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PubMed1982

Production of deferriferrioxamines B and E from a ferroverdin-producing Streptomyces species.

When Streptomyces sp. strain Wak. A-305 is cultured in iron (III)- or cobalt (II)-containing media, tris(p-vinylphenyl-4-hydroxy-3-nitrosobenzoato-N3, O4)ferrate(II) (ferroverdin) or the analogous tris-cobalt(III) complex, respectively, is produced intracellularly. In contrast, when cultured in transition metal ion-limiting media. Streptomyces sp. strain Wak. A-305 did not produce p-vinylphenyl 4-hydroxy-3-nitrosobenzoate (deferroferroverdin). Instead, deferriferrioxamines B and E, which have been characterized from other streptomycetes, were isolated extracellularly and may act as siderophores in this organism.U

Chlorides↗
PubMed1984

Derepression of the Azotobacter vinelandii siderophore system, using iron-containing minerals to limit iron repletion.

Azotobacter vinelandii solubilized iron from certain minerals using only dihydroxybenzoic acid, which appeared to be produced constitutively. Solubilization of iron from other minerals required dihydroxybenzoic acid and the siderophore N,N'-bis-(2,3- dihydroxybenzoyl )-L-lysine ( azotochelin ) or these chelators plus the yellow-green fluorescent siderophore azotobactin . In addition to this sequential production of siderophores, cells also demonstrated partial to hyperproduction relative to the iron-limited control. The iron sources which caused partial derepression of the siderophores caused derepression of all the high-molecular-weight iron-repressible outer membrane proteins except a 77,000-molecular-weight protein, which appeared to be coordinated with azotobactin production. Increased siderophore production correlated with increased production of outer membrane proteins with molecular weights of 93,000, 85,000, and 77,000, but an 81,000-molecular-weight iron-repressible protein appeared at a constant level despite the degree of derepression. When iron was readily available, it appeared to complex with a 60,000-molecular-weight protein believed to form a surface layer on the A. vinelandii cell.

Azotobacter↗
PubMed1997

Redox buffering by melanin and Fe(II) in Cryptococcus neoformans.

Melanin is a fungal extracellular redox buffer which, in principle, can neutralize antimicrobial oxidants generated by immunologic effector cells, but its source of reducing equivalents is not known. We wondered whether Fe(II) generated by the external ferric reductase of fungi might have the physiologic function of reducing fungal melanin and thereby promoting pathogenesis. We observed that exposure of a melanin film electrode to reductants decreased the open-circuit potential (OCP) and reduced the area of a cyclic voltammetric reduction wave whereas exposure to oxidants produced the opposite effects. Exposure to 10, 100, 1,000 or 10,000 microM Fe(II) decreased the OCP of melanin by 0.015, 0.038, 0.100, and 0.120 V, respectively, relative to a silver-silver chloride standard, and decreased the area of the cyclic voltammetric reduction wave by 27, 35, 50, and 83%, respectively. Moreover, exposure to Fe(II) increased the buffering capacity by 44%, while exposure to millimolar dithionite did not increase the buffering capacity. The ratio of the amount of bound iron to the amount of the incremental increase in the following oxidation wave was approximately 1.0, suggesting that bound iron participates in buffering. Light absorption by melanin suspensions was decreased 14% by treatment with Fe(II), consistent with reduction of melanin. Light absorption by suspensions of melanized Cryptococcus neoformans was decreased 1.3% by treatment with Fe(II) (P < 0.05). Cultures of C. neoformans generated between 2 and 160 microM Fe(II) in culture supernatant, depending upon the strain and the conditions [the higher values were achieved by a constitutive ferric reductase mutant in high concentrations of Fe(III)]. We infer that Fe(II) can reduce melanin under physiologic conditions; moreover, it binds to melanin and cooperatively increases redox buffering. The data support a model for physiologic redox cycling of fungal melanin, whereby electrons exported by the yeast to form extracellular Fe(II) maintain the reducing capacity of the extracellular redox buffer.

