Development of Cu(ii)-specific peptide shuttles capable of preventing Cu–amyloid beta toxicity and importing bioavailable Cu into cells

Copper (Cu) in its ionic forms is an essential element for mammals and its homeostasis is tightly controlled. Accordingly, Cu-dyshomeostasis can be lethal as is the case in the well-established genetic Wilson's and Menkes diseases. In Alzheimer's disease (AD), Cu-accumulation occurs in amyloid plaques, where it is bound to the amyloid-beta peptide (Aβ). In vitro, Cu–Aβ is competent to catalyze the production of reactive oxygen species (ROS) in the presence of ascorbate under aerobic conditions, and hence Cu–Aβ is believed to contribute to the oxidative stress in AD. Several molecules that can recover extracellular Cu from Aβ and transport it back into cells with beneficial effects in cell culture and transgenic AD models were identified. However, all the Cu-shuttles currently available are not satisfactory due to various potential limitations including ion selectivity and toxicity. Hence, we designed a novel peptide-based Cu shuttle with the following properties: (i) it contains a Cu(ii)-binding motif that is very selective to Cu(ii) over all other essential metal ions; (ii) it is tagged with a fluorophore sensitive to Cu(ii)-binding and release; (iii) it is made of a peptide platform, which is very versatile to add new functions. The work presented here reports on the characterization of AKH-αR5W4^NBD, which is able to transport Cu ions selectively into PC12 cells and the imported Cu appeared bioavailable, likely via reductive release induced by glutathione. Moreover, AKH-αR5W4^NBD was able to withdraw Cu from the Aβ_1–16 peptide and consequently inhibited the Cu-Aβ based reactive oxygen species production and related cell toxicity. Hence, AKH-αR5W4^NBD could be a valuable new tool for Cu-transport into cells and suitable for mechanistic studies in cell culture, with potential applications in restoring Cu-homeostasis in Cu-related diseases such as AD.

The synthetic peptide AKH-αR5W4^NBD was designed as a shuttle to counteract copper imbalance in Alzheimer’s disease. In vitro, this shuttle is able to abstract Cu(ii) selectively from amyloid-β and transport it into cells in a bioavailable form.

Copper Oxide Nanoparticles Induce Oxidative DNA Damage and Cell Death via Copper Ion-Mediated P38 MAPK Activation in Vascular Endothelial Cells

Background

Inhaled nanoparticles can cross pulmonary air–blood barrier into circulation and cause vascular endothelial injury and progression of cardiovascular disease. However, the molecular mechanism underlying the vascular toxicity of copper oxide nanoparticles (CuONPs) remains unclear. We have recently demonstrated that the release of copper ions and the accumulation of superoxide anions contributed to CuONPs-induced cell death in human umbilical vein endothelial cells (HUVECs). Herein, we further demonstrate the mechanism underlying copper ions-induced cell death in HUVECs.

Methods and Results

CuONPs were suspended in culture medium and vigorously vortexed for several seconds before exposure. After treatment with CuONPs, HUVECs were collected, and cell function assays were conducted to elucidate cellular processes including cell viability, oxidative stress, DNA damage and cell signaling pathways. We demonstrated that CuONPs uptake induced DNA damage in HUVECs as evidenced by γH2AX foci formation and increased phosphorylation levels of ATR, ATM, p53 and H2AX. Meanwhile, we showed that CuONPs exposure induced oxidative stress, indicated by the increase of cellular levels of superoxide anions, the upregulation of protein levels of heme oxygenase-1 (HO-1) and glutamate-cysteine ligase modifier subunit (GCLM), the elevation of the levels of malondialdehyde (MDA), but the reduction of glutathione to glutathione disulfide ratio. We also found that antioxidant N-acetyl-L-cysteine (NAC) could ameliorate CuONPs-induced oxidative stress and cell death. Interestingly, we demonstrated that p38 mitogen-activated protein kinase (MAPK) signaling pathway was activated in CuONPs-treated HUVECs, while p38α MAPK knockdown by siRNA significantly rescued HUVECs from CuONPs-induced DNA damage and cell death. Importantly, we showed that copper ions chelator tetrathiomolybdate (TTM) could alleviate CuONPs-induced oxidative stress, DNA damage, p38 MAPK pathway activation and cell death in HUVECs.

