Mobilization of stored iron in mammals: a review

Ferroptosis inhibitor improves outcome after early and delayed treatment in mild spinal cord injury

We show that redox active iron can induce a regulated form of non-apoptotic cell death and tissue damage called ferroptosis that can contribute to secondary damage and functional loss in the acute and chronic periods after spinal cord injury (SCI) in young, adult, female mice. Phagocytosis of red blood cells at sites of hemorrhage is the main source of iron derived from hemoglobin after SCI. Expression of hemeoxygenase-1 that induces release of iron from heme, is increased in spinal cord macrophages 7 days after injury. While iron is stored safely in ferritin in the injured spinal cord, it can, however, be released by NCOA4-mediated shuttling of ferritin to autophagosomes for degradation (ferritinophagy). This leads to the release of redox active iron that can cause free radical damage. Expression of NCOA4 is increased after SCI, mainly in macrophages. Increase in the ratio of redox active ferrous (Fe2+) to ferric iron (Fe3+) is also detected after SCI by capillary electrophoresis inductively coupled mass spectrometry. These changes are accompanied by other hallmarks of ferroptosis, i.e., deficiency in various elements of the antioxidant glutathione (GSH) pathway. We also detect increases in enzymes that repair membrane lipids (ACSL4 and LPCAT3) and thus promote on-going ferroptosis. These changes are associated with increased levels of 4-hydroxynonenal (4-HNE), a toxic lipid peroxidation product. Mice with mild SCI (30 kdyne force) treated with the ferroptosis inhibitor (UAMC-3203-HCL) either early or delayed times after injury showed improvement in locomotor recovery and secondary damage. Cerebrospinal fluid and serum samples from human SCI cases show evidence of increased iron storage (ferritin), and other iron related molecules, and reduction in GSH. Collectively, these data suggest that ferroptosis contributes to secondary damage after SCI and highlights the possible use of ferroptosis inhibitors to treat SCI.

Ingenious Architecture and Coloration Generation in Enamel of Rodent Teeth

Teeth exemplify architectures comprising an interplay of inorganic and organic constituents, resulting in sophisticated natural composites. Rodents (Rodentia) showcase extraordinary adaptations, with their continuously growing incisors surpassing human teeth in functional and structural optimizations. In this study, employing state-of-the-art direct atomic-scale imaging and nanoscale spectroscopies, we present compelling evidence that the release of material from ameloblasts and the subsequent formation of iron-rich enamel and surface layers in the constantly growing incisors of rodents are complex orchestrated processes, intricately regulated and independent of environmental factors. The synergistic fusion of three-dimensional tomography and imaging techniques of etched rodent́s enamel unveils a direct correlation between the presence of pockets infused with ferrihydrite-like material and the acid resistant properties exhibited by the iron-rich enamel, fortifying it as an efficient protective shield. Moreover, observations using optical microscopy shed light on the role of iron-rich enamel as a microstructural element that acts as a path for color transmission, although the native color remains indistinguishable from that of regular enamel, challenging the prevailing paradigms. The redefinition of "pigmented enamel" to encompass ferrihydrite-like infusion in rodent incisors reshapes our perception of incisor microstructure and color generation. The functional significance of acid-resistant iron-rich enamel and the understanding of the underlying coloration mechanism in rodent incisors have far-reaching implications for human health, development of potentially groundbreaking dental materials, and restorative dentistry. These findings enable the creation of an entirely different class of dental biomaterials with enhanced properties, inspired by the ingenious designs found in nature.

Iron Metabolism and Inflammatory Mediators in Patients with Renal Dysfunction

Chronic kidney disease (CKD) affects around 850 million people worldwide, posing significant challenges in healthcare due to complications like renal anemia, end-stage kidney disease, and cardiovascular diseases. This review focuses on the intricate interplay between iron metabolism, inflammation, and renal dysfunction in CKD. Renal anemia, prevalent in CKD, arises primarily from diminished erythropoietin (EPO) production and iron dysregulation, which worsens with disease progression. Functional and absolute iron deficiencies due to impaired absorption and chronic inflammation are key factors exacerbating erythropoiesis. A notable aspect of CKD is the accumulation of uremic toxins, such as indoxyl sulfate (IS), which hinder iron metabolism and worsen anemia. These toxins directly affect renal EPO synthesis and contribute to renal hypoxia, thus playing a critical role in the pathophysiology of renal anemia. Inflammatory cytokines, especially TNF-α and IL-6, further exacerbate CKD progression and disrupt iron homeostasis, thereby influencing anemia severity. Treatment approaches have evolved to address both iron and EPO deficiencies, with emerging therapies targeting hepcidin and employing hypoxia-inducible factor (HIF) stabilizers showing potential. This review underscores the importance of integrated treatment strategies in CKD, focusing on the complex relationship between iron metabolism, inflammation, and renal dysfunction to improve patient outcomes.

Efficacy of polysaccharide iron complex in IDA rats: A comparative study with iron protein succinylate and ferrous succinate

Iron deficiency anemia (IDA) is the most common nutrient-related health problem in the world. There is still a lack of comprehensive comparative study on the efficacies of commonly used iron supplements such as polysaccharide iron complex (PIC), iron protein succinylate (IPS) and ferrous succinate (FS) for IDA. In this study, we compared the PIC, IPS and FS efficacies in IDA rats via intragastric administration. The results showed that the three iron supplements had similar efficacies. PIC/IPS/FS at a dose of 15 mg Fe/kg/d for 10 d increased the hematological and serum biochemical parameters to 2.15/2.12/2.18 (Hb), 1.71/1.67/1.69 (RBC), 2.10/2.11/2.12 (HCT), 1.26/1.22/1.22 (MCV), all 1.34 (MCH), 1.15/1.15/1.14 (MCHC), 1.94/1.82/1.91 (SF), 9.75/9.67/9.53 (SI), and 23.30/22.68/21.64 (TS) times, and reduced TIBC to 0.42/0.43/0.44 times, compared to untreated IDA rats. PIC performed slightly better than IPS and FS in restoring MCV level. Meanwhile, the heart, spleen and kidney coefficients reduced to 67%/74%/65% (heart), all 59% (spleen) and 87%/88%/88% (kidney), and the liver coefficient increased to 116%/115%/116%, compared to untreated IDA rats. The liver iron content was found to be more affected by IDA than the spleen iron content. PIC/IPS/FS at 15 mg Fe/kg/d increased organ iron contents to 4.20/3.97/4.03 times (liver) and 1.36/1.24/1.41 times (spleen) within 10 d compared to untreated IDA rats, and PIC-H and FS were slightly better than IPS in restoring spleen iron content. The results of this study can provide useful data information for the comparison of three iron supplements, PIC, IPS and FS.

