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Translational studies on augmentation of intratubular renin-angiotensin system in hypertension. Kidney Int Suppl (2011) 2013; 3:321-325. [PMID: 25019012 PMCID: PMC4089772 DOI: 10.1038/kisup.2013.67] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Various models of experimental hypertension and clinical examples of increased renin formation from a stenotic kidney or a juxtaglomerular cell tumor have shown that increased circulating angiotensin II (Ang II) stimulates the intrarenal/intratubular renin–angiotensin system (RAS) that elicits renal vasoconstriction, enhanced tubular sodium reabsorption, and progressive development of hypertension and renal injury. The enhanced intrarenal Ang II activity is due to both receptor-mediated Ang II uptake and Ang II type 1 (AT1) receptor–mediated stimulation of renal angiotensinogen (AGT) mRNA and protein by proximal tubule cells. The increased AGT secretion leads to local formation of Ang II and spillover of AGT into the distal nephron segments as reflected by increased AGT excretion in the urine, which provides an index of intrarenal RAS activity. In clinical studies, increased urinary excretion of AGT has been demonstrated in hypertension, type 1 and type 2 diabetes mellitus, and several types of chronic kidney diseases. In addition, renin secretion from principal cells of the collecting ducts is increased by AT1 receptor activation and acts on AGT from the proximal tubule to form more Ang I. Renin and/or (pro)renin activity is enhanced by binding to the (pro)renin receptor (PRR) on intercalated cells or secreted as soluble PRR contributing further to AGT cleavage, thus making more substrate available for Ang II conversion by local angiotensin-converting enzyme. The augmented intratubular Ang II concentrations together with elevated renal interstitial Ang II concentrations contribute to sustained stimulation of sodium reabsorption, vasoconstriction, development of hypertension, and progressive renal injury and fibrosis.
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Kobori H, Mori H, Masaki T, Nishiyama A. Angiotensin II blockade and renal protection. Curr Pharm Des 2013; 19:3033-42. [PMID: 23176216 DOI: 10.2174/1381612811319170009] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 11/20/2012] [Indexed: 12/15/2022]
Abstract
Current national guidelines have recommended the use of renin-angiotensin system inhibitors, including angiotensin II type 1 receptor blockers (ARBs), in preference to other antihypertensive agents for treating hypertensive patients with chronic kidney disease. However, the mechanisms underlying the renoprotective effects of ARBs are multiple and complex. Blood pressure reduction by systemic vasodilation with an ARB contributes to its beneficial effects in treating kidney disease. Furthermore, ARB-induced renal vasodilation results in an increase in renal blood flow, leading to improvement of renal ischemia and hypoxia. ARBs are also effective in reducing urinary albumin excretion through a reduction in intraglomerular pressure and the protection of glomerular endothelium and/or podocyte injuries. In addition to blocking angiotensin II-induced renal cell and tissue injuries, ARBs can decrease intrarenal angiotensin II levels by reducing proximal tubular angiotensinogen and production of collecting duct renin, as well as angiotensin II accumulation in the kidney. In this review, we will briefly summarize our current understanding of the pharmacological effects of an ARB in the kidney. We will also discuss the possible mechanisms responsible for the renoprotective effects of ARBs on type 2 diabetic nephropathy.
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Affiliation(s)
- Hiroyuki Kobori
- Department of Pharmacology, Faculty of Medicine, Kagawa University, Ikenobe 1750-1, Miki, Kita, Kagawa 761-0793, Japan
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Lumbers ER, Pringle KG, Wang Y, Gibson KJ. The renin-angiotensin system from conception to old age: the good, the bad and the ugly. Clin Exp Pharmacol Physiol 2013; 40:743-52. [DOI: 10.1111/1440-1681.12098] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Revised: 04/08/2013] [Accepted: 04/12/2013] [Indexed: 11/30/2022]
Affiliation(s)
- Eugenie R Lumbers
- School of Biomedical Sciences and Pharmacy; Hunter Medical Research Institute; University of Newcastle and Mothers and Babies Research Centre; Newcastle NSW Australia
| | - Kirsty G Pringle
- School of Biomedical Sciences and Pharmacy; Hunter Medical Research Institute; University of Newcastle and Mothers and Babies Research Centre; Newcastle NSW Australia
| | - Yu Wang
- School of Biomedical Sciences and Pharmacy; Hunter Medical Research Institute; University of Newcastle and Mothers and Babies Research Centre; Newcastle NSW Australia
| | - Karen J Gibson
- School of Medical Sciences; University of New South Wales; Sydney NSW Australia
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Taranta-Janusz K, Wasilewska A, Dębek W, Fiłonowicz R, Michaluk-Skutnik J. Urinary angiotensinogen as a novel marker of obstructive nephropathy in children. Acta Paediatr 2013; 102:e429-33. [PMID: 23772991 DOI: 10.1111/apa.12324] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 05/13/2013] [Accepted: 06/12/2013] [Indexed: 11/28/2022]
Abstract
AIM Obstructive nephropathy due to congenital or acquired urinary tract obstruction is one of the most important causes of chronic renal failure in children. There is a need for identification of new noninvasive urinary biomarkers to provide the clinician with fast, specific and reliable diagnostic and prognostic tool. The aim of the study was to determine whether urinary angiotensinogen (uAGT) may be a useful marker of obstruction in children with hydronephrosis (HN) caused by ureteropelvic junction obstruction (UPJO). METHODS The study cohort consisted of surgical group (SG): 31 children with severe HN who required surgery; nonsurgical group (NSG): 20 patients with mild HN, and reference group (RG): 19 healthy children. Urinary concentrations of angiotensinogen were measured using immunoenzymatic ELISA commercial kit and were expressed in ng/mg Cre (uAGT/uCre). RESULTS uAGT/uCre level was higher in SG when compared to NSG (p < 0.01) and healthy participants (SG vs. RG: p < 0.01). The difference between the uAGT/uCre in NSG and RG was not statistically significant (p > 0.05). uAGT/uCre was correlated negatively with differential renal function (r = -0.46; p < 0.01). CONCLUSION The present pilot study has clearly demonstrated that children with UPJO showed increased uAGT levels, which correlated negatively with differential renal function in radionuclide scan.
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Affiliation(s)
| | - Anna Wasilewska
- Department of Pediatrics and Nephrology; Medical University of Białystok; Białystok Poland
| | - Wojciech Dębek
- Department of Pediatric Surgery; Medical University of Białystok; Białystok Poland
| | - Renata Fiłonowicz
- Department of Pediatrics and Nephrology; Medical University of Białystok; Białystok Poland
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Abstract
Recent interest focuses on urinary renin and angiotensinogen as markers of renal renin-angiotensin system activity. Before concluding that these components are independent markers, we need to exclude that their presence in urine, like that of albumin (a protein of comparable size), is due to (disturbed) glomerular filtration. This review critically discusses their filtration, reabsorption and local release. Given the close correlation between urinary angiotensinogen and albumin in human studies, it concludes that, in humans, urinary angiotensinogen is a filtration barrier damage marker with the same predictive power as urinary albumin. In contrast, in animals, tubular angiotensinogen release may occur, although tubulus-specific knockout studies do not support a functional role for such angiotensinogen. Urinary renin levels, relative to albumin, are >200-fold higher and unrelated to albumin. This may reflect release of renin from the urinary tract, but could also be attributed to activation of filtered, plasma-derived prorenin and/or incomplete tubular reabsorption.
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56
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Lu X, Roksnoer LCW, Danser AHJ. The intrarenal renin-angiotensin system: does it exist? Implications from a recent study in renal angiotensin-converting enzyme knockout mice. Nephrol Dial Transplant 2013; 28:2977-82. [PMID: 23901049 DOI: 10.1093/ndt/gft333] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A large body of evidence supports the presence of local production of angiotensins in the kidney. It is widely believed that renin-angiotensin system (RAS) blockers, through interference with such production and/or the local effects of angiotensin (Ang) II, exert protective renal effects. Yet, whether such production affects blood pressure independently from the circulating RAS is still a matter of debate. To investigate this, a recent study by Gonzalez-Villalobos et al. (J Clin Invest 2013; 123: 2011-2023) has studied the consequences of infusing Ang II or the nitric oxide synthase inhibitor l-NAME in mice lacking renal angiotensin-converting enzyme (ACE). They observed blunted blood pressure and renal responses in the renal ACE knockout mice versus wild-type controls. This review discusses to what degree these findings can be considered as unequivocal evidence for ACE-mediated Ang II formation in the kidney as an independent determinant of hypertension.
