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Event: 1632

Key Event Title

A descriptive phrase which defines a discrete biological change that can be measured. More help

Increase in reactive oxygen and nitrogen species (RONS)

Short name
The KE short name should be a reasonable abbreviation of the KE title and is used in labelling this object throughout the AOP-Wiki. More help
Increase in RONS
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Biological Context

Structured terms, selected from a drop-down menu, are used to identify the level of biological organization for each KE. More help
Level of Biological Organization
Molecular

Cell term

The location/biological environment in which the event takes place.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help

Organ term

The location/biological environment in which the event takes place.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help

Key Event Components

The KE, as defined by a set structured ontology terms consisting of a biological process, object, and action with each term originating from one of 14 biological ontologies (Ives, et al., 2017; https://aopwiki.org/info_pages/2/info_linked_pages/7#List). Biological process describes dynamics of the underlying biological system (e.g., receptor signalling).Biological process describes dynamics of the underlying biological system (e.g., receptor signaling).  The biological object is the subject of the perturbation (e.g., a specific biological receptor that is activated or inhibited). Action represents the direction of perturbation of this system (generally increased or decreased; e.g., ‘decreased’ in the case of a receptor that is inhibited to indicate a decrease in the signaling by that receptor).  Note that when editing Event Components, clicking an existing Event Component from the Suggestions menu will autopopulate these fields, along with their source ID and description.  To clear any fields before submitting the event component, use the 'Clear process,' 'Clear object,' or 'Clear action' buttons.  If a desired term does not exist, a new term request may be made via Term Requests.  Event components may not be edited; to edit an event component, remove the existing event component and create a new one using the terms that you wish to add.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help

Key Event Overview

AOPs Including This Key Event

All of the AOPs that are linked to this KE will automatically be listed in this subsection. This table can be particularly useful for derivation of AOP networks including the KE. Clicking on the name of the AOP will bring you to the individual page for that AOP. More help
AOP Name Role of event in AOP Point of Contact Author Status OECD Status
Increased DNA damage leading to breast cancer KeyEvent Jessica Helm (send email) Under development: Not open for comment. Do not cite Under Development
RONS leading to breast cancer MolecularInitiatingEvent Jessica Helm (send email) Under development: Not open for comment. Do not cite Under Development
Ionizing Radiation-Induced AML KeyEvent Dag Anders Brede (send email) Under development: Not open for comment. Do not cite
Deposition of energy leads to reduced cocoon hatchability MolecularInitiatingEvent Deborah Oughton (send email) Under development: Not open for comment. Do not cite

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 KE.In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help

Life Stages

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

Sex Applicability

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

Key Event Description

A description of the biological state being observed or measured, the biological compartment in which it is measured, and its general role in the biology should be provided. More help

Reactive oxygen and nitrogen species (RONS) are highly reactive oxygen- and nitrogen-based molecules that often contain or generate free radicals. Key molecules include superoxide ([O2]•−), hydrogen peroxide (H2O2), hydroxyl radical ([OH]•), lipid peroxide (ROOH), nitric oxide ([NO]•, and peroxynitrite ([ONOO-]) (Dickinson and Chang 2011; Egea, Fabregat et al. 2017)

RONS are generated in the course of cellular respiration, metabolism, cell signaling, and inflammation (Dickinson and Chang 2011; Egea, Fabregat et al. 2017). Superoxide and hydrogen peroxide are commonly produced by the mitochondrial electron transport chain and cytochrome c and by membrane bound NADPH oxidases and related molecules. Hydrogen peroxide is also made by the endoplasmic reticulum in the course of protein folding. Nitric oxide is produced at the highest levels by nitric oxide synthase in endothelial cells and phagocytes. The other species are produced by reactions with superoxide or peroxide, or by other free radicals or enzymes.

RONS activity is principally local. Most reactive oxygen species (ROS) have short half-lives, ranging from nano- to milliseconds, so diffusion is limited, while reactive nitrogen species (RNS) nitric oxide or peroxynitrate can survive long enough to diffuse across membranes (Calcerrada, Peluffo et al. 2011). Consequently, local concentrations of ROS are much higher than average cellular concentrations and signaling is typically controlled by colocalization with redox buffers (Dickinson and Chang 2011; Egea, Fabregat et al. 2017). The effects of ROS and RNS are countered by cellular antioxidants, with glutathione and peroxiredoxins playing a major role (Dickinson and Chang 2011). Glutathione is slower but broad acting, while peroxiredoxins act quickly and are specific to peroxides. Peroxiredoxins are effective at low peroxide concentrations but can be deactivated at higher concentrations, suggesting the cellular response to peroxides may sometimes be non-linear.

Although their existence is limited temporally and spatially, reactive oxygen species (ROS) interact with other RONS or with other nearby molecules to produce more ROS and participate in a feedback loop to amplify the ROS signal, which can increase Reactive Nitrogen Species (RNS). Both ROS and RNS also move into neighboring cells and ROS can increase intracellular RONS signaling in neighboring cells (Egea, Fabregat et al. 2017).

RONS can modify a range of targets including amino acids, lipids, and nucleic acids to inactivate or alter target functionality (Calcerrada, Peluffo et al. 2011; Dickinson and Chang 2011; Go and Jones 2013; Ravanat, Breton et al. 2014; Egea, Fabregat et al. 2017). For example, phosphatases including the tumor suppressor PTEN can be reversibly deactivated by oxidation, and the movement of HDAC4 is peroxide dependent. Elevated ROS are implicated in proliferation and maintenance of stem cell population size (Dickinson and Chang 2011) and conversely in differentiation of stem cells and oncogene-induced senescence (Egea, Fabregat et al. 2017).

