Iron Sequestration In Macrophages Research Articles

Effect of Eculizumab on Iron Metabolism in Transfusion-independent Patients With Paroxysmal Nocturnal Hemoglobinuria

Effect of Eculizumab on Iron Metabolism in Transfusion-independent Patients With Paroxysmal Nocturnal Hemoglobinuria

Anemia and iron deficiency in cancer patients: the role of intravenous iron supplements (a literature review)

Anemia in patients with malignancies is a common disorder that has a markedly negative impact on quality of life and overall prognosis. The pathogenesis of anemia is complex and multifactorial, depending on the type and stage of malignancy, nutritional status, renal function, age and gender, cytostatic drug, dose, and chemotherapeutic regimen, with iron deficiency often being the main and potentially treatable factor for anemia. In cancer patients, it can be caused by various concomitant mechanisms, including bleeding (e.g., in malignant gastrointestinal tumors or after surgery), malnutrition, medication, and hepcidin-induced iron sequestration in macrophages, with subsequent iron-deficient erythropoiesis. The variety of clinical manifestations of anemia makes it challenging to establish universal criteria to develop optimal treatments. Current therapy for anemia in malignant tumors includes replacement therapy with an iron supplement, erythropoiesis-stimulating agents (erythropoietins), and blood transfusions. However, blood transfusions should be minimized due to the high risks and costs. Therapy with an iron supplement is an effective approach to correcting the iron deficiency. It can increase the efficacy of erythropoiesis-stimulating drugs and reduce the need for blood transfusions. Published guidelines suggest the wide use of intravenous iron supplements. This article discusses possible approaches to treating iron deficiency in cancer patients in various clinical settings. We build on current guidelines and emphasize the need for further research in this area.

Computational Modeling of Macrophage Iron Sequestration during Host Defense against Aspergillus.

ABSTRACTIron is essential to the virulence of Aspergillus species, and restricting iron availability is a critical mechanism of antimicrobial host defense. Macrophages recruited to the site of infection are at the crux of this process, employing multiple intersecting mechanisms to orchestrate iron sequestration from pathogens. To gain an integrated understanding of how this is achieved in aspergillosis, we generated a transcriptomic time series of the response of human monocyte-derived macrophages to Aspergillus and used this and the available literature to construct a mechanistic computational model of iron handling of macrophages during this infection. We found an overwhelming macrophage response beginning 2 to 4 h after exposure to the fungus, which included upregulated transcription of iron import proteins transferrin receptor-1, divalent metal transporter-1, and ZIP family transporters, and downregulated transcription of the iron exporter ferroportin. The computational model, based on a discrete dynamical systems framework, consisted of 21 3-state nodes, and was validated with additional experimental data that were not used in model generation. The model accurately captures the steady state and the trajectories of most of the quantitatively measured nodes. In the experimental data, we surprisingly found that transferrin receptor-1 upregulation preceded the induction of inflammatory cytokines, a feature that deviated from model predictions. Model simulations suggested that direct induction of transferrin receptor-1 (TfR1) after fungal recognition, independent of the iron regulatory protein-labile iron pool (IRP-LIP) system, explains this finding. We anticipate that this model will contribute to a quantitative understanding of iron regulation as a fundamental host defense mechanism during aspergillosis.IMPORTANCE Invasive pulmonary aspergillosis is a major cause of death among immunosuppressed individuals despite the best available therapy. Depriving the pathogen of iron is an essential component of host defense in this infection, but the mechanisms by which the host achieves this are complex. To understand how recruited macrophages mediate iron deprivation during the infection, we developed and validated a mechanistic computational model that integrates the available information in the field. The insights provided by this approach can help in designing iron modulation therapies as anti-fungal treatments.

