m6A reader YTHDC2 mediates NCOA4 mRNA stability affecting ferritinophagy to alleviate secondary injury after intracerebral haemorrhage

Oxidative stress and neuronal dysfunction caused by intracerebral haemorrhage (ICH) can lead to secondary injury. The m6A modification has been implicated in the progression of ICH. This study aimed to investigate the role of the m6A reader YTHDC2 in ICH-induced secondary injury. ICH models were established in rats using autologous blood injection, and neuronal cell models were induced with Hemin. Experiments were conducted to overexpress YTH domain containing 2 (YTHDC2) and examine its effects on neuronal dysfunction, brain injury, and neuronal ferritinophagy. RIP-qPCR and METTL3 silencing were performed to investigate the regulation of YTHDC2 on nuclear receptor coactivator 4 (NCOA4). Finally, NCOA4 overexpression was used to validate the regulatory mechanism of YTHDC2 in ICH. The study found that YTHDC2 expression was significantly downregulated in the brain tissues of ICH rats. However, YTHDC2 overexpression improved neuronal dysfunction and reduced brain water content and neuronal death after ICH. Additionally, it reduced levels of ROS, NCOA4, PTGS2, and ATG5 in the brain tissues of ICH rats, while increasing levels of FTH and FTL. YTHDC2 overexpression also decreased levels of MDA and Fe2+ in the serum, while promoting GSH synthesis. In neuronal cells, YTHDC2 overexpression alleviated Hemin-induced injury, which was reversed by Erastin. Mechanistically, YTHDC2-mediated m6A modification destabilized NCOA4 mRNA, thereby reducing ferritinophagy and alleviating secondary injury after ICH. However, the effects of YTHDC2 were counteracted by NCOA4 overexpression. Overall, YTHDC2 plays a protective role in ICH-induced secondary injury by regulating NCOA4-mediated ferritinophagy.

Cryptochrome 1 regulates ovarian granulosa cell senescence through NCOA4-mediated ferritinophagy

Age-associated decreases in follicle number and oocyte quality result in a decline in female fertility, which is associated with increased infertility. Granulosa cells play a major role in oocyte development and maturation both in vivo and in vitro. However, it is unclear whether a reduction in cryptochrome 1 (Cry1) expression contributes to granulosa cell senescence, and further exploration is needed to understand the underlying mechanisms. In this study, we investigated the role of Cry1, a core component of the molecular circadian clock, in the regulation of senescence in ovarian granulosa cells. Western blotting and qRT-PCR showed that Cry1 expression was downregulated in aged human ovarian granulosa cells and was correlated with age and anti-Müllerian hormone (AMH) levels. RNA-seq analysis suggested that ferritinophagy was increased after Cry1 knockdown in KGN cells. MDA, iron, and reactive oxygen species (ROS) assays were used to detect cellular ferritinophagy levels. Ferroptosis inhibitors, iron chelators, autophagy inhibitors, and nuclear receptor coactivator 4 (NCOA4) knockdown alleviated KGN cell senescence induced by Cry1 knockdown. Immunofluorescence, immunoprecipitation, and ubiquitination assays indicated that Cry1 affected NCOA4 ubiquitination and degradation through HERC2, thereby affecting NCOA4-mediated ferritinophagy and causing granulosa cell senescence. KL201, a Cry1 stabilizer, enhanced ovarian function in naturally aged mice by reducing ferritinophagy. Our study reveals the potential mechanisms of action of Cry1 during ovarian aging and provides new insights for the clinical treatment of age-related fertility decline.

Bortezomib elevates intracellular free Fe2+ by enhancing NCOA4-mediated ferritinophagy and synergizes with RSL-3 to inhibit multiple myeloma cells

Iron contributes to tumor initiation and progression; however, excessive intracellular free Fe2+ can be toxic to cancer cells. Our findings confirmed that multiple myeloma (MM) cells exhibited elevated intracellular iron levels and increased ferritin, a key protein for iron storage, compared with normal cells. Interestingly, Bortezomib (BTZ) was found to trigger ferritin degradation, increase free intracellular Fe2+, and promote ferroptosis in MM cells. Subsequent mechanistic investigation revealed that BTZ effectively increased NCOA4 levels by preventing proteasomal degradation in MM cells. When we knocked down NCOA4 or blocked autophagy using chloroquine, BTZ-induced ferritin degradation and the increase in intracellular free Fe2+ were significantly reduced in MM cells, confirming the role of BTZ in enhancing ferritinophagy. Furthermore, the combination of BTZ with RSL-3, a specific inhibitor of GPX4 and inducer of ferroptosis, synergistically promoted ferroptosis in MM cell lines and increased cell death in both MM cell lines and primary MM cells. The induction of ferroptosis inhibitor liproxstatin-1 successfully counteracted the synergistic effect of BTZ and RSL-3 in MM cells. Altogether, our findings reveal that BTZ elevates intracellular free Fe2+ by enhancing NCOA4-mediated ferritinophagy and synergizes with RSL-3 by increasing ferroptosisin MM cells.

PM2.5-induced iron homeostasis imbalance triggers cardiac hypertrophy through ferroptosis in a selective autophagy crosstalk manner

Exposure to PM2.5 is correlated with cardiac remodeling, of which cardiac hypertrophy is one of the main clinical manifestations. Ferroptosis plays an important role in cardiac hypertrophy. However, the potential mechanism of PM2.5-induced cardiac hypertrophy through ferroptosis remains unclear. This study aimed to explore the molecular mechanism of cardiac hypertrophy caused by PM2.5 and the intervention role of MitoQ involved in this process. The results showed that PM2.5 could induce cardiac hypertrophy and dysfunction in mice. Meanwhile, the characteristics of ferroptosis were observed, such as iron homeostasis imbalance, lipid peroxidation, mitochondrial damage and abnormal expression of key molecules. MitoQ treatment could effectively mitigate these alternations. After treating human cardiomyocyte AC16 with PM2.5, ferroptosis activator (Erastin) and inhibitor (Fer-1), it was found that PM2.5 could promote ferritinophagy and lead to lipid peroxidation, mitochondrial dysfunction as well as the accumulation of intracellular and mitochondrial labile iron. Subsequently, mitophagy was activated and provided an additional source of labile iron, enhancing the sensitivity of AC16 cells to ferroptosis. Furthermore, Fer-1 alleviated PM2.5-induced cytotoxicity and iron overload in the cytoplasm and mitochondria of AC16 cells. It was worth noting that during the process of PM2.5 caused ferroptosis, abnormal iron metabolism mediated the activation of ferritinophagy and mitophagy in a temporal order. In addition, NCOA4 knockdown reversed the iron homeostasis imbalance and lipid peroxidation caused by PM2.5, thereby alleviating ferroptosis. In summary, our study found that iron homeostasis imbalance-mediated the crosstalk of ferritinophagy and mitophagy played an important role in PM2.5-induced ferroptosis and cardiac hypertrophy.

Dihydroartemisinin (DHA) inhibits myofibroblast differentiation through inducing ferroptosis mediated by ferritinophagy

Idiopathic pulmonary fibrosis (IPF) is caused by persistent micro-injuries and aberrant repair processes. Myofibroblast differentiation in lung is a key event for abnormal repair. Dihydroartemisinin(DHA), a well-known anti-malarial drug, have been shown to alleviate pulmonary fibrosis, but its mechanism is not clear. Ferroptosis is involved in the pathgenesis of many diseases, including IPF. Ferritinophagy is a form of cellular autophagy which regulates intracellular iron homeostasis. The function of DHA on myofibroblasts differentiation of pulmonary and whether related with ferroptosis and ferritinophagy are unknown now. Using human fetal lung fibroblast 1(HFL1) cell line and the qRT-PCR, immunofluorescent and Western blotting techniques, we found that after TGF-β1 treatment, the levels of ɑ-SMA expression and ROS increased; the mRNA and protein levels of FTH1 and NCOA4, the content of Fe2+ and 4-HNE increased significantly at 6h, then gradually reduced with time. After DHA treatment, FHL1 cells appeared ferroptosis; the levels of α-SMA mRNA and protein reduced and the levels of ROS and 4-HNE increased; the Fe2+ levels decreased sharply at 6h, then increased with time, and were higher than normal since 24h; the mRNA and protein levels of FTH1 and NCOA4 decreased, exhibited a downward trend. These results show that Fe2+, ROS and lipid peroxidation are involved in and ferritinophagy is inhibited during fibroblast-to-myofibroblast differentiation; The depletion of Fe2+ at early stage induced by DHA treatment triggers the ferritinophagy in HFL1 cells, leading to degradation of FTH1 and NCOA4 and following increase of Fe2+ levels. DHA may inhibit the fibroblast-to-myofibroblast differentiation through inducing ferroptosis mediated by ferritinophagy.

Regulation of NCOA4-mediated iron recycling ameliorates paraquat-induced lung injury by inhibiting ferroptosis

Paraquat (PQ) is an irreplaceable insecticide in many countries for the advantage of fast-acting and broad-spectrum. However, PQ was classified as the most prevailing poisoning substance for suicide with no specific antidote. Therefore, it is imperative to develop more effective therapeutic agents for the treatment of PQ poisoning. In the present study, both the RNA-Seq and the application of various cell death inhibitors reflected that ferroptosis exerts a crucial regulatory role in PQ poisoning. Moreover, we found PQ strengthens lipid peroxidation as evidenced by different experimental approaches. Of note, pretreatment of iron chelation agent DFO could ameliorate the ferroptotic cell death and alleviate the ferroptosis-related events. Mechanistically, PQ treatment intensively impaired mitochondrial homeostasis, enhanced phosphorylation of AMPK, accelerated the autophagy flux and triggered the activation of Nuclear receptor coactivator 4-ferritin heavy chain (NCOA4-FTH) axis. Importantly, the activation of autophagy was observed prior to the degradation of ferritin, and inhibition of autophagy could inhibit the accumulation of iron caused by the ferritinophagy process. Genetic and pharmacological inhibition of ferritinophagy could alleviate the lethal oxidative events, and rescue the ferroptotic cell death. Excitingly, in the mouse models of PQ poisoning, both the administration of DFO and adeno-associated virus-mediated FTH overexpression significantly reduced PQ-induced ferroptosis and improved the pathological characteristics of pulmonary fibrosis. In summary, the current work provides an in-depth study on the mechanism of PQ intoxication, describes a framework for the further understanding of ferroptosis in PQ-associated biological processes, and demonstrates modulation of iron metabolism may act as a promising therapeutic agent for the management of PQ toxicity.

