Clinical surfactant preparations mediate SOD and catalase uptake by type II cells and lung tissue

Pulmonary surfactant mixtures are rapidly taken up by alveolar type II cells and thus may serve as vectors for the pulmonary delivery of antioxidant enzymes to the alveolar epithelium. We prepared emulsions of Survanta with superoxide dismutase (CuZn-SOD) and catalase and quantified their cellular uptake both in vitro and in vivo. Incubations of fetal lung epithelial cells with an emulsion of Survanta plus SOD and catalase mixtures resulted in significant augmentation of SOD and catalase activities (12.8 +/- 4.6 U SOD/mu g DNA; 7.49 +/- 2.21 U catalase/mu g DNA). These numbers were significantly greater than those obtained in controls (1.8 U SOD/mu g DNA; 0.55 +/- 0.52 U catalase/mu g DNA), Survanta alone (0.43 U SOD/mu g DNA; 0.16 U catalase/mu g DNA), and SOD and catalase alone (3.47 +/- 5.2 U SOD/mu g DNA; 4.24 +/- 3.0 U catalase/mu g DNA). Intratracheal instillation of the Survanta plus SOD and catalase mixture resulted in significant augmentation of enzymes by the rat lung homogenates. Confocal microscopic analysis revealed the presence of antioxidant enzymes in the cytoplasm of epithelial cells. We concluded that Survanta supplementation, in addition to replenishing surfactant stores, can also enhance the delivery of antioxidant enzymes to alveolar epithelium both in vitro and in vivo.