CIRBP promotes ferroptosis by interacting with ELAVL1 and activating ferritinophagy during renal ischaemia-reperfusion injury

Renal ischaemia-reperfusion (IR) is a major cause of acute kidney injury (AKI). Cold-inducible RNA-binding protein (CIRBP) may contribute to AKI because its deficiency protects against renal IR injury in a mechanism believed to involve ferroptosis. We aimed to investigate whether ferroptosis is associated with CIRBP-mediated renal damage. The differential expression of CIRBP was examined in tubular epithelial (HK2) cells during hypoxia-reoxygenation (HR) or in response to erastin, an inducer of ferroptosis. CIRBP expression was increased in response to HR or erastin in HK2 cells but the silencing of CIRBP inhibited HR and erastin-induced ferroptosis together with ferritinophagy. We discovered an interaction between CIRBP and ELAVL1 using STRING software, which was verified through co-immunoprecipitation and fluorescence colocalization assays. We found that ELAVL1 is a critical regulator in the activation of ferritinophagy and the promotion of ferroptosis. HR or erastin also induced the expression of ELAVL1. An autophagy inhibitor (hydroxychloroquine) or si-ELAVL1 transfection reversed CIRBP-enhanced ferritinophagy activation and ferroptosis in HK2 cells under HR. Injection of anti-CIRBP antibody into a mouse model of IR inhibited ferroptosis and decreased renal IR injury in vivo. In summary, our results provide evidence that ferritinophagy-mediated ferroptosis could be responsible for CIRBP-enhanced renal IR injury.     

Cellular degradation systems in ferroptosis

In eukaryotic cells, macromolecular homeostasis requires selective degradation of damaged units by the ubiquitin-proteasome system (UPS) and autophagy. Thus, dysfunctional degradation systems contribute to multiple pathological processes. Ferroptosis is a type of iron-dependent oxidative cell death driven by lipid peroxidation. Various antioxidant systems, especially the system xc⁻-glutathione-GPX4 axis, play a significant role in preventing lipid peroxidation-mediated ferroptosis. The endosomal sorting complex required for transport-III (ESCRT-III)–dependent membrane fission machinery counteracts ferroptosis by repairing membrane damage. Moreover, cellular degradation systems play a dual role in regulating the ferroptotic response, depending on the cargo they degrade. The key ferroptosis repressors, such as SLC7A11 and GPX4, are degraded by the UPS. In contrast, the overactivation of selective autophagy, including ferritinophagy, lipophagy, clockophagy and chaperone-mediated autophagy, promotes ferroptotic death by degrading ferritin, lipid droplets, circadian proteins, and GPX4, respectively. Autophagy modulators (e.g., BECN1, STING1/TMEM173, CTSB, HMGB1, PEBP1, MTOR, AMPK, and DUSP1) also determine the ferroptotic response in a context-dependent manner. In this review, we provide an updated overview of the signals and mechanisms of the degradation system regulating ferroptosis, opening new horizons for disease treatment strategies.Subject terms: Cell biology, Molecular biology     

NMN recruits GSH to enhance GPX4-mediated ferroptosis defense in UV irradiation induced skin injury

Oxidative stress and lipid peroxidation are major causes of skin injury induced by ultraviolet (UV) irradiation. Ferroptosis is a form of regulated necrosis driven by iron-dependent peroxidation of phospholipids and contributes to kinds of tissue injuries. However, it remains unclear whether the accumulation of lipid peroxides in UV irradiation-induced skin injury could lead to ferroptosis. We generated UV irradiation-induced skin injury mice model to examine the accumulation of the lipid peroxides and iron. Lipid peroxides 4-HNE, the oxidative enzyme COX2, the oxidative DNA damage biomarker 8-OHdG, and the iron level were increased in UV irradiation-induced skin. The accumulation of iron and lipid peroxidation was also observed in UVB-irradiated epidermal keratinocytes without actual ongoing ferroptotic cell death. Ferroptosis was triggered in UV-irradiated keratinocytes stimulated with ferric ammonium citrate (FAC) to mimic the iron overload. Although GPX4 protected UVB-injured keratinocytes against ferroptotic cell death resulted from dysregulation of iron metabolism and the subsequent increase of lipid ROS, keratinocytes enduring constant UVB treatment were markedly sensitized to ferroptosis. Nicotinamide mononucleotide (NMN) which is a direct and potent NAD⁺ precursor supplement, rescued the imbalanced NAD⁺/NADH ratio, recruited the production of GSH and promoted resistance to lipid peroxidation in a GPX4-dependent manner. Taken together, our data suggest that NMN recruits GSH to enhance GPX4-mediated ferroptosis defense in UV irradiation-induced skin injury and inhibits oxidative skin damage. NMN or ferroptosis inhibitor might become promising therapeutic approaches for treating oxidative stress-induced skin diseases or disorders.     

