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PubMed1992

The effect of different iron compounds on transferrin receptor expression in term human cytotrophoblast cells.

During pregnancy, the mother is faced with an increased food demand. A good example of this increased demand is iron (Fe). Fe is needed in all growing cells. During pregnancy, the Fe transport to the fetus increases enormously. This amount can easily induce an Fe deficiency in the mother. Fe supplementation is very important for her, but not for the Fe status of the fetus, which is protected against Fe toxicity as well as deficiency. The placenta seems to be autonomous in Fe uptake. Likely there is a regulation mechanism. The human placenta is hemomonochorial. The cell layer of the fetus in contact with the maternal blood is formed by syncytiotrophoblasts. Fe is transported to the placenta by transferrin. Transferrin binds to a transferrin receptor on the trophoblast membrane and is internalized via an endocytic pathway. During this cycle, Fe is released from transferrin and the transferrin-transferrin receptor complex is recycled to the membrane. Isolated trophoblast cells from term placentas form a syncytium in vitro, and transferrin receptors are expressed. Expression depends on the number of cells in culture, culture time, the amount of Fe available, and the Fe compound. By regulation of the number of transferrin receptors, trophoblasts are able to control their Fe uptake.

Binding Sites↗
PubMed2006

Polyhydroxylated 4-thiaflavans as multipotent antioxidants: protective effect on oxidative DNA damage in vitro.

Hydroxylated 4-thiaflavans, possessing the antioxidant features of catechol containing flavonoids and/or tocopherols, were evaluated as protective agents against oxidation damage induced in herring sperm DNA by cumene hydroperoxide (CumOOH) or by the glutathione/ferric ion (GSH/Fe(3+)) system. Our data indicate that the effective protection exerted by some of the tested compounds is overall higher than those provided by catechin and alpha-tocopherol, which might be attributed both to the scavenging properties and chelation of Fe(2+) ions.

Animals↗
PubMed2006

In vivo antioxidant activity of procyanidin-rich extracts from grape seed and pine (Pinus maritima) bark in rats.

BACKGROUND: In vitro evidence exists for the potential antioxidant benefits of procyanidin-rich extracts, but in vivo studies are scarce. We have evaluated the effects of selected procyanidin-rich extracts on oxidative stress in rats in condition of prolonged consumption of these compounds and also after single administration i.e. in postprandial conditions. METHODS: Rats were fed for 8 weeks with diets supplemented with either a grape seed extract (GE), a pine bark extract (PE), or a high-degree polymerized pine bark extract (HPE). An additional study was performed in order to assess the postprandial effect of these extracts on plasma antioxidant capacity. The ferric-reducing antioxidant power (FRAP) and thiobarbituric acid-reactive substances (TBARS) were determined in plasma. For lipid peroxidation study of heart tissue, homogenates were prepared and TBARS were measured after lipid peroxidation induced by FeSO4-ascorbate. RESULTS: After 8 weeks of dietary treatment, total antioxidant capacity in plasma was significantly higher in the GE and PE groups as compared with the other two groups. Plasma TBARS concentrations and heart susceptibility to peroxidation were not significantly different between the groups. In the postprandial state, by comparing plasma antioxidant capacity 2 hours after ingestion of the different procyanidin-rich extracts (500 mg/kg body weight), we observed that FRAP values were higher in the procyanidin-rich extracts groups as compared with the control group. Moreover, plasma FRAP concentration was significantly higher in the GE group as compared with the other groups. CONCLUSION: The results of the present experiment constitute positive evidence for an in vivo antioxidant effect at the plasma level of procyanidin-containing plant extracts.

Animals↗
PubMed1988

What is unique about superoxide toxicity as compared to other biological reductants? A hypothesis.

Usually the toxicity of superoxide is attributed to its ability to reduce metal ions and subsequently reoxidation of the metal by hydrogen peroxide yields deleterious oxidizing species. As many other nontoxic biological reductants reduce metal compounds, we suggest that part of the mechanism of superoxide toxicity results from its ability to oxidize metal ions bound to biological targets, which subsequently degrade the target via an intramolecular electron transfer reaction.

Cations↗
PubMed1998

The role of biomineralization in microbiologically influenced corrosion.

