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P2X7 Receptors (p2x7 + receptor)

Distribution by Scientific Domains

Medical Sciences	59%
Life Sciences	40%

Distribution within Medical Sciences

Pharmacology & Pharmaceutical Medicine	84%
Immunology	10%

Selected Abstracts

Dynamics of P2X7 receptor pore dilation: Pharmacological and functional consequences

DRUG DEVELOPMENT RESEARCH, Issue 2-3 2001
I.P. Chessell
Abstract The biophysical and functional properties of the human P2X7 receptor, expressed recombinantly in HEK-293 cells or natively in THP-1 pro-monocytic cells, were investigated in the context of pore dilation and externalisation of mature interleukin 1, (IL1,). In HEK-293 cells, the agonist 2,- and 3,-O-(4-benzoylbenzoyl)-ATP (BzATP) caused concentration-dependent inward currents (EC50 59 ,M) and with prolonged application this agonist caused a gradual increase in inward current culminating in a plateau. This increase in current was associated with pore dilation, determined by intracellular accumulation of YO-PRO-1. BzATP displayed increased potency at the pore-dilated form of the P2X7 receptor (EC50 17 ,M), and positive correlations between apparent receptor density and speed of pore dilation were observed. A monoclonal antibody selectively blocked current mediated by the naïve receptor, while currents through pore-dilated receptors were not significantly affected, which together suggest a conformational change at the level of the receptor during the dilation event. The release of mature IL1, from THP-1 cells was independent of P2X7 -mediated cell lysis, as determined by study of lactate dehydrogenase release. Moreover, using conditions designed to minimise pore dilation (using buffers containing 2 mM Ca2+ and 1 mM Mg2+), BzATP caused significant release of IL1,, but without concomitant YO-PRO-1 accumulation, indicating pore dilation is not required for IL1, release. In addition, short (4-min) incubation of THP-1 cells with BzATP (terminated by enzymatic degradation of BzATP using apyrase) resulted in significant quantities of IL1, release some 60 min later, suggesting commitment of cells to release IL1, can be triggered with only brief receptor ligation. These findings suggest that receptor expression and ligation time are critical factors for selecting multiple functional states of P2X7. Drug Dev. Res. 53:60,65, 2001. © 2001 Wiley-Liss, Inc. [source]

NTPDase1 governs P2X7 -dependent functions in murine macrophages

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 5 2010
Sébastien A. Lévesque
Abstract P2X7 receptor is an adenosine triphosphate (ATP)-gated ion channel within the multiprotein inflammasome complex. Until now, little is known about regulation of P2X7 effector functions in macrophages. In this study, we show that nucleoside triphosphate diphosphohydrolase 1 (NTPDase1)/CD39 is the dominant ectonucleotidase expressed by murine peritoneal macrophages and that it regulates P2X7 -dependent responses in these cells. Macrophages isolated from NTPDase1-null mice (Entpd1,/,) were devoid of all ADPase and most ATPase activities when compared with WT macrophages (Entpd1+/+). Entpd1,/, macrophages exposed to millimolar concentrations of ATP were more susceptible to cell death, released more IL-1, and IL-18 after TLR2 or TLR4 priming, and incorporated the fluorescent dye Yo-Pro-1 more efficiently (suggestive of increased pore formation) than Entpd1+/+ cells. Consistent with these observations, NTPDase1 regulated P2X7 -associated IL-1, release after synthesis, and this process occurred independently of, and prior to, cytokine maturation by caspase-1. NTPDase1 also inhibited IL-1, release in vivo in the air pouch inflammatory model. Exudates of LPS-injected Entpd1,/, mice had significantly higher IL-1, levels when compared with Entpd1+/+ mice. Altogether, our studies suggest that NTPDase1/CD39 plays a key role in the control of P2X7 -dependent macrophage responses. [source]

Nucleotide-mediated calcium signaling in rat cortical astrocytes: Role of P2X and P2Y receptors

