Hepcidin Deficiency Protects Against Atherosclerosis Malhotra, Rajeev; Wunderer, Florian; Barnes, Hanna J ...
Arteriosclerosis, thrombosis, and vascular biology,
02/2019, Letnik:
39, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Objective- Inflammatory stimuli enhance the progression of atherosclerotic disease. Inflammation also increases the expression of hepcidin, a hormonal regulator of iron homeostasis, which decreases ...intestinal iron absorption, reduces serum iron levels and traps iron within macrophages. The role of macrophage iron in the development of atherosclerosis remains incompletely understood. The objective of this study was to investigate the effects of hepcidin deficiency and decreased macrophage iron on the development of atherosclerosis. Approach and Results- Hepcidin- and LDL (low-density lipoprotein) receptor-deficient ( Hamp
/ Ldlr
) mice and Hamp
/ Ldlr
control mice were fed a high-fat diet for 21 weeks. Compared with control mice, Hamp
/ Ldlr
mice had decreased aortic macrophage activity and atherosclerosis. Because hepcidin deficiency is associated with both increased serum iron and decreased macrophage iron, the possibility that increased serum iron was responsible for decreased atherosclerosis in Hamp
/ Ldlr
mice was considered. Hamp
/ Ldlr
mice were treated with iron dextran so as to produce a 2-fold increase in serum iron. Increased serum iron did not decrease atherosclerosis in Hamp
/ Ldlr
mice. Aortic macrophages from Hamp
/ Ldlr
mice had less labile free iron and exhibited a reduced proinflammatory (M1) phenotype compared with macrophages from Hamp
/ Ldlr
mice. THP1 human macrophages treated with an iron chelator were used to model hepcidin deficiency in vitro. Treatment with an iron chelator reduced LPS (lipopolysaccharide)-induced M1 phenotypic expression and decreased uptake of oxidized LDL. Conclusions- In summary, in a hyperlipidemic mouse model, hepcidin deficiency was associated with decreased macrophage iron, a reduced aortic macrophage inflammatory phenotype and protection from atherosclerosis. The results indicate that decreasing hepcidin activity, with the resulting decrease in macrophage iron, may prove to be a novel strategy for the treatment of atherosclerosis.
Iron is an essential molecule for biological processes, but its accumulation can lead to oxidative stress and cellular death. Due to its oxidative effects, iron accumulation is implicated in the ...process of aging and neurodegenerative diseases. However, the mechanism for this increase in iron with aging, and whether this increase is localized to specific cellular compartment(s), are not known. Here, we measured the levels of iron in different tissues of aged mice, and demonstrated that while cytosolic non-heme iron is increased in the liver and muscle tissue, only the aged brain cortex exhibits an increase in both the cytosolic and mitochondrial non-heme iron. This increase in brain iron is associated with elevated levels of local hepcidin mRNA and protein in the brain. We also demonstrate that the increase in hepcidin is associated with increased ubiquitination and reduced levels of the only iron exporter, ferroportin-1 (FPN1). Overall, our studies provide a potential mechanism for iron accumulation in the brain through increased local expression of hepcidin, and subsequent iron accumulation due to decreased iron export. Additionally, our data support that aging is associated with mitochondrial and cytosolic iron accumulation only in the brain and not in other tissues.
We aimed to identify associations between erythroferrone (ERFE), a regulator of hepcidin 25, and biomarkers of erythropoiesis and iron metabolism. We also aimed to determine the effects of ...erythropoiesis-stimulating agents (ESA), continuous erythropoietin receptor activator (CERA) and darbepoetin-α (DA) on ERFE production in patients on hemodialysis (HD).
Blood samples were obtained from 59 patients before HD sessions on day 0 (baseline). Twenty patients who were injected with either CERA (N = 10) or DA (N = 10) at the end of the dialysis week (day 0), who had ferritin ≥ 100 ng/mL and/or transferrin saturation ≥ 20%, and hemoglobin > 9 g/dL were selected from among the 59 patients. Blood was sampled serially before HD sessions on days 3, 5, 7 from patients on DA and on the same days plus day 14 from those on CERA.
Levels of ERFE correlated inversely with those of hepcidin 25 and ferritin, and positively with those of soluble transferrin receptor. The hepcidin 25: ERFE ratio and hepcidin 25 levels positively correlated with ferritin levels. Levels of ERFE significantly increased from day 3 of treatment with DA and CERA and decreased by days 7 and 14, respectively. Erythropoiesis-stimulating agents concomitantly decreased levels of hepcidin 25 as those of ERFE increased.
We identified a novel association between ESA and ERFE in patients on HD. Both DA and CERA increased levels of ERFE that regulated hepcidin 25 and led to iron mobilization from body stores during erythropoiesis.
