Specific Iron Chelator Research Articles

Iron Deficiency Impairs Intra-Hepatic Lymphocyte Mediated Immune Response.

Hepatic expression of iron homeostasis genes and serum iron parameters predict the success of immunosuppression withdrawal following clinical liver transplantation, a phenomenon known as spontaneous operational tolerance. In experimental animal models, spontaneous liver allograft tolerance is established through a process that requires intra-hepatic lymphocyte activation and deletion. Our aim was to determine if changes in systemic iron status regulate intra-hepatic lymphocyte responses. We used a murine model of lymphocyte-mediated acute liver inflammation induced by Concanavalin A (ConA) injection employing mice fed with an iron-deficient (IrDef) or an iron-balanced diet (IrRepl). While the mild iron deficiency induced by the IrDef diet did not significantly modify the steady state immune cell repertoire and systemic cytokine levels, it significantly dampened inflammatory liver damage after ConA challenge. These findings were associated with a marked decrease in T cell and NKT cell activation following ConA injection in IrDef mice. The decreased liver injury observed in IrDef mice was independent from changes in the gut microflora, and was replicated employing an iron specific chelator that did not modify intra-hepatic hepcidin secretion. Furthermore, low-dose iron chelation markedly impaired the activation of isolated T cells in vitro. All together, these results suggest that small changes in iron homeostasis can have a major effect in the regulation of intra-hepatic lymphocyte mediated responses.

Design of novel fluorescent mitochondria-targeted peptides with iron-selective sensing activity.

Mitochondrial labile iron (LI) plays a crucial role in oxidative injuries and pathologies. At present, there is no organelle-specific sensitive iron sensor which can reside exclusively in the mitochondria and reliably monitor levels of LI in this organelle. In the present study, we describe the development of novel fluorescent and highly specific mitochondria iron sensors, using the family of mitochondria-homing 'SS-peptides' (short cell-permeant signal peptides mimicking mitochondrial import sequence) as carriers of highly specific iron chelators for sensitive evaluation of the mitochondrial LI. Microscopic analysis of subcellular localization of a small library of fluorescently labelled SS-like peptides identified dansyl (DNS) as the lead fluorophore for the subsequent synthesis of chimaeric iron chelator-peptides of either catechol (compounds 10 and 11) or hydroxypyridinone (compounds 13 and 14) type. The iron-sensing ability of these chimaeric compounds was confirmed by fluorescent quenching and dequenching studies both in solution and in cells, with compound 13 exhibiting the highest sensitivity towards iron modulation. The intramolecular fluorophore-chelator distance and the iron affinity both influence probe sensitivity towards iron. These probes represent the first example of highly sensitive mitochondria-directed fluorescent iron chelators with potential to monitor mitochondrial LI levels.

AmcA-a putative mitochondrial ornithine transporter supporting fungal siderophore biosynthesis.

Iron is an essential nutrient required for a wide range of cellular processes. The opportunistic fungal pathogen Aspergillus fumigatus employs low-molecular mass iron-specific chelators, termed siderophores, for uptake, storage and intracellular iron distribution, which play a crucial role in the pathogenicity of this fungus. Siderophore biosynthesis (SB) depends on coordination with the supply of its precursor ornithine, produced mitochondrially from glutamate or cytosolically via hydrolysis of arginine. In this study, we demonstrate a role of the putative mitochondrial transporter AmcA (AFUA_8G02760) in SB of A. fumigatus. Consistent with a role in cellular ornithine handling, AmcA-deficiency resulted in decreased cellular ornithine and arginine contents as well as decreased siderophore production on medium containing glutamine as the sole nitrogen source. In support, arginine and ornithine as nitrogen sources did not impact SB due to cytosolic ornithine availability. As revealed by Northern blot analysis, transcript levels of siderophore biosynthetic genes were unresponsive to the cellular ornithine level. In contrast to siderophore production, AmcA deficiency did only mildly decrease the cellular polyamine content, demonstrating cellular prioritization of ornithine use. Nevertheless, AmcA-deficiency increased the susceptibility of A. fumigatus to the polyamine biosynthesis inhibitor eflornithine, most likely due to the decreased ornithine pool. AmcA-deficiency decreased the growth rate particularly on ornithine as the sole nitrogen source during iron starvation and sufficiency, indicating an additional role in the metabolism and fitness of A. fumigatus, possibly in mitochondrial ornithine import. In the Galleria mellonella infection model, AmcA-deficiency did not affect virulence of A. fumigatus, most likely due to the residual siderophore production and arginine availability in this host niche.