GLIA, Issue 3 2003
Marta Fumagalli
Abstract ATP is the dominant messenger for astrocyte-to-astrocyte calcium-mediated communication. Definition of the exact ATP/P2 receptors in astrocytes and of their coupling to intracellular calcium ([Ca2+]i) has important implications for brain physiology and pathology. We show that, with the only exception of the P2X6 receptor, primary rat cortical astrocytes express all cloned ligand-gated P2X (i.e., P2X1,5 and P2X7) and G-protein-coupled P2Y receptors (i.e., P2Y1, P2Y2, P2Y4, P2Y6, and P2Y12). These cells also express the P2Y-like UDP-glucose receptor, which has been recently recognized as the P2Y14 receptor. Single-cell image analysis showed that only some of these receptors are coupled to [Ca2+]i. While ATP induced rapid and transient [Ca2+]i increases (counteracted by the P2 antagonists suramin, pyridoxal-phosphate-6-azophenyl-2,-4,-disulfonic acid and oxidized ATP), the P2X1/P2X3 agonist ,,meATP produced no changes. Conversely, the P2X7 agonist BzATP markedly increased [Ca2+]i; the presence and function of the P2X7 receptor was also confirmed by the formation of the P2X7 pore. ADP and 2meSADP also produced [Ca2+]i increases antagonized by the P2Y1 antagonist MRS2179. Some cells also responded to UTP but not to UDP. Significant responses to sugar-nucleotides were also detected, which represents the first functional response reported for the putative P2Y14 receptor in a native system. Based on agonist preference of known P2 receptors, we conclude that, in rat astrocytes, ATP-induced calcium rises are at least mediated by P2X7 and P2Y1 receptors; additional receptors (i.e., P2X2, P2X4, P2X5, P2Y2, P2Y4, and P2Y14) may also contribute. © 2003 Wiley-Liss, Inc. [source]

Evidence for two conductive pathways in P2X7 receptor: differences in modulation and selectivity

JOURNAL OF NEUROCHEMISTRY, Issue 3 2010
Susanna Alloisio
J. Neurochem. (2010) 113, 796,806. Abstract The P2X7 receptor (P2X7R) is an ATP-gated cation channel whose biophysical properties remain to be unravelled unequivocally. Its activity is modulated by divalent cations and organic messengers such as arachidonic acid (AA). In this study, we analysed the differential modulation of magnesium (Mg2+) and AA on P2X7R by measuring whole-cell currents and intracellular Ca2+ ([Ca2+]i) and Na+ ([Na+]i) dynamics in HEK293 cells stably expressing full-length P2X7R and in cells endowed with the P2X7R variant lacking the entire C-terminus tail (trP2X7R), which is thought to control the pore activation. AA induced a robust potentiation of the P2X7R- and trP2X7R-mediated [Ca2+]i rise but did not affect the ionic currents in both conditions. Extracellular Mg2+ reduced the P2X7R- and trP2X7R-mediated [Ca2+]i rise in a dose-dependent manner through a competitive mechanism. The modulation of the magnitude of the P2X7R-mediated ionic current and [Na+]i rise were strongly dependent on Mg2+ concentration but occurred in a non-competitive manner. In contrast, in cells expressing the trP2X7R, the small ionic currents and [Na+]i signals were totally insensitive to Mg2+. Collectively, these results support the tenet of a functional structure of P2X7R possessing at least two distinct conductive pathways one for Ca2+ and another for monovalent ions, with the latter which depends on the presence of the receptor C-terminus. [source]

Inflammatory Pain Reduction In Rats By Local Treatment With oATP, A Selective Inhibitor Of P2X7 ATP Receptor

JOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 1 2001
G Dell'Antonio
Peptide neurotransmitters, as substance P or ATP, are released during inflammatiory processes by the nerve endings of sensory fibers. ATP is also released from the cytoplasm of damaged cells at the site of inflammation. It acts at the level of many P2X subtypes of purinoreceptors. The receptor for extracellular ATP named P2Z/P2X7 is selectively blocked by the periodate oxidized ATP (oATP). We have hypothesized that P2X subunits present on peripheral sensory nerve terminals, able to initiate a nociceptive signal, could be blocked by local treatment with oATP, so inducing pain relief. Male inbred Fisher rats weighing about 250 g were used. Unilateral inflammation into rat hind paw was induced by intraplantar injection of Freund's complete adjuvant (FCA). The following signs of inflammation, from 3 to 48 h after FCA injection, were detected: increased paw volume, increased paw temperature and hyperalgesia. The latter was evaluated using an algesiometric test wich measured the paw pressure threshold (PPT, expressed in g). We treated some rats, bearing paw inflammation by 12 h, with local injection of 56 ,M oATP. We showed a significant reduction of hyperalgesia in treated rats (PPT = 190 ± 2.3 in inflamed paw of oATP treated vs. PPT = 60 ± 1.6 in inflamed paw of untreated rats, at 60 min following oATP innoculation). We showed also that treatment with oATP was more efficient than treatment with diclofenac in reducing local inflammatory pain (PPT expressed as percentage of the maximum possible effect = 60 ± 0.5, at 120 min following intraplantar administration of oATP, vs. 25 ± 1.9 at the same time following intraplantar administration of diclofenac). The use of polyclonal antibody anti P2X7 receptor to perform immunohistochemical analysis of inflamed tissue, showed a reduction of receptor expression at the level of nerve endings in sections obtained from rat paw treated with oATP with respect to sections obtained from untreated rats. Such an effect was independent on the recruitment of immunocytes in inflamed tissue. Our results demonstrate that ATP exerts a key role in the pathophysiology of peripheral inflammation and that oATP may be effective in treating inflammatory pain. [source]

