Hydrogen ion concentration in airway surface liquid (ASL pH)

Hydrogen ion concentration in airway surface liquid (ASL) determines its pH, which plays an essential role in maintaining healthy lung function. The slightly acidic nature of normal ASL supports optimal mucus properties for trapping pathogens and facilitating their removal via mucociliary clearance. In diseases like cystic fibrosis—where chloride/bicarbonate secretion by CFTR is defective—the resulting lower ASL pH leads to thicker mucus that impairs clearance and increases infection risk. Multiple membrane proteins—including CFTR chloride channel, ATP12A H+/K+ ATPase proton pump (in large airways), vacuolar H+-ATPase subunits like ATP6V0D2 (in small airways), SLC26 family bicarbonate exchangers such as pendrin—coordinate regulation of this microenvironmental acidity through active secretion/reabsorption processes. While correcting abnormal ASL acidity represents an emerging therapeutic strategy for conditions like cystic fibrosis by improving mucus hydration and host defense functions,[1][2][3] "hydrogen ion concentration" itself is not considered a direct molecular target but rather an important physiological endpoint reflecting the integrated activity of several druggable proteins involved in acid–base homeostasis within respiratory epithelia.[5]

Other names

Airway surface liquid pHASL pHAirway epithelial fluid pH

Mechanisms relate to modulation of underlying transport proteins—such as inhibition or activation of proton pumps (ATP12A), chloride/bicarbonate exchangers (CFTR/SLC26 family), and other acid/base transporters—to alter ASL hydrogen ion concentration and thus its pH[2][5].