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Foster VS, Rash LD, King GF, Rank MM. Acid-Sensing Ion Channels: Expression and Function in Resident and Infiltrating Immune Cells in the Central Nervous System. Front Cell Neurosci 2021; 15:738043. [PMID: 34602982 PMCID: PMC8484650 DOI: 10.3389/fncel.2021.738043] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 08/30/2021] [Indexed: 11/15/2022] Open
Abstract
Peripheral and central immune cells are critical for fighting disease, but they can also play a pivotal role in the onset and/or progression of a variety of neurological conditions that affect the central nervous system (CNS). Tissue acidosis is often present in CNS pathologies such as multiple sclerosis, epileptic seizures, and depression, and local pH is also reduced during periods of ischemia following stroke, traumatic brain injury, and spinal cord injury. These pathological increases in extracellular acidity can activate a class of proton-gated channels known as acid-sensing ion channels (ASICs). ASICs have been primarily studied due to their ubiquitous expression throughout the nervous system, but it is less well recognized that they are also found in various types of immune cells. In this review, we explore what is currently known about the expression of ASICs in both peripheral and CNS-resident immune cells, and how channel activation during pathological tissue acidosis may lead to altered immune cell function that in turn modulates inflammatory pathology in the CNS. We identify gaps in the literature where ASICs and immune cell function has not been characterized, such as neurotrauma. Knowledge of the contribution of ASICs to immune cell function in neuropathology will be critical for determining whether the therapeutic benefits of ASIC inhibition might be due in part to an effect on immune cells.
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Affiliation(s)
- Victoria S. Foster
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Lachlan D. Rash
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia
| | - Glenn F. King
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Queensland, St Lucia, QLD, Australia
| | - Michelle M. Rank
- Anatomy and Physiology, Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne, VIC, Australia
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2
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Decker Y, Németh E, Schomburg R, Chemla A, Fülöp L, Menger MD, Liu Y, Fassbender K. Decreased pH in the aging brain and Alzheimer's disease. Neurobiol Aging 2021; 101:40-49. [PMID: 33578193 DOI: 10.1016/j.neurobiolaging.2020.12.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 12/02/2020] [Accepted: 12/05/2020] [Indexed: 10/22/2022]
Abstract
Using publicly available data sets, we compared pH in the human brain and the cerebrospinal fluid (CSF) of postmortem control and Alzheimer's disease cases. We further investigated the effects of long-term acidosis in vivo in the APP-PS1 mouse model of Alzheimer's disease. We finally examined in vitro whether low pH exposure could modulate the release of proinflammatory cytokines and the uptake of amyloid beta by microglia. In the human brain, pH decreased with aging. Similarly, we observed a reduction of pH in the brain of C57BL/6 mice with age. In addition, independent database analyses revealed that postmortem brain and CSF pH is further reduced in Alzheimer's disease cases compared with controls. Moreover, in vivo experiments showed that low pH CSF infusion increased amyloid beta plaque load in APP-PS1 mice. We further observed that mild acidosis reduced the amyloid beta 42-induced release of tumor necrosis factor-alpha by microglia and their capacity to uptake this peptide. Brain acidosis is associated with aging and might affect pathophysiological processes such as amyloid beta aggregation or inflammation in Alzheimer's disease.
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Affiliation(s)
- Yann Decker
- Department of Neurology, University of the Saarland, Homburg/Saar, Germany; German Institute for Dementia Prevention (DIDP), University of the Saarland, Homburg/Saar, Germany.
| | - Eszter Németh
- Department of Neurology, University of the Saarland, Homburg/Saar, Germany; German Institute for Dementia Prevention (DIDP), University of the Saarland, Homburg/Saar, Germany
| | - Robert Schomburg
- Rehaklinik Zihlschlacht, Neurologisches Rehabilitationszentrum, Zihlschlacht, Switzerland
| | - Axel Chemla
- Department of Neurology, University of the Saarland, Homburg/Saar, Germany; German Institute for Dementia Prevention (DIDP), University of the Saarland, Homburg/Saar, Germany
| | - Lívia Fülöp
- Department of Medical Chemistry, University of Szeged, Szeged, Hungary
| | - Michael D Menger
- Institute for Clinical and Experimental Surgery, Saarland University, Homburg/Saar, Germany
| | - Yang Liu
- Department of Neurology, University of the Saarland, Homburg/Saar, Germany; German Institute for Dementia Prevention (DIDP), University of the Saarland, Homburg/Saar, Germany
| | - Klaus Fassbender
- Department of Neurology, University of the Saarland, Homburg/Saar, Germany; German Institute for Dementia Prevention (DIDP), University of the Saarland, Homburg/Saar, Germany.
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3
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Matoba K, Yamashita S, Isaksen TJ, Yamashita T. Proton-sensing receptor GPR132 facilitates migration of astrocytes. Neurosci Res 2020; 170:106-113. [PMID: 33333086 DOI: 10.1016/j.neures.2020.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 09/30/2020] [Accepted: 10/04/2020] [Indexed: 11/26/2022]
Abstract
Astrocytes are one of the first responders to central nervous system (CNS) injuries such as spinal cord injury (SCI). They are thought to repress injury-induced CNS inflammation as well as inhibit axonal regeneration. While reactive astrocytes migrate and accumulate around the lesion core, the mechanism of astrocyte migration towards the lesion site remains unclear. Here, we examined possible involvement of acidification of the lesion site and expression of proton-sensing receptors in astrocyte migration, both in mice models and in vitro. We found that the expression of several proton-sensing receptors was increased at the lesion site after SCI. Among these receptors, Gpr132 was expressed in primary cultured astrocytes and exhibited significant enhanced expression in acidic conditions in vitro. Furthermore, astrocyte motility was enhanced in acidic media and by Gpr132 activation. These results suggest that acidification of the lesion site facilitates astrocyte migration via the proton-sensing receptor Gpr132.
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Affiliation(s)
- Ken Matoba
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, Osaka, Japan
| | | | - Toke Jost Isaksen
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Toshihide Yamashita
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, Osaka, Japan; WPI Immunology Frontier Research Center, Osaka University, Osaka, Japan; Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan; Department of Neuro-Medical Science, Graduate School of Medicine, Osaka University, Osaka, Japan.
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4
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Sato K, Tobo A, Mogi C, Tobo M, Yamane N, Tosaka M, Tomura H, Im DS, Okajima F. The protective role of proton-sensing TDAG8 in the brain injury in a mouse ischemia reperfusion model. Sci Rep 2020; 10:17193. [PMID: 33057165 PMCID: PMC7566628 DOI: 10.1038/s41598-020-74372-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 09/30/2020] [Indexed: 01/09/2023] Open
Abstract
Extracellular acidification in the brain has been observed in ischemia; however, the physiological and pathophysiological implications of the pH reduction remain largely unknown. Here, we analyzed the roles of proton-sensing G protein-coupled receptors, including T-cell death-associated gene 8 (TDAG8), ovarian cancer G protein-coupled receptor 1 (OGR1), and G protein-coupled receptor 4 (GPR4) in a mouse ischemia reperfusion model. Cerebral infarction and dysfunctional behavior with transient middle cerebral artery occlusion (tMCAO) and subsequent reperfusion were exacerbated by the deficiency of TDAG8, whereas no significant effect was observed with the deficiency of OGR1 or GPR4. We confirmed that the pH of the predicted infarction region was 6.5. TDAG8 mRNA was observed in Iba1-positive microglia in the mouse brain. The tMCAO increased the mRNA expression of tumor necrosis factor-α in the ipsilateral cerebral hemisphere and evoked morphological changes in microglia in an evolving cerebral injury. These tMCAO-induced actions were significantly enhanced by the TDAG8 deficiency. Administration of minocycline, which is known to inhibit microglial activation, improved the cerebral infarction and dysfunctional behavior induced by tMCAO in the TDAG8-deficient mouse. Thus, acidic pH/TDAG8 protects against cerebral infarction caused by tMCAO, at least due to the mechanism involving the inhibition of microglial functions.
