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Woodward DF, Jones RL, Narumiya S. International Union of Basic and Clinical Pharmacology. LXXXIII: classification of prostanoid receptors, updating 15 years of progress. Pharmacol Rev 2011; 63:471-538. [PMID: 21752876 DOI: 10.1124/pr.110.003517] [Citation(s) in RCA: 321] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
It is now more than 15 years since the molecular structures of the major prostanoid receptors were elucidated. Since then, substantial progress has been achieved with respect to distribution and function, signal transduction mechanisms, and the design of agonists and antagonists (http://www.iuphar-db.org/DATABASE/FamilyIntroductionForward?familyId=58). This review systematically details these advances. More recent developments in prostanoid receptor research are included. The DP(2) receptor, also termed CRTH2, has little structural resemblance to DP(1) and other receptors described in the original prostanoid receptor classification. DP(2) receptors are more closely related to chemoattractant receptors. Prostanoid receptors have also been found to heterodimerize with other prostanoid receptor subtypes and nonprostanoids. This may extend signal transduction pathways and create new ligand recognition sites: prostacyclin/thromboxane A(2) heterodimeric receptors for 8-epi-prostaglandin E(2), wild-type/alternative (alt4) heterodimers for the prostaglandin FP receptor for bimatoprost and the prostamides. It is anticipated that the 15 years of research progress described herein will lead to novel therapeutic entities.
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Affiliation(s)
- D F Woodward
- Dept. of Biological Sciences RD3-2B, Allergan, Inc., 2525 Dupont Dr., Irvine, CA 92612, USA.
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2
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Jugus MJ, Jaworski JP, Patra PB, Jin J, Morrow DM, Laping NJ, Edwards RM, Thorneloe KS. Dual modulation of urinary bladder activity and urine flow by prostanoid EP3 receptors in the conscious rat. Br J Pharmacol 2009; 158:372-81. [PMID: 19486006 DOI: 10.1111/j.1476-5381.2009.00275.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND AND PURPOSE Cyclooxygenase inhibitors function to reduce levels of prostaglandin E(2) (PGE(2)) and are broadly efficacious in models of bladder overactivity. We therefore investigated a regulation of urinary bladder function in conscious rats by modulation of the EP(3) receptor for PGE(2). EXPERIMENTAL APPROACH The activity of the EP(3) receptor agonist GR63799X, and EP(3) receptor antagonists, CM9 and DG041, at recombinant EP(3) receptors was evaluated in vitro. In vivo, intraduodenal dosing during conscious, continuous-filling cystometry of spontaneously hypertensive rats was utilized to determine the urodynamic effect of EP(3) receptor modulation. KEY RESULTS GR63799X dose-dependently (0.001-1 mg x kg(-1)) reduced bladder capacity, as indicated by a reduction in both the micturition interval and volume of urine per void. In contrast, CM9 (10 and 30 mg x kg(-1)) and DG041 (30 mg x kg(-1)) enhanced bladder capacity, as indicated by significantly longer micturition intervals and larger void volumes. CM9 and DG041 inhibited the responses to GR63799X supporting the in vivo activity of these pharmacological agents at the EP(3) receptor. In addition to its effect on bladder capacity, GR63799X increased endogenous urine production. Intra-arterial infusion of saline mimicked the enhancement of urine flow observed with GR63799X, and the response was inhibited by CM9. CONCLUSIONS AND IMPLICATIONS These data support the EP(3) receptor as a modulator of urinary bladder activity in the conscious rat, and in addition, indicate a role for EP(3) receptor activity in regulating urine flow.
