Regulator Of Systemic Iron Homeostasis Research Articles

Production and characterization of functional recombinant hybrid heteropolymers of camel hepcidin and human ferritin H and L chains.

Hepcidin is a liver-synthesized hormone that plays a central role in the regulation of systemic iron homeostasis. To produce a new tool for its functional properties the cDNA coding for camel hepcidin-25 was cloned at the 5'end of human FTH sequence into the pASK-IBA43plus vector for expression in Escherichia coli The recombinant fusion hepcidin-ferritin-H subunit was isolated as an insoluble iron-containing protein. When alone it did not refold in a 24-mer ferritin molecule, but it did when renatured together with H- or L-ferritin chains. We obtained stable ferritin shells exposing about 4 hepcidin peptides per 24-mer shell. The molecules were then reduced and re-oxidized in a controlled manner to allow the formation of the proper hepcidin disulfide bridges. The functionality of the exposed hepcidin was confirmed by its ability to specifically bind the mouse macrophage cell line J774 that express ferroportin and to promote ferroportin degradation. This chimeric protein may be useful for studying the hepcidin-ferroportin interaction in cells and also as drug-delivery agent.

An essential cell-autonomous role for hepcidin in cardiac iron homeostasis.

Hepcidin is the master regulator of systemic iron homeostasis. Derived primarily from the liver, it inhibits the iron exporter ferroportin in the gut and spleen, the sites of iron absorption and recycling respectively. Recently, we demonstrated that ferroportin is also found in cardiomyocytes, and that its cardiac-specific deletion leads to fatal cardiac iron overload. Hepcidin is also expressed in cardiomyocytes, where its function remains unknown. To define the function of cardiomyocyte hepcidin, we generated mice with cardiomyocyte-specific deletion of hepcidin, or knock-in of hepcidin-resistant ferroportin. We find that while both models maintain normal systemic iron homeostasis, they nonetheless develop fatal contractile and metabolic dysfunction as a consequence of cardiomyocyte iron deficiency. These findings are the first demonstration of a cell-autonomous role for hepcidin in iron homeostasis. They raise the possibility that such function may also be important in other tissues that express both hepcidin and ferroportin, such as the kidney and the brain.

Characterization of hepcidin response to holotransferrin in novel recombinant TfR1 HepG2 cells

Hepcidin is the key regulator of systemic iron homeostasis. The iron-sensing mechanisms and the role of intracellular iron in modulating hepatic hepcidin secretion are unclear. Therefore, we created a novel cell line, recombinant-TfR1 HepG2, expressing iron-response-element-independent TFRC mRNA to promote cellular iron-overload and examined the effect of excess holotransferrin (5g/L) on cell-surface TfR1, iron content, hepcidin secretion and mRNA expressions of TFRC, HAMP, SLC40A1, HFE and TFR2. Results showed that the recombinant cells exceeded levels of cell-surface TfR1 in wild-type cells under basal (2.8-fold; p<0.03) and holotransferrin-supplemented conditions for 24h and 48h (4.4- and 7.5-fold, respectively; p<0.01). Also, these cells showed higher intracellular iron content than wild-type cells under basal (3-fold; p<0.03) and holotransferrin-supplemented conditions (6.6-fold at 4h; p<0.01). However, hepcidin secretion was not higher than wild-type cells. Moreover, holotransferrin treatment to recombinant cells did not elevate HAMP responses compared to untreated or wild-type cells. In conclusion, increased intracellular iron content in recombinant cells did not increase hepcidin responses compared to wild-type cells, resembling hemochromatosis. Furthermore, TFR2 expression altered within 4h of treatment, while HFE expression altered later at 24h and 48h, suggesting that TFR2 may function prior to HFE in HAMP regulation.

