HYPERSECRETION OF MUCIN IN RESPONSE TO INFLAMMATORY MEDIATORS BY GUINEA-PIG TRACHEAL EPITHELIAL-CELLS IN-VITRO IS BLOCKED BY INHIBITION OF NITRIC-OXIDE SYNTHASE

Primary cultures of guinea pig tracheal epithelial cells in air/liquid interface were exposed to one of four agents associated with airway inflammation: the peptide histamine (100 mu M), the lipid mediator platelet-activating factor (1 mu M), the cytokine tumor necrosis factor-alpha (15 ng/ml; specific activity 2.86 x 10(7) U/mg), or enzymatically generated reactive oxygen species (purine [500 mu M] + xanthine oxidase [20 mU/ml]). Effects of each of these substances on release of mucin by guinea pig tracheal epithelial (GPTE) cells were measured using a monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA). Each secretagogue significantly enhanced release of mucin, but the stimulatory effect of each was inhibited by pre- + co-incubation of the cells with the competitive inhibitor of nitric oxide synthase, N-G-monomethyl-L-arginine (L-NMA), but not by N-G-monomethyl-D-arginine (D-NMA), the inactive stereoisomer that does not inhibit nitric oxide synthase, Neither L-NMA nor D-NMA affected mucin secretion by themselves. The results suggest that each of these inflammation-associated mediators provokes airway epithelial mucin secretion via a mechanism involving intracellular production of nitric oxide (NO) as a critical signaling molecule.