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Papaetis GS. SGLT2 inhibitors, intrarenal hypoxia and the diabetic kidney: insights into pathophysiological concepts and current evidence. Arch Med Sci Atheroscler Dis 2023; 8:e155-e168. [PMID: 38283924 PMCID: PMC10811536 DOI: 10.5114/amsad/176658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2023] [Accepted: 12/08/2023] [Indexed: 01/30/2024] Open
Abstract
Approximately 20-40% of all diabetic patients experience chronic kidney disease, which is related to higher mortality (cardiovascular and all-cause). A large body of evidence suggests that renal hypoxia is one of the main forces that drives diabetic kidney disease, both in its early and advanced stages. It promotes inflammation, generation of intrarenal collagen, capillary rarefaction and eventually accumulation of extracellular matrix that destroys normal renal architecture. SGLT2 inhibitors are unquestionably a practice-changing drug class and a valuable weapon for patients with type 2 diabetes and chronic kidney disease. They have achieved several beneficial kidney effects after targeting multiple and interrelated signaling pathways, including renal hypoxia, independent of their antihyperglycemic activities. This manuscript discusses the pathophysiological concepts that underly their possible effects on modulating renal hypoxia. It also comprehensively investigates both preclinical and clinical studies that explored the possible role of SGLT2 inhibitors in this setting, so as to achieve long-term renoprotective benefits.
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Affiliation(s)
- Georgios S. Papaetis
- K.M.P THERAPIS Paphos Medical Center, Internal Medicine and Diabetes Clinic, Paphos, Cyprus
- CDA College, Paphos, Cyprus
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Zhu Q, Hu J, Wang L, Wang W, Wang Z, Li PL, Li N. Overexpression of MicroRNA-429 Transgene Into the Renal Medulla Attenuated Salt-Sensitive Hypertension in Dahl S Rats. Am J Hypertens 2021; 34:1071-1077. [PMID: 34089591 DOI: 10.1093/ajh/hpab089] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 02/28/2021] [Accepted: 06/02/2021] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND We have previously shown that high salt stimulates the expression of miR-429 in the renal medulla, which induces mRNA decay of HIF prolyl-hydroxylase 2 (PHD2), an enzyme to promote the degradation of hypoxia-inducible factor (HIF)-1α, and increases the HIF-1α-mediated activation of antihypertensive genes in the renal medulla, consequently promoting extra sodium excretion. Our preliminary results showed that high salt-induced increase of miR-429 was not observed in Dahl S rats. This present study determined whether correction of this impairment in miR-429 would reduce PHD2 levels, increase antihypertensive gene expression in the renal medulla and attenuate salt-sensitive hypertension in Dahl S rats. METHODS Lentiviruses encoding rat miR-429 were transfected into the renal medulla in uninephrectomized Dahl S rats. Sodium excretion and blood pressure were then measured. RESULTS Transduction of lentiviruses expressing miR-429 into the renal medulla increased miR-429 levels, decreased PHD2 levels, and upregulated HIF-1α target gene NOS-2, which restored the adaptive mechanism to increase the antihypertensive gene after high-salt intake in Dahl S rats. Functionally, overexpression of miR-429 transgene in the renal medulla significantly improved pressure natriuretic response, enhanced urinary sodium excretion, and reduced sodium retention upon extra sodium loading, and consequently, attenuated the salt-sensitive hypertension in Dahl S rats. CONCLUSIONS Our results suggest that the impaired miR-429-mediated PHD2 inhibition in response to high salt in the renal medulla may represent a novel mechanism for salt-sensitive hypertension in Dahl S rats and that correction of this impairment in miR-429 pathway could be a therapeutic approach for salt-sensitive hypertension.
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Affiliation(s)
- Qing Zhu
- Key Laboratory of Glucolipid Metabolic Disorder, Ministry of Education of China, Guangdong Pharmaceutical University, Guangzhou, China
| | - Junping Hu
- Department of Pharmacology & Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Lei Wang
- School of Chinese Materia Medica, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Weili Wang
- Department of Pharmacology & Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Zhengchao Wang
- Laboratory for Developmental Biology and Neurosciences, College of Life Sciences, Fujian Normal University, Fuzhou, China
| | - Pin-Lan Li
- Department of Pharmacology & Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Ningjun Li
- Department of Pharmacology & Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, USA
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Further evidence against the role renal medullary perfusion in short-term control of arterial pressure in normotensive and mildly or overtly hypertensive rats. Pflugers Arch 2021; 473:623-631. [PMID: 33651165 PMCID: PMC8049918 DOI: 10.1007/s00424-021-02534-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 02/01/2021] [Accepted: 02/03/2021] [Indexed: 12/20/2022]
Abstract
Earlier evidence from studies of rat hypertension models undermines the widespread view that the rate of renal medullary blood flow (MBF) is critical in control of arterial pressure (MAP). Here, we examined the role of MBF in rats that were normotensive, with modest short-lasting pressure elevation, or with overt established hypertension. The groups studied were anaesthetised Sprague-Dawley rats: (1) normotensive, (2) with acute i.v. norepinephrine-induced MAP elevation, and (3) with hypertension induced by unilateral nephrectomy followed by administration of deoxycorticosterone-acetate (DOCA) and 1% NaCl drinking fluid for 3 weeks. MBF was measured (laser-Doppler probe) and selectively increased using 4-h renal medullary infusion of bradykinin. MAP, renal excretion parameters and post-experiment medullary tissue osmolality and sodium concentration were determined. In the three experimental groups, baseline MAP was 117, 151 and 171 mmHg, respectively. Intramedullary bradykinin increased MBF by 45%, 65% and 70%, respectively, but this was not associated with a change in MAP. In normotensive rats a significant decrease in medullary tissue sodium was seen. The intramedullary bradykinin specifically increased renal excretion of water, sodium and total solutes in norepinephrine-treated rats but not in the two other groups. As previously shown in models of rat hypertension, in the normotensive rats and those with acute mild pressure elevation (resembling labile borderline human hypertension), 4-h renal medullary hyperperfusion failed to decrease MAP. Nor did it decrease in DOCA-salt model mimicking low-renin human hypertension. Evidently, within the 4-h observation, medullary perfusion was not a critical determinant of MAP in normotensive and hypertensive rats.
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Sadowski J, Bądzyńska B. Altered renal medullary blood flow: A key factor or a parallel event in control of sodium excretion and blood pressure? Clin Exp Pharmacol Physiol 2020; 47:1323-1332. [PMID: 32163610 DOI: 10.1111/1440-1681.13303] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 03/03/2020] [Accepted: 03/09/2020] [Indexed: 11/29/2022]
Abstract
In the context of the ongoing debate on the mechanism of blood pressure (BP) regulation and pathophysiology of arterial hypertension ("renocentric" vs "neural" concepts), attention is focused on the putative regulatory role of changes in renal medullary blood flow (MBF). Experimental evidence is analysed with regard to the question whether an elevation of BP and renal perfusion pressure (RPP) is likely to increase MBF due to its impaired autoregulation. It is concluded that such increases have been clearly documented only in rats with extracellular fluid volume expansion. A possible translation of this finding to BP regulation in health and hypertension in humans may only be a matter of speculation. Within the "renocentric" theory, the key event leading to restoration of initial BP level is pressure natriuresis. Its relation to elevation of renal interstitial hydrostatic pressure and to the phenomenon of "wash-out" of renal medullary solutes by increasing MBF is discussed. We also assessed the validity of data supporting the putative mechanism of short-term restoration of elevated BP owing to the release of a vasodilator lipid (medullipin) by the medulla. The structure of the proposed medullary lipid is still undefined, and there is no sound evidence on its mediatory role in lowering elevated BP level. In conclusion, MBF change can hardly be regarded as a crucial event in the regulation of BP: it can be involved in the control of sodium excretion and BP only in some circumstances, although its contributory role cannot be excluded.
