Airway mucus and respiratory tract secretions

Airway mucus is a complex, viscoelastic gel that lines the respiratory tract, primarily composed of water, ions, and high-molecular-weight glycoproteins known as mucins, specifically MUC5AC and MUC5B (Fahy & Dickey, 2010, NEJM). Its primary biological function is to protect the lungs by trapping inhaled particles, pathogens, and toxins, which are then removed via mucociliary clearance (Boucher, 2002, Nature Reviews Drug Discovery). In chronic respiratory diseases such as cystic fibrosis, chronic obstructive pulmonary disease (COPD), and asthma, mucus becomes hyperviscous and overproduced, leading to airway obstruction and impaired clearance (Rogers, 2007, Paediatric Respiratory Reviews). Therapeutic intervention targets the physical and chemical properties of this secretion to improve clearance and lung function. Drugs like N-acetylcysteine break disulfide bridges in mucin polymers to reduce viscosity (Sadowska, 2012, Pulmonary Pharmacology & Therapeutics), while dornase alfa degrades extracellular DNA released from neutrophils in infected mucus (Bryson & Sorkin, 1994, Drugs). These treatments are essential for managing symptoms and preventing exacerbations in patients with chronic obstructive lung diseases.

Other names

Respiratory secretionsBronchial mucusSputumAirway surface liquidTracheobronchial secretions

Mucoactive agents reduce mucus viscosity by cleaving disulfide bonds in mucin polymers (classic mucolytics), enzymatically degrading extracellular DNA (peptide mucolytics), or increasing airway surface hydration to facilitate clearance (mucokinetics) (Sadowska, 2012; Bryson & Sorkin, 1994).