NCOA4 requires a [3Fe-4S] to sense and maintain the iron homeostasis

NCOA4 is a selective cargo receptor for ferritinophagy, the autophagic turnover of ferritin (FTH), a process critical for regulating intracellular iron bioavailability. However, how ferritinophagy flux is controlled through NCOA4 in iron-dependent processes needs to be better understood. Here, we show that the C-terminal FTH-binding domain of NCOA4 harbors a [3Fe-4S]-binding site with a stoichiometry of approximately one labile [3Fe-4S] cluster per NCOA4 monomer. By analyzing the interaction between NCOA4 and HERC2 ubiquitin ligase or NCOA4 and FTH, we demonstrate that NCOA4 regulates ferritinophagy by sensing the intracellular iron-sulfur cluster levels. Under iron-repletion conditions, HERC2 recognizes and recruits holo-NCOA4 as a substrate for polyubiquitination and degradation, favoring ferritin iron storage. Under iron-depletion conditions, NCOA4 exists in the form of apo-protein and binds ferritin to promote the occurrence of ferritinophagy and release iron. Thus, we identify an iron-sulfur cluster [3Fe-4S] as a critical cofactor in determining the fate of NCOA4 in favoring iron storage in ferritin or iron release via ferritinophagy and provide a dual mechanism for selective interaction between HERC2 and [3Fe-4S]-NCOA4 for proteasomal degradation or between ferritin and apo-NCOA4 for ferritinophagy in the control of iron homeostasis.

Silica nanoparticles induce ferroptosis of HUVECs by triggering NCOA4-mediated ferritinophagy

Silica nanoparticles (SiNPs) have been widely used in electronics, chemistry, and biomedicine. Human exposure to SiNPs and possible health effects have attracted much attention. The potential cardiovascular toxicity of SiNPs and their related mechanisms are still unclear. Therefore, in this study, we investigated the toxic effects of SiNPs on human umbilical vein endothelial cells (HUVECs). We found that SiNPs could induce HUVECs ferroptosis. The results showed that the level of intracellular divalent iron and lipid peroxidation increased, and mitochondrial cristae decreased. In addition, the pretreatment of the iron chelator deferoxamine mesylate (DFO) could alleviate the ferroptosis of cells. Interestingly, pretreatment of 3-methyladenine (3-MA), an autophagy/PI3K inhibitor could partially inhibit autophagy and reduce ferroptosis, which indicated that autophagy played an important role in cell ferroptosis. Additionally, after knocking down nuclear receptor coactivator 4 (NCOA4), Ferritin Heavy Chain 1 (FTH1) expression was up-regulated, and the levels of divalent iron and lipid peroxidation decreased, which suggested that NCOA4 mediated the ferroptosis of HUVECs induced by SiNPs. In conclusion, this study shows that SiNPs can induce cardiovascular toxicity in which there is ferroptosis. NCOA4-mediated ferritinophagy and resultant ferroptosis by SiNPs may play an important role. This study provides a new theoretical strategy for the treatment and prevention of cardiovascular diseases in the future.

Ginkgolide B attenuates cerebral ischemia-reperfusion injury via inhibition of ferroptosis through disrupting NCOA4-FTH1 interaction

ETHNOPHARMACOLOGICAL RELEVANCE

Cerebral ischemia/reperfusion (I/R) injury is a major cause of neuronal damage and death. Ginkgolide B (GB) has been shown to exhibit neuroprotective effects in various brain injury models.

AIM OF STUDY

The aim of study was to investigate the potential role of GB in protecting against cerebral I/R injury and explore the underlying mechanisms.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were exposed to transient middle cerebral artery occlusion (tMCAO) followed by reperfusion in order to trigger cerebral I/R injury. The rats were treated with different doses of GB, vehicle control or positive drug. Neurological function, infarct volume, and levels of ferroptosis markers were evaluated. In vitro experiments were performed using OGD/R-induced PC12 cells to further investigate the effects of GB on ferroptosis and its mechanisms. In addition, molecular docking, and microscale thermophoresis (MST) assay were conducted to explore the combination of GB and NCOA4.

RESULTS

Reduced infarct volume and enhanced neurological function were signs of dose-dependent protection from cerebral I/R injury by GB therapy. Additionally, GB treatment had an impact on the levels of oxidative stress and ferroptosis markers, including reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), and Fe2+ in the cerebral environment during IR injury. Moreover, relevant ferroptosis key factors such as ACSL4, GPX4, FTH1, and NCOA4 can be regulated by GB. In OGD/R-induced PC12 cells, GB protected against ferroptosis by inhibiting autophagy and disrupting the interaction of NCOA4-FTH1.

CONCLUSION

Our findings suggest that GB may protect against cerebral I/R injury by inhibiting ferroptosis through disrupting NCOA4-FTH1 interaction. GB has potential therapeutic applications for cerebral I/R injury, and further investigation of the underlying mechanisms and clinical trials are warranted.

Hypoxia Aggravates Neuron Ferroptosis in Early Brain Injury Following Subarachnoid Hemorrhage via NCOA4-Meditated Ferritinophagy

The occurrence of early brain injury (EBI) significantly contributes to the unfavorable prognosis observed in patients with subarachnoid hemorrhage (SAH). During the process of EBI, a substantial quantity of iron permeates into the subarachnoid space and brain tissue, thereby raising concerns regarding its metabolism. To investigate the role and metabolic processes of excessive iron in neurons, we established both in vivo and in vitro models of SAH. We substantiated that ferritinophagy participates in iron metabolism disorders and promotes neuronal ferroptosis using an in vivo model, as detected by key proteins such as ferritin heavy chain 1, glutathione peroxidase 4, autophagy related 5, nuclear receptor coactivator 4 (NCOA4), LC3B, and electron microscopy results. By interfering with NCOA4 expression in vitro and in vivo, we confirmed the pivotal role of elevated NCOA4 levels in ferritinophagy during EBI. Additionally, our in vitro experiments demonstrated that the addition of oxyhemoglobin alone did not result in a significant upregulation of NCOA4 expression. However, simultaneous addition of oxyhemoglobin and hypoxia exposure provoked a marked increase in NCOA4 expression and heightened ferritinophagy in HT22 cells. Using YC-1 to inhibit hypoxia signaling in in vitro and in vitro models effectively attenuated neuronal ferroptosis. Collectively, we found that the hypoxic microenvironment during the process of EBI exaggerates iron metabolism abnormalities, leading to poor prognoses in SAH. The findings also offer a novel and potentially effective foundation for the treatment of SAH, with the aim of alleviating hypoxia.

Corilagin attenuates intestinal ischemia/reperfusion injury in mice by inhibiting ferritinophagy-mediated ferroptosis through disrupting NCOA4-ferritin interaction

AIMS

Intestinal ischemia reperfusion (II/R) is a common clinical emergency. Ferroptosis is reported to play a role in II/R injury. Our previous studies revealed that corilagin significantly attenuates intestinal ischemia/reperfusion injuries. However, the underlying molecular mechanism is unclear and requires further study.

MATERIALS AND METHODS

DAO, GSSG/T-GSH, MDA, and Fe2+ were measured by assay kits, 4-HNE was assessed by IHC, and 15-LOX was measured by ELISA. Mitochondrial damage was observed by TEM and cellular oxidation levels were detected by C11-BODIPY 581/591 and DHE probes. LC3, p62, Beclin1, ACSL4, GPX4, NCOA4, and ferritin expression were examined by WB in vivo and in vitro. IF, co-IF, q-PCR, and constructed NCOA4-knock-down IEC-6 cells were used to evaluate the role of NCOA4 in the effect of corilagin against II/R injury. Temporal and nucleoplasmic variations with or without corilagin were observed by WB. Co-IP and molecular docking were used to investigate the NCOA4-ferritin interaction.

KEY FINDINGS

Corilagin attenuated II/R-induced ferroptosis both in vitro and in vivo. Further study revealed that the anti-ferroptosis bioactivity of corilagin might be due to the modulation of iron homeostasis via inhibition of ferritinophagy in an NCOA4-dependent manner.

SIGNIFICANCE

Corilagin might be a potential therapeutic agent for II/R-induced tissue injury.

Cyclosporin A-mediated translocation of HuR improves MTX-induced cognitive impairment in a mouse model via NCOA4-mediated ferritinophagy

Chemotherapy-induced cognitive impairment (CICI) is a subject that requires critical solutions in neuroscience and oncology. However, its potential mechanism of action remains ambiguous. The aim of this study was to investigate the vital role of HuR in the neuroprotection of cyclosporin A (CsA) during methotrexate (MTX)-induced cognitive impairment. A series of Hu-antigen R (HuR) gain and loss experiments were used to examine cyclosporin A (CsA)-mediated translocation of HuR's ability to improve MTX-induced cognitive impairment through NCOA4-mediated ferritinophagy in vitro and in vivo. Obtained results show that the administration of CsA alleviated MTX-induced cognitive impairment in mice. The presence of MTX promoted the shuttling of HuR from the cytoplasm to the nucleus, whereas treatment with CsA increased cytoplasmic HuR expression levels and the levels of ferritinophagy-related proteins, such as NCOA4 and LC3II, compared to the MTX group. However, applying KH-3, an inhibitor of HuR, reversed CsA's impact on the expression of ferritinophagy-related proteins in the hippocampus and in vitro. Also, treatment with CsA attenuated microglial activation by altering Iba-1 expression and decreased TNF-α and IL-1β levels in mice hippocampi. Moreover, KH-3 neutralized CsA's effects on the expression of both Iba-1 and HuR in vivo and in vitro. In summary, CsA was confirmed to have a neuroprotective role in CICI. Its possible underlying mechanisms may be involved in the translocation of HuR. Mediating the translocation of HuR during CICI could mitigate neruoinflammation and neuronal apoptosis via NCOA4-mediated ferritinophagy and, thus, alleviate cognitive impairment in mice with CICI.

