1
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Long D, Mao C, Huang Y, Xu Y, Zhu Y. Ferroptosis in ulcerative colitis: Potential mechanisms and promising therapeutic targets. Biomed Pharmacother 2024; 175:116722. [PMID: 38729051 DOI: 10.1016/j.biopha.2024.116722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 05/01/2024] [Accepted: 05/06/2024] [Indexed: 05/12/2024] Open
Abstract
Ulcerative colitis (UC) is a complex immune-mediated chronic inflammatory bowel disease. It is mainly characterized by diffuse inflammation of the colonic and rectal mucosa with barrier function impairment. Identifying new biomarkers for the development of more effective UC therapies remains a pressing task for current research. Ferroptosis is a newly identified form of regulated cell death characterized by iron-dependent lipid peroxidation. As research deepens, ferroptosis has been demonstrated to be involved in the pathological processes of numerous diseases. A growing body of evidence suggests that the pathogenesis of UC is associated with ferroptosis, and the regulation of ferroptosis provides new opportunities for UC treatment. However, the specific mechanisms by which ferroptosis participates in the development of UC remain to be more fully and thoroughly investigated. Therefore, in this review, we focus on the research advances in the mechanism of ferroptosis in recent years and describe the potential role of ferroptosis in the pathogenesis of UC. In addition, we explore the underlying role of the crosslinked pathway between ferroptosis and other mechanisms such as macrophages, neutrophils, autophagy, endoplasmic reticulum stress, and gut microbiota in UC. Finally, we also summarize the potential compounds that may act as ferroptosis inhibitors in UC in the future.
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Affiliation(s)
- Dan Long
- The First Hospital of Hunan University of Chinese Medicine, Changsha, Hunan, China
| | - Chenhan Mao
- Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Yingtao Huang
- The First Clinical Medical College, Liaoning University of Traditional Chinese Medicine, Shenyang, Liaoning, China
| | - Yin Xu
- The First Hospital of Hunan University of Chinese Medicine, Changsha, Hunan, China.
| | - Ying Zhu
- The First Hospital of Hunan University of Chinese Medicine, Changsha, Hunan, China.
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2
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Zhong R, Rua MT, Wei-LaPierre L. Targeting mitochondrial Ca 2+ uptake for the treatment of amyotrophic lateral sclerosis. J Physiol 2024; 602:1519-1549. [PMID: 38010626 PMCID: PMC11032238 DOI: 10.1113/jp284143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 10/31/2023] [Indexed: 11/29/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a rare adult-onset neurodegenerative disease characterized by progressive motor neuron (MN) loss, muscle denervation and paralysis. Over the past several decades, researchers have made tremendous efforts to understand the pathogenic mechanisms underpinning ALS, with much yet to be resolved. ALS is described as a non-cell autonomous condition with pathology detected in both MNs and non-neuronal cells, such as glial cells and skeletal muscle. Studies in ALS patient and animal models reveal ubiquitous abnormalities in mitochondrial structure and function, and disturbance of intracellular calcium homeostasis in various tissue types, suggesting a pivotal role of aberrant mitochondrial calcium uptake and dysfunctional calcium signalling cascades in ALS pathogenesis. Calcium signalling and mitochondrial dysfunction are intricately related to the manifestation of cell death contributing to MN loss and skeletal muscle dysfunction. In this review, we discuss the potential contribution of intracellular calcium signalling, particularly mitochondrial calcium uptake, in ALS pathogenesis. Functional consequences of excessive mitochondrial calcium uptake and possible therapeutic strategies targeting mitochondrial calcium uptake or the mitochondrial calcium uniporter, the main channel mediating mitochondrial calcium influx, are also discussed.
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Affiliation(s)
- Renjia Zhong
- Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, 32611
- Department of Emergency Medicine, the First Affiliated Hospital of China Medical University, Shenyang, Liaoning, China, 110001
| | - Michael T. Rua
- Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, 32611
| | - Lan Wei-LaPierre
- Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, 32611
- Myology Institute, University of Florida, Gainesville, FL 32611
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3
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Izquierdo P, Jolivet RB, Attwell D, Madry C. Amyloid plaques and normal ageing have differential effects on microglial Ca 2+ activity in the mouse brain. Pflugers Arch 2024; 476:257-270. [PMID: 37966547 PMCID: PMC10791787 DOI: 10.1007/s00424-023-02871-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 10/02/2023] [Accepted: 10/24/2023] [Indexed: 11/16/2023]
Abstract
In microglia, changes in intracellular calcium concentration ([Ca2+]i) may regulate process motility, inflammasome activation, and phagocytosis. However, while neurons and astrocytes exhibit frequent spontaneous Ca2+ activity, microglial Ca2+ signals are much rarer and poorly understood. Here, we studied [Ca2+]i changes of microglia in acute brain slices using Fluo-4-loaded cells and mice expressing GCaMP5g in microglia. Spontaneous Ca2+ transients occurred ~ 5 times more frequently in individual microglial processes than in their somata. We assessed whether microglial Ca2+ responses change in Alzheimer's disease (AD) using AppNL-G-F knock-in mice. Proximity to Aβ plaques strongly affected microglial Ca2+ activity. Although spontaneous Ca2+ transients were unaffected in microglial processes, they were fivefold more frequent in microglial somata near Aβ plaques than in wild-type microglia. Microglia away from Aβ plaques in AD mice showed intermediate properties for morphology and Ca2+ responses, partly resembling those of wild-type microglia. By contrast, somatic Ca2+ responses evoked by tissue damage were less intense in microglia near Aβ plaques than in wild-type microglia, suggesting different mechanisms underlying spontaneous vs. damage-evoked Ca2+ signals. Finally, as similar processes occur in neurodegeneration and old age, we studied whether ageing affected microglial [Ca2+]i. Somatic damage-evoked Ca2+ responses were greatly reduced in microglia from old mice, as in the AD mice. In contrast to AD, however, old age did not alter the occurrence of spontaneous Ca2+ signals in microglial somata but reduced the rate of events in processes. Thus, we demonstrate distinct compartmentalised Ca2+ activity in microglia from healthy, aged and AD-like brains.
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Affiliation(s)
- Pablo Izquierdo
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, UK
| | - Renaud B Jolivet
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, UK
- Maastricht Centre for Systems Biology (MaCSBio), Maastricht University, Paul-Henri Spaaklaan 1, 6229 EN, Maastricht, The Netherlands
| | - David Attwell
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, UK.
| | - Christian Madry
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, UK.
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt Universität Zu Berlin, Institute of Neurophysiology, 10117, Berlin, Germany.
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4
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Feng L, Lo H, Hong Z, Zheng J, Yan Y, Ye Z, Chen X, Pan X. Microglial LRRK2-mediated NFATc1 attenuates α-synuclein immunotoxicity in association with CX3CR1-induced migration and the lysosome-initiated degradation. Glia 2023; 71:2266-2284. [PMID: 37300531 DOI: 10.1002/glia.24422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 04/22/2023] [Accepted: 05/22/2023] [Indexed: 06/12/2023]
Abstract
Synucleinopathies refer to a range of neurodegenerative diseases caused by abnormal α-synuclein (α-Syn) deposition, including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). Their pathogenesis is strongly linked to microglial dysfunction and neuroinflammation, which involves the leucine-rich-repeat kinase 2 (LRRK2)-regulated nuclear factor of activated T-cells (NFAT). Of the NFAT family, NFATc1 has been found to be increasingly translocated into the nucleus in α-syn stimulation. However, the specific role of NFATc1-mediated intracellular signaling in PD remains elusive in regulating microglial functions. In the current study, we crossbred LRRK2 or NFATc1 conditional knockout mice with Lyz2Cre mice to generate mice with microglia-specific deletion of LRRK2 or NFATc1, and by stereotactic injection of fibrillary α-Syn, we generated PD models in these mice. We found that LRRK2 deficiency enhanced microglial phagocytosis in the mice after α-Syn exposure and that genetic inhibition of NFATc1 markedly diminished phagocytosis and α-Syn elimination. We further demonstrated that LRRK2 negatively regulated NFATc1 in α-Syn-treated microglia, in which microglial LRRK2-deficiency facilitated NFATc1 nuclear translocation, CX3CR1 upregulation, and microglia migration. Additionally, NFATc1 translocation upregulated the expression of Rab7 and promoted the formation of late lysosomes, resulting in α-Syn degradation. In contrast, the microglial NFATc1 deficiency impaired CX3CR1 upregulation and the formation of Rab7-mediated late lysosomes. These findings highlight the critical role of NFATc1 in modulating microglial migration and phagocytosis, in which the LRRK2-NFATc1 signaling pathway regulates the expression of microglial CX3CR1 and endocytic degradative Rab7 to attenuate α-synuclein immunotoxicity.
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Affiliation(s)
- Linjuan Feng
- Department of Neurology, Center for Cognitive Neurology, Fujian Medical University Union Hospital, Fuzhou, China
- Fujian Institute of Geriatrics, Fujian Medical University Union Hospital, Fuzhou, China
- Institute of Clinical Neurology, Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Molecular Neurology, Fujian Medical University, Fuzhou, China
| | - Hsuan Lo
- Guangdong Cardiovascular Institute, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Zhaoxiang Hong
- Department of Neurology, Center for Cognitive Neurology, Fujian Medical University Union Hospital, Fuzhou, China
- Fujian Institute of Geriatrics, Fujian Medical University Union Hospital, Fuzhou, China
- Department of Neurology, The University of HongKong Shenzhen Hospital, Shenzhen, Guangdong, China
| | - Jiahao Zheng
- Department of Neurology, Center for Cognitive Neurology, Fujian Medical University Union Hospital, Fuzhou, China
- Fujian Institute of Geriatrics, Fujian Medical University Union Hospital, Fuzhou, China
- Institute of Clinical Neurology, Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Molecular Neurology, Fujian Medical University, Fuzhou, China
| | - Yuhong Yan
- Department of Neurology, Center for Cognitive Neurology, Fujian Medical University Union Hospital, Fuzhou, China
- Fujian Institute of Geriatrics, Fujian Medical University Union Hospital, Fuzhou, China
- Institute of Clinical Neurology, Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Molecular Neurology, Fujian Medical University, Fuzhou, China
| | - Zucheng Ye
- Key Laboratory of Brain Aging and Neurodegenerative Diseases, Fujian Medical University, Fuzhou, China
| | - Xiaochun Chen
- Department of Neurology, Center for Cognitive Neurology, Fujian Medical University Union Hospital, Fuzhou, China
- Institute of Clinical Neurology, Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Molecular Neurology, Fujian Medical University, Fuzhou, China
| | - Xiaodong Pan
- Department of Neurology, Center for Cognitive Neurology, Fujian Medical University Union Hospital, Fuzhou, China
- Fujian Institute of Geriatrics, Fujian Medical University Union Hospital, Fuzhou, China
- Institute of Clinical Neurology, Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Molecular Neurology, Fujian Medical University, Fuzhou, China
- Key Laboratory of Brain Aging and Neurodegenerative Diseases, Fujian Medical University, Fuzhou, China
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5
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Tsujikawa S, DeMeulenaere KE, Centeno MV, Ghazisaeidi S, Martin ME, Tapies MR, Maneshi MM, Yamashita M, Stauderman KA, Apkarian AV, Salter MW, Prakriya M. Regulation of neuropathic pain by microglial Orai1 channels. SCIENCE ADVANCES 2023; 9:eade7002. [PMID: 36706180 PMCID: PMC9883051 DOI: 10.1126/sciadv.ade7002] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 12/23/2022] [Indexed: 06/01/2023]
Abstract
Microglia are important mediators of neuroinflammation, which underlies neuropathic pain. However, the molecular checkpoints controlling microglial reactivity are not well-understood. Here, we investigated the role of Orai1 channels for microglia-mediated neuroinflammation following nerve injury and find that deletion of Orai1 in microglia attenuates Ca2+ signaling and the production of inflammatory cytokines by proalgesic agonists. Conditional deletion of Orai1 attenuated microglial proliferation in the dorsal horn, spinal cytokine levels, and potentiation of excitatory neurotransmission following peripheral nerve injury. These cellular effects were accompanied by mitigation of pain hyperalgesia in microglial Orai1 knockout mice. A small-molecule Orai1 inhibitor, CM4620, similarly mitigated allodynia in male mice. Unexpectedly, these protective effects were not seen in female mice, revealing sexual dimorphism in Orai1 regulation of microglial reactivity and hyperalgesia. Together, these findings indicate that Orai1 channels are key regulators of the sexually dimorphic role of microglia for the neuroinflammation that underlies neuropathic pain.
