The fluid lining the lumen of the airways (airway surface liquid, ASL) is critical for defence against inhaled pathogens. Cystic fibrosis disease (CF) exhibits compromised ASL defence properties. The development of CF related diabetes (CFRD) which affects 40-50% of adults with CF is associated with a further decline in lung function and increased exacerbations. While the effect of CF on the proteins of the ASL has been well studied,  the effect of hyperglycaemia on the ASL proteome in non-CF and CF bronchial epithelial cells remains comparatively underexplored.

We exposed Calu3, non-CF bronchial epithelial cells (NHBE) and CF (CFBE) cultured at air-liquid interface to normoglycemia and hyperglycaemia for 24 hours. We then carried out proteomic profiling on the ASL produced by these cells using tandem mass spectrometry.

We found that NHBE and CFBE ASL shared more proteins than Calu3 ASL. In both NHBE and CFBE,  exposure to hyperglycaemia compared to normoglycaemia increased Mucin 5B abundance and pathways associated with peptidyltransferase activity (p<0.05, n=4 respectively). Several proteins involved in immune response to pathogens were decreased (n=4).  In NHBE ASL, hyperglycaemia altered proteins involved in metabolism and glycolysis (GLUD1, ATP5B), indicating metabolic dysfunction and cellular stress.  In CFBE, ASL proteins associated with decreased immune responses (SPON2, HIST1H4A), deregulated oxidative stress response (PARK7) and altered intracellular trafficking (MVB12A) were changed with exposure to hyperglycaemia (n=4).  There were also more unique sequences with AGE adducts in CFBE compared to NHBE ASL (p<0.05, n = 4).  These data indicate that exposure to hyperglycaemia compromises innate immune activity of the ASL and further promotes cellular stress and inflammation, particularly in CF airways.