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Pharmacological blockade of IL-1β/IL-1 receptor type 1 axis during epileptogenesis provides neuroprotection in two rat models of temporal lobe epilepsy. Neurobiol Dis 2013; 59:183-93. [PMID: 23938763 DOI: 10.1016/j.nbd.2013.07.015] [Citation(s) in RCA: 142] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 07/29/2013] [Indexed: 02/06/2023] Open
Abstract
We studied whether pharmacological blockade of the IL-1β-mediated signaling, rapidly activated in forebrain by epileptogenic injuries, affords neuroprotection in two different rat models of status epilepticus (SE). As secondary outcome, we measured treatment's effect on SE-induced epileptogenesis. IL-1β signaling was blocked by systemic administration of two antiinflammatory drugs, namely human recombinant IL-1 receptor antagonist (anakinra), the naturally occurring and clinically used competitive IL-1 receptor type 1 antagonist, and VX-765 a specific non-peptide inhibitor of IL-1β cleavage and release. Antiinflammatory drugs were given 60min after antiepileptic (AED) drug-controlled SE induced by pilocarpine, or 180min after unrestrained electrical SE, for 7days using a protocol yielding therapeutic drug levels in brain. This drug combination significantly decreased both IL-1β expression in astrocytes and cell loss in rat forebrain. Neuroprotection and the antiinflammatory effect were more pronounced in the electrical SE model. Onset of epilepsy, and frequency and duration of seizures 3months after electrical SE were not significantly modified. Transcriptomic analysis in the hippocampus showed that the combined treatment did not affect the broad inflammatory response induced by SE during epileptogenesis. In particular, the treatment did not prevent the induction of the complement system and Toll-like receptors, both contributing to cell loss and seizure generation. We conclude that the IL-1β signaling represents an important target for reducing cell loss after SE. The data highlight a new class of clinically tested agents affording neuroprotection after a delayed post-injury intervention. Earlier blockade of this rapid onset inflammatory pathway during SE, or concomitant treatment with antiinflammatory drugs targeting additional components of the broad inflammatory response to SE, or co-treatment with AEDs, is likely to be required for optimizing beneficial outcomes.
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252
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Vezzani A. Fetal brain inflammation may prime hyperexcitability and behavioral dysfunction later in life. Ann Neurol 2013; 74:1-3. [PMID: 23686675 DOI: 10.1002/ana.23930] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 04/30/2013] [Accepted: 05/08/2013] [Indexed: 12/25/2022]
Affiliation(s)
- Annamaria Vezzani
- Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", Milan, Italy
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253
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Carney PR. Special issue on epilepsy. Exp Neurol 2013; 244:1-3. [PMID: 23651566 DOI: 10.1016/j.expneurol.2013.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Paul R Carney
- Department of Pediatrics, University of Florida, Gainesville, FL 32610, USA
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254
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Abstract
Inflammation is one of the most important endogenous defence mechanisms in an organism. It has been suggested that inflammation plays an important role in the pathophysiology of a number of human epilepsies and convulsive disorders, and there is clinical and experimental evidence to suggest that inflammatory processes within the CNS may either contribute to or be a consequence of epileptogenesis. This review discusses evidence from human studies on the role of inflammation in epilepsy and highlights potential new targets in the inflammatory cascade for antiepileptic drugs. A number of mechanisms have been shown to be involved in CNS inflammatory reactions. These include an inflammatory response at the level of the blood-brain barrier (BBB), immune-mediated damage to the CNS, stress-induced release of inflammatory mediators and direct neuronal dysfunction or damage as a result of inflammatory reactions. Mediators of inflammation in the CNS include interleukin (IL)-1β, tumour necrosis factor-α, nuclear factor-κB and toll-like receptor-4 (TLR4). IL-1β, BBB and high-mobility group box-1-TLR4 signalling appear to be the most promising targets for anticonvulsant agents directed at inflammation. Such agents may provide effective therapy for drug-resistant epilepsies in the future.
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255
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Boison D, Sandau US, Ruskin DN, Kawamura M, Masino SA. Homeostatic control of brain function - new approaches to understand epileptogenesis. Front Cell Neurosci 2013; 7:109. [PMID: 23882181 PMCID: PMC3712329 DOI: 10.3389/fncel.2013.00109] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 06/22/2013] [Indexed: 12/31/2022] Open
Abstract
Neuronal excitability of the brain and ongoing homeostasis depend not only on intrinsic neuronal properties, but also on external environmental factors; together these determine the functionality of neuronal networks. Homeostatic factors become critically important during epileptogenesis, a process that involves complex disruption of self-regulatory mechanisms. Here we focus on the bioenergetic homeostatic network regulator adenosine, a purine nucleoside whose availability is largely regulated by astrocytes. Endogenous adenosine modulates complex network function through multiple mechanisms including adenosine receptor-mediated pathways, mitochondrial bioenergetics, and adenosine receptor-independent changes to the epigenome. Accumulating evidence from our laboratories shows that disruption of adenosine homeostasis plays a major role in epileptogenesis. Conversely, we have found that reconstruction of adenosine's homeostatic functions provides new hope for the prevention of epileptogenesis. We will discuss how adenosine-based therapeutic approaches may interfere with epileptogenesis on an epigenetic level, and how dietary interventions can be used to restore network homeostasis in the brain. We conclude that reconstruction of homeostatic functions in the brain offers a new conceptual advance for the treatment of neurological conditions which goes far beyond current target-centric treatment approaches.
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Affiliation(s)
- Detlev Boison
- Robert Stone Dow Neurobiology Laboratories, Legacy Research Institute Portland, OR, USA
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256
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Yu N, Liu H, Di Q. Modulation of Immunity and the Inflammatory Response: A New Target for Treating Drug-resistant Epilepsy. Curr Neuropharmacol 2013; 11:114-27. [PMID: 23814544 PMCID: PMC3580785 DOI: 10.2174/157015913804999540] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 07/16/2012] [Accepted: 11/17/2012] [Indexed: 12/11/2022] Open
Abstract
Until recently, epilepsy medical therapy is usually limited to anti-epileptic drugs (AEDs). However, approximately 1/3 of epilepsy patients, described as drug-resistant epilepsy (DRE) patients, still suffer from continuous frequent seizures despite receiving adequate AEDs treatment of sufficient duration. More recently, with the remarkable progress of immunology, immunity and inflammation are considered to be key elements of the pathobiology of epilepsy. Activation of inflammatory processes in brain tissue has been observed in both experimental seizure animal models and epilepsy patients. Anti-inflammatory and immunotherapies also showed significant anticonvulsant properties both in clinical and in experimental settings. The above emerging evidence indicates that modulation of immunity and inflammatory processes could serve as novel specific targets to achieve potential anticonvulsant effects for the patients with epilepsy, especially DRE. Herein we review the recent evidence supporting the role of inflammation in the development and perpetuation of seizures, and also discuss the recent achievements in modulation of inflammation and immunotherapy applied to the treatment of epilepsy. Apart from medical therapy, we also discuss the influences of surgery, ketogenic diet, and electroconvulsive therapy on immunity and inflammation in DRE patients. Taken together, a promising perspective is suggested for future immunomodulatory therapies in the treatment of patients with DRE.
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Affiliation(s)
- Nian Yu
- Department of Neurology, Nanjing Brain Hospital affiliated to Nanjing Medical University, Nanjing, Jiangsu, China
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257
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Costello DA, Lynch MA. Toll-like receptor 3 activation modulates hippocampal network excitability, via glial production of interferon-β. Hippocampus 2013; 23:696-707. [PMID: 23554175 DOI: 10.1002/hipo.22129] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/29/2013] [Indexed: 12/26/2022]
Abstract
The family of toll-like receptors (TLR) plays a major role in innate immunity due to their pathogen-recognition abilities. TLR3 is a sensor for double-stranded RNA, and regulates host-defense responses to several viruses, via the production of type I interferons. Interferon-β (IFNβ) is a primary product of TLR3 activation, and its transcription is elevated in the CNS response to the synthetic TLR3 ligand, polyinosinic-polycytidylic acid (poly(I:C)). Peripheral infections, along with TLR-induced inflammatory mediators, are known to have detrimental effects on brain function, exerting a negative impact on cognition and enhancing seizure susceptibility. In this study, we assessed hippocampal function in vitro, in response to systemic delivery of a TLR3 agonist. Unlike agonists of other TLRs, intraperitoneal injection of poly(I:C) did not adversely affect evoked short- and long-term synaptic plasticity in mouse hippocampal slices. However, sustained and interictal-like spontaneous activity was observed in CA1 pyramidal cells in response to poly(I:C) and this was associated with alterations in the expression of phosphorylated NR2B subunit-containing NMDA receptors and an astrocyte-specific glutamate/aspartate transporter (GLAST) which impact on extracellular glutamate concentration and contribute to the genesis of epileptiform activity. We provide evidence for the production of IFNβ from microglia and astrocytes, and using mice deficient in the type I IFN receptor α 1 (IFNAR1), demonstrate that its subsequent activation is likely to underlie the TLR3-mediated modulation of hippocampal excitability.
