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Zicha J, Hojná S, Kopkan L, Červenka L, Vaněčková I. The absence of sympathoexcitation during the development of hypertension in Cyp1a1 Ren-2 transgenic rats. Physiol Res 2019; 68:329-334. [PMID: 31037948 DOI: 10.33549/physiolres.934151] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The insertion of mouse renin gene (Ren-2) into the genome of normotensive rats causes a spontaneous rise of blood pressure (BP), leading to an angiotensin II (Ang II)-dependent form of hypertension in transgenic (mRen-2)27 rats (TGR). However, enhanced sympathetic BP component was demonstrated in heterozygous TGR aged 20 weeks. In the present study we used another model, i.e. Cyp1a1-Ren-2 transgenic rats (iTGR) in which hypertension can be induced by natural xenobiotic indole-3 carbinol (I3C) added to the diet. We investigated whether the development of high blood pressure (BP) in 5-month-old iTGR animals fed I3C diet for 10 days is solely due to enhanced Ang II-dependent vasoconstriction or whether enhanced sympathetic vasoconstriction also participates in BP maintenance in this form of hypertension. Using acute sequential blockade of renin-angiotensin system (RAS), sympathetic nervous system (SNS) and NO synthase (NOS) we have demonstrated that the observed gradual increase of BP in iTGR fed I3C diet was entirely due to the augmentation of Ang II-dependent BP component without significant changes of sympathetic BP component. Thus, the hypertension in iTGR resembles to that of homozygous TGR in which high BP was entirely dependent on Ang II-dependent vasoconstriction. Moreover, our measurements of acute BP response to Rho kinase inhibitor fasudil in animals subjected to a combined blockade of RAS, SNS and NOS indicated the attenuation of basal calcium sensitization in both iTGR and homozygous TGR.
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Affiliation(s)
- J Zicha
- Institute of Physiology CAS, Vídeňská 1083, 142 20 Prague 4, Czech Republic.
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Mullins LJ, Conway BR, Menzies RI, Denby L, Mullins JJ. Renal disease pathophysiology and treatment: contributions from the rat. Dis Model Mech 2017; 9:1419-1433. [PMID: 27935823 PMCID: PMC5200898 DOI: 10.1242/dmm.027276] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The rat has classically been the species of choice for pharmacological studies and disease modeling, providing a source of high-quality physiological data on cardiovascular and renal pathophysiology over many decades. Recent developments in genome engineering now allow us to capitalize on the wealth of knowledge acquired over the last century. Here, we review rat models of hypertension, diabetic nephropathy, and acute and chronic kidney disease. These models have made important contributions to our understanding of renal diseases and have revealed key genes, such as Ace and P2rx7, involved in renal pathogenic processes. By targeting these genes of interest, researchers are gaining a better understanding of the etiology of renal pathologies, with the promised potential of slowing disease progression or even reversing the damage caused. Some, but not all, of these target genes have proved to be of clinical relevance. However, it is now possible to generate more sophisticated and appropriate disease models in the rat, which can recapitulate key aspects of human renal pathology. These advances will ultimately be used to identify new treatments and therapeutic targets of much greater clinical relevance. Summary: This Review highlights the key role that the rat continues to play in improving our understanding of the etiologies of renal pathologies, and how these insights have opened up new therapeutic avenues.
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Affiliation(s)
- Linda J Mullins
- University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
| | - Bryan R Conway
- University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
| | - Robert I Menzies
- University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
| | - Laura Denby
- University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
| | - John J Mullins
- University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
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Efficacy of the superoxide dismutase mimetic tempol in animal hypertension models: a meta-analysis. J Hypertens 2016; 33:14-23. [PMID: 25380160 DOI: 10.1097/hjh.0000000000000422] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVE Considering the growing body of evidence that indicates the contribution of superoxide anions (O2) and other reactive oxygen species (ROS) to the development of hypertension, we assessed whether animal models of hypertension have a benefic effect with tempol, a superoxide dismutase mimetic, to help augment the design of future studies. METHODS Studies published between July 1998 and December 2012 on blood pressure (BP) in different hypertensive models were obtained after an electronic and manual search of PubMed. In-depth analyses of the methodological quality of the studies and the mean arterial pressure (MAP) changes after treatment with tempol were performed, as well as the subgroup analyses on the route of tempol delivery. RESULTS Out of the 144 identified studies, 28 were included after screening. The data showed that tempol reduced MAP by computing the standardized mean difference with the value of 4.622 (95% confidence interval 3.24-5.99). The quality of studies included in the meta-analysis was category II; however, omission of details in the trials might have biased the results. There was substantial heterogeneity in the results with an I of 94.45%, which persisted after stratifying for the route of tempol delivery. CONCLUSION In conclusion, this analysis shows that antioxidant treatment with tempol can reduce BP, suggesting that ROS plays a role in the pathogenesis of increased BP in the hypertension models used in the current research practice.
