Achieving Life through Death: Redox Biology of Lipid Peroxidation in Ferroptosis

Empagliflozin attenuates the renal tubular ferroptosis in diabetic kidney disease through AMPK/NRF2 pathway

Renal tubular damage plays a key role in the pathogenesis of diabetic kidney disease (DKD), and one of the main pathological process associated with DKD in diabetic mice is the ferroptosis, a novel form of cell death caused by iron-dependent lipid peroxidation. Several researches suggested that empagliflozin may treat renal injury, but its effects on diabetic-related ferroptosis and underlying mechanisms were not fully elucidated. In this study, the influence of empagliflozin on renal injury was evaluated in vivo and in vitro in a mouse model and in high-glucose (HG) or Erastin-stimulated renal HK-2 cell line, respectively. Ferroptosis-related markers were assessed, including GSH, labile iron levels, and ferroptosis regulators by Western blot, qRT-PCR, immunohistochemistry, and immunofluorescence. The level of malondialdehyde (MDA) and the fluorescence intensity of BODIPY probe indicated the level of lipid peroxidation. It was demonstrated that solute carrier family 7, member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) were less expressed in renal biopsy samples from patients affected by DKD than in those from non-diabetic renal disease patients (NDRD), proving the ferroptosis of tubular epithelial cells in case of DKD. Furthermore, empagliflozin markedly decreased the ferroptosis impairment in DKD mice, as well as in HG model of HK-2 cells. Our investigations showed the ability of empagliflozin to suppress ferroptosis was partially countered by AMP-activated protein kinase (AMPK) inhibitor, which led to a reduction of the nuclear translocation of the antioxidant transcription factor NFE2-related factor 2 (NRF2) and downregulation of target genes such as GPX4, ferritin heavy chain 1 (FTH1), and SLC7A11, while AMPK agonists were responsible for the enhancement of the protective effects of empagliflozin. Taken together, our findings showed that empagliflozin may prevent the development of ferroptosis by promoting the AMPK-mediated NRF2 activation pathway, providing important insights for possible novel treatment approaches for DKD.

Regulation of the p53‑mediated ferroptosis signaling pathway in cerebral ischemia stroke (Review)

Stroke is one of the most threatening diseases worldwide, particularly in countries with larger populations; it is associated with high morbidity, mortality and disability rates. As a result, extensive research efforts are being made to address these issues. Stroke can include either hemorrhagic stroke (blood vessel ruptures) or ischemic stroke (blockage of an artery). Whilst the incidence of stroke is higher in the elderly population (≥65), it is also increasing in the younger population. Ischemic stroke accounts for ~85% of all stroke cases. The pathogenesis of cerebral ischemic injury can include inflammation, excitotoxic injury, mitochondrial dysfunction, oxidative stress, ion imbalance and increased vascular permeability. All of the aforementioned processes have been extensively studied, providing insights into the disease. Other clinical consequences observed include brain edema, nerve injury, inflammation, motor deficits and cognitive impairment, which not only cause disabilities obstructing daily life but also increase the mortality rates. Ferroptosis is a type of cell death that is characterized by iron accumulation and increased lipid peroxidation in cells. In particular, ferroptosis has been previously implicated in ischemia-reperfusion injury in the central nervous system. It has also been identified as a mechanism involved in cerebral ischemic injury. The tumor suppressor p53 has been reported to modulate the ferroptotic signaling pathway, which both positively and negatively affects the prognosis of cerebral ischemia injury. The present review summarizes the recent findings on the molecular mechanisms of ferroptosis under the regulation of p53 underlying cerebral ischemia injury. Understanding of the p53/ferroptosis signaling pathway may provide insights into developing methods for improving the diagnosis, treatment and even prevention of stroke.

The Potential Role of Regulated Cell Death in Dry Eye Diseases and Ocular Surface Dysfunction

The research on new treatments for dry eye diseases (DED) has exponentially grown over the past decades. The increased prevalence of dry eye conditions, particularly in the younger population, has received much attention. Therefore, it is of utmost importance to identify novel therapeutical targets. Regulated cell death (RCD) is an essential process to control the biological homeostasis of tissues and organisms. The identification of different mechanisms of RCD stimulated the research on their involvement in different human pathologies. Whereas apoptosis has been widely studied in DED and included in the DED vicious cycle, the role of RCD still needs to be completely elucidated. In this review, we will explore the potential roles of different types of RCD in DED and ocular surface dysfunction. Starting from the evidence of oxidative stress and inflammation in dry eye pathology, we will analyse the potential therapeutic applications of the following principal RCD mechanisms: ferroptosis, necroptosis, and pyroptosis.

FERROPTOSIS IN THE PATHOGENESIS OF BRAIN TUMORS

The field of research on ferroptosis has seen explosive growth in the past few years since the term was coined in 2012. This review highlights the current state of knowledge on the developmental mechanism of this unique mode of cell death, induced by iron-dependent phospholipid peroxidation and which is regulated by a variety of cellular metabolic events, including redox homeostasis. Among these factors, the xCT. system, an amino acid antiporter that supports the synthesis of glutathione (GSH) and oxidation protection. The risk of iron accumulation in neurons, astrocytes, oligodendrocytes, microglia, and Schwann cells and the development of oxidative stress is discussed. Ferroptosis triggers a cascade of events including activation of inflammation, oxidation of neurotransmitters, impaired neuronal communication, myelin sheath degeneration, astrocyte dysregulation, dementia, and cell death. On the other hand, the exceptional vulnerability to ferroptosis of cancer cells originating from the nervous tissue is estimated. Evidence is given for the initiation of ferroptosis in tumor cells as a factor in inhibiting the growth and death of these cells. Particular attention is paid to the pharmacological modulation of ferroptosis through its induction and inhibition for the treatment of drug-resistant cancers. The choice of targets for the induction of ferroptosis in cancer cells is discussed. Glutathione peroxidase 4 and xCT amino acid antiporter are recognized as the most preferred targets and the antitumor potential of their inhibition and side effects are being evaluated.

Ferroptosis As a Mechanism for Health Effects of Essential Trace Elements and Potentially Toxic Trace Elements

Ferroptosis is a unique form of programmed cell death driven by iron-dependent phospholipid peroxidation that was proposed in recent years. It plays an important role in processes of various trace element-related diseases and is regulated by redox homeostasis and various cellular metabolic pathways (iron, amino acids, lipids, sugars), as well as disease-related signaling pathways. Some limited pioneering studies have demonstrated ferroptosis as a mechanism for the health effects of essential trace elements and potentially toxic trace elements, with crosstalk among them. The aim of this review is to bring together research articles and identify key direct and indirect evidence regarding essential trace elements (iron, selenium, zinc, copper, chromium, manganese) and potentially toxic trace elements (arsenic, aluminum, mercury) and their possible roles in ferroptosis. Our review may help determine future research priorities and opportunities.

α-Lipoic Acid Alleviated Fluoride-Induced Hepatocyte Injury via Inhibiting Ferroptosis

Fluoride is widely used in agricultural production and food packaging. Excessive fluoride in water and food is a serious threat to liver health. α-Lipoic acid, a natural free radical scavenger, has hepatoprotective properties. However, the protective effect of α-lipoic acid on fluorohepatotoxicity is uncertain. The aim of this study was to investigate the mechanism of ferroptosis in α-lipoic acid preventing fluoride-induced hepatotoxicity. Five-week-old ICR mice were treated with sodium fluoride (100 mg/L) and/or α-lipoic acid (200 mg/kg) for 9 weeks. The results showed that α-lipoic acid attenuated fluoride-induced damage to liver morphology and ultrastructure. Moreover, α-lipoic acid alleviated fluoride-induced iron accumulation, increased oxidative stress, and elevated lipid peroxidation in the liver. In addition, the mechanism study found that α-lipoic acid prevented fluoride-induced ferroptosis through the System Xc^-/GPX4 axis, lipid peroxidation axis, and iron metabolism axis, but it was interestingly not regulated by mitochondrial free radical axis in the hepatocytes. Altogether, this study indicated that α-lipoic acid prevents fluoride-induced liver injury by inhibiting ferroptosis, which has potential implications for the prevention and treatment of fluoride-induced liver injury.

