Hepcidin antimicrobial peptide transgenic mice exhibit features of the anemia of inflammation

Therapeutic Applications of Aptamers

Affinity reagents, or target-binding molecules, are quite versatile and are major workhorses in molecular biology and medicine. Antibodies are the most famous and frequently used type and they have been used for a wide range of applications, including laboratory techniques, diagnostics, and therapeutics. However, antibodies are not the only available affinity reagents and they do have significant drawbacks, including laborious and costly production. Aptamers are one potential alternative that have a variety of unique advantages. They are single stranded DNA or RNA molecules that can be selected for binding to many targets including proteins, carbohydrates, and small molecules-for which antibodies typically have low affinity. There are also a variety of cost-effective methods for producing and modifying nucleic acids in vitro without cells, whereas antibodies typically require cells or even whole animals. While there are also significant drawbacks to using aptamers in therapeutic applications, including low in vivo stability, aptamers have had success in clinical trials for treating a variety of diseases and two aptamer-based drugs have gained FDA approval. Aptamer development is still ongoing, which could lead to additional applications of aptamer therapeutics, including antitoxins, and combinatorial approaches with nanoparticles and other nucleic acid therapeutics that could improve efficacy.

Hepcidin from Onychostoma macrolepis: Response to Aeromonas hydrophila infection by down-regulating expression of inflammatory factor genes and regulating iron homeostasis potentially

Hepcidin, as an antimicrobial peptide, is associated with innate immunity and is considered a potential antibiotic substitute. In the present study, the hepcidin gene from the cavefish - Onychostoma macrolepis was identified and analyzed. The recombinant hepcidin protein (rOmhepc) was obtained by prokaryotic expression, evaluating the inhibitory effect of 5 pathogenic bacteria in vitro. Sixty O. macrolepis injected with 100 μL A. hydrophila (1.5 × 108 CFU/mL) were randomly divided into the therapeutic group and infection group, and therapeutic group was injected with 100 μL rOmhepc (100 μg/mL) at 6 and 18 h. The survival rates of O. macrolepis and bacterial load in liver were measured at 24 h. The liver tissues were collected at 0, 6, 12, and 24 h after A. hydrophila injection for investigating expression levels of immune-related, inflammatory factor genes and FPN1 gene. The results demonstrated that the hepcidin CDS contained 279 bp and encoded 93 aa. Hepcidin protein has a hydrophobic surface formed by multiple hydrophobic residues (CCGCCYC), and the theoretical pI was 7.53. Omhepc gene was expressed at varying levels in tested tissues, with the liver showing the highest expression, followed by the spleen. The expression of hepcidin gene following A. hydrophila infection was up-regulated and then down-regulated in liver, and the highest expression level was found at 12 h with a 10.93-fold. The rOmhepc remarkably inhibited the growth of A. hydrophila, Staphylococcus aureus, and Streptococcus agalactiae, with inhibition rates reaching 69.67 %, 42.97 %, and 65.74 % at 100 μg/mL. The mortality rates of O. macrolepis and bacterial load in liver were significantly decreased in the therapeutic group than that of infection group (p < 0.05). After the rOmhepc therapeutic, interleukin-1β (IL-1β) and interleukin-6 (IL-6) were significantly down-regulated with 14.4-fold and 106.07-fold at 24 h. Furthermore, the expression of immune-related genes (C3, TNF-α, IFN-γ) and Ferroportin gene (FPN1) significantly decreased (p < 0.05). The integrated analyses indicated that the rOmhepc could significantly inhibit the growth of A. hydrophila both in vitro and in vivo, attenuating the over-expression of inflammatory factor, FPN1 and immune-related genes.

Severe anaemia, iron deficiency, and susceptibility to invasive bacterial infections

Severe anaemia and invasive bacterial infections remain important causes of hospitalization and death among young African children. The emergence and spread of antimicrobial resistance demand better understanding of bacteraemia risk factors to inform prevention strategies. Epidemiological studies have reported an association between severe anaemia and bacteraemia. In this review, we explore evidence that severe anaemia is associated with increased risk of invasive bacterial infections in young children. We describe mechanisms of iron dysregulation in severe anaemia that might contribute to increased risk and pathogenesis of invasive bacteria, recent advances in knowledge of how iron deficiency and severe anaemia impair immune responses to bacterial infections and vaccines, and the gaps in our understanding of mechanisms underlying severe anaemia, iron deficiency, and the risk of invasive bacterial infections.

AMP-activated protein kinase α1 phosphorylates PHD2 to maintain systemic iron homeostasis

BACKGROUND

Iron is essential for all mammalian life, and either a deficiency or excess of iron can cause diseases. AMP-activated protein kinase (AMPK) is a critical regulator of metabolic homeostasis; however, it has not been established whether AMPK regulates iron metabolism.

METHODS

Iron, hepcidin and ferroportin levels were examined in mice with global and hepatocyte-specific knockout of AMPKα1 and AMPKα2. Primary AMPKα1 or AMPKα2 deleted hepatocytes were isolated and cultured in hypoxia condition to explore PHD2, HIF and hydroxylated HIF1α levels. We performed immunoprecipitation, in vitro AMPK kinase assay and site-direct mutant assay to detect phosphorylation sites of PHD2. We also obtained liver tissues from patients with anaemia of chronic disease undergoing surgery, AMPKα1 and hydroxylated HIF1α levels were measured by immunohistochemical analysis.

RESULTS

We found that mice with global deficiency of AMPKα1, but not AMPKα2, exhibited hypoferraemia as well as iron sequestration in the spleen and liver. Hepatocyte-specific, but not myeloid-specific, ablation of AMPKα1 also reduced serum iron levels in association with increased hepcidin and decreased ferroportin protein levels. Mechanistically, AMPKα1 directly phosphorylated prolyl hydroxylase domain-containing (PHD)2 at serines 61 and 136, which suppressed PHD2-dependent hydroxylation of hypoxia-inducible factor (HIF)1α and subsequent regulation of hepatic hepcidin-related iron signalling. Inhibition of PHD2 hydroxylation ameliorated abnormal iron metabolism in hepatic AMPKα1-deficient mice. Furthermore, we found hepatic AMPKα/PHD2/HIFα/ hepcidin axes were highly clinically relevant to anaemia of chronic disease.

CONCLUSION

In conclusion, these observations suggest that hepatic AMPKα1 has an essential role in maintaining iron homeostasis by PHD2-dependent regulation of hepcidin, thus providing a potentially promising approach for the treatment of iron disturbances in chronic diseases.

Comparative Effects between Oral Lactoferrin and Ferrous Sulfate Supplementation on Iron-Deficiency Anemia: A Comprehensive Review and Meta-Analysis of Clinical Trials

Ferrous sulfate is a commonly used iron supplement for the correction of iron-deficiency anemia but with frequent gastrointestinal side effects. Milk-derived iron-binding glycoprotein lactoferrin possesses well gastrointestinal tolerance and fewer side effects caused by the intake of high-dose iron. However, the underlying mechanism of the iron-enhancing effect of lactoferrin remains unclear. In addition, the comparative efficacies between lactoferrin and ferrous sulfate are also remained to be determined. We conducted a systematic review and meta-analysis on published intervention studies to investigate how lactoferrin modulate iron metabolism and evaluate the comparative effects between lactoferrin and ferrous sulfate supplementation on iron absorption, iron storage, erythropoiesis and inflammation. Lactoferrin supplementation had better effects on serum iron (WMD: 41.44 ug/dL; p < 0.00001), ferritin (WMD: 13.60 ng/mL; p = 0.003) and hemoglobin concentration (11.80 g/dL; p < 0.00001), but a reducing effect on fractional iron absorption (WMD: −2.08%; p = 0.02) and IL-6 levels (WMD: −45.59 pg/mL; p < 0.00001) compared with ferrous sulfate. In conclusion, this study supports lactoferrin as a superior supplement to ferrous sulfate regarding the improvement in serum iron parameters and hemoglobin levels. Considering the weak influence of lactoferrin on iron absorption, the anti-inflammation effect of lactoferrin may be the potential mechanism to explain its efficacy on iron status and erythropoiesis.

