101
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Involvement of P2X4 receptor in P2X7 receptor-dependent cell death of mouse macrophages. Biochem Biophys Res Commun 2012; 419:374-80. [PMID: 22349510 DOI: 10.1016/j.bbrc.2012.01.156] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Accepted: 01/28/2012] [Indexed: 12/11/2022]
Abstract
Interaction of P2X7 receptor with P2X4 receptor has recently been suggested, but it remains unclear whether P2X4 receptor is involved in P2X7 receptor-mediated events, such as cell death of macrophages induced by high concentrations of extracellular ATP. Here, we present evidence that P2X4 receptor does play a role in P2X7 receptor-dependent cell death. Treatment of mouse macrophage RAW264.7 cells with 1mM ATP induced Ca(2+) influx, non-selective large pore formation, activation of extracellular signal-regulated protein kinase (ERK) 1/2 and p38 mitogen-activated protein kinase (MAPK), and cell death via activation of P2X7 receptor. P2X4-knockdown cells, established by transfecting RAW264.7 cells with two short hairpin RNAs (shRNAs) targeting P2X4 receptor, showed a decrease of the initial peak of intracellular Ca(2+) after treatment with ATP, though pore formation and the P2X7-mediated activation of ERK1/2 and p38 MAPK were not affected. Intriguingly, P2X4 knockdown resulted in significant suppression of cell death induced by ATP or P2X7 agonist BzATP. In conclusion, our results suggest that P2X4 receptor is involved in P2X7 receptor-mediated cell death, but not pore formation or MAPK signaling.
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102
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Fausther M, Gonzales E, Dranoff JA. Role of purinergic P2X receptors in the control of liver homeostasis. ACTA ACUST UNITED AC 2012; 1:341-348. [PMID: 22662313 DOI: 10.1002/wmts.32] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
It is now accepted that extracellular ATP and other nucleotides are potent signaling molecules, akin to neurotransmitters, hormones and lipid mediators. In the liver, several clues support a significant role for extracellular ATP-induced signaling pathways in the control of tissue homeostasis. First, ATP and other nucleotides are physiologically detected in extracellular fluids within the liver, including sinusoidal blood and intraductular bile, in various mammalian species including human and rodents. Moreover, finely tuned mechanisms of ATP release by different liver cell types have been described, under physiological cellular changes. In addition, most hepatic cells constitutively express, at the membrane level, several ATP-metabolizing ectoenzymes and ATP-sensitive receptors that modulate and transduce these mediator signals respectively. Finally, hepatic cells also express numerous membrane transporters that actively contribute to purinergic salvage pathways. Once released in the extracellular medium, unmetabolised ATP molecules can bind to purinergic P2X and P2Y receptors, and subsequently trigger various intracellular signal transduction pathways collectively referred to as purinergic signaling. In the liver, purinergic signaling has been shown to regulate key basic cellular functions, such as glucose/lipid metabolism, protein synthesis and ionic secretion, and homeostatic processes, such as cell cycle, inflammatory response and immunity. Whilst the functional relevance of P2Y receptors in liver physiology has been well documented, limited information is available regarding the potential role of hepatic P2X receptors in the modulation of liver homeostasis.
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Affiliation(s)
- Michel Fausther
- Division of Gastroenterology & Hepatology, Department, of Internal Medicine, College of Medicine, University of Arkansas for, Medical Sciences, Little Rock, AR, USA
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103
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104
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A reassessment of P2X7 receptor inhibition as a neuroprotective strategy in rat models of contusion injury. Exp Neurol 2011; 233:687-92. [PMID: 22078760 DOI: 10.1016/j.expneurol.2011.06.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 06/08/2011] [Accepted: 06/18/2011] [Indexed: 02/07/2023]
Abstract
These experiments were completed as part of an NIH "Facilities of Research Excellence in Spinal Cord Injury" contract to support independent replication of published studies that could be considered for eventual clinical testing. Recent studies have reported that selective inhibition of the P2X7 receptor improves both the functional and histopathological consequences of a contusive spinal cord injury (SCI) in rats. We repeated two published studies reporting the beneficial effects of pyridoxal-5'-phosphate-6-azophenyl-2'-4'-disulphonic acid (PPADS) or Brilliant blue G (BBG) treatment after SCI (Wang et al., 2004 and Peng et al., 2009). Mild thoracic SCI was first produced in Experiment 1 by means of the MASCIS impactor at T10 (height 6.25 mm, weight 10 g) followed by intraspinal administration of a P2X7 antagonist (2 μl/10 mM) after injury. Treatment with PPADS or another highly selective P2X7R antagonist Brilliant Blue G (BBG) (2 μl/02 mM) did not improve locomotive (BBB rating scale) over a 7 week period compared to vehicle treated rats. Also, secondary histopathological changes in terms of overall lesion and cavity volume were not significantly different between the PPADS, BBG, and vehicle treated animals. In the second experiment, the systemic administration of BBG (10 or 50 mg/kg, iv) 15 min, 24 and 72 h after moderate (12.5 mm) SCI failed to significantly improve motor recovery or histopathological outcome over the 6 week observational period. Although we cannot conclude that there will be no long-term beneficial effects in other spinal cord injury models using selective P2X7 receptor antagonists at different doses or treatment durations, we caution researchers that this potentially exciting therapy requires further preclinical investigations before the implementation of clinical trials targeting severe SCI patients.
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105
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106
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Anrather J, Gallo EF, Kawano T, Orio M, Abe T, Gooden C, Zhou P, Iadecola C. Purinergic signaling induces cyclooxygenase-1-dependent prostanoid synthesis in microglia: roles in the outcome of excitotoxic brain injury. PLoS One 2011; 6:e25916. [PMID: 22022466 PMCID: PMC3195085 DOI: 10.1371/journal.pone.0025916] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 09/13/2011] [Indexed: 11/19/2022] Open
Abstract
Cyclooxygenases (COX) are prostanoid synthesizing enzymes constitutively expressed in the brain that contribute to excitotoxic neuronal cell death. While the neurotoxic role of COX-2 is well established and has been linked to prostaglandin E(2) synthesis, the role of COX-1 is not clearly understood. In a model of N-Methyl-D-aspartic acid (NMDA) induced excitotoxicity in the mouse cerebral cortex we found a distinctive temporal profile of COX-1 and COX-2 activation where COX-1, located in microglia, is responsible for the early phase of prostaglandin E(2) synthesis (10 minutes after NMDA), while both COX-1 and COX-2 contribute to the second phase (3-24 hours after NMDA). Microglial COX-1 is strongly activated by ATP but not excitatory neurotransmitters or the Toll-like receptor 4 ligand bacterial lipopolysaccharide. ATP induced microglial COX-1 dependent prostaglandin E(2) synthesis is dependent on P2X7 receptors, extracellular Ca(2+) and cytoplasmic phospholipase A2. NMDA receptor activation induces ATP release from cultured neurons leading to microglial P2X7 receptor activation and COX-1 dependent prostaglandin E(2) synthesis in mixed microglial-neuronal cultures. Pharmacological inhibition of COX-1 has no effect on the cortical lesion produced by NMDA, but counteracts the neuroprotection exerted by inhibition of COX-2 or observed in mice lacking the prostaglandin E(2) receptor type 1. Similarly, the neuroprotection exerted by the prostaglandin E(2) receptor type 2 agonist butaprost is not observed after COX-1 inhibition. P2X7 receptors contribute to NMDA induced prostaglandin E(2) production in vivo and blockage of P2X7 receptors reverses the neuroprotection offered by COX-2 inhibition. These findings suggest that purinergic signaling in microglia triggered by neuronal ATP modulates excitotoxic cortical lesion by regulating COX-1 dependent prostanoid production and unveil a previously unrecognized protective role of microglial COX-1 in excitotoxic brain injury.
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Affiliation(s)
- Josef Anrather
- Division of Neurobiology, Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, New York, United States of America.
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107
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Habbas S, Ango F, Daniel H, Galante M. Purinergic signaling in the cerebellum: Bergmann glial cells express functional ionotropic P2X7 receptors. Glia 2011; 59:1800-12. [PMID: 21830236 DOI: 10.1002/glia.21224] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Accepted: 07/05/2011] [Indexed: 11/07/2022]
Abstract
Astrocytes constitute active networks of intercommunicating cells that support the metabolism and the development of neurons and affect synaptic functions via multiple pathways. ATP is one of the major neurotransmitters mediating signaling between neurons and astrocytes. Potentially acting through both purinergic metabotropic P2Y receptors (P2YRs) and ionotropic P2X receptors (P2XRs), up until now ATP has only been shown to activate P2YRs in Bergmann cells, the radial glia of the cerebellar cortex that envelopes Purkinje cell afferent synapses. In this study, using multiple experimental approaches in acute cerebellar slices we demonstrate the existence of functional P2XRs on Bergmann cells. In particular, we show here that Bergmann cells express uniquely P2X7R subtypes: (i) immunohistochemical analysis revealed the presence of P2X7Rs on Bergmann cell processes, (ii) in whole cell recordings P2XR pharmacological agonists induced depolarizing currents that were blocked by specific antagonists of P2X7Rs, and could not be elicited in slices from P2X₇R-deficient mice and finally, (iii) calcium imaging experiments revealed two distinct calcium signals triggered by application of exogenous ATP: a transient signal deriving from release of calcium from intracellular stores, and a persistent one following activation of P2X7Rs. Our data thus reveal a new pathway by which extracellular ATP may affect glial cell function, thus broadening our knowledge on purinergic signaling in the cerebellum.
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Affiliation(s)
- Samia Habbas
- Laboratoire de Pharmacologie et Biochimie de la Synapse, CNRS UMR 8619, Université Paris-sud 11, 91405 Orsay Cedex, France
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108
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Coddou C, Yan Z, Obsil T, Huidobro-Toro JP, Stojilkovic SS. Activation and regulation of purinergic P2X receptor channels. Pharmacol Rev 2011; 63:641-83. [PMID: 21737531 DOI: 10.1124/pr.110.003129] [Citation(s) in RCA: 394] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Mammalian ATP-gated nonselective cation channels (P2XRs) can be composed of seven possible subunits, denoted P2X1 to P2X7. Each subunit contains a large ectodomain, two transmembrane domains, and intracellular N and C termini. Functional P2XRs are organized as homomeric and heteromeric trimers. This review focuses on the binding sites involved in the activation (orthosteric) and regulation (allosteric) of P2XRs. The ectodomains contain three ATP binding sites, presumably located between neighboring subunits and formed by highly conserved residues. The detection and coordination of three ATP phosphate residues by positively charged amino acids are likely to play a dominant role in determining agonist potency, whereas an AsnPheArg motif may contribute to binding by coordinating the adenine ring. Nonconserved ectodomain histidines provide the binding sites for trace metals, divalent cations, and protons. The transmembrane domains account not only for the formation of the channel pore but also for the binding of ivermectin (a specific P2X4R allosteric regulator) and alcohols. The N- and C- domains provide the structures that determine the kinetics of receptor desensitization and/or pore dilation and are critical for the regulation of receptor functions by intracellular messengers, kinases, reactive oxygen species and mercury. The recent publication of the crystal structure of the zebrafish P2X4.1R in a closed state provides a major advance in the understanding of this family of receptor channels. We will discuss data obtained from numerous site-directed mutagenesis experiments accumulated during the last 15 years with reference to the crystal structure, allowing a structural interpretation of the molecular basis of orthosteric and allosteric ligand actions.
