[Lipopolysaccharide binding protein enhances intratracheally administrated lipopolysaccharide-induced acute lung...

We examined the role of lipopolysaccharide binding protein (LBP) in the airspace and the CD14 receptor on alveolar macrophages in TNF alpha production and neutrophil (PMN) sequestration in lungs induced by intratracheal injection of lipopolysaccharide (LPS). LPS alone (Salmonella minnesota wild-type; 20 ng) or LPS + LBP complex [LPS (20 ng) + rabbit LBP (500 ng); preincubated for 30 min at 37 degrees C] was injected intratracheally into isolated rabbit lungs perfused with lactate-Ringer-albumin solution. Human PMN (5 x 10(7)) were added to the perfusate after 2 hr perfusion. Samples of lung perfusate were collected every 30 min for 180 min, after which bronchoalveolar lavage (BAL) was also performed. TNF alpha concentration in the perfusate and BAL fluid were determined using a bioassay with L-929 fibroblasts. PMN accumulation in the lung was determined by myeloperoxidase assay of the lung homogenate. LPS alone did not significantly increase TNF alpha production or PMN accumulation in lungs, whereas LPS/LBP complex increased TNF alpha concentration in the perfusate and PMN accumulation. Intratracheal injection of anti-CD14 antibody (40 micrograms) with LPS/LBP complex prevented TNF alpha production and subsequent PMN sequestration. We conclude that LBP in the airspace enhances the effect of LPS on TNF alpha production via a CD14-dependent pathway, and this subsequently contributes to PMN sequestration in the lungs. Airspace accumulation of LBP secondary to increased vascular and epithelial permeability may play a critical role in the development of septic shock and lung injury by promoting TNF alpha production via a CD14-dependent mechanism.