Structure−Activity Relationships of Pyridoxal Phosphate Derivatives as Potent and Selective Antagonists of P2X<sub>1</sub> Receptors
作者:Yong-Chul Kim、Sean G. Brown、T. Kendall Harden、José L. Boyer、George Dubyak、Brian F. King、Geoffrey Burnstock、Kenneth A. Jacobson
DOI:10.1021/jm9904203
日期:2001.2.1
Novel analogues of the P2 receptor antagonist pyridoxal-5'-phosphate 6-azophcnyl-2',5'-disulfonate (2) were synthesized and studied as antagonists in functional assays at recombinant rat P2X(1), P2X(2), and P2X(3) receptors expressed in Xenopus oocytes lion flux stimulation) and at turkey erythrocyte P2Y(1) receptors (phospholipase C activation). Selected compounds were also evaluated as antagonists of ion flux and the opening of a large pore at the recombinant human P2X(7) receptor. Modifications were made in the 4-aldehyde and 5'-phosphate groups of the pyridoxal moiety: i.e. a CH2OH group at the 4-position in pyridoxine was either condensed as a cyclic phosphate or phosphorylated separately to form a bisphosphate, which reduced potency at P2 receptors. 5-Methylphosphonate substitution, anticipated to increase stability to hydrolysis, preserved P2 receptor potency. At the g-position, halo, carboxylate, sulfonate, and phosphonate variations made on the phenylazo ring modulated potency at P2 receptors. The p-carboxyphenylazo analogue, 4, of phosphate 2 displayed an IC50 value of 9 nM at recombinant P2X(1) receptors and was 1300-, 16-, and >10000-fold selective for P2X(1) versus P2X(2), P2X(3), and P2Y(1) subtypes, respectively. The corresponding Ei-methylphosphonate was equipotent at P2X(1) receptors. The 5-methylphosphonate analogue containing a 6-[3,5-bis(methylphosphonate)]phenylazo moiety, 9, had IC50 values of 11 and 25 nM at recombinant P2X(1) and P2X(3) receptors, respectively. The analogue containing a phenylazo 4-phosphonate group, 11, was also very potent at both P2X(1) and P2X(3) receptors. However, the corresponding 2,5-disulfonate analogue, 10, was 28-fold selective for P2X(1) versus P2X(3) receptors. None of the analogues were more potent at P2X(7) and P2Y(1) receptors than 2, which acted in the micromolar range at these two subtypes.