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Muscella A, Resta L, Cossa LG, Marsigliante S. Immunolocalization of the AT-1R Ang II Receptor in Human Kidney Cancer. Biomolecules 2023; 13:1181. [PMID: 37627246 PMCID: PMC10452411 DOI: 10.3390/biom13081181] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 06/16/2023] [Accepted: 07/25/2023] [Indexed: 08/27/2023] Open
Abstract
This study aimed to evaluate AT1-R expression in normal and cancerous human kidneys, how these expressions are modified, and AT1-R functionality. AT-1R mRNA expression, determined by real-time PCR, was detected in all samples. AT-1R mRNA increased in well-differentiated cancer (G1, p < 0.01) and decreased 2.9-fold in undifferentiated cancer (G4, p < 0.001) compared with normal kidney tissues. Immunocytochemistry analysis showed that the AT-1R was expressed in the normal tubular epithelium. The glomerulus was also immunoreactive, and as expected, the smooth muscle cells of the vessel walls also expressed the receptor. A total of 35 out of 42 tumors were AT-1R positive, with the cell tumors showing varying numbers of immunoreactive cells, which were stained in a diffuse cytoplasmic and membranous pattern. Computer-assisted counting of the stained tumor cells showed that the number of AT-1R-positive cells increased in the well-differentiated cancers. The functionality of AT-1R was assessed in primary cultures of kidney epithelial cells obtained from three G3 kidney cancer tissues and corresponding histologically proven non-malignant tissue adjacent to the tumor. Indeed, Ang II stimulated, in a dose-dependent manner, the 24 h proliferation of normal kidney cells and cancer cells in the primary culture and phosphorylated extracellular regulated kinases 1 and 2. In conclusion, Ang II may be involved in the growth or function of neoplastic kidney tissue.
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Affiliation(s)
- Antonella Muscella
- Dipartimento di Scienze e Tecnologie Biologiche e Ambientali (Di.S.Te.B.A.), Università del Salento, Via Provinciale per Monteroni, 73100 Lecce, Italy (S.M.)
| | - Leonardo Resta
- Anatomia Patologica, Università di Bari, Piazza Umberto I, 70121 Bari, Italy;
| | - Luca Giulio Cossa
- Dipartimento di Scienze e Tecnologie Biologiche e Ambientali (Di.S.Te.B.A.), Università del Salento, Via Provinciale per Monteroni, 73100 Lecce, Italy (S.M.)
| | - Santo Marsigliante
- Dipartimento di Scienze e Tecnologie Biologiche e Ambientali (Di.S.Te.B.A.), Università del Salento, Via Provinciale per Monteroni, 73100 Lecce, Italy (S.M.)
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2
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Kuo C, Nikan M, Yeh ST, Chappell AE, Tanowitz M, Seth PP, Prakash TP, Mullick AE. Targeted Delivery of Antisense Oligonucleotides Through Angiotensin Type 1 Receptor. Nucleic Acid Ther 2022; 32:300-311. [PMID: 35612431 DOI: 10.1089/nat.2021.0105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We evaluated the potential of AGTR1, the principal receptor for angiotensin II (Ang II) and a member of the G protein-coupled receptor family, for targeted delivery of antisense oligonucleotides (ASOs) in cells and tissues with abundant AGTR1 expression. Ang II peptide ASO conjugates maintained robust AGTR1 signaling and receptor internalization when ASO was placed at the N-terminus of the peptide, but not at C-terminus. Conjugation of Ang II peptide improved ASO potency up to 12- to 17-fold in AGTR1-expressing cells. Additionally, evaluation of Ang II conjugates in cells lacking AGTR1 revealed no enhancement of ASO potency. Ang II peptide conjugation improves potency of ASO in mouse heart, adrenal, and adipose tissues. The data presented in this report add to a growing list of approaches for improving ASO potency in extrahepatic tissues.
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Affiliation(s)
- Carol Kuo
- Ionis Pharmaceuticals, Inc., Carlsbad, California, USA
| | - Mehran Nikan
- Ionis Pharmaceuticals, Inc., Carlsbad, California, USA
| | - Steve T Yeh
- Ionis Pharmaceuticals, Inc., Carlsbad, California, USA
| | | | | | - Punit P Seth
- Ionis Pharmaceuticals, Inc., Carlsbad, California, USA
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3
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Kadam PS, Mueller SC, Ji H, Liu J, Pai AV, Ma J, Speth RC, Sandberg K. Modulation of the rat angiotensin type 1a receptor by an upstream short open reading frame. Peptides 2021; 140:170529. [PMID: 33744369 DOI: 10.1016/j.peptides.2021.170529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 02/23/2021] [Accepted: 03/09/2021] [Indexed: 10/21/2022]
Abstract
The rat angiotensin type 1a receptor (AT1aR) is a peptide hormone G protein-coupled receptor (GPCR) that plays a key role in electrolyte homeostasis and blood pressure control. There is a highly conserved short open reading frame (sORF) in exon 2 (E2) that is downstream from exon 1 (E1) and upstream of the AT1aR coding region located in exon 3 (E3). To determine the role of this E2 sORF in AT1aR signaling, human embryonic kidney-293 (HEK293) cells were transfected with plasmids containing AT1aR cDNA with either an intact or disrupted E2 sORF. The intact sORF attenuated the efficacy of angiotensin (Ang) II (p < 0.001) and sarcosine1,Ile4,Ile8-Ang II (SII), (p < 0.01) to activate AT1aR signaling through extracellular signal-related kinases 1/2 (ERK1/2). A time-course showed agonist-induced AT1aR-mediated ERK1/2 activation was slower in the presence of the intact compared to the disrupted sORF [Ang II: p < 0.01 and SII: p < 0.05]. Ang II-induced ERK1/2 activation was completely inhibited by the protein kinase C (PKC) inhibitor Ro 31-8220 regardless of whether the sORF was intact or disrupted. Flow cytometric analyses suggested the intact sORF improved cell survival; the percentage of live cells increased (p < 0.05) while the percentage of early apoptotic cells decreased (p < 0.01) in cells transfected with the AT1aR plasmid containing the intact sORF. These findings have implications for the regulation of AT1Rs in physiological and pathological conditions and warrant investigation of sORFs in the 5' leader sequence (5'LS) of other GPCRs.
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Affiliation(s)
- Parnika S Kadam
- Department of Biochemistry, Molecular and Cellular Biology, Georgetown University, Washington, DC, United States; Department of Medicine, Georgetown University, Washington, DC, United States
| | - Susette C Mueller
- Department of Oncology, Georgetown University, Washington, DC, United States
| | - Hong Ji
- Department of Medicine, Georgetown University, Washington, DC, United States
| | - Jun Liu
- Department of Medicine, Georgetown University, Washington, DC, United States
| | - Amrita V Pai
- Department of Biochemistry, Molecular and Cellular Biology, Georgetown University, Washington, DC, United States; Department of Medicine, Georgetown University, Washington, DC, United States
| | - Junfeng Ma
- Department of Oncology, Georgetown University, Washington, DC, United States
| | - Robert C Speth
- Department of Pharmacology and Physiology, Georgetown University, Washington, DC, United States; Department of Pharmaceutical Sciences, Nova Southeastern University, Fort Lauderdale, FL, United States
| | - Kathryn Sandberg
- Department of Medicine, Georgetown University, Washington, DC, United States.
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4
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The intracellular angiotensin system buffers deleterious effects of the extracellular paracrine system. Cell Death Dis 2017; 8:e3044. [PMID: 28880266 PMCID: PMC5636983 DOI: 10.1038/cddis.2017.439] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 07/25/2017] [Accepted: 07/31/2017] [Indexed: 12/30/2022]
Abstract
The 'classical' renin-angiotensin system (RAS) is a circulating system that controls blood pressure. Local/paracrine RAS, identified in a variety of tissues, including the brain, is involved in different functions and diseases, and RAS blockers are commonly used in clinical practice. A third type of RAS (intracellular/intracrine RAS) has been observed in some types of cells, including neurons. However, its role is still unknown. The present results indicate that in brain cells the intracellular RAS counteracts the intracellular superoxide/H2O2 and oxidative stress induced by the extracellular/paracrine angiotensin II acting on plasma membrane receptors. Activation of nuclear receptors by intracellular or internalized angiotensin triggers a number of mechanisms that protect the cell, such as an increase in the levels of protective angiotensin type 2 receptors, intracellular angiotensin, PGC-1α and IGF-1/SIRT1. Interestingly, this protective mechanism is altered in isolated nuclei from brains of aged animals. The present results indicate that at least in the brain, AT1 receptor blockers acting only on the extracellular or paracrine RAS may offer better protection of cells.
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5
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Jacques D, Abdel-Karim Abdel-Malak N, Abou Abdallah N, Al-Khoury J, Bkaily G. Difference in the response to angiotensin II between left and right ventricular endocardial endothelial cells. Can J Physiol Pharmacol 2017; 95:1271-1282. [PMID: 28727938 DOI: 10.1139/cjpp-2017-0280] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Previous studies focused on the right ventricular endocardial endothelial cells (EECRs) and showed that angiotensin II (Ang II) induced increase in cytosolic and nuclear calcium via AT1 receptor activation. In the present study, we verified whether the response of left EECs (EECLs) to Ang II is different than that of EECRs. Our results showed that the EC50 of the Ang II-induced increase of cytosolic and nuclear calcium in EECLs was 10× higher (around 2 × 10-13 mol/L) than in EECRs (around 8 × 10-12 mol/L). The densities of both AT1 and AT2 receptors were also higher in EECLs than those previously reported in EECRs. The effect of Ang II was mediated in both cell types via the activation of AT1 receptors. Treatment with Ang II induced a significant increase of cytosolic and nuclear AT1 receptors in EECRs, whereas the opposite was found in EECLs. In both cell types, there was a transient increase of cytosolic and nuclear AT2 receptors following the Ang II treatment. In conclusion, our results showed that both AT1 and AT2 receptors densities are higher in both EECLs compared to what was reported in EECRs. The higher density of AT1 receptors in EECLs compared to REECs may explain, in part, the higher sensitivity of EECLs to Ang II.
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Affiliation(s)
- Danielle Jacques
- Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.,Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Nelly Abdel-Karim Abdel-Malak
- Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.,Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Nadia Abou Abdallah
- Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.,Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Johny Al-Khoury
- Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.,Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Ghassan Bkaily
- Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.,Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
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6
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Morinelli TA, Luttrell LM, Strungs EG, Ullian ME. Angiotensin II receptors and peritoneal dialysis-induced peritoneal fibrosis. Int J Biochem Cell Biol 2016; 77:240-50. [PMID: 27167177 PMCID: PMC5038354 DOI: 10.1016/j.biocel.2016.04.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 04/25/2016] [Accepted: 04/26/2016] [Indexed: 12/22/2022]
Abstract
The vasoactive hormone angiotensin II initiates its major hemodynamic effects through interaction with AT1 receptors, a member of the class of G protein-coupled receptors. Acting through its AT1R, angiotensin II regulates blood pressure and renal salt and water balance. Recent evidence points to additional pathological influences of activation of AT1R, in particular inflammation, fibrosis and atherosclerosis. The transcription factor nuclear factor κB, a key mediator in inflammation and atherosclerosis, can be activated by angiotensin II through a mechanism that may involve arrestin-dependent AT1 receptor internalization. Peritoneal dialysis is a therapeutic modality for treating patients with end-stage kidney disease. The effectiveness of peritoneal dialysis at removing waste from the circulation is compromised over time as a consequence of peritoneal dialysis-induced peritoneal fibrosis. The non-physiological dialysis solution used in peritoneal dialysis, i.e. highly concentrated, hyperosmotic glucose, acidic pH as well as large volumes infused into the peritoneal cavity, contributes to the development of fibrosis. Numerous trials have been conducted altering certain components of the peritoneal dialysis fluid in hopes of preventing or delaying the fibrotic response with limited success. We hypothesize that structural activation of AT1R by hyperosmotic peritoneal dialysis fluid activates the internalization process and subsequent signaling through the transcription factor nuclear factor κB, resulting in the generation of pro-fibrotic/pro-inflammatory mediators producing peritoneal fibrosis.
