The gene encoding the iron regulatory peptide hepcidin is regulated by anemia, hypoxia, and inflammation

Iron in the Tumor Microenvironment-Connecting the Dots

Iron metabolism and tumor biology are intimately linked. Iron facilitates the production of oxygen radicals, which may either result in iron-induced cell death, ferroptosis, or contribute to mutagenicity and malignant transformation. Once transformed, malignant cells require high amounts of iron for proliferation. In addition, iron has multiple regulatory effects on the immune system, thus affecting tumor surveillance by immune cells. For these reasons, inconsiderate iron supplementation in cancer patients has the potential of worsening disease course and outcome. On the other hand, chronic immune activation in the setting of malignancy alters systemic iron homeostasis and directs iron fluxes into myeloid cells. While this response aims at withdrawing iron from tumor cells, it may impair the effector functions of tumor-associated macrophages and will result in iron-restricted erythropoiesis and the development of anemia, subsequently. This review summarizes our current knowledge of the interconnections of iron homeostasis with cancer biology, discusses current clinical controversies in the treatment of anemia of cancer and focuses on the potential roles of iron in the solid tumor microenvironment, also speculating on yet unknown molecular mechanisms.

Ameliorating Iron Overload in Intestinal Tissue of Adult Male Rats: Quercetin vs Deferoxamine

OBJECTIVE

The aim of our study is to compare the role of the new natural alternative (Quercetin) with the current iron-chelation therapy (Deferoxamine (DFO)) in the effect of iron overload on small intestinal tissues and to investigate the possible underlying molecular mechanisms of such toxicity.

METHODS

Forty-two adult male albino rats were divided into six groups: control groups, DFO, Quercetin, iron overload, iron overload+DFO, and iron overload+Quercetin groups. Animals received daily intraperitoneal injection of Deferoxamine (125 mg /kg), Quercetin (10 mg/kg), and ferric dextran (200 mg/kg) for 2 weeks.

RESULTS

Iron overloaded group showed significant increase in serum iron, total iron binding capacity (TIBC), transferrin saturation percentage (TS %) hepcidin (HEPC), serum ferritin, nontransferrin bound iron (NTBI), and small intestinal tissues iron levels. Iron overload significantly increased the serum oxidative stress indicator (MDA) and reduced serum total antioxidant capacity (TAC). On the other hand, iron overload increased IL6 and reduced IL10 in small intestinal tissues reflecting inflammatory condition and increased caspase 3 reactivity indicating apoptosis and increased iNOs expressing cell indicting oxidative stress especially in ileum. In addition, it induced small intestinal tissues pathological alterations. The treatment with Quercetin showed nonsignificant differences as compared to treatment with DFO that chelated the serum and tissue iron and improved the oxidative stress and reduced tissue IL6 and increased IL10 and decreased caspase 3 and iNOs expressing cells in small intestinal tissues. Moreover, it ameliorated the iron overload induced pathological alterations.

CONCLUSION

Our study showed the potential role of Quercetin as iron chelator like DFO in case of iron overload induced small intestinal toxicity in adult rats because of its serum and tissue iron chelation, improvement of serum, and small intestinal oxidative stress, ameliorating iron induced intestinal inflammation, apoptosis, and histopathological alterations.

Liver iron sensing and body iron homeostasis

The liver orchestrates systemic iron balance by producing and secreting hepcidin. Known as the iron hormone, hepcidin induces degradation of the iron exporter ferroportin to control iron entry into the bloodstream from dietary sources, iron recycling macrophages, and body stores. Under physiologic conditions, hepcidin production is reduced by iron deficiency and erythropoietic drive to increase the iron supply when needed to support red blood cell production and other essential functions. Conversely, hepcidin production is induced by iron loading and inflammation to prevent the toxicity of iron excess and limit its availability to pathogens. The inability to appropriately regulate hepcidin production in response to these physiologic cues underlies genetic disorders of iron overload and deficiency, including hereditary hemochromatosis and iron-refractory iron deficiency anemia. Moreover, excess hepcidin suppression in the setting of ineffective erythropoiesis contributes to iron-loading anemias such as β-thalassemia, whereas excess hepcidin induction contributes to iron-restricted erythropoiesis and anemia in chronic inflammatory diseases. These diseases have provided key insights into understanding the mechanisms by which the liver senses plasma and tissue iron levels, the iron demand of erythrocyte precursors, and the presence of potential pathogens and, importantly, how these various signals are integrated to appropriately regulate hepcidin production. This review will focus on recent insights into how the liver senses body iron levels and coordinates this with other signals to regulate hepcidin production and systemic iron homeostasis.

Deferasirox: Over a Decade of Experience in Thalassemia

Thalassemia incorporates a broad clinical spectrum characterized by decreased or absent production of normal hemoglobin leading to decreased red blood cell survival and ineffective erythropoiesis. Chronic iron overload remains an inevitable complication resulting from regular blood transfusions (transfusion-dependent) and/or increased iron absorption (mainly non-transfusion-dependent thalassemia), requiring adequate treatment to prevent the significant associated morbidity and mortality. Iron chelation therapy has become a cornerstone in the management of thalassemia patients, leading to improvements in their outcome and quality of life. Deferasirox (DFX), an oral iron chelating agent, is approved for use in transfusion dependent and non-transfusion-dependent thalassemia and has shown excellent efficacy in this setting. We herein present an updated review of the role of deferasirox in thalassemia, exploring over a decade of experience, which has documented its effectiveness and convenience; in addition to its manageable safety profile.

Effect of atorvastatin on iron metabolism regulation in patients with chronic kidney disease - a randomized double blind crossover study

INTRODUCTION

To determine the effect of 6-month administration of atorvastatin on hepcidin and hemojuvelin levels, inflammatory parameters and iron metabolism in patients with chronic kidney disease (CKD) stages 3 and 4.

METHODS

Thirty six statin- and erythropoiesis-stimulating agent-naive patients with CKD stages 3 and 4 and LDL cholesterol ≥100 mg/dl received atorvastatin or placebo for two 6-month periods in a double blind, randomized crossover study. Hepcidin, hemojuvelin, hsCRP, IL-6, hemoglobin, red blood cell distribution width, iron, total iron binding capacity (TIBC), and unsaturated iron binding capacity (UIBC) were measured before and after each treatment period.

RESULTS

Hepcidin decreased (from 102 [307] to 63 [170] pg/ml (p > .001)) in the course of statin therapy but remained unchanged after placebo administration (173 [256] to 153 [204] pg/ml, respectively). Hemojuvelin did not change after either part of the study. Both IL-6 and hsCRP decreased following statin therapy (from 8.7 [12.0] to 8.1 [13.9] pg/ml; p = .04 and from 4.7 [4.0] to 4.0 [3.6] mg/l; p = .4, respectively), but did not change after placebo administration. Blood hemoglobin increased slightly but significantly after 6-month statin therapy (from 11.6 ± 1.6 to 11.9 ± 1.5 g/dl, p = .002), and was unchanged after placebo treatment. TIBC and UIBC increased significantly after 6-month statin therapy, and serum iron also tended to increase. The change of eGFR during the study did not differ between the two treatment periods.

CONCLUSIONS

Statin may have a small but potentially beneficial effect on serum hepcidin, which may lead to improvement of anemia control in CKD patients.

The Functional Versatility of Transferrin Receptor 2 and Its Therapeutic Value

Iron homeostasis is a tightly regulated process in all living organisms because this metal is essential for cellular metabolism, but could be extremely toxic when present in excess. In mammals, there is a complex pathway devoted to iron regulation, whose key protein is hepcidin (Hepc), which is a powerful iron absorption inhibitor mainly produced by the liver. Transferrin receptor 2 (Tfr2) is one of the hepcidin regulators, and mutations in TFR2 gene are responsible for type 3 hereditary hemochromatosis (HFE3), a genetically heterogeneous disease characterized by systemic iron overload. It has been recently pointed out that Hepc production and iron regulation could be exerted also in tissues other than liver, and that Tfr2 has an extrahepatic role in iron metabolism as well. This review summarizes all the most recent data on Tfr2 extrahepatic role, taking into account the putative distinct roles of the two main Tfr2 isoforms, Tfr2α and Tfr2β. Representing Hepc modulation an effective approach to correct iron balance impairment in common human diseases, and with Tfr2 being one of its regulators, it would be worthwhile to envisage Tfr2 as a therapeutic target.