Conclusion

We demonstrated that CuONPs induced oxidative DNA damage and cell death via copper ions-mediated p38 MAPK activation in HUVECs, suggesting that the release of copper ions was the upstream activator for CuONPs-induced vascular endothelial toxicity, and the copper ions chelator TTM can alleviate CuONPs-associated cardiovascular disease.

Copper accumulation and the effect of chelation treatment on cerebral amyloid angiopathy compared to parenchymal amyloid plaques

Accumulation of fibrillar amyloid β-protein (Aβ) in parenchymal plaques and in blood vessels of the brain, the latter condition known as cerebral amyloid angiopathy (CAA), are hallmark pathologies of Alzheimer's disease (AD) and related disorders. Cerebral amyloid deposits have been reported to accumulate various metals, most notably copper and zinc. Here we show that, in human AD, copper is preferentially accumulated in amyloid-containing brain blood vessels compared to parenchymal amyloid plaques. In light of this observation, we evaluated the effects of reducing copper levels in Tg2576 mice, a transgenic model of AD amyloid pathologies. The copper chelator, tetrathiomolybdate (TTM), was administered to twelve month old Tg2576 mice for a period of five months. Copper chelation treatment significantly reduced both CAA and parenchymal plaque load in Tg2576 mice. Further, copper chelation reduced parenchymal plaque copper content but had no effect on CAA copper levels in this model. These findings indicate that copper is associated with both CAA deposits and parenchymal amyloid plaques in humans, but less in Tg2576 mice. TTM only reduces copper levels in plaques in Tg2576 mice. Reducing copper levels in the brain may beneficially lower amyloid pathologies associated with AD.

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.

Nutrients in Alzheimer’s Disease: The Interaction of Diet, Drugs and Disease

In recent decades, clinical trials in Alzheimer’s disease (AD) have failed at an unprecedented rate. The etiology of AD has since come under renewed scrutiny, both to elucidate the underlying pathologies and to identify novel therapeutic strategies. Here, diet has emerged as a potential causative/protective agent. A variety of nutrients, including lipids, minerals, vitamins, antioxidants and sugars as well as broader dietary patterns and microbiotal interactions have demonstrated associations with AD. Although clinical trials have yet to definitively implicate any singular dietary element as therapeutic or causative, it is apparent that dietary preferences, likely in complex synergies, may influence the risk, onset and course of AD. This review catalogs the impact of major dietary elements on AD. It further examines an unexplored reciprocal association where AD may modulate diet, as well as how potential therapeutics may complicate these interactions. In doing so, we observe diet may have profound effects on the outcome of a clinical trial, either as a confounder of a drug/disease interaction or as a generally disruptive covariate. We therefore conclude that future clinical trials in AD should endeavor to control for diet, either in study design or subsequent analyses.

Oral zinc reduces amyloid burden in Tg2576 mice

The aggregation of amyloid-β in Alzheimer's disease can be affected by free transition metals such as copper and zinc in the brain. Addition of copper and zinc with amyloid acts to increase aggregation and copper additionally promotes the formation of reactive oxygen species. We propose that reduction of brain copper by blocking uptake of copper from the diet is a viable strategy to regulate the formation of insoluble amyloid-β in the brain of Tg2576 mice. Mice were treated with regimens of zinc acetate, which acts with metallothionein to block copper uptake in the gut, at various times along their lifespan to model prevention and treatment paradigms. We found that the mice tolerated zinc acetate well over the six month course of study. While we did not observe significant changes in cognition and behavior, there was a reduction in insoluble amyloid-β in the brain. This observation coincided with a reduction in brain copper and interestingly no change in brain zinc. Our findings show that blocking copper uptake from the diet can redistribute copper from the brain and reduce amyloid-β aggregation.