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Affiliation(s)
- Claudio Coddou
- Section on Cellular Signaling, Program in Developmental Neuroscience, National Institute of Child Health and Human Developmant, National Institutes of Health, Bethesda, MD 20892-4510, USA
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109
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Kushnir R, Cherkas PS, Hanani M. Peripheral inflammation upregulates P2X receptor expression in satellite glial cells of mouse trigeminal ganglia: a calcium imaging study. Neuropharmacology 2011; 61:739-46. [PMID: 21645532 DOI: 10.1016/j.neuropharm.2011.05.019] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 05/13/2011] [Accepted: 05/17/2011] [Indexed: 02/02/2023]
Abstract
Satellite glial cells (SGCs) in sensory ganglia are altered structurally and biochemically as a result of nerve injury. Whereas there is ample evidence that P2 purinergic receptors in central glial cells are altered after injury, there is very little information on similar changes in SGCs, although it is well established that SGCs are endowed with P2 receptors. Using calcium imaging, we characterized changes in P2 receptors in SGCs from mouse trigeminal ganglia in short-term cultures. Seven days after the induction of submandibular inflammation with complete Freund's adjuvant, there was a marked increase in the sensitivity of SGCs to ATP, with the threshold of activation decreasing from 5 μM to 10 nM. A similar observation was made in the intact trigeminal ganglion after infra-orbital nerve axotomy. Using pharmacological tools, we investigated the receptor mechanisms underlying these changes in cultured SGCs. We found that in control tissues response to ATP was mediated by P2Y (metabotropic) receptors, whereas after inflammation the response was mediated predominantly by P2X (ionotropic) receptors. As the contribution of P2X1,3,6 receptors was excluded, and the sensitivity to a P2X7 agonist did not change after inflammation, it appears that after inflammation the responses to ATP are largely due to P2X2 and/or 5 receptors, with a possible contribution of P2X4 receptors. We conclude that inflammation induced a large increase in the sensitivity of SGCs to ATP, which involved a switch from P2Y to P2X receptors. We propose that the over 100-fold augmented sensitivity of SGCs to ATP after injury may contribute to chronic pain states.
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Affiliation(s)
- Raya Kushnir
- Laboratory of Experimental Surgery, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
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110
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Mahaut-Smith MP, Jones S, Evans RJ. The P2X1 receptor and platelet function. Purinergic Signal 2011; 7:341-56. [PMID: 21484087 PMCID: PMC3166991 DOI: 10.1007/s11302-011-9224-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Accepted: 02/22/2011] [Indexed: 12/17/2022] Open
Abstract
Extracellular nucleotides are ubiquitous signalling molecules, acting via the P2 class of surface receptors. Platelets express three P2 receptor subtypes, ADP-dependent P2Y1 and P2Y12 G-protein-coupled receptors and the ATP-gated P2X1 non-selective cation channel. Platelet P2X1 receptors can generate significant increases in intracellular Ca(2+), leading to shape change, movement of secretory granules and low levels of α(IIb)β(3) integrin activation. P2X1 can also synergise with several other receptors to amplify signalling and functional events in the platelet. In particular, activation of P2X1 receptors by ATP released from dense granules amplifies the aggregation responses to low levels of the major agonists, collagen and thrombin. In vivo studies using transgenic murine models show that P2X1 receptors amplify localised thrombosis following damage of small arteries and arterioles and also contribute to thromboembolism induced by intravenous co-injection of collagen and adrenaline. In vitro, under flow conditions, P2X1 receptors contribute more to aggregate formation on collagen-coated surfaces as the shear rate is increased, which may explain their greater contribution to localised thrombosis in arterioles compared to venules within in vivo models. Since shear increases substantially near sites of stenosis, anti-P2X1 therapy represents a potential means of reducing thrombotic events at atherosclerotic plaques.
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Affiliation(s)
- Martyn P Mahaut-Smith
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, LE1 9HN, UK,
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111
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Pharmacochemistry of the platelet purinergic receptors. Purinergic Signal 2011; 7:305-24. [PMID: 21484092 DOI: 10.1007/s11302-011-9216-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Accepted: 01/11/2011] [Indexed: 10/18/2022] Open
Abstract
Platelets contain at least five purinergic G protein-coupled receptors, e.g., the pro-aggregatory P2Y(1) and P2Y(12) receptors, a P2Y(14) receptor (GPR105) of unknown function, and anti-aggregatory A(2A) and A(2B) adenosine receptor (ARs), in addition to the ligand-gated P2X1 ion channel. Probing the structure-activity relationships (SARs) of the P2X and P2Y receptors for extracellular nucleotides has resulted in numerous new agonist and antagonist ligands. Selective agents derived from known ligands and novel chemotypes can be used to help define the subtypes pharmacologically. Some of these agents have entered into clinical trials in spite of the challenges of drug development for these classes of receptors. The functional architecture of P2 receptors was extensively explored using mutagenesis and molecular modeling, which are useful tools in drug discovery. In general, novel drug delivery methods, prodrug approaches, allosteric modulation, and biased agonism would be desirable to overcome side effects that tend to occur even with receptor subtype-selective ligands. Detailed SAR analyses have been constructed for nucleotide and non-nucleotide ligands at the P2Y(1), P2Y(12), and P2Y(14) receptors. The thienopyridine antithrombotic drugs Clopidogrel and Prasugrel require enzymatic pre-activation in vivo and react irreversibly with the P2Y(12) receptor. There is much pharmaceutical development activity aimed at identifying reversible P2Y(12) receptor antagonists. The screening of chemically diverse compound libraries has identified novel chemotypes that act as competitive, non-nucleotide antagonists of the P2Y(1) receptor or the P2Y(12) receptor, and antithrombotic properties of the structurally optimized analogues were demonstrated. In silico screening at the A(2A) AR has identified antagonist molecules having novel chemotypes. Fluorescent and other reporter groups incorporated into ligands can enable new technology for receptor assays and imaging. The A(2A) agonist CGS21680 and the P2Y(1) receptor antagonist MRS2500 were derivatized for covalent attachment to polyamidoamine dendrimeric carriers of MW 20,000, and the resulting multivalent conjugates inhibited ADP-promoted platelet aggregation. In conclusion, a wide range of new pharmacological tools is available to control platelet function by interacting with cell surface purine receptors.
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112
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Baqi Y, Hausmann R, Rosefort C, Rettinger J, Schmalzing G, Müller CE. Discovery of potent competitive antagonists and positive modulators of the P2X2 receptor. J Med Chem 2011; 54:817-30. [PMID: 21207957 DOI: 10.1021/jm1012193] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Evaluation and optimization of anthraquinone derivatives related to Reactive Blue 2 at P2X2 receptors yielded the first potent and selective P2X2 receptor antagonists. The compounds were tested for inhibition of ATP (10 μM) mediated currents in Xenopus oocytes expressing the rat P2X2 receptor. The most potent antagonists were sodium 1-amino-4-[3-(4,6-dichloro[1,3,5]triazine-2-ylamino)phenylamino]-9,10-dioxo-9,10-dihydroanthracene-2-sulfonate (63, PSB-10211, IC(50) 86 nM) and disodium 1-amino-4-[3-(4,6-dichloro[1,3,5]triazine-2-ylamino)-4-sulfophenylamino]-9,10-dioxo-9,10-dihydroanthracene-2-sulfonate (57, PSB-1011, IC(50) 79 nM). Compound 57 exhibited a competitive mechanism of action (pA(2) 7.49). It was >100-fold selective versus P2X4, P2X7, and several investigated P2Y receptor subtypes (P2Y(2,4,6,12)); selectivity versus P2X1 and P2X3 receptors was moderate (>5-fold). Compound 57 was >13-fold more potent at the homomeric P2X2 than at the heteromeric P2X2/3 receptor. Several anthraquinone derivatives were found to act as positive modulators of ATP effects at P2X2 receptors, for example, sodium 1-amino-4-(3-phenoxyphenylamino)-9,10-dioxo-9,10-dihydroanthracene-2-sulfonate (51, PSB-10129, EC(50) 489 nM), which led to about a 3-fold increase in the ATP-elicited current.
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Affiliation(s)
- Younis Baqi
- PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, Pharmaceutical Sciences Bonn (PSB), University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
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113
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Abstract
We examined the effect of 2'-3'-O-(4-benzoylbenzoyl)-adenosine-5'-triphosphate (Bz-ATP), a P2X7 receptor agonist, on action potential-independent glutamate release from nerve terminals attached to mechanically isolated immature hilar neurons. Bz-ATP increased spontaneous excitatory postsynaptic current (sEPSC) frequency, and this effect was blocked by Brilliant blue G, a P2X7 receptor antagonist, suggesting that P2X7 receptors mediate the facilitatory action of Bz-ATP on sEPSCs. In most of hilar neurons tested, the Bz-ATP-induced increase in sEPSC frequency was blocked by tetrodotoxin or Cd, suggesting that the activation of P2X7 receptors leads to a presynaptic depolarization. The P2X7 receptor-mediated facilitation of glutamate release would modulate the excitability of hilar neurons, and eventually have a broad impact on the pathophysiological functions mediated by the hippocampus.
