Effect of inhibition of nitric oxide synthase on Pseudomonas aeruginosa infection of respiratory mucosa in vitro

We studied the effect of the nitric oxide synthase (NOS) inhibitor asymmetr ic dimethyl arginine (ADMA) and the inactive enantiomer N-G-methyl-D-argini ne (D-NMMA) on Pseudomonas aeruginosa infection of the respiratory mucosa i n nasal turbinate organ cultures. We also investigated the effect of P. aer uginosa culture filtrate on the expression of inducible NOS (iNOS) messenge r RNA (mRNA) by an epithelial cell line (A549). Organ cultures were preincu bated with ADMA (0.1 to 4 x 10(-4) M) or D-NMMA (2 x 10(-4) M) for 30 min p rior to bacterial infection. Infected organ cultures (8 h) had significantl y (P less than or equal to 0.05) greater epithelial damage and fewer ciliat ed and unciliated cells than did control cultures. There was an increased l evel of nitrite in the medium feeding infected organ cultures as compared w ith control cultures. ADMA significantly (P less than or equal to 0.05) red uced both bacterially induced epithelial damage and loss of ciliated cells in a concentration-dependent manner. D-NMMA did not influence the effect of P. aeruginosa infection of the mucosa. ADMA, but not D-NMMA, significantly (P less than or equal to 0.04) reduced total bacterial numbers adherent to the respiratory mucosa. P. aeruginosa culture filtrates (24 h and 36 h) si gnificantly (P = 0.02) increased iNOS with respect to glyceraldehyde-3-phos phate dehydrogenase mRNA expression. These results show that P. aeruginosa stimulates iNOS expression by a cell Line and NO production by an organ cul ture. ADMA. reduces mucosal damage and loss of ciliated cells, which sugges ts that NO may be a mediator of epithelial damage caused by P. aeruginosa.