Lysosomal proteolysis is the primary degradation pathway for cytosolic ferritin and cytosolic ferritin degradation is necessary for iron exit

Electromagnetic fields regulate iron metabolism in living organisms: A review of effects and mechanism

The emergence, evolution, and spread of life on Earth have all occurred in the geomagnetic field, and its extensive biological effects on living organisms have been documented. The charged characteristics of metal ions in biological fluids determine that they are affected by electromagnetic field forces, thus affecting life activities. Iron metabolism, as one of the important metal metabolic pathways, keeps iron absorption and excretion in a relatively balanced state, and this process is precisely and completely controlled. It is worth paying attention to how the iron metabolism process of living organisms is changed when exposed to electromagnetic fields. In this paper, the processes of iron absorption, storage and excretion in animals (mammals, fish, arthropods), plants and microorganisms exposed to electromagnetic field were summarized in detail as far as possible, in order to discover the regulation of iron metabolism by electromagnetic field. Studies and data on the effects of electromagnetic field exposure on iron metabolism in organisms show that exposure profiles vary widely across species and cell lines. This process involves a variety of factors, and the complexity of the results is not only related to the magnetic flux density/operating frequency/exposure time and the heterogeneity of the observed object. A systematic review of the biological regulation of iron metabolism by electromagnetic field exposure will not only contributes to a more comprehensive understanding of its biological effects and mechanism, but also is necessary to improve human awareness of the health related risks of electromagnetic field exposure.

The role of lysosomes in airborne particulate matter-induced pulmonary toxicity

An investigation of the potential role of lysosomes in airborne particulate matter (APM) induced health risks is essential to fully comprehend the pathogenic mechanisms of respiratory diseases. It is commonly accepted that APM-induced lung injury is caused by oxidative stress, inflammatory responses, and DNA damage. In addition, there exists abundant evidence that changes in lysosomal function are essential for cellular adaptation to a variety of particulate stimuli. This review emphasizes that disruption of the lysosomal structure/function is a key step in the cellular metabolic imbalance induced by APMs. After being ingested by cells, most particles are localized within lysosomes. Thus, lysosomes become the primary locus where APMs accumulate, and here they undergo degradation and release toxic components. Recent studies have provided incontrovertible evidence that a wide variety of APMs interfere with the normal function of lysosomes. After being stimulated by APMs, lysosome rupture leads to a loss of lysosomal acidic conditions and the inactivation of proteolytic enzymes, promoting an inflammatory response by activating the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome. Moreover, APMs interfere with autophagosome production or block autophagic flux, resulting in autophagy dysfunction. Additionally, APMs disrupt the normal function of lysosomes in iron metabolism, leading to disruption on iron homeostasis. Therefore, understanding the impacts of APM exposure from the perspective of lysosomes will provide new insights into the detrimental consequences of air pollution.

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

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

Ferritinophagy: A novel insight into the double-edged sword in ferritinophagy-ferroptosis axis and human diseases

Nuclear receptor coactive 4 (NCOA4), which functions as a selective cargo receptor, is a critical regulator of the particularly autophagic degradation of ferritin, a process known as ferritinophagy. Mechanistically, NCOA4-mediated ferritinophagy performs an increasingly vital role in the maintenance of intracellular iron homeostasis by promoting ferritin transport and iron release as needed. Ferritinophagy is not only involved in iron-dependent responses but also in the pathogenesis and progression of various human diseases, including metabolism-related, neurodegenerative, cardiovascular and infectious diseases. Therefore, ferritinophagy is of great importance in maintaining cell viability and function and represents a potential therapeutic target. Recent studies indicated that ferritinophagy regulates the signalling pathway associated with ferroptosis, a newly discovered type of cell death characterised by iron-dependent lipid peroxidation. Although accumulating evidence clearly demonstrates the importance of the interplay between dysfunction in iron metabolism and ferroptosis, a deeper understanding of the double-edged sword effect of ferritinophagy in ferroptosis has remained elusive. Details of the mechanisms underlying the ferritinophagy-ferroptosis axis in regulating relevant human diseases remain to be elucidated. In this review, we discuss the latest research findings regarding the mechanisms that regulate the biological function of NCOA4-mediated ferritinophagy and its contribution to the pathophysiology of ferroptosis. The important role of the ferritinophagy-ferroptosis axis in human diseases will be discussed in detail, highlighting the great potential of targeting ferritinophagy in the treatment of diseases.

Clozapine-N-oxide protects dopaminergic neurons against rotenone-induced neurotoxicity by preventing ferritinophagy-mediated ferroptosis

Parkinson's disease (PD) is the second most common neurodegenerative disorder, yet treatment options are limited. Clozapine (CLZ), an antipsychotic used for schizophrenia, has potential as a PD treatment. CLZ and its metabolite, Clozapine-N-Oxide (CNO), show neuroprotective effects on dopaminergic neurons, with mechanisms needing further investigation. This study aimed to confirm the neuroprotective effects of CLZ and CNO in a rotenone-induced mouse model and further explore the underlying mechanisms of CNO-afforded protection. Gait pattern and rotarod activity evaluations showed motor impairments in rotenone-exposed mice, with CLZ or CNO administration ameliorating behavioral deficits. Cell counts and biochemical analysis demonstrated CLZ and CNO's effectiveness in reducing rotenone-induced neurodegeneration of dopaminergic neurons in the nigrostriatal system in mice. Mechanistic investigations revealed that CNO suppressed rotenone-induced ferroptosis of dopaminergic neurons by rectifying iron imbalances, curtailing lipid peroxidation, and mitigating mitochondrial morphological changes. CNO also reversed autolysosome and ferritinophagic activation in rotenone-exposed mice. SH-SY5Y cell cultures validated these findings, indicating ferritinophage involvement, where CNO-afforded protection was diminished by ferritinophagy enhancers. Furthermore, knockdown of NCOA4, a crucial cargo receptor for ferritin degradation in ferritinophagy, hampered rotenone-induced ferroptosis and NCOA4 overexpression countered the anti-ferroptotic effects of CNO. Whereas, iron-chelating agents and ferroptosis enhancers had no effect on the anti-ferritinophagic effects of CNO in rotenone-treated cells. In summary, CNO shielded dopaminergic neurons in the rotenone-induced PD model by modulating NCOA4-mediated ferritinophagy, highlighting a potential therapeutic pathway for PD treatment. This research provided insights into the role of NCOA4 in ferroptosis and suggested new approaches for PD therapy.

To Boost or to Reset: The Role of Lactoferrin in Energy Metabolism

Many pathological conditions, including obesity, diabetes, hypertension, heart disease, and cancer, are associated with abnormal metabolic states. The progressive loss of metabolic control is commonly characterized by insulin resistance, atherogenic dyslipidemia, inflammation, central obesity, and hypertension, a cluster of metabolic dysregulations usually referred to as the "metabolic syndrome". Recently, nutraceuticals have gained attention for the generalized perception that natural substances may be synonymous with health and balance, thus becoming favorable candidates for the adjuvant treatment of metabolic dysregulations. Among nutraceutical proteins, lactoferrin (Lf), an iron-binding glycoprotein of the innate immune system, has been widely recognized for its multifaceted activities and high tolerance. As this review shows, Lf can exert a dual role in human metabolism, either boosting or resetting it under physiological and pathological conditions, respectively. Lf consumption is safe and is associated with several benefits for human health, including the promotion of oral and gastrointestinal homeostasis, control of glucose and lipid metabolism, reduction of systemic inflammation, and regulation of iron absorption and balance. Overall, Lf can be recommended as a promising natural, completely non-toxic adjuvant for application as a long-term prophylaxis in the therapy for metabolic disorders, such as insulin resistance/type II diabetes and the metabolic syndrome.

