Losartan Rescues Inflammation-related Mucociliary Dysfunction in Relevant Models of Cystic Fibrosis.

Abstract

<b>Rationale:</b> Despite therapeutic progress in treating cystic fibrosis (CF) airway disease, airway inflammation with associated mucociliary dysfunction remains largely unaddressed. Inflammation reduces the activity of apically expressed large-conductance Ca²⁺-activated and voltage-dependent K⁺ (BK) channels, critical for mucociliary function in the absence of CFTR (CF transmembrane conductance regulator).<b>Objectives:</b> To test losartan as an antiinflammatory therapy in CF using CF human bronchial epithelial cells and an ovine model of CF-like airway disease.<b>Methods:</b> Losartan's antiinflammatory effectiveness to rescue BK activity and thus mucociliary function was tested <i>in vitro</i> using primary, fully redifferentiated human airway epithelial cells homozygous for F508del and <i>in vivo</i> using a previously validated, now expanded pharmacologic sheep model of CF-like, inflammation-associated mucociliary dysfunction.<b>Measurements and Main Results:</b> Nasal scrapings from patients with CF showed that neutrophilic inflammation correlated with reduced expression of LRRC26 (leucine rich repeat containing 26), the γ subunit mandatory for BK function in the airways. TGF-β1 (transforming growth factor β1), downstream of neutrophil elastase, decreased mucociliary parameters <i>in vitro</i>. These were rescued by losartan at concentrations achieved by nebulization in the airway and oral application in the bloodstream: BK dysfunction recovered acutely and over time (the latter via an increase in LRRC26 expression), ciliary beat frequency and airway surface liquid volume improved, and mucus hyperconcentration and cellular inflammation decreased. These effects did not depend on angiotensin receptor blockade. Expanding on a validated and published nongenetic, CF-like sheep model, ewes inhaled CFTR_inh172 and neutrophil elastase for 3 days, which resulted in prolonged tracheal mucus velocity reduction, mucus hyperconcentration, and increased TGF-β1. Nebulized losartan rescued both mucus transport and mucus hyperconcentration and reduced TGF-β1.<b>Conclusions:</b> Losartan effectively reversed CF- and inflammation-associated mucociliary dysfunction, independent of its angiotensin receptor blockade.