Chronic inflammation may cause spasms, narrowing of the bronchial walls, and hyperplasia.66 In one study, with the deletion of AQP5, increased mucus secretion and higher concentrations of the protein were found in the upper respiratory tract of mice.67 Treatment with hydrogen-rich saline reversed the decrease in AQP5 levels in COPD rats, indicating its potential for regulating mucus hypersecretion through the modulation of AQP5 expression.68 This evidence concerns the gene AQP5 and chronic obstructive pulmonary disease.