Iron in airway macrophages and infective exacerbations of chronic obstructive pulmonary disease

BackgroundExcess pulmonary iron has been implicated in the pathogenesis of lung disease, including asthma and COPD. An association between higher iron content in sputum macrophages and infective exacerbations of COPD has previously been demonstrated.ObjectivesTo assess the mechanisms of pulmonary macrophage iron sequestration, test the effect of macrophage iron-loading on cellular immune function, and prospectively determine if sputum hemosiderin index can predict infectious exacerbations of COPD.MethodsIntra- and extracellular iron was measured in cell-line-derived and in freshly isolated sputum macrophages under various experimental conditions including treatment with exogenous IL-6 and hepcidin. Bacterial uptake and killing were compared in the presence or absence of iron-loading. A prospective cohort of COPD patients with defined sputum hemosiderin indices were monitored to determine the annual rate of severe infectious exacerbations.ResultsGene expression studies suggest that airway macrophages have the requisite apparatus of the hepcidin-ferroportin axis. IL-6 and hepcidin play roles in pulmonary iron sequestration, though IL-6 appears to exert its effect via a hepcidin-independent mechanism. Iron-loaded macrophages had reduced uptake of COPD-relevant organisms and were associated with higher growth rates. Infectious exacerbations were predicted by sputum hemosiderin index (β = 0.035, p = 0.035).ConclusionsWe demonstrate in-vitro and population-level evidence that excess iron in pulmonary macrophages may contribute to recurrent airway infection in COPD. Specifically, IL-6-dependent iron sequestration by sputum macrophages may result in immune cell dysfunction and ultimately lead to increased frequency of infective exacerbation.

Serum neutrophil gelatinase-associated lipocalin for predicting anemia of inflammation in children with urinary tract infection.

Anemia of inflammation (IA), the second most common cause of childhood anemia, results from macrophage iron sequestration and impaired erythropoiesis. Neutrophil gelatinase-associated lipocalin (NGAL) plays an important role in innate microbial immunity through its influence on intracellular iron homeostasis and inhibition of erythropoiesis. The predictive value of NGAL in IA was assessed in 74 children (age 6.30 ±3.64 months) with the first episode of urinary tract infection (UTI). Anemia of inflammation was found in 50% of children, including those with non-febrile UTI, and delayed onset of anemia was observed in 20% of children. There were no differences in NGAL levels between the anemic and non-anemic children, and no correlations between NGAL and hemoglobin (HGB) levels and red blood cell (RBC) count. In multivariate logistic regression analysis elevated C-reactive protein (CRP) was only independently associated with the presence of anemia in children with UTI [OR (95% CI): 1.128 (1.005-1.265), p = 0.040]. In stepwise multiple analysis age independently correlated with RBC (β = 0.051, p = 0.001), while CRP independently correlated with HGB (β = –0.037, p = 0.027) and RBC (β = –0.022, p = 0.014). ROC analysis demonstrated better diagnostic profiles for CRP, procalcitonin (PCT) and fever duration for predicting the risk of IA than NGAL (AUC: 0.690, 0.669, 0.678 vs. 0.638, respectively). Despite the increase in HGB levels after 4-5 weeks from the onset of UTI, HGB values were still significantly lower in the anemic than in non-anemic children. NGAL was not useful for predicting IA in UTI, since its diagnostic value was inferior to conventional inflammatory markers.

Interferon-gamma promotes iron export in human macrophages to limit intracellular bacterial replication.

Salmonellosis and listeriosis together accounted for more than one third of foodborne illnesses in the United States and almost half the hospitalizations for gastrointestinal diseases in 2018 while tuberculosis afflicted over 10 million people worldwide causing almost 2 million deaths. Regardless of the intrinsic virulence differences among Listeria monocytogenes, Salmonella enterica and Mycobacterium tuberculosis, these intracellular pathogens share the ability to survive and persist inside the macrophage and other cells and thrive in iron rich environments. Interferon-gamma (IFN-γ) is a central cytokine in host defense against intracellular pathogens and has been shown to promote iron export in macrophages. We hypothesize that IFN-γ decreases iron availability to intracellular pathogens consequently limiting replication in these cells. In this study, we show that IFN-γ regulates the expression of iron-related proteins hepcidin, ferroportin, and ferritin to induce iron export from macrophages. Listeria monocytogenes, S. enterica, and M. tuberculosis infections significantly induce iron sequestration in human macrophages. In contrast, IFN-γ significantly reduces hepcidin secretion in S. enterica and M. tuberculosis infected macrophages. Similarly, IFN-γ-activated macrophages express higher ferroportin levels than untreated controls even after infection with L. monocytogenes bacilli; bacterial infection greatly down-regulates ferroportin expression. Collectively, IFN-γ significantly inhibits pathogen-associated intracellular iron sequestration in macrophages and consequently retards the growth of intracellular bacterial pathogens by decreasing iron availability.