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Affiliation(s)
- Thomas A Morinelli
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, United States.
| | - Louis M Luttrell
- Division of Endocrinology, Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, United States; Research Service of the Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC 29401, United States
| | - Erik G Strungs
- Division of Endocrinology, Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, United States
| | - Michael E Ullian
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, United States; Research Service of the Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC 29401, United States
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7
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Jiao Y, Yang Q. Downregulation of natriuretic peptide clearance receptor mRNA in vascular smooth muscle cells by angiotensin II. Fundam Clin Pharmacol 2015; 29:260-8. [DOI: 10.1111/fcp.12111] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 02/12/2015] [Accepted: 02/20/2015] [Indexed: 11/29/2022]
Affiliation(s)
- Yuhang Jiao
- Department of Pathogenobiology; College of Basic Medical Sciences; Jilin University; Changchun Jilin 130021 China
| | - Qing Yang
- Department of Pathogenobiology; College of Basic Medical Sciences; Jilin University; Changchun Jilin 130021 China
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8
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Morinelli TA, Walker LP, Velez JCQ, Ullian ME. Clathrin-dependent internalization of the angiotensin II AT₁A receptor links receptor internalization to COX-2 protein expression in rat aortic vascular smooth muscle cells. Eur J Pharmacol 2014; 748:143-8. [PMID: 25542758 DOI: 10.1016/j.ejphar.2014.12.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 12/12/2014] [Accepted: 12/15/2014] [Indexed: 01/14/2023]
Abstract
The major effects of Angiotensin II (AngII) in vascular tissue are mediated by AngII AT1A receptor activation. Certain effects initiated by AT1A receptor activation require receptor internalization. In rat aortic vascular smooth muscle cells (RASMC), AngII stimulates cyclooxygenase 2 protein expression. We have previously shown this is mediated by β-arrestin-dependent receptor internalization and NF-κB activation. In this study, a specific inhibitor of clathrin-mediated endocytosis (CME), pitstop-2, was used to test the hypothesis that clathrin-dependent internalization of activated AT1A receptor mediates NF-κB activation and subsequent cyclooxygenase 2 expression. Radioligand binding assays, real time qt-PCR and immunoblotting were used to document the effects of pitstop-2 on AngII binding and signaling in RASMC. Laser scanning confocal microscopy (LSCM) was used to image pitstop-2׳s effects on AT1 receptor/GFP internalization in HEK-293 cells and p65 NF-κB nuclear localization in RASMC. Pitstop-2 significantly inhibited internalization of AT1A receptor (44.7% ± 3.1% Control vs. 13.2% ± 8.3% Pitstop-2; n=3) as determined by radioligand binding studies in RASMC. Studies utilizing AT1A receptor/GFP expressed in HEK 293 cells and LSCM confirmed these findings. Pitstop-2 significantly inhibited AngII-induced p65 NF-κB phosphorylation and nuclear localization, COX-2 message and protein expression in RASMC without altering activation of p42/44 ERK or TNFα signaling. Pitstop-2, a specific inhibitor of clathrin-mediated endocytosis, confirms that internalization of activated AT1A receptor mediates AngII activation of cyclooxygenase 2 expression in RASMC. These data provide support for additional intracellular signaling pathways activated through β-arrestin mediated internalization of G protein-coupled receptors, such as AT1A receptors.
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Affiliation(s)
- Thomas A Morinelli
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, United States.
| | - Linda P Walker
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, United States
| | - Juan Carlos Q Velez
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, United States; Ralph H. Johnson VA Medical Center, Charleston, SC, United States
| | - Michael E Ullian
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, United States; Ralph H. Johnson VA Medical Center, Charleston, SC, United States
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9
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Czikora I, Feher A, Lucas R, Fulton DJR, Bagi Z. Caveolin-1 prevents sustained angiotensin II-induced resistance artery constriction and obesity-induced high blood pressure. Am J Physiol Heart Circ Physiol 2014; 308:H376-85. [PMID: 25527780 DOI: 10.1152/ajpheart.00649.2014] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The type 1 angiotensin II (ANG II) receptor (AT1R) undergoes internalization following stimulation by ANG II. Internalization reduces cell surface AT1Rs, and it is required for AT1R resensitization. In this process AT1R may interact with caveolin-1 (Cav1), the main scaffolding protein of caveolae. We hypothesized that the interaction between Cav1 and AT1R delays AT1R resensitization and thereby prevents sustained ANG II-induced resistance artery (RA) constriction under normal conditions and in experimental obesity. In rat and mouse skeletal muscle RA (diameter: ∼90-120 μm) ANG II-induced constrictions were reduced upon repeated (30-min apart) administrations. Upon disruption of caveolae with methyl-β-cyclodextrin or in RA of Cav1 knockout mice, repeated ANG II applications resulted in essentially maintained constrictions. In vascular smooth muscle cells, AT1R interacted with Cav1, and the degree of cell surface interactions was reduced by long-term (15-min), but not short-term (2-min), exposure to ANG II. When Cav1 was silenced, the amount of membrane-associated AT1R was significantly reduced by a short-term ANG II exposure. Moreover, Cav1 knockout mice fed a high-fat diet exhibited augmented and sustained RA constriction to ANG II and had elevated systemic blood pressure, when compared with normal or high-fat fed wild-type mice. Thus, Cav1, through a direct interaction, delays internalization and subsequent resensitization of AT1R. We suggest that this mechanism prevents sustained ANG II-induced RA constriction and elevated systemic blood pressure in diet-induced obesity.
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Affiliation(s)
- Istvan Czikora
- Vascular Biology Center, Medical College of Georgia, Georgia Regents University, Augusta, Georgia
| | - Attila Feher
- Vascular Biology Center, Medical College of Georgia, Georgia Regents University, Augusta, Georgia
| | - Rudolf Lucas
- Vascular Biology Center, Medical College of Georgia, Georgia Regents University, Augusta, Georgia
| | - David J R Fulton
- Vascular Biology Center, Medical College of Georgia, Georgia Regents University, Augusta, Georgia
| | - Zsolt Bagi
- Vascular Biology Center, Medical College of Georgia, Georgia Regents University, Augusta, Georgia
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10
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Lu B, Yang XJ, Chen K, Yang DJ, Yan JQ. Dietary sodium deprivation evokes activation of brain regional neurons and down-regulation of angiotensin II type 1 receptor and angiotensin-convertion enzyme mRNA expression. Neuroscience 2009; 164:1303-11. [PMID: 19733634 DOI: 10.1016/j.neuroscience.2009.08.064] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2009] [Revised: 08/27/2009] [Accepted: 08/29/2009] [Indexed: 11/26/2022]
Abstract
Previous studies have indicated that the renin-angiotensin-aldosterone system (RAAS) is implicated in the induction of sodium appetite in rats and that different dietary sodium intakes influence the mRNA expression of central and peripheral RAAS components. To determine whether dietary sodium deprivation activates regional brain neurons related to sodium appetite, and changes their gene expression of RAAS components of rats, the present study examined the c-Fos expression after chronic exposure to low sodium diet, and determined the relationship between plasma and brain angiotensin I (ANG I), angiotensin II (ANG II) and aldosterone (ALD) levels and the sodium ingestive behavior variations, as well as the effects of prolonged dietary sodium deprivation on ANG II type 1 (AT1) and ANG II type 2 (AT2) receptors and angiotensin-convertion enzyme (ACE) mRNA levels in the involved brain regions using the method of real-time polymerase chain reaction (PCR). Results showed that the Fos immunoreactivity (Fos-ir) expression in forebrain areas such as subfornical organ (SFO), paraventricular hypothalamic nuclei (PVN), supraoptic nucleus (SON) and organum vasculosum laminae terminalis (OVLT) all increased significantly and that the levels of ANG I, ANG II and ALD also increased in plasma and forebrain in rats fed with low sodium diet. In contrast, AT1, ACE mRNA in PVN, SON and OVLT decreased significantly in dietary sodium depleted rats, while AT2 mRNA expression did not change in the examined areas. These results suggest that many brain areas are activated by increased levels of plasma and/or brain ANG II and ALD, which underlies the elevated preference for hypertonic salt solution after prolonged exposure to low sodium diet, and that the regional AT1 and ACE mRNA are down-regulated after dietary sodium deprivation, which may be mediated by increased ANG II in plasma and/or brain tissue.
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Affiliation(s)
- B Lu
- Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education, School of Medicine, Xi'an Jiaotong University, 76# W. Yanta Road, Xi'an, 710061, PR China
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11
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Coordination of the secretory compartments via inter-organelle signalling. Semin Cell Dev Biol 2009; 20:801-9. [DOI: 10.1016/j.semcdb.2009.04.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Revised: 04/01/2009] [Accepted: 04/03/2009] [Indexed: 11/18/2022]
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12
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White JG, Cocking-Johnson D, Krumwiede M. Platelet Particle Processing: An Example of Surface Sorting on Single Cells. Platelets 2009; 1:205-11. [DOI: 10.3109/09537109009005490] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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13
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Morinelli TA, Walker LP, Ullian ME. COX-2 expression stimulated by Angiotensin II depends upon AT1 receptor internalization in vascular smooth muscle cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:1048-54. [DOI: 10.1016/j.bbamcr.2008.01.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Revised: 01/03/2008] [Accepted: 01/14/2008] [Indexed: 11/17/2022]
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14
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Li XC, Zhuo JL. Intracellular ANG II directly induces in vitro transcription of TGF-beta1, MCP-1, and NHE-3 mRNAs in isolated rat renal cortical nuclei via activation of nuclear AT1a receptors. Am J Physiol Cell Physiol 2008; 294:C1034-45. [PMID: 18256274 DOI: 10.1152/ajpcell.00432.2007] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The present study tested the hypothesis that intracellular ANG II directly induces transcriptional effects by stimulating AT(1a) receptors in the nucleus of rat renal cortical cells. Intact nuclei were freshly isolated from the rat renal cortex, and transcriptional responses to ANG II were studied using in vitro RNA transcription assays and semiquantitative RT-PCR. High-power phase-contrast micrographs showed that isolated nuclei were encircled by an intact nuclear envelope and stained strongly by the DNA marker 4',6-diamidino-2-phenylindole, but not by the membrane or endosomal markers. Fluorescein isothiocyanate-labeled ANG II and [(125)I]Val(5)-ANG II binding confirmed the presence of ANG II receptors in the nuclei with a predominance of AT(1) receptors. RT-PCR showed that AT(1a) mRNA expression was threefold greater than AT(1b) receptor mRNAs in these nuclei. In freshly isolated nuclei, ANG II increased in vitro [alpha-(32)P]CTP incorporation in a concentration-dependent manner, and the effect was confirmed by autoradiography and RNA electrophoresis. ANG II markedly increased in vitro transcription of mRNAs for transforming growth factor-beta1 by 143% (P < 0.01), macrophage chemoattractant protein-1 by 89% (P < 0.01), and the sodium and hydrogen exchanger-3 by 110% (P < 0.01). These transcriptional effects of ANG II on the nuclei were completely blocked by the AT(1) receptor antagonist losartan (P < 0.01). By contrast, ANG II had no effects on transcription of angiotensinogen and glyceraldehyde-3-phosphate dehydrogenase mRNAs. Because these transcriptional effects of ANG II in isolated nuclei were induced by ANG II in the absence of cell surface receptor-mediated signaling and completely blocked by losartan, we concluded that ANG II may directly stimulate nuclear AT(1a) receptors to induce transcriptional responses that are associated with tubular epithelial sodium transport, cellular growth and hypertrophy, and proinflammatory cytokines.
