Effective chelation of iron in beta thalassaemia with the oral chelator 1,2-dimethyl-3-hydroxypyrid-4-one.

The main iron chelator used for transfusional iron overload is desferrioxamine, which is expensive, has toxic side effects, and has to be given subcutaneously. An orally active iron chelator is therefore required. The effects of oral 1,2-dimethyl-3-hydroxypyrid-4-one on urinary iron excretion were studied in eight patients who had received multiple transfusions: four had myelodysplasia and four beta thalassaemia major. Different daily doses of the drug up to 100 mg/kg/day, alone or in combination with ascorbic acid, were used. In three patients with thalassaemia the effect of the drug was compared with that of subcutaneous desferrioxamine at the same daily dose. In all eight patients a single dose of oral 1,2-dimethyl-3-hydroxypyrid-4-one resulted in substantial urinary iron excretion, mainly in the first 12 hours. Urinary iron excretion increased with the dose and with the degree of iron loading of the patient. Giving two or three divided doses over 24 hours resulted in higher urinary iron excretion than a single dose of the same amount over the same time. In most patients coadministration of oral ascorbic acid further increased urinary iron excretion. 1,2-Dimethyl-3-hydroxypyrid-4-one caused similar iron excretion to that achieved with subcutaneous desferrioxamine at a comparable dose. In some cases the iron excretion was sufficiently high (maximum 99 mg/day) to suggest that a negative iron balance could be easily achieved with these protocols in patients receiving regular transfusions. No evidence of toxicity was observed on thorough clinical examination or haematological and biochemical testing in any of the patients. None of the patients had any symptoms that could be ascribed to the drug. These results suggest that the oral chelator 1,2-dimethyl-3-hydroxypyrid-4-one is as effective as subcutaneous desferrioxamine in increasing urinary iron excretion in patients loaded with iron. Its cheap synthesis, oral activity, and lack of obvious toxicity at effective doses suggest that it should be developed quickly and thoroughly tested for the management of transfusional iron overload.     

Neoplastic transformation in vitro by mixed beams of high-energy iron ions and protons

The radiation environment in space is complex in terms of both the variety of charged particles and their dose rates. Simulation of such an environment for experimental studies is technically very difficult. However, with the variety of beams available at the National Space Research Laboratory (NSRL) at Brookhaven National Laboratory (BNL) it is possible to ask questions about potential interactions of these radiations. In this study, the end point examined was transformation in vitro from a preneoplastic to a neoplastic phenotype. The effects of 1?GeV/n iron ions and 1?GeV/n protons alone provided strong evidence for suppression of transformation at doses ≤5?cGy. These ions were also studied in combination in so-called mixed-beam experiments. The specific protocols were a low dose (10?cGy) of protons followed after either 5-15?min (immediate) or 16-24?h (delayed) by 1?Gy of iron ions and a low dose (10?cGy) of iron ions followed after either 5-15?min or 16-24?h by 1?Gy of protons. Within experimental error the results indicated an additive interaction under all conditions with no evidence of an adaptive response, with the one possible exception of 10?cGy iron ions followed immediately by 1?Gy protons. A similar challenge dose protocol was also used in single-beam studies to test for adaptive responses induced by 232?MeV/n protons and (137)Cs γ radiation and, contrary to expectations, none were observed. However, subsequent tests of 10?cGy of (137)Cs γ radiation followed after either 5-15?min or 8?h by 1?Gy of (137)Cs γ radiation did demonstrate an adaptive response at 8?h, pointing out the importance of the interval between adapting and challenge dose. Furthermore, the dose-response data for each ion alone indicate that the initial adapting dose of 10?cGy used in the mixed-beam setting may have been too high to see any potential adaptive response.     