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

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

Iron-inhibited autophagy via transcription factor ZFP27 in Parkinson's disease

Parkinson's disease (PD) is a challenge because of the ageing of the population and the disease's complicated pathogenesis. Accumulating evidence showed that iron and autophagy were involved in PD. Nevertheless, the molecular mechanism and role of iron and autophagy in PD are not yet elucidated. In the present study, it was shown that PD mice had significant motor dysfunction, increased iron content, less dopamine neurons and more α-synuclein accumulation in the substantia nigra. Meanwhile, PD mice treated with deferoxamine exhibited less iron content, relieved the dyskinesia and had a significant increase in dopamine neurons and a significant decrease in α-synuclein. Autophagy induced by LC3 was inhibited in PD models with iron treatment. Following verification showed that iron aggregation restrained insulin-like growth factor 2 (IGF2) and transcription factor zinc finger protein 27 (ZFP27) in PD models. In addition, LC3-induced autophagy flux was reduced with ZFP27 knockdown. Furthermore, ZFP27 affected autophagy by regulating LC3 promoter activity. These data suggest that iron deposition inhibits IGF2 and ZFP27 to reduce LC3-induced autophagy, and ultimately decrease dopamine neurons, accelerating PD progression. Our findings provide a novel insight that ZFP27-mediated iron-related autophagy and IGF2 may activate the downstream kinase gene to trigger autophagy in the PD model.

Encapsulins: Nanotechnology's future in a shell

Encapsulins, virus capsid-like bacterial nanocompartments have emerged as promising tools in medicine, imaging, and material sciences. Recent work has shown that these protein-bound icosahedral 'organelles' possess distinct properties that make them exceptionally usable for nanotechnology applications. A key factor contributing to their appeal is their ability to self-assemble, coupled with their capacity to encapsulate a wide range of cargos. Their genetic manipulability, stability, biocompatibility, and nano-size further enhance their utility, offering outstanding possibilities for practical biotechnology applications. In particular, their amenability to engineering has led to their extensive modification, including the packaging of non-native cargos and the utilization of the shell surface for displaying immunogenic or targeting proteins and peptides. This inherent versatility, combined with the ease of expressing encapsulins in heterologous hosts, promises to provide broad usability. Although mostly not yet commercialized, encapsulins have started to demonstrate their vast potential for biotechnology, from drug delivery to biofuel production and the synthesis of valuable inorganic materials. In this review, we will initially discuss the structure, function and diversity of encapsulins, which form the basis for these emerging applications, before reviewing ongoing practical uses and highlighting promising applications in medicine, engineering and environmental sciences.

Integrative profiling of metabolome and transcriptome of skeletal muscle after acute exercise intervention in mice

This study aims to explore the molecular regulatory mechanisms of acute exercise in the skeletal muscle of mice. Male C57BL/6 mice were randomly assigned to the control group, and the exercise group, which were sacrificed immediately after an acute bout of exercise. The study was conducted to investigate the metabolic and transcriptional profiling in the quadriceps muscles of mice. The results demonstrated the identification of 34 differentially expressed metabolites (DEMs), with 28 upregulated and 6 downregulated, between the two groups. Metabolic pathway analysis revealed that these DEMs were primarily enriched in several, including the citrate cycle, propanoate metabolism, and lysine degradation pathways. In addition, the results showed a total of 245 differentially expressed genes (DEGs), with 155 genes upregulated and 90 genes downregulated. KEGG analysis indicated that these DEGs were mainly enriched in various pathways such as ubiquitin mediated proteolysis and FoxO signaling pathway. Furthermore, the analysis revealed significant enrichment of DEMs and DEGs in signaling pathways such as protein digestion and absorption, ferroptosis signaling pathway. In summary, the identified multiple metabolic pathways and signaling pathways were involved in the exercise-induced physiological regulation of skeletal muscle, such as the TCA cycle, oxidative phosphorylation, protein digestion and absorption, the FoxO signaling pathway, ubiquitin mediated proteolysis, ferroptosis signaling pathway, and the upregulation of KLF-15, FoxO1, MAFbx, and MuRF1 expression could play a critical role in enhancing skeletal muscle proteolysis.

AKT1 participates in ferroptosis vulnerability by driving autophagic degradation of FTH1 in cisplatin-resistant ovarian cancer

Resistance to cisplatin (DDP)-based chemotherapy is an important reason for the failure of ovarian cancer treatment. However, tumor cells resistant to chemotherapy may expose vulnerability to other cell death pathways. Here, we found that DDP-resistant ovarian cancer cells are more susceptible to erastin-induced ferroptosis. It should be noted that this vulnerability does not depend on the weakening of classical ferroptosis defense proteins, but is caused by the reduction of ferritin heavy chain (FTH1). DDP-resistant ovarian cancer cells maintain a high level of autophagy to escape the pressure of chemotherapy, which ultimately leads to increased autophagic degradation of FTH1. We further revealed that the loss of AKT1 was the reason for the increased autophagy level of DDP-resistant ovarian cancer cells. Our study provides new insights into reversing DDP resistance in ovarian cancer by targeting ferroptosis pathway, and AKT1 may be a molecular marker of susceptibility to ferroptosis.

A ferritin protein is involved in the development and reproduction of the whitefly, Bemisia tabaci

Ferritins are conserved iron-binding proteins that exist in most living organisms and play an essential role in the maintenance of cellular iron homeostasis. Although ferritin has been studied in many species, little is known about its role in the whitefly, Bemisia tabaci. In this study, we identified an iron-binding protein from B. tabaci and named it BtabFer1. The full-length cDNA of BtabFer1 is 1,043 bp and encodes a protein consisting of 224 amino acids with a deduced molecular weight of 25.26 kDa, and phylogenetic analysis shows that BtabFer1 is conserved among Hemiptera insects. The expression levels of BtabFer1 in different developmental stages and tissues were analyzed by real-time PCR, and results showed that BtabFer1 was ubiquitously expressed at all developmental stages and in all examined tissues. The RNAi-mediated knockdown of BtabFer1 caused a significant reduction in survival rate, egg production, and egg hatching rate of whiteflies. Knockdown of BtabFer1 also inhibited the transcription of genes in the juvenile hormone signal transduction pathway. Taken together, these results suggest that BtabFer1 plays a critical role in the development and reproduction of whiteflies. This study can broaden our understanding of ferritin in insect fecundity and development, as well as provide baseline data for future studies.

Perturbed iron biology in the prefrontal cortex of people with schizophrenia

Despite loss of grey matter volume and emergence of distinct cognitive deficits in young adults diagnosed with schizophrenia, current treatments for schizophrenia do not target disruptions in late maturational reshaping of the prefrontal cortex. Iron, the most abundant transition metal in the brain, is essential to brain development and function, but in excess, it can impair major neurotransmission systems and lead to lipid peroxidation, neuroinflammation and accelerated aging. However, analysis of cortical iron biology in schizophrenia has not been reported in modern literature. Using a combination of inductively coupled plasma-mass spectrometry and western blots, we quantified iron and its major-storage protein, ferritin, in post-mortem prefrontal cortex specimens obtained from three independent, well-characterised brain tissue resources. Compared to matched controls (n = 85), among schizophrenia cases (n = 86) we found elevated tissue iron, unlikely to be confounded by demographic and lifestyle variables, by duration, dose and type of antipsychotic medications used or by copper and zinc levels. We further observed a loss of physiologic age-dependent iron accumulation among people with schizophrenia, in that the iron level among cases was already high in young adulthood. Ferritin, which stores iron in a redox-inactive form, was paradoxically decreased in individuals with the disorder. Such iron-ferritin uncoupling could alter free, chemically reactive, tissue iron in key reasoning and planning areas of the young-adult schizophrenia cortex. Using a prediction model based on iron and ferritin, our data provide a pathophysiologic link between perturbed cortical iron biology and schizophrenia and indicate that achievement of optimal cortical iron homeostasis could offer a new therapeutic target.

WDR45 mutation dysregulates iron homeostasis by promoting the chaperone-mediated autophagic degradation of ferritin heavy chain in an ER stress/p38 dependent mechanism

Ferritin is the main iron storage protein that plays a pivotal role in the regulation of iron homeostasis. Mutations in the autophagy protein WD repeat domain 45 (WDR45) that lead to iron overload is associated with the human β-propeller protein-associated neurodegeneration (BPAN). Previous studies have demonstrated that ferritin was decreased in WDR45 deficient cells, but the mechanism remains unclear. In this study, we have demonstrated that the ferritin heavy chain (FTH) could be degraded via chaperone-mediated autophagy (CMA) in ER stress/p38-dependent pathway. In HeLa cells, inducing the ER stress activated CMA, therefore facilitated the degradation of FTH, and increased the content of Fe²⁺. However, the increased CMA activity and Fe²⁺ as well as the decreased FTH by ER stress inducer were restored by pre-treatment with p38 inhibitor. Overexpression of a mutant WDR45 activated CMA thus promoted the degradation of FTH. Furthermore, inhibition of ER stress/p38 pathway resulted in reduced activity of CMA, which consequently elevated the protein level of FTH but reduced the Fe²⁺ level. Our results revealed that WDR45 mutation dysregulates iron homeostasis by activating CMA, and promotes FTH degradation through ER stress/p38 signaling pathway.

