Doxorubicin and its derivatives are among the most potent anticancer drugs known. Unfortunately their therapeutic efficacy is severely restricted by a dose-accumulated cardiotoxicity. Our preliminary results using adult rat cardiomyocytes as a working model, have shown evidence for the mechanism which could explain how reactive oxygen species generated by doxorubicin provoke myofibrillar degeneration while not causing severe oxidative damage. Specifically, 1) we visualized directly doxorubicin accumulation in cardiac mitochondria and subsequent increase in intracellular oxidation in living cardiomyocytes, 2) observed that doxorubicin administration is associated with redistribution of the protein kinase C epsilon isoform from cytosol to myofibrils, and 3) detected disruption of the periodicity of actin staining after repetitive exposure of myocytes to clinically relevant drug concentrations. Based on these data we propose the following sequence of events: doxorubicin rapidly accumulates in cardiac mitochondria; it then initiates lipid peroxidation via formation of superoxide and drug complexes with transition metals; and although the degree of lipid peroxidation is small and no significant membrane damage occurs, it leads to the activation of phospholipases; lipase thereupon release several second messengers, including arachidonic acid, activating a specific protein kinase C isoform; the kinase then initiates myofibrillar degeneration. To support the above hypothesis we aim to 1) establish a causal relationship between observed doxorubicin-induced kinase translocation and increased free radical formation; 2) to determine whether doxorubicin-induced free radicals and/or protein kinase C translocation are prerequisites for changes in myocyte myofibrillar organization and cell contractility; 3) to uncover role of phospholipase A2 in doxorubicin-induced activation of kinase and ensuing changes in myofibrillar organization and contractility. The proposed experiments aim to reveal explicit pathways through which reactive oxygen species are involved in anthracycline- induced cardiomyopathy. The studies will also provide new information about kinases involvement in myofilament degeneration and interaction between reactive oxygen species and signal transduction pathways.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL062419-02
Application #
6184658
Study Section
Chemical Pathology Study Section (CPA)
Program Officer
Forry-Schaudies, Suzanne L
Project Start
1999-04-01
Project End
2003-03-31
Budget Start
2000-04-01
Budget End
2001-03-31
Support Year
2
Fiscal Year
2000
Total Cost
$161,583
Indirect Cost
Name
Texas Tech University
Department
Physiology
Type
Schools of Medicine
DUNS #
609980727
City
Lubbock
State
TX
Country
United States
Zip Code
79430
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Minotti, Giorgio; Sarvazyan, Narine (2007) The anthracyclines: when good things go bad. Cardiovasc Toxicol 7:53-5
McHowat, Jane; Swift, Luther M; Crown, Kimberly N et al. (2004) Changes in phospholipid content and myocardial calcium-independent phospholipase A2 activity during chronic anthracycline administration. J Pharmacol Exp Ther 311:736-41
Arutunyan, Ara; Swift, Luther; Sarvazyan, Narine (2004) Multiple injury approach and its use for toxicity studies. Cardiovasc Toxicol 4:1-10
Swift, Luther; McHowat, Jane; Sarvazyan, Narine (2003) Inhibition of membrane-associated calcium-independent phospholipase A2 as a potential culprit of anthracycline cardiotoxicity. Cancer Res 63:5992-8
Arutunyan, A; Webster, D R; Swift, L M et al. (2001) Localized injury in cardiomyocyte network: a new experimental model of ischemia-reperfusion arrhythmias. Am J Physiol Heart Circ Physiol 280:H1905-15
McHowat, J; Swift, L M; Sarvazyan, N (2001) Oxidant-induced inhibition of myocardial calcium-independent phospholipase A2. Cardiovasc Toxicol 1:309-16
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Swift, L M; Sarvazyan, N (2000) Localization of dichlorofluorescin in cardiac myocytes: implications for assessment of oxidative stress. Am J Physiol Heart Circ Physiol 278:H982-90