Mucociliary clearance (MCC) is an innate defense mechanism that normally keeps airways clean but is dysfunctional in cystic fibrosis (CF) and other muco-obstructive pulmonary diseases. Previously we discovered that activating adenyl cyclase in combination with a cholinergic agonist increased MCC velocity (MCCV) synergistically in ex vivo WT and CF ferret and WT piglets. The present study extends and underpins our earlier findings by showing for the first time, in vivo synergistic MCC in WT rats and in CF sheep models and CF rats using inhalable β-adrenergic and cholinergic drugs approved for human use when delivered to the apical surface and a single dose is tolerated by humans. As for mechanisms via ex vivo experiments, we show the combined agonists increased net fluid secretion mainly by stimulating gland secretion and by inhibiting surface absorption, consequently increased ASL depth. They also increased net base secretion and increased ciliary beat frequency. Additional ex vivo and in vitro experiments show that the combined agonists have additive effects when combined with highly effective CF transmembrane conductance regulator (CFTR) modulator therapy (HEMT). The synergistic increase in MCCV induced by this combination of agonists offers therapeutic potential for treating muco-obstructive pulmonary diseases including CF.
Joo et al. (Thu,) studied this question.