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Role of Mitochondria in Ferroptosis
Abstract
Ferroptosis is a regulated necrosis process driven by
iron-dependent lipid peroxidation. Although ferroptosis
and cellular metabolism interplay with one
another, whether mitochondria are involved in ferroptosis
is under debate. Here, we demonstrate
that mitochondria play a crucial role in cysteinedeprivation-
induced ferroptosis but not in that
induced by inhibiting glutathione peroxidase-4
(GPX4), the most downstream component of the ferroptosis
pathway. Mechanistically, cysteine deprivation
leads to mitochondrial membrane potential
hyperpolarization and lipid peroxide accumulation.
Inhibition of mitochondrial TCA cycle or electron
transfer chain (ETC) mitigated mitochondrial membrane
potential hyperpolarization, lipid peroxide
accumulation, and ferroptosis. Blockage of glutaminolysis
had the same inhibitory effect, which was
counteracted by supplying downstream TCA cycle
intermediates. Importantly, loss of function of fumarate
hydratase, a tumor suppressor and TCA cycle
component, confers resistance to cysteine-deprivation-
induced ferroptosis. Collectively, this work
demonstrates the crucial role of mitochondria in
cysteine-deprivation-induced ferroptosis and implicates
ferroptosis in tumor suppression.
... Organic oxidants promote mitochondrial iron overload. The role of mitochondria in ferroptosis has been controversial, possibly depending on cell types and cellular contexts [35][36][37][38] . Here, we identified a critical role of mitochondria in mediating oxidative stress-induced ferroptosis in cardiomyocytes. ...
... This study also reveals that mitochondria play a key role in oxidative stress-induced ferroptosis in cardiomyocytes. The role of mitochondria in ferroptosis has been controversial [35][36][37][38] . For instance, it has been shown that depletion of mitochondria had no effect on RLS3-induce ferroptosis in HT-1080 cells 35 . ...
... In contrast, subsequent studies found that mitochondrial DNA depletion or mitochondrial ROS quenching inhibited RSL3-induced ferroptosis 37,38 . Moreover, mitochondria depletion prevented ferroptosis induced by cysteine-deprivation or Erastin 36 . Here we showed that mitochondrial free iron levels as well as lipid peroxidation were markedly elevated following oxidative stress. ...
Oxidative stress has been shown to induce cell death in a wide range of human diseases including cardiac ischemia/reperfusion injury, drug induced cardiotoxicity, and heart failure. However, the mechanism of cell death induced by oxidative stress remains incompletely understood. Here we provide new evidence that oxidative stress primarily induces ferroptosis, but not apoptosis, necroptosis, or mitochondria-mediated necrosis, in cardiomyocytes. Intriguingly, oxidative stress induced by organic oxidants such as tert-butyl hydroperoxide (tBHP) and cumene hydroperoxide (CHP), but not hydrogen peroxide (H2O2), promoted glutathione depletion and glutathione peroxidase 4 (GPX4) degradation in cardiomyocytes, leading to increased lipid peroxidation. Moreover, elevated oxidative stress is also linked to labile iron overload through downregulation of the transcription suppressor BTB and CNC homology 1 (Bach1), upregulation of heme oxygenase 1 (HO-1) expression, and enhanced iron release via heme degradation. Strikingly, oxidative stress also promoted HO-1 translocation to mitochondria, leading to mitochondrial iron overload and lipid reactive oxygen species (ROS) accumulation. Targeted inhibition of mitochondrial iron overload or ROS accumulation, by overexpressing mitochondrial ferritin (FTMT) or mitochondrial catalase (mCAT), respectively, markedly inhibited oxidative stress-induced ferroptosis. The levels of mitochondrial iron and lipid peroxides were also markedly increased in cardiomyocytes subjected to simulated ischemia and reperfusion (sI/R) or the chemotherapeutic agent doxorubicin (DOX). Overexpressing FTMT or mCAT effectively prevented cardiomyocyte death induced by sI/R or DOX. Taken together, oxidative stress induced by organic oxidants but not H2O2 primarily triggers ferroptotic cell death in cardiomyocyte through GPX4 and Bach1/HO-1 dependent mechanisms. Our results also reveal mitochondrial iron overload via HO-1 mitochondrial translocation as a key mechanism as well as a potential molecular target for oxidative stress-induced ferroptosis in cardiomyocytes.
... 26,27 Ferroptosis is fundamentally a product of aberrant metabolic behavior including changes in central carbon metabolism such as increased mitochondrial glutaminolysis and increased dependence on glucose flux through the pentose phosphate pathway to generate NADPH. [28][29][30] The impact of PKM2, which also plays a critical role in metabolic reprograming and the management of oxidative stress, on ferroptosis in pancreatic cancer remains poorly characterized. Previous work in our lab demonstrated that PDAC cells use cysteine catabolism to support pyruvate production during PKM2 knockdown. ...
... Glutamine is an obvious candidate, as KRAS mutated pancreatic cancer cells rely on this metabolite, [44][45][46] and mitochondrial glutaminolysis contributes to ferroptosis. 30 Given this connection, we hypothesized that PKM2 expression alters glutamine metabolism and promotes ferroptosis. Thus, we next supplied the cells with uniformly (U) labeled U-13 C5-glutamine and observed its utilization in downstream pathways. ...
... Glutamine metabolism is an important component of ferroptosis. 30 Given the difference in glutamine . CC-BY-NC-ND 4.0 International license available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. ...
Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with high mortality and limited efficacious therapeutic options. PDAC cells undergo metabolic alterations to survive within a nutrient-depleted tumor microenvironment. One critical metabolic shift in PDAC cells occurs through altered isoform expression of the glycolytic enzyme, pyruvate kinase (PK). Pancreatic cancer cells preferentially upregulate pyruvate kinase muscle isoform 2 isoform (PKM2). PKM2 expression reprograms many metabolic pathways, but little is known about its impact on cystine metabolism. Cystine metabolism is critical for supporting survival through its role in defense against ferroptosis, a non-apoptotic iron-dependent form of cell death characterized by unchecked lipid peroxidation. To improve our understanding of the role of PKM2 in cystine metabolism and ferroptosis in PDAC, we generated PKM2 knockout (KO) human PDAC cells. Fascinatingly, PKM2KO cells demonstrate a remarkable resistance to cystine starvation mediated ferroptosis. This resistance to ferroptosis is caused by decreased PK activity, rather than an isoform-specific effect. We further utilized stable isotope tracing to evaluate the impact of glucose and glutamine reprogramming in PKM2KO cells. PKM2KO cells depend on glutamine metabolism to support antioxidant defenses against lipid peroxidation, primarily by increased glutamine flux through the malate aspartate shuttle and utilization of ME1 to produce NADPH. Ferroptosis can be synergistically induced by the combination of PKM2 activation and inhibition of the cystine/glutamate antiporter in vitro . Proof-of-concept in vivo experiments demonstrate the efficacy of this mechanism as a novel treatment strategy for PDAC.
Graphical Abstract
Highlights
PKM2KO in pancreatic ductal adenocarcinoma (PDAC) cells produces enhanced defense against cystine starvation induced ferroptosis.
Pharmacologic activation of pyruvate kinase (PK) activity promotes ferroptosis under cystine starvation, while inhibition promotes ferroptosis survival in PDAC cells.
Decrease in PK activity reprograms glutamine metabolism to increase use of malic enzyme 1 and promote survival under cystine starvation in PDAC cells.
Cystine starvation and activation of pyruvate kinase synergistically decreases progression of pancreatic cancer in vivo .
... Excessive lipid peroxides cannot all be metabolized by the GPX4-catalyzed reduction reaction, leading to the accumulation of ROS [3]. The smallmolecule erastin triggers ferroptosis by inhibiting the activity of the cystine-glutamate antiporter (SLC7A11, system Xc-), inducing the depletion of cellular cysteine and GSH and leading to the collapse of cellular redox homeostasis [4,5]. Besides iron and ROS, ferroptosis is regulated by other pathways such as the p53 pathway in cancer, it can be suppressed by several pathways including ferroptosis suppressor protein 1 (FSP1)-CoQ10 pathway [6,7], GCH1-BH4 pathway [8], and the DHODH-CoQH2 system [9,10] (Fig. 1). ...
... Mitochondria are not only the main energy resources for cells, but also signaling organelles involved in physiological and pathological processes [11][12][13][14]. Paradoxically, mitochondria play a central role in apoptotic cell death [15], pyroptosis [16], necroptosis [17], ferroptosis [4], and other forms of cell death. The classical mitochondrial pathway in apoptosis is related to the increased permeability of mitochondrial outer membrane, which enables some soluble proteins such as cytochrome c in the mitochondrial intermembrane space to be released into the cytoplasm, then apoptotic signaling pathways are activated, causing cell death. ...
... In pyroptosis, mitochondrial outer membrane permeabilization (MOMP) participates in the leakage of cytochrome c from the mitochondrion to the cytosol and subsequently activates caspase proteases and causes cell death [18]. In ferroptosis, mitochondria experience a morphological change including increased membrane density and reduced or vanishing mitochondrial cristae [4]. Moreover, mitochondria energy metabolism changes in ferroptosis, the oxidative phosphorylation synthesis and ATP production are increased correspondingly the glycolysis is decreased [2,19]. ...
Ferroptosis is a form of regulated cell death induced by iron-dependent lipid peroxidation, and it has been studied extensively since its discovery in 2012. Induced by iron overload and ROS accumulation, ferroptosis is modulated by various cellular metabolic and signaling pathways. The GSH-GPX4 pathway, the FSP1-CoQ10 pathway, the GCH1-BH4 pathway, the DHODH-CoQH2 system and the sex hormones suppress ferroptosis. Mitochondrial iron metabolism regulates ferroptosis and mitochondria also undergo a morphological change during ferroptosis, these changes include increased membrane density and reduced mitochondrial cristae. Moreover, mitochondrial energy metabolism changes during ferroptosis, the increased oxidative phosphorylation and ATP production rates lead to a decrease in the glycolysis rate. In addition, excessive oxidative stress induces irreversible damage to mitochondria, diminishing organelle integrity. ROS production, mitochondrial membrane potential, mitochondrial fusion and fission, and mitophagy also function in ferroptosis. Notably, some ferroptosis inhibitors target mitochondria. Ferroptosis is a major mechanism for cell death associated with the progression of cancer. Metastasis-prone or metastatic cancer cells are more susceptible to ferroptosis. Inducing ferroptosis in tumor cells shows very promising potential for treating drug-resistant cancers. In this review, we present a brief retrospect of the discovery and the characteristics of ferroptosis, then we discuss the regulation of ferroptosis and highlight the unique role played by mitochondria in the ferroptosis of cancer cells. Furthermore, we explain how ferroptosis functions as a double-edged sword as well as novel therapies aimed at selectively manipulating cell death for cancer eradication.
... 18 Additionally, several studies have demonstrated the crucial role of mitochondria in ferroptosis, suggesting metabolic alterations during this process. 19,20 In recent years, it has been gradually recog-nised that ferroptosis correlates with the occurrence and progression of various diseases, including ALI. 21 m6A modification has recently attracted attention because of its vital role in gene expression regulation. ...
... Mitochondrial damage was found to be relieved with the inhibition of NETs. 19,34 The performance of the lungs relies on alveolar epithelial cells. Unfortunately, these cells are prone to damage in the case of ALI. ...
Neutrophil extracellular traps (NETs), released by polymorphonuclear neutrophils (PMNs), exert a robust antimicrobial function in infectious diseases such as sepsis. NETs also contribute to the pathogenesis and exacerbation of sepsis. Although the lung is highly vulnerable to infections, few studies have explored the role of NETs in sepsis‐induced acute lung injury (SI‐ALI). We demonstrate that NETs induce SI‐ALI via enhanced ferroptosis in alveolar epithelial cells. Our findings reveal that the excessive release of NETs in patients and mice with SI‐ALI is accompanied by upregulation of ferroptosis depending on METTL3‐induced m6A modification of hypoxia‐inducible factor‐1α (HIF‐1α) and subsequent mitochondrial metabolic reprogramming. In addition to conducting METTL3 overexpression and knockdown experiments in vitro, we also investigated the impact of ferroptosis on SI‐ALI caused by NETs in a caecum ligation and puncture (CLP)‐induced SI‐ALI model using METTL3 condition knockout (CKO) mice and wild‐type mice. Our results indicate the crucial role of NETs in the progression of SI‐ALI via NET‐activated METTL3 m6A‐IGF2BP2‐dependent m6A modification of HIF‐1α, which further contributes to metabolic reprogramming and ferroptosis in alveolar epithelial cells.
... Gln can also fuel the tricarboxylic acid (TCA) cycle in mitochondria through the actions of mitochondrial GLS2 and Glu oxaloacetate transaminase 1 (GOT1) [73,74]. Intriguingly, mitochondrial electron transport chain (ETC) activity and glutaminolysis are indispensable for ferroptosis induced by Cys starvation, but are not required in ferroptosis induced by GPX4 inhibition [75]. Therefore, the relative Gln usage between GSH biosynthesis and glutaminolysis-fueled mitochondrial activity may regulate ferroptosis sensitivity. ...
