Uptake and release of metal ions by transferrin and interaction with receptor 1

Bone aluminum accumulation in the current era

In the last few years, evidence from the Brazilian Registry of Bone Biopsy (REBRABO) has pointed out a high incidence of aluminum (Al) accumulation in the bones of patients with CKD under dialysis. This surprising finding does not appear to be merely a passive metal accumulation, as prospective data from REBRABO suggest that the presence of Al in bone may be independently associated with major adverse cardiovascular events. This information contrasts with the perception of epidemiologic control of this condition around the world. In this opinion paper, we discussed why the diagnosis of Al accumulation in bone is not reported in other parts of the world. We also discuss a range of possibilities to understand why bone Al accumulation still occurs, not as a classical syndrome with systemic signs of intoxication, as occurred it has in the past.

Fenton Reaction in vivo and in vitro. Possibilities and Limitations

The review considers the problem of hydrogen peroxide decomposition and hydroxyl radical formation in the presence of iron in vivo and in vitro. Analysis of the literature data allows us to conclude that, under physiological conditions, transport of iron, carried out with the help of carrier proteins, minimizes the possibility of appearance of free iron ions in cytoplasm of the cell. Under pathological conditions, when the process of transferring an iron ion from a donor protein to an acceptor protein can be disrupted due to modifications of the carrier proteins, iron ions can enter cytosol. However, at pH values close to neutral, which is typical for cytosol, iron ions are converted into water-insoluble hydroxides. This makes it impossible to decompose hydrogen peroxide according to the mechanism of the classical Fenton reaction. A similar situation is observed in vitro, since buffers with pH close to neutral are used to simulate free radical oxidation. At the same time, iron hydroxides are able to catalyze decomposition of hydrogen peroxide with formation of a hydroxyl radical. Decomposition of hydrogen peroxide with iron hydroxides is called Fenton-like reaction. Studying the features of Fenton-like reaction in biological systems is the subject of future research.

Ferroptosis: A potential target of macrophages in plaque vulnerability

Plaque vulnerability has been the subject of several recent studies aimed at reducing the risk of stroke and carotid artery stenosis. Atherosclerotic plaque development is a complex process involving inflammation mediated by macrophages. Plaques become more vulnerable when the equilibrium between macrophage recruitment and clearance is disturbed. Lipoperoxides, which are affected by iron levels in cells, are responsible for the cell death seen in ferroptosis. Ferroptosis results from lipoperoxide-induced mitochondrial membrane toxicity. Atherosclerosis in ApoE(-/-) mice is reduced when ferroptosis is inhibited and iron intake is limited. Single-cell sequencing revealed that a ferroptosis-related gene was substantially expressed in atherosclerosis-modeled macrophages. Since ferroptosis can be regulated, it offers hope as a non-invasive method of treating carotid plaque. In this study, we discuss the role of ferroptosis in atherosclerotic plaque vulnerability, including its mechanism, regulation, and potential future research directions.

Hematologic evaluation of peripheral blood in Sprague Dawley rats by chronic exposure to aluminum chloride (AlCl3)

This study aimed to evaluate whether aluminum chloride (AlCl3) causes hematological changes in the peripheral blood of Sprague-Dawley (SD) rats. Five groups of female SD rats were intragastrically administered with 4 different concentrations of AlCl3 for 5 days a week for a total of 90 days. The aluminum concentration was determined via graphite furnace atomic absorption spectroscopy. Analysis of serum iron-kinetic profiles, blood cytometry outcomes, and blood smears of the blood samples. Scanning electron microscopy (SEM) and Raman spectroscopy were used to search for structural and ultrastructural changes, respectively. Blood aluminum concentration ranged 12.38-16.24 μg/L with no significant difference between experimental treatments. At the AlCl3 concentration of 40 mg Al/kg bw of rats/day, the mean ferritin value in the serum iron kinetic profile was 29.81±6.1 ng/mL, and this value showed a significant difference between experimental treatments. Blood cytometry revealed that there were 6.45-7.11×106 cells/μL erythrocytes, 8.91-9.32×103 cells/μL leukocytes, and 477.2-736.3×103 cells/μL platelets along with a hemoglobin of 37.38-41.93 g/dL and hematocrit level of 37.38-41.93%; the experimental treatments showed no significant differences. Erythrocyte structural analysis using SEM showed no differences between experimental treatments, whereas ultrastructural evaluation using Raman spectroscopy made it possible to identify the following bands: 741, 1123, 1350, 1578, and 1618 cm-1, which were respectively associated with the following vibrational modes and compounds: vibration of the tryptophan ring, asymmetric C-O-C stretching of glucose, C-H curve of tryptophan, C=C stretching of the heme group, and C-N stretching of the heme group, with no significant differences between experimental treatments. Therefore, AlCl3 administration does not induce ultrastructural changes in the erythrocyte membrane. This study revealed that serum ferritin concentration was the only parameter affected by AlCl3 exposure at 40 mg of Al/kg bw of rats/day.

Bloodlettings in Hemochromatosis Result in Increased Blood Lead (Pb) Concentrations

Hemochromatosis is a hereditary disorder, most often associated with mutations of the HFE (High FErrum) gene. If left untreated, it can result in severe parenchymal iron accumulation. Bloodletting is the mainstay treatment. We have previously shown that treatment of hemochromatosis by repeated bloodlettings may induce changes in the serum levels of several trace elements. The aim of this work was to evaluate if whole blood concentrations of the environmental pollutants lead (Pb), mercury (Hg), and cadmium (Cd) could be affected by bloodlettings. We recruited 28 patients and 21 healthy individuals (control group). Whole blood and urine levels of Pb, Hg, and Cd were measured before the start and after the completion of treatment using inductively coupled plasma mass spectrometry, together with serum iron and liver function tests. Concentrations of blood Pb, but not Hg or Cd, were significantly increased after treatment. The increase in Pb was higher in C282Y homozygous patients than in the other patients, and it was positively correlated with the serum concentration of alkaline phosphatase. Bloodlettings in hemochromatosis result in an increase in the blood concentration of Pb. Augmented absorption due to iron loss or Pb mobilization from bone may contribute to the higher blood Pb level.

