Differential Peptidomic Profiles of Airway Epithelial Cell Secretions in Health and Disease: Implications for Innate Immune Response and Airway Integrity

The human airway epithelium plays a crucial role in the innate immunity of the lungs through mucus secretions containing proteins and peptides that interact with immune cells, macromolecules, pathogens, and allergens. Cystic fibrosis (CF) alters mucus concentration and composition, impairing airway function and increasing susceptibility to infections and obstructions. Peptidomic profiling offers insight into epithelial airway defense mechanisms, but it is unknown whether these profiles differ significantly among healthy individuals and people with CF. We hypothesized that peptidomic profiles of airway epithelial cell secretions would differ between health and CF under infectious and inflammatory conditions, reflecting disease-associated changes related to immune responses and epithelial integrity. Using human bronchial epithelial (HBE) cell culture secretions and <em>ex vivo </em>mucus samples from healthy individuals and CF patients, we identified and quantified peptides by mass spectrometry. Baseline analyses of culture secretions revealed reductions in vesicular and microvilli-associated peptides in CF samples. Following exposure to <em>Pseudomonas aeruginosa</em> (PSA), all culture samples displayed increased peptides related to innate immunity, but CF samples exhibited reduced peptide diversity. Elevated albumin levels, marking epithelial barrier integrity disruption, were detected in CF culture samples. Peptidomes between <em>ex vivo </em>mucus samples and <em>in vitro </em>HBE cell secretions differed, reflecting the more complex <em>in vivo </em>environment. This study enhances our understanding of airway epithelial defense mechanisms, providing insights into the pathogenesis of muco-obstructive lung diseases, which could inform the development of therapeutic strategies.