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Affiliation(s)
- Koichi Sato
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, 371-8512, Japan.
| | - Ayaka Tobo
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, 371-8512, Japan
| | - Chihiro Mogi
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, 371-8512, Japan
| | - Masayuki Tobo
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, 371-8512, Japan
| | - Nobuhiro Yamane
- Department of Neurosurgery, Gunma University Graduate School of Medicine, Maebashi, 371-8511, Japan
| | - Masahiko Tosaka
- Department of Neurosurgery, Gunma University Graduate School of Medicine, Maebashi, 371-8511, Japan
| | - Hideaki Tomura
- Laboratory of Cell Signaling Regulation, Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki, 214-8571, Japan
| | - Dong-Soon Im
- College of Pharmacy, Kyung Hee University, Seoul, 02447, Republic of Korea
| | - Fumikazu Okajima
- Laboratory of Signal Transduction, Faculty of Pharmaceutical Sciences, Aomori University, Aomori, 030-0943, Japan
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5
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Shahin-Shamsabadi A, Selvaganapathy PR. π-SACS: pH Induced Self-Assembled Cell Sheets Without the Need for Modified Surfaces. ACS Biomater Sci Eng 2020; 6:5346-5356. [PMID: 33455283 DOI: 10.1021/acsbiomaterials.0c01073] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ability to form tissue-like constructs that have high cell density with proper cell-cell and cell-ECM interactions is critical for many applications including tissue models for drug discovery and tissue regeneration. Newly emerging bioprinting methods sometimes lack the high cellular density needed to provide biophysical cues to orchestrate cellular behavior to recreate tissue architecture and function. Alternate methods using self-assembly can be used to create tissue-like constructs with high cellular density and well-defined microstructure in the form of spheroids, organoids, or cell sheets. Cell sheets have a particularly interesting architecture in the context of tissue regeneration and repair as they can be applied as patches to integrate with surrounding tissues. Until now, the preparation of these sheets has involved culturing on specialized substrates that can be triggered by temperature or phase change (hydrophobic to hydrophilic) to release cells growing on them and form sheets. Here a new technique is proposed that allows delamination of cells and secreted ECM and rapid self-assembly into a cell sheet using a simple pH trigger and without the need to use responsive surfaces or applying external stimuli such as electrical and magnetic fields, only with routine tissue culture plates. This technique can be used with cells that are capable of syncytialization and fusion such as skeletal muscle cells and placenta cells. Using C2C12 myoblast cells we show that the pH trigger induces a rapid delamination of the cells as a continuous layer that self-assembles into a thick dense sheet. The delamination process has little effect on cell viability and maturation and preserves the ECM components that allow sheets to adhere to each other within a short incubation time enabling formation of thicker constructs when multiple sheets are stacked (double- and quadruple-layer constructs are formed here). These thick grafts can be used for regeneration purposes or as in vitro models.
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Affiliation(s)
| | - P Ravi Selvaganapathy
- School of Biomedical Engineering, McMaster University, Ontario L8S4K1, Canada.,Department of Mechanical Engineering, McMaster University, Ontario L8S4L7, Canada
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6
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The role of acid-sensitive ion channels in panic disorder: a systematic review of animal studies and meta-analysis of human studies. Transl Psychiatry 2018; 8:185. [PMID: 30194289 PMCID: PMC6128878 DOI: 10.1038/s41398-018-0238-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 07/28/2018] [Accepted: 08/05/2018] [Indexed: 11/08/2022] Open
Abstract
Acid-sensitive ion channels, such as amiloride-sensitive cation channel (ACCN), transient receptor potential vanilloid-1 (TRPV1), and T-cell death-associated gene 8 (TDAG8) are highly related to the expression of fear and are expressed in several regions of the brain. These molecules can detect acidosis and maintain brain homeostasis. An important role of pH homeostasis has been suggested in the physiology of panic disorder (PD), with acidosis as an interoceptive trigger for panic attacks. To examine the effect of acid-sensitive channels on PD symptoms, we conducted a systematic review and meta-analysis of these chemosensors in rodents and humans. Following PRISMA guidelines, we systematically searched the Web of Science, Medline/Pubmed, Scopus, Science Direct, and SciELO databases. The review included original research in PD patients and animal models of PD that investigated acid-sensitive channels and PD symptoms. Studies without a control group, studies involving patients with a comorbid psychiatric diagnosis, and in vitro studies were excluded. Eleven articles met the inclusion criteria for the systematic review. The majority of the studies showed an association between panic symptoms and acid-sensitive channels. PD patients appear to display polymorphisms in the ACCN gene and elevated levels of TDAG8 mRNA. The results showed a decrease in panic-like symptoms after acid channel blockade in animal models. Despite the relatively limited data on this topic in the literature, our review identified evidence linking acid-sensitive channels to PD in humans and preclinical models. Future research should explore possible underlying mechanisms of this association, attempt to replicate the existing findings in larger populations, and develop new therapeutic strategies based on these biological features.
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7
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Coordinate effects of P2X7 and extracellular acidification in microglial cells. Oncotarget 2018; 9:12718-12731. [PMID: 29560104 PMCID: PMC5849168 DOI: 10.18632/oncotarget.24331] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Accepted: 01/24/2018] [Indexed: 12/26/2022] Open
Abstract
Extracellular adenosine 5′-triphosphate (ATP) is a damage-associated molecular pattern and contributes to inflammation associated diseases including cancer. Extracellular acidosis is a novel danger signal in the inflammatory sites, where it can modulate inflammation, immunity and tumor growth. Extracellular acidification was shown to inhibit P2X7-mediated channel currents, while it remains unknown how acidification and P2X7 together affect cellular responses. Here, we treated BV-2 microglial cells with ATP in a short period (<15 min) or a sustained acidified condition. For short acidification we compared the actions of neutralized ATP and acidic ATP in a condition with pH buffering. For sustained acidification, we treated cells with neutralized ATP in acidic medium or acidic ATP in medium without pH buffering. In the short acidified condition, neutralized ATP induced higher responses than acidic ATP to increase intracellular calcium and reactive oxygen species, decrease intracellular potassium and induce cell death. In contrast, these cellular responses and mitochondrial fission caused by neutralized ATP were enhanced by pH 6.0 and pH 4.5 media. P2X7 activation can also rapidly block mitochondrial ATP turnover and respiration capacity, both of which were mimicked by nigericin and enhanced by acidity. Taken together P2X7-mediated ionic fluxes and reactive oxygen species production are attenuated under short acidification, while sustained acidification itself can induce mitochondrial toxicity which deteriorates the mitochondrial function under P2X7 activation.