Synthetic iron oxides (goethite, alpha-FeO.OH; hematite, Fe2O3; and ferrihydrite, Fe(OH)3) were used as model compounds to simulate the mineralogy of surface films on carbon steel. Dissolution of these oxides exposed to pure cultures of the metal-reducing bacterium, Shewanella putrefaciens, was followed by direct atomic absorption spectroscopy measurement of ferrous iron coupled with microscopic analyses using confocal laser scanning and environmental scanning electron microscopies. During an 8-day exposure the organism colonized mineral surfaces and reduced solid ferric oxides to soluble ferrous ions. Elemental composition, as monitored by energy dispersive x-ray spectroscopy, indicated mineral replacement reactions with both ferrihydrite and goethite as iron reduction occurred. When carbon steel electrodes were exposed to S. putrefaciens, microbiologically influenced corrosion was demonstrated electrochemically and microscopically.

Biodegradation, Environmental↗
PubMed2004

Microbial polysaccharides template assembly of nanocrystal fibers.

Biological systems can produce extraordinary inorganic structures and morphologies. The mechanisms of synthesis are poorly understood but are of great interest for engineering novel materials. We use spectromicroscopy to show that microbially generated submicrometer-diameter iron oxyhydroxide (FeOOH) filaments contain polysaccharides, providing an explanation for the formation of akaganeite pseudo-single crystals with aspect ratios of approximately 1000:1. We infer that the cells extrude the polysaccharide strands to localize FeOOH precipitation in proximity to the cell membrane to harness the proton gradient for energy generation. Characterization of organic compounds with high spatial resolution, correlated with mineralogical information, should improve our understanding of biomineralization mechanisms.

Bacteria↗
PubMed1996

Design of orally active iron chelators.

Three parameters which are critical for the development of non-toxic orally active iron chelators are identified: bioavailability, selectivity for iron (III) and distribution and toxicity. Each is discussed in detail. Arguments are presented for the use of bi- and tridentate ligands as opposed to hexadentate ligands. The discussion leads to the identification of 3-hydroxpyridin-4-ones as compounds with a unique potential for iron chelation under clinical conditions. The prodrug concept utilising efficient liver first-pass kinetics is introduced.

Administration, Oral↗
PubMed2006

Hydrogen-bonding conformations of tyrosine B10 tailor the hemeprotein reactivity of ferryl species.

Ferryl compounds [Fe(IV)=O] in living organisms play an essential role in the radical catalytic cycle and degradation processes of hemeproteins. We studied the reactions between H2O2 and hemoglobin II (HbII) (GlnE7, TyrB10, PheCD1, PheE11), recombinant hemoglobin I (HbI) (GlnE7, PheB10, PheCD1, PheE11), and the HbI PheB10Tyr mutant of L. pectinata. We found that the tyrosine residue in the B10 position tailors, in two very distinct ways, the reactivity of the ferryl species, compounds I and II. First, increasing the reaction pH from 4.86 to 7.50, and then to 11.2, caused the the second-order rate constant for HbII to decrease from 141.60 to 77.78 M-1 s-1, and to 2.96 M-1 s-1, respectively. This pH dependence is associated with the disruption of the heme-tyrosine (603 nm) protein moiety, which controls the access of the H2O2 to the hemeprotein active center, thus regulating the formation of the ferryl species. Second, the presence of compound I was evident in the UV-vis spectra (648-nm band) in the reactions of HbI and recombinant HbI with H2O2, This band, however, is completely absent in the analogous reaction with HbII and the HbI PheB10Tyr mutant. Therefore, the existence of a hydrogen-bonding network between the heme pocket amino acids (i.e., TyrB10) and the ferryl compound I created a path much faster than 3.0x10(-2) s-1 for the decay of compound I to compound II. Furthermore, the decay of the heme ferryl compound I to compound II was independent of the proximal HisF8 trans-ligand strength. Thus, the pH dependence of the heme-tyrosine moiety complex determined the overall reaction rate of the oxidative reaction limiting the interaction with H2O2 at neutral pH. The hydrogen-bonding strength between the TyrB10 and the heme ferryl species suggests the presence of a cycle where the ferryl consumption by the ferric heme increases significantly the pseudoperoxidase activity of these hemeproteins.

