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PubMed1959

The cellular transformation of injected colloidal iron complexes into ferritin and hemosiderin in experimental animals; a study with the aid of electron microscopy.

As revealed by electron microscopy and electron diffraction, the physical state of ferric hydroxide micelles contained in iron-dextran, saccharated iron oxide, and hydrous ferric oxide ("ferric hydroxide") differs notably from the state of the ferric hydroxide in ferritin or hemosiderin. By virtue of this difference one can trace the intracellular transformation of colloidal iron, administered parenterally, into ferritin and hemosiderin. One hour after intraperitoneal injection of iron-dextran or saccharated iron oxide into mice, characteristic deposits were present in splenic macrophages, in sinusoidal endothelial cells of spleen and liver, and in vascular endothelial cells of various renal capillaries. Four hours after injection, small numbers of ferritin molecules were identifiable about intracellular aggregates of injected iron compounds; and by the 6th day, ferritin was abundant in close proximity to deposits of injected iron compounds. The latter were frequently situated in cytoplasmic vesicles delimited by single membranes. These vesicles were most frequently found in tissue obtained during the first 6 days after injection; and in certain of the vesicles ferritin molecules surrounded closely packed aggregates of injected material. Much unchanged ferric hydroxide was still present in macrophages and vascular endothelial cells 3 to 4 weeks after injection. While electron microscopy left no doubt about the identity of injected ferric hydroxide on the one hand, and of ferritin or hemosiderin on the other, histochemical tests for iron failed in this respect. Precipitation of ferric hydroxide (hydrous ferric oxide) from stabilized colloidal dispersions of iron-dextran was brought about in vitro by incubation with minced mouse tissue (e.g. liver), but not by incubation with mouse serum or blood. Subcutaneous injections of hydrous gel of ferric oxide into mice initially produced localized extracellular precipitates. Most of the material was still extracellular 16 days after injection, though part of it was phagocytized by macrophages near the site of injection; but apparently none reached the spleen in unaltered form. Five days after injection and thereafter, much ferritin was present in macrophages about the site of injection and in the spleen. The findings show that iron preparations widely used in therapy can be identified within cells, and that their intracellular disposition and fate can be followed at the molecular level. Considered in the light of previous work, they indicate that the characteristic structure of the ferric hydroxide micelles in molecules of ferritin is specific, and develops during the union of apoferritin with ferric hydroxide. Apparently this union does not depend upon specific cell components.

Animals↗
PubMed1984

Hemoglobin. A biologic fenton reagent.

Iron and iron compounds may facilitate hydroxyl-radical generation from activated oxygen species. Earlier work on the generation of this radical has been focused on simple, low-molecular-weight iron compounds. We hypothesized that free hemoglobin, like other iron-rich substances, might also mediate hydroxyl-radical generation. We find: 1) In the presence of a superoxide anion-generating system (hypoxanthine and xanthine oxidase), hemoglobin promotes hydroxyl-radical formation in a dose-dependent fashion. 2) This generation of hydroxyl radical is greatly decreased by prior oxidation of the hemoglobin, equilibration of hemoglobin with carbon monoxide, or addition of catalase, while added superoxide dismutase has little effect. Therefore, hydroxyl radical probably arises primarily via reaction between the ferrous heme iron and H2O2. 3) In further support of this, hydroxyl radical forms as readily upon the addition of H2O2 to hemoglobin. 4) Hemoglobin also increases hypoxanthine/xanthine oxidase-driven peroxidation of poly-unsaturated fatty acids such as arachidonic acid and human red cell membrane lipids. 5) The addition of sufficient haptoglobin (the plasma hemoglobin-binding protein) suppresses both hemoglobin-driven hydroxyl radical and malondialdehyde generation. Thus, free hemoglobin may be biologically hazardous, in part because it acts as a "Fenton" reagent, having the potential to catalyze hydroxyl-radical generation in areas of inflammation. Haptoglobin, which binds hemoglobin very tightly, blocks this through a presently unknown mechanism. An important physiologic function of haptoglobin may be prevention of such hemoglobin-mediated oxidation.