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Affiliation(s)
- M J Jugus
- Urogenital Biology, Cardiovascular and Urogenital Center for Excellence in Drug Discovery, GlaxoSmithKline Pharmaceuticals, King of Prussia, PA 19406, USA
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3
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Fenton RA, Knepper MA. Mouse models and the urinary concentrating mechanism in the new millennium. Physiol Rev 2007; 87:1083-112. [PMID: 17928581 DOI: 10.1152/physrev.00053.2006] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Our understanding of urinary concentrating and diluting mechanisms at the end of the 20th century was based largely on data from renal micropuncture studies, isolated perfused tubule studies, tissue analysis studies and anatomical studies, combined with mathematical modeling. Despite extensive data, several key questions remained to be answered. With the advent of the 21st century, a new approach, transgenic and knockout mouse technology, is providing critical new information about urinary concentrating processes. The central goal of this review is to summarize findings in transgenic and knockout mice pertinent to our understanding of the urinary concentrating mechanism, focusing chiefly on mice in which expression of specific renal transporters or receptors has been deleted. These include the major renal water channels (aquaporins), urea transporters, ion transporters and channels (NHE3, NKCC2, NCC, ENaC, ROMK, ClC-K1), G protein-coupled receptors (type 2 vasopressin receptor, prostaglandin receptors, endothelin receptors, angiotensin II receptors), and signaling molecules. These studies shed new light on several key questions concerning the urinary concentrating mechanism including: 1) elucidation of the role of water absorption from the descending limb of Henle in countercurrent multiplication, 2) an evaluation of the feasibility of the passive model of Kokko-Rector and Stephenson, 3) explication of the role of inner medullary collecting duct urea transport in water conservation, 4) an evaluation of the role of tubuloglomerular feedback in maintenance of appropriate distal delivery rates for effective regulation of urinary water excretion, and 5) elucidation of the importance of water reabsorption in the connecting tubule versus the collecting duct for maintenance of water balance.
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Affiliation(s)
- Robert A Fenton
- Water and Salt Research Center, Institute of Anatomy, University of Aarhus, Aarhus, Denmark.
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4
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van Rodijnen WF, Korstjens IJ, Legerstee N, Ter Wee PM, Tangelder GJ. Direct vasoconstrictor effect of prostaglandin E2on renal interlobular arteries: role of the EP3 receptor. Am J Physiol Renal Physiol 2007; 292:F1094-101. [PMID: 17148783 DOI: 10.1152/ajprenal.00351.2005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Evidence indicates that prostaglandin E2(PGE2) preferentially affects preglomerular renal vessels. However, whether this is limited to small-caliber arterioles or whether larger vessels farther upstream also respond to PGE2is currently unclear. In the present study, we first investigated the effects of PGE2along the preglomerular vascular tree and subsequently focused on proximal interlobular arteries (ILAs). Proximal ILAs in hydronephrotic rat kidneys as well as isolated vessels from normal kidneys constricted in response to PGE2, both under basal conditions and after the induction of vascular tone. By contrast, smaller vessels, i.e., distal ILAs and afferent arterioles, exhibited PGE2-induced vasodilation. Endothelium removal and pretreatment of single, isolated proximal ILAs with an EP1 receptor blocker (SC51322, 1 μmol/l) or a thromboxane A2receptor blocker (SQ29548, 1 μmol/l) did not prevent vasoconstriction to PGE2. Furthermore, in the presence of SC51322, responses of these vessels to PGE2and the EP1/EP3 agonist sulprostone were superimposable, indicating that PGE2-induced vasoconstriction is mediated by EP3 receptors on smooth muscle cells. Immunohistochemical staining of proximal ILAs confirmed the presence of EP3 receptor protein on these cells and the endothelium. Adding PGE2to normal isolated kidneys induced a biphasic flow response, i.e., an initial flow increase at PGE2concentrations ≤0.1 μmol/l followed by a flow decrease at 1 μmol/l PGE2. Thus our results demonstrate that PGE2affects multiple segments of the preglomerular vascular tree in a different way. At the level of the proximal ILAs, PGE2had a direct vasoconstrictor action mediated by EP3 receptors.
