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Relationship: 953

Title

A descriptive phrase which clearly defines the two KEs being considered and the sequential relationship between them (i.e., which is upstream, and which is downstream). More help

Decrease, Tetrahydrobiopterin leads to Uncoupling, eNOS

Upstream event
The causing Key Event (KE) in a Key Event Relationship (KER). More help
Downstream event
The responding Key Event (KE) in a Key Event Relationship (KER). More help

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes. Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

AOP Name Adjacency Weight of Evidence Quantitative Understanding Point of Contact Author Status OECD Status
Peptide Oxidation Leading to Hypertension adjacent High High Brendan Ferreri-Hanberry (send email) Not under active development Under Development

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KER.In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER.  More help
Term Scientific Term Evidence Link
Homo sapiens Homo sapiens High NCBI
Rattus norvegicus Rattus norvegicus High NCBI
Mus musculus Mus musculus High NCBI
Bos taurus Bos taurus High NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help
Sex Evidence
Unspecific High

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER.  More help
Term Evidence
All life stages High

Key Event Relationship Description

Provides a concise overview of the information given below as well as addressing details that aren’t inherent in the description of the KEs themselves. More help

Oxidative stress leads to the excessive oxidation and depletion of BH4, resulting in eNOS uncoupling where eNOS produces superoxide rather than nitric oxide (Förstermann and Münzel, 2006).

Evidence Collection Strategy

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Evidence Supporting this KER

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help
Biological Plausibility
Addresses the biological rationale for a connection between KEupstream and KEdownstream.  This field can also incorporate additional mechanistic details that help inform the relationship between KEs, this is useful when it is not practical/pragmatic to represent these details as separate KEs due to the difficulty or relative infrequency with which it is likely to be measured.   More help

BH4 is an essential cofactor for eNOS and is required for its enzymatic activity to produce NO. The depletion of BH4 leading to eNOS uncoupling is well-studied, thus there is strong biological plausibility for this link.

Two mouse studies showed limited BH4 availability induced eNOS uncoupling by reducing eNOS activity, leading to decreased nitric oxide and increased superoxide. In the mouse endothelial cell line sEnd.1, BH4 deficiency induced eNOS uncoupling as determined by superoxide production and impaired vasodilation (Crabtree et al., 2009). In primary aortic endothelial cells of GTPCH1-knockout mice, BH4 depletion significantly reduced eNOS activity, increased basal superoxide production and decreased NO bioactivity (Chuaiphichai et al., 2014). In rat hearts, BH4 content and eNOS activity were decreased in a time-dependent manner following myocardial ischemia with a marked decline after thirty minutes, while superoxide generation increased (Dumitrescu et al., 2007).

BAECs undergoing hypoxia and reoxygenation had decreased BH4 and decreased NO production, which was partially restored by treatment with the xanthine oxidase inhibitor oxypurinol, N-acetyl-l-cysteine (NAC) and NAC+BH4 (De Pascali et al., 2014). Inhibition of BH4 due to treatment with 4-HNE decreased eNOS activity and NO production in BAECs (Whitsett et al., 2007).

Many studies demonstrated that BH4 treatment reduced eNOS-mediated superoxide generation and increased NO formation in bovine, mouse, and rat endothelium (Chen et al., 2011; De Pascali et al., 2014; Landmesser et al., 2003; Ozaki et al., 2002; Shinozaki et al., 2000). Clinical studies reported improvement endothelial function in cardiovascular disease after treatment with BH4 (Wang et al., 2014). Oral treatment with BH4 in hypertensive patients significantly decreased blood pressure.

Uncertainties and Inconsistencies
Addresses inconsistencies or uncertainties in the relationship including the identification of experimental details that may explain apparent deviations from the expected patterns of concordance. More help

The uncoupling of eNOS may also occur through other mechanisms such as S-glutathionylation of eNOS and depletion of L-arginine (Zweier et al., 2011).

Known modulating factors

This table captures specific information on the MF, its properties, how it affects the KER and respective references.1.) What is the modulating factor? Name the factor for which solid evidence exists that it influences this KER. Examples: age, sex, genotype, diet 2.) Details of this modulating factor. Specify which features of this MF are relevant for this KER. Examples: a specific age range or a specific biological age (defined by...); a specific gene mutation or variant, a specific nutrient (deficit or surplus); a sex-specific homone; a certain threshold value (e.g. serum levels of a chemical above...) 3.) Description of how this modulating factor affects this KER. Describe the provable modification of the KER (also quantitatively, if known). Examples: increase or decrease of the magnitude of effect (by a factor of...); change of the time-course of the effect (onset delay by...); alteration of the probability of the effect; increase or decrease of the sensitivity of the downstream effect (by a factor of...) 4.) Provision of supporting scientific evidence for an effect of this MF on this KER. Give a list of references.  More help
Response-response Relationship
Provides sources of data that define the response-response relationships between the KEs.  More help
Time-scale
Information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). More help
Known Feedforward/Feedback loops influencing this KER
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Domain of Applicability

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The relationship between BH4 depletion and eNOS uncoupling was observed in humans (Jayaram et al., 2015), cows (Wang et al., 2008; Whitsett et al., 2007), mice (Chuaiphichai et al., 2014; Crabtree et al., 2009) and rats (Cervantes-Pérez et al., 2012; Dumitrescu et al., 2007).

