Defense Date

2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Physiology

First Advisor

EDWARD Jr LESNEFSKY

Abstract

Cardiac injury is increased following ischemia-reperfusion. Mitochondria are the “effector organelles” that are damaged during ischemia (ISC) when there is no blood flow. Resumption of metabolism by damaged mitochondria during reperfusion (REP) results in increased cell injury. Current therapeutic interventions to pre-condition and post-condition the heart during ISC are ineffective during certain conditions like aging and diabetes due to defects in the signaling cascades. In contrast, mitochondrial-based strategies are effective in protecting the heart during ISC-REP. Hence direct therapeutic targeting of dysfunctional mitochondria will provide the potential to bypass the upstream signaling defects and intervene directly upon the effector organelle. Novel mitochondrial-targeted therapy relies on understanding the sites in the electron transport chain (ETC) that are damaged by ISC and produce cell-injury during REP. This project identifies a novel pathological role of cytochrome c in depleting cardiolipin during ischemia after which the mitochondria are in a defective condition that leads to additional cell death during reperfusion. During ischemia oxidants from complex III oxidize cytochrome c, forming a peroxidase, which causes oxidative damage and depletion of cardiolipin. Depletion of cardiolipin disrupts normal physiology and augments cell death. Identification of the innovative pathobiology during ISC-REP recognizes a novel therapeutic target, cytochrome c peroxidase, which can be a focal point for new therapeutic interventions to decrease cardiac injury. In order to maintain homeostatis, living organisms have the methionine sulfoxide reductase system, which reduce both free and protein bound Met(O) back to methionine (Met) in the presence of thioredoxin. Oxidized Trx is inactive and unable to bind to ASK1 thereby activating ASK1 and causing cell death via p38/JNK pathways thereby contributing to the pathogenesis of myocardial ISC-REP injury. In this study we have shown that inhibition of ASK1 protects the heart during REP via the modulation of mitochondria that sustained damage during ISC. The mitochondrial-based mechanism of cardioprotection with ASK1 inhibition enhanced the functional integrity of the inner mitochondrial membrane retaining cytochrome c thereby decreasing cell death. This therapeutic intervention is a key step to achieve the ultimate goal to improve clinical outcomes in patients that suffer an acute myocardial infarction.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

May 2013

Available for download on Wednesday, May 09, 2018

Included in

Physiology Commons

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