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Affiliation(s)
- Xifeng Lu
- Division of Pharmacology and Vascular Medicine, Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands
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57
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Kobori H, Ohashi N, Katsurada A, Miyata K, Satou R, Saito T, Yamamoto T. Urinary angiotensinogen as a potential biomarker of severity of chronic kidney diseases. ACTA ACUST UNITED AC 2013; 2:349-54. [PMID: 18958182 DOI: 10.1016/j.jash.2008.04.008] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We previously reported that urinary excretion rates of angiotensinogen (AGT) provide a specific index of the activity of the intrarenal renin-angiotensin system in angiotensin II-dependent hypertensive rats. Meanwhile, we have recently developed direct enzyme-linked immunosorbent assays (ELISAs) to measure plasma and urinary AGT in humans. This study was performed to test a hypothesis that urinary AGT levels are enhanced in chronic kidney disease (CKD) patients and correlated with some clinical parameters. Eighty patients with CKD (37 women and 43 men, from 18 to 94 years old) and seven healthy volunteers (two women and five men, from 27 to 43 years old) were included. Plasma AGT levels showed a normal distribution; however, urinary AGT-creatinine ratios (UAGT/UCre) deviated from the normal distribution. When a logarithmic transformation was executed, Log(UAGT/UCre) levels showed a normal distribution. Therefore, Log(UAGT/UCre) levels were used for further analyses. Log(UAGT/UCre) levels were not correlated with age, gender, height, body weight, body mass index, systolic blood pressure, diastolic blood pressure, serum sodium levels, serum potassium levels, urinary sodium-creatinine ratios, plasma renin activity, or plasma AGT levels. However, Log(UAGT/UCre) levels were significantly correlated positively with urinary albumin-creatinine ratios, fractional excretion of sodium, urinary protein-creatinine ratios, and serum creatinine, and correlated negatively with estimated glomerular filtration rate. Log(UAGT/UCre) levels were significantly increased in CKD patients compared with control subjects (1.8801 +/- 0.0885 vs. 0.9417 +/- 0.1048; P = .0024). These data confirmed our earlier report and showed that a new ELISA assay is a valid approach for measuring urinary AGT.
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Affiliation(s)
- Hiroyuki Kobori
- Department of Physiology, and Hypertension and Renal Center of Excellence, Tulane University Health Sciences Center, New Orleans, Louisiana, USA
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58
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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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Varagic J, Ahmad S, VonCannon JL, Moniwa N, Brosnihan KB, Wysocki J, Batlle D, Ferrario CM. Predominance of AT(1) blockade over mas-mediated angiotensin-(1-7) mechanisms in the regulation of blood pressure and renin-angiotensin system in mRen2.Lewis rats. Am J Hypertens 2013; 26:583-90. [PMID: 23459599 DOI: 10.1093/ajh/hps090] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND We investigated whether the antihypertensive actions of the angiotensin II (Ang II) receptor (AT(1)-R) blocker, olmesartan medoxomil, may in part be mediated by increased Ang-(1-7) in the absence of significant changes in plasma Ang II. METHODS mRen2.Lewis congenic hypertensive rats were administered either a vehicle (n = 14) or olmesartan (0.5 mg/kg/day; n = 14) by osmotic minipumps. Two weeks later, rats from both groups were further randomized to receive either the mas receptor antagonist A-779 (0.5 mg/kg/day; n = 7 per group) or its vehicle (n = 7 per group) for the next 4 weeks. Blood pressure was monitored by telemetry, and circulating and tissue components of the renin-angiotensin system (RAS) were measured at the completion of the experiments. RESULTS Antihypertensive effects of olmesartan were associated with an increase in plasma renin concentration, plasma Ang I, Ang II, and Ang-(1-7), whereas serum aldosterone levels and kidney Ang II content were reduced. Preserved Ang-(1-7) content in kidneys was associated with increases of ACE2 protein but not activity and no changes on serum and kidney ACE activity. There was no change in cardiac peptide levels after olmesartan treatment. The antihypertensive effects of olmesartan were not altered by concomitant administration of the Ang-(1-7) receptor antagonist except for a mild further increase in plasma renin concentration. CONCLUSIONS Our study highlights the independent regulation of RAS among plasma, heart, and kidney tissue in response to AT(1)-R blockade. Ang-(1-7) through the mas receptor does not mediate long-term effects of olmesartan besides counterbalancing renin release in response to AT(1)-R blockade.
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Affiliation(s)
- Jasmina Varagic
- Hypertension and Vascular Research Center, Wake Forest University, Winston-Salem, NC, USA.
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60
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Kobori H, Kamiyama M, Harrison-Bernard LM, Navar LG. Cardinal Role of the Intrarenal Renin-Angiotensin System in the Pathogenesis of Diabetic Nephropathy. J Investig Med 2013; 61:256-264. [DOI: 10.2310/jim.0b013e31827c28bb] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023]
Abstract
Diabetes mellitus is one of the most prevalent diseases and is associated with increased incidence of structural and functional derangements in the kidneys, eventually leading to end-stage renal disease in a significant fraction of afflicted individuals. The renoprotective effects of renin-angiotensin system (RAS) blockade have been established; however, the mechanistic pathways have not been fully elucidated. In this review article, the cardinal role of an activated RAS in the pathogenesis of diabetic nephropathy (DN) is discussed with a focus on 4 themes: (1) introduction to RAS cascade, (2) intrarenal RAS in diabetes, (3) clinical outcomes of RAS blockade in DN, and (4) potential of urinary angiotensinogen as an early biomarker of intrarenal RAS status in DN. This review article provides a mechanistic rational supporting the hypothesis that an activated intrarenal RAS contributes to the pathogenesis of DN and that urinary angiotensinogen levels provide an index of intrarenal RAS activity.
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Affiliation(s)
- Hiroyuki Kobori
- *Department of Physiology, and Hypertension and Renal Center of Excellence, Tulane University Health Sciences Center
| | - Masumi Kamiyama
- *Department of Physiology, and Hypertension and Renal Center of Excellence, Tulane University Health Sciences Center
| | | | - L. Gabriel Navar
- *Department of Physiology, and Hypertension and Renal Center of Excellence, Tulane University Health Sciences Center
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Burns KD, Hiremath S. Urinary angiotensinogen as a biomarker of chronic kidney disease: ready for prime time? Nephrol Dial Transplant 2013; 27:3010-3. [PMID: 22851623 DOI: 10.1093/ndt/gfs166] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- Kevin D Burns
- Division of Nephrology, Department of Medicine, Kidney Research Centre, Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada.
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Sousa T, Oliveira S, Afonso J, Morato M, Patinha D, Fraga S, Carvalho F, Albino-Teixeira A. Role of H(2)O(2) in hypertension, renin-angiotensin system activation and renal medullary disfunction caused by angiotensin II. Br J Pharmacol 2012; 166:2386-401. [PMID: 22452317 DOI: 10.1111/j.1476-5381.2012.01957.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND AND PURPOSE Activation of the intrarenal renin-angiotensin system (RAS) and increased renal medullary hydrogen peroxide (H(2) O(2) ) contribute to hypertension. We examined whether H(2) O(2) mediated hypertension and intrarenal RAS activation induced by angiotensin II (Ang II). EXPERIMENTAL APPROACH Ang II (200 ng·kg(-1) ·min(-1) ) or saline were infused in Sprague Dawley rats from day 0 to day 14. Polyethylene glycol (PEG)-catalase (10 000 U·kg(-1) ·day(-1) ) was given to Ang II-treated rats, from day 7 to day 14. Systolic blood pressure was measured throughout the study. H(2) O(2) , angiotensin AT(1) receptor and Nox4 expression and nuclear factor-κB (NF-κB) activation were evaluated in the kidney. Plasma and urinary H(2) O(2) and angiotensinogen were also measured. KEY RESULTS Ang II increased H(2) O(2) , AT(1) receptor and Nox4 expression and NF-κB activation in the renal medulla, but not in the cortex. Ang II raised plasma and urinary H(2) O(2) levels, increased urinary angiotensinogen but reduced plasma angiotensinogen. PEG-catalase had a short-term antihypertensive effect and transiently suppressed urinary angiotensinogen. PEG-catalase decreased renal medullary expression of AT(1) receptors and Nox4 in Ang II-infused rats. Renal medullary NF-κB activation was correlated with local H(2) O(2) levels and urinary angiotensinogen excretion. Loss of antihypertensive efficacy was associated with an eightfold increase of plasma angiotensinogen. CONCLUSIONS AND IMPLICATIONS The renal medulla is a major target for Ang II-induced redox dysfunction. H(2) O(2) appears to be the key mediator enhancing intrarenal RAS activation and decreasing systemic RAS activity. The specific control of renal medullary H(2) O(2) levels may provide future grounds for the treatment of hypertension.
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Affiliation(s)
- T Sousa
- Departamento de Farmacologia e Terapêutica, Faculdade de Medicina, Universidade do Porto, Porto, Portugal.