Augmenter of liver regeneration protects the kidney from ischaemia‐reperfusion injury in ferroptosis

Acute kidney injury (AKI) is a common and severe clinical condition with high morbidity and mortality. Ischaemia‐reperfusion (I/R) injury remains the major cause of AKI in the clinic. Ferroptosis is a recently discovered form of programmed cell death (PCD) that is characterized by iron‐dependent accumulation of reactive oxygen species (ROS). Compelling evidence has shown that renal tubular cell death involves ferroptosis, although the underlying mechanisms remain unclear. Augmenter of liver regeneration (ALR) is a widely distributed multifunctional protein that is expressed in many tissues. Our previous study demonstrated that ALR possesses an anti‐oxidant function. However, the modulatory mechanism of ALR remains unclear and warrants further investigation. Here, to elucidate the role of ALR in ferroptosis, ALR expression was inhibited using short hairpin RNA lentivirals (shRNA) in vitro model of I/R‐induced AKI. The results suggest that the level of ferroptosis is increased, particularly in the shRNA/ALR group, accompanied by increased ROS and mitochondrial damage. Furthermore, inhibition of system xc‐ with erastin aggravates ferroptosis, particularly silencing of the expression of ALR. Unexpectedly, we demonstrate a novel signalling pathway of ferroptosis. In summary, we show for the first time that silencing ALR aggravates ferroptosis in an in vitro model of I/R. Notably, we show that I/R induced kidney ferroptosis is mediated by ALR, which is linked to the glutathione‐glutathione peroxidase (GSH‐GPx) system.     

Loss of cysteinyl-tRNA synthetase (CARS) induces the transsulfuration pathway and inhibits ferroptosis induced by cystine deprivation

