P2U Receptor

Extracellular purine and pyrimidine nucleotides produce their pharmacological effects through P2 receptors. These were first named by Geoff Burnstock in an extensive review in 1978. They were then subdivided into P2X and P2Y purinoceptors by Burnstock and Kennedy in 1985, based on applying pharmacological criteria to data generated by functional studies in smooth muscle tissues. Several other P2 subtypes, P2T , P2Z , P2U and P2D were subsequently identified in the following years, again using pharmacological criteria...

Amyloid beta peptides generate oxidative stress in hippocampal astrocytes through a mechanism sensitive to inhibitors of the NADPH oxidase [diphenylene iodonium (DPI) and apocynin]. Seeking evidence for the expression and function of the enzyme in primary hippocampal astrocytes, we confirmed the expression of the subunits of the phagocyte NADPH oxidase by Western blot analysis and by immunofluorescence and coexpression with the astrocyte-specific marker glial fibrillary acidic protein both in cultures and in vivo...

Although almost all GFAP(+) cells in primary astrocyte cultures show functional beta-adrenergic (beta-AR) and metabotropic purinergic (P2Y) receptors, the fewer studies on astrocytes in situ have shown that a much smaller proportion express these same receptor-mediated activities. Here we show, by multiplex single cell RT-PCR, that 44% of freshly isolated, GFAP(+) astrocytes (FIAs) from the CA1 of P8-12 rat hippocampus always co-express beta-adrenergic receptor mRNA subtypes with metabotropic ATP receptor mRNA subtypes (P2Y1, P2Y2 or P2Y4)...

Intercellular spread of Ca2+ waves is the primary manifestation of cell-to-cell communication among astrocytes. Ca2+ waves propagate via the release of a diffusible extracellular messenger that has been identified as ATP. In dorsal spinal astrocytes, Ca2+ waves are mediated by activation of two functionally distinct subtypes of metabotropic purinoceptor: the P2Y1 receptor and a receptor previously classified as P2U. Here, we show that the P2U receptor is molecularly and pharmacologically identical to the cloned P2Y2 receptor...

ATP release from astrocytes contributes to calcium ([Ca(2+)]) wave propagation and may modulate neuronal excitability. In epithelial cells and hepatocytes, cell swelling causes ATP release, which leads to the activation of a volume-sensitive Cl(-) current (I(Cl,swell)) through an autocrine pathway involving purinergic receptors. Astrocyte swelling is counterbalanced by a regulatory volume decrease, involving efflux of metabolites and activation of I(Cl,swell) and K(+) currents. We used whole cell patch-clamp recordings in cultured astrocytes to investigate the autocrine role of ATP in the activation of I(Cl,swell) by hypo-osmotic solution (HOS)...

Propagation of intercellular calcium waves (ICW) between astrocytes depends on the diffusion of signaling molecules through gap junction channels and diffusion through the extracellular space of neuroactive substances acting on plasmalemmal receptors. The relative contributions of these two pathways vary in different brain regions and under certain pathological conditions. We have previously shown that in wild-type spinal cord astrocytes, ICW are primarily gap junction-dependent, but that deletion of the main gap junction protein (Cx43) by homologous recombination results in a switch in mode of ICW propagation to a purinoceptor-dependent mechanism...

To investigate the role of ATP in ovarian tumorigenesis, the present study examined the expression of the P2U purinoceptor (P2U-R) and effect of ATP on growth stimulation in pre-neoplastic and neoplastic ovarian surface epithelial (OSE) cells. The immortalized OSE (IOSE) cell lines, including IOSE-29 (pre-neoplastic), IOSE-29EC (neoplastic), and OVCAR-3 (ovarian adenocarcinoma cell line) were used. Our results indicated that P2U-R mRNA was expressed and that ATP exerted a growth-stimulatory effect in IOSE-29, IOSE-29EC, and OVCAR-3...

We studied the effects of uridine, uridine-5'-monophosphate (UMP), uridine-5'-diphosphate (UDP) and uridine-5'-triphosphate on contractility, coronary flow and heart rate in isolated perfused rat hearts under 60-minute regional ischemia of the left ventricle. All the compounds (50 mumol/l) induced a positive inotropic effect but had no effect on the heart rate. Uridine and UMP prevented the development of the contracture. UDP and especially UTP increased coronary flow. Probably, a protective effect of uridine and UMP is due to activation of myocardial glycogen synthesis while favourable effects of UDP and UTP on contractility and coronary flow are explained by their influence on P2U-receptors of cardiomyocytes...

The effects of purinergic agonists on insulin release are controversial in the literature. In our studies (mainly using INS-1 cells, but also using rat pancreatic islets), ATP had a dual effect on insulin release depending on the ATP concentration: increasing insulin release (EC50 approximately/= 0.0032 microM) and inhibiting insulin release (EC50 approximately/= 0.32 microM) at both 5.6 and 8.3 mM glucose. This is compatible with the view that either two different receptors are involved, or the cells desensitize and (or) the effect of an inhibitory degradation product such as adenosine (ectonucleotidase effect) emerges...

Microglia, the resident macrophages in the central nervous system (CNS), are rapidly activated upon trauma or ischemic injury, releasing cytokines and undertaking tissue repair. Recent studies have indicated that CNS immune cells express ionotropic P2X and metabotropic P2Y purinoceptors and undergo functional changes in response to extracellular ATP. Non-stimulated cultured rat retinal microglia expressed metabotropic P2U(P2Y2, P2Y4) and ionotropic P2Z(P2X7) purinoceptors equally, whereas in LPS-stimulated microglia, P2Z and its CA2+ response became dominant...