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MESH Headings
- Angiotensin II/pharmacology
- Animals
- Arteries/drug effects
- Arteries/physiology
- Arteries/physiopathology
- Bridged Bicyclo Compounds, Heterocyclic
- Dinoprostone/analogs & derivatives
- Dinoprostone/pharmacology
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/physiology
- Endothelium, Vascular/physiopathology
- Fatty Acids, Unsaturated
- Hydrazines/pharmacology
- Hydronephrosis/physiopathology
- In Vitro Techniques
- Kidney Cortex/blood supply
- Male
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Muscle, Smooth, Vascular/physiopathology
- Norepinephrine/pharmacology
- Perfusion
- Rats
- Rats, Sprague-Dawley
- Receptors, Prostaglandin E/analysis
- Receptors, Prostaglandin E/antagonists & inhibitors
- Receptors, Prostaglandin E/physiology
- Receptors, Prostaglandin E, EP1 Subtype
- Receptors, Prostaglandin E, EP3 Subtype
- Receptors, Thromboxane A2, Prostaglandin H2/antagonists & inhibitors
- Renal Circulation/drug effects
- Vasoconstriction/drug effects
- Vasoconstrictor Agents/pharmacology
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Affiliation(s)
- William F van Rodijnen
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
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5
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Lee TK, Stupans I. Radioprotection: the non-steroidal anti-inflammatory drugs (NSAIDs) and prostaglandins. J Pharm Pharmacol 2002; 54:1435-45. [PMID: 12495545 DOI: 10.1211/00223570254] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Clinical and experimental studies of the acute and late effects of radiation on cells have enhanced our knowledge of radiotherapy and have led to the optimisation of radiation treatment schedules and to more precise modes of radiation delivery. However, as both normal and cancerous tissues have similar response to radiation exposure, radiation-induced injury on normal tissues may present either during, or after the completion of, the radiotherapy treatment. Studies on both NSAIDs and prostaglandins have indeed shown some evidence of radioprotection. Both have the potential to increase the survival of cells but by entirely different mechanisms. Studies of cell kinetics reveal that cells in the mitotic (M) and late G2 phases of the cell cycle are generally most sensitive to radiation compared with cells in the early S and G1/G0 phases. Furthermore, radiation leads to a mitotic delay in the cell cycle. Thus, chemical agents that either limit the proportion of cells in the M and G2 phases of the cell cycle or enhance rapid cell growth could in principle be exploited for their potential use as radioprotectors to normal tissue during irradiation. NSAIDs have been shown to exert anti-cancer effects by causing cell-cycle arrest, shifting cells towards a quiescence state (G0/G1). The same mechanism of action was observed in radioprotection of normal tissues. An increase in arachidonic acid concentrations after exposure to NSAIDs also leads to the production of an apoptosis-inducer ceramide. NSAIDs also elevate the level of superoxide dismutase in cells. Activation of heat shock proteins by NSAIDs increases cell survival by alteration of cytokine expression. A role for NSAIDs with respect to inhibition of cellular proliferation possibly by an anti-angiogenesis mechanism has also been suggested. Several in-vivo studies have provided evidence suggesting that NSAIDs may protect normal tissues from radiation injury. Prostaglandins do not regulate the cell cycle, but they do have a variety of effects on cell growth and differentiation. PGE(2) mediates angiogenesis, increasing the supply of oxygen and nutrients, essential for cellular survival and growth. Accordingly, PGE(2) at sufficiently high plasma concentrations enhances cellular survival by inhibiting pro-inflammatory cytokines such as TNF-alpha and IL-1beta. Thus, PGE(2) acts as a modulator, rather than a mediator, of inflammation. Prospective studies have suggested the potential use of misoprostol, a PGE(1) analogue, before irradiation, in prevention of radiation-induced side effects. The current understanding of the pharmacology of NSAIDs and prostaglandins shows great potential to minimise the adverse effects of radiotherapy on normal tissue.
