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Relationship: 2771

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

Oxidative Stress leads to Altered Signaling

Upstream event
The causing Key Event (KE) in a Key Event Relationship (KER). More help
Downstream event
The responding Key Event (KE) in a Key Event Relationship (KER). More help

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 High Low Vinita Chauhan (send email) Open for citation & comment
Deposition of Energy Leading to Learning and Memory Impairment adjacent High Low Vinita Chauhan (send email) Open for citation & comment
Deposition of energy leading to occurrence of bone loss adjacent High Low Vinita Chauhan (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
mouse Mus musculus High NCBI
rat Rattus norvegicus High NCBI
Pig Pig Moderate NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help
Sex Evidence
Male High
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 Moderate

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

Oxidative stress occurs when the production of free radicals exceeds the capacity of cellular antioxidant defenses (Cabrera & Chihuailaf, 2011). Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are both free radicals that can contribute to oxidative stress (Ping et al., 2020); however, ROS are more commonly studied than RNS (Nagane et al., 2021). ROS can mediate oxidative damage to biomacromolecules as they react with DNA, proteins and lipids, resulting in functional changes to these molecules (Ping et al., 2020). For example, ROS acting on lipids creates lipid peroxidation (Cabrera & Chihuailaf, 2011). 

Many signaling pathways control and maintain physiological balance within a living organism, and these can be impacted by oxidative stress. Excessive reactive oxygen and nitrogen species (RONS) during oxidative stress can modify biological molecules and directly cause DNA damage, which can lead to altered signal transduction pathways (Hughson, Helm & Durante, 2018; Lehtinen & Bonni, 2006; Nagane et al., 2021; Ping et al., 2020; Ramadan et al., 2021; Schmidt-Ullrich et al., 2000; Soloviev & Kizub, 2019; Wang, Boerma & Zhou, 2016; Venkatesulu et al., 2018; Zhang et al., 2016). Different cell types can express distinct cellular pathways that can have varied response to an increase in oxidative stress. For example, oxidative stress in endothelial cells has been shown to inhibit the insulin-like growth factor 1 receptor (IGF-1R) and phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) pathway and to activate the mitogen-activated protein kinase (MAPK) pathway, which can then have downstream detrimental effects (Ping et al., 2020). The MAPK family pathway is also activated in the central nervous system (CNS) in response to oxidative stress through calcium-induced phosphorylation of several kinases. These include phosphoinositide 3-kinase (PI3K), protein kinase A (PKA) and protein kinase C (PKC) and calcium/calmodulin-dependent protein kinase II (CaMKII) (Lehtinen & Bonni, 2006; Li et al., 2013; Ramalingam & Kim, 2012). Oxidative stress in bone cells can lead to increased expression of the receptor activator of nuclear factor kappa B ligand (RANKL) and Nrf2 activation (Tahimic & Globus, 2017; Tian et al., 2017). Following activation, Nrf2 then interferes with the activation of runt-related transcription factor 2 (Runx2), and depending on the level of oxidative stress, this may result in altered bone cell function (Kook et al., 2015).

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 Supporting this KER

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

Overall weight of evidence: High

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

Many reviews describe the role of oxidative stress in altered signaling. The mechanisms through which oxidative stress can contribute to changes in various signaling pathways are well-described. For example, oxidative stress can directly alter signaling pathways through protein oxidation (Ping et al., 2020; Schmidt-Ullrich et al., 2000; Valerie et al., 2007). Oxidation of cysteine and methionine residues, which are particularly sensitive to oxidation, can cause conformational change, protein expansion, and degradation, leading to changes in the protein levels of signaling pathways (Ping et al., 2020). Furthermore, oxidation of key residues in signaling proteins can alter their function, resulting in altered signaling. For example, oxidation of methionine 281 and 282 in the Ca2+/calmodulin binding domain of Ca2+/calmodulin-dependent protein kinase II (CaMKII) leads to constitutive activation of its kinase activity and subsequent downstream alterations in signaling pathways (Li et al., 2013; Ping et al., 2020). Similarly, during oxidative stress, tyrosine phosphatases can be inhibited by oxidation of a catalytic cysteine residue, resulting in increased phosphorylation of proteins in various signaling pathways (Schmidt-Ullrich et al., 2000; Valerie et al., 2007). Particularly relevant to this are the MAPK pathways. The extracellular signal-regulated kinase (ERK) pathway is activated by upstream tyrosine kinases and relies on tyrosine phosphatases for deactivation (Lehtinen & Bonni, 2006; Valerie et al., 2007). 

Furthermore, oxidative stress can indirectly influence signaling pathways through oxidative DNA damage which can lead to mutations or changes in the gene expression of proteins in signaling pathways (Ping et al., 2020; Schmidt-Ullrich et al., 2000; Valerie et al., 2007). DNA damage surveillance proteins like ataxia telangiectasia mutated (ATM) kinase and ATM/Rad3-related (ATR) protein kinase phosphorylate over 700 proteins, leading to changes in downstream signaling (Nagane et al., 2021; Schmidt-Ullrich et al., 2000; Valerie et al., 2007). For example, ATM, activated by oxidative DNA damage, phosphorylates many proteins in the ERK, p38, and Jun N-terminal kinase (JNK) MAPK pathways, leading to various downstream effects (Nagane et al., 2021; Schmidt-Ullrich et al., 2000). 

The response of oxidative stress on signaling pathways has been studied extensively in various diseases. Herein presented are examples relevant to a few cell types related to vascular disease, impaired learning and memory, and bone loss. Many other pathways are plausible but available research has highlighted these to be critical to disease. 

Endothelial cells: . Antioxidant enzymes and the glutathione redox buffer control the redox state of vascular tissues. However, the dysregulation of signaling pathways can occur in the endothelium when oxidative stress is favored (Soloviev & Kizub, 2019). Oxidative stress can activate the acidic sphingomyelinase (ASMase)/ceramide pathway, the MAPK pathways, the p53/p21 pathway, and the signaling proteins p16 and p21, as well as inhibit the PI3K/Akt pathway (Hughson, Helm & Durante, 2018; Nagane et al., 2021; Ping et al., 2020; Ramadan et al., 2021; Soloviev & Kizub, 2019; Wang, Boerma & Zhou, 2016). 

Bone cells: Oxidative stress can induce signaling changes in the Wnt/β-catenin pathway, the RANK/RANKL pathway, the Nrf2/HO-1 pathway, and the MAPK pathways (Domazetovic et al., 2017; Manolagas & Almeida, 2007; Tian et al., 2017).  

