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PubMed2005

Transfusional hemosiderosis and combined chelation therapy in sickle thalassemia.

Although the indications for transfusions in sickle cell syndromes are well listed, and chronic transfusion has become practicable since the recent advances in chelation therapy have essentially eliminated the risk of secondary iron overload, multi-transfused, non-compliant to long-term chelation therapy patients confront the complication of iron overload and secondary hemosiderosis. In thalassemia major patients, combined therapy with desferrioxamine and deferiprone has maximized tissue iron removal and may reduce the overall occurrence of hemosiderotic heart failure. Despite this, safety and contradictions of chelating agents are still controversial. The aim of this report is to present the results of this combination in a long-term transfused sickle beta-thalassemic patient suffering from severe heart failure and liver dysfunction.

Adult↗
PubMed2004

Iron chelation therapy in aceruloplasminaemia: study of a patient with a novel missense mutation.

We describe a novel missense mutation of ceruloplasmin in a patient with aceruloplasminaemia causing the replacement of a neutral amino acid (phenylalanine) with a polar one (serine) at position 198, probably leading to abnormal folding and secretion of the protein. The patient showed mild microcytic anaemia, mild hepatic iron overload, and marked brain iron overload. Six months of therapy with deferiprone was ineffective in removing iron from the tissues. Deferoxamine was more efficient in removing excess iron from the liver but aggravated the disease related anaemia. After more than one year of chelation treatment, the brain magnetic resonance imaging signal did not change. Overall, these findings indicate that treatment of iron overload in aceruloplasminaemia is a difficult challenge and that new iron chelators, more efficient in crossing the blood-brain barrier, are needed.

Adult↗
PubMed1997

Removal of erythrocyte membrane iron in vivo ameliorates the pathobiology of murine thalassemia.

Abnormal deposits of free iron are found on the cytoplasmic surface of red blood cell (RBC) membranes in beta-thalassemia. To test the hypothesis that this is of importance to RBC pathobiology, we administered the iron chelator deferiprone (L1) intraperitoneally to beta-thalassemic mice for 4 wk and then studied RBC survival and membrane characteristics. L1 therapy decreased membrane free iron by 50% (P = 0.04) and concomitantly improved oxidation of membrane proteins (P = 0.007), the proportion of RBC gilded with immunoglobulin (P = 0.001), RBC potassium content (P < 0.001), and mean corpuscular volume (P < 0.001). Osmotic gradient ektacytometry confirmed a trend toward improvement of RBC hydration status. As determined by clearance of RBC biotinylated in vivo, RBC survival also was significantly improved in L1-treated mice compared with controls (P = 0.007). Thus, in vivo therapy with L1 removes pathologic free iron deposits from RBC membranes in murine thalassemia, and causes improvement in membrane function and RBC survival. This result provides in vivo confirmation that abnormal membrane free iron deposits contribute to the pathobiology of thalassemic RBC.

Animals↗
PubMed2004

Labile plasma iron (LPI) as an indicator of chelatable plasma redox activity in iron-overloaded beta-thalassemia/HbE patients treated with an oral chelator.

Persistent levels of plasma nontransferrin bound iron (NTBI) have been associated with tissue iron overload and toxicity. We characterized NTBI's susceptibility to deferoxamine (directly chelatable iron [DCI]) and redox activity (labile plasma iron [LPI]) during the course of long-term, continuous L1 (deferiprone) treatment of patients with hemoglobin E disease and beta-thalassemia (n = 17). In 97% of serum samples (n = 267), the LPI levels were more than 0.4 microM (mean +/- SEM, 3.1 +/- 0.2 microM) and the percent transferrin (Tf) saturation more than 85 (111 +/- 6), whereas only in 4% of sera were the LPI levels more than 0.4 microM for Tf saturation less than 85%. Daily administration of L1 (50 mg/kg) for 13 to 17 months caused both LPI and DCI to decrease from respective initial 5.1 +/- 0.5 and 5.4 +/- 0.6 microM to steady mean levels of 2.18 +/- 0.24 and 2.81 +/- 0.14 microM. The steady lowest levels of LPI and DCI were attained after 6 to 8 months, with a half time (t(1/2)) of 2 to 3 months. Serum ferritin and red cell membrane-associated iron followed a similar course but attained steady basal levels only after 10 to 12 months of continuous treatment, with a t(1/2) of 5 to 7 months. These studies indicate that LPI and DCI can serve as early indicators of iron overload and as measures for the effectiveness of iron chelation in reducing potentially toxic iron in the plasma.