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Affiliation(s)
- Shogo Tsujikawa
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Kaitlyn E. DeMeulenaere
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Maria V. Centeno
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | | | - Megan E. Martin
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Martinna R. Tapies
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Mohammad M. Maneshi
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Megumi Yamashita
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | | | - Apkar V. Apkarian
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | | | - Murali Prakriya
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
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6
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Zhu T, Guo J, Wu Y, Lei T, Zhu J, Chen H, Kala S, Wong KF, Cheung CP, Huang X, Zhao X, Yang M, Sun L. The mechanosensitive ion channel Piezo1 modulates the migration and immune response of microglia. iScience 2023; 26:105993. [PMID: 36798430 PMCID: PMC9926228 DOI: 10.1016/j.isci.2023.105993] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 11/28/2022] [Accepted: 01/12/2023] [Indexed: 01/19/2023] Open
Abstract
Microglia are the brain's resident immune cells, performing surveillance to promote homeostasis and healthy functioning. While microglial chemical signaling is well-studied, mechanical cues regulating their function are less well-understood. Here, we investigate the role of the mechanosensitive ion channel Piezo1 in microglia migration, pro-inflammatory cytokine production, and stiffness sensing. In Piezo1 knockout transgenic mice, we demonstrated the functional expression of Piezo1 in microglia and identified genes whose expression was consequently affected. Functional assays revealed that Piezo1 deficiency in microglia enhanced migration toward amyloid β-protein, and decreased levels of pro-inflammatory cytokines produced upon stimulation by lipopolysaccharide, both in vitro and in vivo. The phenomenon could be mimicked or reversed chemically using a Piezo1-specific agonist or antagonist. Finally, we also showed that Piezo1 mediated the effect of substrate stiffness-induced migration and cytokine expression. Altogether, we show that Piezo1 is an important molecular mediator for microglia, its activation modulating microglial migration and immune responses.
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Affiliation(s)
- Ting Zhu
- Department of Biomedical Engineering, the Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR 999077, P. R. China
| | - Jinghui Guo
- Department of Biomedical Engineering, the Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR 999077, P. R. China
| | - Yong Wu
- Department of Biomedical Engineering, the Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR 999077, P. R. China
| | - Ting Lei
- Department of Biomedical Engineering, the Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR 999077, P. R. China
| | - Jiejun Zhu
- Department of Biomedical Engineering, the Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR 999077, P. R. China
| | - Hui Chen
- Biotherapy Centre, the Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China,Cell-gene Therapy Translational Medicine Research Centre, the Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Shashwati Kala
- Department of Biomedical Engineering, the Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR 999077, P. R. China
| | - Kin Fung Wong
- Department of Biomedical Engineering, the Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR 999077, P. R. China
| | - Chi Pong Cheung
- Department of Biomedical Engineering, the Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR 999077, P. R. China
| | - Xiaohui Huang
- Department of Biomedical Engineering, the Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR 999077, P. R. China
| | - Xinyi Zhao
- Department of Biomedical Engineering, the Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR 999077, P. R. China
| | - Minyi Yang
- Department of Biomedical Engineering, the Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR 999077, P. R. China
| | - Lei Sun
- Department of Biomedical Engineering, the Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR 999077, P. R. China,Corresponding author
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7
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Rieder P, Gobbo D, Stopper G, Welle A, Damo E, Kirchhoff F, Scheller A. Astrocytes and Microglia Exhibit Cell-Specific Ca2+ Signaling Dynamics in the Murine Spinal Cord. Front Mol Neurosci 2022; 15:840948. [PMID: 35431801 PMCID: PMC9006623 DOI: 10.3389/fnmol.2022.840948] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 02/22/2022] [Indexed: 12/31/2022] Open
Abstract
The spinal cord is the main pathway connecting brain and peripheral nervous system. Its functionality relies on the orchestrated activity of both neurons and glial cells. To date, most advancement in understanding the spinal cord inner mechanisms has been made either by in vivo exposure of its dorsal surface through laminectomy or by acute ex vivo slice preparation, likely affecting spinal cord physiology in virtue of the necessary extensive manipulation of the spinal cord tissue. This is especially true of cells immediately responding to alterations of the surrounding environment, such as microglia and astrocytes, reacting within seconds or minutes and for up to several days after the original insult. Ca2+ signaling is considered one of the most immediate, versatile, and yet elusive cellular responses of glia. Here, we induced the cell-specific expression of the genetically encoded Ca2+ indicator GCaMP3 to evaluate spontaneous intracellular Ca2+ signaling in astrocytes and microglia. Ca2+ signals were then characterized in acute ex vivo (both gray and white matter) as well as in chronic in vivo (white matter) preparations using MSparkles, a MATLAB-based software for automatic detection and analysis of fluorescence events. As a result, we were able to segregate distinct astroglial and microglial Ca2+ signaling patterns along with method-specific Ca2+ signaling alterations, which must be taken into consideration in the reliable evaluation of any result obtained in physiological as well as pathological conditions. Our study revealed a high degree of Ca2+ signaling diversity in glial cells of the murine spinal cord, thus adding to the current knowledge of the astonishing glial heterogeneity and cell-specific Ca2+ dynamics in non-neuronal networks.
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Affiliation(s)
- Phillip Rieder
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
| | - Davide Gobbo
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
| | - Gebhard Stopper
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
| | - Anna Welle
- Department of Genetics and Epigenetics, University of Saarland, Saarbrücken, Germany
| | - Elisa Damo
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
- Institute of Pharmacology, Medical Faculty Heidelberg, Heidelberg University, Heidelberg, Germany
| | - Frank Kirchhoff
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
| | - Anja Scheller
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
- *Correspondence: Anja Scheller,
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8
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Augusto-Oliveira M, Arrifano GP, Delage CI, Tremblay MÈ, Crespo-Lopez ME, Verkhratsky A. Plasticity of microglia. Biol Rev Camb Philos Soc 2021; 97:217-250. [PMID: 34549510 DOI: 10.1111/brv.12797] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 09/02/2021] [Accepted: 09/06/2021] [Indexed: 02/06/2023]
Abstract
Microglial cells are the scions of foetal macrophages which invade the neural tube early during embryogenesis. The nervous tissue environment instigates the phenotypic metamorphosis of foetal macrophages into idiosyncratic surveilling microglia, which are generally characterised by a small cell body and highly ramified motile processes that constantly scan the nervous tissue for signs of changes in homeostasis and allow microglia to perform crucial homeostatic functions. The surveilling microglial phenotype is evolutionarily conserved from early invertebrates to humans. Despite this evolutionary conservation, microglia show substantial heterogeneity in their gene and protein expression, as well as morphological appearance. These differences are age, region and context specific and reflect a high degree of plasticity underlying the life-long adaptation of microglia, supporting the exceptional adaptive capacity of the central nervous system. Microgliocytes are essential elements of cellular network formation and refinement in the developing nervous tissue. Several distinct patrolling modes of microglial processes contribute to the formation, modification, and pruning of synapses; to the support and protection of neurones through microglial-somatic junctions; and to the control of neuronal and axonal excitability by specific microglia-axonal contacts. In pathology, microglia undergo proliferation and reactive remodelling known as microgliosis, which is context dependent, yet represents an evolutionarily conserved defence response. Microgliosis results in the emergence of multiple disease and context-specific reactive states; in addition, neuropathology is associated with the appearance of specific protective or recovery microglial forms. In summary, the plasticity of microglia supports the development and functional activity of healthy nervous tissue and provides highly sophisticated defences against disease.
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Affiliation(s)
- Marcus Augusto-Oliveira
- Laboratório de Farmacologia Molecular, Instituto de Ciências Biológicas, Universidade Federal do Pará, 66075-110, Belém, Brazil
| | - Gabriela P Arrifano
- Laboratório de Farmacologia Molecular, Instituto de Ciências Biológicas, Universidade Federal do Pará, 66075-110, Belém, Brazil
| | - Charlotte Isabelle Delage
- Division of Medical Sciences, Medical Sciences Building, University of Victoria, Victoria, BC, V8P 5C2, Canada
| | - Marie-Ève Tremblay
- Division of Medical Sciences, Medical Sciences Building, University of Victoria, Victoria, BC, V8P 5C2, Canada.,Axe Neurosciences, Centre de Recherche du CHU de Québec-Université Laval, 2705 Boulevard Laurier, Québec City, QC, G1V 4G2, Canada.,Neurology and Neurosurgery Department, McGill University, 3801 University Street, Montreal, QC, H3A 2B4, Canada.,Department of Molecular Medicine, Université Laval, Pavillon Ferdinand-Vandry, Bureau 4835, 1050 Avenue de la Médecine, Québec City, QC, G1V 0A6, Canada.,Department of Biochemistry and Molecular Biology, The University of British Columbia, Life Sciences Center, 2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Maria Elena Crespo-Lopez
- Laboratório de Farmacologia Molecular, Instituto de Ciências Biológicas, Universidade Federal do Pará, 66075-110, Belém, Brazil
| | - Alexei Verkhratsky
- Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PT, U.K.,Achucarro Center for Neuroscience, IKERBASQUE, 48011, Bilbao, Spain.,Department of Stem Cell Biology, State Research Institute Centre for Innovative Medicine, LT-01102, Vilnius, Lithuania
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9
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Effects of Metformin on Spontaneous Ca 2+ Signals in Cultured Microglia Cells under Normoxic and Hypoxic Conditions. Int J Mol Sci 2021; 22:ijms22179493. [PMID: 34502402 PMCID: PMC8430509 DOI: 10.3390/ijms22179493] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 08/20/2021] [Accepted: 08/28/2021] [Indexed: 12/12/2022] Open
Abstract
Microglial functioning depends on Ca2+ signaling. By using Ca2+ sensitive fluorescence dye, we studied how inhibition of mitochondrial respiration changed spontaneous Ca2+ signals in soma of microglial cells from 5-7-day-old rats grown under normoxic and mild-hypoxic conditions. In microglia under normoxic conditions, metformin or rotenone elevated the rate and the amplitude of Ca2+ signals 10-15 min after drug application. Addition of cyclosporin A, a blocker of mitochondrial permeability transition pore (mPTP), antioxidant trolox, or inositol 1,4,5-trisphosphate receptor (IP3R) blocker caffeine in the presence of rotenone reduced the elevated rate and the amplitude of the signals implying sensitivity to reactive oxygen species (ROS), and involvement of mitochondrial mPTP together with IP3R. Microglial cells exposed to mild hypoxic conditions for 24 h showed elevated rate and increased amplitude of Ca2+ signals. Application of metformin or rotenone but not phenformin before mild hypoxia reduced this elevated rate. Thus, metformin and rotenone had the opposing fast action in normoxia after 10-15 min and the slow action during 24 h mild-hypoxia implying activation of different signaling pathways. The slow action of metformin through inhibition of complex I could stabilize Ca2+ homeostasis after mild hypoxia and could be important for reduction of ischemia-induced microglial activation.
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10
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Mizoguchi Y, Ohgidani M, Haraguchi Y, Murakawa-Hirachi T, Kato TA, Monji A. ProBDNF induces sustained elevation of intracellular Ca 2+ possibly mediated by TRPM7 channels in rodent microglial cells. Glia 2021; 69:1694-1708. [PMID: 33740269 DOI: 10.1002/glia.23996] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 03/03/2021] [Accepted: 03/05/2021] [Indexed: 01/07/2023]
Abstract
Microglia are intrinsic immune cells that release factors including pro- and anti-inflammatory cytokines, nitric oxide (NO) and neurotrophins following activation in the brain. Elevation of intracellular Ca2+ concentration ([Ca2+ ]i) is important for microglial functions, such as the release of cytokines or NO from activated microglia. Brain-derived neurotrophic factor (BDNF) is a neurotrophin well known for its roles in the activation of microglia. Interestingly, proBDNF, the precursor form of mature BDNF, and mature BDNF elicit opposing neuronal responses in the brain. Mature BDNF induces sustained intracellular Ca2+ elevation through the upregulation of the surface expression of TRPC3 channels in rodent microglial cells. In addition, TRPC3 channels are important for the BDNF-induced suppression of NO production in activated microglia. In this study, we observed that proBDNF and mature BDNF have opposite effects on the relative expression of surface p75 neurotrophin receptor (p75NTR ) in rodent microglial cells. ProBDNF induces a sustained elevation of [Ca2+ ]i through binding to the p75NTR , which is possibly mediated by Rac 1 activation and TRPM7 channels in rodent microglial cells. Flow cytometry showed that proBDNF increased the relative surface expression of TRPM7. Although proBDNF did not affect either mRNA expression of pro- and anti-inflammatory cytokines or the phagocytic activity, proBDNF potentiates the generation of NO induced by IFN-γ and TRPM7 channels could be involved in the proBDNF-induced potentiation of IFN-γ-mediated production of NO. We show direct evidence that rodent microglial cells are able to respond to proBDNF, which might be important for the regulation of inflammatory responses in the brain.
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Affiliation(s)
- Yoshito Mizoguchi
- Department of Psychiatry, Faculty of Medicine, Saga University, Saga, Japan
| | - Masahiro Ohgidani
- Department of Psychiatry, Faculty of Medicine, Saga University, Saga, Japan.,Department of Integrative Anatomy, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.,Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | | | | | - Takahiro A Kato
- Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Akira Monji
- Department of Psychiatry, Faculty of Medicine, Saga University, Saga, Japan
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11
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Maksoud MJE, Tellios V, Xiang YY, Lu WY. Nitric oxide displays a biphasic effect on calcium dynamics in microglia. Nitric Oxide 2021; 108:28-39. [PMID: 33418057 DOI: 10.1016/j.niox.2021.01.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 11/11/2020] [Accepted: 01/01/2021] [Indexed: 01/13/2023]
Abstract
Calcium is a critical secondary messenger in microglia. In response to inflammation, microglia mobilize intracellular calcium and increase the expression of inducible nitric oxide synthase (iNOS), which produces nitric oxide (NO). This study set to explore whether NO regulates intracellular calcium dynamics through transient receptor potential (TRP) channels in primary wildtype (WT) and iNOS knockout (iNOS-/-) microglia, and the BV2 microglial cell line using calcium imaging and voltage-clamp recordings. Our results demonstrated that application of the NO-donor SNAP induced a biphasic calcium response in naïve murine microglia. Specifically, phase I was characterized by a rapid decline in calcium influx that was attenuated by pretreatment of the store operated calcium channel (SOCC) inhibitor 2APB, while phase II presented as a slow calcium influx that was abolished by pretreatment with the TRP vanilloid type 2 (TRPV2) channel inhibitor tranilast. Importantly, in the presence of a protein kinase G (PKG) inhibitor, the SNAP-mediated calcium decline in phase I persisted while the calcium influx in phase II was abolished. Application of thapsigargin to activate SOCCs caused a calcium influx through a nonselective cation conductance in BV2 microglia, which was abruptly attenuated by SNAP. Importantly, iNOS-/- microglia displayed a significantly larger calcium influx though SOCCs while expressing less stromal interaction molecule 1, Orai1, and TRP canonical type 1 and 3 mRNA, when compared to WT microglia. Together, these results demonstrate that NO signaling restricts calcium influx through SOCCs independent of PKG signaling and increases calcium influx through TRPV2 channels in a PKG-dependent mechanism in microglia.
