1
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Smith D, Layton A. The intrarenal renin-angiotensin system in hypertension: insights from mathematical modelling. J Math Biol 2023; 86:58. [PMID: 36952058 DOI: 10.1007/s00285-023-01891-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 01/14/2023] [Accepted: 02/21/2023] [Indexed: 03/24/2023]
Abstract
The renin-angiotensin system (RAS) plays a pivotal role in the maintenance of volume homeostasis and blood pressure. In addition to the well-studied systemic RAS, local RAS have been documented in various tissues, including the kidney. Given the role of the intrarenal RAS in the pathogenesis of hypertension, a role established via various pharmacologic and genetic studies, substantial efforts have been made to unravel the processes that govern intrarenal RAS activity. In particular, several mechanisms have been proposed to explain the rise in intrarenal angiotensin II (Ang II) that accompanies Ang II infusion, including increased angiotensin type 1 receptor (AT1R)-mediated uptake of Ang II and enhanced intrarenal Ang II production. However, experimentally isolating their contribution to the intrarenal accumulation of Ang II in Ang II-induced hypertension is challenging, given that they are fundamentally connected. Computational modelling is advantageous because the feedback underlying each mechanism can be removed and the effect on intrarenal Ang II can be studied. In this work, the mechanisms governing the intrarenal accumulation of Ang II during Ang II infusion experiments are delineated and the role of the intrarenal RAS in Ang II-induced hypertension is studied. To accomplish this, a compartmental ODE model of the systemic and intrarenal RAS is developed and Ang II infusion experiments are simulated. Simulations indicate that AT1R-mediated uptake of Ang II is the primary mechanism by which Ang II accumulates in the kidney during Ang II infusion. Enhanced local Ang II production is unnecessary. The results demonstrate the role of the intrarenal RAS in the pathogenesis of Ang II-induced hypertension and consequently, clinical hypertension associated with an overactive RAS.
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Affiliation(s)
- Delaney Smith
- Department of Applied Mathematics, University of Waterloo, 200 University Ave, Waterloo, ON, N2L 3G1, Canada.
| | - Anita Layton
- Department of Applied Mathematics, University of Waterloo, 200 University Ave, Waterloo, ON, N2L 3G1, Canada
- Cheriton School of Computer Science, University of Waterloo, 200 University Ave, Waterloo, ON, N2L 3G1, Canada
- Department of Biology, University of Waterloo, 200 University Ave, Waterloo, ON, N2L 3G1, Canada
- School of Pharmacy, University of Waterloo, 200 University Ave, Waterloo, ON, N2L 3G1, Canada
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2
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Bovée DM, Ren L, Uijl E, Clahsen-van Groningen MC, van Veghel R, Garrelds IM, Domenig O, Poglitsch M, Zlatev I, Kim JB, Huang S, Melton L, Lu X, Hoorn EJ, Foster D, Danser AHJ. Renoprotective Effects of Small Interfering RNA Targeting Liver Angiotensinogen in Experimental Chronic Kidney Disease. Hypertension 2021; 77:1600-1612. [PMID: 33719507 DOI: 10.1161/hypertensionaha.120.16876] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Dominique M Bovée
- Division of Vascular Medicine and Pharmacology (D.M.B., L.R., E.U., R.v.V., I.M.G., A.H.J.D.), Erasmus MC, University Medical Center Rotterdam, the Netherlands.,Division of Nephrology and Transplantation, Department of Internal Medicine (D.M.B., E.U., E.J.H.), Erasmus MC, University Medical Center Rotterdam, the Netherlands
| | - Liwei Ren
- Division of Vascular Medicine and Pharmacology (D.M.B., L.R., E.U., R.v.V., I.M.G., A.H.J.D.), Erasmus MC, University Medical Center Rotterdam, the Netherlands.,Translational Medicine Collaborative Innovation Center, The Second Clinical Medical College (Shenzhen People's Hospital) of Jinan University, China (L.R.)
| | - Estrellita Uijl
- Division of Vascular Medicine and Pharmacology (D.M.B., L.R., E.U., R.v.V., I.M.G., A.H.J.D.), Erasmus MC, University Medical Center Rotterdam, the Netherlands.,Division of Nephrology and Transplantation, Department of Internal Medicine (D.M.B., E.U., E.J.H.), Erasmus MC, University Medical Center Rotterdam, the Netherlands
| | | | - Richard van Veghel
- Division of Vascular Medicine and Pharmacology (D.M.B., L.R., E.U., R.v.V., I.M.G., A.H.J.D.), Erasmus MC, University Medical Center Rotterdam, the Netherlands
| | - Ingrid M Garrelds
- Division of Vascular Medicine and Pharmacology (D.M.B., L.R., E.U., R.v.V., I.M.G., A.H.J.D.), Erasmus MC, University Medical Center Rotterdam, the Netherlands
| | | | | | - Ivan Zlatev
- Alnylam Pharmaceuticals, Cambridge, MA (I.Z., J.B.K., S.H., L.M., D.F.)
| | - Jae B Kim
- Alnylam Pharmaceuticals, Cambridge, MA (I.Z., J.B.K., S.H., L.M., D.F.)
| | - Stephen Huang
- Alnylam Pharmaceuticals, Cambridge, MA (I.Z., J.B.K., S.H., L.M., D.F.)
| | - Lauren Melton
- Alnylam Pharmaceuticals, Cambridge, MA (I.Z., J.B.K., S.H., L.M., D.F.)
| | - Xifeng Lu
- Department of Physiology, AstraZeneca-Shenzhen University Joint Institute of Nephrology, Shenzhen University Health Science Center, Shenzhen University, China (X.L.)
| | - Ewout J Hoorn
- Division of Nephrology and Transplantation, Department of Internal Medicine (D.M.B., E.U., E.J.H.), Erasmus MC, University Medical Center Rotterdam, the Netherlands
| | - Don Foster
- Alnylam Pharmaceuticals, Cambridge, MA (I.Z., J.B.K., S.H., L.M., D.F.)
| | - A H Jan Danser
- Division of Vascular Medicine and Pharmacology (D.M.B., L.R., E.U., R.v.V., I.M.G., A.H.J.D.), Erasmus MC, University Medical Center Rotterdam, the Netherlands
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3
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Bovée DM, Uijl E, Severs D, Rubio-Beltrán E, van Veghel R, Maassen van den Brink A, Joles JA, Zietse R, Cuevas CA, Danser AHJ, Hoorn EJ. Dietary salt modifies the blood pressure response to renin-angiotensin inhibition in experimental chronic kidney disease. Am J Physiol Renal Physiol 2021; 320:F654-F668. [PMID: 33586496 DOI: 10.1152/ajprenal.00603.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic kidney disease contributes to hypertension, but the mechanisms are incompletely understood. To address this, we applied the 5/6th nephrectomy rat model to characterize hypertension and the response to dietary salt and renin-angiotensin inhibition. 5/6th nephrectomy caused low-renin, salt-sensitive hypertension with hyperkalemia and unsuppressed aldosterone. Compared with sham rats, 5/6th nephrectomized rats had lower Na+/H+ exchanger isoform 3, Na+-K+-2Cl- cotransporter, Na+-Cl- cotransporter, α-epithelial Na+ channel (ENaC), and Kir4.1 levels but higher serum and glucocorticoid-regulated kinase 1, prostasin, γ-ENaC, and Kir5.1 levels. These differences correlated with plasma renin, aldosterone, and/or K+. On a normal-salt diet, adrenalectomy (0 ± 9 mmHg) and spironolactone (-11 ± 10 mmHg) prevented a progressive rise in blood pressure (10 ± 8 mmHg), and this was enhanced in combination with losartan (-41 ± 12 and -43 ± 9 mmHg). A high-salt diet caused skin Na+ and water accumulation and aggravated hypertension that could only be attenuated by spironolactone (-16 ± 7 mmHg) and in which the additive effect of losartan was lost. Spironolactone also increased natriuresis, reduced skin water accumulation, and restored vasorelaxation. In summary, in the 5/6th nephrectomy rat chronic kidney disease model, salt-sensitive hypertension develops with a selective increase in γ-ENaC and despite appropriate transporter adaptations to low renin and hyperkalemia. With a normal-salt diet, hypertension in 5/6th nephrectomy depends on angiotensin II and aldosterone, whereas a high-salt diet causes more severe hypertension mediated through the mineralocorticoid receptor.NEW & NOTEWORTHY Chronic kidney disease (CKD) causes salt-sensitive hypertension, but the interactions between dietary salt and the renin-angiotensin system are incompletely understood. In rats with CKD on a normal-salt diet targeting aldosterone, the mineralocorticoid receptor (MR) and especially angiotensin II reduced blood pressure. On a high-salt diet, however, only MR blockade attenuated hypertension. These results reiterate the importance of dietary salt restriction to maintain renin-angiotensin system inhibitor efficacy and specify the MR as a target in CKD.
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Affiliation(s)
- Dominique M Bovée
- Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Estrellita Uijl
- Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands.,Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - David Severs
- Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Eloisa Rubio-Beltrán
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Richard van Veghel
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Antoinette Maassen van den Brink
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Jaap A Joles
- Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Robert Zietse
- Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Catherina A Cuevas
- Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - A H Jan Danser
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Ewout J Hoorn
- Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
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Li XC, Zhou X, Zhuo JL. Evidence for a Physiological Mitochondrial Angiotensin II System in the Kidney Proximal Tubules: Novel Roles of Mitochondrial Ang II/AT 1a/O 2- and Ang II/AT 2/NO Signaling. Hypertension 2020; 76:121-132. [PMID: 32475319 DOI: 10.1161/hypertensionaha.119.13942] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The present study tested the hypotheses that overexpression of an intracellular Ang II (angiotensin II) fusion protein, mito-ECFP/Ang II, selectively in the mitochondria of mouse proximal tubule cells induces mitochondrial oxidative and glycolytic responses and elevates blood pressure via the Ang II/AT1a receptor/superoxide/NHE3 (the Na+/H+ exchanger 3)-dependent mechanisms. A PT-selective, mitochondria-targeting adenoviral construct encoding Ad-sglt2-mito-ECFP/Ang II was used to test the hypotheses. The expression of mito-ECFP/Ang II was colocalized primarily with Mito-Tracker Red FM in mouse PT cells or with TMRM in kidney PTs. Mito-ECFP/Ang II markedly increased oxygen consumption rate as an index of mitochondrial oxidative response (69.5%; P<0.01) and extracellular acidification rate as an index of mitochondrial glycolytic response (34%; P<0.01). The mito-ECFP/Ang II-induced oxygen consumption rate and extracellular acidification rate responses were blocked by AT1 blocker losartan (P<0.01) and a mitochondria-targeting superoxide scavenger mito-TEMPO (P<0.01). By contrast, the nonselective NO inhibitor L-NAME alone increased, whereas the mitochondria-targeting expression of AT2 receptors (mito-AT2/GFP) attenuated the effects of mito-ECFP/Ang II (P<0.01). In the kidney, overexpression of mito-ECFP/Ang II in the mitochondria of the PTs increased systolic blood pressure 12±3 mm Hg (P<0.01), and the response was attenuated in PT-specific PT-Agtr1a-/- and PT-Nhe3-/- mice (P<0.01). Conversely, overexpression of AT2 receptors selectively in the mitochondria of the PTs induced natriuretic responses in PT-Agtr1a-/- and PT-Nhe3-/- mice (P<0.01). Taken together, these results provide new evidence for a physiological role of PT mitochondrial Ang II/AT1a/superoxide/NHE3 and Ang II/AT2/NO/NHE3 signaling pathways in maintaining blood pressure homeostasis.
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Affiliation(s)
- Xiao Chun Li
- From the Tulane Hypertension and Renal Center of Excellence (X.C.L., J.L.Z.), Tulane University School of Medicine, New Orleans, LA.,Department of Physiology (X.C.L., J.L.Z.), Tulane University School of Medicine, New Orleans, LA.,Department of Pharmacology and Toxicology (X.C.L., J.L.Z.), University of Mississippi Medical Center, Jackson
| | - Xinchun Zhou
- Department of Pathology (X.Z.), University of Mississippi Medical Center, Jackson
| | - Jia Long Zhuo
- From the Tulane Hypertension and Renal Center of Excellence (X.C.L., J.L.Z.), Tulane University School of Medicine, New Orleans, LA.,Department of Physiology (X.C.L., J.L.Z.), Tulane University School of Medicine, New Orleans, LA.,Department of Pharmacology and Toxicology (X.C.L., J.L.Z.), University of Mississippi Medical Center, Jackson
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5
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Leipziger J, Praetorius H. Renal Autocrine and Paracrine Signaling: A Story of Self-protection. Physiol Rev 2020; 100:1229-1289. [PMID: 31999508 DOI: 10.1152/physrev.00014.2019] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Autocrine and paracrine signaling in the kidney adds an extra level of diversity and complexity to renal physiology. The extensive scientific production on the topic precludes easy understanding of the fundamental purpose of the vast number of molecules and systems that influence the renal function. This systematic review provides the broader pen strokes for a collected image of renal paracrine signaling. First, we recapitulate the essence of each paracrine system one by one. Thereafter the single components are merged into an overarching physiological concept. The presented survey shows that despite the diversity in the web of paracrine factors, the collected effect on renal function may not be complicated after all. In essence, paracrine activation provides an intelligent system that perceives minor perturbations and reacts with a coordinated and integrated tissue response that relieves the work load from the renal epithelia and favors diuresis and natriuresis. We suggest that the overall function of paracrine signaling is reno-protection and argue that renal paracrine signaling and self-regulation are two sides of the same coin. Thus local paracrine signaling is an intrinsic function of the kidney, and the overall renal effect of changes in blood pressure, volume load, and systemic hormones will always be tinted by its paracrine status.