Brain cells: Oxidative stress can induce alterations to various pathways such as the PI3K/Akt pathway, cAMP response element-binding protein (CREB) pathway, the p53/p21 pathway, as well as the MAPK family pathways, including JNK, ERK and p38 (Lehtinen & Bonni, 2006; Ramalingam & Kim, 2012). 

Additionally, the electron transport chain in the mitochondria is an important source of ROS, which can damage mitochondria by inducing mutations in mitochondrial DNA. These mutations lead to mitochondrial dysfunction due to alterations in cellular respiration mechanisms that perpetuates oxidative stress and can then induce the release of signaling molecules related to apoptosis from the mitochondria. Pro-apoptotic markers (Bax, Bak and Bad) and anti-apoptotic markers (Bcl-2 and Bcl-xL) can regulate the caspase pathway that ultimately mediate apoptosis (Annunziato et al., 2003; Wang & Michaelis, 2010; Wu et al., 2019). 

The mechanisms of oxidative stress leading to altered signaling may be different for each pathway. For example, although both the PI3K/Akt and MAPK pathways can be regulated by insulin-like growth factor (IGF)-1, ROS results in selective inhibition of the IGF-1R/PI3K/Akt pathway by inhibiting the IGF-1 receptor (IGF-1R) activation of IRS1 (Ping et al., 2020). Additionally, ROS-induced MAPK activation can occur through Ras-dependent signaling. Firstly, oxygen radicals mediate the phosphorylation of upstream epidermal growth factor receptors (EGFRs) on tyrosine residues, resulting in increased binding of growth factor receptor-bound protein 2 (Grb2) and subsequent activation of Ras signaling (Lehtinen & Bonni, 2006). Direct inhibition of MAPK phosphatases with hydroxyl radicals also activates this pathway (Li et al., 2013). In another mechanism, ROS competitively inhibit the Wnt/β-catenin pathway through the activation of forkhead box O (FoxO), which are involved in the antioxidant response and require binding of β-catenin for transcriptional activity (Tian et al., 2017).

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
  • MAPK pathways can exhibit varied responses after exposure to oxidative stress. The expected response is an increase in the activity of the ERK, JNK, and p38 pathways as protein phosphatases, involved in the inactivation of MAPK pathways, are deactivated by oxidative stress (Valerie et al., 2007). Although some studies observe this (Azimzadeh et al., 2021; Sakata et al., 2015), others show a decrease (Fan et al., 2017; Yoo, Han & Kim, 2016) or varying changes (Azimzadeh et al., 2015) in the MAPK pathways.

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 

Fenofibrate (PPARα activator, PPARα is a transcription factor that can activate antioxidant response) 

Treatment of mice with 100 mg/kg of body weight daily for 2 weeks before and 2 weeks after radiation restored SOD activity, returned the level of phosphorylated MAPK proteins and increased Nrf2 levels. 

Azimzadeh et al., 2021 

Drug 

L-carnitine (antioxidant) 

L-carnitine injections (100 mg/kg) following irradiation resulted in decreased DHE staining, indicating ROS, and increased p-p38/p38 and p-Nrf2/Nrf2. 

Fan et al., 2017 

Drug 

N-acetyl cysteine (antioxidant) 

Treatment of osteoblast-like cells with 5 mM restored ROS levels, SOD activity, and the level of proteins in the Nrf2/HO-1 pathway. 

Kook et al., 2015 

Drug 

Curcumin (antioxidant) 

Treatment of osteoblast-like cells with 4 µM reduced ROS levels and the RANKL/OPG ratio. Treatment of rats with 40 mg/kg of body weight reduced oxidative stress and the RANKL/OPG ratio. 

Xin et al., 2015 

Drug 

Bradykinin potentiating factor (BFP)  

(antioxidant) 

Treatment with BFP (1ug/g) after irradiation showed decreased AngII and aldosterone levels compared to irradiation alone.  

Hasan, Radwan & Galal, 2020 

Media 

Hydrogen-rich  

(antioxidant) 

Osteoblasts in a medium consisting of 75% H2, 20% O2, and 5% CO2 (vol/vol/vol) showed a reduction in ROS production and restoration of normal signaling. 

Sun et al., 2013 

Drug 

Melatonin 

(antioxidant) 

Treatment with 200 nM melatonin reversed the effect of microgravity on Cu/Zn-SOD and Mn-SOD to control levels.  

Yoo, Han & Kim, 2016 

Drug 

Polyphenol S3  

Polyphenol S3 treatment reverses the effect of microgravity on CAT, SOD and MDA, returning the levels to near control values when S3 is used at high dose (60mg/kg/d). Runx2 mRNA levels and β-catenin/β-actin levels increased following treatment and simulated microgravity. 

Diao et al., 2018 

Drug 

Sildenafil 

Sildenafil (5 uM) inhibits O2- production and attenuates intracellular peroxynitrite in BAECs after 10 Gy irradiation. As well, ASMase activity and ceramide generation was inhibited. 

Wortel et al., 2019 

Drug 

DPI  

(NOX-inhibitor) 

Inhibits O2-  production and intracellular H2O2 in BAECs after 10 Gy irradiation. 

Wortel et al., 2019 

Drug 

Edaravone (EDA) which acts as a free radical scavenger 

EDA treatment was able to reduce the levels of ROS and consequently decrease the expression levels of phosphorylated JNK, p38 and ERK1/2. 

Zhao et al., 2013 

Drug 

Melandrii Herba extract (antioxidant) 

The extract was able to reduce the H2O2-induced phosphorylation of ERK1/2, JNK1/2 and p38 in human neuroblastoma SH-SY5Y cells. 

Lee et al., 2017 

Drug 

N-acetyl-L-cysteine (NAC) (antioxidant) 

Attenuated the effects of H2O2 in BV-2 murine microglial cells as treatment with NAC reduced c-Jun and ERK1/2 phosphorylation. 

Deng et al., 2012 

Drug 

Gallocatechin gallate (GCG) or epigallocatechin-3-gallate (EGCG), both of which have antioxidant properties 

GCG and EGCG inhibits ROS accumulation in mouse hippocampal-derived HT22 cells and Wistar rats, respectively. This consequently reduced glutamate-induced phosphorylation of MAPKs (ERK and JNK) and returned p53 to control levels. 

Park et al., 2021; El-Missiry et al., 2018 

Drug  

Cornus officinalis (CC) and fermented CC (FCC), both of which have antioxidant properties 

Both CC and FCC were able to reduce intracellular ROS generation in H2O2-induced neurotoxicity in SH-SY5Y human neuroblastoma cells. This was accompanied with a decrease in ERK1/2, JNK and p38 phosphorylation. 

Tian et al., 2020 

Drug 

L-165041, a PPARδ agonist (PPARα is a transcription factor that can activate antioxidant response). 

