Online monitoring of volatile organic compounds emitted from human bronchial epithelial cells as markers for oxidative stress

Abstract

Particulate air pollution is associated with adverse respiratory effects and is a major factor for premature deaths. In-vitro assays are commonly used for investigating the direct cytotoxicity and inflammatory impacts due to particulate matter (PM) exposure. However, biological tests are often labor-intensive, destructive and limited to endpoints measured offline at single time points, making it impossible to observe the progression of cell response upon exposure. Here we explored the potential of a high-resolution proton transfer reaction mass spectrometer (PTR-MS) to detect the volatile organic compounds (VOCs) emitted by human bronchial epithelial cells (BEAS-2B) upon exposure to PM. Cells were exposed to single components (1,4-naphthoquinone and Cu(II)) known to induce oxidative stress. We also tested filter extracts of aerosols generated in a smog chamber, including fresh and aged wood burning emissions, as well as α-pinene secondary organic aerosol (SOA). We found that 1,4-naphthoquinone was rapidly internalized by the cells. Exposing cells to each of these samples induced the emission of VOCs, which we tentatively assigned to acetonitrile, benzaldehyde and dimethylbenzaldehyde, respectively. Emission rates upon exposure to fresh and aged OA from α-pinene oxidation and from biomass burning significantly exceeded those observed after exposure to similar doses of Cu(II), a proxy for transition metals with high oxidative potential. Emission rates of biomarkers from cell exposure to α-pinene SOA exhibited a statistically significant, but weak dose dependence. The emission rates of benzaldehyde scaled with cell death, estimated by measuring the apical release of cytosolic lactate dehydrogenase. Particle mass doses delivered to the BEAS-2B cells match those deposited in the human tracheobronchial tract after several hours of inhalation at elevated ambient air pollution. The results presented here show that our method has the potential to determine biomarkers of PM induced pulmonary damage in toxicological and epidemiological research on air pollution.

BreathXplorer: Processing Online Breathomics Data Generated from Direct Analysis Using High-Resolution Mass Spectrometry

“…Exhaled breath has emerged as a compelling biological specimen owing to its rich content of hundreds of volatile compounds . These compounds (e.g., hydrocarbons, acetone) can be originated from tissues and symbiotic bacteria in the gastrointestinal tract, which enter into blood and eventually cross the blood-air barrier in the lung. − Additionally, a substantial portion of the compounds in the exhaled breath is of exogenous origins, including medicine, environmental exposure, , etc. The comprehensive analysis of the diverse array of metabolites in exhaled breath represents a promising approach for gaining a deeper understanding of human health and disease. − It also provides an alternative and more convenient strategy to the metabolomics research routinely based on urine and blood.…”