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Takeda A, Shinozaki Y, Kashiwagi K, Ohno N, Eto K, Wake H, Nabekura J, Koizumi S. Microglia mediate non-cell-autonomous cell death of retinal ganglion cells. Glia 2018; 66:2366-2384. [PMID: 30375063 DOI: 10.1002/glia.23475] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 05/23/2018] [Accepted: 05/28/2018] [Indexed: 12/22/2022]
Abstract
Excitotoxicity is well known in the neuronal death in the brain and is also linked to neuronal damages in the retina. Recent accumulating evidence show that microglia greatly affect excitotoxicity in the brain, but their roles in retina have received only limited attention. Here, we report that retinal excitotoxicity is mediated by microglia. To this end, we employed three discrete methods, that is, pharmacological inhibition of microglia by minocycline, pharmacological ablation by an antagonist for colony stimulating factor 1 receptor (PLX5622), and genetic ablation of microglia using Iba1-tTA::DTAtetO/tetO mice. Intravitreal injection of NMDA increased the number of apoptotic retinal ganglion cells (RGCs) followed by reduction in the number of RGCs. Although microglia did not respond to NMDA directly, they became reactive earlier than RGC damages. Inhibition or ablation of microglia protected RGCs against NMDA. We found up-regulation of proinflammatory cytokine genes including Il1b, Il6 and Tnfa, among which Tnfa was selectively blocked by minocycline. PLX5622 also suppressed Tnfa expression. Tumor necrosis factor α (TNFα) signals were restricted in microglia at very early followed by spreading into other cell types. TNFα up-regulation in microglia and other cells were significantly attenuated by minocycline and PLX5622, suggesting a central role of microglia for TNFα induction. Both inhibition of TNFα and knockdown of TNF receptor type 1 by siRNA protected RGCs against NMDA. Taken together, our data demonstrate that a phenotypic change of microglia into a neurotoxic one is a critical event for the NMDA-induced degeneration of RGCs, suggesting an importance of non-cell-autonomous mechanism in the retinal neuronal excitotoxicity.
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Affiliation(s)
- Akiko Takeda
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Youichi Shinozaki
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Kenji Kashiwagi
- Department of Ophthalmology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Nobuhiko Ohno
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences (NIPS), Aichi, Japan.,Department of Anatomy, Jichi Medical University, Tochigi, Japan
| | - Kei Eto
- Division of Homeostatic Development, NIPS, Aichi, Japan
| | - Hiroaki Wake
- Division of Homeostatic Development, NIPS, Aichi, Japan.,Division of System Neuroscience, Graduate School of Medicine, Kobe University, Hyogo, Japan.,Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Saitama, Japan
| | | | - Schuichi Koizumi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
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Pathogenic Roles of Glutamic Acid Decarboxylase 65 Autoantibodies in Cerebellar Ataxias. J Immunol Res 2017; 2017:2913297. [PMID: 28386570 PMCID: PMC5366212 DOI: 10.1155/2017/2913297] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 12/05/2016] [Accepted: 01/10/2017] [Indexed: 12/12/2022] Open
Abstract
Reports suggesting a pathogenic role of autoantibodies directed against glutamic acid decarboxylase 65 (GAD65Abs) in cerebellar ataxias (CAs) are reviewed, and debatable issues such as internalization of antibodies by neurons and roles of epitopes are discussed. GAD65 is one of two enzymes that catalyze the conversion of glutamate to the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). A pathogenic role of GAD65Ab in CAs is suggested by in vivo and in vitro studies. (1) Intracerebellar administration of cerebrospinal fluid (CSF) immunoglobulins (IgGs) obtained from GAD65Ab-positive CA patients impairs cerebellar modulation of motor control in rats. (2) CSF IgGs act on terminals of GABAergic neurons and decrease the release of GABA in cerebellar slices from rats and mice. (3) Absorption of GAD65Ab by recombinant GAD65 diminishes the above effects, and monoclonal human GAD65Ab (b78) mimic the effects of CSF IgGs in vivo and in vitro. Studies using GAD65-KO mice confirm that the target molecule is GAD65. (4) Notably, the effects of GAD65Ab depend on the epitope specificity of the monoclonal GAD65Ab. Taken together, these results indicate that epitope-specific GAD65Ab-induced impairment of GABA release is involved in the pathogenesis of GAD65Ab-positive CA and support the early detection of GAD65Ab-associated CA to initiate immunotherapy before irreversible neuronal death in the cerebellum.
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Huang CT, Tsai YJ. Docosahexaenoic acid confers analgesic effects after median nerve injury via inhibition of c-Jun N-terminal kinase activation in microglia. J Nutr Biochem 2015; 29:97-106. [PMID: 26895670 DOI: 10.1016/j.jnutbio.2015.11.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 11/03/2015] [Accepted: 11/20/2015] [Indexed: 12/22/2022]
Abstract
The c-Jun N-terminal kinase (JNK) in the central nervous system plays a critical role in the processing of neuropathic pain. Docosahexaenoic acid (DHA), a predominant omega-3 polyunsaturated fatty acid in the central nervous system, has a neuroprotective efficacy. In this study, we examined the relationships between JNK activation in the cuneate nucleus (CN) and behavioral hypersensitivity after chronic constriction injury (CCI) of the median nerve. We further investigated the effects of DHA administration on JNK activation and development of hypersensitivity. Using immunohistochemistry and immunoblotting, low levels of phosphorylated JNK (p-JNK) were detected in the CN of sham-operated rats. As early as 1 day after CCI, p-JNK levels in the ipsilateral CN were significantly increased and peaked at 7 days. Double-immunofluorescence labeling with cell-specific markers showed that p-JNK immunoreactive cells coexpressed OX-42, a microglia activation marker, suggesting the expression of p-JNK in the microglia. Microinjection of SP600125, a JNK inhibitor, into the CN 1 day after CCI attenuated injury-induced behavioral hypersensitivity in a dose-dependent manner. Furthermore, animals received intravenous injection of DHA at doses of 100, 250 or 500 nmol/kg 30 min after median nerve CCI. DHA treatment decreased p-JNK and OX-42 levels, diminished the release of proinflammatory cytokines and improved behavioral hypersensitivity following CCI. In conclusion, median nerve injury-induced microglial JNK activation in the CN modulated development of behavioral hypersensitivity. DHA has analgesic effects on neuropathic pain, at least in part, by means of suppressing a microglia-mediated inflammatory response through the inhibition of JNK signaling pathway.
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Affiliation(s)
- Chun-Ta Huang
- Department of Internal Medicine and Traumatology, National Taiwan University Hospital, Taipei, Taiwan
| | - Yi-Ju Tsai
- Graduate Institute of Basic Medicine and School of Medicine, College of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan.
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Huang CT, Chiang RPY, Chen CL, Tsai YJ. Sleep deprivation aggravates median nerve injury-induced neuropathic pain and enhances microglial activation by suppressing melatonin secretion. Sleep 2014; 37:1513-23. [PMID: 25142572 DOI: 10.5665/sleep.4002] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
STUDY OBJECTIVES Sleep deprivation is common in patients with neuropathic pain, but the effect of sleep deprivation on pathological pain remains uncertain. This study investigated whether sleep deprivation aggravates neuropathic symptoms and enhances microglial activation in the cuneate nucleus (CN) in a median nerve chronic constriction injury (CCI) model. Also, we assessed if melatonin supplements during the sleep deprived period attenuates these effects. DESIGN Rats were subjected to sleep deprivation for 3 days by the disc-on-water method either before or after CCI. In the melatonin treatment group, CCI rats received melatonin supplements at doses of 37.5, 75, 150, or 300 mg/kg during sleep deprivation. Melatonin was administered at 23:00 once a day. PARTICIPANTS Male Sprague-Dawley rats, weighing 180-250 g (n = 190), were used. MEASUREMENTS Seven days after CCI, behavioral testing was conducted, and immunohistochemistry, immunoblotting, and enzyme-linked immunosorbent assay were used for qualitative and quantitative analyses of microglial activation and measurements of proinflammatory cytokines. RESULTS In rats who underwent post-CCI sleep deprivation, microglia were more profoundly activated and neuropathic pain was worse than those receiving pre-CCI sleep deprivation. During the sleep deprived period, serum melatonin levels were low over the 24-h period. Administration of melatonin to CCI rats with sleep deprivation significantly attenuated activation of microglia and development of neuropathic pain, and markedly decreased concentrations of proinflammatory cytokines. CONCLUSIONS Sleep deprivation makes rats more vulnerable to nerve injury-induced neuropathic pain, probably because of associated lower melatonin levels. Melatonin supplements to restore a circadian variation in melatonin concentrations during the sleep deprived period could alleviate nerve injury-induced behavioral hypersensitivity.
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Kawamoto EM, Vasconcelos AR, Degaspari S, Böhmer AE, Scavone C, Marcourakis T. Age-related changes in nitric oxide activity, cyclic GMP, and TBARS levels in platelets and erythrocytes reflect the oxidative status in central nervous system. AGE (DORDRECHT, NETHERLANDS) 2013; 35:331-342. [PMID: 22278206 PMCID: PMC3592952 DOI: 10.1007/s11357-011-9365-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Accepted: 12/05/2011] [Indexed: 05/31/2023]
Abstract
Aging is associated with an increased susceptibility to neurodegenerative disorders which has been linked to chronic inflammation. This process generates oxygen-reactive species, ultimately responsible for a process known as oxidative stress, leading to changes in nitric oxide (NO), and cyclic guanosine monophosphate (cyclic GMP) signaling pathway. In previous studies, we showed that human aging was associated with an increase in NO Synthase (NOS) activity, a decrease in basal cyclic GMP levels in human platelets, and an increase in thiobarbituric acid-reactant substances (TBARS) in erythrocytes. The aim of the present work was to evaluate NOS activity, TBARS and cyclic GMP levels in hippocampus and frontal cortex and its correlation to platelets and erythrocytes of 4-, 12-, and 24-month-old rats. The result showed an age-related decrease in cyclic GMP levels which was linked to an increase in NOS activity and TBARS in both central areas as well as in platelets and erythrocytes of rats. The present data confirmed our previous studies performed in human platelets and erythrocytes and validate NOS activity and cyclic GMP in human platelet as well as TBARS in erythrocytes as biomarkers to study age-related disorders and new anti-aging therapies.