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114
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Expression and contribution of satellite glial cells purinoceptors to pain transmission in sensory ganglia: an update. ACTA ACUST UNITED AC 2010; 6:31-42. [PMID: 20604978 DOI: 10.1017/s1740925x10000086] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The role of adenosine-5'-triphosphate (ATP) and of the ligand-gated P2X3 receptor in neuronal dorsal root ganglia (DRG) pain transmission is relatively well established. Much less is known about the purinergic system in trigeminal ganglia (TG), which are involved in certain types of untreatable neuropathic and inflammatory pain, as well as in migraine. Emerging data suggest that purinergic metabotropic P2Y receptors on both neurons and satellite glial cells (SGCs) may also participate in both physiological and pathological pain development. Here, we provide an updated literature review on the role of purinergic signaling in sensory ganglia, with special emphasis on P2Y receptors on SGCs. We also provide new original data showing a time-dependent downregulation of P2Y2 and P2Y4 receptor expression and function in purified SGCs cultures from TG, in comparison with primary mixed neuron-SGCs cultures. These data highlight the importance of the neuron-glia cross-talk in determining the SGCs phenotype. Finally, we show that, in mixed TG cultures, both adenine and guanosine induce intracellular calcium transients in neurons but not in SGCs, suggesting that also these purinergic-related molecules can participate in pain signaling. These findings may have relevant implications for the development of new therapeutic strategies for chronic pain treatment.
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115
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Friedle SA, Brautigam VM, Nikodemova M, Wright ML, Watters JJ. The P2X7-Egr pathway regulates nucleotide-dependent inflammatory gene expression in microglia. Glia 2010; 59:1-13. [PMID: 20878769 DOI: 10.1002/glia.21071] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Accepted: 08/09/2010] [Indexed: 01/14/2023]
Abstract
Microglial hyperactivity contributes to neuronal damage resulting from CNS injury and disease. Therefore, a better understanding of endogenous microglial receptor systems that can be exploited to modulate their inflammatory functions is important if better, neuroprotective therapeutics are to be designed. Previous studies from our lab and others have demonstrated that the P2X7 purinergic receptor agonist BzATP attenuates microglial inflammatory mediator production stimulated by lipopolysaccharide (LPS), suggesting that purinergic receptors may be one such receptor system that can be used for manipulating microglial activation. However, although P2X7 receptor activation is well recognized to regulate processing and release of cytokines, little is known concerning its role in regulating the transcription of inflammatory genes, nor the molecular mechanisms underlying these transcriptional effects. In the present studies, we identify that the transcription factors early growth response (Egr)-1, -2 and -3 are downstream signaling targets of P2X7 receptors in microglia, and that their activation is sensitive to MEK and p38 mitogen-activated protein kinase (MAPK) inhibitors. Moreover, using RNAi, we demonstrate that Egr factors and P2X7 receptors are necessary for BzATP-mediated attenuation of iNOS, and stimulation of TNF-α and IL-6 gene expression. BzATP also attenuates neuronal death induced by LPS conditioned medium, and P2X7 receptors are required for this effect. These studies are the first to identify Egr factors as regulators of inflammatory gene expression following P2X7 receptor activation, and suggest that P2X7 receptors may utilize the MAPK-Egr pathway to exert differential effects on microglial inflammatory activities which are beneficial to neuron survival.
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Affiliation(s)
- S A Friedle
- Program in Cellular and Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706, USA
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116
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Hu H, Lu W, Zhang M, Zhang X, Argall AJ, Patel S, Lee GE, Kim YC, Jacobson KA, Laties AM, Mitchell CH. Stimulation of the P2X7 receptor kills rat retinal ganglion cells in vivo. Exp Eye Res 2010; 91:425-32. [PMID: 20599962 PMCID: PMC2941978 DOI: 10.1016/j.exer.2010.06.017] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 06/18/2010] [Accepted: 06/18/2010] [Indexed: 12/16/2022]
Abstract
The P2X(7) receptor is associated with the death of many cell types, and growing evidence supports its presence on neurons. Activation of the P2X(7) receptor on isolated retinal ganglion cells increases intracellular calcium levels and can kill the cells. Within the intact eye, however, glia and other cell types surrounding the ganglion cells may provide protection and attenuate the effects of receptor stimulation. This investigation thus asks whether stimulation of the P2X(7) receptor can actually kill retinal ganglion cells in vivo. Drugs were injected intravitreally into the superior/nasal region of Long Evans rats. Cell survival was determined by counting the number of remaining ganglion cells labeled with aminostilbamidine. The P2X(7) receptor agonist BzATP reduced ganglion cell survival as compared to eyes injected with saline solution. Ganglion cell death was inhibited by co-injection of the P2X(7) antagonists Brilliant Blue G and MRS 2540. The loss of ganglion cells following activation of the P2X(7) receptor was also prevented by the adenosine A(3) adenosine receptor agonist MRS 3558. In conclusion, stimulation of the P2X(7) receptor can kill retinal ganglion cells in vivo. The neuroprotective effects of A(3) receptor activation identified in isolated ganglion cells are also apparent in vivo. This implies that the balance between extracellular ATP and its protective metabolite adenosine can influence ganglion cell survival in the living eye.
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Affiliation(s)
- Huiling Hu
- Department of Ophthalmology, University of Pennsylvania, School of Medicine
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, 510060, P.R. China
| | - Wennan Lu
- Department of Physiology, University of Pennsylvania, School of Medicine
- Department of Anatomy and Cell Biology University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104
| | - Mei Zhang
- Department of Ophthalmology, University of Pennsylvania, School of Medicine
| | - Xiulan Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, 510060, P.R. China
| | - Arthur J. Argall
- Department of Physiology, University of Pennsylvania, School of Medicine
- Department of Anatomy and Cell Biology University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104
| | - Shaun Patel
- Department of Physiology, University of Pennsylvania, School of Medicine
| | - Ga Eun Lee
- Department of Life Science, Gwangju Institute of Science and Technology, Buk-gu, Gwangju 500-712, Republic of Korea
| | - Yong-Chul Kim
- Department of Life Science, Gwangju Institute of Science and Technology, Buk-gu, Gwangju 500-712, Republic of Korea
| | - Kenneth A. Jacobson
- Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, Bethesda, MD, 20892
| | - Alan M. Laties
- Department of Ophthalmology, University of Pennsylvania, School of Medicine
| | - Claire H. Mitchell
- Department of Physiology, University of Pennsylvania, School of Medicine
- Department of Anatomy and Cell Biology University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104
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117
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Teixeira JM, Oliveira MCG, Nociti FH, Clemente-Napimoga JT, Pelegrini-da-Silva A, Parada CA, Tambeli CH. Involvement of temporomandibular joint P2X3 and P2X2/3 receptors in carrageenan-induced inflammatory hyperalgesia in rats. Eur J Pharmacol 2010; 645:79-85. [PMID: 20558155 DOI: 10.1016/j.ejphar.2010.06.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Revised: 05/13/2010] [Accepted: 06/07/2010] [Indexed: 11/28/2022]
Abstract
The aim of this study was to investigate the role of P2X3, P2X2/3 and P2X7 receptors in the development of TMJ hyperalgesia induced by carrageenan. We also investigated the expression of mRNA of P2X7 receptors in the trigeminal ganglia and the existence of functional P2X7 receptors in the rat's TMJ. The P2X1, P2X3 and P2X2/3 receptor antagonist TNP-ATP, but not the selective P2X7 receptor antagonist A-438079, significantly reduced carrageenan-induced TMJ inflammatory hyperalgesia. The qPCR assay showed that mRNA of P2X7 receptors are expressed in the trigeminal ganglia but this expression is not increased by the inflammation induced by carrageenan in the TMJ region. The P2X7 receptor agonist BzATP induced TMJ inflammatory hyperalgesia that was significantly reduced by pretreatment with dexamethasone. These results indicate that P2X3 and P2X2/3 but not P2X7 receptors are involved in carrageenan-induced TMJ inflammatory hyperalgesia. However, functional P2X7 receptors are expressed in the TMJ region. The activation of these receptors by BzATP sensitizes the primary afferent nociceptors in the TMJ through the previous release of inflammatory mediators. The findings of this study point out P2X3 and P2X2/3 receptors, but not P2X7 receptors, as potential targets for the development of new analgesic drugs to control TMJ inflammatory pain.
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Affiliation(s)
- Juliana Maia Teixeira
- Department of Physiological Sciences, Laboratory of Orofacial Pain, Piracicaba Dental School, State University of Campinas - UNICAMP, Piracicaba, Sao Paulo, Brazil
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Gandelman M, Peluffo H, Beckman JS, Cassina P, Barbeito L. Extracellular ATP and the P2X7 receptor in astrocyte-mediated motor neuron death: implications for amyotrophic lateral sclerosis. J Neuroinflammation 2010; 7:33. [PMID: 20534165 PMCID: PMC2901222 DOI: 10.1186/1742-2094-7-33] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Accepted: 06/09/2010] [Indexed: 02/01/2023] Open
Abstract
Background During pathology of the nervous system, increased extracellular ATP acts both as a cytotoxic factor and pro-inflammatory mediator through P2X7 receptors. In animal models of amyotrophic lateral sclerosis (ALS), astrocytes expressing superoxide dismutase 1 (SOD1G93A) mutations display a neuroinflammatory phenotype and contribute to disease progression and motor neuron death. Here we studied the role of extracellular ATP acting through P2X7 receptors as an initiator of a neurotoxic phenotype that leads to astrocyte-mediated motor neuron death in non-transgenic and SOD1G93A astrocytes. Methods We evaluated motor neuron survival after co-culture with SOD1G93A or non-transgenic astrocytes pretreated with agents known to modulate ATP release or P2X7 receptor. We also characterized astrocyte proliferation and extracellular ATP degradation. Results Repeated stimulation by ATP or the P2X7-selective agonist BzATP caused astrocytes to become neurotoxic, inducing death of motor neurons. Involvement of P2X7 receptor was further confirmed by Brilliant blue G inhibition of ATP and BzATP effects. In SOD1G93A astrocyte cultures, pharmacological inhibition of P2X7 receptor or increased extracellular ATP degradation with the enzyme apyrase was sufficient to completely abolish their toxicity towards motor neurons. SOD1G93A astrocytes also displayed increased ATP-dependent proliferation and a basal increase in extracellular ATP degradation. Conclusions Here we found that P2X7 receptor activation in spinal cord astrocytes initiated a neurotoxic phenotype that leads to motor neuron death. Remarkably, the neurotoxic phenotype of SOD1G93A astrocytes depended upon basal activation the P2X7 receptor. Thus, pharmacological inhibition of P2X7 receptor might reduce neuroinflammation in ALS through astrocytes.
