Redox speciation of iron, manganese, and copper in cerebrospinal fluid by strong cation exchange chromatography – sector field inductively coupled plasma mass spectrometry

Interplay of Metallome and Metabolome in Amyotrophic Lateral Sclerosis: A Study on Cerebrospinal Fluid of Patients Carrying Disease-Related Gene Mutations

Amyotrophic lateral sclerosis (ALS) is a lethal progressive neurodegenerative disease, characterized by a loss of function of upper and lower motor neurons. This study aimed to explore probable pathological alterations occurring in individuals with ALS compared to neurologically healthy controls through the analysis of cerebrospinal fluid (CSF), a medium, which directly interacts with brain parenchyma. A total of 7 ALS patients with disease-associated mutations (ATXN2, C9ORF72, FUS, SOD1, and TARDBP) and 13 controls were included in the study. Multiple analytical approaches were employed, including metabolomic and metallomics profiling, as well as genetic screening, using CSF samples obtained from the brain compartment. Data analysis involved the application of multivariate statistical methods. Advanced hyphenated selenium and redox metal (iron, copper, and manganese) speciation techniques and nontargeted Fourier transform ion cyclotron resonance mass spectrometry-based metabolomics were used for data acquisition. Nontargeted metabolomics showed reduced steroids, including sex hormones; additionally, copper and manganese species were found to be the most relevant features for ALS patients. This indicates a potential alteration of sex hormone pathways in the ALS-affected brain, as reflected in the CSF.

A Fast and Efficient Procedure of Iron Species Determination Based on HPLC with a Short Column and Detection in High Resolution ICP OES

The optimization and application of a new hyphenated procedure for iron ionic speciation, i.e., high performance liquid chromatography (HPLC) with short cation-exchange column (50 mm × 4 mm) coupled to high resolution inductively coupled plasma optical emission spectrometry (ICP hrOES), is presented in this paper. Fe(III) and Fe(II) species were separated on the column with the mobile phase containing pyridine-2,6-dicarboxylic acid (PDCA). The total time of the analysis was approx. 5 min, with a significantly low eluent flow rate (0.5 mL min^-1) compared to the literature. Additionally, a long cation-exchange column (250 mm × 4.0 mm) was used as reference. Depending on the total iron content in the sample, two plasma views were chosen, e.g., an attenuated axial (<2 g kg^-1) and an attenuated radial. The standard addition method was performed for the method's accuracy studies, and the applicability was presented on three types of samples: sediments, soils, and archaeological pottery. This study introduces a fast, efficient, and green method for leachable iron speciation in both geological and pottery samples.

Monitoring of Copper in Wilson Disease

(1) Introduction: Wilson's disease (WND) is an autosomal recessive disorder of copper (Cu) metabolism. Many tools are available to diagnose and monitor the clinical course of WND. Laboratory tests to determine disorders of Cu metabolism are of significant diagnostic importance. (2) Methods: A systematic review of the literature in the PubMed, Science Direct, and Wiley Online Library databases was conducted. (Results): For many years, Cu metabolism in WND was assessed with serum ceruloplasmin (CP) concentration, radioactive Cu test, total serum Cu concentration, urinary copper excretion, and Cu content in the liver. The results of these studies are not always unambiguous and easy to interpret. New methods have been developed to calculate non-CP Cu (NCC) directly. New parameters, such as relative Cu exchange (REC), reflecting the ratio of CuEXC to total serum Cu, as well as relative Cu exchange (REC), reflecting the ratio of CuEXC to total serum Cu, have been shown to be an accurate tool for the diagnosis of WND. Recently, a direct and fast LC-ICP-MS method for the study of CuEXC was presented. A new method to assess Cu metabolism during treatment with ALXN1840 (bis-choline tetrathiomolybdate [TTM]) has been developed. The assay enables the bioanalysis of CP and different types of Cu, including CP-Cu, direct NCC (dNCC), and labile bound copper (LBC) in human plasma. Conclusions: A few diagnostic and monitoring tools are available for patients with WND. While many patients are diagnosed and adequately assessed with currently available methods, diagnosis and monitoring is a real challenge in a group of patients who are stuck with borderline results, ambiguous genetic findings, and unclear clinical phenotypes. Technological progress and the characterization of new diagnostic parameters, including those related to Cu metabolism, may provide confidence in the more accurate diagnosis of WND in the future.

Intraperitoneal injection of iron dextran induces peripheral iron overload and mild neurodegeneration in the nigrostriatal system in C57BL/6 mice

AIMS

Elevated iron levels in the affected areas of brain are linked to several neurodegenerative diseases including Parkinson's disease (PD). This study investigated the influence of peripheral iron overload in peripheral tissues, as well as its entry into the brain regions on lysosomal functions. The survival of dopaminergic neurons in the nigrostriatal system and motor coordination were also investigated.

