Pseudomonas aeruginosa Pyocyanin Increases Airway Mucin Biosynthesis by SIRT1-Mediated FOXA2 Inactivation

The potent redox-cycling Pseudomonas aeruginosa secondary metabolite pyocyanin induces acute and persistent oxidative stress in diseased airways. Pyocyanin promotes goblet cell hyperplasia and metaplasia and exacerbates the mucus burden. Forkhead Box A2 (FOXA2) is a key pioneer factor that governs the transition of airway basal epithelial and club cells to goblet cells by transcriptionally repressing the expression of MUC5AC and MUC5B mucin genes. FOXA2 activity is negatively regulated by Thr156 phosphorylation in various cell types. However, how post-translational modifications modulate the transcriptional repression of FOXA2 on airway mucin genes remains uncharacterized. Here, we demonstrate that the interaction between SIRT1 and FOXA2 is significantly increased within pyocyanin-exposed MUC5AC-expressing human bronchial epithelial cells, and in human COPD and pyocyanin-exposed mouse lungs. Pyocyanin promotes SIRT1-mediated deacetylation of FOXA2, which serves as a prerequisite for subsequent phosphorylation, inactivation, and MUC5AC derepression. Specifically, under pyocyanin-imposed oxidative stress, SIRT1 deacetylates FOXA2 at Lys259, which dictates phosphorylation at Thr156, leading to nuclear exclusion, ubiquitination, and proteasome-mediated degradation, initiating airway goblet cell transdifferentiation. By contrast, inactivation of SIRT1 by transient knockdown and chemical inhibition impedes pyocyanin-induced FOXA2 phosphorylation and MUC5AC expression. Our results uncover a novel role of SIRT1 in regulating FOXA2 expression dynamics governing airway mucus homeostasis.