251
|
Belik J, Jankov RP, Pan J, Tanswell AK. Chronic O2 exposure enhances vascular and airway smooth muscle contraction in the newborn but not adult rat. J Appl Physiol (1985) 2003; 94:2303-12. [PMID: 12562676 DOI: 10.1152/japplphysiol.00820.2002] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neonatal rats exposed to 60% O(2) for 14 days develop lung changes compatible with human bronchopulmonary dysplasia and pulmonary hypertension. Our aim was to evaluate and compare the newborn and adult rat pulmonary vascular and airway smooth muscle force generation and relaxation potential after exposure to 60% O(2) for 14 days. Vascular and airway intrapulmonary rings 100 microm in diameter were mounted on a myograph and bathed in Krebs-Henseleit solution bubbled with air- 6% CO(2) at 37 degrees C. Significant age-dependent changes in intrapulmonary arteries and their neighboring airway muscle properties were observed. Whereas hyperoxia enhanced force in neonatal vascular and airway muscle, the opposite was seen in adult samples. No changes in endothelium-dependent vascular relaxation were observed at either age, but the dose response to an endothelium-independent NO donor was altered. In the newborn experimental animals, the relaxation was reduced, whereas, in their adult counterparts, it was enhanced. After O(2) exposure, the bronchial muscle relaxation response to epithelium-dependent and -independent stimulation was not altered in either age group, whereas the epithelium-dependent response was decreased only in the adult. The antioxidant Trolox, or an endothelin-A and -B receptor antagonist, reversed the vascular and airway muscle's hyperoxia-induced changes. We conclude that chronic O(2) exposure in the newborn rat results in enhanced lung vascular and airway muscle contraction potential via a mechanism involving reactive oxygen species and the endothelin pathway. The present findings also suggest that the newborn is more susceptible to airway hyperresponsiveness after chronic O(2) exposure.
Collapse
Affiliation(s)
- J Belik
- Department of Pediatrics, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada M5G 1X8.
| | | | | | | |
Collapse
|
252
|
Schiffrin EL, Touyz RM. Inflammation and vascular hypertrophy induced by angiotensin II: role of NADPH oxidase-derived reactive oxygen species independently of blood pressure elevation? Arterioscler Thromb Vasc Biol 2003; 23:707-9. [PMID: 12740221 DOI: 10.1161/01.atv.0000069907.12357.7e] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
253
|
Nakagawa T, Kang DH, Ohashi R, Suga SI, Herrera-Acosta J, Rodriguez-Iturbe B, Johnson RJ. Tubulointerstitial disease: role of ischemia and microvascular disease. Curr Opin Nephrol Hypertens 2003; 12:233-41. [PMID: 12698060 DOI: 10.1097/00041552-200305000-00003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE OF REVIEW Tubulointerstitial injury is characteristic of aging-associated renal injury and progressive renal disease. Salt-sensitive hypertension is also associated with tubulointerstitial inflammation, especially when accompanied by microvascular disease. Here we summarize recent studies on the pathogenesis and consequences of tubulointerstitial disease, emphasizing the role of ischemia and the microvasculature. RECENT FINDINGS Tubulointerstitial injury occurs via several mechanisms of which one of the most important is chronic ischemia. Recent studies suggest that chronic vasoconstriction may contribute to the renal injury associated with angiotensin II, catecholamines, nitric oxide inhibition, hypokalemia, hyperuricemia, and cyclosporine nephropathy. Salt-sensitivity may result as a consequence of the tubulointerstitial inflammatory response to these conditions, and this appears to be perpetuated by the development of preglomerular vascular disease. With progression of tubulointerstitial disease there is also a loss of peritubular capillaries, and stimulating microvascular growth with angiogenic factors can stabilize renal function in these models. SUMMARY Ischemia secondary to vasoconstriction or to structural changes of the renal vasculature may have important consequences both in terms of mediating salt-sensitive hypertension and renal progression. Angiogenic factors may have potential benefit in preventing or treating these conditions.
