Ferritin Gene Research Articles

Iron overload alters iron-regulatory genes and proteins, down-regulates osteoblastic phenotype, and is associated with apoptosis in fetal rat calvaria cultures

Iron overload has been implicated in decreased bone mineral density. However, the effect of iron overload on osteoblast lineage cells remains poorly understood. The purpose of this study was to examine osteoblast differentiation, function, and apoptosis in iron-loaded cells from fetal rat calvaria. Cells were incubated with media supplemented with 0–10 μM ferrous sulfate (FeSO 4) during differentiation (days 6–20). Intracellular iron status was assessed by measuring iron content in cell layers and changes in transferrin receptor (TrfR) and ferritin gene and protein expression. Osteoblast differentiation and function were evaluated by measuring osteoblast phenotypic gene markers and capacity of cultures to form mineralized bone nodules. Apoptotic hallmarks were evaluated by microscopy. A 2.3-fold increase in media iron concentration resulted in saturable accumulation of iron in the cell layer 20-fold higher than control ( p < 0.05) by mid-differentiation (day 15, D15). Iron accumulation resulted in rapid and sustained down-regulation of TrfR gene and protein levels (within 24 h) and up-regulation of light and heavy chain ferritin protein levels at late differentiation (day 20, D20). Concurrently, osteoblast phenotype gene markers were suppressed by D15 and a decreased number of mineralized nodules at D20 were observed. Apoptotic events were observed within 24 h of iron loading. These results provide evidence that iron overload alters iron metabolism and suppresses differentiation and function of cells in the osteoblast lineage associated with increased apoptosis.

Full-length cDNA Cloning and Tissues Expression Analysis of Ferritin Gene from &lt;I&gt;Acipenser sinensis&lt;/I&gt;

According to the conserved sequence of the ferritin gene, a homologous sequence was obtained from the EST database through a BLAST search against the GenBank database. This sequence was amplified with the method of RT-PCR, false sequencing was corrected, and full length cDNA of the ferritin subunit from the Chinese sturgeon was obtained. After being submitted to the GenBank database, the sequence accession number EU348782 was assigned. With the length of 896 bp, this cDNA includes entire coding regions of 53 1bp, which encodes 176 amino acids (aa). The molecular weight was predicted to be 20339.9Mr and the theoretical isoelectric point 5.66. It shares 82.9% protein sequence homology with the ferritin of the Atlantic salmon. This gene is expressed in many organs of the Chinese sturgeon, for example, the liver, pancreas, muscle, brain, heart and gastric mucosa. The highest expression level was found in the pancreas and the heart, while the muscular tissue showed the lowest. Homology modeling was used to predict the 3-D structure of the protein, which included 5 alpha helices and 10 turns. The ferritin protein structure could be overlapped and showed high similarity with that of human, frog and bacteria. It was revealed that this kind of ferritin was highly conserved in structure and function.

TOWARDS THE PRODUCTION OF STRESS TOLERANT GRAPEVINE CULTIVARS

The biotic and abiotic stresses are among the major limiting factors in plant productivity. To overcome these difficulties molecular breeding methods have recently been widely applied to improve the stress- and disease resistance of grapevine cultivars. To this end we tested the suitability of a ferritin gene derived from Medicago sativa (MsFerr). We propose that by sequestering the intracellular iron involved in generation of the very reactive hydroxyl radicals through Fenton-reaction, the increased overall ferritin concentration results in increased protection of plant cells from oxidative damage induced by a wide range of stresses. We have improved the existing regeneration and transformation protocols. In our experiments we raised the number of regenerated plants due to the application of 1 μM benzyladenine (BA). The plant regeneration was supported by the maintenance of plant material on half MS medium without selection agent (after two-year selection), and by cut of abnormal embryos under the hypocotyl. The independent regenerated transformants were tested by PCR, qPCR, Western blot, and were used for various abiotic stress tolerance experiments.

