Risks of Copper and Iron Toxicity during Aging in Humans

Copper induces cellular senescence in human glioblastoma multiforme cells through downregulation of Bmi-1

Most human tumor cells, including glioblastoma multiforme (GBM) cells, have aberrant control of cell aging and apoptosis. Subcytotoxic concentrations of oxidative or stress‑causing agents, such as hydrogen peroxide, may induce human cell senescence. Thus, induction of tumor cells into premature senescence may provide a useful in vitro model for developing novel therapeutic strategy to combat tumors. In the present study, we assessed the molecular mechanism(s) underlying senescence in GBM cells induced by copper sulfate. Following pretreatment with subcytotoxic concentrations of copper sulfate, U87-MG tumor cells showed typical aging characteristics, including reduced cell proliferation, cell enlargement, increased level of senescence-associated β-galactosidase (SA β-gal) activity, and overexpression of several senescence-associated genes, p16, p21, transforming growth factor β-1 (TGF-β1), insulin growth factor binding protein 3 (IGFBP3) and apolipoprotein J (ApoJ). We further demonstrated that the Bmi-1 pathway was downregulated in GBM cells in parallel with the induced senescence. The present study for the first time demonstrates the ability of copper to induce GBM cell senescence by downregulating Bmi-1.

Ferricytochrome (c) directly oxidizes aminoacetone to methylglyoxal, a catabolite accumulated in carbonyl stress

Age-related diseases are associated with increased production of reactive oxygen and carbonyl species such as methylglyoxal. Aminoacetone, a putative threonine catabolite, is reportedly known to undergo metal-catalyzed oxidation to methylglyoxal, NH4(+) ion, and H2O2 coupled with (i) permeabilization of rat liver mitochondria, and (ii) apoptosis of insulin-producing cells. Oxidation of aminoacetone to methylglyoxal is now shown to be accelerated by ferricytochrome c, a reaction initiated by one-electron reduction of ferricytochrome c by aminoacetone without amino acid modifications. The participation of O2(•-) and HO (•) radical intermediates is demonstrated by the inhibitory effect of added superoxide dismutase and Electron Paramagnetic Resonance spin-trapping experiments with 5,5'-dimethyl-1-pyrroline-N-oxide. We hypothesize that two consecutive one-electron transfers from aminoacetone (E0 values = -0.51 and -1.0 V) to ferricytochrome c (E0 = 0.26 V) may lead to aminoacetone enoyl radical and, subsequently, imine aminoacetone, whose hydrolysis yields methylglyoxal and NH4(+) ion. In the presence of oxygen, aminoacetone enoyl and O2(•-) radicals propagate aminoacetone oxidation to methylglyoxal and H2O2. These data endorse the hypothesis that aminoacetone, putatively accumulated in diabetes, may directly reduce ferricyt c yielding methylglyoxal and free radicals, thereby triggering redox imbalance and adverse mitochondrial responses.

Metal concentrations in cerebrospinal fluid and blood plasma from patients with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal degenerative disorder of motor neurons. The cause of this degeneration is unknown, and different causal hypotheses include genetic, viral, traumatic and environmental mechanisms. In this study, we have analyzed metal concentrations in cerebrospinal fluid (CSF) and blood plasma in a well-defined cohort (n = 17) of ALS patients diagnosed with quantitative electromyography. Metal analyses were performed with high-resolution inductively coupled plasma mass spectrometry. Statistically significant higher concentrations of manganese, aluminium, cadmium, cobalt, copper, zinc, lead, vanadium and uranium were found in ALS CSF compared to control CSF. We also report higher concentrations of these metals in ALS CSF than in ALS blood plasma, which indicate mechanisms of accumulation, e.g. inward directed transport. A pattern of multiple toxic metals is seen in ALS CSF. The results support the hypothesis that metals with neurotoxic effects are involved in the pathogenesis of ALS.

Is nanotechnology revolutionizing the paint and lacquer industry? A critical opinion

Many paints for indoor and outdoor applications contain biocides and additives for protection against microbial, physical and chemical deterioration. The biocides should remain active as long as they are incorporated in the paint. Protection against microbial colonization should last at least a decade. Once the biocides are released they should degrade within a short time so that no accumulation in the environment can occur. The paint industry is not only focusing their research in producing better paint formulations with degradable biocides: they also consider using nanomaterials, such as nanosilver, nanocopper, nanozinc oxide, photocatalytic-active nanotitanium dioxide and nanosilica dioxide as additives for the protection of paints, against microbial degradation and physical and chemical deterioration. In the future nanomaterials should replace biodegradable biocides and improve the paint properties as well as impede colonization by microorganisms. At the time there is no guarantee that the nanomaterials in paints and façades will fulfill their task in the long run, since there are no long term studies available. From nanosilver doped paints it is known that silver is easily washed out by rain. Photocatalytic active nanotitanium dioxide adsorbs ultra violet light (UV-light) and generates hydroxyl radicals, which not only inhibit microbial growth but can also initiate or accelerate the photocatalytic degradation of the paint matrix. Thus at this time it is still unknown if it makes sense to incorporate nanomaterials into paints. Intensive research and development are still needed in order to find the answers.

