Degradation and Rearrangement of a Lung Surfactant Lipid at the Air–Water Interface during Exposure to the Pollutant Gas Ozone

Abstract

The presence of unsaturated lipids in lung surfactant is important for proper respiratory function. In this work, we have used neutron reflection and surface pressure measurements to study the reaction of the ubiquitous pollutant gas-phase ozone, O3, with pure and mixed phospholipid monolayers at the air-water interface. The results reveal that the reaction of the unsaturated lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, POPC, with ozone leads to the rapid loss of the terminal C9 portion of the oleoyl strand of POPC from the air-water interface. The loss of the C9 portion from the interface is accompanied by an increase in the surface pressure (decrease in surface tension) of the film at the air-water interface. The results suggest that the portion of the oxidized oleoyl strand that is still attached to the lipid headgroup rapidly reverses its orientation and penetrates the air-water interface alongside the original headgroup, thus increasing the surface pressure. The reaction of POPC with ozone also leads to a loss of material from the palmitoyl strand, but the loss of palmitoyl material occurs after the loss of the terminal C9 portion from the oleoyl strand of the molecule, suggesting that the palmitoyl material is lost in a secondary reaction step. Further experiments studying the reaction of mixed monolayers composed of unsaturated lipid POPC and saturated lipid dipalmitoyl-sn-glycero-3-phosphocholine, DPPC, revealed that no loss of DPPC from the air-water interface occurs, eliminating the possibility that a reactive species such as an OH radical is formed and is able to attack nearby lipid chains. The reaction of ozone with the mixed films does cause a significant change in the surface pressure of the air-water interface. Thus, the reaction of unsaturated lipids in lung surfactant changes and impairs the physical properties of the film at the air-water interface.

Effect of acute ozone exposure on the lung metabolomes of obese and lean mice

“…However, examination of published microarray data from C57BL/6 mice exposed in the same manner as we did (GSE38014) indicates that pulmonary mRNA abundance of most phospholipases is either increased or unchanged after O 3 . Choline containing phosphoplipids make up the majority of the phospholipids in surfactant [36] and O 3 causes oxidation of surfactant phospholipids with consequent loss of their surface active properties [71]. Hence, it is also possible that reductions in lysolipids after O 3 reflect their increased incorporation into surfactant phospholipids in order to replete these lipids after O 3 -induced degradation.…”

Atmospheric chemistry of bioaerosols: heterogeneous and multiphase reactions with atmospheric oxidants and other trace gases

“…Similarly, ozone exposure caused degradation and rearrangement of lung surfactant phospholipid, POPC. 147 Novel mass spectrometric approaches have enabled researchers to enquire the interaction of O 3 with biomolecules at an air–liquid interface. Under conditions relevant to the interaction of ambient O 3 with lung surfactant, these phase-boundary experiments confirm that cysteine (Cys) residues are the preferential sites of oxidation in peptides and proteins.…”

Identification of oxidized phospholipids in bronchoalveolar lavage exposed to low ozone levels using multivariate analysis

“…The lung surfactant is vital for maintaining airway patency but is also involved in the airways’ barrier and defense against inhaled toxic components [4–5]. Removal of unsaturated phospholipids by oxidation has been shown to affect the ability of the surfactant to decrease surface tension [6]. In addition, oxidation of these lipids leads to production of potentially harmful oxidative species, lipid-ozone reaction products.…”