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Affiliation(s)
- Matthew J E Maksoud
- Graduate Program of Neuroscience, The University of Western Ontario, Canada; Robarts Research Institute, The University of Western Ontario, Canada.
| | - Vasiliki Tellios
- Graduate Program of Neuroscience, The University of Western Ontario, Canada; Robarts Research Institute, The University of Western Ontario, Canada.
| | - Yun-Yan Xiang
- Robarts Research Institute, The University of Western Ontario, Canada.
| | - Wei-Yang Lu
- Graduate Program of Neuroscience, The University of Western Ontario, Canada; Robarts Research Institute, The University of Western Ontario, Canada; Department of Physiology and Pharmacology, University of Western Ontario, Canada.
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12
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Changes in mitochondrial morphology modulate LPS-induced loss of calcium homeostasis in BV-2 microglial cells. J Bioenerg Biomembr 2021; 53:109-118. [PMID: 33585958 DOI: 10.1007/s10863-021-09878-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 02/05/2021] [Indexed: 12/18/2022]
Abstract
Microglial activation involves both fragmentation of the mitochondrial network and changes in cellular Ca2+ homeostasis, but possible modifications in mitochondrial calcium uptake have never been described in this context. Here we report that activated microglial BV-2 cells have impaired mitochondrial calcium uptake, including lower calcium retention capacity and calcium uptake rates. These changes were not dependent on altered expression of the mitochondrial calcium uniporter. Respiratory capacity and the inner membrane potential, key determinants of mitochondrial calcium uptake, are both decreased in activated microglial BV-2 cells. Modified mitochondrial calcium uptake correlates with impaired cellular calcium signaling, including reduced ER calcium stores, and decreased replenishment by store operated calcium entry (SOCE). Induction of mitochondrial fragmentation through Mfn2 knockdown in control cells mimicked this effect, while inhibiting LPS-induced mitochondrial fragmentation by a dominant negative form of Drp1 prevented it. Overall, our results show that mitochondrial fragmentation induced by LPS promotes altered Ca2+ homeostasis in microglial cells, a new aspect of microglial activation that could be a key feature in the inflammatory role of these cells.
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13
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Nieman AN, Li G, Zahn NM, Mian MY, Mikulsky BN, Hoffman DA, Wilcox TM, Kehoe AS, Luecke IW, Poe MM, Alvarez-Carbonell D, Cook JM, Stafford DC, Arnold LA. Targeting Nitric Oxide Production in Microglia with Novel Imidazodiazepines for Nonsedative Pain Treatment. ACS Chem Neurosci 2020; 11:2019-2030. [PMID: 32511908 PMCID: PMC7380323 DOI: 10.1021/acschemneuro.0c00324] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The goal of this research is the identification of new treatments for neuropathic pain. We characterized the GABAergic system of immortalized mouse and human microglia using electrophysiology and qRT-PCR. Cells from both species exhibited membrane current changes in response to γ-aminobutyric acid, with an EC50 of 260 and 1940 nM, respectively. Human microglia expressed high levels of the γ-aminobutyric acid type A receptor (GABAAR) α3 subunit, which can assemble with β1 and γ2/δ subunits to form functional GABAARs. Mouse microglia contained α2, α3, and α5, in addition to β1-3, γ1-2, and δ, mRNA, enabling a more diverse array of GABAARs than human microglia. Benzodiazepines are well-established modulators of GABAAR activity, prompting a screen of a library of diverse benzodiazepines in microglia for cellular effects. Several active compounds were identified by reduction of nitric oxide (NO) in interferon gamma and lipopolysaccharide activated microglia. However, further investigation with GABAAR antagonists flumazenil, picrotoxin, and bicuculline demonstrated that GABAARs were not linked to the NO response. A screen of 48 receptors identified the κ-opioid receptor and to a lesser extent the μ-opioid receptor as molecular targets, with opioid receptor antagonist norbinaltorphimine reversing benzodiazepine induced reduction of microglial NO. Functional assays identified the downregulation of inducible NO synthase as the mode of action of imidazodiazepines MP-IV-010 and GL-IV-03. Like other κ-opioid receptor agonists, GL-IV-03 reduced the agitation response in both phases of the formalin nociception test. However, unlike other κ-opioid receptor agonists, MP-IV-010 and GL-IV-03 did not impair sensorimotor coordination in mice. Thus, MP-IV-010 and GL-IV-03 represent a new class of nonsedative drug candidates for inflammatory pain.
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Affiliation(s)
- Amanda N. Nieman
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Guanguan Li
- Shenzhen Grubbs Institute and Department of Chemistry, Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Nicolas M. Zahn
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Md Yeunus Mian
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | | | - Dylan A. Hoffman
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Taylor M. Wilcox
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Alexander S. Kehoe
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Ian W. Luecke
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Michael M. Poe
- Department of Chemistry, Western Michigan University, Kalamazoo MI 49008, United States
| | - David Alvarez-Carbonell
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - James M. Cook
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Douglas C. Stafford
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
- Pantherics Incorporated, La Jolla, California 92037, United States
| | - Leggy A. Arnold
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
- Pantherics Incorporated, La Jolla, California 92037, United States
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14
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Hopp SC. Targeting microglia L-type voltage-dependent calcium channels for the treatment of central nervous system disorders. J Neurosci Res 2020; 99:141-162. [PMID: 31997405 DOI: 10.1002/jnr.24585] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 01/03/2020] [Accepted: 01/08/2020] [Indexed: 12/14/2022]
Abstract
Calcium (Ca2+ ) is a ubiquitous mediator of a multitude of cellular functions in the central nervous system (CNS). Intracellular Ca2+ is tightly regulated by cells, including entry via plasma membrane Ca2+ permeable channels. Of specific interest for this review are L-type voltage-dependent Ca2+ channels (L-VDCCs), due to their pleiotropic role in several CNS disorders. Currently, there are numerous approved drugs that target L-VDCCs, including dihydropyridines. These drugs are safe and effective for the treatment of humans with cardiovascular disease and may also confer neuroprotection. Here, we review the potential of L-VDCCs as a target for the treatment of CNS disorders with a focus on microglia L-VDCCs. Microglia, the resident immune cells of the brain, have attracted recent attention for their emerging inflammatory role in several CNS diseases. Intracellular Ca2+ regulates microglia transition from a resting quiescent state to an "activated" immune-effector state and is thus a valuable target for manipulation of microglia phenotype. We will review the literature on L-VDCC expression and function in the CNS and on microglia in vitro and in vivo and explore the therapeutic landscape of L-VDCC-targeting agents at present and future challenges in the context of Alzheimer's disease, Parkinson's disease, Huntington's disease, neuropsychiatric diseases, and other CNS disorders.
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Affiliation(s)
- Sarah C Hopp
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, University of Texas Health Science Center San Antonio, San Antonio, TX, USA.,Department of Pharmacology, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
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15
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Mustaly-Kalimi S, Littlefield AM, Stutzmann GE. Calcium Signaling Deficits in Glia and Autophagic Pathways Contributing to Neurodegenerative Disease. Antioxid Redox Signal 2018; 29:1158-1175. [PMID: 29634342 DOI: 10.1089/ars.2017.7266] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
SIGNIFICANCE Numerous cellular processes and signaling mechanisms have been identified that contribute to Alzheimer's disease (AD) pathology; however, a comprehensive or unifying pathway that binds together the major disease features remains elusive. As an upstream mechanism, altered calcium (Ca2+) signaling is a common driving force for many pathophysiological events that emerge during normal aging and development of neurodegenerative disease. Recent Advances: Over the previous three decades, accumulated evidence has validated the concept that intracellular Ca2+ dysregulation is centrally involved in AD pathogenesis, including the aggregation of pathogenic β-amyloid (Aβ) and phospho-τ species, synapse loss and dysfunction, cognitive impairment, and neurotoxicity. CRITICAL ISSUES Although neuronal Ca2+ signaling within the cytosol and endoplasmic reticulum (ER) has been well studied, other critical central nervous system-resident cell types affected by aberrant Ca2+ signaling, such as astrocytes and microglia, have not been considered as thoroughly. In addition, certain intracellular Ca2+-harboring organelles have been well studied, such as the ER and mitochondria; however other critical Ca2+-regulated organelles, such as lysosomes and autophagosomes, have only more recently been investigated. In this review, we examine Ca2+ dysregulation in microglia and astrocytes, as well as key intracellular organelles important for cellular maintenance and protein handling. Ca2+ dysregulation within these non-neuronal cells and organelles is hypothesized to disrupt the effective clearance of misaggregated proteins and cellular signaling pathways needed for memory networks. FUTURE DIRECTIONS Overall, we aim to explore how these disrupted mechanisms could be involved in AD pathology and consider their role as potential therapeutic targets. Antioxid. Redox Signal. 29, 1158-1175.
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Affiliation(s)
- Sarah Mustaly-Kalimi
- 1 Department of Neuroscience, School of Graduate and Postdoctoral Studies, Rosalind Franklin University of Medicine and Science , North Chicago, Illinois
| | - Alyssa M Littlefield
- 1 Department of Neuroscience, School of Graduate and Postdoctoral Studies, Rosalind Franklin University of Medicine and Science , North Chicago, Illinois
| | - Grace E Stutzmann
- 2 Department of Neuroscience, The Chicago Medical School, Rosalind Franklin University of Medicine and Science , North Chicago, Illinois
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16
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Lively S, Lam D, Wong R, Schlichter LC. Comparing Effects of Transforming Growth Factor β1 on Microglia From Rat and Mouse: Transcriptional Profiles and Potassium Channels. Front Cell Neurosci 2018; 12:115. [PMID: 29780305 PMCID: PMC5946019 DOI: 10.3389/fncel.2018.00115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 04/11/2018] [Indexed: 12/02/2022] Open
Abstract
The cytokine, transforming growth factor β1 (TGFβ1), is up-regulated after central nervous system (CNS) injuries or diseases involving microglial activation, and it has been proposed as a therapeutic agent for treating neuroinflammation. Microglia can produce and respond to TGFβ1. While rats and mice are commonly used for studying neuroinflammation, very few reports directly compare them. Such studies are important for improving pre-clinical studies and furthering translational progress in developing therapeutic interventions. After intracerebral hemorrhage (ICH) in the rat striatum, the TGFβ1 receptor was highly expressed on microglia/macrophages within the hematoma. We recently found species similarities and differences in response to either a pro-inflammatory (interferon-γ, IFN-γ, +tumor necrosis factor, TNF-α) or anti-inflammatory interleukin-4 (IL-4) stimulus. Here, we assessed whether rat and mouse microglia differ in their responses to TGFβ1. Microglia were isolated from Sprague-Dawley rats and C57BL/6 mice and treated with TGFβ1. We quantified changes in expression of >50 genes, in their morphology, proliferation, apoptosis and in three potassium channels that are considered therapeutic targets. Many inflammatory mediators, immune receptors and modulators showed species similarities, but notable differences included that, for some genes, only one species responded (e.g., Il4r, Il10, Tgfbr2, colony-stimulating factor receptor (Csf1r), Itgam, suppressor of cytokine signaling 1 (Socs1), toll-like receptors 4 (Tlr4), P2rx7, P2ry12), and opposite responses were seen for others (Tgfb1, Myc, Ifngr1). In rat only, TGFβ1 affected microglial morphology and proliferation, but there was no apoptosis in either species. In both species, TGFβ1 dramatically increased Kv1.3 channel expression and current (no effects on Kir2.1). KCa3.1 showed opposite species responses: the current was low in unstimulated rat microglia and greatly increased by TGFβ1 but higher in control mouse cells and decreased by TGFβ1. Finally, we compared TGFβ1 and IL10 (often considered similar anti-inflammatory stimuli) and found many different responses in both species. Overall, the numerous species differences should be considered when characterizing neuroinflammation and microglial activation in vitro and in vivo, and when targeting potassium channels.