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Majid DSA, Prieto MC, Navar LG. Salt-Sensitive Hypertension: Perspectives on Intrarenal Mechanisms. Curr Hypertens Rev 2015; 11:38-48. [PMID: 26028244 DOI: 10.2174/1573402111666150530203858] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 04/22/2015] [Accepted: 04/24/2015] [Indexed: 12/12/2022]
Abstract
Salt sensitive hypertension is characterized by increases in blood pressure in response to increases in dietary salt intake and is associated with an enhanced risk of cardiovascular and renal morbidity. Although researchers have sought for decades to understand how salt sensitivity develops in humans, the mechanisms responsible for the increases in blood pressure in response to high salt intake are complex and only partially understood. Until now, scientists have been unable to explain why some individuals are salt sensitive and others are salt resistant. Although a central role for the kidneys in the development of salt sensitivity and hypertension has been generally accepted, it is also recognized that hypertension is of multifactorial origin and a variety of factors can induce, or prevent, blood pressure responsiveness to the manipulation of salt intake. Excess salt intake in susceptible persons may also induce inappropriate central and sympathetic nervous system responses and increase the production of intrarenal angiotensin II, catecholamines and other factors such as oxidative stress and inflammatory cytokines. One key factor is the concomitant inappropriate or paradoxical activation of the intrarenal renin-angiotensin system, by high salt intake. This is reflected by the increases in urinary angiotensinogen during high salt intake in salt sensitive models. A complex interaction between neuroendocrine factors and the kidney may underlie the propensity for some individuals to retain salt and develop salt-dependent hypertension. In this review, we focus mainly on the renal contributions that provide the mechanistic links between chronic salt intake and the development of hypertension.
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Affiliation(s)
- Dewan S A Majid
- Department of Physiology, SL39, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA.
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Increased sympathetic drive during the onset of hypertension in conscious Cyp1a1-Ren2 rats. Pflugers Arch 2013; 466:459-66. [DOI: 10.1007/s00424-013-1338-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 08/06/2013] [Accepted: 08/14/2013] [Indexed: 12/21/2022]
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Chronic direct renin inhibition with aliskiren prevents the development of hypertension in Cyp1a1-Ren2 transgenic rats with inducible ANG II-dependent hypertension. Am J Med Sci 2013; 344:301-6. [PMID: 22261625 DOI: 10.1097/maj.0b013e3182410d1e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
INTRODUCTION This study was performed to determine whether chronic direct renin inhibition can prevent the development of slowly progressive angiotensin (ANG) II-dependent hypertension and the associated derangements in renal function in Cyplal-Ren2 transgenic rats with inducible expression of the Ren2 gene. METHODS Male Cyplal-Ren2 rats (n = 6) were fed a normal diet containing 0.15% indole-3-carbinol (I3C) for 16 days to induce slowly progressive ANG II-dependent hypertension. Conscious systolic blood pressure was measured daily using tail-cuff plethysmography. The rats were then anesthetized with pentobarbital sodium and surgically prepared for the measurement of mean arterial pressure (MAP) and renal hemodynamics and excretory function. RESULTS In rats induced with I3C, systolic blood pressure increased by day 3 (130 ± 7-160 ± 5 mm Hg, P < 0.01) and continued to increase to 191 ± 6 mm Hg (P < 0.001) by day 16. In a separate group of rats (n = 6), chronic administration of the direct renin inhibitor, aliskiren (30 mg/kg/d, sc), prevented the development of hypertension (113 ± 5 versus 114 ± 5 mm Hg, not significant). Rats treated with aliskiren exhibited significantly lower mean arterial pressure (138 ± 4 versus 201 ± 6 mm Hg, P < 0.001), renal vascular resistance (23 ± 4 versus 38 ± 3 mm Hg/mL/min · g, P < 0.01), urine flow (17.6 ± 1.4 versus 25.1 ± 2.9 μL/min, P < 0.05) and urinary sodium excretion (1.11 ± 0.32 versus 2.35 ± 0.28 μEq/min, P < 0.05) and higher renal plasma flow (4.22 ± 0.23 versus 2.56 ± 0.21 mL/min · g, P < 0.01) and glomerular filtration rate (1.19 ± 0.07 versus 0.78 ± 0.08 mL/min · g, P< 0.01), compared with induced rats not treated chronically with aliskiren. CONCLUSIONS The present findings demonstrate that chronic direct renin inhibition with aliskiren prevents the development of ANG II-dependent hypertension and the associated derangements in renal hemodynamics and excretory function in Cyplal-Ren2 transgenic rats.
