Effect of repeated apotransferrin administrations on serum iron parameters in patients undergoing myeloablative conditioning and allogeneic stem cell transplantation

Iron overload-induced oxidative stress in myelodysplastic syndromes and its cellular sequelae

The myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell disorders. MDS patients often require red blood cell transfusions, resulting in iron overload (IOL). IOL increases production of reactive oxygen species (ROS), oxygen free radicals. We review and illustrate how IOL-induced ROS influence cellular activities relevant to MDS pathophysiology. ROS damage lipids, nucleic acids in mitochondrial and nuclear DNA, structural proteins, transcription factors and enzymes. Cellular consequences include decreased metabolism and tissue and organ dysfunction. In hematopoietic stem cells (HSC), consequences of ROS include decreased glycolysis, shifting the cell from anaerobic to aerobic metabolism and causing HSC to exit the quiescent state, leading to HSC exhaustion or senescence. ROS oxidizes DNA bases, resulting in accumulation of mutations. Membrane oxidation alters fluidity and permeability. In summary, evidence indicates that IOL-induced ROS alters cellular signaling pathways resulting in toxicity to organs and hematopoietic cells, in keeping with adverse clinical outcomes in MDS.

Adjunctive transferrin to reduce the emergence of antibiotic resistance in Gram-negative bacteria

Background

New strategies are needed to slow the emergence of antibiotic resistance among bacterial pathogens. In particular, society is experiencing a crisis of antibiotic-resistant infections caused by Gram-negative bacterial pathogens and novel therapeutics are desperately needed to combat such diseases. Acquisition of iron from the host is a nearly universal requirement for microbial pathogens—including Gram-negative bacteria—to cause infection. We have previously reported that apo-transferrin (lacking iron) can inhibit the growth of Staphylococcus aureus in culture and diminish emergence of resistance to rifampicin.

Objectives

To define the potential of apo-transferrin to inhibit in vitro growth of Klebsiella pneumoniae and Acinetobacter baumannii, key Gram-negative pathogens, and to reduce emergence of resistance to antibiotics.

Methods

The efficacy of apo-transferrin alone or in combination with meropenem or ciprofloxacin against K. pneumoniae and A. baumannii clinical isolates was tested by MIC assay, time–kill assay and assays for the selection of resistant mutants.

Results

We confirmed that apo-transferrin had detectable MICs for all strains tested of both pathogens. Apo-transferrin mediated an additive antimicrobial effect for both antibiotics against multiple strains in time–kill assays. Finally, adding apo-transferrin to ciprofloxacin or meropenem reduced the emergence of resistant mutants during 20 day serial passaging of both species.

Conclusions

These results suggest that apo-transferrin may have promise to suppress the emergence of antibiotic-resistant mutants when treating infections caused by Gram-negative bacteria.

Enhanced labile plasma iron in hematopoietic stem cell transplanted patients promotes Aspergillus outgrowth

Serum-enhanced labile plasma iron in patients undergoing allogeneic HSCT is critical for Aspergillus fumigatus growth in vitro. Transferrin iron in serum is inaccessible for A fumigatus, and uptake of iron in the form of eLPI involves fungal siderophores.

Retrospective Evaluation of Relationship Between Iron Overload and Transplantation Complications in Pediatric Patient Who Underwent Allogeneic Stem Cell Transplantation Due to Acute Leukemia and Myelodysplastic Syndrome

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is a curative therapy option for hematologic malignancies. Iron overload is common in this patient group and can impact short-term and long-term nonrelapse mortality.

STUDY DESIGN

Retrospective observational cohort study.

AIMS

To evaluate the effect of iron load on early and late HSCT outcomes in patients with acute leukemia and myelodysplasia to assess the necessity of reducing iron load.

PATIENTS AND METHODS

Sixty patients who underwent HSCT in pediatric stem cell transplantation unit between 2000 and 2012 were evaluated retrospectively. The patients were divided into those with pretransplantation serum ferritin levels above and below the median value of 1299 ng/mL.

RESULTS

Forty-two (70%) of the patients were male, mean ages of the low and high ferritin groups were 85.43±9.42 and 118.56±10.04 months, respectively. Acute graft-versus-host disease (GVHD) within the first 100 days and acute liver GVHD were significantly more common in the high ferritin group (P<0.011 for both). Ferritin level was not associated with rates of engraftment syndrome, veno-occlusive disease, early/late infection, relapse, or overall and disease-free survival.

