Project description:Interventions: To administere eicosapentaenoic acid before surgery
Primary outcome(s): To evaluate the ability of EPA to suppress oxidative stress when administered before surgery.
Study Design: Single arm Non-randomized
Project description:The TET-family enzymes (TETs) convert methylcytosine to hydroxymethylcytosine, a lately discovered epigenetic modification that can modulate transcription. While recent reports suggest that TETs may play a role in response to oxidative stress, this role remains uncertain. Here we show that Tet1 is sensitive to peroxide and report a global decrease in hydroxymethylcytosine in cells treated with BSO and in the intestinal epithelium of mice lacking the major antioxidant enzymes glutathione peroxidases 1 and 2. Furthermore, genome-wide profiling revealed differentially hydroxymethylated regions in genes involved in responses to oxidative stress. Intriguingly, a considerable proportion of these regions lie in genes encoding microRNAs predicted to target transcripts involved in oxidative stress response. This work thus demonstrates a profound effect of oxidative stress on the hydroxymethylome and opens exciting new avenues of research by highlighting a set of microRNAs that may participate in the prevention or etiology of oxidative-stress-related diseases. Examination of DNA hydroxymethylation landscape in SY5Y cell lines and in intestinal epithelium of mice.
Project description:Integrated-systems model of oxidative stress connecting NRF2 and p53 signaling pathways. Additional crosstalk linking oxidative stress to p53 inhibition, p53 to NRF2 through p21, and NRF2 to MDM2 was incorporated in this model. The NRF2 pathway was encoded as first- and second-order rate equations for KEAP1 oxidation and NRF2 stabilization; NRF2-mediated transcription of antioxidant enzymes was modeled as a Hill function. The p53 pathway was reconstructed from a delay differential equation model of p53 signaling in response to DNA damage. To adapt the p53 DNA-damage model to respond to oxidative stress, we used a first-order oxidation reaction of ATM/CHEK2 by intracellular H2O2.
The integrated base model of NRF2–p53 oxidative-stress signaling contains 42 reactions and 22 ordinary differential equations (ODEs).
Project description:Smith2013 - Regulation of Insulin Signalling by Oxidative Stress
The model describes insulin signalling (in rodent adipocytes), which includes in addition to the core pathway, the transcriptional feedback through the Forkhead box type O (FOXO) transcription factor and interaction with oxidative stress.
This model is described in the article:
Computational modelling of the regulation of Insulin signalling by oxidative stress.
Smith GR, Shanley DP.
BMC Syst Biol. 2013 May 24;7:41.
Abstract:
BACKGROUND:
Existing models of insulin signalling focus on short term dynamics, rather than the longer term dynamics necessary to understand many physiologically relevant behaviours. We have developed a model of insulin signalling in rodent adipocytes that includes both transcriptional feedback through the Forkhead box type O (FOXO) transcription factor, and interaction with oxidative stress, in addition to the core pathway. In the model Reactive Oxygen Species are both generated endogenously and can be applied externally. They regulate signalling though inhibition of phosphatases and induction of the activity of Stress Activated Protein Kinases, which themselves modulate feedbacks to insulin signalling and FOXO.
RESULTS:
Insulin and oxidative stress combined produce a lower degree of activation of insulin signalling than insulin alone. Fasting (nutrient withdrawal) and weak oxidative stress upregulate antioxidant defences while stronger oxidative stress leads to a short term activation of insulin signalling but if prolonged can have other effects including degradation of the insulin receptor substrate (IRS1) and FOXO. At high insulin the protective effect of moderate oxidative stress may disappear.
CONCLUSION:
Our model is consistent with a wide range of experimental data, some of which is difficult to explain. Oxidative stress can have effects that are both up- and down-regulatory on insulin signalling. Our model therefore shows the complexity of the interaction between the two pathways and highlights the need for such integrated computational models to give insight into the dysregulation of insulin signalling along with more data at the individual level.A complete SBML model file can be downloaded from BIOMODELS (https://www.ebi.ac.uk/biomodels-main) with unique identifier MODEL1212210000.Other files and scripts are available as additional files with this journal article and can be downloaded from https://github.com/graham1034/Smith2012_insulin_signalling.
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Project description:To study whether increase in mitochondrial oxidative stress (SOD2 removal) and decrease in mitochondrial DNA repair (Ogg1 dMTS) results into increase in mitochondrial DNA mutation load. Oxidative stress has been suggested to induce mutations in mtDNA. To verify this, we extracted and sequenced (Illumina) mitochondrial DNA from heart Sod2 knockout animals that were also deficient for mitochondrial base-excision repair. The repair deficiency was induced by removing the genomic region encoding for the predicted mitochondrial targeting sequence from endogenous OGG1 (L2 to W23) called Ogg1 dMTS mice, thus excluding the protein from mitochondria. OGG1 is a DNA glycosylase that recognizes and repairs 8-oxo-dG damage from DNA. Oxidative stress can induce 8-oxo-dG lesions, thus we removed the mitochondrial matrix localized superoxide dismutase (SOD2) from these mice to increase the level of oxidative stress. 8-oxo-dG lesion can be mutagenic because some DNA repair polymerases are known to erroneously incorporate adenosine opposite to 8-oxo-dG during replication leading to GC>TA transversion mutations.