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Schaafsma W, Zhang X, van Zomeren KC, Jacobs S, Georgieva PB, Wolf SA, Kettenmann H, Janova H, Saiepour N, Hanisch UK, Meerlo P, van den Elsen PJ, Brouwer N, Boddeke HWGM, Eggen BJL. Long-lasting pro-inflammatory suppression of microglia by LPS-preconditioning is mediated by RelB-dependent epigenetic silencing. Brain Behav Immun 2015; 48:205-21. [PMID: 25843371 DOI: 10.1016/j.bbi.2015.03.013] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 03/27/2015] [Accepted: 03/27/2015] [Indexed: 10/23/2022] Open
Abstract
Microglia, the innate immune cells of the central nervous system (CNS), react to endotoxins like bacterial lipopolysaccharides (LPS) with a pronounced inflammatory response. To avoid excess damage to the CNS, the microglia inflammatory response needs to be tightly regulated. Here we report that a single LPS challenge results in a prolonged blunted pro-inflammatory response to a subsequent LPS stimulation, both in primary microglia cultures (100 ng/ml) and in vivo after intraperitoneal (0.25 and 1mg/kg) or intracerebroventricular (5 μg) LPS administration. Chromatin immunoprecipitation (ChIP) experiments with primary microglia and microglia acutely isolated from mice showed that LPS preconditioning was accompanied by a reduction in active histone modifications AcH3 and H3K4me3 in the promoters of the IL-1β and TNF-α genes. Furthermore, LPS preconditioning resulted in an increase in the amount of repressive histone modification H3K9me2 in the IL-1β promoter. ChIP and knock-down experiments showed that NF-κB subunit RelB was bound to the IL-1β promoter in preconditioned microglia and that RelB is required for the attenuated LPS response. In addition to a suppressed pro-inflammatory response, preconditioned primary microglia displayed enhanced phagocytic activity, increased outward potassium currents and nitric oxide production in response to a second LPS challenge. In vivo, a single i.p. LPS injection resulted in reduced performance in a spatial learning task 4 weeks later, indicating that a single inflammatory episode affected memory formation in these mice. Summarizing, we show that LPS-preconditioned microglia acquire an epigenetically regulated, immune-suppressed phenotype, possibly to prevent excessive damage to the central nervous system in case of recurrent (peripheral) inflammation.
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Affiliation(s)
- W Schaafsma
- Department of Neuroscience, Section Medical Physiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - X Zhang
- Department of Neuroscience, Section Medical Physiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - K C van Zomeren
- Department of Neuroscience, Section Medical Physiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - S Jacobs
- Department of Neuroscience, Section Medical Physiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - P B Georgieva
- Cellular Neurosciences, Max Delbrück Centre for Molecular Medicine, Berlin, Germany
| | - S A Wolf
- Cellular Neurosciences, Max Delbrück Centre for Molecular Medicine, Berlin, Germany
| | - H Kettenmann
- Cellular Neurosciences, Max Delbrück Centre for Molecular Medicine, Berlin, Germany
| | - H Janova
- Institute of Neuropathology, University of Göttingen, Göttingen, Germany
| | - N Saiepour
- Institute of Neuropathology, University of Göttingen, Göttingen, Germany
| | - U-K Hanisch
- Institute of Neuropathology, University of Göttingen, Göttingen, Germany; Universität Leipzig, Paul-Flechsig-Institut für Hirnforschung, Leipzig, Germany
| | - P Meerlo
- Center for Behavior and Neurosciences, University of Groningen, Groningen, The Netherlands
| | - P J van den Elsen
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Centre, The Netherlands; Department of Pathology, VU University Medical Center, Amsterdam, The Netherlands
| | - N Brouwer
- Department of Neuroscience, Section Medical Physiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - H W G M Boddeke
- Department of Neuroscience, Section Medical Physiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - B J L Eggen
- Department of Neuroscience, Section Medical Physiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
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