Speciation of copper in a range of food types by X-ray absorption spectroscopy

Synthesis of photocatalytic cysteine-capped Cu≈10 clusters using Cu5 clusters as catalysts

We report an easily scalable synthesis method for the preparation of cysteine-capped Cu_≈10 clusters through the reduction of Cu(II) ions with NaBH₄, using Cu₅ clusters as catalysts. The presence of such catalytic clusters allows controlling the formation of the larger Cu_≈10 clusters and prevents the production of copper oxides or Cu(I)-cysteine complexes, which are formed when Cu₅ is absent or at lower concentrations, respectively. These results indicate that small catalytic clusters could be involved, as precursor species before the reduction step, in the different methods developed for the synthesis of clusters. The visible light-absorbing Cu_≈10 clusters, obtained by the cluster-catalysed method, display high photocatalytic activities for the decomposition of methyl orange with visible light.

Comparison of X-ray absorption spectra from copper-loaded bovine and ovine livers

BACKGROUND

Copper toxicity and hepatic copper accumulation pose a serious risk to ruminant health and production. Differences in the copper-handling mechanisms of cattle and sheep have been noted, not only in comparison to each other, but also in comparison to 'copper-tolerant' monogastric species. Ruminants appear less able to cope with rising liver copper concentration than monogastric counterparts, with sheep in general less able to cope with elevated copper intake than cattle.

METHODS

X-ray absorption spectroscopy (XAS) was used to investigate the differences between the livers of these species at high copper status.

RESULTS

The X-ray absorption fine structure (XAFS) and X-ray absorption near edge structure (XANES) spectra indicated that the hepatic copper compound is most likely to be bound to metallothionein; consistent with monogastric species.

CONCLUSION

Although, most likely stored as copper-metallothionein, there may be a role for glutathione as a short-term, intermediate copper buffer which may have more relevance to sheep than cattle. The potential that thiomolybdate bound copper can be stored in the liver could not be ruled out.

Alzheimer's Disease: Pathogenesis and Therapeutic Interventions

BACKGROUND

Alzheimer's Disease (AD) is the most common cause of dementia. Genetics, excessive exposure to environmental pollutants, as well as unhealthy lifestyle practices are often linked to the development of AD. No therapeutic approach has achieved complete success in treating AD; however, early detection and management with appropriate drugs are key to improving prognosis.

INTERVENTIONS

The pathogenesis of AD was extensively discussed in order to understand the reasons for the interventions suggested. The interventions reviewed include the use of different therapeutic agents and approaches, gene therapy, adherence to healthy dietary plans (Mediterranean diet, Okinawan diet and MIND diet), as well as the use of medicinal plants. The potential of nanotechnology as a multidisciplinary and interdisciplinary approach in the design of nano-formulations of AD drugs and the use of Superparamagnetic Iron Oxide Nanoparticles (SPIONs) as theranostic tools for early detection of Alzheimer's disease were also discussed.

Revealing differences in the chemical form of zinc in brain tissue using K-edge X-ray absorption near-edge structure spectroscopy

Zinc is a prominent trace metal required for normal memory function. Memory loss and cognitive decline during natural ageing and neurodegenerative disease have been associated with altered brain-Zn homeostasis. Yet, the exact chemical pathways through which Zn influences memory function during health, natural ageing, or neurodegenerative disease remain unknown. The gap in the literature may in part be due to the difficulty to simultaneously image, and therefore, study the different chemical forms of Zn within the brain (or biological samples in general). To this extent, we have begun developing and optimising protocols that incorporate X-ray absorption near-edge structure (XANES) spectroscopic analysis of tissue at the Zn K-edge as an analytical tool to study Zn speciation in the brain. XANES is ideally suited for this task as all chemical forms of Zn are detected, the technique requires minimal sample preparation that may otherwise redistribute or alter the chemical form of Zn, and the Zn K-edge has known sensitivity to coordination geometry and ligand type. Herein, we report our initial results where we fit K-edge spectra collected from micro-dissected flash-frozen brain tissue, to a spectral library prepared from standard solutions, to demonstrate differences in the chemical form of Zn that exist between two brain regions, the hippocampus and cerebellum. Lastly, we have used an X-ray microprobe to demonstrate differences in Zn speciation within sub-regions of thin air-dried sections of the murine hippocampus; but, the corresponding results highlight that the chemical form of Zn is easily perturbed by sample preparation such as tissue sectioning or air-drying, which must be a critical consideration for future work.