Copper (II) adsorption by the extracellular polymeric substance extracted from waste activated sludge after short-time aerobic digestion

The extracellular polymeric substance (EPS) extracted from waste activated sludge (WAS) after short-time aerobic digestion was investigated to be used as a novel biosorbent for Cu(2+) removal from water. The EPS consisted of protein (52.6 %, w/w), polysaccharide (30.7 %, w/w), and nucleic acid (16.7 %, w/w). Short-time aerobic digestion process of WAS for about 4 h promoted the productivity growth of the EPS for about 10 %. With a molecular weight of about 1.9 × 10(6) Da, the EPS showed a linear structure with long chains, and contained carboxyl, hydroxyl, and amino groups. The sorption kinetics was well fit for the pseudo-second-order model, and the maximum sorption capacity of the EPS (700.3 mg Cu(2+)/g EPS) was markedly greater than those of the reported biosorbents. Both Langmuir model and Freundlich model commendably described the sorption isotherm. The Gibbs free energy analysis of the adsorption showed that the sorption process was feasible and spontaneous. According to the complex results of multiple analytical techniques, including scanning electron microscopy, Fourier transform infrared spectroscopy, atomic force microscopy, etc., the adsorption process took place via both physical and chemical sorption, but the electrostatic interaction between sorption sites with the functional groups and Cu(2+) is the major mechanism.

Micronutrient-gene interactions related to inflammatory/immune response and antioxidant activity in ageing and inflammation. A systematic review

Recent longitudinal studies in dietary daily intake in human centenarians have shown that a satisfactory content of some micronutrients within the cells maintain several immune functions, a low grade of inflammation and preserve antioxidant activity. Micronutrients (zinc, copper, selenium) play a pivotal role in maintaining and reinforcing the performances of the immune and antioxidant systems as well as in affecting the complex network of the genes (nutrigenomic) with anti- and pro-inflammatory tasks. Genes of pro- and anti-inflammatory cytokines and some key regulators of trace elements homeostasis, such as Metallothioneins (MT), are involved in the susceptibility to major geriatric disease/disorders. Moreover, the genetic inter-individual variability may affect the nutrients' absorption (nutrigenetic) with altered effects on inflammatory/immune response and antioxidant activity. The interaction between genetic factors and micronutrients (nutrigenomic and nutrigenetic approaches) may influence ageing and longevity because the micronutrients may become also toxic. This review reports the micronutrient-gene interactions in ageing and their impact on the healthy state with a focus on the method of protein-metal speciation analysis. The association between micronutrient-gene interactions and the protein-metal speciation analysis can give a complete picture for a personalized nutrient supplementation or chelation in order to reach healthy ageing and longevity.

Effects of a copper-deficient diet on the biochemistry, neural morphology and behavior of aged mice

Copper dyshomeostasis has been suggested as an aetiological risk factor for some neurodegenerative diseases, such as Alzheimer’s disease. However, the precise mechanism at the base of this involvement is still obscure. In this work, we show the effects of a copper-deficient diet in aged CD1 mice and the influence of such a diet on: a) the concentration of various metal ions (aluminium, copper, iron, calcium, zinc) in the main organs and in different brain areas; b) the alteration of metallothioneins I-II and tyrosine hydroxylase immunopositivity in the brain; c) behavioural tests (open field, pole, predatory aggression, and habituation/dishabituation smell tests). Our data suggested that the copper-deficiency was able to produce a sort of “domino effect” which altered the concentration of the other tested metal ions in the main organs as well as in the brain, without, however, significantly affecting the animal behaviour.

Therapeutic interventions targeting Beta amyloid pathogenesis in an aging dog model

Aged dogs and humans share complex cognitive and pathological responses to aging. Specifically, dogs develop Alzheimer's Disease (AD) like beta-amyloid (Aβ) that are associated with cognitive deficits. Currently, therapeutic approaches to prevent AD are targeted towards reduced production, aggregation and increased clearance of Aβ. The current review discusses cognition and neuropathology of the aging canine model and how it has and continues to be useful in further understanding the safety and efficacy of potential AD prevention therapies targeting Aβ.

