Simple and sensitive quantification of bioactive peptides in biological matrices using liquid chromatography/selected reaction monitoring mass spectrometry coupled with trichloroacetic acid clean-up

A 70-year-old Woman with Asymptomatic Ferroportin Disease

A 59-year-old Japanese woman presented with hyperferritinemia. We decided against iron removal treatment because there were no symptoms or signs of iron-induced organ damage. A follow-up study revealed a gradual increase in transferrin saturation. The patient underwent a second examination at 66 years old. A liver biopsy showed substantial iron deposits in hepatocytes and Kupffer cells but no inflammation or fibrosis. Serum hepcidin-25 levels were highly parallel with hyperferritinemia. A genetic analysis revealed a G80S mutation in SLC40A1. These features are compatible with those of ferroportin disease. The patient remained asymptomatic at 70 years old, suggesting that the iron-loading condition may have been benign.

A Revised Classification of Primary Iron Overload Syndromes

Background and Aims

The clinical introduction of hepcidin25 (Hep25) has led to a more detailed understanding of its relationship with ferroportin (FP) and divalent metal transporter1 in primary iron overload syndromes (PIOSs). In 2012, we proposed a classification of PIOSs based on the Hep25/FP system, which consists of prehepatic aceruloplasminemia, hepatic hemochromatosis (HC), and posthepatic FP disease (FP-D). However, in consideration of accumulated evidence on PIOSs, we aimed to renew the classification.

Methods

We reviewed the 2012 classification and retrospectively renewed it according to new information on PIOSs.

Results

Iron-loading anemia was included in PIOSs as a prehepatic form because of the newly discovered erythroferrone-induced suppression of Hep25, and the state of traditional FP-D was remodeled as the BIOIRON proposal. The key molecules responsible for prehepatic PIOSs are low transferrin saturation in aceruloplasminemia and increased erythroferrone production by erythroblasts in iron-loading anemia. Hepatic PIOSs comprise four genotypes of HC, in each of which the synthesis of Hep25 is inappropriately reduced in the liver. Hepatic Hep25 synthesis is adequate in posthepatic PIOSs; however, two mutant FP molecules may resist Hep25 differently, resulting in SLC40A1-HC and FP-D, respectively. PIOS phenotypes are diagnosed using laboratory tests, including circulating Hep25, followed by suitable treatments. Direct sequencing of the candidate genes may be outsourced to gene centers when needed. Laboratory kits for the prevalent mutations, such as C282Y, may be the first choice for a genetic analysis of HC in Caucasians.

Conclusions

The revised classification may be useful worldwide.

Measurement of serum hepcidin-25 by latex agglutination in healthy volunteers and patients with hematologic disorders

Iron is an essential trace metal, vital for various physiologic processes, but excess levels can harm health. Maintaining iron homeostasis is critical, with hepcidin playing a key role. The isoform hepcidin-25 exerts the most significant influence on iron metabolism, making its serum levels a valuable diagnostic tool. However, mass-spectrometry and other conventional measurement methods can be difficult to perform, and some immunoassays lack reliability. In this study, we employed a recently developed latex agglutination method integrated with a readily available automated analyzer to quantify serum hepcidin-25 levels in both volunteers recruited from personnel of our hospital (n = 93) and patients with various hematological disorders (n = 112). Our findings unveiled a robust positive correlation between serum hepcidin-25 and ferritin, as well as C-reactive protein levels, in both volunteers and patients. Among the patients with hematological disorders, there was a noteworthy negative correlation between hepcidin-25 levels and hemoglobin concentrations, as well as reticulocyte counts. Interestingly, the hepcidin-25/ferritin ratio was remarkably low in patients with hemolytic anemia and myelodysplastic syndromes with ring sideroblasts. Our findings suggest that quantifying serum hepcidin-25 and the hepcidin-25/ferritin ratio using this method may be valuable for screening of hematopoietic diseases and other iron metabolism disorders.

Application of a robust analytical method for quantifying progestins in environmental samples from three Portuguese Estuaries

In the last years, progestins have raised special concerns for their documented negative effects on aquatic species, yet little is known about their environmental levels in surface waters and bioaccumulation in the trophic web. This study aimed to 1) adapt an extraction method for quantifying progestins in freeze-dried matrices, 2) validate the analytical procedure for three matrices: bivalve, polychaete, and crustacean, and 3) characterize levels of the four most prescribed synthetic progestins in key species across three Portuguese estuaries. Through the validated method, progestins were only quantifiable for the crustacean. Values were generally low, peaking with drospirenone values in Ria de Aveiro (1.33 ± 0.26 ng/g ww) and Tagus estuary (1.42 ± 0.55 ng/g ww), while Ria Formosa exhibited the lowest progestin concentrations (< 1 ng/g ww). This study enabled the development of a precise extraction and analytical method for quantifying steroid hormones in three distinct biological matrices.

Oral Iron Absorption of Ferric Citrate Hydrate and Hepcidin-25 in Hemodialysis Patients: A Prospective, Multicenter, Observational Riona-Oral Iron Absorption Trial

Oral ferric citrate hydrate (FCH) is effective for iron deficiencies in hemodialysis patients; however, how iron balance in the body affects iron absorption in the intestinal tract remains unclear. This prospective observational study (Riona-Oral Iron Absorption Trial, R-OIAT, UMIN 000031406) was conducted at 42 hemodialysis centers in Japan, wherein 268 hemodialysis patients without inflammation were enrolled and treated with a fixed amount of FCH for 6 months. We assessed the predictive value of hepcidin-25 for iron absorption and iron shift between ferritin (FTN) and red blood cells (RBCs) following FCH therapy. Serum iron changes at 2 h (ΔFe2h) after FCH ingestion were evaluated as iron absorption. The primary outcome was the quantitative delineation of iron variables with respect to ΔFe2h, and the secondary outcome was the description of the predictors of the body's iron balance. Generalized estimating equations (GEEs) were used to identify the determinants of iron absorption during each phase of FCH treatment. ΔFe2h increased when hepcidin-25 and TSAT decreased (-0.459, -0.643 to -0.276, p = 0.000; -0.648, -1.099 to -0.197, p = 0.005, respectively) in GEEs. FTN increased when RBCs decreased (-1.392, -1.749 to -1.035, p = 0.000) and hepcidin-25 increased (0.297, 0.239 to 0.355, p = 0.000). Limiting erythropoiesis to maintain hemoglobin levels induces RBC reduction in hemodialysis patients, resulting in increased hepcidin-25 and FTN levels. Hepcidin-25 production may prompt an iron shift from RBC iron to FTN iron, inhibiting iron absorption even with continued FCH intake.