SLC7A11 as a Gateway of Metabolic Perturbation and Ferroptosis Vulnerability in Cancer

SLC7A11 is a cell transmembrane protein composing the light chain of system xc^-, transporting extracellular cystine into cells for cysteine production and GSH biosynthesis. SLC7A11 is a critical gateway for redox homeostasis by maintaining the cellular levels of GSH that counter cellular oxidative stress and suppress ferroptosis. SLC7A11 is overexpressed in various human cancers and regulates tumor development, proliferation, metastasis, microenvironment, and treatment resistance. Upregulation of SLC7A11 in cancers is needed to adapt to high oxidative stress microenvironments and maintain cellular redox homeostasis. High basal ROS levels and SLC7A11 dependences in cancer cells render them vulnerable to further oxidative stress. Therefore, cyst(e)ine depletion may be an effective new strategy for cancer treatment. However, the effectiveness of the SLC7A11 inhibitors or cyst(e)inase has been established in many preclinical studies but has not reached the stage of clinical trials for cancer patients. A better understanding of cysteine and SLC7A11 functions regulating and interacting with redox-active proteins and their substrates could be a promising strategy for cancer treatment. Therefore, this review intends to understand the role of cysteine in antioxidant and redox signaling, the regulators of cysteine bioavailability in cancer, the role of SLC7A11 linking cysteine redox signaling in cancer metabolism and targeting SLC7A11 for novel cancer therapeutics.

Emerging roles of ferroptosis in infectious diseases

In living organisms, lipid peroxidation is a continuously occurring cellular process and therefore involved in various physiological and pathological contexts. Among the broad variety of lipids, polyunsaturated fatty acids (PUFA) constitute a major target of oxygenation either when released as mediators by phospholipases or when present in membranous phospholipids. The last decade has seen the characterization of an iron- and lipid peroxidation-dependent cell necrosis, namely, ferroptosis, that involves the accumulation of peroxidized PUFA-containing phospholipids. Further studies could link ferroptosis in a very large body of (physio)-pathological processes, including cancer, neurodegenerative, and metabolic diseases. In this review, we mostly focus on the emerging involvement of lipid peroxidation-driven ferroptosis in infectious diseases, and the immune consequences. We also discuss the putative ability of microbial virulence factors to exploit or to dampen ferroptosis regulatory pathways to their own benefit.

Signaling pathways and defense mechanisms of ferroptosis

As a type of lytic cell death driven by unrestricted lipid peroxidation and subsequent plasma membrane damage, ferroptosis occurs and develops because of sophisticated signals and regulatory mechanisms. The reactive oxygen species (ROS) used to initiate ferroptosis come from a variety of sources, including iron-mediated Fenton reactions, mitochondrial ROS, and membrane-associated ROS driven by the NOX protein family. Polyunsaturated fatty acid-containing phospholipids are the main substrates of lipid peroxidation in ferroptosis, which is positively regulated by enzymes, such as ACSL4, LPCAT3, ALOXs, or POR. Selective activation of autophagic degradation pathways promotes ferroptosis by increasing iron accumulation to cause lipid peroxidation. In contrast, system xc^- -glutathione-GPX4 axis plays a central role in limiting lipid peroxidation, although other antioxidants (such as coenzyme Q10 and tetrahydrobiopterin) can also inhibit ferroptosis. A main nuclear mechanism of cell defense against ferroptosis is the activation of the NFE2L2-dependent antioxidant response by transcriptionally upregulating the expression of antioxidants or cytoprotective genes. Additionally, the membrane damage caused by ferroptotic stimulus can be repaired by ESCRT-III-dependent membrane scission machinery. In this review, we summarize recent progress in understanding the signaling pathways and defense mechanisms of ferroptosis.

Inhibition of ferroptosis and iron accumulation alleviates pulmonary fibrosis in a bleomycin model

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive disease characterized by excessive proliferation of fibroblasts and excessive accumulation of extracellular matrix (ECM). Ferroptosis is a novel form of cell death characterized by the lethal accumulation of iron and lipid peroxidation, which is associated with many diseases. Our study addressed the potential role played by ferroptosis and iron accumulation in the progression of pulmonary fibrosis. We found that the inducers of pulmonary fibrosis and injury, namely, bleomycin (BLM) and lipopolysaccharide (LPS), induced ferroptosis of lung epithelial cells. Both the ferroptosis inhibitor liproxstatin-1 (Lip-1) and the iron chelator deferoxamine (DFO) alleviated the symptoms of pulmonary fibrosis induced by bleomycin or LPS. TGF-β stimulation upregulated the expression of transferrin receptor protein 1 (TFRC) in the human lung fibroblast cell line (MRC-5) and mouse primary lung fibroblasts, resulting in increased intracellular Fe2+, which promoted the transformation of fibroblasts into myofibroblasts. Mechanistically, TGF-β enhanced the expression and nuclear localization of the transcriptional coactivator tafazzin (TAZ), which combined with the transcription factor TEA domain protein (TEAD)-4 to promote the transcription of TFRC. In addition, elevated Fe2+ failed to induce the ferroptosis of fibroblasts, which might be related to the regulation of iron export and lipid metabolism. Finally, we specifically knocked out TFRC expression in fibroblasts in mice, and compared with those in the control mice, the symptoms of pulmonary fibrosis were reduced in the knockout mice after bleomycin induction. Collectively, these findings suggest the therapeutic potential of ferroptosis inhibitors and iron chelators in treating pulmonary fibrosis.

1H, 13C, and 15N resonance assignments of human glutathione peroxidase 4

Glutathione peroxidase 4 (GPx4) behaves as an antioxidant enzyme capable of directly reducing peroxidized phospholipids within cell membranes. Recently, GPx4 has attracted attention as a target molecule for cancer therapy because it induces the immortalization of cancer cells suppressing ferroptosis. In this study, to analyze the function and structure of GPx4 by solution NMR, we performed resonance assignments of GPx4 and assigned almost all backbone ¹H, ¹³C, and ¹⁵N resonances and most of the side chain ¹H and ¹³C resonances. Using these assignments, the secondary structure of GPx4 was analyzed by the TALOS + program. GPx4 has six helices and seven strands. Then, the backbone dynamics were examined by the {¹H}-¹⁵N heteronuclear NOE experiment. GPx4 was found to be rigid except for a short loop region. These results will provide basis for functional analysis and the first solution structure determination of GPx4.

Antioxidant action of persulfides and polysulfides against free radical-mediated lipid peroxidation

Hydrogen sulfide, hydropersulfides, and hydropolysulfides have been revealed to play important physiological roles such as cell signaling and protection against oxidative stress, but the underlying mechanisms and dynamics of action remain elusive. It is generally accepted that these species act by two-electron redox mechanisms, while the involvement of one-electron redox chemistry has received less attention. In this study, the radical-scavenging activity of hydrogen persulfide, hydrogen polysulfides (HSnH n = 2-4), and diallyl- or dialkyl-sulfides (RSnR, n = 1-4) was measured. Furthermore, their antioxidant effects against free radical-mediated human plasma lipid peroxidation were assessed by measuring lipid hydroperoxides. It was found that disodium disulfide, trisulfide, and tetrasulfide acted as potent peroxyl radical scavengers, the rate constant for scavenging peroxyl radical being 3.5 × 105, 4.0 × 105, and 6.0 × 105 M-1 s-1 in PBS pH 7.4 at 37 °C respectively and that they inhibited plasma lipid peroxidation efficiently, the efficacy is increased with the catenation number. Disodium tetrasulfide was 1.5 times as reactive as Trolox toward peroxyl radical and inhibited plasma lipid peroxidation more efficiently than ascorbate and Trolox. On the other hand, diallyl- and dialkyl-sulfides did not exert significant radical-scavenging activity, nor did they inhibit lipid peroxidation efficiently, except for diallyl tetrasulfide, which suppressed plasma lipid peroxidation, despite less significantly than disodium tetrasulfide. Collectively, this study shows that hydrogen persulfide and hydrogen polysulfides act as potent radical-scavenging antioxidants and that, in addition to two-electron redox mechanisms, one electron redox reaction may also play important role in the in vivo defense against deleterious oxidative stress.

