BioMetals (v.25, #5)

Mercury (Hg) contamination in soils has become a great concern as a result of its natural release and anthropogenic activities. This review presents broad aspects of our recent understanding of mercury contamination and toxicology in plants including source of Hg contamination, toxicology, tolerant regulation in plants, and minimization strategy. We first introduced the sources of mercury contamination in soils. Mercury exists in different forms, but ionic mercury (Hg2+) is the predominant form in soils and readily absorbed by plants. The second issue to be discussed is the uptake, transport, and localization of Hg2+ in plants. Mercury accumulated in plants evokes severe phytotoxicity and impairs numerous metabolic processes including nutrient uptake, water status, and photosynthesis. The mechanisms of mercury-induced toxicology, molecular response and gene networks for regulating plant tolerance will be reviewed. In the case of Hg recent much progress has been made in profiling of transcriptome and more importantly, uncovering a group of small RNAs that potentially mediates plant tolerance to Hg. Several newly discovered signaling molecules such as nitric oxide and carbon monoxide have now been described as regulators of plant tolerance to Hg. A recently emerged strategy, namely selection and breeding of plant cultivars to minimize Hg (or other metals) accumulation will be discussed in the last part of the review.
Keywords: Mercury; Plants; Toxicology; Tolerance; Small RNA; Gene expression; Molecular response

The role of fluoride on the process of titanium corrosion in oral cavity by Juliana Noguti; Flavia de Oliveira; Rogério Correa Peres; Ana Claudia Muniz Renno; Daniel Araki Ribeiro (859-862).
Titanium is known to possess excellent biocompatibility as a result of corrosion resistance, lack of allergenicity when compared with many other metals. Fluoride is well known as a specific and effective caries prophylactic agent and its systemic application has been recommended widely over recent decades. Nevertheless, high fluoride concentrations impair the corrosion resistance of titanium. The purpose of this article is to summarize the current data regarding the influence of fluoride on titanium corrosion process in the last 5 years. These data demonstrate noxious effects induced by high fluoride concentration as well as low pH in the oral cavity. Therefore, such conditions should be considered when prophylactic actions are administrated in patients containing titanium implants or other dental devices.
Keywords: Titanium; Corrosion process; Fluoride; Oral cavity

Lithium preparations are commonly used drug in treating mental disorders and bipolar diseases, but metal’s cytotoxic mechanisms have not yet been completely understood. In this study, we investigated the cytotoxic mechanisms of lithium in freshly isolated rat hepatocytes. Lithium cytotoxicity were associated with reactive oxygen species (ROS) formation and collapse of mitochondrial membrane potential and cytochrome c release into the hepatocyte cytosol. All of the mentioned lithium-induced cytotoxicity markers were significantly (P < 0.05) prevented by ROS scavengers, antioxidants, mitochondrial permeability transition pore sealing agents and adenosine triphosphate generators. Hepatocyte glutathione (GSH) was also rapidly oxidized and GSH-depleted hepatocytes were more resistant to lithium-induced oxidative stress markers. This suggests that lithium is activated by GSH. Our results also showed that CYP2E1 is involved in lithium oxidative stress mechanism. Lithium cytotoxicity was also associated with mitochondrial injuries initiated by increased ROS formation resulted from metal-CYP2E1 destructive interaction or metal-induced disruption of mitochondrial electron transfer chain. Methyl donors such as betaine, methionine, or folic acid prevented lithium cytotoxicity, and this suggests that this metal is detoxified by phase II metabolic methylation. In conclusion lithium-induced cytotoxicity could be attributed to oxidative stress and mitochondrial dysfunction.
Keywords: Lithium; Glutathione; Oxidative stress; Methylation; Hepatotoxicity

