P2Y(2) receptor expression is regulated by C/EBPβ during inflammation in intestinal epithelial cells

Inflammatory bowel diseases are characterized by relapses and remission periods during which numerous factors, including stress factors and nucleotides, are mobilized to re-establish intestinal mucosal homeostasis. We have previously found that expression of the P2Y(2) nucleotide receptor is increased in colonic tissue isolated from inflammatory bowel disease patients as well as in a mouse model of colitis, and that P2Y(2) transcription is regulated in part by nuclear factor κB (NF-κB) p65. Transcription factor DNA-binding site analysis identified three potential CCAAT/enhancer-binding protein β (C/EBPβ) binding sites in the P2Y(2) proximal promoter. We then assessed the role of C/EBP transcription factors in the regulation of P2Y(2) in intestinal epithelial cells (IECs). We identified a region between -229 and -220 bp upstream of the transcription initiation site as a DNA-binding site for C/EBPβ, by electrophoretic mobility and supershift assays. Mutagenesis of this site decreased C/EBPβ-dependent P2Y(2) expression, as assessed by luciferase assays. In vivo, C/EBPβ as well as P2Y(2) expression was increased in colonic IECs isolated from mice with dextran sulfate sodium-induced acute colitis. In contrast, P2Y(2) expression was decreased in C/EBPβ-deficient mice treated with dextran sulfate sodium. Although C/EBPβ was sufficient to induce P2Y(2) transcription, the effect of C/EBPβ and NF-κB p65 on receptor transcription was synergistic. Chromatin immunoprecipitation assays revealed that both proteins simultaneously bind to the P2Y(2) promoter. Thus, we have identified C/EBPβ as a novel regulator of P2Y(2) expression.