Doxorubicin (Dox) is an anthracycline antineoplastic drug commonly used against hematologic malignancies and solid tumors for over 30 years. However, its use is largely limited by a cumulative dose-related cardiotoxicity, which includes cardiomyopathy and congestive heart failure. A central mechanism of cardiotoxicity involves generation of reactive oxygen species (ROS), in which Dox generates superoxide, hydrogen peroxide, and hydroxyl radicals leading to mitochondrial damage. Many antioxidants have been used to prevent and minimize Dox-induced cardiotoxicity, but with mixed results. Based upon our cellular studies of ischemia/reperfusion injury, some herbal antioxidants may be more potent than traditional antioxidants in attenuating mitochondrial oxidant injury, and thus could play an important role in preventing cardiac side effects of Dox. The proposed work tests whether two highly effective herbal antioxidants, grape seed proanthocyanidin extract (GSPE) and Scutellaria baicalensis extract (SbE), can prevent Dox-induced cardiotoxicity in our cardiomyocyte model. We will test whether 1) Dox increases mitochondrial oxidant stress and injury in cardiomyocytes, testing whether exposure (1-24 hours) to increasing doses of Dox (1 -100 uM) increases oxidant stress and death in chick cardiomyocytes, measuring oxidation of DCFH and DHE as indicators of hydrogen peroxide, hydroxyl radicals and superoxide generation respectively, and uptake of propidium iodide as a marker of cell death. We will also observe changes in cell membrane morphology and synchronous contractions as a result of Dox exposure to test its effect on contractile function in this model. We will also test whether Dox-induced ROS generation originates from mitochondrial versus nonmitochondrial sources. We will then test whether 2) GSPE (1-100 _ug/ml) and SbE (0.1 -1 mg/ml) individually or in combination, can attenuate Dox-induced ROS generation and ameliorate ROS-mediated injury. We will compare these protective effects to other antioxidants such as tocopherol and N-acetylcysteine. Finally, we will 3) determine whether GSPE or SbE affect the tumoricidal action of Dox on cancer cell lines. This work has the potential to increase our understanding of Dox oxidant cardiotoxicity, and could lead to new applications for herbal antioxidant treatment, which make Dox safer and more effective.
