Modeling Lung Surfactant Interactions with Benzo[a]pyrene

Abstract

By reducing the surface tension of the air-water interface in alveoli, lung surfactant (LS) is crucial for proper functioning of the lungs. It also forms the first barrier against inhaled pathogens. In this study we inspect the interactions of LS models with a dangerous air pollutant, benzo[a]pyrene (BaP). Dipalmitoylphosphatidylcholine (DPPC), 1-palmitoyl-2-oleoylphosphatidylcholine, and their 1:1 mixture are used as LS models. Pressure-area isotherms are employed to study macroscopic properties of the monolayers. We find that addition of BaP has a condensing effect, manifested by lowering the values of surface pressure and shifting the isotherms to smaller areas. Atomistic details of this process are examined by means of molecular dynamics simulations. We show that initially BaP molecules are accumulated in the monolayers. Upon compression, they are forced to the headgroups region and eventually expelled to the subphase. BaP presence results in reduction of monolayer hydration in the hydrophilic region. In the hydrophobic region it induces increased chain ordering, reduction of monolayer fluidity, and advances transition to the liquid condensed phase in the DPPC system.

Interactions of particulate matter and pulmonary surfactant: Implications for human health

“…A variety of nanoparticles, such as simple metal oxides [ [96] , [97] , [98] , [99] , [100] ], non-metal oxides [ 101 , 102 ], polymer-coated and polymer nanoparticles [ [103] , [104] , [105] ], metal nanoparticles [ [106] , [107] , [108] ], carbon nanomaterials [ 100 , 109 ], and other compounds containing carcinogenic matters [ [110] , [111] , [112] , [113] ], have been investigated in the studies of particle-surfactant interactions. A few studies on environmental PM dust exposure have also been conducted [ 110 , 114 , 115 ], but they are still in the very early stage compared to those using engineered nanoparticles.…”

“…There are several different methods to expose lung surfactants to PM. One is to mix the surfactant solution with particles and then inject the mixture onto the interface by microsyringe [ 101 , 103 , 108 , 112 , 126 ]. This conventional method enables an easier control over the feed ratio, and a sufficient exposure of surfactant to particles can also be achieved.…”

“…Stachowicz-Kusnierz et al . [ 112 ] compared DPPC, POPC monolayers, and a monolayer of a mixture of DPPC and POPC. The Π-A isotherms of both the binary monolayer and pure POPC monolayer showed larger mean molecular areas than that of DPPC because of the double bond in POPC.…”

“…Upon the addition of Benzo[a]pyrene, the condensing effect became more obvious on the binary monolayer than on the one-component monolayers. Molecular dynamics simulations validated this difference by demonstrating that the unsaturated lipids such as POPC and POPG could make surfactant more fluidized, and meanwhile, they might sustain a larger pressure increase at low initial pressure [ 79 , 112 ]. Zhao et al .…”

“…[ 205 ] confirmed that the mixed phospholipids in natural surfactant were responsible for the solubilization of PAHs. A molecular dynamics simulation [ 112 ] and experimental results [ 76 ] indicated that benzo[a]pyrene caused a condensing effect on surfactant monolayer and reduced the hydration of the monolayer, leading to a decreased fluidity. Benzo[a]pyrene also destabilizes DPPC/DPPG monolayer by decreasing the surface pressure.…”