Effect of High Glucose on Superoxide in Human Mesangial Cells: Role of Angiotensin II

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Abstract

Background/Aims: Reactive oxygen species, and especially superoxide (O2·–),have been implicated in diabetic nephropathy. O2·– accumulation in cells is dependent on O2·– production (by NADH/NADPH oxidase) as well as scavenging by superoxide dismutase (SOD) activity. This study was designed to investigate the effects of high glucose (HG) on O2·– accumulation and SOD activity in human mesangial cells (HMC) and to determine if these effects are mediated by angiotensin II (Ang II). Methods: HMC were incubated in media containing 10 m Mglucose (control, C), 30 m M glucose (HG), 10 m M glucose + either 20 m M 2-deoxy- D-glucose (2-DG) or 20 m M mannitol (high mannitol, HM) (osmotic controls), or Ang II (10–5 M). Ang II action was antagonized by employing 10–4 M of Ang II receptor antagonists (losartan or irbesartan) or 10–4 M of NADH/NADPH oxidase inhibitors [diphenyleneiodonium chloride (DPI) or apocynin]. Superoxide and total SOD activity were assayed using chemiluminescence of lucigenin. Results: Incubation of HMC in HG resulted in a 1.6-fold increase in Ang I (p < 0.05) and a 1.4-fold increase in Ang II levels (p < 0.05) in cell lysates. These changes were accompanied by a >2-fold increase in O2·– accumulation (p < 0.01), which was inhibited by losartan and irbesartan. Exogenous Ang II increased net O2·– accumulation by 2.7-fold (p < 0.01), which was normalized by losartan and irbesartan. DPI and apocynin blocked the HG and Ang II-induced increases in O2·– (p < 0.01). HG but not exogenous Ang II inhibited total SOD activity by 30%, which was not affected by losartan. Conclusion: High glucose increases O2–· accumulation in HMC primarily by increasing its production via the Ang II-NADH/NADPH oxidase system.

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Role of p47 phox in Vascular Oxidative Stress and Hypertension Caused by Angiotensin II

Ulf Landmesser, Hua Cai, Sergey Dikalov … (2002)

Hypertension caused by angiotensin II is dependent on vascular superoxide (O 2 ·−) production. The nicotinamide adenine dinucleotide phosphate (NAD[P]H) oxidase is a major source of vascular O 2 ·− and is activated by angiotensin II in vitro. However, its role in angiotensin II-induced hypertension in vivo is less clear. In the present studies, we used mice deficient in p47 phox , a cytosolic subunit of the NADPH oxidase, to study the role of this enzyme system in vivo. In vivo, angiotensin II infusion (0.7 mg/kg per day for 7 days) increased systolic blood pressure from 105±2 to 151±6 mm Hg and increased vascular O 2 ·− formation 2- to 3-fold in wild-type (WT) mice. In contrast, in p47 phox-/- mice the hypertensive response to angiotensin II infusion (122±4 mm Hg; P <0.05) was markedly blunted, and there was no increase of vascular O 2 ·− production. In situ staining for O 2 ·− using dihydroethidium revealed a marked increase of O 2 ·−production in both endothelial and vascular smooth muscle cells of angiotensin II-treated WT mice, but not in those of p47 phox-/- mice. To directly examine the role of the NAD(P)H oxidase in endothelial production of O 2 ·−, endothelial cells from WT and p47 phox-/- mice were cultured. Western blotting confirmed the absence of p47 phox in p47 phox-/- mice. Angiotensin II increased O 2 ·− production in endothelial cells from WT mice, but not in those from p47 phox-/- mice, as determined by electron spin resonance spectroscopy. These results suggest a pivotal role of the NAD(P)H oxidase and its subunit p47 phox in the vascular oxidant stress and the blood pressure response to angiotensin II in vivo.

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Interaction of metabolic and haemodynamic factors in mediating experimental diabetic nephropathy.

