Pulmonary surfactant proteins A and D are involved in the early response to intratracheally aerosolized lipopolysaccharide.

SP-A and SP-D are proteins that belong to the family of collectins (C-type lectins group 111). The proteins of this group are multimeric proteins characterized by carbohydrate recognition domains bound to collagen stalks. It is thought that SP-A and SPD may play a role in innate immunity in the lung [ I ] . LPS is an important mediator in the pathogenesis of septic shock and ARDS SP-A and SP-D are able to bind LPS in vitro. SP-A binds the lipid A region of LPS, the region implicated in the pathogenesis of septic shock, and SP-D binds the core domain of LPS [2,3]. Intratracheal aerosolization of LPS in rats is a model to induce typical features of human ARDS [4]. We used this rat model to investigate whether SP-A and SP-D are involved in the immediate response to intratracheally aerosolized LPS. Briefly, rats received either LPS (from Salmonella Enteritidis; 0.5 ml, 16 mg/kg) or PBS (0.5 ml) by intratracheal aerosolization using a miniature nebulizer. The animals continued to breath spontaneously. At timepoints 0, 1, 2, 5, 10 and 24 hours after aerosolization rats were killed and bronchoalveolar lavage was performed. Surfactant phospholipids, total amounts of SP-A and SP-D were measured in bronchoalveolar lavage as a function of time. Carbohydrate binding properties of SP-D were determined in 96-well plates with immobilized mannan-BSA as substrate. LPS-treated rats all showed typical features of ARDS 24 hours after LPS was aerosolied [4]. LPS aerosoliation did not have an effect on total amounts of surfactant phospholipid over time. Total amounts of SP-D did not change during the first 24 hours after LPS aerosolization. In contrast, SP-A levels rose sharply within the first hour after LPS aerosolization and peaked 10 hours after LPS aerosolization (Table 1). LEST", MARTIN VAN EIJK', HERMAN P.M. VAN HELDEN'