Determination of Specific Iron Chelator by Using LC-ICP-MS and LC-ESI-MS

Identification and quantification of siderophore type chelate was undertaken using recently developed high-performance liquid chromatography-mass spectrometry methods. Five different siderophore type chelates were detected and the compounds comprised of two groups; ferrioxamines. In the dissolved phase, three types of hydroxamate siderophore have been identified; Ferioxamine B (FOB), Ferrioxamine G (FOG) and ferrioxamine E (FOE). Concentration of dissolved FOB, FOG and FOE are extremely low between 0–135 x 10-18 M, and their distribution is spatially and temporally variable in this region. The concentration and diversity of siderophore type chelates determined during this study, was lower than those reported previously for dissolved ferrioxamine siderophore concentrations at lower latitudes in the Atlantic Ocean. The initial data from this study suggested that dissolved siderophores in this region is not an important fraction (< 0.1%) of the natural organic Fe(III) binding ligand pool.

Clinically Approved Iron Chelators Influence Zebrafish Mortality, Hatching Morphology and Cardiac Function

Iron chelation therapy using iron (III) specific chelators such as desferrioxamine (DFO, Desferal), deferasirox (Exjade or ICL-670), and deferiprone (Ferriprox or L1) are the current standard of care for the treatment of iron overload. Although each chelator is capable of promoting some degree of iron excretion, these chelators are also associated with a wide range of well documented toxicities. However, there is currently very limited data available on their effects in developing embryos. In this study, we took advantage of the rapid development and transparency of the zebrafish embryo, Danio rerio to assess and compare the toxicity of iron chelators. All three iron chelators described above were delivered to zebrafish embryos by direct soaking and their effects on mortality, hatching and developmental morphology were monitored for 96 hpf. To determine whether toxicity was specific to embryos, we examined the effects of chelator exposure via intra peritoneal injection on the cardiac function and gene expression in adult zebrafish. Chelators varied significantly in their effects on embryo mortality, hatching and morphology. While none of the embryos or adults exposed to DFO were negatively affected, ICL -treated embryos and adults differed significantly from controls, and L1 exerted toxic effects in embryos alone. ICL-670 significantly increased the mortality of embryos treated with doses of 0.25 mM or higher and also affected embryo morphology, causing curvature of larvae treated with concentrations above 0.5 mM. ICL-670 exposure (10 µL of 0.1 mM injection) also significantly increased the heart rate and cardiac output of adult zebrafish. While L1 exposure did not cause toxicity in adults, it did cause morphological defects in embryos at 0.5 mM. This study provides first evidence on iron chelator toxicity in early development and will help to guide our approach on better understanding the mechanism of iron chelator toxicity.