XAS analysis of a nanostructured iron polysaccharide produced anaerobically by a strain of Klebsiella oxytoca by Iztok Arčon; Oreste Piccolo; Stefano Paganelli; Franco Baldi (875-881).
A strain of Klebsiella oxytoca, isolated from acid pyrite-mine drainage, characteristically produces a ferric hydrogel, consisting of branched heptasaccharide repeating units exopolysaccharide (EPS), with metal content of 36 wt%. The high content of iron in the EPS matrix cannot be explained by a simple ferric ion bond to the sugar skeleton. The bio-generated Fe–EPS is investigated by X-ray absorption spectroscopy. Fe K-edge XANES analysis shows that iron is mostly in trivalent form, with a non-negligible amount of Fe2+ in the structure. The Fe EXAFS results indicate that iron in the sample is in a mineralized form, prevalently in the form of nano-sized particles of iron oxides/hydroxides, most probably a mixture of different nano-crystalline forms. TEM shows that these nanoparticles are located in the interior of the EPS matrix, as in ferritin. The strain produces Fe–EPS to modulate Fe-ions uptake from the cytoplasm to avoid iron toxicity under anaerobic conditions. This microbial material is potentially applicable as iron regulator.
Keywords: Anaerobic growth; Citrate fermentation; Fe–EPS; Fe K-edge; XANES; EXAFS

Genetic modification of iron metabolism in mice affects the gut microbiota by Keren Buhnik-Rosenblau; Shirly Moshe-Belizowski; Yael Danin-Poleg; Esther G. Meyron-Holtz (883-892).
The composition of the gut microbiota is affected by environmental factors as well as host genetics. Iron is one of the important elements essential for bacterial growth, thus we hypothesized that changes in host iron homeostasis, may affect the luminal iron content of the gut and thereby the composition of intestinal bacteria. The iron regulatory protein 2 (Irp2) and one of the genes mutated in hereditary hemochromatosis Hfe , are both proteins involved in the regulation of systemic iron homeostasis. To test our hypothesis, fecal metal content and a selected spectrum of the fecal microbiota were analyzed from Hfe−/−, Irp2−/− and their wild type control mice. Elevated levels of iron as well as other minerals in feces of Irp2−/− mice compared to wild type and Hfe−/− mice were observed. Interestingly significant variation in the general fecal-bacterial population-patterns was observed between Irp2−/− and Hfe−/− mice. Furthermore the relative abundance of five species, mainly lactic acid bacteria, was significantly different among the mouse lines. Lactobacillus (L.) murinus and L. intestinalis were highly abundant in Irp2−/− mice, Enterococcus faecium species cluster and a species most similar to Olsenella were highly abundant in Hfe-/- mice and L. johnsonii was highly abundant in the wild type mice. These results suggest that deletion of iron metabolism genes in the mouse host affects the composition of its intestinal bacteria. Further studying the relationship between gut microbiota and genetic mutations affecting systemic iron metabolism in human should lead to clinical implications.
Keywords: Iron; Gut microbiota; Mineral absorption; Hemochromatosis; Iron regulatory protein 2 (IRP2)

Physiological metal uptake by Nostoc punctiforme by L. Hudek; S. Rai; A. Michalczyk; L. C. Rai; B. A. Neilan; M. Leigh Ackland (893-903).
Trace metals are required for many cellular processes. The acquisition of trace elements from the environment includes a rapid adsorption of metals to the cell surface, followed by a slower internalization. We investigated the uptake of the trace elements Co2+, Cu2+, Mn2+, Ni2+, and Zn2+ and the non-essential divalent cation Cd2+ in the cyanobacterium Nostoc punctiforme. For each metal, a dose response study based on cell viability showed that the highest non-toxic concentrations were: 0.5 μM Cd2+, 2 μM Co2+, 0.5 μM Cu2+, 500 μM Mn2+, 1 μM Ni2+, and 18 μM Zn2+. Cells exposed to these non-toxic concentrations with combinations of Zn2+ and Cd2+, Zn2+ and Co2+, Zn2+ and Cu2+ or Zn2+ and Ni2+, had reduced growth in comparison to controls. Cells exposed to metal combinations with the addition of 500 μM Mn2+ showed similar growth compared to the untreated controls. Metal levels were measured after one and 72 h for whole cells and absorbed (EDTA-resistant) fractions and used to calculate differential uptake rates for each metal. The differences in binding and internalisation between different metals indicate different uptake processes exist for each metal. For each metal, competitive uptake experiments using 65Zn showed that after 72 h of exposure Zn2+ uptake was reduced by most metals particularly 0.5 μM Cd2+, while 2 μM Co2+ increased Zn2+ uptake. This study demonstrates that N. punctiforme discriminates between different metals and favourably substitutes their uptake to avoid the toxic effects of particular metals.
Keywords: Cyanobacteria; Divalent cations; Metal uptake; Adsorption; Absorption; Bioremediation