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Affiliation(s)
- Elisa Mitiko Kawamoto
- />Department of Pharmacology, Institute of Biomedical Science—ICB-1, University of São Paulo, Avenida Professor Lineu Prestes, 1524, 05508-900 São Paulo, Brazil
- />Laboratory of Neurosciences, NIA, NIH, Baltimore, MD USA
| | - Andrea Rodrigues Vasconcelos
- />Department of Pharmacology, Institute of Biomedical Science—ICB-1, University of São Paulo, Avenida Professor Lineu Prestes, 1524, 05508-900 São Paulo, Brazil
| | - Sabrina Degaspari
- />Department of Pharmacology, Institute of Biomedical Science—ICB-1, University of São Paulo, Avenida Professor Lineu Prestes, 1524, 05508-900 São Paulo, Brazil
| | - Ana Elisa Böhmer
- />Department of Pharmacology, Institute of Biomedical Science—ICB-1, University of São Paulo, Avenida Professor Lineu Prestes, 1524, 05508-900 São Paulo, Brazil
| | - Cristoforo Scavone
- />Department of Pharmacology, Institute of Biomedical Science—ICB-1, University of São Paulo, Avenida Professor Lineu Prestes, 1524, 05508-900 São Paulo, Brazil
| | - Tania Marcourakis
- />Department of Clinical Chemistry and Toxicology, School of Pharmaceutical Sciences, University of São Paulo, São Paulo, Brazil
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Chiang RPY, Huang CT, Tsai YJ. Melatonin reduces median nerve injury-induced mechanical hypersensitivity via inhibition of microglial p38 mitogen-activated protein kinase activation in rat cuneate nucleus. J Pineal Res 2013; 54:232-44. [PMID: 23237358 DOI: 10.1111/jpi.12029] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2012] [Accepted: 11/07/2012] [Indexed: 12/30/2022]
Abstract
In this study, we examined the relationships between p38 mitogen-activated protein kinase (MAPK) activation in the cuneate nucleus (CN) and behavioral hypersensitivity after chronic constriction injury (CCI) of the median nerve. We further investigated effects of melatonin administration and pinealectomy on p38 MAPK activation and development of hypersensitivity. Using immunohistochemistry and immunoblotting, low levels of phosphorylated p38 (p-p38) MAPK were detected in CN of normal rats. As early as 1 day after CCI, p-p38 MAPK levels in the ipsilateral CN were significantly increased (1.4 ± 0.2-fold, P < 0.05), which reached a maximum at 7 days (5.1 ± 0.4-fold, P < 0.001). Double immunofluorescence labeling with cell-specific markers showed that p-p38 MAPK immunoreactive cells co-expressed OX-42, a microglia activation maker, suggesting the expression of p-p38 MAPK in microglia. Microinjection of SB203580, a p38 MAPK inhibitor, into the CN 1 day after CCI attenuated injury-induced behavioral hypersensitivity in a dose-dependent manner. Furthermore, animals received melatonin treatment at daily doses of 37.5, 75, 150, or 300 mg/kg from 30 min before until 3 days after CCI. Melatonin treatment dose-dependently attenuated p-p38 MAPK levels, release of pro-inflammatory cytokines, and behavioral hypersensitivity following CCI; conversely, pinealectomy that resulted in a reduction in endogenous melatonin levels exacerbated these effects. In conclusion, median nerve injury-induced microglial p38 MAPK activation in the CN modulated development of behavioral hypersensitivity. Melatonin supplementation eased neuropathic pain via inhibition of p38 MAPK signaling pathway; contrarily, reducing endogenous blood melatonin levels by pinealectomy promoted phosphorylation of p38 MAPK and made rats more vulnerable to nerve injury-induced neuropathic pain.
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N-Methyl-D-aspartate receptor antagonists memantine and MK-801 attenuate the cerebral infarct accelerated by intracorpus callosum injection of lipopolysaccharides. Neurosci Lett 2013; 538:9-14. [PMID: 23376060 DOI: 10.1016/j.neulet.2013.01.031] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 01/03/2013] [Accepted: 01/23/2013] [Indexed: 11/22/2022]
Abstract
Inflammatory responses have been shown to modulate the pattern and degree of ischemic injury. Previously, we demonstrated that intracorpus callosum microinjection of lipopolysaccharide (LPS, a well-known endotoxin) markedly induced inflammatory responses confined to ipsilateral hemisphere and aggravated cerebral ischemic injury. Here we report that LPS injection increases the degree of N-methyl-d-aspartate (NMDA) receptor-mediated excitotoxicity, one of major causes of cerebral ischemic injury. Intracorpus callosum microinjection of LPS 1 day prior to ischemic insults augmented intraneuronal Ca(2+) rise in rat brains subjected to transient occlusion of middle cerebral artery. Intraperitoneal administration of memantine, a NMDA receptor antagonist, reduced the LPS-enhanced calcium response as well as ischemic tissue damage. Western blot and immunohistochemistry data showed that the level of IL-1β was enhanced in LPS-injected rat brains, particularly in isolectin-B4 immunoreactive cells. Intraventricular microinjection of recombinant rat IL-1β aggravated cerebral ischemic injury, which was significantly reduced by memantine. Intraventricular injection of anti-IL-1β antibody significantly reduced the cerebral infarction aggravated by LPS preinjection. The results indicate that IL-1β released from isolectin-B4 immunoreactive cells enhanced excitotoxicity, consequently aggravating ischemic brain injury.
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Ryu KY, Cho GS, Piao HZ, Kim WK. Role of TGF-β in Survival of Phagocytizing Microglia: Autocrine Suppression of TNF-α Production and Oxidative Stress. Exp Neurobiol 2012; 21:151-7. [PMID: 23319875 PMCID: PMC3538179 DOI: 10.5607/en.2012.21.4.151] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 12/10/2012] [Indexed: 01/24/2023] Open
Abstract
Microglia are recognized as residential macrophageal cells in the brain. Activated microglia play a critical role in removal of dead or damaged cells through phagocytosis activity. During phagocytosis, however, microglia should survive under the harmful condition of self-producing ROS and pro-inflammatory mediators. TGF-β has been known as a classic anti-inflammatory cytokine and controls both initiation and resolution of inflammation by counter-acting inflammatory cytokines. In the present study, to understand the self-protective mechanism, we studied time-dependent change of TNF-α and TGF-β production in microglia phagocytizing opsonized-beads (i.e., polystyrene microspheres). We found that microglia phagocytized opsonized-bead in a time-dependent manner and simultaneously produced both TNF-α and TGF-β. However, while TNF-α production gradually decreased after 6 h, TGF-β production remained at increased level. Microglial cells pre-treated with lipopolysaccharides (a strong immunostimulant, LPS) synergistically increased the production of TNF-α and TGF-β both. However, LPS-pretreated microglia produced TNF-α in a more sustained manner and became more vulnerable, probably due to the marked and sustained production of TNF-α and reduced TGF-β. Intracellular oxidative stress appears to change in parallel with the microglial production of TNF-α. These results indicate TGF-β contributes for the survival of phagocytizing microglia through autocrine suppression of TNF-α production and oxidative stress.
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Affiliation(s)
- Keun-Young Ryu
- College of Medicine, Korea University, Seoul 136-705, Korea
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Contestabile A. Role of nitric oxide in cerebellar development and function: focus on granule neurons. THE CEREBELLUM 2012; 11:50-61. [PMID: 21104176 DOI: 10.1007/s12311-010-0234-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
More than 20 years of research have firmly established important roles of the diffusible messenger molecule, nitric oxide (NO), in cerebellar development and function. Granule neurons are main players in every NO-related mechanism involving cerebellar function and dysfunction. Granule neurons are endowed with remarkable amounts of the Ca(2+)-dependent neuronal isoform of nitric oxide synthase and can directly respond to endogenously produced NO or induce responses in neighboring cells taking advantage of the high diffusibility of the molecule. Nitric oxide acts as a negative regulator of granule cell precursor proliferation and promotes survival and differentiation of these neurons. Nitric oxide is neuroprotective towards granule neurons challenged with toxic insults. Nitric oxide is a main regulator of bidirectional plasticity at parallel fiber-Purkinje neuron synapses, inducing long-term depression (LTD) or long-term potentiation (LTP) depending on postsynaptic Ca(2+) levels, thus playing a central role in cerebellar learning related to motor control. Granule neurons cooperate with glial cells, in particular with microglia, in the regulation of NO production through the respective forms of NOS present in the two cellular types. Aim of the present paper is to review the state of the art and the improvement of our understanding of NO functions in cerebellar granule neurons obtained during the last two decades and to outline possible future development of the research.
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Affiliation(s)
- Antonio Contestabile
- Department of Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy.
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Contestabile A, Monti B, Polazzi E. Neuronal-glial Interactions Define the Role of Nitric Oxide in Neural Functional Processes. Curr Neuropharmacol 2012; 10:303-10. [PMID: 23730254 PMCID: PMC3520040 DOI: 10.2174/157015912804143522] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Revised: 06/07/2012] [Accepted: 06/24/2012] [Indexed: 01/01/2023] Open
Abstract
Nitric oxide (NO) is a versatile cellular messenger performing a variety of physiologic and pathologic actions in most tissues. It is particularly important in the nervous system, where it is involved in multiple functions, as well as in neuropathology, when produced in excess. Several of these functions are based on interactions between NO produced by neurons and NO produced by glial cells, mainly astrocytes and microglia. The present paper briefly reviews some of these interactions, in particular those involved in metabolic regulation, control of cerebral blood flow, axonogenesis, synaptic function and neurogenesis. Aim of the paper is mainly to underline the physiologic aspects of these interactions rather than the pathologic ones.
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Ebrahimi F, Koch M, Pieroh P, Ghadban C, Hobusch C, Bechmann I, Dehghani F. Time dependent neuroprotection of mycophenolate mofetil: effects on temporal dynamics in glial proliferation, apoptosis, and scar formation. J Neuroinflammation 2012; 9:89. [PMID: 22569136 PMCID: PMC3430572 DOI: 10.1186/1742-2094-9-89] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Accepted: 05/08/2012] [Indexed: 12/14/2022] Open
Abstract
Background Immunosuppressants such as mycophenolate mofetil (MMF) have the capacity to inhibit microglial and astrocytic activation and to reduce the extent of cell death after neuronal injury. This study was designed to determine the effective neuroprotective time frame in which MMF elicits its beneficial effects, by analyzing glial cell proliferation, migration, and apoptosis. Methods Using organotypic hippocampal slice cultures (OHSCs), temporal dynamics of proliferation and apoptosis after N-methyl-D-aspartate (NMDA)-mediated excitotoxicity were analyzed by quantitative morphometry of Ki-67 or cleaved caspase-3 immunoreactive glial cells. Treatment on NMDA-lesioned OHSCs with mycophenolate mofetil (MMF)100 μg/mL was started at different time points after injury or performed within specific time frames, and the numbers of propidium iodide (PI)+ degenerating neurons and isolectin (I)B4+ microglial cells were determined. Pre-treatment with guanosine 100 μmol/l was performed to counteract MMF-induced effects. The effects of MMF on reactive astrocytic scar formation were investigated in the scratch-wound model of astrocyte monolayers. Results Excitotoxic lesion induction led to significant increases in glial proliferation rates between 12 and 36 hours after injury and to increased levels of apoptotic cells between 24 and 72 hours after injury. MMF treatment significantly reduced glial proliferation rates without affecting apoptosis. Continuous MMF treatment potently reduced the extent of neuronal cell demise when started within the first 12 hours after injury. A crucial time-frame of significant neuroprotection was identified between 12 and 36 hours after injury. Pre-treatment with the neuroprotective nucleoside guanosine reversed MMF-induced antiproliferative effects on glial cells. In the scratch-wound model, gap closure was reached within 48 hours in controls, and was potently inhibited by MMF. Conclusions Our data indicate that immunosuppression by MMF significantly attenuates the extent of neuronal cell death when administered within a crucial time frame after injury. Moreover, long-lasting immunosuppression, as required after solid-organ transplantation, does not seem to be necessary. Targeting inosine 5-monophosphate dehydrogenase, the rate-limiting enzyme of purine synthesis, is an effective strategy to modulate the temporal dynamics of proliferation and migration of microglia and astrocytes, and thus to reduce the extent of secondary neuronal damage and scar formation.