Phospholipid peroxidation-driven modification of chondrogenic transcription factor mediates alkoxyl radicals-induced impairment of embryonic bone development

Maternal stress has been associated with poor birth outcomes, including preterm birth, infant mortality, and low birth weight. Bone development disorders in the embryo as a result of maternal stress are believed to be mediated through oxidative stress damage. Various species of free radicals, such as alkoxyl radicals, can be formed through endogenous redox response or exogenous stimuli in the womb and transmitted to embryos. Yet, whether these free radicals lead to abnormal fetal bone development is unclear. Here, we demonstrate prenatal bone growth retardation and ferroptosis-related signals of chondrocytes were induced by classic alkoxyl radical generators. We also show that alkoxyl radicals lead to significant accumulation of oxidized phospholipids in chondrocytes, through the iron-mediated Fenton reaction in embryos. We further demonstrate a role for the lipid peroxidation end product, 4-HNE, which forms adducts with the pivotal chondrogenesis transcription factor SOX9, leading to its degradation, therefore dampening chondrogenesis. Our data define a critical role for phospholipid peroxidation in alkoxyl radicals-evoked abnormal chondrogenesis, and pinpoint it being a precise target for treating oxidative stress-related bone development disorders.

New Insights into the Regulatory Role of Ferroptosis in Ankylosing Spondylitis via Consensus Clustering of Ferroptosis-Related Genes and Weighted Gene Co-Expression Network Analysis

Background: The pathogenesis of ankylosing spondylitis (AS) remains undetermined. Ferroptosis is a newly discovered form of regulated cell death involved in multiple autoimmune diseases. Currently, there are no reports on the connection between ferroptosis and AS. Methods: AS samples from the Gene Expression Omnibus were divided into two subgroups using consensus clustering of ferroptosis-related genes (FRGs). Weighted gene co-expression network analysis (WGCNA) of the intergroup differentially expressed genes (DEGs) and protein–protein interaction (PPI) analysis of the key module were used to screen out hub genes. A multifactor regulatory network was then constructed based on hub genes. Results: The 52 AS patients in dataset GSE73754 were divided into cluster 1 (n = 24) and cluster 2 (n = 28). DEGs were mainly enriched in pathways related to mitochondria, ubiquitin, and neurodegeneration. Candidate hub genes, screened by PPI and WGCNA, were intersected. Subsequently, 12 overlapping genes were identified as definitive hub genes. A multifactor interaction network with 45 nodes and 150 edges was generated, comprising the 12 hub genes and 32 non-coding RNAs. Conclusions: AS can be divided into two subtypes according to FRG expression. Ferroptosis might play a regulatory role in AS. Tailoring treatment according to the ferroptosis status of AS patients can be a promising direction.

Raw material “Trifolii pratense herba” originated from southern Ukraine: diagnostic microscopic features and its antioxidant activity

As a result of pharmacognostic and pharmacological studies, diagnostic signs of Trifolii pratense grass collected in the phenophase of active flowering in the area of southern Ukraine were revealed. We have proposed the adoption of an appendix to the existing monograph of the State Service of Ukraine on Medicines and Drugs Control “Trifolii inflorescences”, with raw material of grass Trifolii pratense, with appropriate microscopic identification of diagnostic signs of leaves and stems of the plant. According to our previously found optimal conditions for extraction of medicinal plant raw materials (ratio of solvent-plant material, time and temperature of extraction), selected aqueous extract (1: 5) of clover grass with yields of maximum active substances to the extract from 60 min to 24 hours, which showed lower values of TBARS (0.541 ± 0.0291 μM / g, mean ± SD), which gives grounds to recommend the use of raw materials as an antioxidant, compared with the action of ascorbic acid.

TFRC upregulation promotes ferroptosis in CVB3 infection via nucleus recruitment of Sp1

CVB3 is a single positive-strand enterovirus, and a common pathogen in myocarditis etiology. Although a number of antiviral candidates are under development, specific targeted therapy is not available for CVB3. Ferroptosis is a new type of regulatory cell death discovered in recent years. In this study, our team provided the first evidence that ferroptosis existed in CVB3 infection in vivo and in vitro by iron overload, and massive accumulation of lipid peroxides. Mechanistically, we construct a classical model of HeLa cells following a time-course infection (6, 12, 24, 36, 48 h) with CVB3 (MOI = 10). We demonstrated that the TFRC gene plays an important role in promoting ferroptosis in CVB3 infection and downregulation of TFRC attenuated the ferroptosis. Interestingly, we observed that TFRC was nuclear translocation induced by the CVB3, which was predominantly localized in the cell membrane, but redistributed to the nucleus during CVB3 infection. Moreover, we found that the transcription factor Sp1 was an essential factor that could bind to the TFRC promoter and upregulate the TFRC transcription. Collectively, these results suggest that the Sp1/TFRC/Fe axis may provide a new target for the development of therapies against CVB3 infection.

UBIAD1 alleviates ferroptotic neuronal death by enhancing antioxidative capacity by cooperatively restoring impaired mitochondria and Golgi apparatus upon cerebral ischemic/reperfusion insult

Background

Neuronal death due to over-oxidative stress responses defines the pathology of cerebral ischemic/reperfusion (I/R) insult. Ferroptosis is a form of oxidative cell death that is induced by disruption of the balance between antioxidants and pro-oxidants in cells. However, the potential mechanisms responsible for cerebral I/R-induced ferroptotic neuronal death have not been conclusively determined. UBIAD1, is a newly identified antioxidant enzyme that catalyzes coenzyme Q10 (CoQ10) and vitamin K2 biosynthesis in the Golgi apparatus membrane and mitochondria, respectively. Even though UBIAD1 is a significant mediator of apoptosis in cerebral I/R challenge, its roles in ferroptotic neuronal death remain undefined. Therefore, we investigated whether ferroptotic neuronal death is involved in cerebral I/R injury. Further, we evaluated the functions and possible mechanisms of UBIAD1 in cerebral I/R-induced ferroptotic neuronal death, with a major focus on mitochondrial and Golgi apparatus dysfunctions.

Results

Ferroptosis occurred in cerebral I/R. Ferroptotic neuronal death promoted cerebral I/R-induced brain tissue injury and neuronal impairment. UBIAD1 was expressed in cerebral tissues and was localized in neurons, astrocytes, and microglia. Under cerebral I/R conditions overexpressed UBIAD1 significantly suppressed lipid peroxidation and ferroptosis. Moreover, upregulated UBIAD1 protected against brain tissue damage and neuronal death by alleviating I/R-mediated lipid peroxidation and ferroptosis. However, UBIAD1 knockdown reversed these changes. Enhanced UBIAD1-mediated ferroptosis elevated the antioxidative capacity by rescuing mitochondrial and Golgi apparatus dysfunction in cerebral I/R-mediated neuronal injury. They improved the morphology and biofunctions of the mitochondria and Golgi apparatus, thereby elevating the levels of SOD, T-AOC and production of CoQ10, endothelial nitric oxide synthase (eNOS)-regulated nitric oxide (NO) generation as well as suppressed MDA generation.

Conclusions

The neuroprotective agent, UBIAD1, modulates I/R-mediated ferroptosis by restoring mitochondrial and Golgi apparatus dysfunction in damaged brain tissues and neurons, thereby enhancing antioxidative capacities. Moreover, the rescue of impaired mitochondrial and Golgi apparatus as a possible mechanism of regulating ferroptotic neuronal death is a potential treatment strategy for ischemic stroke.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00776-9.

