Identification, characterization and expression analysis of hepcidin gene in sheep

Antimicrobial Peptides and Copper(II) Ions: Novel Therapeutic Opportunities

The emergence of new pathogens and multidrug resistant bacteria is an important public health issue that requires the development of novel classes of antibiotics. Antimicrobial peptides (AMPs) are a promising platform with great potential for the identification of new lead compounds that can combat the aforementioned pathogens due to their broad-spectrum antimicrobial activity and relatively low rate of resistance emergence. AMPs of multicellular organisms made their debut four decades ago thanks to ingenious researchers who asked simple questions about the resistance to bacterial infections of insects. Questions such as "Do fruit flies ever get sick?", combined with pioneering studies, have led to an understanding of AMPs as universal weapons of the immune system. This review focuses on a subclass of AMPs that feature a metal binding motif known as the amino terminal copper and nickel (ATCUN) motif. One of the metal-based strategies of hosts facing a pathogen, it includes wielding the inherent toxicity of copper and deliberately trafficking this metal ion into sites of infection. The sudden increase in the concentration of copper ions in the presence of ATCUN-containing AMPs (ATCUN-AMPs) likely results in a synergistic interaction. Herein, we examine common structural features in ATCUN-AMPs that exist across species, and we highlight unique features that deserve additional attention. We also present the current state of knowledge about the molecular mechanisms behind their antimicrobial activity and the methods available to study this promising class of AMPs.

Expression of iron regulatory proteins in full-term swine placenta

In swine, even though the pregnant sows were with iron abundance, the inborn iron reserve of piglets was compromised. This indicates the insufficiency of molecular machinery involved in local placental iron flux. Here, we investigated the expression of iron regulatory proteins like hepcidin and ferroportin and also their association with iron reserve, inflammation and oxidative stress in placenta of full-term pregnant sows (n = 6). Amplification and sequencing of placental DNA confirmed the presence of hepcidin (MN579557) and ferroportin (MN565887) sequences and their 100% identity with existing GenBank data. Real-time amplification of placental mRNA revealed significant higher expression of hepcidin (p < .05) than ferroportin. Western blot analysis of placental tissues revealed specific bands for both hepcidin (~8 kDa) and ferroportin (~62 kDa) molecules. Immunohistochemistry revealed the immunoreactivity for both proteins in the cytoplasm and membrane of trophoblastic cells of the placenta. Hepcidin and ferroportin expressions were positively associated with placental non-haem iron reserve (p < .0001; p = .033), lipid peroxidation (p = .0060; p < .0001) and reactive oxygen species level (p = .0092; p = .0292). Hepcidin expression was positively associated with interleukin - 6 (p = .0002) and interferon gamma (p < .0001) expressions but ferroportin expression was negatively associated with interleukin-6 (p = .0005), interleukin-1β (p = .0226) and interferon gamma (p = .0059) expressions. This indicates hepcidin and ferroportin may have a role in controlling the local placental iron flux by acting as a molecular bridge between iron trafficking and inflammation.

Hepcidin cDNA evolution in vertebrates

Hepcidin, belonging to the β-defensin family, was isolated for the first time from plasma and human urine. It is a cationic peptide, rich in cysteine bound with four disulfide bridges, which plays a major role in innate immunity and iron homeostasis. Some vertebrate species have multiple hepcidin homolog genes and each contains only one copy that functions as an iron regulator except hepcidin sequences in the pigeon (Columba livia). The aim of this chapter is to investigate the molecular evolution of several hepcidin gene from searches of the literature and public genomic databases from 17 different species, all among the vertebrates.

Cardiomyocyte hepcidin: From intracellular iron homeostasis to physiological function

Cellular iron is required for the utilization of oxygen in the cell. Iron in iron-sulfur and heme groups is required for electron transfer and oxygen activation in oxidative phosphorylation, while labile free iron is required for oxygen activation by dioxygenases, and as a catalyst for redox signaling. At the same time, this reactivity with oxygen underpins the production of cell-damaging free radicals in the presence of excess iron. Because the cardiac cell is a major site of oxygen flux, it requires tight control of intracellular iron levels. Until recently, such control was thought to be mediated predominantly by the action of iron regulatory proteins. However, new evidence reveals that cardiomyocyte hepcidin is indispensable for the control of intracellular iron levels, normal metabolism and heart function. This new evidence highlights the need for better understanding of the regulation of cardiomyocyte hepcidin in health and disease.