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Affiliation(s)
- Fahim Ebrahimi
- Institute of Anatomy, Leipzig University, Leipzig, Germany
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Linl SC, Yehl JH, Chenl CL, Choul SH, Tsail YJ. Effects of local lidocaine treatment before and after median nerve injury on mechanical hypersensitivity and microglia activation in rat cuneate nucleus. Eur J Pain 2012; 15:359-67. [DOI: 10.1016/j.ejpain.2010.08.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2010] [Revised: 08/08/2010] [Accepted: 08/19/2010] [Indexed: 11/28/2022]
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Murugan M, Sivakumar V, Lu J, Ling EA, Kaur C. Expression of N-methyl D-aspartate receptor subunits in amoeboid microglia mediates production of nitric oxide via NF-κB signaling pathway and oligodendrocyte cell death in hypoxic postnatal rats. Glia 2011; 59:521-39. [PMID: 21319220 DOI: 10.1002/glia.21121] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Accepted: 11/11/2010] [Indexed: 11/10/2022]
Abstract
The present study was focused on identifying the expression of N-methyl D-aspartate receptor (NMDAR) subunits on activated microglia and to determine their role in the pathogenesis of periventricular white matter damage (PWMD) in neonatal rats following hypoxia. One day old wistar rats were subjected to hypoxia (5% O(2) ; 95% N(2) ) and the mRNA and protein expression of NMDAR subunits (NR1, NR2A-D, and NR3A) in the periventricular white matter (PWM) was determined at different time points (3,24 h, 3, 7, and 14 days) following hypoxic exposure. Immunoexpression of NR1 and NR2A-D was localized in amoeboid microglial cells (AMC) suggesting the presence of functional NMDARs in them. The expression of NMDAR in primary microglial cultures was ascertained by RT-PCR analysis and double immunofluorescence studies. The functionality of the microglial NMDAR in cultured microglial cells was examined by monitoring calcium movements in cells with fura-2. In primary microglial cultures, hypoxia induced the nuclear translocation of NF-κB which was suppressed by administration of MK801, an NMDAR antagonist. MK801 also down regulated the hypoxia-induced expression of tumor necrosis factor-α, interleukin-1β, inducible nitric oxide synthase (iNOS), and nitric oxide (NO) production by microglia which may be mediated by the NF-κB signaling pathway. NO produced by microglia is known to cause death of oligodendrocytes in the developing PWM. In this connection, pharmacological agents such as MK801, BAY (NF-κB inhibitor), and 1400w (iNOS inhibitor) proved to be beneficial since they reduced the hypoxia-induced iNOS expression, NO production, and a corresponding reduction in the death of oligodendrocytes following hypoxia.
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Affiliation(s)
- Madhuvika Murugan
- Department of Anatomy, Yong Loo Lin School of Medicine, Blk MD10, 4 Medical Drive, National University of Singapore, Singapore
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Chakraborty S, Kaushik DK, Gupta M, Basu A. Inflammasome signaling at the heart of central nervous system pathology. J Neurosci Res 2010; 88:1615-31. [PMID: 20127816 DOI: 10.1002/jnr.22343] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Neuroinflammation is a complex innate response of neural tissue against harmful effects of diverse stimuli viz., pathogens, damaged cells and irritants within the Central Nervous System (CNS). Studies show that multiple inflammatory mediators including cytokines, chemokines and prostaglandins are elevated in the Cerebrospinal Fluid (CSF) and in post-mortem brain tissues of patients with history of neuroinflammatory conditions as well as neurodegenerative disorders like Alzheimer's disease, Parkinson's disease and Multiple Sclerosis. The innate immunity mediators in the brain, namely microglia and astrocytes, express certain Pattern Recognition Receptors (PRRs), which are always on 'high-alert' for pathogens or other inflammatory triggers and participate in the assembly and activation of the inflammasome. The inflammasome orchestrates the activation of the precursors of proinflammatory caspases, which in turn, cleave the precursor forms of interleukin-1beta, IL-18 and IL-33 into their active forms; the secretion of which leads to a potent inflammatory response, and/or influences the release of toxins from glial and endothelial cells. Altered expression of inflammasome mediators can either promote or inhibit neurodegenerative processes. Therefore, modulating the inflammasome machinery seems a better combat strategy than summarily suppressing all inflammation in most neuroinflammatory conditions. In the current review we have surveyed the identified triggers and pathways of inflammasome activation and the following events which ultimately accomplish the innate inflammatory response in the CNS, with a goal to provide an analytical insight into disease pathogenesis that might provide cues for devising novel therapeutic strategies.
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Clausen F, Hånell A, Björk M, Hillered L, Mir AK, Gram H, Marklund N. Neutralization of interleukin-1beta modifies the inflammatory response and improves histological and cognitive outcome following traumatic brain injury in mice. Eur J Neurosci 2009; 30:385-96. [PMID: 19614750 DOI: 10.1111/j.1460-9568.2009.06820.x] [Citation(s) in RCA: 147] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Interleukin-1beta (IL-1beta) may play a central role in the inflammatory response following traumatic brain injury (TBI). We subjected 91 mice to controlled cortical impact (CCI) brain injury or sham injury. Beginning 5 min post-injury, the IL-1beta neutralizing antibody IgG2a/k (1.5 microg/mL) or control antibody was infused at a rate of 0.25 microL/h into the contralateral ventricle for up to 14 days using osmotic minipumps. Neutrophil and T-cell infiltration and microglial activation was evaluated at days 1-7 post-injury. Cognition was assessed using Morris water maze, and motor function using rotarod and cylinder tests. Lesion volume and hemispheric tissue loss were evaluated at 18 days post-injury. Using this treatment strategy, cortical and hippocampal tissue levels of IgG2a/k reached 50 ng/mL, sufficient to effectively inhibit IL-1betain vitro. IL-1beta neutralization attenuated the CCI-induced cortical and hippocampal microglial activation (P < 0.05 at post-injury days 3 and 7), and cortical infiltration of neutrophils (P < 0.05 at post-injury day 7). There was only a minimal cortical infiltration of activated T-cells, attenuated by IL-1beta neutralization (P < 0.05 at post-injury day 7). CCI induced a significant deficit in neurological motor and cognitive function, and caused a loss of hemispheric tissue (P < 0.05). In brain-injured animals, IL-1beta neutralizing treatment resulted in reduced lesion volume, hemispheric tissue loss and attenuated cognitive deficits (P < 0.05) without influencing neurological motor function. Our results indicate that IL-1beta is a central component in the post-injury inflammatory response that, in view of the observed positive neuroprotective and cognitive effects, may be a suitable pharmacological target for the treatment of TBI.
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Affiliation(s)
- Fredrik Clausen
- Department of Neuroscience, Section for Neurosurgery, Uppsala University, Uppsala, Sweden
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16
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Kaur C, Ling E. Periventricular white matter damage in the hypoxic neonatal brain: Role of microglial cells. Prog Neurobiol 2009; 87:264-80. [DOI: 10.1016/j.pneurobio.2009.01.003] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 11/12/2008] [Accepted: 01/08/2009] [Indexed: 01/22/2023]
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17
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Park JS, Park EM, Kim DH, Jung K, Jung JS, Lee EJ, Hyun JW, Kang JL, Kim HS. Anti-inflammatory mechanism of ginseng saponins in activated microglia. J Neuroimmunol 2009; 209:40-9. [DOI: 10.1016/j.jneuroim.2009.01.020] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Revised: 01/19/2009] [Accepted: 01/20/2009] [Indexed: 11/29/2022]
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18
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Piao HZ, Choi IY, Park JS, Kim HS, Cheong JH, Son KH, Jeon SJ, Ko KH, Kim WK. Wogonin inhibits microglial cell migration via suppression of nuclear factor-kappa B activity. Int Immunopharmacol 2008; 8:1658-62. [PMID: 18725324 DOI: 10.1016/j.intimp.2008.07.018] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Accepted: 07/29/2008] [Indexed: 01/06/2023]
Abstract
Previously, we and others have demonstrated that wogonin, an active component from the root of Scutellaria baicalensis Georgi, has a neuroprotective effect in cerebral ischemic insult. The neuroprotective effect of wogonin may at least in part be due to its anti-inflammatory properties. Microglial cells, well-known residential macrophages in the central nervous system, migrate to the ischemic lesion and play a pivotal role in the development of chronic inflammation. In the present study, we observed that wogonin potently inhibited microglial migration toward a chemokine, monocyte chemoattractant protein-1 (MCP-1). The anti-migratory effect of wogonin was provoked at nanomolar concentrations, at which wogonin did not significantly inhibit the production of cytokines and chemokines. NF-kappaB has previously shown to regulate microglial cell migration, and activation of cAMP-signaling pathway has also been associated with inhibition of microglial cell motility. In the present study, wogonin at low micromolar concentrations completely suppressed the activity of NF-kappaB in MCP-1-stimulated microglia, and NF-kappaB inhibitors such as N-acetyl cysteine and pyrrolidinedithiocarbamate inhibited the MCP-1-induced migration of microglial cells. However, wogonin did not stimulate the production of cAMP in microglial cells. Our results indicate that the anti-inflammatory activity of wogonin is exerted at least in part by suppressing microglial cell motility via inhibition of NF-kappaB activity.
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Affiliation(s)
- Hua Zi Piao
- Department of Pharmacology, College of Medicine, Yanbian University, Yanji, China
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19
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Woo MS, Park JS, Choi IY, Kim WK, Kim HS. Inhibition of MMP-3 or -9 suppresses lipopolysaccharide-induced expression of proinflammatory cytokines and iNOS in microglia. J Neurochem 2008; 106:770-80. [DOI: 10.1111/j.1471-4159.2008.05430.x] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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20
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Microglia cells protect neurons by direct engulfment of invading neutrophil granulocytes: a new mechanism of CNS immune privilege. J Neurosci 2008; 28:5965-75. [PMID: 18524901 DOI: 10.1523/jneurosci.0060-08.2008] [Citation(s) in RCA: 205] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Microglial cells maintain the immunological integrity of the healthy brain and can exert protection from traumatic injury. During ischemic tissue damage such as stroke, peripheral immune cells acutely infiltrate the brain and may exacerbate neurodegeneration. Whether and how microglia can protect from this insult is unknown. Polymorphonuclear neutrophils (PMNs) are a prominent immunologic infiltrate of ischemic lesions in vivo. Here, we show in organotypic brain slices that externally applied invading PMNs massively enhance ischemic neurotoxicity. This, however, is counteracted by additional application of microglia. Time-lapse imaging shows that microglia exert protection by rapid engulfment of apoptotic, but, strikingly, also viable, motile PMNs in cell culture and within brain slices. PMN engulfment is mediated by integrin- and lectin-based recognition. Interference with this process using RGDS peptides and N-acetyl-glucosamine blocks engulfment of PMNs and completely abrogates the neuroprotective function of microglia. Thus, engulfment of invading PMNs by microglia may represent an entirely new mechanism of CNS immune privilege.
