TNFα and IL-17 alkalinize airway surface liquid through CFTR and pendrin

T Rehman, IM Thornell, AA Pezzulo… - … of Physiology-Cell …, 2020 - journals.physiology.org
T Rehman, IM Thornell, AA Pezzulo, AL Thurman, GS Romano Ibarra, PH Karp, P Tan…
American Journal of Physiology-Cell Physiology, 2020journals.physiology.org
The pH of airway surface liquid (ASL) is a key factor that determines respiratory host
defense; ASL acidification impairs and alkalinization enhances key defense mechanisms.
Under healthy conditions, airway epithelia secrete base (HCO 3−) and acid (H+) to control
ASL pH (pHASL). Neutrophil-predominant inflammation is a hallmark of several airway
diseases, and TNFα and IL-17 are key drivers. However, how these cytokines perturb
pHASL regulation is uncertain. In primary cultures of differentiated human airway epithelia …
The pH of airway surface liquid (ASL) is a key factor that determines respiratory host defense; ASL acidification impairs and alkalinization enhances key defense mechanisms. Under healthy conditions, airway epithelia secrete base () and acid (H+) to control ASL pH (pHASL). Neutrophil-predominant inflammation is a hallmark of several airway diseases, and TNFα and IL-17 are key drivers. However, how these cytokines perturb pHASL regulation is uncertain. In primary cultures of differentiated human airway epithelia, TNFα decreased and IL-17 did not change pHASL. However, the combination (TNFα+IL-17) markedly increased pHASL by increasing secretion. TNFα+IL-17 increased expression and function of two apical transporters, CFTR anion channels and pendrin Cl/ exchangers. Both were required for maximal alkalinization. TNFα+IL-17 induced pendrin expression primarily in secretory cells where it was coexpressed with CFTR. Interestingly, significant pendrin expression was not detected in CFTR-rich ionocytes. These results indicate that TNFα+IL-17 stimulate secretion via CFTR and pendrin to alkalinize ASL, which may represent an important defense mechanism in inflamed airways.
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