Effect of surfactant protein A on the physical properties and surface activity of KL4-surfactant |
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| Authors: | Sáenz Alejandra Cañadas Olga Bagatolli Luís A Sánchez-Barbero Fernando Johnson Mark E Casals Cristina |
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| Affiliation: | Department of Biochemistry and Molecular Biology I, Complutense University of Madrid, Madrid, Spain. |
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| Abstract: | SP-A, the major protein component of pulmonary surfactant, is absent in exogenous surfactants currently used in clinical practice. However, it is thought that therapeutic properties of natural surfactants improve after enrichment with SP-A. The objective of this study was to determine SP-A effects on physical properties and surface activity of a new synthetic lung surfactant based on a cationic and hydrophobic 21-residue peptide KLLLLKLLLLKLLLLKLLLLK, KL(4). We have analyzed the interaction of SP-A with liposomes consisting of DPPC/POPG/PA (28:9:5.6, w/w/w) with and without 0.57 mol % KL(4) peptide. We found that SP-A had a concentration-dependent effect on the surface activity of KL(4)-DPPC/POPG/PA membranes but not on that of an animal-derived LES. The surface activity of KL(4)-surfactant significantly improved after enrichment with 2.5-5 wt % SP-A. However, it worsened at SP-A concentrations > or =10 wt %. This was due to the fluidizing effect of supraphysiological SP-A concentrations on KL(4)-DPPC/POPG/PA membranes as determined by fluorescence anisotropy measurements, calorimetric studies, and confocal fluorescence microscopy of GUVs. High SP-A concentrations caused disappearance of the solid/fluid phase coexistence of KL(4)-surfactant, suggesting that phase coexistence might be important for the surface adsorption process. |
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| Keywords: | λm, emission wavelength (nm) λx, excitation wavelength (nm) ARDS, adult respiratory distress syndrome BODIPY-PC, 2-(4,4-difluoro-5,7-dimethyl-4-bora-3α,4α-diaza-s-indacene-3-pentanoyl)-1-hexadecanoyl-sn-glycero-3-phosphocholine Ch, cholesterol CRD, carbohydrate recognition domain DPH, 1,6-diphenyl-1,3,5-hexatriene DPPC, 1,2-dipalmitoyl-phosphatidylcholine DSC, differential scanning calorimetry GUV, giant unilamellar vesicle HPLC, high-performance liquid chromatography LES, lipid extract surfactant MLV, multilamellar vesicle PA, palmitic acid PG, phosphatidylglycerol PL, phospholipid POPG, 1-palmitoyl-2-oleoyl-phosphatidylglycerol RDS, respiratory distress syndrome SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis SP-A, surfactant protein A SP-B, surfactant protein B SP-C, surfactant protein C SP-D, surfactant protein D Tm, gel to fluid main phase transition temperature |
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