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Affiliation(s)
- Janusz Sadowski
- Department of Renal and Body Fluid Physiology, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
| | - Bożena Bądzyńska
- Department of Renal and Body Fluid Physiology, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
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Bądzyńska B, Baranowska I, Gawryś O, Sadowski J. Evidence against a crucial role of renal medullary perfusion in blood pressure control of hypertensive rats. J Physiol 2018; 597:211-223. [PMID: 30334256 DOI: 10.1113/jp276342] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 10/17/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The development of new effective methods of treating arterial hypertension is hindered by uncertainty regarding its causes. According to one widespread concept hypertension is caused by abnormal blood circulation in the kidney, specifically by reduction of blood flow through the kidney medulla; however, this causal relationship has never been rigorously verified. We investigated whether in rats with three different forms of experimental hypertension prolonged selective elevation of renal medullary blood flow using local infusion of the vasodilator bradykinin would lower arterial pressure. We found that increasing medullary blood flow by almost 50% did not result in alleviation of hypertension, which argues against a causal role of such changes in the control of arterial pressure and suggests that attempts at improving renal medullary circulation are not likely to be a promising approach to combating hypertension. ABSTRACT The crucial role of renal medullary blood flow (MBF) in the control of arterial pressure (MAP) has been widely accepted but not rigorously verified. We examined the effects of experimental selective MBF elevation on MAP, medullary tissue hypertonicity and renal excretion in hypertensive rats. We used three hypertensive rat models: (1) rats with hypertension induced by chronic angiotensin II infusions (AngII model), (2) rats with hypertension induced by unilateral nephrectomy followed by high salt diet (HS/UNX), and (3) spontaneously hypertensive rats (SHR). In acute experiments, MBF (laser-Doppler measurement) was selectively increased with an intramedullary infusion of bradykinin (Bk) at 0.27 mg h-1 kg-1 BW over 4 h. MAP, renal artery blood flow (Transonic probe) and renal excretion parameters were measured simultaneously. In chronic studies with AngII and HS/UNX rats, Bk was infused over 2 weeks and MAP (telemetry probe) and renal excretion were repeatedly determined. In acute studies, with AngII, SHR and HS/UNX groups, Bk infusion caused a 47% increase in MBF (P < 0.01-0.001), whereas solvent infusion was without effect. During the experiments MAP decreased slightly and to the same extent with Bk and solvent infusion. Medullary tissue osmolality and [Na+ ] were lower in Bk- than in solvent-infused AngII rats and in SHR. Two weeks of intramedullary Bk infusion tested in AngII and HS/UNX rats did not alter MAP or renal excretion; though in the latter group a significant MBF increase and medullary hypertonicity decrease was observed. Since no decrease in MAP in hypertensive rats was seen with Bk-induced major renal medullary hyperperfusion or with a wash-out of medullary solutes, our data argue against a crucial role of MBF in the pathogenesis of arterial hypertension.
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Affiliation(s)
- Bożena Bądzyńska
- Department of Renal and Body Fluid Physiology, Mossakowski Medical Research Centre , Polish Academy of Sciences, 5 Pawińskiego St, 02-106, Warsaw, Poland
| | - Iwona Baranowska
- Department of Renal and Body Fluid Physiology, Mossakowski Medical Research Centre , Polish Academy of Sciences, 5 Pawińskiego St, 02-106, Warsaw, Poland
| | - Olga Gawryś
- Department of Renal and Body Fluid Physiology, Mossakowski Medical Research Centre , Polish Academy of Sciences, 5 Pawińskiego St, 02-106, Warsaw, Poland
| | - Janusz Sadowski
- Department of Renal and Body Fluid Physiology, Mossakowski Medical Research Centre , Polish Academy of Sciences, 5 Pawińskiego St, 02-106, Warsaw, Poland
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Emans TW, Janssen BJ, Joles JA, Krediet CP. Nitric Oxide Synthase Inhibition Induces Renal Medullary Hypoxia in Conscious Rats. J Am Heart Assoc 2018; 7:e009501. [PMID: 30371226 PMCID: PMC6201463 DOI: 10.1161/jaha.118.009501] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 06/18/2018] [Indexed: 12/14/2022]
Abstract
Background Renal hypoxia, implicated as crucial factor in onset and progression of chronic kidney disease, may be attributed to reduced nitric oxide because nitric oxide dilates vasculature and inhibits mitochondrial oxygen consumption. We hypothesized that chronic nitric oxide synthase inhibition would induce renal hypoxia. Methods and Results Oxygen-sensitive electrodes, attached to telemeters, were implanted in either renal cortex (n=6) or medulla (n=7) in rats. After recovery and stabilization, baseline oxygenation ( pO 2) was recorded for 1 week. To inhibit nitric oxide synthase, N-ω-nitro-l-arginine (L-NNA; 40 mg/kg/day) was administered via drinking water for 2 weeks. A separate group (n=8), instrumented with blood pressure telemeters, followed the same protocol. L-NNA rapidly induced hypertension (165±6 versus 108±3 mm Hg; P<0.001) and proteinuria (79±12 versus 17±2 mg/day; P<0.001). Cortical pO 2, after initially dipping, returned to baseline and then increased. Medullary pO 2 decreased progressively (up to -19±6% versus baseline; P<0.05). After 14 days of L-NNA, amplitude of diurnal medullary pO 2 was decreased (3.7 [2.2-5.3] versus 7.9 [7.5-8.4]; P<0.01), whereas amplitudes of blood pressure and cortical pO 2 were unaltered. Terminal glomerular filtration rate (1374±74 versus 2098±122 μL/min), renal blood flow (5014±336 versus 9966±905 μL/min), and sodium reabsorption efficiency (13.0±0.8 versus 22.8±1.7 μmol/μmol) decreased (all P<0.001). Conclusions For the first time, we show temporal development of renal cortical and medullary oxygenation during chronic nitric oxide synthase inhibition in unrestrained conscious rats. Whereas cortical pO 2 shows transient changes, medullary pO 2 decreased progressively. Chronic L-NNA leads to decreased renal perfusion and sodium reabsorption efficiency, resulting in progressive medullary hypoxia, suggesting that juxtamedullary nephrons are potentially vulnerable to prolonged nitric oxide depletion.
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Affiliation(s)
- Tonja W. Emans
- Internal Medicine‐NephrologyAmsterdam UMC / Academic Medical Centre at the University of AmsterdamThe Netherlands
- Nephrology and HypertensionUniversity Medical Centre UtrechtThe Netherlands
| | - Ben J. Janssen
- Pharmacology and ToxicologyMaastricht UniversityThe Netherlands
| | - Jaap A. Joles
- Nephrology and HypertensionUniversity Medical Centre UtrechtThe Netherlands
| | - C.T. Paul Krediet
- Internal Medicine‐NephrologyAmsterdam UMC / Academic Medical Centre at the University of AmsterdamThe Netherlands
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Braun D, Dietze S, Pahlitzsch TMJ, Wennysia IC, Persson PB, Ludwig M, Patzak A. Short-term hypoxia and vasa recta function in kidney slices. Clin Hemorheol Microcirc 2018; 67:475-484. [PMID: 28922144 DOI: 10.3233/ch-179230] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Descending vasa recta (DVR) supply the inner part of outer renal medulla an area at risk for hypoxic damages. OBJECTIVE We hypothesize increased vasoreactivity after hypoxia/re-oxygenation (H/R) in DVR, which might contribute to the reduced medullary perfusion after an ischemic event. METHODS Live kidney slices (200μm) from SD rats were used for functional experiments. TUNEL assay and H&E staining were used to estimate slice viability. Kidney slices were treated with carbogen or hypoxia (1% O2) for 60 or 90 min and vasoreactivity to Ang II (10-7 M) was recorded by DIC microscopy after re-oxygenation with carbogen. Expression of NOS and NADPH enzymes mRNA were determined in iron-perfusion isolated VR. RESULTS Percentage of apoptotic cells increased in control and H/R after 90 min in the medulla. Ang II- induced constriction of DVR was reduced after 90 min in control (compared to 60 min), but not after H/R. NOS enzymes mRNA expression levels decreased over 90 min hypoxia. CONCLUSIONS Increased reactivity of DVR to Ang II after H/R compared to control (90 min) suggest a role of DVR in renal ischemia/reperfusion injury.
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Affiliation(s)
- Diana Braun
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Germany
| | - Stefanie Dietze
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Germany
| | | | - Inggrid C Wennysia
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Germany
| | - Pontus B Persson
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Germany
| | - Marion Ludwig
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Germany
| | - Andreas Patzak
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Germany
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Inhibition of microRNA-429 in the renal medulla increased salt sensitivity of blood pressure in Sprague Dawley rats. J Hypertens 2018; 35:1872-1880. [PMID: 28445205 DOI: 10.1097/hjh.0000000000001373] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND We have previously shown that high salt intake suppresses the expression of prolyl hydroxylase domain-containing protein 2 (PHD2), an enzyme promoting the degradation of hypoxia-inducible factor (HIF)-1α, and increases HIF-1α along with its target genes in the renal medulla, which promotes sodium excretion and regulates salt sensitivity of blood pressure. However, it remains unknown how high salt inhibits the expression of PHD2. METHOD AND RESULTS The current study first revealed that high-salt-induced PHD2 inhibition was due to the enhanced decay of mRNA. We then found that high salt significantly increased the expression of miR-429, which was subsequently proven to target the 3'-untranslated region of PHD2 and reduce PHD2 levels, in the renal medulla. To define the functional role of renal medullary miR-429 in the regulation of PHD2/HIF-1α-mediated renal adaptation to high salt intake and salt sensitivity of blood pressure, we locally inhibited miR-429 in the renal medulla by locked nucleic acid anti-miR-429 in uninephrectomized rats. Our results demonstrated that inhibition of miR-429 remarkably increased the levels of PHD2, which disrupted PHD2-associated adaptive activation of HIF-1α-mediated gene expression in response to high salt in the renal medulla and consequently inhibited urinary sodium excretion, enhanced sodium retention in response to chronic sodium overloading, and as a result, produced a salt-sensitive hypertension. CONCLUSION It is concluded that miR-429 is an important upstream mediator in PHD2/HIF-1α-associated renal adaptation to high salt intake and that deficiency in miR-429-mediated PHD2 inhibition in response to high salt in the renal medulla may represent a pathogenic mechanism for salt-sensitive hypertension.
