Background: Cardio-Oncology focuses on the detection, prevention, and treatment of cardiovascular complications in individuals receiving cancer therapy. While the combination of Doxorubicin (DOX) and Trastuzumab (TRZ) reduces the progression and recurrence of breast cancer, these anti-cancer drugs are associated with significant cardiotoxic side effects. Little is known on the potential cardioprotective role of flaxseed (FLX) in the prevention of DOX+TRZ mediated cardiotoxicity.

Objective: To investigate whether prophylactic administration of FLX and its bioactive components, alpha-linolenic acid (ALA) or secoisolariciresinol-diglucoside (SDG), will be cardioprotective against DOX+TRZ mediated cardiotoxicity in a chronic in vivo female murine model.

Methods: A total of 195 wild-type C57Bl/6 female mice were divided into four groups and received daily prophylactic treatment with either: i) regular chow (RC); ii) FLX; iii) ALA; or iv) SDG for the entire 6-week study period. Within each arm, mice received 3 weekly injections of either: i) 0.9% Saline; ii) DOX (8 mg/kg); TRZ (3 mg/kg); or DOX+TRZ, at weeks 4, 5, and 6 to model chemotherapy associated cardiotoxicity. Following serial echocardiography, cardiac tissue was collected for histological analysis. Plasma oxylipins and biochemical analyses were performed to evaluate markers of: i) inflammation; ii) oxidative stress (OS) and apoptosis; and iii) mitochondrial dysfunction, using liquid chromatography electrospray ionization tandem mass spectrometry and Western blotting.

Results: In our chronic in vivo model of DOX and TRZ induced cardiotoxicity, prophylactic treatment with FLX, ALA, or SDG prevented the development of left ventricular systolic dysfunction (LVSD). The echocardiographic findings revealed that in RC+DOX treated mice, left ventricular ejection fraction (LVEF) decreased from 75±2% to 49±2% at week-6. Prophylactic administration of FLX, ALA, or SDG partially preserved LVEF with values of 66±3%, 63±3% and 65±4%, respectively. Similarly, in mice treated with RC+DOX+TRZ, the LVEF decreased from 73±2% to 38±2% at week-6. Addition of FLX, ALA, or SDG partially preserved LVEF with values of 61±2%, 60±3% and 61±4%, respectively. Animals treated with RC+DOX or RC+DOX+TRZ demonstrated increased loss of cellular integrity and myofibril disarray, which was partially attenuated by the FLX, ALA, and SDG diets. Plasma analysis confirmed that COX-derived oxylipins (inflammation) and 8,9-DiHETrE (OS) concentrations were significantly upregulated in the RC+DOX+TRZ treated mice. However, the FLX and ALA diets significantly downregulated COX-derived metabolites while 8,9-DiHETrE concentrations were significantly reduced by prophylactic treatment with FLX, ALA, and SDG. Western blot analysis detected a significant increase in the expression of NF-kB (inflammation), PARP (apoptosis), Bax/Bcl-xL (apoptosis), and Bnip3 (mitochondrial dysfunction) in the RC+DOX+TRZ group. However, these increases were attenuated by the prophylactic treatment with either FLX, ALA, or SDG.

Conclusion: In a chronic in vivo female murine model of DOX+TRZ mediated cardiotoxicity, FLX, ALA, and SDG partially prevented adverse cardiovascular remodeling by attenuating the degree of inflammation, apoptosis, and mitochondrial dysfunction.