Coordination of iron homeostasis by bone morphogenetic proteins: Current understanding and unanswered questions

Iron homeostasis is tightly regulated to balance the iron requirement for erythropoiesis and other vital cellular functions, while preventing cellular injury from iron excess. The liver hormone hepcidin is the master regulator of systemic iron balance by controlling the degradation and function of the sole known mammalian iron exporter ferroportin. Liver hepcidin expression is coordinately regulated by several signals that indicate the need for more or less iron, including plasma and tissue iron levels, inflammation, and erythropoietic drive. Most of these signals regulate hepcidin expression by modulating the activity of the bone morphogenetic protein (BMP)-SMAD pathway, which controls hepcidin transcription. Genetic disorders of iron overload and iron deficiency have identified several hepatocyte membrane proteins that play a critical role in mediating the BMP-SMAD and hepcidin regulatory response to iron. However, the precise molecular mechanisms by which serum and tissue iron levels are sensed to regulate BMP ligand production and promote the physical and/or functional interaction of these proteins to modulate SMAD signaling and hepcidin expression remain uncertain. This critical commentary will focus on the current understanding and key unanswered questions regarding how the liver senses iron levels to regulate BMP-SMAD signaling and thereby hepcidin expression to control systemic iron homeostasis.

Macrophages form erythropoietic niches and regulate iron homeostasis to adapt erythropoiesis in response to infections and inflammation

It has recently emerged that tissue-resident macrophages are key regulators of several stem cell niches orchestrating tissue formation during development, as well as postnatally, when they also organize the repair and regeneration of many tissues including the hemopoietic tissue. The fact that macrophages are also master regulators and effectors of innate immunity and inflammation allows them to coordinate hematopoietic response to infections, injuries, and inflammation. After recently reviewing the roles of phagocytes and macrophages in regulating normal and pathologic hematopoietic stem cell niches, we now focus on the key roles of macrophages in regulating erythropoiesis and iron homeostasis. We review herein the recent advances in understanding how macrophages at the center of erythroblastic islands form an erythropoietic niche that controls the terminal differentiation and maturation of erythroblasts into reticulocytes; how red pulp macrophages in the spleen control iron recycling and homeostasis; how these macrophages coordinate emergency erythropoiesis in response to blood loss, infections, and inflammation; and how persistent infections or inflammation can lead to anemia of inflammation via macrophages. Finally, we discuss the technical challenges associated with the molecular characterization of erythroid island macrophages and red pulp macrophages.

Hepcidin Upregulation in Lung Cancer: A Potential Therapeutic Target Associated With Immune Infiltration

Lung cancer has the highest death rate among cancers globally. Hepcidin is a fascinating regulator of iron metabolism; however, the prognostic value of hepcidin and its correlation with immune cell infiltration in lung cancer remain unclear. Here, we comprehensively clarified the prognostic value and potential function of hepcidin in lung cancer. Hepcidin expression was significantly increased in lung cancer. High hepcidin expression was associated with sex, age, metastasis, and pathological stage and significantly predicted an unfavorable prognosis in lung cancer patients. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Set Enrichment Analysis (GSEA) results suggested that hepcidin is involved in the immune response. Furthermore, hepcidin expression was positively correlated with the infiltration levels of immune cells and the expression of diverse immune cell marker sets. Importantly, hepcidin may affect prognosis partially by regulating immune infiltration in lung cancer patients. Hepcidin may serve as a candidate prognostic biomarker for determining prognosis associated with immune infiltration in lung cancer.

Intermittent Hypoxia Exposure Can Prevent Reductions in Hemoglobin Concentration After Intense Exercise Training in Rats

Intense exercise training can induce low concentrations of hemoglobin, which may be followed by maladaptation. Therefore, it is important for athletes to prevent low concentrations of hemoglobin during intense exercise training. In this study, we explored whether different protocols of intermittent hypoxic exposure (IHE, normobaric hypoxia, 14.5% O₂) could prevent the exercise training-induced reduction in hemoglobin concentration in rats. Six-week-old male Sprague-Dawley rats were subjected to progressive intense treadmill exercise training over three weeks followed by three weeks of training with IHE after exercise. IHE lasted either 1 h, 2 h, or 1 h + 1 h (separated by a 3-h interval) after the exercise sessions. Hematological parameters, including hemoglobin concentration [(Hb)], red blood cells (RBCs), and hematocrit (Hct), and both renal and serum erythropoietin (EPO) were examined. We found that intense exercise training significantly reduced [Hb], RBCs, Hct, food intake and body weight (P < 0.01). Analysis of reticulocyte hemoglobin content (CHr) and reticulocyte counts in the serum of the rats suggested that this reduction was not due to iron deficiency or other cofounding factors. The addition of IHE after the intense exercise training sessions significantly alleviated the reduction in [Hb], RBCs, and Hct (P < 0.05) without an obvious impact on either food intake or body weight (P > 0.05). Increase in reticulocyte count in the rats from the IHE groups (P < 0.05 or P < 0.01) suggests that IHE promotes erythropoiesis to increase the hemoglobin concentration. Furthermore, the addition of IHE after the intense exercise training sessions also significantly increased the concentration of renal EPO (P < 0.05), although the increase of the serum EPO level was statistically insignificant (P > 0.05). The different IHE protocols were similarly effective at increasing renal EPO and preventing the training-induced decreases in [Hb], RBCs, and Hct. Collectively, this study suggests that IHE may be used as a new strategy to prevent intense exercise training-induced reductions in [Hb], and deserves future exploration in athletes.

Correlation of hepcidin and serum ferritin levels in thalassemia patients at Chiang Mai University Hospital

Hepcidin is a key iron-regulatory hormone, the production of which is controlled by iron stores, inflammation, hypoxia and erythropoiesis. The regulation of iron by hepcidin is of clinical importance in thalassemia patients in which anemia occurs along with iron overload. The present study aimed to evaluate the correlation between serum hepcidin and ferritin levels in thalassemia patients. This cross-sectional study investigated 64 patients with thalassemia; 16 β-thalassemia major (BTM), 31 β-thalassemia/hemoglobin (Hb) E (BE), and 17 Hb H + AE Bart’s disease (Hb H + AE Bart’s). The levels of serum hepcidin and ferritin, and Hb of the three groups were measured. The median values of serum ferritin and Hb were significantly different among the three groups, whereas serum hepcidin values were not observed to be significantly different. The correlation of the serum hepcidin and ferritin levels was not statistically significant in any of the three groups of thalassemia patients with BTM, BE, or Hb H + AE Bart’s (r = −0.141, 0.065 and −0.016, respectively). In conclusion, no statistically significant correlations were observed between serum hepcidin with any variables including serum ferritin, Hb, age, labile plasma iron (LPI), and number of blood transfusion units among the three groups of thalassemia patients. Likely, the regulation of hepcidin in thalassemia patients is affected more by erythropoietic activity than iron storage.

