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Moussa O, Ciupek A, Watson DK, Halushka PV. Urinary thromboxane B2 and thromboxane receptors in bladder cancer: opportunity for detection and monitoring. Prostaglandins Other Lipid Mediat 2011; 96:41-4. [PMID: 21983220 PMCID: PMC3215826 DOI: 10.1016/j.prostaglandins.2011.09.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 09/20/2011] [Accepted: 09/22/2011] [Indexed: 11/25/2022]
Abstract
We have previously found increased expression of thromboxane synthase (TXAS) and thromboxane receptor (TP) beta isoform in the tissues of patients with bladder cancer. Studies in cell lines and mice have indicated a potential significant role of the thromboxane signaling pathway in the pathogenesis of human bladder cancer. This study was designed to determine if the changes observed in the tissues of patients with bladder cancer were mirrored by changes in the urine of these patients. We found increased levels of thromboxane B(2) (TXB(2)) the major metabolite of TXAS and increased levels of the TPβ receptor. These results raised the possibility that patients with bladder cancer may be followed for progression or remission of their disease by quantitation of these substances in their urine.
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Affiliation(s)
- Omar Moussa
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC29425
- Hollings Cancer Center, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC29425
| | - Andrew Ciupek
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC29425
- Hollings Cancer Center, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC29425
| | - Dennis K. Watson
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC29425
- Hollings Cancer Center, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC29425
| | - Perry V. Halushka
- Departments of Pharmacology and Medicine, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC29425
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2
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Mishra RG, Stanczyk FZ, Burry KA, Oparil S, Katzenellenbogen BS, Nealen ML, Katzenellenbogen JA, Hermsmeyer RK. Metabolite ligands of estrogen receptor-beta reduce primate coronary hyperreactivity. Am J Physiol Heart Circ Physiol 2005; 290:H295-303. [PMID: 16199482 DOI: 10.1152/ajpheart.00468.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Previous reports showed that 17beta-estradiol implants attenuate in vivo coronary hyperreactivity (CH), characterized by long-duration vasoconstrictions (in coronary angiographic experiments), in menopausal rhesus monkeys. Prolonged Ca2+ contraction signals that correspond with CH in coronary vascular muscle cells (VMC) to the same dual-constrictor stimulus, serotonin + the thromboxane analog U-46619, in estrogen-deprived VMC were suppressed by >72 h in 17beta-estradiol. The purpose of this study was to test whether an endogenous estrogen metabolite with estrogen receptor-beta (ER-beta) binding activity, estriol (E3), suppresses in vivo and in vitro CH. E3 treatment in vivo for 4 wk significantly attenuated the angiographically evaluated vasoconstrictor response to intracoronary serotonin + U-46619 challenge. In vitro treatment of rhesus coronary VMC for >72 h with nanomolar E3 attenuated late Ca2+ signals. This reduction of late Ca2+ signals also appeared after >72 h of treatment with subnanomolar 5alpha-androstane-3beta,17beta-diol (3beta-Adiol), an endogenous dihydrotestosterone metabolite with ER-beta binding activity. R,R-tetrahydrochrysene, a selective ER-beta antagonist, significantly blocked the E3- and 3beta-Adiol-mediated attenuation of late Ca2+ signal increases. ER-beta and thromboxane-prostanoid receptor (TPR) were coexpressed in coronary arteries and aorta. In vivo E3 treatment attenuated aortic TPR expression. Furthermore, in vitro treatment with E3 or 3beta-Adiol downregulated TPR expression in VMC, which was blocked for both agonists by pretreatment with R,R-tetrahydrochrysene. E3- and 3beta-Adiol-mediated reduction in persistent Ca2+ signals is associated with ER-beta-mediated attenuation of TPR expression and may partly explain estrogen benefits in coronary vascular muscle.
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Affiliation(s)
- Rajesh G Mishra
- Dimera Incorporated, 2525 NW Lovejoy, Suite 311, Portland, OR 97210, USA
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3
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Thomas DW, Rocha PN, Nataraj C, Robinson LA, Spurney RF, Koller BH, Coffman TM. Proinflammatory actions of thromboxane receptors to enhance cellular immune responses. J Immunol 2004; 171:6389-95. [PMID: 14662837 DOI: 10.4049/jimmunol.171.12.6389] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Metabolism of arachidonic acid by the cyclo-oxygenase (COX) pathway generates a family of prostanoid mediators. Nonsteroidal anti-inflammatory drugs (NSAIDs) act by inhibiting COX, thereby reducing prostanoid synthesis. The efficacy of these agents in reducing inflammation suggests a dominant proinflammatory role for the COX pathway. However, the actions of COX metabolites are complex, and certain prostanoids, such as PGE(2), in some circumstances actually inhibit immune and inflammatory responses. In these studies, we examine the hypothesis that anti-inflammatory actions of NSAIDs may be due, in part, to inhibition of thromboxane A(2) synthesis. To study the immunoregulatory actions of thromboxane A(2), we used mice with a targeted disruption of the gene encoding the thromboxane-prostanoid (TP) receptor. Both mitogen-induced responses and cellular responses to alloantigen were substantially reduced in TP(-/-) spleen cells. Similar attenuation was observed with pharmacological inhibition of TP signaling in wild-type splenocytes, suggesting that reduced responsiveness was not due to subtle developmental abnormalities in the TP-deficient mice. The absence of TP receptors reduced immune-mediated tissue injury following cardiac transplant rejection, an in vivo model of intense inflammation. Taken together, these findings show that thromboxane augments cellular immune responses and inflammatory tissue injury. Specific inhibition of the TP receptor may provide a more precise approach to limit inflammation without some of the untoward effects associated with NSAIDs.