Transforming Growth Factor β1 (TGF-β1) Activates Hepcidin mRNA Expression in Hepatocytes

The hepatic hormone hepcidin is the master regulator of systemic iron homeostasis. Its expression level is adjusted to alterations in iron levels, inflammatory cues, and iron requirements for erythropoiesis. Bone morphogenetic protein 6 (BMP6) contributes to the iron-dependent control of hepcidin. In addition, TGF-β1 may stimulate hepcidin mRNA expression in murine hepatocytes and human leukocytes. However, receptors and downstream signaling proteins involved in TGF-β1-induced hepcidin expression are still unclear. Here we show that TGF-β1 treatment of mouse and human hepatocytes, as well as ectopic expression of TGF-β1 in mice, increases hepcidin mRNA levels. The hepcidin response to TGF-β1 depends on functional TGF-β1 type I receptor (ALK5) and TGF-β1 type II receptor (TβRII) and is mediated by a noncanonical mechanism that involves Smad1/5/8 phosphorylation. Interestingly, increasing availability of canonical Smad2/3 decreases TGF-β1-induced hepcidin regulation, whereas the BMP6-hepcidin signal was enhanced, indicating a signaling component stoichiometry-dependent cross-talk between the two pathways. Although ALK2/3-dependent hepcidin activation by BMP6 can be modulated by each of the three hemochromatosis-associated proteins: HJV (hemojuvelin), HFE (hemochromatosis protein), and TfR2 (transferrin receptor 2), these proteins do not control the ALK5-mediated hepcidin response to TGF-β1. TGF-β1 mRNA levels are increased in mouse models of iron overload, indicating that TGF-β1 may contribute to hepcidin synthesis under these conditions. In conclusion, these data demonstrate that a complex regulatory network involving TGF-β1 and BMP6 may control the sensing of systemic and/or hepatic iron levels.

Regulation of Hepcidin by Erythropoiesis: The Story So Far.

Hepcidin is the master regulator of systemic iron homeostasis, facilitating iron balance by controlling intestinal iron absorption and recycling. Hepcidin levels are suppressed when erythropoiesis is stimulated, for example following acute blood loss, appropriately enhancing cellular iron export to the plasma to support production of new red blood cells. However, persistent increased and ineffective erythropoiesis, for example in thalassemia, results in sustained elevations in iron absorption, which cause iron overload with associated organ toxicities. The ligands, receptors, and canonical pathways by which iron loading and inflammation upregulate hepcidin expression have been largely established. However, although several mechanisms have been proposed, the means by which erythropoiesis causes hepcidin suppression have been unclear. The erythroid-derived hormone erythroferrone appears to be a convincing candidate for the link between increased erythropoiesis and hepcidin suppression. If confirmed to be clinically and physiologically relevant in humans, potentiation or inhibition of erythroferrone activity could be a crucial pharmaceutical strategy.

The mutual control of iron and erythropoiesis.

Iron is essential for hemoglobin synthesis during terminal erythropoiesis. To supply adequate iron the carrier transferrin is required together with transferrin receptor endosomal cycle and normal mitochondrial iron utilization. Iron and iron protein deficiencies result in different types of anemia. Iron-deficiency anemia is the commonest anemia worldwide due to increased requirements, malnutrition, chronic blood losses and malabsorption. Mutations of transferrin, transferrin receptor cycle proteins, enzymes of the first step of heme synthesis and iron sulfur cluster biogenesis lead to rare anemias, usually accompanied by iron overload. Hepcidin plays an indirect role in erythropoiesis by controlling plasma iron. Inappropriately high hepcidin levels characterize the rare genetic iron-refractory iron-deficiency anemia (IRIDA) and the common anemia of chronic disease. Iron modulates both effective and ineffective erythropoiesis: iron restriction reduces heme and alpha-globin synthesis that may be of benefit in thalassemia. This review relies on the analysis of the most recent literature and personal data. Erythropoiesis controls iron homeostasis, by releasing erythroferrone that inhibits hepcidin transcription to increase iron acquisition in iron deficiency, hypoxia and EPO treatment. Erythroferrone, produced by EPO-stimulated erythropoiesis, inhibits hepcidin only when the activity of BMP/SMAD pathway is low, suggesting that EPO somehow modulates the latter signaling. Erythroblasts sense circulating iron through the second transferrin receptor (TFR2) that, in animal models, modulates the sensitivity of the erythroid cells to EPO. The advanced knowledge of the regulation of systemic iron homeostasis and erythropoiesis-mediated hepcidin regulation is leading to the development of targeted therapies for anemias and iron disorders.

