Iron Recycling Research Articles

Role of Exosomes in Hepcidin Regulation in β-Thalassemia

β-thalassemia is characterized by ineffective erythropoiesis and iron overload. Ineffective erythropoiesis causes iron overload by suppressing hepcidin, the main negative regulator of iron absorption and recycling, and is mediated by secretion of erythroferrone from bone marrow cells. Targeted treatment for ineffective erythropoiesis is unavailable. Furthermore, molecular mechanisms involved in ineffective erythropoiesis and the details of how erythropoiesis regulates iron metabolism are incompletely understood. Lastly, while loss of erythroferrone in β-thalassemic mice leads to partial reversal of iron overload [Kautz Blood 2015], erythroferrone ablated mice are still able to suppress hepcidin after phlebotomy [Kautz Nat Med 2014]. These finding provide evidence of additional regulatory crosstalk between erythropoiesis and iron metabolism. We hypothesize that bone-marrow derived exosomes regulate iron metabolism by modulating hepcidin. Exosomes are small extracellular vesicles derived from multi-vesicular bodies forming intraluminal vesicles which fuse with the plasma membrane and are released by many different cell types [Thery Nat Rev Immun 2002]. In light of their capacity for cell-cell communication and modification of the microenvironment, exosomes have been widely studied in multiple diseases [Valadi Nat Cell Bio 2007] despite which, erythropoiesis-derived exosomes and their role in iron metabolism regulation remain unexplored. Our preliminary data demonstrate that phlebotomy in wild type mice results in increased exosome concentration in serum and that exosomes are increased in th3/+ mouse serum (Figure 1a). Furthermore, hepcidin induction by exosome depleted-FBS is decreased relative to FBS (Figure 1b), and exosomes isolated from FBS induce hepcidin in a dose response manner in vitro (Figure 1c). We thus propose to explore the mechanistic relationship between exosomes and hepcidin regulation in β-thalassemia. Serum samples from patients with β-thalassemia major and age / gender matched controls were collected; all patients were treated with iron chelation therapy and all samples were collected immediately prior to transfusion. Exosome fractions were purified and analyzed in patients relative to controls. Although there is no difference in the number of exosomes or mean particle size within the exosomal fraction, exosomal protein content per volume of serum is significantly decreased in patients relative to controls. In addition, the treatment of primary wild type mouse hepatocytes with sera from patients and controls reveals the expected relatively decreased hepcidin induction in β-thalassemic patient sera treated hepatocytes relative to control sera; a similar difference is seen in hepatocytes treated with exosome-depleted sera from patients and controls (Figure 2a). These findings suggest that hepcidin suppression is a consequence of the exosome-free portion of serum from control and β-thalassemic samples. Furthermore, only exosomes derived from β-thalassemic patient sera induces hepcidin expression in primary wild type mouse hepatocyte cultures (Figure 2b). Lastly, exosomes derived from β-thalassemic patient sera do not affect ERK1/2 and STAT3 signaling in primary hepatocytes but increase SMAD1/5/8 (Figure 2c) and decrease AKT signaling (Figure 2d). Taken together, these findings demonstrate that exosomes enhance hepcidin expression via increased SMAD1/5/8 signaling, that increased hepcidin may influence multiple signaling pathways by an autocrine mechanism in response to exosomes, and that exosomes counterbalance hepcidin suppressive substances in the exosome-depleted serum from β-thalassemic samples. Our studies provide novel insights into the important previously unexplored mechanism of hepcidin regulation by exosomes in both physiologic and pathologic states. Disclosures Coates: apo pharma: Consultancy, Honoraria, Speakers Bureau; vifor: Consultancy, Honoraria; celgene: Consultancy, Honoraria, Other: steering committee of clinical study; agios pharma: Consultancy, Honoraria. Ginzburg:La Jolla Pharma: Membership on an entity's Board of Directors or advisory committees.

