CD14-dependent lipopolysaccharide-induced beta-defensin-2 expression in human tracheobronchial epithelium

The induction of host antimicrobial molecules following binding of pathogen components to pattern recognition receptors such as CD14 and the Toll-like receptors (TLRs) is a key feature of innate immunity. The human airway epithelium is an important environmental interface, but LPS recognition pathways have not been determined. We hypothesized that LPS would trigger beta-defensin (hBD2) mRNA in human tracheobronchial epithelial (hTBE) cells through a CD14-dependent mechanism, ultimately activating NF-kappa B. An average 3-fold increase in hBD2 mRNA occurs 24 h after LPS challenge of hTBE cells. For the first time, we demonstrate the presence of CD14 mRNA and cell surface protein in hTBE cells and show that CD14 neutralization abolishes LPS induction of hBD2 mRNA. Furthermore, we demonstrate TLR mRNA in hTBE cells and NF-kappa B activation following LPS. Thus, LPS induction of hBD2 in hTBE cells requires CD14, which may complex with a TLR to ultimately activate NF-kappa B.