In Vivo Assessment of Ferroptosis and Ferroptotic Stress in Mice

Ferroptosis is iron-dependent, lipid peroxidation-driven, regulated cell death that is triggered when cellular glutathione peroxidase 4 (GPX4)-mediated cellular defense is insufficient to prevent pathologic accumulation of toxic lipid peroxides. Ferroptosis is implicated in various human pathologies, including neurodegeneration, chemotherapy-resistant cancers, ischemia-reperfusion injury, and acute and chronic kidney diseases. Despite the fact that the ferroptotic process has been rigorously interrogated in multiple preclinical models, the lack of specific and readily available biomarkers to detect ferroptosis in vivo in mouse models makes it challenging to delineate its contribution to key pathologic events in vivo. Critical steps to practically evaluate ferroptosis include, but are not limited to, detecting increased cell death and pathologic accumulation of toxic lipid peroxides and testing augmentation of observed pathologic events by genetic inhibition of the glutathione-GPX4 axis or mitigation of the pathologic process by ferroptosis inhibitors. Here, we describe methods to evaluate these key features of the ferroptotic process in mice in vivo. Specifically, we describe methods to detect toxic lipid peroxides (4-hydroxynonenal) and cell death (based on terminal deoxynucleotidyl transferase dUTP nick end labeling staining) as well as a protocol to pharmacologically inhibit ferroptotic stress using liproxstatin-1. These protocols provide tools for understanding the ferroptotic process in mouse genetic or disease models. © 2022 Wiley Periodicals LLC. Basic Protocol 1: How to use liproxstatin-1 Basic Protocol 2: How to evaluate ferroptosis in mouse kidneys.

Ferroptosis: A New Road towards Cancer Management

Ferroptosis is a recently described programmed cell death mechanism that is characterized by the buildup of iron (Fe)-dependent lipid peroxides in cells and is morphologically, biochemically, and genetically distinct from other forms of cell death, having emerged to play an important role in cancer biology. Ferroptosis has significant importance during cancer treatment because of the combination of factors, including suppression of the glutathione peroxidase 4 (Gpx4), cysteine deficiency, and arachidonoyl (AA) peroxidation, which cause cells to undergo ferroptosis. However, the physiological significance of ferroptosis throughout development is still not fully understood. This current review is focused on the factors and molecular mechanisms with the diagrammatic illustrations of ferroptosis that have a role in the initiation and sensitivity of ferroptosis in various malignancies. This knowledge will open a new road for research in oncology and cancer management.

Oxidative Stress and 4-hydroxy-2-nonenal (4-HNE): Implications in the Pathogenesis and Treatment of Aging-related Diseases

Oxidative stress plays an important role in the development of aging-related diseases by accelerating the lipid peroxidation of polyunsaturated fatty acids in the cell membrane, resulting in the production of aldehydes, such as malondialdehyde and 4-hydroxy-2-nonenal (4-HNE) and other toxic substances. The compound 4-HNE forms adducts with DNA or proteins, disrupting many cell signaling pathways including the regulation of apoptosis signal transduction pathways. The binding of proteins to 4-HNE (4-HNE-protein) acts as an important marker of lipid peroxidation, and its increasing concentration in brain tissues and fluids because of aging, ultimately gives rise to some hallmark disorders, such as neurodegenerative diseases (Alzheimer's and Parkinson's diseases), ophthalmic diseases (dry eye, macular degeneration), hearing loss, and cancer. This review aims to describe the physiological origin of 4-HNE, elucidate its toxicity in aging-related diseases, and discuss the detoxifying effect of aldehyde dehydrogenase and glutathione in 4-HNE-driven aging-related diseases.

The Role of Ferric Nitrilotriacetate in Renal Carcinogenesis and Cell Death: From Animal Models to Clinical Implications

Iron is essential for cellular growth, and various ferroproteins and heme-containing proteins are involved in a myriad of cellular functions, such as DNA synthesis, oxygen transport, and catalytic reactions. As a consequence, iron deficiency causes pleiotropic effects, such as hypochromic microcytic anemia and growth disturbance, while iron overload is also deleterious by oxidative injury. To prevent the generation of iron-mediated reactive oxygen species (ROS), ferritin is synthesized to store excess iron in cells that are consistent with the clinical utility of the serum ferritin concentration to monitor the therapeutic effect of iron-chelation. Among the animal models exploring iron-induced oxidative stress, ferric nitrilotriacetate (Fe-NTA) was shown to initiate hepatic and renal lipid peroxidation and the development of renal cell carcinoma (RCC) after repeated intraperitoneal injections of Fe-NTA. Here, current understanding of Fe-NTA-induced oxidative stress mediated by glutathione-cycle-dependent iron reduction and the molecular mechanisms of renal carcinogenesis are summarized in combination with a summary of the relationship between the pathogenesis of human RCC and iron metabolism. In addition to iron-mediated carcinogenesis, the ferroptosis that is triggered by the iron-dependent accumulation of lipid peroxidation and is implicated in the carcinogenesis is discussed.

Targeting iNOS Alleviates Early Brain Injury After Experimental Subarachnoid Hemorrhage via Promoting Ferroptosis of M1 Microglia and Reducing Neuroinflammation

Numerous studies have demonstrated the role of neuroinflammation in mediating acute pathophysiological events of early brain injury after subarachnoid hemorrhage (SAH). However, it is not clear how to target this inflammatory cascade after SAH. M1 activation of microglia is an important pathological mechanism driving neuroinflammation in SAH, which is considered aggressive, leading to cytotoxicity and robust inflammation related to the release of proinflammatory cytokines and chemokines after SAH. Thus, reducing the number of M1 microglia represents a potential target for therapies to improve outcomes after SAH. Previous studies have found that inducible nitric oxide synthase (iNOS/NO•) plays an essential role in promoting the survival of M1 microglia by blocking ferroptosis. Ferroptosis is a new type of iron-dependent cellular procedural death associated with pathological cell death related to mammalian degenerative diseases, cerebral hemorrhage, and traumatic brain injury. Here, we investigated the effect of L-NIL, an inhibitor of iNOS, on M1 microglia, neuroinflammation, neuronal cell death, brain edema, and neurological function in an experimental SAH model in vivo and in vitro. We found that L-NIL reduced the number of M1 microglia and alleviated neuroinflammation following SAH. Notably, treatment with L-NIL relieves brain edema and neuronal injury and improves outcomes of neurological function after SAH in rats. Mechanistically, we found that L-NIL inhibited the expression of iNOS and promoted ferroptosis of M1 microglia by increasing the expression of ferroptosis-related proteins and lipid peroxidation in an in vitro model of SAH, which was reversed by a ferroptosis inhibitor, liproxstatin-1. In addition, inhibiting iNOS had no significant effect on ferroptosis of neurons after oxyhemoglobin stimulation in vitro. Thus, our research demonstrated that inhibition of iNOS might represent a potential therapeutic strategy to improve outcomes after SAH by promoting ferroptosis of M1 microglia and reducing neuroinflammation.

Superoxide Radicals in the Execution of Cell Death

Superoxide is a primary oxygen radical that is produced when an oxygen molecule receives one electron. Superoxide dismutase (SOD) plays a primary role in the cellular defense against an oxidative insult by ROS. However, the resulting hydrogen peroxide is still reactive and, in the presence of free ferrous iron, may produce hydroxyl radicals and exacerbate diseases. Polyunsaturated fatty acids are the preferred target of hydroxyl radicals. Ferroptosis, a type of necrotic cell death induced by lipid peroxides in the presence of free iron, has attracted considerable interest because of its role in the pathogenesis of many diseases. Radical electrons, namely those released from mitochondrial electron transfer complexes, and those produced by enzymatic reactions, such as lipoxygenases, appear to cause lipid peroxidation. While GPX4 is the most potent anti-ferroptotic enzyme that is known to reduce lipid peroxides to alcohols, other antioxidative enzymes are also indirectly involved in protection against ferroptosis. Moreover, several low molecular weight compounds that include α-tocopherol, ascorbate, and nitric oxide also efficiently neutralize radical electrons, thereby suppressing ferroptosis. The removal of radical electrons in the early stages is of primary importance in protecting against ferroptosis and other diseases that are related to oxidative stress.

