151
|
Tsuda M, Masuda T, Tozaki-Saitoh H, Inoue K. Microglial Regulation of Neuropathic Pain. J Pharmacol Sci 2013; 121:89-94. [DOI: 10.1254/jphs.12r14cp] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
|
152
|
Kobayashi K, Yamanaka H, Noguchi K. Expression of ATP receptors in the rat dorsal root ganglion and spinal cord. Anat Sci Int 2012. [PMID: 23179910 DOI: 10.1007/s12565-012-0163-9] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Extracellular purine nucleotides and nucleosides play important roles in the nervous system, e.g., neurotransmission, neuromodulation, chemoattraction and acute inflammation. Extracellular nucleotides act through ATP receptors (P2 receptors). P2 receptors are classified into two families: the P2X receptors are ionotropic ligand-gated ion channels and the P2Y receptors are metabotropic G-protein-coupled receptors. Currently, seven P2X receptors (P2X1-7) and eight P2Y receptors (P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13 and P2Y14) are recognized. In the sensory nervous system, ATP is suggested to be one of first mediators of tissue damage, which activates primary afferents. Nerve injury often leads to neuropathic pain, such as mechanical allodynia and painful responses to normally innocuous stimuli. Peripheral nerve injury induces the upregulation of molecules in activated microglia in the spinal cord. Microglia in the spinal cord may play an important role in the development and maintenance of neuropathic pain. A prominent signaling pathway in the development of neuropathic pain involves ATP acting on microglial purinergic receptors. This review focuses on the expression of P2X and P2Y receptors mRNAs in the pain transmission pathway, i.e., in the dorsal root ganglion (DRG) and spinal cord. Furthermore, we suggest that the multiple microglial P2Y receptors activated by peripheral nerve injury may play a key role in the development of neuropathic pain.
Collapse
Affiliation(s)
- Kimiko Kobayashi
- Department of Anatomy and Neuroscience, Hyogo College of Medicine, Mukogawa-cho, Nishinomiya, Hyogo, Japan.
| | | | | |
Collapse
|
153
|
Su X, Floyd DH, Hughes A, Xiang J, Schneider JG, Uluckan O, Heller E, Deng H, Zou W, Craft CS, Wu K, Hirbe AC, Grabowska D, Eagleton MC, Townsley S, Collins L, Piwnica-Worms D, Steinberg TH, Novack DV, Conley PB, Hurchla MA, Rogers M, Weilbaecher KN. The ADP receptor P2RY12 regulates osteoclast function and pathologic bone remodeling. J Clin Invest 2012; 122:3579-92. [PMID: 22996695 DOI: 10.1172/jci38576] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 07/26/2012] [Indexed: 12/16/2022] Open
Abstract
The adenosine diphosphate (ADP) receptor P2RY12 (purinergic receptor P2Y, G protein coupled, 12) plays a critical role in platelet aggregation, and P2RY12 inhibitors are used clinically to prevent cardiac and cerebral thrombotic events. Extracellular ADP has also been shown to increase osteoclast (OC) activity, but the role of P2RY12 in OC biology is unknown. Here, we examined the role of mouse P2RY12 in OC function. Mice lacking P2ry12 had decreased OC activity and were partially protected from age-associated bone loss. P2ry12-/- OCs exhibited intact differentiation markers, but diminished resorptive function. Extracellular ADP enhanced OC adhesion and resorptive activity of WT, but not P2ry12-/-, OCs. In platelets, ADP stimulation of P2RY12 resulted in GTPase Ras-related protein (RAP1) activation and subsequent αIIbβ3 integrin activation. Likewise, we found that ADP stimulation induced RAP1 activation in WT and integrin β3 gene knockout (Itgb3-/-) OCs, but its effects were substantially blunted in P2ry12-/- OCs. In vivo, P2ry12-/- mice were partially protected from pathologic bone loss associated with serum transfer arthritis, tumor growth in bone, and ovariectomy-induced osteoporosis: all conditions associated with increased extracellular ADP. Finally, mice treated with the clinical inhibitor of P2RY12, clopidogrel, were protected from pathologic osteolysis. These results demonstrate that P2RY12 is the primary ADP receptor in OCs and suggest that P2RY12 inhibition is a potential therapeutic target for pathologic bone loss.
Collapse
Affiliation(s)
- Xinming Su
- Department of Medicine, Division of Oncology, Washington University in St. Louis School of Medicine, St. Louis, Missouri 63110, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
154
|
Corriden R, Insel PA. New insights regarding the regulation of chemotaxis by nucleotides, adenosine, and their receptors. Purinergic Signal 2012; 8:587-98. [PMID: 22528684 PMCID: PMC3360098 DOI: 10.1007/s11302-012-9311-x] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 01/05/2012] [Indexed: 12/23/2022] Open
Abstract
The directional movement of cells can be regulated by ATP, certain other nucleotides (e.g., ADP, UTP), and adenosine. Such regulation occurs for cells that are "professional phagocytes" (e.g., neutrophils, macrophages, certain lymphocytes, and microglia) and that undergo directional migration and subsequent phagocytosis. Numerous other cell types (e.g., fibroblasts, endothelial cells, neurons, and keratinocytes) also change motility and migration in response to ATP, other nucleotides, and adenosine. In this article, we review how nucleotides and adenosine modulate chemotaxis and motility and highlight the importance of nucleotide- and adenosine-regulated cell migration in several cell types: neutrophils, microglia, endothelial cells, and cancer cells. We also discuss difficulties in conducting experiments and drawing conclusions regarding the ability of nucleotides and adenosine to modulate the migration of professional and non-professional phagocytes.
Collapse
Affiliation(s)
- Ross Corriden
- Institute of Cell Signalling, University of Nottingham, Nottingham, UK
| | - Paul A. Insel
- Departments of Pharmacology and Medicine, University of California, San Diego, CA USA
- Department of Pharmacology, University of California San Diego, 9500 Gilman Drive, Mail code 0636, La Jolla, CA 92093 USA
| |
Collapse
|
155
|
Tsuda M, Beggs S, Salter MW, Inoue K. Microglia and intractable chronic pain. Glia 2012; 61:55-61. [DOI: 10.1002/glia.22379] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 06/05/2012] [Indexed: 11/06/2022]
|
156
|
Koizumi S, Ohsawa K, Inoue K, Kohsaka S. Purinergic receptors in microglia: Functional modal shifts of microglia mediated by P2 and P1 receptors. Glia 2012; 61:47-54. [DOI: 10.1002/glia.22358] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2012] [Accepted: 04/30/2012] [Indexed: 11/09/2022]
|
157
|
Lee SH, Hollingsworth R, Kwon HY, Lee N, Chung CY. β-arrestin 2-dependent activation of ERK1/2 is required for ADP-induced paxillin phosphorylation at Ser(83) and microglia chemotaxis. Glia 2012; 60:1366-77. [PMID: 22638989 DOI: 10.1002/glia.22355] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 04/25/2012] [Indexed: 12/24/2022]
Abstract
Microglia play crucial roles in increased inflammation in the central nervous system upon brain injuries and diseases. Extracellular ADP has been reported to induce microglia chemotaxis and membrane ruffle formation through P2Y(12) receptor. In this study, we examined the role of ERK1/2 activation in ADP-induced microglia chemotaxis. ADP stimulation increases the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and paxillin phosphorylation at Tyr(31) and Ser(83) . Inhibition of ERK1/2 significantly inhibited paxillin phosphorylation at Ser(83) and the retraction of membrane ruffles, causing inefficient chemotaxis. Close examination of dynamics of focal adhesion (FA) formation with green fluorescent protein-paxillin revealed that the disassembly of FAs in U0126-treated cells was significantly impaired. Depletion of β-Arrestin 2 (β-Arr2) with short hairpin RNA markedly reduced the phosphorylation of ERK1/2 and Pax/Ser(83) , indicating that β-Arr2 is required for ERK1/2 activation upon ADP stimulation. A large fraction of phosphorylated ERK1/2 and β-Arr2 were translocated and co-localized at focal contacts in the newly forming lamellipodia. Examination of kinetics and rate constant of paxillin formation and disassembly revealed that the phosphorylation of paxillin at Tyr(31) by c-Src appears to be involved in adhesion formation upon ADP stimulation while Ser(83) required for adhesion disassembly.
Collapse
Affiliation(s)
- Sang-Hyun Lee
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232-6600, USA
| | | | | | | | | |
Collapse
|
158
|
Weisman GA, Ajit D, Garrad R, Peterson TS, Woods LT, Thebeau C, Camden JM, Erb L. Neuroprotective roles of the P2Y(2) receptor. Purinergic Signal 2012; 8:559-78. [PMID: 22528682 DOI: 10.1007/s11302-012-9307-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 10/04/2011] [Indexed: 02/07/2023] Open
Abstract
Purinergic signaling plays a unique role in the brain by integrating neuronal and glial cellular circuits. The metabotropic P1 adenosine receptors and P2Y nucleotide receptors and ionotropic P2X receptors control numerous physiological functions of neuronal and glial cells and have been implicated in a wide variety of neuropathologies. Emerging research suggests that purinergic receptor interactions between cells of the central nervous system (CNS) have relevance in the prevention and attenuation of neurodegenerative diseases resulting from chronic inflammation. CNS responses to chronic inflammation are largely dependent on interactions between different cell types (i.e., neurons and glia) and activation of signaling molecules including P2X and P2Y receptors. Whereas numerous P2 receptors contribute to functions of the CNS, the P2Y(2) receptor is believed to play an important role in neuroprotection under inflammatory conditions. While acute inflammation is necessary for tissue repair due to injury, chronic inflammation contributes to neurodegeneration in Alzheimer's disease and occurs when glial cells undergo prolonged activation resulting in extended release of proinflammatory cytokines and nucleotides. This review describes cell-specific and tissue-integrated functions of P2 receptors in the CNS with an emphasis on P2Y(2) receptor signaling pathways in neurons, glia, and endothelium and their role in neuroprotection.