Collapse
Affiliation(s)
- Takahiko Nakagawa
- Division of Nephrology, Baylor College of Medicine, Houston, Texas 77030, USA.
| | | | | | | | | | | | | |
Collapse
|
254
|
Farjah M, Roxas BP, Geenen DL, Danziger RS. Dietary salt regulates renal SGK1 abundance: relevance to salt sensitivity in the Dahl rat. Hypertension 2003; 41:874-8. [PMID: 12642512 DOI: 10.1161/01.hyp.0000063885.48344.ea] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Serum and glucocorticoid-induced kinase 1 (SGK1) activates the epithelial sodium channel (eNaC) in tubules. We examined renal SGK1 abundance in salt-adaptation and in salt-sensitive hypertension. Sprague-Dawley and Dahl salt-sensitive rats were placed on either 8% or 0.3% NaCl diets for 10 days. Plasma aldosterone levels were approximately 2.5-fold greater on 0.3% versus 8% NaCl diets in both rat strains. Both serum and glucocorticoid-induced kinase 1 transcript and protein abundance were less (P<0.01) in Sprague-Dawley rats and greater (P<0.01) in Dahl salt-sensitive rats on 8% versus 0.3% NaCl diets. The cDNA sequences of serum and glucocorticoid-induced kinase 1 in both strains of rat were the same. The present results provide evidence that the abundance of serum and glucocorticoid-induced kinase 1 in rat kidney may play a role in salt adaptation and the pathogenesis of hypertension and suggests that aldosterone is not the primary inducer of SGK1 in the Sprague-Dawley rat.
Collapse
Affiliation(s)
- Mariam Farjah
- Department of Medicine, University of Illinois at Chicago, 840 S Wood St, Chicago, Ill 60612, USA
| | | | | | | |
Collapse
|
255
|
Fortepiani LA, Zhang H, Racusen L, Roberts LJ, Reckelhoff JF. Characterization of an animal model of postmenopausal hypertension in spontaneously hypertensive rats. Hypertension 2003; 41:640-5. [PMID: 12623972 DOI: 10.1161/01.hyp.0000046924.94886.ef] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Blood pressure (BP) increases in postmenopausal women. The mechanisms responsible are unknown. The present study was performed to characterize a model of postmenopausal hypertension in the rat and to determine the role that oxidative stress may play in mediating the postmenopausal hypertension. Spontaneously hypertensive rats were ovariectomized (ovx) or left intact (PMR) at 8 months and were aged to 18 months. These animals were compared with young females (YF; 4 or 8 months of age) and old males (18 months) for some measurements. Estradiol levels were decreased in PMR rats to levels not different from YF rats in proestrous or from old males. BP increased progressively with age in PMR rats but not in ovx or male rats, such that the gender difference in hypertension disappeared by 18 months. Glomerular filtration rate was lower in ovx and PMR rats than in YF rats. Renal plasma flow and renal vascular resistance were similar between YF and ovx rats, but lower and higher, respectively, in PMR rats. Serum testosterone increased by 60% in ovx rats and 400% in PMR rats compared with YF rats. Plasma renin activity also increased in PMR rats but not in ovx rats. Chronic treatment (for 8 months beginning at 8 months of age) of PMR rats with vitamins E and C, but not tempol, resulted in a significant reduction in BP and excretion of F2-isoprostanes. In contrast, tempol, but not vitamins E and C, reduced BP in old males. These data suggest that the PMR rats, but not ovx rats, may be a suitable model for the study of postmenopausal hypertension, and that oxidative stress plays a role in the increased BP.
Collapse
Affiliation(s)
- Lourdes A Fortepiani
- Department of Physiology and Biophysics, University of Mississippi Medical Center, 2500 N State St, Jackson, MS 39216-4505, USA
| | | | | | | | | |
Collapse
|
256
|
Nava M, Quiroz Y, Vaziri N, Rodriguez-Iturbe B. Melatonin reduces renal interstitial inflammation and improves hypertension in spontaneously hypertensive rats. Am J Physiol Renal Physiol 2003; 284:F447-54. [PMID: 12441307 DOI: 10.1152/ajprenal.00264.2002] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Several studies have demonstrated that treatment with antioxidants improves hypertension in spontaneously hypertensive rats (SHR). Because our laboratory has shown that renal infiltration of immune cells plays a role in the development of hypertension (Rodriguez-Iturbe B, Quiroz Y, Nava M, Bonet L, Chavez M, Herrera-Acosta J, Johnson RJ, and Pons HA. Am J Physiol Renal Physiol 282: F191-F201, 2002), we did the present studies to define whether the antihypertensive effect of antioxidants was associated with an improvement in renal inflammation. Melatonin was administered as an antioxidant. For 6 wk, melatonin was added to the drinking water (10 mg/100 ml) given to a group of SHR (SHR-Mel; n = 10), and we compared them with groups of untreated SHR (n = 10) and Wistar-Kyoto (WKY) control rats (n = 10). Hypertension became increasingly severe in the SHR group [195 +/- 14.3 (SD) mmHg at the end of the experiment] and improved in the SHR-Mel group (149 +/- 20.4 mmHg, P < 0.001) in association with a 40-60% reduction in the renal infiltration of lymphocytes, macrophages, and angiotensin II-positive cells. Intracellular superoxide and renal malondialdehyde content were reduced by melatonin treatment as was the immunohistological expression of the 65-kDA DNA-binding subunit of NF-kappaB. We conclude that melatonin treatment ameliorates hypertension in SHR in association with a reduction in interstitial renal inflammation. Decreased activation of NF-kappaB, likely resulting from a reduction in local oxidative stress, may play a role in the suppression of renal immune infiltration and, thereby, in the antihypertensive effects of melatonin.