The effect of chronic intermittent hypobaric hypoxia improving liver damage in metabolic syndrome rats through ferritinophagy

Studies have confirmed that hepatic iron overload is one of the important factors causing liver damage in the metabolic syndrome (MS). As a special form of autophagy, ferritinophagy is involved in the regulation of iron metabolism. Our previous studies have shown that chronic intermittent hypobaric hypoxia (CIHH) can improve the iron metabolism disorder. The aim of this study was to investigate how CIHH improves liver damage through ferritinophagy in MS rats. Male Sprague-Dawley rats aged 8-10 weeks were randomly divided into four groups: control (CON), CIHH (exposed to hypoxia at a simulated altitude of 5000 m for 28 days, 6 h daily), MS model (induced by a 16-week high-fat diet and 10% fructose water feeding), and MS + CIHH (exposed to CIHH after a 16-week MS inducement) groups. Liver index, liver function, iron content, tissue morphology, oxidative stress, ferritinophagy, ferroptosis, and iron metabolism-related protein expression were measured, and the ferritinophagy flux in the liver was further analyzed. Compared with CON rats, MS rats had an increased liver index, damaged liver tissue and function, increased iron content and iron deposition, disrupted iron metabolism, significantly increased oxidative stress indicators in the liver, significantly upregulated expression of ferroptosis-related proteins, and downregulated expression of nuclear receptor coactivator 4 (NCOA4) and ferritinophagy flux. After CIHH treatment, the degree of liver damage and various abnormal indicators in MS rats were significantly improved. CIHH may improve liver damage by promoting NCOA4-mediated ferritinophagy, reducing iron overload and oxidative stress, and thereby alleviating ferroptosis in MS rats.

The induction of ferroptosis by KLF11/NCOA4 axis: the inhibitory role in clear cell renal cell carcinoma

Ferroptosis is a form of cell death and has great potential application in the treatment of many cancers, including clear cell renal cell carcinoma (ccRCC). Herein, we identified the essential roles of Krüppel-like factor 11 (KLF11) in suppressing the progression of ccRCC. By analyzing mRNA expression data from the Gene Expression Omnibus (GEO) database, we found that KLF11 was a significantly downregulated gene in ccRCC tissues. The results of subsequent functional assays verified that KLF11 played an antiproliferative role in ccRCC cells and xenograft tumors. Furthermore, gene set enrichment analysis indicated that ferroptosis was involved in ccRCC development, and correlation analysis revealed that KLF11 was positively related to ferroptosis drivers. We also found that KLF11 promoted ferroptosis in ccRCC by downregulating the protein expression of ferritin, system xc (-) cystine/glutamate antiporter (xCT), and glutathione peroxidase 4 (GPX4), acting as the inhibitory factors of ferroptosis and increasing the intracellular levels of lipid reactive oxygen species (ROS). As a transcriptional regulator, KLF11 significantly increased the promoter activity of nuclear receptor coactivator 4 (NCOA4), a gene significantly downregulated in ccRCC and whose low expression is associated with poor survival. The characteristics of ccRCC cells caused by KLF11 overexpression were reversed after NCOA4 silencing. In summary, the present study suggests that KLF11 suppresses the progression of ccRCC by increasing NCOA4 transcription. Therefore, the KLF11/NCOA4 axis may serve as a novel therapeutic target for human ccRCC.

Fraxetin alleviates BLM-induced idiopathic pulmonary fibrosis by inhibiting NCOA4-mediated epithelial cell ferroptosis

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is a debilitating lung condition with few available treatments. The early driver of wound repair that contributes to IPF has been extensively identified as repetitive alveolar epithelial damage. According to recent reports, IPF is linked to ferroptosis, a unique type of cell death characterized by a fatal buildup of iron and lipid peroxidation.

OBJECTIVE AND METHOD

There is little information on epithelial cells that induce pulmonary fibrosis by going through ferroptosis. In this study, we used bleomycin (BLM) to examine the impact of ferroptosis on IPF in mouse lung epithelial cells (MLE-12).

RESULTS

We discovered that BLM increases ferroptosis in MLE-12. Additionally, we found that NCOA4 is overexpressed and plays a key role in the ferroptosis of epithelial cells throughout the IPF process. Using Molecular docking, we found that Fraxetin, a natural component extracted from Fraxinus rhynchophylla, formed a stable binding to NCOA4. In vitro investigations showed that Fraxetin administration greatly decreased ferroptosis and NCOA4 expression, which in turn lowered the release of inflammatory cytokines.

CONCLUSION

Fraxetin treatment significantly alleviated BLM-induced lung inflammation and fibrosis. Our findings imply that fraxetin possesses inhibitory roles in ferroptosis and can be a potential drug against IPF.

Ferroptosis induces detrimental effects in chronic EAE and its implications for progressive MS

Ferroptosis is a form of lipid peroxidation-mediated cell death and damage triggered by excess iron and insufficiency in the glutathione antioxidant pathway. Oxidative stress is thought to play a crucial role in progressive forms of multiple sclerosis (MS) in which iron deposition occurs. In this study we assessed if ferroptosis plays a role in a chronic form of experimental autoimmune encephalomyelitis (CH-EAE), a mouse model used to study MS. Changes were detected in the mRNA levels of several ferroptosis genes in CH-EAE but not in relapsing-remitting EAE. At the protein level, expression of iron importers is increased in the earlier stages of CH-EAE (onset and peak). While expression of hemoxygenase-1, which mobilizes iron from heme, likely from phagocytosed material, is increased in macrophages at the peak and progressive stages. Excess iron in cells is stored safely in ferritin, which increases with disease progression. Harmful, redox active iron is released from ferritin when shuttled to autophagosomes by 'nuclear receptor coactivator 4' (NCOA4). NCOA4 expression increases at the peak and progressive stages of CH-EAE and accompanied by increase in redox active ferrous iron. These changes occur in parallel with reduction in the antioxidant pathway (system xCT, glutathione peroxidase 4 and glutathione), and accompanied by increased lipid peroxidation. Mice treated with a ferroptosis inhibitor for 2 weeks starting at the peak of CH-EAE paralysis, show significant improvements in function and pathology. Autopsy samples of tissue sections of secondary progressive MS (SPMS) showed NCOA4 expression in macrophages and oligodendrocytes along the rim of mixed active/inactive lesions, where ferritin+ and iron containing cells are located. Cells expressing NCOA4 express less ferritin, suggesting ferritin degradation and release of redox active iron, as indicated by increased lipid peroxidation. These data suggest that ferroptosis is likely to contribute to pathogenesis in CH-EAE and SPMS.

ATM orchestrates ferritinophagy and ferroptosis by phosphorylating NCOA4

Ferroptosis is a newly characterized form of programmed cell death, which is driven by the lethal accumulation of lipid peroxides catalyzed by the intracellular bioactive iron. Targeted induction of ferroptotic cell death holds great promise for therapeutic design against other therapy-resistant cancers. To date, multiple post-translational modifications have been elucidated to impinge on the ferroptotic sensitivity. Here we report that the Ser/Thr protein kinase ATM, the major sensor of DNA double-strand break damage, is indispensable for ferroptosis execution. Pharmacological inhibition or genetic ablation of ATM significantly antagonizes ferroptosis. Besides, ATM ablation-induced ferroptotic resistance is largely independent of its downstream target TRP53, as cells defective in both Trp53 and Atm are still more insensitive to ferroptotic inducers than the trp53 single knockout cells. Mechanistically, ATM dominates the intracellular labile free iron by phosphorylating NCOA4, facilitating NCOA4-ferritin interaction and therefore sustaining ferritinophagy, a selective type of macroautophagy/autophagy specifically degrading ferritin for iron recycling. Our results thus uncover a novel regulatory circuit of ferroptosis comprising ATM-NCOA4 in orchestrating ferritinophagy and iron bioavailability.Abbreviations: AMPK: AMP-activated protein kinase; ATM: ataxia telangiectasia mutated; BSO: buthionine sulphoximine; CDKN1A: cyclin-dependent kinase inhibitor 1A (P21); CQ: chloroquine; DFO: deferoxamine; DFP: deferiprone; Fer: ferrostatin-1; FTH1: ferritin heavy polypeptide 1; GPX4: glutathione peroxidase 4; GSH: glutathione; MEF: mouse embryonic fibroblast; NCOA4: nuclear receptor coactivator 4; PFTα: pifithrin-α; PTGS2: prostaglandin-endoperoxide synthase 2; Slc7a11: solute carrier family 7 member 11; Sul: sulfasalazine; TFRC: transferrin receptor; TRP53: transformation related protein 53.

2D MoS2 Nanosheets Induce Ferroptosis by Promoting NCOA4-Dependent Ferritinophagy and Inhibiting Ferroportin

The exposure of MoS₂ nanosheets can cause cytotoxicity, which causes health risks and affects its medical applications. However, knowledge of the underlying molecular mechanisms remains limited. This study reports that MoS₂ nanosheets induces ferroptosis in vivo and in vitro, which is caused by the nanosheet themselves rather than by the dissolved ions. MoS₂ nanosheets induce ferroptosis in epithelial (BEAS-2B) and macrophage (RAW264.7) cells due to nuclear receptor coactivator 4 (NCOA4)-dependent excusive ferritinophagy and the inhibition of ferroportin-1 (FPN). In this process, most of the MoS₂ nanosheets enter the cells via macropinocytosis and are localized to the lysosome, contributing to an increase in the lysosomal membrane permeability. At the same time, NCOA4-dependent ferritinophagy is activated, and ferritin is degraded in the lysosome, which generates Fe²⁺ .Fe²⁺ leaks into the cytoplasm, leading to ferroptosis. Furthermore, the inhibition of FPN further aggravates the overload of Fe²⁺ in the cell. It has also been observed that ferroptosis is increased in lung tissue in mouse models exposed to MoS₂ nanosheets. This work highlights a novel mechanism by which MoS₂ nanosheets induce ferroptosis by promoting NCOA4-dependent ferritinophagy and inhibiting FPN, which could be of importance to elucidate the toxicity and identify the medical applications of 2D nanoparticles.

