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PubMed1989

Interferon gamma-activated human monocytes downregulate transferrin receptors and inhibit the intracellular multiplication of Legionella pneumophila by limiting the availability of iron.

We have investigated the role of iron in the intracellular biology of Legionella pneumophila in human monocytes and in the effector arm of cell-mediated immune defense against this intracellular bacterial pathogen. To determine if L. pneumophila intracellular multiplication is iron dependent, we studied the effect of the iron chelator deferoxamine on L. pneumophila infection of monocytes. Deferoxamine at 15 microM completely inhibited L. pneumophila intracellular multiplication. The inhibitory effect of deferoxamine was reversed with equimolar iron-saturated transferrin but not apotransferrin. To examine the potential role of iron in monocyte activation, we investigated the influence of iron-saturated transferrin on L. pneumophila multiplication in IFN gamma-activated monocytes. Iron transferrin, but not apotransferrin, neutralized the capacity of activated monocytes to inhibit L. pneumophila multiplication. To explore a potential mechanism by which activated monocytes might limit the availability of intracellular iron, we examined transferrin receptor expression on nonactivated and activated monocytes cultured in vitro for 5 d. By fluorescence-activated flow cytometry, activated monocytes exhibited markedly fewer transferrin receptors than nonactivated monocytes. By Scatchard analysis of 125I-transferrin binding to monocytes, nonactivated monocytes had 38,300 +/- 12,700 (mean +/- SE) transferrin binding sites, whereas activated monocytes had 10,300 +/- 1,600, a reduction of 73%. Activated and nonactivated monocytes had a similar mean Kd (1.8 +/- 0.2 nM). This study demonstrates that (a) L. pneumophila intracellular multiplication is iron dependent; (b) activated monocytes inhibit L. pneumophila multiplication by limiting the availability of intracellular iron; and (c) transferrin receptors are downregulated on IFN gamma-activated monocytes.

Adult↗
PubMed2001

Clinical use, therapeutic aspects and future potential of deferiprone in thalassemia and other conditions of iron and other metal toxicity.

The therapeutic aspects and future prospects of the new iron chelating drug deferiprone are reviewed, with an emphasis on its clinical use in thalassemia and other conditions of iron overload, imbalance and toxicity, as well as its possible use in other metal toxicity conditions. Orally administered deferiprone appears to be as effective as subcutaneous deferoxamine in the removal of iron in transfused iron loaded patients, with an equivalent therapeutic index profile in both animals and humans. Only about 10% of patients requiring iron chelation therapy worldwide receive deferoxamine mainly because of its high cost, toxicity and low compliance with subcutaneous administration. Deferiprone has been used by over 6000 patients in 40 countries worldwide, in some cases daily for more than 10 years, with very promising results. Doses of 50-120 mg/kg/day are effective in bringing patients to negative iron balance. Deferiprone increases urinary iron excretion, decreases serum ferritin levels and reduces liver iron in the majority of chronically transfused iron loaded patients. All of the toxic side effects of deferiprone are considered reversible and manageable, and include agranulocytosis, musculoskeletal and joint pains, gastrointestinal complaints and zinc deficiency. In general, the incidence of toxic side effects could be reduced by using lower doses or combination therapy with deferoxamine. The suggestion that deferiprone therapy may cause liver fibrosis has not been confirmed. New therapeutic protocols for maximizing the efficacy and minimizing the toxicity of deferiprone are being considered based on new findings in relation to its metal chelation, pharmacological, toxicological and metabolic properties. (c) 2001 Prous Science. All rights reserved.

Journal Article↗
PubMed1991

Treatment of chronic iron overload.