... Mitochondrial respiratory chain activity and glutaminolysis are required for ferroptosis induced by Cys deprivation [75]. SLC1A5 is an important protein that stimulates the TCA cycle with α-KG by importing Gln [142,143]. ...
Ferroptosis has been conceptualized as a novel cell death modality distinct from apoptosis, necroptosis, pyroptosis and autophagic cell death. The sensitivity of cellular ferroptosis is regulated at multiple layers, including polyunsaturated fatty acid metabolism, glutathione-GPX4 axis, iron homeostasis, mitochondria and other parallel pathways. In addition, microRNAs (miRNAs) have been implicated in modulating ferroptosis susceptibility through targeting different players involved in the execution or avoidance of ferroptosis. A growing body of evidence pinpoints the deregulation of miRNA-regulated ferroptosis as a critical factor in the development and progression of various pathophysiological conditions related to iron overload. The revelation of mechanisms of miRNA-dependent ferroptosis provides novel insights into the etiology of diseases and offers opportunities for therapeutic intervention. In this review, we discuss the interplay of emerging miRNA regulators and ferroptosis players under different pathological conditions, such as cancers, ischemia/reperfusion, neurodegenerative diseases, acute kidney injury and cardiomyopathy. We emphasize on the relevance of miRNA-regulated ferroptosis to disease progression and the targetability for therapeutic interventions.
... When intracellular Fe 2+ is surcharged, the high level of free Fe 2+ facilitates the Fenton reaction [60]. Furthermore, Fe 2+ as a cofactor heightens the activity of multifarious metabolic enzymes, elevates the production of lipid peroxidation and ROS, and then induces ferroptosis [61]. Knockout TfR1 or increasing the storage of iron is effective methods to inhibit ferroptosis [3,25,62]. ...
... Explaining the function of iron in ferroptosis and how this unique pattern of cell death is heavily reliant on iron. Firstly, the metabolic enzymes of phospholipid peroxidation and lots of metabolic enzymes contained in the production of cellular ROS require iron catalysis [61]. In the second place, iron-relevant Fenton chain reaction may be necessary for ferroptosis: PLOOHs sustain for a longer time when GPX4 is inhibited; PLOOHs respond to ferrous and ferric ions to come into being free radicals PLO and PLOO, respectively, which react with PUFA-PLs to further diffuse PLOOH production [42]. ...
The discovery of the role of autophagy, particularly the selective form like ferritinophagy, in promoting cells to undergo ferroptosis has inspired us to investigate functional connections between diseases and cell death. Ferroptosis is a novel model of procedural cell death characterized by the accumulation of iron-dependent reactive oxygen species (ROS), mitochondrial dysfunction, and neuroinflammatory response. Based on ferroptosis, the study of ferritinophagy is particularly important. In recent years, extensive research has elucidated the role of ferroptosis and ferritinophagy in neurological diseases and anemia, suggesting their potential as therapeutic targets. Besides, the global emergence and rapid transmission of COVID-19, which is caused by SARS-CoV-2, represents a considerable risk to public health worldwide. The potential involvement of ferroptosis in the pathophysiology of brain injury associated with COVID-19 is still unclear. This review summarizes the pathophysiological changes of ferroptosis and ferritinophagy in neurological diseases, anemia, and COVID-19, and hypothesizes that ferritinophagy may be a potential mechanism of ferroptosis. Advancements in these fields will enhance our comprehension of methods to prevent and address neurological disorders, anemia, and COVID-19.
... Among them, ferroptosis is characterized by irondependent and lipid reactive oxygen species (ROS) accumulation that does not depend upon caspase-mediated cell death (Mou et al., 2019). Morphologically, a typical feature of ferroptosis includes mitochondrial volume reduction, mitochondrial cristae decrease and disappearance, outer membrane fragmentation, and decreased mitochondrial membrane potential (MMP) (Gao et al., 2019). Glutathione peroxidase-4 (GPX4) is a widespread peroxidation inhibiting enzyme that catalyzes the conversion of harmful lipid peroxides into nontoxic alcohols . ...
... MMP produced by the mitochondrial proton pump is essential for ATP production by coupling with oxidative phosphorylation (Zorova et al., 2018). Different ferroptosis inducers, including cystine starvation and amino acid-free medium, can induce mitochondrial hyperpolarization and destroy MMP (Gao et al., 2019). Additionally, mito-ROS promotes ferroptosis (Wu et al., 2021). ...
The study aimed to investigate the protective effects and biological mechanisms of glycyrrhizin arginine salt (Gly-Arg) against cisplatin (Cis)-induced liver injury. Our data showed that Gly-Arg improved Cis-induced liver injury. Further study showed that BECN1 (beclin1) and LC3-II/LC3-I protein expression was significantly increased in primary hepatocytes and mouse liver tissues after Cis treatment, but Gly-Arg reduced the protein levels of BECN1 and LC3-II/LC3-I in primary hepatocytes and mouse liver tissues. Also, Gly-Arg improved indicators related to Cis-induced ferroptosis. Furthermore, Cis increased colocalization of lysosomal membrane-associated protein 1A (LAMP1) with ferritin heavy chain 1 (FTH1) in primary mouse hepatocytes, while Gly-Arg intervention attenuated this colocalization in primary hepatocytes. More improtantly, Cis enhanced the formation of the BECN1-xCT complex, thus inhibiting solute carrier family 7 member 11 (SLC7A11, xCT) and glutathione peroxidase-4 (GPX4) activity. In contrast, Gly-Arg intervention disrupted the formation of this complex. However, Gly-Arg alleviated Cis-induced liver injury in mice by preventing autophagic death and ferroptosis through the inhibition of BECN1-xCT complex formation.
... Mitochondria are considered the most prominent generators of reactive oxygen species (ROS) in a cell due to incomplete reduction of molecular oxygen; thus, mitochondrial ROS are required for ferroptosis 29 . Notably, inhibiting the electron transport chain, which can generate superoxide anion (O 2 − •) by releasing electrons, blocks ferroptosis induced by GSH depletion 30 . Superoxide is mainly deposited in the mitochondrial matrix and generated in the intermembrane space via complex III, and superoxide can be exported from mitochondria to the cytoplasm via voltage-dependent anion channels. ...
... Inhibition of oxidative phosphorylation by deleting cytochrome c oxidase assembly factor 10 causes lysosomal and mitochondrial defects, resulting in the lipid peroxidation and ferroptosis of cardiac cells 34 . Furthermore, mitochondria are dispensable for ferroptosis induced by GPX4 inhibition because GPX4 rapidly amplifies the small number of lipid peroxides already present in the cell membrane 30 . Although the mitochondria-independent pathway driven by GPX4 inhibitors is crucial for understanding and improving cancer treatment, -dependent ferroptosis induced by cysteine deficiency or GSH depletion may be more relevant to the pathophysiological context of chronic human diseases. ...
Ferroptosis is a form of regulated cell death characterized by iron-dependent lipid peroxidation. This process contributes to cellular and tissue damage in various human diseases, such as cardiovascular diseases, neurodegeneration, liver disease, and cancer. Although polyunsaturated fatty acids (PUFAs) in membrane phospholipids are preferentially oxidized, saturated/monounsaturated fatty acids (SFAs/MUFAs) also influence lipid peroxidation and ferroptosis. In this review, we first explain how cells differentially synthesize SFA/MUFAs and PUFAs and how they control fatty acid pools via fatty acid uptake and β-oxidation, impacting ferroptosis. Furthermore, we discuss how fatty acids are stored in different lipids, such as diacyl or ether phospholipids with different head groups; triglycerides; and cholesterols. Moreover, we explain how these fatty acids are released from these molecules. In summary, we provide an integrated view of the diverse and dynamic metabolic processes in the context of ferroptosis by revisiting lipidomic studies. Thus, this review contributes to the development of therapeutic strategies for ferroptosis-related diseases.
... Following ferroptosis, the most important mechanism related to plasma membrane damages is lipid peroxidation [14]. Imperfections in the structure and morphology of the mitochondria are one of the typical morphological characteristics of ferroptosis [15]. Damage to the mitochondria cause lipid peroxidation and ferroptosis, which leads to mitochondrial fragmentation, an increase in ROS production, and a slowing down of mitochondrial metabolism. ...
... The ndings demonstrated that a pretreatment with ozone prevented an increase in the amount of Fe 2+ , LPO, and MDA that was present in the brain tissue of MCAO/R model rats. Disruption of mitochondrial morphology is a typical feature of ferroptosis, these disruptions included reductions in the number of mitochondrial cristae, hypodense matrix, as well as shorter length and swollen mitochondrial morphologies [15,56]. The results of transmission electron microscopy demonstrated that the morphology of mitochondria in neurons of MCAO/R rats was considerably damaged. ...
Background
The pathogenesis of brain ischemic/reperfusion (I/R) insult is characterised by the loss of neurons as a result of excessive oxidative stress responses. A form of oxidative cell death known as ferroptosis can be triggered when there is a breakdown in the equilibrium that exists between antioxidants and pro-oxidants in cells. As a natural bioactive molecule with antioxidant/anti-apoptotic and pro-autophagic properties, ozone can enhance the capacity of the antioxidant system and ameliorate oxidative stress. Yet, the mechanism of its role in neuronal ferroptosis remains unclear. Therefore, we investigated the functions and possible mechanisms of ozone in cerebral I/R-induced ferroptotic neuronal death.
Methods
A model of cerebral ischemia-reperfusion injury was created in S-D rats that had been pretreated with ozone. Intraperitoneal administration of the Nrf2 inhibitor ML385, the Slc7a11 inhibitor Erastin, and the Gpx4 inhibitor RSL3 was performed 1h prior to the creation of the model.
Results
According to the findings of our research, ozone preconditioning was able to mitigate neuronal damage caused by cerebral ischemia-reperfusion (I/R), lessen the severity of neurological deficits, lower the volume of cerebral infarcts, and reduce cerebral infarct volume in MCAO rats. One possible mechanism for this protective effect is the suppression of neuronal ferroptosis. Transmission electron microscopy, immunofluorescence, and Western blotting findings all pointed to ferroptosis in the aftermath of MCAO-induced brain damage. The present study found that MCAO caused morphological damage to neuronal mitochondria, enhanced the accumulation of lipid peroxidation, and promoted MDA production. Moreover, MCAO decreased the levels of FTH1 and GPX4, which act as negative regulators of ferroptosis, and increased the levels of ACSL4, which acts as a positive regulator of ferroptosis. Ozone preconditioning has been shown to have a protective impact on neuronal by increasing the nuclear translocation of Nrf2 and the expression of Slc7a11 and Gpx4. Meanwhile, treatment with ML385, Erastin and RSL3 significantly reversed the protective effect of ozone preconditioning on neuronal ferroptosis.
Conclusion
Ozone treatment attenuates the ferroptosis in cerebral ischemia/reperfusion injury rat model via Nrf2/Slc7a11/Gpx4 Pathway, which lays a new theoretical foundation for the use of ozone as a possible therapy to prevent ischemic stroke.
... In brief, the downregulation of FTH1 promotes iron storage and upregulates TFR1 expression, which enhances iron uptake and contributes to iron overload, especially in mitochondria. Excessive iron generates abundant reactive oxygen species (ROS) which contributes to lipid peroxidation and results in ferroptosis through the Fenton reaction [44,45]. Of note, DOX treatment was reported to downregulate GPX4 (glutathione peroxidase 4) and induce an excess of lipid peroxidation, leading to mitochondria-dependent ferroptosis through the DOX-Fe 2+ complex in mitochondria [46]. ...
... Our experiments revealed for the first time that Neu5Ac activated ferroptosis in vascular endothelial by triggering accumulation of ROS, Fe 2+ , and lipid peroxidation, which are typical features of ferroptosis [21]. As mitochondrial plays an essential role in ferroptosis [72], we also noticed that Neu5Ac induces mitochondrial oxidative stress and promotes ferroptosis, supporting the study that mitochondrial oxidative stress induces Fe 2+ disorder and activated ferroptosis [73]. Furthermore, we found that Fer-1 was effective in reducing endothelial cell inflammation, restoring mitochondrial function, and suppressing the atherosclerotic progression, which was also consistent with the previous report [74]. ...
... Distinct from the pH-induced PMF increase, the ψdependent increase results from a series of biochemical reactions in bacterial cells (Gao et al., 2019). The ψ, a part of the PMF, improves aminoglycoside activity. ...
Introduction
Antimicrobial resistance, especially the development of multidrug-resistant strains, is an urgent public health threat. Antibiotic adjuvants have been shown to improve the treatment of resistant bacterial infections.
Methods
We verified that exogenous L-arginine promoted the killing effect of gentamicin against Salmonella in vitro and in vivo , and measured intracellular ATP, NADH, and PMF of bacteria. Gene expression was determined using real-time quantitative PCR.
