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PubMed1997

Iron and virulence of Haemophilus ducreyi in a primate model.

BACKGROUND AND OBJECTIVES: The pathogenesis of chancroid is currently unclear. There are discrepancies between the virulence of Haemophilus ducreyi in the human and animal experiments. Iron availability influences the virulence of many pathogens. The objective of this study was to investigate the role of iron in virulence of H. ducreyi. STUDY DESIGN: Intradermal inoculation of the primate Macaca mulatta was studied as an animal model for pathogenesis of chancroid. This model then was used to study the influence of iron availability on virulence of H. ducreyi. Eleven strains of H. ducreyi with proven avirulence in the rabbit intradermal test and one virulent control strain were used. Two of the strains had been shown to cause ulcers in a human inoculation experiment. Strains were suspended in fluid with different iron compounds before intradermal injection. Other monkeys were treated with injectable iron before inoculation with bacteria suspended. RESULTS: All but one of the test strains produced a chancroid-like ulcer from which H. ducreyi could be isolated. The minimal ulcerative dose was 10(5) cfu. Iron in the injection fluid decreased this dose 10-fold. In animals pretreated with intramuscular iron, the minimal ulcerative dose decreased to 10(4) cfu and all eleven strains became ulcerative. CONCLUSIONS: The availability of iron increases virulence of H. ducreyi. The iron pretreated primate model is useful for the study of virulence factors of H. ducreyi because of its ability to produce lesions with strains that avirulent in other animal models but pathogenic to humans.

Animals↗
PubMed2004

Iron-source preference of Staphylococcus aureus infections.

Although bacteria use different iron compounds in vitGro, the possibility that microbes distinguish between these iron sources during infection has hitherto not been examined. We applied stable isotope labeling to detect source-specific iron by mass spectrometry and show that Staphylococcus aureus preferentially imports heme iron over transferrin iron. By combining this approach with computational genome analysis, we identified hts (heme transport system), a gene cluster that promotes preferred heme iron import by S. aureus. Heme iron scavenging by means of hts is required for staphylococcal pathogenesis in animal hosts, indicating that heme iron is the preferred iron source during the initiation of infection.

ATP-Binding Cassette Transporters↗
PubMed2003

Development and optimization of the drug release determination of iron from iron prolonged release tablets.

The aim of this research was to develop and optimize the drug release determination of iron from iron prolonged release tablets. First, solubility characteristics of ferrous sulfate in different aqueous media with a pH in the range of 1 to 8 were studied. According to the results obtained different physicochemical conditions that influence drug release of iron from iron prolonged release tablets were checked. Various aqueous media with a pH in the range of 1 to 7.4, different volumes of dissolution media, various rotation speeds of stirring elements, different dissolution apparatus (apparatus 1/basket apparatus and apparatus 2/paddle apparatus according to USP/Ph. Eur.) were verified. For evaluation of dissolved iron two different methods were checked: atomic absorption spectrometry and redox titration. Redox titration was proved to be a reproducible, discriminatory, selective and cost effective method for evaluation of dissolved iron from iron prolonged release tablets and can be applied in the quality control of solid dosage forms containing iron compounds.

Delayed-Action Preparations↗
PubMed1988

Growth-stimulating effect of ferric citrate on hybridoma cells: characterization and relation to transferrin function.

The growth of mouse hybridomas in the defined medium with ferric citrate at the optimum growth-stimulating concentration of 500 microM in place of transferrin is fully comparable with the growth in the medium with transferrin at the optimum concentration of 5 micrograms/ml. Experiments with monoclonal antibody to mouse transferrin receptor demonstrate that the growth-stimulating effect of ferric citrate is not based on the action of residual transferrin or the action of transferrin secreted by hybridoma cells. Such growth-stimulating effect is specific for iron compounds while other metal trace elements are ineffective. Hybridoma cells can absorb iron from medium containing iron salt without the presence of transferrin.

Animals↗
PubMed1991

Chloroquine inhibits the intracellular multiplication of Legionella pneumophila by limiting the availability of iron. A potential new mechanism for the therapeutic effect of chloroquine against intracellular pathogens.