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Affiliation(s)
- Starlee Lively
- Krembil Research Institute, Genes and Development Division, University Health Network, Toronto, ON, Canada
| | - Doris Lam
- Krembil Research Institute, Genes and Development Division, University Health Network, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Raymond Wong
- Krembil Research Institute, Genes and Development Division, University Health Network, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Lyanne C Schlichter
- Krembil Research Institute, Genes and Development Division, University Health Network, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada
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17
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Socodato R, Portugal CC, Rodrigues A, Henriques J, Rodrigues C, Figueira C, Relvas JB. Redox tuning of Ca 2+ signaling in microglia drives glutamate release during hypoxia. Free Radic Biol Med 2018; 118:137-149. [PMID: 29501565 DOI: 10.1016/j.freeradbiomed.2018.02.036] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 01/31/2018] [Accepted: 02/27/2018] [Indexed: 02/07/2023]
Abstract
Hypoxia causes oxidative stress and excitotoxicity, culminating in neuronal damage during brain ischemia. Hypoxia also activates microglia, the myeloid resident cells of the brain parenchyma. Upon activation, microglia release high amounts of the neurotransmitter glutamate, contributing for neuronal excitotoxicity during brain insults. Here, we reveal a signaling pathway controlling glutamate release from human microglia during hypoxia. We show that hypoxia-mediated redox imbalance promotes the activation of endoplasmic reticulum inositol 1,4,5-trisphosphate (InsP3) receptors leading to Ca2+ mobilization into the cytosol. Increasing cytosolic Ca2+ signaling in microglia activates the non-receptor protein tyrosine kinase Src at the plasma membrane. Src activation enhances the permeability of microglial gap junctions promoting the release of glutamate during hypoxia. Preventing the hypoxia-triggered redox imbalance, using the dietary antioxidants neochlorogenic acid or vitamin C, inhibits InsP3-dependent Ca2+ signaling and abrogates the release of glutamate. Overall, modulating microglial Ca2+ signaling in response to changes in the redox microenvironment might be critical for controlling glutamate excitotoxicity during hypoxia.
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Affiliation(s)
- Renato Socodato
- Instituto de Investigação e Inovação em Saúde and Instituto de Biologia Molecular e Celular (IBMC) and The Discoveries Centre for Regeneration and Precision Medicine - Porto campus, Universidade do Porto, Porto, Portugal.
| | - Camila C Portugal
- Instituto de Investigação e Inovação em Saúde and Instituto de Biologia Molecular e Celular (IBMC) and The Discoveries Centre for Regeneration and Precision Medicine - Porto campus, Universidade do Porto, Porto, Portugal
| | - Artur Rodrigues
- Instituto de Investigação e Inovação em Saúde and Instituto de Biologia Molecular e Celular (IBMC) and The Discoveries Centre for Regeneration and Precision Medicine - Porto campus, Universidade do Porto, Porto, Portugal
| | - Joana Henriques
- Instituto de Investigação e Inovação em Saúde and Instituto de Biologia Molecular e Celular (IBMC) and The Discoveries Centre for Regeneration and Precision Medicine - Porto campus, Universidade do Porto, Porto, Portugal
| | - Carla Rodrigues
- Diverge, Grupo Nabeiro Innovation Center, Alameda dos Oceanos 65, 1.1, 1900-208 Lisbon, Portugal
| | - Cláudia Figueira
- Diverge, Grupo Nabeiro Innovation Center, Alameda dos Oceanos 65, 1.1, 1900-208 Lisbon, Portugal
| | - João B Relvas
- Instituto de Investigação e Inovação em Saúde and Instituto de Biologia Molecular e Celular (IBMC) and The Discoveries Centre for Regeneration and Precision Medicine - Porto campus, Universidade do Porto, Porto, Portugal.
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18
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Tvrdik P, Kalani MYS. In Vivo Imaging of Microglial Calcium Signaling in Brain Inflammation and Injury. Int J Mol Sci 2017; 18:ijms18112366. [PMID: 29117112 PMCID: PMC5713335 DOI: 10.3390/ijms18112366] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Revised: 11/01/2017] [Accepted: 11/04/2017] [Indexed: 12/20/2022] Open
Abstract
Microglia, the innate immune sentinels of the central nervous system, are the most dynamic cells in the brain parenchyma. They are the first responders to insult and mediate neuroinflammation. Following cellular damage, microglia extend their processes towards the lesion, modify their morphology, release cytokines and other mediators, and eventually migrate towards the damaged area and remove cellular debris by phagocytosis. Intracellular Ca2+ signaling plays important roles in many of these functions. However, Ca2+ in microglia has not been systematically studied in vivo. Here we review recent findings using genetically encoded Ca2+ indicators and two-photon imaging, which have enabled new insights into Ca2+ dynamics and signaling pathways in large populations of microglia in vivo. These new approaches will help to evaluate pre-clinical interventions and immunomodulation for pathological brain conditions such as stroke and neurodegenerative diseases.
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Affiliation(s)
- Petr Tvrdik
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
| | - M Yashar S Kalani
- Department of Neurosurgery, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
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19
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Sayeed MSB, Alhadidi Q, Shah ZA. Cofilin signaling in hemin-induced microglial activation and inflammation. J Neuroimmunol 2017; 313:46-55. [PMID: 29153608 DOI: 10.1016/j.jneuroim.2017.10.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 09/28/2017] [Accepted: 10/13/2017] [Indexed: 02/07/2023]
Abstract
Intracerebral hemorrhage (ICH) is the most severe form of stroke and is further exacerbated by the secondary injury involving inflammatory response due to the activation of microglia. This secondary injury is partly due to the toxic effects of hemin, an endogenous breakdown product of hemoglobin. Cofilin, an actin depolymerizing factor, controls actin dynamics and has been previously shown to be involved in mediating neuronal cell death in ischemic conditions and during bacterial lipopolysaccharide induced microglial activation. There are limited studies regarding the deleterious effects of extremely high concentrations of hemin released during ICH and its effects on microglia and subsequent cofilin response. Therefore, investigations were conducted to study the effects of hemin on microglial activation induced inflammation and the critical role of cofilin in mediating the response. We observed that hemin treated microglia had a concentration dependent increase in cofilin expression and NO production. There were increased levels of iNOS, TNF-α, HO1, Nrf2, Wfs-1, XBP-1 and spliced XBP-1 observed in response to hemin treatment and the signaling was found to be partly mediated by cofilin. Acute hemin treatment did not evoke Ca2+ signaling and long-term treatment of hemin also resulted in the failure of microglial response to acetylcholine-evoked Ca2+ signaling. Knockdown of cofilin by siRNA also reduced acetylcholine-evoked Ca2+ signaling. These studies demonstrate that cofilin signaling is important in hemin-induced inflammation, oxidative stress, ER stress, microglial migration, and the ability to evoke Ca2+ signaling. Therefore, cofilin inhibition could be a potential therapy in brain injuries triggered by hemin toxicity in conditions like ICH.
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Affiliation(s)
- Muhammad Shahdaat Bin Sayeed
- Department of Pharmacology and Experimental Therapeutics, College of Pharmacy and Pharmaceutical Sciences, The University of Toledo, Toledo, OH 43614, USA
| | - Qasim Alhadidi
- Department of Medicinal and Biological Chemistry, College of Pharmacy and Pharmaceutical Sciences, The University of Toledo, Toledo, OH 43614, USA
| | - Zahoor A Shah
- Department of Pharmacology and Experimental Therapeutics, College of Pharmacy and Pharmaceutical Sciences, The University of Toledo, Toledo, OH 43614, USA; Department of Medicinal and Biological Chemistry, College of Pharmacy and Pharmaceutical Sciences, The University of Toledo, Toledo, OH 43614, USA.
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20
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Brawek B, Garaschuk O. Monitoring in vivo function of cortical microglia. Cell Calcium 2017; 64:109-117. [DOI: 10.1016/j.ceca.2017.02.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 02/08/2017] [Indexed: 02/01/2023]
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21
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Mizoguchi Y, Monji A. TRPC Channels and Brain Inflammation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 976:111-121. [DOI: 10.1007/978-94-024-1088-4_10] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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22
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Au NPB, Ma CHE. Recent Advances in the Study of Bipolar/Rod-Shaped Microglia and their Roles in Neurodegeneration. Front Aging Neurosci 2017; 9:128. [PMID: 28522972 PMCID: PMC5415568 DOI: 10.3389/fnagi.2017.00128] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 04/18/2017] [Indexed: 01/06/2023] Open
Abstract
Microglia are the resident immune cells of the central nervous system (CNS) and they contribute to primary inflammatory responses following CNS injuries. The morphology of microglia is closely associated with their functional activities. Most previous research efforts have attempted to delineate the role of ramified and amoeboid microglia in the pathogenesis of neurodegenerative diseases. In addition to ramified and amoeboid microglia, bipolar/rod-shaped microglia were first described by Franz Nissl in 1899 and their presence in the brain was closely associated with the pathology of infectious diseases and sleeping disorders. However, studies relating to bipolar/rod-shaped microglia are very limited, largely due to the lack of appropriate in vitro and in vivo experimental models. Recent studies have reported the formation of bipolar/rod-shaped microglia trains in in vivo models of CNS injury, including diffuse brain injury, focal transient ischemia, optic nerve transection and laser-induced ocular hypertension (OHT). These bipolar/rod-shaped microglia formed end-to-end alignments in close proximity to the adjacent injured axons, but they showed no interactions with blood vessels or other types of glial cell. Recent studies have also reported on a highly reproducible in vitro culture model system to enrich bipolar/rod-shaped microglia that acts as a powerful tool with which to characterize this form of microglia. The molecular aspects of bipolar/rod-shaped microglia are of great interest in the field of CNS repair. This review article focuses on studies relating to the morphology and transformation of microglia into the bipolar/rod-shaped form, along with the differential gene expression and spatial distribution of bipolar/rod-shaped microglia in normal and pathological CNSs. The spatial arrangement of bipolar/rod-shaped microglia is crucial in the reorganization and remodeling of neuronal and synaptic circuitry following CNS injuries. Finally, we discuss the potential neuroprotective roles of bipolar/rod-shaped microglia, and the possibility of transforming ramified/amoeboid microglia into bipolar/rod-shaped microglia. This will be of considerable clinical benefit in the development of novel therapeutic strategies for treating various neurodegenerative diseases and promoting CNS repair after injury.
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Affiliation(s)
- Ngan Pan Bennett Au
- Department of Biomedical Sciences, City University of Hong KongKowloon Tong, Hong Kong
| | - Chi Him Eddie Ma
- Department of Biomedical Sciences, City University of Hong KongKowloon Tong, Hong Kong.,Centre for Biosystems, Neuroscience, and Nanotechnology, City University of Hong KongKowloon Tong, Hong Kong.,State Key Laboratory in Marine Pollution, City University of Hong KongKowloon Tong, Hong Kong
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23
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Mizoguchi Y, Monji A. Microglial Intracellular Ca 2+ Signaling in Synaptic Development and its Alterations in Neurodevelopmental Disorders. Front Cell Neurosci 2017; 11:69. [PMID: 28367116 PMCID: PMC5355421 DOI: 10.3389/fncel.2017.00069] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 02/24/2017] [Indexed: 12/27/2022] Open
Abstract
Autism spectrum disorders (ASDs) are neurodevelopmental disorders characterized by deficits in social interaction, difficulties with language and repetitive/restricted behaviors. Microglia are resident innate immune cells which release many factors including proinflammatory cytokines, nitric oxide (NO) and brain-derived neurotrophic factor (BDNF) when they are activated in response to immunological stimuli. Recent in vivo imaging has shown that microglia sculpt and refine the synaptic circuitry by removing excess and unwanted synapses and be involved in the development of neural circuits or synaptic plasticity thereby maintaining the brain homeostasis. BDNF, one of the neurotrophins, has various important roles in cell survival, neurite outgrowth, neuronal differentiation, synaptic plasticity and the maintenance of neural circuits in the CNS. Intracellular Ca2+ signaling is important for microglial functions including ramification, de-ramification, migration, phagocytosis and release of cytokines, NO and BDNF. BDNF induces a sustained intracellular Ca2+ elevation through the upregulation of the surface expression of canonical transient receptor potential 3 (TRPC3) channels in rodent microglia. BDNF might have an anti-inflammatory effect through the inhibition of microglial activation and TRPC3 could play important roles in not only inflammatory processes but also formation of synapse through the modulation of microglial phagocytic activity in the brain. This review article summarizes recent findings on emerging dual, inflammatory and non-inflammatory, roles of microglia in the brain and reinforces the importance of intracellular Ca2+ signaling for microglial functions in both normal neurodevelopment and their potential contributing to neurodevelopmental disorders such as ASDs.
