Mechanisms of Disease: the role of hepcidin in iron homeostasis—implications for hemochromatosis and other disorders

MRI-Based Iron Phenotyping and Patient Selection for Next-Generation Sequencing of Non-Homeostatic Iron Regulator Hemochromatosis Genes

BACKGROUND AND AIMS

High serum ferritin is frequent among patients with chronic liver disease and commonly associated with hepatic iron overload. Genetic causes of high liver iron include homozygosity for the p.Cys282Tyr variant in homeostatic iron regulator (HFE) and rare variants in non-HFE genes. The aims of the present study were to describe the landscape and frequency of mutations in hemochromatosis genes and determine whether patient selection by noninvasive hepatic iron quantification using MRI improves the diagnostic yield of next-generation sequencing (NGS) in patients with hyperferritinemia.

APPROACH AND RESULTS

A cohort of 410 unselected liver clinic patients with high serum ferritin (defined as ≥200 μg/L for women and ≥300 μg/L for men) was investigated by HFE genotyping and abdominal MRI R2*. Forty-one (10%) patients were homozygous for the p.Cys282Tyr variant in HFE. Of the remaining 369 patients, 256 (69%) had high transferrin saturation (TSAT; ≥45%) and 199 (53%) had confirmed hepatic iron overload (liver R2* ≥70 s^-1 ). NGS of hemochromatosis genes was carried out in 180 patients with hepatic iron overload, and likely pathogenic variants were identified in 68 of 180 (38%) patients, mainly in HFE (79%), ceruloplasmin (25%), and transferrin receptor 2 (19%). Low spleen iron (R2* <50 s^-1 ), but not TSAT, was significantly associated with the presence of mutations. In 167 patients (93%), no monogenic cause of hepatic iron overload could be identified.

CONCLUSIONS

In patients without homozygosity for p.Cys282Tyr, coincident pathogenic variants in HFE and non-HFE genes could explain hyperferritinemia with hepatic iron overload in a subset of patients. Unlike HFE hemochromatosis, this type of polygenic hepatic iron overload presents with variable TSAT. High ferritin in blood is an indicator of the iron storage disease, hemochromatosis. A simple genetic test establishes this diagnosis in the majority of patients affected. MRI of the abdomen can guide further genetic testing.

Significance of Endogenous Antimicrobial Peptides on the Health of Food Animals

Acquired resistance to in-feed antibiotic growth promoters continues to be an imperative problem in the livestock industries, thereby necessitating continuous pursuit for alternatives. Antimicrobial peptides (AMPs) represent a critical part of the host's innate immune system and have been documented to have immunomodulatory activity. Increasing research evidence suggests that in contrast to antibiotics, AMPs exert broad-spectrum antibacterial activity in a manner that reduces bacterial acquisition of resistance genes. This review summarizes current knowledge on the protective effects of endogenous (natural) AMPs in the gastrointestinal tract of food animals. Factors limiting the efficacy of these AMPs were also discussed and mitigating strategies were proposed.

Hepcidin, an overview of biochemical and clinical properties

Hepcidin is a peptide hormone which helps in regulating iron homeostasis in the human body. Iron obtained from daily diet is passed through the intestinal enterocyte apical membrane via divalent metal transporter 1 (DMT1), which is either stored as ferritin or moved into the plasma by hepcidin-ferroportin (Fpn) as an exporter. Hepcidin (hepatic bactericidal protein) is a cysteine rich peptide, was initially identified as a urinary antimicrobial peptide. It contains 25 amino acids and four disulfide bridges. It has significant role in regulation of iron in the body. Stimulation of iron in plasma and further its storage is linked with the production of hepcidin. This enhancement of iron hampers the absorption of iron from the diet. The cause of hereditary recessive anemia also known as Iron-refractory iron deficiency anemia (IRIDA) is characterized by increased hepcidin production due to a gene mutation in the suppressor matriptase-2/TMPRSS6. During infection, hepcidin plays a defensive role against various infections by depleting the extracellular iron from the body. Moreover, hepcidin lowers the concentrations of iron from the duodenal enterocytes, macrophages and also decrease its transport across the placenta.This review highlights the significant role of hepcidin in the iron homeostasis and as an antimicrobial agent.

Baseline Red Blood Cell Distribution Width as a Predictor of Stroke Occurrence and Outcome: A Comprehensive Meta-Analysis of 31 Studies

Background: Red blood cell distribution width (RDW) may be a potential biomarker of inflammation in patients with stroke. Elevated RDW is associated with higher incidence of stroke, unfavorable functional outcome, and increased mortality, although results are inconsistent in the reported literature. This study aims to evaluate the predictive power of RDW regarding stroke occurrence and outcome. Methods: A thorough literature search was conducted utilizing the PubMed Central (PMC) and EMBASE databases to identify studies up to May 2019. Data from these studies were pooled, and combined odds ratios/risk ratios (ORs/RRs) were estimated for the risk of stroke, functional outcome, and mortality. A subgroup analysis was also performed to explore heterogeneity in terms of population status, demographic factors (age, gender distribution, and country), and vascular risk factors (hypertension, diabetes mellitus, and current smoking). Results: A total of 31 studies with 3,487,896 patients were included in the analysis. Elevated RDW was found to be a risk factor in ischemic stroke (OR/RR 1.528; 95% confidence interval [CI] = 1.372-1.703), whereas combined OR in subarachnoid hemorrhage (SAH) was not statistically significant (OR/RR 1.835; 95% CI = 0.888-3.792). Elevated RDW posed increased risk in populations with conventionally higher risk of stroke, such as atrial fibrillation (AF) (OR/RR 1.292; 95% CI = 1.107-1.508) and diabetes mellitus (OR/RR 2.101; 95% CI = 1.488-2.968), and in community cohorts (OR/RR 1.245; 95% CI = 1.216-1.275). In addition, higher RDW was associated with unfavorable functional outcome, either at discharge (OR/RR 1.220; 95% CI = 1.070-1.39) or at 90 days (OR/RR 1.277; 95% CI = 1.155-1.413). Higher mortality was found in patients with increased RDW (OR/RR 1.278; 95% CI = 1.221-1.337), independent of demographic factors (age, gender distribution, and country). Conclusions: Baseline RDW should be integrated into clinical practice as a predictor of ischemic stroke occurrence and outcome. Future studies should also explore the dynamic change of RDW in post-stroke patients to evaluate the clinical significance of RDW and its impact on the inflammatory state of ischemic stroke.