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Affiliation(s)
- Jens Leipziger
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; and Aarhus Institute of Advanced Studies (AIAS), Aarhus University, Aarhus, Denmark
| | - Helle Praetorius
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; and Aarhus Institute of Advanced Studies (AIAS), Aarhus University, Aarhus, Denmark
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6
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Intratubular and intracellular renin-angiotensin system in the kidney: a unifying perspective in blood pressure control. Clin Sci (Lond) 2018; 132:1383-1401. [PMID: 29986878 DOI: 10.1042/cs20180121] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 06/05/2018] [Accepted: 06/13/2018] [Indexed: 12/18/2022]
Abstract
The renin-angiotensin system (RAS) is widely recognized as one of the most important vasoactive hormonal systems in the physiological regulation of blood pressure and the development of hypertension. This recognition is derived from, and supported by, extensive molecular, cellular, genetic, and pharmacological studies on the circulating (tissue-to-tissue), paracrine (cell-to-cell), and intracrine (intracellular, mitochondrial, nuclear) RAS during last several decades. Now, it is widely accepted that circulating and local RAS may act independently or interactively, to regulate sympathetic activity, systemic and renal hemodynamics, body salt and fluid balance, and blood pressure homeostasis. However, there remains continuous debate with respect to the specific sources of intratubular and intracellular RAS in the kidney and other tissues, the relative contributions of the circulating RAS to intratubular and intracellular RAS, and the roles of intratubular compared with intracellular RAS to the normal control of blood pressure or the development of angiotensin II (ANG II)-dependent hypertension. Based on a lecture given at the recent XI International Symposium on Vasoactive Peptides held in Horizonte, Brazil, this article reviews recent studies using mouse models with global, kidney- or proximal tubule-specific overexpression (knockin) or deletion (knockout) of components of the RAS or its receptors. Although much knowledge has been gained from cell- and tissue-specific transgenic or knockout models, a unifying and integrative approach is now required to better understand how the circulating and local intratubular/intracellular RAS act independently, or with other vasoactive systems, to regulate blood pressure, cardiovascular and kidney function.
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7
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Li XC, Zhuo JL. Recent Updates on the Proximal Tubule Renin-Angiotensin System in Angiotensin II-Dependent Hypertension. Curr Hypertens Rep 2017; 18:63. [PMID: 27372447 DOI: 10.1007/s11906-016-0668-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
It is well recognized that the renin-angiotensin system (RAS) exists not only as circulating, paracrine (cell to cell), but also intracrine (intracellular) system. In the kidney, however, it is difficult to dissect the respective contributions of circulating RAS versus intrarenal RAS to the physiological regulation of proximal tubular Na(+) reabsorption and hypertension. Here, we review recent studies to provide an update in this research field with a focus on the proximal tubular RAS in angiotensin II (ANG II)-induced hypertension. Careful analysis of available evidence supports the hypothesis that both local synthesis or formation and AT1 (AT1a) receptor- and/or megalin-mediated uptake of angiotensinogen (AGT), ANG I and ANG II contribute to high levels of ANG II in the proximal tubules of the kidney. Under physiological conditions, nearly all major components of the RAS including AGT, prorenin, renin, ANG I, and ANG II would be filtered by the glomerulus and taken up by the proximal tubules. In ANG II-dependent hypertension, the expression of AGT, prorenin, and (pro)renin receptors, and angiotensin-converting enzyme (ACE) is upregulated rather than downregulated in the kidney. Furthermore, hypertension damages the glomerular filtration barrier, which augments the filtration of circulating AGT, prorenin, renin, ANG I, and ANG II and their uptake in the proximal tubules. Together, increased local ANG II formation and augmented uptake of circulating ANG II in the proximal tubules, via activation of AT1 (AT1a) receptors and Na(+)/H(+) exchanger 3, may provide a powerful feedforward mechanism for promoting Na(+) retention and the development of ANG II-induced hypertension.
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Affiliation(s)
- Xiao C Li
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, 2500 North State Street, Jackson, MS, 39216-4505, USA
| | - Jia L Zhuo
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, 2500 North State Street, Jackson, MS, 39216-4505, USA.
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8
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Yang T, Xu C. Physiology and Pathophysiology of the Intrarenal Renin-Angiotensin System: An Update. J Am Soc Nephrol 2017; 28:1040-1049. [PMID: 28255001 DOI: 10.1681/asn.2016070734] [Citation(s) in RCA: 125] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The renin-angiotensin system (RAS) has a pivotal role in the maintenance of extracellular volume homeostasis and blood pressure through complex mechanisms. Apart from the well known systemic RAS, occurrence of a local RAS has been documented in multiple tissues, including the kidney. A large body of recent evidence from pharmacologic and genetic studies, particularly those using various transgenic approaches to manipulate intrarenal levels of RAS components, has established the important role of intrarenal RAS in hypertension. Recent studies have also begun to unravel the molecular mechanisms that govern intrarenal RAS activity. This local system is under the control of complex regulatory networks consisting of positive regulators of (pro)renin receptor, Wnt/β-catenin signaling, and PGE2/PGE2 receptor EP4 subtype, and negative regulators of Klotho, vitamin D receptor, and liver X receptors. This review highlights recent advances in defining the regulation and function of intrarenal RAS as a unique entity separate from systemic angiotensin II generation.
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Affiliation(s)
- Tianxin Yang
- Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, Utah; and .,Institute of Hypertension, Sun Yat-sen University School of Medicine, Guangzhou, China
| | - Chuanming Xu
- Institute of Hypertension, Sun Yat-sen University School of Medicine, Guangzhou, China
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9
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Zhuo JL, Kobori H, Li XC, Satou R, Katsurada A, Navar LG. Augmentation of angiotensinogen expression in the proximal tubule by intracellular angiotensin II via AT1a/MAPK/NF-кB signaling pathways. Am J Physiol Renal Physiol 2016; 310:F1103-12. [PMID: 26864937 PMCID: PMC4889322 DOI: 10.1152/ajprenal.00350.2015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 02/02/2016] [Indexed: 11/22/2022] Open
Abstract
Long-term angiotensin II (ANG II) infusion significantly increases ANG II levels in the kidney through two major mechanisms: AT1 receptor-mediated augmentation of angiotensinogen (AGT) expression and uptake of circulating ANG II by the proximal tubules. However, it is not known whether intracellular ANG II stimulates AGT expression in the proximal tubule. In the present study, we overexpressed an intracellular cyan fluorescent ANG II fusion protein (Ad-sglt2-ECFP/ANG II) selectively in the proximal tubule of rats and mice using the sodium and glucose cotransporter 2 (sglt2) promoter. AGT mRNA and protein expression in the renal cortex and 24-h urinary AGT excretion were determined 4 wk following overexpression of ECFP/ANG II in the proximal tubule. Systolic blood pressure was significantly increased with a small antinatriuretic effect in rats and mice with proximal tubule-selective expression of ECFP/ANG II (P < 0.01). AGT mRNA and protein expression in the cortex were increased by >1.5-fold and 61 ± 16% (P < 0.05), whereas urinary AGT excretion was increased from 48.7 ± 5.7 (n = 13) to 102 ± 13.5 (n = 13) ng/24 h (P < 0.05). However, plasma AGT, renin activity, and ANG II levels remained unaltered by ECFP/ANG II. The increased AGT mRNA and protein expressions in the cortex by ECFP/ANG II were blocked in AT1a-knockout (KO) mice. Studies in cultured mouse proximal tubule cells demonstrated involvement of AT1a receptor/MAP kinases/NF-кB signaling pathways. These results indicate that intracellular ANG II stimulates AGT expression in the proximal tubules, leading to increased AGT formation and secretion into the tubular fluid, which contributes to ANG II-dependent hypertension.
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Affiliation(s)
- Jia L Zhuo
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi; and
| | - H Kobori
- Department of Physiology and Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - Xiao C Li
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi; and
| | - R Satou
- Department of Physiology and Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - A Katsurada
- Department of Physiology and Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - L Gabriel Navar
- Department of Physiology and Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
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10
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Hypertensive retinopathy in a transgenic angiotensin-based model. Clin Sci (Lond) 2016; 130:1075-88. [PMID: 27026533 DOI: 10.1042/cs20160092] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 03/29/2016] [Indexed: 12/18/2022]
Abstract
Severe hypertension destroys eyesight. The RAS (renin-angiotensin system) may contribute to this. This study relied on an established angiotensin, AngII (angiotensin II)-elevated dTGR (double-transgenic rat) model and same-background SD (Sprague-Dawley) rat controls. In dTGRs, plasma levels of AngII were increased. We determined the general retinal phenotype and observed degeneration of ganglion cells that we defined as vascular degeneration. We also inspected relevant gene expression and lastly observed alterations in the outer blood-retinal barrier. We found that both scotopic a-wave and b-wave as well as oscillatory potential amplitude were significantly decreased in dTGRs, compared with SD rat controls. However, the b/a-wave ratio remained unchanged. Fluorescence angiography of the peripheral retina indicated that exudates, or fluorescein leakage, from peripheral vessels were increased in dTGRs compared with controls. Immunohistological analysis of blood vessels in retina whole-mount preparations showed structural alterations in the retina of dTGRs. We then determined the general retinal phenotype. We observed the degeneration of ganglion cells, defined vascular degenerations and finally found differential expression of RAS-related genes and angiogenic genes. We found the expression of both human angiotensinogen and human renin in the hypertensive retina. Although the renin gene expression was not altered, the AngII levels in the retina were increased 4-fold in the dTGR retina compared with that in SD rats, a finding with mechanistic implications. We suggest that alterations in the outer blood-retinal barrier could foster an area of visual-related research based on our findings. Finally, we introduce the dTGR model of retinal disease.
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Abstract
Experimental models of hypertension and patients with inappropriately increased renin formation due to a stenotic kidney, arteriosclerotic narrowing of the renal arterioles or a rare juxtaglomerular cell tumor have shown a progressive augmentation of the intrarenal/intratubular renin-angiotensin system (RAS). The increased intrarenal angiotensin II (Ang II) elicits renal vasoconstriction and enhanced tubular sodium reabsorption in proximal and distal nephron segments. The enhanced intrarenal Ang II levels are due to both increased Ang II type 1 (AT1) receptor mediated Ang II uptake and AT1 receptor dependent stimulation of renal angiotensinogen (AGT) mRNA and augmented AGT production. The increased AGT formation and secretion into the proximal tubular lumen leads to local formation of Ang II, which stimulates proximal transporters such as the sodium/hydrogen exchanger. Enhanced AGT production also leads to spillover of AGT into the distal nephron segments as reflected by AGT in the urine, which provides an index of intrarenal RAS activity. There is also increased Ang II concentration in distal nephron with stimulation of distal sodium transport. Increased urinary excretion of AGT has been demonstrated in patients with hypertension, type 1 and type 2 diabetes mellitus, and several types of chronic kidney diseases indicating an upregulation of intrarenal RAS activity.
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Affiliation(s)
- Ryousuke Satou
- Department of Physiology and the Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Weijian Shao
- Department of Physiology and the Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - L Gabriel Navar
- Department of Physiology, Tulane University Health Sciences Center, SL39, 1430 Tulane Avenue, New Orleans, LA 70112, USA
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12
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Carey RM. The intrarenal renin-angiotensin system in hypertension. Adv Chronic Kidney Dis 2015; 22:204-10. [PMID: 25908469 DOI: 10.1053/j.ackd.2014.11.004] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 11/05/2014] [Accepted: 11/05/2014] [Indexed: 12/22/2022]
Abstract
The renin-angiotensin system (RAS) is a well-studied hormonal cascade controlling fluid and electrolyte balance and blood pressure through systemic actions. The classical RAS includes renin, an enzyme catalyzing the conversion of angiotensinogen to angiotensin (Ang) I, followed by angiotensin-converting enzyme (ACE) cleavage of Ang I to II, and activation of AT1 receptors, which are responsible for all RAS biologic actions. Recent discoveries have transformed the RAS into a far more complex system with several new pathways: the (des-aspartyl(1))-Ang II (Ang III)/AT2 receptor pathway, the ACE-2/Ang (1-7)/Mas receptor pathway, and the prorenin-renin/prorenin receptor/mitogen-activated protein kinase pathway, among others. Although the classical RAS pathway induces Na(+) reabsorption and increases blood pressure, several new pathways constitute a natriuretic/vasodilator arm of the system, opposing detrimental actions of Ang II through Ang II type 1 receptors. Instead of a simple circulating RAS, several independently functioning tissue RASs exist, the most important of which is the intrarenal RAS. Several physiological characteristics of the intrarenal RAS differ from those of the circulating RAS, autoamplifying the activity of the intrarenal RAS and leading to hypertension. This review will update current knowledge on the RAS with particular attention to the intrarenal RAS and its role in the pathophysiology of hypertension.
