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Tetrahydrobiopterin reverses the inhibition of nitric oxide by high glucose in cultured murine mesangial cells

Tetrahydrobiopterin reverses the inhibition of nitric oxide by high glucose in cultured murine... Abstract Alterations of intrarenal nitric oxide (NO) synthesis play an important role in the pathogenesis and progression of diabetic nephropathy. We tested the hypothesis that hyperglycemia modulates intrarenal NO synthesis, which might mediate the mesangial cell proliferation and matrix production. Murine mesangial cells were grown in media containing varying glucose concentrations, and cytokine-induced NO synthesis was assayed by chemiluminescence using an NO analyzer. High media glucose (25 mM) inhibited NO synthesis in a time-dependent fashion. This inhibition was posttranslational as revealed by analysis of inducible nitric oxide synthase (iNOS) gene and protein expression. l -Arginine supplementation partially reversed the inhibition whereas addition of tetrahydrobiopterin (BH 4 ), a cofactor for NOS, restored the inducibility of NO synthesis. The in vitro 3 Hcitrulline assay for iNOS activity indicated that high glucose decreased BH 4 availability whereas examination of the BH 4 synthetic pathway suggested decreased BH 4 stability rather than synthesis, a defect that was corrected by ascorbic acid. We conclude that hyperglycemia inhibits NO synthesis in mesangial cells by a posttranslational defect that might involve the stability and hence availability of BH 4 . hyperglycemia inducible nitric oxide synthase ascorbic acid Footnotes Parts of this work were presented at the annual meetings of the Southern Society of Clinical Investigation in New Orleans, LA, February 2000, and the American Society of Nephrology meetings in Toronto, ONT, October 2000. These studies are partly funded by intramural grants from Texas Tech University Health Sciences Center and a departmental seed grant. Address for reprint requests and other correspondence: S. S. Prabhakar, Div. of Nephrology, Dept. of Internal Medicine, Texas Tech Univ. Health Sciences Ctr., Lubbock, TX 79430 (E-mail: medssp2@ttuhsc.edu ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Copyright © 2001 the American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Renal Physiology The American Physiological Society

Tetrahydrobiopterin reverses the inhibition of nitric oxide by high glucose in cultured murine mesangial cells

Prabhakar, Sharma S.
AJP - Renal Physiology , Volume 281 (1): F179 – Jul 1, 2001
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Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
0363-6127
eISSN
1522-1466
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Abstract

Abstract Alterations of intrarenal nitric oxide (NO) synthesis play an important role in the pathogenesis and progression of diabetic nephropathy. We tested the hypothesis that hyperglycemia modulates intrarenal NO synthesis, which might mediate the mesangial cell proliferation and matrix production. Murine mesangial cells were grown in media containing varying glucose concentrations, and cytokine-induced NO synthesis was assayed by chemiluminescence using an NO analyzer. High media glucose (25 mM) inhibited NO synthesis in a time-dependent fashion. This inhibition was posttranslational as revealed by analysis of inducible nitric oxide synthase (iNOS) gene and protein expression. l -Arginine supplementation partially reversed the inhibition whereas addition of tetrahydrobiopterin (BH 4 ), a cofactor for NOS, restored the inducibility of NO synthesis. The in vitro 3 Hcitrulline assay for iNOS activity indicated that high glucose decreased BH 4 availability whereas examination of the BH 4 synthetic pathway suggested decreased BH 4 stability rather than synthesis, a defect that was corrected by ascorbic acid. We conclude that hyperglycemia inhibits NO synthesis in mesangial cells by a posttranslational defect that might involve the stability and hence availability of BH 4 . hyperglycemia inducible nitric oxide synthase ascorbic acid Footnotes Parts of this work were presented at the annual meetings of the Southern Society of Clinical Investigation in New Orleans, LA, February 2000, and the American Society of Nephrology meetings in Toronto, ONT, October 2000. These studies are partly funded by intramural grants from Texas Tech University Health Sciences Center and a departmental seed grant. Address for reprint requests and other correspondence: S. S. Prabhakar, Div. of Nephrology, Dept. of Internal Medicine, Texas Tech Univ. Health Sciences Ctr., Lubbock, TX 79430 (E-mail: medssp2@ttuhsc.edu ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Copyright © 2001 the American Physiological Society

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AJP - Renal Physiology – The American Physiological Society

Published: Jul 1, 2001

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