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Therapeutic effects of JLX001 on cerebral ischemia through inhibiting platelet activation and thrombus formation in rats. Biomed Pharmacother 2018; 106:805-812. [DOI: 10.1016/j.biopha.2018.07.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 07/03/2018] [Accepted: 07/03/2018] [Indexed: 02/02/2023] Open
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Wright DH, Abran D, Bhattacharya M, Hou X, Bernier SG, Bouayad A, Fouron JC, Vazquez-Tello A, Beauchamp MH, Clyman RI, Peri K, Varma DR, Chemtob S. Prostanoid receptors: ontogeny and implications in vascular physiology. Am J Physiol Regul Integr Comp Physiol 2001; 281:R1343-60. [PMID: 11641101 DOI: 10.1152/ajpregu.2001.281.5.r1343] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Prostanoids exert significant effects on circulatory beds. They play a role in the response of the vasculature to adjustments in perfusion pressure and oxygen and carbon dioxide tension, and they mediate the actions of numerous factors. The role of prostanoids in governing circulation of the perinate is suggested to surpass that in the adult. Prostanoids are abundantly generated in the perinate. They have been implicated in autoregulation of blood flow as studied in brain and eyes. Prostaglandins are also dominant regulators of ductus arteriosus tone. The effects of these autacoids are mediated through specific G protein-coupled receptors. In addition to the pharmacological characterization of the prostanoid receptors, important advances in understanding the biology of these receptors have been made in the last decade. Their cloning and the development of animals with disrupted genes of these receptors have been very informative. The involvement of prostanoid receptors in the developing subject, especially on brain and ocular vasculature and on ductus arteriosus, has also begun to be investigated; the expression of these receptors changes with development. Some but not all of the ontogenic changes in these receptors are attributed to homologous regulation. Interestingly, in the process of elucidating their effects, functional perinuclear prostaglandin E2 receptors have been uncovered. This article reviews prostanoid receptors and addresses implications on the developing subject with attention to vascular physiology.
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Affiliation(s)
- D H Wright
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec H3G-1Y6, Canada
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Oliw EH, Stark K, Bylund J. Oxidation of prostaglandin H(2) and prostaglandin H(2) analogues by human cytochromes P450: analysis of omega-side chain hydroxy metabolites and four steroisomers of 5-hydroxyprostaglandin I(1) by mass spectrometry. Biochem Pharmacol 2001; 62:407-15. [PMID: 11448449 DOI: 10.1016/s0006-2952(01)00683-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The objective was to examine the NADPH-dependent oxygenation of prostaglandin H(2) (PGH(2)) and three PGH(2) analogues, 9,11-diazo-15-deoxy-PGH(2) (U51605), 9,11-epoxymethano-PGH(2) (U44069), and 11,9-epoxymethano-PGH(2) (U46619), by cytochromes P450, and to characterize the metabolites by mass spectrometry. CYP2C19, CYP4A11, CYP4F8, and liver and renal cortical microsomes oxidized the omega-side chain of U44069, U46619, and U51605, whereas only CYP4F8 oxidized the omega-side chain of PGH(2). PGH(2) was transformed to four stereoisomers of 5-hydroxy-PGI(1) by recombinant cytochromes P450. CYP4F8 formed the 5-hydroxy-PGI(1) isomers in small amounts compared to the 19-hydroxy metabolites of PGH(2). Isomers of 5-hydroxy-PGI(1) and 6-keto-PGF(1 alpha) were detectable when PGH(2) decomposed in the presence of hemin, hemoglobin, or heat-inactivated microsomes. 5-Hydroxy-PGI(1) is likely formed from PGH(2) in a pseudo-enzymatic reaction involving homolytic scission of the endoperoxide and formation of an ether between C-9 and C-6 and a carbon-centered radical at C-5, which reacts with molecular oxygen. CYP4F8 catalyzes 19-hydroxylation of PGH(2), but the absolute configuration of the 19-hydroxy group is unknown, whereas human seminal fluid contains (19R)-hydroxy-PGE(2). CYP4F8 was found to metabolize U51605 to 90% of the (19R)-hydroxy metabolite, providing further evidence in favor of a role of CYP4F8 in biosynthesis of (19R)-hydroxy PGE in human seminal vesicles. We conclude that omega-side chain hydroxylation of PGH(2) analogues may be catalyzed by many different cytochromes P450, but only CYP4F8 oxidizes the omega-side chain of PGH(2) efficiently.