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8
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Kawai T, Okochi Y, Ozaki T, Imura Y, Koizumi S, Yamazaki M, Abe M, Sakimura K, Yamashita T, Okamura Y. Unconventional role of voltage‐gated proton channels (
VSOP
/Hv1) in regulation of microglial
ROS
production. J Neurochem 2017. [DOI: 10.1111/jnc.14106] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Takafumi Kawai
- Integrative Physiology Department of Physiology Graduate School of Medicine & Frontier Biosciences Osaka University Suita Osaka Japan
| | - Yoshifumi Okochi
- Integrative Physiology Department of Physiology Graduate School of Medicine & Frontier Biosciences Osaka University Suita Osaka Japan
| | - Tomohiko Ozaki
- Department of Molecular Neuroscience Graduate School of Medicine Osaka University Suita Osaka Japan
| | - Yoshio Imura
- Department of Neuropharmacology Interdisciplinary Graduate School of Medicine University of Yamanashi Chuo Yamanashi Japan
| | - Schuichi Koizumi
- Department of Neuropharmacology Interdisciplinary Graduate School of Medicine University of Yamanashi Chuo Yamanashi Japan
| | - Maya Yamazaki
- Department of Cellular Neurobiology Brain Research Institute Niigata University Niigata Japan
| | - Manabu Abe
- Department of Cellular Neurobiology Brain Research Institute Niigata University Niigata Japan
| | - Kenji Sakimura
- Department of Cellular Neurobiology Brain Research Institute Niigata University Niigata Japan
| | - Toshihide Yamashita
- Department of Molecular Neuroscience Graduate School of Medicine Osaka University Suita Osaka Japan
| | - Yasushi Okamura
- Integrative Physiology Department of Physiology Graduate School of Medicine & Frontier Biosciences Osaka University Suita Osaka Japan
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9
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Vollmer LL, Ghosal S, McGuire JL, Ahlbrand RL, Li KY, Santin JM, Ratliff-Rang CA, Patrone LGA, Rush J, Lewkowich IP, Herman JP, Putnam RW, Sah R. Microglial Acid Sensing Regulates Carbon Dioxide-Evoked Fear. Biol Psychiatry 2016; 80:541-51. [PMID: 27422366 PMCID: PMC5014599 DOI: 10.1016/j.biopsych.2016.04.022] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 04/08/2016] [Accepted: 04/13/2016] [Indexed: 12/11/2022]
Abstract
BACKGROUND Carbon dioxide (CO2) inhalation, a biological challenge and pathologic marker in panic disorder, evokes intense fear and panic attacks in susceptible individuals. The molecular identity and anatomic location of CO2-sensing systems that translate CO2-evoked fear remain unclear. We investigated contributions of microglial acid sensor T cell death-associated gene-8 (TDAG8) and microglial proinflammatory responses in CO2-evoked behavioral and physiological responses. METHODS CO2-evoked freezing, autonomic, and respiratory responses were assessed in TDAG8-deficient ((-/-)) and wild-type ((+/+)) mice. Involvement of TDAG8-dependent microglial activation and proinflammatory cytokine interleukin (IL)-1β with CO2-evoked responses was investigated using microglial blocker, minocycline, and IL-1β antagonist IL-1RA. CO2-chemosensitive firing responses using single-cell patch clamping were measured in TDAG8(-/-) and TDAG8(+/+) mice to gain functional insights. RESULTS TDAG8 expression was localized in microglia enriched within the sensory circumventricular organs. TDAG8(-/-) mice displayed attenuated CO2-evoked freezing and sympathetic responses. TDAG8 deficiency was associated with reduced microglial activation and proinflammatory cytokine IL-1β within the subfornical organ. Central infusion of microglial activation blocker minocycline and IL-1β antagonist IL-1RA attenuated CO2-evoked freezing. Finally, CO2-evoked neuronal firing in patch-clamped subfornical organ neurons was dependent on acid sensor TDAG8 and IL-1β. CONCLUSIONS Our data identify TDAG8-dependent microglial acid sensing as a unique chemosensor for detecting and translating hypercapnia to fear-associated behavioral and physiological responses, providing a novel mechanism for homeostatic threat detection of relevance to psychiatric conditions such as panic disorder.
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Affiliation(s)
- Lauren Larke Vollmer
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati; Neuroscience Graduate Program, University of Cincinnati, Cincinnati
| | - Sriparna Ghosal
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati; Neuroscience Graduate Program, University of Cincinnati, Cincinnati
| | - Jennifer L McGuire
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati
| | - Rebecca L Ahlbrand
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati
| | - Ke-Yong Li
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton
| | - Joseph M Santin
- Department of Biological Sciences, Wright State University, Dayton
| | | | - Luis G A Patrone
- Department of Animal Morphology and Physiology, São Paulo State University, FCAV, Jaboticabal, São Paulo, Brazil
| | - Jennifer Rush
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati
| | - Ian P Lewkowich
- Division of Immunobiology, Children's Hospital Medical Center, Cincinnati
| | - James P Herman
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati; Neuroscience Graduate Program, University of Cincinnati, Cincinnati
| | - Robert W Putnam
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton
| | - Renu Sah
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati; Neuroscience Graduate Program, University of Cincinnati, Cincinnati; Veterans Affairs (VA) Medical Center, Cincinnati, Ohio.
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10
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Shin SP, Zenke K, Yokoyama H, Yoshinaga T. Factors affecting sporoplasm release in Kudoa septempunctata. Parasitol Res 2015; 114:795-9. [DOI: 10.1007/s00436-014-4305-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 12/23/2014] [Indexed: 01/21/2023]
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11
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LRRK2 and neuroinflammation: partners in crime in Parkinson's disease? J Neuroinflammation 2014; 11:52. [PMID: 24655756 PMCID: PMC3994422 DOI: 10.1186/1742-2094-11-52] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Accepted: 02/25/2014] [Indexed: 02/07/2023] Open
Abstract
It is now well established that chronic inflammation is a prominent feature of several neurodegenerative disorders including Parkinson’s disease (PD). Growing evidence indicates that neuroinflammation can contribute greatly to dopaminergic neuron degeneration and progression of the disease. Recent literature highlights that leucine-rich repeat kinase 2 (LRRK2), a kinase mutated in both autosomal-dominantly inherited and sporadic PD cases, modulates inflammation in response to different pathological stimuli. In this review, we outline the state of the art of LRRK2 functions in microglia cells and in neuroinflammation. Furthermore, we discuss the potential role of LRRK2 in cytoskeleton remodeling and vesicle trafficking in microglia cells under physiological and pathological conditions. We also hypothesize that LRRK2 mutations might sensitize microglia cells toward a pro-inflammatory state, which in turn results in exacerbated inflammation with consequent neurodegeneration.