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Faria RX, Cascabulho CM, Reis RAM, Alves LA. Large-conductance channel formation mediated by P2X7 receptor activation is regulated through distinct intracellular signaling pathways in peritoneal macrophages and 2BH4 cells. Naunyn Schmiedebergs Arch Pharmacol 2010; 382:73-87. [PMID: 20508916 DOI: 10.1007/s00210-010-0523-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Accepted: 05/05/2010] [Indexed: 10/19/2022]
Abstract
The P2X(7) receptor (P2X7R) is a ligand-gated ATP receptor that acts as a low- and large-conductance channel (pore) and is known to be coupled to several downstream effectors. Recently, we demonstrated that the formation of a large-conductance channel associated with the P2X(7) receptor is induced by increasing the intracellular Ca(2+) concentration (Faria et al., Am J Physiol Cell Physiol 297:C28-C42, 2005). Here, we investigated the intracellular signaling pathways associated with P2X(7) large-conductance channel formation using the patch clamp technique in conjunction with fluorescent imaging and flow cytometry assays in 2BH4 cells and peritoneal macrophages. Different antagonists were applied to investigate the following pathways: Ca(2+)-calmodulin, phospholipase A, phospholipase D, phospholipase C, protein kinase C (PKC), mitogen-activated protein kinase (MAPK), MAPK/extracellular signal-regulated kinase, phosphoinositide 3-kinase (PI3K), and cytoskeletal proteins. Macroscopic ionic currents induced by 1 mM ATP were reduced by 85% in the presence of PKC antagonists. The addition of antagonists for MAPK, PI3K, and the cytoskeleton (actin, intermediary filament, and microtubule) blocked 92%, 83%, and 95% of the ionic currents induced by 1 mM ATP, respectively. Our results show that PKC, MAPK, PI3K, and cytoskeletal components are involved in P2X(7) receptor large-channel formation in 2BH4 cells and peritoneal macrophages.
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Affiliation(s)
- R X Faria
- Laboratory of Cellular Communication, Department of Immunology, Oswaldo Cruz Institute, FIOCRUZ (Oswaldo Cruz Foundation), Av. Brazil, 4365, Manguinhos, Rio de Janeiro 21045-900, Brazil.
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ATP-gated P2X3 receptors constitute a positive autocrine signal for insulin release in the human pancreatic beta cell. Proc Natl Acad Sci U S A 2010; 107:6465-70. [PMID: 20308565 DOI: 10.1073/pnas.0908935107] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Extracellular ATP has been proposed as a paracrine signal in rodent islets, but it is unclear what role ATP plays in human islets. We now show the presence of an ATP signaling pathway that enhances the human beta cell's sensitivity and responsiveness to glucose fluctuations. By using in situ hybridization, RT-PCR, immunohistochemistry, and Western blotting as well as recordings of cytoplasmic-free Ca(2+) concentration, [Ca(2+)](i), and hormone release in vitro, we show that human beta cells express ionotropic ATP receptors of the P2X(3) type and that activation of these receptors by ATP coreleased with insulin amplifies glucose-induced insulin secretion. Released ATP activates P2X(3) receptors in the beta-cell plasma membrane, resulting in increased [Ca(2+)](i) and enhanced insulin secretion. Therefore, in human islets, released ATP forms a positive autocrine feedback loop that sensitizes the beta cell's secretory machinery. This may explain how the human pancreatic beta cell can respond so effectively to relatively modest changes in glucose concentration under physiological conditions in vivo.
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Friedle SA, Curet MA, Watters JJ. Recent patents on novel P2X(7) receptor antagonists and their potential for reducing central nervous system inflammation. ACTA ACUST UNITED AC 2010; 5:35-45. [PMID: 19705995 DOI: 10.2174/157488910789753530] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Accepted: 07/13/2009] [Indexed: 01/24/2023]
Abstract
Inflammation arises in the CNS from a number of neurodegenerative and oncogenic disorders, as well as from ischemic and traumatic brain injuries. These pathologies give rise to increased levels of extracellular adenine nucleotides which, via activation of a variety of cell surface P2 purinergic receptors, influence the inflammatory activities of responding immune cells. One P2 receptor subtype in particular, the P2X(7) receptor, potentiates the release of pro-inflammatory cytokines, such as interleukin-1beta (IL-1beta) from macrophage-like cells. It is also thought to contribute to secondary brain injury by inducing neuronal cell death. Therefore, antagonism of this receptor could have significant therapeutic impact on all disorders, not just CNS, to which excessive inflammatory activities contribute. The use of currently available P2X(7) receptor antagonists for the treatment of CNS inflammation has been limited to the generally non-selective antagonists PPADS, oxidized ATP, Brilliant Blue G, suramin, calmidizolium, and KN-62. However, the recent patents and development of novel P2X(7) receptor antagonists, as discussed in this review, will provide new tools both for clinical and research purposes. Here we discuss compounds for which patents have been applied since 2006, from the following categories: benzamide inhibitors, bicycloheteroaryl compounds, acylhdranzine antagonists, biaromatic P2X(7) antagonists, heterocyclic compounds and amide derivatives, and aromatic amine antagonists.
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Affiliation(s)
- Scott A Friedle
- Program in Cellular and Molecular Biology and Department of Comparative Biosciences, University of Wisconsin, Madison, WI 53706, USA
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Chang H, Yanachkov IB, Michelson AD, Li Y, Barnard MR, Wright GE, Frelinger AL. Agonist and antagonist effects of diadenosine tetraphosphate, a platelet dense granule constituent, on platelet P2Y1, P2Y12 and P2X1 receptors. Thromb Res 2009; 125:159-65. [PMID: 19945153 DOI: 10.1016/j.thromres.2009.11.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Revised: 09/30/2009] [Accepted: 11/05/2009] [Indexed: 10/20/2022]
Abstract
INTRODUCTION Diadenosine 5',5'''-P(1),P(4)- tetraphosphate (Ap(4)A) is stored in platelet dense granules, but its effects on platelet function are not well understood. METHODS AND RESULTS We examined the effects of Ap(4)A on platelet purinergic receptors P2Y(1), P2Y(12) and P2X(1). Flow cytometry was used to measure the effects of Ap(4)A in the presence or absence of ADP on: a) P2Y(12)-mediated decrease in intraplatelet phosphorylated vasodilator stimulated phosphoprotein (VASP), b) P2Y(1)-mediated increase in platelet cytosolic Ca(2+), and c) P2X(1)-mediated intraplatelet entry of extracellular Ca(2+). ADP-stimulated platelet shape change (P2Y(1)-mediated) and aggregation (P2Y(1)- and P2Y(12)-mediated) were measured optically. Ap(4)A inhibited 3 microM ADP-induced: a) platelet aggregation (IC(50) 9.8+/-2.8 microM), b) P2Y(1)-mediated shape change, c) P2Y(1)-mediated increase in platelet cytosolic Ca(2+) (IC(50) 40.8+/-12.3 microM), and d) P2Y(12)-mediated decrease in VASP phosphorylation (IC(50)>250 microM). In the absence of added ADP, Ap(4)A had agonist effects on platelet P2X(1) and P2Y(12), but not P2Y(1), receptors. CONCLUSION Ap(4)A, a constituent of platelet dense granules, is a) an antagonist of platelet P2Y(1) and P2Y(12) receptors, where it inhibits the effects of ADP, and b) an agonist of platelet P2X(1) and P2Y(12) receptors.
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Affiliation(s)
- Hung Chang
- Center for Platelet Function Studies, Department of Pediatrics, University of Massachusetts Medical School, Worcester, MA, USA
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Schulz P, Dueck B, Mourot A, Hatahet L, Fendler K. Measuring ion channels on solid supported membranes. Biophys J 2009; 97:388-96. [PMID: 19580777 DOI: 10.1016/j.bpj.2009.04.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Revised: 04/06/2009] [Accepted: 04/13/2009] [Indexed: 10/20/2022] Open
Abstract
Application of solid supported membranes (SSMs) for the functional investigation of ion channels is presented. SSM-based electrophysiology, which has been introduced previously for the investigation of active transport systems, is expanded for the analysis of ion channels. Membranes or liposomes containing ion channels are adsorbed to an SSM and a concentration gradient of a permeant ion is applied. Transient currents representing ion channel transport activity are recorded via capacitive coupling. We demonstrate the application of the technique to liposomes reconstituted with the peptide cation channel gramicidin, vesicles from native tissue containing the nicotinic acetylcholine receptor, and membranes from a recombinant cell line expressing the ionotropic P2X2 receptor. It is shown that stable ion gradients, both inside as well as outside directed, can be applied and currents are recorded with an excellent signal/noise ratio. For the nicotinic acetylcholine receptor and the P2X2 receptor excellent assay quality factors of Z' = 0.55 and Z' = 0.67, respectively, are obtained. This technique opens up new possibilities in cases where conventional electrophysiology fails like the functional characterization of ion channels from intracellular compartments. It also allows for robust fully automatic assays for drug screening.
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Affiliation(s)
- Patrick Schulz
- Max Planck Institut für Biophysik, D-60438 Frankfurt/Main, Germany
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Abstract
The innate immune system is critical in recognizing bacterial and viral infections to evoke a proper immune response. Certain members of the intracellular nucleotide-binding and oligomerization domain (NOD)-like receptor (NLR) family detect microbial components in the cytosol and trigger the assembly of large caspase-1-activating complexes termed inflammasomes. Autoproteolytic maturation of caspase-1 zymogens within these inflammasomes leads to maturation and secretion of the pro-inflammatory cytokines interleukin-1 beta (IL-1 beta) and IL-18. The NLR proteins ICE protease-activating factor (IPAF), NALP1b (NACHT domain-, leucine-rich repeat-, and PYD-containing protein 1b), and cryopyrin/NALP3 assemble caspase-1-activating inflammasomes in a stimulus-dependent manner. Bacterial flagellin is sensed by IPAF, whereas mouse NALP1b detects anthrax lethal toxin. Cryopyrin/NALP3 mediates caspase-1 activation in response to a wide variety of microbial components and in response to crystalline substances such as the endogenous danger signal uric acid. Genetic variations in Nalp1 and cryopyrin/Nalp3 are associated with autoinflammatory disorders and increased susceptibility to microbial infection. Further understanding of inflammasomes and their role in innate immunity should provide new insights into the mechanisms of host defense and the pathogenesis of autoimmune diseases.
