Mucoid Pseudomonas aeruginosa, TNF-alpha, and IL-1 beta, but not IL-6, induce human beta-defensin-2 in respiratory epithelia

Cultured lung epithelial cells release antibacterial activity upon contact with Pseudomonas aeruginosa (PA), which is impaired in cystic fibrosis (CF) . In order to identify the factors responsible for killing PA by a biochemi cal approach, we purified antimicrobial activity from supernatants of the A 549 lung epithelial cell line, previously stimulated with PA bacteria, by s ubsequent high performance liquid chromatography. NH,terminal sequencing of a major bactericidal compound revealed it to be identical with human beta- defensin-2 (hBD-2). A mucoid phenotype of PA, but not two nonmucoid PA stra ins, high concentrations (> 10 mu g/ml) of PA lipopolysaccharide, tumor nec rosis factor alpha, and interleukin (IL)-1 beta, but not IL-6, dose-depende ntly induced hBD-2 messenger RNA in cultured normal bronchial, tracheal, as well as normal and CF-derived nasal epithelial cells. Genomic analysis of hBD-2 revealed a promoter region containing several putative transcription factor binding sites, including nuclear factor (NF) KB, activator protein ( AP)-1, AP-2, and NF-IL-6, known to be involved in the regulation of inflamm atory responses. Thus, hBD-2 represents a major inducible antimicrobial fac tor released by airway epithelial cells either on contact with mucoid PA or by endogenously produced primary cytokines. Therefore, it might be importa nt in lung infections caused by mucoid PA, including those seen in patients with CF.