Immunological aspects of phosphodiesterase inhibition in the respiratory system.

Phosphodiesterases (PDEs) are known as a super-family of 11 isoenzymes, which can exert various functions based on their organ distribution. Aside from non-selective PDE inhibitors (methylxanthines, e.g. theophylline) used many years in clinical settings, increasing attention is focused on the involvement of selective PDE inhibitors in therapy of obstructive airway diseases associated with chronic inflammation. There are mostly PDE3, PDE4, and PDE7 isoforms present in the respiratory system. This paper describes the mechanisms of action, adverse effects, and potential clinical use of both non-selective and selective PDE inhibitors. The focus of the review is on the influence of PDE inhibitors on the immune system.