David M L Cooper (2001)

Diabetic nephropathy seems to occur as a result of an interaction of metabolic and haemodynamic factors. Glucose dependent pathways are activated within the diabetic kidney. These include increased oxidative stress, renal polyol formation and accumulation of advanced glycated end-products. Haemodynamic factors are also implicated in the pathogenesis of diabetic nephropathy and include increased systemic and intraglomerular pressure and activation of various vasoactive hormone pathways including the renin-angiotensin system and endothelin. These haemodynamic pathways, independently and with metabolic pathways, activate intracellular second messengers such as protein kinase C and MAP kinase, nuclear transcription factors such as NF-kappaB and various growth factors such as the prosclerotic cytokine, TGF-beta and the angiogenic, permeability enhancing growth factor, VEGF. These pathways ultimately lead to increased renal albumin permeability and extracellular matrix accumulation which results in increasing proteinuria, glomerulosclerosis and tubulointerstitial fibrosis. Therapeutic strategies involved in the management and prevention of diabetic nephropathy include currently available treatments such as intensified glycaemic control and antihypertensive agents, particularly those which interrupt the renin-angiotensin system. More novel strategies to influence vasoactive hormone action or to inhibit various metabolic pathways such as inhibitors of advanced glycation, specific protein kinase C isoforms and aldose reductase are at present under experimental and clinical investigation. It is predicted that multiple therapies will be required to reduce the progression of diabetic nephropathy.

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Regulation of intrarenal angiotensin II in hypertension.

L. Bernard, Akira Nishiyama, Hiroyuki Kobori … (2002)

Intrarenal angiotensin II (Ang II) is regulated by several complex processes involving formation from both systemically delivered and intrarenally formed substrate, as well as receptor-mediated internalization. There is substantial compartmentalization of intrarenal Ang II, with levels in the renal interstitial fluid and in proximal tubule fluid being much greater than can be explained from the circulating levels. In Ang II--dependent hypertension, elevated intrarenal Ang II levels occur even when intrarenal renin expression and content are suppressed. Studies in Ang II--infused rats have demonstrated that augmentation of intrarenal Ang II is due, in part, to uptake of circulating Ang II via an Ang II type 1 (AT(1)) receptor mechanism and also to sustained endogenous production of Ang II. Some of the internalized Ang II accumulates in the light and heavy endosomes and is therefore potentially available for intracellular actions. The enhanced intrarenal Ang II also exerts a positive feedback action to augment intrarenal levels of angiotensinogen (AGT) mRNA and protein, which contribute further to the increased intrarenal Ang II in hypertensive states. In addition, renal AT(1) receptor protein and mRNA levels are maintained, allowing increased Ang II levels to elicit progressive effects. The increased intrarenal Ang II activity and AGT production are associated with increased urinary AGT excretion rates. The urinary AGT excretion rates show a clear relationship to kidney Ang II content, suggesting that urinary AGT may serve as an index of Ang II--dependent hypertension. Collectively, the data support a powerful role for intrarenal Ang II in the pathogenesis of hypertension.

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Author and article information

Journal

Journal ID (publisher-id): NEE

Journal ID (nlm-ta): Nephron Exp Nephrol

Journal ID (doi): 10.1159/issn.1660-2129

Title: Cardiorenal Medicine

Publisher: S. Karger AG

ISSN (Electronic): 1660-2129

Publication date Subscription-year: 2005

Publication date (Print): May 2005

Publication date (Electronic): 10 March 2005

Volume: 100

Issue: 1

Pages: 46-53

Affiliations

^aVeterans Affairs Hospital, Hines, Ill. and Loyola University Medical Center, Maywood, Ill.; ^bHektoen Institute for Medical Research, Chicago, Ill., USA

Article

Publisher ID: 84348 Other ID: Nephron Exp Nephrol 2005;100:46–53

DOI: 10.1159/000084348

PubMed ID: 15761243

SO-VID: fb89d22d-7437-444b-bc65-a46e039328e3

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Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

History

Date received : 20 June 2004

Date accepted : 01 October 2004

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Figures: 5, References: 38, Pages: 8

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Effect of High Glucose on Superoxide in Human Mesangial Cells: Role of Angiotensin II

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Karger: Nephrology

Most cited references 23

Role of p47 phox in Vascular Oxidative Stress and Hypertension Caused by Angiotensin II

Interaction of metabolic and haemodynamic factors in mediating experimental diabetic nephropathy.

Regulation of intrarenal angiotensin II in hypertension.

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