P26 - Effect of novel 1-phenyl-3-methyl-4-acylpyrazolones on iron chelation and Fenton reaction

Iron is an essential element in many physiological processes due to its ability to easily convert between two oxidation states Fe(III)/Fe(II). However, at a pathological state, unbound iron may promote the production of highly toxic hydroxyl radicals via Fenton reaction, particularly when it is present in the excess.Iron chelators forming tight complexes with iron may prevent this reaction.In this study, novel synthetic 1-phenyl-3-methyl-4-acyl-pyrazol-5-ones were analyzed for their iron-chelating properties at four pathophysiologically relevant pH conditions (4.5-7.5) as well as for their effects on iron-based Fenton reaction. For the former competitive ferrozine spectrophotometric assay and for the latter HPLC method using salicylic acid as the indicator of hydroxyl radical production were used.All of the tested acylpyrazolones were efficient ferric chelators, however, their ferrous-chelating properties were clearly dependent on an acyl substitution. Interestingly, several acylpyrazolones had ferrous-chelating properties superior to those of the standard iron chelator – deferoxamine. Of particular interest is H2QpyQ, i.e. 2,6-bis[4(1-phenyl-3-methylpyrazol-5-one)carbonyl]pyridine, whose ferrous-chelating properties were increasing while pH was decreasing. In spite of large differences in ferrous chelation, a majority of the tested acylpyrazolones were powerful inhibitors of Fenton reaction as deferoxamine.In conclusion, the novel 1-phenyl-3-methyl-4-acyl-pyrazol-5-ones are efficient iron chelators and H2QpyQ may represent a prototype of specific iron chelators designed for chelation at acidic conditions in particular.

Genome mining and functional genomics for siderophore production in Aspergillus niger.

Iron is an essential metal for many organisms, but the biologically relevant form of iron is scarce because of rapid oxidation resulting in low solubility. Simultaneously, excessive accumulation of iron is toxic. Consequently, iron uptake is a highly controlled process. In most fungal species, siderophores play a central role in iron handling. Siderophores are small iron-specific chelators that can be secreted to scavenge environmental iron or bind intracellular iron with high affinity. A second high-affinity iron uptake mechanism is reductive iron assimilation (RIA). As shown in Aspergillus fumigatus and Aspergillus nidulans, synthesis of siderophores in Aspergilli is predominantly under control of the transcription factors SreA and HapX, which are connected by a negative transcriptional feedback loop. Abolishing this fine-tuned regulation corroborates iron homeostasis, including heme biosynthesis, which could be biotechnologically of interest, e.g. the heterologous production of heme-dependent peroxidases. Aspergillus niger genome inspection identified orthologues of several genes relevant for RIA and siderophore metabolism, as well as sreA and hapX. Interestingly, genes related to synthesis of the common fungal extracellular siderophore triacetylfusarinine C were absent. Reverse-phase high-performance liquid chromatography (HPLC) confirmed the absence of triacetylfusarinine C, and demonstrated that the major secreted siderophores of A. niger are coprogen B and ferrichrome, which is also the dominant intracellular siderophore. In A. niger wild type grown under iron-replete conditions, the expression of genes involved in coprogen biosynthesis and RIA was low in the exponential growth phase but significantly induced during ascospore germination. Deletion of sreA in A. niger resulted in elevated iron uptake and increased cellular ferrichrome accumulation. Increased sensitivity toward phleomycin and high iron concentration reflected the toxic effects of excessive iron uptake. Moreover, SreA-deficiency resulted in increased accumulation of heme intermediates, but no significant increase in heme content. Together with the upregulation of several heme biosynthesis genes, these results reveal a complex heme regulatory mechanism.

Scavenging Iron: A Novel Mechanism of Plant Immunity Activation by Microbial Siderophores

