Actions of a series of PPADS analogs at P2X₁ and P2X₃ receptors

Abstract

[Table: see text] Seven PPADS (yridoxal-5'-hosphate 6-zophenyl 2',4'-iulfonate) analogs were investigated at Group 1 P2X receptors expressed in Xenopus oocytes. All seven analogs potently inhibited P2X (IC range, 5-32 nM) and P2X (IC range, 22-345 nM), the two Group I P2X receptor subtypes. Analogs showed greater inhibitory activity where the pyridoxal moiety of PPADS contained a 5'-phosphonate group, rather than a 5'-phosphate group. Analogs also showed greater potency where disulfonate groups were removed from, or substituted at, the azophenyl moiety. The most active analog was MRS 2257 (pyridoxal-5'-phosphonate 6-azophenyl 3',5'-bismethylenephosphonate) at P2X (IC, 5 nM) and P2X (IC, 22 nM) receptors, being 14-fold and 10-fold more potent than PPADS itself. MRS 2257 produced a nonsurmountable inhibition when tested against a range of ATP concentrations, although blockade was reversed by about 85% after 20 minutes of washout. TNP-ATP and IpI were equipotent with MRS 2257 at P2X receptors, whereas TNP-ATP was 64-fold more potent than MRS 2257 at P2X receptors. In conclusion, the PPADS template can be altered at the pyridoxal and phenyl moieties to produce P2X and P2X receptor antagonists showing higher potency and greater degree of reversibility than the parent compound at these Group I P2X receptors.

Molecular Recognition at Purine and Pyrimidine Nucleotide (P2) Receptors

“…For example, the phosphonate analogue MRS 2257 22 is a highly potent antagonist at both rat P2X 1 (IC 50 5.1 nM) and P2X 3 (IC 50 21.8 nM) receptors (with the receptors expressed in the Xenopus oocyte). Analogues in the PPADS series in which the diazo linkage has been replaced with carbon bridges have been synthesized [20]. One such analogue, MRS 2335 24, was roughly equipotent to the corresponding diazo derivative at the P2X 1 receptor.…”

“…One such analogue, MRS 2335 24, was roughly equipotent to the corresponding diazo derivative at the P2X 1 receptor. While high potency at P2X receptors has been achieved for PPADS derivatives, a disadvantage is the noncompetitive binding they display, accompanied by slow on-and off-rates [20].…”

2′,3′-O-Substituted ATP derivatives as potent antagonists of purinergic P2X3 receptors and potential analgesic agents

“…The first identified P2X3 antagonists were negatively charged and/or high molecular weight arylpolysulfonate molecules [44], which showed to be unselective, as they were able to antagonize also the metabotropic P2Y receptors [45]. Further studies led to the discovery of a potent and selective P2X3 receptor antagonist, named A-317491 ( Fig.…”

The impact of commercially available purinergic ligands on purinergic signalling research

“…The non-specific, potent P2 receptor antagonist pyridoxalphosphate-6-azophenyl-2′,5′-disulfonic acid (PPADS) has been readily and commercially available for some time and blocks the P2X 1 , P2X 2 , P2X 3 , P2X 5 and P2X 4 receptors (IC 50 =1, 2, 1, 27.5, 3, 4.2 nM at P2X 1, 2, 3, 4, 5, 7 , respectively and 6 and 15 nM at the P2Y 1 , 4 receptors, respectively [3,30,31]). Although a standard tool, PPADS has played a significant role in unravelling purinergic physiology and signalling.…”

“…The further discovery and subsequent cloning of the purinergic receptors prompted the establishment of the P1 (adenosine) and P2 receptor groups of which the P1 receptor group is subcategorised into the A 1 , A 2A , A 2B and A 3 receptors and the P2 receptor group into the P2X subcategory, composed of the P2X [1][2][3][4][5][6][7] receptors and the P2Y subcategory composed of P2Y 1, 2, 4, 6, 11-14 receptors [1].…”