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Cell Death Differ. 2013 Nov;20(11):1546-57. doi: 10.1038/cdd.2013.108. Epub 2013 Sep 6.

Potent and multiple regulatory actions of microglial glucocorticoid receptors during CNS inflammation.

Author information

1
1] Department of Physiopathology of CNS diseases, Centre National de la Recherche Scientifique, UMR 7224, Molecular Genetics, Neurophysiology and Behavior Lab, Paris, France [2] Institut National de la santé et de la Recherche Médicale, UMR 952, Paris, France [3] Université Pierre et Marie Curie, Paris, France [4] Clinical and Experimental Neuroscience (NiCE-CIBERNED), School of Medicine, University of Murcia, Regional Campus of International Excellence 'Campus Mare Nostrum', Murcia, Spain.

Abstract

In CNS, glucocorticoids (GCs) activate both GC receptor (GR) and mineralocorticoid receptor (MR), whereas GR is widely expressed, the expression of MR is restricted. However, both are present in the microglia, the resident macrophages of the brain and their activation can lead to pro- or anti-inflammatory effects. We have therefore addressed the specific functions of GR in microglia. In mice lacking GR in macrophages/microglia and in the absence of modifications in MR expression, intraparenchymal injection of lipopolysaccharide (LPS) activating Toll-like receptor 4 signaling pathway resulted in exacerbated cellular lesion, neuronal and axonal damage. Global inhibition of GR by RU486 pre-treatment revealed that microglial GR is the principal mediator preventing neuronal degeneration triggered by lipopolysaccharide (LPS) and contributes with GRs of other cell types to the protection of non-neuronal cells. In vivo and in vitro data show GR functions in microglial differentiation, proliferation and motility. Interestingly, microglial GR also abolishes the LPS-induced delayed outward rectifier currents by downregulating Kv1.3 expression known to control microglia proliferation and oxygen radical production. Analysis of GR transcriptional function revealed its powerful negative control of pro-inflammatory effectors as well as upstream inflammatory activators. Finally, we analyzed the role of GR in chronic unpredictable mild stress and aging, both known to prime or sensitize microglia in vivo. We found that microglial GR suppresses rather than mediates the deleterious effects of stress or aging on neuronal survival. Overall, the results show that microglial GR acts on several key processes limiting pro-inflammatory actions of activated microglia.

PMID:
24013726
PMCID:
PMC3792430
DOI:
10.1038/cdd.2013.108
[Indexed for MEDLINE]
Free PMC Article

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