Putting on the brakes: cyclic AMP as a multipronged controller of macrophage function

Macrophages orchestrate innate immune responses in tissues by activating various proinflammatory signaling programs. A key mechanism for preventing inflammatory disease states that result from excessive activation of such programs is the generation of the second messenger cyclic adenosine monophosphate (cAMP) by ligation of certain guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs). The pleiotropic actions of this cyclic nucleotide on various inflammatory functions of macrophages are mediated by diverse molecular mechanisms, including the assembly of distinct multiprotein complexes. A better understanding of crosstalk between cAMP signaling and proinflammatory pathways in macrophages may provide a basis for improved immunomodulatory strategies.