Item – Theses Canada

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OCLC number
426219776
Link(s) to full text
LAC copy
LAC copy
Author
León Ardila, Hernando,1974-
Title
Protein targets of oxidative stress in the heart.
Degree
Ph. D. -- University of Alberta, 2006
Publisher
Ottawa : Library and Archives Canada = Bibliothèque et Archives Canada, [2007]
Description
3 microfiches
Notes
Includes bibliographical references.
Abstract
Oxidative stress plays an important role in the pathogenesis of cardiovascular diseases. It may cause the modification and activation of proteins such as matrix metalloproteinases (MMPs) and AMP-dependant protein kinase (AMPK) which are implicated in the development of cardiac diseases. I investigated their role in the development of cardiac contractile dysfunction caused by oxidative stress in two different models: (a) the direct infusion of reactive oxygen species into the heart and, (b) endogenous oxidative stress caused by ischemia and reperfusion (I/R) injury. In isolated working rat hearts exposed to a bolus of hydrogen peroxide (H2O2), I found that AMPK and MMP-2 were activated in parallel with the contractile dysfunction caused by H2O2. The use of pyruvate as an antioxidant prevented both AMPK activation and release of MMP-2. However, cardiac dysfunction was prevented by pyruvate but not by MMP inhibitors. In contrast, isolated cardiac myocytes subjected to a continuous infusion of peroxynitrite (ONOO-) developed contractile dysfunction along with activation of MMP-2. The MMP inhibitors doxycycline or PD 166793 prevented contractile dysfunction in this model. I also attempted to determine whether MMPs inhibition by doxycycline reduces contractile dysfunction in myocytes challenged with a single bolus of ONOO- by inhibiting the proteolysis of sarcomeric proteins by MMPs. Interestingly, I found that ONOO- almost enhances (p=0.06) the degradation of myosin light chain 1 (MLC1) as well as doxycycline prevented the reduction in cell viability caused by ONOO-. Doxycycline not only inhibited MMPs but also partially scavenged ONOO-. Our lab has previously shown that endogenous oxidative stress produced by I/R in the heart activates MMP-2 which then proteolyzes specific intracellular protein targets such as troponin I. Therefore, I examined in isolated rat hearts subjected to I/R whether MMP-2 can degrade other proteins besides troponin I using a pharmaco-proteomics approach. I found that MMP-2 co-localizes with MLC1 in the thick filament of cardiac myocytes. In addition, MMP-2 degrades MLC1 in cardiac I/R which is prevented by MMP inhibitors. I found that the actual cleavage site in which MLC1 is degraded by MMP-2 is located between tyrosine 189 and glutamine 190 at the C-terminal domain. In summary, these studies show preventing oxidative stress or inhibiting the activation of MMPs in the heart holds promise in the treatment of cardiac diseases.
ISBN
9780494230640
0494230649