Iron Regulation in Elderly Asian Elephants (Elephas maximus) Chronically Infected With Mycobacterium tuberculosis.

Restriction of nutrients to pathogens (nutritional immunity) is a critical innate immune response mechanism that operates when pathogens such as Mycobacterium tuberculosis have the potential to evade humoral immunity. Tuberculosis is of growing concern for zoological collections worldwide and is well-illustrated by infections of Asian and African elephants, where tuberculosis is difficult to diagnose. Here, we investigated hematological parameters and iron deposition in liver, lung, and spleen of three Asian elephants (Elephas maximus) infected with Mycobacterium tuberculosis. For reference purposes, we analyzed tissue samples from control M. tuberculosis-negative elephants with and without evidence of inflammation and/or chronic disease. Molecular analyses of bacterial lesions of post mortally collected tissues confirmed M. tuberculosis infection in three elephants. DNA sequencing of the bacterial cultures demonstrated a single source of infection, most likely of human origin. In these elephants, we observed moderate microcytic anemia as well as liver (mild), lung (moderate) and spleen (severe) iron accumulation, the latter mainly occurring in macrophages. Macrophage iron sequestration in response to infection and inflammation is caused by inhibition of iron export via hepcidin-dependent and independent mechanisms. The hepatic mRNA levels of the iron-regulating hormone hepcidin were increased in only one control elephant suffering from chronic inflammation without mycobacterial infection. By contrast, all three tuberculosis-infected elephants showed low hepcidin mRNA levels in the liver and low serum hepcidin concentrations. In addition, hepatic ferroportin mRNA expression was high. This suggests that the hepcidin/ferroportin regulatory system aims to counteract iron restriction in splenic macrophages in M. tuberculosis infected elephants to provide iron for erythropoiesis and to limit iron availability for a pathogen that predominantly proliferates in macrophages. Tuberculosis infections appear to have lingered for more than 30 years in the three infected elephants, and decreased iron availability for mycobacterial proliferation may have forced the bacteria into a persistent, non-proliferative state. As a result, therapeutic iron substitution may not have been beneficial in these elephants, as this therapy may have enhanced progression of the infection.

Role of the hepcidin-ferroportin axis in pathogen-mediated intracellular iron sequestration in human phagocytic cells

AbstractUpon infection, pathogen and host compete for the same iron pool, because this trace metal is a crucial micronutrient for all living cells. Iron dysregulation in the host is strongly associated with poor outcomes in several infectious diseases, including tuberculosis, AIDS, and malaria, and inefficient iron scavenging by pathogens severely affects their virulence. Hepcidin is the master regulator of iron homeostasis in vertebrates, responsible for diminishing iron export from macrophages during iron overload or infection. Hepcidin regulation in hepatocytes is well characterized and mostly dependent on interleukin-6 signaling during inflammation, although in myeloid cells, hepcidin induction and the mechanisms leading to intracellular iron regulation remain elusive. Here we show that activation of different Toll-like receptors (TLRs) by their respective ligands leads to increased iron sequestration in macrophages. By measuring the transcriptional levels of iron-related proteins (eg, hepcidin, ferroportin, and ferritin), we observed that TLR signaling can induce intracellular iron sequestration in macrophages through 2 independent but redundant mechanisms. Interestingly, TLR2 ligands or infection with Listeria monocytogenes lead to direct ferroportin transcriptional downregulation, whereas TLR4 ligands, such as lipopolysaccharide, induce hepcidin expression. Infection with Mycobacterium bovis Bacillus Calmette-Guerin promotes intracellular iron sequestration through both hepcidin upregulation and ferroportin downregulation. This is the first study in which TLR1-9–mediated iron homeostasis in human macrophages was evaluated, and the outcome of this study elucidates the mechanism of iron dysregulation in macrophages during infection.