Ferroptosis is a form of regulated non-apoptotic cell death that has been implicated in several disease contexts. A better understanding of the ferroptotic death mechanism could lead to the development of new therapeutics for degenerative diseases, and a better understanding of how to induce ferroptosis in specific tumor contexts. We performed an unbiased genome-wide siRNA screen to find genetic suppressors of ferroptosis. We determined that loss of CARS, the cysteinyl-tRNA synthetase, suppresses ferroptosis induced by erastin, which inhibits the cystine–glutamate antiporter known as system x_c⁻. Knockdown of CARS inhibited erastin-induced death by preventing the induction of lipid reactive oxygen species, without altering iron homeostasis. Knockdown of CARS led to the accumulation of cystathionine, a metabolite on the transsulfuration pathway, and upregulated genes associated with serine biosynthesis and transsulfuration. In addition, inhibition of the transsulfuration pathway resensitized cells to erastin, even after CARS knockdown. These studies demonstrate a new mechanism of resistance to ferroptosis and may lead to strategies for inducing and suppressing ferroptosis in diverse contexts.Precise regulation of cell death is essential for tissue homeostasis. Dysregulation of cell death processes is implicated in a variety of pathological conditions, such as ischemia and neurodegenerative diseases, providing a rationale for exploring cell-death-modulating compounds as potential therapeutics.¹ However, an incomplete understanding of cell death mechanisms in specific disease contexts has hindered efforts to develop therapeutics. Mechanistic analyses of cell death processes in disease contexts may uncover new strategies for drug discovery. Ferroptosis, a form of oxidative, non-apoptotic cell death, has recently been described and implicated in several pathological conditions, including Huntington''s disease (HD), periventricular leukomalacia (PVL) and kidney dysfunction.^{2, 3, 4} Ferroptotic cell death can be induced through perturbation of redox homeostasis maintained by glutathione, a key regulator of the intracellular redox state.Glutathione (GSH) is a tripeptide, the synthesis of which is dependent on the availability of the amino acid cysteine. A substantial fraction of extracellular cysteine exists as its oxidized disulfide form, cystine, because of the oxidative extracellular environment.⁵ Some cells primarily obtain cysteine by importing extracellular cystine through system x_c⁻, the cystine–glutamate antiporter. Cystine is then reduced to cysteine inside cells, fueling GSH synthesis. GSH maintains redox homeostasis by acting as a reductive substrate for reactive oxygen species (ROS)-detoxifying enzymes. As one example, glutathione peroxidase 4 (GPX4) uses GSH to reduce lipid hydroperoxides and organic hydroperoxides to alcohols, serving a critical role in lipid repair and detoxification. GPX4 was recently shown to be a central regulator of ferroptosis.⁶Ferroptosis can be induced by two classes of compounds, exemplified by erastin and (1 S, 3 R)-RSL3.^{6, 7, 8, 9} These two compounds target different parts of the ferroptotic pathway. Erastin inhibits system x_c⁻ to deplete GSH, which effectively inactivates all cellular glutathione peroxidases, including GPX4. RSL3, on the other hand, acts downstream, inhibiting GPX4 directly. In both cases, the loss of GPX4 activity causes accumulation of lipid peroxides, and ultimately, cell death. Recently, the FDA-approved drugs sorafenib and sulfasalazine were also found to induce ferroptosis through inhibition of system x_c⁻ activity,^{10, 11} although these lower-potency compounds may also activate other competing processes at similar or slightly higher concentrations. A specific inhibitor of ferroptosis, ferrostatin-1, and its analogs have been shown to suppress cell death in several degenerative disease models, including HD, PVL and kidney dysfunction, as well as in a model of glutamate toxicity, suggesting the involvement of ferroptosis in these conditions.^{4, 12} Collectively, these findings suggest that modulation of ferroptosis is of potential therapeutic relevance in several pathological conditions.Given the involvement of ferroptosis in these different contexts, we sought to identify specific features and regulators of ferroptosis. Ferroptosis is biochemically and morphologically distinct from necrosis and apoptosis.¹² Genetic analysis of ferroptosis has been performed using a limited set of genes related to mitochondrial function.¹² This previous analysis revealed that ferroptosis requires a distinct set of genes compared with apoptosis. However, this analysis cast a relatively narrow net; therefore, we sought to extend our understanding of the genetic regulation of ferroptosis further to identify essential genes and pathways using a genome-wide siRNA screen. Such genes may illuminate novel targets whose inhibition could be therapeutic in disease conditions involving aberrant activation of ferroptosis, or suggest strategies for inducing ferroptosis in specific tumor contexts.     

Directly targeting glutathione peroxidase 4 may be more effective than disrupting glutathione on ferroptosis-based cancer therapy

BackgroundCancer is one of the major threats to human health and current cancer therapies have been unsuccessful in eradicating it. Ferroptosis is characterized by iron-dependence and lipid hydroperoxides accumulation, and its primary mechanism involves the suppression of system X_c⁻-GSH (glutathione)-GPX4 (glutathione peroxidase 4) axis. Co-incidentally, cancer cells are also metabolically characterized by iron addiction and ROS tolerance, which makes them vulnerable to ferroptosis. This may provide a new tactic for cancer therapy.Scope of reviewThe general features and mechanisms of ferroptosis, and the basis that makes cancer cells vulnerable to ferroptosis are described. Further, we emphatically discussed that disrupting GSH may not be ideal for triggering ferroptosis of cancer cells in vivo, but directly inhibiting GPX4 and its compensatory members could be more effective. Finally, the various approaches to directly inhibit GPX4 without disturbing GSH were described.Major conclusionsTargeting system X_c⁻ or GSH may not effectively trigger cancer cells' ferroptosis in vivo the existence of other compensatory pathways. However, directly targeting GPX4 and its compensatory members without disrupting GSH may be more effective to induce ferroptosis in cancer cells in vivo, as GPX4 is essential in preventing ferroptosis.General significanceCancer is a severe threat to human health. Ferroptosis-based cancer therapy strategies are promising, but how to effectively induce ferroptosis in cancer cells in vivo is still a question without clear answers. Thus, the viewpoints raised in this review may provide some references and different perspectives for researchers working on ferroptosis-based cancer therapy.     