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Affiliation(s)
- Xiao C Li
- Division of Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital, Detroit, MI 48202, USA
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15
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Singh VP, Le B, Bhat VB, Baker KM, Kumar R. High-glucose-induced regulation of intracellular ANG II synthesis and nuclear redistribution in cardiac myocytes. Am J Physiol Heart Circ Physiol 2007; 293:H939-48. [PMID: 17483239 DOI: 10.1152/ajpheart.00391.2007] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The prevailing paradigm is that cardiac ANG II is synthesized in the extracellular space from components of the circulating and/or local renin-angiotensin system. The recent discovery of intracrine effects of ANG II led us to determine whether ANG II is synthesized intracellularly in neonatal rat ventricular myocytes (NRVM). NRVM, incubated in serum-free medium, were exposed to isoproterenol or high glucose in the absence or presence of candesartan, which was used to prevent angiotensin type 1 (AT1) receptor-mediated internalization of ANG II. ANG II was measured in cell lysates and the culture medium, which represented intra- and extracellularly synthesized ANG II, respectively. Isoproterenol increased ANG II concentration in cell lysates and medium of NRVM in the absence or presence of candesartan. High glucose markedly increased ANG II synthesis only in cell lysates in the absence and presence of candesartan. Western analysis showed increased intracellular levels of angiotensinogen, renin, and chymase in high-glucose-exposed cells. Confocal immunofluorocytometry confirmed the presence of ANG II in the cytoplasm and nucleus of high-glucose-exposed NRVM and along the actin filaments in isoproterenol-exposed cells. ANG II synthesis was dependent on renin and chymase in high-glucose-exposed cells and on renin and angiotensin-converting enzyme in isoproterenol-exposed cells. In summary, the site of ANG II synthesis, intracellular localization, and the synthetic pathway in NRVM are stimulus dependent. Significantly, NRVM synthesized and retained ANG II intracellularly, which redistributed to the nucleus under high-glucose conditions, suggesting a role for an intracrine mechanism in diabetic conditions.
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MESH Headings
- Actin Cytoskeleton/metabolism
- Active Transport, Cell Nucleus
- Angiotensin II/biosynthesis
- Angiotensin II Type 1 Receptor Blockers/pharmacology
- Angiotensinogen/biosynthesis
- Animals
- Animals, Newborn
- Benzimidazoles/pharmacology
- Biphenyl Compounds
- Cell Nucleus/drug effects
- Cell Nucleus/metabolism
- Cells, Cultured
- Chymases/biosynthesis
- Cytoplasm/metabolism
- Dose-Response Relationship, Drug
- Extracellular Space/metabolism
- Glucose/metabolism
- Glucose/pharmacology
- Heart Ventricles/cytology
- Heart Ventricles/metabolism
- Isoproterenol/pharmacology
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/enzymology
- Myocytes, Cardiac/metabolism
- Peptidyl-Dipeptidase A/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptor, Angiotensin, Type 1/metabolism
- Renin/biosynthesis
- Renin-Angiotensin System/drug effects
- Sympathomimetics/pharmacology
- Tetrazoles/pharmacology
- Time Factors
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Affiliation(s)
- Vivek P Singh
- Division of Molecular Cardiology, Cardiovascular Research Institute, Texas A & M Health Science Center, College of Medicine, Temple, TX 76504, USA
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16
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Zhuo JL, Li XC. Novel roles of intracrine angiotensin II and signalling mechanisms in kidney cells. J Renin Angiotensin Aldosterone Syst 2007; 8:23-33. [PMID: 17487823 PMCID: PMC2276849 DOI: 10.3317/jraas.2007.003] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Angiotensin II (Ang II) has powerful sodium-retaining, growth-promoting and pro- inflammatory properties in addition to its physiological role in maintaining body salt and fluid balance and blood pressure homeostasis. Increased circulating and local tissue Ang II is one of the most important factors contributing to the development of sodium and fluid retention, hypertension and target organ damage. The importance of Ang II in the pathogenesis of hypertension and target organ injury is best demonstrated by the effectiveness of angiotensin- converting enzyme (ACE) inhibitors and AT1-receptor antagonists in treating hypertension and progressive renal disease including diabetic nephropathy. The detrimental effects of Ang II are mediated primarily by the AT1-receptor, while the AT2-receptor may oppose the AT1-receptor. The classical view of the AT1-receptor-mediated effects of Ang II is that the agonist binds its receptors at the cell surface, and following receptor phosphorylation, activates downstream signal transduction pathways and intracellular responses. However, evidence is emerging that binding of Ang II to its cell surface AT1-receptors also activates endocytotic (or internalisation) processes that promote trafficking of both the effector and the receptor into intracellular compartments. Whether internalised Ang II has important intracrine and signalling actions is not well understood. The purpose of this article is to review recent advances in Ang II research with focus on the mechanisms underlying high levels of intracellular Ang II in proximal tubule cells and the contribution of receptor-mediated endocytosis of extracellular Ang II. Further attention is devoted to the question whether intracellular and/or internalised Ang II plays a physiological role by activating cytoplasmic or nuclear receptors in proximal tubule cells. This information may aid future development of drugs to prevent and treat Ang II-induced target organ injury in cardiovascular and renal diseases by blocking intracellular and/or nuclear actions of Ang II.
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Affiliation(s)
- Jia L Zhuo
- Laboratory of Receptor and Signal Transduction, Henry Ford Hospital, and Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48202, USA.
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17
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Ruiz E, Redondo S, Padilla E, Gordillo-Moscoso A, Salaices M, Balfagón G, Tejerina T. Importance of intracellular Angiotensin II in vascular smooth muscle cell apoptosis: Inhibition by the Angiotensin AT1 receptor antagonist irbesartan. Eur J Pharmacol 2007; 567:231-9. [PMID: 17509562 DOI: 10.1016/j.ejphar.2007.03.053] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2006] [Revised: 02/28/2007] [Accepted: 03/13/2007] [Indexed: 11/19/2022]
Abstract
The intracellular uptake of Angiotensin II has been described, although its physiological role is not yet understood. We aimed to study the role of Angiotensin II internalization in Angiotensin II-induced apoptosis. Vascular smooth muscle cells were cultured from male Wistar-Kyoto rats and treated with Angiotensin II (1 microM, 48 h). Apoptosis was assessed by DNA fragmentation, cell cytometry and caspase-3 activity. The Angiotensin AT(1) receptor antagonist irbesartan (0.1-10 microM) and the inhibitors of Angiotensin II internalization phenylarsine oxide (PAO, 20 microM), but not the AT(2) receptor antagonist PD123319 (S-(+)-1-[(4-(Dimethylamino)-3-methylphenyl)methyl]-5-(diphenylacetyl)-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid di(trifluoroacetate) salt), decreased Angiotensin II-mediated apoptosis. Pre-treatment with irbesartan, but not with PD123319, blocked Angiotensin II internalization. We found a strong correlation between intracellular Angiotensin II staining and Angiotensin II-induced apoptosis for all compared groups. We therefore conclude that internalization of Angiotensin II is involved in apoptosis of vascular smooth muscle cells induced by this peptide.
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MESH Headings
- Angiotensin II/physiology
- Angiotensin II Type 1 Receptor Blockers/pharmacology
- Animals
- Apoptosis/drug effects
- Apoptosis/physiology
- Arsenicals/pharmacology
- Biphenyl Compounds/pharmacology
- Blotting, Western
- Caspase 3/metabolism
- DNA Fragmentation/drug effects
- Flow Cytometry
- Fluorescent Antibody Technique
- Imidazoles/pharmacology
- Irbesartan
- Male
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Pyridines/pharmacology
- Rats
- Rats, Inbred WKY
- Receptor, Angiotensin, Type 2/drug effects
- Tetrazoles/pharmacology
- Transfection
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Affiliation(s)
- Emilio Ruiz
- Department of Pharmacology, School of Medicine, Universidad Complutense de Madrid, Av. Complutense, s/n. 28040 Madrid, Spain
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18
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Thomas WG, Thekkumkara TJ, Baker KM. Proceedings of the Symposium ‘Angiotensin AT1 Receptors: From Molecular Physiology to Therapeutics’: MOLECULAR MECHANISMS OF ANGIOTENSIN II (AT1a) RECEPTOR ENDOCYTOSIS. Clin Exp Pharmacol Physiol 2007; 23 Suppl 3:S74-80. [DOI: 10.1111/j.1440-1681.1996.tb02817.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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19
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Oliveira L, Costa-Neto CM, Nakaie CR, Schreier S, Shimuta SI, Paiva ACM. The Angiotensin II AT1 Receptor Structure-Activity Correlations in the Light of Rhodopsin Structure. Physiol Rev 2007; 87:565-92. [PMID: 17429042 DOI: 10.1152/physrev.00040.2005] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The most prevalent physiological effects of ANG II, the main product of the renin-angiotensin system, are mediated by the AT1 receptor, a rhodopsin-like AGPCR. Numerous studies of the cardiovascular effects of synthetic peptide analogs allowed a detailed mapping of ANG II's structural requirements for receptor binding and activation, which were complemented by site-directed mutagenesis studies on the AT1 receptor to investigate the role of its structure in ligand binding, signal transduction, phosphorylation, binding to arrestins, internalization, desensitization, tachyphylaxis, and other properties. The knowledge of the high-resolution structure of rhodopsin allowed homology modeling of the AT1 receptor. The models thus built and mutagenesis data indicate that physiological (agonist binding) or constitutive (mutated receptor) activation may involve different degrees of expansion of the receptor's central cavity. Residues in ANG II structure seem to control these conformational changes and to dictate the type of cytosolic event elicited during the activation. 1) Agonist aromatic residues (Phe8 and Tyr4) favor the coupling to G protein, and 2) absence of these residues can favor a mechanism leading directly to receptor internalization via phosphorylation by specific kinases of the receptor's COOH-terminal Ser and Thr residues, arrestin binding, and clathrin-dependent coated-pit vesicles. On the other hand, the NH2-terminal residues of the agonists ANG II and [Sar1]-ANG II were found to bind by two distinct modes to the AT1 receptor extracellular site flanked by the COOH-terminal segments of the EC-3 loop and the NH2-terminal domain. Since the [Sar1]-ligand is the most potent molecule to trigger tachyphylaxis in AT1 receptors, it was suggested that its corresponding binding mode might be associated with this special condition of receptors.
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Affiliation(s)
- Laerte Oliveira
- Department of Biophysics, Escola Paulista de Medicina, Federal University of São Paulo, Brazil.
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20
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Zhang H, Sun GY. Expression and regulation of AT1 receptor in rat lung microvascular endothelial cell. J Surg Res 2006; 134:190-7. [PMID: 16580689 DOI: 10.1016/j.jss.2006.01.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2005] [Revised: 12/27/2005] [Accepted: 01/26/2006] [Indexed: 11/25/2022]
Abstract
BACKGROUND The renin-angiotensin system is thought to be involved in the development and progression of vascular endothelium inflammation, thereby contributing to vascular endothelium injury. To clarify the role of angiotensin II (Ang II) in rat pulmonary microvascular endothelial cells (RPMVECs), we examined the expression and functional significance of angiotensin II (Ang II) receptors in normal and lipopolysacchride (LPS) treated RPMVECs. METHODS The expressions of Ang II type 1(AT(1)) and Ang II type 2 (AT(2)) receptors in cultured RPMVECs were identified by the reverse transcription-polymerase chain reaction (RT-PCR) technique, Western blot and (125)I-labeled [Sar(1),Ile(8)] Ang II binding assays. The RPMVECs were treated with LPS (0.1-100 microg/ml) and Ang II (10(-8)-10(-5) M) for 24 h, respectively. Next, RPMVECs were treated with 10 microg/ml LPS or 10(-7) M Ang II for various times (3, 6, 12, and 24 h). The mRNA and protein levels of, AT(1) and AT(2) receptors, were evaluated at 3, 6, 12, and 24 h, respectively. RESULTS The presence of specific Ang II binding sites in RPMVECs was found by Ang II saturated assays. RT-PCR revealed that only the AT(1) receptor mRNA is presented in RPMVECs. Western blot analysis of the RPMVECs protein extracts showed only one prominent band of the protein at approximately 41 KDa when probed with anti-AT(1) antibody and anti-AT(2) antibody. No AT(2) receptor mRNA and protein was detected. LPS treated cells resulted in an increase in the mRNA and protein levels of AT(1) receptor, whereas, Ang II treated cells showed a decrease in the mRNA and protein levels of AT(1) receptor. CONCLUSIONS We found that primary cultured RPMVECs expressed only AT(1) receptor, but not AT(2) receptor. LPS up-regulated the transcriptional and post-transcriptional expression of AT(1) receptor in RPMVECS; in contrast, Ang II treatment caused a reduction in the mRNA and protein of AT(1) receptor in a time-dependent manner.
