Interleukin-1beta and tumor necrosis factor-alpha are expressed by different subsets of microglia and macrophages after ischemic stroke in mice

Clausen, Lambertsen, Babcock, Holm, Dagnaes-Hansen Frederik, Finsen, Finsen Bente

Description

Interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) are expressed by microglia and infiltrating macrophages following ischemic stroke. Whereas IL-1β is primarily neurotoxic in ischemic stroke, TNF-α may have neurotoxic and/or neuroprotective effects. We investigated whether IL-1β and TNF-α are synthesized by overlapping or segregated populations of cells after ischemic stroke in mice. Methods We used flow cytometry and immunohistochemistry to examine cellular co-expression of IL-1β and TNF-α at 6, 12 and 24 hours after permanent middle cerebral artery occlusion in mice, validating the results by the use of bone marrow chimeric mice. Results We found that IL-1β and TNF-α were expressed in largely segregated populations of CD11b + CD45 dim microglia and CD11b + CD45 high macrophages, with cells expressing both cytokines only rarely. The number of Gr1 + granulocytes producing IL-1β or TNF-α was very low, and we observed no IL-1β- or TNF-α-expressing T cells or astrocytes. Conclusion Taken together, the results show that IL-1β and TNF-α are produced by largely segregated populations of microglia and macrophages after ischemic stroke in mice. Our findings provide evidence of a functional diversity among different subsets of microglia and macrophages that is potentially relevant to future design of anti-inflammatory therapies in stroke.

Informations

• Publié par: biomed
• Publié le: 01 janvier 2008
• Nombre de lectures: 3
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

Journal of Neuroinflammation

BioMedCentral

Open Access Research Interleukin-1beta and tumor necrosis factor-alpha are expressed by different subsets of microglia and macrophages after ischemic stroke in mice †1 †11 Bettina H Clausen, Kate L Lambertsen*, Alicia A Babcock, 1 21 Thomas H Holm, Frederik DagnaesHansenand Bente Finsen

1 2 Address: MedicalBiotechnology Center, University of Southern Denmark, Odense, Denmark andDepartment of Medical Microbiology and Immunology, University of Aarhus, Aarhus, Denmark Email: Bettina H Clausen  [e-mail]; Kate L Lambertsen*  [e-mail]; Alicia A Babcock  [e-mail]; Thomas H Holm  [e-mail]; Frederik Dagnaes Hansen  [e-mail]; Bente Finsen  [e-mail] * Corresponding author†Equal contributors

Published: 23 October 2008Received: 17 May 2008 Accepted: 23 October 2008 Journal of Neuroinflammation2008,5:46 doi:10.1186/1742-2094-5-46 This article is available from: http://www.jneuroinflammation.com/content/5/1/46 © 2008 Clausen et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract Background:Interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) are expressed by microglia and infiltrating macrophages following ischemic stroke. Whereas IL-1β isprimarily neurotoxic in ischemic stroke, TNF-αmay have neurotoxic and/or neuroprotective effects. We investigated whether IL-1βand TNF-αare synthesized by overlapping or segregated populations of cells after ischemic stroke in mice. Methods:We used flow cytometry and immunohistochemistry to examine cellular co-expression of IL-1βand TNF-αat 6, 12 and 24 hours after permanent middle cerebral artery occlusion in mice, validating the results by the use of bone marrow chimeric mice. Results:We found that IL-1β andTNF-α wereexpressed in largely segregated populations of + dim+ high CD11b CD45microglia and CD11bCD45 macrophages,with cells expressing both + cytokines only rarely. The number of Gr1granulocytes producing IL-1βor TNF-αwas very low, and we observed no IL-1β- or TNF-α-expressing T cells or astrocytes. Conclusion:Taken together, the results show that IL-1βTNF- andαproduced by largely are segregated populations of microglia and macrophages after ischemic stroke in mice. Our findings provide evidence of a functional diversity among different subsets of microglia and macrophages that is potentially relevant to future design of anti-inflammatory therapies in stroke.

Background The proinflammatory cytokines interleukin1β (IL1β) and tumor necrosis factorα(TNFα) play key roles in the pathogenesis of ischemic stroke [13]. IL1βexerts neuro toxic effects in ischemic stroke and blocking its action has been shown to reduce ischemic brain damage [4,5]. In

comparison, there is evidence that TNFαhas both neuro toxic [6,7] and neuroprotective [810] roles after ischemic stroke in rats and in mice. Increasing evidence implicates both cytokines in the early inflammatory response that precedes and accompanies ischemiainduced neuronal damage [6,11]. However, detailed knowledge about the

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