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

초록

Background: Exposure to ozone (O-3) 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 O-3-induced airway injury. Thus, we evaluated the role of Slc26a4 and the protective effects of ammonium chloride (NH4Cl) in O-3-induced airway injury in mice. Methods: Six-week-old female BALB/c mice were exposed to filtered air or O(3 )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)-alpha, interferon (IFN)-gamma, interleukin (IL)-17, IL-1 beta, 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 O-3 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 O-3-induced increases in IFN-gamma, TNF-alpha, IL-17, IL-1 beta, and p20-activated caspase-1. Conclusion: Slc26a4 may be involved in O-3-induced inflammatory and epithelial changes in the airways via activation of the inflammasome and the induction of IL-17 and IFN-gamma. NH4Cl shows a potential as a therapeutic agent for controlling O-3-induced airway inflammation and epithelial damage by modulating Slc26a4 expression.

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