Normalization of Muc5b ameliorates airway mucus plugging during persistent Pseudomonas aeruginosa infection in the CFTR-/- rat.

In cystic fibrosis, the airway gel-forming mucin MUC5B accumulates in the airways, preventing clearance of pathogens like Pseudomonas aeruginosa (PA). The cystic fibrosis transmembrane conductance regulator (CFTR)^-/- (KO) rat model exhibits a similar accumulation of Muc5b. Our lab has shown that increased Muc5b precipitates the development of chronic PA infection. We hypothesized that reducing Muc5b in the KO rat airway would prevent occlusive mucus plugs and development of persistent PA infection. Six-month-old KO rats received Muc5b or scramble siRNA via intratracheal instillation. Rats were then inoculated with 10⁶ colony-forming units of mucoid P. aeruginosa isolate PAM57-15 and euthanized at 3- or 14-days post infection (dpi) to assess acute and persistent infection. At 14 dpi, Muc5b siRNA-treated KO rats had increased weight, decreased neutrophilic inflammation, and reduced mucus plugging in the small airways compared with scramble-treated KO and WT rats. These results indicate that pharmacological intervention of Muc5b reduces mucus plugging during persistent PA infection.NEW & NOTEWORTHY Although highly effective modulator therapies for cystic fibrosis (CF) have improved mucus-related outcomes of disease for people with CF, eradication of Pseudomonas aeruginosa (PA) infection has not been achieved in this population. In addition, current therapies for CF do not target mucin hypersecretion directly. Here, we show that a novel approach of normalizing airway Muc5b hypersecretion ameliorates infection-induced mucus plugging and neutrophilic inflammation during persistent PA infection in CFTR^-/- rats.