Siderophores are specific ferric iron chelators synthesized by virtually all microorganisms in response to iron deficiency. We have previously shown that they promote infection by the phytopathogenic enterobacteria Dickeya dadantii and Erwinia amylovora. Siderophores also have the ability to activate plant immunity. We have used complete Arabidopsis transcriptome microarrays to investigate the global transcriptional modifications in roots and leaves of Arabidopsis (Arabidopsis thaliana) plants after leaf treatment with the siderophore deferrioxamine (DFO). Physiological relevance of these transcriptional modifications was validated experimentally. Immunity and heavy-metal homeostasis were the major processes affected by DFO. These two physiological responses could be activated by a synthetic iron chelator ethylenediamine-di(o-hydroxyphenylacetic) acid, indicating that siderophores eliciting activities rely on their strong iron-chelating capacity. DFO was able to protect Arabidopsis against the pathogenic bacterium Pseudomonas syringae pv tomato DC3000. Siderophore treatment caused local modifications of iron distribution in leaf cells visible by ferrocyanide and diaminobenzidine-H₂O₂ staining. Metal quantifications showed that DFO causes a transient iron and zinc uptake at the root level, which is presumably mediated by the metal transporter iron regulated transporter1 (IRT1). Defense gene expression and callose deposition in response to DFO were compromised in an irt1 mutant. Consistently, plant susceptibility to D. dadantii was increased in the irt1 mutant. Our work shows that iron scavenging is a unique mechanism of immunity activation in plants. It highlights the strong relationship between heavy-metal homeostasis and immunity.

Zn/Ga−DFO iron–chelating complex attenuates the inflammatory process in a mouse model of asthma

BackgroundRedox-active iron, a catalyst in the production of hydroxyl radicals via the Fenton reaction, is one of the key participants in ROS-induced tissue injury and general inflammation. According to our recent findings, an excess of tissue iron is involved in several airway-related pathologies such as nasal polyposis and asthma. ObjectiveTo examine the anti-inflammatory properties of a newly developed specific iron–chelating complex, Zn/Ga−DFO, in a mouse model of asthma. Materials and methodsAsthma was induced in BALBc mice by ovalbumin, using aluminum hydroxide as an adjuvant. Mice were divided into four groups: (i) control, (ii) asthmatic and sham-treated, (iii) asthmatic treated with Zn/Ga−DFO [intra-peritoneally (i/p) and intra-nasally (i/n)], and (iv) asthmatic treated with Zn/Ga−DFO, i/n only. Lung histology and cytology were examined. Biochemical analysis of pulmonary levels of ferritin and iron-saturated ferritin was conducted. ResultsThe amount of neutrophils and eosinophils in bronchoalveolar lavage fluid, goblet cell hyperplasia, mucus secretion, and peri-bronchial edema, showed markedly better values in both asthmatic-treated groups compared to the asthmatic non-treated group. The non-treated asthmatic group showed elevated ferritin levels, while in the two treated groups it returned to baseline levels. Interestingly, i/n-treatment demonstrated a more profound effect alone than in a combination with i/p injections. ConclusionIn this mouse model of allergic asthma, Zn/Ga−DFO attenuated allergic airway inflammation. The beneficial effects of treatment were in accord with iron overload abatement in asthmatic lungs by Zn/Ga−DFO. The findings in both cellular and tissue levels supported the existence of a significant anti-inflammatory effect of Zn/Ga−DFO.

Acrolein, A Reactive Product of Lipid Peroxidation, Induces Oxidative Modification of Cytochrome c

Jung Hoon KangDepartment of Genetic Engineering, Cheongju University, Cheongju 360-764, Korea. E-mail: jhkang@cju.ac.krReceived July 25, 2013, Accepted August 19, 2013Acrolein (ACR) is a well-known carbonyl toxin produced by lipid peroxidation of polyunsaturated fatty acids,which is involved in the pathogenesis of neurodegenerative disorders such as Alzheimer’s disease (AD). InAlzheimer's brain, ACR was found to be elevated in hippocampus and temporal cortex where oxidative stressis high. In this study, we evaluated oxidative modification of cytochrome c occurring after incubation withACR. When cytochrome c was incubated with ACR, protein aggregation increased in a dose-dependentmanner. The formation of carbonyl compounds and the release of iron were obtained in ACR-treatedcytochrome c. Reactive oxygen species scavengers and iron specific chelator inhibited the ACR-mediatedcytochrome c modification and carbonyl compound formation. Our data demonstrate that oxidative damage ofcytochrome c by ACR might induce disruption of cyotochrome c structure and iron mishandling as acontributing factor to the pathology of AD.Key Words : Acrolein, Cytochrome c, Reactive oxygen species, IronIntroductionAcrolein (ACR) occurs in the environment as a ubiquitouspollutant that is generated as a by-product of overheatedorganic materials. ACR formed in vivo, through iron-cata-lyzed oxidation of arachidonic and docosahexanoic acids,exhibits facile reactivity with various biological macro-molecules, including proteins and phospholipids, has thepotential to inhibit many enzymes, and quickly depletescellular glutathione levels.