Disbalanced Erythroid Ferroportin Expression Contributes to Ineffective Erythroid Output in Anemia of Chronic Disease

Iron is essential for proper red blood cell development. During erythroid maturation in the bone marrow iron dependency starts at the basophilic stage, and lasts until the reticulocyte stage. Thereby the majority of iron is delivered in a Tf-TfR dependent manner and is incorporated in hemoglobin of developing red cells. Just recently, it has been discovered that erythroblasts and mature red blood cells not only incorporate iron but also express the sole known iron exporter, ferroportin (Fpn), throughout their development, and thus can also effectively export iron that is not used for heme synthesis. Fpn surface expression is regulated via hepcidin, a hepatocyte-derived peptide, which binds directly to surface-Fpn, inducing its internalization and consequent degradation in lysosomes. Among patients suffering from anemia of chronic disease (ACD), hepcidin is constantly induced due to long-lasting inflammation, leading to impaired iron export capacity. While splenic tissue iron overload, which is associated with the restricted capacity of red pulp macrophages to export recycled iron form degraded erythrocytes is well established, the effect of high hepcidin levels in ACD and its consequences on developing erythroblasts in the bone marrow has not been investigated. First we induced chronic kidney disease (CKD) in C57BL/6 mice via an Adenine - diet. Alongside microcytic anemia, reduced Tf-saturation, increased hepcidin levels and splenic tissue iron overload, we found a ~38% increase in tissue iron content in bone marrows of CKD mice compared to control mice. In parallel, Western blot analysis revealed massively reduced Fpn protein levels in the bone marrow. Moreover, the individual iron-dependent erythroblast precursor populations (i.e. basophilic, polychromatic, orthochromatic erythroblasts and reticulocytes) showed higher levels of intracellular iron as measured by Calcein fluorescence via flow cytometry. We could further corroborate these results by Western blot analysis and flow cytometric work-up of reticulocytes and mature red blood cells in the blood stream, both revealing highly reduced Fpn protein levels on these cells in mice suffering from CKD. Based on these findings we performed additional experiments to investigate the detrimental effect of iron overload on erythroid development and to exclude the possibility of a direct inflammation-regulated process in the CKD model. Therefor we established an iron-overload mouse model via repeated parenteral iron dextran applications. Despite significantly increased Tf-saturation levels as well as hepatic hepcidin levels (>4-fold) and reduced bone marrow Fpn protein levels among iron-treated mice, iron overload led to higher stress levels among erythroid precursor populations. In detail, we could demonstrate via flow cytometry that higher intracellular iron pools (measured by Calcein), correlated with higher levels of mitochondrial stress and higher levels of lipid peroxidation (determined by mean fluorescence intensity of MitoSOX and Bodipy 581/59, respectively). These data indicate that iron is a critical regulator of stress during erythroid development and can be regulated via the hepcidin-Fpn axis. In conclusion, we clearly show that Fpn expression on erythroid precursor cells is inversely regulated to systemic hepcidin levels and affects the erythropoietic bone marrow iron content. Moreover our results reveal a novel model for ineffective erythroid output in patients suffering from ACD due to hepcidin-triggered Fpn internalistation. Based on our data, anti-hepcidin treatment strategies are promising to overcome restricted erythropoiesis, which will be evaluated in future experiments. Disclosures Theurl: Kymab Ltd: Consultancy, Equity Ownership.

IFN-γ-Dependent Reduction of Erythrocyte Life Span Leads to Anemia during Mycobacterial Infection.

Anemia is a frequent and challenging complication of mycobacterial infections. We used a model of disseminated Mycobacterium avium infection in mice to investigate the mechanisms of mycobacteria-induced anemia. We found increased formation of RBC in the bone marrow and spleen of infected mice. Infection induced reticulocytosis and the premature egress of immature progenitors to the systemic circulation in an IFN-γ (IFNG)-dependent way. The newly formed RBC had reduced CD47 surface expression and a reduced life span and were phagocytosed in the liver of infected mice, increasing iron recycling in this organ. The increased engulfment and degradation of RBC was independent of IFNG sensing by macrophages. Together, our findings demonstrate that mycobacterial infection alters the formation of erythrocytes, leading to their accelerated removal from circulation and hemolytic anemia. This comprehensive elucidation of the mechanisms underlying mycobacteria-induced anemia has important implications for its efficient clinical management.

