Iron Unloading Research Articles

Beta-Thalassemia Major and Myocardial Iron Overload: A Longitudinal Study with Magnetic Resonance Imaging.

Patients with β-thalassemia major depend on lifelong transfusion, resulting in tissue iron overload. This longitudinal retrospective observational study aims to assess myocardial and liver iron overload using magnetic resonance imaging (MRI) and investigate the lag between myocardial and liver iron unloading in β-thalassemia patients undergoing chelation therapy. Beta-thalassemia major patients with at least two MRI studies between 2016 and 2020 were enrolled. Myocardial and liver iron overload were defined as T2 ∗ less than 20 and 2.1, respectively. Outcomes included mortality, myocardial and liver T2 ∗ changes, and systolic dysfunction assessed by cardiac MRI. Fifty-five patients with a mean age of 24.62 ± 7.94 years, a mean follow-up duration of 24.3 ± 12.9 months, and a mean ferritin level of 1475.75 ± 771.12 ng/mL were enrolled. All of the abovementioned patients only took deferoxamine as the iron-chelating medication. Mortality occurred in three patients (5.5%) during follow-up. Liver T2 ∗ significantly increased (p value <0.05), while myocardial T2 ∗ showed a nonsignificant increase. Iron unloading of the myocardium was not significantly different from that of the liver and did not result in a significant lag (56% vs. 44%; p value = 0.419). Baseline myocardial T2 ∗ correlated with extramedullary hematopoiesis, weekly number of deferoxamine injections (p value <0.01), timing between the transfusions, and serum ferritin (p value <0.05). Liver T2 ∗ reduced during deferoxamine chelation therapy, while myocardial T2 ∗ remained unchanged. No significant lag was observed between myocardial and liver iron unloading. Further studies are required to elucidate these findings.

Effect of Luspatercept on Red Blood Cell (RBC) Transfusion Burden, Iron Chelation Therapy (ICT), and Iron Overload in Adults with Transfusion-Dependent β-Thalassemia (TDT) from the BELIEVE Trial: A Long-Term Analysis

Effect of Luspatercept on Red Blood Cell (RBC) Transfusion Burden, Iron Chelation Therapy (ICT), and Iron Overload in Adults with Transfusion-Dependent β-Thalassemia (TDT) from the BELIEVE Trial: A Long-Term Analysis

GSTM1 and Liver Iron Content in Children with Sickle Cell Anemia and Iron Overload.

Chronic blood transfusions in patients with sickle cell anemia (SCA) cause iron overload, which occurs with a degree of interpatient variability in serum ferritin and liver iron content (LIC). Reasons for this variability are unclear and may be influenced by genes that regulate iron metabolism. We evaluated the association of the copy number of the glutathione S-transferase M1 (GSTM1) gene and degree of iron overload among patients with SCA. We compared LIC in 38 children with SCA and ≥12 lifetime erythrocyte transfusions stratified by GSTM1 genotype. Baseline LIC was measured using magnetic resonance imaging (MRI), R2*MRI within 3 months prior to, and again after, starting iron unloading therapy. After controlling for weight-corrected transfusion burden (mL/kg) and splenectomy, mean pre-chelation LIC (mg/g dry liver dry weight) was similar in all groups: GSTM1 wild-type (WT) (11.45, SD±6.8), heterozygous (8.2, SD±4.52), and homozygous GSTM1 deletion (GSTM1-null; 7.8, SD±6.9, p = 0.09). However, after >12 months of chelation, GSTM1-null genotype subjects had the least decrease in LIC compared to non-null genotype subjects (mean LIC change for GSTM1-null = 0.1 (SD±3.3); versus −0.3 (SD±3.0) and −1.9 (SD±4.9) mg/g liver dry weight for heterozygous and WT, respectively, p = 0.047). GSTM1 homozygous deletion may prevent effective chelation in children with SCA and iron overload.

