Erythroferrone, the new iron regulator: evaluation of its levels in Egyptian patients with beta thalassemia

The association between growth differentiation factor-15, erythroferrone, and iron status in thalassemic patients

BACKGROUND

Iron overload can result in grave consequences in thalassemic patients, despite the availability of iron chelators. Therefore, alternative pathways aiming to reduce iron toxicity are currently investigated. Among which, reduction of iron absorption through control of hepcidin production appears to be promising. In this study, we investigated growth differentiation factor-15 (GDF15) and erythroferrone (ERFE) as potential suppressors of hepcidin.

METHODS

This cross-sectional study was conducted on 61 thalassemic patients and 60 healthy controls. The frequency of GDF15 gene polymorphism (rs4808793) (-3148C/G), serum level of GDF15 and erythroferrone were measured and correlated with those of hepcidin and serum ferritin.

RESULTS

The presence of GDF15 gene mutations were significantly higher in the patients' group compared to controls (P value 0.035). Also, thalassemia patients had significantly higher levels of GDF15 and ERFE and lower hepcidin levels than controls (P value < 0.001). Serum hepcidin level showed significantly negative correlations with GDF15, ERFE, reticulocyte count, LDH level, and serum ferritin. Contrarily, it had highly significant positive correlation with hemoglobin.

CONCLUSIONS

High level of GDF15 and/or ERFE may inhibit hepcidin production and increase iron load in patients with thalassemia; therefore, medications that suppress their actions may provide new therapeutic potentials for iron toxicity.

IMPACT

Iron overload continues to be a major contributor to high morbidity and mortality in patients with thalassemia. New strategies together with proper chelation, need to be developed to minimize the effect of iron toxicity. Growth differentiation factor-15 (GDF15) and erythroferrone (ERFE) inhibit hepcidin production and increase iron levels in conditions with ineffective erythropoiesis. Medications that suppress the production or interfere with the action of GDF15 or ERFE may represent new therapeutic potentials for iron toxicity. Prevention of iron toxicity will significantly reduce morbidity and mortality and improve the quality of life of thalassemia patients.

The effect of erythroferrone suppression by transfusion on the erythropoietin–erythroferrone–hepcidin axis in transfusion‐dependent thalassaemia: A pre–post cohort study

To track post-transfusion changes on the erythropoietin (EPO)-erythroferrone (ERFE)-hepcidin axis, we collected blood samples from 82 regularly transfused patients with β-thalassaemia major (β-TM) immediately before and 4-6 days after transfusion. The post-transfusion haemoglobin, hepcidin, and ferritin levels were increased, while the EPO, ERFE, and soluble transferrin receptor were suppressed. In addition, hepcidin change was inversely associated with erythropoietic change, which was confirmed by an increase in the hepcidin-to-ERFE ratio after transfusion. Age was the main predictor of serum ERFE, followed by EPO, transfusion frequencies, and ferritin. We found ERFE to be a highly sensitive indicator of erythroid activity in β-TM and that the hepcidin-to-ERFE ratio after transfusion may be used as an appropriateness index of serum hepcidin regulation relative to the degree of erythropoiesis.

Is the Role of Hepcidin and Erythroferrone in the Pathogenesis of Beta Thalassemia the Key to Developing Novel Treatment Strategies?

Thalassemia is a disease of erythrocytes that varies largely on its genetic composition and associated clinical presentation. Though some patients may remain asymptomatic, those with a complicated course may experience severe anemia early in childhood, carrying into adulthood and requiring recurrent blood transfusions as a pillar of symptom management. Due to the consequences of ineffective erythropoiesis and frequent transfusions, patients with severe beta thalassemia may be subsequently susceptible to hemochromatosis. In light of the established role of hepcidin and erythroferrone in the pathogenesis of beta thalassemia, this review aims to discuss current clinical trials and studies in the field while presenting clinical implications of the HAMP gene polymorphisms and novel treatments. Research suggested incorporating erythroferrone and serum hepcidin testing as a part of routine workups for beta thalassemia, as they could be a predictive tool for early iron accumulation. Furthermore, ameliorating low hepcidin and high erythroferrone appeared to be crucial in treating beta thalassemia and its complications due to iron overload. Currently, hepcidin-like compounds, such as minihepcidins, LJPC-401, PTG-300, VIT-2763, and agents that promote hepcidin production by inhibiting TMPRSS6 expression or erythroferrone, were shown to be effective in restoring iron homeostasis in preliminary studies. Moreover, the natural bioactives astragalus polysaccharide and icariin have been recently recognized as hepcidin expression inductors.

Direct modulation of hepatocyte hepcidin signaling by iron

BACKGROUND

Liver-secreted hepcidin is the systemic master switch of iron homeostasis and decreased levels of hepcidin are considered to cause iron overload not only in hereditary hemochromatosis but also in hemolytic anemia and chronic liver diseases. The regulation of hepcidin is complex and its response to iron is still not completely understood.

AIM

To study the direct effect of iron on various established hepcidin signaling pathways in hepatoma cells or primary hepatocytes.