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The complex interplay between cyclooxygenase-2 and angiotensin II in regulating kidney function. Curr Opin Nephrol Hypertens 2012; 21:7-14. [PMID: 22080858 DOI: 10.1097/mnh.0b013e32834d9d75] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
PURPOSE OF REVIEW Cyclooxygenase-2 (COX-2) plays a critical role in modulating deleterious actions of angiotensin II (Ang II) where there is an inappropriate activation of the renin-angiotensin system (RAS). This review discusses the recent developments regarding the complex interactions by which COX-2 modulates the impact of an activated RAS on kidney function and blood pressure. RECENT FINDINGS Normal rats with increased COX-2 activity but with different intrarenal Ang II activity because of sodium restriction or chronic treatment with angiotensin-converting enzyme (ACE) inhibitors showed similar renal hemodynamic responses to COX-2-selective inhibition (nimesulide) indicating independence from the intrarenal Ang II activity. COX-2-dependent maintenance of medullary blood flow was consistent and not dependent on dietary salt or ACE inhibition. In contrast, COX-2 influences on sodium excretion were contingent on the prevailing RAS activity. In chronic hypertensive models, COX-2 inhibition elicited similar reductions in kidney function, but COX-2 metabolites contribute to rather than ameliorate the hypertension. SUMMARY The maintenance of renal hemodynamics reflects direct and opposing effects of Ang II and COX-2 metabolites. The antagonism in water and electrolyte reabsorption is dependent on the prevailing intrarenal Ang II activity. The recent functional experiments demonstrate a beneficial modulation of Ang II by COX-2 except in the presence of inflammation promoted by hypertension, hyperglycemia, and oxidative stress.
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Transient induction of ANG II-dependent malignant hypertension causes sustained elevation of blood pressure and augmentation of the pressor response to ANG II in CYP1A1-REN2 transgenic rats. Am J Med Sci 2010; 339:543-8. [PMID: 20375689 DOI: 10.1097/maj.0b013e3181d82a62] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
INTRODUCTION Transgenic rats with inducible expression of the mouse Ren2 renin gene [strain name: TGR(Cyp1a1Ren2)] allow induction of various degrees of ANG II-dependent hypertension. Dietary administration of the aryl hydrocarbon indole-3-carbinol (I3C) at a dose of 0.15% induces a slowly developing form of ANG II-dependent hypertension, whereas dietary administration of a higher dose (0.3%) of I3C results in the development of ANG II-dependent malignant hypertension. Cessation of administration of 0.15% I3C results in the normalization of blood pressure, indicating the reversibility of hypertension induced by this dose of I3C. The present study was performed to determine if ANG II-dependent malignant hypertension is similarly reversible following cessation of dietary administration of 0.3% I3C. METHODS Cyp1a1-Ren2 rats (n = 6) were fed a normal diet containing 0.3% I3C for 11 days to induce malignant hypertension. RESULTS Cyp1a1-Ren2 rats induced with I3C exhibited pronounced increases in systolic blood pressure (SBP) (132 +/- 3-229 +/- 11 mm Hg, P < 0.001) and marked decreases in body weight (303 +/- 4-222 +/- 2 g, P < 0.001). When I3C administration was terminated, SBP decreased to 167 +/- 4 mm Hg (P < 0.01) and body weight increased to normal levels (309 +/- 2 g, P < 0.01) within 12 days. However, SBP remained significantly elevated (172 +/- 1 mm Hg, P < 0.01) for up to 3 weeks after termination of dietary administration of 0.3% I3C. In addition, the magnitude of the blood pressure response to intravenous bolus administration of 50 ng of ANG II (50 microL in volume) 3 weeks after cessation of dietary I3C administration was substantially higher than that observed in normotensive control rats (134 +/- 1 mm Hg, n = 6) not previously induced with 0.3% I3C (53 +/- 2 versus 38 +/- 3 mm Hg, P < 0.05). CONCLUSIONS The present findings demonstrate that transient induction of ANG II-dependent malignant hypertension results in prolonged elevations of arterial blood pressure and marked augmentation of the magnitude of the pressor response to ANG II in Cyp1a1-Ren2 transgenic rats.