Synaptic localization of P2X7 receptors in the rat retina

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 1 2004
Theresa Puthussery
Abstract The distribution of P2X7 receptor (P2X7R) subunits was studied in the rat retina using a subunit-specific antiserum. Punctate immunofluorescence was observed in the inner and outer plexiform layers. Double labeling of P2X7 and the horizontal cell marker, calbindin, revealed extensive colocalization in the outer plexiform layer (OPL). Significant colocalization of P2X7R and kinesin, a marker of photoreceptor ribbons, was also observed, indicating that this receptor may be expressed at photoreceptor terminals. Furthermore, another band of P2X7R puncta was identified below the level of the photoreceptor terminals, adjacent to the inner nuclear layer (INL). This band of P2X7R puncta colocalized with the active-zone protein, bassoon, suggesting that "synapse-like" structures exist outside photoreceptor terminals. Preembedding immunoelectron microscopy demonstrated P2X7R labeling of photoreceptor terminals adjacent to ribbons. In addition, some horizontal cell dendrites and putative "desmosome-like" junctions below cone pedicles were labeled. In the inner plexiform layer (IPL), P2X7R puncta were observed surrounding terminals immunoreactive for protein kinase C-,, a marker of rod bipolar cells. Double labeling with bassoon in the IPL revealed extensive colocalization, indicating that P2X7R is likely to be found at conventional cell synapses. This finding was confirmed at the ultrastructural level: only processes presynaptic to rod bipolar cells were found to be labeled for the P2X7R, as well as other conventional synapses. These findings suggest that purines play a significant role in neurotransmission within the retina, and may modulate both photoreceptor and rod bipolar cell responses. J. Comp. Neurol. 472:13,23, 2004. © 2004 Wiley-Liss, Inc. [source]

Effect of P2X7 receptor knockout on exocrine secretion of pancreas, salivary glands and lacrimal glands

THE JOURNAL OF PHYSIOLOGY, Issue 18 2010
Ivana Novak
The purinergic P2X7 receptors are expressed in different cell types where they have varied functions, including regulation of cell survival. The P2X7 receptors are also expressed in exocrine glands, but their integrated role in secretion is unclear. The aim of our study was to determine whether the P2X7 receptors affect fluid secretion in pancreas, salivary glands and tear glands. We monitored gland secretions in in vivo preparations of wild-type and P2X7,/, (Pfizer) mice stimulated with pilocarpine. In cell preparations from pancreas, parotid and lacrimal glands we measured ATP release and intracellular Ca2+ activity using Fura-2. The data showed that pancreatic secretion and salivary secretions were reduced in P2X7,/, mice, and in contrast, tear secretion was increased in P2X7,/, mice. The secretory phenotype was also dependent on the sex of the animal, such that males were more dependent on the P2X7 receptor expression. ATP release in all cell preparations could be elicited by carbachol and other agonists, and this was independent of the P2X7 receptor expression. ATP and carbachol increased intracellular Ca2+ activity, but responses depended on the gland type, presence of the P2X7 receptor and the sex of the animal. Together, these results demonstrate that cholinergic stimulation leads to release of ATP that can via P2X7 receptors up-regulate pancreatic and salivary secretion but down-regulate tear secretion. Our data also indicate that there is an interaction between purinergic and cholinergic receptor signalling and that function of the P2X7 receptor is suppressed in females. We conclude that the P2X7 receptors are important in short-term physiological regulation of exocrine gland secretion. [source]