Collapse
Affiliation(s)
- Mayerly Nava
- Renal Service and Laboratory, Hospital Universitario, Instituto de Investigaciones Biomédicas (Fundacite-Zulia), Universidad del Zulia, Maracaibo 4001-A, Venezuela
| | | | | | | |
Collapse
|
257
|
Abstract
PURPOSE OF REVIEW Transmission of external signals from the cell surface to the internal cellular environment occurs via tightly controlled complex transduction pathways. Alterations in these highly regulated signalling cascades in vascular smooth cells may play a fundamental role in the structural, mechanical and functional abnormalities that underlie vascular pathological processes in hypertension. The present review focuses on recent developments relating to two novel signalling pathways: angiotensin II signalling through tyrosine kinases; and oxidative stress and redox-dependent signal transduction. These pathways are emerging as critical mediators of hypertensive vascular disease because they influence multiple cellular responses that are involved in structural remodelling, vascular inflammation and altered tone. RECENT FINDINGS A recent advance in the field of angiotensin II signalling was the demonstration that, in addition to its vasoconstrictor properties, angiotensin II has potent mitogenic-like and proinflammatory-like characteristics. These actions are mediated through phosphorylation of both nonreceptor tyrosine kinases and receptor tyrosine kinases. It is also becoming increasingly apparent that many signalling events that underlie abnormal vascular function in hypertension are influenced by changes in intracellular redox status. In particular, increased bioavailability of reactive oxygen species (oxidative stress) stimulates growth-signalling pathways, induces expression of proinflammatory genes, alters contraction-excitation coupling and impairs endothelial function. SUMMARY A better understanding of the molecular pathways that regulate vascular smooth muscle cell function will provide further insights into the pathophysiological mechanisms that contribute to vascular changes and end-organ damage associated with high blood pressure, and could permit identification of potential novel therapeutic targets in the prevention and management of hypertension.
Collapse
Affiliation(s)
- Rhian M Touyz
- Canadian Institute of Health Research Multidisciplinary Research Group on Hypertension, Quebec, Canada.
| |
Collapse
|
258
|
Rodriguez-Iturbe B, Zhan CD, Quiroz Y, Sindhu RK, Vaziri ND. Antioxidant-rich diet relieves hypertension and reduces renal immune infiltration in spontaneously hypertensive rats. Hypertension 2003; 41:341-6. [PMID: 12574105 DOI: 10.1161/01.hyp.0000052833.20759.64] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Previous studies have demonstrated that oxidative stress contributes to hypertension and treatments with either antioxidant or immunosuppressive/anti-inflammatory agents improve hypertension in spontaneously hypertensive rats (SHR). The present study was performed to determine if the antihypertensive effects of an antioxidant-rich diet are associated with reduction in the renal immune infiltration. Rats were divided into experimental groups (n=5 each) that were followed 7 months after birth, during which they were fed either a regular or antioxidant-enriched (test) diet as follows: SHR-R group=regular diet; SHR-T group=test diet throughout the experiment; SHR-S group=test diet for 4 months switched to regular diet thereafter; WKY group=control rats given regular diet. The SHR-T rats showed a significant reduction in systolic blood pressure (mm Hg): SHR-T=179.6+/-12.9 versus SHR-R=207.5+/-9.6 (P<0.001) and plasma hydrogen peroxide concentration (SHR-T=15+/-4 micro mol/L versus 34+/-9 in SHR-R rats). This was accompanied by significant reductions of renal tissue nitrotyrosine abundance, tubulointerstitial infiltration (cells/mm(2)) of lymphocytes (SHR-T=18+/-3 versus SHR-R=30+/-4, P<0.001), macrophages (SHR-T= 17+/-3 versus SHR-R=22+/-3), and angiotensin II-positive cells (SHR-T= 17+/-2 versus SHR-R=25+/-5, P<0.01). Results in the SHR-S group were intermediate between the SHR-R and SHR-T groups. The intensity of the infiltration of lymphocytes, macrophages, and angiotensin II-positive cells significantly correlated with systolic blood pressure. Thus, the present study demonstrates that an antioxidant-enriched diet reduces the renal interstitial inflammation and improves hypertension in SHR. These findings point to interrelation between oxidative stress and inflammatory reactivity in the pathogenesis of hypertension.
