Iron chelating agents in clinical practice

Screen-printed Gold Electrode Functionalized with Deferoxamine for Iron(III) Detection

Deferoxamine (DFO), a hydroxamic siderophore with a high affinity for Fe(III), is immobilized as a functionalized self-assembled monolayer of a thiol (SAM) on the gold surface of a screen-printed cell to develop a voltammetric sensor for iron(III). The surface of the working electrode was characterized, before and after functionalization, by determining surface properties such as the area and the double-layer capacitance. The Fe(III) detection was performed by DPV analysis after preconcentration of the cation at the open circuit potential in solution at pH = 1 for two minutes. The method was applied to the iron(III) quantification in water samples giving promising results.

Biosynthesis Pathways, Transport Mechanisms and Biotechnological Applications of Fungal Siderophores

Iron (Fe) is the fourth most abundant element on earth and represents an essential nutrient for life. As a fundamental mineral element for cell growth and development, iron is available for uptake as ferric ions, which are usually oxidized into complex oxyhydroxide polymers, insoluble under aerobic conditions. In these conditions, the bioavailability of iron is dramatically reduced. As a result, microorganisms face problems of iron acquisition, especially under low concentrations of this element. However, some microbes have evolved mechanisms for obtaining ferric irons from the extracellular medium or environment by forming small molecules often regarded as siderophores. Siderophores are high affinity iron-binding molecules produced by a repertoire of proteins found in the cytoplasm of cyanobacteria, bacteria, fungi, and plants. Common groups of siderophores include hydroxamates, catecholates, carboxylates, and hydroximates. The hydroxamate siderophores are commonly synthesized by fungi. L-ornithine is a biosynthetic precursor of siderophores, which is synthesized from multimodular large enzyme complexes through non-ribosomal peptide synthetases (NRPSs), while siderophore-Fe chelators cell wall mannoproteins (FIT1, FIT2, and FIT3) help the retention of siderophores. S. cerevisiae, for example, can express these proteins in two genetically separate systems (reductive and nonreductive) in the plasma membrane. These proteins can convert Fe (III) into Fe (II) by a ferrous-specific metalloreductase enzyme complex and flavin reductases (FREs). However, regulation of the siderophore through Fur Box protein on the DNA promoter region and its activation or repression depend primarily on the Fe availability in the external medium. Siderophores are essential due to their wide range of applications in biotechnology, medicine, bioremediation of heavy metal polluted environments, biocontrol of plant pathogens, and plant growth enhancement.

Hydroxypyridinone-Based Iron Chelators with Broad-Ranging Biological Activities

Iron plays an essential role in all living cells because of its unique chemical properties. It is also the most abundant trace element in mammals. However, when iron is present in excess or inappropriately located, it becomes toxic. Excess iron can become involved in free radical formation, resulting in oxidative stress and cellular damage. Iron chelators are used to treat serious pathological disorders associated with systemic iron overload. Hydroxypyridinones stand out for their outstanding chelation properties, including high selectivity for Fe³⁺ in the biological environment, ease of derivatization, and good biocompatibility. Herein, we overview the potential for multifunctional hydroxypyridinone-based chelators to be used as therapeutic agents against a wide range of diseases associated either with systemic or local elevated iron levels.

Five new complexes with deferiprone and N,N-donor ligands: evaluation of cytotoxicity against breast cancer MCF-7 cell line and HSA-binding determination