Activation of pyroptosis and ferroptosis is involved in the hepatotoxicity induced by polystyrene microplastics in mice

Microplastics (MPs) are new environmental pollutants and have received widespread attention in recent years, but the toxicity of the MPs remains to be fully elucidated. To explore the effect of MPs on hepatotoxicity in mice and unravel the mechanism of pyroptosis and ferroptosis in the process of liver injury, we treated mice with 5.0 μm polypropylene microplastics (MPs) at 0.1, 0.5 and 1 mg/mL for 4 weeks. Results revealed that MPs could damage liver structure and function with broken and reduced mitochondrial cristae, as well as increased levels of aspartate minotransferase (AST), alanine aminotransferase (ALT), AST/ALT, alkaline phosphatase (ALP) and lactate dehydrogenase (LDH). Treatment with MPs resulted in pyroptosis as evidenced by increasing expressions of interleukin IL-1β, IL-18. Additionally, MPs were shown to induce the NOD-like receptor protein 3 (NLRP3) inflammasomes and apoptosis associated speck-like protein (ASC) containing a caspase recruitment domain activation in liver tissue, enabling activation of Caspase-1-dependent signaling pathway induced by inflammatory stimuli resulting from oxidative stress. In addition, the increase of malondialdehyde (MDA) and decrease of glutathione (GSH) and superoxide dismutase (SOD) in the liver indicated that MPs could induce oxidative damage. Moreover, MPs induced lipid peroxidation in the liver of mice could activate the expression of ferroptosis related proteins, including iron metabolism, such as transferrin receptor (TFRC) was active but ferritin heavy chain 1 (FTH1) was inhibited; amino acid metabolism, such as XCT system and glutathione peroxidase 4 (GPX4) were inhibited; lipid metabolism, such as acyl-CoA synthetase long-chain family member 4 (ACSL4) was inhibited. Collectively, these findings evidenced that pyroptosis and ferroptosis occurred in MPs-induced liver injury accompanied by intense oxidative stress and inflammation.

Hemojuvelin deficiency promotes liver mitochondrial dysfunction and predisposes mice to hepatocellular carcinoma

Hemojuvelin (HJV) enhances signaling to the iron hormone hepcidin and its deficiency causes iron overload, a risk factor for hepatocellular carcinoma (HCC). We utilized Hjv^−/− mice to dissect mechanisms for hepatocarcinogenesis. We show that suboptimal treatment with diethylnitrosamine (DEN) triggers HCC only in Hjv^−/− but not wt mice. Liver proteomics data were obtained by mass spectrometry. Hierarchical clustering analysis revealed that Hjv deficiency and DEN elicit similar liver proteomic responses, including induction of mitochondrial proteins. Dietary iron overload of wt mice does not recapitulate the liver proteomic phenotype of Hjv^−/− animals, which is only partially corrected by iron depletion. Consistent with these data, primary Hjv^−/− hepatocytes exhibit mitochondrial hyperactivity, while aged Hjv^−/− mice develop spontaneous HCC. Moreover, low expression of HJV or hepcidin (HAMP) mRNAs predicts poor prognosis in HCC patients. We conclude that Hjv has a hepatoprotective function and its deficiency in mice promotes mitochondrial dysfunction and hepatocarcinogenesis.

Hemojuvelin (HJV), a BMP co-receptor promoting hepcidin expression in the liver, has a hepatoprotective function and its deficiency in mice triggers mitochondrial dysfunction and hepatocarcinogenesis.

Bufotalin induces ferroptosis in non-small cell lung cancer cells by facilitating the ubiquitination and degradation of GPX4

Ferroptosis is a new form of regulated cell death that is dependent on iron- and lipid reactive oxygen species. Emerging evidence indicate that induction of ferroptosis could inhibit the proliferation of diverse cancer cells, which functions as a potent tumor suppressor in cancer. Here, we firstly reported Bufotalin (BT), a natural small molecule, was a novel glutathione peroxidase 4 (GPX4) inhibitor, which could trigger the ferroptosis in non-small cell lung cancer cells. In vitro, BT significantly inhibited the proliferation of A549 cells and induced the ferroptosis, whereas ferroptosis inhibitor or iron chelator significantly reversed the cytotoxicity of BT on A549 cells. Moreover, BT also increased the intracellular Fe²⁺. Subsequently, immunoblotting showed that BT could inhibit the protein expression of GPX4. Notably, BT dramatically accelerated the degradation of GPX4 in A549 cells. Immunoprecipitation assay further certified the increased ubiquitination of GPX4 induced by BT. Nevertheless, BT could not further increase the lipid ROS after silencing of GPX4, suggesting the induction of ferroptosis by BT was dependent on GPX4. Furthermore, BT also observably inhibited tumor growth and promoted lipid peroxidation in vivo. In conclusion, our findings indicated that BT could induce ferroptosis and cause lipid peroxidation by accelerating the degradation of GPX4 and raising the intracellular Fe²⁺, and BT will hopefully serve as a lead compound in developing anti-tumor agents for targeting ferroptosis.

Electroacupuncture Alleviates LPS-Induced ARDS Through α7 Nicotinic Acetylcholine Receptor-Mediated Inhibition of Ferroptosis

Acute respiratory distress syndrome (ARDS) is an uncontrollable, progressive pulmonary inflammatory disease, and as a common clinical critical disease, there is no effective treatment available. Electroacupuncture (EA) therapy is a type of traditional Chinese medicine physiotherapy that can alleviate the inflammatory response. However, the potential mechanism of EA in the treatment of ARDS is not yet clear. Ferroptosis is a new type of programmed cell death characterized by intracellular iron accumulation and lipid peroxidation. Recently, emerging evidence has shown that ferroptosis is closely related to the occurrence and development of ARDS caused by various pathological factors. Here, we further investigated whether EA-mediated inhibition of ferroptosis in lung tissue could attenuate lipopolysaccharide (LPS)-induced ARDS and explored its underlying mechanisms. In this study, mice were administered LPS intraperitoneally to establish a model of LPS-induced ARDS. We found that EA stimulation could not only reduce the exudation of inflammatory cells and proteins in the alveolar lumen but also significantly alleviate the pathological changes of lung tissue, inhibit the production of proinflammatory cytokines and improve the survival rate of mice. Concurrently, we also found that ferroptosis events occurred in the lung tissue of LPS-induced ARDS mice, manifested by elevated iron levels, ROS production and lipid peroxidation. Intriguingly, our results showed that EA stimulation at the Zusanli (ST36) acupoint activated α7 nicotinic acetylcholine receptor (α7nAchR) in lung tissue mainly through the sciatic nerve and cervical vagus nerve, thus exerting anti-ferroptosis and pulmonary protective effects. Additionally, these effects were eliminated by methyllycaconitine (MLA), a selective antagonist of α7nAchR. In vitro experiments, activation of α7nAchR protected alveolar epithelial cells from LPS-induced ferroptosis. Furthermore, our experiments showed that the pulmonary protective effects of EA stimulation were effectively reversed by erastin, a ferroptosis activator. Collectively, we demonstrated that EA stimulation could alleviate LPS-induced ARDS by activating α7nAchR to inhibit LPS-induced ferroptosis in alveolar epithelial cells. Targeting and regulating ferroptosis in alveolar epithelial cells may be a potential intervention approach for the treatment of LPS-induced ALI/ARDS in the future.