Ferric Compounds↗
PubMed1994

A study on superoxide dismutase activity of some model compounds.

The synthesis and characteristics of a binuclear ligand N,N,N',N'-tetrakis (2'-benzimidazolyl methyl)-1,4-diethylene amino glycol ether (EGTB) and its series of coordination compounds containing copper(II), iron(III), and manganese(II) with and without exogenous bridging ligand which was imidazolate ion (Im-), bipyridine (bpy), or 1,10-phenanthroline (phen) are reported. Depending on the redox potentials by cyclic voltammetry, the coordination compounds can act as catalysts for the dismutation of superoxide radicals (O2-). The detection of the rate constant of the reaction of superoxide ion with nitroblue tetrazolium (NBT) which is inhibited by superoxide dismutase (SOD) and its model compounds of the EGTB system has been performed by a modified illumination method. The rate constants kQ of the catalytic dismutation have been obtained.

Copper↗
PubMed1997

Mutagenesis of the Mn2+-binding site of manganese peroxidase affects oxidation of Mn2+ by both compound I and compound II.

The present study investigates whether compound I and compound II of manganese peroxidase from the white-rot fungus Phanerochaete chrysosporium utilize the same Mn-binding site for catalysis. Manganese peroxidase was expressed from its cDNA in Escherichia coli and refolded from inclusion bodies to yield fully active enzyme. Three mutants of the enzyme were generated by site-directed mutagenesis. Each of the three amino acid residues proposed to be involved in Mn2+ binding, E35, D179, and E39, was mutated. The acidic side chains of E35 and E39 were shortened by one carbon to the acidic group D, and the acidic side chain of D179 was shortened by one carbon to the alkyl group A. These mutants, E35D, D179A, and E39D, were used to determine whether Mn2+ reacts at the same site with both compound I and compound II of manganese peroxidase and to determine whether phenolic substrates for the enzyme react at this site. Our results conclusively demonstrate that E35 and D179 residues are involved not only in Mn2+ binding but also in electron transfer from Mn2+ to the enzyme for both compound I and compound II. In contrast, E39 is not critically important to either process. None of the three residues is involved in reactions with phenolic substrates or with H2O2.

Basidiomycota↗
PubMed1987

Metal chelates as urographic contrast agents for magnetic resonance imaging. A comparative study.

Paramagnetic metal chelates including Fe-EDTA, Fe-CDTA, Fe-DTPA, and Gd-DTPA were compared as intravenous urographic contrast agents for magnetic resonance (MR) imaging in rats. Each compound, administered intravenously at three different doses (0.05, 0.1, and 0.2 mmol./kg.), was rapidly excreted through the kidneys yielding renal signal enhancement between 5 min. and 50 min. after injection. Gd-DTPA was most effective vor the enhancement of the renal parenchyma and pelvis. Lesser enhancement was achieved by administration of Fe-CDTA followed by Fe-EDTA and Fe-DTPA. Enhancement of skeletal muscle and liver parenchyma could not be achieved with any of the compounds included in this study. We conclude that the iron chelates mentioned above are less effective as urographic agents for MR imaging than Gd-DTPA.

Animals↗
PubMed1997

Probing the chloroquine resistance locus of Plasmodium falciparum with a novel class of multidentate metal(III) coordination complexes.