3-Hydroxyanthranilic Acid↗
PubMed1981

Analysis of parameters affecting the hemagglutination activity of Escherichia coli possessing colonization factor antigens: improved medium for observing erythrocyte agglutination.

The hemagglutination (HA) activity of two strains of Escherichia coli, each possessing different colonization factor antigens (CFA), was examined under different test conditions. The effects of ionic strength, temperature, pH, cations, and reaction surface on erythrocyte (RBC) agglutination were analyzed. Strain H-10407 (CFA/I) caused the agglutination of human, bovine, and chicken RBC, whereas strain CL-9699 (CFA/II) agglutinated only bovine and chicken RBC. The HA activity of both strains increased with decreasing ionic strength, pH, and temperature, the effects of temperature being negligible at low ionic strength. When accounting for ionic strength, the presence of Ca2+, Mg2+, Fe2+, or Fe3+ ions did not increase the HA activity of these bacteria. Optimum conditions for HA of reactive RBC by bacteria included low ionic strength (less than 50 mM) and slightly acidic pH (6.0 to 7.0). Use of a low-ionic-strength medium permitted application of microtitration methods to visualize the HA reactions. Storage of RBC in low-ionic-strength medium did not change their HA properties, and the use of this medium proved superior to saline in overcoming HA variation observed with different preparations of RBC.

Animals↗
PubMed1996

Evidence in pre-2.2 Ga paleosols for the early evolution of atmospheric oxygen and terrestrial biota

The loss of Fe from some pre-2.2 Ga paleosols has been considered by previous investigators as the best evidence for a reduced atmosphere prior to 2.2 Ga. I have examined the behavior of Fe in both pre- and post-2.2 Ga paleosols from depth profiles of Fe3+/Ti, Fe2+/Ti, and sigma Fe/Ti ratios, and Fe3+/Ti vs. Fe2+/Ti plots. This new approach reveals a previously unrecognized history of paleosols. Essentially all paleosols, regardless of age, retain some characteristics of soils formed under an oxic atmosphere, such as increased Fe3+/Ti ratios from their parental rocks. The minimum oxygen pressure (PO2) for the 3.0-2.2 Ga atmosphere is calculated to be about 1.5% of the present atmospheric level, which is the same as that for the post-1.9 Ga atmosphere. The loss of sigma Fe, common in paleosol sections of all ages, was not due to a reducing atmosphere, but to reductive dissolution of ferric hydroxides formed under an oxic atmosphere. This reductive dissolution of ferric hydroxides occurred either (1) after soil formation by hydrothermal fluids or (2) during and/or after soil formation by organic acids generated from the decay of terrestrial organic matter. Terrestrial biomass on the early continents may have been more extensive than previously recognized.

Atmosphere↗
PubMed1986

A comparison of two procedures used for complexing Fe(III) with human apotransferrin: I. Physicochemical properties of the Fe(III) . transferrin products.