Hydroxyl radical-modified fibrinogen as a marker of thrombosis: the role of iron

Excessive free iron in blood and in organ tissues (so called iron overload) has been observed in degenerative diseases such as atherosclerosis, cancer, neurological, and certain autoimmune diseases, in which fibrin-like deposits are also found. Although most of the body iron is bound to hemoglobin and myoglobin in a divalent ferrous form, a certain amount of iron exists in blood as a trivalent (ferric) ion. This particular chemical state of iron has been shown to be toxic to the human body when not controlled by endogenous and/or dietary chelating agents. Experiments described in this paper show for the first time that ferric ions (Fe(3+)) can generate hydroxyl radicals without participation of any redox agent, thus making it a special case of the Fenton reaction. Ferric chloride was also demonstrated to induce aggregation of purified fibrinogen at the same molar concentrations that were used for the generation of hydroxyl radicals. Iron-aggregated fibrinogen, by contrast to native molecule, could not be dissociated into polypeptide subunit chains as shown in a polyacrylamide gel electrophoresis. The mechanism of this phenomenon is very likely based on hydroxyl radical-induced modification of fibrinogen tertiary structure with the formation of insoluble aggregates resistant to enzymatic and chemical degradations. Soluble modified fibrinogen species can be determined in blood of thrombotic patients by the reaction with protamine sulfate and/or by scanning electron microscopy. In view of these findings, it is postulated that iron-induced alterations in fibrinogen structure is involved in pathogenesis of certain degenerative diseases associated with iron overload and persistent thrombosis. It is concluded that the detection of hydroxyl radical-modified fibrinogen may be utilized as a marker of a thrombotic condition in human subjects.

Copper ability to induce premature senescence in human fibroblasts

Human diploid fibroblasts (HDFs) exposed to subcytotoxic concentrations of oxidative or stressful agents, such as hydrogen peroxide, tert-butylhydroperoxide, or ethanol, undergo stress-induced premature senescence (SIPS). This condition is characterized by the appearance of replicative senescence biomarkers such as irreversible growth arrest, increase in senescence-associated β-galactosidase (SA β-gal) activity, altered cell morphology, and overexpression of several senescence-associated genes. Copper is an essential trace element known to accumulate with ageing and to be involved in the pathogenesis of some age-related disorders. Past studies using either yeast or human cellular models of ageing provided evidence in favor of the role of intracellular copper as a longevity modulator. In the present study, copper ability to cause the appearance of senescent features in HDFs was assessed. WI-38 fibroblasts exposed to a subcytotoxic concentration of copper sulfate presented inhibition of cell proliferation, cell enlargement, increased SA β-gal activity, and mRNA overexpression of several senescence-associated genes such as p21, apolipoprotein J (ApoJ), fibronectin, transforming growth factor β-1 (TGF β1), insulin growth factor binding protein 3, and heme oxygenase 1. Western blotting results confirmed enhanced intracellular p21, ApoJ, and TGF β1 in copper-treated cells. Thus, similar to other SIPS-inducing agents, HDF exposure to subcytotoxic concentration of copper results in premature senescence. Further studies will unravel molecular mechanisms and the biological meaning of copper-associated senescence and lead to a better understanding of copper-related disorder establishment and progression.

Penicillamine increases free copper and enhances oxidative stress in the brain of toxic milk mice