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Červenka L, Bíbová J, Husková Z, Vaňourková Z, Kramer HJ, Herget J, Jíchová Š, Sadowski J, Hampl V. Combined suppression of the intrarenal and circulating vasoconstrictor renin-ACE-ANG II axis and augmentation of the vasodilator ACE2-ANG 1-7-Mas axis attenuates the systemic hypertension in Ren-2 transgenic rats exposed to chronic hypoxia. Physiol Res 2014; 64:11-24. [PMID: 25194129 DOI: 10.33549/physiolres.932842] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The aim of the present study was to test the hypothesis that chronic hypoxia would aggravate hypertension in Ren-2 transgenic rats (TGR), a well-defined monogenetic model of hypertension with increased activity of endogenous renin-angiotensin system (RAS). Systolic blood pressure (SBP) in conscious rats and mean arterial pressure (MAP) in anesthetized TGR and normotensive Hannover Sprague-Dawley (HanSD) rats were determined under normoxia that was either continuous or interrupted by two weeks´ hypoxia. Expression, activities and concentrations of individual components of RAS were studied in plasma and kidney of TGR and HanSD rats under normoxic conditions and after exposure to chronic hypoxia. In HanSD rats two weeks´ exposure to chronic hypoxia did not alter SBP and MAP. Surprisingly, in TGR it decreased markedly SBP and MAP; this was associated with substantial reduction in plasma and kidney renin activities and also of angiotensin II (ANG II) levels, without altering angiotensin-converting enzyme (ACE) activities. Simultaneously, in TGR the exposure to hypoxia increased kidney ACE type 2 (ACE2) activity and angiotensin 1-7 (ANG 1-7) concentrations as compared with TGR under continuous normoxia. Based on these results, we propose that suppression of the hypertensiogenic ACE-ANG II axis in the circulation and kidney tissue, combined with augmentation of the intrarenal vasodilator ACE2-ANG 1-7 axis, is the main mechanism responsible for the blood pressure-lowering effects of chronic hypoxia in TGR.
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Affiliation(s)
- L Červenka
- Department of Pathophysiology, Second Faculty of Medicine, Charles University, Prague, Czech Republic.
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Ferrão FM, Lara LS, Lowe J. Renin-angiotensin system in the kidney: What is new? World J Nephrol 2014; 3:64-76. [PMID: 25332897 PMCID: PMC4202493 DOI: 10.5527/wjn.v3.i3.64] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 07/07/2014] [Accepted: 07/29/2014] [Indexed: 02/06/2023] Open
Abstract
The renin-angiotensin system (RAS) has been known for more than a century as a cascade that regulates body fluid balance and blood pressure. Angiotensin II(Ang II) has many functions in different tissues; however it is on the kidney that this peptide exerts its main functions. New enzymes, alternative routes for Ang IIformation or even active Ang II-derived peptides have now been described acting on Ang II AT1 or AT2 receptors, or in receptors which have recently been cloned, such as Mas and AT4. Another interesting observation was that old members of the RAS, such as angiotensin converting enzyme (ACE), renin and prorenin, well known by its enzymatic activity, can also activate intracellular signaling pathways, acting as an outside-in signal transduction molecule or on the renin/(Pro)renin receptor. Moreover, the endocrine RAS, now is also known to have paracrine, autocrine and intracrine action on different tissues, expressing necessary components for local Ang II formation. This in situ formation, especially in the kidney, increases Ang II levels to regulate blood pressure and renal functions. These discoveries, such as the ACE2/Ang-(1-7)/Mas axis and its antangonistic effect rather than classical deleterious Ang II effects, improves the development of new drugs for treating hypertension and cardiovascular diseases.
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Li XC, Zhuo JL. Mechanisms of AT1a receptor-mediated uptake of angiotensin II by proximal tubule cells: a novel role of the multiligand endocytic receptor megalin. Am J Physiol Renal Physiol 2014; 307:F222-33. [PMID: 24740791 DOI: 10.1152/ajprenal.00693.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The present study tested the hypothesis that the multiligand endocytic receptor megalin is partially involved in the uptake of ANG II and downstream signaling responses in mouse proximal tubule cells (mPCT) by interacting with AT1a receptors. mPCT cells of wild-type (WT) and AT1a receptor-deficient (AT1a-KO) mice were treated with vehicle, the AT1 receptor blocker losartan (10 μM), or a selective megalin small interfering (si) RNA for 48 h. The uptake of fluorescein (FITC)-labeled ANG II (10 nM, 37°C) and downstream signaling responses were analyzed by fluorescence imaging and Western blotting. AT1a receptors and megalin were abundantly expressed in mPCT cells, whereas AT1a receptors were absent in AT1a-KO mPCT cells (P < 0.01). In WT mPCT cells, FITC-ANG II uptake was visualized at 30 min in the cytoplasm and in the nuclei 1 h after exposure. Losartan alone completely blocked the uptake of FITC-ANG II, whereas megalin siRNA inhibited only 30% of the response (P < 0.01). The remaining FITC-ANG II uptake in the presence of megalin siRNA was completely abolished by losartan. ANG II induced threefold increases in phosphorylated MAP kinases ERK1/2 and a onefold increase in phosphorylated sodium and hydrogen exchanger 3 (NHE3) proteins, which were also blocked by losartan and megalin-siRNA. By contrast, losartan and megalin siRNA had no effects on these signaling proteins in AT1a-KO mPCT cells. We conclude that the uptake of ANG II and downstream MAP kinases ERK1/2 and NHE3 signaling responses in mPCT cells are mediated primarily by AT1a receptors. However, megalin may also play a partial role in these responses to ANG II.
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Affiliation(s)
- Xiao C Li
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, Cardiovascular and Renal Research Center, Division of Nephrology, Department of Medicine, University of Mississippi Medical Center, Jackson, Mississippi
| | - Jia L Zhuo
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, Cardiovascular and Renal Research Center, Division of Nephrology, Department of Medicine, University of Mississippi Medical Center, Jackson, Mississippi
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Zhuo JL, Ferrao FM, Zheng Y, Li XC. New frontiers in the intrarenal Renin-Angiotensin system: a critical review of classical and new paradigms. Front Endocrinol (Lausanne) 2013; 4:166. [PMID: 24273531 PMCID: PMC3822323 DOI: 10.3389/fendo.2013.00166] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 10/22/2013] [Indexed: 12/23/2022] Open
Abstract
The renin-angiotensin system (RAS) is well-recognized as one of the oldest and most important regulators of arterial blood pressure, cardiovascular, and renal function. New frontiers have recently emerged in the RAS research well beyond its classic paradigm as a potent vasoconstrictor, an aldosterone release stimulator, or a sodium-retaining hormone. First, two new members of the RAS have been uncovered, which include the renin/(Pro)renin receptor (PRR) and angiotensin-converting enzyme 2 (ACE2). Recent studies suggest that prorenin may act on the PRR independent of the classical ACE/ANG II/AT1 receptor axis, whereas ACE2 may degrade ANG II to generate ANG (1-7), which activates the Mas receptor. Second, there is increasing evidence that ANG II may function as an intracellular peptide to activate intracellular and/or nuclear receptors. Third, currently there is a debate on the relative contribution of systemic versus intrarenal RAS to the physiological regulation of blood pressure and the development of hypertension. The objectives of this article are to review and discuss the new insights and perspectives derived from recent studies using novel transgenic mice that either overexpress or are deficient of one key enzyme, ANG peptide, or receptor of the RAS. This information may help us better understand how ANG II acts, both independently or through interactions with other members of the system, to regulate the kidney function and blood pressure in health and disease.
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Affiliation(s)
- Jia L. Zhuo
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, MS, USA
- Department of Medicine, Division of Nephrology, University of Mississippi Medical Center, Jackson, MS, USA
| | - Fernanda M. Ferrao
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, MS, USA
| | - Yun Zheng
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, MS, USA
| | - Xiao C. Li
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, MS, USA
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Ohnishi K, Murase M, Nakano D, Pelisch N, Hitomi H, Kobori H, Morimoto S, Mori H, Masaki T, Ohmori K, Kohno M, Ichihara A, Nishiyama A. Angiotensin-converting enzyme inhibitor does not suppress renal angiotensin II levels in angiotensin I-infused rats. J Pharmacol Sci 2013; 122:103-8. [PMID: 23698111 DOI: 10.1254/jphs.13045fp] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Angiotensin II (Ang II) infusion into rats elevates local angiotensin II levels through an AT1 receptor-dependent pathway in the kidney. We examined whether treatment with an angiotensin-converting enzyme (ACE) inhibitor, temocapril, or an AT1-receptor blocker, olmesartan, prevented elevation of Ang II levels in the kidney of angiotensin I (Ang I)-infused rats. Rats were infused with Ang I (100 ng/min) and treated with temocapril (30 mg/kg per day, n = 10) or olmesartan (10 mg/kg per day, n = 9) for 4 weeks. Ang I infusion significantly elevated blood pressure compared with vehicle-infused rats (n = 6). Treatment with temocapril or olmesartan suppressed Ang I-induced hypertension. Temocapril suppressed both plasma and renal ACE activity. Ang I infusion increased Ang II content in the kidney. Interestingly, temocapril failed to reduce the level of Ang II in the kidney, while olmesartan markedly suppressed an increase in renal Ang II levels. These results suggest a limitation of temocapril and a benefit of olmesartan to inhibit the renal renin-angiotensin system and suggest the possible existence of an ACE inhibitor-insensitive pathway that increases Ang II levels in rat kidney.
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Affiliation(s)
- Keisuke Ohnishi
- Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa, Japan
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Xia H, Suda S, Bindom S, Feng Y, Gurley SB, Seth D, Navar LG, Lazartigues E. ACE2-mediated reduction of oxidative stress in the central nervous system is associated with improvement of autonomic function. PLoS One 2011; 6:e22682. [PMID: 21818366 PMCID: PMC3144922 DOI: 10.1371/journal.pone.0022682] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 06/28/2011] [Indexed: 02/07/2023] Open
Abstract
Oxidative stress in the central nervous system mediates the increase in sympathetic tone that precedes the development of hypertension. We hypothesized that by transforming Angiotensin-II (AngII) into Ang-(1–7), ACE2 might reduce AngII-mediated oxidative stress in the brain and prevent autonomic dysfunction. To test this hypothesis, a relationship between ACE2 and oxidative stress was first confirmed in a mouse neuroblastoma cell line (Neuro2A cells) treated with AngII and infected with Ad-hACE2. ACE2 overexpression resulted in a reduction of reactive oxygen species (ROS) formation. In vivo, ACE2 knockout (ACE2−/y) mice and non-transgenic (NT) littermates were infused with AngII (10 days) and infected with Ad-hACE2 in the paraventricular nucleus (PVN). Baseline blood pressure (BP), AngII and brain ROS levels were not different between young mice (12 weeks). However, cardiac sympathetic tone, brain NADPH oxidase and SOD activities were significantly increased in ACE2−/y. Post infusion, plasma and brain AngII levels were also significantly higher in ACE2−/y, although BP was similarly increased in both genotypes. ROS formation in the PVN and RVLM was significantly higher in ACE2−/y mice following AngII infusion. Similar phenotypes, i.e. increased oxidative stress, exacerbated dysautonomia and hypertension, were also observed on baseline in mature ACE2−/y mice (48 weeks). ACE2 gene therapy to the PVN reduced AngII-mediated increase in NADPH oxidase activity and normalized cardiac dysautonomia in ACE2−/y mice. Altogether, these data indicate that ACE2 gene deletion promotes age-dependent oxidative stress, autonomic dysfunction and hypertension, while PVN-targeted ACE2 gene therapy decreases ROS formation via NADPH oxidase inhibition and improves autonomic function. Accordingly, ACE2 could represent a new target for the treatment of hypertension-associated dysautonomia and oxidative stress.
