Microarray Analysis Supports a Role for CCAAT/Enhancer-binding Protein-β in Brain Injury

Abstract

CCAAT/enhancer-binding protein-␤ (C/EBP␤) is a transcription factor that plays an important role in regulating cell growth and differentiation. This protein plays a central role in lymphocyte and adipocyte differentiation and hepatic regeneration and in the control of inflammation and immunity in the liver and in cells of the myelomonocytic lineage. Our previous studies suggested that this protein could also have important functions in the brain. Therefore, we were interested in the identification of downstream targets of this transcription factor in cells of neural origin. We performed cDNA microarray analysis and found that a total of 48 genes were up-regulated in C/EBP␤-overexpressing neuronal cells. Of the genes that displayed significant changes in expression, several were involved in inflammatory processes and brain injury. Northern blot analysis confirmed the up-regulation of ornithine decarboxylase, 24p3/LCN2, GRO1/KC, spermidine/spermine N 1 -acetyltransferase, xanthine dehydrogenase, histidine decarboxylase, decorin, and TM4SF1/L6. Using promoter-luciferase reporter transfection assays, we showed the ornithine decarboxylase and 24p3 genes to be biological downstream targets of C/EBP␤ in neuroblastoma cells. Moreover, the levels of C/EBP␤ protein were significantly induced after neuronal injury, which was accompanied by increased levels of cyclooxygenase-2 enzyme. This strongly supports the concept that C/EBP␤ may play an important role in brain injury.

Stress Activation of Mammary Epithelial Cell Xanthine Oxidoreductase Is Mediated by p38 MAPK and CCAAT/Enhancer-binding Protein-β

“…Thus, C/EBP␤ is essential for XOR expression and regulation in mouse mammary epithelial cells, and its association with the XOR upstream DNA can be blocked by inhibition of p38 MAPK. These data are consistent with results for rat XOR activation by C/EBP␤ in NIH3T3 cells (42) and amplify a recent report that revealed increased XOR mRNA accumulation in mouse neuronal cells following transfection with a C/EBP␤ cDNA expression clone (43). Thus, C/EBP␤ may be essential for XOR regulation in many different cells.…”

Loss of c/EBP-β activity promotes the adaptive to apoptotic switch in hypoxic cortical neurons

“…Although not directly confirmed, the relative benefit of the full-length over the ΔTAD construct suggests that c/EBP-β may directly induce the expression of pro-survival genes. Microarray analyses indicate that c/EBP-β regulates a class of genes involved in polyamine synthesis including ornithine decarboxylase (ODC) and spermidine acetyl-transferase (Cortes-Canteli et al, 2004). Both enzymes are important for developing and mature neurons, and the observation that knock-down of ODC exacerbates stroke size following middle cerebral artery occlusion suggest these encode some survival function as well (Raghavendra Rao et al, 2001).…”

CCAAT/Enhancer-Binding Protein α

“…We have previously demonstrated that cell lines stably transfected with C/EBPβ exhibited an increase in the expression of many genes involved in inflammation and brain injury (Cortes-Canteli et al, 2004). In addition, we have shown that when these cells were subjected to injury using an in vitro "scratch-wound" model, the expression of C/EBPβ was also up-regulated.…”

“…We have demonstrated that C/EBPβ serves as a critical factor in neuronal differentiation (Cortes-Canteli et al, 2002). In addition, using microarray analysis in neuronal cells overexpressing C/EBPβ, we have found that this protein induces the expression of several genes involved in inflammatory processes and brain injury (Cortes-Canteli et al, 2004).…”

“…Next, we analyzed the expression of 24p3/LCN2 and histidine decarboxylase, two genes up-regulated by C/EBPβ (Cortes-Canteli et al, 2004) and probably implicated in inflammation and brain injury. Fig.…”