Recycling of iron and titanium resources from early tailings: From fundamental work to industrial application.

The comprehensive recovery of iron and titanium resources from early tailings were systematically attempted from fundamental work to industrial application. Geochemical characterization of the tailings was first conducted, followed by the iron recovery and titanium recovery. Iron recovery was mainly achieved through a series of magnetic separation, and titanium recovery was on the combination of magnetic pre-concentration and flotation separation. Special for titanium recovery, different pretreatment methods including ultrasonic cleaning and attrition-scrubbing were studied to reduce the influence of serious surface pollution of early tailings on ilmenite floatability, and attrition-scrubbing proved to be the best one. Associated mechanisms of flocculants influence on ilmenite floatability and the attrition-scrubbing effects were explored using micro-flotation and XPS tests. After a series of fundamental studies, the industrial production of iron and ilmenite concentrate went into operation and the industrial debugging results were roughly satisfactory. At last, a brief economic analysis was given for the present work.

Effects of disinfection efficiency on microbial communities and corrosion processes in drinking water distribution systems simulated with actual running conditions

The effects of disinfection efficiency on microbial communities and the corrosion of cast iron pipes in drinking water distribution systems (DWDSs) were studied. Two annular reactors (ARs) that simulated actual running conditions with UV/Cl2 disinfection and chlorination alone were used. High chlorine consumption and corrosion rate were found in the AR with UV/Cl2. According to functional genes and pyrosequencing tests, a high percentage of iron recycling bacteria was detected within the biofilm of the AR with Cl2 at early running stage, whereas siderophore-producing bacteria were dominant in the biofilm of the AR with UV/Cl2. At the early running stage, the sequential use of UV light and an initial high chlorine dosage suppressed the biomass and iron-recycling bacteria in both bulk water and biofilms, thereby forming less protective scales against further corrosion, which enhanced chlorine consumption. Non-metric multidimensional scaling analysis showed that the bacterial communities in the ARs shaped from within rather than being imported by influents. These results indicate that the initial high disinfection efficiency within the distribution system had not contributed to the accumulation of iron-recycling bacteria at the early running stages. This study offer certain implications for controlling corrosion and water quality in DWDSs.

Hepcidin and Anemia: A Tight Relationship

Hepcidin, the master regulator of systemic iron homeostasis, tightly influences erythrocyte production. High hepcidin levels block intestinal iron absorption and macrophage iron recycling, causing iron restricted erythropoiesis and anemia. Low hepcidin levels favor bone marrow iron supply for hemoglobin synthesis and red blood cells production. Expanded erythropoiesis, as after hemorrhage or erythropoietin treatment, blocks hepcidin through an acute reduction of transferrin saturation and the release of the erythroblast hormone and hepcidin inhibitor erythroferrone. Quantitatively reduced erythropoiesis, limiting iron consumption, increases transferrin saturation and stimulates hepcidin transcription. Deregulation of hepcidin synthesis is associated with anemia in three conditions: iron refractory iron deficiency anemia (IRIDA), the common anemia of acute and chronic inflammatory disorders, and the extremely rare hepcidin-producing adenomas that may develop in the liver of children with an inborn error of glucose metabolism. Inappropriately high levels of hepcidin cause iron-restricted or even iron-deficient erythropoiesis in all these conditions. Patients with IRIDA or anemia of inflammation do not respond to oral iron supplementation and show a delayed or partial response to intravenous iron. In hepcidin-producing adenomas, anemia is reverted by surgery. Other hepcidin-related anemias are the “iron loading anemias” characterized by ineffective erythropoiesis and hepcidin suppression. This group of anemias includes thalassemia syndromes, congenital dyserythropoietic anemias, congenital sideroblastic anemias, and some forms of hemolytic anemias as pyruvate kinase deficiency. The paradigm is non-transfusion-dependent thalassemia where the release of erythroferrone from the expanded pool of immature erythroid cells results in hepcidin suppression and secondary iron overload that in turn worsens ineffective erythropoiesis and anemia. In thalassemia murine models, approaches that induce iron restriction ameliorate both anemia and the iron phenotype. Manipulations of hepcidin might benefit all the above-described anemias. Compounds that antagonize hepcidin or its effect may be useful in inflammation and IRIDA, while hepcidin agonists may improve ineffective erythropoiesis. Correcting ineffective erythropoiesis in animal models ameliorates not only anemia but also iron homeostasis by reducing hepcidin inhibition. Some targeted approaches are now in clinical trials: hopefully they will result in novel treatments for a variety of anemias.