Collapse
Affiliation(s)
- Gary A Weisman
- Department of Biochemistry, University of Missouri, 540E Life Sciences Center, 1201 Rollins Road, Columbia, MO 65211-7310, USA.
| | | | | | | | | | | | | | | |
Collapse
|
159
|
Uesugi A, Kataoka A, Tozaki-Saitoh H, Koga Y, Tsuda M, Robaye B, Boeynaems JM, Inoue K. Involvement of protein kinase D in uridine diphosphate-induced microglial macropinocytosis and phagocytosis. Glia 2012; 60:1094-105. [PMID: 22488958 DOI: 10.1002/glia.22337] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2011] [Accepted: 03/13/2012] [Indexed: 11/09/2022]
Abstract
The clearance of tissue debris by microglia is a crucial component of maintaining brain homeostasis. Microglia continuously survey the brain parenchyma and utilize extracellular nucleotides to trigger the initiation of their dynamic responses. Extracellular uridine diphosphate (UDP), which leaks or is released from damaged neurons, has been reported to stimulate the phagocytotic activity of microglia through P2Y(6) receptor activation. However, the intracellular mechanisms underlying microglial P2Y(6) receptor signals have not been identified. In this study, we demonstrated that UDP stimulation induced immediate and long-lasting dynamic movements in the cell membrane. After 60 min of UDP stimulation, there was an upregulation in the number of large vacuoles formed in the cell that incorporate extracellular fluorescent-labeled dextran, which indicates microglial macropinocytosis. In addition, UDP-induced vacuole formation and continuous membrane motility were suppressed by the protein kinase D (PKD) inhibitors, Gö6976 and CID755673, unlike Gö6983, which is far less sensitive to PKD. The inhibition of PKD also reduced UDP-induced incorporation of fluorescent-labeled dextran and soluble β-amyloid and phagocytosis of microspheres. UDP induced rapid phosphorylation and membrane translocation of PKD, which was abrogated by the inhibition of protein kinase C (PKC) with Gö6983. However, Gö6983 failed to suppress UDP-induced incorporation of microspheres. Finally, we found that inhibition of PKD by CID755673 significantly suppressed UDP-induced engulfment of IgG-opsonized microspheres. These data suggest that a PKC-independent function of PKD regulates UDP-induced membrane movement and contributes to the increased uptake of extracellular fluid and microspheres in microglia.
Collapse
Affiliation(s)
- Ayumi Uesugi
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Higashi, Fukuoka, Japan
| | | | | | | | | | | | | | | |
Collapse
|
160
|
Hidetoshi TS, Makoto T, Inoue K. P2Y receptors in microglia and neuroinflammation. ACTA ACUST UNITED AC 2012. [DOI: 10.1002/wmts.46] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
|
161
|
Ohsawa K, Sanagi T, Nakamura Y, Suzuki E, Inoue K, Kohsaka S. Adenosine A3 receptor is involved in ADP-induced microglial process extension and migration. J Neurochem 2012; 121:217-27. [PMID: 22335470 DOI: 10.1111/j.1471-4159.2012.07693.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The extension of microglial processes toward injured sites in the brain is triggered by the stimulation of the purinergic receptor P2Y(12) by extracellular ATP. We recently showed that P2Y(12) stimulation by ATP induces microglial process extension in collagen gels. In the present study, we found that a P2Y(12) agonist, 2-methylthio-ADP (2MeSADP), failed to induce the process extension of microglia in collagen gels and that co-stimulation with adenosine, a phosphohydrolytic derivative of ATP, and 2MeSADP restored the chemotactic process extension. An adenosine A3 receptor (A3R)-selective agonist restored the chemotactic process extension, but other receptor subtype agonists did not. The removal of adenosine by adenosine deaminase and the blocking of A3R by an A3R-selective antagonist inhibited ADP-induced process extension. The A3R antagonist inhibited ADP-induced microglial migration, and an A3R agonist promoted 2MeSADP-stimulated migration. ADP and the A3R agonist activated Jun N-terminal kinase in microglia, and a Jun N-terminal kinase inhibitor inhibited the ADP-induced process extension. An RT-PCR analysis showed that A1R and A3R were expressed by microglia sorted from adult rat brains and that the A2AR expression level was very low. These results suggested that A3R signaling may be involved in the ADP-induced process extension and migration of microglia.
Collapse
Affiliation(s)
- Keiko Ohsawa
- Department of Neurochemistry, National Institute of Neuroscience, 4-1-1 Ogawahigashi Kodaira, Tokyo 187-8502, Japan
| | | | | | | | | | | |
Collapse
|
162
|
Toyomitsu E, Tsuda M, Yamashita T, Tozaki-Saitoh H, Tanaka Y, Inoue K. CCL2 promotes P2X4 receptor trafficking to the cell surface of microglia. Purinergic Signal 2012; 8:301-10. [PMID: 22222817 DOI: 10.1007/s11302-011-9288-x] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 12/08/2011] [Indexed: 01/06/2023] Open
Abstract
P2X4 receptors (P2X4Rs), a subtype of the purinergic P2X family, play important roles in regulating neuronal and glial functions in the nervous system. We have previously shown that the expression of P2X4Rs is upregulated in activated microglia after peripheral nerve injury and that activation of the receptors by extracellular ATP is crucial for maintaining nerve injury-induced pain hypersensitivity. However, the regulation of P2X4R expression on the cell surface of microglia is poorly understood. Here, we identify the CC chemokine receptor CCR2 as a regulator of P2X4R trafficking to the cell surface of microglia. In a quantitative cell surface biotinylation assay, we found that applying CCL2 or CCL12, endogenous ligands for CCR2, to primary cultured microglial cells, increased the levels of P2X4R protein on the cell surface without changing total cellular expression. This effect of CCL2 was prevented by an antagonist of CCR2. Time-lapse imaging of green fluorescent protein (GFP)-tagged P2X4R in living microglial cells showed that CCL2 stimulation increased the movement of P2X4R-GFP particles. The subcellular localization of P2X4R immunofluorescence was restricted to lysosomes around the perinuclear region. Notably, CCL2 changed the distribution of lysosomes with P2X4R immunofluorescence within microglial cells and induced release of the lysosomal enzyme β-hexosaminidase, indicating lysosomal exocytosis. Moreover, CCL2-stimulated microglia enhanced Akt phosphorylation by ATP applied extracellularly, a P2X4R-mediated response. These results indicate that CCL2 promotes expression of P2X4R protein on the cell surface of microglia through exocytosis of P2X4R-containing lysosomes, which may be a possible mechanism for pain hypersensitivity after nerve injury.
Collapse
Affiliation(s)
- Emika Toyomitsu
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
| | | | | | | | | | | |
Collapse
|
163
|
Dennis J, Morgan MK, Graf MR, Fuss B. P2Y12 receptor expression is a critical determinant of functional responsiveness to ATX's MORFO domain. Purinergic Signal 2011; 8:181-90. [PMID: 22139091 DOI: 10.1007/s11302-011-9283-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Accepted: 11/11/2011] [Indexed: 01/13/2023] Open
Abstract
In the central nervous system, the formation of the myelin sheath and the differentiation of the myelinating cells, namely oligodendrocytes, are regulated by complex signaling networks that involve purinergic receptors and the extracellular matrix. However, the exact nature of the molecular interactions underlying these networks still needs to be defined. In this respect, the data presented here reveal a signaling mechanism that is characterized by an interaction between the purinergic P2Y(12) receptor and the matricellular extracellular matrix protein autotaxin (ATX), also known as ENPP2, phosphodiesterase-Iα/ATX, or lysoPLD. ATX has been previously described by us to mediate intermediate states of oligodendrocyte adhesion and to enable changes in oligodendrocyte morphology that are thought to be crucial for the formation of a fully functional myelin sheath. This functional property of ATX is mediated by ATX's modulator of oligodendrocyte remodeling and focal adhesion organization (MORFO) domain. Here, we show that the expression of the P2Y(12) receptor is necessary for ATX's MORFO domain to exert its effects on differentiating oligodendrocytes. In addition, our data demonstrate that exogenous expression of the P2Y(12) receptor can render cells responsive to the known effects of ATX's MORFO domain, and they identify Rac1 as an intracellular factor mediating the effect of ATX-MORFO-P2Y(12) signaling on the assembly of focal adhesions. Our data further support the idea that a physical interaction between ATX and the P2Y(12) receptor provides the basis for an ATX-MORFO-P2Y(12) signaling axis that is crucial for mediating cellular states of intermediate adhesion and morphological/structural plasticity.
Collapse
Affiliation(s)
- Jameel Dennis
- Department of Anatomy, Virginia Commonwealth University Medical Center, Richmond, VA 23298, USA.
| | | | | | | |
Collapse
|
164
|
Trang T, Beggs S, Salter MW. ATP receptors gate microglia signaling in neuropathic pain. Exp Neurol 2011; 234:354-61. [PMID: 22116040 DOI: 10.1016/j.expneurol.2011.11.012] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Revised: 10/31/2011] [Accepted: 11/08/2011] [Indexed: 01/30/2023]
Abstract
Microglia were described by Pio del Rio-Hortega (1932) as being the 'third element' distinct from neurons and astrocytes. Decades after this observation, the function and even the very existence of microglia as a distinct cell type were topics of intense debate and conjecture. However, considerable advances have been made towards understanding the neurobiology of microglia resulting in a radical shift in our view of them as being passive bystanders that have solely immune and supportive roles, to being active principal players that contribute to central nervous system pathologies caused by disease or following injury. Converging lines of evidence implicate microglia as being essential in the pathogenesis of neuropathic pain, a debilitating chronic pain condition that can occur after peripheral nerve damage caused by disease, infection, or physical injury. A key molecule that modulates microglial activity is ATP, an endogenous ligand of the P2-purinoceptor family consisting of P2X ionotropic and P2Y metabotropic receptors. Microglia express several P2 receptor subtypes, and of these the P2X4, P2X7, and P2Y12 receptor subtypes have been implicated in neuropathic pain. The P2X4 receptor has emerged as the core microglia-neuron signaling pathway: activation of this receptor causes release of brain-derived neurotrophic factor (BDNF) which causes disinhibition of pain-transmission neurons in spinal lamina I. The present review highlights recent advances in understanding the signaling and regulation of P2 receptors expressed in microglia and the implications for microglia-neuron interactions for the management of neuropathic pain.
Collapse
Affiliation(s)
- Tuan Trang
- Program in Neuroscience and Mental Health, Hospital for Sick Children, University of Toronto Centre for the Study of Pain, Toronto, Ontario, Canada M5G 1X8
| | | | | |
Collapse
|
165
|
Purinergic system, microglia and neuropathic pain. Curr Opin Pharmacol 2011; 12:74-9. [PMID: 22036170 DOI: 10.1016/j.coph.2011.10.014] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 10/12/2011] [Accepted: 10/12/2011] [Indexed: 01/23/2023]
Abstract
Extracellular nucleotides play pivotal roles in the regulation of neuronal and glial functions in the nervous system through P2X receptors (P2XRs) and P2Y receptors (P2YRs). A growing body of evidence shows that microglia express several subtypes of P2XRs and P2YRs, and that these receptors play a key role in pain signaling in the spinal cord under pathological conditions, such as following peripheral nerve injury (neuropathic pain). Following peripheral nerve injury, dorsal horn microglia become activated and show upregulated expression of purinergic receptors, and interference with the function or expression of these receptors strongly suppresses neuropathic pain. This article highlights recent advances that further increase our understanding of the mechanisms by which microglial purinergic receptors contribute to the pathogenesis of neuropathic pain.
