Regulation of German cockroach extract-induced IL-8 expression in human airway epithelial cells

Abstract

BACKGROUND: Cockroaches have been known as a cause of respiratory allergies such as asthma. IL-8 plays an integral role in the coordination and persistence of the inflammatory process in the chronic inflammation of the airways in asthma. OBJECTIVE: We investigated the mechanism by which German cockroach extract (GCE) triggers IL-8 release from human airway epithelial cells. METHODS: Chemical inhibitors were pretreated before addition of GCE for promoter activity and protein synthesis of IL-8. The Transcriptional activity of IL-8 promoter was analysed by mutational, deletional anaylsis and electrophoretic mobility shift assay (EMSA). RESULTS: Stimulation of H292 cells with GCE resulted in a time- and concentration-dependent induction of IL-8 transcription and protein synthesis. IL-8 promoter deletion analysis indicated that position -132 to +41 was essential for GCE-induced IL-8 transcription, and mutants with substitutions in activator protein (AP)-1, nuclear factor (NF)-IL6 and NF-kappaB-binding sites revealed a requirement for NF-kappaB and NF-IL6, but not AP-1, in GCE-induced activation of the IL-8 promoter. The DNA-binding activities of NF-kappaB and NF-IL6 were induced by GCE, as determined by EMSA. The chemical inhibition of extracellular signal-regulated kinase (ERK) attenuated GCE-induced transcriptional activity and protein synthesis. In addition, through aprotinin treatment and PAR2 small interfering RNA transfection, it was proven that protease of GCE is consistent with the regulation of GCE-induced IL-8. CONCLUSION: We conclude that GCE with protease activity-induced IL-8 expression is regulated by transcriptional activation of NF-kappaB and NF-IL6 coordinating with the ERK pathway in human airway epithelial cells.