Human Nasal and Bronchial Epithelium in Cystic Fibrosis: Differences in Expression of Airway pH Regulatory Proteins

Decreased apical bicarbonate transport into the airway surface liquid (ASL) has been associated with decreased ASL pH, which can have adverse respiratory effects. However, the human CF epithelium can normalize ASL pH. Thus, we hypothesized that pH regulatory proteins other than the CFTR could be altered in the CF epithelium.

Primary human nasal and bronchial epithelial cells from healthy controls and CF subjects were grown at air-liquid interface until fully ciliated. Western blot was used to measure proteins known to affect human epithelial pH: carbonic anhydrases (CA) 1, 2, and 12; voltage-gated proton channel (Hv1); lactate dehydrogenases (LDH) A, B, D; dual oxidases (DUOX) 1, 2; Na⁺/H⁺ exchange regulatory factor; potassium-transporting ATPase alpha chain 2 (ATP12A), S-nitrosoglutathione reductase (GSNOR); glutaminase; vacuolar-type ATPase (VTP-ase); and NADPH oxidases (NOX) 1-4.

NOX2 was decreased in CF nasal epithelial cells compared to controls. CA1, CA2, CA12, Hv1, LDHA, LDHD, ATP12A, GSNOR and NOX4 expression were increased in CF bronchial epithelial cells relative to the controls. Beta actin expression was variable, making normalization challenging.

Expression of CA's, Hv1, LDH's, ATP12A, GSNOR, and NOX4 were generally increased in bronchial epithelium from patients with CF. These proteins could serve to normalize the CF epithelial pH. Nasal cells did not have these changes, arguing that findings from primary nasal cells in culture cannot uniformly be extrapolated to understand the biology of primary bronchial epithelial cells in culture.