Iron supplementation and oxidative damage to DNA in healthy individuals with high plasma ascorbate

Previously, we have investigated the potential for a pro-oxidant interaction of iron and ascorbate in vivo in iron and ascorbate cosupplementation or ascorbate supplementation studies. In this study, for the first time, the effects of iron supplementation on oxidative damage to DNA in healthy individuals with plasma ascorbate levels at the upper end of the normal range were examined. Forty female and male volunteers (mean plasma ascorbate approximately equal to 70 micromol/L) were supplemented with a daily dose of syrup (ferrous glycine sulphate equivalent to 12.5 mg iron) for 6 weeks. Serum ferritin, transferrin bound iron, % saturation of transferrin and plasma ascorbate were assessed and the mean dietary intakes of all subjects were estimated through food frequency questionnaires. Oxidative damage to DNA bases from white blood cells was measured by gas chromatography/mass spectrometry with selected-ion monitoring (GC/MS-SIM), using isotope-labelled standards for quantification. Iron supplementation did not affect any of the iron status parameters. There were also no detrimental effects, over the period under investigation, in terms of oxidative damage to DNA. However, the effects of larger doses or of longer supplementation periods should also be investigated.     

The effect of short-term exposure to low-iron diets on the mucosal processing of ionic iron

Short-term alterations in the amount of iron in the diets of rats caused substantial differences in the distribution of a test dose of radioiron between mucosal transferrin and mucosal ferritin, and also caused a change in the relative amounts of these two proteins in mucosal tissue without resulting in any detectable change in liver iron stores. These differences correlated with changes in the retention of radioiron by the intestinal mucosa and the transport of radioiron to the blood stream. These studies emphasize the importance of local changes in the intestinal mucosa in the regulation of dietary iron absorption.     

Non-heme Iron as Ferrous Sulfate Does Not Interact with Heme Iron Absorption in Humans

The absorption of heme iron has been described as distinctly different from that of non-heme iron. Moreover, whether heme and non-heme iron compete for absorption has not been well established. Our objective was to investigate the potential competition between heme and non-heme iron as ferrous sulfate for absorption, when both iron forms are ingested on an empty stomach. Twenty-six healthy nonpregnant women were selected to participate in two iron absorption studies using iron radioactive tracers. We obtained the dose?Cresponse curve for absorption of 0.5, 10, 20, and 50?mg heme iron doses, as concentrated red blood cells. Then, we evaluated the absorption of the same doses, but additionally we added non-heme iron, as ferrous sulfate, at constant heme/non-heme iron molar ratio (1:1). Finally, we compare the two curves by a two-way ANOVA. Iron sources were administered on an empty stomach. One factor analysis showed that heme iron absorption was diminished just by increasing total heme iron (P?<?0.0001). The addition of non-heme iron as ferrous sulfate did not have any effect on heme iron absorption (P?=?NS). We reported evidence that heme and non-heme iron as ferrous sulfate does not compete for absorption. The mechanism behind the absorption of these iron sources is not clear.     

Epigallocatechin gallate (EGCG) (TEAVIGO) does not impair nonhaem-iron absorption in man.

A number of studies have shown that tea catechins can inhibit intestinal iron absorption, mostly iron in the nonhaem form. This randomized, double-blind, placebo-controlled, 3-periods cross-over study examined the degree of inhibition of nonhaem iron absorption by pure crystalline epigallocatechin gallate (EGCG). The study was designed to show the maximum inhibitory action of EGCG by selecting 30 healthy women with low iron stores. Treatments were 150 mg, 300 mg EGCG and placebo each for 8 consecutive study days with a wash-out period of 14 days between treatments. Iron incorporation was assessed by supplying 57Fe orally and 58Fe intravenously. Differences in fractional nonhaem iron absorption between the treatments were evaluated by using two-sided ANOVA. Results showed a relative nonhaem iron absorption reduction of 14% with 150mg EGCG and 27% for 300mg EGCG treatment compared to placebo. Differences were statistically significant (p < or = 0.05) between the placebo and the 300mg EGCG treatments and between the 150 and 300 mg EGCG treatments. The inverse relation between EGCG dose and fractional nonhaem iron absorption was linear (p = 0.0002). In this study the magnitude of the inhibitory action of EGCG on nonhaem iron absorption was found to be much lower than that reported in the literature for black tea and similar compounds. The doses of EGCG in supplements, which will be lower than those used in this study, are not expected to have any health relevant effects on iron absorption in subjects with normal iron stores.     