METHODS

Hepcidin mRNA expression was studied by quantitative real-time (qRT)-PCR in the presence of various forms of iron including ferric ammonium citrate (FAC) in hepatoma cells (Huh7), murine primary hepatocytes and an established co-culture model of phorbol myristate acetate-differentiated THP-1 monocytes and Huh7 cells. To analyze hepcidin signaling, the response to bone morphogenetic protein 6 (BMP6), interleukin (IL)-6, IL-1β, hypoxia and lipopolysaccharide (LPS) were studied. Hepcidin and small mothers against decapentaplegic 6 (SMAD6) mRNA levels were assessed by qRT-PCR and the expression of phosphorylated signal transducer and activator of transcription 3 (phospho-STAT3), STAT3, phospho-SMAD1/5/8 and SMAD1 proteins were analyzed by western blot.

RESULTS

All iron III forms including FAC efficiently blocked hepcidin mRNA expression at non-toxic dosages in Huh7 cells or primary hepatocytes in a time and dose-dependent manner (P < 0.001; P < 0.05). Hepcidin blockage could be efficiently blunted by iron chelators salicylaldehyde isonicotinoyl hydrazone (SIH) and Desferal (P < 0.001). FAC also inhibited BMP6, hypoxia, IL-1β and IL-6-mediated hepcidin induction (P < 0.001; P < 0.001; P < 0.05; P < 0.001), and FAC also inhibited LPS-mediated hepatic hepcidin induction in co-culture model (P < 0.001). Moreover, FAC reduced SMAD6 mRNA and p-SMAD1/5/8 protein expression at basal or upon stimulation by BMP6 (P < 0.05; P < 0.01), and FAC also reduced SMAD6 and p-SMAD1/5/8 expression under hypoxia (P < 0.01; P < 0.05). However, FAC has no significant effect on p-STAT3 protein expression at basal or upon stimulation by various stimuli. Notably, in the presence of the BMP/SMAD signaling pathway inhibitor LDN193189 Hydrochloride (LDN), FAC was unable to further decrease hepcidin, SMAD6 and p-SMAD1/5/8 expression compared with LDN alone.

CONCLUSION

Iron directly blocks hepatocellular hepcidin signaling through the BMP/SMAD pathway but independent of STAT3. This mechanism may contribute to continued iron overload in many pathophysiological conditions ultimately causing a vicious cycle of continued hepcidin suppression.

Erythroferrone Expression in Anemic Rheumatoid Arthritis Patients: Is It Disordered Iron Trafficking or Disease Activity?

Purpose

Erythroferrone (ERFE) is well acknowledged for its inhibitory function on hepcidin synthesis in the liver during stress erythropoiesis, thereby ensuring sufficient iron supply to bone marrow erythroblasts. Hepcidin plays an indispensable role in the pathogenesis of anemia of chronic disease (ACD). Thus, ERFE was suggested to protect against ACD in various diseases. Rheumatoid arthritis (RA) is commonly involved with ACD and high hepcidin levels, with a further increase of the latter in active states. The present study is a case-control study that aimed to determine the pattern of ERFE expression in RA patients with concomitant ACD and study its relationship with hepcidin, erythropoietin (EPO) and disease activity.

Patients and Methods

Fifty-five RA patients with ACD were categorized into active and inactive RA using the disease activity score (DAS28); 15 healthy subjects were included as control subjects. ERFE was measured for patients and control subjects using quantitative real-time polymerase chain reaction, in addition to testing for CBC, ESR, CRP, iron profile parameters and hepcidin. EPO was assessed for patients of both active and inactive RA groups.

Results

ERFE and hepcidin showed the highest levels in active RA; ERFE values were similar in control subjects and inactive RA patients, while hepcidin was significantly higher in inactive RA than control subjects. Patients with high ERFE levels had higher RBC, Hct, MCV, hepcidin and EPO levels. Stepwise regression analysis has identified DAS28 and disease duration as the best predictors of ERFE values, whereas ERFE and hepcidin were independent predictors of disease activity.

Conclusion

We introduce ERFE as a novel marker of RA activity. Although the inhibitory effect of ERFE on hepcidin is not evident, our results still indicate that ERFE may have a beneficial erythropoietic effect in the context of ACD in RA disease activity.

Erythropoiesis and Iron Parameters in Transfusion-dependent and Nontransfusion-dependent Thalassemias

INTRODUCTION

To clarify mechanisms of ineffective erythropoiesis on iron metabolism, studies on erythroid factors that regulating hepcidin suppression have been carried out. The aim of the current study is to identify associations between erythropoiesis and iron homeostasis parameters in β-thalassemias.

MATERIALS AND METHODS

This study consisted of 83 subjects: 21 thalassemia major (TM), 20 thalassemia intermedia (TI), 20 thalassemia trait (TT), and 22 healthy subjects (HS). Erythroferrone (ERFE), hepcidin, growth differentiation factor-15 (GDF15), erythropoietin (EPO), and iron status parameters were measured.

RESULTS

Our results showed that TM and TI patients had higher hepcidin than the TT and control groups. The hepcidin/ferritin in TM patients was significantly lower than the other groups. GDF15 in TM and TI patients was significantly higher than in the TT and control groups. Also, TI group had significantly higher ERFE concentration and EPO activity when compared with the TM, TT, and HS groups. EPO activity showed positive correlation with ERFE and GDF15 concentrations. We could not find any correlation between ERFE and hepcidin concentrations.

CONCLUSIONS

ERFE may be one of the parameters used to demonstrate erythropoietic activity level in thalassemias. More detailed studies are needed to clarify the role of ERFE in iron metabolism in the patients with thalassemias.