Changes of biomarkers for erythropoiesis, iron metabolism, and FGF23 by supplementation with roxadustat in patients on hemodialysis

This study aimed to confirm changes in biomarkers of erythropoiesis and iron metabolism and serum fibroblast growth factor 23 (FGF-23) during darbepoetin-α treatment and then switching to the hypoxia-inducible factor prolyl hydroxylase inhibitor roxadustat. A total of 28 patients on hemodialysis who received weekly doses of darbepoetin-α were switched to roxadustat. Biomarkers for erythropoiesis and iron metabolism and intact and C-terminal FGF-23 were measured in blood samples collected before the HD session on days - 7 (darbepoetin-α injection), - 4, and - 2, and days 0 (switch to roxadustat treatment, three times weekly), 3, 5, 7, 14, 21, and 28. Erythropoietin and erythroferrone levels were elevated on day - 4 by darbepoetin-α injection and decreased to baseline levels at day 0. Levels of erythropoietin were not significantly increased by roxadustat supplementation, but erythroferrone levels were continuously elevated, similar to darbepoetin-α treatment. Hepcidin-25 and total iron binding capacity were significantly decreased or increased in patients treated with roxadustat compared with darbepoetin-α. Changes of intact and C-terminal FGF-23 levels were parallel to changes of phosphate levels during roxadustat treatment. However, the actual and percentage changes of intact FGF-23 and C-terminal FGF-23 in patients with low ferritin levels were greater than those in patients with high ferritin levels. Roxadustat might stimulate erythropoiesis by increasing iron usage through hepcidin-25, which was suppressed by erythroferrone in the physiological erythropoietin condition. Changes of intact FGF-23 and C-terminal FGF-23 levels might be affected by roxadustat in patients on hemodialysis, especially those with a low-iron condition.

An easy, fast, and efficient assay for the quantification of peptide Hepcidin-25 in serum and plasma with LC-MS/MS

BACKGROUND

The peptide hormone hepcidin-25 plays an important role in iron metabolism. Low or high levels of hepcidin-25 are associated with various iron disorders; therefore, hepcidin-25 is an important biomarker. This study describes an easy and fast analytical assay for the quantification of hepcidin-25 with liquid chromatography-tandem mass spectrometry (LC-MS/MS).

METHODS

Sample preparation was performed by protein precipitation with trichloroacetic acid, and injection onto a LC-MS/MS was directly conducted from a LoBind 96-well plate.

RESULTS

The concentration range covered by the quality control samples, ranged from 0.25 nmol/L (12.3% CV) to 11.9 nmol/L (CV < 9%). Matrix effect was limited (mean recovery of 99.9% with a CV of 6.4%). The assay was validated for serum, EDTA and heparin plasma. An international secondary reference material was used for calibration. The reference interval (90% CL) was estimated for hepcidin-25 by analysing serum and plasma samples from 156 healthy subjects with a lower limit: 0.12 (0.07-0.19) and upper limit: 11.2 nmol/L (9.5-13.0).

CONCLUSIONS

We present a fast and easy assay for the quantification of hepcidin-25 in serum and plasma samples. The assay was successfully used for the detection of various forms of hereditary haemolytic anaemias, to characterize the interplay between erythropoiesis and iron levels.

Saccharated ferric oxide attenuates haematopoietic response induced by epoetin beta pegol in patients undergoing haemodialysis

Background

Decreased erythropoietin levels and impaired iron metabolism due to excessive hepcidin levels are responsible for renal anaemia in patients undergoing haemodialysis. Recently, erythroferrone (ERFE) has been identified as a factor that regulates hepcidin. In addition, fibroblast growth factor 23 (FGF23), which has been recognized as a phosphorus-regulating hormone, appears to be involved in haematopoietic regulation. Clarification of the detailed mechanism of haematopoiesis could lead to the improvement of renal anaemia treatment.

Methods

Epoetin beta pegol (CERA) was administered to patients undergoing haemodialysis at week 0, and the same amount of CERA with saccharated ferric oxide (SFO) was administered at week 4. The changes in haematopoiesis-related biomarkers, including ERFE, intact FGF23 (iFGF23), C-terminal FGF23 (cFGF23), and inflammatory markers, were examined.

Results

Administration of CERA increased ERFE levels, decreased hepcidin levels, and stimulated iron usage for haematopoiesis, leading to an increase in reticulocytes (Ret) and haemoglobin (Hb). Simultaneous administration of SFO with CERA (CERA + SFO) significantly attenuated the responses of ERFE, Ret, and Hb compared with CERA alone. Although iFGF23 levels were not affected by either CERA or CERA + SFO, cFGF23 was significantly elevated from baseline after CERA. Since cFGF23 levels were not affected by CERA + SFO, cFGF23 levels after CERA + SFO were significantly lower than those after CERA alone. The ratio of iFGF23 to cFGF23 (i/cFGF23 ratio) was significantly higher after CERA + SFO than that after CERA alone. In addition, high-sensitivity C-reactive protein (hsCRP) levels were significantly higher after CERA + SFO than after CERA alone.

Conclusion

Administration of SFO suppressed haematopoietic responses induced by CERA. Elevation of i/cFGF23 ratio and hsCRP could account for the inhibitory effects of SFO on haematopoiesis.

Trial registration

This study was registered with the University Hospital Medical Information Network (ID UMIN000016552).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02320-2.

The structural reconformation of peptides in enhancing functional and therapeutic properties: Insights into their solid state crystallizations

Therapeutic peptides derived proteins with alpha-reconformation states like antibody shape have shown potential effects in combating terrible diseases linked with earlier signs of angiogensis, mutagenesis and transgenesis. Alpha reconformation in material design refers to the folding of the peptide chains and their transitions under reversible chemical bonds of disulfide chemical bridges and further non-covalence lesions. Thus, the rational design of signal peptides into alpha-helix is intended in increasing the defending effects of peptides into cores like adjuvant antibiotic and/or vaccines. Thereby, the signal peptides are able in displaying multiple eradicating regions by changing crystal-depositions and deviation angles. These types of molecular structures could have multiple advantages in tracing disease syndromes and impurities by increasing the host defense against the fates of pathogens and viruses, eventually leading to the loss in signaling by increasing peptide susceptibility levels to folding and unfolding and therefore, formation of transgenic peptide models. Alpha reconformation peptides is aimed in triggering as well as other regulatory functions such as remodulating metabolic chain disorders of lipolysis and glucolysis by increasing the insulin and leptin resistance for best lipid storages and lipoprotein density distributions.