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Affiliation(s)
- Hong Zhang
- Department of Respiratory Medicine, Department of Emergency Medicine, First Affiliated Hospital of Anhui Medical University, Anhui, Hefei, China
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21
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Cheung WJ, Kent MAH, El-Shahat E, Wang H, Tan J, White R, Leenen FHH. Central and peripheral renin-angiotensin systems in ouabain-induced hypertension. Am J Physiol Heart Circ Physiol 2006; 291:H624-30. [PMID: 16565308 DOI: 10.1152/ajpheart.01148.2005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chronic subcutaneous infusion of ouabain causes hypertension via central pathways involving angiotensin type 1 (AT(1)) receptor stimulation. The present study assessed plasma and tissue ANG I and II levels as well as AT1 receptor and angiotensin-converting enzyme (ACE) mRNA levels and binding densities by real-time PCR and in vitro autoradiography in relevant brain nuclei and peripheral tissues (heart and kidney) in rats at 1 and/or 2 wk after start of ouabain infusion at 50 microg/day. After 2 wk (but not after 1 wk), blood pressures significantly increased (+15 mmHg). At 2 wk, plasma ANG I and II levels were markedly suppressed by ouabain. In contrast, in the heart and kidneys, ANG I levels were not affected, and ANG II levels tended to decrease, whereas in the hypothalamus ANG II content clearly increased. At 1 wk, no changes in ACE and AT1 receptor densities were seen. After 2 wk, there were significant decreases in AT(1) receptor mRNA and densities in the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO), and paraventricular nucleus (PVN). ACE densities decreased only in the OVLT and SFO, but ACE mRNA showed more variable responses (decrease in OVLT vs. increase in PVN). In the kidneys, at 2 wk both AT1 receptor and ACE densities were decreased, but mRNA abundance did not change. The heart showed no significant changes. The increase in hypothalamic ANG II content and associated decreases in central AT1 receptor and ACE densities support the involvement of the brain renin-angiotensin system in the central hypertensive mechanism of action of ouabain.
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Affiliation(s)
- Warren J Cheung
- Hypertension Unit, Univ. of Ottawa Heart Institute, Ottawa, Ontario, Canada K1Y 4W7
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22
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Pendergrass KD, Averill DB, Ferrario CM, Diz DI, Chappell MC. Differential expression of nuclear AT1 receptors and angiotensin II within the kidney of the male congenic mRen2. Lewis rat. Am J Physiol Renal Physiol 2006; 290:F1497-506. [PMID: 16403834 DOI: 10.1152/ajprenal.00317.2005] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
We established a new congenic model of hypertension, the mRen(2). Lewis rat and assessed the intracellular expression of angiotensin peptides and receptors in the kidney. The congenic strain was established from the backcross of the (mRen2)27 transgenic rat that expresses the mouse renin 2 gene onto the Lewis strain. The 20-wk-old male congenic rats were markedly hypertensive compared with the Lewis controls (systolic blood pressure: 195 +/- 2 vs. 107 +/- 2 mmHg, P < 0.01). Although plasma ANG II levels were not different between strains, circulating levels of ANG-(1-7) were 270% higher and ANG I concentrations were 40% lower in the mRen2. Lewis rats. In contrast, both cortical (CORT) and medullary (MED) ANG II concentrations were 60% higher in the mRen2. Lewis rats, whereas tissue ANG I was 66 and 84% lower in CORT and MED. For both strains, MED ANG II, ANG I, and ANG-(1-7) were significantly higher than CORT levels. Intracellular ANG II binding distinguished nuclear (NUC) and plasma membrane (PM) receptor using the ANG II radioligand 125I-sarthran. Isolated CORT nuclei exhibited a high density (Bmax >200 fmol/mg protein) and affinity for the sarthran ligand (KD<0.5 nM); the majority of these sites (>95%) were the AT1 receptor subtype. CORT ANG II receptor Bmax and KD values in nuclei were 75 and 50% lower, respectively, for the mRen2. Lewis vs. the Lewis rats. In the MED, the PM receptor density (Lewis: 50 +/- 4 vs. mRen2. Lewis: 21 +/- 5 fmol/mg protein) and affinity (Lewis: 0.31 +/- 0.1 vs. 0.69 +/- 0.1 nM) were lower in the mRen2. Lewis rats. In summary, the hypertensive mRen2. Lewis rats exhibit higher ANG II in both CORT and MED regions of the kidney. Evaluation of intracellular ANG II receptors revealed lower CORT NUC and MED PM AT1 sites in the mRen2. Lewis. The downregulation of AT1 sites in the mRen2. Lewis rats may reflect a compensatory response to dampen the elevated levels of intrarenal ANG II.
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Affiliation(s)
- Karl D Pendergrass
- Hypertension and Vascular Disease Ctr., Wake Forest Univ. Health Sciences, Medical Center Blvd., Winston-Salem, NC 27157-1095, USA
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23
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Brismar H, Hua X, Adachi S, Holtbäck U. The role of endocytosis in renal dopamine D1 receptor signaling. Pflugers Arch 2005; 451:793-802. [PMID: 16217657 DOI: 10.1007/s00424-005-1510-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2005] [Revised: 07/09/2005] [Accepted: 08/19/2005] [Indexed: 01/11/2023]
Abstract
Desensitization of G-protein-coupled receptors (GPCR) includes receptor endocytosis. This phenomenon is suggested, at least for some receptors, to be associated with receptor resensitization. Here, we examined the role of receptor endocytosis for two different GPCR, the dopamine-1 (D1) receptor and the beta1-adrenoceptor (beta(1)-AR) in renal tissue. The functional role of receptor endocytosis was examined on Na+, K+ -ATPase activity in microdissected proximal tubules from rat kidney. The spatial regulation of endogenous D1 receptors and beta(1)-AR was examined by confocal microscopy techniques in LLCPK cells. Phenylarsine oxide (PAO) an endocytosis inhibitor, attenuated isoproterenol-induced decrease in Na+, K+ -ATPase activity but had no such effect on dopamine-induced decrease in Na+, K+ -ATPase activity. We have previously shown that isoproterenol sensitizes the renal dopamine system, by recruiting silent D1 receptors from the interior of the cell towards the plasma membrane. This effect was attenuated by PAO as well as by cytochalasin D while these substances had no effect on dopamine-induced D1 receptor recruitment. The beta(1)-AR was localized to the plasma membrane in control cells. Isoproterenol induced a rapid internalization of the beta(1)-AR; which was prevented by PAO. The results suggest that endocytosis of beta(1)-AR in renal proximal tubular cells is an important step in signal generation, while endocytosis of proximal tubular D1 receptor is not.
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Affiliation(s)
- Hjalmar Brismar
- Department of Woman and Child Health, Pediatric Unit, Astrid Lindgren Children's Hospital, Karolinska Institute, 17176 Stockholm, Sweden
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24
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Ullian ME, Gelasco AK, Fitzgibbon WR, Beck CN, Morinelli TA. N-Acetylcysteine Decreases Angiotensin II Receptor Binding in Vascular Smooth Muscle Cells. J Am Soc Nephrol 2005; 16:2346-53. [PMID: 15944340 DOI: 10.1681/asn.2004060458] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Antioxidants seem to inhibit angiotensin II (Ang II) actions by consuming stimulated reactive oxygen species. An alternative hypothesis was investigated: Antioxidants that are also strong reducers of disulfide bonds inhibit the binding of Ang II to its surface receptors with consequent attenuation of signal transduction and cell action. Incubation of cultured vascular smooth muscle cells, which possess Ang II type 1a receptors, with the reducing agent n-acetylcysteine (NAC) for 1 h at 37 degrees C resulted in decreased Ang II radioligand binding in a concentration-dependent pattern. NAC removal restored Ang II binding within 30 min. Incubation with n-acetylserine, a nonreducing analogue of NAC, did not lower Ang II binding, and oxidized NAC was less effective than reduced NAC in lowering Ang II binding. NAC did not decrease Ang II type 1a receptor protein content. Other antioxidants regulated Ang II receptors differently: alpha-Lipoic acid lowered Ang II binding after 24 h, and vitamin E did not lower Ang II binding at all. NAC inhibited Ang II binding in cell membranes at 21 or 37 but not 4 degrees C. Dihydrolipoic acid (the reduced form of alpha-lipoic acid), which contains free sulfhydryl groups as NAC does, decreased Ang II receptor binding in cell membranes, whereas alpha-lipoic acid, which does not contain free sulfhydryl groups, did not. Ang II-stimulated inositol phosphate formation was decreased by preincubation with NAC (1 h) or alpha-lipoic acid (24 h) but not vitamin E. In conclusion, certain antioxidants that are reducing agents lower Ang II receptor binding, and Ang II-stimulated signal transduction is decreased in proportion to decreased receptor binding.
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Affiliation(s)
- Michael E Ullian
- Medical University of South Carolina, Division of Nephrology, CSB 829, 96 Jonathan Lucas Street, P.O. Box 250623, Charleston, SC 29425, USA.
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25
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Pfab T, Stoltenburg-Didinger G, Trautner C, Godes M, Bauer C, Hocher B. The endothelin system in Morris hepatoma-7777: an endothelin receptor antagonist inhibits growth in vitro and in vivo. Br J Pharmacol 2003; 141:215-22. [PMID: 14662722 PMCID: PMC1574189 DOI: 10.1038/sj.bjp.0705601] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. Plasma concentrations of endothelin are increased in patients with hepatocellular cancer as well as in patients with liver metastasis. However, the impact of these findings remains uncertain. 2. We thus analyzed the endothelin system in a rat hepatoma model (Morris hepatoma 7777) in vitro and in vivo. 3. Our study revealed that tissue concentrations of endothelin-1 (ET-1) and big-ET-1, the precursor of ET-1, were significantly elevated in Morris hepatoma 7777 as compared to normal liver. The ETA receptor density was significantly elevated, whereas the density of the ETB receptor was decreased in Morris hepatoma 7777. 4. We could also demonstrate that hepatoma cells secrete ET-1. 5. Exogenously added ET-1 enhances hepatoma cell growth in a dose-dependent manner. Endothelin receptor antagonists (ETA and combined ETA/ETB receptor antagonists) inhibit tumor cell growth in vitro. Since the combined ETA/ETB receptor antagonist was more effective in vitro, we used this compound also for in vivo studies and could demonstrate that a combined ETA/ETB receptor antagonist is able to reduce hepatoma growth in vivo. 6. In conclusion, the endothelin system is activated in Morris hepatoma 7777 and contributes to hepatoma growth. Since endothelin receptor antagonists are well-tolerated upcoming clinically used drugs without major side effects, our data might provide a new pharmacological approach to reduce hepatoma growth in vivo.
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Affiliation(s)
- Thiemo Pfab
- Center for Cardiovascular Research (CCR)/Department of Nephrology, Medical School Charité, Humboldt University of Berlin, Germany
| | | | - Christoph Trautner
- Fachhochschule, Department of Health Care, Braunschweig/Wolfenbüttel, Germany
| | - Michael Godes
- Center for Cardiovascular Research (CCR)/Department of Nephrology, Medical School Charité, Humboldt University of Berlin, Germany
| | - Christian Bauer
- Institute of Molecular Biology and Biochemistry, Free University of Berlin, Germany
| | - Berthold Hocher
- Center for Cardiovascular Research (CCR)/Department of Nephrology, Medical School Charité, Humboldt University of Berlin, Germany
- Author for correspondence:
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26
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Calegari VC, Bezerra RMN, Torsoni MA, Torsoni AS, Franchini KG, Saad MJA, Velloso LA. Suppressor of cytokine signaling 3 is induced by angiotensin II in heart and isolated cardiomyocytes, and participates in desensitization. Endocrinology 2003; 144:4586-96. [PMID: 12960061 DOI: 10.1210/en.2003-0046] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Angiotensin II (Ang II) exerts a potent growth stimulus on the heart and vascular wall. Activation of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) intracellular signaling pathway by Ang II mediates at least some of the mitogenic responses to this hormone. In other signaling systems that use the JAK/STAT pathway, proteins of the suppressor of cytokine signaling (SOCS) family participate in signal regulation. In the present study it is demonstrated that SOCS3 is constitutively expressed at a low level in rat heart and neonatal rat ventricular myocytes. Ang II at a physiological concentration enhances the expression of SOCS3 mRNA and protein, mainly via AT1 receptors. After induction, SOCS3 associates with JAK2 and impairs further activation of the JAK2/STAT1 pathway. Pretreatment of rats with a specific phosphorthioate antisense oligonucleotide to SOCS3, reverses the desensitization to angiotensin signaling, as detected by a fall in c-Jun expression after repetitive infusions of the hormone. Thus, SOCS3 is induced by Ang II in rat heart and neonatal rat ventricular myocytes and participates in the modulation of the signal generated by this hormone.