High dosage desferrioxamine therapy in a female patient with acquired aplastic anaemia and transfusion siderosis

A 32 year old woman with severe aplastic anaemia required frequent transfusions and consequently developed hyperferrioxaemia (54 microMol/l) and hyperferritinaemia (1,700 ng/ml). For the treatment of transfusion siderosis she was given 18 high dose courses each comprising 35 g of desferrioxamine. Because of pre-existing thrombocytopenia (platelet count 5 X 10(9)/l) the iron chelating agent was given by continuous intravenous infusion over 3 1/2 days. High dose desferrioxamine had to be abandoned because of severe bone pain. The desferrioxamine infusions achieved a negative iron balance, iron loss after each infusion being 100 to 200 mg in the urine and 400 mg in the faeces. Serum iron and ferritin concentrations fell almost to normal. This report shows that faecal iron excretion must be taken into account in assessing the balance of iron input and output during desferrioxamine treatment.     

Intravenous Iron Supplementation Practices and Short-Term Risk of Cardiovascular Events in Hemodialysis Patients

Background & Objectives

Intravenous iron supplementation is widespread in the hemodialysis population, but there is uncertainty about the safest dosing strategy. We compared the safety of different intravenous iron dosing practices on the risk of adverse cardiovascular outcomes in a large population of hemodialysis patients.

Design settings, participants, & measurements

A retrospective cohort was created from the clinical database of a large dialysis provider (years 2004-2008) merged with administrative data from the United States Renal Data System. Dosing comparisons were (1) bolus (consecutive doses ≥ 100 mg exceeding 600 mg during one month) versus maintenance (all other iron doses during the month); and (2) high (> 200 mg over 1 month) versus low dose (≤ 200 mg over 1 month). We established a 6-month baseline period (to identify potential confounders and effect modifiers), a one-month iron exposure period, and a three-month follow-up period. Outcomes were myocardial infarction, stroke, and death from cardiovascular disease.

Results

117,050 patients contributed 776,203 unique iron exposure/follow-up periods. After adjustment, we found no significant associations of bolus dose versus maintenance, hazards ratio for composite outcome, 1.03 (95% C.I. 0.99, 1.07), or high dose versus low dose intravenous iron, hazards ratio for composite outcome, 0.99 (95% C.I. 0.96, 1.03). There were no consistent associations of either high or bolus dose versus low or maintenance respectively among pre-specified subgroups.

Conclusions

Strategies favoring large doses of intravenous iron were not associated with increased short-term cardiovascular morbidity and mortality. Investigation of the long-term safety of the various intravenous iron supplementation strategies may still be warranted.     

Endogenous iron excretion

The effects of supplemental oral (0, 40, and 400 ppm) and parenteral iron (0 and 2.72 mg Fe iv given initially as a single dose) on iron absorption, excretion, and retention were determined in 30 rats. Endogenous fecal iron excretion was determined by the radioisotope dilution technique after im injection of 80 kBq Fe-59, using blood and certain body tissues as reference sources for the estimation of the specific activity (Bq Fe-59/micrograms Fe) of endogenous iron. The basal diet contained 3.6 ppm Fe. Fe(III)-hydroxide-polymaltose was used as the sole iron source in oral, iv, and im iron treatments. Iron balance as determined from day 14 to 20 of the experiment was not significantly affected by iv iron administration. Nevertheless, a temporarily reduced retention should have occurred, since differences in final body iron contents were lower than 2.72 mg, as compared to the respective untreated groups. Apparent iron absorption and iron retention increased with surplus oral iron, and the efficiency rates were highest with adequate iron supply (40 ppm). True absorption rates of iron were similar without any, and with 40 ppm Fe amounting 40 to 50% of the intake. In the iron deficient rats, half of the actually absorbed iron (about 16 micrograms/d) was lost by endogenous fecal re-excretion, and another 3 micrograms/d by the urinary route. Endogenous loss with feces and with urine increased with further oral iron supply, but at a considerably lower rate as total fecal excretion. Parenterally administered iron did not affect endogenous loss at all. The results indicate that endogenous excretion cannot be regarded as a means to eliminate excessive iron, and might actually be an inevitable loss.     