The clinical features and therapy of chronic iron overload are reviewed. Chronic iron overload is classified as primary or secondary hemochromatosis. In primary hemochromatosis a genetic defect in iron metabolism results in increased absorption of iron from the gastrointestinal tract. The excess iron in secondary hemochromatosis may be derived from increased gastrointestinal absorption due to ineffective erythropoiesis or from medicinal, dietary, or transfusional sources. Phlebotomy is the treatment of choice in patients with primary hemochromatosis. Iron chelation therapy is indicated in patients who are not candidates for phlebotomy. Deferoxamine mesylate, the only commercially available iron chelator, is usually administered subcutaneously or intravenously over 10-12 hours/day. Serum ferritin concentrations are measured every three to six months to monitor the effectiveness of therapy. The adverse effects of deferoxamine include local skin reactions, ototoxicity, cataracts, growth impairment, and increased susceptibility to infectious organisms. Patient compliance may be compromised by the routes of administration and cost of deferoxamine. Early detection and prompt treatment are necessary to prevent organ damage. Phlebotomy and iron chelation therapy are effective in the treatment of chronic iron overload.

Bloodletting↗
PubMed1990

Involvement of intracellular iron in the toxicity of oxidized low density lipoprotein to cultured endothelial cells.

We evaluated the role of iron in the toxicity of oxidized low density lipoprotein (Ox-LDL) to cultured vascular endothelial cells. Exposure of the endothelial cells to Ox-LDL led to cell lysis as judged by the release of lactate dehydrogenase into the medium. The presence of deferoxamine, an iron chelator, in the reaction medium containing Ox-LDL prevented the lysis of cells by Ox-LDL. Pretreatment of the cells with deferoxamine also reduced their susceptibility to the cytotoxicity of Ox-LDL. The formation of thiobarbituric acid-reacting substances (TBARS) was observed in the cells exposed to Ox-LDL. Pretreatment of cells with deferoxamine reduced the formation of TBARS which was induced by Ox-LDL. These observations suggest that the toxicity of Ox-LDL to cultured endothelial cells involves the lipid peroxidation of cellular membrane catalyzed by iron derived from the target (endothelial) cells.

Animals↗
PubMed1990

Hydroxyl radical is not a product of the reaction of xanthine oxidase and xanthine. The confounding problem of adventitious iron bound to xanthine oxidase.

The reaction of xanthine and xanthine oxidase generates superoxide and hydrogen peroxide. In contrast to earlier works, recent spin trapping data (Kuppusamy, P., and Zweier, J.L. (1989) J. Biol. Chem. 264, 9880-9884) suggested that hydroxyl radical may also be a product of this reaction. Determining if hydroxyl radical results directly from the xanthine/xanthine oxidase reaction is important for 1) interpreting experimental data in which this reaction is used as a model of oxidant stress, and 2) understanding the pathogenesis of ischemia/reperfusion injury. Consequently, we evaluated the conditions required for hydroxyl radical generation during the oxidation of xanthine by xanthine oxidase. Following the addition of some, but not all, commercial preparations of xanthine oxidase to a mixture of xanthine, deferoxamine, and either 5,5-dimethyl-1-pyrroline-N-oxide or a combination of alpha-phenyl-N-tert-butyl-nitrone and dimethyl sulfoxide, hydroxyl radical-derived spin adducts were detected. With other preparations, no evidence of hydroxyl radical formation was noted. Xanthine oxidase preparations that generated hydroxyl radical had greater iron associated with them, suggesting that adventitious iron was a possible contributing factor. Consistent with this hypothesis, addition of H2O2, in the absence of xanthine, to "high iron" xanthine oxidase preparations generated hydroxyl radical. Substitution of a different iron chelator, diethylenetriaminepentaacetic acid for deferoxamine, or preincubation of high iron xanthine oxidase preparations with chelating resin, or overnight dialysis of the enzyme against deferoxamine decreased or eliminated hydroxyl radical generation without altering the rate of superoxide production. Therefore, hydroxyl radical does not appear to be a product of the oxidation of xanthine by xanthine oxidase. However, commercial xanthine oxidase preparations may contain adventitious iron bound to the enzyme, which can catalyze hydroxyl radical formation from hydrogen peroxide.

Animals↗
PubMed1985

[Frequent occurrence of Yersinia infection in hemosiderosis].

