Cooperation of interleukin-17 and interferon-γ on chemokine secretion in human fetal intestinal epithelial cells

Interleukin (IL)-17 is a newly identified T cell-derived cytokine that can regulate the functions of a variety of cell types. In this study, we investigated the effects of IL-17 and interferon (IFN)-gamma on chemokine secretion in human fetal intestinal epithelial cells. IL-8 and monocyte chemoattractant protein (MCP)-1 secretion by the human fetal intestinal epithelial cell line, intestine-407, was evaluated by ELISA and Northern blot. The expression of IL-17 receptor (R) was analysed by a binding assay using [I-125]-labelled IL-17. The activation of nuclear factor-kappaB (NF-kappaB), NF-IL6 and AP-1 was assessed by an electrophoretic gel mobility shift assay (EMSA). IL-17 induced a dose-dependent increase in IL-8 and MCP-1 secretion. The inducing effects of IL-17 on IL-8 and MCP-1 mRNA abundance reached a maximum as early as 3 h, and then gradually decreased. IL-17 and IFN-gamma synergistically increased IL-8 and MCP-1 secretion and mRNA abundance. IFN-gamma induced a weak increase in IL-17 R mRNA abundance, and incubation with IFN-gamma for 24 h enhanced [I-125]-labelled IL-17-binding by 2.4-fold. IL-17 rapidly induced the phosphorylation and degradation of I kappaB alpha molecules, and the combination of IL-17 and IFN-gamma induced a marked increase in NF-kappaB DNA-binding activity as early as 1.5 h after the stimulation. Furthermore, this combination induced an increase in NF-IL-6 and AP-1 DNA-binding activity. In conclusion, it becomes clear that IL-17 is an inducer of IL-8 and MCP-1 secretion by human fetal intestinal epithelial cells. The combination of IL-17 with IFN-gamma synergistically enhanced chemokine secretion. These effects of IL-17 and IFN-gamma might play an important role in the inflammatory responses in the intestinal mucosa.