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Proximal tubular angiotensinogen in renal biopsy suggests nondipper BP rhythm accompanied by enhanced tubular sodium reabsorption. J Hypertens 2012; 30:1453-9. [PMID: 22573118 DOI: 10.1097/hjh.0b013e328353e807] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
OBJECTIVES The renal capacity for sodium excretion is impaired by a reduction in the glomerular ultrafiltration coefficient and by enhancement of the fractional tubular sodium reabsorption (FRNa), leading to a nondipper circadian blood pressure (BP) rhythm. Angiotensin II in the systemic circulation can be easily filtered across the glomerular capillary walls and stimulates renal proximal tubular angiotensinogen (PT-AGT) production, leading to the activation of intrarenal angiotensin II, which is known to augment the FRNa in animal models. METHODS We performed an immunohistochemical investigation to determine the contribution of PT-AGT to enhancement of FRNa and the nondipper circadian BP rhythm in 40 consecutive patients with primary IgA nephropathy (IgAN). RESULTS Immunostaining for PT-AGT was increased in the IgAN patients compared with control individuals (P = 0.04), and correlated directly with the FRNa (r = 0.39, P = 0.01) and the night/day ratio of BP (r = 0.38, P = 0.02), but not creatinine clearance (r = -0.008, P = 0.9). The night/day ratio of BP was determined by both creatinine clearance (r = -0.36, P = 0.03) and FRNa (r = 0.47, P = 0.006). CONCLUSION Tubular sodium reabsorption is stimulated by intrarenal angiotensin II, as indicated by PT-AGT, and contributes to the genesis of the nondipper BP rhythm. Further studies are needed to evaluate whether or not treatment to prevent sodium retention is useful for patients who exhibit increased PT-AGT in renal biopsies.
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Intrarenal Angiotensin ii is associated with inflammation, renal damage and dysfunction in dahl salt-sensitive hypertension. ACTA ACUST UNITED AC 2012; 3:306-14. [PMID: 20160914 DOI: 10.1016/j.jash.2009.08.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
BACKGROUND The goal of this study was to test the hypothesis that intrarenal Ang II has a proinflammatory effect leading to renal damage and dysfunction in Dahl S rats on high Na intake. METHODS Forty-six 7-to 8-week old Dahl S or R/Rapp strain rats were maintained for 5 weeks on high sodium (8%) with or without candesartan cilexetil in daily doses of 10-15 mg/kg/day. Arterial catheters were implanted at day 28. RESULTS By day 35 in the high Na S + candesartan rats, renal tissue Ang II concentration, renal monocytes/macrophages, TNFalpha, and MCP-1 significantly decreased. Plasma Ang II remained at very low levels in all groups. Reduced renal damage in candesartan-treated Dahl S rats was demonstrated by marked decreases in urinary protein excretion and renal glomerular and interstitial damage. After 5 weeks of high Na, compared to high Na Dahl S rats, arterial pressure was unchanged in candesartan S rats, but creatinine clearance was increased. CONCLUSIONS Therefore, candesartan reduced renal tissue Ang II, renal damage, infiltration of immune cells, cytokines, chemokines, and improved renal hemodynamics. These data suggest that intrarenal Ang II plays an important role in causing renal inflammation which leads to renal cortical damage, proteinuria, and decreases in renal hemodynamics.
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Kobori H, Urushihara M. Augmented intrarenal and urinary angiotensinogen in hypertension and chronic kidney disease. Pflugers Arch 2012; 465:3-12. [PMID: 22918624 DOI: 10.1007/s00424-012-1143-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/03/2012] [Accepted: 08/06/2012] [Indexed: 12/22/2022]
Abstract
Activated intrarenal renin-angiotensin system plays a cardinal role in the pathogenesis of hypertension and chronic kidney disease. Angiotensinogen is the only known substrate for renin, which is the rate-limiting enzyme of the renin-angiotensin system. Because the levels of angiotensinogen are close to the Michaelis-Menten constant values for renin, angiotensinogen levels as well as renin levels can control the renin-angiotensin system activity, and thus, upregulation of angiotensinogen leads to an increase in the angiotensin II levels and ultimately increases blood pressure. Recent studies using experimental animal models have documented the involvement of angiotensinogen in the intrarenal renin-angiotensin system activation and development of hypertension. Enhanced intrarenal angiotensinogen mRNA and/or protein levels were observed in experimental models of hypertension and chronic kidney disease, supporting the important roles of angiotensinogen in the development and the progression of hypertension and chronic kidney disease. Urinary excretion rates of angiotensinogen provide a specific index of the intrarenal renin-angiotensin system status in angiotensin II-infused rats. Also, a direct quantitative method has been developed recently to measure urinary angiotensinogen using human angiotensinogen enzyme-linked immunosorbent assay. These data prompted us to measure urinary angiotensinogen in patients with hypertension and chronic kidney disease, and investigate correlations with clinical parameters. This short article will focus on the role of the augmented intrarenal angiotensinogen in the pathophysiology of hypertension and chronic kidney disease. In addition, the potential of urinary angiotensinogen as a novel biomarker of the intrarenal renin-angiotensin system status in hypertension and chronic kidney disease will be also discussed.
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Affiliation(s)
- Hiroyuki Kobori
- Department of Physiology, Tulane University Health Sciences Center, 1430 Tulane Avenue, #SL39, New Orleans, LA 70112-2699, USA.
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66
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Jang HR, Kim SM, Lee YJ, Lee JE, Huh W, Kim DJ, Oh HY, Kim YG. The origin and the clinical significance of urinary angiotensinogen in proteinuric IgA nephropathy patients. Ann Med 2012; 44:448-57. [PMID: 21366514 DOI: 10.3109/07853890.2011.558518] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Urinary angiotensinogen (AGT) was reported as a marker of renal injury in chronic kidney disease patients. However, the main source of urinary AGT is unknown in proteinuric patients because the disrupted filtration barrier might cause AGT filtration. We investigated the origin and the clinical importance of urinary AGT in proteinuric IgA nephropathy (IgAN) patients. METHODS In patients with biopsy-proven IgAN, urinary and plasma AGT was measured using a sandwich ELISA and compared with intrarenal AGT expression. The patients were followed up for 3 years. RESULTS Natural logarithm of the urinary AGT/creatinine (ln (urinary AGT/Cr)) was positively correlated with intrarenal expression of AGT (ln (urinary AGT/Cr) versus AGT/β-actin, r = 0.620, P < 0.0001; ln (urinary AGT/Cr) versus AGT density, r = 0.452, P = 0.007). Ln (urinary AGT/Cr) showed a positive correlation with urinary protein/creatinine ratio (PCR) but a negative correlation with estimated glomerular filtration rate (eGFR). Regression analyses showed that ln (urinary AGT/Cr) was a significant determinant of urinary PCR and eGFR 3 years after biopsy. CONCLUSIONS Urinary AGT reflects intrarenal AGT expression and correlates with the extent of proteinuria and renal function. Our study indicates the intrarenal compartment as the main source of urinary AGT, suggesting its clinical implication as an important biomarker in proteinuric IgAN patients.
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Affiliation(s)
- Hye Ryoun Jang
- Nephrology Division, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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Kamiyama M, Zsombok A, Kobori H. Urinary angiotensinogen as a novel early biomarker of intrarenal renin-angiotensin system activation in experimental type 1 diabetes. J Pharmacol Sci 2012; 119:314-23. [PMID: 22850612 DOI: 10.1254/jphs.12076fp] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Urinary excretion of albumin (UAlb) is used clinically as a marker of diabetic nephropathy (DN). Although DN was thought to be a unidirectional process, recent studies demonstrated that a large proportion of patients diagnosed with DN reverted to normoalbuminuria. Moreover, despite the normoalbuminuria, one-third of them exhibited reduced renal function even during the microalbuminuric stage. This study was performed to investigate whether urinary angiotensinogen (UAGT) level may serve as a useful marker of the early stage of experimental type 1 diabetes (T1DM). T1DM was induced by a single intraperitoneal injection of streptozotocin. Control mice were injected with citrate buffer. Two days after streptozotocin injection, half of the mice received continuous insulin treatment. Our data showed that UAlb excretion was increased 6 days after streptozotocin injection compared to controls, whereas UAGT excretion was increased at an earlier time point. These increases were reversed by insulin treatment. The UAGT to UAlb ratio was increased in diabetic mice compared to control mice. Furthermore, the increased AGT expression in the kidneys was observed in diabetic mice. These data suggest that UAGT might be useful as a novel early biomarker of activation of the renin-angiotensin system in experimental type 1 diabetes.