Iron-refractory iron deficiency anemia

The major causes of iron deficiency anemia (IDA) include iron loss due to bleeding, increased iron requirements, and decreased iron absorption by the intestine. The most common cause of IDA in Japanese women is iron loss during menstruation. Autoimmune atrophic gastritis and Helicobacter pylori infection can also cause IDA by reducing intestinal iron absorption. In addition to these common etiologies, germline mutations of TMPRSS6 can cause iron-refractory IDA (IRIDA). TMPRSS6 encodes matriptase-2, a membrane-bound serine protease primarily expressed in the liver. Functional loss of matriptase-2 due to homozygous mutations results in an increase in the expression of hepcidin, which is the key regulator of systemic iron homeostasis. The serum hepcidin increase in turn leads to a decrease in iron supply from the intestine and macrophages to erythropoietic cells. IRIDA is microcytic and hypochromic, but decreased serum ferritin is not observed as in IDA. IRIDA is refractory to oral iron supplementation, but does respond to intravenous iron supplementation to some extent. Because genetic testing is required for the diagnoses of IRIDA, a considerable number of cases may go undiagnosed and may thus be overlooked.

Lack of Difference in Hepcidin Levels in Sickle Cell Anemia and Sickle Cell Beta Thalassemia

Introduction: Sickle cell disease (SCD) may be associated with iron overload following repeated RBC transfusions. In beta thalassemia major, a disease characterized by hemolysis and ineffective erythropoiesis, iron overload occurs due to both repeated RBC transfusions and hyperabsorption of iron. Hyperabsorption of iron occurs due to ineffective erythropoiesis and subsequent downregulation of hepcidin, the main regulator of systemic iron homeostasis. With the presence of a thalassemia gene, HbSβ-thalassemia patients may have an increased tendency to hyperabsorb iron compared to HbSS patients. The purpose of this exploratory study was to compare hepcidin levels in HbSS and HbSβ-thalassemia as well as the levels of GDF-15 and any associations between hepcidin and ferritin, other measures of iron balance, erythropoietin and markers of inflammation.Methods: Eligible patients with HbSS or HbSβ-thalassemia (HbSβ0-thalassemia or HbSβ+-thalassemia) were evaluated during routine clinic visits. Hepcidin, GDF -15 and erythropoietin were analyzed using commercially available ELISA kits, while plasma cytokines were analyzed by Luminex® multi-analyte profiling technology. Complete blood counts, serum iron, transferrin, transferrin saturation and ferritin, high-sensitivity CRP and routine chemistries were performed at the clinical laboratories of UNC Hospitals. Patients' clinical data, including SCD-related clinical complications and estimates of the number of lifetime RBC transfusions, were obtained at the time of evaluation combined with reviews of their medical records. The levels of hepcidin and GDF-15 were compared in HbSS and HbSβ-thalassemia (and SCD vs. healthy controls) using Wilcoxon rank sum tests, and the association of hepcidin and laboratory covariates was evaluated using Spearman correlation coefficient. Reported p-values are for individual tests, unadjusted for multiple comparisons.Results: Baseline demographic variables were similar in HbSS and HbSβ-thalassemia patients, but platelet counts, lactate dehydrogenase, total bilirubin, direct bilirubin, indirect bilirubin, aspartate transaminase and alkaline phosphatase were significantly higher in HbSS patients (Table 1). No significant differences were observed when hepcidin levels were compared between control subjects (N = 15) and SCD patients (N = 40) (25.2 ± 14.3 ng/mL vs. 19.5 ± 17.3 ng/mL, p = 0.13). In addition, no difference was observed in hepcidin levels (16.1 ± 11.4 ng/mL vs. 23.7 ± 22.2 ng/mL, p = 0.53) or GDF-15 levels (1635.1 ± 1357.7 pg/mL vs. 2051 ± 2385.4 pg/mL, p = 0.9) when HbSS patients were compared with HbSβ-thalassemia. Hepcidin was associated with ferritin (r= 0.57, p = 0.0001) and transferrin (r = -0.46, p = 0.0029) in SCD patients. However, no significant correlations were observed between hepcidin and erythropoietin, high sensitivity CRP, IL-6, IL-8, IL-10 and TNFα.Conclusion: No differences in hepcidin levels were observed in SCD patients compared with healthy controls, and in HbSS patients compared with HbSβ-thalassemia patients. We confirm the association of hepcidin with ferritin, but surprisingly find no association of hepcidin with IL-6.Table 1Baseline VariablesVariableHbSS (N = 22)Mean ± SD (or %)HbSβ-thalassemia (N = 18)Mean ± SD (or %)95% CI for Mean DifferenceAge (years)37.96 ± 12.736.4 ± 11.4(-6.2,9.2)Gender (females)15 (68.2)12 (66.7)Weight (kg)70.8 ± 15.174.7 ± 14.8(-13.7,5.9)Transfusions 0 - 5 6 - 10 11 - 20 21 - 509 (23.1) 5 (12.8) 5 (12.8) 2 (5.1)11 (28.2) 3 (7.7) 3 (7.7) 1 (2.6)White Blood Cell Count (× 109/L)9.5 ± 3.19.4 ± 3.1(-1.9,2.04)Hemoglobin(g/dL)9.4 ± 1.710 ± 1.99(-1.7,0.6)Platelet Count (× 109/L)402.6 ± 134.9310.1 ± 151.6(1.8,183.1)Ferritin (ng/mL)346.3 ± 406.9174 ± 257.7(-50.3,395)Reticulocyte Count (× 109/L)233.5 ± 139.9215.7 ± 138.9(-71.8,107.6)Lactate Dehydrogenase (U/L)954.3 ± 322.95720.4 ± 174.2(73.8,394)Total Bilirubin (mg/dL)3.9 ± 3.11.4 ± 0.9(1.2,3.9)Direct Bilirubin (mg/dL)0.56 ± 0.50.3 ± 0.1(0.04,0.48)Indirect Bilirubin (mg/dL)3.3 ± 2.81.06 ± 0.8(1.03,3.5)Aspartate Transaminase (U/L)46.5 ± 18.832.8 ± 11.9(3.4,23.9)Alanine Transaminase (U/L)30.7 ± 13.528.7 ± 9.7(-5.6,9.6)Alkaline Phosphatase (U/L)110.6 ± 45.678.1 ± 24.7(9.7,55.3)Creatinine (mg/dL)0.67 ± 0.171.1 ± 1.25(-1.07,0.18) DisclosuresNo relevant conflicts of interest to declare.