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Affiliation(s)
- Derek A Costello
- Department of Physiology, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland.
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258
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Vezzani A, Friedman A, Dingledine RJ. The role of inflammation in epileptogenesis. Neuropharmacology 2013; 69:16-24. [PMID: 22521336 PMCID: PMC3447120 DOI: 10.1016/j.neuropharm.2012.04.004] [Citation(s) in RCA: 353] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 03/19/2012] [Accepted: 04/02/2012] [Indexed: 12/20/2022]
Abstract
One compelling challenge in the therapy of epilepsy is to develop anti-epileptogenic drugs with an impact on the disease progression. The search for novel targets has focused recently on brain inflammation since this phenomenon appears to be an integral part of the diseased hyperexcitable brain tissue from which spontaneous and recurrent seizures originate. Although the contribution of specific proinflammatory pathways to the mechanism of ictogenesis in epileptic tissue has been demonstrated in experimental models, the role of these pathways in epileptogenesis is still under evaluation. We review the evidence conceptually supporting the involvement of brain inflammation and the associated blood-brain barrier damage in epileptogenesis, and describe the available pharmacological evidence where post-injury intervention with anti-inflammatory drugs has been attempted. Our review will focus on three main inflammatory pathways, namely the IL-1 receptor/Toll-like receptor signaling, COX-2 and the TGF-β signaling. The mechanisms underlying neuronal-glia network dysfunctions induced by brain inflammation are also discussed, highlighting novel neuromodulatory effects of classical inflammatory mediators such as cytokines and prostaglandins. The increase in knowledge about a role of inflammation in disease progression, may prompt the use of specific anti-inflammatory drugs for developing disease-modifying treatments. This article is part of the Special Issue entitled 'New Targets and Approaches to the Treatment of Epilepsy'.
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Affiliation(s)
- Annamaria Vezzani
- Laboratory Experimental Neurology, Department of Neuroscience, Mario Negri Institute for Pharmacological Research, Via G. La Masa 19, 20156 Milano, Italy.
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259
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Downer EJ, Jones RS, McDonald CL, Greco E, Brennan S, Connor TJ, Robertson IH, Lynch MA. Identifying early inflammatory changes in monocyte-derived macrophages from a population with IQ-discrepant episodic memory. PLoS One 2013; 8:e63194. [PMID: 23671673 PMCID: PMC3646027 DOI: 10.1371/journal.pone.0063194] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 04/02/2013] [Indexed: 12/24/2022] Open
Abstract
Background Cells of the innate immune system including monocytes and macrophages are the first line of defence against infections and are critical regulators of the inflammatory response. These cells express toll-like receptors (TLRs), innate immune receptors which govern tailored inflammatory gene expression patterns. Monocytes, which produce pro-inflammatory mediators, are readily recruited to the central nervous system (CNS) in neurodegenerative diseases. Methods This study explored the expression of receptors (CD11b, TLR2 and TLR4) on circulating monocyte-derived macrophages (MDMs) and peripheral blood mononuclear cells (PBMCs) isolated from healthy elderly adults who we classified as either IQ memory-consistent (high-performing, HP) or IQ memory-discrepant (low-performing, LP). Results The expression of CD11b, TLR4 and TLR2 was increased in MDMs from the LP group when compared to HP cohort. MDMs from both groups responded robustly to treatment with the TLR4 activator, lipopolysaccharide (LPS), in terms of cytokine production. Significantly, MDMs from the LP group displayed hypersensitivity to LPS exposure. Interpretation Overall these findings define differential receptor expression and cytokine profiles that occur in MDMs derived from a cohort of IQ memory-discrepant individuals. These changes are indicative of inflammation and may be involved in the prodromal processes leading to the development of neurodegenerative disease.
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Affiliation(s)
- Eric J Downer
- Trinity College Institute of Neuroscience and Physiology Department, Trinity College, Dublin, Ireland.
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260
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Asavarut P, Zhao H, Gu J, Ma D. The role of HMGB1 in inflammation-mediated organ injury. ACTA ACUST UNITED AC 2013; 51:28-33. [PMID: 23711603 DOI: 10.1016/j.aat.2013.03.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 10/29/2012] [Accepted: 11/01/2012] [Indexed: 02/09/2023]
Abstract
HMGB1 is a chromosome-binding protein that also acts as a damage-associated molecular pattern molecule. It has potent proinflammatory effects and is one of key mediators of organ injury. Evidence from research has revealed its involvement in the signaling mechanisms of Toll-like receptors and the receptor for advanced glycation end-products in organ injury. HMGB1-mediated organ injuries are acute damage including ischemic, mechanical, allograft rejection and toxicity, and chronic diseases of the heart, kidneys, lungs, and brain. Strategies against HMGB1 and its associated cellular signal pathways need to be developed and may have preventive and therapeutic potentials in organ injury.
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Affiliation(s)
- Paladd Asavarut
- Section of Anaesthetics, Pain Medicine & Intensive Care, Department of Surgery and Cancer, Imperial College London, Chelsea and Westminster Hospital, London, UK
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261
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Crews FT, Qin L, Sheedy D, Vetreno RP, Zou J. High mobility group box 1/Toll-like receptor danger signaling increases brain neuroimmune activation in alcohol dependence. Biol Psychiatry 2013; 73:602-12. [PMID: 23206318 PMCID: PMC3602398 DOI: 10.1016/j.biopsych.2012.09.030] [Citation(s) in RCA: 209] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 08/30/2012] [Accepted: 09/19/2012] [Indexed: 12/30/2022]
Abstract
BACKGROUND Innate immune gene expression is regulated in part through high mobility group box 1 (HMGB1), an endogenous proinflammatory cytokine, that activates multiple members of the interleukin-1/Toll-like receptor (TLR) family associated with danger signaling. We investigated expression of HMGB1, TLR2, TLR3, and TLR4 in chronic ethanol-treated mouse brain, postmortem human alcoholic brain, and rat brain slice culture to test the hypothesis that neuroimmune activation in alcoholic brain involves ethanol activation of HMGB1/TLR danger signaling. METHODS Protein levels were assessed using Western blot, enzyme-linked immunosorbent assay, and immunohistochemical immunoreactivity (+IR), and messenger RNA (mRNA) levels were measured by real time polymerase chain reaction in ethanol-treated mice (5 g/kg/day, intragastric, 10 days + 24 hours), rat brain slice culture, and postmortem human alcoholic brain. RESULTS Ethanol treatment of mice increased brain mRNA and +IR protein expression of HMGB1, TLR2, TLR3, and TLR4. Postmortem human alcoholic brain also showed increased HMGB1, TLR2, TLR3, and TLR4 +IR cells that correlated with lifetime alcohol consumption, as well as each other. Ethanol treatment of brain slice culture released HMGB1 into the media and induced the proinflammatory cytokine, interleukin-1 beta (IL-1β). Neutralizing antibodies to HMGB1 and small inhibitory mRNA to HMGB1 or TLR4 blunted ethanol induction of IL-1β. CONCLUSIONS Ethanol-induced HMGB1/TLR signaling contributes to induction of the proinflammatory cytokine, IL-1β. Increased expression of HMGB1, TLR2, TLR3, and TLR4 in alcoholic brain and in mice treated with ethanol suggests that chronic alcohol-induced brain neuroimmune activation occurs through HMGB1/TLR signaling.
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Affiliation(s)
- Fulton T Crews
- Bowles Center for Alcohol Studies, Department of Pharmacology and Psychiatry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7178, USA.
