Dipyridamole analogs as pharmacological inhibitors of equilibrative nucleoside transporters. Identification of novel potent and selective inhibitors of the adenosine transporter function of human equilibrative nucleoside transporter 4 (hENT4)

Abstract

To identify needed human equilibrative nucleoside transporter 4 (hENT4) inhibitors, we cloned and stably expressed the recombinant protein in PK15NTD (nucleoside transporter deficient) cells, and, investigated its interaction with a series of dipyridamole analogues synthesized in our laboratory. Compounds were tested in this newly established hENT4 expressing system as well in previous stably expressed hENT1 and hENT2 expressing systems. Of the dipyridamole analogues evaluated, about one fourth of the compounds inhibited hENT4 with higher potencies than dipyridamole. The most potent of them, Compound 30 displayed an IC50 of 74.4 nM, making it about 38 times more potent than dipyridamole (IC50 = 2.8 μM), and selectivities of about 80-fold and 20-fold relative to ENT1 and ENT2, respectively. Structure-activity relationship showed nitrogen-containing monocyclic rings and noncyclic substituents at the 4-and 8-positions of the pyrimido[5,4-d]pyrimidine were important for the inhibitory activity against hENT4. The most potent and selective hENT4 inhibitors tended to have a 2,6-di(N-monohydroxyethyl) substitution on the pyrimidopyrimidine ring system. The inhibitors of hENT4 identified in this study are the most selective and potent inhibitors of hENT4 adenosine transporter function to date, and should serve as useful pharmacological/biochemical tools and/or potential leads for ENT4-based therapeutics. Also, the new hENT4-expressing PK15 cell line established will serve as a useful screening tool for the discovery and design of hENT4 ligands.

Clearance of rapid adenosine release is regulated by nucleoside transporters and metabolism

“…); however, selective inhibitors are not widely available yet (Wang et al. ). There are three types of CNTs (1–3), however, there is no evidence that CNTs are regulating physiological levels of adenosine (Parkinson et al.…”

Ocular Purine Receptors as Drug Targets in the Eye

“…However, a range of other G protein-dependent and independent signaling mechanisms are associated with activation of ARs. 1 Nucleoside derivatives that activate ARs (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) are shown in Fig. 1, and AR antagonists (both nucleosides and nonnucleosides, 25-49) are shown in Fig.…”

“…For example, the approved vasodilator dipyridamole (Persantine, structure not shown) inhibits the equilibrative transporter ENT1 and other ENTs to increase the amount of extracellular adenosine. 10 The therapeutic modulation of enzymes and transporters associated with the extracellular concentrations of purines and pyrimidines is also being considered for clinical development. AMP.…”

Regulation of hepatic glucose production and AMPK by AICAR but not by metformin depends on drug uptake through the equilibrative nucleoside transporter 1 (ENT1)

“…In addition to adenosine, ENT1 also transports uridine, which promotes feeding via activation of hypothalamic uridine diphosphate receptor, P2Y6,39 and which may also contribute AMPK‐independent effects of AICAR on metabolism. Several clinically used drugs inhibit ENT1 as a secondary mode of action, including rosuvastatin40 and dipyridamole 41. Interestingly, rosuvastatin increases HbA1c in individuals with and without diabetes,42 and dipyridamole increases glycaemia in mice 43.…”