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.

Ferroptosis in Neurological Disease

Iron accumulation in the CNS occurs in many neurological disorders. It can contribute to neuropathology as iron is a redox-active metal that can generate free radicals. The reasons for the iron buildup in these conditions are varied and depend on which aspects of iron influx, efflux, or sequestration that help maintain iron homeostasis are dysregulated. Iron was shown recently to induce cell death and damage via lipid peroxidation under conditions in which there is deficient glutathione-dependent antioxidant defense. This form of cell death is called ferroptosis. Iron chelation has had limited success in the treatment of neurological disease. There is therefore much interest in ferroptosis as it potentially offers new drugs that could be more effective in reducing iron-mediated lipid peroxidation within the lipid-rich environment of the CNS. In this review, we focus on the molecular mechanisms that induce ferroptosis. We also address how iron enters and leaves the CNS, as well as the evidence for ferroptosis in several neurological disorders. Finally, we highlight biomarkers of ferroptosis and potential therapeutic strategies.

Cardiac iron metabolism during aging - Role of inflammation and proteolysis

Iron is the most abundant trace element in the human body. Since iron can switch between its 2-valent and 3-valent form it is essential in various physiological processes such as energy production, proliferation or DNA synthesis. Especially high metabolic organs such as the heart rely on iron-associated iron-sulfur and heme proteins. However, due to switches in iron oxidation state, iron overload exhibits high toxicity through formation of reactive oxygen species, underlining the importance of balanced iron levels. Growing evidence demonstrates disturbance of this balance during aging. While age-associated cardiovascular diseases are often related to iron deficiency, in physiological aging cardiac iron accumulates. To understand these changes, we focused on inflammation and proteolysis, two hallmarks of aging, and their role in iron metabolism. Via the IL-6-hepcidin axis, inflammation and iron status are strongly connected often resulting in anemia accompanied by infiltration of macrophages. This tight connection between anemia and inflammation highlights the importance of the macrophage iron metabolism during inflammation. Age-related decrease in proteolytic activity additionally affects iron balance due to impaired degradation of iron metabolism proteins. Therefore, this review accentuates alterations in iron metabolism during aging with regards to inflammation and proteolysis to draw attention to their implications and associations.

Metal ion content of internal organs in the calorically restricted Wistar rat

BACKGROUND

Despite the agreed principle that access to food is a human right, undernourishment and metal ion deficiencies are public health problems worldwide, exacerbated in impoverished or war-affected areas. It is known that maternal malnutrition causes growth retardation and affects behavioral and cognitive development of the newborn. Here we ask whether severe caloric restriction leads per se to disrupted metal accumulation in different organs of the Wistar rat.

METHODS

Inductively coupled plasma optical emission spectroscopy was used to determine the concentration of multiple elements in the small and large intestine, heart, lung, liver, kidney, pancreas, spleen, brain, spinal cord, and three skeletal muscles from control and calorically restricted Wistar rats. The caloric restriction protocol was initiated from the mothers prior to mating and continued throughout gestation, lactation, and post-weaning up to sixty days of age.

RESULTS

Both sexes were analyzed but dimorphism was rare. The pancreas was the most affected organ presenting a higher concentration of all the elements analyzed. Copper concentration decreased in the kidney and increased in the liver. Each skeletal muscle responded to the treatment differentially: Extensor Digitorum Longus accumulated calcium and manganese, gastrocnemius decreased copper and manganese, whereas soleus decreased iron concentrations. Differences were also observed in the concentration of elements between organs independently of treatment: The soleus muscle presents a higher concentration of Zn compared to the other muscles and the rest of the organs. Notably, the spinal cord showed large accumulations of calcium and half the concentration of zinc compared to brain. X-ray fluorescence imaging suggests that the extra calcium is attributable to the presence of ossifications whereas the latter finding is attributable to the low abundance of zinc synapses in the spinal cord.

CONCLUSION

Severe caloric restriction did not lead to systemic metal deficiencies but caused instead specific metal responses in few organs.

Iron Homeostasis in Insects

Iron is an essential micronutrient for all types of organisms; however, iron has chemical properties that can be harmful to cells. Because iron is both necessary and potentially damaging, insects have homeostatic processes that control the redox state, quantity, and location of iron in the body. These processes include uptake of iron from the diet, intracellular and extracellular iron transport, and iron storage. Early studies of iron-binding proteins in insects suggested that insects and mammals have surprisingly different mechanisms of iron homeostasis, including different primary mechanisms for exporting iron from cells and for transporting iron from one cell to another, and subsequent studies have continued to support this view. This review summarizes current knowledge about iron homeostasis in insects, compares insect and mammalian iron homeostasis mechanisms, and calls attention to key remaining knowledge gaps.

Ferritin, transferrin, and transferrin receptor in relation to metabolic obesity phenotypes: Findings from the China Health and Nutrition Survey

Background

This study aimed to explore the relationship between iron markers and metabolic obesity phenotypes and the role of age.

Methods

Data were from the China Health and Nutrition Survey 2009. Metabolic obesity phenotypes included metabolically healthy with normal weight (MHNW), metabolically unhealthy with normal weight (MUNW), metabolically healthy with overweight/obesity (MHO), and metabolically unhealthy with overweight/obesity (MUO). Iron markers including ferritin, transferrin, and soluble transferrin receptor were calculated as Log and quartered. The linear regression and multinomial logistic regression were used to explore the association of iron markers with age and metabolic obesity phenotypes, respectively.

Results

Ferritin was linearly related with age, with β (95% confidence interval, CI) of 0.029 (0.027 to 0.032) and -0.005 (-0.007 to -0.002) for women and men. Transferrin was negatively associated with age in both men and women (β < -0.011). Furthermore, compared with participants in the quartile 1 ferritin group, those in the quartile 4 had increased odds of MUNW, MHO, and MUO, with odds ratio and 95% confidence interval (OR, 95% CI) of 3.06 (2.20 to 4.25), 1.66 (1.35 to 2.05), and 5.27 (4.17 to 6.66). Transferrin showed similar relationships with MUNW, MUO, and MHO; whereas transferrin receptor showed no significance. We also found joint associations of ferritin and transferrin with MUNW, MUO, and MHO. The interactive effect of ferritin and transferrin on MUO was significant (P = 0.015).

Conclusion

Increased ferritin and transferrin were associated with MUNW, MHO, and MUO. Age should be considered when investigating iron.