The malaria organism Plasmodium falciparum detoxifies heme released during degradation of host erythrocyte hemoglobin by sequestering it within the parasite digestive vacuole as a polymer called hemozoin. Antimalarial agents such as chloroquine appear to work by interrupting the heme polymerization process, but their efficacy has been impaired by the emergence of drug-resistant organisms. We report here the identification of a new class of antimalarial compounds, hexadentate ethylenediamine-N, N'-bis[propyl(2-hydroxy-(R)-benzylimino)]metal(III) complexes [(R)-ENBPI-M(III)] and a corresponding ((R)-benzylamino)] analog [(R)-ENBPA-M(III)], a group of lipophilic monocationic leads amenable to metallopharmaceutical development. Racemic mixtures of Al(III), Fe(III), or Ga(III) but not In(III) (R)-ENBPI metallo-complexes killed intraerythrocytic malaria parasites in a stage-specific manner, the R = 4,6-dimethoxy-substituted ENBPI Fe(III) complex being most potent (IC50 approximately 1 microM). Inhibiting both chloroquine-sensitive and -resistant parasites, potency of these imino complexes correlated in a free metal-independent manner with their ability to inhibit heme polymerization in vitro. In contrast, the reduced (amino) 3-MeO-ENBPA Ga(III) complex (MR045) was found to be selectively toxic to chloroquine-resistant parasites in a verapamil-insensitive manner. In 21 independent recombinant progeny of a genetic cross, susceptibility to this agent mapped in perfect linkage with the chloroquine resistance phenotype suggesting that a locus for 3-MeO-ENBPA Ga(III) susceptibility was located on the same 36-kilobase segment of chromosome 7 as the chloroquine resistance determinant. These compounds may be useful as novel probes of chloroquine resistance mechanisms and for antimalarial drug development.

ATP-Binding Cassette Transporters↗
PubMed1977

Uptake of ferrienterochelin by Escherichia coli: energy dependent stage of uptake.

The uptake of the siderophore-iron complex ferrienterochelin was found to be strongly dependent upon an energized membrane state, as demonstrated by its sensitivity to dinitrophenol, azide, and cyanide. Ferrienterochelin uptake may also be dependent upon phosphate bond energy, as indicated by sensitivity to arsenate and iodoacetic acid. Although the adenosine triphosphatase does not appear to be involved in this energy coupling mechanism, ferrienterochelin uptake was shown to be less dependent upon phosphate bond energy than was glutamine uptake. Sensitivity of ferrienterochelin uptake to osmotic shock was shown to be due to the release of a ferrienterochelin binding compound located in the outer membrane of the cells and probably identical to the colicin B receptor protein.

Adenosine Triphosphatases↗
PubMed1990

Ferrous sulfate reduces methyldopa absorption: methyldopa: iron complex formation as a likely mechanism.

Ferrous sulfate and sodium sulfate reduce methyldopa absorption in humans. This current study was conducted to investigate some of the potential factors by which these compounds could reduce methyldopa absorption. A rat model developed to examine drug absorption was used. Solutions of 14C methyldopa alone and with ferrous sulfate or sodium sulfate were injected in vivo into closed duodenal segments. Ferrous sulfate reduced methyldopa absorption 52.9% (p less than 0.01), while sodium sulfate had no significant effect on methyldopa absorption. In vitro iron in its ferrous form rapidly oxidizes to the ferric form in the presence of methyldopa. The ferric form of iron binds strongly to methyldopa, presumably resulting in the decreased methyldopa absorption. Methyldopa was stable in vivo and in vitro in the presence of ferrous sulfate and sodium sulfate. These studies are consistent with ferrous sulfate reducing methyldopa absorption by the formation of ferric iron: methyldopa complexes.

Animals↗
PubMed1995

Identification of a porphyrin pi cation radical in ascorbate peroxidase compound I.

Electron paramagnetic resonance (EPR) spectroscopy has been used to analyze the ascorbate peroxidase Fe3+ resting state and to compare the reaction product between the enzyme and H2O2, compound I, with that of cytochrome c peroxidase. Because ascorbate peroxidase has a Trp residue in the proximal heme pocket at the same location as the Trp191 compound I free radical in cytochrome c peroxidase [Patterson, W. R., & Poulos, T. L. (1995) Biochemistry 34, 4331-4341], it was anticipated that ascorbate peroxidase compound I might also contain a Trp-centered radical. However, the ascorbate peroxidase compound I EPR spectrum is totally different from that of cytochrome c peroxidase. Immediately after the addition of H2O2, the 7.5 K EPR spectrum of ascorbate peroxidase compound I exhibits an axial resonance extending from g perpendicular = 3.27 to g parallel approximately 2 that disappears within 30 s, presumably due to endogenous reduction of compound I. In contrast, cytochrome c peroxidase compound I exhibits a long-lived g approximately 2 signal associated with the Trp191 cation free-radical [Houseman, A. L. P., et al. (1993) Biochemistry 32, 4430-4443]. Recently, the 2 K EPR spectrum of a catalase compound I was found to exhibit a broad signal extending from g perpendicular = 3.45 to g parallel approximately 2 and was interpreted as a porphyrin pi cation radical [Benecky, M. J., et al. (1993) Biochemistry 32, 11929-11933]. On the basis of these comparisons, we conclude that ascorbate peroxidase forms an unstable compound I porphyrin pi cation radical, even though it has a Trp residue positioned precisely where the Trp191 radical is located in cytochrome c peroxidase.

