BioMetals (v.26, #6)

Zinc and myocardial ischemia/reperfusion injury by Zhelong Xu; Juan Zhou (863-878).
As an important trace element, zinc is required for the normal cellular structure and function, and impairment of zinc homeostasis is associated with a variety of health problems including cardiovascular disease. Zinc homeostasis is regulated through zinc transporters, zinc binding molecules, and zinc sensors. Zinc also plays a critical role in cellular signaling. Studies have documented that zinc homeostasis is impaired by ischemia/reperfusion in the heart and zinc dyshomeostasis may play a role in the pathogenesis of myocardial ischemia/reperfusion injury. Both exogenous and endogenously released zinc may play an important role in cardioprotection against ischemia/reperfusion injury. The goal of this review is to summarize the current understanding of the roles of zinc homeostasis and zinc signaling in myocardial ischemia/reperfusion injury.
Keywords: Zinc; Zinc homeostasis; Zinc transporters; Zinc signaling; Myocardial ischemia/reperfusion injury

The role of GSTs in the tolerance of Rhizobium leguminosarum to cadmium by Sofia Corticeiro; Rosa Freitas; Etelvina Figueira (879-886).
A high intraspecific difference in cadmium (Cd) tolerance exits among Rhizobium leguminosarum strains. The higher tolerance to Cd appeared to be related to the efficiency of the glutathione (GSH)–Cd chelation mechanism, but it is not known how efficiency is influenced. Thus, in this work it was intended to investigate the traits behind the efficiency of intracellular Cd chelation by GSH. Glutathione-S-transferases (GST; EC are a family of multi-functional dimeric proteins, found in both prokaryotes and eukaryotes, which are implicated in a variety of stress conditions. The common feature of these enzymes is to catalyze the conjugation of the sulfur atom of GSH with a large variety of hydrophobic toxic compounds of both endogenous and exogenous origin. Taking into account the reactions catalyzed by GSTs, it was hypothesized that they could be involved in the GSH–Cd complex formation in R. leguminosarum. Differences in GSTs activity between strains could explain variation in Cd chelation efficiency detected among strains and, consequently, discrepancy in tolerance to Cd. Thus, GST isoforms of R. leguminosarum strains with distinct tolerances to Cd were purified and their activity investigated. The relationship between chelation efficiency and enzymatic activity of GSTs was demonstrated, supporting the hypothesis that GSTs, in particular one isoform, was involved in the formation of GSH–Cd complexes and in the tolerance of Rhizobium to Cd.
Keywords: Rhizobium leguminosarum ; Glutathione; Cadmium; Glutathione-S-transferases; Metal complexes

Metal stoichiometry of isolated and arsenic substituted metallothionein: PIXE and ESI-MS study by Roobee Garla; Biraja P. Mohanty; Renuka Ganger; M. Sudarshan; Mohinder P. Bansal; Mohan L. Garg (887-896).
The stoichiometric analysis of the metal induced Metallothionein (MT) is pertinent for understanding the metal-MT interactions. Despite innumerable publications on MT, the literature addressing these aspects is limited. To bridge this gap, PIXE and ESI-MS analysis of the commercial rabbit liver MT1 (an isoform of MT), zinc induced isolated rat liver MT1, apo and Arsenic substituted rabbit liver MT1 have been carried out. These techniques in combination provide information about number and the signature of all the metal ions bound to MT. By using ESI-MS in the rabbit MT1, ions of Zn n MT1 (n = 0, 1, 4, 5, 6, 7) whereas, in rat MT1, the Zn1MT1 and Zn5MT1 ions are observed. PIXE analysis shows that some copper along with zinc is also present in the rabbit as well as rat MT1 which could not be assessed with ESI-MS. During As metallation reaction with rabbit MT1, with increase in arsenic concentration, the amount of arsenic bound to MT1 also increases, though not proportionally. The presence of both Zn and Cu in MT1 on Zn supplementation can be related to the role of MT in Zn and Cu homeostasis. Further, the presence of partially metallated MT1 suggests that MT1 may donate fractional amount of metal from it’s fully metallated form to other proteins where Zn acts as a cofactor.
Keywords: Metallothionein; Arsenic; Zinc; PIXE; ESI-MS