Fin56-induced ferroptosis is supported by autophagy-mediated GPX4 degradation and functions synergistically with mTOR inhibition to kill bladder cancer cells

Ferroptosis is a form of regulated cell death that emerges to be relevant for therapy-resistant and dedifferentiating cancers. Although several lines of evidence suggest that ferroptosis is a type of autophagy-dependent cell death, the underlying molecular mechanisms remain unclear. Fin56, a type 3 ferroptosis inducer, triggers ferroptosis by promoting glutathione peroxidase 4 (GPX4) protein degradation via a not fully understood pathway. Here, we determined that Fin56 induces ferroptosis and autophagy in bladder cancer cells and that Fin56-triggered ferroptosis mechanistically depends on the autophagic machinery. Furthermore, we found that autophagy inhibition at different stages attenuates Fin56-induced oxidative stress and GPX4 degradation. Moreover, we investigated the effects of Fin56 in combination with Torin 2, a potent mTOR inhibitor used to activate autophagy, on cell viability. We found that Fin56 synergizes with Torin 2 in cytotoxicity against bladder cancer cells. Collectively, our findings not only support the concept that ferroptosis is a type of autophagy-dependent cell death but imply that the combined application of ferroptosis inducers and mTOR inhibitors is a promising approach to improve therapeutic options in the treatment of bladder cancer.Subject terms: Macroautophagy, Macroautophagy     

HMGB1 regulates ferroptosis through Nrf2 pathway in mesangial cells in response to high glucose

Ferroptosis, a novel type of programmed cell death, is involved in inflammation and oxidation of various human diseases, including diabetic kidney disease. The present study explored the role of high-mobility group box-1 (HMGB1) on the regulation of ferroptosis in mesangial cells in response to high glucose. Compared with healthy control, levels of serum ferritin, lactate dehydrogenase (LDH), reactive oxygen species (ROS), malonaldehyde (MDA), and HMGB1 were significantly elevated in diabetic nephropathy (DN) patients, accompanied with deregulated ferroptosis-related molecules, including long-chain acyl-CoA synthetase 4 (ACSL4), prostaglandin-endoperoxide synthase 2 (PTGS2), NADPH oxidase 1 (NOX1), and glutathione peroxidase 4 (GPX4). In vitro assay revealed that erastin and high glucose both induced ferroptosis in mesangial cells. Suppression of HMGB1 restored cellular proliferation, prevented ROS and LDH generation, decreased ACSL4, PTGS2, and NOX1, and increased GPX4 levels in mesangial cells. Furthermore, nuclear factor E2-related factor 2 (Nrf2) was decreased in DN patients and high glucose-mediated translocation of HMGB1 in mesangial cells. Knockdown of HMGB1 suppressed high glucose-induced activation of TLR4/NF-κB axis and promoted Nrf2 expression as well as its downstream targets including HO-1, NQO-1, GCLC, and GCLM. Collectively, these findings suggest that HMGB1 regulates glucose-induced ferroptosis via Nrf2 pathway in mesangial cells.     

GPX4 and vitamin E cooperatively protect hematopoietic stem and progenitor cells from lipid peroxidation and ferroptosis

Ferroptosis, a newly defined mode of regulated cell death caused by unbalanced lipid redox metabolism, is implicated in various tissue injuries and tumorigenesis. However, the role of ferroptosis in stem cells has not yet been investigated. Glutathione peroxidase 4 (GPX4) is a critical suppressor of lipid peroxidation and ferroptosis. Here, we study the function of GPX4 and ferroptosis in hematopoietic stem and progenitor cells (HSPCs) in mice with Gpx4 deficiency in the hematopoietic system. We find that Gpx4 deletion solely in the hematopoietic system has no significant effect on the number and function of HSPCs in mice. Notably, hematopoietic stem cells (HSCs) and hematopoietic progenitor cells lacking Gpx4 accumulated lipid peroxidation and underwent ferroptosis in vitro. α-Tocopherol, the main component of vitamin E, was shown to rescue the Gpx4-deficient HSPCs from ferroptosis in vitro. When Gpx4 knockout mice were fed a vitamin E-depleted diet, a reduced number of HSPCs and impaired function of HSCs were found. Furthermore, increased levels of lipid peroxidation and cell death indicated that HSPCs undergo ferroptosis. Collectively, we demonstrate that GPX4 and vitamin E cooperatively maintain lipid redox balance and prevent ferroptosis in HSPCs.Subject terms: Cell biology, Physiology, Stem-cell research     