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21
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Shin CY, Lee WJ, Choi JW, Choi MS, Ryu JR, Oh SJ, Cheong JH, Choi EY, Ko KH. Down-regulation of matrix metalloproteinase-9 expression by nitric oxide in lipopolysaccharide-stimulated rat primary astrocytes. Nitric Oxide 2007; 16:425-32. [PMID: 17452115 DOI: 10.1016/j.niox.2007.03.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2006] [Revised: 03/07/2007] [Accepted: 03/17/2007] [Indexed: 10/23/2022]
Abstract
Immunologically activated astrocytes over-express matrix metalloproteinase-9 (MMP-9) and nitric oxide (NO). Because they have both beneficial and detrimental effects on the pathophyiological outcomes of several neurological diseases, their expression should be tightly regulated in the CNS. NO can modify the activity of other proteins either by directly modifying protein structure or regulating the expression of target proteins. In this study, we investigated the role of NO on the expression of MMPs in rat primary astrocytes. Rat primary astrocytes were stimulated with lipopolysaccharide (LPS), resulting in the over-expression of both MMP-9 and NO. Inhibition of NO production using nitric oxide synthase inhibitor, Nomega-nitro-l-arginine methyl ester (l-NAME), further increased MMP-9 expression, suggesting NO inhibits MMP-9 expression. In line with this observation, exogenous addition of NO donor, sodium nitroprusside (SNP) or S-nitroso-N-acetylpenicillamine (SNAP), inhibited MMP-9 expression in astrocytes. The inhibitory effect of NO was mediated by the down-regulation of mRNA and protein levels of MMP-9 but not by the direct modification of the enzymatic activity of MMP-9. The effect of NO on MMP-9 expression was mimicked by dibutyryl-cGMP and inhibited by PKG inhibitor KT5823, suggesting NO regulates MMP-9 expression via guanylate cyclase-PKG pathway. Finally, SNP or dibutyryl-cGMP inhibited the activation of ERK1/2 in LPS-stimulated astrocytes, which is an essential regulator of MMP-9 expression in astrocytes. The regulation of MMP-9 expression by NO may confer additional levels of fine-tuning of the level of MMP-9 during brain inflammatory conditions.
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Affiliation(s)
- Chan Young Shin
- Department of Pharmacology, School of Medicine, Konkuk University, Republic of Korea
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22
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Wenk GL, Parsons CG, Danysz W. Potential role of N-methyl-D-aspartate receptors as executors of neurodegeneration resulting from diverse insults: focus on memantine. Behav Pharmacol 2007; 17:411-24. [PMID: 16940762 DOI: 10.1097/00008877-200609000-00007] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Glutamatergic neurotransmission is critical to normal learning and memory and when the activity of glutamate neurons becomes excessive, or the normal function of its primary receptors becomes dysfunctional, this may lead to pathological changes associated with age-related neurodegenerative diseases. Anomalous glutamatergic activity associated with Alzheimer's disease may be due to a postsynaptic receptor and downstream defects that produce inappropriately timed or sustained glutamate activation of N-methyl-D-aspartate receptors, leading to neuronal injury and death and cognitive deficits associated with dementia. The mechanisms leading to the condition of chronically depolarized membranes on vulnerable neurons in the Alzheimer's disease brain are likely due to a complex interaction between oxidative stress, mitochondrial failure, chronic brain inflammation and the presence of amyloid-beta and hyperphosphorylated-tau; each of these factors are highly interrelated with each other and are discussed with an emphasis upon potential therapeutic mechanisms underlying the neuroprotective actions of memantine.
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Affiliation(s)
- Gary L Wenk
- Department Psychology & Neuroscience, Ohio State University, Ohio, USA
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23
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Kim JM, Lee JC, Chang N, Chun HS, Kim WK. S-Allyl-L-cysteine attenuates cerebral ischemic injury by scavenging peroxynitrite and inhibiting the activity of extracellular signal-regulated kinase. Free Radic Res 2007; 40:827-35. [PMID: 17015261 DOI: 10.1080/10715760600719540] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
S-Allyl-L-cysteine (SAC) has been shown to reduce ischemic injury due to its antioxidant activity. However, the antioxidant property of SAC has been controversial. The present study investigated the neuroprotective mechanism of SAC in cerebral ischemic insults. SAC decreased the size of infarction after transient or global ischemic insults. While it did not alter the N-methyl-D-aspartate excitotoxicity, SAC significantly scavenged the endogenously or exogenously produced ONOO- and reduced ONOO- cytotoxicity. In contrast, SAC has much lower scavenging activity against H2O2, O2*(-) or NO. Further, SAC inhibited the activity of extracellular signal-regulated kinase (ERK) increased in cultured neurons exposed to oxygen-glucose deprivation or in rat brain tissue after transient middle cerebral artery occlusion. The neuroprotective effect of SAC was mimicked by the ERK inhibitor U0125. The present results indicate that SAC exert its neuroprotective effect by scavenging ONOO- and inhibiting the ERK signaling pathway activated during initial hypoxic/ischemic insults.
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Affiliation(s)
- Ji-Myung Kim
- Food Function Research Division, Korea Food Research Institute, Sungnam, South Korea
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24
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Neurodegenerative diseases and memory. Neurobiol Learn Mem 2007. [DOI: 10.1016/b978-012372540-0/50017-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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25
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Jung KK, Lee HS, Cho JY, Shin WC, Rhee MH, Kim TG, Kang JH, Kim SH, Hong S, Kang SY. Inhibitory effect of curcumin on nitric oxide production from lipopolysaccharide-activated primary microglia. Life Sci 2006; 79:2022-31. [PMID: 16934299 DOI: 10.1016/j.lfs.2006.06.048] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2005] [Revised: 06/20/2006] [Accepted: 06/26/2006] [Indexed: 10/24/2022]
Abstract
Curcumin has been shown to exhibit anti-inflammatory, antimutagenic, and anticarcinogenic activities. However, the modulatory effect of curcumin on the functional activation of primary microglial cells, brain mononuclear phagocytes causing the neuronal damage, largely remains unknown. The current study examined whether curcumin influenced NO production in rat primary microglia and investigated its underlying signaling pathways. Curcumin decreased NO production in LPS-stimulated microglial cells in a dose-dependent manner, with an IC(50) value of 3.7 microM. It also suppressed both mRNA and protein levels of inducible nitric oxide synthase (iNOS), indicating that this drug may affect iNOS gene expression process. Indeed, curcumin altered biochemical patterns induced by LPS such as phosphorylation of all mitogen-activated protein kinases (MAPKs), and DNA binding activities of nuclear factor-kappaB (NF-kappaB) and activator protein (AP)-1, assessed by reporter gene assay. By analysis of inhibitory features of specific MAPK inhibitors, a series of signaling cascades including c-Jun N-terminal kinase (JNK), p38 and NF-kappaB was found to play a critical role in curcumin-mediated NO inhibition in microglial cells. The current results suggest that curcumin is a promising agent for the prevention and treatment of both NO and microglial cell-mediated neurodegenerative disorders.
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Affiliation(s)
- Ki Kyung Jung
- Pharmacology Department, National Institute of Toxicological Research, KFDA, Seoul 122-704, Republic of Korea
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26
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Kreutz S, Koch M, Ghadban C, Korf HW, Dehghani F. Cannabinoids and neuronal damage: differential effects of THC, AEA and 2-AG on activated microglial cells and degenerating neurons in excitotoxically lesioned rat organotypic hippocampal slice cultures. Exp Neurol 2006; 203:246-57. [PMID: 17010339 DOI: 10.1016/j.expneurol.2006.08.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Revised: 08/07/2006] [Accepted: 08/10/2006] [Indexed: 11/25/2022]
Abstract
Cannabinoids (CBs) are attributed neuroprotective effects in vivo. Here, we determined the neuroprotective potential of CBs during neuronal damage in excitotoxically lesioned organotypic hippocampal slice cultures (OHSCs). OHSCs are the best characterized in vitro model to investigate the function of microglial cells in neuronal damage since blood-borne monocytes and T-lymphocytes are absent and microglial cells represent the only immunocompetent cell type. Excitotoxic neuronal damage was induced by NMDA (50 microM) application for 4 h. Neuroprotective properties of 9-carboxy-11-nor-delta-9-tetrahydrocannabinol (THC), N-arachidonoylethanolamide (AEA) or 2-arachidonoylglycerol (2-AG) in different concentrations were determined after co-application with NMDA by counting degenerating neurons identified by propidium iodide labeling (PI(+)) and microglial cells labeled by isolectin B(4) (IB(4)(+)). All three CBs used significantly decreased the number of IB(4)(+) microglial cells in the dentate gyrus but the number of PI(+) neurons was reduced only after 2-AG treatment. Application of AM630, antagonizing CB2 receptors highly expressed by activated microglial cells, did not counteract neuroprotective effects of 2-AG, but affected THC-mediated reduction of IB(4)(+) microglial cells. Our results indicate that (1) only 2-AG exerts neuroprotective effects in OHSCs; (2) reduction of IB(4)(+) microglial cells is not a neuroprotective event per se and involves other CB receptors than the CB2 receptor; (3) the discrepancy in the neuroprotective effects of CBs observed in vivo and in our in vitro model system may underline the functional relevance of invading monocytes and T-lymphocytes that are absent in OHSCs.
