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Relationship: 1698

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

Peptide Oxidation leads to S-Glutathionylation, eNOS

Upstream event

The causing Key Event (KE) in a Key Event Relationship (KER). More help

Peptide Oxidation

Downstream event

The responding Key Event (KE) in a Key Event Relationship (KER). More help

S-Glutathionylation, eNOS

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	Moderate	Low	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
rat	Rattus norvegicus	Moderate	NCBI
human	Homo sapiens	High	NCBI
mouse	Mus musculus	High	NCBI
cow	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

Oxidation of GSH results in the formation of a disulphide-bridged glutathione dimer (GSSG). GSSG is either rapidly re-reduced back to GSH by nicotinamide adenine dinucleotide phosphate (NADPH)-dependent GSSG-reductases or extruded from the cell by adenosine triphosphate (ATP)-dependent translocases. However, when these mechanisms become overwhelmed by high local oxidant concentrations, GSSG can interact with protein thiol groups to form protein-GSSG adducts, a process termed S-glutathionylation. Interestingly, glutathione disulfide-protein formation has been suggested to occur with a certain degree of specificity to cellular proteins, since protein thiol groups exhibit a considerable heterogeneity in terms of their individual pK_a values and their location in protein structures (Schuppe et al. 1992). The oxidation of GSH to GSSG elevates levels of GSSG, which then covalently bind to critical serine residues on endothelial nitric oxide synthase (eNOS; Chen et al 2010, Du et al. 2013, De Pascali et al. 2014).

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

When antioxidant defence mechanisms become overwhelmed by high local oxidant concentrations, GSSG can interact with protein thiol groups to form protein-GSSG adducts, a process termed S-glutathionylation (Schuppe et al. 1992).

Hypoxia/reoxygenation-induced oxidative stress (associated with ischaemia-reperfusion injury) was shown to deplete GSH in bovine aortic endothelial cells, which led to S-glutathionylation of eNOS and eNOS uncoupling. This phenomenon was partially reversible, in bovine aortic endothelial cells and rat aortic rings, by raising intracellular GSH levels upon administration of N-acetylcysteine (Chen et al. 2010, DePascali et al. 2014).

Empirical Evidence

Provides specific (citable) evidence that supports the idea of a change in the upstream KE (KEupstream) leading to, or being associated with, a subsequent change in the downstream KE (KEdownstream), assuming the perturbation of KEupstream is sufficient. More help

Chen and colleagues (2010) have shown that eNOS is particularly sensitive to S-glutathionylation at cysteine residues 689 and 908 of the reductase domain, a phenomenon that is dose-dependent with application of exogenous GSSG. This finding was corroborated by Peng et al. (2015) using mutated eNOS constructs in E. coli, demonstrating that superoxide was produced by the eNOS phosphorylation site in the reductase domain.

Wu et al. (2014) studied responses in human lung microvascular endothelial cells to lipopolysaccharide (LPS) in vitro. Upon LPS administration, NADPH oxidase 2 (NOX2) expression levels were increased with a subsequent rise in superoxide production, which led to S-glutathionylation of eNOS. Furthermore, in mice, co-immunoprecipitation studies revealed that NOX2 associated with eNOS, and that S-glutathionylation in response to LPS was much more apparent in elderly animals compared to younger animals. Similar observations were made by De Pascali et al. (2014) following hypoxia-induced oxidative stress in bovine aortic endothelial cells.

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

Quantitative data for humans is very limited.

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

Quantitative Understanding of the Linkage

Captures information that helps to define how much change in the upstream KE, and/or for how long, is needed to elicit a detectable and defined change in the downstream KE. More help

Chen et al. (2013) demonstrated that co-administration of glutaredoxin-1 and GSH reversed GSSG-mediated eNOS S-glutathionylation and restored eNOS-mediated NO production, also in bovine aortic cells. Interestingly, inhibition of eNOS function occurred when the GSH/GSSG ratio was >0.2 and function was restored at a ratio of <0.1.

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

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 above evidence demonstrates similar responses to stressors in cows, mice and humans. A functional response using aortic rings was demonstrated in rats.

References

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

Chen CA, Wang TY, Varadharaj, S et al. S-glutathionylation uncouples eNOS and regulates its cellular and vascular function. Nature (2010) 468: 1115–1118.

Chen CA, De Pascali F, Basye A et al. Redox modulation of endothelial nitric oxide synthase by glutaredoxin-1 through reversible oxidative post-translational modification. (2013) Biochemistry. 52(38):6712-23

Dhar A, Dhar I, Desai KM et al. Methylglyoxal scavengers attenuate endothelial dysfunction induced by methylglyoxal and high concentrations of glucose. (2010) Br. J. Pharmacol. 161: 1843–1856.

De Pascali F, Hemann C, Samons, K et al. Hypoxia and reoxygenation induce endothelial nitric oxide synthase uncoupling in endothelial cells through tetrahydrobiopterin depletion and S-glutathionylation. Biochemistry (2014). 53 : 3679–3688.

Du Y, Navab M, Shen M, et al. Ambient ultrafine particles reduce endothelial nitric oxide production via S-glutathionylation of eNOS. Biochem. Biophys. Res. Commun. (2013) 436 : 462–466.

Peng H, Zhuang Y, Chen Y et al. The Characteristics and Regulatory Mechanisms of Superoxide Generation from eNOS Reductase Domain. (2015) PLoS One. 10(10):e0140365

Schuppe I, Moldéus P, and Cotgreave IA. Protein-specific S-thiolation in human endothelial cells during oxidative stress. (1992) Biochem. Pharmacol. 44: 1757–1764.

Wu F, Szczepaniak WS, Shiva S et al. Nox2-dependent glutathionylation of endothelial NOS leads to uncoupled superoxide production and endothelial barrier dysfunction in acute lung injury. (2014) Am J Physiol Lung Cell Mol Physiol. 307(12):L987-97.