Wilson disease (WD) is characterized by the accumulation of copper arising from a mutation in the ATP7B gene. Penicillamine (PA) makes 10–50% of the patients with neurologic symptoms neurologically worse at the early stage of administration. The aim of this study was to determine how the copper metabolism changes and whether the change impairs the brain of toxic milk (tx) mice, an animal model of WD, during the PA administration. The free copper and protein-bound copper concentrations in the serum, cortex and basal ganglia of tx mice with PA administration for 3 days, 10 days and 14 days, respectively, were investigated. The expression of copper transporters, ATP7A and CTR1,was analyzed by real-time quantitative PCR, immunofluorescence and Western blot. Then SOD, MDA and GSH/GSSG were detected to determine whether the oxidative stress changed correspondingly. The results revealed the elevated free copper concentrations in the serum and brain, and declined protein-bound copper concentrations in the brain of tx mice during PA administration. Meanwhile, transiently increased expression of ATP7A and CTR1 was observed generally in the brain parenchyma by immunofluorescence, real-time quantitative PCR and Western blot. Additionally, ATP7A and CTR1 were observed to locate mainly at Golgi apparatus and cellular membrane respectively. Intense staining of ATP7A in the choroid plexus was found in tx mice on the 3rd and 10th day of PA treatment, but rare staining of ATP7A and CTR1 in the blood-brain barrier (BBB). Decreased GSH/GSSG and increased MDA concentrations were also viewed in the cortex and basal ganglia. Our results suggested the elevated free copper concentrations in the brain might lead to the enhanced oxidative stress during PA administration. The increased free copper in the brain might come from the copper mobilized from brain parenchyma cells but not from the serum according to the ATP7A and CTR1 expression analysis.

RNA modifications by oxidation: a novel disease mechanism?

The past decade has provided exciting insights into a novel class of central (small) RNA molecules intimately involved in gene regulation. Only a small percentage of our DNA is translated into proteins by mRNA, yet 80% or more of the DNA is transcribed into RNA, and this RNA has been found to encompass various classes of novel regulatory RNAs, including, e.g., microRNAs. It is well known that DNA is constantly oxidized and repaired by complex genome maintenance mechanisms. Analogously, RNA also undergoes significant oxidation, and there are now convincing data suggesting that oxidation, and the consequent loss of integrity of RNA, is a mechanism for disease development. Oxidized RNA is found in a large variety of diseases, and interest has been especially devoted to degenerative brain diseases such as Alzheimer disease, in which up to 50-70% of specific mRNA molecules are reported oxidized, whereas other RNA molecules show virtually no oxidation. The iron-storage disease hemochromatosis exhibits the most prominent general increase in RNA oxidation ever observed. Oxidation of RNA primarily leads to strand breaks and to oxidative base modifications. Oxidized mRNA is recognized by the ribosomes, but the oxidation results in ribosomal stalling and dysfunction, followed by decreased levels of functional protein as well as the production of truncated proteins that do not undergo proper folding and may result in protein aggregation within the cell. Ribosomal dysfunction may also signal apoptosis by p53-independent pathways. There are very few reports on interventions that reduce RNA oxidation, one interesting observation being a reduction in RNA oxidation by ingestion of raw olive oil. High urinary excretion of 8-oxo-guanosine, a biomarker for RNA oxidation, is highly predictive of death in newly diagnosed type 2 diabetics; this demonstrates the clinical relevance of RNA oxidation. Taken collectively the available data suggest that RNA oxidation is a contributing factor in several diseases such as diabetes, hemochromatosis, heart failure, and β-cell destruction. The mechanism involves free iron and hydrogen peroxide from mitochondrial dysfunction that together lead to RNA oxidation that in turn gives rise to truncated proteins that may cause aggregation. Thus RNA oxidation may well be an important novel contributing mechanism for several diseases.

Dual role of selected antioxidants found in dietary supplements: crossover between anti- and pro-oxidant activities in the presence of copper

Overproduction of reactive oxygen species (ROS) in vivo can result in damage associated with many aging-associated diseases. Defenses against ROS that have evolved include antioxidant enzymes, such as superoxide dismutases, peroxidases, and catalases, which can scavenge ROS. In addition, endogenous and dietary antioxidants play an important role in moderating damage associated with ROS. In this study, we use four common dietary antioxidants to demonstrate that, in the presence of copper (cupric sulfate and cupric gluconate) and physiologically relevant levels of hydrogen peroxide, these antioxidants can also act as pro-oxidants by producing hydroxyl radicals. Using electron spin resonance (ESR) spin trapping techniques, we demonstrate that the level of hydroxyl radical formation is a function of the pH of the medium and the relative amounts of antioxidant and copper. On the basis of the level of hydroxyl radical formation, the relative pro-oxidant potential of these antioxidants is cysteine > ascorbate > EGCG > GSH. It has been reported that copper sequestered by protein ligands, as happens in vivo, loses its redox activity (diminishing/abolishing the formation of free radicals). However, in the presence of hydrogen peroxide, cysteine and GSH efficiently react with cupric sulfate sequestered with bovine serum albumin to generate hydroxyl radicals. Overall, the results demonstrate that in the presence of copper, endogenous and dietary antioxidants can also exhibit pro-oxidative activity.