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Affiliation(s)
- E H Oliw
- Division of Biochemical Pharmacology, Department of Pharmaceutical Biosciences, Uppsala Biomedical Centre, Uppsala University, SE-751 24 Uppsala, Sweden.
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Chang TS, Lee KS, Lee GY, Jeon SD, So DS, Khil LY, Chung MK, Moon CK. NQ-Y15 inhibits the calcium mobilization by elevation of cyclic AMP in rat platelets. Biol Pharm Bull 2001; 24:480-3. [PMID: 11379764 DOI: 10.1248/bpb.24.480] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
2-1(4-Cyanophenyl)aminol-3-chloro-1,4-naphthalenedione (NQ-Y15) is a dual action drug which acts as a thromboxane A2 (TXA2) synthase inhibitor and TXA2/PGH2 receptor antagonist. In the present study, we examined the effects of NQ-Y15 on Ca2+ mobilization, which is the common event in various types of platelet activation, in arachidonic acid (AA)-stimulated rat platelets. The elevation of cytosolic Ca2+ concentration ([Ca2+]i) induced by AA was inhibited by NQ-Y15 in a concentration-dependent manner. This inhibition-effect of NQ-Y15 was found to be based on the suppression of the rise in [Ca2+]i by the inhibition of both Ca2+ release from internal stores and Ca2+ influx from the extracellular space. Our successive trial was focused on the role of cyclic AMP (cAMP) in the action of NQ-Y15, because cAMP was reported to be increased by dual action drugs such as picotamide and to inhibit the increase in [Ca2+]i. NQ-Y15 was confirmed to increase cAMP in AA-stimulated rat platelets. These results suggested that NQ-Y15 might inhibit the rise in [Ca2+]i in AA-treated rat platelets by increasing cAMP, which is involved in the inhibition of platelet activation.
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Affiliation(s)
- T S Chang
- College of Pharmacy, Seoul National University, Korea
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5
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Paul BZ, Jin J, Kunapuli SP. Molecular mechanism of thromboxane A(2)-induced platelet aggregation. Essential role for p2t(ac) and alpha(2a) receptors. J Biol Chem 1999; 274:29108-14. [PMID: 10506165 DOI: 10.1074/jbc.274.41.29108] [Citation(s) in RCA: 204] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thromboxane A(2) is a positive feedback lipid mediator produced following platelet activation. The G(q)-coupled thromboxane A(2) receptor subtype, TPalpha, and G(i)-coupled TPbeta subtype have been shown in human platelets. ADP-induced platelet aggregation requires concomitant signaling from two P2 receptor subtypes, P2Y1 and P2T(AC), coupled to G(q) and G(i), respectively. We investigated whether the stable thromboxane A(2) mimetic, (15S)-hydroxy-9, 11-epoxymethanoprosta-5Z,13E-dienoic acid (U46619), also causes platelet aggregation by concomitant signaling through G(q) and G(i), through co-activation of TPalpha and TPbeta receptor subtypes. Here we report that secretion blockade with Ro 31-8220, a protein kinase C inhibitor, completely inhibited U46619-induced, but not ADP- or thrombin-induced, platelet aggregation. Ro 31-8220 had no effect on U46619-induced intracellular calcium mobilization or platelet shape change. Furthermore, U46619-induced intracellular calcium mobilization and shape change were unaffected by A3P5P, a P2Y1 receptor-selective antagonist, and/or cyproheptadine, a 5-hydroxytryptamine subtype 2A receptor antagonist. Either Ro 31-8220 or AR-C66096, a P2T(AC) receptor selective antagonist, abolished U46619-induced inhibition of adenylyl cyclase. In addition, AR-C66096 drastically inhibited U46619-mediated platelet aggregation, which was further inhibited by yohimbine, an alpha(2A)-adrenergic receptor antagonist. Furthermore, inhibition of U46619-induced platelet aggregation by Ro 31-8220 was relieved by activation of the G(i) pathway by selective activation of either the P2T(AC) receptor or the alpha(2A)-adrenergic receptor. We conclude that whereas thromboxane A(2) causes intracellular calcium mobilization and shape change independently, thromboxane A(2)-induced inhibition of adenylyl cyclase and platelet aggregation depends exclusively upon secretion of other agonists that stimulate G(i)-coupled receptors.