Could hepcidin, a marker of iron metabolism, serve as an indicator of low energy availability in male and females?

Hepcidin, a peptide hormone produced in the liver with an acknowledged evolutionary function in iron homeostasis, regulates iron status through its interaction with ferroportin channels within the body. Elevation of hepcidin within the body internalises and degrades ferroportin channels, inhibiting movement of iron from stores in the liver, recycling of iron from macrophages and absorption of iron from dietary intake in the duodenum. Within a sporting context, peaks in hepcidin ∼3–6 hours post-exercise have been suggested to reduce iron absorption and recycling, likely leading to an increased risk of exercise-induced iron deficiency.

Tissue Iron Promotes Wound Repair via M2 Macrophage Polarization and the Chemokine (C-C Motif) Ligands 17 and 22

Macrophages are important for effective iron recycling and erythropoiesis, but they also play a crucial role in wound healing, orchestrating tissue repair. Recently, we demonstrated a significant accumulation of iron in healing wounds and a requirement of iron for effective repair. Herein, we sought to determine the influence of iron on macrophage function in the context of wound healing. Interestingly, wound macrophages extensively sequestered iron throughout healing, associated with a prohealing M2 phenotype. In delayed healing diabetic mouse wounds, both macrophage polarization and iron sequestration were impaired. Invitro studies revealed that iron promotes differentiation, while skewing macrophages toward a hypersecretory M2-like polarization state. These macrophages produced high levels of chemokine (C-C motif) ligands 17 and 22, promoting wound reepithelialization and extracellular matrix deposition in a human exvivo wound healing model. Together, these findings reveal a novel, unappreciated role for iron in modulating macrophage behavior to promote subsequent wound repair. These findings support therapeutic evaluation of iron use to promote wound healing in the clinic.

Vertebrate Hematoma Resolution Is Directed By Activating Transcription Factor 1 (Atf1) And Adenosine-Monophosphate-Activated-Protein-Kinase (Ampk)

Background and Aims: The successful resolution of tissue hemorrhage is an important vertebrate homeostatic function. Its regulatory mechanism is still largely unknown. In human macrophages in vitro, heme activates an AMPK/ATF1 pathway that coregulates HMOX1 and lipid homeostasis genes, coordinating separation and recycling of iron and lipid. We asked whether this pathway had an in vivo role in mice. Perifemoral hematomas are clinically relevant, and therefore used as a model of hematoma resolution.

Identification and transcriptome analysis of erythroblastic island macrophages

AbstractThe erythroblastic island (EBI), composed of a central macrophage and surrounding erythroid cells, was the first hematopoietic niche discovered. The identity of EBI macrophages has thus far remained elusive. Given that Epo is essential for erythropoiesis and that Epor is expressed in numerous nonerythroid cells, we hypothesized that EBI macrophages express Epor so that Epo can act on both erythroid cells and EBI macrophages simultaneously to ensure efficient erythropoiesis. To test this notion, we used Epor-eGFPcre knockin mouse model. We show that in bone marrow (BM) and fetal liver, a subset of macrophages express Epor-eGFP. Imaging flow cytometry analyses revealed that >90% of native EBIs comprised F4/80+Epor-eGFP+ macrophages. Human fetal liver EBIs also comprised EPOR+ macrophages. Gene expression profiles of BM F4/80+Epor-eGFP+ macrophages suggest a specialized function in supporting erythropoiesis. Molecules known to be important for EBI macrophage function such as Vcam1, CD169, Mertk, and Dnase2α were highly expressed in F4/80+Epor-eGFP+ macrophages compared with F4/80+Epor-eGFP− macrophages. Key molecules involved in iron recycling were also highly expressed in BM F4/80+Epor-eGFP+ macrophages, suggesting that EBI macrophages may provide an iron source for erythropoiesis within this niche. Thus, we have characterized EBI macrophages in mouse and man. Our findings provide important resources for future studies of EBI macrophage function during normal as well as disordered erythropoiesis in hematologic diseases such as thalassemia, polycythemia vera, and myelodysplastic syndromes.