Role of HAMP Genetic Variants on Pathophysiology of Iron Deficiency Anemia

Hepcidin is a 25-amino acid peptide hormone produced by hepatocytes and plays a key role in body iron metabolism. Hepcidin deficiency is the cause of iron overload in hereditary hemochromatosis, iron-loading anemia, and its excess is associated with anemia of inflammation, chronic disease and iron deficiency anemia (IDA). The aims of this study was to evaluate HAMP gene mutation, namely IVS2 + 1(-G) (c.148-150 + 1del) and Gly71 Asp (c.212G > A (rs104894696) association with iron status in IDA conditions. Our study participants were 500 IDA patients and 550 age and sex-matched healthy controls. Hepcidin, ferritin and CRP analysis was done by ELISA method while ESR analysis was done according to Wintrobe method. CBC analysis was done by auto-analyzer. Two mutations in the HAMP genes were analysed by PCR RFLP method. Among the IDA patients, 7 were heterozygous for Met50del IVS2 + 1(-G) mutation. Nine IDA patients were heterozygous for G71D G-A mutation and homozygous were not identified in both mutations.Controls were showing heterozygous frequency 1.8 and 2.1% of Met50del IVS2 + 1(-G) and G71D G-A mutations respectively. Mutation of HAMP (Met50del IVS2 + 1(-G) and G71D G-A) were clinically associated with IDA and act as modulator of disease.

Hematological responses to iron-folate supplementation and its determinants in pregnant women attending antenatal cares in Mekelle City, Ethiopia

OBJECTIVE

To characterize anemia and evaluate hematological responses to universal iron-folic acid (IFA) supplementation in Ethiopian pregnant women.

METHOD

A hospital- based prospective follow up study was done between December 2016 and June 2017. Hematological profiles were measured in pregnant women before and after a minimum of one-month IFA supplementation. Mean values and abnormal proportions of hematological profiles were compared before and after supplementation using paired t-test and McNemar test, respectively. Univariate and multivariate analysis were used to analyze the association between independent variables and poor treatment responses.

RESULT

Lack of adequate hemoglobin response was found in 48.5%(95/196) of the participants. Prevalence of anemia and low hematocrit value were decreased significantly after IFA supplementation (p = 0.002, and p = 0.001, respectively). Normocytic hypochromic anemia was the commonest form of anemia found in this study followed by normocytic normochromic anemia. There was no statistically significant association between poor hemoglobin responses and all studied factors such as educational level, household size, parity, recent illness, stage of pregnancy, coffee consumption, and duration of iron treatment.

CONCLUSION

Our study revealed poor hemoglobin responses in nearly half of the study participants and a high proportion of anemias morphologically atypical of iron deficiency anemia. There is a need to consider anemia attributable to etiologies other than an iron deficiency in anemia intervention programs.

Dysregulated iron metabolism in polycythemia vera: etiology and consequences

Polycythemia vera (PV) is a chronic myeloproliferative neoplasm. Virtually all PV patients are iron deficient at presentation and/or during the course of their disease. The co-existence of iron deficiency and polycythemia presents a physiological disconnect. Hepcidin, the master regulator of iron metabolism, is regulated by circulating iron levels, erythroblast secretion of erythroferrone, and inflammation. Both decreased circulating iron and increased erythroferrone levels, which occur as a consequence of erythroid hyperplasia in PV, are anticipated to suppress hepcidin and enable recovery from iron deficiency. Inflammation which accompanies PV is likely to counteract hepcidin suppression, but the relatively low serum ferritin levels observed suggest that inflammation is not a major contributor to the dysregulated iron metabolism. Furthermore, potential defects in iron absorption, aberrant hypoxia sensing and signaling, and frequency of bleeding to account for iron deficiency in PV patients have not been fully elucidated. Insufficiently suppressed hepcidin given the degree of iron deficiency in PV patients strongly suggests that disordered iron metabolism is an important component of the pathobiology of PV. Normalization of hematocrit levels using therapeutic phlebotomy is the most common approach for reducing the incidence of thrombotic complications, a therapy which exacerbates iron deficiency, contributing to a variety of non-hematological symptoms. The use of cytoreductive therapy in high-risk PV patients frequently works more effectively to reverse PV-associated symptoms in iron-deficient relative to iron-replete patients. Lastly, differences in iron-related parameters between PV patients and mice with JAK2 V617F and JAK2 exon 12 mutations suggest that specific regions in JAK2 may influence iron metabolism by nuanced changes of erythropoietin receptor signaling. In this review, we comprehensively discuss the clinical consequences of iron deficiency in PV, provide a framework for understanding the potential dysregulation of iron metabolism, and present a rationale for additional therapeutic options for iron-deficient PV patients.

Modulation of Iron Metabolism in Response to Infection: Twists for All Tastes

Iron is an essential nutrient for almost all living organisms, but is not easily made available. Hosts and pathogens engage in a fight for the metal during an infection, leading to major alterations in the host’s iron metabolism. Important pathological consequences can emerge from the mentioned interaction, including anemia. Several recent reports have highlighted the alterations in iron metabolism caused by different types of infection, and several possible therapeutic strategies emerge, based on the targeting of the host’s iron metabolism. Here, we review the most recent literature on iron metabolism alterations that are induced by infection, the consequent development of anemia, and the potential therapeutic approaches to modulate iron metabolism in order to correct iron-related pathologies and control the ongoing infection.

Hepcidin as a potential predictor for preoperative anemia treatment with intravenous iron-A retrospective pilot study

Preoperative anemia occurs in about one third of patients who undergo elective surgery and is associated with an impaired outcome. Therefore, screening of preoperative anemia was established in the context of a multidisciplinary Patient Blood Management (PBM) program at the University Hospital of Muenster, Germany. Anemic patients without contraindications were treated with intravenous (IV) iron (ferric carboxymaltose) to increase their hemoglobin (Hgb) levels and hence to treat anemia prior to surgery. Interestingly, we detected a large variability in the response of Hgb levels after IV iron administration. Systemic iron homeostasis is mainly regulated by the hepatic hormone hepcidin, which regulates the cell surface expression of the sole known iron exporter ferroportin. The objective of this retrospective pilot study was to analyze the potential of hepcidin to predict the response of anemic patients to preoperative IV iron treatment measured as increase in Hgb.

Serum samples of non-anemic (n = 48), untreated anemic (n = 64) and anemic patients treated with IV iron (n = 79), in total 191 patients, were collected between October 2014 until June 2016. Serum hepcidin levels were determined and data were analyzed retrospectively.

The analysis revealed at first a correlation between serum hepcidin levels and the parameters of the iron status. Second, patients treated with IV iron showed a noticeably higher increase in their delta Hgb level between PBM consultation and surgery (0.45g/dl [0.05, 1.05] compared to patients without IV iron (0.1g/dl [-0.48, 0.73], *p = 0.03). Patients were then grouped into ‘non-responders’, defined as delta Hgb <0.6g/dl and ‘responders’, with delta Hgb ≥0.6g/dl between the day of IV iron treatment and the day of surgery. Within normal ranges and clinically unapparent, a statistically noticeable difference between responders and non-responders was found for CRP and leukocytes. Serum hepcidin levels were higher in the group of non-responders (10.6ng/ml [3.93, 34.77]) compared to responders (2.1ng/ml [0.25, 7.97], *p = 0.04).

To conclude, the data of this retrospective pilot study indicate that hepcidin might be a promising biomarker to predict a patient`s responsiveness to IV iron in preoperative anemia treatment. Prospective studies have to investigate serum hepcidin levels as a biomarker to guide physician`s decision on IV iron substitution.

Hepcidin, an Iron Regulatory Hormone of Innate Immunity, is Differentially Expressed in Premature Fetuses with Early-Onset Neonatal Sepsis

OBJECTIVE

Hepcidin, a mediator of innate immunity, binds the iron exporter ferroportin, leading to functional hypoferremia through intracellular iron sequestration. We explored hepcidin-ferroportin interactions in neonates clinically diagnosed with early-onset neonatal sepsis (EONS).

STUDY DESIGN

Hepcidin and interleukin (IL)-6 were quantified by enzyme-linked immunosorbent assay (ELISA) in 92 paired cord blood-maternal blood samples in the following groups: "Yes" EONS (n = 41, gestational age [GA] 29 ± 1 weeks) and "No" EONS (n = 51, GA 26 ± 1 weeks). Placental hepcidin and ferroportin expression were evaluated by immunohistochemistry and real-time-polymerase chain reaction (RT-PCR). Liver hepcidin and ferroportin expression patterns were ascertained in autopsy specimens of neonates (n = 8) who died secondary to culture-proven sepsis.