Micro-analytical, physiological and molecular aspects of Fe acquisition in leaves of Fe-deficient tomato plants re-supplied with natural Fe-complexes in nutrient solution

It is well known that in the rhizosphere soluble Fe sources available for plants are mainly a mixture of complexes between the micronutrient and organic ligands such as organic acids and phytosiderophores (PS) released by roots, microbial siderophores as well as fractions of humified organic matter. In the present work, mechanisms of Fe acquisition operating at the leaf level of plants fed with different Fe-complexes were investigated at the micro-analytical, physiological and molecular levels. Fe-deficient tomato plants (Solanum Lycopersicum L., cv. ‘Marmande’) were fed for 24 h with a solution (pH 7.5) containing 1 µM Fe as Fe-PS, Fe-citrate or Fe-WEHS. Thereafter, leaf tissue was used for the visualization of Fe distribution, measurements of Fe content, reduction and uptake, and evaluation of expression of Fe-chelate reductase (LeFRO1), Fe-transporter (LeIRT1) and Ferritin (Ferritin2) genes. Leaf discs isolated from Fe-deficient plants treated for 24 h with Fe-WEHS developed higher rates of translocation, Fe-chelate reduction and 59Fe uptake as compared to plants supplied with Fe-citrate or Fe-PS. Leaves of plants treated with Fe-WEHS also showed higher transcript levels of LeFRO1, LeIRT1 and Ferritin2 genes with respect to plants fed with the other Fe-sources. Data obtained support the idea that the efficient use of Fe complexed to WEHS-like humic fractions involves, at least in part, also the activation of Fe-acquisition mechanisms operating at the leaf level.

New insights into ferritin synthesis and function highlight a link between iron homeostasis and oxidative stress in plants

Iron is an essential element for both plant productivity and nutritional quality. Improving plant iron content was attempted through genetic engineering of plants overexpressing ferritins. However, both the roles of these proteins in plant physiology, and the mechanisms involved in the regulation of their expression are largely unknown. Although the structure of ferritins is highly conserved between plants and animals, their cellular localization differs. Furthermore, regulation of ferritin gene expression in response to iron excess occurs at the transcriptional level in plants, in contrast to animals which regulate ferritin expression at the translational level. In this review, an overview of our knowledge of bacterial and mammalian ferritin synthesis and functions is presented. Then the following will be reviewed: (a) the specific features of plant ferritins; (b) the regulation of their synthesis during development and in response to various environmental cues; and (c) their function in plant physiology, with special emphasis on the role that both bacterial and plant ferritins play during plant-bacteria interactions. Arabidopsis ferritins are encoded by a small nuclear gene family of four members which are differentially expressed. Recent results obtained by using this model plant enabled progress to be made in our understanding of the regulation of the synthesis and the in planta function of these various ferritins. Studies on plant ferritin functions and regulation of their synthesis revealed strong links between these proteins and protection against oxidative stress. In contrast, their putative iron-storage function to furnish iron during various development processes is unlikely to be essential. Ferritins, by buffering iron, exert a fine tuning of the quantity of metal required for metabolic purposes, and help plants to cope with adverse situations, the deleterious effects of which would be amplified if no system had evolved to take care of free reactive iron.

Microbial Siderophores Exert a Subtle Role in Arabidopsis during Infection by Manipulating the Immune Response and the Iron Status

Siderophores (ferric ion chelators) are secreted by organisms in response to iron deficiency. The pathogenic enterobacterium Erwinia chrysanthemi produces two siderophores, achromobactin and chrysobactin (CB), which are required for systemic dissemination in host plants. Previous studies have shown that CB is produced in planta and can trigger the up-regulation of the plant ferritin gene AtFER1. To further investigate the function of CB during pathogenesis, we analyzed its effect in Arabidopsis (Arabidopsis thaliana) plants following leaf infiltration. CB activates the salicylic acid (SA)-mediated signaling pathway, while the CB ferric complex is ineffective, suggesting that the elicitor activity of this siderophore is due to its iron-binding property. We confirmed this hypothesis by testing the effect of siderophores structurally unrelated to CB, including deferrioxamine. There was no activation of SA-dependent defense in plants grown under iron deficiency before CB treatment. Transcriptional analysis of the genes encoding the root ferrous ion transporter and ferric chelate reductase, and determination of the activity of this enzyme in response to CB or deferrioxamine, showed that these compounds induce a leaf-to-root iron deficiency signal. This root response as well as ferritin gene up-regulation in the leaf were not compromised in a SA-deficient mutant line. Using the Arabidopsis-E. chrysanthemi pathosystem, we have shown that CB promotes bacterial growth in planta and can modulate plant defenses through an antagonistic mechanism between SA and jasmonic acid signaling cascades. Collectively, these data reveal a new link between two processes mediated by SA and iron in response to microbial siderophores.

