The microRNA miR-181c controls microglia-mediated neuronal apoptosis by suppressing tumor necrosis factor

Li Zhang, Dong Lian-Yan, Li Ya-Jian, Hong Zhen, Wei, Wei Wen-Shi

Description

Post-ischemic microglial activation may contribute to neuronal damage through the release of large amounts of pro-inflammatory cytokines and neurotoxic factors. The involvement of microRNAs (miRNAs) in the pathogenesis of disorders related to the brain and central nervous system has been previously studied, but it remains unknown whether the production of pro-inflammatory cytokines is regulated by miRNAs. Methods BV-2 and primary rat microglial cells were activated by exposure to oxygen-glucose deprivation (OGD). Global cerebral ischemia was induced using the four-vessel occlusion (4-VO) model in rats. Induction of pro-inflammatory and neurotoxic factors, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and nitric oxide (NO), were assessed by ELISA, immunofluorescence, and the Griess assay, respectively. The miRNA expression profiles of OGD-activated BV-2 cells were subsequently compared with the profiles of resting cells in a miRNA microarray. BV-2 and primary rat microglial cells were transfected with miR-181c to evaluate its effects on TNF-α production after OGD. In addition, a luciferase reporter assay was conducted to confirm whether TNF-α is a direct target of miR-181c. Results OGD induced BV-2 microglial activation in vitro , as indicated by the overproduction of TNF-α, IL-1β, and NO. Global cerebral ischemia/reperfusion injury induced microglial activation and the release of pro-inflammatory cytokines in the hippocampus. OGD also downregulated miR-181c expression and upregulated TNF-α expression. Overproduction of TNF-α after OGD-induced microglial activation provoked neuronal apoptosis, whereas the ectopic expression of miR-181c partially protected neurons from cell death caused by OGD-activated microglia. RNAinterference-mediated knockdown of TNF-α phenocopied the effect of miR-181c-mediated neuronal protection, whereas overexpression of TNF-α blocked the miR-181c-dependent suppression of apoptosis. Further studies showed that miR-181c could directly target the 3′-untranslated region of TNF-α mRNA, suppressing its mRNA and protein expression. Conclusions Our data suggest a potential role for miR-181c in the regulation of TNF-α expression after ischemia/hypoxia and microglia-mediated neuronal injury.

Sujets

• Hypoxia

Informations

• Publié par: biomed
• Publié le: 01 janvier 2012
• Nombre de lectures: 4
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Zhanget al. Journal of Neuroinflammation2012,9:211 http://www.jneuroinflammation.com/content/9/1/211

JOURNAL OF NEUROINFLAMMATION

R E S E A R C HOpen Access The microRNA miR181c controls microgliamediated neuronal apoptosis by suppressing tumor necrosis factor 1,3 21 3*1* Li Zhang, LianYan Dong , YaJian Li , Zhen Hongand WenShi Wei

Abstract Background:Postischemic microglial activation may contribute to neuronal damage through the release of large amounts of proinflammatory cytokines and neurotoxic factors. The involvement of microRNAs (miRNAs) in the pathogenesis of disorders related to the brain and central nervous system has been previously studied, but it remains unknown whether the production of proinflammatory cytokines is regulated by miRNAs. Methods:BV2 and primary rat microglial cells were activated by exposure to oxygenglucose deprivation (OGD). Global cerebral ischemia was induced using the fourvessel occlusion (4VO) model in rats. Induction of pro inflammatory and neurotoxic factors, such as tumor necrosis factor (TNF)α, interleukin (IL)1β, and nitric oxide (NO), were assessed by ELISA, immunofluorescence, and the Griess assay, respectively. The miRNA expression profiles of OGDactivated BV2 cells were subsequently compared with the profiles of resting cells in a miRNA microarray. BV2 and primary rat microglial cells were transfected with miR181c to evaluate its effects on TNFαproduction after OGD. In addition, a luciferase reporter assay was conducted to confirm whether TNFαis a direct target of miR181c. Results:OGD induced BV2 microglial activationin vitro, as indicated by the overproduction of TNFα, IL1β, and NO. Global cerebral ischemia/reperfusion injury induced microglial activation and the release of proinflammatory cytokines in the hippocampus. OGD also downregulated miR181c expression and upregulated TNFαexpression. Overproduction of TNFαafter OGDinduced microglial activation provoked neuronal apoptosis, whereas the ectopic expression of miR181c partially protected neurons from cell death caused by OGDactivated microglia. RNAinterferencemediated knockdown of TNFαphenocopied the effect of miR181cmediated neuronal protection, whereas overexpression of TNFαblocked the miR181cdependent suppression of apoptosis. Further studies 0 showed that miR181c could directly target the 3 untranslated region of TNFαmRNA, suppressing its mRNA and protein expression. Conclusions:Our data suggest a potential role for miR181c in the regulation of TNFαexpression after ischemia/ hypoxia and microgliamediated neuronal injury. Keywords:Microglial activation, Hypoxia, Neuronal apoptosis, miR181c, TNFα

* Correspondence: [e-mail]; wenshiwei0206@yahoo. com.cn 3 Department of Neurology, Huashan Hospital, Fudan University, 12 Wulumuqi Road Central, Shanghai 200040, China 1 Department of Neurology, Huadong Hospital, Fudan University, 221 West Yan An Road, Shanghai 200040, China Full list of author information is available at the end of the article

© 2012 Zhang 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.