Collapse
|
166
|
Sosa RA, Forsthuber TG. The critical role of antigen-presentation-induced cytokine crosstalk in the central nervous system in multiple sclerosis and experimental autoimmune encephalomyelitis. J Interferon Cytokine Res 2011; 31:753-68. [PMID: 21919736 PMCID: PMC3189551 DOI: 10.1089/jir.2011.0052] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 06/23/2011] [Indexed: 12/17/2022] Open
Abstract
Multiple sclerosis (MS) is a debilitating disease of the central nervous system (CNS) that has been extensively studied using the animal model experimental autoimmune encephalomyelitis (EAE). It is believed that CD4(+) T lymphocytes play an important role in the pathogenesis of this disease by mediating the demyelination of neuronal axons via secretion of proinflammatory cytokines resulting in the clinical manifestations. Although a great deal of information has been gained in the last several decades about the cells involved in the inflammatory and disease mediating process, important questions have remained unanswered. It has long been held that initial neuroantigen presentation and T cell activation events occur in the immune periphery and then translocate to the CNS. However, an increasing body of evidence suggests that antigen (Ag) presentation might initiate within the CNS itself. Importantly, it has remained unresolved which antigen presenting cells (APCs) in the CNS are the first to acquire and present neuroantigens during EAE/MS to T cells, and what the conditions are under which this takes place, ie, whether this occurs in the healthy CNS or only during inflammatory conditions and what the related cytokine microenvironment is comprised of. In particular, the central role of interferon-γ as a primary mediator of CNS pathology during EAE has been challenged by the emergence of Th17 cells producing interleukin-17. This review describes our current understanding of potential APCs in the CNS and the contribution of these and other CNS-resident cells to disease pathology. Additionally, we discuss the question of where Ag presentation is initiated and under what conditions neuroantigens are made available to APCs with special emphasis on which cytokines may be important in this process.
Collapse
Affiliation(s)
- Rebecca A Sosa
- Department of Biology, University of Texas at San Antonio, Texas 78249, USA
| | | |
Collapse
|
167
|
Romero S, Grompone G, Carayol N, Mounier J, Guadagnini S, Prevost MC, Sansonetti PJ, Van Nhieu GT. ATP-mediated Erk1/2 activation stimulates bacterial capture by filopodia, which precedes Shigella invasion of epithelial cells. Cell Host Microbe 2011; 9:508-19. [PMID: 21669399 DOI: 10.1016/j.chom.2011.05.005] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 04/19/2011] [Accepted: 05/23/2011] [Indexed: 11/29/2022]
Abstract
Shigella, the causative agent of bacillary dysentery in humans, invades epithelial cells, using a type III secretory system (T3SS) to inject bacterial effectors into host cells and remodel the actin cytoskeleton. ATP released through connexin hemichanels on the epithelial membrane stimulates Shigella invasion and dissemination in epithelial cells. Here, we show that prior to contact with the cell body, Shigella is captured by nanometer-thin micropodial extensions (NMEs) at a distance from the cell surface, in a process involving the T3SS tip complex proteins and stimulated by ATP- and connexin-mediated signaling. Upon bacterial contact, NMEs retract, bringing bacteria in contact with the cell body, where invasion occurs. ATP stimulates Erk1/2 activation, which controls actin retrograde flow in NMEs and their retraction. These findings reveal previously unappreciated facets of interaction of an invasive bacterium with host cells and a prominent role for Erk1/2 in the control of filopodial dynamics.
Collapse
Affiliation(s)
- Stéphane Romero
- Equipe Communication Intercellulaire et Infections Microbiennes, Centre de Recherche Interdisciplinaire en Biologie, Collège de France, 75005 Paris, France
| | | | | | | | | | | | | | | |
Collapse
|
168
|
Sargsyan SA, Blackburn DJ, Barber SC, Grosskreutz J, De Vos KJ, Monk PN, Shaw PJ. A comparison of in vitro properties of resting SOD1 transgenic microglia reveals evidence of reduced neuroprotective function. BMC Neurosci 2011; 12:91. [PMID: 21943126 PMCID: PMC3191510 DOI: 10.1186/1471-2202-12-91] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2011] [Accepted: 09/23/2011] [Indexed: 12/11/2022] Open
Abstract
Background Overexpression of mutant copper/zinc superoxide dismutase (SOD1) in rodents has provided useful models for studying the pathogenesis of amyotrophic lateral sclerosis (ALS). Microglia have been shown to contribute to ALS disease progression in these models, although the mechanism of this contribution remains to be elucidated. Here, we present the first evidence of the effects of overexpression of mutant (TG G93A) and wild type (TG WT) human SOD1 transgenes on a set of functional properties of microglia relevant to ALS progression, including expression of integrin β-1, spreading and migration, phagocytosis of apoptotic neuronal cell debris, and intracellular calcium changes in response to an inflammatory stimulus. Results TG SOD1 G93A but not TG SOD1 WT microglia had lower expression levels of the cell adhesion molecule subunit integrin β-1 than their NTG control cells [NTG (G93A) and NTG (WT), respectively, 92.8 ± 2.8% on TG G93A, 92.0 ± 6.6% on TG WT, 100.0 ± 1.6% on NTG (G93A), and 100.0 ± 2.7% on NTG (WT) cells], resulting in decreased spreading ability, with no effect on ability to migrate. Both TG G93A and TG WT microglia had reduced capacity to phagocytose apoptotic neuronal cell debris (13.0 ± 1.3% for TG G93A, 16.5 ± 1.9% for TG WT, 28.6 ± 1.8% for NTG (G93A), and 26.9 ± 2.8% for NTG (WT) cells). Extracellular stimulation of microglia with ATP resulted in smaller increase in intracellular free calcium in TG G93A and TG WT microglia relative to NTG controls (0.28 ± 0.02 μM for TG G93A, 0.24 ± 0.03 μM for TG WT, 0.39 ± 0.03 μM for NTG (G93A), and 0.37 ± 0.05 μM for NTG (WT) microglia). Conclusions These findings indicate that, under resting conditions, microglia from mutant SOD1 transgenic mice have a reduced capacity to elicit physiological responses following tissue disturbances and that higher levels of stimulatory signals, and/or prolonged stimulation may be necessary to initiate these responses. Overall, resting mutant SOD1-overexpressing microglia may have reduced capacity to function as sensors of disturbed tissue/cellular homeostasis in the CNS and thus have reduced neuroprotective function.
Collapse
Affiliation(s)
- Siranush A Sargsyan
- Department of Medicine, University of Colorado Denver School of Medicine, CO, USA.
| | | | | | | | | | | | | |
Collapse
|
169
|
Ohsawa K, Kohsaka S. Dynamic motility of microglia: Purinergic modulation of microglial movement in the normal and pathological brain. Glia 2011; 59:1793-9. [DOI: 10.1002/glia.21238] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 08/02/2011] [Indexed: 01/23/2023]
|
170
|
The mechanisms of microgliosis and pain following peripheral nerve injury. Exp Neurol 2011; 234:271-82. [PMID: 21893056 DOI: 10.1016/j.expneurol.2011.08.018] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 08/10/2011] [Accepted: 08/18/2011] [Indexed: 12/23/2022]
Abstract
Microglia are the resident macrophages in the central nervous system (CNS). Any insult to the CNS homeostasis will induce a rapid change in microglia morphology, gene expression profile and functional behaviour. These responses of microglia have been collectively known as 'microgliosis'. Interestingly, damage to the nervous system outside the CNS, such as axotomy of a peripheral nerve, can lead to microgliosis in the spinal cord. There is a variation in the degree of microgliosis depending on the model of nerve injury employed for instance this response is more marked following traumatic nerve injury than in models of chemotherapy induced neuropathy. Following peripheral nerve injury nociceptive inputs from sensory neurons appear to be critical in triggering the development of spinal microgliosis. A number of signalling pathways including growth factors such as Neuregulin-1, matrix metalloproteases such as MMP-9 and multiple chemokines enable direct communication between injured primary afferents and microglia. In addition, we describe a group of mediators which although not demonstrably shown to be released from neurons are known to modulate microglial phenotype. There is a great functional diversity of the microglial response to peripheral nerve injury which includes: Cellular migration, proliferation, cytokine release, phagocytosis, antigen presentation and recruitment of T cells. It should also be noted that in certain contexts microglia may have a role in the resolution of neuro-inflammation. Although there is still no direct evidence demonstrating that spinal microglia have a role in neuropathic pain in humans, these patients present a pro-inflammatory cytokine profile and it is a reasonable hypothesis that these cells may contribute to this inflammatory response. Modulating microglial functions offers a novel therapeutic opportunity following nerve injury which ideally would involve reducing the pro-inflammatory nature of these cells whilst retaining their potential beneficial functions.
Collapse
|
171
|
Higashi Y, Segawa S, Matsuo T, Nakamura S, Kikkawa Y, Nishida K, Nagasawa K. Microglial zinc uptake via zinc transporters induces ATP release and the activation of microglia. Glia 2011; 59:1933-45. [PMID: 22253048 DOI: 10.1002/glia.21235] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 07/27/2011] [Indexed: 01/14/2023]
Abstract
Previously, we demonstrated that extracellular zinc plays a key role in transient global ischemia-induced microglial activation through sequential activation of NADPH oxidase and poly(ADP-ribose) polymerase (PARP)-1. However, it remains unclear how zinc causes the sequential activation of microglia. Here, we examined whether transporter-mediated zinc uptake is necessary for microglial activation. Administration of zinc to microglia activated them through reactive oxygen species (ROS) generation and poly(ADP-ribose) (PAR) formation, which were suppressed by intracellular zinc chelation with 25 μM TPEN (N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine) or 2 μM BAPTA-AM (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester). The (65)Zn uptake by microglia was temperature- and dose-dependent, and it was blocked by metal cations, but not by L-type calcium channel blockers nifedipine and nimodipine. Expression of Zrt-Irt-like protein (ZIP)1, a plasma membrane-type zinc transporter, was detected in microglia, and nickel, a relatively sensitive substrate/inhibitor of ZIP1, showed cis- and trans-inhibitory effects on the (65)Zn uptake. Exposure of microglia to zinc increased the extracellular ATP concentration, which was suppressed by intracellular zinc chelation and inhibition of hemichannels. mRNA expression of several types of P2 receptors was detected in microglia, and periodate-oxidized ATP, a selective P2×7 receptor antagonist, attenuated the zinc-induced microglial activation via NADPH oxidase and PARP-1. Exogenous ATP and 2'(3')-O-(4-benzoyl-benzoyl) ATP also caused microglial activation through ROS generation and PAR formation. These findings demonstrate that ZIP1-mediated uptake of zinc induces ATP release and autocrine/paracrine activation of P2X(7) receptors, and then activates microglia, suggesting that zinc transporter-mediated uptake of zinc is a trigger for microglial activation via the NADPH oxidase and PARP-1 pathway. © 2011 Wiley-Liss, Inc.