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MESH Headings
- Adjuvants, Immunologic/deficiency
- Adjuvants, Immunologic/genetics
- Adjuvants, Immunologic/physiology
- Animals
- Calcium Signaling/genetics
- Calcium Signaling/immunology
- Cell Division/genetics
- Cell Division/immunology
- Cells, Cultured
- Enzyme Inhibitors/pharmacology
- Graft Rejection/genetics
- Graft Rejection/immunology
- Graft Rejection/pathology
- Heart Transplantation/immunology
- Heart Transplantation/pathology
- Immunity, Cellular/genetics
- Inflammation Mediators/metabolism
- Inflammation Mediators/physiology
- Lymphocyte Culture Test, Mixed
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Mice, Knockout
- Receptors, Thromboxane/biosynthesis
- Receptors, Thromboxane/deficiency
- Receptors, Thromboxane/genetics
- Receptors, Thromboxane/physiology
- Ribonucleases/metabolism
- Spleen/cytology
- Spleen/enzymology
- Spleen/immunology
- Spleen/metabolism
- T-Lymphocytes/cytology
- T-Lymphocytes/enzymology
- T-Lymphocytes/immunology
- T-Lymphocytes/metabolism
- Thromboxane-A Synthase/antagonists & inhibitors
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Affiliation(s)
- Dennis W Thomas
- Division of Nephrology, Duke University and Durham Veterans Affairs Medical Centers, Durham, NC 27705, USA
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4
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Coyle AT, Miggin SM, Kinsella BT. Characterization of the 5' untranslated region of alpha and beta isoforms of the human thromboxane A2 receptor (TP). Differential promoter utilization by the TP isoforms. Eur J Biochem 2002; 269:4058-73. [PMID: 12180983 DOI: 10.1046/j.1432-1033.2002.03098.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In humans, thromboxane (TX) A2 signals through two TXA2 receptor (TP) isoforms, TPalpha and TPbeta, that diverge within their carboxyl terminal cytoplasmic (C) tail regions and arise by differential splicing. The human TP gene contains three exons E1-E3; while E1 exclusively encodes 5' untranslated region (UTR) sequence, E2 and E3 represent the main coding exons. An additional noncoding exon, E1b was identified within intron 1. Additionally, the TP gene contains two promoters P1 and P2 located 5' of E1 and E1b, respectively. Herein, we investigated the molecular basis of the differential expression of the TP isoforms by characterizing the 5' UTR of the TP transcripts. While E1 and E1b were found associated with TP transcript(s), their expression was mutually exclusive. 5' rapid amplification of cDNA ends (5' RACE) established that the major transcription initiation (TI) sites were clustered between -115 and -92 within E1 and at -99 within E1b. While E1 and E1b sequences were identified on TPalpha transcript(s), neither existed on TPbeta transcript(s). More specifically, TPalpha and TPbeta transcripts diverged within E2 and the major TI sites for TPbeta transcripts mapped to -12/-15 therein. Through genetic reporter assays, a previously unrecognized promoter, termed P3, was identified on the TP gene located immediately 5' of -12. The proximity of P3 to the TI site of TPbeta suggests a role for P3 in the control of TPbeta expression and implies that TPalpha and TPbeta, in addition to being products of differential splicing, are under the transcriptional control of distinct promoters.
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Affiliation(s)
- Adrian T Coyle
- Department of Biochemistry, University College Dublin, Ireland
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5
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Nakagawa T, Hirakata H, Sato M, Nakamura K, Hatano Y, Nakamura T, Fukuda K. Ketamine suppresses platelet aggregation possibly by suppressed inositol triphosphate formation and subsequent suppression of cytosolic calcium increase. Anesthesiology 2002; 96:1147-52. [PMID: 11981155 DOI: 10.1097/00000542-200205000-00018] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Ketamine has been shown to suppress platelet aggregation, but its mechanisms of action have not been defined. The purpose of the current study is to clarify the effects of ketamine on human platelet aggregation and to elucidate the underlying mechanisms of its action. METHODS Platelet aggregation was measured using an eight-channel aggregometer, and cytosolic free calcium concentration was measured in Fura-2/AM-loaded platelets using a fluorometer. Inositol 1,4,5-triphosphate (IP3) was measured with use of a commercially available IP3 assay kit. To estimate thromboxane A2 (TXA2) receptor binding affinity and expression, Scatchard analysis was performed using [3H]S145, a specific TXA2 receptor antagonist. TXA2 agonist binding assay was also performed. The membrane-bound guanosine 5'-triphosphatase activity was determined using [gamma-32P]guanosine triphosphate by liquid scintillation analyzer. RESULTS Ketamine (500 microm) suppressed aggregation induced by adenosine diphosphate (0.5 microm), epinephrine (1 microm), (+)-9,11-epithia-11,12-methano-TXA2 (STA2) (0.5 microm), and thrombin (0.02 U/ml) to 39.1 +/- 30.9, 46.3 +/- 4.3, -2.0 +/- 16.8, and 86.6 +/- 1.4% of zero-control, respectively. Ketamine (250 microm-1 mm) also suppressed thrombin- and STA2-induced cytosolic free calcium concentration increase dose dependently. Although ketamine (2 mm) had no effect on TXA2 receptor expression and its binding affinity, it (1 mm) suppressed intracellular peak IP3 concentrations induced by thrombin and STA2 from 6.60 +/- 1.82 and 4.39 +/- 2.41 to 2.41 +/- 0.98 and 1.90 +/- 0.86 pmol/109 platelets, respectively, and it suppressed guanosine triphosphate hydrolysis induced by thrombin (0.02 units/ml) and STA2 (0.5 microm) to 50.3 +/- 3.2 and 67.5 +/- 5.5% versus zero-control, respectively. CONCLUSION Ketamine inhibits human platelet aggregation possibly by suppressed IP3 formation and subsequent suppression of cytosolic free calcium concentration. The site of action of ketamine is neither TXA2 nor thrombin binding sites but possibly receptor-coupled mechanisms, including G-protein.
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Affiliation(s)
- Takefumi Nakagawa
- Departments of Orthopaedic Surgery and Anesthesia, Kyoto University Hospital, Kyoto, Japan
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6
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Sugawara A, Uruno A, Kudo M, Ikeda Y, Sato K, Taniyama Y, Ito S, Takeuchi K. Transcription suppression of thromboxane receptor gene by peroxisome proliferator-activated receptor-gamma via an interaction with Sp1 in vascular smooth muscle cells. J Biol Chem 2002; 277:9676-83. [PMID: 11777901 DOI: 10.1074/jbc.m104560200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thromboxane (TX) A(2) exerts contraction and proliferation of vascular smooth muscle cells (VSMCs) via its specific membrane TX receptor (TXR), possibly leading to the progression of atherosclerosis. A nuclear hormone receptor, peroxisome proliferator-activated receptor (PPAR)-gamma, has recently been reported to be expressed in VSMCs. Here we examined a role of PPAR-gamma in TXR gene expression in VSMCs. PPAR-gamma ligands 15-deoxy-Delta(12,14)-prostaglandin J(2) and troglitazone reduced TXR mRNA expression levels as well as cell growth as assessed by [(3)H]thymidine incorporation. Transcriptional activity of the TXR gene promoter was suppressed with PPAR-gamma ligands, and the suppression was augmented further by PPAR-gamma overexpression. By deletion and mutation analyses, the transcription suppression was shown to be the result of a -22/-7 GC box-related sequence (upstream of transcription start site). Electrophoretic mobility shift assays also showed that the sequence was bound by Sp1 but not by PPAR-gamma, and the formation of a Sp1 small middle dotDNA complex was inhibited either by coincubation with PPAR-gamma or PPAR-gamma ligand treatment of VSMCs. Moreover, glutathione S-transferase pull-down assays demonstrated a direct interaction between PPAR-gamma and Sp1. In conclusion, PPAR-gamma suppresses TXR gene transcription via an interaction with Sp1. PPAR-gamma may possibly have an antiatherosclerotic action by inhibiting TXR gene expression in VSMCs.
