PHAGOCYTES, GRANULOCYTES, AND MYELOPOIESIS Glucocorticoids promote survival of anti-inflammatory macrophages via stimulation of adenosine receptor A3 *Katarzyna Barczyk,1 *Jan Ehrchen,1-3

Active resolution of inflammation is a previously unrecognized process essential for tissue homeostasis. Monocytes play a pivotal role in the generation as well as resolution of inflammation. Glucocorticoids (GCs) are widely used antiinflammatory agents. We demonstrate that GCs exhibit antiapoptotic effects in monocytes resulting in differentiation to an anti-inflammatory phenotype. The molecular basis of this novel antiapoptotic effect is a prolonged activation of the extracellular signal regulated kinase/mitogenactivated protein kinase (ERK/MAPK) pathway resulting in inhibition of caspase activities and expression of antiapoptotic genes via activation of c-Myc. We identified up-regulation and activation of A3 adenosine receptor (A3AR) as the initial trigger of this antiapoptotic pathway. In summary, we deciphered a novel molecular pathway promoting survival of anti-inflammatory monocytes. Specific activation of A3AR or its downstream signaling pathways may thus be a novel strategy to modulate inflammation in autoimmune disorders with fewer side effects via induction of inflammatory resolution rather than immunosuppression. (Blood. 2010;116(3):446-455)