Structure of hepcidin-bound ferroportin reveals iron homeostatic mechanisms

The serum iron level in humans is tightly controlled by the action of the hormone hepcidin on the iron efflux transporter ferroportin. Hepcidin regulates iron absorption and recycling by inducing ferroportin internalization and degradation¹. Aberrant ferroportin activity can lead to diseases of iron overload, like hemochromatosis, or iron limitation anemias². Here, we determined cryogenic electron microscopy (cryo-EM) structures of ferroportin in lipid nanodiscs, both in the apo state and in complex with cobalt, an iron mimetic, and hepcidin. These structures and accompanying molecular dynamics simulations identify two metal binding sites within the N- and C-domains of ferroportin. Hepcidin binds ferroportin in an outward-open conformation and completely occludes the iron efflux pathway to inhibit transport. The carboxy-terminus of hepcidin directly contacts the divalent metal in the ferroportin C-domain. We further show that hepcidin binding to ferroportin is coupled to iron binding, with an 80-fold increase in hepcidin affinity in the presence of iron. These results suggest a model for hepcidin regulation of ferroportin, where only iron loaded ferroportin molecules are targeted for degradation. More broadly, our structural and functional insights are likely to enable more targeted manipulation of the hepcidin-ferroportin axis in disorders of iron homeostasis.

Mu opioid receptor knockout mouse: Phenotypes with implications on restless legs syndrome

Restless legs syndrome (RLS) is characterized by an irresistible need to move the legs while sitting or lying at night with insomnia as a frequent consequence. Human RLS has been associated with abnormalities in the endogenous opioid system, the dopaminergic system, the iron regulatory system, anemia, and inflammatory and auto-immune disorders. Our previous work indicates that mice lacking all three subtypes of opioid receptors have a phenotype similar to that of human RLS. To study the roles of each opioid receptor subtype in RLS, we first used mu opioid receptor knockout (MOR KO) mice based on our earlier studies using postmortem brain and cell culture. The KO mice showed decreased hemoglobin, hematocrit, and red blood cells (RBCs), with an appearance of microcytic RBCs indicating anemia. Together with decreased serum iron and transferrin, but increased ferritin levels, the anemia is similar to that seen with chronic inflammation in humans. A decreased serum iron level was also observed in the wildtype mice treated with an MOR antagonist. Iron was increased in the liver and spleen of the KO mice. Normal circadian variations in the dopaminergic and serotoninergic systems were absent in the KO mice. The KO mice showed hyperactivity and increased thermal sensitivity in wakefulness primarily during what would normally be the sleep phase similar to that seen in human RLS. Deficits in endogenous opioid system transmission could predispose to anemia of inflammation and loss of circadian variations in dopaminergic or serotonergic systems, thereby contributing to an RLS-like phenotype.

Antibacterial and immunoregulatory activity of a novel hepcidin homologue in diploid hybrid fish (Carassius auratus cuvieri ♀ × Carassius auratus red var ♂)

Hepcidin, a multifunctional hormone oligopeptide, not only exhibits a regulatory role in iron metabolism, but also participates in the regulation of teleostean immunity. In this study, ORF sequence of WR-hepcidin was 258 bp and encoded 85 amino acid residues. Tissue-specific analysis revealed that the highest expression of WR-hepcidin was observed in liver. Aeromonas hydrophila challenge can sharply increased WR-hepcidin mRNA expression in liver, trunk kidney and spleen. The purified WR-hepcidin fusion peptide can directly bind to A. hydrophila and Streptococcus agalactiae, reduce the relative bacterial activity, limit bacterial growth and attenuate their dissemination to tissues in vivo. In addition, the treatment of WR-hepcidin fusion protein can diminish the production of pro-inflammatory cytokines. These results indicated that WR-hepcidin can play a negative regulatory role in bacteria-stimulated pro-inflammatory cytokines production and MyD88-IRAK4 activation.

The Influence of Inflammation on Anemia in CKD Patients

Anemia is frequently observed in the course of chronic kidney disease (CKD) and it is associated with diminishing the quality of a patient’s life. It also enhances morbidity and mortality and hastens the CKD progression rate. Patients with CKD frequently suffer from a chronic inflammatory state which is related to a vast range of underlying factors. The results of studies have demonstrated that persistent inflammation may contribute to the variability in Hb levels and hyporesponsiveness to erythropoietin stimulating agents (ESA), which are frequently observed in CKD patients. The understanding of the impact of inflammatory cytokines on erythropoietin production and hepcidin synthesis will enable one to unravel the net of interactions of multiple factors involved in the pathogenesis of the anemia of chronic disease. It seems that anti-cytokine and anti-oxidative treatment strategies may be the future of pharmacological interventions aiming at the treatment of inflammation-associated hyporesponsiveness to ESA. The discovery of new therapeutic approaches towards the treatment of anemia in CKD patients has become highly awaited. The treatment of anemia with erythropoietin (EPO) was associated with great benefits for some patients but not all.

Animal Models of Normal and Disturbed Iron and Copper Metabolism

Research on the interplay between iron and copper metabolism in humans began to flourish in the mid-20th century, and diseases associated with dysregulated homeostasis of these essential trace minerals are common even today. Iron deficiency is the most frequent cause of anemia worldwide, leading to significant morbidity, particularly in developing countries. Iron overload is also quite common, usually being the result of genetic mutations which lead to inappropriate expression of the iron-regulatory hormone hepcidin. Perturbations of copper homeostasis in humans have also been described, including rare genetic conditions which lead to severe copper deficiency (Menkes disease) or copper overload (Wilson disease). Historically, the common laboratory rat (Rattus norvegicus) was the most frequently utilized species to model human physiology and pathophysiology. Recently, however, the development of genetic-engineering technology combined with the worldwide availability of numerous genetically homogenous (i.e., inbred) mouse strains shifted most research on iron and copper metabolism to laboratory mice. This created new opportunities to understand the function of individual genes in the context of a living animal, but thoughtful consideration of whether mice are the most appropriate models of human pathophysiology was not necessarily involved. Given this background, this review is intended to provide a guide for future research on iron- and copper-related disorders in humans. Generation of complementary experimental models in rats, swine, and other mammals is now facile given the advent of newer genetic technologies, thus providing the opportunity to accelerate the identification of pathogenic mechanisms and expedite the development of new treatments to mitigate these important human disorders.

The Role of Iron Regulation in Immunometabolism and Immune-Related Disease

Immunometabolism explores how the intracellular metabolic pathways in immune cells can regulate their function under different micro-environmental and (patho-)-physiological conditions (Pearce, 2010; Buck et al., 2015; O'Neill and Pearce, 2016). In the last decade great advances have been made in studying and manipulating metabolic programs in immune cells. Immunometabolism has primarily focused on glycolysis, the TCA cycle and oxidative phosphorylation (OXPHOS) as well as free fatty acid synthesis and oxidation. These pathways are important for providing the energy needs of cell growth, membrane rigidity, cytokine production and proliferation. In this review, we will however, highlight the specific role of iron metabolism at the cellular and organismal level, as well as how the bioavailability of this metal orchestrates complex metabolic programs in immune cell homeostasis and inflammation. We will also discuss how dysregulation of iron metabolism contributes to alterations in the immune system and how these novel insights into iron regulation can be targeted to metabolically manipulate immune cell function under pathophysiological conditions, providing new therapeutic opportunities for autoimmunity and cancer.