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Affiliation(s)
- B Z Paul
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
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6
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Platelet Arachidonic Acid Metabolism and Eicosanoid Receptors. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s1569-2558(08)60414-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Teixeira CF, Farmer P, Laporte J, Jancar S, Sirois P. Increased permeability of bovine aortic endothelial cell monolayers in response to a thromboxane A2-mimetic. AGENTS AND ACTIONS. SUPPLEMENTS 1995; 45:47-52. [PMID: 7717200 DOI: 10.1007/978-3-0348-7346-8_7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The present study was designed to investigate the ability of thromboxane to modulate the clearance rate of 125I-albumin through bovine aortic endothelial cell (BAEC) monolayer grown on polycarbonate micropore membrane. Stimulation of BAEC with the TXA2 mimetic U44069 (10(-8), 10(-7) and 10(-6) M) elicited a dose-dependent increase of labeled albumin passage across BAEC monolayers. This effect was markedly reduced by the TXA2 antagonist L655240 (10(-7) and 10(-6) M). Our results suggest that TXA2 may modulate the permeability of endothelial cells directly through activation of specific receptors.
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Affiliation(s)
- C F Teixeira
- Lab. Pharmacology, Instituto Butantan, Universidade de São Paulo, Brasil
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Yu SM, Wu TS, Teng CM. Pharmacological characterization of cinnamophilin, a novel dual inhibitor of thromboxane synthase and thromboxane A2 receptor. Br J Pharmacol 1994; 111:906-12. [PMID: 8019768 PMCID: PMC1910103 DOI: 10.1111/j.1476-5381.1994.tb14824.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
1. The pharmacological effects of cinnamophilin, a new lignan, isolated from Cinnamomum philippinense, was determined in vitro in human platelet, rat isolated aorta and guinea-pig isolated trachea and in vivo in mice and guinea-pigs. 2. Cinnamophilin inhibited dose-dependently human platelet-rich plasma (PRP) aggregation induced by arachidonic acid (AA), collagen and U-46619 with IC50 of 5.0 +/- 0.4, 5.6 +/- 0.6 and 3.0 +/- 0.4 microM, respectively. The second wave of ADP- or adrenaline-induced platelet aggregation was inhibited by cinnamophilin, while the first wave was only slightly inhibited by cinnamophilin above 30 microM. 3. Cinnamophilin was found to be a thromboxane A2 (TXA2) receptor blocking agent in human platelet, rat aorta and guinea-pig trachea as revealed by its competitive antagonism of U-46619-induced aggregation of human-PRP, contraction of rat aortic rings and guinea-pig tracheal rings with pA2 values of 7.3 +/- 0.2, 6.3 +/- 0.1 and 5.2 +/- 0.2, respectively. 4. [3H]-inositol monophosphate formation and the rise of intracellular Ca2+ caused by U-46619 in human platelet was suppressed by cinnamophilin (10 microM). 5. Cinnamophilin induced a dose-dependent inhibition of thromboxane B2 (TXB2) formation, while the prostaglandin E2 (PGE2) formation was increased. Cinnamophilin did not affect unstimulated platelet adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels. When the platelets were challenged with AA, a dose-dependent rise in cyclic AMP was observed. Dazoxiben (a pure TX synthase inhibitor) and SQ 29548 (a pure TXA2 receptor antagonist) did not affect cyclic AMP levels in AA-treated platelets. 6. A high concentration of cinnamophilin (100 MicroM), failed to attenuate the contractile response of rat aorta to endothelin-l, angiotensin II, 5-hydroxytryptamine or noradrenaline. Contraction of tracheal rings induced by histamine, carbachol or KCl was also not inhibited by cinnamophilin (100 MicroM).7. Thirty min after intraperitoneal (i.p.) administration of cinnamophilin (100 microg kg-1), tail bleeding time of mice was prolonged more markedly than with indomethacin, dazoxiben or SQ 29548.8. Intravenous administration of AA (50 microg kg-1) to guinea-pig induced bronchoconstriction. Cinnamophilin(0.1 mg kg-1, i.v.) was administered 1 min before AA, the bronchoconstriction response to AA was abolished.9. It is concluded that cinnamophilin is a novel dual TX synthase inhibitor and TXA2 receptor antagonist and that it may be a useful tool for the investigation and treatment of diseases involving TXA2 disorders.
