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PubMed1998

Modulation of metal-induced cytotoxicity by maillard reaction products isolated from coffee brew.

Nondialyzable Maillard reaction products (MRPs) were recovered from three different coffee brew extracts (i.e., brewed, boiled, instant) to evaluate the efficacy of MRPs in modulating in vitro metal-induced cytotoxicity in C3H/10T1/2 mouse embryo fibroblast cells, cultured in the presence of Fe2+, Fe3+, or Cu2+ ions. Preliminary experiments were performed in an vitro linoleic acid emulsion model system to characterize the anti- or pro-oxidant activity of coffee MRPs. Cytotoxicity experimental protocols involved both the direct application of metal ions and coffee MRPs to fibroblast cells, and the premixing of metal ions with coffee MRPs at room temperature prior to incubating with fibroblast cells. Fe2+ and Cu2+ significantly lowered the colonization efficiency (CE) of cells at all three concentrations (i.e., 0.1, 10, 50 microM) used. Similar Fe3+ activity was observed only at 50 microM concentration. None of the coffee MRPs alone or together with 0.1 and 10 microM of Fe2+ or Fe3+ produced cytotoxic effects during direct application. The premixing step, however, significantly enhanced the CE of cells compared to the control, denoting cytoprotection, only in the presence of Fe2+. In addition, the application of MRPs with 0.1 or 10 microM of Cu2+ significantly lowered the CE of cells than the control, but enhanced the CE of cells than the Cu2+ added control. These results corresponded directly with the results of model linoleic acid emulsion test, thereby demonstrating that lipid hydroperoxide generation is the source for fibroblast cell toxicity when MRPs are added to cells together with metal ions. These results further indicate that coffee MRPs can suppress in vitro metal-induced cytotoxicity to a certain extent when Fe2+, Cu2+, or Fe3+ ions are present below a concentration of 50 microM, possibly by chelating the metal ions. Ionic reducing capacity of coffee MRPs, albeit small, may explain the potential for increased cytotoxicity at higher coffee MRP concentrations.

Animals↗
PubMed2005

The influence of ferrous/ferric ions on the efficiency of photocatalytic oxidation of pollutants in groundwater.

The complex influence of ferrous/ferric ions on the efficiency of aqueous photocatalytic oxidation (PCO) of 2-ethoxyethanol (2-EE), methyl tert-butyl ether (MTBE) and humic substances (HS) was established. A drastic efficiency increase at lower concentration of ferrous/ferric ions was observed to change to a sharp decrease at higher concentrations for 2-EE and MTBE, whereas for HS only an inhibitive effect of Fe2+/3+ on the PCO efficiency was noticed. The authors proposed an explanation for the observed phenomena based on the different sensitivities of pollutants towards radical-oxidation reactions and the competitive adsorption of metallic ions and pollutants on the TiO2 surface.

Catalysis↗
PubMed1978

Iron sources used in food fortification and their changes due to food processing.

The effect of food processing on the biological availability of iron in iron-fortified foods is critically reviewed. Studies on changes in the chemistry of the iron in processed foods are examined. Various iron sources currently used in food fortification in the U.S. are defined with emphasis on their biological availabilities under various conditions. The availability of iron in foods depends upon numerous factors, most of which are not fully understood. A factor which is often overlooked is the interaction of the iron with the food during events such as cooking or processing. Chemical changes in the iron compounds occur which may correlate with changes in the biological availability.

Adult↗
PubMed1998

Carvedilol inhibition of lipid peroxidation. A new antioxidative mechanism.