Collapse
Affiliation(s)
- Bernardo Rodriguez-Iturbe
- Renal Service and Laboratory, Hospital Universitario, Instituto de Investigaciones Biomédicas (Fundacite-Zulia), Universidad del Zulia, Maracaibo, Venezuela.
| | | | | | | | | |
Collapse
|
259
|
Shokoji T, Nishiyama A, Fujisawa Y, Hitomi H, Kiyomoto H, Takahashi N, Kimura S, Kohno M, Abe Y. Renal sympathetic nerve responses to tempol in spontaneously hypertensive rats. Hypertension 2003; 41:266-73. [PMID: 12574093 DOI: 10.1161/01.hyp.0000049621.85474.cf] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Recent studies have implicated a contribution of oxidative stress to the development of hypertension. Studies were performed to determine the effects of the superoxide dismutase (SOD) mimetic 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (Tempol) on vascular superoxide production and renal sympathetic nerve activity (RSNA) in anesthetized Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). Compared with WKY rats (n=6), SHR showed a doubled vascular superoxide production, which was normalized by treatment with Tempol (3 mmol/L, n=7). In WKY rats (n=6), Tempol (30 mg/kg IV) significantly decreased mean arterial pressure (MAP) from 108+/-5 to 88+/-6 mm Hg and HR from 304+/-9 to 282+/-6 beats/min. In SHR (n=6), Tempol significantly decreased MAP from 166+/-4 to 123+/-9 mm Hg and HR from 380+/-7 to 329+/-12 beats/min. Furthermore, Tempol significantly decreased RSNA in both WKY rats and SHR. On the basis of group comparisons, the percentage decreases in MAP (-28+/-4%), HR (-16+/-3%) and integrated RSNA (-63+/-6%) in SHR were significantly greater than in WKY rats (-17+/-3%, -9+/-2%, and -30+/-4%, respectively). In SHR, changes in integrated RSNA were highly correlated with changes in MAP (r=0.85, P<0.0001) during administration of Tempol (3, 10, and 30 mg/kg IV). In both WKY rats and SHR (n=4, respectively), intracerebroventricular injection of Tempol (300 micro g/1 micro L) did not alter MAP, HR, or RSNA. Intravenous administration of a SOD inhibitor, diethyldithio-carbamic acid (30 mg/kg), significantly increased MAP, HR, and integrated RSNA in both WKY rats and SHR (n=6, respectively). These results suggest that augmented superoxide production contributes to the development of hypertension through activation of the sympathetic nervous system.
Collapse
Affiliation(s)
- Takatomi Shokoji
- Second Department of Medicine, Kagawa Medical University, Kita-Gun, Kagawa, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
260
|
Pallone TL, Zhang Z, Rhinehart K. Physiology of the renal medullary microcirculation. Am J Physiol Renal Physiol 2003; 284:F253-66. [PMID: 12529271 DOI: 10.1152/ajprenal.00304.2002] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Perfusion of the renal medulla plays an important role in salt and water balance. Pericytes are smooth muscle-like cells that impart contractile function to descending vasa recta (DVR), the arteriolar segments that supply the medulla with blood flow. DVR contraction by ANG II is mediated by depolarization resulting from an increase in plasma membrane Cl(-) conductance that secondarily gates voltage-activated Ca(2+) entry. In this respect, DVR may differ from other parts of the efferent microcirculation of the kidney. Elevation of extracellular K(+) constricts DVR to a lesser degree than ANG II or endothelin-1, implying that other events, in addition to membrane depolarization, are needed to maximize vasoconstriction. DVR endothelial cytoplasmic Ca(2+) is increased by bradykinin, a response that is inhibited by ANG II. ANG II inhibition of endothelial Ca(2+) signaling might serve to regulate the site of origin of vasodilatory paracrine agents generated in the vicinity of outer medullary vascular bundles. In the hydropenic kidney, DVR plasma equilibrates with the interstitium both by diffusion and through water efflux across aquaporin-1. That process is predicted to optimize urinary concentration by lowering blood flow to the inner medulla. To optimize urea trapping, DVR endothelia express the UT-B facilitated urea transporter. These and other features show that vasa recta have physiological mechanisms specific to their role in the renal medulla.