The immunotoxicity of natural and depleted uranium: From cells to people

Uranium is a naturally occurring element found in the environment as a mixture of isotopes with differing radioactive properties. Enrichment of mined material results in depleted uranium waste with substantially reduced radioactivity but retains the capacity for chemical toxicity. Uranium mine and milling waste are dispersed by wind and rain leading to environmental exposures through soil, air, and water contamination. Uranium exposure is associated with numerous adverse health outcomes in humans, yet there is limited understanding of the effects of depleted uranium on the immune system. The purpose of this review is to summarize findings on uranium immunotoxicity obtained from cell, rodent and human population studies. We also highlight how each model contributes to an understanding of mechanisms that lead to immunotoxicity and limitations inherent within each system. Information from population, animal, and laboratory studies will be needed to significantly expand our knowledge of the contributions of depleted uranium to immune dysregulation, which may then inform prevention or intervention measures for exposed communities.

Controversial Role of Transferrin in the Transport of Ruthenium Anticancer Drugs

Ruthenium complexes are at the forefront of developments in metal-based anticancer drugs, but many questions remain open regarding their reactivity in biological media, including the role of transferrin (Tf) in their transport and cellular uptake. A well-known anticancer drug, KP1019 ((IndH)[Ru^IIICl₄(Ind)₂], where Ind = indazole) and a reference complex, [Ru^III(nta)₂]^3- (nta = nitrilotriacetato(3-)) interacted differently with human apoTf, monoFeTf, or Fe₂Tf. These reactions were studied by biolayer interferometry (BLI) measurements of Ru-Fe-Tf binding to recombinant human transferrin receptor 1 (TfR1) in conjunction with UV-vis spectroscopy and particle size analysis. Cellular Ru uptake in human hepatoma (HepG2) cells was measured under the conditions of the BLI assays. The mode of Tf binding and cellular Ru uptake were critically dependent on the nature of Ru complex, availability of Fe(III) binding sites of Tf, and the presence of proteins that competed for metal binding, particularly serum albumin. Cellular uptake of KP1019 was not Tf-mediated and occurred mostly by passive diffusion, which may also be suitable for treatments of inoperable cancers by intratumoral injections. High cellular Ru uptake from a combination of [Ru^III(nta)₂]^3- and Fe₂Tf in the absence of significant Ru-Tf binding was likely to be due to trapping of Ru(III) species into the endosome during TfR1-mediated endocytosis of Fe₂Tf.

Advantageous Reactivity of Unstable Metal Complexes: Potential Applications of Metal-Based Anticancer Drugs for Intratumoral Injections

Injections of highly cytotoxic or immunomodulating drugs directly into the inoperable tumor is a procedure that is increasingly applied in the clinic and uses established Pt-based drugs. It is advantageous for less stable anticancer metal complexes that fail administration by the standard intravenous route. Such hydrophobic metal-containing complexes are rapidly taken up into cancer cells and cause cell death, while the release of their relatively non-toxic decomposition products into the blood has low systemic toxicity and, in some cases, may even be beneficial. This concept was recently proposed for V(V) complexes with hydrophobic organic ligands, but it can potentially be applied to other metal complexes, such as Ti(IV), Ga(III) and Ru(III) complexes, some of which were previously unsuccessful in human clinical trials when administered via intravenous injections. The potential beneficial effects include antidiabetic, neuroprotective and tissue-regenerating activities for V(V/IV); antimicrobial activities for Ga(III); and antimetastatic and potentially immunogenic activities for Ru(III). Utilizing organic ligands with limited stability under biological conditions, such as Schiff bases, further enhances the tuning of the reactivities of the metal complexes under the conditions of intratumoral injections. However, nanocarrier formulations are likely to be required for the delivery of unstable metal complexes into the tumor.

Investigation of iron release from the N- and C-lobes of human serum transferrin by quantum chemical calculations

Cluster models of iron binding sites of the N- and C-lobes highlights the inequivalence of each lobe in iron release.

In vitro evidence of the influence of complexation of Pu and Am on uptake by human lung epithelial cells Calu-3

Understanding the mechanisms involved in retention and clearance of actinides from the lungs after accidental intake is essential for the evaluation of the associated radiological risks. Although the absorption of radioelements has been shown in vivo to depend on their nature and physico-chemical properties, their mechanisms of translocation remain unknown. In this study, we have evaluated in vitro the binding and uptake by bronchial epithelial cells Calu-3 of 2 transuranic actinides, plutonium (Pu) and americium (Am), as the first steps of translocation across the pulmonary barrier. For this purpose, Calu-3 cells grown to confluence in 24-well plates were exposed to the radioelements for 24 h under various culture conditions. Two compartments were identified for the association of actinides to cells, corresponding to the membrane bound and internalized fractions. Binding of Pu was slightly higher than of Am, and depended on its initial chemical form (nitrate, citrate, colloids). Uptake of Pu and Am nitrate was higher in serum-free conditions than in supplemented medium, with an active mechanism involved in Pu internalization. Overall, our results suggest that complexation of actinides to bioligands may have an influence on their uptake by pulmonary epithelial cells, and therefore possibly on their subsequent absorption into blood.

Identification of novel yolk ferritins unique to planarians: planarians supply aluminum rather than iron to vitellaria in egg capsules

All animals, other than Platyhelminthes, produce eggs containing yolk, referred to as "entolecithal" eggs. However, only Neoophora, in the phylum Platyhelminthes, produce "ectolecithal" eggs (egg capsules), in which yolk is stored in the vitelline cells surrounding oocytes. Vitelline cells are derived from vitellaria (yolk glands). Vitellaria are important reproductive organs that may be studied to elucidate unique mechanisms that have been evolutionarily conserved within Platyhelminthes. Currently, only limited molecular level information is available on vitellaria. The current study identified major vitellaria-specific proteins in a freshwater planarian, Dugesia ryukyuensis, using peptide mass fingerprinting (PMF) and expression analyses. Amino acid sequence analysis and orthology analysis via OrthoFinder ver.2.3.8 indicated that the identified major vitellaria-specific novel yolk ferritins were conserved in planarians (Tricladida). Because ferritins play an important role in Fe (iron) storage, we examined the metal elements contained in vitellaria and ectolecithal eggs, using non-heme iron histochemistry, elemental analysis based on inductively coupled plasma mass spectrometry and transmission electron microscopy- energy-dispersive X-ray spectroscopy analysis. Interestingly, vitellaria and egg capsules contained large amounts of aluminum (Al), but not Fe. The knockdown of the yolk ferritin genes caused a decrease in the volume of egg capsules, abnormality in juveniles, and increase in Al content in vitellaria. Yolk ferritins of D. ryukyuensis may regulate Al concentration in vitellaria via their pooling function of Al and protect the egg capsule production and normal embryogenesis from Al toxicity.

