Resolving the Role of Lipoxygenases in the Initiation and Execution of Ferroptosis

CircCDK14 Promotes Tumor Progression and Resists Ferroptosis in Glioma by Regulating PDGFRA

CircRNAs have garnered significant interest in recent years due to their regulation in human tumorigenesis, yet, the function of most glioma-related circRNAs remains unclear. In this study, using RNA-Seq, we screened differentially regulated circRNAs in glioma, in comparison to non-tumor brain tissue. Loss- and gain-of-function strategies were used to assess the effect of circCDK14 on tumor progression both in vitro and in vivo. Luciferase reporter, RNA pull-down and fluorescence in situ hybridization assays were carried out to validate interactions between circCDK14 and miR-3938 as well as miR-3938 and PDGFRA. Transmission electron microscopic observation of mitochondria, iron and reactive oxygen species assays were employed for the detection of circCDK14 effect on glioma cells' sensitivity to erastin-induced ferroptosis (Fp). Our findings indicated that circCDK14 was overexpressed in glioma tissues and cell lines, and elevated levels of circCDK14 induced poor prognosis of glioma patients. CircCDK14 promotes the migration, invasion and proliferation of glioma cells in vitro as well as tumorigenesis in vivo. An evaluation of the underlying mechanism revealed that circCDK14 sponged miR-3938 to upregulate oncogenic gene PDGFRA expression. Moreover, we also found that circCDK14 reduced glioma cells' sensitivity to Fp by regulating PDGFRA expression. In conclusion, circCDK14 induces tumor in glioma and increases malignant tumor behavior via the miR-3938/PDGFRA axis. Hence, the miR-3938/PDGFRA axis may be an excellent candidate of anti-glioma therapy.

Double-edge sword roles of iron in driving energy production versus instigating ferroptosis

Iron is vital for many physiological functions, including energy production, and dysregulated iron homeostasis underlies a number of pathologies. Ferroptosis is a recently recognized form of regulated cell death that is characterized by iron dependency and lipid peroxidation, and this process has been reported to be involved in multiple diseases. The mechanisms underlying ferroptosis are complex, and involve both well-described pathways (including the iron-induced Fenton reaction, impaired antioxidant capacity, and mitochondrial dysfunction) and novel interactions linked to cellular energy production. In this review, we examine the contribution of iron to diverse metabolic activities and their relationship to ferroptosis. There is an emphasis on the role of iron in driving energy production and its link to ferroptosis under both physiological and pathological conditions. In conclusion, excess reactive oxygen species production driven by disordered iron metabolism, which induces Fenton reaction and/or impairs mitochondrial function and energy metabolism, is a key inducer of ferroptosis.

Ferroptosis and Its Potential Role in Lung Cancer: Updated Evidence from Pathogenesis to Therapy

Lung cancer is characterized by high morbidity and mortality rates, and its occurrence is associated with many types of cell death. As a new form of regulated cell death, ferroptosis is an iron- dependent pattern of cell death and characterized by lethal accumulation of lipid-based reactive oxygen species (ROS), which is different from apoptosis, necrosis and autophagy at both the morphological and biochemical levels. It plays an important role in the development of lung cancer and induction of ferroptosis in lung cancer cells has become a new strategy for anti- lung cancer treatment. However, a few reviews summarized ferroptosis and its role in lung cancer has not been elucidated, and the precise mechanism of ferroptosis modeling lung cancer has not yet been revealed till date. Herein, we review the latest literature on the process of ferroptosis regarding lung cancer, including basic molecular or biology mechanistic studies both in vivo and in vitro, as well as human studies with a more translational or clinical approach. This review provides a practical, concise and updated outline on the mechanisms and therapeutic strategies in lung cancer with ferroptosis alterations. Looking ahead, further studies are required to uncover the possible modulatory relationship between ferroptosis and lung cancer.

The Potential of Ferroptosis-Targeting Therapies for Alzheimer's Disease: From Mechanism to Transcriptomic Analysis

Alzheimer’s disease (AD), the most common form of dementia, currently affects 40–50 million people worldwide. Despite the extensive research into amyloid β (Aβ) deposition and tau protein hyperphosphorylation (p-tau), an effective treatment to stop or slow down the progression of neurodegeneration is missing. Emerging evidence suggests that ferroptosis, an iron-dependent and lipid peroxidation-driven type of programmed cell death, contributes to neurodegeneration in AD. Therefore, how to intervene against ferroptosis in the context of AD has become one of the questions addressed by studies aiming to develop novel therapeutic strategies. However, the underlying molecular mechanism of ferroptosis in AD, when ferroptosis occurs in the disease course, and which ferroptosis-related genes are differentially expressed in AD remains to be established. In this review, we summarize the current knowledge on cell mechanisms involved in ferroptosis, we discuss how these processes relate to AD, and we analyze which ferroptosis-related genes are differentially expressed in AD brain dependant on cell type, disease progression and gender. In addition, we point out the existing targets for therapeutic options to prevent ferroptosis in AD. Future studies should focus on developing new tools able to demonstrate where and when cells undergo ferroptosis in AD brain and build more translatable AD models for identifying anti-ferroptotic agents able to slow down neurodegeneration.

15-Lipoxygenase worsens renal fibrosis, inflammation, and metabolism in a murine model of ureteral obstruction

15-Lipoxygenase (15-LO) is a nonheme iron-containing dioxygenase that has both pro- and anti-inflammatory roles in many tissues and disease states. 15-LO is thought to influence macrophage phenotype, and silencing 15-LO reduces fibrosis after acute inflammatory triggers. The goal of the present study was to determine whether altering 15-LO expression influences inflammation and fibrogenesis in a murine model of unilateral ureteral obstruction (UUO). C57BL/6J mice, 15-LO knockout (Alox15-/-) mice, and 15-LO transgenic overexpressing (15LOTG) mice were subjected UUO, and kidneys were analyzed at 3, 10, and 14 days postinjury. Histology for fibrosis, inflammation, cytokine quantification, flow cytometry, and metabolomics were performed on injured tissues and controls. PD146176, a specific 15-LO inhibitor, was used to complement experiments involving knockout animals. Compared with wild-type animals undergoing UUO, Alox15-/- mouse kidneys had less proinflammatory, profibrotic message along with less fibrosis and macrophage infiltration. PD146176 inhibited 15-LO and resulted in reduced fibrosis and macrophage infiltration similar to Alox15-/- mice. Flow cytometry revealed that Alox15-/- UUO-injured kidneys had a dynamic change in macrophage phenotype, with an early blunting of CD11bHiLy6CHi "M1" macrophages and an increase in anti-inflammatory CD11bHiLy6CInt "M2c" macrophages and reduced expression of the fractalkine receptor chemokine (C-X3-C motif) receptor 1. Many of these findings were reversed when UUO was performed on 15LOTG mice. Metabolomics analysis revealed that wild-type kidneys developed a glycolytic shift postinjury, while Alox15-/- kidneys exhibited increased oxidative phosphorylation. In conclusion, 15-LO manipulation by genetic or pharmacological means induces dynamic changes in the inflammatory microenvironment in the UUO model and appears to be critical in the progression of UUO-induced fibrosis.NEW & NOTEWORTHY 15-Lipoxygenase (15-LO) has both pro- and anti-inflammatory functions in leukocytes, and its role in kidney injury and repair is unexplored. Our study showed that 15-LO worsens inflammation and fibrosis in a rodent model of chronic kidney disease using genetic and pharmacological manipulation. Silencing 15-LO promotes an increase in M2c-like wound-healing macrophages in the kidney and alters kidney metabolism globally, protecting against anaerobic glycolysis after injury.

A prognostic model for cervical cancer based on ferroptosis-related genes

BACKGROUND

Ferroptosis is widely involved in the occurrence and development of various cancers, but a specific mechanism involving ferroptosis in cervical cancer is still unclear.

METHODS

Based on the expressions of ferroptosis-related genes, a prognostic model was constructed using lasso regression, and the overall predictive performance of this model was verified. An in-depth analysis of the prognostic model was then conducted.