Prognostic role of pretreatment red blood cell distribution width in patients with cancer: A meta-analysis of 49 studies

Red blood cell distribution width (RDW) has been recently demonstrated to be a predictor of inflammation. High pretreatment RDW level is associated with poor survival outcomes in various malignancies, although the results are controversial. We aimed to investigate the prognostic role of RDW. A systematic literature search was performed in MEDLINE and EMBASE till April 2018. Pooled hazard ratios (HRs) were estimated for overall survival (OS) and combined disease-free survival, progression-free survival, and recurrence-free survival (DFS/PFS/RFS). 49 studies with 19,790 individuals were included in the final analysis. High RDW level adversely affected both OS and DFS/PFS/RFS. For solid cancers, colorectal cancer (CRC) had the strongest relationship with poor OS, followed by hepatic cancer (HCC). Negative OS outcomes were also observed in hematological malignancies. Furthermore, patients at either early or advanced stage had inverse relationship between high pretreatment RDW and poor OS. Studies with cut-off values between 13% and 14% had worse HRs for OS and DFS/PFS/RFS than others. Furthermore, region under the curve (ROC) analysis was used widely to define cut-off values and had relatively closer relationship with poorer HRs. In conclusion, our results suggested that elevated pretreatment RDW level could be a negative predictor for cancer prognosis.

Safety and efficacy of sucrosomial iron in inflammatory bowel disease patients with iron deficiency anemia

Iron deficiency anemia (IDA) is one of the most common complications of inflammatory bowel disease (IBD). We planned a prospective study to address tolerability and efficacy of sucrosomial iron, a new oral formulation of ferric pyrophosphate, in IBD patients. Thirty patients with a confirmed diagnosis of Crohn's Disease (CD) or ulcerative colitis (UC) and mild IDA were enrolled. Patients with severe IBD were excluded. All patients underwent 12 weeks of oral treatment with 30 mg/day of sucrosomial iron. Treatment compliance and adverse events were investigated every 4 weeks. Iron status, hematological parameters and IBD activity scores were determined at baseline and at the end of treatment, as well as serum hepcidin and non-transferrin bound iron (NTBI) levels. Twenty-four (80%) patients took more than 90% of the prescribed regimen. Forty-four adverse events (AEs) were recorded, but none of them is considered certainly or probably related to the study treatment. Interestingly, only eleven gastrointestinal events were recorded in 9 (30%) patients. At the end of treatment, all iron parameters improved significantly and Hb increased in 86% of patients (from 11.67 to 12.37 g/dl, p = 0.001). Serum hepcidin showed a significant increase in 79% of patients and became positively correlated with C-reactive protein (CRP) at the end of the study, while NTBI remained below the detection threshold after iron supplementation. The IBD activity scores improved in both CD and UC. This pilot interventional study supports the therapeutic use of sucrosomial iron in IBD and paves the way for future studies in larger or more difficult IBD populations.

Impact of chronic and acute inflammation on extra- and intracellular iron homeostasis

Inflammation has a major impact on iron homeostasis. This review focuses on acute and chronic inflammation as it affects iron trafficking and, as a result, the availability of this essential micronutrient to the host. In situations of microbial infection, not only the host is affected but also the offending microorganisms, which, in general, not only require iron for their own growth but have evolved mechanisms to obtain it from the infected host. Key players in mammalian iron trafficking include several types of cells important to iron acquisition, homeostasis, and hematopoiesis (enterocytes, hepatocytes, macrophages, hematopoietic cells, and in the case of pregnancy, placental syncytiotrophoblast cells) and several forms of chaperone proteins, including, for nonheme iron, the transport protein transferrin and the intracellular iron-storage protein ferritin, and for heme iron, the chaperone proteins haptoglobin and hemopexin. Additional key players are the cell membrane-associated iron transporters, particularly ferroportin (FPN), the only protein known to modulate iron export from cells, and finally, the iron-regulatory hormone hepcidin, which, in addition to having antibacterial activity, regulates the functions of FPN. Interestingly, the impact of infection on iron homeostasis differs among pathogens whose mode of infection is mainly intracellular or extracellular. Understanding how inflammation affects each of these processes may be crucial for understanding how inflammation affects iron status, indicators of iron sufficiency, and iron supplementation during inflammation and how it may potentially result in a beneficial or detrimental impact on the host.

Decreased Bone Formation Explains Osteoporosis in a Genetic Mouse Model of Hemochromatosiss

Osteoporosis may complicate iron overload diseases such as genetic hemochromatosis. However, molecular mechanisms involved in the iron-related osteoporosis remains poorly understood. Recent in vitro studies support a role of osteoblast impairment in iron-related osteoporosis. Our aim was to analyse the impact of excess iron in Hfe-/- mice on osteoblast activity and on bone microarchitecture. We studied the bone formation rate, a dynamic parameter reflecting osteoblast activity, and the bone phenotype of Hfe-/- male mice, a mouse model of human hemochromatosis, by using histomorphometry. Hfe-/- animals were sacrificed at 6 months and compared to controls. We found that bone contains excess iron associated with increased hepatic iron concentration in Hfe-/- mice. We have shown that animals with iron overload have decreased bone formation rate, suggesting a direct impact of iron excess on active osteoblasts number. For bone mass parameters, we showed that iron deposition was associated with bone loss by producing microarchitectural impairment with a decreased tendency in bone trabecular volume and trabecular number. A disorganization of trabecular network was found with marrow spaces increased, which was confirmed by enhanced trabecular separation and star volume of marrow spaces. These microarchitectural changes led to a loss of connectivity and complexity in the trabecular network, which was confirmed by decreased interconnectivity index and increased Minkowski's fractal dimension. Our results suggest for the first time in a genetic hemochromatosis mouse model, that iron overload decreases bone formation and leads to alterations in bone mass and microarchitecture. These observations support a negative effect of iron on osteoblast recruitment and/or function, which may contribute to iron-related osteoporosis.

Branched-chain amino acid supplementation reduces oxidative stress and prolongs survival in rats with advanced liver cirrhosis

Long-term supplementation with branched-chain amino acids (BCAA) is associated with prolonged survival and decreased frequency of development of hepatocellular carcinoma (HCC) in patients with liver cirrhosis. However, the pharmaceutical mechanism underlying this association is still unclear. We investigated whether continuous BCAA supplementation increases survival rate of rats exposed to a fibrogenic agent and influences the iron accumulation, oxidative stress, fibrosis, and gluconeogenesis in the liver. Further, the effects of BCAA on gluconeogenesis in cultured cells were also investigated. A significant improvement in cumulative survival was observed in BCAA-supplemented rats with advanced cirrhosis compared to untreated rats with cirrhosis (P<0.05). The prolonged survival due to BCAA supplementation was associated with reduction of iron contents, reactive oxygen species production and attenuated fibrosis in the liver. In addition, BCAA ameliorated glucose metabolism by forkhead box protein O1 pathway in the liver. BCAA prolongs survival in cirrhotic rats and this was likely the consequences of reduced iron accumulation, oxidative stress and fibrosis and improved glucose metabolism in the liver.

Avian iron storage disease: variations on a common theme?

