We investigated the potential role of IL-17A in the induction of granulocyte colony-stimulating factor (G-CSF), a critical granulopoietic growth factor, in human renal proximal tubular epithelial cells. Human renal proximal tubular cells (HK-2, ATCC) were used to characterize the effects of IL-17A or IL-17F on G-CSF production, using ELISA, real-time RT-PCR, and immunoblotting. The cell surface expression of IL-17 receptors (IL-17Rs) was analyzed by flow cytometry. IL-17A stimulation of proximal tubular cells led to a dose- and time-dependent increase in secreted G-CSF. This effect was dependent on mRNA transcription and protein translation. Real-time RT-PCR demonstrated that G-CSF mRNA expression reached a maximum level at 6 h following IL-17A stimulation and that this increase was dose dependent. Both IL-17RA and IL-17RC were expressed on proximal tubular cells. IL-17A also enhanced TNF-α- or IL-1β-mediated G-CSF secretion from cells. Additionally, IL-17A induced MAPK (ERK1/2 but not p38 MAPK or JNK) activation, and pharmacological inhibitors of MEK1/2 (U0126) but not of p38 MAPK (SB203580) or JNK (SP600125), significantly blocked the IL-17A-mediated G-CSF release. We demonstrated the potential ability of IL-17A to induce G-CSF in renal proximal tubular cells. It is proposed that IL-17A may play an important role in neutrophil transmigration and activation via stimulation of G-CSF in tubular injury.