Proinflammatory cytokines induce liver and activation-regulated chemokine/macrophage inflammatory protein-3α/CCL20 in mucosal epithelial cells through NF-κB

Abstract

Liver and activation-regulated chemokine (LARC)/CCL20 is expressed by surface-lining epithelial and epidermal cells, and is likely to link innate and acquired immunity by attracting immature dendritic cells, effector memory T cells and B cells via CCR6. Here we examined the mechanism of LARC expression in epithelial-type cells. Either IL-1β or tumor necrosis factor (TNF)-α strongly induced LARC mRNA in intestinal cell lines Caco-2 and T84, while both were effective on HEK 293T cells. Induction of LARC was also demonstrated in the intestinal epithelium of BALB/c mice upon treatment with IL-1α or TNF-α. Transient transfection assays using murine LARC promoter–reporter constructs identified a region essential for IL-1β- or TNF-α-induced promoter activation in Caco-2 and 293T cells. Using site-directed mutagenesis, we demonstrated that an NF-κB site located between –96 and –87 bp upstream from the transcriptional start site was both necessary and sufficient for IL-1β- or TNF-α-induced promoter activation in Caco-2 and 293T cells. Electrophoretic mobility shift assays demonstrated that p50/p65 heterodimer and p65 homodimer of NF-κB bound to this site in 293T cells upon treatment with IL-1β and TNF-α, and p50/p65 heterodimer bound to this site in Caco-2 cells upon treatment with IL-1β. Co-expression of constitutively active p65 strongly activated the promoter construct carrying the intact NF-κB site in 293T and Caco-2 cells. Collectively, LARC expression in intestinal epithelial-type cells is induced by proinflammatory cytokines such as IL-1 and TNF-α primarily through activation of NF-κB.