10 Gy of 137Cs irradiation resulted in an increase in intracellular ROS and c-Jun, MEK1/2 and ERK1/2 phosphorylation in BV-2 cells, all of which were attenuated with L-165041 treatment. 

Schnegg et al., 2012 

Drug 

Fucoxanthin (antioxidant) 

Fucoxanthin was able to inhibit the LPS-induced increase in intracellular ROS and phosphorylation of JNK, ERK and p38. 

Zhao et al., 2017 

Media 

Mesenchymal stem-cell conditioned medium (MSC-CM) 

MSC-CM was able to inhibit the X-ray-induced increase in ROS and MDA levels and decrease in SOD and GSH levels, resulting in activation of PI3/Akt. 

Huang et al., 2021 

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 

Azimzadeh et al., 2017 

In vitro. HCAECs were irradiated with 0.5 Gy of X-rays (0.5 Gy/min). Protein carbonylation and GSTO1 antioxidant levels were measured with a carbonylation assay and immunoblotting, respectively. Proteins from various signaling pathways including RhoGDI, p16, and p21 were measured with immunoblotting. 

After 0.5 Gy, carbonyl content increased a maximum of 1.2-fold and GSTO1 decreased a maximum of 0.78-fold. After 0.5 Gy, p-RhoGDI decreased a maximum of 0.7-fold, p16 increased a maximum of 1.5-fold, and p21 increased a maximum of 1.2-fold. 

Kenchegowda et al., 2018 

In vivo. Male 3- to 5-month-old Gottingen minipigs and Sinclair minipigs were whole-body irradiated with 1.7-2.3 Gy of 60Co gamma rays (0.6 Gy/min). Both survivors (n=23) and euthanized moribund animals (n=17) had measurements taken for oxidative stress and altered signaling taken from the heart. SOD, CAT, and p67 (subunit of NADPH oxidase/NOX, involved in producing superoxide) levels were determined with western blot. ELISA and western blot were used to measure altered signaling in the IGF/PI3K/Akt pathway. 

Compared to survivors, radiation induced a 2.1-fold increase in p67, 0.87-fold decrease in SOD, and a 0.83-fold decrease in CAT (non-significant, ns) in the deceased group. Compared to survivors, the ratio of activated (phosphorylated) to total IGF-1R and the ratio of activated (phosphorylated) to total Akt both decreased 0.5-fold in the deceased group. 

Kook et al., 2015 

In vitro. MC3T3-E1 osteoblast-like cells were irradiated with 2, 4, and 8 Gy of X-rays (1.5 Gy/min). ROS were measured with a fluorescent probe, and SOD, CAT, and GSH antioxidant activities were determined with assay kits. Protein levels in the Nrf2/HO-1 signaling pathway were determined by either western blot or RT-PCR. 

ROS increased linearly at 2 and 4 Gy up to 1.4-fold at 8 Gy (significant changes at 4 Gy and 8 Gy). GSH and SOD were decreased 0.7-fold at 4 Gy and 0.5-fold at 8 Gy (insignificant increases at 2 Gy). CAT was also decreased but not significantly. HO-1 increased 3.3-fold after 4 Gy and 4.9-fold after 8 Gy (insignificant increase at 2 Gy). Nrf2 increased 2.3-fold after 8 Gy. Runx2 mRNA was decreased 0.5-fold after 8 Gy. 

Bai et al., 2020 

In vitro. Rat-derived bone marrow-derived mesenchymal stem cells (bmMSCs) were irradiated with 2, 5, and 10 Gy of 137Cs gamma rays. Mitochondrial and cellular ROS levels were determined with fluorescent probes. RT-qPCR was performed to measure antioxidant enzyme expression. Protein expression in various signaling pathways was measured by western blot. 

Mitochondrial ROS increased 1.6-fold at 2 Gy (non-significant), 2-fold at 5 Gy, and 2.3-fold at 10 Gy. Cellular ROS increased 1.2-fold at 2 Gy, 1.5-fold at 5 Gy, and 2.1-fold at 10 Gy. Antioxidants SOD1, SOD2, and CAT all decreased about 0.9-fold (ns for SOD2) after 2 Gy, 0.8- to 0.7-fold at 5 Gy, and 0.7- to 0.4-fold at 10 Gy. Runx2 decreased 0.9-fold at 2 and 5 Gy and 0.6-fold at 10 Gy. p21 increased 1.6-fold at 5 Gy and 2.5-fold at 10 Gy. p53 increased 1.6-fold at 5 Gy and 1.7-fold at 10 Gy. p16 remained unchanged. 

Fan et al., 2017 

In vivo. 10-week-old male C57BL/6J mice were irradiated with 60Co gamma rays at 3 Gy/day for 5 days. Left ventricular cardiac tissue was harvested for analysis. ROS was detected by dihydroethidium (DHE) staining. MAPK and Nrf2 signaling molecules were measured by western blot. 

Following irradiation, ROS production increased by 3.6-fold. 

p-p38/p38 decreased by 0.36-fold and p-Nrf2/Nrf2 decreased by 0.14-fold. 

Hasan, Radwan & Galal, 2020 

In vivo. 6-week-old male Wistar rats were irradiated with 6 Gy 137Cs gamma rays. Oxidative stress was measured by MDA and GSH in heart tissue. Angiotensin II (AngII) and aldosterone, key molecules in the RAAS pathway, were measured with ELISA kits in serum. 

Following irradiation, MDA levels increased by 1.5-fold and GSH levels decreased by 0.5-fold. AngII and aldosterone increased 1.4-fold compared to control. 

  

Azimzadeh et al., 2015 

In vivo. Male 10-week-old C57BL/6 mice were irradiated with 8 and 16 Gy of X-rays. SOD, MDA, and protein carbonylation levels were determined with immunoblotting, lipid peroxidation, and protein carbonylation assays, respectively, in heart tissue. Proteins in various signaling pathways were measured with immunoblotting in heart tissue. 

SOD decreased 0.7-fold at both 8 and 16 Gy and MDA increased 1.4-fold after 8 Gy and 2.1-fold after 16 Gy. Protein carbonylation increased 1.4-fold after 16 Gy. Levels and activity of proteins in the PI3K/Akt pathway were decreased between 0.5- and 0.1-fold at both 8 and 16 Gy. The ERK/MAPK pathway was found decreased 0.5-fold at 16 Gy and the p38/MAPK pathway was found increased 1.3-fold at 16 Gy. p16 was increased 1.6-fold at both 8 and 16 Gy. p21 was increased 2.4-fold at both 8 and 16 Gy. 