Expression of hepcidin and ferroportin in full term placenta of pregnant cows

Hepcidin (HEP) and ferroportin (FPN) play a central role in systemic iron homeostasis. The HEP/FPN axis controls both extracellular iron concentration and total body iron levels. HEP is synthesized mainly by hepatocytes and controls the absorption of dietary iron and the distribution of iron to the various cell types; its synthesis is regulated by both iron and innate immunity. FPN is a membrane protein and the major exporter of iron from mammalian cells, including iron recycling macrophages, iron absorbing duodenal enterocytes, and iron storing hepatocytes. HEP limits the pool of extracellular iron by binding FPN and mediating its degradation, thus preventing its release from intracellular sources. Here we investigated, for the first time, the molecular and morphological expression of HEP and FPN in placenta of pregnant cows at term. Their expression has been evaluated investigating their mRNAs by reverse transcriptase PCR (RT-PCR). Sequencing of related amplicons revealed a 100% identity with HEP and FPN sequences from Bos taurus as reported in the GeneBank (mRNASequence ID: NM_001114508.2 and ID: NM_001077970.1, respectively). HEP and FPN proteins have also been revealed by Western blot analysis and immunohistochemistry. The strongest immunoreactivity for both proteins was observed in the cytoplasm of the trophoblastic cells of the villi and the caruncular crypts of the placentome. Hep mRNA was more representative in caruncular rather cotyledonar areas; on the contrary, Fpn mRNA was more expressed in cotyledonar rather than in caruncular areas. Transcripts of ferritin, transferrin and its receptor have been also documented by real time RT-PCR. HEP and FPN placental proteins may play a dual role. HEP/FPN axis seems to have a central role in infections, with microorganisms within macrophages or that survive in the bloodstream or other cellular spaces. In addition, HEP may be responsible for iron flux regulation as a molecular bridge for iron trafficking and response to infection. FPN may also have a significant role for embryonic development, growth and organogenesis.

Insights into the antimicrobial properties of hepcidins: advantages and drawbacks as potential therapeutic agents

The increasing frequency of multi-drug resistant microorganisms has driven research into alternative therapeutic strategies. In this respect, natural antimicrobial peptides (AMPs) hold much promise as candidates for the development of novel antibiotics. However, AMPs have some intrinsic drawbacks, such as partial degradation by host proteases or inhibition by host body fluid composition, potential toxicity, and high production costs. This review focuses on the hepcidins, which are peptides produced by the human liver with a known role in iron homeostasis, as well by numerous other organisms (including fish, reptiles, other mammals), and their potential as antibacterial and antifungal agents. Interestingly, the antimicrobial properties of human hepcidins are enhanced at acidic pH, rendering these peptides appealing for the design of new drugs targeting infections that occur in body areas with acidic physiological pH. This review not only considers current research on the direct killing activity of these peptides, but evaluates the potential application of these molecules as coating agents preventing biofilm formation and critically assesses technical obstacles preventing their therapeutic application.

A competitive enzyme-linked immunosorbent assay specific for murine hepcidin-1: correlation with hepatic mRNA expression in established and novel models of dysregulated iron homeostasis

Mice have been essential for distinguishing the role of hepcidin in iron homeostasis. Currently, investigators monitor levels of murine hepatic hepcidin-1 mRNA as a surrogate marker for the bioactive hepcidin protein itself. Here, we describe and validate a competitive, enzyme-linked immunosorbent assay that quantifies hepcidin-1 in mouse serum and urine. The assay exhibits a biologically relevant lower limit of detection, high precision, and excellent linearity and recovery. We also demonstrate correlation between serum and urine hepcidin-1 values and validate the competitive enzyme-linked immunosorbent assay by analyzing plasma hepcidin response of mice to physiological challenges, including iron deficiency, iron overload, acute blood loss, and inflammation. Furthermore, we analyze multiple murine genetic models of iron dysregulation, including β-thalassemia intermedia (Hbb(th3/+)), hereditary hemochromatosis (Hfe(-/-), Hjv(-/-), and Tfr2(Y245X/Y245X)), hypotransferrinemia (Trf(hpx/hpx)), heterozygous transferrin receptor 1 deficiency (Tfrc(+/-)) and iron refractory iron deficiency anemia (Tmprss6(-/-) and Tmprss6(hem8/hem8)). Novel compound iron metabolism mutants were also phenotypically characterized here for the first time. We demonstrate that serum hepcidin concentrations correlate with liver hepcidin mRNA expression, transferrin saturation and non-heme liver iron. In some circumstances, serum hepcidin-1 more accurately predicts iron parameters than hepcidin mRNA, and distinguishes smaller, statistically significant differences between experimental groups.