MAIN METHODS

An intraperitoneal injection of iron dextran (FeDx) mouse model was established. Western blot was used to detect iron deposition and lysosomal functions in the liver, spleen, hippocampal (HC), striatum (STR), substantia nigra (SN) and olfactory bulb (OB). Iron in serum and cerebrospinal fluid (CSF) was determined by an iron assay kit. Immunofluorescence and immunohistochemical staining were applied to detect dopaminergic neurons and fibers. Motor behavior was evaluated by gait analysis.

KEY FINDINGS

Iron was deposited consistently in the liver and spleen, and serum iron was elevated. While iron deposition occurred late in the HC, STR and SN, without apparently affecting CSF iron levels. Although cathepsin B (CTSB), cathepsin D (CTSD), glucocerebrosidase (GCase) and lysosome integrated membrane protein 2 (LIMP-2) protein levels were dramatically up-regulated in the liver and spleen, they were almost unchanged in the brain regions. However, CTSB was up-regulated in acute iron-overloaded OB and primary cultured astrocytes. The number of dopaminergic neurons in the SN remained unchanged, and mice did not exhibit significant motor incoordination.

SIGNIFICANCE

Intraperitoneal injection of FeDx in mice induces largely peripheral iron overload while not necessarily sufficient to cause severe disruption of the nigrostriatal system.

Microwave-Assisted Rapid Synthesis of Luminescent Tryptophan-Stabilized Silver Nanoclusters for Ultra-Sensitive Detection of Fe(III), and Their Application in a Test Strip

A new preparation method for extreme fluorescent green emission tryptophan-stabilized silver nanoclusters (Tryp-AgNCs) is presented in this scientific research. The produced silver nanoclusters are dependent on tryptophan amino acid which contributes to normal growth in infants and the sublimation and recovery of human protein, muscles, and enzymes. Herein, we have introduced a green method by using microwave-assisted rapid synthesis. The subsequent silver nanoclusters (AgNCs) have excitation/emission peaks at 408/498 nm and display a considerable selectivity to Fe(III) ions. The tryptophan amino acid molecule was used in the synthesis process as a reducing and stabilizing agent. The Tryp-AgNCs' properties were investigated in terms of morphology, dispersity, and modification of the synthesized particles using different advanced instruments. The luminescent nanoclusters traced the Fe(III) ions by the luminescence-quenching mechanism of the Tryp-AgNCs luminescence. Therefore, the extreme selectivity of the prepared nanoclusters was exhibited to the Fe(III) ions, permitting the sensitive tracing of ferric ions in the lab and in the real environmental samples. The limit of detection for Fe(III) ions based on Tryp-AgNCs was calculated to be 16.99 nM. The Tryp-AgNCs can be efficiently applied to a paper test strip method. The synthesized nanoclusters were used efficiently to detect the Fe(III) ions in the environmental samples. Moreover, we examined the reactivity of Tryp-AgNCs on various human tumor cell lines. The results show that the Tryp-AgNCs exhibited their activity versus the cancer cells in a dose-dependent routine for the perceived performance versus the greatest-used cancer cell lines.

Review about Powerful Combinations of Advanced and Hyphenated Sample Introduction Techniques with Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) for Elucidating Trace Element Species in Pathologic Conditions on a Molecular Level

Element analysis in clinical or biological samples is important due to the essential role in clinical diagnostics, drug development, and drug-effect monitoring. Particularly, the specific forms of element binding, actual redox state, or their spatial distribution in tissue or in single cells are of interest in medical research. This review summarized exciting combinations of sophisticated sample delivery systems hyphenated to inductively coupled plasma-mass spectrometry (ICP-MS), enabling a broadening of information beyond the well-established outstanding detection capability. Deeper insights into pathological disease processes or intracellular distribution of active substances were provided, enabling a better understanding of biological processes and their dynamics. Examples were presented from spatial elemental mapping in tissue, cells, or spheroids, also considering elemental tagging. The use of natural or artificial tags for drug monitoring was shown. In the context of oxidative stress and ferroptosis iron, redox speciation gained importance. Quantification methods for Fe2+, Fe3+, and ferritin-bound iron were introduced. In Wilson’s disease, free and exchangeable copper play decisive roles; the respective paragraph provided information about hyphenated Cu speciation techniques, which provide their fast and reliable quantification. Finally, single cell ICP-MS provides highly valuable information on cell-to-cell variance, insights into uptake of metal-containing drugs, and their accumulation and release on the single-cell level.

