Targeted eicosanoids lipidomics of exhaled breath condensate in healthy subjects

Abstract

Background Exhaled breath condensate collection is a non-invasive method of sampling the respiratory tract that can be repeated several times in a wide range of clinical settings. Quantitation of non-volatile compounds in the condensate requires highly sensitive analytical methods, e.g. mass spectrometry. Objective To validate cross-platform measurements of eicosanoids using high performance liquid chromatography or gas chromatography coupled with mass spectrometry in exhaled breath condensate sampled from 58 healthy individuals. Methods Twenty different eicosanoid compounds, representing major arachidonic acid lipoxygenation and cyclooxygenation pathways were measured using a stable isotope dilution method. We applied a free palmitic acid concentration as a surrogate marker for the condensate dilution factor. Results Eicosanoids concentrations in the condensates were consistent with their content in other biological fluids. Prostaglandin E 2 was the most abundant mediator, represented by its stable metabolite tetranor-PGEM. Prostaglandin D 2 products were at low concentration, while hydroxyacids derived from lipoxygenation were abundant. 5-HETE was elevated in current tobacco smokers. Leukotriene B 4 has the highest concentration of all 5-LO products. 15-LO analogues of cysteinyl leukotrienes–eoxins were detectable and metabolized to eoxin E 4. Two main vascular prostanoids: prostacyclin and thromboxane B 2 were present as metabolites. A marker for non-enzymatic lipid peroxidation, 8-iso-PGF 2α isoprostane was increased in smokers. Conclusion Presented targeted lipidomics analysis of exhaled breath condensate in healthy subjects justifies its application to investigation of inflammatory lung diseases. Measurements of non-volatile mediators of inflammation in the condensates might characterize disease-specific pathological mechanisms and responses to treatment.