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Affiliation(s)
- Yoshito Mizoguchi
- Department of Psychiatry, Faculty of Medicine, Saga University Saga, Japan
| | - Akira Monji
- Department of Psychiatry, Faculty of Medicine, Saga University Saga, Japan
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Savchenko E, Malm T, Konttinen H, Hämäläinen RH, Guerrero-Toro C, Wojciechowski S, Giniatullin R, Koistinaho J, Magga J. Aβ and Inflammatory Stimulus Activate Diverse Signaling Pathways in Monocytic Cells: Implications in Retaining Phagocytosis in Aβ-Laden Environment. Front Cell Neurosci 2016; 10:279. [PMID: 27994540 PMCID: PMC5136556 DOI: 10.3389/fncel.2016.00279] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 11/21/2016] [Indexed: 12/21/2022] Open
Abstract
Background: Accumulation of amyloid β (Aβ) is one of the main hallmarks of Alzheimer’s disease (AD). The enhancement of Aβ clearance may provide therapeutic means to restrict AD pathology. The cellular responses to different forms of Aβ in monocytic cells are poorly known. We aimed to study whether different forms of Aβ induce inflammatory responses in monocytic phagocytes and how Aβ may affect monocytic cell survival and function to retain phagocytosis in Aβ-laden environment. Methods: Monocytic cells were differentiated from bone marrow hematopoietic stem cells (HSC) in the presence of macrophage-colony stimulating factor. Monocytic cells were stimulated with synthetic Aβ42 and intracellular calcium responses were recorded with calcium imaging. The formation of reactive oxygen species (ROS), secretion of cytokines and cell viability were also assessed. Finally, monocytic cells were introduced to native Aβ deposits ex vivo and the cellular responses in terms of cell viability, pro-inflammatory activation and phagocytosis were determined. The ability of monocytic cells to phagocytose Aβ plaques was determined after intrahippocampal transplantation in vivo. Results: Freshly solubilized Aβ induced calcium oscillations, which persisted after removal of the stimulus. After few hours of aggregation, Aβ was not able to induce oscillations in monocytic cells. Instead, lipopolysaccharide (LPS) induced calcium responses divergent from Aβ-induced response. Furthermore, while LPS induced massive production of pro-inflammatory cytokines, neither synthetic Aβ species nor native Aβ deposits were able to induce pro-inflammatory activation of monocytic cells, contrary to primary microglia. Finally, monocytic cells retained their viability in the presence of Aβ and exhibited phagocytic activity towards native fibrillar Aβ deposits and congophilic Aβ plaques. Conclusion: Monocytic cells carry diverse cellular responses to Aβ and inflammatory stimulus LPS. Even though Aβ species cause specific responses in calcium signaling, they completely lack the ability to induce pro-inflammatory phenotype of monocytic cells. Monocytes retain their viability and function in Aβ-laden brain.
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Affiliation(s)
- Ekaterina Savchenko
- Department of Neurobiology, A.I.Virtanen Institute for Molecular Sciences, University of Eastern Finland Kuopio, Finland
| | - Tarja Malm
- Department of Neurobiology, A.I.Virtanen Institute for Molecular Sciences, University of Eastern Finland Kuopio, Finland
| | - Henna Konttinen
- Department of Neurobiology, A.I.Virtanen Institute for Molecular Sciences, University of Eastern Finland Kuopio, Finland
| | - Riikka H Hämäläinen
- Department of Neurobiology, A.I.Virtanen Institute for Molecular Sciences, University of Eastern Finland Kuopio, Finland
| | - Cindy Guerrero-Toro
- Department of Neurobiology, A.I.Virtanen Institute for Molecular Sciences, University of Eastern Finland Kuopio, Finland
| | - Sara Wojciechowski
- Department of Neurobiology, A.I.Virtanen Institute for Molecular Sciences, University of Eastern Finland Kuopio, Finland
| | - Rashid Giniatullin
- Department of Neurobiology, A.I.Virtanen Institute for Molecular Sciences, University of Eastern Finland Kuopio, Finland
| | - Jari Koistinaho
- Department of Neurobiology, A.I.Virtanen Institute for Molecular Sciences, University of Eastern Finland Kuopio, Finland
| | - Johanna Magga
- Department of Neurobiology, A.I.Virtanen Institute for Molecular Sciences, University of Eastern FinlandKuopio, Finland; Department of Pharmacology and Toxicology, Research Unit of Biomedicine, University of OuluOulu, Finland
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Aripiprazole inhibits polyI:C-induced microglial activation possibly via TRPM7. Schizophr Res 2016; 178:35-43. [PMID: 27614570 DOI: 10.1016/j.schres.2016.08.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 08/20/2016] [Accepted: 08/20/2016] [Indexed: 12/13/2022]
Abstract
Viral infections during fetal and adolescent periods, as well as during the course of schizophrenia itself have been linked to the onset and/or relapse of a psychosis. We previously reported that the unique antipsychotic aripiprazole, a partial D2 agonist, inhibits the release of tumor necrosis factor (TNF)-α from interferon-γ-activated rodent microglial cells. Polyinosinic-polycytidylic acid (polyI:C) has recently been used as a standard model of viral infections, and recent in vitro studies have shown that microglia are activated by polyI:C. Aripiprazole has been reported to ameliorate behavioral abnormalities in polyI:C-induced mice. To clarify the anti-inflammatory properties of aripiprazole, we investigated the effects of aripiprazole on polyI:C-induced microglial activation in a cellular model of murine microglial cells and possible surrogate cells for human microglia. PolyI:C treatment of murine microglial cells activated the production of TNF-α and enhanced the p38 mitogen-activated protein kinase (MAPK) pathway, whereas aripiprazole inhibited these responses. In addition, polyI:C treatment of possible surrogate cells for human microglia markedly increased TNF-α mRNA expression in cells from three healthy volunteers. Aripiprazole inhibited this increase in cells from two individuals. PolyI:C consistently increased intracellular Ca2+ concentration ([Ca2+]i) in murine microglial cells by influx of extracellular Ca2+. We demonstrated that transient receptor potential in melastatin 7 (TRPM7) channels contributed to this polyI:C-induced increase in [Ca2+]i. Taken together, these data suggest that aripiprazole may be therapeutic for schizophrenia by reducing microglial inflammatory reactions, and TRPM7 may be a novel therapeutic target for schizophrenia. Further studies are needed to validate these findings.
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Kurland DB, Gerzanich V, Karimy JK, Woo SK, Vennekens R, Freichel M, Nilius B, Bryan J, Simard JM. The Sur1-Trpm4 channel regulates NOS2 transcription in TLR4-activated microglia. J Neuroinflammation 2016; 13:130. [PMID: 27246103 PMCID: PMC4888589 DOI: 10.1186/s12974-016-0599-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 05/24/2016] [Indexed: 12/12/2022] Open
Abstract
Background Harmful effects of activated microglia are due, in part, to the formation of peroxynitrite radicals, which is attributable to the upregulation of inducible nitric oxide (NO) synthase (NOS2). Because NOS2 expression is determined by Ca2+-sensitive calcineurin (CN) dephosphorylating nuclear factor of activated T cells (NFAT), and because Sur1-Trpm4 channels are crucial for regulating Ca2+ influx, we hypothesized that, in activated microglia, Sur1-Trpm4 channels play a central role in regulating CN/NFAT and downstream target genes such as Nos2. Methods We studied microglia in vivo and in primary culture from adult rats, and from wild type, Abcc8−/− and Trpm4−/− mice, and immortalized N9 microglia, following activation of Toll-like receptor 4 (TLR4) by lipopolysaccharide (LPS), using in situ hybridization, immunohistochemistry, co-immunoprecipitation, immunoblot, qPCR, patch clamp electrophysiology, calcium imaging, the Griess assay, and chromatin immunoprecipitation. Results In microglia in vivo and in vitro, LPS activation of TLR4 led to de novo upregulation of Sur1-Trpm4 channels and CN/NFAT-dependent upregulation of Nos2 mRNA, NOS2 protein, and NO. Pharmacological inhibition of Sur1 (glibenclamide), Trpm4 (9-phenanthrol), or gene silencing of Abcc8 or Trpm4 reduced Nos2 upregulation. Inhibiting Sur1-Trpm4 increased the intracellular calcium concentration ([Ca2+]i), as expected, but also decreased NFAT nuclear translocation. The increase in [Ca2+]i induced by inhibiting or silencing Sur1-Trpm4 resulted in phosphorylation of Ca2+/calmodulin protein kinase II and of CN, consistent with reduced nuclear translocation of NFAT. The regulation of NFAT by Sur1-Trpm4 was confirmed using chromatin immunoprecipitation. Conclusions Sur1-Trpm4 constitutes a novel mechanism by which TLR4-activated microglia regulate pro-inflammatory, Ca2+-sensitive gene expression, including Nos2.
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Affiliation(s)
- David B Kurland
- Department of Neurosurgery, University of Maryland School of Medicine, 22 S. Greene St., Suite S12D, Baltimore, MD, 21201-1595, USA. .,Neurosurgery Research Laboratories, 10 S. Pine St, Baltimore, MD, 21201-1595, USA.
| | - Volodymyr Gerzanich
- Department of Neurosurgery, University of Maryland School of Medicine, 22 S. Greene St., Suite S12D, Baltimore, MD, 21201-1595, USA
| | - Jason K Karimy
- Department of Neurosurgery, University of Maryland School of Medicine, 22 S. Greene St., Suite S12D, Baltimore, MD, 21201-1595, USA
| | - Seung Kyoon Woo
- Department of Neurosurgery, University of Maryland School of Medicine, 22 S. Greene St., Suite S12D, Baltimore, MD, 21201-1595, USA
| | - Rudi Vennekens
- Department Cell Molecular Medicine, Laboratory Ion Channel Research, Campus Gasthuisberg, Herestraat 49-Bus 802, Leuven, 3000, Belgium
| | - Marc Freichel
- Pharmakologisches Institut, Universität Heidelberg, Im Neuenheimer Feld 366, Heidelberg, 69120, Germany
| | - Bernd Nilius
- Department Cell Molecular Medicine, Laboratory Ion Channel Research, Campus Gasthuisberg, Herestraat 49-Bus 802, Leuven, 3000, Belgium
| | - Joseph Bryan
- Pacific Northwest Diabetes Research Institute, 720 Broadway, Seattle, WA, 98122, USA
| | - J Marc Simard
- Department of Neurosurgery, University of Maryland School of Medicine, 22 S. Greene St., Suite S12D, Baltimore, MD, 21201-1595, USA. .,Department of Pathology, University of Maryland School of Medicine, Baltimore, MD, USA. .,Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.
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Li L, Eter N, Heiduschka P. The microglia in healthy and diseased retina. Exp Eye Res 2015; 136:116-30. [PMID: 25952657 DOI: 10.1016/j.exer.2015.04.020] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 04/28/2015] [Accepted: 04/29/2015] [Indexed: 12/25/2022]
Abstract
The microglia are the immune cells of the central nervous system and, also the retina. They fulfil several tasks of surveillance in the healthy retina. In case of an injury or disease, microglia become activated and tries to repair the damage. However, in a lot of cases it does not work, and microglia deteriorate the situation by releasing toxic and pro-inflammatory compounds. Moreover, they further promote degenerative processes by attacking and phagocytosing damaged neurones and photoreceptors that otherwise would possibly have the chance to survive. Such deleterious action of the microglia has been observed in degeneration of retinal ganglion cells and photoreceptors, and it takes place in hereditary diseases, infections as well as in case of traumatic or light injuries. Therefore, a number of attempts has been undertaken so far to inhibit the microglia, with varying success. The task remains to study behaviour of the microglia and their interaction with other retinal cell populations in more detail with respect to released factors and expressed receptors including the time points of the corresponding events. The goal has to be to find a better balance between helpful and detrimental actions of the microglia.
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Affiliation(s)
- Lu Li
- University of Münster Medical School, Department of Ophthalmology, Domagkstr. 15, D-48149 Münster, Germany
| | - Nicole Eter
- University of Münster Medical School, Department of Ophthalmology, Domagkstr. 15, D-48149 Münster, Germany
| | - Peter Heiduschka
- University of Münster Medical School, Department of Ophthalmology, Domagkstr. 15, D-48149 Münster, Germany.
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Migration and Phagocytic Ability of Activated Microglia During Post-natal Development is Mediated by Calcium-Dependent Purinergic Signalling. Mol Neurobiol 2015; 53:944-954. [PMID: 25575683 DOI: 10.1007/s12035-014-9064-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 12/09/2014] [Indexed: 01/10/2023]
Abstract
Microglia play an important role in synaptic pruning and controlled phagocytosis of neuronal cells during developmental stages. However, the mechanisms that regulate these functions are not completely understood. The present study was designed to investigate the role of purinergic signalling in microglial migration and phagocytic activity during post-natal brain development. One-day-old BALB/c mice received lipopolysaccharide (LPS) and/or a purinergic analogue (2-methylthioladenosine-5'-diphosphate; 2MeSADP), intracerebroventrically (i.c.v.). Combined administration of LPS and 2MeSADP resulted in activation of microglia as evident from increased expression of ionised calcium-binding adapter molecule 1 (Iba1). Activated microglia showed increased expression of purinergic receptors (P2Y2, P2Y6 and P2Y12). LPS either alone or in combination with 2MeSADP induced the expression of Na(+)/Ca(2+) exchanger (NCX-1) and P/Q-type Ca(2+) channels along with MARCKS-related protein (MRP), which is an integral component of cell migration machinery. In addition, LPS and 2MeSADP administration induced the expression of microglial CD11b and DAP12 (DNAX-activation protein 12), which are known to be involved in phagocytosis of neurons during development. Interestingly, administration of thapsigargin (TG), a specific Ca(2+)-ATPase inhibitor of endoplasmic reticulum, prevented the LPS/2MeSADP-induced microglial activation and migration by down-regulating the expression of Iba1 and MRP, respectively. Moreover, TG also reduced the LPS/2MeSADP-induced expression of CD11b/DAP12. Taken together, the findings reveal for the first time that Ca(2+)-mediated purinergic receptors regulate the migration and phagocytic ability of microglia during post-natal brain development.
