Identification of TWSG1 as a second novel erythroid regulator of hepcidin expression in murine and human cells.

In thalassemia and other iron loading anemias, ineffective erythropoiesis and erythroid signaling molecules are thought to cause inappropriate suppression of a small peptide produced by hepatocytes named hepcidin. Previously, it was reported that the erythrokine GDF15 is expressed at very high levels in thalassemia and suppresses hepcidin expression. In this study, erythroblast expression of a second molecule named twisted gastrulation (TWSG1) was explored as a potential erythroid regulator of hepcidin.

Hepcidin--a potential novel biomarker for iron status in chronic kidney disease.

Background And Objectives: Hepcidin is a key regulator of iron homeostasis, but its study in the setting of chronic kidney disease (CKD) has been hampered by the lack of validated serum assays.

Design, Setting, Participants, & Measurements: This study reports the first measurements of bioactive serum hepcidin using a novel competitive ELISA in 48 pediatric (PCKD2-4) and 32 adult (ACKD2-4) patients with stages 2 to 4 CKD along with 26 pediatric patients with stage 5 CKD (PCKD5D) on peritoneal dialysis.

Results: When compared with their respective controls (pediatric median = 25.

Iron absorption in dysmetabolic iron overload syndrome is decreased and correlates with increased plasma hepcidin.

Background/aims: The dysmetabolic iron overload syndrome (DIOS) is a common disorder but its origin remains unclear.

Methods: A case-control study was conducted to compare intestinal absorption of iron in 16 men with DIOS (age 53 +/- 11 years, serum ferritin 750 +/- 372 microg/l, hepatic iron 78 +/- 25 micromol/g) and in 32 age-matched controls with normal body iron stores (16 overweight subjects and 16 lean subjects). Intestinal absorption was calculated as the area under the curve (AUC) of 58Fe administered orally and correlated with plasma hepcidin and with insulin resistance parameters including HOMA.

The molecular basis of hepcidin-resistant hereditary hemochromatosis.

The interaction between the hormone hepcidin and the iron exporter ferroportin (Fpn) regulates plasma iron concentrations. Hepcidin binds to Fpn and induces its internalization and degradation, resulting in decreased iron efflux from cells into plasma. Fpn mutations in N144, Y64N, and C326 residue cause autosomal dominant disease with parenchymal iron overload, apparently due to the resistance of mutant Fpn to hepcidin-mediated internalization.

Daily regulation of serum and urinary hepcidin is not influenced by submaximal cycling exercise in humans with normal iron metabolism.

Hepcidin and hemojuvelin (HJV) are two critical regulators of iron metabolism as indicated by the development of major iron overload associated to mutations in hepcidin and HJV genes. Hepcidin and HJV are highly expressed in liver and muscles, respectively. Intensive muscular exercise has been reported to modify serum iron parameters and to increase hepcidinuria.

Iron in innate immunity: starve the invaders.

Iron is essential for nearly all living organisms. Innate immunity effectively restricts iron availability to microbial invaders. Some microbes have evolved effective countermeasures that blunt the effect of iron restriction.

Differential Processing of {alpha}- and {beta}-Defensin Precursors by Matrix Metalloproteinase-7 (MMP-7).

Proteolytic processing of defensins is a critical mode of posttranslational regulation of peptide activity. Because mouse alpha-defensin precursors are cleaved and activated by matrix metalloproteinase-7 (MMP-7), we determined if additional defensin molecules, namely human neutrophil defensin pro-HNP-1 and beta-defensins, are targets for MMP-7. We found that MMP-7 cleaves within the pro-domain of the HNP-1 precursor, a reaction that does not generate the mature peptide but produces a 59-amino acid intermediate.

Immunoassay for human serum hepcidin.

We developed and validated the first serum enzyme-linked immunosorbent assay for hepcidin, the principal iron-regulatory hormone that has been very difficult to measure. In healthy volunteers, the 5% to 95% range of hepcidin concentrations was 29 to 254 ng/mL in men (n = 65) and 17 to 286 ng/mL in women (n = 49), with median concentrations 112 versus 65 (P < .001).

Involvement of hepcidin in the anemia of multiple myeloma.