To define the molecular mechanism(s) of carvedilol inhibition of lipid peroxidation we have utilized model systems that allow us to study the different reactions involved in this complex process. Carvedilol inhibits the peroxidation of sonicated phosphatidylcholine liposomes triggered by FeCl2 addition whereas atenolol, pindolol and labetalol are ineffective. The inhibition proved not to be ascribable (a) to an effect on Fe2+ autoxidation and thus on the generation of oxygen derived radical initiators; (b) to the scavenging of the inorganic initiators O2*- and *OH; (c) to an effect on the reductive cleavage of organic hydroperoxides by FeCl2; (d) to the scavenging of organic initiators. The observations that (a) carvedilol effectiveness is inversely proportional to the concentration of FeCl2 and lipid hydroperoxides in the assay; (b) the drug prevents the onset of lipid peroxidation stimulated by FeCl3 addition and; (c) it can form a complex with Fe3+, suggest a molecular mechanism for carvedilol action. It may inhibit lipid peroxidation by binding the Fe3+ generated during the oxidation of Fe2+ by lipid hydroperoxides in the substrate. The lag time that carvedilol introduces in the peroxidative process would correspond to the time taken for carvedilol to be titrated by Fe3+; when the drug is consumed the Fe3+ accumulates to reach the critical parameter that stimulates peroxidation. According to this molecular mechanism the antioxidant potency of carvedilol can be ascribed to its ability to bind a species, Fe3+, that is a catalyst of the process and to its lipophilic nature that concentrates it in the membranes where Fe3+ is generated by a site specific mechanism.

Antioxidants↗
PubMed1999

Reduction of transition metals by human (THP-1) monocytes is enhanced by activators of protein kinase C.

Macrophages oxidize low density lipoprotein (LDL) by enzymatic and non-enzymatic mechanisms; however, it is evident that macrophage reduction of transition metals can accelerate LDL oxidation in vitro, and possibly in vivo. Distinct cellular pathways contribute to this process, including trans-plasma membrane electron transport (TPMET), and production of free thiols or superoxide. Here, we explore the role of protein kinase C (PKC) in regulating transition metal reduction by each of these redox-active pathways, in human (THP-1) monocytes. We demonstrate that PKC agonists and/or inhibitors modulate reduction of transition metals by monocytes: both thiol-independent (direct) and thiol-dependent (indirect) pathways for transition metal reduction are enhanced by PKC activation, suggesting a potential strategy for therapeutic intervention.

Cell Line↗
PubMed1997

Iron as a possible mediator of the oxic-to-anoxic transition in Paracoccus denitrificans.

Expression of the lacZ gene from the Fnr-regulated FF-melR promoter on a plasmid in iron-deprived Paracoccus denitrificans cells required not only a decreased oxygen tension but also supplementation with iron. The levels of beta-galactosidase and 5-aminolevulinate synthase showed comparable responses to changes in iron availability. The presence of soluble and particulate enzymes catalyzing the reduction of Fe(III) by NADH suggests a hypothesis in which the redox state of the cytoplasmic NAD-couple determines the concentration of free Fe(II) and thereby modulates the activity of a common regulator of the Fnr type.

5-Aminolevulinate Synthetase↗
PubMed2000

Ferrocenes (F168, F169) and fero-sorbitol-citrate (FSC): potential anticancer drugs.

We have shown earlier that the iron containing, ferric-sorbitol-citrate complex (FSC) inhibited proliferation of cultured mouse melanoma B16, GHC, KB, HeLa and CaCo2 cells and caused mouse melanoma regression in vivo. This drug did not affect the proliferation of the nonmalignant fibroblast L929 line, human bone marrow-HBS, VERO and HEF cell line. It is also known, that some metallocene derivatives posses antitumour properties resulting principally from their action on the metabolism of DNA, and subsequently, RNA and proteins. We synthesized in our laboratory some ferrocene analogs (F168 and F169) and tested their antiproliferative ability for malignant human carcinoma Hep2 and mouse melanoma F10 cell lines. As control cell lines, human HEF and mice L929 fibroblasts were used. The tested iron substances were very potent in inhibiting the growth of malignant cell lines, whereas they had no significant inhibitory effect on the viability of nonmalignant fibroblasts. The most pronounced growth inhibitory and cytotoxic effect was found in the malignant F10 cells and the most potent was ferrocene F169. Because of their selective effect on malignant cells, the ferric-sorbitol-citrate complex as well as tested ferrocenes will be further investigated and submitted as new antitumour substances.