Ferroptosis: The functions of Nrf2 in human embryonic stem cells

Human embryonic stem cells (hESCs) have the capacity of self-renewal as well as differentiation towards three germ layer derivatives which makes them as a source of therapeutic application. hESCs are tremendously prone to cell death after dissociation into single cells. Therefore, it technically hinders their applications. Our recent study has revealed that hESCs can be prone to ferroptosis which differs from those in earlier explorations reporting that cellular detachment results in a process cited as anoikis. Ferroptosis occurs via increasing intracellular iron. Therefore, this form of programmed cell death is distinct from other cell deaths in terms of biochemistry, morphology, and genetics. Ferroptosis is found by excessive iron which plays an important part role in reactive oxygen species (ROS) generation through the Fenton reaction as a cofactor. Many genes are related to ferroptosis under the control of nuclear factor erythroid 2-related factor 2 (Nrf2) which is a transcription factor regulating the expression of genes to protect cells from oxidative stress. Nrf2 was demonstrated to take a perilous role in the suppression of ferroptosis by regulating the iron, antioxidant defense enzymes, usage, and restoration of glutathione, thioredoxin, and NADPH. Mitochondrial function is another target of Nrf2 to control cell homeostasis through the modulation of ROS production. In this review, we will give a succinct overview of lipid peroxidation and discuss the major players in the ferroptotic cascade. Additionally, we discussed the important role of the Nrf2 signaling pathway in mediating lipid peroxidation and ferroptosis, with a focus on known Nrf2 target genes that inhibit these processes and their possible role in hESCs.

Modeling the iron storage protein ferritin reveals how residual ferrihydrite iron determines initial ferritin iron sequestration kinetics

Computational models can be created more efficiently by composing them from smaller, well-defined sub-models that represent specific cellular structures that appear often in different contexts. Cellular iron metabolism is a prime example of this as multiple cell types tend to rely on a similar set of components (proteins and regulatory mechanisms) to ensure iron balance. One recurrent component, ferritin, is the primary iron storage protein in mammalian cells and is necessary for cellular iron homeostasis. Its ability to sequester iron protects cells from rising concentrations of ferrous iron limiting oxidative cell damage. The focus of the present work is establishing a model that tractably represents the ferritin iron sequestration kinetics such that it can be incorporated into larger cell models, in addition to contributing to the understanding of general ferritin iron sequestration dynamics within cells. The model's parameter values were determined from published kinetic and binding experiments and the model was validated against independent data not used in its construction. Simulation results indicate that FT concentration is the most impactful on overall sequestration dynamics, while the FT iron saturation (number of iron atoms sequestered per FT cage) fine tunes the initial rates. Finally, because this model has a small number of reactions and species, was built to represent important details of FT kinetics, and has flexibility to include subtle changes in subunit composition, we propose it to be used as a building block in a variety of specific cell type models of iron metabolism.

Lysosome signaling in cell survival and programmed cell death for cellular homeostasis

Recent developments in lysosome biology have transformed our view of lysosomes from static garbage disposals that can also act as suicide bags to decidedly dynamic multirole adaptive operators of cellular homeostasis. Lysosome-governed signaling pathways, proteins, and transcription factors equilibrate the rate of catabolism and anabolism (autophagy to lysosomal biogenesis and metabolite pool maintenance) by sensing cellular metabolic status. Lysosomes also interact with other organelles by establishing contact sites through which they exchange cellular contents. Lysosomal function is critically assessed by lysosomal positioning and motility for cellular adaptation. In this setting, mechanistic target of rapamycin kinase (MTOR) is the chief architect of lysosomal signaling to control cellular homeostasis. Notably, lysosomes can orchestrate explicit cell death mechanisms, such as autophagic cell death and lysosomal membrane permeabilization-associated regulated necrotic cell death, to maintain cellular homeostasis. These lines of evidence emphasize that the lysosomes serve as a central signaling hub for cellular homeostasis.

Review of ferroptosis in colorectal cancer: Friends or foes?

Ferroptosis is a newly discovered type of cell-regulated death. It is characterized by the accumulation of iron-dependent lipid peroxidation and can be distinguished from other forms of cell-regulated death by different morphology, biochemistry, and genetics. Recently, studies have shown that ferroptosis is associated with a variety of diseases, including liver, kidney and neurological diseases, as well as cancer. Ferroptosis has been shown to be associated with colorectal epithelial disorders, which can lead to cancerous changes in the gut. However, the potential role of ferroptosis in the occurrence and development of colorectal cancer (CRC) is still controversial. To elucidate the underlying mechanisms of ferroptosis in CRC, this article systematically reviews ferroptosis, and its cellular functions in CRC, for furthering the understanding of the pathogenesis of CRC to aid clinical treatment.

On the Chemical and Biological Characteristics of Multifunctional Compounds for the Treatment of Parkinson's Disease

Protein aggregation, mitochondrial dysfunction, iron dyshomeostasis, increased oxidative damage and inflammation are pathognomonic features of Parkinson's disease (PD) and other neurodegenerative disorders characterized by abnormal iron accumulation. Moreover, the existence of positive feed-back loops between these pathological components, which accelerate, and sometimes make irreversible, the neurodegenerative process, is apparent. At present, the available treatments for PD aim to relieve the symptoms, thus improving quality of life, but no treatments to stop the progression of the disease are available. Recently, the use of multifunctional compounds with the capacity to attack several of the key components of neurodegenerative processes has been proposed as a strategy to slow down the progression of neurodegenerative processes. For the treatment of PD specifically, the necessary properties of new-generation drugs should include mitochondrial destination, the center of iron-reactive oxygen species interaction, iron chelation capacity to decrease iron-mediated oxidative damage, the capacity to quench free radicals to decrease the risk of ferroptotic neuronal death, the capacity to disrupt α-synuclein aggregates and the capacity to decrease inflammatory conditions. Desirable additional characteristics are dopaminergic neurons to lessen unwanted secondary effects during long-term treatment, and the inhibition of the MAO-B and COMPT activities to increase intraneuronal dopamine content. On the basis of the published evidence, in this work, we review the molecular basis underlying the pathological events associated with PD and the clinical trials that have used single-target drugs to stop the progress of the disease. We also review the current information on multifunctional compounds that may be used for the treatment of PD and discuss the chemical characteristics that underlie their functionality. As a projection, some of these compounds or modifications could be used to treat diseases that share common pathology features with PD, such as Friedreich's ataxia, Multiple sclerosis, Huntington disease and Alzheimer's disease.

Deferiprone attenuates neuropathology and improves outcome following traumatic brain injury

BACKGROUND AND PURPOSE

Traumatic brain injury (TBI) remains a leading cause of mortality and morbidity in young adults. The role of iron in potentiating neurodegeneration following TBI has gained recent interest as iron deposition has been detected in the injured brain in the weeks to months post-TBI, in both the preclinical and clinical setting. A failure in iron homeostasis can lead to oxidative stress, inflammation and excitotoxicity; and whether this is a cause or consequence of the long-term effects of TBI remains unknown.

EXPERIMENTAL APPROACH

We investigated the role of iron and the effect of therapeutic intervention using a brain-permeable iron chelator, deferiprone, in a controlled cortical impact mouse model of TBI. An extensive assessment of cognitive, motor and anxiety/depressive outcome measures were examined, and neuropathological and biochemical changes, over a 3-month period post-TBI.

KEY RESULTS

Lesion volume was significantly reduced at 3 months, which was preceded by a reduction in astrogliosis, microglia/macrophages and preservation of neurons in the injured brain at 2 weeks and/or 1 month post-TBI in mice receiving oral deferiprone. Deferiprone treatment showed significant improvements in neurological severity scores, locomotor/gait performance and cognitive function, and attenuated anxiety-like symptoms post-TBI. Deferiprone reduced iron levels, lipid peroxidation/oxidative stress and altered expression of neurotrophins in the injured brain over this period.

