PULMONARY SURFACTANT INHIBITS CATIONIC LIPOSOME-MEDIATED GENE DELIVERY TO RESPIRATORY EPITHELIAL-CELLS IN-VITRO

Cationic lipid-mediated transfection of the alveolar epithelium in viv o will require exposure of plasmid DNA and cationic lipids to endogeno us surfactant lipids and proteins in the alveolar space, Effects of pu lmonary surfactant and of surfactant constituents on transfection in v itro of two respiratory epithelial cell lines (MLE-15 and H441) with a plasmid encoding the luciferase reporter gene were studied using two cationic lipid formulations: 1,2-dimyristyloxypropyl-3-dimethyl-hydrox yethyl ammonium bromide/cholesterol (DMRIE/C) and 1,2-dioleoyl-3-trime thylammonium propane/dioleoyl phosphatidylethanolamine (DOTAP/DOPE), G ene expression, as assessed by luciferase activity, decreased as incre asing concentrations of natural surfactant were added to cationic lipi d-DNA complexes, Incorporation of phospholipids DOPC/DOPG or surfactan t proteins SP-B or SP-C in the cationic lipid formulation inhibited tr ansfection, A fluorescent lipid mixing assay was used to determine the effects of surfactant proteins SP-B and SP-C on mixing between cation ic lipid-DNA complexes and surfactant lipid vesicles, Mixing between D OPC/DOPG vesicles and cationic lipid-DNA complexes in the absence of a dded proteins amounted to 10-20%, Addition of SP-B or SP-C increased t he mixing of DOPC/DOPG vesicles with DOTAP/DOPE-DNA complexes, but not DMRIEC-DNA complexes, These results demonstrate that pulmonary surfac tant lipids and proteins inhibit transfection with cationic lipid-DNA complexes in vitro, and may therefore represent a barrier to gene tran sfer in the lung.