A salicylaldehyde benzoyl hydrazone based near-infrared probe for copper(ii) and its bioimaging applications

Developing highly sensitive and selective methods for Cu²⁺ detection in living systems is of great significance in clinical copper-related disease diagnosis. In this work, a near infrared (NIR) fluorescent probe, CySBH, with a salicylaldehyde benzoyl hydrazone group as a selective and sensitive receptor for Cu²⁺ was designed and synthesized. The specific coordination of the salicylaldehyde benzoyl hydrazone group in CySBH with Cu²⁺ can induce a distinct quench of the fluorescence intensity, allowing for real-time tracking of Cu²⁺. We have demonstrated that CySBH could rapidly recognize Cu²⁺ with good selectivity and high sensitivity. Moreover, on the basis of low cell cytotoxicity, the probe was used to visualize Cu²⁺ in two cell lines by fluorescence imaging. Furthermore, CySBH can also be used to monitor Cu²⁺in vivo due to its NIR emission properties. These overall results illustrate that the NIR fluorescent probe CySBH provides a novel approach for the selective and sensitive monitoring of Cu²⁺ in living systems.

A near infrared fluorescent probe utilizing the salicylaldehyde benzoyl hydrazone group as the Cu²⁺ receptor was developed and used to selectively and sensitively monitor Cu²⁺ in living systems.

Novel Extraction Method for Combined Lipid and Metal Speciation From Caenorhabditis elegans With Focus on Iron Redox Status and Lipid Profiling

Parkinson´s disease progression is linked to iron redox status homeostasis via reactive oxygen species (ROS) formation, and lipids are the primary targets of ROS. The determination of iron redox status in vivo is challenging and requires specific extraction methods, which are so far tedious and very time-consuming. We demonstrated a novel, faster, and less laborious extraction method using the chelator ethylene glycol l-bis(β-aminoethyl ether)-N,N,N′,N′-tetra acetic acid (EGTA) as a stabilizing agent and synthetic quartz beads for homogenization under an argon atmosphere. Additionally, we combined the metal extraction with a well-established lipid extraction protocol using methyl-tert-butyl ether (MTBE) to avoid the problems of lipid precipitation in frozen samples and to determine lipid profiles and metal species from the same batch. The nonextractable matrix, such as the debris, is removed by centrifugation and digested to determine the total metal content of the sample as well. Lipid profiling using RP-LC–MS demonstrated high accordance of the modified extraction method to the reference method, and the organic solvent does not affect the iron redox status equilibrium. Furthermore, rigorous testing demonstrated the stability of the iron redox status equilibrium during the extraction process, secured by complexation, inert atmosphere, fast preparation, and immediately deep frozen extracts.

Kinetics of Cu(II) complexation by ATCUN/NTS and related peptides: a gold mine of novel ideas for copper biology

Cu(II)-peptide complexes are intensely studied as models for biological peptides and proteins and for their direct importance in copper homeostasis and dyshomeostasis in human diseases. In particular, high-affinity ATCUN/NTS (amino-terminal copper and nickel/N-terminal site) motifs present in proteins and peptides are considered as Cu(II) transport agents for copper delivery to cells. The information on the affinities and structures of such complexes derived from steady-state methods appears to be insufficient to resolve the mechanisms of copper trafficking, while kinetic studies have recently shown promise in explaining them. Stopped-flow experiments of Cu(II) complexation to ATCUN/NTS peptides revealed the presence of reaction steps with rates much slower than the diffusion limit due to the formation of novel intermediate species. Herein, the state of the field in Cu(II)-peptide kinetics is reviewed in the context of physiological data, leading to novel ideas in copper biology, together with the discussion of current methodological issues.

LC-ICP-MS method for the determination of "extractable copper" in serum

Copper is an essential element for biological functions within humans and animals. There are several known diseases associated with Cu deficiency or overload, such as Menkes disease and Wilson disease, respectively. A common clinical method for determining extractable Cu levels in serum, which is thought to be potentially dangerous if in excess, is to subtract the value of tightly incorporated Cu in ceruloplasmin from total serum Cu. In this work, an automated sample preparation and liquid chromatography (LC) system was combined with inductively coupled plasma-mass spectrometry (ICP-MS) to determine bound Cu and extractable Cu in serum. This LC-ICP-MS method took 250 s for sample preparation and analysis, followed by a column recondition/system reset, thus, a 6 minute sample-to-sample time including sample preparation. The method was validated using serum collected from either control (Atp7b+/-) or Wilson disease rats (Atp7b-/-). The extractable Cu was found to be 4.0 ± 2.3 μM Cu in healthy control rats, but 2.1 ± 0.6 μM Cu in healthy Wilson rats, and 27 ± 16 μM Cu in diseased Wilson rats, respectively. In addition, the extractable Cu/bound Cu ratio was found to be 6.4 ± 3.5%, 38 ± 29%, and 34 ± 22%, respectively. These results suggest that the developed method could be of diagnostic value for Wilson disease, and possibly other copper related diseases.