P2X7 receptors in rat parotid acinar cells: formation of large pores

AUTONOMIC & AUTACOID PHARMACOLOGY, Issue 4 2001
Simon J. Gibbons
1 Permeabilization of cells mediated by P2X7 receptors occurs to varied degrees in native and heterologous expression systems. Previous studies on P2X7 receptors in parotid acinar cells suggested that ATP does not permeabilize these cells. 2 Modification of the assay conditions showed that ATP permeabilizes freshly dissociated rat parotid acinar cells to the fluorescent dye YOPRO-1. 3 The pharmacological and physiological properties of this effect indicate that permeabilization is mediated by the P2X7 receptor. Adenosine 5,-triphosphate (ATP) and 3,- O -(4-benzoyl)benzoyl adenosine 5,-triphosphate (BzBzATP) were effective agonists with EC50 values of 49.3 and 0.6 ,M, respectively. 4 Permeabilization was best observed in low divalent cation concentrations and at physiological temperatures. Previous studies failed to detect permeabilization because of the sensitivity of this effect to temperature and divalent cations. 5 An important consideration in understanding the effect of divalent cations is that the fluorescence of YOPRO-1/nucleic acid complexes is directly quenched by addition of divalent cations. This must be considered if quantitative study of the interaction of divalent cations with P2X7 receptors is carried out using fluorescent DNA-binding dyes. 6 In summary, our data show that P2X7 receptors in parotid acinar cells can form large pores in the plasma membrane. This property likely contributes to signalling and may be cytotoxic and have particular significance in damaged or inflamed salivary glands. [source]

Electrophysiological classification of P2X7 receptors in rat cultured neocortical astroglia

BRITISH JOURNAL OF PHARMACOLOGY, Issue 8 2010
W Nörenberg
Background and purpose:, P2X7 receptors are ATP-gated cation channels mediating important functions in microglial cells, such as the release of cytokines and phagocytosis. Electrophysiological evidence that these receptors also occur in CNS astroglia is rare and rather incomplete. Experimental approach:, We used whole-cell patch-clamp recordings to search for P2X7 receptors in astroglial,neuronal co-cultures prepared from the cerebral cortex of rats. Key results:, All the astroglial cells investigated responded to ATP with membrane currents, reversing around 0 mV. These currents could be also detected in isolated outside-out patch vesicles. The results of the experiments with the P2X [,,,-methylene ATP and 2,-3,-O-(4-benzoyl) ATP] and P2Y receptor agonists [adenosine 5,-O-(2-thiodiphosphate), uridine 5,-diphosphate, uridine 5,-triphosphate (UTP) and UDP-glucose] suggested the involvement of P2X receptors in this response. The potentiation of ATP responses in a low divalent cation or alkaline bath, but not by ivermectin, made it likely that a P2X7 receptor is operational. Blockade of the ATP effect by the P2X7 antagonists Brilliant Blue G, calmidazolium and oxidized ATP corroborated this assumption. Conclusions and implications:, Rat cultured cortical astroglia possesses functional P2X7 receptors. It is suggested that astrocytic P2X7 receptors respond to high local ATP concentrations during neuronal injury. [source]

Cloning and pharmacological characterization of the dog P2X7 receptor

BRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2009
S Roman
Background and purpose:, Human and rodent P2X7 receptors exhibit differences in their sensitivity to antagonists. In this study we have cloned and characterized the dog P2X7 receptor to determine if its antagonist sensitivity more closely resembles the human or rodent orthologues. Experimental approach:, A cDNA encoding the dog P2X7 receptor was isolated from a dog heart cDNA library, expressed in U-2 OS cells using the BacMam viral expression system and characterized in electrophysiological, ethidium accumulation and radioligand binding studies. Native P2X7 receptors were examined by measuring ATP-stimulated interleukin-1, release in dog and human whole blood. Key results:, The dog P2X7 receptor was 595 amino acids long and exhibited high homology (>70%) to the human and rodent orthologues although it contained an additional threonine at position 284 and an amino acid deletion at position 538. ATP possessed low millimolar potency at dog P2X7 receptors. 2,-&3,-O-(4benzoylbenzoyl) ATP had slightly higher potency but was a partial agonist. Dog P2X7 receptors possessed relatively high affinity for a number of selective antagonists of the human P2X7 receptor although there were some differences in potency between the species. Compound affinities in human and dog blood exhibited a similar rank order of potency as observed in studies on the recombinant receptor although absolute potency was considerably lower. Conclusions and implications:, Dog recombinant and native P2X7 receptors display a number of pharmacological similarities to the human P2X7 receptor. Thus, dog may be a suitable species for assessing target-related toxicity of antagonists intended for evaluation in the clinic. [source]