In this study, five new complexes containing deferiprone (dfp) and N,N-donor ligands [bipyridine (bpy), 1,10-phenanthroline (phen) and ethylenediamine (en)] were synthesized: [Fe(dfp)₂(bpy)](PF₆) (1), [Fe(dfp)₂(phen)](PF₆) (2), [Cu₂(dfp)₂(bpy)₂](PF₆)₂ (3), [Ga(dfp)₂(bpy)](PF₆) (4), and [Fe(dfp)₂(en)](PF₆) (5). Characterization of these complexes was carried out through elemental analysis and FT-IR, and single-crystal X-ray crystallography was used to determine their structures. Whilst the polyhedron has a distorted octahedral geometry in 1, 2, 4, and 5, it adopts a distorted square-pyramidal geometry in 3. Interaction of these compounds with human serum albumin (HSA) has been investigated through electronic absorption and fluorescence titration techniques. Emission quenching was performed separately for each complex at three different temperatures and thermodynamic parameters were calculated using binding constants to better understand the power of different binding forces with the HSA. Results demonstrated that compounds interact strongly with the HSA with a static quenching mechanism. Our evaluation of the cytotoxicity of complexes against the breast cancer MCF-7 cell line showed that complex 2 presents a better cytotoxicity than the standard cis-Pt. Finally, using the AutoDock 4.2 program, simulations to analyze the mechanism of complex-HSA interactions and their binding mode were carried out. Results showed that the best binding mode is located in subdomain IB for 1, 2, and 4, in I/II for 3, and in IA/IIA for 5. Communicated by Ramaswamy H. Sarma.

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

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

The Effects of Biodegradation on the Cytocompatibility of Bioresorbable Fe-Based Scaffolds: A Review

This work aims to review current trends in research within the field of iron-based scaffolds for orthopaedic applications. Current research is trapped in a ‘see-saw’ type problem where an increase in corrosion rate of the base metal is required to accelerate the degradation process making the resorption time compatible with the healing time. This is done via several methods including porosity control, cathodic element addition and/or patterning and alloying. In turn, this increase in corrosion rate causes the local concentration of metallic ions to increase beyond the toxicity limit for osteoblast type cells, thus negatively effecting cytocompatibility. This is most pronounced when considering the orthopaedic environment, in which static conditions provide for increased local ion concentrations, resulting in local toxicity. However, research from the medical field of Thalassemia may help solve this dilemma by providing chelation medicine for patients undergoing implantation of resorbable orthopaedic scaffolds, throughout the resorption period. Excretion of iron would then be provided mainly through bowel movement and urination.

A Study of Potential Toxic Effects After Repeated 10-Week Administration of a New Iron Chelator – Salicylaldehyde Isonicotinoyl Hydrazone (SIH) to Rabbits

Salicylaldehyde Isonicotinoyl Hydrazone (SIH) – a Pyridoxal Isonicotinoyl Hydrazone (PIH) analogue – is an effective iron chelator with antioxidant and antimalarial effects, as documented in numerous in vitro studies. However, no toxicological data obtained from in vivo studies have been made available yet. In this study, the potential toxic effects of repeated administration of SIH (50 mg/kg, once weekly, 10 weeks, i.p.), partially dissolved in a 10 % Cremophor solution, on various biochemical, haematological, and cardiovascular parameters and on morphology of selected tissues were investigated in rabbits. The obtained values were compared with data from the control (saline, 1 ml/kg, i.v.) and the Cremophor (10 % Cremophor solution, 2 ml/kg, i.p.) groups. In this study, SIH did not induced marked signs of toxicity: No premature deaths occurred, the body weight increase was comparable with the control and Cremophor groups. Only few and mild changes in some biochemical and haematological parameters could be determined, most of them were noticed also in the control or Cremophor groups. The morphological changes in the kidney were mild and did not manifest in the biochemical examination. The cardiac function was also not affected markedly – the values of left ventricular ejection fraction and systolic time interval did not differ from the values of control group. Only an increased left ventricular contractility (dP/dtmax) was noticed in the SIH group at the end of the experiment as compared to the controls (13354±1191 vs. 9339±647 mmHg/s, resp.). These results seem to be promising from the standpoint of possible clinical use of SIH.

DIBI, a polymeric hydroxypyridinone iron chelator, reduces ocular inflammation in local and systemic endotoxin-induced uveitis

BACKGROUND/OBJECTIVE

Non-infectious uveitis is an inflammatory disease of the eye commonly treated by corticosteroids, though important side effects may result. A main mediator of inflammation are oxygen free radicals generated in iron-dependent pathways. As such, we investigated the efficacy of a novel iron chelator, DIBI, as an anti-inflammatory agent in local and systemic models of endotoxin induced uveitis (EIU).