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262
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Kharatishvili I, Shan ZY, She DT, Foong S, Kurniawan ND, Reutens DC. MRI changes and complement activation correlate with epileptogenicity in a mouse model of temporal lobe epilepsy. Brain Struct Funct 2013; 219:683-706. [PMID: 23474541 DOI: 10.1007/s00429-013-0528-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Accepted: 02/14/2013] [Indexed: 12/27/2022]
Abstract
The complex pathogenesis of temporal lobe epilepsy includes neuronal and glial pathology, synaptic reorganization, and an immune response. However, the spatio-temporal pattern of structural changes in the brain that provide a substrate for seizure generation and modulate the seizure phenotype is yet to be completely elucidated. We used quantitative magnetic resonance imaging (MRI) to study structural changes triggered by status epilepticus (SE) and their association with epileptogenesis and with activation of complement component 3 (C3). SE was induced by injection of pilocarpine in CD1 mice. Quantitative diffusion-weighted imaging and T2 relaxometry was performed using a 16.4-Tesla MRI scanner at 3 h and 1, 2, 7, 14, 28, 35, and 49 days post-SE. Following longitudinal MRI examinations, spontaneous recurrent seizures and interictal spikes were quantified using continuous video-EEG monitoring. Immunohistochemical analysis of C3 expression was performed at 48 h, 7 days, and 4 months post-SE. MRI changes were dynamic, reflecting different outcomes in relation to the development of epilepsy. Apparent diffusion coefficient changes in the hippocampus at 7 days post-SE correlated with the severity of the evolving epilepsy. C3 activation was found in all stages of epileptogenesis within the areas with significant MRI changes and correlated with the severity of epileptic condition.
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Affiliation(s)
- Irina Kharatishvili
- Centre for Advanced Imaging, The University of Queensland, St Lucia, QLD, 4072, Australia,
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263
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Ramani V, Madhusoodhanan R, Kosanke S, Awasthi S. A TLR4-interacting SPA4 peptide inhibits LPS-induced lung inflammation. Innate Immun 2013; 19:596-610. [PMID: 23475791 DOI: 10.1177/1753425912474851] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The interaction between surfactant protein-A (SP-A) and TLR4 is important for host defense. We have recently identified an SPA4 peptide region from the interface of SP-A-TLR4 complex. Here, we studied the involvement of the SPA4 peptide region in SP-A-TLR4 interaction using a two-hybrid system, and biological effects of SPA4 peptide in cell systems and a mouse model. HEK293 cells were transfected with plasmid DNAs encoding SP-A or a SP-A-mutant lacking SPA4 peptide region and TLR4. Luciferase activity was measured as the end-point of SP-A-TLR4 interaction. NF-κB activity was also assessed simultaneously. Next, the dendritic cells or mice were challenged with Escherichia coli-derived LPS and treated with SPA4 peptide. Endotoxic shock-like symptoms and inflammatory parameters (TNF-α, NF-κB, leukocyte influx) were assessed. Our results reveal that the SPA4 peptide region contributes to the SP-A-TLR4 interaction and inhibits the LPS-induced NF-κB activity and TNF-α. We also observed that the SPA4 peptide inhibits LPS-induced expression of TNF-α, nuclear localization of NF-κB-p65 and cell influx, and alleviates the endotoxic shock-like symptoms in a mouse model. Our results suggest that the anti-inflammatory activity of the SPA4 peptide through its binding to TLR4 can be of therapeutic benefit.
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Affiliation(s)
- Vijay Ramani
- 1Department of Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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264
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Devinsky O, Vezzani A, Najjar S, De Lanerolle NC, Rogawski MA. Glia and epilepsy: excitability and inflammation. Trends Neurosci 2013; 36:174-84. [PMID: 23298414 DOI: 10.1016/j.tins.2012.11.008] [Citation(s) in RCA: 556] [Impact Index Per Article: 50.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2012] [Revised: 11/15/2012] [Accepted: 11/29/2012] [Indexed: 12/26/2022]
Abstract
Epilepsy is characterized by recurrent spontaneous seizures due to hyperexcitability and hypersynchrony of brain neurons. Current theories of pathophysiology stress neuronal dysfunction and damage, and aberrant connections as relevant factors. Most antiepileptic drugs target neuronal mechanisms. However, nearly one-third of patients have seizures that are refractory to available medications; a deeper understanding of mechanisms may be required to conceive more effective therapies. Recent studies point to a significant contribution by non-neuronal cells, the glia--especially astrocytes and microglia--in the pathophysiology of epilepsy. This review critically evaluates the role of glia-induced hyperexcitability and inflammation in epilepsy.
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Affiliation(s)
- Orrin Devinsky
- Epilepsy Center, Department of Neurology, NYU School of Medicine, New York, NY 10016, USA.
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265
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Abstract
Invasion of the central nervous system (CNS) is a most devastating complication of a parasitic infection. Several physical and immunological barriers provide obstacles to such an invasion. In this broad overview focus is given to the physical barriers to neuroinvasion of parasites provided at the portal of entry of the parasites, i.e., the skin and epithelial cells of the gastrointestinal tract, and between the blood and the brain parenchyma, i.e., the blood-brain barrier (BBB). A description is given on how human pathogenic parasites can reach the CNS via the bloodstream either as free-living or extracellular parasites, by embolization of eggs, or within red or white blood cells when adapted to intracellular life. Molecular mechanisms are discussed by which parasites can interact with or pass across the BBB. The possible targeting of the circumventricular organs by parasites, as well as the parasites' direct entry to the brain from the nasal cavity through the olfactory nerve pathway, is also highlighted. Finally, examples are given which illustrate different mechanisms by which parasites can cause dysfunction or damage in the CNS related to toxic effects of parasite-derived molecules or to immune responses to the infection.
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266
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Zurolo E, de Groot M, Iyer A, Anink J, van Vliet EA, Heimans JJ, Reijneveld JC, Gorter JA, Aronica E. Regulation of Kir4.1 expression in astrocytes and astrocytic tumors: a role for interleukin-1 β. J Neuroinflammation 2012; 9:280. [PMID: 23270518 PMCID: PMC3538650 DOI: 10.1186/1742-2094-9-280] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Accepted: 12/09/2012] [Indexed: 01/08/2023] Open
Abstract
OBJECTIVE Decreased expression of inwardly rectifying potassium (Kir) channels in astrocytes and glioma cells may contribute to impaired K⁺ buffering and increased propensity for seizures. Here, we evaluated the potential effect of inflammatory molecules, such as interleukin-1β (IL-1β) on Kir4.1 mRNA and protein expression. METHODS We investigated Kir4.1 (Kcnj10) and IL-1β mRNA expression in the temporal cortex in a rat model of temporal lobe epilepsy 24 h and 1 week after induction of status epilepticus (SE), using real-time PCR and western blot analysis. The U373 glioblastoma cell line and human fetal astrocytes were used to study the regulation of Kir4.1 expression in response to pro-inflammatory cytokines. Expression of Kir4.1 protein was also evaluated by means of immunohistochemistry in surgical specimens of patients with astrocytic tumors (n = 64), comparing the expression in tumor patients with (n = 38) and without epilepsy (n = 26). RESULTS Twenty-four hours after onset of SE, Kir4.1 mRNA and protein were significantly down-regulated in temporal cortex of epileptic rats. This decrease in expression was followed by a return to control level at 1 week after SE. The transient downregulation of Kir4.1 corresponded to the time of prominent upregulation of IL-1β mRNA. Expression of Kir4.1 mRNA and protein in glial cells in culture was downregulated after exposure to IL-1β. Evaluation of Kir4.1 in tumor specimens showed a significantly lower Kir4.1 expression in the specimens of patients with epilepsy compared to patients without epilepsy. This paralleled the increased presence of activated microglial cells, as well as the increased expression of IL-1β and the cytoplasmic translocation of high mobility group box 1 (HMGB1). CONCLUSIONS Taken together, these findings indicate that alterations in expression of Kir4.1 occurring in epilepsy-associated lesions are possibly influenced by the local inflammatory environment and in particular by the inflammatory cytokine IL-1β.