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Schreier B, Hünerberg M, Mildenberger S, Rabe S, Bethmann D, Wickenhauser C, Gekle M. Deletion of the EGF receptor in vascular smooth muscle cells prevents chronic angiotensin II-induced arterial wall stiffening and media thickening. Acta Physiol (Oxf) 2018; 222. [PMID: 29152859 DOI: 10.1111/apha.12996] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 11/09/2017] [Accepted: 11/10/2017] [Indexed: 01/13/2023]
Abstract
AIM In vivo vascular smooth muscle cell (VSMC) EGF receptor (EGFR) contributes to acute angiotensin II (AII) effects on vascular tone and blood pressure. The ubiquitously expressed EGFR has been implicated in vascular remodelling preceding end-organ damage by pharmacological inhibition, and AII signalling in cultured vascular cells is partly EGFR-dependent. However, the role of VSMC-EGFR in vivo during AII-induced pathophysiological processes is not known. METHODS This study assesses the in vivo relevance of VSMC-EGFR during chronic AII challenge without further stressors, using a mouse model with inducible, VSMC-specific EGFR knock out (VSMC-EGFR-KO). In these mice functional and structural vascular, renal and cardiac effects or biomarkers were investigated in vivo and ex vivo. RESULTS Vascular smooth muscle cell-EGFR-KO prevented AII-induced media hypertrophy of mesenteric arteries, renal arterioles and the aorta, VSMC ERK1/2-phosphorylation as well as the impairment of vascular compliance. Furthermore, induction of vascular fibrosis, creatinineamia, renal interstitial fibrosis as well as the increase in fractional water excretion was prevented. AII-induced increase in systolic blood pressure was mitigated. By contrast, endothelial dysfunction, induction of vascular inflammatory marker mRNA and albuminuria were not inhibited. Cardiac and cardiomyocyte hypertrophy were also not prevented by VSMC-EGFR-KO. CONCLUSION Vascular smooth muscle cell-EGFRs are relevant for pathological AII action in vivo. Our data show in vivo and ex vivo the necessity of VSMC-EGFR for AII-induced structural and functional vascular remodelling, not including endothelial dysfunction. Hereby, VSMC-EGFR gains importance for complete AII-induced renal end-organ damage succeeding vascular remodelling.
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Affiliation(s)
- B. Schreier
- Julius-Bernstein-Institute of Physiology; Martin Luther University Halle-Wittenberg; Halle Germany
| | - M. Hünerberg
- Julius-Bernstein-Institute of Physiology; Martin Luther University Halle-Wittenberg; Halle Germany
| | - S. Mildenberger
- Julius-Bernstein-Institute of Physiology; Martin Luther University Halle-Wittenberg; Halle Germany
| | - S. Rabe
- Julius-Bernstein-Institute of Physiology; Martin Luther University Halle-Wittenberg; Halle Germany
| | - D. Bethmann
- Institute of Pathology; Martin Luther University Halle-Wittenberg; Halle Germany
| | - C. Wickenhauser
- Institute of Pathology; Martin Luther University Halle-Wittenberg; Halle Germany
| | - M. Gekle
- Julius-Bernstein-Institute of Physiology; Martin Luther University Halle-Wittenberg; Halle Germany
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Wang Z, Zhu Q, Wang W, Yi F, Li PL, Boini KM, Li N. Infusion of Valproic Acid Into the Renal Medulla Activates Stem Cell Population and Attenuates Salt-Sensitive Hypertension in Dahl S Rats. Cell Physiol Biochem 2017; 42:1264-1273. [PMID: 28693025 DOI: 10.1159/000478955] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 04/25/2017] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Our previous study has detected a stem cell deficiency in the renal medulla in Dahl salt-sensitive (S) rats. This study determined whether infusion of valproic acid (VA), an agent known to stimulate the stem cell function, attenuated salt-sensitive hypertension in Dahl S rats. METHODS Uninephrectomized Dahl S rats were infused with vehicle or VA (50mg/kg/d) into the renal medulla and fed with a low (LS) or high salt diet (HS). Stem cell marker and number were analyzed by immunohistochemistry, Real-time RT-PCR and Western blot. Sodium excretion and blood pressure were measured. RESULTS VA significantly increased the mRNA and protein levels of FGF2, a stem cell niche factor, and CD133, a stem cell marker. The number of CD133+ cells was significantly increased in the renal medulla in VA-treated rats. Meanwhile, high salt-induced increases in the mRNA level of proinflammatory factors interleukin-1β and interleukin-6 were blocked in VA-treated rats. Functionally, sodium excretion in response to the blood pressure increase and acute sodium loading was significantly enhanced, sodium retention attenuated, high salt-induced increase of blood pressure reduced in VA-treated rats. CONCLUSION Activation of stem cell function by VA inhibits the activation of proinflammatory factors and attenuates salt-sensitive hypertension in Dahl S rats.
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Affiliation(s)
- Zhengchao Wang
- Laboratory for Developmental Biology and Neurosciences, College of Life Sciences, Fujian Normal University, Fuzhou, China.,Department of Pharmacology & Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Qing Zhu
- Department of Pharmacology & Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia, USA.,Institute of Hypertension, Sun Yat-sen University School of Medicine, Guangzhou, China
| | - Weili Wang
- Department of Pharmacology & Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Fan Yi
- Department of Pharmacology, Shandong University School of Medicine, Jinan, China
| | - Pin-Lan Li
- Department of Pharmacology & Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Krishna M Boini
- Department of Pharmacology & Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Ningjun Li
- Department of Pharmacology & Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia, USA
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Zhu Q, Li XX, Wang W, Hu J, Li PL, Conley S, Li N. Mesenchymal stem cell transplantation inhibited high salt-induced activation of the NLRP3 inflammasome in the renal medulla in Dahl S rats. Am J Physiol Renal Physiol 2016; 310:F621-F627. [PMID: 26764201 DOI: 10.1152/ajprenal.00344.2015] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 01/07/2016] [Indexed: 12/22/2022] Open
Abstract
Inflammasomes activate caspase-1 to produce interleukin (IL)-1β. Activation of the NLRP3 inflammasome is involved in various renal pathological conditions. It remains unknown whether the NLRP3 inflammasome activation participates in the abnormal renal response to high-salt (HS) diet in Dahl salt-sensitive (S) rats. In addition, our lab recently showed that transplantation of mesenchymal stem cells (MSCs) attenuated HS-induced inflammation in the renal medulla in Dahl S rat. However, it is unclear whether the anti-inflammatory action of MSCs is associated with inhibition of the NLRP3 inflammasome. The present study determined the response of the NLRP3 inflammasome to HS intake and the effect of MSC transplantation on the NLRP3 inflammasome in the renal medulla in Dahl S rats. Immunostaining showed that the inflammasome components NLRP3, ASC, and caspase-1 were mainly present in distal tubules and collecting ducts. Interestingly, the renal medullary levels of these inflammasome components were remarkably increased after a HS diet in Dahl S rats, while remaining unchanged in normal rats. This HS-induced activation of the NLRP3 inflammasome was significantly blocked by MSC transplantation into the renal medulla in Dahl S rats. Furthermore, infusion of a caspase-1 inhibitor into the renal medulla significantly attenuated HS-induced hypertension in Dahl S rats. These data suggest that HS-induced activation of the NLRP3 inflammasome may contribute to renal medullary dysfunction in Dahl S rats and that inhibition of inflammasome activation may be one of the mechanisms for the anti-inflammatory and anti-hypertensive effects of stem cells in the renal medulla in Dahl S rats.
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Affiliation(s)
- Qing Zhu
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Xiao-Xue Li
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Weili Wang
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Junping Hu
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Pin-Lan Li
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Sabena Conley
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Ningjun Li
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
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Suzuki M. Physical exercise and renal function. JOURNAL OF PHYSICAL FITNESS AND SPORTS MEDICINE 2015. [DOI: 10.7600/jpfsm.4.17] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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13
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Transplantation of mesenchymal stem cells into the renal medulla attenuated salt-sensitive hypertension in Dahl S rat. J Mol Med (Berl) 2014; 92:1139-45. [PMID: 25131934 DOI: 10.1007/s00109-014-1199-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 07/27/2014] [Accepted: 07/31/2014] [Indexed: 10/24/2022]
Abstract
UNLABELLED Adult stem cell deficiency has been implicated in the pathogenic mechanism for various diseases. Renal medullary dysfunction is one of the major mechanisms for the development of hypertension in Dahl salt-sensitive (S) rats. The present study first detected a stem cell deficiency in the renal medulla in Dahl S rats and then tested the hypothesis that transplantation of mesenchymal stem cells (MSCs) into the renal medulla improves salt-sensitive hypertension in Dahl S rats. Immunohistochemistry and flowcytometry analyses showed a significantly reduced number of stem cell marker CD133+ cells in the renal medulla from Dahl S rats compared with controls, suggesting a stem cell deficiency. Rat MSCs or control cells were transplanted into the renal medulla in uninephrectomized Dahl S rats, which were then treated with a low- or high-salt diet for 20 days. High-salt-induced sodium retention and hypertension was significantly attenuated in MSC-treated rats compared with control cell-treated rats. Meanwhile, high-salt-induced increases of proinflammatory factors, monocyte chemoattractant protein-1, and interleukin-1β, in the renal medulla were blocked by MSC treatment. Furthermore, immunostaining showed that high-salt-induced immune cell infiltration into the renal medulla was substantially inhibited by MSC treatment. These results suggested that stem cell defect in the renal medulla may contribute to the hypertension in Dahl S rats and that correction of this stem cell defect by MSCs attenuated hypertension in Dahl S rats through anti-inflammation. KEY MESSAGE Stem cell defect in the renal medulla may contribute to salt-sensitive hypertension Stem cell therapy is a potential therapeutic strategy for salt-sensitive hypertension Normal stem cell inhibits the inflammatory response to high salt in the renal medulla.