METHODS

Firstly, the effects of DIBI in systemic EIU in Lewis rats were established. 2 hours post intravenous LPS or LPS/DIBI injections, leukocyte activation and functional capillary density (FCD) were examined using intravital microscopy (IVM) of the iridial microcirculation. Secondly, the toxicity of DIBI was evaluated in BALB/C mice for both acute and chronic dosages through gross ocular examination, intraocular pressure measurements and hematoxylin-eosin staining of ocular tissue. Lastly, three groups of BALB/C mice, control, LPS or DIBI + LPS, were studied to evaluate the effectiveness of DIBI in treating local EIU. Five hours post-local intravitreal (i.v) injection, leukocyte activation and capillary density were examined via IVM.

RESULTS

Treatment of systemic EIU with DIBI resulted in a reduction of leukocyte activation and FCD improvement within the iridial microcirculation. Toxicity studies suggested that acute and chronic DIBI administration had no adverse effects in the eye. In the local EIU model, DIBI was shown to reduce leukocyte activation and restored the FCD/DCD ratio, providing evidence for its anti-inflammatory properties.

CONCLUSIONS

Our study has provided evidence that DIBI has anti-inflammatory effects in experimental uveitis. Additionally, no local ocular toxicity was observed.

Metallomics for Alzheimer's disease treatment: Use of new generation of chelators combining metal-cation binding and transport properties

Alzheimer's disease (AD) is a progressive neurodegenerative disorder affecting tens of million people. Currently marketed drugs have limited therapeutic efficacy and only slowing down the neurodegenerative process. Interestingly, it has been suggested that biometal cations in the amyloid beta (Aβ) aggregate deposits contribute to neurotoxicity and degenerative changes in AD. Thus, chelation therapy could represent novel mode of therapeutic intervention. Here we describe the features of chelators with therapeutically relevant mechanism of action. We have found that the tested compounds effectively reduce the toxicity of exogenous Aβ and suppress its endogenous production as well as decrease oxidative stress. Cholyl hydrazones were found to be the most active compounds. In summary, our data show that cation complexation, together with improving transport efficacy may represent basis for eventual treatment strategy in AD.

Development of a sensor for trivalent iron: AHP fixed on mesoporous silica

Optical sensor for iron(iii) detection via Fe(iii) complexation in the solid phase.

Synthesis of whey peptide-iron complexes: Influence of using different iron precursor compounds

Iron-binding peptides are an alternative for increasing the bioavailability of iron and to decreasing its pro-oxidant effect. This study aimed to synthesize and characterize peptide-iron complexes using FeCl₂ or FeSO₄ as the iron precursor compounds. Whey protein isolate (WPI), WPI hydrolyzed with pancreatin, and its fractions obtained via ultrafiltration (cut-off 5kDa) were used as ligands. The fluorescence intensity of the ligands significantly decreased as the iron concentration increased as a result of metal coordination with the iron-binding sites, which may have led to changes in the microenvironment of tryptophan. For both iron precursor compounds, the primary iron-binding site was carboxylate groups, and the linkage occurred via a bidentate coordination mode with two vibrational modes assigned to the COOFe linkage. However, infrared spectroscopy and thermal analysis results showed that the dynamics of the interaction is different for the iron precursor. The iron source may be of great importance because it may impact iron absorption and the pro-oxidant effect of the mineral.

Chemical features of in use and in progress chelators for iron overload

An excessive amount of iron may become extremely toxic both for its ability to generate reactive oxygen species, and for the lack of regulatory mechanisms for iron excretion in humans. Chelation therapy has been introduced in clinical practice in the 1970's to defend thalassemia patients from the effects of iron overload and it has dramatically changed both life expectancy and quality of life. The disadvantages of the drugs in clinical use make the research for new, more suitable iron chelating agents, urgent. This review defines the requirements of an iron chelator, then points out the principal chemical features of the iron chelators in use. Finally, a survey on the last ten years of the literature relative to iron chelators is done, and the most interesting ligands are presented, with particular emphasis to those that reached clinical trials.

