Ferritin is the main intracellular iron storage protein. Ferritin iron may be released by many reducing agents including ascorbate. In this work we report ferritin to catalyze the oxidation of ascorbate. The kinetics of this process were studied in detail in phosphate buffer (pH 7.40), at 37 degrees C by using the Clark electrode technique and ESR. The catalytic effect of ferritin manifested itself as the increase both in the rate of oxygen uptake and steady-state concentration of the ascorbate radical. The ferritin catalytic activity was found to be modified by iron chelators, EDTA. Desferal (DFO) as well as by ferrozine (FRZ) which is widely used in kinetic studies on ferritin iron release thanks to the formation of a coloured complex with Fe(II). While EDTA promotes the catalytic action of ferritin, DFO and FRZ diminished it. From the comparison of the kinetics of ascorbate oxidation obtained in the current work and data on the kinetics of ferritin iron release reported by Boyer and McCleary ((1987) Free Rad. Biol. Med. 3, 389-395), we conclude that iron bound to ferritin rather than the iron released is likely responsible for ferritin catalytic action. In addition, it has been concluded that the use of FRZ as an analytical reagent in kinetic studies of reductive ferritin iron release requires taking into account the competitive character of the formation of the Fe(II)-FRZ complex.

Release of neutrophil extracellular traps (NETs) is one of the neutrophils' mechanisms involved in the response to infection. NETs are released from the cell in response to a biological or synthetic stimulus to entrap, immobilize and kill pathogens. Metal ions and metal binding proteins were identified in the structure of NETs, but their role in NET release remains unclear. The aim of this study was to assess how lack of iron and zinc generated by ion sequestration using chelators affects NET release. Neutrophils were isolated from whole blood or buffy coats of healthy blood donors by density gradient centrifugation and incubated with zinc chelators: 20 µM N,N,N',N'-Tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), 40 µM diethylenetriaminepentaacetic acid (DTPA) or iron chelators: 400 µM deferoxamine mesylate salt (DFO) and 50 µM iminodiacetic acid (IDA). Next, 100 nM phorbol 12-myristate 13-acetate (PMA) was added to stimulate release of NETs. The amount of released DNA was measured by fluorometry and NETs were visualized by immunofluorescence microscopy. This study demonstrates that iron and zinc chelators are able to modulate NET release. Here we show that preincubation of neutrophils with TPEN and IDA inhibits NET release in cells stimulated with PMA. On the other hand, DFO stimulates NET release. Incubation of cells with DTPA does not affect release of NETs.

The aim of this study is to evaluate eye structures and function in patients receiving iron chelating therapy and to assess whether a correlation exists between the onset of ocular alterations and the intake of iron chelating drugs.

MAO-B leads to an increase in the levels of hydrogen peroxide and oxidative free radicals, which contribute to the aetiology of the AD. Thus, both iron ion chelators and MAO-B inhibitors can be used to treat AD. Taking the coumarin derivatives and hydroxypyridinones as the lead compounds, a series of dual-target hybrids were designed and synthesised by Click Chemistry. The compounds were biologically evaluated for their iron ion chelating and MAO-B inhibitory activity. Most of the compounds displayed excellent iron ion chelating activity and moderate to good anti-MAO-B activity. Compounds 27b and 27j exhibited the most potent MAO-B inhibitory activity, with IC50 values of 0.68 and 0.86 μM, respectively. In summary, these dual-target compounds have the potential anti-AD activity.

Bacterial growth and proliferation can be restricted by limiting the availability of metal ions in their environment. Humans sequester iron, manganese, and zinc to help prevent infection by pathogens, a system termed nutritional immunity. Commercially used chelants have high binding affinities with a variety of metal ions, which may lead to antibacterial properties that mimic these innate immune processes. However, the modes of action of many of these chelating agents in bacterial growth inhibition and their selectivity in metal deprivation in cellulo remain ill-defined. We address this shortcoming by examining the effect of 11 chelators on Escherichia coli growth and their impact on the cellular concentration of five metals. The following four distinct effects were uncovered: (i) no apparent alteration in metal composition, (ii) depletion of manganese alongside reductions in iron and zinc levels, (iii) reduced zinc levels with a modest reduction in manganese, and (iv) reduced iron levels coupled with elevated manganese. These effects do not correlate with the absolute known chelant metal ion affinities in solution; however, for at least five chelators for which key data are available, they can be explained by differences in the relative affinity of chelants for each metal ion. The results reveal significant insights into the mechanism of growth inhibition by chelants, highlighting their potential as antibacterials and as tools to probe how bacteria tolerate selective metal deprivation. IMPORTANCE Chelating agents are widely used in industry and consumer goods to control metal availability, with bacterial growth restriction as a secondary benefit for preservation. However, the antibacterial mechanism of action of chelants is largely unknown, particularly with respect to the impact on cellular metal concentrations. The work presented here uncovers distinct metal starvation effects imposed by different chelants on the model Gram-negative bacterium Escherichia coli. The chelators were studied both individually and in pairs, with the majority producing synergistic effects in combinations that maximize antibacterial hostility. The judicious selection of chelants based on contrasting cellular effects should enable reductions in the quantities of chelant required in numerous commercial products and presents opportunities to replace problematic chemistries with biodegradable alternatives.