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Ergin B, Kapucu A, Demirci-Tansel C, Ince C. The renal microcirculation in sepsis. Nephrol Dial Transplant 2014; 30:169-77. [PMID: 24848133 DOI: 10.1093/ndt/gfu105] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Despite identification of several cellular mechanisms being thought to underlie the development of septic acute kidney injury (AKI), the pathophysiology of the occurrence of AKI is still poorly understood. It is clear, however, that instead of a single mechanism being responsible for its aetiology, an orchestra of cellular mechanisms failing is associated with AKI. The integrative physiological compartment where these mechanisms come together and exert their integrative deleterious action is the renal microcirculation (MC). This is why it is opportune to review the response of the renal MC to sepsis and discuss the determinants of its (dys)function and how it contributes to the pathogenesis of renal failure. A main determinant of adequate organ function is the adequate supply and utilization of oxygen at the microcirculatory and cellular level to perform organ function. The highly complex architecture of the renal microvasculature, the need to meet a high energy demand and the fact that the kidney is borderline ischaemic makes the kidney a highly vulnerable organ to hypoxaemic injury. Under normal, steady-state conditions, oxygen (O2) supply to the renal tissues is well regulated; however, under septic conditions the delicate balance of oxygen supply versus demand is disturbed due to renal microvasculature dysfunction. This dysfunction is largely due to the interaction of renal oxygen handling, nitric oxide metabolism and radical formation. Renal tissue oxygenation is highly heterogeneous not only between the cortex and medulla but also within these renal compartments. Integrative evaluation of the different determinants of tissue oxygen in sepsis models has identified the deterioration of microcirculatory oxygenation as a key component in the development AKI. It is becoming clear that resuscitation of the failing kidney needs to integratively correct the homeostasis between oxygen, and reactive oxygen and nitrogen species. Several experimental therapeutic modalities have been found to be effective in restoring microcirculatory oxygenation in parallel to improving renal function following septic AKI. However, these have to be verified in clinical studies. The development of clinical physiological biomarkers of AKI specifically aimed at the MC should form a valuable contribution to monitoring such new therapeutic modalities.
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Affiliation(s)
- Bulent Ergin
- Department of Translational Physiology, Academic Medical Center, Amsterdam, The Netherlands
| | - Aysegul Kapucu
- Department of Translational Physiology, Academic Medical Center, Amsterdam, The Netherlands Department of Biology and Zoology Division, University of Istanbul, Istanbul, Turkey
| | - Cihan Demirci-Tansel
- Department of Biology and Zoology Division, University of Istanbul, Istanbul, Turkey
| | - Can Ince
- Department of Translational Physiology, Academic Medical Center, Amsterdam, The Netherlands
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Zhu Q, Liu M, Han WQ, Li PL, Wang Z, Li N. Overexpression of HIF prolyl-hydoxylase-2 transgene in the renal medulla induced a salt sensitive hypertension. J Cell Mol Med 2014; 16:2701-7. [PMID: 22686466 PMCID: PMC3461349 DOI: 10.1111/j.1582-4934.2012.01590.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Renal medullary hypoxia-inducible factor (HIF)-1α and its target genes, such as haem oxygenase and nitric oxide synthase, have been indicated to play an important role in the regulation of sodium excretion and blood pressure. HIF prolyl hydroxylase domain-containing proteins (PHDs) are major enzymes to promote the degradation of HIF-1α. We recently reported that high salt intake suppressed the renal medullary PHD2 expression and thereby activated HIF-1α-mediated gene regulation in the renal medulla in response to high salt. To further define the functional role of renal medullary PHD2 in the regulation of renal adaptation to high salt intake and the longer term control of blood pressure, we transfected PHD2 expression plasmids into the renal medulla in uninephrectomized rats and determined its effects on pressure natriuresis, sodium excretion after salt overloading and the long-term control of arterial pressure after high salt challenge. It was shown that overexpression of PHD2 transgene increased PHD2 levels and decreased HIF-1α levels in the renal medulla, which blunted pressure natriuresis, attenuated sodium excretion, promoted sodium retention and produced salt sensitive hypertension after high salt challenge compared with rats treated with control plasmids. There was no blood pressure change in PHD2-treated rats that were maintained in low salt diet. These results suggested that renal medullary PHD2 is an important regulator in renal adaptation to high salt intake and a deficiency in PHD2-mediated molecular adaptation in response to high salt intake in the renal medulla may represent a pathogenic mechanism producing salt sensitive hypertension.
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Affiliation(s)
- Qing Zhu
- Department of Pharmacology & Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298, USA
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16
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Zhu Q, Hu J, Han WQ, Zhang F, Li PL, Wang Z, Li N. Silencing of HIF prolyl-hydroxylase 2 gene in the renal medulla attenuates salt-sensitive hypertension in Dahl S rats. Am J Hypertens 2014; 27:107-13. [PMID: 24190904 DOI: 10.1093/ajh/hpt207] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND In response to high salt intake, transcription factor hypoxia-inducible factor (HIF) 1α activates many antihypertensive genes, such as heme oxygenase 1 (HO-1) 1 and cyclooxygenase 2 (COX-2) in the renal medulla, which is an important molecular adaptation to promote extra sodium excretion. We recently showed that high salt inhibited the expression of HIF prolyl-hydroxylase 2 (PHD2), an enzyme that promotes the degradation of HIF-1α, thereby upregulating HIF-1α, and that high salt-induced inhibition in PHD2 and subsequent activation of HIF-1α in the renal medulla was blunted in Dahl salt-sensitive hypertensive rats. This study tested the hypothesis that silencing the PHD2 gene to increase HIF-1α levels in the renal medulla attenuates salt-sensitive hypertension in Dahl S rats. METHODS PHD2 short hairpin RNA (shRNA) plasmids were transfected into the renal medulla in uninephrectomized Dahl S rats. Renal function and blood pressure were then measured. RESULTS PHD2 shRNA reduced PHD2 levels by >60% and significantly increased HIF-1α protein levels and the expression of HIF-1α target genes HO-1 and COX-2 by >3-fold in the renal medulla. Functionally, pressure natriuresis was remarkably enhanced, urinary sodium excretion was doubled after acute intravenous sodium loading, and chronic high salt-induced sodium retention was remarkably decreased, and as a result, salt-sensitive hypertension was significantly attenuated in PHD2 shRNA rats compared with control rats. CONCLUSIONS Impaired PHD2 response to high salt intake in the renal medulla may represent a novel mechanism for hypertension in Dahl S rats, and inhibition of PHD2 in the renal medulla could be a therapeutic approach for salt-sensitive hypertension.
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Affiliation(s)
- Qing Zhu
- Department of Pharmacology & Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA
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He W, Zhang M, Zhao M, Davis LS, Blackwell TS, Yull F, Breyer MD, Hao CM. Increased dietary sodium induces COX2 expression by activating NFκB in renal medullary interstitial cells. Pflugers Arch 2013; 466:357-367. [PMID: 23900806 DOI: 10.1007/s00424-013-1328-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 07/11/2013] [Accepted: 07/13/2013] [Indexed: 10/26/2022]
Abstract
High salt diet induces renal medullary cyclooxygenase 2 (COX2) expression. Selective blockade of renal medullary COX2 activity in rats causes salt-sensitive hypertension, suggesting a role for renal medullary COX2 in maintaining systemic sodium balance. The present study characterized the cellular location of COX2 induction in the kidney of mice following high salt diet and examined the role of NFκB in mediating this COX2 induction in response to increased dietary salt. High salt diet (8 % NaCl) for 3 days markedly increased renal medullary COX2 expression in C57Bl/6 J mice. Co-immunofluorescence using a COX2 antibody and antibodies against aquaporin-2, ClC-K, aquaporin-1, and CD31 showed that high salt diet-induced COX2 was selectively expressed in renal medullary interstitial cells. By using NFκB reporter transgenic mice, we observed a sevenfold increase of luciferase activity in the renal medulla of the NFκB-luciferase reporter mice following high salt diet, and a robust induction of enhanced green fluorescent protein (EGFP) expression mainly in renal medullary interstitial cells of the NFκB-EGFP reporter mice following high salt diet. Treating high salt diet-fed C57Bl/6 J mice with selective IκB kinase inhibitor IMD-0354 (8 mg/kg bw) substantially suppressed COX2 induction in renal medulla, and also significantly reduced urinary prostaglandin E2 (PGE2). These data therefore suggest that renal medullary interstitial cell NFκB plays an important role in mediating renal medullary COX2 expression and promoting renal PGE2 synthesis in response to increased dietary sodium.