Results
This study found that alkaline arginine significantly increased gentamicin, tobramycin, kanamycin, and apramycin-mediated killing of drug-resistant Salmonella , including multidrug-resistant strains. Mechanistic studies showed that exogenous arginine was shown to increase the proton motive force, increasing the uptake of gentamicin and ultimately inducing bacterial cell death. Furthermore, in mouse infection model, arginine effectively improved gentamicin activity against Salmonella typhimurium .
Discussion
These findings confirm that arginine is a highly effective and harmless aminoglycoside adjuvant and provide important evidence for its use in combination with antimicrobial agents to treat drug-resistant bacterial infections.
... The out-of-control respiration of mitochondria is assumed to act as a promoting effect on ferroptosis because of the generation of more ROS [43]. Glutaminolysis is assumed to be an important factor for the run-out mitochondrial respiration. ...
Ferroptosis is an iron-dependent and lipid peroxidation-driven cell death cascade, occurring when there is an imbalance of redox homeostasis in the cell. Nuclear factor erythroid 2-related factor 2 (NFE2L2, also known as NRF2) is key for cellular antioxidant responses, which promotes downstream genes transcription by binding to their antioxidant response elements (AREs). Numerous studies suggest that NRF2 assumes an extremely important role in the regulation of ferroptosis, for its various functions in iron, lipid, and amino acid metabolism, and so on. Many pathological states are relevant to ferroptosis. Abnormal suppression of ferroptosis is found in many cases of cancer, promoting their progression and metastasis. While during tissue damages, ferroptosis is recurrently promoted, resulting in a large number of cell deaths and even dysfunctions of the corresponding organs. Therefore, targeting NRF2-related signaling pathways, to induce or inhibit ferroptosis, has become a great potential therapy for combating cancers, as well as preventing neurodegenerative and ischemic diseases. In this review, a brief overview of the research process of ferroptosis over the past decade will be presented. In particular, the mechanisms of ferroptosis and a focus on the regulation of ferroptosis by NRF2 will be discussed. Finally, the review will briefly list some clinical applications of targeting the NRF2 signaling pathway in the treatment of diseases.
... Neuronal in ammation is a prominent characteristic of SAE and is histopathologically connected to brain dysfunction 48 . It is well-documented that damaged cells propagate the release of in ammatory factors, thereby exacerbating tissue damage 48,49 . Ferroptosis, in concert with other forms of regulatory necrosis, is postulated to stimulate the progression of in ammation 48 . ...
Sepsis-associated encephalopathy (SAE) is a prevalent complication of sepsis, with hippocampal neuroinflammation playing a crucial role in SAE-induced cognitive impairment. Maresin1 (MaR1), a bioactive docosahexaenoic acid (DHA) metabolite, demonstrates comprehensive anti-inflammatory and neuroprotective attributes. Yet, its protective efficacy against SAE-induced cognitive decline remains unexplored. In this investigation, we implemented a rat SAE model via cecal ligation and puncture (CLP), while lipopolysaccharide (LPS) stimulation of HT22 cells simulated an in vitro SAE model; both models were pre-treated with MaR1. We evaluated rat learning and memory using a water maze, assessed hippocampal neuron damage via Nissl and FJC staining, and observed mitochondrial alterations through TEM. In vivo and in vitro assays gauged levels of Fe ²⁺ , MDA, GSH, and SOD. Additionally, Iba1 expression in the hippocampus was examined via immunofluorescence, while SLC7A11 and GPX4 protein expression levels were determined using western blot. Our findings indicated CLP-induced learning and memory impairment in rats, along with heightened ROS, Fe ²⁺ , and MDA levels in hippocampal neurons, diminished GSH and SOD levels, and down-regulated ferroptosis-related proteins (GPX4 and SLC7A11). Remarkably, MaR1 treatment attenuated these adverse effects. In LPS-stimulated HT22 cells, MaR1 lowered lipid ROS and bolstered mitochondrial membrane potential. Nonetheless, the ferroptosis inducer Erastin reversed MaR1's protective effects. Transwell experiments further showed MaR1's potential to inhibit microglia activation triggered by ferroptosis in HT22 cells. Consequently, MaR1 may mitigate hippocampal neuroinflammation via activating the SLC7A11/GPX4 ferroptosis signaling pathway, thus ameliorating SAE-related cognitive impairment.
... High iron levels are linked to lipid peroxidation and abnormal mercaptan iron metabolism, leading to increased ROS production [118]. A transferrin receptor binds to circulating iron as Fe 3+ , allowing it to enter the cell [119]. Through DMT1, iron oxide reductase reduces Fe 3+ to Fe 2 +, which is then pumped into the iron pool producing ROS. ...
Gastric cancer (GC) is the fifth most common cancer worldwide and makes up a significant component of the global cancer burden. Helicobacter pylori (H. pylori) is the most influential risk factor for GC, with the International Agency for Research on Cancer classifying it as a Class I carcinogen for GC. H. pylori has been shown to persist in stomach acid for decades, causing damage to the stomach’s mucosal lining, altering gastric hormone release patterns, and potentially altering gastric function. Epidemiological studies have shown that eliminating H. pylori reduces metachronous cancer. Evidence shows that various molecular alterations are present in gastric cancer and precancerous lesions associated with an H. pylori infection. However, although H. pylori can cause oxidative stress-induced gastric cancer, with antioxidants potentially being a treatment for GC, the exact mechanism underlying GC etiology is not fully understood. This review provides an overview of recent research exploring the pathophysiology of H. pylori-induced oxidative stress that can cause cancer and the antioxidant supplements that can reduce or even eliminate GC occurrence.
... Malonaldehyde (MDA) is a lipid peroxidation product and was also elevated after TgCtwh3 infection (Fig 2G). Mitochondrial abnormalities could increase the sensitivity of ferroptosis [42]. Cells with normal nuclei but damaged mitochondria could be observed in our electron microscopic results (Fig 2H). ...
Iron is a trace metal element that is essential for the survival of cells and parasites. The role of iron in cerebral toxoplasmosis (CT) is still unclear. Deferiprone (DFP) is the orally active iron chelator that binds iron in a molar ratio of 3:1 (ligand:iron) and promotes urinary iron excretion to remove excess iron from the body. The aims of this experiment were to observe the alterations in iron in brains with Toxoplasma gondii (T. gondii) acute infections and to investigate the mechanism of ferroptosis in CT using DFP. We established a cerebral toxoplasmosis model in vivo using TgCtwh3, the dominant strains of which are prevalent in China, and treated the mice with DFP at a dose of 75 mg/kg/d. Meanwhile, we treated the HT-22 cells with 100 μM DFP for half an hour and then infected cells with TgCtwh3 in vitro. A qRT-PCR assay of TgSAG1 levels showed a response to the T. gondii burden. We used inductively coupled plasma mass spectrometry, an iron ion assay kit, Western blot analysis, glutathione and glutathione disulfide assay kits, a malonaldehyde assay kit, and immunofluorescence to detect the ferroptosis-related indexes in the mouse hippocampus and HT-22 cells. The inflammatory factors interferon-γ, tumor necrosis factor-α, transforming growth factor-β, and arginase 1 in the hippocampus and cells were detected using the Western blot assay. Hematoxylin and eosin staining, electron microscopy, and the Morris water maze experiment were used to evaluate the brain injuries of the mice. The results showed that TgCtwh3 infection is followed by the activation of ferroptosis-related signaling pathways and hippocampal pathological damage in mice. The use of DFP led to ferroptosis resistance and attenuated pathological changes, inflammatory reactions and T. gondii burden of the mice, prolonging their survival time. The HT-22 cells with TgCtwh3 activated the ferroptosis pathway and was inhibit by DFP in vitro. In TgCtwh3-infected cells, inflammatory response and mitochondrial damage were severe, but these effects could be reduced by DFP. Our study elucidates the mechanism by which T. gondii interferes with the host's iron metabolism and activates ferroptosis, complementing the pathogenic mechanism of CT and further demonstrating the potential value of DFP for the treatment of CT.
... Iron accumulation has been found in cartilage and synovium during the progression of OA, and ferroptosis may play an important role in the development of OA (Miao et al. 2022). Mitochondria are essential for ferroptosis due to their ability to promote metabolism and regulate lipid ROS production (Gao et al. 2019). Furthermore, mitochondria are important regulators in the development of OA (He et al. 2020). ...
The mitochondria are an important organelle in cells responsible for producing energy, and its abnormal function is closely related to the occurrence and development of osteoarthritis. Finding key genes associated with mitochondrial dysfunction in osteoarthritis can provide new ideas for the study of its pathogenesis. Firstly, 371 differential expressed genes (DEGs) were obtained through bioinformatics analysis of the GSE12021 and GSE55235 datasets in the GEO database, and 24 mitochondria-related DEGs (Mito-DEGs) were obtained by crossing differential genes with mitochondrial related genes. Next, KEGG and GO analysis of Mito-DEGs showed that upregulated Mito-DEGs were mainly enriched in small molecule catabolic process and tryptophan metabolism, while downregulated Mito-DEGs were mainly enriched in acetyl-CoA metabolic process and fatty acid biosynthesis. Furthermore, the key genes ME2 and MAOB were obtained through protein–protein interaction network analysis and lasso cox analysis of the 24 Mito-DEGs. In addition, the comparison results of immune cell scores showed differences between T cells CD4 memory resting, T cells regulatory (Tregs), Mast cells resting, and Mast cells activated in the OA group and the control group. More importantly, the potential regulatory mechanisms of key genes were studied through GSEA analysis and their correlation with immune infiltrating cells, immune checkpoints, m6A, and ferroptosis. Finally, in LPS-induced C28/I2 cells, silencing MAOB reduced inflammation injury and inhibited mitochondrial damage. Our research findings suggest that MAOB may hold potential as a target for the diagnosis and treatment of osteoarthritis.
... Currently, the extent of ferroptosis is mainly reflected by detecting the level of peroxisomal phospholipids, which is mainly due to the fact that excessive peroxisomal phospholipids can cause membrane damage and even pore formation, compromising membrane integrity and ultimately leading to cell death [15]. A study found that lipid cross-linking may be an important factor in ferroptosis, the main reason may be that crosslinked lipids reduce the mobility of membrane components, leading to the failure of important functions associated with membranes and causing cell death [52]. In addition, it has been suggested that peroxidized PUFA is also capable of causing cell death by disrupting macromolecules that are closely related to cellular activity and thus causing cell death [53]. ...
Distant metastasis is currently the main factor affecting the prognosis of nasopharyngeal carcinoma (NPC), and understanding the mechanisms of metastasis and identifying reliable therapeutic targets are critical for improving prognosis and achieving clinical translation. Macrophages, as important immune cells in the tumor microenvironment (TME), have been shown to regulate metastasis. And extracellular vesicles (EVs) secreted by stromal cells and tumor cells play the important role in intercellular communication in the tumor microenvironment. However, the role of NPC-EVs on macrophages and their function in regulating macrophages to affect metastasis has not been fully clarified. In this study, we report that NPC-EVs can be uptake by macrophages and alter macrophage polarization, for the first time, we identified the genes implicated in these regulatory functions: SCARB1, HAAO, and CYP1B1. Moreover, we found that SCARB1 was positively associated with metastasis and poor prognosis of NPC. Interestingly, we found that SCARB1-rich EVs promoted M1 macrophages ferroptosis to decrease M1 macrophages infiltration by upregulating the HAAO level while decreasing phagocytosis of M2 macrophages by upregulating the CYP1B1 level. Finally, we identified the SCARB1-binding gene KLF9, which is involved in the transcription of HAAO and CYP1B1. Our findings showed that SCARB1-EVs promoted metastasis by co-regulating M1 and M2 macrophage function. The related mechanism will provide a new therapeutic strategy to help patients with NPC improve their prognosis.
... Remarkably, in the 75 patients with lung adenocarcinoma, 32 exhibited co-expression of Cyclin D1 and APR3, suggesting a positive correlation between Cyclin D1 and APR3 expression in lung cancer. This implies that APR3-mediated inhibition of Cyclin D1 expression may be in mitochondria are essential for ferroptosis [105,106]. Furthermore, oxidative stress regulates calcium influx or competitively inhibits system x c − in response to glutamate receptor activation [107]. Within the ferroptosis pathway, system x c − is a widely recognized protective system, preventing the formation of lipid peroxides by facilitating the synthesis of glutathione through cystine absorption [108]. ...
APR3 (Apoptosis-related protein 3) is a gene that has recently been identified to be associated with apoptosis. The gene is located on human chromosome 2p22.3 and contains both transmembrane and EGF (epidermal growth factor)-like domains. Additionally, it has structural sites, including AP1, SP1, and MEF2D, that indicate NFAT (nuclear factor of activated T cells) and NF-κB (nuclear factor kappa-B) may be transcription factors for this gene. Functionally, APR3 participates in apoptosis due to the induction of mitochondrial damage to release mitochondrial cytochrome C. Concurrently, APR3 affects the cell cycle by altering the expression of Cyclin D1, which, in turn, affects the incidence and growth of malignancies and promotes cell differentiation. Previous reports indicate that APR3 is located in lysosomal membranes, where it contributes to lysosomal activity and participates in autophagy. While further research is required to determine the precise role and molecular mechanisms of APR3, earlier studies have laid the groundwork for APR3 research. There is growing evidence supporting the significance of APR3 in oncology. Therefore, this review aims to examine the current state of knowledge on the role of the newly discovered APR3 in tumorigenesis and to generate fresh insights and suggestions for future research.