Comparison of the effects of weekly and biweekly intravenous CERA administration on erythropoiesis: A randomized controlled trial

Although continuous erythropoietin receptor activators (CERAs) are widely used erythropoiesis‐stimulating agents for correcting renal anemia in patients undergoing hemodialysis (HD), few reports have examined weekly CERA administration. In this randomized controlled trial, we compared the efficacy and changes in the parameters of iron metabolism and erythropoiesis between weekly and biweekly CERA administration. In total, 120 patients undergoing maintenance HD were randomized to the weekly or biweekly group. The primary end point was the total CERA dose needed to maintain the target hemoglobin (Hb) levels during a 12‐week evaluation period. There was no significant difference in the total dose between the weekly and biweekly groups (median 175.0 [interquartile range (IQR) 93.8–337.5] µg/12 weeks vs. 300.0 [IQR 125.0–375.0] µg/12 weeks, P = .18). The mean Hb levels during the evaluation period were 10.9 ± 0.8 g/dL in the weekly group and 10.7 ± 0.8 g/dL in the biweekly group (P = .25). Weekly CERA administration was well tolerated. Weekly CERA administration similarly managed anemia as biweekly administration in patients undergoing HD.

Optimizing hepcidin measurement with a proficiency test framework and standardization improvement

Objectives

Hepcidin measurement advances insights in pathophysiology, diagnosis, and treatment of iron disorders, but requires analytically sound and standardized measurement procedures (MPs). Recent development of a two-level secondary reference material (sRM) for hepcidin assays allows worldwide standardization. However, no proficiency testing (PT) schemes to ensure external quality assurance (EQA) exist and the absence of a high calibrator in the sRM set precludes optimal standardization.

Methods

We developed a pilot PT together with the Dutch EQA organization Stichting Kwaliteitsbewaking Medische Laboratoriumdiagnostiek (SKML) that included 16 international hepcidin MPs. The design included 12 human serum samples that allowed us to evaluate accuracy, linearity, precision and standardization potential. We manufactured, value-assigned, and validated a high-level calibrator in a similar manner to the existing low- and middle-level sRM.

Results

The pilot PT confirmed logistical feasibility of an annual scheme. Most MPs demonstrated linearity (R2>0.99) and precision (duplicate CV>12.2%), although the need for EQA was shown by large variability in accuracy. The high-level calibrator proved effective, reducing the inter-assay CV from 42.0% (unstandardized) to 14.0%, compared to 17.6% with the two-leveled set. The calibrator passed international homogeneity criteria and was assigned a value of 9.07±0.24 nmol/L.

Conclusions

We established a framework for future PT to enable laboratory accreditation, which is essential to ensure quality of hepcidin measurement and its use in patient care. Additionally, we showed optimized standardization is possible by extending the current sRM with a third high calibrator, although international implementation of the sRM is a prerequisite for its success.

A sensitive and cost-effective high-performance liquid chromatography/tandem mass spectrometry (multiple reaction monitoring) method for the clinical measurement of serum hepcidin

RATIONALE

Hepcidin is a peptide hormone that plays a central role in regulating iron metabolism. It is a potential biomarker for the diagnosis, monitoring and treatment of iron metabolism disorders. Serum hepcidin level can differ by 3 orders of magnitude depending on the patient's condition. Existing liquid chromatography/mass spectrometry (LC/MS) assays lack clinical sensitivity or require costly sample preparation steps. A simple, sensitive, robust and cost-effective assay for serum hepcidin quantitation in routine clinical laboratories is needed.

METHODS

A high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) method was developed to quantify hepcidin in human serum using chemically synthesized hepcidin as a standard and stable-isotope-labeled hepcidin as the internal standard. The method was validated according to CLSI-C62A guidelines. Calibrators were prepared with hepcidin-free serum. Clinical samples were separately processed and compared using solid-phase extraction (SPE) and acetonitrile (ACN) protein precipitation.

RESULTS

The calibration curve was validated over the range of 0.1-100 nmol/L with R²  >0.99. Both the SPE and the ACN precipitation methods had excellent and comparable reproducibility. The intra-day and inter-day coefficients of variation (CVs) were <3% and <6%. There was 89% and 88% hepcidin recovery by SPE and ACN preparation. Measurement of secondary reference material using non-traceable calibrators yielded up to 30% positive bias, comparable with values obtained by an external comparator. Hepcidin was stable in serum at ambient temperature and at 4°C. The relative errors (REs) were ≤1.2% and ≤4.4%, respectively. The freeze-thaw (-70°C) stability after 3 cycles showed a relative error (RE) of ≤1.8%. The impact on hepcidin recovery due to hemolysis (4+), lipemia (4+) and Icterus (4+) was <3%.

CONCLUSIONS

We have developed and validated a simple, sensitive, robust and cost-effective HPLC/MS/MS method for the quantitation of serum hepcidin. The method uses ACN protein precipitation for sample preparation and reversed-phase normal-flow HPLC. Sample preparation is inexpensive; it can be automated with a liquid handling system to allow high-throughput application.

Synthesis of isotopically labelled αCGRP8-37 and its lipidated analogue

α-Calcitonin gene related peptide (αCGRP) inhibitors are important medicinal targets due to their ability to produce antimigraine effects, thus, the discovery of long-acting αCGRP inhibitors is of significant interest. Herein we report the synthesis of an isotopically labelled version of the well-known CGRP receptor antagonist, αCGRP8-37 , as well as lipidated αCGRP8-37 with comparable antagonistic activity. These isotopically labelled peptides can be employed in assays to determine the metabolic stability of the lipidated αCGRP8-37 and compare this with the stability of known αCGRP8-37 .