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AT1 receptor blockade prevents the increase in blood pressure and the augmentation of intrarenal ANG II levels in hypertensive Cyp1a1-Ren2 transgenic rats fed with a high-salt diet. Am J Med Sci 2010; 339:356-61. [PMID: 20224314 DOI: 10.1097/maj.0b013e3181d2b0a8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
INTRODUCTION This study was performed to determine the effects of high-salt diet on the magnitude of the increases in systolic blood pressure (SBP) and kidney tissue angiotensin (ANG) II levels that occur after induction of ANG II-dependent malignant hypertension in Cyp1a1-Ren2 transgenic rats with inducible expression of the mouse Ren2 renin gene [strain name: TGR(Cyp1a1Ren2)]. METHODS 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 increases in SBP and elevations of ANG II levels in kidney cortex and medulla. In a second group of rats (n = 6), high-salt intake alone did not alter basal SBP; however, subsequent dietary administration of 0.3% I3C during continued high-salt intake elicited a substantially greater increase in SBP than observed in rats fed a normal salt diet. ANG II levels in kidney cortex and medulla of rats induced with I3C and fed a high-salt diet were elevated similarly to those in rats induced with I3C alone. Chronic administration of the AT1 receptor antagonist, losartan (100 mg/L in drinking water, n = 6), markedly attenuated the I3C-induced increase in SBP and prevented the augmentation of ANG II levels in kidney cortex and medulla in rats induced with I3C and maintained on a high-salt diet. CONCLUSIONS Activation of AT1 receptors contributes to the augmented blood pressure and elevated kidney tissue ANG II levels that occur in Cyp1a1-Ren2 transgenic rats with malignant hypertension maintained on a high-salt diet.
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Abstract
In cardiovascular research, the rat has been the main model of choice for decades. Experimental procedures were developed to generate cardiovascular disease states in this species, such as systemic and pulmonary hypertension, cardiac hypertrophy and failure, myocardial infarction, and stroke. Furthermore, rats have been bred, which spontaneously develop such diseases. They became extremely valuable models to understand the genetics of these diseases, since powerful genomic tools are now available for the rat. One of these tools is transgenic technology, which has allowed the creation of even more disease models in the rat. This review summarizes the experimental, genetic, and transgenic rat models for cardiovascular diseases.
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Affiliation(s)
- Michael Bader
- Max-Delbrück-Center for Molecular Medicine (MDC), Berlin, Germany
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Peters J, Schlüter T, Riegel T, Peters BS, Beineke A, Maschke U, Hosten N, Mullins JJ, Rettig R. Lack of cardiac fibrosis in a new model of high prorenin hyperaldosteronism. Am J Physiol Heart Circ Physiol 2009; 297:H1845-52. [PMID: 19749160 PMCID: PMC2781377 DOI: 10.1152/ajpheart.01135.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of the present study was to test the hypothesis that elevation of prorenin in plasma is sufficient to induce cardiac fibrosis. Normotensive cyp1a1ren-2 transgenic rats with normal plasma prorenin and aldosterone levels were given 0.125% indole-3-carbinol (I3C) orally for a period of 12 wk. Plasma prorenin and aldosterone levels were determined in 4-wk intervals, and cardiac marker enzymes for hypertrophy, fibrosis, and oxidative stress as well as cardiac pathology were investigated. In I3C-treated cyp1a1 ren-2 transgenic rats, plasma prorenin concentrations were >100-fold elevated (> or = 7.1 + or - 2.6 microg ANG I.ml(-1).h(-1) vs. < or = 0.07 + or - 0.1; P < 0.001), whereas active renin levels were suppressed (0.09 + or - 0.02 vs. 0.2 + or - 0.1; P < 0.05). Aldosterone concentrations were elevated three- to fourfold for a period of >4 wk (574 + or - 51 vs. 160 + or - 68 pg/ml; P < 0.01). After 12 wk of I3C, rats exhibited moderate cardiac hypertrophy (heart weight/body weight 2.5 + or - 0.04 vs. 3.1 + or - 0.1 mg/g; P < 0.01). There was a slight increase in mRNA contents of endothelin 1 (1.21 + or - 0.08 vs. 0.75 + or - 0.007; P < 0.001), NADP oxidase-2 (1.03 + or - 0.006 vs. 0.76 + or - 0.04; P < 0.001), transforming growth factor-beta (0.99 + or - 0.06 vs. 0.84 + or - 0.04; P < 0.05), collagen type I (1.32 + or - 0.32 vs. 0.94 + or - 0.18; P < 0.05), and intercellular adhesion molecule-1 (1.12 + or - 0.12 vs. 0.84 + or - 0.08; P < 0.05). These genes are known to be stimulated by the renin-angiotensin system. There were no histological signs of fibrosis in the heart. We found that prorenin and aldosterone alone are not sufficient to induce considerable cardiac fibrosis in the absence of sodium load.
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Affiliation(s)
- Jörg Peters
- Institute of Physiology, Univ. of Greifswald, Greifswalder Str. 11C, D-17495 Karlsburg, Germany.