Iron is a trace element important for the proper folding and function of various proteins. Physiological regulation of iron stores is of critical importance for RBC production and antimicrobial ...defense. Hepcidin is a key regulator of iron levels within the body. Under conditions of iron deficiency, hepcidin expression is reduced to promote increased iron uptake from the diet and release from cells, whereas during conditions of iron excess, induction of hepcidin restricts iron uptake and movement within the body. The cytokine IL-6 is well established as an important inducer of hepcidin. The presence of this cytokine during inflammatory states can induce hepcidin production, iron deficiency, and anemia. In this study, we show that IL-22 also influences hepcidin production in vivo. Injection of mice with exogenous mouse IgG1 Fc fused to the N terminus of mouse IL-22 (Fc-IL-22), an IL-22R agonist with prolonged and enhanced functional potency, induced hepcidin production, with a subsequent decrease in circulating serum iron and hemoglobin levels and a concomitant increase in iron accumulation within the spleen. This response was independent of IL-6 and was attenuated in the absence of the IL-22R-associated signaling kinase, Tyk2. Ab-mediated blockade of hepcidin partially reversed the effects on iron biology caused by IL-22R stimulation. Taken together, these data suggest that exogenous IL-22 regulates hepcidin production to physiologically influence iron usage.
Hepcidin is an antimicrobial peptide and a regulator of iron homeostasis. In turbot (Scophthalmus maximus), two types of hepcidins have been identified, which share approximately 50% sequence ...identity. In this study, we examined the antimicrobial potentials of the two hepcidins in the form of synthesized peptides, SmHep1P and SmHep2P. We found that SmHep1P and SmHep2P exhibited apparent bactericidal activities against both Gram-positive and Gram-negative bacteria in a dose-dependent manner. The bactericidal effect of SmHep1P was stronger against Gram-positive bacteria, while the bactericidal effect of SmHep2P was stronger against Gram-negative bacteria. Fluorescence and electron microscopy showed that both peptides were able to bind to the target bacterial cells and alter the surface structure of the cells. In vitro studies showed that SmHep1P and SmHep2P reduced bacterial invasion into cultured fish cells. In vivo studies showed that turbot administered with SmHep1P and SmHep2P exhibited significantly enhanced resistance against bacterial and viral infection. In both in vivo and in vitro studies, the antimicrobial activities of SmHep2P were in most cases significantly stronger than those of SmHep1P. Together these results indicate that the two hepcidins of turbot most likely possess antimicrobial properties and play a role in the innate immune defense against bacterial and viral pathogens.
•SmHep1P and SmHep2P are the mature peptides of two hepcidins from turbot.•SmHep1P and SmHep2P exhibited bactericidal activities.•Both peptides bound to and altered the surface structure of target bacterial cells.•SmHep1P and SmHep2P reduced viable bacterial cells in host cell culture.•SmHep1P and SmHep2P enhanced turbot resistance to bacterial and viral infection.
The current treatments applied in aquaculture to limit disease dissemination are mostly based on the use of antibiotics, either as prophylactic or therapeutic agents, with vaccines being available ...for a limited number of fish species and pathogens. Antimicrobial peptides are considered as promising novel substances to be used in aquaculture, due to their antimicrobial and immunomodulatory activities. Hepcidin, the major iron metabolism regulator, is found as a single gene in most mammals, but in certain fish species, including the European sea bass (
), two different hepcidin types are found, with specialized roles: the single type 1 hepcidin is involved in iron homeostasis trough the regulation of ferroportin, the only known iron exporter; and the various type 2 hepcidins present antimicrobial activity against a number of different pathogens. In this study, we tested the administration of sea bass derived hepcidins in models of infection and iron overload. Administration with hamp2 substantially reduced fish mortalities and bacterial loads, presenting itself as a viable alternative to the use of antibiotics. On the other hand, hamp1 seems to attenuate the effects of iron overload. Further studies are necessary to test the potential protective effects of hamp2 against other pathogens, as well as to understand how hamp2 stimulate the inflammatory responses, leading to an increased fish survival upon infection.
Iron homeostasis is strictly governed in mammals; however, disordered iron metabolism (such as excess iron burden) is recognized as a risk factor for various types of diseases including cancers. ...Burgeoning evidence indicates that the central signaling of iron homeostasis, the hepcidin–ferroportin axis, is misregulated in cancers. Nonetheless, the mechanisms of misregulated expression of iron-related genes along this signaling in cancers remain largely unknown. In the current study, we found increased levels of serum hepcidin in breast cancer patients. Reduction of hepatic hepcidin through administration of heparin restrained tumorigenic properties of breast tumor cells. Mechanistic investigation revealed that increased iron, bone morphogenetic protein-6 (BMP6) and interleukin-6 (IL-6) jointly promoted the synthesis of hepatic hepcidin. Tumor hepcidin expression was marginally increased in breast tumors relative to adjacent tissues. In contrast, tumor ferroportin concentration was greatly reduced in breast tumors, especially in malignant tumors, compared to adjacent tissues. Elevation of ferroportin concentration inhibited cell proliferation in vitro and in vivo by knocking down tumor hepcidin expression. Additionally, increased IL-6 was demonstrated to jointly enhance the tumorigenic effects of iron through enforcing cell growth. Our combined data overall deciphered the machinery that altered the hepcidin–ferroportin signaling in breast cancers. Thus, targeting the hepcidin–ferroportin signaling would represent a promising therapeutics to restrain breast cancer growth.