CONCLUSIONS

In our study, significant result especially in terms of acute liver GVHD, was important to emphasize the need to be more careful in terms of acute liver GVHD risk in early liver pathologies in patients with high levels of ferritin after transplantation. In future large studies may be helpful to explain the relationship between acute liver GVHD and high ferritin levels.

Iron overload and its impact on outcome of patients with hematological diseases

Systemic iron overload (SIO) is a common challenge in patients with hematological diseases and develops as a result of ineffective erythropoiesis, multiple red blood cell (RBC) transfusions and disease-specific therapies. Iron homeostasis is tightly regulated as there is no physiological pathway to excrete iron from the body. Excess iron is, therefore, stored in tissues like liver, heart and bone marrow and can lead to progressive organ damage. The presence of free iron in the form of non-transferrin bound iron (NTBI) is especially detrimental. Reactive oxygen species can also cause stromal damage in the bone marrow and promote leukemic cell growth in vitro. In acute leukemias and myelodysplastic syndromes outcome is worse in patients with SIO compared to patients without. Especially in patients undergoing allogeneic HSCT presence of NTBI before or during transplant has been shown to negatively affect non-relapse mortality and overall survival. Although the mechanisms, of how these effects are mediated by SIO are not very well understood monitoring of iron status by serum markers and imaging techniques is, therefore, mandatory especially in these patients. Whether peri-interventional iron chelation may improve outcome of these patients is part of current clinical research.

Apotransferrin in Combination with Ciprofloxacin Slows Bacterial Replication, Prevents Resistance Amplification, and Increases Antimicrobial Regimen Effect

There has been renewed interest in combining traditional small-molecule antimicrobial agents with nontraditional therapies to potentiate antimicrobial effects. Apotransferrin, which decreases iron availability to microbes, is one such approach. We conducted a 48-h one-compartment in vitro infection model to explore the impact of apotransferrin on the bactericidal activity of ciprofloxacin. The challenge panel included four Klebsiella pneumoniae isolates with ciprofloxacin MIC values ranging from 0.08 to 32 mg/liter. Each challenge isolate was subjected to an ineffective ciprofloxacin monotherapy exposure (free-drug area under the concentration-time curve over 24 h divided by the MIC [AUC/MIC ratio] ranging from 0.19 to 96.6) with and without apotransferrin. As expected, the no-treatment and apotransferrin control arms showed unaltered prototypical logarithmic bacterial growth. We identified relationships between exposure and change in bacterial density for ciprofloxacin alone (R ² = 0.64) and ciprofloxacin in combination with apotransferrin (R ² = 0.84). Addition of apotransferrin to ciprofloxacin enabled a remarkable reduction in bacterial density across a wide range of ciprofloxacin exposures. For instance, at a ciprofloxacin AUC/MIC ratio of 20, ciprofloxacin monotherapy resulted in nearly 2 log₁₀ CFU increase in bacterial density, while the combination of apotransferrin and ciprofloxacin resulted in 2 log₁₀ CFU reduction in bacterial density. Furthermore, addition of apotransferrin significantly reduced the emergence of ciprofloxacin-resistant subpopulations compared to monotherapy. These data demonstrate that decreasing the rate of bacterial replication with apotransferrin in combination with antimicrobial therapy represents an opportunity to increase the magnitude of the bactericidal effect and to suppress the growth rate of drug-resistant subpopulations.

Transferrin and transferrin receptors update

In vertebrates, transferrin (Tf) safely delivers iron through circulation to cells. Tf-bound iron is incorporated through Tf receptor (TfR) 1-mediated endocytosis. TfR1 can mediate cellular uptake of both Tf and H-ferritin, an iron storage protein. New World arenaviruses, which cause hemorrhagic fever, and Plasmodium vivax use TfR1 for entry into host cells. Human TfR2, another receptor for Tf, is predominantly expressed in hepatocytes and erythroid precursors, and holo-Tf dramatically upregulates its expression. TfR2 forms a complex with hemochromatosis protein, HFE, and serves as a component of the iron sensing machinery in hepatocytes. Defects in TfR2 cause systemic iron overload, hemochromatosis, through down-regulation of hepcidin. In erythroid cells, TfR2 forms a complex with the erythropoietin receptor and regulates erythropoiesis. TfR2 facilitates iron transport from lysosomes to mitochondria in erythroblasts and dopaminergic neurons. Administration of apo-Tf, which scavenges free iron, has been explored for various clinical conditions including atransferrinemia, iron overload, and tissue ischemia. Apo-Tf has also been shown to ameliorate anemia in animal models of β-thalassemia. In this review, I provide an update and summary on our knowledge of mammalian Tf and its receptors.