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Affiliation(s)
- Mohamed Lamkanfi
- Department of Physiological Chemistry, Genentech, South San Francisco, CA 94080, USA
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Gomes DA, Song Z, Stevens W, Sladek CD. Sustained stimulation of vasopressin and oxytocin release by ATP and phenylephrine requires recruitment of desensitization-resistant P2X purinergic receptors. Am J Physiol Regul Integr Comp Physiol 2009; 297:R940-9. [PMID: 19625689 DOI: 10.1152/ajpregu.00358.2009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Coexposure of hypothalamo-neurohypophyseal system explants to ATP and phenylephrine [PE; an alpha1-adrenergic receptor (alpha1-AR) agonist] induces an extended elevation in vasopressin and oxytocin (VP/OT) release. New evidence is presented that this extended response is mediated by recruitment of desensitization-resistant ionotropic purinergic receptor subtypes (P2X-Rs): 1) Antagonists of the P2X2/3 and P2X7-Rs truncated the sustained VP/OT release induced by ATP+PE but did not alter the transient response to ATP alone. 2) The P2X2/3 and P2X7-R antagonists did not alter either ATP or ATP+PE-induced increases in [Ca(2+)](i). 3) P2X2/3 and P2X7-R agonists failed to elevate [Ca(2+)](i), while ATP-gamma-S, an agonist for P2X2-Rs increased [Ca(2+)](i) and induced a transient increase in VP/OT release. 4) A P2Y1-R antagonist did not prevent initiation of the synergistic, sustained stimulation of VP/OT release by ATP+PE but did reduce its duration. Thus, the desensitization-resistant P2X2/3 and P2X7-R subtypes are required for the sustained, synergistic hormone response to ATP+PE, while P2X2-Rs are responsible for the initial activation of Ca(2+)-influx by ATP and ATP stimulation of VP/OT release. Immunohistochemistry, coimmunoprecipitation, and Western blot analysis confirmed the presence of P2X2 and P2X3, P2X2/3, and P2X7-R protein, respectively in SON. These findings support the hypothesis that concurrent activation of P2X2-R and alpha1-AR induces calcium-driven recruitment of P2X2/3 and 7-Rs, allowing sustained activation of a homeostatic circuit. Recruitment of these receptors may provide sustained release of VP during dehydration and may be important for preventing hemorrhagic and septic shock.
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Affiliation(s)
- Dayane A Gomes
- Department of Physiology and Biophysics, University of Colorado Denver School of Medicine, Denver, Colorado 80045, USA
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Grote A, Boldogkoi Z, Zimmer A, Steinhäuser C, Jabs R. Functional characterization of P2X3receptors fused with fluorescent proteins. Mol Membr Biol 2009; 22:497-506. [PMID: 16373321 DOI: 10.1080/09687860500370638] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
P2X receptor function in the CNS is poorly understood, and currently available data are partly inconsistent. In the presented study, we investigated P2X3 receptors stably expressed in HEK293 cells. Non-stationary noise analysis of whole cell currents and rapid ATP application through flash photolysis allowed for assessing the single channel conductance (6.6 pS) and the fast activation kinetics of the receptor (20 ms). The characteristics of channel desensitization and pharmacological properties matched previous findings. The properties of wild type receptors were compared with P2X3 constructs carrying a fluorescent tag (ECFP or DsRed2) at the C-terminus. These fluorescently labeled subunits formed functional receptors, with neither the affinity of the ligand binding site nor channel properties (ion selectivity, gating kinetics, single channel conductance) differing from wild type. We conclude that both fusion proteins tested here are suitable for generating transgenic mice, which can be expected to promote understanding of the physiological role of P2X3 receptors in CNS signaling.
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Affiliation(s)
- Alexander Grote
- Experimental Neurobiology, Neurosurgery, Sigmund-Freud-Strasse 25, 53105, Bonn, Germany
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Milenkovic I, Rinke I, Witte M, Dietz B, Rübsamen R. P2 receptor-mediated signaling in spherical bushy cells of the mammalian cochlear nucleus. J Neurophysiol 2009; 102:1821-33. [PMID: 19571200 DOI: 10.1152/jn.00186.2009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Purinoreceptors of the P2 family contribute strongly to signaling in the cochlea, but little is known about the effects of purinergic neurotransmission in the central auditory system. Here we examine P2 receptor-mediated signaling in the large spherical bushy cells (SBCs) of Mongolian gerbils around the onset of acoustically evoked signal processing (P9-P14). Brief adenosine 5'-O-(3-thiotriphosphate) (ATPgammaS) application evoked inward current, membrane depolarization, and somatic Ca2+ signals. Moreover, ATPgammaS changed the SBCs firing pattern from phasic to tonic, when the application was synchronized with depolarizing current injection. This bursting discharge activity was dependent on [Ca2+]i and Ca2+-dependent protein kinase (PKC) activity and is presumably caused by modulation of low-threshold K+ conductance. Activation of P2Y1 receptors could not evoke these changes per se, thus it was concluded that the involvement of P2X receptors seems to be necessary. Ca2+ imaging data showed that both P2X and P2Y1 receptors mediate Ca2+ signals in SBCs where P2Y1 receptors most likely activate the PLC-IP3 (inositol trisphosphate) pathway and release Ca2+ from internal stores. Immunohistochemical staining confirmed the expression of P2X2 and P2Y1 receptor proteins in SBCs, providing additional evidence for the involvement of both receptors in signal transduction in these neurons. Purinergic signaling might modulate excitability of SBCs and thereby contribute to regulation of synaptic strength. Functionally, the increase in firing rate mediated by P2 receptors could reduce temporal precision of the postsynaptic firing, e.g., phase locking, which has an immediate effect on signal processing related to sound localization. This might provide a mechanism for adaptation to the ambient acoustic environment.
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Affiliation(s)
- Ivan Milenkovic
- Institute of Biology II, Faculty of Biosciences, Pharmacy and Psychology, University of Leipzig, Talstrasse 33, D-04103 Leipzig, Germany.
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Jankowski V, van der Giet M, Mischak H, Morgan M, Zidek W, Jankowski J. Dinucleoside polyphosphates: strong endogenous agonists of the purinergic system. Br J Pharmacol 2009; 157:1142-53. [PMID: 19563527 DOI: 10.1111/j.1476-5381.2009.00337.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The purinergic system is composed of mononucleosides, mononucleoside polyphosphates and dinucleoside polyphosphates as agonists, as well as the respective purinergic receptors. Interest in the role of the purinergic system in cardiovascular physiology and pathophysiology is on the rise. This review focuses on the overall impact of dinucleoside polyphosphates in the purinergic system. Platelets, adrenal glands, endothelial cells, cardiomyocytes and tubular cells release dinucleoside polyphosphates. Plasma concentrations of dinucleoside polyphosphates are sufficient to cause direct vasoregulatory effects and to induce proliferative effects on vascular smooth muscle cells and mesangial cells. In addition, increased plasma concentrations of a dinucleoside polyphosphate were recently demonstrated in juvenile hypertensive patients. In conclusion, the current literature accentuates the strong physiological and pathophysiological impact of dinucleoside polyphosphates on the cardiovascular system.
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Affiliation(s)
- Vera Jankowski
- Charité-Universitaetsmedizin Berlin, Campus Benjamin Franklin, Medizinische Klinik IV, Berlin, Germany
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Donnelly-Roberts DL, Namovic MT, Han P, Jarvis MF. Mammalian P2X7 receptor pharmacology: comparison of recombinant mouse, rat and human P2X7 receptors. Br J Pharmacol 2009; 157:1203-14. [PMID: 19558545 DOI: 10.1111/j.1476-5381.2009.00233.x] [Citation(s) in RCA: 196] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND AND PURPOSE Acute activation of P2X7 receptors rapidly opens a non-selective cation channel. Sustained P2X7 receptor activation leads to the formation of cytolytic pores, mediated by downstream recruitment of hemichannels to the cell surface. Species- and single-nucleotide polymorphism-mediated differences in P2X7 receptor activation have been reported that complicate understanding of the physiological role of P2X7 receptors. Studies were conducted to determine pharmacological differences between human, rat and mouse P2X7 receptors. EXPERIMENTAL APPROACH Receptor-mediated changes in calcium influx and Yo-Pro uptake were compared between recombinant mouse, rat and human P2X7 receptors. For mouse P2X7 receptors, wild-type (BALB/c) and a reported loss of function (C57BL/6) P2X7 receptor were also compared. KEY RESULTS BzATP [2,3-O-(4-benzoylbenzoyl)-ATP] was more potent than ATP in stimulating calcium influx and Yo-Pro uptake at rat, human, BALB/c and C57BL/6 mouse P2X7 receptors. Two selective P2X7 receptor antagonists, A-740003 and A-438079, potently blocked P2X7 receptor activation across mammalian species. Several reported P2X1 receptor antagonists [e.g. MRS 2159 (4-[(4-formyl-5-hydroxy-6-methyl-3-[(phosphonooxy)methyl}-2-pyridinyl)azo]-benzoic acid), PPNDS and NF279] blocked P2X7 receptors. NF279 fully blocked human P2X7 receptors, but only partially blocked BALB/c P2X7 receptors and was inactive at C57BL/6 P2X7 receptors. CONCLUSIONS AND IMPLICATIONS These data provide new insights into P2X7 receptor antagonist pharmacology across mammalian species. P2X7 receptor pharmacology in a widely used knockout background mouse strain (C57BL/6) was similar to wild-type mouse P2X7 receptors. Several structurally novel, selective and competitive P2X7 receptor antagonists show less species differences compared with earlier non-selective antagonists.
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Affiliation(s)
- Diana L Donnelly-Roberts
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60024, USA
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Honore P, Donnelly-Roberts D, Namovic M, Zhong C, Wade C, Chandran P, Zhu C, Carroll W, Perez-Medrano A, Iwakura Y, Jarvis MF. The antihyperalgesic activity of a selective P2X7 receptor antagonist, A-839977, is lost in IL-1alphabeta knockout mice. Behav Brain Res 2009; 204:77-81. [PMID: 19464323 DOI: 10.1016/j.bbr.2009.05.018] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Revised: 05/11/2009] [Accepted: 05/15/2009] [Indexed: 10/20/2022]
Abstract
The pro-inflammatory cytokine interleukin-1beta (IL-1beta) has been implicated in both inflammatory processes and nociceptive neurotransmission. Activation of P2X7 receptors is the mechanism by which ATP stimulates the rapid maturation and release of IL-1beta from macrophages and microglial cells. Recently, selective P2X7 receptor antagonists have been shown to reduce inflammatory and neuropathic pain in animal models. However, the mechanisms underlying these analgesic effects are unknown. The present studies characterize the pharmacology and antinociceptive effects of a structurally novel P2X7 antagonist. A-839977 potently (IC50=20-150 nM) blocked BzATP-evoked calcium influx at recombinant human, rat and mouse P2X7 receptors. A-839977 also potently blocked agonist-evoked YO-PRO uptake and IL-1beta release from differentiated human THP-1 cells. Systemic administration of A-839977 dose-dependently reduced thermal hyperalgesia produced by intraplantar administration of complete Freund's adjuvant (CFA) (ED50=100 micromol/kg, i.p.) in rats. A-839977 also produced robust antihyperalgesia in the CFA model of inflammatory pain in wild-type mice (ED50=40 micromol/kg, i.p.), but the antihyperalgesic effects of A-839977 were completely absent in IL-1alphabeta knockout mice. These data demonstrate that selective blockade of P2X7 receptors in vivo produces significant antinociception in animal models of inflammatory pain and suggest that the antihyperalgesic effects of P2X7 receptor blockade in an inflammatory pain model in mice are mediated by blocking the release of IL-1beta.
