Sickle cell disease (SCD) is characterized by increased
hemolysis, which results in plasma
heme overload and ultimately cardiovascular complications. Here, we hypothesized that increased
heme in SCD causes upregulation of
heme oxygenase 1 (Hmox1), which consequently drives
cardiomyopathy through ferroptosis, an
iron-dependent non-apoptotic form of cell death. First, we demonstrated that the Townes SCD mice had higher levels of
hemopexin-free
heme in the serum and increased
cardiomyopathy, which was corrected by
hemopexin supplementation.
Cardiomyopathy in SCD mice was associated with upregulation of cardiac Hmox1, and inhibition or induction of Hmox1 improved or worsened cardiac damage, respectively. Because free
iron, a product of
heme degradation through Hmox1, has been implicated in toxicities including ferroptosis, we evaluated the downstream effects of elevated
heme in SCD. Consistent with Hmox1 upregulation and
iron overload, levels of lipid peroxidation and ferroptotic markers increased in SCD mice, which were corrected by
hemopexin administration. Moreover, ferroptosis inhibitors decreased
cardiomyopathy, whereas a ferroptosis inducer
erastin exacerbated cardiac damage in SCD and induced cardiac ferroptosis in nonsickling mice. Finally, inhibition or induction of Hmox1 decreased or increased cardiac ferroptosis in SCD mice, respectively. Together, our results identify ferroptosis as a key mechanism of
cardiomyopathy in SCD.