Deficiency in Beclin1 attenuates alcohol-induced cardiac dysfunction via inhibition of ferroptosis

BackgroundBinge drinking leads to compromised mitochondrial integrity and contractile function in the heart although little effective remedy is readily available. Given the possible derangement of autophagy in ethanol-induced cardiac anomalies, this study was designed to examine involvement of Beclin1 in acute ethanol-induced cardiac contractile dysfunction, in any, and the impact of Beclin1 haploinsufficiency on ethanol cardiotoxicity with a focus on autophagy-related ferroptosis.MethodsWT and Beclin1 haploinsufficiency (BECN^+/?) mice were challenged with ethanol for one week (2 g/kg, i.p. on day 1, 3 and 7) prior to assessment of cardiac injury markers (LDH, CK-MB), cardiac geometry, contractile and mitochondrial integrity, oxidative stress, lipid peroxidation, apoptosis and ferroptosis.ResultsEthanol exposure compromised cardiac geometry and contractile function accompanied with upregulated Beclin1 and autophagy, mitochondrial injury, oxidative stress, lipid peroxidation and apoptosis, and ferroptosis (GPx4, SLC7A11, NCOA4). Although Beclin1 deficiency did not affect cardiac function in the absence of ethanol challenge, it alleviated ethanol-induced changes in cardiac injury biomarkers, cardiomyocyte area, interstitial fibrosis, echocardiographic and cardiomyocyte mechanical properties along with mitochondrial integrity, oxidative stress, lipid peroxidation, apoptosis and ferroptosis. Ethanol challenge evoked pronounced ferroptosis (downregulated GPx4, SLC7A11 and elevated NCOA4, lipid peroxidation), the effect was alleviated by Beclin1 haploinsufficiency. Inhibition of ferroptosis using LIP-1 rescued ethanol-induced cardiac mechanical anomalies. In vitro study noted that ferroptosis induction using erastin abrogated Beclin1 haploinsufficiency-induced response against ethanol.ConclusionsIn sum, our data suggest that Beclin1 haploinsufficiency benefits acute ethanol challenge-induced myocardial remodeling and contractile dysfunction through ferroptosis-mediated manner.     

Acid sphingomyelinase-dependent autophagic degradation of GPX4 is critical for the execution of ferroptosis

Ferroptosis is a type of regulated cell death characterized by ROS accumulation and devastating lipid peroxidation (LPO). The role of acid sphingomyelinase (ASM), a key enzyme in sphingolipid metabolism, in the induction of apoptosis has been studied; however, to date its role in ferroptosis is unclear. In this study, we report that ASM plays a hitherto unanticipated role in promoting ferroptosis. Mechanistically, Erastin (Era) treatment results in the activation of ASM and generation of ceramide, which are required for the Era-induced reactive oxygen species (ROS) generation and LPO. Inhibition of nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) or removal of intracellular ROS, significantly reduced Era-induced ASM activation, suggesting that NADPH oxidase-derived ROS regulated ASM-initiated redox signaling in a positive feedback manner. Moreover, ASM-mediated activation of autophagy plays a critical role in ferroptosis inducers (FINs)-induced glutathione peroxidase 4 (GPX4) degradation and ferroptosis activation. Genetic or pharmacological inhibition of ASM diminishes Era-induced features of autophagy, GPX4 degradation, LPO, and subsequent ferroptosis. Importantly, genetic activation of ASM increases ferroptosis in cancer cells induced by various FINs. Collectively, these findings reveal that ASM plays a novel role in ferroptosis that could be exploited to improve pathological conditions that link to ferroptosis.Subject terms: Lipid peroxides, Cancer models, Macroautophagy, Lipid signalling     

