Untargeted Exhaled Breath Condensate Metabolomics for Detecting Cystic Fibrosis Exacerbations

MARÍA EUGENIA MONGE; XIAOLING ZANG; NAEL A. MCCARTY; ARLENE A. STECENKO; FACUNDO M. FERNÁNDEZ

Los Cocos

Congreso; Segundo Congreso Argentino de Espectrometría de Mas; 2014

SAEM

Progressive lung disease and eventual respiratory failure account for almost 90% of morbidity and mortality in cystic fibrosis (CF).1 The loss of lung function is disrupted with the occurrence of acute pulmonary exacerbations (APEs), which are discrete episodes of increased bacterial burden, oxidative stress, and neutrophil-mediated inflammation. The frequency of APEs is related to irreversible lung function decline and a risk factor for death in CF. Prediction of an oncoming APE before the symptoms appear would allow early treatment to slow CF progression by preventing irreversible lung damage. The chemical composition of airway secretions is affected by pulmonary diseases, and can be determined non-invasively through sampling exhaled breath condensate (EBC). The present study aims to identify EBC biomarkers of CF progression that would assist in predicting an APE in the pre-symptomatic phase, through an untargeted metabolomics approach using reversed-phase ultraperformance liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry. Metabolomic profiling was performed on EBC from age-matched healthy individuals and CF patients in different phases of the disease: i) 1 to 3 months prior to an APE (?pre-APE?); ii) during the APE event (?APE?); iii) within 3 months after an APE event (?post-APE?); and iv) from CF subjects who are clinically stable without an APE for at least 3 months (?stable?). EBC samples were lyophilized and reconstituted in the initial composition of the chromatographic mobile phase. High resolution mass spectra were acquired by positive and negative ion electrospray ionization (ESI) in the 50-1500 m/z range. Metabolic features were extracted using MZmine 2.10. Paired comparisons between the different sample classes were performed through orthogonal projection to latent structures-discriminant analysis (oPLS-DA) to explore differential features. A panel of 13 spectral features discriminated the 4 pre-APE EBC samples from the 19 stable EBC samples analyzed in negative ESI mode with 100% accuracy, specificity and sensitivity. Three of the differentiating metabolites which were elevated in pre-APE EBC were tentatively identified as organic acids: lactic acid, decanoic (capric) acid, and tetradecanoic (myristic) acid. Interestingly, there is evidence showing that children with CF or asthma have EBC with pH values lower than control subjects. Other two tentatively identified metabolites were 5-oxoproline and sorbitol. Ongoing work focuses on performing a longitudinal study with samples collected from the same patient along the different phases of the disease; and on analyzing the results obtained in ESI positive mode. This first exploratory study shows promise and feasibility of early detection of a pending APE through EBC metabolomics, allowing new insight into biochemical and inflammatory processes in the lung, and potentially point to therapeutic strategies. References: 1- Kreindler, J. L. Pharmacol. Therapeut. 2010, 125, 219-229.