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Affiliation(s)
- Wenjuan He
- Division of Nephrology, Department of Medicine and Cancer Biology, Vanderbilt University, Veteran Affair Medical Center, Nashville, TN
| | - Min Zhang
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China
| | - Min Zhao
- Division of Nephrology, Department of Medicine and Cancer Biology, Vanderbilt University, Veteran Affair Medical Center, Nashville, TN
| | - Linda S Davis
- Division of Nephrology, Department of Medicine and Cancer Biology, Vanderbilt University, Veteran Affair Medical Center, Nashville, TN
| | - Timothy S Blackwell
- Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, TN, 37232
| | - Fiona Yull
- Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, TN, 37232
| | - Matthew D Breyer
- Biotechnology Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46225, USA
| | - Chuan-Ming Hao
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China.,Division of Nephrology, Department of Medicine and Cancer Biology, Vanderbilt University, Veteran Affair Medical Center, Nashville, TN
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Bądzyńska B, Sadowski J. Experimental selective elevation of renal medullary blood flow in hypertensive rats: evidence against short-term hypotensive effect. Acta Physiol (Oxf) 2012; 205:484-93. [PMID: 22429683 DOI: 10.1111/j.1748-1716.2012.02435.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 01/27/2012] [Accepted: 03/07/2012] [Indexed: 11/28/2022]
Abstract
AIM Renal medullary blood flow (MBF) can be selectively increased by intrarenal or systemic infusion of bradykinin (Bk) in anaesthetized normotensive rats. We reproduced this effect in a number of rat models of arterial hypertension and examined whether increased perfusion of the renal medulla can cause a short-term decrease in blood pressure (BP) that is not mediated by increased renal excretion and depletion of body fluids. METHODS In uninephrectomized Sprague-Dawley rats, BP was elevated to approx. 145 mmHg by acute i.v. infusion of noradrenaline (NA) or angiotensin II (Ang II) (groups 1, 2), 2-week exposure to high-salt diet (3), high-salt diet + chronic low-dose infusion of Ang II using osmotic minipumps (4) or chronic high-dose Ang II infusion on normal diet (5). Uninephrectomized spontaneous hypertensive rats (SHR) were also examined (6,7). To selectively increase medullary perfusion, in anaesthetized rats, bradykinin was infused during 30-75 min into the renal medullary interstitium or intravenously. RESULTS AND CONCLUSION Bradykinin increased outer- and inner-medullary blood flow (laser-Doppler fluxes) by 10-20% in groups (1, 2), by 30-50% in groups (3, 4, 5) and approx. 20% in SHR (6, 7). The concurrent increase in total renal blood flow (Transonic probe) was < 3%. A minor (<3%) decrease in BP was seen only in rats acutely rendered hypertensive by NA or Ang II infusions; however, the decreases in BP and increases in medullary perfusion were not correlated. Thus, there was no evidence that in hypertensive rats, substantial selective increases in medullary perfusion can cause a short-term decrease in BP.
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Affiliation(s)
- B. Bądzyńska
- Laboratory of Renal and Body Fluid Physiology; M. Mossakowski Medical Research Centre of the Polish Academy of Sciences; Warsaw; Poland
| | - J. Sadowski
- Laboratory of Renal and Body Fluid Physiology; M. Mossakowski Medical Research Centre of the Polish Academy of Sciences; Warsaw; Poland
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Damkjaer M, Vafaee M, Braad PE, Petersen H, Høilund-Carlsen PF, Bie P. Renal cortical and medullary blood flow during modest saline loading in humans. Acta Physiol (Oxf) 2012; 205:472-83. [PMID: 22433079 DOI: 10.1111/j.1748-1716.2012.02436.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 01/05/2012] [Accepted: 03/13/2012] [Indexed: 02/02/2023]
Abstract
AIM Renal medullary blood flow (RMBF) is considered an important element of sodium homeostasis, but the experimental evidence is incongruent. Studies in anaesthetized animals generally support the concept in contrast to measurements in conscious animals. We hypothesized that saline-induced natriuresis is associated with changes in RMBF in humans. METHODS After 4 days of low-sodium diet, healthy men were subjected to slow intravenous saline loading (12 μmol kg(-1) min(-1)) for 4 h. Renal medullary and cortical blood flow was determined by positron emission tomography with H(2)(15)O before and after saline infusion using two independent imaging processing methods. One based on a previously published algorithm (voxel peeling) and a novel method based on contrast-enhanced computed tomography (CT). Blood pressure was measured oscillometrically every 10 min. Cardiac output, heart rate and total peripheral resistance were recorded continuously. RESULTS Saline loading increased the urinary sodium excretion by 3.6-fold (21-76 μmol min(-1) , P < 0.01). The RMBF was 2.6 ± 0.2 mL g(-1) tissue min(-1) before and 2.7 ± 0.1 mL g(-1) tissue min(-1) after saline (n.s.). Cortical blood flow was 3.6 ± 0.1 before and 3.4 ± 0.2 after saline (n.s.). Mean arterial blood pressure did not change measurably (90 vs. 90 mmHg). Bland-Altman analysis suggested agreement between results obtained with voxel peeling (2.6 ± 0.2 mL g(-1) tissue min(-1)) and contrast-enhanced CT (2.0 ± 0.1 mL g(-1) tissue min(-1)). CONCLUSION In normal humans, changes in RMBF are not necessarily involved in the natriuretic response to modest saline loading. This result is in line with data from conscious rodents.
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Affiliation(s)
- M. Damkjaer
- Institute of Molecular Medicine; University of Southern Denmark; Odense; Denmark
| | - M. Vafaee
- Department of Neuroscience and Pharmacology; Faculty of Health Sciences; University of Copenhagen; Copenhagen; Denmark
| | - P. E. Braad
- Department of Nuclear Medicine; Odense University Hospital; Odense; Denmark
| | - H. Petersen
- Department of Nuclear Medicine; Odense University Hospital; Odense; Denmark
| | | | - P. Bie
- Institute of Molecular Medicine; University of Southern Denmark; Odense; Denmark
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Zhu Q, Wang Z, Xia M, Li PL, Zhang F, Li N. Overexpression of HIF-1α transgene in the renal medulla attenuated salt sensitive hypertension in Dahl S rats. Biochim Biophys Acta Mol Basis Dis 2012; 1822:936-41. [PMID: 22349312 DOI: 10.1016/j.bbadis.2012.02.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Revised: 02/05/2012] [Accepted: 02/06/2012] [Indexed: 12/13/2022]
Abstract
Hypoxia inducible factor (HIF)-1α-mediated gene activation in the renal medulla in response to high salt intake plays an important role in the control of salt sensitivity of blood pressure. High salt-induced activation of HIF-1α in the renal medulla is blunted in Dahl S rats. The present study determined whether the impairment of the renal medullary HIF-1α pathway was responsible for salt sensitive hypertension in Dahl S rats. Renal medullary HIF-1α levels were induced by either transfection of HIF-1α expression plasmid or chronic infusion of CoCl₂ into the renal medulla, which was accompanied by increased expressions of anti-hypertensive genes, cyclooxygenase-2 and heme oxygenase-1. Overexpression of HIF-1α transgenes in the renal medulla enhanced the pressure natriuresis, promoted the sodium excretion and reduced sodium retention after salt overload. As a result, hypertension induced by 2-week high salt was significantly attenuated in rats treated with HIF-1α plasmid or CoCl₂. These results suggest that an abnormal HIF-1α in the renal medulla may represent a novel mechanism mediating salt-sensitive hypertension in Dahl S rats and that induction of HIF-1α levels in the renal medulla could be a therapeutic approach for the treatment of salt-sensitive hypertension.
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Affiliation(s)
- Qing Zhu
- Department of Pharmacology & Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richnond VA 23298, USA
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Arnold AC, Shaltout HA, Gilliam-Davis S, Kock ND, Diz DI. Autonomic control of the heart is altered in Sprague-Dawley rats with spontaneous hydronephrosis. Am J Physiol Heart Circ Physiol 2011; 300:H2206-13. [PMID: 21460193 DOI: 10.1152/ajpheart.01263.2010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The renal medulla plays an important role in cardiovascular regulation, through interactions with the autonomic nervous system. Hydronephrosis is characterized by substantial loss of renal medullary tissue. However, whether alterations in autonomic control of the heart are observed in this condition is unknown. Thus we assessed resting hemodynamics and baroreflex sensitivity (BRS) for control of heart rate in urethane/chloralose-anesthetized Sprague-Dawley rats with normal or hydronephrotic kidneys. While resting arterial pressure was similar, heart rate was higher in rats with hydronephrosis (290 ± 12 normal vs. 344 ± 11 mild/moderate vs. 355 ± 13 beats/min severe; P < 0.05). The evoked BRS to increases, but not decreases, in pressure was lower in hydronephrotic rats (1.06 ± 0.06 normal vs. 0.72 ± 0.10 mild/moderate vs. 0.63 ± 0.07 ms/mmHg severe; P < 0.05). Spectral analysis methods confirmed reduced parasympathetic function in hydronephrosis, with no differences in measures of indirect sympathetic activity among conditions. As a secondary aim, we investigated whether autonomic dysfunction in hydronephrosis is associated with activation of the renin-angiotensin system (RAS). There were no differences in circulating angiotensin peptides among conditions, suggesting that the impaired autonomic function in hydronephrosis is independent of peripheral RAS activation. A possible site for angiotensin II-mediated BRS impairment is the solitary tract nucleus (NTS). In normal and mild/moderate hydronephrotic rats, NTS administration of the angiotensin II type 1 receptor antagonist candesartan significantly improved the BRS, suggesting that angiotensin II provides tonic suppression to the baroreflex. In contrast, angiotensin II blockade produced no significant effect in severe hydronephrosis, indicating that at least within the NTS baroreflex suppression in these animals is independent of angiotensin II.
