Repeated Exposure of High-Concentration Ammonium Bisulfate (Ammonium Hydrogen Sulfate) to Asthmatic Mice and Human Epithelial Cells

Abstract

There is a paucity of data on the inhalation toxicity of sulfuric acids contained as inorganic components of the airborne PM_2.5. This study aimed to ascertain whether ammonium bisulfate has exacerbating effects on asthmatic symptoms because ammonium bisulfate is known to be a greater irritant to respiratory tracts than other sulfuric acids. Ovalbumin-induced asthmatic BALB/c mice were repeatedly exposed to 5 or 50 mg/m³ of an ammonium bisulfate aerosol for 2 weeks. No clear exacerbation of asthmatic responses was observed in the histopathology, cytological and biochemical analyses of bronchoalveolar lavage fluid, and gene expression analysis. However, some results showed, despite not being statistically significant, exposure-related and concentration-dependent changes. Additionally, a series of submerged exposures of ammonium bisulfate to A549 and Calu-3 cells were performed at a range of 0.001 to 3 mg/mL for 24 hours. While no overt inflammatory response was induced by the exposures, a significant increase in the cellular reactive oxygen species production and a decrease in the transepithelial electrical resistance in a concentration-dependent manner were observed. Although no statistically significant changes were detected in the animal experiments, our results suggest that the test article possibly exacerbates asthma symptoms by the induction of oxidative stress or reduction of the barrier functions of the epithelium.