Transcriptional regulation of interleukin (IL)-8 by bradykinin in human airway smooth muscle cells involves prostanoid-dependent activation of AP-1 and nuclear factor (NF)-IL-6 and prostanoid-independent activation of NF-kappaB.

Bradykinin (BK) is a potent neutrophil chemotractant, proinflammatory mediator, and angiogenic factor, which acts through G protein-coupled receptors (GPCRs). Here we studied the mechanisms involved in IL-8 generation by BK in human airway smooth muscle cells focusing on the transcription factors involved and role of endogenous prostanoids in transcription factor activation. Transfection experiments with wild-type IL-8 promoter constructs or constructs with NF-kappaB, AP-1, and NF-IL-6 binding site mutations suggested that all three transcription factors were necessary for optimal IL-8 expression. BK increased NF-kappaB, AP-1, and NF-IL-6 binding to the IL-8 promoter by electrophoretic mobility shift assay. NF-kappaB, the most important transcription factor in the current study, was translocated to the nucleus after BK stimulation. Indomethacin, a cyclooxygenase inhibitor, partially inhibited IL-8 release and the promoter binding of AP-1 and NF-IL-6, but not NF-kappaB. Furthermore, exogenous prostaglandin E2 stimulated AP-1 and NF-IL-6 binding to the IL-8 promoter. The anti-inflammatory glucocorticoid dexamethasone inhibited NF-kappaB translocation and the promoter binding of NF-kappaB, AP-1, and NF-IL-6. These results are the first to delineate the transcription factors involved in BK induced IL-8 release. Transcriptional activation of the IL-8 promoter by BK involves the prostanoid-independent activation of NF-kappaB, and prostanoid-dependent activation of AP-1 and NF-IL-6 plays a key role in augmenting the response. Endogenous prostanoid generation in response to GPCR ligands such as BK may be an important mechanism whereby GPCRs signal to the nucleus to maximize the transcription of inflammatory response genes.