Fig. 7. The cellular pathways implicated in potentiating the expression of COX-2 in neutrophils, following activation of the A_2A receptor. Different agonists cause the induction of COX-2 in human neutrophils by activating distinct classes of receptors, which in turn differentially activate the p38, PI-3K and ERK1/2 pathways. Some of these agonists can also transiently elevate cAMP_i. Activation of A_2AR elevates cAMP_i, which has a positive impact on COX-2 by further activating the p38, PI-3K and ERK1/2 pathways and also through the classic PKA/CREB pathway.