Alteration of surface properties of dipalmitoyl phosphatidylcholine by benzo[a]pyrene: a model of pulmonary effects of diesel exhaust inhalation.

Effects of benzo[a]pyrene (BaP) on the surface properties of dipalmitoyl phosphatidylcholine (DPPC) being the basic component of pulmonary surfactant and lipid membranes were studied experimentally and analyzed by molecular dynamics simulations. Isotherms and surface compressibility of mixed BaP/DPPC monolayers on water were determined using Langmuir-Wilhelmy film balance. It was demonstrated that BaP induced concentration-dependent deviations from the initial surface activity of the phospholipid film and a noticeable decrease of its fluidity. Results obtained by molecular dynamics simulations allow to explain the observed effects indicating a migration of BaP molecules towards hydrophobic part of the interfacial layer of DPPC and the concentration-dependent restriction of flexibility of the hydrocarbon chains of phospholipid molecules. The results of the study may be related to the physicochemical disturbance of the pulmonary surfactant system after breathing with air contaminated by diesel exhaust components. It is speculated that such phenomena may have an input to undesired health effects.