In vitro modelling of lung inflammatory processes

Exhaled breath analysis has a high potential for early non-invasive diagnosis of lung conditions. The inflammation processes associated with oxidative stress yield to the conversion of membranes components into volatile organic compounds (VOC) secreted by the lungs. The characterization and understanding of the inflammatory metabolic pathways involved into VOC production is necessary to define proper medication. In this study, lung inflammation was simulated in-vitro on lung epithelial cells. We compared the VOC production following a conventional oxidative stress in-vitro using hydrogen peroxide (H2O2) with a biological model using inflammatory sputum from asthmatic patients. The VOC were extracted and analyzed by solid-phase microextraction comprehensive two-dimensional gas chromatography hyphenated to time-of-flight mass spectrometry. In the oxidative stress experiments, we exposed the epithelial cells to 0.1 mM H2O2 for 1 h. In the biological stress experiment, the epithelial cells were exposed to 50 % (v/v) inflammatory and non-inflammatory pool of sputum supernatants for 24 h. These optimal conditions were used to induce metabolic response, releasing specific metabolites, without causing significant cellular apoptosis. According to the type of inflammation induced, different VOCs were produced by the cells. For both chemical and biological challenges, an increase of carbonyl compounds and hydrocarbons was observed. However, 36% of the specific VOCs were produced only after a biological stress. Taken together, these results highlight that in-vitro VOC analysis is a very promising approach to characterize complex lung inflammatory mechanisms. The future implementation of multi-omics screening could reveal new information on the molecular mechanisms involved in lung inflammation.