A perspective essay on the use of Ga3+ as a proxy for Fe3+ in bioinorganic model studies and its successful use for therapeutic purposes

The use of Ga³⁺ as a structural mimic for Fe³⁺ in model bioinorganic investigations is usually based on a common assumption that Ga³⁺ and Fe³⁺ should form bioligand complexes of similar stabilities due to their similar charge/radius ratio (z/r). However, the literature survey presented here is contrary to this notion, showing that under laboratory conditions often Ga³⁺ forms weaker bioligand complexes than Fe³⁺in aqueous medium. We hypothesize that this is because Ga³⁺ is more aquaphilic than Fe³⁺ as suggested by their relative heats of hydration (ΔH_hyd). The successful use of Ga³⁺ as a therapeutic agent is also briefly reviewed, showing this success often stems from the redox inertness as well as different pharmacokinetics of Ga³⁺ than Fe³⁺, but similar metabolic pathways as Fe³⁺ in human serum.

A selective drug delivery system based on phospholipid-type nanobubbles for lung cancer therapy

Aim: To develop a micelle-type nanobubble decorated with fluorescein-5-isothiocyanate-conjugated transferrin, with encapsulation of paclitaxel (PTX@FT-NB) for lung cancer treatment. Materials & methods: PTX@FT-NBs were characterized to determine their physicochemical properties, structural stability and cytotoxicity. Lung cancer cell and mouse xenograft tumor models were used to evaluate the therapeutic effectiveness of PTX@FT-NB. Results: The PTX@FT-NBs not only showed selective targeting to lung cancer cells but also inhibited tumor growth significantly via paclitaxel release. Furthermore, paclitaxel-induced microtubule stabilization demonstrated the release of the drug from PTX@FT-NB in the targeted tumor cell both in vitro and in vivo. Conclusion: PTX@FT-NB has the potential as an anticancer nanocarrier against lung cancer cells because of its specific targeting and better drug delivery capacity.

Exploring Serum Transferrin Regulation of Nonferric Metal Therapeutic Function and Toxicity

Serum transferrin (sTf) plays a pivotal role in regulating iron biodistribution and homeostasis within the body. The molecular details of sTf Fe(III) binding blood transport, and cellular delivery through transferrin receptor-mediated endocytosis are generally well-understood. Emerging interest exists in exploring sTf complexation of nonferric metals as it facilitates the therapeutic potential and toxicity of several of them. This review explores recent X-ray structural and physiologically relevant metal speciation studies to understand how sTf partakes in the bioactivity of key non-redox active hard Lewis acidic metals. It challenges preconceived notions of sTf structure function correlations that were based exclusively on the Fe(III) model by revealing distinct coordination modalities that nonferric metal ions can adopt and different modes of binding to metal-free and Fe(III)-bound sTf that can directly influence how they enter into cells and, ultimately, how they may impact human health. This knowledge informs on biomedical strategies to engineer sTf as a delivery vehicle for metal-based diagnostic and therapeutic agents in the cancer field. It is the intention of this work to open new avenues for characterizing the functionality and medical utility of nonferric-bound sTf and to expand the significance of this protein in the context of bioinorganic chemistry.

Aqueous inorganic uranium speciation in European stream waters from the FOREGS dataset using geochemical modelling and determination of a U bioavailability baseline

The concentration of the bioavailable uranium fraction (U_bio) at the European scale was deduced by geochemical modelling considering several definitions found in the literature and the FOREGS European stream waters geochemical atlas dataset to produce a U_bio baseline. A sensitivity analysis was performed using three thermodynamic databases. We also investigated the link between total dissolved uranium (U_aq) concentrations, speciation and global stream water chemistry on the one hand, and the lithology and ages of the surrounding rocks on the other. The more U-enriched the stream sediments or rock type contexts are, which tends to be the case with rocks containing silicates (4.1 mg/kg), the less U-concentrated the stream waters are (0.15 μg/L). Sedimentary rocks lead to slightly higher U_aq concentrations (0.34 μg/L) even if the concentration in sediment (U_sed) is relatively low (1.6 mg/kg). This trend is reversed for U_bio, with higher concentrations in a crystalline context. The mean estimated U_bio value ranges from 1.5.10^-3 to 65.3 ng/L and can fluctuate by 3 orders of magnitude depending on the considered definition as opposed to by 2 orders of magnitude accountable to differences between thermodynamic databases. The classification of the water in relation to the two surrounding rock lithologies makes it possible to reduce the mean variability for the U_bio concentrations. Irrespective of the definition of U_bio considered, in 59% of cases the U_bio fraction represents less than 1% of U_aq. Several threshold values relating to U_bio were proposed, assuming knowledge only of the aqueous concentrations of the major elements and U_aq.

Competition between Al3+ and Fe3+ binding to human transferrin and toxicological implications: structural investigations using ultra-high resolution ESI MS and CD spectroscopy

Human serum transferrin (hTF) is an iron binding protein with the primary task of ensuring well-controlled transport of Fe3+-ions in the bloodstream. Furthermore, hTF has been identified as a key component in the trafficking of Al3+-ions from the serum to cells. It is clear that binding alone does not guarantee cellular uptake via the transferrin receptor, since this is determined by the structural properties of the metal-protein complex. The conformation of the metallated hTF is critically important for delivery of Fe3+ or any other metal into the cell. The combination of ultra-high resolution ESI mass spectrometry and CD spectroscopy together provide accurate species distribution of the Fe3+ during stepwise addition to apo-hTF and an indirect indication of the tertiary structure of the metallated protein. These two methods together are extremely fine probes of structural changes as a function of precise metal binding status at micromolar concentrations. Simulation of the precise domain distribution could be determined during the stepwise metallation from 0 to 2 Fe3+ added. Analysis of the ESI-MS data for the stepwise metallation of apo-hTF and Al1 or 2-hTF with Fe3+ was carried out and used to simulate the experimental speciation based on the reported KF values. There are six main conclusions: (1) Fe3+ binds predominantly, initially to the C-lobe. (2) The CD spectral properties indicate that the C-lobe metallation dominates the structural properties of both binding sites; N-lobe metallation modifies the C-lobe structure. (3) Fe3+ metallation of the mixed Al1-2-hTF results in the dominant form of Fe1Al1-hTF. (4) The first Fe3+ bound to Al1-hTF binds predominantly in the C-lobe domain. (5) The CD spectral properties when Fe3+ binds to Al1-2-hTF indicates that Al-N-lobe occupation mirrors the structural effects of N-lobe occupation by Fe3+. (6) With respect to how Al3+ might enter the cell, the formation of a hybrid form Al1Fe1-hTF might enable the Al3+ to enter the cell via receptor-mediated endocytosis due to the binding of Fe3+ in the C-lobe of the protein which is primarily responsible for the structure of the metal-protein complex.