... Major defining features of ferroptotic aging human white matter microglia were the accumulation of myelin debris in iron-enriched senescent microglia, which displayed mitochondrial metabolic stress, lipid peroxidation injury, and DNA damage. [65][66][67] Recurrent microvascular ischemia to aging WM enhances the burden of iron-rich myelin debris to be cleared by WM microglia. 68 Moreover, axonal injury related to Wallerian degeneration in AD may also constitute another significant mechanism that contributes to myelin loss. ...
Objective:
Since the role of white matter (WM) degenerating microglia in myelination failure is unclear, we sought to define the core features of this novel population of aging human microglia.
Methods:
We analyzed post-mortem human brain tissue to define a population of degenerative microglia (DM) in aging white matter lesions. We employed immunofluorescence staining and gene expression analysis to investigate molecular mechanisms related to the degeneration of DM.
Results:
We found that DM accumulated myelin debris, were selectively enriched in the iron-binding protein light chain ferritin, and accumulated PLIN2-labeled lipid droplets. DM displayed lipid peroxidation injury and enhanced expression for TOM20, a mitochondrial translocase, and a sensor of oxidative stress. DM also displayed enhanced expression of the DNA fragmentation marker phospho-histone H2A.X. We identified a unique set of ferroptosis-related genes involving iron-mediated lipid dysmetabolism and oxidative stress that were preferentially expressed in white matter injury relative to gray matter neurodegeneration.
Interpretation:
Ferroptosis appears to be a major mechanism of white matter injury in Alzheimer's disease and vascular dementia. White matter DM are a novel therapeutic target to potentially reduce the impact of white matter injury and myelin loss on the progression of cognitive impairment. This article is protected by copyright. All rights reserved.
... After CT26 cells were treated with MMP NDs, the expression level of GPX4 in CT26 cells was markedly decreased, proving that MMP NDs could effectively reduce the level of GSH in tumor cells and inactivate GPX4 (Fig. 3h). The change in mitochondrial membrane potential is an important indicator of ferroptosis [34][35][36]. When ferroptosis occurs in cells, the membrane potential is significantly reduced or even lost. ...
Certain types of cationic metal ions, such as Mn2+ are able to activate immune functions via the stimulator of interferon genes (STING) pathway, showing potential applications in eliciting antitumor immunity. How anionic ions interact with immune cells remains largely unknown. Herein, selecting from a range of cationic and anionic ions, we were excited to discover that MoO42- could act as a cGAS-STING agonist and further confirmed the capability of Mn2+ to activate the cGAS-STING pathway. Inspired by such findings, we synthesized manganese molybdate nanoparticles with polyethylene glycol modification (MMP NDs) for cancer metalloimmunotherapy. Meanwhile, MMP NDs could consume glutathione (GSH) over-expressed in tumors and induce ferroptosis owing to high-valence Mo and Mn to elicit tumor-specific immune responses, which was further amplified by MMP-triggered the cGAS-STING activation. In turn, activated CD8+ T cells to secrete high levels of interferon γ (IFN-γ) and reduced GPX4 expression in tumor cells to trigger ferroptosis-specific lipid peroxidation, which constituted a "cycle" of therapy. As a result, the metalloimmunotherapy with systemic administration of MMP NDs offered a remarkable tumor inhibition effect for a variety of tumor models. Our work for the first time discovered the ability of anionic metal ions to activate the immune system and rationally designed bimetallic oxide nanostructures as a multifunctional therapeutic nanoplatform for tumor immunotherapy.
... Ferroptosis is defined as iron-dependent lipid peroxidation process, which is closely related to many diseases [8][9][10]. The morphologic changes of mitochondria including the reduction of mitochondrial cristae and the increase of mitochondrial outer membrane density were characteristic [11]. Increased iron uptake and iron release from intracellular ferritin autophagy will lead to iron accumulation [12]. ...
Background:
Ferroptosis, a newly discovered mode of cell death, emerges as a new target for atherosclerosis (AS). Long noncoding RNAs (lncRNAs) are involved in the regulation of ferroptosis. In our previous study, lnc-MRGPRF-6:1 was highly expressed in patients with coronary atherosclerotic disease (CAD) and closely associated with macrophage-mediated inflammation in AS. In the present study, we aim to investigate the role of lnc-MRGPRF-6:1 in oxidized-low-density lipoprotein (ox-LDL)-induced macrophage ferroptosis in AS.
Methods:
Firstly, ox-LDL-treated macrophages were used to simulate macrophage injury in AS. Then, ferroptosis-related biomarkers and mitochondrial morphology were detected and observed in ox-LDL-treated macrophages. Subsequently, we constructed lnc-MRGPRF-6:1 knockdown and overexpression of THP-1-derived macrophages and investigated the role of lnc-MRGPRF-6:1 in ox-LDL-induced ferroptosis. Then human monocytes were isolated successfully and were used to explore the role of lnc-MRGPRF-6:1 in macrophage ferroptosis. Likely, we constructed lnc-MRGPRF-6:1 knockdown and overexpression of human monocyte-derived macrophages and detected the expression levels of ferroptosis-related biomarkers. Then, transcriptome sequencing, literature searching, and following quantitative real-time polymerase chain reaction and western blot were implemented to explore specific signaling pathway in the process. It was demonstrated that lnc-MRGPRF-6:1 may regulate ox-LDL-induced macrophage ferroptosis through glutathione peroxidase 4 (GPX4). Eventually, the correlation between lnc-MRGPRF-6:1 and GPX4 was measured in monocyte-derived macrophages of CAD patients and controls.
Results:
The ox-LDL-induced injury in macrophages was involved in ferroptosis. The knockdown of lnc-MRGPRF-6:1 could alleviate ox-LDL-induced ferroptosis in macrophages. Meanwhile, the overexpression of lnc-MRGPRF-6:1 could intensify ox-LDL-induced ferroptosis. Furthermore, the knockdown of lnc-MRGPRF-6:1 could alleviate the decrease of GPX4 induced by RAS-selective lethal compounds 3 (RSL-3). These indicated that lnc-MRGPRF-6:1 may suppress GPX4 to induce macrophage ferroptosis. Eventually, lnc-MRGPRF-6:1 was highly expressed in the monocyte-derived macrophages of CAD patients and was negatively correlated with the expression of GPX4.
Conclusion:
lnc-MRGPRF-6:1 can promote ox-LDL-induced macrophage ferroptosis through inhibiting GPX4.
... During the reperfusion state, mitochondrial damage, electrolyte imbalance, and increased mitochondrial respiration trigger a burst of ROS, lipid peroxidation, and ferroptosis presented by a reduction in mitochondrial volume, reduced or even lost mitochondrial cristae, and condensed mitochondrial membrane densities. These morphological characteristics are distinguished from other forms of cell death, further highlighting the relevance of ferroptosis [7]. Moreover, the therapeutic strategy of targeting ferroptosis has been shown to attenuate pathological impairment in a variety of I/R models [8]. ...
(1) Background: Despite the evidence that ferroptosis is involved in myocardial ischemia-reperfusion (MIR), the critical regulator of ferroptosis in MIR remains unclear. (2) Methods: We included three GEO datasets and a set of ferroptosis-related genes with 259 genes. Following the identification of the differentially expressed ferroptosis-related genes (DEFRGs) and hub genes, we performed the functional annotation, protein–protein interaction network, and immune infiltration analysis. The GSE168610 dataset, a cell model, and an animal model were then used to verify key genes. (3) Results: We identified 17 DEFRGs and 9 hub genes in the MIR samples compared to the control. Heme oxygenase 1 (Hmox1), activating transcription factor 3 (Atf3), epidermal growth factor receptor (Egfr), and X-box binding protein 1 (Xbp1) were significantly upregulated in response to ischemic and hypoxic stimuli. In contrast, glutathione peroxidase 4 (Gpx4) and vascular endothelial growth factor A (Vegfa) were consistently decreased in either the oxygen and glucose deprivation/reoxygenation cell or the MIR mouse model. (4) Conclusions: This study emphasized the relevance of ferroptosis in MIR. It has been successfully demonstrated that nine ferroptosis-related genes (Hmox1, Atf3, Egfr, Gpx4, Cd44, Vegfa, asparagine synthetase (Asns), Xbp1, and bromodomain containing 4 (Brd4)) are involved in the process. Additional studies are needed to explore potential therapeutic targets for MIR.
... In addition, mitochondria are responsible for maintaining redox balance and generating energy through oxidative phosphorylation (OXPHOS), which in turn is a constant source of ROS production. Substantial mitochondrial dysfunction and damage include loss of mitochondrial membrane potential, mitochondrial ROS accumulation, and impaired respiration, which is followed by mitochondrial outer membrane permeabilization (MOMP) and the detrimental release of cytochrome c or apoptosis-inducing factor (AIF) and, therefore, has been referred to as the point of no return after initiation of (oxidative) cell death in different cell types [8,[20][21][22][23][24]. ...
Ferroptosis is a form of oxidative cell death that is characterized by enhanced lipid peroxidation and mitochondrial impairment. The enzymes acyl-CoA synthetase long-chain family member 4 (ACSL4) and lysophosphatidylcholine acyltransferase (LPCAT) play an essential role in the biosynthesis of polyunsaturated fatty acid (PUFA)-containing phospholipids, thereby providing the substrates for lipid peroxidation and promoting ferroptosis. To examine the impact of mitochondria in ACSL4/LPCAT2-driven ferroptosis, HEK293T cells overexpressing ACSL4 and LPCAT2 (OE) or empty vector controls (LV) were exposed to 1S, 3R-RSL3 (RSL3) for induction of ferroptosis. The ACSL4/LPCAT2 overexpression resulted in higher sensitivity against RSL3-induced cell death compared to LV-transfected controls. Moreover, mitochondrial parameters such as mitochondrial reactive oxygen species (ROS) formation, mitochondrial membrane potential, and mitochondrial respiration deteriorated in the OE cells, supporting the conclusion that mitochondria play a significant role in ACSL4/LPCAT2-driven ferroptosis. This was further confirmed through the protection of OE cells against RSL3-mediated cell death by the mitochondrial ROS scavenger mitoquinone (MitoQ), which exerted protection via antioxidative properties rather than through previously reported metabolic effects. Our findings implicate that mitochondrial ROS production and the accompanying organelle disintegration are essential for mediating oxidative cell death initiated through lipid peroxidation in ferroptosis.
Cerebral ischemia, a leading cause of disability and mortality worldwide, triggers a cascade of molecular and cellular pathologies linked to several central nervous system (CNS) disorders. These disorders primarily encompass ischemic stroke, Alzheimer’s disease (AD), Parkinson’s disease (PD), epilepsy, and other CNS conditions. Despite substantial progress in understanding and treating the underlying pathological processes in various neurological diseases, there is still a notable absence of effective therapeutic approaches aimed specifically at mitigating the damage caused by these illnesses. Remarkably, ischemia causes severe damage to cells in ischemia-associated CNS diseases. Cerebral ischemia initiates oxygen and glucose deprivation, which subsequently promotes mitochondrial dysfunction, including mitochondrial permeability transition pore (MPTP) opening, mitophagy dysfunction, and excessive mitochondrial fission, triggering various forms of cell death such as autophagy, apoptosis, as well as ferroptosis. Ferroptosis, a novel type of regulated cell death (RCD), is characterized by iron-dependent accumulation of lethal reactive oxygen species (ROS) and lipid peroxidation. Mitochondrial dysfunction and ferroptosis both play critical roles in the pathogenic progression of ischemia-associated CNS diseases. In recent years, growing evidence has indicated that mitochondrial dysfunction interplays with ferroptosis to aggravate cerebral ischemia injury. However, the potential connections between mitochondrial dysfunction and ferroptosis in cerebral ischemia have not yet been clarified. Thus, we analyzed the underlying mechanism between mitochondrial dysfunction and ferroptosis in ischemia-associated CNS diseases. We also discovered that GSH depletion and GPX4 inactivation cause lipoxygenase activation and calcium influx following cerebral ischemia injury, resulting in MPTP opening and mitochondrial dysfunction. Additionally, dysfunction in mitochondrial electron transport and an imbalanced fusion-to-fission ratio can lead to the accumulation of ROS and iron overload, which further contribute to the occurrence of ferroptosis. This creates a vicious cycle that continuously worsens cerebral ischemia injury. In this study, our focus is on exploring the interplay between mitochondrial dysfunction and ferroptosis, which may offer new insights into potential therapeutic approaches for the treatment of ischemia-associated CNS diseases.
Reactive oxygen, nitrogen, sulfur, carbonyl, chlorine, bromine, and iodine species (RXS, X = O, N, S, C, Cl, Br, and I) play important roles in normal physiological processes through governing cell signaling, immune balance, and tissue homeostasis.