Samples of human Fe.transferrin (Fe.HTr) were prepared from a single batch of apotransferrin (apo.HTr) by either the Fe(III)-citrate or the Fe(II)-ceruloplasmin (ferroxidase) method. By using 55Fe, 55Fe.HTr prepared by the citrate method and 55Fe.HTr prepared by the ceruloplasmin method contained 2.2-2.3 and 2.0 Fe/mol, respectively. For both 55Fe.HTr preparations, the isotope was shown to be associated with the protein from the measurement of absorbance at 465 nm and dialysis studies. However, passage of the 55Fe.HTr (ceruloplasmin) reaction mixture through DEAE-cellulose caused 55-60% of 55Fe to be lost from the protein, although no decrease in absorbance at 465 nm was observed. Ion-exchange chromatography of 55Fe.HTr (citrate) did not induce loss of 55Fe. Absorbance measurements showed significant differences between the two Fe.HTr preparations with respect to the ratios A212/A278 and A463/A278. Using an excitation wavelength of 275 nm, the fluorescence intensity ratios relative to apo.HTr were 0.275 and 0.309 for Fe.HTr (citrate) and Fe.HTr (ceruloplasmin), respectively. Electron spin resonance (ESR) measurements confirmed that Fe.HTr (citrate) and Fe.HTr (ceruloplasmin) were saturated with Fe. Hyperfine coupling constants and other features of the resonance profile revealed distinct differences between the two Fe.HTr preparations. Dialysis against H2O caused Fe.HTr (citrate), but not Fe.HTr (ceruloplasmin), to lose absorbance at 465 nm. The ESR profile of Fe.HTr (citrate), after dialysis against H2O, was reduced to multiple splittings and a lack of resolution of the central hyperfine structure. Addition of Na2CO3 restored the absorbance (465 nm) and the ESR pattern of Fe.HTr (citrate). In contrast, these properties of Fe.HTr (ceruloplasmin) were little affected by dialysis against H2O. However, the addition of trisodium citrate to Fe.HTr (ceruloplasmin) caused a reduction in absorbance at 465 nm and a change in ESR profile to resemble that of Fe.HTr (citrate) after dialysis in H2O; these changes, caused by citrate binding to Fe.HTr (ceruloplasmin), were restored to normal by the addition of Na2CO3. The data indicate that different protein conformations result from complexing Fe(III) with apo.HTr by these two different procedures. The two Fe.HTr products may differ, conceivably, in their abilities to transfer Fe to cells.

Apoproteins↗
PubMed2006

Electron transport pathways for the oxidation of endogenous substrate(s) in Acidithiobacillus ferrooxidans.

Oxidation of endogenous substrate(s) of Acidithiobacillus ferrooxidans with O2 or Fe3+ as electron acceptor was studied in the presence of uncouplers and electron transport inhibitors. Endogenous substrate was oxidized with a respiratory quotient (CO2 produced/O2 consumed) of 1.0, indicating its carbohydrate nature. The oxidation was inhibited by complex I inhibitors (rotenone, amytal, and piericidin A) only partially, but piericidin A inhibited the oxidation with Fe3+ nearly completely. The oxidation was stimulated by uncouplers, and the stimulated activity was more sensitive to inhibition by complex I inhibitors. HQNO (2-heptyl-4-hydroxyquinoline N-oxide) also stimulated the oxidation, and the stimulated respiration was more sensitive to KCN inhibition than uncoupler stimulated respiration. Fructose, among 20 sugars and sugar alcohols including glucose and mannose, was oxidized with a CO2/O2 ratio of 1.0 by the organism. Iron chelators in general stimulated endogenous respiration, but some of them reduced Fe3+ chemically, introducing complications. The results are discussed in view of a branched electron transport system of the organism and its possible control.

Acidithiobacillus↗
PubMed1989

Augmentation of bleomycin-induced DNA damage in intact cells.

Bleomycin, an important cause of pulmonary fibrosis, is known to produce DNA damage. The mechanism for this damage in vitro is related to free radical production by a bleomycin and iron complex. To determine whether bleomycin causes damage to DNA in vivo by a similar mechanism, we used a viral minichromosome that is replicated in cultured cells. Bleomycin causes dose-dependent damage to intracellular DNA, and this damage is augmented by Fe2+ but not Fe3+. The augmentation of the bleomycin-induced DNA damage caused by Fe2+ is also dose dependent in that increasing DNA damage occurs with increasing amounts of Fe2+. These studies demonstrate that bleomycin causes damage to DNA in vivo and suggest that bleomycin must rely on Fe2+ to donate an electron for oxygen radical-induced DNA strand scission.

Animals↗
PubMed2002

Iron activates NF-kappaB in Kupffer cells.