Significance of conformation changes during the binding and release of chromium(III) from human serum transferrin

Trivalent chromium has been proposed to be transported in vivo from the bloodstream to the tissues via endocytosis by transferrin (Tf), the major iron transport protein in the blood. While both Cr(III) binding and release from Tf have been proposed to be too slow to be physiologically relevant, recent kinetic studies under physiological conditions demonstrate that Cr(III) binding and release are sufficiently fast to occur during the time of the endocytosis cycle (circa 15 min). Consequently, the release of Cr(III) from human and bovine serum Tf has been examined under conditions mimicking an endosome during endocytosis. These studies have also found that Cr(III)2-Tf can exist in multiple conformations giving rise to different spectroscopic properties and different rates of Cr(III) release. Time-dependent spectroscopic studies of the binding and release of Cr(III) from human serum Tf have been used to identify three different conformations of Cr(III)2-Tf. The conformation of Cr(III)2-Tf used in most previous studies forms too slowly to be physiologically relevant and slowly releases Cr(III) in endosomal pH range. The conformation formed between 5 min to 60 min after the addition of Cr(III) to apoTf at pH 7.4 in 25 mM bicarbonate resembles the conformation of Cr(III)2-Tf in its complex with Tf receptor (TfR) and loses Cr(III) rapidly at endosomal pH, although not as fast as the Tf-TfR complex. The significance of these conformations and the potential role of Tf in detoxification of Cr(III) are described.

Iron-oxide minerals in the human tissues

Iron is critically important and highly regulated trace metal in the human body. However, in its free ion form, it is known to be cytotoxic; therefore, it is bound to iron storing protein, ferritin. Ferritin is a key regulator of body iron homeostasis able to form various types of minerals depending on the tissue environment. Each mineral, e.g. magnetite, maghemite, goethite, akaganeite or hematite, present in the ferritin core carry different characteristics possibly affecting cells in the tissue. In specific cases, it can lead to disease development. Widely studied connection with neurodegenerative conditions is widely studied, including Alzheimer disease. Although the exact ferritin structure and its distribution throughout a human body are still not fully known, many studies have attempted to elucidate the mechanisms involved in its regulation and pathogenesis. In this review, we try to summarize the iron uptake into the body. Next, we discuss the known occurrence of ferritin in human tissues. Lastly, we also examine the formation of iron oxides and their involvement in brain functions.

Iron and leukemia: new insights for future treatments

Iron, an indispensable element for life, is involved in all kinds of important physiological activities. Iron promotes cell growth and proliferation, but it also causes oxidative stress damage. The body has a strict regulation mechanism of iron metabolism due to its potential toxicity. As a cancer of the bone marrow and blood cells, leukemia threatens human health seriously. Current studies suggest that dysregulation of iron metabolism and subsequent accumulation of excess iron are closely associated with the occurrence and progress of leukemia. Specifically, excess iron promotes the development of leukemia due to the pro-oxidative nature of iron and its damaging effects on DNA. On the other hand, leukemia cells acquire large amounts of iron to maintain rapid growth and proliferation. Therefore, targeting iron metabolism may provide new insights for approaches to the treatment of leukemia. This review summarizes physiologic iron metabolism, alternations of iron metabolism in leukemia and therapeutic opportunities of targeting the altered iron metabolism in leukemia, with a focus on acute leukemia.

Transferrin Cycle and Clinical Roles of Citrate and Ascorbate in Improved Iron Metabolism

Fe(III) delivery from blood plasma to cells via the transferrin (Tf) cycle was studied intensively due to its crucial role in Fe homeostasis. Tf-cycle disruptions are linked to anemia, infections, immunodeficiency, and neurodegeneration. Biolayer interferometry (BLI) enabled direct kinetic and thermodynamic measurements for all Tf-cycle steps in a single in vitro experiment using Tf within blood serum or released into the medium by cultured liver cells. In these media, known Tf cycle features were reproduced, and unprecedented insights were gained into conditions of rapid endosomal (pH 5.6) Fe(III) release from the Tf-Tf receptor 1 (TfR1) adduct. This release occurred via synergistic citrate and ascorbate effects, which pointed to respective roles as the likely elusive Fe chelator and reductant within the Tf cycle. These results explain enhanced cellular Fe uptake by ascorbate, the clinical efficacy of anemia treatment with Fe citrate and ascorbate, and dietary effects associated with loss of Fe homeostasis, including the large health burden of infections and neurodegeneration.

Iron metabolism and its contribution to cancer (Review)

Iron is an essential element for biological processes. Iron homeostasis is regulated through several mechanisms, from absorption by enterocytes to recycling by macrophages and storage in hepatocytes. Iron has dual properties, which may facilitate tumor growth or cell death. Cancer cells exhibit an increased dependence on iron compared with normal cells. Macrophages potentially deliver iron to cancer cells, resulting in tumor promotion. Mitochondria utilize cellular iron to synthesize cofactors, including heme and iron sulfur clusters. The latter is composed of essential enzymes involved in DNA synthesis and repair, oxidation‑reduction reactions, and other cellular processes. However, highly increased iron concentrations result in cell death through membrane lipid peroxidation, termed ferroptosis. Ferroptosis, an emerging pathway for cancer treatment, is similar to pyroptosis, apoptosis and necroptosis. In the present review, previous studies on the physiology of iron metabolism and its role in cancer are summarized. Additionally, the significance of iron regulation, and the association between iron homeostasis and carcinogenic mechanisms are discussed.