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MESH Headings
- Animals
- Blotting, Northern
- Cell Division
- Cells, Cultured
- DNA, Complementary/metabolism
- Glutathione Transferase/metabolism
- Ligands
- Luciferases/metabolism
- Muscle, Smooth, Vascular/cytology
- Plasmids/metabolism
- Promoter Regions, Genetic
- Protein Biosynthesis
- RNA, Messenger/metabolism
- Rats
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Thromboxane/biosynthesis
- Receptors, Thromboxane/genetics
- Sp1 Transcription Factor/metabolism
- Transcription Factors/metabolism
- Transcription, Genetic
- Transfection
- Up-Regulation
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Affiliation(s)
- Akira Sugawara
- Division of Nephrology, Department of Medicine, Tohoku University Graduate School of Medicine, 1-1 Seiryo-cho, Aoba-ku, Sendai 980-8574, Japan.
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7
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Gao Y, Yokota R, Tang S, Ashton AW, Ware JA. Reversal of angiogenesis in vitro, induction of apoptosis, and inhibition of AKT phosphorylation in endothelial cells by thromboxane A(2). Circ Res 2000; 87:739-45. [PMID: 11055976 DOI: 10.1161/01.res.87.9.739] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Thromboxane A(2) (TxA(2)) causes platelet aggregation, vasoconstriction, and inhibition of endothelial cell (EC) migration and prevents vascular tube formation via its specific receptors (TP), of which there are two isoforms (TPalpha and TPbeta), both expressed in human ECs. In this study, we demonstrate that the TxA(2) mimetic IBOP increases apoptosis of human ECs and inhibits the phosphorylation of Akt kinase, an intracellular mediator required for cell survival. Treatment with IBOP destroyed EC networks formed on a basement membrane matrix in vitro. To distinguish the role of the TP isoforms, each isoform was expressed in TP-null ECs to create TPalpha and TPbeta ECs. IBOP induced apoptosis and inhibited phosphorylation of Akt kinase in both TPalpha and TPbeta. IBOP increased cAMP levels in TPalpha but not in TPbeta. Apoptosis induced by IBOP in TPalpha was not affected by either the adenylyl cyclase activator forskolin or the protein kinase A inhibitor 14-22 amide or H-89, whereas that in TPbeta was suppressed by forskolin and enhanced by the protein kinase A inhibitor 14-22 amide or H-89, suggesting that the TP isoforms differ in their signal pathways in mediating apoptosis. In conclusion, apoptosis may be the mechanism by which TxA(2)-mediated destruction of vascular structures in ECs occurs; although both TP isoforms induce apoptosis, possibly via inhibiting Akt phosphorylation, the signaling differs in each isoform, in that activation of the adenylyl cyclase pathway prevents apoptosis caused by TPbeta, but not by TPalpha, stimulation.
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Affiliation(s)
- Y Gao
- Departments of Medicine (Cardiovascular Division), Albert Einstein College of Medicine of Yeshiva University, Bronx, NY, USA
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8
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Walsh M, Foley JF, Kinsella BT. Investigation of the role of the carboxyl-terminal tails of the alpha and beta isoforms of the human thromboxane A(2) receptor (TP) in mediating receptor:effector coupling. Biochim Biophys Acta 2000; 1496:164-82. [PMID: 10771086 DOI: 10.1016/s0167-4889(00)00031-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have investigated the functional coupling of alpha and beta isoforms of the human thromboxane A(2) receptor (TP) to Galpha(16) and Galpha(12) members of the G(q) and G(12) families of heterotrimeric G proteins in human embryonic kidney (HEK) 293 cell lines HEK.alpha10 or HEK.beta3, stably over-expressing TPalpha and TPbeta, respectively. Moreover, using HEK.TP(Delta328) cells which over-express a variant of TP truncated at the point of divergence of TPalpha and TPbeta, we investigated the requirement of the C-tail per se in mediating G protein coupling and effector activation. Both TPalpha and TPbeta couple similarly to Galpha(16) to affect increases in inositol 1,4,5-trisphosphate (IP(3)) and mobilisation of intracellular calcium ([Ca(2+)](i)) in response to the TP agonist U46619. Whilst both TP isoforms mediated [Ca(2+)](i) mobilisation in cells co-transfected with Galpha(12), neither receptor generated corresponding increases in IP(3), indicating that the Galpha(12)-mediated increases in [Ca(2+)](i) do not involve PLC activation. Verapamil, an inhibitor of voltage dependent Ca(2+) channels, reduced [Ca(2+)](i) mobilisation in TPalpha and TPbeta cells co-transfected with Galpha(12) to approximately 40% of that mobilised in its absence, whereas [8-(N,N-diethylamino)-octyl-3,4, 5-trimethoxybenzoate, hydrochloride] (TMB-8), an antagonist of intracellular Ca(2+) release, had no effect on [Ca(2+)](i) mobilisation by either receptor isoform co-transfected with Galpha(12). Despite the lack of differential coupling specificity by TPalpha and TPbeta, TP(Delta328) signalled more efficiently in the absence of a co-transfected G protein compared to the wild type receptors but, on the other hand, displayed an impaired ability to couple to co-transfected Galpha(11), Galpha(12) or Galpha(16) subunits. In studies investigating the role of the C-tail in influencing coupling to the effector adenylyl cyclase, similar to TPalpha but not TPbeta, TP(Delta328) coupled to Galpha(s), leading to increased adenosine 3',5'-cyclic monophosphate (cAMP), rather than to Galpha(i). Whereas TP(Delta328) signalled more efficiently in the absence of co-transfected G protein compared to the wild type TPalpha, co-transfection of Galpha(s) did not augment cAMP generation by TP(Delta328). Hence, from these studies involving the wild type TPalpha, TPbeta and TP(Delta328), we conclude that the C-tail sequences of TP are not a major determinant of G protein coupling specificity to Galpha(11) and Galpha(16) members of the G(q) family or to Galpha(12); it may play a role in determining G(s) versus G(i) coupling and may act as a determinant of coupling efficiency.