Enhanced labile plasma iron and outcome in acute myeloid leukaemia and myelodysplastic syndrome after allogeneic haemopoietic cell transplantation (ALLIVE): a prospective, multicentre, observational trial

BACKGROUND

The effect of systemic iron overload on outcomes after allogeneic haemopoietic cell transplantation (HCT) has been a matter of substantial debate. We aimed to investigate the predictive value of both stored (MRI-derived liver iron content) and biologically active iron (enhanced labile plasma iron; eLPI) on post-transplantation outcomes in patients with acute myeloid leukaemia or myelodysplastic syndrome undergoing allogenic HCT.

METHODS

The prospective, multicentre, observational, ALLogeneic Iron inVEstigators (ALLIVE) trial recruited patients at five centres in Germany. We enrolled patients with acute myeloid leukaemia or myelodysplastic syndrome undergoing allogeneic HCT. Patients underwent cytotoxic conditioning for a median of 6 days (IQR 6-7) before undergoing allogeneic HCT and were followed up for up to 1 year (±3 months) post-transplantation. eLPI was measured in serum samples with the FeROS eLPI kit (Aferrix, Tel-Aviv, Israel) and values greater than 0·4 μmol/L were considered to represent raised eLPI. Liver iron content was measured by MRI. The primary endpoints were the quantitative delineation of eLPI dynamics during allogeneic HCT and the correlation coefficient between liver iron content before HCT and dynamic eLPI (eLPI_dyn; maximum eLPI minus baseline eLPI). All patients with available data were included in all analyses. This is the final analysis of this completed trial, which is registered with ClinicalTrials.gov, number NCT01746147.

FINDINGS

Between Dec 13, 2012, and Dec 23, 2014, 112 patients underwent allogeneic HCT. Liver iron content before allogeneic HCT was not significantly correlated with eLPI_dyn (ρ=0·116, p=0·22). Serum eLPI concentrations rapidly increased during conditioning, and most (79 [73%] of 108) patients had raised eLPI by the day of transplantation. Patients with a pretransplant liver iron content greater than or equal to 125 μmol/g had an increased incidence of non-relapse mortality (20%, 95% CI 14-26) compared with those with lower concentrations (7%, 2-12; p=0·039) at day 100. Patients who had raised eLPI at baseline also had a significantly increased incidence of non-relapse mortality at day 100 (33%, 15-52) compared with those who had normal eLPI at baseline (7%, 2-13; p=0·00034).

INTERPRETATION

eLPI is a possible biological mediator of iron-related toxicity. Peritransplantation eLPI-scavenging strategies could be explored in prospective interventional clinical trials for patients with systemic iron overload.

FUNDING

The Technical University of Dresden and Novartis.

Therapeutic use of transferrin to modulate anemia and conditions of iron toxicity

As the main iron transporter, transferrin delivers iron to target tissues like the bone marrow for erythropoiesis. Also, by binding free iron, transferrin prevents formation of reactive oxygen species. Transferrin deficiency due to congenital hypotransferrinemia is characterized by anemia as well as oxidative stress related to toxic free iron. Transferrin supplementation may be beneficial in two ways. First, transferrin can correct anemia by modulating the amount of iron that is available for erythropoiesis. This is obvious for patients that suffer from hypotransferrinemia, but may also have beneficial effects for β-thalassemia patients. Second, under conditions of iron overload, transferrin reduces oxidative stress by binding free iron in the circulation and in tissues. Hereby, transferrin protects the host against the reactive oxygen species that can be formed as a consequence of free iron. This beneficial effect is shown in hematological patients undergoing chemotherapy and stem cell transplantation. Transferrin may also be beneficial in lung injury, ischemia-reperfusion injury and hypomyelination. This review summarizes the preclinical and clinical data on the efficacy of exogenous transferrin administration to modulate certain forms of anemia and to prevent the toxic effects of free iron. Thereby, we show that transferrin has promising therapeutic potential in a wide variety of conditions.

