MECHANISMS OF ACTION OF PSEUDOMONAS-AERUGINOSA PYOCYANIN ON HUMAN CILIARY BEAT IN-VITRO

Pyocyanin is a blue redox active pigment produced by Pseudomonas aerug inosa. It is present at concentrations of up to 10(-4) M in SpUta from patients with cystic fibrosis and bronchiectasis who are heavily colo nized with this organism. Pyocyanin, at physiologically relevant conce ntrations, slows human nasal ciliary beat frequency (CBF) in vitro and leads to disruption of the epithelium. Pyocyanin-induced slowing of C BF after 2 h was associated with a significant fall in intracellular c yclic AMP (cAMP) (90%) and ATP (66%) and was reversible after the pyoc yanin was removed by washing. These effects were not mediated through interaction with neutrophils. The pyocyanin-induced fall in CBF was no t affected by EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N', N'-tetraacetic acid], pyrazinamide, 8-phenyltheophylline, indomethacin , or antioxidants, including catalase (500 U/ml), superoxide dismutase , and N-acetylcysteine. Ciliary slowing was, however, prevented (>70%) by isobutylmethylxanthine and forskolin, both of which increase intra cellular cAMP, and also by the cAMP analog, dibutyryl cAMP. There was also a concomitant protection against the fall in both cAMP and ATP. T hese agents also delayed the onset of epithelial disruption associated with pyocyanin treatment. In contrast, treatment with the iron chelat or desferrioxamine prevented epithelial disruption, although it had no effect on pyocyanin-induced slowing of CBF. It appears that ciliary s lowing can be dissociated from epithelial disruption and that the effe cts of pyocyanin on CBF are associated with a fall in both intracellul ar cAMP and ATP.