Biomarkers↗
PubMed2005

Intracellular labile iron pools as direct targets of iron chelators: a fluorescence study of chelator action in living cells.

The primary targets of iron chelators used for treating transfusional iron overload are prevention of iron ingress into tissues and its intracellular scavenging. The present study was aimed at elucidating the capacity of clinically important iron chelators such as deferiprone (DFP), desferrioxamine, and ICL670 to (a) gain direct access to intracellular iron pools of key cells of iron accumulation (macrophages, hepatocytes, and cardiomyocyte cell lines); (b) chelate the labile iron present in discrete cell compartments/organelles; and (c) prevent labile iron involvement in the generation of reactive oxidant species. Chelation of cytosolic and organellar cell iron was visualized dynamically and quantitatively in living cells by fluorescence microscopic imaging of fluorescent metallosensors (used as iron-quenched complexes of calceins) targeted to either cytosol, endosome-lysosomes, or mitochondria. The rate and extent of fluorescence recovery provided an in situ measure of the accessibility of chelators to particular cell sites/organelles. Complementary, fluorogenic redox probes associated with cell compartments enabled identification of chelator-sensitive, localized reactive oxidant production. Our studies indicate that chelation by desferrioxamine is slow and is enhanced in cells with relatively high endocytic activities, while ICL670 and DFP readily enter most cells and efficiently reach the major intracellular sites of iron accumulation.

Animals↗
PubMed2005

Monitoring long-term efficacy of iron chelation treatment with biomagnetic liver susceptometry.

In patients with thalassemia, the assessment of liver iron concentration (LIC) can be used to initiate chelation treatment with desferrioxamine (DFO), deferiprone (DFP), or novel chelators (deferasirox); to adjust chelation dose according to the actual blood transfusion rate; and to monitor chelation efficacy. The results from measurements by SQUID biomagnetic liver susceptometry in the LIC range 17-11,500 microg/g of liver in about 1000 patients were used to derive nonstandard parameters, which may be useful in the treatment monitoring of patients with thalassemia. From these measurements, including liver volumes, the documented chelation dose rates, and the blood transfusion rates, the chelator index (equivalent Therapeutical Index), the total body iron elimination rate, and the molar efficacy were calculated. Chelator indices (CIs) ranged from 0.1 to 11.7 mmol/d/g of Fe for DFO, with a threshold of CI greater than 1.2 mmol/d/g of Fe indicating DFO toxicity. For DFP, CI ranged from 0.1 to 23.2 mmol/d/g of Fe. In long-term studies (2 and 4 years), mean molar efficacies of DFO and DFP were found to be quite stable with 17.6 +/- 4.8% and 4.9 +/- 1.4%, respectively. Currently, specific chelation dose is based upon body weight. Because liver iron measurements by biosusceptometry are now regularly available in Europe and America, as well as quantitative MRI worldwide, these methods may be used to adjust chelation treatment regimens to body iron stores.

Algorithms↗
PubMed2005

T2* magnetic resonance and myocardial iron in thalassemia.

