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Chade AR, Krier JD, Rodriguez-Porcel M, Breen JF, McKusick MA, Lerman A, Lerman LO. Comparison of acute and chronic antioxidant interventions in experimental renovascular disease. Am J Physiol Renal Physiol 2004; 286:F1079-86. [PMID: 14722019 DOI: 10.1152/ajprenal.00385.2003] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Reactive oxygen species (ROS) can modulate renal hemodynamics and function both directly, by leading to vasoconstriction, and indirectly, by inducing renal inflammation and tissue growth. The involvement of oxidative stress in the pathogenesis of renovascular disease (RVD) is increasingly recognized, but the relative contribution of long-term tissue injury to renal dysfunction remains unclear. We hypothesized that functional and structural alterations elicited by oxidative stress in RVD would be more effectively modulated by chronic than by acute antioxidant intervention. Renal hemodynamics and function were quantified in vivo in pigs using electron-beam computed tomography at baseline and after vasoactive challenge (ACh and sodium nitroprusside); after 12 wk of RVD (simulated by concurrent hypercholesterolemia and renal artery stenosis, n = 7); RVD acutely infused with the SOD-mimetic tempol (RVD+tempol, n = 7); RVD chronically supplemented with antioxidant vitamins C (1 g) and E (100 IU/kg; RVD+vitamins, n = 7); or control (normal, n = 7). Renal tissue was studied ex vivo using immunoblotting and immunohistochemistry. Basal renal blood flow (RBF) and glomerular filtration rate were similarly decreased in all RVD groups. ACh-stimulated RBF remained unchanged in RVD, increased in RVD+tempol, but further increased (similarly to normal) in RVD+vitamins ( P < 0.05 vs. RVD). Furthermore, RVD+vitamins also showed a decreased presence of superoxide anion, decreased NAD(P)H-oxidase and nitrotyrosine expression, increased endothelial nitric oxide synthase expression, and attenuated renal fibrosis. Chronic antioxidant intervention in early RVD improved renal hemodynamic responses more effectively than acute intervention, likely due to increased nitric oxide bioavailability and decreased structural injury. These suggest that chronic tissue changes play an important role in renal compromise mediated by oxidative stress in RVD.
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Affiliation(s)
- Alejandro R Chade
- Div. of Hypertension, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, USA
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152
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Abstract
OBJECTIVE To assess the relationship between microalbuminuria and oxidative stress in mononuclear peripherals cells in essential hypertension. METHODS A total of 123 hypertensive patients in absence of antihypertensive treatment were included. A 24-h ambulatory blood pressure (BP) monitoring was performed using a Spacelabs 90207 monitor, and microalbuminuria was measured in 24-h urine collections. Oxidized/reduced glutathione ratio and the content of malondialdehide and damaged base 8-oxo-2'-deoxyguanosine in genomic and mitochondrial DNA were measured in peripheral mononuclear cells. RESULTS In the 29 (24%) microalbuminuric subjects, the amount of reduced glutathione was significantly lower and the ratio oxidized/reduced glutathione was significantly higher than in the normoalbuminuric subjects. In contrast, the simultaneous measurement of the levels of malondialdehide and 8-oxo-2'-deoxyguanosine from both genomic and mitochondrial DNA oxidation did not achieve statistical significance between the two groups. Subjects with the highest oxidized/reduced glutathione ratio tertile showed the highest urinary albumin excretion (UAE) (P = 0.04 for trend). In a stepwise multiple regression analysis, oxidized/reduced glutathione ratio was the main significant determinant of UAE accounting for the 9% of the variance when 24-h mean BP, age, sex, body mass index, glucose and total cholesterol were included in the model. CONCLUSIONS Oxidative stress seems to be a determinant of UAE independent of BP levels even in hypertensive subjects.
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Affiliation(s)
- V Giner
- Department of Biochemistry of the Medical School, Hypertension Clinic, University of Valencia, Avda. Blasco Ibañez 17, 46010 Valencia, Spain
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153
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Varela M, Herrera M, Garvin JL. Inhibition of Na-K-ATPase in thick ascending limbs by NO depends on O2- and is diminished by a high-salt diet. Am J Physiol Renal Physiol 2004; 287:F224-30. [PMID: 15113751 DOI: 10.1152/ajprenal.00427.2003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A high-salt diet enhances nitric oxide (NO)-induced inhibition of transport in the thick ascending limb (THAL). Long exposures to NO inhibit Na-K-ATPase in cultured cells. We hypothesized that NO inhibits THAL Na-K-ATPase after long exposures and a high-salt diet would augment this effect. Rats drank either tap water or 1% NaCl for 7-10 days. Na-K-ATPase activity was assessed by measuring ouabain-sensitive ATP hydrolysis by THAL suspensions. After 2 h, spermine NONOate (SPM; 5 microM) reduced Na-K-ATPase activity from 0.44 +/- 0.03 to 0.30 +/- 0.04 nmol P(i).microg protein(-1).min(-1) in THALs from rats on a normal diet (P < 0.03). Nitroglycerin also reduced Na-K-ATPase activity (P < 0.04). After 20 min, SPM had no effect (change -0.07 +/- 0.05 nmol P(i).microg protein(-1).min(-1)). When rats were fed high salt, SPM did not inhibit Na-K-ATPase after 120 min. To investigate whether ONOO(-) formed by NO reacting with O(2)(-) was involved, we measured O(2)(-) production. THALs from rats on normal and high salt produced 35.8 +/- 0.3 and 23.7 +/- 0.8 nmol O(2)(-).min(-1).mg protein(-1), respectively (P < 0.01). Because O(2)(-) production differed, we studied the effects of the O(2)(-) scavenger tempol. In the presence of 50 microM tempol, SPM did not inhibit Na-K-ATPase after 120 min (0.50 +/- 0.05 vs. 0.52 +/- 0.07 nmol P(i).microg protein(-1).min(-1)). Propyl gallate, another O(2)(-) scavenger, also prevented SPM-induced inhibition of Na-K-ATPase activity. SPM inhibited pump activity in tubules from rats on high salt when O(2)(-) levels were increased with xanthine oxidase and hypoxanthine. We concluded that NO inhibits Na-K-ATPase after long exposures when rats are on a normal diet and this inhibition depends on O(2)(-). NO donors do not inhibit Na-K-ATPase in THALs from rats on high salt due to decreased O(2)(-) production.