Copper chelator induced efficient episodic memory recovery in a non-transgenic Alzheimer's mouse model

Alzheimer’s disease (AD) is a neurodegenerative syndrom involving many different biological parameters, including the accumulation of copper metal ions in Aβ amyloid peptides due to a perturbation of copper circulation and homeostasis within the brain. Copper-containing amyloids activated by endogenous reductants are able to generate an oxidative stress that is involved in the toxicity of abnormal amyloids and contribute to the progressive loss of neurons in AD. Since only few drugs are currently available for the treatment of AD, we decided to design small molecules able to interact with copper and we evaluated these drug-candidates with non-transgenic mice, since AD is mainly an aging disease, not related to genetic disorders. We created a memory deficit mouse model by a single icv injection of Aβ_1–42 peptide, in order to mimic the early stage of the disease and the key role of amyloid oligomers in AD. No memory deficit was observed in the control mice with the antisense Aβ_42-1 peptide. Here we report the capacity of a new copper-specific chelating agent, a bis-8-aminoquinoline PA1637, to fully reverse the deficit of episodic memory after three weeks of treatment by oral route on non-transgenic amyloid-impaired mice. Clioquinol and memantine have been used as comparators to validate this fast and efficient mouse model.

Micronutrient (Zn, Cu, Fe)-gene interactions in ageing and inflammatory age-related diseases: implications for treatments

In ageing, alterations in inflammatory/immune response and antioxidant capacity lead to increased susceptibility to diseases and loss of mobility and agility. Various essential micronutrients in the diet are involved in age-altered biological functions. Micronutrients (zinc, copper, iron) play a pivotal role either in maintaining and reinforcing the immune and antioxidant performances or in affecting the complex network of genes (nutrigenomic approach) involved in encoding proteins for a correct inflammatory/immune response. By the other side, the genetic inter-individual variability may affect the absorption and uptake of the micronutrients (nutrigenetic approach) with subsequent altered effects on inflammatory/immune response and antioxidant activity. Therefore, the individual micronutrient-gene interactions are fundamental to achieve healthy ageing. In this review, we report and discuss the role of micronutrients (Zn, Cu, Fe)-gene interactions in relation to the inflammatory status and the possibility of a supplement in the event of a micronutrient deficiency or chelation in presence of micronutrient overload in relation to specific polymorphisms of inflammatory proteins or proteins related of the delivery of the micronutriemts to various organs and tissues. In this last context, we report the protein-metal speciation analysis in order to have, coupled with micronutrient-gene interactions, a more complete picture of the individual need in micronutrient supplementation or chelation to achieve healthy ageing and longevity.

Issues raised involving the copper hypotheses in the causation of Alzheimer's disease

I present evidence that the epidemic of Alzheimer's disease is a new phenomenon exploding in the latter part of the 20th century in developed countries. I postulate that a major causative factor in the epidemic is the coincident use of copper plumbing, and the ingestion of inorganic copper leaching from the copper plumbing. I present evidence to support this hypothesis and discuss various objections and criticisms that have been raised about the hypothesis, and my responses to these criticisms. I conclude that the hypothesis is well supported by the evidence and deserves serious consideration, because if it is valid, it indentifies a partially preventable cause of Alzheimer's disease.

Reliability and validity of food frequency questionnaire and nutrient biomarkers in elders with and without mild cognitive impairment

INTRODUCTION

There is great interest in the nutritional strategies for the prevention of age-related cognitive decline, yet the best methods for nutritional assessment in the populations at risk for dementia are still evolving. Our study objective was to examine the reliability and validity of the 2 common nutritional assessments (plasma nutrient biomarkers and Food Frequency Questionnaire) in the people at risk for dementia.

