Molecular dynamics exploring of atmosphere components interacting with lung surfactant phospholipid bilayers

Abstract

Sulfur dioxide (SO2), nitrogen oxide (NO2) and ozone (O3) in the atmosphere are significantly correlated with various respiratory and cardiovascular diseases. High doses of each of these gases or a mixture can change the physical and chemical properties of the lung membrane, thus leading to an increased pulmonary vascular permeability and structural failure of the alveolar cell membrane. In the present study, detailed molecular dynamic (MD) modeling was applied to investigate the effects of SO2, NO2, O3 and mixtures of these gases on the dipalmitoyl phosphatidylcholine (DPPC) phospholipid bilayer. The results showed that several key physical properties, including the mass density, lipid ordering parameter, lipid diffusion, and electrostatic potential of the cell membrane, have been changed by the binding of different compounds. This resulted in significant variations and more disorder in the DPPC bilayer. The multiple analyses of membrane properties proved the toxicity of NO2, O3, and SO2 to the DPPC bilayer, providing a theoretical basis for the experimental phenomenon that SO2, NO2 and O3 can cause lung cell apoptosis. For the single systems, the damage to DPPC bilayer caused by O3 was more serious than NO2 and SO2. More importantly, the MD simulations using the mixtures of SO2, NO2, and O3 showed a much greater decline of membrane fluidity and the aggravation of membrane damage than the single systems, indicating a synergistic effect when NO2, SO2, and O3 coexisted in the atmosphere, which could lead to much more severe damage and greater toxicities to the lung.