NF-κB acts downstream of EGFR in regulating low dose cadmium induced primary lung cell proliferation by Subhadip Kundu; Suman Sengupta; Arindam Bhattacharyya (897-911).
Apart from cytotoxicity cadmium has no special attributes towards cell’s physiological function. The role of cadmium with respect to cell growth is still under debate. Mitogen activated protein kinase and Ca2+/calmodulin dependent protein kinase dependent pathways are the two elaborately studied concerning cadmium induced cell proliferation. Low concentration of cadmium chloride (2.5 μM) was applied to mice primary lung epithelial cells and cell proliferation was measured both by cell cycle analysis and Brdu incorporation assay. Effects of differential dose of cadmium chloride on lung epithelial cells were evaluated morphologically by atomic force microscopy. RT-PCR and western blot altogether corroborated the specific signalling pathways concerning cadmium induced lung cell proliferation. Cadmium induced lung epithelial cells which over-expressed EGFR, were transfected with siEGFR, revealed downstream molecules and RNAi induced EGFR silencing. Use of siEGFR effectively prevents expression of proinflammatory and cell proliferative markers. Moreover N-acetyl cysteine and ascorbic acid mediated inhibition of EGFR and downstream signalling molecules indicate the involvement of reactive oxygen species. Exposure to low concentration of cadmium promotes the growth of primary mice lung epithelial cell by EGFR signalling. We have also transfected the primary lung epithelial cell with siRNA against the regulatory subunit of nuclear factor-κB (NF-κB) and the data shows that cadmium induced lung cell proliferation is the effect of EGFR mediated NF-κB activation.
Keywords: Cadmium chloride; Epithelial cell; Lethal dose; Reactive oxygen species (ROS); Non-small cell lung cancer (NSCLC)

Fungal plant pathogens such as Fusarium graminearum cause severe global economic losses in cereals crops, and current control measures are limited. This work addresses the potential for ZnO nanoparticles (NPs) and biocontrol bacteria to be used in plant fungal control strategies. Growth of F. graminearum was significantly (p = 0.05) inhibited by inclusion of the NPs in a mung bean broth agar and in sand. Suspension in mung bean broth medium modified the surface charge, dissolution, and aggregation state of the ZnO NPs, in comparison to processes occurring in water suspension. The ZnO NPs were significantly more inhibitory to fungal growth than micro-sized particles of ZnO, although both types of particles released similar levels of soluble Zn, indicating size-dependent toxicity of the particles. Zn ions produced dose-dependent inhibition, noticeable at the level of soluble Zn released from NPs after seven-day suspension in medium; inhibitory levels caused acidification of the growth medium. Transfer of fungal inoculum after exposure to the ZnO NPs to fresh medium did not indicate adaptation to the stress because growth was still inhibited by the NPs. The ZnO NPs did not prevent metabolites from a biocontrol bacterium, Pseudomonas chlororaphis O6, from inhibiting Fusarium growth: no synergism was observed in the mung bean agar. Because other studies find that soil amendment with ZnO NPs required high doses for inhibition of plant growth, the findings of pathogen growth control reported in this paper open the possibility of using ZnO NP-based formulations to complement existing strategies for improving crop health in field settings.
Keywords: Biocontrol; Fungi; Fusarium graminearum ; Nanocontrol; Pseudomonas chlororaphis O6; Zinc; ZnO nanoparticles