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12
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Jin Y, Sato K, Tobo A, Mogi C, Tobo M, Murata N, Ishii S, Im DS, Okajima F. Inhibition of interleukin-1β production by extracellular acidification through the TDAG8/cAMP pathway in mouse microglia. J Neurochem 2014; 129:683-95. [PMID: 24447140 DOI: 10.1111/jnc.12661] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Accepted: 01/16/2014] [Indexed: 12/23/2022]
Abstract
Interleukin-1β (IL-1β) is released from activated microglia and involved in the neurodegeneration of acute and chronic brain disorders, such as stroke and Alzheimer's disease, in which extracellular acidification has been shown to occur. Here, we examined the extracellular acidic pH regulation of IL-1β production, especially focusing on TDAG8, a major proton-sensing G-protein-coupled receptor, in mouse microglia. Extracellular acidification inhibited lipopolysaccharide -induced IL-1β production, which was associated with the inhibition of IL-1β cytoplasmic precursor and mRNA expression. The IL-1β mRNA and protein responses were significantly, though not completely, attenuated in microglia derived from TDAG8-deficient mice compared with those from wild-type mice. The acidic pH also stimulated cellular cAMP accumulation, which was completely inhibited by TDAG8 deficiency. Forskolin and a cAMP derivative, which specifically stimulates protein kinase A (PKA), mimicked the proton actions, and PKA inhibitors reversed the acidic pH-induced IL-1β mRNA expression. The acidic pH-induced inhibitory IL-1β responses were accompanied by the inhibition of extracellular signal-related kinase and c-Jun N-terminal kinase activities. The inhibitory enzyme activities in response to acidic pH were reversed by the PKA inhibitor and TDAG8 deficiency. We conclude that extracellular acidic pH inhibits lipopolysaccharide-induced IL-1β production, at least partly, through the TDAG8/cAMP/PKA pathway, by inhibiting extracellular signal-related kinase and c-Jun N-terminal kinase activities, in mouse microglia.
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Affiliation(s)
- Ye Jin
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
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13
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Jagielska A, Wilhite KD, Van Vliet KJ. Extracellular acidic pH inhibits oligodendrocyte precursor viability, migration, and differentiation. PLoS One 2013; 8:e76048. [PMID: 24098762 PMCID: PMC3786906 DOI: 10.1371/journal.pone.0076048] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 08/22/2013] [Indexed: 02/04/2023] Open
Abstract
Axon remyelination in the central nervous system requires oligodendrocytes that produce myelin. Failure of this repair process is characteristic of neurodegeneration in demyelinating diseases such as multiple sclerosis, and it remains unclear how the lesion microenvironment contributes to decreased remyelination potential of oligodendrocytes. Here, we show that acidic extracellular pH, which is characteristic of demyelinating lesions, decreases the migration, proliferation, and survival of oligodendrocyte precursor cells (OPCs), and reduces their differentiation into oligodendrocytes. Further, OPCs exhibit directional migration along pH gradients toward acidic pH. These in vitro findings support a possible in vivo scenario whereby pH gradients attract OPCs toward acidic lesions, but resulting reduction in OPC survival and motility in acid decreases progress toward demyelinated axons and is further compounded by decreased differentiation into myelin-producing oligodendrocytes. As these processes are integral to OPC response to nerve demyelination, our results suggest that lesion acidity could contribute to decreased remyelination.
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Affiliation(s)
- Anna Jagielska
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Kristen D. Wilhite
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Krystyn J. Van Vliet
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- * E-mail:
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14
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Karperien A, Ahammer H, Jelinek HF. Quantitating the subtleties of microglial morphology with fractal analysis. Front Cell Neurosci 2013; 7:3. [PMID: 23386810 PMCID: PMC3558688 DOI: 10.3389/fncel.2013.00003] [Citation(s) in RCA: 320] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 01/08/2013] [Indexed: 01/17/2023] Open
Abstract
It is well established that microglial form and function are inextricably linked. In recent years, the traditional view that microglial form ranges between “ramified resting” and “activated amoeboid” has been emphasized through advancing imaging techniques that point to microglial form being highly dynamic even within the currently accepted morphological categories. Moreover, microglia adopt meaningful intermediate forms between categories, with considerable crossover in function and varying morphologies as they cycle, migrate, wave, phagocytose, and extend and retract fine and gross processes. From a quantitative perspective, it is problematic to measure such variability using traditional methods, but one way of quantitating such detail is through fractal analysis. The techniques of fractal analysis have been used for quantitating microglial morphology, to categorize gross differences but also to differentiate subtle differences (e.g., amongst ramified cells). Multifractal analysis in particular is one technique of fractal analysis that may be useful for identifying intermediate forms. Here we review current trends and methods of fractal analysis, focusing on box counting analysis, including lacunarity and multifractal analysis, as applied to microglial morphology.
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Affiliation(s)
- Audrey Karperien
- Centre for Research in Complex Systems, School of Community Health, Charles Sturt University Albury, NSW, Australia
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Directional cell migration in an extracellular pH gradient: a model study with an engineered cell line and primary microvascular endothelial cells. Exp Cell Res 2012; 319:487-97. [PMID: 23153553 DOI: 10.1016/j.yexcr.2012.11.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 11/03/2012] [Accepted: 11/05/2012] [Indexed: 11/20/2022]
Abstract
Extracellular pH (pH(e)) gradients are characteristic of tumor and wound environments. Cell migration in these environments is critical to tumor progression and wound healing. While it has been shown previously that cell migration can be modulated in conditions of spatially invariant acidic pH(e) due to acid-induced activation of cell surface integrin receptors, the effects of pH(e) gradients on cell migration remain unknown. Here, we investigate cell migration in an extracellular pH(e) gradient, using both model α(v)β(3) CHO-B2 cells and primary microvascular endothelial cells. For both cell types, we find that the mean cell position shifts toward the acidic end of the gradient over time, and that cells preferentially polarize toward the acidic end of the gradient during migration. We further demonstrate that cell membrane protrusion stability and actin-integrin adhesion complex formation are increased in acidic pH(e), which could contribute to the preferential polarization toward acidic pH(e) that we observed for cells in pH(e) gradients. These results provide the first demonstration of preferential cell migration toward acid in a pH(e) gradient, with intriguing implications for directed cell migration in the tumor and wound healing environments.
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Effects of acute hypoxia/acidosis on intracellular pH in differentiating neural progenitor cells. Brain Res 2012; 1461:10-23. [PMID: 22608071 DOI: 10.1016/j.brainres.2012.04.043] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 03/26/2012] [Accepted: 04/20/2012] [Indexed: 01/19/2023]
Abstract
The response of differentiating mouse neural progenitor cells, migrating out from neurospheres, to conditions simulating ischemia (hypoxia and extracellular or intracellular acidosis) was studied. We show here, by using BCECF and single cell imaging to monitor intracellular pH (pH(i)), that two main populations can be distinguished by exposing migrating neural progenitor cells to low extracellular pH or by performing an acidifying ammonium prepulse. The cells dominating at the periphery of the neurosphere culture, which were positive for neuron specific markers MAP-2, calbindin and NeuN had lower initial resting pH(i) and could also easily be further acidified by lowering the extracellular pH. Moreover, in this population, a more profound acidification was seen when the cells were acidified using the ammonium prepulse technique. However, when the cell population was exposed to depolarizing potassium concentrations no alterations in pH(i) took place in this population. In contrast, depolarization caused an increase in pH(i) (by 0.5 pH units) in the cell population closer to the neurosphere body, which region was positive for the radial cell marker (GLAST). This cell population, having higher resting pH(i) (pH 6.9-7.1) also responded to acute hypoxia. During hypoxic treatment the resting pH(i) decreased by 0.1 pH units and recovered rapidly after reoxygenation. Our results show that migrating neural progenitor cells are highly sensitive to extracellular acidosis and that irreversible damage becomes evident at pH 6.2. Moreover, our results show that a response to acidosis clearly distinguishes two individual cell populations probably representing neuronal and radial cells.