RESULTS

Cord blood hepcidin was significantly elevated (GA corrected, p = 0.018) and was positively correlated with IL-6 (r = 0.379, p = 0.001) in EONS. Hepcidin localized at syncytiotrophoblast and fetal vascular endothelium. Placental ferroportin, but not hepcidin mRNA correlated with cord blood hepcidin levels (r = 0.46, p = 0.039) and funisitis severity (r = 0.50, p = 0.018). Newborns who died from sepsis (n = 4) had higher hepatic hepcidin and iron sequestration, but lower ferroportin staining than those who died of nonsepsis causes (n = 4).

CONCLUSION

Premature fetuses with EONS have elevated circulating hepcidin, likely related to lower placenta and liver ferroportin expression. Fetal hepcidin-ferroportin interaction appears to play a role in EONS pathophysiology independent of maternal response to intrauterine inflammation.

Iron Overload Is Associated With Oxidative Stress and Nutritional Immunity During Viral Infection in Fish

Iron is a trace element, essential to support life due to its inherent ability to exchange electrons with a variety of molecules. The use of iron as a cofactor in basic metabolic pathways is essential to both pathogenic microorganisms and their hosts. During evolution, the shared requirement of micro- and macro-organisms for this important nutrient has shaped the pathogen-host relationship. Infectious pancreatic necrosis virus (IPNv) affects salmonids constituting a sanitary problem for this industry as it has an important impact on post-smolt survival. While immune modulation induced by IPNv infection has been widely characterized on Salmo salar, viral impact on iron host metabolism has not yet been elucidated. In the present work, we evaluate short-term effect of IPNv on several infected tissues from Salmo salar. We observed that IPNv displayed high tropism to headkidney, which directly correlates with a rise in oxidative stress and antiviral responses. Transcriptional profiling on headkidney showed a massive modulation of gene expression, from which biological pathways involved with iron metabolism were remarkable. Our findings suggest that IPNv infection increase oxidative stress on headkidney as a consequence of iron overload induced by a massive upregulation of genes involved in iron metabolism.

Association of Colecalciferol, Ferritin, and Anemia among Pregnant Women: Result from Cohort Study on Vitamin D Status and Its Impact during Pregnancy and Childhood in Indonesia

Studies had shown that iron-cycling was disturbed by inflammatory process through the role of hepcidin. Pregnancy is characterized by shifts of interleukin. Our objective was to determine if 25(OH) vitamin D (colecalciferol) status was associated with ferritin, anemia, and its changes during pregnancy. Method. A cohort study was done in 4 cities in West Java, Indonesia, beginning in July 2016. Subjects were followed up until third trimester. Examinations included were maternal ferritin, colecalciferol, and haemoglobin level. Result. 191 (95.5%) subjects had low colecalciferol, and 151 (75.5%) among them were at deficient state. Anemia is found in 15 (7.5%) subjects, much lower than previous report. Proportion of anemia increased by trimester among women with colecalciferol deficiency. Ferritin status and prepregnancy body mass index in the first trimester were correlated with anemia (r = 0.147, p = 0.038 and r = -0.56, p = 0.03). Anemia in the second trimester was strongly correlated with anemia in the third trimester (r = 0.676, p < 0.01). Conclusion. Our study showed that the state of colecalciferol was not associated with either ferritin state or anemia, but proportion of anemia tends to increase by trimester in the colecalciferol deficient subjects.

Longitudinal Effects of Iron Deficiency Anemia and Subsequent Repletion on Blood Parameters and the Rate and Composition of Growth in Pigs

Iron deficiency is reported as the most common nutrient deficiency worldwide. Due to rapid growth, infants are at particular risk for developing iron deficiency, which can easily progress to iron deficiency anemia (IDA), if not treated. The aim of this study was to determine the lasting effects of an early-life iron deficiency after a period of dietary iron repletion. Forty-two intact male pigs were fed, ad libitum, either control (CONT, 21.3 mg Fe/L) or iron-deficient (ID 2.72 mg Fe/L) milk replacer from postnatal day (PND) 2 to 32 (phase 1). From PND 33 to 61 (phase 2), all pigs were transitioned onto a series of industry-standard, iron-adequate diets. Blood was collected weekly from PND 7 to 28, and again on PND 35 and 56, and tissues were collected at either PND 32 or PND 61. At the end of phase 1, ID pigs exhibited reduced hematocrit (Hct; p < 0.0001) and hemoglobin (Hb; p < 0.0001) compared with CONT pigs, but neither Hct (p = 0.5968) nor Hb (p = 0.6291) differed between treatment groups after dietary iron repletion at the end of phase 2. Body weight gain was reduced (p < 0.0001) 58% at PND 32 in ID pigs compared with CONT pigs during phase 1, and this effect remained significant at the end of phase 2 (p = 0.0001), with ID pigs weighing 34% less than CONT pigs at PND 61. Analysis of peripheral protein and messenger RNA (mRNA) gene expression biomarkers yielded inconclusive results, as would be expected based on previous biomarker analyses across multiple species. These findings suggest that early-life iron status negatively influences blood parameters and growth performance, with dietary iron repletion allowing for full recovery of hematological outcomes, but not growth performance.

Ultrafiltered recombinant AAV8 vector can be safely administered in vivo and efficiently transduces liver

Viral vectors are extensively purified for use in biomedical research, in order to separate biologically active virus particles and to eliminate production related impurities that are assumed to be detrimental to the host. For recombinant adeno-associated virus (rAAV) vectors this is typically accomplished using density gradient-based methods, which are tedious and require specialized ultracentrifugation equipment. In order to streamline the preparation of rAAV vectors for pilot and small animal studies, we recently devised a simple ultrafiltration approach that permits rapid virus concentration and partial removal of production-related impurities. Here we show that systemic administration of such rapidly prepared (RP) rAAV8 vectors in mice is safe and efficiently transduces the liver. Across a range of doses, delivery of RP rAAV8-CMV-eGFP vector induced enhanced green fluorescent protein (eGFP) expression in liver that was comparable to that obtained from a conventional iodixanol gradient-purified (IP) vector. Surprisingly, no liver inflammation or systemic cytokine induction was detected in RP rAAV injected animals, revealing that residual impurities in the viral vector preparation are not deleterious to the host. Together, these data demonstrate that partially purified rAAV vector can be safely and effectively administered in vivo. The speed and versatility of the RP method and lack of need for cumbersome density gradients or expensive ultracentrifuge equipment will enable more widespread use of RP prepared rAAV vectors, such as for pilot liver gene transfer studies.

Adenine alleviates iron overload by cAMP/PKA mediated hepatic hepcidin in mice

Hemochromatosis is prevalent and often associated with high rates of morbidity and mortality worldwide. The safe alternative iron-reducing approaches are urgently needed in order to better control iron overload. Our unbiased vitamin screen for modulators of hepcidin, a master iron regulatory hormone, identifies adenine (vitamin B4) as a potent hepcidin agonist. Adenine significantly induced hepcidin mRNA level and promoter activity activation in human cell lines, possibly through BMP/SMAD pathway. Further studies in mice validated the effect of adenine on hepcidin upregulation. Consistently, adenine dietary supplement in mice led to an increase of hepatic hepcidin expression compared with normal diet-fed mice via BMP/SMAD pathway. Notably, adenine-rich diet significantly ameliorated iron overload accompanied by the enhanced hepcidin expression in both high iron-fed mice and in Hfe^-/- mice, a murine model of hereditary hemochromatosis. To further validate this finding, we selected pharmacological inhibitors against BMP (LDN193189). We found LDN193189 strongly blocked the hepcidin induction by adenine. Moreover, we uncovered an essential role of cAMP/PKA-dependent axis in triggering adenine-induced hepcidin expression in primary hepatocytes by using 8 br cAMP, a cAMP analog, and H89, a potent inhibitor for PKA signaling. These findings suggest a potential therapeutic role of adenine for hereditary hemochromatosis.

Hepcidin agonists as therapeutic tools

Hepcidin agonists are a new class of compounds that regulate blood iron levels, limit iron absorption, and could improve the treatment of hemochromatosis, β-thalassemia, polycythemia vera, and other disorders in which disrupted iron homeostasis causes or contributes to disease. Hepcidin agonists also have the potential to prevent severe complications of siderophilic infections in patients with iron overload or chronic liver disease. This review highlights the preclinical studies that support the development of hepcidin agonists for the treatment of these disorders.