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Affiliation(s)
- Amy C Arnold
- The Hypertension & Vascular Research Center, Wake Forest Univ. School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157-1032, USA.
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Yang R, Smolders I, Dupont AG. Blood pressure and renal hemodynamic effects of angiotensin fragments. Hypertens Res 2011; 34:674-83. [PMID: 21412242 DOI: 10.1038/hr.2011.24] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Angiotensin (Ang) II, the main effector peptide of the renin-Ang system, increases arterial blood pressure through Ang II type 1A (AT(1a)) receptor-dependent arterial vasoconstriction and by decreasing renal salt and water excretion through extrarenal and intrarenal mechanisms. AT(2) receptors are assumed to oppose these responses mediated by AT(1) receptors, thereby attenuating the pressor effects of Ang II. Nevertheless, a possible role of AT(2) receptors in the regulation of renal hemodynamics and sodium homeostasis remains to be unclear. Several other Ang fragments such as Ang III, Ang IV, Ang-(1-7) and Ang A have also been shown to display biological activity. In this review, we focus on the effects of these Ang on blood pressure, renal hemodynamics and sodium water handling, and discuss the receptors involved in these actions.
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Affiliation(s)
- Rui Yang
- Department of Pharmacology, Brussels, Belgium
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Damkjær M, Vafaee M, Møller ML, Braad PE, Petersen H, Høilund-Carlsen PF, Bie P. Renal cortical and medullary blood flow responses to altered NO availability in humans. Am J Physiol Regul Integr Comp Physiol 2010; 299:R1449-55. [PMID: 20881099 DOI: 10.1152/ajpregu.00440.2010] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objective of this study was to quantify regional renal blood flow in humans. In nine young volunteers on a controlled diet, the lower abdomen was CT-scanned, and regional renal blood flow was determined by positron emission tomography (PET) scanning using H(2)(15)O as tracer. Measurements were performed at baseline, during constant intravenous infusion of nitric oxide (NO) donor glyceryl nitrate and after intravenous injection of NO synthase inhibitor N(ω)-monomethyl-L-arginine (L-NMMA). Using the CT image, the kidney pole areas were delineated as volumes of interest (VOI). In the data analysis, tissue layers with a thickness of one voxel were eliminated stepwise from the external surface of the VOI (voxel peeling), and the blood flow subsequently was determined in each new, reduced VOI. Blood flow in the shrinking VOIs decreased as the number of cycles of voxel peeling increased. After 4-5 cycles, blood flow was not reduced further by additional voxel peeling. This volume-insensitive flow was measured to be 2.30 ± 0.17 ml·g tissue(-1)·min(-1) during the control period; it increased during infusion of glyceryl nitrate to 2.97 ± 0.18 ml·g tissue(-1)·min(-1) (P < 0.05) and decreased after L-NMMA injection to 1.57 ± 0.17 ml·g tissue(-1)·min(-1) (P < 0.05). Cortical blood flow was 4.67 ± 0.31 ml·g tissue(-1)·min(-1) during control, unchanged by glyceryl nitrate, and decreased after L-NMMA [3.48 ± 0.23 ml·(g·min)(-1), P < 0.05]. PET/CT scanning allows identification of a renal medullary region in which the measured blood flow is 1) low, 2) independent of reduction in the VOI, and 3) reactive to changes in systemic NO supply. The technique seems to provide indices of renal medullary blood flow in humans.
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Affiliation(s)
- Mads Damkjær
- Institute of Molecular Medicine, Univ. of Southern Denmark, 21 J. B. Winsloews Vej, DK-5000 Odense, Denmark
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Evans RG, Head GA, Eppel GA, Burke SL, Rajapakse NW. Angiotensin II and neurohumoral control of the renal medullary circulation. Clin Exp Pharmacol Physiol 2010; 37:e58-69. [DOI: 10.1111/j.1440-1681.2009.05233.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Badzyńska B, Sadowski J. Differential action of bradykinin on intrarenal regional perfusion in the rat: waning effect in the cortex and major impact in the medulla. J Physiol 2009; 587:3943-53. [PMID: 19528250 DOI: 10.1113/jphysiol.2009.172007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The renal kallikrein-kinin system is involved in the control of the intrarenal circulation and arterial pressure but bradykinin (Bk) effects on perfusion of individual kidney zones have not been examined in detail. Effects of Bk infused into renal artery, renal cortex or medulla on perfusion of whole kidney (RBF, renal artery probe) and of the cortex, outer- and inner medulla (CBF, OMBF, IMBF: laser-Doppler fluxes), were examined in anaesthetized rats. Renal artery infusion of Bk, 0.3-0.6 mg kg(-1) h(-1), induced no sustained increase in RBF or CBF. OMBF and IMBF increased initially 6 or 16%, respectively; only the IMBF increase (+10%) was sustained. Pre-treatment with L-NAME, 2.4 mg kg(-1) I.V., prevented the sustained but not initial transient elevation of medullary perfusion. Intracortical Bk infusion, 0.75-1.5 mg kg(-1) h(-1), did not alter RBF or CBF but caused a sustained 33% increase in IMBF. Intramedullary Bk, 0.3 mg kg(-1) h(-1), did not alter RBF or CBF but caused sustained increases in OMBF (+10%) and IMBF (+23%). These responses were not altered by pre-treatment with 1-aminobenzotriazole, 10 mg kg(-1)i.v., a cytochrome P-450 (CYP450) inhibitor, but were prevented or significantly attenuated by L-NAME or intramedullary clotrimazole, 3.9 mg kg(-1) h(-1), an inhibitor of CYP450 epoxygenase and of calcium-dependent K(+) channels (K(Ca)). Thus, cortical vasodilatation induced by Bk is only transient so that the agent is unlikely to control perfusion of the cortex. Bk selectively increases perfusion of the medulla, especially of its inner layer, via activation of the NO system and of K(Ca) channels.
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Affiliation(s)
- Bozena Badzyńska
- Laboratory of Renal and Body Fluid Physiology, Medical Research Centre of the Polish Academy of Sciences, Pawiskiego 5, 02-106 Warsaw, Poland
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Liu KL. REGULATION OF RENAL MEDULLARY CIRCULATION BY THE RENIN-ANGIOTENSIN SYSTEM IN GENETICALLY HYPERTENSIVE RATS. Clin Exp Pharmacol Physiol 2009; 36:455-61. [DOI: 10.1111/j.1440-1681.2009.05153.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Chen J, Zhao M, He W, Milne GL, Howard JRH, Morrow J, Hébert RL, Breyer RM, Chen J, Hao CM. Increased dietary NaCl induces renal medullary PGE2 production and natriuresis via the EP2 receptor. Am J Physiol Renal Physiol 2008; 295:F818-25. [PMID: 18632796 DOI: 10.1152/ajprenal.90253.2008] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A high-NaCl diet induces renal medullary cyclooxygenase (COX)2 expression, and selective intramedullary infusion of a COX2 inhibitor increases blood pressure in rats on a high-salt diet. The present study characterized the specific prostanoid contributing to the antihypertensive effect of COX2. C57BL/6J mice placed on a high-NaCl diet exhibited increased medullary COX2 and microsomal prostaglandin E synthase1 (mPGES1) expression as determined by immunoblot and real-time PCR. Cytosolic prostaglandin E synthase and prostacyclin synthase were not induced by the high-salt diet. Immunofluorescence showed mPGES1 in collecting ducts and interstitial cells. High salt increased renal medullary PGE(2) as determined by gas chromatography/negative ion chemical ionization mass spectrometry. The effect of direct intramedullary PGE(2) infusion was examined in anesthetized uninephrectomized mice. Intramedullary PGE(2) infusion (10 ng/h) increased urine volume (from 3.3 +/- 0.6 to 9.5 +/- 1.6 mul/min) and urine sodium excretion (0.11 +/- 0.02 to 0.32 +/- 0.05 mueq/min). To determine which E-prostanoid (EP) receptor(s) mediated PGE(2)- dependent natriuresis, EP-selective prostanoids were infused. The EP(2) agonist butaprost produced natriuresis (from 0.06 +/- 0.02 to 0.32 +/- 0.05 mueq/min). The natriuretic effect of intramedullary PGE(2) or butaprost was abolished in EP2-deficient mice, which exhibit NaCl-dependent hypertension. In conclusion, a high-salt diet increases renal medullary COX2 and mPGES1 expression, and increases renal medullary PGE(2) synthesis. Renal medullary PGE(2) promotes renal sodium excretion via the EP2 receptor, thereby maintaining normotension in the setting of high salt intake.