Protein-based nanomaterials: a new tool for targeted drug delivery

Protein nanomaterials are well-defined, hollow protein nanoparticles comprised of virus capsids, virus-like particles, ferritin, heat shock proteins, chaperonins and many more. Protein-based nanomaterials are formed by the self-assembly of protein subunits and have numerous desired properties as drug-delivery vehicles, including being optimally sized for endocytosis, nontoxic, biocompatible, biodegradable and functionalized at three separate interfaces (external, internal and intersubunit). As a result, protein nanomaterials have been intensively investigated as functional entities in bionanotechnology, including drug delivery, nanoreactors and templates for organic and inorganic nanomaterials. Several variables influence efficient administration, particularly active targeting, cellular uptake, the kinetics of the release and systemic elimination. This review examines the wide range of medicines, loading/release processes, targeted therapies and treatment effectiveness.

Iron Mobilization from Ferritin in Yeast Cell Lysate and Physiological Implications

Most in vitro iron mobilization studies from ferritin have been performed in aqueous buffered solutions using a variety of reducing substances. The kinetics of iron mobilization from ferritin in a medium that resembles the complex milieu of cells could dramatically differ from those in aqueous solutions, and to our knowledge, no such studies have been performed. Here, we have studied the kinetics of iron release from ferritin in fresh yeast cell lysates and examined the effect of cellular metabolites on this process. Our results show that iron release from ferritin in buffer is extremely slow compared to cell lysate under identical experimental conditions, suggesting that certain cellular metabolites present in yeast cell lysate facilitate the reductive release of ferric iron from the ferritin core. Using filtration membranes with different molecular weight cut-offs (3, 10, 30, 50, and 100 kDa), we demonstrate that a cellular component >50 kDa is implicated in the reductive release of iron. When the cell lysate was washed three times with buffer, or when NADPH was omitted from the solution, a dramatic decrease in iron mobilization rates was observed. The addition of physiological concentrations of free flavins, such as FMN, FAD, and riboflavin showed about a two-fold increase in the amount of released iron. Notably, all iron release kinetics occurred while the solution oxygen level was still high. Altogether, our results indicate that in addition to ferritin proteolysis, there exists an auxiliary iron reductive mechanism that involves long-range electron transfer reactions facilitated by the ferritin shell. The physiological implications of such iron reductive mechanisms are discussed.

Lysosomal iron recycling in mouse macrophages is dependent upon both LcytB and Steap3 reductases

Iron that is stored in macrophages as ferritin can be made bioavailable by degrading ferritin in the lysosome and releasing iron back into the cytosol. Iron stored in ferritin is found as Fe3+ and must be reduced to Fe2+ before it can be exported from the lysosome. Here we report that the lysosomal reductase Cyb561a3 (LcytB) and the endosomal reductase six-transmembrane epithelial antigen of prostate 3 (Steap3) act as lysosomal ferrireductases in the mouse macrophage cell line RAW264.7 converting Fe3+ to Fe2+ for iron recycling. We determined that when lysosomes were loaded with horse cationic ferritin, reductions or loss of LcytB or Steap3 using CRISPR/Cas9-mediated knockout technology resulted in decreased lysosomal iron export. Loss of both reductases was additive in decreasing lysosomal iron export. Decreased reductase activity resulted in increased transcripts for iron acquisition proteins DMT1 and transferrin receptor 1 (Tfrc1) suggesting that cells were iron limited. We show that transcript expression of LcytB and Steap3 is decreased in macrophages exposed to Escherichia coli pathogen UTI89, which supports a role for these reductases in regulating iron availability for pathogens. We further show that loss of LcytB and Steap3 in macrophages infected with UTI89 led to increased proliferation of intracellular UTI89 suggesting that the endolysosomal system is retaining Fe3+ that can be used for proliferation of intravesicular pathogens. Together, our findings reveal an important role for both LcytB and Steap3 in macrophage iron recycling and suggest that limiting iron recycling by decreasing expression of endolysosomal reductases is an innate immune response to protect against pathogen proliferation and sepsis.

Berberine alleviates liver fibrosis through inducing ferrous redox to activate ROS-mediated hepatic stellate cells ferroptosis

Berberine (BBR) has been explored as a potential anti-liver fibrosis agent, but the underlying mechanisms are unknown. In the current study, we aimed to investigate the molecular mechanisms underlying the effect of BBR against liver fibrogenesis in thioacetamide (TAA) and carbon tetrachloride (CCl₄) induced mouse liver fibrosis. In addition to i.p. injection with TAA or CCl₄, mice in the treatment group received BBR intragastrically. Concurrently, combined with TAA and BBR treatment, mice in the inhibitor group were injected i.p. with ferrostatin-1 (Fer-1). Hepatic stellate cells (HSCs) were also used in the study. Our results showed that BBR obviously alleviated mouse liver fibrosis and restored mouse liver function; however, the pharmacological effects of BBR against liver fibrosis were significantly diminished by Fer-1 treatment. Mechanically, BBR impaired the autophagy-lysosome pathway (ALP) and increased cell reactive oxygen species (ROS) production in HSCs. ROS accelerated the breakdown of the iron-storage protein ferritin and sped up iron release from ferritin, which resulted in redox-active iron accumulation in HSCs. Lipid peroxidation and glutathione (GSH) depletion triggered by the Fenton reaction promoted ferroptosis and attenuated liver fibrosis. Furthermore, impaired autophagy enhanced BBR-mediated ferritin proteolysis to increase cellular ferrous overload via the ubiquitin-proteasome pathway (UPS) in HSCs and triggered HSC ferroptosis. Collectively, BBR alleviated liver fibrosis by inducing ferrous redox to activate ROS-mediated HSC ferroptosis. Our findings may be exploited clinically to provide a potential novel therapeutic strategy for liver fibrosis.

Iron-Dependent Autophagic Cell Death Induced by Radiation in MDA-MB-231 Breast Cancer Cells

In radiation oncology, ionizing radiation is used to kill cancer cells, in other words, the induction of different types of cell death. To investigate this cellular death and the associated iron accumulation, the transfer, release, and participation of iron after radiation treatment was analyzed. We found that radiation-induced cell death varied in different breast cancer cells and autophagy was induced in MDA-MB-231 and BT549 cells (triple negative breast cancer cell line) rather than in MCF-7 and zr-75 cells. Iron chelator deferoxamine (DFO), the autophagy inhibitor 3MA, silencing of the autophagy-related genes ATG5, and Beclin 1 could decrease radiation induced cell death in MDA-MB-231 cells, while inhibitors of apoptosis such as Z-VAD-FMK, ferroptosis inhibitor ferrostatin-1 (Fer-1), and necroptosis inhibitor Necrostatin-1 showed no change. This suggests the occurrence of autophagic cell death. Furthermore, we found that iron accumulation and iron regulatory proteins, including transferrin (Tf), transferrin receptor (CD71), and Ferritin (FTH), increased after radiation treatment, and the silencing of transferrin decreased radiation-induced cell death. In addition, radiation increased lysosomal membrane permeabilization (LMP) and the release of lysosomal iron and cathepsins, while cathepsins silencing failed to change cell viability. Radiation-induced iron accumulation increased Reactive oxygen species (ROS) generation via the Fenton reaction and increased autophagy in a time-dependent manner. DFO, N-acetylcysteine (NAC), and overexpression of superoxide dismutase 2 (SOD2) decreased ROS generation, autophagy, and cell death. To summarize, for the first time, we found that radiation-induced autophagic cell death was iron-dependent in breast cancer MDA-MB-231 cells. These results provide new insights into the cell death process of cancers and might conduce to the development and application of novel therapeutic strategies for patients with apoptosis-resistant breast cancer.