The Postinjury Inflammatory State and the Bone Marrow Response to Anemia

RATIONALE

The pathophysiology of persistent injury-associated anemia is incompletely understood, and human data are sparse.

OBJECTIVES

To characterize persistent injury-associated anemia among critically ill trauma patients with the hypothesis that severe trauma would be associated with neuroendocrine activation, erythropoietin dysfunction, iron dysregulation, and decreased erythropoiesis.

METHODS

A translational prospective observational cohort study comparing severely injured, blunt trauma patients who had operative fixation of a hip or femur fracture (n = 17) with elective hip repair patients (n = 22). Bone marrow and plasma obtained at the index operation were assessed for circulating catecholamines, systemic inflammation, erythropoietin, iron trafficking pathways, and erythroid progenitor growth. Bone marrow was also obtained from healthy donors from a commercial source (n = 8).

MEASUREMENTS AND MAIN RESULTS

During admission, trauma patients had a median of 625 ml operative blood loss and 5 units of red blood cell transfusions, and Hb decreased from 10.5 to 9.3 g/dl. Compared with hip repair, trauma patients had higher median plasma norepinephrine (21.9 vs. 8.9 ng/ml) and hepcidin (56.3 vs. 12.2 ng/ml) concentrations (both P < 0.05). Bone marrow erythropoietin and erythropoietin receptor expression were significantly increased among patients undergoing hip repair (23% and 14% increases, respectively; both P < 0.05), but not in trauma patients (3% and 5% increases, respectively), compared with healthy control subjects. Trauma patients had lower bone marrow transferrin receptor expression than did hip repair patients (57% decrease; P < 0.05). Erythroid progenitor growth was decreased in trauma patients (39.0 colonies per plate; P < 0.05) compared with those with hip repair (57.0 colonies per plate; P < 0.05 compared with healthy control subjects) and healthy control subjects (66.5 colonies per plate).

CONCLUSIONS

Severe blunt trauma was associated with neuroendocrine activation, erythropoietin dysfunction, iron dysregulation, erythroid progenitor growth suppression, and persistent injury-associated anemia. Clinical trial registered with www.clinicaltrials.gov (NCT 02577731).

Tinospora cordifolia protects against inflammation associated anemia by modulating inflammatory cytokines and hepcidin expression in male Wistar rats

Systemic iron homeostasis dysregulation is primarily associated with inflammation- associated anemia (AI) due to hepcidin up-regulation. Tinospora cordifolia (TC) has shown remarkable anti-inflammatory properties and has been found useful in the treatment of inflammatory disorders. However, the effects and mechanisms of TC on AI have not been studied yet. We conducted in vivo and in vitro studies to evaluate the effect of TC on AI. HPLC studies were also carried out to find out active constituents in TC extract. Model system exhibiting AI was developed by repeated injections of HKBA in Wistar rats. TC treated groups showed significantly higher levels of Hb and RBC count compared to the inflammatory control group. TC treatment showed reduction in the expression of the HAMP (hepcidin) gene in the rat liver. TC extract also inhibited gene expression of inflammatory cytokines (TNF-α, IL-1β) and decreased NO production in RAW 264.7 cells. The HPLC analysis revealed the presence of tinosporaside, which could have synergistically contributed to the above findings. Overall results indicate that TC therapy was able to maintain circulating iron through reduction of inflammatory cytokines and expression of hepcidin in rats.

Lipogenic SREBP-1a/c transcription factors activate expression of the iron regulator hepcidin, revealing cross-talk between lipid and iron metabolisms

The sterol regulatory element-binding proteins (SREBPs) are a family of transcription factors best known for stimulating the expression of genes encoding key lipogenic enzymes. However, SREBP functions beyond lipid metabolism are less understood. Here, we show that hepcidin antimicrobial peptide (Hamp), encoding the hormone hepcidin essential for iron homeostasis and regulated by dietary iron and inflammation, is a target gene of the two SREBP isoforms SREBP-1a/c. We found that in tissue culture, mature, active, and nuclear forms of the SREBP-1a/c proteins induce endogenous Hamp gene expression and increase the Hamp promoter activity primarily via three regulatory sequences, including an E-box. Moreover, ChIP experiments revealed that SREBP-1a binds to the Hamp gene promoter. Overexpression of nuclear SREBP-1a under the control of the phosphoenolpyruvate carboxylase-1 (Pck1) promoter in mice increased hepatic Hamp mRNA and blood hepcidin levels, and as expected, caused fatty liver. Consistent with the known effects of Hamp up-regulation, SREBP-1a-overexpressing mice displayed signs of dysregulation in iron metabolism, including reduced serum iron and increased hepatic and splenic iron storage. Conversely, liver-specific depletion of the nuclear forms of SREBPs, as in SREBP cleavage-activating protein knockout mice, impaired lipopolysaccharide-induced up-regulation of hepatic Hamp Together, these results indicate that the SREBP-1a/c transcription regulators activate hepcidin expression and thereby contribute to the control of mammalian iron metabolism.

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

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

Targeting the hepcidin-ferroportin pathway in anaemia of chronic kidney disease

AIMS

Erythropoiesis-stimulating agents used to treat anaemia in patients with chronic kidney disease (CKD) have been associated with cardiovascular adverse events. Hepcidin production, controlled by bone morphogenic protein 6 (BMP6), regulates iron homeostasis via interactions with the iron transporter, ferroportin. High hepcidin levels are thought to contribute to increased iron sequestration and subsequent anaemia in CKD patients. To investigate alternative therapies to erythropoiesis-stimulating agents for CKD patients, monoclonal antibodies, LY3113593 and LY2928057, targeting BMP6 and ferroportin respectively, were tested in CKD patients.

METHODS

Preclinical in vitro/vivo data and clinical data in healthy subjects and CKD patients were used to illustrate the translation of pharmacological properties of LY3113593 and LY2928057, highlighting the novelty of targeting these nodes within the hepcidin-ferroportin pathway.

RESULTS

LY2928057 bound ferroportin and blocked interactions with hepcidin, allowing iron efflux, leading to increased serum iron and transferrin saturation levels and increased hepcidin in monkeys and humans. In CKD patients, LY2928057 led to slower haemoglobin decline and reduction in ferritin (compared to placebo). Serum iron increase was (mean [90% confidence interval]) 1.98 [1.46-2.68] and 1.36 [1.22-1.51] fold-relative to baseline following LY2928057 600 mg and LY311593 150 mg respectively in CKD patients. LY3113593 specifically blocked BMP6 binding to its receptor and produced increases in iron and transferrin saturation and decreases in hepcidin preclinically and clinically. In CKD patients, LY3113593 produced an increase in haemoglobin and reduction in ferritin (compared to placebo).

CONCLUSION

LY3113593 and LY2928057 pharmacological effects (serum iron and ferritin) were translated from preclinical-to-clinical development. Such interventions may lead to new CKD anaemia treatments.