Intestinal expression of metal transporters in Wilson’s disease by Adam Przybyłkowski; Grażyna Gromadzka; Adriana Wawer; Tomasz Grygorowicz; Anna Cybulska; Anna Członkowska (925-934).
In Wilson’s disease (WND), biallelic ATP7B gene mutation is responsible for pathological copper accumulation in the liver, brain and other organs. It has been proposed that copper transporter 1 (CTR1) and the divalent metal transporter 1 (DMT1) translocate copper across the human intestinal epithelium, while Cu-ATPases: ATP7A and ATP7B serve as copper efflux pumps. In this study, we investigated the expression of CTR1, DMT1 and ATP7A in the intestines of both WND patients and healthy controls to examine whether any adaptive mechanisms to systemic copper overload function in the enterocytes. Duodenal biopsy samples were taken from 108 patients with Wilson’s disease and from 90 controls. CTR1, DMT1, ATP7A and ATP7B expression was assessed by polymerase chain reaction and Western blot. Duodenal CTR1 mRNA and protein expression was decreased in WND patients in comparison to control subjects, while ATP7A mRNA and protein production was increased. The variable expression of copper transporters may serve as a defense mechanism against systemic copper overload resulting from functional impairment of ATP7B.
Keywords: Wilson’s disease; Metal transporters; Intestine; Copper; ATP7A; DMT1; CTR1; ATP7B

Gallium nitrate induces fibrinogen flocculation: an explanation for its hemostatic effect? by A. Bauters; D. J. Holt; P. Zerbib; M. Rogosnitzky (935-939).
A novel hemostatic effect of gallium nitrate has recently been discovered. Our aim was to perform a preliminary investigation into its mode of action. Thromboelastography® showed no effect on coagulation but pointed instead to changes in fibrinogen concentration. We measured functional fibrinogen in whole blood after addition of gallium nitrate and nitric acid. We found that gallium nitrate induces fibrinogen precipitation in whole blood to a significantly higher degree than solutions of nitric acid alone. This precipitate is not primarily pH driven, and appears to occur via flocculation. This behavior is in line with the generally observed ability of metals to induce fibrinogen precipitation. Further investigation is required into this novel phenomenon.
Keywords: Fibrinogen; Flocculation; Aggregation; Gallium; Gallium nitrate; Hemostasis

Kinetics of manganese transport and gene expressions of manganese transport carriers in Caco-2 cell monolayers by Xiaoli Li; Jingjing Xie; Lin Lu; Liyang Zhang; Lingyan Zhang; Yaxue Zou; Qiuyue Wang; Xugang Luo; Sufen Li (941-953).
Two experiments were conducted to investigate the kinetics of manganese (Mn) transport in Caco-2 cell monolayers and the gene expressions of Mn transport carriers in apical (AP) and basolateral (BL) membranes. In experiment 1, the cells were treated with the medium containing 146 μmol/L of Mn (MnSO4·H2O). Both the uptake and transport of Mn from AP–BL or from BL–AP at different time-points were assessed to determine the optimal time for kinetics of Mn transport. The transport of Mn increased linearly with higher efficiency values in AP–BL than in BL–AP direction, however, the uptake of Mn revealed an asymptotic pattern within 120 min. In experiment 2, the kinetics of Mn transport in AP–BL was determined with media containing Mn concentrations from 0 to 2,500 μmol/L at 40 and 120 min, respectively, and mRNA levels of divalent metal transporter 1 (DMT1) and ferroportin (FPN1) were determined in Caco-2 cells treated with the medium containing 0 or 800 μmol/L of Mn for 120 min. The kinetics of Mn transport showed a carrier-mediated process when Mn concentrations were lower than 1,000 μmol/L and a linear increment when Mn concentrations exceeded 1,000 μmol/L at either 40 or 120 min. Mn treatment decreased (P < 0.01) DMT1 mRNA level and increased (P < 0.01) FPN1 mRNA level. The results from the present study suggested that Mn transport in AP–BL fit both carrier-mediated saturable and non-saturable diffusion processes, and Mn transport carriers DMT1 and FPN1 mediate the apical uptake and basolateral exit of Mn in Caco-2 cells.
Keywords: Manganese; Transport; Divalent metal transporter 1; Ferroportin; Caco-2 cell