Antibodies against Yersinia were found in 12 of 50 patients with hemosiderosis, in 11 of 47 patients with thalassemia major and in one of three patients with Blackfan-Diamond anemia. All patients were treated with subcutaneous continuous deferoxamin-infusions. A systemic yersiniosis occurred in seven patients, all with homozygous beta-thalassemia, in five during and in two before treatment with deferoxamin. Hemosiderosis and infusions with deferoxamin seem to increase the risk of yersinia septicemia.

Adolescent↗
PubMed1994

Heart-lung protection from ischemic injury during 8 hour hypothermic preservation.

Optimal techniques of heart-lung preservation are yet to be defined. The aim of this study was to develop, in a canine model, a method of heart-lung preservation which would permit distant procurement of the organs. The animals were divided into 2 groups. In the experimental group (N = 6) the method of preservation consisted of cold cardioplegic arrest of the heart with St. Thomas' Hospital solution containing superoxide dismutase, catalase and deferoxamine, followed by cold pulmonary artery flush with modified Euro-Collins solution to which prostaglandin E1, superoxide dismutase, catalase, deferoxamine and Dextran 40 were added. Following harvesting, the heart-lung block was stored for 8 hours in cold (4 degrees C) Euro-Collins solution containing superoxide dismutase, catalase, deferoxamine, lactobionic acid, raffinose, mannitol, Dextran 40, magnesium sulfate, insulin and penicillin. In the control group (n = 6), the heart-lung block underwent the same treatment as the experimental group except that lactobionic acid, raffinose and insulin were omitted from the storage solution, and that oxygen radical scavengers were excluded from the cardioplegic, pneumoplegic and storage solutions. Histologic and electron microscopic examinations of heart-lung specimens taken before and after 8 hours cold storage of the organs suggested that our preservation technique may be effective in preventing ischemia-induced injury.

Animals↗
PubMed1993

Acute iron intoxication: a case report with ferric chloride ingestion.

A 24 y/o male, after attempting suicide by ingesting liquid ferric chloride, presented with protracted vomiting and epigastric pain. He was noted to have leukocytosis, a metabolic acidosis and an elevated serum iron level. Hemorrhagic gastritis, coagulation defects and an increase in urine beta 2-microglobulin, indicating renal tubular damages were found in the following day. He later recovered after treatment with deferoxamine and good supportive care. This is Taiwan's first reported case of acute iron intoxication in an attempted suicide. We discussed the characteristics of this liquid form of iron intoxication, the limitations of local laboratories in providing support and how to diagnose and treat acute iron intoxication without waiting for serum iron and total iron binding capacity levels. In conclusion, to evaluate the severity of iron intoxication, a deferoxamine challenge test and the severity of symptoms and signs should be assessed without relying only on serum iron and total iron binding capacity levels. Deferoxamine and good supportive care should be given to all serious iron intoxications.

Acute Disease↗
PubMed1993

[Aluminum-related bone disease in chronic hemodialysis patients].

Plasma aluminum (pAl) was measured in 58 patients coming from three centers using different preparation of dialysis water: deionizer (29 patients), softener (16 patients) and reverse osmosis (13 patients). Twenty five healthy subjects were used as controls. A deferoxamine test was performed to 11 of 19 patients with pAl between 40 and 200 micrograms/dl and a bone biopsy with double tetracycline staining was executed to 15 patients with pAl over 40 micrograms/dl. Mean pAl was 9.5 +/- 1.7 micrograms/dl in controls and 34.3 +/- 6.1 169 +/- 27.8 and 50.8 +/- 10.3 micrograms/dl in patients coming form centers using deionizers, softeners and reverse osmosis respectively. Seventy six percent of patients coming from centers using deionizers and 85% of patients coming from centers with reverse osmosis had pAl below 40 micrograms/dl and all had values below 200 micrograms/dl. Plasma aluminum had a increase of over 200 micrograms/dl in 6 of 11 patients in which the deferoxamine test was performed. Six patients had a positive staining for aluminum in bone biopsies (three with basal pAl over 200 micrograms/dl and one with a increase in pAL after deferoxamine < 200 micrograms/dl). Of these, 2 patients had a mixed osteodystrophy and 4 a low turnover bone disease. Centers with deionizers and reverse osmosis had very low aluminum levels in dialysis water and five of six patients with aluminum levels related bone disease came from the center using softener.

