Early Responses to Oxidative Stress In Heart Cells: Signals From The Cell Membrane To The Nucleus and Beyond

Persistent Link:
http://hdl.handle.net/10150/194381
Title:
Early Responses to Oxidative Stress In Heart Cells: Signals From The Cell Membrane To The Nucleus and Beyond
Author:
Purdom-Dickinson, Sally Elizabeth
Issue Date:
2005
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Oxidative stress is known to contribute to many forms of heart disease. Oxidants such as H₂O₂ can cause hypertrophy of cardiomyocytes (CMCs). Heart fibroblasts (HFs) also contribute to oxidant-induced heart disease by disordering the extracellular matrix and causing fibrosis. Since both of these cells encounter the same stressors in vivo, we examined the signaling pathways involved in responding to oxidative stress in both cell types. We have established the EGF Receptor, Src and matrix metalloproteinases (MMPs) as key regulators of oxidant-mediated phosphorylation of the MAPKs ERK1/2 and JNKs but not p38 in CMCs and HFs. We used oligonucleotide microarrays to examine the differences in global gene expression after H₂O₂ treatment in CMCs and HFs. Twenty-four hours after treatment, significant numbers of upregulated genes could be classified as being related to antioxidant or detoxification responses in both cell types. This trend lead us to examine the role of activation of promoters containing the Antioxidant Response Element (ARE) in the reaction of CMCs to H₂O₂. We have shown that H₂O₂ activates the ARE in CMCs in a manner that is dependant on the transcription factor Nf-E2 related factor 2 (Nrf2). ARE activation by H₂O₂ seems to induce cytoprotection. CMCs pretreated with H₂O₂ showed significantly less activation of caspase-3 when exposed to another oxidant, Doxorubicin. Overexpression of Nrf2 mediates this cytoprotection, possibly by protecting the cells from caspase-independent cell death. Although ARE-dependant genes were upregulated in the presence of excess Nrf2, two contractile proteins were repressed, suggesting that Nrf2 overexpression may have unknown side-effects in CMCs. We also studied the activation mechanism of Nrf2 in CMCs. Nrf2 protein levels increased after 10 min of exposure to 100 μM H₂O₂ and peaked at about 1 hr. Pharmacological and genetic inhibition of the PI3-Kinase pathway blocked AREluciferase activity in these cells. The PI3-Kinase inhibitor LY294002 also blocked Nrf2 protein accumulation, but not nuclear translocation. Here I present evidence that Nrf2 accumulation after H₂O₂ exposure is due to PI3-Kinase-mediated translational regulation. Since phosphorylation of translation initiation factors eIF4E and eIF2alpha are both inhibited by LY294002, Nrf2 translation initiation may be through non-5’ cap-mediated means.
Type:
text; Electronic Dissertation
Keywords:
oxidant; Nrf2; cardiomyocyte; fibroblast; cytoprotection; PI3Kinase
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Genetics; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Chen, Qin M.
Committee Chair:
Chen, Qin M.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleEarly Responses to Oxidative Stress In Heart Cells: Signals From The Cell Membrane To The Nucleus and Beyonden_US
dc.creatorPurdom-Dickinson, Sally Elizabethen_US
dc.contributor.authorPurdom-Dickinson, Sally Elizabethen_US
dc.date.issued2005en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractOxidative stress is known to contribute to many forms of heart disease. Oxidants such as H₂O₂ can cause hypertrophy of cardiomyocytes (CMCs). Heart fibroblasts (HFs) also contribute to oxidant-induced heart disease by disordering the extracellular matrix and causing fibrosis. Since both of these cells encounter the same stressors in vivo, we examined the signaling pathways involved in responding to oxidative stress in both cell types. We have established the EGF Receptor, Src and matrix metalloproteinases (MMPs) as key regulators of oxidant-mediated phosphorylation of the MAPKs ERK1/2 and JNKs but not p38 in CMCs and HFs. We used oligonucleotide microarrays to examine the differences in global gene expression after H₂O₂ treatment in CMCs and HFs. Twenty-four hours after treatment, significant numbers of upregulated genes could be classified as being related to antioxidant or detoxification responses in both cell types. This trend lead us to examine the role of activation of promoters containing the Antioxidant Response Element (ARE) in the reaction of CMCs to H₂O₂. We have shown that H₂O₂ activates the ARE in CMCs in a manner that is dependant on the transcription factor Nf-E2 related factor 2 (Nrf2). ARE activation by H₂O₂ seems to induce cytoprotection. CMCs pretreated with H₂O₂ showed significantly less activation of caspase-3 when exposed to another oxidant, Doxorubicin. Overexpression of Nrf2 mediates this cytoprotection, possibly by protecting the cells from caspase-independent cell death. Although ARE-dependant genes were upregulated in the presence of excess Nrf2, two contractile proteins were repressed, suggesting that Nrf2 overexpression may have unknown side-effects in CMCs. We also studied the activation mechanism of Nrf2 in CMCs. Nrf2 protein levels increased after 10 min of exposure to 100 μM H₂O₂ and peaked at about 1 hr. Pharmacological and genetic inhibition of the PI3-Kinase pathway blocked AREluciferase activity in these cells. The PI3-Kinase inhibitor LY294002 also blocked Nrf2 protein accumulation, but not nuclear translocation. Here I present evidence that Nrf2 accumulation after H₂O₂ exposure is due to PI3-Kinase-mediated translational regulation. Since phosphorylation of translation initiation factors eIF4E and eIF2alpha are both inhibited by LY294002, Nrf2 translation initiation may be through non-5’ cap-mediated means.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectoxidanten_US
dc.subjectNrf2en_US
dc.subjectcardiomyocyteen_US
dc.subjectfibroblasten_US
dc.subjectcytoprotectionen_US
dc.subjectPI3Kinaseen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeneticsen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorChen, Qin M.en_US
dc.contributor.chairChen, Qin M.en_US
dc.contributor.committeememberBowden, Timen_US
dc.contributor.committeememberErickson, Roberten_US
dc.contributor.committeememberBriehl, Margareten_US
dc.contributor.committeememberRomagnolo, Donatoen_US
dc.identifier.proquest1310en_US
dc.identifier.oclc137354953en_US
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