Iron exacerbates various types of liver injury in which nuclear factor (NF)-kappaB-driven genes are implicated. This study tested a hypothesis that iron directly elicits the signaling required for activation of NF-kappaB and stimulation of tumor necrosis factor (TNF)-alpha gene expression in Kupffer cells. Addition of Fe2+ but not Fe3+ (approximately 5-50 microM) to cultured rat Kupffer cells increased TNF-alpha release and TNF-alpha promoter activity in a NF-kappaB-dependent manner. Cu+ but not Cu2+ stimulated TNF-alpha protein release and promoter activity but with less potency. Fe2+ caused a disappearance of the cytosolic inhibitor kappaBalpha, a concomitant increase in nuclear p65 protein, and increased DNA binding of p50/p50 and p65/p50 without affecting activator protein-1 binding. Addition of Fe2+ to the cells resulted in an increase in electron paramagnetic resonance-detectable.OH peaking at 15 min, preceding activation of NF-kappaB but coinciding with activation of inhibitor kappaB kinase (IKK) but not c-Jun NH2-terminal kinase. In conclusion, Fe2+ serves as a direct agonist to activate IKK, NF-kappaB, and TNF-alpha promoter activity and to induce the release of TNF-alpha protein by cultured Kupffer cells in a redox status-dependent manner. We propose that this finding offers a molecular basis for iron-mediated accentuation of TNF-alpha-dependent liver injury.

Animals↗
PubMed1996

Defective iron uptake by the duodenum of Belgrade rats fed diets of different iron contents.

Homozygous Belgrade rats have an inherited hypochromic, microcytic anemia that is due to impaired iron transport into immature erythrocytes. There is also evidence for abnormal iron transport in other tissues such as the intestine. This study was aimed at investigating the intestinal defect in rats that had been fed diets for 12 days that are normal, low, or high in iron. The duodenal uptake, transfer, and absorption of Fe(III)-nitrilotriacetate and Fe(II)-ascorbate were studied using in vivo tied-off gut sacs in genetically normal rats and in heterozygous or homozygous Belgrade rats. In normal and heterozygous Belgrade rats, the handling of Fe(III) and Fe(II) was similar; uptake, transfer, and absorption of Fe(III) and Fe(II) changed inversely with the iron content of the diet. In contrast, in homozygous Belgrade rats the uptake of both Fe(III) and Fe(II) was markedly reduced and absorption of Fe(III) did not change when animals were fed an iron-deficient diet. Since absorption of Fe(II) was similar to Fe(III), there is no evidence that the defect in iron absorption is due to failure of a mechanism for reduction of Fe(III). The lowered uptake of Fe(III) and Fe(II) in homozygous Belgrade rats probably involves a defective iron carrier associated with the microvillous membrane of the duodenum.

Absorption↗
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↗
PubMed1979

Generation and use of three types of iron-oxide aerosol.

Three distinct submicrometric aerosols of iron oxide can be reproducibly generated by combustion of iron pentacarbonyl vapors under varying conditions. Each aerosol was sized with a concentric aerosol spectrometer and was examined with an electron microscope; the specific surface area of each aerosol type was also determined. The "feathers" hematite has a man median aerodynamic diameter (MMAD) of 0.17 micrometer and a large surface area because it is an agglomerate of units 0.005 micrometer in diameter. The "birdshot" hematite has a MMAD of 0.31 micrometer, but has a smaller surface area because the subunits are 0.03 micrometer in diameter. The third aerosol, "gamma-oxide," has a MMAD of 0.73 micrometer and has crystalline subunits 0.2 micrometer in diameter; it is a magnetic form of hematite, gamma-Fe2O3. These aerosols are well suited for studies of deposition and clearance in animal lungs because the particles can be visualized in both light and electron microscopy and can be quantified colorimetrically. The magnetic properties of gamma-Fe2O3 permit enhancement of deposition and noninvasive detection.

Aerosols↗
PubMed1997

Role of iron in ischemia-reperfusion oxidative injury of rat lungs.