Iron species determination by high performance liquid chromatography with plasma based optical emission detectors: HPLC-MIP OES and HPLC-ICP OES

The paper presents an independent application of two hyphenated techniques, wherein an identical chromatographic system i.e. high performance liquid chromatography (HPLC) was coupled to microwave induced plasma optical emission spectrometry (MIP OES) or inductively coupled plasma optical emission spectrometry (ICP OES). A cation-exchange column and a mobile phase based on pyridine-2,6-dicarboxylic acid (PDCA) were employed to separate Fe(II) and Fe(III) within 300 s. Additionally, two methods of sample preparation were employed. Optimization and validation of both methods were conducted parallel. The applicability was presented with different sample matrix types: post-glacial sediments, archaeological pottery, soils located in the proximity of industry wastes disposal site, river sediments and yerba mate (Ilex paraguariensis). Obtained results were compared in terms of the excitation source (microwave induced or inductively coupled) and supplied gas (nitrogen or argon). The research introduces HPLC-MIP OES for iron speciation analysis and its applicability were critically evaluated with HPLC-ICP OES.

The study of levels from redox-active elements in cerebrospinal fluid of amyotrophic lateral sclerosis patients carrying disease-related gene mutations shows potential copper dyshomeostasis

Amyotrophic lateral sclerosis is a progressive neurodegenerative disease characterized by a loss of function of motor neurons. The etiology of this disorder is still largely unknown. Gene-environment interaction arises as a possible key factor in the development of amyotrophic lateral sclerosis. We assessed the levels of trace metals, copper (Cu), iron (Fe), and manganese (Mn), of 9 amyotrophic lateral sclerosis cases and 40 controls by measuring their content in cerebrospinal fluid. The following trace element species were quantified using ion chromatography-inductively coupled plasma mass spectrometry: univalent copper (Cu-I), divalent Cu (Cu-II), divalent Fe (Fe-II), trivalent Fe (Fe-III), divalent Mn (Mn-II), trivalent Mn (Mn-III), and also unidentified Mn species (Mn-unknown) were present in some samples. When computing the relative risks for amyotrophic lateral sclerosis through an unconditional logistic regression model, we observed a weak and imprecise positive association for iron (Fe III, adjusted odds ratio 1.48, 95% CI 0.46-4.76) and manganese (total-Mn and Mn-II; adjusted odds ratio 1.11, 95% CI 0.74-1.67, and 1.13, 95% CI 0.79-1.61, respectively). Increased risk for copper was found both in the crude analysis (odds ratio 1.14, 95% CI 0.99-1.31) and in multivariable analysis after adjusting for sex, age, and year of storage (1.09, 95% CI 0.90-1.32). Our results suggest a possible positive association between Cu and genetic amyotrophic lateral sclerosis, while they give little indication of involvement of Fe and Mn in disease, though some correlations found also for these elements deserve further investigation.

Multi-mode Sample Introduction System (MSIS) as an interface in the hyphenated system 2 HPLC-MSIS-ICP-OES in simultaneous determination of metals and metalloids species

The paper presents a usage of a new hyphenated technique, wherein a Multi-mode Sample Introduction System (MSIS) was applied as an interface of two high pressure liquid chromatography units and inductively coupled plasma optical emission spectrometry (2 HPLC-MSIS-ICP-OES). Simultaneous separation and detection of non-hydride forming and hydride forming elements was possible due to the application of two different HPLC column, cation-exchange and anion-exchange respectively. The method was able to determine 15 elements quantitatively with a distinction of three arsenic and two iron species and it was validated obtaining acceptable LODs (2.67-28.7 μg L^-1) and recoveries (80-120%). The method applicability was presented and confirmed on 5 varied sample matrix types i.e. post-glacial sediments, yerba mate (Ilex paraguariensis), soil samples located in the proximity of industry wastes disposal site, river sediments, and archaeological pottery. In addition to the above, unknown Cu, Fe, Mn and Zn species were detected in real samples (qualitative speciation analysis) and the identification was attempted according to the literature.

Cr and Mn total, accessible species, and protein-fraction contents in plants used for traditional anti-diabetes treatment

BACKGROUND

Our survey has found eleven plants that have being consumed for traditional treatment of diabetes mellitus, particularly in Saudi Arabia and generally in many countries across the world. The literature reported about trace elements such as Cr and Mn positively affecting diabetes mellitus. The aim of this work is to determine the total, accessible element species, and protein-fraction contents of Cr and Mn in the edible parts of those plants.

METHODS

The total contents of Mn were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES), while the total contents of Cr was determined by ICP-sector field (sf)-mass spectrometry (MS) due to lower concentration. The protein-fraction contents were determined in accessible element species by size-exclusion chromatography (SEC)-ICP-MS.