•Diminished tumor growth upon hepcidin deficit.•Iron, BMP6 and IL-6 jointly govern hepcidin in breast cancers.•Excessive iron greatly induces BMP6 synthesis in breast cancers.•Tumor ferroportin is reduced in breast tumors.
Summary
Hepcidin (HAMP) synthesis is suppressed by erythropoiesis to increase iron availability for red blood cell production. This effect is thought to result from factors secreted by erythroid ...precursors. Growth differentiation factor 11 (GDF11) expression was recently shown to increase in erythroid cells of β‐thalassaemia, and decrease with improvement in anaemia. Whether GDF11 regulates hepatic HAMP production has never been experimentally studied. Here, we explore GDF11 function during erythropoiesis‐triggered HAMP suppression. Our results confirm that exogenous erythropoietin significantly increases Gdf11 as well as Erfe (erythroferrone) expression, and Gdf11 is also increased, albeit at a lower degree than Erfe, in phlebotomized wild type and β‐thalassaemic mice. GDF11 is expressed predominantly in erythroid burst forming unit‐ and erythroid colony‐forming unit‐ cells during erythropoiesis. Exogeneous GDF11 administration results in HAMP suppression in vivo and in vitro. Furthermore, exogenous GDF11 decreases BMP‐SMAD signalling, enhances SMAD ubiquitin regulatory factor 1 (SMURF1) expression and induces ERK1/2 (MAPK3/1) signalling. ERK1/2 signalling activation is required for GDF11 or SMURF1‐mediated suppression in BMP‐SMAD signalling and HAMP expression. This research newly characterizes GDF11 in erythropoiesis‐mediated HAMP suppression, in addition to ERFE.
Cholangiocarcinoma (CHOL), the second most common malignant liver tumor, is clinically heterogeneous. In this study, we used gene expression profiles of CHOL obtained from The Cancer Genome Atlas ...(TCGA) and the Gene Expression Omnibus (GEO) databases to identify novel mutation signatures in CHOL. Hepcidin antimicrobial peptide (HAMP) was identified as a novel diagnostic biomarker for CHOL using the intersection of mutation analysis and receiver operating characteristic (ROC) analysis. We then explored the expression signatures of HAMP in CHOL. HAMP-related differentially expressed genes (DEGs) were selected for the identification of hub genes related to HAMP and for prognostic prediction model analysis. Gene set enrichment analysis (GSEA) showed that the HAMP-related DEGs were mainly enriched for signaling pathways related to cholangiocarcinoma development. Through immunohistochemistry validation, clinical cohorts analysis, and TCGA analysis, we investigated the association between HAMP and clinical parameters and found that decreased HAMP expression was correlated with advanced pathological grade and poor prognosis. Besides, we estimated the immune infiltration level in CHOL and its relationship with HAMP expression. The proportion of tumor-infiltrating cells revealed that gamma delta T cells and monocytes were positively correlated with HAMP expression. Besides, HAMP was also correlated with chemokine, CCL16. This evidence suggested that HAMP might contribute to immune activation in the CHOL microenvironment. Therefore, HAMP may play a synergistic role with these immune cells and chemokines to inhibit CHOL development. HAMP serves as a valuable biomarker in CHOL and is closely correlated with its progression.
Iron delivery to the plasma is closely coupled to erythropoiesis, the production of red blood cells, as this process consumes most of the circulating plasma iron. In response to hemorrhage and other ...erythropoietic stresses, increased erythropoietin stimulates the production of the hormone erythroferrone (ERFE) by erythrocyte precursors (erythroblasts) developing in erythropoietic tissues. ERFE acts on the liver to inhibit bone morphogenetic protein (BMP) signaling and thereby decrease hepcidin production. Decreased circulating hepcidin concentrations then allow the release of iron from stores and increase iron absorption from the diet. Guided by evolutionary analysis and Alphafold2 protein complex modeling, we used targeted ERFE mutations, deletions, and synthetic ERFE segments together with cell-based bioassays and surface plasmon resonance to probe the structural features required for bioactivity and BMP binding. We define the ERFE active domain and multiple structural features that act together to entrap BMP ligands. In particular, the hydrophobic helical segment 81 to 86 and specifically the highly conserved tryptophan W82 in the N-terminal region are essential for ERFE bioactivity and Alphafold2 modeling places W82 between two tryptophans in its ligands BMP2, BMP6, and the BMP2/6 heterodimer, an interaction similar to those that bind BMPs to their cognate receptors. Finally, we identify the cationic region 96-107 and the globular TNFα-like domain 186-354 as structural determinants of ERFE multimerization that increase the avidity of ERFE for BMP ligands. Collectively, our results provide further insight into the ERFE-mediated inhibition of BMP signaling in response to erythropoietic stress.
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