Sakata et al., 2015 

In vitro. HUVECs were irradiated with 10 Gy X-rays at a dose rate of 5 Gy/min. Measurements were performed 0-72 h post-irradiation. ROS were detected by fluorescence microscopy. MAPK, Akt, p-p38, JNK and ERK1/2 signaling molecules were measured by western blot. 

Following 10 Gy irradiation, the intensity representing ROS generation increased 20- and 30-fold at the 24 and 72 h timepoints, respectively. 

MAPK, p38 and JNK remained unchanged for the 72 h measured following 10 Gy irradiation.  

p-Akt/Akt in HUVECs after 10 Gy irradiation showed an initial decrease at 5 min and a delayed decrease of 0.5-fold at 6-24 h. p-ERK1/2 decreased at 5 min then increased to a maximum 1.75-fold change. 

Wortel et al., 2019 

In vitro. BAECs were irradiated with 10 Gy 137Cs gamma rays at a rate of 1.66 Gy/min. Extracellular H2O2 was measured by Amplex Red Assay, intracellular H2O2 levels were determined by HyPer sensor and peroxynitrite was quantified by chemiluminescence assay. Superoxide levels were quantified by luminescence after treatment with Diogenes Complete Enhancer Solution. The activation of the ASMase enzyme and the levels of ceramide were quantified by radioenzymatic assay to deter mine the changes on the ASMase/ceramide pathway. 

Following 10 Gy irradiation, intracellular H2O2 increased to a maximum 1.35-fold. Extracellular H2O2 increased by 1.75-fold. Peroxynitrite increased by 2.86-fold after 10 Gy (Fig 5). Superoxide levels increased over 350% at 2 minutes after 10 Gy irradiation. ASMase activity increased to a maximum 5.6-fold at 5 min after irradiation, then decreased and remained unchanged until the 30 min time-point. Ceramide increased from -500 to over 3000 pmol/106 cells. The significance of these changes was not indicated against a control. 

Azimzadeh et al., 2021 

In vivo. Male C57BL/6J mice 8 weeks of age were irradiated with 16 Gy of X-rays to the heart. SOD antioxidant activity and MDA in heart tissue were determined with an assay kit and lipid peroxidation assay, respectively. The level of proteins in MAPK pathways were determined by ELISA in heart tissue. 

After 16 Gy, SOD decreased 0.8-fold and MDA increased 1.3-fold. After 16 Gy, p-ERK increased 1.5-fold, p-p38 increased 1.3-fold, and p-JNK increased 1.3-fold. 

Xin et al., 2015 

In vitro and in vivo

In vitro. MC3T3-E1 osteoblast-like cells were exposed to microgravity for 96 hours. ROS were determined with a fluorescent probe and the RANK/RANKL pathway was measured using RANKL and OPG assay kits. 

In vivo. Male 8-week-old Sprague-Dawley rats were exposed to hind-limb suspension for 6 weeks. Femur and plasma MDA and femur sulfhydryl levels were measured with assay kits and the RANK/RANKL pathway was measured in the femur using RANKL and OPG assay kits. 

In vitro. ROS increased 1.5-fold and the RANKL/OPG ratio increased 1.6-fold. 

In vivo. Serum and femur MDA increased 1.4-fold and femur sulfhydryl decreased 0.6-fold. The RANKL/OPG ratio increased 3.5-fold. 

Sun et al., 2013 

In vitro. MC3T3-E1 osteoblast-like cells were exposed to microgravity (0.01G) for 96 hours. ROS production was measured by a fluorescent probe. The RANKL/OPG ratio was determined by assay kit and Runx2 mRNA expression was determined by RT-qPCR 

ROS increased 1.5-fold. The RANKL/OPG ratio increased 1.6-fold. Runx2 expression decreased 0.4-fold. 

Yoo, Han & Kim, 2016 

In vitro. Preosteoblast MC3T3-E1 cells were exposed to microgravity conditions by a 3D clinostat at a speed from 1-10 rpm. Oxidative stress was measured by Cu/Zn-SOD, Mn-SOD and catalase activity. Signaling molecules, p-Akt, phosphorylation of the mechanistic target of rapamycin p-(mTOR), and p-ERK were measured by western blot. 

Following microgravity exposure, Cu/Zn-SOD and Mn-SOD levels decreased by 0.24 and 0.65-fold, respectively. Signaling molecules p-Akt decreased by 0.36-fold. p-mTOR and p-ERK decreased by 0.58-fold. 

Diao et al., 2018 

In vivo. The left femur of rats was studied after exposure to simulated microgravity. Oxidative stress was measured by MDA, SOD, and CAT levels. RANK/RANKL signaling pathway was measured in rat femur by enzyme-linked immunoassay detection of OPG/RANKL molecules. Signaling molecule, Runx2, mRNA levels were measured by quantitative real time PCR. The Wnt/β-catenin pathway was measured by western blot for β-catenin protein levels. 

MDA increased by 1.4-fold. SOD and CAT levels decreased by 0.4-fold. OPG/RANKL decreased by 0.6-fold. Runx2 mRNA levels decreased 0.04-fold (Fig 8d). β-catenin decreased 0.6-fold. 

El-Missiry et al., 2018 

In vivo. Male Wistar rats were irradiated with gamma rays (137Cs source, 4 Gy, 0.695 cGy/s) and measurements were taken from the hippocampus. Assay kits were used to assess levels of oxidative stress for marker 4-HNE (4-hydroxy-2-nonenal) and antioxidant markers GSH, glutathione peroxidase (GPx) and glutathione reductase (GR). Levels of p53 were determined using an assay kit. 

After 4 Gy, 4-HNE increased 2.4-fold, protein carbonylation increased 3.2-fold, GSH decreased 0.4-fold, GPx decreased 0.3-fold, GR decreased 0.2-fold, and p53 increased 2.7-fold. 

Suman et al., 2013 

In vivo. Female adult C57BL/6J mice were irradiated with 1.6 Gy of 56Fe or 2 Gy of 137Cs gamma irradiation at 1 Gy/min, then measurements were taken from the cerebral cortex. ROS levels were determined with flow cytometry and 4-HNE levels were assessed with immunohistochemical staining. p21 and p53 levels were determined with immunoblotting. 

ROS increased a maximum of 1.2-fold after gamma rays and 1.4-fold after 56Fe radiation. The number of 4-HNE+ cells increased a maximum of 4.4-fold after gamma radiation and 14-fold after 56Fe radiation. p21 increased a maximum of 1.5-fold after gamma rays and 3-fold after 56Fe radiation. p53 increased a maximum of 8.4-fold after gamma rays and 9-fold after 56Fe radiation. 