CONCLUSION AND IMPLICATIONS

Our findings support a detrimental role of iron in the injured brain and suggest that deferiprone (or similar iron chelators) may be promising therapeutic approaches to improve survival, functional outcomes and quality of life following TBI.

Lactoferrin: from the structure to the functional orchestration of iron homeostasis

Iron is by far the most widespread and essential transition metal, possessing crucial biological functions for living systems. Despite chemical advantages, iron biology has forced organisms to face with some issues: ferric iron insolubility and ferrous-driven formation of toxic radicals. For these reasons, acquisition and transport of iron constitutes a formidable challenge for cells and organisms, which need to maintain adequate iron concentrations within a narrow range, allowing biological processes without triggering toxic effects. Higher organisms have evolved extracellular carrier proteins to acquire, transport and manage iron. In recent years, a renewed interest in iron biology has highlighted the role of iron-proteins dysregulation in the onset and/or exacerbation of different pathological conditions. However, to date, no resolutive therapy for iron disorders has been found. In this review, we outline the efficacy of Lactoferrin, a member of the transferrin family mainly secreted by exocrine glands and neutrophils, as a new emerging orchestrator of iron metabolism and homeostasis, able to counteract iron disorders associated to different pathologies, including iron deficiency and anemia of inflammation in blood, Parkinson and Alzheimer diseases in the brain and cystic fibrosis in the lung.

Co-regulation of hepatic steatosis by ferritinophagy and unsaturated fatty acid supply

Both iron overload and iron deficiency have been reported in obesity and metabolic syndromes. Due to the presence of multiple intracellular iron pools and the dynamic nature of iron mobilization and use, the actual status and contribution of free and metabolically active iron toward metabolic syndrome remain to be established. The discovery of nuclear receptor coactivator 4 (NCOA4) as a ferritinophagy receptor provides an opening to address the connection between iron and metabolic diseases. This study aims to specifically dissect the role of hepatic ferritinophagy in lipid metabolism and hepatic steatosis. We conducted a series of Ncoa4 gain- and loss-of-function experiments to examine how ferritinophagy affects lipid metabolism through phenotypic and lipidomic analyses both in vitro and in vivo. We show that ferritinophagy is required to release iron from ferritin cages for biological use, and is induced by lipid loading in vitro and during the development of obesity in vivo. Ncoa4 knockdown impairs mitochondrial morphology and reduces palmitate-induced lipid droplet formation in cultured cells and the development of hepatic steatosis in obese mice models. Importantly, the effect of Ncoa4 deficiency on mitochondrial morphology and lipid accumulation is specifically linked to lipidomic reductions in unsaturated fatty acid content in triglycerides and cardiolipins, and an external supply of unsaturated fatty acids reverses these phenotypes. Conclusion: This study shows that ferritinophagy-derived iron supports fatty acid desaturation and the synthesis of unsaturated fatty acid-rich lipids to reduce lipotoxicity. However, the continuous activation of ferritinophagy contributes to the development of hepatic steatosis and liver damage in obesity.

Mechanism of Ferroptosis and Its Role in Spinal Cord Injury

Ferroptosis is a non-necrotic form of regulated cell death (RCD) that is primarily characterized by iron-dependent membrane lipid peroxidation and is regulated by cysteine transport, glutathione synthesis, and glutathione peroxidase 4 function as well as other proteins including ferroptosis suppressor protein 1. It has been found that ferroptosis played an important role in many diseases, such as neurodegenerative diseases and ischemia-reperfusion injury. Spinal cord injury (SCI), especially traumatic SCI, is an urgent problem worldwide due to its high morbidity and mortality, as well as the destruction of functions of the human body. Various RCDs, including ferroptosis, are found in SCI. Different from necrosis, since RCD is a form of cell death regulated by various molecular mechanisms in cells, the study of the role played by RCD in SCI will contribute to a deeper understanding of the pathophysiological process, as well as the treatment and functional recovery. The present review mainly introduces the main mechanism of ferroptosis and its role in SCI, so as to provide a new idea for further exploration.

Light and heavy ferritin chain expression in the liver and kidneys of Wistar rats: aging, sex differences, and impact of gonadectomy

Ferritin is the main intracellular storage of iron. Animal studies show that female liver and kidney express more ferritin and accumulate more iron than male. However, no study so far has investigated sex and age differences in light (FtL) and heavy (FtH) ferritin chain expression. To address this, we relied on specific antibodies and immunochemical methods to analyse the expression of both ferritin chains in the liver and kidney of 3-month and 2-year-old male and female Wistar rats. To see how sex hormones may affect expression we also studied adult animals gonadectomised at the age of 10 weeks. FtL and FtH were more expressed in both organs of female rats, while gonadectomy increased the expression in males and decreased it in females, which suggests that it is stimulated by female and inhibited by male steroid hormones. Normal kidney ferritin distribution and change with aging warrant more attention in studies of (patho) physiological and toxicological processes.

Non-canonical vs. Canonical Functions of Heme Oxygenase-1 in Cancer

Heme oxygenase-1 (HO-1) is a critical stress-responsive enzyme that has antioxidant and anti-inflammatory functions. HO-1 catalyzes heme degradation, which gives rise to the formation of carbon monoxide (CO), biliverdin, and iron. The upregulation of HO-1 under pathological conditions associated with cellular stress represents an important cytoprotective defense mechanism by virtue of the anti-oxidant properties of the bilirubin and the anti-inflammatory effect of the CO produced. The same mechanism is hijacked by premalignant and cancerous cells. In recent years, however, there has been accumulating evidence supporting that the upregulation of HO-1 promotes cancer progression, independently of its catalytic activity. Such non-canonical functions of HO-1 are associated with its interaction with other proteins, particularly transcription factors. HO-1 also undergoes post-translational modifications that influence its stability, functional activity, cellular translocation, etc. HO-1 is normally present in the endoplasmic reticulum, but distinct subcellular localizations, especially in the nucleus, are observed in multiple cancers. The nuclear HO-1 modulates the activation of various transcription factors, which does not appear to be mediated by carbon monoxide and iron. This commentary summarizes the non-canonical functions of HO-1 in the context of cancer growth and progression and underlying regulatory mechanisms.

Non-canonical vs. Canonical Functions of Heme Oxygenase-1 in Cancer

Heme oxygenase-1 (HO-1) is a critical stress-responsive enzyme that has antioxidant and anti-inflammatory functions. HO-1 catalyzes heme degradation, which gives rise to the formation of carbon monoxide (CO), biliverdin, and iron. The upregulation of HO-1 under pathological conditions associated with cellular stress represents an important cytoprotective defense mechanism by virtue of the anti-oxidant properties of the bilirubin and the anti-inflammatory effect of the CO produced. The same mechanism is hijacked by premalignant and cancerous cells. In recent years, however, there has been accumulating evidence supporting that the upregulation of HO-1 promotes cancer progression, independently of its catalytic activity. Such non-canonical functions of HO-1 are associated with its interaction with other proteins, particularly transcription factors. HO-1 also undergoes post-translational modifications that influence its stability, functional activity, cellular translocation, etc. HO-1 is normally present in the endoplasmic reticulum, but distinct subcellular localizations, especially in the nucleus, are observed in multiple cancers. The nuclear HO-1 modulates the activation of various transcription factors, which does not appear to be mediated by carbon monoxide and iron. This commentary summarizes the non-canonical functions of HO-1 in the context of cancer growth and progression and underlying regulatory mechanisms.