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Affiliation(s)
- Emanuele Zurolo
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, AZ 1105, The Netherlands
| | - Marjolein de Groot
- Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands
| | - Anand Iyer
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, AZ 1105, The Netherlands
| | - Jasper Anink
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, AZ 1105, The Netherlands
| | - Erwin A van Vliet
- Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, The Netherlands
| | - Jan J Heimans
- Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands
| | - Jaap C Reijneveld
- Department of Neurology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
- Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands
| | - Jan A Gorter
- Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, The Netherlands
- Epilepsy Institute in The Netherlands Foundation (Stichting Epilepsie Instellingen Nederland, SEIN), Heemstede, The Netherlands
| | - Eleonora Aronica
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, AZ 1105, The Netherlands
- Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, The Netherlands
- Epilepsy Institute in The Netherlands Foundation (Stichting Epilepsie Instellingen Nederland, SEIN), Heemstede, The Netherlands
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267
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Mills KHG, Dungan LS, Jones SA, Harris J. The role of inflammasome-derived IL-1 in driving IL-17 responses. J Leukoc Biol 2012; 93:489-97. [PMID: 23271701 DOI: 10.1189/jlb.1012543] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
NLRs are members of the PRR family that sense microbial pathogens and mediate host innate immune responses to infection. Certain NLRs can assemble into a multiprotein complex called the inflammasome, which activates casapse-1 required for the cleavage of immature forms of IL-1β and IL-18 into active, mature cytokines. The inflammasome is activated by conserved, exogenous molecules from microbes and nonmicrobial molecules, such as asbestos, alum, or silica, as well as by endogenous danger signals, such as ATP, amyloid-β, and sodium urate crystals. Activation of the inflammasome is a critical event triggering IL-1-driven inflammation and is central to the pathology of autoinflammatory diseases, such as gout and MWS. Recent studies have also shown IL-1 or IL-18, in synergy with IL-23, can promote IL-17-prduction from Th17 cells and γδ T cells, and this process can be regulated by autophagy. IL-1-driven IL-17 production plays a critical role in host protective immunity to infection with fungi, bacteria, and certain viruses. However, Th17 cells and IL-17-seceting γδ T cells, activated by inflammasome-derived IL-1 or IL-18, have major pathogenic roles in many autoimmune diseases. Consequently, inflammasomes are now major drug targets for many autoimmune and chronic inflammatory diseases, as well as autoinflammatory diseases.
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Affiliation(s)
- Kingston H G Mills
- Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
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Marsh ED. Fishing for the mechanisms causing febrile seizures: employing a novel model to uncover the physiological generators of seizures with fever. Exp Neurol 2012. [PMID: 23178581 DOI: 10.1016/j.expneurol.2012.11.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Eric D Marsh
- Division of Neurology, Children's Hospital of Philadelphia and Department of Neurology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
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269
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Kim SY, Buckwalter M, Soreq H, Vezzani A, Kaufer D. Blood-brain barrier dysfunction-induced inflammatory signaling in brain pathology and epileptogenesis. Epilepsia 2012; 53 Suppl 6:37-44. [PMID: 23134494 PMCID: PMC3703535 DOI: 10.1111/j.1528-1167.2012.03701.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The protection of the brain from blood-borne toxins, proteins, and cells is critical to the brain's normal function. Accordingly, a compromise in the blood-brain barrier (BBB) function accompanies many neurologic disorders, and is tightly associated with brain inflammatory processes initiated by both infiltrating leukocytes from the blood, and activation of glial cells. Those inflammatory processes contribute to determining the severity and prognosis of numerous neurologic disorders, and can both cause, and result from BBB dysfunction. In this review we examine the role of BBB and inflammatory responses, in particular activation of transforming grown factor β (TGFβ) signaling, in epilepsy, stroke, and Parkinson's disease.
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Affiliation(s)
- Soo Young Kim
- Department of Integrative Biology & Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, California, U.S.A
| | - Marion Buckwalter
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, U.S.A
| | - Hermona Soreq
- The Edmond and Lily Safra Center for Brain Sciences and the Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Annamaria Vezzani
- Department of Neuroscience, Mario Negri Institute for Pharmacological Research, Milan, Italy
| | - Daniela Kaufer
- Department of Integrative Biology & Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, California, U.S.A
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270
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Frigerio F, Frasca A, Weissberg I, Parrella S, Friedman A, Vezzani A, Noé FM. Long-lasting pro-ictogenic effects induced in vivo by rat brain exposure to serum albumin in the absence of concomitant pathology. Epilepsia 2012; 53:1887-97. [PMID: 22984896 PMCID: PMC3651831 DOI: 10.1111/j.1528-1167.2012.03666.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
PURPOSE Dysfunction of the blood-brain barrier (BBB) is a common finding during seizures or following epileptogenic brain injuries, and experimentally induced BBB opening promotes seizures both in naive and epileptic animals. Brain albumin extravasation was reported to promote hyperexcitability by inducing astrocytes dysfunction. To provide in vivo evidence for a direct role of extravasated serum albumin in seizures independently on the pathologic context, we did the following: (1) quantified the amount of serum albumin extravasated in the rat brain parenchyma during status epilepticus (SE); (2) reproduced a similar concentration in the hippocampus by intracerebroventricular (i.c.v.) albumin injection in naive rats; (3) measured electroencephalography (EEG) activity in these rats, their susceptibility to kainic acid (KA)-induced seizures, and their hippocampal afterdischarge threshold (ADT). METHODS Brain albumin concentration was measured in the rat hippocampus and other forebrain regions 2 and 24 h after SE by western blot analysis. Brain distribution of serum albumin or fluorescein isothiocyanate (FITC)-albumin was studied by immunohistochemistry and immunofluorescence, respectively. Naive rats were injected with rat albumin or FITC-albumin, i.c.v., to mimic the brain concentration attained after SE, or with dextran used as control. Inflammation was evaluated by immunohistochemistry by measuring glial induction of interleukin (IL)-1β. Western blot analysis was used to measure inward rectifying potassium channel subunit Kir4.1 protein levels in the hippocampus. Seizures were induced in rats by intrahippocampal injection of 80 ng KA and quantified by EEG analysis, 2 or 24 h after rat albumin or dextran administration. ADT was measured by electrical stimulation of the hippocampus 3 months after albumin injection. In these rats, EEG was continuously monitored for 2 weeks to search for spontaneous seizures. KEY FINDINGS The hippocampal serum albumin concentration 24 h post-SE was 0.76 ± 0.21 μm. Similar concentrations were measured in other forebrain regions, whereas no changes were found in cerebellum. The hippocampal albumin concentration was similarly reproduced in naive rats by i.c.v. administration of 500 μg/4 μl rat albumin: albumin was predominantly detected extracellularly 2 h after injection, whereas at 24 h it was visible inside pyramidal neurons and in only a few scattered chondroitin sulphate proteoglycan (NG2)-positive cells, but not in glial fibrillary acidic protein (GFAP)-positive astrocytes or CR-3 complement receptor (OX-42)-positive microglia. The presence of albumin in naive rat hippocampus was associated with induced IL-1β in GFAP-positive astrocytes and a concomitant tissue down-regulation of Kir4.1. Spiking activity was evoked by albumin in the hippocampus lasting for 2 h. When KA was intrahippocampally applied either 2 or 24 h after albumin injection, the number of total interictal spikes in 3 h EEG recording was significantly increased by twofold on average. Three months after albumin injection, neither albumin nor inflammation was detected in brain tissue; at this time, the ADT was reduced by 50% but no spontaneous seizures were observed. SIGNIFICANCE Transient hippocampal exposure to albumin levels similar to those attained after prominent BBB breakdown resulted in increased seizure susceptibility and long-term reduction in seizure threshold, but it did not evoke spontaneous seizures. These effects may be mediated by albumin-induced astrocytes dysfunction and the associated induction of proinflammatory molecules.
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Affiliation(s)
- Federica Frigerio
- Department of Neuroscience, Mario Negri Institute for Pharmacological Research, Via G. La Masa 19, Milan, Italy.
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271
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17α-Ethynyl-androst-5-ene-3β,7β,17β-triol (HE3286) Is Neuroprotective and Reduces Motor Impairment and Neuroinflammation in a Murine MPTP Model of Parkinson's Disease. PARKINSONS DISEASE 2012; 2012:969418. [PMID: 23050197 PMCID: PMC3463191 DOI: 10.1155/2012/969418] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 08/21/2012] [Accepted: 08/21/2012] [Indexed: 12/14/2022]
Abstract
17α-Ethynyl-androst-5-ene-3β,7β,17β-triol (HE3286) is a synthetic androstenetriol in Phase II clinical development for the treatment of inflammatory diseases. HE3286 was evaluated for blood-brain barrier (BBB) permeability in mice, and efficacy in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) murine model of Parkinson's disease (PD). We found that HE3286 freely penetrated the BBB. HE3286 treatment significantly improved motor function compared to vehicle in the rotarod test (mean 58.2 sec versus 90.9 sec, P < 0.0001), and reduced inflammatory mediator gene expression in the brain (inducible nitric oxide synthase, 20%, P = 0.002; tumor necrosis factor α, 40%, P = 0.038, and interleukin-1β, 33%, P = 0.02) measured by reverse-transcriptase polymerase chain reaction. Brain tissue histopathology and immunohistochemistry showed that HE3286 treatment increased the numbers of tyrosine hydroxylase-positive cells by 17% compared to vehicle (P = 0.003), and decreased the numbers of damaged neurons by 38% relative to vehicle (P = 0.029). L-3,4-dihydroxyphenylalanine (L-DOPA) efficacy was not enhanced by concurrent administration of HE3286. HE3286 administration prior to MPTP did not enhance efficacy. Our data suggest a potential role for HE3286 in PD treatment, and provides incentive for further investigation.