Chronic copper exposure directs microglia towards degenerative expression signatures in wild-type and J20 mouse model of Alzheimer's disease

BACKGROUND

Copper (Cu) is an essential metal mediating a variety of vital biological reactions with its redox property. Its dyshomeostasis has been associated with accelerated cognitive decline and neurodegenerative disorders, such as Alzheimer's disease (AD). However, underlying neurotoxic mechanisms elicited by dysregulated Cu remain largely elusive. We and others previously demonstrated that exposure to Cu in drinking water significantly exacerbated pathological hallmarks of AD and pro-inflammatory activation of microglia, coupled with impaired phagocytic capacity, in mouse models of AD.

METHODS

In the present study, we extended our investigation to evaluate whether chronic Cu exposure to wild-type (WT) and J20 mouse model of AD perturbs homeostatic dynamics of microglia and contributes to accelerated transformation of microglia towards degenerative phenotypes that are closely associated with neurodegeneration. We further looked for evidence of alterations in the microglial morphology and spatial memory of the Cu-exposed mice to assess the extent of the Cu toxicity.

RESULTS

We find that chronic Cu exposure to pre-pathological J20 mice upregulates the translation of degenerative genes and represses homeostatic genes within microglia even in the absence amyloid-beta plaques. We also observe similar expression signatures in Cu-exposed WT mice, suggesting that excess Cu exposure alone could lead to perturbed microglial homeostatic phenotypes and contribute to accelerated cognitive decline.

CONCLUSION

Our findings highlight the risk of chronic Cu exposure on cognitive decline and altered microglia activation towards degenerative phenotypes. These changes may represent one of the key mechanisms linking Cu exposure or its dyshomeostasis to an increased risk for AD.

Copper-Induced Upregulation of MicroRNAs Directs the Suppression of Endothelial LRP1 in Alzheimer's Disease Model

Chronic exposure to copper and its dyshomeostasis have been linked to accelerated cognitive decline and potentially increasing risk for Alzheimer's disease (AD). We and others have previously demonstrated that exposure to copper through drinking water significantly increased parenchymal amyloid-beta (Aβ) plaques and decreased endothelial low-density lipoprotein receptor-related protein 1 (LRP1) in mouse models of AD. In this study, we determined the underlying mechanisms that microRNA critically mediated the copper-induced loss of endothelial LRP1. In human primary microvascular endothelial cells (MVECs), microRNA-200b-3p, -200c-3p, and -205-5p were significantly elevated within the 24-h exposure to copper and returned to baseline after 48-h postexposure, which corresponded with the temporal change of LRP1 expression in these cells. Transient expression of synthetic microRNA-200b-3p, -200c-3p, or -205-5p on MVECs significantly decreased endothelial LRP1, and cotreatment of synthetic antagomirs effectively prevented the loss of LRP1 during copper exposure, collectively supporting the key regulatory role of these microRNAs in copper-induced loss of LRP1. In mice, a significant reduction of LRP1 in cortical vasculature was evident following 9 months exposure to 1.3 ppm copper in drinking water, although the levels of cortical microRNA-205-5p, -200b-3p, and -200c-3p were only marginally elevated. This, however, correlated with increased vascular accumulation of Aβ and impairment of spatial memory, indicating that copper exposure has the pivotal role in the vascular damage and development of cognitive decline.

Inorganic content of rock dust waste from northwest of Rio de Janeiro, Brazil: do environmental risks incur from its use as natural fertilizer?

The ornamental rock exploration and coating industry has led to significant environmental impacts due to the inadequate manner in which these residues are released into the environment. This impact may be reduced by using these residues for soil enrichment, as they contain high levels of inorganic nutrients. However, some elements may be potential contaminants, thus requiring a thorough previous research before employing these substances in agriculture. In this context, this study aims to determine potentially toxic elements present in rock dust residues, As, Cd, Cr, Cu, Pb, and V, through Inductively Coupled Plasma Optical Emission Spectroscopy (ICP OES) after wet decomposition. Cd concentrations in residual rock dust waste surpassed the maximum limit established by the Brazilian Ministry of Agriculture, Livestock and Supply stipulated in normative instruction No. 5/2016 for remineralizers and substrates for plants intended for agriculture. In addition, the official digestion method adopted by the Brazilian Agricultural Research Corporation Embrapa (used for soil analysis) was used for a rock dust waste analysis and compared to two different block digester-based procedures. Accuracy was confirmed by using the Certified Reference Material (CRM) NIST SRM 1646^a (Estuarine Sediments) and addition/recovery tests. The limits of detection for the aforementioned elements, after aqua-regia-induced digestion, were of 0.07 mg kg^-1 for As, 0.06 mg kg^-1 for Cd, 0.01 mg kg^-1 for Cr, 0.2 mg kg^-1 for Cu, 0.03 mg kg^-1 for Pb, and 0.09 mg kg^-1 for V.

