Intestinal ischemia–reperfusion (I/R) injury is an injury to the intestine caused by the restoration of intestinal blood supply after a brief or prolonged interruption of blood supply to the intestine. It can lead to distal multi-organ dysfunction and is prone to intestinal obstruction, various types of shock, necrotizing enterocolitis, and intestinal transplantation, etc. It will not only aggravate local tissue injury but also cause mucosal necrosis, which is an important cause of intestinal endothelial dysfunction [1], with high morbidity and mortality [2], [3], [4]. Massive epithelial cell death is a major cause of intestinal mucosal barrier dysfunction [4]. In order to address this I/R-induced injury, several approaches have been reported in recent years,with an increasing number of non-apoptotic pathways,such as necrosis [5], [6], pyroptosis [7], [8] and ferroptosis [9], [10], which has attracted widespread attention, providing a new direction for the treatment of intestinal ischemia–reperfusion injury.Ferroptosis is a recently recognized form of regulated cell death (RCD) and differs from other classical nonapoptotic cell death procedures, characterized by mitochondrial contraction, mitochondrial crest loss, iron dependence, and lipid-reactive oxygen species accumulation [11], [12].

Lipid peroxidation leads to the oxidation of membrane lipid polyunsaturated fatty acids, involving arachidonic acid (AA) and its esterifiable product, phosphatidylethanolamine (PE) [13], [14], [15]. Both are types of abundant polyunsaturated fatty acids (PUFAs) in the intestinal epithelium [16], [17]. It has been documented that 15-lipoxygena-se (LOX)-mediated oxidation of phosphatidylethanolamine (PE) in lipids is a critical cause of ferroptosis and this process is facilitated by the assistance of Acyl-CoA synthetase long-chain family member 4 (ACSL4) by catalyzing the synthesis of arachidonic acid (AA), resulting in PUFA enrichment of cell membranes [18], [19]. However, ferroptosis is also a consequence of a redox imbalance between the production of oxidants and antioxidants, and deficiency of anti-lipid oxidation activities will trigger the occurrence of ferroptosis [20]. For instance, glutathione (GSH) and Glutathione peroxidase 4 (GPX4) are important in mitigating lipid peroxidation to alleviate ferroptosis.Depletion of GSH content may weaken the function of GPX4 and reduce the reduction of lipid peroxides to lipid alcohol [20], [21].

Ferroptosis has been implicated in several pathophysiological contexts such as degenerative diseases, tumor suppression, cardiac diseases, and strokes [11], [12]. Recently, NCOA4-mediated ferritin degradation has been increasingly recognized as a critical mechanism regulating ferroptosis, and its over-activation directly causes an outbreak of ferroptosis by degrading ferritin to produce labile iron.However, whether ferritin degradation is involved in ferroptosis in intestinal ischemia–reperfusion accompanied by autophagy activation remains unknown and therefore requires further investigation

.NCOA4 is highly enriched in autophagic vesicles and is associated with ATG proteins, which introduce cargo receptor complexes into autophagic vesicles [22], [23], [24].

Autophagy is a lysosome-dependent degradation system, and the selective autophagic pathway is newly known as ferritinophagy. During this process, ferritin is delivered to lysosomes to degrade and release labile iron, which plays a critical role in maintaining systemic iron homeostasis [25]. NCOA4 has been identified as a selective autophagy receptor necessary for delivering ferritin to lysosomes. It plays a crucial role in mediating ferritinophagy in certain tissues and cells, but its role has not been assessed in intestinal ischemia–reperfusion [26], [27]. Therefore, it is necessary to further understand the functional role and significance of NCOA4 and its correlation with ferroptosis in the context of intestinal I/R injury.

In this study, we found that in vivo and in vitro, I/R injury promotes ferroptosis in the intestine of mice.Next, we demonstrated that the ferritinophagy process is also involv-ed in intestinal ischemia–reperfusion injury, accompanied by an increase in NCOA4 protein expression. By cellular knockdown, we found that NCOA4 deficiency significantly inhibited ferritin degradation, thereby protecting against ischemia–reperfusion mediated intestinal ferroptosis induced tissue injury.Furthermore, NCOA4 overexpression promotes the degradation of ferritin and the occurrence of ferroptosis. In conclusion, these findings provide a new perspective and target for the treatment of intestinal ischemia–reperfusion.