[Molecular Mechanisms Underlying Cellular Responses to the Loading of Non-thermal Atmospheric Pressure Plasma-activated Solutions]

Plasma medicine is a rapidly expanding new field of interdisciplinary research that combines physics, chemistry, biology, and medicine. Non-thermal atmospheric pressure plasma (NTAPP) has recently been applied to living cells and tissues, and has emerged as a novel technology for medical applications, such as wound healing, blood coagulation, and cancer treatment. NTAPP was found to affect cells indirectly through the treatment of cells with previously prepared medium irradiated by NTAPP, termed plasma-activated medium (PAM). The treatment of culture media with NTAPP results in the generation of a large amount of reactive oxygen species and reactive nitrogen species, and their derived species. We found that PAM triggered a spiral apoptotic cascade in the mitochondrial-nuclear network in A549 cancer cells. This process induced the depletion of total cellular NAD⁺ and elevations in intracellular calcium ion, ultimately leading to cell death. We also detected the production of hydroxyl radical and elevations in intracellular ferrous ions in PAM-treated cells. The elevations observed in ferrous ions may have been due to their release from the intracellular iron store, ferritin. However, difficulties are associated with applying PAM to the clinical phase because culture media cannot be used for medical treatments. The anti-tumor activity of plasma-activated Ringer's solution was significantly stronger than that of PAM. At the end, we herein demonstrated the advantages of the combined application of plasma-activated acetate Ringer's solution and hyperthermia, a heat treatment at 42℃, for A549 cancer cell death and elucidated the underlying mechanisms.

Release of Iron-Loaded Ferritin in Sodium Iodate-Induced Model of Age Related Macular Degeneration: An In-Vitro and In-Vivo Study

To evaluate the role of iron in sodium iodate (NaIO3)-induced model of age-related macular degeneration (AMD) in ARPE-19 cells in-vitro and in mouse models in-vivo. ARPE-19 cells, a human retinal pigment epithelial cell line, was exposed to 10 mM NaIO3 for 24 h, and the expression and localization of major iron modulating proteins was evaluated by Western blotting (WB) and immunostaining. Synthesis and maturation of cathepsin-D (cat-D), a lysosomal enzyme, was evaluated by quantitative reverse-transcriptase polymerase chain reaction (RT-qPCR) and WB, respectively. For in-vivo studies, C57BL/6 mice were injected with 40 mg/kg mouse body weight of NaIO3 intraperitoneally, and their retina was evaluated after 3 weeks as above. NaIO3 induced a 10-fold increase in ferritin in ARPE-19 cells, which co-localized with LC3II, an autophagosomal marker, and LAMP-1, a lysosomal marker. A similar increase in ferritin was noted in retinal lysates and retinal sections of NaIO3-injected mice by WB and immunostaining. Impaired synthesis and maturation of cat-D was also noted. Accumulated ferritin was loaded with iron, and released from retinal pigmented epithelial (RPE) cells in Perls' and LAMP-1 positive vesicles. NaIO3 impairs lysosomal degradation of ferritin by decreasing the transcription and maturation of cat-D in RPE cells. Iron-loaded ferritin accumulates in lysosomes and is released in lysosomal membrane-enclosed vesicles to the extracellular milieu. Accumulation of ferritin in RPE cells and fusion of ferritin-containing vesicles with adjacent photoreceptor cells is likely to create an iron overload, compromising their viability. Moreover, reduced activity of cat-D is likely to promote accumulation of other cellular debris in lysosomal vesicles, contributing to AMD-like pathology.

Iron robbery by intracellular pathogen via bacterial effector-induced ferritinophagy

Ehrlichia chaffeensis infects and proliferates inside monocytes and macrophages by acquiring iron from the cellular labile iron pool and causes a potentially fatal disease called human monocytic ehrlichiosis. This report reveals a unique bacterial iron hijacking mechanism. Ehrlichia deploys a protein Etf-3 via the bacteria type IV secretion system. Etf-3 binds ferritin and induces ferritinophagy, thereby increasing the cellular labile iron pool for Ehrlichia to acquire iron for intracellular proliferation. This, in concert with coregulation of bacterial and host cell superoxide dismutases with type IV secretion system, enables Ehrlichia to prevent reactive oxygen species–induced host cell damage mediated by labile iron. This finding unifies current concepts of intracellular bacterial infection, ferritinophagy, and ROS, which may be exploited to inhibit Ehrlichia infection.

Iron is essential for survival and proliferation of Ehrlichia chaffeensis, an obligatory intracellular bacterium that causes an emerging zoonosis, human monocytic ehrlichiosis. However, how Ehrlichia acquires iron in the host cells is poorly understood. Here, we found that native and recombinant (cloned into the Ehrlichia genome) Ehrlichia translocated factor-3 (Etf-3), a previously predicted effector of the Ehrlichia type IV secretion system (T4SS), is secreted into the host cell cytoplasm. Secreted Etf-3 directly bound ferritin light chain with high affinity and induced ferritinophagy by recruiting NCOA4, a cargo receptor that mediates ferritinophagy, a selective form of autophagy, and LC3, an autophagosome biogenesis protein. Etf-3−induced ferritinophagy caused ferritin degradation and significantly increased the labile cellular iron pool, which feeds Ehrlichia. Indeed, an increase in cellular ferritin by ferric ammonium citrate or overexpression of Etf-3 or NCOA4 enhanced Ehrlichia proliferation, whereas knockdown of Etf-3 in Ehrlichia via transfection with a plasmid encoding an Etf-3 antisense peptide nucleic acid inhibited Ehrlichia proliferation. Excessive ferritinophagy induces the generation of toxic reactive oxygen species (ROS), which could presumably kill both Ehrlichia and host cells. However, during Ehrlichia proliferation, we observed concomitant up-regulation of Ehrlichia Fe-superoxide dismutase, which is an integral component of Ehrlichia T4SS operon, and increased mitochondrial Mn-superoxide dismutase by cosecreted T4SS effector Etf-1. Consequently, despite enhanced ferritinophagy, cellular ROS levels were reduced in Ehrlichia-infected cells compared with uninfected cells. Thus, Ehrlichia safely robs host cell iron sequestered in ferritin. Etf-3 is a unique example of a bacterial protein that induces ferritinophagy to facilitate pathogen iron capture.

WDR45, one gene associated with multiple neurodevelopmental disorders

The WDR45 gene is localized on the X-chromosome and variants in this gene are linked to six different neurodegenerative disorders, i.e., ß-propeller protein associated neurodegeneration, Rett-like syndrome, intellectual disability, and epileptic encephalopathies including developmental and epileptic encephalopathy, early-onset epileptic encephalopathy and West syndrome and potentially also specific malignancies. WDR45/WIPI4 is a WD-repeat β-propeller protein that belongs to the WIPI (WD repeat domain, phosphoinositide interacting) family. The precise cellular function of WDR45 is still largely unknown, but deletions or conventional variants in WDR45 can lead to macroautophagy/autophagy defects, malfunctioning mitochondria, endoplasmic reticulum stress and unbalanced iron homeostasis, suggesting that this protein functions in one or more pathways regulating directly or indirectly those processes. As a result, the underlying cause of the WDR45-associated disorders remains unknown. In this review, we summarize the current knowledge about the cellular and physiological functions of WDR45 and highlight how genetic variants in its encoding gene may contribute to the pathophysiology of the associated diseases. In particular, we connect clinical manifestations of the disorders with their potential cellular origin of malfunctioning and critically discuss whether it is possible that one of the most prominent shared features, i.e., brain iron accumulation, is the primary cause for those disorders.

Abbreviations: ATG/Atg: autophagy related; BPAN: ß-propeller protein associated neurodegeneration; CNS: central nervous system; DEE: developmental and epileptic encephalopathy; EEG: electroencephalograph; ENO2/neuron-specific enolase, enolase 2; EOEE: early-onset epileptic encephalopathy; ER: endoplasmic reticulum; ID: intellectual disability; IDR: intrinsically disordered region; MRI: magnetic resonance imaging; NBIA: neurodegeneration with brain iron accumulation; NCOA4: nuclear receptor coactivator 4; PtdIns3P: phosphatidylinositol-3-phosphate; RLS: Rett-like syndrome; WDR45: WD repeat domain 45; WIPI: WD repeat domain, phosphoinositide interacting

NCOA4 is regulated by HIF and mediates mobilization of murine hepatic iron stores after blood loss

The mechanisms by which phlebotomy promotes the mobilization of hepatic iron stores are not well understood. NCOA4 (nuclear receptor coactivator 4) is a widely expressed intracellular protein previously shown to mediate the autophagic degradation of ferritin. Here, we investigate a local requirement for NCOA4 in the regulation of hepatic iron stores and examine mechanisms of NCOA4 regulation. Hepatocyte-targeted Ncoa4 knockdown in nonphlebotomized mice had only modest effects on hepatic ferritin subunit levels and nonheme iron concentration. After phlebotomy, mice with hepatocyte-targeted Ncoa4 knockdown exhibited anemia and hypoferremia similar to control mice with intact Ncoa4 regulation but showed a markedly impaired ability to lower hepatic ferritin subunit levels and hepatic nonheme iron concentration. This impaired hepatic response was observed even when dietary iron was limited. In both human and murine hepatoma cell lines, treatment with chemicals that stabilize hypoxia inducible factor (HIF), including desferrioxamine, cobalt chloride, and dimethyloxalylglycine, raised NCOA4 messenger RNA. This NCOA4 messenger RNA induction occurred within 3 hours, preceded a rise in NCOA4 protein, and was attenuated in the setting of dual HIF-1α and HIF-2α knockdown. In summary, we show for the first time that NCOA4 plays a local role in facilitating iron mobilization from the liver after blood loss and that HIF regulates NCOA4 expression in cells of hepatic origin. Because the prolyl hydroxylases that regulate HIF stability are oxygen- and iron-dependent enzymes, our findings suggest a novel mechanism by which hypoxia and iron deficiency may modulate NCOA4 expression to impact iron homeostasis.