Uptake and molecular impact of aluminum-containing nanomaterials on human intestinal caco-2 cells

Aluminum (Al) is one of the most common elements in the earth crust and increasingly used in food, consumer products and packaging. Its hazard potential for humans is still not completely understood. Besides the metallic form, Al also exists as mineral, including the insoluble oxide, and in soluble ionic forms. Representatives of these three species, namely a metallic and an oxidic species of Al-containing nanoparticles and soluble aluminum chloride, were applied to human intestinal cell lines as models for the intestinal barrier. We characterized physicochemical particle parameters, protein corona composition, ion release and cellular uptake. Different in vitro assays were performed to determine potential effects and molecular modes of action related to the individual chemical species. For a deeper insight into signaling processes, microarray transcriptome analyses followed by bioinformatic data analysis were employed. The particulate Al species showed different solubility in biological media. Metallic Al nanoparticles released more ions than Al₂O₃ nanoparticles, while AlCl₃ showed a mixture of dissolved and agglomerated particulate entities in biological media. The protein corona composition differed between both nanoparticle species. Cellular uptake, investigated in transwell experiments, occurred predominantly in particulate form, whereas ionic Al was not taken up by intestinal cell lines. Transcellular transport was not observed. None of the Al species showed cytotoxic effects up to 200 µg Al/mL. The transcriptome analysis indicated mainly effects on oxidative stress pathways, xenobiotic metabolism and metal homeostasis. We have shown for the first time that intestinal cellular uptake of Al occurs preferably in the particle form, while toxicological effects appear to be ion-related.

Reversal of behavioral decline and neuropathology by a complex vitamin supplement involves modulation of key neurochemical stressors

Metal ions are crucial for normal neurochemical signaling and perturbations in their homeostasis have been associated with neurodegenerative processes. Hypothesizing that in vivo modulation of key neurochemical processes including metal ion regulation (by transferrin receptor-1: TfR-1) in cells can improve disease outcome, we investigated the efficacy of a complex vitamin supplement (CVS) containing B-vitamins and ascorbic acid in preventing/reversing behavioral decline and neuropathology in rats. Wistar rats (eight weeks-old) were assigned into five groups (n = 8), including controls and those administered CVS (400 mg/kg/day) for two weeks before or after AlCl₃ (100 mg/kg)-induced neurotoxicity. Following behavioral assessments, prefrontal cortex (PFC) and hippocampus were prepared for biochemical analyses, histology and histochemistry. CVS significantly reversed reduction of exploratory/working memory, frontal-dependent motor deficits, cognitive decline, memory dysfunction and anxiety. These correlated with CVS-dependent modulation of TfP-1 expression that were accompanied by significant reversal of neural oxidative stress in expressed superoxide dismutase, nitric oxide, catalase, glutathione peroxidase and malondialdehyde. Furthermore, CVS inhibited neural bioenergetics dysfunction, with increased labelling of glucokinase within PFC and hippocampus correlating with increased glucose-6-phosphate dehydrogenase and decreased lactate dehydrogenase expressions. These relates to inhibition of over-expressed acetylcholinesterase and increased total protein synthesis. Histological and Nissl staining of thin sections corroborated roles of CVS in reversing AlCl₃-induced neuropathology. Summarily, we showed the role of CVS in normalizing important neurochemical molecules linking concurrent progression of oxidative stress, bioenergetics deficits, synaptic dysfunction and cellular hypertrophy during neurodegeneration.

Endosomal vacuoles of the prepupal salivary glands of Drosophila play an essential role in the metabolic reallocation of iron

In the recent past, we demonstrated that a great deal is going on in the salivary glands of Drosophila in the interval after they release their glycoprotein-rich secretory glue during pupariation. The early-to-mid prepupal salivary glands undergo extensive endocytosis with widespread vacuolation of the cytoplasm followed by massive apocrine secretion. Here, we describe additional novel properties of these endosomes. The use of vital pH-sensitive probes provided confirmatory evidence that these endosomes have acidic contents and that there are two types of endocytosis seen in the prepupal glands. The salivary glands simultaneously generate mildly acidic, small, basally-derived endosomes and strongly acidic, large and apical endosomes. Staining of the large vacuoles with vital acidic probes is possible only after there is ambipolar fusion of both basal and apical endosomes, since only basally-derived endosomes can bring fluorescent probes into the vesicular system. We obtained multiple lines of evidence that the small basally-derived endosomes are chiefly involved in the uptake of dietary Fe³⁺ iron. The fusion of basal endosomes with the larger and strongly acidic apical endosomes appears to facilitate optimal conditions for ferrireductase activity inside the vacuoles to release metabolic Fe²⁺ iron. While iron was not detectable directly due to limited staining sensitivity, we found increasing fluorescence of the glutathione-sensitive probe CellTracker Blue CMAC in large vacuoles, which appeared to depend on the amount of iron released by ferrireductase. Moreover, heterologous fluorescently-labeled mammalian iron-bound transferrin is actively taken up, providing direct evidence for active iron uptake by basal endocytosis. In addition, we serendipitously found that small (basal) endosomes were uniquely recognized by PNA lectin, whereas large (apical) vacuoles bound DBA lectin.

Dopamine promotes cellular iron accumulation and oxidative stress responses in macrophages

Iron is essential for many biological functions including neurotransmitter synthesis, where the metal is a co-factor of tyrosine hydroxylase, which converts tyrosine to dopamine and further to norepinephrine. As the shared chemical structure, called catechol, may potentially bind iron we questioned whether tyrosine derived hormones would impact on cellular iron homeostasis in macrophages, which are central for the maintenance of body iron homeostasis. Using murine bone marrow-derived macrophages (BMDMs), we investigated the effect of catecholamines and found that only dopamine but neither tyrosine, nor norepinephrine, affected cellular iron homeostasis. Exposure of macrophages to dopamine increased the uptake of non-transferrin bound iron into cells. The expansion of intracellular iron upon dopamine treatment resulted in oxidative stress responses as evidenced by increased expression of nuclear factor erythroid 2-related factor (Nrf2) and hypoxia inducible factor-1α. As a consequence, the transcriptional expression of stress response genes such as heme oxygenase-1 and the iron export protein ferroportin1 were significantly increased. Genetic deletion of Nrf2 abolished these effects of dopamine. Dopamine directly affects cellular iron homeostasis by increasing iron incorporation into macrophages and subsequently promoting intracellular oxidative stress responses. Our observations are of interest for disorders involving dopamine and iron dyshomeostasis such as Parkinson's disease and restless legs syndrome, partly enlightening the underlying pathology or the therapeutic efficacy of dopamine agonists to overcome neuronal iron deficiency.