Modulation of intestinal sulfur assimilation metabolism regulates iron homeostasis

Regulation of iron homeostasis is perturbed in numerous pathologic states. Thus, identifications of mechanisms responsible for iron metabolism have broad implications for disease modification. Here, we link the sulfur assimilation pathway to iron-deficiency anemia. Deletion of bisphosphate 3′-nucleotidase (Bpnt1), a key component of the sulfur assimilation pathway, leads to accumulation of phosphoadenosine phosphate (PAP), causing iron deficiency anemia in part due to inhibition of hypoxia-inducible factor 2-α. Reduction of PAP through introduction of a hypomorphic mutation in 3′-phosphoadenosine 5-phosphosulfate synthase 2 gene (Papss2, the enzyme responsible for PAP production) rescues the iron deficiency phenotype.

Sulfur assimilation is an evolutionarily conserved pathway that plays an essential role in cellular and metabolic processes, including sulfation, amino acid biosynthesis, and organismal development. We report that loss of a key enzymatic component of the pathway, bisphosphate 3′-nucleotidase (Bpnt1), in mice, both whole animal and intestine-specific, leads to iron-deficiency anemia. Analysis of mutant enterocytes demonstrates that modulation of their substrate 3′-phosphoadenosine 5′-phosphate (PAP) influences levels of key iron homeostasis factors involved in dietary iron reduction, import and transport, that in part mimic those reported for the loss of hypoxic-induced transcription factor, HIF-2α. Our studies define a genetic basis for iron-deficiency anemia, a molecular approach for rescuing loss of nucleotidase function, and an unanticipated link between nucleotide hydrolysis in the sulfur assimilation pathway and iron homeostasis.

What can we learn from ineffective erythropoiesis in thalassemia?

Erythropoiesis is a dynamic process regulated at multiple levels to balance proliferation, differentiation and survival of erythroid progenitors. Ineffective erythropoiesis is a key feature of various diseases, including β-thalassemia. The pathogenic mechanisms leading to ineffective erythropoiesis are complex and still not fully understood. Altered survival and decreased differentiation of erythroid progenitors are both critical processes contributing to reduced production of mature red blood cells. Recent studies have identified novel important players and provided major advances in the development of targeted therapeutic approaches. In this review, β-thalassemia is used as a paradigmatic example to describe our current knowledge on the mechanisms leading to ineffective erythropoiesis and novel treatments that may have the potential to improve the clinical phenotype of associated diseases in the future.

Effects of an Acute Exercise Bout on Serum Hepcidin Levels

Iron deficiency is a frequent and multifactorial disorder in the career of athletes, particularly in females. Exercise-induced disturbances in iron homeostasis produce deleterious effects on performance and adaptation to training; thus, the identification of strategies that restore or maintain iron homeostasis in athletes is required. Hepcidin is a liver-derived hormone that degrades the ferroportin transport channel, thus reducing the ability of macrophages to recycle damaged iron, and decreasing iron availability. Although it has been suggested that the circulating fraction of hepcidin increases during early post-exercise recovery (~3 h), it remains unknown how an acute exercise bout may modify the circulating expression of hepcidin. Therefore, the current review aims to determine the post-exercise expression of serum hepcidin in response to a single session of exercise. The review was carried out in the Dialnet, Elsevier, Medline, Pubmed, Scielo and SPORTDiscus databases, using hepcidin (and “exercise” or “sport” or “physical activity”) as a strategy of search. A total of 19 articles were included in the review after the application of the inclusion/exclusion criteria. This search found that a single session of endurance exercise (intervallic or continuous) at moderate or vigorous intensity (60–90% VO_2peak) stimulates an increase in the circulating levels of hepcidin between 0 h and 6 h after the end of the exercise bout, peaking at ~3 h post-exercise. The magnitude of the response of hepcidin to exercise seems to be dependent on the pre-exercise status of iron (ferritin) and inflammation (IL-6). Moreover, oxygen disturbances and the activation of a hypoxia-induced factor during or after exercise may stimulate a reduction of hepcidin expression. Meanwhile, cranberry flavonoids supplementation promotes an anti-oxidant effect that may facilitate the post-exercise expression of hepcidin. Further studies are required to explore the effect of resistance exercise on hepcidin expression.

Hypoxia enhances H2O2-mediated upregulation of hepcidin: Evidence for NOX4-mediated iron regulation

The exact regulation of the liver-secreted peptide hepcidin, the key regulator of systemic iron homeostasis, is still poorly understood. It is potently induced by iron, inflammation, cytokines or H₂O₂ but conflicting results have been reported on hypoxia. In our current study, we first show that pronounced (1%) and mild (5%) hypoxia strongly induces hepcidin in human Huh7 hepatoma and primary liver cells predominantly at the transcriptional level via STAT3 using two hypoxia systems (hypoxia chamber and enzymatic hypoxia by the GOX/CAT system). SiRNA silencing of JAK1, STAT3 and NOX4 diminished the hypoxia-mediated effect while a role of HIF1α could be clearly ruled out by the response to hypoxia-mimetics and competition experiments with a plasmid harboring the oxygen-dependent degradation domain of HIF1α. Specifically, hypoxia drastically enhances the H₂O₂-mediated induction of hepcidin strongly pointing towards an oxidase as powerful upstream control of hepcidin. We finally provide evidences for an efficient regulation of hepcidin expression by NADPH-dependent oxidase 4 (NOX4) in liver cells. In summary, our data demonstrate that hypoxia strongly potentiates the peroxide-mediated induction of hepcidin via STAT3 signaling pathway. Moreover, oxidases such as NOX4 or artificially overexpressed urate oxidase (UOX) can induce hepcidin. It remains to be studied whether the peroxide-STAT3-hepcidin axis simply acts to continuously compensate for oxygen fluctuations or is directly involved in iron sensing per se.

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Hypoxia strongly induces hepcidin via STAT3 signaling.

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HIF1α is not involved in hepcidin regulation under hypoxia.

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Hypoxia enhances hydrogen peroxide-mediated hepcidin induction.

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Oxidases, such as NOX4 are powerful inducers of hepcidin.

Non-Transfusion-Dependent Thalassemia: An Update on Complications and Management

Patients with non-transfusion-dependent thalassemia (NTDT) experience many clinical complications despite their independence from frequent transfusions. Morbidities in NTDT stem from the interaction of multiple pathophysiological factors: ineffective erythropoiesis, iron overload (IOL), and hypercoagulability. Ineffective erythropoiesis and hemolysis are associated with chronic hypoxia and a hypercoagulable state. The latter are linked to a high prevalence of thromboembolic and cerebrovascular events, as well as leg ulcers and pulmonary hypertension. IOL in NTDT patients is a cumulative process that can lead to several iron-related morbidities in the liver (liver fibrosis), kidneys, endocrine glands (endocrinopathies), and vascular system (vascular disease). This review sheds light on the pathophysiology underlying morbidities associated with NTDT and summarizes the mainstays of treatment and some of the possible future therapeutic interventions.

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.

Iron Therapy in Heart Failure: Ready for Primetime?

There is an increasing awareness of the prevalence of iron deficiency (ID) in patients with heart failure (HF) and its contributory role in the morbidity and mortality of HF. It is important to note that many HF patients have ID without being anaemic, hence it is vital to screen for ID even in patients with haemoglobin within the normal laboratory range. This review summarises the pathophysiology and epidemiology of ID in HF before discussing the evidence for iron replacement therapy in HF patients. Finally, it discusses the ongoing large outcome trials evaluating iron replacement in HF.

Ineffective Erythropoiesis: Anemia and Iron Overload

Stress erythropoiesis (SE) is characterized by an imbalance in erythroid proliferation and differentiation under increased demands of erythrocyte generation and tissue oxygenation. β-thalassemia represents a chronic state of SE, called ineffective erythropoiesis (IE), exhibiting an expansion of erythroid-progenitor pool and deposition of alpha chains on erythrocyte membranes, causing cell death and anemia. Concurrently, there is a decrease in hepcidin expression and a subsequent state of iron overload. There are substantial investigative efforts to target increased iron absorption under IE. There are also avenues for targeting cell contact and signaling within erythroblastic islands under SE, for therapeutic benefits.