Collapse
Affiliation(s)
- Youichirou Higashi
- Department of Environmental Biochemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto, Japan
| | | | | | | | | | | | | |
Collapse
|
172
|
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.
Collapse
|
173
|
Involvement of vasodilator-stimulated phosphoprotein in UDP-induced microglial actin aggregation via PKC- and Rho-dependent pathways. Purinergic Signal 2011; 7:403-11. [PMID: 21567128 DOI: 10.1007/s11302-011-9237-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Accepted: 05/02/2011] [Indexed: 12/22/2022] Open
Abstract
Microglia are major immunocompetent cells in the central nervous system and retain highly dynamic motility. The processes which allow these cells to move, such as chemotaxis and phagocytosis, are considered part of their functions and are closely related to purinergic signaling. Previously, we reported that the activation of the P2Y(6) receptor by UDP stimulation in microglia evoked dynamic cell motility which enhanced their phagocytic capacity, as reported by Koizumi et al. (Nature 446(7139):1091-1095, 2007). These responses require actin cytoskeletal rearrangement, which is seen after UDP stimulation. However, the intracellular signaling pathway has not been defined. In this study, we found that UDP in rat primary microglia rapidly induced the transient phosphorylation at Ser157 of vasodilator-stimulated phosphoprotein (VASP). VASP, one of actin binding protein, accumulated at the plasma membrane where filamentous (F)-actin aggregated in a time-dependent manner. The phosphorylation of VASP was suppressed by inhibition of PKC. UDP-induced local actin aggregations were also abrogated by PKC inhibitors. The Rho inhibitor CT04 and the expression of p115-RGS, which suppresses G(12/13) signaling, attenuated UDP-induced phosphorylation of VASP and actin aggregation. These results indicate that PKC- and Rho-dependent phosphorylation of VASP is involved in UDP-induced actin aggregation of microglia.
Collapse
|
174
|
Lee SH, Schneider C, Higdon AN, Darley-Usmar VM, Chung CY. Role of iPLA(2) in the regulation of Src trafficking and microglia chemotaxis. Traffic 2011; 12:878-89. [PMID: 21438970 DOI: 10.1111/j.1600-0854.2011.01195.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Microglia are immune effector cells in the central nervous system (CNS) and their activation, migration and proliferation play crucial roles in brain injuries and diseases. We examined the role of intracellular Ca(2+) -independent phospholipase A(2) (iPLA(2)) in the regulation of microglia chemotaxis toward ADP. Inhibition of iPLA(2) by 4-bromoenol lactone (BEL) or iPLA(2) knockdown exerted a significant inhibition on phosphatidylinositol-3-kinase (PI3K) activation and chemotaxis. Further examination revealed that iPLA(2) knockdown abrogated Src activation, which is required for PI3K activation and chemotaxis. Colocalization studies showed that cSrc-GFP was retained in the endosomal recycling compartment (ERC) in iPLA(2) knockdown cells, but the addition of arachidonic acid (AA) could restore cSrc trafficking to the plasma membrane by allowing the formation/release of recycling endosomes associated with cSrc-GFP. Using BODIPY-AA, we showed that AA is selectively enriched in recycling endosomes. These results suggest that AA is required for the cSrc trafficking to the plasma membrane by controlling the formation/release of recycling endosomes from the ERC.
Collapse
Affiliation(s)
- Sang-Hyun Lee
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232-6600, USA
| | | | | | | | | |
Collapse
|
175
|
Chen D, Wang W, Guo W, Yu Q, Burnstock G, He C, Xiang Z, Zheng H. Expression of P2Y(6) receptors in the developing mouse skeletal muscle and after injury and repair. J Anat 2011; 218:643-51. [PMID: 21413988 DOI: 10.1111/j.1469-7580.2011.01364.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
In this study, single and double-labeling immunofluorescence histochemistry, Western blot and real-time polymerase chain reaction were used to study the expression of P2Y(6) receptors in developing mouse skeletal muscle and during injury and repair. The results show that P2Y(6) receptor immunoreactive (ir) cells were first detected in the dermamyotome at embryonic (E) day 9. The number and immunostaining intensity of the P2Y(6) receptor-ir cells increased from E9 to E13, but decreased from E15 to postnatal day 60 in the developing skeletal muscle system. The expression levels of P2Y(6) receptor protein and mRNA increased rapidly from 1 to 5 days after skeletal muscle injury and then decreased almost to the control level from 7 to 10 days, at the beginning of regeneration. P2Y(6) receptor-immunoreactivity was mainly localized to the ends of single myoblasts and myotube processes in the developing and injury-repair skeletal muscle tissues. These data suggest that the P2Y(6) receptor may be involved in the development and regeneration of skeletal muscle, especially in the migration and extension of the myoblast and myotube in developing and regenerating skeletal muscle.
Collapse
Affiliation(s)
- Donghui Chen
- Department of Otolaryngology & Head and Neck Surgery, Changhai Hospital, Shanghai, China
| | | | | | | | | | | | | | | |
Collapse
|
176
|
Bjelobaba I, Parabucki A, Lavrnja I, Stojkov D, Dacic S, Pekovic S, Rakic L, Stojiljkovic M, Nedeljkovic N. Dynamic changes in the expression pattern of ecto-5'-nucleotidase in the rat model of cortical stab injury. J Neurosci Res 2011; 89:862-73. [PMID: 21337375 DOI: 10.1002/jnr.22599] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Revised: 12/10/2010] [Accepted: 12/18/2010] [Indexed: 02/06/2023]
Abstract
Traumatic injury induces massive release of ATP in the extracellular space, where it influences numerous aspects of neuronal, astrocytic, and microglial responses to injury by activating P2X and P2Y receptors. The extracellular ATP actions are controlled by the ectonucleotidase enzyme pathway, which hydrolyses ATP to adenosine at all neuronal and nonneuronal cell types. Adenosine activates its P1 receptors, which have important neuroprotective roles. The rate-limiting enzyme in the ectonucleotidase pathway is ecto-5'-nucleotidase (e-5NT), which catalyzes the final step of dephosphorylation of AMP to adenosine. The aim of the present study was to characterize the expression pattern and cellular distribution of e-5NT in the perilesioned cortex at 4 hr and 1, 2, 7, and 15 days after unilateral cortical stab injury (CSI). Immunoblot and immunohistochemical studies showed that overall e-5NT expression was lower 4 hr and 1 day postinjury and then gradually increased above the control levels. Double-immunofluorescence studies further showed in control tissue the presence of the enzyme in the membranes surrounding neuronal somata and apical dendrites and less frequently in astrocytes. CSI caused a rapid (after 4 hr) and irreversible loss of the enzyme from neurons, accounting for a decrease in the overall enzyme expression. This was accompanied with a gradual increase in e-5NT-positive astrocytes, accounting for up-regulation of the enzyme levels in the injured area. Thus, CSI induced dynamic changes in the expression pattern of e-5NT that modify the ATP/adenosine ratio and the extent of P1 and P2 receptors activation and, therefore, outcome of the pathological processes after CSI.
Collapse
Affiliation(s)
- Ivana Bjelobaba
- Department for Neurobiology, Institute for Biological Research Sinisa Stankovic, University Belgrade, Belgrade, Serbia
| | | | | | | | | | | | | | | | | |
Collapse
|
177
|
Maeda M, Tsuda M, Tozaki-Saitoh H, Inoue K, Kiyama H. Nerve injury-activated microglia engulf myelinated axons in a P2Y12 signaling-dependent manner in the dorsal horn. Glia 2011; 58:1838-46. [PMID: 20665560 DOI: 10.1002/glia.21053] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The mechanisms underlying neuropathic pain are poorly understood. However, several studies have implied a role for reactive microglia located in the dorsal horn in neuropathic pain. To clarify the roles of activated microglia in neuropathic pain, we investigated the interactions among microglia and other neural components in the dorsal horn using electron microscopy. Microglia were more abundantly localized in layers II-III of the dorsal horn than in other areas, and some of them adhered to and engulfed both injured and uninjured myelinated axons. This microglial engulfment was rarely observed in the normal dorsal horn, and the number of microglia attached to myelinated axons was markedly increased on postoperative day 7 on the operated side. However, after blocking the P2Y12 ATP receptor in microglia by intrathecal administration of its antagonist, AR-C69931MX, the increase in the number of microglia attached to myelinated axons, as well as the development of tactile allodynia, were markedly suppressed, although the number of activated microglia did not change remarkably. These results indicate that engulfment of myelinated axons by activated microglia via P2Y12 signaling in the dorsal horn may be a critical event in the pathogenesis of neuropathic pain.