Arachidonic Acid↗
PubMed2000

Iron bioavailability in infants from an infant cereal fortified with ferric pyrophosphate or ferrous fumarate.

BACKGROUND: Infant cereals are commonly fortified with insoluble iron compounds with low relative bioavailability, such as ferric pyrophosphate, because of organoleptic changes that occur after addition of water-soluble iron sources. OBJECTIVE: Our objective was to compare iron bioavailability from ferric pyrophosphate with an alternative iron source that is soluble in dilute acid, ferrous fumarate, and to evaluate the influence of ascorbic acid on iron bioavailability from ferrous fumarate in infants. DESIGN: Iron bioavailability was measured as the incorporation of stable iron isotopes into erythrocytes 14 d after administration of labeled test meals (25 g dry wheat and soy infant cereal, 100 g water, and 2.5 mg Fe as [57Fe]ferric pyrophosphate or [57Fe]ferrous fumarate). Ascorbic acid was added to all test meals (25 mg in study 1 or 25 or 50 mg in study 2). Infants were fed each test meal on 4 consecutive days under standardized conditions. The 2 different test meals within each study were administered 2 wk apart in a crossover design. RESULTS: Geometric mean iron bioavailability was significantly higher from [57Fe]ferrous fumarate than from [57Fe]ferric pyrophosphate [4.1% (range: 1.7-14.7%) compared with 1.3% (range: 0. 7-2.7%); n = 8, P = 0.008]. In this study, doubling the ascorbic acid content did not further enhance iron bioavailability; the geometric means (range) were 3.4% (1.9-6.6%) and 4.2% (1.2-18.7%) for the test meals with 25 and 50 mg ascorbic acid added, respectively (n = 9). CONCLUSION: Iron bioavailability from iron-fortified infant cereals can be improved by using an iron compound with high relative bioavailability and by ensuring adequate ascorbic acid content of the product.

Biological Availability↗
PubMed1993

Regulation of proteolytic activity of Vibrio vulnificus by iron-containing compounds.

Previous studies have shown that the Vibrio vulnificus is able to use hemoglobin and the hemoglobin-haptoglobin complex to reverse iron limitation. In addition, we report here that free hemin, as well as hemin bound to albumin, will reverse iron-limited growth. While protease negative mutants were able to use hemin and hemoglobin, they were unable to compete as successfully for albumin-bound hemin. Using Luria broth with the iron chelator ethylenediamine-di(o-hydroxyphenylacetic acid) (EDDA), no changes in proteolytic activity were seen. In contrast, growth in a low iron defined medium resulted in a loss of proteolytic activity. This loss was reversed by the addition of hemin or hemoglobin but not by inorganic iron or globin alone. Since one portal of entry of this organism is pre-existing wounds, hemoglobin released during cell damage may be important in activating extracellular proteases leading to the massive cell damage seen with this vibrio.

Albumins↗
PubMed1982

Sequence of development of iron deficiency in the rat.

This study was designed to determine the interrelationships among storage iron, transport iron, and iron compounds that serve known physiological functions (Hb, myoglobin, and cytochrome c) during the gradual progression of dietary iron deficiency. These three categories of iron compounds are generally considered to become depleted in three corresponding, sequential stages. However, there is scattered evidence of substantial overlap between these stages in man. The presence of such overlap may prove pertinent to the interpretation of laboratory tests used in the diagnosis of iron deficiency. The rat was used as an experimental model to allow more complete evaluation of the interrelationships between the stages of iron deficiency than would be possible in man. Rats were given diets containing 2, 6 and 50 mg iron/kg diet during early adult development, between 36 and 90 days of age. The iron-deficient diets (2 and 6 mg iron/kg diet) resulted in decreases in hematocrit and in muscle and intestinal cytochrome c well before storage iron in the liver and spleen was exhausted. The results in the rat model may help to explain why there is not a consistent pattern of laboratory abnormalities in individuals with chronic, mild dietary iron deficiency.

Aging↗
PubMed1998

Acquisition of iron by Gardnerella vaginalis.

