Ferritinophagy activation and sideroflexin1-dependent mitochondrial iron overload contribute to patulin-induced cardiac inflammation and fibrosis

Patulin (PAT) is a mycotoxin that is commonly present throughout the ecosystem where fungi grow and mainly contaminates food, soil, and water. PAT was found to be cardiotoxic in previous studies. However, the detailed mechanism has not been fully elucidated. The present study aimed to explore the role and underlying mechanism of ferroptosis in PAT-induced cardiac injury. Here, we confirmed in vivo and in vitro that ferroptosis is involved in PAT-induced myocardial inflammation and fibrosis. Mice exposed to PAT (1 and 2 mg/kg body weight/day for 14 days) exhibited myocardial inflammation and fibrosis along with disrupted iron homeostasis, elevated lipid peroxidation, depletion of glutathione peroxidase 4, and abnormal mitochondrial morphology. When primary neonatal rat cardiomyocytes (NRCMs) and H9c2 cells were exposed to PAT, ferroptosis was initiated in a dose-dependent manner, and this process could be significantly attenuated by ferrostatin-1. Mechanistically, we found that nuclear receptor coactivator (NCOA) 4, a master regulator of ferritinophagy, bound to and degraded ferritin in response to PAT treatment, thereby releasing large amounts of ferrous iron and further leading to sideroflexin (SFXN) 1-dependent mitochondrial iron overload. Conversely, knockdown of NCOA4 or SFXN1 with small interfering RNAs could effectively ameliorate ferroptotic cell death, cellular or mitochondrial iron overload and lipid peroxides accumulation. Furthermore, myocardial inflammation and fibrosis in PAT-exposed mice was alleviated by the mitochondrial iron chelator deferiprone. Overall, our findings underscore that ferritinophagy activation and SFXN1-dependent mitochondrial iron overload play critical roles in PAT-induced myocardial ferroptosis and consequent cardiotoxicity.