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Affiliation(s)
- Prisca Honore
- Abbott Laboratories, Neuroscience Research, Abbott Park, IL 60064, USA
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Carrasquero LMG, Delicado EG, Bustillo D, Gutiérrez-Martín Y, Artalejo AR, Miras-Portugal MT. P2X7 and P2Y13 purinergic receptors mediate intracellular calcium responses to BzATP in rat cerebellar astrocytes. J Neurochem 2009; 110:879-89. [PMID: 19457067 DOI: 10.1111/j.1471-4159.2009.06179.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Previous work has established the presence of functional P2X(7) subunits in rat cerebellar astrocytes, which after stimulation with 3'-O-(4-benzoyl)benzoyl ATP (BzATP) evoked morphological changes that were not reproduced by any other nucleotide. To further characterize the receptor(s) and signaling mechanisms involved in the action of BzATP, we have employed fura-2 microfluorometry and the patch-clamp technique. BzATP elicited intracellular calcium responses that typically exhibited two components: the first one was transient and metabotropic in nature--sensitive to phospholipase C inhibition and pertussis toxin treatment, whereas the second one was sustained and depended on the presence of extracellular calcium. The ionotropic nature of this latter component was corroborated by measurements of Mn(2+) entry and macroscopic non-selective cation currents evoked by either BzATP (100 muM) or ATP (1 mM). The two components of the calcium response to BzATP differed in their pharmacological sensitivity. The metabotropic component was partially sensitive to pyridoxalphosphate-5'-phosphate-6-azo-(-2-chloro-5-nitrophenyl)-2,4-disulfonate, a selective antagonist of P2Y(13) receptors, while the ionotropic component was modulated by external magnesium and markedly reduced by brilliant blue G and 3-(5-(2,3-dichlorophenyl)-1H-tetrazol-1-yl)methyl pyridine (A438079), thus implying the involvement of P2X(7) purinergic receptors. It is concluded that P2Y(13) and P2X(7) purinergic receptors are functionally expressed in rat cerebellar astrocytes and mediate the increase in intracellular calcium elicited by BzATP in these cells.
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Affiliation(s)
- Luz María G Carrasquero
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid, Spain
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134
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Wang LY, Cai WQ, Chen PH, Deng QY, Zhao CM. Downregulation of P2X7 receptor expression in rat oligodendrocyte precursor cells after hypoxia ischemia. Glia 2009; 57:307-19. [PMID: 18942747 DOI: 10.1002/glia.20758] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Oligodendrocyte precursor cells (OPCs) are the predominant oligodendrocyte-lineage stage in the cerebral hemispheres of neonatal rat. Prior studies have shown that OPCs are highly vulnerable to hypoxic-ischemic injury, yet the mechanisms are not well understood. P2X(7) receptor (P2X(7)R) is an ATP-gated ion channel that has unusual properties and plays very complex roles in a variety of neuropathologic conditions. However, little is known about the involvement of P2X(7)R in OPCs development and injury. The present study was aimed at examining the presence of P2X(7)R in OPCs and evaluating the change of the receptor expression after hypoxia ischemia. Using Immunofluorescence, RT-PCR, and western blot analysis, we demonstrated that OPCs expressed P2X(7)R in vitro and in vivo. Activation of P2X(7)R in OPCs in response to 3'-O-(4-benzoyl) benzoyl-ATP (BzATP) led to an increased mobilization of intracellular calcium [Ca(2+)]i, formation of large pores and cell death. These functional responses were sensitive to pretreatment of cells with the P2X(7)R antagonist, Brilliant Blue G (BBG, 100 nM), which was a selective antagonist for P2X(7)R in nanomole range. A decrease in P2X(7)R expression was observed in cultured OPCs after exposure to oxygen-glucose deprivation (OGD) for 2 h in vitro. Using a neonatal hypoxic-ischemic injury model in postnatal 3 rats, the similar downregulation was also detected in ischemic cerebral cortex, subcortical white matter and hippocampus compared with sham operation controls. In conclusion, the present data demonstrated that OPCs expressed functional P2X(7)R. The post-ischemic downregulation of P2X(7)R suggested a role for this receptor in the pathophysiology of hypoxic-ischemic brain injury.
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Affiliation(s)
- Li-Yan Wang
- Department of Neurobiology, Third Military Medical University, Chongqing 40038, China
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135
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Nagata K, Imai T, Yamashita T, Tsuda M, Tozaki-Saitoh H, Inoue K. Antidepressants inhibit P2X4 receptor function: a possible involvement in neuropathic pain relief. Mol Pain 2009; 5:20. [PMID: 19389225 PMCID: PMC2680826 DOI: 10.1186/1744-8069-5-20] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Accepted: 04/23/2009] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Neuropathic pain is characterized by pain hypersensitivity to innocuous stimuli (tactile allodynia) that is nearly always resistant to known treatments such as non-steroidal anti-inflammatory drugs or even opioids. It has been reported that some antidepressants are effective for treating neuropathic pain. However, the underlying molecular mechanisms are not well understood. We have recently demonstrated that blocking P2X4 receptors in the spinal cord reverses tactile allodynia after peripheral nerve injury in rats, implying that P2X4 receptors are a key molecule in neuropathic pain. We investigated a possible role of antidepressants as inhibitors of P2X4 receptors and analysed their analgesic mechanism using an animal model of neuropathic pain. RESULTS Antidepressants strongly inhibited ATP-mediated Ca2+ responses in P2X4 receptor-expressing 1321N1 cells, which are known to have no endogenous ATP receptors. Paroxetine exhibited the most powerful inhibition of calcium influx via rat and human P2X4 receptors, with IC50 values of 2.45 microM and 1.87 microM, respectively. Intrathecal administration of paroxetine produced a striking antiallodynic effect in an animal model of neuropathic pain. Co-administration of WAY100635, ketanserin or ondansetron with paroxetine induced no significant change in the antiallodynic effect of paroxetine. Furthermore, the antiallodynic effect of paroxetine was observed even in rats that had received intrathecal pretreatment with 5,7-dihydroxytryptamine, which dramatically depletes spinal 5-hydroxytryptamine. CONCLUSION These results suggest that paroxetine acts as a potent analgesic in the spinal cord via a mechanism independent of its inhibitory effect on serotonin transporters. Powerful inhibition on P2X4 receptors may underlie the analgesic effect of paroxetine, and it is possible that some antidepressants clinically used in patients with neuropathic pain show antiallodynic effects, at least in part via their inhibitory effects on P2X4 receptors.
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Affiliation(s)
- Kenichiro Nagata
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
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136
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The P2X(7) receptor in retinal ganglion cells: A neuronal model of pressure-induced damage and protection by a shifting purinergic balance. Purinergic Signal 2009; 5:241-9. [PMID: 19241145 DOI: 10.1007/s11302-009-9142-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2008] [Accepted: 09/12/2008] [Indexed: 01/19/2023] Open
Abstract
Retinal ganglion cells process the visual signal and transmit it along their axons in the optic nerve to the brain. Molecular, immunohistochemical, and functional analyses indicate that the majority of retinal ganglion cells express the ionotropic P2X(7) receptor. Stimulation of the receptor can lead to a rise in intracellular calcium and cell death, although death does not involve the opening of a large diameter pore. Adenosine acting at A(3) receptors can attenuate the rise in calcium and death accompanying P2X(7) receptor activation, suggesting that dephosphorylation of ATP into adenosine is neuroprotective and that the balance of extracellular purines can influence neuronal survival. Increased intraocular pressure can lead to release of excessive extracellular ATP in the retina and damage ganglion cells by acting on P2X(7) receptors, implicating a role for the receptor in the loss of ganglion cell activity in glaucoma. In summary, the activation of P2X(7) receptors has both physiologic and pathophysiologic implications for ganglion cell function. These characteristics may also provide an insight into the contributions the P2X(7) receptor makes to neurons elsewhere.
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137
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P2X7 nucleotide receptor is coupled to GSK-3 inhibition and neuroprotection in cerebellar granule neurons. Neurotox Res 2009; 15:193-204. [PMID: 19384592 DOI: 10.1007/s12640-009-9020-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Revised: 11/25/2008] [Accepted: 11/25/2008] [Indexed: 12/19/2022]
Abstract
In this study we report the coupling of nucleotide receptors to GSK-3 signalling, a relevant survival pathway in cerebellar granule neurons. P2X(7) agonist BzATP induced a 3-4-fold increase in GSK-3 phosphorylation, which is reported to be associated with the catalytic activity inhibition. This effect was dependent on extracellular calcium and PKC, and independent of PI3-K (phosphatidyl-inositol-3-kinase)/Akt, the main survival route of neurotrophins. BzATP also prevented the apoptosis of granule neurons induced by the pharmacological inhibition of the PI3-K signalling. Both effects, BzATP-mediated GSK-3 phosphorylation and neuroprotection, were abolished by P2X(7) receptor antagonists, BBG, PPADS and A-438079. We found that BzATP prevented the progressive GSK-3 dephosphorylation and caspase-3 activation occurring under conditions of sustained PI3-K inhibition. These results reveal that P2X(7) receptor activation could provide a relevant survival route alternative to classical neurotrophic factors.
