Characterization and prevention of chemotherapy induced cardiac dysfunction
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Background: Anthracyclines, in particular Doxorubicin (DOX), are highly effective chemotherapeutic agents in the breast cancer setting, which are limited by their cardiotoxic side effects. Recently, the introduction of Trastuzumab (TRZ), a novel monoclonal antibody against the HER2 receptor, in the breast cancer setting compounds the issue of DOX mediated cardiac dysfunction. Amongst the potential mechanisms for the deleterious effects of this drug-induced cardiomyopathy, the relationship between nitric oxide synthase 3 (NOS3) and oxidative stress has gained recent attention. Objective: To determine the role of NOS3 in a clinically relevant female murine model of DOX+TRZ induced heart failure. Methods: A total of 120 C57Bl/6 female mice [60 wild type (WT) and 60 NOS3 knockout (NOS3-/-)] were treated with either 0.9% saline, DOX (20 mg/kg), TRZ (10 mg/kg), or DOX+TRZ. Serial echocardiography was performed daily for a total of 10 days, after which the mice were euthanized for histological and biochemical analyses. Results: As compared to WT, NOS3-/- mice demonstrated increased cardiotoxicity following treatment with DOX. This effect was potentiated with DOX+TRZ combination therapy. In WT female mice receiving DOX+TRZ, left ventricular ejection fraction (LVEF) decreased from 75±3% at baseline to 46±2% at day 10 (p<0.05). In the NOS3-/- group, LVEF decreased from 72±3% at baseline to 35±2% at day 10 (p<0.05). LVEF was significantly lower in NOS3-/- mice than WT at day 10 in those receiving DOX+TRZ (p<0.05). As compared to WT, NOS3-/- mice also demonstrated increased mortality following treatment with DOX+TRZ, corroborating the echocardiographic findings. Histological analysis using light and electron microscopy demonstrated increased loss of cell integrity including myofibrillar degradation, cytoplasmic vacuolization, and enlargement of the smooth endoplasmic reticulum in both the WT and NOS3-/- mice treated with DOX+TRZ. There was no significant difference, however, in the degree of cardiac remodeling between the WT and NOS3-/- groups. There was an increasing trend in the degree of cardiac apoptosis in both WT and NOS3-/- mice treated with DOX+TRZ therapy. Conclusion: Congenital absence of NOS3 potentiates the cardiotoxic effects of DOX+TRZ in an acute female murine model of chemotherapy-induced cardiomyopathy.