Interleukin-17 augments tumor necrosis factor-α-induced granulocyte and granulocyte/macrophage colony-stimulating factor release from human colonic myofibroblasts

Background: Interleukin (IL)-17 is a newly identified T-cell-specific cytokine. In this study, we investigated the effects of IL-17 on colony-stimulating factor (CSF) release in human colonic subepithelial myofibroblasts (SEMFs). Methods: CSF release and mRNA expression were determined by enzyme-linked immunosorbent assay (ELISA) and Northern blotting, respectively. Nuclear factor (NF)-kappa B- and activating protein (AP-1)-DNA binding activities were evaluated by electrophoretic gel mobility shift assays (EMSAs). Results: Unstimulated cells secreted a small amount of granulocyte G- and granulocyte/macrophage (GM)-CSF, and a considerable amount of M-CSF. IL-17 weakly enhanced G-CSF release, but did not affect GM- and M-CSF release. IL-17 selectively enhanced tumor necrosis factor (TNF)-alpha-induced G- and GM-CSF release. The combination of IL-17 plus TNF-alpha induced a marked increase in NF-kappa B- and AP-1-DNA binding activities. The adenovirus-mediated transfer of a stable form of I kappa B alpha and/or a dominant negative mutant of c-Jun markedly inhibited the IL-17 plus TNF-alpha-induced G- and GM-CSF mRNA expression. Furthermore, a stability study showed that IL-17 plus TNF-alpha markedly enhanced the stability of G- and GM-CSF mRNA. Conclusions: IL-17 augments TNF-alpha-induced G- and GM-CSF release via transcriptional and posttranscriptional mechanisms.