Magnetic resonance T2* values of the myocardium are directly related to tissue iron levels. Minor effects from myocardial oxygenation and fibrosis are overwhelmed by the highly dominant iron effect in clinically relevant levels of myocardial iron overload. Myocardial T2* values less than 20 ms indicate iron overload, and this is considered severe when T2* is less than 10 ms. Decreasing myocardial T2* levels are associated with systolic and diastolic ventricular dysfunction. Most recorded cases of heart failure in thalassemia to date have occurred in patients with very low T2* values (in the severe range). Exceptions to this have occurred in patients with other causes of heart failure such as concomitant congenital heart disease. In patients presenting with heart failure who undergo aggressive chelation with continuous intravenous deferoxamine, longitudinal studies show that myocardial T2* increases, and this is accompanied by increases in ejection fraction and relief of heart failure. In cross-sectional studies, the myocardial T2* and ejection fraction of patients on deferiprone was superior to that of patients on deferoxamine. Randomized controlled prospective trials comparing these two drugs for their action in clearing myocardial iron, as measured by myocardial T2*, are under way and should report in 2005/2006. These trials will clarify the role of different chelators in the management of myocardial iron overload and may be valuable in reducing the toll of death in thalassemia from heart failure.

Adult↗
PubMed2000

Design, synthesis and evaluation of N-basic substituted 3-hydroxypyridin-4-ones: orally active iron chelators with lysosomotrophic potential.

To investigate the possibility of targeting chelators into the lysosomal iron pool, nine bidentate 3-hydroxypyridin-4-ones with basic chains have been synthesized. As the turnover of ferritin iron is centred in the lysosome, such strategy is predicted to increase chelator efficacy of bidentate ligands. The pKa values of the ligands together with their distribution coefficients between 1-octanol and 4-morpholinepropane sulphonic acid (MOPS) buffer pH 7.4 have been determined. The in-vivo iron mobilization efficacy of these basic 3-hydroxypyridin-4-ones has been investigated in a 59Fe-ferritin-loaded rat model. No obvious correlation was observed between efficacy and the pKa value of the side chain, although those with pKa > 7.0 tended to be more efficient than those with pKa < 7.0. The imidazole-containing molecules are much less effective than the tertiary amine derivatives. A dose-response study suggested that basic pyridinones are relatively more effective at lower doses when compared with N-alkyl hydroxypyridinones. Optimal effects were observed with the piperidine derivatives 4h and 4i. The derivative 4i at a dose of 150 micromol kg(-1) was more effective than 450 micromol kg(-1) deferiprone, the widely adopted clinical dose.

Alkalies↗
PubMed2001

Radiation sensitization of mammalian cells by metal chelators.

The cell cycle effects, alteration in radiation response, and inherent cytotoxicity of the metal chelators mimosine, desferrioxamine (DFO), N,N'-bis(o-hydroxybenzyl)-ethylenediamine-N,N'-diacetic acid (HBED), and deferiprone (L1) were studied in exponentially growing Chinese hamster V79 cells. Incubation of cells with 200-1000 microM mimosine for 12 h reduced clonogenic survival to 50-60%, while incubation for 24 h reduced survival further to 0.5%. Mimosine treatment resulted in cell cycle blocks at the G(1)/S-phase border and in S phase. Pulse labeling with 5-bromodeoxyuridine indicated that the S-phase cells ceased to actively replicate DNA after only 2 h of mimosine treatment and were unable to replicate DNA for extended periods. Treatment of V79 cells with 600 microM mimosine for 12 h resulted in radiosensitization, yielding a sensitizer enhancement ratio (SER) of 2.7 +/- 0.3 at the 10% survival level. To study the kinetics of the sensitization, V79 cells were incubated with mimosine for various times up to 12 h and irradiated with a single 10-Gy dose of X rays. It was found that the radiosensitization increased continually up to 8 h (from a 3- to a 100-fold difference in survival) and then reached a plateau after 8 h. Mimosine also equally radiosensitized human lung cancer cells having either a normal or mutated TP53 gene, suggesting a TP53-independent mechanism. To test whether iron binding by mimosine was responsible for the observed radiosensitization, additional experiments were performed using the iron chelators DFO, HBED and L1. V79 cells treated with 500 microM of these agents for 8 h followed by various doses of X rays gave SERs similar to that for mimosine (2.0-2.7). These studies indicate that metal chelators are potent radiosensitizers in V79 and human cells. Importantly, when the DFO was preloaded together with Fe(3+) [Fe(III)-DFO], the radiosensitizing effect was lost. These preliminary findings warrant further studies for the possible application of metal chelators as radiation sensitizers in radiation oncology.