Six Gardnerella vaginalis strains were examined for the ability to utilize various iron-containing compounds as iron sources. In a plate bioassay, all six strains acquired iron from ferrous chloride, ferric chloride, ferrous sulfate, ferric ammonium citrate, ferrous ammonium sulfate, bovine and equine hemin, bovine catalase, and equine, bovine, rabbit, and human hemoglobin. All six strains also acquired iron from human lactoferrin, but not from human transferrin, as determined by a liquid broth growth assay. Siderophore production was detected in eight G. vaginalis strains by the chrome azurol S universal chemical assay. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the cytoplasmic membrane proteins isolated from G. vaginalis 594 grown under iron-replete and iron-restricted conditions revealed several iron-regulated proteins ranging in molecular mass from 33 to 94 kDa. These results indicate that G. vaginalis may acquire iron from iron salts and host iron compounds.

Bacterial Proteins↗
PubMed2004

Enhanced expression of natural resistance-associated macrophage protein 1 in atherosclerotic lesions may be associated with oxidized lipid-induced apoptosis.

The natural resistance-associated macrophage proteins (Nramps) can modulate inflammatory reactions. Nramps are not only responsible for intracellular divalent metal transport but also determine the macrophage functions in inflammatory processes. In the present study we tested whether Nramp1 is involved in macrophage apoptosis induced by oxidized lipids in atherogenesis. Arterial segments of Watanabe heritable hyperlipidemic rabbits were used for an examination of Nramp1 mRNA by in situ RT-PCR and macrophage immunohistochemistry. Annexin V/PI staining and terminal dUTP nick-end labeling (TUNEL) techniques were used for apoptosis detection. We found that, in macrophage-rich areas (positive to RMA-11) of the rabbit atherosclerotic aorta, there were lesion-dependent increases in Nramp1 mRNA, which are mainly apoptotic foamy macrophages that are positive to TUNEL staining. U937 cells were treated with 7beta-hydroxycholesterol (7beta-OH) in the presence or absence of the redox-active iron chelator desferrioxamine (DFO) or 1,10-phenanthroline. The cellular iron chelators considerably reduced, whereas iron compounds enhanced, 7beta-OH-induced apoptosis and necrosis. DFO also decreased mRNA levels of Nramp1, whereas both iron compounds and 7beta-OH dramatically enhanced the expression of Nramp1 mRNA, particularly among 7beta-OH-induced apoptotic cells. We conclude that the enhanced expression of Nramp1 in macrophage regions of atherosclerotic lesions may be associated with ferrous iron-enhanced, oxidized lipid-induced apoptosis. This finding reveals a novel function of Nramp1 in atherogenesis.

Animals↗
PubMed1990

Iron-binding compounds and related outer membrane proteins in Vibrio cholerae non-O1 strains from aquatic environments.

A total of 156 strains of Vibrio cholerae non-O1 from aquatic origins were examined for the presence of iron uptake mechanisms and compared with O1 strains and other Vibrio species. All non-O1 strains were able to grow in iron-limiting conditions, with MICs of ethylenediaminedi (O-hydroxyphenylacetic acid) ranging from 20 microM to 2 mM. The production of siderophores was demonstrated by growth in chrome azurol S agar and cross-feeding assays. All strains produced phenolate-type compounds, as assessed by the chemical tests and by bioassays with Salmonella typhimurium enb-7. Some of the strains also promoted the growth of S. typhimurium enb-1 (which can use only enterobactin as a siderophore) as well as some strains of Vibrio anguillarum deficient in the anguibactin-mediated system. The chromatographic analyses and absorption spectra of siderophores extracted from culture supernatants suggest that vibriobactin may be produced by the strains examined. Interestingly, some strains also produced hydroxamate-type compounds, as determined by chemical tests, and were able to promote the growth of an aerobactin-deficient strain of Escherichia coli. These results were confirmed by the absorption spectra and chromatographic analyses of the culture extracts. The synthesis of iron-regulated outer membrane proteins in representative strains was also examined. The molecular sizes of the main induced proteins ranged from 70 to 78 kilodaltons. These results indicate that several iron uptake mechanisms which could be involved in environmental survival and pathogenicity are present in environmental V. cholerae non-O1 strains.