RESULTS

The prognostic model showed good predictive performance in both the validation and test sets. Mechanism analysis indicated that differences in the tumor microenvironment were the basis of the predictive ability of the model. Notably, CA9 mRNA was significantly overexpressed in cervical carcinoma, tissues but not in normal cervix tissues. A pair of ceRNAs (CA9/ULBP2) could be involved in the carcinogenesis and development of cervical cancer, and the potential target might be hsa-miR-34a. In addition, predicted miRNAs and drugs for these DEGs were identified.

CONCLUSIONS

We constructed a prognostic model with good predictive performance, based on the expression of ferroptosis-related genes. Further research found that the ceRNA pairs of ULBP2/CA9 could regulate cervical cancer through hsa-miR-34a. These results identified the mechanism of ferroptosis in cervical cancer, and might provide novel therapeutics for cervical cancer patients.

Ferroptosis: a promising target for cancer immunotherapy

Ferroptosis is a recently recognized type of programmed cell death and emerges to play an important role in cancer biology and therapies. This unique form of cell death, characterized by iron-dependent lipid peroxidation, is exquisitely regulated by the cellular metabolic networks such as lipid, iron and amino acid metabolism. The sensitivity to ferroptosis varies among different tumors. Recent evidence reveals that triple-negative breast cancer (TNBC), a highly aggressive disease with limited effective targeted therapies is particularly vulnerable to ferroptosis inducers, suggesting this new form of non-apoptotic cell death as an attractive target for the treatment of the "difficult-to-treat" tumor. Intriguingly, ferroptosis has recently been implicated to be involved in T cell-mediated anti-tumor immunity and affect the efficacy of cancer immunotherapy. Better understanding of this ferroptotic cell death will shed light on the discovery of novel combination therapeutic strategies for cancer treatment. Herein, we provide an overview of the key hallmarks of ferroptosis, use TNBC as a model to characterize the regulation of ferroptosis in cancer, and highlight ferroptosis-modulating combination therapeutic strategies in the context of cancer immunotherapy.

Identification of a Novel Ferroptosis-Related Gene Prediction Model for Clinical Prognosis and Immunotherapy of Colorectal Cancer

Background

Colorectal cancer (CRC) is the third most common malignancies worldwide. Ferroptosis is a programmed, iron-dependent cell death observed in cancer cells. However, the prognostic potential and immunotherapy biomarker potential of ferroptosis-related genes (FRGs) in CRC patients remains to be clarified.

Methods

At first, we comprehensively analysed the different expression and prognosis of related FRGs in CRC patients based on TCGA cohort. The relationship between functional enrichment of these genes and immune microenvironment in CRC was investigated using the TCGA database. Prognostic model was constructed to determine the association between FRGs and the prognosis of CRC. Relative verification was done based on the GEO database. Meanwhile, the ceRNA network of FRGs in the model was also performed to explore the regulatory mechanisms.

Results

Eight differentially expressed FRGs were associated with the prognosis of CRC patients. Patients from the TCGA database were classified into the A, B, and C FRG clusters with different features. And FRG scores were constructed to quantify the FRG pattern of individual patients with colorectal cancer. The CRC patients with higher FRG score showed worse survival outcomes, higher immune dysfunction, and lower response to immunotherapy. The prognostic model showed a high accuracy for predicting the OS of CRC. Finally, a ceRNA network was analysed to show the concrete regulation mechanisms of critical FRGs in CRC.

Conclusions

The FRG risk score prognostic model based on 8 FRGs exhibit superior predictive performance, providing a novel prognostic model with a high accuracy for CRC patients. Moreover, FRG score can be the potential biomarker of the response of immunotherapy for CRC.

Vitamin E research: Past, now and future

The early history of vitamin E from its discovery by Herbert M. Evans and Katharine J. S. Bishop in 1922 up to its chemical synthesis by Paul Karrer and coworkers in 1938 and the development of the concept that vitamin E acts as an antioxidant in vivo are recalled. Some more recent results shedding doubt on this hypothesis are reviewed. They comprise influence of vitamin E on enzyme activities, signaling cascades, gene expression and bio-membrane structure. The overall conclusion is that our knowledge of the vitamin's mechanism of action still remains fragmentary. The metabolism of tocopherols and tocotrienols is presented and discussed in respect to bioactivity of the metabolites, interference with drug metabolism and the future design of clinical trials. Some strategies are recommended how to reach the final goal: the identification of the primary vitamin E target(s) and the analysis of the downstream events up to the physiological phenomena.

p53: A Double-Edged Sword in Tumor Ferroptosis

Ferroptosis is a type of lipid peroxidation-induced cell death that can be regulated in various ways, from changing the activity of antioxidant enzymes to the levels of transcription factors. The p53 tumor suppressor gene is the "guardian of the genome" and is involved in controlling cell survival and division under various pressures. In addition to its effects on apoptosis, autophagy, and cell cycle, p53, through the way of transcription dependent or independent two-way, also regulates the biological processes of tumor cell sensitivity to ferroptosis, including the metabolism of amino acids, nicotinamide adenine dinucleotide phosphate, and lipid peroxidation, as well as the biosynthesis of glutathione, phospholipids, NADPH and coenzyme Q10.As reviewed here, we summarized the metabolic network of p53 and its signaling pathway in regulating ferroptosis and elucidated possible factors and potential clinical application of p53 regulating ferroptosis. This review will provide a basis for further understanding the role of p53 in tumor ferroptosis and new strategies for cancer therapeutic avenues.

Radical-Trapping Antioxidant Activity of Copper and Nickel Bis(Thiosemicarbazone) Complexes Underlies Their Potency as Inhibitors of Ferroptotic Cell Death

Herein we demonstrate that copper(II)-diacetyl-bis(N⁴-methylthiosemicarbazone)(CuATSM), clinical candidate for the treatment of ALS and Parkinson's disease, is a highly potent radical-trapping antioxidant (RTA) and inhibitor of (phospho)lipid peroxidation. In THF autoxidations, CuATSM reacts with THF-derived peroxyl radicals with k_inh = 2.2 × 10⁶ M^-1 s^-1─roughly 10-fold greater than α-tocopherol (α-TOH), Nature's best RTA. Mechanistic studies reveal no H/D kinetic isotope effects and a lack of rate-suppressing effects from H-bonding interactions, implying a different mechanism from α-TOH and other canonical RTAs, which react by H-atom transfer (HAT). Similar reactivity was observed for the corresponding Ni²⁺ complex and complexes of both Cu²⁺ and Ni²⁺ with other bis(thiosemicarbazone) ligands. Computations corroborate the experimental finding that rate-limiting HAT cannot account for the observed RTA activity and instead suggest that the reversible addition of a peroxyl radical to the bis(thiosemicarbazone) ligand is responsible. Subsequent HAT or combination with another peroxyl radical drives the reaction forward, such that a maximum of four radicals are trapped per molecule of CuATSM. This sequence is supported by spectroscopic and mass spectrometric experiments on isolated intermediates. Importantly, the RTA activity of CuATSM (and its analogues) translates from organic solution to phospholipid bilayers, thereby accounting for its (their) ability to inhibit ferroptosis. Experiments in mouse embryonic fibroblasts and hippocampal cells reveal that lipophilicity as well as inherent RTA activity contribute to the potency of ferroptosis rescue, and that one compound (CuATSP) is almost 20-fold more potent than CuATSM and among the most potent ferroptosis inhibitors reported to date.

