The airway mucosal microenvironment is crucial for host defense against inhaled pathogens but remains poorly understood. We report here that the airway surface normally undergoes surprisingly large excursions in pH during breathing that can reach pH 9.0 during inhalation, making it the most alkaline fluid in the body. Transient alkalinization requires luminal bicarbonate and membrane-bound carbonic anhydrase 12 (CA12) and is antimicrobial. Luminal bicarbonate concentration and CA12 expression are both reduced in cystic fibrosis (CF), and mucus accumulation both buffers the pH and obstructs airflow, further suppressing the oscillations and bacterial-killing efficacy. Defective pH oscillations may compromise airway host defense in other respiratory diseases and explain CF-like airway infections in people with CA12 mutations.
Large pH oscillations promote host defense against human airways infection
Disclosures: M.A. Tewfik reported "other" from Sanofi, "other" from AstraZeneca, personal fees from Novartis, personal fees from Mylan, and personal fees from Stryker outside the submitted work. No other disclosures were reported.
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Dusik Kim, Jie Liao, Nathan B. Scales, Carolina Martini, Xiaojie Luan, Asmahan Abu-Arish, Renaud Robert, Yishan Luo, Geoffrey A. McKay, Dao Nguyen, Marc A. Tewfik, Charles D. Poirier, Elias Matouk, Juan P. Ianowski, Saul Frenkiel, John W. Hanrahan; Large pH oscillations promote host defense against human airways infection. J Exp Med 5 April 2021; 218 (4): e20201831. doi: https://doi.org/10.1084/jem.20201831
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