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Affiliation(s)
- Huijing Xia
- Department of Pharmacology & Experimental Therapeutics and Cardiovascular Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Sonia Suda
- Department of Pharmacology & Experimental Therapeutics and Cardiovascular Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Sharell Bindom
- Department of Pharmacology & Experimental Therapeutics and Cardiovascular Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Yumei Feng
- Department of Pharmacology & Experimental Therapeutics and Cardiovascular Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
- Department of Physiology Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana, United States of America
| | - Susan B. Gurley
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Dale Seth
- Department of Physiology Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana, United States of America
| | - L. Gabriel Navar
- Department of Physiology Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana, United States of America
| | - Eric Lazartigues
- Department of Pharmacology & Experimental Therapeutics and Cardiovascular Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
- * E-mail:
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Zhuo JL, Li XC. New insights and perspectives on intrarenal renin-angiotensin system: focus on intracrine/intracellular angiotensin II. Peptides 2011; 32:1551-65. [PMID: 21699940 PMCID: PMC3137727 DOI: 10.1016/j.peptides.2011.05.012] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 05/05/2011] [Accepted: 05/09/2011] [Indexed: 02/06/2023]
Abstract
Although renin, the rate-limiting enzyme of the renin-angiotensin system (RAS), was first discovered by Robert Tigerstedt and Bergman more than a century ago, the research on the RAS still remains stronger than ever. The RAS, once considered to be an endocrine system, is now widely recognized as dual (circulating and local/tissue) or multiple hormonal systems (endocrine, paracrine and intracrine). In addition to the classical renin/angiotensin I-converting enzyme (ACE)/angiotensin II (Ang II)/Ang II receptor (AT₁/AT₂) axis, the prorenin/(Pro)renin receptor (PRR)/MAP kinase axis, the ACE2/Ang (1-7)/Mas receptor axis, and the Ang IV/AT₄/insulin-regulated aminopeptidase (IRAP) axis have recently been discovered. Furthermore, the roles of the evolving RAS have been extended far beyond blood pressure control, aldosterone synthesis, and body fluid and electrolyte homeostasis. Indeed, novel actions and underlying signaling mechanisms for each member of the RAS in physiology and diseases are continuously uncovered. However, many challenges still remain in the RAS research field despite of more than one century's research effort. It is expected that the research on the expanded RAS will continue to play a prominent role in cardiovascular, renal and hypertension research. The purpose of this article is to review the progress recently being made in the RAS research, with special emphasis on the local RAS in the kidney and the newly discovered prorenin/PRR/MAP kinase axis, the ACE2/Ang (1-7)/Mas receptor axis, the Ang IV/AT₄/IRAP axis, and intracrine/intracellular Ang II. The improved knowledge of the expanded RAS will help us better understand how the classical renin/ACE/Ang II/AT₁ receptor axis, extracellular and/or intracellular origin, interacts with other novel RAS axes to regulate blood pressure and cardiovascular and kidney function in both physiological and diseased states.
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Affiliation(s)
- Jia L Zhuo
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, the University of Mississippi Medical Center, Jackson, MS 39216-4505, USA.
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Neuman RC, Gerig JT. Interactions of Nonprotic Organic Solvents with [Val5]angiotensin in Water. J Phys Chem B 2011; 115:1712-9. [DOI: 10.1021/jp1107125] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Robert C. Neuman
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - John T. Gerig
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
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Enhanced urinary angiotensinogen excretion in Cyp1a1-Ren2 transgenic rats with inducible ANG II-dependent malignant hypertension. Am J Med Sci 2010; 340:389-94. [PMID: 20724906 DOI: 10.1097/maj.0b013e3181eabd28] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
INTRODUCTION Previous studies have demonstrated that the urinary excretion of angiotensinogen is significantly increased in ANG II-infused hypertensive rats, which is associated with an augmentation of intrarenal ANG II levels. These findings suggest that urinary angiotensinogen excretion rates provide an index of intrarenal ANG II levels in ANG II-dependent hypertensive states. However, little information is available regarding the urinary excretion of angiotensinogen in ANG II-dependent malignant hypertension. METHODS This study was performed to determine if urinary angiotensinogen excretion is increased in Cyp1a1-Ren2 transgenic rats [strain name: TGR(Cyp1aRen2)] with inducible ANG II-dependent malignant hypertension. Adult male Cyp1a1-Ren2 rats (n = 6) were fed a normal diet containing 0.3% indole-3-carbinol (I3C) for 10 days to induce ANG II-dependent malignant hypertension. RESULTS Rats induced with I3C exhibited pronounced increases in systolic blood pressure (208 ± 7 versus 127 ± 3 mm Hg; P < 0.001), marked proteinuria (29.4 ± 3.6 versus 5.9 ± 0.3 mg/d; P < 0.001) and augmented urinary angiotensinogen excretion (996 ± 186 versus 241 ± 31 ng/d; P < 0.01). Chronic administration of the AT₁ receptor antagonist, candesartan (25 mg/L in drinking water, n = 6), prevented the I3C-induced increases in systolic blood pressure (125 ± 5 mm Hg; P < 0.001), proteinuria (7.3 ± 1.0 mg/d; P < 0.001) and urinary angiotensinogen excretion (488 ± 51 ng/d, P < 0.01). CONCLUSIONS These data demonstrate that the urinary excretion of angiotensinogen is markedly augmented in ANG II-dependent malignant hypertension. Such increased urinary angiotensinogen excretion may contribute to augmented intrarenal ANG II levels and, thereby, to the increased blood pressure in Cyp1a1-Ren2 transgenic rats with inducible ANG II-dependent malignant hypertension.
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Kujal P, Chábová VČ, Vernerová Z, Walkowska A, Kompanowska-Jezierska E, Sadowski J, Vaňourková Z, Husková Z, Opočenský M, Škaroupková P, Schejbalová S, Kramer HJ, Rakušan D, Malý J, Netuka I, Vaněčková I, Kopkan L, Červenka L. Similar renoprotection after renin-angiotensin-dependent and -independent antihypertensive therapy in 5/6-nephrectomized Ren-2 transgenic rats: are there blood pressure-independent effects? Clin Exp Pharmacol Physiol 2010; 37:1159-69. [DOI: 10.1111/j.1440-1681.2010.05453.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Prieto MC, Williams DE, Liu L, Kavanagh KL, Mullins JJ, Mitchell KD. Enhancement of renin and prorenin receptor in collecting duct of Cyp1a1-Ren2 rats may contribute to development and progression of malignant hypertension. Am J Physiol Renal Physiol 2010; 300:F581-8. [PMID: 21068087 DOI: 10.1152/ajprenal.00433.2010] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
To determine whether in the transgenic rat model [TGR(Cyp1a1Ren2)] with inducible ANG II-dependent malignant hypertension changes in the activation of intrarenal renin-angiotensin system may contribute to the pathogenesis of hypertension, we examined the gene expression of angiotensinogen (AGT) in renal cortical tissues and renin and prorenin receptor [(P)RR] in the collecting duct (CD) of the kidneys from Cyp1a1Ren2 rats (n = 6) fed a normal diet containing 0.3% indole-3-carbinol (I3C) for 10 days and noninduced rats maintained on a normal diet (0.6% NaCl diet; n = 6). Rats induced with I3C developed malignant hypertension and exhibited alterations in the expression of renin and (P)RR expressed by the CD cells. In the renal medullary tissues of the Cyp1a1Ren2 transgenic rats with malignant hypertension, renin protein levels in CD cells were associated with maintained renin content and lack of suppression of the endogenous Ren1c gene expression. Furthermore, these tissues exhibited increased levels of (P)RR transcript, as well as of the protein levels of the soluble form of this receptor, the s(P)RR. Intriguingly, although previous findings demonstrated that urinary AGT excretion is augmented in Cyp1a1Ren2 transgenic rats with malignant hypertension, in the present study we did not find changes in the gene expression of AGT in renal cortical tissues of these rats. The data suggest that upregulation of renin and the s(P)RR in the CD, especially in the renal medullary tissues of Cyp1a1Ren2 transgenic rats with malignant hypertension, along with the previously demonstrated increased availability of AGT in the urine of these rats, may constitute a leading mechanism to explain elevated formation of kidney ANG II levels in this model of ANG II-dependent hypertension.
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Affiliation(s)
- Minolfa C Prieto
- Department of Physiology, Tulane University, School of Medicine, New Orleans, LA 70112, USA.
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Shao W, Seth DM, Navar LG. Angiotensin II type 1 receptor-mediated augmentation of urinary excretion of endogenous angiotensin II in Val5-angiotensin II-infused rats. Hypertension 2010; 56:378-83. [PMID: 20625079 DOI: 10.1161/hypertensionaha.110.153106] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Rats infused chronically with Val(5)-Angiotensin (Ang) II exhibit increased urinary excretion of endogenous Ile(5)-Ang II by the 12th day of infusion, suggesting the stimulation of endogenous Ang II formation by Val(5)-Ang II infusion. The present study determined the time course of increased urinary Ang II excretion and the effects of Ang II type 1 receptor blockade (candesartan, 2 mg/kg per day) on the urinary excretion rates of Ile(5)-Ang II in Val(5)-Ang II-infused (80 ng/min) rats. Ile(5)-Ang II was separated from Val(5)-Ang II by high-performance liquid chromatography and measured by radioimmunoassay. Systolic blood pressure increased progressively (215+/-2 mm Hg) in Val(5)-Ang II-infused rats (n=5), whereas the candesartan-treated group (n=6) remained normotensive (124+/-3 mm Hg). Candesartan treatment significantly increased the level of plasma Ile(5)-Ang II (24.0+/-7.6 versus 156.9+/-24.6 fmol/mL; P<0.01); in contrast, there was a markedly lower intrarenal Ile(5)-Ang II content (357.9+/-76.6 versus 21.1+/-2.8 fmol/g; P<0.01). Urinary Ile(5)-Ang II excretion rates were elevated by day 9 (2185.7+/-283.2 fmol/24 hours) in Val(5)-Ang II-infused rats but not in candesartan-treated rats (740.6+/-110.3 fmol/24 hours). Thus, Ang II type 1 receptor blockade prevents the increase in urinary excretion of endogenous Ang II in rats subjected to chronic Ang II infusion. These data indicate that the increased urinary excretion of endogenous Ang II in Val(5)-Ang II-infused rats is primarily attributed to Ang II type 1 receptor-dependent secretion into and/or de novo formation of Ang II within the tubular lumen.
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Affiliation(s)
- Weijian Shao
- Department of Physiology, SL39, Tulane University Health Sciences Center, 1430 Tulane Ave, New Orleans, LA 70112.
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Pelisch N, Hosomi N, Ueno M, Masugata H, Murao K, Hitomi H, Nakano D, Kobori H, Nishiyama A, Kohno M. Systemic candesartan reduces brain angiotensin II via downregulation of brain renin-angiotensin system. Hypertens Res 2009; 33:161-4. [PMID: 19942928 DOI: 10.1038/hr.2009.200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The renin-angiotensin system has an important function in the regulation of blood pressure as well as in pathophysiological processes in the central nervous system. We examined the effects of the angiotensin receptor blocker candesartan (10 mg kg(-1) per day, p.o.) on brain angiotensin II levels in angiotensin II-infused hypertensive rats. Angiotensin II or vehicle was infused subcutaneously for 14 days in Sprague-Dawley rats. Angiotensin II infusion resulted in increased blood pressure, an effect that was blocked by candesartan treatment. There was no effect of the angiotensin II infusion on Angiotensin II levels in the brain or on blood-brain barrier permeability. Brain tissue angiotensinogen and angiotensin converting enzyme mRNA levels were not changed by angiotensin II infusion but were decreased by candesartan treatment. At 2 weeks of treatment, CV11974, an active form of candesartan, was detectable in the plasma but was not detectable in brain tissue. These data suggest that treatment with candesartan decreases brain angiotensin II by decreasing brain angiotensinogen and angiotensin converting enzyme gene expression.
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Affiliation(s)
- Nicolas Pelisch
- Department of Cardiorenal and Cerebrovascular Medicine, Kagawa University Medical School, Kagawa, Japan.