Animals↗
PubMed2005

Chelating agents used for plutonium and uranium removal in radiation emergency medicine.

The prospects of using chelating agents for increasing the excretion of actinides are reviewed. The removal of plutonium by chelating agents is of great importance because plutonium is extremely dangerous and induces cancer due to radiation toxicity. Similarly, uranium is a radionuclide, which causes severe renal dysfunction within a short time period due to chemical toxicity. It may also induce cancers such as leukemia and osteosarcoma in cases of long-term internal radiation exposure. Investigations on chelating agents for the removal of plutonium were initiated in the 1960's and 1970's. Diethylenetriaminepentaacetic acid (DTPA) is recognized as a chelating agent that accelerates the excretion of plutonium in early treatment after an accident. Thereafter, there has long been an interest in finding new chelating agents with radionuclide removal properties for use in therapy, and many chelating agents such as 3,4,3-LIHOPO and CBMIDA have been studied for their ability to remove plutonium and uranium. Recently, the focus has turned to drugs that have been used successfully in the treatment of a variety of other diseases, for example the iron chelating drug deferiprone or 1,2-dimethyl-3-hydroxypyrid-4-one (L1), which is used in thalassaemia and ethane-1-hydroxy-1,1-bisphosphonate (EHBP), which is used in osteoporosis. Within this context, it is important to examine the clinical use of these two drugs as well as the properties of the experimental chelators 3,4,3-LIHOPO and CBMIDA in order to identify possible uses in the treatment of radiation workers contaminated with plutonium and uranium.

Animals↗
PubMed2005

Molecular factors and mechanisms affecting iron and other metal excretion or absorption in health and disease: the role of natural and synthetic chelators.

The maintenance of iron and other essential metal ion balance in humans is based on the presence of homeostatic mechanisms of regulatory absorption, storage, re-utilisation and excretion. There are a number of factors and mechanisms that can affect the level of iron excretion or absorption and overall body iron stores. Net iron loss due to increased iron excretion by comparison to dietary iron absorption is considered as one of the causes of iron deficiency anaemia. Body iron loss greater than normal has been shown in many other conditions. These include the increase in urinary iron excretion observed in iron loaded patients, the substantial reduction in serum ferritin and liver iron of ex-thalassaemia patients several years following bone marrow transplantation and the increase in iron excretion in normal individuals following long term sport activities. There are differences in the metabolism, mode of action, interactions with the iron pools and routes of iron excretion, of the iron chelating drugs deferiprone (L1), deferoxamine and other experimental chelators such as ICL670 in iron-loaded patients. Naturally occurring chelators and some synthetic drugs are known to bind iron and affect iron absorption and excretion. The molecular characteristics of naturally occurring or synthetic chelators can influence other aspects of iron metabolism in addition to iron absorption or excretion. Similar mechanisms and factors can affect the metabolism of other essential metals. The understanding of the mechanisms involved in iron excretion and their overall effects on body iron levels can facilitate the design of new chelators and improved therapeutic protocols for the treatment of conditions of iron and other metal metabolic imbalance and toxicity.

Benzoates↗
PubMed1998

Bone density and metabolism in thalassaemia.