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272
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Vetreno RP, Crews FT. Adolescent binge drinking increases expression of the danger signal receptor agonist HMGB1 and Toll-like receptors in the adult prefrontal cortex. Neuroscience 2012; 226:475-88. [PMID: 22986167 DOI: 10.1016/j.neuroscience.2012.08.046] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Revised: 08/09/2012] [Accepted: 08/23/2012] [Indexed: 02/02/2023]
Abstract
Adolescence is a critical developmental stage of life during which the prefrontal cortex (PFC) matures, and binge drinking and alcohol abuse are common. Recent studies have found that ethanol increases neuroinflammation via upregulated high-mobility group box 1 (HMGB1) signaling through Toll-like receptors (TLRs). HMGB1/TLR 'danger signaling' induces multiple brain innate immune genes that could alter brain function. To determine whether adolescent binge drinking persistently increases innate immune gene expression in the PFC, rats (P25-P55) were exposed to adolescent intermittent ethanol (AIE [5.0 g/kg, 2-day on/2-day off schedule]). On P56, HMGB1/TLR danger signaling was assessed using immunohistochemistry (i.e., +immunoreactivity [+IR]). In a separate group of subjects, spatial and reversal learning on the Barnes maze was assessed in early adulthood (P64-P75), and HMGB1/TLR danger signaling was measured using immunohistochemistry for +IR and RT-PCR for mRNA in adulthood (P80). Immunohistochemical assessment at P56 and 24 days later at P80 revealed increased frontal cortical HMGB1, TLR4, and TLR3 in the AIE-treated rats. Adolescent intermittent ethanol treatment did not alter adult spatial learning on the Barnes maze, but did cause reversal learning deficits and increased perseverative behavior. Barnes maze deficits correlated with the expression of danger signal receptors in the PFC. Taken together, these findings provide evidence that adolescent binge drinking leads to persistent upregulation of innate immune danger signaling in the adult PFC that correlates with adult neurocognitive dysfunction.
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Affiliation(s)
- R P Vetreno
- The Bowles Center for Alcohol Studies, Department of Psychiatry, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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273
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Iyer A, Zurolo E, Prabowo A, Fluiter K, Spliet WGM, van Rijen PC, Gorter JA, Aronica E. MicroRNA-146a: a key regulator of astrocyte-mediated inflammatory response. PLoS One 2012; 7:e44789. [PMID: 23028621 PMCID: PMC3441440 DOI: 10.1371/journal.pone.0044789] [Citation(s) in RCA: 249] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Accepted: 08/13/2012] [Indexed: 12/20/2022] Open
Abstract
Increasing evidence supports the involvement of microRNAs (miRNA) in the regulation of inflammation in human neurological disorders. In the present study we investigated the role of miR-146a, a key regulator of the innate immune response, in the modulation of astrocyte-mediated inflammation. Using Taqman PCR and in situ hybridization, we studied the expression of miR-146a in epilepsy-associated glioneuronal lesions which are characterized by prominent activation of the innate immune response. In addition, cultured human astrocytes were used to study the regulation of miR-146a expression in response to proinflammatory cytokines. qPCR and western blot were used to evaluate the effects of overexpression or knockdown of miR-146a on IL-1β signaling. Downstream signaling in the IL-1β pathway, as well as the expression of IL-6 and COX-2 were evaluated by western blot and ELISA. Release several cytokines was evaluated using a human magnetic multiplex cytokine assay on a Luminex® 100™/200™ platform. Increased expression of miR-146a was observed in glioneuronal lesions by Taqman PCR. MiR-146a expression in human glial cell cultures was strongly induced by IL-1β and blocked by IL-1β receptor antagonist. Modulation of miR-146a expression by transfection of astrocytes with anti-miR146a or mimic, regulated the mRNA expression levels of downstream targets of miR-146a (IRAK-1, IRAK-2 and TRAF-6) and the expression of IRAK-1 protein. In addition, the expression of IL-6 and COX-2 upon IL-1β stimulation was suppressed by increased levels of miR-146a and increased by the reduction of miR-146a. Modulation of miR-146a expression affected also the release of several cytokines such as IL-6 and TNF-α. Our observations indicate that in response to inflammatory cues, miR-146a was induced as a negative-feedback regulator of the astrocyte-mediated inflammatory response. This supports an important role of miR-146a in human neurological disorders associated with chronic inflammation and suggests that this miR may represent a novel target for therapeutic strategies.
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Affiliation(s)
- Anand Iyer
- Department of Neuro-Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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274
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Qulu L, Daniels WMU, Mabandla MV. Exposure to prenatal stress enhances the development of seizures in young rats. Metab Brain Dis 2012; 27:399-404. [PMID: 22527993 DOI: 10.1007/s11011-012-9300-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 03/22/2012] [Indexed: 11/29/2022]
Abstract
A febrile seizure is a neurological disorder that occurs following an infection that results in a rapid rise in body temperature. It commonly affects 3-5% of children between the ages of 3 months and 5 years. Interleukin-1 beta IL-1β a pro-inflammatory cytokine has been suggested to play a role in the manifestation of febrile seizures. There is evidence suggesting that neurological disorders can be exacerbated in an offspring that was exposed to stress prenatally. The aim of our study was therefore to investigate whether febrile seizures are exacerbated in the offspring of rats that were prenatally stressed. The offspring of pregnant Sprague-Dawley dams were used in the study. Prenatal stress consisted of exposing the pregnant dams to 45 min of restraint, 3 times per day with 3 h intervals in-between, for 7 days starting on gestational day 14 (GND14). On postnatal day (PND) 14, the pups were injected with lipopolysaccharide (LPS, 200 μg/kg, i.p.) followed 2.5 h later by an i.p. injection of kainic acid (KA, 1.75 mg/kg). All the animals were decapitated on PND 21. Trunk blood was collected to detect plasma interleukin-1beta (IL-1β) levels in the various groups. Our data showed that i.p. injections of LPS followed by KA led to the development of seizure activity that was associated with increased plasma IL-1β levels. Prior exposure to prenatal stress resulted in the development of advanced stages of seizure development, leading to an exaggerated seizure response. Prenatal stress alone also led to elevated plasma IL-1β levels, while previously stressed animals receiving LPS and KA yielded the highest plasma levels of IL-1β levels. Our data therefore shows that IL-1β levels may play an important role in the development of febrile seizures.
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MESH Headings
- Animals
- Animals, Newborn
- Disease Models, Animal
- Female
- Male
- Pregnancy
- Prenatal Exposure Delayed Effects/metabolism
- Prenatal Exposure Delayed Effects/physiopathology
- Rats
- Rats, Sprague-Dawley
- Restraint, Physical
- Seizures, Febrile/chemically induced
- Seizures, Febrile/complications
- Seizures, Febrile/physiopathology
- Stress, Psychological/blood
- Stress, Psychological/complications
- Stress, Psychological/physiopathology
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Affiliation(s)
- Lihle Qulu
- Department of Human Physiology, College of Health Sciences, University of KwaZulu-Natal, Durban 4000, South Africa
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275
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Prabowo AS, Anink JJ, Lammens M, Nellist M, van den Ouweland AMW, Adle-Biassette H, Sarnat HB, Flores-Sarnat L, Crino PB, Aronica E. Fetal brain lesions in tuberous sclerosis complex: TORC1 activation and inflammation. Brain Pathol 2012; 23:45-59. [PMID: 22805177 DOI: 10.1111/j.1750-3639.2012.00616.x] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 07/01/2012] [Indexed: 01/06/2023] Open
Abstract
Tuberous sclerosis complex (TSC) is an autosomal dominant disorder caused by mutations in either the TSC1 or TSC2 genes and characterized by developmental brain abnormalities. We defined the spectrum of brain abnormalities in fetal TSC brain ranging from 23 to 38 gestational weeks. We hypothesized (i) prenatal activation of the target-of-rapamycin complex 1 (TORC1) signaling pathway; and (ii) activation of inflammatory pathways in fetal brain lesions. Immunocytochemical analysis of cortical tubers, as well as subependymal lesions in all cases confirmed the cell-associated activation of the TORC1 signaling pathway in both the cortical tubers and subependymal lesions (including a congenital subependymal giant cell astrocytoma) with expression of pS6, p4EBP1 and c-myc proteins, as well as of p70 S6 kinase 1. The lesions contained macrophages and T-lymphocytes; giant cells within the lesions expressed inflammatory response markers including major histocompatibility complex class I and II, Toll-like receptors (TLR) 2 and 4 and receptor for advanced glycation end products (RAGE). These observations indicate that brain malformations in TSC are likely a consequence of increased TORC1 activation during embryonic brain development. We also provide evidence supporting the possible immunogenicity of giant cells and the early activation of inflammatory pathways in TSC brain.