Hydroxysafflor yellow A and anhydrosafflor yellow B alleviate ferroptosis and parthanatos in PC12 cells injured by OGD/R

Ferroptosis and parthanatos are two types of programmed cell death associated with cerebral ischemia. There is a sizeable interest in seeking chemical components for the regulation of ferroptosis and parthanatos. Hydroxysafflor yellow A (HSYA) and anhydrosafflor yellow B (AHSYB) mitigated cell death caused by oxidative stress due to antioxidant capacity, yet the mechanism is still uncertain. Thus, we investigated whether HSYA and AHSYB prevent death through these two pathways with the aim to elucidate their potential protective mechanisms of cerebral ischemia. In this study, oxidative stress model was established by treating PC12 cells with oxygen glucose deprivation and reperfusion (OGD/R). Cellular functions and signaling pathways were analyzed in PC12 cells using cell counting kit-8 (CCK-8), flow cytometry, ELISA, iron assay kit, transmission electron microscopy (TEM), immunofluorescence, and western blot analysis. And the research proved HSYA and AHSYB protected cells from oxidative stress. The phenomenon is associated with ferroptosis and parthanatos. HSYA and AHSYB upregulated cystine/glutamate antiporter system x_c^- (system x_c^-) and glutathione peroxidase 4 (GPX4), returned the levels of GSH/GSSG ratio, reactive oxygen species (ROS) and iron ion, as well as alleviated lipid peroxidation. By reason of reducing ROS, HSYA and AHSYB restrained poly(ADP-ribose) polymerase-1 (PARP-1) overactivation, reduced the production of excess poly(ADP-ribose) (PAR) polymer and apoptosis inducing factor (AIF) nuclear translocation. The results suggested that HSYA and AHSYB limited ferroptosis and parthanatos to alleviate oxidative stress in PC12 cells. These findings may have implications for improving understanding of how drugs reduce oxidative stress and develop new strategies for treating degenerative diseases such as cerebral ischemia.

Live-cell imaging reveals impaired detoxification of lipid-derived electrophiles is a hallmark of ferroptosis

The central mechanism in ferroptosis linking lipid hydroperoxide accumulation with cell death remains poorly understood. Although lipid hydroperoxides are known to break down to reactive lipid-derived electrophiles (LDEs), the ability of cells to detoxify increasing LDE levels during ferroptosis has not been studied. Here, we developed an assay (ElectrophileQ) correlating the cellular retention vs. excretion of a fluorogenic lipophilic electrophile (AcroB) that enables live-cell assessment of the glutathione-mediated LDE conjugation and adduct export steps of the LDE detoxification pathway. This method revealed that during ferroptosis, LDE detoxification failure occurs through decreased conjugation or export impairment, amplifying cellular electrophile accumulation. Notably, ferroptosis susceptibility was increased following exacerbation of LDE-adduct export impairment through export channel inhibition. Our results expand understanding of the ferroptosis molecular cell death mechanism to position the LDE detoxification pathway as a ferroptosis-relevant therapeutic target. We envision the ElectrophileQ assay becoming an invaluable tool for studying ferroptosis and cellular health.

A link between altered lipid-derived electrophile (LDE) metabolism during ferroptosis and associated cell death was uncovered using a new imaging method developed to monitor cellular LDE detoxification that employs a fluorogenic LDE analogue.

Unique assemble of carbonylpyridinium and chromene reveal mitochondrial thiol starvation under ferroptosis and novel ferroptosis inducer

To reveal the delicate function of mitochondrial, precise detection tools in spatiotemporal manner remains highly desirable. However, current probes with positive charge warheads for targeting mitochondria diffuse out of the...

Diluted aqueous extract of heat-not-burn tobacco product smoke causes less oxidative damage in fibroblasts than conventional cigarette

Smoke from conventional cigarettes (C-cigarettes) contains various reactive oxygen species and toxic chemicals, which potentially cause oxidative damage not only to airways but also to the whole body, leading eventually to diseases, including emphysema, advanced atherosclerosis, and cancer. Many heat-not-burn tobacco products (HTPs) have been commercialized recently in Japan to maintain the smoking population by advertising that HTPs are less toxic. However, there were few studies reported from neutral organizations whether HTPs are indeed less damaging. To evaluate the potential capacity of HTPs to induce oxidative stress, we here compared two different HTPs with two types of C-cigarettes, using human fibroblast IMR90SV cells and 5% aqueous extracts in 10-ml phosphate-buffered saline (50-ml smoke/10 s). HTPs exhibited significantly lower oxidative toxicity in comparison to C-cigarettes. Whereas C-cigarettes induced ferroptosis in fibroblasts, the effects of HTPs were significantly reduced by measuring the levels of peroxides, pro-inflammatory cytokine expression, autophagy, catalytic Fe(II) and 8-hydroxy-2'-deoxyguanosine. Notably, major portions of C-cigarettes-induced pathogenic responses were inhibited by catalase. However, HTPs still induced p62 autophagy-adaptor at 5%-dilution and caused lethal effects to fibroblasts with undiluted solution. In conclusion, HTPs smoke per se can be toxic despite less toxicity in comparison to C-cigarettes, which warrants further investigation.

Suppression of uterine and placental ferroptosis by N-acetylcysteine in a rat model of polycystic ovary syndrome

The mechanisms that link hyperandrogenism and insulin (INS) resistance (HAIR) to the increased miscarriage rate in women with polycystic ovary syndrome (PCOS) remain elusive. Previous studies demonstrate that increased uterine and placental ferroptosis is associated with oxidative stress-induced fetal loss in a pre-clinical PCOS-like rat model. Here, we investigated the efficacy and molecular mechanism of action of the antioxidant N-acetylcysteine (NAC) in reversing gravid uterine and placental ferroptosis in pregnant rats exposed to 5α-dihydrotestosterone (DHT) and INS. Molecular and histological analyses showed that NAC attenuated DHT and INS-induced uterine ferroptosis, including dose-dependent increases in anti-ferroptosis gene content. Changes in other molecular factors after NAC treatment were also observed in the placenta exposed to DHT and INS, such as increased glutathione peroxidase 4 protein level. Furthermore, increased apoptosis-inducing factor mitochondria-associated 2 mRNA expression was seen in the placenta but not in the uterus. Additionally, NAC was not sufficient to rescue DHT + INS-induced mitochondria-morphological abnormalities in the uterus, whereas the same treatment partially reversed such abnormalities in the placenta. Finally, we demonstrated that NAC selectively normalized uterine leukemia inhibitory factor, osteopontin/secreted phosphoprotein 1, progesterone receptor, homeobox A11 mRNA expression and placental estrogen-related receptor beta and trophoblast-specific protein alpha mRNA expression. Collectively, our data provide insight into how NAC exerts beneficial effects on differentially attenuating gravid uterine and placental ferroptosis in a PCOS-like rat model with fetal loss. These results indicate that exogenous administration of NAC represents a potential therapeutic strategy in the treatment of HAIR-induced uterine and placental dysfunction.

Ferroptosis: New Dawn for Overcoming the Cardio-Cerebrovascular Diseases

The dynamic balance of cardiomyocytes and neurons is essential to maintain the normal physiological functions of heart and brain. If excessive cells die in tissues, serious Cardio-Cerebrovascular Diseases would occur, namely, hypertension, myocardial infarction, and ischemic stroke. The regulation of cell death plays a role in promoting or alleviating Cardio-Cerebrovascular Diseases. Ferroptosis is an iron-dependent new type of cell death that has been proved to occur in a variety of diseases. In our review, we focus on the critical role of ferroptosis and its regulatory mechanisms involved in Cardio-Cerebrovascular Diseases, and discuss the important function of ferroptosis-related inhibitors in order to propose potential implications for the prevention and treatment of Cardio-Cerebrovascular Diseases.

Mitochondrial dysfunction in mouse livers depleted of iron chaperone PCBP1

Iron is an essential nutrient that forms cofactors required for the activity of hundreds of cellular proteins. However, iron can be toxic and must be precisely managed. Poly r(C) binding protein 1 (PCBP1) is an essential, multifunctional protein that binds both iron and nucleic acids, regulating the fate of both. As an iron chaperone, PCBP1 binds cytosolic iron and delivers it to iron enzymes for activation and to ferritin for storage. Mice deleted for PCBP1 in the liver exhibit dysregulated iron balance, with lower levels of liver iron stores and iron enzymes, but higher levels of chemically-reactive iron. Unchaperoned iron triggers the formation of reactive oxygen species, leading to lipid peroxidation and ferroptotic cell death. Hepatic PCBP1 deletion produces chronic liver disease in mice, with steatosis, triglyceride accumulation, and elevated plasma ALT levels. Human and mouse models of fatty liver disease are associated with mitochondrial dysfunction. Here we show that, although deletion of PCBP1 does not affect mitochondrial iron balance, it does affect mitochondrial function. PCBP1 deletion affected mitochondrial morphology and reduced levels of respiratory complexes II and IV, oxygen consumption, and ATP production. Depletion of mitochondrial lipids cardiolipin and coenzyme Q, along with reduction of mitochondrial oxygen consumption, were the first manifestations of mitochondrial dysfunction. Although dietary supplementation with vitamin E ameliorated the liver disease in mice with hepatic PCBP1 deletion, supplementation with coenzyme Q was required to fully restore mitochondrial lipids and function. In conclusion, our studies indicate that mitochondrial function can be restored in livers subjected to ongoing oxidative damage from unchaperoned iron by supplementation with coenzyme Q, a mitochondrial lipid essential for respiration that also functions as a lipophilic radical-trapping agent.