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17
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Acidic extracellular pH promotes activation of integrin α(v)β(3). PLoS One 2011; 6:e15746. [PMID: 21283814 PMCID: PMC3023767 DOI: 10.1371/journal.pone.0015746] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Accepted: 11/26/2010] [Indexed: 12/12/2022] Open
Abstract
Acidic extracellular pH is characteristic of the cell microenvironment in several important physiological and pathological contexts. Although it is well established that acidic extracellular pH can have profound effects on processes such as cell adhesion and migration, the underlying molecular mechanisms are largely unknown. Integrin receptors physically connect cells to the extracellular matrix, and are thus likely to modulate cell responses to extracellular conditions. Here, we examine the role of acidic extracellular pH in regulating activation of integrin αvβ3. Through computational molecular dynamics simulations, we find that acidic extracellular pH promotes opening of the αvβ3 headpiece, indicating that acidic pH can thereby facilitate integrin activation. This prediction is consistent with our flow cytometry and atomic force microscope-mediated force spectroscopy assays of integrin αvβ3 on live cells, which both demonstrate that acidic pH promotes activation at the intact cell surface. Finally, quantification of cell morphology and migration measurements shows that acidic extracellular pH affects cell behavior in a manner that is consistent with increased integrin activation. Taken together, these computational and experimental results suggest a new and complementary mechanism of integrin activation regulation, with associated implications for cell adhesion and migration in regions of altered pH that are relevant to wound healing and cancer.
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Yu Y, Kuebler J, Groos S, Metzelder M, Kurpanik S, Ure BM, Vieten G. Carbon dioxide modifies the morphology and function of mesothelial cells and facilitates transepithelial neuroblastoma cell migration. Pediatr Surg Int 2010; 26:29-36. [PMID: 19847444 DOI: 10.1007/s00383-009-2503-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND The response of mesothelial cells to surgical trauma and bacterial contamination is poorly defined. We have recently shown that CO(2) pneumoperitoneum increases systemic metastasis of neuroblastoma cells in a murine model. Thus, we hypothesized that CO(2) alters the morphology and function of mesothelial cells and facilitates transmesothelial tumor cell migration. MATERIALS AND METHODS Murine mesothelial cells were exposed to 100% CO(2) and 5% CO(2) as control. Scanning electron microscopy (SEM) investigations, as well as LPS-induced granulocyte-colony stimulating factor (G-CSF) production and mitochondrial activity (MTT assay) were measured. Transmesothelial migration of neuroblastoma cells (Neuro2a) was determined using a transwell chamber system. RESULTS CO(2) incubation was associated with a significant destruction of the microvillar formation in SEM. Migration studies showed that the barrier function of the mesothelial monolayer decreased. A significantly increased migration of neuroblastoma cells was identified after 100% CO(2) exposure (P < 0.05). Although the conversion of MTT as an indicator of mitochondrial activity was only slightly and not significantly reduced after CO(2) incubation, the release of G-CSF induced by LPS was completely blocked during the incubation with 100% CO(2) (P < 0.05). The capacity of G-CSF release recovered after the incubation. CONCLUSION We observed that peritoneal mesothelial cells lose their typical cell morphology by CO(2) incubation, which is accompanied by facilitated migration of neuroblastoma cells. Moreover, the synthesis of immunological factors is blocked, but this effect is not long lasting. These mechanisms may explain an increased metastasis rate of neuroblastoma cells after CO(2) pneumoperitoneum, which was recently observed in a murine model.
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Affiliation(s)
- Yi Yu
- Department of Pediatric Surgery, Hannover Medical School, Carl-Neuberg-Str.1, 30625, Hannover, Germany
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19
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Hydrogen sulfide regulates intracellular pH in rat primary cultured glia cells. Neurosci Res 2010; 66:92-8. [DOI: 10.1016/j.neures.2009.09.1713] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 09/04/2009] [Accepted: 09/29/2009] [Indexed: 11/21/2022]
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Wang ZZ, Li G, Chen XY, Zhao M, Yuan YH, Wang XL, Chen NH. Chemokine-like factor 1, a novel cytokine, induces nerve cell migration through the non-extracellular Ca2+-dependent tyrosine kinases pathway. Brain Res 2009; 1308:24-34. [PMID: 19857473 DOI: 10.1016/j.brainres.2009.10.047] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 10/15/2009] [Accepted: 10/19/2009] [Indexed: 10/20/2022]
Abstract
Chemokine-like factor 1 (CKLF1) is a newly cloned chemotactic cytokine. The roles of CKLF1 in the immune system and the respiratory system have been reported, but its function in the nervous system is still remaining unclear. We aimed to investigate the role of CKLF1 in the nerve cell migration and its regulatory mechanisms. By chemotaxis assays and wound-healing assays, CKLF1 stimulated the migration of SH-SY5Y cells dose-dependently. By immunofluorescence staining, CKLF1 induced actin polymerization. By western blotting, proline-rich tyrosine kinase 2 (PYK2) was phosphorylated at Tyr-402 in response to CKLF1 and this phosphorylation was apparently suppressed by phospholipase C-gamma inhibitor U73122, but not extracellular Ca(2+) chelator EGTA. Furthermore, after transfection of dominant-negative mutant PYK2 plasmid, the chemotaxis upon CKLF1 was significantly attenuated in SH-SY5Y cells. Concluding, CKLF1 stimulates the migration of SH-SY5Y cells dose-dependently by activating non-extracellular Ca(2+)-dependent tyrosine kinases pathway and inducing actin polymerization.
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Affiliation(s)
- Zhen-Zhen Wang
- Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, PR China
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21
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Morihata H, Kawawaki J, Okina M, Sakai H, Notomi T, Sawada M, Kuno M. Early and late activation of the voltage-gated proton channel during lactic acidosis through pH-dependent and -independent mechanisms. Pflugers Arch 2007; 455:829-38. [PMID: 17876602 DOI: 10.1007/s00424-007-0339-7] [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: 06/10/2007] [Accepted: 08/27/2007] [Indexed: 11/25/2022]
Abstract
Voltage-gated proton (H+) channels play a pivotal role in compensating charge and pH imbalances during respiratory bursts in phagocytes. Lactic acidosis is a clinically important metabolic condition accompanying various tissue disorders in which the extracellular pH and the intracellular pH often change in parallel. In this study, we investigated the responses of the H+ channel in microglia to lactate-induced pH disturbances using the perforated-patch recordings. Na-lactate (pH 6.8) acidified the cells and activated the H+ channel within 5 min. This early activation was correlated with increases in the pH gradient across the plasma membrane (DeltapH) and was dose-dependent over a concentration range of 10-150 mM. At 10 mM, the change in DeltapH was only slight, but the H+ currents continued to increase over an hour after the cell acidosis was stabilized. Prolonged exposure to lactate (10-20 mM, >1 h) increased the amplitude by two to threefold. The late activation was not explained by increased DeltapH but by changes in the property of the channel per se. Pretreatment with staurosporine and chelerythrine, inhibitors for protein kinase C, prevented the late activation. These results suggest that the H+ channel could be activated greatly during long-lasting lactic acidosis through both DeltapH-dependent and -independent mechanisms.