Many frugivorous avian species kept in captivity develop iron storage disease (ISD) as indicated by high concentrations of hepatic iron and hemosiderin deposits in hepatocytes or phagocytes. In several susceptible species fed diets containing moderate levels of iron, ISD develops because of an inability to match rates of iron absorption to tissue needs. Evidence suggests that the pathophysiologic basis of excess iron absorption is due to high levels of expression of divalent metal transporter-1 that transports iron into enterocytes in the proximal intestine, and ferroportin that exports iron to the circulation. The regulatory basis for this inability to sufficiently down-regulate iron absorption is unknown, but disruptions in the hepcidin-ferroportin axis are likely candidates based on recent research in humans and laboratory rodents. It is likely that ISD-susceptible avian species evolved on foods that were very low in bioavailable iron, so there was strong selection pressure for the efficient capture of the small amount of dietary iron but low selection pressure for preventing iron toxicities. Thus, the transporters and regulatory networks for iron absorption seem to be heavily skewed toward iron storage even when food items that are high in iron are consumed. Infections, trauma and neoplasias that trigger an acute phase response may exacerbate ISD in susceptible species and may be the primary cause in species that are normally resistant to ISD (i.e., those that are normally able to shut down intestinal iron absorption when iron stores are replete). The evolutionary basis that resulted in some avian species to be susceptible to ISD (e.g., dietary cause) seems to differ from many inherited ISD disorders in humans that are thought to have evolved to bolster protection against infectious diseases. However the evolutionary basis of ISD in other mammalian species might be more similar to that in ISD-susceptible avian species.

Iron regulator hepcidin exhibits antiviral activity against hepatitis C virus

Hepatitis C viral infection affects 170 million people worldwide. It causes serious chronic liver diseases. HCV infection has been implicated in iron accumulation in the liver and iron overload has been shown to be a potential cofactor for HCV associated hepatocellular carcinoma progression. The underlying mechanisms are not understood. Human hepcidin, a 25 amino acid peptide mainly produced by hepatocytes, is a key regulator of iron metabolism. Alteration of hepcidin expression levels has been reported in the setting of chronic HCV infection and hepatocellular carcinoma. In this study, we aim to examine the interactions between HCV infection and hepcidin expression in liver cells. We found that hepcidin expression was suppressed in HCV infected cells. The suppressive effect appears to be regulated by histone acetylation but not DNA methylation. Moreover, we found that hepcidin had a direct antiviral activity against HCV replication in cell culture. The antiviral effect is associated with STAT3 activation. In conclusion, hepcidin can induce intracellular antiviral state while HCV has a strategy to suppress hepcidin expression. This may be a novel mechanism by which HCV circumvents hepatic innate antiviral defense.

Iron excess limits HHIPL-2 gene expression and decreases osteoblastic activity in human MG-63 cells

In order to understand mechanisms involved in osteoporosis observed during iron overload diseases, we analyzed the impact of iron on a human osteoblast-like cell line. Iron exposure decreases osteoblast phenotype. HHIPL-2 is an iron-modulated gene which could contribute to these alterations. Our results suggest osteoblast impairment in iron-related osteoporosis.

INTRODUCTION

Iron overload may cause osteoporosis. An iron-related decrease in osteoblast activity has been suggested.

METHODS

We investigated the effect of iron exposure on human osteoblast cells (MG-63) by analyzing the impact of ferric ammonium citrate (FAC) and iron citrate (FeCi) on the expression of genes involved in iron metabolism or associated with osteoblast phenotype. A transcriptomic analysis was performed to identify iron-modulated genes.

RESULTS

FAC and FeCi exposure modulated cellular iron status with a decrease in TFRC mRNA level and an increase in intracellular ferritin level. FAC increased ROS level and caspase 3 activity. Ferroportin, HFE and TFR2 mRNAs were expressed in MG-63 cells under basal conditions. The level of ferroportin mRNA was increased by iron, whereas HFE mRNA level was decreased. The level of mRNA alpha 1 collagen type I chain, osteocalcin and the transcriptional factor RUNX2 were decreased by iron. Transcriptomic analysis revealed that the mRNA level of HedgeHog Interacting Protein Like-2 (HHIPL-2) gene, encoding an inhibitor of the hedgehog signaling pathway, was decreased in the presence of FAC. Specific inhibition of HHIPL-2 expression decreased osteoblast marker mRNA levels. Purmorphamine, hedgehog pathway activator, increased the mRNA level of GLI1, a target gene for the hedgehog pathway, and decreased osteoblast marker levels. GLI1 mRNA level was increased under iron exposure.

CONCLUSION

We showed that in human MG-63 cells, iron exposure impacts iron metabolism and osteoblast gene expression. HHIPL-2 gene expression modulation may contribute to these alterations. Our results support a role of osteoblast impairment in iron-related osteoporosis.

Liver hepcidin mRNA expression is inappropriately low in alcoholic patients compared with healthy controls

BACKGROUND AND AIMS

Hepcidin plays a crucial role in iron metabolism, preventing its absorption at the basolateral enterocyte membrane. Hepcidin regulation is complex and regulated at the transcriptional level. The relation between iron overload and alcoholic liver disease is well known, but its mechanism is not clear. We present an observational, case-control study, aimed at evaluating the effects of alcohol on the expression of hepcidin in human participants. We intended to assess whether iron overload related to alcohol ingestion was caused by hepcidin-impaired expression by determining hepcidin mRNA expression and relating it to iron stores, both in alcoholic patients and in normal controls.

METHODS

We compared liver hepcidin mRNA expression between 25 active drinkers with alcoholic liver disease, without cirrhosis, and 20 healthy controls. All individuals were evaluated for HFE mutations, complete blood count, coagulation, glucose, kidney function, liver function, viral hepatitis, C-reactive protein, interleukin 6, tumor necrosis factor α, and serum iron, ferritin, and transferrin saturation. Total RNA was isolated from liver samples, cDNA was obtained by reverse transcription, and hepatic expression levels of hepcidin were determined by real-time PCR using the comparative Ct method (2(-ΔΔCt)).

RESULTS

Serum ferritin and transferrin saturation were significantly higher in patients. Hepcidin was downregulated in patients compared with the controls by a mean factor of -0.44 (log10 2(-ΔΔCt)) (P=0.009). Hepcidin expression was not significantly different between the several grades of fibrosis, necroinflammatory activity, and liver iron stores. Heavy alcohol consumption caused the highest hepcidin mRNA suppression. The hepcidin mRNA expression/serum ferritin ratio was significantly lower in alcoholic patients (P<0.0001).

CONCLUSION

Hepcidin liver expression is inappropriately low in alcoholic patients with active alcoholism and preserved hepatic function, and we conclude that this is the mechanism for alcohol consumption-associated iron overload in humans.