The molecular mechanisms of ferroptosis and its role in cardiovascular disease

Ferroptosis is a programmed iron-dependent cell death characterized by accumulation of lipid peroxides (LOOH) and redox disequilibrium. Ferroptosis shows unique characteristics in biology, chemistry, and gene levels, compared to other cell death forms. The metabolic disorder of intracellular LOOH catalyzed by iron causes the inactivity of GPX4, disrupts the redox balance, and triggers cell death. Metabolism of amino acid, iron, and lipid, including associated pathways, is considered as a specific hallmark of ferroptosis. Epidemiological studies and animal experiments have shown that ferroptosis plays an important character in the pathophysiology of cardiovascular disease such as atherosclerosis, myocardial infarction (MI), ischemia/reperfusion (I/R), heart failure (HF), cardiac hypertrophy, cardiomyopathy, and abdominal aortic aneurysm (AAA). This review systematically summarized the latest research progress on the mechanisms of ferroptosis. Then we report the contribution of ferroptosis in cardiovascular diseases. Finally, we discuss and analyze the therapeutic approaches targeting for ferroptosis associated with cardiovascular diseases.

The calcium-iron connection in ferroptosis-mediated neuronal death

Iron, through its participation in oxidation/reduction processes, is essential for the physiological function of biological systems. In the brain, iron is involved in the development of normal cognitive functions, and its lack during development causes irreversible cognitive damage. Yet, deregulation of iron homeostasis provokes neuronal damage and death. Ferroptosis, a newly described iron-dependent cell death pathway, differs at the morphological, biochemical, and genetic levels from other cell death types. Ferroptosis is characterized by iron-mediated lipid peroxidation, depletion of the endogenous antioxidant glutathione and altered mitochondrial morphology. Although iron promotes the emergence of Ca²⁺ signals via activation of redox-sensitive Ca²⁺ channels, the role of Ca²⁺ signaling in ferroptosis has not been established. The early dysregulation of the cellular redox state observed in ferroptosis is likely to disturb Ca²⁺ homeostasis and signaling, facilitating ferroptotic neuronal death. This review presents an overview of the role of iron and ferroptosis in neuronal function, emphasizing the possible involvement of Ca²⁺ signaling in these processes. We propose, accordingly, that the iron-ferroptosis-Ca²⁺ association orchestrates the progression of cognitive dysfunctions and memory loss that occurs in neurodegenerative diseases. Therefore, to prevent iron dyshomeostasis and ferroptosis, we suggest the use of drugs that target the abnormal Ca²⁺ signaling caused by excessive iron levels as therapy for neurological disorders.

Is Ferroptosis a Key Component of the Process Leading to Multiorgan Damage in COVID-19?

Even though COVID-19 is mostly well-known for affecting respiratory pathology, it can also result in several extrapulmonary manifestations, leading to multiorgan damage. A recent reported case of SARS-CoV-2 myocarditis with cardiogenic shock showed a signature of myocardial and kidney ferroptosis, a novel, iron-dependent programmed cell death. The term ferroptosis was coined in the last decade to describe the form of cell death induced by the small molecule erastin. As a specific inducer of ferroptosis, erastin inhibits cystine-glutamate antiporter system Xc-, blocking transportation into the cytoplasm of cystine, a precursor of glutathione (GSH) in exchange with glutamate and the consequent malfunction of GPX4. Ferroptosis is also promoted by intracellular iron overload and by the iron-dependent accumulation of polyunsaturated fatty acids (PUFA)-derived lipid peroxides. Since depletion of GSH, inactivation of GPX4, altered iron metabolism, and upregulation of PUFA peroxidation by reactive oxygen species are peculiar signs of COVID-19, there is the possibility that SARS-CoV-2 may trigger ferroptosis in the cells of multiple organs, thus contributing to multiorgan damage. Here, we review the molecular mechanisms of ferroptosis and its possible relationship with SARS-CoV-2 infection and multiorgan damage. Finally, we analyze the potential interventions that may combat ferroptosis and, therefore, reduce multiorgan damage.

Emerging Pathological Engagement of Ferroptosis in Gut Diseases

Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, is mainly characterized by chronic and progressive inflammation that damages the gastrointestinal mucosa. Increasing studies have enlightened that dysregulated cell death occurs in the inflamed sites, leading to the disruption of the intestinal barrier and aggravating inflammatory response. Ferroptosis, a newly characterized form of regulated cell death, is driven by the lethal accumulation of lipid peroxides catalyzed by cellular free iron. It has been widely documented that the fundamental features of ferroptosis, including iron deposition, GSH exhaustion, GPX4 inactivation, and lipid peroxidation, are manifested in the injured gastrointestinal tract in IBD patients. Furthermore, manipulation of the critical ferroptotic genes could alter the progression, severity, or even morbidity of the experimental colitis. Herein, we critically summarize the recent advances in the field of ferroptosis, focusing on interpreting the potential engagement of ferroptosis in the pathogenesis of IBD. Moreover, we are attempting to shed light on a perspective insight into the possibility of targeting ferroptosis as novel therapeutic designs for the clinical intervention of these gastrointestinal diseases.

Ferroptosis and NRF2: an emerging battlefield in the neurodegeneration of Alzheimer's disease

Ferroptosis is an iron- and lipid peroxidation-dependent cell death modality and emerging evidence indicates that ferroptosis has great explanatory potential for neuronal loss and associated CNS dysfunction in a range of neurodegenerative diseases (e.g., Alzheimer's, Parkinson's and Huntington's diseases, Motor neuron disease, Friedreich ataxia (FRDA)). Ferroptotic death results from lethal levels of phospholipid hydroperoxides that are generated by iron-dependent peroxidation of polyunsaturated fatty acids (PUFAs), such as arachidonic and adrenic acids, which are conjugated to specific phospholipids (e.g., phosphatidylethanolamines (PEs)). The major cellular protector against ferroptosis is glutathione peroxidase 4 (GPX4), a membrane-associated selenoenzyme that reduces deleterious phospholipid hydroperoxides to their corresponding benign phospholipid alcohols in a glutathione-dependent manner. Other complementary protective systems have also been identified that act to bolster cellular defences against ferroptosis. Many pharmacological modulators of the ferroptosis pathway have been identified, targeting proteins involved in iron homoeostasis and autophagy; the production and detoxification of lipid peroxides, and cyst(e)ine/glutathione metabolism. While a growing number of cell signalling pathways converge to regulate the ferroptosis cascade, an emerging understanding of ferroptosis regulation suggests that the ferroptotic 'tone' of cells can be set by the transcription factor, nuclear factor erythroid 2-related factor 2 (NRF2), which transcriptionally controls many key components of the ferroptosis pathway. In this review, we provide a critical overview of the relationship between ferroptosis and NRF2 signalling. With a focus on the role of ferroptosis in Alzheimer's disease (AD), we discuss how therapeutic modulation of the NRF2 pathway is a viable strategy to explore in the treatment of ferroptosis-driven neurodegeneration.

Clarification of the Complexation Behaviour of 2,6-di-O-Methylated β-Cyclodextrin and Vitamin E and Radical Scavenging Ability of the Complex in Aqueous Solution

The precise understanding of the behaviour of vitamin E (α-tocopherol; Toc) complexed with cyclodextrin (CD) additives in aqueous solution is a fundamental issue for further development of their aqua-related biological applications. In this study, the solubilisation and complexation behaviours of Toc with methyl-substituted CD derivatives and the radical scavenging ability of the resulting complexes were precisely investigated in water media. Several problems were encountered upon pre-dissolving Toc in an organic solvent prior to the addition to the water media, such as enhancement of the dispersibility and decrease in the complexation capacity. Additionally, dispersions were obtained in some cases when mixing CD and Toc even in the absence of an organic solvent; therefore, to perform the measurements, a transparent solution was prepared via filtration with a nanopore filter. Consequently, unexpectedly, the addition of certain CD methylated derivatives did not always enhance the solubility of Toc significantly. However, 2,6-di-O-methylated β-CD (2,6-DMCD) formed a water-soluble inclusion complex with Toc, effectively enhancing its solubility. A phase solubility study indicated the formation of 1:2 or 1:3 Toc/CD inclusion complexes, and the interaction of 2,6-DMCD with both the chromanol head and the phytol chain of Toc was revealed by 2D ROESY nuclear magnetic resonance analysis. The interaction between 2,6-DMCD and the chromanol head was also confirmed for a 2,6-DMCD-2,2,5,7,8-pentamethyl-6-chromanol inclusion complex. Additionally, a rapid scavenging effect for molecularly dissolved Toc was demonstrated even in a system comprising a chromanol head directly encapsulated by CD. Hence, this work elucidated the precise complexation and radical scavenging ability of 2,6-DMCD-Toc in an aqueous solution, which paves the way for its biological applications.