RESULTS AND DISCUSSION

The separation was successfully carried out to quantify Cr and Mn bound up to 11 protein fractions. The examined plants recorded wide ranges of total contents (Cr 44.7-1880.0 μg/kg and Mn 3.7-59.0 mg/kg) and accessible element species contents (Cr 0.93-29.40 μg/kg and Mn 0.82-35.85 mg/kg). Also wide ranges of percentages of accessible element species contents to total contents of Cr (0.65-4.21%) and Mn (5.43-68.42%) were obtained. The hazardous indices of both trace elements Cr and Mn for all examined plants consumed by both children and adults were all < 1, indicating no probability of health risk to occur. Moreover, Cr as carcinogen element reported no probability of cancer risk to occur from the consumption of all examined plants. Irrespective of plant species, Cr was quantified in all SEC fractions (mainly protein fractions), with the exception of 1.9-3.7 kDa, while Mn was quantified in all SEC fractions with the exception of 100-120 and 1.3-3.7 kDa. Nevertheless, the majority of accessible Cr species contents bound to the 10-14 and 0.05-0.40 kDa fractions, while that of Mn bound to 0.05-0.40 kDa fraction. To gather, the benefits of specific plant species in terms of accessible Cr and Mn species contents, in addition to accessible Zn species contents reported in our previous study, Haloxylon Salicornicum, Olea Europaea Momordica and Charantia are recommended to be consumed for traditionally controlling T2DM.

ICP-MS trace element analysis in serum and whole blood

Trace elements and minerals are compounds that are essential for the support of a variety of biological functions and play an important role in the formation of and the defense against oxidative stress. Here we describe a technique, allowing sequential detection of the trace elements (K, Zn, Se, Cu, Mn, Fe, Mg) in serum and whole blood by an ICP-MS method using single work-up, which is a simple, quick and robust method for the sequential measurement and quantification of the trace elements Sodium (Na), Potassium (K), Calcium (Ca), Zinc (Zn), Selenium (Se), Copper (Cu), Iron (Fe), Manganese (Mn) and Magnesium (Mg) in whole blood as well as Copper (Cu), Selenium (Se), Zinc (Zn), Iron (Fe), Magnesium (Mg), Manganese (Mn), Chromium (Cr), Nickel (Ni), Gold (Au) and Lithium (Li) in human serum. For analysis, only 100 μl of serum or whole blood is sufficient, which make this method suitable for detecting trace element deficiency or excess in newborns and infants. All samples were processed and analyzed by ICP-MS (Agilent Technologies). The accuracy, precision, linearity and the limit of quantification (LOQ), Limit of Blank (LOB) and the limit of detection (LOD) of the method were assessed. Recovery rates were between 80–130% for most of the analyzed elements; repeatabilities (C_v %) calculated were below 15% for most of the measured elements. The validity of the proposed methodology was assessed by analyzing a certified human serum and whole blood material with known concentrations for all elements; the method described is ready for routine use in biomonitoring studies.

Selenoprotein P and its potential role in Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease associated with cognitive decline, loss of memory, and progressive cerebral atrophy. The trace element selenium (Se) is known to be involved in brain pathology. Selenoprotein P (SELENOP), as the main Se transport protein, is, to a great extent, responsible for maintaining Se homeostasis and the hierarchy of selenoprotein expression in the body. Adequate Se supply through SELENOP is vital for proper brain development and function. Additionally, SELENOP may be implicated in pathological processes in the central nervous system, including those in AD. The current review summarizes recent findings on the possible role of SELENOP in AD, with a focus on probable mechanisms: Se delivery to neurons, antioxidant activity, cytoskeleton assembly, interaction with redox-active metals (e.g., copper and iron), and misfolded proteins (amyloid beta and tau protein). The use of SELENOP as a biomarker of Se status is also briefly discussed. Epidemiological studies on Se supplementation are beyond the scope of the current review.

Selenium and iodine in diabetes mellitus with a focus on the interplay and speciation of the elements

Diabetes mellitus is a chronic metabolic disease caused by insulin deficiency (type I) or dysfunction (type II). Diabetes is a threatening public health concern. It is considered as one of the priority non-communicable diseases, due to its high and increasing incidence, the associated healthcare costs, and threatening medical complications. Two trace elements selenium (Se) and iodine (I) were intensively discussed in the context of diabetic pathology and, possibly, etiology. It seems there is a multilayer involvement of these essential nutrients in glucose tolerance, energy metabolism, insulin signaling and resistance, which are mainly related to the antioxidant selenoenzymes and the thyroid hormones. Other factors might be related to (auto)immunity, protection against endoplasmic reticulum stress, and leptin signaling. The aim of the current review is to evaluate the current understanding of the role of selenium and iodine in diabetes with a focus on the biochemical interplay between the elements, their possible role as biomarkers, and their chemical speciation. Possible impacts from novel analytical techniques related to trace element speciation and isotopic analysis are outlined.

