| Pulmonary surfactant is a lipoprotein complex that forms a film at the air-water interface which lowers the surface tension (gamma) and thus reduces the work of breathing and prevents alveolar collapse. This study, using the captive bubble tensiometer, showed that SP-B and/or SP-C is required for rapid phospholipid (PL) adsorption to the interface, their ability to reach and maintain low gammas during film compression and for proper PL respreading during expansion. The results confirmed the existence of specific interactions between SP-B and phosphatidylglycerol. SPA acts synergistically with SP-B but not with SP-C.;Surface activity of reconstituted mixtures combining PL, SP-B and/or SP-C isolated from BLES (oxidized/non-oxidized) indicated that oxidative modifications of these surfactant proteins affected the surface activity to a greater extent than the PL modifications. Whereas the presence of non-oxidized SP-C in samples containing oxidized SP-B could not rescue the surface activity, when control SP-B was added to samples reconstituted with control PL and oxidized SP-C, a significant improvement was observed in adsorption, gamma reduction and respreading.;These studies provided insights regarding events that could occur under oxidative stress in vivo where the surfactant system is inactivated. The ultimate relevance of this study is to provide insights for the improvement of pulmonary therapies.;Reactive oxygen species damage surfactant. Employing HOCl/-OCl or the Fenton reaction I oxidized bovine lipid extract surfactant (BLES) and investigated its biochemical alterations and biophysical activity. Both, PLs and the surfactant proteins SP-B and SP-C, undergo changes during oxidation that significantly decreased their biophysical activity. ROS inhibited BLES surface. PL adsorption was prolonged, gammamin and gammamax were elevated and surface activity deteriorated progressively during cycling. SP-A addition restored surface properties to preoxidation levels. SP-A decreased the film compressibility allowing films to achieve low surface tensions; stabilized films at low gammas; and enhanced surfactant respreadability during film expansion. Studies using recombinant SP-As demonstrated that an intact carbohydrate-recognition domain and oligomeric assembly are essential for this function. |