Recent Advances in Iron Metabolism: Relevance for Health, Exercise, and Performance.

Iron is necessary for physiological processes essential for athletic performance, such as oxygen transport, energy production, and cell division. However, an excess of "free" iron is toxic because it produces reactive hydroxyl radicals that damage biological molecules, thus leading to cell and tissue injury. Therefore, iron homeostasis is strictly regulated; and in recent years, there have been important advancements in our knowledge of the underlying processes. Hepcidin is the central regulator of systemic iron homeostasis and exerts its function by controlling the presence of the iron exporter ferroportin on the cell membrane. Hepcidin binding induces ferroportin degradation, thus leading to cellular iron retention and decreased levels of circulating iron. As iron is required for hemoglobin synthesis, the tight link between erythropoiesis and iron metabolism is particularly relevant to sports physiology. The iron needed for hemoglobin synthesis is ensured by inhibiting hepcidin to increase ferroportin activity and iron availability and hence to make certain that efficient blood oxygen transport occurs for aerobic exercise. However, hepcidin expression is also affected by exercise-associated conditions, such as iron deficiency, anemia or hypoxia, and, particularly, inflammation, which can play a role in the pathogenesis of sports anemia. Here, we review recent advances showing the relevance of iron for physical exercise and athletic performance. Low body iron levels can cause anemia and thus limit the delivery of oxygen to exercising muscle, but tissue iron deficiency may also affect performance by, for example, hampering muscle oxidative metabolism. Accordingly, a hemoglobin-independent effect of iron on exercise capacity has been demonstrated in animal models and humans. Here, we review recent advances showing the relevance of iron for physical exercise and athletic performance.

