Pro-inflammatory gene expression and neurotoxic effects of activated microglia are attenuated by absence of CCAAT/enhancer binding protein β

Background: microglia and astrocytes respond to homeostatic disturbances with profound changes of gene expression. this response,known as glial activation or neuroinflammation,can be detrimental to the surrounding tissue. the transcription factor ccaat/enhancer binding protein β (c/ebpβ) is an important regulator of gene expression in inflammation but little is known about its involvement in glial activation. to explore the functional role of c/ebpβ in glial activation we have analyzed pro-inflammatory gene expression and neurotoxicity in murine wild type and c/ebpβ-null glial cultures.methods: due to fertility and mortality problems associated with the c/ebpβ-null genotype we developed a protocol to prepare mixed glial cultures from cerebral cortex of a single mouse embryo with high yield. wild-type and c/ebpβ-null glial cultures were compared in terms of total cell density by hoechst-33258 staining; microglial content by cd11b immunocytochemistry; astroglial content by gfap western blot; gene expression by quantitative real-time pcr,western blot,immunocytochemistry and griess reaction; and microglial neurotoxicity by estimating map2 content in neuronal/microglial cocultures. c/ebpβ dna binding activity was evaluated by electrophoretic mobility shift assay and quantitative chromatin immunoprecipitation.results: c/ebpβ mrna and protein levels,as well as dna binding,were increased in glial cultures by treatment with lipopolysaccharide (lps) or lps + interferon γ (ifnγ). quantitative chromatin immunoprecipitation showed binding of c/ebpβ to pro-inflammatory gene promoters in glial activation in a stimulus- and gene-dependent manner. in agreement with these results,lps and lps+ifnγ induced different transcriptional patterns between pro-inflammatory cytokines and no synthase-2 genes. furthermore,the expressions of il-1β and no synthase-2,and consequent no production,were reduced in the absence of c/ebpβ. in addition,neurotoxicity elicited by lps+ifnγ-treated microglia co-cultured with neurons was completely abolished by the absence of c/ebpβ in microglia.conclusions: these findings show involvement of c/ebpβ in the regulation of pro-inflammatory gene expression in glial activation,and demonstrate for the first time a key role for c/ebpβ in the induction of neurotoxic effects by activated microglia. © 2011 straccia et al; licensee biomed central ltd.