Effects of natural products on doxorubicin-induced cyctotoxicity in H9C2 cells

Doxorubicin (Adriamycin, DOX) is a widely used anticancer drug which has a well demonstrated clinical efficacy. However, it also causes damage to the heart which limits its clinical use. The main mechanism of doxorubicin-induced cardiotoxicity involves oxidative stress of cardiac cells. Recently, nitric oxide (NO) pathway has been suggested to play a significant role in doxorubicin-induced cardiotoxicity. Certain natural products, including traditional Chinese herbal medicines, have been demonstrated with protective actions on doxorubicin-induced cardiotoxicity. However, the scope of their actions and related mechanisms are generally not clear. The aims of this project are: 1) to conduct a literature review of actions of natural products on doxorubicin-induced cardiotoxicity, and 2) to investigate the effects of tanshinone IIa, the active compound of Salvia miltiorrhiza, and its synthetic derivatives on doxorubicin-induced cardiotoxicity in H9C2 cells, and their relationships to endogenous NO pathways. Method: For the literature review, extensive literature search was conducted and relevant research publications were identified. For experimental studies, H9C2 cells were cultured under standard cell culture operation procedure. Cardiac cell toxicity was assessed by cell viability assay. NO production was determined by DAF-2DA and nitrite assays. Results: The actions of various natural compounds/products published previously on doxorubicin-induced cardiotoxicity have been reviewed, including their relevant mechanisms and relationships to anticancer actions of doxorubicin. Experiments studies found that doxorubicin caused a concentration and time dependent cell death in H9C2 cells, which was significantly inhibited by the cell permeable superoxide dismutase (SOD) mimetic and peroxynitrite scavenger MnTBAP and the inducible NO synthase (iNOS) inhibitors L-NIL. NO production in the cell media was also increased by doxorubicin which was inhibited by L-NIL. Tanshinone IIa at concentrations did not affect the cell viability significantly inhibited doxorubicin-induced cell death. It also inhibited doxorubicin-induced increase in NO production. Among 8 synthetic derivatives tested, AFC1 was shown with a protective effect on doxorubicin-induced cardiotoxicity at relative low concentrations (0.3µM-10µM). Similar effects were observed for AFC2. In conclusion, a number of natural products have been shown with protective actions against doxorubicin-induced cardiotoxicity, and some exhibit a potential therapeutic value for clinical applications. In addition, tanshinone IIa and related synthetic compounds has been demonstrated for the first time that its protective actions are associated with endogenous NO pathways. Further studies on these compounds may lead to identify new effective therapies to reduce or prevent doxorubicin-induced cardiotoxicity.