Au nanoclusters/porous silica particles nanocomposites as fluorescence enhanced sensors for sensing and mapping of copper(II) in cells

In this work, we first report Au nanoclusters/porous silica particles nanocomposites as fluorescence enhanced sensors for selective and sensitive detection of Cu (II). As red-emitting GSH-protected Au nanoclusters (Au NCs) were self-assemble into porous silica particles (PSPs) after ultrasonic treatment. As a result, the Au NCs can be immobilized in the nano-channels of PSPs, which leads to the observation of an immobilized induced emission enhancement phenomenon. The photoluminscence (PL) intensity of the nanocomposites can enhance dozens of times compared with Au NCs. As a result, we obtain a novel PL enhanced sensor of Au NCs/PSPs nanocomposites with excellent PL properties. The as-prepared Au NCs/PSPs nanocomposites show good water-solubility, high stability, low toxicity, and exhibit a high PL quenching for reliable, sensitive and selective detection of Cu²⁺. The limit of detection can reach as low as 1 ppb. What is more, the Au NCs/PSPs nanocomposites also show sensitive detection of Cu²⁺ in living cells. These properties provide the Au NCs/PSPs nanocomposites with promising PL sensors for Cu²⁺ detection in various environmental and biological systems.

Environmental Selenium and Human Health: an Update

PURPOSE OF REVIEW

Selenium, a trace element, is ubiquitous in the environment. The main source of human exposure is diet. Despite its nutritional benefits, it is one of the most toxic naturally occurring elements. Selenium deficiency and overexposure have been associated with adverse health effects. Its level of toxicity may depend on its chemical form, as inorganic and organic species have distinct biological properties.

RECENT FINDINGS

Nonexperimental and experimental studies have generated insufficient evidence for a role of selenium deficiency in human disease, with the exception of Keshan disease, a cardiomyopathy. Conversely, recent randomized trials have indicated that selenium overexposure is positively associated with type 2 diabetes and high-grade prostate cancer. In addition, a natural experiment has suggested an association between overexposure to inorganic hexavalent selenium and two neurodegenerative diseases, amyotrophic lateral sclerosis and Parkinson's disease. Risk assessments should be revised to incorporate the results of studies demonstrating toxic effects of selenium. Additional observational studies and secondary analyses of completed randomized trials are needed to address the uncertainties regarding the health risks of selenium exposure.

Selenium and selenium species in the etiology of Alzheimer's dementia: The potential for bias of the case-control study design

Several human studies imply that the trace element selenium and its species may influence the onset of neurological disease, including Alzheimer's dementia (AD). Nevertheless, the literature is conflicting, with reported associations between exposure and risk in opposite direction, possibly due to biases in exposure assessment. After conducting a cohort study that detected an excess AD risk associated with higher levels of inorganic-hexavalent selenium in subjects with mild cognitive impairment (MCI), we investigated the relation between selenium and AD using a case-control study design. We determined cerebrospinal fluid levels of selenium species in 56 MCI participants already included in the cohort study, considered as referents, and in 33 patients with established AD. AD risk was inversely correlated with inorganic selenium species and with the organic form bound to selenoprotein P. Selenium bound to other organo-selenium species was positively correlated with AD risk, suggesting compensatory selenoprotein upregulation following increased oxidative stress. The finding of an increased AD risk associated with inorganic-hexavalent selenium from the cohort study was not replicated. This case-control study yielded entirely different results than those generated by a cohort study with a partially overlapping participant population, suggesting that case-control design does not allow to reliably assess the role of selenium exposure in AD etiology. This inability appears to be due to exposure misclassification, falsely indicating an etiologic role of selenium deficiency likely due to reverse causation, and involving most selenium species. The case-control design may instead lend insights into the pathologic process underlying disease progression.