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Affiliation(s)
- Tat Khuen Lee
- Center for Pharmaceutical Research, School of Pharmaceutical Molecular and Biomedical Sciences, University of South Australia, SA, 5000, Australia
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6
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Takeuchi K. Molecular biology of blood pressure regulatory genes. TOHOKU J EXP MED 2002; 197:1-8. [PMID: 12180788 DOI: 10.1620/tjem.197.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Blood pressure is determined by vascular resistance and circulating volume. Activation of vascular angiotensin II or thromboxane receptor is mostly involved in the former, and function of renal prostagalandin EP3 receptor or thiazide-sensitive sodium-chloride co-transporter is also in the latter. We have cloned rat genes for these blood pressure regulatory factors, and studied their gene expression. Here we review the molecular biology of those genes, based on our observations.
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Affiliation(s)
- Kazuhisa Takeuchi
- Division of Nephrology, Endocrinology, and Vascular Biology, Tohoku University Graduate School of Medicine, Sendai, Japan.
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7
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Abstract
Cyclooxygenases metabolize arachidonate to five primary prostanoids: PGE(2), PGF(2 alpha), PGI(2), TxA(2), and PGD(2). These autacrine lipid mediators interact with specific members of a family of distinct G-protein-coupled prostanoid receptors, designated EP, FP, IP, TP, and DP, respectively. Each of these receptors has been cloned, expressed, and characterized. This family of eight prostanoid receptor complementary DNAs encodes seven transmembrane proteins which are typical of G-protein-coupled receptors and these receptors are distinguished by their ligand-binding profiles and the signal transduction pathways activated on ligand binding. Ligand-binding selectivity of these receptors is determined by both the transmembrane sequences and amino acid residues in the putative extracellular-loop regions. The selectivity of interaction between the receptors and G proteins appears to be mediated at least in part by the C-terminal tail region. Each of the EP(1), EP(3), FP, and TP receptors has alternative splice variants described that alter the coding sequence in the C-terminal intracellular tail region. The C-terminal variants modulate signal transduction, phosphorylation, and desensitization of these receptors, as well as altering agonist-independent constitutive activity.
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Affiliation(s)
- R M Breyer
- Division of Nephrology, Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USA.
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8
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Oldfield S, Grubb BD, Donaldson LF. Identification of a prostaglandin E2 receptor splice variant and its expression in rat tissues. Prostaglandins Other Lipid Mediat 2001; 63:165-73. [PMID: 11305694 DOI: 10.1016/s0090-6980(00)00104-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The intercellular signalling actions of the lipid mediators, the eicosanoids, are transduced by a family of seven transmembrane domain receptors. Members of this receptor family with high affinity for PGE2 are termed EP receptors. There are four known EP receptor genes that are transcribed to generate EP1, EP2, EP3 and EP4 receptors. Two of these receptor transcripts, EP1 and EP3, are further modified by RNA splicing to give multiple receptor isoforms. The EP3 receptor is known to have multiple splice variants in human (9 variants), cow (4 variants), mouse (3 variants) and rat (3 variants). In the rat the three EP3 splice variants differ in the sequence of the intracellular C-terminus. We have identified a fourth splice variant of the rat prostaglandin EP3 receptor that has a greatly truncated intracellular C-terminus when compared to the other EP3 receptor isoforms. Using nested RT-PCR we have shown that this novel splice variant is strongly expressed in rat brain and is also found in spinal cord, kidney and spleen.