Collapse
Affiliation(s)
- Thomas L Pallone
- Division of Nephrology, University of Maryland School of Medicine, Baltimore, Maryland 21201-1595, USA.
| | | | | |
Collapse
|
261
|
Alvarez V, Quiroz Y, Nava M, Pons H, Rodríguez-Iturbe B. Overload proteinuria is followed by salt-sensitive hypertension caused by renal infiltration of immune cells. Am J Physiol Renal Physiol 2002; 283:F1132-41. [PMID: 12372790 DOI: 10.1152/ajprenal.00199.2002] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent evidence suggests that salt-sensitive hypertension develops as a consequence of renal infiltration with immunocompetent cells. We investigated whether proteinuria, which is known to induce interstitial nephritis, causes salt-sensitive hypertension. Female Lewis rats received 2 g of BSA intraperitoneally daily for 2 wk. After protein overload (PO), 6 wk of a high-salt diet induced hypertension [systolic blood pressure (SBP) = 156 +/- 11.8 mmHg], whereas rats that remained on a normal-salt diet and control rats (without PO) on a high-salt diet were normotensive. Administration of mycophenolate mofetil (20 mg. kg(-1). day(-1)) during PO resulted in prevention of proteinuria-related interstitial nephritis, reduction of renal angiotensin II-positive cells and oxidative stress (superoxide-positive cells and renal malondialdehyde content), and resistance to the hypertensive effect of the high-salt diet (SBP = 129 +/- 12.2 mmHg). The present studies support the participation of renal inflammatory infiltrate in the pathogenesis of salt-sensitive hypertension and provide a direct link between two risk factors of progressive renal damage: proteinuria and hypertension.
Collapse
Affiliation(s)
- Violeta Alvarez
- Renal Service and Laboratory and Instituto de Investigaciones Biomédicas, Fundacite-Zulia, Hospital Universitario, Universidad del Zulia, Maracaibo 4001-A, Venezuela
| | | | | | | | | |
Collapse
|
262
|
Herrera MD, Bueno R, De Sotomayor MA, Pérez-Guerrero C, Vázquez CM, Marhuenda E. Endothelium-dependent vasorelaxation induced by L-carnitine in isolated aorta from normotensive and hypertensive rats. J Pharm Pharmacol 2002; 54:1423-7. [PMID: 12396307 DOI: 10.1211/002235702760345536] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The aim of this work was to investigate the mechanism of the vasodilatory effect induced by L-carnitine. Relaxation produced by L-carnitine was studied in rat aortic rings with and without functional endothelium, pre-contracted with phenylephrine by adding cumulative doses of L-carnitine (10(-7) to 10(-3) M). The relaxation evoked by L-carnitine reached higher values in aortic rings from spontaneously hypertensive rats than those obtained in arteries from normotensive rats; no relaxation was produced in de-endothelialized arteries. However, in the presence of N(G)-nitro-L-arginine (3 x 10(-5) M, a nitric oxide synthase inhibitor), Ro 68070 (10(-4) M, a thromboxane synthetase inhibitor-thromboxane A2/prostaglandin H2 receptor antagonist) or ICI 192605 (10(-5) M, a thromboxane A2 receptor antagonist) the relaxant response to L-carnitine was significantly inhibited. These results show that L-carnitine induced endothelium-dependent relaxation in the rat aorta and the mechanism of this relaxation appeared to be mostly mediated by endothelial production of nitric oxide but#10; also could involve prevention of the action of cyclooxygenase endothelial products acting on the thromboxane A2/prostaglandin H2 receptor.
Collapse
Affiliation(s)
- María Dolores Herrera
- Department of Pharmacology, Faculty of Pharmacy, University of Seville, C/ Profesor García González s/n, 41012-Seville, Spain.
| | | | | | | | | | | |
Collapse
|
263
|
|