Low copper-2 intake in Switzerland does not result in lower incidence of Alzheimer's disease and contradicts the Copper-2 Hypothesis

In recent years, the “Copper-2 Hypothesis” has been put forth in an attempt to explain the epidemic of Alzheimer’s disease (AD) in the Western world. According to this hypothesis, “free” copper (copper-2) in drinking water, dietary supplements, and meat is the chief cause of the increased incidence of AD in recent decades. In contrast to the US, copper plumbing for drinking water is not used in Switzerland and tap water is very low in copper. Other “risk” factors including dietary supplements and meat consumption are also lower in Switzerland than in the US. Yet, the incidence of AD is closely similar in the two countries. This contradicts the Copper-2 Hypothesis.

Impact statement

The Western world is faced with an Alzheimer’s epidemic. Identifying the life style and anthropogenic factors involved has become a priority. This is a formidable challenge due to the complexity and the slow progression of the disease. A hypothesis put forth by George Brewer postulates divalent copper (copper-2), chiefly present in drinking water from copper pipes, to be a major risk factor for Alzheimer’s disease. In Switzerland, copper pipes are not used for drinking water, but the frequency of Alzheimer’s disease is similar to that of other Western countries. This contradicts Brewer’s hypothesis and suggests that other factors are responsible for today’s Alzheimer’s epidemic.

Critical Review of Exposure and Effects: Implications for Setting Regulatory Health Criteria for Ingested Copper

Decades of study indicate that copper oral exposures are typically not a human health concern. Ingesting high levels of soluble copper salts can cause acute gastrointestinal symptoms and, in uncommon cases, liver toxicity in susceptible individuals with repeated exposure. This focused toxicological review evaluated the current literature since the last comprehensive reviews (2007-2010). Our review identified limitations in the existing United States and international guidance for determining an oral reference dose (RfD) for essential metals like copper. Instead, an alternative method using categorical regression analysis to develop an optimal dose that considers deficiency, toxicity, and integrates information from human and animal studies was reviewed for interpreting an oral RfD for copper. We also considered subchronic or chronic toxicity from genetic susceptibility to copper dysregulation leading to rare occurrences of liver and other organ toxicity with elevated copper exposure. Based on this approach, an oral RfD of 0.04 mg Cu/kg/day would be protective of acute or chronic toxicity in adults and children. This RfD is also protective for possible genetic susceptibility to elevated copper exposure and allows for background dietary exposures. This dose is not intended to be protective of patients with rare genetic disorders for copper sensitivity within typical nutritional intake ranges, nor is it protective for those with excessive supplement intake. Less soluble mineral forms of copper in soil have reduced bioavailability as compared with more soluble copper in water and diet, which should be considered in using this RfD for risk assessments of copper.

Environmental and Dietary Exposure to Copper and Its Cellular Mechanisms Linking to Alzheimer's Disease

Metals are commonly found in the environment, household, and workplaces in various forms, and a significant segment of the population is routinely exposed to the trace amount of metals from variety of sources. Exposure to metals, such as aluminum, lead, iron, and copper, from environment has long been debated as a potential environmental risk factor for Alzheimer's disease (AD) for decades, yet results from in vitro, in vivo, and human population remain controversial. In the case of copper, the neurotoxic mechanism of action was classically viewed as its strong affinity to amyloid-beta (Aβ) to help its aggregation and increase oxidative stress via Fenton reaction. Thus, it has been thought that accumulation of copper mediates neurotoxicity, and removing it from the brain prevents or reverse Aβ plaque burden. Recent evidence, however, suggests dyshomeostasis of copper and its valency in the body, instead of the accumulation and interaction with Aβ, are major determinants of its beneficial effects as an essential metal or its neurotoxic counterpart. This notion is also supported by the fact that genetic loss-of-function mutations on copper transporters lead to severe neurological symptoms. Along with its altered distribution, recent studies have also proposed novel mechanisms of copper neurotoxicity mediated by nonneuronal cell lineages in the brain, such as capillary endothelial cells, leading to development of AD neuropathology. This review covers recent findings of multifactorial toxic mechanisms of copper and discusses the risk of environmental exposure as a potential factor in accounting for the variability of AD incidence.