Involvement of hepcidin in iron metabolism dysregulation in Gaucher disease.

Gaucher disease (GD) is an inherited deficiency of glucocerebrosidase leading to accumulation of glucosylceramide in tissues such as the spleen, liver, and bone marrow. The resulting lipid-laden macrophages lead to the appearance of “Gaucher cells”. Anemia associated with an unexplained hyperferritinemia is a frequent finding in GD, but whether this pathogenesis is related to an iron metabolism disorder has remained unclear. To investigate this issue, we explored the iron status of a large cohort of 90 type I GD patients, including 66 patients treated with enzyme replacement therapy. Ten of the patients treated with enzyme replacement were followed up before and during treatment. Serum levels of hepcidin, the iron regulatory peptide, remained within the physiological range, while the transferrin saturation was slightly decreased in children. Inflammation-independent hyperferritinemia was found in 65% of the patients, and Perl’s staining of the spleen and marrow smear revealed iron accumulation in Gaucher cells. Treated patients exhibited reduced hyperferritinemia, increased transferrin saturation and transiently increased systemic hepcidin. In addition, the hepcidin and ferritin correlation was markedly improved, and, in most patients, the hemoglobin level was normalized. To further explore eventual iron sequestration in macrophages, we produce a Gaucher cells model by treating the J774 macrophage cell line with a glucocerebrosidase inhibitor and showed induced local hepcidin and membrane retrieval of the iron exporter, ferroportin. These data reveal the involvement of Gaucher cells in abnormal iron sequestration, which may explain the mechanism of hyperferritinemia in GD patients. Local hepcidin-ferroportin interaction was involved in this pathogenesis.

Investigation of Iron Metabolism for Regulating Megakaryopoiesis and Platelet Count According to the Mechanisms of Anemia

Iron deficiency anemia (IDA) is characterized by depletion of total body iron stores or a poor supply of plasma iron. By contrast, chronic inflammation makes iron unavailable for hematopoiesis through a cytokinemediated cascade and leads to a condition known as anemia of chronic disease (AOC). However, the laboratory data regarding the regulatory role of iron metabolism on platelet count has not been fully discussed yet. In this study, we investigated the relationship between iron status and platelet production according to different anemic mechanisms representing different iron metabolisms. The study included a total of 759 specimens. Blood samples were obtained through venipuncture. The complete blood count was measured using an Advia 2120 (Siemens Healthcare Diagnostics Inc., USA). Biochemical indices including iron level were estimated using a Toshiba chemical analyzer (Toshiba, Japan). In the AOC group, we found a significant relationship between platelet count and serum iron level (p < 0.27), whereas there was no correlation in the IDA group. Moreover, when the AOC patient group was subdivided by serum iron level, a remarkable difference was observed as follows. The platelet count was significantly correlated with serum iron level only in the AOC group with decreased serum iron levels (serum iron < 50 µg/dL) (p < 0.0001), while there was no correlation in the AOC group with normal serum iron levels (serum iron 50 - 100 µg/dL). Iron deficiency in AOC involves upregulated hepcidin production induced by elevated inflammatory cytokines. This can cause increased iron sequestration in macrophages and decreased iron absorption for bone marrow. The condition of decreased megakaryocytic iron supply makes megakaryocytes with higher ploidy which can release more platelets than lower ploidy. Moreover, reactive thrombocytosis in inflammatory states occurs by cytokine cascades involving interleukin 6 and thrombopoietin in AOC. These two features may enhance thrombocytosis in patients of AOC with decreased iron level. In the future, further study should be performed to elucidate regulating mechanism of iron metabolism for megakaryopoiesis in AOC patients, and guide proper supplemental therapy of iron to decrease thrombotic risk due to reactive thrombocytosis in various kinds of anemia.

