Ferroptosis is a newly recognized form of regulated cell death that is characterized by severe lipid peroxidation initiated by iron overload and the generation of reactive oxygen species (ROS). However, the role of iron in ionizing radiation (IR)-induced intestinal injury has not been fully illustrated yet. In this study, we found that IR induced ferroptosis in intestinal epithelial cells, as indicated by the increase in intracellular iron levels and lipid peroxidation, upregulation of prostaglandin-endoperoxide synthase 2 (PTGS2) mRNA, reduced glutathione peroxidase 4 (GPX4) mRNA and glutathione (GSH) levels, and significant mitochondrial damage. In addition, the iron chelator deferoxamine (DFO) attenuated IR-induced ferroptosis and intestinal injury in vitro and in vivo. Intriguingly, pharmacological inhibition of autophagy with 3-methyladenine (3-MA) mitigated IR-induced ferritin downregulation, iron overload and ferroptosis. IR increased the levels of nuclear receptor coactivator 4 (NCOA4) mRNA and protein. NCOA4 knockdown significantly inhibited the reduction of ferritin, decreased the level of intracellular free iron, and mitigated ferroptosis induced by IR in HIEC cells, indicating that NCOA4-mediated autophagic degradation of ferritin (ferritinophagy) was required for IR-induced ferroptosis. Furthermore, cytoplasmic iron further activated mitoferrin2 (Mfrn2) on the mitochondrial membrane, which in turn increased iron transport into the mitochondria, resulting in increased ROS production and ferroptosis. In addition, mice fed with an iron-deficient diet for 3 weeks showed a significant reversal in the intestinal injury induced by abdominal IR exposure. Taken together, ferroptosis is a novel mechanism of IR-induced intestinal epithelial cytotoxicity, and is dependent on NCOA4-mediated ferritinophagy.

铁死亡是一种新认识的受调节细胞死亡形式，其特征是由铁过载和活性氧（ROS）的产生引发的严重脂质过氧化。然而，铁在电离辐射（IR）引起的肠道损伤中的作用尚未得到充分阐明。在这项研究中，我们发现IR诱导肠上皮细胞铁死亡，表现为细胞内铁水平和脂质过氧化增加、前列腺素内过氧化物合酶2 (PTGS2) mRNA、还原型谷胱甘肽过氧化物酶4 (GPX4) mRNA和谷胱甘肽的上调(GSH) 水平和显着的线粒体损伤。此外，铁螯合剂去铁胺 (DFO)在体外和体内减轻了 IR 诱导的铁死亡和肠道损伤。有趣的是，3-甲基腺嘌呤 (3-MA) 对自噬的药理学抑制可减轻 IR 诱导的铁蛋白下调、铁过载和铁死亡。IR 增加了核受体辅激活因子 4 (NCOA4) mRNA 和蛋白质的水平。NCOA4敲低显着抑制铁蛋白的减少，降低细胞内游离铁的水平，并减轻HIEC细胞中IR诱导的铁死亡，表明NCOA4介导的铁蛋白自噬降解（铁蛋白自噬）是IR诱导的铁死亡所必需的。此外，细胞质铁进一步激活线粒体膜上的线粒体铁蛋白2（Mfrn2），进而增加铁向线粒体的转运，导致ROS产生增加和铁死亡。此外，用缺铁饮食喂养 3 周的小鼠，腹部红外线照射引起的肠道损伤出现了显着逆转。总而言之，铁死亡是 IR 诱导的肠上皮细胞毒性的一种新机制，并且依赖于 NCOA4 介导的铁蛋白自噬。