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Relationship: 2775

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

Altered Signaling leads to Increase, Endothelial Dysfunction

Upstream event

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

Altered Signaling

Downstream event

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

Increase, Endothelial Dysfunction

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
Deposition of energy leads to vascular remodeling	adjacent	Moderate	Low	Cataia Ives (send email)	Open for citation & comment

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
human	Homo sapiens	Low	NCBI
rat	Rattus norvegicus	Moderate	NCBI

Sex Applicability

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

Sex	Evidence
Male	Moderate
Female	Low
Unspecific	Low

Life Stage Applicability

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

Term	Evidence
Adult	Moderate
Juvenile	Low

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

Altered signaling pathways can disrupt cellular homeostasis and induce endothelial dysfunction, characterized by a prolonged state of endothelial activation (Deanfield et al., 2007). Signaling pathways involved in triggering endothelial dysfunction include the p53-p21 pathway, the Akt/phosphtidylinositol-3-kinase (PI3K)/mechanistic target of rapamycin (mTOR) pathway, the RhoA-Rho-kinase pathway, and the acid sphingomyelinase (ASM)/ceramide (Cer) pathway (Venkatsulu et al., 2018; Soloviev et al., 2019; Wang et al., 2016). Activation of the signaling molecule p53 by phosphorylation enhances its stability, leading to cell cycle arrest and premature senescence in endothelial cells and can alternatively lead to a caspase cascade resulting in cellular apoptosis. Activation of the sphingomyelinase ceramide pathway can also contribute to endothelial apoptosis through production of ceramide that activates mitogen-activated protein kinase (MAPK) and extracellular-signal-regulated kinase (ERK). Signaling molecules MAPK and ERK can also be activated as a direct response to a stressor and prompt a cascade of events resulting in endothelial cell apoptosis. Impairment of the Akt/PI3K/mTOR pathway can lead to apoptosis by preventing cell survival signaling and can also lead to downregulation of Rho cytoskeletal proteins for senescence of endothelial cells (Venkatesulu et al., 2018; Soloviev et al., 2019; Nagane et al., 2021; Ramadan et al., 2021; Hughson et al., 2018).

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

The strategy for collating the evidence on radiation stressors to support the relationship is described in Kozbenko et al 2022. Briefly, a scoping review methodology was used to prioritize studies based on a population, exposure, outcome, endpoint statement.

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

Much of the evidence for this relationship comes from in vitro studies; further work is needed to determine the certainty of the relationship at the tissue level.

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	Details	Effects on the KER	References
Drug	Ceramide-6 (Cer-6)	Increases downstream caspase-3 and apoptosis	(Cheng et al., 2017; Su et al., 2020)
Media	Mesenchymal stem cell conditioned media	Prevented an increase in cleaved capsase-3, increased both Akt and p-Akt, and decreased apoptosis	(Chang et al., 2017)
Drug	Y27632 (Rho kinase inhibitor)	Recovered contractile response that was attenuated by HU	(Summers et al., 2008)
Drug	Desipramine (dpm) (ASM inhibitor)	Partially decreased caspase-3 and apoptosis	(Cheng et al., 2017; Su et al., 2020)
Drug	Dopexin hydrochloride (DOX) (ASM inhibitor)	Partially decreased caspase-3 and apoptosis	(Cheng et al., 2017; Su et al., 2020)

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 following are a few examples of quantitative understanding of the relationship. All data that is represented is statistically significant unless otherwise indicated.