Systemic inflammation up-regulates serum hepcidin in exacerbations and stabile chronic obstructive pulmonary disease

ObjectivesHepcidin is the main regulator of systemic iron homeostasis and its expression is modulated by iron status, hypoxia, erythroid factors and inflammation. The aim of our study was to examine a relationship between level of hepcidin and iron status, erythropoietic activity, hypoxia and inflammation in exacerbations and stable COPD patients. We hypothesized that hepcidin concentration is changed in COPD patients and is substantially influenced by inflammation and/or hypoxia. Design and methodsThe study included 40 COPD patients and 30 healthy subjects. We measured haemoglobin, serum level of hepcidin and parameters indicative for inflammation: interleukin-6 (IL-6) and C reactive protein (CRP); hypoxia: partial oxygen pressure and haemoglobin oxygen saturation; iron status: iron, total iron binding capacity (TIBC), transferring saturation and ferritin; and erythropoietic activity: soluble transferrin receptors, reticulocytes, and erythropoietin. ResultsHepcidin was elevated in exacerbations and in a stable phase compared to the control group and we found positive correlations of hepcidin with inflammatory markers IL-6 and CRP. Hepcidin also correlated positively with ferritin and inversely with TIBC. However, in COPD patients reticulocyte count was significantly reduced and negative correlation with hepcidin was established in exacerbation. No correlations were observed with iron, or indices of hypoxia. In the control group, positive associations were observed only with indices of iron status, positive with ferritin and negative one with TIBC. ConclusionSystemic inflammation and elevated values of IL-6 present in exacerbations and stabile COPD might be responsible for the observed increased hepcidin level.

A HAMP promoter bioassay system for identifying chemical compounds that modulate hepcidin expression

Hepcidin is the central regulator of systemic iron homeostasis; dysregulation of hepcidin expression causes various iron metabolic disorders, including hereditary hemochromatosis and anemia of inflammation. To identify molecules that modulate hepcidin expression, we developed a bioassay system for hepcidin gene (HAMP) promoter activity by stable transfection of Hep3B hepatoma cells with an expression plasmid in which EGFP was linked to a 2.5-kb human HAMP promoter. Interleukin 6, bone morphogenetic protein 6 (BMP-6), and oncostatin M, well-characterized stimulators of the HAMP promoter, strongly enhanced the green fluorescence intensity of these cells. Dorsomorphin, heparin, and cobalt chloride, known inhibitors of hepcidin expression, significantly suppressed green fluorescence intensity, and these inhibitory effects were more prominent when the cells were stimulated with BMP-6. Employing this system, we screened 1,280 biologically active small molecules and found several candidate inhibitors of hepcidin expression. Apomorphine, benzamil, etoposide, CGS-15943, kenpaullone, and rutaecarpine (all at 10μmol/L) significantly inhibited hepcidin mRNA expression by Hep3B cells without affecting cell viability. CGS-15943 was the strongest suppressor of BMP-6-induced hepcidin-25 secretion in these cells. We conclude that our newly developed hepcidin promoter bioassay system is useful for identifying and evaluating compounds that modulate hepcidin expression.

A Rapid and Sensitive LC–MS–MS Method for Determination of Hepcidin-25 in Human Serum, and Measurement of its Diurnal Rhythm for Healthy Subjects

Hepcidin is a recently discovered small defensin-like peptide hormone which is a key regulator of systemic iron homeostasis. Serum and urine hepcidin levels may be of diagnostic importance for iron-related disorders. We have developed a sensitive and selective ultra-performance liquid chromatographic–tandem mass spectrometric (UPLC–MS–MS) method for quantitative determination of the concentration of hepcidin in clinical samples. Solid-phase extraction was used to isolate the analyte from biological matrices, and the extracts were injected on to a Waters Acquity UPLC BEH C18 column with gradient elution. Detection was performed by triple-quadrupole tandem mass spectrometry in multiple reaction monitoring mode with positive electrospray ionization. This UPLC–MS–MS method was validated by use of a recently introduced validation strategy based on accuracy profiles. Accuracy, precision, and linearity were good in the concentration range 0.50–500 ng mL−1. The lower limit of quantification was 0.50 ng mL−1 serum. A diurnal rhythm of serum hepcidin-25 levels was found by standardizing the sampling time from 07:30 on one day to 07:30 on the third day for eight healthy volunteers. The results indicated that circulating hepcidin-25 concentrations are different between genders and for different diurnal rhythms.

The iron-regulatory hormone hepcidin: a possible therapeutic target?