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Affiliation(s)
- Hirokazu Morihata
- Department of Physiology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, 545-8585, Japan
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22
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Ngu EM, Sahley CL, Muller KJ. Reduced axon sprouting after treatment that diminishes microglia accumulation at lesions in the leech CNS. J Comp Neurol 2007; 503:101-9. [PMID: 17480028 DOI: 10.1002/cne.21386] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The role of mammalian microglia in central nervous system (CNS) repair is controversial. Microglia accumulate at lesions where they act as immune cells and phagocytize debris, and they may secrete neurotrophins, but they also produce molecules that can be cytotoxic, like nitric oxide (NO). To determine the importance of microglial accumulation at lesions on growth of severed CNS axons in the leech (Hirudo medicinalis), in which axon and synapse regeneration are notably successful even when isolated in tissue culture medium, microglial migration to lesions was reduced. Pressure (P) sensory neurons were injected with biocytin to reveal the extent of their sprouting 24 hours after lesioning. To reduce microglia accumulation at lesions, cords were treated for 3.5 hours with 3 mM ATP or 2 mM N(omega)-nitro-L-arginine methyl ester (L-NAME) or 50 microM Reactive blue-2 (RB2) beginning 30 minutes before injury. Lesioned controls were either not treated with drug or treated 3 hours later with one of the drugs, after the migration and subsequent accumulation of most microglia had occurred, but before the onset of axon sprouting, for a total of seven separate conditions. There was a significant reduction in total sprout lengths compared with controls when microglial accumulation was reduced. The results suggest that microglial cells are necessary for the usual sprouting of injured axons.
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Affiliation(s)
- Emmanuel Mbaku Ngu
- Department of Physiology & Biophysics, University of Miami School of Medicine, Miami, FL 33136, USA.
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23
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Christensen RN, Ha BK, Sun F, Bresnahan JC, Beattie MS. Kainate induces rapid redistribution of the actin cytoskeleton in ameboid microglia. J Neurosci Res 2006; 84:170-81. [PMID: 16625662 DOI: 10.1002/jnr.20865] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Microglia are key mediators of the immune response in the central nervous system (CNS). They are closely related to macrophages and undergo dramatic morphological and functional changes after CNS trauma or excitotoxic lesions. Microglia can be directly stimulated by excitatory neurotransmitters and are known to express many neurotransmitter receptors. The role of these receptors, however, is not clear. This study describes the microglial response to the glutamate receptor agonist kainate (KA) and shows via immunochemistry that the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-type glutamate receptor subunit GluR1 is present on cultured microglia. In the presence of 100 microM or 1 mM KA, cultured microglia underwent dramatic morphological and cytoskeletal changes as observed by time-lapse photography and quantitative confocal analysis of phalloidin labeling. KA-stimulated microglia showed condensation of cytoplasmic actin filaments, rapid de- and repolymerization, and cytoplasmic redistribution of condensed actin bundles. Rearrangement of actin filaments-thought to be involved in locomotion and phagocytosis and to indicate an increased level of activation (for reviews see Greenberg [ 1995] Trends Cell Biol. 5:93-99; Imai and Kohsaka [ 2002] Glia 40:164-174)-was significantly increased in treated vs. control cultures. Morphological plasticity and membrane ruffling were also seen. These findings suggest direct microglial excitation via glutamate receptor pathways. Thus, neurotransmitter release after brain or spinal cord injury might directly modulate the inflammatory response.
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Godbout C, Frenette J. Periodic direct current does not promote wound closure in an in vitro dynamic model of cell migration. Phys Ther 2006; 86:50-9; discussion 59-65. [PMID: 16386062 DOI: 10.1093/ptj/86.1.50] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND AND PURPOSE A prevailing paradigm is that electrical fields can promote cell migration and tissue healing. To further validate this paradigm, we tested the hypothesis that periodic direct current (DC) can enhance wound closure using an in vitro dynamic model of cell migration. METHODS AND RESULTS Layers of primary fibroblasts were wounded and treated with DC under various voltages. Repair area, cell velocity, and directionality as well as lamellipodium area were evaluated at different times. Direct current had no beneficial effect on cell migration. Moreover, prolonged stimulation under the highest voltage led to significant reduction in wound closure and cell velocity. The reduction of membrane protusions in stimulated cells may be associated with the deleterious effect of DC. DISCUSSION AND CONCLUSION Contrary to the authors' expectations, they found that periodic DC did not promote wound closure, a finding that emphasizes the need to clarify the complex effects of electrical fields on migrating cells.
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Affiliation(s)
- Charles Godbout
- Department of Rehabilitation, Laval University, Quebec City, Canada G1V 4G2
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25
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Stock C, Gassner B, Hauck CR, Arnold H, Mally S, Eble JA, Dieterich P, Schwab A. Migration of human melanoma cells depends on extracellular pH and Na+/H+ exchange. J Physiol 2005; 567:225-38. [PMID: 15946960 PMCID: PMC1474168 DOI: 10.1113/jphysiol.2005.088344] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Their glycolytic metabolism imposes an increased acid load upon tumour cells. The surplus protons are extruded by the Na+/H+ exchanger (NHE) which causes an extracellular acidification. It is not yet known by what mechanism extracellular pH (pHe) and NHE activity affect tumour cell migration and thus metastasis. We studied the impact of pHe and NHE activity on the motility of human melanoma (MV3) cells. Cells were seeded on/in collagen I matrices. Migration was monitored employing time lapse video microscopy and then quantified as the movement of the cell centre. Intracellular pH (pHi) was measured fluorometrically. Cell-matrix interactions were tested in cell adhesion assays and by the displacement of microbeads inside a collagen matrix. Migration depended on the integrin alpha2beta1. Cells reached their maximum motility at pHe approximately 7.0. They hardly migrated at pHe 6.6 or 7.5, when NHE was inhibited, or when NHE activity was stimulated by loading cells with propionic acid. These procedures also caused characteristic changes in cell morphology and pHi. The changes in pHi, however, did not account for the changes in morphology and migratory behaviour. Migration and morphology more likely correlate with the strength of cell-matrix interactions. Adhesion was the strongest at pHe 6.6. It weakened at basic pHe, upon NHE inhibition, or upon blockage of the integrin alpha2beta1. We propose that pHe and NHE activity affect migration of human melanoma cells by modulating cell-matrix interactions. Migration is hindered when the interaction is too strong (acidic pHe) or too weak (alkaline pHe or NHE inhibition).
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Affiliation(s)
- Christian Stock
- Institute of Physiology II, University of Münster, Robert-Koch-Str.27b, D-48149 Münster, Germany.