Endogenous hepcidin and its agonist mediate resistance to selected infections by clearing non–transferrin-bound iron

AbstractThe iron-regulatory hormone hepcidin is induced early in infection, causing iron sequestration in macrophages and decreased plasma iron; this is proposed to limit the replication of extracellular microbes, but could also promote infection with macrophage-tropic pathogens. The mechanisms by which hepcidin and hypoferremia modulate host defense, and the spectrum of microbes affected, are poorly understood. Using mouse models, we show that hepcidin was selectively protective against siderophilic extracellular pathogens (Yersinia enterocolitica O9) by controlling non–transferrin-bound iron (NTBI) rather than iron-transferrin concentration. NTBI promoted the rapid growth of siderophilic but not nonsiderophilic bacteria in mice with either genetic or iatrogenic iron overload and in human plasma. Hepcidin or iron loading did not affect other key components of innate immunity, did not indiscriminately promote intracellular infections (Mycobacterium tuberculosis), and had no effect on extracellular nonsiderophilic Y enterocolitica O8 or Staphylococcus aureus. Hepcidin analogs may be useful for treatment of siderophilic infections.

Hemolytic anemia repressed hepcidin level without hepatocyte iron overload: lesson from Günther disease model.

Hemolysis occurring in hematologic diseases is often associated with an iron loading anemia. This iron overload is the result of a massive outflow of hemoglobin into the bloodstream, but the mechanism of hemoglobin handling has not been fully elucidated. Here, in a congenital erythropoietic porphyria mouse model, we evaluate the impact of hemolysis and regenerative anemia on hepcidin synthesis and iron metabolism. Hemolysis was confirmed by a complete drop in haptoglobin, hemopexin and increased plasma lactate dehydrogenase, an increased red blood cell distribution width and osmotic fragility, a reduced half-life of red blood cells, and increased expression of heme oxygenase 1. The erythropoiesis-induced Fam132b was increased, hepcidin mRNA repressed, and transepithelial iron transport in isolated duodenal loops increased. Iron was mostly accumulated in liver and spleen macrophages but transferrin saturation remained within the normal range. The expression levels of hemoglobin-haptoglobin receptor CD163 and hemopexin receptor CD91 were drastically reduced in both liver and spleen, resulting in heme- and hemoglobin-derived iron elimination in urine. In the kidney, the megalin/cubilin endocytic complex, heme oxygenase 1 and the iron exporter ferroportin were induced, which is reminiscent of significant renal handling of hemoglobin-derived iron. Our results highlight ironbound hemoglobin urinary clearance mechanism and strongly suggest that, in addition to the sequestration of iron in macrophages, kidney may play a major role in protecting hepatocytes from iron overload in chronic hemolysis.

Driving Up the Dose: Implications for High-Dose Vitamin D Therapy

Driving Up the Dose: Implications for High-Dose Vitamin D Therapy

Hepcidin and Host Defense against Infectious Diseases

Hepcidin is the master regulator of iron homeostasis in vertebrates. The synthesis of hepcidin is induced by systemic iron levels and by inflammatory stimuli. While the role of hepcidin in iron regulation is well established, its contribution to host defense is emerging as complex and multifaceted. In this review, we summarize the literature on the role of hepcidin as a mediator of antimicrobial immunity. Hepcidin induction during infection causes depletion of extracellular iron, which is thought to be a general defense mechanism against many infections by withholding iron from invading pathogens. Conversely, by promoting iron sequestration in macrophages, hepcidin may be detrimental to cellular defense against certain intracellular infections, although critical in vivo studies are needed to confirm this concept. It is not yet clear whether hepcidin exerts any iron-independent effects on host defenses.