MYCN mediates TFRC-dependent ferroptosis and reveals vulnerabilities in neuroblastoma

MYCN amplification is tightly associated with the poor prognosis of pediatric neuroblastoma (NB). The regulation of NB cell death by MYCN represents an important aspect, as it directly contributes to tumor progression and therapeutic resistance. However, the relationship between MYCN and cell death remains elusive. Ferroptosis is a newly identified cell death mode featured by lipid peroxide accumulation that can be attenuated by GPX4, yet whether and how MYCN regulates ferroptosis are not fully understood. Here, we report that MYCN-amplified NB cells are sensitive to GPX4-targeting ferroptosis inducers. Mechanically, MYCN expression reprograms the cellular iron metabolism by upregulating the expression of TFRC, which encodes transferrin receptor 1 as a key iron transporter on the cell membrane. Further, the increased iron uptake promotes the accumulation of labile iron pool, leading to enhanced lipid peroxide production. Consistently, TFRC overexpression in NB cells also induces selective sensitivity to GPX4 inhibition and ferroptosis. Moreover, we found that MYCN fails to alter the general lipid metabolism and the amount of cystine imported by System X_c(−) for glutathione synthesis, both of which contribute to ferroptosis in alternative contexts. In conclusion, NB cells harboring MYCN amplification are prone to undergo ferroptosis conferred by TFRC upregulation, suggesting that GPX4-targeting ferroptosis inducers or TFRC agonists can be potential strategies in treating MYCN-amplified NB.Subject terms: Cancer metabolism, Cell death     

SIRT3 deficiency is resistant to autophagy-dependent ferroptosis by inhibiting the AMPK/mTOR pathway and promoting GPX4 levels

Ferroptosis, an autophagy-dependent cell death, is characterized by lipid peroxidation and iron accumulation, closely associated with pathogenesis of gestational diabetes mellitus (GDM). Sirtuin 3 (SIRT3) has positive regulation on phosphorylation of activated protein kinase (AMPK), related to maintenance of cellular redox homeostasis. However, whether SIRT3 can confer autophagy by activating the AMPK-mTOR pathway and consequently promote induction of ferroptosis is unknown. We used human trophoblastic cell line HTR8/SVneo and porcine trophoblastic cell line pTr2 to deterimine the mechanism of SIRT3 on autophagy and ferroptosis. The expression of SIRT3 protein was significantly elevated in trophoblastic cells exposed to high concentrations of glucose and ferroptosis-inducing compounds. Increased SIRT3 expression contributed to classical ferroptotic events and autophagy activation, whereas SIRT3 silencing led to resistance against both ferroptosis and autophagy. In addition, autophagy inhibition impaired SIRT3-enhanced ferroptosis. On the contrary, autophagy induction had a synergistic effect with SIRT3. Based on mechanistic investigations, SIRT3 depletion inhibited activation of the AMPK-mTOR pathway and enhanced glutathione peroxidase 4 (GPX4) level, thereby suppressing autophagy and ferroptosis. Furthermore, depletion of AMPK blocked induction of ferroptosis in trophoblasts. We concluded that upregulated SIRT3-enhanced autophagy activation by promoting AMPK-mTOR pathway and decreasing GPX4 level to induce ferroptosis in trophoblastic cells. SIRT3 deficiency was resistant to high glucose- and erastin-induced autophagy-dependent ferroptosis and is, therefore, a potential therapeutic approach for treating GDM.     

Ginkgetin derived from Ginkgo biloba leaves enhances the therapeutic effect of cisplatin via ferroptosis-mediated disruption of the Nrf2/HO-1 axis in EGFR wild-type non-small-cell lung cancer