Bacterial Outer Membrane Proteins↗
PubMed2005

Comparison of density functionals for differences between the high- (5T2g) and low- (1A1g) spin states of iron(II) compounds. IV. Results for the ferrous complexes [Fe(L)('NHS4')].

Previous work testing density functionals for use in calculating high-spin-low-spin energy differences, deltaE(HL), for iron(II) spin-crossover transitions has tended to conclude that only properly reparametrized hybrid functionals can predict deltaE(HL) since it seems to depend critically on a correct description of the electron pairing energy governed by the exchange term. Exceptions to this rule are the previous three papers (I, II, and III in the present series of papers) where it was found that modern generalized gradient approximations (GGAs) and meta-GGAs could do as well as hybrid functionals, if not better, for this type of problem. In the present paper, we extend these previous studies to five more molecules which are too large to treat with high-quality ab initio calculations, namely, the series [Fe(L)('NHS(4)')], where NHS(4)=2.2'-bis(2-mercaptophenylthio)diethylamine dianion, and L=NH(3), N(2)H(4), PMe(3), CO, and NO(+). Since we know of no reliable experimental estimate of deltaE(HL), we content ourselves with a comparison against the experimentally determined ground-state spin symmetry including, in so far as possible, finite-temperature effects. Together with the results of Papers I, II, and III, this paper provides a test of a large number of functionals against the high-spin/low-spin properties of a diverse set of Fe(II) compounds, making it possible to draw some particularly interesting conclusions. Trends among different classes of functionals are discussed and it is pointed out that there is at least one functional, namely, the OLYP generalized gradient approximation, which is able to give a reasonably good description of the delicate spin energetics of Fe(II) coordination compounds without resorting to hybrid functionals which require the relatively more expensive calculation of a Hartree-Fock-type exchange term.

Journal Article↗
PubMed1995

Siderophores: structure and function of microbial iron transport compounds.

Siderophores are common products of aerobic and facultative anaerobic bacteria and of fungi. Elucidation of the molecular genetics of siderophore synthesis, and the regulation of this process by iron, has been facilitated by the fact that E. coli uses its own siderophores as well as those derived from other species, including fungi. Overproduction of the siderophore and its transport system at low iron is in this species well established to be the result of negative transcriptional repression, but the detailed mechanism may be positive in other organisms. Siderophores are transported across the double membrane envelope of E. coli via a gating mechanism linking the inner and outer membranes.

Agriculture↗
PubMed1983

Iron-chelating compounds produced by soil pseudomonads: correlation with fungal growth inhibition.

Strains of Pseudomonas putida, Pseudomonas sp., and Pseudomonas aeruginosa were examined for their ability to grow in the presence of the iron chelator, ethylenediamine-di-(o-hydroxyphenylacetic acid). In vitro fungal inhibition assays showed that the isolates varied in their ability to inhibit the growth of representative fungal plant pathogens. Fungal inhibition in vitro was superior to that of previously reported Pseudomonas sp. Studies with Fusarium oxysporum forma sp. lycopersici and a susceptible tomato cultivar demonstrated that Pseudomonas putida PPU3.1 was able to significantly reduce wilt disease.

Journal Article↗
PubMed1998

Aluminum treatment induces nitric oxide synthase in the rat brain.

In an attempt to delineate the capacity of aluminum to promote pro-oxidant events in the central nervous system, levels of nitric oxide synthase (NOS) have been determined in the cerebellum of rats exposed to an aluminum salt, either alone or in combination with an iron compound. Relatively acute treatment with aluminum over a three-day period, increased cerebellar levels of NOS. Parallel results were obtained when animals were dosed over a more extended three-week period. Dosing with an iron compound resulted in no changes in levels of this enzyme. Concurrent treatment with aluminum and iron did not potentiate the NOS-inducing effects of aluminum. By use of selective inhibitors, the specific induction of iNOS by aluminum treatment was found. The results suggest that the presence of aluminum can induce cerebellar NOS and that these changes are independent of any interaction between aluminum and erogenous iron.

Aluminum↗