We have previously shown that isolated, oxygen-ventilated rat lungs generate reactive oxygen species during ischemia and reperfusion. To evaluate the role of free iron in lung ischemia/reperfusion injury, we measured desferrioxamine-chelatable iron (DC-Fe), protein carbonyls, and thiobarbituric acid reactive substances (TBARS) in lungs subjected to global ischemia and reperfusion. There were no changes in DC-Fe, TBARS, or protein carbonyls during 2 h of control perfusion. There was a 2.3-fold increase in DC-Fe during 1 h ischemia and a further doubling during reperfusion. Results were similar when lungs were ventilated with O2 or N2. Lung TBARS increased 214% during ischemia/reperfusion with oxygen ventilation; unlike DC-Fe release, this change was blocked by N2 ventilation. Protein carbonyl content of the lung also increased significantly (113%) with ischemia/reperfusion. Ferric 8-hydroxyquinoline added to the perfusate before ischemia increased DC-Fe in lung tissue and significantly enhanced the lipid and protein oxidation of ischemic/reperfused lungs. The added perfusate iron had no effect on control lungs. Proteins isolated from the iron-supplemented ischemic/reperfused lungs were resistant to further in vitro oxidation induced by hydrogen peroxide (30 microM) whereas proteins from control perfused lungs were oxidized under these conditions. These results indicate that DC-Fe plays an important role in lung oxidative injury with ischemia/reperfusion. DC-Fe is released from iron-storage sites during ischemia and promotes tissue oxidation when oxygenation is maintained during ischemia or restored during reperfusion.

Animals↗
PubMed2006

Synthesis and characterization of uncapped gamma-Fe2O3 nanoparticles prepared by flame pyrolysis of ferrocene in ethanol.

Nanoparticles of iron(III) oxide were synthesized by spontaneous combustion of ferrocene in ethanol solution using a simple spirit lamp. X-ray powder diffraction and electron diffraction analysis of the powder suggested the formation of gamma-Fe2O3 (Maghemite phase) having lattice constant 8.3539 +/- 0.0209 A. Transmission Electron Micrograph suggested the formation of spherical particles with an average diameter of 24.7 +/- 1.6 nm. A sextet with an isomeric shift of 0.328 mm s(-1) seen in the Mossbauer spectrum recorded at room temperature, further supports the formation of gamma-Fe2O3. The particles were dispersed freely in the polar solvents like ethanol, dimethyl sulfoxide, and water. Infra Red spectrum gave bands at 400, 432, 565, and 638 cm(-1), which confirms the presence of gamma-Fe2O3 phase.

Crystallization↗
PubMed1985

Characterization of iron-mediated peroxidative injury in isolated hepatic lysosomes.

Peroxidative degradation of the lysosomal membrane and the resultant release of hydrolytic enzymes may be responsible for hepatocellular injury in iron toxicity. In this study, highly purified hepatic lysosomes were exposed to iron salts in vitro; the nature of this iron-mediated process of injury and the susceptibility of the lysosomal integrity were studied. Native hepatic lysosomes from rats were isolated by free flow electrophoresis. Incubation of the lysosomes at 37 degrees C with Fe3+-ADP in the presence of ascorbate resulted in rapid generation of malondialdehyde, which approached a plateau at 20 min. Subsequently, the loss of lysosomal latency, determined as an increased percentage free activity of N-acetyl-beta-glucosaminidase, also occurred and reached a maximum loss at 30 min. The half-maximal level of ascorbate, required to promote the Fe3+-ADP mediated lysosomal peroxidation, was approximately 10 microM; high concentrations of ascorbate were inhibitory and half-maximal inhibition was achieved at a concentration of 2 mM. The iron-mediated lysosomal peroxidation was not inhibited by most active oxygen scavengers and appeared to depend solely on the generation of Fe2+ species. When a fresh solution of Fe2+ was incubated with the lysosomes, both the extent of lipid peroxidation and the degree of latency loss increased as a function of increasing Fe2+ concentration. High concentrations of Fe2+ stimulated lysosomal lipid peroxidation instantaneously and reached the highest level within 10 min; whereas the subsequent maximum loss of latency was achieved within 20 min. Both the MDA formation and the loss of latency in either the Fe3+-ADP + ascorbate or the Fe2+ system were effectively prevented by the presence of vitamin A or vitamin E.

Adenosine Diphosphate↗