Estrogen receptor alpha is required for macrophage iron sequestration and homeostasis in female mice (INM1P.438)

Abstract Sexual dimorphisms in immunity are known to confer protection against infections at the cost of heightened risk for autoimmunity in women. The female sex hormone, estradiol, can modulate both pro/anti-inflammatory macrophage signals and the mechanisms of action remain unclear. Iron sequestration by macrophages is fundamentally important to limit bacterial infection, and since estradiol is thought to influence iron metabolism in females, we asked whether ERα impacts the innate immune response by regulating macrophage iron metabolism. To address this question, we crossed floxed Esr1 (fl/fl control) and LysM-Cre transgenic animals to generate myeloid-specific ERα knockout (MACER) mice. We studied the effect of ERα deletion on iron homeostasis upon endotoxin treatment in female MACER and fl/fl conrols. MACER mice had increased serum iron (92%; p=0.01) compared to fl/fl under basal conditions. As expected, endotoxin treatment reduced serum iron levels in fl/fl controls (41%, p=.008), however there was no change in serum iron in MACER mice. Consistent with impaired macrophage iron homeostasis, expression of genes associated with iron absorption (TfR, Slc11a2, Cybrd1), efflux (Fpn), and storage (Ftl) were significantly altered in female MACER mice compared to fl/fl controls. Together, these data suggest that ERα regulates macrophage iron metabolism in females, is required for systemic iron homeostasis, and may play a previously unrecognized role in female innate immunity.

Increased ferroportin-1 expression and rapid splenic iron loss occur with anemia caused by Salmonella enterica Serovar Typhimurium infection in mice.

The Gram-negative intracellular bacterium Salmonella enterica serovar Typhimurium causes persistent systemic inflammatory disease in immunocompetent mice. Following oral inoculation with S. Typhimurium, mice develop a hematopathological syndrome akin to typhoid fever with splenomegaly, microcytic anemia, extramedullary erythropoiesis, and increased hemophagocytic macrophages in the bone marrow, liver, and spleen. Additionally, there is marked loss of iron from the spleen, an unanticipated result, given the iron sequestration reported in anemia of inflammatory disease. To establish why tissue iron does not accumulate, we evaluated multiple measures of pathology for 4 weeks following oral infection in mice. We demonstrate a quantitative decrease in splenic iron following infection despite increased numbers of splenic phagocytes. Infected mice have increased duodenal expression of the iron exporter ferroportin-1, consistent with increased uptake of dietary iron. Liver and splenic macrophages also express high levels of ferroportin-1. These observations indicate that splenic and hepatic macrophages export iron during S. Typhimurium infection, in contrast to macrophage iron sequestration observed in anemia of inflammatory disease. Tissue macrophage export of iron occurs concurrent with high serum concentrations of interferon gamma (IFN-γ) and interleukin 12 (IL-12). In individual mice, high concentrations of both proinflammatory (tumor necrosis factor alpha [TNF-α]) and anti-inflammatory (IL-10) cytokines in serum correlate with increased tissue bacterial loads throughout 4 weeks of infection. These in vivo observations are consistent with previous cell culture studies and suggest that the relocation of iron from tissue macrophages during infection may contribute to anemia and also to host survival of acute S. Typhimurium infection.

Effect of intense physical exercise on hepcidin levels and selected parameters of iron metabolism in rowing athletes.

PurposePhysical exercise, especially intense physical exercise, causes a number of unfavorable changes, including an increase in the level of pro-inflammatory cytokines with the resultant sequestration of iron in macrophages and decreased iron absorption. This can lead to a reduced supply of iron for erythroid progenitor cells and promote the development of anemia.MethodThis study included a group of 20 rowing athletes, members of the National Polish Rowing Team. The participants performed a 2,000-m maximum test on a rowing ergometer. Blood samples were taken from the antecubital vein prior to the exercise test, 1 min after completing the test, and after a 24-h recovery period. We determined the levels of hepcidin, interleukin 6 (IL-6), tumor necrosis factor α, soluble transferrin receptor, ferritin, total iron-binding capacity, unbound iron-binding capacity, iron, red blood cells, hemoglobin, hematocrit, mean corpuscular volume, creatine kinase, and myoglobin.ResultThe high-intensity exercise test caused significant changes in hepcidin levels, IL-6, and iron metabolism parameters, with their subsequent return to baseline values during the recovery period. The serum iron levels decreased significantly during the recovery compared with pre- and post-exercise levels.ConclusionThese results suggest that the high-intensity ergometric test was reflected by a marked decrease in serum level of iron during the recovery period, but did not induce concomitant changes in the remaining erythrocyte parameters.