Systemic hepcidin quantified with LC-MS/MS in dementia in association with disease pathology and severity and with structural changes in the brain

Hepcidin is a peptide hormone regulating iron metabolism, the dyshomeostasis of which has been implicated in dementia. Yet, data on hepcidin status in dementia are scanty, limited to Alzheimer's disease (AD) and inconsistent due to methodological problems with its determination using immunoassays and/or lack of homogeneity of evaluated groups. Hepcidin association with vascular dementia (VaD) remains unknown. We proposed a mass spectrometry method of hepcidin quantification in sera and aimed at determining hepcidin systemic status in patients with dementia of AD, VaD, or mixed (MD) pathology, with reference to the degree of cognitive loss and structural changes in the brain as well as at evaluating the diagnostic potential of hepcidin as a biomarker. We found that hepcidin concentrations were significantly elevated in VaD and insignificantly so in AD or MD and that they positively correlated with the Clinical Dementia Rating and inversely with the Mini Mental State Examination. Hepcidin tended to be more pronouncedly elevated in patients with advanced cortical atrophy and white matter lesions. It displayed a biphasic relationship with the Hachinski Ischemic Scale and a good accuracy as dementia but not differential marker. Taken together, our results demonstrated that dementia of vascular and not neurodegenerative pathology is associated with significant elevation of systemic hepcidin. Hepcidin elevation reflects the degree of cognitive loss as well as the severity of structural changes in the brain. If confirmed in a prospective study, hepcidin quantification may hold promise as a diagnostic marker; its accuracy as a differential marker of VaD is insufficient.

T2 ∗ Relaxation Time Obtained from Magnetic Resonance Imaging of the Liver Is a Useful Parameter for Use in the Construction of a Murine Model of Iron Overload

Aim

Iron overload is a life-threatening disorder that can increase the risks of cancer, cardiovascular disease, and liver cirrhosis. There is also a risk of iron overload in patients with chronic kidney disease. In patients with renal failure, iron storage is increased due to inadequate iron utilization associated with decreased erythropoiesis and also to the inflammatory status. To evade the risk of iron overload, an accurate and versatile indicator of body iron storage in patients with iron overload is needed. In this study, we aimed to find useful iron-related parameters that could accurately reflect body iron storage in mice in order to construct a murine model of iron overload.

Methods

To select an appropriate indicator of body iron status, a variety of parameters involved in iron metabolism were evaluated. Noninvasively measured parameters were R1, R2, and R2^∗ derived from magnetic resonance imaging (MRI). Invasively measured parameters included serum hepcidin levels, serum ferritin levels, and liver iron contents. Histopathological analysis was also conducted.

Results/Conclusion

Among the several parameters evaluated, the MRI T2^∗ relaxation time was able to detect iron storage in the liver as sensitively as serum ferritin levels. Moreover, it is expected that using an MRI parameter will allow accurate evaluation of body iron storage in mice over time.

Bioanalytical method development and validation for determination of fibroblast growth factor peptide and its application to pharmacokinetic studies

Fibroblast growth factor peptide (FGF-P) is a polypeptide analog of FGF-2 that could be a potential mitigation and treatment agent for radiation syndromes. Prior to conducting preclinical pharmacokinetics, we developed and validated the LC-MS/MS bioanalytical method for determination of FGF-P in rat plasma for the first time. FGF-P was extracted from rat plasma using the protein precipitation technique followed liquid-liquid extraction using dichloromethane as a solvent. The mobile phases consisted of two components: (a) 0.1% formic acid in water; and (b) acetonitrile: 0.1% formic acid in water (95:5) under gradient elution. The validated method was also successfully applied to a pharmacokinetic study of FGF-P (10 mg/kg, intravenous) in Wistar rats. The method proved to be specific, accurate, precise, and linear over the concentration range of 2-500 ng/mL with coefficient of determination greater than 0.99 in all validation batches. The within-run and between-run accuracy was 87.97-115.00% with a precision of less than 14%. The mean recoveries ranged from 88.14% to 101.73%. The stability of the compound in plasma samples was proven under various storage conditions. After intravenous administration of FGF-P (10 mg/kg) the C₀ was 70.4 µg/mL and the AUC was 86.2 µg*min/mL.

Provisional standardization of hepcidin assays: creating a traceability chain with a primary reference material, candidate reference method and a commutable secondary reference material

Background

Hepcidin concentrations measured by various methods differ considerably, complicating interpretation. Here, a previously identified plasma-based candidate secondary reference material (csRM) was modified into a serum-based two-leveled sRM. We validated its functionality to increase the equivalence between methods for international standardization.

Methods

We applied technical procedures developed by the International Consortium for Harmonization of Clinical Laboratory Results. The sRM, consisting of lyophilized serum with cryolyoprotectant, appeared commutable among nine different measurement procedures using 16 native human serum samples in a first round robin (RR1). Harmonization potential of the sRM was simulated in RR1 and evaluated in practice in RR2 among 11 measurement procedures using three native human plasma samples. Comprehensive purity analysis of a candidate primary RM (cpRM) was performed by state of the art procedures. The sRM was value assigned with an isotope dilution mass spectrometry-based candidate reference method calibrated using the certified pRM.

Results

The inter-assay CV without harmonization was 42.1% and 52.8% in RR1 and RR2, respectively. In RR1, simulation of harmonization with sRM resulted in an inter-assay CV of 11.0%, whereas in RR2 calibration with the material resulted in an inter-assay CV of 19.1%. Both the sRM and pRM passed international homogeneity criteria and showed long-term stability. We assigned values to the low (0.95±0.11 nmol/L) and middle concentration (3.75±0.17 nmol/L) calibrators of the sRM.

Conclusions

Standardization of hepcidin is possible with our sRM, which value is assigned by a pRM. We propose the implementation of this material as an international calibrator for hepcidin.

A 10-year Follow-up Study of a Japanese Family with Ferroportin Disease A: Mild Iron Overload with Mild Hyperferritinemia Co-occurring with Hyperhepcidinemia May Be Benign

This is a 10-year follow-up study of a family with ferroportin disease A. The proband, a 59-year-old man showed no noteworthy findings with the exception of an abnormal iron level. The proband's 90-year-old father showed reduced abilities in gait and cognition; however, with the exception of his iron level, his biochemistry results were almost normal. Brain imaging showed age-matched atrophy and iron deposition. In both patients, the serum levels of ferritin and hepcidin25, and liver computed tomography scores declined over a 10-year period. These changes were mainly due to a habitual change to a low-iron diet. The iron disorder in this family was not associated with major organ damage.