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Affiliation(s)
- Masumi Kamiyama
- Department of Physiology, Tulane University Health Sciences Center, USA
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68
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Navar LG, Satou R, Gonzalez-Villalobos RA. The increasing complexity of the intratubular Renin-Angiotensin system. J Am Soc Nephrol 2012; 23:1130-2. [PMID: 22677556 DOI: 10.1681/asn.2012050493] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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69
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Nishiyama A. Mechanisms Responsible for Renoprotective Effects of Renin-Angiotensin Inhibitors. YAKUGAKU ZASSHI 2012; 132:455-9. [DOI: 10.1248/yakushi.132.455] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Akira Nishiyama
- Department of Pharmacology, Kagawa University Medical School
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70
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Sato A, Piao H, Nozawa Y, Morioka T, Kawachi H, Oite T. Local delivery of a direct renin inhibitor into the kidney ameliorates progression of experimental glomerulonephritis. Clin Exp Nephrol 2012; 16:539-48. [PMID: 22327564 DOI: 10.1007/s10157-012-0601-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Accepted: 01/18/2012] [Indexed: 01/06/2023]
Abstract
BACKGROUND Increasing evidence indicates that locally blocking renin-angiotensin system activity exerts a beneficial effect on glomerulonephritis (GN) progression leading to irreversible glomerulosclerosis. This is the first study on the pharmacological effect of the renal delivery of aliskiren, a direct renin inhibitor, in a progressive model of anti-Thy-1 GN. METHODS Local blockade of renin activity was accomplished by subrenal capsular implantation of a collagen sponge with aliskiren. The pharmacological effect was evaluated by semiquantitative and quantitative analysis of immunohistological findings and by analysis of glomerular microcirculation using an intravital microscope system. RESULTS Quantitative mesangial matrix analysis showed that local treatment with aliskiren significantly suppressed mesangial matrix expansion and ameliorated the glomerular sclerotic index in the progressive model of ATS GN. Immunofluorescent studies revealed that renin expression at the juxtaglomerular region was enhanced in the ATS + aliskiren group, and pathological expressions of α-smooth muscle cell actin and type I collagen in ATS GN were remarkably decreased by local treatment with aliskiren. Furthermore, local delivery of aliskiren significantly improved glomerular blood flow levels. CONCLUSION This study revealed that renally delivered aliskiren has a renoprotective effect on potentially progressive glomerulosclerosis.
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Affiliation(s)
- Ayako Sato
- Department of Cellular Physiology, Institute of Nephrology, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
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71
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Rafiq K, Noma T, Fujisawa Y, Ishihara Y, Arai Y, Nabi AHMN, Suzuki F, Nagai Y, Nakano D, Hitomi H, Kitada K, Urushihara M, Kobori H, Kohno M, Nishiyama A. Renal sympathetic denervation suppresses de novo podocyte injury and albuminuria in rats with aortic regurgitation. Circulation 2012; 125:1402-13. [PMID: 22328542 DOI: 10.1161/circulationaha.111.064097] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND The presence of chronic kidney disease is a significant independent risk factor for poor prognosis in patients with chronic heart failure. However, the mechanisms and mediators underlying this interaction are poorly understood. In this study, we tested our hypothesis that chronic cardiac volume overload leads to de novo renal dysfunction by coactivating the sympathetic nervous system and renin-angiotensin system in the kidney. We also examined the therapeutic potential of renal denervation and renin-angiotensin system inhibition to suppress renal injury in chronic heart failure. METHODS AND RESULTS Sprague-Dawley rats underwent aortic regurgitation and were treated for 6 months with vehicle, olmesartan (an angiotensin II receptor blocker), or hydralazine. At 6 months, albuminuria and glomerular podocyte injury were significantly increased in aortic regurgitation rats. These changes were associated with increased urinary angiotensinogen excretion, kidney angiotensin II and norepinephrine (NE) levels, and enhanced angiotensinogen and angiotensin type 1a receptor gene expression and oxidative stress in renal cortical tissues. Aortic regurgitation rats with renal denervation had decreased albuminuria and glomerular podocyte injury, which were associated with reduced kidney NE, angiotensinogen, angiotensin II, and oxidative stress. Renal denervation combined with olmesartan prevented podocyte injury and albuminuria induced by aortic regurgitation. CONCLUSIONS In this chronic cardiac volume-overload animal model, activation of the sympathetic nervous system augments kidney renin-angiotensin system and oxidative stress, which act as crucial cardiorenal mediators. Renal denervation and olmesartan prevent the onset and progression of renal injury, providing new insight into the treatment of cardiorenal syndrome.
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Affiliation(s)
- Kazi Rafiq
- Department of Cardiorenal and Cerebrovascular Medicine Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, Japan.
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72
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Rocchetti MT, Tamma G, Lasorsa D, Suriano IV, D'Apollo A, Papale M, Mastrofrancesco L, Grandaliano G, Svelto M, Valenti G, Gesualdo L, Di Paolo S. Altered urinary excretion of aquaporin 2 in IgA nephropathy. Eur J Endocrinol 2011; 165:657-64. [PMID: 21824900 DOI: 10.1530/eje-11-0512] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE The intrarenal renin-angiotensin system (RAS) activation plays a pivotal role in immunoglobulin A nephropathy (IgAN) pathogenesis, which is still largely undefined. Recently, vasopressin (AVP) has been advocated to contribute to the genesis and progression of chronic kidney diseases (CKD) directly, and indirectly, via RAS activation. Our aim is to explore the intrarenal activity of AVP, its relationship with RAS activity, as well as its modulation by therapies in IgAN. DESIGN In this observational study, we measured plasma copeptin, a surrogate marker of AVP, the urine excretion of aquaporin 2 (AQP2), a protein reflecting renal AVP action, and angiotensinogen (AGT), a parameter of renal RAS activation, and their relationship with renal function in 44 IgAN patients at the time of renal biopsy, without any drug therapy, and after 6-month treatment with ACEi or steroid+ACEi. Twenty-one patients with other CKD and 40 healthy subjects were recruited as controls. METHODS ELISAs were used to measure all variables of interest. RESULTS At baseline, IgAN patients showed higher urinary levels of AQP2, compared with controls and patients with other CKD. Urinary AQP2 and AGT levels strongly correlated with the presence of arterial hypertension. Steroids+ACEi caused the decrease of all the variables examined. The fall of urinary AQP2 and AGT following drug treatments was associated with the decrease of daily proteinuria. CONCLUSION Our findings would support the involvement of AVP-AQP2 axis, interacting with the RAS, in the progression of IgAN and candidate AQP2 as a possible novel marker of the disease.
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Affiliation(s)
- Maria Teresa Rocchetti
- Section of Nephrology and Bioagromed, Department of Biomedical Sciences, University of Foggia, 71122 Foggia, Italy
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Urushihara M, Kagami S. Urinary angiotensinogen as a biomarker of nephropathy in childhood. Int J Nephrol 2011; 2011:206835. [PMID: 21860793 PMCID: PMC3153924 DOI: 10.4061/2011/206835] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 06/21/2011] [Accepted: 06/21/2011] [Indexed: 12/24/2022] Open
Abstract
While most circulating angiotensinogen (AGT) is synthesized in the liver, the kidneys also produce AGT. Recently, we reported that urinary AGT is mainly originated from AGT. Using newly developed human AGT ELISA, we measured urinary AGT levels in chronic glomerulonephritis (GN) patients and patients with type 1 diabetes in childhood. Urinary AGT level was positively correlated with diastolic blood pressure, urinary albumin, urinary protein levels, and urinary occult blood in chronic GN patients. Furthermore, urinary AGT level was significantly increased in chronic GN patients not treated with renin-angiotensin system (RAS) blockers compared with control subjects. Importantly, patients treated with RAS blockers had a marked attenuation of this increase. Also, urinary AGT level was significantly higher in patients with diabetic nephropathy in the premicroalbuminuric phase than in control subjects. These results suggest that urinary AGT reflects intrarenal RAS status in chronic GN and may be an early marker of diabetic nephropathy.
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Affiliation(s)
- Maki Urushihara
- Department of Pediatrics, Institute of Health Biosciences, The University of Tokushima Graduate School, Kuramoto-cho 3-18-15, Tokushima 770-8503, Japan
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Kim YG, Song SB, Lee SH, Moon JY, Jeong KH, Lee TW, Ihm CG. Urinary angiotensinogen as a predictive marker in patients with immunoglobulin A nephropathy. Clin Exp Nephrol 2011; 15:720-726. [PMID: 21695414 DOI: 10.1007/s10157-011-0475-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Accepted: 06/01/2011] [Indexed: 12/22/2022]
Abstract
BACKGROUND The intrarenal renin-angiotensinogen system (RAS) plays a major role in the progression of chronic kidney disease. Urinary angiotensinogen (UAGT) provides a specific index of the intrarenal RAS status. This study was conducted to find the role of UAGT as a predictive marker in patients with immunoglobulin A nephropathy (IgAN). METHODS Thirty-six patients with IgAN, 14 non-IgAN and 15 healthy controls were included. The UAGT concentration was measured using human ELISA kits and adjusted by urinary creatinine. RESULTS UAGT levels were significantly higher in patients with IgAN and non-IgAN than in healthy subjects (104.96 vs. 6.71 ng/mgCr, p < 0.01). Using univariate regression analysis, UAGT was found to correlate with the urine protein-to-creatinine ratio (UPCR), serum creatinine, and systolic and diastolic blood pressure in patients with IgAN. Multivariate regression analysis revealed that UAGT correlated positively with UPCR. Patients with levels of UAGT >100 ng/mgCr showed higher serum creatinine after treatment than patients with UAGT levels <100 ng/mgCr. CONCLUSION This study showed that UAGT levels are increased and correlate positively with the UPCR in IgAN. Patients with high levels of UAGT may have poor renal function following treatment.