Vitamin C suppresses oxidative lipid damage in vivo, even in the presence of iron overload

Ascorbate is a strong antioxidant; however, it can also act as a prooxidant in vitro by reducing transition metals. To investigate the in vivo relevance of this prooxidant activity, we performed a study using guinea pigs fed high or low ascorbate doses with or without prior loading with iron dextran. Iron-loaded animals gained less weight and exhibited increased plasma beta-N-acetyl-D-glucosaminidase activity, a marker of tissue lysosomal membrane damage, compared with control animals. The iron-loaded animals fed the low ascorbate dose had decreased plasma alpha-tocopherol levels and increased plasma levels of triglycerides and F(2)-isoprostanes, specific and sensitive markers of in vivo lipid peroxidation. In contrast, the two groups of animals fed the high ascorbate dose had significantly lower hepatic F(2)-isoprostane levels than the groups fed the low ascorbate dose, irrespective of iron load. These data indicate that 1) ascorbate acts as an antioxidant toward lipids in vivo, even in the presence of iron overload; 2) iron loading per se does not cause oxidative lipid damage but is associated with growth retardation and tissue damage, both of which are not affected by vitamin C; and 3) the combination of iron loading with a low ascorbate status causes additional pathophysiological changes, in particular, increased plasma triglycerides.     

Antimalarial iron chelator, FBS0701, shows asexual and gametocyte Plasmodium falciparum activity and single oral dose cure in a murine malaria model

Iron chelators for the treatment of malaria have proven therapeutic activity in vitro and in vivo in both humans and mice, but their clinical use is limited by the unsuitable absorption and pharmacokinetic properties of the few available iron chelators. FBS0701, (S)3"-(HO)-desazadesferrithiocin-polyether [DADFT-PE], is an oral iron chelator currently in Phase 2 human studies for the treatment of transfusional iron overload. The drug has very favorable absorption and pharmacokinetic properties allowing for once-daily use to deplete circulating free iron with human plasma concentrations in the high μM range. Here we show that FBS0701 has inhibition concentration 50% (IC(50)) of 6 μM for Plasmodium falciparum in contrast to the IC(50) for deferiprone and deferoxamine at 15 and 30 μM respectively. In combination, FBS0701 interfered with artemisinin parasite inhibition and was additive with chloroquine or quinine parasite inhibition. FBS0701 killed early stage P. falciparum gametocytes. In the P. berghei Thompson suppression test, a single dose of 100 mg/kg reduced day three parasitemia and prolonged survival, but did not cure mice. Treatment with a single oral dose of 100 mg/kg one day after infection with 10 million lethal P. yoelii 17XL cured all the mice. Pretreatment of mice with a single oral dose of FBS0701 seven days or one day before resulted in the cure of some mice. Plasma exposures and other pharmacokinetics parameters in mice of the 100 mg/kg dose are similar to a 3 mg/kg dose in humans. In conclusion, FBS0701 demonstrates a single oral dose cure of the lethal P. yoelii model. Significantly, this effect persists after the chelator has cleared from plasma. FBS0701 was demonstrated to remove labile iron from erythrocytes as well as enter erythrocytes to chelate iron. FBS0701 may find clinically utility as monotherapy, a malarial prophylactic or, more likely, in combination with other antimalarials.     

Liver iron depletion and toxicity of the iron chelator Deferiprone (L, CP20) in the guinea pig

The use of the iron chelator deferiprone (L, CP20, 1,2-dimethyl-3-hydroxypyrid-4-one) for the treatment of diseases of iron overload and other disorders is problematic and requires further evaluation. In this study the efficacy, toxicity and mechanism of action of orally administered L were investigated in the guinea pig using the carbonyl iron model of iron overload. In an acute trial, depletion of liver non-heme iron in drug-treated guinea pigs (normal iron status) was maximal (approximately 50% of control) after a single oral dose of L1 of 200 mg kg, suggesting a limited chelatable pool in normal tissue. There was no apparent toxicity up to 600 mg kg. In each of two sub-acute trials, normal and iron-loaded animals were fed L (300 mg kg day) or placebo for six days. Final mortalities were 12/20 (L) and 0/20 (placebo). Symptoms included weakness, weight loss and eye discharge. Iron-loaded as well as normal guinea pigs were affected, indicating that at this drug level iron loading was not protective. In a chronic trial guinea pigs received L (50 mg kg day) or placebo for six days per week over eight months. Liver non-heme iron was reduced in animals iron-loaded prior to the trial. The increase in a wave latency (electroretinogram), the foci of hepatic, myocardial and musculo-skeletal necrosis, and the decrease in white blood cells in the drug-treated/normal diet group even at the low dose of 50 mg kg day suggests that L may be unsuitable for the treatment of diseases which do not involve Fe overload. However, the low level of pathology in animals treated with iron prior to the trial suggests that even a small degree of iron overload (two-fold after eight months) is protective at this drug level. We conclude that the relationship between drug dose and iron status is critical in avoiding toxicity and must be monitored rigorously as cellular iron is depleted.     

