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Cardiac peroxynitrite formation and left ventricular dysfunction following doxorubicin treatment in mice
D M Weinstein1, M J Mihm, J A Bauer
1Division of Pharmacology, College of Pharmacy, The Ohio State University, Columbus, Ohio, USA.
Abstract:
Selective cardiotoxicity of doxorubicin remains a significant and dose-limiting clinical problem. The mechanisms involved have not been fully defined but may involve the production of reactive oxygen species and/or alteration of cardiac energetics. Here, we tested the hypotheses that doxorubicin causes left ventricular dysfunction in mice and is associated with dysregulation of nitric oxide in cardiac tissue, leading to the accumulation of 3-nitrotyrosine (a biomarker of peroxynitrite formation). Animals were dosed with doxorubicin (20 mg/kg i.p.), and left ventricular performance was assessed in vivo using M-mode and Doppler echocardiography. Five days after doxorubicin administration, left ventricular fractional shortening, cardiac output, and stroke volume parameters were significantly reduced relative to control values (30.0 +/- 3.6 versus 46.1 +/- 1. 6%, 8.9 +/- 0.9 versus 11.5 +/- 0.6 ml/min, and 21.2 +/- 0.1 versus 29.5 +/- 0.1 microl for doxorubicin versus control, P <.05). Statistically significant (P <.05) increases in the immunoprevalence of myocardial inducible nitric oxide synthase (33 +/- 18 versus 9 +/- 2%, via quantitative image analysis) and 3-nitrotyrosine formation (56 +/- 24 versus 0.3 +/- 0.4%) were also observed after doxorubicin. Correlation analyses revealed a highly significant inverse relationship between left ventricular fractional shortening and cardiac 3-nitrotyrosine immunoprevalence (P <.01). No such relationship was observed for inducible nitric oxide synthase. Western blot analyses of cardiac myofibrillar fractions revealed extensive nitration of an abundant 40-kDa protein, shown to be the myofibrillar isoform of creatine kinase. These data demonstrate that alteration of cardiac nitric oxide control and attendant peroxynitrite formation may be an important contributor to doxorubicin-induced cardiac dysfunction. Furthermore, nitration of key myofibrillar proteins and alteration of myocyte energetics are implicated.
Insights
Doxorubicin chemotherapy causes heart dysfunction by increasing harmful nitric oxide and peroxynitrite in cardiac tissue. This leads to protein damage and reduced heart performance, highlighting a key mechanism in cardiotoxicity.
Area of Science:
- Cardiology
- Oncology
- Biochemistry
Background:
- Doxorubicin is a widely used chemotherapy agent with dose-limiting cardiotoxicity.
- The exact mechanisms of doxorubicin-induced cardiotoxicity are not fully understood.
- Potential mechanisms include reactive oxygen species production and altered cardiac energetics.
Purpose of the Study:
- To investigate if doxorubicin causes left ventricular dysfunction in mice.
- To determine if doxorubicin is associated with nitric oxide dysregulation in cardiac tissue.
- To examine the accumulation of 3-nitrotyrosine as a biomarker of peroxynitrite formation.
Main Methods:
- Mice were administered doxorubicin (20 mg/kg i.p.).
- Left ventricular performance was assessed using echocardiography.
- Myocardial inducible nitric oxide synthase and 3-nitrotyrosine levels were measured via immunoprevalence.
- Cardiac myofibrillar fractions were analyzed by Western blot.
Main Results:
- Doxorubicin significantly reduced left ventricular fractional shortening, cardiac output, and stroke volume.
- Increased myocardial inducible nitric oxide synthase and 3-nitrotyrosine formation were observed post-doxorubicin.
- A significant inverse correlation was found between fractional shortening and cardiac 3-nitrotyrosine.
- Myofibrillar creatine kinase was identified as a nitrated protein.
Conclusions:
- Alterations in cardiac nitric oxide control and peroxynitrite formation contribute to doxorubicin-induced cardiac dysfunction.
- Nitration of myofibrillar proteins, such as creatine kinase, and altered myocyte energetics are implicated in this process.