Chloroquine and ammonium chloride, by virtue of their basic properties, have been shown to raise endocytic and lysosomal pH and thereby interfere with normal iron metabolism in a variety of cell types, including mononuclear phagocytes. Cellular iron metabolism is of critical importance to Legionella pneumophila, an intracellular bacterial pathogen whose capacity to multiply in human mononuclear phagocytes is dependent upon the availability of intracellular iron. In view of this, we have studied the effects of chloroquine and ammonium chloride on L. pneumophila intracellular multiplication in human monocytes. Chloroquine, at a concentration of 20 microM, and ammonium chloride, at a concentration of 20 mM, inhibited L. pneumophila intracellular multiplication by 1.4 +/- 0.2 (SEM) logs and 1.5 +/- 0.2 logs, respectively. Chloroquine- and ammonium chloride-induced inhibition of L. pneumophila intracellular multiplication was completely reversed by iron nitrilotriacetate, an iron compound which is soluble in the neutral to alkaline pH range, but not by iron transferrin, which depends upon acidic intracellular conditions to release iron. Chloroquine had no major direct effect on L. pneumophila multiplication in artificial media except at extremely high concentrations (15,000-fold that which inhibited L. pneumophila multiplication in mononuclear phagocytes), and inhibition at such concentrations was not reversed by iron nitrilotriacetate. This study demonstrates that chloroquine and ammonium chloride inhibit the intracellular multiplication of L. pneumophila by limiting the availability of iron to the bacterium. It is possible that such a mechanism of action underlies chloroquine's antimicrobial effect against other intracellular pathogens, such as the agents of malaria and tuberculosis.

Adult↗
PubMed2005

A method for rapid mouse siderocyte enrichment.

OBJECTIVE: Iron overload is a key contributor to the pathogenesis of multiple disorders including the sideroblastic anemias. The specific iron compounds present in tissues or cells that are the target of iron deposition remain poorly understood, but there is evidence that some forms are magnetically active. We have developed a simple and specific method to purify iron-overloaded red blood cells using magnetic affinity columns. Here we describe this method and characterize purified Sod2-deficient siderocytes. MATERIALS AND METHODS: RBC derived from mice transplanted with Sod2-deficient hematopoietic stem cells served as a source of iron-laden cells. Purification was based upon the observation that iron deposits in Sod2-deficient cells are "magnetically susceptible" and allow for retention of iron-laden cells in a strong magnetic field. Peripheral blood from Sod2-deficient chimeric mice was passed through magnetic separation columns; iron-overloaded cells were eluted and characterized by flow cytometry, Western blot, and microscopy. RESULTS: We were able to purify 2.8% of the total red cells as iron-laden siderocytes. The magnetically purified Sod2-deficient cells were predominantly identified as reticulocytes. They had numerous siderotic granules, produced enhanced levels of reactive oxygen species, and showed increased protein oxidative damage, mitochondrial enrichment, and mitochondrial hyperpolarization. CONCLUSIONS: Our method can be used to purify iron-laden cells as well as iron-associated subcellular fractions prepared from iron-loaded tissues, allowing elucidation of the structure, location, and protein composition of such iron deposits. This data will help develop our understanding of the pathogenesis of SA and other disorders characterized by iron overload.

Anemia, Sideroblastic↗
PubMed1985

Iron overload of the liver in the baboon. An ultrastructural study.

Liver biopsies from 4 baboons taken during 15 months of iron-polymaltose injections, were compared with specimens from 2 controls. A morphometric method was used to assess ferritin concentration in various cells. Initially, ferritin and siderosomes were conspicuous in reticuloendothelial cells but rare in hepatocytes. Unusual findings included intranuclear ferritin and coalesced ferritin within bile canaliculi. With advancing overload, ferritin and hemosiderin increased not only in sinusoidal cells, but also in hepatocytes, with concomitant elevation of transaminases. The hepatocytes now showed evidence of damage and excessive collagen was present mainly around portal spaces. A year after cessation of iron injections, hepatocyte ultrastructure was near normal while sinusoidal cells were still heavily overloaded. The baboon appeared to be a useful model for the study of iron overload. Although in this study most of the damage was reversible, it is suspected that more prolonged overload, a different route of administration or other, more toxic iron compounds, may lead to cirrhosis similar to that of the iron-loading anemias.

Animals↗
PubMed2003

Iron uptake by Escherichia coli.