New Insights into the Role of Ferritin in Iron Homeostasis and Neurodegenerative Diseases

Growing evidence has indicated that iron deposition is one of the key factors leading to neuronal death in the neurodegenerative diseases. Ferritin is a hollow iron storage protein composed of 24 subunits of two types, ferritin heavy chain (FTH) and ferritin light chain (FTL), which plays an important role in maintaining iron homeostasis. Recently, the discovery of extracellular ferritin and ferritin in exosomes indicates that ferritin might be not only an iron storage protein within the cell, but might also be an important factor in the regulation of tissue and body iron homeostasis. In this review, we first described the structural characteristics, regulation and the physiological functions of ferritin. Secondly, we reviewed the current evidence concerning the mechanisms underlying the secretion of ferritin and the possible role of secreted ferritin in the brain. Then, we summarized the relationship between ferritin and the neurodegenerative diseases including Parkinson's disease (PD), Alzheimer's disease (AD) and neuroferritinopathy (NF). Given the importance and relationship between iron and neurodegenerative diseases, understanding the role of ferritin in the brain can be expected to contribute to our knowledge of iron dysfunction and neurodegenerative diseases.

Role of ferritinophagy in cystine deprivation-induced cell death in glioblastoma cells

Ferroptosis is a form of cell death caused by iron-dependent lipid peroxidation. Cancer cells increase cystine uptake for the synthesis of glutathione (GSH), which is used by glutathione peroxidase 4 to reduce lipid peroxides. Here, we report that cystine deprivation in glioblastoma cells, but not inhibition of GSH synthesis by l-buthionine sulfoximine (BSO), induces ferroptosis. We found that cystine deprivation decreased the protein levels of ferritin heavy chain FTH1, whereas it was increased by BSO treatment. The lysosome inhibitor bafilomycin A1 or deletion of nuclear receptor coactivator 4 (NCOA4) inhibited cystine deprivation-induced decrease in FTH1 protein levels and cell death. In addition, cystine deprivation induced microtubule-associated protein light chain 3 (LC3)-II protein accumulation, suggesting that cystine deprivation induces ferritinophagy. BSO causes cell death when glioblastoma cells are treated with iron inducers, ferrous ammonium sulfate or hemin. On the other hand, cystine deprivation-induced degradation of FTH1 and cell death required glutamine. This study suggests that ferritinophagy, in addition to GSH depletion, plays an important role in cystine deprivation-induced ferroptosis in glioblastoma cells.

The Role of NCOA4-Mediated Ferritinophagy in Ferroptosis

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

The role of lysosome in regulated necrosis

Lysosome is a ubiquitous acidic organelle fundamental for the turnover of unwanted cellular molecules, particles, and organelles. Currently, the pivotal role of lysosome in regulating cell death is drawing great attention. Over the past decades, we largely focused on how lysosome influences apoptosis and autophagic cell death. However, extensive studies showed that lysosome is also prerequisite for the execution of regulated necrosis (RN). Different types of RN have been uncovered, among which, necroptosis, ferroptosis, and pyroptosis are under the most intensive investigation. It becomes a hot topic nowadays to target RN as a therapeutic intervention, since it is important in many patho/physiological settings and contributing to numerous diseases. It is promising to target lysosome to control the occurrence of RN thus altering the outcomes of diseases. Therefore, we aim to give an introduction about the common factors influencing lysosomal stability and then summarize the current knowledge on the role of lysosome in the execution of RN, especially in that of necroptosis, ferroptosis, and pyroptosis.

Iron Metabolism in Oligodendrocytes and Astrocytes, Implications for Myelination and Remyelination

Iron is a key nutrient for normal central nervous system (CNS) development and function; thus, iron deficiency as well as iron excess may result in harmful effects in the CNS. Oligodendrocytes and astrocytes are crucial players in brain iron equilibrium. However, the mechanisms of iron uptake, storage, and efflux in oligodendrocytes and astrocytes during CNS development or under pathological situations such as demyelination are not completely understood. In the CNS, iron is directly required for myelin production as a cofactor for enzymes involved in ATP, cholesterol and lipid synthesis, and oligodendrocytes are the cells with the highest iron levels in the brain which is linked to their elevated metabolic needs associated with the process of myelination. Unlike oligodendrocytes, astrocytes do not have a high metabolic requirement for iron. However, these cells are in close contact with blood vessel and have a strong iron transport capacity. In several pathological situations, changes in iron homoeostasis result in altered cellular iron distribution and accumulation and oxidative stress. In inflammatory demyelinating diseases such as multiple sclerosis, reactive astrocytes accumulate iron and upregulate iron efflux and influx molecules, which suggest that they are outfitted to take up and safely recycle iron. In this review, we will discuss the participation of oligodendrocytes and astrocytes in CNS iron homeostasis. Understanding the molecular mechanisms of iron uptake, storage, and efflux in oligodendrocytes and astrocytes is necessary for planning effective strategies for iron management during CNS development as well as for the treatment of demyelinating diseases.

Biochemistry of mammalian ferritins in the regulation of cellular iron homeostasis and oxidative responses

Ferritin, an iron-storage protein, regulates cellular iron metabolism and oxidative stress. The ferritin structure is characterized as a spherical cage, inside which large amounts of iron are deposited in a safe, compact and bioavailable form. All ferritins readily catalyze Fe(II) oxidation by peroxides at the ferroxidase center to prevent free Fe(II) from participating in oxygen free radical formation via Fenton chemistry. Thus, ferritin is generally recognized as a cytoprotective stratagem against intracellular oxidative damage The expression of cytosolic ferritins is usually regulated by iron status and oxidative stress at both the transcriptional and post-transcriptional levels. The mechanism of ferritin-mediated iron recycling is far from clarified, though nuclear receptor co-activator 4 (NCOA4) was recently identified as a cargo receptor for ferritin-based lysosomal degradation. Cytosolic ferritins are heteropolymers assembled by H- and L-chains in different proportions. The mitochondrial ferritins are homopolymers and distributed in restricted tissues. They play protective roles in mitochondria where heme- and Fe/S-enzymes are synthesized and high levels of ROS are produced. Genetic ferritin disorders are mainly related to the L-chain mutations, which generally cause severe movement diseases. This review is focused on the biochemistry and function of mammalian intracellular ferritin as the major iron-storage and anti-oxidation protein.

High-Throughput Screening for the Discovery of Iron Homeostasis Modulators Using an Extremely Sensitive Fluorescent Probe

High-throughput methods for monitoring subcellular labile Fe(II) are important for conducting studies on iron homeostasis and for the discovery of potential drug candidates for the treatment of iron deficiency or overload. Herein, a highly sensitive and robust fluorescent probe for the detection of intracellular labile Fe(II) is described. The probe was designed through the rational optimization of the reactivity and responsiveness for an Fe(II)-induced fluorogenic reaction based on deoxygenation of an N-oxide, which was developed in-house. The probe is ready to use for a 96-well-plate-based high-content imaging of labile Fe(II) in living cells. Using this simple method, we were able to conduct high-throughput screening of a chemical library containing 3399 compounds. The compound lomofungin was identified as a potential drug candidate for the intracellular enhancement of labile Fe(II) via a novel mechanism in which the ferritin protein was downregulated.

