Screening of approved drugs regarding their P2X3 receptor activity

The P2X3 receptor (P2X3R), one of the seven members of the ATP-gated P2X receptor family, plays a crucial role in sensory neurotransmission. P2X3 receptor antagonists have been identified as promising drugs to treat chronic cough and are suggested to offer pain relief in chronic pain pain. We have analyzed whether compounds affect P2X3 receptor activity by high-throughput screening (HTS) of the Spectrum Collection of 2000 approved drugs, natural products and bioactive substances (in collaboration with Prof. Michael Schaefer, Rudolf-Boehm-Institut of Pharmacology and Toxicology, University of Leipzig).

Among several hits that markedly inhibited P2X3R activation by ATP, we identified aurintricarboxylic acid (ATA) as a nanomolar-potency antagonist of P2X3 receptor-mediated responses. Two-electrode voltage clamp electrophysiology-based concentration–response analysis and selectivity profiling revealed that ATA strongly inhibits the rP2X1 and rP2X3 receptors.

Molecular docking studies, site-directed mutagenesis and concentration-response analysis revealed that ATA binds to the negative allosteric site of the hP2X3 receptor.

Concentration-response curves of aurintricarboxylic acid (ATA) at the indicated P2XRs (left) and molecular-docking of ATA and AF-219 (a known P2X3R antagonist) into the negative allosteric site of the hP2X3R.
Concentration-response curves of aurintricarboxylic acid (ATA) at the indicated P2XRs (left) and molecular-docking of ATA and AF-219 (a known P2X3R antagonist) into the negative allosteric site of the hP2X3R.

In another study we have demonstrated the inhibition of the human P2X3 receptor by various non-steroidal anti-inflammatory drugs (NSAIDs). Diclofenac was the most effective antagonist. Due to their involvement in nociception, inhibition of hP2X3R and hP2X2/3R by micromolar concentrations of diclofenac, which are rarely reached in the human body, may play a minor role in analgesia but may explain the known side effect of taste disturbances caused by diclofenac.

Details on the identification of ATA and Diclofenac as a P2X3R antagonists can be found in the publications below.

Obrecht AS, Urban N, Schaefer M, Röse A, Kless A, Meents JE, Lampert A, Abdelrahman A, Müller CE, Schmalzing G, Hausmann R (2019). Identification of aurintricarboxylic acid as a potent allosteric antagonist of P2X1 and P2X3 receptors. Neuropharmacology 2019, 158:107749. https://www.ncbi.nlm.nih.gov/pubmed/31461640

Grohs L, Cheng L, Cönen S, Haddad BG, Bülow A, Toklucu I, Ernst L, Körner J, Schmalzing G, Lampert A, Machtens JP, Hausmann R (2023) Diclofenac and other non-steroidal anti-inflammatory drugs (NSAIDs) are competitive antagonists of the human P2X3 receptor. Front Pharmacol. 14:1120360. https://www.ncbi.nlm.nih.gov/pubmed/37007008/