The ferritin genes: their response to iron status.

Iron is a required nutrient which, at high concentrations, can peroxidize cell lipids and other cellular components. To prevent excess iron from damaging cells, it is stored in ferritin, which consists of a shell of protein subunits of two related types, H (heavy) and L (light), surrounding a cavity in which the iron can be deposited. In order to prepare for a rapid increase in ferritin in response to a rise in cellular iron, a large number of dormant ferritin mRNAs are accumulated in the cytoplasm. These can be rapidly activated to yield a large population of ferritin subunits. Regulation is achieved through a 28-nucleotide "stem-and-loop" structure near the beginning of the H- and L-ferritin mRNAs. When this structure is associated with a binding protein (iron regulatory element binding protein, IRE-BP), translation of the ferritin mRNA cannot proceed. However, when intracellular iron accumulates, IRE-BP releases its hold and translation of the mRNA then takes place. IRE-BP has been identified as a cytosolic form of aconitase, containing several fourfold iron-sulfur clusters. Within each cluster one iron atom is labile; this may be the mechanism by which IRE-BP responds to intracellular iron levels. Finally, transcription of the L- and H-genes shows that L is preferentially transcribed in response to increased iron intake, whereas H responds to cell differentiation and other factors. More work is needed to define independent transcription of the individual genes, including regulation of components other than the 28-nucleotide segment.

종자 특이 프로모터와 대두 Ferritin 유전자에 의한 벼 종실의 철분강화

The recombinant DNAs, pGBF, pGTF, and pZ4F, using soybean ferritin gene have constructed with the promoters derived from seed proteins, glutelin, globulin, and zein. The recombinant ferritin genes were transformed into rice plant by Agrobacterium-mediated transformation. Iron contents and agronomic traits have been evaluated in the transgenic progenies. The embryogenic calli survived from second selection medium were regenerated at the rates of 19.2% with pGBF, 15.0% with pGTF, and 18.4% with pZ4F in Donganbyeo and 6.7% with pGBF, 11.7% with pGTF, and 3.4% with pZ4F in Hwashinbyeo. The introduction of ferritin gene in putative transgenic rice plants was confirmed by PCR and Southern blot analysis and also the expression of ferritin gene was identified by Northern blot and Western blot analysis. The iron accumulation in transgenic rice grains of the transgenic rice plant, T1-2, with zein promoter and ferritin gene contained 171.4 ppm showing 6.4 times higher than 26.7 ppm of Hwashinbyeo seed as wild type rice, but the transgenic plants with globulin and glutelin showed a bit higher iron contents with a range from 2.1 to 3.0 times compare to wild type grain. The growth responses of transgenic plants showed the large variances in plant height and number of tillers. However, there were some transgenic plants having similar phenotype to wild type plants. In the T1 generation of transgenic plants, plant height, culm length, panicle length, and number of tillers were similar to those of wild type plants, but ripened grain ratio ranged from 53.3% to 82.2% with relatively high variation. The transgenic rice plants would be useful for developing rice varieties with high iron content in rice grains.

Abscisic acid and oxidative stress implications in overall ferritin synthesis by African rice (Oryza glaberrima Steud.) seedlings exposed to short term iron toxicity