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Affiliation(s)
- Jian Chen
- Division of Nephrology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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Abstract
Cyclooxygenase-derived prostanoids exert complex and diverse functions within the kidney. The biological effect of each prostanoid is controlled at multiple levels, including (a) enzymatic reactions catalyzed sequentially by cyclooxygenase and prostanoid synthase for the synthesis of bioactive prostanoid and (b) the interaction with its receptors that mediate its functions. Cyclooxygenase-derived prostanoids act in an autocrine or a paracrine fashion and can serve as physiological buffers, protecting the kidney from excessive functional changes during physiological stress. Through these actions, prostanoids play important roles in maintaining renal function, body fluid homeostasis, and blood pressure. Renal cortical COX2-derived prostanoids, particularly PGI2 and PGE2, play critical roles in maintaining blood pressure and renal function in volume-contracted states. Renal medullary COX2-derived prostanoids appear to have an antihypertensive effect in individuals challenged with a high-salt diet. Loss of EP2 or IP receptor is associated with salt-sensitive hypertension. COX2 also plays a role in maintaining renal medullary interstitial cell viability in the hypertonic environment of the medulla. Cyclooxygenase-derived prostanoids also are involved in certain pathological processes. The cortical COX2-derived PGI2 participates in the pathogenesis of renal vascular hypertension through stimulating renal renin synthesis and release. COX-derived prostanoids also appear to be involved in the pathogenesis of diabetic nephropathy. COXs, prostanoid synthases, and prostanoid receptors should provide fruitful targets for intervention in the pharmacological treatment of renal disease.
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Affiliation(s)
- Chuan-Ming Hao
- Division of Nephrology, Department of Medicine, Vanderbilt University, and Veterans Affair Medical Center, Nashville, TN 37232, USA.
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Li N, Chen L, Yi F, Xia M, Li PL. Salt-sensitive hypertension induced by decoy of transcription factor hypoxia-inducible factor-1alpha in the renal medulla. Circ Res 2008; 102:1101-8. [PMID: 18356541 DOI: 10.1161/circresaha.107.169201] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Hypoxia inducible factor (HIF)-1alpha, a transcription factor, is abundantly expressed in the renal medulla and regulates many oxygen-sensitive genes such as nitric oxide synthase, cyclooxygenase-2, and heme oxygenase-1. Given the important roles of these genes in the control of arterial pressure, the present study was to test the hypothesis that HIF-1alpha-mediated gene activation serves as an antihypertensive pathway by regulating renal medullary function and sodium excretion. HIF-1alpha decoy oligodeoxynucleotides (ODNs) or scrambled ODNs were transfected into the renal medulla in uninephrectomized Sprague-Dawley rats. Two weeks after ODN transfection, the HIF-1alpha binding activities were significantly inhibited by 45%, and high salt-induced increases of nitric oxide synthase-2 and heme oxygenase-1 transcriptions were also inhibited by 70% and 61% in the renal medulla from decoy rats. The natriuretic responses and increases of renal medullary blood flow responding to the elevations of renal perfusion pressure were significantly blunted by 50% and 37% in decoy rats. Intravenously acute sodium loading increased medullary blood flow and urinary sodium excretion, which was remarkably attenuated in decoy rats. In decoy rats, high salt intake caused a greater positive sodium balance. Consequently, arterial pressure was remarkably increased (from 118+/-1.9 to 154+/-6.3 mm Hg) in decoy rats but not in control rats when the rats were challenged with a high salt diet. There was no blood pressure change in decoy rats that were maintained in normal salt diet. In conclusion, HIF-1alpha-mediated gene activation importantly participates in the regulation of renal medullary function and long-term arterial blood pressure.
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Affiliation(s)
- Ningjun Li
- Department of Pharmacology & Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, PO Box 980613, Richmond, VA 23298, USA.
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Gomez S, Strick D, Romero J. Role of nitric oxide and prostaglandin in the maintenance of cortical and renal medullary blood flow. Braz J Med Biol Res 2008; 41:170-5. [DOI: 10.1590/s0100-879x2008000200014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2007] [Accepted: 10/30/2007] [Indexed: 11/21/2022] Open
Affiliation(s)
- S.I Gomez
- Mayo Clinic College of Medicine, USA
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31
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Abstract
Small lipids such as eicosanoids exert diverse and complex functions. In addition to their role in regulating normal kidney function, these lipids also play important roles in the pathogenesis of kidney diseases. Cyclooxygenase (COX)-derived prostanoids play important role in maintaining renal function, body fluid homeostasis, and blood pressure. Renal cortical COX2-derived prostanoids, particularly (PGI2) and PGE2 play critical roles in maintaining blood pressure and renal function in volume contracted states. Renal medullary COX2-derived prostanoids appear to have antihypertensive effect in individuals challenged with a high salt diet. 5-Lipoxygenase (LO)-derived leukotrienes are involved in inflammatory glomerular injury. LO product 12-hydroxyeicosatetraenoic acid (12-HETE) is associated with pathogenesis of hypertension, and may mediate angiotensin II and TGFbeta induced mesengial cell abnormality in diabetic nephropathy. P450 hydroxylase-derived 20-HETE is a potent vasoconstrictor and is involved in the pathogenesis of hypertension. P450 epoxygenase derived epoxyeicosatrienoic acids (EETs) have vasodilator and natriuretic effect. Blockade of EET formation is associated with salt-sensitive hypertension. Ceramide has also been demonstrated to be an important signaling molecule, which is involved in pathogenesis of acute kidney injury caused by ischemia/reperfusion, and toxic insults. Those pathways should provide fruitful targets for intervention in the pharmacologic treatment of renal disease.
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Affiliation(s)
- C-M Hao
- Division of Nephrology, Department of Medicine, Vanderbilt University, Veterans Administration Medical Center, Nashville, Tennessee 37232, USA.
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Li N, Yi F, dos Santos EA, Donley DK, Li PL. Role of Renal Medullary Heme Oxygenase in the Regulation of Pressure Natriuresis and Arterial Blood Pressure. Hypertension 2007; 49:148-54. [PMID: 17075028 DOI: 10.1161/01.hyp.0000250086.06137.fb] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Recent studies have demonstrated that inhibition of renal medullary heme oxygenase (HO) activity and carbon monoxide (CO) significantly decreases renal medullary blood flow and sodium excretion. Given the crucial role of renal medullary blood flow in the control of pressure natriuresis, the present study was designed to determine whether renal medullary HO activity and resulting CO production participate in the regulation of pressure natriuresis and thereby the long-term control of arterial blood pressure. In anesthetized Sprague-Dawley rats, increases in renal perfusion pressure induced significant elevations of CO concentrations in the renal medulla. Renal medullary infusion of chromium mesoporphyrin (CrMP), an inhibitor of HO activity, remarkably inhibited HO activity and the renal perfusion pressure-dependent increases in CO levels in the renal medulla and significantly blunted pressure natriuresis. In conscious Sprague-Dawley rats, continuous infusion of CrMP into the renal medulla significantly increased mean arterial pressure (129±2.5 mm Hg in CrMP group versus 118±1.6 mm Hg in vehicle group) when animals were fed a normal salt diet (1% NaCl). After rats were switched to a high-salt diet (8% NaCl) for 10 days, CrMP-treated animals exhibited further increases in mean arterial pressure compared with CrMP-treated animals that were kept on normal salt diet (152±4.1 versus 130±4.2 mm Hg). These results suggest that renal medullary HO activity plays a crucial role in the control of pressure natriuresis and arterial blood pressure and that impairment of this HO/CO-mediated antihypertensive mechanism in the renal medulla may result in the development of hypertension.
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Affiliation(s)
- Ningjun Li
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298, USA.