Iron Unloading By Therapeutic Phlebotomy in Previously Transfused Children with Sickle Cell Anemia: The Twitch Experience

▪Background: TCD With Transfusions Changing to Hydroxyurea (TWiTCH, ClinicalTrials.gov NCT01425307), an NHLBI-sponsored Phase III multicenter trial, compared transfusions to hydroxyurea for maintaining TCD velocities in children with sickle cell anemia who previously received transfusions for abnormal TCD velocities. Iron overload was treated with serial phlebotomy in children randomized to hydroxyurea. At the first scheduled interim analysis, non-inferiority of hydroxyurea was demonstrated and the study was terminated prematurely.Methods: Participants randomized to hydroxyurea received decreasing volumes of monthly transfusions during hydroxyurea dose escalation to maximum tolerated dose (MTD), averaging 6-7 months. During this transfusion overlap period, no chelation therapy was given. After hydroxyurea MTD was reached, transfusions were discontinued and children started monthly phlebotomy if their entry liver iron concentration (LIC) by MRI-R2 (FerriScan®) was ≥2 mg Fe/g dry weight liver (DWL). The prescribed phlebotomy volume was 10 mL/kg (maximum 500 mL) with adjustments for anemia (5 mL/kg for Hb 8.0-8.5 g/dL and held if Hb <8.0 g/dL). Phlebotomy was performed over 30 minutes with immediate equal volume normal saline replacement, typically using peripheral venous access. LIC was assessed at study entry, midpoint (12 months), and exit (24 months/early closure). Ferritin was monitored monthly using a centralized laboratory. Iron loading calculations were based on actual transfusion and phlebotomy volumes.Results: Sixty children (mean age 9.7±3.2 years; range 5.2-19.0 years; 48% male) were randomized to the Hydroxyurea Treatment Arm. The average duration of previous transfusions was 4.5±2.8 years. Almost all (51/60, 85%) had previously received chelation, primarily deferasirox, and 48 (80%) were on chelation therapy at study enrollment.Hydroxyurea MTD was achieved in 57 children (95%), and 54 commenced phlebotomy (two had low iron burden with LIC <2 and one had Hb <8.0 g/dL). A total of 914 phlebotomy procedures were scheduled per protocol for these 54 children and 756 (83%) were fully completed. There were 77 procedures cancelled due to anemia and another 81 procedures cancelled due to planned anesthesia (16), provider preference (14), hydroxyurea-related cytopenia (13), intercurrent illness (11), inadequate iv access (9), family request (5) or other (13). In 94% of phlebotomy procedures that were initiated, the full volume was removed; for the remaining 6% (47 procedures), a reduced volume was removed due to loss of venous access (37), symptoms such as headache or lightheadedness (7), or other reasons (3).A total of 18 Adverse Events (17 Grade 2 and one Grade 3) occurred in 14 participants in association with phlebotomy (2.3% prevalence). The most common complication was light headedness/near-syncope (6) followed by anemia (4), hypotension (3), headache (3), and pain at the venous access site (1). One subject had a syncopal episode followed by transient weakness, which was centrally adjudicated as TIA.An average of 53.6±21.8 mL/kg blood was administered in the hydroxyurea-treated arm, which calculates to an average iron loading of 40.1±16.3 mg Fe/kg, while an average of 112 mL/kg of venous blood was removed by phlebotomy, which calculates to an average iron unloading of 36.1±15.7 mg Fe/kg. For the 54 children who received phlebotomy, the average LIC was 12.0± 9.7 mg/g at study entry, 13.4±10.3 at midpoint reflecting overlap transfusions without chelation, and 9.7±8.9 at study exit reflecting serial phlebotomy, for an average net LIC decrease of 2.3±4.1 mg/g. Average serum ferritin at study entry was 3105±741 ng/mL and 1392±1542 ng/mL at study exit. For 39 children who completed all 24 months of treatment before study closure, the overall average LIC decrease was 3.2±3.8 mg/gram DWL and 10 had final LIC measurements <3 mg Fe/g. Calculated net iron loading was not significantly associated with measured changes in LIC or ferritin.Conclusions: In the TWiTCH trial, phlebotomy was a feasible, safe, well-tolerated, and effective treatment for transfusional iron overload in children with sickle cell anemia. Although initial overlap transfusions without chelation limited the phlebotomy effects, in children who reached hydroxyurea MTD and discontinued chronic transfusions, monthly phlebotomy led to net iron unloading and lower LIC, and significantly reduced iron burden. DisclosuresRogers:Apopharma: Consultancy. Kalfa:Baxter/Baxalta/Shire: Research Funding. Kwiatkowski:Sideris Pharmaceuticals: Consultancy; Luitpold Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Apopharma: Research Funding; Ionis pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Shire Pharmaceuticals: Consultancy. Wood:World Care Clinical: Consultancy; Biomed Informatics: Consultancy; Biomed Informatics: Consultancy; Celgene: Consultancy; Celgene: Consultancy; AMAG: Consultancy; Apopharma: Consultancy; Apopharma: Consultancy; AMAG: Consultancy; World Care Clinical: Consultancy; Vifor: Consultancy; Vifor: Consultancy; Ionis Pharmaceuticals: Consultancy; Ionis Pharmaceuticals: Consultancy. Ware:Global Blood Therapeutics: Consultancy; Biomedomics: Research Funding; Bayer Pharmaceuticals: Consultancy; Addmedica: Research Funding; Nova Laboratories: Consultancy; Bristol Myers Squibb: Research Funding.