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Affiliation(s)
- Yang-Gyun Kim
- Division of Nephrology, Kyung Hee University School of Medicine, Seoul, Korea
| | - Se-Bin Song
- Division of Nephrology, Kyung Hee University School of Medicine, Seoul, Korea
| | - Sang-Ho Lee
- Division of Nephrology, Kyung Hee University School of Medicine, Seoul, Korea
| | - Ju-Young Moon
- Division of Nephrology, Kyung Hee University School of Medicine, Seoul, Korea
| | - Kyung-Hwan Jeong
- Division of Nephrology, Kyung Hee University School of Medicine, Seoul, Korea
| | - Tae-Won Lee
- Division of Nephrology, Kyung Hee University School of Medicine, Seoul, Korea
| | - Chun-Gyoo Ihm
- Division of Nephrology, Kyung Hee University School of Medicine, Seoul, Korea. .,Department of Nephrology, Kyung Hee University Medical Center, 1 Hoegi-dong, Dongdaemun-gu, Seoul, 130-702, Korea.
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75
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Kobori H, Ozawa Y, Acres OW, Miyata K, Satou R. Rho-kinase/nuclear factor-κβ/angiotensinogen axis in angiotensin II-induced renal injury. Hypertens Res 2011; 34:976-9. [PMID: 21633359 DOI: 10.1038/hr.2011.66] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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76
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Navar LG. Counterpoint: Activation of the intrarenal renin-angiotensin system is the dominant contributor to systemic hypertension. J Appl Physiol (1985) 2011; 109:1998-2000; discussion 2015. [PMID: 21148349 DOI: 10.1152/japplphysiol.00182.2010a] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Affiliation(s)
- L Gabriel Navar
- Department of Physiology, Center of Biomedical Research Excellence in Hypertension and Renal Biology, Tulane University Health Sciences Center, 1430 Tulane Avenue, SL39 New Orleans, LA 70112, USA.
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77
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Navar LG, Kobori H, Prieto MC, Gonzalez-Villalobos RA. Intratubular renin-angiotensin system in hypertension. Hypertension 2011; 57:355-62. [PMID: 21282552 PMCID: PMC3073668 DOI: 10.1161/hypertensionaha.110.163519] [Citation(s) in RCA: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- L Gabriel Navar
- Department of Physiology, SL39, Tulane University Health Science Center, 1430 Tulane Ave, New Orleans, LA 70112, USA.
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Navar LG, Prieto MC, Satou R, Kobori H. Intrarenal angiotensin II and its contribution to the genesis of chronic hypertension. Curr Opin Pharmacol 2011; 11:180-6. [PMID: 21339086 DOI: 10.1016/j.coph.2011.01.009] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 01/27/2011] [Accepted: 01/28/2011] [Indexed: 12/20/2022]
Abstract
The increased activity of intrarenal renin-angiotensin system (RAS) in a setting of elevated arterial pressure elicits renal vasoconstriction, increased sodium reabsorption, proliferation, fibrosis and renal injury. Increases in intrarenal and interstitial angiotensin (Ang) II levels are due to increased AT(1) receptor mediated Ang II uptake and stimulation of renal angiotensinogen (AGT) mRNA and protein expression. Augmented proximal tubule AGT production increases tubular AGT secretion and spillover of AGT into the distal nephron and urine. Increased renin formation by principal cells of the collecting ducts forms Ang I from AGT thus increasing Ang II. The catalytic actions of renin and prorenin are enhanced by prorenin receptors (PRRs) on the intercalated cells. The resultant increased intrarenal Ang II levels contribute to the genesis of chronic hypertension.
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Affiliation(s)
- L Gabriel Navar
- Department of Physiology and the Hypertension and Renal Center of Excellence, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA, USA.
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Regression of superficial glomerular podocyte injury in type 2 diabetic rats with overt albuminuria: effect of angiotensin II blockade. J Hypertens 2011; 28:2289-98. [PMID: 20706133 DOI: 10.1097/hjh.0b013e32833dfcda] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
OBJECTIVE Clinical studies indicate that the remission, regression or both of nephrotic-range albuminuria are exerted by angiotensin II receptor blockers (ARBs) in diabetes. The current study was performed to test the hypothesis that these effects of ARBs are associated with regression of glomerular podocyte injury. METHODS We examined the effects of an ARB, olmesartan, on glomerular podocyte injury in type 2 diabetic Otsuka-Long-Evans-Tokushima-Fatty rats with overt albuminuria. RESULTS At baseline (55-week-old), diabetic Otsuka-Long-Evans-Tokushima-Fatty rats showed severe albuminuria with desmin-positive areas (an index of podocyte injury) in both superficial and juxtamedullary glomeruli, and podocyte injury was much greater in juxtamedullary than in superficial glomeruli. At 75-week-old, Otsuka-Long-Evans-Tokushima-Fatty rats had developed more severe albuminuria and superficial glomerular podocyte injury, whereas juxtamedullary glomerular podocyte injury did not advance further. Olmesartan (10 mg/kg per day) decreased albuminuria and superficial glomerular desmin staining to levels that were lower than those at baseline, whereas advanced juxtamedullary glomerular podocyte injury was not changed. CONCLUSION The current study demonstrates for the first time that juxtamedullary glomerular podocyte injury reaches a severe condition at an earlier time than superficial glomerular podocyte injury during the progression of overt albuminuria in type 2 diabetic rats. Our data also support the hypothesis that the antialbuminuric effects of ARBs are associated with regression of superficial glomerular podocyte injury in type 2 diabetes with nephrotic-range albuminuria.
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Gonzalez AA, Liu L, Lara LS, Seth DM, Navar LG, Prieto MC. Angiotensin II stimulates renin in inner medullary collecting duct cells via protein kinase C and independent of epithelial sodium channel and mineralocorticoid receptor activity. Hypertension 2011; 57:594-9. [PMID: 21282553 DOI: 10.1161/hypertensionaha.110.165902] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Collecting duct (CD) renin is stimulated by angiotensin (Ang) II, providing a pathway for Ang I generation and further conversion to Ang II. Ang II stimulates the epithelial sodium channel via the Ang II type 1 receptor and increases mineralocorticoid receptor activity attributed to increased aldosterone release. Our objective was to determine whether CD renin augmentation is mediated directly by Ang II type 1 receptor or via the epithelial sodium channel and mineralocorticoid receptor. In vivo studies examined the effects of epithelial sodium channel blockade (amiloride; 5 mg/kg per day) on CD renin expression and urinary renin content in Ang II-infused rats (80 ng/min, 2 weeks). Ang II infusion increased systolic blood pressure, medullary renin mRNA, urinary renin content, and intrarenal Ang II levels. Amiloride cotreatment did not alter these responses despite a reduction in the rate of progression of systolic blood pressure. In primary cultures of inner medullary CD cells, renin mRNA and (pro)renin protein levels increased with Ang II (100 nmol/L), and candesartan (Ang II type 1 receptor antagonist) prevented this effect. Aldosterone (10(-10) to 10(-7) mol/L) with or without amiloride did not modify the upregulation of renin mRNA in Ang II-treated cells. However, inhibition of protein kinase C with calphostin C prevented the Ang II-mediated increases in renin mRNA and (pro)renin protein levels. Furthermore, protein kinase C activation with phorbol 12-myristate 13-acetate increased renin expression to the same extent as Ang II. These data indicate that an Ang II type 1 receptor-mediated increase in CD renin is induced directly by Ang II via the protein kinase C pathway and that this regulation is independent of mineralocorticoid receptor activation or epithelial sodium channel activity.