The interactions between iron and copper in genetic iron overload syndromes and primary copper toxicoses in Japan

Iron and copper are trace elements essential for health, and iron metabolism is tightly regulated by cuproproteins. Clarification of the interactions between iron and copper may provide a better understanding of the pathophysiology and treatment strategy for hemochromatosis, Wilson disease, and related disorders. The hepcidin/ferroportin system was used to classify genetic iron overload syndromes in Japan, and ceruloplasmin and ATP7B were introduced for subtyping Wilson disease into the severe hepatic and classical forms. Interactions between iron and copper were reviewed in these genetic diseases. Iron overload syndromes were classified into pre-hepatic iron loading anemia and aceruloplasminemia, hepatic hemochromatosis, and post-hepatic ferroportin disease. The ATP7B-classical form with hypoceruloplasminemia has primary hepatopathy and late extra-hepatic complications, while the severe hepatic form is free from ATP7B mutation and hypoceruloplasminemia, and silently progresses to liver failure. A large amount of iron and trace copper co-exist in hepatocellular dense bodies of all iron overload syndromes. Cuproprotein induction to stabilize excess iron should be differentiated from copper retention in Wilson disease. The classical form of Wilson disease associated with suppressed hepacidin25 secretion may be double-loaded with copper and iron, and transformed to an iron disease after long-term copper chelation. Iron disease may not be complicated with the severe hepatic form with normal ferroxidase activity. Hepatocellular dense bodies of iron overload syndromes may be loaded with a large amount of iron and trace copper, while the classical Wilson disease may be double-loaded with copper and iron.

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.

Measurement of hepcidin isoforms in human serum by liquid chromatography with high resolution mass spectrometry

Aim: Hepcidin-25 is the master regulator of iron homeostasis. N-truncated isoforms of hepcidin-25 have been identified (hepcidin-20, -22, -24), although data on the concentrations of these isoforms are sparse. Materials & methods: Serum was mixed with aqueous formic acid, and the supernatant loaded onto a 96-well-SPE-plate. Eluted analytes were analyzed using LC–HR-MS. Forty-seven paired dipotassium-EDTA human plasma and serum samples were analyzed. Results: The LLOQ was 1 μg/l (all analytes). Accuracy and precision were acceptable. There was a good correlation (R2 >0.90, all analytes) between matrices. The median (range) serum hepcidin-20, -22, -24 and -25 concentrations measured were 4 (1–40), 8 (2–20), 8 (1–50) and 39 (1–334) μg/l, respectively. Conclusion: LC–HR-MS is widely applicable to the measurement of hepcidin-25, and truncated isoforms.

Toward Worldwide Hepcidin Assay Harmonization: Identification of a Commutable Secondary Reference Material

BACKGROUND

Absolute plasma hepcidin concentrations measured by various procedures differ substantially, complicating interpretation of results and rendering reference intervals method dependent. We investigated the degree of equivalence achievable by harmonization and the identification of a commutable secondary reference material to accomplish this goal.

METHODS

We applied technical procedures to achieve harmonization developed by the Consortium for Harmonization of Clinical Laboratory Results. Eleven plasma hepcidin measurement procedures (5 mass spectrometry based and 6 immunochemical based) quantified native individual plasma samples (n = 32) and native plasma pools (n = 8) to assess analytical performance and current and achievable equivalence. In addition, 8 types of candidate reference materials (3 concentrations each, n = 24) were assessed for their suitability, most notably in terms of commutability, to serve as secondary reference material.

RESULTS

Absolute hepcidin values and reproducibility (intrameasurement procedure CVs 2.9%–8.7%) differed substantially between measurement procedures, but all were linear and correlated well. The current equivalence (intermeasurement procedure CV 28.6%) between the methods was mainly attributable to differences in calibration and could thus be improved by harmonization with a common calibrator. Linear regression analysis and standardized residuals showed that a candidate reference material consisting of native lyophilized plasma with cryolyoprotectant was commutable for all measurement procedures. Mathematically simulated harmonization with this calibrator resulted in a maximum achievable equivalence of 7.7%.

CONCLUSIONS

The secondary reference material identified in this study has the potential to substantially improve equivalence between hepcidin measurement procedures and contributes to the establishment of a traceability chain that will ultimately allow standardization of hepcidin measurement results.

Treatment with anti-IL-6 receptor antibody prevented increase in serum hepcidin levels and improved anemia in mice inoculated with IL-6-producing lung carcinoma cells

Background

Hepcidin, a key regulator of iron metabolism, is produced mainly by interleukin-6 (IL-6) during inflammation. A mechanism linking cancer-related anemia and IL-6 through hepcidin production is suggested. To clarify the hypothesis that overproduction of IL-6 elevates hepcidin levels and contributes to the development of cancer-related anemia, we evaluated anti-IL-6 receptor antibody treatment of cancer-related anemia in an IL-6–producing human lung cancer xenograft model.

Methods

Nude mice were subcutaneously inoculated with cells of the IL-6–producing human lung cancer cell line LC-06-JCK and assessed as a model of cancer-related anemia. Mice bearing LC-06-JCK were administered rat anti-mouse IL-6 receptor antibody MR16-1 and their serum hepcidin levels and hematological parameters were determined.

Results

LC-06-JCK–bearing mice developed anemia according to the production of human IL-6 from xenografts, with decreased values of hemoglobin, hematocrit, and mean corpuscular volume (MCV) compared to non–tumor-bearing (NTB) mice. LC-06-JCK–bearing mice showed decreased body weight and serum albumin with increased serum amyloid A. MR16-1 treatment showed significant inhibition of decreased body weight and serum albumin levels, and suppressed serum amyloid A level. There was no difference in tumor volume between MR16-1-treated mice and immunoglobulin G (IgG)-treated control mice. Decreased hemoglobin, hematocrit, and MCV in LC-06-JCK–bearing mice was significantly relieved by MR16-1 treatment. LC-06-JCK–bearing mice showed high red blood cell counts and erythropoietin levels as compared to NTB mice, whereas MR16-1 treatment did not affect their levels. Serum hepcidin and ferritin levels were statistically elevated in mice bearing LC-06-JCK. LC-06-JCK–bearing mice showed lower values of MCV, mean corpuscular hemoglobin (MCH), and serum iron as compared to NTB mice. Administration of MR16-1 to mice bearing LC-06-JCK significantly suppressed levels of both serum hepcidin and ferritin, with increased values of MCV and MCH.

Conclusions

Our results suggest that overproduction of hepcidin by IL-6 signaling might be a major factor that leads to functionally iron-deficient cancer-related anemia in the LC-06-JCK model. We demonstrated that inhibition of the IL-6 signaling pathway by MR16-1 treatment resulted in significant recovery of iron-deficiency anemia and alleviation of cancer-related symptoms. These results indicate that IL-6 signaling might be one possible target pathway to treat cancer-related anemia disorders.

