Taub M, Parker R, Mathivanan P, Ariff MA, Rudra T. Antagonism of the prostaglandin E 2 EP1 receptor in MDCK cells increases growth through activation of Akt and the epidermal growth factor receptor. Am J Physiol Renal Physiol 307: F539 -F550, 2014. First published July 9, 2014; doi:10.1152/ajprenal.00510.2013.-The actions of prostaglandin E 2 (PGE2) in the kidney are mediated by G protein-coupled E-prostanoid (EP) receptors, which affect renal growth and function. This report examines the role of EP receptors in mediating the effects of PGE 2 on Madin-Darby canine kidney (MDCK) cell growth. The results indicate that activation of Gscoupled EP2 and EP4 by PGE 2 results in increased growth, while EP1 activation is growth inhibitory. Indeed, two EP1 antagonists (ONO-8711 and SC51089) stimulate, rather than inhibit, MDCK cell growth, an effect that is lost following an EP1 knockdown. Similar observations were made with M1 collecting duct and rabbit kidney proximal tubule cells. ONO-8711 even stimulates growth in the absence of exogenous PGE 2, an effect that is prevented by ibuprofen (indicating a dependence upon endogenous PGE 2). The involvement of Akt was indicated by the observation that 1) ONO-8711 and SC51089 increase Akt phosphorylation, and 2) MK2206, an Akt inhibitor, prevents the increased growth caused by ONO-8711. The involvement of the EGF receptor (EGFR) was indicated by 1) the increased phosphorylation of the EGFR caused by SC51089 and 2) the loss of the growthstimulatory effect of ONO-8711 and SC51089 caused by the EGFR kinase inhibitor AG1478. The growth-stimulatory effect of ONO-8711 was lost following an EGFR knockdown, and transduction of MDCK cells with a dominant negative EGFR. These results support the hypothesis that 1) signaling via the EP1 receptor involves Akt as well as the EGFR, and 2), EP1 receptor pharmacology may be employed to prevent the aberrant growth associated with a number of renal diseases. prostaglandin E2; kidney epithelial cell growth; EP receptors PROSTAGLANDIN E2 (PGE2), the predominant product of arachidonic acid in the kidney, controls renal function by a number of different means (5). PGE 2 regulates salt and water reabsorption by tubular epithelial cells, glomerular filtration (41), renal blood flow (34), and the renin-angiotensin system (11). In addition, PGE 2 has been implicated as playing a role in the progression of a number of renal diseases, including diabetic nephropathy (36), glomerulonephritis (44), and autosomal dominant polycystic kidney disease (ADPKD) (33).The effects of PGE 2 are mediated by its interaction with four different subtypes of G protein-coupled EP receptors (8), including Gs-coupled EP2 and EP4, which activate adenylate cyclase (AC), Gi-coupled EP3, coupled to Gi, which reduces AC activity as well as Gq-coupled EP1, which activates PLC, resulting in an increase in intracellular Ca 2ϩ , and the activation of PKC. All four subtypes of EP receptors are present in the kidney (9). Especially high levels of EP1, EP3, and EP4 are present in the col...

Prostaglandin E2 (PGE2) plays a number of roles in the kidney that are mediated by 4 classes of E‐prostanoid (EP) receptors, including EP2 and EP4, which activate adenylate cyclase (AC), EP3 that inhibits AC, and EP1, that activates Phospholipase C. Each of these receptors contributes to a number of renal diseases. Here, the role of EP1, EP2 and EP4 in mediating the effects of PGE2 on MDCK cell growth is examined. The results indicate that EP2 and EP4 contribute to the growth stimulatory effect of PGE2, unlike EP1, which is growth inhibitory. Indeed, the EP1 antagonists ONO‐8711 and SC51089 increase, rather than inhibit MDCK cell growth. Growth stimulatory effects of ONO‐8711 and SC51089 were observed in the absence of exogenous PGE2. This latter effect was prevented by the cyclooxygenase inhibitor ibuprofen, indicating that EP1 mediated growth inhibition was dependent upon endogenous PGE2. Evidence was obtained that EP1 activation results in the inhibition of Akt signaling, including the observation that 1) ONO‐8711 and SC51089 increase Akt phosphorylation, and 2) MK2206, an Akt inhibitor, prevents the increased growth caused by EP1 antagonists. In addition, evidence was obtained for the involvement of the EGF Receptor (EGFR), including the observation that 1) SC51089 increases the phosphorylation of the EGF Receptor (EGFR), and 2) the EGFR kinase inhibitor AG1478 prevents the growth stimulatory effects of ONO‐8711 and SC51089. These latter results support the hypothesis that EP1 receptor activation also affects signaling via the EGFR. Thus, EP1 receptor pharmacology may prevent aberrant growth associated with a number of renal diseases. Grant Funding Source: NIH