Changes in Extrahepatic Iron Load in Response to Iron Chelation Versus Phlebotomy: Observations from the Twitch Trial

▪Introduction: The TCD with Transfusions Changing to Hydroxyurea (TWiTCH) trial was an NHLBI-funded multicenter phase 3 randomized trial that demonstrated non-inferiority of hydroxyurea versus continued transfusion therapy in children with sickle cell anemia and abnormal TCD velocities but no severe vasculopathy. Children who were randomized to continue transfusions (Standard Arm) received conventional iron chelation therapy with deferasirox, while children receiving hydroxyurea (Alternative Arm) received serial phlebotomy (10 mL/kg, maximum 500 mL) every 4 weeks. Extrahepatic iron burden was monitored by R2* MRI in the kidney, pancreas, and spleen to monitor the changes in iron overload phenotype between the two groups.Methods: R2* MRI of the abdomen was performed at baseline, 1 year, and 2 years following enrollment. Liver, spleen, pancreas, and kidney R2* were measured from axial and coronal multiecho, gradient echo images. Images were analyzed centrally at an experienced core laboratory using an exponential plus constant model for signal decay. Iron burden in the different organs was assessed using repeated measures analysis of variance (ANOVA) using JMP 11.0.Results: 120 patients underwent baseline R2* assessment, 83 completed the midpoint, and 89 patients completed the endpoint examination. Figure 1 (left) summarizes the changes in kidney R2* across the three time points. Kidney R2* was elevated at baseline in both treatment arms and correlated with LDH (r2 =0.28, p<0.0001) and total iron binding capacity, but not with age, sex, LIC, serum ferritin, years of transfusion and years of chelation. Kidney R2* and markers of hemolysis (LDH, total bilirubin), remained stable in the transfusion arm. In contrast, kidney R2* declined monotonically in the patients on hydroxyurea (F value 6.9, p=0.0021 for time-treatment interaction). These changes paralleled reductions in LDH (F value 8.1, p=0.0007) and total bilirubin (F value 28, p<0.0001) in the hydroxyurea group compared to the transfusion group. There were no group differences in mean serum creatinine or urine albumin to creatinine ratio (ACR). However, the frequency and severity of albuminuria (ACR > 30 mg albumin per g creatinine) trended lower in patients on hydroxyurea, (5/45 at baseline (p=1), 1/44 at midpoint (p=0.03), and 4/52 at endpoint (p=0.33). Figure 1 (right) demonstrates the temporal evolution of ACR in 11 study participants with baseline albuminuria; 4/6 patients on standard arm continued to have significant proteinuria on their terminal examination compared with only 1/5 patients on hydroxyurea (p=0.24).There were no groupwise differences in mean pancreas R2* at any time point and clinically significant pancreas iron deposition (R2* > 100 Hz) was only observed in two patients at the mid timepoint. Spleen R2* was markedly elevated at baseline (503 ± 396 Hz), but did not change systematically over time in either group. The change in spleen R2* was correlated with the change in liver iron (r2=0.21, p=0.003), regardless of the treatment group, suggesting that the spleen iron stores are part of the dynamic iron storage pool. 37% of the patients had no MRI-detectable spleen (surgical + autosplenectomy). The change of liver iron was not different in patients with or without a spleen.Conclusion: Hydroxyurea therapy was associated with lower intravascular hemolysis and kidney iron deposition. Further studies are necessary to determine whether these changes are associated with decreased proteinuria or improved renal function. Splenic iron burden remained high but stable in all patients, and its role in iron unloading needs further investigation. Pancreas iron loading remained rare, consistent with the low prevalence of endocrinopathies in SCD. [Display omitted] DisclosuresWood:Apopharma: Consultancy; Ionis Pharmaceuticals: Consultancy; Vifor: Consultancy; Vifor: Consultancy; Biomed Informatics: Consultancy; AMAG: Consultancy; Biomed Informatics: Consultancy; Ionis Pharmaceuticals: Consultancy; World Care Clinical: Consultancy; World Care Clinical: Consultancy; Celgene: Consultancy; Apopharma: Consultancy; Celgene: Consultancy; AMAG: Consultancy. Heeney:Sancilio and Company: Consultancy, Research Funding; Eli Lilly and Company: Research Funding; Pfizer: Research Funding. Ware:Global Blood Therapeutics: Consultancy; Nova Laboratories: Consultancy; Biomedomics: Research Funding; Bristol Myers Squibb: Research Funding; Addmedica: Research Funding; Bayer Pharmaceuticals: Consultancy.