Mycobacterium tuberculosis induces host autophagic ferritin degradation for enhanced iron bioavailability and bacterial growth

ABBREVIATIONS

Mtb, Mycobacterium tuberculosis; TB, tuberculosis; NCOA4, nuclear receptor coactivator 4; p38, p38 protein kinase; AKT1, AKT serine/threonine kinase 1; TRIM21, tripartite motif containing 21; FTH1, ferritin heavy chain 1; FTL, ferritin light chain; HERC2, HECT and RLD domain containing E3 ubiquitin protein ligase 2.

A novel sesquiterpene lactone fraction from Eupatorium chinense L. suppresses hepatocellular carcinoma growth by triggering ferritinophagy and mitochondrial damage

BACKGROUND

Hepatocellular carcinoma (HCC) is an aggressive tumor with limited treatment options, and it is the third leading cause of cancer-related deaths. Hence, novel therapeutic strategies are required to treat HCC. Eupatorium chinense L. is a traditional Chinese medicine (TCM) that can effectively neutralize heat and smoothen the flow of "Qi" through the liver. However, the anti-HCC effects of Eupatorium chinense L. remain unknown.

PURPOSE

The present study investigated the anti-HCC effects and the underlying mechanisms of the electrophilic sesquiterpenes isolated from E. chinense L. (EChLESs) in the regulation of ferroptosis and apoptosis in HCC cells.

STUDY DESIGN/METHODS

Cell viability was assessed by the MTT assay. Cell apoptosis was confirmed by flow cytometry and western blotting assay. Ferroptosis was assessed by flow cytometry, transmission electron microscopy, and western blotting assay. Ferritinophagy was detected by acridine orange staining and western blotting assay. Small interfering RNA of nuclear receptor coactivator 4 (NCOA4) was used to confirm the role of ferritinophagy in the therapeutic effect of EChLESs on HCC cells. A mouse xenograft model was constructed to determine the inhibitory effect of EChLESs on HCC in vivo.

RESULTS

EChLESs induced apoptosis by disrupting mitochondrial membrane potential depolarization and mitochondrial reactive oxygen species. EChLESs induced ferroptosis as noted by a significant increase in mitochondrial disruption, lipid peroxidation, and intracellular iron level and decreased glutathione level. The apoptosis inhibitor Z-VAD-FMK and lipid reactive oxygen species scavenger ferrostatin 1 attenuated EChLESs-induced cell death. NCOA4-mediated ferritinophagy through autophagic flux was the crucial pathway for ferroptosis induced by EChLESs. NCOA4 knockdown alleviated EChLESs-induced cell death. EChLESs controlled the expression of NCOA4 at the transcriptional and post-transcriptional levels. In the in vivo experiment, EChLESs suppressed HCC growth in the xenograft tumor mouse model.

CONCLUSION

EChLESs enhances cell apoptosis through mitochondrial dysfunction and ferroptosis through NCOA4-mediated ferritinophagy. Thus, Eupatorium chinense L. could be a potential TCM for treating HCC.

JNK-JUN-NCOA4 axis contributes to chondrocyte ferroptosis and aggravates osteoarthritis via ferritinophagy

Interruption of iron homeostasis is correlated with cell ferroptosis and degenerative diseases. Nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy has been reported as a vital mechanism to control cellular iron levels, but its impact on osteoarthritis (OA) pathology and the underline mechanism are unknown. Herein we aimed to investigate the role and regulatory mechanism of NCOA4 in chondrocyte ferroptosis and OA pathogenesis. We demonstrated that NCOA4 was highly expressed in cartilage of patients with OA, aged mice, post-traumatic OA mice, and inflammatory chondrocytes. Importantly, Ncoa4 knockdown inhibited IL-1β-induced chondrocyte ferroptosis and extracellular matrix degradation. Contrarily, overexpression of NCOA4 promoted chondrocyte ferroptosis and the delivery of Ncoa4 adeno-associated virus 9 into knee joint of mice aggravated post-traumatic OA. Mechanistic study revealed that NCOA4 was upregulated in a JNK-JUN signaling-dependent manner in which JUN could directly bind to the promoter of Ncoa4 and initial the transcription of Ncoa4. NCOA4 could interact with ferritin and increase autophagic degradation of ferritin and iron levels, which caused chondrocyte ferroptosis and extracellular matrix degradation. In addition, inhibition of JNK-JUN-NCOA4 axis by SP600125, a specific inhibitor of JNK, attenuated development of post-traumatic OA. This work highlights the role of JNK-JUN-NCOA4 axis and ferritinophagy in chondrocyte ferroptosis and OA pathogenesis, suggesting this axis as a potential target for OA treatment.

Mechanism of YY1 mediating autophagy dependent ferroptosis in PM2.5 induced cardiac fibrosis

Epidemiological studies have demonstrated strong associations between exposure to ambient fine particulate matter (PM2.5) and cardiac disease. To investigate the potential mechanism of cardiac fibrosis induced by PM2.5, we established PM2.5 exposure models in vivo and in vitro, and then cardiac fibrosis was evaluated. The ferroptosis and ferritinophagy was detected to characterize the effects of PM2.5 exposure. The results indicated that PM2.5 exposure could induce cardiac fibrosis in mice. YY1 was induced by PM2.5 exposure and then increased NCOA4, a cargo receptor for ferritinophagy, which interacted with FHC and promoted the transport of ferritin to the autophagosome for degradation. The release of large amounts of free iron from ferritinophagy led to lipid peroxidation directly via the Fenton reaction, thereby triggering ferroptosis. Moreover, siNCOA4 could partly restore the FHC protein level in HL-1 cells and inhibit the occurrence of downstream ferroptosis. Functionally, NCOA4 knockdown inhibited ferroptosis and alleviated HL-1 cell death induced by PM2.5. Ferroptosis inhibitor (Ferrostatin-1) could reverse the promoting effect of ferritinophagy mediated ferroptosis on cardiac fibrosis induced by PM2.5 exposure in mice. Our study indicated that PM2.5 induced cardiac fibrosis through YY1 regulating ferritinophagy-dependent ferroptosis.

The PTBP1‑NCOA4 axis promotes ferroptosis in liver cancer cells

Polypyrimidine tract‑binding protein 1 (PTBP1) plays an important role in tumor immunity, cell proliferation, apoptosis, and autophagy by regulating RNA metabolism. However, the specific function and mechanism of PTBP1 in ferroptosis remain unclear. In the present study, it was investigated whether PTBP1 regulates ferroptosis and the exact mechanism. The iron, malondialdehyde (MDA), and GSH levels were detected in sorafenib (SF)‑treated liver cancer cells. si‑PTBP1 introduction into SF‑treated liver cancer cells resulted in a significant reduction in the levels of MDA and iron. Additionally, a significant recovery of GSH levels was observed after silencing PTBP1. StarBase v2.0 database was used to predict potential transcripts that can physically interact with PTBP1 and nuclear receptor coactivator 4 (NCOA4) mRNA was identified as the most enriched binding partner in the PTBP1‑RNA complex. A dual‑luciferase assay then demonstrated that PTBP1 directly interacted with NCOA4. PTBP1 silencing did not affect NCOA4 stability following treatment with cycloheximide. A pull‑down assay revealed that the PTBP1‑binding region was in the 5'‑UTR of the NCOA4 mRNA sequence. These results suggest that PTBP1 mediates ferroptosis in liver cancer cells by regulating NCOA4 translation. In vivo experiments reconfirmed the role of the PTBP1‑NCOA4 axis in a xenograft transplantation model. It was observed that the mean tumor weight increased after PTBP1 knockout. In conclusion, silencing of PTBP1 decreased the sensitivity of liver cancer cells to ferroptosis after SF treatment and regulated ferritinophagy by mediating NCOA4 translation.

Inhibitory Effects of Esculetin on Liver Cancer Through Triggering NCOA4 Pathway-Mediation Ferritinophagy in vivo and in vitro

Objective

To explore the effects of Esculetin on liver cancer and explore potential mechanisms of Esculetin-inducing cells death.

Methods

Esculetin's effects on the proliferation, migration and apoptosis of HUH7 and HCCLM3 cells were detected by using CCK8, crystal violet staining, wound healing, Transwell^TM and Annexin V-FITC/PI. Flow cytometry, fluorescence staining, Western blot, T-AOC, DPPH radical scavenging assay, hydroxyl radical's inhibitory capability and GSH test were used to examine the esculetin's effects on the ROS level, the oxidation-related substances and proteins' expression in hepatoma cells. In vivo experiment was performed by xenograft model. Ferrostatin-1 was used to determine the death way of hepatoma cells induced by esculetin. Live cell probe, Western blot, Fe²⁺ content, MDA, HE staining, Prussian blue staining and immunohistochemistry were used to examine the ferritinophagy-related phenomenon induced by esculetin in hepatoma cells. The relationship between esculetin and NCOA4-mediated ferritinophagy was confirmed through gene silence and overexpression, immunofluorescence staining and Western blot.

Results

Esculetin suppressed the proliferation, migration and apoptosis of HUH7 and HCCLM3 cells significantly, influenced the oxidative stress level, altered the autophagy and iron metabolism levels in cells, and produced a ferritinophagy-related phenomena. Esculetin increased the levels of cellular lipid peroxidation and reactive oxygen species. In vivo, esculetin could decrease tumour volume, promote LC3 and NCOA4 expressions, suppresse hydroxyl radical's inhibiting capacity and GSH, increase Fe²⁺ and MDA levels, decrease antioxidant proteins expression in tumour tissue. In addition, Esculetin could also increase the iron deposition of tumour tissues, promote ferritinophagy, and induce tumours' ferroptosis.