The Dual Personality of Iron Chelators: Growth Inhibitors or Promoters?

Iron is an essential nutrient for almost all living cells, and pathogenic bacteria are faced with severe iron limitation in the mammalian host ([1][1]). To make iron available during infection, most microorganisms produce and transport into the cell specific iron chelators (siderophores) or acquire

Salsolinol, a catechol neurotoxin, induces oxidative modification of cytochrome c

Methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol), an endogenous neurotoxin, is known to perform a role in the pathogenesis of Parkinson’s disease (PD). In this study, we evaluated oxidative modification of cytochrome c occurring after incubation with salsolinol. When cytochrome c was incubated with salsolinol, protein aggregation increased in a dosedependent manner. The formation of carbonyl compounds and the release of iron were obtained in salsolinol- treated cytochrome c. Salsolinol also led to the release of iron from cytochrome c. Reactive oxygen species (ROS) scavengers and iron specific chelator inhibited the salsolinol-mediated cytochrome c modification and carbonyl compound formation. It is suggested that oxidative damage of cytochrome c by salsolinol might induce the increase of iron content in cells, subsequently leading to the deleterious condition which was observed. This mechanism may, in part, provide an explanation for the deterioration of organs under neurodegenerative disorders such as PD. [BMB Reports 2013; 46(2): 119-123]

Oxidative Modification of Cytochrome c by Tetrahydropapaveroline, an Isoquinoline-Derived Neurotoxin

Tetrahyropapaveroline (THP) is compound derived from dopamine metabolism and is capable of causing dopaminergic neurodegenerative disorder, such as Parkinson’s disease (PD). The aim of this study was to evaluate the potential of THP to cause oxidative damage on the structure of cytochrome c (cyt c). Our data showed that THP led to protein aggregation and the formation of carbonyl compound in protein aggregates. THP also induced the release of iron from cyt c. Reactive oxygen species (ROS) scavengers and iron specific chelator inhibited the THP-mediated cyt c modification and carbonyl compound formation. The results of this study show that ROS may play a critical role in THP-induced cyt c modification and iron releasing of cyt c. When cyt c that has been exposed to THP was subsequently analyzed by amino acid analysis, lysine, histidine and methionine residues were particularly sensitive. It is suggested that oxidative damage of cyt c by THP might induce the increase of iron content in cells and subsequently led to the deleterious condition. This mechanism is associated with the deterioration of organs under neurodegenerative disorder such as PD.

Coordination of iron ions in the form of histidinyl dinitrosyl complexes does not prevent their genotoxicity

Formation of dinitrosyl iron complexes (DNICs) was observed in a wide spectrum of pathophysiological conditions associated with overproduction of NO. To gain insight into the possible genotoxic effects of DNIC, we examined the interaction of histidinyl dinitrosyl iron complexes (HIS-DNIC) with DNA by means of circular dichroism. Formation of DNIC was monitored by EPR and FT/IR spectroscopy. Vibrational bands for aquated HIS-DNIC are reported. Dichroism results indicate that HIS-DNIC changes the conformation of the DNA in a dose-dependent manner in 10mM phosphate buffer (pH 6). Increase of the buffer pH or ionic strength decreased the effect. Comparison of HIS-DNIC DNA interaction with the effect of hydrated Fe2+ ion revealed many similarities. The importance of iron ions in HIS-DNIC induced genotoxicity is confirmed by plasmid nicking assay. Treatment of pUC19 plasmid with 1μM HIS-DNIC did not affect the plasmid supercoiling. Higher concentrations of HIS-DNIC induced single strand breaks. The effect was completely abrogated by addition of deferoxamine, a specific strong iron chelator. Our data reveal that formation of HIS-DNIC does not prevent DNA from iron-induced damage and imply that there is no direct interrelationship between iron–NO coordination and their mutual toxicity modulation.