A holistic view of mammalian (vertebrate) cellular iron uptake

Cell iron uptake in mammals is commonly distinguished by whether the iron is presented to the cell as transferrin-bound or not: TBI or NTBI. This generic perspective conflates TBI with canonical transferrin receptor, endosomal iron uptake, and NTBI with uptake supported by a plasma membrane-localized divalent metal ion transporter, most often identified as DMT1. In fact, iron uptake by mammalian cells is far more nuanced than this somewhat proscribed view suggests. This view fails to accommodate the substantial role that ZIP8 and ZIP14 play in iron uptake, while adhering to the traditional premise that a relatively high endosomal [H+] is thermodynamically required for release of iron from holo-Tf. The canonical view of iron uptake also does not encompass the fact that plasma membrane electron transport - PMET - has long been linked to cell iron uptake. In fact, the known mammalian metallo-reductases - Dcytb and the STEAP proteins - are members of this cohort of cytochrome-dependent oxido-reductases that shuttle reducing equivalents across the plasma membrane. A not commonly appreciated fact is the reduction potential of ferric iron in holo-Tf is accessible to cytoplasmic reducing equivalents - reduced pyridine and flavin mono- and di-nucleotides and dihydroascorbic acid. This allows for the reductive release of Fe2+ at the extracellular surface of the PM and subsequent transport into the cytoplasm by a neutral pH transporter - a ZIP protein. What this perspective emphasizes is that there are two TfR-dependent uptake pathways, one which does and one which does not involve clathrin-dependent, endolysosomal trafficking. This raises the question as to the selective advantage of having two Tf, TfR-dependent routes of iron accumulation. This review of canonical and non-canonical iron uptake uses cerebral iron trafficking as a point of discussion, a focus that encourages inclusion also of the importance of ferritin as a circulating 'chaperone' of ferric iron.

Possible mechanisms by which silkworm faeces extract ameliorates adenine-induced renal anaemia in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Silkworm faeces are the dry faeces of the insect Bombyx mori (Linnaeus) and have historically been used in traditional Chinese medicine to treat blood deficiency and rheumatic pain. Silkworm faeces extract (SFE) is derived from silkworm faeces.

AIM OF THE STUDY

Clinical observations of patients in the Department of Nephrology have shown that SFE effectively improves renal anaemia. However, the molecular mechanism remains unclear. This article mainly explores the regulatory effects of SFE on erythropoietin (EPO) and hepcidin to identify the molecular mechanism of SFE.

MATERIALS AND METHODS

A rat model of renal anaemia was established by feeding rats food containing 0.75% adenine. SFE was orally administered to the rats, while recombinant human erythropoietin (rhEPO) was used as a positive control drug. Haematological parameters and inflammation levels were compared between rats from each group, and pathological kidney sections from each rat were observed. The serum EPO and hepcidin levels were detected using enzyme-linked immunosorbent assay (ELISA) kits, while Western blot analyses were performed to detect the levels of proteins involved in the EPO-related hypoxia-inducible factor 2α (HIF-2α)/prolyl hydroxylase 2 (PHD2) signalling pathway and hepcidin-related BMP6/SMAD4 and interleukin-6 (IL-6)/STAT3 signalling pathways.

RESULTS

SFE significantly ameliorated haematological parameters, renal function, and inflammation levels in the rats. A mechanistic study showed that SFE promoted EPO expression by upregulating HIF-2α expression and inhibiting the expression of NF-κB and GATA2 both in vivo and in vitro. In particular, SFE inhibited PHD2 expression, resulting in a decrease in the enzymatic reaction of HIF-2α to increase EPO expression. Furthermore, SFE inhibited hepcidin expression by blocking the BMP6/SMAD4 and IL-6/STAT3 pathways.

CONCLUSIONS

SFE regulated iron metabolism by inhibiting hepcidin and simultaneously promoted EPO synthesis to improve renal anaemia in rats.

An Overview of Dps: Dual Acting Nanovehicles in Prokaryotes with DNA Binding and Ferroxidation Properties

DNA binding proteins under starvation (Dps) are proteins belonging to the ferritin family with the capacity for DNA binding, in addition to iron storage and ferroxidation. Present only in the prokaryotes, these multifaceted proteins have been assigned with a number of roles, from pathogenesis to nucleoid condensation and protection. They have a significant role in protecting the cells from free radical assaults, indirectly by sequestration of iron and by directly binding to the DNA. Due to their symmetry, stability and biomineralization capacity, these proteins have ever increasing potential applications in biotechnology and drug delivery. This chapter tries to bring together all these aspects of Dps in the view of current understanding and older perspectives by studies of our group as well as other experts in the field.

Contribution of Major Groups of Food Products to the Daily Intake of Selected Elements-Results from Analytical Determinations Supported by Chemometric Analysis

Food is a major source of minerals for humans. The main objective of this study was to determine the intake level of 10 essential macro- (Na, K, Ca, and Mg) and trace elements (Cu, Zn, Mn, Fe, Cr, and Se) with major food groups among young adults. Dietary intake of elements was evaluated using the 24-h dietary recall technique in combination with F-AASand ICP-OES methods. A very high intake of sodium and a very low intake of calcium, combined with inappropriate sodium/potassium ratio, may be harmful to the health of the population. Dietary intake of trace elements was within the range of reference values in the subjects, with cereals being the major source of a majority of those elements, while meat (38% for Na), vegetables (25% for K), and milk products (75% for Ca) were the main contributors to the daily dietary intake of macroelements. PCA revealed several visible trends in the datasetAmong men, the intake of Zn, Cr Na and K was significantly correlated with the consumption of meat and vegetables, whereas Mg, Se, Fe and Cu with cereals and water and beverages. Among women, the intake of Mg was significantly correlated with the consumption of meat and vegetables.