The GATA-type transcriptional repressor structural gene SRE1 was isolated from both the genomic DNA and mRNA of the marine yeast Aureobasidium pullulans HN6.2 by inverse PCR and RACE. An open reading frame (ORF) of 1,002 bp encoding a 334 amino acid protein (a calculated isoelectric point: 8.6) with a calculated molecular weight of 35.1 kDa was characterized. The corresponding gene had one single intron of 51 bp, and in its promoter two putative 5′-HGATAR-3′ sequences could be recognized. The deduced protein from the cloned gene contained two conserved zinc-finger domains [Cys-(X2)-Cys-(X17)-Cys-(X2)-Cys)], nine sequences of Ser(Thr)-Pro-X-X which was characteristics of the regulator, and one cysteine-rich central domain which was located between the two zinc fingers. The SRE1 gene in A. pullulans HN6.2 was disrupted by integrating the hygromycin B phosphotransferase gene into the ORF of the SRE1 gene using homologous recombination. Two hundreds of the disruptants (Δsre1) (one of them was named R6) obtained still synthesized both intracellular and extracellular siderophores in the presence of added Fe3+ and the expression of the SidA gene encoding l-ornithine N5-oxygenase in the disruptant R6 was also partially derepressed in the presence of added Fe3+. The colonies of the disruptant R6 grown on the iron-replete medium with 1.5 and 2.0 mM Fe3+ and also with 1.5 mM Fe2+ became brown. In contrast, A. pullulans HN6.2 could not grow in the iron-replete medium with 1.5 mM and 2.0 mM Fe3+. The brown-colored colonies of the disruptant R6 also had high level of siderophore and iron.
Keywords: The transcriptional repressor; Marine-derived yeasts; SRE1 gene; Gene disruption; Derepression

Linear fusigen as the major hydroxamate siderophore of the ectomycorrhizal Basidiomycota Laccaria laccata and Laccaria bicolor by Kurt Haselwandter; Gerlinde Häninger; Markus Ganzera; Hubertus Haas; Graeme Nicholson; Günther Winkelmann (969-979).
A screening for siderophores produced by the ectomycorrhizal fungi Laccaria laccata and Laccaria bicolor in synthetic low iron medium revealed the release of several different hydroxamate siderophores of which four major siderophores could be identified by high resolution mass spectrometry. While ferricrocin, coprogen and triacetylfusarinine C were assigned as well as other known fungal siderophores, a major peak of the siderophore mixture revealed an average molecular mass of 797 for the iron-loaded compound. High resolution mass spectrometry indicated an absolute mass of m/z = 798.30973 ([M + H]+). With a relative error of Δ = 0.56 ppm this corresponds to linear fusigen (C33H52N6O13Fe; MW = 797.3). The production of large amounts of linear fusigen by these basidiomycetous mycorrhizal fungi may possibly explain the observed suppression of plant pathogenic Fusarium species. For comparative purposes Fusarium roseum was included in this study as a well known producer of cyclic and linear fusigen.
Keywords: Siderophores; Iron; Mycorrhiza; Fusarium roseum

Iron status and lipopolysaccharide regulate Ndfip1 by activation of nuclear factor-kappa B by Huamin Xu; Qing Chang; Wenting Jia; Hong Jiang; Peng Sun; Junxia Xie (981-988).
Nedd4 family interacting protein 1 (Ndfip1) is an adaptor protein for the Nedd4 family of ubiquitin ligases that target proteins for degradation. Recent studies confirmed the role of Ndfip1 as a regulator of iron metabolism and pointed out that Ndfip1 was involved in iron homeostasis by regulating the degradation of iron importer divalent metal transporter 1 (DMT1). However, little is known about how Ndfip1 is regulated. The aim of this article was to investigate the regulation of Ndfip1 levels and the possible mechanisms. In this study, we investigated the effect of various stimuli, including iron status and lipopolysaccharide (LPS) on Ndfip1 expression in MES23.5 dopaminergic cell lines. Results showed that Ndfip1 expression in these cells was enhanced by ferrous iron overload, but not ferric iron overload, and decreased after iron deprivation by deferoxamine. In addition, LPS could significantly increase the expression of Ndfip1. Furthermore, we demonstrated that the regulation of Ndfip1 expression by these various stimuli was achieving by activation of nuclear factor-kappa B. We speculate that iron status and LPS may contribute to the changes of Ndfip1 expression by activation of nuclear factor-kappa B.
Keywords: Ndfip1; Iron overload; Lipopolysaccharide; Deferoxamine