Iron toxicity occurs under flooded conditions such as those prevailing in lowland rice fields and is due to an excess of ferrous ions. Ferritin is a multimeric protein responsible for Fe sequestration and storage, playing a key role in Fe homeostasis. Our aim was to study the modalities of overall ferritin synthesis in different organs of young seedlings from the African rice species (Oryza glaberrima) in relation to the putative involvement of abscisic acid (ABA) and oxidative stress in signalling processes. Seedlings from a moderately resistant to iron toxicity cultivar were grown in hydroponic culture for 2 weeks and treated with 500 mg l−1 Fe2+ in the presence or in the absence of 200 µM ABA, 50 µM methylviologen or 50 µM fluridone. Iron treatment increased iron and malondialdehyde concentration in all organs as well as ABA in roots and laminae. Although ferritin protein was detected in controls plants, iron treatment strongly reinforced its accumulation in sheaths and laminae after 24 h and 72 h. Ferritin mRNA was induced as early as 24 h after the beginning of the Fe-treatment in sheaths and, to a higher extent, in laminae. In the absence of iron treatment, exogenous ABA increased ferritin mRNA in laminae only but did not lead to further ferritin accumulation. Unexpectedly, it decreased ferritin mRNA levels in the sheaths of iron-treated plants and may thus have a dual influence depending on the considered organ. The inhibitor of ABA synthesis fluridone reduced endogenous ABA but did not compromise ferritin gene expression or ferritin synthesis, whatever the iron dose. Methyviologen application induced obvious oxidative damages but reduced ferritin synthesis. It is suggested that the signalling pathway leading to ferritin synthesis in the semi-aquatic African rice species may involve other components than those reported for typical terrestrial plants.

Bilateral cataract in a subject carrying a C to A transition in the L ferritin promoter region

Objectives The aim of this study is to evaluate the potential impact of mutations in the promoter region of the L ferritin gene on its transcriptional activity. Design and methods To search for the presence of mutations in the promoter of the L gene, we amplified by PCR a DNA region of about 385 n.t. in 100 healthy subjects from Southern Italy. Results A subject carrying a C to A transition in position − 216 was identified. This transition causes an increased transcriptional activity in vitro. This finding was substantiated by Real Time Quantitative PCR, which showed increased levels of L ferritin mRNA. Conclusions A previously unidentified mutation in the promoter region of the L ferritin gene was detected in an individual. Interestingly, this subject is affected by bilateral cataract, a disease that has been correlated, in a subset of patients, with high levels of circulating ferritin. We hypothesize that changes in the expression of the L ferritin might be linked, at least to a certain extent, to the pathogenesis of this rare eye disease.

Screening for Hemochromatosis and Iron Overload: Satisfaction with Results Notification and Understanding of Mailed Results in Unaffected Participants of the HEIRS Study

The purpose of this study was to assess the level of satisfaction and understanding of test results, by a sample of non-C282Y homozygous participants in the hemochromatosis and iron overload screening (HEIRS) study, who received serum ferritin (SF), transferrin saturation (TS), and HFE gene test results by mail. Approximately 1 month after receiving test results by mail, participants were surveyed about understanding of and satisfaction with results notification. Overall, participants were satisfied with receiving test results by mail. Participants receiving results with one or two HFE mutations or TS and/or SF levels outside the normal range (an "alert value") were less likely to be satisfied with this method of notification. Participants with normal HFE test results understood their results and recommendations better than those with one or two mutations. Although all participants received results letters in their native language, English-speaking participants had higher mean understanding scores than Mandarin, Vietnamese, or Spanish-speaking participants. Participants were satisfied with receiving test results by mail. However, the level of understanding of the results was not sufficient for this mode of results notification to stand alone, especially for non-English speaking participants, and all participants with one or more test results outside the normal range.

Molecular Cloning and Characterization of a Ferritin Gene Upregulated by Cold Stress in Chorispora bungeana

The ability of iron to accept and donate electrons makes it important for plant growth, but it can also damage plants when they are under environmental stress. Ferritin, a protein encoded by the gene Fer, catalyzes the oxidation of Fe(2+) and subsequent storage of Fe(3+) within the mineral core. Ferritin may reduce the adverse effects of iron on Chorispora bungeana Fisch. & C.A. May during the course of cold stress. C. bungeana is a rare alpine subnival plant species that is highly resistant to a freezing environment. We have isolated and characterized the ferritin cDNA (CbFer) from C. bungeana. It is 975 bp in length with an open reading frame of 260 amino acids, corresponding to a protein of predicted molecular mass of 29.17 kDa and an isoelectric point of 5.44. Amino acid analysis of the polypeptides indicated that CbFer codes for a ferritin subunit plus a chloroplast-targeting transit peptide. Reverse transcription polymerase chain reaction analysis confirmed that CbFer was a tissue-specific gene since the expression could only be detected in leaves. The gene expression patterns were investigated in relation to cold stress (4 degrees C and -4 degrees C) and to various exogenous signals, including excessive iron, hydrogen peroxide (H(2)O(2)), and nitrogen monoxidum (NO). The amount of CbFer mRNA increased in response to low temperatures and gene expression at -4 degrees C was both more distinct and quicker than that at 4 degrees C. Two exogenous signals, excessive iron and H(2)O(2), upregulated the expression of the CbFer gene, but NO had no effect. The CbFer gene may play an important role in response to cold stress, while the expression of the gene during stress may be influenced by major and minor factors such as iron and H(2)O(2), respectively.

