Effects of ammonium chloride on ozone-induced airway inflammation: The role of Slc26a4 in the lungs of mice

Abstract

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. NH4Clshow potential as a therapeutic agent for controlling O3-induced airway inflammation and epithelial damage by modulating Slc26a4 expression.