Schurmann, V. | bioRxiv Science

bioRxiv2020

Durable Changes to Airway Mucus and Fluid Secretion Following Cholinergic Challenge

PurposeMucus abnormalities are central to the pathophysiology of several chronic airway diseases. Mucus secretion and clearance are regulated, in part, by cholinergic innervation. Prolonged cholinergic stimulation may contribute to mucus abnormalities in disease. Thus, we tested the hypothesis that prolonged cholinergic stimulation gives rise to lasting mucus abnormalities in airways. MethodsWe delivered aerosolized bethanechol, a cholinergic agonist, to pig airways. Forty-eight hours later, we measured mucus secretion and mucociliary transport in tracheal segments ex vivo. Tracheal and bronchoalveolar lavage concentrations of the major secreted mucus glycoproteins, mucin5B (MUC5B) or mucin5AC (MUC5AC), were measured with ELISA and antibody labeling. Pig airway epithelia were cultured at the air-liquid interface and treated with bethanechol for forty-eight hours. Stimulated fluid secretion was measured with reflected microscopy and Ussing chambers were used to measure ion transport. ResultsAirways from bethanechol-challenged pigs exhibited sheet-like mucus films, which were not associated with a greater abundance of MUC5AC or MUC5B. Epithelia treated with bethanechol had diminished fluid secretion and decreased Cl- transport. However, mucus and fluid alterations were not associated with impaired mucociliary transport. ConclusionsThese data suggest that cholinergic transmission induces sustained alterations in airway mucus properties. Such defects might compound and/or contribute to persistent mucus phenotypes found after the resolution of airway inflammation.

physiology↗

bioRxiv2019

Acid exposure impairs mucus secretion and disrupts mucus transport in neonatal piglet airways

Tenacious mucus produced by tracheal and bronchial submucosal glands is a defining feature of cystic fibrosis (CF). Although airway acidification occurs early in CF, whether transient acidification is sufficient to initiate mucus abnormalities is unknown. We studied mucus secretion and mucus transport in piglets forty-eight hours following an intra-airway acid challenge. Acid-challenged piglet airways were distinguished by increased mucin 5B (MUC5B) in the submucosal gland but decreased lung lavage fluid MUC5B, following in vivo cholinergic stimulation, suggesting a failure in submucosal gland secretion. Concomitantly, intrapulmonary airways were obstructed with glycoprotein rich material under both basal and methacholine-stimulated conditions. To mimic a CF-like environment, we also studied mucus secretion and transport under diminished bicarbonate and chloride transport conditions ex vivo. Cholinergic stimulation in acid-challenged piglet airways induced extensive mucus films, greater mucus strand formation, increased dilation of submucosal gland duct openings and decreased mucociliary transport. Finally, to elucidate potential mediators of acid-induced mucus defects, we investigated diminazene aceturate, a small molecule that inhibits the acid-sensing ion channel (ASIC). Diminazene aceturate restored surface MUC5B in acid-challenged piglet airways under basal conditions, mitigated acid-induced airway obstruction, and magnified the number of dilated submucosal gland duct openings. These findings suggest that even transient airway acidification early in life might have profound impacts on mucus secretion and transport properties. Further they highlight diminazene aceturate as an agent that might be beneficial in alleviating certain mucus defects in CF airway disease.\n\nOne sentence summaryEarly life airway acidification has profound impacts on mucus secretion and transport.

physiology↗