Novel DFO-functionalized mesoporous silica for iron sensing. Part 2. Experimental detection of free iron concentration (pFe) in urine samples

Successful in vivo chelation treatment of iron(iii) overload pathologies requires that a significant fraction of the administered drug actually chelates the toxic metal. Increased mobilization of the iron(iii) in experiments on animals or humans, most often evaluated from urinary output, is usually used as an assessment tool for chelation therapy. Alternatively, the efficiency of a drug is estimated by calculating the complexing ability of a chelating agent towards Fe(iii). The latter is calculated by the pFe value, defined as the negative logarithm of the concentration of the free metal ion in a solution containing 10 μM total ligand and 1 μM total metal at a physiological pH of 7.4. In theory, pFe has to be calculated taking into account all the complexation equilibria involving the metal and the possible ligands. Nevertheless, complexation reactions in complex systems such as serum and urine may hardly be accurately modelled by computer software. The experimental determination of the bioavailable fraction of iron(iii) in biological fluids would therefore be of the utmost relevance in the clinical practice. The efficiency of the therapy could be more easily estimated as well as the course of overload pathologies. In this context, the aim of the present work was the development of a sensor to assess the free iron directly in biological fluids (urine) of patients under treatment with chelating agents. In the proposed device (DFO-MS), the strong iron chelator deferoxamine (DFO) is immobilized on the MCM-41 mesoporous silica. The characterization of the iron(iii) sorption on DFO-MS was undertaken, firstly in 0.1 M KNO3, then directly in urine samples, in order to identify the sorption mechanism. The stoichiometry of the reaction in the solid phase was found to be: with an exchange constant (average value) of log βex = 40(1). The application of DFO-MS to assess pFe in SPU (Simulating Pathology Urine) samples was also considered. The results obtained were very promising for a future validation and subsequent application of the sensor in samples of patients undergoing chelation therapy.

A prochelator with a modular masking group featuring hydrogen peroxide activation with concurrent fluorescent reporting

Metal chelators masked with protecting groups for targeted release have the potential to conditionally modulate cellular metals. We report a new route to prepare cis-cinnamate protecting groups that enabled development of a prochelator with chemical stimulus response, fluorescent reporting and active compound release in a single structure.

Iron Chelating Agents for Iron Overload Diseases

Although iron is an essential element for life, an excessive amount may become extremely toxic both for its ability to generate reactive oxygen species, and for the lack in humans of regulatory mechanisms for iron excretion. Chelation therapy has been introduced in clinical practice in the seventies of last century to defend thalassemic patients from the effects of iron overload and, in spite of all its limitations, it has dramatically changed both life expectancy and quality of life of patients. It has to be considered that the drugs in clinical use present some disadvantages too, this makes urgent new more suitable chelating agents. The requirements of an iron chelator have been better and better defined over the years and in this paper they will be discussed in detail. As a final point the most interesting ligands studied in the last years will be presented.

The interaction of phenolic acids with Fe(III) in the presence of citrate as studied by isothermal titration calorimetry

Under physiological conditions, exogenous chelators such as polyphenols might interact with non-protein bound ferric complexes, such as Fe(III)-citrate. Additionally, Fe(III) and citrate are widely distributed in various fruits and vegetables which are also rich in phenolic acids. In this study, we focus on the interaction between phenolic acids (gallic acid, methyl gallate and protocatechuic acid) and Fe(III) in the presence of excessive citrate by isothermal titration calorimetry (ITC) for thermodynamic studies, and stopped-flow absorption spectrometry for fast kinetic studies. Results reveal that all of these three phenolic acids can bind to the Fe(III) with the same stoichiometry (3:1). Moreover, the binding constants of these three compounds with Fe(III) are greatly dependent on ligand structure, and are much higher than that of Fe(III)-citrate. Based on their stoichiometry and superhigh binding constants, it is most likely that these three phenolic acids can displace the citrate to bind with one iron(III) ion to form a stable octahedral geometric structure, albeit at different rates. These findings shed light on the interaction between phenolic acids and Fe(III) in the presence of citrate under either physiological conditions or in a food system.

