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Relationship: 948

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 Oxidation, Glutathione

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

Oxidation, Glutathione

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

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

Under physiological conditions, glutathione (GSH) functions as an anti-oxidant by defending the cell from oxidative stress (Kalinina et al., 2014). It is predominantly found in the reduced form while the oxidized form glutathione disulfide (GSSG) generally does not exceed 1% of its total cellular content. Exposure to oxidants like peroxides leads to the oxidation of intracellular GSH, resulting in the formation of GSSG which alters the redox state of the cell (Pullar et al., 2001). This imbalance in the GSH/GSSG ratio is a marker of oxidative stress.

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

Multiple studies demonstrated that oxidative stress leads to the oxidation of GSH in the vascular endothelium, thus providing extensive understanding of the mechanistic relationship between these key events and strong biological plausibility. Exposure of human umbilical endothelial cells (HUVECs) to tert-butyl hydroperoxide (tBH), hydrogen peroxide (H₂O₂), and diamide caused a decrease in levels of GSH, which is indicative of its oxidation to GSSG (Montecinos et al., 2007; Park et al., 2013; Schuppe et al., 1992; van Gorp et al., 2002, 1999). Treatment with methylglyoxal and glucose also significantly reduced GSH levels in HUVECs and rat aortic endothelial cells (Dhar et al., 2010). Additional support for this link was observed in studies following ischemia-reperfusion injury and ultrafine particle exposure in bovine aortic endothelial cells and human aortic endothelial cells, respectively (De Pascali et al., 2014; Du et al., 2013).

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

Include consideration of temporal concordance here

The following studies demonstrated a dose-dependent relationship between known inducers of oxidative stress and GSH levels; therefore, the empirical support for this link is moderate.

Tert-butyl hydroperoxide treatment (0.1 mM) decreased GSH levels immediately after one minute to 30% of the resting value (van Gorp et al., 1999). The percentage of GSH slowly increased to 41% after 10 minutes and to 68% after 60 minutes, but did not fully restore to 100%. Higher concentrations of tBH led to more severe GSH oxidation.

Treatment of HUVECs with H₂O₂ (0.01-1 mM) caused a dose-dependent decrease in GSH levels after 15 minutes followed by a slow recovery phase (Montecinos et al., 2007).

Methylglyoxal (30 μM) and high concentrations of glucose (25 mM) significantly increased ROS levels and reduced GSH levels in HUVECs and rat aortic endothelial cells after 24 hours (Dhar et al., 2010), showing a dependency between oxidative stress and GSH oxidation.

Exposure to 50 μg/mL ultrafine particles (diameter<200nm) for 6 hours led to a decrease in GSH levels from 17.1±1.8 μM to 12.0±2.4 μM and an increase in GSSG from 0.62±0.26 μM to 1.60±0.2 μM in human aortic endothelial cells (Du et al., 2013)

In HUVECs, H₂O₂ treatment at doses of 100 μM, 200 μM, and 300 μM increased ROS production to 152%, 130% and 182%, respectively compared to control. This dose-dependent change was accompanied by GSH depletion (21.3% depletion at 200 μM H₂O₂ and 21.4% depletion at 300 μM H₂O₂) (Park et al., 2013).

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

One study reported that only a small amount of GSH was oxidized to GSSG in a concentration-dependent manner when HUVECs were exposed to hypochlorous acid (HOCl) while the remaining GSH was converted to another product glutathione sulfonamide. This discrepancy may be due to the different oxidant used in this study (Pullar et al., 2001).

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

Is it known how much change in the first event is needed to impact the second? Are there known modulators of the response-response relationships? Are there models or extrapolation approaches that help describe those relationships?

From the studies mentioned above, it appears that any oxidant (e.g. tBH, H₂O₂, ultrafine particles) with a minimum concentration of 10 μM would be sufficient to induce oxidation of GSH and cause an increase in GSSG levels. However, treatment with a concentration of25 nM of HOCl was shown to oxidize GSH, but did not produce GSSG (Pullar et al., 2001).

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

There are many studies showing oxidation of GSH following oxidant exposure in human endothelial cells, particularly umbilical and aortic endothelial cells (Dhar et al., 2010; Du et al., 2013; Montecinos et al., 2007; Park, 2013; Schuppe et al., 1992; van Gorp et al., 1999, 2002), while two studies in rat and bovine aortic endothelial cells support this relationship (Dhar et al., 2010; De Pascali et al., 2014).

References

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

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.

Dhar, A., Dhar, I., Desai, K.M., and Wu, L. (2010). Methylglyoxal scavengers attenuate endothelial dysfunction induced by methylglyoxal and high concentrations of glucose. Br. J. Pharmacol. 161, 1843–1856.

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.

Kalinina, E.V., Chernov, N.N., and Novichkova, M.D. (2014). Role of glutathione, glutathione transferase, and glutaredoxin in regulation of redox-dependent processes. Biochem. Biokhimii︠a︡ 79, 1562–1583.

Montecinos, V., Guzmán, P., Barra, V., Villagrán, M., Muñoz-Montesino, C., Sotomayor, K., Escobar, E., Godoy, A., Mardones, L., Sotomayor, P., et al. (2007). Vitamin C is an essential antioxidant that enhances survival of oxidatively stressed human vascular endothelial cells in the presence of a vast molar excess of glutathione. J. Biol. Chem. 282, 15506–15515.

Park, W.H. (2013). The effects of exogenous H2O2 on cell death, reactive oxygen species and glutathione levels in calf pulmonary artery and human umbilical vein endothelial cells. Int. J. Mol. Med. 31, 471–476.

Pullar, J.M., Vissers, M.C., and Winterbourn, C.C. (2001). Glutathione oxidation by hypochlorous acid in endothelial cells produces glutathione sulfonamide as a major product but not glutathione disulfide. J. Biol. Chem. 276, 22120–22125.

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

van Gorp, R.M.A., Heeneman, S., Broers, J.L.V., Bronnenberg, N.M.H.J., van Dam-Mieras, M.C.E., and Heemskerk, J.W.M. (2002). Glutathione oxidation in calcium- and p38 MAPK-dependent membrane blebbing of endothelial cells. Biochim. Biophys. Acta 1591, 129–138.

van Gorp, R.M., Broers, J.L., Reutelingsperger, C.P., Bronnenberg, N.M., Hornstra, G., van Dam-Mieras, M.C., and Heemskerk, J.W. (1999). Peroxide-induced membrane blebbing in endothelial cells associated with glutathione oxidation but not apoptosis. Am. J. Physiol. 277, C20–C28.