A potential reason for the failure of tumor therapies is treatment resistance. Resistance to chemotherapy, radiotherapy, and immunotherapy continues to be a major obstacle in clinic, resulting in tumor recurrence and metastasis. The major mechanisms of therapy resistance are inhibitions of cell deaths, like apoptosis and necrosis, through drug inactivation and excretion, repair of DNA damage, tumor heterogeneity, or changes in tumor microenvironment, etc. Recent studies have shown that ferroptosis play a major role in therapies resistance by inducing phospholipid peroxidation and iron-dependent cell death. Some ferroptosis inducers in combination with clinical treatment techniques have been used to enhance the effect in tumor therapy. Notably, versatile ferroptosis nanoinducers exhibit an extensive range of functions in reversing therapy resistance, including directly triggering ferroptosis and feedback regulation. Herein, we provide a detailed description of the design, mechanism, and therapeutic application of ferroptosis-mediated synergistic tumor therapeutics. We also discuss the prospect and challenge of nanomedicine in tumor therapy resistance by regulating ferroptosis and combination therapy.
Glioblastoma (GBM) cells require large amounts of iron for tumor growth and progression, which makes these cells vulnerable to destruction via ferroptosis induction. Mitochondria are critical for iron metabolism and ferroptosis. Sirtuin-3 (SIRT3) is a deacetylase found in mitochondria that regulates mitochondrial quality and function. This study aimed to characterize SIRT3 expression and activity in GBM and investigate the potential therapeutic effects of targeting SIRT3 while also inducing ferroptosis in these cells. We first found that SIRT3 expression was higher in GBM tissues than in normal brain tissues and that SIRT3 protein expression was upregulated during RAS-selective lethal 3 (RSL3)-induced GBM cell ferroptosis. We then observed that inhibition of SIRT3 expression and activity in GBM cells sensitized GBM cells to RSL3-induced ferroptosis both in vitro and in vivo . Mechanistically, SIRT3 inhibition led to ferrous iron and ROS accumulation in the mitochondria, which triggered mitophagy. RNA-Sequencing analysis revealed that upon SIRT3 knockdown in GBM cells, the mitophagy pathway was upregulated and SLC7A11, a critical antagonist of ferroptosis via cellular import of cystine for glutathione (GSH) synthesis, was downregulated. Forced expression of SLC7A11 in GBM cells with SIRT3 knockdown restored cellular cystine uptake and consequently the cellular GSH level, thereby partially rescuing cell viability upon RSL3 treatment. Furthermore, in GBM cells, SIRT3 regulated SLC7A11 transcription through ATF4. Overall, our study results elucidated novel mechanisms underlying the ability of SIRT3 to protect GBM from ferroptosis and provided insight into a potential combinatorial approach of targeting SIRT3 and inducing ferroptosis for GBM treatment.
Ferroptosis, a newly form of regulated cell death (RCD), is characterized by iron dyshomeostasis and unrestricted lipid peroxidation. Emerging evidence depicts a pivotal role for ferroptosis in driving some pathological processes, especially in cancer. Triggering ferroptosis can suppress tumor growth and induce an anti-tumor immune response, denoting the therapeutic promises for targeting ferroptosis in the management of cancer. As an autophagic phenomenon, ferritinophagy is critical to induce ferroptosis by degradation of ferritin to release intracellular free iron. Recently, a great deal of effort has gone into designing and developing anti-cancer strategies based on targeting ferritinophagy to induce ferroptosis.
This review delineates the regulatory mechanism of ferritinophagy firstly and summarizes the role of ferritinophagy-induced ferroptosis in cancer. Moreover, the strategies targeting ferritinophagy to induce ferroptosis are highlighted to unveil the therapeutic value of ferritinophagy as a target to manage cancer. Finally, the future research directions on how to cope with the challenges in developing ferritinophagy promoters into clinical therapeutics are discussed.
Ferroptosis is a regulated form of necrotic cell death reliant on iron-catalyzed lipid peroxidation. Although the precise involvement of mitochondria in ferroptosis remains incompletely elucidated, recent research indicates that mitochondrial oxidative events wield a pivotal influence in this mechanism. This article centers on the most recent discoveries, spotlighting the significance of mitochondrial lipid peroxidation in the occurrence of ferroptosis. Modern investigative tools, such as mitochondria-specific dyes responsive to lipid peroxidation and antioxidants targeting mitochondria, have been employed to delve into this phenomenon. The authors’ recent empirical evidence demonstrates that mitochondrial lipid peroxidation, quantified using the innovative fluorescent ratiometric probe MitoCLox, takes place prior to the onset of ferroptotic cell death. The mitochondria-targeted antioxidant SkQ1 hinders mitochondrial lipid peroxidation and thwarts ferroptosis, all while leaving unaffected the buildup of reactive oxygen species within the cytoplasm, an antecedent to mitochondrial lipid peroxidation. Similarly, the redox agent methylene blue, impeding the genesis of reactive oxygen species in complex I of the electron transport chain, also imparts a comparable protective effect. These findings collectively imply that reactive oxygen species originating from complex I might hold particular significance in fomenting mitochondrial lipid peroxidation, a pivotal trigger of ferroptosis.
Oxidative stress is involved in the pathogenesis of Alzheimer’s disease (AD), which is linked to reactive oxygen species (ROS), lipid peroxidation, and neurotoxicity. Emerging evidence suggests a role of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a major source of antioxidant response elements in AD. The molecular mechanism of oxidative stress and ferroptosis in astrocytes in AD is not yet fully understood. Here, we aim to investigate the mechanism by which Nrf2 regulates the ferroptosis of astrocytes in AD. We found decreased expression of Nrf2 and upregulated expression of the ROS marker NADPH oxidase 4 (NOX4) in the frontal cortex from patients with AD and in the cortex of 3×Tg mice compared to control mice. We demonstrated that Nrf2 deficiency led to ferroptosis-dependent oxidative stress-induced ROS with downregulated heme oxygenase-1 and glutathione peroxidase 4 and upregulated cystine glutamate expression. Moreover, Nrf2 deficiency increased lipid peroxidation, DNA oxidation, and mitochondrial fragmentation in mouse astrocytes. In conclusion, these results suggest that Nrf2 deficiency promotes ferroptosis of astrocytes involving oxidative stress in AD.
Mastitis is a common and serious bacterial infection of the mammary gland. Saikosaponin A (SSA) is a triterpenoid saponin isolated from Bupleurum falcatum that has the ability to treat various diseases. However, little is known about the role of SSA in achieving mastitis remission. Here, we found that SSA alleviated Staphylococcus aureus (S. aureus)-induced mastitis by attenuating inflammation and maintaining blood-milk barrier integrity. Furthermore, S. aureus activated nuclear factor kappa B (NF-κB) pathway by upregulated p-p65 and p-IκB. S. aureus also induced ferroptosis in mammary gland in mice, mainly characterized by excessive iron accumulation, mitochondrial morphological changes and impaired antioxidant production. However, S. aureus-induced NF-κB activation and ferroptosis were prevented by SSA. Moreover, SAA could upregulate the expression of SIRT1, Nrf2, HO-1 and GPX4. And the inhibitory effects of SAA on inflammation and ferroptosis were reversed by SIRT1 inhibitor EX-527. In conclusion, SAA protected S. aureus-induced mastitis through suppressing inflammation and ferroptosis by activating SIRT1/Nrf2 pathway.
Prenylated flavonoids are promising nutraceuticals with diverse bioactivities. However, publications on the mechanism of action and structure–activity relationship of prenylated flavonoids are limited. In the present work, six novel prenylated flavonoids (C8–C13) with diversity structure were prepared. Their estrogen receptor (ER) modulator activity and neuroprotective activity were investigated by cell assays. C8, C9, and C10 with 8‐C‐prenyl and 7‐OH showed agonistic activities toward ERα and ERβ, along with high ERβ selectivity. However, C11 and C12 were ERα‐selective agonists. The position and substituent moiety of prenylation, C‐ring configuration, and flavonoid skeleton were important for the ER modulating activities. Hydrogen bonds between 3′‐OH and Leu339 in ERβ, and 5′‐OH and Glu305 in ERβ might respond for the higher agonistic activity of C8 and C10, respectively. C8, C9, C11, and C12 showed more potency than 17β‐estradiol on neuroprotection in glutamate‐treated PC‐12 cells. C8 and C12 could reverse reactive oxygen species overproduction and reduction of Δψm induced by glutamate through increase of the expression of ERS1 , SOD1 , SOD2 , CAT , and GPx4 and decrease of caspase‐3 expression, suggesting C8, and C9 might interact with ERα, promote antioxidant defense, mitigate oxidative stress, and improve mitochondrial function to exert the neuroprotection activities.
Liver iron overload is a common and serious organ injury in β -thalassemia patients. Ferroptosis has been shown to play a crucial role in the pathological injury in iron overloaded hepatocytes. In our study, we focused on the protective effects of baicalein, a natural, active flavone extracted from an herb used in traditional Chinese medicine against RSL3-induced ferroptosis in hepatocytes and high iron diet (HID) induced liver iron-overload in a murine β ⁶⁵⁴ -thalassemia model. In vitro , the effects of baicalein on RSL3-induced hepatocyte ferroptosis were examined by testing ferroptosis related genes, protein, and the GSH, MDA, iron ion level by RT-PCR, Western blot and the commercial kits respectively. The anti-iron overload injury effects of baicalein were assessed in a β ⁶⁵⁴ -thalassemia mouse model of high iron diet induced liver injury by the same method In vitro experiments. Here, we found that baicalein could reverse cell ferroptosis in hepatocytes treated with RSL3. Importantly, changes in the iron ion content, and MDA and GSH levels in β ⁶⁵⁴ -thalassemia mouse livers were significantly restored by baicalein. Mechanistically, baicalein may activated the NRF2 antioxidant pathway and increased the expression of GPX4 in vivo and In vitro . We concluded that baicalein is a potential therapeutic drug for the treatment of iron overload in β -thalassemia.
Endometriosis is strongly associated with infertility. Several mechanisms have been reported in an attempt to elucidate the pathophysiological effects that lead to reduced fertility in women with endometriosis. However, the mechanisms by which endometriosis affects fertility have not been fully elucidated. Ferroptosis is a novel form of nonapoptotic cell death that is characterized by iron-dependent lipid peroxidation membrane damage. In past reports, elevated iron levels in ectopic lesions, peritoneal fluid and follicular fluid have been reported in patients with endometriosis. The high-iron environment is closely associated with ferroptosis, which appears to exhibit a double-edged effect on endometriosis. Ferroptosis can cause damage to ovarian granulosa cells, oocytes, and embryos, leading to endometriosis-related infertility. This article summarizes the main pathways and regulatory mechanisms of ferroptosis and explores the possible mechanisms of the formation of an iron-overloaded environment in endometriotic ectopic lesions, peritoneal fluid and follicular fluid. Finally, we reviewed recent studies on the main and potential mechanisms of ferroptosis in endometriosis and endometriosis-related infertility.
Renal fibrosis, characterized by glomerulosclerosis and tubulointerstitial fibrosis, is a typical pathological alteration in the progression of chronic kidney disease (CKD) to end-stage renal disease (ESRD). However, the limited and expensive options for treating renal fibrosis place a heavy financial burden on patients and healthcare systems. Therefore, it is significant to find an effective treatment for renal fibrosis. Ferroptosis, a non-traditional form of cell death, has been found to play an important role in acute kidney injury (AKI), tumors, neurodegenerative diseases, and so on. Moreover, a growing body of research suggests that ferroptosis might be a potential target of renal fibrosis. Meanwhile, mitophagy is a type of selective autophagy that can selectively degrade damaged or dysfunctional mitochondria as a form of mitochondrial quality control, reducing the production of reactive oxygen species (ROS), the accumulation of which is the main cause of renal fibrosis. Additionally, as a receptor of mitophagy, NIX can release beclin1 to induce mitophagy, which can also bind to solute carrier family 7 member 11 (SLC7A11) to block the activity of cystine/glutamate antitransporter (system Xc-) and inhibit ferroptosis, thereby suggesting a link between mitophagy and ferroptosis. However, there have been only limited studies on the relationship among mitophagy, ferroptosis and renal fibrosis. In this paper, we review the mechanisms of mitophagy, and describe how ferroptosis and mitophagy are related to renal fibrosis in an effort to identify potential novel targets for the treatment of renal fibrosis.