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Praddaude F, Cousins SW, Pêcher C, Marin-Castaño ME. Angiotensin II-induced hypertension regulates AT1 receptor subtypes and extracellular matrix turnover in mouse retinal pigment epithelium. Exp Eye Res 2009; 89:109-18. [PMID: 19281810 PMCID: PMC2744298 DOI: 10.1016/j.exer.2009.02.020] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Revised: 02/24/2009] [Accepted: 02/24/2009] [Indexed: 01/21/2023]
Abstract
Accumulation of specific deposits and extracellular molecules under the retinal pigment epithelium (RPE) has been previously observed in eyes with age-related macular degeneration (AMD) and may play a role in the pathogenesis of AMD. Even though age is the major determinant for developing AMD, clinical studies have revealed hypertension (HTN) as another systemic risk factor. Angiotensin II (Ang II) is considered the most important hormone associated with HTN. To evaluate the relationship of Ang II to AMD, we studied whether mouse RPE expresses functional Ang II receptor subtypes and whether HTN-induced Ang II regulates expression of these receptors as well as critical ECM molecules (MMP-2 and type IV collagen) involved in ECM turnover in RPE. We used 9-month-old C57BL/6 male mice infused with Ang II alone or Ang II in combination with the AT1 receptor antagonist candesartan or the AT2 receptor antagonist PD123319 for 4 weeks to determine whether HTN-associated Ang II was important for ECM regulation in RPE. We found that mouse RPE expressed both Ang II receptor subtypes at the mRNA and protein levels. Infusion with Ang II induced HTN and elevated plasma and ocular Ang II levels. Ang II also regulated AT1a and AT1b receptor mRNA expression, the intracellular concentration of calcium [Ca(2+)](i), MMP-2 activity, and type IV collagen accumulation. Concurrent administration of Ang II with the AT1 receptor blocker prevented the increase in blood pressure and rise in ocular Ang II levels, as well as the calcium and MMP-2 responses. In contrast, the type IV collagen response to Ang II was prevented by blockade of AT2 receptors, but not AT1 receptors. Plasma Ang II levels were not modified by the AT1 or AT2 receptor blockade. Since the effects of Ang II on MMP-2 and type IV collagen require inhibition of both Ang II receptor subtypes, these receptors may play a role as a potential therapeutic targets to prevent ECM turnover dysregulation in the RPE basement membrane, suggesting a pathogenic mechanism to explain the link between HTN and AMD.
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MESH Headings
- Angiotensin II/pharmacokinetics
- Angiotensin II/pharmacology
- Animals
- Blood Pressure/drug effects
- Calcium Signaling/drug effects
- Collagen Type IV/metabolism
- Extracellular Matrix/drug effects
- Extracellular Matrix/metabolism
- Eye/metabolism
- Eye Proteins/biosynthesis
- Eye Proteins/genetics
- Eye Proteins/physiology
- Gene Expression Regulation/drug effects
- Hypertension/metabolism
- Macular Degeneration/metabolism
- Male
- Matrix Metalloproteinase 2/metabolism
- Mice
- Mice, Inbred C57BL
- RNA, Messenger/genetics
- Receptor, Angiotensin, Type 1/biosynthesis
- Receptor, Angiotensin, Type 1/genetics
- Receptor, Angiotensin, Type 1/physiology
- Receptor, Angiotensin, Type 2/biosynthesis
- Receptor, Angiotensin, Type 2/genetics
- Receptor, Angiotensin, Type 2/physiology
- Retinal Pigment Epithelium/drug effects
- Retinal Pigment Epithelium/metabolism
- Tissue Inhibitor of Metalloproteinase-2/metabolism
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Affiliation(s)
| | - Scott W. Cousins
- Duke Center for Macular Diseases, Duke University Eye Center, Durham, North Caroline
| | - Christiane Pêcher
- Physiology, University Paul Sabatier, School of Medicine, Toulouse, France
| | - Maria E. Marin-Castaño
- Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, Florida
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Nistala R, Wei Y, Sowers JR, Whaley-Connell A. Renin-angiotensin-aldosterone system-mediated redox effects in chronic kidney disease. Transl Res 2009; 153:102-13. [PMID: 19218092 PMCID: PMC2680726 DOI: 10.1016/j.trsl.2008.12.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2008] [Accepted: 12/24/2008] [Indexed: 12/24/2022]
Abstract
The renin-angiotensin-aldosterone system (RAAS) is central to the pathogenesis of hypertension, cardiovascular disease, and kidney disease. Evidence supports various pathways through which a local renal RAAS can affect kidney function, hypertension, and cardiovascular disease. A prominent mechanism seems to be the loss of reduction-oxidation (redox) homeostasis and the formation of excessive free radicals. Free radicals such as reactive oxygen species (ROS) are necessary in normal physiologic processes, which include the development of nephrons, erythropoeisis, and tubular sodium transport. However, the loss of redox homeostasis contributes to proinflammatory and profibrotic pathways in the kidney that in turn lead to decreased vascular compliance, podocyte pathology, and proteinuria. Both the blockade of the RAAS and the oxidative stress produce salutary effects on hypertension and glomerular filtration barrier injury. Thus, the focus of current research is on understanding the pathophysiology of chronic kidney disease in the context of an increased RAAS and unbalanced redox mechanisms.
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Affiliation(s)
- Ravi Nistala
- Department of Internal Medicine, University of Missouri-Columbia School of Medicine, Columbia, MO 65212, USA.
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28
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Shao W, Seth DM, Navar LG. Augmentation of endogenous intrarenal angiotensin II levels in Val5-ANG II-infused rats. Am J Physiol Renal Physiol 2009; 296:F1067-71. [PMID: 19244403 DOI: 10.1152/ajprenal.90596.2008] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
In angiotensin II (ANG II)-induced hypertension, intrarenal ANG II levels are increased by AT(1) receptor-mediated ANG II internalization and endogenous ANG II generation. The objective of the present study was to determine the relative contribution of de novo formation of endogenous ANG II. Male Sprague-Dawley rats were divided into three groups: sham operated (n = 6), Val(5)-ANG II infused (n = 16), and Ile(5)-ANG II infused (n = 6). Val(5)-ANG II and Ile(5)-ANG II were infused at 80 ng/min via subcutaneous osmotic minipump for 13 days, followed by harvesting of blood and kidney samples. In six Val(5)-ANG II-infused rats, urine was collected on the day before infusion and on day 12 of infusion. Extracted samples were subjected to HPLC to separate Val(5)-ANG II from Ile(5)-ANG II followed by RIA. Systolic blood pressure increased significantly from 121 +/- 2 to 206 +/- 4 mmHg in the Val(5)-ANG II-infused rats and from 124 +/- 3 to 215 +/- 5 mmHg in the Ile(5)-ANG II-infused rats. In the Val(5)-ANG II-infused rats, the plasma Ile(5)-ANG II levels increased 196.2 +/- 70.1% compared with sham plasma Ile(5)-ANG II concentration. Val(5)-ANG II levels were 150.0 +/- 28.2 fmol/ml which accounted for 53.5 +/- 10.1% of the total ANG II in plasma. The kidney Ile(5)-ANG II levels in the Val(5)-ANG II-infused rats increased 69.9 +/- 30.7% compared with sham kidney Ile(5)-ANG II concentrations. Intrarenal accumulation of Val(5)-ANG II accounted for 52.5 +/- 5.3% of the total kidney ANG II during Val(5)-ANG II infusion while endogenous Ile(5)-ANG II accounted for 47.5 +/- 8.6%. The urinary Ile(5)-ANG II excretion rate on day 12 increased 93.2 +/- 32.1% compared with preinfusion level indicating increased formation of endogenous ANG II. Thus, the increases in intrarenal ANG II levels during chronic ANG II infusions involve substantial stimulation of endogenous ANG II formation which contributes to overall augmentation of intrarenal ANG II.
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Affiliation(s)
- Weijian Shao
- Department of Physiology, SL39, Tulane University Health Sciences Center, 1430 Tulane Ave., New Orleans, LA 70112, USA.
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29
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Xu F, Mao C, Liu Y, Wu L, Xu Z, Zhang L. Losartan chemistry and its effects via AT1 mechanisms in the kidney. Curr Med Chem 2009; 16:3701-15. [PMID: 19747145 PMCID: PMC2819278 DOI: 10.2174/092986709789105000] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Accepted: 07/27/2009] [Indexed: 12/12/2022]
Abstract
Besides the importance of the renin-angiotensin system (RAS) in the circulation and other organs, the local RAS in the kidney has attracted a great attention in research in last decades. The renal RAS plays an important role in the body fluid homeostasis and long-term cardiovascular regulation. All major components and key enzymes for the establishment of a local RAS as well as two important angiotensin II (Ang II) receptor subtypes, AT1 and AT2 receptors, have been confirmed in the kidney. In additional to renal contribution to the systemic RAS, the intrarenal RAS plays a critical role in the regulation of renal function as well as in the development of kidney disease. Notably, kidney AT1 receptors locating at different cells and compartments inside the kidney are important for normal renal physiological functions and abnormal pathophysiological processes. This mini-review focuses on: 1) the local renal RAS and its receptors, particularly the AT1 receptor and its mechanisms in physiological and pathophysiological processes; and 2) the chemistry of the selective AT1 receptor blocker, losartan, and the potential mechanisms for its actions in the renal RAS-mediated disease.
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Affiliation(s)
- Feichao Xu
- Perinatal Biology Center, Soochow University School of Medicine, Suzhou, People's Republic of China
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30
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Ortiz RM. Delineating the contributions of AT1a and AT1b receptor-mediated uptake of ANG II in kidneys and adrenals. Am J Physiol Renal Physiol 2008; 294:F291-2. [DOI: 10.1152/ajprenal.00589.2007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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31
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Li XC, Zhuo JL. In vivo regulation of AT1a receptor-mediated intracellular uptake of [125I]Val5-ANG II in the kidneys and adrenals of AT1a receptor-deficient mice. Am J Physiol Renal Physiol 2007; 294:F293-302. [PMID: 18045833 DOI: 10.1152/ajprenal.00398.2007] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Using type 1a angiotensin receptor (AT1a) receptor-deficient (Agtr1a-/-) mice and in vivo autoradiography, we tested the hypothesis that intracellular uptake of ANG II in the kidney and adrenal glands is primarily mediated by AT1a receptors and that the response is regulated by prevailing endogenous ANG II. After pretreatment of wild-type (Agtr1a+/+) and Agtr1a-/- mice (n = 6-9 each group) with or without captopril (25 mg.kg(-1).day(-1)) or losartan (10 mg.kg(-1).day(-1)) for 2 wk, [125I]Val5-ANG II was infused for 60 min. Intracellular uptake of [125I]Val5-ANG II was determined by quantitative in vivo autoradiography after washout of circulating [125I]Val5-ANG II. Basal intracellular ANG II levels were 65% lower in the kidney (P < 0.001), but plasma ANG II levels were threefold higher, in Agtr1a-/- than wild-type mice (P < 0.01). Although plasma [125I]Val5-ANG II levels were similar, urinary excretion of [125I]Val5-ANG II was fourfold higher in Agtr1a-/- mice (P < 0.001). By contrast, intracellular [125I]Val5-ANG II levels were approximately 80% lower in the kidney and adrenal glands of Agtr1a-/- mice (P < 0.01). Captopril decreased endogenous plasma and renal ANG II levels (P < 0.01) but increased intracellular uptake of [125I]Val5-ANG II in the kidney and adrenal glands of wild-type and Agtr1a-/- mice (P < 0.01). Losartan largely blocked renal and adrenal uptake of [125I]Val5-ANG II in wild-type and Agtr1a-/- mice. Thus 80% of intracellular ANG II uptake in the kidney and adrenal glands is mediated by AT1a receptors, whereas AT1b receptor- and other non-receptor-mediated mechanisms account for 20% of the response. Our results suggest that AT1a receptor-mediated uptake of extracellular ANG II may play a physiological role in the kidney and adrenal glands.
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32
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Bivol LM, Berge RK, Iversen BM. Tetradecylthioacetic acid prevents the inflammatory response in two-kidney, one-clip hypertension. Am J Physiol Regul Integr Comp Physiol 2007; 294:R438-47. [PMID: 18032469 DOI: 10.1152/ajpregu.00590.2007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
ANG II promotes inflammation through nuclear factor-kappaB (NF-kappaB)-mediated induction of cytokines and reactive oxygen species (ROS). The aim of the present study was to examine the effect of tetradecylthioacetic acid (TTA), a modified fatty acid, on NF-kappaB, proinflammatory markers, ROS, and nitric oxide (NO) production in two-kidney, one-clip (2K1C) hypertension. The 2K1C TTA-treated group had lower blood pressure (128 +/- 3 mmHg) compared with 2K1C nontreated (178 +/- 5 mmHg, P < 0.001). The p50 and p65 subunits of NF-kappaB were higher in the clipped kidney (0.44 +/- 0.01 and 0.22 +/- 0.01, respectively) compared with controls (0.25 +/- 0.03 and 0.12 +/- 0.02, respectively, P < 0.001). In the 2K1C TTA-treated group, these values were similar to control levels. The same pattern of response was seen in the nonclipped kidney. In 2K1C hypertension, cytokines plasma were higher than in control: TNF-alpha was 13.5 +/- 2 pg/ml (P < 0.03), IL-1beta was 58.8 +/- 10 pg/ml (P = 0.003), IL-6 was 210 +/- 33 pg/ml (P < 0.001), and monocyte chemoattractant protein-1 was 429 +/- 21 pg/ml (P = 0.04). In the 2K1C TTA-treated group, these values were similar to controls, and the same pattern was seen in the clipped kidney. Clipping increased 8-iso-PGF-2alpha (P < 0.01) and decreased NO production (P < 0.01 vs. control) in the urine. TTA treatment normalized these values. NO production was also lower in clipped and nonclipped kidney (P < 0.001). After TTA treatment, these values were similar to controls. The results indicate that TTA has a potent anti-inflammatory effect in 2K1C by inhibition of p50/p65 NF-kappaB subunit activation, reduction of cytokines production and ROS, and enhanced NO production.