Ascorbate Peroxidases↗
PubMed1984

Effect of phenytoin and corticosteroids on seizures and lipid peroxidation in experimental posttraumatic epilepsy.

Head trauma, intracerebral hematoma formation, and hemorrhagic cerebral infarction cause extravasation of the intravascular contents, red blood cell (RBC) hemolysis, hemosiderin deposition within the neuropil, and an increased incidence of epilepsy. Reports conflict regarding the efficacy of the administration of prophylactic anticonvulsant drugs to head-injured patients to prevent the development of posttraumatic epilepsy. In this study, rats received a 10-microliter injection of 100 mM FeCl2 at a depth of 1.8 mm into the isocortex, or an equal volume of saline. Rats were then treated with 30 mg/kg methylprednisolone (MPS), 90 mg/kg MPS, 100 mg/kg phenytoin, or with an equal volume of propylene glycol. Behavioral or electroencephalographic (EEG) seizures occurred in all control-treated iron-injected rats within 93 +/- 6 minutes of injection. Brain injury responses as measured by the occurrence of fluorescent product formation from iron-induced lipid peroxidation showed 6.6 +/- 0.8 units/gm in the saline-injected animals, and 16.7 +/- 2.5 units/gm in the control-treated iron-injected rats. Of the 90-mg/kg MPS-treated rats, 8% had seizures; fluorescence in those animals was 5.7 +/- 0.5 units/gm. Phenytoin treatment prevented the occurrence of convulsive and EEG seizures; however, lipid peroxidation was unaffected (16.5 +/- 4.1 units/gm). If posttraumatic epilepsy develops because of RBC extravasation, hemolysis, parenchymal deposition of heme compounds, and initiation of lipid peroxidation, then treatments designed to prevent peroxidation may be more effective for epilepsy prophylaxis than administration of anticonvulsant drugs that mask convulsive seizures while biochemical brain injury continues.

Animals↗
PubMed2002

Doxorubicin induces an increase of nitric oxide synthesis in rat cardiac cells that is inhibited by iron supplementation.

Doxorubicin is an anthracycline antibiotic generally used in the treatment of solid tumors, but its use is limited by a severe cardiotoxicity, which has been related to the generation of oxygen- and nitrogen-derived free radicals. We have demonstrated that doxorubicin induces nitric oxide (NO) synthesis in the rat cardiac cells H9c2: the drug, after a 24-h incubation, evoked a dose-dependent increase of both NO synthase (NOS) activity in the cells and nitrite levels in the culture supernatant; the accumulation of nitrite (a stable derivative of NO) was prevented by different NOS inhibitors. The increase of NO production was associated with an increased expression of the inducible NOS isoform gene. These effects were significantly inhibited by the coincubation of doxorubicin with iron nitrilotriacetate, a compound that releases iron into the cells. Our results suggest that doxorubicin could induce NO generation in cardiac cells by modifying the iron homeostasis.

Animals↗
PubMed2006

Monomeric iron(II) hydroxo and iron(III) dihydroxo complexes stabilized by intermolecular hydrogen bonding.

Using the multidentate ligand bis(N-methylimidazol-2-yl)-3-methylthiopropanol (L), the mononuclear iron(II) hydroxo and iron(III) dihydroxo complexes [Fe(II)(L)2(OH)](BF4) (1) and [Fe(III)(L)2(OH)2](BF4) (2) have been synthesized and characterized by X-ray diffraction and spectroscopic methods. The X-ray data suggest that the remarkable stability of the Fe-OH bond(s) in both compounds results from intermolecular hydrogen-bonding interactions between the hydroxo ligand(s) and the tertiary hydroxyl of the L ligands, which prevent further intermolecular reactions.

Crystallography, X-Ray↗