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Affiliation(s)
- Marisela Varela
- Division of Nephrology, Henry Ford Hospital, Detroit, Michigan 48202, USA
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154
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Textor SC. Stable patients with atherosclerotic renal artery stenosis should be treated first with medical management. Am J Kidney Dis 2004; 42:858-63. [PMID: 14582031 DOI: 10.1016/j.ajkd.2003.08.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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155
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Abstract
Several cardiovascular risk factors are characterized by the coexistence of low-grade inflammation, enhanced oxidative stress and lipid peroxidation. It has been hypothesized that F2-isoprostanes, a product of in vivo lipid peroxidation, may transduce the effects of metabolic and hemodynamic abnormalities into increased cardiovascular risk. Thus, the formation of these compounds, including urinary 8-iso-Prostaglandin (PG) F2alpha, has been investigated in clinical settings putatively associated with oxidant stress. Enhanced lipid peroxidation together with increased in vivo platelet activation have been found in association with the major cardiovascular risk factors. Thus, F2-isoprostanes may transduce the effects of oxidant stress associated with complex metabolic disorders into specialized forms of cellular activation. In particular, the low-grade inflammatory state characterizing metabolic disorders such as obesity, hypercholesterolemia, type 2 diabetes mellitus, and homozygous homocystinuria may be the primary trigger of thromboxane-dependent platelet activation mediated, at least in part, through enhanced lipid peroxidation. Moreover, oxidative stress may promote endothelial dysfunction through increased production of reactive oxygen species that inactivate nitric oxide. Accumulation and activation of leukocytes plays a key role in atherosclerosis and its complications. Interestingly, neutrophil adhesion induced by minimally modified low-density lipoproteins is mainly mediated by F2-isoprostanes. Although epidemiological studies suggest an inverse relationship between antioxidant vitamin intake and cardiovascular disease, several clinical trials have obtained conflicting results on the effects of vitamin E supplementation on the risk of cardiovascular events. On the other hand, the use of F2-isoprostane formation as a biochemical end-point for dose-finding studies of vitamin E supplementation has helped clarifying the unique features of its pharmacodynamic effects on lipid peroxidation. This information could be extremely valuable in the selection of the appropriate patient subgroups that may benefit from antioxidant interventions.
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Affiliation(s)
- Giovanni Davì
- Center of Excellence on Aging, School of Medicine, University of Chieti G. D'Annunzio, via Colle dell'Ara, 66013 Chieti, Italy
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156
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Garvin JL, Ortiz PA. The role of reactive oxygen species in the regulation of tubular function. ACTA ACUST UNITED AC 2004; 179:225-32. [PMID: 14616238 DOI: 10.1046/j.0001-6772.2003.01203.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
UNLABELLED The phrase reactive oxygen species covers a number of molecules and atoms, including the quintessential member of the group, O2-; singlet oxygen; H2O2; organic peroxides; and OONO-. While nitric oxide (NO) is also technically a member of the reactive oxygen species family, it is generally considered with a different class of compounds and will not be considered here. To our knowledge, there are currently no published data reporting the effects of reactive oxygen species on net transepithelial flux in the proximal nephron. However, there is evidence that OONO- regulates Na+/K+ adenosine triphosphatase (ATPase) activity as well as paracellular permeability. While it is easy to speculate that such an effect on the pump would decrease net transepithelial solute and water reabsorption, one cannot do so without knowing how other transporters are affected. O2- stimulates NaCl absorption by the thick ascending limb by activating protein kinase C and blunting the effects of NO. The effects of O2- on thick ascending limb NaCl absorption may be important for the initiation of salt-sensitive hypertension. To our knowledge, there are no published data concerning the role of reactive oxygen species in the regulation of solute absorption in either the distal convoluted tubule or the collecting duct. However, OONO- inhibits basolateral K+ channels in the cortical collecting duct, although the net effect of such inhibition is unknown. CONCLUSION While the regulation of tubular transport by reactive oxygen species is important to overall salt and water balance, we know very little about where and how these regulators act along the nephron.
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Affiliation(s)
- J L Garvin
- Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, MI, USA
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157
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Yang JG, Hu D, Li T, Peng J, Yu H, Pang W, Wang C, Xiao J, Xu Y. Angiotensin-Converting Enzyme Inhibitor Usage in Patients with Incidental Atherosclerotic Renal Artery Stenosis. Hypertens Res 2004; 27:339-44. [PMID: 15198481 DOI: 10.1291/hypres.27.339] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The efficacy of angiotensin converting enzyme (ACE) inhibitors in treatment of renovascular disease has been controversial. It has been reported that patients with incidental atherosclerotic renal artery stenosis (ARAS) are sometimes treated with ACE inhibitors before being considered for renal revascularization. This study was designed to describe the frequency and the characteristics of patients with incidental ARAS, and to examine the frequency of ACE inhibitor usage in such patients. We studied a cohort of consecutive patients undergoing abdominal aortography at the time of cardiac catheterization. Patients were stratified and compared based on the presence and severity of ARAS. ARAS (> or =50%) was present in 146 (17.0%) of 859 evaluable patients. Factors independently related to the presence of ARAS were age (odds ratio (OR)=1.07, p < 0.001), severity of coronary artery disease (OR=2.13, p < 0.001) and peripheral vascular disease (OR=1.79, p = 0.021). Among all patients with ARAS, the percentage of ACE inhibitor usage was 74.7% (109/146). Among patients with severe ARAS, moderate ARAS, mild ARAS, insignificant ARAS and normal renal arteries, the percentage of ACE inhibitor usage was 85.7% (95% confidence interval (CI): 69-100%), 82.9% (95% CI: 71-95%), 68.5% (95% CI: 59-78%), 68.6% (95% CI: 55-82%) and 53.9% (95% CI: 50-58%), respectively (contingency coefficient=0.17, p < 0.001). In patients with severe ARAS, ACE inhibitor use, calcium channel blocker use and diuretic use were shown to correlate significantly with serum creatinine levels after controlling for potential confounding factors. In this study, ACE inhibitors were used commonly in patients with incidental ARAS; the frequency of ACE inhibitor use correlated with the severity of ARAS.
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Affiliation(s)
- Jin Gang Yang
- Department of Cardiology, People's Hospital of Peking University, Peking University Health Science Center, Beijing, PR China
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158
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Haller C, Keim M. Current issues in the diagnosis and management of patients with renal artery stenosis: a cardiologic perspective. Prog Cardiovasc Dis 2003; 46:271-86. [PMID: 14685944 DOI: 10.1016/s0033-0620(03)00074-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Renal artery stenosis most often is caused by atherosclerosis. Although patients with renal artery stenosis can be managed conservatively, renal revascularization may be indicated, particularly in patients with refractory hypertension on a multidrug regimen and patients with declining renal function. Duplex ultrasonography of the renal arteries and magnetic resonance angiography are currently the most efficient noninvasive methods for the evaluation of renal artery stenosis. Selective digital subtraction renal arteriography remains the gold standard for the definitive diagnosis. In selected patients undergoing coronary studies and angiography immediately after the coronary procedure can be efficient. Atherosclerotic renal artery lesions, which commonly affect the renal artery ostium, can be treated safely and effectively with balloon-expandable stents. Successful angioplasty commonly results in improved control of hypertension, but an overall benefit on renal function and/or patient survival has not been shown. Generally the risk/benefit ratio of renal artery stenting seems favorable, but further randomized studies are needed for evidence-based decision making. All patients with atherosclerotic renal artery stenosis should receive rigorous secondary prevention measures including platelet inhibitors, statins, and beta-blockers.