Collapse
Affiliation(s)
- Mitsuyo Maeda
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Osaka City University, 1-4-3 Asahimachi, Abeno-Ku, Osaka 545-8585, Japan
| | | | | | | | | |
Collapse
|
178
|
Fontainhas AM, Wang M, Liang KJ, Chen S, Mettu P, Damani M, Fariss RN, Li W, Wong WT. Microglial morphology and dynamic behavior is regulated by ionotropic glutamatergic and GABAergic neurotransmission. PLoS One 2011; 6:e15973. [PMID: 21283568 PMCID: PMC3026789 DOI: 10.1371/journal.pone.0015973] [Citation(s) in RCA: 243] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Accepted: 12/01/2010] [Indexed: 02/01/2023] Open
Abstract
PURPOSE Microglia represent the primary resident immune cells in the CNS, and have been implicated in the pathology of neurodegenerative diseases. Under basal or "resting" conditions, microglia possess ramified morphologies and exhibit dynamic surveying movements in their processes. Despite the prominence of this phenomenon, the function and regulation of microglial morphology and dynamic behavior are incompletely understood. We investigate here whether and how neurotransmission regulates "resting" microglial morphology and behavior. METHODS We employed an ex vivo mouse retinal explant system in which endogenous neurotransmission and dynamic microglial behavior are present. We utilized live-cell time-lapse confocal imaging to study the morphology and behavior of GFP-labeled retinal microglia in response to neurotransmitter agonists and antagonists. Patch clamp electrophysiology and immunohistochemical localization of glutamate receptors were also used to investigate direct-versus-indirect effects of neurotransmission by microglia. RESULTS Retinal microglial morphology and dynamic behavior were not cell-autonomously regulated but are instead modulated by endogenous neurotransmission. Morphological parameters and process motility were differentially regulated by different modes of neurotransmission and were increased by ionotropic glutamatergic neurotransmission and decreased by ionotropic GABAergic neurotransmission. These neurotransmitter influences on retinal microglia were however unlikely to be directly mediated; local applications of neurotransmitters were unable to elicit electrical responses on microglia patch-clamp recordings and ionotropic glutamatergic receptors were not located on microglial cell bodies or processes by immunofluorescent labeling. Instead, these influences were mediated indirectly via extracellular ATP, released in response to glutamatergic neurotransmission through probenecid-sensitive pannexin hemichannels. CONCLUSIONS Our results demonstrate that neurotransmission plays an endogenous role in regulating the morphology and behavior of "resting" microglia in the retina. These findings illustrate a mode of constitutive signaling between the neural and immune compartments of the CNS through which immune cells may be regulated in concert with levels of neural activity.
Collapse
Affiliation(s)
- Aurora M. Fontainhas
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Minhua Wang
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Katharine J. Liang
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Shan Chen
- Unit on Retinal Neurophysiology, National Eye Institute, Bethesda, Maryland, United States of America
| | - Pradeep Mettu
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Mausam Damani
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Robert N. Fariss
- Biological Imaging Core, Office of the Scientific Director, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Wei Li
- Unit on Retinal Neurophysiology, National Eye Institute, Bethesda, Maryland, United States of America
| | - Wai T. Wong
- Unit on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
| |
Collapse
|
179
|
Calvo M, Zhu N, Grist J, Ma Z, Loeb JA, Bennett DLH. Following nerve injury neuregulin-1 drives microglial proliferation and neuropathic pain via the MEK/ERK pathway. Glia 2011; 59:554-68. [PMID: 21319222 PMCID: PMC3222694 DOI: 10.1002/glia.21124] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Accepted: 11/22/2010] [Indexed: 12/16/2022]
Abstract
Following peripheral nerve injury microglia accumulate within the spinal cord and adopt a proinflammatory phenotype a process which contributes to the development of neuropathic pain. We have recently shown that neuregulin-1, a growth factor released following nerve injury, activates erbB 2, 3, and 4 receptors on microglia and stimulates proliferation, survival and chemotaxis of these cells. Here we studied the intracellular signaling pathways downstream of neuregulin-1-erbB activation in microglial cells. We found that neuregulin-1 in vitro induced phosphorylation of ERK1/2 and Akt without activating p38MAPK. Using specific kinase inhibitors we found that the mitogenic effect of neuregulin-1 on microglia was dependant on MEK/ERK1/2 pathway, the chemotactic effect was dependant on PI3K/Akt signaling and survival was dependant on both pathways. Intrathecal treatment with neuregulin-1 was associated with microgliosis and development of mechanical and cold pain related hypersensitivity which was dependant on ERK1/2 phosphorylation in microglia. Spinal nerve ligation results in a robust microgliosis and sustained ERK1/2 phosphorylation within these cells. This pathway is downstream of neuregulin-1/erbB signaling since its blockade resulted in a significant reduction in microglial ERK1/2 phosphorylation. Inhibition of the MEK/ERK1/2 pathway resulted in decreased spinal microgliosis and in reduced mechanical and cold hypersensitivity after peripheral nerve damage. We conclude that neuregulin-1 released after nerve injury activates microglial erbB receptors which consequently stimulates the MEK/ERK1/2 pathway that drives microglial proliferation and contributes to the development of neuropathic pain.
Collapse
Affiliation(s)
- Margarita Calvo
- Wolfson CARD, Kings College London, Hodgkin Building, Guys Campus, SE1 1UL, London, United Kingdom
| | | | | | | | | | | |
Collapse
|
180
|
Tozaki-Saitoh H, Tsuda M, Inoue K. Role of purinergic receptors in CNS function and neuroprotection. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2011; 61:495-528. [PMID: 21586368 DOI: 10.1016/b978-0-12-385526-8.00015-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The purinergic receptor family contains some of the most abundant receptors in living organisms. A growing body of evidence indicates that extracellular nucleotides play important roles in the regulation of neuronal and glial functions in the nervous system through purinergic receptors. Nucleotides are released from or leaked through nonexcitable cells and neurons during normal physiological and pathophysiological conditions. Ionotropic P2X and metabotropic P2Y purinergic receptors are expressed in the central nervous system (CNS), participate in the synaptic processes, and mediate intercellular communications between neuron and gila and between glia and other glia. Glial cells in the CNS are classified into astrocytes, oligodendrocytes, and microglia. Astrocytes express many types of purinergic receptors, which are integral to their activation. Astrocytes release adenosine triphosphate (ATP) as a "gliotransmitter" that allows communication with neurons, the vascular walls of capillaries, oligodendrocytes, and microglia. Oligodendrocytes are myelin-forming cells that construct insulating layers of myelin sheets around axons, and using purinergic receptor signaling for their development and for myelination. Microglia also express many types of purinergic receptors and are known to function as immunocompetent cells in the CNS. ATP and other nucleotides work as "warning molecules" especially by activating microglia in pathophysiological conditions. Studies on purinergic signaling could facilitate the development of novel therapeutic strategies for disorder of the CNS.
Collapse
Affiliation(s)
- Hidetoshi Tozaki-Saitoh
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Higashi, Fukuoka, Japan
| | | | | |
Collapse
|
181
|
Fang KM, Wang YL, Huang MC, Sun SH, Cheng H, Tzeng SF. Expression of macrophage inflammatory protein-1α and monocyte chemoattractant protein-1 in glioma-infiltrating microglia: involvement of ATP and P2X₇ receptor. J Neurosci Res 2010; 89:199-211. [PMID: 21162127 DOI: 10.1002/jnr.22538] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Revised: 09/21/2010] [Accepted: 09/27/2010] [Indexed: 01/21/2023]
Abstract
Chemokines can be produced by gliomas, which mediate the infiltration of microglia, a characteristic feature of glioma-associated neuropathogenesis. ATP that is released at a high level from glioma has been reported to play a regulatory role in chemokine production in cultured glioma cells. The objective of this study was to define the potential role of extracellular ATP in the regulation of macrophage inflammatory protein-1α (MIP-1α) and monocyte chemoattractant protein-1(MCP-1) expression in glioma-associated microglia/macrophages. The results showed that Iba1(+) and ED1(+) microglia existed in the tumor at 3 and 7 day after injection of C6 glioma cells into the rat cerebral cortex (dpi). ED1(+) microglia/macrophages or Iba1(+) microglia in the glioma were also colocalized to MIP-1α- and MCP-1-expressing cells. In vitro study indicated that treatment with ATP and BzATP (an agonist for ATP ionotropic receptor P2X₇R) caused an increase in the intracellular levels of microglial MIP-1α and MCP-1. By using an extracellular Ca(2+) chelator (EGTA) and P2X₇R antagonists, oxidized ATP (oxATP) and brilliant blue G (BBG), we demonstrated that BzATP-induced production of MIP-1α and MCP-1 levels was due to P2X₇R activation and Ca(2+) -dependent regulation. Coadministration of C6 glioma cells and oxATP into the rat cerebral cortex resulted in a reduction of MIP-1α- and MCP-1-expressing microglia/macrophages. We suggest, based on the results from in vivo and in vitro studies, that a massive amount of ATP molecules released in the glioma tumor site may act as the regulator with P2X₇R signaling that increases MIP-1α and MCP-1 expression in tumor-infiltrating microglia/macrophages.
Collapse
Affiliation(s)
- Kuan-Min Fang
- Department of Life Sciences, National Cheng Kung University, Tainan, Taiwan
| | | | | | | | | | | |
Collapse
|
182
|
Lambert C, Ase AR, Séguéla P, Antel JP. Distinct migratory and cytokine responses of human microglia and macrophages to ATP. Brain Behav Immun 2010; 24:1241-8. [PMID: 20206681 DOI: 10.1016/j.bbi.2010.02.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 02/24/2010] [Accepted: 02/24/2010] [Indexed: 10/19/2022] Open
Abstract
Microglia and hematogenous myeloid cells are prominent components of inflammatory central nervous system (CNS) lesions associated with tissue injury. To help define the basis for recruitment of such cells into lesions and their contribution to the disease process, we characterized the migratory and cytokine responses of human adult and fetal microglia in the presence of extracellular ATP comparing them to monocytes and macrophages. Adult microglia showed increased migration in response to low ATP concentrations (1-10 μM) whereas fetal microglia also migrated in response to higher ATP dosages (100-300 μM). The enhanced migration of microglia was reproduced with 2-MeSADP, a P2Y1/12/13 agonist. In contrast, the chemokine CCL2 did not promote migration of microglia, but promoted the migration of monocytes. Monocyte migration was also enhanced with low concentrations of ATP, whereas higher concentrations of ATP mediated an inhibitory effect. ATP had only an inhibitory effect on macrophages, which was not reproduced with hydrolysis products ADP or adenosine. ATP led to a decrease in LPS-induced pro-inflammatory cytokine release (TNFα, IL-6) in both microglia and macrophages without suppression of an anti-inflammatory response (IL-10). These in vitro based results suggest that ATP can selectively favor the recruitment of microglia rather than hematogenous myeloid cells while promoting an anti-inflammatory state in both hematogenous and resident myeloid cells of the CNS. Our results highlight the importance of environmental signals in shaping the properties of the innate immune response to injury in the CNS.