BackgroundCisplatin (DDP) is the first-in-class drug for advanced and non-targetable non-small-cell lung cancer (NSCLC). A recent study indicated that DDP could slightly induce non-apoptotic cell death ferroptosis, and the cytotoxicity was promoted by ferroptosis inducer. The agents enhancing the ferroptosis may therefore increase the anticancer effect of DDP. Several lines of evidence supporting the use of phytochemicals in NSCLC therapy. Ginkgetin, a bioflavonoid derived from Ginkgo biloba leaves, showed anticancer effects on NSCLC by triggering autophagy. Ferroptosis can be triggered by autophagy, which regulates redox homeostasis. Thus, we aimed to elucidate the possible role of ferroptosis involved in the synergistic effect of ginkgetin and DDP in cancer therapy.MethodsThe promotion of DDP-induced anticancer effects by ginkgetin was examined via a cytotoxicity assay and western blot. Ferroptosis triggered by ginkgetin in DDP-treated NSCLC was observed via a lipid peroxidation assay, a labile iron pool assay, western blot, and qPCR. With ferroptosis blocking, the contribution of ferroptosis to ginkgetin + DDP-induced cytotoxicity, the Nrf2/HO-1 axis, and apoptosis were determined via a luciferase assay, immunostaining, chromatin immunoprecipitation (CHIP), and flow cytometry. The role of ferroptosis in ginkgetin + DDP-treated NSCLC cells was illustrated by the application of ferroptosis inhibitors, which was further demonstrated in a xenograft nude mouse model.ResultsGinkgetin synergized with DDP to increase cytotoxicity in NSCLC cells, which was concomitant with increased labile iron pool and lipid peroxidation. Both these processes were key characteristics of ferroptosis. The induction of ferroptosis mediated by ginkgetin was further confirmed by the decreased expression of SLC7A11 and GPX4, and a decreased GSH/GSSG ratio. Simultaneously, ginkgetin disrupted redox hemostasis in DDP-treated cells, as demonstrated by the enhanced ROS formation and inactivation of the Nrf2/HO-1 axis. Ginkgetin also enhanced DDP-induced mitochondrial membrane potential (MMP) loss and apoptosis in cultured NSCLC cells. Furthermore, blocking ferroptosis reversed the ginkgetin-induced inactivation of Nrf2/HO-1 as well as the elevation of ROS formation, MMP loss, and apoptosis in DDP-treated NSCLC cells.ConclusionThis study is the first to report that ginkgetin derived from Ginkgo biloba leaves promotes DDP-induced anticancer effects, which can be due to the induction of ferroptosis.     

Ferroptosis: Role of lipid peroxidation,iron and ferritinophagy

Ferroptosis is a form of regulated cell death that is dependent on iron and reactive oxygen species (ROS) and is characterized by lipid peroxidation. It is morphologically and biochemically distinct and disparate from other processes of cell death. As ferroptosis is induced by inhibition of cysteine uptake or inactivation of the lipid repair enzyme glutathione peroxidase 4 (GPX4), the process is favored by chemical or mutational inhibition of the cystine/glutamate antiporter and culminates in the accumulation of reactive oxygen species (ROS) in the form of lipid hydroperoxides. Excessive lipid peroxidation leads to death by ferroptosis and the phenotype is accentuated respectively by the repletion and depletion of iron and glutathione in cells. Furthermore, oxidized phosphatidylethanolamines (PE) harbouring arachidonoyl (AA) and adrenoyl moieties (AdA) have been shown as proximate executioners of ferroptosis. Induction of ferroptosis due to cysteine depletion leads to the degradation of ferritin (i.e. ferritinophagy), which releases iron via the NCOA4-mediated autophagy pathway. Evidence of the manifestation of ferroptosis in vivo in iron overload mice mutants is emerging. Thus, a concerted synchronization of iron availability, ROS generation, glutamate excess and cysteine deficit leads to ferroptosis. A number of questions on the molecular mechanisms of some features of ferroptosis are highlighted as subjects for future investigations.     

Ferroptosis: an iron-dependent form of nonapoptotic cell death

Nonapoptotic forms of cell death may facilitate the selective elimination of some tumor cells or be activated in specific pathological states. The oncogenic RAS-selective lethal small molecule erastin triggers a unique iron-dependent form of nonapoptotic cell death that we term ferroptosis. Ferroptosis is dependent upon intracellular iron, but not other metals, and is morphologically, biochemically, and genetically distinct from apoptosis, necrosis, and autophagy. We identify the small molecule ferrostatin-1 as a potent inhibitor of ferroptosis in cancer cells and glutamate-induced cell death in organotypic rat brain slices, suggesting similarities between these two processes. Indeed, erastin, like glutamate, inhibits cystine uptake by the cystine/glutamate antiporter (system x(c)(-)), creating a void in the antioxidant defenses of the cell and ultimately leading to iron-dependent, oxidative death. Thus, activation of ferroptosis results in the nonapoptotic destruction of certain cancer cells, whereas inhibition of this process may protect organisms from neurodegeneration.     