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MESH Headings
- Animals
- Animals, Newborn
- Arachidonic Acids/pharmacology
- Arachidonic Acids/therapeutic use
- Brain/drug effects
- Brain/pathology
- Brain/physiopathology
- Brain Damage, Chronic/drug therapy
- Brain Damage, Chronic/metabolism
- Brain Damage, Chronic/physiopathology
- Cannabinoids/pharmacology
- Cannabinoids/therapeutic use
- Cell Count
- Disease Models, Animal
- Dronabinol/pharmacology
- Dronabinol/therapeutic use
- Endocannabinoids
- Gliosis/drug therapy
- Gliosis/metabolism
- Gliosis/physiopathology
- Glycerides/pharmacology
- Glycerides/therapeutic use
- Microglia/drug effects
- Microglia/metabolism
- N-Methylaspartate/antagonists & inhibitors
- N-Methylaspartate/toxicity
- Nerve Degeneration/drug therapy
- Nerve Degeneration/metabolism
- Nerve Degeneration/physiopathology
- Neurons/drug effects
- Neurons/metabolism
- Neurons/pathology
- Neuroprotective Agents/pharmacology
- Neuroprotective Agents/therapeutic use
- Neurotoxins/antagonists & inhibitors
- Neurotoxins/toxicity
- Organ Culture Techniques
- Plant Lectins
- Polyunsaturated Alkamides/pharmacology
- Polyunsaturated Alkamides/therapeutic use
- Rats
- Rats, Wistar
- Receptor, Cannabinoid, CB2/antagonists & inhibitors
- Receptor, Cannabinoid, CB2/metabolism
- Treatment Outcome
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Affiliation(s)
- Susanne Kreutz
- Dr. Senckenbergische Anatomie, Institut für Anatomie 2, Johann Wolfgang Goethe-Universität Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt/Main, Germany
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27
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Toward prevention of Alzheimers disease--potential nutraceutical strategies for suppressing the production of amyloid beta peptides. Med Hypotheses 2006; 67:682-97. [PMID: 16828233 DOI: 10.1016/j.mehy.2006.04.067] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2006] [Accepted: 04/10/2006] [Indexed: 12/30/2022]
Abstract
Alzheimers disease (AD) can be viewed as a vicious cycle in which excess production and deposition of amyloid beta (Abeta) peptides promote microglial activation, and the resultant production of inflammatory mediators further boosts Abeta production while inducing death and dysfunction of neurons. Abeta production is mediated by beta- and gamma-secretase activities; it is prevented by alpha-secretase activity, and insulin-degrading enzyme (IDE) catabolizes Abeta. High cellular cholesterol content increases Abeta synthesis by boosting beta-secretase activity; inhibition of cholesterol syntheses and/or stimulation of cholesterol export thus diminishes Abeta production. PPARgamma activity decreases Abeta production by promoting harmless catabolism of amyloid precursor protein while blocking the up-regulatory impact of cytokines on beta-secretase expression. Nitric oxide produced by the healthy cerebral microvasculature can suppress Abeta production by boosting expression of alpha-secretase while suppressing that of beta-secretase; conversely, cerebral ischemia provokes increased APP expression. Good insulin sensitivity and efficient brain insulin function protect by inhibiting gamma-secretase activity and increasing expression of IDE. The DHA provided by fish oil diminishes cerebral Abeta deposition in rodent AD models, for unclear reasons. Various measures which oppose microglial activation can inhibit up-regulation of beta-secretase and gamma-secretase by oxidants and cytokines, respectively. These considerations suggest that a number of nutraceutical or lifestyle measures may have potential for preventing or slowing AD: policosanol; 9-cis-beta-carotene; isomerized hops extract; DHA; measures which promote efficient endothelial NO generation, such as low-salt/potassium-rich diets, exercise training, high-dose folate, and flavanol-rich cocoa; chromium picolinate and cinnamon extract as aids for insulin sensitivity; and various agents which can oppose microglial activation, including vitamin D, genistein, and sesamin. The impact of these measures on Abeta production in rodent models of AD should be evaluated, with the intent of defining practical strategies for AD prevention.
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28
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Parathath SR, Parathath S, Tsirka SE. Nitric oxide mediates neurodegeneration and breakdown of the blood-brain barrier in tPA-dependent excitotoxic injury in mice. J Cell Sci 2006; 119:339-49. [PMID: 16410551 DOI: 10.1242/jcs.02734] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Stroke and many neurodegenerative diseases culminate in neuronal death through a mechanism known as excitotoxicity. Excitotoxicity proceeds through a complex signaling pathway that includes the participation of the serine protease tissue plasminogen activator (tPA). tPA mediates neurotoxic effects on resident central nervous system cells as well alters blood-brain barrier (BBB) permeability, which further promotes neurodegeneration. Another signaling molecule that promotes neurodegeneration and BBB dysfunction is nitric oxide (NO), although its precise role in pathological progression remains unclear. We examine here the potentially interrelated roles of tPA, NO and peroxynitrite (ONOO-), which is the toxic metabolite of NO, in BBB breakdown and neurodegeneration following intrahippocampal injection of the glutamate analog kainite (KA). We find that NO and ONOO- production are linked to tPA-mediated excitotoxic injury, and demonstrate that NO provision suffices to restore the toxic effects of KA in tPA-deficient mice that are normally resistant to excitotoxicity. NO also promotes BBB breakdown and excitotoxicity. Interestingly, BBB breakdown in itself does not suffice to elicit neurodegeneration; a subsequent ONOO(-)-mediated event is required. In conclusion, NO and ONOO- function as downstream effectors of tPA-mediated excitotoxicity.
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Affiliation(s)
- Susana R Parathath
- Program in Molecular and Cellular Biology, Department of Pharmacological Sciences, University Medical Center at Stony Brook, Stony Brook, NY 11794-8651, USA
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29
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Floden AM, Li S, Combs CK. Beta-amyloid-stimulated microglia induce neuron death via synergistic stimulation of tumor necrosis factor alpha and NMDA receptors. J Neurosci 2006; 25:2566-75. [PMID: 15758166 PMCID: PMC6725188 DOI: 10.1523/jneurosci.4998-04.2005] [Citation(s) in RCA: 183] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Although abundant reactive microglia are found associated with beta-amyloid (Abeta) plaques in Alzheimer's disease (AD) brains, their contribution to cell loss remains speculative. A variety of studies have documented the ability of Abeta fibrils to directly stimulate microglia in vitro to assume a neurotoxic phenotype characterized by secretion of a plethora of proinflammatory molecules. Collectively, these data suggest that activated microglia play a direct role in contributing to neuron death in AD rather than simply a role in clearance after plaque deposition. Although it is clear the Abeta-stimulated microglia acutely secrete toxic oxidizing species, the identity of longer-lived neurotoxic agents remains less defined. We used Abeta-stimulated conditioned media from primary mouse microglia to identify more stable neurotoxic secretions. The NMDA receptor antagonists memantine and 2-amino-5-phosphopetanoic acid as well as soluble tumor necrosis factor alpha (TNFalpha) receptor protect neurons from microglial-conditioned media-dependent death, implicating the excitatory neurotransmitter glutamate and the proinflammatory cytokine TNFalpha as effectors of microglial-stimulated death. Neuron death occurs in an oxidative damage-dependent manner, requiring activity of inducible nitric oxide synthase. Toxicity results from coincident stimulation of the TNFalpha and NMDA receptors, because stimulations of either alone are insufficient to initiate cell death. These findings suggest the hypothesis that AD brains provide the appropriate microglial-mediated inflammatory environment for TNFalpha and glutamate to synergistically stimulate toxic activation of their respective signaling pathways in neurons as a contributing mechanism of cell death.
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Affiliation(s)
- Angela M Floden
- Department of Pharmacology, Physiology, and Therapeutics, University of North Dakota, School of Medicine and Health Sciences, Grand Forks, North Dakota 58202, USA
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30
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Neumann J, Gunzer M, Gutzeit HO, Ullrich O, Reymann KG, Dinkel K. Microglia provide neuroprotection after ischemia. FASEB J 2006; 20:714-6. [PMID: 16473887 DOI: 10.1096/fj.05-4882fje] [Citation(s) in RCA: 211] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Many neurological insults are accompanied by a marked acute inflammatory reaction, involving the activation of microglia. Using a model of exogenous application of fluorescence-labeled BV2 microglia in pathophysiologically relevant concentrations onto organotypic hippocampal slice cultures, we investigated the specific effects of microglia on neuronal damage after ischemic injury. Neuronal cell death after oxygen-glucose deprivation (OGD) was determined by propidium iodide incorporation and Nissl staining. Migration and interaction with neurons were analyzed by time resolved 3-D two-photon microscopy. We show that microglia protect against OGD-induced neuronal damage and engage in close physical cell-cell contact with neurons in the damaged brain area. Neuroprotection and migration of microglia were not seen with integrin regulator CD11a-deficient microglia or HL-60 granulocytes. The induction of migration and neuron-microglia interaction deep inside the slice was markedly increased under OGD conditions. Lipopolysaccharide-prestimulated microglia failed to provide neuroprotection after OGD. Pharmacological interference with microglia function resulted in a reduced neuroprotection. Microglia proved to be neuroprotective even when applied up to 4 h after OGD, thus defining a "protective time window." In acute injury such as trauma or stroke, appropriately activated microglia may primarily have a neuroprotective role. Anti-inflammatory treatment within the protective time window of microglia would therefore be counterintuitive.
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Affiliation(s)
- Jens Neumann
- Leibniz Institute for Neurobiology, Project Group Neuropharmacology, Magdeburg, Germany
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31
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Lee JC, Cho GS, Kwon JH, Shin MH, Lim JH, Kim WK. Macrophageal/microglial cell activation and cerebral injury induced by excretory–secretory products secreted by Paragonimus westermani. Neurosci Res 2006; 54:133-9. [PMID: 16325294 DOI: 10.1016/j.neures.2005.11.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2005] [Revised: 10/11/2005] [Accepted: 11/02/2005] [Indexed: 11/22/2022]
Abstract
Cerebral paragonimiasis causes various neurological disorders including seizures, visual impairment and hemiplegia. The excretory-secretory product (ESP) released by Paragonimus westermani has a cysteine protease activity and plays important roles in its migration in the host tissue and modulation of host immune responses. To gain more insight into the pathogenesis of ESP in the brain, we investigated the inflammatory reaction and cerebral injury following microinjection of ESP into rat striatum. The size of injury was maximally observed 3 days after microinjection of ESP and then declined to control levels as astrocytes have repopulated the injury. ED1-positive monocytes and microglia were confluently found inside the injury. The mRNA expression of inducible nitric oxide synthase (iNOS) occurred as early as 9h after ESP injection and then declined to control levels within 1 day. The iNOS inhibitor aminoguanidine largely decreased the expression of iNOS but did not reduce the size of lesion caused by ESP. Interestingly, however, heat inactivation of ESP caused a decrease of injury formation with no altered expression of iNOS. The data indicate that ESP produces brain tissue injury by recruiting activated monocytes/microglia via heat-labile protease activity.
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Affiliation(s)
- Jae-Chul Lee
- Department of Pharmacology, College of Medicine, Ewha Women's Univeristy, Seoul, Republic of Korea
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32
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McCarty MF. Down-regulation of microglial activation may represent a practical strategy for combating neurodegenerative disorders. Med Hypotheses 2006; 67:251-69. [PMID: 16513287 DOI: 10.1016/j.mehy.2006.01.013] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Accepted: 01/02/2006] [Indexed: 01/03/2023]
Abstract
Chronic neurodegenerative disorders are characterized by activation of microglia in the affected neural pathways. Peroxynitrite, prostanoids, and cytokines generated by these microglia can potentiate the excitotoxicity that contributes to neuronal death and dysfunction in these disorders--both by direct effects on neurons, and by impairing the capacity of astrocytes to sequester and metabolize glutamate. This suggests a vicious cycle in which the death of neurons leads to microglial activation, which in turn potentiates neuronal damage. If this model is correct, measures which down-regulate microglial activation may have a favorable effect on the induction and progression of neurodegenerative disease, independent of the particular trigger or target involved in a given disorder. Consistent with this possibility, the antibiotic minocycline, which inhibits microglial activation, shows broad utility in rodent models of neurodegeneration. Other agents which may have potential in this regard include PPARgamma agonists, genistein, vitamin D, COX-2 inhibitors, statins (and possibly policosanol), caffeine, cannabinoids, and sesamin; some of these agents could also be expected to be directly protective to neurons threatened with excitotoxicity. To achieve optimal clinical outcomes, regimens which down-regulate microglial activation could be used in conjunction with complementary measures which address other aspects of excitotoxicity.
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Affiliation(s)
- Mark F McCarty
- Natural Alternatives International, 1185 Linda Vista Dr., San Marcos, CA 92078, USA.