Hepcidin gene of Indian major carp, Labeo rohita: Molecular, structural and functional characterization, and antibacterial activity of recombinant hepcidin

Hepcidin, an antimicrobial peptide produced in the liver, also regulates iron balance and recycling in vertebrates. To study the antibacterial activity of Labeo rohita hepcidin (LrHep), full-length cDNA of LrHep was cloned. The 800 bp amplicon contained an open reading frame of 276 bp, encoding 91 amino acids including a signal peptide of 24 amino acid residues. The 3D structure and domain architecture of LrHep were predicted. Phylogenetic analysis of the LrHep sequence showed that it formed a sister group with another carp, Sinocyclocheilus rhinocerous. LrHep has eight cysteine residues at C73, C76, C77, C79, C80, C85, C88 and C89 positions conserved throughout evolution. Besides cysteine residues, like in all teleosts, A24, P26, E34 and R63 were also found to be conserved in LrHep. Expression analysis of LrHep using 12 different tissues of naïve rohu juveniles revealed that its expression is being the highest in the liver followed by anterior kidney. To study the role of LrHep during disease, its expression kinetics was observed in three infection models (Aeromonas hydrophila, poly I:C, and Argulus siamensis, representatives of bacterial, viral, and parasitic infections, respectively). Significant up-regulation of LrHep was observed in the liver in all the three experimental groups (at 12 h with A. hydrophila infection, 3 h with poly I:C stimulation and 24 h with A. siamensis infection). Significant up-regulation in anterior kidney was observed at 3 and 6 h only in A. hydrophila infected fish. The antimicrobial activity of LrHep was evaluated both in vitro and in vivo by producing recombinant hepcidin (approximately 11 kDa) of rohu (rLrHep) in Escherichia coli. The recombinant LrHep inhibited growth of the bacteria, Edwardsiella tarda and A. hydrophila, in vitro at concentrations of 50 and 100 μg (4.54 and 9.09 μM), respectively, at 6 h post-incubation. Administration of rLrHep to rohu juveniles rendered protection against A. hydrophila challenge with a relative percent survival (RPS) of 73%. Overall, the findings of this study suggest that owing to its potential antimicrobial activity, LrHep could be an effective immunomodulator providing protection against A. hydrophila infection.

The commensal bacterium Bacteroides fragilis down-regulates ferroportin expression and alters iron homeostasis in macrophages.

The intestinal microbiota has several effects on host physiology. Previous work from our laboratory demonstrated that the microbiota influences systemic iron homeostasis in mouse colitis models by altering inflammation-induced expression of the iron-regulating hormone hepcidin. In the present study, we examined the impact of the gut commensal bacterium Bacteroides fragilis on the expression of the iron exporter ferroportin, the target of hepcidin action, in macrophages, the cell type that plays a pivotal role in iron recycling. Mouse bone marrow-derived macrophages were exposed to B. fragilis and were analyzed by quantitative real-time polymerase chain reaction and Western blotting. We found that B. fragilis down-regulated ferroportin transcription independently of bacterial viability. Medium conditioned by the bacteria also reduced ferroportin expression, indicating the involvement of soluble factors, possibly Toll-like receptor ligands. Consistent with this idea, several of these ligands were able to down-regulate ferroportin. The B. fragilis-induced decrease in ferroportin was functionally important since it produced a significant increase in intracellular iron concentrations that prevented the effects of the iron chelator deferoxamine on Salmonella-induced IL-6 and IL-1β production. Our results thus reveal that B. fragilis can influence macrophage iron handling and inflammatory responses by modulating ferroportin expression.