Aluminum↗
PubMed1997

Iron-chelating therapy and the treatment of thalassemia.

Iron-chelating therapy with deferoxamine in patients with thalassemia major has dramatically altered the prognosis of this previously fatal disease. The successes achieved with deferoxamine, as well as the limitations of this treatment, have stimulated the design of alternative strategies of iron-chelating therapy, including orally active iron chelators. The development of the most promising of these, deferiprone, has progressed rapidly over the last 5 years; data from several trials have provided direct and supportive evidence for its short-term efficacy. At the same time, the toxicity of this agent mandates a careful evaluation of the balance between risk and benefit of deferiprone in patients with thalassemia, in most of whom long-term deferoxamine is safe and efficacious therapy.

Animals↗
PubMed1986

Effect of iron chelation on severity of ocular inflammation in an animal model.

Metabolites of oxygen-free radicals generated by polymorphonuclear leukocytes and macrophages are believed to inflict the initial tissue damage in acute inflammations. Of the various oxygen products, hydroxyl radicals are known to be potent toxic agents, and their generation depends largely on the presence of free iron. Treatment of experimental uveitis in Lewis rats with an iron chelator, deferoxamine mesylate, resulted in marked reduction in choroidal inflammation and suppression of retinal damage. These findings suggest that in experimental uveitis the severity of ocular inflammation and tissue damage may be mediated by the iron-catalyzed generation of hydroxyl radicals, and deferoxamine may thus serve as an anti-inflammatory agent.

Animals↗
PubMed1991

The total iron-binding capacity in iron poisoning. Is it useful?

Traditionally, a serum iron concentration in excess of the total iron-binding capacity (TIBC) is considered as an indication for deferoxamine therapy in acute iron poisoning. We observed a reversible elevation of the TIBC in patients with iron poisoning that coincided with their acute hyperferremia and have hypothesized that this is a laboratory aberration. We tested this hypothesis in vitro and found that the addition of iron to test serum samples produced a related increase in the TIBC, and alteration of the assay by providing additional adsorbent prevented this occurrence. We also evaluated the reproducibility of the TIBC as performed by 500 laboratories on 10 different reference samples. The mean coefficient of variation was 16%, which was unsatisfactory. We concluded that the TIBC should not be used in the decision for the initiation of deferoxamine therapy in acute iron poisoning. Furthermore, high TIBC values that are occasionally seen in patients with iron poisoning should not be considered as providing a protective effect.

Binding Sites↗
PubMed1994

Ferric iron potentiates cell depolarization by a circulating shock protein.

OBJECTIVE: To determine whether or nor iron affects the depolarizing activity of a circulating shock protein that appears in plasma after hemorrhage. DESIGN: Randomized design. SETTING: University laboratory. ANIMALS: Healthy male Sprague-Dawley rats weighing 300 to 400 g with femoral artery and vein cannulas placed 4 days before hemorrhage. INTERVENTION: A 20-mL/kg hemorrhage and plasma collection. MAIN OUTCOME MEASURES: Depolarizing activity was measured as the increased fluorescence of an oxonol dye in the presence of Fe3+, Fe2+, or the iron chelator deferoxamine mesylate and was titrated against increasing concentrations of circulating shock protein or iron. Circulating shock protein was derived from plasma and was purified in two steps: stepwise ammonium sulfate precipitation followed by denaturing ion-exchange chromatography and refolding. RESULTS: At physiologic concentrations, Fe3+ but not Fe2+ potentiated the depolarizing activity of plasma after ammonium sulfate. Addition of deferoxamine abolished activity. Denaturing chromatography removed nearly all the depolarizing activity; however, Fe3+ restored activity to this fraction. Fe3+ increased total activity and decreased the concentration at which 50% activity was observed. CONCLUSION: These data indicate that physiologic concentrations of Fe3+ may act to modulate the depolarizing activity of circulating shock protein that in turn mediates the intracellular accumulation of salt and water in shock.

Animals↗
PubMed1987

NMR changes in experimental allergic encephalomyelitis: NMR changes precede clinical and pathological events.