Emerging role of ferroptosis in breast cancer: New dawn for overcoming tumor progression

Breast cancer has become a serious threat to women's health. Cancer progression is mainly derived from resistance to apoptosis induced by procedures or therapies. Therefore, new drugs or models that can overcome apoptosis resistance should be identified. Ferroptosis is a recently identified mode of cell death characterized by excess reactive oxygen species-induced lipid peroxidation. Since ferroptosis is distinct from apoptosis, necrosis and autophagy, its induction successfully eliminates cancer cells that are resistant to other modes of cell death. Therefore, ferroptosis may become a new direction around which to design breast cancer treatment. Unfortunately, the complete appearance of ferroptosis in breast cancer has not yet been fully elucidated. Furthermore, whether ferroptosis inducers can be used in combination with traditional anti- breast cancer drugs is still unknown. Moreover, a summary of ferroptosis in breast cancer progression and therapy is currently not available. In this review, we discuss the roles of ferroptosis-associated modulators glutathione, glutathione peroxidase 4, iron, nuclear factor erythroid-2 related factor-2, superoxide dismutases, lipoxygenase and coenzyme Q in breast cancer. Furthermore, we provide evidence that traditional drugs against breast cancer induce ferroptosis, and that ferroptosis inducers eliminate breast cancer cells. Finally, we put forward prospect of using ferroptosis inducers in breast cancer therapy, and predict possible obstacles and corresponding solutions. This review will deepen our understanding of the relationship between ferroptosis and breast cancer, and provide new insights into breast cancer-related therapeutic strategies.

Ferroptosis Meets Cell-Cell Contacts

Ferroptosis is a regulated form of cell death characterized by iron dependency and increased lipid peroxidation. Initially assumed to be selectively induced in tumour cells, there is increasing evidence that ferroptosis plays an important role in pathophysiology and numerous cell types and tissues. Deregulated ferroptosis has been linked to human diseases, such as neurodegenerative diseases, cardiovascular disorders, and cancer. Along these lines, ferroptosis is a promising pathway to overcoming therapy resistance of cancer cells. It is therefore of utmost importance to understand the cellular signalling pathways and the molecular mechanisms underlying ferroptosis regulation, including context-specific effects mediated by the neighbouring cells through cell–cell contacts. Here, we give an overview on the molecular events and machinery linked to ferroptosis induction and commitment. We further summarize and discuss current knowledge about the role of cell–cell contacts, which differ in ferroptosis regulation between normal somatic cells and cancer cells. We present emerging concepts on the underlying mechanisms, address open questions, and discuss the possible impact of cell–cell contacts on exploiting ferroptosis in cancer therapy.

Liproxstatin-1 attenuates unilateral ureteral obstruction-induced renal fibrosis by inhibiting renal tubular epithelial cells ferroptosis

Renal fibrosis is a common pathological process that occurs with diverse etiologies in chronic kidney disease. However, its regulatory mechanisms have not yet been fully elucidated. Ferroptosis is a form of non-apoptotic regulated cell death driven by iron-dependent lipid peroxidation. It is currently unknown whether ferroptosis is initiated during unilateral ureteral obstruction (UUO)-induced renal fibrosis and its role has not been determined. In this study, we demonstrated that ureteral obstruction induced ferroptosis in renal tubular epithelial cells (TECs) in vivo. The ferroptosis inhibitor liproxstatin-1 (Lip-1) reduced iron deposition, cell death, lipid peroxidation, and inhibited the downregulation of GPX4 expression induced by UUO, ultimately inhibiting ferroptosis in TECs. We found that Lip-1 significantly attenuated UUO-induced morphological and pathological changes and collagen deposition of renal fibrosis in mice. In addition, Lip-1 attenuated the expression of profibrotic factors in the UUO model. In vitro, we used RSL3 treatment and knocked down of GPX4 level by RNAi in HK2 cells to induce ferroptosis. Our results indicated HK2 cells secreted various profibrotic factors during ferroptosis. Lip-1 was able to inhibit ferroptosis and thereby inhibit the secretion of the profibrotic factors during the process. Incubation of kidney fibroblasts with culture medium from RSL3-induced HK2 cells promoted fibroblast proliferation and activation, whereas Lip-1 impeded the profibrotic effects. Our study found that Lip-1 may relieve renal fibrosis by inhibiting ferroptosis in TECs. Mechanistically, Lip-1 could reduce the activation of surrounding fibroblasts by inhibiting the paracrine of profibrotic factors in HK2 cells. Lip-1 may potentially be used as a therapeutic approach for the treatment of UUO-induced renal fibrosis.

Emerging Role of Ferroptosis in the Pathogenesis of Ischemic Stroke: A New Therapeutic Target?

Ischemic stroke is one of the main causes of high morbidity, mortality, and disability worldwide; however, the treatment methods are limited and do not always achieve satisfactory results. The pathogenesis of ischemic stroke is complex, defined by multiple mechanisms; among them, programmed death of neuronal cells plays a significant role. Ferroptosis is a novel type of regulated cell death characterized by iron redistribution or accumulation and increased lipid peroxidation in the membrane. Ferroptosis is implicated in many pathological conditions, such as cancer, neurodegenerative diseases, and ischemia-reperfusion injury. In this review, we summarize current research findings on ferroptosis, including possible molecular mechanisms and therapeutic applications of ferroptosis regulators, with a focus on the involvement of ferroptosis in the pathogenesis and treatment of ischemic stroke. Understanding the role of ferroptosis in ischemic stroke will throw some light on the development of methods for diagnosis, treatment, and prevention of this devastating disease.

A new thiol-independent mechanism of epithelial host defense against Pseudomonas aeruginosa: iNOS/NO• sabotage of theft-ferroptosis

Ferroptosis is a redox-driven type of regulated cell death program arising from maladaptation of three metabolic pathways: glutathione homeostasis, iron handling and lipid peroxidation. Though GSH/Gpx4 is the predominant system detoxifying phospholipid hydroperoxides (PLOOH) in mammalian cells, recently Gpx4-independent regulators of ferroptosis like ferroptosis suppressor protein 1 (FSP1) in resistant cancer lines and iNOS/NO^• in M1 macrophages have been discovered. We previously reported that Pseudomonas aeruginosa (PA) utilizes its 15- lipoxygenase (pLoxA) to trigger ferroptotic death in epithelial cells by oxidizing the host arachidonoyl-phosphatidylethanolamine (ETE-PE) into pro-ferroptotic 15-hydroperoxy- arachidonyl-PE (15-HpETE-PE). Here we demonstrate that PA degrades the host GPx4 defense by activating the lysosomal chaperone-mediated autophagy (CMA). In response, the host stimulates the iNOS/NO^•-driven anti-ferroptotic mechanism to stymie lipid peroxidation and protect GPx4/GSH-deficient cells. By using a co-culture model system, we showed that macrophage-produced NO^• can distantly prevent PA stimulated ferroptosis in epithelial cells as an inter-cellular mechanism. We further established that suppression of ferroptosis in epithelial cells by NO^• is enabled through the suppression of phospholipid peroxidation, particularly the production of pro-ferroptotic 15-HpETE-PE signals. Pharmacological targeting of iNOS (NO^• generation) attenuated its anti-ferroptotic function. In conclusion, our findings define a new inter-cellular ferroptosis suppression mechanism which may represent a new strategy of the host against P. aeruginosa induced theft-ferroptosis.

