Fig. 1

Subtle damage to airway epithelium and increased leakiness occurs after SO₂ exposure which is mitigated by pretreatment with AZM. a. Schematic depiction of the SO₂ exposure system. 500 ppm SO₂ is downmixed to the desired concentration in a positive pressure control unit. Downmixed gas is passed over the animals in a tower, ensuring constant and comparable exposure to all animals. Up to 12 animals were treated simultaneously. Outflow gas was passed through a NaOH solution for scrubbing SO₂ gas from the air mixture. Outflow pressure was monitored in order to maintain a small positive pressure (1 cm H₂O) in the exposure tower. b. Weight changes in mice exposed to 100 ppm SO₂ for 4 h. Overall, mice placed in the tower lost a significant (8%; *** p < 0.0001) amount of body weight after exposure to SO₂ in the inhalation system. This weight loss did not occur in control animals. Weight loss was recovered quickly, and mice reached their starting weights within a week after exposure. Data are means of ± SD of n = 18 for SO₂ exposed mice and n = 4 for control mice. c. No histological changes were observed after exposure to SO₂ H&E stained lung tissue. No histological changes were observed. Scale bars are 500 μm. d. HSA in BALF is increased upon SO₂ exposure. Increased HSA in SO₂ exposed mice compared with control mice was seen, as determined by ELISA. Average HSA in control and SO₂ treated mice was 143 and 440 ng/ml, respectively. Data are represented as box and whiskers plots with boxes encompassing the 25th – 75th quartiles, and whiskers demonstrating minimum and maximum values. n = 5 mice in each group. p = 0.0044. e. AZM pre-treatment results in decreased epithelial permeability to HSA. Mice orally gavaged with 2 mg/kg AZM 5 times per week had a trend for reduced HSA concentration in BALF observed after SO₂ exposure when compared to placebo mice, indicating a protective effect. Average HSA in control, SO₂ and AZM, SO₂ groups was 238, 350 and 150 ng/ml, respectively. Data are represented as box and whiskers plots with boxes encompassing the 25th – 75th quartiles, and whiskers minimum and maximum values. n = 5 observations per treatment group. p = 0.13