Iron Overload and Chelation Therapy in Non-Transfusion Dependent Thalassemia

Iron overload (IOL) due to increased intestinal iron absorption constitutes a major clinical problem in patients with non-transfusion-dependent thalassemia (NTDT), which is a cumulative process with advancing age. Current models for iron metabolism in patients with NTDT suggest that suppression of serum hepcidin leads to an increase in iron absorption and subsequent release of iron from the reticuloendothelial system, leading to depletion of macrophage iron, relatively low levels of serum ferritin, and liver iron loading. The consequences of IOL in patients with NTDT are multiple and multifactorial. Accurate and reliable methods of diagnosis and monitoring of body iron levels are essential, and the method of choice for measuring iron accumulation will depend on the patient's needs and on the available facilities. Iron chelation therapy (ICT) remains the backbone of NTDT management and is one of the most effective and practical ways of decreasing morbidity and mortality. The aim of this review is to describe the mechanism of IOL in NTDT, and the clinical complications that can develop as a result, in addition to the current and future therapeutic options available for the management of IOL in NTDT.

HIF-prolyl hydroxylases as therapeutic targets in erythropoiesis and iron metabolism

A classic response to systemic hypoxia is the increase in red blood cell production. This response is controlled by the prolyl hydroxylase domain/hypoxia-inducible factor (HIF) pathway, which regulates a broad spectrum of cellular functions. The discovery of this pathway as a key regulator of erythropoiesis has led to the development of small molecules that stimulate the production of endogenous erythropoietin and enhance iron metabolism. This review provides a concise overview of the cellular and molecular mechanisms that govern HIF-induced erythropoietic responses and provides an update on clinical experience with compounds that target HIF-prolyl hydroxylases for anemia therapy.

Hepatocyte toll-like receptor 4 mediates lipopolysaccharide-induced hepcidin expression

Hepcidin expression is induced by inflammatory molecules such as lipopolysaccharide (LPS) via a macrophage-mediated pathway. Although hepatocytes directly respond to LPS, the molecular mechanism underlying toll-like receptor (TLR)-dependent hepcidin expression by hepatocytes is mostly unknown. Here we show that LPS can directly induce the mRNA expression and secretion of hepcidin by hepatocytes via TLR4 activation. Using hepatocytes deficient in TLR4, myeloid differentiation factor 88 (MyD88) and TIR domain-containing adaptor inducing interferon-β (TRIF), we demonstrated that LPS-induced hepcidin expression by hepatocytes is regulated by its specific receptor, TLR4, via a MyD88-dependent signaling pathway. Hepcidin promoter activity was significantly increased by MyD88-dependent downstream signaling molecules (interleukin-1 receptor-associated kinase (IRAK) and tumor necrosis factor receptor-associated factor 6 (TRAF6), which activate c-Jun N-terminal kinase (JNK) and activator protein-1 (AP-1). We then confirmed that LPS stimulation induced the phosphorylation of JNK and c-Jun, and observed strong occupancy of the hepcidin promoter by c-Jun. Promoter mutation analysis also identified the AP-1-binding site on the hepcidin promoter. Finally, bone marrow transplantation between wild-type and TLR4 knockout mice revealed that hepatic TLR4-dependent hepcidin expression was comparable to macrophage TLR4-dependent hepcidin expression induced by LPS. Taken together, these results suggest that TLR4 expressed by hepatocytes regulates hepcidin expression via the IRAK–TRAF6–JNK–AP-1 axis.

Iron-related markers are associated with infection after liver transplantation

Though serum iron has been known to be associated with an increased risk of infection, hepcidin, the major regulator of iron metabolism, has never been systematically explored in this setting. Finding early biomarkers of infection, such as hepcidin, could help identify patients in whom early empiric antimicrobial therapy would be beneficial. We prospectively enrolled consecutive patients (n = 128) undergoing first-time, single-organ orthotopic liver transplantation (OLT) without known iron overload disorders at 2 academic hospitals in Boston from August 2009 to November 2012. Cox regression compared the associations between different iron markers and the development of first infection at least 1 week after OLT; 47 (37%) patients developed a primary outcome of infection at least 1 week after OLT and 1 patient died. After adjusting for perioperative bleeding complications, number of hospital days, and hepatic artery thrombosis, changes in iron markers were associated with the development of infection post-OLT including increasing ferritin (hazard ratio [HR], 1.51; 95% confidence interval [CI], 1.12-2.05), rising ferritin slope (HR, 1.10; 95% CI, 1.03-1.17), and increasing hepcidin (HR, 1.43; 95% CI, 1.05-1.93). A decreasing iron (HR, 1.76; 95% CI, 1.20-2.57) and a decreasing iron slope (HR, 4.21; 95% CI, 2.51-7.06) were also associated with subsequent infections. In conclusion, hepcidin and other serum iron markers and their slope patterns or their combination are associated with infection in vulnerable patient populations. Liver Transplantation 23 1541-1552 2017 AASLD.

Role of Activins in Hepcidin Regulation during Malaria

Epidemiological observations have linked increased host iron with malaria susceptibility, and perturbed iron handling has been hypothesized to contribute to the potentially life-threatening anemia that may accompany blood-stage malaria infection. To improve our understanding of these relationships, we examined the pathways involved in regulation of the master controller of iron metabolism, the hormone hepcidin, in malaria infection. We show that hepcidin upregulation in Plasmodium berghei murine malaria infection was accompanied by changes in expression of bone morphogenetic protein (BMP)/sons of mothers against decapentaplegic (SMAD) pathway target genes, a key pathway involved in hepcidin regulation. We therefore investigated known agonists of the BMP/SMAD pathway and found that Bmp gene expression was not increased in infection. In contrast, activin B, which can signal through the BMP/SMAD pathway and has been associated with increased hepcidin during inflammation, was upregulated in the livers of Plasmodium berghei-infected mice; hepatic activin B was also upregulated at peak parasitemia during infection with Plasmodium chabaudi Concentrations of the closely related protein activin A increased in parallel with hepcidin in serum from malaria-naive volunteers infected in controlled human malaria infection (CHMI) clinical trials. However, antibody-mediated neutralization of activin activity during murine malaria infection did not affect hepcidin expression, suggesting that these proteins do not stimulate hepcidin upregulation directly. In conclusion, we present evidence that the BMP/SMAD signaling pathway is perturbed in malaria infection but that activins, although raised in malaria infection, may not have a critical role in hepcidin upregulation in this setting.

The relationship between systemic iron homeostasis and erythropoiesis

Red blood cell production (erythropoiesis) is the single largest consumer of iron in the body; this need is satisfied by maintaining a sensitive regulation of iron levels. The level of erythropoietic demand regulates the expression of the iron hormone hepcidin and thus iron absorption. Erythropoiesis-mediated regulation of hepcidin is an area of increasing importance and recent studies have identified a number of potential regulatory proteins. This review summarizes our current knowledge about these candidate erythroid regulators of hepcidin and the relation between transferrin receptors and erythropoiesis.

Identification of Antibody and Small Molecule Antagonists of Ferroportin-Hepcidin Interaction

The iron exporter ferroportin and its ligand, the hormone hepcidin, control fluxes of stored and recycled iron for use in a variety of essential biochemical processes. Inflammatory disorders and malignancies are often associated with high hepcidin levels, leading to ferroportin down-regulation, iron sequestration in tissue macrophages and subsequent anemia. The objective of this research was to develop reagents to characterize the expression of ferroportin, the interaction between ferroportin and hepcidin, as well as to identify novel ferroportin antagonists capable of maintaining iron export in the presence of hepcidin. Development of investigative tools that enabled cell-based screening assays is described in detail, including specific and sensitive monoclonal antibodies that detect endogenously-expressed human and mouse ferroportin and fluorescently-labeled chemically-synthesized human hepcidin. Large and small molecule antagonists inhibiting hepcidin-mediated ferroportin internalization were identified, and unique insights into the requirements for interaction between these two key iron homeostasis molecules are provided.

Normalizing serum hepcidin but not α-1-antitrypsin level during effective treatment of chronic hepatitis C

Aim of the study

We investigated the impact of pegylated interferon α-2 in combination with ribavirin (PEG-IFNα/RBV) treatment on hepcidin and α-1-antitrypsin concentrations in the serum of patients with chronic hepatitis C.

Material and methods

We measured serum concentrations of hepcidin, prohepcidin and α-1-antitrypsin by enzyme-linked immunosorbent assays in patients with chronic hepatitis C before and during antiviral therapy.

Results

Hepcidin concentrations were increased in both genotype 1b and 3a hepatitis C virus (HCV) infected patients as compared with the control group. During treatment of patients infected with genotype 1b HCV hepcidin levels gradually declined, reaching significantly lower values at the treatment termination than before therapy. Treatment responders showed an increased concentration of hepcidin at week 4 of therapy and a subsequent decrease to values significantly lower than observed among non-responders at week 48 of treatment. α-1-antitrypsin concentration was not affected by the treatment efficacy.