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Affiliation(s)
- Christlieb Haller
- Department of Medicine I, Hegau-Klinikum, Singen, Germany. haller@hegau-klinikum,de
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159
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160
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Chade AR, Best PJ, Rodriguez-Porcel M, Herrmann J, Zhu X, Sawamura T, Napoli C, Lerman A, Lerman LO. Endothelin-1 receptor blockade prevents renal injury in experimental hypercholesterolemia. Kidney Int 2003; 64:962-9. [PMID: 12911546 DOI: 10.1046/j.1523-1755.2003.00170.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND The potent vasoconstrictor endothelin-1 is involved in regulation of renal function, and is up-regulated in hypercholesterolemia (HC), a risk factor for renal disease that increases oxidative stress and impairs renal hemodynamic responses. However, the involvement of endothelin (ET) in this disease process is yet unknown. METHODS Regional renal hemodynamics and function in vivo were quantified in pigs at baseline and during infusion of acetylcholine using electron beam computed tomography after a 12-week normal diet (N = 6), HC diet (N = 6), and HC diet orally supplemented (4 mg/kg/day) with the selective ET receptor-A (ET-A) blocker ABT-627 (HC+ET-A, N = 6). Plasma levels of 8-epi-PGF2-alpha-isoprostanes, markers of oxidative stress, were measured using enzyme immunoassay, and renal tissue was studied ex vivo using Western blotting, electrophoretic mobility shift assay, and immunohistochemistry. RESULTS Total and low-density lipoprotein (LDL) cholesterol were similarly increased, but isoprostanes were decreased in HC+ET-A compared to HC alone. Basal renal perfusion was similar among the groups, while glomerular filtration rate (GFR) increased in HC+ET-A compared to HC. Stimulated perfusion and GFR were blunted in HC, but normalized in HC+ET-A. Moreover, ET blockade increased expression of endothelial nitric oxide synthase, and decreased endothelial expression of the oxidized-LDL receptor LOX-1, as well as tubular immunoreactivity of inducible nitric oxide synthase, nitrotyrosine, nuclear factor-kappaB, transforming growth factor-beta, and tubulointerstitial and perivascular trichrome staining. CONCLUSION ET-A blockade improves renal hemodynamic and function in HC, and decreases oxidative stress, and renal vascular and tubulointerstitial inflammation and fibrosis. These findings support a role for the endogenous ET system in renal injury in HC and atherosclerosis.
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Affiliation(s)
- Alejandro R Chade
- Department of Internal Medicine, Division of Hypertension, Mayo Clinic, Rochester, Minnesota, USA
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161
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Dohi Y, Ohashi M, Sugiyama M, Takase H, Sato K, Ueda R. Candesartan reduces oxidative stress and inflammation in patients with essential hypertension. Hypertens Res 2003; 26:691-7. [PMID: 14620923 DOI: 10.1291/hypres.26.691] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The present study was designed to test the hypothesis that blockade of angiotensin II type-1 receptors reduces oxidative stress and inflammation in patients with essential hypertension. The study population comprised 132 hypertensive patients, some receiving and others not receiving medical treatment. At enrollment their systolic and/or diastolic blood pressures were > or = 140 and/or > or = 90 mmHg, respectively. The serum concentration of C-reactive protein, and the urine concentrations of 8-epi-prostaglandin F2alpha and 8-hydroxydeoxyguanosine were measured at baseline and after 12 weeks of treatment either with an angiotensin II type-1 receptor blocker, candesartan (8 mg daily) (age 64 +/- 12 years; male/female 28/39; n = 67), or other antihypertensive agents that do not block the renin-angiotensin system (age 65 +/- 10 years, male/female 25/40, n = 65). Candesartan reduced the levels of C-reactive protein (from 0.07 +/- 0.04 [median value +/- median absolute deviation] to 0.06 +/- 0.03 mg/dl, p < 0.0001), 8-epi-prostaglandin F2alpha (from 210 +/- 92 to 148 +/- 59 pg/mg creatinine, p < 0.0001), and 8-hydroxydeoxyguanosine (from 5.7 +/- 1.9 to 4.0 +/- 1.3 ng/mg creatinine, p < 0.0001), while the levels of these markers were not altered after the treatment with other antihypertensive agents. Blood pressure decreased by a similar amount in both groups, and the reductions in the levels of the markers did not correlate with that of blood pressure. These results suggest that candesartan reduces oxidative stress and inflammation in hypertensive patients independently of its effects on blood pressure. This may provide useful information for determining therapeutic strategies to minimize tissue injury by inflammation and oxidative stress in hypertensive patients.
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Affiliation(s)
- Yasuaki Dohi
- Division of Hypertension and Vascular Research, Internal Medicine and Molecular Science, Graduate School of Medical Sciences, Nagoya City University, Mizuho-ku, Nagoya 467-8601, Japan.
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162
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Ortiz MC, Manriquez MC, Nath KA, Lager DJ, Romero JC, Juncos LA. Vitamin E prevents renal dysfunction induced by experimental chronic bile duct ligation. Kidney Int 2003; 64:950-61. [PMID: 12911545 DOI: 10.1046/j.1523-1755.2003.00168.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND The mechanisms by which prolonged cholestasis alters renal hemodynamics and excretory function are unknown but may be related to increased oxidative stress, with subsequent formation of lipid peroxidation-derived products (e.g., F2-isoprostanes) and endothelin (ET). We investigated whether antioxidant therapy prevents chronic bile duct ligation (CBDL)-induced alterations in systemic and renal hemodynamics, and reduces F2-isoprostane and ET levels. METHODS Sprague-Dawley rats were placed on either a normal or a high vitamin E diet for 7 days and then underwent either CBDL or sham surgery. They were then maintained on their respective diets for 21 more days, at which time the physiologic studies were performed. RESULTS Thirty-three percent of the CBDL rats died by day 21. The remaining rats had a lower mean arterial pressure (MAP), renal blood flow (RBF), glomerular filtration rate (GFR), and sodium and water excretion than control rats. CBDL rats had higher portal pressure, renal venous pressure, and renal vascular resistance (RVR). These changes were associated with increased levels of systemic and renal venous F2-isoprostanes and ET. Vitamin E normalized MAP, RBF, GFR, RVR, and sodium and water excretion, and improved the 21-day survival without altering portal or renal venous pressures. Surprisingly, vitamin E did not alter the systemic levels of F2-isoprostanes but markedly reduced their levels in the renal venous circulation. CONCLUSION Vitamin E improves MAP and renal function in CBDL rats, and selectively decreases renal levels of oxidative stress and ET, suggesting that local redox balance is implicated in CBDL-induced renal dysfunction.
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Affiliation(s)
- M Clara Ortiz
- Department of Physiology and Biophysics, Mayo School of Medicine, Mayo Clinic, Rochester, Minnesota, USA
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163
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Li JM, Shah AM. ROS generation by nonphagocytic NADPH oxidase: potential relevance in diabetic nephropathy. J Am Soc Nephrol 2003; 14:S221-6. [PMID: 12874435 DOI: 10.1097/01.asn.0000077406.67663.e7] [Citation(s) in RCA: 205] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Oxidative stress has emerged as an important pathogenic factor in the development of long-term complications, such as atherosclerosis and nephropathy, in patients with diabetes. Whereas multiple enzymes and processes can contribute to oxidative stress, recent studies indicate that a multicomponent phagocyte-type NADPH oxidase is a major source of reactive oxygen species (ROS) production in many nonphagocytic cells, including fibroblasts, vascular smooth muscle cells, endothelial cells, renal mesangial cells, and tubular cells. Under physiologic conditions, nonphagocytic NADPH oxidases have very low-level constitutive activity. However, enzyme activity can be upregulated both acutely and chronically in response to stimuli such as growth factors, cytokines, high glucose, and hyperlipidemia. ROS production by the oxidase may serve a signaling role or may lead to oxidative damage. This article reviews current knowledge of the nonphagocyte-NADPH oxidases at both structural and biochemical levels and discusses the possible role of these enzymes in the pathophysiology of diabetic nephropathy.