The maintenance of stable extracellular and intracellular iron concentrations requires the coordinated regulation of iron transport into plasma. Iron is a fundamental cofactor for several enzymes involved in oxidation-reduction reactions. The redox ability of iron can lead to the production of oxygen free radicals, which can damage various cellular components. Therefore, the appropriate regulation of systemic iron homeostasis is decisive in vital processes. Hepcidin has emerged as the central regulatory molecule of systemic iron homeostasis. It is synthesized in hepatocytes and in other cells and released into the circulation. It inhibits the release of iron from enterocytes of the duodenum and from macrophages by binding to the iron exporter protein, ferroportin (FPN). FPN is a transmembrane protein responsible for iron export from cells into the plasma. Hepcidin is internalized with FPN and both are degraded in lysosomes. The hepcidin-FPN axis is the principal regulator of extracellular iron homeostasis in health and disease. Its manipulation via agonists and antagonists is an attractive and novel therapeutic strategy. Hepcidin agonists include compounds that mimic the activity of hepcidin and agents that increase the production of hepcidin by targeting hepcidin-regulatory molecules. The inhibition of hepcidin could be a potentially attractive therapeutic strategy in patients suffering from anaemia or chronic inflammation. In this review, we will summarize the role of hepcidin in iron homeostasis and its contribution to the pathophysiology of inflammation and iron disorders. We will examine emerging new strategies that modulate hepcidin metabolism.

Ferritin polarization and iron transport across monolayer epithelial barriers in mammals.

Epithelial barriers are found in many tissues such as the intestine, kidney and brain where they separate the external environment from the body or a specific compartment from its periphery. Due to the tight junctions that connect epithelial barrier-cells (EBCs), the transport of compounds takes place nearly exclusively across the apical or basolateral membrane, the cell-body and the opposite membrane of the polarized EBC, and is regulated on numerous levels including barrier-specific adapted trafficking-machineries. Iron is an essential element but toxic at excess. Therefore, all iron-requiring organisms tightly regulate iron concentrations on systemic and cellular levels. In contrast to most cell types that control just their own iron homeostasis, EBCs also regulate homeostasis of the compartment they enclose or the body as a whole. Iron is transported across EBCs by specialized transporters such as the transferrin receptor and ferroportin. Recently, the iron storage protein ferritin was also attributed a role in the regulation of systemic iron homeostasis and we gathered evidence from the literature and original data that ferritin is polarized in EBC, suggesting also a role for ferritin in iron trafficking across EBCs.

Intestinal inflammation modulates expression of the iron-regulating hormone hepcidin depending on erythropoietic activity and the commensal microbiota.

States of chronic inflammation such as inflammatory bowel disease are often associated with dysregulated iron metabolism and the consequent development of an anemia that is caused by maldistribution of iron. Abnormally elevated expression of the hormone hepcidin, the central regulator of systemic iron homeostasis, has been implicated in these abnormalities. However, the mechanisms that regulate hepcidin expression in conditions such as inflammatory bowel disease are not completely understood. To clarify this issue, we studied hepcidin expression in mouse models of colitis. We found that dextran sulfate sodium-induced colitis inhibited hepcidin expression in wild-type mice but upregulated it in IL-10-deficient animals. We identified two mechanisms contributing to this difference. Firstly, erythropoietic activity, as indicated by serum erythropoietin concentrations and splenic erythropoiesis, was higher in the wild-type mice, and pharmacologic inhibition of erythropoiesis prevented colitis-associated hepcidin downregulation in these animals. Secondly, the IL-10 knockout mice had higher expression of multiple inflammatory genes in the liver, including several controlled by STAT3, a key regulator of hepcidin. The results of cohousing and fecal transplantation experiments indicated that the microbiota was involved in modulating the expression of hepcidin and other STAT3-dependent hepatic genes in the context of intestinal inflammation. Our observations thus demonstrate the importance of erythropoietic activity and the microbiota in influencing hepcidin expression during colitis and provide insight into the dysregulated iron homeostasis seen in inflammatory diseases.

