Respiratory epithelial cells regulate lung inflammation in response to inhaled endotoxin

Abstract

To determine the role of respiratory epithelial cells in the inflammatory response to inhaled endotoxin, we selectively inhibited NF-κB activation in the respiratory epithelium using a mutant IκB-α construct that functioned as a dominant negative inhibitor of NF-κB translocation (dnIκB-α). We developed two lines of transgenic mice in which expression of dnIκB-α was targeted to the distal airway epithelium using the human surfactant apoprotein C promoter. Transgene expression was localized to the epithelium of the terminal bronchioles and alveoli. After inhalation of LPS, nuclear translocation of NF-κB was evident in bronchiolar epithelium of nontransgenic but not of transgenic mice. This defect was associated with impaired neutrophilic lung inflammation 4 h after LPS challenge and diminished levels of TNF-α, IL-1β, macrophage inflammatory protein-2, and KC in lung homogenates. Expression of TNF-α within bronchiolar epithelial cells and of VCAM-1 within peribronchiolar endothelial cells was reduced in transgenic animals. Thus targeted inhibition of NF-κB activation in distal airway epithelial cells impaired the inflammatory response to inhaled LPS. These data provide causal evidence that distal airway epithelial cells and the signals they transduce play a physiological role in lung inflammation in vivo.