Fetal iron levels are regulated by maternal and fetal Hfe genotype and dietary iron

BACKGROUND

Iron metabolism during pregnancy maintains fetal iron levels at the expense of the mother. The mechanism behind this regulation is still not clear despite recent advances. Here we examine the role of maternal and fetal Hfe, its downstream signaling molecule, hepcidin and dietary iron in the regulation of placental iron transfer.

DESIGN AND METHODS

Hfe wild-type, knockout and heterozygote dams were fed iron deficient (12.5 ppm), adequate (50 ppm) and replete (150 ppm) iron diets and mated with heterozygote males to produce pups of all genotypes. Dams and pups were sacrificed at Day 18 of gestation; serum, placenta, body and liver iron parameters were measured. Protein and mRNA levels of various iron transporter genes were determined in duodenum, liver and placenta by Western blotting and real time PCR.

RESULTS

Maternal liver iron levels were dependent on both dietary iron intake and Hfe genotype. Increasing iron levels in the maternal diet resulted in increased total iron in the fetus, primarily in the liver. However, fetuses of Hfe-knockout mothers showed further elevation of liver iron levels, concomitant with elevated expression of Tfr1, Dmt1 and Fpn in the placenta. Hfe-knockout fetuses that express low levels of liver hepcidin accumulated more iron in their liver than wild-type fetuses due to increased ferroportin levels in the placenta.

CONCLUSIONS

Maternal and fetal status, as well as dietary iron, is important in regulating iron transfer across placenta. Maternal Hfe regulates iron transfer by altering gene expression in the placenta. Fetal Hfe is important in regulating placental iron transfer by modulating fetal liver hepcidin expression.

Diagnosing anemia in inflammatory bowel disease: beyond the established markers

The main types of anemia in inflammatory bowel disease (IBD) are iron deficiency anemia (IDA) and anemia of inflammatory etiology, or anemia of chronic disease (ACD). In the management of IBD patients with anemia it is essential for the physician to diagnose the type of anemia in order to decide in an evidence-based manner for the appropriate treatment. However, the assessment of iron status in IBD in many cases is rather difficult due to coexistent inflammation. For this assessment several indices and markers have been suggested. Ferritin, seems to play a central role in the definition and diagnosis of anemia in IBD and transferrin, transferrin saturation (Tsat), and soluble transferrin receptors are also valuable markers. All these biochemical markers have several limitations because they are not consistently reliable indices, since they are influenced by factors other than changes in iron balance. In this review, in addition to them, we discuss the newer alternative markers for iron status that may be useful when serum ferritin and Tsat are not sufficient. The iron metabolism regulators, hepcidin and prohepcidin, are still under investigation in IBD. Erythrocytes parameters like the red cell distribution width (RDW) and the percentage of hypochromic red cells as well as reticulocyte parameters such as hemoglobin concentration of reticulocytes, red blood cell size factor and reticulocyte distribution width could be useful markers for the evaluation of anemia in IBD.

Decoupling ferritin synthesis from free cytosolic iron results in ferritin secretion

Ferritin is a multisubunit protein that is responsible for storing and detoxifying cytosolic iron. Ferritin can be found in serum but is relatively iron poor. Serum ferritin occurs in iron overload disorders, in inflammation, and in the genetic disorder hyperferritinemia with cataracts. We show that ferritin secretion results when cellular ferritin synthesis occurs in the relative absence of free cytosolic iron. In yeast and mammalian cells, newly synthesized ferritin monomers can be translocated into the endoplasmic reticulum and transits through the secretory apparatus. Ferritin chains can be translocated into the endoplasmic reticulum in an in vitro translation and membrane insertion system. The insertion of ferritin monomers into the ER occurs under low-free-iron conditions, as iron will induce the assembly of ferritin. Secretion of ferritin chains provides a mechanism that limits ferritin nanocage assembly and ferritin-mediated iron sequestration in the absence of the translational inhibition of ferritin synthesis.

Genetic and biochemical analysis of high iron toxicity in yeast: iron toxicity is due to the accumulation of cytosolic iron and occurs under both aerobic and anaerobic conditions

Iron storage in yeast requires the activity of the vacuolar iron transporter Ccc1. Yeast with an intact CCC1 are resistant to iron toxicity, but deletion of CCC1 renders yeast susceptible to iron toxicity. We used genetic and biochemical analysis to identify suppressors of high iron toxicity in Δccc1 cells to probe the mechanism of high iron toxicity. All genes identified as suppressors of high iron toxicity in aerobically grown Δccc1 cells encode organelle iron transporters including mitochondrial iron transporters MRS3, MRS4, and RIM2. Overexpression of MRS3 suppressed high iron toxicity by decreasing cytosolic iron through mitochondrial iron accumulation. Under anaerobic conditions, Δccc1 cells were still sensitive to high iron toxicity, but overexpression of MRS3 did not suppress iron toxicity and did not result in mitochondrial iron accumulation. We conclude that Mrs3/Mrs4 can sequester iron within mitochondria under aerobic conditions but not anaerobic conditions. We show that iron toxicity in Δccc1 cells occurred under both aerobic and anaerobic conditions. Microarray analysis showed no evidence of oxidative damage under anaerobic conditions, suggesting that iron toxicity may not be solely due to oxidative damage. Deletion of TSA1, which encodes a peroxiredoxin, exacerbated iron toxicity in Δccc1 cells under both aerobic and anaerobic conditions, suggesting a unique role for Tsa1 in iron toxicity.

Iron status, inflammation and hepcidin in ESRD patients: The confounding role of intravenous iron therapy

Uremia is a state of heightened inflammatory activation. This might have an impact on several parameters including anemia management. Inflammation interferes with iron utilization in chronic kidney disease through hepcidin. We studied the body iron stores, degree of inflammatory activation, and pro-hepcidin levels in newly diagnosed patients with end-stage renal disease (ESRD), and compared them with normal population. In addition to clinical examination and anthropometry, the levels of iron, ferritin, C-reactive protein, tumor necrosis factor alfa, interleukin-6, and prohepcidin were estimated. A total of 74 ESRD patients and 52 healthy controls were studied. The ESRD patients had a significantly lower estimated body fat percentage, muscle mass, and albumin; and higher transferrin saturation (TSAT) and raised serum ferritin. Inflammatory activation was evident in the ESRD group as shown by the significantly higher CRP, IL-6, and TNF-α levels. The pro-hepcidin levels were also increased in this group. Half of the ESRD patients had received parenteral iron before referral. Patients who had received intravenous iron showed higher iron, ferritin, and TSAT levels. These patients also showed more marked inflammatory activation, as shown by the significantly higher CRP, TNF-α, and IL-6 levels. We conclude that our ESRD patients showed marked inflammatory activation, which was more pronounced in patients who had received IV iron. High hepcidin levels could explain the functional iron deficiency. The cause of the relatively greater degree of inflammatory activation as well as the relationship with IV iron administration needs further studies.

