Revised: 10/10/2003] [Accepted: 10/31/2003] [Indexed: 11/26/2022]
Abstract
During the initial minutes of cerebral ischemia, lactic acid accumulates and acidifies brain pH to 6.0-6.7. Glutamate is also released during ischemia that activates glutamate receptors and induces excitotoxicity. While glutamate excitotoxicity is well established to induce ischemic injury, a role of lactic acidosis in ischemic brain damage is poorly understood. This study analyzes acidosis neurotoxicity in hippocampal slice cultures in the presence or absence of lactate. At pH 6.7, neuronal loss was similar whether or not lactate was present. At pH 6.4, neuronal loss was significantly greater in the presence of lactate suggesting that lactate potentiates the acidosis toxicity. At pH 6.4 in the presence of lactate, NMDA or non-NMDA receptor antagonists reduced neuronal loss, while in the absence of lactate, NMDA or non-NMDA receptor antagonists had little effect. [3H]-Glutamate uptake was inhibited by acidic pH, and the amount of inhibition was significantly greater in the presence of lactate. These findings suggest that lactate plays a role in acidosis neurotoxicity by inducing excitotoxicity. Lactic acidosis and excitotoxicity have been previously thought to be independent events during ischemia. This study suggests that during ischemia, lactic acidosis contributes to excitotoxic neuronal loss.
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Affiliation(s)
- Zhongmin Xiang
- Department of Physiology and Pharmacology, State University New York-Downstate Medical Center, Brooklyn, NY 11203, USA
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24
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Nabekura T, Morishima S, Cover TL, Mori SI, Kannan H, Komune S, Okada Y. Recovery from lactacidosis-induced glial cell swelling with the aid of exogenous anion channels. Glia 2003; 41:247-59. [PMID: 12528180 DOI: 10.1002/glia.10190] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Hypotonic challenge induces transient swelling in glial cells, which is typically followed by a regulatory volume decrease (RVD). In contrast, lactic acidosis (lactacidosis) induces persistent cell swelling in astrocytes without an accompanying RVD. In the present study, we studied the mechanisms by which lactacidosis interferes with normal volume regulation in rat astrocytic glioma C6 cells. Following exposure of C6 cells to a hypotonic challenge, a current was detected that exhibited properties consistent with those of volume-sensitive outwardly rectifying (VSOR) anion channels. When exposed to in vitro conditions designed to simulate lactacidosis, C6 cells failed to respond to hypotonic stress with an RVD, and VSOR anion currents were not activated. When added to C6 cells, an anion channel-forming protein purified from Helicobacter pylori, VacA, was found to form anion-selective channels in the plasma membrane, and the activity of the VacA channel was not affected by lactacidosis (pH 6.2). Cells preincubated with VacA and then exposed to lactacidotic conditions underwent transient swelling followed by RVD. In contrast, application of a cation ionophore, gramicidin, failed to inhibit lactacidosis-induced persistent cell swelling. From these results, we conclude that inhibition of a volume-sensitive anion channel contributes to persistent swelling induced by lactacidosis in glial cells. Introduction of anion channel activity into glial cells might provide a novel approach for treating cerebral edema, which is associated with lactacidosis in cerebral ischemia or head injury.
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Affiliation(s)
- Takashi Nabekura
- Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, Japan
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25
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Mori SI, Morishima S, Takasaki M, Okada Y. Impaired activity of volume-sensitive anion channel during lactacidosis-induced swelling in neuronally differentiated NG108-15 cells. Brain Res 2002; 957:1-11. [PMID: 12443974 DOI: 10.1016/s0006-8993(02)03574-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Acidosis coupled to lactate accumulation, called lactacidosis, occurs in cerebral ischemia or trauma and is known to cause persistent swelling in neuronal and glial cells. It is therefore possible that mechanisms of cell volume regulation are impaired during lactacidosis. Here we tested this possibility using neuronally differentiated NG108-15 cells. These cells responded to a hypotonic challenge with osmotic swelling followed by a regulatory volume decrease (RVD) under physiological pH conditions in the absence of lactate. Under normotonic conditions, sustained cell swelling without subsequent RVD was induced by exposure to lactate-containing solution with acidic pH (6.4 or 6.2), but not with physiological pH (7.4). Under whole-cell patch-clamp, osmotic swelling was found to activate outwardly rectifying Cl(-) currents in cells exposed to control hypotonic solution. A Cl(-) channel blocker, NPPB, inhibited both RVD and the swelling-activated Cl(-) current. RVD and the volume-sensitive Cl(-) current were also markedly inhibited by lactacidosis (pH 6.4 or 6.2), but neither by application of lactate with physiological pH (7.4) nor by acidification without lactate (pH 6.2). RT-PCR analysis showed mRNA expression of two isoforms of proton-coupled monocarboxylate transporters, MCT1 and MCT8, in differentiated NG108-15 cells. Thus, we conclude that persistence of neuronal cell swelling under lactacidosis is coupled to an impairment of the activity of the volume-sensitive Cl(-) channel and to dysfunction of RVD. It is also suggested that the volume-sensitive Cl(-) channel is inhibited by intracellular acidification induced by MCT-mediated proton influx under lactacidosis.