Iron – A Key Nexus in the Virulence of Aspergillus fumigatus

Iron is an essential but, in excess, toxic nutrient. Therefore, fungi evolved fine-tuned mechanisms for uptake and storage of iron, such as the production of siderophores (low-molecular mass iron-specific chelators). In Aspergillus fumigatus, iron starvation causes extensive transcriptional remodeling involving two central transcription factors, which are interconnected in a negative transcriptional feed-back loop: the GATA-factor SreA and the bZip-factor HapX. During iron sufficiency, SreA represses iron uptake, including reductive iron assimilation and siderophore-mediated iron uptake, to avoid toxic effects. During iron starvation, HapX represses iron-consuming pathways, including heme biosynthesis and respiration, to spare iron and activates synthesis of ribotoxin AspF1 and siderophores, the latter partly by ensuring supply of the precursor, ornithine. In accordance with the expression pattern and mode of action, detrimental effects of inactivation of SreA and HapX are confined to growth during iron sufficiency and iron starvation, respectively. Deficiency in HapX, but not SreA, attenuates virulence of A. fumigatus in a murine model of aspergillosis, which underlines the crucial role of adaptation to iron limitation in virulence. Consistently, production of both extra and intracellular siderophores is crucial for virulence of A. fumigatus. Recently, the sterol regulatory element binding protein SrbA was found to be essential for adaptation to iron starvation, thereby linking regulation of iron metabolism, ergosterol biosynthesis, azole drug resistance, and hypoxia adaptation.

A Study of Magnetic Resonance Imaging Assessment of Cardiac and Liver Iron Load in Patients with Haemoglobinopathies, Myelodysplastic Syndromes or Other Anaemias Treated with Deferasirox (the MILE study CICL670AAU01) – Results of An Interim Analysis At a Planned Sample Size Reassessment,