Recent studies have demonstrated that several chelators possess marked potential as potent anti-neoplastic drugs and as agents that can ameliorate some of the adverse effects associated with standard chemotherapy. Anti-cancer treatment employs combinations of several drugs that have different mechanisms of action. However, data regarding the potential interactions between iron chelators and established chemotherapeutics are lacking. Using estrogen receptor-positive MCF-7 breast cancer cells, we explored the combined anti-proliferative potential of four iron chelators, namely: desferrioxamine (DFO), salicylaldehyde isonicotinoyl hydrazone (SIH), (E)-N'-[1-(2-hydroxy-5-nitrophenyl)ethyliden] isonicotinoyl hydrazone (NHAPI), and di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), plus six selected anti-neoplastic drugs. These six agents are used for breast cancer treatment and include: paclitaxel, 5-fluorouracil, doxorubicin, methotrexate, tamoxifen and 4-hydroperoxycyclophosphamide (an active metabolite of cyclophosphamide). Our quantitative chelator-drug analyses were designed according to the Chou-Talalay method for drug combination assessment. All combinations of these agents yielded concentration-dependent, anti-proliferative effects. The hydrophilic siderophore, DFO, imposed antagonism when used in combination with all six anti-tumor agents and this antagonistic effect increased with increasing dose. Conversely, synergistic interactions were observed with combinations of the lipophilic chelators, NHAPI or Dp44mT, with doxorubicin and also the combinations of SIH, NHAPI or Dp44mT with tamoxifen. The combination of Dp44mT with anti-neoplastic agents was further enhanced following formation of its redox-active iron and especially copper complexes. The most potent combinations of Dp44mT and NHAPI with tamoxifen were confirmed as synergistic using another estrogen receptor-expressing breast cancer cell line, T47D, but not estrogen receptor-negative MDA-MB-231 cells. Furthermore, the synergy of NHAPI and tamoxifen was confirmed using MCF-7 cells by electrical impedance data, a mitochondrial inner membrane potential assay and cell cycle analyses. This is the first systematic investigation to quantitatively assess interactions between Fe chelators and standard chemotherapies using breast cancer cells. These studies are vital for their future clinical development.

Labile redox-active iron ions have been implicated in various neurodegenerative disorders, including the Parkinson's disease (PD). Iron chelation has been successfully used in clinical practice to manage iron overload in diseases such as thalassemia major; however, the use of conventional iron chelators in pathological states without systemic iron overload remains at the preclinical investigative level and is complicated by the risk of adverse outcomes due to systemic iron depletion. In this study, we examined three clinically-used chelators, namely, desferrioxamine, deferiprone and deferasirox and compared them with experimental agent salicylaldehyde isonicotinoyl hydrazone (SIH) and its boronate-masked prochelator BSIH for protection of differentiated PC12 cells against the toxicity of catecholamines 6-hydroxydopamine and dopamine and their oxidation products. All the assayed chelating agents were able to significantly reduce the catecholamine toxicity in a dose-dependent manner. Whereas hydrophilic chelator desferrioxamine exerted protection only at high and clinically unachievable concentrations, deferiprone and deferasirox significantly reduced the catecholamine neurotoxicity at concentrations that are within their plasma levels following standard dosage. SIH was the most effective iron chelator to protect the cells with the lowest own toxicity of all the assayed conventional chelators. This favorable feature was even more pronounced in prochelator BSIH that does not chelate iron unless its protective group is cleaved in disease-specific oxidative stress conditions. Hence, this study demonstrated that while iron chelation may have general neuroprotective potential against catecholamine auto-oxidation and toxicity, SIH and BSIH represent promising lead molecules and warrant further studies in more complex animal models.