In guinea pigs immunized with myelin basic protein (MBP) in complete Freund's adjuvant, experimental allergic encephalomyelitis (EAE) shows a characteristic clinical and pathological course. This study characterized the proton nuclear magnetic resonance (NMR) properties of the central nervous system prior to the onset of clinical signs of EAE. At this time (Days 7-9), the blood brain barrier is disrupted. The effects of the injection of paramagnetic contrast agents gadolinium-DTPA and gadolinium-deferoxamine on the tissue NMR relaxation times were examined. Both proton T1 and T2 relaxation times were prolonged in the spinal cord and the brain prior to the onset of clinical and pathological changes. The largest change was in the thoracolumbar spinal cord where T2 prolongation was 22.9%. Gadolinium-DTPA produced a moderate (5-11%) or marked (9-19%) decrease in control and MBP-treated animals, respectively. Gadolinium-deferoxamine also decreased proton relaxation times but was toxic to all animals, producing respiratory arrest. Changes in proton T2 relaxation times in cord and cerebellum were sufficiently large (greater than 10%) to suggest that they might be visualized by magnetic resonance imaging techniques. We have previously described the changes in proton relaxation times during the acute phase of EAE (S.J. Karlik, G. Strejan, J.J. Gilbert, and J.H. Noseworthy, Neurology 36, 1112 (1986]. This study indicates that proton relaxation times are significantly altered at a time when blood brain barrier disruption occurs prior to the onset of clinical or pathological signs.

Animals↗
PubMed1993

Generation of free radicals from hydrogen peroxide and lipid hydroperoxides in the presence of Cr(III).

Free radical generation from H2O2 and lipid hydroperoxides in the presence of Cr(III) was investigated by electron spin resonance (ESR) spin trapping methodology. Incubation of Cr(III) with H2O2 at physiological pH generated hydroxyl (.OH) radical, the yield of which reached saturation level in about 6 min. Deferoxamine reduced the .OH radical yield by only about 20%, diethylenetriamine pentaacetic acid (DTPA) reduced it by about 70%, while cysteine, glutathione, and NADH exhibited no significant effect. The yield of .OH radical formation also depended on the pH being 15 times higher at pH 10 than that at pH 7.2. At pH 3.0, .OH radical generation became nondetectable, and addition of H2O2 to Cr(III) solution did not affect the intensity of the Cr(III) ESR signal while at pH 10, addition of H2O2 reduced the Cr(III) intensity by about 40%, showing that reaction of Cr(III) with H2O2 occurred only at higher pH. Incubation of Cr(III) with the model lipid hydroperoxides, cumene hydroperoxide and t-butyl hydroperoxide, generated lipid hydroperoxide-derived free radicals. Addition of deferoxamine or DTPA had a minor inhibitory effect on that generation. These results show that Cr(III) is capable of producing free radicals from H2O2 and lipid hydroperoxides, which may have significant implications regarding the mechanism of chromium-induced carcinogenesis.

Benzene Derivatives↗
PubMed1995

The absence of extracellular calcium potentiates the killing of cultured hepatocytes by aluminum maltolate.