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Affiliation(s)
- M Walsh
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, Merville House, University College Dublin, Belfield, Dublin, Ireland
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9
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Senchyna M, Crankshaw DJ. Operational correlates of prostanoid TP receptor expression in human non-pregnant myometrium are unaffected by excision site or menstrual cycle status of the donor. Br J Pharmacol 1999; 128:1524-8. [PMID: 10602332 PMCID: PMC1571797 DOI: 10.1038/sj.bjp.0702964] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/1999] [Revised: 09/24/1999] [Accepted: 09/27/1999] [Indexed: 11/08/2022] Open
Abstract
1. Cumulative concentration-effect curves for the selective prostanoid TP receptor agonist, U46619, were constructed in strips of human non-pregnant myometrium grouped according to tissue excision site (top, lateral wall, lower uterine segment, sub-serosal or sub-endometrial), tissue orientation (strips cut either parallel or perpendicular to the serosa) and donor menstrual status (proliferative or secretory phase). 2. U46619 was excitatory in all tissues. There was no significant difference in either pEC50 or maximum response between groups (P<0.05). The range of pEC50 values was 6.8+/-0.1 (lateral wall, proliferative phase, n=5) to 7.1+/-0.3 (lateral wall, secretory phase, n=5). The range of maximum response values was 0.9+/-0.8 N cm-2 (lateral wall, proliferative phase, n=5) to 3.1+/-1.0 N cm-2 (lateral wall, secretory phase, n=5). 3. Saturation binding analyses were conducted using the radiolabelled TP receptor agonist, [125I]-BOP. Binding parameters were estimated for membranes prepared from human non-pregnant myometrium excised from the lateral wall and grouped according to donor menstrual status. 4. There were no significant differences in the mean pKd and [R]tot values for [125I]-BOP binding between the two groups (proliferative phase: pKd=8.3+/-0.3, [R]tot=412+/-319 fmol mg protein-1, n=5; secretory phase: pKd=8.5+/-0.4, [R]tot=369+/-192 fmol mg protein-1, n=6; P<0.05). 5. These data indicate that U46619-mediated responses in human non-pregnant myometrium are not influenced by tissue excision site, tissue orientation or donor menstrual status and that [125I]-BOP binding is not influenced by donor menstrual status. This suggests that the TP receptor population is homogeneous throughout the human non-pregnant myometrium, and not subject to hormonal regulation.
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Affiliation(s)
- Michelle Senchyna
- Department of Obstetrics and Gynecology, McMaster University, Hamilton, Ontario, Canada
| | - D J Crankshaw
- Department of Obstetrics and Gynecology, McMaster University, Hamilton, Ontario, Canada
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10
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Miggin SM, Kinsella BT. Expression and tissue distribution of the mRNAs encoding the human thromboxane A2 receptor (TP) alpha and beta isoforms. Biochim Biophys Acta 1998; 1425:543-59. [PMID: 9838218 DOI: 10.1016/s0304-4165(98)00109-3] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The human thromboxane A2 receptor (TP), a G protein-coupled receptor, exists as two isoforms, TPalpha and TPbeta, which arise by alternative mRNA splicing and differ exclusively in their carboxyl terminal cytoplasmic regions. In this study, a reverse transcriptase-polymerase chain reaction (RT-PCR)-based strategy was developed to examine the expression of the TPs in tissues of physiologic relevance to TXA2. Although most of the 17 different cell/tissue types examined expressed both TP isoforms, the liver hepatoblastoma HepG2 cell line was found to exclusively express TPalpha mRNA. In most cell types, TPalpha mRNA predominated over TPbeta mRNA. Moreover, although the levels of TPalpha mRNA expression were similar in most of the cell/tissue types examined, extensive differences in the levels of TPbeta mRNA were observed. Consequently, the relative expression of TPalpha: TPbeta mRNA varied considerably due to extensive differences in TPbeta mRNA expression. Most strikingly, primary HUVECs were found to express: (i) low levels of TPbeta and (ii) approximately 6-fold greater levels of TPalpha than TPbeta. These data were confirmed in the spontaneously transformed HUVEC derived ECV304 cell line. Expression of TP mRNAs in the various tissue/cells correlated with protein expression, as assessed by radioligand binding using the selective TP antagonist [3H]SQ29,548.
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MESH Headings
- Blotting, Southern
- Brain/metabolism
- Bridged Bicyclo Compounds, Heterocyclic
- Cell Line
- Endothelium, Vascular/metabolism
- Fatty Acids, Unsaturated
- Humans
- Hydrazines/pharmacology
- Intestine, Small/metabolism
- Protein Isoforms/biosynthesis
- RNA, Messenger/biosynthesis
- Receptors, Thromboxane/antagonists & inhibitors
- Receptors, Thromboxane/biosynthesis
- Receptors, Thromboxane/genetics
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Thromboxane A2/metabolism
- Thymus Gland/metabolism
- Trophoblasts/metabolism
- Tumor Cells, Cultured
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Affiliation(s)
- S M Miggin
- Department of Biochemistry, Merville House, University College Dublin, Belfield, Dublin 4, Ireland
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11
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Walsh MT, Foley JF, Kinsella BT. Characterization of the role of N-linked glycosylation on the cell signaling and expression of the human thromboxane A2 receptor alpha and beta isoforms. J Pharmacol Exp Ther 1998; 286:1026-36. [PMID: 9694965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The alpha and beta isoforms of the thromboxane A2 receptor (TP) mediate the actions of the prostanoid thromboxane A2 and its mimetics in humans. The amino terminal region of the TPs contains two consensus N-linked glycosylation sites at asparagine (N) residues N4 and N16. In this study, we explored the significance of N-linked glycosylation on the signaling and surface expression of the human TP isoforms. Inhibition of N-linked glycosylation reduced selective radioligand ([3H]SQ29,548) binding by either TP in both human erythroleukemia cells and in transfected human embryonic kidney 293 cells. Moreover, site-directed mutagenesis of the putative glycosylation sites of TPalpha revealed that radioligand binding also was reduced greatly for both the single (TPalphaN4-Q4, TPalphaN16-Q16) and double (TPalphaN4,N16-Q4,Q16) mutants, yielding levels of 8% binding relative to the wild-type TPalpha for the double mutants. Reductions in ligand binding were caused by decreased maximal binding and not by changes in affinity (Kd) or in specificity of the receptors for [3H]SQ29,548 or other ligands. Subcellular fractionation confirmed that, in relation to total TP expression, membrane expression was not altered in TPalphaN4-Q4 or TPalphaN16-Q16 but was reduced to levels of 55% of total expression in TPalphaN4,Q4-N16,Q16. Inhibition of glycosylation reduced, but did not abolish, agonist (U46619) mediated intracellular Ca++ mobilization by TPalpha or TPbeta and cAMP production by TPalpha. Thus, N-linked glycosylation of the human TP isoforms is important for ligand binding, efficient second messenger signaling and efficient membrane expression.