Conclusion

Esculetin has an inhibitory effect on liver cancer in vivo and in vitro through triggering NCOA4 pathway-mediation ferritinophagy.

Inhibition of HSPA8 by rifampicin contributes to ferroptosis via enhancing autophagy

BACKGROUND AND AIM

Rifampicin is the most common pathogenic factor in anti-tuberculosis drug-induced liver injury (AT-DILI), the mechanisms that it promotes hepatocyte damage in AT-DILI are not yet to be thoroughly elucidated. In this study, we investigated the potential molecular mechanisms for ferroptosis involving rifampicin hepatotoxicity.

METHODS

Animal and cell injury models of rifampicin were constructed, and the toxicity of rifampicin was assessed by physicochemical staining and cell viability assay. Next, flow cytometry was employed to detect changes in ferroptosis-related markers, and Western blotting was used to detect protein expression. Then, the important role of autophagy and ferroptosis was verified with small molecule compound intervention.

RESULTS

We found that ferritinophagy-induced ferroptosis participates in the toxicity of rifampicin, and the mechanism is that rifampicin precisely activates high-throughput autophagy, which leads to the massive degradation of ferritin and the increase of free iron. Moreover, rifampicin exhibited conspicuous inhibition of Human 71 kDa heat shock cognate protein (HSPA8) that is intimately associated with Microtubule-associated protein light chain 3 isoform B (LC3B) expression, in turn, HSPA8 inducer attenuated intracellular autophagy flux. Of note, inducing HSPA8 or inhibition of autophagy and ferroptosis considerably relieved the hepatotoxicity of rifampicin in mouse model.

CONCLUSIONS

The present study highlights the crucial roles of the HSPA8 and autophagy in ferroptotic cell death driving by rifampicin, particularly illumines multiple promising regulatory nodes for therapeutic interventions in diseases involving AT-DILI.

Curcumol alleviates liver fibrosis through inducing autophagy and ferroptosis in hepatic stellate cells

To explore the effect of curcumol on autophagy and ferroptosis of hepatic stellate cells, and to clarify the molecular mechanism of its anti-hepatic fibrosis. In the present study, we report that curcumol promotes the death of activated HSCs and reduces the deposition of extracellular matrix. Interestingly, curcumol treatment can trigger ferroptosis to eliminate activated HSCs characterized by iron overload, lipid ROS accumulation, glutathione depletion, and lipid peroxidation. Curcumol promotes HSC autophagy, which may be the key mechanism for its induction of ferroptosis. It is worth noting that the upregulation of nuclear receptor coactivator 4 (NCOA4) may play a key molecular mechanism. NCOA4 mediates the release of iron ions and induces the occurrence of ferroptosis. Overall, curcumol promotes autophagy in hepatic stellate cells, mediates the degradation of NCOA4 and FTH1 complexes, releases iron ions, leads to iron overload, and induces ferroptosis, which may be an important mechanism for its anti-hepatic fibrosis effect.

WDR45 variants cause ferrous iron loss due to impaired ferritinophagy associated with nuclear receptor coactivator 4 and WD repeat domain phosphoinositide interacting protein 4 reduction

Static encephalopathy of childhood with neurodegeneration in adulthood/β-propeller protein-associated neurodegeneration is a neurodegenerative disorder with brain iron accumulation caused by the variants of WDR45, a core autophagy-related gene that encodes WD repeat domain phosphoinositide interacting protein 4. However, the pathophysiology of the disease, particularly the function of WDR45/WD repeat domain phosphoinositide interacting protein 4 in iron metabolism, is largely unknown. As no other variants of core autophagy-related genes show abnormalities in iron metabolism, the relation between autophagy and iron metabolism remains to be elucidated. Since iron deposition in the brain is the hallmark of static encephalopathy of childhood with neurodegeneration in adulthood/β-propeller protein-associated neurodegeneration, iron chelation therapy has been attempted, but it was found to worsen the symptoms; thus, the establishment of a curative treatment is essential. Here, we evaluated autophagy and iron metabolism in patient-derived cells. The expression of ferritin and ferric iron increased and that of ferrous iron decreased in the patient cells with WDR45 variants. In addition, the expression of nuclear receptor coactivator 4 was markedly reduced in patient-derived cells. Furthermore, divalent metal transporter 1, which takes in ferrous iron, was upregulated, while ferroportin, which exports ferrous iron, was downregulated in patient-derived cells. The transfer of WDR45 via an adeno-associated virus vector restored WD repeat domain phosphoinositide interacting protein 4 and nuclear receptor coactivator 4 expression, reduced ferritin levels, and improved other phenotypes observed in patient-derived cells. As nuclear receptor coactivator 4 mediates the ferritin-specific autophagy, i.e. ferritinophagy, its deficiency impaired ferritinophagy, leading to the accumulation of ferric iron-containing ferritin and insufficiency of ferrous iron. Because ferrous iron is required for various essential biochemical reactions, the changes in divalent metal transporter 1 and ferroportin levels may indicate a compensatory response for maintaining the intracellular levels of ferrous iron. Our study revealed that the pathophysiology of static encephalopathy of childhood with neurodegeneration in adulthood/β-propeller protein-associated neurodegeneration involves ferrous iron insufficiency via impaired ferritinophagy through nuclear receptor coactivator 4 expression reduction. Our findings could aid in developing a treatment strategy involving WDR45 manipulation, which may have clinical applications.

The SPATA2/CYLD pathway contributes to doxorubicin-induced cardiomyocyte ferroptosis via enhancing ferritinophagy

Ferroptosis is an iron-dependent cell death and contributes to doxorubicin-induced cardiotoxicity, but the mechanisms behind intracellular iron overload in cardiomyocyte after administration of doxorubicin remain largely unknown. Ferritinophagy is a selective type of autophagy and could be a novel source for intracellular free iron. Spermatogenesis-associated protein 2 (SPATA2), a member of the TNF signaling pathway, can recruit cylindromatosis (CYLD, a deubiquitinating enzyme) to regulate cell death. This study aims to explore whether ferritinophagy is the source for intracellular iron overload in cardiomyocyte upon doxorubicin treatment and whether the SPATA2/CYLD pathway is involved in regulation of nuclear receptor coactivator 4 (NCOA4) level, the selective cargo receptor for ferritinophagy. The C57BL/6J mice were subjected to a single injection of doxorubicin, which showed the compromised cardiac functions, accompanied by the upregulation of SPATA2 and CYLD and the enhanced interaction between them, the increases in ferritinophagy (reflecting by increases in NCOA4 and ratio of LC3Ⅱ/LC3Ⅰ while decreases in NCOA4 ubiquitination and ferritin) and ferroptosis (reflecting by intracellular iron overload and increase of acyl-CoA synthetase long chain family member 4). Consistently, similar results were achieved in the cultured cardiomyocytes after incubation with doxorubicin. Knocked down of SPATA2 notably reduced doxorubicin-induced cardiomyocyte injury concomitant with the attenuated ferritinophagy and the decreased ferroptosis. Based on these observations, we conclude that a novel pathway of SPATA2/CYLD has been identified, which contributes to doxorubicin-induced cardiomyocyte ferroptosis via enhancing ferritinophagy through a mechanism involving the deubiquitination of NCOA4.

Mutant WDR45 Leads to Altered Ferritinophagy and Ferroptosis in β-Propeller Protein-Associated Neurodegeneration

Beta-propeller protein-associated neurodegeneration (BPAN) is a subtype of neurodegeneration with brain iron accumulation (NBIA) caused by loss-of-function variants in WDR45. The underlying mechanism of iron accumulation in WDR45 deficiency remains elusive. We established a primary skin fibroblast culture of a new BPAN patient with a missense variant p.(Asn61Lys) in WDR45 (NM_007075.3: c.183C>A). The female patient has generalized dystonia, anarthria, parkinsonism, spasticity, stereotypies, and a distinctive cranial MRI with generalized brain atrophy, predominantly of the cerebellum. For the functional characterization of this variant and to provide a molecular link of WDR45 and iron accumulation, we looked for disease- and variant-related changes in the patient’s fibroblasts by qPCR, immunoblotting and immunofluorescence comparing to three controls and a previously reported WDR45 patient. We demonstrated molecular changes in mutant cells comprising an impaired mitochondrial network, decreased levels of lysosomal proteins and enzymes, and altered autophagy, confirming the pathogenicity of the variant. Compared to increased levels of the ferritinophagy marker Nuclear Coactivator 4 (NCOA4) in control cells upon iron treatment, patients’ cells revealed unchanged NCOA4 protein levels, indicating disturbed ferritinophagy. Additionally, we observed abnormal protein levels of markers of the iron-dependent cell death ferroptosis in patients’ cells. Altogether, our data suggests that WDR45 deficiency affects ferritinophagy and ferroptosis, consequentially disturbing iron recycling.

NCOA4 links iron bioavailability to DNA metabolism

Iron is essential for deoxyribonucleotides production and for enzymes containing an Fe-S cluster involved in DNA replication and repair. How iron bioavailability and DNA metabolism are coordinated remains poorly understood. NCOA4 protein mediates autophagic degradation of ferritin to maintain iron homeostasis and inhibits DNA replication origin activation via hindrance of the MCM2-7 DNA helicase. Here, we show that iron deficiency inhibits DNA replication, parallel to nuclear NCOA4 stabilization. In iron-depleted cells, NCOA4 knockdown leads to unscheduled DNA synthesis, with replication stress, genome instability, and cell death. In mice, NCOA4 genetic inactivation causes defective intestinal regeneration upon dextran sulfate sodium-mediated injury, with DNA damage, defective cell proliferation, and cell death; in intestinal organoids, this is fostered by iron depletion. In summary, we describe a NCOA4-dependent mechanism that coordinates iron bioavailability and DNA replication. This function prevents replication stress, maintains genome integrity, and sustains high rates of cell proliferation during tissue regeneration.