Extracellular ATP and adenosine induce cell apoptosis of human hepatoma Li-7A cells via the A3 adenosine receptor

BRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2003
Long T Wen
Extracellular ATP is a potent signaling molecule that modulates a myriad of cellular functions through the activation of P2 purinergic receptors and is cytotoxic to a variety of cells at higher concentrations. The mechanism of ATP-elicited cytotoxicity is not fully understood. In this study, we investigated the effect of extracellular ATP on the human hepatoma Li-7A cells. We observed a time- and dose-dependent growth inhibition of Li-7A cells by ATP, which is accompanied by an increase in the active form of caspase-3 as well as increased cleavage of its substrate, poly (ADP-ribose) polymerase. The cytotoxic effect of extracellular ATP was not mediated by the P2X7 receptor, since (1) the effect was not abolished by the P2X7 receptor antagonists oxidized ATP and KN-62, and (2) extracellular ADP, AMP, and adenosine were also cytotoxic. We found that ATP and ADP were degraded to adenosine by Li-7A cells and that treatment of Li-7A cells by adenosine resulted in growth inhibition and caspase-3 activation, indicating that adenosine is the apoptotic agent. Using adenosine receptor agonists and antagonists, as well as inhibitors of adenosine transport and deamination, we showed that the cytotoxic effect of adenosine is specifically mediated by the A3 receptor even though transcripts of A1, A2A, A2B, and a splice variant of the P2X7 receptors were detected in Li-7A cells by RT,PCR. Cytotoxicity caused by exogenous ATP and adenosine was completely abolished by the caspase-3 inhibitor Z-DEVD-FMK, demonstrating the central role of caspase-3 in apoptosis of Li-7A cells. British Journal of Pharmacology (2003) 140, 1009,1018. doi:10.1038/sj.bjp.0705523 [source]

Expression and function of the purinergic receptor P2X7 in patients with pulmonary tuberculosis

CLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 2 2006
S. Franco-Martínez
Summary P2X7 is a channel receptor gated by adenosine triphosphate (ATP) that is involved in the killing of intracellular mycobacteria. To explore further the role of P2X7 in immunity against Mycobacterium tuberculosis, we studied its expression and function in 19 patients with pulmonary tuberculosis (TB) and 19 healthy contacts. Flow cytometry analysis showed a similar and variable expression of P2X7 in TB patients and healthy subjects. In contrast, P2X7 mARN levels were significantly higher in TB patients. When the function of the P2X7 receptor in peripheral blood mononuclear cells (PBMC) was assessed by the effect of exogenous ATP on apoptosis, the uptake of the fluorescent marker Lucifer yellow or extracellular signal regulated kinase (ERK) phosphorylation, no significant differences were detected in patients and controls. However, mRNA macroarray analysis showed that upon stimulation with ATP, the PBMC from TB patients showed a significant induction of a higher number of cytokine genes (27 of 96), and a lower number of apoptosis genes (20 of 96) compared to healthy controls (17 and 76 genes, respectively). These results suggest that although the PBMC from TB patients do not show apparent abnormalities in the expression of P2X7, and the intracellular signals generated through it, the pattern of gene expression induced by ATP in these cells is different from that found in healthy contacts. This phenomenon suggests a defective function of P2X7 in the immune cells from TB patients, a condition that may contribute to the inability of these patients to eliminate the mycobacteria. [source]