Alteration of macromolecular events and elemental levels in the skin of UVC exposed hairless mice

Swiss mice (S/RV/Cri-ba) were exposed to a spectral range of UV light emitting predominantly lambda 253.7 nm. Following a cumulative dose of 22.5 X 10(3) KJ/m2 tumours were induced. The tumour development occurred after 52 weeks, relatively a longer time interval following exposure, compared with shorter time intervals required for production of tumours in mice by spectral range UVA and UVB as observed by other workers. A study of biochemical events viz. levels of protein, DNA, zinc, iron, sodium and potassium has been made in the skin samples of control and irradiated animals following ultraviolet irradiation with a dose of 22.5 X 10(3) KJ/m2. Study of macromolecular events in the skin of control and irradiated mice, showed fluctuations in the levels of DNA. A particularly notable event is the occurrence of increased levels of DNA and zinc and their persistence during the 9-39 weeks post UV interval prior to tumour production. No such variation was observed in the control group in any of the intervals. Increased levels were also seen in case of iron, sodium and potassium at different intervals in the post UV periods. These fluctuations in various biochemical events are deemed to be indicative of UV initiated biochemical changes.     

Genotoxicity and mutagenicity of iron and copper in mice

The toxicity of trace metals is still incompletely understood. We have previously shown that a single oral dose of iron or copper induces genotoxic effects in mice in vivo, as detected by single cell gel electrophoresis (comet assay). Here, we report the effect of these metals on subchronic exposure. Mice were gavaged for six consecutive days with either water, 33.2 mg/kg iron, or 8.5 mg/kg copper. On the 7th day, the neutral and alkaline comet assays in whole blood and the bone marrow micronucleus (MN) test were used as genotoxicity and mutagenicity endpoints, respectively. Particle induced X-ray emission was used to determine liver levels of the metals. Females showed a slightly lower DNA damage background, but there was no significant difference between genders for any endpoint. Iron and copper were genotoxic and mutagenic. While copper was more genotoxic in the neutral version, iron was more genotoxic in the alkaline version of the comet assay. Copper induced the highest mutagenicity as evaluated by the MN test. Iron was not mutagenic to male mice. Iron is thought to induce more oxidative lesions than copper, which are primarily detected in the alkaline comet assay. Treatment with iron, but not with copper, induced a significant increase in the hepatic level of the respective metal, reflecting different excretion strategies.     

Cytotoxic aldehyde generation in heart following acute iron-loading

Although the mechanism of myocardial failure following acute iron poisoning is not known, excess iron-catalyzed free radical generation is conjectured to play a role. The effects of time (0 to 360 minutes) on total iron concentrations, glutathione peroxidase activity, and cytotoxic aldehyde production in heart of mice (B6D2F1, n = 65) were first investigated following acute iron-loading (20 mg iron dextran i.p./mouse). In a subsequent experiment, the effects of dose (0 to 80 mg iron dextran i.p./mouse, n = 75) on the aforementioned parameters were investigated. Our results show that the concentrations of cytotoxic aldehydes: (1) significantly differ over-time, with corresponding increases in total concentrations of iron (r = 0.93, p < 0.001); and (2) increase parallel to the total dose of iron administered (r = 0.95, p < 0.001). Furthermore, dose-and time-dependent alterations to glutathione peroxidase activity are observed, which is most likely due to an acute up-regulation of the enzyme as an endogenous protective response to increased free radical activity in the heart subsequent to iron-loading. While no single mechanism is likely to account for the complex pathophysiology of acute iron-induced heart failure, our results shown that iron-loading can result in significant free radical generation, as quantified by cytotoxic aldehydes, in heart tissue of mice. This is the first report on the effects of time and dose on cytotoxic aldehyde generation and glutathione peroxidase activity in heart of mice following acute iron-loading.     