NCOA4 Mediates Ferritin Responses to Iron, Erythrophagocytosis, and Hepcidin in Macrophages (P24-056-19)

ObjectivesIron recycled from erythrophagocytosis by macrophages serves as a primary source of systemic iron. NCOA4 mediates ferritin turnover via ferritinophagy. Yet, whether NCOA4 is important in macrophages or erythrophagocytosis-mediated iron recycling remains unclear, and thus was assessed in vitro. MethodsJ774 cells were employed as an in vitro model of macrophages. Iron studies involved treatments of ferric ammonium citrate (FAC) or an iron chelator, deferoxamine (Dfo). To recapitulate systemic iron recycling and overload, cells were treated with opsonized erythrocytes and minihepcidin, respectively. NCOA4 knock-down was achieved by siRNA transfection. Iron gene responses were measured by qPCR and western analyses, and viable cell counts were colorimetrically determined by CCK8 assays as functional outcomes. ResultsNCOA4 protein abundance was inversely related to iron availability and ferritin in macrophages. Loss of NCOA4 resulted in impaired ferritin turnover, and led to a reduction in viable cells when combined with iron deficiency. By erythrophagocytosis, a peak in ferritin abundance was observed at 12 h with a subsequent decrease at 24 h. This loss in ferritin was NCOA4-dependent. Minihepcidin caused accumulation of ferritin, along with a repression of NCOA4 in both control and erythrocyte-laden macrophages. Hepcidin activity had no effect on ferritin when NCOA4 was depleted. ConclusionsNCOA4 mediates the release of ferritin iron during cellular iron restriction and iron recycling by macrophages. Moreover, our studies suggest that macrophage NCOA4 is integral to systemic iron homeostasis by responding to the iron regulatory hormone, hepcidin. Thus, NCOA4 and ferritinophagy may potentially serve as therapeutic targets for treatments of iron disorders and anemia of chronic disease. Funding SourcesSupported by the NIFA, USDA, Hatch project under MIN-18–118 and intramural support to M-S.R.

Mechanisms, mishaps and manipulation of iron uptake

Mechanisms, mishaps and manipulation of iron uptake

S904 THE FUNCTIONAL RESPONSE OF IRON‐RECYCLING AND INFECTION CONTROL‐SPECIALIZED MACROPHAGES IS IMPAIRED BY TRANSFUSIONS AND AMELIORATED BY IRON CHELATION

Background:Iron overload is common in anemic patients who require regular transfusions. Transfusional iron overload is associated with enhanced susceptibility to infections, a common cause of morbidity/mortality in these patient populations.Aims:Here we studied how iron overload, besides supporting bacterial growth, may alter macrophage response to infectious stimuli.Methods:We applied a mouse model of repeated allogeneic RBC transfusions and investigated the impact of transfusions on the phenotypic plasticity of different macrophage populations as well as their responses to infectious cues.Results:Using this model, we have recently shown that repeated transfusions promote macrophage switching to a M2‐like anti‐inflammatory phenotype, hallmarked by reduced inflammatory marker expression and inflammatory cytokine release. Consistently, in transfused animals, macrophages develop a blunted M1‐like inflammatory phenotype in response to LPS, leading to reduced circulating inflammatory cytokines. These observations indicate that transfusion‐induced erythrophagocytosis dampens the inflammatory response to infectious cues by impairing macrophage functions. Transfusion‐blunted M1 polarization occurs in both iron‐recycling hepatic Kupffer cells and splenic red pulp macrophages (RPM). We now have extended our analysis to additional macrophage sub‐populations of the spleen which play a critical role in the phagocytosis of blood‐borne pathogens and control of innate/adaptive immune response to infections and found that also these cells, marginal zone (MZM) and marginal metallophilic (MMM) macrophages, are affected by RBC transfusions and show a suppression of M1 markers. Since MZMs and MMMs are not directly involved in erythrophagocytosis, we speculate that the blunted M1 polarization of iron‐recycling macrophages attenuates the pro‐inflammatory activation of other macrophages, including MZMs and MMMs, with potential impact on the susceptibility and response to infections. We now have administered an iron chelator, deferasirox, during the transfusion period, and show that iron chelation therapy partially restores the phenotype of Kupffer cells and RPMs by rescuing marker expression and shifting the transfusion‐triggered M2‐like macrophage population to a M1‐like (both with and without LPS). Interestingly, chelation therapy significantly improves the expression of M1 markers also in MZMs and MMMs, suggesting that chelation would help to control infections by improving the response of different macrophage sub‐populations. Importantly, we have confirmed our findings in a mouse model of MDS receiving repeated transfusions. Combined with marked cytopenias and iron‐boosted microorganism growth, the weak pro‐inflammatory activation of macrophages might contribute to the increased propensity of transfused MDS patients to develop infections.Summary/Conclusion:Our data indicate that transfusions blunt macrophage inflammatory response by affecting macrophage plasticity towards an anti‐inflammatory phenotype with reduced potential to counteract infections. By restoring cell polarization, iron chelation likely improves the functional response of macrophages to invading microorganisms. Transfusion practice might therefore increase the risk of infections not solely through increased iron availability to microorganisms, but also through the impaired activation of a broad plethora of macrophages, involved in iron recycling and infection control. Transfused patients might benefit from chelation by both restricting iron from pathogens and improving macrophage‐induced immune response.