Ferric iron is transported into Escherichia coli by a number of chelating compounds. Iron transport through the outer membrane by citrate, ferrichrome, enterobactin, aerobactin, yersiniabactin, and heme is catalyzed by highly specific proteins and across the cytoplasmic membrane by ABC transport systems with lower specificity. Transport across the outer membrane requires energy, which is provided by the proton motive force of the cytoplasmic membrane and transmitted to the outer membrane via the TonB-ExbB-ExbD proteins. Binding of substrates induces large long-range structural changes in the transport proteins, but does not open the channel. It is thought that the channel is opened by energy input from the cytoplasmic membrane. Although a basic understanding of how the transport proteins might function has been obtained from the crystal structures of three outer membrane proteins of E. coli and from many genetic and biochemical experiments, numerous fundamental questions still remain open. Transcription of the transport protein genes is regulated by the Fur protein, which when loaded with ferrous iron functions as a repressor. Fur also positively regulates genes of iron-containing proteins by repressing synthesis of an anti-sense RNA. Regulation of ferric citrate transport genes via a transmembrane device has become the paradigm of the regulation of a variety of systems, including the hypersensitivity response of plants to bacterial infections.

Biological Transport, Active↗
PubMed1983

Development of a blood-free Campylobacter medium: screening tests on basal media and supplements, and the ability of selected supplements to facilitate aerotolerance.

The capacity of six basal media to support the growth of thermophilic campylobacters was tested. The most successful was Nutrient Broth No. 2 (Oxoid) solidified with New Zealand agar but it gave at best only a 9% recovery rate. Various blood products, iron compounds, detoxifying agents, reducing agents, growth stimulants and an antimetabolite were added to the selected basal medium and counts of inoculated organisms were compared with counts on basal medium containing 5% lysed horse blood. Of 22 supplements tried only blood, Fildes' peptic digest of blood, heamatin, iron salts, charcoal, sodium metabisulphite and sodium pyruvate greatly improved the basal medium. The ability of these supplements used singly and in combinations to facilitate aerotolerance of campylobacters was investigated. Two aspects of aerotolerance were tested; (a) the ability of the supplements to sustain the viability of campylobacters seeded onto culture plates left on the bench for up to 6 h before microaerobic incubation; and (b) the ability of the supplements to facilitate the growth of campylobacters at increasing oxygen tension (6, 10 and 17% oxygen). A combination of 0.4% charcoal, 0.025% ferrous sulphate and 0.025% sodium pyruvate was found to be as effective as blood in both tests.

Campylobacter↗
PubMed2002

Characterization of commercial iron chelates and their behavior in an alkaline and calcareous soil.

Iron deficiency is a common problem for many plants grown in alkaline and calcareous soils. To correct this problem, iron is supplied to plants as chelates. Several iron chelates are sold under diverse trademarks with different characteristics. This work evaluated 18 commercial products containing the most representative chelated iron sources used in agricultural practice in Spain when the study was done, namely the ferric chelates of EDDHA, EDDHMA, EDDCHA, EDDHSA, EDTA, and DTPA. The chelates were comprehensively characterized and quantitated by several techniques, including several chromatographic methods. Iron and chelate dynamics in soil were also studied in a model alkaline and calcareous soil. Results indicate that, in this model soil, among the different iron compounds studied only FeEDDHA and analogues have the capacity to maintain soluble iron in soil solution over time. These results are in agreement with general experience under field conditions. Furthermore, among the different ortho-ortho isomers of FeEDDHA's, FeEDDHSA and FeEDDCHA showed greater capacity than FeEDDHA and FeEDDHMA to maintain the chelated iron in soil solution over time.

Agriculture↗
PubMed1975

Effect of milk and casein on the absorption of supplemental iron in the mouse and chick.

Milk is an attractive vehicle for introducing iron supplements into iron-deficient infants and children. This study compares the effects of milk and caseins on the whole-body absorption of radioactive iron complexes in an attempt to resolve the controversy over whether milk and its constituent phosphoproteins seriously impair iron absorption. Evidence is presented to clarify the role of the calcium-casein micelles of cow's milk in binding iron donated by the ferric-nitrilotriacetate (NTA) complex. The absorption of iron from isolated Fe(III)-casein complexes was studied in mice as a function of the casein--to--Fe ratio and was compared with the absorption of Fe(III)-NTA at equivalent levels. Even at casein--to--Fe ratios higher than those found in conventional iron-supplemented cow's milk (10-15 mg Fe/qt; casein P:Fe congruent to 34), absorption of iron(III) from the casein or NTA complex was not significantly different. There was no significant difference in the absorption of iron administered to mice and chicks as ferrous ion, ferric-NTA, or ferric fructose; nonfat cow's milk did not inhibit the absorption of these iron compounds. For the chick, in fact, milk significantly enhanced the absorption of iron from the ferric-NTA chelate. In order to affect iron absorption significantly casein would have to be present considerably in excess of that found in conventionally supplemented cow's milk.

