Cell density impacts the susceptibility to ferroptosis by modulating IRP1-mediated iron homeostasis.

Ferroptosis has been implicated in several neurological disorders and may be therapeutically targeted. However, the susceptibility to ferroptosis varies in different cells, and inconsistent results have been reported even using the same cell line. Understanding the effects of key variables of in vitro studies on ferroptosis susceptibility is of critical importance to facilitate drug discoveries targeting ferroptosis. Here, we showed that increased cell seeding density leads to enhanced resistance to ferroptosis by reducing intracellular iron levels. We further identified iron-responsive protein 1 (IRP1) as the key protein affected by cell density, which affects the expression of ferroportin or transferrin receptor and results in altered iron levels. Such observations were consistent across different cell lines, indicating that cell density should be tightly controlled in studies of ferroptosis. Since cell densities vary in different brain regions, these results may also shed light on selective regional vulnerability observed in neurological disorders.

Thrombin induces ACSL4-dependent ferroptosis during cerebral ischemia/reperfusion.

Ischemic stroke represents a significant danger to human beings, especially the elderly. Interventions are only available to remove the clot, and the mechanism of neuronal death during ischemic stroke is still in debate. Ferroptosis is increasingly appreciated as a mechanism of cell death after ischemia in various organs. Here we report that the serine protease, thrombin, instigates ferroptotic signaling by promoting arachidonic acid mobilization and subsequent esterification by the ferroptotic gene, acyl-CoA synthetase long-chain family member 4 (ACSL4). An unbiased multi-omics approach identified thrombin and ACSL4 genes/proteins, and their pro-ferroptotic phosphatidylethanolamine lipid products, as prominently altered upon the middle cerebral artery occlusion in rodents. Genetically or pharmacologically inhibiting multiple points in this pathway attenuated outcomes of models of ischemia in vitro and in vivo. Therefore, the thrombin-ACSL4 axis may be a key therapeutic target to ameliorate ferroptotic neuronal injury during ischemic stroke.

Ferroptosis: mechanisms and links with diseases.

Ferroptosis is an iron-dependent cell death, which is different from apoptosis, necrosis, autophagy, and other forms of cell death. The process of ferroptotic cell death is defined by the accumulation of lethal lipid species derived from the peroxidation of lipids, which can be prevented by iron chelators (e.g., deferiprone, deferoxamine) and small lipophilic antioxidants (e.g., ferrostatin, liproxstatin). This review summarizes current knowledge about the regulatory mechanism of ferroptosis and its association with several pathways, including iron, lipid, and cysteine metabolism. We have further discussed the contribution of ferroptosis to the pathogenesis of several diseases such as cancer, ischemia/reperfusion, and various neurodegenerative diseases (e.g., Alzheimer's disease and Parkinson's disease), and evaluated the therapeutic applications of ferroptosis inhibitors in clinics.

The pathological role of ferroptosis in ischemia/reperfusion-related injury.

Ischemia/reperfusion (I/R) is a pathological process that occurs in numerous organs throughout the human body, and it is frequently associated with severe cellular damage and death. Recently it has emerged that ferroptosis, a new form of regulated cell death that is caused by iron-dependent lipid peroxidation, plays a significantly detrimental role in many I/R models. In this review, we aim to revise the pathological process of I/R and then explore the molecular pathogenesis of ferroptosis. Furthermore, we aim to evaluate the role that ferroptosis plays in I/R, providing evidence to support the targeting of ferroptosis in the I/R pathway may present as a therapeutic intervention to alleviate ischemia/reperfusion injury (IRI) associated cell damage and death.

Deferoxamine ameliorates adipocyte dysfunction by modulating iron metabolism in ob/ob mice.

OBJECTIVE: The mechanisms underlying obesity and anti-obesity processes have garnered remarkable attention as potential therapeutic targets for obesity-associated metabolic syndromes. Our prior work has shown the healing efficacy of iron reduction therapies for hepatic steatosis in a rodent model of diabetes and obesity. In this study, we investigated how iron depletion by deferoxamine (DFO) affected adipocyte dysfunction in the epididymal adipose tissues of ob/ob mice. METHODS: Male ob/ob mice were assigned to either a vehicle-treated or DFO-treated group. DFO (100 mg/kg body weight) was injected intraperitoneally for 15 days. RESULTS: We confirmed that iron deposits were statistically increased in the epididymal fat pad of 26-week-old ob/ob mice compared with wild-type (WT) mice. DFO significantly improved vital parameters of adipose tissue biology by reducing reactive oxygen species and inflammatory marker (TNFα, IL-2, IL-6, and Hepcidin) secretion, by increasing the levels of antioxidant enzymes, hypoxia-inducible factor-1α (HIF-1α) and HIF-1α-targeted proteins, and by altering adipocytic iron-, glucose- and lipid-associated metabolism proteins. Meanwhile, hypertrophic adipocytes were decreased in size, and insulin signaling pathway-related proteins were also activated after 15 days of DFO treatment. CONCLUSIONS: These findings suggest that dysfunctional iron homeostasis contributes to the pathophysiology of obesity and insulin resistance in adipose tissues of ob/ob mice. Further investigation is required to develop safe iron chelators as effective treatment strategies against obesity, with potential for rapid clinical application.