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Affiliation(s)
- M T Walsh
- Department of Biochemistry, Merville House, University College Dublin, Belfield, Dublin, Ireland
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12
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Abstract
We examined the effects of thromboxane A2 (TxA2) on the activities of the plasminogen-plasmin system in glomerular mesangial cells. When mesangial cells are exposed to the TxA2 agonist U-46619, a substantial increase in production of plasminogen activator inhibitor-1 (PAI-1) protein is observed that is significantly greater than that induced by 10% serum alone. This increase in PAI-1 protein production is accompanied by an increase in steady-state levels of PAI-1 mRNA. This stimulation is specifically mediated by TxA2 (thromboxane prostanoid, TP) receptors, since U-46619 also stimulates PAI-1 expression in cells that are transfected with TP receptors, and this stimulation of PAI-1 production is completely blocked by the TxA2 receptor antagonist, SQ-29,548. Despite the increase in PAI-1 production, there was net stimulation of plasmin activity in the medium of mesangial cells that had been exposed to U-46619. Furthermore, U-46619 also caused an increase in tissue plasminogen activator (tPA) mRNA levels. Thus TxA2 stimulates the production of PAI-1 and plasminogen activators by mesangial cells through a receptor-dependent mechanism. In inflammatory renal diseases, the balance of these effects may modulate glomerular thrombosis and renal fibrosis.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Animals
- Bridged Bicyclo Compounds, Heterocyclic
- Cells, Cultured
- Fatty Acids, Unsaturated
- Fibrinolysin/metabolism
- Fibrinolysis/drug effects
- Glomerular Mesangium/drug effects
- Glomerular Mesangium/physiology
- Hydrazines/pharmacology
- Kinetics
- Plasminogen Activator Inhibitor 1/biosynthesis
- Plasminogen Activator Inhibitor 1/genetics
- RNA, Messenger/biosynthesis
- Rats
- Receptors, Thromboxane/antagonists & inhibitors
- Receptors, Thromboxane/biosynthesis
- Receptors, Thromboxane/physiology
- Recombinant Proteins/biosynthesis
- Thromboxane A2/agonists
- Thromboxane A2/physiology
- Tissue Plasminogen Activator/biosynthesis
- Tissue Plasminogen Activator/genetics
- Transcription, Genetic
- Transfection
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Affiliation(s)
- T M Coffman
- Department of Medicine, Duke University and Durham Veterans Affairs Medical Center, Durham, North Carolina 27705, USA
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13
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MESH Headings
- Amino Acid Sequence
- Animals
- Cattle
- Cells, Cultured
- Cloning, Molecular
- Coronary Vessels/cytology
- Coronary Vessels/drug effects
- Coronary Vessels/metabolism
- Female
- Humans
- Kinetics
- Mice
- Molecular Sequence Data
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Polymerase Chain Reaction
- Rats
- Receptors, Thromboxane/biosynthesis
- Receptors, Thromboxane/chemistry
- Recombinant Proteins/biosynthesis
- Sequence Alignment
- Sequence Homology, Amino Acid
- Thrombin/pharmacology
- Up-Regulation/drug effects
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Affiliation(s)
- S Muck
- Institut für Pharmakologie, Heinrich-Heine-Universität Düsseldorf, Germany
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14
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Zucker TP, Bönisch D, Muck S, Weber AA, Bretschneider E, Glusa E, Schrör K. Thromboxane A2 potentiates thrombin-induced proliferation of coronary artery smooth muscle cells. Adv Exp Med Biol 1998; 433:387-90. [PMID: 9561177 DOI: 10.1007/978-1-4899-1810-9_84] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The activation of thrombin is the key event in clot formation after vascular injury. Thrombin itself, but also other clot-derived factors, such as thromboxane A2 (TXA2), are mitogenic for vascular smooth muscle cells. We have studied the possible interactions between thrombin and TXA2 in stimulation of coronary artery smooth muscle cell (SMC) proliferation. Thrombin (1 U/ml) caused a significant proliferatory response in SMC. U 46619, a stable TXA2 mimetic, had only a minor stimulating effect by its own but markedly potentiated the thrombin-induced mitogenesis. A possible mechanism for these potentiating effects is provided by the demonstration of a marked (6 fold) but transient (maximum after 20 min) increase in the expression of TXA2 receptor (TP receptor) mRNA in SMC by thrombin. Since a significant clot-related TXA2 generation was detected for at least 2 hours, the up-regulation of TP receptors by thrombin may represent a mechanism that is relevant for the in vivo situation of SMC proliferation after vessel injury.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Animals
- Blood Coagulation
- Blood Platelets/physiology
- Cattle
- Cell Division/drug effects
- Cells, Cultured
- Coronary Vessels/cytology
- Coronary Vessels/drug effects
- Coronary Vessels/physiology
- Drug Synergism
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Receptors, Thromboxane/biosynthesis
- Thrombin/pharmacology
- Thromboxane A2/biosynthesis
- Thromboxane A2/blood
- Thromboxane A2/pharmacology
- Time Factors
- Up-Regulation
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Affiliation(s)
- T P Zucker
- Institute für Klinische Anaesthesiologie, Heinrich-Heine-Universität Düsseldorf, Germany
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15
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Pratico D, O'Mahony D, Lawson J, Kinsella T, Fitzgerald GA. Cellular activation by thromboxane A2 and 8-EPI-PGF2 alpha. Adv Exp Med Biol 1998; 400A:229-33. [PMID: 9547562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- D Pratico
- Dept. of Medicine and Experimental Therapeutics, University College, Dublin, Ireland
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16
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Muck S, Weber AA, Meyer-Kirchrath J, Schrör K. The bovine thromboxane A2 receptor: molecular cloning, expression, and functional characterization. Naunyn Schmiedebergs Arch Pharmacol 1998; 357:10-6. [PMID: 9459567 DOI: 10.1007/pl00005132] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This study describes the molecular cloning and functional characterization of the bovine thromboxane A2 (TP) receptor. Two partial nucleotide sequences coding for the bovine TP receptor were isolated from a bovine genomic and a bovine heart cDNA library. The deduced amino acid sequence suggests a heptahelical protein of 343 amino acids. The receptor protein is homologous with that of human placenta and endothelium at 84.0% and 81.4%, respectively. COS-7 cells were transfected with the bovine TP receptor cDNA, and binding affinities were assessed by radioligand binding studies. Specific displacement of [3H]SQ 29548 was demonstrated in COS-7 cell membranes with the unlabeled TP receptor antagonist SQ 29548 (Kd = 12.6+/-1.1 nM) and the TP receptor agonist U46619 (Kd = 192.1+/-58.9 nM), but not with other prostaglandins (PGD2, PGE1, PGF2alpha), or the PGI2 mimetic cicaprost. Agonist-induced stimulation of adenylyl cyclase in transfected COS-7 cells indicates a linkage to the cAMP signal transduction pathway via coupling to a stimulatory G-protein. Since bovine cells, e.g. vascular smooth muscle cells, are an established model to study the role of eicosanoids in cell signaling, this report on the molecular structure of the bovine TP receptor will allow further studies on receptor regulation.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/metabolism