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Affiliation(s)
- S M Yu
- Department of Pharmacology, Chang Gung Medical College, Kwei-San, Tao-Yuan, Taiwan
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9
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Knezevic I, Borg C, Le Breton GC. Identification of Gq as one of the G-proteins which copurify with human platelet thromboxane A2/prostaglandin H2 receptors. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74486-x] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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10
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Faili A, Randon J, Vargaftig BB, Hatmi M. Reduction by arachidonic acid of prostaglandin I2-induced cyclic AMP formation. Involvement of prostaglandins E2 and F2 alpha. Biochem Pharmacol 1993; 45:1815-20. [PMID: 8388209 DOI: 10.1016/0006-2952(93)90438-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Arachidonic acid reverses the increase in cyclic AMP levels of washed human platelets exposed to prostaglandin (PG)I2, under conditions where the PGH2 analogue U46619 is ineffective. This effect of arachidonic acid was inhibited by aspirin, a cyclooxygenase inhibitor, but not by the thromboxane (Tx) synthase inhibitor Ridogrel, which induces, by inhibiting the conversion of PGH2 into TxA2, an overproduction of PGE2, PGD2 and PGF2 alpha. Addition of PGE2 or PGF2 alpha, which share a receptor with PGI2, to washed human platelets also induced a decrease in cyclic AMP levels, but PGD2, which interacts with a different receptor, had no effect. Thus neither PGD2, PGG2, PGH2, TxA2 nor TxB2 formed from arachidonic acid via the cyclooxygenase pathway is involved in the decrease in cyclic AMP levels. These findings were confirmed using forskolin, a diterpene from the labdane family, which enhanced the formation of cyclic AMP synergistically with the PGs. Also, arachidonic acid, unlike U46619, is able to reverse the inhibition of platelet aggregation by PGI2 after a lag phase of about 4 min. Our data indicate that arachidonic acid decreased cyclic AMP levels through its cyclooxygenase metabolites PGE2 and PGF2 alpha probably interacting competitively with the receptor of PGI2. In addition, intracellular cyclic AMP levels and the degree of aggregation of platelets by arachidonic acid seem to be inversely correlated.
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Affiliation(s)
- A Faili
- Unité de Pharmacologie Cellulaire, Unité Associée Institut Pasteur/INSERM U285, Paris, France
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11
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Horton AA, Wood JM. Prevention of Ca(2+)-induced or thromboxane B2-induced hepatocyte plasma membrane bleb formation by thromboxane receptor antagonists. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1133:31-7. [PMID: 1836358 DOI: 10.1016/0167-4889(91)90238-s] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Isolated hepatocytes incubated in the presence of either Ca2+ ionophore A23187 or thromboxane B2 develop many plasma membrane blebs which are a characteristic feature of toxic or ischaemic cell injury. When hepatocytes are incubated in the presence of both Ca2+ ionophore A23187 and any one of three thromboxane receptor antagonists (SK and F 88046, B.M. 13505, B.M. 13177), bleb formation is strongly inhibited. Hepatocytes incubated in the presence of both thromboxane B2 and any one of the three thromboxane receptor antagonists are also well protected from the formation of blebs. Treatment of isolated hepatocytes with Ca2+ ionophore A23187 is known to stimulate the production of thromboxanes. The data presented are consistent with thromboxane B2 acting as an intermediary in a proposed mechanism of cell injury and death in which elevated cytosolic free Ca2+ levels activate phospholipase A2 and the arachidonate cascade.