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Affiliation(s)
- Avanita S Prabowo
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Amsterdam
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276
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Inflammation and epilepsy: the foundations for a new therapeutic approach in epilepsy? Epilepsy Curr 2012; 12:8-12. [PMID: 22368518 DOI: 10.5698/1535-7511-12.1.8] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Emerging data from experimental epilepsy models and resected human brain tissue support the proposed involvement of innate immune system activation and consequent inflammation in epilepsy. Key mediators of this process include interleukin-1β, high-mobility group box protein 1 (HMGB1), and Toll-like receptor (TLR) signaling. These recent findings constitute the basis for a novel avenue of drug development in epilepsy, one that is not only distinct from previous approaches but uniquely based on sound neurobiological evidence.
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277
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Abstract
Although long granted the status of immune privilege, the central nervous system is not completely isolated from the immune system. Increasing evidence suggests that this system contributes to seizures and epilepsy and that the molecular mediators of inflammation and immunity may serve as appropriate targets in the quest to develop novel antiepileptic drugs that are more efficacious and potentially disease modifying.
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278
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Due MR, Piekarz AD, Wilson N, Feldman P, Ripsch MS, Chavez S, Yin H, Khanna R, White FA. Neuroexcitatory effects of morphine-3-glucuronide are dependent on Toll-like receptor 4 signaling. J Neuroinflammation 2012; 9:200. [PMID: 22898544 PMCID: PMC3519737 DOI: 10.1186/1742-2094-9-200] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 07/31/2012] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Multiple adverse events are associated with the use of morphine for the treatment of chronic non-cancer pain, including opioid-induced hyperalgesia (OIH). Mechanisms of OIH are independent of opioid tolerance and may involve the morphine metabolite morphine-3-glucuronide (M3G). M3G exhibits limited affinity for opioid receptors and no analgesic effect. Previous reports suggest that M3G can act via the Toll-like receptor 4 (TLR4)/myeloid differentiation protein-2 (MD-2) heterodimer in the central nervous system to elicit pain. METHODS Immunoblot and immunocytochemistry methods were used to characterize the protein expression of TLR4 present in lumbar dorsal root ganglion (DRG). Using in vitro intracellular calcium and current clamp techniques, we determined whether TLR4 activation as elicited by the prototypical agonists of TLR4, lipopolysaccharide (LPS) and M3G, contributed to changes in intracellular calcium and increased excitation. Rodents were also injected with M3G to determine the degree to which M3G-induced tactile hyperalgesia could be diminished using either a small molecule inhibitor of the MD-2/TLR4 complex in rats or TLR4 knockout mice. Whole cell voltage-clamp recordings were made from small- and medium-diameter DRG neurons (25 μm < DRG diameter <45 μm) for both control and M3G-treated neurons to determine the potential influence on voltage-gated sodium channels (NaVs). RESULTS We observed that TLR4 immunoreactivity was present in peptidergic and non-peptidergic sensory neurons in the DRG. Non-neuronal cells in the DRG lacked evidence of TLR4 expression. Approximately 15% of assayed small- and medium-diameter sensory neurons exhibited a change in intracellular calcium following LPS administration. Both nociceptive and non-nociceptive neurons were observed to respond, and approximately 40% of these cells were capsaicin-insensitive. Increased excitability observed in sensory neurons following LPS or M3G could be eliminated using Compound 15, a small molecule inhibitor of the TLR4/MD-2 complex. Likewise, systemic injection of M3G induced rapid tactile, but not thermal, nociceptive behavioral changes in the rat, which were prevented by pre-treating animals with Compound 15. Unlike TLR4 wild-type mice, TLR4 knockout mice did not exhibit M3G-induced hyperalgesia. As abnormal pain sensitivity is often associated with NaVs, we predicted that M3G acting via the MD-2/TLR4 complex may affect the density and gating of NaVs in sensory neurons. We show that M3G increases tetrodotoxin-sensitive and tetrodotoxin-resistant (NaV1.9) current densities. CONCLUSIONS These outcomes provide evidence that M3G may play a role in OIH via the TLR4/MD-2 heterodimer complex and biophysical properties of tetrodotoxin-sensitive and tetrodotoxin-resistant NaV currents.
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Affiliation(s)
- Michael R Due
- Department of Anesthesia, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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279
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Abstract
The term long-term epilepsy associated tumor (LEAT) encompasses lesions identified in patients investigated for long histories (often 2 years or more) of drug-resistant epilepsy. They are generally slowly growing, low grade, cortically based tumors, more often arising in younger age groups and in many cases exhibit neuronal in addition to glial differentiation. Gangliogliomas and dysembryoplastic neuroepithelial tumors predominate in this group. LEATs are further united by cyto-architectural changes that may be present in the adjacent cortex which have some similarities to developmental focal cortical dysplasias (FCD); these are now grouped as FCD type IIIb in the updated International League Against Epilepsy (ILAE) classification. In the majority of cases, surgical treatments are beneficial from both perspectives of managing the seizures and the tumor. However, in a minority, seizures may recur, tumors may show regrowth or recurrence, and rarely undergo anaplastic progression. Predicting and identifying tumors likely to behave less favorably are key objectives of the neuropathologist. With immunohistochemistry and modern molecular pathology, it is becoming increasingly possible to refine diagnostic groups. Despite this, some LEATs remain difficult to classify, particularly tumors with "non-specific" or diffuse growth patterns. Modification of LEAT classification is inevitable with the goal of unifying terminological criteria applied between centers for accurate clinico-pathological-molecular correlative data to emerge. Finally, establishing the epileptogenic components of LEAT, either within the lesion or perilesional cortex, will elucidate the cellular mechanisms of epileptogenesis, which in turn will guide optimal surgical management of these lesions.
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Affiliation(s)
- Maria Thom
- Department of Clinical and Experimental Epilepsy, UCL, Institute of Neurology, Queen Square, London, UK.
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280
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Bilbo SD, Schwarz JM. The immune system and developmental programming of brain and behavior. Front Neuroendocrinol 2012; 33:267-86. [PMID: 22982535 PMCID: PMC3484177 DOI: 10.1016/j.yfrne.2012.08.006] [Citation(s) in RCA: 396] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 08/28/2012] [Accepted: 08/29/2012] [Indexed: 12/16/2022]
Abstract
The brain, endocrine, and immune systems are inextricably linked. Immune molecules have a powerful impact on neuroendocrine function, including hormone-behavior interactions, during health as well as sickness. Similarly, alterations in hormones, such as during stress, can powerfully impact immune function or reactivity. These functional shifts are evolved, adaptive responses that organize changes in behavior and mobilize immune resources, but can also lead to pathology or exacerbate disease if prolonged or exaggerated. The developing brain in particular is exquisitely sensitive to both endogenous and exogenous signals, and increasing evidence suggests the immune system has a critical role in brain development and associated behavioral outcomes for the life of the individual. Indeed, there are associations between many neuropsychiatric disorders and immune dysfunction, with a distinct etiology in neurodevelopment. The goal of this review is to describe the important role of the immune system during brain development, and to discuss some of the many ways in which immune activation during early brain development can affect the later-life outcomes of neural function, immune function, mood and cognition.
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Affiliation(s)
- Staci D Bilbo
- Department of Psychology and Neuroscience, Duke University, 572 Research Drive, Box 91050, Durham, NC 27708, USA.
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281
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Dinarello CA, Simon A, van der Meer JWM. Treating inflammation by blocking interleukin-1 in a broad spectrum of diseases. Nat Rev Drug Discov 2012; 11:633-52. [PMID: 22850787 PMCID: PMC3644509 DOI: 10.1038/nrd3800] [Citation(s) in RCA: 1278] [Impact Index Per Article: 106.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Interleukin-1 (IL-1) is a highly active pro-inflammatory cytokine that lowers pain thresholds and damages tissues. Monotherapy blocking IL-1 activity in autoinflammatory syndromes results in a rapid and sustained reduction in disease severity, including reversal of inflammation-mediated loss of sight, hearing and organ function. This approach can therefore be effective in treating common conditions such as post-infarction heart failure, and trials targeting a broad spectrum of new indications are underway. So far, three IL-1-targeted agents have been approved: the IL-1 receptor antagonist anakinra, the soluble decoy receptor rilonacept and the neutralizing monoclonal anti-IL-1β antibody canakinumab. In addition, a monoclonal antibody directed against the IL-1 receptor and a neutralizing anti-IL-1α antibody are in clinical trials.