Evaluation of reduction behavior of blast furnace dust particles during in-flight process with experiment aided mathematical modeling

• BF dust particle velocity variation and residence times in the reaction zone are evaluated accurately. • Detailed BF dust particle thermal history during the in-flight reduction process is determined. • Transformation of the reduction degree of BF dust particle is found when particle temperature is over than 1640 K. • An iterative algorithm is developed to improve prediction accuracy of the mathematical model. In-flight reduction technology is a flexible process that allows recycling of the fine iron bearing metallurgical dusts efficiently. In this work, a mathematical model, incorporating introduced experimental kinetic parameters, was developed to accurately evaluate the reduction behavior of blast furnace (BF) dust particles during flight. A detailed evaluation of particle residence time, thermal history and reduction degree conversion were used to eliminate the deviations related to the assumptions of constant particle velocity and temperature in the experiment. The results show that the particle velocity decreases along the longitudinal direction of the reactor for a long distance and reaches a constant low velocity at the middle part of the reaction zone. The calculated particle residence time is 0.15–0.44 s less than the experimentally estimated value. The particle temperature reaches the isothermal temperature at the 0.15 m position from the reaction zone bottom. An obvious transition of reduction degree of dust particle is found when particle temperature reaches over 1640 K. The prediction accuracy of the model was improved by using the optimized kinetic parameters, namely pre-exponential factor and activation energy.

Hepcidin as a Prospective Individualized Biomarker for Individuals at Risk of Low Energy Availability.

Hepcidin, a peptide hormone with an acknowledged evolutionary function in iron homeostasis, was discovered at the turn of the 21st century. Since then, the implications of increased hepcidin activity have been investigated as a potential advocate for the increased risk of iron deficiency in various health settings. Such implications are particularly relevant in the sporting community where peaks in hepcidin postexercise (∼3-6hr) are suggested to reduce iron absorption and recycling, and contribute to the development of exercise-induced iron deficiency in athletes. Over the last decade, hepcidin research in sport has focused on acute and chronic hepcidin activity following single and repeated training blocks. This research has led to investigations examining possible methods to attenuate postexercise hepcidin expression through dietary interventions. The majority of macronutrient dietary interventions have focused on manipulating the carbohydrate content of the diet in an attempt to determine the health of athletes adopting the low-carbohydrate or ketogenic diets, a practice that is a growing trend among endurance athletes. During the process of these macronutrient dietary intervention studies, an observable coincidence of increased cumulative hepcidin activity to low energy availability has emerged. Therefore, this review aims to summarize the existing literature on nutritional interventions on hepcidin activity, thus, highlighting the link of hepcidin to energy availability, while also making a case for the use of hepcidin as an individualized biomarker for low energy availability in males and females.

The emerging roles of eryptosis in liver diseases.