Effect of Camellia sinensis on Fat Peroxidation and Ox-LDL in Rats

Green tea (GT) is believed to have antioxidant properties and beneficial effects on the treatment of some diseases. However, few findings were found concerning the impact of GT on oxidative stress. In the present study, the protective influence of GT against the oxidative stress caused by hydrogen peroxide (H₂O₂) in rats was evaluated. The research groups included a control (Con) group and five groups supplemented with 10g GT(G1), 20g GT(G2), 1% H₂O₂(P), 1% H₂O₂and10g GT (GP1), as well as 1% H₂O₂ and 20g GT(GP2). The effects of GT and H₂O₂ administration on serum biochemical parameters, such as lipid profile, malondialdehyde (MDA), and oxidized low-density lipoprotein (Ox-LDL) were assessed. The findings of this research revealed that the usage of GT lowered the level of cholesterol, triglyceride, LDL, MDA, Ox-LDL and coronary risk index. Moreover, an increase in high-density lipoprotein and very-low-density lipoprotein (VLDL) was observed in subjects who received GT, compared to the rats of the P group. The baseline lipid profile and GT consumption with or without H₂O₂ were the same between the Con and GT-treated groups. Therefore, GT usage was found to be advantageous in reducing Ox-LDL and lipid peroxidation in rats. These results confirm the traditionally claimed benefits of GT for protection against lipid peroxidation and atherosclerosis.

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.

Targeting Ferroptosis for Lung Diseases: Exploring Novel Strategies in Ferroptosis-Associated Mechanisms

Ferroptosis is an iron-dependent regulated necrosis characterized by the peroxidation damage of lipid molecular containing unsaturated fatty acid long chain on the cell membrane or organelle membrane after cellular deactivation restitution system, resulting in the cell membrane rupture. Ferroptosis is biochemically and morphologically distinct and disparate from other forms of regulated cell death. Recently, mounting studies have investigated the mechanism of ferroptosis, and numerous proteins play vital roles in regulating ferroptosis. With detailed studies, emerging evidence indicates that ferroptosis is found in multiple lung diseases, demonstrating that ferroptosis appears to be particularly important for lung diseases. The mounting interest in ferroptosis drugs specifically targeting the ferroptosis mechanism holds substantial therapeutic promise in lung diseases. The present review emphatically summarizes the functions and integrated molecular mechanisms of ferroptosis in various lung diseases, proposing that multiangle regulation of ferroptosis might be a promising strategy for the clinical treatment of lung diseases.

Reactive oxygen species, proinflammatory and immunosuppressive mediators induced in COVID-19: overlapping biology with cancer

This review analyzes the published literature linking the different mechanisms focused on oxidative stress and inflammation that contribute to COVID-19 disease severity. The objective is to bring together potential proinflammatory mechanisms of COVID-19 pathogenesis and address mitigation strategies using naturally occurring compounds and FDA-approved drugs. Outstanding questions addressed include the following: What is the mechanistic basis for linking enhanced vulnerability in COVID-19 to increased oxidative damage and proinflammatory mediators (e.g., cytokines), especially in high-risk people? Can we repurpose anti-inflammatory and immunomodulatory agents to mitigate inflammation in COVID-19 patients? How does 2-deoxy-d-glucose function as an anti-COVID drug? COVID-19, cancer biology, and immunotherapy share many mechanistic similarities. Repurposing drugs that already have been FDA-approved for mitigating inflammation and immunosuppression in cancer may be a way to counteract disease severity, progression, and chronic inflammation in COVID-19. What are the long-term effects of reactive oxygen species-inducing immune cells and sustained inflammation in so-called long-haulers (long COVID) after recovery from COVID-19? Can we use mitochondria-targeted agents prophylactically to prevent inflammation and boost immunity in long-haulers? Addressing the oxidative chemical biology of COVID-19 and the mechanistic commonalities with cancer may provide new insights potentially leading to appropriate clinical trials and new treatments.

Diabetic ferroptosis plays an important role in triggering on inflammation in diabetic wound

Impaired wound healing is a major complication of diabetes and involves sustained inflammation and oxidative stress at the wound site. Here, we investigated the potential involvement of ferroptosis, a newly discovered form of cell death characterized by iron-dependent accumulation of lipid peroxides in the pathogenesis of diabetic wound healing. Fibroblasts and vascular endothelial cells exposed to high glucose concentrations in vitro contained elevated levels of reactive oxygen species (ROS), lipid peroxidation products, and ferroptosis-associated proteins and displayed reduced survival and migration. These effects of high glucose were all significantly reduced by treatment with the ferroptosis inhibitor ferrostatin-1 (Fer-1). Similarly, in a rat model of diabetes, direct application of Fer-1 to the wound site reduced the expression of oxidative stress and inflammation markers and accelerated wound healing via activation of the anti-inflammatory phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway. Our results implicate ferroptosis in wound healing and identify a potential new therapeutic target for difficult-to-treat diabetic wounds.NEW & NOTEWORTHY Ferroptosis-related characteristic changes were found in diabetic wound models. Inhibition of ferroptosis improved inflammatory infiltration of diabetic wounds. PI3K/AKT signal pathway was rescued by restraining of ferroptosis. Mitigation of ferroptosis in diabetic wound promoted the wound healing.

A sequentially activated bioluminescent probe for observation of cellular H2O2 production induced by cysteine

We report herein a caged luciferin probe Cy-Hy as a sequentially activated probe to selectively and sensitively sense L-Cys and H₂O₂. The probe displayed fluorescence and bioluminescence responses toward the two analytes. Utilizing the present probe, cellular excess L-Cys-induced H₂O₂ up-regulation was observed for the first time in living MDA-MB-231 cells.

PIEZO1 Ion Channel Mediates Ionizing Radiation-Induced Pulmonary Endothelial Cell Ferroptosis via Ca2+/Calpain/VE-Cadherin Signaling

Pulmonary endothelial cell dysfunction plays an important role in ionizing radiation (IR)-induced lung injury. Whether pulmonary endothelial cell ferroptosis occurs after IR and what are the underlying mechanisms remain elusive. Here, we demonstrate that 15-Gy IR induced ferroptosis characterized by lethal accumulation of reactive oxygen species (ROS), lipid peroxidation, mitochondria shrinkage, and decreased glutathione peroxidase 4 (GPX4) and SLC7A11 expression in pulmonary endothelial cells. The phenomena could be mimicked by Yoda1, a specific activator of mechanosensitive calcium channel PIEZO1. PIEZO1 protein expression was upregulated by IR in vivo and in vitro. The increased PIEZO1 expression after IR was accompanied with increased calcium influx and increased calpain activity. The effects of radiation on lung endothelial cell ferroptosis was partly reversed by inhibition of PIEZO1 activity using the selective inhibitor GsMTx4 or inhibition of downstreaming Ca²⁺/calpain signaling using PD151746. Both IR and activation of PIEZO1 led to increased degradation of VE-cadherin, while PD151746 blocked these effects. VE-cadherin knockdown by specific siRNA causes ferroptosis-like phenomena with increased ROS and lipid peroxidation in the lung endothelial cells. Overexpression of VE-cadherin partly recused the ferroptosis caused by IR or PIEZO1 activation as supported by decreased ROS production, lipid peroxidation and mitochondria shrinkage compared to IR or PIEZO1 activation alone. In summary, our study reveals a previously unrecognized role of PIEZO1 in modulating ferroptosis, providing a new target for future mitigation of radiation-induced lung injury.