Regulators of hepcidin expression

Iron, an essential nutrient, is required for many biological processes but is also toxic in excess. The lack of a mechanism to excrete excess iron makes it crucial for the body to regulate the amount of iron absorbed from the diet. This regulation is mediated by the hepatic hormone hepcidin. Hepcidin also controls iron release from macrophages that recycle iron and from hepatocytes that store iron. Hepcidin binds to the only known iron export protein, ferroportin, inducing its internalization and degradation and thus limiting the amount of iron released into the plasma. Important regulators of hepcidin, and therefore of systemic iron homeostasis, include plasma iron concentrations, body iron stores, infection and inflammation, hypoxia and erythropoiesis, and, to a lesser extent, testosterone. Dysregulation of hepcidin production contributes to the pathogenesis of many iron disorders: hepcidin deficiency causes iron overload in hereditary hemochromatosis and non-transfused β-thalassemia, whereas overproduction of hepcidin is associated with iron-restricted anemias seen in patients with chronic inflammatory diseases and inherited iron-refractory iron-deficiency anemia. The present review summarizes our current understanding of the molecular mechanisms and signaling pathways contributing to hepcidin regulation by these factors and highlights the issues that still need clarification.

A computational model to understand mouse iron physiology and disease

It is well known that iron is an essential element for life but is toxic when in excess or in certain forms. Accordingly there are many diseases that result directly from either lack or excess of iron. Yet many molecular and physiological aspects of iron regulation have only been discovered recently and others are still elusive. There is still no good quantitative and dynamic description of iron absorption, distribution, storage and mobilization that agrees with the wide array of phenotypes presented in several iron-related diseases. The present work addresses this issue by developing a mathematical model of iron distribution in mice calibrated with ferrokinetic data and subsequently validated against data from mouse models of iron disorders, such as hemochromatosis, β-thalassemia, atransferrinemia and anemia of inflammation. To adequately fit the ferrokinetic data required inclusion of the following mechanisms: a) transferrin-mediated iron delivery to tissues, b) induction of hepcidin by transferrin-bound iron, c) ferroportin-dependent iron export regulated by hepcidin, d) erythropoietin regulation of erythropoiesis, and e) liver uptake of NTBI. The utility of the model to simulate disease interventions was demonstrated by using it to investigate the outcome of different schedules of transferrin treatment in β-thalassemia.

Iron is an essential nutrient in almost all life forms. In humans and animals iron is used for respiration and for transporting oxygen inside red blood cells. But in excess iron can be toxic and therefore the body regulates its distribution and absortion through the action of hormones, which is not yet completely understood. Here we created a computational model of the regulation of iron distribution in the body of a mouse based on experimental data. The model can accurately simulate many iron diseases such as anemia, hemochromatosis, and thalassemia. This computational model is helpful to understand the basis of these diseases and plan therapies to address them.

Dysregulated myelopoiesis and hematopoietic function following acute physiologic insult

PURPOSE OF REVIEW

The purpose of this review is to describe recent findings in the context of previous work regarding dysregulated myelopoiesis and hematopoietic function following an acute physiologic insult, focusing on the expansion and persistence of myeloid-deriver suppressor cells, the deterioration of lymphocyte number and function, and the inadequacy of stress erythropoiesis.

RECENT FINDINGS

Persistent myeloid-derived suppressor cell (MDSC) expansion among critically ill septic patients is associated with T-cell suppression, vulnerability to nosocomial infection, chronic critical illness, and poor long-term functional status. Multiple approaches targeting MDSC expansion and suppressor cell activity may serve as a primary or adjunctive therapeutic intervention. Traumatic injury and the neuroendocrine stress response suppress bone marrow erythropoietin receptor expression in a process that may be reversed by nonselective beta-adrenergic receptor blockade. Hepcidin-mediated iron-restricted anemia of critical illness requires further investigation of novel approaches involving erythropoiesis-stimulating agents, iron administration, and hepcidin modulation.

SUMMARY

Emergency myelopoiesis is a dynamic process with unique phenotypes for different physiologic insults and host factors. Following an acute physiologic insult, critically ill patients are subject to persistent MDSC expansion, deterioration of lymphocyte number and function, and inadequate stress erythropoiesis. Better strategies are required to identify patients who are most likely to benefit from targeted therapies.

SRM-MS Method Development for Hepcidin-25 Peptide

As advanced mass spectrometry- (MS-) based hepcidin analysis offers to overcome the limitations in analytical methods using antihepcidin, further improvement of MS detection sensitivity for the peptide may enhance the diagnostic value of the hepcidin for various iron-related disorders. Here, improved MS detection sensitivity of hepcidin has been achieved by reducing the disulfide bonds in hepcidin, by which proton accessibility increased, compared to the intact hepcidin peptide. Comparing the ionization efficiencies of reduced and nonreduced forms of hepcidin, the reduced form of hepcidin showed an increase in ionization efficiency more than two times compared to the nonreduced form of hepcidin. We also demonstrated improved detection sensitivity of the peptide in SRM assay. We observed a significant improvement of detection sensitivity at the triple-quadrupole MS platform, that the ionization efficiency increased at least twice more, and that the limit of detection (LOD) increased more than 10 times in the concentration ranges of 1 fmol to 10 fmol of hepcidin. In this study, we demonstrated the usefulness of the hepcidin modification for overall enhancement of the ionization efficiencies of the hepcidin peptide in the MS-based quantitative measurement assay.

Investigation of iron deficiency anaemia

Iron deficiency anaemia (IDA) is an important, common clinical condition and 8-15% of these patients will be diagnosed with a gastrointestinal cancer. IDA is defined as haemoglobin below the lower limit of normal, in the presence of characteristic iron studies. This article will discuss the causes and clinical diagnosis of iron deficiency, including interpretation of common laboratory tests that differentiate this from other causes of anaemia. We suggest an initial approach for investigating the cause of iron deficiency in these patients and also consider the subsequent treatment and indications for further investigation.

Sustained plasma hepcidin suppression and iron elevation by Anticalin-derived hepcidin antagonist in cynomolgus monkey

BACKGROUND AND PURPOSE

Anaemia of chronic disease (ACD) has been linked to iron-restricted erythropoiesis imposed by high circulating levels of hepcidin, a 25 amino acid hepatocyte-derived peptide that controls systemic iron homeostasis. Here, we report the engineering of the human lipocalin-derived, small protein-based anticalin PRS-080 hepcidin antagonist with high affinity and selectivity.

EXPERIMENTAL APPROACH

Anticalin- and hepcidin-specific pharmacokinetic (PK)/pharmacodynamic modelling (PD) was used to design and select the suitable drug candidate based on t_1/2 extension and duration of hepcidin suppression. The development of a novel free hepcidin assay enabled accurate analysis of bioactive hepcidin suppression and elucidation of the observed plasma iron levels after PRS-080-PEG30 administration in vivo.

KEY RESULTS

PRS-080 had a hepcidin-binding affinity of 0.07 nM and, after coupling to 30 kD PEG (PRS-080-PEG30), a t_1/2 of 43 h in cynomolgus monkeys. Dose-dependent iron mobilization and hepcidin suppression were observed after a single i.v. dose of PRS-080-PEG30 in cynomolgus monkeys. Importantly, in these animals, suppression of free hepcidin and subsequent plasma iron elevation were sustained during repeated s.c. dosing. After repeated dosing and followed by a treatment-free interval, all iron parameters returned to pre-dose values.

CONCLUSIONS AND IMPLICATIONS

In conclusion, we developed a dose-dependent and safe approach for the direct suppression of hepcidin, resulting in prolonged iron mobilization to alleviate iron-restricted erythropoiesis that can address the root cause of ACD. PRS-080-PEG30 is currently in early clinical development.