Conclusions

Successful therapy of patients persistently infected with HCV was associated with restoration of serum hepcidin concentration to values similar to the control group. Differential dynamics of hepcidin during PEG-IFNα/RBV therapy in responders and non-responders might indicate the direct influence of viral eradication on iron homeostasis.

Physical exercise intervention at school improved hepcidin, inflammation, and iron metabolism in overweight and obese children and adolescents

BackgroundObesity is often associated with iron deficiency in children and adolescents. We aimed to study the effect of an 8-month physical exercise (PE) intervention on hepcidin and other markers of inflammation and on iron status in overweight/obese children and adolescents.MethodsSeventy-three overweight/obese children and adolescents participated in the 8-month-long longitudinal study. They were divided into two groups according to their participation in an after-school PE program: the PE group (n=44) and the control group (n=29). Hepcidin, interleukin (IL)-6, C-reactive protein (CRP), iron, ferritin, transferrin, and soluble transferrin receptor (sTfR) were evaluated.ResultsAt baseline, IL-6 correlated positively with hepcidin and negatively with iron and transferrin saturation, suggesting that increasing adiposity associates with increasing IL-6 and hepcidin synthesis, reducing iron availability. After 8 months, the PE group showed a decrease in BMI z-score (P=0.003), body fat mass (P=0.012), CRP (P=0.002), IL-6 (P=0.048), ferritin (P=0.013), hepcidin (P=0.040), and sTfR (P=0.010), and an increase in iron concentration (P=0.002). Moreover, the PE group, when compared with the control group, showed lower weight (P=0.026), BMI (P=0.040), waist circumference (P=0.010), and waist-to-height ratio (P=0.046).ConclusionWe showed that an 8-month-long intervention at school allowed a reduction in BMI z-score and an improvement in inflammation, reducing hepcidin levels and the disturbances in iron status.

Does Hypoxia Cause Carcinogenic Iron Accumulation in Alcoholic Liver Disease (ALD)?

Alcoholic liver disease (ALD) is a leading health risk worldwide. Hepatic iron overload is frequently observed in ALD patients and it is an important and independent factor for disease progression, survival, and the development of primary liver cancer (HCC). At a systemic level, iron homeostasis is controlled by the liver-secreted hormone hepcidin. Hepcidin regulation is complex and still not completely understood. It is modulated by many pathophysiological conditions associated with ALD, such as inflammation, anemia, oxidative stress/H₂O_2, or hypoxia. Namely, the data on hypoxia-signaling of hepcidin are conflicting, which seems to be mainly due to interpretational limitations of in vivo data and methodological challenges. Hence, it is often overlooked that hepcidin-secreting hepatocytes are physiologically exposed to 2–7% oxygen, and that key oxygen species such as H₂O₂ act as signaling messengers in such a hypoxic environment. Indeed, with the recently introduced glucose oxidase/catalase (GOX/CAT) system it has been possible to independently study hypoxia and H₂O₂ signaling. First preliminary data indicate that hypoxia enhances H₂O₂-mediated induction of hepcidin, pointing towards oxidases such as NADPH oxidase 4 (NOX4). We here review and discuss novel concepts of hypoxia signaling that could help to better understand hepcidin-associated iron overload in ALD.

Serum Hepcidin as a Diagnostic Marker of Severe Iron Overload in Beta-thalassemia Major

OBJECTIVES

To investigate potential usefulness of serum hepcidin in the diagnosis of iron overload in children with β-thalassemia.

METHODS

A study was conducted on 30 thalassemia major (TM), 30 thalassemia intermedia (TI) and 60 healthy children as controls. Serum hepcidin was measured by Human Hepcidin, ELISA Kit.

RESULTS

β-thalassemia patients had a higher serum hepcidin compared to the controls (p < 0.001). TM group had higher hepcidin and ferritin compared to the TI group (p = 0.034; < 0.001, respectively). Among controls, hepcidin did not correlate with age (r = 0.225, p = 0.084). Among β-thalassemia patients, it correlated positively with age (r = 0.4; p = 0.001), disease duration (r = 0.5; p < 0.001), transfusion frequency (r = 0.35; p = 0.007), total number of transfusions (r = 0.4; p = 0.003), and ferritin (r = 0.3; p = 0.027). Total hemoglobin and serum ferritin were significantly related to hepcidin, which tended to increase by 0.514 ng/ml with each 1 g/dl rise in hemoglobin (p = 0.023) and by 0.002 ng/ml with each 1 ng/ml rise in serum ferritin (p = 0.002). Iron overload [serum ferritin (SF) ≥ 1500 ng/ml] was independently associated with TM (p = 0.001) and elevated serum hepcidin (p = 0.02). The overall predictability of serum hepcidin in severe iron overload was statistically significant when compared to hepcidin to serum ferritin ratio.

CONCLUSIONS

Serum hepcidin is elevated in children with β-thalassemia; but this elevation is more evident in TM patients with severe iron overload. Thus, hepcidin can be a potential marker of severe iron overload in patients with TM. Further studies are recommended to compare serum hepcidin and serum ferritin in the prediction of severe iron overload in steady state and during infection or inflammation.

Hepcidin is regulated by promoter-associated histone acetylation and HDAC3

Hepcidin regulates systemic iron homeostasis. Suppression of hepcidin expression occurs physiologically in iron deficiency and increased erythropoiesis but is pathologic in thalassemia and hemochromatosis. Here we show that epigenetic events govern hepcidin expression. Erythropoiesis and iron deficiency suppress hepcidin via erythroferrone-dependent and -independent mechanisms, respectively, in vivo, but both involve reversible loss of H3K9ac and H3K4me3 at the hepcidin locus. In vitro, pan-histone deacetylase inhibition elevates hepcidin expression, and in vivo maintains H3K9ac at hepcidin-associated chromatin and abrogates hepcidin suppression by erythropoietin, iron deficiency, thalassemia, and hemochromatosis. Histone deacetylase 3 and its cofactor NCOR1 regulate hepcidin; histone deacetylase 3 binds chromatin at the hepcidin locus, and histone deacetylase 3 knockdown counteracts hepcidin suppression induced either by erythroferrone or by inhibiting bone morphogenetic protein signaling. In iron deficient mice, the histone deacetylase 3 inhibitor RGFP966 increases hepcidin, and RNA sequencing confirms hepcidin is one of the genes most differentially regulated by this drug in vivo. We conclude that suppression of hepcidin expression involves epigenetic regulation by histone deacetylase 3.Hepcidin controls systemic iron levels by inhibiting intestinal iron absorption and iron recycling. Here, Pasricha et al. demonstrate that the hepcidin-chromatin locus displays HDAC3-mediated reversible epigenetic modifications during both erythropoiesis and iron deficiency.

Iron Supplementation during Three Consecutive Days of Endurance Training Augmented Hepcidin Levels

Iron supplementation contributes an effort to improving iron status among athletes, but it does not always prevent iron deficiency. In the present study, we explored the effect of three consecutive days of endurance training (twice daily) on the hepcidin-25 (hepcidin) level. The effect of iron supplementation during this period was also determined. Fourteen male endurance athletes were enrolled and randomly assigned to either an iron-treated condition (Fe condition, n = 7) or a placebo condition (Control condition; CON, n = 7). They engaged in two 75-min sessions of treadmill running at 75% of maximal oxygen uptake on three consecutive days (days 1-3). The Fe condition took 12 mg of iron twice daily (24 mg/day), and the CON condition did not. On day 1, both conditions exhibited significant increases in serum hepcidin and plasma interleukin-6 levels after exercise (p < 0.05). In the CON condition, the hepcidin level did not change significantly throughout the training period. However, in the Fe condition, the serum hepcidin level on day 4 was significantly higher than that of the CON condition (p < 0.05). In conclusion, the hepcidin level was significantly elevated following three consecutive days of endurance training when moderate doses of iron were taken.

Daily propranolol administration reduces persistent injury-associated anemia after severe trauma and chronic stress

BACKGROUND

After severe trauma, patients develop a norepinephrine-mediated persistent, injury-associated anemia. This anemia is associated with suppression of bone marrow (BM) erythroid colony growth, along with decreased iron levels, and elevated erythropoietin (EPO) levels, which are insufficient to promote effective erythropoiesis. The impact of norepinephrine on iron regulators, such as ferroportin, transferrin, and transferrin receptor-1 (TFR-1), is unknown. Using a clinically relevant rodent model of lung contusion (LC), hemorrhagic shock (HS), and chronic stress (CS), we hypothesize that daily propranolol (BB), a nonselective β blocker, restores BM function and improves iron homeostasis.