Collapse
Affiliation(s)
- Caroline Lambert
- Neuroimmunology Unit, Department of Neurology & Neurosurgery, Montreal Neurological Institute, McGill University, Montréal, Québec, Canada
| | | | | | | |
Collapse
|
183
|
Tozaki-Saitoh H, Tsuda M, Inoue K. [Purinergic regulation of microglia]. Nihon Yakurigaku Zasshi 2010; 136:93-7. [PMID: 20702968 DOI: 10.1254/fpj.136.93] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
184
|
De Simone R, Niturad CE, De Nuccio C, Ajmone-Cat MA, Visentin S, Minghetti L. TGF-β and LPS modulate ADP-induced migration of microglial cells through P2Y1 and P2Y12 receptor expression. J Neurochem 2010; 115:450-9. [PMID: 20681951 DOI: 10.1111/j.1471-4159.2010.06937.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nucleotides act as early signals for microglial recruitment to sites of CNS injury. As microglial motility and activation can be influenced by several local factors at the site of the lesion, we investigated the effects of interferon-gamma, lipopolysaccharide (LPS) or transforming growth factor-β (TGF-β) addition to mixed glial cell cultures, on microglial migration in response to ADP, P2Y12 and P2Y1 mRNA expression as well as on the expression of an array of genes associated with the process of microglial activation. First, we demonstrated, by pharmacological inhibition and by using small interfering RNAs, that in addition to P2Y12, P2Y1 is involved in ADP-stimulated microglial migration. The ability of specific agonists to induce Ca(2+) mobilization further confirmed the expression of functional P2Y receptors in microglia. Then, we found that migratory capability and expression of both P2Y receptors were abrogated in microglial cells from LPS-stimulated mixed glial cultures, while TGF-β increased ADP-induced migration and the expression of P2Y12 and P2Y1 receptors. Interferon-gamma did not influence receptor expression or microglial migration. Finally, the patterns of gene expression induced in microglia by LPS or TGF-β treatment of mixed glial cultures were clearly distinct. LPS induced a set of classical pro-inflammatory genes, whereas TGF-β increased the expression of genes associated with atypical microglial phenotype, namely arginase-1 and TGF-β genes. These results imply that both P2Y1 and P2Y12 may guide microglia toward the lesion. They also suggest that the modulation of microglial purinergic receptors expression by local factors, through direct and/or astrocyte-mediated actions, may represent a novel mechanism affecting neuroinflammatory response.
Collapse
Affiliation(s)
- Roberta De Simone
- Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome, Italy.
| | | | | | | | | | | |
Collapse
|
185
|
Yamasaki R, Tanaka M, Fukunaga M, Tateishi T, Kikuchi H, Motomura K, Matsushita T, Ohyagi Y, Kira JI. Restoration of microglial function by granulocyte-colony stimulating factor in ALS model mice. J Neuroimmunol 2010; 229:51-62. [PMID: 20659772 DOI: 10.1016/j.jneuroim.2010.07.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Revised: 06/14/2010] [Accepted: 07/04/2010] [Indexed: 10/19/2022]
Abstract
We studied the effects of G-CSF on microglial reactions in mutant SOD1 (mSOD1)-Tg (G93A) ALS model mice. Following hypoglossal axotomy, the numbers of neurons and microglia expressing GDNF were significantly lower in mSOD1-Tg mice than in non-transgenic (NTG) littermates. This decrease in the number of neurons after axotomy and a decrease in the number of large myelinated axons in mSOD1-Tg mice over the disease course were improved by G-CSF, which also increased microglial recruitment. Impaired migration of cultured mSOD1-Tg microglia to MCP-1 was recovered following G-CSF treatment. Restoration of microglial responses by G-CSF may contribute to its neuroprotective effects.
Collapse
Affiliation(s)
- Ryo Yamasaki
- Department of Neurology, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
186
|
Purinergic receptor-mediated morphological changes in microglia are transient and independent from inflammatory cytokine release. Eur J Pharmacol 2010; 643:202-10. [PMID: 20621081 DOI: 10.1016/j.ejphar.2010.06.046] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 06/01/2010] [Accepted: 06/24/2010] [Indexed: 01/01/2023]
Abstract
Microglia are commonly described as existing in resting or active states based on morphology or level of cytokine production. Extracellular ATP is a physiologically-relevant activator of microglia, which express a number of purinergic receptors. As P2Y(12) has been linked to chemotaxis, we used a panel of purinergic compounds to understand the role of ATP receptors in morphological transformation and correlate this with TNFalpha production. We quantified activation of cultured microglia with LPS or purinergic receptor agonists by using automated image analysis of cell morphology and CD11b expression and correlated this with TNFalpha release measured by ELISA. Treatment with both ATP and the P2Y(12) receptor agonist, 2-methylthio adenosine diphosphate (2MeSADP), caused a transient increase in CD11b expression (EC(50)=1.2 microM and 187 nM, respectively) and a reduction in process count that reversed within 90 min later. These changes were not accompanied by the release of TNFalpha. Forskolin, IBMX, and pertussis toxin inhibited these changes, but the PLC inhibitor, U73122, did not. 2MeSAMP blocked the ATP response, while AP4A blocked the 2MeSADP response, implicating P2Y(12/13). Microglia activation by LPS also caused an increase in CD11b expression and a reduction in process count; however, in contrast to activation by ATP, morphological transformation was accompanied by a concentration-dependent increase in TNFalpha secretion These data demonstrate that morphological transformation and TNFalpha release are separable events mediated by different, or non-convergent pathways and that although ATP can initiate morphological changes, additional factors are required to maintain activation over sustained periods.
Collapse
|
187
|
Ohsawa K, Irino Y, Sanagi T, Nakamura Y, Suzuki E, Inoue K, Kohsaka S. P2Y12 receptor-mediated integrin-beta1 activation regulates microglial process extension induced by ATP. Glia 2010; 58:790-801. [PMID: 20091784 DOI: 10.1002/glia.20963] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Microglia are the primary immune surveillance cells in the brain, and when activated they play critical roles in inflammatory reactions and tissue repair in the damaged brain. Microglia rapidly extend their processes toward the damaged areas in response to stimulation of the metabotropic ATP receptor P2Y(12) by ATP released from damaged tissue. This chemotactic response is a highly important step that enables microglia to function properly at normal and pathological sites in the brain. To investigate the molecular pathways that underlie microglial process extension, we developed a novel method of modeling microglial process extension that uses transwell chambers in which the insert membrane is coated with collagen gel. In this study, we showed that ATP increased microglial adhesion to collagen gel, and that the ATP-induced process extension and increase in microglial adhesion were inhibited by integrin blocking peptides, RGD, and a functional blocking antibody against integrin-beta1. An immunoprecipitation analysis with an antibody against the active form of integrin-beta1 showed that P2Y(12) mediated the integrin-beta1 activation by ATP. In addition, time-lapse imaging of EGFP-labeled microglia in mice hippocampal slices showed that RGD inhibited the directional process extension toward the nucleotide source, and immunohistochemical staining showed that integrin-beta1 accumulated in the tips of the microglial processes in rat hippocampal slices stimulated with ADP. These findings indicate that ATP induces the integrin-beta1 activation in microglia through P2Y(12) and suggest that the integrin-beta1 activation is involved in the directional process extension by microglia in brain tissue.
Collapse
Affiliation(s)
- Keiko Ohsawa
- Department of Neurochemistry, National Institute of Neuroscience, Kodaira, Tokyo 187-8502, Japan
| | | | | | | | | | | | | |
Collapse
|
188
|
Horvath RJ, Romero-Sandoval AE, De Leo JA. Inhibition of microglial P2X4 receptors attenuates morphine tolerance, Iba1, GFAP and mu opioid receptor protein expression while enhancing perivascular microglial ED2. Pain 2010; 150:401-413. [PMID: 20573450 DOI: 10.1016/j.pain.2010.02.042] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Revised: 02/24/2010] [Accepted: 02/26/2010] [Indexed: 02/04/2023]
Abstract
Anti-nociceptive tolerance to opioids is a well-described phenomenon, which severely limits the clinical efficacy of opioids for the treatment of chronic pain syndromes. The mechanisms that drive anti-nociceptive tolerance, however, are less well understood. We have previously shown that glia have a central role in the development of morphine tolerance and that administration of a glial modulating agent attenuated tolerance formation. Recently, we have demonstrated that morphine enhances microglial Iba1 expression and P2X4 receptor-mediated microglial migration via direct mu opioid receptor signaling in in vitro microglial cultures. We hypothesize that P2X4 receptors drive morphine tolerance and modulate morphine-induced spinal glial reactivity. Additionally, we hypothesize that perivascular microglia play a role in morphine tolerance and that P2X4 receptor expression regulates perivascular microglia ED2 expression. To test these hypotheses, rats were implanted with osmotic minipumps releasing morphine or saline subcutaneously for seven days. Beginning three days prior to morphine treatment, P2X4 receptor antisense oligonucleotide (asODN) was injected intrathecally daily, to selectively inhibit P2X4 receptor expression. P2X4 receptor asODN treatment inhibited morphine-induced P2X4 receptor expression and blocked anti-nociceptive tolerance to systemically administered morphine. P2X4 receptor asODN treatment also attenuated the morphine-dependent increase of spinal ionized calcium binding protein (Iba1), glial fibrillary acidic protein (GFAP) and mu opioid receptor protein expression. Chronic morphine also decreased perivascular microglial ED2 expression, which was reversed by P2X4 receptor asODN. Together, these data suggest that the modulation of P2X4 receptor expression on microglia and perivascular microglia may prove an attractive target for adjuvant therapy to attenuate opioid-induced anti-nociceptive tolerance.