Lactoferrin: A Natural Glycoprotein Involved in Iron and Inflammatory Homeostasis

Human lactoferrin (hLf), an iron-binding multifunctional cationic glycoprotein secreted by exocrine glands and by neutrophils, is a key element of host defenses. HLf and bovine Lf (bLf), possessing high sequence homology and identical functions, inhibit bacterial growth and biofilm dependently from iron binding ability while, independently, bacterial adhesion to and the entry into cells. In infected/inflamed host cells, bLf exerts an anti-inflammatory activity against interleukin-6 (IL-6), thus up-regulating ferroportin (Fpn) and transferrin receptor 1 (TfR1) and down-regulating ferritin (Ftn), pivotal actors of iron and inflammatory homeostasis (IIH). Consequently, bLf inhibits intracellular iron overload, an unsafe condition enhancing in vivo susceptibility to infections, as well as anemia of inflammation (AI), re-establishing IIH. In pregnant women, affected by AI, bLf oral administration decreases IL-6 and increases hematological parameters. This surprising effect is unrelated to iron supplementation by bLf (80 μg instead of 1-2 mg/day), but to its role on IIH. AI is unrelated to the lack of iron, but to iron delocalization: cellular/tissue overload and blood deficiency. BLf cures AI by restoring iron from cells to blood through Fpn up-expression. Indeed, anti-inflammatory activity of oral and intravaginal bLf prevents preterm delivery. Promising bLf treatments can prevent/cure transitory inflammation/anemia/oral pathologies in athletes.

Lactoferrin: A Natural Glycoprotein Involved in Iron and Inflammatory Homeostasis

Human lactoferrin (hLf), an iron-binding multifunctional cationic glycoprotein secreted by exocrine glands and by neutrophils, is a key element of host defenses. HLf and bovine Lf (bLf), possessing high sequence homology and identical functions, inhibit bacterial growth and biofilm dependently from iron binding ability while, independently, bacterial adhesion to and the entry into cells. In infected/inflamed host cells, bLf exerts an anti-inflammatory activity against interleukin-6 (IL-6), thus up-regulating ferroportin (Fpn) and transferrin receptor 1 (TfR1) and down-regulating ferritin (Ftn), pivotal actors of iron and inflammatory homeostasis (IIH). Consequently, bLf inhibits intracellular iron overload, an unsafe condition enhancing in vivo susceptibility to infections, as well as anemia of inflammation (AI), re-establishing IIH. In pregnant women, affected by AI, bLf oral administration decreases IL-6 and increases hematological parameters. This surprising effect is unrelated to iron supplementation by bLf (80 μg instead of 1-2 mg/day), but to its role on IIH. AI is unrelated to the lack of iron, but to iron delocalization: cellular/tissue overload and blood deficiency. BLf cures AI by restoring iron from cells to blood through Fpn up-expression. Indeed, anti-inflammatory activity of oral and intravaginal bLf prevents preterm delivery. Promising bLf treatments can prevent/cure transitory inflammation/anemia/oral pathologies in athletes.

A microscale protocol for the isolation of transferrin directly from serum

A microscale procedure for the isolation of transferrin directly from human serum (hTf) is described in this study. The protocol is based on three precipitation steps without application of chromatography. It lasts 90min with the initial sample volume of 250μL. The yield of the isolated hTf is 58%, which is considerable in biochemical terms. The purity of the isolated hTf is 97%, as assessed by three methods: electrophoresis followed by protein staining, immunoblotting and HPLC. Immunoblotting with antibodies against other major serum proteins indicated that isolated hTf does not contain albumin, immunoglobulin G or alpha-2-macroglobulin. Lectin dot-blot demonstrated that isolated hTf preserved its glycan moieties. Fluorescent emission spectroscopy of the isolated hTf has shown no changes in tertiary structure. Isolated hTf was approximately 26% saturated with iron ion, which is comparable to physiological value (although a degree of saturation decreases to some extent during isolation procedure). Finally, co-immunoprecipitation experiment confirmed that isolated hTf retained its ligand characteristics crucial for the ligand-receptor type of interaction with the hTf receptor. To conclude, the procedure described in this work, is time and cost-effective, allows multiple sample handling and provides high-purity hTf isolate with preserved structural and functional properties.

Biogeochemical Controls of Uranium Bioavailability from the Dissolved Phase in Natural Freshwaters

To gain insights into the risks associated with uranium (U) mining and processing, we investigated the biogeochemical controls of U bioavailability in the model freshwater species Lymnaea stagnalis (Gastropoda). Bioavailability of dissolved U(VI) was characterized in controlled laboratory experiments over a range of water hardness, pH, and in the presence of complexing ligands in the form of dissolved natural organic matter (DOM). Results show that dissolved U is bioavailable under all the geochemical conditions tested. Uranium uptake rates follow first order kinetics over a range encompassing most environmental concentrations. Uranium uptake rates in L. stagnalis ultimately demonstrate saturation uptake kinetics when exposure concentrations exceed 100 nM, suggesting uptake via a finite number of carriers or ion channels. The lack of a relationship between U uptake rate constants and Ca uptake rates suggest that U does not exclusively use Ca membrane transporters. In general, U bioavailability decreases with increasing pH, increasing Ca and Mg concentrations, and when DOM is present. Competing ions did not affect U uptake rates. Speciation modeling that includes formation constants for U ternary complexes reveals that the aqueous concentration of dicarbonato U species (UO2(CO3)2(-2)) best predicts U bioavailability to L. stagnalis, challenging the free-ion activity model postulate.

Hepcidin independent iron recycling in a mouse model of β-thalassaemia intermedia

In conditions such as β-thalassaemia, stimulated erythropoiesis can reduce the expression of the iron regulatory hormone hepcidin, increasing both macrophage iron release and intestinal iron absorption and leading to iron loading. However, in certain conditions, sustained elevation of erythropoiesis can occur without an increase in body iron load. To investigate this in more detail, we made use of a novel mouse strain (RBC14), which exhibits mild β-thalassaemia intermedia with minimal iron loading. We compared iron homeostasis in RBC14 mice to that of Hbb^th3/+ mice, a more severe model of β-thalassaemia intermedia. Both mouse strains showed a decrease in plasma iron half-life, although the changes were less severe in RBC14 mice. Despite this, intestinal ferroportin and serum hepcidin levels were unaltered in RBC14 mice. In contrast, Hbb^th3/+ mice exhibited reduced serum hepcidin and increased intestinal ferroportin. However, splenic ferroportin levels were increased in both mouse strains. These data suggest that in low-grade chronic haemolytic anaemia, such as that seen in RBC14 mice, the increased erythroid iron requirements can be met through enhanced macrophage iron release without the need to increase iron absorption, implying that hepcidin is not the sole regulator of macrophage iron release in vivo.