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Affiliation(s)
- S Oldfield
- Department of Physiology, University of Bristol, UK
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9
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Averbeck B, Reeh PW. Interactions of inflammatory mediators stimulating release of calcitonin gene-related peptide, substance P and prostaglandin E(2) from isolated rat skin. Neuropharmacology 2001; 40:416-23. [PMID: 11166334 DOI: 10.1016/s0028-3908(00)00171-4] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Inflammatory mediators acting directly on nociceptive primary afferents induce neuropeptide release. In this study we investigated interactions between bradykinin, serotonin, histamine, prostaglandin and acid pH in stimulating the release of substance P (SP), calcitonin gene-related peptide (CGRP) and prostaglandin E(2) (PGE(2)) from isolated flaps of rat back skin using enzyme immunoassays. Stimulation with bradykinin (10(-5) M) augmented the release of SP, CGRP and PGE(2) significantly. Serotonin, histamine and PGE(2) individually tested (10(-5) M) had no effect on neuropeptide release but they facilitated the bradykinin-evoked neuropeptide release. When bradykinin was combined with both serotonin and histamine, neither additional PGE(2) nor acid pH showed any further effect, suggesting that the facilitation had reached a maximum. Exposure of the skin to acid pH (6.1 or 5.2) significantly increased CGRP release. SP release was only slightly enhanced and PGE(2) release, in contrast, was suppressed by low pH stimulation, probably due to pH-dependent inhibition of phospholipase A(2). Treatment of the rats with flurbiprofen (25 mg/kg i.p.) one hour before dissection reduced PGE(2) to detection level and inhibited the CGRP secretion evoked by the combination of bradykinin, serotonin and histamine (all 10(-6) M). As this suppression could not be overcome by substitution of PGE(2) (10(-6) M), it is likely that exogenously applied PGE(2) differs in effect from endogenous, intracellularly synthesized prostaglandins that are accompanied by active intermediates and byproducts.
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Affiliation(s)
- B Averbeck
- Institute of Physiology and Experimental Pathophysiology, University of Erlangen-Nürnberg, 91054, Erlangen, Germany.
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10
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Donaldson LF, Humphrey PS, Oldfield S, Giblett S, Grubb BD. Expression and regulation of prostaglandin E receptor subtype mRNAs in rat sensory ganglia and spinal cord in response to peripheral inflammation. Prostaglandins Other Lipid Mediat 2001; 63:109-22. [PMID: 11204738 DOI: 10.1016/s0090-6980(00)00101-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Prostaglandins are known to act via seven transmembrane domain receptors to exert actions on both peripheral and central neurons resulting in changes in neuronal excitability. Prostaglandin E2, the prostaglandin most often associated with inflammation, itself acts on a family of closely related receptors, the EP receptors. Using semi-quantitative reverse transcription polymerase chain reaction (RT-PCR), we have shown that rat primary afferent neurons express the mRNA for all EP receptor subtypes, and that some, but not all EP receptor subtype mRNAs are down-regulated in sensory neurons in response to an acute peripheral inflammation. We also show for the first time that all EP receptor subtype mRNAs are expressed in rat lumbar spinal cord. Spinal cord EP receptor subtype mRNAs are also regulated in acute inflammation in a pattern distinct from the changes seen in sensory ganglia in response to the same inflammatory stimulus.
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Affiliation(s)
- L F Donaldson
- Department of Physiology, University of Bristol, UK.
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11
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Hohlfeld T, Meyer-Kirchrath J, Vogel YC, Schrör K. Reduction of infarct size by selective stimulation of prostaglandin EP(3)receptors in the reperfused ischemic pig heart. J Mol Cell Cardiol 2000; 32:285-96. [PMID: 10722804 DOI: 10.1006/jmcc.1999.1072] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have previously identified prostaglandin EP(3)receptors in left ventricular myocardium. To assess the potential contribution of this receptor subtype to the anti-ischemic properties of E-type prostaglandins (i.e. PGE(1)), two groups of anesthetized open-chest minipigs were subjected to LAD occlusion (1 h) and reperfusion (3 h). In one group, the selective EP(3)receptor agonist M&B 28.767 (2 pmol/kgxmin) was infused into the LAD from 20 min before ischemia until the end of reperfusion. The other group received vehicle. M&B 28.767 did not alter the systemic hemodynamics, but significantly reduced infarct size (tetrazolium staining) and creatine kinase release by 53% and 48%, respectively. Ischemia-induced ventricular arrhythmias were mostly reduced. Further experiments analysed the effects of EP(3)receptor stimulation on normoxic myocardium. PGE(1), an unselective agonist to all EP receptor subtypes, as well as M&B 28.767 (2 pmol/kgxmin of each into the LAD) reduced the action potential duration (epicardial monophasic electrodes) and almost prevented the inotropic response to intravenous isoprenaline. This dual response is consistent with the EP(3)receptor coupling to an inhibitory G protein. This was confirmed in separate experiments with stable Chinese hamster ovary cell transfectants expressing the porcine EP(3)receptor, where M&B 28.767 inhibited the forskolin-induced increase in cAMP in a concentration-dependent manner. It is concluded that the protection of reperfused ischemic myocardium by E-type prostaglandins is mediated by EP(3)receptors, which seems to involve a combined activation of repolarizing membrane currents and an inhibition of deleterious effects caused by ischemia-induced catecholamine release.