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Affiliation(s)
- Vivian C Calegari
- Department of Internal Medicine, State University of Campinas, 13084 970 Campinas SP, Brazil
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27
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Seta K, Sadoshima J. Phosphorylation of tyrosine 319 of the angiotensin II type 1 receptor mediates angiotensin II-induced trans-activation of the epidermal growth factor receptor. J Biol Chem 2003; 278:9019-26. [PMID: 12522132 DOI: 10.1074/jbc.m208017200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although tyrosine kinases are critically involved in the angiotensin II (Ang II) type 1 (AT1) receptor signaling, how AT1 receptors activate tyrosine kinases is not fully understood. We examined the structural requirements of the AT1 receptor for transactivation of the epidermal growth factor (EGF) receptor (EGFR). Studies using carboxyl terminal-truncated AT1 receptors indicated that the amino acid sequence between 312 and 337 is required for activation of EGFR. The role of the conserved YIPP motif in this sequence in transactivation of EGFR was investigated by mutating tyrosine 319. Ang II failed to activate EGFR in cells expressing AT1-Y319F, whereas EGFR was activated even without Ang II in cells expressing AT1-Y319E, which mimics the AT1 receptor phosphorylated at Tyr-319. Immunoblot analyses using anti-phospho Tyr-319-specific antibody showed that Ang II increased phosphorylation of Tyr-319. EGFR interacted with the AT1 receptor but not with AT1-Y319F in response to Ang II stimulation, whereas the EGFR-AT1 receptor interaction was inhibited in the presence of dominant negative SHP-2. The requirement of Tyr-319 seems specific for EGFR because Ang II-induced activation of other tyrosine kinases, including Src and JAK2, was preserved in cells expressing AT1-Y319F. Extracellular signal-regulated kinase activation was also maintained in AT1-Y319F through activation of Src. Overexpression of wild type AT1 receptor in cardiac fibroblasts enhanced Ang II-induced proliferation. By contrast, overexpression of AT1-Y319F failed to enhance cell proliferation. In summary, Tyr-319 of the AT1 receptor is phosphorylated in response to Ang II and plays a key role in mediating Ang II-induced transactivation of EGFR and cell proliferation, possibly through its interaction with SHP-2 and EGFR.
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MESH Headings
- Amino Acid Motifs
- Amino Acid Sequence
- Animals
- COS Cells
- Calcium/metabolism
- Cell Division
- Cells, Cultured
- Conserved Sequence
- DNA, Complementary/metabolism
- ErbB Receptors/metabolism
- Fibroblasts/metabolism
- Genes, Dominant
- Humans
- Immunoblotting
- Intracellular Signaling Peptides and Proteins
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Mutation
- Myocardium/cytology
- Phosphorylation
- Plasmids/metabolism
- Precipitin Tests
- Protein Binding
- Protein Structure, Tertiary
- Protein Tyrosine Phosphatase, Non-Receptor Type 1
- Protein Tyrosine Phosphatase, Non-Receptor Type 11
- Protein Tyrosine Phosphatases/metabolism
- Protein-Tyrosine Kinases/metabolism
- Rats
- Rats, Wistar
- Receptor, Angiotensin, Type 1
- Receptors, Angiotensin/chemistry
- Receptors, Angiotensin/metabolism
- Sequence Homology, Amino Acid
- Time Factors
- Transcriptional Activation
- Transfection
- Tyrosine/chemistry
- Tyrosine/metabolism
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Affiliation(s)
- Koichi Seta
- Cardiovascular Research Institute, Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey 07103, USA
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28
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Chen R, Huang C, Morinelli TA, Trojanowska M, Paul RV. Blockade of the effects of TGF-beta1 on mesangial cells by overexpression of Smad7. J Am Soc Nephrol 2002; 13:887-893. [PMID: 11912247 DOI: 10.1681/asn.v134887] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Smad7, a protein induced by transforming growth factor-beta1 (TGF-beta1) in many target cells, inhibits TGF-beta1 signal transduction and is thought to mediate an intracellular negative feedback response that limits TGF-beta1 effects. It is possible that overexpression of Smad7 could block specified effects of TGF-beta1 on mesangial cells, a TGF-beta target in glomerular disease. Smad7 mRNA was induced by TGF-beta1 within 1 h in a concentration-dependent manner in a transformed mouse mesangial cell (MMC) line. Uptake of (14)C-spermidine from the medium by MMC and the transcriptional activity of a segment of the human collagen pro-alpha2 type 1 chain (COL1A2) promoter fused to a luciferase reporter gene were used as indices of TGF-beta1. Treatment with TGF-beta1 increased (14)C-spermidine uptake rate in a time-, concentration-, and temperature-dependent manner. For example, exposure to 1 ng/ml TGF-beta1 for 15 h increased uptake approximately twofold, a response that was attenuated by cycloheximide. Transfection of Smad7 expression vector into MMC abrogated both TGF-beta1-dependent stimulation of spermidine uptake and COL1A2 promoter activity. It is concluded that: (1) TGF-beta1 induces Smad7 in MMC; (2) (14)C-spermidine uptake is a convenient quantitative index of TGF-beta1 effect in these cells; and (3) overexpression of Smad7 is a highly effective method of blocking at least some mesangial cell effects of TGF-beta1 that may warrant evaluation in vivo in experimental glomerular disease.
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Affiliation(s)
- Ruihua Chen
- *Departments of Medicine and Microbiology and Immunology, Medical University of South Carolina, Charleston, South Carolina; and Medical Specialty Service, Ralph H. Johnson VA Medical Center, Charleston, South Carolina
| | - Cancan Huang
- *Departments of Medicine and Microbiology and Immunology, Medical University of South Carolina, Charleston, South Carolina; and Medical Specialty Service, Ralph H. Johnson VA Medical Center, Charleston, South Carolina
| | - Thomas A Morinelli
- *Departments of Medicine and Microbiology and Immunology, Medical University of South Carolina, Charleston, South Carolina; and Medical Specialty Service, Ralph H. Johnson VA Medical Center, Charleston, South Carolina
| | - Maria Trojanowska
- *Departments of Medicine and Microbiology and Immunology, Medical University of South Carolina, Charleston, South Carolina; and Medical Specialty Service, Ralph H. Johnson VA Medical Center, Charleston, South Carolina
| | - Richard V Paul
- *Departments of Medicine and Microbiology and Immunology, Medical University of South Carolina, Charleston, South Carolina; and Medical Specialty Service, Ralph H. Johnson VA Medical Center, Charleston, South Carolina
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29
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Seta K, Nanamori M, Modrall JG, Neubig RR, Sadoshima J. AT1 receptor mutant lacking heterotrimeric G protein coupling activates the Src-Ras-ERK pathway without nuclear translocation of ERKs. J Biol Chem 2002; 277:9268-77. [PMID: 11777928 DOI: 10.1074/jbc.m109221200] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Angiotensin II (Ang II) type 1 receptors (AT1Rs) activate tyrosine kinases, including Src. Whether or not tyrosine kinase activation by AT1R occurs independently of heterotrimeric G protein coupling and, if so, the cellular function of such a mechanism are unknown. To address these questions, we used an AT1aR intracellular second loop mutant, which lacks heterotrimeric G protein coupling (AT1a-i2m). Surprisingly, Ang II-induced Src activation was preserved in AT1a-i2m, which was not attenuated by inhibiting protein kinase C and Ca(2+) or by inhibiting Galpha(i) or Galpha(q) in CHO-K1 cells. By contrast, Ang II-induced Src activation was abolished in a C-terminally truncated AT1a-(1--309), where Ang II-induced inositol phosphate response was preserved. Ang II activates ERKs via a Src-Ras-dependent mechanism in AT1a-i2m. ERKs activated by AT1a-i2m phosphorylate their cytoplasmic targets, including p90(RSK), but fail to translocate into the nucleus or to cause cell proliferation. Ang II-induced nuclear translocation of ERKs by wild type AT1aR was inhibited by overexpression of nuclear exportin Crm-1, while that by AT1a-i2m was restored by leptomycin B, an inhibitor of Crm-1. In summary, while Src and ERKs are activated by Ang II even without heterotrimeric G protein coupling, the carboxyl terminus of the AT1 receptor is required for activation of Src. Interestingly, ERKs activated by heterotrimeric G protein-independent mechanisms fail to phosphorylate nuclear targets due to lack of inhibition of Crm-1-induced nuclear export of ERKs. These results suggest that heterotrimeric G protein-dependent and -independent signaling mechanisms play distinct roles in Ang II-mediated cellular responses.
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Affiliation(s)
- Koichi Seta
- Cardiovascular Research Institute, Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey 07103, USA
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30
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Eto K, Ohya Y, Nakamura Y, Abe I, Iida M. Intracellular angiotensin II stimulates voltage-operated Ca(2+) channels in arterial myocytes. Hypertension 2002; 39:474-8. [PMID: 11882593 DOI: 10.1161/hy02t2.102961] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Although the presence of intracellular angiotensin II (Ang II) and of Ang II-binding sites has been reported, their roles in cell function have not been fully clarified. The purpose of the present study was to test the hypothesis that intracellular Ang II modifies voltage-operated Ca(2+) channels in vascular smooth muscle. Ca(2+) channel currents were recorded in guinea pig mesenteric arterial myocytes with the whole-cell patch-clamp method. Intracellular dialysis of Ang II increased the amplitudes of Ca(2+) channel current (133 +/- 9% of the control with 10 nmol/L Ang II, n=16). Concomitant dialysis of the Ang II type 1 receptor antagonist, CV-11974 (1 micromol/L, n=11), but not the bath application of this drug, suppressed this Ang II action. In contrast, the dialysis of the Ang II type 2 receptor antagonist, PD123319 (1 micromol/L, n=5), failed to affect the Ang II action. Dialysis of either a phospholipase C inhibitor (U-73122, 10 micromol/L, n=5) or protein kinase C inhibitors (calphostin C, 100 nmol/L, n=5; protein kinase C inhibitor peptide-[19-36], 1 micromol/L, n=5) suppressed the Ang II action. Dialysis of KT5720 (100 nmol/L, n=5), an inhibitor of cAMP-dependent protein kinase, did not affect the Ang II action. Intracellular dialysis of angiotensin I (10 nmol/L) enhanced Ca(2+) channel currents (13 3 +/- 8%, n=6), which were sensitive to intracellular enalaprilat (1 micromol/L, n=5) or CV-11974 (n=5). These results suggest that intracellular Ang II has a stimulating action on voltage-operated Ca(2+) channels in vascular smooth muscle, possibly through intracellular binding sites similar to the Ang II type 1 receptor, which are associated with phospholipase C and protein kinase C.
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Affiliation(s)
- Kimika Eto
- Department of Medicine and Clinical Science, Kyushu University, Graduate School of Medical Sciences, Fukuoka, Japan
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31
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Abstract
To differentiate the relative effects of nuclear and cell surface angiotensin II (Ang II) receptors, we mutated the angiotensinogen cDNA by removing the signal sequence-encoding region to produce a nonsecreted form of angiotensinogen [Ang(-S)Exp]. Rat hepatoma cells (which produce renin and angiotensin-converting enzyme mRNAs) were stably transfected with Ang(-S)Exp/pSVL (or a corresponding control) expression plasmid, and mitotic indices were measured for stably transfected cell lines. Experimental clonal cell lines demonstrate an average of 33+/-4.4% (P<0.001) increase in percentage-labeled nuclei compared with control cell lines. The mitogenic effect is blocked by 10(-6) mol/L losartan and by 1 micromol/L renin antisense phosphorothioate oligomers but not by 10(-6) mol/L candesartan. In addition, phenylarsine oxide, which blocks angiotensin receptor internalization, abolishes the losartan inhibitory effect, suggesting that after cell-surface receptor-mediated endocytosis, losartan blocks Ang II nuclear receptors. PDGF mRNA levels are elevated 2.2-fold in Ang(-S)Exp transfected cell lines; addition of anti-PDGF antibodies to the culture medium partially blocks the mitogenic effect of Ang(-S)Exp, while anti-Ang II antibodies have no effect. These results suggest that the Ang(-S)Exp growth effect is due, in part, to autocrine/paracrine stimulation by secreted PDGF after Ang II/Ang II receptor intracellular interactions. We further demonstrate that these cells produce the alternative renin transcript, renin 1A, which apparently lacks a signal sequence and is maintained intracellularly. Collectively, these studies of cultured cells suggest that some cell types may possess components of the renin-angiotensin system that permit intracellular processing of angiotensinogen to Ang II and that Ang II generated intracellularly may be mitogenic.