Racial differences in iron measures and outcomes observed during an iron reduction trial in peripheral arterial disease.

Elevated body iron (ferritin) levels may contribute to adverse health outcomes. Racial differences in iron measures and clinical outcomes were observed during an iron reduction trial in peripheral arterial disease. At entry, Black compared with White participants had higher ferritin and lower red cell measures, as well as differing ferritin and percent transferrin saturation (%TS) responses, and HDL/LDL ratios associated with statin use. Lower hematocrit levels during follow-up resulted in fewer phlebotomies, less iron unloading (ferritin reduction, p=.035) and 32% less iron removed in Black compared with White participants randomized to iron reduction. Improved primary (all-cause mortality) and secondary (death plus non-fatal myocardial infarction and stroke) outcomes among White participants correlated with lower ferritin levels (p=.005 and p=.053, respectively) and higher %TS levels (p&lt;.001 and p=.001 respectively), associations not observed in Black participants. Variant iron homeostasis contributory to racial health disparities warrants personalized intervention strategies and race-specific clinical trial design.

Serum Ferritin and Liver Iron Concentration in Patients with Iron Overload.

Despite its limitations, serum ferritin (SF) is commonly used to monitor chelation therapy in primary and secondary hemochromatosis. To better predict liver iron concentration (LIC), we prospectively investigated the relationship between SF and LIC in a total of 421 patients with primary (HFE-1 associated, n=241) or secondary hemochromatosis (n=180), consisting of chronically transfused thalassemia (Tx-Thal: n=89) or sickle cell disease patients (Tx-SCD: n=45) and transfusion independent thalassemia patients (nTx-Thal: n=26). In all patients, LIC was measured by SQUID biosusceptometry. SF correlated with LIC (RS = 0.51–0.83, p < 0.001) but was a poor predictor for LIC. SF was significantly lower (p < 0.001) in nTx-Thal and HFE-1 patients despite similar LIC (421 – 5524 μg/g-liver) and it was higher in Tx-SCD compared to Tx-Thal (p = 0.03). In order to improve the value of SF, we calculated the SF/LIC ratio for each group. SF/LIC remained stable over time in patients whose therapy did not change. In iron loaded patients without blood transfusion therapy (nTx-Thal and HFE-1), the median SF/LIC ratio was significant lower (0.32 and 0.43) as compared to transfused patients (Tx-Thal: 0.87, HCV-Thal: 0.99, Tx-SCD: 1.2), probably, indicating differences in the secretion of ferritin into plasma. We conclude that SF alone can mislead the iron unloading therapy as it underestimates LIC in nTx-Thal patients and overestimates LIC in Tx-SCD patients. Once the initial LIC value is obtained and the individual SF/LIC ratio is determined in a patient, the ratio together with SF may be more useful than SF alone to monitor iron overload and predict LIC.

An Iron Delivery Pathway Mediated by a Lipocalin

Despite the critical need for iron in many cellular reactions, deletion of the transferrin pathway does not block organogenesis, suggesting the presence of alternative methods to deliver iron. We show that a member of the lipocalin superfamily (24p3/Ngal) delivers iron to the cytoplasm where it activates or represses iron-responsive genes. Iron unloading depends on the cycling of 24p3/Ngal through acidic endosomes, but its pH sensitivity and its subcellular targeting differed from transferrin. Indeed, during the conversion of mesenchyme into epithelia (where we discovered the protein), 24p3/Ngal and transferrin were endocytosed by different cells that characterize different stages of development, and they triggered unique responses. These studies identify an iron delivery pathway active in development and cell physiology.