Molecular characterization of a novel hepcidin (HepcD) from Camelus dromedarius. Synthetic peptide forms exhibit antibacterial activity

Hepcidin is a cysteine-rich peptide widely characterized in immunological processes and antimicrobial activity in several vertebrate species. Obviously, this hormone plays a central role in the regulation of systemic iron homeostasis. However, its role in camelids' immune response and whether it is involved in antibacterial immunity have not yet been proven. In this study, we characterized the Arabian camel hepcidin nucleotide sequence with an open reading frame of 252 bp encoding an 83-amino acid preprohepcidin peptide. Eight cysteine key residues conserved in all mammalian hepcidin sequences were identified. The model structure analysis of hepcidin-25 peptide showed a high homology structure and sequence identity to the human hepcidin. Two different hepcidin-25 analogs manually synthesized by SPPS shared significant cytotoxic capacity toward the Gram-negative bacterium Escherichia coli American Type Culture Collection (ATCC) 8739 as well as the Gram-positive bacteria Bacillus subtilis ATCC 11779 and Staphylococcus aureus ATCC 6538 in vitro. The three disulfide bridges hepcidin analog demonstrated bactericidal activity, against B. subtilis ATCC 11779 and S. aureus ATCC 6538 strains, at the concentration of 15 μM (50 µg/ml) or above at pH 6.2. This result correlates with the revealed structural features suggesting that camel hepcidin is proposed to be involved in antibacterial process of innate immune response.

Characterization of the hepcidin gene in eight species of bats

Hemochromatosis, or iron storage disease, has been associated with significant liver disease and mortality in captive Egyptian fruit bats (Rousettus aegyptiacus). The physiologic basis for this susceptibility has not been established. In humans, a deficiency or resistance to the iron regulatory hormone, hepcidin has been implicated in the development of hereditary hemochromatosis. In the present study, we compared the coding sequence of the hepcidin gene in eight species of bats representing three distinct taxonomic families with diverse life histories and dietary preferences. Bat hepcidin mRNA encoded a 23 amino acid signal peptide, a 34 or 35 amino acid pro-region, and a 25 amino acid mature peptide, similar to other mammalian species. Differences in the sequence of the portion of the hepcidin gene that encodes the mature peptide that might account for the increased susceptibility of the Egyptian fruit bat to iron storage disease were not identified. Variability in gene sequence corresponded to the taxonomic relationship amongst species.

Artificial synthesis of swine hepcidin gene and expression in Pichia pastoris

In order to express swine hepcidin gene in Pichia pastoris, a DNA fragment coding hepcidin gene was synthesized with adaptation to yeast codon usage of highly expressed genes. A Kex2 signal cleavage site was fused in the 5' end of the DNA fragment for getting a peptide with the same N-end as native hepcidin. The 96-bp DNA fragment was ligated into the expression plasmid of pGAPZaA to construct pGAPZaA-hepcidin vector, which was transferred into P. pastoris (X33) to express hepcidin gene for extracellular secretion of protein at 86 µg/mL. A band of 2.76 kD molecular mass was detected by Tricine sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) analysis. Through antibacterial assay, the expressed hepcidin displayed obvious antibacterial activity. The minimal inhibitory concentration (MIC) was 5.38 and 2.69 µg/mL for Staphylococcus aureus and Bacillus subtilis prolification inhibitions, respectively.

Molecular cloning and expression analysis of liver-expressed antimicrobial peptide 1 (LEAP-1) and LEAP-2 genes in the blunt snout bream (Megalobrama amblycephala)

Liver-expressed antimicrobial peptide 1 (LEAP-1) and LEAP-2 are widespread in fish and extremely important components of the host innate immune system. In this study, full-length cDNAs of LEAP-1 and LEAP-2 were cloned and sequenced from blunt snout bream, Megalobrama amblycephala. The open reading frames (ORF) of LEAP-1 and LEAP-2 genes encode putative peptides of 94 and 92 amino acids, which possess eight and four conserved cysteine residues, respectively. The homologous identities of deduced amino acid sequences show that the LEAP-1 and LEAP-2 of blunt snout bream share considerable similarity with those of grass carp. The mRNA expressions of LEAP-1 and LEAP-2 were detectable at different early developmental stages of blunt snout bream and varied with embryonic and larval growth. LEAP-1 and LEAP-2 were expressed in a wide range of adult tissues, with the highest expression levels in the liver and midgut, respectively. Bacterial challenge experiments showed that the levels of LEAP-1 and LEAP-2 mRNA expression were up-regulated in the liver, spleen, gill and brain of juvenile blunt snout bream. These results indicate that the LEAP-1 and LEAP-2 may play important roles in early development of embryos and fry, and may contribute to the defense against the pathogenic bacterial invasion. This study will further our understanding of the function of LEAP-1 and LEAP-2 and the molecular mechanism of innate immunity in teleosts.

