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NF-kB Regulates Gene Expression of Pro-Apoptotic Factor Nix in Late Ischemic Preconditioning

Forde, Tiffany L.
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1291147865

Abstract Details

2010, MS, University of Cincinnati, Medicine: Molecular, Cellular and Biochemical Pharmacology.
Myocardial ischemia (MI), a common initiator of ischemic heart disease, occurs when there is reduced blood supply to the heart. The subsequent tissue damage following restoration of blood flow is known as ischemia reperfusion (I/R) injury. During I/R injury cardiomyocytes undergo various forms of cell death including necrosis, apoptosis, and oncosis. Ischemic preconditioning (IPC) is a biphasic endogenous mechanism that serves to protect the myocardium from injury associated with myocardial infarction (MI). The early phase of IPC occurs approximately 3 hours after the injury with the second wave of protection known as the late phase (LPC) occurring 12-24 hours later. The transcription factor nuclear factor kappa B (NF-κB) is an integral part of the late phase preconditioning as it regulates the expression of hundreds of genes necessary for mediating the protective response. NF-κB has been implicated in regulating over 500 genes in various disease processes, but the specific gene classes that are regulated by NF-κB during the cardioprotection of late IPC are still largely unknown. To understand how NF-κB contributes to this late phase protection against ischemia, we conducted a large-scale microarray analysis to determine which genes were transcriptionally regulated by NF-κB as a part of the IPC stimulus. We employed the use of a cardiac specific IκBa dominant negative transgenic mouse (2M) model to inactivate NF-κB and assessed changes in mRNA levels in the absence the transcription factors activity. These analyses identified Nix as a proapoptotic Bcl-2 family member, whose expression is suppressed after late IPC, by NF-κB. This finding was in contrast to previous publications that do not support a role for Nix in ischemic responses. We performed late preconditioning prior to I/R injury on cardiac-specific Nix overexpression mice and demonstrated that Nix replacement partially abrogated late phase cardioprotection. This result was the first evidence of Nix repression having a functional role inthe cardioprotection against MI seen after late IPC. We also conducted qRT-PCR on sham and I/R samples using 2M and wild type mice. This analysis indicated that Nix mRNA levels were significantly changed 6 hours after I/R, but not in an NF-κB-dependent manner. Ischemia reperfusion (I/R) injury performed on cardiac Nix knockout mice demonstrated a significant reduction in infarction after both 1 hour and 30 minute of ischemia, followed by 24 hours of reperfusion (approx 50% reduction vs. wild type controls). This evidence of endogenous Nix exerting myocardial injury in a model of I/R injury is a novel finding since Nix has not previously been shown to contribute to ischemic injury in the myocardium. Finally we employed an apoptotic gene array to screen for other genes that may be regulated by NF-κB after IPC. The analysis, performed on 84 programmed cell death genes, identified that NF-κB-dependent repressesion of the proapoptotic factors, Fadd, and Fas in addition to the mitochondrial mediated factor Nix. This last discovery indicates that NF-κB may mediate cardioprotection during IPC by repressing pro-cell death activity mediated by both the mitochondrial and the death receptor mediated pathways.
Walter Keith Jones, PhD (Committee Chair)
Guochang Fan, PhD (Committee Member)
Mohammed Matlib, PhD (Committee Member)
Arnold Schwartz, PhD, DSci (Committee Member)
112 p.
Pharmacology
Cardiac; ischemia; NF-kB; Nix; apoptosis

Recommended Citations

Citations

  • Forde, T. L. (2010). NF-kB Regulates Gene Expression of Pro-Apoptotic Factor Nix in Late Ischemic Preconditioning [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1291147865

    APA Style (7th edition)

  • Forde, Tiffany. NF-kB Regulates Gene Expression of Pro-Apoptotic Factor Nix in Late Ischemic Preconditioning. 2010. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1291147865.

    MLA Style (8th edition)

  • Forde, Tiffany. "NF-kB Regulates Gene Expression of Pro-Apoptotic Factor Nix in Late Ischemic Preconditioning." Master's thesis, University of Cincinnati, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1291147865

    Chicago Manual of Style (17th edition)

ucin1291147865
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© 2010, some rights reserved.Creative Commons License NF-kB Regulates Gene Expression of Pro-Apoptotic Factor Nix in Late Ischemic Preconditioning by Tiffany L. Forde is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.