Inhibition of phospholipase A2-mediated arachidonic acid release by cyclic AMP defines a negative feedback loop for P2Y receptor activation in Madin-Darby canine kidney D1 cells

In Madin-Darby canine kidney D-1 cells extracellular nucleotides activate P-2Y receptors that couple to several signal transduction pathways, including stimulation of multiple phospholipases and adenylyl cyclase, For one class of P-2Y receptors, P-2Y2 receptors, this stimulation of adenylyl cyclase and increase in cAMP occurs via the conversion of phospholipase A(2) (PLA(2))-generated arachidonic acid (AA) to prostaglandins (e.g. PGE(2)). These prostaglandins then stimulate adenylyl cyclase activity, presumably via activation of prostanoid receptors, In the current study we show that agents that increase cellular cAMP levels (including PGE(2), forskolin, and the beta-adrenergic agonist isoproterenol) can inhibit P-2Y receptor-promoted AA release. The protein kinase A (PKA) inhibitor H89 blocks this effect, suggesting that this feedback inhibition occurs via activation of PKA. Studies with PGE(2) indicate that inhibition of AA release is attributable to inhibition of mitogen-activated protein kinase activity and in turn of P-2Y receptor stimulated PLA(2) activity. Although cAMP/PKA-mediated inhibition occurs for P-2Y receptor-promoted AA release, we did not find such inhibition for epinephrine (alpha(1)-adrenergic) or bradykinin-mediated AA release. Taken together, these results indicate that negative feedback regulation via cAMP/PKA-mediated inhibition of mitogen-activated protein kinase occurs for some, but not all, classes of receptors that promote PLA(2) activation and AA release. We speculate that receptor-selective feedback inhibition occurs because PLA(2) activation by different receptors in Madin-Darby canine kidney D-1 cells involves the utilization of different signaling components that are differentially sensitive to increases in cAMP or, alternatively, because of compartmentation of signaling components.