Quantitative analysis of dietary iron utilization for erythropoiesis in response to body iron status

Erythropoiesis requires large amounts of iron for hemoglobin synthesis. There are two sources of iron for erythropoiesis, dietary and stored iron; however, their relative contributions to erythropoiesis remain unknown. In this study, we used the stable iron isotope (57)Fe to quantify synthesis of hemoglobin derived from dietary iron. Using this method, we investigated the activities of dietary iron absorption and the utilization of dietary iron for erythropoiesis in responses to stimulated erythropoiesis and to interventions to alter body iron status. Under iron-loaded conditions, the activity of dietary iron absorption was clearly lowered in response to up-regulation of hepcidin, although the estimated activity of iron release from stored iron was not compared with that under control conditions. This result was supported by the observation that two duodenal iron transporters, divalent metal transporter 1 (DMT1) and ferroportin, were downregulated by iron loading, although the levels of expression of ferroportin in iron storage tissues were not changed by iron loading under erythropoietic stimulation by epoetin-β pegol (C.E.R.A., a long-acting erythropoiesis-stimulating agent). These results indicate that the dietary iron absorption system is more sensitive to body iron status than are reticuloendothelial iron- release mechanisms. Our data indicated that there could be a regulatory mechanism favoring use of stored iron over dietary iron under iron-loaded conditions.

Reduction of a marker of oxidative stress with enhancement of iron utilization by erythropoiesis activation following epoetin beta pegol administration in iron-loaded db/db mice

Iron, an essential element for various biological processes, can induce oxidative stress. We hypothesized that iron utilization for erythropoiesis, stimulated by epoetin beta pegol (C.E.R.A.), a long-acting erythropoiesis-stimulating agent, contributes to the reduction of iron-induced oxidative stress. We first investigated the sensitivity of several biomarkers to detect oxidative stress in mice by altering the amount of total body iron; we then investigated whether C.E.R.A. ameliorated oxidative stress through enhanced iron utilization. We treated db/db mice with intravenous iron-dextran and evaluated several biomarkers of iron-induced oxidative stress. In mice loaded with 5 mg/head iron, hepatic iron content was elevated and the oxidative stress marker d-ROMs (serum derivatives of reactive oxygen metabolites) was increased, whereas urinary 8-hydroxy-2'-deoxyguanosine and serum malondialdehyde were not, indicating that d-ROMs is a sensitive marker of iron-induced oxidative stress. To investigate whether C.E.R.A. ameliorated oxidative stress, db/db mice were intravenously administered iron-dextran or dextran only, followed by C.E.R.A. Hemoglobin level increased, while hepatic iron content decreased after C.E.R.A.

TREATMENT

Serum d-ROMs decreased after C.E.R.A. treatment in the iron-dextran-treated group. Our results suggest that C.E.R.A. promotes iron utilization for erythropoiesis through mobilization of hepatic iron storage, leading to a decrease in serum oxidative stress markers in iron-loaded db/db mice.

Modulation of hepcidin to treat iron deregulation: potential clinical applications

The secreted peptide hormone hepcidin regulates systemic and local iron homeostasis through degradation of the iron exporter ferroportin. Dysregulation of hepcidin leads to altered iron homeostasis and development of pathological disorders including hemochromatosis, and iron loading and iron restrictive anemias. Therapeutic modulation of hepcidin is a promising method to ameliorate these conditions. Several approaches have been taken to enhance or reduce the effects of hepcidin in vitro and in vivo. Based on these approaches, hepcidin modulating drugs have been developed and are undergoing clinical evaluation. In this article we review the rationale for development of these drugs, the data concerning their safety and efficacy, their therapeutic uses, and potential future prospects.

Copper Accumulates in Hemosiderins in Livers of Patients with Iron Overload Syndromes

In biology, redox reactions are essential and sometimes harmful, and therefore, iron metabolism is tightly regulated by cuproproteins. Since the state of copper in iron overload syndromes remains unclear, we investigated whether copper metabolism is altered in these syndromes. Eleven patients with iron overload syndromes participated in this study. The clinical diagnoses were aceruloplasminemia (n=2), hemochromatosis (n=5), ferroportin disease (n=2), and receiving excess intravenous iron supplementation (n=2). Liver specimens were analyzed using a light microscope and transmission electron microscope equipped with an X-ray analyzer. In addition to a large amount of iron associated with oxygen and phosphorus, the iron-rich hemosiderins of hepatocytes and Kupffer cells contained small amounts of copper and sulfur, regardless of disease etiology. Two-dimensional imaging clearly showed that cuproproteins were distributed homogenously with iron complexes within hemosiderins. Copper stasis was unlikely in noncirrhotic patients. The enhanced induction of cuproproteins by excess iron may contribute to copper accumulation in hemosiderins. In conclusion, we have demonstrated that copper accumulates in hemosiderins in iron overload conditions, perhaps due to alterations in copper metabolism.

Branched-chain amino acids reduce hepatic iron accumulation and oxidative stress in hepatitis C virus polyprotein-expressing mice

BACKGROUND & AIMS

Branched-chain amino acids (BCAA) reduce the incidence of hepatocellular carcinoma (HCC) in patients with cirrhosis. However, the mechanisms that underlie these effects remain unknown. Previously, we reported that oxidative stress in male transgenic mice that expressed hepatitis C virus polyprotein (HCVTgM) caused hepatic iron accumulation by reducing hepcidin transcription, thereby leading to HCC development. This study investigated whether long-term treatment with BCAA reduced hepatic iron accumulation and oxidative stress in iron-overloaded HCVTgM and in patients with HCV-related advanced fibrosis.

METHODS

Male HCVTgM were fed an excess-iron diet that comprised either casein or 3.0% BCAA, or a control diet, for 6 months.

RESULTS

For HCVTgM, BCAA supplementation increased the serum hepcidin-25 levels and antioxidant status [ratio of biological antioxidant potential (BAP) relative to derivatives of reactive oxygen metabolites (dROM)], decreased the hepatic iron contents, attenuated reactive oxygen species generation, and restored mitochondrial superoxide dismutase expression and mitochondrial complex I activity in the liver compared with mice fed the control diet. After 48 weeks of BCAA supplementation in patients with HCV-related advanced fibrosis, BAP/dROM and serum hepcidin-25 increased and serum ferritin decreased compared with the pretreatment levels.