Absorption↗
PubMed2006

Apoptotic stress pathway activation mediated by iron on endothelial cells in vitro.

BACKGROUND: Iron sucrose (Fe-S) and low-molecular-weight iron dextran (Fe-D) have been used successfully in the treatment of anaemia in chronic kidney disease patients. However, some side effects, such as endothelial cell dysfunction have been reported. Mechanisms by which iron can induce endothelial cell damage have not been completely understood. This study was designed to examine the effect of Fe-S and Fe-D on bovine aortic endothelial cells in vitro. METHODS: Cell proliferation was determined by [3H] thymidine incorporation, cytotoxicity by lactate dehydrogenase, pro-Caspase-3 by immunoblotting; and Caspase-3 activity using a colorimetric assay. Expression of the apoptosis stress pathway proteins Bcl-2 and Bax and cycle arrest proteins p53 and p21WAF/CIP1 were examined by immunoblot. Cell apoptosis was tested by terminal deoxynucleotidyltransferase-mediated nick-end labelling (TUNEL) and DNA fragmentation. RESULTS: Both iron preparations inhibited cell proliferation. This effect was more important and occurred at lower concentrations in Fe-S than Fe-D cultured cells. Expression of p53 and p21WAF/CIP1 increased in cells incubated with Fe-S, but not with Fe-D. Bcl-2 expression was significantly down-regulated in cells incubated with Fe-S in comparison with Fe-D, while Bax expression was not modified by the iron compounds. Pro-Caspase-3 expression and Caspase-3 activity increased only in cells treated with Fe-S. Apoptosis was present in cells treated with Fe-S. CONCLUSIONS: Our results demonstrate that Fe-S exerts a greater inhibitory effect on endothelial cell proliferation than Fe-D. The mechanisms involved in this process may be related, at least in part, to over expression of proteins related to the cell cycle arrest and apoptosis stress pathway.

Animals↗
PubMed1992

Bioavailability in man of iron in human milk and cow's milk in relation to their calcium contents.

Iron absorption from human milk and cow's milk was compared in the same subjects using two radio-iron tracers and extrinsic labeling of the iron. Previously observed higher iron absorption from human milk was confirmed as 19.5 +/- 17.3% (mean +/- SD) in cow's milk versus 48.0 +/- 25.5% in human milk; mean individual absorption ratio was 0.39 +/- 0.18 (p less than 0.0001). Cow's milk has a several times higher content of calcium, recently established to be a potent inhibitor of iron absorption. Adding calcium chloride to human milk in amounts to equate the calcium content of cow's milk significantly reduced iron absorption [39.1 +/- 17.8% (mean +/- SD) versus 21.3 +/- 10.6%]; mean individual absorption ratio with or without added calcium was 0.58 +/- 0.12 (mean +/- SD) (p less than 0.0001). Differences in calcium content could explain at least 70% of the difference in iron bioavailability between milks. It is suggested that the remaining 30% difference may mainly be an artifact related to inhomogeneous radioiron-labeling of milk iron compounds, especially in human milk, and that the main difference in true iron absorption between human and cow's milk is related to their different calcium contents. The rather high fractional iron absorption from human milk can be explained by its low iron content. There is nothing to indicate that human milk contains any enhancer of iron absorption. The marked inhibiting effect of calcium on iron absorption should be considered in the design of infant formulas to achieve an optimal balance in the contents of calcium and iron.

Adult↗
PubMed1990

A review of the biochemical roles, toxicity and interactions of zinc, copper and iron: III. Iron.