The function and mechanism of ferroptosis in cancer

Ferroptosis is a newly defined form of regulated cell death (RCD) characterized by iron overload, lipid reactive oxygen species (ROS) accumulation, and lipid peroxidation, which is different from necrosis, apoptosis, autophagy and other forms of RCD in morphology, biochemistry, function and gene expression. Increasing evidence has shown that ferroptosis is intimately associated with cancer initiation, progression, and suppression. In this review, we summarize the primary mechanisms and signal pathways relevant to ferroptosis and then discuss the potential roles of ferroptosis in cancer, including those related to p53, noncoding RNA (ncRNA), and the tumor microenvironment (TME), to demonstrate the associations between ferroptosis and cancer. Moreover, we list some ferroptosis-based cancer therapies, such as clinical drugs, nanomaterials, exosomes and gene technology, based on previous studies. Finally, we propose some development avenues, challenges, and opportunities for further research on ferroptosis.

Impaired Postnatal Myelination in a Conditional Knockout Mouse for the Ferritin Heavy Chain in Oligodendroglial Cells

To define the importance of iron storage in oligodendrocyte development and function, the ferritin heavy subunit (Fth) was specifically deleted in oligodendroglial cells. Blocking Fth synthesis in Sox10 or NG2-positive oligodendrocytes during the first or the third postnatal week significantly reduces oligodendrocyte iron storage and maturation. The brain of Fth KO animals presented an important decrease in the expression of myelin proteins and a substantial reduction in the percentage of myelinated axons. This hypomyelination was accompanied by a decline in the number of myelinating oligodendrocytes and with a reduction in proliferating oligodendrocyte progenitor cells (OPCs). Importantly, deleting Fth in Sox10-positive oligodendroglial cells after postnatal day 60 has no effect on myelin production and/or oligodendrocyte quantities. We also tested the capacity of Fth-deficient OPCs to remyelinate the adult brain in the cuprizone model of myelin injury and repair. Fth deletion in NG2-positive OPCs significantly reduces the number of mature oligodendrocytes and myelin production throughout the remyelination process. Furthermore, the corpus callosum of Fth KO animals presented a significant decrease in the percentage of remyelinated axons and a substantial reduction in the average myelin thickness. These results indicate that Fth synthesis during the first three postnatal weeks is important for an appropriate oligodendrocyte development, and suggest that Fth iron storage in adult OPCs is also essential for an effective remyelination of the mouse brain.SIGNIFICANCE STATEMENT To define the importance of iron storage in oligodendrocyte function, we have deleted the ferritin heavy chain (Fth) specifically in the oligodendrocyte lineage. Fth ablation in oligodendroglial cells throughout early postnatal development significantly reduces oligodendrocyte maturation and myelination. In contrast, deletion of Fth in oligodendroglial cells after postnatal day 60 has no effect on myelin production and/or oligodendrocyte numbers. We have also tested the consequences of disrupting Fth iron storage in oligodendrocyte progenitor cells (OPCs) after demyelination. We have found that Fth deletion in NG2-positive OPCs significantly delays the remyelination process in the adult brain. Therefore, Fth iron storage is essential for early oligodendrocyte development as well as for OPC maturation in the demyelinated adult brain.

Whole-Genome Resequencing of Twenty Branchiostoma belcheri Individuals Provides a Brand-New Variant Dataset for Branchiostoma

As the extant representatives of the basal chordate lineage, amphioxi (including the genera Branchiostoma, Asymmetron and Epigonichthys) play important roles in tracing the state of chordate ancestry. Previous studies have reported that members of the Branchiostoma species have similar morphological phenotypic characteristics, but in contrast, there are high levels of genetic polymorphisms in the populations. Here, we resequenced 20 Branchiostomabelcheri genomes to an average depth of approximately 12.5X using the Illumina HiSeq 2000 platform. In this study, over 52 million variations (~12% of the total genome) were detected in the B. belcheri population, and an average of 12.8 million variations (~3% of the total genome) were detected in each individual, confirming that Branchiostoma is one of the most genetically diverse species sequenced to date. Demographic inference analysis highlighted the role of historical global temperature in the long-term population dynamics of Branchiostoma, and revealed a population expansion at the Greenlandian stage of the current geological epoch. We detected 594 Single nucleotide polymorphism and 148 Indels in the Branchiostoma mitochondrial genome, and further analyzed their genetic mutations. A recent study found that the epithelial cells of the digestive tract in Branchiostoma can directly phagocytize food particles and convert them into absorbable nontoxic nutrients using powerful digestive and immune gene groups. In this study, we predicted all potential mutations in intracellular digestion-associated genes. The results showed that most “probably damaging” mutations were related to rare variants (MAF<0.05) involved in strengthening or weakening the intracellular digestive capacity of Branchiostoma. Due to the extremely high number of polymorphisms in the Branchiostoma genome, our analysis with a depth of approximately 12.5X can only be considered a preliminary analysis. However, the novel variant dataset provided here is a valuable resource for further investigation of phagocytic intracellular digestion in Branchiostoma and determination of the phenotypic and genotypic features of Branchiostoma.

O-GlcNAcylation-dependent upregulation of HO1 triggers ammonia-induced oxidative stress and senescence in hepatic encephalopathy

BACKGROUND & AIMS

Cerebral oxidative stress plays an important role in the pathogenesis of hepatic encephalopathy (HE), but the underlying mechanisms are incompletely understood. Herein, we analyzed a role of heme oxygenase (HO)1, iron and NADPH oxidase 4 (Nox4) for the induction of oxidative stress and senescence in HE.

METHODS

Gene and protein expression in human post-mortem brain samples was analyzed by gene array and western blot analysis. Mechanisms and functional consequences of HO1 upregulation were studied in NH₄Cl-exposed astrocytes in vitro by western blot, qPCR and super-resolution microscopy.

RESULTS

HO1 and the endoplasmic reticulum (ER) stress marker grp78 were upregulated, together with changes in the expression of multiple iron metabolism-related genes, in post-mortem brain samples from patients with liver cirrhosis and HE. NH₄Cl elevated HO1 protein and mRNA in cultured astrocytes through glutamine synthetase (GS)-dependent upregulation of glutamine/fructose amidotransferases 1/2 (GFAT1/2), which blocked the transcription of the HO1-targeting miR326-3p in a O-GlcNAcylation dependent manner. Upregulation of HO1 by NH₄Cl triggered ER stress and was associated with elevated levels of free ferrous iron and expression changes in iron metabolism-related genes, which were largely abolished after knockdown or inhibition of GS, GFAT1/2, HO1 or iron chelation. NH₄Cl, glucosamine (GlcN) and inhibition of miR326-3p upregulated Nox4, while knockdown of Nox4, GS, GFAT1/2, HO1 or iron chelation prevented NH₄Cl-induced RNA oxidation and astrocyte senescence. Elevated levels of grp78 and O-GlcNAcylated proteins were also found in brain samples from patients with liver cirrhosis and HE.

CONCLUSION

The present study identified glucosamine synthesis-dependent protein O-GlcNAcylation as a novel mechanism in the pathogenesis of HE that triggers oxidative and ER stress, as well as senescence, through upregulation of HO1 and Nox4.

LAY SUMMARY

Patients with liver cirrhosis frequently exhibit hyperammonemia and suffer from cognitive and motoric dysfunctions, which at least in part involve premature ageing of the astrocytes in the brain. This study identifies glucosamine and an O-GlcNAcylation-dependent disruption of iron homeostasis as novel triggers of oxidative stress, thereby mediating ammonia toxicity in the brain.