Ferritin Contains Less Iron (59Fe) in Cells When the Protein Pores Are Unfolded by Mutation

Ferric minerals in ferritins are protected from cytoplasmic reductants and Fe2+ release by the protein nanocage until iron need is signaled. Deletion of ferritin genes is lethal; two critical ferritin functions are concentrating iron and oxidant protection (consuming cytoplasmic iron and oxygen in the mineral). In solution, opening/closing (gating) of eight ferritin protein pores controls reactions between external reductant and the ferritin mineral; pore gating is altered by mutation, low heat, and physiological urea (1 mm) and monitored by CD spectroscopy, protein crystallography, and Fe2+ release rates. To study the effects of a ferritin pore gating mutation in living cells, we cloned/expressed human ferritin H and H L138P, homologous to the frog open pore model that was unexpressable in human cells. Human ferritin H L138P behaved like the open pore ferritin model in vitro as follows: (i) normal protein cage assembly and mineralization, (ii) increased iron release (t1/2) decreased 17-fold), and (iii) decreased alpha-helix (8%). Overexpression (> 4-fold), in HeLa cells, showed for ferritin H L138P equal protein expression and total cell 59Fe but increased chelatable iron, 16%, p < 0.01 (59Fe in the deferoxamine-containing medium), and decreased 59Fe in ferritin, 28%, p < 0.01, compared with wild type. The coincidence of decreased 59Fe in open pore ferritin with increased chelatable 59Fe in cells expressing the ferritin open pore mutation suggests that ferritin pore gating influences to the amount of iron (59Fe) in ferritin in vivo.

Iron-mediated Aggregation and a Localized Structural Change Characterize Ferritin from a Mutant Light Chain Polypeptide That Causes Neurodegeneration

Nucleotide insertions in the ferritin light chain (FTL) polypeptide gene cause hereditary ferritinopathy, a neurodegenerative disease characterized by abnormal accumulation of ferritin and iron in the central nervous system. Here we describe for the first time the protein structure and iron storage function of the FTL mutant p.Phe167SerfsX26 (MT-FTL), which has a C terminus altered in sequence and extended in length. MT-FTL polypeptides assembled spontaneously into soluble, spherical 24-mers that were ultrastructurally indistinguishable from those of the wild type. Far-UV CD showed a decrease in α-helical content, and 8-anilino-1-naphthalenesulfonate fluorescence revealed the appearance of hydrophobic binding sites. Near-UV CD and proteolysis studies suggested little or no structural alteration outside of the C-terminal region. In contrast to wild type, MT-FTL homopolymers precipitated at much lower iron loading, had a diminished capacity to incorporate iron, and were less thermostable. However, precipitation was significantly reversed by addition of iron chelators both in vitro and in vivo. Our results reveal substantial protein conformational changes localized at the 4-fold pore of MT-FTL homopolymers and imply that the C terminus of the MT-FTL polypeptide plays an important role in ferritin solubility, stability, and iron management. We propose that the protrusion of some portion of the C terminus above the spherical shell allows it to cross-link with other mutant polypeptides through iron bridging, leading to enhanced mutant precipitation by iron. Our data suggest that hereditary ferritinopathy pathogenesis is likely to result from a combination of reduction in iron storage function and enhanced toxicity associated with iron-induced ferritin aggregates.