Purpose: Hepcidin is a liver-produced peptide implicated in the anemia of inflammation. Because interleukin (IL)-6 is a potent inducer of hepcidin expression and its levels are elevated in multiple myeloma, we studied the role of hepcidin in the anemia of multiple myeloma.

Experimental Design: Urinary hepcidin and serum levels of IL-6, ferritin, C-reactive protein, tumor necrosis factor-alpha, and IL-1 beta were studied in newly diagnosed myeloma patients.

Hepcidin and iron-related gene expression in subjects with Dysmetabolic Hepatic Iron Overload.

Background/aims: Many patients with hepatic iron overload do not have identifiable mutations and often present with metabolic disorders and hepatic steatosis. Since the pathophysiology of Dysmetabolic Hepatic Iron Overload (DHIO) is still obscure, the aim of this study was to evaluate, in these patients, possible alterations in iron-related molecule expression.

Methods: Iron-related gene mRNA levels were determined by quantitative-PCR in liver biopsies of subjects with NAFLD without iron overload and patients with HFE-hemochromatosis, beta-thalassemia major and DHIO.

Iron homeostasis: fitting the puzzle pieces together.

Here, recent insights into iron homeostasis are highlighted. Three studies demonstrate the importance of the IRE-IRP system for enterocytes in balancing extracellular iron demand against cellular iron requirements, show that the hemochromatosis protein HFE exerts its iron-regulatory activity principally in hepatocytes by modulating the production of hepcidin, and provide strong support for a proposed mechanism of transcriptional regulation of hepcidin through a signaling cascade initiated by holotransferrin displacing HFE from transferrin receptor 1.

Measurement of urinary hepcidin levels by SELDI-TOF-MS in HFE-hemochromatosis.

Introduction: Insufficient production of hepcidin, the master regulator of iron metabolism, is recognized as the key pathogenetic feature of HFE-related hereditary hemochromatosis (HH). There is a growing interest in measuring the hepcidin levels, which may improve the diagnosis, prognostic evaluation and clinical management of HH. Nevertheless, few investigative tools are available: an immunodot method for urinary hepcidin developed by a single centre (UCLA), not yet ready for large-scale diffusion, and mass spectrometry (MS) based assays, such as surface-enhanced laser desorption/ionization time-of-flight (SELDI-TOF-MS).

Psychological stress downregulates epidermal antimicrobial peptide expression and increases severity of cutaneous infections in mice.

The skin is the first line of defense against microbial infection, and psychological stress (PS) has been shown to have adverse effects on cutaneous barrier function. Here we show that PS increased the severity of group A Streptococcus pyogenes (GAS) cutaneous skin infection in mice; this was accompanied by increased production of endogenous glucocorticoids (GCs), which inhibited epidermal lipid synthesis and decreased lamellar body (LB) secretion. LBs encapsulate antimicrobial peptides (AMPs), and PS or systemic or topical GC administration downregulated epidermal expression of murine AMPs cathelin-related AMP and beta-defensin 3.

Co-regulation and interdependence of the mammalian epidermal permeability and antimicrobial barriers.

Human epidermis elaborates two small cationic, highly hydrophobic antimicrobial peptides (AMP), beta-defensin 2 (hBD2), and the carboxypeptide cleavage product of human cathelicidin (hCAP18), LL-37, which are co-packaged along with lipids within epidermal lamellar bodies (LBs) before their secretion. Because of their colocalization, we hypothesized that AMP and barrier lipid production could be coregulated by altered permeability barrier requirements. mRNA and immunostainable protein levels for mBD3 and cathelin-related antimicrobial peptide (CRAMP) (murine homologues of hBD2 and LL-37, respectively) increase 1-8 hours after acute permeability barrier disruption and normalize by 24 hours, kinetics that mirror the lipid metabolic response to permeability barrier disruption.

Posttranslational processing of hepcidin in human hepatocytes is mediated by the prohormone convertase furin.