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Affiliation(s)
- Liliana M Bivol
- Renal Research Group, Institute of Medicine, Haukeland Hospital, Bergen, Norway.
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33
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Kobori H, Nangaku M, Navar LG, Nishiyama A. The intrarenal renin-angiotensin system: from physiology to the pathobiology of hypertension and kidney disease. Pharmacol Rev 2007; 59:251-87. [PMID: 17878513 DOI: 10.1124/pr.59.3.3] [Citation(s) in RCA: 866] [Impact Index Per Article: 50.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
In recent years, the focus of interest on the role of the renin-angiotensin system (RAS) in the pathophysiology of hypertension and organ injury has changed to a major emphasis on the role of the local RAS in specific tissues. In the kidney, all of the RAS components are present and intrarenal angiotensin II (Ang II) is formed by independent multiple mechanisms. Proximal tubular angiotensinogen, collecting duct renin, and tubular angiotensin II type 1 (AT1) receptors are positively augmented by intrarenal Ang II. In addition to the classic RAS pathways, prorenin receptors and chymase are also involved in local Ang II formation in the kidney. Moreover, circulating Ang II is actively internalized into proximal tubular cells by AT1 receptor-dependent mechanisms. Consequently, Ang II is compartmentalized in the renal interstitial fluid and the proximal tubular compartments with much higher concentrations than those existing in the circulation. Recent evidence has also revealed that inappropriate activation of the intrarenal RAS is an important contributor to the pathogenesis of hypertension and renal injury. Thus, it is necessary to understand the mechanisms responsible for independent regulation of the intrarenal RAS. In this review, we will briefly summarize our current understanding of independent regulation of the intrarenal RAS and discuss how inappropriate activation of this system contributes to the development and maintenance of hypertension and renal injury. We will also discuss the impact of antihypertensive agents in preventing the progressive increases in the intrarenal RAS during the development of hypertension and renal injury.
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Affiliation(s)
- Hiroyuki Kobori
- Department of Medicine, Director of the Molecular Core in Hypertension and Renal Center of Excellence, Tulane University Health Sciences Center, New Orleans, LA 70112-2699, USA.
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34
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Chatterjee C, Martinez D, Gerig JT. Interactions of Trifluoroethanol with [val5]angiotensin II. J Phys Chem B 2007; 111:9355-62. [PMID: 17630790 DOI: 10.1021/jp0711343] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Intermolecular 1H{19F} NOE experiments have been used to explore the interactions of trifluoroethanol (TFE) with the octapeptide hormone [val5]angiotensin II at temperatures from 5 to 25 degrees C. Circular dichroism spectra indicate that 40% trifluoroethanol has an influence on the conformations of the peptide, probably leading to beta-structures. Diffusion experiments show that the mean hydrodynamic radius of the peptide in 40% trifluoroethanol-water is about 8 A, consistent with significant folding of the peptide in this medium. Distance constraints derived from intramolecular NOESY data along with observed vicinal coupling constants (3JCalphaHNH) were used to develop conformations consistent with available data. Assuming that intermolecular 1H{19F} NOEs are the result of diffusive encounters of TFE and peptide molecules, it is shown that no single conformation is consistent with the experimental values of the sigmaHF cross-relaxation parameters. It is argued that the disagreements between observed and expected values of sigmaHF are the result of formation of long-lived (approximately 0.5 ns) fluoroalcohol-peptide complexes, a conclusion consonant with similar studies of other peptide-fluoroalcohol systems. Complex formation appears to be especially prevalent near the charged amino acid side chains of the hormone.
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Affiliation(s)
- Chiradip Chatterjee
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, USA
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35
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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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Li XC, Navar LG, Shao Y, Zhuo JL. Genetic deletion of AT1a receptors attenuates intracellular accumulation of ANG II in the kidney of AT1a receptor-deficient mice. Am J Physiol Renal Physiol 2007; 293:F586-93. [PMID: 17537986 PMCID: PMC2277521 DOI: 10.1152/ajprenal.00489.2006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We and others have previously shown that high levels of ANG II are accumulated in the rat kidney via a type 1 (AT(1)) receptor-mediated mechanism, but it is not known which AT(1) receptor is involved in this process in rodents. We tested the hypothesis that AT(1a) receptor-deficient mice (Agtr1a-/-) are unable to accumulate ANG II intracellularly in the kidney because of the absence of AT(1a) receptor-mediated endocytosis. Adult male wild-type (Agtr1a+/+), heterozygous (Agtr1a+/-), and Agtr1a-/- were treated with vehicle, ANG II (40 ng/min ip via osmotic minipump), or ANG II plus the AT(1) antagonist losartan (10 mg.kg(-1).day(-1) po) for 2 wk. In wild-type mice, ANG II induced hypertension (168 +/- 4 vs. 113 +/- 3 mmHg, P < 0.001), increased kidney-to-body weight ratio (P < 0.01), caused pressure natriuresis (P < 0.05), and elevated plasma and whole kidney ANG II levels (P < 0.001). Concurrent administration of ANG II with losartan attenuated these responses to ANG II. In contrast, Agtr1a-/- mice had lower basal systolic pressures (P < 0.001), smaller kidneys with much fewer AT(1b) receptors (P < 0.001), higher basal 24-h urinary sodium excretion (P < 0.01), as well as basal plasma and whole kidney ANG II levels (P < 0.01). However, intracellular ANG II levels in the kidney were lower in Agtr1a-/- mice. In Agtr1a-/- mice, ANG II slightly increased systolic pressure (P < 0.05) but had no effect on the kidney weight, urinary sodium excretion, and whole kidney ANG II levels. Losartan restored systolic pressure to basal levels and decreased whole kidney ANG II levels by approximately 20% (P < 0.05). These results demonstrate a predominant role of AT(1a) receptors in blood pressure regulation and in the renal responses to long-term ANG II administration, that AT(1b) receptors may play a limited role in blood pressure control and mediating intrarenal ANG II accumulation in the absence of AT(1a) receptors.
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Affiliation(s)
- Xiao C Li
- Laboratory of Receptor and Signal Transduction, Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, MI 48202, USA
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Li XC, Zhuo JL. Selective knockdown of AT1 receptors by RNA interference inhibits Val5-ANG II endocytosis and NHE-3 expression in immortalized rabbit proximal tubule cells. Am J Physiol Cell Physiol 2007; 293:C367-78. [PMID: 17428839 PMCID: PMC2277517 DOI: 10.1152/ajpcell.00463.2006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Receptor-mediated endocytosis of extracellular ANG II has been suggested to play an important role in the regulation of proximal tubule cell (PTC) function. Using immortalized rabbit PTCs as an in vitro cell culture model, we tested the hypothesis that extracellular ANG II is taken up by PTCs through angiotensin type 1 receptor (AT(1); or AT(1a)) receptor-mediated endocytosis and that inhibition of ANG II endocytosis using a selective AT(1) receptor small-interfering RNA (siRNA; AT(1)R siRNA) or endocytotic inhibitors exerts a physiological effect on total and apical sodium and hydrogen exchanger isoform 3 (NHE-3) protein abundance. Western blots and live cell imaging with FITC-labeled ANG II confirmed that transfection of PTCs with a human specific AT(1)R siRNA for 48 h selectively knocked down AT(1) receptor protein by 76 +/- 5% (P < 0.01), whereas transfection with a scrambled siRNA had little effect. In nontransfected PTCs, exposure to extracellular ANG II (1 nM) for 60 min at 37 degrees C increased intracellular ANG II accumulation by 67% (control: 566 +/- 55 vs. ANG II: 943 +/- 160 pg/mg protein, P < 0.05) and induced mitogen-activated protein kinase extracellular signal-regulated kinase (ERK) 1/2 phosphorylation (163 +/- 15% of control, P < 0.01). AT(1)R siRNA reduced ANG II endocytosis to a level similar to losartan, which blocks cell surface AT(1) receptors (557 +/- 37 pg/mg protein, P < 0.05 vs. ANG II), or to colchicine, which disrupts cytoskeleton microtubules (613 +/- 12 pg/mg protein, P < 0.05 vs. ANG II). AT(1)R siRNA, losartan, and colchicine all attenuated ANG II-induced ERK1/2 activation and total cell lysate and apical membrane NHE-3 abundance. The scrambled siRNA had no effect on ANG II endocytosis, ERK1/2 activation, or NHE-3 expression. These results suggest that AT(1) receptor-mediated endocytosis of extracellular ANG II may regulate proximal tubule sodium transport by increasing total and apical NHE-3 proteins.
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MESH Headings
- Angiotensin II/metabolism
- Angiotensin II Type 1 Receptor Blockers/pharmacology
- Animals
- Cell Line
- Colchicine/pharmacology
- Cold Temperature
- Down-Regulation
- Endocytosis/drug effects
- Kidney Tubules, Proximal/cytology
- Kidney Tubules, Proximal/drug effects
- Kidney Tubules, Proximal/metabolism
- Losartan/pharmacology
- Microtubules/metabolism
- Mitogen-Activated Protein Kinase 1/metabolism
- Mitogen-Activated Protein Kinase 3/metabolism
- Phosphorylation
- RNA Interference
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- Rabbits
- Receptor, Angiotensin, Type 1/deficiency
- Receptor, Angiotensin, Type 1/genetics
- Receptor, Angiotensin, Type 1/metabolism
- Sodium/metabolism
- Sodium-Hydrogen Exchanger 3
- Sodium-Hydrogen Exchangers/metabolism
- Time Factors
- Transfection
- Tubulin Modulators/pharmacology
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Affiliation(s)
- Xiao C Li
- Div. of Hypertension and Vascular Research, Henry Ford Hospital, 2799 West Grand Blvd., Detroit, MI 48202, USA
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38
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Schalekamp MADH. A local pre-receptor mechanism of hormone stimulus amplification: focus on angiotensin II in resistance blood vessels. J Hypertens 2007; 24:1787-96. [PMID: 16915028 DOI: 10.1097/01.hjh.0000242403.91332.70] [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: 11/26/2022]
Abstract
BACKGROUND The in-vivo correlation between vascular tone and the concentration of free angiotensin (Ang) II at the level of the arterioles, under (patho)physiological conditions, is not known. OBJECTIVE To examine the in-vivo kinetics of binding of Ang II to Ang II type 1 (AT1) receptors in vascular tissue. METHODS AND RESULTS A plane vascular smooth muscle (VSM) sheet containing a single layer of cells, at one side exposed to Ang II, was the starting point for designing a mathematical model based on local receptor density and geometric considerations and on kinetic parameters of Ang II diffusion and Ang II-AT1 receptor complex formation and internalization. Calculations demonstrate that a diffusing Ang II molecule at short distance from the receptor has an almost 100% chance to be actually bound, so that the apparent binding rate constant (per unit of receptor concentration) is greatly augmented. This pre-receptor stimulus amplification (PRESTAMP) mechanism is sustained by AT1 receptor-mediated endocytosis and receptor recycling. On the other hand, PRESTAMP also enhances endocytotic receptor downregulation, and calculations predict that steady-state levels of Ang II above threshold have relatively little additional effect. CONCLUSION The results explain why physiological concentrations of free Ang II far below the equilibrium dissociation constant of its reaction with AT1 receptors are sufficient to increase vascular resistance, and why a correlation between blood pressure and the concentration of free Ang II is often difficult to demonstrate.