Unraveling the Amycolatopsis tucumanensis copper-resistome by José Sebastián Dávila Costa; Erika Kothe; Carlos Mauricio Abate; María Julia Amoroso (905-917).
Heavy metal pollution is widespread causing serious ecological problems in many parts of the world; especially in developing countries where a budget for remediation technology is not affordable. Therefore, screening for microbes with high accumulation capacities and studying their stable resistance characteristics is advisable to define cost-effective any remediation strategies. Herein, the copper-resistome of the novel copper-resistant strain Amycolatopsis tucumanensis was studied using several approaches. Two dimensional gel electrophoresis revealed that proteins of the central metabolism, energy production, transcriptional regulators, two-component system, antioxidants and protective metabolites increased their abundance upon copper-stress conditions. Transcriptome analysis revealed that in presence of copper, superoxide dismutase, alkyl hydroperoxide reductase and mycothiol reductase genes were markedly induced in expression. The oxidative damage of protein and lipid from A. tucumanensis was negligible compared with that observed in the copper-sensitive strain Amycolatopsis eurytherma. Thus, we provide evidence that A. tucumamensis shows a high adaptation towards copper, the sum of which is proposed as the copper-resistome. This adaptation allows the strain to accumulate copper and survive this stress; besides, it constitutes the first report in which the copper-resistome of a strain of the genus Amycolatopsis with bioremediation potential has been evaluated.
Keywords: Amycolatopsis ; Copper-resistome; Oxidative stress

Effects of aurothiomalate and gold(III) complexes on spontaneous motility of isolated human oviduct by Slobodan M. Janković; Ana Djeković; Živadin Bugarčić; Snezana V. Janković; Goran Lukić; Marko Folić; Dragan Čanović (919-925).
Organic gold complexes have different biological activity, depending on their potential for interactions with key functional molecules.The aim of this study was to investigate potential of several newly synthesized organic gold complexes to influence spontaneous motility of the Fallopian tubes.The effects of [Au(bipy)Cl2]+ (dichloride(2,2′-bipyridyl)aurate(III)-ion), aurothiomalate, [Au(DMSO)2Cl2]Cl and DMSO on spontaneous motility of Fallopian tubes were tested on the isolated tube segments in vitro. Aurothiomalate (from 2.9 × 10−9 to 4.9 × 10−4 M/l), [Au(bipy)Cl2]Cl (from 3.3 × 10−9 to 4.2 × 10−5 M/l) and DMSO (from 1.9 × 10−8 to 1.0 × 10−5 M/l) did not affect spontaneous contractions of the isolated Fallopian tube ampulla, while [Au(DMSO)2Cl2]Cl (from 2.9 × 10−9 to 4.2 × 10−5 M/l) showed concentration-dependent increase (stimulation) of spontaneous contractions of the isolated Fallopian tube isthmus, and remained without effect on the isolated ampulla.The drugs designed as organic gold complexes with weaker bonds between the gold itself and organic part of a molecule could adversely affect motility of the Fallopian tubes, and theoretically fertility of women taking such drugs in their reproductive age.
Keywords: Gold(III); Complexes; Kinetics; Cytotoxicity; 5′-GMP; Fallopian tubes

Impairment of antioxidant defenses as a contributor to arsenite-induced cell transformation by Jing Wu; Anna Sowinska; Xi Huang; Catherine B. Klein; Edward Pelle; Krystyna Frenkel (927-937).
Arsenite (As) causes transformation of human osteogenic sarcoma cells (HOS) when applied continuously at low doses (0.1–0.5 μM) during 8-weeks of exposure. However, the mechanisms by which As transforms human cells are not known. We investigated whether alterations occurred in gene expression and protein levels of antioxidant defense proteins, such as superoxide dismutase 1 (SOD1) and ferritin. In comparison to control HOS cells, 0.1 μM As induced greater cell proliferation and decreased anti-oxidant defenses. The tumor suppressor protein p53 was also decreased at both mRNA and protein levels. Further, pig3 (p53-induced-gene 3), a homolog of NQO1 (NADPH quinone oxidoreductase 1), was also down-regulated after 8 weeks of As challenge. The treatment of HOS cells with dicumarol, a NQO1 inhibitor, caused a dose-dependent decline in p53 protein levels, proving the effect of an antioxidant enzyme on p53 expression and, potentially, down-stream processes. Caffeic acid phenethyl ester, an antioxidant, prevented the As-induced decreases in SOD1, p53, and ferritin mRNA and protein levels. SOD1, p53 and ferritin levels were inversely related to As-induced cell proliferation. Cumulatively, these results strongly suggest that impairment in antioxidant defenses contributes to As-induced human cell transformation and that the p53 pathway is involved in the process.
Keywords: Arsenite; CAPE; Ferritin; NQO1; p53; SOD1