Collapse
MESH Headings
- Analysis of Variance
- Animals
- Antigens, CD/metabolism
- Antigens, Differentiation, Myelomonocytic/metabolism
- Behavior, Animal/drug effects
- CD11b Antigen/metabolism
- Calcium-Binding Proteins/metabolism
- Disease Models, Animal
- Drug Interactions
- Drug Tolerance/physiology
- Gene Expression Regulation/drug effects
- Gene Expression Regulation/physiology
- Glial Fibrillary Acidic Protein/metabolism
- Hyperalgesia/drug therapy
- Male
- Microfilament Proteins
- Microglia/drug effects
- Microglia/metabolism
- Morphine/administration & dosage
- Naloxone/pharmacology
- Narcotic Antagonists/pharmacology
- Nerve Tissue Proteins/metabolism
- Oligodeoxyribonucleotides, Antisense/pharmacology
- Pain Measurement
- Random Allocation
- Rats
- Rats, Sprague-Dawley
- Receptors, Cell Surface/metabolism
- Receptors, Opioid/metabolism
- Receptors, Purinergic P2X4/genetics
- Receptors, Purinergic P2X4/metabolism
- Signal Transduction
- Spinal Cord/pathology
- Time Factors
Collapse
Affiliation(s)
- Ryan J Horvath
- Department of Pharmacology, Dartmouth Medical School, Hanover, NH 03755, USA Neuroscience Center at Dartmouth, Lebanon, NH 03756, USA Department of Anesthesiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756, USA
| | | | | |
Collapse
|
189
|
Grimm I, Ullsperger SN, Zimmermann H. Nucleotides and epidermal growth factor induce parallel cytoskeletal rearrangements and migration in cultured adult murine neural stem cells. Acta Physiol (Oxf) 2010; 199:181-9. [PMID: 20121711 DOI: 10.1111/j.1748-1716.2010.02092.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
AIM The adult subventricular zone (SVZ) contains neural stem cells that generate neuroblasts migrating to the olfactory bulb (OB) and differentiating into interneurones. The molecular cues controlling essential functions within the neurogenesis pathway such as proliferation, short and long distance migration, functional integration and cell survival are poorly understood. We have previously shown that cultured adult neural stem cells express a considerable variety of nucleotide receptors and that nucleotides and epidermal growth factor (EGF) induce converging intracellular signalling pathways that carry potential for synergism in the control of neural stem cell proliferation and cell survival. Here we investigate the role of EGF and the nucleotides ATP, ADPbetaS and UTP in neural stem cell migration. METHODS Neural stem cells were prepared from adult mice and subjected to adherent culture. Labelling of F-actin was performed with tetramethylrhodamine isothiocyanate-phalloidin. Images were processed for quantitative evaluation of fluorescence labelling. Agonist-induced phosphorylation of AKT and focal adhesion kinase was analysed by quantitative Western blotting. Agonist-dependent cell migration was assayed using 48-well microchemotaxis chambers. RESULTS Nucleotides and EGF induce the formation of stress fibres, an increase in the cortical actin cytoskeleton and in cell spreading. This is associated with increased phosphorylation of AKT and focal adhesion kinase. Using microchemotaxis chambers we demonstrate a parallel increase in cell migration. CONCLUSION Our results suggest that nucleotides and EGF acting as paracrine or autocrine signalling substances can be of relevance for structuring and maintaining the cytoarchitecture of the SVZ and the stream of neuroblasts migrating to the OB.
Collapse
Affiliation(s)
- I Grimm
- Institute of Cell Biology and Neuroscience, Biocenter, Goethe-University, Frankfurt, Germany
| | | | | |
Collapse
|
190
|
Toulme E, Garcia A, Samways D, Egan TM, Carson MJ, Khakh BS. P2X4 receptors in activated C8-B4 cells of cerebellar microglial origin. ACTA ACUST UNITED AC 2010; 135:333-53. [PMID: 20231374 PMCID: PMC2847917 DOI: 10.1085/jgp.200910336] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
We investigated the properties and regulation of P2X receptors in immortalized C8-B4 cells of cerebellar microglial origin. Resting C8-B4 cells expressed virtually no functional P2X receptors, but largely increased functional expression of P2X4 receptors within 2–6 h of entering the activated state. Using real-time polymerase chain reaction, we found that P2X4 transcripts were increased during the activated state by 2.4-fold, but this increase was not reflected by a parallel increase in total P2X4 proteins. In resting C8-B4 cells, P2X4 subunits were mainly localized within intracellular compartments, including lysosomes. We found that cell surface P2X4 receptor levels increased by ∼3.5-fold during the activated state. This change was accompanied by a decrease in the lysosomal pool of P2X4 proteins. We next exploited our findings with C8-B4 cells to investigate the mechanism by which antidepressants reduce P2X4 responses. We found little evidence to suggest that several antidepressants were antagonists of P2X4 receptors in C8-B4 cells. However, we found that moderate concentrations of the same antidepressants reduced P2X4 responses in activated microglia by affecting lysosomal function, which indirectly reduced cell surface P2X4 levels. In summary, our data suggest that activated C8-B4 cells express P2X4 receptors when the membrane insertion of these proteins by lysosomal secretion exceeds their removal, and that antidepressants indirectly reduce P2X4 responses by interfering with lysosomal trafficking.
Collapse
Affiliation(s)
- Estelle Toulme
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | | | | | | | | | | |
Collapse
|
191
|
Kaminska B, Gozdz A, Zawadzka M, Ellert-Miklaszewska A, Lipko M. MAPK signal transduction underlying brain inflammation and gliosis as therapeutic target. Anat Rec (Hoboken) 2010; 292:1902-13. [PMID: 19943344 DOI: 10.1002/ar.21047] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A majority, if not all, acute and progressive neurodegenerative diseases are accompanied by local microglia-mediated inflammation, astrogliosis, infiltration of immune cells, and activation of the adaptive immunity. These processes progress by the expression of cytokines, adhesion molecules, proteases, and other inflammation mediators. In response to brain injury or infection, intracellular signaling pathways are activated in microglia, which turn on inflammatory and antigen-presenting cell functions. Different extrinsic signals shape microglial activation toward neuroprotective or neurotoxic phenotype under pathological conditions. This review discusses recent advances regarding molecular mechanisms of inflammatory signal transduction in neurological disorders and in in vitro models of inflammation/gliosis. Mitogen-activated protein kinases (MAPKs) are a family of serine/threonine protein kinases responsible for most cellular responses to cytokines and external stress signals and crucial for regulation of the production of inflammation mediators. Increased activity of MAPKs in activated microglia and astrocytes, and their regulatory role in the synthesis of inflammatory cytokines mediators, make them potential targets for novel therapeutics. MAPK inhibitors emerge as attractive anti-inflammatory drugs, because they are capable of reducing both the synthesis of inflammation mediators at multiple levels and are effective in blocking inflammatory cytokine signaling. Small molecule inhibitors targeting of p38 MAPK and JNK pathways have been developed and offer a great potential as potent modulators of brain inflammation and gliosis in neurological disorders, where cytokine overproduction contributes to disease progression. Many of the pharmacological MAPK inhibitors can be administered orally and initial results show therapeutic benefits in preclinical animal models.
Collapse
Affiliation(s)
- Bozena Kaminska
- Laboratory of Transcription Regulation, Nencki Institute of Experimental Biology, 3 Pasteur Str., Warsaw, Poland.
| | | | | | | | | |
Collapse
|
192
|
Choi MS, Cho KS, Shin SM, Ko HM, Kwon KJ, Shin CY, Ko KH. ATP induced microglial cell migration through non-transcriptional activation of matrix metalloproteinase-9. Arch Pharm Res 2010; 33:257-65. [PMID: 20195827 DOI: 10.1007/s12272-010-0211-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 11/15/2009] [Accepted: 11/27/2009] [Indexed: 12/01/2022]
Abstract
In response to brain insults, microglia, the resident inflammatory cells in CNS, migrate into injured sites to initiate inflammatory responses in brain. ATP, released from apoptotic or necrotic cells induce chemoattractive responses but the mechanism is not clear yet. In this study, we investigated whether ATP modulates microglial migration by regulating the activity of matrix metalloproteinases (MMPs). ATP induced rapid microglial migration and increased the activity of MMP-9 in the culture supernatants (secreted compartments) in a concentration-dependent manner. The increased activity of secreted MMP-9 is due to the increased protein secretion, but not by the increased MMP-9 mRNA and protein expression. Inhibition of MMP-9 activity by treatment with specific inhibitors including GM6001 and SB-3CT prevented ATP-induced microglial migration. ATP-induced microglial migration was also inhibited by P2Y receptor antagonists including clopidogrel as well as PI3K inhibitor such as wortmanin. Taken together, ATP non-transcriptionally increased MMP-9 activity by activation of P2Y and PI3K. The results from the present investigation may provide further insights into the regulation of the activity of MMP-9 during microglial migration, which may play essential role in the regulation of inflammatory responses in pathological situations such as neurodegenerative disorders.
Collapse
Affiliation(s)
- Min Sik Choi
- Department of Pharmacology, College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul 151-742, Korea
| | | | | | | | | | | | | |
Collapse
|
193
|
Andó RD, Méhész B, Gyires K, Illes P, Sperlágh B. A comparative analysis of the activity of ligands acting at P2X and P2Y receptor subtypes in models of neuropathic, acute and inflammatory pain. Br J Pharmacol 2010; 159:1106-17. [PMID: 20136836 DOI: 10.1111/j.1476-5381.2009.00596.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND AND PURPOSE This study was undertaken to compare the analgesic activity of antagonists acting at P2X1, P2X7, and P2Y12 receptors and agonists acting at P2Y1, P2Y2, P2Y4, and P2Y6 receptors in neuropathic, acute, and inflammatory pain. EXPERIMENTAL APPROACH The effect of the wide spectrum P2 receptor antagonist PPADS, the selective P2X7 receptor antagonist Brilliant Blue G (BBG), the P2X1 receptor antagonist (4,4',4'',4-[carbonylbis(imino-5,1,3-benzenetriyl-bis(carbonylimino))]tetrakis-1,3-benzenedisulfonic acid, octasodium salt (NF449) and (8,8'-[carbonylbis(imino-3,1-phenylenecarbonylimino)]bis-1,3,5-naphthalene-trisulphonic acid, hexasodium salt (NF023), the P2Y12 receptor antagonist (2,2-dimethyl-propionic acid 3-(2-chloro-6-methylaminopurin-9-yl)-2-(2,2-dimethyl-propionyloxymethyl)-propylester (MRS2395), the selective P2Y1 receptor agonist ([[(1R,2R,3S,4R,5S)-4-[6-amino-2-(methylthio)-9H-purin-9-yl]-2,3-dihydroxybicyclo[3.1.0]hex-1-yl]methyl] diphosphoric acid mono ester trisodium salt (MRS2365), the P2Y2/P2Y4 agonist uridine-5'-triphosphate (UTP), and the P2Y4/P2Y6 agonist uridine-5'-diphosphate (UDP) were examined on mechanical allodynia in the Seltzer model of neuropathic pain, on acute thermal nociception, and on the inflammatory pain and oedema induced by complete Freund's adjuvant (CFA). KEY RESULTS MRS2365, MRS2395 and UTP, but not the other compounds, significantly alleviated mechanical allodynia in the neuropathic pain model, with the following rank order of minimal effective dose (mED) values: MRS2365 > MRS2395 > UTP. All compounds had a dose-dependent analgesic action in acute pain except BBG, which elicited hyperalgesia at a single dose. The rank order of mED values in acute pain was the following: MRS2365 > MRS2395 > NF449 > NF023 > UDP = UTP > PPADS. MRS2365 and MRS2395 had a profound, while BBG had a mild effect on inflammatory pain, with a following rank order of mED values: MRS2395 > MRS2365 > BBG. None of the tested compounds had significant action on oedema evoked by intraplantar injection of CFA. CONCLUSIONS AND IMPLICATIONS Our results show that antagonism at P2X1, P2Y12, and P2X7 receptors and agonism at P2Y1 receptors define promising therapeutic strategies in acute, neuropathic, and inflammatory pain respectively.