Iron Redox Speciation Analysis Using Capillary Electrophoresis Coupled to Inductively Coupled Plasma Mass Spectrometry (CE-ICP-MS)

Neuronal iron dyshomeostasis occurs in multiple neurodegenerative diseases. Changes in the Fe(II)/Fe(III) ratio toward Fe(II) is closely related to oxidative stress, lipid peroxidation, and represents a hallmark feature of ferroptosis. In particular for body fluids, like cerebrospinal fluid (CSF), reliable quantitative methods for Fe(II)/(III) redox-speciation analysis are needed to better assess the risk of Fe(II)-mediated damage in brain tissue. Currently in the field of metallomics, the most direct method to analyze both iron species is via LC-ICP-MS. However, this Fe(II)/(III) speciation analysis method suffers from several limitations. Here, we describe a unique method using capillary electrophoresis (CE)-ICP-MS for quantitative Fe(II)/(III) speciation analysis that can be applied for cell lysates and biofluid samples. Compared to LC, CE offers various advantages: (1) Capillaries have no stationary phase and do not depend on batch identity of stationary phases; (2) Replacement of aged or blocked capillaries is quick with no performance change; (3) Purge steps are effective and short; (4) Short sample analysis time. The final method employed 20 mM HCl as background electrolyte and a separation voltage of +25 kV. In contrary to the LC-method, no complexation of Fe-species with pyridine dicarboxylic acid (PDCA) was applied, since it hampered separation. Peak shapes and concentration detection limits were improved by combined conductivity-pH-stacking achieving 3 μg/L detection limit (3σ) at 13 nL injection volume. Calibrations from LOD—150 μg/L were linear [r²_[Fe(II)] = 0.9999, r²_[Fe(III)] = 0.9951]. At higher concentrations Fe(II) curve flattened significantly. Measurement precision was 3.5% [Fe(II) at 62 μg/L] or 2.2% [Fe(III) at 112 μg/L] and migration time precision was 2% for Fe(III) and 3% for Fe(II), each determined in 1:2 diluted lysates of human neuroblastoma cells. Concentration determination accuracy was checked by parallel measurements of SH-SY5Y cell lysates with validated LC-ICP-MS method and by recovery experiments after standard addition. Accuracy (n = 6) was 97.6 ± 3.7% Fe(III) and 105 ± 6.6%Fe(II). Recovery [(a) +33 μg/L or (b) +500 μg/L, addition per species] was (a): 97.2 ± 13% [Fe(II)], 108 ± 15% [Fe(III)], 102.5 ± 7% (sum of species), and (b) 99±4% [Fe(II)], 101 ± 6% [Fe(III)], 100 ± 5% (sum of species). Migration time shifts in CSF samples were due to high salinity, but both Fe-species were identified by standard addition.

Dietary intake of cadmium, chromium, copper, manganese, selenium and zinc in a Northern Italy community

This study provides the dietary intakes of six trace elements (cadmium, chromium, copper, manganese, selenium and zinc), generally characterized by both nutritional and toxicological features depending on their exposure. Being diet the most relevant source of exposure to trace elements in non-professionally exposed subjects, we measured content of these trace elements in foods composing the typical Italian diet using inductively coupled plasma-mass spectrometry, and assessing dietary habits using a validated semi-quantitative food frequency questionnaire we eventually estimated dietary daily intake of trace elements in a Northern Italian community. In the 890 analyzed food samples, the main contributors to cadmium intake are cereals, vegetables and sweets, while cereals, beverages and vegetable are to primary source of manganese. The primary contributors for copper are cereals, fresh fruits and vegetables, while for chromium are beverages, cereals and meat. The main source of selenium intake are cereals and meat, followed by fish, seafood and milk and dairy products, while of zinc intake are meat, cereals, milk and dairy products. In our Italian population sample, the estimated median (interquartile range) dietary daily intakes are 5.00 (3.17-7.65), 56.70 (36.08-86.70) and 66.53 (40.04-101.32) μg/day for cadmium, chromium and selenium, and corresponding figures are 0.98 (0.61-1.49), 2.34 (1.46-3.52) and 8.50 (5.21-12.48) mg/day for copper, manganese and zinc. The estimated intakes are generally within the average intake reported in other European populations, and in such cases well above the daily dietary intakes recommended by national international agencies, avoiding the risk of excess or deficiency. The present estimated intake data can be used to examine a specific trace element of interest and would afford enhanced health protection from those trace elements characterized by both nutritional and toxicological effects.

Manganese causes neurotoxic iron accumulation via translational repression of amyloid precursor protein and H-Ferritin

