IL-1β activates C/EBP-β and δ in human enterocytes through a mitogen-activated protein kinase signaling pathway

Abstract

The enterocyte is an active participant in the inflammatory and metabolic response to sepsis, endotoxemia and other critical illnesses and is the site for cytokine and acute phase protein production in these conditions. The role of the CCAAT/enhancer binding protein (C/EBP) family of transcription factors in the response to inflammatory stimuli in the enterocyte is not well understood. In the present study, we treated Caco-2 cells with IL-1β and determined C/EBP DNA binding activity by electrophoretic mobility shift assay. The involvement of the α, β, and δ isoforms was determined by supershift analysis and Western blot analysis of proteins from the nuclear fraction. The role of the mitogen-activated protein kinase (MAPK) signaling pathway was assessed by treating cells with the MAPK inhibitor PD-98059. Treatment of the Caco-2 cells with IL-1β resulted in increased CCAAT/enhancer binding protein DNA binding activity. Supershift analysis and Western blotting indicated that this response to IL-1β mainly reflected the δ isoform, and to a lesser degree the β isoform. Treatment of the cells with PD-98059 inhibited the IL-1β-induced increase in β and δ activity. The results suggest that members of the CCAAT/enhancer binding protein family of transcription factors are activated in enterocytes during inflammatory conditions characterized by high levels of IL-1β.