Erythrocytes undergo programmed cell death, similar to apoptosis, known as eryptosis. This process is a result of several factors including hyperosmolarity, oxidative stress, and exposure to xenobiotics, and is characterized by the breakdown of membrane phospholipid asymmetry, the clustering of band 3, and the generation of red blood cell-derived microparticles. Under pathological conditions, the liver is the primary site of erythrocyte clearance and plays an important role in iron recycling. Phosphatidylserine exposure and band-3 clustering on eryptotic erythrocytes represent mainly pro-phagocytic signals. Further, the percentage of eryptotic erythrocytes is enhanced in the circulating blood of patients with hepatic failure, hyperbilirubinemia, and nonalcoholic steatohepatitis. In this review, we concentrate on recent progress regarding the pathophysiological roles of eryptosis in liver diseases.

IL-1 beta-mediated macrophage-hepatocyte crosstalk upregulates hepcidin under physiological low oxygen levels

In mammals, the iron masterswitch hepcidin efficiently controls iron recycling by the macrophage-liver axis but the exact interplay between macrophages and hepatocytes remains poorly understood. We here study hepcidin response during macrophage differentiation as well as the macrophage-hepatocyte crosstalk and its subsequent effects on hepatocyte hepcidin using an in vitro co-culture model that mimics the physiological liver microenvironment. We show that macrophage differentiation strongly induces hepcidin by 60-fold both in THP1 macrophages and primary isolated monocyte-derived macrophages. Removal of H2O2 by catalase or inhibition of NOX2 efficiently blocked hepcidin induction. After differentiation, macrophage hepcidin accounted for 10% of total hepatocyte hepcidin and did not respond to low oxygen levels. In contrast, co-culture of differentiated macrophages with Huh7 cells significantly induced hepatocyte hepcidin, which was further potentiated under low oxygen levels. Hepatocyte hepcidin was also upregulated when Huh7 cells were solely exposed to macrophage-conditioned hypoxic medium. A cytokine screen identified macrophage secreted IL-1β as major inducer of hepcidin in hepatocytes. In confirmation, treatment of Huh7 cells with the IL-1 receptor antagonist (anakinra) completely blunted macrophage-mediated hepcidin transcription in hepatocytes. Finally, detailed analysis of potentially involved signaling pathways points toward STAT3 and CEBPδ-mediated hepcidin induction independent of IL-6. In conclusion, our study demonstrates a strong NOX2-mediated hepcidin induction during macrophage differentiation. These differentiated macrophages are able to efficiently induce hepatocyte hepcidin mainly through secretion of IL-1β. Our data highlight a hitherto unrecognized role of macrophage-hepatocyte crosstalk for a joint and oxygen-dependent hepcidin production through STAT3 and CEBPδ.

Interpreting 14C Measurements on 3rd–4th Century AD Iron Artifacts from Nydam, Denmark

ABSTRACTRadiocarbon (14C) ages were determined for 10 iron samples from the war booty offering site in the Nydam peat bog (SE Denmark), and compared to archaeologically inferred periods of deposition. Additional 14C measurements were carried out for modern iron standards made with charcoal of known isotopic composition to evaluate possible effects of handling. Modern iron standards give depleted 14C concentrations, compared to the initial charcoal 14C composition, and may indicate carbon fractionation effects during carbon dissolution in the iron lattice. Further studies are needed to verify if this is a common effect during iron production. 14C dating of two swords and one ax head are in comparatively good agreement with expected deposition times and indicate only small old-wood effects. In contrast, 14C dating of iron rivets from the Nydam (B) oak boat proved difficult due to corrosion with siderite (FeCO3) and conservation with wax. A step-combustion procedure was applied, using a low (∼570–600°C) temperature prior to the high (∼970–1000°C) combustion temperature for carbon extraction, aiming to remove siderite and wax before collecting the original carbon dissolved in the iron lattice. Nevertheless, measured 14C ages of the iron rivets differ by about 200–300 years from the dendro-date of the Nydam (B) oak boat they belong to, indicating persisting aging effects (e.g. old-wood, contamination with fossil carbon added during iron making and/or handling prior 14C dating). Also, a possible recycling of older iron cannot be excluded.