Ferroptosis and its emerging role in tumor

Ferroptosis is a novel form of programmed cell death characterized by iron-dependent lipid peroxidation accumulation. It is morphologically, biochemically, and genetically distinct from other known cell death, such as apoptosis, necrosis, and pyroptosis. Its regulatory mechanisms include iron metabolism, fatty acid metabolism, mitochondrial respiration, and antioxidative systems eliminating lipid peroxidation, such as glutathione synthesis, selenium-dependent glutathione peroxidase 4, and ubiquinone. The disruption of cellular redox systems causes damage to the cellular membrane leading to ferroptotic cell death. Recent studies have shown that numerous pathological diseases, like tumors, neurodegenerative disorders, and ischemia-reperfusion injury are associated with ferroptosis. As such, pharmacological regulation of ferroptosis either by activation or by suppression will provide a vast potential for treatments of relevant diseases. This review will discuss the advanced progress in ferroptosis and its regulatory mechanisms from both the antioxidative and oxidative sides. In addition, the roles of ferroptosis in various tumorigenesis, development, and therapeutic strategies will be addressed, particularly to chemotherapy and immunotherapy, as well as the discoveries from Traditional Chinese Medicine. This review will lead us to have a comprehensive understanding of the future exploration of ferroptosis and cancer therapy.

Research Progress of Ferroptosis: A Bibliometrics and Visual Analysis Study

Background

Ferroptosis is a type of cell death with major topic of debate under current research and plays an important role in disease regulation.

Objective

In this study, the literature management software Bibexcel and knowledge graph tool VOSviewer were used to summarize and analyze the international research trends and hotspots about ferroptosis in recent years, which highlight the disease mechanism, diagnosis, and treatment related to ferroptosis. Material/Methods. The core collection database of Web of Science was used for retrieving ferroptosis research literature. The information such as the amount of text, the country, the period, the institution, the fund, and the keywords was extracted by the bibliometric tool Bibexcel. The cooccurrence and clustering function of VOSviewer were used to analyze the high-frequency keywords and the cooperative network of the author, institution, and country.

Results

The research of ferroptosis started late and was formally proposed in 2012. It has developed rapidly and presented an “exponential” growth trend. China, the United States, Germany, Japan, and France are the main national forces of ferroptosis research development. The United States and China have a relatively high degree of support and attention to ferroptosis. Exploring oxidative stress, inducers/inhibitors, synergistic antitumor effect, relationships with other cell death types, GSH/GPX4 and iron metabolism imbalance related mechanisms of ferroptosis, and ferroptosis in the nervous system disease, ischemia-reperfusion injury, tumor, inflammation, and age-related diseases are the hot research directions.

Conclusion

Ferroptosis has been a research hotspot in the field of biomedicine in recent years and has attracted the attention of scholars all over the world. The occurrence mechanism of ferroptosis and its application in neurological diseases, ischemia and reperfusion injury, tumors, inflammation, and aging are the hot directions of current research. In the future, ferroptosis can be appropriately considered for strengthening new approaches, new diseases, new inductors, new inhibitors, clinical transformation, and traditional medicine research.

Ferroptosis: Biological Rust of Lipid Membranes

Significance: Iron is an essential element required for growth and proper functioning of the body. However, an excess of labile ferrous iron increases the risk of oxidative stress-induced injury due to the high reactivity of the unpaired reactive electrons of both ferrous iron and oxygen. This high reactivity can be exemplified in the outside world by one of its consequences, rust formation. In cells, this redox-active iron is involved in the formation of lipid radicals. Recent Advances: Defect or insufficient membrane-protective mechanisms can result in iron-catalyzed excessive lipid peroxidation and subsequent cell death, now conceptualized as ferroptosis. Growing reports propose the detrimental role of iron and ferroptosis in many experimental disease models such as ischemia-reperfusion, acute and chronic organ injuries. Critical Issues: This review first provides a snapshot of iron metabolism, followed by a brief introduction of the molecular mechanisms of ferroptosis, as an iron-dependent lipid peroxidation-driven mode of cell death. Upon describing how iron dysbiosis affects ferroptosis induction, we elaborate on the detrimental role of the iron-ferroptosis axis in several diseases. Future Directions: Despite compelling findings suggesting a role of ferroptosis in experimental animal models, the exact contribution of ferroptosis in human contexts still needs further investigation. Development of reliable ferroptosis biomarkers will be an important step in characterizing ferroptosis in human disease. This can provide therapeutic opportunities aiming at targeting ferroptosis in human diseases. Antioxid. Redox Signal. 35, 487-509.

Lipid Metabolism Regulates Oxidative Stress and Ferroptosis in RAS-Driven Cancers: A Perspective on Cancer Progression and Therapy

HRAS, NRAS and KRAS, collectively referred to as oncogenic RAS, are the most frequently mutated driver proto-oncogenes in cancer. Oncogenic RAS aberrantly rewires metabolic pathways promoting the generation of intracellular reactive oxygen species (ROS). In particular, lipids have gained increasing attention serving critical biological roles as building blocks for cellular membranes, moieties for post-translational protein modifications, signaling molecules and substrates for ß-oxidation. However, thus far, the understanding of lipid metabolism in cancer has been hampered by the lack of sensitive analytical platforms able to identify and quantify such complex molecules and to assess their metabolic flux in vitro and, even more so, in primary tumors. Similarly, the role of ROS in RAS-driven cancer cells has remained elusive. On the one hand, ROS are beneficial to the development and progression of precancerous lesions, by upregulating survival and growth factor signaling, on the other, they promote accumulation of oxidative by-products that decrease the threshold of cancer cells to undergo ferroptosis. Here, we overview the recent advances in the study of the relation between RAS and lipid metabolism, in the context of different cancer types. In particular, we will focus our attention on how lipids and oxidative stress can either promote or sensitize to ferroptosis RAS driven cancers. Finally, we will explore whether this fine balance could be modulated for therapeutic gain.

Punicic Acid Triggers Ferroptotic Cell Death in Carcinoma Cells

Plant-derived conjugated linolenic acids (CLnA) have been widely studied for their preventive and therapeutic properties against diverse diseases such as cancer. In particular, punicic acid (PunA), a conjugated linolenic acid isomer (C18:3 c9t11c13) present at up to 83% in pomegranate seed oil, has been shown to exert anti-cancer effects, although the mechanism behind its cytotoxicity remains unclear. Ferroptosis, a cell death triggered by an overwhelming accumulation of lipid peroxides, has recently arisen as a potential mechanism underlying CLnA cytotoxicity. In the present study, we show that PunA is highly cytotoxic to HCT-116 colorectal and FaDu hypopharyngeal carcinoma cells grown either in monolayers or as three-dimensional spheroids. Moreover, our data indicate that PunA triggers ferroptosis in carcinoma cells. It induces significant lipid peroxidation and its effects are prevented by the addition of ferroptosis inhibitors. A combination with docosahexaenoic acid (DHA), a known polyunsaturated fatty acid with anticancer properties, synergistically increases PunA cytotoxicity. Our findings highlight the potential of using PunA as a ferroptosis-sensitizing phytochemical for the prevention and treatment of cancer.

Ferroptosis: the potential value target in atherosclerosis

In advanced atherosclerosis (AS), defective function-induced cell death leads to the formation of the characteristic necrotic core and vulnerable plaque. The forms and mechanisms of cell death in AS have recently been elucidated. Among them, ferroptosis, an iron-dependent form of necrosis that is characterized by oxidative damage to phospholipids, promotes AS by accelerating endothelial dysfunction in lipid peroxidation. Moreover, disordered intracellular iron causes damage to macrophages, vascular smooth muscle cells (VSMCs), vascular endothelial cells (VECs), and affects many risk factors or pathologic processes of AS such as disturbances in lipid peroxidation, oxidative stress, inflammation, and dyslipidemia. However, the mechanisms through which ferroptosis initiates the development and progression of AS have not been established. This review explains the possible correlations between AS and ferroptosis, and provides a reliable theoretical basis for future studies on its mechanism.