Because of its essentiality, iron occurs in tissues of all living matter especially aerobes. Iron compounds have been utilized in various aspects of argo-industry. Iron-binding proteins and their vital role in intestinal uptake, distribution and storage of iron are concisely examined. Ceruloplasmin (cuproenzyme) is imperative for iron mobilization from storage sites for hemoglobin synthesis. There is evidence of relationship between enhance susceptibility to infection and iron deficiency. The extent to which behavioral abnormalities and iron depletion are related remains to be established. The efficacy of chelating agents such as desferroxamine, bicarbonates and ethylene diamine tetraacetic acid (EDTA) against iron overload has been tested.

Anemia, Hypochromic↗
PubMed1982

Mucosal uptake, mucosal transfer and retention of a therapeutic dose of iron.

The absorption of a pharmacological dose of iron was assessed by determination of mucosal uptake, mucosal transfer and retention of 33 mg (Fe(II) as ferrous sulphate and ferrous ascorbate. 20 subjects were studed in a cross-over trial, 11 with normal iron stores and 9 with iron deficiency according to the serum ferritin concentrations. The activity of 59Fe and 51Cr (administered as a non-absorbable indicator) was measured by whole-body counting. There was no difference in absorption between the two iron compounds in normal subjects. Absorption of ferrous ascorbate averaged 52% higher than ferrous sulphate in subjects with iron deficiency. The difference was the result of higher mucosal uptake, probably because oxidation of Fe(II) in the alkaline milieu of the intestine, which leads to formation of non-absorbable Fe(III) complexes, was prevented. The mucosal transfer fraction of both compounds was identical.

Administration, Oral↗
PubMed2001

New application of a traditional analytical method--arsenic removal from water works sludge during iron(III) chloride coagulant production.

The Marsh Test, the original means of determination of arsenic by hydride generation, has been modified to remove arsenic from water works sludge, with iron used instead of zinc as the main agent. Water works sludge (main compound iron(III) oxyhydrate) generated during groundwater treatment can be enriched in arsenic up to several gkg(-1). Acidic dissolution of this sludge to produce FeCl3 coagulant liberates the arsenic. Addition of elemental iron reduces this dissolved As(V) mainly to dispersed elemental As(0) particles, which can be removed by filtration. If the reaction temperature is kept below 50 degrees C, more than 99% of the arsenic can be removed from the coagulant solution and less than 10% will escape as gaseous arsine (AsH3). Severe foaming and silicic acid gel formation occurs during the acidic dissolution, however. For technical and economic reasons the use of the water works sludge for FeCl3 coagulant production is not competitive when compared with other recycling methods.

Arsenic↗
PubMed1993

Iron uptake mechanisms of pathogenic bacteria.

Most of the iron in a mammalian body is complexed with various proteins. Moreover, in response to infection, iron availability is reduced in both extracellular and intracellular compartments. Bacteria need iron for growth and successful bacterial pathogens have therefore evolved to compete successfully for iron in the highly iron-stressed environment of the host's tissues and body fluids. Several strategies have been identified among pathogenic bacteria, including reduction of ferric to ferrous iron, occupation of intracellular niches, utilisation of host iron compounds, and production of siderophores. While direct evidence that high affinity mechanisms for iron acquisition function as bacterial virulence determinants has been provided in only a small number of cases, it is likely that many if not all such systems play a central role in the pathogenesis of infection.

Animals↗
PubMed2002

Iron increases expression of iron-export protein MTP1 in lung cells.

Accumulation of reactive iron in acute and chronic lung disease suggests that iron-driven free radical formation could contribute to tissue injury. Safe transport and sequestration of this metal is likely to be of importance in lung defense. We provide evidence for the expression and iron-induced upregulation of the metal transporter protein-1 (MTP1) genes in human and rodent lung cells at both the protein and mRNA levels. In human bronchial epithelial cells, a 3.8-fold increase in mRNA level and a 2.4-fold increase in protein level of MTP1 were observed after iron exposure. In freshly isolated human macrophages, as much as an 18-fold increase in the MTP1 protein level was detected after incubation with an iron compound. The elevation in expression of MTP1 gene was also demonstrated in iron-instilled rat lungs and in hypotransferrinemic mouse lungs. This is similar to our previous findings with divalent metal transporter-1 (DMT1), an iron transporter that is required for iron uptake and intracellular iron trafficking. These studies suggest the presence of iron mobilization and/or detoxification pathways in the lung that are crucial for iron homeostasis and lung defense.

Animals↗