ABSTRACT
2,3-Butanedione (DA), a component of artificial butter flavoring, is associated with the development of occupational bronchiolitis obliterans (BO), a disease of progressive airway fibrosis resulting in lung function decline. Neutrophilic airway inflammation is a consistent feature of BO across a range of clinical contexts and may contribute to disease pathogenesis. Therefore, we sought to determine the importance of the neutrophil chemotactic cytokine interleukin-8 (IL-8) in DA-induced lung disease using in vivo and in vitro model systems. First, we demonstrated that levels of Cinc-1, the rat homolog of IL-8, are increased in the lung fluid and tissue compartment in a rat model of DA-induced BO. Next, we demonstrated that DA increased IL-8 production by the pulmonary epithelial cell line NCI-H292 and by primary human airway epithelial cells grown under physiologically relevant conditions at an air-liquid interface. We then tested the hypothesis that DA-induced epithelial IL-8 protein occurs in an epidermal growth factor receptor (EGFR)-dependent manner. In these in vitro experiments we demonstrated that epithelial IL-8 protein is blocked by the EGFR tyrosine kinase inhibitor AG1478 and by inhibition of tumor necrosis factor-alpha converting enzyme using the small molecule inhibitor, TAPI-1. Finally, we demonstrated that DA-induced IL-8 is dependent upon ERK1/2 and Mitogen activated protein kinase kinase activation downstream of EGFR signaling using the small molecule inhibitors AG1478 and PD98059. Together these novel in vivo and in vitro observations support that EGFR-dependent IL-8 production occurs in DA-induced BO. Further studies are warranted to determine the importance of IL-8 in BO pathogenesis.