Limoli et al., 2004 

In vivo. Adult male C57BL/6J mice were irradiated with 1-10 Gy of X-ray at 1.75 Gy/min. MDA levels in the hippocampus were measured using an assay kit and western blot was used to determine p53 and p21 levels. 

In vitro. Neural precursor cells from the rat hippocampus were irradiated with 1-10 Gy of X-ray at 4.5 Gy/min. ROS levels were measured using CM-H2DCFDA dye and Western blot was used to measure p53 and p21 levels. 

MDA levels increased about 30% at 10 Gy. ROS increased a maximum of 31% at 1 Gy and 35% at 5 Gy, after 24 and 12 hours, respectively. At 5 Gy, p53 levels increased a maximum of 4-fold, while p- p21 also increased at this dose. 

Tian et al., 2020 

In vivo. C57BL/6J mice (including miR-137-/- and Src-/- models) underwent middle cerebral artery occlusion (MCAO) to simulate ischemic stroke and measurements were taken 7 days later in the cerebral cortex. ROS levels were measured with DCFH-DA fluorescent dye. Signaling molecules were measured with western blotting or RT-qPCR. 

ROS increased 1.8-fold. ERK1/2, p38 and JNK mRNA increased 2- to 3- fold. The ratios of phosphorylated to total ERK1/2, p38 and JNK increased 2- to 3- fold as well. 

Hladik et al., 2020 

In vivo. Female B6C3F1 mice were exposed to total body 60Co gamma irradiation at 0.063, 0.125, or 0.5 Gy and at a dose rate of 0.063 Gy/min. Measurements from the hippocampus were taken up to 24 months post-irradiation. Protein levels in various signaling pathways (CREB, p38, ERK1/2, pro-apoptotic Bax and cleaved caspase 3, anti-apoptotic Bcl-xL) were determined with immunoblotting. 

Carbonylated proteins (indicative of ROS levels) were elevated in the 0.125 and 0.5 Gy group by approximately 25% and 30%, respectively. CREB phosphorylation increased by approximately 20% and 25% at 0.063 and 0.125 Gy, respectively. Phosphorylated p38 increased by approximately 100% and 80% at 0.063 and 0.125 Gy, respectively. Phosphorylated ERK1/2 increased by approximately 100% and 90% at 0.063 and 0.125 Gy, respectively.  

Anti-apoptotic BCL-xL decreased by 1.7-fold at 0.5 Gy, whereas pro-apoptotic Bax increased by approximately 2-fold at this dose. Caspase 3 also increased by approximately 2-fold at 0.5 Gy. 

Carvour et al., 2008 

In vitro. Mesencephalic dopaminergic neuronal cell line (N27) derived from rat mesencephalon were exposed to 3, 10, or 30 μM of H2O2. ROS levels were detected using dihydroethidine dye and flow cytometry. Western blot was used to detect cleaved PKCδ and Sytox fluorescence was used to measure caspase-3 enzyme activity.  

Exposure to 10 and 30 μM of H2O2 resulted in 34 and 58% increases in ROS production, respectively, compared to untreated N27 cells. Exposure to 3, 10, and 30 μM hydrogen peroxide resulted in 2-, 10-, and 9-fold increases in caspase-3 enzyme activity. Lastly, exposure to 10 and 30 μM of H2O2 dose-dependently induced proteolytic cleavage of PKCδ. 

Chen et al., 2009 

In vitro. PC12 and SH-SY5Y human cells were incubated with H2O2. The production of ROS was measured by detecting the fluorescent intensity of oxidant-sensitive probe CM-H2DCFDA. Western blot analysis was used to assess activation of MAPKs. 

Treatment with H2O2 for 24 h resulted in a concentration-dependent increase of ROS production at the concentrations of 0–1 mM in PC12 and SH-SY5Y cells. In comparison with PC12, SH-SY5Y cells appeared to be more sensitive to H2O2, thereby showing a decreased ROS production at 2 mM. Additionally, treatment of PC12 cells with H2O2 for 2 h increased phosphorylation of Erk1/2 and p38 in a concentration-dependent manner. Noticeably, H2O2-activation of JNK resulted in a robust (5–10-fold) increase of protein expression and phosphorylation of c-Jun at 0.3–1 mM. Similar results were also seen in SH-SY5Y cells (data not shown). 

Time-scale
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Time Concordance 

Reference 

Experiment Description 

Result 

Azimzadeh et al., 2017 

In vitro. HCAECs were irradiated with 0.5 Gy of X-rays (0.5 Gy/min). Protein carbonylation and GSTO1 antioxidant level were measured with a carbonylation assay and immunoblotting, respectively. Proteins from various signaling pathways including RhoGDI, p16 and p21 were measured with immunoblotting. Measurements were taken at 1, 7, and 14 days after irradiation. 

After 7 and 14 days, carbonyl content increased 1.2-fold (insignificant increase at 1 day post-irradiation). After 1-14 days, GSTO1 decreased 0.78-fold (significant decreases at all timepoints). After 1 and 7 days, p-RhoGDI decreased 0.7-fold (non-significant decrease at 14 days post-irradiation). p16 increased 1.2-fold after 7 days and 1.5-fold after 14 days (non-significant increase at 1 day post-irradiation). p21 increased 1.2-fold after 7 and 14 days (insignificant increase at 1 day post-irradiation). 

Wortel et al., 2019 

In vitro. BAECs were irradiated with 10 Gy 137Cs gamma rays at a rate of 1.66 Gy/min. Superoxide levels were quantified by luminescence after treatment with Diogenes Complete Enhancer Solution. The activation of the ASMase enzyme and the levels of ceramide were quantified by radioenzymatic assay to deter mine the changes on the ASMase/ceramide pathway. 

Superoxide increased by over 350% at 2 minutes post-irradiation. ASMase activity increased to a maximum 5.6-fold at 5 min post-irradiation. Ceramide increased from -500 to over 3000 pmol/106 cells at 5 minutes post-irradiation. The significance of these changes was not indicated against a control. 

Kook et al., 2015 

In vitro. MC3T3-E1 osteoblast-like cells were irradiated with X-rays (1.5 Gy/min). ROS were measured with a fluorescent probe, and SOD, CAT, and GSH antioxidant activities were determined with assay kits. Protein levels in the Nrf2/HO-1 signaling pathway were determined by either western blot or RT-PCR. 

After 1 day and 8 Gy, ROS increased 1.4-fold, GSH decreased 0.5-fold, and SOD decreased 0.5-fold. CAT was also decreased but not significantly. After 1 day and 8 Gy, Nrf2 increased 2.3-fold. After 2 days and 8 Gy, HO-1 increased 4.9-fold. After 3 days and 8 Gy, Runx2 mRNA was decreased 0.5-fold. 