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Affiliation(s)
- Alexis A Gonzalez
- Department of Physiology and Tulane Renal Hypertension and Renal Center , Tulane University, School of Medicine, New Orleans, LA 70112, USa
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Urushihara M, Kobori H. Angiotensinogen Expression Is Enhanced in the Progression of Glomerular Disease. ACTA ACUST UNITED AC 2011; 2:378-387. [PMID: 22247811 DOI: 10.4236/ijcm.2011.24064] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Intrarenal renin-angiotensin system (RAS) activation plays a critical role in the development and progression of renal injury. In the kidney, all of the RAS components are present and intrarenal angiotensin II (Ang II) is formed by multiple independent mechanisms. Angiotensinogen (AGT) is the only known substrate for renin that is a rate-limiting enzyme of the RAS. Recently, enhanced intrarenal AGT levels have been shown to reflect the intrarenal RAS status in hypertension, chronic glomerular disease and diabetic nephropathy. In this review, we focus on AGT expression of the diseased glomeruli in the progression of glomerular disease. An anti-glomerular basement membrane nephritis rat model developed progressive proteinuria and glomerular crescent formation, accompanied by increased macrophage infiltration and glomerular expression of AGT and Ang II. The addition of Ang II type 1 receptor blocker to CC-chemokine recaptor 2 antagonist markedly attenuated the induction of macrophage infiltration, AGT and Ang II, and reduced glomerular crescent formation. Next, the levels of glomerular AGT expression and marker of reactive oxygen species in Zucker diabetic fatty (ZDF) obese rats were higher than those in ZDF lean rats. Hydrogen peroxide (H(2)O(2)) induced an increase in the AGT expression in primary rat mesangial cells. Furthermore, the H(2)O(2)-induced upregulation of AGT was inhibited by a mitogen-activated protein kinase kinase and a c-Jun N-terminal kinase inhibitor. These data suggest the potential contribution of enhanced AGT expression in glomeruli to the intrarenal RAS activation for the development of glomerular disease.
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Affiliation(s)
- Maki Urushihara
- Department of Physiology, and Hypertension and Renal Center of Excellence Tulane University Health Sciences Center, New Orleans, USA
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Kobori H, Navar LG. Urinary Angiotensinogen as a Novel Biomarker of Intrarenal Renin-Angiotensin System in Chronic Kidney Disease. INTERNATIONAL REVIEW OF THROMBOSIS 2011; 6:108-116. [PMID: 22022346 PMCID: PMC3183743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
An activated intrarenal reninangiotensin system (RAS) plays a crucial role in the pathogenesis of hypertension and chronic kidney diseases (CKD). Angiotensinogen (AGT) is the only known substrate for renin, which is the rate-limiting enzyme of the RAS. Because the levels of AGT are close to the Michaelis-Menten constant for renin, AGT levels can also control the RAS activity, and upregulation of AGT may lead to elevated angiotensin peptide levels and increases in blood pressure. Recent studies on experimental animal models have documented the involvement of AGT in the intrarenal RAS activation and development of hypertension. Enhanced intrarenal AGT mRNA and/or protein levels occur in experimental models of hypertension and kidney diseases supporting important roles in the development and progression of hypertension and kidney diseases. Urinary excretion rates of AGT provide a specific index of intrarenal RAS status in angiotensin II-infused rats. Also, a direct quantitative method was recently developed to measure urinary AGT using human AGT ELISA. These data prompted us to measure urinary AGT in patients with hypertension and CKD, and investigate correlations with clinical parameters. This brief review will address the potential of urinary AGT as a novel biomarker of the intrarenal RAS status in hypertension and CKD.
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Affiliation(s)
- Hiroyuki Kobori
- Departments of Medicine and Physiology, and Hypertension and Renal Center of Excellence, Tulane University Health Sciences Center, New Orleans, USA
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Abstract
BACKGROUND The Bogalusa Heart Study is a long-term study on cardiovascular disease and has followed a biracial (black/white) population from childhood. Risk factor data pertaining to many patients have been collected over 35 years, and the time course of hypertension has been documented by repeated examinations and measurements. Considerable sex and racial differences have been found to be related to cardiovascular disease. Urinary angiotensinogen (UAGT) is a novel biomarker for the intrarenal activity of the renin-angiotensin system in hypertension and kidney disease. We aimed to determine the relationship of UAGT with traditional cardiovascular disease risk factors in asymptomatic young adults in this biracial population. METHOD We recruited 251 individuals and collected a single random spot urine sample from each one. Because UAGT is significantly increased in diabetic patients and the use of antihypertensive drugs affects UAGT levels, we excluded patients who had diabetes, who were receiving antihypertensive treatment, or both. Consequently, 190 participants were included for this analysis. RESULTS UAGT levels did not differ with race or sex, but were significantly correlated with SBP (r = +0.23, P = 0.0015) and DBP (r = +0.24, P = 0.0012). Moreover, high correlations were shown in men, especially in black men (SBP, r = +0.85, P = 0.0005 and DBP, r = +0.72, P = 0.0079). Thus, UAGT is correlated with blood pressure in men, even when they do not show overt proteinuria or albuminuria. CONCLUSION The biomarker, UAGT, may facilitate the identification of individuals that are at increased risk for the development of hypertension and early asymptomatic renal disease.
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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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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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86
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Benigni A, Cassis P, Remuzzi G. Angiotensin II revisited: new roles in inflammation, immunology and aging. EMBO Mol Med 2010; 2:247-57. [PMID: 20597104 PMCID: PMC3377325 DOI: 10.1002/emmm.201000080] [Citation(s) in RCA: 528] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
That the renin–angiotensin system (RAS) is involved in regulation of blood pressure, vasoconstriction, sodium intake and potassium excretion is well established. Studies in the last few years have however documented new roles for this molecule as a pro-inflammatory molecule and more recently as a possible pro-fibrotic agent that contributes to progressive deterioration of organ function in disease. Binding of Ang II to its receptors (in particular AT1) mediates intracellular free radical generation that contributes to tissue damage by promoting mitochondrial dysfunction. Blocking Ang II signalling protects against neurodegenerative processes and promotes longevity in rodents. Altogether these findings open the unanticipated perspective for exploring Ang II signalling in therapeutic interventions in inflammatory diseases and aging-related tissue injury. This review extends from the discovery of Ang II and its implications in renal and cardiovascular physiology to cover the roles of the system in inflammation, tissue injury, autoimmunity, oxidative stress and aging.
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Affiliation(s)
- Ariela Benigni
- Mario Negri Institute for Pharmacological Research, Bergamo, Italy
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87
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Shao W, Seth DM, Navar LG. Response to On the Origin of Urinary Angiotensin II. Hypertension 2010. [DOI: 10.1161/hypertensionaha.110.160036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Weijian Shao
- Department of Physiology, Hypertension, and Renal Center of Excellence, Tulane University Health Sciences Center, New Orleans, La
| | - Dale M. Seth
- Department of Physiology, Hypertension, and Renal Center of Excellence, Tulane University Health Sciences Center, New Orleans, La
| | - L. Gabriel Navar
- Department of Physiology, Hypertension, and Renal Center of Excellence, Tulane University Health Sciences Center, New Orleans, La
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88
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Yoon HE, Ghee JY, Piao S, Song JH, Han DH, Kim S, Ohashi N, Kobori H, Kuro-o M, Yang CW. Angiotensin II blockade upregulates the expression of Klotho, the anti-ageing gene, in an experimental model of chronic cyclosporine nephropathy. Nephrol Dial Transplant 2010; 26:800-13. [PMID: 20813770 DOI: 10.1093/ndt/gfq537] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The Klotho gene plays a role in suppressing ageing-related disorders. It is suggested that activation of renin-angiotensin system (RAS) or oxidative stress suppresses Klotho in the kidney. This study evaluated the association between Klotho expression and RAS in cyclosporine (CsA)-induced renal injury. METHODS Chronic CsA nephropathy was induced by administering CsA (30 mg/kg) to mice on a low-salt diet (LSD) for 4 weeks. A normal-salt diet (NSD) was used as the control. Reverse transcription-polymerase chain reaction, western blot and immunohistochemistry were performed for Klotho and intrarenal RAS activity was measured using immunohistochemistry for angiotensinogen and renin. Oxidative stress was measured with urinary excretion of 8-hydroxy-2'-deoxyguanosine (8-OHdG). RESULTS CsA treatment decreased Klotho mRNA and protein in mouse kidney in a dose-dependent and time-dependent manner, but a concurrent treatment with losartan, an angiotensin II type 1 (AT1) receptor blocker, reversed the decrease in Klotho expression with histological improvement. This finding was more marked in the LSD than the NSD. Klotho expression was correlated with angiotensinogen and renin expression, tubulointerstitial fibrosis score and urinary 8-OHdG excretion. CONCLUSIONS Angiotensin II may play a pivotal role in regulating Klotho expression in CsA-induced renal injury. AT1 receptor blocker may inhibit the ageing process by decreasing oxidative stress caused by CsA.