NDUFA4 is a component of respiratory chain-oxidative phosphorylation pathway. NDUFA4 is highly expressed in tumor tissues, but little is known about the function of NDUFA4 in head and neck paraganglioma (HNPGL). We examined NDUFA4 expression in tissues from 10 HNPGL patients and 6 controls using qRT-PCR and Western blotting. NDUFA4 knockdown PGL-626 cells were established by using lentivirus infection and puromycin screening. Cell viability, ATP production, lipid reactive oxygen species, and mitochondrial membrane potential assays were performed to investigate the ferroptotic effects in NDUFA4 deficiency HNPGL cancer cells. Xenograft mouse model was created to detect the synergetic antitumor action between NDUFA4 deficiency and Metformin. NDUFA4 was upregulated in tumor tissues of HNPGL patients. NDUFA4 knockdown impaired the assembly of mitochondrial respiratory chain complexes and decreased the production of ATP and reduced cancer cell viability. Mechanistically, NDUFA4 knockdown increased cell ferroptosis, which further promoted Metformin-induced ferroptosis in PGL-626 cells. Therefore, NDUFA4 deficiency enhanced Metformin-mediated inhibition of the HNPGL progression in mice. In conclusion, NDUFA4 promotes the progression of HNPGL, and NDUFA4 knockdown enhances Metformin-mediated inhibition of the HNPGL progression in a mouse model.
Ferroptosis is a type of regulated necrosis driven by uncontrolled membrane lipid peroxidation. Mitochondria, which are membrane-bound organelles present in almost all eukaryotic cells and play a central role in energy metabolism and various types of cell death, have a complicated role in ferroptosis. On one hand, mitochondrial-derived iron metabolism and reactive oxygen species (ROS) production may promote ferroptosis. On the other hand, mitochondria also possess a dihydroorotate dehydrogenase (DHODH)-dependent antioxidant system that detoxifies lipid peroxides. This chapter summarizes several methods, such as western blotting, immunofluorescence, cell viability assays, mitochondrial fluorescent probes, adenosine 5'-triphosphate (ATP) assay kits, mitochondrial respiration, and mitophagy tests, that may enable researchers to gain a deeper understanding of the dual role of mitochondria in ferroptosis.
The cystine transporter solute carrier family 7 member 11 (SLC7A11) (also known as xCT) promotes glutathione synthesis and counters oxidative stress-induced cell death, including ferroptosis, by importing cystine. Also, SLC7A11 plays a crucial role in tumor development. However, recent studies have uncovered an unexpected role of SLC7A11 in promoting disulfidptosis, a novel form of regulated cell death induced by disulfide stress. In this review, we examine the opposing roles of SLC7A11 in regulating redox homeostasis and cell survival/death, summarize current knowledge on disulfidptosis, and explore its potential in disease treatment. A deeper understanding of disulfidptosis will offer new insights into fundamental cellular homeostasis and facilitate the development of innovative therapies for disease treatment.
Ferroptosis is a form of non-apoptotic programmed cell death, and its mechanisms mainly involve the accumulation of lipid peroxides, imbalance in the amino acid antioxidant system, and disordered iron metabolism. The primary organelle responsible for coordinating external challenges and internal cell demands is the endoplasmic reticulum, and the progression of inflammatory diseases can trigger endoplasmic reticulum stress. Evidence has suggested that ferroptosis may share pathways or interact with endoplasmic reticulum stress in many diseases and plays a role in cell survival. Ferroptosis and endoplasmic reticulum stress may occur after ischemic stroke. However, there are few reports on the interactions of ferroptosis and endoplasmic reticulum stress with ischemic stroke. This review summarized the recent research on the relationships between ferroptosis and endoplasmic reticulum stress and ischemic stroke, aiming to provide a reference for developing treatments for ischemic stroke.
Acute central nervous system injuries (ACNSI), encompassing traumatic brain injury (TBI), non-traumatic brain injury like stroke and encephalomeningitis, as well as spinal cord injuries, are linked to significant rates of disability and mortality globally. Nevertheless, effective and feasible treatment plans are still to be formulated. There are primary and secondary injuries occurred after ACNSI. Most ACNSIs exhibit comparable secondary injuries, which offer numerous potential therapeutic targets for enhancing clinical outcomes. Ferroptosis, a newly discovered form of cell death, is characterized as a lipid peroxidation process that is dependent on iron and oxidative conditions, which is also indispensable to mitochondria. Ferroptosis play a vital role in many neuropathological pathways, and ACNSIs may induce mitochondrial dysfunction, thereby indicating the essentiality of the mitochondrial connection to ferroptosis in ACNSIs. Nevertheless, there remains a lack of clarity regarding the involvement of mitochondria in the occurrence of ferroptosis as a secondary injuries of ACNSIs. In recent studies, anti-ferroptosis agents such as the ferroptosis inhibitor Ferrostain-1 and iron chelation therapy have shown potential in ameliorating the deleterious effects of ferroptosis in cases of traumatic ACNSI. The importance of this evidence is extremely significant in relation to the research and control of ACNSIs. Therefore, our review aims to provide researchers focusing on enhancing the therapeutic outcomes of ACNSIs with valuable insights by summarizing the physiopathological mechanisms of ACNSIs and exploring the correlation between ferroptosis, mitochondrial dysfunction, and ACNSIs.
The presence of hydrogen peroxide along with ferrous iron produces hydroxyl radicals that preferably oxidize polyunsaturated fatty acids (PUFA) to alkyl radicals (L•). The reaction of L• with an oxygen molecule produces lipid peroxyl radical (LOO•) that collectively trigger chain reactions, which results in the accumulation of lipid peroxidation products (LOOH). Oxygenase enzymes, such as lipoxygenase, also stimulate the peroxidation of PUFA. The production of phospholipid hydroperoxides (P-LOOH) can result in the destruction of the architecture of cell membranes and ultimate cell death. This iron-dependent regulated cell death is generally referred to as ferroptosis. Radical scavengers, which include tocopherol and nitric oxide (•NO), react with lipid radicals and terminate the chain reaction. When tocopherol reductively detoxifies lipid radicals, the resultant tocopherol radicals are recycled via reduction by coenzyme Q or ascorbate. CoQ radicals are reduced back by the anti-ferroptotic enzyme FSP1. •NO reacts with lipid radicals and produces less reactive nitroso compounds. The resulting P-LOOH is reductively detoxified by the action of glutathione peroxidase 4 (GPX4) or peroxiredoxin 6 (PRDX6). The hydrolytic removal of LOOH from P-LOOH by calcium-independent phospholipase A2 leads the preservation of membrane structure. While the expression of such protective genes or the presence of these anti-oxidant compounds serve to maintain a healthy condition, tumor cells employ them to make themselves resistant to anti-tumor treatments. Thus, these defense mechanisms against ferroptosis are protective in ordinary cells but are also potential targets for cancer treatment.
Cerebral ischemia, which is a leading cause of disability and mortality worldwide, sets off a chain of molecular and cellular pathologies that are associated with some central nervous system (CNS) disorders, mainly including ischemic stroke, Alzheimer's disease (AD), Parkinson's disease (PD), epilepsy and other CNS diseases. In recent times, despite significant advancements in the treatment of the pathological processes underlying various neurological illnesses, effective therapeutic approaches specifically targeted at minimizing the damage of such diseases remain absent. Remarkably, ischemia causes severe damage to cells in Ischemia-associated CNS Diseases. Cerebral ischemia initiates oxygen and glucose deprivation, which subsequently promotes mitochondrial dysfunction, including MPTP opening, mitophagy dysfunction, and excessive mitochondrial fission, triggering various forms of cell death, such as autophagy, apoptosis, as well as ferroptosis. Ferroptosis, a novel type of regulated cell death (RCD), is characterized by iron-dependent accumulation of lethal reactive oxygen species and lipid peroxidation. Mitochondrial dysfunction and ferroptosis both play critical roles in the pathogenic progression of Ischemia-associated CNS Diseases. In recent years, growing evidence has indicated that mitochondrial dysfunction interplays with ferroptosis to aggravate cerebral ischemia injury. However, the potential connections between mitochondrial dysfunction and ferroptosis in Cerebral Ischemia have not yet been clarified. Thus, we analyze the underlying mechanism between mitochondrial dysfunction and ferroptosis in Ischemia-associated CNS Diseases. We also discovered that GSH depletion and GPX4 inactivation cause lipoxygenase activation and calcium influx following cerebral ischemia injury, resulting in MPTP opening and mitochondrial dysfunction. Additionally, dysfunction in mitochondrial electron transport and an imbalanced fusion-to-fission ratio can lead to the accumulation of reactive oxygen species and iron overload, which further contribute to the occurrence of ferroptosis. This creates a vicious cycle that continuously worsens cerebral ischemia injury. In this study, our focus is on exploring the interplay between mitochondrial dysfunction and ferroptosis, which may offer new insights into potential therapeutic approaches for the treatment of Ischemia-associated CNS Diseases.
Over the last few decades, various forms of regulated cell death (RCD) have been discovered and were found to improve cancer treatment. Although there are several reviews on RCD induced by photodynamic therapy (PDT), a comprehensive summary covering metal-based photosensitizers (PSs) as RCD inducers has not yet been presented. In this review, we systematically summarize the works on metal-based PSs that induce different types of RCD, including ferroptosis, immunogenic cell death (ICD), and pyroptosis. The characteristics and mechanisms of each RCD are explained. At the end of each section, a summary of the reported commonalities between different metal-based PSs inducing the same RCD is emphasized, and future perspectives on metal-based PSs inducing novel forms of RCD are discussed at the end of the review. Considering the essential roles of metal-based PSs and RCD in cancer therapy, we hope that this review will provide the stage for future advances in metal-based PSs as RCD inducers.
Acquired drug resistance prevents cancer therapies from achieving stable and complete responses. Emerging evidence implicates a key role for non-mutational drug resistance mechanisms underlying the survival of residual cancer 'persister' cells. The persister cell pool constitutes a reservoir from which drug-resistant tumours may emerge. Targeting persister cells therefore presents a therapeutic opportunity to impede tumour relapse. We previously found that cancer cells in a high mesenchymal therapy-resistant cell state are dependent on the lipid hydroperoxidase GPX4 for survival. Here we show that a similar therapy-resistant cell state underlies the behaviour of persister cells derived from a wide range of cancers and drug treatments. Consequently, we demonstrate that persister cells acquire a dependency on GPX4. Loss of GPX4 function results in selective persister cell ferroptotic death in vitro and prevents tumour relapse in mice. These findings suggest that targeting of GPX4 may represent a therapeutic strategy to prevent acquired drug resistance. Citation Format: Hangauer MJ, Viswanathan VS, Ryan MJ, Bole D, Eaton JK, Matov A, Galeas J, Dhruv HD, Berens ME, Schreiber SL, McCormick F, McManus MT. Drug-tolerant persister cancer cells are vulnerable to GPX4 inhibition [doi: 10.1038/nature24297].
Plasticity of the cell state has been proposed to drive resistance to multiple classes of cancer therapies, thereby limiting their effectiveness. A high-mesenchymal cell state observed in human tumours and cancer cell lines has been associated with resistance to multiple treatment modalities across diverse cancer lineages, but the mechanistic underpinning for this state has remained incompletely understood. Here we molecularly characterize this therapy-resistant high-mesenchymal cell state in human cancer cell lines and organoids and show that it depends on a druggable lipid-peroxidase pathway that protects against ferroptosis, a non-apoptotic form of cell death induced by the build-up of toxic lipid peroxides. We show that this cell state is characterized by activity of enzymes that promote the synthesis of polyunsaturated lipids. These lipids are the substrates for lipid peroxidation by lipoxygenase enzymes. This lipid metabolism creates a dependency on pathways converging on the phospholipid glutathione peroxidase (GPX4), a selenocysteine-containing enzyme that dissipates lipid peroxides and thereby prevents the iron-mediated reactions of peroxides that induce ferroptotic cell death. Dependency on GPX4 was found to exist across diverse therapy-resistant states characterized by high expression of ZEB1, including epithelial-mesenchymal transition in epithelial-derived carcinomas, TGFβ-mediated therapy-resistance in melanoma, treatment-induced neuroendocrine transdifferentiation in prostate cancer, and sarcomas, which are fixed in a mesenchymal state owing to their cells of origin. We identify vulnerability to ferroptic cell death induced by inhibition of a lipid peroxidase pathway as a feature of therapy-resistant cancer cells across diverse mesenchymal cell-state contexts.
Although previous studies indicate that loss of p53-mediated cell cycle arrest, apoptosis, and senescence does not completely abrogate its tumor suppression function, it is unclear how the remaining activities of p53 are regulated. Here, we have identified an acetylation site at lysine K98 in mouse p53 (or K101 for human p53). Whereas the loss of K98 acetylation (p53K98R) alone has very modest effects on p53-mediated transactivation, simultaneous mutations at all four acetylation sites (p534KR: K98R+ 3KR[K117R+K161R+K162R]) completely abolish its ability to regulate metabolic targets, such as TIGAR and SLC7A11. Notably, in contrast to p533KR, p534KR is severely defective in suppressing tumor growth in mouse xenograft models. Moreover, p534KR is still capable of inducing the p53-Mdm2 feedback loop, but p53-dependent ferroptotic responses are markedly abrogated. Together, these data indicate the critical role of p53 acetylation in ferroptotic responses and its remaining tumor suppression activity.