Suman et al., 2013 

In vivo. Female adult C57BL/6J mice were irradiated with 1.6 Gy of 56Fe or 2 Gy of 137Cs gamma irradiation at 1 Gy/min, then measurements were taken from the cerebral cortex until up to 12 months. ROS levels were determined with flow cytometry and 4-HNE levels were determined with immunohistochemical staining. p21 and p53 levels were determined with immunoblotting. 

All changes after 56Fe radiation were found after both 2 and 12 months post-irradiation. Most endpoints were also increased at both time points following gamma irradiation, however, p21 only increased at 12 months by 3-fold, but not 2 months, while oxidative stress was shown at 2 months (0.2-fold increase). 

Xu et al., 2019 

In vitro. Adult male C57BL/6 mice experienced chronic cold stress for various lengths (1, 2 and 3 weeks). Brain tissue was then collected, and Western blot was used to measure MDA and proteins of MAPK (JNK, ERK and p38). 

MDA levels increased in a time-dependent manner. At 1 week, there was an approximate 3-fold increase, at 2 weeks was an approx. 4-fold increase and for 3 weeks, there was an approx. 5-fold increase in response to cold stress. Phosphorylated JNK increased by ∼10% (1 week) and ∼30% at 2 and 3 weeks compared to room temperature control. Phosphorylated ERK increased by ∼60% at 1 week, ∼150% at 2 weeks and ∼140% at 3 weeks. Phosphorylated p38 increased by ∼50% at 1 week, ∼100% at 2 weeks and ∼150% at 3 weeks. 

Chen et al., 2009 

In vitro. PC12 and SH-SY5Y human cells were incubated with hydrogen peroxide. The production of ROS was measured by detecting the fluorescent intensity of oxidant-sensitive probe CM-H2DCFDA. Western blot analysis was used to assess activation of MAPKs. 

They observed that H2O2 induced phosphorylation of MAPKs in a time-dependent fashion. Within 5–15 min, H2O2 increased phosphorylation of Erk1/2, JNK and p38, and such phosphorylation was sustained for over 2 h. Consistently, high levels of c-Jun and phospho-c-Jun were induced.

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

ROS can upregulate protein kinase C, which stimulates the production of ceramide from sphingomyelinase. Ceramide activates NADPH oxidase, which can then produce more ROS (Soloviev & Kizub, 2019). Another feedback loop exists between the Nrf2/HO-1 signaling pathway and oxidative stress. The Nrf2/HO-1 signaling pathway is involved in negative feedback of oxidative stress, activating transcription of anti-oxidative enzymes to regulate cellular ROS and maintain a redox balance (Tahimic & Globus, 2017; Tian et al., 2017). Lastly, the MAPK pathway also exhibits a feedback loop. ERK can regulate ROS levels indirectly through p22phox, which increases ROS and upregulates antioxidants by Nrf2 activation. JNK activation can lead to FoxO activation, thereby resulting in antioxidant production (Arfin et al., 2021; Essers et al., 2004).

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

Based on the prioritized studies presented here, the evidence of taxonomic applicability is low for humans despite there being strong plausibility as the evidence only includes in vitro human cell-derived models. The taxonomic applicability for mice and rats is considered high as there is much available data using in vivo rodent models that demonstrate the concordance of the relationship. The taxonomic applicability was determined to be moderate for pigs as only one in vivo study provided meaningful support to the relationship. In terms of sex applicability, all in vivo studies that indicated the sex of the animals used male animals, therefore, the evidence for males is high and females is considered to be low for this KER. The majority of studies used adolescent animals, with a few using adult animals. Preadolescent animals were not used to support the KER; however, the relationship in preadolescent animals is still plausible.

References

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

Annunziato, L. (2003), "Apoptosis induced in neuronal cells by oxidative stress: role played by caspases and intracellular calcium ions", Toxicology Letters, Vol. 139/2–3, https://doi.org/10.1016/S0378-4274(02)00427-7.

Arfin, S. et al. (2021), “Oxidative Stress in Cancer Cell Metabolism”, Antioxidants 2021, Vol. 10/5, MDPI, Basel, https://doi.org/10.3390/ANTIOX10050642  

Azimzadeh, O. et al. (2021), "Activation of pparα by fenofibrate attenuates the effect of local heart high dose irradiation on the mouse cardiac proteome", Biomedicines, Vol. 9/12, MDPI, Basel, https://doi.org/10.3390/biomedicines9121845 

Azimzadeh, O. et al. (2017), "Proteome analysis of irradiated endothelial cells reveals persistent alteration in protein degradation and the RhoGDI and NO signalling pathways", International Journal of Radiation Biology, Vol. 93/9, Informa, London, https://doi.org/10.1080/09553002.2017.1339332 

Azimzadeh, O. et al. (2015), "Integrative proteomics and targeted transcriptomics analyses in cardiac endothelial cells unravel mechanisms of long-term radiation-induced vascular dysfunction", Journal of Proteome Research, Vol. 14/2, American Chemical Society, Washington, https://doi.org/10.1021/pr501141b 

Bai, J. et al. (2020), "Irradiation-induced senescence of bone marrow mesenchymal stem cells aggravates osteogenic differentiation dysfunction via paracrine signaling", American Journal of Physiology - Cell Physiology, Vol. 318/5, American Physiological Society, https://doi.org/10.1152/ajpcell.00520.2019 

Boyce, B. F. and L. Xing. (2007), "The RANKL/RANK/OPG pathway", Current Osteoporosis Reports, Vol. 5/3, https://doi.org/10.1007/s11914-007-0024-y  

Cabrera, M. P. and R. H. Chihuailaf. (2011), "Antioxidants and the Integrity of Ocular Tissues", Veterinary Medicine International, Vol. 2011, Hindawi, London, https://doi.org/10.4061/2011/905153 

Carvour, M. et al. (2008), "Chronic Low-Dose Oxidative Stress Induces Caspase-3-Dependent PKCδ Proteolytic Activation and Apoptosis in a Cell Culture Model of Dopaminergic Neurodegeneration", Annals of the New York Academy of Sciences, Vol. 1139/1, https://doi.org/10.1196/annals.1432.020.

Chen, L. et al. (2009), "Hydrogen peroxide-induced neuronal apoptosis is associated with inhibition of protein phosphatase 2A and 5, leading to activation of MAPK pathway", The International Journal of Biochemistry & Cell Biology, Vol. 41/6, Elsevier, Amsterdam, https://doi.org/10.1016/j.biocel.2008.10.029

Crossthwaite, A. J., S. Hasan and R. J. Williams. (2002), "Hydrogen peroxide-mediated phosphorylation of ERK1/2, Akt/PKB and JNK in cortical neurones: dependence on Ca2+ and PI3-kinase", Journal of Neurochemistry, Vol. 80/1, John Wiley & Sons, Hoboken, https://doi.org/10.1046/j.0022-3042.2001.00637.x.