- Adenylyl Cyclases/biosynthesis
- Amino Acid Sequence
- Animals
- Base Sequence
- Binding, Competitive
- Bridged Bicyclo Compounds, Heterocyclic
- COS Cells
- Cloning, Molecular
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- Endothelium, Vascular/metabolism
- Fatty Acids, Unsaturated
- Gene Library
- Humans
- Hydrazines/metabolism
- Molecular Sequence Data
- Prostaglandins/metabolism
- Radioligand Assay
- Receptors, Thromboxane/biosynthesis
- Receptors, Thromboxane/genetics
- Sequence Homology
- Transfection
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Affiliation(s)
- S Muck
- Institut für Pharmakologie, Heinrich-Heine-Universität Düsseldorf, Germany
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17
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Feng G, Zhou Y, Yang Z. [Changes of thromboxane A2 receptors and their mRNA expression and effects of their antagonist phenol red in the lung of acute lung injury of rats]. Zhonghua Jie He He Hu Xi Za Zhi 1998; 21:19-22. [PMID: 11263294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
OBJECTIVE To investigate the changes of thromboxane A2 receptors and the influence of their antagonist phenol red, and to study in molecular level the mechanism of action of thromboxane A2 in acute lung injury. METHODS Acute lung injury model of rats was produced by oleic acid, and phenol red (5 mg/kg, 50 mg/kg) was injected via vein 5 minutes before oleic acid injection. Changes of thromboxane A2 receptors and their mRNA expression in the lung were determined at 6 hours after oleic acid injection. RESULTS Down-regulation of thromboxane A2 receptors were observed, but their mRNA transcription increased significantly in the lung after oleic acid injection. The injection of phenol red before oleic acid could induce down-regulation of thromboxane A2 receptors and abolish the increase of their mRNA transcription after oleic acid injection. Phenol red could reduce LBI, RLW and improve PaO2. Histological examination of lung tissues demonstrated that the degree of lung injury had been reduced significantly. CONCLUSION Thromboxane A2 plays an important role plays in pathological processes of acute lung injury. Phenol red in vivo could effectively reduce severity of acute lung injury by blocking thromboxane A2 receptors and regulating the expression of thromboxane A2 receptors.
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Affiliation(s)
- G Feng
- Research Institute of Surgery, Daping Hospital, Chongqing 400042
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18
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Abstract
The tubuloglomerular feedback (TGF) response is potentiated by thromboxane A2 (TxA2) and/or prostaglandin endoperoxide (PGH2) acting on specific receptors. Infusion of the TxA2/PGH2 mimetic, U-46,619, into conscious rats leads to hypertension that is potentiated by a high-salt intake. Therefore, we tested the hypothesis that a high-salt intake enhances the expression of transcripts for TxA2/PGH2 receptors in the kidney and glomeruli and enhances the response of TGF to TxA2/PGH2 receptor stimulation. Groups of rats were accommodated to a low-salt (LS), normal salt (NS), or high-salt (HS) diet for 8-10 days. TxA2/PGH2 receptor mRNA was detected by reverse transcription-polymerase chain reaction in kidney cortex, isolated glomeruli, and abdominal aorta. TxA2/PGH2 mRNA abundance was significantly (P < 0.001) increased during intake of high-salt compared with low-salt diets in the kidney cortex (1.34 +/- 0.10 vs. 0.84 +/- 0.04 arbitrary units) and isolated outer cortical glomeruli (0.68 +/- 0.04 vs. 0.32 +/- 0.03 arbitrary units), but there was no effect of salt on TxA2/PGH2 receptor mRNA expression in the aorta. Maximal TGF responses were assessed from the increase in proximal stop flow pressure (an index of glomerular capillary pressure) during increases in loop of Henle perfusion with artificial tubular fluid from 0 to 40 nl/min. Compared with vehicle, the enhancement of maximal TGF with U-46,619 (10(-6) M) added to the perfusate was greater in rats adapted to high-salt than normal salt (HS: +9.6 +/- 1.1 vs. NS: +5.1 +/- 0.4 mmHg; P < 0.001) or low-salt (LS: +3.8 +/- 1.3 mmHg; P < 0.001) intakes. Responses to U-46,619 at each level of salt intake were blocked by > 70% by the TxA2/PGH2 receptor antagonist ifetroban. In contrast, enhancement of TGF by peritubular capillary perfusion of arginine vasopressin (AVP; 10(-7) M) was similar in high-salt and low-salt rats (HS: +1.5 +/- 0.6 vs. LS: +1.6 +/- 0.5 mmHg; not significant). We conclude that salt loading increases selectively the abundance of TxA2/PGH2 receptor transcripts in the kidney cortex and glomerulus, relative to the aorta, and enhances selectively TGF responses to TxA2/PGH2 receptor activation but not to AVP.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Animals
- Aorta, Abdominal/physiology
- Feedback
- Gene Expression Regulation/drug effects
- Hypertension/chemically induced
- Hypertension/physiopathology
- Kidney/drug effects
- Kidney/physiology
- Kidney Cortex/physiology
- Kidney Glomerulus/physiology
- Loop of Henle/physiology
- Male
- Muscle, Smooth, Vascular/physiology
- Polymerase Chain Reaction
- RNA, Messenger/biosynthesis
- Rats
- Rats, Sprague-Dawley
- Receptors, Prostaglandin/biosynthesis
- Receptors, Thromboxane/biosynthesis
- Receptors, Thromboxane A2, Prostaglandin H2
- Reference Values
- Sodium, Dietary/pharmacology
- Transcription, Genetic/drug effects
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Affiliation(s)
- W J Welch
- Division of Nephrology and Hypertension, Georgetown University Medical Center, Washington, District of Columbia 20007, USA
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19
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Asano K, Taniguchi S, Nakao A, Maruyama T, Watanabe T, Kurokawa K. Distribution of thromboxane A2 receptor mRNA along the mouse nephron segments. Biochem Biophys Res Commun 1996; 226:613-7. [PMID: 8831666 DOI: 10.1006/bbrc.1996.1404] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Thromboxane A2 (TXA2) receptor mRNA was semi-quantitated in microdissected mouse nephron segments by reverse transcription-polymerase chain reaction (RT-PCR). TXA2 receptor mRNA was most abundantly expressed in the glomerulus, followed by the distal convoluted tubule > proximal tubule, thick ascending limb of Henle, and outer medullary collecting duct. These results suggest the potential physiological roles of TXA2 in the entire renal tubule as well as in the glomerulus.