Iron-induced NCOA4 condensation regulates ferritin fate and iron homeostasis

Iron is not only essential but also a toxic trace element. Under iron repletion, ferritin maintains cellular iron homeostasis by storing iron to avoid iron toxicity. Under iron depletion, the ferritin-specific autophagy adaptor NCOA4 delivers ferritin to lysosomes via macroautophagy to enable cells to use stored iron. Here, we show that NCOA4 also plays crucial roles in the regulation of ferritin fate under iron repletion. NCOA4 forms insoluble condensates via multivalent interactions generated by the binding of iron to its intrinsically disordered region. This sequesters NCOA4 away from ferritin and allows ferritin accumulation in the early phase of iron repletion. Under prolonged iron repletion, NCOA4 condensates can deliver ferritin to lysosomes via a TAX1BP1-dependent non-canonical autophagy pathway, thereby preventing relative iron deficiency due to excessive iron storage and reduced iron uptake. Together, these observations suggest that the NCOA4-ferritin axis modulates intracellular iron homeostasis in accordance with cellular iron availability.

NCOA4-Mediated Ferroptosis in Bronchial Epithelial Cells Promotes Macrophage M2 Polarization in COPD Emphysema

Background

Macrophage polarization plays an important role in the pathogenesis of COPD emphysema. Changes in macrophage polarization in COPD remain unclear, while polarization and ferroptosis are essential factors in its pathogenesis. Therefore, this study investigated the relationship between macrophage polarization and ferroptosis in COPD emphysema.

Methods

We measured macrophage polarization and the levels of matrix metalloproteinases (MMPs) in the lung tissues of COPD patients and cigarette smoke (CS)-exposed mice. Flow cytometry was used to determine macrophage (THP-M cell) polarization changes. Ferroptosis was examined by FerroOrange, Perls' DAB, C11-BODIPY and 4-HNE staining. Nuclear receptor coactivator 4 (NCOA4) was measured in the lung tissues of COPD patients and CS-exposed mice by western blotting. A cell study was performed to confirm the regulatory effect of NCOA4 on macrophage polarization.

Results

Increased M2 macrophages and MMP9 and MMP12 levels were observed in COPD patients, CS-exposed mice and THP-M cells cocultured with CS extract (CSE)-treated human bronchial epithelial (HBE) cells. Increased NCOA4 levels and ferroptosis were confirmed in COPD. Treatment with NCOA4 siRNA and the ferroptosis inhibitor ferrostatin-1 revealed an association between ferroptosis and M2 macrophages. These findings support a role for NCOA4, which induces an increase in M2 macrophages, in the pathogenesis of COPD emphysema.

Conclusion

In our study, CS led to the dominance of the M2 phenotype in COPD. We identified NCOA4 as a regulator of M2 macrophages and emphysema by mediating ferroptosis, which offers a new direction for research into COPD diagnostics and treatment.

Cerebral ischemia induced iron deposit, ferritin accumulation, nuclear receptor coactivator 4-depletion and ferroptosis

BACKGROUND

The neuronal death upon cerebral ischemia shares not only characteristics of necrosis, apoptosis and autophagy, but exhibits also biochemical and morphological characteristics of ferroptosis. Ferroptosis is a regulated form of cell death which is considered to be an oxidative iron-dependent process. It is now commonly accepted that iron and free radicals are considered to cause lipid peroxidation as well as the oxidation of proteins and nucleic acids, leading to increased membrane and enzymatic dysfunction, and finally contributing to cell death. Although ferroptosis was first described in cancer cells, emerging evidence now links mechanisms of ferroptosis to many different diseases, including cerebral ischemia.

METHODS

The objective of this study was to identify the ferroptosis key players and the underlying biochemical pathways leading to cell death upon focal cerebral ischemia in mice by using immunofluorescence, Western blotting, histochemistry and densitometry.

RESULTS

In this study, we demonstrated that cerebral ischemia induced iron-deposition, down-regulated dramatically the expression of the glutathione peroxidase 4 (GPX4), decreased the expression of the nuclear receptor coactivator 4 (NCOA4) and induced inappropriate accumulation of ferritin in the ischemic brain. This supports the hypothesis that an ischemic insult may induce ferroptosis through inhibition of GPX4.

CONCLUSION

We conclude that iron excess following cerebral ischemia leads to cell death despite activation of compensatory mechanisms for iron homeostasis, as illustrated by the accumulation of ferritins. These data emphasize the presence of a cellular mechanism that allows neuronal cells to handle restriction in iron overload.

NCOA4-Mediated Ferritinophagy: A Vicious Culprit in COVID-19 Pathogenesis?

Coronavirus disease 2019 (COVID-19) is a global pandemic that has caused widespread loss of life. Notably, in this disease, severe inflammatory reactions characterized by cytokine storms are caused by severe acute respiratory syndrome coronavirus 2. The cytokine storms may promote hyper-ferritinemia which can further intensify the inflammation. Moreover, elevated ferritin levels trigger nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy, in which ferritin is degraded and iron is released. Excess iron released from ferritinophagy can promote ferroptosis and cellular damage. Therefore, we propose that NCOA4-mediated ferritinophagy can be targeted to limit the ferroptosis and prevent the multi-organ damage and severity in COVID-19 patients.

Nuclear receptor coactivator 4-mediated ferritinophagy contributes to cerebral ischemia-induced ferroptosis in ischemic stroke

Ischemic stroke poses a significant health risk due to its high rate of disability and mortality. To address this problem, several therapeutic approaches have been proposed, including interruption targeting programmed cell death (PCD). Ferroptosis is a newly defined PCD characterized by iron-dependent accumulation of lipid peroxidation, and is becoming a promising target for treating numerous diseases. To explore the underlying mechanisms of the initiation and execution of ferroptosis in ischemic stroke, we established stroke models in vivo and in vitro simulating ischemia/reperfusion (I/R) neuronal injury. Different from previous reports on stroke, we tested ferroptosis by measuring the levels of core proteins, such as ACSL4, 15-LOX2, Ferritin and GPX4. In addition, I/R injury induces excessive degradation of ferritin via the autophagy pathway and subsequent increase of free iron in neurons. This phenomenon has recently been termed ferritinophagy and reported to be regulated by nuclear receptor coactivator 4 (NCOA4) in some cell lines. Increased NCOA4 in cytoplasm was detected in our study and then silenced by shRNA to investigate its function. Both in vivo and in vitro, NCOA4 deletion notably abrogated ferritinophagy caused by I/R injury and thus inhibited ferroptosis. Furthermore, we found that NCOA4 was upregulated by ubiquitin specific peptidase 14 (USP14) via a deubiquitination process in damaged neurons, and we found evidence of pharmacological inhibition of USP14 effectively reducing NCOA4 levels to protect neurons from ferritinophagy-mediated ferroptosis. These findings suggest a novel and effective target for treating ischemic stroke.

Dihydroartemisinin alleviates hepatic fibrosis through inducing ferroptosis in hepatic stellate cells

Targeting the elimination of activated hepatic stellate cells (HSCs) and blocking excessive deposition of extracellular matrix are recognized as an effective strategy for the treatment of hepatic fibrosis. As a newly discovered programmed cell death mode, the regulatory mechanism of ferroptosis in the clearance of activated HSCs has not been fully elucidated. In the present study, we reported that the induction of ferroptosis in activated HSCs was required for dihydroartemisinin (DHA) to alleviate hepatic fibrosis. Treatment with DHA could improve the damage of hepatic fibrosis in vivo and inhibit the activation of HSCs in vitro. Interestingly, DHA treatment could trigger ferroptosis to eliminate activated HSCs characterized by iron overload, lipid ROS accumulation, glutathione depletion, and lipid peroxidation. Specific ferroptosis inhibitors ferrostatin-1 and liproxstatin-1 could impair DHA-induced ferroptosis and also damage DHA-mediated the inhibition of activated HSCs. Importantly, autophagy activation may be closely related to DHA-induced ferroptosis. ATG5 siRNA could prevent DHA-mediated autophagy activation and ferroptosis induction, whereas ATG5 plasmid could promote the effect of DHA on autophagy and ferroptosis. Of note, the upregulation of nuclear receptor coactivator 4 (NCOA4) may play a critical role in the molecular mechanism. NCOA4 siRNA could impair DHA-induced ferroptosis, whereas NCOA4 plasmid could enhance the promoting effect of DHA on ferroptosis. Overall, our study revealed the potential mechanism of DHA against hepatic fibrosis and showed that ferroptosis could be a new way to eliminate activated HSCs.

Involvement of oxidative stress-induced annulus fibrosus cell and nucleus pulposus cell ferroptosis in intervertebral disc degeneration pathogenesis

Ferroptosis is a necrotic form of regulated cell death that was associated with lipid peroxidation and free iron-mediated Fenton reactions. It has been reported that iron deficiency had been implicated in the pathogenesis of intervertebral disc degeneration (IVDD) by activating apoptosis. However, the role of ferroptosis in the process of IVDD has not been illuminated. Here, we demonstrate the involvement of ferroptosis in IVDD pathogenesis. Our in vitro models show the changes in protein levels of ferroptosis marker and enhanced lipid peroxidation level during oxidative stress. Safranin O staining, hematoxylin-eosin staining, and immunohistochemical were used to assess the IVDD after 8 weeks of surgical procedure in vivo. Treatment with ferrostatin-1, deferoxamine, and RSL3 demonstrate the role of ferroptosis in tert-butyl hydroperoxide (TBHP)-treated annulus fibrosus cells (AFCs) and nucleus pulposus cells (NPCs). Ferritinophagy, nuclear receptor coactivator 4 (NCOA4)-mediated ferritin selective autophagy, is originated during the process of ferroptosis in response to TBHP treatment. Knockdown and overexpression NCOA4 further prove TBHP may induce ferroptosis of AFCs and NPCs in an autophagy-dependent way. These findings support a role for oxidative stress-induced ferroptosis in the pathogenesis of IVDD.