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Affiliation(s)
- Charles A Dinarello
- Department of Medicine, University of Colorado Denver, Aurora, Colorado 80045, USA.
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282
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Feldman P, Due MR, Ripsch MS, Khanna R, White FA. The persistent release of HMGB1 contributes to tactile hyperalgesia in a rodent model of neuropathic pain. J Neuroinflammation 2012; 9:180. [PMID: 22824385 PMCID: PMC3488576 DOI: 10.1186/1742-2094-9-180] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 06/29/2012] [Indexed: 11/10/2022] Open
Abstract
Background High-mobility group box-1 protein (HMGB1) is a nuclear protein that regulates gene expression throughout the body. It can also become cytoplasmic and function as a neuromodulatory cytokine after tissue damage or injury. The manner in which HMGB1 influences the peripheral nervous system following nerve injury is unclear. The present study investigated the degree to which HMGB1 signaling contributes to the maintenance of neuropathic pain behavior in the rodent. Results Redistribution of HMGB1 from the nucleus to the cytoplasm occurred in both sensory neurons derived from a tibial nerve injured (TNI) rat and in a sensory neuron-like cell line following exposure to a depolarizing stimulus. We also observe that exogenous administration of HMGB1 to acutely dissociated sensory neurons derived from naïve or TNI rodents elicit increased excitability. Furthermore systemic injection of glycyrrhizin (50 mg/kg; i.p.), a known inhibitor of HMGB1, reversed TNI-induced mechanical hyperalgesia at fourteen days and three months following nerve injury. Conclusions We have identified that a persistent endogenous release of HMGB1 by sensory neurons may be a potent, physiologically relevant modulator of neuronal excitability. More importantly, the use of the anti-inflammatory compound and known inhibitor of HMGB1, glycyrrhizin, has the ability to diminish persistent pain behavior in a model of peripheral neuropathy, presumably through its ability to neutralize the cyotkine. The identification of HMGB1 as a potential therapeutic target may contribute to a better understanding of mechanisms associated with chronic pain syndromes.
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Affiliation(s)
- Polina Feldman
- Program in Medical Neurosciences, Paul and Carole Stark Neurosciences Research Institute, Indiana University, School of Medicine, 950 West Walnut Street, Indianapolis, IN 46202, USA
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283
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Librizzi L, Noè F, Vezzani A, de Curtis M, Ravizza T. Seizure-induced brain-borne inflammation sustains seizure recurrence and blood-brain barrier damage. Ann Neurol 2012; 72:82-90. [DOI: 10.1002/ana.23567] [Citation(s) in RCA: 189] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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284
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Yu Y, Zhong Q, Li C, Jiang L, Wang Y, Sun Y, Wang X, Wang Z, Zhang Q. Identification and characterization of IL-1 receptor-associated kinase-4 (IRAK-4) in half-smooth tongue sole Cynoglossus semilaevis. FISH & SHELLFISH IMMUNOLOGY 2012; 32:609-615. [PMID: 22230843 DOI: 10.1016/j.fsi.2011.12.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 12/26/2011] [Accepted: 12/26/2011] [Indexed: 05/31/2023]
Abstract
As a crucial component in TLR/IL-1R signaling pathways, IRAK-4 plays a central role in innate and adaptive immunity. In the present study, the cDNA of IRAK-4 was cloned for the first time from half-smooth tongue sole (Cynoglossus semilaevis). The full-length cDNA of csIRAK-4 was 2149 bp and contained a 168 bp 5' UTR, a 580 bp 3' UTR and a 1401 bp CDS. The predicted protein sequence of csIRAK-4 had two typical domains, a death domain (DD) at the N terminus and a serine/threonine/tyrosine protein kinase domain (STYKc) at the C terminus. RT-PCR showed that csIRAK-4 mRNA was detected in all tested tissues, especially in immune-related organs, gonads and brain. After injected with inactivated Vibrio anguillarum, the expressions of csIRAK-4 were up-regulated significantly (P<0.05) in spleen and head kidney. During development, csIRAK-4 was expressed at all selected stages and low-level expression was detected at metamorphosis. Taken together, the present study indicated that csIRAK-4 played a crucial role in immune responses and might be involved in the process of development.
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Affiliation(s)
- Yan Yu
- Department of Life Science, Huainan Normal University, PR China
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285
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Pineda EA, Hensler JG, Sankar R, Shin D, Burke TF, Mazarati AM. Interleukin-1β causes fluoxetine resistance in an animal model of epilepsy-associated depression. Neurotherapeutics 2012; 9:477-85. [PMID: 22427156 PMCID: PMC3337012 DOI: 10.1007/s13311-012-0110-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Depression represents a common comorbidity of epilepsy and is frequently resistant to selective serotonin reuptake inhibitors (SSRI). We tested the hypothesis that the SSRI resistance in epilepsy associated depression may be a result of a pathologically enhanced interleukin-1β (IL1-β) signaling, and consequently that the blockade of IL1-β may restore the effectiveness of SSRI. Epilepsy and concurrent depression-like impairments were induced in Wistar rats by pilocarpine status epilepticus (SE). The effects of the 2-week long treatment with fluoxetine, interleukin-1 receptor antagonist (IL-1ra), and their combination were examined using behavioral, biochemical, neuroendocrine, and autoradiographic assays. In post-SE rats, depression-like impairments included behavioral deficits indicative of hopelessness and anhedonia; the hyperactivity of the hypothalamo-pituitary-adrenocortical axis; the diminished serotonin output from raphe nucleus; and the upregulation of presynaptic serotonin 1-A (5-HT1A) receptors. Fluoxetine monotherapy exerted no antidepressant effects, whereas the treatment with IL-1ra led to the complete reversal of anhedonia and to a partial improvement of all other depressive impairments. Combined administration of fluoxetine and IL-1ra completely abolished all hallmarks of epilepsy-associated depressive abnormalities, with the exception of the hyperactivity of the hypothalamo-pituitary-adrenocortical axis, the latter remaining only partially improved. We propose that in certain forms of depression, including but not limited to depression associated with epilepsy, the resistance to SSRI may be driven by the pathologically enhanced interleukin-1β signaling and by the subsequent upregulation of presynaptic 5-HT1A receptors. In such forms of depression, the use of interleukin-1β blockers in conjunction with SSRI may represent an effective therapeutic approach.
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Affiliation(s)
- Eduardo A. Pineda
- />Department of Pediatrics, Neurology Division, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095 USA
| | - Julie G. Hensler
- />Department of Pharmacology, University of Texas Health Science Center-San Antonio, San Antonio, TX 78229 USA
| | - Raman Sankar
- />Department of Pediatrics, Neurology Division, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095 USA
| | - Don Shin
- />Department of Pediatrics, Neurology Division, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095 USA
| | - Teresa F. Burke
- />Department of Pharmacology, University of Texas Health Science Center-San Antonio, San Antonio, TX 78229 USA
| | - Andréy M. Mazarati
- />Department of Pediatrics, Neurology Division, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095 USA
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286
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Aronica E, Ravizza T, Zurolo E, Vezzani A. Astrocyte immune responses in epilepsy. Glia 2012; 60:1258-68. [PMID: 22331574 DOI: 10.1002/glia.22312] [Citation(s) in RCA: 145] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 01/27/2012] [Indexed: 12/25/2022]
Abstract
Astrocytes, the major glial cell type of the central nervous system (CNS), are known to play a major role in the regulation of the immune/inflammatory response in several human CNS diseases. In epilepsy-associated pathologies, the presence of astrogliosis has stimulated extensive research focused on the role of reactive astrocytes in the pathophysiological processes that underlie the development of epilepsy. In brain tissue from patients with epilepsy, astrocytes undergo significant changes in their physiological properties, including the activation of inflammatory pathways. Accumulating experimental evidence suggests that proinflammatory molecules can alter glio-neuronal communications contributing to the generation of seizures and seizure-related neuronal damage. In particular, both in vitro and in vivo data point to the role of astrocytes as both major source and target of epileptogenic inflammatory signaling. In this context, understanding the astroglial inflammatory response occurring in epileptic brain tissue may provide new strategies for targeting astrocyte-mediated epileptogenesis. This article reviews current evidence regarding the role of astrocytes in the regulation of the innate immune responses in epilepsy. Both clinical observations in drug-resistant human epilepsies and experimental findings in clinically relevant models will be discussed and elaborated, highlighting specific inflammatory pathways (such as interleukin-1β/toll-like receptor 4) that could be potential targets for antiepileptic, disease-modifying therapeutic strategies.
