The effect of selective and non‐selective phosphodiesterase inhibitors on allergen‐ and leukotriene C4‐induced contractions in passively sensitized human airways

• Published in: British journal of pharmacology Vol. 131; no. 8; pp. 1607 - 1618
• Main Authors: Schmidt, Dunja T, Watson, Nikki, Dent, Gordon, Rühlmann, Elke, Branscheid, Detlev, Magnussen, Helgo, Rabe, Klaus F
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-12-2000; Nature Publishing
• Subjects: allergen; Biological and medical sciences; bronchoconstriction; bronchus, human; leukotriene C4; Medical sciences; passive sensitization; Pharmacology. Drug treatments; phosphodiesterase inhibitors; Phosphodiesterase isoenzymes; Respiratory system; Human; Immunopathology; Allergy; 3',5'-Cyclic-nucleotide phosphodiesterase; Respiratory disease; Enzyme; Bronchodilator; Enzyme inhibitor; Smooth muscle; Esterases; Phosphoric diester hydrolases; In vitro; Biological activity; Bronchospasm; Bronchus disease; Hydrolases; Mechanism of action
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0703725

Non‐selective inhibitors of cyclic nucleotide phosphodiesterase (PDE) block allergen‐induced contraction of passively sensitized human airways in vitro by a dual mechanism involving a direct relaxant effect on smooth muscle and inhibition of histamine and cysteinyl leukotriene (LT) release from airways. We investigated the effects of non‐selective PDE inhibitors and selective inhibitors of PDE3 and PDE4 in order to determine the involvement of PDE isoenzymes in the suppression of allergic bronchoconstriction.
Macroscopically normal airways from 76 patients were sensitized with IgE‐rich sera (>250 u ml−1) containing specific antibodies against allergen (Dermatophagoides farinae). Contractile responses of bronchial rings were assessed using standard organ bath techniques.
Passive sensitization caused increased contractile responses to allergen, histamine and LTC4. Non‐selective PDE inhibitors (theophylline, 3‐isobutyl‐1‐methylxanthine [IBMX]), a PDE3‐selective inhibitor (motapizone), PDE4‐selective inhibitors (RP73401, rolipram, AWD 12‐281) and a mixed PDE3/4 inhibitor (zardaverine) all significantly relaxed inherent bronchial tone at resting tension and to a similar degree. Theophylline, IBMX, zardaverine and the combination of motapizone and RP73401 inhibited the contractile responses to allergen and LTC4. Pre‐treatment with motapizone, RP73401, rolipram or the methylxanthine adenosine receptor antagonist, 8‐phenyltheophylline, did not significantly decrease responses to either allergen or LTC4.
We conclude that combined inhibition of PDE3 and PDE4, but not selective inhibition of either isoenzyme or antagonism of adenosine receptors, is effective in suppressing allergen‐induced contractions of passively sensitized human airways. The relationship between allergen‐ and LTC4‐induced responses suggests that PDE inhibitors with PDE3 and PDE4 selectivity are likely to act in part through inhibition of mediator release and not simply through direct relaxant actions on airway smooth muscle.
British Journal of Pharmacology (2000) 131, 1607–1618; doi:10.1038/sj.bjp.0703725