Interactions of Peroxynitrite, Tetrahydrobiopterin, Ascorbic Acid, and Thiols

By Nermin Kuzkaya, N. Weissmann, D. Harrison, S. Dikalov. Journal of Biological Chemistry, 2003

694 citations recorded by the source corpus.

Tetrahydrobiopterin (BH4) serves as a critical co-factor for the endothelial nitric-oxide synthase (eNOS). A deficiency of BH4 results in eNOS uncoupling, which is associated with increased superoxide and decreased NO• production. BH4 has been suggested to be a target for oxidation by peroxynitrite (ONOO–), and ascorbate has been shown to preserve BH4 levels and enhance endothelial NO• production; however, the mechanisms underlying these processes remain poorly defined. To gain further insight into these interactions, the reaction of ONOO– with BH4 was studied using electron spin resonance and the spin probe 1-hydroxy-3-carboxy-2,2,5-tetramethyl-pyrrolidine. ONOO– reacted with BH4 6–10 times faster than with ascorbate or thiols. The immediate product of the reaction between ONOO– and BH4 was the trihydrobiopterin radical (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(BH_{3}^{{\cdot}}\) \end{document}), which was reduced back to BH4 by ascorbate, whereas thiols were not efficient in recycling of BH4. Uncoupling of eNOS caused by peroxynitrite was investigated in cultured bovine aortic endothelial cells (BAECs) by measuring superoxide and NO• using spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine and the NO•-spin trap iron-diethyldithiocarbamate. Bolus ONOO–, the ONOO– donor 3-morpholinosydnonimine, and an inhibitor of BH4 synthesis (2,4-diamino-6-hydroxypyrimidine) uncoupled eNOS, increasing superoxide and decreasing NO• production. Exogenous BH4 supplementation restored endothelial NO• production. Treatment of BAECs with both BH4 and ascorbate prior to ONOO– prevented uncoupling of eNOS by ONOO–. This study demonstrates that endothelial BH4 is a crucial target for oxidation by ONOO– and that the BH4 reaction rate constant exceeds those of thiols or ascorbate. We confirmed that ONOO– uncouples eNOS by oxidation of tetrahydrobiopterin and that ascorbate does not fully protect BH4 from oxidation but recycles \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(BH_{3}^{{\cdot}}\) \end{document} radical back to BH4.

Subfields: Biochemistry, Biophysics, Physiology

View Paper: https://www.semanticscholar.org/paper/0da9f67cbdffdce6d2b3da23d6d9fb1ae02d5e0c

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In Biochemistry

1. C. Szabó
2. Rafael Radi
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In Biophysics

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Citations in the corpus

• Endothelial dysfunction: a multifaceted disorder (The Wiggers Award Lecture). (2006, background): “Endothelial xanthine oxidase, NADPH oxidase, as well as endothelial NO synthase (eNOS) itself [when uncoupled because of substrate (L-arginine) deficiency and or because of oxidation or deficiency of the cofactor, tetrahydrobiopterin (30, 131, 274, 290)] can contribute to the generation of superoxid”
• Peroxynitrite: biochemistry, pathophysiology and development of therapeutics (2007, background): “It has been proposed that low levels of BH 4 can, in turn, promote a cycle of its own destruction, which is mediated by the NOS-dependent formation of peroxynitrit”
• Endothelial Dysfunction and Diabetes: Effects on Angiogenesis, Vascular Remodeling, and Wound Healing (2012, background): “Specifically, peroxynitrite rapidly oxidizes the active BH4 to inactive dihydrobiopterin (BH2), leading to eNOS uncoupling [197].”
• Vitamins C and E: Beneficial effects from a mechanistic perspective (2011, background): “As stated above, one explanation is that vitamin C eliminates superoxide intracellularly [12,103,104] that would otherwise deactivate NO by forming peroxynitrite [105].”
• Copper, oxidative stress, and human health. (2005, background): “For example, peroxynitrite reacts with the essential NOS cofactor, BH4, 10 times faster than with ascorbate and six times faster than with glutathione or cysteine (Kuzkaya et al., 2003).”