Sequence analysis of dolphin ferritin H and L subunits and possible iron-dependent translational control of dolphin ferritin gene

BackgroundIron-storage protein, ferritin plays a central role in iron metabolism. Ferritin has dual function to store iron and segregate iron for protection of iron-catalyzed reactive oxygen species. Tissue ferritin is composed of two kinds of subunits (H: heavy chain or heart-type subunit; L: light chain or liver-type subunit). Ferritin gene expression is controlled at translational level in iron-dependent manner or at transcriptional level in iron-independent manner. However, sequencing analysis of marine mammalian ferritin subunits has not yet been performed fully. The purpose of this study is to reveal cDNA-derived amino acid sequences of cetacean ferritin H and L subunits, and demonstrate the possibility of expression of these subunits, especially H subunit, by iron.MethodsSequence analyses of cetacean ferritin H and L subunits were performed by direct sequencing of polymerase chain reaction (PCR) fragments from cDNAs generated via reverse transcription-PCR of leukocyte total RNA prepared from blood samples of six different dolphin species (Pseudorca crassidens, Lagenorhynchus obliquidens, Grampus griseus, Globicephala macrorhynchus, Tursiops truncatus, and Delphinapterus leucas). The putative iron-responsive element sequence in the 5'-untranslated region of the six different dolphin species was revealed by direct sequencing of PCR fragments obtained using leukocyte genomic DNA.ResultsDolphin H and L subunits consist of 182 and 174 amino acids, respectively, and amino acid sequence identities of ferritin subunits among these dolphins are highly conserved (H: 99–100%, (99→98) ; L: 98–100%). The conserved 28 bp IRE sequence was located -144 bp upstream from the initiation codon in the six different dolphin species.ConclusionThese results indicate that six different dolphin species have conserved ferritin sequences, and suggest that these genes are iron-dependently expressed.

Ferritin is required for rapid remodeling of the photosynthetic apparatus and minimizes photo‐oxidative stress in response to iron availability in Chlamydomonas reinhardtii

Ferritin is a key player in the iron homeostasis due to its ability to store large quantities of iron. Chlamydomonas reinhardtii contains two nuclear genes for ferritin (ferr1 and ferr2) that are induced when Chlamydomonas cells are shifted to iron-deficient conditions. In response to the reduced iron availability, degradation of photosystem I (PSI) and remodeling of its light-harvesting complex occur. This active PSI degradation slows down under photo-autotrophic conditions where photosynthesis is indispensable. We observed a strong induction of ferritin correlated with the degree of PSI degradation during iron deficiency. The PSI level can be restored to normal within 24 h after iron repletion at the expense of the accumulated ferritin, indicating that the ferritin-stored iron allows fast adjustment of the photosynthetic apparatus with respect to iron availability. RNAi strains that are significantly reduced in the amount of ferritin show a striking delay in the degradation of PSI under iron deficiency. Furthermore, these strains are more susceptible to photo-oxidative stress under high-light conditions. We conclude that (i) ferritin is used to buffer the iron released by degradation of the photosynthetic complexes, (ii) the physiological status of the cell determines the strategy used to overcome the impact of iron deficiency, (iii) the availability of ferritin is important for rapid degradation of PSI under iron deficiency, and (iv) ferritin plays a protective role under photo-oxidative stress conditions.

Expression and Iron Storage Properties of Recombinant Human Ferritins in Escherichia Coli: Relevance for Functional Ferritins in Food Systems

Ferritin is an iron storage protein found in most living organisms. Human heavy chain (H-) and light chain (L-) ferritin were amplified from human heart cDNA library. Each ferritin gene was inserted down stream of the T7 promoter of bacterial expression, and finally four types of H-, L-, and co-expression vectors were constructed. Recombinant human ferritins were overexpressed and identified with SDS-PAGE and western blotting. The expression levels of recombinant ferritin proteins ranged about 29–36% of whole cell total protein. From atomic absorption spectrometry (AAS) analysis, the rate of iron uptake for H-ferritin was significantly faster than that for the HL-, LH-, and L‐ferritin, respectively. From AAS analysis, the levels of iron content in cells progressively increased in transformants with 0–30 mM ferric citrate in the media. Among these ferritin transformants, the highest amount of cellular iron was observed with H‐ferritin transformant. The total amounts of iron content in E. coli could be sequentially ranked as H-ferritin > HL-ferritin > LH-ferritin > L-ferritin > negative transformants. Expressed recombinant human ferritins indicated that their assembled subunits were able to store iron in the cells. The results of this study further enhances our understanding of iron uptake properties in vivo and suggest similar strategies for using food-grade ferritins for functional foods or iron-fortified food ingredients.