Avoiding Alzheimer's disease: The important causative role of divalent copper ingestion

IMPACT STATEMENT

The work described in this review is very important to scientists working on Alzheimer's disease (AD) because it reveals a cause for the explosive epidemic of this disease. It is also important to the public because it provides a method to avoid this newly revealed cause, and thereby avoid AD. The field is advanced because this review reveals new information about the mechanism of AD pathogenesis, namely copper, and specifically divalent copper, toxicity is important. New information about divalent copper toxicity in the brain affecting cognition is revealed. The field is impacted strongly because, in view of the frustrations that have occurred in treatment developed, now most AD can be prevented. This means the suffering of the patient, the prolonged and difficult care required by caregivers, and the enormous expenditures for this one disease, can now be avoided.

Copper signalling: causes and consequences

Copper-containing enzymes perform fundamental functions by activating dioxygen (O2) and therefore allowing chemical energy-transfer for aerobic metabolism. The copper-dependence of O2 transport, metabolism and production of signalling molecules are supported by molecular systems that regulate and preserve tightly-bound static and weakly-bound dynamic cellular copper pools. Disruption of the reducing intracellular environment, characterized by glutathione shortage and ambient Cu(II) abundance drives oxidative stress and interferes with the bidirectional, copper-dependent communication between neurons and astrocytes, eventually leading to various brain disease forms. A deeper understanding of of the regulatory effects of copper on neuro-glia coupling via polyamine metabolism may reveal novel copper signalling functions and new directions for therapeutic intervention in brain disorders associated with aberrant copper metabolism.

Investigation of bioaccessibility of Cu, Fe, Mn, and Zn in market vegetables in the colon using PBET combined with SHIME

The in vitro bioaccessibility of trace metals associated with oral ingestion of market vegetables (lettuce, pak choi, cole, and leaf lettuce) of Beijing, China was studied. The physiologically based extraction test (PBET) combined with the Simulator of Human Intestinal Microbial Ecosystem (SHIME) was applied to simulate stomach, small intestine, and colon of human. In the gastro-intestinal phases, the bioaccessibility of Cu, Fe, Mn, and Zn varied within 5.7–75.5%, 17.3–50.4%, 13.3–49.1%, and 19.9–63.7%, respectively. There was no significant difference in the metal bioaccessibility between the gastric and small intestinal phases, except for higher Cu bioaccessibility in the small intestine. Besides, the bioaccessibility of the four trace metals in the colon phase was first ever reported. A significant decline in Cu bioaccessibility (1.8–63.7%) and slight increases in the bioaccessibility of Fe (16.7–56.4%), Mn (21.2–71.6%), and Zn (15.7–69.7%) were revealed, which could mainly be attributed to the effect of colon microbiota. In addition, the estimated daily intakes (EDIs) of Cu, Fe, Mn, and Zn were worked out to be 0.7, 8.8, 2.7, and 4.5 μg kg⁻¹ body weight d⁻¹, based on which the potential influences of these trace metals in vegetables on the health of the local consumers was demonstrated.

Fe3O4/hydroxyapatite/graphene quantum dots as a novel nano-sorbent for preconcentration of copper residue in Thai food ingredients: Optimization of ultrasound-assisted magnetic solid phase extraction

Fe₃O₄/hydroxyapatite/graphene quantum dots (Fe₃O₄/HAP/GQDs) nanocomposite was synthesized and used as a novel magnetic adsorbent. This nanocomposite was characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and magnetization property. The Fe₃O₄/HAP/GQDs was applied to pre-concentrate copper residues in Thai food ingredients (so-called "Tom Yum Kung") prior to determination by inductively coupled plasma-atomic emission spectrometry. Based on ultrasound-assisted extraction optimization, various parameters affecting the magnetic solid-phase extraction, such as solution pH, amount of magnetic nanoparticles, adsorption and desorption time, and type of elution solvent and its concentration were evaluated. Under optimal conditions, the linear range was 0.05-1500ngmL^-1 (R²>0.999), limit of detection was 0.58ngmL^-1, and limit of quantification was 1.94ngmL^-1. The precision, expressed as the relative standard deviation of the calibration curve slope (n=5), for intra-day and inter-day analyses was 0.87% and 4.47%, respectively. The recovery study of Cu for real samples was ranged between 83.5% and 104.8%. This approach gave the enrichment factor of 39.2, which guarantees trace analysis of Cu residues. Therefore, Fe₃O₄/HAP/GQDs can be a potential and suitable candidate for the pre-concentration and separation of Cu from food samples. It can easily be reused after treatment with deionized water.