Deng, Z. et al. (2012), "Radiation-Induced c-Jun Activation Depends on MEK1-ERK1/2 Signaling Pathway in Microglial Cells", (I. Ulasov, Ed.) PLoS ONE, Vol. 7/5, https://doi.org/10.1371/journal.pone.0036739

Diao, Y. et al. (2018), "Polyphenols (S3) Isolated from Cone Scales of Pinus koraiensis Alleviate Decreased Bone Formation in Rat under Simulated Microgravity", Scientific Reports, Vol. 8/1, Nature, https://doi.org/10.1038/s41598-018-30992-8 

Domazetovic, V. et al. (2017), "Oxidative stress in bone remodeling: role of antioxidants", Clinical cases in mineral and bone metabolism, Vol. 14/2, pp. 209-216 

El-Missiry, M. A. et al. (2018), "Neuroprotective effect of epigallocatechin-3-gallate (EGCG) on radiation-induced damage and apoptosis in the rat hippocampus", International Journal of Radiation Biology, Vol. 94/9, https://doi.org/10.1080/09553002.2018.1492755

Fan, Z. et al. (2017), "L-carnitine preserves cardiac function by activating p38 MAPK/Nrf2 signalling in hearts exposed to irradiation", European Journal of Pharmacology, Vol. 804, Elsevier, Amsterdam, https://doi.org/10.1016/j.ejphar.2017.04.003 

Hasan, H. F., R. R. Radwan and S. M. Galal. (2020), "Bradykinin‐potentiating factor isolated from Leiurus quinquestriatus scorpion venom alleviates cardiomyopathy in irradiated rats via remodelling of the RAAS pathway", Clinical and Experimental Pharmacology and Physiology, Vol. 47/2, Wiley, https://doi.org/10.1111/1440-1681.13202 

Hladik, D. et al. (2020), "CREB Signaling Mediates Dose-Dependent Radiation Response in the Murine Hippocampus Two Years after Total Body Exposure", Journal of Proteome Research, Vol. 19/1, https://doi.org/10.1021/acs.jproteome.9b00552

Huang, Y. et al. (2021), "Mesenchymal Stem Cell-Conditioned Medium Protects Hippocampal Neurons From Radiation Damage by Suppressing Oxidative Stress and Apoptosis", Dose-Response, Vol. 19/1, https://doi.org/10.1177/1559325820984944

Hughson, R. L., A. Helm and M. Durante. (2018), "Heart in space: Effect of the extraterrestrial environment on the cardiovascular system", Nature Reviews Cardiology, Vol. 15/3, Nature, https://doi.org/10.1038/nrcardio.2017.157 

Kenchegowda, D. et al. (2018), "Selective Insulin-like Growth Factor Resistance Associated with Heart Hemorrhages and Poor Prognosis in a Novel Preclinical Model of the Hematopoietic Acute Radiation Syndrome", Radiation Research, Vol. 190/2, BioOne, https://doi.org/10.1667/RR14993.1 

Kook, S. H. et al. (2015), "Irradiation inhibits the maturation and mineralization of osteoblasts via the activation of Nrf2/HO-1 pathway", Molecular and Cellular Biochemistry, Vol. 410/1–2, Nature, https://doi.org/10.1007/s11010-015-2559-z 

Kozbenko, T. et al. (2022), “Deploying elements of scoping review methods for adverse outcome pathway development: a space travel case example”, International Journal of Radiation Biology, Vol. 98/12. https://doi.org/10.1080/09553002.2022.2110306

Lee, K., A. Lee and I. Choi. (2017), "Melandrii Herba Extract Attenuates H2O2-Induced Neurotoxicity in Human Neuroblastoma SH-SY5Y Cells and Scopolamine-Induced Memory Impairment in Mice", Molecules, Vol. 22/10, MDPI, Basel, https://doi.org/10.3390/molecules22101646

Lehtinen, M. and A. Bonni. (2006), "Modeling Oxidative Stress in the Central Nervous System", Current Molecular Medicine, Vol. 6/8, https://doi.org/10.2174/156652406779010786

Li, J. et al. (2013), "Oxidative Stress and Neurodegenerative Disorders", International Journal of Molecular Sciences, Vol. 14/12, https://doi.org/10.3390/ijms141224438

Limoli, C. L. et al. (2004), "Radiation Response of Neural Precursor Cells: Linking Cellular Sensitivity to Cell Cycle Checkpoints, Apoptosis and Oxidative Stress", Radiation Research, Vol. 161/1, https://doi.org/10.1667/RR3112

Manolagas, S. C. and M. Almeida. (2007), "Gone with the Wnts: β-Catenin, T-Cell Factor, Forkhead Box O, and Oxidative Stress in Age-Dependent Diseases of Bone, Lipid, and Glucose Metabolism", Molecular Endocrinology, Vol. 21/11, Oxford University Press, Oxford, https://doi.org/10.1210/me.2007-0259 

Essers, M. A. et al. (2004), “FOXO transcription factor activation by oxidative stress mediated by the small GTPase Ral and JNK”. The EMBO journal, Vol. 23/24, EMBO, https://doi.org/10.1038/sj.emboj.7600476  

Nagane, M. et al. (2021), "DNA damage response in vascular endothelial senescence: Implication for radiation-induced cardiovascular diseases", Journal of Radiation Research, Vol. 62/4, Oxford University Press, Oxford, https://doi.org/10.1093/jrr/rrab032 

Park, H. et al. (2016), "GDF15 contributes to radiation-induced senescence through the ROS-mediated p16 pathway in human endothelial cells", Oncotarget, Vol. 7/9, https://doi.org/10.18632/oncotarget.7457 

Park, D. H. et al. (2021), "Neuroprotective Effect of Gallocatechin Gallate on Glutamate-Induced Oxidative Stress in Hippocampal HT22 Cells", Molecules, Vol. 26/5, MDPI, Basel, https://doi.org/10.3390/molecules26051387

Ping, Z. et al. (2020), "Oxidative Stress in Radiation-Induced Cardiotoxicity", Oxidative Medicine and Cellular Longevity, Vol. 2020, Hindawi, London, https://doi.org/10.1155/2020/3579143 

Ramadan, R. et al. (2021), "The role of connexin proteins and their channels in radiation-induced atherosclerosis", Cellular and Molecular Life Sciences, Vol. 78, Nature, https://doi.org/10.1007/s00018-020-03716-3 