Changes in morphology, cell wall composition and soluble proteome in Rhodobacter sphaeroides cells exposed to chromate by Francesca Italiano; Sara Rinalducci; Angela Agostiano; Lello Zolla; Francesca De Leo; Luigi R. Ceci; Massimo Trotta (939-949).
The response of the carotenoidless Rhodobacter sphaeroides mutant R26 to chromate stress under photosynthetic conditions is investigated by biochemical and spectroscopic measurements, proteomic analysis and cell imaging. Cell cultures were found able to reduce chromate within 3–4 days. Chromate induces marked changes in the cellular dimension and morphology, as revealed by atomic force microscopy, along with compositional changes in the cell wall revealed by infrared spectroscopy. These effects are accompanied by significant changes in the level of several proteins: 15 proteins were found up-regulated and 15 down-regulated. The protein content found in chromate exposed cells is in good agreement with the biochemical, spectroscopic and microscopic results. Moreover at the present stage no specific chromate-reductase could be found in the soluble proteome, indicating that detoxification of the pollutant proceeds via aspecific reductants.
Keywords: Chromate reduction; Photosynthesis; Rhodobacter sphaeroides ; Two-dimensional gel electrophoresis; Atomic force microscopy; Attenuated total reflection-fourier transformed infra red spectroscopy

Copper(II)–fluoroquinolone complexes with anti-Trypanosoma cruzi activity and DNA binding ability by Darliane A. Martins; Ligiane R. Gouvea; Denise da Gama Jean Batista; Patrícia Bernardino da Silva; Sonia R. W. Louro; Maria de Nazaré C. Soeiro; Letícia R. Teixeira (951-960).
Copper(II) complexes of fluoroquinolone antibacterial agents levofloxacin (LEV) and sparfloxacin (SPAR), containing or not a nitrogen donor heterocyclic ligand, 2,2′-bipyridine (bipy) or 1,10-phenathroline (phen), were prepared and characterized. The complexes are of the type [CuCl2(H2O)(L)], [CuCl(bipy)(L)]Cl and [CuCl2(phen)(L)], where L = LEV or SPAR. The data suggest that LEV and SPAR act as zwitterionic bidentade ligands coordinated to Cu(II) through the carboxylate and ketone oxygen atoms. The electron paramagnetic resonance spectra of the [CuCl(bipy)(L)]Cl and [CuCl2(phen)(L)] complexes (L = LEV and SPAR) in aqueous and DMSO solutions indicate mixture of mononuclear and binuclear forms. The Cu(II) complexes, together with the corresponding ligands, were evaluated for their trypanocidal activity in vitro against Trypanosoma cruzi, the causative agent of Chagas disease. The assays performed against bloodstream trypomastigotes showed that all complexes were more active than their corresponding ligands. Complexes [CuCl2(phen)(LEV)] and [CuCl2(phen)(SPAR)] were revealed, among all studied compounds, to be the most active with IC50 = 1.6 and 4.7 μM, respectively, both presenting a superior effect than benznidazole. The interactions of fluoroquinolones and their Cu(II) complexes with calf-thymus DNA were investigated. These compounds showed binding properties towards DNA, with moderated binding constants values, suggesting that this structure may represent a parasite target.
Keywords: Fluoroquinolones; Copper(II) complexes; Anti-T. cruzi activity; UV–Vis spectroscopy; Interaction with calf-thymus DNA