Twenty-seven thalassaemic patients (13 F, 14 M, aged 8.1-14.9 yr), regularly transfused and chelated with desferrioxamine (30-40 mg/kg/day) were studied. Every patient was submitted to auxological evaluations, dual X-ray absorptiometry to measure bone mineral density (BMD), and to the determination of bone metabolic markers of osteoclastic activity (total urinary hydroxylysylpyridinoline crosslinks, carboxyterminal pyridinoline crosslinked telopeptide of type I collagen [ICTP]) and of osteoblastic activity (bone Gla protein [BGP] and carboxyterminal propeptide of type I procollagen [PIPC]). The evaluations were repeated after 1 year, during which 13 patients continued desferrioxamine chelation while 14 underwent deferiprone chelation (75 mg/kg/day in 3 doses). The data demonstrate widespread bone alterations consisting of osteoporosis, growth failure and bone age delay. Lumber spine (L2-L4) BMD areal values (Z score) inversely correlated with age, as did height SDS of both male and female patients, indicating osteoporosis progressing with age in parallel with growth insufficiency. No clear-cut alterations in bone mineral metabolism were found in basal state and after 1 year. Extensive MR imaging studies are needed to define the contribution of residual bone marrow hyperplasia to thalassaemic osteopathy suggested by subtle radiological signs as enlargement of bone marrow cavities with thinning of the cortical bone and abnormalities of the trabecules of spongy bone.

Absorptiometry, Photon↗
PubMed2000

Combined oral and parenteral iron chelation in beta thalassaemia major.

Thalassaemics in Malaysia are poorly chelated because desferrioxamine is too expensive and cumbersome for long term compliance. The efficacy and tolerability of the oral chelator deferiprone, and the effects of using a combination therapy in our patients were studied. Ten patients completed the study and the mean serum ferritin reduced from 7066.11 ug/L (2577-12,896 ug/L) to 3242.24 ug/L (955-6120 ug/L). The liver iron concentration did not show a significant drop (19.6 vs 18.2 mg/g dry weight) although 3 patients showed reductions ranging from 30-40%. Concomitant use of desferrioxamine increased the urinary excretion from a mean of 13.66 mg/day to 27.38 mg/day. Main side effects seen were nausea and rashes.

Administration, Oral↗
PubMed2006

[Magnetic resonance imaging evidence of the effectiveness of combination chelation therapy in iron overload cardiomyopathy].

Heart failure secondary to iron overload is the main cause of death in patients with beta-thalassemia major. Combination therapy with deferoxamine and deferiprone has been shown to be more effective than either drug used alone in patients with beta-thalassemia major and symptomatic cardiomyopathy. Although monitoring the response to chelation therapy is usually carried out by indirect measurement of the serum ferritin level or by direct determination of tissue iron content in biopsy specimens, magnetic resonance imaging (MRI) seems to be useful for noninvasive qualitative and quantitative assessment of iron deposition. We present a case in which the efficacy of double chelation therapy in a patient with beta-thalassemia major and heart failure was demonstrated by MRI.

Adult↗
PubMed2006

Survival of medically treated thalassemia patients in Cyprus. Trends and risk factors over the period 1980-2004.

BACKGROUND AND OBJECTIVES: A large number of patients with thalassemia major have been born and treated exclusively in Cyprus. They have been managed according to standard international practice, but few have been transplanted. In 1999, a combination chelation regime with desferrioxamine and deferiprone was introduced. We analyzed survival trends in Cypriots and tried to identify factors associated with prolonged survival. DESIGN AND METHODS: We had incomplete information on births pre-1974 and complete information from 1974 onwards. Clinical data were incomplete pre-1980 and complete thereafter. We analyzed data on 539 patients born after 1960 and followed over the period 1980 to the end of 2004. RESULTS: There were 58 deaths, 31 (53.4%) of which where due to cardiac causes. In the complete birth cohort of 284 patients born after 1974, survival (95% CI) at 10, 20 and 30 years was 100% (0); 98.5% (96.1-99.4) and 92.7% (86.7-96.1) respectively. There was a significant trend of increasing cardiac deaths between 1980 and 2000 (p<0.001) and a decline after 2000 (p=0.06). In multivariate survival analysis, protective effects were found for female sex (hazard ratio, 0.37, 95% CI 0.21-0.66; p<0.001), and post-2000 follow-up (hazard ratio, 0.44, 95% CI 0.20-0.99; p<0.05), but not for genotype, treatment center or birth cohort. INTERPRETATION AND CONCLUSIONS: Most patients born after 1974 survive to at least the age of 30. There has been a marked improvement in survival for patients of all ages since 2000, which may be due to the introduction of combination chelation therapy.