How It Is Measured or Detected

A description of the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements.These can range from citation of specific validated test guidelines, citation of specific methods published in the peer reviewed literature, or outlines of a general protocol or approach (e.g., a protein may be measured by ELISA). Do not provide detailed protocols. More help

RONS is typically measured using fluorescent or other probes that react with RONS to change state, or by measuring the redox state of proteins or DNA (Dickinson and Chang 2011; Wang, Fang et al. 2013; Griendling, Touyz et al. 2016). Optimal methods for RONS detection have high sensitivity, selectivity, and spatiotemporal resolution to distinguish transient and localized activity, but most methods lack one or more of these parameters.

Molecular probes that indicate the presence of RONS species vary in specificity and kinetics (Dickinson and Chang 2011; Wang, Fang et al. 2013; Griendling, Touyz et al. 2016). Small molecule fluorescent probes can be applied to any tissue in vitro, but cannot be finely targeted to different cellular compartments. The non-selective probe DCHF was widely used in the past, but can produce false positive signals and is no longer recommended. Newer more selective small molecule probes such as boronate-based molecules are being developed but are not yet widely used. Alternatively, fluorescent protein-based probes can be genetically engineered, expressed in vivo, and targeted to cellular compartments and specific cells. However, these probes are very sensitive to pH in the physiological range and must be carefully controlled.  EPR (electron paramagnetic resonance spectroscopy) provide the most direct and specific detection of free radicals, but requires specialized equipment.

Alternative methods involve the detection of redox-dependent changes to cellular constituents such as proteins, DNA, lipids, or glutathione (Dickinson and Chang 2011; Wang, Fang et al. 2013; Griendling, Touyz et al. 2016). However, these methods cannot generally distinguish between the oxidative species behind the changes, and cannot provide good resolution for kinetics of oxidative activity.

Table 1. Common methods for detecting oxidative activity

Target

Name

Method

Strengths/Weaknesses

Hydrogen peroxide- extracellular

AmplexRed

Small molecule fluorescent probes

Can be applied to any tissue in vitro.

Hydrogen peroxide- mitochondrial

MitoPy1

Small molecule fluorescent probes

Can be applied to any tissue in vitro.

Hydrogen peroxide

HyPer

Protein-based fluorescent probes

Sensitive, can be targeted to specific cells and compartments. Slower and pH sensitive.

Hydrogen peroxide

HyPer3

Protein-based fluorescent probes

Rapid kinetics and larger dynamic range, can be targeted to specific cells and compartments. Sensitive to pH, less sensitive to H2O2.

Hydrogen peroxide

Boronate-based indicators

Small molecule fluorescent probe

Selective for H2O2 but can interact with peroxynitrite.

Superoxide- intracellular

DHE (dihydroethidium)

Small molecule fluorescent probe

Can be applied to any tissue in vitro, but not targeted to different compartments.

Superoxide- intracellular

cpYFP

Protein-based fluorescent probes

Reversible. Can be targeted to specific cells and compartments.

Superoxide- mitochondrial

MitoSox

Small molecule fluorescent probe

Can be applied to any tissue in vitro.

Superoxide- mitochondrial

mt-cpYFP

Protein-based fluorescent probes

Reversible. Can be targeted to specific cells and compartments.

Superoxide- extracellular

nitroblue tetrazolium

Small molecule fluorescent probe

Can be applied to any tissue in vitro.

Superoxide- intracellular or extracelluar

various trityl probes

EPR

Very specific, but requires specialized equipment, not as sensitive in tissue.

Nitric oxide

Fe[DETC]2 and

Fe[MGD]2,

EPR

Very specific, but requires specialized equipment, not as sensitive in tissue.

Nitric oxide

DAF-FM

Small molecule fluorescent probe

Can be applied to any tissue in vitro, but not targeted to different compartments

Peroxynitrite

EMPO

EPR

Very specific, but requires specialized equipment, not as sensitive in tissue.

Peroxynitrite

Boronate-based indicators

Small molecule fluorescent probe

Selective for H2O2 but can interact with (is inhibited by) peroxynitrite.

Peroxynitrite

8-nitroguanine (DNA) content

HPLC-MS/MS

Destruction of sample required for measurement.

Non-specific oxidation

DCHF

Small molecule fluorescent probe

Very non selective, and can produce false positive signals.

Non-specific oxidation

roGFP or FRET

Protein-based fluorescent probes

Slow acting. Good to look at steady state activity.

Non-specific oxidation

ratio of reduced to oxidized glutathione or cysteine

Redox state detectors

Slow acting. Good to look at steady state activity. Destruction of sample required for measurement.

Non-specific oxidation

8-oxoguanine (DNA) or protein carbonyl content

HPLC-MS/MS

Destruction of sample required for measurement.

Non-specific oxidation

TBARS (thiobarbituric acid reactive substance)

Lipid peroxidation

Destruction of sample required for measurement.

Domain of Applicability

A description of the scientific basis for the indicated domains of applicability and the WoE calls (if provided).  More help

This KE is broadly applicable across species.

References

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