Dose- and time-dependent killing of cultured rat hepatocytes was produced by aluminum maltolate (AlM), a neutral, water-soluble complex of aluminum 3-hydroxy-2-methyl-4H-pyran-4-one. Treatment with 10 mM AlM for 1 h killed 50% or more of the cells within 3 h. Removal of calcium from the culture medium or treatment with calcium channel blockers (verapamil, nifedipine, diltiazem) potentiated the cell killing. By contrast, inhibition by thapsigargin of the sequestration of intracellular calcium by the endoplasmic reticulum reduced the toxicity of AlM. In turn, activation of protein kinase C with 12-O-tetradecanoylphorbol 13-acetate or activation of protein kinase A with 8-[4-chlorophenyl-thio]adenosine 3',5'-cyclic monophosphate also reduced the toxicity of AlM. By contrast, inhibition of protein kinase activity by staurosporine potentiated the cell killing. Staurosporine, however, did not reverse the protection afforded by thapsigargin. Hepatocytes treated with AlM for 1 h were rescued by adding deferoxamine as late as 90 min following the removal of AlM, whereas pretreatment for 1 h with deferoxamine did not prevent the toxicity of AlM. ATP depletion did not precede loss of viability. Pharmacologic probes excluded oxidative stress as a mechanism of lethal injury by AlM, and inhibition of protein synthesis by cycloheximide did not protect the hepatocytes, thereby excluding activation of a cell death program. These data define a new model in which aluminum kills liver cells by a mechanisms distinct from previously recognized pathways of lethal cell injury. It is hypothesized that aluminum binds to cytoskeletal proteins intimately associated with the plasma membrane. This interaction eventually disrupts the permeability barrier function of the cell membrane, an event that heralds the death of the hepatocyte. The intracellular calcium ion concentration and protein phosphorylation may modify the interaction of aluminum with its critical targets. Alternatively, aluminum may inhibit the phosphorylation of cytoskeletal elements, thereby interfering with their function.

Aluminum↗
PubMed1997

Mechanisms for metabolism of ethanol to 1-hydroxyethyl radicals in rat liver microsomes.

Experiments have been designed to reevaluate mechanisms for metabolism of ethanol to 1-hydroxyethyl radicals (HER) in rat liver microsomes. The variables tested include addition of azide, catalase, superoxide dismutase, and deferoxamine, or use of phosphate or Tris buffers. The results indicate that several mechanisms of HER formation are possible, depending on the experimental conditions used to study this process. In the presence of phosphate buffer, which has been used extensively in spite of its ability to chelate iron, HER formation is quite sensitive to changes in hydrogen peroxide availability. These results suggest that Fenton-type reactions produced the oxidizing intermediate responsible for conversion of ethanol to a free radical in phosphate buffer. However, in Tris buffer, HER formation was inhibited markedly by addition of superoxide dismutase, whereas catalase or azide had little effect. These data indicate that the apparent mechanism of radical formation may be influenced by the choice of buffer used. HER formation was almost abolished by the combination of superoxide dismutase and deferoxamine in both buffers, suggesting little enzymatic HER formation by the cytochrome P450 enzymes. When changes in HER formation were compared with rates of ethanol oxidation, it was inferred that 25 to 50% of the acetaldehyde formed during microsomal ethanol oxidation under different experimental conditions could arise via the HER intermediate.

Animals↗
PubMed1996

Murine bispecific antibody 1A10 directed to human transferrin receptor and a 42-kDa tumor-associated glycoprotein.

Previously, we observed that bispecific antibodies ("antigen forks") that bound to certain pairs of different tumor surface antigens could inhibit cell growth. The chemically linked heteroconjugate of MAb 454A12 (murine IgG1 recognizing human transferrin receptor) and 317G5 (murine IgG1 recognizing a 42-kDa tumor-associated glycoprotein) was particularly inhibitory toward human colorectal cancer cell lines, and the iron-chelating agent deferoxamine was found to augment inhibition of tumor cell growth by this antigen fork. Further experiments revealed that an antigen fork constructed by linking Fab' fragments instead of whole antibodies retained activity, which led us to construct a fork-secreting hybrid hybridoma. Hybridoma 454A12 was fused with hybridoma 34F2 (murine IgG1 with the same specificity as 317G5). Hybrid hybridomas whose supernatants blocked binding of both 454A12 and 34F2 probes were further tested for the ability to block growth of SW948 human colorectal cancer cells in an MTT growth assay, and were chosen for subcloning. Ascites produced by clone 1A10 was purified by affinity and cation exchange chromatography. Purified 1A10 bispecific antibody showed growth inhibitory activity comparable to that of a chemically linked heteroconjugate of its parental antibodies 34F2 and 454A12. Adding deferoxamine greatly enhanced the inhibitory activity of 1A10 and effectively prevented regrowth of tumor cells in vitro. By heterologously crosslinking two antigens that are coexpressed on many tumor cells, this bispecific antibody is able to inhibit tumor growth with enhanced selectivity.

Animals↗