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Relationship: 955


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

S-Glutathionylation, eNOS 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 Moderate 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
Bos taurus Bos taurus High NCBI
Rattus norvegicus Rattus norvegicus 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 can trigger S-glutathionylation of eNOS at cysteine residues Cys689 and Cys908, which are known to be critical for normal eNOS function (Zweier et al., 2011). S-glutathionylation directly causes eNOS uncoupling, a state in which eNOS switches from producing NO to generating superoxide, thus impairing endothelium-dependent vasodilation and contributing to endothelial dysfunction. Uncoupling of eNOS via S-glutathionylation is different from BH4-mediated eNOS uncoupling in that superoxide is produced in the reductase domain rather than the oxygenase domain and superoxide generation cannot be inhibited by L-NG-nitroarginine methyl ester (L-NAME), suggesting that S-glutathionylation occurs independent of calcium/calmodulin and heme.

Evidence Collection Strategy

Include a description of the approach for identification and assembly of the evidence base for the KER. For evidence identification, include, for example, a description of the sources and dates of information consulted including expert knowledge, databases searched and associated search terms/strings.  Include also a description of study screening criteria and methodology, study quality assessment considerations, the data extraction strategy and links to any repositories/databases of relevant references.Tabular summaries and links to relevant supporting documentation are encouraged, wherever possible. More help

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

In vitro experiments showed that S-glutathionylation of eNOS significantly decreased NO activity in dose-dependent manner and greatly increased superoxide generation (Chen et al., 2010). NOS inhibitor L-NAME partially blocked superoxide generation. These results were observed in bovine aortic endothelial cells (BAECs) and in aortae of spontaneously hypertensive (SHR) rats. Treatment of BAECs with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of glutathione reductase, induced eNOS S-glutathionylation, resulting in decreased NO and increased superoxide generation. Gene silencing of eNOS in BAECs also induced superoxide production. In aortae of SHR rats, S-glutathionylation as determined by immunohistology was associated with a decrease in endothelium-dependent vasodilation as a result of decreased NO. Exposure of human aortic endothelial cells (HAECs) to ultrafine particles (UFP) caused S-glutathionylation of eNOS and a dose-dependent decrease in NO production (Du et al., 2013). Decreased NO production was found to be mediated by S-glutathionylation since overexpression of glutaredoxin, an inhibitor of S-glutathionylation, significantly reduced UPF-mediated decrease in NO production. Cardiac reperfusion patients exhibited decreased eNOS activity which was identified to be a result of eNOS S-glutathionylation (Jayaram et al., 2015). Additional evidence was observed in BAECs undergoing hypoxia and reoxygenation in which eNOS S-glutathionylation increased by three-fold compared to control cells and NO production was decreased (De Pascali et al., 2014). These effects were reversed with treatment of N-acetyl-l-cysteine, which increased cellular concentration of GSH. These results demonstrate a clear interaction between S-glutathionylation and eNOS uncoupling, therefore this link has strong biological plausibility.

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

No uncertainties or inconsistencies were found for this KER.

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
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
Define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits. More help

Domain of Applicability

A free-text section of the KER description that the developers can use to explain their rationale for the taxonomic, life stage, or sex applicability structured terms. More help

The evidence supporting this key event relationship are from human subjects, HAECs, BAECs, and SHR rats (Chen et al., 2010; De Pascali et al., 2014; Du et al., 2013; Jayaram et al., 2015).


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

Chen, C.-A., Wang, T.-Y., Varadharaj, S., Reyes, L.A., Hemann, C., Talukder, M.A.H., Chen, Y.-R., Druhan, L.J., and Zweier, J.L. (2010). S-glutathionylation uncouples eNOS and regulates its cellular and vascular function. Nature 468, 1115–1118.

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.

Du, Y., Navab, M., Shen, M., Hill, J., Pakbin, P., Sioutas, C., Hsiai, T.K., and Li, R. (2013). Ambient ultrafine particles reduce endothelial nitric oxide production via S-glutathionylation of eNOS. Biochem. Biophys. Res. Commun. 436, 462–466.

Galougahi, K.K., Liu, C.-C., Gentile, C., Kok, C., Nunez, A., Garcia, A., Fry, N.A.S., Davies, M.J., Hawkins, C.L., Rasmussen, H.H., et al. (2014). Glutathionylation Mediates Angiotensin II–Induced eNOS Uncoupling, Amplifying NADPH Oxidase-Dependent Endothelial Dysfunction. J. Am. Heart Assoc. 3, e000731.

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.

Zweier, J.L., Chen, C.-A., and Druhan, L.J. (2011). S-glutathionylation reshapes our understanding of endothelial nitric oxide synthase uncoupling and nitric oxide/reactive oxygen species-mediated signaling. Antioxid. Redox Signal. 14, 1769–1775.