Synthetic surfactant scavenges oxidants and protects against hyperoxic lung injury

Injury and mortality after exposure to 100% oxygen can be diminished by surfactants that may operate by mechanisms other than those responsible for surface tension effects. We tested the hypotheses that 1) synthetic surfactant and its components function as antioxidants in vitro and 2) decrements in hyperoxic injury after treatment with a surfactant and its components are associated with decreases in oxidative stress to the lung. A synthetic surfactant (Exosurf) and its non-surface-active components tyloxapol and cetyl alcohol were incubated in an iron-containing hydroxyl radical-generating system to determine their abilities to prevent oxidation of deoxyribose. Doses of tyloxapol, cetyl alcohol, and artificial surfactant diminished the absorbance of thiobarbituric acid-reactive products of deoxyribose. Similarly, tyloxapol, cetyl alcohol, and the surfactant decreased hydroxylated products of salicylate in the same system. Rats were instilled intratracheally with saline, tyloxapol, tyloxapol plus cetyl alcohol, or artificial surfactant and immediately exposed to air or 100% oxygen. After 61 h of oxygen exposure, pleural fluid volume and wet-to-dry lung weight ratios were decreased in animals treated with surfactant and/or its components. There were also decrements in thiobarbituric acid-reactive products of lung tissue. In separate experiments, mean survival of saline-treated rats exposed to 100% oxygen was 67.3 +/- 8.1 h and > 96 h for rats given the surfactant or its components. We conclude that tyloxapol, cetyl alcohol, and Exosurf can function as antioxidants in vitro and their in vivo instillation is associated with reduction in measures of hyperoxic injury, oxidized tissue products, and mortality.