Theophylline is a phosphodiesterase inhibitor, which gives rise to higher intracellular levels of PKA and PKG. The increase in PKA and PKG activity is associated with smooth muscle relaxation and decreased inflammatory responses. Although it should be said that the anti-inflammatory effect is clinically not spectacular.
Also shown in the graphic are the additional theoretical benefits of β-agonists. See also: β-effect in lung
Theophylline decreases intracellular AMP and GMP.
Extra info: After incorporation into the cell, theophylline inhibits the conversion of cAMP and cGMP. Thus decreasing the cellular levels of AMP and GMP
Theophylline acts on β-receptors.
Extra info: Theophylline is a phosphodiesterase inhibitor, thus does not work on β-receptors, but can work in cooperation with β-receptors to enhance PKA stimulation.