Defining a pharmacological inhibitor fingerprint for oxytosis/ferroptosis

Ferroptosis was first described in 2012 as an iron- and lipid peroxidation-dependent form of regulated cell death. Since its initial description, these two characteristics have informed numerous cell culture studies where inhibitors of lipid peroxidation and/or iron chelators have been shown to prevent cell death induced by a wide range of insults. However, it is not clear whether these two characteristics are sufficient to distinguish ferroptosis from other forms of regulated cell death. Thus, the primary goal of this study was to determine whether a unique combination of features could be identified that would provide an approach to more clearly separate ferroptosis from other forms of regulated cell death. To this end, multiple pharmacological inhibitors based on a variety of studies were tested. Many of these inhibitors were previously shown to protect cells from oxytosis, a regulated cell death pathway that mechanistically overlaps with ferroptosis and is induced by some of the same chemicals as ferroptosis. These inhibitors were not only tested against both known ferroptosis and oxytosis inducers but also a number of other insults that have been suggested to induce ferroptosis. The results show that a pharmacological fingerprint for ferroptosis can be established and used to categorize toxic insults into those that overlap with oxytosis/ferroptosis and those that do not.

Mitochondrial regulation of ferroptosis

Ferroptosis is a form of iron-dependent regulated cell death driven by uncontrolled lipid peroxidation. Mitochondria are double-membrane organelles that have essential roles in energy production, cellular metabolism, and cell death regulation. However, their role in ferroptosis has been unclear and somewhat controversial. In this Perspective, I summarize the diverse metabolic processes in mitochondria that actively drive ferroptosis, discuss recently discovered mitochondria-localized defense systems that detoxify mitochondrial lipid peroxides and protect against ferroptosis, present new evidence for the roles of mitochondria in regulating ferroptosis, and outline outstanding questions on this fascinating topic for future investigations. An in-depth understanding of mitochondria functions in ferroptosis will have important implications for both fundamental cell biology and disease treatment.

Ferroptosis: a cell death connecting oxidative stress, inflammation and cardiovascular diseases

Ferroptosis, a recently identified and iron-dependent cell death, differs from other cell death such as apoptosis, necroptosis, pyroptosis, and autophagy-dependent cell death. This form of cell death does not exhibit typical morphological and biochemical characteristics, including cell shrinkage, mitochondrial fragmentation, nuclear condensation. The dysfunction of lipid peroxide clearance, the presence of redox-active iron as well as oxidation of polyunsaturated fatty acid (PUFA)-containing phospholipids are three essential features of ferroptosis. Iron metabolism and lipid peroxidation signaling are increasingly recognized as central mediators of ferroptosis. Ferroptosis plays an important role in the regulation of oxidative stress and inflammatory responses. Accumulating evidence suggests that ferroptosis is implicated in a variety of cardiovascular diseases such as atherosclerosis, stroke, ischemia-reperfusion injury, and heart failure, indicating that targeting ferroptosis will present a novel therapeutic approach against cardiovascular diseases. Here, we provide an overview of the features, process, function, and mechanisms of ferroptosis, and its increasingly connected relevance to oxidative stress, inflammation, and cardiovascular diseases.

Dysfunction of the key ferroptosis-surveilling systems hypersensitizes mice to tubular necrosis during acute kidney injury

Acute kidney injury (AKI) is morphologically characterized by a synchronized plasma membrane rupture of cells in a specific section of a nephron, referred to as acute tubular necrosis (ATN). Whereas the involvement of necroptosis is well characterized, genetic evidence supporting the contribution of ferroptosis is lacking. Here, we demonstrate that the loss of ferroptosis suppressor protein 1 (Fsp1) or the targeted manipulation of the active center of the selenoprotein glutathione peroxidase 4 (Gpx4cys/-) sensitize kidneys to tubular ferroptosis, resulting in a unique morphological pattern of tubular necrosis. Given the unmet medical need to clinically inhibit AKI, we generated a combined small molecule inhibitor (Nec-1f) that simultaneously targets receptor interacting protein kinase 1 (RIPK1) and ferroptosis in cell lines, in freshly isolated primary kidney tubules and in mouse models of cardiac transplantation and of AKI and improved survival in models of ischemia-reperfusion injury. Based on genetic and pharmacological evidence, we conclude that GPX4 dysfunction hypersensitizes mice to ATN during AKI. Additionally, we introduce Nec-1f, a solid inhibitor of RIPK1 and weak inhibitor of ferroptosis.

Ferroptosis and Its Role in Epilepsy

Epilepsy is one of the most common symptoms of many neurological disorders. The typical excessive, synchronous and aberrant firing of neurons originating from different cerebral areas cause spontaneous recurrent epileptic seizures. Prolonged epilepsy can lead to neuronal damage and cell death. The mechanisms underlying epileptic pathogenesis and neuronal death remain unclear. Ferroptosis is a newly defined form of regulated cell death that is characterized by the overload of intracellular iron ions, leading to the accumulation of lethal lipid-based reactive oxygen species (ROS). To date, studies have mainly focused on its role in tumors and various neurological disorders, including epilepsy. Current research shows that inhibition of ferroptosis is likely to be an effective therapeutic approach for epilepsy. In this review, we outline the pathogenesis of ferroptosis, regulatory mechanisms of ferroptosis, related regulatory molecules, and their effects on epilepsy, providing a new direction for discovering new therapeutic targets in epilepsy.

Ferroptosis and Its Potential Role in Metabolic Diseases: A Curse or Revitalization?

Ferroptosis is classified as an iron-dependent form of regulated cell death (RCD) attributed to the accumulation of lipid hydroperoxides and redox imbalance. In recent years, accumulating researches have suggested that ferroptosis may play a vital role in the development of diverse metabolic diseases, for example, diabetes and its complications (e.g., diabetic nephropathy, diabetic cardiomyopathy, diabetic myocardial ischemia/reperfusion injury and atherosclerosis [AS]), metabolic bone disease and adrenal injury. However, the specific physiopathological mechanism and precise therapeutic effect is still not clear. In this review, we summarized recent advances about the development of ferroptosis, focused on its potential character as the therapeutic target in metabolic diseases, and put forward our insights on this topic, largely to offer some help to forecast further directions.

Autoxidation vs. antioxidants - the fight for forever

Autoxidation limits the longevity of essentially all hydrocarbons and materials made therefrom - including us. The radical chain reaction responsible often leads to complex mixtures of hydroperoxides, alkyl peroxides, alcohols, carbonyls and carboxylic acids, which change the physical properties of the material - be it a lubricating oil or biological membrane. Autoxidation is inhibited by addtitives such as radical-trapping antioxidants, which intervene directly in the chain reaction. Herein we review the most salient features of autoxidation and its inhibition, emphasizing concepts and mechanistic considerations important in understanding this chemistry across the wide range of contexts in which it is relevant.

Juggling with lipids, a game of Russian roulette

Lipid peroxidation (LPO) is the molecular mechanism involved in oxidative damage of cellular membranes and the hallmark of a nonapoptotic form of cell death, known as ferroptosis. This iron-dependent cell death is an emerging strategy in cancer treatment and one of the central cell death mechanisms accounting for early cell loss and organ dysfunction in both neurodegenerative disease and ischemia-reperfusion injury. Although the biological roles of LPO products have attracted considerable attention, not only for their pathological mechanisms but also for their potential clinical application as biomarkers, the existence of a common lethal lipid death signal generated during ferroptosis remains poorly explored. A better understanding of the LPO process, however, may unleash unprecedented opportunities for therapeutic intervention of as-yet incurable diseases.