Collapse
Affiliation(s)
- R D Andó
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | | | | | | | | |
Collapse
|
194
|
Hung J, Chansard M, Ousman SS, Nguyen MD, Colicos MA. Activation of microglia by neuronal activity: results from a new in vitro paradigm based on neuronal-silicon interfacing technology. Brain Behav Immun 2010; 24:31-40. [PMID: 19559784 DOI: 10.1016/j.bbi.2009.06.150] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 06/17/2009] [Accepted: 06/19/2009] [Indexed: 11/29/2022] Open
Abstract
Cognition and behavior primarily arise from the communication that occurs between brain cells. By using photoconductive stimulation to trigger localized regions of neuronal action potentials and astrocyte Ca(2+) waves in dissociated rat hippocampal cultures, we can directly study microglia behavior in response to physiological and pathological levels of activity. Connections between neurons can be modified by microglia, which regulate gap junctions and synapses through secretion of proteins such as cytokines, proteases and neurotrophic factors. Activated microglia participate in bidirectional communication with the excitable tissues that they support. Through feedback from the many ion channels and surface receptors they express, microglia are informed of neuronal and astrocytic activity that may indicate disruption in the homeostasis of the CNS. Such disturbances alert microglia to locations of such activity and promote their transformation into a reactive state, in which they perform adaptive functions that can be either neuroprotective, neurotoxic, or neuromodulatory. Under physiological conditions, normal brain activity has the effect of suppressing microglia inflammatory responses. This report summarizes available data about the interaction of microglia and brain activity and presents a new in vitro paradigm to study the mechanisms involved. We propose that photoconductive stimulation is a powerful tool for studying the cellular and molecular mechanisms underlying the dynamic interactions between neurons, astrocytes and microglia.
Collapse
Affiliation(s)
- Johanna Hung
- Department of Physiology & Pharmacology, University of Calgary, Calgary, AB, Canada T2N 4N1
| | | | | | | | | |
Collapse
|
195
|
Pain and purinergic signaling. ACTA ACUST UNITED AC 2009; 63:222-32. [PMID: 19931560 DOI: 10.1016/j.brainresrev.2009.11.003] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 11/10/2009] [Accepted: 11/11/2009] [Indexed: 01/12/2023]
Abstract
A growing body of evidence indicates that extracellular nucleotides play important roles in the regulation of neuronal and glial functions in the nervous system through P2 purinoceptors. P2 purinoceptors are divided into two families, ionotropic receptors (P2X) and metabotropic receptors (P2Y). P2X receptors (seven types; P2X1-P2X7) contain intrinsic pores that open by binding with ATP, and P2Y receptors (eight types; P2Y1, 2, 4, 6, 11, 12, 13 and 14) are activated by nucleotides and couple to intracellular second-messenger systems through heterotrimeric G-proteins. Nucleotides are released or leaked from non-excitable cells as well as neurons in physiological and pathophysiological conditions. Studies have shown that microglia, a type of glial cells known as resident macrophages in the CNS, express several subtypes of P2X and P2Y receptors, and these receptors play a key role in pain signaling in the spinal cord under pathological conditions such as by peripheral nerve injury (called neuropathic pain). Within the spinal dorsal horn, peripheral nerve injury leads to a progressive series of changes in microglia including morphological hypertrophy of the cell body and proliferation, which are considered indicative of activation. These activated microglia upregulate expression of P2X/Y receptors (e.g., P2X4 and P2Y12). Importantly, pharmacological, molecular and genetic manipulations of the function or expression of these microglial molecules strongly suppress neuropathic pain. We expect that further investigation to determine how ATP signaling via P2X receptors participates in the pathogenesis of chronic pain will lead to a better understanding of the molecular mechanisms of pathological pain and provide clues for the development of new therapeutic drugs.
Collapse
|
196
|
Fang KM, Yang CS, Sun SH, Tzeng SF. Microglial phagocytosis attenuated by short-term exposure to exogenous ATP through P2X receptor action. J Neurochem 2009; 111:1225-37. [PMID: 19860838 DOI: 10.1111/j.1471-4159.2009.06409.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Microglia, the CNS resident macrophages responsible for the clearance of degenerating cellular fragments, are essential to tissue remodeling and repair after CNS injury. ATP can be released in large amounts after CNS injury and may mediate microglial activity through the ionotropic P2X and the metabotropic P2Y receptors. This study indicates that exposure to a high concentration of ATP for 30 min rapidly induces changes of the microglial cytoskeleton, and significantly attenuates microglial phagocytosis. A pharmacological approach showed that ATP-induced inhibition of microglial phagocytotic activity was due to P2X(7)R activation, rather than that of P2YR. Activation of P2X(7)R by its agonist, 2'-3'-O-(4-benzoyl)benzoyl-ATP (BzATP), produced a Ca(2+)-independent reduction in microglial phagocytotic activity. In addition, the knockdown of P2X(7)R expression by lentiviral-mediated shRNA interference or the blockade of P2X(7)R activation by the specific antagonists, oxidized ATP (oxATP) and brilliant blue G, has efficiently restored the phagocytotic activity of ATP and BzATP-treated microglia. Our results reveal that P2X(7)R activation may induce the formation of a Ca(2+)-independent signaling complex, which results in the reduction of microglial phagocytosis. This suggests that exposure to ATP for a short-term period may cause insufficient clearance of tissue debris by microglia through P2X(7)R activation after CNS injury, and that blockade of this receptor may preserve the phagocytosis of microglia and facilitate CNS tissue repair.
Collapse
Affiliation(s)
- Kuan-Min Fang
- Department of Life Sciences, National Cheng Kung University, Tainan, Taiwan
| | | | | | | |
Collapse
|
197
|
Rizzo R, Ferrari D, Melchiorri L, Stignani M, Gulinelli S, Baricordi OR, Di Virgilio F. Extracellular ATP Acting at the P2X7Receptor Inhibits Secretion of Soluble HLA-G from Human Monocytes. THE JOURNAL OF IMMUNOLOGY 2009; 183:4302-11. [DOI: 10.4049/jimmunol.0804265] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|
198
|
D'Ambrosi N, Finocchi P, Apolloni S, Cozzolino M, Ferri A, Padovano V, Pietrini G, Carrì MT, Volonté C. The Proinflammatory Action of Microglial P2 Receptors Is Enhanced in SOD1 Models for Amyotrophic Lateral Sclerosis. THE JOURNAL OF IMMUNOLOGY 2009; 183:4648-56. [DOI: 10.4049/jimmunol.0901212] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
|
199
|
Lee S, Chung CY. Role of VASP phosphorylation for the regulation of microglia chemotaxis via the regulation of focal adhesion formation/maturation. Mol Cell Neurosci 2009; 42:382-90. [PMID: 19733667 DOI: 10.1016/j.mcn.2009.08.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Revised: 08/11/2009] [Accepted: 08/19/2009] [Indexed: 01/09/2023] Open
Abstract
Microglia activation and migration are known to play crucial roles for the response to brain injuries. Extracellular ADP was reported to induce microglia chemotaxis and membrane ruffles through P2Y12 receptor. In this study, we examined the role of VASP phosphorylation in ADP-induced microglia chemotaxis and membrane ruffle formation. ADP stimulation transiently increased intracellular cAMP level, VASP phosphorylation at Ser153, membrane ruffle formation, and chemotaxis. PKA inhibitor effectively inhibited VASP phosphorylation and chemotaxis, indicating that P2Y12-mediated activation of PKA and subsequent VASP phosphorylation are involved in the regulation of microglia chemotaxis. Forskolin and okadaic acid induced sustained VASP phosphorylation at a high level, causing a significant reduction of the retraction of membrane ruffles and chemotaxis. In forskolin- or okadaic acid-treated cells, phosphorylated VASP remained at the membrane cortex, and size and number of mature focal adhesions were not increased, indicating that prolonged phosphorylation of VASP could inhibit transformation of focal complexes into focal adhesions. VASP knockdown cells showed markedly reduced frequency and distance of membrane ruffling upon ADP stimulation, reinforcing the idea that VASP is required for the ruffle formation. Cells expressing GFP-VASP(S153A) also showed a significant reduction of protrusion distance during ruffle formation, but the frequency and the distance of retraction were not affected by FSK at all. This result suggests that dephosphorylation of VASP might be required for the growth of adhesion strength during membrane retraction. Our results suggest that VASP phosphorylation by PKA plays an important role in membrane ruffle formation and chemotaxis via the regulation of focal adhesion formation/maturation.
Collapse
Affiliation(s)
- S Lee
- Department of Pharmacology, Vanderbilt University Medical Center, 468 Robinson Research Building (MRB I), 1215 21st Ave., South@Pierce, Nashville, TN 37232-6600, USA
| | | |
Collapse
|
200
|
Crain JM, Nikodemova M, Watters JJ. Expression of P2 nucleotide receptors varies with age and sex in murine brain microglia. J Neuroinflammation 2009; 6:24. [PMID: 19706184 PMCID: PMC2744668 DOI: 10.1186/1742-2094-6-24] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Accepted: 08/25/2009] [Indexed: 12/21/2022] Open
Abstract
Microglia are implicated in multiple neurodegenerative disorders, many of which display sexual dimorphisms and have symptom onsets at different ages. P2 purinergic receptors are critical for regulating various microglial functions, but little is known about how their expression varies with age or sex. Therefore, comprehensive information about purinergic receptor expression in normal microglia, in both sexes, over age is necessary if we are to better understand their roles in the healthy and diseased CNS. We analyzed the expression of all fourteen rodent P2X and P2Y receptors in CD11b+ cells freshly-isolated from the brains of C57Bl/6 mice at five different ages ranging from postnatal day 3 to 12 months, in males and females, using quantitative RT-PCR. We also compared purinergic receptor expression in microglia freshly-isolated from 3 day-old pups to that in primary neonatal microglial cultures created from mice of the same age. We observed patterns in P2 receptor expression with age, most notably increased expression with age and age-restricted expression. There were also several receptors that showed sexually dimorphic expression. Lastly, we noted that in vitro culturing of neonatal microglia greatly changed their P2 receptor expression profiles. These data represent the first complete and systematic report of changes in purinergic receptor expression of microglia with age and sex, and provide important information necessary for accurate in vitro modeling of healthy animals.
Collapse
Affiliation(s)
- Jessica M Crain
- Department of Comparative Biosciences, University of Wisconsin, Madison, WI 53706, USA.
| | | | | |
Collapse
|