Fucoidan Protects against Doxorubicin-Induced Cardiotoxicity by Reducing Oxidative Stress and Preventing Mitochondrial Function Injury

Abstract

Doxorubicin (DOXO) is a potent chemotherapeutic drug widely used to treat various cancers. However, its clinical application is limited due to serious adverse effects on dose-dependent cardiotoxicity. Although the underlying mechanism has not been fully clarified, DOXO-induced cardiotoxicity has been mainly attributed to the accumulation of reactive oxygen species (ROS) in cardiomyocytes. Fucoidan, as a kind of sulphated polysaccharide existing in numerous brown seaweed, has potent anti-oxidant, immune-regulatory, anti-tumor, anti-coagulate and anti-viral activities. Here, we explore the potential protective role and mechanism of fucoidan in DOXO-induced cardiotoxicity in mice. Our results show that oral fucoidan supplement exerts potent protective effects against DOXO-induced cardiotoxicity by reducing oxidative stress and preventing mitochondrial function injury. The improved effect of fucoidan on DOXO-induced cardiotoxicity was evaluated by echocardiography, cardiac myocytes size and cardiac fibrosis analysis, and the expression of genes related to cardiac dysfunction and remodeling. Fucoidan reduced the ROS content and the MDA levels but enhanced the activity of antioxidant enzymes GSH-PX and SOD in the mouse serum in a DOXO-induced cardiotoxicity model. In addition, fucoidan also increased the ATP production capacity and restored the levels of a mitochondrial respiratory chain complex in heart tissue. Collectively, this study highlights fucoidan as a potential polysaccharide for protecting against DOXO-induced cardiovascular diseases.

Keywords: cardiotoxicity; doxorubicin; fucoidan; mitochondrial function; oxidative stress.

Figure 1

Fucoidan protects against DOXO-induced cardiotoxicity. (A) Schematic protocol of treatment and echocardiography in mice. C57/BL6J mice were divided into three groups randomly (n = 6 mice in each group). On day 0, mice in the pre-treated fucoidan + DOXO group were fed orally with fucoidan every day for 21 days, while the mice of the ctl and DOXO groups were given water gavage. On day 15, after daily pre-treatment with water or fucoidan, mice in the DOXO group and the pre-treated fucoidan + DOXO group were intraperitoneally injected with DOXO for the following 7 days, while mice of the ctl group were treated with the saline solution. Cardiac function was monitored by echocardiographic analysis on day 21. Mice were sacrificed after the analysis for subsequent ex vivo assays. (B) Fucoidan prevented DOXO-induced left ventricular dilation. Sample M-model short-axis echocardiographic image showing left ventricular dilation caused by DOXO and the protective effect of fucoidan in the mice of the fucoidan + DOXO group. (C) Left ventricular systole/diastole diameter (LVTDs/LVTDd) and left ventricular end-systolic/end-diastolic volume (LVESv/LVEDv) were significantly lower in fucoidan–DOXO-treated mice than in those in the DOXO group, and on the contrary, stroke volume (SV), cardiac output (CO), ejection fraction (EF) and left ventricular fractional shortening (LVFS) were significantly higher. ** p < 0.01; *** p < 0.001. The red asterisk is used to indicate the difference between the DOXO group and the Ctl group, and the black asterisk is used to indicate the difference between the DOXO group and the Fucoidan + DOXO group.

Figure 2

Effects on cardiac myocytes size and cardiac fibrosis of three groups, and fucoidan can improve DOXO-induced myocardial damage. (A) The cardiac myocardial cell area of ctl, DOXO and DOXO + fucoidan groups observed by H&E staining. (B) The rates of cardiac fibrosis of ctl, DOXO and DOXO + fucoidan groups observed by PicroSirius red staining. Each experiment was repeated in 6 samples. *** p < 0.001. The red asterisk is used to indicate the difference between the DOXO group and the Ctl group, and the black asterisk is used to indicate the difference between the DOXO group and the Fucoidan + DOXO group.

Figure 3

Fucoidan plays a key role in DOXO-induced cardiac structure and function damage prevention. (A) Levels of AST, CK-MB and LDH-1 in the mice serum. (B) Levels of CK and LDH in the mice serum. (C) Levels of cardiac dysfunction-related genes’ mRNA expression: ANP, BNP and Myh7. (D) Levels of cardiac remodeling-related genes mRNA expression: CTGF and MMP2. Repeating n = 6 in each group. Both C and D show that DOXO group had higher expression than ctl group, and fucoidan gavage was capable of impairing the cardiac function. * p < 0.05, *** p < 0.001. The red asterisk is used to indicate the difference between the DOXO group and the Ctl group, and the black asterisk is used to indicate the difference between the DOXO group and the Fucoidan + DOXO group.

Figure 4

Fucoidan has a significant effect on reducing oxidative stress in DOXO-treated mice. (A) Levels of ROS in the mice heart tissues. (B) Levels of MDA in the mice serum. (C) Content of GSH-PX in the mice serum. (D) Content of SOD in the mice serum. n = 6 in each group. ** p < 0.05, *** p < 0.001. The red asterisk is used to indicate the difference between the DOXO group and the Ctl group, and the black asterisk is used to indicate the difference between the DOXO group and the Fucoidan + DOXO group.

Figure 5

Fucoidan reduces DOXO-induced cardiotoxicity by preventing mitochondrial function injury. (A) Levels of ATP in the heart tissues of each mouse (all three groups). (B) Levels of mitochondrial function-related genes mRNA expression: mt-Cytb and mt-Atp6. (C) Levels of mitochondrial complex-related genes mRNA expression: NDUFB8, SDHB, UQCR2, MTCO2 and ATP5F1. The results of (B,C) show that the DOXO group exhibits less expression than the ctl group while fucoidan administration can increase the expression level to improve the mitochondrial function. n = 6 in each group. * p < 0.05, ** p < 0.01, *** p < 0.001. The red asterisk is used to indicate the difference between the DOXO group and the Ctl group, and the black asterisk is used to indicate the difference between the DOXO group and the Fucoidan + DOXO group.

Figure 6

Schematic illustration of fucoidan preventing DOXO-induced cardiotoxicity. DOXO triggers cardiotoxicity via elevating oxidative stress and increasing mitochondrial function injury (left). Fucoidan protects against DOXO-induced cardiotoxicity by reducing oxidative stress and enhancing mitochondrial energy metabolism (right).