Reticuloendothelial blockade in hemodialysis patients prevents optimal intravenous (IV) iron utilization. Vitamin C has emerged as a potential therapy to improve anemia treatment by enhancing iron mobilization. However, Vitamin C can act as a pro-oxidant in the presence of iron. This was a prospective, open-label, crossover study. Thirteen patients with end-stage renal disease on hemodialysis and four healthy controls were assigned to receive 100 mg of IV iron sucrose (IS) or 100 mg of IV IS co-administered with 300 mg of IV Vitamin C (IS + C) in random sequence. Serum samples for IL-1, IL-6, TNF-α and IL-10 and non-transferrin bound iron were obtained at baseline, 45 min and 105 min post study medication administration. Peripheral blood mononuclear cells were isolated at the same time points and stained with fluorescent probes to identify intracellular reactive oxygen species and mitochondrial membrane potential (Δψm) by flow cytometry. Lipid peroxidation was assessed by plasma F2-isoprosatane concentration. Both IS and IS + C were associated with increased plasma F2-isoprostanes concentrations post-infusion. Maximal plasma F2-isoprostane concentrations after IS + C were significantly elevated from baseline (234 ± 0.04 vs. 0.198 ± 0.028 ng/mL, p = 0.02). After IS + C, IL-1, IL-6, IL-10, and TNF-alpha were significantly elevated compared to baseline. After IS alone only IL-6 was noted to be elevated. Intracellular production of H2O2 and loss of mitochondrial membrane potential (Δψm) was observed after IS while IS + C was associated with increased O 2 ·− production. Both IS and IS + C induced serum cytokine activation accompanied by lipid peroxidation, however, IS + C induced higher plasma concentrations of F2-isoprostanes, IL-1, IL-10, and TNF-α post-infusion. Long-term safety studies of IV iron co-administered with Vitamin C are warranted.
Keywords: Oxygen radicals; Inflammation; Cytokines; Iron sucrose; Vitamin C; Hemodialysis

Unincorporated iron pool is linked to oxidative stress and iron levels in Caenorhabditis elegans by Natalie A. Rangel; Lawrence Lin; Kanyasiri Rakariyatham; Albert Bach; Kim Trinh; Matthew H. S. Clement; Chandra Srinivasan (971-985).
Free radicals or reactive oxygen species (ROS) are relatively short-lived and are difficult to measure directly; so indirect methods have been explored for measuring these transient species. One technique that has been developed using Escherichia coli and Saccharomyces cerevisiae systems, relies on a connection between elevated superoxide levels and the build-up of a high-spin form of iron (Fe(III)) that is detectable by electron paramagnetic resonance (EPR) spectroscopy at g = 4.3. This form of iron is referred to as “free” iron. EPR signals at g = 4.3 are commonly encountered in biological samples owing to mononuclear high-spin (S = 5/2) Fe(III) ions in sites of low symmetry. Unincorporated iron in this study refers to this high-spin Fe(III) that is captured by desferrioxamine which is detected by EPR at g value of 4.3. Previously, we published an adaptation of Fe(III) EPR methodology that was developed for Caenorhabditis elegans, a multi-cellular organism. In the current study, we have systematically characterized various factors that modulate this unincorporated iron pool. Our results demonstrate that the unincorporated iron as monitored by Fe(III) EPR at g = 4.3 increased under conditions that were known to elevate steady-state ROS levels in vivo, including: paraquat treatment, hydrogen peroxide exposure, heat shock treatment, or exposure to higher growth temperature. Besides the exogenous inducers of oxidative stress, physiological aging, which is associated with elevated ROS and ROS-mediated macromolecular damage, also caused a build-up of this iron. In addition, increased iron availability increased the unincorporated iron pool as well as generalized oxidative stress. Overall, unincorporated iron increased under conditions of oxidative stress with no change in total iron levels. However, when total iron levels increased in vivo, an increase in both the pool of unincorporated iron and oxidative stress was observed suggesting that the status of the unincorporated iron pool is linked to oxidative stress and iron levels.
Keywords: Oxidative stress; Reactive oxygen species; Iron electron paramagnetic resonance; Free iron; Unincorporated iron; Iron