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138
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Alqallaf SM, Evans BAJ, Kidd EJ. Atypical P2X receptor pharmacology in two human osteoblast-like cell lines. Br J Pharmacol 2009; 156:1124-35. [PMID: 19226284 DOI: 10.1111/j.1476-5381.2009.00119.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND AND PURPOSE The expression and function of P2X(7) receptors in osteoclasts is well established, but less is known about their role in osteoblast-like cells. A study in P2X(7) receptor knockout mice suggested the involvement of these receptors in bone formation. We have investigated the expression and pharmacology of several P2X receptors in two human osteosarcoma cell lines to see if they could be involved in bone turnover in man. EXPERIMENTAL APPROACH Reverse transcriptase-polymerase chain reaction and Western blotting were used to study P2X(2), P2X(4) and P2X(7) receptor expression at mRNA and protein levels, respectively, in human osteoblast-like cells. P2X(7) receptor pharmacology was studied by measuring pore formation in the presence of different agonists and antagonists using the YO-PRO 1 uptake method. KEY RESULTS P2X(4) and P2X(7) receptor mRNA and protein were found to be expressed by these cell lines. No evidence was found for P2X(4)/P2X(7) receptor heteropolymerization. 2'-3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate (DBzATP) was equipotent to ATP and the antagonists used were either ineffective or weakly blocked pore formation. CONCLUSIONS AND IMPLICATIONS This study demonstrates that P2X(4) and P2X(7) receptors are expressed by human osteoblast-like cells. The affinities of the different agonists suggest that the P2X(7) receptor is mainly responsible for pore formation although P2X(4) receptors may also be involved. The low affinity of DBzATP and the weak action of the antagonists support the previously described atypical pharmacology of the P2X(7) receptor in osteoblasts. Targeting the P2X(7) receptor in osteoblasts could represent a promising new treatment for bone diseases such as osteoporosis and rheumatoid arthritis.
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Affiliation(s)
- S M Alqallaf
- Welsh School of Pharmacy, Cardiff University, King Edward VII Avenue, Cardiff, UK
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139
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Grahnert A, Klein C, Hauschildt S. Involvement of P2X receptors in the NAD(+)-induced rise in [Ca (2+)] (i) in human monocytes. Purinergic Signal 2009; 5:309-19. [PMID: 19221895 DOI: 10.1007/s11302-009-9144-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2008] [Accepted: 01/27/2009] [Indexed: 01/06/2023] Open
Abstract
In the present study, we show that the extracellular addition of nicotinamide adenine dinucleotide (NAD(+)) induces a transient rise in [Ca(2+)](i) in human monocytes caused by an influx of extracellular calcium. The NAD(+)-induced Ca(2+) response was prevented by adenosine triphosphate (ATP), suggesting the involvement of ATP receptors. Of the two subtypes of ATP receptors (P2X and P2Y), the P2X receptors were considered the most likely candidates. By the use of subtype preferential agonists and antagonists, we identified P2X(1), P2X(4), and P2X(7) receptors being engaged in the NAD(+)-induced rise in [Ca(2+)](i). Among the P2X receptor subtypes, the P2X(7) receptor is unique in facilitating the induction of nonselective pores that allow entry of ethidium upon stimulation with ATP. In monocytes, opening of P2X(7) receptor-dependent pores strongly depends on specific ionic conditions. Measuring pore formation in response to NAD(+), we found that NAD(+) unlike ATP lacks the ability to induce this pore-forming response. Whereas as little as 100 muM ATP was sufficient to activate the nonselective pore, NAD(+) at concentrations up to 2 mM had no effect. Taken together, these data indicate that despite similarities in the action of extracellular NAD(+) and ATP there are nucleotide-specific variations. So far, common and distinct features of the two nucleotides are only beginning to be understood.
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Affiliation(s)
- Anja Grahnert
- Department of Immunobiology, Institute of Biology II, University of Leipzig, Talstrasse 33, 04103, Leipzig, Germany
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140
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Cotrina ML, Nedergaard M. Physiological and pathological functions of P2X7 receptor in the spinal cord. Purinergic Signal 2009; 5:223-32. [PMID: 19205927 DOI: 10.1007/s11302-009-9138-2] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 07/15/2008] [Indexed: 12/24/2022] Open
Abstract
ATP-mediated signaling has widespread actions in the nervous system from neurotransmission to regulation of proliferation. In addition, ATP is released during injury and associated to immune and inflammatory responses. Still, the potential of therapeutic intervention of purinergic signaling during pathological states is only now beginning to be explored because of the large number of purinergic receptors subtypes involved, the complex and often overlapping pharmacology and because ATP has effects on every major cell type present in the CNS. In this review, we will focus on a subclass of purinergic-ligand-gated ion channels, the P2X7 receptor, its pattern of expression and its function in the spinal cord where it is abundantly expressed. We will discuss the mechanisms for P2X7R actions and the potential that manipulating the P2X7R signaling pathway may have for therapeutic intervention in pathological events, specifically in the spinal cord.
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Affiliation(s)
- Maria Luisa Cotrina
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY, 14642, USA,
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141
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The P2X(7) receptor in retinal ganglion cells: A neuronal model of pressure-induced damage and protection by a shifting purinergic balance. Purinergic Signal 2008; 4:313-21. [PMID: 18923921 DOI: 10.1007/s11302-008-9125-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2008] [Accepted: 09/12/2008] [Indexed: 10/21/2022] Open
Abstract
Retinal ganglion cells process the visual signal and transmit it along their axons in the optic nerve to the brain. Molecular, immunohistochemical, and functional analyses indicate that the majority of retinal ganglion cells express the ionotropic P2X(7) receptor. Stimulation of the receptor can lead to a rise in intracellular calcium and cell death, although death does not involve the opening of a large diameter pore. Adenosine acting at A(3) receptors can attenuate the rise in calcium and death accompanying P2X(7) receptor activation, suggesting that dephosphorylation of ATP into adenosine is neuroprotective and that the balance of extracellular purines can influence neuronal survival. Increased intraocular pressure can lead to release of excessive extracellular ATP in the retina and damage ganglion cells by acting on P2X(7) receptors, implicating a role for the receptor in the loss of ganglion cell activity in glaucoma. In summary, the activation of P2X(7) receptors has both physiologic and pathophysiologic implications for ganglion cell function. These characteristics may also provide an insight into the contributions the P2X(7) receptor makes to neurons elsewhere.
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142
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Resende RR, Britto LRG, Ulrich H. Pharmacological properties of purinergic receptors and their effects on proliferation and induction of neuronal differentiation of P19 embryonal carcinoma cells. Int J Dev Neurosci 2008; 26:763-77. [PMID: 18675894 DOI: 10.1016/j.ijdevneu.2008.07.008] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 07/01/2008] [Accepted: 07/01/2008] [Indexed: 11/18/2022] Open
Abstract
We have used P19 embryonal carcinoma cells as in vitro model for early neurogenesis to study ionotropic P2X and metabotropic P2Y receptor-induced Ca(2+) transients and their participation in induction of proliferation and differentiation. In embryonic P19 cells, P2Y(1), P2Y(2) and P2X(4) receptors or P2X-heteromultimers with similar P2X(4) pharmacology were responsible for ATP and ATP analogue-induced Ca(2+) transients. In neuronal-differentiated cells, P2Y(2,) P2Y(6), P2X(2) and possibly P2X(2)/P2X(6) heteromeric receptors were the major mediators of the elevations in intracellular free calcium concentration [Ca(2+)](i). We have collected evidence for the involvement of metabotropic purinergic receptors in proliferation induction of undifferentiated and neural progenitor cells by using a BrdU-incorporation assay. ATP-, UTP-, ADP-, 2-MeS-ATP- and ADP-betaS-induced proliferation in P19 cells was mediated by P2Y(1) and P2Y(2) receptors as judged from pharmacological profiles of receptor responses. ATP-provoked acceleration of neuronal differentiation, determined by analysis of nestin and neuron-specific enolase gene and protein expression, also resulted from P2Y(1) and P2Y(2) receptor activation. Proliferation- and differentiation-induction involved the activation of inositol-trisphosphate sensitive intracellular Ca(2+) stores.
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Affiliation(s)
- R R Resende
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-900 São Paulo, SP, Brazil
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143
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Gavala ML, Pfeiffer ZA, Bertics PJ. The nucleotide receptor P2RX7 mediates ATP-induced CREB activation in human and murine monocytic cells. J Leukoc Biol 2008; 84:1159-71. [PMID: 18625910 DOI: 10.1189/jlb.0907612] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Nucleotide receptors serve as sensors of extracellular ATP and are important for immune function. The nucleotide receptor P2RX7 is a cell-surface, ligand-gated cation channel that has been implicated in many diseases, including arthritis, granuloma formation, sepsis, and tuberculosis. These disorders are often exacerbated by excessive mediator release from activated macrophages in the inflammatory microenvironment. Although P2RX7 activation can modulate monocyte/macrophage-induced inflammatory events, the relevant molecular mechanisms are poorly understood. Previous studies suggest that MAPK cascades and transcriptional control via CREB-linked pathways regulate the inflammatory capacity of monocytic cells. As P2RX7 promotes MAPK activation and inflammatory mediator production, we examined the involvement MAPK-induced CREB activation in P2RX7 action. Our data reveal that stimulation of multiple monocytic cell lines with P2RX7 agonists induces rapid CREB phosphorylation. In addition, we observed a lack of nucleotide-induced CREB phosphorylation in RAW 264.7 cells expressing nonfunctional P2RX7 and a gain of nucleotide-induced CREB phosphorylation in human embryonic kidney-293 cells that heterologously express human P2RX7. Furthermore, our results indicate that P2RX7 agonist-induced CREB phosphorylation is partly mediated via Ca(2+) fluxes and the MEK/ERK system. Mechanistic analyses revealed that macrophage stimulation with a P2RX7 agonist induces CREB/CREB-binding protein complex formation, which is necessary for CREB transcriptional activation. Also, we demonstrate that P2RX7 activation induces a known CREB-dependent gene (c-fos) and that dominant-negative CREB constructs attenuate this response. These studies support the idea that P2RX7 stimulation can directly regulate protein expression that is not dependent on costimulation with other immune modulators such as LPS.
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Affiliation(s)
- Monica L Gavala
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI 53706, USA
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144
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Li Z, Liang D, Chen L. Potential therapeutic targets for ATP-gated P2X receptor ion channels. Assay Drug Dev Technol 2008; 6:277-84. [PMID: 18471080 DOI: 10.1089/adt.2007.121] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
P2X receptors make up a novel family of ligand-gated ion channels that are activated by binding of extracellular ATP. These receptors can form a number of homomeric and heteromeric ion channels, which are widely distributed throughout the human body. They are thought to play an important role in many cellular processes, including synaptic transmission and thrombocyte aggregation. These ion channels are also involved in the pathology of several disease states, including chronic inflammation and neuropathic pain, and thus are the potential targets for drug development. The recent discovery of potent and highly selective antagonists for P2X(7) receptors, through the use of high-throughput screening, has helped to further understand the P2X receptor pharmacology and provided new evidence that P2X(7) receptors play a specific role in chronic pain states. In this review, we discuss how the P2X family of ion channels has distinguished itself as a potential new drug target. We are optimistic that safe and effective candidate drugs will be suitable for progression into clinical development.