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Affiliation(s)
- Jian-Mei Li
- Department of Cardiology, Guy's King's & St Thomas's School of Medicine, King's College London, London, United Kingdom.
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164
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Gouvêa SA, Moysés MR, Bissoli NS, Pires JGP, Cabral AM, Abreu GR. Oral administration of L-arginine decreases blood pressure and increases renal excretion of sodium and water in renovascular hypertensive rats. Braz J Med Biol Res 2003; 36:943-9. [PMID: 12845383 DOI: 10.1590/s0100-879x2003000700017] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The two-kidney, one-clip renovascular (2K1C) hypertension model is characterized by a reduction in renal flow on the clipped artery that activates the renin-angiotensin system. Endothelium dysfunction, including diminished nitric oxide production, is also believed to play a role in the pathophysiology of this model. Some studies have shown an effect of L-arginine (L-Arg, a nitric oxide precursor) on hypertension. In the present study we determined the ability of L-Arg (7 days of treatment) to reduce blood pressure and alter renal excretions of water, Na+ and K+ in a model of 2K1C-induced hypertension. Under ether anesthesia, male Wistar rats (150-170 g) had a silver clip (0.20 mm) placed around the left renal artery to produce the 2K1C renovascular hypertension model. In the experimental group, the drinking water was replaced with an L-Arg solution (10 mg/ml; average intake of 300 mg/day) from the 7th to the 14th day after surgery. Sham-operated rats were used as controls. At the end of the treatment period, mean blood pressure was measured in conscious animals. The animals were then killed and the kidneys were removed and weighed. There was a significant reduction of mean blood pressure in the L-Arg-treated group when compared to control (129 7 vs 168 6 mmHg, N = 8-10 per group; P<0.05). Concomitantly, a significant enhancement of water and Na+ excretion was observed in the 2K1C L-Arg-treated group when compared to control (water: 13.0 0.7 vs 9.2 0.5 ml/day, P<0.01; Na+: 1.1 0.05 vs 0.8 0.05 mEq/day, respectively, P<0.01). These results show that orally administered L-Arg acts on the kidney, possibly inducing changes in renal hemodynamics or tubular transport due to an increase in nitric oxide formation.
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Affiliation(s)
- S A Gouvêa
- Departamento de Ciências Fisiológicas, Centro Biomédico, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
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165
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Abstract
Treating patients with renovascular disease is complex, particularly as imaging and medical techniques become more effective. Atherosclerotic renal artery disease is present in 7% of the general population above age 65 and in 20 to 45% of patients with coronary disease or aortoiliac disease. Most patients are treated medically, but when progressive hypertension, renal insufficiency, or circulatory congestion develops, revascularization should be considered. Endovascular procedures with arterial stents are now widely employed. These procedures sometimes offer major benefits in blood pressure control and stabilization of renal function. Stent procedures continue to entail hazards, including atheroemboli, arterial dissections, and thrombosis, in addition to restenosis rates of 14 to 20%. Small, randomized trials to date demonstrate no survival benefit to either endovascular or surgical revascularization as compared with medical management. Recognizing renal artery disease and directing revascularization procedures to those with the most benefit remains a premier challenge for the clinician.
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Affiliation(s)
- Stephen C Textor
- Mayo Medical School, Division of Hypertension, Mayo Clinic Rochester, Minnesota 55905, USA.
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166
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Chabrashvili T, Kitiyakara C, Blau J, Karber A, Aslam S, Welch WJ, Wilcox CS. Effects of ANG II type 1 and 2 receptors on oxidative stress, renal NADPH oxidase, and SOD expression. Am J Physiol Regul Integr Comp Physiol 2003; 285:R117-24. [PMID: 12609817 DOI: 10.1152/ajpregu.00476.2002] [Citation(s) in RCA: 254] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Oxidative stress accompanies angiotensin (ANG) II infusion, but the role of ANG type 1 vs. type 2 receptors (AT1-R and AT2-R, respectively) is unknown. We infused ANG II subcutaneously in rats for 1 wk. Excretion of 8-isoprostaglandin F2alpha (8-Iso) and malonyldialdehyde (MDA) were related to renal cortical mRNA abundance for subunits of NADPH oxidase and superoxide dismutases (SODs) using real-time PCR. Subsets of ANG II-infused rats were given the AT1-R antagonist candesartan cilexetil (Cand) or the AT2-R antagonist PD-123,319 (PD). Compared to vehicle (Veh), ANG II increased 8-Iso excretion by 41% (Veh, 5.4 +/- 0.8 vs. ANG II, 7.6 +/- 0.5 pg/24 h; P < 0.05). This was prevented by Cand (5.6 +/- 0.5 pg/24 h; P < 0.05) and increased by PD (15.8 +/- 2.0 pg/24 h; P < 0.005). There were similar changes in MDA excretion. Compared to Veh, ANG II significantly (P < 0.005) increased the renal cortical mRNA expression of p22phox (twofold), Nox-1 (2.6-fold), and Mn-SOD (1.5-fold) and decreased expression of Nox-4 (2.1-fold) and extracellular (EC)-SOD (2.1-fold). Cand prevented all of these changes except for the increase in Mn-SOD. PD accentuated changes in p22phox and Nox-1 and increased p67phox. We conclude that ANG II infusion stimulates oxidative stress via AT1-R, which increases the renal cortical mRNA expression of p22phox and Nox-1 and reduces abundance of Nox-4 and EC-SOD. This is offset by strong protective effects of AT2-R, which are accompanied by decreased expression of p22phox, Nox-1, and p67phox.
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Affiliation(s)
- Tina Chabrashvili
- Division of Nephrology and Hypertension, Georgetown Univ. Hospital, 3800 Reservoir Rd, N.W., PHC F6003, Washington, DC 20007, USA
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Parildar M, Parildar Z, Oran I, Kabaroglu C, Memis A, Bayindir O. Nitric oxide and oxidative stress in atherosclerotic renovascular hypertension: effect of endovascular treatment. J Vasc Interv Radiol 2003; 14:887-92. [PMID: 12847196 DOI: 10.1097/01.rvi.0000083841.97061.12] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE Because activation of the renin-angiotensin system leads to an increase in oxidative stress, the authors investigated nitric oxide (NO; nitrite + nitrate), superoxide dismutase (SOD), catalase, and malondialdehyde (MDA) levels and the effect of endovascular treatment on these parameters in patients with atherosclerotic renovascular hypertension. The relationship of NO with blood pressure and renal functional indexes was also investigated. MATERIALS AND METHODS In this prospective cohort study, serum creatinine, NO, SOD, catalase, plasma MDA, urinary microalbumin, and NO levels, and blood pressure were determined in 21 patients with hypertension and unilateral renal artery stenosis caused by atherosclerosis at entry and after 24 hours, 2 weeks, and 6 weeks of endovascular treatment. RESULTS MDA concentrations decreased 24 hours after intervention and remained low 2 and 6 weeks later. In addition, serum SOD and NO and urine NO levels were increased significantly 24 hours after endovascular treatment and decreased after 2 and 6 weeks. However, serum catalase levels did not differ after the intervention. Blood pressures decreased after treatment. There were no significant differences in urinary microalbumin levels, estimated glomerular filtration rates, and creatinine levels after endovascular treatment. CONCLUSIONS Endovascular treatment decreases oxidative stress and may offer new benefits in the treatment of patients with hypertension associated with renal artery stenosis. The decrease in oxidative stress and/or the upregulation of SOD may increase the bioavailability of NO, which in turn may lead to the rapid hypotensive response.