METHODS

Male Sprague-Dawley rats were subjected to LCHS ± BB and LCHS/CS ± BB. BB was achieved with propranolol (10 mg/kg) daily until the day of sacrifice. Hemoglobin, plasma EPO, plasma hepcidin, BM cellularity and BM erythroid colony growth were assessed. RNA was isolated to measure transferrin, TFR-1 and ferroportin expression. Data are presented as mean ± SD; *p < 0.05 versus untreated counterpart by t test.

RESULTS

The addition of CS to LCHS leads to persistent anemia on posttrauma day 7, while the addition of BB improved hemoglobin levels (LCHS/CS: 10.6 ± 0.8 vs. LCHS/CS + BB: 13.9 ± 0.4* g/dL). Daily BB use after LCHS/CS improved BM cellularity, colony-forming units granulocyte, erythrocyte, monocyte megakaryocyte, burst-forming unit erythroid and colony-forming unit erythroid cell colony growth. LCHS/CS + BB significantly reduced plasma EPO levels and increased plasma hepcidin levels on day 7. The addition of CS to LCHS resulted in decreased liver ferroportin expression as well as decreased BM transferrin and TFR-1 expression, thus, blocking iron supply to erythroid cells. However, daily BB after LCHS/CS improved expression of all iron regulators.

CONCLUSION

Daily propranolol administration after LCHS/CS restored BM function and improved anemia after severe trauma. In addition, iron regulators are significantly reduced after LCHS/CS, which may contribute to iron restriction after injury. However, daily propranolol administration after LCHS/CS improved iron homeostasis.

Characterization of erythropoietin and hepcidin in the regulation of persistent injury-associated anemia

BACKGROUND

The cause of persistent injury-associated anemia is multifactorial and includes acute blood loss, an altered erythropoietin (EPO) response, dysregulation of iron homeostasis, and impaired erythropoiesis in the setting of chronic inflammation/stress. Hepcidin plays a key role in iron homeostasis and is regulated by anemia and inflammation. Erythropoietin is a main regulator of erythropoiesis induced by hypoxia. A unique rodent model of combined lung injury (LC)/hemorrhagic shock (HS) (LCHS)/chronic restraint stress (CS) was used to produce persistent injury-associated anemia to further investigate the roles of EPO, hepcidin, iron, ferritin, and the expression of EPO receptors (EPOr).

METHODS

Male Sprague-Dawley rats were randomly assigned into one of the four groups of rodent models: naive, CS alone, combined LCHS, or LCHS/CS. Plasma was used to evaluate levels of EPO, hepcidin, iron, and ferritin. RNA was isolated from bone marrow and lung tissue to evaluate expression of EPOr. Comparisons between models were performed by t tests followed by one-way analysis of variance.

RESULTS

After 7 days, only LCHS/CS was associated with persistent anemia despite significant elevation of plasma EPO. Combined LCHS and LCHS/CS led to a persistent decrease in EPOr expression in bone marrow on Day 7. The LCHS/CS significantly decreased plasma hepcidin levels by 75% on Day 1 and 84% on Day 7 compared to LCHS alone. Hepcidin plasma levels are inversely proportional to EPO plasma levels (Pearson R = -0.362, p < 0.05).

CONCLUSION

Tissue injury, hemorrhagic shock, and stress stimulate and maintain high levels of plasma EPO while hepcidin levels are decreased. In addition, bone marrow EPOr and plasma iron availability are significantly reduced following LCHS/CS. The combined deficit of reduced iron availability and reduced bone marrow EPOr expression may play a key role in the ineffective EPO response associated with persistent injury-associated anemia.

Hepcidin: Homeostasis and Diseases Related to Iron Metabolism

Iron is an essential metal for cell survival that is regulated by the peptide hormone hepcidin. However, its influence on certain diseases is directly related to iron metabolism or secondary to underlying diseases. Genetic alterations influence the serum hepcidin concentration, which can lead to an iron overload in tissues, as observed in haemochromatosis, in which serum hepcidin or defective hepcidin synthesis is observed. Another genetic imbalance of iron is iron-refractory anaemia, in which serum concentrations of hepcidin are increased, precluding the flow and efflux of extra- and intracellular iron. During the pathogenesis of certain diseases, the resulting oxidative stress, as well as the increase in inflammatory cytokines, influences the transcription of the HAMP gene to generate a secondary anaemia due to the increase in the serum concentration of hepcidin. To date, there is no available drug to inhibit or enhance hepcidin transcription, mostly due to the cytotoxicity described in the in vitro models. The proposed therapeutic targets are still in the early stages of clinical trials. Some candidates are promising, such as heparin derivatives and minihepcidins. This review describes the main pathways of systemic and genetic regulation of hepcidin, as well as its influence on the disorders related to iron metabolism.

Effect of Oral Iron Repletion on Exercise Capacity in Patients With Heart Failure With Reduced Ejection Fraction and Iron Deficiency: The IRONOUT HF Randomized Clinical Trial

IMPORTANCE

Iron deficiency is present in approximately 50% of patients with heart failure with reduced left ventricular ejection fraction (HFrEF) and is an independent predictor of reduced functional capacity and mortality. However, the efficacy of inexpensive readily available oral iron supplementation in heart failure is unknown.

OBJECTIVE

To test whether therapy with oral iron improves peak exercise capacity in patients with HFrEF and iron deficiency.

DESIGN, SETTING, AND PARTICIPANTS

Phase 2, double-blind, placebo-controlled randomized clinical trial of patients with HFrEF (<40%) and iron deficiency, defined as a serum ferritin level of 15 to 100 ng/mL or a serum ferritin level of 101 to 299 ng/mL with transferrin saturation of less than 20%. Participants were enrolled between September 2014 and November 2015 at 23 US sites.

INTERVENTIONS

Oral iron polysaccharide (n = 111) or placebo (n = 114), 150 mg twice daily for 16 weeks.

MAIN OUTCOMES AND MEASURES

The primary end point was a change in peak oxygen uptake (V̇o2) from baseline to 16 weeks. Secondary end points were change in 6-minute walk distance, plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels, and health status as assessed by Kansas City Cardiomyopathy Questionnaire (KCCQ, range 0-100, higher scores reflect better quality of life).

RESULTS

Among 225 randomized participants (median age, 63 years; 36% women) 203 completed the study. The median baseline peak V̇o2 was 1196 mL/min (interquartile range [IQR], 887-1448 mL/min) in the oral iron group and 1167 mL/min (IQR, 887-1449 mL/min) in the placebo group. The primary end point, change in peak V̇o2 at 16 weeks, did not significantly differ between the oral iron and placebo groups (+23 mL/min vs -2 mL/min; difference, 21 mL/min [95% CI, -34 to +76 mL/min]; P = .46). Similarly, at 16 weeks, there were no significant differences between treatment groups in changes in 6-minute walk distance (-13 m; 95% CI, -32 to 6 m), NT-proBNP levels (159; 95% CI, -280 to 599 pg/mL), or KCCQ score (1; 95% CI, -2.4 to 4.4), all P > .05.

CONCLUSIONS AND RELEVANCE

Among participants with HFrEF with iron deficiency, high-dose oral iron did not improve exercise capacity over 16 weeks. These results do not support use of oral iron supplementation in patients with HFrEF.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT02188784.

Therapeutic targeting of the HIF oxygen-sensing pathway: Lessons learned from clinical studies

The oxygen-sensitive hypoxia-inducible factor (HIF) pathway plays a central role in the control of erythropoiesis and iron metabolism. The discovery of prolyl hydroxylase domain (PHD) proteins as key regulators of HIF activity has led to the development of inhibitory compounds that are now in phase 3 clinical development for the treatment of renal anemia, a condition that is commonly found in patients with advanced chronic kidney disease. This review provides a concise overview of clinical effects associated with pharmacologic PHD inhibition and was written in memory of Professor Lorenz Poellinger.