Uptake and subcellular partitioning of trivalent metals in a green alga: comparison between Al and Sc by Anne Crémazy; Jacqueline L. Levy; Peter G. C. Campbell; Claude Fortin (989-1001).
Despite 40+ years of research on aluminum (Al) toxicity in aquatic organisms, Al transport mechanisms through biological membranes, and the intracellular fate of Al once assimilated, remain poorly understood. The trivalent metal scandium shares chemical similarities with Al and, unlike Al, it has a convenient radioactive tracer (Sc-46) allowing for relatively simple measurements at environmentally relevant concentrations. Thus, we investigated the potential of Sc to substitute for Al in uptake and intracellular fate studies with the green alga Chlamydomonas reinhardtii. Short-term (<60 min) competitive uptake experiments indicated that Al does not inhibit Sc influx, implying that these metals do not share a common transport mechanism. Also, internalized Al concentrations were ~4 times higher than Sc concentrations after long-term (72 h) exposures under similar conditions (4.5 μM AlT or ScT, 380 μM FT, pH 7.0, 3.8 pM Al calc 3+ and 1.0 pM Sc calc 3+ ). However, interesting similarities were observed in their relative subcellular distributions, suggesting possible common toxicity/tolerance mechanisms. Both metals mostly distributed to the organelles fraction and almost no association was found with the cytosolic proteins. The greatest difference was observed in the cellular debris fraction (membranes and nucleus) where Al was much more concentrated than Sc. However, it is not clear whether or not this fraction contained extracellular metal associated with the algal surface. To summarize, Sc does not seem to be an adequate substitute of Al for transport/uptake studies, but could be for investigations of toxicity/tolerance mechanisms in C. reinhardtii. Further work is needed to verify this latter suggestion.
Keywords: Metal uptake; Subcellular distribution; Unicellular alga; Aluminum; Scandium; Detoxification

We have determined the structure and coordination chemistry of rhizoferrin (Rf), which is a particular type of siderophore, and its Fe(III) complexes using density functional theory calculations. Our results show that the Fe(III) ion binds in an octahedral coordination, with a low-spin (S = 1/2) charge-neutral chiral complex having the largest binding energy of the investigated complexes. We have also calculated nuclear magnetic resonance parameters, such as chemical shifts for 1H and 13C, and indirect nuclear spin–spin couplings for 1H–1H and 13C–1H in free Rf and in a low-spin neutral Rf metal complex, as well as nuclear quadrupole interaction parameters, such as asymmetry parameter and nuclear quadrupole coupling constants for 14N. Our calculated values for the chemical shifts for free Rf are in excellent agreement with experimental data while the calculated NMR parameters for Fe(III) complexes are predictions for future experimental work.
Keywords: Rhizoferrin; Siderophore; Iron transport

Developmental neurotoxicity of cadmium on enzyme activities of crucial offspring rat brain regions by Vasileios Stolakis; Stylianos Tsakiris; Konstantinos Kalafatakis; Apostolos Zarros; Nikolina Skandali; Vasiliki Gkanti; Argyro Kyriakaki; Charis Liapi (1013-1021).
Cadmium (Cd) is an environmental contaminant known to exert significant neurotoxic effects on both humans and experimental animals. The aim of this study was to shed more light on the effects of gestational (in utero) and lactational maternal exposure to Cd (50 ppm of Cd as Cd-chloride in the drinking water) on crucial brain enzyme activities in important rat offspring brain regions (frontal cortex, hippocampus, hypothalamus, pons and cerebellum). Our study provides a brain region-specific view of the changes in the activities of three crucial brain enzymes as a result of the developmental neurotoxicity of Cd. Maternal exposure to Cd during both gestation and lactation results into significant changes in the activities of acetylcholinesterase and Na+,K+-ATPase in the frontal cortex and the cerebellum of the offspring rats, as well as in a significant increase in the hippocampal Mg2+-ATPase activity. These brain-region-specific findings underline the need for further research in the field of Cd-induced developmental neurotoxicity. Deeper understanding of the mechanisms underlying the neurodevelopmental deficits taking place due to in utero and early age exposure to Cd could shed more light on the causes of its well-established cognitive implications.
Keywords: Cadmium; Acetylcholinesterase; Na+,K+-ATPase; Mg2+-ATPase; Rat; Frontal cortex; Hippocampus; Cerebellum