Interaction of Ag with communities of soil saprotrophic organisms was studied in two different soils using a metagenomic approach. Three levels of Ag were applied to the soil samples: 0, 0.008 and 0.505 μg Ag/g soil. Silver was applied in mineral form as well as naturally bound in dry fruit-body biomass of the Ag-hyperaccumulating ectomycorrhizal fungus Amanita solitaria. Contrasting behavior of fungi and bacteria in reaction to Ag dosages was observed. The majority of bacterial ribotypes tended to prefer the soil with low doses of Ag, the ribotypes of fungi were more abundant in untreated soils and soils treated with the highest Ag concentration. Organically bound and mineral forms of Ag did not differ substantially in their effects on microbes in samples. The results indicate that decomposing Ag-rich fungal biomass can significantly alter the soil microbiota. This can contribute to formation of spot-like non-homogeneities in soil microbial distribution.
Keywords: Soil fungi; Bacteria; Microbiota; Heavy metals; Toxicity; T-RFLP

Tellurite resistance gene trgB confers copper tolerance to Rhodobacter capsulatus by Corinna Rademacher; Marie-Christine Hoffmann; Jan-Wilm Lackmann; Roman Moser; Yvonne Pfänder; Silke Leimkühler; Franz Narberhaus; Bernd Masepohl (995-1008).
To identify copper homeostasis genes in Rhodobacter capsulatus, we performed random transposon Tn5 mutagenesis. Screening of more than 10,000 Tn5 mutants identified tellurite resistance gene trgB as a so far unrecognized major copper tolerance determinant. The trgB gene is flanked by tellurite resistance gene trgA and cysteine synthase gene cysK2. While growth of trgA mutants was only moderately restricted by tellurite, trgB and cysK2 mutants were severely affected by tellurite, which implies that viability under tellurite stress requires increased cysteine levels. Mutational analyses revealed that trgB was the only gene in this chromosomal region conferring cross-tolerance towards copper. Expression of the monocistronic trgB gene required promoter elements overlapping the trgA coding region as shown by nested deletions. Neither copper nor tellurite affected trgB transcription as demonstrated by reverse transcriptase PCR and trgBlacZ fusions. Addition of tellurite or copper gave rise to increased cellular tellurium and copper concentrations, respectively, as determined by inductively coupled plasma-optical emission spectroscopy. By contrast, cellular iron concentrations remained fairly constant irrespective of tellurite or copper addition. This is the first study demonstrating a direct link between copper and tellurite response in bacteria.
Keywords: Copper; Tellurite; Nudix hydrolase; Metal homeostasis; Rhodobacter

Comparative analysis of stability and toxicity profile of three differently capped gold nanoparticles for biomedical usage by Sumistha Das; Nitai Debnath; Shouvik Mitra; Alokmay Datta; Arunava Goswami (1009-1022).
Nowadays gold nanoparticle (GNP) is increasingly being used in drug delivery and diagnostics. Here we have reported a comparative analysis of detailed stability and toxicity (in vitro and in vivo) profile of three water soluble spherical GNPs, having nearly similar size, but the surfaces of which were modified with three different capping materials aspartic acid (GNPA), trisodium citrate dihydrate (GNPC) or bovine serum albumin (GNPB). Spectral analyses on the stability of these GNPs revealed that depending on the nature of capping agents, GNPs behave differently at different environmental modalities like wide range of pH, high salt concentrations, or in solutions and buffers of biological usage. GNPB was found to be extremely stable, where capped protein molecule successfully maintained its secondary structure and helicity on the nanoparticle, whereas colloidal stability of GNPA was most susceptible to altered conditions. In vitro cytotoxicity of these nanoparticle formulations in vitro were determined by water soluble tetrazolium and lactate dehydrogenase assay in human fibroblast cell line (MRC-5) and acute oral toxicity was performed in murine model system. All the GNPs were non-toxic to MRC-5 cells. GNPC had slight hepatotoxic and nephrotoxic responses. Hepatotoxicity was also evident for GNPA treatment. Present study established that there is a correlation between capping material and stability together with toxicity of nanoparticles. GNPB was found to be most biocompatible among the three GNPs tested.
Keywords: Gold nanoparticles; Surface plasmon resonance; Stability; Cytotoxicity; Acute oral toxicity

