IL-17 enhances IL-1β-mediated CXCL-8 release from human airway smooth muscle cells

Recent studies into the pathogenesis of airway disorders such as asthma have revealed a dynamic role for airway smooth muscle cells in the perpetuation of airway inflammation via secretion of cytokines and chemokines. In this study, we evaluated whether IL-17 could enhance IL-1 beta-mediated CXCL- 8 release from human airway smooth muscle cells ( HASMC) and investigated the upstream and downstream signaling events regulating the induction of CXCL-8. CXCL- 8 mRNA and protein induction were assessed by real- time RT- PCR and ELISA from primary HASMC cultures. HASMC transfected with site- mutated activator protein ( AP)-1/NF-kappa B CXCL-8 promoter constructs were treated with selective p38, MEK1/2, and phosphatidylinositol 3-kinase ( PI3K) inhibitors to determine the importance of MAPK and PI3K signaling pathways as well as AP-1 and NF-kappa B promoter binding sites. We demonstrate IL-17 induced and synergized with IL-1 beta to upregulate CXCL-8 mRNA and protein levels. Erk1/2 and p38 modulated IL-17 and IL-1 beta CXCL- 8 promoter activity; however, IL-1 beta also activated the PI3K pathway. The synergistic response mediating CXCL- 8 promoter activity was dependent on both MAPK and PI3K signal transduction pathways and required the cooperation of AP-1 and NF-kappa B cis-acting elements upstream of the CXCL-8 gene. Collectively, our observations indicate MAPK and PI3K pathways regulate the synergy of IL-17 and IL-1 beta to enhance CXCL-8 promoter activity, mRNA induction, and protein synthesis in HASMC via the cooperative activation of AP-1 and NF-kappa B trans-acting elements.