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Mitchell KD, Bagatell SJ, Miller CS, Mouton CR, Seth DM, Mullins JJ. Genetic clamping of renin gene expression induces hypertension and elevation of intrarenal Ang II levels of graded severity in Cyp1a1-Ren2 transgenic rats. J Renin Angiotensin Aldosterone Syst 2007; 7:74-86. [PMID: 17083061 DOI: 10.3317/jraas.2006.013] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
INTRODUCTION Transgenic rats with inducible angiotensin II (Ang II)-dependent hypertension (strain name: TGR[Cyp1a1-Ren2]) were generated by inserting the mouse Ren2 renin gene, fused to the cytochrome P450 1a1 (Cyp1a1) promoter, into the genome of the rat. The present study was performed to characterise the changes in plasma and kidney tissue Ang II levels and in renal haemodynamic function in Cyp1a1-Ren2 rats following induction of either slowly developing or malignant hypertension in these transgenic rats. MATERIALS AND METHODS Arterial blood pressure (BP) and renal haemodynamics and excretory function were measured in pentobarbital sodium-anaesthetised Cyp1a1- Ren2 rats fed a normal diet containing either a low dose (0.15%, w/w for 1415 days) or high dose (0.3%, w/w for 1112 days) of the aryl hydrocarbon indole-3-carbinol (I3C) to induce slowly developing and malignant hypertension, respectively. In parallel experiments, arterial blood samples and kidneys were harvested for measurement of Ang II levels by radioimmunoassay. RESULTS Dietary I3C increased plasma renin activity (PRA), plasma Ang II levels, and arterial BP in a dose-dependent manner. Induction of different fixed levels of renin gene expression and PRA produced hypertensive phenotypes of varying severity with rats developing either mild or malignant forms of hypertensive disease. Administration of I3C, at a dose of 0.15% (w/w), induced a slowly developing form of hypertension whereas administration of a higher dose (0.3%) induced a more rapidly developing hypertension and the clinical manifestations of malignant hypertension including severe weight loss. Both hypertensive phenotypes were characterised by reduced renal plasma flow, increased filtration fraction, elevated PRA, and increased plasma and intrarenal Ang II levels. These I3C-induced changes in renal haemodynamics, PRA and kidney Ang II levels were more pronounced in Cyp1a1-Ren2 rats with malignant hypertension. Chronic administration of the AT1-receptor antagonist, hypertension, the associated changes in renal haemodynamics, and the augmentation of intrarenal Ang II levels. CONCLUSIONS Activation of AT1-receptors by Ang II generated as a consequence of induction of the Cyp1a1-Ren2 transgene mediates the increased arterial pressure and the associated reduction of renal haemodynamics and enhancement of intrarenal Ang II levels in hypertensive Cyp1a1-Ren2 transgenic rats.
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Affiliation(s)
- Kenneth D Mitchell
- Department of Physiology, Tulane University Health Sciences Center, New Orleans, Louisiana, USA.
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Vanourková Z, Kramer HJ, Husková Z, Vanecková I, Opocenský M, Chábová VC, Tesar V, Skaroupková P, Thumová M, Dohnalová M, Mullins JJ, Cervenka L. AT1 receptor blockade is superior to conventional triple therapy in protecting against end-organ damage in Cyp1a1-Ren-2 transgenic rats with inducible hypertension. J Hypertens 2006; 24:2465-72. [PMID: 17082731 DOI: 10.1097/01.hjh.0000251909.00923.22] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE In the present study we compared the effects of treatment with the AT1 receptor antagonist candesartan and of 'triple therapy' (hydralazine, hydrochlorothiazide, reserpine) on the course of blood pressure, cardiac hypertrophy and angiotensin II concentrations after induction of hypertension in transgenic rats with inducible expression of the mouse renin gene (Cyp1a1-Ren-2 rats). METHODS Hypertension was induced in Cyp1a1-Ren-2 rats through dietary administration of the natural xenobiotic indole-3-carbinol (I3C, 0.3%) for 4 days. Starting on the day before administration of I3C, rats were treated either with candesartan or received triple therapy for 9 days. Systolic blood pressure was measured in conscious animals. Rats were decapitated and angiotensin II levels in plasma and in whole kidney and left ventricular tissues were determined by radioimmunoassay. RESULTS Administration of I3C resulted in the development of severe hypertension and cardiac hypertrophy that was accompanied by marked elevations of plasma and tissue angiotensin II concentrations. Candesartan treatment prevented the development of hypertension and cardiac hypertrophy and was associated with a reduction of tissue angiotensin II concentrations. In contrast, triple therapy, despite maintaining systolic blood pressure in the normotensive range, did not prevent the development of cardiac hypertrophy and tissue angiotensin II augmentations. CONCLUSIONS Our findings indicate that hypertension in Cyp1a1-Ren-2 rats is a clearly angiotensin II-dependent model of hypertension with elevated circulating and tissue angiotensin II concentrations, and that antihypertensive treatment with AT1 receptor blockade is superior to conventional triple therapy in effective protection against hypertension-induced end-organ damage in this rat model.
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Affiliation(s)
- Zdenka Vanourková
- Center for Experimental Medicine, Institute for Clinical and Experimental Medicine, Prague, Germany
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Hayden MR, Chowdhury NA, Cooper SA, Whaley-Connell A, Habibi J, Witte L, Wiedmeyer C, Manrique CM, Lastra G, Ferrario C, Stump C, Sowers JR. Proximal tubule microvilli remodeling and albuminuria in the Ren2 transgenic rat. Am J Physiol Renal Physiol 2006; 292:F861-7. [PMID: 17032939 DOI: 10.1152/ajprenal.00252.2006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
TG(mRen2)27 (Ren2) transgenic rats overexpress the mouse renin gene, with subsequent elevated tissue ANG II, hypertension, and nephropathy. The proximal tubule cell (PTC) is responsible for the reabsorption of 5-8 g of glomerular filtered albumin each day. Excess filtered albumin may contribute to PTC damage and tubulointerstitial disease. This investigation examined the role of ANG II-induced oxidative stress in PTC structural remodeling: whether such changes could be modified with in vivo treatment with ANG type 1 receptor (AT(1)R) blockade (valsartan) or SOD/catalase mimetic (tempol). Male Ren2 (6-7 wk old) and age-matched Sprague-Dawley rats were treated with valsartan (30 mg/kg), tempol (1 mmol/l), or placebo for 3 wk. Systolic blood pressure, albuminuria, N-acetyl-beta-D-glucosaminidase, and kidney tissue malondialdehyde (MDA) were measured, and x60,000 transmission electron microscopy images were used to assess PTC microvilli structure. There were significant differences in systolic blood pressure, albuminuria, lipid peroxidation (MDA and nitrotyrosine staining), and PTC structure in Ren2 vs. Sprague-Dawley rats (each P < 0.05). Increased mean diameter of PTC microvilli in the placebo-treated Ren2 rats (P < 0.05) correlated strongly with albuminuria (r(2) = 0.83) and moderately with MDA (r(2) = 0.49), and there was an increase in the ratio of abnormal forms of microvilli in placebo-treated Ren2 rats compared with Sprague-Dawley control rats (P < 0.05). AT(1)R blockade, but not tempol treatment, abrogated albuminuria and N-acetyl-beta-d-glucosaminidase; both therapies corrected abnormalities in oxidative stress and PTC microvilli remodeling. These data indicate that PTC structural damage in the Ren2 rat is related to the oxidative stress response to ANG II and/or albuminuria.
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Affiliation(s)
- Melvin R Hayden
- Department of Internal Medicine, University of Missouri, Columbia, USA
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Schalekamp MADH, Danser AHJ. Angiotensin II production and distribution in the kidney: I. A kinetic model. Kidney Int 2006; 69:1543-52. [PMID: 16572118 DOI: 10.1038/sj.ki.5000303] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Information on the levels of angiotensin II (Ang II) and its receptors in the various renal tissue compartments is still incomplete. A model is presented describing the kinetics of Ang II production, distribution, and disposal in the renal cortex. Basic features are: (1) the model is designed to derive, from Ang II measurements in blood and in whole tissue, estimates of the local densities of the Ang II type 1 (AT(1)) and type 2 (AT(2)) receptors, and to calculate the concentrations of endocrine and paracrine Ang II they actually 'see'; (2) glomerular and peritubular tissue are conceived as separate regions (glomerular region (Glom), peritubular region (Pt)); (3) in Glom and in Pt, Ang II is homogeneously distributed in capillary blood and in interstitial fluid; (4) the model allows for local Ang II concentration gradients between interstitium and blood; (5) Ang II from the circulation diffuses into the interstitium of Glom after convective transcapillary transport; (6) Ang II produced in tubules or Pt enters the microcirculation through diffusive overflow from interstitium; (7) the presence of cell-surface-bound Ang II depends on the reaction with AT(1) and AT(2) receptors, and the presence of intracellular Ang II depends on the internalization of Ang II - AT(1) receptor complex; and (8) the model provides for glomerular filtration, vasopeptidase-mediated degradation, and intracellular degradation as mechanisms of elimination. This model can serve as a framework for detailed quantitative studies of the renin-angiotensin system in the kidney.
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Husková Z, Kramer HJ, Vanourková Z, Cervenka L. Effects of changes in sodium balance on plasma and kidney angiotensin II levels in anesthetized and conscious Ren-2 transgenic rats. J Hypertens 2006; 24:517-27. [PMID: 16467655 DOI: 10.1097/01.hjh.0000209988.51606.c7] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Since there is as yet no general agreement regarding the role of plasma and kidney angiotensin II (ANG II) in the development of hypertension in Ren-2 transgenic rats (TGR), in the present study we evaluated plasma and kidney ANG II levels in anesthetized and conscious TGR and in normotensive Hannover-Sprague-Dawley rats (HanSD) fed a normal salt diet (NS). Given the importance of ANG II in the development of salt-sensitive hypertension, and the fact that hypertensinogenic actions of ANG II are mediated via ANG II type 1 (AT1) receptors, the effects of high salt (HS) intake and of sodium depletion on blood pressure (BP), ANG II levels and kidney AT1 receptor protein expression in TGR and HanSD were also examined. METHODS Rats were maintained on a NS diet (0.6% NaCl) or fed a HS diet (2% NaCl) for 4 days or were sodium depleted (40 mg/l furosemide for 1 day followed by 3 days of 0.01% NaCl diet). They were sacrificed either by an overdose of anesthetic (thiopental sodium) or by decapitation (without anesthetic) and plasma and kidney ANG II levels were determined by radioimmunoassay during the prehypertensive (32 days old), the early (52 days) and the maintenance (90 days) phases of hypertension. Total kidney AT1 receptor protein levels were assessed by Western blot analysis. RESULTS In anesthetized animals fed the NS diet, plasma ANG II levels were lower in 32-day-old TGR than in HanSD, but at 52 and 90 days of age no significant differences were noted. ANG II concentrations in kidney tissue were similar in 32- and 90-day-old TGR and HanSD, but were higher in 52-day-old TGR than in HanSD. In contrast, in conscious animals immediately after decapitation, plasma and kidney ANG II levels were higher in TGR than in HanSD at all ages. HS diet did not change BP but suppressed ANG II levels in HanSD at all ages. In contrast, HS diet increased BP but did not decrease plasma and kidney ANG II levels in TGR at all ages. Sodium restriction did not alter BP and resulted in a marked increase in ANG II levels in HanSD, but caused a significant decrease in BP in TGR without altering plasma or tissue ANG II concentrations. There were no significant differences in renal AT1 receptor protein expression between HanSD and TGR at any age of any of the experimental groups. CONCLUSIONS On the basis of our present results we conclude that TGR exhibit a disrupted interaction between sodium homeostasis and the regulation of the renin-angiotensin system (RAS) activity which results in the loss of BP regulation in this model.
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Affiliation(s)
- Zuzana Husková
- Center for Experimental Medicine, Institute for Clinical and Experimental Medicine, Prague, Czech Republic
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Li XC, Carretero OA, Navar LG, Zhuo JL. AT1 receptor-mediated accumulation of extracellular angiotensin II in proximal tubule cells: role of cytoskeleton microtubules and tyrosine phosphatases. Am J Physiol Renal Physiol 2006; 291:F375-83. [PMID: 16478976 PMCID: PMC2276851 DOI: 10.1152/ajprenal.00405.2005] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Long-term angiotensin II (ANG II) administration is associated with increased ANG II accumulation in the kidney, but intrarenal compartment(s) involved in this response remains to be determined. We tested the hypothesis that 1) extracellular ANG II is taken up by proximal tubule cells (PTCs) through AT(1) receptor-mediated endocytosis, 2) this process is regulated by cytoskeleton microtubule- and tyrosine phosphatase-dependent mechanisms, and 3) AT(1) receptor-mediated endocytosis of ANG II has a functional relevance by modulating intracellular cAMP signaling. In cultured PTCs, [(125)I]Tyr-labeled ANG II and fluorescein labeled-ANG II were internalized in a time-dependent manner and colocalized with the endosome marker Alexa Fluor 594-transferrin. Endocytosis of extracellular ANG II was inhibited by the AT(1) receptor blocker losartan (16.5 +/- 4.6%, P < 0.01 vs. ANG II, 78.3 +/- 6.2%) and by the tyrosine phosphatase inhibitor phenylarsine oxide (PAO; 30.0 +/- 3.5%, P < 0.05 vs. ANG II). Intracellular ANG II levels were increased by approximately 58% (basal, 229.8 +/- 11.4 vs. ANG II, 361.3 +/- 11.8 pg ANG II/mg protein, P < 0.01), and the responses were blocked by losartan (P < 0.01), the cytoskeleton microtubule inhibitor colchicine (P < 0.05), and PAO (P < 0.01), whereas depletion of clathrin-coated pits with hyperosmotic sucrose had no effect (356.1 +/- 25.5 pg ANG II/mg protein, not significant). ANG II accumulation was associated with significant inhibition of both basal (control, 15.5 +/- 2.8 vs. ANG II, 9.1 +/- 2.4 pmol/mg protein, P < 0.05) and forskolin-stimulated cAMP signaling (forskolin, 68.7 +/- 8.6 vs. forskolin + ANG II, 42.8 +/- 13.8 pmol/mg protein, P < 0.01). These effects were blocked by losartan and PAO. We conclude that extracellular ANG II is internalized in PTCs through AT(1) receptor-mediated endocytosis and that internalized ANG II may play a functional role in proximal tubule cells by inhibiting intracellular cAMP signaling.