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Hirai T, Okumura K, Nishimoto Y, Shumiya T, Murakami R, Takahashi R, Asai T, Murakami H, Numaguchi Y, Matsui H, Murohara T. Upregulation of renal eNOS by high-sodium diet facilitates hypertension in doxorubicin-treated rats through enhanced oxidative stress. Toxicology 2006; 225:81-9. [PMID: 16870316 DOI: 10.1016/j.tox.2006.05.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Revised: 05/02/2006] [Accepted: 05/04/2006] [Indexed: 11/18/2022]
Abstract
It is known that renal nitric oxide (NO) is an important controller of urinary sodium excretion. A defect in the kidney's NO system could cause salt-sensitive hypertension. Since it has been demonstrated that doxorubicin binds to the reductase domain of endothelial NO synthase (eNOS) and generates superoxide in vitro, we tested our hypothesis that a high-sodium diet would upregulate the expression of eNOS and enhance oxidative stress in the kidney of doxorubicin-treated rats, resulting in a facilitation of hypertension. At 4 weeks after treatment with doxorubicin in Sprague-Dawley rats, the systolic blood pressure significantly increased only in the high-sodium diet group. The expressions of eNOS protein in the renal cortex and medulla were significantly higher in high-sodium groups than in normal-sodium groups, regardless of doxorubicin treatment. In rats treated with doxorubicin, a biomarker of oxidative damage 8-hydroxy-2'-deoxyguanosine (8-OHdG) immunohistological staining of renal tissues showed strong staining of the proximal and distal tubules. In particular, rats with doxorubicin in the high-sodium diet group demonstrated a significant increase in urinary exertion of 8-OHdG as well as more prominently stained tubules against 8-OHdG antibody, but markedly lower urinary NO(x) excretion than in rats without doxorubicin, even than in the untreated, low-sodium group. In conclusion, these results indicate that the oxidative stress induced by doxorubicin impairs NO production in the kidney. As such, doxorubicin treatment appears to contribute to the development of salt-sensitive hypertension through reductive activation of upregulated eNOS by a high-sodium diet instead of NO production.
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Affiliation(s)
- Toshihisa Hirai
- Department of Cardiology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
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Sandgaard NCF, Andersen JL, Holstein-Rathlou NH, Bie P. Saline-induced natriuresis and renal blood flow in conscious dogs: effects of sodium infusion rate and concentration. ACTA ACUST UNITED AC 2005; 185:237-50. [PMID: 16218929 DOI: 10.1111/j.1365-201x.2005.01480.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM This study focused on static and dynamic changes in total renal blood flow (RBF) during volume expansion and tested whether a change in RBF characteristics is a necessary effector mechanism in saline-induced natriuresis. METHODS The aortic flow subtraction technique was used to measure RBF continuously. Identical amounts of NaCl (2.4 mmol kg(-1)) were given as slow isotonic (Iso, 120 min), slow hypertonic (Hyper, 120 min), and rapid isotonic loads (IsoRapid, 30 min). RESULTS During Iso and IsoRapid, arterial blood pressure increased slightly (6-7 mmHg), and during Hyper it remained unchanged. Iso and Hyper increased sodium excretion (4 +/- 1 to 57 +/- 27 and 10 +/- 4 to 79 +/- 28 micromol min(-1), respectively) and decreased plasma renin activity (by 38% and 29%), angiotensin II (by 56% and 58%) and aldosterone (by 47% and 65%), while RBF remained unchanged. IsoRapid caused a similar increase in sodium excretion (to 72 +/- 19 micromol min(-1)), a similar decrease in renin system activity, but a 15% elevation of RBF (282 +/- 22 to 324 +/- 35 mL min(-1)). Selected frequency domain parameters of RBF autoregulation did not change in response to any load. CONCLUSIONS In response to slow saline loading simulating daily sodium intake, the rate of sodium excretion may increase 10-20-fold without any change in mean arterial blood pressure or in RBF. Regulatory responses to changes in total body NaCl levels appears, therefore, to be mediated primarily by neurohumoral mechanisms and may occur independent of changes in arterial pressure or RBF.
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Affiliation(s)
- N C F Sandgaard
- Department of Physiology and Pharmacology, University of Southern Denmark, Odense, Denmark.
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López-Hernández FJ, López-Novoa JM. The lord of the ring: mandatory role of the kidney in drug therapy of hypertension. Pharmacol Ther 2005; 111:53-80. [PMID: 16154201 DOI: 10.1016/j.pharmthera.2005.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Accepted: 08/01/2005] [Indexed: 12/21/2022]
Abstract
Strong evidence supports the idea that total peripheral resistance (TPR) is increased in all forms of human and experimental hypertension. Although the etiological participation of TPR in the origin and long-term maintenance of hypertension has been extensively debated, it now seems clear that the renal, nonadaptive, infinite gain-working, pressure-sensitive natriuresis and diuresis is the main mechanism of blood pressure control in the long term. The tissue, cellular, biochemical, and genetic sensors and executors of this process have not been fully identified yet, but the role of the renal medulla has gained growing attention as the physiopathological scenario in which the key regulatory elements reside. Specifically, the functionality of the renomedullary vasculature seems to be highly responsible for blood pressure control. The vasculature of the renal medulla becomes a new and more specific target for the therapeutic intervention of hypertension. Recent data on the effect of baroreceptor-controlled renal sympathetic activity on the long-term regulation of blood pressure are integrated. The renomedullary effects of the main antihypertensive drugs are discussed, and new perspectives for the therapeutic intervention of hypertension are outlined. Comparison of the genetic program of the renal medulla before and after the development of hypertension in spontaneously hypertensive and experimentally induced animal models might provide a mechanism for identifying the key genes that become activated or suppressed in the development of high blood pressure. These genes, their encoded proteins, or other elements related to their signalling and genetic pathways might serve as new and more specific targets for the pharmacological treatment of abnormally elevated blood pressure. Besides, proteins specifically located to the luminal side of the renomedullary vascular endothelium may serve as potential targets for site-directed drug and gene therapy.
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Affiliation(s)
- Francisco J López-Hernández
- Unidad de Investigación, Hospital Universitario de Salamanca, Paseo de San Vicente, 58-182, 37007 Salamanca, Spain.
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Dobrowolski L, Sadowski J. Furosemide-induced renal medullary hypoperfusion in the rat: role of tissue tonicity, prostaglandins and angiotensin II. J Physiol 2005; 567:613-20. [PMID: 15961422 PMCID: PMC1474203 DOI: 10.1113/jphysiol.2005.090027] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Furosemide (frusemide)-induced renal medullary hypoperfusion provides a model for studies of the dependence of local circulation on tissue tonicity. We examined the role of medullary prostaglandins (PG) and adenosine (Ado) as possible mediators of the response to furosemide. Furosemide was infused i.v. at 0.25 mg kg(-1) h(-1) in anaesthetized rats, untreated or treated with intramedullary indomethacin (Indo) or Ado. An integrated set-up was used to measure renal medullary laser-Doppler flux (MBF) and medullary ionic tonicity (electrical admittance, Y), and to infuse Indo and Ado directly into the medulla. The cortical flux was measured on kidney surface. The excretion of water, sodium and total solute was also determined. Intramedullary Indo (1 mg kg(-1) h(-1)) decreased MBF 18 +/- 5% and increased tissue Y 14 +/- 3% (both significant); the treatment abolished the post-furosemide decrease in MBF (-22% in untreated group) and enhanced slightly the increase in renal excretion. Intramedullary Ado (5 mg kg(-1) h(-1)) did not change baseline MBF or Y; the post-furosemide decreases in MBF (-22%) and Y, and the increase in renal excretion were preserved. We conclude that a decrease in intramedullary PG activity secondary to decreased medullary hypertonicity mediates the fall in medullary perfusion in response to furosemide; the hypoperfusion may help restore the initial tonicity. Together with the earlier evidence on the dependence of post-furosemide medullary hypoperfusion on angiotensin II, the study exposes its interaction with PG in the control of medullary circulation. Adenosine is not involved in medullary vascular responses to decreased tissue hypertonicity.
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Affiliation(s)
- Leszek Dobrowolski
- Laboratory of Renal Physiology, M. Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland.
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Evans RG, Fitzgerald SM. Nitric oxide and superoxide in the renal medulla: a delicate balancing act. Curr Opin Nephrol Hypertens 2005; 14:9-15. [PMID: 15586010 DOI: 10.1097/00041552-200501000-00003] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW Endothelial nitric oxide synthase (eNOS) and nicotinamide adenine dinucleotide (phosphate) oxidase [NAD(P)H oxidase] are both expressed in tubular epithelial cells within the renal medulla, particularly the thick ascending limb of the loop of Henle (mTALH). Thick ascending limbs contribute to long-term blood pressure control, both because they reabsorb approximately 30% of filtered sodium, and because they produce paracrine factors like nitric oxide (NO) that control medullary blood flow (MBF), which in turn has a major impact on tubular sodium reabsorption. Herein, we review recent evidence for roles of NO and superoxide (O2*-) in autocrine control of tubular sodium reabsorption, and in paracrine control of MBF. RECENT FINDINGS O2*- can have a direct action to reduce MBF, and to enhance sodium reabsorption from mTALH. These actions oppose those of NO produced in mTALH, which inhibits tubular sodium reabsorption (autocrine) and increases MBF (paracrine). NO and O2*- also oppose each other's actions through chemical combination to produce peroxynitrite. Thus, interactions between NO and O2*-, at both the chemical and cellular levels, likely contribute to long-term blood pressure control. This hypothesis is supported by recent data showing that sodium retention and hypertension can develop when the balance of production of these free radicals is tipped towards O2*-, such as in diabetes, atherosclerosis and renin-angiotensin-system activation. SUMMARY Interactions between O2*- and NO produced within the mTALH regulate tubular and vascular function in the renal medulla. Dysregulation of these systems in states of oxidative stress likely promotes salt and water retention, and thus hypertension.
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Affiliation(s)
- Roger G Evans
- Department of Physiology, Monash University, Melbourne, Victoria 3800, Australia.
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