Cyprus↗
PubMed1994

Studies of aluminium mobilization in renal dialysis patients using the oral chelator 1,2-dimethyl-3-hydroxypyrid-4-one.

The oral chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1, deferiprone, CAS 30652-11-0) has been tested in 11 renal dialysis patients, 10 for aluminium and 1 for iron mobilization. L1 was administered just after the patients were placed on the haemodialyser and blood samples were collected before haemodialysis at 1 h and for some patients at longer intervals. Plasma aluminium levels before treatment ranged from 12 to 264 micrograms/l. A mean increase of 90% was observed within the first hour of oral administration in 6 patients who received a dose of L1 of 40-60 mg/kg. Plasma aluminium levels then progressively decreased after this period. Three patients with plasma aluminium of 30-66 micrograms/l who received a dose of L1 of less than 30 mg/kg had no significant changes in their plasma aluminium. In 2 other cases administration of L1 resulted in an over 30-fold increase of aluminium concentration in the dialysate of a continuous ambulatory peritoneal dialysis patient and of over 3 times the iron concentration in the dialysate of an iron loaded haemodialysis patient. In the last patient HPLC analysis of the dialysate samples obtained from the haemodialyser has shown complete clearance of L1 within 4 h but not of its glucuronide metabolite within 6.5 h of the L1 administration. No toxic side effects were observed in any of the 11 patients who received oral L1. These are the first clinical trials of an oral chelator in renal dialysis patients which suggest that oral L1 and possibly other alpha-ketohydroxypyridine chelators may have a use in the treatment of patients with aluminium overload.

Adult↗
PubMed1997

EPR determination of low molecular weight iron content applied to whole rat hepatocytes.

Electron paramagnetic resonance (EPR) has been described as suitable for the evaluation of low molecular weight (LMW) iron in liver homogenates after chelation by desferrioxamine. LMW iron is a highly toxic iron species incriminated in free radical production. The first aim of the study was to evaluate the conditions of EPR application for LMW iron content determination in whole rat hepatocytes. For this purpose, LMW iron was simultaneously quantified by EPR and by atomic absorption spectrometry, EPR determination of LMW iron needed a preincubation of hepatocyte cultures with the iron chelator for at least on hr. Deferiprone as LMW iron chelator was revealed to be more suited than desferrioxamine. Secondly, we showed the applicability of this methods for evaluating the prooxidant status during an oxidative stress. As an example, oxidative stress induced by ethanol in hepatocytes was studied during inflammatory circumstances, well-known to lead to nitric oxide production. In hepatocyte cultures supplemented with ethanol, an evaluation of LMW iron content was observed in cells. But when nitric oxide donors or a supplementation constituted of lipopolysaccharide and gamma-interferon, able to induce nitric oxide synthase, were added, LMW iron content decreased. Thus EPR determination of LMW iron content in whole hepatocytes could give some insight about the mechanism of induction or inhibition of a oxidative stress.

Animals↗
PubMed1998

Iron as a potential co-factor in the pathogenesis of Kaposi's sarcoma?

The role of iron in the pathogenesis of several tumours is being increasingly investigated. In particular, its involvement in the pathogenesis of Kaposi's sarcoma (KS) is suggested by the distribution of the endemic form of KS corresponding to continental rifts and associated iron-oxide-rich volcanic clays. We investigated in vitro to what extent iron supplementation or withdrawal could affect the growth of KS-derived cells, by analysing the effects of adding iron salts (iron chloride and ferric nitrilotriacetate) and/or reducing iron by iron chelators (desferrioxamine) on KS-derived cell cultures. The addition of iron salts strongly stimulated the growth of KS cells, as reflected by increase in thymidine incorporation and cell number. Conversely, desferrioxamine and deferiprone inhibited cell growth. The inhibitory effect of iron chelation was more pronounced on rapidly dividing basic fibroblast-growth-factor-stimulated cells. These results may point to a novel therapeutic approach to KS.

Carcinogens↗