Sulfuric/Sulfurous Acids Induce Self-Protection of Phospholipids Against Air–Water Interfacial Ozonolysis

Sulfides are ubiquity in atmosphere and can convert to be H₂SO₃/H₂SO₄, which could affect the inflammatory responses induced by ozone. However, the mixing effect and mechanism of H₂SO₃/H₂SO₄ and ozone at molecular-level on the lung surface is still indefinable. Herein, using 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol (POPG) monolayer as a model, effects of H₂SO₄/H₂SO₃ on interfacial ozonolysis of phospholipids were explored. Both H₂SO₄ and H₂SO₃ could decrease ozonolysis efficiencies of POPG and showed a remarkable concentration dependence. The main components of H₂SO₄ and H₂SO₃ in investigated system and their effects on POPG ozonolysis were separately explored, and the mechanism was proposed. The observed decrease of ozonolysis efficiencies resulted from POPG hydrolysis induced by H⁺ and reactive activity of HSO₃⁻ and SO₃²⁻ towards ozone. The hydrolysis of POPG could provide oleic acids, which further lowered the ozonolysis efficiency. In addition, the efficiency of POPG ozonolysis in H₂SO₃ case was lower than that in H₂SO₄ case, and the self-sacrificing oxidation of HSO₃⁻ and SO₃²⁻ by ozone was responsible for this process. Considering extra phospholipids in epithelial lining fluid of lung, the short-term or low concentration exposure of H₂SO₄/H₂SO₃ was thought to trigger the self-protection of lung. However, the long-term or high concentration exposure would lead to irreversible damage.