Iron acquisition in Leishmania and its crucial role in infection

Iron is an essential cofactor for many basic metabolic pathways in pathogenic microbes and their hosts. It is also dangerous as it can catalyse the production of reactive free radicals. This dual character makes the host can either limit iron availability to invading microbes or exploit iron to induce toxicity to pathogens. Successful pathogens, including Leishmania species, must possess mechanisms to circumvent host's iron limitation and iron-induced toxicity in order to survive. In this review, we discuss the regulation of iron metabolism in the setting of infection and delineate the iron acquisition strategies used by Leishmania parasites and their subversions to host iron metabolism to overcome host's iron-related defences.

Investigation of the roles of trace elements during hepatitis C virus infection using protein-protein interactions and a shortest path algorithm

BACKGROUND

Hepatitis is a type of infectious disease that induces inflammation of the liver without pinpointing a particular pathogen or pathogenesis. Type C hepatitis, as a type of hepatitis, has been reported to induce cirrhosis and hepatocellular carcinoma within a very short amount of time. It is a great threat to human health. Some studies have revealed that trace elements are associated with infection with and immune rejection against hepatitis C virus (HCV). However, the mechanism underlying this phenomenon is still unclear.

METHODS

In this study, we aimed to expand our knowledge of this phenomenon by designing a computational method to identify genes that may be related to both HCV and trace element metabolic processes. The searching procedure included three stages. First, a shortest path algorithm was applied to a large network, constructed by protein-protein interactions, to identify potential genes of interest. Second, a permutation test was executed to exclude false discoveries. Finally, some rules based on the betweenness and associations between candidate genes and HCV and trace elements were built to select core genes among the remaining genes.

RESULTS

12 lists of genes, corresponding to 12 types of trace elements, were obtained. These genes are deemed to be associated with HCV infection and trace elements metabolism.

CONCLUSIONS

The analyses indicate that some genes may be related to both HCV and trace element metabolic processes, further confirming the associations between HCV and trace elements. The method was further tested on another set of HCV genes, the results indicate that this method is quite robustness.

GENERAL SIGNIFICANCE

The newly found genes may partially reveal unknown mechanisms between HCV infection and trace element metabolism. This article is part of a Special Issue entitled "System Genetics" Guest Editor: Dr. Yudong Cai and Dr. Tao Huang.

Targeted Delivery of Amoxicillin to C. trachomatis by the Transferrin Iron Acquisition Pathway

Weak intracellular penetration of antibiotics makes some infections difficult to treat. The Trojan horse strategy for targeted drug delivery is among the interesting routes being explored to overcome this therapeutic difficulty. Chlamydia trachomatis, as an obligate intracellular human pathogen, is responsible for both trachoma and sexually transmitted diseases. Chlamydia develops in a vacuole and is therefore protected by four membranes (plasma membrane, bacterial inclusion membrane, and bacterial membranes). In this work, the iron-transport protein, human serum-transferrin, was used as a Trojan horse for antibiotic delivery into the bacterial vacuole. Amoxicillin was grafted onto transferrin. The transferrin-amoxicillin construct was characterized by mass spectrometry and absorption spectroscopy. Its affinity for transferrin receptor 1, determined by fluorescence emission titration [K_affTf-amox = (1.3 ± 1.0) x 10⁸], is very close to that of transferrin [4.3 x 10⁸]. Transmission electron and confocal microscopies showed a co-localization of transferrin with the bacteria in the vacuole and were also used to evaluate the antibiotic capability of the construct. It is significantly more effective than amoxicillin alone. These promising results demonstrate targeted delivery of amoxicillin to suppress Chlamydia and are of interest for Chlamydiaceae and maybe other intracellular bacteria therapies.

Predicting long term cooperativity and specific modulators of receptor interactions in human transferrin from dynamics within a single microstate

PRS identifies regions contacting rapidly evolving residues that mechanically manipulate dissociation from the pathogen in the human transferrin–bacterial receptor complex.

Respiratory metabolism of salivary glands during the late larval and prepupal development of Drosophila melanogaster

During the late larval period, the salivary glands (SG) of Drosophila show a cascade of cytological changes associated with exocytosis and the expectoration of the proteinaceous glue that is used to affix the pupariating larva to a substrate. After puparium formation (APF), SG undergo extensive cytoplasmic vacuolation due to endocytosis, vacuole consolidation and massive apocrine secretion. Here we investigated possible correlations between cytological changes, the puffing pattern in polytene chromosomes and respiratory metabolism of the SG. The carefully staged SG were explanted into small amounts (1 or 2μl) of tissue culture medium. The respiratory metabolism of single or up to 3 pairs of glands was evaluated by recording the rate of O2 consumption using a scanning microrespirographic technique sensitive to subnanoliter volumes of the respiratory O2 or CO2. The recordings were carried out at times between 8h before pupariation (BPF), until 16h APF, at which point the SG completely disintegrate. At the early wandering larval stage (8h BPF), the glands consume 2nl of O2/gland/min (=2500μl O2/g/h). This relatively high metabolic rate decreases down to 1.2-1.3nl of O2 during the endogenous peak in ecdysteroid concentration that culminates around pupariation. The metabolic decline coincides with the exocytosis of the proteinaceous glue. During and shortly after puparium formation, which is accompanied cytologically by intense vacuolation, O2 consumption in the SG temporarily increases to 1.6nl O2/gland/min. After this time, the metabolic rate of the SG decreases downward steadily until 16h APF, when the glands disintegrate and cease to consume oxygen. The SG we analyzed from Drosophila larvae were composed of 134 intrinsic cells, with the average volume of one lobe being 37nl. Therefore, a single SG cell of the wandering larva (with O2 consumption of 2nl/gland/min), consumes each about 16pl of O2/cell/min. A simultaneous analysis of the rate of protein and RNA synthesis in the SG shows a course similar to that found in respiratory metabolism.

Gallium-68-labeled anti-HER2 single-chain Fv fragment: development and in vivo monitoring of HER2 expression

PURPOSE

We aimed to develop a gallium-68 (Ga-68)-labeled single-chain variable fragment (scFv) targeting the human epidermal growth factor receptor 2 (HER2) to rapidly and noninvasively evaluate the status of HER2 expression.