The impact of ionic mercury on antioxidant defenses in two mercury-sensitive anaerobic bacteria by Yingjiao Wang; Tyler Robison; Heather Wiatrowski (1023-1031).
While the toxicological effects of mercury (Hg) are well studied in mammals, little is known about the mechanisms of toxicity to bacterial cells lacking an Hg resistance (mer) operon. We determined that Shewanella oneidensis MR-1 is more sensitive to ionic mercury [Hg(II)] under aerobic conditions than in fumarate reducing conditions, with minimum inhibitory concentrations of 0.25 and 2 μM respectively. This increased sensitivity in aerobic conditions is not due to increased import, as more Hg is associated with cellular material in fumarate reducing conditions than in aerobic conditions. In fumarate reducing conditions, glutathione may provide protection, as glutathione levels decrease in a dose-dependent manner, but this does not occur in aerobic conditions. Hg(II) does not change the redox state of thioredoxin in MR1 in either fumarate reducing conditions or aerobic conditions, although thioredoxin is oxidized in Geobacter sulfurreducens PCA in response to Hg(II) treatment. However, treatment with 0.5 μM Hg(II) increases lipid peroxidation in aerobic conditions but not in fumarate reducing conditions in MR-1. We conclude that the enhanced sensitivity of MR-1 to Hg(II) in aerobic conditions is not due to differences in intracellular responses, but due to damage at the cell envelope.
Keywords: Shewanella oneidensis ; Geobacter sulfurreducens ; Mercury; Glutathione; Antioxidant; Lipid peroxidation; Thioredoxin

Physiological copper exposure in Jurkat cells induces changes in the expression of genes encoding cholesterol biosynthesis proteins by Ricardo Gutiérrez-García; Talía del Pozo; Miriam Suazo; Verónica Cambiazo; Mauricio González (1033-1040).
Copper is an essential micronutrient that functions as an enzymatic cofactor in a wide range of cellular processes. Although adequate Cu levels are essential for normal metabolism, excess Cu can be toxic to cells. Cellular responses to copper deficiency and overload involve changes in the expression of genes directly and indirectly involved in copper metabolism. However little is known on the effect of physiological copper concentration on gene expression changes. In the current study we aimed to establish whether the expression of genes encoding enzymes related to cholesterol (hmgcs1, hmgcr, fdft) and fatty acid biosynthesis and LDL receptor can be induced by an iso-physiological copper concentration. The iso-physiological copper concentration was determined as the bioavailable plasmatic copper in a healthy adult population. In doing so, two blood cell lines (Jurkat and THP-1) were exposed for 6 or 24 h to iso- or supraphysiological copper concentrations. Our results indicated that in cells exposed to an iso-physiological copper concentration the early induction of genes involved in lipid metabolism was not mediated by copper itself but by the modification of the cellular redox status. Thus our results contributed to understand the involvement of copper in the regulation of cholesterol metabolism under physiological conditions.
Keywords: Gene expression; Copper; Cholesterol; ROS; Jurkat; THP-1