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Lee JC, Cho GS, Choi BO, Kim HC, Kim YS, Kim WK. Intracerebral Hemorrhage-Induced Brain Injury Is Aggravated in Senescence-Accelerated Prone Mice. Stroke 2006; 37:216-22. [PMID: 16322488 DOI: 10.1161/01.str.0000195151.46926.7b] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background and Purpose—
In cerebral stroke, the overall mortality rate of older individuals is higher than that of younger individuals. We therefore investigated aging-related changes in brain tissue damage and immune response in response to intracerebral hemorrhage (ICH) in mice.
Methods—
ICH was induced by microinjecting autologous whole blood (5 μL) into the striatum of 4- or 14-month-old senescence-accelerated prone (SAMP8) mice or senescence-accelerated resistant (SAMR1) mice.
Results—
In all groups, neurological deficits occurred within 6 hours and gradually improved after the first day, but improvement was most delayed in 14-month-old SAMP8 mice. Isolectin B4-positive and amoeboid microglia/macrophages were abundantly distributed around and inside the hemorrhagic lesions in 14-month-old SAMP8 mice. In contrast, myeloperoxidase-immunoreactive neutrophils and reactive astrocytes with intensified glial fibrillary acidic protein–stained processes and swollen cytoplasm did not differ in number or distribution between SAMP8 and SAMR1 mice. Regardless of their age, the immunoreactivity of Mn-SOD, a major antioxidant enzyme in mitochondria, was much weaker in SAMP8 than in SAMR1 mice. The expression of inducible nitric oxide, however, was higher in old SAMP8 mice than in the other experimental groups.
Conclusions—
These results suggest that activated microglia/monocytes may aggravate intracerebral hemorrhagic damage in old SAMP8 mice. Further studies on the exact role of activated microglia/monocytes and the altered activities of antioxidant enzymes in old SAMP8 mice may provide useful information for ICH-induced brain injury in relation with aging.
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Affiliation(s)
- Jae-Chul Lee
- Division of Nano Sciences, Department of Pharmacology, College of Medicine, Ewha Women's University, Seoul, Republic of Korea
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Jin Y, Lee JC, Choi IY, Kim EA, Shin MH, Kim WK. Excretory-Secretory Products Produced by Paragonimus westermani Differentially Regulate the Nitric Oxide Production and Viability of Microglial Cells. Int Arch Allergy Immunol 2005; 139:16-24. [PMID: 16272822 DOI: 10.1159/000089518] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Accepted: 08/18/2005] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Tissue-invading helminth parasites secrete a large amount of cysteine proteases that may play critical roles in tissue invasion and immune modulation. However, roles of excretory-secretory products (ESP) secreted by Paragonimus westermani in the activation and death of microglial cells in brain are poorly understood. OBJECTIVES In the present study, we investigated whether ESP could regulate microglial nitric oxide (NO) production and viability. METHODS The NO production and cell viability were assessed by respectively measuring the formation of nitrite and the release of lactate dehyrogenase. RESULTS At a low (0.2 microg/ml) concentration, ESP significantly stimulated NO production with no apparent cell injury or death in cultured microglial cells. However, at high (> or =2 microg/ml) concentrations, ESP induced severe cell death. Inhibition of inducible NO synthase significantly reduced the NO productivity, but not cytotoxicity, of ESP. Similarly, inhibitors of the extracellular signal-regulated kinase, p38 and nuclear factor kappa B also blocked only the NO productivity of ESP. Interestingly, heat inactivation did not hamper the ability of ESP to stimulate microglial NO production. Similarly, pretreatment with thiol-crosslinking reagents dramatically reduced both proteolytic activity and cytotoxicity of ESP, but did not alter NO production in microglial cells. Interestingly, although cysteine protease competitive inhibitors and thiol-alkylating reagents markedly reduced the proteolytic activity of ESP, they did not influence the NO productivity and cytotoxicity of ESP. CONCLUSION The present results indicate that the NO production and cytotoxicity by ESP may be differentially regulated via unknown mechanisms, not related with cysteine protease activity.
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Affiliation(s)
- Youngnam Jin
- Department of Pharmacology, Ewha Medical School and Ewha Institute of Neuroscience, Ewha Woman's University, Seoul, South Korea
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Ellis RC, O'Steen WA, Hayes RL, Nick HS, Wang KKW, Anderson DK. Cellular localization and enzymatic activity of cathepsin B after spinal cord injury in the rat. Exp Neurol 2005; 193:19-28. [PMID: 15817261 DOI: 10.1016/j.expneurol.2004.11.034] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2004] [Revised: 11/19/2004] [Accepted: 11/30/2004] [Indexed: 11/24/2022]
Abstract
Mechanical spinal cord injury (SCI) initiates a cascade of pathochemical and pathophysiological events, collectively known as the secondary injury. There has been a long-standing interest in understanding the activation and involvement of proteases in this secondary injury process. Several proteases including the calpains, caspases and matrix metalloproteinases are activated by perturbations to the spinal cord and have been linked to cell death following SCI and in other models of CNS disease and insult. Cathepsin B (Cath B), a potent lysosomal protease, has also been implicated in the pathology of CNS diseases including brain tumors, Alzheimer's disease, amyotrophic lateral sclerosis and stroke. Previously, we reported significant increases in Cath B mRNA and protein expression following contusion-SCI. This characterization of Cath B continues with the experiments reported herein, which were designed to examine Cath B enzymatic activity and cellular localization following contusion-SCI in the rat. Cath B enzymatic activity was significantly increased in the injury epicenter at 5 and 7 days post-injury and was highly correlated with increases in the active forms of the Cath B protein reported earlier. Furthermore, the immunohistochemical analyses revealed that the post-injury increases in expression and enzymatic activity at the injury epicenter were due to the presence of a large and diverse population of inflammatory cells. However, in areas adjacent to the injury epicenter, it appears that parenchymal neurons may also contribute to these increases. Our findings coupled with the documented role of Cath B in other CNS pathologies make this potent protease an attractive candidate for involvement in the tissue destruction associated with the secondary injury cascade following SCI.
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Affiliation(s)
- Rebecca C Ellis
- Department of Neuroscience, University of Florida, PO Box 100244, Gainesville, FL 32610, USA
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Hailer NP, Vogt C, Korf HW, Dehghani F. Interleukin-1β exacerbates and interleukin-1 receptor antagonist attenuates neuronal injury and microglial activation after excitotoxic damage in organotypic hippocampal slice cultures. Eur J Neurosci 2005; 21:2347-60. [PMID: 15932594 DOI: 10.1111/j.1460-9568.2005.04067.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The effects of interleukin (IL)-1beta and IL-1 receptor antagonist (IL-1ra) on neurons and microglial cells were investigated in organotypic hippocampal slice cultures (OHSCs). OHSCs obtained from rats were excitotoxically lesioned after 6 days in vitro by application of N-methyl-D-aspartate (NMDA) and treated with IL-1beta (6 ng/mL) or IL-1ra (40, 100 or 500 ng/mL) for up to 10 days. OHSCs were then analysed by bright field microscopy after hematoxylin staining and confocal laser scanning microscopy after labeling of damaged neurons with propidium iodide (PI) and fluorescent staining of microglial cells. The specificity of PI labeling of damaged neurons was validated by triple staining with neuronal and glial markers and it was observed that PI accumulated in damaged neurons only but not in microglial cells or astrocytes. Treatment of unlesioned OHSCs with IL-1beta did not induce neuronal damage but caused an increase in the number of microglial cells. NMDA lesioning alone resulted in a massive increase in the number of microglial cells and degenerating neurons. Treatment of NMDA-lesioned OHSCs with IL-1beta exacerbated neuronal cell death and further enhanced microglial cell numbers. Treatment of NMDA-lesioned cultures with IL-1ra significantly attenuated NMDA-induced neuronal damage and reduced the number of microglial cells, whereas application of IL-1ra in unlesioned OHSCs did not induce significant changes in either cell population. Our findings indicate that: (i) IL-1beta directly affects the central nervous system and acts independently of infiltrating hematogenous cells; (ii) IL-1beta induces microglial activation but is not neurotoxic per se; (iii) IL-1beta enhances excitotoxic neuronal damage and microglial activation and (iv) IL-1ra, even when applied for only 4 h, reduces neuronal cell death and the number of microglial cells after excitotoxic damage.
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Affiliation(s)
- Nils P Hailer
- Dr Senckenbergische Anatomie, Institute of Anatomy 2, Johann Wolfgang Goethe-University, D-60590 Frankfurt am Main, Federal Republic of Germany
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Mitrasinovic OM, Grattan A, Robinson CC, Lapustea NB, Poon C, Ryan H, Phong C, Murphy GM. Microglia overexpressing the macrophage colony-stimulating factor receptor are neuroprotective in a microglial-hippocampal organotypic coculture system. J Neurosci 2005; 25:4442-51. [PMID: 15858070 PMCID: PMC6725106 DOI: 10.1523/jneurosci.0514-05.2005] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2004] [Revised: 03/25/2005] [Accepted: 03/25/2005] [Indexed: 11/21/2022] Open
Abstract
Microglia with increased expression of the macrophage colony-stimulating factor receptor (M-CSFR; c-fms) are found surrounding plaques in Alzheimer's disease (AD) and in mouse models for AD and after ischemic or traumatic brain injury. Increased expression of M-CSFR causes microglia to adopt an activated state that results in proliferation, release of cytokines, and enhanced phagocytosis. To determine whether M-CSFR-induced microglial activation affects neuronal survival, we assembled a coculture system consisting of BV-2 microglia transfected to overexpress the M-CSFR and hippocampal organotypic slices treated with NMDA. Twenty-four hours after assembly of the coculture, microglia overexpressing M-CSFR proliferated at a higher rate than nontransfected control cells and exhibited enhanced migration toward NMDA-injured hippocampal cultures. Surprisingly, coculture with c-fms-transfected microglia resulted in a dramatic reduction in NMDA-induced neurotoxicity. Similar results were observed when cocultures were treated with the teratogen cyclophosphamide. Biolistic overexpression of M-CSFR on microglia endogenous to the organotypic culture also rescued neurons from excitotoxicity. Furthermore, c-fms-transfected microglia increased neuronal expression of macrophage colony-stimulating factor (M-CSF), the M-CSFR, and neurotrophin receptors in the NMDA-treated slices, as determined with laser capture microdissection. In the coculture system, direct contact between the exogenous microglia and the slice was necessary for neuroprotection. Finally, blocking expression of the M-CSF ligand by exogenous c-fms-transfected microglia with a hammerhead ribozyme compromised their neuroprotective properties. These results demonstrate a protective role for microglia overexpressing M-CSFR in our coculture system and suggest under certain circumstances, activated microglia can help rather than harm neurons subjected to excitotoxic and teratogen-induced injury.