Iron-induced changes in rat liver isoferritins.

The effects of single and of multiple iron injection on the distribution of isoferritins was studied in rat liver with the aid of 14C-labelling either after or before iron treatment. Several effects of iron can be seen. Analysis of protein and labelling patterns show that it not only produces a disproportionate increase in the more-basic isoferritins, but may, in sufficient dose, actually lead to a decrease in the more-acidic isoferritins. Use of iron injection after radioactivity shows that it must give rise to post-assembly changes causing acidic isoferritins to become more basic. With a moderate iron dose this change is relatively slow, taking several hours, and seems to occur in addition to a differential stimulation of the synthesis of the more-basic isoferritins. With higher iron dosage the post-assembly changes may be so rapid that it is difficult to distinguish them from a switch in the pattern of synthesis.     

Cobalt Excretion Test for the Assessment of Body Iron Stores

Iron absorption is under delicate control and the level of absorption is adjusted to comply with the body''s need for iron. To measure the intestinal setting for iron absorption, and thereby indirectly assess body iron requirements, cobaltous chloride labelled with ⁵⁷Co or ⁶⁰Co was given by mouth and the percentage of the test dose excreted in the urine in 24 hours was measured in a gamma counter. Seventeen control subjects with normal iron stores excreted 18% (9-23%) of the dose. Increased excretion, 31% (23-42%), was found in 10 patients with iron deficiency anemia and in 15 patients with depleted iron stores in the absence of anemia. In contrast, 12 patients with anemia due to causes other than iron deficiency excreted amounts of radiocobalt within the normal control range. In patients with iron deficiency, replenishment of iron stores by either oral or parenteral iron caused the previously high results to return to normal.Excretion of the test dose was normal in portal cirrhosis with normal iron stores but it was markedly increased in patients with cirrhosis complicated by either iron deficiency or endogenous iron overload. It was also raised in primary hemochromatosis. Excretion of the dose was reduced in gluten-sensitive enteropathy. Gastrointestinal surgery and inflammatory disease of the lower small intestine had no effect on the results except that some patients with steatorrhea had diminished excretion.The cobalt excretion test provides the clinician with a tool for the assessment of iron absorption, the detection of a reduction in body iron stores below the level that is normal for the subject in question, the differentiation of iron deficiency anemia from anemia due to other causes, and the investigation of patients with iron-loading disorders.     

Variation of nitric oxide content regulates the development of apoptosis in the retina

It was shown that retinal ischemia entailed apoptosis in the inner layers of the retina. Administration of an NO-synthase inhibitor suppressed the development of ischemic apoptosis. To ascertain whether nitric oxide could induce the retinal apoptosis by itself, a nontoxic NO donor—dinitrosyl iron complex (DNIC) with glutathione—was injected into the vitreous body. DNIC at low concentrations induced apoptosis in the same retinal layers as in ischemia. However, with increasing DNIC doses, the number of apoptotic nuclei decreased markedly. Simultaneous administration of excess glutathione prevented apoptosis at any DNIC dose. The obtained data demonstrate the neurotoxic properties of the excess of nitric oxide in the retina.     

Iron Supplementation During Pregnancy- A Necessary or Toxic Supplement?

The effects of a single intramuscular iron dose, 10mg, to pregnant rats on Day of pregnancy, on the outcome of pregnancy, with respect to foetal weight and mother’s immune function has been investigated. Despite significantly elevated hepatic iron stores after iron supplementation in pregnant rats this had no significant effect upon blood haemoglobin or transferrin saturation levels. However the mean weight of the foetuses at Day 20-21 was significantly lower than that of the non-supplemented pregnant rats. Iron supplements significantly increased the activity of NADPH oxidase in the maternal alveolar macrophages, the primary event in the formation of the phagolysosome to combat invading organisms. However inducible nitric oxide synthase activity was significantly reduced in these macrophages as shown by decreases in LPSinduced and LPS+IFNγ-induced NOS activation. Iron supplementation to rats of normal iron status at the commencement of pregnancy did not show any beneficial effects to either the foetus or the mother.