Combined and Independent Action of Proteins SP-B and SP-C in the Surface Behavior and Mechanical Stability of Pulmonary Surfactant Films

Abstract

The hydrophobic proteins SP-B and SP-C are essential for pulmonary surfactant function, even though they are a relatively minor component (<2% of surfactant dry mass). Despite countless studies, their specific differential action and their possible concerted role to optimize the surface properties of surfactant films have not been completely elucidated. Under conditions kept as physiologically relevant as possible, we tested the surface activity and mechanical stability of several surfactant films of varying protein composition in vitro using a captive bubble surfactometer and a novel (to our knowledge) stability test. We found that in the naturally derived surfactant lipid mixtures, surfactant protein SP-B promoted film formation and reextension to lower surface tensions than SP-C, and in particular played a vital role in sustaining film stability at the most compressed states, whereas SP-C produced no stabilization. Preparations containing both proteins together revealed a slight combined effect in enhancing film formation. These results provide a qualitative and quantitative framework for the development of future synthetic therapeutic surfactants, and illustrate the crucial need to include SP-B or an efficient SP-B analog for optimal function.

Interfacial behavior and structural properties of a clinical lung surfactant from porcine source

“…The surface activity of the different surfactant samples was also evaluated using a fully computer-controlled CBS evolved from the apparatus described earlier [28], operated as described elsewhere [29]. The chamber of the CBS was filled with a buffer solution (5 mM TRIS, 150 mM NaCl, pH 7) containing 10% (by mass) sucrose, to increase the density of the buffer solution (1.04 g/mL) above that of surfactants (~1.01 g/mL).…”

Nanoparticles in the lung and their protein corona: the few proteins that count

“…SP-A has multiple functions in innate immunity, PSf spreading and recycling (Kishore et al 2006). SP-B, which was also observed to bind to NPs is a hydrophobic protein that interacts and assists spreading of PSf to maintain low surface tension (Schürch et al 2010). Hence, sequestering of these surfactant proteins could have an influence of the surface tension lowering properties of surfactant.…”

In vitro and in vivo comparison between poractant alfa and the new generation synthetic surfactant CHF5633

“…Further research clearly showed that the dynamic properties of DPPC alone are suboptimal (9), and that the presence of the hydrophobic surfactant proteins (SP), SP-B and SP-C, in natural surfactants significantly enhances the surface tension reduction action and provides stability to compressed films (10,11). Surfactant preparations containing both SP-B and SP-C show a combined effect of surfactant function (12). In fact, animal-derived surfactant preparations, commonly used in clinical practice, contain both SP-B and SP-C (13).…”