WITHDRAWN: Can Traditional Chinese Medicine provide insights into controlling the COVID-19 pandemic: Serpentinization-induced lithospheric long-wavelength magnetic anomalies in Proterozoic bedrocks in a weakened geomagnetic field mediate the aberrant transformation of biogenic molecules in COVID-19 via magnetic catalysis

This article has been withdrawn at the request of the authors and the editors. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

A Perspective on Erythropoietin as a Potential Adjuvant Therapy for Acute Lung Injury/Acute Respiratory Distress Syndrome in Patients with COVID-19

The novel coronavirus 2019-nCoV (SARS-CoV-2) infection that emerged in China in December 2019 has rapidly spread to become a global pandemic. This article summarizes the potential benefits of erythropoietin (EPO) in alleviating SARS-CoV-2 pathogenesis which is now called COVID-19. As with other coronavirus infection, the lethality of COVID-19 is associated with respiratory dysfunction due to overexpression of proinflammatory cytokines induced by the host immune responses. The resulting cytokine storm leads to the development of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Erythropoietin, well known for its role in the regulation of erythropoiesis, may have protective effects against ALI/ARDS induced by viral and other pathogens. EPO exerts antiapoptotic and cytoprotective properties under various pathological conditions. With a high safety profile, EPO promotes the production of endothelial progenitor cells and reduce inflammatory processes through inhibition of the nuclear factor-κB (NF-κB) and JAK-STAT3 signaling pathways. Thus, it may be considered as a safe drug candidate for COVID-19 patients if given at the early stage of the disease. The potential effects of erythropoietin on different aspects of ALI/ARDS associated with SARS-CoV-2 infection are reviewed.

Ferritin exhibits Michaelis-Menten behavior with oxygen but not with iron during iron oxidation and core mineralization

The excessively high and inconsistent literature values for Km,Fe and Km,O2 prompted us to examine the iron oxidation kinetics in ferritin, the major iron storage protein in mammals, and to determine whether a traditional Michaelis-Menten enzymatic behavior is obeyed. The kinetics of Fe(ii) oxidation and mineralization catalyzed by three different types of ferritins (recombinant human homopolymer 24H, HuHF, human heteropolymer ∼21H:3L, HL, and horse spleen heteropolymer ∼3.3H:20.7L, HosF) were therefore studied under physiologically relevant O2 concentrations, but also in the presence of excess Fe(ii) and O2 concentrations. The observed iron oxidation kinetics exhibited two distinct phases (phase I and phase II), neither of which obeyed Michaelis-Menten kinetics. While phase I was very rapid and corresponded to the oxidation of approximately 2 Fe(ii) ions per H-subunit, phase II was much slower and varied linearly with the concentration of iron(ii) cations in solution, independent of the size of the iron core. Under low oxygen concentration close to physiological, the iron uptake kinetics revealed a Michaelis-Menten behavior with Km,O2 values in the low μM range (i.e. ∼1-2 μM range). Our experimental Km,O2 values are significantly lower than typical cellular oxygen concentration, indicating that iron oxidation and mineralization in ferritin should not be affected by the oxygenation level of cells, and should proceed even under hypoxic events. A kinetic model is proposed in which the inhibition of the protein's activity is caused by bound iron(iii) cations at the ferroxidase center, with the rate limiting step corresponding to an exchange or a displacement reaction between incoming Fe(ii) cations and bound Fe(iii) cations.

Expression of vascular endothelial growth factor A in liver tissues of infants with biliary atresia

Aim of the study

Assessment of hepatic expression of vascular endothelial growth factor A (VEGF-A) in liver tissues of infants with biliary atresia (BA).

Material and methods

This retrospective study included 35 infants with BA (BA group), and 38 infants with cholestasis due to causes other than BA (non-BA group). All patients had undergone full history taking, through clinical examination, routine investigations and immunostaining of liver tissue for VEGF-A and cytokeratin 7 (CK7). The diagnosis of BA was confirmed by intraoperative cholangiography. In the non-BA group, other specific laboratory tests according to the expected etiology were done.

Results

Most of the BA group showed positive VEGF-A expression with variable degrees in both bile ducts (BDs; 80%), and arterial walls (AWs; 77.2%), while most of the non-BA group showed negative staining of VEGF in both BDs and AWs (89.5% and 86.8% respectively) (p < 0.0001). Positive VEGF expression in the portal structures in both BDs and AWs had 84.9% and 82.19% accuracy; respectively. The majority of BA group showed either grade II of positive cytokeratin-7 expression in liver tissues (45.7%) or grade III (34.3%), while most of the non-BA group showed grade I (71.1%) (p < 0.0001). Positive CK7 expression in > 25% of the liver tissues had 80.8% accuracy in discriminating between BA and non-BA.

Conclusions

VEGF-A expression in the portal structures in liver tissues in both BDs and AWs had very good accuracy in discriminating between BA and non-BA patients.

Endothelial cells are critical regulators of iron transport in a model of the human blood-brain barrier

Iron delivery to the brain is essential for multiple neurological processes such as myelination, neurotransmitter synthesis, and energy production. Loss of brain iron homeostasis is a significant factor in multiple neurological disorders. Understanding the mechanism by which the transport of iron across the blood-brain barrier (BBB) is regulated is crucial to address the impact of iron deficiency on brain development and excessive accumulation of iron in neurodegenerative diseases. Using induced pluripotent stem cell (iPSC)-derived brain endothelial cells (huECs) as a human BBB model, we demonstrate the ability of transferrin, hepcidin, and DMT1 to impact iron transport and release. Our model reveals a new function for H-ferritin to transport iron across the BBB by binding to the T-cell immunoglobulin and mucin receptor 1. We show that huECs secrete both transferrin and H-ferritin, which can serve as iron sources for the brain. Based on our data, brain iron status can exert control of iron transport across the endothelial cells that constitute the BBB. These data address a number of pertinent questions such as how brain iron uptake is regulated at the regional level, the source of iron delivery to the brain, and the clinical strategies for attempting to treat brain iron deficiency.

Deciphering the Role Played by Autophagy in Leishmania Infection

In recent decades, studies have shown that, depending on parasite species and host background, autophagy can either favor infection or promote parasite clearance. To date, relatively few studies have attempted to assess the role played by autophagy in Leishmania infection. While it has been consistently shown that Leishmania spp. induce autophagy in a variety of cell types, published results regarding the effects of autophagic modulation on Leishmania survival are contradictory. The present review, after a short overview of the general aspects of autophagy, aims to summarize the current body of knowledge surrounding how Leishmania spp. adaptively interact with macrophages, the host cells mainly involved in controlling leishmaniasis. We then explore the scarce studies that have investigated interactions between these parasite species and the autophagic pathway, and finally present a critical perspective on how autophagy influences infection outcome.

