Potent Human A3 Adenosine Receptor Research Articles

Subtle Chemical Changes Cross the Boundary between Agonist and Antagonist: New A3 Adenosine Receptor Homology Models and Structural Network Analysis Can Predict This Boundary.

Distinguishing compounds' agonistic or antagonistic behavior would be of great utility for the rational discovery of selective modulators. We synthesized truncated nucleoside derivatives and discovered 6c (Ki = 2.40 nM) as a potent human A3 adenosine receptor (hA3AR) agonist, and subtle chemical modification induced a shift from antagonist to agonist. We elucidated this shift by developing new hA3AR homology models that consider the pharmacological profiles of the ligands. Taken together with molecular dynamics (MD) simulation and three-dimensional (3D) structural network analysis of the receptor-ligand complex, the results indicated that the hydrogen bonding with Thr943.36 and His2727.43 could make a stable interaction between the 3'-amino group with TM3 and TM7, and the corresponding induced-fit effects may play important roles in rendering the agonistic effect. Our results provide a more precise understanding of the compounds' actions at the atomic level and a rationale for the design of new drugs with specific pharmacological profiles.

Determination and validation of LJ-2698, a potent human A3 adenosine receptor antagonist, in rat plasma by liquid chromatography-tandem massspectrometry and its application in pharmacokinetic study.

LJ-2698, a highly potent human A3 adenosine receptor antagonist with nucleoside structure, was designed to have a minimal species dependence. For further pre-clinical studies, analytical method for the detection of LJ-2698 in rat plasma was developed by liquid chromatography-tandem mass. Plasma samples were processed by protein precipitation method with acetonitrile, using losartan as the internal standard (IS). Chromatographic separation was carried out using a Kinetex C18 column (100×4.6mm; 100 Å; 2.6 μ) with acetonitrile/water with 0.2% (v/v) formic acid (65:35, v/v) in the isocratic mode at a flow rate of 0.4mL/min. Mass spectrometric detection in multiple reaction monitoring mode was performed with positive electrospray ionization. The mass transitions of LJ-2698 and IS were m/z 412.3→294.1 and m/z 423.1→207.2, respectively. The calibration curves were linear in the range 5.00-5000ng/mL (r 2≥0.998). The lower limit of quantification was established as 5.00ng/mL. Within- and between-run precisions were<7.01%, as relative standard deviation; and accuracies were in the range 3.37-3.64%, as relative error. The validated method was successfully applied to its pharmacokinetic evaluation after intravenous and oral administration in rats, and the dose-dependent pharmacokinetic behavior of LJ-2698 was elucidated for the first time.

Pharmacophore elucidation for a new series of 2-aryl-pyrazolo-triazolo-pyrimidines as potent human A3 adenosine receptor antagonists

A ligand-based pharmacophore was obtained for a new series of 2-unsubstituted and 2-(para-substituted)phenyl-pyrazolo-triazolo-pyrimidines as potent human A(3) adenosine receptor antagonists. Through comparative molecular field analysis-based quantitative structure-activity relationship studies, structural features at the N(5)-, N(8)- and C(2)-positions of the tricyclic nucleus were deeply investigated, with emphasis given to the unprecedentedly explored C(2)-position. The resulting model showed good correlation and predictability (r(2)=0.936; q(2)=0.703; r(pred)(2)=0.663). Overall, the contribution of steric effect was found relatively more predominant for the optimal interaction of these antagonists to the human A(3) receptor.