High serum levels of TNF-α and IL-6 predict the clinical outcome of treatment with human recombinant erythropoietin in anaemic cancer patients

BACKGROUND

A number of anaemic cancer patients are not responsive to treatment with recombinant human erythropoietin (rHuEPO). The aim of the present study is to investigate whether serum levels of tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6 and additional laboratory parameters, together with clinical variables, can predict the clinical outcome of treatment with rHuEPO in anaemic cancer patients.

PATIENTS AND METHODS

Thirty-five cancer patients and 25 healthy controls were enrolled in this study. Patients were treated with epoetin alfa at the dose of 150 IU/kg s.c. three times a week for 12 weeks. If the haemoglobin (Hb) level failed to improve at least 2 g/dl above baseline by week 6 of treatment, dose was increased to 300 IU/kg s.c. for the remainder of the treatment period. All patients filled out the Brief Fatigue Inventory (BFI), a questionnaire for the self-evaluation of cancer-related fatigue. Serum samples from patients and control groups were frozen at -80 degrees C and TNF-alpha, IL-1beta and IL-6 were later examined by enzyme-linked immunosorbent assay.

RESULTS

Fatigued cancer patients had significant higher levels of circulating TNF-alpha, IL-1beta and IL-6 than healthy controls. Responders (Rs) to erythropoietin had significant lower medium levels of TNF-alpha and IL-6 than nonresponders (NRs). Fatigued patients with a general BFI score > or =6 presented higher medium level of cytokines than nonfatigued patients (general BFI score <6), but each group responded similarly to treatment with rHuEPO.

CONCLUSIONS

High serum levels of TNF-alpha and IL-6 at the baseline are significantly correlated with a negative response to administration with rHuEPO. Thus, pretreatment evaluation of TNF-alpha and IL-6 serum levels can help to select those patients who are most likely to benefit from treatment with rHuEPO. On the contrary, Hb level, red blood cell count, lactate dehydrogenase and BFI score do not predict the outcome of treatment with rHuEPO.

Association of hepcidin promoter c.-582 A>G variant and iron overload in thalassemia major

Hepcidin is a 25-amino acid peptide, derived from cleavage of an 84 amino acid pro-peptide produced predominantly by hepatocytes. This molecule, encoded by the hepcidin antimicrobial peptide (HAMP) gene shows structural and functional properties consistent with a role in innate immunity. Moreover, as demonstrated in mice and humans, hepcidin is a major regulator of iron metabolism, and acts by binding to ferroportin and controlling its concentration and trafficking. In this study we investigated the influence that mutations in HAMP and/or hemocromatosis (HFE) genes might exert on iron metabolism in a group of poly-transfused thalassemic patients in preparation for bone marrow transplantation. Our results showed that the presence of the c.-582 A>G polymorphism (rs10421768) placed in HAMP promoter (HAMP-P) might play a role in iron metabolism, perhaps varying the transcriptional activation that occurs through E-boxes located within the promoter.

Iron overload, hematopoietic cell transplantation, and graft-versus-host disease

Many patients who undergo hematopoietic cell transplantation (HCT) present with anemia and have received red blood cell transfusions before HCT. As a result, iron overload is frequent and appears to be particularly prominent in patients with myelodysplastic syndromes. There is evidence that peritransplant events contribute to further iron accumulation, although the mechanism that disrupts normal iron homeostasis remains to be determined. Recent studies suggest that iron overload, as determined by ferritin levels, a surrogate marker for iron, is a risk factor for increased non-relapse mortality after HCT. Iron overload is associated with an increased rate of infections, in particular with fungal organisms. Furthermore anecdotal data suggest that increased hepatic iron may mimic the clinical picture of (chronic) graft-versus-host-disease (GVHD). Whether excess iron contributes to GVHD and whether iron depletion, be it by phlebotomy or chelation, reduces the post-transplantation complication rate and improves transplant outcome is yet to be determined.

A fish antimicrobial peptide, tilapia hepcidin TH2-3, shows potent antitumor activity against human fibrosarcoma cells

As part of a continuing search for potential anticancer drug candidates from antimicrobial peptides of marine organisms, tilapia (Oreochromis mossambicus) hepcidin TH2-3 was evaluated in several tumor cell lines. The results indicated that TH2-3, a synthetic 20-mer antimicrobial peptide, specifically inhibited human fibrosarcoma cell (HT1080 cell line) proliferation and migration. The way in which TH2-3 inhibited HT1080 cell growth was then studied. TH2-3 inhibited HT1080 cell growth in a concentration-dependent manner according to an MTT analysis, which was confirmed by a soft-agar assay and AO/EtBr staining. Scanning electron microscopy revealed that TH2-3 caused lethal membrane disruption in HT1080 cancer cells, and a wound healing assay supported that TH2-3 decreased the migration of HT1080 cells. In addition, c-Jun mRNA expression was downregulated after treatment with TH2-3 for 48-96 h compared to the untreated group. These findings suggest a mechanism of cytotoxic action of TH2-3 and indicate that TH2-3 may be a promising chemotherapeutic agent against human fibrosarcoma cells.

Comparative analysis of IL6 promoter and receptor polymorphisms in myelodysplasia and multiple myeloma

The serum levels of interleukin 6 (IL6) are known to be elevated in two diseases of the elderly age, myelodysplastic syndrome (MDS) and multiple myeloma (MM). Authors suppose that one of the possible causes of this elevation could be a difference between these patients and healthy subjects in the frequency of polymorphic variants of the genes regulating IL6 levels. Scarce and contradictory comparative data are available for MM and to our best knowledge this is the first study on IL6 promoter and IL6 receptor (IL6R) polymorphism in MDS. Therefore we determined the Asp358Ala polymorphism of the IL6 receptor gene and the -174 G>C promoter polymorphism of the IL6 gene in blood samples of 102 MDS and 100 MM patients and 99 age- and sex-matched hospitalized controls had been tested for this purpose as well. There was no significant difference between patients with either disease and controls regarding IL6 promoter/L-6R. Authors therefore assume other mechanisms causing high IL6 levels are not related to either of these polymorphisms. Moreover authors consider important to propose a hypothesis how elements of signal transduction in iron metabolism might be involved in the development of MM and MDS in elderly age.