Expanding field of purinergic signaling

DRUG DEVELOPMENT RESEARCH, Issue 1-2 2001
Geoffrey Burnstock
Abstract This article attempts to paint a broad picture of the extraordinary explosive recent developments in the purinergic signaling field. After a brief historical review and update of purinoceptor subtypes, the focus is on the physiological roles of purines and pyrimidines. These are considered both in terms of short-term signaling in neurotransmission, secretion, and vasodilatation and in long-term (trophic) signaling in development, regeneration, proliferation, and cell death. Examples of trophic signaling include cartilage development in limb buds, glial cell proliferation, development of skeletal muscle, changes in receptor expression in smooth-muscle phenotypes, maturation of testicular spermatids, and bone remodeling. Plasticity of purinoceptor expression in pathological conditions is described, including the increase in the purinergic component of parasympathetic nervous control of the human bladder in interstitial cystitis and outflow obstruction and in sympathetic cotransmitter control of blood vessels in hypertensive rats, the appearance of P2X7 receptors in the glomeruli of the kidney from diabetic and transgenic hypertensive animal models, and up-regulation of P2X1 and P2Y2 receptor mRNA in hearts of rats with congestive heart failure. The role of P2X3 receptors in nociception is considered, and a new hypothesis about purinergic mechanosensory transduction in the gut is explored. A personal view of some of the areas ripe for future development concludes this article, including a discussion of different strategies that could lead to the development of purinergic therapeutic agents. Drug Dev. Res. 52:1,10, 2001. © 2001 Wiley-Liss, Inc. [source]

Evidence for the involvement of purinergic P2X7 receptors in outer retinal processing

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2006
Theresa Puthussery
Abstract Extracellular ATP mediates fast excitatory neurotransmission in many regions of the central nervous system through activation of P2X receptors. Although several P2X receptor subunits have been identified in the mammalian retina, little is known about the functional role of these receptors in retinal signalling. The purpose of the present study was to investigate whether purinergic P2X7 receptors are involved in outer retinal processing by assessing receptor localization, degradation of extracellular ATP and the effect of functional activation of P2X7 receptors on the electroretinogram (ERG). Using light and electron microscopy, we demonstrated that P2X7 receptors are expressed postsynaptically on horizontal cell processes as well as presynaptically on photoreceptor synaptic terminals in both the rat and marmoset retina. Using an enzyme cytochemical method, we showed that ecto-ATPases are active in the outer plexiform layer of the rat retina, providing a mechanism by which purinergic synaptic transmission can be rapidly terminated. Finally, we evaluated the role of P2X7 receptors in retinal function by assessing changes to the ERG response of rats after intravitreal delivery of the P2X7 receptor agonist benzoyl benzoyl ATP (BzATP). Intravitreal injection of BzATP resulted in a sustained increase (up to 58%) in the amplitude of the photoreceptor-derived a-wave of the ERG. In contrast, BzATP caused a transient reduction in the rod- and cone-derived postreceptoral responses. These results provide three lines of evidence for the involvement of extracellular purines in outer retinal processing. [source]

Supersensitivity of P2X7 receptors in cerebrocortical cell cultures after in vitro ischemia

JOURNAL OF NEUROCHEMISTRY, Issue 5 2005
Kerstin Wirkner
Abstract Neuronally enriched primary cerebrocortical cultures were exposed to glucose-free medium saturated with argon (in vitro ischemia) instead of oxygen (normoxia). Ischemia did not alter P2X7 receptor mRNA, although serum deprivation clearly increased it. Accordingly, P2X7 receptor immunoreactivity (IR) of microtubuline-associated protein 2 (MAP2)-IR neurons or of glial fibrillary acidic protein (GFAP)-IR astrocytes was not affected; serum deprivation augmented the P2X7 receptor IR only in the astrocytic, but not the neuronal cell population. However, ischemia markedly increased the ATP- and 2,-3,- O -(4-benzoylbenzoyl)-adenosine 5,-triphosphate (BzATP)-induced release of previously incorporated [3H]GABA. Both Brilliant Blue G and oxidized ATP inhibited the release of [3H]GABA caused by ATP application; the Brilliant Blue G-sensitive, P2X7 receptor-mediated fraction, was much larger after ischemia than after normoxia. Whereas ischemic stimulation failed to alter the amplitude of ATP- and BzATP-induced small inward currents recorded from a subset of non-pyramidal neurons, BzATP caused a more pronounced increase in the frequency of miniature inhibitory postsynaptic currents (mIPSCs) after ischemia than after normoxia. Brilliant Blue G almost abolished the effect of BzATP in normoxic neurons. Since neither the amplitude of mIPSCs nor that of the muscimol-induced inward currents was affected by BzATP, it is assumed that BzATP acts at presynaptic P2X7 receptors. Finally, P2X7 receptors did not enhance the intracellular free Ca2+ concentration either in proximal dendrites or in astrocytes, irrespective of the normoxic or ischemic pre-incubation conditions. Hence, facilitatory P2X7 receptors may be situated at the axon terminals of GABAergic non-pyramidal neurons. When compared with normoxia, ischemia appears to markedly increase P2X7 receptor-mediated GABA release, which may limit the severity of the ischemic damage. At the same time we did not find an accompanying enhancement of P2X7 mRNA or protein expression, suggesting that receptors may become hypersensitive because of an increased efficiency of their transduction pathways. [source]

