Ferroptosis contributes to the development of cardiac dysfunction in iron overload cardiomyopathy

Abstract Background Ferroptosis is a novel form of cell death, and its role in iron overload cardiomyopathy (IOC) has not been elucidated. Purpose To explore whether ferroptosis of cardiomyocytes contributes to cardiac dysfunction in IOC by cardiac MR (CMR) and molecular biology techniques in vivo. Methods A total of 14 Sprague-Dawley (SD) rats were randomly divided into two groups: the control group (n=6) and the IOC group (n=8). The latter was induced by intraperitoneal injection of iron dextran on alternate days for 9 weeks and underwent a 7T CMR for assessment of cardiac function, including left ventricular ejection fraction (LVEF) and global longitude strain (GLS), along with the assessment of iron overload severity and fibrosis using Cine, T2 mapping, and late gadolinium enhancement (LGE), respectively. Circulating iron overload was determined via blood biochemistry analysis, measuring serum iron, ferritin, and transferrin levels. Furthermore, Prussian blue and Masson staining were employed to identify iron and fibrosis deposition within the myocardium, respectively. Cardiac ultrastructure, especially mitochondria, was examined via transmission electron microscopy (TEM). A sensitive fluorescent probe, dihydroethidium (DHE), was employed for the detection of reactive oxygen species (ROS) levels. Malondialdehyde (MDA), prostaglandin-endoperoxide synthase 2 (PTGS2), and glutathione peroxidase 4 (GPX4) were utilized to identify and quantify levels of lipid peroxidation, thereby providing comprehensive insights into cardiac cellular ferroptosis. Results 6 rats survived in the control group and 5 in the IOC group. Compared with the control group, the IOC rats had reduced T2 values of the cardiac septum (P<0.001), with normal LVEF (P>0.05) but decreased GLS (P<0.01), seen in Fig 1A. Based on blood biochemistry and Prussian blue staining, they were evident that IOC rats exhibited both circulating and cardiac iron overload, as seen in Figure 1B, C. Masson staining showed no obvious myocardial fibrosis, which was consistent with negative CMR LGE results, seen in Fig 1A, B. TEM further elucidated cardiac mitochondrial injuries in IOC rats, including focal vacuolization, swelling, crest disruption, and even disappearance, seen in Fig 2A. The fluorescent probe results revealed a striking increase in red fluorescence within the myocardium of IOC rats, seen in Fig 2B. Additionally, IOC rats exhibited significantly elevated levels of MDA and PTGS2mRNA (P<0.001), accompanied by notable downregulation of GPX4mRNA expression (P<0.001), seen in Fig 2C. These findings suggested the occurrence of ferroptosis in the myocardium of IOC rats. Conclusions In IOC, ferroptosis rather than necrosis is the primary driver of cardiac dysfunction, which is characterized by maintaining normal LVEF but experiencing a reduction in GLS without accompanying myocardial fibrosis. Our study sheds light on the potential involvement of ferroptosis in the pathogenesis of IOC.