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Freitag MT, Márton G, Pajer K, Hartmann J, Walder N, Rossmann M, Parzer P, Redl H, Nógrádi A, Stieltjes B. Monitoring of Short-Term Erythropoietin Therapy in Rats with Acute Spinal Cord Injury Using Manganese-Enhanced Magnetic Resonance Imaging. J Neuroimaging 2014; 25:582-9. [DOI: 10.1111/jon.12202] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 07/29/2014] [Accepted: 09/13/2014] [Indexed: 11/28/2022] Open
Affiliation(s)
- Martin Thomas Freitag
- Quantitative Imaging-Based Disease Characterization; Department of Radiology; German Cancer Research Center; Heidelberg Germany
| | - Gábor Márton
- Laboratory of Neural Regeneration; Department of Anatomy; Histology, and Embryology; Faculty of Medicine; University of Szeged; Hungary
| | - Krisztián Pajer
- Laboratory of Neural Regeneration; Department of Anatomy; Histology, and Embryology; Faculty of Medicine; University of Szeged; Hungary
| | - Jens Hartmann
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology; Research Center of the AUVA; Vienna Austria
| | - Nadja Walder
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology; Research Center of the AUVA; Vienna Austria
| | - Markus Rossmann
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology; Research Center of the AUVA; Vienna Austria
| | - Peter Parzer
- Section Disorders of Personality Development; Department of Child and Adolescent Psychiatry; Center for Psychosocial Medicine; University of Heidelberg; Germany
| | - Heinz Redl
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology; Research Center of the AUVA; Vienna Austria
| | - Antal Nógrádi
- Laboratory of Neural Regeneration; Department of Anatomy; Histology, and Embryology; Faculty of Medicine; University of Szeged; Hungary
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology; Research Center of the AUVA; Vienna Austria
| | - Bram Stieltjes
- Quantitative Imaging-Based Disease Characterization; Department of Radiology; German Cancer Research Center; Heidelberg Germany
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Mizoguchi Y, Kato TA, Horikawa H, Monji A. Microglial intracellular Ca(2+) signaling as a target of antipsychotic actions for the treatment of schizophrenia. Front Cell Neurosci 2014; 8:370. [PMID: 25414641 PMCID: PMC4220695 DOI: 10.3389/fncel.2014.00370] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 10/20/2014] [Indexed: 11/18/2022] Open
Abstract
Microglia are resident innate immune cells which release many factors including proinflammatory cytokines, nitric oxide (NO) and neurotrophic factors when they are activated in response to immunological stimuli. Recent reports show that pathophysiology of schizophrenia is related to the inflammatory responses mediated by microglia. Intracellular Ca2+ signaling, which is mainly controlled by the endoplasmic reticulum (ER), is important for microglial functions such as release of NO and cytokines, migration, ramification and deramification. In addition, alteration of intracellular Ca2+ signaling underlies the pathophysiology of schizophrenia, while it remains unclear how typical or atypical antipsychotics affect intracellular Ca2+ mobilization in microglial cells. This mini-review article summarizes recent findings on cellular mechanisms underlying the characteristic differences in the actions of antipsychotics on microglial intracellular Ca2+ signaling and reinforces the importance of the ER of microglial cells as a target of antipsychotics for the treatment of schizophrenia.
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Affiliation(s)
- Yoshito Mizoguchi
- Department of Psychiatry, Faculty of Medicine, Saga University Saga, Japan
| | - Takahiro A Kato
- Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University Fukuoka, Japan ; Innovation Center for Medical Redox Navigation, Kyushu University Fukuoka, Japan
| | - Hideki Horikawa
- Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University Fukuoka, Japan
| | - Akira Monji
- Department of Psychiatry, Faculty of Medicine, Saga University Saga, Japan
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Hurley MJ, Gentleman SM, Dexter DT. Calcium CaV1 channel subtype mRNA expression in Parkinson's disease examined by in situ hybridization. J Mol Neurosci 2014; 55:715-24. [PMID: 25173401 DOI: 10.1007/s12031-014-0410-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Accepted: 08/20/2014] [Indexed: 12/12/2022]
Abstract
The factors which make some neurons vulnerable to neurodegeneration in Parkinson's disease while others remain resistant are not fully understood. Studies in animal models of Parkinson's disease suggest that preferential use of CaV1.3 subtypes by neurons may contribute to the neurodegenerative process by increasing mitochondrial oxidant stress. This study quantified the level of mRNA for the CaV1 subtypes found in the brain by in situ hybridization using CaV1 subtype-specific [(35)S]-radiolabelled oligonucleotide probes. In normal brain, the greatest amount of messenger RNA (mRNA) for each CaV1 subtype was found in the midbrain (substantia nigra), with a moderate level in the pons (locus coeruleus) and lower quantities in cerebral cortex (cingulate and primary motor). In Parkinson's disease, the level of CaV1 subtype mRNA was maintained in the midbrain and pons, despite cell loss in these areas. In cingulate cortex, CaV1.2 and CaV1.3 mRNA increased in cases with late-stage Parkinson's disease. In primary motor cortex, the level of CaV1.2 mRNA increased in late-stage Parkinson's disease. The level of CaV1.3 mRNA increased in primary motor cortex of cases with early-stage Parkinson's disease and normalized to near the control level in cases from late-stage Parkinson's disease. The finding of elevated CaV1 subtype expression in cortical brain regions supports the view that disturbed calcium homeostasis is a feature of Parkinson's disease throughout brain and not only a compensatory consequence to the neurodegenerative process in areas of cell loss.
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Affiliation(s)
- Michael J Hurley
- Centre for Neuroinflammation and Neurodegeneration, Division of Brain Sciences, Department of Medicine, Imperial College London, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK,
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Gofman L, Cenna JM, Potula R. P2X4 receptor regulates alcohol-induced responses in microglia. J Neuroimmune Pharmacol 2014; 9:668-78. [PMID: 25135400 DOI: 10.1007/s11481-014-9559-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 07/28/2014] [Indexed: 12/18/2022]
Abstract
Mounting evidence indicates that alcohol-induced neuropathology may result from multicellular responses in which microglia cells play a prominent role. Purinergic receptor signaling plays a key role in regulating microglial function and, more importantly, mediates alcohol-induced effects. Our findings demonstrate that alcohol increases expression of P2X4 receptor (P2X4R), which alters the function of microglia, including calcium mobilization, migration and phagocytosis. Our results show a significant up-regulation of P2X4 gene expression as analyzed by real-time qPCR (***p < 0.002) and protein expression as analyzed by flow cytometry (**p < 0.004) in embryonic stem cell-derived microglial cells (ESdM) after 48 hours of alcohol treatment, as compared to untreated controls. Calcium mobilization in ethanol treated ESdM cells was found to be P2X4R dependent using 5-BDBD, a P2X4R selective antagonist. Alcohol decreased migration of microglia towards fractalkine (CX3CL1) by 75 % following 48 h of treatment compared to control (***p < 0.001). CX3CL1-dependent migration was confirmed to be P2X4 receptor-dependent using the antagonist 5-BDBD, which reversed the effects as compared to alcohol alone (***p < 0.001). Similarly, 48 h of alcohol treatment significantly decreased phagocytosis of microglia by 15 % compared to control (*p < 0.05). 5-BDBD pre-treatment prior to alcohol treatment significantly increased microglial phagocytosis (***p < 0.001). Blocking P2X4R signaling with 5-BDBD decreased the level of calcium mobilization compared to ethanol treatment alone. These findings demonstrate that P2X4 receptor may play a role in modulating microglial function in the context of alcohol abuse.
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Affiliation(s)
- Larisa Gofman
- Department of Pathology and Laboratory Medicine, Temple University School of Medicine, 3500 N. Broad Street, MERB 845A, Philadelphia, PA, 19140, USA
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Persson AK, Estacion M, Ahn H, Liu S, Stamboulian-Platel S, Waxman SG, Black JA. Contribution of sodium channels to lamellipodial protrusion and Rac1 and ERK1/2 activation in ATP-stimulated microglia. Glia 2014; 62:2080-95. [PMID: 25043721 DOI: 10.1002/glia.22728] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 06/11/2014] [Accepted: 07/08/2014] [Indexed: 12/19/2022]
Abstract
Microglia are motile resident immune cells of the central nervous system (CNS) that continuously explore their territories for threats to tissue homeostasis. Following CNS insult (e.g., cellular injury, infection, or ischemia), microglia respond to signals such as ATP, transform into an activated state, and migrate towards the threat. Directed migration is a complex and highly-coordinated process involving multiple intersecting cellular pathways, including signal transduction, membrane adhesion and retraction, cellular polarization, and rearrangement of cytoskeletal elements. We previously demonstrated that the activity of sodium channels contributes to ATP-induced migration of microglia. Here we show that TTX-sensitive sodium channels, specifically NaV 1.6, participate in an initial event in the migratory process, i.e., the formation in ATP-stimulated microglia of polymerized actin-rich membrane protrusions, lamellipodia, containing accumulations of Rac1 and phosphorylated ERK1/2. We also examined Ca(2+) transients in microglia and found that blockade of sodium channels with TTX produced a downward shift in the level of [Ca(2+) ]i during the delayed, slower recovery of [Ca(2+) ]i following ATP stimulation. These observations demonstrate a modulatory role of sodium channels on Ca(2+) transients in microglia that are likely to affect down-stream signaling cascades. Consistent with these observations, we demonstrate that ATP-induced microglial migration is mediated via Rac1 and ERK1/2, but not p38α/β and JNK, dependent pathways, and that activation of both Rac1 and ERK1/2 is modulated by sodium channel activity. Our results provide evidence for a direct link between sodium channel activity and modulation of Rac1 and ERK1/2 activation in ATP-stimulated microglia, possibly by regulating Ca(2+) transients.
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Affiliation(s)
- Anna-Karin Persson
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, Connecticut
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Hyperforin attenuates microglia activation and inhibits p65-Ser276 NFκB phosphorylation in the rat piriform cortex following status epilepticus. Neurosci Res 2014; 85:39-50. [PMID: 24881563 DOI: 10.1016/j.neures.2014.05.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 05/16/2014] [Accepted: 05/21/2014] [Indexed: 01/23/2023]
Abstract
Hyperforin, a lipophilic constituent of medicinal herb St. John's Wort, has neurobiological effects including antidepressant activity, antibiotic potency, anti-inflammatory activity and anti-tumoral properties. Furthermore, hyperforin activates transient receptor potential conical channel-6 (TRPC6), a nonselective cation channel. To elucidate the roles of hyperforin and TRPC6 in neuroinflammation in vivo, we investigated the effect of hyperforin on neuroinflammatory responses and its related events in the rat piriform cortex (PC) following status epilepticus (SE). Hyperforin attenuated microglial activation, p65-serine 276 NFκB phosphorylation, and suppressed TNF-α expression in the PC following SE. Hyperforin also effectively alleviated SE-induced vasogenic edema formation, neuronal damage, microglial TRPC6 induction and blood-derived monocyte infiltration. Our findings suggest that hyperforin may effectively attenuate microglia-mediated neuroinflammation in the TRPC6-independent manner.
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35
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Network-wide dysregulation of calcium homeostasis in Alzheimer’s disease. Cell Tissue Res 2014; 357:427-38. [DOI: 10.1007/s00441-014-1798-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 01/09/2014] [Indexed: 12/19/2022]
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Cataldi M. The changing landscape of voltage-gated calcium channels in neurovascular disorders and in neurodegenerative diseases. Curr Neuropharmacol 2013; 11:276-97. [PMID: 24179464 PMCID: PMC3648780 DOI: 10.2174/1570159x11311030004] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 02/02/2013] [Accepted: 02/14/2013] [Indexed: 12/12/2022] Open
Abstract
It is a common belief that voltage-gated calcium channels (VGCC) cannot carry toxic amounts of Ca2+ in neurons. Also, some of them as L-type channels are essential for Ca2+-dependent regulation of prosurvival gene-programs. However, a wealth of data show a beneficial effect of drugs acting on VGCCs in several neurodegenerative and neurovascular diseases. In the present review, we explore several mechanisms by which the “harmless” VGCCs may become “toxic” for neurons. These mechanisms could explain how, though usually required for neuronal survival, VGCCs may take part in neurodegeneration. We will present evidence showing that VGCCs can carry toxic Ca2+ when: a) their density or activity increases because of aging, chronic hypoxia or exposure to β-amyloid peptides or b) Ca2+-dependent action potentials carry high Ca2+ loads in pacemaker neurons. Besides, we will examine conditions in which VGCCs promote neuronal cell death without carrying excess Ca2+. This can happen, for instance, when they carry metal ions into the neuronal cytoplasm or when a pathological decrease in their activity weakens Ca2+-dependent prosurvival gene programs. Finally, we will explore the role of VGCCs in the control of nonneuronal cells that take part to neurodegeneration like those of the neurovascular unit or of microglia.
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Affiliation(s)
- Mauro Cataldi
- Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, Federico II University of Naples, Italy
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Microglial ion channels as potential targets for neuroprotection in Parkinson's disease. Neural Plast 2013; 2013:587418. [PMID: 24288626 PMCID: PMC3832972 DOI: 10.1155/2013/587418] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 09/19/2013] [Indexed: 12/13/2022] Open
Abstract
Parkinson's disease (PD) is a chronic, degenerative neurological disorder that is estimated to affect at least 1 million individuals in the USA and over 10 million worldwide. It is thought that the loss of neurons and development of inclusion bodies occur gradually over decades until they progress to the point where ~60% of the dopamine neurons are lost and patients present with motor dysfunction. At present, it is not clear what causes this progression, and there are no current therapies that have been successful in preventing PD progression. Although there are many hypotheses regarding the mechanism of PD progression, neuroinflammation may be a major contributor to PD pathogenesis. Indeed, activated microglia and subsequent neuroinflammation have been consistently associated with the pathogenesis of PD. Thus, interference with this process could provide a means of neuroprotection in PD. This review will discuss the potential of targeting microglia to reduce neuroinflammation in PD. Further, we discuss the potential of microglial ion channels to serve as novel targets for neuroprotection in PD.