肿瘤细胞死亡的一种新形式——铁死亡

铁死亡是近年来发现的一种程序性细胞死亡新形式,其主要特征是在发生于线粒体内的铁依赖性脂质过氧化物损伤诱导的细胞死亡。铁死亡细胞在形态、蛋白质及基因水平的变化均不同于细胞凋亡、坏死和自噬。2012年,铁死亡概念首次被提出后,铁死亡逐渐成为科学研究的热点。Erastin以及RSL3是铁死亡的诱导剂,谷胱甘肽过氧化物酶4（glutathione peroxidase 4,GPX4）是铁死亡的关键调节点,GPX4的表达量减少或活性降低均可诱导铁死亡的发生。胱氨酸-谷氨酸逆向转运蛋白（system Xc^-）可将细胞内的谷氨酸排出,同时将细胞外胱氨酸转运入细胞内,促进细胞内谷胱甘肽的合成,维持GPX4酶的活性。新近的研究表明,p62-keap1-Nrf2、P53-SAT1-ALOX15是铁死亡的关键调控通路,p53、BECN1以及BAP1是铁死亡的关键调节因子。Erastin以及RSL3可以选择性杀死RAS突变的肿瘤细胞,且越来越多的研究也证明,诱导肿瘤细胞铁死亡在免疫治疗以及逆转耐药方面均有着重要作用。因此,调控肿瘤细胞铁死亡很可能成为治疗肿瘤的新手段。本文就诱导肿瘤细胞铁死亡的机制及其进展作一综述。     

Ferroptosis in myocardial infarction: not a marker but a maker

Identification of effective cardiac biomarkers and therapeutic targets for myocardial infarction (MI) will play an important role in early diagnosis and improving prognosis. Ferroptosis, a cell death process driven by cellular metabolism and iron-dependent lipid peroxidation, has been implicated in diseases such as ischaemic organ damage, cancer and neurological diseases. Its modulators were involved in transferrin receptor, iron chelator, clock protein ARNTL, etc. Its mechanisms included the inhibition of system X_C⁻, diminished GPX4 activity, change of mitochondrial voltage-dependent anion channels and rising intracellular reactive oxygen species level. Further, the inhibitors of apoptosis, pyroptosis and autophagy did not prevent the occurrence of ferroptosis, but iron chelating agents and antioxidants could inhibit it. Noticeably, ferroptosis is an important pattern of cardiomyocyte death in the infarcted area, which may play a vital role in support of the myocardial pathological process of heart disease. However, the molecular mechanism of ferroptosis in the pathogenesis and the development of MI is not clear. Therefore, a greater depth of exploration of the mechanism of ferroptosis and its inhibitors will undoubtedly improve the pathological process of MI, which may be expected to identify ferroptosis as novel diagnostic and therapeutic targets of MI.     

Ferroptotic agent-induced endoplasmic reticulum stress response plays a pivotal role in the autophagic process outcome

Ferroptosis has been reported as a unique form of cell death. However, in recent years, researchers have increasingly challenged the uniqueness of ferroptosis compared to other types of cell death. In this study, we examined whether ferroptosis shares cell death pathways with other types of cell death, especially autophagy, via the autophagic process. Here, we observed that ferroptosis inducers (artesunate [ART] and erastin [ERA]) and autophagy inducers (bortezomib [BOR] and XIE62-1004) led to autophagosome formation via the endoplasmic reticulum (ER) stress response. Unlike XIE62-1004, ART, ERA, and BOR, which affect glutathione production or utilization, induced oxidative stress responses—an increase in the levels of heme oxygenase-1 and lipid peroxidation. Oxidative stress responses were attenuated by deletion of autophagy-related gene-5 or treatment with autophagy inhibitors (bafilomycin and chloroquine). Our studies provide an overview of common death pathways—the ER stress response-associated autophagic process in ferroptosis and autophagy. We also highlight the role played by glutathione redox system in the outcome of the autophagic process.