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Affiliation(s)
- Mustafa Parildar
- Department of Radiology, Ege University Faculty of Medicine, 35100 Bornova, Izmir, Turkey
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168
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Uddin M, Yang H, Shi M, Polley-Mandal M, Guo Z. Elevation of oxidative stress in the aorta of genetically hypertensive mice. Mech Ageing Dev 2003; 124:811-7. [PMID: 12875744 DOI: 10.1016/s0047-6374(03)00135-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hypertension is an age-dependent disorder. Oxidative stress has been suggested to play a role in aging and age-dependent disorders. The objective of this study is to examine the oxidant and antioxidant status in the aorta of a mouse model with high blood pressure (BPH). Our results showed that the level of malondialdehyde (MDA) in the aorta of BPH mice was approximately 2.6-fold higher than that of the normal blood pressure (BPN) mice, suggesting an increased in vivo oxidative stress in the arterial wall of BPH mice. In addition, the release of hydrogen peroxide (H2O2) from the aorta of BPH mice was significantly faster than that of BPN mice. To determine if the increased H2O2 release is related to a down-regulation of antioxidant enzymes in the arterial wall, we measured the activities of the major antioxidant enzymes in mouse aortas. We observed that the activities of Cu/Zn-superoxide dismutase (SOD) and glutathione peroxidase-1 in BPH mice were similar to BPN mice. On the other hand, the catalase activity in the aorta of BPH mice was significantly reduced while the activities of Mn-SOD and extracellular (EC)-SOD in the aorta of BPH mice were significantly elevated as compared with BPN mice. These results suggest that increase in SOD activity and decrease in catalase activity might be responsible for the increased release of H2O2 in the arterial wall of BPH mice.
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Affiliation(s)
- Mukarram Uddin
- Department of Anatomy and Physiology, School of Medicine, Meharry Medical College, 1005 Dr. D.B. Todd Jr. Blvd., Nashville, TN 37208, USA
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169
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Reckelhoff JF, Romero JC. Role of oxidative stress in angiotensin-induced hypertension. Am J Physiol Regul Integr Comp Physiol 2003; 284:R893-912. [PMID: 12626356 DOI: 10.1152/ajpregu.00491.2002] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Infusion of ANG II at a rate not sufficient to evoke an immediate vasoconstrictor response, produces a slow increase in blood pressure. Circulating levels of ANG II may be within ranges found in normotensive individuals, although inappropriately high with respect to sodium intake. When ANG II levels are dissociated from sodium levels, oxidative stress (OXST) occurs, which can increase blood pressure by several mechanisms. These include inadequate production or reduction of bioavailability of nitric oxide, alterations in metabolism of arachidonic acid, resulting in an increase in vasoconstrictors and decrease in vasodilators, and upregulation of endothelin. This cascade of events appears to be linked, because ANG II hypertension can be blocked by inhibition of any factor located distally, blockade of ANG II, OXST, or endothelin. Such characteristics are shared by other models of hypertension, such as essential hypertension, hypertension induced by reduction in renal mass, and renovascular hypertension. Thus these findings are clinically important because they reveal 1) uncoupling between ANG II and sodium, which can trigger pathological conditions; 2) the various OXST mechanisms that may be involved in hypertension; and 3) therapeutic interventions for hypertension developed with the knowledge of the cascade involving OXST.
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Affiliation(s)
- Jane F Reckelhoff
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA
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170
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Wilson SH, Chade AR, Feldstein A, Sawamura T, Napoli C, Lerman A, Lerman LO. Lipid-lowering-independent effects of simvastatin on the kidney in experimental hypercholesterolaemia. Nephrol Dial Transplant 2003; 18:703-9. [PMID: 12637638 DOI: 10.1093/ndt/gfg143] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Hypercholesterolaemia (HC), an independent risk factor for renal injury, is associated with formation of oxidized low-density-lipoprotein (ox-LDL), increased oxidative-stress and renal inflammation. HMG-CoA-reductase inhibitors are commonly used in HC, but their effects on renal haemodynamics and function in HC are poorly understood. METHODS Pigs were studied after a 12-week normal diet, a 2% high-cholesterol diet (HC) or an HC diet supplemented with simvastatin (HC+simvastatin, 80 mg/day) (n=6-8 each group). Renal haemodynamics and function were quantified in vivo with electron-beam computed tomography (EBCT). Shock-frozen renal tissue was subsequently studied using immunohistochemistry. RESULTS LDL cholesterol was similarly increased in HC and HC+simvastatin. Simvastatin-treated animals showed increased expression of endothelial nitric-oxide-synthase (eNOS), and decreased expression of the ox-LDL receptor LOX-1 in renal endothelial cells. Simvastatin also decreased tubular immunoreactivity of inducible-NOS, nitrotyrosine, nuclear-factor-kappaB, and tubuloglomerular trichrome staining. These were associated with a significant increase in cortical (6.1+/-0.1 vs 5.0+/-0.3 and 5.0+/-0.1 ml/min/cc, respectively, P<0.001) and medullary perfusion in HC+simvastatin compared to normal and HC. CONCLUSIONS Simvastatin attenuated the inflammatory and pro-oxidative environment as well as fibrosis in kidneys in pigs with diet-induced HC, in association with enhanced renal perfusion. These cholesterol-lowering-independent changes imply novel renoprotective effects of statins in the setting of HC and atherosclerosis.
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171
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Renal Ischemia as a Predictor of Cardiovascular Morbidity. J Vasc Interv Radiol 2003. [DOI: 10.1016/s1051-0443(03)70144-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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172
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Ettarh RR, Odigie IP, Adigun SA. Vitamin C lowers blood pressure and alters vascular responsiveness in salt-induced hypertension. Can J Physiol Pharmacol 2002; 80:1199-202. [PMID: 12564647 DOI: 10.1139/y02-147] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The present study was undertaken to investigate the effect of vitamin C treatment on blood pressure and vascular reactivity in salt-induced hypertension. Male Sprague-Dawley rats were fed a normal rat diet, a high-sodium (8% NaCl) diet, a normal rat diet plus vitamin C treament (100 mg x kg(-1) x day(-1)), or a high-sodium diet plus vitamin C treatment for 6 weeks. Salt loading significantly increased blood pressure, which was attenuated by vitamin C treatment. Aortic rings from the different groups were suspended for isometric-tension recording. The contractile response to noradrenaline was significantly increased in the salt-loaded rats. Vitamin C reduced the sensitivity of aortic rings to noradrenaline in rats on normal and high-sodium diets. In noradrenaline-precontracted rings, the relaxation response to acetylcholine, which was attenuated in the salt-loaded rats, was restored by vitamin C treatment. Pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME) abolished the enhanced response to acetylcholine caused by vitamin C. The results suggest that the antihypertensive effect of vitamin C is associated with a reduction in vascular sensitivity to noradrenaline and enhancement of endothelium-dependent relaxation due to increased nitric oxide bioavailability.