Antineoplastic Agents↗
PubMed2005

A Comparative study of Fe(II) and Fe(III) interactions with DNA duplex: major and minor grooves bindings.

The involvement of the Fe cations in autoxidation in cells and tissues is well documented. DNA is a major target in such reaction, and can chelate Fe cation in many ways. The present study was designed to examine the interaction of calf-thymus DNA with Fe(II) and Fe(III), in aqueous solution at pH 6.5 with cation/DNA (P) (P = phosphate) molar ratios (r) of 1:160 to 1:2. Capillary electrophoresis and Fourier transform infrared (FTIR) difference spectroscopic methods were used to determine the cation binding site, the binding constant, helix stability and DNA conformation in Fe-DNA complexes. Structural analysis showed that at low cation concentration (r = 1/80 and 1/40), Fe(II) binds DNA through guanine N-7 and the backbone PO(2) group with specific binding constants of K(G) = 5.40 x 10(4) M(1) and K(P) = 2.40 x 10(4) M(1). At higher cation content, Fe(II) bindings to adenine N-7 and thymine O-2 are included. The Fe(III) cation shows stronger interaction with DNA bases and the backbone phosphate group. At low cation concentration (r = 1:80), Fe(III) binds mainly to the backbone phosphate group, while at higher metal ion content, cation binding to both guanine N-7 atom and the backbone phosphate group is prevailing with specific binding constants of K(G) = 1.36 x 10(5) M(-1) and K(P) = 5.50 x 10(4) M(-1). At r = 1:10, Fe(II) binding causes a minor helix destabilization, whereas Fe(III) induces DNA condensation. No major DNA conformational changes occurred upon iron complexation and DNA remains in the B-family structure.

Animals↗
PubMed1981

Effect of cysteine on iron absorption in man.

Cysteine significantly increases, about 2-fold, the absorption from nonheme iron present in vegetable foods, hemosiderin, and of a ferric salt, when this amino acid is administered during the ingestion of foods. No enhancing effect was obtained when the amino acid was mixed with the food before the final cooking. A slight but significant enhancement of heme iron absorption was observed when a large dose of cysteine was administered during the ingestion of hemoglobin. This amino acid mimics the enhancing effect from proteins present in animal foods such as beef, lamb, pork, fish, chicken, and liver. It could be possible that proteins and cysteine share the same mechanism by which they induce an increase of iron absorption.

Absorption↗
PubMed1994

Sodium iron EDTA [NaFe(III)EDTA] as a food fortificant: the effect on the absorption and retention of zinc and calcium in women.

The iron fortificant NaFeEDTA could have a potential negative effect on the metabolism of other minerals. We have used stable isotopes to monitor zinc and calcium metabolism in 10 women consuming a single meal of high-extraction wheat rolls (100 g flour) fortified with 5 mg Fe as either FeSO4 or NaFeEDTA. Six-day chemical balances were made simultaneously to study apparent zinc and calcium retention from the complete diet containing the differently iron-fortified breads (200 g flour; 10 mg added Fe/d). Mean 70Zn absorption from the bread meal increased from 20.9% with FeSO4 to 33.5% with NaFeEDTA (P < 0.05) whereas mean 44Ca absorption was 53.3% from both breads. When NaFeEDTA-fortified bread was consumed, there was a small but significant increase in urinary excretion of 70Zn and 44Ca. There was a similar small increase in urinary zinc excretion during the 6-d balance, although the apparent retention of zinc and calcium was not different. Thus, we found no negative overall effect of NaFeEDTA consumption on the metabolism of zinc and calcium. In contrast, the results suggest that NaFeEDTA added to low-bioavailability diets might increase zinc absorption as well as provide iron with high bioavailability.

Absorption↗
PubMed1992

Iron availability and free radical induced injury in the isolated ischaemic/reperfused rat heart.

