NF-κB-dependent synergistic regulation of CXCL10 gene expression by IL-1β and IFN-γ in human intestinal epithelial cell lines

BACKGROUND AND AIMS: Little is known about the intestinal epithelial expression and secretion of CXCL10 (IP-10), a chemokine involved in recruiting T cells and monocytes. We aimed to study CXCL10 gene expression and regulation by the pro-inflammatory cytokines interleukin (IL)-1β, interferon (IFN)-γ and tumour necrosis factor (TNF)-α in intestinal epithelial cell lines. MATERIALS AND METHODS: CXCL10 expression and secretion kinetics were assessed in Caco-2, HT-29 and DLD1 human colon epithelial cells, treated with IL-1β, TNF-α, IFN-γ alone or in combination with each other by real-time polymerase chain reaction (PCR), Northern blotting and enzyme-linked immunoabsorbent assay (ELISA). Transient transfections with TGL-IP10 (CXCL10 promoter) and TGL-IP10-κB2 mutant promoter and gelshifts and supershifts for nuclear factor (NF)-κB were also performed. RESULTS: Real-time PCRs and ELISA experiments revealed that IL-1β was the strongest and earliest inducer of CXCL10 messenger ribonucleic acid (mRNA) expression and protein secretion in Caco-2 cell line, whereas INF-γ had a delayed kinetics. There was a strong synergistic effect of either TNF-α or IL-1β with IFN-γ both on CXCL10 mRNA expression and protein secretion in all three cell lines. Real-time PCR and ELISA experiments using a specific NF-κB inhibitor and transfection experiments with a NF-κB-binding defective CXCL10 promoter construct revealed that the induction of CXCL10 by IL-1β and its synergism with IFN-γ is NF-κB dependent. CONCLUSION: These data demonstrate that in colonic epithelial cells, depending on the cellular context and utilizing the NF-κB pathway, IL-1β alone and/or in synergism with IFN-γ may play a major role in the induction of CXCL10.