title: Inhibition of CD200R1 expression by C/EBP β in reactive microglial cells.
abstract: BACKGROUND
  In physiological conditions, it is postulated that neurons control microglial reactivity through a series of inhibitory mechanisms, involving either cell contact-dependent, soluble-factor-dependent or neurotransmitter-associated pathways. In the current study, we focus on CD200R1, a microglial receptor involved in one of these cell contact-dependent mechanisms. CD200R1 activation by its ligand, CD200 (mainly expressed by neurons in the central nervous system),is postulated to inhibit the pro-inflammatory phenotype of microglial cells, while alterations in CD200-CD200R1 signalling potentiate this phenotype. Little is known about the regulation of CD200R1 expression in microglia or possible alterations in the presence of pro-inflammatory stimuli.
  
  
  METHODS
  Murine primary microglial cultures, mixed glial cultures from wild-type and CCAAT/enhancer binding protein β (C/EBPβ)-deficient mice, and the BV2 murine cell line overexpressing C/EBPβ were used to study the involvement of C/EBPβ transcription factor in the regulation of CD200R1 expression in response to a proinflammatory stimulus (lipopolysaccharide (LPS)). Binding of C/EBPβ to the CD200R1 promoter was determined by quantitative chromatin immunoprecipitation (qChIP). The involvement of histone deacetylase 1 in the control of CD200R1 expression by C/EBPβ was also determined by co-immunoprecipitation and qChIP.
  
  
  RESULTS
  LPS treatment induced a decrease in CD200R1 mRNA and protein expression in microglial cells, an effect that was not observed in the absence of C/EBPβ. C/EBPβ overexpression in BV2 cells resulted in a decrease in basal CD200R1 mRNA and protein expression. In addition, C/EBPβ binding to the CD200R1 promoter was observed in LPS-treated but not in control glial cells, and also in control BV2 cells overexpressing C/EBPβ. Finally, we observed that histone deacetylase 1 co-immunoprecipitated with C/EBPβ and showed binding to a C/EBPβ consensus sequence of the CD200R1 promoter in LPS-treated glial cells. Moreover, histone deacetylase 1 inhibitors reversed the decrease in CD200R1 expression induced by LPS treatment.
  
  
  CONCLUSIONS
  CD200R1 expression decreases in microglial cells in the presence of a pro-inflammatory stimulus, an effect that is regulated, at least in part, by C/EBPβ. Histone deacetylase 1 may mediate C/EBPβ inhibition of CD200R1 expression, through a direct effect on C/EBPβ transcriptional activity and/or on chromatin structure.
authors: Department of Cerebral Ischemia and Neurodegeneration, Institut d'Investigacions Biomèdiques de Barcelona-Consejo Superior de Investigaciones Científicas (CSIC), Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.
authors: Guido
authors: G
authors: Dentesano
authors: Marco
authors: M
authors: Straccia
authors: Aroa
authors: A
authors: Ejarque-Ortiz
authors: Josep M
authors: JM
authors: Tusell
authors: Joan
authors: J
authors: Serratosa
authors: Josep
authors: J
authors: Saura
authors: Carme
authors: C
authors: Solà
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000096:biosynthesis* / Q000235:genetics; D022782:CCAAT-Enhancer-Binding Protein-beta; D022762:CCAAT-Enhancer-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D002478:Cells, Cultured; D018920:Coculture Techniques; D005786:Gene Expression Regulation; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017628:Microglia / Q000378:metabolism*; D064446:Orexin Receptors; D011485:Protein Binding / Q000502:physiology; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors* / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D000954:Antigens, Surface; D022782:CCAAT-Enhancer-Binding Protein-beta; D022762:CCAAT-Enhancer-Binding Proteins; C545012:CEBPB protein, human; C501103:Cd200r1 protein, mouse; D064446:Orexin Receptors; D011956:Receptors, Cell Surface