Molecular mechanisms of cell death in neurological diseases

Tightly orchestrated programmed cell death (PCD) signalling events occur during normal neuronal development in a spatially and temporally restricted manner to establish the neural architecture and shaping the CNS. Abnormalities in PCD signalling cascades, such as apoptosis, necroptosis, pyroptosis, ferroptosis, and cell death associated with autophagy as well as in unprogrammed necrosis can be observed in the pathogenesis of various neurological diseases. These cell deaths can be activated in response to various forms of cellular stress (exerted by intracellular or extracellular stimuli) and inflammatory processes. Aberrant activation of PCD pathways is a common feature in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease, Parkinson's disease, and Huntington's disease, resulting in unwanted loss of neuronal cells and function. Conversely, inactivation of PCD is thought to contribute to the development of brain cancers and to impact their response to therapy. For many neurodegenerative diseases and brain cancers current treatment strategies have only modest effect, engendering the need for investigations into the origins of these diseases. With many diseases of the brain displaying aberrations in PCD pathways, it appears that agents that can either inhibit or induce PCD may be critical components of future therapeutic strategies. The development of such therapies will have to be guided by preclinical studies in animal models that faithfully mimic the human disease. In this review, we briefly describe PCD and unprogrammed cell death processes and the roles they play in contributing to neurodegenerative diseases or tumorigenesis in the brain. We also discuss the interplay between distinct cell death signalling cascades and disease pathogenesis and describe pharmacological agents targeting key players in the cell death signalling pathways that have progressed through to clinical trials.

Antisense overlapping long non-coding RNA regulates coding arachidonate 12-lipoxygenase gene by translational interference

The arachidonate 12-lipoxygenase (ALOX12) enzyme catalyzes polyunsaturated fatty acids and facilitates generation of bioactive lipid mediators associated with various biological processes and disease pathologies. The human genome assembly revealed that the ALOX12 gene overlaps an antisense non-coding gene designated as ALOX12-antisense 1 (ALOX12-AS1). This arrangement indicates that the uncharacterized ALOX12-AS1 long non-coding RNA (lncRNA) may bind to the sense coding ALOX12 mRNA to form an antisense-sense duplex providing the basis of a novel ALOX12 regulatory mechanism. Therefore, this study was designed to determine whether the interaction of ALOX12-AS1 with ALOX12 mRNA functions as an anti-sense/sense duplex-mediated regulatory mechanism controlling the cellular content of ALOX12. Our findings indicate that two major isoforms of ALOX12-AS1 lncRNA are ubiquitously expressed in a variety of primary adult human tissues and different transformed cell types. RNA-FISH revealed cell-type-specific cytosolic as well as nuclear and nucleolar localization of the lncRNA. Interestingly, phorbol ester-induced nucleo-cytoplasmic translocation of the lncRNA in monocytic THP-1 cells resulted in a reduction of ALOX12 protein without a concomitant change in its mRNA level. This indicated ALOX12-AS1 operates via an antisense-sense duplex-mediated translational downregulation mechanism. This deduction was validated by demonstrating sense/antisense duplex formation and an association of the duplex with ribosomal proteins in HEK293 cells. Overall, this study revealed a hitherto unknown mechanism of antisense lncRNA-mediated translational downregulation of ALOX12 that adds to the existing regulatory mechanisms for the modulation of potent bioactive lipid mediators that contribute to both health and disease.

Non-enzymatic lipid peroxidation initiated by photodynamic therapy drives a distinct ferroptosis-like cell death pathway

Ferroptosis is primarily triggered by a failure of the glutathione (GSH)-glutathione peroxidase 4 (GPX4) reductive system and associated overwhelming lipid peroxidation, in which enzymes regulating polyunsaturated fatty acid (PUFA) metabolism, and in particular acyl-CoA synthetase long chain family member 4 (ACSL4), are central. Here, we found that exogenous oxygen radicals generated by photodynamic therapy (PDT) can directly peroxidize PUFAs and initiate lipid autoxidation, coinciding with cellular GSH depletion. Different from canonical ferroptosis induced by RSL3 or erastin, PDT-initiated lipid peroxidation and ferroptotis-like cell death is independent of lipoxygenase (ALOXs) and ACSL4. Especially, this form of cell death modality can be triggered in malignant cells insensitive to or acquired resistance to canonical ferroptosis inducers. We also observed a distinct iron metabolism pathway in this PDT-triggered cell death modality, in which cytosolic labile iron is decreased probably due to its relocation to mitochondria. Inhibition of the mitochondrial Ca²⁺ and Fe²⁺ uniporter (MCU) effectively prevented PDT-triggered lipid peroxidation and subsequent cell death. Therefore, we tentatively term this distinct ferroptosis-like cell death as liperoptosis. Moreover, using the clinically approved photosensitizer Verteporfin, PDT inhibited tumor growth through inducing prevailing ferroptosis-like cell death in a mouse xenograft model. With its site-specific advantages, these findings highlight the value of using PDT to trigger lipid peroxidation and ferroptosis-like cell death in vivo, and will benefit exploring the exact molecular mechanism of immunological effects of PDT in cancer treatment.

Effects of acute iron overload on Nrf2-related glutathione metabolism in rat brain

Iron (Fe) overload triggers free radical production and lipid peroxidation processes that may lead to cell death (ferroptosis). The hypothesis of this work was that acute Fe-dextran treatment triggers Nrf2-mediated antioxidant regulation in rat brain involving glutathione (GSH) metabolism. Over the initial 8 h after Fe-dextran administration (single dose of 500 mg Fe-dextran/kg), total Fe, malondialdehyde (MDA) content, glutathione peroxidase (GPx), GPx-Se dependent (GPx-Se) and glutathione S-transferases (GST) activities were increased in rat whole brain. The content of GSH and the activity of glutathione reductase (GR) showed decreases (p < 0.05) after 6 and 8 h post injection in cortex. A significant increase in nuclear Nrf2 protein levels over control values was achieved after 6 h of Fe-dextran administration, while no significant differences were observed in the cytosolic fraction. Nuclear Nrf2/cytosolic Nrf2 ratios showed enhancement (p < 0.05) after 6 h of Fe overload, suggesting a greater translocation of the factor to the nucleus. No significant differences were observed in the expression of Keap1 in nuclear or cytosolic extracts. It is concluded that acute Fe overload induces oxidative stress in rat brain with the concomitant lipid peroxidation increase and GSH depletion, leading to the elevation of Nrf2-controlled GPx, GPx-Se and GST protein expression as a protective adaptive response. Further studies are required to fully comprehend the complex network of interrelated processes keeping the balance of GSH functions as chelator, antioxidant and redox buffer in the understanding of the ferroptotic and hormetic mechanisms triggered by Fe overload in brain.

Ferroptosis as a New Mechanism in Parkinson's Disease Therapy Using Traditional Chinese Medicine

Parkinson’s disease (PD) is one of the most common neurodegenerative diseases. To date, among medications used to treat PD, only levodopa exhibits a limited disease-modifying effect on early-onset PD, but it cannot delay the progression of the disease. In 2018, for the first time, the World Health Organization included traditional Chinese medicine (TCM) in its influential global medical compendium. The use of TCM in the treatment of PD has a long history. At present, TCM can help treat and prevent PD. Iron metabolism is closely associated with PD. Ferroptosis, which is characterized by the accumulation of lipid peroxides, is a recently discovered form of iron-dependent cell death. The research literature indicates that ferroptosis in dopaminergic neurons is an important pathogenetic mechanism of PD. TCM may thus play unique roles in the treatment of PD and provide new ideas for the treatment of PD by regulating pathways associated with ferroptosis.

A compendium of kinetic modulatory profiles identifies ferroptosis regulators

Cell death can be executed by regulated apoptotic and nonapoptotic pathways, including the iron-dependent process of ferroptosis. Small molecules are essential tools for studying the regulation of cell death. Using time-lapse imaging and a library of 1,833 bioactive compounds, we assembled a large compendium of kinetic cell death modulatory profiles for inducers of apoptosis and ferroptosis. From this dataset we identify dozens of ferroptosis suppressors, including numerous compounds that appear to act via cryptic off-target antioxidant or iron chelating activities. We show that the FDA-approved drug bazedoxifene acts as a potent radical trapping antioxidant inhibitor of ferroptosis both in vitro and in vivo. ATP-competitive mechanistic target of rapamycin (mTOR) inhibitors, by contrast, are on-target ferroptosis inhibitors. Further investigation revealed both mTOR-dependent and mTOR-independent mechanisms that link amino acid metabolism to ferroptosis sensitivity. These results highlight kinetic modulatory profiling as a useful tool to investigate cell death regulation.