Ramalingam, M. and S.-J. Kim. (2012), "Reactive oxygen/nitrogen species and their functional correlations in neurodegenerative diseases", Journal of Neural Transmission, Vol. 119/8, Springer Nature, Berlin, https://doi.org/10.1007/s00702-011-0758-7

Ruffels, J., M. Griffin and J. M. Dickenson. (2004), "Activation of ERK1/2, JNK and PKB by hydrogen peroxide in human SH-SY5Y neuroblastoma cells: role of ERK1/2 in H2O2-induced cell death", European Journal of Pharmacology, Vol. 483/2–3, Elsevier, Amsterdam https://doi.org/10.1016/j.ejphar.2003.10.032

Sakata, K. et al. (2015), "Roles of ROS and PKC-βII in ionizing radiation-induced eNOS activation in human vascular endothelial cells", Vascular Pharmacology, Vol. 70, Elsevier, Amsterdam, https://doi.org/10.1016/j.vph.2015.03.016 

Schmidt-Ullrich, R. K. et al. (2000), "Signal transduction and cellular radiation responses.", Radiation research, Vol. 153/3, BioOne, https://doi.org/10.1667/0033-7587(2000)153[0245:stacrr]2.0.co;2 

Schnegg, C. I. et al. (2012), "PPARδ prevents radiation-induced proinflammatory responses in microglia via transrepression of NF-κB and inhibition of the PKCα/MEK1/2/ERK1/2/AP-1 pathway", Free Radical Biology and Medicine, Vol. 52/9, https://doi.org/10.1016/j.freeradbiomed.2012.02.032

Soloviev, A. I. and I. V. Kizub. (2019), "Mechanisms of vascular dysfunction evoked by ionizing radiation and possible targets for its pharmacological correction", Biochemical Pharmacology, Vol. 159, Elsevier, Amsterdam, https://doi.org/10.1016/j.bcp.2018.11.019 

Suman, S. et al. (2013), "Therapeutic and space radiation exposure of mouse brain causes impaired DNA repair response and premature senescence by chronic oxidant production", Aging, Vol. 5/8, https://doi.org/10.18632/aging.100587

Sun, Y. et al. (2013), "Treatment of hydrogen molecule abates oxidative stress and alleviates bone loss induced by modeled microgravity in rats", Osteoporosis International, Vol. 24/3, Nature, https://doi.org/10.1007/s00198-012-2028-4 

Tahimic, C. G. T. and R. K. Globus. (2017), “Redox Signaling and Its Impact on Skeletal and Vascular Responses to Spaceflight”, International Journal of Molecular Sciences, Vol. 18/10, MDPI, Basel, https://doi.org/10.3390/IJMS18102153  

Tian, Y. et al. (2017), "The impact of oxidative stress on the bone system in response to the space special environment", International Journal of Molecular Sciences, Vol. 18/10, MDPI, Basel, https://doi.org/10.3390/ijms18102132 

Tian, W. et al. (2019), "Neuroprotective Effects of Cornus officinalis on Stress-Induced Hippocampal Deficits in Rats and H2O2-Induced Neurotoxicity in SH-SY5Y Neuroblastoma Cells", Antioxidants, Vol. 9/1, MDPI, Basel, https://doi.org/10.3390/antiox9010027

Tian, R. et al. (2020), "miR-137 prevents inflammatory response, oxidative stress, neuronal injury and cognitive impairment via blockade of Src-mediated MAPK signaling pathway in ischemic stroke", Aging, Vol. 12/11, https://doi.org/10.18632/aging.103301

Valerie, K. et al. (2007), "Radiation-induced cell signaling: inside-out and outside-in", Molecular Cancer Therapeutics, Vol. 6/3, American Association for Cancer Research, https://doi.org/10.1158/1535-7163.MCT-06-0596 

Venkatesulu, B. P. et al. (2018), “Radiation-Induced Endothelial Vascular Injury: A Review of Possible Mechanisms”, JACC: Basic to translational science, Vol. 3/4, Elsevier, Amsterdam, https://doi.org/10.1016/j.jacbts.2018.01.014. 

Wang. (2010), "Selective neuronal vulnerability to oxidative stress in the brain", Frontiers in Aging Neuroscience, https://doi.org/10.3389/fnagi.2010.00012. 

Wang, Y., M. Boerma and D. Zhou. (2016), "Ionizing Radiation-Induced Endothelial Cell Senescence and Cardiovascular Diseases", Radiation Research, Vol. 186/2, BioOne, https://doi.org/10.1667/RR14445.1 

Wortel, R. C. et al. (2019), "Sildenafil Protects Endothelial Cells From Radiation-Induced Oxidative Stress", The Journal of Sexual Medicine, Vol. 16/11, Elsevier, Amsterdam, https://doi.org/10.1016/j.jsxm.2019.08.015 

Wu, Y., M. Chen and J. Jiang. (2019), "Mitochondrial dysfunction in neurodegenerative diseases and drug targets via apoptotic signaling", Mitochondrion, Vol. 49, https://doi.org/10.1016/j.mito.2019.07.003. 

Xin, M. et al. (2015), "Attenuation of hind-limb suspension-induced bone loss by curcumin is associated with reduced oxidative stress and increased vitamin D receptor expression", Osteoporosis International, Vol. 26/11, Nature,  https://doi.org/10.1007/s00198-015-3153-7 

Xu, B. et al. (2019), "Oxidation Stress-Mediated MAPK Signaling Pathway Activation Induces Neuronal Loss in the CA1 and CA3 Regions of the Hippocampus of Mice Following Chronic Cold Exposure", Brain Sciences, Vol. 9/10, MDPI, Basel, https://doi.org/10.3390/brainsci9100273

Yoo, Y. M., T. Y. Han and H. S. Kim. (2016), "Melatonin suppresses autophagy induced by clinostat in preosteoblast MC3T3-E1 cells", International Journal of Molecular Sciences, Vol. 17/4, MDPI, Basel, https://doi.org/10.3390/ijms17040526 

Zhao, Z.-Y. et al. (2013), "Edaravone Protects HT22 Neurons from H 2 O 2 -induced Apoptosis by Inhibiting the MAPK Signaling Pathway", CNS Neuroscience & Therapeutics, Vol. 19/3, John Wiley & Sons, Hoboken, https://doi.org/10.1111/cns.12044

Zhao, D. et al. (2017), "Anti-Neuroinflammatory Effects of Fucoxanthin via Inhibition of Akt/NF-κB and MAPKs/AP-1 Pathways and Activation of PKA/CREB Pathway in Lipopolysaccharide-Activated BV-2 Microglial Cells", Neurochemical Research, Vol. 42/2, Springer Nature, Berlin, https://doi.org/10.1007/s11064-016-2123-6