Endotoxin alters the expression of extracellular matrix proteins by cultured endothelial cells

In order to understand changes that occur in the extracellular matrix during acute lung injury, we have observed the effects of endotoxin on cultured bovine pulmonary artery endothelial cells. Following treatment with endotoxin, endothelial cell monolayers altered their production of [3H] proline-labeled procollagen (types III and V), fibronectin, and a 43 kDa protein, Secreted Protein Acidic and Rich in Cysteines (SPARC). Following their secretion into the culture medium, these proteins were immunoprecipitated with specific antibodies for characterization and quantification. Our results show that endotoxin decreased the levels of procollagen and fibronectin, whereas the production of SPARC was augmented approximately twofold. Northern blot analyses revealed no changes in the expression of SPARC or beta-actin transcripts, whereas the expression of fibronectin transcript increased two- to threefold. Our data suggest that under acute exposure to endotoxin, cultured bovine pulmonary endothelial cells differentially change their expression of extracellular proteins.