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Affiliation(s)
- J L Cook
- Division of Research, Ochsner Clinic Foundation, New Orleans, LA, USA.
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32
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Filipeanu CM, Henning RH, Nelemans SA, de Zeeuw D. Intracellular angiotensin II: from myth to reality? J Renin Angiotensin Aldosterone Syst 2001; 2:219-26. [PMID: 11881127 DOI: 10.3317/jraas.2001.035] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Affiliation(s)
- C M Filipeanu
- Department of Clinical Pharmacology, University of Groningen, The Netherlands
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33
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Fryer JN, Burns KD, Ghorbani M, Levine DZ. Effect of potassium depletion on proximal tubule AT1 receptor localization in normal and remnant rat kidney. Kidney Int 2001; 60:1792-9. [PMID: 11703597 DOI: 10.1046/j.1523-1755.2001.00992.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Since both potassium depletion and renal ablation result in proximal tubule hypertrophy and the angiotensin II type 1 (AT1) receptor has been localized in rat proximal tubules, we explored the possibility that the AT1 receptor intracellular distribution is modulated by potassium depletion in proximal tubular cells of 5/6 nephrectomized (Nx) rats. METHODS Four groups of rats were studied: sham operated, potassium-depleted sham-operated rats, 5/6 Nx rats two weeks postsurgery, and potassium-depleted 5/6 Nx rats two weeks postsurgery. After the morphometry of proximal tubular cells was defined, by using immmunogold electron microscopy techniques the subcellular distribution of AT1 receptors were visualized and quantitated. RESULTS Hypertrophy of proximal tubule cells due to both 5/6 Nx and potassium depletion was documented. Furthermore, to our knowledge for the first time, the results showed that in potassium depletion, with and without superimposed 5/6 Nx, the AT1 receptor density in proximal tubular cells was dramatically enhanced in the apical membrane, the basal membrane, and in nuclei. CONCLUSION In normal rats and those subjected to renal ablation, these immunocytochemical data provide intracellular proximal tubule AT1 receptor localization and demonstrate loci of increased receptor density after potassium depletion.
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Affiliation(s)
- J N Fryer
- Department of Cellular and Molecular Medicine, Kidney Research Centre of the Ottawa Health Research Institute, University of Ottawa, Ottawa, Ontario, Canada
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34
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Modrall JG, Nanamori M, Sadoshima J, Barnhart DC, Stanley JC, Neubig RR. ANG II type 1 receptor downregulation does not require receptor endocytosis or G protein coupling. Am J Physiol Cell Physiol 2001; 281:C801-9. [PMID: 11502557 DOI: 10.1152/ajpcell.2001.281.3.c801] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
ANG II type 1 (AT(1)) receptors respond to sustained exposure to ANG II by undergoing downregulation of absolute receptor numbers. It has been assumed previously that downregulation involves endocytosis. The present study hypothesized that AT(1) receptor downregulation occurs independently of receptor endocytosis or G protein coupling. Mutant AT(1) receptors with carboxy-terminal deletions internalized <5% of radioligand compared with 65% for wild-type AT(1) receptors. The truncated AT(1) receptors retained the ability to undergo downregulation. These data suggest the existence of an alternative pathway to AT(1) receptor degradation that does not require endocytosis, per se. Point mutations in either the second transmembrane region or second intracellular loop impaired G protein (G(q)) coupling. These receptors exhibited a biphasic pattern of downregulation. The earliest phase of downregulation (0-2 h) was independent of coupling to G(q), but no additional downregulation was observed after 2 h of ANG II exposure in the receptors with impaired coupling to G(q). These data suggest that coupling to G(q) is required for the later phase (2-24 h) of AT(1) receptor downregulation.
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Affiliation(s)
- J G Modrall
- Department of Surgery, Dallas Veterans Affairs Medical Center and the University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA.
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35
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Merjan AJ, Kanashiro CA, Krieger JE, Han SW, Paiva AC. Ligand-induced endocytosis and nuclear localization of angiotensin II receptors expressed in CHO cells. Braz J Med Biol Res 2001; 34:1175-83. [PMID: 11514842 DOI: 10.1590/s0100-879x2001000900011] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A construct (AT1R-NF) containing a "Flag" sequence added to the N-terminus of the rat AT1 receptor was stably expressed in Chinese hamster ovary cells and quantified in the cell membrane by confocal microscopy after reaction with a fluorescein-labeled anti-Flag monoclonal antibody. Angiotensin II bound to AT1R-NF and induced endocytosis with a half-time of 2 min. After 60-90 min, fluorescence accumulated around the cell nucleus, suggesting migration of the ligand-receptor complex to the nuclear membrane. Angiotensin antagonists also induced endocytosis, suggesting that a common step in the transduction signal mechanism occurring after ligand binding may be responsible for the ligand-receptor complex internalization.
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Affiliation(s)
- A J Merjan
- Departamento de Biofísica, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brasil
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36
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Jerez S, Bruno MPD, Coviello A. Endothelium-dependent desensitization to angiotensin II in rabbit aorta: the mechanisms involved. Can J Physiol Pharmacol 2001. [DOI: 10.1139/y01-015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to characterize the role of the endothelium in angiotensin II-desensitization and its mechanisms of action. Rabbit aortic rings were exposed to increasing doses of angiotensin II (Ang II, 109 to 2.5 × 106) to generate two cumulative dose-response curves (CDRC I and II). A 50-min interval separated CDRC I and II. Desensitization was observed at all doses in unrubbed aortic tissue and at lower doses in rubbed aortic tissue. Tachyphylaxis was greater in arteries with endothelium. Treatment of intact rings with L-NG-nitroarginine methyl ester (L-NAME, 104 M) did not prevent this phenomenon. However, indomethacin (105 M) and miconazol (106 M) attenuated Ang II-desensitization. Treatment of unrubbed rings with nifedipine (106 M) and cromakalim (106 M) inhibited the effect of indomethacin. To confirm the involvement of K+ channels, unrubbed and rubbed aortic rings were treated with the KCa2+ blockers apamin (107 M), tetraethylammonium (TEA, 103 M), and iberiotoxin (108 M), and the KATP blocker glibenclamide (105 M). In both arteries apamin, TEA, and glibenclamide abolished the tachyphylaxis without changes in the maximal response. Iberiotoxin diminished Ang II-desensitization in rubbed but not unrubbed arteries. Results from this study suggest that Ang II-desensitization involves endothelium-dependent and -independent mechanisms. Endothelium-dependent desensitization could be mediated by a cyclooxygenase-cytochrome P450 product, which could act by increasing KCa2+ channel activity.Key words: angiotensin II, rabbit aorta, desensitization, endothelium, cyclooxygenase products.
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37
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Fierensa FL, Vanderheyden PM, Roggeman C, De Backer J, Thekkumkara TJ, Vauquelin G. Tight binding of the angiotensin AT(1) receptor antagonist. Biochem Pharmacol 2001; 61:1227-35. [PMID: 11322926 DOI: 10.1016/s0006-2952(01)00614-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Angiotensin II induces angiotensin AT(1) receptor internalization via Clathrin coated pits formation. We investigated whether insurmountable inhibition by the non-peptide antagonist 2-ethoxy-1-[(2'-(1H-tetrazol-5-yl) biphenyl-4-yl) methyl]-1H-benzimidazoline-7-carboxylic acid (candesartan) was related to receptor internalization. Mild acid treatment can discriminate between internalized and cell surface bound [(3)H]angiotensin II. In contrast, it provides no information about the subcellular localization of bound [(3)H]candesartan since this binding is acid resistant. The internalization of [(3)H]angiotensin II is rapidly inhibited in the presence of 0.4 M sucrose. Yet, no such rapid effect was noticed for [(3)H]candesartan. [(3)H]candesartan displays insurmountable/long lasting binding to the vast majority of both wild type and L(314) truncated rat angiotensin AT(1A) receptors with impaired receptor internalization. In agreement with previously published AT(1) angiotensin receptor visualization experiments, the present data suggest that non-peptide antagonist-angiotensin AT(1) receptor complexes remain at the cell surface. Insurmountable antagonism of candesartan is therefore independent from receptor internalization via clathrin-coated pits.
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Affiliation(s)
- F L Fierensa
- Department of Molecular and Biochemical Pharmacology, Institute for Molecular Biology, Free University of Brussels, Paardenstraat 65, B-1640, Sint-Genesius Rode, Belgium.
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38
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Schubert B, Fassnacht M, Beuschlein F, Zenkert S, Allolio B, Reincke M. Angiotensin II type 1 receptor and ACTH receptor expression in human adrenocortical neoplasms. Clin Endocrinol (Oxf) 2001; 54:627-32. [PMID: 11380493 DOI: 10.1046/j.1365-2265.2001.01253.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Type 1 angiotensin II (Ang II) receptors transduce most of the known actions of Ang II, including steroidogenesis and trophic actions on the adrenal cortex. We investigated the type 1 Ang II receptor expression in adrenocortical tissues to define its regulation in adrenocortical neoplasms and to compare its expression with that of the ACTH receptor (ACTH-R). PATIENTS AND MEASUREMENTS Poly A RNA was extracted from tumour tissue and electrophoresed through a 1.0% agarose gel, blotted and hybridized with alpha32P-CTP labelled PCR generated type 1 Ang II receptor cDNA probe. Receptor autoradiography was performed on slices from normal adrenals and tumour tissue by incubation with 125I-Sar1, Ile8-Ang II with and without pretreatment with cold Ang II or with the selective type 1 receptor antagonist losartan. RESULTS Ang II type 1 receptor mRNA was high in cortisol producing (CPA; n = 5) and aldosterone producing (APA; n = 4) adenomas (normal adrenals 100 +/- 12% vs. 180 +/- 16% in CPA and 154 +/- 26% in APA, mean +/- SEM), but was low in nonfunctioning adenomas (NFA; n = 2; 2 +/- 1%). ACTH receptor mRNA followed a similar pattern (CPA 178 +/- 17, APA 196 +/- 30, NFA 0%, carcinomas 56 +/- 11%) with a good correlation between Ang II type 1 receptor and ACTH-R mRNA of r = 0.692, P = 0.0019. Receptor autoradiography in normal adrenals demonstrated Ang II type 1 receptors predominantly in the zona glomerulosa. In tumour tissue, mainly type 1 receptor expression was found confirming the Northern blot data. CONCLUSIONS Angiotensin II type 1 receptor and ACTH receptor expression seems to be correlated with the functional status of adrenocortical tumours, suggesting regulation by similar factors. The predominant receptor expressed in adrenocortical tumours is the Angiotensin II type 1 receptor whereas type 2 receptor expression is minimal.