Discovering compounds and mechanisms for inhibiting ferroptosis, a form of regulated, nonapoptotic cell death, has been of great interest in recent years. In this study, we demonstrate the ability of XJB-5-131, JP4-039, and other nitroxide-based lipid peroxidation mitigators to prevent ferroptotic cell death in HT-1080, BJeLR, and panc-1 cells. Several analogues of the reactive oxygen species (ROS) scavengers XJB-5-131 and JP4-039 were synthesized to probe structure−activity relationships and the influence of subcellular localization on the potency of these novel ferroptosis suppressors. Their biological activity correlated well over several orders of magnitude with their structure, relative lipophilicity, and respective enrichment in mitochondria, revealing a critical role of intramitochondrial lipid peroxidation in ferroptosis. These results also suggest that preventing mitochondrial lipid oxidation might offer a viable therapeutic opportunity in ischemia/reperfusion-induced tissue injury, acute kidney injury, and other pathologies that involve ferroptotic cell death pathways.
A nonsynonymous single-nucleotide polymorphism at codon 47 inTP53exists in African-descent populations (P47S, rs1800371; referred to here as S47). Here we report that, in human cell lines and a mouse model, the S47 variant exhibits a modest decrease in apoptosis in response to most genotoxic stresses compared with wild-type p53 but exhibits a significant defect in cell death induced by cisplatin. We show that, compared with wild-type p53, S47 has nearly indistinguishable transcriptional function but shows impaired ability to transactivate a subset of p53 target genes, including two involved in metabolism:Gls2(glutaminase 2) andSco2 We also show that human and mouse cells expressing the S47 variant are markedly resistant to cell death by agents that induce ferroptosis (iron-mediated nonapoptotic cell death). We show that mice expressing S47 in homozygous or heterozygous form are susceptible to spontaneous cancers of diverse histological types. Our data suggest that the S47 variant may contribute to increased cancer risk in individuals of African descent, and our findings highlight the need to assess the contribution of this variant to cancer risk in these populations. These data also confirm the potential relevance of metabolism and ferroptosis to tumor suppression by p53.
Glutathione peroxidase 4(Gpx4), an antioxidant defense enzyme in repairing oxidative damage to lipids, is a key inhibitor of ferroptosis, a non-apoptotic form of cell death involving lipid reactive oxygen species. Here we show that Gpx4 is essential for motor neuron health and survival in vivo. Conditional ablation of Gpx4 in neurons of adult mice resulted in rapid onset and progression of paralysis, and death. Pathological inspection revealed that the paralyzed mice had a dramatic degeneration of motor neurons in spinal cord, but had no overt neuron degeneration in cerebral cortex. Consistent with Gpx4's role as a ferroptosis inhibitor, spinal motor neuron degeneration induced by Gpx4 ablation exhibited features of ferroptosis including no caspase-3 activation, no TUNEL staining, activation of ERKs, and elevated spinal inflammation. Supplement of vitamin E, another inhibitor of ferroptosis, delayed the onset of paralysis and death induced by Gpx4 ablation. And lipid peroxidation and mitochondrial dysfunction appeared to be involved in ferroptosis of motor neurons induced by Gpx4 ablation. Taken together, the dramatic motor neuron degeneration and paralysis induced by Gpx4 ablation suggest that ferroptosis inhibition by Gpx4 is essential for motor neuron health and survival in vivo.
Programmed cell death (PCD) plays critical roles in development and tissue homeostasis of multicellular organisms, and malfunction of programmed cell death contributes to the pathogenesis of a variety of human diseases, including cancer [1]. While apoptosis had been the main focus of the PCD study for decades, recent advances demonstrate that there exist multiple other forms of cell death that are also genetically “programmed”, such as receptor-interacting protein kinase 3 (RIPK3)-dependent necroptosis and iron-dependent ferroptosis [1].
Ferroptosis has emerged as a new form of regulated necrosis that is implicated in various human diseases. However, the mechanisms of ferroptosis are not well defined. This study reports the discovery of multiple molecular components of ferroptosis and its intimate interplay with cellular metabolism and redox machinery. Nutrient starvation often leads to sporadic apoptosis. Strikingly, we found that upon deprivation of amino acids, a more rapid and potent necrosis process can be induced in a serum-dependent manner, which was subsequently determined to be ferroptosis. Two serum factors, the iron-carrier protein transferrin and amino acid glutamine, were identified as the inducers of ferroptosis. We further found that the cell surface transferrin receptor and the glutamine-fueled intracellular metabolic pathway, glutaminolysis, played crucial roles in the death process. Inhibition of glutaminolysis, the essential component of ferroptosis, can reduce heart injury triggered by ischemia/reperfusion, suggesting a potential therapeutic approach for treating related diseases.
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Significance
Cell death by regulated necrosis causes tremendous tissue damage in a wide variety of diseases, including myocardial infarction, stroke, sepsis, and ischemia–reperfusion injury upon solid organ transplantation. Here, we demonstrate that an iron-dependent form of regulated necrosis, referred to as ferroptosis, mediates regulated necrosis and synchronized death of functional units in diverse organs upon ischemia and other stimuli, thereby triggering a detrimental immune response. We developed a novel third-generation inhibitor of ferroptosis that is the first compound in this class that is stable in plasma and liver microsomes and that demonstrates high efficacy when supplied alone or in combination therapy.
Glutamine is an essential nutrient for cancer cell proliferation, especially in the context of citric acid cycle anaplerosis. In this manuscript we present results that collectively demonstrate that, of the three major mammalian glutaminases identified to date, the lesser studied splice variant of the gene gls, known as Glutaminase C (GAC), is important for tumor metabolism. We show that, although levels of both the kidney-type isoforms are elevated in tumor vs. normal tissues, GAC is distinctly mitochondrial. GAC is also most responsive to the activator inorganic phosphate, the content of which is supposedly higher in mitochondria subject to hypoxia. Analysis of X-ray crystal structures of GAC in different bound states suggests a mechanism that introduces the tetramerization-induced lifting of a "gating loop" as essential for the phosphate-dependent activation process. Surprisingly, phosphate binds inside the catalytic pocket rather than at the oligomerization interface. Phosphate also mediates substrate entry by competing with glutamate. A greater tendency to oligomerize differentiates GAC from its alternatively spliced isoform and the cycling of phosphate in and out of the active site distinguishes it from the liver-type isozyme, which is known to be less dependent on this ion.
The Krebs cycle enzyme fumarate hydratase (FH) is a human tumor suppressor whose inactivation is associated with the development of leiomyomata, renal cysts, and tumors. It has been proposed that activation of hypoxia inducible factor (HIF) by fumarate-mediated inhibition of HIF prolyl hydroxylases drives oncogenesis. Using a mouse model, we provide genetic evidence that Fh1-associated cyst formation is Hif independent, as is striking upregulation of antioxidant signaling pathways revealed by gene expression profiling. Mechanistic analysis revealed that fumarate modifies cysteine residues within the Kelch-like ECH-associated protein 1 (KEAP1), abrogating its ability to repress the Nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-mediated antioxidant response pathway, suggesting a role for Nrf2 dysregulation in FH-associated cysts and tumors.
Uterine leiomyomata (fibroids) are common and clinically important tumors, but little is known about their etiology and pathogenesis1, 2, 3. We previously mapped a gene that predisposes to multiple fibroids, cutaneous leiomyomata and renal cell carcinoma to chromosome 1q42.3−q43 (refs 4−6). Here we show, through a combination of mapping critical recombinants, identifying individuals with germline mutations and screening known and predicted transcripts, that this gene encodes fumarate hydratase, an enzyme of the tricarboxylic acid cycle. Leiomyomatosis-associated mutations are predicted to result in absent or truncated protein, or substitutions or deletions of highly conserved amino acids. Activity of fumarate hydratase is reduced in lymphoblastoid cells from individuals with leiomyomatosis. This enzyme acts as a tumor suppressor in familial leiomyomata, and its measured activity is very low or absent in tumors from individuals with leiomyomatosis. Mutations in FH also occur in the recessive condition fumarate hydratase deficiency7, 8, 9, 10, 11, and some parents of people with this condition are susceptible to leiomyomata. Thus, heterozygous and homozygous or compound heterozygous mutants have very different clinical phenotypes. Our results provide clues to the pathogenesis of fibroids and emphasize the importance of mutations of housekeeping and mitochondrial proteins in the pathogenesis of common types of tumor12, 13, 14.
Loss-of-function mutations in Park2, the gene coding for the ubiquitin ligase Parkin, are a significant cause of early onset Parkinson's disease. Although the role of Parkin in neuron maintenance is unknown, recent work has linked Parkin to the regulation of mitochondria. Its loss is associated with swollen mitochondria and muscle degeneration in Drosophila melanogaster, as well as mitochondrial dysfunction and increased susceptibility to mitochondrial toxins in other species. Here, we show that Parkin is selectively recruited to dysfunctional mitochondria with low membrane potential in mammalian cells. After recruitment, Parkin mediates the engulfment of mitochondria by autophagosomes and the selective elimination of impaired mitochondria. These results show that Parkin promotes autophagy of damaged mitochondria and implicate a failure to eliminate dysfunctional mitochondria in the pathogenesis of Parkinson's disease.
Ferroptosis is a form of non-apoptotic cell death characterized by the unchecked accumulation of lipid peroxides. Ferrostatin-1 and its analogs (ferrostatins) specifically prevent ferroptosis in multiple contexts, but many aspects of their molecular mechanism of action remain poorly described. Here, we employed stimulated Raman scattering (SRS) microscopy coupled with small vibrational tags to image the distribution of ferrostatins in cells, and found that they accumulate in lysosomes, mitochondria, and endoplasmic reticulum. We then evaluated the functional relevance of lysosomes and mitochondria to ferroptosis suppression by ferrostatins, and found that neither is required for effective ferroptosis suppression.
Selenoproteins are rare proteins among all kingdoms of life containing the 21st amino acid, selenocysteine. Selenocysteine resembles cysteine, differing only by the substitution of selenium for sulfur. Yet the actual advantage of selenolate- versus thiolate-based catalysis has remained enigmatic, as most of the known selenoproteins also exist as cysteine-containing homologs. Here, we demonstrate that selenolate-based catalysis of the essential mammalian selenoprotein GPX4 is unexpectedly dispensable for normal embryogenesis. Yet the survival of a specific type of interneurons emerges to exclusively depend on selenocysteine-containing GPX4, thereby preventing fatal epileptic seizures. Mechanistically, selenocysteine utilization by GPX4 confers exquisite resistance to irreversible overoxidation as cells expressing a cysteine variant are highly sensitive toward peroxide-induced ferroptosis. Remarkably, concomitant deletion of all selenoproteins in Gpx4cys/cys cells revealed that selenoproteins are dispensable for cell viability provided partial GPX4 activity is retained. Conclusively, 200 years after its discovery, a specific and indispensable role for selenium is provided.
Ferroptosis is a newly defined iron-dependent, non-apoptotic mode of cell death with necrotic morphology. Distinctive from other death mechanisms, ferroptosis requires cellular iron and lipid peroxides, and is dictated by specific cellular metabolic processes. Importantly, ferroptosis has been implicated in a plethora of human diseases. This paper reviews the recent advances and outstanding questions of the field by focusing on the role of cellular metabolism in ferroptosis. The relevance of ferroptosis to disease and therapy is also discussed.
Ferroptosis is a form of regulated cell death characterized by the iron-dependent accumulation of lipid hydroperoxides to lethal levels. Emerging evidence suggests that ferroptosis represents an ancient vulnerability caused by the incorporation of polyunsaturated fatty acids into cellular membranes, and cells have developed complex systems that exploit and defend against this vulnerability in different contexts. The sensitivity to ferroptosis is tightly linked to numerous biological processes, including amino acid, iron, and polyunsaturated fatty acid metabolism, and the biosynthesis of glutathione, phospholipids, NADPH, and coenzyme Q10. Ferroptosis has been implicated in the pathological cell death associated with degenerative diseases (i.e., Alzheimer’s, Huntington’s, and Parkinson’s diseases), carcinogenesis, stroke, intracerebral hemorrhage, traumatic brain injury, ischemia-reperfusion injury, and kidney degeneration in mammals and is also implicated in heat stress in plants. Ferroptosis may also have a tumor-suppressor function that could be harnessed for cancer therapy. This Primer reviews the mechanisms underlying ferroptosis, highlights connections to other areas of biology and medicine, and recommends tools and guidelines for studying this emerging form of regulated cell death.
The past decade has yielded tremendous insights into how cells die. This has come with our understanding that several distinct forms of cell death are encompassed under the umbrella term necrosis. Among these distinct forms of regulated necrotic cell death, ferroptosis has attracted considerable attention owing to its putative involvement in diverse pathophysiological processes. A key feature of the ferroptosis process is the requirement of phospholipid peroxidation, a process that has been linked with several human pathologies. Now with the establishment of a connection between lipid peroxidation and a distinctive cell death pathway, the search for new small molecules able to suppress lipid peroxidation has gained momentum and may yield novel cytoprotective strategies. We review here advances in our understanding of the ferroptotic process and summarize the development of lipid peroxidation inhibitors with the ultimate goal of suppressing ferroptosis-relevant cell death and related pathologies.
