P2-receptor antagonists: IV. Blockade of P2-receptor subtypes and ecto-nucleotidases by compounds related to reactive blue 2

Abstract

Effects of reactive blue 2 and twelve structurally related compounds were studied on contractions of the rat vas deferens elicited by alpha,beta-methylene ATP (alpha,beta-MeATP; mediated by P2X-receptors), relaxations of the carbachol-precontracted guinea-pig taenia coli elicited by adenosine 5'-O-(2-thiodiphosphate) (ADPbetaS; mediated by P2Y-receptors), and the degradation of ATP by rat vas deferens tissue. All compounds, except acid blue 41 and acid blue 129 (at up to 100 microM), shifted the concentration-response curve of alpha,beta-MeATP in the rat vas deferens to the right. Most increased, but uniblue A greatly decreased, the maximum of the curve. In the case of cibacron blue 3GA and reactive blue 19, of which three concentrations were tested, the Arunlakshana-Schild regression was linear, and the slope did not differ from unity. The apparent Kd values of the effective substances ranged between 0.7 and 111 microM. Most compounds increased the contraction of the rat vas deferens elicited by high K+. In the guinea-pig taenia coli, all compounds, except uniblue A and reactive blue 19 (at up to 100 microM), shifted the concentration-response curve of ADPbetaS to the right in a parallel manner. In the case of acid blue 129 and acid blue 80, of which three concentrations were tested, the slope of the Arunlakshana-Schild regression did not differ from unity. The apparent Kd values of the effective substances were between 0.7 and 69 microM. Most compounds also reduced the relaxation of the guinea-pig taenia coli elicited by noradrenaline. The removal of ATP from the medium by vas deferens tissue was decreased only by reactive blue 2, cibacron blue 3GA, uniblue A and reactive blue 19, with IC25% values between 17 and 62 microM. The structure-activity relationships for P2X- and P2Y-receptor blockade in this series are strikingly dissimilar. In reactive blue 2 and its isomers, for example, both the 1-amino-anthraquinone-2-sulphonate core and the 'side-chain' of the molecule are involved in P2X-receptor binding; P2Y-receptor affinity, in contrast, resides largely or totally in the anthraquinone core. The most promising antagonists are uniblue A which is P2X- versus P2Y-selective and acid blue 129 which is P2Y- versus P2X-selective, both with few, if any, non-P2-receptor effects at concentrations blocking the respective P2-subtype.

ATP transduces signals from ASGM1, a glycolipid that functions as a bacterial receptor

“…Among the most extensively studied GPCRs known to exist on epithelial cells are receptors of the P2Y family that are activated by extracellular nucleotides (12)(13)(14). We observed that P2Y antagonists Reactive Blue 2 and Acid Blue 129 (15,16) strongly inhibited mucin gene expression whereas inhibitors of P2X nucleotide-gated ion channels (PPADS and NF023) did not (Fig. 5A).…”

NF449: a subnanomolar potency antagonist at recombinant rat P2X 1 receptors

“…1B, NF449 produced concentration-related rightward displacements of the concentration-contraction curve to αβmeATP (solvent controls: apparent pEC 50 =5.07±0.02, maximum response at 100 µM 2461±103 mg tension; n=12) and simultaneously increased the slope. Although the reason for this increase in slope is unclear, the same effect has been observed with a series of structurally unrelated P2 antagonists in rat vas deferens (Tuluc et al 1998). It was not possible to construct reliable full concentration-response curves of αβmeATP in the absence and presence of NF449, due to difficulties (limited availability of αβmeATP and desensitization) with using the agonist at the high concentrations which would be required.…”

Activation and Regulation of Purinergic P2X Receptor Channels

“…Several other related compounds, such as RB-4, RB-5, 1519, and acid blue-25, -41, -80, and -129, have also been tested for their antagonistic actions at P2Rs (Tuluc et al, 1998). A series of RB-2 type anthraquinone derivatives were also synthesized, re-evaluated, and tested for their potency at P2Rs.…”