OBJECTIVE: A proposal that injury in ischaemic/reperfused rat heart is critically dependent on the availability of free iron rather than on the efficiency of O2-. and H2O2 production was examined. METHODS: Isolated working rat hearts from 152 male Wistar rats (200-250 g weight), subjected to 20-40 min of global ischaemia and reperfused for 30 min, were perfused with 10 mumol.litre-1 Fe[III] or Fe[II] and/or 0.6 mmol.litre-1 desferrioxamine, 10 mmol.litre-1 dimethylthiourea, and 1 mmol.litre-1 allopurinol. Curves relating the recoveries of haemodynamic functions and the reperfusion lactate dehydrogenase release to the duration of the preceding ischaemic period were constructed. Morphological examination was also performed. RESULTS: In the untreated hearts, the duration of ischaemia resulting in 50% loss of cardiac output was 29 min. This time was decreased to 24 min and 20 min by Fe[III] and Fe[II], respectively, and was increased to 36 min and 37 min by desferrioxamine and dimethylthiourea, respectively. Desferrioxamine prevented the effect of Fe[III] but not that of Fe[II], whereas dimethylthiourea prevented the effect of Fe[II]. Neither the effect of Fe[III] nor that of Fe[II] was prevented by allopurinol which, however, proved to be beneficial in the untreated hearts. CONCLUSIONS: The beneficial effect of desferrioxamine and dimethylthiourea suggest that it is intensification of the Fenton reaction by iron which accounts for iron induced aggravation of the reperfusion injury. Thus we speculate that the availability of free iron, rather than O2-. and H2O2, is a limiting factor in the development of injury in an ischaemic/reperfused rat heart. What remains unclear is why allopurinol is unable to prevent iron induced changes.

Allopurinol↗
PubMed2006

Enhancement by cigarette smoke extract of the radical formation in a reaction mixture of 13-hydroperoxide octadecadienoic acid and ferric ions.

The effects of cigarette smoke extract on radical formation were examined in reaction mixtures containing 13-hydroperoxide octadecadienoic acid (13-HPODE), FeCl3, cigarette smoke extract, ethylenediaminetetraacetic acid (EDTA), alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN), and phosphate buffer (pH 7.4). Cigarette smoke extract enhanced the formation of both 7-carboxyheptyl and pentyl radicals in the reaction. Ferric ions were reduced in the reaction mixture, suggesting that cigarette smoke extract enhances the formation of 7-carboxyheptyl and pentyl radicals by reducing ferric irons. Although there is a large body of evidence supporting the involvement of radicals such as the semiquinone radical, hydroxyl radical, superoxide radical, nitric oxide radicals in smoking-related diseases, the enhancement by cigarette smoke of lipid-derived radical formation, which we first report here, may be one of the other causes of smoking-related diseases.

Chromatography, High Pressure Liquid↗
PubMed1976

Isolation of monoferric phytate from wheat bran and its biological value as an iron source to the rat.

The objectives of the study were to isolate and chemically characterize the iron in wheat and to determine the biological availability to the rat of the iron as the purified complex(es). Hard wheat bran contained no butanol extractable or water extractable iron, but approximately 60% of the iron was extracted by 1 to 1.2 M NaCl or ammonium acetate solution. This salt extractable iron complex was purified and identified as monoferric phytate. The purified monoferric phytate was soluble in water. Synthetic monoferric phytate was prepared from sodium phytate and ferric chloride and determined to have spectral characteristics and gel filtration chromatography behavior identical to the complex isolated from wheat bran. The butanol-water-salt extracted bran residue contained no detectable phytate and an as yet uncharacterized form of iron. The biological availability of the iron to the rat was determined by a hemoglobin depletion-repletion bioassay. The relative biological value of the iron as monoferric phytate, either isolated from wheat bran or the synthetic product, was equal to the reference compound, ferrous ammonium sulfate. In contrast, the biological availability of the iron in the bran residue was significantly lower and the low biological availability of an insoluble form of ferric phytate was confirmed. It is concluded that the major portion of the iron in wheat is monoferric phytate and has a high biological availability to the rat. Monoferric phytate in bran may be bound to cationic sites of proteins or other cellular components and utilization of the iron may be through solubilization of the monoferric phytate by ion exchange type mechanism rather than by hydrolysis of the phytate as has been postulated.