Antioxidant activity of different parts of Tetrataenium lasiopetalum

CONTEXT

In Iranian traditional medicine, different species of the genus Tetrataenium are used as antiseptic, spice and food additives.

OBJECTIVE

The present study examined the possible antioxidant effects of hydro-alcoholic extracts of different parts of Tetrataenium lasiopetalum (Boiss.) Manden (Apiaceae).

MATERIALS AND METHODS

Laminas, stems, petioles, fruits, peduncles and flowers of T. lasiopetalum were collected, dried and then extracted by ethanol and water (70:30). Antioxidant activities of extracts were examined by employing different in vitro assays, i.e., 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, metal chelating, reducing power activities and hemoglobin-induced linoleic acid system. Also, total phenolic and flavonoid contents of the extracts were evaluated.

RESULTS

Hydro-alcoholic extract of T. lasiopetalum flower showed the highest activity in scavenging of DPPH (IC50 = 170 ± 7 μg/mL). In metal chelating assay, lamina extract possesses a better iron ion chelating activity than other extracts (230 ± 10 μg/mL). Lamina hydro-alcoholic extract demonstrated better activity in reducing the power and hemoglobin-induced linoleic acid system than other parts of T. lasiopetalum.

DISCUSSION AND CONCLUSION

These results showed the antioxidant activity of different parts of T. lasiopetalum based on its usage in traditional medicine.

Deferoxamine blocks death induced by glutathione depletion in PC 12 cells

The purpose of the present work was to investigate the mechanisms by which glutathione depletion induced by treatment with buthionine sulfoximine (BSO) led within 24-30 h to PC 12 cells apoptosis. Our results showed that treatment by relatively low concentrations (10-30 μM) of deferoxamine (DFx), a natural iron-specific chelator, almost completely shielded the cells from BSO-induced toxicity and that DFx still remained protective when added up to 9-12h after BSO treatment. On the other hand, phosphopeptides derived from milk casein and known to carry iron across cell membranes, markedly potentiated the toxic action of BSO when loaded with iron but were ineffective in sodium form. Kept for 24 h in serum-free medium, the cells underwent a decrease in glutathione content after BSO treatment, but remained viable. However, these BSO-pre-treated cells showed a rapid (90-120 min) decrease in cell viability when incubated with low doses of iron, whereas a great proportion of them remained viable in the presence of higher concentrations of copper and zinc. We also observed in PC 12 cells an early (4-8 h) and transient increase in the expression of ferritin subunits following BSO addition. Taken together these results suggest that BSO-induced glutathione depletion leads to an alteration of cellular iron homeostasis, which may contribute to its toxicity.

Different approaches to the study of chelating agents for iron and aluminium overload pathologies

Our objective is to illustrate the activity of the groups operating in Italy involved in identification and study of new chelating agents, mainly intended for treatment of human pathology correlated with metal overload. The objective of "chelation therapy" is removal of toxic metal ions from the human body or attenuation of their toxicity by transforming them into less toxic compounds or by dislocating them from the site at which they exert a toxic action. Because most of this research activity is related to chelating agents for iron and aluminium, diseases related to these two metal ions are briefly treated. Iron overload is the most common metal toxicity disease worldwide. The toxicity of aluminium in dialysis patients was a serious problem for haemodialysis units in the seventies and eighties of the last century. In particular, this review focuses on research performed by the group at Cagliari and Ferrara, and by that at Padova. The former is studying, above all, bisphosphonate and kojic acid derivatives, and the latter is investigating 3,4-hydroxypyridinecarboxylic acids with differently substituted pyridinic rings.