Characterization of the aqueous iron(III) chelation chemistry of a potential Trojan Horse antimicrobial agent: chelate structure, stability and pH dependent speciation by James M. Harrington; Tom Gootz; Mark Flanagan; Majinder Lall; John O’Donnell; Jennifer Winton; John Mueller; Alvin L. Crumbliss (1023-1036).
The aqueous solution equilibria of a β-lactam antimicrobial agent containing a 3-hydroxy, 4-pyridinone group (L PF) binding to Fe(III) in aqueous solution has been characterized through spectrophotometric and potentiometric titrations. The metal-free ligand has four observable protonation constants, pKa1 = 2.6, pKa2 = 3.43, pKa3 = 6.43, and pKa4 = 9.62. L PF forms a 3:1 ligand:Fe(III) complex in aqueous solution through coordinate-covalent bond formation exclusively involving the bidentate hydroxypyridinone moiety. This 3:1 L PF:Fe complex was found to have a stability constant of log β130 = 33.46. A speciation diagram for the L PF system demonstrates that in the region of physiological pH the tris-(L PF)Fe(III) complex, Fe(LPF) 3 6− , predominates. This complex exhibits two irreversible reduction waves in solution at −30 mV versus NHE, corresponding to a ligand-based reduction, and at −385 mV versus NHE, corresponding to an irreversible Fe3+/Fe2+ reduction of the Fe(LPF) 3 6− complex.
Keywords: Trojan horse; Antimicrobial; Chelation; Siderophore; Hydroxypyridinone; Iron; Redox

Differential gene regulation by VIV and VV ions in the branchial sac, intestine, and blood cells of a vanadium-rich ascidian, Ciona intestinalis by Satoshi Kume; Tatsuya Ueki; Hiroki Matsuoka; Mayuko Hamada; Nori Satoh; Hitoshi Michibata (1037-1050).
Ascidians are hyperaccumulators that have been studied in detail. Proteins and genes involved in the accumulation process have been identified, but regulation of gene expression related to vanadium accumulation remains unknown. To gain insights into the regulation of gene expression by vanadium in a genome-wide manner, we performed a comprehensive study on the effect of excess vanadium ions on a vanadium-rich ascidian, Ciona intestinalis, using a microarray. RT-PCR and enzyme activity assay were performed from the perspective of redox and accumulation of metal ions in each tissue. Glutathione metabolism-related proteins were significantly up-regulated by VIV treatment. Several genes involved in the transport of vanadium and protons, such as Nramp and V-ATPase, were significantly up-regulated by VIV treatment. We observed significant up-regulation of glutathione synthesis and degradation pathways in the intestine and branchial sac. In blood cells, expression of Ci-Vanabin4, glutathione reductase activity, glutathione levels, and vanadium concentration increased after VIV treatment. VIV treatment induced significant changes related to vanadium exclusion, seclusion, and redox pathways in the intestine and branchial sac. It also induced an enhancement of the vanadium reduction and accumulation cascade in blood cells. These differential responses in each tissue in the presence of excess vanadium ions suggest that vanadium accumulation and reduction may have regulatory functions. This is the first report on the gene regulation by the treatment of vanadium-rich ascidians with excess vanadium ions. It provided much information for the mechanism of regulation of gene expression related to vanadium accumulation.
Keywords: Ascidian; Vanadium; Microarray; Gene regulation; Glutathione

Bioavailability of chromium(III)-supplements in rats and humans by Niels Laschinsky; Karin Kottwitz; Barbara Freund; Bernd Dresow; Roland Fischer; Peter Nielsen (1051-1060).
Chromium(III) is long regarded as essential trace element but the biochemical function and even basic transport ways in the body are still unclear. For a more rational discussion on beneficial as well as toxic effects of Cr(III), we re-investigated the bioavailability of the most important oral Cr supplements by using radiolabeled compounds and whole-body-counting in rats and in the first time also in humans. The apparent absorption of 51Cr(III) from Cr-picolinate, Cr-nicotinate, Cr-phenylalaninate, Cr-proprionate, or Cr-chloride was generally low (0.04–0.24 %) in rats with slightly higher values for Cr-chloride and -phenylalaninate. Taking a fast urine excretion into account, the true absorption of 51Cr was clearly higher for CrPic3 (0.99 %), probably indicating a different uptake mechanism of this rather stable organic Cr complex. The bioavailability of CrPic3 and Cr(d-Phen)3, the leading compounds in actual investigations, was analysed also in human volunteer by intraindividual comparison. The apparent absorption (=Cr bioavailability) of 51Cr from both compounds was substantially higher in humans (0.8–1 %) than in rats. Again, most of freshly absorbed CrPic3 was excreted into the urine resulting in the same low whole-body retention after 7 days for both compounds. In summary, the bioavailability of Cr from pharmaceutical Cr compound is lower than hitherto assumed. Importantly, humans absorb Cr(III) clearly better than rats. The absorption mechanism of CrPic3 seems to be different from ionic Cr(III) but, as only the same low amount of Cr is retained from this compound, it is also not more bioavailable than other Cr compounds.
Keywords: Chromium; Cr-picolinate; Cr-nicotinate; Cr-phenylalaninate; 51Cr-absorption; Whole-body-counting