Diurnal cycle influences peripheral and brain iron levels in mice

Iron movement between organ pools involves a dynamic equilibrium of iron efflux and uptake, and homeostatic mechanisms are likely involved in providing iron to cells and organs when required. Daily iron levels in the plasma pool fluctuate with the diurnal cycle, but clear explanations regarding the objectives and regulation of the flux are lacking. The association between diurnal cycle and iron flux is relevant in the disease of restless legs syndrome (RLS), where individuals display diurnal deficits in motor control, have impaired brain iron metabolism, and perhaps altered iron uptake from the plasma pool. The goal of the present study was to examine diurnal variations in peripheral and regional brain iron to evaluate iron flux between organs in iron-sufficient and iron-deficient mice. In mice fed control diet, liver iron was elevated 30-40%, and plasma iron was reduced 20-30% in the active dark period compared with the inactive light phase. Dietary iron deficiency eliminated this variation in liver iron in male and female mice and in plasma iron in male mice. Reductions in ventral midbrain and nucleus accumbens iron and ferritin were apparent in iron-deficient mice during both diurnal phases, but only during the light phase was an approximately 25% reduction in whole brain iron observed, suggesting different brain iron requirements between phases. These data demonstrate that iron flux between organs is sensitive to diurnal regulatory biology. Importantly, variations in brain iron may have temporal implications regarding neural functioning and may contribute to the diurnal cycle-dependent symptoms of RLS.

Expression of hepcidin mRNA is uniformly suppressed in hepatocellular carcinoma

Background

The present study evaluated the expression of hepcidin mRNA in hepatocellular carcinoma (HCC).

Methods

Samples of cancerous and non-cancerous liver tissue were taken from 40 patients with HCC who underwent hepatectomy. Expression of hepcidin mRNA was evaluated by real-time PCR, and compared in tumors differing in their degree of differentiation, number of tumors, and vessel invasion. Correlations between hepcidin expression and the interval until HCC recurrence, and the serum concentration of hepcidin were evaluated, together with the expression of mRNAs for other iron metabolism molecules, ferroportin and transferrin receptor 2 (Trf2).

Results

Hepcidin mRNA expression in non-cancerous and cancerous tissues was 1891.8 (32.3–23187.4) and 53.4 (1.9–3185.8), respectively (P < 0.0001). There were no significant differences in hepcidin expression among tumors differing in their degree of differentiation, number of tumors, or vessel invasion. There was no significant correlation between hepcidin expression and the interval until HCC recurrence. The serum concentration of hepcidin-25 was not correlated with hepcidin-mRNA expression. Finally, there were no significant differences in the expression of mRNA for ferroportin and Trf2 between cancerous and non-cancerous tissues.

Conclusion

Expression of hepcidin mRNA is strikingly suppressed in cancerous, but not in non-cancerous tissues, in patients with HCC, irrespective of ferroportin or Trf2 expression. Uniform suppression of hepcidin may be linked to the development of HCC.

The role of Hfe in transferrin-bound iron uptake by hepatocytes

HFE-related hereditary hemochromatosis results in hepatic iron overload. Hepatocytes acquire transferrin-bound iron via transferrin receptor (Tfr) 1 and Tfr1-independent pathways (possibly Tfr2-mediated). In this study, the role of Hfe in the regulation of hepatic transferrin-bound iron uptake by these pathways was investigated using Hfe knockout mice. Iron and transferrin uptake by hepatocytes from Hfe knockout, non-iron-loaded and iron-loaded wild-type mice were measured after incubation with 50 nM (125)I-Tf-(59)Fe (Tfr1 pathway) and 5 microM (125)I-Tf-(59)Fe (Tfr1-independent or putative Tfr2 pathway). Tfr1 and Tfr2 messenger RNA (mRNA) and protein expression were measured by real-time polymerase chain reaction and western blotting, respectively. Tfr1-mediated iron and transferrin uptake by Hfe knockout hepatocytes were increased by 40% to 70% compared with iron-loaded wild-type hepatocytes with similar iron levels and Tfr1 expression. Iron and transferrin uptake by the Tfr1-independent pathway was approximately 100-fold greater than by the Tfr1 pathway and was not affected by the absence of Hfe. Diferric transferrin increased hepatocyte Tfr2 protein expression, resulting in a small increase in transferrin but not iron uptake by the Tfr1-independent pathway.

CONCLUSION

Tfr1-mediated iron uptake is regulated by Hfe in hepatocytes. The Tfr1-independent pathway exhibited a much greater capacity for iron uptake than the Tfr1 pathway but it was not regulated by Hfe. Diferric transferrin up-regulated hepatocyte Tfr2 protein expression but not iron uptake, suggesting that Tfr2 may have a limited role in the Tfr1-independent pathway.

2-Oxoglutarate-dependent oxygenases control hepcidin gene expression

BACKGROUND/AIMS

Hepcidin is a liver-produced hormone that regulates systemic iron homeostasis. Hepcidin expression is stimulated upon iron overload or inflammation while iron deficiency, anemia and tissue hypoxia are negative regulators. We investigated the involvement of 2-oxoglutarate-dependent oxygenases, HIF-1 and other transcription factors in the hypoxic suppression of hepcidin.

METHODS

Northern blotting analysis and real time PCR were used to determine hepcidin mRNA levels in hepatoma cells and hepcidin promoter activity was measured using Huh7 cells transfected with suitable reporter constructs under various conditions.

RESULTS

Treatment of human cultured hepatoma cells with hypoxia or known inhibitors of 2-oxoglutarate-dependent oxygenases, such as the iron chelator desferrioxamine, cobalt or the 2-oxoglutarate analogue dimethyl-oxalylglycine significantly reduced hepcidin mRNA levels and down-regulated its gene promoter activity. This effect was not dependent on the HREs or other known putative response elements in the hepcidin promoter and was observed even under interleukin-6 treatment.

CONCLUSIONS

2-Oxoglutarate-dependent oxygenases are important to maintain high hepcidin mRNA expression in a HIF-1-independent manner. We suggest that modulation of oxygenase activity may be of therapeutic value in iron-related disorders.

The influence of metallothionein on exposure to metals: an in vitro study on cellular models

In the present study, the interactions between zinc (Zn) and copper (Cu) or iron (Fe) have been examined. Rat hepatoma cell line H4-II-E-C3, fibroblast cell line mutant MT-/-, and wild-type MT+/+ cells treated with ZnSO4 or CuSO4 or FeSO4 or CuSO4+ZnSO4 or ZnSO4+FeSO4 for different times have been employed to study the effect of metallothionein (MT), glutathione (GSH) and metal (Cu, Fe and Zn) accumulation during cellular adaptation to supraphysiological metal concentrations. To investigate the different biological functions in the processes of metal homeostasis and detoxification, the levels of both MT-1 and MT-2 mRNAs have been evaluated. The three cell lines responded differently to metal treatments suggesting that the uptake and storage of these metals are affected by the specific cellular model and MT presence. In particular, Zn treatment significantly decreased Fe accumulation (p<0.05), whereas MT induced by Zn increased intracellular Cu content (p<0.05). Moreover, in H4-II-E-C3 cells administration of metals resulted in a rapid and transient induction of MT (p<0.05) and in GSH accumulation (p<0.05) suggesting synergistic interactions in which both appear essential for a protective regulatory function against the redox activity of metals. Taken together these results demonstrate that Zn affects the cellular levels of Cu and Fe by competition with the same ligand sites and/or by coordinate regulation of MT and GSH content.