An association between environmental factors and the IVS4+44C>A polymorphism of the DMT1 gene in age-related macular degeneration

Background

Age-related macular degeneration (AMD) is an ocular disease affecting macula — the central part of the retina, resulting in the degeneration of photoreceptors and retinal epithelium and causing severe central vision impairment. The pathophysiology of the disease is not completely known, but a significant role is attributed to genetic factors. The contribution of oxidative stress in AMD as a trigger of the degenerative process is well-established. Iron ions may act as a source of reactive oxygen species; therefore, maintaining iron homeostasis is important for redox balance in the organism. Diversity in iron homeostasis genes may counterpart in unbalanced redox state, and thus be involved in AMD pathophysiology.

Methods

In this work, we searched for an association between some single nucleotide polymorphisms in the divalent metal transporter 1 (DMT1) gene intronic IVS4+44C>A (rs224589) and 3’-UTR c.2044T>C (rs2285230) and environmental factors and AMD. Genotyping was performed using the PCR-RFLP method. DNA was obtained from 436 AMD patients and 168 controls.

Results

We did not find any association between the genotypes of the two polymorphisms and AMD occurrence. However, we observed that AMD patients living in a rural environment and having the CC genotype of the IVS4+44C>A polymorphism had an increased risk of AMD, while individuals with the CA genotype or the A allele had a decreased risk of the disease. Moreover, in male AMD patients the C allele increased the risk of the disease, while the AA genotype decreased it.

Conclusions

These results suggest that the VS4+44C>A polymorphism of the DMT1 gene may interact with place of living and gender to modulate the risk of AMD.

Gold-containing indoles as anticancer agents that potentiate the cytotoxic effects of ionizing radiation

This report describes the design and application of several distinct gold-containing indoles as anticancer agents. When used individually, all gold-bearing compounds display cytostatic effects against leukemia and adherent cancer cell lines. However, two gold-bearing indoles show unique behavior by increasing the cytotoxic effects of clinically relevant levels of ionizing radiation. Quantifying the amount of DNA damage demonstrates that each gold-indole enhances apoptosis by inhibiting DNA repair. Both Au(I)-indoles were tested for inhibitory effects against various cellular targets including thioredoxin reductase, a known target of several gold compounds, and various ATP-dependent kinases. While neither compound significantly inhibits the activity of thioreoxin reductase, both showed inhibitory effects against several kinases associated with cancer initiation and progression. The inhibition of these kinases provides a possible mechanism for the ability of these Au(I)-indoles to potentiate the cytotoxic effects of ionizing radiation. Clinical applications of combining Au(I)-indoles with ionizing radiation are discussed as a new strategy to achieve chemosensitization of cancer cells.

Characterization of tannery effluent wastewater by proton-induced X-ray emission (PIXE) analysis to investigate their role in water pollution

INTRODUCTION

Over the last few decades, the chromium-based tanning industry has shown rapid growth in Pakistan. However, the rules and regulations promulgated by the government are not strictly followed for processing the effluent discharge from the tanneries. Consequently, tannery effluents have become a great source of water pollution in surrounding areas.

MATERIALS AND METHODS

In this case study, characterization of tannery effluent wastewater (TW), shallow groundwater (SW), and deep groundwater (DW) samples was carried out to determine the source of water pollution in the district of Kasur, Pakistan.

RESULTS

The concentrations of calcium (Ca), chlorine (Cl), chromium (Cr), iron (Fe), potassium (K), Mg, sulfur (S), silicon (Si), and Sr in TW were significantly higher than SW and DW, which also exceeded the international limits. In addition, increased concentrations of major toxic elements (Cl, Cr, Fe, K, Ni, and Si) were also observed in SW, which were higher in comparison to DW. Strikingly, the concentrations of Cr and Si in various DW samples were also beyond World Health Organization (WHO) safe limit, which reinforced the trend that water pollution in the area is directly linked to the distance from the source (TW). The particle-induced X-ray emission (PIXE) indices also suggested that TW is a main contributory source of water-based pollution in the area, which is imposing great threat to local inhabitants due to known hazardous and carcinogenic potential of these elements.

CONCLUSION

Protecting the water resources will be a formidable challenge in the study area, which requires modernization of tannery industry, thereby improving the recovery and recycling of TW. Moreover, PIXE analysis presented here as a successful tool, could serve as landmark for the contemporary research in environmental toxicology.

Are reproduction impairments of free spawning marine invertebrates exposed to zero-valent nano-iron associated with dissolution of nanoparticles?