METHODS

Thirty-eight elders, half with amnestic-mild cognitive impairment were recruited. Nutritional assessments were collected together at the baseline and again at 1 month. Intraclass and Pearson correlation coefficients quantified reliability and validity.

RESULTS

Twenty-six nutrients were examined. The reliability was very good or better for 77% (20/26, intraclass correlation coefficients or ICC ≥0.75) of the plasma nutrient biomarkers and for 88% of the food frequency questionnaires (FFQ) estimates. Twelve of the nutrient biomarkers were as reliable as the commonly measured plasma cholesterol (ICC≥0.92). FFQ and plasma long-chain fatty acids (docosahexaenoic acid, r=0.39, eicosapentaenoic acid, r=0.39) and carotenoids (α-carotene, r=0.49; lutein + zeaxanthin, r=0.48; β-carotene, r=0.43; β-cryptoxanthin, r=0.41) were correlated, but these significant correlations were present only in non-impaired elders.

CONCLUSION

The reliability and validity of the FFQ and nutrient biomarkers vary according to the nutrient of interest. Memory deficit attenuates validity and inflates reliability of FFQ reports. Many plasma nutrient biomarkers have very good reliability over 1-month, regardless of memory state. This objective method can circumvent sources of error seen in other less direct and subjective methods of nutritional assessment.

Assessment of heavy metals in the particulate matter of two Brazilian metropolitan areas by using Tillandsia usneoides as atmospheric biomonitor

PURPOSE

The aims of this paper were to quantify the heavy metals (HM) in the air of different sites in Rio de Janeiro (RJ) and Salvador (SA) using Tillandsia usneoides (Bromeliaceae) as a biomonitor, and to study the morphology and elemental composition of the air particulate matter (PM) retained on the Tillandsia surface.

METHODS

Tillandsia samples were collected in a noncontaminated area and exposed to the air of five sites in RJ State and seven in SA for 45 days, in two seasons. Samples were prepared to HM quantification by flame atomic absorption spectrophotometry, while morphological and elemental characterizations were studied by using scanning electron microscopy.

RESULTS

HM concentrations were significantly higher when compared to control sites. We found an increasing metal concentration as follows: Cd < Cr < Pb < Cu < Zn. PM exhibited a morphology varying from amorphous- to polygonal-shaped particles. Size measurements indicated that more than 80% of particles were less than 10 μm. PM contained aluminosilicates iron-rich particles, but Zn, Cu, Cr, and Ba were also detected.

CONCLUSION

HM input in the atmosphere was mainly associated with anthropogenic sources such as vehicle exhaust. Elemental analysis detected HM in the inhalable particles, indicating that those HMs may intensify the toxic effects of PM on human health. Our results indicated T. usneoides as an adequate biomonitor of HM in the PM belonging to the inhalable fraction.

A copper-lowering strategy attenuates amyloid pathology in a transgenic mouse model of Alzheimer's disease

There is increasing evidence for the crucial role of metals in the pathology of Alzheimer's disease. Both the aggregation and neurotoxicity of amyloid-β are dependent on the presence of copper. This study investigated the ability of the copper-complexing drug tetrathiomolybdate to reduce amyloid-β pathology and spatial memory impairment in both a prevention and a treatment paradigm in the Tg2576 mouse model of Alzheimer's disease. Tetrathiomolybdate treatment lowered brain copper and reduced amyloid-β levels in the prevention paradigm, but not in the treatment paradigm. Our data suggests that controlled lowering of systemic copper may achieve anti-amyloid effects if initiated early in the disease process.