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Affiliation(s)
- Hye Eun Yoon
- Division of Nephrology, Department of Internal Medicine, Incheon St Mary’s Hospital, College of Medicine, The Catholic University of Korea, Incheon, South Korea
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89
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Makhanova NA, Crowley SD, Griffiths RC, Coffman TM. Gene expression profiles linked to AT1 angiotensin receptors in the kidney. Physiol Genomics 2010; 42A:211-8. [PMID: 20807774 DOI: 10.1152/physiolgenomics.00063.2010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
To characterize gene expression networks linked to AT(1) angiotensin receptors in the kidney, we carried out genome-wide transcriptional analysis of RNA from kidneys of wild-type (WT) and AT(1A) receptor-deficient mice (KOs) at baseline and after 2 days of angiotensin II infusion (1,000 ng·kg(-1)·min(-1)). At baseline, 405 genes were differentially expressed (>1.5×) between WT and KO kidneys. Of these, >80% were upregulated in the KO group including genes involved in inflammation, oxidative stress, and cell proliferation. After 2 days of angiotensin II infusion in WT mice, expression of ≈805 genes was altered (18% upregulated, 82% repressed). Genes in metabolism and ion transport pathways were upregulated while there was attenuated expression of genes protective against oxidative stress including glutathione synthetase and mitochondrial superoxide dismutase 2. Angiotensin II infusion had little effect on blood pressure in KOs. Nonetheless, expression of >250 genes was altered in kidneys from KO mice during angiotensin II infusion; 14% were upregulated, while 86% were repressed including genes involved in immune responses, angiogenesis, and glutathione metabolism. Between WT and KO kidneys during angiotensin II infusion, 728 genes were differentially expressed; 10% were increased and 90% were decreased in the WT group. Differentially regulated pathways included those involved in ion transport, immune responses, metabolism, apoptosis, cell proliferation, and oxidative stress. This genome-wide assessment should facilitate identification of critical distal pathways linked to blood pressure regulation.
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Affiliation(s)
- Natalia A Makhanova
- Department of Medicine, Division of Nephrology, Duke University and Durham Veterans Affairs Medical Centers, Durham, North Carolina, USA
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90
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Wakui H, Tamura K, Matsuda M, Bai Y, Dejima T, Shigenaga AI, Masuda SI, Azuma K, Maeda A, Hirose T, Ishigami T, Toya Y, Yabana M, Minamisawa S, Umemura S. Intrarenal suppression of angiotensin II type 1 receptor binding molecule in angiotensin II-infused mice. Am J Physiol Renal Physiol 2010; 299:F991-F1003. [PMID: 20739392 DOI: 10.1152/ajprenal.00738.2009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
ATRAP [ANG II type 1 receptor (AT1R)-associated protein] is a molecule which directly interacts with AT1R and inhibits AT1R signaling. The aim of this study was to examine the effects of continuous ANG II infusion on the intrarenal expression and distribution of ATRAP and to determine the role of AT1R signaling in mediating these effects. C57BL/6 male mice were subjected to vehicle or ANG II infusions at doses of 200, 1,000, or 2,500 ng·kg(-1)·min(-1) for 14 days. ANG II infusion caused significant suppression of ATRAP expression in the kidney but did not affect ATRAP expression in the testis or liver. Although only the highest ANG II dose (2,500 ng·kg(-1)·min(-1)) provoked renal pathological responses, such as an increase in the mRNA expression of angiotensinogen and the α-subunit of the epithelial sodium channel, ANG II-induced decreases in ATRAP were observed even at the lowest dose (200 ng·kg(-1)·min(-1)), particularly in the outer medulla of the kidney, based on immunohistochemical staining and Western blot analysis. The decrease in renal ATRAP expression by ANG II infusion was prevented by treatment with the AT1R-specific blocker olmesartan. In addition, the ANG II-mediated decrease in renal ATRAP expression through AT1R signaling occurred without an ANG II-induced decrease in plasma membrane AT1R expression in the kidney. On the other hand, a transgenic model increase in renal ATRAP expression beyond baseline was accompanied by a constitutive reduction of renal plasma membrane AT1R expression and by the promotion of renal AT1R internalization as well as the decreased induction of angiotensinogen gene expression in response to ANG II. These results suggest that the plasma membrane AT1R level in the kidney is modulated by intrarenal ATRAP expression under physiological and pathophysiological conditions in vivo.
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Affiliation(s)
- Hiromichi Wakui
- Dept. of Medical Science and Cardiorenal Medicine, Yokohama City Univ. Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan
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91
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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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92
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Kim S, Soltani-Bejnood M, Quignard-Boulange A, Massiera F, Teboul M, Ailhaud G, Kim JH, Moustaid-Moussa N, Voy BH. The adipose renin-angiotensin system modulates systemic markers of insulin sensitivity and activates the intrarenal renin-angiotensin system. J Biomed Biotechnol 2010; 2006:27012. [PMID: 17489015 PMCID: PMC1698261 DOI: 10.1155/jbb/2006/27012] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Background. The adipose tissue
renin-angiotensin system (RAS) contributes to regulation of fat mass and may also impact systemic functions such as blood pressure and metabolism. Methods and results. A panel of mouse models including mice lacking angiotensinogen, Agt (Agt-KO), mice expressing Agt solely in adipose tissue (aP2-Agt/Agt-KO), and mice overexpressing Agt in adipose tissue (aP2-Agt) was studied. Total body weight, epididymal fat pad weight, and circulating levels of leptin, insulin, and resistin were significantly decreased in Agt-KO mice, while plasma adiponectin levels were increased. aP2-Agt mice exhibited increased adiposity and
plasma leptin and insulin levels compared to wild type (WT) controls. Angiotensinogen and type I Ang II receptor protein levels were also elevated in kidney of aP2-Agt mice. Conclusion. These findings demonstrate that alterations in
adipose RAS activity significantly impact both local and systemic physiology in a way that may contribute to the detrimental health effects of obesity.
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Affiliation(s)
- Suyeon Kim
- Department of Nutrition and Agricultural Experiment Station, University of Tennessee, Knoxville, TN 37996, USA
| | - Morvarid Soltani-Bejnood
- Department of Nutrition and Agricultural Experiment Station, University of Tennessee, Knoxville, TN 37996, USA
| | | | | | | | | | - Jung Han Kim
- Department of Nutrition and Agricultural Experiment Station, University of Tennessee, Knoxville, TN 37996, USA
| | - Naima Moustaid-Moussa
- Department of Nutrition and Agricultural Experiment Station, University of Tennessee, Knoxville, TN 37996, USA
| | - Brynn H. Voy
- Life Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- *Brynn H. Voy:
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93
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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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94
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Urushihara M, Kondo S, Kagami S, Kobori H. Urinary angiotensinogen accurately reflects intrarenal Renin-Angiotensin system activity. Am J Nephrol 2010; 31:318-25. [PMID: 20160435 DOI: 10.1159/000286037] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Accepted: 01/19/2010] [Indexed: 12/19/2022]
Abstract
BACKGROUND We recently reported that immunoreactivity of intrarenal angiotensinogen (AGT) is significantly increased in IgA nephropathy patients. Meanwhile, we have developed direct enzyme-linked immunosorbent assays to measure plasma and urinary AGT (UAGT) in humans. This study was performed to test the hypothesis that UAGT levels are increased in chronic glomerulonephritis patients. METHODS We analyzed 100 urine samples from 70 chronic glomerulonephritis patients (26 from IgA nephropathy, 24 from purpura nephritis, 8 from lupus nephritis, 7 from focal segmental glomerulosclerosis, and 5 from non-IgA mesangial proliferative glomerulonephritis) and 30 normal control subjects. RESULTS UAGT-creatinine ratio (UAGT/UCre) was correlated positively with diastolic blood pressure (p = 0.0326), urinary albumin-creatinine ratio (p < 0.0001), urinary protein-creatinine ratio (p < 0.0001) and urinary occult blood (p = 0.0094). UAGT/UCre was significantly increased in chronic glomerulonephritis patients not treated with renin-angiotensin system (RAS) blockers compared with control subjects (p < 0.0001). Importantly, glomerulonephritis patients treated with RAS blockers had a marked attenuation of this augmentation (p = 0.0021). CONCLUSION These data indicate that UAGT are increased in chronic glomerulonephritis patients and treatment with RAS blockers suppressed UAGT. The efficacy of RAS blockade to reduce the intrarenal RAS activity can be confirmed by measurement of UAGT in chronic glomerulonephritis patients.