Studies were carried out to assess the effects of coating applied to zero-valent nano-iron (nZVI) on early life stage development of three key marine invertebrate species Mytilus galloprovincialis, Ciona intestinalis and Psammechinus milliaris. Embryo development was assessed following a 2-h exposure of the sperm to concentrations of two nZVIs of up to 10 mg l(-1) followed by in vitro fertilisation. Disruption of embryo development was most severe in sea squirts followed by mussel, while the urchin embryos were not significantly affected as compared with controls. An over twofold decrease in fertilisation success alongside significant delay in the embryo development was observed, and the effect was more severe with the coated form, possibly owing to its better colloidal stability. We provide in vitro evidence for the rapid dissolution (within 2 h) of nZVI in seawater to a degree that concentration of total solute Fe released from the coated ZVI particles exceeds safe limits of NOECs established for dissolved Fe.

Structural and mechanistic implications of metal binding in the small heat-shock protein αB-crystallin

The human small heat-shock protein αB-crystallin (αB) rescues misfolded proteins from irreversible aggregation during cellular stress. Binding of Cu(II) was shown to modulate the oligomeric architecture and the chaperone activity of αB. However, the mechanistic basis of this stimulation is so far not understood. We provide here first structural insights into this Cu(II)-mediated modulation of chaperone function using NMR spectroscopy and other biophysical approaches. We show that the α-crystallin domain is the elementary Cu(II)-binding unit specifically coordinating one Cu(II) ion with picomolar binding affinity. Putative Cu(II) ligands are His(83), His(104), His(111), and Asp(109) at the dimer interface. These loop residues are conserved among different metazoans, but also for human αA-crystallin, HSP20, and HSP27. The involvement of Asp(109) has direct implications for dimer stability, because this residue forms a salt bridge with the disease-related Arg(120) of the neighboring monomer. Furthermore, we observe structural reorganization of strands β2-β3 triggered by Cu(II) binding. This N-terminal region is known to mediate both the intermolecular arrangement in αB oligomers and the binding of client proteins. In the presence of Cu(II), the size and the heterogeneity of αB multimers are increased. At the same time, Cu(II) increases the chaperone activity of αB toward the lens-specific protein β(L)-crystallin. We therefore suggest that Cu(II) binding unblocks potential client binding sites and alters quaternary dynamics of both the dimeric building block as well as the higher order assemblies of αB.

Electrochemically controlled drug-mimicking protein release from iron-alginate thin-films associated with an electrode

Novel biocompatible hybrid-material composed of iron-ion-cross-linked alginate with embedded protein molecules has been designed for the signal-triggered drug release. Electrochemically controlled oxidation of Fe(2+) ions in the presence of soluble natural alginate polymer and drug-mimicking protein (bovine serum albumin, BSA) results in the formation of an alginate-based thin-film cross-linked by Fe(3+) ions at the electrode interface with the entrapped protein. The electrochemically generated composite thin-film was characterized by electrochemistry and atomic force microscopy (AFM). Preliminary experiments demonstrated that the electrochemically controlled deposition of the protein-containing thin-film can be performed at microscale using scanning electrochemical microscopy (SECM) as the deposition tool producing polymer-patterned spots potentially containing various entrapped drugs. Application of reductive potentials on the modified electrode produced Fe(2+) cations which do not keep complexation with alginate, thus resulting in the electrochemically triggered thin-film dissolution and the protein release. Different experimental parameters, such as the film-deposition time, concentrations of compounds and applied potentials, were varied in order to demonstrate that the electrodepositon and electrodissolution of the alginate composite film can be tuned to the optimum performance. A statistical modeling technique was applied to find optimal conditions for the formation of the composite thin-film for the maximal encapsulation and release of the drug-mimicking protein at the lowest possible potential.

Small molecule probes for plant cell wall polysaccharide imaging

Plant cell walls are composed of interlinked polymer networks consisting of cellulose, hemicelluloses, pectins, proteins, and lignin. The ordered deposition of these components is a dynamic process that critically affects the development and differentiation of plant cells. However, our understanding of cell wall synthesis and remodeling, as well as the diverse cell wall architectures that result from these processes, has been limited by a lack of suitable chemical probes that are compatible with live-cell imaging. In this review, we summarize the currently available molecular toolbox of probes for cell wall polysaccharide imaging in plants, with particular emphasis on recent advances in small molecule-based fluorescent probes. We also discuss the potential for further development of small molecule probes for the analysis of cell wall architecture and dynamics.

Magnetic nanoparticles: an update of application for drug delivery and possible toxic effects

Magnetic nanoparticles (MNPs) represent a subclass within the overall category of nanomaterials and are widely used in many applications, particularly in the biomedical sciences such as targeted delivery of drugs or genes, in magnetic resonance imaging, and in hyperthermia (treating tumors with heat). Although the potential benefits of MNPs are considerable, there is a distinct need to identify any potential toxicity associated with these MNPs. The potential of MNPs in drug delivery stems from the intrinsic properties of the magnetic core combined with their drug loading capability and the biomedical properties of MNPs generated by different surface coatings. These surface modifications alter the particokinetics and toxicity of MNPs by changing protein-MNP or cell-MNP interactions. This review contains current advances in MNPs for drug delivery and their possible organ toxicities associated with disturbance in body iron homeostasis. The importance of protein-MNP interactions and various safety considerations relating to MNP exposure are also addressed.

