Effects of Ammonium Chloride on Ozone-induced Airway Inflammation: the Role of Slc26a4 in the Lungs of Mice.

Background: Exposure to ozone (O₃) induces neutrophilic inflammation and goblet cell hyperplasia in humans and experimental animals. Because the solute carrier family 26-member 4 (Slc26a4; pendrin) gene induces mucin production and intraluminal acidification in the airways, it was hypothesized to be a key molecule in O₃-induced airway injury. Thus, we evaluated the role of Slc26a4 and the protective effects of ammonium chloride (NH₄Cl) in O₃-induced airway injury in mice.

Methods: Six-week-old female BALB/c mice were exposed to filtered air or O₃ for 21 days (2 ppm for 3 hr/day). NH₄Cl (0, 0.1, 1, and 10 mM) was administered intratracheally into the airways. Airway resistance was measured using a flexiVent system, and bronchoalveolar lavage fluid (BALF) cells were differentially counted. Slc26a4 and Muc5ac proteins and mRNA were measured via western blotting, real-time polymerase chain reaction, and immunostaining. Tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-17, IL-1β, and caspase-1 were analyzed via western blotting.

Results: The levels Slc26a4 protein and mRNA significantly increased in lung tissues from Day 7 to Day 21 of O₃ exposure, with concomitant increases in lung resistance, numbers of goblet cells in lung tissues, and inflammatory cells and thiocyanate (SCN) levels in BALF in a time-dependent manner. Treatment with NH₄Cl significantly reduced these changes to levels similar to those of sham-treated mice, with a concomitant reduction of Slc26a4 proteins in lung lysates and SCN levels in BALF. Slc26a4 protein was co-expressed with muc5ac protein in the bronchial epithelium, as indicated by immunofluorescence staining. NH₄Cl treatment also significantly attenuated the O₃-induced increases in IFN-γ, TNF-α, IL-17, IL-1β, and p20-activated caspase-1.

Conclusion: Slc26a4 may be involved in O₃-induced inflammatory and epithelial changes in the airways via activation of the inflammasome and the induction of IL-17 and IFN-γ. NH₄Cl shows a potential as a therapeutic agent for controlling O₃-induced airway inflammation and epithelial damage by modulating Slc26a4 expression.