Interferon lambda polymorphisms associate with body iron indices and hepatic expression of interferon-responsive long non-coding RNA in chronic hepatitis C

Single nucleotide polymorphisms (SNPs) within DNA region containing interferon lambda 3 (IFNL3) and IFNL4 genes are prognostic factors of treatment response in chronic hepatitis C (CHC). Iron overload, frequently diagnosed in CHC, is associated with unfavorable disease course and a risk of carcinogenesis. Its etiology and relationship with the immune response in CHC are not fully explained. Our aim was to determine whether IFNL polymorphisms in CHC patients associate with body iron indices, and whether they are linked with hepatic expression of genes involved in iron homeostasis and IFN signaling. For 192 CHC patients, four SNPs within IFNL3-IFNL4 region (rs12979860, rs368234815, rs8099917, rs12980275) were genotyped. In 185 liver biopsies, histopathological analyses were performed. Expression of five mRNAs and three long non-coding RNAs (lncRNAs) was determined with qRT-PCR in 105 liver samples. Rs12979860 TT or rs8099917 GG genotypes as well as markers of serum and hepatocyte iron overload associated with higher activity of gamma-glutamyl transpeptidase and liver steatosis. The presence of two minor alleles in any of the tested SNPs predisposed to abnormally high serum iron concentration and correlated with higher hepatic expression of lncRNA NRIR. On the other hand, homozygosity in any major allele associated with higher viral load. Patients bearing rs12979860 CC genotype had lower hepatic expression of hepcidin (HAMP; P = 0.03). HAMP mRNA level positively correlated with serum iron indices and degree of hepatocyte iron deposits. IFNL polymorphisms influence regulatory pathways of cellular response to IFN and affect body iron balance in chronic hepatitis C virus infection.

Smad1/5 is required for erythropoietin-mediated suppression of hepcidin in mice

Anemia suppresses liver hepcidin expression to supply adequate iron for erythropoiesis. Erythroferrone mediates hepcidin suppression by anemia, but its mechanism of action remains uncertain. The bone morphogenetic protein (BMP)-SMAD signaling pathway has a central role in hepcidin transcriptional regulation. Here, we explored the contribution of individual receptor-activated SMADs in hepcidin regulation and their involvement in erythroferrone suppression of hepcidin. In Hep3B cells, SMAD5 or SMAD1 but not SMAD8, knockdown inhibited hepcidin (HAMP) messenger RNA (mRNA) expression. Hepatocyte-specific double-knockout Smad1^fl/fl;Smad5^fl/fl;Cre⁺ mice exhibited ∼90% transferrin saturation and massive liver iron overload, whereas Smad1^fl/fl;Smad5^fl/wt;Cre⁺ mice or Smad1^fl/wt;Smad5^fl/fl;Cre⁺ female mice with 1 functional Smad5 or Smad1 allele had modestly increased serum and liver iron, and single-knockout Smad5^fl/fl;Cre⁺ or Smad1^fl/fl;Cre⁺ mice had minimal to no iron loading, suggesting a gene dosage effect. Hamp mRNA was reduced in all Cre⁺ mouse livers at 12 days and in all Cre⁺ primary hepatocytes. However, only double-knockout mice continued to exhibit low liver Hamp at 8 weeks and failed to induce Hamp in response to Bmp6 in primary hepatocyte cultures. Epoetin alfa (EPO) robustly induced bone marrow erythroferrone (Fam132b) mRNA in control and Smad1^fl/fl;Smad5^fl/fl;Cre⁺ mice but suppressed hepcidin only in control mice. Likewise, erythroferrone failed to decrease Hamp mRNA in Smad1^fl/fl;Smad5^fl/fl;Cre⁺ primary hepatocytes and SMAD1/SMAD5 knockdown Hep3B cells. EPO and erythroferrone reduced liver Smad1/5 phosphorylation in parallel with Hamp mRNA in control mice and Hep3B cells. Thus, Smad1 and Smad5 have overlapping functions to govern hepcidin transcription. Moreover, erythropoietin and erythroferrone target Smad1/5 signaling and require Smad1/5 to suppress hepcidin expression.

Change in iron metabolism in rats after renal ischemia/reperfusion injury

Previous studies have indicated that hepcidin, which can regulate iron efflux by binding to ferroportin-1 (FPN1) and inducing its internalization and degradation, acts as the critical factor in the regulation of iron metabolism. However, it is unknown whether hepcidin is involved in acute renal ischemia/reperfusion injury (IRI). In this study, an IRI rat model was established via right renal excision and blood interruption for 45 min in the left kidney, and iron metabolism indexes were examined to investigate the change in iron metabolism and to analyze the role of hepcidin during IRI. From 1 to 24 h after renal reperfusion, serum creatinine and blood urea nitrogen were found to be time-dependently increased with different degrees of kidney injury. Regular variations in iron metabolism indexes in the blood and kidneys were observed in renal IRI. Renal iron content, serum iron and serum ferritin increased early after reperfusion and then declined. Hepcidin expression in the liver significantly increased early after reperfusion, and its serum concentration increased beginning at 8 h after reperfusion. The splenic iron content decreased significantly in the early stage after reperfusion and then increased time-dependently with increasing reperfusion time, and the hepatic iron content showed a decrease in the early stage after reperfusion. The early decrease of the splenic iron content and hepatic iron content might indicate their contribution to the increase in serum iron in renal IRI. In addition, the duodenal iron content showed time-dependently decreased since 12 h after reperfusion in the IRI groups compared to the control group. Along with the spleen, the duodenum might contribute to the decrease in serum iron in the later stage after reperfusion. The changes in iron metabolism indexes observed in our study demonstrate an iron metabolism disorder in renal IRI, and hepcidin might be involved in maintaining iron homeostasis in renal IRI. These findings might suggest a self-protection mechanism regulating iron homeostasis in IRI and provide a new perspective on iron metabolism in attenuating renal IRI.

Hepcidin suppression in β-thalassemia is associated with the down-regulation of atonal homolog 8

Atonal homolog 8 (ATOH8) is defined as a positive regulator of hepcidin transcription, which links erythropoietic activity with iron-sensing molecules. In the present study, we investigated the association between hepcidin and ATOH8 expression in β-thalassemia. We found that inhibition of hepcidin expression in β-thalassemia is correlated with reduced ATOH8 expression. Hepatic hepcidin 1 (Hamp1) and Atoh8 mRNA expression were down-regulated in β-thalassemic mice. Hepcidin (HAMP) and ATOH8 mRNA expression were consistently suppressed in Huh7 cells cultured in medium supplemented with β-thalassemia patient serum. The Huh7 cells, which were transfected with ATOH8-FLAG expression plasmid and cultured in the supplemented medium, exhibited increased levels of ATOH8 mRNA, ATOH8-FLAG protein, pSMAD1,5,8, and HAMP mRNA. Interestingly, over-expression of ATOH8 reversed the effects of hepcidin suppression induced by the β-thalassemia patient sera. In conclusion, hepcidin suppression in β-thalassemia is associated with the down-regulation of ATOH8 in response to anemia. We, therefore, suggest that ATOH8 is an important transcriptional regulator of hepcidin in β-thalassemia.

Role of hepcidin-ferroportin axis in the pathophysiology, diagnosis, and treatment of anemia of chronic inflammation

Anemia of chronic inflammation (ACI) is a frequently diagnosed anemia and portends an independently increased morbidity and poor outcome associated with multiple underlying diseases. The pathophysiology of ACI is multifactorial, resulting from the effects of inflammatory cytokines which both directly and indirectly suppress erythropoiesis. Recent advances in molecular understanding of iron metabolism provide strong evidence that immune mediators, such as IL-6, lead to hepcidin-induced hypoferremia, iron sequestration, and decreased iron availability for erythropoiesis. The role of hepcidin-ferroportin axis in the pathophysiology of ACI is stimulating the development of new diagnostics and targeted therapies. In this review, we present an overview of and rationale for inflammation-, iron-, and erythropoiesis-related strategies currently in development.

Elevated Serum Hepcidin Levels during an Intensified Training Period in Well-Trained Female Long-Distance Runners

Iron is essential for providing oxygen to working muscles during exercise, and iron deficiency leads to decreased exercise capacity during endurance events. However, the mechanism of iron deficiency among endurance athletes remains unclear. In this study, we compared iron status between two periods involving different training regimens. Sixteen female long-distance runners participated. Over a seven-month period, fasting blood samples were collected during their regular training period (LOW; middle of February) and during an intensified training period (INT; late of August) to determine blood hematological, iron, and inflammatory parameters. Three-day food diaries were also assessed. Body weight and lean body mass did not differ significantly between LOW and INT, while body fat and body fat percentage were significantly lower in INT (p < 0.05). Blood hemoglobin, serum ferritin, total protein, and iron levels, total iron-binding capacity, and transferrin saturation did not differ significantly between the two periods. Serum hepcidin levels were significantly higher during INT than LOW (p < 0.05). Carbohydrate and iron intakes from the daily diet were significantly higher during INT than LOW (p < 0.05). In conclusion, an elevated hepcidin level was observed during an intensified training period in long-distance runners, despite an apparently adequate daily intake of iron.