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26
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Persson M, Brantefjord M, Hansson E, Rönnbäck L. Lipopolysaccharide increases microglial GLT-1 expression and glutamate uptake capacity in vitro by a mechanism dependent on TNF-α. Glia 2005; 51:111-20. [PMID: 15789431 DOI: 10.1002/glia.20191] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
This study investigates the effect of microglial activation on microglial glutamate transporters in vitro. Stimuli known to activate microglia and/or to be associated with pathological conditions with an impaired astroglial glutamate uptake were compared. Morphological changes and marked increases in ED1 antigen expression were found after 8-h incubation of rat microglia in 56 mM KCl, 1 ng/ml lipopolysaccharide (LPS), and 100 microM glutamate, as well as in acidic and basic conditions, showing that the cells were activated. Of the stimuli used, only LPS induced a significant release of the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), and was the only stimulus that increased microglial GLT-1 expression and glutamate uptake capacity after 12-h incubation. This effect was probably mediated by TNF-alpha, since this cytokine mimicked the effect of LPS. Furthermore, the effect of LPS was blocked by thalidomide, an inhibitor of TNF-alpha synthesis. Additionally, neutralizing antibodies against TNF-alpha also blocked the increase, indicating TNF-alpha as an inducer of GLT-1 expression in microglia. It was also found that preincubation with glutamate dose-dependently inhibited the microglial glutamate uptake. This could suggest different physiological functions for microglial and astroglial glutamate uptake and might indicate a reciprocal control of GLT-1 expression between microglia and astrocytes.
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Affiliation(s)
- Mikael Persson
- Institute of Clinical Neuroscience, Göteborg University, Göteborg, Sweden.
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27
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Pyza E, Borycz J, Giebultowicz JM, Meinertzhagen IA. Involvement of V-ATPase in the regulation of cell size in the fly's visual system. JOURNAL OF INSECT PHYSIOLOGY 2004; 50:985-994. [PMID: 15607501 DOI: 10.1016/j.jinsphys.2004.08.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2003] [Revised: 08/06/2004] [Accepted: 08/06/2004] [Indexed: 05/24/2023]
Abstract
In the fly's visual system, two classes of lamina interneuron, L1 and L2, cyclically change both their size and shape in a rhythm that is circadian. Several neurotransmitters and the lamina's glial cells are known to be involved in regulating these rhythms. Moreover, vacuolar-type H+-ATPase (V-ATPase) in the optic lobe is thought also to participate in such regulation. We have detected V-ATPase-like immunoreactivity in the heads of both Drosophilla melanogaster and Musca domestica using antibodies raised against either the B- or H-subunits of V-ATPase from D. melanogaster or against the B-subunit from two other insect species Culex quinquefasciatus and Manduca sexta. In the visual systems of both fly species V-ATPase was localized immunocytochemically to the compound eye photoreceptors. In D. melanogaster immunoreactivity oscillated during the day and night and under constant darkness the signal was stronger during the subjective night than the subjective day. In turn, blocking V-ATPase by injecting a V-ATPase blocker, bafilomycin, in M. domestica increased the axon sizes of L1 and L2, but only when bafilomycin was applied during the night. As a result bafilomycin abolished the day/night difference in axon size in L1 and L2, their sizes being similar during the day and night.
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Affiliation(s)
- E Pyza
- Department of Cytology and Histology, Institute of Zoology, Jagiellonian University, Ingardena 6, 30-060 Kraków, Poland.
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28
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Sánchez-López A, Cuadros MA, Calvente R, Tassi M, Marín-Teva JL, Navascués J. Radial migration of developing microglial cells in quail retina: A confocal microscopy study. Glia 2004; 46:261-73. [PMID: 15048849 DOI: 10.1002/glia.20007] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Microglial cells spread within the nervous system by tangential and radial migration. The cellular mechanism of tangential migration of microglia has been described in the quail retina but the mechanism of their radial migration has not been studied. In this work, we clarify some aspects of this mechanism by analyzing morphological features of microglial cells at different steps of their radial migration in the quail retina. Microglial cells migrate in the vitreal half of the retina by successive jumps from the vitreal border to progressively more scleral levels located at the vitreal border, intermediate regions, and scleral border of the inner plexiform layer (IPL). The cellular mechanism used for each jump consists of the emission of a leading thin radial process that ramifies at a more scleral level before retraction of the rear of the cell. Hence, radial migration and ramification of microglial cells are simultaneous events. Once at the scleral border of the IPL, microglial cells migrate through the inner nuclear layer to the outer plexiform layer by another mechanism: they retract cell processes, become round, and squeeze through neuronal bodies. Microglial cells use radial processes of s-laminin-expressing Müller cells as substratum for radial migration. Levels where microglial cells stop and ramify at each jump are always interfaces between retinal strata with strong tenascin immunostaining and strata showing weak or no tenascin immunoreactivity. When microglial cell radial migration ends, tenascin immunostaining is no longer present in the retina. These findings suggest that tenascin plays a role in the stopping and ramification of radially migrating microglial cells.
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Affiliation(s)
- Ana Sánchez-López
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, Granada, Spain
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29
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Okada M, Irie S, Sawada M, Urae R, Urae A, Iwata N, Ozaki N, Akazawa K, Nakanishi H. Pepstatin A induces extracellular acidification distinct from aspartic protease inhibition in microglial cell lines. Glia 2003; 43:167-74. [PMID: 12838508 DOI: 10.1002/glia.10237] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The extrusion of protons is considered a very general parameter of the activation of many kinds of membrane or intracellular molecules, such as receptors, ion channels, and enzymes. We found that pepstatin A caused a reproducible, concentration-related increase in the extracellular acidification rate in two microglial cell lines, Ra2 and 6-3. Washing abolished pepstatin A-induced acidification immediately. However, pepstatin A did not cause the extracellular acidification in other cell types, such as CHO, C6 glioma, and NIH3T3 cells. These observations strongly suggest that pepstatin A interacts with certain membrane proteins specific to both Ra2 and 6-3 cells from outside. N-methylmaleimide and N,N'-dicyclohexylcarbodiimide, inhibitors of H(+)-ATPase, were found to reduce pepstatin A-induced response strongly, while bafilomycin A1, a vacuolar H(+)-ATPase inhibitor, vanadate, a P-type H(+)-ATPase inhibitor, and NaN3, an F1 ATPase inhibitor, virtually did not. 5-(N-ethyl-N-isopropyl) amiloride, an inhibitor of Na(+)/H(+) exchanger isoform 1, greatly enhanced pepstatin-induced response, while amiloride did not. Zn(2+), a voltage-dependent proton channel blocker, did not affect pepstatin-induced response neither. Staurosporine, a nonspecific inhibitor of protein kinase C, inhibited pepstatin A-induced response, while chelerythrine, more selective inhibitor of protein kinase C, greatly enhanced it. H-7 and H-8 did not affected the response. These findings suggest that pepstatin A induces extracellular acidification in microglia cell lines, Ra2 and 6-3, through an N-methylmaleimide- and N,N'-dicyclohexylcarbodiimide-sensitive, but bafilomycin A1-insensitive, ATPase, which seems to be distinct from protein kinase C-dependent process.
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Affiliation(s)
- Mitsuko Okada
- Laboratory of Molecular and Cellular Neurogenetics, LTA Medical Corporation, Fukuoka, Japan.
