Inhibition of lipopolysaccharide-induced pulmonary edema by isozyme-selective phosphodiesterase inhibitors in guinea pigs.

There is a need for pharmacological agents for the treatment of pulmonary edema associated with the adult respiratory distress syndrome. Therefore, we examined the effects of isozyme-selective cyclic AMP phosphodiesterase (cAMP PDE) inhibitors, as well as aminophylline and dexamethasone, on the pulmonary edema, protein leakage into the airways and airway neutrophilia induced by aerosolized lipopolysaccharide (LPS) in intact guinea pigs. Twenty-four hours after LPS exposure lung wet/dry weight ratios increased from 4.9 +/- 0.004 to 5.8 +/- 0.02. Rolipram (PDE4 selective), CI-930 (PDE3 selective), aminophylline and dexamethasone (given p.o. 1 hr before and 4 hr after LPS exposure) inhibited pulmonary edema formation with ED50 values of 1.7, 0.5, 31 and 2.8 mg/kg, respectively. Maximum inhibition occurred with rolipram at 10 mg/kg (70 +/- 17%), CI-930 at 10 mg/kg (101 +/- 4%), aminophylline at 50 mg/kg (88 +/- 14%) and dexamethasone at 3 mg/kg (64 +/- 6%). Denbufylline and milrinone also inhibited pulmonary edema formation at 10 mg/kg i.p., supporting the inhibition of PDE4 and PDE3 as the mechanisms of action of rolipram and CI-930, respectively. Rolipram, CI-930, aminophylline and dexamethasone (at maximum doses for inhibiting pulmonary edema) inhibited the 3-fold increase in bronchoalveolar lavage albumin concentration 24 hr after LPS exposure (42 +/- 14%, 98 +/- 2%, 70 +/- 9% and 53 +/- 13%, respectively). However, none of these compounds (at maximum doses for inhibiting pulmonary edema) inhibited the corresponding 400-fold increase in lavage neutrophil counts.(ABSTRACT TRUNCATED AT 250 WORDS)