Mechanisms of Regulated Cell Death: Current Perspectives

Balancing cell survival and cell death is fundamental to development and homeostasis. Cell death is regulated by multiple interconnected signaling pathways and molecular mechanisms. Regulated cell death (RCD) is implicated in fundamental processes such as organogenesis and tissue remodeling, removal of unnecessary structures or cells, and regulation of cell numbers. RCD can also be triggered by exogenous perturbations of the intracellular or extracellular microenvironment when the adaptive processes that respond to stress fail. During the past few years, many novel forms of non-apoptotic RCD have been identified, and the characterization of RCD mechanisms at a molecular level has deepened our understanding of diseases encountered in human and veterinary medicine. Given the complexity of these processes, it has become clear that the identification of RCD cannot be based simply on morphologic characteristics and that descriptive and diagnostic terms presently used by pathologists-such as individual cell apoptosis or necrosis-appear inadequate and possibly misleading. In this review, the current understanding of the molecular machinery of each type of non-apoptotic RCD mechanisms is outlined. Due to the continuous discovery of new mechanisms or nuances of previously described processes, the limitations of the terms apoptosis and necrosis to indicate microscopic findings are also reported. In addition, the need for a standard panel of biomarkers and functional tests to adequately characterize the underlying RCD and its role as a mechanism of disease is considered.

Lipid Metabolism in Ferroptosis

Lipid metabolism is a complex biochemical process that participates in the regulation of cell survival and death. Ferroptosis is a form of iron-dependent regulated cell death driven by abnormal lipid metabolism, leading to lipid peroxidation and subsequent plasma membrane rupture. A variety of antioxidant systems and membrane repair pathways can diminish oxidative damage, enabling survival and growth in response to ferroptotic signals. Such impairment of ferroptosis machinery is implicated in various pathological conditions and diseases, especially cancer and tissue damage. It is discussed here how lipid metabolism pathways, including lipid synthesis, degradation, storage, transformation, and utilization, modulate ferroptosis sensitivity or tolerance in different models, especially cancer.

NO● Represses the Oxygenation of Arachidonoyl PE by 15LOX/PEBP1: Mechanism and Role in Ferroptosis

We recently discovered an anti-ferroptotic mechanism inherent to M1 macrophages whereby high levels of NO^● suppressed ferroptosis via inhibition of hydroperoxy-eicosatetraenoyl-phosphatidylethanolamine (HpETE-PE) production by 15-lipoxygenase (15LOX) complexed with PE-binding protein 1 (PEBP1). However, the mechanism of NO^● interference with 15LOX/PEBP1 activity remained unclear. Here, we use a biochemical model of recombinant 15LOX-2 complexed with PEBP1, LC-MS redox lipidomics, and structure-based modeling and simulations to uncover the mechanism through which NO^● suppresses ETE-PE oxidation. Our study reveals that O₂ and NO^● use the same entry pores and channels connecting to 15LOX-2 catalytic site, resulting in a competition for the catalytic site. We identified residues that direct O₂ and NO^● to the catalytic site, as well as those stabilizing the esterified ETE-PE phospholipid tail. The functional significance of these residues is supported by in silico saturation mutagenesis. We detected nitrosylated PE species in a biochemical system consisting of 15LOX-2/PEBP1 and NO^● donor and in RAW264.7 M2 macrophages treated with ferroptosis-inducer RSL3 in the presence of NO^●, in further support of the ability of NO^● to diffuse to, and react at, the 15LOX-2 catalytic site. The results provide first insights into the molecular mechanism of repression of the ferroptotic Hp-ETE-PE production by NO^●.

The Chemistry and Biology of Ferroptosis

Ferroptosis is a recently described form of cell death driven by iron-dependent lipid peroxidation. This type of cell death was first observed in response to treatment of tumor cells with a small-molecule chemical probe named erastin. Most subsequent advances in understanding the mechanisms governing ferroptosis involved the use of genetic screens and small-molecule probes. We describe herein the utility and limitations of chemical probes that have been used to analyze and perturb ferroptosis, as well as mechanistic studies of ferroptosis that benefitted from the use of these probes and genetic screens. We also suggest probes for ferroptosis and highlight mechanistic questions surrounding this form of cell death that will be a high priority for exploration in the future.

Targeting programmed cell death in metabolic dysfunction-associated fatty liver disease (MAFLD): a promising new therapy

Most currently recommended therapies for metabolic dysfunction-associated fatty liver disease (MAFLD) involve diet control and exercise therapy. We searched PubMed and compiled the most recent research into possible forms of programmed cell death in MAFLD, including apoptosis, necroptosis, autophagy, pyroptosis and ferroptosis. Here, we summarize the state of knowledge on the signaling mechanisms for each type and, based on their characteristics, discuss how they might be relevant in MAFLD-related pathological mechanisms. Although significant challenges exist in the translation of fundamental science into clinical therapy, this review should provide a theoretical basis for innovative MAFLD clinical treatment plans that target programmed cell death.

Ferroptotic Cell Death: New Regulatory Mechanisms for Metabolic Diseases

Background:

Cell death is a fundamental biological phenomenon that contributes to the pathogenesis of various diseases. Regulation of iron and iron metabolism has received considerable research interests especially concerning the progression of metabolic diseases.

Discussion:

Emerging evidence shows that ferroptosis, a non-apoptotic programmed cell death induced by iron-dependent lipid peroxidation, contributes to the development of complex diseases such as non-alcoholic steatohepatitis, cardiomyopathy, renal ischemia-reperfusion, and neurodegenerative diseases. Therefore, inhibiting ferroptosis can improve the pathophysiology of associated metabolic diseases. This review describes the vital role of ferroptosis in mediating the development of certain metabolic diseases. Besides, the potential risk of iron and ferroptosis in atherosclerosis and cardiovascular diseases is also described. Iron overload and ferroptosis are potential secondary causes of death in metabolic diseases. Moreover, this review also provides potential novel approaches against ferroptosis based on recent research advances.

Conclusion:

Several controversies exist concerning mechanisms underlying ferroptotic cell death in metabolic diseases, particularly in atherosclerosis. Since ferroptosis participates in the progression of metabolic diseases such as non-alcoholic steatohepatitis (NASH), there is a need to develop new drugs targeting ferroptosis to alleviate such diseases.

Investigating the effects of two novel 4-MMPB analogs as potent lipoxygenase inhibitors for prostate cancer treatment

Background

Lipoxygenases are one of the critical signaling mediators which can be targeted for human prostate cancer (PC) therapy. In this study, 4-methyl-2-(4-methylpiperazinyl)pyrimido[4,5-b]benzothiazine (4-MMPB) and its two analogs, 4-propyl-2-(4-methylpiperazinyl)pyrimido[4,5-b]benzothiazine (4-PMPB) and 4-ethyl-2-(4-methylpiperazinyl)pyrimido[4,5-b]benzothiazine (4-EMPB), were proposed to have anti-tumor properties in prostate cancer.

Methods

After synthesizing the compounds, cytotoxic effects of 4-MMPB and its two analogs against PC-3 cancerous and HDF normal cells were investigated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and then mechanism of cell death was assessed by flow cytometry. Finally, the anti-tumor effects of the mentioned compounds were investigated in an immunocompromised C57BL/6 mouse model.

Results

4-PMPB and 4-EMPB had similar anti-cancer effects on PC-3 cells as compared with 4-MMPB, while they were not effective on normal cells. Moreover, apoptosis and ferroptosis were the main mechanisms of induced cell death in these cancerous cells. Furthermore, in vivo results indicated that both analogs had similar anti-cancer effects as 4-MMPB, leading to delayed tumor growth without any noticeable side effects in weight loss and histological investigations.

Conclusion

Thus, our results suggest that specific targeting of lipoxygenases via 4-MMPB analogs can be considered as a treatment of choice for PC therapy, although it requires further investigations.