Selective removal of copper(II) from natural waters by nanoporous sorbents functionalized with chelating diamines

Copper has been identified as a pollutant of concern by the U.S. Environmental Protection Agency (EPA) because of its widespread occurrence and toxic impact in the environment. Three nanoporous sorbents containing chelating diamine functionalities were evaluated for Cu(2+) adsorption from natural waters: ethylenediamine functionalized self-assembled monolayers on mesoporous supports (EDA-SAMMS), ethylenediamine functionalized activated carbon (AC-CH(2)-EDA), and 1,10-phenanthroline functionalized mesoporous carbon (Phen-FMC). The pH dependence of Cu(2+) sorption, Cu(2+) sorption capacities, rates, and selectivity of the sorbents were determined and compared with those of commercial sorbents (Chelex-100 ion-exchange resin and Darco KB-B activated carbon). All three chelating diamine sorbents showed excellent Cu(2+) removal (approximately 95-99%) from river water and seawater over the pH range 6.0-8.0. EDA-SAMMS and AC-CH(2)-EDA demonstrated rapid Cu(2+) sorption kinetics (minutes) and good sorption capacities (26 and 17 mg Cu/g sorbent, respectively) in seawater, whereas Phen-FMC had excellent selectivity for Cu(2+) over other metal ions (e.g., Ca(2+), Fe(2+), Ni(2+), and Zn(2+)) and was able to achieve Cu below the EPA recommended levels for river and sea waters.

In vitro evaluation of surface topographic changes and nickel release of lingual orthodontic archwires

The objective of the article is to study surface topographic changes and nickel release in lingual orthodontic archwires in vitro. Stainless steel (SS), nickel-titanium (NiTi) and copper-nickel-titanium (CuNiTi) lingual orthodontic archwires were studied using atomic absorption spectrometry for nickel release after immersion in a saline solution. Surface roughness changes were measured using atomic force microscopy. Differences between groups were analyzed using independent sample t-tests. Statistically significant changes in roughness were seen in all archwires except NiTi. Surface changes were most severe in the CuNiTi alloy. SS archwires released the highest amount of nickel. In conclusion, only roughness changes in CuNiTi archwires seemed to be clinically significant. The amount of nickel released for all archwires tested is below the levels known to cause cell damage.

Expression of the neuronal adaptor protein X11alpha protects against memory dysfunction in a transgenic mouse model of Alzheimer's disease

X11alpha is a neuronal-specific adaptor protein that binds to the amyloid-beta protein precursor (AbetaPP). Overexpression of X11alpha reduces Abeta production but whether X11alpha also protects against Abeta-related memory dysfunction is not known. To test this possibility, we crossed X11alpha transgenic mice with AbetaPP-Tg2576 mice. AbetaPP-Tg2576 mice produce high levels of brain Abeta and develop age-related defects in memory function that correlate with increasing Abeta load. Overexpression of X11alpha alone had no detectable adverse effect upon behavior. However, X11alpha reduced brain Abeta levels and corrected spatial reference memory defects in aged X11alpha/AbetaPP double transgenics. Thus, X11alpha may be a therapeutic target for Alzheimer's disease.

Metal ion physiopathology in neurodegenerative disorders

Metal dyshomeostasis in the brain (BMD) has often been proposed as a possible cause for several neurodegenerative disorders (NDs). Nevertheless, the precise nature of the biochemical mechanisms of metal involvement in NDs is still largely unknown. Mounting evidence suggests that normal aging itself is characterized by, among other features, a significant degree of metal ion dysmetabolism in the brain. This is probably the result of a progressive deterioration of the metal regulatory systems and, at least in some cases, of life-long metal exposure and brain accumulation. Although alterations of metal metabolism do occur to some extent in normal aging, they appear to be highly enhanced under various neuropathological conditions, causing increased oxidative stress and favoring abnormal metal-protein interactions. Intriguingly, despite the fact that most common NDs have a distinct etiological basis, they share striking similarities as they are all characterized by a documented brain metal impairment. This review will primarily focus on the alterations of metal homeostasis that are observed in normal aging and in Alzheimer's disease. We also present a brief survey on BMD in other NDs (Amyotrophic Lateral Sclerosis, Parkinson's, and Prion Protein disease) in order to highlight what represents the most reliable evidence supporting a crucial involvement of metals in neurodegeneration. The opportunities for metal-targeted pharmacological strategies in the major NDs are briefly outlined as well.