Pharmacology of P2X channels

Adenine nucleotides acting at P2X 1 receptors are potent vasoconstrictors. Recently, we demonstrated that activation of adenosine A 2B receptors on human coronary smooth muscle cells inhibits cell proliferation by the induction of the nuclear receptor subfamily 4, group A, member 1 (NR4A1; alternative notation Nur77). In the present study, we searched for long-term effects mediated by P2X 1 receptors by analyzing receptor-mediated changes in cell proliferation and in the expression of NR4A1. Cultured human coronary smooth muscle cells were treated with selective receptor ligands. Effects on proliferation were determined by counting cells and measuring changes in impedance. The induction of transcription factors was assessed by qPCR. The P2X receptor agonist α,β-methylene-ATP and its analog β,γ-methylene-ATP inhibited cell proliferation by about 50 % after 5 days in culture with half-maximal concentrations of 0.3 and 0.08 μM, respectively. The effects were abolished or markedly attenuated by the P2X 1 receptor antagonist NF449 (carbonylbis-imino-benzenetriylbis-(carbonylimino)tetrakis-benzene-1,3-disulfonic acid; 100 nM and 1 μM). α,β-methylene-ATP and β,γ-methylene-ATP applied for 30 min to 4 h increased the expression of NR4A1; NF449 blocked or attenuated this effect. Small interfering RNA directed against NR4A1 diminished the antiproliferative effects of α,β-methylene-ATP and β,γ-methylene-ATP. α,β-methylene-ATP (0.1 to 30 μM) decreased migration of cultured human coronary smooth muscle cells in a chamber measuring changes in impedance; NF449 blocked the effect. In conclusion, our results demonstrate for the first time that adenine nucleotides acting at P2X 1 receptors inhibit the proliferation of human coronary smooth muscle cells via the induction of the early gene NR4A1.

Section: Introductionmentioning

confidence: 99%

P2X1 receptor-mediated inhibition of the proliferation of human coronary smooth muscle cells involving the transcription factor NR4A1

Hinze

Mayer

Harst

et al. 2013

“…Consistent with these data, ATP-evoked activation of capsaicin-insensitive spinal P2X2/3 receptors underlies an N-methyl-D-aspartate (NMDA)-dependent long lasting allodynic sensitivity in rodents [34]. Another structurally different and potent P2X2/3 and P2X3 antagonist, RO-4 (compound 4), has been reported to reverse both inflammatory and bone cancer pain in experimental models [35,36]. Following peripheral administration, RO-4 is effective in nerve injury induced pain models, presumably resulting from its ability to readily cross the blood-brain barrier [36].…”

Section: Gabapentinmentioning

confidence: 53%

“…A-317491(compound 7) was the first selective small molecule compound for P2X3 and P2X2/3. Subsequently, other potent P2X3 antagonists were reported including RO-3 (compound 9), and RO-4 (compound 10) that are at least 100-fold less active across a wide range of kinases, receptors, and ion channels [35,36,39]. These compounds have improved drug-like properties relative to earlier P2X3 antagonists (e.g., compounds 1-6) (Fig.…”

Section: Gabapentinmentioning

confidence: 99%

P2X receptor antagonists for pain management: examination of binding and physicochemical properties

Gum

Wakefield

Jarvis

2011

Enhanced sensitivity to noxious stimuli and the perception of non-noxious stimuli as painful are hallmark sensory perturbations associated with chronic pain. It is now appreciated that ATP, through its actions as an excitatory neurotransmitter, plays a prominent role in the initiation and maintenance of chronic pain states. Mechanistically, the ability of ATP to drive nociceptive sensitivity is mediated through direct interactions at neuronal P2X3 and P2X2/3 receptors. Extracellular ATP also activates P2X4, P2X7, and several P2Y receptors on glial cells within the spinal cord, which leads to a heightened state of neural-glial cell interaction in ongoing pain states. Following the molecular identification of the P2 receptor superfamilies, selective small molecule antagonists for several P2 receptor subtypes were identified, which have been useful for investigating the role of specific P2X receptors in preclinical chronic pain models. More recently, several P2X receptor antagonists have advanced into clinical trials for inflammation and pain. The development of orally bioavailable blockers for ion channels, including the P2X receptors, has been traditionally difficult due to the necessity of combining requirements for target potency and selectivity with suitable absorption distribution, metabolism, and elimination properties. Recent studies on the physicochemical properties of marketed orally bioavailable drugs, have identified several parameters that appear critical for increasing the probability of achieving suitable bioavailability, central nervous system exposure, and acceptable safety necessary for clinical efficacy. This review provides an overview of the antinociceptive pharmacology of P2X receptor antagonists and the chemical diversity and drug-like properties for emerging antagonists of P2X3, P2X2/3, P2X4, and P2X7 receptors. Keywords

“…P2X2, P2X4, and P2X7 are the predominant isoforms. These P2X isoforms can form homomeric and heteromeric channels to influx cations when ATP binds to the binding site [15,31]. The recorded inward current also shows slow desensitization (Figs.…”

Section: Discussionmentioning

confidence: 95%

ATP-mediated potassium recycling in the cochlear supporting cells

Zhu

Zhao

2010

Gap junction-mediated K + recycling in the cochlear supporting cell has been proposed to play a critical role in hearing. However, how potassium ions enter into the supporting cells to recycle K + remains undetermined. In this paper, we report that ATP can mediate K + sinking to recycle K + in the cochlear supporting cells. We found that micromolar or submicromolar levels of ATP could evoke a K + -dependent inward current in the cochlear supporting cells. At negative membrane potentials and the resting membrane potential of −80 mV, the amplitude of the ATPevoked inward current demonstrated a linear relationship to the extracellular concentration of K + , increasing as the extracellular concentration of K + increased. The inward current also increased as the concentration of ATP was increased. In the absence of ATP, there was no evoked inward current for extracellular K + challenge in the cochlear supporting cells. The ATP-evoked inward current could be inhibited by ionotropic purinergic (P2X) receptor antagonists. Application of pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS, 50 µM) or pre-incubation with an irreversible P2X7 antagonist oxidized ATP (oATP, 0.1 mM) completely abolished the ATP-evoked inward current at the negative membrane potential. ATP also evoked an inward current at cell depolarization, which could be inhibited by intracellular Cs + and eliminated by positive holding potentials. Our data indicate that ATP can activate P2X receptors to recycle K + in the cochlear supporting cells at the resting membrane potential under normal physiological and pathological conditions. This ATP-mediated K + recycling may play an important role in the maintenance of cochlear ionic homeostasis.