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MESH Headings
- Actins/biosynthesis
- Animals
- Blotting, Southern
- DNA Primers
- Dissection/methods
- Kidney Glomerulus/metabolism
- Kidney Medulla/metabolism
- Kidney Tubules, Collecting/metabolism
- Kidney Tubules, Distal/metabolism
- Kidney Tubules, Proximal/metabolism
- Loop of Henle/metabolism
- Male
- Mice
- Mice, Inbred ICR
- Nephrons/anatomy & histology
- Nephrons/metabolism
- Nephrons/physiology
- Organ Specificity
- Polymerase Chain Reaction/methods
- RNA, Messenger/analysis
- RNA, Messenger/biosynthesis
- Receptors, Thromboxane/biosynthesis
- Receptors, Thromboxane/genetics
- Receptors, Thromboxane/physiology
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Affiliation(s)
- K Asano
- First Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan
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20
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Raychowdhury MK, Yukawa M, Collins LJ, McGrail SH, Kent KC, Ware JA. Alternative splicing produces a divergent cytoplasmic tail in the human endothelial thromboxane A2 receptor. J Biol Chem 1994; 269:19256-61. [PMID: 8034687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Thromboxane A2 (TxA2) causes contraction of vascular smooth muscle and aggregation of platelets; paradoxically, it also induces formation of the vasodilator and antiaggregant prostacyclin by human endothelium. To determine if the molecular structure of the endothelial TxA2 receptor differs from that of the previously characterized receptor from placenta, we isolated a putative TxA2 receptor cDNA from a human endothelial library. The predicted amino acid sequence revealed a structure of 369 amino acids, in which a novel cytoplasmic tail replaced the carboxyl-terminal portion of the previously characterized TxA2 receptor; this divergence in cytoplasmic domains resulted from the nonsplicing of a potential intron in the placenta TxA2 receptor. Northern hybridization reveals that the expression of the TxA2 receptor in endothelial RNA decreases 6-fold following stimulation with an endoperoxide analog. Polymerase chain reaction using oligonucleotide primers specific to each cytoplasmic domain revealed that only the novel receptor was expressed in endothelium, while both receptors were expressed in placenta. Overexpression of the endothelial TxA2 receptor cDNA in Chinese hamster ovary cells conferred the ability to bind a known receptor antagonist and mobilize Ca2+ in response to TxA2 mimetics. This finding of a new TxA2 receptor in endothelium suggests that a family of these receptors may result from alternative splicing of the cytoplasmic (carboxyl) tail.
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MESH Headings
- Alternative Splicing
- Amino Acid Sequence
- Animals
- Base Sequence
- Bridged Bicyclo Compounds, Heterocyclic
- CHO Cells
- Calcium/metabolism
- Cloning, Molecular
- Cricetinae
- DNA, Complementary/genetics
- Down-Regulation
- Endothelium, Vascular
- Fatty Acids, Unsaturated
- Humans
- Hydrazines/metabolism
- Molecular Sequence Data
- Placenta
- Receptors, Thromboxane/antagonists & inhibitors
- Receptors, Thromboxane/biosynthesis
- Receptors, Thromboxane/genetics
- Recombinant Proteins/biosynthesis
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Thromboxane A2/antagonists & inhibitors
- Thromboxane A2/metabolism
- Transfection
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Affiliation(s)
- M K Raychowdhury
- Harvard-Thorndike Laboratories, Department of Medicine (Cardiovascular Division), Beth Israel Hospital, Boston, Massachusetts 02215
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21
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Abstract
Platelet protein makeup is determined during transformation of megakaryoblasts to mature megakaryocytes, the immediate precursor of circulating platelets. To better understand the molecular mechanisms of megakaryocyte formation, gene expression was characterized by Northern analysis and RNA fingerprinting of cultured human CHRF-288 megakaryoblastic cells undergoing phorbol ester-stimulated megakaryocytic differentiation or serum-stimulated megakaryoblast proliferation. Protooncogenes c-fos and c-jun were coordinately upregulated in both proliferating and differentiating cells, whereas c-myc transcripts were upregulated during proliferation only. In contrast, mRNAs for transforming growth factor-beta 1 (TGF-beta 1) and thromboxane receptors were coordinately upregulated during differentiation but differentially regulated during proliferation. RNA fingerprinting revealed multiple transcripts specific to either proliferating or differentiated cells. Three of these were identified by homology to known DNA sequence: CDw44 adhesion molecule (upregulated during differentiation), glutathione sulfhydryl peroxidase (downregulated during differentiation), and plectin cytoskeletal protein (upregulated during differentiation). Thus, although megakaryoblast proliferation and megakaryocyte differentiation both involve DNA and protein synthesis, each growth response is characterized by a distinct pattern of gene expression.
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MESH Headings
- Base Sequence
- Cell Differentiation
- Cell Division
- Cell Line
- DNA Primers
- Gene Expression/drug effects
- Gene Expression/physiology
- Gene Expression Regulation, Neoplastic/drug effects
- Genes, fos/drug effects
- Genes, jun/drug effects
- Genes, myc/drug effects
- Humans
- Infant
- Leukemia, Megakaryoblastic, Acute
- Megakaryocytes/cytology
- Megakaryocytes/drug effects
- Molecular Sequence Data
- Proto-Oncogenes/drug effects
- RNA, Messenger/analysis
- RNA, Messenger/biosynthesis
- RNA, Neoplasm/analysis
- RNA, Neoplasm/biosynthesis
- Receptors, Thromboxane/biosynthesis
- Tetradecanoylphorbol Acetate/pharmacology
- Transcription, Genetic/drug effects
- Transforming Growth Factor beta/biosynthesis
- Tumor Cells, Cultured
- Up-Regulation/drug effects
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Affiliation(s)
- G W Dorn
- Department of Internal Medicine, University of Cincinnati, Ohio 45267-0542
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22
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Abstract
Thromboxane A2 is an abundant and potent product of arachidonic acid metabolism in human platelets. Its clinical importance is highlighted by the efficacy of aspirin, which, due to its irreversible inhibition of the enzyme PGG/H synthase, selects the anucleate platelet as a particular target for extended duration of action. A single thromboxane receptor gene has been identified by southern blot; sequence polymorphism in the gene sequence has been identified. The recombinant receptor is also subject to posttranslational modifications, which may modify its affinity for natural ligands. Pharmacological studies have suggested some heterogeneity among thromboxane receptors. These observations have been rendered more interesting by the discovery of an F prostaglandin isomer, 8-epi-PGF2 alpha, which exerts its biological effects through a thromboxane (or closely related) receptor. This isomer can be generated in a free radical-catalyzed or cyclooxygenase-dependent manner.
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Affiliation(s)
- B T Kinsella
- Department of Medicine and Experimental Therapeutics University College, Dublin, Ireland
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23
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Abstract
The human thromboxane A2 receptor (TXA2-R)-coding gene was introduced into Chinese hamster ovary cells and a cell line (TCHO-25) stably expressing TXA2-R, at a level of 3 x 10(5)/cell, was obtained. An anti-asthmatic agent AA-2414 [(+-)-7-(3,5,6-trimethyl-1,4-benzoquinon-2-yl)-7- phenylheptanoic acid] competitively inhibited the specific binding of a TXA2 mimic ([3H]U-46619) to the TCHO-25 cells, with an IC50 of 6.0 x 10(-8) M, indicating that the drug is an antagonist of human TXA2-R. The TCHO-25 cells offer a tool for the screening and characterization of human TXA2-R antagonists.