Abstract 3181 Background:Cardiac failure is the leading cause of death in patients with thalassaemia major. However, the introduction of new monitoring techniques, such as cardiac iron Magnetic Resonance Imaging (MRI), may lead to the improvement of patient care and prolong survival. Although the impact of cardiac siderosis in patients with thalassaemia major has been extensively studied, further examination of the effect of specific iron chelators such as deferasirox are important in the development of treatment protocols, while the clinical consequences of cardiac iron accumulation in patients with myelodysplastic syndromes (MDS) is still controversial. Aim:The primary objective of this study is to investigate the effect of single agent deferasirox on cardiac iron levels and cardiac function, in a cohort of patients receiving regular red blood cell transfusions. Methods:Patients with transfusional siderosis were enrolled in this study and received deferasirox for 53 weeks. Doses up to 40 mg/kg/day were allowed according to transfusional requirement, response to chelation therapy and safety markers. Cardiac siderosis (cardiac T2* measured by linear fitting to the decay of logarithmic magnetic resonance signal) and left ventricular ejection fraction (LVEF) were measured at baseline and at 53 weeks. The sample size was originally calculated based on the standard deviation (SD) of the change in log(T2*) (0.47), according to previously published reports. A planned sample size reassessment as per protocol was undertaken when 42 patients had follow-up data. For the sample size reassessment, log(T2*) was calculated for each result and the change in log(T2*) estimated for each patient. Results from the interim sample size reassessment and the analysis of cardiac iron and function are described below. Results:Results were available for 36 patients with haemoglobinopathies (mainly represented by thalassaemia major), 5 patients with MDS and one post-bone marrow transplant patient. The SD observed for change in log(T2*) with the current data was 0.26 (original assumption 0.47). Assuming the SD for the final data does not increase above 0.34 the current cohort should be sufficient to detect a change in log(T2*) of the pre-specified 0.14. Safety assessments were consistent with previous studies on deferasirox. An overall increase in cardiac T2* from 23.0 to 26.1 ms was observed (p<0.001). Further analysis was performed based on the T2* baseline values: 5–10 ms, no significant change (n=6; 8.5 to 7.9 ms; p=0.6; non-significant); 10–20 ms, improvement of 26% (n=8; from 14.8 to 18.7 ms; p=0.001); >20 ms, increase of 10% (n=28; 32.3 to 35.6 ms; p=0.04). Overall, an increase in LVEF of 2.1% was observed, just below statistical significance (from 60.9% to 63.0%, p=0.076). The largest increase in LVEF was observed in patients with moderate cardiac siderosis (baseline T2* 10–20 ms; statistically significant increase in LVEF of 5.7%, from 56.8% to 62.5%, p=0.045). Descriptive preliminary analyses of the MDS subgroup showed that all 5 patients had baseline cardiac T2* >20 ms (median 32 ms; range: 29.7 to 34 ms). Similarly to the overall patient pool, deferasirox induced a 12% increase in cardiac T2* although not statistically significant (32.2 to 35.9 ms, p=0.13). In this subgroup of MDS patients, a statistically significant increase in LVEF was also observed (56.4% to 63.6%, p=0.04). Results on liver iron concentration will also be presented. Conclusion:The interim results from this study showed for the first time that once-daily deferasirox induced a simultaneous and statistically significant increase in both cardiac T2* levels and cardiac function in patients with moderate cardiac siderosis. Although the small number of patients in the MDS subgroup had cardiac T2* levels above 20 ms, chelation therapy induced an increase in LVEF in all 5 patients enrolled to date. Taken together, these results also confirm previous reports showing that single agent deferasirox is an effective therapy for maintenance and reduction of cardiac iron levels, especially for patients with cardiac T2* >10 ms. Recruitment has been halted based on the recommendations of the interim sample size re-estimation in consultation with the Data Monitoring Committee. Six patients are ongoing, and will be included in the final analysis of the study. [Display omitted] Disclosures:Ho:Novartis: Honoraria, Invited speaker, Membership on an entity's Board of Directors or advisory committees. Tay:Novartis: Membership on an entity's Board of Directors or advisory committees. Teo:Novartis: Research Funding. Marlton:Novartis: Membership on an entity's Board of Directors or advisory committees. Grigg:Novartis: Invited speaker, Membership on an entity's Board of Directors or advisory committees. Pierre:Resonance Health: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Research Funding, Speakers Bureau. Brown:Novartis: Consultancy, Invited speaker. Gervasio:Novartis: Employment. Bowden:Novartis: Honoraria, Research Funding, Speakers Bureau.

Impact of JNK1, JNK2, and ligase Itch on reactive oxygen species formation and survival of prostate cancer cells treated with diallyl trisulfide

In our previous study, we demonstrated that diallyl trisulfide (DATS) induced iron-dependent G2-M arrest of prostate cancer cell cycle. Moreover, ferritin degradation and an increase of labile iron pool has been linked to the activation of the JNK signaling axis. In the present work, we extended this study to determine which of the c-jun kinases is responsible for ferritin degradation and the role of iron in DATS-induced cell death. We hypothesized that JNK1 activates Itch ligase which will lead to ferritin ubiquitination, an increase in iron-dependent ROS formation and cell death. PC-3 prostate cancer cells were used in this study. Cell viability, concentration of ROS, labile iron pool, and changes in ferritin and P-Itch and DNA damage were determined. We observed that DATS induced ferritin degradation through JNK, Itch signaling axis. DATS did not induce neither ROS formation nor increase the LIP in JNK1-DN transfected cells. We also observed that DATS increased JNK-dependent activating phosphorylation of E3ligase Itch. The cells transfected with inactive form of Itch were more resistant against cytotoxicity of DATS and showed lower DATS-induced ferritin degradation. Desferrioxamine a specific iron chelator had no effect neither on cell viability nor DNA damage evaluated by comet assay. These results suggest that JNK1-dependent increase in LIP is mediated by Itch ubiquitin ligase.

