title: Sulfhydryl-mediated depression of ciliary activity: an adverse effect of acetylcysteine.
abstract: Although N-acetyl-L-cysteine (Mucomyst) is an effective mycolytic, numerous investigations have failed to demonstrate a consistent improvement in pulmonary mechanics following its use. In order to determine whether its beneficial mucolytic activity might be counterbalanced by a deleterious direct effect on cilia, we studied its effect on the activity of ciliated epithelium in the ferret tracheal organ culture system. N-acetyl-L-cysteine consistently caused progressive time-dependent ciliostasis at concentrations clinically employed, with complete ciliary paralysis within 8 hr. The effect was only partially reversed by the removal of the drug. Control preparations retained full ciliary activity for 3 to 12 weeks. In order to determine the active site on the N-acetyl-L-cysteine molecule, we investigated the ciliostatic effects of five of its chemical analogs. Isomolar N-acetyl-L-alanine was not ciliostatic, indicating the necessity of a sulfhydryl group for activity. Ciliostasis was independent of isomeric structure, acetylation, and chain length, as evidenced by the similar ciliostatic effects of L-cysteine, D-cysteine, 2-mercaptoethylamine, and N-acetyl-L-homocysteine. We conclude that N-acetyl-L-cysteine induces partially reversible ciliostasis of tracheal epithelium via its sulfhydryl group; prolonged use of this drug may impair mucociliary clearance.
mesh_terms: D000111:Acetylcysteine / Q000009:adverse effects*; D002923:Cilia / Q000187:drug effects*; D003550:Cystic Fibrosis / Q000628:therapy; D003864:Depression, Chemical; D013438:Sulfhydryl Compounds / Q000494:pharmacology*
chemical_list: D013438:Sulfhydryl Compounds; D000111:Acetylcysteine