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Liu X, Bellamy COC, Bailey MA, Mullins LJ, Dunbar DR, Kenyon CJ, Brooker G, Kantachuvesiri S, Maratou K, Ashek A, Clark AF, Fleming S, Mullins JJ. Angiotensin-converting enzyme is a modifier of hypertensive end organ damage. J Biol Chem 2009; 284:15564-72. [PMID: 19307186 PMCID: PMC2708853 DOI: 10.1074/jbc.m806584200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2008] [Revised: 03/06/2009] [Indexed: 11/06/2022] Open
Abstract
Severe forms of hypertension are characterized by high blood pressure combined with end organ damage. Through the development and refinement of a transgenic rat model of malignant hypertension incorporating the mouse renin gene, we previously identified a quantitative trait locus on chromosome 10, which affects malignant hypertension severity and morbidity. We next generated an inducible malignant hypertensive model where the timing, severity, and duration of hypertension was placed under the control of the researcher, allowing development of and recovery from end organ damage to be investigated. We have now generated novel consomic Lewis and Fischer rat strains with inducible hypertension and additional strains that are reciprocally congenic for the refined chromosome 10 quantitative trait locus. We have captured a modifier of end organ damage within the congenic region and, using a range of bioinformatic, biochemical and molecular biological techniques, have identified angiotensin-converting enzyme as the modifier of hypertension-induced tissue microvascular injury. Reciprocal differences between angiotensin-converting enzyme and the anti-inflammatory tetrapeptide, N-acetyl-Ser-Asp-Lys-Pro in the kidney, a tissue susceptible to end organ damage, suggest a mechanism for the amelioration of hypertension-dependent damage.
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Affiliation(s)
- Xiaojun Liu
- From the Molecular Physiology Laboratory, Centre for Cardiovascular Science, Queen's Medical Research Institute, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | | | - Matthew A. Bailey
- From the Molecular Physiology Laboratory, Centre for Cardiovascular Science, Queen's Medical Research Institute, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | - Linda J. Mullins
- From the Molecular Physiology Laboratory, Centre for Cardiovascular Science, Queen's Medical Research Institute, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | - Donald R. Dunbar
- From the Molecular Physiology Laboratory, Centre for Cardiovascular Science, Queen's Medical Research Institute, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | - Christopher J. Kenyon
- From the Molecular Physiology Laboratory, Centre for Cardiovascular Science, Queen's Medical Research Institute, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | - Gillian Brooker
- From the Molecular Physiology Laboratory, Centre for Cardiovascular Science, Queen's Medical Research Institute, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | | | - Klio Maratou
- the Medical Research Council Clinical Sciences Centre, Hammersmith Hospital, London W12 ONN, United Kingdom, and
| | - Ali Ashek
- From the Molecular Physiology Laboratory, Centre for Cardiovascular Science, Queen's Medical Research Institute, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | - Allan F. Clark
- From the Molecular Physiology Laboratory, Centre for Cardiovascular Science, Queen's Medical Research Institute, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | | | - John J. Mullins
- From the Molecular Physiology Laboratory, Centre for Cardiovascular Science, Queen's Medical Research Institute, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
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Endothelin receptor blockade does not affect blood pressure or angiotensin II levels in CYP1A1-Ren-2 transgenic rats with acutely induced hypertension. Vascul Pharmacol 2009; 50:194-9. [DOI: 10.1016/j.vph.2009.01.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 12/08/2008] [Accepted: 01/21/2009] [Indexed: 11/22/2022]
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Wilcox CS, Pearlman A. Chemistry and antihypertensive effects of tempol and other nitroxides. Pharmacol Rev 2009; 60:418-69. [PMID: 19112152 DOI: 10.1124/pr.108.000240] [Citation(s) in RCA: 280] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Nitroxides can undergo one- or two-electron reduction reactions to hydroxylamines or oxammonium cations, respectively, which themselves are interconvertible, thereby providing redox metabolic actions. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (tempol) is the most extensively studied nitroxide. It is a cell membrane-permeable amphilite that dismutates superoxide catalytically, facilitates hydrogen peroxide metabolism by catalase-like actions, and limits formation of toxic hydroxyl radicals produced by Fenton reactions. It is broadly effective in detoxifying these reactive oxygen species in cell and animal studies. When administered intravenously to hypertensive rodent models, tempol caused rapid and reversible dose-dependent reductions in blood pressure in 22 of 26 studies. This was accompanied by vasodilation, increased nitric oxide activity, reduced sympathetic nervous system activity at central and peripheral sites, and enhanced potassium channel conductance in blood vessels and neurons. When administered orally or by infusion over days or weeks to hypertensive rodent models, it reduced blood pressure in 59 of 68 studies. This was accompanied by correction of salt sensitivity and endothelial dysfunction and reduced agonist-evoked oxidative stress and contractility of blood vessels, reduced renal vascular resistance, and increased renal tissue oxygen tension. Thus, tempol is broadly effective in reducing blood pressure, whether given by acute intravenous injection or by prolonged administration, in a wide range of rodent models of hypertension.