Comparison of various iron chelators used in clinical practice as protecting agents against catecholamine-induced oxidative injury and cardiotoxicity

Catecholamines are stress hormones and sympathetic neurotransmitters essential for control of cardiac function and metabolism. However, pathologically increased catecholamine levels may be cardiotoxic by mechanism that includes iron-catalyzed formation of reactive oxygen species. In this study, five iron chelators used in clinical practice were examined for their potential to protect cardiomyoblast-derived cell line H9c2 from the oxidative stress and toxicity induced by catecholamines epinephrine and isoprenaline and their oxidation products. Hydroxamate iron chelator desferrioxamine (DFO) significantly reduced oxidation of catecholamines to more toxic products and abolished redox activity of the catecholamine-iron complex at pH 7.4. However, due to its hydrophilicity and large molecule, DFO was able to protects cells only at very high and clinically unachievable concentrations. Two newer chelators, deferiprone (L1) and deferasirox (ICL670A), showed much better protective potential and were effective at one or two orders of magnitude lower concentrations as compared to DFO that were within their clinically relevant plasma levels. Ethylenediaminetetraacetic acid (EDTA), dexrazoxane (ICRF-187, clinically approved cardioprotective agent against anthracycline-induced cardiotoxicity) as well as selected beta adrenoreceptor antagonists and calcium channel blockers exerted no effect. Hence, results of the present study indicate that small, lipophilic and iron-specific chelators L1 and ICL670A can provide significant protection against the oxidative stress and cardiomyocyte damage exerted by catecholamines and/or their reactive oxidation intermediates. This potential new application of the clinically approved drugs L1 and ICL670A warrants further investigation, preferably using more complex in vivo animal models.

Enhancing the selectivity of an iron binding hydrogel

Iron overload is a critical clinical condition that can be controlled by diet and the use of iron-specific chelating agents. An effective oral formulation of an iron chelator should be nontoxic and selective toward iron while maintaining high affinity for iron. In this study, hydrogels containing 2,3 dihydroxybenzoic acid (2,3 DHBA), a portion of the metal chelating domain of enterobactin, were synthesized as a potential non-absorbed chelator for iron in the gastrointestinal tract. A series of polymeric chelators with various hydrogel:DHBA ratios were prepared. The iron-binding properties of the hydrogels were found to depend on the concentration of 2,3 DHBA groups on polymer chains. A 0.005 ratio of PAAm:DHBA was found to have an optimum affinity (log K = 27.01), selectivity, and high binding capacity for Fe(III).

The effect of desferrioxamine on antigen-induced inflammation in the rat air pouch.

The effect of desferrioxamine, a relatively specific iron chelating drug, has been examined in an allergic air pouch model of inflammation in the rat. The model has both an acute and chronic phase and allows quantitative measurements of the cellular and exudative response within the pouch fluid and the tissue response in the membrane that develops around the preformed cavity. Desferrioxamine given as a single bolus injection, directly into the cavity, stimulated the acute inflammatory phase, increasing both the exudative and leukocyte response, in a dose-dependent fashion. In marked contrast, repeated injections during the acute to chronic phase or during the established chronic reaction, led to a reduction in both leukocyte numbers within the cavity and the amount of granulation tissue surrounding it. The exudative response was, however, unaltered. These results are discussed in relation to the potential role of iron in promoting an acute and chronic inflammatory reaction.