EGCG inhibit chemical reactivity of iron through forming an Ngal–EGCG–iron complex by Guan-Hu Bao; Jie Xu; Feng-Lin Hu; Xiao-Chun Wan; Shi-Xian Deng; Jonathan Barasch (1041-1050).
Accumulated evidence indicates that the interconversion of iron between ferric (Fe3+) and ferrous (Fe2+) can be realized through interaction with reactive oxygen species in the Fenton and Haber–Weiss reactions and thereby physiologically effects redox cycling. The imbalance of iron and ROS may eventually cause tissue damage such as renal proximal tubule injury and necrosis. Many approaches were exploited to ameliorate the oxidative stress caused by the imbalance. (−)-Epigallocatechin-3-gallate, the most active and most abundant catechin in tea, was found to be involved in the protection of a spectrum of renal injuries caused by oxidative stress. Most of studies suggested that EGCG works as an antioxidant. In this paper, Multivariate analysis of the LC–MS data of tea extracts and binding assays showed that the tea polyphenol EGCG can form stable complex with iron through the protein Ngal, a biomarker of acute kidney injury. UV–Vis and Luminescence spectrum methods showed that Ngal can inhibit the chemical reactivity of iron and EGCG through forming an Ngal–EGCG–iron complex. In thinking of the interaction of iron and ROS, we proposed that EGCG may work as both antioxidant and Ngal binding siderphore in protection of kidney from injuries.
Keywords: EGCG; Ngal; Siderophore; Antioxidant; Renal injury

Hepcidin is an antimicrobial peptide hormone that plays a central role in the metabolism of iron and its expression in the liver can be induced through two major pathways: the inflammatory pathway, mainly via IL-6; and the iron-sensing pathway, mediated by BMP-6. GATA-proteins are group of evolutionary conserved transcriptional regulators that bind to the consensus motif—WGATAR—in the promoter region. In hepatoma cells, GATA-proteins 4 and 6 in conjunction with the co-factor friend of GATA (FOG) were shown to modulate the transcription of HAMP. However, it is unclear as to which of the GATA-proteins drive the expression of HAMP in vivo. In this study, using in vitro and in vivo approaches, we investigated the relevance of GATA and FOG proteins in the expression of hepcidin following treatment with IL-6 and BMP-6. We found that treatment of Huh7 cells with either IL-6 or BMP-6 increased the HAMP promoter activity. The HAMP promoter activity following treatment with IL-6 or BMP-6 was further increased by co-transfection of the promoter with GATA proteins 4 and 6. However, co-transfection of the HAMP promoter with FOG proteins 1 or 2 repressed the promoter response to treatments with either IL-6 or BMP-6. The effects of both GATA and FOG proteins on the promoter activity in response to IL-6 or BMP-6 treatment were abrogated by mutation of the GATA response element—TTATCT—in the HAMP promoter region −103/−98. In vivo, treatment of mice with lipopolysaccharide led to a transient increase of Gata-6 expression in the liver that was positively correlated with the expression of hepcidin. Our results indicate that during inflammation GATA-6 is up-regulated in concert with hepcidin while GATA-4 and FOG (1 and 2) are repressed.
Keywords: Hepcidin; Iron; Inflammation; Interleukin-6; Hemochromatosis; Bone morphogenic protein 6; GATA-6; FOG

The enantiomeric siderophores pyochelin and enantiopyochelin of Pseudomonas aeruginosa and Pseudomonas protegens promote growth under iron limitation and activate transcription of their biosynthesis and uptake genes via the AraC-type regulator PchR. Here we investigated siderophore binding to PchR in vitro using fluorescence spectroscopy. A fusion of the N-terminal domain of P. aeruginosa PchR with maltose binding protein (MBP-PchR′PAO) bound iron-loaded (ferri-) pyochelin with an affinity (Kd) of 41 ± 5 μM. By contrast, no binding occurred with ferri-enantiopyochelin. Stereospecificity of a similar fusion protein of the P. protegens PchR (MBP-PchR′CHA0) was less pronounced. The Kd’s of MBP-PchR′CHA0 for ferri-enantiopyochelin and ferri-pyochelin were 24 ± 5 and 40 ± 7 μM, respectively. None of the proteins interacted with the iron-free siderophore enantiomers, suggesting that transcriptional activation by PchR occurs only when the respective siderophore actively procures iron to the cell.
Keywords: Siderophore; Pseudomonas ; Iron; Pyochelin; AraC-type regulator