Ferroptosis is a form of regulated necrotic cell death controlled by glutathione peroxidase 4 (GPX4). At present, mechanisms that could predict sensitivity and/or resistance and that may be exploited to modulate ferroptosis are needed. We applied two independent approaches-a genome-wide CRISPR-based genetic screen and microarray analysis of ferroptosis-resistant cell lines-to uncover acyl-CoA synthetase long-chain family member 4 (ACSL4) as an essential component for ferroptosis execution. Specifically, Gpx4-Acsl4 double-knockout cells showed marked resistance to ferroptosis. Mechanistically, ACSL4 enriched cellular membranes with long polyunsaturated ω6 fatty acids. Moreover, ACSL4 was preferentially expressed in a panel of basal-like breast cancer cell lines and predicted their sensitivity to ferroptosis. Pharmacological targeting of ACSL4 with thiazolidinediones, a class of antidiabetic compound, ameliorated tissue demise in a mouse model of ferroptosis, suggesting that ACSL4 inhibition is a viable therapeutic approach to preventing ferroptosis-related diseases.
Ferroptosis is an iron-dependent form of regulated necrosis. It is implicated in various human diseases, including ischemic organ damage and cancer. Here, we report the crucial role of autophagy, particularly autophagic degradation of cellular iron storage proteins (a process known as ferritinophagy), in ferroptosis. Using RNAi screening coupled with subsequent genetic analysis, we identified multiple autophagy-related genes as positive regulators of ferroptosis. Ferroptosis induction led to autophagy activation and consequent degradation of ferritin and ferritinophagy cargo receptor NCOA4. Consistently, inhibition of ferritinophagy by blockage of autophagy or knockdown of NCOA4 abrogated the accumulation of ferroptosis-associated cellular labile iron and reactive oxygen species, as well as eventual ferroptotic cell death. Therefore, ferroptosis is an autophagic cell death process, and NCOA4-mediated ferritinophagy supports ferroptosis by controlling cellular iron homeostasis.
Macroautophagy/autophagy is an evolutionarily-conserved degradation pathway that maintains homeostasis. Ferroptosis, a novel form of regulated cell death, is characterized by a production of reactive oxygen species from accumulated iron and lipid peroxidation. However, the relationship between autophagy and ferroptosis at the genetic level remains unclear. Here, we demonstrated that autophagy contributes to ferroptosis by degradation of ferritin in fibroblasts and cancer cells. Knockout or knockdown of Atg5 (autophagy related 5) and Atg7 limited erastin-induced ferroptosis with decreased intracellular ferrous iron levels, and lipid peroxidation. Remarkably, NCOA4 (nuclear receptor coactivator 4) was a selective cargo receptor for the selective autophagic turnover of ferritin (namely ferritinophagy) in ferroptosis. Consistently, genetic inhibition of NCOA4 inhibited ferritin degradation and suppressed ferroptosis. In contrast, overexpression of NCOA4 increased ferritin degradation and promoted ferroptosis. These findings provide novel insight into the interplay between autophagy and regulated cell death.
Ferroptosis is a regulated form of cell death driven by loss of activity of the lipid repair enzyme glutathione peroxidase 4 (GPX4) and subsequent accumulation of lipid-based reactive oxygen species (ROS), particularly lipid hydroperoxides. This form of iron-dependent cell death is genetically, biochemically, and morphologically distinct from other cell death modalities, including apoptosis, unregulated necrosis, and necroptosis. Ferroptosis is regulated by specific pathways and is involved in diverse biological contexts. Here we summarize the discovery of ferroptosis, the mechanism of ferroptosis regulation, and its increasingly appreciated relevance to both normal and pathological physiology.
Cell death and differentiation is a monthly research journal focused on the exciting field of programmed cell death and apoptosis. It provides a single accessible source of information for both scientists and clinicians, keeping them up-to-date with advances in the field. It encompasses programmed cell death, cell death induced by toxic agents, differentiation and the interrelation of these with cell proliferation.
Although p53-mediated cell-cycle arrest, senescence and apoptosis serve as critical barriers to cancer development, emerging evidence suggests that the metabolic activities of p53 are also important. Here we show that p53 inhibits cystine uptake and sensitizes cells to ferroptosis, a non-apoptotic form of cell death, by repressing expression of SLC7A11, a key component of the cystine/glutamate antiporter. Notably, p53(3KR), an acetylation-defective mutant that fails to induce cell-cycle arrest, senescence and apoptosis, fully retains the ability to regulate SLC7A11 expression and induce ferroptosis upon reactive oxygen species (ROS)-induced stress. Analysis of mutant mice shows that these non-canonical p53 activities contribute to embryonic development and the lethality associated with loss of Mdm2. Moreover, SLC7A11 is highly expressed in human tumours, and its overexpression inhibits ROS-induced ferroptosis and abrogates p53(3KR)-mediated tumour growth suppression in xenograft models. Our findings uncover a new mode of tumour suppression based on p53 regulation of cystine metabolism, ROS responses and ferroptosis.
The role of cellular metabolism in regulating cell proliferation and differentiation remains poorly understood. For example, most mammalian cells cannot proliferate without exogenous glutamine supplementation even though glutamine is a non-essential amino acid. Here we show that mouse embryonic stem (ES) cells grown under conditions that maintain naive pluripotency are capable of proliferation in the absence of exogenous glutamine. Despite this, ES cells consume high levels of exogenous glutamine when the metabolite is available. In comparison to more differentiated cells, naive ES cells utilize both glucose and glutamine catabolism to maintain a high level of intracellular α-ketoglutarate (αKG). Consequently, naive ES cells exhibit an elevated αKG to succinate ratio that promotes histone/DNA demethylation and maintains pluripotency. Direct manipulation of the intracellular αKG/succinate ratio is sufficient to regulate multiple chromatin modifications, including H3K27me3 and ten-eleven translocation (Tet)-dependent DNA demethylation, which contribute to the regulation of pluripotency-associated gene expression. In vitro, supplementation with cell-permeable αKG directly supports ES-cell self-renewal while cell-permeable succinate promotes differentiation. This work reveals that intracellular αKG/succinate levels can contribute to the maintenance of cellular identity and have a mechanistic role in the transcriptional and epigenetic state of stem cells.
Ferroptosis is a non-apoptotic form of cell death induced by small molecules in specific tumour types, and in engineered cells overexpressing oncogenic RAS. Yet, its relevance in non-transformed cells and tissues is unexplored and remains enigmatic. Here, we provide direct genetic evidence that the knockout of glutathione peroxidase 4 (Gpx4) causes cell death in a pathologically relevant form of ferroptosis. Using inducible Gpx4(-/-) mice, we elucidate an essential role for the glutathione/Gpx4 axis in preventing lipid-oxidation-induced acute renal failure and associated death. We furthermore systematically evaluated a library of small molecules for possible ferroptosis inhibitors, leading to the discovery of a potent spiroquinoxalinamine derivative called Liproxstatin-1, which is able to suppress ferroptosis in cells, in Gpx4(-/-) mice, and in a pre-clinical model of ischaemia/reperfusion-induced hepatic damage. In sum, we demonstrate that ferroptosis is a pervasive and dynamic form of cell death, which, when impeded, promises substantial cytoprotection.
Ferrostatin-1 (Fer-1) inhibits ferroptosis,
a form of regulated,
oxidative, nonapoptotic cell death. We found that Fer-1 inhibited
cell death in cellular models of Huntington’s disease (HD),
periventricular leukomalacia (PVL), and kidney dysfunction; Fer-1
inhibited lipid peroxidation, but not mitochondrial reactive oxygen
species formation or lysosomal membrane permeability. We developed
a mechanistic model to explain the activity of Fer-1, which guided
the development of ferrostatins with improved properties. These studies
suggest numerous therapeutic uses for ferrostatins, and that lipid
peroxidation mediates diverse disease phenotypes.
Ferroptosis is a form of nonapoptotic cell death for which key regulators remain unknown. We sought a common mediator for the lethality of 12 ferroptosis-inducing small molecules. We used targeted metabolomic profiling to discover that depletion of glutathione causes inactivation of glutathione peroxidases (GPXs) in response to one class of compounds and a chemoproteomics strategy to discover that GPX4 is directly inhibited by a second class of compounds. GPX4 overexpression and knockdown modulated the lethality of 12 ferroptosis inducers, but not of 11 compounds with other lethal mechanisms. In addition, two representative ferroptosis inducers prevented tumor growth in xenograft mouse tumor models. Sensitivity profiling in 177 cancer cell lines revealed that diffuse large B cell lymphomas and renal cell carcinomas are particularly susceptible to GPX4-regulated ferroptosis. Thus, GPX4 is an essential regulator of ferroptotic cancer 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.
Inactivation of the TCA cycle enzyme, fumarate hydratase (FH), drives a metabolic shift to aerobic glycolysis in FH-deficient kidney tumors and cell lines from patients with hereditary leiomyomatosis renal cell cancer (HLRCC), resulting in decreased levels of AMP-activated kinase (AMPK) and p53 tumor suppressor, and activation of the anabolic factors, acetyl-CoA carboxylase and ribosomal protein S6. Reduced AMPK levels lead to diminished expression of the DMT1 iron transporter, and the resulting cytosolic iron deficiency activates the iron regulatory proteins, IRP1 and IRP2, and increases expression of the hypoxia inducible factor HIF-1α, but not HIF-2α. Silencing of HIF-1α or activation of AMPK diminishes invasive activities, indicating that alterations of HIF-1α and AMPK contribute to the oncogenic growth of FH-deficient cells.
Autophagy not only recycles intracellular components to compensate for nutrient deprivation but also selectively eliminates organelles to regulate their number and maintain quality control. Mitophagy, the specific autophagic elimination of mitochondria, has been identified in yeast, mediated by autophagy-related 32 (Atg32), and in mammals during red blood cell differentiation, mediated by NIP3-like protein X (NIX; also known as BNIP3L). Moreover, mitophagy is regulated in many metazoan cell types by parkin and PTEN-induced putative kinase protein 1 (PINK1), and mutations in the genes encoding these proteins have been linked to forms of Parkinson's disease.
Two human cell lines (termed rho 0), which had been completely depleted of mitochondrial DNA (mtDNA) by long-term exposure
to ethidium bromide, were found to be dependent on uridine and pyruvate for growth because of the absence of a functional
respiratory chain. Loss of either of these two metabolic requirements was used as a selectable marker for the repopulation
of rho 0 cells with exogenous mitochondria by complementation. Transformants obtained with various mitochondrial donors exhibited
a respiratory phenotype that was in most cases distinct from that of the rho 0 parent or the donor, indicating that the genotypes
of the mitochondrial and nuclear genomes as well as their specific interactions play a role in the respiratory competence
of a cell.
This chapter discusses isolation of human cell lines lacking mitochondrial DNA. An understanding of the molecular genetic mechanisms by which these mutations act can provide insights into the etiology, pathogenesis, and ultimately the treatment of these diseases, and may enhance the knowledge of mitochondrial biogenesis. For investigating nucleomitochondrial interactions and the molecular pathogenetic mechanisms of mtDNA mutations, it is useful to manipulate the mtDNA complement of a cell, move mitochondria from one cellular environment to another, or introduce new genes into mitochondria. As an initial step towards these goals, there is an isolation human cell lines that completely lack mtDNA (ρ0 cell lines). The chapter describes the theory and the methods utilized to isolate such cell lines.
REVIEW
A variety of key events in apoptosis focus on mitochondria, including the release of caspase activators (such as cytochrome
c), changes in electron transport, loss of mitochondrial transmembrane potential, altered cellular oxidation-reduction, and
participation of pro- and antiapoptotic Bcl-2 family proteins. The different signals that converge on mitochondria to trigger
or inhibit these events and their downstream effects delineate several major pathways in physiological cell death.
Apoptosis, or programmed cell death, is involved in development, elimination of damaged cells, and maintenance of cell homeostasis. Deregulation of apoptosis may cause diseases, such as cancers, immune diseases, and neurodegenerative disorders. Apoptosis is executed by a subfamily of cysteine proteases known as caspases. In mammalian cells, a major caspase activation pathway is the cytochrome c-initiated pathway. In this pathway, a variety of apoptotic stimuli cause cytochrome c release from mitochondria, which in turn induces a series of biochemical reactions that result in caspase activation and subsequent cell death. In this review, we focus on the recent progress in understanding the biochemical mechanisms and regulation of the pathway, the roles of the pathway in physiology and disease, and their potential therapeutic values.
Several mitochondrial proteins are tumor suppressors. These include succinate dehydrogenase (SDH) and fumarate hydratase, both enzymes of the tricarboxylic acid (TCA) cycle. However, to date, the mechanisms by which defects in the TCA cycle contribute to tumor formation have not been elucidated. Here we describe a mitochondrion-to-cytosol signaling pathway that links mitochondrial dysfunction to oncogenic events: succinate, which accumulates as a result of SDH inhibition, inhibits HIF-alpha prolyl hydroxylases in the cytosol, leading to stabilization and activation of HIF-1alpha. These results suggest a mechanistic link between SDH mutations and HIF-1alpha induction, providing an explanation for the highly vascular tumors that develop in the absence of VHL mutations.