This month in J Lab Clin Med

This month in J Lab Clin Med

New developments and applications in quantitative electron spectroscopic imaging of iron in human liver biopsies

Reliable iron concentration data can be obtained by quantitative analyses of image sequences, acquired by electron spectroscopic imaging. A number of requirements are formulated for the successful application of this recently developed in situ quantitative type of analysis. A demonstration of the procedures is given. By application of the technique it is established that there are no significant differences in the average iron loading of structures analysed in liver parenchymal cells of a patient with an iron storage disease, before and after phlebotomy. This supports the hypothesis that the process of iron unloading is an organelle specific process. Measurement of the binary morphology, represented by the area and contour ratio of the iron containing objects revealed no information about differences between the objects. This finding contradicts the visual suggestion that ferritin clusters are more irregularly shaped than the other iron objects. Also, no differences could be found in this sense between the situations before and after phlebotomy. With respect to the density appearance, objects that have an inhomogeneous iron loading averagely contain more iron. This observation does correspond well with the visual impression of the increasingly irregular appearance of more well-loaded structures.

Transferrin and the transferrin cycle in Belgrade rat reticulocytes

Belgrade rats have an autosomal recessive anemia with hypochromia and microcytosis. Iron uptake into reticulocytes is approximately 20% of normal, but transferrin uptake is unimpaired. We have systematically compared the transferrin cycle in Belgrade versus normal reticulocytes to locate the defect more precisely. Belgrade transferrin was functionally normal as purified transferrin or whole plasma. Transferrin affinity of Belgrade receptors was indistinguishable from normal, but Belgrade reticulocytes had twice as many receptors. Belgrade transferrin endocytosis was 1.5 times faster than normal, whereas exocytosis is about twice as fast. Initially Belgrade reticulocytes internalize iron at an unimpaired rate, but they lag behind normal by 5 min. During reincubation, they release 25-33% of iron taken up during a 30-min preincubation, whereas normal cells do not lose a detectable fraction. Unexpectedly, transferrin cycle time was unchanged. Hence another kinetic step of the cycle is slower, compensating for increases in Belgrade endocytosis and exocytosis. After one cycle, Belgrade reticulocytes retain only half of the iron that entered, but over 90% of iron entering normal cells remains within. Iron unloading is ineffective inside the Belgrade vesicle; 85% of iron that entered on transferrin returned to the medium after exocytosis, whereas only 45% of iron entering normal reticulocytes exits. Ineffective utilization of iron in or near Belgrade endosomes accounts for the Belgrade defect.

Perturbation of intracellular pH by DIDS on endocytosis of transferrin and iron uptake in rabbit reticulocytes

DIDS (4,4′-diisothiocyanostilbene-2,2′-disulfonic acid) inhibited transferrin and iron uptake by rabbit reticulocytes in a dose-dependent manner. Measurement of intracellular pH shows that DIDS neutralized the pH in the intracellular vesicles and at the same time, rendered the cytoplasmic pH more acidic. The latter may be the result of a perturbance in the acid-extruding mechanism(s) by DIDS, a known anion exchange blocker. Examination of the single-cycle endocytosis of transferrin with pulse-chased technique suggests that DIDS retarded transferrin internalization, iron unloading and transferrin receptor recycling in the cells.

The Occurrence of Phytoferritin and Its Relationship to Effectiveness of Soybean Nodules

Polyacrylamide gel electrophoresis and electron microscopy revealed that accumulation of iron-protein in soybean nodules is influenced by nodule age, mutation in bradyrhizobia, and rhizobial/bradyrhizobial strain-soybean cultivar interactions. Iron-protein concentrations (micrograms per milligram protein) were inversely related to heme concentrations (nanomoles per milligram protein), with correlation coefficients (r values) ranging from -0.98 in young nodules to -0.83 in mature ones. Bradyrhizobium japonicum symbiotic mutants HS 129 and HS 145 (Nod(+) Fix(-)) produced nodules high in iron-protein. Electrophoresis of homogenate prepared from nodules on Lee 68 produced by B. japonicum HS 129 yielded two different forms of the iron-proteins, 570 and 600 kilodaltons. The 570 kilodalton iron-protein isolated by preparative polyacrylamide gel electrophoresis behaved like horse-spleen-ferritin in responses to iron-stains, heat stability, ultraviolet absorption spectrum, iron unloading and reloading, and characteristic appearance in electron micrographs. These properties led to the conclusion that the 570 kilodalton iron-protein is phytoferritin. The nodule phytoferritin differed from horse-spleen-ferritin in electrophoretic mobility, serological properties, and molecular size and was distinct from most other known phytoferritins in that it was composed of different subunit types.