Anti-oxidant effects of commercial surfactants

Several investigators have assessed the role of reactive oxygen species (ROS) in the development of respiratory distress syndrome (RDS) and bronchopulmonary dysplasia, as well as the importance of antioxidant enzymes (AOEs) in preventing them. In particular, increased lung cell superoxide dismutase (SOD) and catalase (CAT) activities have been consistently associated with protection from oxygen toxicity. The failure to increase AOE activities during hyperoxia results in increased susceptibility to severe lung injury. Moreover, increased oxidant stress to the lung determines also an injury of surfactant, with surfactant replacement mitigating the pathophysiology of oxygen toxicity. Furthermore, since surfactant is continuously taken up by type II cells, it may serve as effective vector for the delivery of AOEs to the epithelium. Therefore, as also suggested by preliminary studies, supplementation of commercial surfactant preparations with AOEs may further enhance surfactant anti-oxidant effects.
An Italian group has conducted an in vitro study to evaluate the potential anti-oxidant properties of exogenous natural surfactants commonly used for the treatment of preterm infants with nRDS, namely Infasurf, Curosurf, Survanta, and Alveofact, before and after SOD and CAT supplementation. In particular, the superoxide dismutase (SOD) and catalase (CAT) activity, the scavenger activity against hydrogen peroxide (H₂O₂), and its changes after the addition of SOD and CAT were measured.
Overall, results showed that all the surfactants exhibited a measurable amount of SOD and CAT activity even without supplementation. Curosurf and Survanta seem to have higher antioxidant effect than Infasurf and Alveofact. It is likely that differences observed among surfactants are related to their particular composition. The highest phospholipid concentration and recommended dose of Curosurf suggests that its scavenger activity for each treatment dose is higher than that of Survanta.
Finally, supplementation with SOD and CAT induced a remarkable increase of antioxidant action in all studied surfactants. Supplementation of commercial surfactant preparations with SOD and CAT might therefore represents a promising progress in the treatment of preterm infants with nRDS. Further studies on this topic will provide new evidence to confirm and complete these findings.

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