Non-melanoma skin cancers are the most frequently occurring type of cancer worldwide. They can be effectively treated using topical dermatological photodynamic therapy (PDT) employing protoporphyrin IX (PpIX) as the active photosensitising agent as long as the disease remains superficial. Novel iron chelating agents are being investigated to enhance the effectiveness and extend the applications of this treatment modality, as limiting free iron increases the accumulation of PpIX available for light activation and thus cell kill.

Alzheimer's disease (AD) is a neurodegenerative disease characterized by cognitive and memory problems. Scopolamine (SCOP) is a natural anticholinergic drug that was proven to cause memory impairment in rats. Chelating agents are potential neuroprotective and memory enhancing agents as they can trap iron that enters in pathological deposition of β-amyloid (Aβ) which is a hallmark in AD and memory disorders. This study investigated the potential neuroprotective and memory enhancing effects of the iron chelating drug, Deferiprone. Three doses (5, 10, and 20 mg/kg) were administered to rats treated with SCOP (1.14 mg/kg/day). Systemic administration of SCOP for seven days caused memory impairment which manifested as decreased time spent in platform quadrant in Morris water maze test, decreased retention latencies in passive avoidance test, and increased acetylcholinesterase (AChE) activity, Aβ, and free iron deposition. It was observed that pretreatment with Deferiprone increased platform quadrant time in Morris water maze and increased retention latencies in the passive avoidance test. It also attenuated the increase in AChE activity and decreased Aβ and iron deposition. Overall, Deferiprone (10 mg/kg) was determined as the most effective dose. Therefore, this study suggests neuroprotective and memory enhancing effects for Deferiprone in SCOP-treated rats which might be attributed to its iron chelating action and anti-oxidative effect.

A 24-year-old man was admitted to our hospital because of severe heart failure. Although he was treated with diuretics and positive inotropic agents, his heart failure progressed. An endomyocardial biopsy revealed iron deposition in his myocytes. Finally, he was diagnosed with hereditary hemochromatosis. After starting administration of an iron-chelating agent in addition to conventional treatment for heart failure, his condition improved. We should consider hemochromatosis in heart failure patients with severe right ventricular dysfunction in addition to left ventricular dysfunction.

Differentiating agents have been proposed to overcome the impaired cellular differentiation in acute myeloid leukemia (AML). However, only the combinations of all-trans retinoic acid or arsenic trioxide with chemotherapy have been successful, and only in treating acute promyelocytic leukemia (also called AML3). We show that iron homeostasis is an effective target in the treatment of AML. Iron chelating therapy induces the differentiation of leukemia blasts and normal bone marrow precursors into monocytes/macrophages in a manner involving modulation of reactive oxygen species expression and the activation of mitogen-activated protein kinases (MAPKs). 30% of the genes most strongly induced by iron deprivation are also targeted by vitamin D3 (VD), a well known differentiating agent. Iron chelating agents induce expression and phosphorylation of the VD receptor (VDR), and iron deprivation and VD act synergistically. VD magnifies activation of MAPK JNK and the induction of VDR target genes. When used to treat one AML patient refractory to chemotherapy, the combination of iron-chelating agents and VD resulted in reversal of pancytopenia and in blast differentiation. We propose that iron availability modulates myeloid cell commitment and that targeting this cellular differentiation pathway together with conventional differentiating agents provides new therapeutic modalities for AML.

It is well-known that individuals with increased iron levels are more prone to thrombotic diseases, mainly due to the presence of unliganded iron, and thereby the increased production of hydroxyl radicals. It is also known that erythrocytes (RBCs) may play an important role during thrombotic events. Therefore the purpose of the current study was to assess whether RBCs had an altered morphology in individuals with hereditary hemochromatosis (HH), as well as some who displayed hyperferritinemia (HF). Using scanning electron microscopy, we also assessed means by which the RBC and fibrin morphology might be normalized. An important objective was to test the hypothesis that the altered RBC morphology was due to the presence of excess unliganded iron by removing it through chelation. Very striking differences were observed, in that the erythrocytes from HH and HF individuals were distorted and had a much greater axial ratio compared to that accompanying the discoid appearance seen in the normal samples. The response to thrombin, and the appearance of a platelet-rich plasma smear, were also markedly different. These differences could largely be reversed by the iron chelator desferal and to some degree by the iron chelator clioquinol, or by the free radical trapping agents salicylate or selenite (that may themselves also be iron chelators). These findings are consistent with the view that the aberrant morphology of the HH and HF erythrocytes is caused, at least in part, by unliganded ('free') iron, whether derived directly via raised ferritin levels or otherwise, and that lowering it or affecting the consequences of its action may be of therapeutic benefit. The findings also bear on the question of the extent to which accepting blood donations from HH individuals may be desirable or otherwise.