Disruption of Iron Regulation after Radiation and Donor Cell Infusion

Iron overload is common in patients undergoing hematopoietic cell transplantation (HCT). Peritransplant events, such as total body irradiation (TBI), and the effects of donor cell infusion may contribute to iron overload, in addition to disease-associated anemia and RBC transfusions. Using murine models we show complex time- and dose-dependent interactions of TBI and transplanted donor cells with expression patterns of iron regulatory genes in the liver. Infusion of allogeneic or syngeneic donor T lymphocytes increased serum iron, transiently up-regulated interleukin-6 (IL-6) and hepcidin (Hamp), and down-regulated ferroportin1 (Fpn1). After 7 to 14 days, however, changes were significant only with allogeneic cells. TBI (200 to 400 Gy) also induced IL-6 and Hamp expression but had little effect on Fpn1. TBI combined with allogeneic donor cell infusion resulted in modest early up-regulation of IL-6, followed by a decline in IL-6 levels and Hamp as well as Fpn1, and was accompanied by increased liver iron content. Injection of Fas ligand-deficient T lymphocytes from gld mice resulted in substantially lower alterations of gene expression than infusion of wild-type T cells. The agonistic anti-Fas antibody, JO2, triggered early up-regulation of Stat3 and IL-6, followed by an increase in Hamp and decreased expression of Fpn1 by 7 to 14 days, implicating Fas as a key modulator of gene expression in HCT. Minimal histologic changes were observed in mouse liver and duodenum. These data show profound and interacting effects of TBI and cell transplantation on the expression of iron regulatory genes in murine recipients. Alterations are largely related to induction of cytokines and Fas-dependent signals.

Transferrin-mediated iron sequestration as a novel therapy for bacterial and fungal infections

Pathogenic microbes must acquire essential nutrients, including iron, from the host in order to proliferate and cause infections. Iron sequestration is an ancient host antimicrobial strategy. Thus, enhancing iron sequestration is a promising, novel anti-infective strategy. Unfortunately, small molecule iron chelators have proven difficult to develop as anti-infective treatments, in part due to unacceptable toxicities. Iron sequestration in mammals is predominantly mediated by the transferrin family of iron-binding proteins. In this review, we explore the possibility of administering supraphysiological levels of exogenous transferrin as an iron sequestering therapy for infections, which could overcome some of the problems associated with small molecule chelation. Recent studies suggest that transferrin delivery may represent a promising approach to augment both natural resistance and traditional antibiotic therapy.

Efficacy and safety of oral deferasirox treatment in the posttransplant period for patients who have undergone allogeneic hematopoietic stem cell transplantation (alloHSCT)

Iron overload is considered to be associated with various complications in patients who undergo both allogeneic (allo) and autologous hematopoietic stem cell transplantation (HSCT). A total of 23 alloHSCT recipients who started deferasirox treatment due to hyperferritinemia (ferritin ≥1,000 ng/mL) were analyzed retrospectively. The demographic characteristics, data about deferasirox treatment, and history of phlebotomy were obtained from the patients' files. The reduction in posttreatment ferritin levels was found statistically significant compared with pretreatment ferritin levels in both def+phlebotomy and def+nonphlebotomy groups (p = 0.025 and 0.017, respectively). The liver enzymes, especially ALT and bilirubins, were significantly reduced after the treatment (p < 0.05). The deferasirox treatment reduced pretreatment ferritin levels below the level of 1,000 ng/mL in a median period of 94 days, and these data were found to be statistically significant (p < 0.05). The median treatment duration time with deferasirox was 94 days (72-122). The most common adverse effects were nausea and vomiting, which occurred in three of the patients (13%). In conclusion, our data suggest that oral deferasirox treatment may be used as a safe and effective alternative method for reducing iron overload in alloHSCT recipients, whether combined with or without phlebotomy.

Preanalytical factors and reference intervals for serum hepcidin LC-MS/MS method

BACKGROUND

Hepcidin is a potential biomarker for anemia of chronic diseases and disorders of iron metabolism. Thus, data of preanalytical factors, reference values and method characteristics are critical for clinical use of hepcidin determination.

METHODS

We studied the effects of sample storage, sampling device and a meal on hepcidin levels using a liquid-chromatography tandem mass spectrometric (LC-MS/MS) method for serum hepcidin. Age- and gender-dependent reference values were determined using serum samples from healthy volunteers (n=231). The results were also compared with those obtained by a commercial competitive ELISA for hepcidin.

RESULTS

In serum samples, hepcidin is stable for one day at room temperature, six days at +4°C and at least 42 days at -20°C. Breakfast or type of sampling device does not affect hepcidin concentration. Significantly lower hepcidin concentrations were observed in women ≤50 than >50 years of age or in men (p<0.0001 for both). Reference values for females aged 18-50 years were 0.4-9.2 nmol/L, for those >50 years 0.7-16.8 nmol/L and for males ≥18 years 1.1-15.6 nmol/L. Comparison with a competitive ELISA showed poor correlation.