Time-dependent hemeoxygenase-1, lipocalin-2 and ferritin induction after non-contusion traumatic brain injury

Traumatic brain injury (TBI) often presents with focal contusion and parenchymal bleeds, activating heme oxygenase (HO) to degrade released hemoglobin. Here we show that diffuse, midline fluid percussion injury causes time-dependent induction of HO-1 and iron binding proteins within both hemorrhagic neocortex and non-hemorrhagic hippocampus. Rats subjected to midline fluid percussion injury (FPI) survived 1-15d postinjury and tissue was collected for Western blot and immunohistochemical assays. HO-1 was elevated 1d after FPI, peaked at 3d, and returned to control baseline 7-15d. Iron management proteins lipocalin 2 (LCN2) and ferritin (FTL) exhibited distinct postinjury time courses, where peak LCN2 response preceded, and FTL followed that of HO-1. LCN2 elevation supported not only its role in iron transport, but also mediation of matrix metalloproteinase 9 (MMP9) activity. Upregulation of FTL for intracellular iron sequestration was delayed relative to both HO-1 and LCN2 induction. In the neocortex IBA-1+ microglia around the injury core expressed HO-1, but astrocytes co-localized with HO-1 in perilesional parenchyma. Non-hemorrhagic dentate gyrus showed predominant HO-1 labeling in hilar microglia and in molecular layer astrocytes. At 1d postinjury, LCN2 and HO-1 co-localized in a subpopulation of reactive glia within both brain regions. Notably, FTL was distributed within cells around injured vessels, damaged subcortical white matter, and along vessels of the hippocampal fissure. Together these results confirm that even the moderate, non-contusional insult of diffuse midline FPI can significantly activate postinjury HO-1 heme processing pathways and iron management proteins. Moreover, this activation is time-dependent and occurs in the absence of overt hemorrhage.

Repression of ferritin light chain translation by human eIF3

A central problem in human biology remains the discovery of causal molecular links between mutations identified in genome-wide association studies (GWAS) and their corresponding disease traits. This challenge is magnified for variants residing in non-coding regions of the genome. Single-nucleotide polymorphisms (SNPs) in the 5ʹ untranslated region (5ʹ-UTR) of the ferritin light chain (FTL) gene that cause hyperferritinemia are reported to disrupt translation repression by altering iron regulatory protein (IRP) interactions with the FTL mRNA 5ʹ-UTR. Here, we show that human eukaryotic translation initiation factor 3 (eIF3) acts as a distinct repressor of FTL mRNA translation, and eIF3-mediated FTL repression is disrupted by a subset of SNPs in FTL that cause hyperferritinemia. These results identify a direct role for eIF3-mediated translational control in a specific human disease.

Evaluating the efficacy of a ferrous-ion-chelating peptide from Alaska pollock frame for the improvement of iron nutritional status in rats

This study aimed to investigate the effects of ferrous-ion-chelating peptides from Alaska pollock frames (APFP-Fe) on iron deficiency in anaemic rats. We hydrolysed the Alaska pollock frames to obtain a peptide with an average molecular weight of 822 Da. The bioavailability of APFP-Fe was tested using animal experiments. Wistar rats were randomly divided into six groups: an iron deficiency control group, a normal control group, and iron deficiency groups treated with ferrous sulfate (FeSO₄) or low-, medium-, or high-dose APFP-Fe. Rats in the iron deficiency groups were fed an iron-deficient diet to establish the iron deficiency anaemia (IDA) model. After the model was established, different iron supplements were given to rats once per day via intragastric administration for 21 days. The results showed that APFP-Fe had restorative effects, returning the body weight, weight gain, height, and haematological parameters in IDA rats to normal levels. In addition, compared with FeSO₄, APFP-Fe promoted significant weight gain and effectively improved haemoglobin, serum iron and transferrin levels, and recovery of the capacity of iron binding with transferrin, especially at the medium and high doses. These findings suggest that APFP-Fe is an effective source of iron for improving the iron nutritional status in IDA rats and shows promise as a new source of iron supplementation.

Ascorbate and ferritin interactions: Consequences for iron release in vitro and in vivo and implications for inflammation

This review discusses the chemical mechanisms of ascorbate-dependent reduction and solubilization of ferritin's ferric iron core and subsequent release of ferrous iron. The process is accelerated by low concentrations of Fe(II) that increase ferritin's intrinsic ascorbate oxidase activity, hence increasing the rate of ascorbate radical formation. These increased rates of ascorbate oxidation provide reducing equivalents (electrons) to ferritin's core and speed the core reduction rates with subsequent solubilization and release of Fe(II). Ascorbate-dependent solubilization of ferritin's iron core has consequences relating to the interpretation of ⁵⁹Fe uptake sourced from ⁵⁹Fe-lebelled holotransferrin into ferritin. Ascorbate-dependent reduction of the ferritin core iron solubility increases the size of ferritin's iron exchangeable pool and hence the rate and amount of exchange uptake of ⁵⁹Fe into ferritin, whilst simultaneously increasing net iron release rate from ferritin. This may rationalize the inconsistency that ascorbate apparently stabilizes ⁵⁹Fe ferritin and retards lysosomal ferritinolysis and whole cell ⁵⁹Fe release, whilst paradoxically increasing the rate of net iron release from ferritin. This capacity of ascorbate and iron to synergise ferritin iron release has pathological significance, as it lowers the concentration at which ascorbate activates ferritin's iron release to within the physiological range (50-250 μM). These effects have relevance to inflammatory pathology and to the pro-oxidant effects of ascorbate in cancer therapy and cell death by ferroptosis.

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.

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.

Emerging and Dynamic Biomedical Uses of Ferritin

Ferritin, a ubiquitously expressed protein, has classically been considered the main iron cellular storage molecule in the body. Owing to the ferroxidase activity of the H-subunit and the nucleation ability of the L-subunit, ferritin can store a large amount of iron within its mineral core. However, recent evidence has demonstrated a range of abilities of ferritin that extends well beyond the scope of iron storage. This review aims to discuss novel functions and biomedical uses of ferritin in the processes of iron delivery, delivery of biologics such as chemotherapies and contrast agents, and the utility of ferritin as a biomarker in a number of neurological diseases.