CONCLUSIONS

BCAA supplementation reduced oxidative stress by restoring mitochondrial function and improved iron metabolism by increasing hepcidin-25 in both iron-overloaded HCVTgM and patients with HCV-related advanced fibrosis. These activities of BCAA may partially account for their inhibitory effects on HCC development in cirrhosis patients.

Hepcidin/ferroportin expression levels involve efficacy of pegylated-interferon plus ribavirin in hepatitis C virus-infected liver

AIM: To investigate the relationship between the iron-metabolism-related gene expression profiles and efficacy of antiviral therapy in chronic hepatitis C patients.

METHODS: The hepatic expression profile of iron-metabolism-related genes was analyzed and its association with virological response to pegylated-interferon plus ribavirin combination therapy was evaluated. A hundred patients with chronic hepatitis C (genotype1b, n = 50; genotype 2, n = 50) were enrolled and retrospectively analyzed. Liver biopsy samples were subjected to quantitative polymerase chain reaction for iron-metabolism-related genes and protein expression (Western blotting analysis) for ferroportin. As a control, normal liver tissue was obtained from 18 living donors of liver transplantation. Serum hepcidin level was measured by sensitive liquid chromatography/electrospray ionization tandem mass spectrometry.

RESULTS: Iron overload is associated with liver damage by increasing oxidative stress and hepatitis C virus (HCV) is reported to induce iron accumulation in hepatocytes in vivo. Conversely, iron administration suppresses HCV replication in vitro. Therefore, the association between HCV infection and iron metabolism remains unclear. Compared with controls, patients had significantly higher gene expression for transferrin, iron-regulatory proteins 1 and 2, divalent metal transporter 1, and ferroportin, but similar for transferrin receptors 1 and 2, and hepcidin. When the expression profiles were compared between sustained virological response (SVR) and non-SVR patients, the former showed significantly lower transcription and protein expression of hepcidin and ferroportin. Expression of hepcidin-regulating genes, BMPR1, BMPR2, and hemojuvelin, was significantly increased, whereas BMP2 was decreased in HCV-infected liver. BMPR2 and hemojuvelin expression was significantly lower in the SVR than non-SVR group. HCV infection affects the expression of iron-metabolism-related genes, leading to iron accumulation in hepatocytes.

CONCLUSION: Decreased expression of hepcidin and ferroportin in SVR patients indicates the importance of hepatocytic iron retention for viral response during pegylated-interferon plus ribavirin treatment.

Serum hepcidin-25 level linked with high mortality in patients with non-Hodgkin lymphoma

Hepatic hepcidin-25 production is stimulated by systemic inflammation, and it interferes with the body's utilization of iron, leading to anemia. A 1-year prospective study was conducted to elucidate an association of serum hepcidin-25 concentration with mortality in anemic patients with non-Hodgkin lymphoma (NHL). Serum hepcidin-25 levels were measured in 50 NHL patients using liquid chromatography-tandem mass spectrometry. The patients were stratified into a high- and a low-hepcidin-25 group according to the median of serum hepcidin-25 concentrations. Factors associated with hemoglobin (Hb) were determined by multivariate regression analysis, incorporating serum hepcidin-25 and inflammatory markers including ferritin and interleukin-6 (IL-6) as covariates. The association between serum hepcidin-25 and mortality was analyzed using both the Kaplan-Meier method and a multivariate proportional hazards regression model. The median of serum hepcidin-25 concentrations was 49.8 (0.6-269) ng/mL, a level approximately nine times greater than the reference value for healthy individuals. Hb level was significantly lower in the high than in the low-hepcidin-25 group. Serum hepcidin-25 was extracted as the significant factor associated with Hb, but neither ferritin nor IL-6 was. The cumulative mortality was significantly greater in the high than in the low-hepcidin-25 group (56.0 vs. 24.0 %; P = 0.0222). The mortality risk for the presence of high hepcidin-25 was four times greater (hazard ratio [95 % confidence interval]: 3.66 [1.12-16.4]). In conclusion, serum hepcidin-25 levels are elevated in anemic NHL patients, and in this study, the group with higher hepcidin-25 levels manifested advanced anemia and poor survival.

Twice-monthly administration of a lower dose of epoetin beta pegol can maintain adequate hemoglobin levels in hemodialysis patients

Epoetin beta pegol is a continuous erythropoietin receptor activator (CERA) with a long half-life. Although CERA has been shown to maintain adequate hemoglobin (Hb) levels at prolonged dosing intervals, the optimal dosing schedule remains unclear. We therefore compared the efficacy of maintaining hemoglobin levels with administration of twice-monthly CERA (TWICE) versus once-monthly CERA (ONCE). Twenty hemodialysis patients receiving epoetin beta (EPO) were enrolled in this crossover study. Patients were assigned to either the TWICE or the ONCE group based on matching Hb levels and EPO doses. After 6 months of treatment, the CERA dosage was interchanged between the groups and the study was continued for an additional 6 months. The effect of the different regimens on iron metabolism was also assessed during the first 6 months of the study. Hb levels significantly increased in the TWICE group, allowing for a reduction in CERA dosage, while the dose of CERA required to maintain Hb levels in the ONCE group remained unchanged. After the interchange, a decrease in Hb levels with incremental increase in CERA dosage was observed in the TWICE→ONCE group, with the opposite effect observed in the ONCE→TWICE group. Although increases in ferritin and hepcidin-25 levels in the ONCE group were noted at one month, they disappeared at 6 months. Although Hb levels were maintained in both the ONCE and TWICE groups, a twice-monthly administration was advantageous, as it required a lower dose of CERA.

Development of LC-MS methods for quantitation of hepcidin and demonstration of siRNA-mediated hepcidin suppression in serum

INTRODUCTION

A requisite step in developing a therapeutic to modulate the levels of hepcidin is the development of a quantitative method for measuring the concentration of serum hepcidin.

METHODS

To this end, an LC-MS method, based on selected reaction monitoring (SRM) with a triple quadrupole MS and an isotopically labeled hepcidin as internal standard, was developed to measure hepcidin in mouse and monkey sera.

RESULTS

Initially, 40 normal cynomolgus monkeys and 40 normal mice were studied to determine the normal endogenous levels of hepcidin, and an average of 50ng/mL was found in the monkeys and 46ng/mL in the mice. Next, experiments were conducted where an siRNA, targeting hepcidin, was administered to cynomolgus monkeys, resulting in effective hepcidin reduction (inhibition rate) of 87% after 24h and 74% after 48h, demonstrating to effectively reduce serume level of hepcidin.