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Ikeda M, Tsuno S, Sugiyama T, Hashimoto A, Yamoto K, Takeuchi K, Kishi H, Mizuguchi H, Kohsaka SI, Yoshioka T. Ca(2+) spiking activity caused by the activation of store-operated Ca(2+) channels mediates TNF-α release from microglial cells under chronic purinergic stimulation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2573-2585. [PMID: 23830920 DOI: 10.1016/j.bbamcr.2013.06.022] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 06/21/2013] [Accepted: 06/24/2013] [Indexed: 02/07/2023]
Abstract
Cytokines released from microglia mediate defensive responses in the brain, but the underlying mechanisms are obscure. One proposed process is that nucleotide leakage or release from surrounding cells is sensed by metabotropic (P2Y) and ionotropic (P2X) purinergic receptors, which may trigger long-term intracellular Ca(2+) flux and tumor necrosis factor α (TNF-α) release. Indeed, 3h of exposure to ATP was required to evoke TNF-α release from a murine microglial cell line (MG5). A Ca(2+) chelator, ethylene glycol tetraacetic acid (EGTA), reduced ATP-induced TNF-α release, suggesting that intracellular Ca(2+) is important in this response. Therefore, Ca(2+) sensor genes (YC3.6) were transfected into MG5 cells to investigate the Ca(2+) dynamics underlying ATP-induced TNF-α release. The results demonstrated ATP-induced biphasic Ca(2+) mobilization mediated by P2Y (~5min) and P2X7 receptors (5-30min). Moreover, Ca(2+) spiking activity in cell processes progressively increased with a reduction in P2X7 receptor-mediated Ca(2+) elevation during 3-h ATP stimulation. Increased Ca(2+) spiking activity paralleled the reduction in thapsigargin-sensitive internal Ca(2+) stores, dendrite extension, and expression of macrophage scavenger receptors with collagenous structure. The Ca(2+) spiking activity was enhanced by a P2X7 receptor antagonist (A438079), but inhibited by a store-operated channel antagonist (SKF96365) or by co-transfection of small interference ribonucleic acid (siRNA) targeted on the channel component (Orai1). Furthermore, ATP-induced TNF-α release was enhanced by A438079 but was inhibited by SKF96365. Because store-operated channels (Stim1/Orai1) were expressed both in MG5 and primary microglial cultures, we suggest that P2X7 receptor signaling inhibits store-operated channels during ATP stimulation, and disinhibition of this process gates TNF-α release from microglial cells.
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Affiliation(s)
- Masayuki Ikeda
- Graduate School of Science and Engineering, University of Toyama, Toyama City, Toyama 930-8555, Japan; Graduate School of Innovative Life Science, University of Toyama, Toyama City, Toyama 930-8555, Japan.
| | - Saki Tsuno
- Graduate School of Science and Engineering, University of Toyama, Toyama City, Toyama 930-8555, Japan
| | - Takashi Sugiyama
- Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo Shinjuku-ku, Tokyo 169-8555, Japan; Advanced Core Technology Department, Research and Development Division, Corporate R&D Center, Olympus Corporation, Hachioji, Tokyo 192-8512, Japan
| | - Ayami Hashimoto
- Graduate School of Science and Engineering, University of Toyama, Toyama City, Toyama 930-8555, Japan
| | - Kurumi Yamoto
- Graduate School of Science and Engineering, University of Toyama, Toyama City, Toyama 930-8555, Japan
| | - Kouhei Takeuchi
- Graduate School of Innovative Life Science, University of Toyama, Toyama City, Toyama 930-8555, Japan
| | - Hiroyuki Kishi
- Graduate School of Innovative Life Science, University of Toyama, Toyama City, Toyama 930-8555, Japan; Department of Immunology, Faculty of Medicine, University of Toyama, 2630, Sugitani, Toyama 930-01, Japan
| | - Hiroyuki Mizuguchi
- Laboratory of Biochemistry and Molecular Biology, Graduate School of Pharmaceutical Sciences, Osaka University, Suita City, Osaka 565-0871, Japan; Laboratory of Stem Cell Regulation, National Institute of Biomedical Innovation, Suita City, Osaka 567-0085, Japan; The Center for Advanced Medical Engineering and Informatics, Osaka University, Suita City, Osaka, 565-0871, Japan
| | - Shin-Ichi Kohsaka
- Department of Neurochemistry, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502, Japan
| | - Tohru Yoshioka
- Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo Shinjuku-ku, Tokyo 169-8555, Japan; Graduate School of Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan
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Verkhratsky A, Parpura V. Store-operated calcium entry in neuroglia. Neurosci Bull 2013; 30:125-33. [PMID: 23677809 DOI: 10.1007/s12264-013-1343-x] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Accepted: 02/14/2013] [Indexed: 11/30/2022] Open
Abstract
Neuroglial cells are homeostatic neural cells. Generally, they are electrically non-excitable and their activation is associated with the generation of complex intracellular Ca(2+) signals that define the "Ca(2+) excitability" of glia. In mammalian glial cells the major source of Ca(2+) for this excitability is the lumen of the endoplasmic reticulum (ER), which is ultimately (re)filled from the extracellular space. This occurs via store-operated Ca(2+) entry (SOCE) which is supported by a specific signaling system connecting the ER with plasmalemmal Ca(2+) entry. Here, emptying of the ER Ca(2+) store is necessary and sufficient for the activation of SOCE, and without Ca(2+) influx via SOCE the ER store cannot be refilled. The molecular arrangements underlying SOCE are relatively complex and include plasmalemmal channels, ER Ca(2+) sensors, such as stromal interaction molecule, and possibly ER Ca(2+) pumps (of the SERCA type). There are at least two sets of plasmalemmal channels mediating SOCE, the Ca(2+)-release activated channels, Orai, and transient receptor potential (TRP) channels. The molecular identity of neuroglial SOCE has not been yet identified unequivocally. However, it seems that Orai is predominantly expressed in microglia, whereas astrocytes and oligodendrocytes rely more on TRP channels to produce SOCE. In physiological conditions the SOCE pathway is instrumental for the sustained phase of the Ca(2+) signal observed following stimulation of metabotropic receptors on glial cells.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Life Sciences, The University of Manchester, Manchester, M13 9PT, UK,
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ATP is required and advances cytokine-induced gap junction formation in microglia in vitro. Mediators Inflamm 2013; 2013:216402. [PMID: 23737642 PMCID: PMC3655668 DOI: 10.1155/2013/216402] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 03/21/2013] [Accepted: 03/22/2013] [Indexed: 01/18/2023] Open
Abstract
Microglia are the immune cells in the central nervous system. After injury microglia release bioactive molecules, including cytokines and ATP, which modify the functional state of hemichannels (HCs) and gap junction channels (GJCs), affecting the intercellular communication via extracellular and intracellular compartments, respectively. Here, we studied the role of extracellular ATP and several cytokines as modulators of the functional state of microglial HCs and GJCs using dye uptake and dye coupling techniques, respectively. In microglia and the microglia cell line EOC20, ATP advanced the TNF-α/IFN-γ-induced dye coupling, probably through the induction of IL-1β release. Moreover, TNF-α/IFN-γ, but not TNF-α plus ATP, increased dye uptake in EOC20 cells. Blockade of Cx43 and Panx1 HCs prevented dye coupling induced by TNF-α/IFN-γ, but not TNF-α plus ATP. In addition, IL-6 prevented the induction of dye coupling and HC activity induced by TNF-α/IFN-γ in EOC20 cells. Our data support the notion that extracellular ATP affects the cellular communication between microglia through autocrine and paracrine mechanisms, which might affect the timing of immune response under neuroinflammatory conditions.
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Ferreira R, Schlichter LC. Selective activation of KCa3.1 and CRAC channels by P2Y2 receptors promotes Ca(2+) signaling, store refilling and migration of rat microglial cells. PLoS One 2013; 8:e62345. [PMID: 23620825 PMCID: PMC3631179 DOI: 10.1371/journal.pone.0062345] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 03/20/2013] [Indexed: 12/26/2022] Open
Abstract
Microglial activation involves Ca(2+) signaling, and numerous receptors can evoke elevation of intracellular Ca(2+). ATP released from damaged brain cells can activate ionotropic and metabotropic purinergic receptors, and act as a chemoattractant for microglia. Metabotropic P2Y receptors evoke a Ca(2+) rise through release from intracellular Ca(2+) stores and store-operated Ca(2+) entry, and some have been implicated in microglial migration. This Ca(2+) rise is expected to activate small-conductance Ca(2+)-dependent K(+) (SK) channels, if present. We previously found that SK3 (KCa2.3) and KCa3.1 (SK4/IK1) are expressed in rat microglia and contribute to LPS-mediated activation and neurotoxicity. However, neither current has been studied by elevating Ca(2+) during whole-cell recordings. We hypothesized that, rather than responding only to Ca(2+), each channel type might be coupled to different receptor-mediated pathways. Here, our objective was to determine whether the channels are differentially activated by P2Y receptors, and, if so, whether they play differing roles. We used primary rat microglia and a rat microglial cell line (MLS-9) in which riluzole robustly activates both SK3 and KCa3.1 currents. Using electrophysiological, Ca(2+) imaging and pharmacological approaches, we show selective functional coupling of KCa3.1 to UTP-mediated P2Y2 receptor activation. KCa3.1 current is activated by Ca(2+) entry through Ca(2+)-release-activated Ca(2+) (CRAC/Orai1) channels, and both CRAC/Orai1 and KCa3.1 channels facilitate refilling of Ca(2+) stores. The Ca(2+) dependence of KCa3.1 channel activation was skewed to abnormally high concentrations, and we present evidence for a close physical association of the two channel types. Finally, migration of primary rat microglia was stimulated by UTP and inhibited by blocking either KCa3.1 or CRAC/Orai1 channels. This is the first report of selective coupling of one type of SK channel to purinergic stimulation of microglia, transactivation of KCa3.1 channels by CRAC/Orai1, and coordinated roles for both channels in store refilling, Ca(2+) signaling and microglial migration.
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Affiliation(s)
- Roger Ferreira
- Genes and Development Division, Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Lyanne C. Schlichter
- Genes and Development Division, Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
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Brawek B, Garaschuk O. Microglial calcium signaling in the adult, aged and diseased brain. Cell Calcium 2013; 53:159-69. [PMID: 23395344 DOI: 10.1016/j.ceca.2012.12.003] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 12/10/2012] [Indexed: 10/27/2022]
Abstract
Microglial cells are the resident immune cells of the CNS. They mediate innate immune response of the brain to injury, inflammation and neurodegenerative diseases. Apart from their role in disease they are critically involved in the development and plasticity-driven reorganization of neuronal networks and the homeostatic maintenance of brain tissue. Accumulating in vitro evidence suggests that executive functions of microglia are coupled to the intracellular Ca(2+) signaling of these cells. So far, however, very little is known about microglial Ca(2+) signaling in situ or in vivo, both in the healthy and in the diseased brain. Here, we summarize the recent in vivo/in situ findings and compare the properties of surveillant microglia in these preparations with those of microglia in vitro. The data suggest that surveillant microglia rarely show spontaneous Ca(2+) transients, express fewer functional receptors directly coupled to changes in the intracellular free Ca(2+) concentration on their surface, but vividly respond with Ca(2+) transients to cell or tissue damage in their microenvironment. Interestingly, some of these properties microglia share with monocytes engrafting in the brain under pathological conditions.
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Affiliation(s)
- Bianca Brawek
- Institute of Physiology II, Eberhard Karls University of Tuebingen, Keplerstr. 15, 72074 Tuebingen, Germany
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43
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Wu X, Pan L, Liu Y, Jiang P, Lee I, Drevensek-Olenik I, Zhang X, Xu J. Cell-cell communication induces random spikes of spontaneous calcium oscillations in multi-BV-2 microglial cells. Biochem Biophys Res Commun 2013; 431:664-9. [PMID: 23357419 DOI: 10.1016/j.bbrc.2013.01.064] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 01/16/2013] [Indexed: 01/11/2023]
Abstract
As the first and main form of active immune defense in the central nervous system, microglial cells usually exhibit complicated intracellular calcium (Ca²⁺) activity that can regulate the downstream components of signaling cascades. In the present work, spontaneous oscillations of the cytosolic calcium concentration ([Ca²⁺]c) in multi-BV-2 microglial cells were observed by video microscopy. These cells exhibited random spikes of Ca²⁺ oscillations. Cross-correlation analysis of the temporal dependence of the oscillations indicated the existence of cell-cell communication mediated by extracellular messengers. Numerical simulations based on a simple mathematical model suggested that these communications could induce random spikes of spontaneous Ca oscillations in the multi-cell system. Short-time imaging analysis of random spikes in different regions of a single cell showed that spontaneous Ca²⁺ oscillations resulted from Ca²⁺ wave generated by other cells as well as from calcium elevation inside the cell. Taken together, our data demonstrate that cell-cell communication existed between the BV-2 microglial cells in vitro and further resulted in the random spikes of spontaneous Ca²⁺ oscillations.