Biological and cytoselective anticancer properties of copper(II)-polypyridyl complexes modulated by auxiliary methylated glycine ligand by Hoi-Ling Seng; Wai-San Wang; Siew-Ming Kong; Han-Kiat Alan Ong; Yip-Foo Win; Raja Noor Zaliha Raja Abd. Rahman; Makoto Chikira; Weng-Kee Leong; Munirah Ahmad; Alan Soo-Beng Khoo; Chew-Hee Ng (1061-1081).
A series of ternary copper(II)-1,10-phenanthroline complexes with glycine and methylated glycine derivatives, [Cu(phen)(aa)(H2O)]NO3·xH2O 14 (amino acid (aa): glycine (gly), 1; dl-alanine (dl-ala), 2; 2,2-dimethylglycine (C-dmg), 3; sarcosine (sar), 4), were synthesized and characterized by FTIR, elemental analysis, electrospray ionization–mass spectra (ESI–MS), UV–visible spectroscopy and molar conductivity measurement. The determined X-ray crystallographic structures of 2 and 3 show each to consist of distorted square pyramidal [Cu(phen)(aa)(H2O)]+ cation, a nitrate counter anion, and with or without lattice water, similar to previously reported structure of [Cu(phen)(gly)(H2O)]NO3·1½H2O. It is found that 14 exist as 1:1 electrolytes in aqueous solution, and the cationic copper(II) complexes are at least stable up to 24 h. Positive-ion ESI–MS spectra show existence of only undissociated [Cu(phen)(aa)]+ species. Electron paramagnetic resonance, gel electrophoresis, fluorescence quenching, and restriction enzyme inhibition assay were used to study the binding interaction, binding affinity and selectivity of these complexes for various types of B-form DNA duplexes and G-quadruplex. All complexes can bind selectively to DNA by intercalation and electrostatic forces, and inhibit topoisomerase I. The effect of the methyl substituents of the coordinated amino acid in the above complexes on these biological properties are presented and discussed. The IC50 values (24 h) of 14 for nasopharyngeal cancer cell line HK1 are in the range 2.2–5.2 μM while the corresponding values for normal cell line NP69 are greater than 13.0 μM. All complexes, at 5 μM, induced 41–60 % apoptotic cell death in HK1 cells but no significant cell death in NP69 cells.
Keywords: Ternary copper(II) complexes; Crystal structure; DNA binding; G-quadruplex; Topoisomerase I; Anticancer selectivity

Iron-dependent binding of bovine milk α-casein with holo-lactoferrin, but not holo-transferrin by Naoko Shibuya; Yasunaga Yoshikawa; Kiyotaka Watanabe; Hiromichi Ohtsuka; Koichi Orino (1083-1088).
Bovine milk α-casein has been identified as an iron- and heme-binding protein. However, the physiological role of its iron-binding remains to be elucidated in more detail. α-Casein was immobilized on CNBr-activated Sepharose 4B beads, and the α-casein agarose beads efficiently bound hemin as well as ferrous ammonium sulfate (Fe2+) as compared with control beads. Additionally, α-casein-beads bound bovine holo-lactoferrin (Lf), but not holo-transferrin. Lf caused the release of Fe2+ which had bound to the α-casein–agarose beads beforehand. These results suggest that bovine α-casein iron-dependently binds holo-bovine Lf more strongly than Fe2+, and that strong binding between them may play a physiological role in regulating iron homeostasis in the bovine mammary gland.
Keywords: α-Casein; Holo-lactoferrin; Holo-transferrin; Iron; Milk