Kinetics of tissue iron in experimental autoimmune encephalomyelitis in rats

To elucidate the role of iron in the pathomechanisms of autoimmune CNS disorders, we estimated the tissue concentrations of Fe(2+) in the brain, spinal cord, and liver in the chronic relapsing form of experimental autoimmune encephalomyelitis (EAE). The disease was induced in Dark Agouti (DA) strain of rats, by subcutaneous injection of bovine brain homogenate in complete Freund's adjuvant (CFA). Control rats consisted of unsensitized rats and of rats treated with CFA or saline. The data obtained by clinical assessment and by inductively coupled plasma spectrometry have shown that the attacks of disease (on the 12th and 22nd post-immunization day) were followed by high accumulation of iron in the liver. Additionally, during the second attack of disease, the decreased concentration of Fe(2+) was found in cervical spinal cord. The data point to regulatory effects of iron and hepatic trace elements regulating mechanisms in the pathogenesis of EAE.

Identification of [PtCl2(phen)] binding modes in amyloid-β peptide and the mechanism of aggregation inhibition

Platinum phenanthroline complexes inhibit amyloid-β (Aβ) aggregation and reduce Aβ-caused neurotoxicity [Proc. Natl. Acad. Sci., 2008, 105, 6813-6818]. In this study, we investigated the interactions of Aβ(1-16) with [PtCl(2)(phen)] (phen=1,10-phenanthroline) using HPLC, ESI-MS, and NMR spectroscopy , and characterized the identity of products using tandem mass spectrometry. Results indicated that the phenanthroline ligand could induce noncovalent interactions between Aβ peptide and platinum complexes, leading to rapid Aβ platination. Multiple products were generated in the reaction, in which His6/His14 chelation was preferentially formed. Coordination of Asp7, His13, and Lys16 was also detected in other products. The majority of products were monoplatinated adducts with binding of the {Pt(phen)} scaffold, which impeded intermolecular interactions between Aβ peptides. Moreover, noncovalent interactions were confirmed by the interaction between Aβ peptide and [Pt(phen)(2)]Cl(2). The synergistic roles of the phen ligand and platinum(II) atom in the inhibition of Aβ aggregation are discussed.

Age-associated variation in sensory perception of iron in drinking water and the potential for overexposure in the human population

Humans interact with their environment through the five senses, but little is known about population variability in the ability to assess contaminants. Sensory thresholds and biochemical indicators of metallic flavor perception in humans were evaluated for ferrous (Fe(2+)) iron in drinking water; subjects aged 19-84 years participated. Metallic flavor thresholds for individuals and subpopulations based on age were determined. Oral lipid oxidation and oral pH were measured in saliva as potential biochemical indicators. Individual thresholds were 0.007-14.14 mg/L Fe(2+) and the overall population threshold was 0.17 mg/L Fe(2+) in reagent water. Average thresholds for individuals younger and older than 50 years of age (grouped by the daily recommended nutritional guidelines for iron intake) were significantly different (p = 0.013); the population thresholds for each group were 0.045 mg/L Fe(2+) and 0.498 mg/L Fe(2+), respectively. Many subjects >50 and a few subjects <50 years were insensitive to metallic flavor. There was no correlation between age, oral lipid oxidation, and oral pH. Standardized olfactory assessment found poor sensitivity for Fe(2+) corresponded with conditions of mild, moderate, and total anosmia. The findings demonstrate an age-dependent sensitivity to iron indicating as people age they are less sensitive to metallic perception.

Copper and iron in Alzheimer's disease: a systematic review and its dietary implications

Fe and Cu could represent dietary risk factors for Alzheimer's disease (AD), which has become a global health concern. To establish the relationship between diets high in Cu and Fe and cognitive decline or AD, we have conducted a systematic review of the literature (up to January 2011). We identified two meta-analyses, two systematic reviews, eleven placebo-controlled trials, five observational studies, forty-five case-control studies, thirty autopsy and five uncontrolled studies, and one case report. There were eleven interventional trials that tried to either supplement or deplete Fe and Cu, but none of them provided clear evidence of a beneficial effect on cognitive performance in patients with AD. The prospective studies revealed an association between a diet simultaneously high in SFA and Cu and cognitive decline. Case-control and autopsy studies showed elevated Fe levels in the brains of AD patients, whereas the evidence was less consistent for Cu. In most of the studies, Cu concentrations were unchanged in the cerebrospinal fluid and the brain but increased in the serum. In conclusion, the existing data suggest that diets excessive in Fe or Cu, together with a high intake of SFA, should be avoided in the elderly who are not at risk of anaemia. Basic studies and, building on this, clinical investigations are needed to further elucidate in which dietary patterns and in which patient groups an Fe- and Cu-rich diet might foster the risk of developing AD.