Amelioration of metal-induced toxicity in Caenorhabditis elegans: utility of chelating agents in the bioremediation of metals

The presence of toxic amounts of transition metals in the environment may originate from a range of human activities and natural processes. One method for the removal of toxic levels of metals is through chelation by small molecules. However, chelation is not synonymous with detoxification and may not affect the bioavailability of the metal. To test the bioavailability of chelated metals in vivo, the effects of several metal/chelator combinations were tested in the environmentally relevant organism Caenorhabditis elegans. The effect of metal exposure on nematode growth was used to determine the toxicity of cadmium, copper, nickel, and zinc. The restoration of growth to levels observed in nonexposed nematodes was used to determine the protective effects of the polydentate chelators: acetohydroxamic acid (AHA), cyclam, cysteine, calcium EDTA, desferrioxamine B, 1,2-dimethyl,3-hydroxy,4-pyridinone, and histidine. Cadmium toxicity was removed only by EDTA; copper toxicity was removed by all of the chelators except AHA; nickel toxicity was removed by cyclam, EDTA, and histidine; and zinc toxicity was removed by only EDTA. These results demonstrate the utility of polydentate chelators in the remediation of metal-contaminated systems. They also demonstrate that although the application of a chelator to metal contaminants may be effective, binding alone cannot be used to predict the level of remediation. Remediation depends on a number of factors, including metal complex speciation in the environment.

Iron(III) selective molecular and supramolecular fluorescent probes

Iron is one of the most important elements in metabolic processes, being indispensable for all living systems and therefore it is extensively distributed in environmental and biological materials. However, both its deficiency and excess from the normal permissible limit can induce serious disorders. Therefore, several analytical techniques have been adopted for the detection of iron. Among the various techniques used for its detection, the method based on fluorescent sensors has received considerable interest in recent years because of its ability to provide online monitoring of very low concentrations without any pre-treatment of the sample together with the advantages of spatial and temporal resolution. In this article, efforts have been made to review the various molecular and supramolecular fluorescent sensors that have been developed for the selective detection of iron(III).

The effect of pyrophosphate, tripolyphosphate and ATP on the rate of the Fenton reaction

It has been recently reported that pyrophosphate, tri-polyphosphate, ATP and analogous ligands considerably decrease the yield of hydroxyl radicals by the Fenton reaction under conditions where [H(2)O(2)]>>[Fe(II)L(n)]. It was suggested that this effect is due to the slowing down of the Fenton reaction by these ligands. This suggestion seemed surprising as polyphosphate ligands stabilize Fe(III). Indeed, a kinetic study points out that these ligands accelerate the rate of the Fenton reaction by several orders of magnitude. Thus it is suggested that the effect of the ligands on the yield of the hydroxyl radicals is due to the stabilization of the Fe(III) complexes which slows down, or inhibits, their reduction by the radicals formed in the system and thus decreases the overall yield of hydroxyl radicals.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Potentiometric, spectrophotometric and calorimetric study on iron(III) and copper(II) complexes with 1,2-dimethyl-3-hydroxy-4-pyridinone

The iron(III)-1,2-dimethyl-3-hydroxy-4-pyridinone (Deferiprone) system is carefully characterized by a combined potentiometric-spectrophotometric procedure at 25 and 37 degrees C at different ionic strengths, and by thermochemical and quantum-chemical studies. The main purpose of this work was to determine how the temperature dependence of both complex-formation and protonation constants can affect the pFe values on going from 25 degrees C (pFe is normally calculated using 25 degrees C stability constants) to the physiological temperature of 37 degrees C at which chelating agents are active in vivo. The copper(II)-Deferiprone system is also studied and the iron(III)-Deferiprone distribution diagrams in presence of variable copper(II) amounts are shown so as to explain possible side effects due to a competing metal ion during the chelating therapy of iron overload.

Potentiometric and spectrophotometric equilibrium study on Fe(III) and new catechol-bisphosphonate conjugates

The coordination properties of mixed catechol-bisphosphonates towards Fe(III) are presented. From the potentiometric and spectroscopic results it was possible to state that iron coordination takes place only on the bisphosphonate moiety at acidic pH, and involves both catechol and bisphosphonate groups on two different iron(III) ions at higher pH values. Steric constracts keep both groups from chelating the same metal ion. Quantum mechanical calculations confirm this statement and allow to determine the minimum length of the linker for a stable conformation of complexes in which the same iron(III) ion is coordinated by both catechol and bisphosphonate.