CONCLUSIONS

Fasting before sampling and type of blood collection were not critical. Samples can be transported to laboratory at room temperature if they arrive within a day. Significantly lower concentrations of serum hepcidin were observed in menstruating than in post-menopausal women and in men.

Transferrin therapy ameliorates disease in beta-thalassemic mice

Individuals with beta-thalassemia develop progressive systemic iron overload, resulting in high morbidity and mortality. These complications are caused by labile plasma iron, which is taken up by parenchymal cells in a dysregulated manner; in contrast, erythropoiesis depends on transferrin-bound iron uptake via the transferrin receptor. We hypothesized that the ineffective erythropoiesis and anemia observed in beta-thalassemia might be ameliorated by increasing the amount of circulating transferrin. We tested the ability of transferrin injections to modulate iron metabolism and erythropoiesis in Hbb(th1/th1) mice, an experimental model of beta-thalassemia. Injected transferrin reversed or markedly improved the thalassemia phenotype in these mice. Specifically, transferrin injections normalized labile plasma iron concentrations, increased hepcidin expression, normalized red blood cell survival and increased hemoglobin production; this treatment concomitantly decreased reticulocytosis, erythropoietin abundance and splenomegaly. These results indicate that transferrin is a limiting factor contributing to anemia in these mice and suggest that transferrin therapy might be beneficial in human beta-thalassemia.

Iron overload, hematopoietic cell transplantation, and graft-versus-host disease

Many patients who undergo hematopoietic cell transplantation (HCT) present with anemia and have received red blood cell transfusions before HCT. As a result, iron overload is frequent and appears to be particularly prominent in patients with myelodysplastic syndromes. There is evidence that peritransplant events contribute to further iron accumulation, although the mechanism that disrupts normal iron homeostasis remains to be determined. Recent studies suggest that iron overload, as determined by ferritin levels, a surrogate marker for iron, is a risk factor for increased non-relapse mortality after HCT. Iron overload is associated with an increased rate of infections, in particular with fungal organisms. Furthermore anecdotal data suggest that increased hepatic iron may mimic the clinical picture of (chronic) graft-versus-host-disease (GVHD). Whether excess iron contributes to GVHD and whether iron depletion, be it by phlebotomy or chelation, reduces the post-transplantation complication rate and improves transplant outcome is yet to be determined.

Transplantation of allogeneic T cells alters iron homeostasis in NOD/SCID mice

Iron overload is common in patients undergoing allogeneic hematopoietic cell transplantation (HCT), but the mechanisms leading to overload are unknown. Here, we determined iron levels and the expression of iron regulatory proteins in the liver and gut of nonobese diabetic-severe combined immunodeficient (NOD/SCID) mice that underwent transplantation with syngeneic (histocompatible) or allogeneic (histoincompatible) T lymphocytes. Infusion of histoincompatible T cells resulted in a significant rise in serum iron levels and liver iron content. Iron deposition was accompanied by hepatocyte injury and intestinal villous damage. Feeding of low- or high-iron diet was associated with appropriate ferroportin 1 and hepcidin responses in mice given histocompatible T cells, whereas mice given histoincompatible T cells showed inappropriate up-regulation of duodenal ferroportin 1 and a loss of expression of hepatic hepcidin. These findings suggest that alloreactive T cell-dependent signals induced dysregulation of intestinal iron absorption, which contributed to liver iron overload after HCT.

The effects of lactoferrin in a rat model of catecholamine cardiotoxicity

Lactoferrin is recently under intense investigation because of its proposed several pharmacologically positive effects. Based on its iron-binding properties and its physiological presence in the human body, it may have a significant impact on pathological conditions associated with iron-catalysed reactive oxygen species (ROS). Its effect on a catecholamine model of myocardial injury, which shares several pathophysiological features with acute myocardial infarction (AMI) in humans, was examined. Male Wistar rats were randomly divided into four groups according to the received medication: control (saline), isoprenaline (ISO, 100 mg kg(-1) s.c.), bovine lactoferrin (La, 50 mg kg(-1) i.v.) or a combination of La + ISO in the above-mentioned doses. After 24 h, haemodynamic functional parameters were measured, a sample of blood was withdrawn and the heart was removed for analysis of various parameters. Lactoferrin premedication reduced some impairment caused by ISO (e.g. a stroke volume decrease, an increase in peripheral resistance and calcium overload). These positive effects were likely to have been mediated by the positive inotropic effect of lactoferrin and by inhibition of ROS formation due to chelation of free iron. The failure of lactoferrin to provide higher protection seems to be associated with the complexity of catecholamine cardiotoxicity and with its hydrophilic character.