Effect of Dexamethasone and ACC on Bacterial Induced Mucin Expression in Human Airway Mucosa

Gram-negative bacteria can stimulate mucin production but excessive mucus supports bacterial infection and consequently leads to airway obstruction. Therefore the effect of dexamethasone (DEX) and the antioxidant acetyl-cysteine (ACC) on bacterial induced mucus expression was investigated. Explanted human airway mucosa and mucoepidermoid cells (Calu-3) were stimulated with lipopolysaccharide (LPS) or PAM3 (a synthetic lipoprotein). DEX or ACC were added to either LPS or PAM3 stimulated airway mucosa or Calu-3 cells. Mucin mRNA expression (MUC5AC) and total mucus glycoconjugates (mucin protein) was quantified using real-time PCR and PAS staining. LPS and PAM3 significantly increased mucin expression in airway mucosa and Calu3 cells (P < 0.05). DEX alone had no significant effect on mucin expression in airway mucosa or Calu-3 cells (P > 0.05). In contrast DEX significantly reduced LPSand PAM3-induced mucin expression in explanted mucosal tissue and mucin expression in Calu-3 cells (P < 0.05). In explanted human airway mucosa ACC alone significantly increased mucin expression (P < 0.05). In contrast ACC significantly decreased LPSand PAM3-induced mucin expression (P < 0.05). In Calu-3 cells ACC alone had no significant effect on mucin expression (P > 0.05). ACC decreased LPSand PAM3-induced mucin expression but this effect was not significant (P > 0.05). These data suggest that DEX can effectively reduce bacterial induced mucin expression in the airways. ACC alone may increase mucin expression in non-infected mucosa but it decreased bacterial induced mucin expression. Further studies are warranted to evaluate whether the effect of DEX or ACC is clinically relevant.