CONCLUSIONS

For better sensitivity, especially for the low volumes available for mouse sera, a second LC-MS method, based on parallel reaction monitoring (PRM) using a Orbitrap MS was developed and shown to be at least 10 fold lower in detection limits (or consumption of serum volume) than the SRM approach.

Mechanism underlying the transient increase of serum iron during FOLFOX/FOLFIRI therapy

In patients with advanced colorectal cancer (CRC), a transient significant increase of serum iron is observed during chemotherapy with leucovorin and fluorouracil plus oxaliplatin (FOLFOX) or leucovorin and fluorouracil plus irinotecan (FOLFIRI). Serum iron may be a useful and convenient predictor of the response to chemotherapy; however, the mechanism underlying its increase has not been fully elucidated. Accordingly, the mechanism underlying the elevation of serum iron during chemotherapy was investigated in 20 patients with advanced CRC who were treated between September, 2012 and July, 2013. The levels of iron, ferritin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), hemoglobin (Hb), hepcidin-25, interleukin (IL)-6 and soluble transferrin receptor (sTfR) were measured before and 48 h after chemotherapy. The serum levels of iron and hepcidin-25 were found to be significantly increased after chemotherapy (P<0.0001), whereas those of IL-6 were significantly decreased (P=0.0057). There were no significant changes in any of the other parameters. The lack of significant changes in AST, ALT and Hb suggested that the elevation of serum iron was not due to the destruction of hepatocytes, whereas the stable sTfR level suggested no destruction of erythroblasts. Hepcidin-25 regulates iron metabolism and decreases serum iron levels; it is increased by an iron load and IL-6, but is decreased under anemic or hypoxic conditions. The suppression of erythropoiesis increases serum iron levels and chemotherapy suppresses erythropoiesis. As serum iron and hepcidin-25 were both significantly increased and IL-6 was significantly decreased, with no significant changes in sTfR, it appears that the elevation of serum iron during chemotherapy may be secondary to reduced iron consumption by erythropoiesis, leading to increased expression of hepcidin-25 and suppression of Il-6 via negative feedback.

Hemodialysis restored iron distribution that was sequestered in the spleen by bilateral nephrectomy

Acute kidney injury (AKI) is associated with dysregulated iron metabolism, which may play a significant role in cellular injury. The effect of hemodialysis (HD) on iron metabolism in AKI therapy has not been well defined. The effects of HD on iron parameters were tested in control rats and bilateral nephrectomy (BNx) rats. The BNx rats were divided into the following three groups: 1) the sham-operated group (BNx-Sham), 2) the BNx group, and 3) the HD group (BNx-HD), which received HD therapy 40–45 h after BNx. Sections of the liver or spleen were stained with Berlin blue to examine the accumulation of iron. The mRNA levels of hepcidin and ferroportin 1 in the spleen and liver were also quantified using RT-PCR. In the BNx group, the plasma iron and hematocrit levels were decreased, and hepcidin levels were increased. The iron staining in the spleen in the BNx group was significantly more intense than that in the BNx-Sham group; however, after an HD session, splenic iron staining diminished to the level of the sham group along with an increase in plasma iron and a decrease in hepcidin. BNx moved iron from hemoglobin and the plasma to the spleen, which is associated with an increase in plasma hepcidin. A single HD session accelerated the release of iron from the spleen, and the increased plasma iron was linked to the removal of hepcidin. Our data suggested that hepcidin might dynamically modulate the iron metabolism in BNx as well as in HD.

Upregulation of iron regulatory hormone hepcidin by interferon α

BACKGROUND AND AIM

Interferon (IFN) activates various immune systems in vivo and is administered to patients with diseases such as viral hepatitis B, C, and malignant tumors. Iron dysregulation has been reported during treatment with IFN; however, it remains unclear whether IFN itself affects iron metabolism. We therefore determined the effect of IFN on iron metabolism.

METHODS

Mouse IFNα was administered to mice, and serum, spleen, bone marrow, liver, and duodenum tissue samples were subsequently collected. The messenger RNA (mRNA) and protein expression of genes involved in iron metabolism were then analyzed by real-time reverse transcription-polymerase chain reaction, Western blotting, and liquid chromatography-tandem mass spectrometry. Immunofluorescence for ferroportin was also performed.

RESULTS

Among the gene expressions analyzed, we found that the expression of hepcidin, an iron regulatory hormone produced in the liver, was highly upregulated after IFNα treatment. Serum hepcidin levels and hepcidin mRNA expression in the liver were both found to be increased in the IFNα-treated mice. The expression of ferroportin (the target molecule of hepcidin) in the duodenum of the IFNα-treated mice was observed to be decreased, indicating that hepcidin upregulation could be physiologically functional. In vitro analysis of primary hepatocytes treated with IFNα and human hepatoma-derived cells showed an upregulation of hepcidin mRNA, including an activation of signal transducer and activator of transcription3, which was shown to be involved in the hepcidin upregulation.

CONCLUSIONS

Results indicate that iron absorption is decreased during IFN treatment; this favorable effect could inhibit iron overload during IFN treatment and may enhance the action of IFN.

Hepcidin production in response to iron is controlled by monocyte-derived humoral factors

Hepcidin, which is mainly produced by the liver, is the key regulator in iron homeostasis. Hepcidin expression is up-regulated by iron loading in vivo, but the mechanism underlying this process is not completely understood. In the present study, we investigated the mechanism, following the hypothesis that hepcidin production in response to iron loading is regulated by extra-hepatic iron sensors. We measured serum hepcidin concentrations and iron indices in Wistar rats treated with saccharated ferric oxide (SFO). Human hepatoma-derived HepG2 cells were stimulated using SFO-administered rat sera, and co-cultured with rat spleen cells, human monocyte-derived THP-1 cells, or human monocytes with diferric transferrin (holo-Tf), and hepcidin concentrations in the conditioned media were measured. SFO elevated rat serum hepcidin concentrations. SFO-treated rat sera increased hepcidin production from HepG2 cells, and this induction correlated with serum hepcidin levels, but not with iron indices. Holo-Tf up-regulated hepcidin concentrations in media from HepG2 cells co-cultured with rat spleen cells, THP-1 cells, or human monocytes with or without cell-to-cell contacts, while holo-Tf did not up-regulate hepcidin from HepG2 cells alone. Our results suggest the existence of humoral factors capable of inducing hepcidin production that are secreted by extra-hepatic cells, such as reticuloendothelial monocytes, in response to iron.