Surfactant components modulate fibroblast apoptosis and type I collagen and collagenase-1 expression

During lung injury, fibroblasts migrate into the alveolar spaces where they can be exposed to pulmonary surfactant. We examined the effects of Survanta and surfactant protein A (SP-A) on fibroblast growth and apoptosis and on type I collagen, collagenase-1, and tissue inhibitor of metalloproteinase (TIMP)-1 expression. Lung fibroblasts were treated with 100, 500, and 1,000 microg/ml of Survanta; 10, 50, and 100 microg/ml of SP-A; and 500 microg/ml of Survanta plus 50 microg/ml of SP-A. Growth rate was evaluated by a formazan-based chromogenic assay, apoptosis was evaluated by DNA end labeling and ELISA, and collagen, collagenase-1, and TIMP-1 were evaluated by Northern blotting. Survanta provoked fibroblast apoptosis, induced collagenase-1 expression, and decreased type I collagen affecting mRNA stability approximately 10-fold as assessed with the use of actinomycin D. Collagen synthesis and collagenase activity paralleled the gene expression results. SP-A increased collagen expression approximately 2-fold and had no effect on collagenase-1, TIMP-1, or growth rate. When fibroblasts were exposed to a combination of Survanta plus SP-A, the effects of Survanta were partially reversed. These findings suggest that surfactant lipids may protect against intraluminal fibrogenesis by inducing fibroblast apoptosis and decreasing collagen accumulation.