The role of hepcidin in iron metabolism in inflammatory bowel diseases

Hepcidin is a 25-amino-acid peptide synthesized predominantly in hepatocytes, which plays an essential role in the regulation of systemic iron homeostasis. As a result of inflammation, hepcidin binds to ferroportin resulting in its internalization and degradation in enterocytes and macrophages. Thus iron is trapped in both enterocytes and macrophages, leading to functional hypoferremia. In iron deficiency or enhanced erythropoiesis, hepcidin expression is reduced. That fact results in increase of iron absorption and releasing iron storage from macrophages. The discovery of the biological properties of hepcidin clarified the relationship between iron homeostasis, immune response, and anaemia of chronic disease. Anaemia is the most common extra intestinal manifestation of inflammatory bowel disease. Anaemia significantly reduces the quality-of-life among patients and can lead to a number of serious complications, even life-threatening. The main types of anaemia in inflammatory bowel diseases are iron deficiency anaemia and anaemia of chronic disease. These two types of anaemia coexist commonly. The key issue is differentiation these types of anaemia to implement a proper management. Commonly used parameters as iron concentration, ferritin and transferrin, are rather unreliable indices for the evaluation of anaemia in inflammatory bowel diseases. In recent studies the important role of hepcidin as a potential alternative marker of anemia and iron status has been shown. Moreover, there are data that antihepcidin treatment may be an effective treatment of anaemia of chronic disease in inflammatory bowel disease. This paper presents hepcidin structure, mechanism of action and regulation, and highlights hepcidin function in anaemia in inflammatory bowel disease.

Molecular characterization of a novel hepcidin (HepcD) from Camelus dromedarius. Synthetic peptide forms exhibit antibacterial activity.

Hepcidin is a cysteine-rich peptide widely characterized in immunological processes and antimicrobial activity in several vertebrate species. Obviously, this hormone plays a central role in the regulation of systemic iron homeostasis. However, its role in camelids' immune response and whether it is involved in antibacterial immunity have not yet been proven. In this study, we characterized the Arabian camel hepcidin nucleotide sequence with an open reading frame of 252 bp encoding an 83-amino acid preprohepcidin peptide. Eight cysteine key residues conserved in all mammalian hepcidin sequences were identified. The model structure analysis of hepcidin-25 peptide showed a high homology structure and sequence identity to the human hepcidin. Two different hepcidin-25 analogs manually synthesized by SPPS shared significant cytotoxic capacity toward the Gram-negative bacterium Escherichia coli American Type Culture Collection (ATCC) 8739 as well as the Gram-positive bacteria Bacillus subtilis ATCC 11779 and Staphylococcus aureus ATCC 6538 in vitro. The three disulfide bridges hepcidin analog demonstrated bactericidal activity, against B. subtilis ATCC 11779 and S. aureus ATCC 6538 strains, at the concentration of 15 μM (50 µg/ml) or above at pH 6.2. This result correlates with the revealed structural features suggesting that camel hepcidin is proposed to be involved in antibacterial process of innate immune response.

Inflammatory regulation of iron metabolism during thioacetamide-induced acute liver injury in rats

Systemic iron homeostasis is tightly regulated by the interaction between iron regulatory molecules, mainly produced by the liver. However, the molecular mechanisms of iron regulation in liver diseases remain to be elucidated. Here we analyzed the expression profiles of iron regulatory molecules during transient iron overload in a rat model of thioacetamide (TAA)-induced acute liver injury. After TAA treatment, mild hepatocellular degeneration and extensive necrosis were observed in the centrilobular region at hour 10 and on day 1, respectively. Serum iron increased transiently at hour 10 and on day 1, in contrast to hypoferremia in other rodent models of acute inflammation reported previously. Thereafter, up-regulation of hepcidin, a central regulator of systemic iron homeostasis, was observed in hepatocytes on day 2. Expression of transferrin receptor 1 and ferritin subunits increased to a peak on day 3, followed by increases in liver iron content and stainable iron on day 5, in parallel with regeneration of hepatocytes. Histopathological lesions and hepatocellular iron accumulation disappeared until day 10. The hepcidin induction was preceded by activation of IL6/STAT3 pathway, whereas other pathways known to induce hepcidin were down-regulated. IL6 was expressed by MHC class II-positive macrophages in the portal area, suggestive of dendritic cells. Our results suggest that IL6 released by portal macrophages may regulate hepatocyte hepcidin expression via STAT3 activation during transient iron overload in TAA-induced acute liver injury.

Involvement of proprotein convertase PCSK7 in the regulation of systemic iron homeostasis

Involvement of proprotein convertase PCSK7 in the regulation of systemic iron homeostasis

Involvement of proprotein convertase PCSK7 in the regulation of systemic iron homeostasis

Involvement of proprotein convertase PCSK7 in the regulation of systemic iron homeostasis