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Affiliation(s)
- Maki Urushihara
- Department of Physiology, and Hypertension and Renal Center of Excellence, Tulane University Health Sciences Center, New Orleans, LA 70112-2699, USA
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95
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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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96
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Prenatal exposure to lipopolysaccharide alters the intrarenal renin–angiotensin system and renal damage in offspring rats. Hypertens Res 2009; 33:76-82. [DOI: 10.1038/hr.2009.185] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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97
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Gonzalez-Villalobos RA, Satou R, Ohashi N, Semprun-Prieto LC, Katsurada A, Kim C, Upchurch GM, Prieto MC, Kobori H, Navar LG. Intrarenal mouse renin-angiotensin system during ANG II-induced hypertension and ACE inhibition. Am J Physiol Renal Physiol 2009; 298:F150-7. [PMID: 19846570 DOI: 10.1152/ajprenal.00477.2009] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Angiotensin-converting enzyme (ACE) inhibition (ACEi) ameliorates the development of hypertension and the intrarenal ANG II augmentation in ANG II-infused mice. To determine if these effects are associated with changes in the mouse intrarenal renin-angiotensin system, the expression of angiotensinogen (AGT), renin, ACE, angiotensin type 1 receptor (AT(1)R) mRNA (by quanitative RT-PCR) and protein [by Western blot (WB) and/or immunohistochemistry (IHC)] were analyzed. C57BL/6J male mice (9-12 wk old) were distributed as controls (n = 10), ANG II infused (ANG II = 8, 400 ng x kg(-1) x min(-1) for 12 days), ACEi only (ACEi = 10, lisinopril, 100 mg/l), and ANG II infused + ACEi (ANG II + ACEi = 11). When compared with controls (1.00), AGT protein (by WB) was increased by ANG II (1.29 +/- 0.13, P < 0.05), and this was not prevented by ACEi (ACEi + ANG II, 1.31 +/- 0.14, P < 0.05). ACE protein (by WB) was increased by ANG II (1.21 +/- 0.08, P < 0.05), and it was reduced by ACEi alone (0.88 +/- 0.07, P < 0.05) or in combination with ANG II (0.80 +/- 0.07, P < 0.05). AT(1)R protein (by WB) was increased by ANG II (1.27 +/- 0.06, P < 0.05) and ACEi (1.17 +/- 0.06, P < 0.05) but not ANG II + ACEi [1.15 +/- 0.06, not significant (NS)]. Tubular renin protein (semiquantified by IHC) was increased by ANG II (1.49 +/- 0.23, P < 0.05) and ACEi (1.57 +/- 0.15, P < 0.05), but not ANG II + ACEi (1.10 +/- 0.15, NS). No significant changes were observed in AGT, ACE, or AT(1)R mRNA. In summary, reduced responses of intrarenal tubular renin, ACE, and the AT(1)R protein to the stimulatory effects of chronic ANG II infusions, in the presence of ACEi, are associated with the effects of this treatment to ameliorate augmentations in blood pressure and intrarenal ANG II content during ANG II-induced hypertension.
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Affiliation(s)
- Romer A Gonzalez-Villalobos
- Dept. of Physiology, Tulane Univ. Health Sciences Center, 1430 Tulane Ave., SL39, New Orleans, LA 70112, USA.
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98
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Bouley R, Palomino Z, Tang SS, Nunes P, Kobori H, Lu HA, Shum WW, Sabolic I, Brown D, Ingelfinger JR, Jung FF. Angiotensin II and hypertonicity modulate proximal tubular aquaporin 1 expression. Am J Physiol Renal Physiol 2009; 297:F1575-86. [PMID: 19776169 DOI: 10.1152/ajprenal.90762.2008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Aquaporin 1 (AQP1) is the major water channel in the renal proximal tubule (PT) and thin descending limb of Henle, but its regulation remains elusive. Here, we investigated the effect of ANG II, a key mediator of body water homeostasis, on AQP1 expression in immortalized rat proximal tubule cells (IRPTC) and rat kidney. Real-time PCR on IRPTC exposed to ANG II for 12 h revealed a biphasic effect AQP1 mRNA increased dose dependently in response to 10(-12) to 10(-8) M ANG II but decreased by 50% with 10(-7) M ANG II. The twofold increase of AQP1 mRNA in the presence of 10(-8) M ANG II was abolished by the AT(1) receptor blocker losartan. Hypertonicity due to either NaCl or mannitol also upregulated AQP1 mRNA by three- and twofold, respectively. Immunocytochemistry and Western blotting revealed a two- to threefold increase in AQP1 protein expression in IRPTC exposed concomitantly to ANG II (10(-8)M) and hypertonic medium (either NaCl or mannitol), indicating that these stimuli were not additive. Three-dimensional reconstruction of confocal images suggested that AQP1 expression was increased by ANG II in both the apical and basolateral poles of IRPTC. In vivo studies showed that short-term ANG II infusion had a diuretic effect, while this effect was attenuated after several days of ANG II infusion. After 10 days, we observed a twofold increase in AQP1 expression in the PT and thin descending limb of Henle of ANG II-infused rats that was abolished when rats were treated with the selective AT(1)-receptor antagonist olmesartan. Thus ANG II increases AQP1 expression in vitro and in vivo via direct interaction with the AT(1) receptor, providing an important regulatory mechanism to link PT water reabsorption to body fluid homeostasis via the renin-angiotensin system.
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Affiliation(s)
- Richard Bouley
- Center for Systems Biology, Program in Membrane Biology, Nephrology Division, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
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99
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Fan YY, Nishiyama A, Fujisawa Y, Kobori H, Nakano D, Matsuura J, Hase N, Hitomi H, Kiyomoto H, Urata H, Kohno M. Contribution of chymase-dependent angiotensin II formation to the progression of tubulointerstitial fibrosis in obstructed kidneys in hamsters. J Pharmacol Sci 2009; 111:82-90. [PMID: 19721329 DOI: 10.1254/jphs.09152fp] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Recent studies indicate a role of chymase in the regulation of angiotensin II (AngII) formation in cardiovascular and renal tissues. We investigated a possible contribution of chymase to AngII formation and to renal fibrosis in unilateral ureteral obstruction (UUO). Eight-week-old Syrian hamsters were subjected to UUO and treated with vehicle, the specific chymase inhibitor (CI) 4-[1-(4-methyl-benzo[b]thiophen-3-ylmethyl)-1H-benzimidazol-2-ylsulfanyl]-butyric acid (50 mg/kg, twice a day, p.o.), or the selective AT(1)-receptor blocker olmesartan (10 mg/kg per day, p.o.) for 14 days. UUO-induced renal interstitial fibrosis was associated with increases in renal mRNA levels of alpha-smooth muscle actin (SMA), type I collagen, and transforming growth factor (TGF)-beta. The UUO hamsters showed markedly higher AngII contents and increased AT(1)-receptor mRNA level in the obstructed kidney than sham-operated ones. In contrast, angiotensin-converting enzyme (ACE) protein expression was significantly lower in UUO hamsters. In UUO hamsters, treatment with CI or olmesartan significantly decreased AngII levels in renal tissue and mRNA levels of alpha-SMA, type I collagen, and TGF-beta and ameliorated tubulointerstitial injury. On the other hand, neither CI nor olmesartan changed systolic blood pressure, renal ACE, and AT(1)-receptor protein levels. These data suggest that chymase-dependent intrarenal AngII formation contributes to the pathogenesis of interstitial fibrosis in obstructed kidneys of hamsters.
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Affiliation(s)
- Yu-Yan Fan
- Department of Cardiorenal and Cerebrovascular Medicine, Kagawa University Medical School, Japan
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Hobo A, Yuzawa Y, Kosugi T, Kato N, Asai N, Sato W, Maruyama S, Ito Y, Kobori H, Ikematsu S, Nishiyama A, Matsuo S, Kadomatsu K. The growth factor midkine regulates the renin-angiotensin system in mice. J Clin Invest 2009; 119:1616-25. [PMID: 19451697 DOI: 10.1172/jci37249] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2008] [Accepted: 03/25/2009] [Indexed: 12/24/2022] Open
Abstract
The renin-angiotensin system plays a pivotal role in regulating blood pressure and is involved in the pathogenesis of kidney disorders and other diseases. Here, we report that the growth factor midkine is what we believe to be a novel regulator of the renin-angiotensin system. The hypertension induced in mice by 5/6 nephrectomy was accompanied by renal damage and elevated plasma angiotensin II levels and was ameliorated by an angiotensin-converting enzyme (ACE) inhibitor and an angiotensin receptor blocker. Notably, ACE activity in the lung, midkine expression in the lung, and midkine levels in the plasma were all increased after 5/6 nephrectomy. Exposure to midkine protein enhanced ACE expression in primary cultured human lung microvascular endothelial cells. Furthermore, hypertension was not induced and renal damage was less severe in midkine-deficient mice. Supplemental administration of midkine protein to midkine-deficient mice restored ACE expression in the lung and hypertension after 5/6 nephrectomy. Oxidative stress might be involved in midkine expression, since expression of NADH/NADPH oxidase-1, -2, and -4 was induced in the lung after 5/6 nephrectomy. Indeed, the antioxidative reagent tempol reduced midkine expression and plasma angiotensin II levels and consequently ameliorated hypertension. These results suggest that midkine regulates the renin-angiotensin system and mediates the kidney-lung interaction after 5/6 nephrectomy.
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Affiliation(s)
- Akinori Hobo
- Department of Biochemistry, Nagoya University Graduate School of Medicine, Nagoya, Japan
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