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Affiliation(s)
- Christopher S Wilcox
- Division of Nephrology and Hypertension, Kidney and Vascular Disorder Center, Georgetown University, Washington, DC 20007, USA.
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Dose-dependent titration of prorenin and blood pressure in Cyp1a1ren-2 transgenic rats: absence of prorenin-induced glomerulosclerosis. J Hypertens 2008; 26:102-9. [PMID: 18090546 DOI: 10.1097/hjh.0b013e3282f0ab66] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
OBJECTIVE Prorenin has been associated with cardiovascular disease and the development of glomerulosclerosis via a renin/prorenin receptor. In cyp1a1ren-2 transgenic rats, prorenin levels and arterial pressure can be increased by oral administration of indole-3-carbinol (I3C). The transgenic strain has been used as a model of malignant hypertension. METHODS The present study was designed to test the hypotheses that (i) low doses of I3C would result in dose-dependent sustained increases in arterial pressure without signs of malignancy, making cyp1a1ren-2 transgenic rats a useful model to study nonmalignant hypertension, and (ii) cyp1a1ren-2 transgenic rats would develop glomerulosclerosis when they were chronically exposed to 0.125% I3C in their diet. RESULTS I3C treatment for 2 weeks resulted in increases of plasma prorenin concentrations and arterial pressure in a dose-dependent manner. Rats thrived well over a period of 12 weeks on dietary I3C concentrations (wt/wt) of 0.125%. Plasma prorenin concentration rose from 0.1 +/- 0.1 microg to 17.9 +/- 5.0 mug angiotensin I/ml per h (P < 0.01) and mean arterial pressure increased to a plateau of 170 +/- 5 mmHg (P < 0.001) between weeks 6 and 12. After 12 weeks of 0.125% I3C, rats exhibited moderate hypertensive renal vasculopathy, but no histological signs of glomerulosclerosis. CONCLUSIONS The cyp1a1ren-2 transgenic rat model allows for chronic dose-dependent titration of arterial pressure by a simple and non-invasive intervention, making this strain a useful model to study malignant and nonmalignant arterial hypertension. High circulating prorenin levels per se do not cause glomerulosclerosis.
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Majid DSA, Kopkan L. Nitric oxide and superoxide interactions in the kidney and their implication in the development of salt-sensitive hypertension. Clin Exp Pharmacol Physiol 2007; 34:946-52. [PMID: 17645645 DOI: 10.1111/j.1440-1681.2007.04642.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
1. Enhanced superoxide (O2(-)) activity as a result of the inhibition of the superoxide dismutase (SOD) enzyme results in vasoconstrictor and antinatriuretic responses in the canine kidney; these responses were shown to be greatly enhanced during inhibition of nitric oxide synthase (NOS). Glomerular filtration rate remained mostly unchanged during SOD inhibition in the intact nitric oxide (NO) condition, but was markedly reduced during NOS inhibition. These findings indicate that endogenous NO has a major renoprotective effect against O2(-) by acting as an anti-oxidant. Nitric oxide synthase inhibition was also shown to enhance endogenous O2(-) activity. 2. Experiments in our laboratory using dogs, rats and gene knockout mice have shown that renal vasoconstrictor and antinatriuretic responses to acute or chronic angiotensin (Ang) II administration are mediated, in part, by O2(-) generation. In the absence of NO, enhanced O2(-) activity largely contributes to AngII-induced renal tubular sodium reabsorption. Acute or chronic treatment with the O2(-) scavenger tempol in experimental models of hypertension (induced by chronic low-dose treatment with AngII and NO inhibitors) causes an improvement in renal haemodynamics and in excretory function, abolishes salt sensitivity and reduces blood pressure. 3. The present mini review also discusses related studies from many other laboratories implicating a role for O2(-) and its interaction with NO in the development of salt-sensitive hypertension. 4. Overall, the collective data support the hypothesis that an imbalance between the production of NO and O2(-) in the kidney primarily determines the condition of oxidative stress that alters renal haemodynamics and excretory function leading to sodium retention and, thus, contributes to the development of salt-sensitive hypertension.
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Affiliation(s)
- Dewan S A Majid
- Department of Physiology, Tulane Hypertension and Renal Center of Excellence, Tulane University Health Sciences Center, New Orleans, Louisiana 70112, USA.