The effects of ATP on the pancreatic vascular bed were studied on the isolated rat pancreas perfused at a constant pressure so as any change in the vascular tone induces a modification in the flow rate. This study was performed in two different experimental conditions: 1) In the presence of indomethacin, inhibiting the cyclo-oxygenase and prostacyclin (PGI2) synthesis, ATP (which acts on vasodilatator P2Y receptors and vasoconstrictor P2X and P2U receptors) was used at a concentration (165 microM) which did not modify per se the vascular flow rate...

The P2U purinoceptor (P2UR) has been identified pharmacologically in the ovary. However, the expression and regulation of the P2UR messenger RNA (mRNA) in human ovarian cells are still poorly characterized. The present study was designed to examine the expression and regulation of the P2UR in human granulosa-luteal cells (hGLCs) by RT-PCR and Northern blot analysis. A PCR product corresponding to the expected 599-bp P2UR complementary DNA was obtained from hGLCs. Molecular cloning and sequencing of the PCR product revealed an identical sequence to the reported P2UR complementary DNA...

1. Unlike some interfaces between the blood and the nervous system (e.g., nerve perineurium), the brain endothelium forming the blood-brain barrier can be modulated by a range of inflammatory mediators. The mechanisms underlying this modulation are reviewed, and the implications for therapy of the brain discussed. 2. Methods for measuring blood-brain barrier permeability in situ include the use of radiolabeled tracers in parenchymal vessels and measurements of transendothelial resistance and rate of loss of fluorescent dye in single pial microvessels...

A spectroscopic method, using fluorescent Ca2+, K+ and Na+ ion indicators in combination with the use of fast-kinetic techniques on the time scale of 0.00004-10 s has been applied to study mechanisms of P2 pyrimidoceptor-mediated signal transduction in brain homogenates. Effects of the known P2 receptor ligands (ATP, alpha, beta-methylene-ATP, UTP, UDP and uridine) and the P1 receptor ligand, adenosine, were compared by measuring the rates of transmembrane Ca2+, K+ and Na+ ion fluxes in resealed plasmalemma fragments and nerve endings from the rat cerebral cortex...

Adenosine 5'-triphosphate (ATP) functions as a neurotransmitter or neuromodulator in the brain. To understand the role of ATP during brain development, we investigated the effects of ATP on morphology of cultured astrocytes obtained from the cerebral cortices of embryonic day 18 (E18) and postnatal day 2 (PN2) rats. In E18 astrocytes, ATP (10-1000 microM) alone did not affect astrocyte morphology, but significantly suppressed astrocyte stellation induced by the beta-adrenoceptor agonist isoproterenol or the membrane-permeable cyclic AMP analog dibutyryl cyclic AMP...

The activation of macrophages by various stimuli leading to chemotactic migration and phagocytosis is known to be mediated by an increase in intracellular Ca2+ concentration ([Ca2+]i). We measured changes in [Ca2+]i using a Ca2+ imaging method in individual human macrophages differentiated from freshly prepared peripheral blood monocytes during culture of 1-2 days. A transient rise in [Ca2+]i (duration 3-4 min) occurred in 10-15 macrophages in the vicinity of a single tumour cell that was attacked and permeabilized by a natural killer cell in a dish...

Vasoactive agonists like adenosine-5'-triphosphate (ATP) increase intracellular Ca2+ ([Ca2+]i) in vascular endothelial cells with an initial peak due to inositol 1,4,5-triphosphate-mediated Ca2+ release from intracellular stores followed by a sustained plateau that is dependent on the presence of extracellular Ca2+, thus leading to an increased synthesis and release of prostacyclin and nitric oxide. We studied the effects of nucleotides on membrane potential and [Ca2+]i in confluent human microvascular cardiac endothelial cells obtained from patients with dilated cardiomyopathy...

Rat mucosal mast cells express P2 purinoceptors, occupation of which mobilizes cytosolic Ca2+ and activates a potassium conductance. The primary function of this P2 system in mast cell biology remains unknown. Here, we show that extracellular ADP causes morphological changes in rat bone marrow-cultured mast cells (BMMC) typical of those occurring in cells stimulated by chemotaxins, and that the nucleotides ADP, ATP, and UTP are effective chemoattractants for rat BMMC. ADP was also a chemotaxin for murine J774 monocytes...

BACKGROUND AND PURPOSE: Stimulation of P2u purinoceptors by UTP on endothelium dilates the rat middle cerebral artery (MCA) through the release of endothelium-derived relaxing factor/nitric oxide (EDRF/NO) and an unknown relaxing factor. The purpose of this study was to determine whether this unknown relaxing factor is endothelium-derived hyperpolarizing factor (EDHF). METHODS: Rat MCAs were isolated, cannulated, pressurized, and luminally perfused. UTP was added to the luminal perfusate to elicit dilations...

1. The effect of external ATP on the membrane current was investigated in PC12 cells by whole-cell voltage-clamp techniques. 2. Lower concentrations of ATP (1 or 10 mumol/L) induced only an inward current at 1 mmol/L EGTA in the K+ pipette solution, while higher concentrations of ATP (100 mumol/L and 1 mmol/L) induced an outward current following the inward current. 3. Lowering the EGTA concentration in the pipette solution induced a larger outward current following ATP application. The membrane potential at which the outward current crossed with the control before ATP application was more negative at lower concentrations of EGTA in the pipette...