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Affiliation(s)
- Olivera M Mitrasinovic
- Neuroscience Research Laboratories, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California 94305, USA
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Lee JC, Cho GS, Kim HJ, Lim JH, Oh YK, Nam W, Chung JH, Kim WK. Accelerated cerebral ischemic injury by activated macrophages/microglia after lipopolysaccharide microinjection into rat corpus callosum. Glia 2005; 50:168-81. [PMID: 15702482 DOI: 10.1002/glia.20164] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In cerebral ischemic insults, activated inflammatory cells such as microglia and macrophages may be implicated in the pattern and degree of ischemic injury by producing various bioactive mediators. In the present study, we provide the evidence that activated microglia/macrophages accelerate cerebral ischemic injury by overexpression of inducible nitric oxide synthase (iNOS). To activate microglia/macrophages, a potent inflammation inducer lipopolysaccharide (LPS, 5 microg/5 microl) was microinjected into rat corpus callosum. Isolectin B4-positive microglia/macrophages were abundantly observed in ipsilateral hemisphere at 1 day after LPS injection. RT-PCR showed that LPS injection induced iNOS mRNA expression mostly in microglia/macrophages, peaking in intensity at 15 h after LPS injection. While ischemic injury was little evoked in control rats by 2-h middle cerebral artery occlusion (MCAO) followed by 3-h reperfusion, it was markedly increased in rats pre-injected with LPS 1 day before MCAO. However, no significant difference between control and LPS-pretreated groups was observed after 24-h reperfusion. The increased ischemic injury in LPS-treated rats was well correlated with iNOS level expressed over 3 orders of magnitude than in LPS-untreated rats. Immunohistochemical studies showed that iNOS- and nitrotyrosine (a peroxynitrite marker)-positive cells were prominent throughout the infarct area. NOS inhibitors aminoguanidine or N(G)-nitro-L-arginine, simultaneously injected with LPS, reduced the iNOS immunoreactivity and infarct volume, especially in penumbra regions. Total glutathione levels in ischemic regions were decreased more in LPS pre-injected rats than in control ones. Further defining the role of NO in cerebral ischemic insults would provide the rationale for new therapeutic strategies based on modulation of microglial and macrophageal NO production in the brain.
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Affiliation(s)
- Jae-Chul Lee
- Department of Pharmacology, College of Medicine, Laboratory of Neurodegenerative Diseases, Ewha Institute of Neuroscience, Seoul, Republic of Korea
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Piao HZ, Jin SA, Chun HS, Lee JC, Kim WK. Neuroprotective effect of wogonin: Potential roles of inflammatory cytokines. Arch Pharm Res 2004; 27:930-6. [PMID: 15473663 DOI: 10.1007/bf02975846] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Wogonin (5,7-dihydroxy-8-methoxyflavone), an active component originated from the root of Scutellaria baicalensis Georgi, has been reported to possess antioxidant and anti-inflammatory properties. In this study, we investigated the neuroprotective effect of wogonin in a focal cerebral ischemia rat model. Wogonin markedly reduced the infarct volume after 2 h middle cerebral artery occlusion followed by 22 h reperfusion. Wogonin decreased the production of nitric oxide and inflammatory cytokines such as TNF-alpha and IL-6 in lipopolisaccharide-stimulated microglial cells. While wogonin reduced the activity of NF-kappaB, it did not change the activity of mitogen-activated protein kinases family members, p38, ERK and JNK. The lipopolisaccharide-stimulated production of NO and cytokines was significantly blocked by various kinds of NF-kappaB inhibitors such as N-acetyl cysteine, pyrrolidinedithiocarbamate and MG-132. The data may indicate that wogonin has neuroprotective effect by preventing the overactivation of microglial cells, possibly by inactivating NF-kappaB signaling pathway.
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Affiliation(s)
- Hua Zi Piao
- Department of Pharmacology, College of Medicine, Ewha Institute of Neuroscience, Ewha Womens University, Seoul, Korea
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Pérez-Capote K, Serratosa J, Solà C. Glial activation modulates glutamate neurotoxicity in cerebellar granule cell cultures. Glia 2003; 45:258-68. [PMID: 14730699 DOI: 10.1002/glia.10329] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We studied the influence of glial cells on the neuronal response to glutamate toxicity in cerebellar granule cell cultures. We compared the effect of glutamate on neuronal viability in neuronal vs. neuronal-glial cultures and determined this effect after pretreating the cultures with the lipopolysaccharide (LPS) of Escherichia coli, agent widely used to induce glial activation. Morphological changes in glial cells and nitric oxide (NO) production were evaluated as indicators of glial activation. We observed that glutamate neurotoxicity in neuronal-glial cultures was attenuated in a certain range of glutamate concentration when compared to neuronal cultures, but it was enhanced at higher glutamate concentrations. This enhanced neurotoxicity was associated with morphological changes in astrocytes and microglial cells in the absence of NO production. LPS treatment induced morphological changes in glial cells in neuronal-glial cultures as well as NO production. These effects occurred in the absence of significant neuronal death. However, when LPS-pretreated cultures were treated with glutamate, the sensitivity of neuronal-glial cultures to glutamate neurotoxicity was increased. This was accompanied by additional morphological changes in glial cells in the absence of a further increase in NO production. These results suggest that quiescent glial cells protect neuronal cells from glutamate neurotoxicity, but reactive glial cells increase glutamate neurotoxicity. Therefore, glial cells play a key role in the neuronal response to a negative stimulus, suggesting that this response can be modified through an action on glial cells.
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Affiliation(s)
- Kamil Pérez-Capote
- Department of Pharmacology and Toxicology, Institut d'Investigacions Biomèdiques de Barcelona-Consejo Superior de Investigaciones Cientificas (CSIC), Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
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Abstract
We investigated the role of matrix metalloproteinases (MMPs) in acute spinal cord injury (SCI). Transcripts encoding 22 of the 23 known mammalian MMPs were measured in the mouse spinal cord at various time points after injury. Although there were significant changes in the expression levels of multiple MMPs, MMP-12 was increased 189-fold over normal levels, the highest of all MMPs examined. To evaluate the role of MMP-12 in SCI, spinal cord compression was performed in wild-type (WT) and MMP-12 null mice. Behavioral analyses were conducted for 4 weeks using the Basso-Beattie-Bresnahan (BBB) locomotor rating scale as well as the inclined plane test. The results show that MMP-12 null mice exhibited significantly improved functional recovery compared with WT controls. Twenty-eight days after injury, the BBB score in the MMP-12 group was 7, representing extensive movement of all three hindlimb joints, compared with 4 in the WT group, representing only slight movement of these joints. Furthermore, MMP-12 null mice showed recovery of hindlimb strength more rapidly than control mice, with significantly higher inclined plane scores on days 14 and 21 after SCI. Mechanistically, there was decreased permeability of the blood-spinal barrier and reduced microglial and macrophage density in MMP-12 null mice compared with WT controls. This is the first study to profile the expression patterns of a majority of the known MMPs after spinal cord compression. The data indicate that MMP-12 expression after spinal cord trauma is deleterious and contributes to the development of secondary injury in SCI.
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Brown GC, Bal-Price A. Inflammatory neurodegeneration mediated by nitric oxide, glutamate, and mitochondria. Mol Neurobiol 2003; 27:325-55. [PMID: 12845153 DOI: 10.1385/mn:27:3:325] [Citation(s) in RCA: 334] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2002] [Accepted: 12/27/2002] [Indexed: 11/11/2022]
Abstract
In inflammatory, infectious, ischemic, and neurodegenerative pathologies of the central nervous system (CNS) glia become "activated" by inflammatory mediators, and express new proteins such as the inducible isoform of nitric oxide synthase (iNOS). Although these activated glia have benefi- cial roles, in vitro they potently kill cocultured neurons, and there is increasing evidence that they contribute to pathology in vivo. Nitric oxide (NO) from iNOS appears to be a key mediator of such glial-induced neuronal death. The high sensitivity of neurons to NO is partly due to NO causing inhibition of respiration, rapid glutamate release from both astrocytes and neurons, and subsequent excitotoxic death of the neurons. NO is a potent inhibitor of mitochondrial respiration, due to reversible binding of NO to cytochrome oxidase in competition with oxygen, resulting in inhibition of energy production and sensitization to hypoxia. Activated astrocytes or microglia cause a potent inhibition of respiration in cocultured neurons due to glial NO inhibiting cytochrome oxidase within the neurons, resulting in ATP depletion and glutamate release. In some conditions, glutamate- induced neuronal death can itself be mediated by N-methyl-D-aspartate (NMDA)-receptor activation of the neuronal isoform of NO synthase (nNOS) causing mitochondrial damage. In addition NO can be converted to a number of reactive derivatives such as peroxynitrite, NO2, N2O3, and S-nitrosothiols that can kill cells in part by inhibiting mitochondrial respiration or activation of mitochondrial permeability transition, triggering neuronal apoptosis or necrosis.
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Affiliation(s)
- Guy C Brown
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK.
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Kohl A, Dehghani F, Korf HW, Hailer NP. The bisphosphonate clodronate depletes microglial cells in excitotoxically injured organotypic hippocampal slice cultures. Exp Neurol 2003; 181:1-11. [PMID: 12710928 DOI: 10.1016/s0014-4886(02)00049-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The bisphosphonate clodronate, clinically used in the treatment of osteoporosis, is known to deplete cells of the monocytic lineage. Using an in vitro model of excitotoxic damage in organotypic hippocampal slice cultures (OHSC), we investigated whether clodronate can also prevent microglial activation that occurs in CNS pathologies. Lesioning of OHSC was performed by application of 50 microM N-methyl-D-aspartate (NMDA) for 4 h after 6 days in vitro (div). Treatment of lesioned OHSC with clodronate (1000, 100, or 10 microg/ml) resulted in an almost complete abrogation of the microglial reaction after 3 further div: Confocal laser scanning microscopy showed that the number of Griffonia simplicifolia isolectin B(4)-labeled (IB4+) microglial cells in the dentate gyrus (DG) was reduced to 4.25% compared with OHSC treated with NMDA alone. Continuous treatment with clodronate (100 or 10 microg/ml) of lesioned OHSC for 9 days resulted in a further reduction in the number of microglial cells (reduction to 2.72%). The number of degenerating, propidium iodide-labeled (PI(+)) neurons in lesioned OHSC that received clodronate treatment between 6 and 9 div was not significantly different from OHSC treated with NMDA alone. However, the number of PI(+) neurons in lesioned OHSC that received continuous clodronate treatment for 9 div was significantly higher when compared to NMDA-lesioned OHSC. In summary, clodronate is able to reduce microglial activation induced by excitotoxic neuronal injury. Our results demonstrate that clodronate is a useful tool in the investigation of neuron-glia interactions because it induces an efficient depletion of microglial cells that are activated after excitotoxic CNS injury.