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Ortiz RM, Graciano ML, Mullins JJ, Mitchell KD. Aldosterone receptor antagonism alleviates proteinuria, but not malignant hypertension, in Cyp1a1-Ren2 transgenic rats. Am J Physiol Renal Physiol 2007; 293:F1584-91. [PMID: 17715265 DOI: 10.1152/ajprenal.00124.2007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The contribution of elevated aldosterone to the pathogenesis of malignant, ANG II-dependent hypertension remains uncertain. Therefore, we examined whether chronic mineralocorticoid receptor blockade attenuates the development of malignant hypertension in transgenic rats (TGRs) with inducible expression of the Ren2 gene [TGR(Cyp1a1Ren2)]. Systolic blood pressure (SBP) was measured by radiotelemetry in male TGRs in three groups: 1) control (n = 9), 2) hypertensives (HT; n = 8), and 3) hypertensives + spironolactone (11 mg.kg(-1).day(-1) sc; HTS; n = 8). Malignant hypertension was induced with dietary indole-3-carbinol (0.3%) for 10 days. Metabolic measurements were taken at the beginning of the study and at days 2 and 9. HT exhibited elevated SBP (125 +/- 3 vs. 187 +/- 5 mmHg), plasma renin activity (5 +/- 1 vs. 29 +/- 10 ng ANG I.ml(-1).h(-1)), plasma ANG II (175 +/- 39 vs. 611 +/- 74 fmol/ml), and plasma aldosterone (0.31 +/- 0.04 vs. 5.42 +/- 1.02 nmol/l). Urinary aldosterone excretion increased 5.5-fold by day 2 and an additional 90% by day 9. HT was associated with a 1.8-fold increase in proteinuria by day 9 that was alleviated by treatment with spironolactone (25 +/- 5 vs. 13 +/- 3 mg/day), suggesting that aldosterone contributes to the renal damage observed in malignant hypertension. Urinary Na+ excretion was decreased 76% on day 2, despite a sixfold increase in urinary aldosterone excretion. Decrease in urinary Na+ excretion on day 2 in HT suggests that Na+ reabsorption was increased in response to the increase in aldosterone; however, the lack of a change in SBP between HT and HTS suggests that mechanisms independent of aldosterone stimulation make a greater contribution to the maintenance of elevated arterial pressure in malignant hypertension in Cyp1a1-Ren2 transgenic rats.
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Affiliation(s)
- Rudy M Ortiz
- Department of Physiology, Tulane University Health Sciences Center, New Orleans, Louisiana, USA.
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Graciano ML, Mouton CR, Patterson ME, Seth DM, Mullins JJ, Mitchell KD. Renal vascular and tubulointerstitial inflammation and proliferation in Cyp1a1-Ren2 transgenic rats with inducible ANG II-dependent malignant hypertension. Am J Physiol Renal Physiol 2007; 292:F1858-66. [PMID: 17344186 DOI: 10.1152/ajprenal.00469.2006] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Transgenic rats with inducible ANG II-dependent malignant hypertension [TGR(Cyp1a1Ren2)] were generated by inserting the mouse Ren2 renin gene into the genome of the rat. The present study was performed to assess renal morphological changes occurring during the development of ANG II-dependent malignant hypertension in these rats. Male Cyp1a1-Ren2 rats (n = 10) were fed normal rat food containing indole-3-carbinol (I3C; 0.3%) for 10 days to induce malignant hypertension. Rats induced with I3C had higher mean arterial pressures (173 +/- 9 vs. 112 +/- 11 mmHg, P < 0.01) than noninduced normotensive rats (n = 9). Glomerular damage was evaluated by determination of the glomerulosclerosis index (GSI) in tissue sections stained with periodic acid-Schiff. Kidneys of hypertensive rats had a higher GSI than normotensive rats (21.3 +/- 5.6 vs. 3.5 +/- 1.31 units). Quantitative analysis of macrophage ED-1-positive cells and proliferating cell nuclear antigen using immunohistochemistry demonstrated increased macrophage numbers in the renal interstitium (106.4 +/- 11.4 vs. 58.7 +/- 5.0 cells/mm(2)) and increased proliferating cell number in cortical tubules (37.8 +/- 5.7 vs. 24.2 +/- 2.1 cells/mm(2)), renal cortical vessels (2.2 +/- 0.5 vs. 0.13 +/- 0.07 cells/vessel), and the cortical interstitium (33.6 +/- 5.7 vs. 4.2 +/- 1.4 cells/mm(2)) of hypertensive rat kidneys. These findings demonstrate that the renal pathological changes that occur during the development of malignant hypertension in Cyp1a1-Ren2 rats are characterized by inflammation and cellular proliferation in cortical vessels and tubulointerstitium.