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MESH Headings
- Action Potentials/drug effects
- Adenylyl Cyclases/metabolism
- Adrenergic beta-Agonists/administration & dosage
- Adrenergic beta-Agonists/pharmacology
- Alprostadil/administration & dosage
- Alprostadil/analogs & derivatives
- Alprostadil/pharmacology
- Animals
- Arrhythmias, Cardiac/etiology
- Arrhythmias, Cardiac/prevention & control
- CHO Cells
- Cardiotonic Agents/administration & dosage
- Cardiotonic Agents/pharmacology
- Colforsin/pharmacology
- Coronary Vessels
- Creatine Kinase/analysis
- Cricetinae
- Cricetulus
- Cyclic AMP/pharmacology
- Female
- GTP-Binding Protein alpha Subunits, Gi-Go/physiology
- Heart Ventricles/drug effects
- Hemodynamics/drug effects
- Infusions, Intra-Arterial
- Isoenzymes
- Isoproterenol/administration & dosage
- Isoproterenol/pharmacology
- Male
- Muscle Proteins/metabolism
- Myocardial Contraction/drug effects
- Myocardial Infarction/complications
- Myocardial Infarction/pathology
- Myocardial Reperfusion Injury/pathology
- Myocardial Reperfusion Injury/prevention & control
- Receptors, Prostaglandin E/agonists
- Receptors, Prostaglandin E/genetics
- Receptors, Prostaglandin E/physiology
- Receptors, Prostaglandin E, EP3 Subtype
- Second Messenger Systems/drug effects
- Staining and Labeling
- Swine
- Swine, Miniature
- Transfection
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Affiliation(s)
- T Hohlfeld
- Institut für Pharmakologie und klinische Pharmakologie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, D-40225, Germany
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12
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Fleming EF, Athirakul K, Oliverio MI, Key M, Goulet J, Koller BH, Coffman TM. Urinary concentrating function in mice lacking EP3 receptors for prostaglandin E2. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:F955-61. [PMID: 9843913 DOI: 10.1152/ajprenal.1998.275.6.f955] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The actions of prostaglandin (PG) E2 are mediated by four distinct classes of PGE2 E-prostanoid (EP) receptors (EP1 through EP4). However, the in vivo functions of the individual EP receptor subtypes have not been delineated. To study the functions of one of these subtypes, the EP3 receptor, we generated EP3-deficient (-/-) mice by gene targeting. EP3 -/- animals survived in expected numbers, reproduced, and had no obvious abnormalities in their major organ systems. Because the EP3 receptor is expressed at high levels in the renal medulla and cortical collecting duct, and because previous studies have suggested that the EP3 receptor might antagonize the effects of vasopressin in the distal nephron, we examined urinary concentrating functions in EP3 -/- mice. Basal urine osmolality (UOsm) was similar in groups of EP3 -/- and wild-type (EP3 +/+) mice. However, after inhibition of endogenous PGE2 production by indomethacin, UOsm increased significantly in EP3 +/+ but not in EP3 -/- mice. Despite this insensitivity to acute inhibition of prostanoid production, EP3 -/- mice concentrated and diluted their urine normally in response to a series of physiological stimuli. This suggests that PGE2 acts through the EP3 receptor to modulate urinary concentrating mechanisms in the kidney, but these effects are not essential for normal regulation of urinary osmolality.