Exposure to multiple metals from groundwater-a global crisis: geology, climate change, health effects, testing, and mitigation

This paper presents an overview of the global extent of naturally occurring toxic metals in groundwater. Adverse health effects attributed to the toxic metals most commonly found in groundwater are reviewed, as well as chemical, biochemical, and physiological interactions between these metals. Synergistic and antagonistic effects that have been reported between the toxic metals found in groundwater and the dietary trace elements are highlighted, and common behavioural, cultural, and dietary practices that are likely to significantly modify health risks due to use of metal-contaminated groundwater are reviewed. Methods for analytical testing of samples containing multiple metals are discussed, with special attention to analytical interferences between metals and reagents. An overview is presented of approaches to providing safe water when groundwater contains multiple metallic toxins.

Metal-based anti-diabetic drugs: advances and challenges

The current status and likely future directions of complexes of V(V/IV), Cr(III), Mo(VI), W(VI), Zn(II), Cu(II), and Mn(III) as potential oral drugs against type 2 diabetes are reviewed. We propose a unified model of extra- and intracellular mechanisms of anti-diabetic efficacies of V(V/IV), Mo(VI), W(VI), and Cr(III), centred on high-oxidation-state oxido/peroxido species that inhibit protein tyrosine phosphatases (PTPs) involved in insulin signalling. The postulated oxidative mechanism of anti-diabetic activity of Cr(III) via carcinogenic Cr(VI/V) (which adds to safety concerns) is consistent with recent clinical trials on Cr(III) picolinate, where activity was apparent only in patients with poorly controlled diabetes (high oxidative stress), and the correlation between the anti-diabetic activities and ease of oxidation of Cr(III) supplements and their metabolites in vivo. Zn(II) and Cu(II) anti-diabetics act via different mechanisms and are unlikely to be used as specific anti-diabetics due to their diverse and unpredictable biological activities. Hence, future research directions are likely to centre on enhancing the bioavailability and selectivity of V(V/IV), Mo(VI), or W(VI) drugs. The strategy of potentiating circulating insulin with metal ions has distinct therapeutic advantages over interventions that stimulate the release of more insulin, or use insulin mimetics, because of many adverse side-effects of increased levels of insulin, including increased risks of cancer and cardiovascular diseases.

Nanoparticles and colloids as contributing factors in neurodegenerative disease

This review explores the processes underlying the deleterious effects of the presence of insoluble or colloidal depositions within the central nervous system. These materials are chemically unreactive and can have a prolonged residence in the brain. They can be composed of mineral or proteinaceous materials of intrinsic or exogenous origin. Such nanoparticulates and colloids are associated with a range of slow-progressing neurodegenerative states. The potential common basis of toxicity of these materials is discussed. A shared feature of these disorders involves the appearance of deleterious inflammatory changes in the CNS. This may be due to extended and ineffective immune responses. Another aspect is the presence of excess levels of reactive oxygen species within the brain. In addition with their induction by inflammatory events, these may be further heightened by the presence of redox active transition metals to the large surface area afforded by nanoparticles and amphipathic micelles.

Towards a unifying, systems biology understanding of large-scale cellular death and destruction caused by poorly liganded iron: Parkinson's, Huntington's, Alzheimer's, prions, bactericides, chemical toxicology and others as examples

Exposure to a variety of toxins and/or infectious agents leads to disease, degeneration and death, often characterised by circumstances in which cells or tissues do not merely die and cease to function but may be more or less entirely obliterated. It is then legitimate to ask the question as to whether, despite the many kinds of agent involved, there may be at least some unifying mechanisms of such cell death and destruction. I summarise the evidence that in a great many cases, one underlying mechanism, providing major stresses of this type, entails continuing and autocatalytic production (based on positive feedback mechanisms) of hydroxyl radicals via Fenton chemistry involving poorly liganded iron, leading to cell death via apoptosis (probably including via pathways induced by changes in the NF-κB system). While every pathway is in some sense connected to every other one, I highlight the literature evidence suggesting that the degenerative effects of many diseases and toxicological insults converge on iron dysregulation. This highlights specifically the role of iron metabolism, and the detailed speciation of iron, in chemical and other toxicology, and has significant implications for the use of iron chelating substances (probably in partnership with appropriate anti-oxidants) as nutritional or therapeutic agents in inhibiting both the progression of these mainly degenerative diseases and the sequelae of both chronic and acute toxin exposure. The complexity of biochemical networks, especially those involving autocatalytic behaviour and positive feedbacks, means that multiple interventions (e.g. of iron chelators plus antioxidants) are likely to prove most effective. A variety of systems biology approaches, that I summarise, can predict both the mechanisms involved in these cell death pathways and the optimal sites of action for nutritional or pharmacological interventions.