Beta-propeller protein-associated neurodegeneration (BPAN) as a genetically simple model of multifaceted neuropathology resulting from defects in autophagy

Autophagy is an essential and conserved cellular homeostatic process. Defects in the core and accessory components of the autophagic machinery would most severely impact terminally differentiated cells, such as neurons. The neurodevelopmental/neurodegenerative disorder β-propeller protein-associated neurodegeneration (BPAN) resulted from heterozygous or hemizygous germline mutations/pathogenic variant of the X chromosome geneWDR45, encoding WD40 repeat protein interacting with phosphoinositides 4 (WIPI4). This most recently identified subtype of the spectrum of neurodegeneration with brain iron accumulation diseases is characterized by a biphasic mode of disease manifestation and progression. The first phase involves early-onset of epileptic seizures, global developmental delay, intellectual disability and autistic syndrome. Subsequently, Parkinsonism and dystonia, as well as dementia, emerge in a subacute manner in adolescence or early adulthood. BPAN disease phenotypes are thus complex and linked to a wide range of other neuropathological disorders. WIPI4/WDR45 has an essential role in autophagy, acting as a phosphatidylinositol 3-phosphate binding effector that participates in autophagosome biogenesis and size control. Here, we discuss recent updates on WIPI4’s mechanistic role in autophagy and link the neuropathological manifestations of BPAN’s biphasic infantile onset (epilepsy, autism) and adolescent onset (dystonic, Parkinsonism, dementia) phenotypes to neurological consequences of autophagy impairment that are now known or emerging in many other neurodevelopmental and neurodegenerative disorders. As monogenicWDR45mutations in BPAN result in a large spectrum of disease phenotypes that stem from autophagic dysfunctions, it could potentially serve as a simple and unique genetic model to investigate disease pathology and therapeutics for a wider range of neuropathological conditions with autophagy defects.

Phagocytic intracellular digestion in amphioxus (Branchiostoma)

The digestive methods employed by amphioxus (Branchiostoma)—both intracellular phagocytic digestion and extracellular digestion—have been discussed since 1937. Recent studies also show that epithelial cells lining the Branchiostoma digestive tract can express many immune genes. Here, in Branchiostoma belcheri, using a special tissue fixation method, we show that some epithelial cells, especially those lining the large diverticulum protruding from the gut tube, phagocytize food particles directly, and Branchiostoma can rely on this kind of phagocytic intracellular digestion to obtain energy throughout all stages of its life. Gene expression profiles suggest that diverticulum epithelial cells have functional features of both digestive cells and phagocytes. In starved Branchiostoma, these cells accumulate endogenous digestive and hydrolytic enzymes, whereas, when sated, they express many kinds of immune genes in response to stimulation by phagocytized food particles. We also found that the distal hindgut epithelium can phagocytize food particles, but not as many. These results illustrate phagocytic intercellular digestion in Branchiostoma, explain why Branchiostoma digestive tract epithelial cells express typical immune genes and suggest that the main physiological function of the Branchiostoma diverticulum is different from that of the vertebrate liver.

Iron catalysis of lipid peroxidation in ferroptosis: Regulated enzymatic or random free radical reaction?

Duality of iron as an essential cofactor of many enzymatic metabolic processes and as a catalyst of poorly controlled redox-cycling reactions defines its possible biological beneficial and hazardous role in the body. In this review, we discuss these two "faces" of iron in a newly conceptualized program of regulated cell death, ferroptosis. Ferroptosis is a genetically programmed iron-dependent form of regulated cell death driven by enhanced lipid peroxidation and insufficient capacity of thiol-dependent mechanisms (glutathione peroxidase 4, GPX4) to eliminate hydroperoxy-lipids. We present arguments favoring the enzymatic mechanisms of ferroptotically engaged non-heme iron of 15-lipoxygenases (15-LOX) in complexes with phosphatidylethanolamine binding protein 1 (PEBP1) as a catalyst of highly selective and specific oxidation reactions of arachidonoyl- (AA) and adrenoyl-phosphatidylethanolamines (PE). We discuss possible role of iron chaperons as control mechanisms for guided iron delivery directly to their "protein clients" thus limiting non-enzymatic redox-cycling reactions. We also consider opportunities of loosely-bound iron to contribute to the production of pro-ferroptotic lipid oxidation products. Finally, we propose a two-stage iron-dependent mechanism for iron in ferroptosis by combining its catalytic role in the 15-LOX-driven production of 15-hydroperoxy-AA-PE (HOO-AA-PE) as well as possible involvement of loosely-bound iron in oxidative cleavage of HOO-AA-PE to oxidatively truncated electrophiles capable of attacking nucleophilic targets in yet to be identified proteins leading to cell demise.

Iron Dysregulation in Parkinson's Disease: Focused on the Autophagy-Lysosome Pathway

Parkinson's disease (PD) is the second most common neurodegenerative disease and is characterized by dopaminergic neuron loss in the substantia nigra pars compacta (SNpc). Although both iron accumulation and a defective autophagy-lysosome pathway contribute to the pathological development of PD, the connection between these two causes is poorly documented. The autophagy-lysosome pathway not only responds to regulation by iron chelators and channels but also participates in cellular iron recycling through the degradation of ferritin and other iron-containing components. Previously, ferritin has been posited to be the bridge between iron accumulation and autophagy impairment in PD. In addition, iron directly interacts with α-synuclein in Lewy bodies, which are primarily digested through the autophagy-lysosome pathway. These findings indicate that some link exists between iron deposition and autophagy impairment in PD. In this review, the basic mechanisms of the autophagy-lysosome pathway and iron trafficking are introduced, and then their interaction under physiological conditions is explained. Finally, we finish by discussing the dysfunction of iron deposition and autophagy in PD, as well as their potential relationship, which will provide some insight for further study.

Mobilization of iron from ferritin: new steps and details

Much evidence indicates that iron stored in ferritin is mobilized through protein degradation in lysosomes, but concerns about this process have lingered, and the mechanistic details of its aspects are lacking. In the studies presented here, ⁵⁹Fe-labeled ferritin was induced by preloading hepatic (HepG2) cells with radiolabeled Fe. Placing these cells in a medium containing desferrioxamine resulted in the loss of ferritin-⁵⁹Fe, but adding high concentrations of reducing agents or modulating the internal GSH concentration failed to alter the rates of ferritin-⁵⁹Fe release. Confocal microscopy showed that Fe deprivation increased the movement of ferritin into lysosomes and hyperaccumulation was observed when lysosomal proteolysis was inhibited. It also resulted in the rapid movement of DMT1 to lysosomes, which was inhibited by bafilomycin. Ferrihydrite crystals isolated from purified rat liver/spleen ferritin were solubilized at pH 5 and 7 by GSH, ascorbate, citrate and lysosomal fluids obtained from livers and J774a.1 macrophages. The inhibition of DMT1/Nramp2 and siRNA knockdown of Nramp1 each reduced the transfer of ⁵⁹Fe from lysosomes to the cytosol; and hepatocyte-specific knockout of DMT1 in mice prevented the release of Fe from the liver responding to EPO treatment, but did not inhibit lysosomal ferritin degradation. We conclude that ferritin-Fe mobilization does not occur through changes in cellular concentrations of reducing/chelating agents but by the coordinated movement of ferritin and DMT1 to lysosomes, where the ferrihydrite crystals exposed by ferritin degradation dissolve in the lysosomal fluid, and the reduced iron is transported back to the cytosol via DMT1 in hepatocytes, and by both DMT1 and Nramp1 in macrophages, prior to release into the blood or storage in ferritin.

The flux of iron through ferritin in erythrocyte development

PURPOSE OF REVIEW

Terminal differentiation of erythropoietic progenitors requires the rapid accumulation of large amounts of iron, which is transported to the mitochondria, where it is incorporated into heme. Ferritin is the sole site of iron storage present in the cytosol. Yet the role of iron accumulation into ferritin in the context of red cell development had not been clearly defined. Early studies indicated that at the onset of terminal differentiation, iron initially accumulates in ferritin and precedes heme synthesis. Whether this accumulation is physiologically important for red cell development was unclear until recent studies defined an obligatory pathway of iron flux through ferritin.

RECENT FINDINGS

The iron chaperone functions of poly rC-binding protein 1 (PCBP1) and the autophagic cargo receptor for ferritin, nuclear co-activator 4 (NCOA4) are required for the flux of iron through ferritin in developing red cells. In the absence of these functions, iron delivery to mitochondria for heme synthesis is impaired.

SUMMARY

The regulated trafficking of iron through ferritin is important for maintaining a consistent flow of iron to mitochondria without releasing potentially damaging redox-active species in the cell. Other components of the iron trafficking machinery are likely to be important in red cell development.

Phenothiazines and phenoxazines: as electron transfer mediators for ferritin iron release

Redox active phenothiazine and phenoxazine dyes facilitate ferritin iron release by acting as electron transfer (ET) mediators following Marcus theory.