Hepcidin is encoded as an 84 amino acid prepropeptide containing a typical N-terminal 24 amino acid endoplasmic reticulum targeting signal sequence, and a 35 amino acid proregion (pro) with a consensus furin cleavage site immediately followed by the C-terminal 25 amino acid bioactive iron-regulatory hormone (mature peptide). We performed pulse-chase studies of posttranslational processing of hepcidin in human hepatoma HepG2 cells and in primary human hepatocytes induced with bone morphogenic protein (BMP-9). In some experiments, the cells were treated with the furin protease inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethylketone (CMK) or furin siRNA.

Soluble hemojuvelin is released by proprotein convertase-mediated cleavage at a conserved polybasic RNRR site.

As the principal iron-regulatory hormone, hepcidin plays an important role in systemic iron homeostasis. The regulation of hepcidin expression by iron loading appears to be unexpectedly complex and has attracted much interest. The GPI-linked membrane protein hemojuvelin (GPI-hemojuvelin) is an essential upstream regulator of hepcidin expression.

Functional analysis of the host defense peptide Human Beta Defensin-1: new insight into its potential role in cancer.

Although it is known that innate immunity is key for protecting the body against foreign agents such as bacteria, little is known about elements of the innate immune system that have anti-tumor activity. Human Beta Defensin-1 (hBD-1), an important component of the innate immune response, is lost at high frequencies in malignant prostatic tissue, while high levels of expression are maintained in adjacent benign regions. In prostate carcinoma, frequent genetic alterations occur in the 8p22-23 region and several studies indicate there may be multiple tumor suppressor genes present within this region.

Effects of plasma transfusion on hepcidin production in human congenital hypotransferrinemia.

Hepcidin is the key regulator of systemic iron homeostasis. We describe the modulation of hepcidin production induced by plasma transfusions in a patient with congenital hypotransferrinemia that offers a unique model in which to study the mechanism of hepcidin regulation by iron and erythropoiesis. Urinary hepcidin increased from zero at baseline, when hemoglobin and serum transferrin was low, to a maximum of 98 ng/mg creatinine on day 60, and subsequently decreased.

Blunted hepcidin response to oral iron challenge in HFE-related hemochromatosis.

Inadequate hepcidin synthesis leads to iron overload in HFE-related hemochromatosis. We explored the regulation of hepcidin by iron in 88 hemochromatosis patients (61 C282Y/C282Y, 27 C282Y/H63D) and 23 healthy controls by analyzing urinary hepcidin before and 24 hours after a 65-mg oral iron dose. Thirty-four patients were studied at diagnosis and had iron overload, and 54 patients were iron depleted.

High levels of GDF15 in thalassemia suppress expression of the iron regulatory protein hepcidin.

In thalassemia, deficient globin-chain production during erythropoiesis results in anemia. Thalassemia may be further complicated by iron overload (frequently exacerbated by blood transfusion), which induces numerous endocrine diseases, hepatic cirrhosis, cardiac failure and even death. Accumulation of iron in the absence of blood transfusions may result from inappropriate suppression of the iron-regulating peptide hepcidin by an erythropoietic mechanism.

Iron transferrin regulates hepcidin synthesis in primary hepatocyte culture through hemojuvelin and BMP2/4.

The peptide hormone hepcidin is the principal regulator of systemic iron homeostasis. We examined the pathway by which iron stimulates the production of hepcidin. In humans who ingested 65 mg of iron, the increase in transferrin saturation preceded by hours the increase in urinary hepcidin excretion.

Liver iron concentrations and urinary hepcidin in beta-thalassemia.

Background And Objectives: Patients with beta-thalassemia, like those with genetic hemochromatosis, develop iron overload due to increased iron absorption, and their iron burden is further exacerbated by transfusion therapy. Hepcidin, a hepatic hormone, regulates systemic iron homeostasis by inhibiting the absorption of iron from the diet and the recycling of iron by macrophages. In turn, hepcidin release is increased by iron loading and inhibited by erythropoietic activity.

The molecular mechanism of hepcidin-mediated ferroportin down-regulation.

Ferroportin (Fpn) is the only known iron exporter in vertebrates. Hepcidin, a peptide secreted by the liver in response to iron or inflammation, binds to Fpn, inducing its internalization and degradation. We show that after binding of hepcidin, Fpn is tyrosine phosphorylated at the plasma membrane.