Animals↗
PubMed1986

Competitive interaction of iron and zinc in the diet: consequences for human nutrition.

The degree to which inhibitors of zinc bioavailability actually influence the zinc status of humans who consume usual meals and diets is not known. The interaction of iron and zinc and competitive inhibition of zinc uptake by excess iron in ratios of 2:1 or greater, when the total amount of ionic species is greater than 25 mg, appear to have a measurable effect on human zinc nutriture. The physiological basis is the competition of these chemically similar ions for some portions of a common absorptive pathway shared between inorganic (nonheme) iron and zinc; this has been demonstrated in animal experiments and in zinc absorption studies in human volunteers. Thus, studies involving formula-fed infants, experimental zinc-depletion diets and pregnant women who took prenatal vitamin-mineral supplements containing high levels of iron have shown growth delay (infants) and a decreased circulating zinc pool (all age groups), suggesting a determinant impact of excessively high Fe/Zn ratios in the diet. Consideration of solutions to these problems, including conscious adjustment of the Fe/Zn ratios in human diets, foods and therapeutic nutrient supplements in order to reduce the zinc-inhibiting effects of iron, should become a priority in policy and marketing discussions within government regulatory agencies, industry and the scientific community of human and clinical nutritionists.

Absorption↗
PubMed1991

Ferric iron absorption in rats: relationship to iron status, endogenous sulfhydryl and other redox components in the intestinal lumen.

Based on the hypothesis that Fe+3 must be reduced before Fe absorption, we investigated luminal factors that might participate in the physiological Fe+3 reduction. Rats were fed diets containing 7 mg Fe/kg diet [adequate iron (+Fe]) for 3 wk prior to a 10-min test of 59Fe absorption from an in vivo ligated duodenal segment. During absorption of 59Fe, the oxidation-reduction potential became more reducing and the pH rose in segment contents. There were small but significant differences between the -Fe and +Fe rats. In one experiment, the lumen environment was modified by bile duct ligation and/or intestinal perfusion prior to the absorption test. Ascorbic acid, nonprotein sulfhydryl compounds, Fe+2 and total ionizable Fe were measured in luminal contents. Nonprotein sulfhydryl concentration was positively correlated with, and the best predictor of, Fe absorption in -Fe rats.

Animals↗
PubMed1995

Reduction of Fe(III) is required for uptake of nonheme iron by Caco-2 cells.

Differentiated cultures of Caco-2 human colonic cells were used to examine the importance of reduction of nonheme ferric iron, Fe(III), for transport across the brush border surface. Cultures accumulated approximately 100 pmol Fe/(h.mg protein) when 10 mumol Fe(III) as the nitrilotriacetic acid complex (1Fe:2NTA) was added to the apical compartment. Ascorbic acid enhanced cellular acquisition of iron in a dose-dependent manner, with a concentration as low as 8 mumol/L ascorbate increasing iron uptake by 50%. Similarly, the rate of iron transport from the apical to the basolateral compartment increased 5.6- and 30-fold when 100 and 1000 mumol/L ascorbic acid, respectively, were present in the apical chamber. Ascorbate-mediated stimulation of iron uptake was temperature dependent and required the reduction of Fe(III) to Fe(II), because it was inhibited by ascorbate oxidase and chelators of Fe(II). Moreover, Caco-2 cells recycled dehydroascorbic acid to ascorbic acid. Ferricyanide and Fe(II) chelators also partially inhibited iron uptake from a medium devoid of ascorbic acid. Intact Caco-2 cells exhibited a ferrireductase activity on the apical surface that accounted for the majority of iron accumulated by cells incubated in the absence of exogenous reductant. These data suggest that reduction of Fe(III) within the lumen or at the cell surface is required for transfer of this essential micronutrient across the intestinal brush border surface.

Ascorbic Acid↗