Regulation of cytokine- and phorbol ester-mediated interleukin (IL)-8 expression in the absence of presence of pyocyanin in human bronchial epithelial cell line: roles of protein kinase C and mitogen-activated protein kinases

Abstract

Airway epithelial cells are among the first target of environmental stimuli and local cytokine. Pyocyanin, a blue phenazine pigment produced by Pseudomonas aeruginosa, has been shown to synergise with IL-1 in triggering IL-8 release. We hypothesized that the potentiation of IL-8 release would result from activation of protein kinase C (PKC) and subsequent activation of the specific mitogen-activated protein kinase (MAPK) pathways, so we investigated the signaling pathways in human bronchial epithelial cells (BEAS-2B). IL-1β and phorbol 12,13-dibutyrate (PDBu) induced the release of IL-8 but not pyocyanin alone. Pyocyanin potentiated IL-1β- and PDBu-mediated IL-8 release dose-dependently. The PDBu- or IL-1β-stimulated IL-8 release in the presence of pyocyanin required activation of PKC [inhibition by Go 6976 (an selective inhibitor of classic PKC isoforms)]. U0126 (a potent and specific inhibitor of MEK-1/MEK-2), and SB203580 (a selective inhibitor of p38 MAPK) also showed inhibition on IL-1β- and PDBu-mediated IL-8 release in the presence of pyocyanin but SP600125 (a novel selective JNK inhibitor; 10mM) failed to inhibit PDBu-mediated IL-8 release in the presence of pyocyanin. The data demonstrate regulation of IL-8 release by PKC pathways converging on the specific MAPK pathways in the local airway responses.