Cardioprotective role of vitamin C in the mitigation of oxidative/nitrosative stress in doxorubicin-induced cardiotoxicity
Doxorubicin (Dox) cardiotoxicity is a serious concern in its use for the treatment of cancers. Oxidative stress (OS) and nitrosative stress (NS) are suggested to be the main causes of this cardiotoxicity. We used rat cardiomyocytes as well as whole animals to characterize changes in Dox-induced apoptosis, inflammation, OS/NS, cardiac structure/function and Vitamin C (Vit C) transporter proteins and the mitigation of these effects by Vit C. In cardiomyocytes, Dox (10 µM) caused an increase in both superoxide radical and Nitric oxide (NO), resulting in the generation of peroxynitrite, protein nitration and nitrosylation. Dox increased Nitric oxide synthase (NOS) activity via the upregulated protein expression of inducible NOS (iNOS) and the altered protein expression as well as activation of endothelial NOS (eNOS). Dox also reduced the stability of dimeric eNOS and increased ratio of monomeric/dimeric eNOS. Dox-induced increase in TNF-α and a reduction in IL-10 was also noted. These Dox-mediated alterations in cardiomyocytes were attenuated by Vit C (25 µM) pretreatment. In the rat model of Dox-induced cardiotoxicity (cumulative dose, 15mg/kg), both systolic and diastolic functions were decreased and there was structural damage in hearts. These changes were associated with increased levels of myocardial reactive oxygen species; reduction in anti-oxidant enzyme activities (SOD, GPx and catalase); increased expression of apoptotic proteins (Bax, Bnip-3, Bak and Caspase-3) and inflammation. An increase in OS/NS was indicated by an increase in superoxide, protein carbonyl formation, lipid peroxidation, NO, NOS activity, protein nitrosylation and iNOS expression. Dox increased the levels of cardiac TNF-α, IL-1β and IL-6 while the expression of Vit C transporter proteins (SVCT-2 and Glut-4) was reduced. Vit C (50 mg/kg) prevented all these changes, improved Dox-mediated systolic and diastolic dysfunctions, prevented structural damage and improved animal survival. These results suggest that Vit C provides cardioprotection by reducing OS/NS as well as inflammation via modulation of Dox-induced increase in the NO levels and NOS activity. The molecular details in this study provide a rationale for a prophylactic use of Vit C to reduce chemotherapy induced cardiotoxicity.