The Hereditary Hemochromatosis protein HFE and its chaperone β2-microglobulin localise predominantly to the endosomal-recycling compartment

Hereditary Hemochromatosis is an iron overload disease most frequently associated with mutations in the HFE gene. While clinical studies of the disease have received extensive attention by various groups, the localisation, trafficking and function of the HFE protein, and its chaperone beta2-microglobulin (beta2M), require further investigation. In this study, we present data on the cellular localisation of HFE and its clinically relevant mutants in HuTu 80 cells. We find by confocal microscopy that HFE localises to the endosomal-recycling compartment (ERC), with minimal localisation to sorting or late endosomes. Interestingly, we also demonstrate that beta2M localises to the ERC where it co-localises with HFE. We find that exogenous expression of HFE results in enhanced beta2M cellular levels and that beta2M is necessary for cell surface expression of HFE. Finally, we have analysed the functional effects of exogenous expression of HFE and beta2M on transferrin binding to the cell surface. In summary, our study sheds light on the localisation and functional effects of the HFE and its chaperone protein beta2M.

HFE genotypes in patients with chronic pancreatitis and pancreatic adenocarcinoma

PURPOSE

The homozygous p.C282Y variant of the HFE gene is a major risk factor for hereditary hemochromatosis, a disorder of iron metabolism resulting in progressive iron accumulation in a variety of organs including the pancreas. Heterozygosity of p.C282Y and p.H63D may increase susceptibility to chronic liver and pancreatic disease. This study determines the frequencies of p.C282Y and p.H63D alterations in patients with chronic pancreatitis and pancreatic adenocarcinoma.

METHODS

In total, 958 patients (349 with alcoholic pancreatitis, 343 with idiopathic pancreatitis, 64 with familial chronic pancreatitis, 34 with acute pancreatitis, and 168 with pancreatic adenocarcinoma) were enrolled and compared with 681 healthy and 100 alcoholic controls. Furthermore, 45 parent-offspring trios were included for segregation analysis. Genotyping of p.C282Y and p.H63D was performed by restriction fragment length polymorphism or melting curve analyses.

RESULTS

No significant differences were found in heterozygosity for p.C282Y and p.H63D when patients with alcoholic (8.0/21.5%), idiopathic (7.3/24.5%), or familial (9.8/23.0%) pancreatitis, or pancreatic adenocarcinoma (5.4/28.6%) were compared with healthy (6.2/24.8%) and alcoholic (7.0/25.0%) controls. Neither genotype was associated with the presence of secondary diabetes mellitus in patients with chronic pancreatitis.

CONCLUSION

Although hemochromatosis is associated with pancreatic pathology, the p.C282Y and p.H63D variants do not play a significant role in the pathogenesis of chronic pancreatitis or pancreatic adenocarcinoma.

Effects of alcohol consumption on iron metabolism in mice with hemochromatosis mutations

BACKGROUND

Alcoholic liver disease is associated with increased hepatic iron accumulation. The liver-derived peptide hepcidin is the central regulator of iron homeostasis and recent animal studies have demonstrated that exposure to alcohol reduces hepcidin expression. This down-regulation of hepcidin in vivo implies that disturbed iron sensing may contribute to the hepatosiderosis seen in alcoholic liver disease. Alcohol intake is also a major factor in expression of the hemochromatosis phenotype in patients homozygous for the C282Y mutation of the HFE gene.

METHODS

To assess the effect of alcohol in mice with iron overload, alcohol was administered to mice with disrupted Hfe and IL-6 genes and Tfr2 mutant mice and their respective 129x1/SvJ, C57BL/6J, and AKR/J wild-type congenic strains. Iron absorption, serum iron levels, and hepcidin expression levels were then measured in these mice compared with water-treated control mice.

RESULTS

Alcohol was shown to have a strain-specific effect in 129x1/SvJ mice, with treated 129x1/SvJ mice showing a significant increase in iron absorption, serum iron levels, and a corresponding decrease in hepcidin expression. C57BL/6J and AKR/J strain mice showed no effect from alcohol treatment. 129x1/SvJ mice heterozygous or homozygous for the Hfe knockout had a diminished response to alcohol. All 3 strains were shown to have high blood alcohol levels.

CONCLUSIONS

The effect of alcohol on iron homeostasis is dependent on the genetic background in mice. In an alcohol-susceptible strain, mutation of the Hfe gene diminished the response of the measured iron indices to alcohol treatment. This indicates that either maximal suppression of hepcidin levels had already occurred as a result of the Hfe mutation or that Hfe was a component of the pathway utilized by EtOH in suppressing hepcidin production and increasing iron absorption.

Iron overload syndromes and the liver

Iron can accumulate in the liver in a variety of conditions, including congenital, systemic iron-loading conditions (hereditary hemochromatosis), conditions associated with systemic macrophage iron accumulation (transfusions, hemolytic conditions, anemia of chronic disease, etc), in some hepatitidies (hepatitis C, alcoholic liver disease, porphyria cutanea tarda), and liver-specific iron accumulation of uncertain pathogenesis in cirrhosis. The anatomic pathologist will be faced with the task of determining whether iron accumulation in the liver is significant and, if so, the nature of the disease that lead to the accumulation (ie diagnosis). The tools available to the pathologist include (most importantly) histologic examination with iron stain, quantitative iron analysis, clinical history, laboratory iron tests (serum iron and iron-binding capacity, serum ferritin) and germline genetic analysis for mutations in genes known to be associated with hemochromatosis (HFE, ferroportin, hepcidin, hemojuvelin, transferrin receptor-2). This article provides an overview of the above.

Efficacy of zinc treatment against iron-induced toxicity in rat hepatoma cell line H4-II-E-C3

OBJECTIVE

In this study, we have attempted to explore the possible protection afforded by Zn with regard to its antioxidant potential properties in the iron-induced toxicity.

METHODS

Rat hepatoma cell line H4-II-E-C3 was treated with 150 muM ZnSO4, 200 muM FeSO4 or 150 muM ZnSO4+ 200 muM FeSO4 for 24 h. We studied the effect of metallothionein (MT), glutathione and metal (Fe and Zn) accumulation. We evaluated the levels of both MT-1 and MT-2 mRNAs, activities of antioxidant enzymes, and also determined the distribution of MT and cell death index.

RESULTS

The cotreatment produced highest levels of MT. Fe concentration was significantly lower in the Zn-Fe-treated cells compared with Fe-treated cells. In both Zn treatments, the superoxide dismutase/glutathione peroxidase ratio was similar to control. The cell death index was lower in the Zn-Fe-treated cells compared with Fe-treated cells.

CONCLUSIONS

Zn may act as antioxidant by competitive inhibition of iron uptake by the divalent metal transporter and/or by MT induction.