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Affiliation(s)
- A A Horton
- School of Biochemistry, University of Birmingham, U.K
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12
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Gresele P, Deckmyn H, Nenci GG, Vermylen J. Thromboxane synthase inhibitors, thromboxane receptor antagonists and dual blockers in thrombotic disorders. Trends Pharmacol Sci 1991; 12:158-63. [PMID: 1829559 DOI: 10.1016/0165-6147(91)90533-x] [Citation(s) in RCA: 97] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Thromboxane A2 (TXA2) plays a pivotal role in platelet activation and is involved in the development of thrombosis. Thromboxane synthase inhibitors suppress TXA2 formation and increase the synthesis of the antiaggregatory prostaglandins PGI2 and PGD2; however, accumulated PGH2 may interact with the platelet and vessel wall TXA2 receptor, thus reducing the antiplatelet effects of this class of drug. TXA2 receptor antagonists block the activity of both TXA2 and PGH2 on platelets and the vessel wall. Very recently, drugs possessing both thromboxane synthase-inhibitory and thromboxane receptor-antagonist properties have been developed. Paolo Gresele and colleagues explain here why these drugs can be more efficacious than traditional antiplatelet agents and review the available experimental studies involving these drugs.
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Affiliation(s)
- P Gresele
- Istituto di Semeiotica Medica, University of Perugia, Italy
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13
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Gray SJ, Heptinstall S. Interactions between prostaglandin E2 and inhibitors of platelet aggregation which act through cyclic AMP. Eur J Pharmacol 1991; 194:63-70. [PMID: 1647965 DOI: 10.1016/0014-2999(91)90124-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Prostaglandin (PG) E2 potentiates platelet aggregation at low concentrations (10(-8)-10(-6) M). It also inhibits aggregation at a higher concentration (10(-5) M), probably by acting through cyclic adenosine 3',5'-monophosphate (cyclic AMP). The mechanism of this biphasic effect of PGE2 and its implications for thrombosis are not clearly understood. Using a sensitive cyclic AMP assay, in conjunction with platelet aggregation studies, we have examined the interactions between PGE2 and other inhibitors of platelet aggregation which act through cyclic AMP. Low concentrations of PGE2 reversed the inhibition of platelet aggregation and increase in cyclic AMP levels induced by PGI2, PGD2 and adenosine (which stimulate adenylate cyclase (AC) through separate and specific platelet receptors). In contrast, low concentrations of PGE2 added to the inhibition of platelet aggregation and increase in cyclic AMP levels induced by forskolin (which stimulates AC directly) and AH-P 719 and DN-9693 (which inhibit cyclic AMP phosphodiesterase (PDE]. These results suggest that the biphasic effect of PGE2 may be mediated by interaction with two separate platelet receptors. Low concentrations appear to potentiate aggregation by acting at a receptor which is directly coupled to an inhibitory guanine nucleotide-binding protein (Gi), possibly the putative PG endoperoxide receptor. High concentrations of PGE2 appear to inhibit aggregation by acting at an additional receptor, probably the PGI2 receptor. The ease with which PGE2 reverses the effects of PGI2, PGD2 and adenosine, but adds to the effects of AH-P 719 and DN-9693, suggests that PDE inhibitors might offer greater potential than these AC stimulators as an anti-thrombotic strategy.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S J Gray
- Department of Medicine, University Hospital, Nottingham, U.K
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14
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Hirata M, Hayashi Y, Ushikubi F, Yokota Y, Kageyama R, Nakanishi S, Narumiya S. Cloning and expression of cDNA for a human thromboxane A2 receptor. Nature 1991; 349:617-20. [PMID: 1825698 DOI: 10.1038/349617a0] [Citation(s) in RCA: 575] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Thromboxane A2 is a very unstable arachidonate metabolite, yet a potent stimulator of platelet aggregation and a constrictor of vascular and respiratory smooth muscles. It has been implicated as a mediator in diseases such as myocardial infarction, stroke and bronchial asthma. Using a stable analogue of this compound we recently purified the human platelet thromboxane A2 receptor to apparent homogeneity. Using an oligonucleotide probe corresponding to its partial amino-acid sequence, we have obtained a complementary DNA clone encoding this receptor from human placenta and a partial clone from cultured human megakaryocytic leukaemia cells. The placenta cDNA encodes a protein of 343 amino acids with seven putative transmembrane domains. The protein expressed in COS-7 cells binds drugs with affinities identical to those of the platelet receptor, and that in Xenopus oocytes opens Ca2(+)-activated Cl- channel on agonist stimulation. Northern blot analysis and nucleotide sequences of the two clones suggest that an identical species of the thromboxane A2 receptor is present in platelets and vascular tissues. This first report on the molecular structure of an eicosanoid receptor will promote the molecular pharmacology and pathophysiology of these bioactive compounds.
