Development of a High-Affinity Inhibitor of the Prostaglandin Transporter

Abstract

Prostaglandin E 2 (PGE 2 ) triggers a vast array of biological signals and physiological events. The prostaglandin transporter (PGT) controls PGE 2 influx and is rate-limiting for PGE 2 metabolism and signaling termination. PGT global knockout mice die on postnatal day 1 from patent ductus arteriosus. A high-affinity PGT inhibitor would thus be a powerful tool for studying PGT function in adult animals. Moreover, such an inhibitor could be potentially developed into a therapeutic drug targeting PGT. Based on structure-activity relationship studies that built on recently identified inhibitors of PGT, we obtained N-(2-(2-(2-azidoethoxy)ethoxy)ethyl)-4-((4-((2-(2-(2-benzamidoethoxy) ethoxy)ethyl)amino)-6-((4-hydroxyphenyl)amino)-1,3,5-triazin-2-yl)amino)benzamide (T26A), a competitive inhibitor of PGT, with a K i of 378 nM. T26A seems to be highly selective for PGT, because it neither interacts with a PGT homolog in the organic anion transporter family nor affects PGE 2 synthesis. In Madin-Darby canine kidney cells stably transfected with PGT, T26A blocked PGE 2 metabolism, resulting in retention of PGE 2 in the extracellular compartment and the negligible appearance of PGE 2 metabolites in the intracellular compartment. Compared with vehicle, T26A injected intravenously into rats effectively doubled the amount of endogenous PGE 2 in the circulation and reduced the level of circulating endogenous PGE 2 metabolites to 50%. Intravenous T26A was also able to slow the metabolism of exogenously injected PGE 2 . These results confirm that PGT directly regulates PGE 2 metabolism and demonstrate that a high-affinity inhibitor of PGT can effectively prevent PGE 2 metabolism and prolong the half-life of circulating PGE 2 .

Regulation and function of renal medullary cyclooxygenase-2 during high salt loading

“…They are designated membrane-associated PGES (mPGES)-1, mPGES-2, and cytosolic PGES (cPGES) with mPGES-1 be the best characterized PGES (64). mPGES-1 couples with COX-2 to mediate PGE 2 production in response to inflammatory stimuli and mPGES-1 deletion blunts pain and inflammatory responses (65, 66). Besides inflammatory cells, mPGES-1 is widely expressed in adipose tissues, stomach, spleen, and kidney.…”

Regulation of prostaglandin EP1 and EP4 receptor signaling by carrier‐mediated ligand reuptake

“…In the same way that inhibitors of neurotransmitter reuptake have been useful in the management of psychiatric diseases (Mann ), inhibitors of prostaglandin reuptake, by raising endogenous PG levels (Chi et al. ; Syeda et al. ), might be medicinally applicable for conditions in which exogenous prostaglandins are currently used, such as glaucoma (Stjernschantz ), pulmonary artery hypertension (Gomberg‐Maitland and Olschewski ), and vascular insufficiency (Amendt ).…”

“…These experiments were performed in the absence or presence of the PGT inhibitor T26A (Chi et al. ) (5 μ mol/L) at 37°C for 10 min. Immediately before harvesting the cells, media were collected to determine the result of contact with the cell monolayers on extracellular PGE 2 concentrations.…”

Human platelets generate phospholipid-esterified prostaglandins via cyclooxygenase-1 that are inhibited by low dose aspirin supplementation

“…Thus, the lack of PGE 2 -d4 esterification might also be due to an inability of platelets to take up this lipid through the absence of prostaglandin transporters on the cell surface. To date, nothing is known regarding expression of these proteins by platelets nor how they utilize oxidized fatty acids as substrates (27). …”