Endogenous glutamate determines ferroptosis sensitivity via ADCY10-dependent YAP suppression in lung adenocarcinoma

Rationale: Ferroptosis, a newly identified form of regulated cell death, can be induced following the inhibition of cystine-glutamate antiporter system X_C^- because of the impaired uptake of cystine. However, the outcome following the accumulation of endogenous glutamate in lung adenocarcinoma (LUAD) has not yet been determined. Yes-associated protein (YAP) is sustained by the hexosamine biosynthesis pathway (HBP)-dependent O-linked beta-N-acetylglucosaminylation (O-GlcNAcylation), and glutamine-fructose-6-phosphate transaminase (GFPT1), the rate-limiting enzyme of the HBP, can be phosphorylated and inhibited by adenylyl cyclase (ADCY)-mediated activation of protein kinase A (PKA). However, whether accumulated endogenous glutamate determines ferroptosis sensitivity by influencing the ADCY/PKA/HBP/YAP axis in LUAD cells is not understood.

Methods: Cell viability, cell death and the generation of lipid reactive oxygen species (ROS) and malondialdehyde (MDA) were measured to evaluate the responses to the induction of ferroptosis following the inhibition of system X_C^-. Tandem mass tags (TMTs) were employed to explore potential factors critical for the ferroptosis sensitivity of LUAD cells. Immunoblotting (IB) and quantitative RT-PCR (qPCR) were used to analyze protein and mRNA expression. Co-immunoprecipitation (co-IP) assays were performed to identify protein-protein interactions and posttranslational modifications. Metabolite levels were measured using the appropriate kits. Transcriptional regulation was evaluated using a luciferase reporter assay, chromatin immunoprecipitation (ChIP), and electrophoretic mobility shift assay (EMSA). Drug administration and limiting dilution cell transplantation were performed with cell-derived xenograft (CDX) and patient-derived xenograft (PDX) mouse models. The associations among clinical outcome, drug efficacy and ADCY10 expression were determined based on data from patients who underwent curative surgery and evaluated with patient-derived primary LUAD cells and tissues.

Results: The accumulation of endogenous glutamate following system X_C^- inhibition has been shown to determine ferroptosis sensitivity by suppressing YAP in LUAD cells. YAP O-GlcNAcylation and expression cannot be sustained in LUAD cells upon impairment of GFPT1. Thus, Hippo pathway-like phosphorylation and ubiquitination of YAP are enhanced. ADCY10 acts as a key downstream target and diversifies the effects of glutamate on the PKA-dependent suppression of GFPT1. We also discovered that the protumorigenic and proferroptotic effects of ADCY10 are mediated separately. Advanced-stage LUADs with high ADCY10 expression are sensitive to ferroptosis. Moreover, LUAD cells with acquired therapy resistance are also prone to higher ADCY10 expression and are more likely to respond to ferroptosis. Finally, a varying degree of secondary labile iron increase is caused by the failure to sustain YAP-stimulated transcriptional compensation for ferritin at later stages further explains why ferroptosis sensitivity varies among LUAD cells.

Conclusions: Endogenous glutamate is critical for ferroptosis sensitivity following the inhibition of system X_C^- in LUAD cells, and ferroptosis-based treatment is a good choice for LUAD patients with later-stage and/or therapy-resistant tumors.

Dexmedetomidine reverses MTX-induced neurotoxicity and inflammation in hippocampal HT22 cell lines via NCOA4-mediated ferritinophagy

The incidence of chemotherapy-induced cognitive impairment (CICI) has attracted massive attention. Some studies have demonstrated the neuroprotective effects of dexmedetomidine (DEX). Here, alterations in nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy were investigated as the possible causes of DEX’s neuroprotection of HT22 cells against methotrexate (MTX)-induced neurotoxicity. We used various concentrations of DEX and NCOA4-siRNA to treat MTX-induced neurotoxicity and inflammation in HT22 cells. The biomarkers of HT22 cells viability, apoptosis and inflammatory were tested. The expression of ferritinophagy markers were detected in the HT22 cells by using western blot and Immunofluorescence. We found that 10 and 50 ng/mL of DEX alleviated MTX-induced hippocampal neuronal inflammatory injuries. Meanwhile, DEX also reversed MTX-induced iron and ROS overproduction. Increasing DEX concentrations caused significant falls in the expression of ferritin heavy chain 1 (FTH1). DEX also increased vital ferritinophagy markers, NCOA4 and LC3II. NCOA4-siRNA transfection annulled the neuroprotective effects of DEX on MTX-induced inflammation in HT22 cells. Additionally, because NCOA4-siRNA disrupted ferritinophagy, DEX’s inhibitory impact on MTX-induced iron and ROS overproduction in HT22 cells was also annihilated. DEX weakened MTX-provoked neurontoxicity in HT22 cells, possibly by improving NCOA4-mediated ferritinophagy. Our discoveries present further mechanisms for understanding the protective effects of DEX against MTX-induced cognitive impairment.

Human Parainfluenza Virus Type 2 V Protein Modulates Iron Homeostasis

Intracellular iron concentration is tightly controlled for cell viability. It is known to affect the growth of several viruses, but the molecular mechanisms are not well understood. We found that iron chelators inhibit growth of human parainfluenza virus type 2 (hPIV-2). Furthermore, infection with hPIV-2 alters ferritin localization from granules to a homogenous distribution within cytoplasm of iron-stimulated cells. The V protein of hPIV-2 interacts with ferritin heavy chain 1 (FTH1), a ferritin subunit. It also binds to nuclear receptor coactivator 4 (NCOA4), which mediates autophagic degradation of ferritin, so-called ferritinophagy. V protein consequently interferes with interaction between FTH1 and NCOA4. hPIV-2 growth is inhibited in FTH1 knockdown cell line where severe hPIV-2-induced apoptosis is shown. In contrast, NCOA4 knockdown results in the promotion of hPIV-2 growth and limited apoptosis. Our data collectively suggest that hPIV-2 V protein inhibits FTH1-NCOA4 interaction and subsequent ferritinophagy. This iron homeostasis modulation allows infected cells to avoid apoptotic cell death, resulting in effective growth of hPIV-2.IMPORTANCE hPIV-2 V protein interferes with interaction between FTH1 and NCOA4 and inhibits NCOA4-mediated ferritin degradation, leading to the inhibition of iron release to the cytoplasm. This iron homeostasis modulation allows infected cells to avoid apoptotic cell death, resulting in effective growth of hPIV-2.

Low expression of ferritinophagy-related NCOA4 gene in relation to unfavorable outcome and defective immune cells infiltration in clear cell renal carcinoma

Background

Clear cell renal cell carcinoma is susceptible to ferroptosis, and immunotherapy is recently recommended as a priority for the initial treatment of metastatic clear cell renal carcinoma. Increased ferroptosis and immune activation can synergistically reinforce each other in killing cancer cells. NCOA4 depletion can eliminate iron accumulation and thus weaken ferroptosis. Here, we aim to identify and validate the association between NCOA4 expression, clinicopathologic characteristics, and overall survival in ccRCC by using The Cancer Genome Atlas and Gene Expression Omnibus databases. We further analyze the interacted proteins of NCOA4 and infiltrated immune cells via TIMER and GEPIA databases.

Methods

NCOA4 expression in clear cell renal carcinoma (ccRCC) tissues and normal adjacent tissues in The Cancer Genome Atlas (TCGA) data were primarily screened, and further validated in another independent cohort from the gene expression omnibus (GEO) database and human protein atlas. The relationships of NCOA4 expression and clinicopathologic parameters and overall survival (OS) were assessed using multivariate methods and Kaplan-Meier survival curves. And the proteins network with which NCOA4 interacted were also built using the online STRING website. Meanwhile, we use TIMER and GEPIA databases to investigate the relationships between NCOA4 expression and infiltrated immune cells and their corresponding gene marker sets.

Results

Contrast to normal tissue, NCOA4 expression was lower in ccRCC tumor tissue(p < 0.05). Lower NCOA4 expression was closely associated with high-grade malignancy and advanced TNM stage. Univariate and multivariate analysis indicated the overall survival of ccRCC cases with low NCOA4 level is shorter than those of patients with high NCOA4 expression (p < 0.05). FTL and FTH1 were the important proteins interacting with NCOA4. ccRCC with NCOA4 deficiency presented the paucity of infiltrated immune cells and their matching marker sets, including CD8+ T cells.

Conclusion

Deficient NCOA4 expression was related to disease progression and poor prognosis, as well as impaired infiltration of immune cells in ccRCC.

The Role of NCOA4-Mediated Ferritinophagy in Ferroptosis

Nuclear receptor coactivator 4 (NCOA4) is a selective cargo receptor that mediates the autophagic degradation of ferritin, the cytosolic iron storage complex, in a process known as ferritinophagy. NCOA4-mediated ferritinophagy is required to maintain intracellular and systemic iron homeostasis and thereby iron-dependent physiologic processes such as erythropoiesis. Given this role of ferritinophagy in regulating iron homeostasis, modulating NCOA4-mediated ferritinophagic flux alters sensitivity to ferroptosis, a non-apoptotic iron-dependent form of cell death triggered by peroxidation of polyunsaturated fatty acids (PUFAs). A role for ferroptosis has been established in the pathophysiology of cancer and neurodegeneration; however, the importance of ferritinophagy in these pathologies remains largely unknown. Here, we review the available evidence on biochemical regulation of NCOA4-mediated ferritinophagy and its role in modulating sensitivity to innate and induced ferroptosis in neurodegenerative diseases and cancer. Finally, we evaluate the potential of modulating ferritinophagy in combination with ferroptosis inducers as a therapeutic strategy.