PROCEDURES

Anti-HER2 scFv was labeled with Ga-68 by using deferoxamine (Df) as a bifunctional chelate. Biodistribution of [(68)Ga]Df-anti-HER2 scFv was examined with tumor-bearing mice and positron emission tomography (PET) imaging was performed. The changes in HER2 expression after anti-HER2 therapy were monitored by PET imaging.

RESULTS

[(68)Ga]Df-anti-HER2 scFv was obtained with high radiochemical yield after only a 5-min reaction at room temperature. The probe showed high accumulation in HER2-positive xenografts and the intratumoral distribution of radioactivity coincided with HER2-positive regions. Furthermore, [(68)Ga]Df-anti-HER2 scFv helped visualize HER2-positive xenografts and monitor the changes in HER2 expression after anti-HER2 therapy.

CONCLUSION

[(68)Ga]Df-anti-HER2 scFv could be a promising probe to evaluate HER2 status by in vivo PET imaging, unless trastuzumab is prescribed as part of the therapy.

Transferrin: Endocytosis and Cell Signaling in Parasitic Protozoa

Iron is the fourth most abundant element on Earth and the most abundant metal in the human body. This element is crucial for life because almost all organisms need iron for several biological activities. This is the case with pathogenic organisms, which are at the vanguard in the battle with the human host for iron. The latest regulates Fe concentration through several iron-containing proteins, such as transferrin. The transferrin receptor transports iron to each cell that needs it and maintains it away from pathogens. Parasites have developed several strategies to obtain iron as the expression of specific transferrin receptors localized on plasma membrane, internalized through endocytosis. Signal transduction pathways related to the activation of the receptor have functional importance in proliferation. The study of transferrin receptors and other proteins with action in the signaling networks is important because these proteins could be used as therapeutic targets due to their specificity or to differences with the human counterpart. In this work, we describe proteins that participate in signal transduction processes, especially those that involve transferrin endocytosis, and we compare these processes with those found in T. brucei, T. cruzi, Leishmania spp., and E. histolytica parasites.

The binding, transport and fate of aluminium in biological cells

Aluminium is the most abundant metal in the Earth's crust and yet, paradoxically, it has no known biological function. Aluminium is biochemically reactive, it is simply that it is not required for any essential process in extant biota. There is evidence neither of element-specific nor evolutionarily conserved aluminium biochemistry. This means that there are no ligands or chaperones which are specific to its transport, there are no transporters or channels to selectively facilitate its passage across membranes, there are no intracellular storage proteins to aid its cellular homeostasis and there are no pathways which evolved to enable the metabolism and excretion of aluminium. Of course, aluminium is found in every compartment of every cell of every organism, from virus through to Man. Herein we have investigated each of the 'silent' pathways and metabolic events which together constitute a form of aluminium homeostasis in biota, identifying and evaluating as far as is possible what is known and, equally importantly, what is unknown about its uptake, transport, storage and excretion.

Bloodletting therapy in hemochromatosis: Does it affect trace element homeostasis?

Hemochromatosis is the most common hereditary disorder in the Nordic population, if left untreated it can result in severe parenchymal iron accumulation. Bloodletting is mainstay treatment. Iron and trace elements partially share cellular uptake and transport mechanisms, and the aim of the present study was to see if bloodletting for hemochromatosis affects trace elements homeostasis. We recruited patients referred for diagnosis and treatment of hemochromatosis, four women and 22 men 23-68 years of age. Thirteen were C282Y homozygote, one was C282Y heterozygote, three were H63D homozygote, seven were compound heterozygote and two had none of the mutations above. Iron and liver function tests were performed; serum levels of trace elements were measured using inductively coupled plasma mass spectrometry. Results before the start of treatment and after normalization of iron parameters were compared. On completion of the bloodlettings the following average serum concentrations increased: Co from 5.6 to 11.5 nmol/L, serum Cu 16.2-17.6 μmol/L, Ni increased from 50.0 to 52.6 nmol/L and Sb from 13.2 to 16.3 nmol/L. Average serum Mn concentration declined from 30.2 to 28.3 nmol/L. All changes were statistically significant (by paired t-test). B, Ba, Cs, Mo, Se, Sr and Zn were not significantly changed. We conclude that bloodlettings in hemochromatosis lead to changes in trace element metabolism, including increased absorption of potentially toxic elements.

Chromium

Chromium is ubiquitous in the environment as Cr(III) and Cr(VI) oxidation states, which interconvert under environmentally and biologically relevant conditions (although Cr(III) usually predominates). While Cr(VI) is an established human carcinogen and a major occupational and environmental hazard, Cr(III) has long been regarded as an essential human micronutrient, although recent literature has cast serious doubts on the validity of this postulate. Despite five decades of research, no functional Cr-containing enzymes or cofactors have been characterized conclusively, and several hypotheses on their possible structures have been refuted. Gastrointestinal absorption pathways for both Cr(III) and Cr(VI) are apparent and whole-blood speciation can involve Cr(VI) uptake and reduction by red blood cells, as well as Cr(III) binding to both proteins and low-molecular-mass ligands in the plasma. DNA-damaging effects of Cr(VI) and anti-diabetic activities of Cr(III) are likely to arise from common mechanistic pathways that involve reactive Cr(VI/V/IV) intermediates and kinetically inert Cr(III)-protein and Cr(III)-DNA adducts. Both Cr(III) and Cr(VI) are toxic to plants and microorganisms, particularly Cr(VI) due to its higher bioavailability and redox chemistry. Some bacteria reduce Cr(VI) to Cr(III) without the formation of toxic Cr(V) intermediates and these bacteria are being considered for use in the bioremediation of Cr(VI)-polluted environments.

Iron, hepcidin, and the metal connection

Identification of new players in iron metabolism, such as hepcidin, which regulates ferroportin and divalent metal transporter 1 expression, has improved our knowledge of iron metabolism and iron-related diseases. However, from both experimental data and clinical findings, "iron-related proteins" appear to also be involved in the metabolism of other metals, especially divalent cations. Reports have demonstrated that some metals may affect, directly or indirectly, the expression of proteins involved in iron metabolism. Throughout their lives, individuals are exposed to various metals during personal and/or occupational activities. Therefore, better knowledge of the connections between iron and other metals could improve our understanding of iron-related diseases, especially the variability in phenotypic expression, as well as a variety of diseases in which iron metabolism is secondarily affected. Controlling the metabolism of other metals could represent a promising innovative therapeutic approach.