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Affiliation(s)
- Eleonora Aronica
- Department of (Neuro)Pathology, Academisch Medisch Centrum, Amsterdam, The Netherlands.
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287
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Mishra A, Kim HJ, Shin AH, Thayer SA. Synapse loss induced by interleukin-1β requires pre- and post-synaptic mechanisms. J Neuroimmune Pharmacol 2012; 7:571-8. [PMID: 22311599 DOI: 10.1007/s11481-012-9342-7] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 01/13/2012] [Indexed: 01/31/2023]
Abstract
Interleukin-1β (IL-1β) is an inflammatory cytokine that exerts marked effects on neuronal function and survival. Here we examined the effects of IL-1β on synapses between rat hippocampal neurons in culture using an imaging-based assay to quantify clusters of the scaffolding protein postsynaptic density 95 fused to green fluorescent protein. Treatment with IL-1β for 24 h induced a 23 ± 3% loss in the number of synaptic sites. Pharmacological studies indicated that synapse loss was mediated by the IL-1 receptor with subsequent activation of two pathways. COX2-mediated prostaglandin production and postsynaptic activation of a Src family tyrosine kinase were required. Presynaptic release of glutamate with subsequent activation of NMDA receptors was necessary for IL-1β-induced synapse loss. Neither Src activation nor prostaglandin E2 (PGE2) application alone was sufficient to reduce the number of synapses. However, in cells expressing constitutively active or pharmacologically activated Src, PGE2 induced synapse loss. Thus, IL-1β reduces the number of synaptic connections by simultaneously activating multiple pathways that require both pre- and post-synaptic activity. These results highlight targets that may prove important for pharmacotherapy of neuroinflammatory disease.
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Affiliation(s)
- Anjuli Mishra
- Department of Pharmacology, University of Minnesota Medical School, 321 Church Street SE, 6-120 Jackson Hall, Minneapolis, MN 55455, USA
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288
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Beggs S, Currie G, Salter MW, Fitzgerald M, Walker SM. Priming of adult pain responses by neonatal pain experience: maintenance by central neuroimmune activity. ACTA ACUST UNITED AC 2011; 135:404-17. [PMID: 22102650 DOI: 10.1093/brain/awr288] [Citation(s) in RCA: 155] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Adult brain connectivity is shaped by the balance of sensory inputs in early life. In the case of pain pathways, it is less clear whether nociceptive inputs in infancy can have a lasting influence upon central pain processing and adult pain sensitivity. Here, we show that adult pain responses in the rat are 'primed' by tissue injury in the neonatal period. Rats that experience hind-paw incision injury at 3 days of age, display an increased magnitude and duration of hyperalgesia following incision in adulthood when compared with those with no early life pain experience. This priming of spinal reflex sensitivity was measured by both reductions in behavioural withdrawal thresholds and increased flexor muscle electromyographic responses to graded suprathreshold hind-paw stimuli in the 4 weeks following adult incision. Prior neonatal injury also 'primed' the spinal microglial response to adult injury, resulting in an increased intensity, spatial distribution and duration of ionized calcium-binding adaptor molecule-1-positive microglial reactivity in the dorsal horn. Intrathecal minocycline at the time of adult injury selectively prevented both the hyperalgesia and early microglial reactivity associated with prior neonatal injury. The enhanced neuroimmune response seen in neonatally primed animals could also be demonstrated in the absence of peripheral tissue injury by direct electrical stimulation of tibial nerve fibres, confirming that centrally mediated mechanisms contribute to these long-term effects. These data suggest that early life injury may predispose individuals to enhanced sensitivity to painful events.
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Affiliation(s)
- Simon Beggs
- Portex Unit: Pain Research, UCL Institute of Child Health and Great Ormond St Hospital NHS Trust, 30 Guilford St, London WC1N 1EH, UK
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289
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Vezzani A, Bartfai T, Bianchi M, Rossetti C, French J. Therapeutic potential of new antiinflammatory drugs. Epilepsia 2011; 52 Suppl 8:67-9. [PMID: 21967368 DOI: 10.1111/j.1528-1167.2011.03242.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Experimental and clinical findings have shown in the past decade that specific proinflammatory mediators and their cognate receptors are upregulated in epileptic brain tissue. In particular, the IL-1 receptor (R)/Toll-like receptor (TLR) signaling pathways are activated in experimental models of seizures and in human epileptic tissue from drug-resistant patients. Pharmacological targeting of these proinflammatory pathways using selective receptor antagonists, or the use of transgenic mice with perturbed cell signaling, demostrated that the activation of IL-1R type 1 and TLR4 by their respective endogenous ligands, i.e., interleukin (IL)-1b and High Mobility Group Box 1, is implicated in the precipitation and recurrence of experimentally induced seizures in rodents. This evidence highlights a new target system for pharmacological intervention to inhibit seizures by interfering with mechanisms involved in their genesis and recurrence.
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Affiliation(s)
- Annamaria Vezzani
- Department of Neuroscience, Mario Negri Institute for Pharmacological Research, Via G. La Masa 19, Milan, Italy.
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290
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Vezzani A, Aronica E, Mazarati A, Pittman QJ. Epilepsy and brain inflammation. Exp Neurol 2011; 244:11-21. [PMID: 21985866 DOI: 10.1016/j.expneurol.2011.09.033] [Citation(s) in RCA: 404] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2011] [Revised: 09/15/2011] [Accepted: 09/26/2011] [Indexed: 02/06/2023]
Abstract
During the last decade, experimental research has demonstrated a prominent role of glial cells, activated in brain by various injuries, in the mechanisms of seizure precipitation and recurrence. In particular, alterations in the phenotype and function of activated astrocytes and microglial cells have been described in experimental and human epileptic tissue, including modifications in potassium and water channels, alterations of glutamine/glutamate cycle, changes in glutamate receptor expression and transporters, release of neuromodulatory molecules (e.g. gliotransmitters, neurotrophic factors), and induction of molecules involved in inflammatory processes (e.g. cytokines, chemokines, prostaglandins, complement factors, cell adhesion molecules) (Seifert et al., 2006; Vezzani et al., 2011; Wetherington et al., 2008). In particular, brain injury or proconvulsant events can activate microglia and astrocytes to release a number of proinflammatory mediators, thus initiating a cascade of inflammatory processes in brain tissue. Proinflammatory molecules can alter neuronal excitability and affect the physiological functions of glia by paracrine or autocrine actions, thus perturbing the glioneuronal communications. In experimental models, these changes contribute to decreasing the threshold to seizures and may compromise neuronal survival (Riazi et al., 2010; Vezzani et al., 2008). In this context, understanding which are the soluble mediators and the molecular mechanisms crucially involved in glio-neuronal interactions is instrumental to shed light on how brain inflammation may contribute to neuronal hyperexcitability in epilepsy. This review will report the clinical observations in drug-resistant human epilepsies and the experimental findings in adult and immature rodents linking brain inflammation to the epileptic process in a causal and reciprocal manner. By confronting the clinical evidence with the experimental findings, we will discuss the role of specific soluble inflammatory mediators in the etiopathogenesis of seizures, reporting evidence for both their acute and long term effects on seizure threshold. The possible contribution of these mediators to co-morbidities often described in epilepsy patients will be also discussed. Finally, we will report on the anti-inflammatory treatments with anticonvulsant actions in experimental models highlighting possible therapeutic options for treating drug-resistant seizures and for prevention of epileptogenesis.
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Affiliation(s)
- Annamaria Vezzani
- Department of Neuroscience, Mario Negri Institute for Pharmacological Research, Via G. La Masa 19, 20156 Milano, Italy.
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291
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292
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Friedman A, Dingledine R. Molecular cascades that mediate the influence of inflammation on epilepsy. Epilepsia 2011; 52 Suppl 3:33-9. [PMID: 21542844 DOI: 10.1111/j.1528-1167.2011.03034.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Experimental evidence strongly indicates a significant role for inflammatory and immune mediators in initiation of seizures and epileptogenesis. Here we will summarize data supporting the involvement of IL-1β, TNF-α and toll-like receptor 4 in seizure generation and the process of epileptogenesis. The physiological homeostasis and control over brain immune response depends on the integrity of the blood-brain barrier, transforming growth factor (TGF)-β signaling and leukocyte migration. To what extent targeting the immune system is successful in preventing epileptogenesis, and which signaling pathway should be beleaguered is still under intensive research.
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Affiliation(s)
- Alon Friedman
- Department of Physiology and Neurobiology, Faculty of Health Sciences, Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
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