A novel missense mutation in SLC40A1 results in resistance to hepcidin and confirms the existence of two ferroportin‐associated iron overload diseases

Ferroportin-related iron overload disease differs from haemochromatosis in that it has a dominant mode of inheritance and is usually associated with macrophage iron sequestration. However, it is thought that mutations with opposite effects on protein functions, i.e. loss-of-function versus gain-of-function mutations, are responsible for variable phenotype presentations. The present study investigated the functional relevance of a novel ferroportin variant: the c.1502 A>G transition, which changes amino acid 501 from tyrosine to cysteine (p.Y501C). This novel variant was identified in a pedigree originating from Central Italy and, although an intra-familial phenotype heterogeneity was observed, it co-segregated with an iron overload picture similar to that of the HFE-related typical haemochromatosis. In cultured cells, the p.Y501C mutant protein reached the plasma membrane and retained a full iron export ability. By contrast, it was resistant to inhibition by hepcidin. These findings confirm that certain ferroportin mutations compromise the activity of hepcidin in iron homeostasis, mimicking hepcidin deficiency as described in all types of hemochromatosis.

A Novel Immunological Assay for Hepcidin Quantification in Human Serum

BackgroundHepcidin is a 25-aminoacid cysteine-rich iron regulating peptide. Increased hepcidin concentrations lead to iron sequestration in macrophages, contributing to the pathogenesis of anaemia of chronic disease whereas decreased hepcidin is observed in iron deficiency and primary iron overload diseases such as hereditary hemochromatosis. Hepcidin quantification in human blood or urine may provide further insights for the pathogenesis of disorders of iron homeostasis and might prove a valuable tool for clinicians for the differential diagnosis of anaemia. This study describes a specific and non-operator demanding immunoassay for hepcidin quantification in human sera.Methods and FindingsAn ELISA assay was developed for measuring hepcidin serum concentration using a recombinant hepcidin25-His peptide and a polyclonal antibody against this peptide, which was able to identify native hepcidin. The ELISA assay had a detection range of 10–1500 µg/L and a detection limit of 5.4 µg/L. The intra- and interassay coefficients of variance ranged from 8–15% and 5–16%, respectively. Mean linearity and recovery were 101% and 107%, respectively. Mean hepcidin levels were significantly lower in 7 patients with juvenile hemochromatosis (12.8 µg/L) and 10 patients with iron deficiency anemia (15.7 µg/L) and higher in 7 patients with Hodgkin lymphoma (116.7 µg/L) compared to 32 age-matched healthy controls (42.7 µg/L).ConclusionsWe describe a new simple ELISA assay for measuring hepcidin in human serum with sufficient accuracy and reproducibility.

Molecular Control of Iron Transport

The iron-regulatory hormone hepcidin is a 25-amino acid peptide that is synthesized in hepatocytes. Hepcidin binds to the cellular iron export channel ferroportin and causes its internalization and degradation and thereby decreases iron efflux from iron exporting tissues into plasma. By this mechanism, hepcidin inhibits dietary iron absorption, the efflux of recycled iron from splenic and hepatic macrophages, and the release of iron from storage in hepatocytes. Hepcidin synthesis is stimulated by plasma iron and iron stores and is inhibited by erythropoietic activity, ensuring that extracellular plasma iron concentrations and iron stores remain stable and the erythropoietic demand for iron is met. During inflammation, increased hepcidin concentrations cause iron sequestration in macrophages, resulting in hypoferremia and eventually anemia of inflammation. Hepcidin deficiency plays a central role in most iron overload disorders. The role of hepcidin abnormalities in anemias that are associated with renal disease and in resistance to erythropoietic therapies remains to be elucidated.