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MESH Headings
- Angiotensin II/metabolism
- Angiotensin II/pharmacology
- Angiotensin II Type 1 Receptor Blockers/pharmacology
- Animals
- Arsenicals/pharmacology
- Cells, Cultured
- Colchicine/pharmacology
- Colforsin/pharmacology
- Cyclic AMP/physiology
- Cytoskeleton/drug effects
- Cytoskeleton/metabolism
- Endocytosis/physiology
- Enzyme Inhibitors/pharmacology
- Gene Expression Regulation/physiology
- Imidazoles/pharmacology
- Kidney Tubules, Proximal/cytology
- Kidney Tubules, Proximal/metabolism
- Losartan/pharmacology
- Microtubules/drug effects
- Microtubules/metabolism
- Protein Tyrosine Phosphatase, Non-Receptor Type 1
- Protein Tyrosine Phosphatases/antagonists & inhibitors
- Protein Tyrosine Phosphatases/physiology
- Pyridines/pharmacology
- Rabbits
- Receptor, Angiotensin, Type 1/drug effects
- Receptor, Angiotensin, Type 1/genetics
- Receptor, Angiotensin, Type 1/physiology
- Receptor, Angiotensin, Type 2/analysis
- Receptor, Angiotensin, Type 2/drug effects
- Receptor, Angiotensin, Type 2/genetics
- Receptor, Angiotensin, Type 2/physiology
- Signal Transduction/physiology
- Sucrose/pharmacology
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Affiliation(s)
- Xiao C Li
- Laboratory of Receptor and Signal Transduction, Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit 48202, USA
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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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Zhuo JL, Li XC, Garvin JL, Navar LG, Carretero OA. Intracellular ANG II induces cytosolic Ca2+ mobilization by stimulating intracellular AT1 receptors in proximal tubule cells. Am J Physiol Renal Physiol 2005; 290:F1382-90. [PMID: 16380461 PMCID: PMC2276850 DOI: 10.1152/ajprenal.00269.2005] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Intracellular ANG II induces biological effects in nonrenal cells, but it is not known whether it plays a physiological role in renal proximal tubule cells (PTCs). PTCs express angiotensinogen, renin, and angiotensin-converting enzyme mRNAs, suggesting the presence of high levels of intracellular ANG II. We determined if microinjection of ANG II directly in single PTCs increases intracellular calcium concentration ([Ca2+]i) and, if so, elucidated the cellular mechanisms involved. Changes in [Ca2+]i responses were studied by fluorescence imaging using the Ca2+ indicator fluo 3. ANG II (1 nM) was microinjected directly in the cells, whereas cell-surface angiotensin type 1 (AT1) receptors were blocked by losartan (10 microM). When ANG II (1 nM) was added to the perfusate, there was a marked increase in [Ca2+]i that was blocked by extracellular losartan. With losartan in the perfusate, intracellular microinjection of ANG II elicited a robust increase in cytoplasmic [Ca2+]i that peaked at 30 s (basal: 2.2 +/- 0.3 vs. ANG II: 14.9 +/- 0.4 relative fluorescence units; P < 0.01). Chelation of extracellular Ca2+ with EGTA (2 mM) did not alter microinjected ANG II-induced [Ca2+]i responses (Ca2+ free + ANG II: 12.3 +/- 2.6 relative fluorescence units, not significant vs. ANG II); however, pretreatment with thapsigargin to deplete intracellular Ca2+ stores or with U-73122 to inhibit phospholipase C (1 microM each) markedly attenuated microinjected ANG II-induced [Ca2+]i responses. Combined microinjection of ANG II and losartan abolished [Ca2+]i responses, whereas a combination of ANG II and PD-123319 had no effect. These data demonstrate for the first time that direct microinjection of ANG II in single PTCs increases [Ca2+]i by stimulating intracellular AT1 receptors and releases Ca2+ from intracellular stores, suggesting that intracellular ANG II may play a physiological role in PTC function.
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MESH Headings
- Angiotensin II/analysis
- Angiotensin II/pharmacology
- Animals
- Blotting, Western
- Calcium/metabolism
- Calcium/pharmacology
- Cells, Cultured
- Cytosol/metabolism
- Enzyme Activation/drug effects
- Kidney Tubules, Proximal/chemistry
- Kidney Tubules, Proximal/metabolism
- Kidney Tubules, Proximal/ultrastructure
- Microinjections
- Rabbits
- Receptor, Angiotensin, Type 1/analysis
- Receptor, Angiotensin, Type 1/drug effects
- Receptor, Angiotensin, Type 1/physiology
- Receptor, Angiotensin, Type 2/drug effects
- Receptor, Angiotensin, Type 2/physiology
- Thapsigargin/pharmacology
- Type C Phospholipases/metabolism
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Affiliation(s)
- Jia L Zhuo
- Division of Hypertension and Vascular Research, Henry Ford Hospital, 2799 West Grand Blvd., Detroit, MI 48202, USA.
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Fujihara CK, Velho M, Malheiros DMAC, Zatz R. An extremely high dose of losartan affords superior renoprotection in the remnant model. Kidney Int 2005; 67:1913-24. [PMID: 15840039 DOI: 10.1111/j.1523-1755.2005.00290.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Rats subjected to 5/6 renal ablation (NX) exhibit large renal amounts of angiotensin II (Ang II) and of its main receptor, AT-1R. At previously used doses, AT-1R blockers (ARB) offer only partial renal protection. A possible explanation for this limited effect is that these doses are insufficient to block most of the abnormally expressed AT-1R. We investigated whether extremely high doses of the ARB, losartan (L), offer better protection than conventional doses in the NX model. METHODS Thirty days after NX, tail-cuff pressure (TCP), albuminuria (U(alb)V, mg/day), glomerulosclerosis index (GSI), fractional interstitial area (%INT), and macrophage infiltration (MO) were evaluated in a separate group (NX(pre)). The remaining rats were then subdivided among 4 groups: NX+V, receiving vehicle; NX+L50, treated with L, at the "conventional" dose of 50 mg/kg/day; NX+L500, receiving L, 500 mg/kg/day; and NX+HH, receiving hydrochlorothiazide and hydralazine to lower blood pressure to a similar extent as in group L500. RESULTS After a month of treatment, blood pressure and renal vascular resistance were lowest in group L500. Glomerular pressure was lowered by a similar extent by L50 and L500, while GFR was similar among groups. U(alb)V, TCP, and renal injury were only partially reduced by L50 120 days after renal ablation. By contrast, L500 arrested renal inflammation and glomerular/interstitial injury at pretreatment levels, and promoted regression of hypertension and U(alb)V, causing no apparent untoward effects. CONCLUSION The renal protection afforded by ARB in NX is dose dependent. Maximal protection may require doses several fold higher than those currently employed.
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Affiliation(s)
- Clarice Kazue Fujihara
- Renal Division, Department of Clinical Medicine, Faculty of Medicine, University of São Paulo, São Paulo, Brazil
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Ando K, Takahashi K, Shibata S, Matsui H, Fujita M, Shibagaki Y, Shimosawa T, Isshiki M, Fujita T. Two cases of renovascular hypertension and ischemic renal dysfunction: reliable choice of examinations and treatments. Hypertens Res 2005; 27:985-92. [PMID: 15894840 DOI: 10.1291/hypres.27.985] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We experienced two aged patients with atherosclerotic renovascular stenosis associated with hypertension and ischemic nephropathy. Both patients exhibited sudden rise in blood pressure (BP) and progressive aggravation of renal dysfunction. In these patients, the use of contrast medium to screen for renal artery stenosis (RAS) ran the risk of further deterioration of renal function. We therefore used magnetic resonance angiography (MRA), which is less conducive to renal damage, to screen for RAS. One-sided RAS was treated by percutaneous transluminal angioplasty of the renal artery (PTRA) and stenting. As a result, BP decreased in both patients. Serum creatinine (Cr) decreased slightly in one patient, whereas, in the other, serum Cr increased transiently and then decreased and stabilized to pre-treatment levels. Thus, although it is unclear whether the combination of PTRA and stenting is among the best treatments for patients with RAS and moderate-to-severe renal dysfunction, PTRA and stenting are clearly of benefit in selected patients. In addition, recent progress in characterizing the pathophysiology of ischemic nephropathy associated with renovascular hypertension has created interest in the therapeutic potential of angiotensin II receptor antagonists, sympatholytic agents, and antioxidants. Therefore, we discuss the therapeutic utility of PTRA and stenting and the above-mentioned medications in patients with RAS and renal dysfunction.
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Affiliation(s)
- Katsuyuki Ando
- Department of Nephrology and Endocrinology, Faculty of Medicine, University of Tokyo, Hongo, Tokyo, Japan
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Bivol LM, Vågnes OB, Iversen BM. The renal vascular response to ANG II injection is reduced in the nonclipped kidney of two-kidney, one-clip hypertension. Am J Physiol Renal Physiol 2005; 289:F393-400. [PMID: 15784843 DOI: 10.1152/ajprenal.00319.2004] [Citation(s) in RCA: 14] [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
The ANG II receptor 1 (AT(1)R) level in the nonclipped kidney of two-kidney, one-clip hypertension (2K1C) has shown to be unchanged despite a high circulating angiotensin (ANG) II level. To examine the vasoreactive response to ANG II in this kidney, injections of ANG II into renal artery were performed 6 wk after clipping of the kidney and compared with normotensive controls. The renal blood flow (RBF) response to 2.5 ng ANG II was measured by a Transonic transit-time flowmeter, before and after indomethacin and candesartan treatment, and analyzed by a computer program. The RBF response to 5 ng arginine-vasopressin (AVP) was examined for comparison with ANG II. The mRNA for AT(1A) and AT(1B) as well as Western blotting for AT(1)R in renal resistance vessels were determined, and plasma renin activity (PRA) was measured. Systolic blood pressure was 183 +/- 4 mmHg in 2K1C rats compared with 113 +/- 1 mmHg in controls (P < 0.001). PRA was significantly increased in 2K1C animals (P < 0.05). Injection of ANG II reduced RBF with 10 +/- 2% in the nonclipped kidney and 24 +/- 3% in controls (P < 0.001). After indomethacin, the RBF response increased from 10 +/- 2 to 20 +/- 3% (P < 0.02) in 2K1C rats and from 24 +/- 3 to 34 +/- 6% in controls (P < 0.01). The doses of candesartan needed to completely inhibit RBF response to ANG II were 30 microg/kg in the nonclipped kidney and 100 microg/kg in controls (P < 0.001). Western blotting and mRNA for AT(1A) and AT(1B) in the nonclipped kidney were similar to the controls. The results indicate that despite no difference in total AT(1)R levels, functional AT(1)R is downregulated in the nonclipped kidney of 2K1C rats.
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Abstract
PURPOSE OF REVIEW Recent studies have reported that intrarenal angiotensin II content and angiotensin II concentrations in the proximal tubular fluid and renal interstitial fluid are much greater than the circulating angiotensin II levels. These high intrarenal angiotensin II levels are responsible for regulating renal hemodynamics and tubular transport. RECENT FINDINGS Intrarenal angiotensin II levels have been assessed from total tissue contents as well as renal interstitial fluid and proximal tubular fluid concentrations. Total tissue contents expressed per gram of tissue weight are greater than plasma angiotensin II concentrations; tubular fluid concentrations and renal interstitial fluid concentrations are even greater in the range of 3-10 pmoles/ml. In hypertensive states, there is also an increased intracellular accumulation of angiotensin II mediated by angiotensin type 1 receptor-dependent endocytosis. The high intrarenal angiotensin II levels are also caused by the presence of angiotensinogen messenger RNA and protein in the proximal tubule cells. Furthermore, there is positive amplification by which increases in circulating angiotensin II stimulate increased production and secretion of angiotensinogen, which is also manifested as an increased urinary excretion rate. SUMMARY The ability of the kidney to generate high intratubular and interstitial concentrations allows the kidney to regulate intrarenal levels in accord with the homeostatic needs for the regulation of renal hemodynamics and tubular reabsorption and the regulation of sodium balance. When inappropriately stimulated, high intrarenal angiotensin II levels contribute to excessive salt and water retention, the development of hypertension, and long-term proliferative effects leading to renal injury.
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Affiliation(s)
- L Gabriel Navar
- Department of Physiology and Hypertension, Renal Center of Excellence, Tulane University Health Scences Center, New Orleans, Louisiana 70112, USA.
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