Involvement of nerve injury and activation of peripheral glial cells in tetanic sciatic stimulation-induced persistent pain in rats

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 13 2010
Lingli Liang
Abstract Tetanic stimulation of the sciatic nerve (TSS) produces long-lasting pain hypersensitivity in rats. Long-term potentiation (LTP) of C- and A-fiber-evoked field potentials in the spinal cord has been explored as contributing to central sensitization in pain pathways. However, the peripheral mechanism underlying TSS-induced pain hypersensitivity remains largely unknown. We investigated the effect of TSS on peripheral nerve and the expression of activating transcription factor 3 (ATF3) in dorsal root ganglion (DRG) as a marker of neuronal injury. TSS induced a mechanical allodynia for at least 35 days and induced ATF3 expression in the ipsilateral DRG. ATF3 is colocalized with NF200-labeled myelinated DRG neurons or CGRP- and IB4-labeled unmyelinated ones. Furthermore, we found that TSS induced Wallerian degeneration of sciatic nerve at the level of myelinisation by S100 protein (to label Schwann cells) immunohistochemistry, luxol fast blue staining, and electron microscopy. TSS also elicited the activation of satellite glial cells (SGCs) and enhanced the colocalization of GFAP and P2X7 receptors. Repeated local treatment with tetrodotoxin decreased GFAP expression in SGCs and behavioral allodynia induced by TSS. Furthermore, reactive microglia and astrocytes were found in the spinal dorsal horn after TSS. These results suggest that TSS-induced nerve injury and glial activation in the DRG and spinal dorsal horn may be involved in cellular mechanisms underlying the development of persistent pain after TSS and that TSS-induced nerve injury may be used as a novel neuropathic pain model. © 2010 Wiley-Liss, Inc. [source]

Synaptic localization of P2X7 receptors in the rat retina

Effect of P2X7 receptor knockout on exocrine secretion of pancreas, salivary glands and lacrimal glands

P2X7 receptors in rat parotid acinar cells: formation of large pores

Electrophysiological classification of P2X7 receptors in rat cultured neocortical astroglia

Cloning and pharmacological characterization of the dog P2X7 receptor

Extracellular ATP and adenosine induce cell apoptosis of human hepatoma Li-7A cells via the A3 adenosine receptor

Effects of extracellular nucleotides and nucleosides on prostate carcinoma cells

BRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2001
Rodolphe Janssens
The purpose of this work was to characterize the receptors involved in the action of nucleotides on the human prostate carcinoma cell lines LNCaP, PC-3 and DU145. Northern blotting revealed the presence of P2Y2, P2Y6 and P2Y11 messengers in the three cell lines. P2Y1 mRNA was only observed in the DU145 cells. In both PC-3 and DU145 cells, ATP and UTP stimulated inositol phosphate accumulation in an equipotent, equiactive and non-additive way, suggesting the involvement of P2Y2 receptors. ATP also increased cyclic AMP, but this effect is likely to result from degradation into adenosine and activation of A2 receptor. A2 receptor activation led to a synergistic enhancement of prostate-specific antigen secretion induced by vasoactive intestinal peptide. RT , PCR experiments detected the expression of the P2X4 and P2X5 receptors in the DU145 cells and the P2X4, P2X5 and P2X7 receptors in the PC-3 cells. The calcium influx induced by BzATP confirmed the functional expression of P2X receptors. ATP inhibited the growth of PC-3 and DU145 cells. This effect was mimicked neither by UTP nor by adenosine, indicating that it does not result from phospholipase C or adenylyl cyclase activation. On the contrary, in PC-3 cells, BzATP reproduced the effect of ATP, which was associated to a moderate decrease of proliferation and an increase of apoptosis. In DU145 cells, ATP was more potent than BzATP and growth inhibition was mainly associated with necrosis. We suggest that P2X receptors might be involved in the inhibition by nucleotides of prostate carcinoma cell growth. British Journal of Pharmacology (2001) 132, 536,546; doi:10.1038/sj.bjp.0703833 [source]