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Affiliation(s)
- T Kurokawa
- DDS Research Laboratories, Takeda Chemical Industries, Ltd., Osaka, Japan
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24
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Schrör K, Morinelli TA, Masuda A, Matsuda K, Mathur RS, Halushka PV. Testosterone treatment enhances thromboxane A2 mimetic induced coronary artery vasoconstriction in guinea pigs. Eur J Clin Invest 1994; 24 Suppl 1:50-2. [PMID: 8013532 DOI: 10.1111/j.1365-2362.1994.tb02428.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Thromboxane A2 (TXA2) has been implicated as an important mediator of cardiovascular diseases. There have been several clinical reports of acute myocardial infarctions occurring in young male athletes abusing anabolic steroids. The effects of treatment of male Guinea pigs with testosterone on the responses to U46619, a TXA2 receptor agonist, in the isolated perfused heart were determined. The maximum pressor responses of the isolated perfused Guinea pig heart to U46619 were significantly (P < 0.05) greater in the Guinea pigs treated with testosterone compared to the controls. These results indicate that testosterone can enhance coronary artery vascular reactivity to TXA2.
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Affiliation(s)
- K Schrör
- Department of Pharmacology, Medical University of South Carolina, Charleston 29425
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25
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Matsuda K, Mathur RS, Duzic E, Halushka PV. Androgen regulation of thromboxane A2/prostaglandin H2 receptor expression in human erythroleukemia cells. Am J Physiol 1993; 265:E928-34. [PMID: 8279549 DOI: 10.1152/ajpendo.1993.265.6.e928] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Thromboxane A2 (TxA2), a platelet aggregator and vasoconstrictor, has been implicated as a potential mediator of cardiovascular diseases. Abuse of androgenic steroids has been associated with thrombotic cardiovascular diseases. Human erythroleukemia (HEL) cells, a megakaryocyte-like cell line, express functional TxA2/prostaglandin H2 (PGH2) receptors with characteristics similar to those seen in platelets. This study characterized testosterone regulation of HEL cell TxA2/PGH2 receptors. TxA2/PGH2 receptor affinity (Kd) and density (Bmax) were determined via equilibrium binding experiments using the radiolabeled TxA2 mimetic (1S-[1 alpha,2 beta(5Z),3 alpha(1E,3R*),4 alpha])-7-(3-[3-hydroxy-4-(4'- iodophenoxy)-1-butenyl]-7-oxabicyclo[2.2.1]heptan-2-yl)-5-he ptenoic acid (125I-labeled BOP). Testosterone (200 nM) but not estradiol increased Bmax from 108 +/- 9 fmol/mg protein to 157 +/- 9 fmol/mg protein (n = 7 experiments; P < 0.01) without any significant change in Kd. Testosterone had no significant effect on alpha 2-adrenergic receptor density. The maximum increase in intracellular free calcium induced by the TxA2 agonists I-BOP or U-46619 was significantly (P < 0.005) greater in testosterone-treated cells compared with controls. Hydroxyflutamide (1 microM), an androgen-receptor antagonist, completely blocked the effect of testosterone (P < 0.01). Dihydrotestosterone, the active metabolite of testosterone, also increased Bmax in a concentration-dependent manner and was more potent than testosterone. The effect of testosterone to increase Bmax was significantly (P < 0.01) inhibited by coincubation with cycloheximide (0.1 microgram/ml) or actinomycin D (10 ng/ml). These results indicate that androgenic steroids regulate the expression of functional TxA2/PGH2 receptors in HEL cells. These findings may have relevance to cardiovascular disease.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid
- 5-alpha Reductase Inhibitors
- Azasteroids/pharmacology
- Calcium/metabolism
- Cell Line
- Cycloheximide/pharmacology
- Dactinomycin/pharmacology
- Dihydrotestosterone/analogs & derivatives
- Dihydrotestosterone/pharmacology
- Estradiol/pharmacology
- Gene Expression Regulation, Neoplastic/drug effects
- Humans
- Kinetics
- Leukemia, Erythroblastic, Acute
- Prostaglandin Endoperoxides, Synthetic/pharmacology
- Prostaglandin H2
- Prostaglandins H/metabolism
- Receptors, Prostaglandin/biosynthesis
- Receptors, Thromboxane/biosynthesis
- Receptors, Thromboxane A2, Prostaglandin H2
- Testosterone/pharmacology
- Thromboxane A2/analogs & derivatives
- Thromboxane A2/pharmacology
- Tumor Cells, Cultured
- Vasoconstrictor Agents/pharmacology
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Affiliation(s)
- K Matsuda
- Department of Pharmacology and Medicine, Medical University of South Carolina, Charleston 29425
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26
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Ushikubi F, Aiba Y, Nakamura K, Namba T, Hirata M, Mazda O, Katsura Y, Narumiya S. Thromboxane A2 receptor is highly expressed in mouse immature thymocytes and mediates DNA fragmentation and apoptosis. J Exp Med 1993; 178:1825-30. [PMID: 8228829 PMCID: PMC2191260 DOI: 10.1084/jem.178.5.1825] [Citation(s) in RCA: 110] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
We have recently revealed that the thymus is the organ showing the highest expression of thromboxane (TX) A2 receptor in mice. In this study, thymic cell populations expressing the receptor were identified, and the effects of a TXA2 agonist on these cells were examined. Radioligand binding using a TXA2 receptor-specific radioligand revealed a single class of binding sites in the thymocytes with an affinity and specificity identical to those reported for the TXA2 receptor. The receptor density in these cells was comparable to that seen in blood platelets. This receptor is most highly expressed in CD4-8- and CD4+8+ immature thymocytes, followed by CD4+8- and CD4-8+ cells. The receptor density in splenic T cells was less than one fifth of that in CD4+8+ cells and no binding activity was detectable in splenic B cells. The addition of a TXA2 agonist, STA2, to thymocytes induced the disappearance of the CD4+8+ cells in a time- and concentration-dependent manner and caused DNA fragmentation. These changes were blocked by a specific TXA2 antagonist, S-145. These results demonstrate that TXA2 induces apoptotic cell death in immature thymocytes by acting on the TXA2 receptor on their cell surface and suggest a role for the TXA2/TXA2 receptor system in the thymic micro-environment.
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Affiliation(s)
- F Ushikubi
- Department of Pharmacology, Kyoto University Faculty of Medicine, Japan
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