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Affiliation(s)
- R R Ettarh
- Department of Physiology, College of Medicine, University of Lagos, PMB 12003, Idi-Araba, Lagos, Nigeria.
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173
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Hanna IR, Taniyama Y, Szöcs K, Rocic P, Griendling KK. NAD(P)H oxidase-derived reactive oxygen species as mediators of angiotensin II signaling. Antioxid Redox Signal 2002; 4:899-914. [PMID: 12573139 DOI: 10.1089/152308602762197443] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Angiotensin II has been shown to participate in both physiological processes, such as sodium and water homeostasis and vascular contraction, and pathophysiological processes, including atherosclerosis and hypertension. The effects of this molecule on vascular tissue are mediated at least in part by the modification of the redox milieu of its target cells. Angiotensin II has been shown to activate the vascular NAD(P)H oxidase(s) resulting in the production of reactive oxygen species, namely superoxide and hydrogen peroxide. In this article, we review what is known about the molecular steps that link angiotensin II and its receptor to production of reactive oxygen species and subsequent redox-mediated events, focusing on the structural and functional properties of the vascular NAD(P)H oxidases and their downstream mediators. As such, we provide a framework linking angiotensin II to crucial vascular pathologies, such as hypertension, atherosclerosis, and restenosis after angioplasty, by means of the NAD(P)H-dependent oxidases and their effector molecules.
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Affiliation(s)
- Ibrahim R Hanna
- Emory University, Division of Cardiology, Atlanta, GA 30322, USA
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174
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Rundback JH, Murphy TP, Cooper C, Weintraub JL. Chronic renal ischemia: pathophysiologic mechanisms of cardiovascular and renal disease. J Vasc Interv Radiol 2002; 13:1085-92. [PMID: 12427806 DOI: 10.1016/s1051-0443(07)61948-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Chronic renal ischemia caused by renal artery stenosis (RAS) elicits a complex biologic response. Although the traditional pathophysiologic pathways underlying renal ischemia have been well studied, there is emerging evidence that additional mechanisms may be responsible for producing many of the hemodynamic alterations and end-organ injury seen in patients with RAS, including persistent hypertension, renal insufficiency, and cardiac disturbance syndromes. A better understanding of these mechanisms may allow earlier identification of RAS, provide markers to predict the response to revascularization, or allow unique therapeutic targets for drug development. This and a subsequent article will explore the pathophysiologic and clinical implications of chronic renal ischemia.
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Affiliation(s)
- John H Rundback
- Department of Radiology, New York Presbyterian Hospital/Columbia University Medical Center, New York, New York 10031, USA.
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175
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Rule AD, Bajzer Z, Ritman EL, Lerman LO. Renal handling of X-ray contrast media imaging and exploration with electron beam CT. Ann N Y Acad Sci 2002; 972:317-24. [PMID: 12496035 DOI: 10.1111/j.1749-6632.2002.tb04590.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Physiologic changes in renal hemodynamics and function reflect its role as a regulatory organ in maintaining homeostasis, whereas other alterations may mirror development of renal injury and often precede overt signs of morphologic changes. Furthermore, intrarenal alterations may be discreet and manifest only in the renal cortical, medullary, or papillary zones. The high spatial and temporal resolution of electron-beam computed tomography enables external detection and quantification of cortical, medullary, and papillary tissue density changes following an intravenous bolus injection of X-ray contrast media. These changes reflect flow of contrast media in these renal zones through the successive renal vascular, glomerular, and tubular compartments that can be individually plotted as time-density curves (TDC). Mathematical modeling then allows calculation of unique parameters of renal function from these TDC. This ability to quantify renal regional attributes may not only shed light on the physiologic mechanisms that the kidney controls, but also assist in detecting subtle impairment in its function.
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Affiliation(s)
- Andrew D Rule
- Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
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176
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Rundback JH, Weintraub JL. Renal vascular interventions. Semin Roentgenol 2002; 37:312-26. [PMID: 12455129 DOI: 10.1016/s0037-198x(02)80008-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- John H Rundback
- New York Presbyterian Hospital, College of Physicians and Surgeons of Columbia University, New York, NY, USA
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177
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Krier JD, Rodriguez-Porcel M, Best PJM, Romero JC, Lerman A, Lerman LO. Vascular responses in vivo to 8-epi PGF(2alpha) in normal and hypercholesterolemic pigs. Am J Physiol Regul Integr Comp Physiol 2002; 283:R303-8. [PMID: 12121841 DOI: 10.1152/ajpregu.00602.2001] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hypercholesterolemia (HC) is characterized by increased circulating 8-epi-prostaglandin-F(2alpha) (isoprostane), a vasoconstrictor, marker, and mediator of increased oxidative stress, whose vascular effects might be augmented in HC. Anesthetized pigs were studied in vivo with electron beam computed tomography after a 12-wk normal (n = 8) or HC (n = 8) diet. Mean arterial pressure (MAP), single-kidney perfusion, and glomerular filtration rate (GFR) were quantified before and during unilateral intrarenal infusions of U46619 (10 ng x kg(-1) x min(-1)) or isoprostane (1 microg x kg(-1) x min(-1)). Basal renal perfusion and function were similar, and isoprostane infusion elevated its systemic levels similarly in normal and HC (333 +/- 89 vs. 366 +/- 48 pg/ml, respectively, P < 0.01 vs. baseline). Both drugs markedly and comparably decreased cortical perfusion and GFR in both groups, whereas medullary perfusion decreased significantly only in HC. Moreover, MAP increased significantly only in HC (+9 +/- 3 and +11 +/- 3 mmHg, respectively, P<or= 0.05). Hence, in HC, renal functional responses to high-dose isoprostane are largely similar to normal, but the systemic circulation exhibits augmented sensitivity to pathophysiological levels of isoprostane and U46619, which may potentially play a role in development of hypertension and vascular injury associated with increased oxidative stress.
