Transforming Growth Factor-β and Interleukin-1 β Signaling Pathways Converge on the Chemokine CCL20 Promoter

CCL20 is the only chemokine ligand for the chemokine receptor CCR6, which is expressed by the critical antigen presenting cells, dendritic cells. Increased expression of CCL20 is likely involved in the increased recruitment of dendritic cells observed in fibroinflammatory diseases such as chronic obstructive pulmonary disease (COPD). CCL20 expression is increased by the proinflammatory cytokine IL-1 beta. We have determined that IL-1 beta-dependent CCL20 expression is also dependent on the multifunctional cytokine TGF-beta. TGF-beta is expressed in a latent form that must be activated to function, and activation is achieved through binding to the integrin alpha v beta 8 (itgb8). Here we confirm correlative increases in alpha v beta 8 and IL-1 beta with CCL20 protein in lung parenchymal lysates of a large cohort of COPD patients. How IL-1 beta- and alpha v beta 8-mediated TGF-beta activation conspire to increase fibroblast CCL20 expression remains unknown, because these pathways have not been shown to directly interact. We evaluate the 5'-flanking region of CCL20 to determine that IL-1 beta -driven CCL20 expression is dependent on alpha v beta 8-mediated activation of TGF-beta. We identify a TGF-beta-responsive element (i. e. SMAD) located on an upstream enhancer of the human CCL20 promoter required for efficient IL-1 beta-dependent CCL20 expression. By chromatin immunoprecipitation, this upstream enhancer complexes with the p50 subunit of NF-kappa B-on a NF-kappa B-binding element close to the transcriptional start site of CCL20. These interactions are confirmed by electromobility shift assays in nuclear extracts from human lung fibroblasts. These data define a mechanism by which alpha v beta 8-dependent activation of TGF-beta regulates IL-1 beta-dependent CCL20 expression in COPD.