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Affiliation(s)
- Miguel L Graciano
- Department of Physiology, Hypertension and Renal Center of Excellence, Tulane University Health Sciences Center, New Orleans, Louisiana 70112, USA
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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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Ozawa Y, Kobori H, Suzaki Y, Navar LG. Sustained renal interstitial macrophage infiltration following chronic angiotensin II infusions. Am J Physiol Renal Physiol 2006; 292:F330-9. [PMID: 16804106 PMCID: PMC2001287 DOI: 10.1152/ajprenal.00059.2006] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Chronic angiotensin (ANG) II infusions into rats lead to augmented intrarenal levels of ANG II and inflammatory factors, impaired renal function, and progressive hypertension. Residual effects persist after cessation of ANG II infusions, as manifested by a hypertensive response to high-salt intake. This study was performed to determine the residual cytokines and chemokines following the cessation of ANG II infusion. Male Sprague-Dawley rats, maintained on a normal diet, received either a sham operation or continuous ANG II infusion (120 ng/min) subcutaneously via minipumps. The ANG II-infused rats were further subdivided into three subgroups. Minipumps were removed on day 12 with subsequent harvesting of kidneys at 0, 3, and 6 days after cessation of ANG II infusion. After 12 days of ANG II infusion, systolic blood pressure, interstitial fibrosis, preglomerular hypertrophy, and interstitial macrophage infiltration were significantly enhanced compared with the shams. By 3 days following the cessation of ANG II infusion, systolic blood pressure was normalized; however, interstitial fibrosis and preglomerular hypertrophy were still present. Furthermore, increased interstitial macrophage infiltration was still present 6 days after cessation of ANG II infusion. Importantly, augmented mRNA levels of monocyte chemotactic protein (MCP)-1 (1.55 +/- 0.15 vs. 1.00 +/- 0.13, relative ratio) and transforming growth factor (TGF)-beta(1) (1.52 +/- 0.16 vs. 1.00 +/- 0.08) persisted 6 days after the withdrawal of ANG II infusion (1.60 +/- 0.20 for MCP-1 and 1.43 +/- 0.17 for TGF-beta(1)). Thus, the ANG II-induced activation of MCP-1 and TGF-beta(1) is sustained and may account for the persistent effect of chronic ANG II infusions on interstitial macrophage infiltration, suggesting a possible mechanism for the development of salt sensitivity in ANG II-dependent hypertension.
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Affiliation(s)
- Yuri Ozawa
- Department of Physiology and Hypertension and Renal Center of Excellence, Tulane University Health Sciences Center, New Orleans, Louisiana 70112-2699, USA
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Kopkan L, Majid DSA. Superoxide contributes to development of salt sensitivity and hypertension induced by nitric oxide deficiency. Hypertension 2005; 46:1026-31. [PMID: 16103275 DOI: 10.1161/01.hyp.0000174989.39003.58] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
This study was performed to examine the role of superoxide (O2-) in the development of salt sensitivity and hypertension induced by inhibition of nitric oxide (NO) generation. Male Sprague-Dawley rats were fed with diet containing either normal salt (NS) (0.4% NaCl) or high salt (HS) (4% NaCl). These rats were treated with or without an NO synthase inhibitor, nitro-L-arginine methylester (L-NAME) (15 mg/kg/d) and O2- scavenger, tempol (30 mg/kg per day) in the drinking water for 4 weeks. Systolic blood pressure (SBP) was measured by tail-cuff plethysmography and urine collection was performed during the course of experimental periods. At the end of 4 weeks, L-NAME treatment resulted in greater increases in SBP in HS rats (127+/-2 to 172+/-3 mm Hg; n=8) than in NS rats (130+/-2 to 156+/-2 mm Hg; n=9). Co-administration of tempol with L-NAME markedly attenuated these SBP responses to a similar level in both HS (128+/-3 to 147+/-2 mm Hg; n=8) and NS rats (126+/-2 to 142+/-3 mm Hg; n=8). Urinary 8-isoprostane excretion (UIsoV) increased in response to L-NAME treatment that was higher in HS (10.6+/-0.5 to 21.5+/-0.8 ng/d) than in NS rats (10.8+/-0.7 to 16.9+/-0.6 ng/d). Co-treatment with tempol completely abolished these UIsoV responses to L-NAME in both HS and NS rats but did not alter urinary H2O2 excretion rate. The decreases in urinary nitrate/nitrite excretion in response to L-NAME treatment were not altered by co-administration of tempol in both HS and NS rats. These data suggest that enhancement of O2- activity during NO inhibition contributes to the development of salt sensitivity that is associated with NO-deficient hypertension.
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Affiliation(s)
- Libor Kopkan
- Department of Physiology, Tulane Hypertension and Renal Center of Excellence, Tulane University Health Sciences Center, New Orleans, LA, USA
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