Calorie restriction up-regulates iron and copper transport genes in Saccharomyces cerevisiae

Calorie restriction (CR) is a non genetic intervention, known to confer longevity benefits across the various phyla from unicellular yeast to mammals. CR also invokes homeostatic responses similar to stress, however the sequence of molecular events leading to longevity is still illusive. In this study, we analysed the whole genome gene expression profile in response to CR, mutations mimicking CR, heat shock and H(2)O(2) from a gene ontology perspective. Our analysis revealed that mitochondrion is a common hub in the gene expression programme under these conditions and the electron transport chain (ETC) is a major player. Consequently the genes involved in the metal ion transport were also significantly up-regulated. We confirmed the results of the in silico analysis using quantitative real time PCR which showed up-regulation of genes involved in respiration and transport of iron and copper. The promoter activity of one of the representative genes, FET3, was also found to be higher upon calorie restriction. Altogether, our results indicate that upon calorie restriction the levels of iron and copper fall in cells, which elicits a transcriptional response up-regulating the genes involved in their uptake to maintain cellular homeostasis.

Highly sensitive multiplexed heavy metal detection using quantum-dot-labeled DNAzymes

We developed highly sensitive and specific nanosensors based on quantum dots (QDs) and DNAzyme for multiplexed detection of heavy metal ions in liquid. The QDs were coated with a thin silica layer for increased stability and higher quantum yield while maintaining a relatively small size for highly efficient energy transfer. The QD-DNAzyme nanosensors were constructed by conjugating quencher-labeled DNAzymes onto the surface of carboxyl-silanized QDs. In the presence of metal ions, the emission is restored due to the cleavage of DNAzymes. The detection could be completed within 25 min with a single laser excitation source. The detection limit of 0.2 and 0.5 nM was experimentally achieved for Pb(2+) and Cu(2+), respectively, which is a 50- and 70-fold improvement over the recent results obtained with dye molecules. Multiplexed detection was also demonstrated using two different colors of QDs, showing negligible cross-talk between the Pb(2+) detection and Cu(2+) detection.

Intralysosomal iron induces lysosomal membrane permeabilization and cathepsin D-mediated cell death in trabecular meshwork cells exposed to oxidative stress

PURPOSE

To investigate the role of intralysosomal redox-active iron in oxidative stress-induced damage in trabecular meshwork (TM) cells.

METHODS

Chronic oxidative stress was applied using the hyperoxic model; acute oxidative stress was applied with H(2)O(2). Microarray analysis was performed using microarrays. mRNA and protein levels were quantified by real-time PCR and Western blot analysis, respectively. Redox-active iron was monitored using calcein-AM. Apoptosis was quantified using double staining. DNA damage was evaluated by single-cell gel electrophoresis assay. Lysosomal permeabilization was monitored using uptake and acridine orange relocation techniques. Intracellular ROS production was quantified using H(2)DCFDA. Cytosolic translocation of cathepsins was visualized with pepstatin-A-BODIPY-FL. Chemical inhibition of cathepsins was achieved with leupeptin and pepstatin A. Silencing of cathepsin expression was accomplished with miRNA sequences. Lysosomal iron chelation was achieved with desferrioxamine.

RESULTS

Chronically stressed TM cells showed elevated levels of redox-active iron and altered expression of genes involved in intracellular iron homeostasis. Although iron increased ROS production and lipofuscin levels and sensitized TM cells to H(2)O(2), intralysosomal iron chelation completely protected the cells against H(2)O(2)-induced cell death and apoptosis. The protective effect of desferrioxamine was mediated by the prevention of lysosomal ROS generation and the rupture of lysosomal membrane, with the subsequent release of cathepsin D into the cytosol.

CONCLUSIONS

These results indicate that the generation of intralysosomal ROS induces lysosomal membrane permeabilization and the release of cathepsin D into the cytosol, leading to TM cell death. Here, the authors propose a mechanism by which oxidative stress might contribute to the decrease in cellularity reported in the TM tissue with both aging and disease.