Enhanced eryptosis contributes to anemia in lung cancer patients

Objectives

Anemia is a common complication of malignancy, which could result from either compromised erythropoiesis or decreased lifespan of circulating erythrocytes. Premature suicidal erythrocyte death, characterized by cell shrinkage and phosphatidylserine (PS) externalization, decreases erythrocyte lifespan and could thus cause anemia. Here, we explored whether accelerated eryptosis participates in the pathophysiology of anemia associated with lung cancer (LC) and its treatment.

Methods

Erythrocytes were drawn from healthy volunteers and LC patients with and without cytostatic treatment. PS exposure (annexin V-binding), cell volume (forward scatter), cytosolic Ca²⁺ (Fluo3 fluorescence), reactive oxygen species (ROS) production (DCFDA fluorescence) and ceramide formation (anti-ceramide antibody) were determined by flow cytometry.

Results

Hemoglobin concentration and hematocrit were significantly lower in LC patients as compared to healthy controls, even though reticulocyte number was higher in LC (3.0±0.6%) than in controls (1.4±0.2%). The percentage of PS-exposing erythrocytes was significantly higher in LC patients with (1.4±0.1%) and without (1.2±0.3%) cytostatic treatment as compared to healthy controls (0.6±0.1%). Erythrocyte ROS production and ceramide abundance, but not Fluo3 fluorescence, were significantly higher in freshly drawn erythrocytes from LC patients than in freshly drawn erythrocytes from healthy controls. PS exposure of erythrocytes drawn from healthy volunteers was significantly more pronounced following incubation in plasma from LC patients than following incubation in plasma from healthy controls.

Conclusion

Anemia in LC patients with and without cytostatic treatment is paralleled by increased eryptosis, which is triggered, at least in part, by increased oxidative stress and ceramide formation.

Insights into the diagnosis and management of iron deficiency in inflammatory bowel disease

INTRODUCTION

Iron deficiency is a frequent comorbidity of chronic diseases such as inflammatory bowel disease that can severely impact the health and quality of life of affected individuals. It can exist as a silent condition and manifest in non-specific symptoms even in the absence of anemia. Even though iron deficiency anemia is the most common complication and extra-intestinal manifestation of inflammatory bowel disease, the majority of inflammatory bowel disease patients who are diagnosed with iron deficiency anemia are not treated. Areas covered: In this review, we discuss iron deficiency and iron deficiency anemia in patients with inflammatory bowel disease, and review diagnostic and therapeutic options. Expert commentary: We invite international gastroenterological societies and associations to refine the practice guidelines and include iron deficiency as a potential morbidity associated with IBD in analogy to arthritis, uveitis or any other extra intestinal manifestations. There should a more unanimous agreement among different societies on the specific diagnostic cutoff values for C-reactive protein levels, serum ferritin, and transferrin saturation in order to differentiate iron deficiency anemia from anemia of chronic disease.

A Red Carpet for Iron Metabolism

200 billion red blood cells (RBCs) are produced every day, requiring more than 2 × 10¹⁵ iron atoms every second to maintain adequate erythropoiesis. These numbers translate into 20 mL of blood being produced each day, containing 6 g of hemoglobin and 20 mg of iron. These impressive numbers illustrate why the making and breaking of RBCs is at the heart of iron physiology, providing an ideal context to discuss recent progress in understanding the systemic and cellular mechanisms that underlie the regulation of iron homeostasis and its disorders.

Safety, pharmacokinetics and pharmacodynamics of the anti-hepcidin Spiegelmer lexaptepid pegol in healthy subjects

BACKGROUND AND PURPOSE

Anaemia of chronic disease is characterized by impaired erythropoiesis due to functional iron deficiency, often caused by excessive hepcidin. Lexaptepid pegol, a pegylated structured l-oligoribonucleotide, binds and inactivates hepcidin.

EXPERIMENTAL APPROACH

We conducted a placebo-controlled study on the safety, pharmacokinetics and pharmacodynamics of lexaptepid after single and repeated i.v. and s.c. administration to 64 healthy subjects at doses from 0.3 to 4.8 mg·kg(-1) .

KEY RESULTS

After treatment with lexaptepid, serum iron concentration and transferrin increased dose-dependently. Iron increased from approximately 20 μmol·L(-1) at baseline by 67% at 8 h after i.v. infusion of 1.2 mg·kg(-1) lexaptepid. The pharmacokinetics showed dose-proportional increases in peak plasma concentrations and moderately over-proportional increases in systemic exposure. Lexaptepid had no effect on hepcidin production or anti-drug antibodies. Treatment with lexaptepid was generally safe and well tolerated, with mild and transient transaminase increases at doses ≥2.4 mg·kg(-1) and with local injection site reactions after s.c. but not after i.v. administration.

CONCLUSIONS AND IMPLICATIONS

Lexaptepid pegol inhibited hepcidin and dose-dependently raised serum iron and transferrin saturation. The compound is being further developed to treat anaemia of chronic disease.

New insights into iron regulation and erythropoiesis

PURPOSE OF REVIEW

Iron homeostasis and erythropoiesis regulate each other to ensure optimal delivery of oxygen and iron to cells and tissues. Defining the mechanisms of this crosstalk is important for understanding the pathogenesis of common conditions associated with disordered iron metabolism and erythropoiesis.

RECENT FINDINGS

Stress erythropoiesis causes suppression of hepcidin to increase iron availability for hemoglobin synthesis. The erythroid hormone erythroferrone (ERFE) was identified as the mediator of this process. ERFE and additional candidates (TWSG1 and GDF15) may also mediate hepcidin suppression in ineffective erythropoiesis. Several mechanisms by which iron regulates erythropoiesis were also recently identified. Iron deficiency suppresses erythropoietin production via the IRP1-HIF2α axis to prevent excessive iron usage by erythropoiesis during systemic iron restriction. Iron restriction also directly impairs erythroid maturation by inhibiting aconitase, and this can be reversed by the administration of the aconitase product isocitrate. Another novel target is GDF11, which is thought to autoinhibit erythroid maturation. GDF11 traps show promising pharmacologic activity in models of both ineffective erythropoiesis and iron-restricted anemia.

SUMMARY

This review summarizes exciting advances in understanding the mechanisms of iron and erythropoietic regulation, and development of novel therapeutic tools for disorders resulting from dysregulation of iron metabolism or erythropoiesis.

Iron and Neurodegeneration: Is Ferritinophagy the Link?

Mounting evidence indicates that the lysosome-autophagy pathway plays a critical role in iron release from ferritin, the main iron storage cellular protein, hence in the distribution of iron to the cells. The recent identification of nuclear receptor co-activator 4 as the receptor for ferritin delivery to selective autophagy sheds further light on the understanding of the mechanisms underlying this pathway. The emerging view is that iron release from ferritin through the lysosomes is a general mechanism in normal and tumour cells of different tissue origins, but it has not yet been investigated in brain cells. Defects in the lysosome-autophagy pathway are often involved in the pathogenesis of neurodegenerative disorders, and brain iron homeostasis disruption is a hallmark of many of these diseases. However, in most cases, it has not been established whether iron dysregulation is directly involved in the pathogenesis of the diseases or if it is a secondary effect derived from other pathogenic mechanisms. The recent evidence of the crucial involvement of autophagy in cellular iron handling offers new perspectives about the role of iron in neurodegeneration, suggesting that autophagy dysregulation could cause iron dyshomeostasis. In this review, we recapitulate our current knowledge on the routes through which iron is released from ferritin, focusing on the most recent advances. We summarise the current evidence concerning lysosome-autophagy pathway dysfunctions and those of iron metabolism and discuss their potential interconnections in several neurodegenerative disorders, such as Alzheimer's, Parkinson's and Huntington's diseases; amyotrophic lateral sclerosis; and frontotemporal lobar dementia.