Identification and expression of a ferritin homolog in amphioxus Branchiostoma belcheri: Evidence for its dual role in immune response and iron metabolism

Ferritin plays a key role in cellular iron metabolism including iron storage and detoxification, which has been identified in a wide range of organisms including bacteria, fungi, plants and animals. However, little information is available regarding ferritin in the protochordates to date. Here we demonstrate the presence of a ferritin gene homolog, BbFRT, in amphioxus Branchiostoma belcheri. Analysis of the BbFRT 5′-UTR indicated the existence of a putative iron-responsive element (IRE) with a predicated stem-loop structure. BbFRT encoded a deduced protein of 172 amino acids with the conserved motif for ferroxidase center typical of heavy chains of vertebrate ferritins. Sequence comparison showed that BbFRT shared more identity to H-chains (68%) of vertebrate ferritins than to the L-chains (46–51%). Both in situ hybridization histochemistry and immunohistochemical staining revealed that BbFRT was ubiquitously expressed in B. belcheri. In addition, BbFRT expression was up-regulated by 1.6-fold and 1.5-fold, respectively, following exposure to LPS at both transcriptional and translational levels. Similarly, exposure to iron resulted in about 1.6-fold increase in BbFRT in the humoral fluids. These suggest that BbFRT seems a protein with a dual function functioning in both immune response and iron metabolism.

Changes in iron-regulatory proteins in the aged rodent neural retina

Iron accumulation is associated with age-related neurodegenerations and may contribute to age-related increased susceptibility of neurons to damage. We compared young and old rodent retinas to assess iron homeostasis during normal aging and the effects of increased iron on the susceptibility of retinal neurons to degeneration. Retinal iron was significantly increased with age. Quantitative RT-PCR showed that transferrin and ferritin genes were upregulated in the aged retina. At the protein level, we found decreased transferrin, and increased transferrin receptor, ferritin, ferroportin, and ceruloplasmin in the aged retina. These results support an increased steady state of iron with age in the retina. We tested susceptibility of retinal neurons with increased intracellular iron to damage in vitro. Exposure of RGC-5 cells to increased iron potentiated the neurotoxicity induced by paraquat, glutamate, and TNFα. Our results demonstrate that iron homeostasis in the retina is altered with age and suggest that iron accumulation, due to altered levels of iron-regulatory proteins in the aged retina, could be a susceptibility factor in age-related retinal diseases.

Dietary inulin affects the expression of intestinal enterocyte iron transporters, receptors and storage protein and alters the microbiota in the pig intestine

Inulin, a linear beta fructan, is present in a variety of plants including chicory root and wheat. It exhibits prebiotic properties and has been shown to enhance mineral absorption and increase beneficial bacteria in the colon. The aim of the present study was to assess the effect of dietary inulin on the gene expression of selected intestinal Fe transporters and binding proteins. Anaemic piglets at age 5 weeks were allocated to a standard maize-soya diet (control) or the same diet supplemented with inulin at a level of 4 %. After 6 weeks, the animals were killed and caecum contents and sections of the duodenum and colon were removed. Segments of the genes encoding for the pig divalent metal transporter 1 (DMT1) and duodenal cytochrome-b reductase (Dcytb) were isolated and sequenced. Semi-quantitative RT-PCR analyses were performed to evaluate the expression of DMT1, Dcytb, ferroportin, ferritin, transferrin receptor (TfR) and mucin genes. DMT1, Dcytb, ferroportin, ferritin and TfR mRNA levels in duodenal samples were significantly higher in the inulin group (P < or = 0.05) compared with the control. In colon, DMT1, TfR and ferritin mRNA levels significantly increased in the inulin group. Additionally, the caecal content microflora was examined using 16S rDNA targeted probes from bacterial DNA. The Lactobacillus and Bifidobacterium populations were significantly increased in the inulin group (P < or = 0.05) compared with the control group. These results indicate that dietary inulin might trigger an up regulation of genes encoding for Fe transporters in the enterocyte. The specific mechanism for this effect remains to be elucidated.