NCOA4-mediated ferritinophagy promotes ferroptosis induced by erastin, but not by RSL3 in HeLa cells

Ferroptosis is a regulated cell death characterized by a lethal accumulation of lipid peroxides due to an increase of intracellular iron and a decrease of antioxidant capacity. The reduction of antioxidant activity is obtained by using chemical agents, such as erastin and RSL3, the first one inhibiting the transmembrane cystine-glutamate antiporter causing a cysteine and glutathione depletion and the second one inactivating directly the glutathione peroxidase 4 (GPX4) respectively. The role of iron and its related proteins in supporting the formation of lipid peroxides, is not completely understood hence to try to shed light on it we generated HeLa clones with altered ferritinophagy, the ferritin degradation process, by knocking-out or overexpressing Nuclear Receptor Coactivator 4 (NCOA4), the ferritin autophagic cargo-receptor. NCOA4 deficiency abolished ferritinophagy increasing ferritin level and making the cells more resistant to erastin, but unexpectedly more sensitive to RSL3. Interestingly, we found that erastin promoted ferritinophagy in HeLa cells expressing NCOA4, increasing the free iron, lipid peroxidation and the sensitivity to ferroptosis. In contrast, RSL3 did not modulate ferritinophagy, while NCOA4 overexpression delayed RSL3-induced cell death suggesting that RSL3 mechanism of action is independent of ferritin degradation process. Therefore, the ferritin-iron release in the execution of ferroptosis seems to depend on the inducing compound, its target and downstream pathway of cell death activation.

Ferritinophagy-mediated ferroptosis is involved in sepsis-induced cardiac injury

Ferroptosis is a reactive oxygen species (ROS)- and iron-dependent form of regulated cell death (RCD), playing critical roles in organ injury and targeting therapy of cancers. Previous studies have demonstrated that ferroptosis participates in the development of cardiomyopathy including cardiac hypertrophy, diabetic cardiomyopathy and doxorubicin-induced cardiotoxicity. However, the role of ferroptosis in sepsis-induced cardiac injury remains unclear. This study aimed to explore the role and underlying mechanism of ferroptosis on lipopolysaccharide (LPS)-induced cardiac injury. Mice were injected with LPS (10 mg/kg) for 12 h to generate experimental sepsis. Ferrostatin-1 (Fer-1) and Dexrazoxane (DXZ) were used to suppress ferroptosis of mice with sepsis-induced cardiac injury. LPS increased the levels of ferroptotic markers involving prostaglandin endoperoxide synthase 2 (PTGS2), malonaldehyde (MDA) and lipid ROS, apart from resulting in obvious mitochondria damage, which were alleviated by Fer-1 and DXZ. In vitro experiments showed that Fer-1 inhibited LPS-induced lipid peroxidation and injury of H9c2 myofibroblasts while erastin and sorafenib aggravated LPS-induced ferroptosis. Additionally, Fer-1 and DXZ improved survival rate and cardiac function of mice with sepsis. Mechanistically, LPS increased the expression of nuclear receptor coactivator 4 (NCOA4) and the level of intracellular Fe²⁺ but decreased the level of ferritin. NCOA4 could directly interact with ferritin and degrade it in a ferritinophagy-dependent manner, which subsequently released a great amount of iron. Cytoplasmic Fe²⁺ further activated the expression of siderofexin (SFXN1) on mitochondrial membrane, which in turn transported cytoplasmic Fe²⁺ into mitochondria, giving rise to the production of mitochondrial ROS and ferroptosis. Based on these findings, we concluded that ferritinophagy-mediated ferroptosis is one of the critical mechanisms contributing to sepsis-induced cardiac injury. Targeting ferroptosis in cardiomyocytes may be a therapeutic strategy for preventing sepsis in the future.

Hypoxia inhibits ferritinophagy, increases mitochondrial ferritin, and protects from ferroptosis

Cellular iron, at the physiological level, is essential to maintain several metabolic pathways, while an excess of free iron may cause oxidative damage and/or provoke cell death. Consequently, iron homeostasis has to be tightly controlled. Under hypoxia these regulatory mechanisms for human macrophages are not well understood. Hypoxic primary human macrophages reduced intracellular free iron and increased ferritin expression, including mitochondrial ferritin (FTMT), to store iron. In parallel, nuclear receptor coactivator 4 (NCOA4), a master regulator of ferritinophagy, decreased and was proven to directly regulate FTMT expression. Reduced NCOA4 expression resulted from a lower rate of hypoxic NCOA4 transcription combined with a micro RNA 6862-5p-dependent degradation of NCOA4 mRNA, the latter being regulated by c-jun N-terminal kinase (JNK). Pharmacological inhibition of JNK under hypoxia increased NCOA4 and prevented FTMT induction. FTMT and ferritin heavy chain (FTH) cooperated to protect macrophages from RSL-3-induced ferroptosis under hypoxia as this form of cell death is linked to iron metabolism. In contrast, in HT1080 fibrosarcome cells, which are sensitive to ferroptosis, NCOA4 and FTMT are not regulated. Our study helps to understand mechanisms of hypoxic FTMT regulation and to link ferritinophagy and macrophage sensitivity to ferroptosis.

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Hypoxia decreases NCOA4 transcription in primary human macrophages.

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NCOA4 mRNA is a target of miR-6862-5p.

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Lowering NCOA4 increases FTMT abundance under hypoxia.

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FTMT and FTH protect from ferroptosis.

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Tumor cells lack the hypoxic decrease of NCOA4 and fail to stabilize FTMT.

The Protective Effects of Cryptochlorogenic Acid on β-Cells Function in Diabetes in vivo and vitro via Inhibition of Ferroptosis

PURPOSE

Mulberry leaf extract has exerted better antidiabetic activities, while the effects of major active components in mulberry leaf extract are still unclear. Cryptochlorogenic acid (CCA) as the major active component in mulberry leaf extracts was investigated herein.

MATERIALS AND METHODS

Rats were treated with 50mg/kg streptozotocin for the establishment of diabetic model in vivo, and cells were treated with 33.3 mM glucose for the establishment of cell model in vitro. HE staining assay was performed for observation of pancreatic pathology and aldehyde fuchsin staining assay for examining islet cell numbers. The iron content was detected via Perls staining assay with iron assay kit (ab83366). The malondialdehyde (MDA), glutathione (GSH) and oxidized glutathione (GSSG) were detected by corresponding kits. Real-time quantitative polymerase chain reaction (RT-qPCR) was performed for assessment of gene level and Western blot for measurement of protein expression level. The cell survival was detected via CCK-8 assay.

RESULTS

The blood glucose level, iron content, accumulation of lipid peroxides and islet injury in diabetic model were all improved by CCA via a concentration-dependent manner. CCA functions via inhibition of ferroptosis by activation of cystine/glutamate transporter system (XC^-)/glutathione peroxidase 4(GPX4)/Nrf2 and inhibition of nuclear receptor coactivator 4 (NCOA4) in diabetes.

CONCLUSION

CCA exerted excellent antidiabetic effects via inhibition of ferroptosis, so it may be a promising agent for diabetes therapy, providing a new avenue for diabetes treatment.

Iron Supply via NCOA4-Mediated Ferritin Degradation Maintains Mitochondrial Functions

Iron is an essential nutrient for mitochondrial metabolic processes, including mitochondrial respiration. Ferritin complexes store excess iron and protect cells from iron toxicity. Therefore, iron stored in the ferritin complex might be utilized under iron-depleted conditions. In this study, we show that the inhibition of lysosome-dependent protein degradation by bafilomycin A1 and the knockdown of NCOA4, an autophagic receptor for ferritin, reduced mitochondrial respiration, respiratory chain complex assembly, and membrane potential under iron-sufficient conditions. However, autophagy did not contribute to degradation of the ferritin complex under iron-sufficient conditions. Knockout of the ferritin light chain, a subunit of the ferritin complex, inhibited ferritin degradation by decreasing interactions with NCOA4. However, ferritin light chain knockout did not affect mitochondrial functions under iron-sufficient conditions, and ferritin light chain knockout cells showed a rapid reduction of mitochondrial functions compared with wild-type cells under iron-depleted conditions. These results indicate that the constitutive degradation of the ferritin complex contributes to the maintenance of mitochondrial functions.

NCOA4-Mediated Ferritinophagy: A Potential Link to Neurodegeneration

NCOA4 (Nuclear receptor coactivator 4) mediates the selective autophagic degradation of ferritin, the cellular cytosolic iron storage complex, thereby playing a critical role in intracellular and systemic iron homeostasis. Disruptions in iron homeostasis and autophagy are observed in several neurodegenerative disorders raising the possibility that NCOA4-mediated ferritinophagy links these two observations and may underlie, in part, the pathophysiology of neurodegeneration. Here, we review the available evidence detailing the molecular mechanisms of NCOA4-mediated ferritinophagy and recent studies examining its role in systemic iron homeostasis and erythropoiesis. We propose additional studies to examine the potential role of NCOA4 in the brain in the context of neurodegenerative diseases.

The Role of NCOA4-Mediated Ferritinophagy in Health and Disease

Nuclear receptor coactivator 4 (NCOA4) is a selective cargo receptor that mediates the autophagic degradation of ferritin ("ferritinophagy"), the cytosolic iron storage complex. NCOA4-mediated ferritinophagy maintains intracellular iron homeostasis by facilitating ferritin iron storage or release according to demand. Ferritinophagy is involved in iron-dependent physiological processes such as erythropoiesis, where NCOA4 mediates ferritin iron release for mitochondrial heme synthesis. Recently, ferritinophagy has been shown to regulate ferroptosis, a newly described form of iron-dependent cell death mediated by excess lipid peroxidation. Dysregulation of iron metabolism and ferroptosis have been described in neurodegeneration, cancer, and infection, but little is known about the role of ferritinophagy in the pathogenesis of these diseases. Here, we will review the biochemical regulation of NCOA4, its contribution to physiological processes and its role in disease. Finally, we will discuss the potential of activating or inhibiting ferritinophagy and ferroptosis for therapeutic purposes.