S-carboxymethylcysteine normalises airway responsiveness in sensitised and challenged mice

S -carboxymethylcysteine ( S -CMC) has been used as a mucoregulator in respiratory diseases. However, the mechanism of action of S -CMC on allergic airway inflammation has not yet been defined. In the present study, BALB/c mice were initially sensitised and challenged to ovalbumin (OVA) and, weeks later, re-challenged with OVA (secondary challenge). S -CMC (5–100 mg·kg −1 ) was administered from 2 days before the secondary challenge through to the day of assay. Mice developed airway hyperresponsiveness (AHR) 6 h after the secondary challenge and increased numbers of neutrophils were present in the bronchoalveolar lavage (BAL) fluid. At 72 h after secondary challenge, mice again developed AHR, but the BAL fluid contained large numbers of eosinophils. S -CMC treatment was found to reduce AHR and neutrophilia at 6 h, as well as eosinophilia and AHR at 72 h. These effects appeared to be dose dependent. Goblet cell hyperplasia, observed at 72 h, was reduced by S -CMC. In BAL fluid, increased levels of interferon-γ, interleukin (IL)-12 and IL-10 and decreased levels of IL-5 and IL-13 were detected. In conclusion, the data indicate that S -carboxymethylcysteine is effective in reducing airway hyperresponsiveness and airway inflammation at two distinct phases of the response to the secondary allergen challenge in sensitised mice.