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Affiliation(s)
- James D Krier
- Department of Internal Medicine, Division of Hypertension, Mayo Clinic, Rochester, Minnesota 55905, USA
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178
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179
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Higashi Y, Sasaki S, Nakagawa K, Matsuura H, Oshima T, Chayama K. Endothelial function and oxidative stress in renovascular hypertension. N Engl J Med 2002; 346:1954-62. [PMID: 12075056 DOI: 10.1056/nejmoa013591] [Citation(s) in RCA: 404] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND It has been reported that renovascular hypertension activates the renin-angiotensin system, leading to an increase in oxidative stress. We sought to determine whether renal-artery angioplasty improves endothelial dysfunction in patients with renovascular hypertension through a reduction in oxidative stress. METHODS We evaluated the response of forearm blood flow to acetylcholine, an endothelium-dependent vasodilator, and isosorbide dinitrate, an endothelium-independent vasodilator, before and after renal-artery angioplasty in 15 subjects with renovascular hypertension and 15 controls without hypertension who were matched for age and sex. Forearm blood flow was measured with the use of a mercury-filled Silastic strain-gauge plethysmograph. RESULTS The forearm blood flow in response to acetylcholine was less in subjects with renovascular hypertension than in controls, although the forearm blood flow in response to isosorbide dinitrate was similar in the two groups. Angioplasty decreased systolic and diastolic blood pressures, forearm vascular resistance, and urinary excretion of 8-hydroxy-2'-deoxyguanosine and serum malondialdehyde-modified low-density lipoprotein (LDL), indexes of oxidative stress. After angioplasty, the mean (+/-SD) forearm blood flow in response to acetylcholine was increased in the patients with renovascular hypertension (19.3+/-6.8 vs. 29.6+/-7.1 ml per minute per 100 ml, P=0.002). The increase in the maximal forearm blood flow in response to acetylcholine correlated significantly with the decrease in urinary excretion of 8-hydroxy-2'-deoxyguanosine (r=-0.51, P=0.004) and serum malondialdehyde-modified LDL (r=-0.39, P=0.02). Coinfusion of ascorbic acid (vitamin C) augmented the response of forearm blood flow to acetylcholine before angioplasty (P<0.001) but not after angioplasty. CONCLUSIONS These findings suggest that excessive oxidative stress is involved, at least in part, in impaired endothelium-dependent vasodilatation in patients with renovascular hypertension.
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Affiliation(s)
- Yukihito Higashi
- First Department of Internal Medicine, Hiroshima University, Faculty of Medicine, Hiroshima, Japan.
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180
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181
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Abstract
Oxidative stress in blood vessels and the kidney in hypertension can be induced by diverse vasoconstrictor mechanisms, including blockade of nitric oxide synthase and activation of angiotensin II type I receptors and thromboxane receptors. It can cause vasoconstriction via bioinactivation of nitric oxide, and by nitric oxide synthase independent mechanisms that include increased generation of endothelin-1 and the effects of superoxide anion and hydrogen peroxide on vascular smooth muscle cells. Oxidative stress can accompany hypertension in many models including the spontaneously hypertensive rat, the angiotensin II-infused rat, renovascular hypertension, the deoxycorticosterone acetate-salt model, and obesity-related hypertension. In the kidney, NADPH oxidase-generating superoxide anion is expressed in the vasculature, interstitium, juxtaglomerular apparatus, and the distal nephron. Much progress has been made in defining the pathways that intervene between agonist stimulation of blood vessels and reactive oxygen species-mediated contractile and renal functional responses in animal models in hypertension.
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Affiliation(s)
- Christopher S Wilcox
- Division of Nephrology and Hypertension, Georgetown University Hospital, 3800 Reservoir Rd, NW PHC F6003, Washington, DC 20007, USA.
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182
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Hodgson JM, Croft KD, Mori TA, Burke V, Beilin LJ, Puddey IB. Regular ingestion of tea does not inhibit in vivo lipid peroxidation in humans. J Nutr 2002; 132:55-8. [PMID: 11773508 DOI: 10.1093/jn/132.1.55] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Prospective studies suggest that tea may protect against cardiovascular disease. A potential mechanism for such an effect involves inhibition of lipid peroxidation by polyphenolic antioxidants derived from tea. Our objective was to determine whether regular ingestion of tea could inhibit in vivo lipid peroxidation. Two controlled intervention studies assessed the effects of regular ingestion of tea on lipid peroxidation determined by measurement of urinary F(2)-isoprostane excretion. Study 1: The effects of 1000 mL/d of green tea and black tea were compared with hot water containing caffeine in 13 subjects with elevated blood pressure using a randomized 3-period (7 d each) crossover design. Study 2: The effects of 1250 mL/d of black tea were compared with hot water in 22 subjects with mildly raised serum total cholesterol concentrations using a randomized 2-period (4 wk each) crossover design. F(2)-isoprostane excretion was not altered after regular ingestion of green tea (273 +/- 48 pmol/mmol creatinine) or black tea (274 +/- 39 pmol/mmol creatinine) in comparison with hot water (263 +/- 47 pmol/mmol creatinine; Study 1), or by regular ingestion of black tea (334 +/- 71 pmol/mmol creatinine) in comparison with hot water (355 +/- 75 pmol/mmol creatinine; Study 2). These results do not support the suggestion that polyphenolic antioxidants derived from tea inhibit in vivo lipid peroxidation.
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Affiliation(s)
- Jonathan M Hodgson
- University of Western Australia, Department of Medicine and HeartSearch, Royal Perth Hospital, Perth, WA 6001, Australia.
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183
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Artigues-Varin C, Richard V, Renet S, Henry JP, Thuillez C. Lack of impairment of nitric oxide-mediated responses in a rat model of high-renin hypertension. Clin Exp Pharmacol Physiol 2002; 29:26-31. [PMID: 11906458 DOI: 10.1046/j.1440-1681.2002.03599.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. Angiotensin (Ang) II triggers the expression of a pro- oxidant phenotype in the vascular wall, suggesting that activation of the renin-angiotensin system (RAS) causes endothelial dysfunction in various pathological situations, such as hypertension. However, this hypothesis has been mostly tested in a setting of exogenous administration of AngII. 2. We tested the hypothesis of a role for endogenous activation of the RAS leading to oxidant stress and endothelial dysfunction in a high-renin model of hypertension (i.e. two-kidney, one-clip hypertension) in rats. One month after clipping or sham surgery, aorta were isolated from untreated rats or rats treated by the angiotensin AT1 receptor antagonist irbesartan (10 mg/kg per day). Mesenteric artery segments were also isolated from normotensive or hypertensive rats. 3. Hypertension reduced the relaxations to acetylcholine but did not affect the ratio of contractions to phenylephrine in the presence compared with the absence of a nitric oxide (NO) synthase inhibitor, used as an index of basal release of NO. 4. The free radical scavenger tempol reduced the contractions to phenylephrine in the absence, but not in the presence, of an inhibitor of NO synthesis. This index of free radical-mediated degradation of NO was not affected by hypertension. In parallel, hypertension did not affect the expression of p22phox, a component of the free radical generating enzyme reduced nicotinamide adenine dinucleotide phosphate oxidase. 5. Chronic treatment with the AT1 receptor antagonist decreased blood pressure, moderately improved the response to acetylcholine, but did not affect basal NO release in hypertensive rats, although it did increase basal NO release in normotensive rats. 6. Thus, this model of hypertension is characterized by an impaired stimulated NO release but not of basal NO release in isolated arteries. Furthermore, there was no functional evidence of an increased oxidative stress-mediated impairment of NO release. This is not in favour of a direct link between activation of the RAS and development of endothelial dysfunction in experimental hypertension.