Hepcidin in Anemia and Inflammation in Chronic Kidney Disease

Maintaining the correct iron balance is crucial for health. Our understanding of the molecular control of iron metabolism has increased dramatically over the past 5 years due to the discovery of hepcidin. This is a circulating antimicrobial peptide mainly synthesized in the liver, which has been recently proposed as a factor regulating the uptake of dietary iron and its mobilization from macrophages and hepatic stores. Inflammation causes an increase of production of hepcidin, which is a potent mediator of anemia of chronic diseases. Anemia in chronic kidney disease is mainly due to erythropoietin deficiency but these patients often have a chronic inflammatory state. The aim of this review is to summarize the current knowledge dealing with a possible role of hepcidin in iron metabolism and its regulation, particularly in kidney disease. In addition, current methods of determination of hepcidin are reviewed.

STAT3 is required for IL-6-gp130-dependent activation of hepcidin in vivo

BACKGROUND & AIMS

Hepcidin is a peptide hormone that is central to the regulation of iron homeostasis. In response to interleukin 6 (IL-6), hepatocytes produce hepcidin that decreases iron release/transfer from enterocytes and macrophages and causes hypoferremia. To clarify the molecular pathways involved in hepcidin activation by IL-6, we used different mice strains in which the main IL-6/gp130 signaling pathways have been genetically disrupted.

METHODS

We generated mice with hepatocyte-specific deletion of the IL-6 signal-transducing gp130 receptor (alfpgp130 (LoxP/LoxP)), with a gp130 receptor lacking the essential region for STAT1 and -3 activation (alfpCre gp130(DeltaSTAT/LoxP)) or mice expressing a gp130 allele lacking the essential tyrosine for RAS-MAPK activation (alfpCregp130(Y757F/LoxP)). We studied gp130-dependent pathways and hepcidin mRNA expression by Western blot, reverse-transcription polymerase chain reaction, and Northern blot in vivo and ex vivo.

RESULTS

IL-6 stimulated phospho STAT3, serum amyloid A (SAA), and suppressor of cytokine signaling 3 (SOCS3) expression in livers of wild-type and alfpCregp130(Y757F/LoxP) mice, whereas this response was blocked in alfpCre gp130(LoxP/LoxP) and alfpCre gp130(DeltaSTAT/LoxP) mice. In wild-type and alfpCregp130(Y757F/LoxP) animals, significantly higher hepcidin mRNA expression was found 3 to 6 hours after IL-6 stimulation. In contrast, no IL-6-dependent regulation of hepcidin mRNA expression was found in alfpgp130 (DeltaSTAT/LoxP) and AlfpCre gp130 (LoxP/LoxP) animals. In primary hepatocytes, higher hepcidin mRNA expression after IL-6 stimulation was only observed when gp130-STAT3-dependent signaling was intact.

CONCLUSIONS

We have demonstrated that both in vivo and in vitro STAT3 is the key transcription factor responsible for IL-6 activation of hepcidin gene expression in the liver.

Is ferroportin–hepcidin signaling altered in restless legs syndrome?

Restless legs syndrome (RLS) is a neurological disorder characterized by a strong urge to move the legs. Sufferers of RLS often experience chronic sleep deprivation, due to the characteristic worsening of symptoms both when at rest and during the night. MRI data, autopsy studies, and a consistent decrease in CSF ferritin all suggest that early-onset RLS is associated with insufficient iron in the brain. In this study, we examined the relationship between the iron regulatory hormone hepcidin and RLS. Hepcidin serves as a hormone that signals iron release from cells by interacting with ferroportin. We measured the expression and concentration of pro-hepcidin in the brain and cerebrospinal fluid of both RLS patients and control individuals. In CSF, we found that pro-hepcidin levels were significantly decreased in early-onset RLS patient samples, but not in late-onset RLS patients, when compared to controls. Conversely, in neuromelanin cells, substantia nigra, and putamen, the concentration of pro-hepcidin in RLS samples is significantly increased compared to controls. Functionally, hepcidin binds to ferroportin to limit iron movement from cells. Therefore, we provide immunocytochemical evidence that ferroportin is expressed by the epithelial cells of the choroid plexus and the ependymal cells lining the ventricles. These data suggest that sites of action for hepcidin include signaling the ventricular system for movement between brain and CSF. At this time, it cannot be determined if the lower levels of pro-hepcidin in the CSF represent a compensatory response to the decreased levels of iron in the brain or a defective signaling mechanism in RLS. Nonetheless, these data support the mounting evidence that there is a biological basis for RLS and the underlying mechanism involves iron management.

Novel urine hepcidin assay by mass spectrometry

The hepatic peptide hormone hepcidin is the central regulator of iron metabolism and mediator of anemia of inflammation. To date, only one specific immuno-dot assay to measure hepcidin in urine had been documented. Here we report an alternative approach for quantification of hepcidin in urine by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). Peptide peaks were detected corresponding to the 3 forms of hepcidin normally found in urine. The identity of the peptide peak equivalent to hepcidin-25 was confirmed using synthetic human hepcidin-25. Validation of our MS data on samples with various hepcidin levels showed a strong correlation with previous immuno-dot assay results (Spearman R = 0.9275, P &lt; .001). Most importantly, this hepcidin assay clearly discriminates between relevant clinical iron disorders. In conclusion, this novel MS urine hepcidin assay is easy to perform and available to a wide audience. This enables the implementation of hepcidin measurements in large clinical studies.

Using histamine (H1) antagonists, in particular atypical antipsychotics, to treat anemia of chronic disease via interleukin-6 suppression

Anemia of chronic disease (ACD) is a condition of decreased red cell mass secondary to some other chronic inflammatory condition. In ACD total body iron stores are normal, though serum iron is typically low secondary to iron sequestration by macrophages, and often iron supplementation is not an effective treatment for ACD for the same reason. The pathogenesis of ACD had been poorly understood, but recently there has been important progress: upregulation of interleukin-6 (Il-6) secondary to the underlying chronic inflammatory disease upregulates expression of the protein hepcidin. Upregulation of hepcidin causes anemia by a number of mechanisms: decreased intestinal absorption of iron from the duodenum, increased sequestration of iron by macrophages. Thus, downregulation of Il-6 may represent a most important treatment avenue for ACD. Anti-Il-6 antibodies might be a way to lower Il-6 levels, but such antibodies besides being expensive would have to be given intravenously or intramuscularly, and such large immunogenic molecules may not be appropriate in patients already with a chronic inflammatory condition. Here, we note that an immediately available and potentially effective treatment for ACD is to decrease Il-6 levels by histamine (H1) receptor antagonism, given that histamine acting through the H1 receptor is known to be a potent positive regulator of Il-6. Among the classes of medications that are H1 antagonists we point out that atypical antipsychotic medications such as olanzapine and quetiapine are among the most potent H1 antagonists, and can have simple daily dosing schedules and thus may be particularly useful in ACD.