Response-response Relationship

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

Dose/incidence concordance

Reference	Experiment Description	Result
Yentrapalli et al., 2013a	In vitro. Human umbilical vein endothelial cells (HUVECs) were irradiated with ¹³⁷Cs gamma radiation at 1.4 mGy/h or 2.4 mGy/h dose rates over a period of 12 weeks. Signaling molecules were used as measures of altered signaling. Cell senescence was used as a measure of endothelial dysfunction.	1.4 mGy/h dose rate: This dose rate led to alterations in the Akt/PI3K/mTOR pathway including a 3-fold increase in p21, a 0.7-fold decrease in p-Akt and PI3K, and a 0.8-fold decrease in mTOR. However, this dose rate did not induce endothelial dysfunction (no significant changes in SA-β-gal staining). 2.4 mGy/h dose rate: This dose rate led to alterations in the Akt/PI3K/mTOR pathway including a 3-fold increase in p21, a 1.5-fold increase in Akt, a 0.7-fold decrease in p-Akt and PI3K, a 0.8-fold decrease in mTOR and a 0.5-fold decrease in p-ERK. This dose rate induced endothelial dysfunction as indicated by a 2-fold increase in SA-β-gal staining, a marker for endothelial cell senescence.
Yentrapalli et al., 2013b	In vitro. HUVECs were irradiated with ¹³⁷Cs gamma radiation at a 4.1 mGy/h dose rate over the course of 6 weeks. Signaling molecules were used as measures of altered signaling. Cell senescence was used as a measure of endothelial dysfunction.	Chronic irradiation led to a 2.5-fold increase in p-p53, a key signaling molecule in initiating endothelial cell senescence, after week 6 (4.13 Gy). There was no significant change in total p53 or p-ERK2 at any time point, while total ERK2 showed a 0.5-fold decrease after 3 weeks (2.07 Gy). p21, which acts downstream of p53, increased 3.5-fold by week 6 (4.13 Gy). Alterations in the above signaling molecules correlated with an increase in endothelial dysfunction as indicated by a 1.5-fold increase in SA-β-gal staining, a marker for endothelial cell senescence, after 3 weeks and 3-fold after 6 weeks (4.13 Gy).
Chang et al., 2017	In vitro. HUVECs were irradiated with 10 Gy of X-rays. Signaling molecules were used as measures of altered signaling. Apoptosis was used as a measure of endothelial dysfunction.	A 2-fold increase in cleaved caspase-3, part of the apoptosis signaling cascade, in the irradiated endothelial cells was correlated with an increase in endothelial dysfunction indicated by a 4-fold increase in the percentage of apoptotic cells.
Summers et al., 2008	In vivo. Adult male Wistar rats underwent 20-day HU after which abdominal aortas were harvested. Signaling molecules were used as measures of altered signaling. Contractile response was used as a measure of endothelial dysfunction.	Following HU, signaling molecule RhoA decreased by 0.5-fold and endothelial dysfunction was induced in the form of reduced contractile response to phenylephrine by 0.5-fold.
Su et al., 2020	In vivo. Sprague-Dawley male rats underwent 4 weeks of HU, following which cerebral and mesenteric arteries were harvested. Signaling molecules were used as measures of altered signaling. Apoptosis was used as a measure of endothelial dysfunction.	Simulated microgravity revealed a decrease in signaling molecules ASM and Cer in cerebral arteries but an increase in mesenteric arteries of rats. Caspase-3, a signaling molecule in the apoptosis cascade, decreased 0.5-fold in cerebral arteries and increased 2-fold in mesenteric arteries. This was associated with an increase in endothelial function in cerebral arteries by decreasing apoptosis 0.3-fold and an increase in endothelial dysfunction in mesenteric arteries by increasing apoptosis 2-fold.
Cheng et al., 2017	In vivo. Sprague-Dawley male rats underwent 4 weeks of hindlimb unloading following which carotid arteries were harvested. Signaling molecules were used as measures of altered signaling. Apoptosis was used as a measure of endothelial dysfunction.	2 weeks of simulated microgravity resulted in a 0.6-fold decrease in signaling molecules ASM and caspase-3, which led to a decrease of endothelial dysfunction indicated by 0.5-fold reduced apoptosis in the carotid arteries of rats.

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

Time concordance

Reference

Experiment Description

Result

Yentrapalli et al., 2013a

In vitro. HUVECs were irradiated with ¹³⁷Cs gamma radiation at 1.4 mGy/h or 2.4 mGy/h dose rates over a period of 10 weeks. Signaling molecules were used as measures of altered signaling. Cell senescence was used as a measure of endothelial dysfunction.

1.4 mGy/h dose rate: This dose rate led to alterations in the Akt/PI3K/mTOR pathway including a 3-fold increase in p21 after 10 weeks, a 0.7-fold decrease in p-Akt and PI3K after 6 and 10 weeks, and a 0.8-fold decrease in mTOR after 10 weeks. However, this dose rate did not induce endothelial dysfunction (no significant changes in SA-β-gal staining at any timepoint).

2.4 mGy/h dose rate: This dose rate caused alterations in the Akt/PI3K/mTOR pathway including a 3-fold increase in p21 after 10 weeks, a 1.5-fold increase in Akt after 1 week, a 0.7-fold decrease in p-Akt and PI3K after 6 and 10 weeks, a 0.8-fold decrease in mTOR and a 0.5-fold decrease in p-ERK after 10 weeks. This dose rate induced endothelial dysfunction indicated by a 2-fold increase in SA-β-gal staining, after 12 weeks.

Yentrapalli et al., 2013b

In vitro. HUVECs were irradiated with ¹³⁷Cs gamma radiation at a 4.1 mGy/h dose rate over the course of 6 weeks. Signaling molecules were used as measures of altered signaling. Cell senescence was used as a measure of endothelial dysfunction.

Chronic irradiation led to a 2.5-fold increase in p-p53, a key signaling molecule in initiating endothelial cell senescence, after week 6 (4.13 Gy). There was no significant change in total p53 or p-ERK2 at any time point, while total ERK2 showed a 0.5-fold decrease after 3 weeks (2.07 Gy). p21, which acts downstream of p53, increased 3.5-fold by week 6 (4.13 Gy). Alterations in the above signaling molecules correlated with an increase in endothelial dysfunction as indicated by a 1.5-fold increase in SA-β-gal staining after 3 weeks and 3-fold after 6 weeks (4.13 Gy).

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

Not identified.

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

Evidence for this KER is supported through in vivo rat and in vitro human studies. The in vivo studies were conducted in male animals, although the relationship is still plausible in females. The in vivo studies were undertaken in adolescent and adult rats.