Isocitrate treatment of acute anemia of inflammation in a mouse model

Acute and severe anemia of inflammation (AI) is a common complication of various clinical syndromes, including fulminant infections, critical illness with multiorgan failure, and exacerbations of autoimmune diseases. Building on recent data showing beneficial results with isocitrate treatment for chronic low-grade AI in a rat model, we used a mouse model of acute and severe AI induced by intraperitoneal heat-killed Brucella abortus to determine if isocitrate would be effective in this more stringent application. Inflamed mice treated with isocitrate developed an early but transient improvement in hemoglobin compared to solvent-treated controls, with a robust improvement on day 7, and only a trend towards improvement by day 14. Reticulocyte counts were increased in treated mice transiently, with no significant difference by day 21. Serum erythropoietin (EPO) levels were similar in treated versus control mice, indicating that isocitrate increased sensitivity to EPO. Serum and tissue iron levels showed no significant differences between the treated and control mice, ruling out improved iron availability as the cause of the increased response to endogenous EPO. Compared to the milder rat model, much higher doses of isocitrate were required for a relatively modest benefit.

Kynurenine, by activating aryl hydrocarbon receptor, decreases erythropoietin and increases hepcidin production in HepG2 cells: A new mechanism for anemia of inflammation

It is known that inadequate erythropoietin (EPO) production contributes to the pathogenesis of anemia of inflammation, although the exact molecular mechanism is unknown. Aryl hydrocarbon receptor (AhR) may compete with hypoxia-inducible factor 2α (HIF-2α), the master regulator of EPO production, for binding with HIF-1β. The effect of kynurenine, an endogenous AhR activator that increases in inflammation, on EPO and hepcidin production was evaluated. HepG2 cells were treated with the hypoxia mimetic CoCl2, kynurenine, the AhR inhibitor CH223191, and combinations of these. EPO and hepcidin production was measured with enzyme-linked immunosorbent assay. HIF-2α and CYP1A1 levels, a transcriptional target of AhR, were assessed by Western blotting. CoCl2 increased EPO production and decreased hepcidin and CYP1A1. Kynurenine exerted the opposite effects. Wherever CH223191 was added, the inhibitor overcorrected kynurenine-induced alterations in both the presence and the absence of CoCl2. Also, treatment with CH223191 alone increased EPO and decreased hepcidin, indicating that there is a degree of constitutive AhR activation, possibly by other endogenous AhR activators. In conclusion, kynurenine, by competing with HIF-2α, may contribute to anemia of inflammation by decreasing EPO and increasing hepcidin production. The fact that inactivation of AhR alone induces EPO makes this transcription factor a potential therapeutic target in situations that require increased EPO.

Iron and hepcidin as risk factors in atherosclerosis: what do the genes say?

Background

Previous reports suggested a role for iron and hepcidin in atherosclerosis. Here, we evaluated the causality of these associations from a genetic perspective via (i) a Mendelian randomization (MR) approach, (ii) study of association of atherosclerosis-related single nucleotide polymorphisms (SNPs) with iron and hepcidin, and (iii) estimation of genomic correlations between hepcidin, iron and atherosclerosis.

Results

Analyses were performed in a general population sample. Iron parameters (serum iron, serum ferritin, total iron-binding capacity and transferrin saturation), serum hepcidin and genome-wide SNP data were available for N = 1,819; non-invasive measurements of atherosclerosis (NIMA), i.e., presence of plaque, intima media thickness and ankle-brachial index (ABI), for N = 549. For the MR, we used 12 iron-related SNPs that were previously identified in a genome-wide association meta-analysis on iron status, and assessed associations of individual SNPs and quartiles of a multi-SNP score with NIMA. Quartile 4 versus quartile 1 of the multi-SNP score showed directionally consistent associations with the hypothesized direction of effect for all NIMA in women, indicating that increased body iron status is a risk factor for atherosclerosis in women. We observed no single SNP associations that fit the hypothesized directions of effect between iron and NIMA, except for rs651007, associated with decreased ferritin concentration and decreased atherosclerosis risk. Two of six NIMA-related SNPs showed association with the ratio hepcidin/ferritin, suggesting that an increased hepcidin/ferritin ratio increases atherosclerosis risk. Genomic correlations were close to zero, except for hepcidin and ferritin with ABI at rest [−0.27 (SE 0.34) and −0.22 (SE 0.35), respectively] and ABI after exercise [−0.29 (SE 0.34) and −0.30 (0.35), respectively]. The negative sign indicates an increased atherosclerosis risk with increased hepcidin and ferritin concentrations.

Conclusions

Our results suggest a potential causal role for hepcidin and ferritin in atherosclerosis, and may indicate that iron status is causally related to atherosclerosis in women.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0246-4) contains supplementary material, which is available to authorized users.

Relationship Between Serum Hepcidin and Ferritin Levels in Patients With Thalassemia Major and Intermedia in Southern Iran

BACKGROUND

Hepcidin is a key regulator of iron absorption in humans. It is mainly affected by hypoxia and iron stores.

OBJECTIVES

The current study aimed to determine the correlation between serum hepcidin and ferritin levels in patients with Thalassemia Major (TM) and Thalassemia Intermedia (TI).

PATIENTS AND METHODS

The current cross-sectional study investigated 88 randomly selected patients with Thalassemia, 48 TM and 40 TI, registered at the Thalassemia Clinic of Shiraz University of Medical Sciences, a referral center for Thalassemia in Southern Iran in 2013. All patients with TI were receiving Hydroxyurea (HU) 10 - 15 mg/kg/day for at least 10 years. The serum hepcidin, ferritin levels, hemoglobin (Hb) and nucleated Red Blood Cell (RBC) of the two groups were measured.

RESULTS

No statistically significant correlation was observed between serum hepcidin and ferritin levels in any of the two groups of patients with TM (rs = 0.02, P = 0.892) or TI (rs = 0.055, P = 0.734). The median Interquartile Range (IQR) for serum hepcidin and ferritin levels were significantly higher in TM compared to TI group, (hepcidin: 87.6 (43.9) vs. 51.8 (23.4), P < 0.001; ferritin: 2208 (3761) vs. 465 (632), P < 0.001).

CONCLUSIONS

There was insignificant correlation between serum hepcidin and ferritin levels in the two groups of patients with TM and TI. It seems that regulation of hepcidin in patients with Thalassemia is more affected by erythropoeitic activity than iron stores. Also, hepcidin levels were significantly higher in patients with TM than TI, possibly due to higher erythropoeitic activity in TI. In TI, it seems that low dose HU increases Hb levels and leads to transfusion-independence, but it is not high enough to suppress bone marrow activity and ineffective erythropoiesis. Consequently, serum hepcidin level decreases.

Regulation of Iron Metabolism by Hepcidin under Conditions of Inflammation

Iron is a redox-active metal required as a cofactor in multiple metalloproteins essential for a host of life processes. The metal is highly toxic when present in excess and must be strictly regulated to prevent tissue and organ damage. Hepcidin, a molecule first characterized as an antimicrobial peptide, plays a critical role in the regulation of iron homeostasis. Multiple stimuli positively influence the expression of hepcidin, including iron, inflammation, and infection by pathogens. In this Minireview, I will discuss how inflammation regulates hepcidin transcription, allowing for sufficient concentrations of iron for organismal needs while sequestering the metal from infectious pathogens.