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MESH Headings
- Adenoma/chemistry
- Adenoma/metabolism
- Adolescent
- Adrenal Cortex Neoplasms/chemistry
- Adrenal Cortex Neoplasms/metabolism
- Adult
- Aged
- Aldosterone/metabolism
- Autoradiography
- Blotting, Northern
- Female
- Humans
- Hydrocortisone/metabolism
- Male
- Middle Aged
- RNA, Messenger/analysis
- Receptor, Angiotensin, Type 1
- Receptor, Angiotensin, Type 2
- Receptors, Angiotensin/genetics
- Receptors, Angiotensin/metabolism
- Receptors, Corticotropin/genetics
- Receptors, Corticotropin/metabolism
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Affiliation(s)
- B Schubert
- Schwerpunkt Endokrinologie, Department of Medicine, University of Würzburg, Germany
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39
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Fujimoto Y, Sasaki T, Tsuchida A, Chayama K. Angiotensin II type 1 receptor expression in human pancreatic cancer and growth inhibition by angiotensin II type 1 receptor antagonist. FEBS Lett 2001; 495:197-200. [PMID: 11334891 DOI: 10.1016/s0014-5793(01)02377-8] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We investigated the expression of angiotensin II type 1 receptor (AT1) in pancreatic cancer. Both AT1 mRNA and protein were expressed in human pancreatic cancer tissues and cell lines. Binding assays showed that pancreatic cancer cells have specific binding sites for angiotensin II and that binding could be eliminated by treatment with a selective AT1 antagonist in a dose-dependent fashion. Surprisingly, the growth of cancer cells was significantly suppressed by treatment with antagonist, also in a dose-dependent manner. These observations suggest AT1 plays an important role in pancreatic cancer growth. Furthermore, ligand-induced inhibition of AT1 may be a useful therapeutic strategy.
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MESH Headings
- Angiotensin II/metabolism
- Angiotensin Receptor Antagonists
- Cell Division/drug effects
- Dose-Response Relationship, Drug
- Humans
- Imidazoles/pharmacology
- Pancreatic Neoplasms/genetics
- Pancreatic Neoplasms/metabolism
- Pancreatic Neoplasms/pathology
- RNA, Messenger/biosynthesis
- Receptor, Angiotensin, Type 1
- Receptor, Angiotensin, Type 2
- Receptors, Angiotensin/biosynthesis
- Receptors, Angiotensin/genetics
- Tetrazoles/pharmacology
- Transcription, Genetic
- Tumor Cells, Cultured
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Affiliation(s)
- Y Fujimoto
- First Department of Internal Medicine, Hiroshima University School of Medicine, 1-2-3 Kasumi, Minami-ku, 734-8551, Hiroshima, Japan
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40
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Moellenhoff E, Blume A, Culman J, Chatterjee B, Herdegen T, Lebrun CJ, Unger T. Effect of repetitive icv injections of ANG II on c-Fos and AT(1)-receptor expression in the rat brain. Am J Physiol Regul Integr Comp Physiol 2001; 280:R1095-104. [PMID: 11247832 DOI: 10.1152/ajpregu.2001.280.4.r1095] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
ANG II has been implicated in neuroplastic processes via stimulation of inducible transcription factors (ITF) in the brain. In the present study, we investigated the effects of acute vs. repetitive once daily intracerebroventricular injections of ANG II for 7 days on the expression of ITF and constitutive transcription factor (CTF) and the AT1 receptor in the median preoptic area (MnPO), the subfornical organ (SFO), and the hypothalamic paraventricular (PVN) and supraoptic nuclei (SON). After repetitive injections, the expression of c-Fos declined by approximately 50% in MnPO, SFO, PVN, and SON compared with controls injected once. The desensitization of c-Fos occurred on the transcriptional level as shown in the SON by RT-PCR. Apart from a novel expression of c-Jun in the SON, the ITF c-Jun, JunB, JunD, and Krox-24 did not change after repetitive stimulation. Neither were the CTF, calcium response element binding protein, activating transcription factor 2, and serum response factor altered after repetitive vs. single injections of ANG II. The AT1 receptor was coexpressed with c-Fos/c-Jun. Immunohistochemical stainings suggest an increase in AT1-receptor number in MnPO, SFO, PVN, and SON on chronic stimulation compared with once-injected controls. These findings demonstrate that repetitive periventricular stimulation with ANG II essentially alters the expression of transcription factors compared with acute stimulation and suggest c-Fos and c-Jun as major intermediates of the AT1-receptor transcription.
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MESH Headings
- Activating Transcription Factor 2
- Angiotensin II/administration & dosage
- Angiotensin II/pharmacology
- Animals
- Brain/drug effects
- Brain/physiology
- Cerebral Ventricles/drug effects
- Cerebral Ventricles/physiology
- Cyclic AMP Response Element-Binding Protein/metabolism
- DNA-Binding Proteins/metabolism
- Drosophila Proteins
- Drug Administration Schedule
- Genes, fos/drug effects
- Genes, jun/drug effects
- Injections, Intraventricular
- Male
- Membrane Proteins/metabolism
- Nuclear Proteins/metabolism
- Organ Specificity
- Paraventricular Hypothalamic Nucleus/drug effects
- Paraventricular Hypothalamic Nucleus/physiology
- Preoptic Area/drug effects
- Preoptic Area/physiology
- Proto-Oncogene Proteins c-fos/analysis
- Proto-Oncogene Proteins c-fos/genetics
- Rats
- Rats, Wistar
- Receptor, Angiotensin, Type 1
- Receptor, Angiotensin, Type 2
- Receptors, Angiotensin/analysis
- Receptors, Angiotensin/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Serum Response Factor
- Subfornical Organ/drug effects
- Subfornical Organ/physiology
- Supraoptic Nucleus/drug effects
- Supraoptic Nucleus/physiology
- Time Factors
- Transcription Factors/metabolism
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Affiliation(s)
- E Moellenhoff
- Institute of Pharmacology, University of Kiel, Hospitalstrasse 4, 24105 Kiel, Germany
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41
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Clark MA, Tallant EA, Diz DI. Downregulation of the AT1A receptor by pharmacologic concentrations of Angiotensin-(1-7). J Cardiovasc Pharmacol 2001; 37:437-48. [PMID: 11300657 DOI: 10.1097/00005344-200104000-00011] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Angiotensin (Ang)-(1-7), the amino terminal heptapeptide fragment of Ang II, is an endogenous Ang peptide with vasodilatory and antiproliferative actions. Because Ang II causes vasoconstriction and promotes growth through activation of Ang type 1 (AT1) receptors, we investigated whether the actions of Ang-(1-7) are due to its regulation of these receptors. Studies were performed in CHO cells stably transfected with the AT1A receptor. Ang-(1-7) competed poorly with [125I]-Ang II for the AT1A binding site and was ineffective at shifting the IC50 for Ang II competition with [125I]-Ang II for binding to the AT1A receptor. However, if CHO-AT1A cells were pretreated with Ang-(1-7) and then treated with acidic glycine to remove surface-bound ligand, the heptapeptide caused a concentration-dependent reduction in Ang II binding, with a maximal inhibition to 67.8 +/- 4.6% of total (p < 0.05) at 1 microM Ang-(1-7) compared with a reduction to 24% of total by 10 nM Ang II. Ang-(1-7) pretreatment caused a small but significant decrease in the affinity of [125I]-Ang II for the AT1A receptor and a significant reduction in the total number of binding sites. The Ang-(1-7)-induced reduction in binding was rapid (occurring as early as 5 min after exposure to the peptide), was maintained for 30 min during continued exposure of the cells to Ang-(1-7), and rapidly recovered after removal of the heptapeptide. The AT1 receptor antagonist L-158,809 reduced the Ang-(1-7)-induced downregulation of the AT1A receptor, suggesting that interactions with AT1A receptors mediate the regulatory events. Pretreatment with 1 microM or 10 microM Ang-(1-7) significantly reduced inositol phosphate production in response to 10 nM Ang II. The decrease in binding and responsiveness of the AT1A receptor after exposure to micromolar concentrations of Ang-(1-7) suggests that the heptapeptide downregulates the AT1A receptor to reduce responses to Ang II. Because downregulation of the receptor only occurred at micromolar concentrations of the heptapeptide, our findings suggest that Ang-(1-7) is not a potent antagonist at the AT1A receptor. However, when the balance between Ang II and Ang-(1-7) is shifted in favor of Ang-(1-7), such as during inhibition of Ang-converting enzyme, some contribution of this mechanism may come into play.
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Affiliation(s)
- M A Clark
- Hypertension and Vascular Disease Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1032, USA.
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Navar LG, Mitchell KD, Harrison-Bernard LM, Kobori H, Nishiyama A. Review: Intrarenal angiotensin II levels in normal and hypertensive states. J Renin Angiotensin Aldosterone Syst 2001; 2:S176-S184. [PMID: 19644566 PMCID: PMC2717721 DOI: 10.1177/14703203010020013001] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- L Gabriel Navar
- Department of Physiology, Tulane University School of Medicine, 1430 Tulane Avenue New Orleans, LA 70112 USA,
| | - Kenneth D Mitchell
- Department of Physiology, Tulane University School of Medicine, 1430 Tulane Avenue New Orleans, LA 70112 USA
| | - Lisa M Harrison-Bernard
- Department of Physiology, Tulane University School of Medicine, 1430 Tulane Avenue New Orleans, LA 70112 USA
| | - Hiroyuki Kobori
- Department of Physiology, Tulane University School of Medicine, 1430 Tulane Avenue New Orleans, LA 70112 USA
| | - Akira Nishiyama
- Department of Physiology, Tulane University School of Medicine, 1430 Tulane Avenue New Orleans, LA 70112 USA
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43
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El-Sabban ME, Hassan KA, Birbari AE, Bitar KM, Bikhazi AB. Angiotensin II binding and extracellular matrix remodelling in a rat model of myocardial infarction. J Renin Angiotensin Aldosterone Syst 2000; 1:369-78. [PMID: 11967826 DOI: 10.3317/jraas.2000.069] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Clinical evidence points to a role for angiotensin II (Ang II) in the post-infarction remodelling of cardiac hypertrophy. The present study was designed to investigate the remodelling process in an animal model of myocardial infarction (MI) using the following criteria: 1) histological studies to examine the re-vascularisation process and collagen deposition in different regions of the myocardium; 2) histological evidence to investigate the cell type distribution using cell-specific markers; 3) histological and Western blot analysis to localise Ang II receptor subtypes (AT(1)-receptor and AT(2)-receptor) and to study their regulation; 4) kinetics of the binding of Ang II to its receptors in a heart perfusion model; and 5) to assess the effect of the Ang II antagonist (losartan) on these parameters. MI was induced by ligation of the left anterior descending coronary artery of Sprague-Dawley rats. Four different animal groups were established: 1) sham-operated, non-treated; 2) sham-operated, treated with losartan; 3) myocardial infarct, non-treated; and 4) myocardial infarct, treated with losartan. In infarcted rat hearts, fibroblasts and collagen types I and III increased in the remnant viable region of the left ventricle compared with sham-operated rats. One month of losartan treatment in myocardial infarcted rats revealed insignificant changes in fibroblasts and collagen types I and III compared with sham controls. Also, myocardial infarction increased AT(1)-receptor protein levels compared with sham-operated controls, as judged by Western blotting. In losartan-treated myocardial infarct animals, no changes were detected at the level of AT(1)-receptor expression compared with non-treated myocardial infarct rats. Binding studies of Ang II on endothelial cell lining and directly on myocytes in sham-operated and infarcted perfused rat hearts revealed that, in myocardial infarcted-animals, Ang II binding affinity increased both in the endothelium and in myofibres. This may be considered a major putative effect of the peptide in potentiating the pharmacodynamics of hypertrophy. In losartan-treated myocardial infarcted-animals, a marked increase in the binding affinities of Ang II for the AT(2)-receptor subtype was observed. Hence, potential cardioprotective effects of the AT(1)-receptor antagonist are proposed.
