MUC5AC drives COPD exacerbation severity through amplification of virus-induced airway inflammation

Aran Singanayagam; Joseph Footitt; Benjamin T Kasdorf; Matthias Marczynski; Michael T Cross; Lydia J Finney; Maria-Belen Trujillo Torralbo; Maria Calderazzo; Jie Zhu; Julia Aniscenko; Thomas B Clarke; Philip L Molyneaux; Nathan W Bartlett; Miriam F Moffatt; William O Cookson; Jadwiga Wedzicha; Christopher M Evans; Oliver Lieleg; Patrick Mallia; Sebastian L Johnston

Given our prior observations that Muc5ac deletion was anti-inflammatory, while augmentation with exogenous MUC5AC protein in mice had broad pro-inflammatory effects, we reasoned that this mucin could be mediating its effects via a danger signal that promotes inflammatory mediator release and cell recruitment. A previous study demonstrated that supernatants of mucopurulent material from subjects with cystic fibrosis can induce epithelial release of extracellular adenosine triphosphate (ATP) 20 , a well-recognised promoter of inflammation 21 that is also virus-inducible 22 . We therefore hypothesised that MUC5AC exerts its pro-inflammatory effects during RV infection via induction of extracellular ATP and examined the effect of ATP neutralisation using the ATP-hydrolysing enzyme apyrase in exogenous MUC5AC-treated RV-infected mice (Fig 5a) . Exogenous MUC5AC protein administration augmented BAL concentrations of ATP in RV-infected mice, an effect that was abrogated by instillation of apyrase (Fig 5b) . Apyrase administration also suppressed exogenous MUC5AC-mediated increases in airway inflammation during RV infection including BAL total cells and neutrophils (Fig. 5c) , inflammatory chemokines CXCL1/KC, CXCL2/MIP-2 and CCL5/RANTES (Fig. 5d) and pro-inflammatory cytokines TNF and IL-1b (Fig. 5e) . Apyrase also prevented the exogenous MUC5AC-mediated increase in neutrophil elastase, reversed the MUC5AC-mediated suppression of SLPI and suppressed MUC5ACmediated increased bacterial loads in RV-infected mice (Fig 5f-g) . Apyrase-mediated reversal of pro-inflammatory effects of MUC5AC did not occur via interference with antiviral immune responses or virus control, as we also observed no effect of apyrase on RVinduction of IFN-α, IFN-l2/3 (Supplementary Fig.6a -c) or lung virus loads ( Supplementary Fig.6d) .