Hepcidin-25 in diabetic chronic kidney disease is predictive for mortality and progression to end stage renal disease

Background

Anemia is common and is associated with impaired clinical outcomes in diabetic chronic kidney disease (CKD). It may be explained by reduced erythropoietin (EPO) synthesis, but recent data suggest that EPO-resistance and diminished iron availability due to inflammation contribute significantly. In this cohort study, we evaluated the impact of hepcidin-25—the key hormone of iron-metabolism—on clinical outcomes in diabetic patients with CKD along with endogenous EPO levels.

Methods

249 diabetic patients with CKD of any stage, excluding end-stage renal disease (ESRD), were enrolled (2003–2005), if they were not on EPO-stimulating agent and iron therapy. Hepcidin-25 levels were measured by radioimmunoassay. The association of hepcidin-25 at baseline with clinical variables was investigated using linear regression models. All-cause mortality and a composite endpoint of CKD progression (ESRD or doubling of serum creatinine) were analyzed by Cox proportional hazards models.

Results

Patients (age 67 yrs, 53% male, GFR 51 ml/min, hemoglobin 131 g/L, EPO 13.5 U/L, hepcidin-25 62.0 ng/ml) were followed for a median time of 4.2 yrs. Forty-nine patients died (19.7%) and forty (16.1%) patients reached the composite endpoint. Elevated hepcidin levels were independently associated with higher ferritin-levels, lower EPO-levels and impaired kidney function (all p<0.05). Hepcidin was related to mortality, along with its interaction with EPO, older age, greater proteinuria and elevated CRP (all p<0.05). Hepcidin was also predictive for progression of CKD, aside from baseline GFR, proteinuria, low albumin- and hemoglobin-levels and a history of CVD (all p<0.05).

Conclusions

We found hepcidin-25 to be associated with EPO and impaired kidney function in diabetic CKD. Elevated hepcidin-25 and EPO-levels were independent predictors of mortality, while hepcidin-25 was also predictive for progression of CKD. Both hepcidin-25 and EPO may represent important prognostic factors of clinical outcome and have the potential to further define “high risk” populations in CKD.

A novel inflammatory pathway mediating rapid hepcidin-independent hypoferremia

Regulation of iron metabolism and innate immunity are tightly interlinked. The acute phase response to infection and inflammation induces alterations in iron homeostasis that reduce iron supplies to pathogens. The iron hormone hepcidin is activated by such stimuli causing degradation of the iron exporter ferroportin and reduced iron release from macrophages, suggesting that hepcidin is the crucial effector of inflammatory hypoferremia. Here, we report the discovery of an acute inflammatory condition that is mediated by Toll-like receptors 2 and 6 (TLR2 and TLR6) and which induces hypoferremia in mice injected with TLR ligands. Stimulation of TLR2/TLR6 triggers profound decreases in ferroportin messenger RNA and protein expression in bone marrow-derived macrophages, liver, and spleen of mice without changing hepcidin expression. Furthermore, C326S ferroportin mutant mice with a disrupted hepcidin/ferroportin regulatory circuitry respond to injection of the TLR2/6 ligands FSL1 or PAM3CSK4 by ferroportin downregulation and a reduction of serum iron levels. Our findings challenge the prevailing role of hepcidin in hypoferremia and suggest that rapid hepcidin-independent ferroportin downregulation in the major sites of iron recycling may represent a first-line response to restrict iron access for numerous pathogens.

RAP-011, an activin receptor ligand trap, increases hemoglobin concentration in hepcidin transgenic mice

Over expression of hepcidin antimicrobial peptide is a common feature of iron-restricted anemia in humans. We investigated the erythroid response to either erythropoietin or RAP-011, a "murinized" ortholog of sotatercept, in C57BL/6 mice and in hepcidin antimicrobial peptide 1 over expressing mice. Sotatercept, a soluble, activin receptor type IIA ligand trap, is currently being evaluated for the treatment of anemias associated with chronic renal disease, myelodysplastic syndrome, β-thalassemia, and Diamond Blackfan anemia and acts by inhibiting signaling downstream of activin and other Transforming Growth Factor-β superfamily members. We found that erythropoietin and RAP-011 increased hemoglobin concentration in C57BL/6 mice and in hepcidin antimicrobial peptide 1 over expressing mice. While erythropoietin treatment depleted splenic iron stores in C57BL/6 mice, RAP-011 treatment did not deplete splenic iron stores in mice of either genotype. Bone marrow erythroid progenitors from erythropoietin-treated mice exhibited iron-restricted erythropoiesis, as indicated by increased median fluorescence intensity of transferrin receptor immunostaining by flow cytometry. In contrast, RAP-011-treated mice did not exhibit the same degree of iron-restricted erythropoiesis. In conclusion, we have demonstrated that RAP-011 can improve hemoglobin concentration in hepcidin antimicrobial peptide 1 transgenic mice. Our data support the hypothesis that RAP-011 has unique biologic effects which prevent or circumvent depletion of mouse splenic iron stores. RAP-011 may, therefore, be an appropriate therapeutic for trials in human anemias characterized by increased expression of hepcidin antimicrobial peptide and iron-restricted erythropoiesis.

Iron age: novel targets for iron overload

Excess iron deposition in vital organs is the main cause of morbidity and mortality in patients affected by β-thalassemia and hereditary hemochromatosis. In both disorders, inappropriately low levels of the liver hormone hepcidin are responsible for the increased iron absorption, leading to toxic iron accumulation in many organs. Several studies have shown that targeting iron absorption could be beneficial in reducing or preventing iron overload in these 2 disorders, with promising preclinical data. New approaches target Tmprss6, the main suppressor of hepcidin expression, or use minihepcidins, small peptide hepcidin agonists. Additional strategies in β-thalassemia are showing beneficial effects in ameliorating ineffective erythropoiesis and anemia. Due to the suppressive nature of the erythropoiesis on hepcidin expression, these approaches are also showing beneficial effects on iron metabolism. The goal of this review is to discuss the major factors controlling iron metabolism and erythropoiesis and to discuss potential novel therapeutic approaches to reduce or prevent iron overload in these 2 disorders and ameliorate anemia in β-thalassemia.

Effect of the antihepcidin Spiegelmer lexaptepid on inflammation-induced decrease in serum iron in humans

Increased hepcidin production is key to the development of anemia of inflammation. We investigated whether lexaptepid, an antihepcidin l-oligoribonucleotide, prevents the decrease in serum iron during experimental human endotoxemia. This randomized, double-blind, placebo-controlled trial was carried out in 24 healthy males. At T = 0 hours, 2 ng/kg Escherichia coli lipopolysaccharide was intravenously administered, followed by an intravenous injection of 1.2 mg/kg lexaptepid or placebo at T = 0.5 hours. The lipopolysaccharide-induced inflammatory response was similar in subjects treated with lexaptepid or placebo regarding clinical and biochemical parameters. At T = 9 hours, serum iron had increased by 15.9 ± 9.8 µmol/L from baseline in lexaptepid-treated subjects compared with a decrease of 8.3 ± 9.0 µmol/L in controls (P < .0001). This study delivers proof of concept that lexaptepid achieves clinically relevant hepcidin inhibition enabling investigations in the treatment of anemia of inflammation. This trial was registered at www.clinicaltrial.gov as #NCT01522794.