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.

Sources and triggers of oxidative damage in neurodegeneration

Neurodegeneration describes a group of more than 300 neurological diseases, characterised by neuronal loss and intra- or extracellular protein depositions, as key neuropathological features. Multiple factors play role in the pathogenesis of these group of disorders: mitochondrial dysfunction, membrane damage, calcium dyshomeostasis, metallostasis, defect clearance and renewal mechanisms, to name a few. All these factors, without exceptions, have in common the involvement of immensely increased generation of free radicals and occurrence of oxidative stress, and as a result - exhaustion of the scavenging potency of the cellular redox defence mechanisms. Besides genetic predisposition and environmental exposure to toxins, the main risk factor for developing neurodegeneration is age. And although the "Free radical theory of ageing" was declared dead, it is undisputable that accumulation of damage occurs with age, especially in systems that are regulated by free radical messengers and those that oppose oxidative stress, protein oxidation and the accuracy in protein synthesis and degradation machinery has difficulties to be maintained. This brief review provides a comprehensive summary on the main sources of free radical damage, occurring in the setting of neurodegeneration.

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: A potential therapeutic target for neurodegenerative diseases

Ferroptosis is a newly identified regulated form of cell death, which is thought to play a major role in neurodegenerative diseases. In this review, we discuss recent studies elucidating the molecular mechanisms involved in the regulation and execution of ferroptotic cell death and also its role in the brain. Ferroptosis is regulated mainly via iron homeostasis, glutathione metabolism, and lipid peroxidation. Ferroptotic cell death and pro-ferroptotic factors are correlated with the etiopathogenesis of Parkinson's disease (PD) and Alzheimer's disease (AD). Ferroptosis and etiological factors act synergistically in PD and AD pathogenesis. Furthermore, several preclinical and clinical studies targeting ferroptosis in PD and AD have also shown positive results. Evidence of ferroptosis in the brain thus gives new insights into understanding neurodegenerative diseases. Ferroptosis studies in the brain are still in their infancy, but the existing pieces of evidence suggest a strong correlation between ferroptotic cell death and neurodegenerative diseases. Thus, ferroptosis might be a promising target for treating neurodegenerative diseases.

Cell Death via Lipid Peroxidation and Protein Aggregation Diseases

Lipid peroxidation of cellular membranes is a complicated cellular event, and it is both the cause and result of various diseases, such as ischemia-reperfusion injury, neurodegenerative diseases, and atherosclerosis. Lipid peroxidation causes non-apoptotic cell death, which is associated with cell fate determination: survival or cell death. During the radical chain reaction of lipid peroxidation, various oxidized lipid products accumulate in cells, followed by organelle dysfunction and the induction of non-apoptotic cell death. Highly reactive oxidized products from unsaturated fatty acids are detected under pathological conditions. Pathological protein aggregation is the general cause of these diseases. The cellular response to misfolded proteins is well-known as the unfolded protein response (UPR) and it is partially concomitant with the response to lipid peroxidation. Moreover, the association between protein aggregation and non-apoptotic cell death by lipid peroxidation is attracting attention. The link between lipid peroxidation and protein aggregation is a matter of concern in biomedical fields. Here, we focus on lethal protein aggregation in non-apoptotic cell death via lipid peroxidation. We reviewed the roles of protein aggregation in the initiation and execution of non-apoptotic cell death. We also considered the relationship between protein aggregation and oxidized lipid production. We provide an overview of non-apoptotic cell death with a focus on lipid peroxidation for therapeutic targeting during protein aggregation diseases.

Shuganning injection, a traditional Chinese patent medicine, induces ferroptosis and suppresses tumor growth in triple-negative breast cancer cells

BACKGROUND

Triple-negative breast cancer (TNBC), lacking targeted therapies currently, is susceptible to ferroptosis, a recently defined form of cell death.

PURPOSE

To evaluate the anticancer activity of Shuganning injection (SGNI), a traditional Chinese patent medicine, on TNBC cells; To elucidate the mechanism of SGNI induced ferroptosis.

METHODS

The anticancer activity of SGNI was examined via in vitro cell proliferation assays and in vivo xenograft growth assay. Ferroptosis was determined by flow-cytometric analysis of lipid ROS, labile iron pool measurement, and propidium iodide exclusion assay. The dependency on heme oxygenase 1 (HO-1) of SGNI induced ferroptosis was confirmed by genetic knockdown and pharmacological inhibition of the protein.

RESULTS

SGNI selectively inhibited the proliferation of TNBC cells compared to non-TNBC breast cancer cells and normal cells. The cell death induced by SGNI in TNBC cells showed distinct morphology from apoptosis and could not be rescued by the pan-caspase inhibitor Z-VAD(OMe)-FMK. On the other hand, SGNI induced cell death was blocked by the lipid ROS scavengers ferrostatin-1 and liproxstatin-1, the acyl-CoA synthetase long chain family member 4 inhibitor rosiglitazone, and the iron chelators 1,10-phenanthroline and deferoxamine. These data indicated that SGNI induced a ferroptotic cell death of TNBC cells. Mechanistically, SGNI induced ferroptosis was dependent on HO-1, which promotes intracellular labile iron pool accumulation, and was alleviated by HO-1 knockdown and inhibition by tin protoporphyrin IX. In line with the in vitro data, SGNI significantly inhibited the xenograft growth of TNBC cell line MD-MB-231 in nude mice.

CONCLUSION

Collectively, our study elaborates on a promising regimen for TNBC treatment through induction of ferroptosis by SGNI, a traditional Chinese patent medicine currently available in the clinic, which merits further investigation.

Iron Accumulation and Lipid Peroxidation in the Aging Retina: Implication of Ferroptosis in Age-Related Macular Degeneration

Iron is an essential component in many biological processes in the human body. It is critical for the visual phototransduction cascade in the retina. However, excess iron can be toxic. Iron accumulation and reduced efficiency of intracellular antioxidative defense systems predispose the aging retina to oxidative stress-induced cell death. Age-related macular degeneration (AMD) is characterized by retinal iron accumulation and lipid peroxidation. The mechanisms underlying AMD include oxidative stress-mediated death of retinal pigment epithelium (RPE) cells and subsequent death of retinal photoreceptors. Understanding the mechanism of the disruption of iron and redox homeostasis in the aging retina and AMD is crucial to decipher these mechanisms of cell death and AMD pathogenesis. The mechanisms of retinal cell death in AMD are an area of active investigation; previous studies have proposed several types of cell death as major mechanisms. Ferroptosis, a newly discovered programmed cell death pathway, has been associated with the pathogenesis of several neurodegenerative diseases. Ferroptosis is initiated by lipid peroxidation and is characterized by iron-dependent accumulation. In this review, we provide an overview of the mechanisms of iron accumulation and lipid peroxidation in the aging retina and AMD, with an emphasis on ferroptosis.

A Novel Defined Risk Signature of the Ferroptosis-Related Genes for Predicting the Prognosis of Ovarian Cancer

Ferroptosis is an iron-dependent, regulated form of cell death, and the process is complex, consisting of a variety of metabolites and biological molecules. Ovarian cancer (OC) is a highly malignant gynecologic tumor with a poor survival rate. However, the predictive role of ferroptosis-related genes in ovarian cancer prognosis remains unknown. In this study, we demonstrated that the 57 ferroptosis-related genes were expressed differently between ovarian cancer and normal ovarian tissue, and based on these genes, all OC cases can be well divided into 2 subgroups by applying consensus clustering. We utilized the least absolute shrinkage and selection operator (LASSO) cox regression model to develop a multigene risk signature from the TCGA cohort and then validated it in an OC cohort from the GEO database. A 5-gene signature was built and reveals a favorable predictive efficacy in both TCGA and GEO cohort (P < 0.001 and P = 0.03). The GO and KEGG analysis revealed that the differentially expressed genes (DEGs) between the low- and high-risk subgroup divided by our risk model were associated with tumor immunity, and lower immune status in the high-risk group was discovered. In conclusion, ferroptosis-related genes are vital factors predicting the prognosis of OC and could be a novel potential treatment target.