Reductive Mobilization of Iron from Intact Ferritin: Mechanisms and Physiological Implication

Ferritins are highly conserved supramolecular protein nanostructures composed of two different subunit types, H (heavy) and L (light). The two subunits co-assemble into a 24-subunit heteropolymer, with tissue specific distributions, to form shell-like protein structures within which thousands of iron atoms are stored as a soluble inorganic ferric iron core. In-vitro (or in cell free systems), the mechanisms of iron(II) oxidation and formation of the mineral core have been extensively investigated, although it is still unclear how iron is loaded into the protein in-vivo. In contrast, there is a wide spread belief that the major pathway of iron mobilization from ferritin involves a lysosomal proteolytic degradation of ferritin, and the dissolution of the iron mineral core. However, it is still unclear whether other auxiliary iron mobilization mechanisms, involving physiological reducing agents and/or cellular reductases, contribute to the release of iron from ferritin. In vitro iron mobilization from ferritin can be achieved using different reducing agents, capable of easily reducing the ferritin iron core, to produce soluble ferrous ions that are subsequently chelated by strong iron(II)-chelating agents. Here, we review our current understanding of iron mobilization from ferritin by various reducing agents, and report on recent results from our laboratory, in support of a mechanism that involves a one-electron transfer through the protein shell to the iron mineral core. The physiological significance of the iron reductive mobilization from ferritin by the non-enzymatic FMN/NAD(P)H system is also discussed.

Absorption Mechanisms of Iron, Copper, and Zinc: An Overview

Essential trace elements play pivotal roles in numerous structural and catalytic functions of proteins. Adequate intake of essential trace elements from the daily diet is indispensable to the maintenance of health, and their deficiency leads to a variety of conditions. However, excessive amounts of these trace elements may be highly toxic, and in some cases, may cause damage by the production of harmful reactive oxygen species. Homeostatic dysregulation of their metabolism increases the risk of developing diseases. Specific transport proteins that facilitate influx or efflux of trace elements play key roles in maintaining the homeostasis. Recent elucidation of their crucial functions significantly facilitated our understanding of the molecular mechanisms of iron (Fe), copper (Cu), and zinc (Zn) absorption in the small intestine. This paper summarizes their absorption mechanisms, with a focus on indispensable functions of the molecules involved in it, and briefly discusses the mechanisms of homeostatic control of each element at the cellular and systemic levels.

Autophagic Induction Greatly Enhances Leishmania major Intracellular Survival Compared to Leishmania amazonensis in CBA/j-Infected Macrophages

CBA mouse macrophages control Leishmania major infection yet are permissive to Leishmania amazonensis. Few studies have been conducted to assess the role played by autophagy in Leishmania infection. Therefore, we assessed whether the autophagic response of infected macrophages may account for the differential behavior of these two parasite strains. After 24 h of infection, the LC3-II/Act ratio increased in both L. amazonensis- and L. major-infected macrophages compared to uninfected controls, but less than in chloroquine-treated cells. This suggests that L. amazonensis and L. major activate autophagy in infected macrophages, without altering the autophagic flux. Furthermore, L. major-infected cells exhibited higher percentages of DQ-BSA-labeled parasitophorous vacuoles (50%) than those infected by L. amazonensis (25%). However, L. major- and L. amazonensis-induced parasitophorous vacuoles accumulated LysoTracker similarly, indicating that the acidity in both compartment was equivalent. At as early as 30 min, endogenous LC3 was recruited to both L. amazonensis- and L. major-induced parasitophorous vacuoles, while after 24 h a greater percentage of LC3 positive vacuoles was observed in L. amazonensis-infected cells (42.36%) compared to those infected by L. major (18.10%). Noteworthy, principal component analysis (PCA) and an hierarchical cluster analysis completely discriminated L. major-infected macrophages from L. amazonensis-infected cells accordingly to infection intensity and autophagic features of parasite-induced vacuoles. Then, we evaluated whether the modulation of autophagy exerted an influence on parasite infection in macrophages. No significant changes were observed in both infection rate or parasite load in macrophages treated with the autophagic inhibitors wortmannin, chloroquine or VPS34-IN1, as well as with the autophagic inducers rapamycin or physiological starvation, in comparison to untreated control cells. Interestingly, both autophagic inducers enhanced intracellular L. amazonensis and L. major viability, while the pharmacological inhibition of autophagy exerted no effects on intracellular parasite viability. We also demonstrated that autophagy induction reduced NO production by L. amazonensis- and L. major-infected macrophages but not alters arginase activity. These findings provide evidence that although L. amazonensis-induced parasitophorous vacuoles recruit LC3 more markedly, L. amazonensis and L. major similarly activate the autophagic pathway in CBA macrophages. Interestingly, the exogenous induction of autophagy favors L. major intracellular viability to a greater extent than L. amazonensis related to a reduction in the levels of NO.

Dysregulation of Neuronal Iron Homeostasis as an Alternative Unifying Effect of Mutations Causing Familial Alzheimer's Disease

The overwhelming majority of dominant mutations causing early onset familial Alzheimer’s disease (EOfAD) occur in only three genes, PSEN1, PSEN2, and APP. An effect-in-common of these mutations is alteration of production of the APP-derived peptide, amyloid β (Aβ). It is this key fact that underlies the authority of the Amyloid Hypothesis that has informed Alzheimer’s disease research for over two decades. Any challenge to this authority must offer an alternative explanation for the relationship between the PSEN genes and APP. In this paper, we explore one possible alternative relationship – the dysregulation of cellular iron homeostasis as a common effect of EOfAD mutations in these genes. This idea is attractive since it provides clear connections between EOfAD mutations and major characteristics of Alzheimer’s disease such as dysfunctional mitochondria, vascular risk factors/hypoxia, energy metabolism, and inflammation. We combine our ideas with observations by others to describe a “Stress Threshold Change of State” model of Alzheimer’s disease that may begin to explain the existence of both EOfAD and late onset sporadic (LOsAD) forms of the disease. Directing research to investigate the role of dysregulation of iron homeostasis in EOfAD may be a profitable way forward in our struggle to understand this form of dementia.

The Aging of Iron Man

Brain iron is tightly regulated by a multitude of proteins to ensure homeostasis. Iron dyshomeostasis has become a molecular signature associated with aging which is accompanied by progressive decline in cognitive processes. A common theme in neurodegenerative diseases where age is the major risk factor, iron dyshomeostasis coincides with neuroinflammation, abnormal protein aggregation, neurodegeneration, and neurobehavioral deficits. There is a great need to determine the mechanisms governing perturbations in iron metabolism, in particular to distinguish between physiological and pathological aging to generate fruitful therapeutic targets for neurodegenerative diseases. The aim of the present review is to focus on the age-related alterations in brain iron metabolism from a cellular and molecular biology perspective, alongside genetics, and neuroimaging aspects in man and rodent models, with respect to normal aging and neurodegeneration. In particular, the relationship between iron dyshomeostasis and neuroinflammation will be evaluated, as well as the effects of systemic iron overload on the brain. Based on the evidence discussed here, we suggest a synergistic use of iron-chelators and anti-inflammatories as putative anti-brain aging therapies to counteract pathological aging in neurodegenerative diseases.