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Affiliation(s)
- Shin-ichiro Mori
- Department of Cell Physiology, National Institute for Physiological Sciences, Myodaiji-cho, Okazaki 444-8585, Japan
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26
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Rastaldo R, Paolocci N, Chiribiri A, Penna C, Gattullo D, Pagliaro P. Cytochrome P-450 metabolite of arachidonic acid mediates bradykinin-induced negative inotropic effect. Am J Physiol Heart Circ Physiol 2001; 280:H2823-32. [PMID: 11356641 DOI: 10.1152/ajpheart.2001.280.6.h2823] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
This study focused on the mechanisms of the negative inotropic response to bradykinin (BK) in isolated rat hearts perfused at constant flow. BK (100 nM) significantly reduced developed left ventricular pressure (LVP) and the maximal derivative of systolic LVP by 20-22%. The cytochrome P-450 (CYP) inhibitors 1-aminobenzotriazole (1 mM and 100 microM) or proadifen (5 microM) abolished the cardiodepression by BK, which was not affected by nitric oxide and cyclooxygenase inhibitors (35 microM NG-nitro-L-arginine methyl ester and 10 microM indomethacin, respectively). The CYP metabolite 14,15-epoxyeicosatrienoic acid (14,15-EET; 50 ng/ml) produced effects similar to those of BK in terms of the reduction in contractility. After the coronary endothelium was made dysfunctional by Triton X-100 (0.5 microl), the BK-induced negative inotropic effect was completely abolished, whereas the 14,15-EET-induced cardiodepression was not affected. In hearts with normal endothelium, after recovery from 14,15-EET effects, BK reduced developed LVP to a 35% greater extent than BK in the control. In conclusion, CYP inhibition or endothelial dysfunction prevents BK from causing cardiodepression, suggesting that, in the rat heart, endothelial CYP products mediate the negative inotropic effect of BK. One of these mediators appears to be 14,15-EET.
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MESH Headings
- 8,11,14-Eicosatrienoic Acid/analogs & derivatives
- 8,11,14-Eicosatrienoic Acid/metabolism
- 8,11,14-Eicosatrienoic Acid/pharmacology
- Animals
- Arachidonic Acid/metabolism
- Blood Pressure/drug effects
- Bradykinin/metabolism
- Bradykinin/pharmacology
- Coronary Vessels/drug effects
- Coronary Vessels/physiology
- Cytochrome P-450 Enzyme Inhibitors
- Cytochrome P-450 Enzyme System/metabolism
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Enzyme Inhibitors/pharmacology
- Heart/drug effects
- Heart/physiology
- Heart Rate/drug effects
- Heart Rate/physiology
- In Vitro Techniques
- Indomethacin/pharmacology
- Male
- Myocardium/metabolism
- NG-Nitroarginine Methyl Ester/pharmacology
- Nitric Oxide Synthase/antagonists & inhibitors
- Octoxynol/pharmacology
- Proadifen/pharmacology
- Rats
- Rats, Wistar
- Tachyphylaxis/physiology
- Triazoles/pharmacology
- Ventricular Function, Left/drug effects
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Affiliation(s)
- R Rastaldo
- Dipartimento di Neuroscienze, Sezione di Fisiologia, dell'Università di Torino, 10043 Orbassano, TO, Italy
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27
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Kochanek PM, Clark RS, Ruppel RA, Dixon CE. Cerebral resuscitation after traumatic brain injury and cardiopulmonary arrest in infants and children in the new millennium. Pediatr Clin North Am 2001; 48:661-81. [PMID: 11411299 DOI: 10.1016/s0031-3955(05)70333-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
As outlined in Figure 1, it is likely that a series of interventions beginning in the field and continuing through the emergency department, ICU, rehabilitation center, and possibly beyond, will be needed to optimize clinical outcome after severe TBI or asphyxial CA in infants and children. Despite the many differences between these two important pediatric insults, it is likely that many of the therapies targeting neuronal death, in either condition, will need to be administered early after the insult, possibly at the injury scene. Even cerebral swelling, a pathophysiologic derangement routinely treated in the PICU, almost certainly is better prevented rather than treated. Finally, this review includes, for one of the first times, a brief discussion of additional horizons in the management of patients with severe brain injury, namely, manipulation of the injured circuitry and stimulation of regeneration. Further research is needed to define better the pathobiology of these two important conditions at the bedside, to understand the optimal application of contemporary therapies, and to develop and apply novel therapies. The tools necessary to carry out these studies are materializing, although the obstacles are great. This difficult but important challenge awaits further investigation by clinician-scientists in pediatric neurointensive care.