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Affiliation(s)
- M Hirata
- Department of Pharmacology, Kyoto University Faculty of Medicine, Japan
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15
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The response to thromboxane A2 analogues in human platelets. Discrimination of two binding sites linked to distinct effector systems. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39224-5] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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16
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de Chaffoy de Courcelles D, De Clerck F. Effect of thromboxane A2 synthetase inhibition, singly and combined with thromboxane A2/prostaglandin endoperoxide receptor antagonism, on inositol phospholipid turnover and on 5-HT release by washed human platelets. Eur J Pharmacol 1990; 188:161-9. [PMID: 2318257 DOI: 10.1016/0922-4106(90)90051-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Differential effects on human platelet function of thromboxane A2 (TXA2) synthetase inhibition singly and of TXA2 synthetase inhibition combined with TXA2/prostaglandin endoperoxide receptor antagonism were revealed, using ridogrel as a probe. Ridogrel combines selective TXA2 synthetase inhibition with TXA2/prostaglandin receptor antagonism in one molecule: in washed human platelets, the compound reduces the production of TXB2 (IC50 = 1.3 X 10(-8) M) and increases that of PGF2 alpha, PGE2, PGD2 from [14C]arachidonic acid. Additionally, at higher concentrations (Ki = 0.52 X 10(-6) M), it selectively antagonizes the breakdown of inositol phospholipids, subsequent to stimulation of TXA2/prostaglandin endoperoxide receptors with U 46619. The latter happens in a competitive way with fast receptor association-dissociation characteristics. At low concentrations (1 X 10(-9)-1 X 10(-7) M) producing single TXA2 synthetase inhibition, ridogrel reduces the collagen-induced formation of TXB2 by washed platelets, but enhances [32P]phosphatidic acid (PA) accumulation and [3H]5-hydroxytryptamine (5-HT) release. At higher concentrations (1 X 10(-6)-1 X 10(-5) M) which additionally block U 46619-induced [32P]PA accumulation, ridogrel inhibits the [32P]PA accumulation and release of [3H]5-HT by human platelets stimulated with collagen. These observations, corroborated by results obtained with OKY 1581, sulotroban, indomethacin and human serum albumin, suggest a causal role for prostaglandin endoperoxides in the stimulation by TXA2 synthetase inhibition of platelet reactions to collagen. They reinforce the concept that TXA2 synthetase inhibition-induced reorientation of cyclic endoperoxide metabolism, away from TXA2 into inhibitory prostanoids, requires additional TXA2/prostaglandin endoperoxide receptor antagonism to achieve optimal anti-platelet effects.
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17
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Ushikubi F, Nakajima M, Hirata M, Okuma M, Fujiwara M, Narumiya S. Purification of the thromboxane A2/prostaglandin H2 receptor from human blood platelets. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)84733-6] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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18
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Affiliation(s)
- W L Smith
- Department of Biochemistry, Michigan State University, East Lansing 48824
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19
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FitzGerald GA, Murray R, Price P, Catella F. The molecular, biochemical and human pharmacology of thromboxane A2 in renal disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1989; 259:325-60. [PMID: 2516412 DOI: 10.1007/978-1-4684-5700-1_14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- G A FitzGerald
- Division of Clinical Pharmacology, Vanderbilt University, Nashville, Tennessee 37232
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20
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Murray R, FitzGerald GA. Regulation of thromboxane receptor activation in human platelets. Proc Natl Acad Sci U S A 1989; 86:124-8. [PMID: 2521385 PMCID: PMC286416 DOI: 10.1073/pnas.86.1.124] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Thromboxane A2 (TxA2) is a potent platelet agonist that serves as an amplifying signal after exposure of platelets to other stimulants, such as thrombin, in vitro. Exposure of platelets to the TxA2 receptor agonists U46619 and SQ 26,655 (1.4 microM) resulted in a 60-90% decrease in subsequent TxA2 receptor-stimulated aggregation, calcium release, and protein kinase C activation. The desensitization was rapid, with a half-time of 2-3 min. The sequence of events involved in TxA2 receptor desensitization involves initial uncoupling of the receptor from a guanine nucleotide binding (G) protein followed by eventual receptor down-regulation. Consistent with this hypothesis were (i) a 60-70% decrease in SQ 26,655-stimulated platelet GTPase activity, (ii) a shift to the right of the dose-response curve for U46619-stimulated release of calcium [EC50, 275 +/- 51 nM (control)] vs. 475 +/- 71 nM (desensitized); P less than 0.01], and (iii) a delayed loss of receptor sites. In summary, exposure of platelets to TxA2 receptor agonists results in rapid desensitization of the biochemical and functional responses to interaction with its receptor in human platelets. The kinetics of these events are consistent with the hypothesis that this icosanoid functions in the regulation as well as amplification of platelet activation in vivo.