Releasing iron from ferritin protein nanocage by reductive method: The role of electron transfer mediator

BACKGROUND

Ferritin detoxifies excess of free Fe(II) and concentrates it in the form of ferrihydrite (Fe₂O₃·xH₂O) mineral. When in need, ferritin iron is released for cellular metabolic activities. However, the low solubility of Fe(III) at neutral pH, its encapsulation by stable protein nanocage and presence of dissolved O₂ limits in vitro ferritin iron release.

METHODS

Physiological reducing agent, NADH (E_1/2 = -330 mV) was inefficient in releasing the ferritin iron (E_1/2 = +183 mV), when used alone. Thus, current work investigates the role of low concentration (5-50 μM) of phenazine based electron transfer (ET) mediators such as FMN, PYO - a redox active virulence factor secreted by Pseudomonas aeruginosa and PMS towards iron mobilization from recombinant frog M ferritin.

RESULTS

The presence of dissolved O₂, resulting in initial lag phase and low iron release in FMN, had little impact in case of PMS and PYO, reflecting their better ET relay ability that facilitates iron mobilization. The molecular modeling as well as fluorescence studies provided further structural insight towards interaction of redox mediators on ferritin surface for electron relay.

CONCLUSIONS

Reductive mobilization of iron from ferritin is dependent on the relative rate of NADH oxidation, dissolved O₂ consumption and mineral core reduction, which in turn depends on E_1/2 of these mediators and their interaction with ferritin.

GENERAL SIGNIFICANCE

The current mechanism of in vitro iron mobilization from ferritin by using redox mediators involves different ET steps, which may help to understand the iron release pathway in vivo and to check microbial growth.

Associations of plasma hepcidin with mortality risk in patients with coronary artery disease

Background

Increased blood hepcidin may be associated with the presence and promotion of atherosclerosis, the association of hepcidin with mortality among coronary artery disease (CAD) patients remains unknown. We sought to assess the relationship of hepcidin and all-cause and cardiovascular disease (CVD) mortality among CAD patients with and without acute coronary syndrome (ACS).

Methods and Results

This study included 759 patients with ACS and 526 patients with stable CAD. After an average follow-up of 4.1 years, 154 deaths were recorded, 114 were due to CVD. After adjusting for CVD risk factors and inflammatory markers, the plasma hepcidin was positively associated with all-cause and CVD mortality in the ACS patients, the multivariable-adjusted hazard ratios (HRs) across tertiles of hepcidin were 1.00, 2.18 (95% CI 1.23-3.94), and 2.82 (95% CI 1.59-5.12) for all-cause mortality (P_trend=0.006), and 1.00, 2.20 (95% CI 1.12-4.05), and 2.64 (95% CI 1.41-5.65) for CVD mortality (P_trend=0.01). The C-index and net reclassification improvement when including hepcidin in traditional CVD models were 1.6% and 21.5% for all-cause mortality, 1.4% and 23.5% for CVD mortality, respectively, (P<0.001).

Conclusions

Plasma hepcidin was positively associated with mortality in ACS patients. Hepcidin may be a potential biomarker for risk prediction in ACS patients.

Iron and inflammation - the gut reaction

Anemia is a frequent complication of many inflammatory disorders, including inflammatory bowel disease. Although the pathogenesis of this problem is multifactorial, a key component is the abnormal elevation of the hormone hepcidin, the central regulator of systemic iron homeostasis. Investigations over the last decade have resulted in important insights into the role of hepcidin in iron metabolism and the mechanisms that lead to hepcidin dysregulation in the context of inflammation. These insights provide the foundation for novel strategies to prevent and treat the anemia associated with inflammatory diseases.

Acute loss of the hepatic endo-lysosomal system in vivo causes compensatory changes in iron homeostasis

Liver cells communicate with the extracellular environment to take up nutrients via endocytosis. Iron uptake is essential for metabolic activities and cell homeostasis. Here, we investigated the role of the endocytic system for maintaining iron homeostasis. We specifically depleted the small GTPase Rab5 in the mouse liver, causing a transient loss of the entire endo-lysosomal system. Strikingly, endosome depletion led to a fast reduction of hepatic iron levels, which was preceded by an increased abundance of the iron exporter ferroportin. Compensatory changes in livers of Rab5-depleted mice include increased expression of transferrin receptor 1 as well as reduced expression of the iron-regulatory hormone hepcidin. Serum iron indices (serum iron, free iron binding capacity and total iron binding capacity) in Rab5-KD mice were increased, consistent with an elevated splenic and hepatic iron export. Our data emphasize the critical importance of the endosomal compartments in hepatocytes to maintain hepatic and systemic iron homeostasis in vivo. The short time period (between day four and five) upon which these changes occur underscore the fast dynamics of the liver iron pool.

Oxidant-induced autophagy and ferritin degradation contribute to epithelial-mesenchymal transition through lysosomal iron

Purpose

Transforming growth factor (TGF)-β1 triggers epithelial–mesenchymal transition (EMT) through autophagy, which is partly driven by reactive oxygen species (ROS). The aim of this study was to determine whether leaking lysosomes and enhanced degradation of H-ferritin could be involved in EMT and whether it could be possible to prevent EMT by iron chelation targeting of the lysosome.

Materials and methods

EMT, H-ferritin, and autophagy were evaluated in TGF-β1-stimulated A549 human lung epithelial cells cultured in vitro using Western blotting, with the additional morphological assessment of EMT. By using immunofluorescence and flow cytometry, lysosomes and ROS were assessed by acridine orange and 6-carboxy-2′,7′-dichlorodihydrofluorescein acetate assays, respectively.

Results

TGF-β1-stimulated cells demonstrated a loss of H-ferritin, which was prevented by the antioxidant N-acetyl-L-cysteine (NAC) and inhibitors of lysosomal degradation. TGF-β1 stimulation generated ROS and autophagosome formation and led to EMT, which was further promoted by the additional ROS-generating cytokine, tumor necrosis factor-α. Lysosomes of TGF-β1-stimulated cells were sensitized to oxidants but also completely protected by lysosomal loading with dextran-bound deferoxamine (DFO). Autophagy and EMT were prevented by NAC, DFO, and inhibitors of autophagy and lysosomal degradation.

Conclusion

The findings of this study support the role of enhanced autophagic degradation of H-ferritin as a mechanism for increasing the vulnerability of lysosomes to iron-driven oxidant injury that triggers further autophagy during EMT. This study proposes that lysosomal leakage is a novel pathway of TGF-β1-induced EMT that may be prevented by iron-chelating drugs that target the lysosome.