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Relationship: 2878

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

Depletion, GSH leads to Increased, Reactive oxygen species

Upstream event

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

Depletion, GSH

Downstream event

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

Increased, Reactive oxygen species

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
Glutathione conjugation leading to reproductive dysfunction via oxidative stress	adjacent	High	High	Allie Always (send email)	Under Development: Contributions and Comments Welcome

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

Sex Applicability

An indication of the the relevant sex for this KER. More help

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER. More help

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

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 Map 2.0

ID	Experimental Design	Species	Upstream Observation	Downstream Observation	Citation (first author, year)	Notes

Evidence Map

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help

Title	First Author	Biological Plausibility	Dose Concordance	Temporal Concordance	Incidence Concordance

Biological Plausibility

Dose Concordance Evidence

Temporal Concordance Evidence

Incidence Concordance Evidence

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

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

Modulating Factor (MF)	MF Specification	Effect(s) on the KER	Reference(s)
antioxidant	vitamin E	restores the activity of antioxidant enzymes	Singh, Sandhir, and Kiran 2010

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

The close relation between GSH depletion and increase in ROS levels is a well-established biological process, which is a result of diverse experimental evidence.

Response-response Relationship

Provides sources of data that define the response-response relationships between the KEs. More help

Drop in GSH levels and increase in ROS generation changes cellular redox potential, which can be calculated by the Nernst equation (Han et al. 2006):

where E_cell is cell electrochemical voltage, E^o is the electromotive force, R is molar gas constant, T is the temperature in Kelvin, F is the Faraday constant, n is the number of electrons transferred in the reaction, and Q is [GSH]2/[GSSG].

If GSH levels drop until a certain threshold (~30 - 40% of depletion) in mitochondria, there is an excessive H₂O₂ release in cells (Han et al. 2006) and, hence, ROS exacerbation.

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

For HT22 cells exposed to 50 µM BSO (for 10 h), ROS production occurs in two phases: an initial slow increase for the first 6 h, followed by a much higher rate. The latter high rate of increase in ROS only starts after the cellular GSH levels drop to nearly zero (Tan et al. 1998).

Moreover, isolated rat hepatocyte suspensions exposed to DEM (0.5, 1, 2.5 and 5 mM) for 5 h reach maximum levels of GSH depletion after 1 h of exposure (Tirmenstein et al. 2000), whereas the maximum increase in ROS levels is observed only after four hours at the two highest concentrations of each depleter.

GSH has its levels reduced by more than 95% in PW cells after around 8 h of exposure to BSO and reacher maximum depletion level at 48 h, when mitochondrial GSH supplies become undetectable as well, whereas ROS levels undergo a slight increase only 24 h post-exposure and reaches maximum values after 60 h of treatment (Armstrong et al. 2002).

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