β-Thalassemia is characterized by ineffective erythropoiesis leading to chronic anemia. Thus, increased iron absorption from the duodenum and via blood transfusions is required to maintain normal blood hemoglobin (Hb) levels and iron chelators in the removal of excessive iron. Certain agents are also needed for the improvement of stress erythropoiesis and iron dysregulation. Green tea extract (GTE), which is rich in epigallocatechin-3-gallate (EGCG), is known to possess radical scavenging and iron-chelating activities. We aimed to assess the effects of green tea extract on erythroid regulators, iron mobilization and anti-lipid peroxidation in the liver, spleen, and kidneys of iron-loaded β-globin gene knockout thalassemic (BKO) mice. Our results indicate that treatments of green tea extract and/or deferiprone (DFP) diminished levels of plasma erythropoietin (EPO) and erythroferrone (ERFE), and consistently suppressed kidney Epo and spleen Erfe mRNA expressions (p < .05) in iron- loaded BKO mice when compared with untreated mice. Coincidently, the treatments decreased plasma ferritin (Ft) levels, iron content levels in the liver (p < .05), spleen (p < .05), and kidney tissues of iron-loaded BKO mice. Furthermore, lipid-peroxidation products in the tissues and plasma were also decreased when compared with untreated mice. This is the first evidence of the orchestral role of green tea extract abundant with epigallocatechin-3-gallate in improving ineffective erythropoiesis, iron dysregulation and oxidative stress in iron-overloaded β-thalassemic mice.

IscR is a global transcription regulator responsible for governing various physiological processes during growth and stress responses. The IscR-mediated regulation of the Pseudomonas aeruginosa isc operon, which is involved in iron-sulphur cluster ([Fe-S]) biogenesis, was analysed. The expression of iscR was highly induced through the exposure of the bacteria to various oxidants, such as peroxides, redox-cycling drugs, intracellular iron-chelating agents, and high salts. Two putative type 1 IscR-binding sites were found around RNA polymerase recognition sites, in which IscR-promoter binding could preclude RNA polymerase from binding to the promoter and resulting in repression of the isc operon expression. An analysis of the phenotypes of mutants and cells with altered gene expression revealed the diverse physiological roles of this regulator. High-level IscR strongly inhibited anaerobic, but not aerobic, growth. iscR contributes significantly to the bacteria overall resistance to oxidative stress, as demonstrated through mutants with increased sensitivity to oxidants, such as peroxides and redox-cycling drugs. Moreover, the regulator also plays important roles in modulating intracellular iron homeostasis, potentially through sensing the levels of [Fe-S]. The increased expression of the isc operon in the mutant not only diverts iron away from the available pool but also reduces the total intracellular iron content, affecting many iron metabolism pathways leading to alterations in siderophores and haem levels. The diverse expression patterns and phenotypic changes of the mutant support the role of P. aeruginosa IscR as a global transcriptional regulator that senses [Fe-S] and directly represses or activates the transcription of genes affecting many physiological pathways.

Bile salts exhibit potent antibacterial properties, acting as detergents to disrupt cell membranes and as DNA-damaging agents. Although bacteria inhabiting the intestinal tract are able to resist bile's antimicrobial effects, relatively little is known about how bile influences virulence of enteric pathogens. Escherichia coli O157:H7 is an important pathogen of humans, capable of causing severe diarrhea and more serious sequelae. In this study, the transcriptome response of E. coli O157:H7 to bile was determined. Bile exposure induced significant changes in mRNA levels of genes related to virulence potential, including a reduction of mRNA for the 41 genes making up the locus of enterocyte effacement (LEE) pathogenicity island. Bile treatment had an unusual effect on mRNA levels for the entire flagella-chemotaxis regulon, resulting in two- to four-fold increases in mRNA levels for genes associated with the flagella hook-basal body structure, but a two-fold decrease for "late" flagella genes associated with the flagella filament, stator motor, and chemotaxis. Bile salts also caused increased mRNA levels for seventeen genes associated with iron scavenging and metabolism, and counteracted the inhibitory effect of the iron chelating agent 2,2'-dipyridyl on growth of E. coli O157:H7. These findings suggest that E. coli O157:H7 may use bile as an environmental signal to adapt to changing conditions associated with the small intestine, including adaptation to an iron-scarce environment.