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Affiliation(s)
- A Kohl
- University Hospital for Orthopaedic Surgery Friedrichsheim, Marienburgstrasse 2, D-60528 Frankfurt am Main, Federal Republic of Germany
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Eskes C, Juillerat-Jeanneret L, Leuba G, Honegger P, Monnet-Tschudi F. Involvement of microglia-neuron interactions in the tumor necrosis factor-alpha release, microglial activation, and neurodegeneration induced by trimethyltin. J Neurosci Res 2003; 71:583-90. [PMID: 12548715 DOI: 10.1002/jnr.10508] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Trimethyltin (TMT) is a neurotoxicant known to induce early microglial activation. The present study was undertaken to investigate the role played by these microglial cells in the TMT-induced neurotoxicity. The effects of TMT were investigated in monolayer cultures of isolated microglia or in neuron-enriched cultures and in neuron-microglia and astrocyte-microglia cocultures. The end points used were morphological criteria; evaluation of cell death and cell proliferation; and measurements of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and nitric oxide (NO) release in culture supernatant. The results showed that, in cultures of microglia, TMT (10(-6) M) caused, after a 5-day treatment, an increased release of TNF-alpha, without affecting microglial shape or cell viability. When microglia were cocultured with astrocytes, TNF-alpha release was decreased to undetectable levels. In contrast, in neuron-microglia cocultures, TNF-alpha levels were found to increase at lower concentrations of TMT (i.e., 10(-8) M). Moreover, at 10(-6) M of TMT, microglia displayed further morphological activation, as suggested by process retraction and by decrease in cell size. No morphological activation was observed in cultures of isolated microglial cells and in astrocyte-microglia cocultures. With regard to neurons, 10(-6) M of TMT induced about 30% of cell death, when applied to neuron-enriched cultures, whereas close to 100% of neuronal death was observed in neuron-microglia cocultures. In conclusion, whereas astrocytes may rather dampen the microglial activation by decreasing microglial TNF-alpha production, neuronal-microglial interactions lead to enhanced microglial activation. This microglial activation, in turn, exacerbates the neurotoxic effects of TMT. TNF-alpha may play a major role in such cell-cell communications.
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Affiliation(s)
- C Eskes
- Institute of Physiology, CHUV, Lausanne, Switzerland
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45
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Pocock JM, Liddle AC, Hooper C, Taylor DL, Davenport CM, Morgan SC. Activated microglia in Alzheimer's disease and stroke. ERNST SCHERING RESEARCH FOUNDATION WORKSHOP 2002:105-32. [PMID: 12066408 DOI: 10.1007/978-3-662-05073-6_7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- J M Pocock
- Cell Signalling Laboratory, Institute of Neurology, University College, 1 Wakefield Street, London WC1NPJ, UK.
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Morimoto K, Murasugi T, Oda T. Acute neuroinflammation exacerbates excitotoxicity in rat hippocampus in vivo. Exp Neurol 2002; 177:95-104. [PMID: 12429214 DOI: 10.1006/exnr.2002.7991] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Accumulating evidence suggests that inflammation may play an important part in neurodegenerative diseases such as Alzheimer's disease. Inflammation itself, however, is insufficient to produce acute neurodegeneration in vivo. In this report, we determined whether inflammation increases excitotoxicity in hippocampal neurons. A proinflammagen, bacterial endotoxin lipopolysaccharide, was coinjected with ibotenate, an N-methyl-D-aspartate receptor agonist, into rat hippocampus. One week after coinjection, significant neuronal degeneration and severe tissue collapse were observed in the hippocampus. Astroglial and microglial infiltration were also detected. The neurodegeneration was suppressed by dizocilpine maleate, an N-methyl-D-aspartate receptor antagonist. We then examined whether microglial activation takes part in synergistic neuronal loss. One day after the lipopolysaccharide injection into the rat hippocampus, substantial microglial activation and induction of inducible nitric oxide synthase were observed, while neither neuronal nor astrocytic changes were detected. On the other hand, ibotenate injection at the same place 1 day after lipopolysaccharide injection in the hippocampus produced significant neuronal degeneration and gross microglial activation. These results suggest that inflammation by lipopolysaccharide might play an important role in ibotenate/lipopolysaccharide neurotoxicity.
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Affiliation(s)
- Kiyoshi Morimoto
- Neuroscience and Immunology Research Laboratories, Sankyo Co., Ltd. 2-58, Hiromachi 1-chome, Shinagawa-ku, Tokyo, 140-8710, Japan.
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Contestabile A. Cerebellar granule cells as a model to study mechanisms of neuronal apoptosis or survival in vivo and in vitro. CEREBELLUM (LONDON, ENGLAND) 2002; 1:41-55. [PMID: 12879973 DOI: 10.1080/147342202753203087] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Granule cells of the cerebellum constitute the largest homogeneous neuronal population of mammalian brain. Due to their postnatal generation and the feasibility of well characterized primary in vitro cultures, cerebellar granule cells are a model of election for the study of cellular and molecular correlates of mechanisms of survival/apoptosis and neurodegeneration/neuroprotection. The present review mainly deals with recent data on mechanisms and factors promoting survival or apoptotic elimination of cerebellar granule neurons, with a particular focus on the molecular correlates at the level of gene expression and induction of cellular signal pathways. The in vivo development is first analysed with particular reference to the role played by several neurotrophic factors and by the NMDA subtype of glutamate receptor. Then, mechanisms of survival/apoptosis are examined in the model of primary in vitro cultures, where the role of neurotrophins acting on cerebellar granule cells is followed by the large deal of data coming from the paradigm of potassium/serum withdrawal. The role of some key genes of the Bcl family, of some kinase systems and of transcriptional factors is primarily highlighted. Furthermore, the involvement of mitochondria, free radicals and proteases of the caspase family is considered. Finally, the use of cerebellar granule neurons in primary culture to experimentally address the issue of neurodegeneration and pharmacological neuroprotection is considered, with some comments on models at the borderline between necrosis and apoptosis, such as the excitotoxic neuronal damage. The overlapping of cellular signal pathways activated in granule neurons by apparently unrelated stimuli, such as neurotrophins and neurotransmitters/neuromodulators is stressed to put into light the special 'trophic' role played by activity in neurons. Finally, the advantage of designing and performing conceptually equivalent experiments on cerebellar granule neurons during development in vivo and in vitro, is stressed. On the basis of the reviewed material, it is concluded that cerebellar granule neurons have acquired a special position in modern neuroscience as one of the most reliable models for the study of neural development, function and pathology.
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Hailer NP, Wirjatijasa F, Roser N, Hischebeth GT, Korf HW, Dehghani F. Astrocytic factors protect neuronal integrity and reduce microglial activation in an in vitro model of N-methyl-D-aspartate-induced excitotoxic injury in organotypic hippocampal slice cultures. Eur J Neurosci 2001; 14:315-26. [PMID: 11553282 DOI: 10.1046/j.0953-816x.2001.01649.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Acute CNS lesions lead to neuronal injury and a parallel glial activation that is accompanied by the release of neurotoxic substances. The extent of the original neuronal damage can therefore be potentiated in a process called secondary damage. As astrocytes are known to secrete immunomodulatory and neuroprotective substances, we investigated whether astrocytic factors can attenuate the amount of neuronal injury as well as the degree of microglial activation in a model of excitotoxic neurodegeneration. Treatment of organotypic hippocampal slice cultures with N-methyl-D-aspartate (NMDA) resulted in a reproducible loss of viable granule cells, partial destruction of the regular hippocampal cytoarchitecture and a concomitant accumulation of amoeboid microglial cells at sites of neuronal damage. Astrocyte-conditioned media reduced the amount of NMDA-induced neuronal injury by 45.3%, diminished the degree of microglial activation and resulted in an improved preservation of the hippocampal cytoarchitecture. Transforming growth factor (TGF)-beta failed to act as a neuroprotectant and even enhanced the amount of neuronal injury by 52.5%. Direct effects of astrocytic factors on isolated microglial cells consisted of increased microglial ramification and down-regulated expression of intercellular adhesion molecule-1, whereas incubation with TGF-beta had no such effects. In summary, our findings show that hitherto unidentified astrocyte-derived factors that are probably not identical with TGF-beta can substantially enhance neuronal survival, either by eliciting direct neuroprotective effects or by modulating the microglial response to neuronal injury.
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Affiliation(s)
- N P Hailer
- University Hospital for Orthopaedic Surgery, Friedrichsheim, Marienburgstr. 2, D-60528 Frankfurt am Main, Germany.
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Tikka TM, Koistinaho JE. Minocycline provides neuroprotection against N-methyl-D-aspartate neurotoxicity by inhibiting microglia. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 166:7527-33. [PMID: 11390507 DOI: 10.4049/jimmunol.166.12.7527] [Citation(s) in RCA: 427] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Glutamate excitotoxicity to a large extent is mediated through activation of the N-methyl-D-aspartate (NMDA)-gated ion channels in several neurodegenerative diseases and ischemic stroke. Minocycline, a tetracycline derivative with antiinflammatory effects, inhibits IL-1beta-converting enzyme and inducible nitric oxide synthase up-regulation in animal models of ischemic stroke and Huntington's disease and is therapeutic in these disease animal models. Here we report that nanomolar concentrations of minocycline protect neurons in mixed spinal cord cultures against NMDA excitotoxicity. NMDA treatment alone induced microglial proliferation, which preceded neuronal death, and administration of extra microglial cells on top of these cultures enhanced the NMDA neurotoxicity. Minocycline inhibited all these responses to NMDA. Minocycline also prevented the NMDA-induced proliferation of microglial cells and the increased release of IL-1beta and nitric oxide in pure microglia cultures. Finally, minocycline inhibited the NMDA-induced activation of p38 mitogen-activated protein kinase (MAPK) in microglial cells, and a specific p38 MAPK inhibitor, but not a p44/42 MAPK inhibitor, reduced the NMDA toxicity. Together, these results suggest that microglial activation contributes to NMDA excitotoxicity and that minocycline, a tetracycline derivative, represents a potential therapeutic agent for brain diseases.
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Affiliation(s)
- T M Tikka
- A. I. Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland
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Minocycline, a tetracycline derivative, is neuroprotective against excitotoxicity by inhibiting activation and proliferation of microglia. J Neurosci 2001. [PMID: 11306611 DOI: 10.1523/jneurosci.21-08-02580.2001] [Citation(s) in RCA: 694] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Minocycline, a semisynthetic tetracycline derivative, protects brain against global and focal ischemia in rodents. We examined whether minocycline reduces excitotoxicity in primary neuronal cultures. Minocycline (0.02 microm) significantly increased neuronal survival in mixed spinal cord (SC) cultures treated with 500 microm glutamate or 100 microm kainate for 24 hr. Treatment with these excitotoxins induced a dose-dependent proliferation of microglia that was associated with increased release of interleukin-1beta (IL-1beta) and was followed by increased lactate dehydrogenase (LDH) release. The excitotoxicity was enhanced when microglial cells were cultured on top of SC cultures. Minocycline prevented excitotoxin-induced microglial proliferation and the increased release of nitric oxide (NO) metabolites and IL-1beta. Excitotoxins induced microglial proliferation and increased the release of NO metabolites and IL-1beta also in pure microglia cultures, and these responses were inhibited by minocycline. In both SC and pure microglia cultures, excitotoxins activated p38 mitogen-activated protein kinase (p38 MAPK) exclusively in microglia. Minocycline inhibited p38 MAPK activation in SC cultures, and treatment with SB203580, a p38 MAPK inhibitor, but not with PD98059, a p44/42 MAPK inhibitor, increased neuronal survival. In pure microglia cultures, glutamate induced transient activation of p38 MAPK, and this was inhibited by minocycline. These findings indicate that the proliferation and activation of microglia contributes to excitotoxicity, which is inhibited by minocycline, an antibiotic used in severe human infections.
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