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Affiliation(s)
- C Artigues-Varin
- Department of Pharmacology, INSERM EMI 9920, IFRMP n 23rd, Rouen University Medical School, Rouen, France
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184
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Radermacher J, Weinkove R, Haller H. Techniques for predicting a favourable response to renal angioplasty in patients with renovascular disease. Curr Opin Nephrol Hypertens 2001; 10:799-805. [PMID: 11706308 DOI: 10.1097/00041552-200111000-00011] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Renovascular disease is present in some 10-40% of patients with end-stage renal disease, and constitutes the fastest-growing group of end-stage renal disease patients. The unselective correction of renal artery stenosis has led to disappointing results. Most studies that compared conservative treatment with angioplasty found only modest or no beneficial effects of angioplasty on renal function and blood pressure. It is therefore mandatory to evaluate the functional significance of a stenosis before intervention. Patients with a high likelihood of a favourable response should be identified. Factors that affect outcome include the severity of renal artery stenosis, the procedure used to treat renal artery stenosis (antihypertensive drugs, angioplasty with or without stenting, or surgery), radiocontrast nephrotoxicity, atheroembolism and, most importantly, underlying renal disease, forestalling a favourable response of renal function or blood pressure even after the successful correction of renal artery stenosis. Evaluation of the renal resistance index using Doppler ultrasound or captopril scintigraphy are the best methods by which to classify patients as responders or non-responders to intervention. Each factor has to be considered before the correction of renal artery stenosis to achieve satisfactory results with regard to an improvement in renal function and blood pressure.
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Affiliation(s)
- J Radermacher
- Department of Nephrology, Hannover Medical School, Germany.
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185
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Stulak JM, Lerman A, Porcel MR, Caccitolo JA, Romero JC, Schaff HV, Napoli C, Lerman LO. Renal vascular function in hypercholesterolemia is preserved by chronic antioxidant supplementation. J Am Soc Nephrol 2001; 12:1882-1891. [PMID: 11518781 DOI: 10.1681/asn.v1291882] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Hypercholesterolemia impairs systemic vascular reactivity in response to endothelium-dependent vasodilators, which may be mediated partly through increased formation of lipid peroxides. However, it is unclear whether these pathophysiological mechanisms play a role in renal vascular impairment in experimental hypercholesterolemia. Hence, pigs were studied after a 3-mo normal (n = 7) or high cholesterol (HC) (n = 7) diet, HC diet supplemented daily with antioxidant vitamins E (100 IU/kg) and C (1000 mg; HC+vitamins, n = 5), or normal diet supplemented with vitamins (N+vitamins, n = 5). Renal blood flow was measured with electron-beam computed tomography before and during infusion of acetylcholine (Ach). Endothelial function, endothelial and inducible nitric oxide synthase (NOS), and nitrotyrosine immunoreactivity were studied in renal arteries ex vivo. Despite similar cholesterol levels, LDL oxidizability (lag time, malondialdehyde, and relative electrophoretic mobility) was increased in pigs that were fed the HC diet but was significantly decreased in pigs that were fed the HC+vitamins diet. Renal blood flow response to Ach was blunted in pigs that were fed the HC diet but was preserved in pigs that were fed the HC+vitamins diet. Maximal relaxation to Ach was attenuated in pigs that were fed the HC diet compared with those that were fed the normal diet (51.5 +/- 6.4% versus 97.0 +/- 2.9%; P < 0.01) but was preserved in pigs that were fed the HC+vitamins diet (103.1 +/- 3.0%; P = 0.39) and N+vitamins diet (87.7 +/- 3.0%; P = 0.1), as were relaxation responses to calcium ionophore A23187. Vascular smooth-muscle relaxation to diethylamine was enhanced in endothelium-denuded HC vessel but was restored in pigs that were on the HC+vitamins regimen. In HC, immuno-reactivity of endothelial NOS was decreased, that of inducible NOS was increased, and both were preserved in pigs that were fed the HC+vitamins and N+vitamins diets, whereas nitrotyrosine was not detected. The present study demonstrates that antioxidant intervention in experimental HC reduces LDL oxidizability and preserves renal vascular responses to endothelium-dependent vasodilators. Therefore, this beneficial effect potentially can protect the kidney from hypercholesterolemia-induced damage.
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MESH Headings
- Animals
- Antioxidants/therapeutic use
- Ascorbic Acid/therapeutic use
- Cholesterol/blood
- Cholesterol, Dietary/administration & dosage
- Cholesterol, Dietary/pharmacology
- Cyclic GMP/biosynthesis
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/physiopathology
- Hemodynamics
- Hypercholesterolemia/diagnostic imaging
- Hypercholesterolemia/drug therapy
- Hypercholesterolemia/physiopathology
- Immunohistochemistry
- In Vitro Techniques
- Lipoproteins, LDL/blood
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiopathology
- Reference Values
- Renal Circulation/drug effects
- Swine
- Time Factors
- Tomography, X-Ray Computed
- Vitamin E/therapeutic use
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Affiliation(s)
- John M Stulak
- Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota
| | - Amir Lerman
- Departments of Physiology and Biophysics, Mayo Clinic, Rochester, Minnesota
| | | | | | - J Carlos Romero
- Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota
| | | | - Claudio Napoli
- Department of Medicine, University of Naples, Italy and Department of Medicine, University of California, San Diego, California
| | - Lilach O Lerman
- Department of Internal Medicine, Division of Hypertension, Mayo Clinic, Rochester, Minnesota
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186
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Napoli C, Lerman LO. Involvement of oxidation-sensitive mechanisms in the cardiovascular effects of hypercholesterolemia. Mayo Clin Proc 2001; 76:619-31. [PMID: 11393501 DOI: 10.4065/76.6.619] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Hypercholesterolemia is a common clinical metabolic and/or genetic disorder that promotes functional and structural vascular wall injury. The underlying mechanisms for these deleterious effects involve a local inflammatory response and release of cytokines and growth factors. Consequent activation of oxidation-sensitive mechanisms in the arterial wall, modulation of intracellular signaling pathways, increased oxidation of low-density lipoprotein cholesterol, and quenching of nitric oxide can all impair the functions controlled by the vascular wall and lead to the development of atherosclerosis. This cascade represents a common pathological mechanism activated by various cardiovascular risk factors and may partly underlie synergism among them as well as the early pathogenesis of atherosclerosis. Antioxidant intervention and restoration of the bioavailability of nitric oxide have been shown to mitigate functional and structural arterial alterations and improve cardiovascular outcomes. Elucidation of the precise nature and role of early transductional signaling pathways and transcriptional events activated in hypercholesterolemia in children and adults, including mothers during pregnancy, and understanding their downstream effects responsible for atherogenesis may help in directing preventive and interventional measures against atherogenesis and vascular dysfunction.
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Affiliation(s)
- C Napoli
- Department of Medicine, University of Naples, Italy.
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187
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Abstract
Studies of the renin-angiotension system and the effects of pharmacologic blockade have enhanced our understanding of renovascular hypertension. A critical degree of arterial stenosis produces kidney ischemia sufficient to activate this hormonal system, whose actions include vasoconstriction and sodium retention. Accurate clinical evaluation may depend upon recognizing the differences in pathophysiology between "one-kidney" and "two-kidney" forms and the dynamic nature of this condition.
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