References

List of the literature that was cited for this KER description. More help

Cervantes-Pérez, L.G., Ibarra-Lara, M. de la L., Escalante, B., Del Valle-Mondragón, L., Vargas-Robles, H., Pérez-Severiano, F., Pastelín, G., and Sánchez-Mendoza, M.A. (2012). Endothelial nitric oxide synthase impairment is restored by clofibrate treatment in an animal model of hypertension. Eur. J. Pharmacol. 685, 108–115.

Chen, C.-A., Lin, C.-H., Druhan, L.J., Wang, T.-Y., Chen, Y.-R., and Zweier, J.L. (2011). Superoxide induces endothelial nitric-oxide synthase protein thiyl radical formation, a novel mechanism regulating eNOS function and coupling. J. Biol. Chem. 286, 29098–29107.

Chuaiphichai, S., McNeill, E., Douglas, G., Crabtree, M.J., Bendall, J.K., Hale, A.B., Alp, N.J., and Channon, K.M. (2014). Cell-autonomous role of endothelial GTP cyclohydrolase 1 and tetrahydrobiopterin in blood pressure regulation. Hypertension 64, 530–540.

Crabtree, M.J., Tatham, A.L., Al-Wakeel, Y., Warrick, N., Hale, A.B., Cai, S., Channon, K.M., and Alp, N.J. (2009). Quantitative regulation of intracellular endothelial nitric-oxide synthase (eNOS) coupling by both tetrahydrobiopterin-eNOS stoichiometry and biopterin redox status: insights from cells with tet-regulated GTP cyclohydrolase I expression. J. Biol. Chem. 284, 1136–1144.

De Pascali, F., Hemann, C., Samons, K., Chen, C.-A., and Zweier, J.L. (2014). Hypoxia and reoxygenation induce endothelial nitric oxide synthase uncoupling in endothelial cells through tetrahydrobiopterin depletion and S-glutathionylation. Biochemistry (Mosc.) 53, 3679–3688.

Dumitrescu, C., Biondi, R., Xia, Y., Cardounel, A.J., Druhan, L.J., Ambrosio, G., and Zweier, J.L. (2007). Myocardial ischemia results in tetrahydrobiopterin (BH4) oxidation with impaired endothelial function ameliorated by BH4. Proc. Natl. Acad. Sci. U. S. A. 104, 15081–15086.

Förstermann, U., and Münzel, T. (2006). Endothelial nitric oxide synthase in vascular disease: from marvel to menace. Circulation 113, 1708–1714.

Jayaram, R., Goodfellow, N., Zhang, M.H., Reilly, S., Crabtree, M., De Silva, R., Sayeed, R., and Casadei, B. (2015). Molecular mechanisms of myocardial nitroso-redox imbalance during on-pump cardiac surgery. Lancet Lond. Engl. 385 Suppl 1, S49.

Landmesser, U., Dikalov, S., Price, S.R., McCann, L., Fukai, T., Holland, S.M., Mitch, W.E., and Harrison, D.G. (2003). Oxidation of tetrahydrobiopterin leads to uncoupling of endothelial cell nitric oxide synthase in hypertension. J. Clin. Invest. 111, 1201–1209.

Ozaki, M., Kawashima, S., Yamashita, T., Hirase, T., Namiki, M., Inoue, N., Hirata, K., Yasui, H., Sakurai, H., Yoshida, Y., et al. (2002). Overexpression of endothelial nitric oxide synthase accelerates atherosclerotic lesion formation in apoE-deficient mice. J. Clin. Invest. 110, 331–340.

Shinozaki, K., Nishio, Y., Okamura, T., Yoshida, Y., Maegawa, H., Kojima, H., Masada, M., Toda, N., Kikkawa, R., and Kashiwagi, A. (2000). Oral administration of tetrahydrobiopterin prevents endothelial dysfunction and vascular oxidative stress in the aortas of insulin-resistant rats. Circ. Res. 87, 566–573.

Wang, Q., Yang, M., Xu, H., and Yu, J. (2014). Tetrahydrobiopterin improves endothelial function in cardiovascular disease: a systematic review. Evid.-Based Complement. Altern. Med. ECAM 2014, 850312.

Wang, S., Xu, J., Song, P., Wu, Y., Zhang, J., Chul Choi, H., and Zou, M.-H. (2008). Acute inhibition of guanosine triphosphate cyclohydrolase 1 uncouples endothelial nitric oxide synthase and elevates blood pressure. Hypertension 52, 484–490.

Whitsett, J., Picklo, M.J., and Vasquez-Vivar, J. (2007). 4-Hydroxy-2-nonenal increases superoxide anion radical in endothelial cells via stimulated GTP cyclohydrolase proteasomal degradation. Arterioscler. Thromb. Vasc. Biol. 27, 2340–2347.