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30
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Benedetti CE, Kobarg J, Pertinhez TA, Gatti RM, de Souza ON, Spisni A, Meneghini R. Plasmodium falciparum histidine-rich protein II binds to actin, phosphatidylinositol 4,5-bisphosphate and erythrocyte ghosts in a pH-dependent manner and undergoes coil-to-helix transitions in anionic micelles. Mol Biochem Parasitol 2003; 128:157-66. [PMID: 12742582 DOI: 10.1016/s0166-6851(03)00057-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The recombinant histidine-rich protein II (HRPII) from Plasmodium falciparum was shown to bind actin and phosphatidylinositol 4,5-bisphosphate (PIP(2)) in vitro in a pH-dependent manner, very similar to hisactophilin, an actin-binding protein from ameba. Binding of HRPII to actin and PIP(2) occurred at pH 6.0 and 6.5, but not above pH 7.0. Circular dichroism (CD) spectroscopy confirmed that HRPII interacts with actin at pH below 7.0, as judged by the changes induced in the secondary structure of the HRPII/actin mixture. Further CD analysis demonstrated that HRPII adopts a predominantly alpha-helical conformation with anionic micelles of PIP(2) and SDS, but not with neutral micelles of phosphatidylcholine (PC), a feature that is common to many actin-binding proteins involved in cytoskeleton remodeling. Similarly to hisactophilin, a GFP-HRPII fusion protein shuttled from the cytoplasm to the nucleus of HeLa cells as the cellular pH was lowered from 8.0 to 6.0. HeLa cells transfected with the HRPII gene showed increased levels of histidine-rich proteins (HRPs) in the soluble cell fraction at pH 8.0. At pH 6.0, however, HRPs were detected mainly in the insoluble cell fraction. Interestingly, we found that HRPII binds to human erythrocyte membranes at pH 6.0 and 6.5 but not at pH above 7.0. Our results point to remarkable similarities between HRPII, hisactophilin, and actin-binding proteins. Possible roles of the HRPII during Plasmodium infection are discussed in the light of these findings.
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Affiliation(s)
- Celso Eduardo Benedetti
- Centro de Biologia Molecular Estrutural (CEBIME), Laboratório Nacional de Luz Sincrotron (LNLS), CP6192, Campinas, SP CEP 13084-971, Brazil.
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Microglia-Müller glia cell interactions control neurotrophic factor production during light-induced retinal degeneration. J Neurosci 2002. [PMID: 12417648 DOI: 10.1523/jneurosci.22-21-09228.2002] [Citation(s) in RCA: 270] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Activation of microglia commonly occurs in response to a wide variety of pathological stimuli including trauma, axotomy, ischemia, and degeneration in the CNS. In the retina, prolonged or high-intensity exposure to visible light leads to photoreceptor cell apoptosis. In such a light-reared retina, we found that activated microglia invade the degenerating photoreceptor layer and alter expression of neurotrophic factors such as nerve growth factor (NGF), ciliary neurotrophic factor (CNTF), and glial cell line-derived neurotrophic factor (GDNF). Because these neurotrophic factors modulate secondary trophic factor expression in Müller glial cells, microglia-Müller glia cell interaction may contribute to protection of photoreceptors or increase photoreceptor apoptosis. In the present study, we demonstrate the possibility that such functional glia-glia interactions constitute the key mechanism by which microglia-derived NGF, brain-derived neurotrophic factor (BDNF), and CNTF indirectly influence photoreceptor survival, although the receptors for these neurotrophic factors are absent from photoreceptors, by modulating basic fibroblast growth factor (bFGF) and GDNF production and release from Müller glia. These observations suggest that microglia regulate the microglia-Müller glia-photoreceptor network that serves as a trophic factor-controlling system during retinal degeneration.
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Rezaie P, Trillo-Pazos G, Greenwood J, Everall IP, Male DK. Motility and ramification of human fetal microglia in culture: an investigation using time-lapse video microscopy and image analysis. Exp Cell Res 2002; 274:68-82. [PMID: 11855858 DOI: 10.1006/excr.2001.5431] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Microglia are mononuclear phagocytes of the central nervous system and are considered to derive from circulating bone marrow progenitors that colonize the developing human nervous system in the second trimester. They first appear as ameboid forms and progressively differentiate to process-bearing "ramified" forms with maturation. Signals driving this transformation are known to be partly derived from astrocytes. In this investigation we have used cocultures of astrocytes and microglia to demonstrate the relationship between motility and morphology of microglia associated with signals derived from astrocytes. Analysis of progressive cultures using time-lapse video microscopy clearly demonstrates the dynamic nature of microglia. We observe that ameboid microglial cells progressively ramify when cocultured with astrocytes, mirroring the "differentiation" of microglia in situ during development. We further demonstrate that individual cells undergo morphological transformations from "ramified" to "bipolar" to "tripolar" and "ameboid" states in accordance with local environmental cues associated with astrocytes in subconfluent cultures. Remarkably, cells are still capable of migration at velocities of 20-35 microm/h in a fully ramified state overlying confluent astrocytes, as determined by image analysis of motility. This is in keeping with the capacity of microglia for a rapid response to inflammatory cues in the CNS. We also demonstrate selective expression of the chemokines MIP-1alpha and MCP-1 by confluent human fetal astrocytes in cocultures and propose a role for these chemotactic cytokines as regulators of microglial motility and differentiation. The interchangeable morphological continuum of microglia supports the view that these cells represent a single heterogeneous population of resident mononuclear phagocytes capable of marked plasticity.
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Affiliation(s)
- P Rezaie
- Department of Neuropathology, Institute of Psychiatry, King's College London, DeCrespigny Park, London, SE5 8AF, United Kingdom.
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Abstract
Microglia, macrophages that reside in the brain, can express at least 12 different ion channels, including voltage-gated proton channels. The properties of H+ currents in microglia are similar to those in other phagocytes. Proton currents are elicited by depolarizing the membrane potential, but activation also depends strongly on both intracellular pH (pH(i)) and extracellular pH (pH(o)). Increasing pH(o) or lowering pH(i) promotes H+ channel opening by shifting the activation threshold to more negative potentials. H+ channels in microglia open only when the pH gradient is outward, so they carry only outward current in the steady state. Time-dependent activation of H+ currents is slow, with a time constant roughly 1 s at room temperature. Microglial H+ currents are inhibited by inorganic polyvalent cations, which reduce H+ current amplitude and shift the voltage dependence of activation to more positive potentials. Cytoskeletal disruptive agents modulate H+ currents in microglia. Cytochalasin D and colchicine decrease the current density and slow the activation of H+ currents. Similar changes of H+ currents, possibly due to cytoskeletal reorganization, occur in microglia during the transformation from ameboid to ramified morphology. Phagocytes, including microglia, undergo a respiratory burst, in which NADPH oxidase releases bactericidal superoxide anions into the phagosome and stoichiometrically releases protons into the cell, tending to depolarize and acidify the cell. H+ currents may help regulate both the membrane potential and pH(i) during the respiratory burst. By compensating for the efflux of electrons and counteracting intracellular acidification, H+ channels help maintain superoxide anion production.
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Affiliation(s)
- C Eder
- Institut für Physiologie der Charité, Humboldt Universität, Tucholskystr. 2, D 10117 Berlin, Germany.
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