Abstract Body: Background: Doxorubicin (DOX), a cancer chemotherapeutic agent, causes sex-specific cardiotoxicity. Lower cardiotoxicity in females compared to males is typically attributed to the cardioprotective effects of estrogen (E2). However, the role of the sex hormones, E2 and testosterone (T), in modulating DOX induced cardiac dysfunction and its underlying mechanisms are not known.
Methods: C57BL/6J mice were divided into four groups, 1) Control, 2) DOX (5 mg/kg/week for 6 weeks), 3) Reverse hormone profile (RevH, castrated males+E2 and ovariectomized females+T), and 4) RevH + DOX. Mouse morbidity was tracked daily. Total body weight and cardiac function was assessed biweekly for 6 weeks by echocardiography, ECG and optical mapping. Dependence on fatty acid versus glucose for metabolism was measured by seahorse analysis.
Results: DOX treatment reduced total body weight (11%) in males, and increased morbidity in males and females. This was associated with reduced mechanical function (15% decrease in stroke volume) in males and electrical remodeling (29% action potential duration prolongation) in females.
In RevH mice, no changes in morbidity or cardiac function were observed compared to Control.
In RevH+DOX males, the onset of morbidity was delayed by two weeks compared to DOX males. This cardioprotective effect was associated with preserved mechanical and electrical function. On the other hand, in RevH+DOX females, morbidity was increased, and this correlated with mechanical (20% reduction in cardiac output) and electrical remodeling (22% increase in action potential duration). Comparing RevH+DOX males to females, males had greater fatty acid dependency while females had greater glucose dependency for metabolism.
Conclusions: These results suggest that sex hormones play a significant role in modulating specific aspects of DOX cardiotoxicity. While E2 has a critical role in preserving cardiac mechanics during DOX therapy, high T levels were associated with mechanical dysfunction in both males and RevH females. Switching of metabolic substrates with greater preference for fatty acid metabolism in mice with higher E2 could underlie cardiac mechanics preservation. Finally, DOX induced electrical remodeling was not altered by sex hormones.