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Affiliation(s)
- P M Kochanek
- Department of Anesthesiology and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
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28
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Xiang Z, Bergold PJ. Synaptic depression and neuronal loss in transiently acidic hippocampal slice cultures. Brain Res 2000; 881:77-87. [PMID: 11033097 DOI: 10.1016/s0006-8993(00)02795-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Acidosis is a rapid and inevitable event accompanying cerebral ischemia or trauma. We used hippocampal slice cultures to examine an immediate effect of acidosis, synaptic depression; and a delayed effect, neuronal loss. Exposure to low bicarbonate artificial cerebral spinal fluid (aCSF), pH 6.70 for 30 min at 32 degrees C, acidified intracellular pH from 7.31+/-0.12 to 6.53+/-0.08. Accompanying intracellular acidosis was a depression of synaptic responses. Both effects rapidly reversed after treatment with normal aCSF pH 7.35. Death analysis after acidosis treatment revealed no delayed neuronal loss. Increasing the duration of the acidosis to 60 min, however, induced irreversible synaptic depression and delayed neuronal loss. Increasing acidosis temperature to 37 degrees C acidified intracellular pH and depressed synaptic responses. Delayed neuronal loss was also observed. Acidosis using lactate aCSF, pH 6. 70 for 30 min at 32 degrees C acidified intracellular pH from 7. 19+/-0.13 to 6.43+/-0.07 and depressed synaptic responses. After reperfusion with lactate containing aCSF pH 7.35, intracellular pH recovered yet synaptic responses remained depressed and delayed neuronal loss was observed. This suggested that, for a 30-min treatment at 32 degrees C, lactate acidosis was neurotoxic while low bicarbonate acidosis was not. Increasing the duration or temperature of low bicarbonate acidosis induced neuronal loss. These data provide additional evidence that acidosis contributes to the neurotoxicity during stroke and trauma.
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Affiliation(s)
- Z Xiang
- Department of Physiology and Pharmacology, State University of New York-Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA
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29
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Abstract
One of the early sequelae of ischemia is an increase of circulating lactic acid that occurs in response to anaerobic metabolism. The purpose of the present study was to investigate whether lactic acidosis can induce endothelial swelling in vitro under closely controlled extracellular conditions. Cell volume of suspended cultured bovine aortic endothelial cells was measured by use of an advanced Coulter technique employing the "pulse area analysis" signal-processing technique (CASY1). The isosmotic reduction of pH from 7.4 to 6.8 had no effect on cell volume. Lowering of pH to 6.6, 6.4, or 6.0, however, led to significant, pH-dependent increases of cell volume. Swelling was more pronounced in bicarbonate-buffered media than in HEPES buffer. Specific inhibition of Na(+)/H(+) exchange by ethylisopropylamiloride completely prevented swelling in HEPES-buffered media. Pretreatment with ouabain to partially depolarize the cells did not affect the degree of acidosis-induced swelling. In bicarbonate-buffered media, the inhibition of transmembrane HCO(3)(-) transport by DIDS reduced swelling to a level comparable with that seen in the absence of bicarbonate ions. Lactacidosis-induced endothelial swelling, therefore, is a result of intracellular pH regulatory mechanisms, namely, Na(+)/H(+) exchange and bicarbonate-transporting carriers.