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Affiliation(s)
- E F Fleming
- Program in Genetics, Department of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599-3360, USA
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13
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Billotte C, Vesin MF. Comparative study of prostaglandin E2 production in chick spinal cord and meninges. Prostaglandins Leukot Essent Fatty Acids 1997; 56:169-75. [PMID: 9089794 DOI: 10.1016/s0952-3278(97)90530-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In chick spinal cord the presence of low affinity (KD = 2.2 microM) receptors for prostaglandin E2 (PGE2) raises the question whether spinal cord possesses a PGE2 biosynthetic capacity able to activate these receptors. The production of PGE2 in spinal cord and meninges was investigated by enzyme immunoassay. Spinal cord exhibited a 30- to 100-fold lower PGE2 biosynthetic capacity compared to meninges, but can generate PGE2 resulting in micromolar concentrations, sufficient to activate the low affinity PGE2 receptors. It is suggested that in physiological conditions, PGE2 synthesized within the spinal cord might locally activate the low affinity PGE2 receptors, whereas in pathological situations, after disruption of the blood-spinal cord barrier, PGE2 produced by the meninges might be accessible to spinal cord PGE2 receptors, and thus largely contribute to their saturation.
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Affiliation(s)
- C Billotte
- Institut d'Histologie et d'Embryologie, Faculté de Médecine, Lausanne, Switzerland
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14
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Abstract
A wide array of prostanoids, which includes prostaglandins D(2), E(2), F(2alpha), I(2), and thromboxane A(2), has been known to exert regulatory effects in many endocrine systems for over 3 decades. More recently, however, molecular biological techniques have uncovered new findings that have brought about radical changes in our thinking about prostaglandin pharmacology and physiology. Two separate forms of cyclooxygenase (COX), a constitutive and an inducible form, have been identified. These two forms arise from separate genes whose expression is regulated differently. Moreover, genes for different receptor types and sub-types of prostanoid receptors have also been cloned. The various prostanoid receptor types and subtypes are coupled to transduction systems that cause alterations in intracellular calcium and cAMP concentrations. As importantly, new sites of inhibitory action for corticosteroids and nonsteroidal antiinflammatory drugs in the COX-2 synthetic pathway have been uncovered that decrease COX-2 mRNA levels and enzyme mass. Most of the nonsteroidal antiinflammatory drugs are more effective in inhibiting activity of COX-1 compared with COX-2. This carries important clinical relevance, because COX-1 is proposed to play a role in normal physiologic processes rather than in mediating inflammation, which may explain the undesirable side effects of some of these drugs. Possible implications of these new developments on regulation of bone resorption as a representative endocrine system are considered.
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Affiliation(s)
- R P Robertson
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, University of Minnesota Medical School, Minneapolis, MN 55455, USA
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15
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Negishi M, Sugimoto Y, Ichikawa A. Molecular mechanisms of diverse actions of prostanoid receptors. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1259:109-19. [PMID: 7492609 DOI: 10.1016/0005-2760(95)00146-4] [Citation(s) in RCA: 316] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
This review summarizes recent advances in the molecular characterization of prostanoid receptors. Prostanoids exert versatile actions in diverse tissues and cells through specific cell surface receptors. Molecular biological studies revealed the primary structure of eight types and subtypes of prostanoid receptor from various species. These include the thromboxane A2 receptor, prostacyclin receptor, prostaglandin (PG) F receptor, PGD receptor and four subtypes of PGE receptors. They are coupled to different signal transduction systems. In addition, multiple isoforms of PGE receptor EP3 subtype have been identified in various species. They are produced through alternative RNA splicing from a single gene and differ only in their carboxy-terminal tails. These isoforms differ in the efficiency of G protein activation, in the specificity of coupling to G proteins or in sensitivity to desensitization. This molecular characterization is useful for understanding the diverse physiological roles of prostanoids.
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Affiliation(s)
- M Negishi
- Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Kyoto University, Japan
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