Alcohol exposure during late ovine gestation alters fetal liver iron homeostasis without apparent dysmorphology

High levels of alcohol (ethanol) exposure during fetal life can affect liver development and can increase susceptibility to infection after birth. Our aim was to determine the effects of a moderate level of ethanol exposure in late gestation on the morphology, iron status, and inflammatory status of the ovine fetal liver. Pregnant ewes were chronically catheterized at 91 days of gestation (DG; term ∼145 DG) for daily intravenous infusion of ethanol (0.75 g/kg maternal body wt; n = 8) or saline ( n = 7) over 1 h from 95 to 133 DG. At necropsy (134 DG), fetal livers were collected for analysis. Liver weight, general liver morphology, hepatic cell proliferation and apoptosis, perivascular collagen deposition, and interleukin ( IL) -1β, IL-6, or IL-8 mRNA levels were not different between groups. However, ethanol exposure led to significant decreases in hepatic content of ferric iron and gene expression of the iron-regulating hormone hepcidin and tumor necrosis factor ( TNF) -α (all P < 0.05). In the placenta, there was no difference in transferrin receptor, divalent metal transporter 1, and ferritin mRNA levels; however, ferroportin mRNA levels were increased in ethanol-exposed animals ( P < 0.05), and ferroportin protein tended to be increased ( P = 0.054). Plasma iron concentration was not different between control and ethanol-exposed groups; control fetuses had significantly higher iron concentrations than their mothers, whereas maternal and fetal iron concentrations were similar in ethanol-exposed animals. We conclude that daily ethanol exposure during the third-trimester-equivalent in sheep does not alter fetal liver morphology; however, decreased fetal liver ferric iron content and altered hepcidin and ferroportin gene expression indicate that iron homeostasis is altered.

Role of hepcidin in iron metabolism and potential clinical applications

The relatively recent discovery of hepcidin has stimulated renewed research interest in iron metabolism and iron-related disorders, emphasizing the importance of this hormone in many normal and pathologic processes. Important questions still remain to be answered; however, research to date offers promising diagnostic and therapeutic implications for both humans and veterinary species.

Buffalo hepcidin: characterization of cDNA and study of antimicrobial property

Hepcidin, a novel gene encoded, 25 residue, 2-3 KDa cysteine rich cationic peptide synthesized in liver cells play an important role in iron metabolism in addition to its antimicrobial activity. In this study hepcidin cDNA expressed on hepatocytes of Bubalus bubalis has been characterized and the antibacterial activity of buffalo hepcidin analog has been determined. The complete buffalo hepcidin sequence is of 324 bp and have an ORF of 249 nucleotides from 14 to 262. The sequence analysis at nucleotide level showed homology of 98.0% with cattle, 84.3% with pig, whereas with human, chimpanzee and gorilla 80.3%, 80.7% and 81.5% respectively. The percent identity of buffalo hepcidin cDNA to that of japanese macaque, dog, gibbon, mouse and norway rat are81.9%, 79.9%, 79.9%, 67.9% and 65.9% respectively. The hepcidin cDNA of buffalo and cattle showed a total difference of five nucleotides at position 15, 108, 225, 240 and 246 with no difference in deduced amino acid sequence. The base A(15), C(108), A(225), C(240), A(246) in cattle are replaced by G(15), G(108), G(225), T(240) and G(246) respectively in buffalo. The deduced amino acid sequence of buffalo preprohepcidin consists of 82 amino acids containing 10 strongly basic, 3 strongly acidic, 27 hydrophobic and 29 polar amino acids. The predicted molecular weight and isoelectric point (P(I)) for the peptide is 8883.67 Daltons and 8.804 respectively. Phylogenetic analysis both at nucleotide and amino acid level indicate that buffalo and cattle hepcidin sequences comprises one clad which is more closely related to pig compared to human. The chemically synthesized analog of buffalo hepcidin using Fmoc chemistry in solid phase had antibacterial activity.