Cardiac iron overload promotes ferroptosis and cardiac dysfunction in mice with sickle cell disease

Abstract

Ferroptosis is a recently defined form of iron‐dependent, non‐apoptotic programmed cell death that is characterized by accumulation of lipid peroxides. Although ferroptosis was first identified in cancer cells, recent studies have demonstrated its implications in a wide range of physiological disorders such as ischemic and hemorrhagic stroke, Alzheimer’s disease, and epilepsy. Notably, there is a significant association between iron loading and heart failure. For example, cardiomyopathy is the leading cause of mortality in thalassemia and accounts for 30% of mortality in iron overload sickle cell disease (SCD). However, the underlying mechanisms of iron‐induced cardiotoxicity are not well understood. Although cell death mechanisms such as apoptosis and necrosis have been recognized in the context of heart disease, the role of ferroptosis in cardiac damage is largely unexplored. Here we hypothesized that cardiac iron overload promotes ferroptosis and cardiac dysfunction in the Townes mouse model of SCD. To test our hypothesis, we determined and compared iron levels, cardiotoxicity and ferroptotic markers between sickling HbSS (homozygous for the human βS globin gene) and their non‐sickling heterozygous HbAS littermates. First, we observed an increase in systemic and tissue iron levels in HbSS mice. We also found increased expression of the cardiotoxic markers ANP (atrial natriuretic peptide) and BNP (brain natriuretic peptide). These results were associated with an upregulation of the ferroptotic marker, Ptgs2, and increased levels of lipid peroxidation, a characteristic of ferroptosis, in the cardiac tissue of HbSS mice. However, no differences were found in caspase‐3 levels, suggesting that cardiotoxicity does not result from apoptotic mechanisms. To distinguish between the effects of the sickling gene and iron loading, we induced iron overload in non‐sickling mice by iron dextran treatment, an established model of secondary iron overload. Similar to our findings in sickling mice, we demonstrated that induced iron overload displayed increased lipid peroxidation and cardiac damage, consistent with cardiac ferroptosis. Finally, inhibition of ferroptosis, either by chelating excess iron (using an iron chelator deferoxamine) or by inhibiting lipid peroxidation (using ferrostatin‐1, a lipid radical scavenger), improved cardiac dysfunction in sickling mice. These findings suggest a novel mechanism of cardiac cell death in SCD and could provide potential protective targets against iron‐induced cardiotoxicity.