WNK Inhibition Increases Surface Liquid pH and Host Defense in Cystic Fibrosis Airway Epithelia.
Tayyab RehmanPhilip H KarpAndrew L ThurmanSteven E MatherAkansha JainAshley L CooneyPatrick L SinnAlejandro A PezzuloMichael E DuffeyMichael J WelshPublished in: American journal of respiratory cell and molecular biology (2022)
In cystic fibrosis (CF), reduced HCO<sub>3</sub><sup>-</sup> secretion acidifies the airway surface liquid (ASL), and the acidic pH disrupts host defenses. Thus, understanding the control of ASL pH (pH<sub>ASL</sub>) in CF may help identify novel targets and facilitate therapeutic development. In diverse epithelia, the WNK (with-no-lysine [K]) kinases coordinate HCO<sub>3</sub><sup>-</sup> and Cl<sup>-</sup> transport, but their functions in airway epithelia are poorly understood. Here, we tested the hypothesis that WNK kinases regulate CF pH<sub>ASL</sub>. In primary cultures of differentiated human airway epithelia, inhibiting WNK kinases acutely increased both CF and non-CF pH<sub>ASL</sub>. This response was HCO<sub>3</sub><sup>-</sup> dependent and involved downstream SPAK/OSR1 (Ste20/SPS1-related proline-alanine-rich protein kinase/oxidative stress responsive 1 kinase). Importantly, WNK inhibition enhanced key host defenses otherwise impaired in CF. Human airway epithelia expressed two <i>WNK</i> isoforms in secretory cells and ionocytes, and knockdown of either <i>WNK1</i> or <i>WNK2</i> increased CF pH<sub>ASL</sub>. WNK inhibition decreased Cl<sup>-</sup> secretion and the response to bumetanide, an NKCC1 (sodium-potassium-chloride cotransporter 1) inhibitor. Surprisingly, bumetanide alone or basolateral Cl<sup>-</sup> substitution also alkalinized CF pH<sub>ASL</sub>. These data suggest that WNK kinases influence the balance between transepithelial Cl<sup>-</sup> versus HCO<sub>3</sub><sup>-</sup> secretion. Moreover, reducing basolateral Cl<sup>-</sup> entry may increase HCO<sub>3</sub><sup>-</sup> secretion and raise pH<sub>ASL</sub>, thereby improving CF host defenses.