Interactions between theophylline and salbutamol on cytokine release in human monocytes.

The combination of beta(2)-adrenoceptor agonists (beta(2)-agonists) with inhaled steroids has become the standard treatment for mild to moderate asthma. Theophylline has also been combined successfully with inhaled steroids. However, the possible interaction between theophylline and beta(2)-agonists, with regard to their anti-inflammatory effects, has not been clarified. The aim of this study was to investigate the in vitro interaction between theophylline and salbutamol on cytokine generation from human monocytes and compare it with a similar interaction between dexamethasone and salbutamol. Purified monocytes from normal donors were pretreated with the drugs (alone or in combination) and stimulated with lipopolysaccharide for 24 h. Released tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), and their corresponding mRNA expressions, were determined and analyzed. Salbutamol (>or= 0.1 microM) significantly inhibited the release of TNF-alpha, but also significantly enhanced that of IL-6. In contrast, theophylline (50 microM) and dexamethasone (0.1 microM) strongly inhibited the generation of both cytokines. It is noteworthy that when the drugs were used in combination the effects of theophylline and salbutamol were additive in inhibiting TNF-alpha release, but theophylline blocked the IL-6-enhancing effect of salbutamol. A similar effect was seen when dexamethasone was combined with salbutamol. These results show that beta(2)-agonists have opposing effects on the generation of TNF-alpha and IL-6, but that when they were combined with clinically relevant concentrations of theophylline, theophylline, like dexamethasone, was capable of augmenting the anti-inflammatory effects of the beta(2)-agonists while at the same time preventing their proinflammatory effect. Thus, theophylline may have a potentially useful steroid-sparing effect.