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Affiliation(s)
- R Murray
- Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN 37232
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Williams KA, Murphy W, Haslam RJ. Effects of activation of protein kinase C on the agonist-induced stimulation and inhibition of cyclic AMP formation in intact human platelets. Biochem J 1987; 243:667-78. [PMID: 2444206 PMCID: PMC1147911 DOI: 10.1042/bj2430667] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Jakobs, Bauer & Watanabe [(1985) Eur. J. Biochem. 151, 425-430] reported that treatment of platelets with phorbol 12-myristate 13-acetate (PMA) prevented GTP- and agonist-induced inhibition of adenylate cyclase in membranes from the platelets. This was attributed to the phosphorylation of the inhibitory guanine nucleotide-binding protein (Gi) by protein kinase C. In the present study, the effects of PMA on cyclic [3H]AMP formation and protein phosphorylation were studied in intact human platelets labelled with [3H]adenine and [32P]Pi. Incubation mixtures contained indomethacin to block prostaglandin synthesis, phosphocreatine and creatine kinase to remove ADP released from the platelets, and 3-isobutyl-1-methylxanthine to inhibit cyclic AMP phosphodiesterases. Under these conditions, PMA partially inhibited the initial formation of cyclic [3H]AMP induced by prostaglandin E1 (PGE1), but later enhanced cyclic [3H]AMP accumulation by blocking the slow decrease in activation of adenylate cyclase that follows addition of PGE1. PMA had more marked and exclusively inhibitory effects on cyclic [3H]AMP formation induced by prostaglandin D2 and also inhibited the action of forskolin. Adrenaline, high thrombin concentrations and, in the absence of phosphocreatine and creatine kinase, ADP inhibited cyclic [3H]AMP formation induced by PGE1. The actions of adrenaline and thrombin were attenuated by PMA, but that of ADP was little affected, suggesting differences in the mechanisms by which these agonists inhibit adenylate cyclase. sn-1,2-Dioctanoylglycerol (diC8) had effects similar to those of PMA. The actions of increasing concentrations of PMA or diC8 on the modulation of cyclic [3H]AMP formation by PGE1 or adrenaline correlated with intracellular protein kinase C activity, as determined by 32P incorporation into the 47 kDa substrate of the enzyme. Parallel increases in phosphorylation of 20 kDa and 39-41 kDa proteins were also observed. Platelet-activating factor, [Arg8]vasopressin and low thrombin concentrations, all of which inhibit adenylate cyclase in isolated platelet membranes, did not affect cyclic [3H]AMP formation in intact platelets. However, the activation of protein kinase C by these agonists was insufficient to account for their failure to inhibit cyclic [3H]AMP formation. Moreover, high thrombin concentrations simultaneously activated protein kinase C and inhibited cyclic [3H]AMP formation. The results show that, in the intact platelet, the predominant effects of activation of protein kinase C on adenylate cyclase activity are inhibitory, suggesting actions additional to inactivation of Gi.
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Affiliation(s)
- K A Williams
- Department of Pathology, McMaster University, Hamilton, Ontario, Canada
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