Abstract Rationale Ozone is an oxidant air pollutant known to cause lung injury and alter pulmonary functioning, especially in vulnerable populations including the elderly and individuals with co-morbidities; these effects are more pronounced after prolonged ozone exposure. Surfactant protein (SP)-D is a pulmonary collectin that plays a role in regulating macrophage responses to inhaled xenobiotics. In previous studies we showed that ozone-induced lung injury and macrophage accumulation in the lungs are exacerbated in mice lacking SP-D. Herein we assessed the effects of loss of SP-D on metabolomic and lipidomic profiles in the lungs following prolonged episodic inhalation of ozone. Methods Mice (female C57Bl6/J WT and SP-D-/-, 12-13 wk.) were exposed to air or ozone (1.5 ppm, 2 h, 2x/3.5 wk). Bronchoalveolar lavage fluid (BAL) was collected 24 h after the last exposure and analyzed for cell, protein, phospholipids and IgM content. Polar metabolites were extracted from cell-free BAL by rapid enzyme quenching; chromatography and high-resolution MS were used to separate and specify the metabolites; MS/MS was used in some cases to differentiate isomers. Lipid metabolites were identified and quantified by LC-MS. Data were analyzed using MetaboAnalyst software to generate heatmaps. Results Exposure of SP-D-/- mice to ozone significantly increased number of cells, protein, and total phospholipid levels in BAL, when compared to WT mice. Metabolomic analysis of BAL revealed that ozone exposure resulted in an increase in 69 polar water-soluble metabolites and a decrease in 91 metabolites in WT mice, while 13 metabolites increased and 141 metabolites decreased in SP-D-/- mice, when compared to air controls. Ozone exposure also resulted in an increase in 32 and 57 lipid metabolites in WT and SP-D-/- mice respectively, while 243 and 201 lipid metabolites decreased. Whereas 3 lipid metabolites increased significantly in WT mice after ozone, 16 metabolites, important in surfactant biosynthesis, decreased in SP-D-/- mice. Conclusions Taken together these data suggest that prolonged ozone exposure decreases polar metabolites involved in protein and nucleic acid synthesis, and decreases lipids linked to surfactant synthesis in the lungs of mice lacking SP-D. Identifying the nature of these metabolites and their role in ozone toxicity may lead to a better understanding of the role of surfactants in chronic lung pathologies. This abstract is funded by: NIH
Sunil et al. (Fri,) studied this question.