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Affiliation(s)
- Xian Wu
- The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics and TEDA Applied Physics School, Nankai University, Tianjin 300457, PR China
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White MC, Johnson GG, Zhang W, Hobrath JV, Piazza GA, Grimaldi M. Sulindac sulfide inhibits sarcoendoplasmic reticulum Ca2+ ATPase, induces endoplasmic reticulum stress response, and exerts toxicity in glioma cells: relevant similarities to and important differences from celecoxib. J Neurosci Res 2012; 91:393-406. [PMID: 23280445 DOI: 10.1002/jnr.23169] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 09/28/2012] [Accepted: 10/03/2012] [Indexed: 11/09/2022]
Abstract
Malignant gliomas have low survival expectations regardless of current treatments. Nonsteroidal anti-inflammatory drugs (NSAIDs) prevent cell transformation and slow cancer cell growth by mechanisms independent of cyclooxygenase (COX) inhibition. Certain NSAIDs trigger the endoplasmic reticulum stress response (ERSR), as revealed by upregulation of molecular chaperones such as GRP78 and C/EBP homologous protein (CHOP). Although celecoxib (CELE) inhibits the sarcoendoplasmic reticulum Ca(2+) ATPase (SERCA), an effect known to induce ERSR, sulindac sulfide (SS) has not been reported to affect SERCA. Here, we investigated these two drugs for their effects on Ca(2+) homeostasis, ERSR, and glioma cell survival. Our findings indicate that SS is a reversible inhibitor of SERCA and that both SS and CELE bind SERCA at its cyclopiazonic acid binding site. Furthermore, CELE releases additional Ca(2+) from the mitochondria. In glioma cells, both NSAIDS upregulate GRP78 and activate ER-associated caspase-4 and caspase-3. Although only CELE upregulates the expression of CHOP, it appears that CHOP induction could be associated with mitochondrial poisoning. In addition, CHOP induction appears to be uncorrelated with the gliotoxicity of these NSAIDS in our experiments. Our data suggest that activation of ERSR is primarily responsible for the gliotoxic effect of these NSAIDS. Because SS has good brain bioavailability, has lower COX-2 inhibition, and has no mitochondrial effects, it represents a more appealing molecular candidate than CELE to achieve gliotoxicity via activation of ERSR.
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Affiliation(s)
- M C White
- Laboratory of Neuropharmacology, Medicinal Chemistry Department, Drug Discovery Division, Southern Research Institute, Birmingham, Alabama 35205, USA
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Dolga AM, Letsche T, Gold M, Doti N, Bacher M, Chiamvimonvat N, Dodel R, Culmsee C. Activation of KCNN3/SK3/K(Ca)2.3 channels attenuates enhanced calcium influx and inflammatory cytokine production in activated microglia. Glia 2012; 60:2050-64. [PMID: 23002008 DOI: 10.1002/glia.22419] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Accepted: 08/23/2012] [Indexed: 11/10/2022]
Abstract
In neurons, small-conductance calcium-activated potassium (KCNN/SK/K(Ca)2) channels maintain calcium homeostasis after N-methyl-D-aspartate (NMDA) receptor activation, thereby preventing excitotoxic neuronal death. So far, little is known about the function of KCNN/SK/K(Ca)2 channels in non-neuronal cells, such as microglial cells. In this study, we addressed the question whether KCNN/SK/K(Ca)2 channels activation affected inflammatory responses of primary mouse microglial cells upon lipopolysaccharide (LPS) stimulation. We found that N-cyclohexyl-N-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-4-pyrimidinamine (CyPPA), a positive pharmacological activator of KCNN/SK/K(Ca)2 channels, significantly reduced LPS-stimulated activation of microglia in a concentration-dependent manner. The general KCNN/SK/K(Ca)2 channel blocker apamin reverted these effects of CyPPA on microglial proliferation. Since calcium plays a central role in microglial activation, we further addressed whether KCNN/SK/K(Ca)2 channel activation affected the changes of intracellular calcium levels, [Ca(2+)](i), in microglial cells. Our data show that LPS-induced elevation of [Ca(2+)](i) was attenuated following activation of KCNN2/3/K(Ca)2.2/K(Ca)2.3 channels by CyPPA. Furthermore, CyPPA reduced downstream events including tumor necrosis factor alpha and interleukin 6 cytokine production and nitric oxide release in activated microglia. Further, we applied specific peptide inhibitors of the KCNN/SK/K(Ca)2 channel subtypes to identify which particular channel subtype mediated the observed anti-inflammatory effects. Only inhibitory peptides targeting KCNN3/SK3/K(Ca)2.3 channels, but not KCNN2/SK2/K(Ca)2.2 channel inhibition, reversed the CyPPA-effects on LPS-induced microglial proliferation. These findings revealed that KCNN3/SK3/K(Ca)2.3 channels can modulate the LPS-induced inflammatory responses in microglial cells. Thus, KCNN3/SK3/K(Ca)2.3 channels may serve as a therapeutic target for reducing microglial activity and related inflammatory responses in the central nervous system.
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Affiliation(s)
- Amalia M Dolga
- Institute of Pharmacology and Clinical Pharmacy, Philipps University of Marburg, 35032, Marburg, Germany.
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Hu X, Zhou H, Zhang D, Yang S, Qian L, Wu HM, Chen PS, Wilson B, Gao HM, Lu RB, Hong JS. Clozapine protects dopaminergic neurons from inflammation-induced damage by inhibiting microglial overactivation. J Neuroimmune Pharmacol 2012; 7:187-201. [PMID: 21870076 PMCID: PMC3633602 DOI: 10.1007/s11481-011-9309-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Accepted: 08/16/2011] [Indexed: 10/17/2022]
Abstract
Increasing evidence suggests a possible involvement of neuroinflammation in some psychiatric disorders, and also pharmacological reports indicate that anti-inflammatory effects are associated with therapeutic actions of psychoactive drugs, such as anti-depressants and antipsychotics. The purpose of this study was to explore whether clozapine, a widely used antipsychotic drugs, displays anti-inflammatory and neuroprotective effects. Using primary cortical and mesencephalic neuron-glia cultures, we found that clozapine was protective against inflammation-related neurodegeneration induced by lipopolysaccharide (LPS). Pretreatment of cortical or mesencephalic neuron-glia cultures with clozapine (0.1 or 1 μM) for 24 h attenuated LPS-induced neurotoxicity. Clozapine also protected neurons against 1-methyl-4-phenylpyridinium(+) (MPP(+))-induced neurotoxicity, but only in cultures containing microglia, indicating an indispensable role of microglia in clozapine-afforded neuroprotection. Further observation revealed attenuated LPS-induced microglial activation in primary neuron-glia cultures and in HAPI microglial cell line with clozapine pretreatment. Clozapine ameliorated the production of microglia-derived superoxide and intracellular reactive oxygen species (ROS), as well as the production of nitric oxide and TNF-α following LPS. In addition, the protective effect of clozapine was not observed in neuron-glia cultures from mice lacking functional NADPH oxidase (PHOX), a key enzyme for superoxide production in immune cells. Further mechanistic studies demonstrated that clozapine pretreatment inhibited LPS-induced translocation of cytosolic subunit p47(phox) to the membrane in microglia, which was most likely through inhibiting the phosphoinositide 3-kinase (PI3K) pathway. Taken together, this study demonstrates that clozapine exerts neuroprotective effect via the attenuation of microglia activation through inhibition of PHOX-generated ROS production and suggests potential use of antipsychotic drugs for neuroprotection.
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Affiliation(s)
- Xiaoming Hu
- Neuropharmacology Section, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709
- Department of Neurology and Pittsburgh Institute of Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Hui Zhou
- Neuropharmacology Section, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709
| | - Dan Zhang
- Neuropharmacology Section, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709
| | - Sufen Yang
- Neuropharmacology Section, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709
| | - Li Qian
- Neuropharmacology Section, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709
| | - Hung-Ming Wu
- Neuropharmacology Section, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709
- Institute of Behavioral Medicine and Department of Psychiatry, College of Medicine & Hospital, National Cheng-Kung University, Tainan, Taiwan
| | - Po-See Chen
- Neuropharmacology Section, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709
| | - Belinda Wilson
- Neuropharmacology Section, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709
| | - Hui-Ming Gao
- Neuropharmacology Section, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709
| | - Ru-band Lu
- Institute of Behavioral Medicine and Department of Psychiatry, College of Medicine & Hospital, National Cheng-Kung University, Tainan, Taiwan
| | - Jau-Shyong Hong
- Neuropharmacology Section, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709
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Garaschuk O. Imaging microcircuit function in healthy and diseased brain. Exp Neurol 2012; 242:41-9. [PMID: 22370088 DOI: 10.1016/j.expneurol.2012.02.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Revised: 11/15/2011] [Accepted: 02/13/2012] [Indexed: 11/26/2022]
Abstract
Neural microcircuits are the computational units of the mammalian brain. Recent evidence suggests that they are not composed exclusively of neurons but also involve other cell types such as astrocytes and microglia. In the healthy brain microglia, the resident immune cell, closely interacts with synapses and is likely to be involved in their structural plasticity. The interaction between the nervous and the immune systems is even more prominent under pathological conditions such as brain injury, inflammation and neurodegenerative diseases. This review discusses the techniques for high resolution imaging of microcircuit function in health and disease by focusing on some of the most recent advances in the field of in vivo calcium imaging of neurons, astrocytes and microglia.
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Affiliation(s)
- Olga Garaschuk
- Dept. of Physiology II, University of Tuebingen, Keplerstrasse 15, 72074 Tuebingen, Germany.
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48
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Black JA, Waxman SG. Sodium channels and microglial function. Exp Neurol 2011; 234:302-15. [PMID: 21985863 DOI: 10.1016/j.expneurol.2011.09.030] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 09/09/2011] [Accepted: 09/26/2011] [Indexed: 12/19/2022]
Abstract
Microglia are resident immune cells that provide continuous surveillance within the central nervous system (CNS) and respond to perturbations of brain and spinal cord parenchyma with an array of effector functions, including proliferation, migration, phagocytosis, secretions of multiple cytokines/chemokines and promotion of repair. To sense alterations within their environment, microglia express a large number of cell surface receptors, ion channels and adhesion molecules, which activate complex and dynamic signaling pathways. In the present chapter, we review studies that demonstrate that microglia in vivo and in vitro express specific voltage-gated sodium channel isoforms, and that blockade of sodium channel activity can attenuate several effector functions of microglia. These studies also provide strong evidence that Nav1.6 is the predominant sodium channel isoform expressed in microglia and that its activity contributes to the response of microglia to multiple activating signals.
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Affiliation(s)
- Joel A Black
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06511, USA.
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Abstract
Microglial cells are the resident macrophages in the central nervous system. These cells of mesodermal/mesenchymal origin migrate into all regions of the central nervous system, disseminate through the brain parenchyma, and acquire a specific ramified morphological phenotype termed "resting microglia." Recent studies indicate that even in the normal brain, microglia have highly motile processes by which they scan their territorial domains. By a large number of signaling pathways they can communicate with macroglial cells and neurons and with cells of the immune system. Likewise, microglial cells express receptors classically described for brain-specific communication such as neurotransmitter receptors and those first discovered as immune cell-specific such as for cytokines. Microglial cells are considered the most susceptible sensors of brain pathology. Upon any detection of signs for brain lesions or nervous system dysfunction, microglial cells undergo a complex, multistage activation process that converts them into the "activated microglial cell." This cell form has the capacity to release a large number of substances that can act detrimental or beneficial for the surrounding cells. Activated microglial cells can migrate to the site of injury, proliferate, and phagocytose cells and cellular compartments.
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50
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Van den Eynden J, Notelaers K, Brône B, Janssen D, Nelissen K, Sahebali S, Smolders I, Hellings N, Steels P, Rigo JM. Glycine enhances microglial intracellular calcium signaling. A role for sodium-coupled neutral amino acid transporters. Pflugers Arch 2011; 461:481-91. [PMID: 21350800 DOI: 10.1007/s00424-011-0939-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2010] [Revised: 01/31/2011] [Accepted: 02/09/2011] [Indexed: 12/17/2022]
Abstract
The inhibitory neurotransmitter glycine is known to enhance microglial nitric oxide production. However, up to now, the mechanism is undocumented. Since calcium is an important second messenger in both immune and glial cells, we studied the effects of glycine on intracellular calcium signaling. We found that millimolar concentrations of glycine enhance microglial intracellular calcium transients induced by 100 μM ATP or by 500 nM thapsigargin. This modulation was unaffected by the glycine receptor antagonist strychnine and could not be mimicked by glycine receptor agonists such as taurine or β-alanine, indicating glycine receptor independency. The modulation of calcium responses could be mimicked by several structurally related amino acids (e.g., serine, alanine, or glutamine) and was inhibited in the presence of the neutral amino acid transporter substrate α-aminoisobutyric acid (AIB). We correlated these findings to immunofluorescence glycine uptake experiments which showed a clear glycine uptake which was inhibited by AIB. Furthermore, all amino acids that were shown to modulate calcium responses also evoked AIB-sensitive inward currents, mainly carried by sodium, as demonstrated by patch clamp experiments. Based on these findings, we propose that sodium-coupled neutral amino acid transporters are responsible for the observed glycine modulation of intracellular calcium responses.
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Affiliation(s)
- Jimmy Van den Eynden
- Institute of Biomedical Research, Hasselt University and Transnationale Universiteit Limburg, Agoralaan, Diepenbeek, Belgium
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