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Affiliation(s)
- Zhiyuan Li
- Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, People's Republic of China.
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145
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Jarvis MF, Khakh BS. ATP-gated P2X cation-channels. Neuropharmacology 2008; 56:208-15. [PMID: 18657557 DOI: 10.1016/j.neuropharm.2008.06.067] [Citation(s) in RCA: 260] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2008] [Revised: 06/24/2008] [Accepted: 06/30/2008] [Indexed: 12/20/2022]
Abstract
P2X receptors are ATP-gated cation channels with important roles in diverse pathophysiological processes. Substantial progress has been made in the last few years with the discovery of both subunit selective antagonists and modulators. The purpose of this brief review is to summarize the advances in the pharmacology of P2X receptors, with key properties presented in an easy to access format. Ligand-gated ion channels consist of three families in mammals; the ionotropic glutamate receptors, the Cys-loop receptors (for GABA, ACh, glycine and serotonin) and the P2X receptors for ATP. The first two of these are considered in articles accompanying this Special Issue. Here we consider the pharmacological properties of P2X receptors. We do not present a detailed discussion of P2X receptor physiological roles or structure-function studies. Moreover, the pharmacological basis for discriminating between the main subtypes of P2X receptor and their nomenclature has been published by the Nomenclature Committee of the International Union of Pharmacology (NC-IUPHAR) P2X Receptor Subcommittee, and so these aspects are not revisited here. Instead in this brief article we seek to present a summary of the pharmacology of recombinant homomeric and heteromeric P2X receptors, with particular emphasis on new antagonists. In this article we have tried to present as much information as possible in two tables in the hope this will be useful as a day-to-day resource, and also because an excellent and detailed review has recently been published.
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Affiliation(s)
- Michael F Jarvis
- Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064, USA.
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146
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Donnelly-Roberts DL, Namovic MT, Surber B, Vaidyanathan SX, Perez-Medrano A, Wang Y, Carroll WA, Jarvis MF. [3H]A-804598 ([3H]2-cyano-1-[(1S)-1-phenylethyl]-3-quinolin-5-ylguanidine) is a novel, potent, and selective antagonist radioligand for P2X7 receptors. Neuropharmacology 2008; 56:223-9. [PMID: 18602931 DOI: 10.1016/j.neuropharm.2008.06.012] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Accepted: 06/09/2008] [Indexed: 11/20/2022]
Abstract
ATP-sensitive P2X7 receptors are localized on cells of immunological origin including peripheral macrophages and glial cells in the CNS. Activation of P2X7 receptors leads to rapid changes in intracellular calcium concentrations, release of the pro-inflammatory cytokine IL-1beta, and following prolonged agonist exposure, the formation of cytolytic pores in plasma membranes. Data from gene knockout studies and recently described selective antagonists indicate a role for P2X7 receptor activation in inflammation and pain. While several species selective P2X7 antagonists exist, A-804598 represents a structurally novel, competitive, and selective antagonist that has equivalent high affinity at rat (IC50 = 10 nM), mouse (IC50 = 9 nM) and human (IC50 = 11 nM) P2X7 receptors. A-804598 also potently blocked agonist stimulated release of IL-1beta and Yo-Pro uptake from differentiated THP-1 cells that natively express human P2X7 receptors. A-804598 was tritiated ([3H]A-804598; 8.1Ci/mmol) and utilized to study recombinant rat P2X7 receptors expressed in 1321N1 cells. [3H]A-804598 labeled a single class of high affinity binding sites (Kd=2.4 nM and apparent Bmax=0.56 pmol/mg). No specific binding was observed in untransfected 1321N1 cells. The pharmacological profile for P2X antagonists to inhibit [3H]A-804598 binding correlated with their ability to block functional activation of P2X7 receptors (r=0.95, P<0.05). These data demonstrate that A-804598 is one of the most potent and selective antagonists for mammalian P2X7 receptors described to date and [3H]A-804598 is a high affinity antagonist radioligand that specifically labels rat P2X7 receptors.
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Affiliation(s)
- Diana L Donnelly-Roberts
- Neuroscience Research, Abbott Laboratories, 100 Abbott Park Road, Building. AP9A, Department R4PM, Abbott Park, IL 60064-6123, USA
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147
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Nelson DW, Sarris K, Kalvin DM, Namovic MT, Grayson G, Donnelly-Roberts DL, Harris R, Honore P, Jarvis MF, Faltynek CR, Carroll WA. Structure−Activity Relationship Studies on N′-Aryl Carbohydrazide P2X7 Antagonists. J Med Chem 2008; 51:3030-4. [DOI: 10.1021/jm701516f] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Derek W. Nelson
- Abbott Laboratories, Neuroscience Research and Advanced Technology, Global Pharmaceutical Research and Development, Abbott Park, Illinois 60064-6101
| | - Kathy Sarris
- Abbott Laboratories, Neuroscience Research and Advanced Technology, Global Pharmaceutical Research and Development, Abbott Park, Illinois 60064-6101
| | - Douglas M. Kalvin
- Abbott Laboratories, Neuroscience Research and Advanced Technology, Global Pharmaceutical Research and Development, Abbott Park, Illinois 60064-6101
| | - Marian T. Namovic
- Abbott Laboratories, Neuroscience Research and Advanced Technology, Global Pharmaceutical Research and Development, Abbott Park, Illinois 60064-6101
| | - George Grayson
- Abbott Laboratories, Neuroscience Research and Advanced Technology, Global Pharmaceutical Research and Development, Abbott Park, Illinois 60064-6101
| | - Diana L. Donnelly-Roberts
- Abbott Laboratories, Neuroscience Research and Advanced Technology, Global Pharmaceutical Research and Development, Abbott Park, Illinois 60064-6101
| | - Richard Harris
- Abbott Laboratories, Neuroscience Research and Advanced Technology, Global Pharmaceutical Research and Development, Abbott Park, Illinois 60064-6101
| | - Prisca Honore
- Abbott Laboratories, Neuroscience Research and Advanced Technology, Global Pharmaceutical Research and Development, Abbott Park, Illinois 60064-6101
| | - Michael F. Jarvis
- Abbott Laboratories, Neuroscience Research and Advanced Technology, Global Pharmaceutical Research and Development, Abbott Park, Illinois 60064-6101
| | - Connie R. Faltynek
- Abbott Laboratories, Neuroscience Research and Advanced Technology, Global Pharmaceutical Research and Development, Abbott Park, Illinois 60064-6101
| | - William A. Carroll
- Abbott Laboratories, Neuroscience Research and Advanced Technology, Global Pharmaceutical Research and Development, Abbott Park, Illinois 60064-6101
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Lu ZM, Xie F, Fu H, Liu MG, Cao FL, Hao J, Chen J. Roles of peripheral P2X and P2Y receptors in the development of melittin-induced nociception and hypersensitivity. Neurochem Res 2008; 33:2085-91. [PMID: 18404374 DOI: 10.1007/s11064-008-9689-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2007] [Accepted: 03/26/2008] [Indexed: 01/16/2023]
Abstract
A recent report from our laboratory shows that subcutaneous (s.c.) injection of melittin could induce persistent spontaneous nociception (PSN) and primary thermal or mechanical hyperalgesia. However, the exact peripheral mechanisms underlying melittin-induced multiple pain-related behaviors remain unclear. In this study, behavioral tests combined with pharmacological manipulations were used to explore potential roles of local P2X and P2Y receptors in melittin-induced inflammatory pain and hyperalgesia. Post-treatment of the primary injury site with s.c. injection of A-317491 (a potent P2X(3)/P2X(2/3) receptor antagonist) and Reactive Blue 2 (a potent P2Y receptor antagonist) could significantly suppress the development of melittin-evoked PSN and hypersensitivity (thermal and mechanical). Our control experiments demonstrated that local administration of either antagonist into the contralateral hindpaw produced no significant effect on any kind of pain-associated behaviors. Taken together, these data indicate that activation of P2X and P2Y receptors might be essential to the maintenance of melittin-induced primary thermal and mechanical hyperalgesia as well as on-going pain.
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Affiliation(s)
- Zhuo-Min Lu
- Institute for Biomedical Sciences of Pain and Institute for Functional Brain Disorders, Tangdu Hospital, Fourth Military Medical University, #1 Xinsi Road, Baqiao, Xi'an 710038, People's Republic of China
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149
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Conant AR, Theologou T, Dihmis WC, Simpson AWM. Diadenosine polyphosphates are selective vasoconstrictors in human coronary artery bypass grafts. Vascul Pharmacol 2008; 48:157-64. [PMID: 18325842 DOI: 10.1016/j.vph.2008.01.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Accepted: 01/17/2008] [Indexed: 11/16/2022]
Abstract
Diadenosine polyphosphates (Ap(n)A) are released by degranulating platelets and high, local concentrations may form at sites of platelet activation. Radial artery grafts, now often used alongside the internal mammary artery in coronary artery bypass surgery, are particularly reactive to several vasoconstrictors but the response to Ap(n)A has not been investigated. This study compared the vasoconstrictor activity of Ap(n)A in human radial artery with other vessels commonly used as bypass grafts. Radial artery demonstrated robust concentration-dependent vasoconstriction to Ap(n)A (n=4-6) at concentrations in the micromolar range. In contrast, average responses in internal mammary artery were negligible. Cross-desensitization revealed that Ap(n)A-mediated vasoconstriction occurred via an alphabetamethyleneATP-sensitive receptor. Responses to both Ap(5)A and alphabetamethyleneATP were inhibited by suramin but were insensitive to the P2X(1) receptor antagonist 8,8'-[Carbonylbis(imino-4,1-phenylenecarbonylimino-4,1-phenylenecarbonylimino)]bis-1,3,5-naphthalenetrisulfonic acid (NF279). Pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) enhanced responses to Ap(5)A. Similar responses were obtained in saphenous vein. In conclusion, diadenosine polyphosphates contract radial artery and saphenous vein by an as yet uncharacterized P2X receptor but have only limited activity in internal mammary artery. The selective activity of diadenosine polyphosphates in radial artery would implicate them as potential mediators of post-operative contraction in this graft.
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Affiliation(s)
- Alan R Conant
- The Cardiothoracic Centre, Liverpool NHS Trust, Thomas Drive, Liverpool L14 3PE, UK.
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150
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Sun JH, Cai GJ, Xiang ZH. EXPRESSION OF P2X PURINOCEPTORS IN PC12 PHAEOCHROMOCYTOMA CELLS. Clin Exp Pharmacol Physiol 2007; 34:1282-6. [DOI: 10.1111/j.1440-1681.2007.04718.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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