Copper-2 Hypothesis for Causation of the Current Alzheimer's Disease Epidemic Together with Dietary Changes That Enhance the Epidemic

Alzheimer's disease, the most common cause of dementia, is at epidemic proportions (15 to 44% depending on age, of those age 65 to 84) in the U.S. and other developed countries but remains relatively rare in undeveloped countries. Surprisingly, solid historical data reveal the epidemic is a creature of the last century. That is, the disease was also rare in developed countries, until the 20th century. It is disappointing that these historical and demographic facts have been ignored by the Alzheimer's disease scientific community. Disappointing because these facts clearly point at an environmental change in the 20th century in developed countries as a major factor in causing the epidemic. Some scientists have discarded the claimed rarity of the disease in the 19th century as incorrect, saying that Alzheimer's disease is a disease of aging and that the increasing lifespan of people accounts for the current high prevalence of the disease, but this cavalier attitude ignores historical data indicating there were many elderly people in the 19th century who were not getting Alzheimer's disease with any significant frequency. In this review, after documenting that the observed assertions about historical and demographic facts are correct, evidence is amassed that the main environmental culprit causing the Alzheimer's epidemic is ingestion of divalent copper or copper-2. The two sources of copper-2 ingestion are drinking water and multimineral supplement pills containing copper. The increase in copper plumbing use in developed countries parallels the increasing prevalence of Alzheimer's disease. It has been shown that enough copper is leached from copper plumbing in most households to cause Alzheimer's disease, using the Alzheimer's disease animal model studies as a guide to toxic levels. It is relatively easy to avoid or greatly diminish copper-2 ingestion by not using copper containing supplement pills and testing drinking water for copper levels. If the copper in water is too high, a simple device can be put on the tap to remove copper. In addition to the copper-2 hypothesis, this review covers dietary changes that enhance the epidemic.

Copper Uptake, Intracellular Localization, and Speciation in Marine Microalgae Measured by Synchrotron Radiation X-ray Fluorescence and Absorption Microspectroscopy

Metal toxicity to aquatic organisms depends on the speciation of the metal and its binding to the critical receptor site(s) (biotic ligand) of the organism. The intracellular nature of the biotic ligand for Cu in microalgal cells was investigated using the high elemental sensitivity of microprobe synchrotron radiation X-ray fluorescence (SR-XRF) and X-ray absorption near-edge spectroscopy (XANES). The marine microalgae, Ceratoneis closterium, Phaeodactylum tricornutum, and Tetraselmis sp. were selected based on their varying sensitivities to Cu (72-h 50% population growth inhibitions of 8-47 μg Cu/L). Intracellular Cu in control cells was similar for all three species (2.5-3.2 × 10(-15) g Cu/cell) and increased 4-fold in C. closterium and Tetraselmis sp. when exposed to copper, but was unchanged in P. tricornutum (72-h exposure to 19, 40, and 40 μg Cu/L, respectively). Whole cell microprobe SR-XRF identified endogenous Cu in the central compartment (cytoplasm) of control (unexposed) cells. After Cu exposure, Cu was colocated with organelles/granules dense in P, S, Ca, and Si and this was clearly evident in thin sections of Tetraselmis sp. XANES indicated coexistence of Cu(I) and Cu(II) in control and Cu-exposed cells, with the Cu ligand (e.g., phytochelatin) in P. tricornutum different from that in C. closterium and Tetraselmis sp. This study supports the hypothesis that Cu(II) is reduced to Cu(I) and that polyphosphate bodies and phytochelatins play a significant role in the internalization and detoxification of Cu in marine microalgae.

Copper-2 Ingestion, Plus Increased Meat Eating Leading to Increased Copper Absorption, Are Major Factors Behind the Current Epidemic of Alzheimer's Disease

It has become clear that copper toxicity is playing a major role in Alzheimer's disease; but why is the brain copper toxicity with cognition loss in Alzheimer's disease so much different clinically than brain copper toxicity in Wilson's disease, which results in a movement disorder? Furthermore, why is the inorganic copper of supplement pills and in drinking water so much more damaging to cognition than the organic copper in food? A recent paper, which shows that almost all food copper is copper-1, that is the copper-2 of foods reverts to the reduced copper-1 form at death or harvest, gives new insight into these questions. The body has an intestinal transport system for copper-1, Ctr1, which channels copper-1 through the liver and into safe channels. Ctr1 cannot absorb copper-2, and some copper-2 bypasses the liver, ends up in the blood quickly, and is toxic to cognition. Humans evolved to handle copper-1 safely, but not copper-2. Alzheimer's is at least in part, a copper-2 toxicity disease, while Wilson's is a general copper overload disease. In this review, we will show that the epidemiology of the Alzheimer's epidemic occurring in developed, but not undeveloped countries, fits with the epidemiology of exposure to copper-2 ingestion leached from copper plumbing and from copper supplement pill ingestion. Increased meat eating in developed countries is also a factor, because it increases copper absorption, and thus over all copper exposure.