Deferoxamine (DFO) is an FDA-approved iron-chelating agent which shows good therapeutic efficacy, however, its short blood half-life presents challenges such as the need for repeated injections or continuous infusions. Considering the lifelong need of chelating agents for iron overload patients, a sustained-release formulation that can reduce the number of chelator administrations is essential. Here, injectable hydrogel formulations prepared by integrating crosslinked hyaluronic acid into Pluronic F127 for an extended release of DFO nanochelators are reported. The subcutaneously injected hydrogel shows a thermosensitive sol-gel transition at physiological body temperature and provides a prolonged release of renal clearable nanochelators over 2 weeks, resulting in a half-life 47-fold longer than that of the nanochelator alone. In addition, no chronic toxicity of the nanochelator-loaded hydrogel is confirmed by biochemical and histological analyses. This injectable hydrogel formulation with DFO nanochelators has the potential to be a promising formulation for the treatment of iron overload disorders.

Nanoparticles from magnetotactic bacteria have been used in conventional imaging, drug delivery, and magnetic manipulations. Here, we show that these natural nanoparticles and their bioinspired hybrids with near-infrared gold nanorods and folic acid can serve as molecular high-contrast photoacoustic probes for single-cell diagnostics and as photothermal agents for single-cell therapy using laser-induced vapor nanobubbles and magnetic field as significant signal and therapy amplifiers. These theranostics agents enable the detection and photomechanical killing of triple negative breast cancer cells that are resistant to conventional chemotherapy, with just one or a few low-energy laser pulses. In studies in vivo, we discovered that circulating tumor cells labeled with the nanohybrids generate transient ultrasharp photoacoustic resonances directly in the bloodstream as the basis for new super-resolution photoacoustic flow cytometry in vivo. These properties make natural and bioinspired magnetic nanoparticles promising biocompatible, multimodal, high-contrast, and clinically relevant cellular probes for many in vitro and in vivo biomedical applications.

Iron is an essential nutrient that plays a complex role in cancer biology. Iron metabolism must be tightly controlled within cells. Whilst fundamental to many cellular processes and required for cell survival, excess labile iron is toxic to cells. Increased iron metabolism is associated with malignant transformation, cancer progression, drug resistance and immune evasion. Depleting intracellular iron stores, either with the use of iron chelating agents or mimicking endogenous regulation mechanisms, such as microRNAs, present attractive therapeutic opportunities, some of which are currently under clinical investigation. Alternatively, iron overload can result in a form of regulated cell death, ferroptosis, which can be activated in cancer cells presenting an alternative anti-cancer strategy. This review focuses on alterations in iron metabolism that enable cancer cells to meet metabolic demands required during different stages of tumorigenesis in relation to metastasis and immune response. The strength of current evidence is considered, gaps in knowledge are highlighted and controversies relating to the role of iron and therapeutic targeting potential are discussed. The key question we address within this review is whether iron modulation represents a useful approach for treating metastatic disease and whether it could be employed in combination with existing targeted drugs and immune-based therapies to enhance their efficacy.

The increasing morbidity of fungal infections and the prevalence of drug resistance highlighted the discovery of novel antifungal agents and investigation of their modes of action. Iron chelators have been used to treat superficial fungal infections or potentiate the efficacy of certain antifungal drugs. Hinokitiol exhibits potent antifungal activity and iron-chelating ability. However, their relationships have not been established.

Alzheimer's disease (AD) is generally recognized as a multifactorial neurodegenerative pathology with an increasing impact on society. Tenuazonic acid (TA) is a natural compound that was recently identified as a potential multitarget ligand with anti-cholinesterase, anti-amyloidogenic and antioxidant activities. Using its structure as a chemical scaffold, we synthesized and evaluated new derivatives (1-5), including tenuazonic-donepezil (TA-DNP) hybrids (4 and 5) due to the clinical importance of the anti-AD drug donepezil. These novel compounds all achieved activity in the micromolar range towards all selected targets and demonstrated to be potentially orally absorbed. Moreover, a selected compound (1) was further investigated as a chelating agent towards copper (II), zinc (II) and iron (III) and showed good chelating ability (pFe = 16.6, pCu = 11.6, pZn = 6.0 at pH 7.4). Therefore, the TA motif can be considered an interesting building block in the search for innovative multi-functional anti-neurodegenerative drugs, as exemplified by hybrid 5, a promising non-cytotoxic lead compound adequate for the early stages of AD, and capable of ameliorating the oxidative status of SH-SY5Y human neuroblastoma cells.