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Affiliation(s)
- S Behmanesh
- Institute for Neurosurgical Pathophysiology, Johannes Gutenberg-University, 55101 Mainz, Germany
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30
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Ringel F, Chang RC, Staub F, Baethmann A, Plesnila N. Contribution of anion transporters to the acidosis-induced swelling and intracellular acidification of glial cells. J Neurochem 2000; 75:125-32. [PMID: 10854255 DOI: 10.1046/j.1471-4159.2000.0750125.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This study examines the contribution of anion transporters to the swelling and intracellular acidification of glial cells from an extracellular lactacidosis, a condition well-known to accompany cerebral ischemia and traumatic brain injury. Suspended C6 glioma cells were exposed to lactacidosis in physiological or anion-depleted media, and different anion transport inhibitors were applied. Changes in cell volume and intracellular pH (pH(i)) were simultaneously quantified by flow cytometry. Extracellular lactacidosis (pH 6.2) led to an increase in cell volume to 125.1 +/- 2.5% of baseline within 60 min, whereas the pH(i) dropped from the physiological value of 7.13 +/- 0.05 to 6.32 +/- 0.03. Suspension in Cl(-)-free or HCO(3)(-)/CO(2)-free media or application of anion transport inhibitors [0.1 mM bumetanide or 0.5 mM 4, 4'-diisothio-cyanatostilbene-2,2'-disulfonic acid (DIDS)] did not affect cell volume during baseline conditions but significantly reduced cell swelling from lactacidosis. In addition, the Cl(-)-free or HCO(3)(-)/CO(2)-free media and DIDS attenuated intracellular acidosis on extracellular acidification. From these findings it is concluded that besides the known activation of the Na(+)/H(+) exchanger, activation of the Na(+)-independent Cl(-)/HCO(3)(-) exchanger and the Na(+)-K(+)-Cl(-) cotransporter contributes to acidosis-induced glial swelling and the intracellular acidification. Inhibition of these processes may be of interest for future strategies in the treatment of cytotoxic brain edema from cerebral ischemia or traumatic brain injury.
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Affiliation(s)
- F Ringel
- Institute for Surgical Research, Klinikum Grosshadern, Ludwig-Maximilians-University, Munich Department of Neurosurgery, University of Cologne, Cologne, Germany
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31
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Plesnila N, Muller E, Guretzki S, Ringel F, Staub F, Baethmann A. Effect of hypothermia on the volume of rat glial cells. J Physiol 2000; 523 Pt 1:155-62. [PMID: 10673552 PMCID: PMC2269776 DOI: 10.1111/j.1469-7793.2000.00155.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
1. The cell volume of suspended C6 glioma cells and primary cultured rat astrocytes was measured at normothermia (37 degrees C), and at mild (32 degrees C) and moderate (27 degrees C) hypothermia by flow cytometry with electrical cell sizing. 2. Under control conditions (37 degrees C), C6 glioma cells had a volume of 809 +/- 29 microm3. Moderate hypothermia (27 degrees C) led to rapid cell swelling, with a maximum volume of 113.1 +/- 1.3 % of control being achieved after 50 min. After rewarming to 37 degrees C, cell volume recovered very slowly and incompletely (to 107.2 +/- 0.4 % of control). Less severe hypothermia (32 degrees C) led to a smaller increase in cell volume (108.7 +/- 0.5 % of control). 3. The maximal cell swelling response and the kinetics of swelling were similar in C6 glioma cells and primary cultured astrocytes. 4. Hypothermia-induced cell swelling was dependent on the presence of extracellular Na+ and was reduced by the Na+-H+ antiporter inhibitor EIPA. 5. The underlying mechanisms of hypothermia-induced cell swelling are an intracellular accumulation of Na+ by (1) differential effects of hypothermia on the membrane permeabilities of Na+ and K+ and (2) activation of the Na+-H+ antiporter by a shift of its activation curve to a more alkaline value.
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Affiliation(s)
- N Plesnila
- Institute for Surgical Research, Klinikum Grosshadern, Ludwig-Maximilians-University, Munich, Germany.
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