Adenosine - cyclic AMP pathways and cytokine expression.

Adenosine and cAMP are potent modulators of immune-triggered cytokine production. Their effects overlap with regard to the inhibition of the pro-inflammatory cytokines TNF-alpha, IFN-gamma, IL-12, and the stimulation of production of the major anti-inflammatory cytokine IL-10. They may tentatively be considered to be upregulators of the production of Th2 cytokines (IL-10, IL-6), but downregulators of the production of Th1 cytokines (IL-2 and IFN-gamma). Cytokines produced in common by Th0, Th1 and Th2 cells are affected as well, although the low quantity and heterogeneity of the contemporary experimental data do not allow unambiguous conclusions to be drawn. Nevertheless, IL-3, IL-4, MIP-1alpha/beta and GM-CSF have usually been found to be inhibited, IL-5 stimulated, while IL-1 remains largely unaffected by adenosine or cAMP. These effects, and in particular the inhibition of TNF-alpha and stimulation of IL-10 expression, might be of therapeutic value in a variety of pathophysiological conditions.