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Affiliation(s)
- M E El-Sabban
- Department of Human Morphology, Amercian University of Beirut, Beirut, 11-0236, Lebanon
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44
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Wolf G, Wenzel U, Assmann KJ, Stahl RA. Renal expression of aminopeptidase A in rats with two-kidney, one-clip hypertension. Nephrol Dial Transplant 2000; 15:1935-42. [PMID: 11096137 DOI: 10.1093/ndt/15.12.1935] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Angiotensin II (ANG II) is a major factor involved in the progression of chronic renal disease. Although the generation of this vasoactive peptide has been investigated in great detail, only a few studies have hitherto addressed the metabolism of ANG II into fragments such as angiotensin III and IV (ANG III, IV) which may exert physiological effects independent of ANG II. Aminopeptidase A (APA) is the major enzyme degrading ANG II. The aim of the current study was to evaluate glomerular APA expression in rats with two-kidney, one-clip hypertension. METHODS The left renal artery was restricted with a 0.2-mm silver clip. Kidneys were harvested 1 and 4 weeks after surgery. APA enzyme and protein expression was evaluated in kidney sections. Total APA enzyme activity and mRNA expression was assessed in isolated glomeruli. Degradation of exogenous ANG II by isolated glomeruli was measured with reverse-phase high-performance liquid chromatography. RESULTS APA enzyme activity, protein, and mRNA expression were stimulated in the clipped kidney 1 week after surgery compared with the contralateral kidney or normal controls. In contrast, 4 weeks after clipping APA activity and expression was higher in the contralateral kidney. In parallel to these findings, degradation of ANG II was greatest in isolated glomeruli obtained from the clipped kidney after 1 week. However, preparations from the contralateral kidney 4 weeks after surgery were more active in the metabolism of exogenous ANG II. CONCLUSION The present study provides evidence that APA is complexly regulated in in vivo situations with an activated local renin-ANG II system. ANG II appears to play a direct role in this regulation. However, since conversion of ANG II to ANG III by APA is the initial step leading to the formation of ANG IV which may exert detrimental effects not mediated through classical ANG II receptors, a local increase in APA activity may contribute to the progression of chronic renal disease even during complete AT(1)-receptor blockade.
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Affiliation(s)
- G Wolf
- Department of Medicine, Division of Nephrology and Osteology, University of Hamburg, Hamburg, Germany
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Chen R, Mukhin YV, Garnovskaya MN, Thielen TE, Iijima Y, Huang C, Raymond JR, Ullian ME, Paul RV. A functional angiotensin II receptor-GFP fusion protein: evidence for agonist-dependent nuclear translocation. Am J Physiol Renal Physiol 2000; 279:F440-8. [PMID: 10966923 DOI: 10.1152/ajprenal.2000.279.3.f440] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We constructed an expression vector for a fusion protein [ANG II type 1a receptor-green fluorescent protein (AT(1a)R-GFP)] consisting of enhanced GFP attached to the COOH terminus of the rat AT(1a)R. Chinese hamster ovary (CHO) cells transfected with AT(1a)R-GFP demonstrated specific, high-affinity (125)I-labeled ANG II binding (IC(50) 21 nM). ANG II exposure stimulated sodium-proton exchange and cytoplasmic calcium release to a similar extent in cells transfected with AT(1a)R or AT(1a)R-GFP; these responses were desensitized by prior exposure to ANG II and were sensitive to the AT(1)R blocker losartan. ANG II-driven internalization of AT(1a)R-GFP in transfected CHO cells was demonstrated both by radioligand binding and by laser scanning confocal microscopy. Colocalization of GFP fluorescence with that of the nuclear stain TOTO-3 in confocal images was increased more than twofold after 1 h of ANG II exposure. We conclude that AT(1a)R-GFP exhibits similar pharmacological behavior to that of the native AT(1a)R. Our observations also support previous evidence for the presence of AT(1a)R in the nucleus and suggest that the density of AT(1a)R in the nucleus may be regulated by exposure to its ligand.
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Affiliation(s)
- R Chen
- Division of Nephrology, Medical University of South Carolina, USA
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Hunyady L, Catt KJ, Clark AJ, Gáborik Z. Mechanisms and functions of AT(1) angiotensin receptor internalization. REGULATORY PEPTIDES 2000; 91:29-44. [PMID: 10967200 DOI: 10.1016/s0167-0115(00)00137-3] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The type 1 (AT(1)) angiotensin receptor, which mediates the known physiological and pharmacological actions of angiotensin II, activates numerous intracellular signaling pathways and undergoes rapid internalization upon agonist binding. Morphological and biochemical studies have shown that agonist-induced endocytosis of the AT(1) receptor occurs via clathrin-coated pits, and is dependent on two regions in the cytoplasmic tail of the receptor. However, it is independent of G protein activation and signaling, and does not require the conserved NPXXY motif in the seventh transmembrane helix. The dependence of internalization of the AT(1) receptor on a cytoplasmic serine-threonine-rich region that is phosphorylated during agonist stimulation suggests that endocytosis is regulated by phosphorylation of the AT(1) receptor tail. beta-Arrestins have been implicated in the desensitization and endocytosis of several G protein-coupled receptors, but the exact nature of the adaptor protein required for association of the AT(1) receptor with clathrin-coated pits, and the role of dynamin in the internalization process, are still controversial. There is increasing evidence for a role of internalization in sustained signal generation from the AT(1) receptor. Several aspects of the mechanisms and specific function of AT(1) receptor internalization, including its precise mode and route of endocytosis, and the potential roles of cytoplasmic and nuclear receptors, remain to be elucidated.
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MESH Headings
- Animals
- Arrestins/metabolism
- Cell Nucleus/metabolism
- Cytoplasm/metabolism
- Dynamins
- Endocytosis
- GTP Phosphohydrolases/metabolism
- Humans
- Kinetics
- Ligands
- Microscopy, Confocal
- Models, Biological
- Mutation
- Phosphorylation
- Protein Structure, Secondary
- Receptor, Angiotensin, Type 1
- Receptor, Angiotensin, Type 2
- Receptors, Angiotensin/genetics
- Receptors, Angiotensin/metabolism
- Receptors, Angiotensin/physiology
- beta-Arrestins
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Affiliation(s)
- L Hunyady
- Department of Physiology, Semmelweis University, Faculty of Medicine, P.O. Box 259, H-1444 Budapest, Hungary.
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Muto S, Ebata S, Okada K, Saito T, Asano Y. Glucocorticoid modulates Na+/H+ exchange activity in vascular smooth muscle cells by nongenomic and genomic mechanisms. Kidney Int 2000; 57:2319-33. [PMID: 10844602 DOI: 10.1046/j.1523-1755.2000.00092.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND In vascular smooth muscle cells (VSMCs), Na+/H+ exchange (NHE) plays an important role in intracellular pH (pHi) regulation. The genomic effect of glucocorticoid (GC) on NHE activity has been suggested in VSMCs. However, the nongenomic and genomic effects of GC on NHE activity and the underlying intracellular signaling mechanisms have not yet been demonstrated in VSMCs. Also, it is not known whether there are specific surface-binding sites of GC to the plasma membrane of VSMCs. METHODS The effects of short (3 h)- and long (24 h)-term exposure to corticosterone (CORTI) on NHE activity were studied in cultured rat aortic VSMCs by using pHi measurement with the pH-sensitive fluorescent dye 2'7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. The NHE activity was calculated from the initial rate of Na+-dependent pHi recovery after the acid load. RESULTS Short-term exposure of VSMCs to CORTI (10-6 mol/L) increased NHE activity, whereas long-term exposure to CORTI decreased it. The inhibitors of gene transcription (actinomycin D) and of protein synthesis (cycloheximide) did not affect the short-term effect of CORTI on NHE activity, but inhibited the long-term effect of CORTI on NHE activity. The cytosolic GC receptor (GR) antagonist (RU38486) inhibited both the short- and long-term effects of CORTI on NHE activity, but the cytosolic mineralocorticoid receptor antagonist (spironolactone) did not influence either the short- or long-term CORTI effects. Two protein kinase C (PKC) inhibitors (staurosporine A and calphostin C) and PKC down-regulation [24-h pre-exposure to phorbol 12-myristate 13-acetate (PMA)] inhibited both short- and long-term CORTI effects. Exposure to PMA for three hours mimicked the short-term CORTI effect. The short-term CORTI effect was inhibited by the disruptor of microtubule (colchicine), but not by the disruptor of filamentous-actin (cytochalasin B). The long-term exposure to CORTI decreased NHE (NHE-1) mRNA levels to 0.65 times the control level, whereas the short-term exposure to CORTI caused no effect. Scatchard analysis of [3H]CORTI surface binding to VSMCs showed a single class of CORTI binding sites with a Bmax of 876.2 fmol per mg of cell protein and a Kd of 12.2 nmol/L. RU38486 also inhibited [3H]CORTI surface binding to VSMCs. CONCLUSIONS In VSMCs, NHE activity is stimulated by short-term exposure to CORTI, but is inhibited by long-term exposure to CORTI. The short-term stimulatory effect of CORTI on NHE activity is independent of gene transcription and protein synthesis, is mediated through the CORTI surface receptor, and occurs through a microtubule-dependent process. The long-term inhibitory effect of CORTI on NHE activity requires gene transcription and protein synthesis and occurs only through the cytosolic GR. The short- and long-term effects of CORTI on NHE activity occur via PKC activation. Therefore, CORTI differentially modulates NHE activity in VSMCs by nongenomic and genomic mechanisms.
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Affiliation(s)
- S Muto
- Departments of Nephrology and Endocrinology and Metabolism, Jichi Medical School, Tochigi, Japan.
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48
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Sica DA, Harris RC. Potential Mechanisms and Physiologic Actions of Intracellular Angiotensin II. Am J Med Sci 1999. [DOI: 10.1016/s0002-9629(15)40662-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Nozawa Y, Matsuura N, Miyake H, Yamada S, Kimura R. Effects of TH-142177 on angiotensin II-induced proliferation, migration and intracellular signaling in vascular smooth muscle cells and on neointimal thickening after balloon injury. Life Sci 1999; 64:2061-70. [PMID: 10374931 DOI: 10.1016/s0024-3205(99)00153-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We investigated the effects of TH-142177 (N-n-butyl-N-[2'-(1-H-tetrazole-5-yl) biphenyl-4-yl]-methyl-(N-carboxy methyl-benzylamino)-acetamide), a novel selective antagonist of angiotensin II type 1-receptor (AT1-R) on angiotensin II (AII)-induced proliferation and migration of vascular smooth muscle cells (VSMC), and on neointimal formation in the rat carotid artery after balloon injury, and on the intracellular signaling by the stimulation of AT1-R. High affinity AII receptor sites were detected in rat VSMC by the use of [125I]Sar1,Ile8-AII. TH-142177 and losartan competed with [125I]Sar1,Ile8-AII for the binding sites in VSMC in a monophasic manner, although PD123177, a selective antagonist of angiotensin II type 2-receptor (AT2-R), had little inhibitory effect, demonstrating the predominant existence of AT1-R in rat VSMC. TH-142177 prevented AII-induced DNA synthesis and migration, with a significant inhibition of 74 and 55%, respectively, at the concentration of 100 nM. AII-induced activation of p21ras, mitogen-activated protein kinase (p42MAPK and p44MAPK), and protein kinase C was significantly (50-78%) inhibited by TH-142177 (100 nM), suggesting that the activation of these enzymes is mediated through the stimulation of AT1-R. Balloon-injured left carotid arteries in rats showed extensive neointimal thickening, and TH-142177 (3 mg/kg) brought out a marked decrease in the neointimal thickening after balloon injury. In conclusion, TH-142177 inhibited AII-induced proliferation and migration of rat VSMC and neointimal formation in the carotid artery after balloon injury, and these effects may be related, in part, to the suppression of ras, p42MAPK and p44MAPK, and protein kinase C activities through the blockade of AT1-R. Thus, TH-142177 may have therapeutic potential for the treatment of vascular diseases such as atherosclerosis and restenosis.
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MESH Headings
- 1-Sarcosine-8-Isoleucine Angiotensin II/metabolism
- Angiotensin II/pharmacology
- Angiotensin Receptor Antagonists
- Animals
- Arteriosclerosis/drug therapy
- Carotid Artery Injuries
- Carotid Artery, Common/drug effects
- Carotid Artery, Common/metabolism
- Catheterization/adverse effects
- Cell Division/drug effects
- Cell Movement/drug effects
- Cells, Cultured
- Glycine/analogs & derivatives
- Glycine/pharmacology
- Hyperplasia
- Male
- Mitogen-Activated Protein Kinase 1/metabolism
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Protein Kinase C/metabolism
- Proto-Oncogene Proteins p21(ras)/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptor, Angiotensin, Type 1
- Receptor, Angiotensin, Type 2
- Signal Transduction/drug effects
- Tetrazoles/pharmacology
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Affiliation(s)
- Y Nozawa
- Pharmacology Research Laboratory, Taiho Pharmaceutical Co., Ltd., Tokushima, Japan.
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