For more than 150 years, it is known that occupational overexposure of manganese (Mn) causes movement disorders resembling Parkinson's disease (PD) and PD-like syndromes. However, the mechanisms of Mn toxicity are still poorly understood. Here, we demonstrate that Mn dose- and time-dependently blocks the protein translation of amyloid precursor protein (APP) and heavy-chain Ferritin (H-Ferritin), both iron homeostatic proteins with neuroprotective features. APP and H-Ferritin are post-transcriptionally regulated by iron responsive proteins, which bind to homologous iron responsive elements (IREs) located in the 5'-untranslated regions (5'-UTRs) within their mRNA transcripts. Using reporter assays, we demonstrate that Mn exposure repressed the 5'-UTR-activity of APP and H-Ferritin, presumably via increased iron responsive proteins-iron responsive elements binding, ultimately blocking their protein translation. Using two specific Fe2+ -specific probes (RhoNox-1 and IP-1) and ion chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS), we show that loss of the protective axis of APP and H-Ferritin resulted in unchecked accumulation of redox-active ferrous iron (Fe2+ ) fueling neurotoxic oxidative stress. Enforced APP expression partially attenuated Mn-induced generation of cellular and lipid reactive oxygen species and neurotoxicity. Lastly, we could validate the Mn-mediated suppression of APP and H-Ferritin in two rodent in vivo models (C57BL6/N mice and RjHan:SD rats) mimicking acute and chronic Mn exposure. Together, these results suggest that Mn-induced neurotoxicity is partly attributable to the translational inhibition of APP and H-Ferritin resulting in impaired iron metabolism and exacerbated neurotoxic oxidative stress. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Selenium, selenoprotein P, and Alzheimer's disease: is there a link?

The essential trace element, selenium (Se), is crucial to the brain but it may be potentially neurotoxic, depending on dosage and speciation; Se has been discussed for decades in relation to Alzheimer's disease (AD). Selenoprotein P (SELENOP) is a secreted heparin-binding glycoprotein which serves as the main Se transport protein in mammals. In vivo studies showed that this protein might have additional functions such as a contribution to redox regulation. The current review focuses on recent research on the possible role of SELENOP in AD pathology, based on model and human studies. The review also briefly summarizes results of epidemiological studies on Se supplementation in relation to brain diseases, including PREADViSE, EVA, and AIBL. Although mainly positive effects of Se are assessed in this review, possible detrimental effects of Se supplementation or exposure, including potential neurotoxicity, are also mentioned. In relation to AD, various roles of SELENOP are discussed, i.e. as the means of Se delivery to neurons, as an antioxidant, in cytoskeleton assembly, in interaction with redox-active metals (copper, iron, and mercury) and with misfolded proteins (amyloid-beta and hyperphosphorylated tau-protein).

Accumulation Patterns of Sub-chronic Aluminum Toxicity Model After Gastrointestinal Administration in Rats

Although aluminum chronic neurotoxicity is well documented, there are no well-established experimental protocols of Al exposure. In the current study, toxic effects of sub-chronic Al exposure have been evaluated in outbreed male rats (gastrointestinal administration). Forty animals were used: 10 were administered with AlCl₃ water solution (2 mg/kg Al per day) for 1 month, 10 received the same concentration of AlCl₃ for 3 month, and 20 (10 per observation period) saline as control. After 30 and 90 days, the animals underwent behavioral tests: open field, passive avoidance, extrapolation escape task, and grip strength. At the end of the study, the blood, liver, kidney, and brain were excised for analytical and morphological studies. The Al content was measured by inductively coupled plasma mass-spectrometry. Essential trace elements-Co, Cr, Cu, Fe, Mg, Mn, Mo, Se, and Zn-were measured in whole blood samples. Although no morphological changes were observed in the brain, liver, or kidney for both exposure terms, dose-dependent Al accumulation and behavioral differences (increased locomotor activity after 30 days) between treatment and control groups were indicated. Moreover, for 30 days exposure, strong positive correlation between Al content in the brain and blood for individual animals was established, which surprisingly disappeared by the third month. This may indicate neural barrier adaptation to the Al exposure or the saturation of Al transport into the brain. Notably, we could not see a clear neurodegeneration process after rather prolonged sub-chronic Al exposure, so probably longer exposure periods are required.

Species fractionation in a case-control study concerning Parkinson's disease: Cu-amino acids discriminate CSF of PD from controls

BACKGROUND

Parkinson's disease is affecting about 1% of the population above 65 years. Improvements in medicine support prolonged lifetime which increases the total concentration of humans affected by the disease. It is suggested that occupational and environmental exposure to metals like iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn) can influence the risk for Parkinson's disease. These metals play a key role as cofactors in many enzymes and proteins.

METHODS

In this case-control study, we investigated the Mn-, Fe-, Cu- and Zn-species in cerebrospinal fluid (CSF) by size-exclusion chromatography hyphenated to inductively coupled plasma mass spectrometry (SEC-ICP-MS) and the total concentration of these metals by inductively coupled plasma sector field mass spectrometry (ICP-sf-MS).

RESULTS

The investigation of total metal concentration and speciation provided only minor changes, but it produced strong significance for a number of ratios. The analysis revealed a strong change in the ratio between total concentration of Fe and the amino acid-fraction of Cu. This could be observed when analyzing both the respective element concentrations of the fraction (which also depends on individual variation of the total element concentration) as well as when being expressed as percentage of total concentration (normalization) which more clearly shows changes of distribution pattern independent of individual variation of total element concentrations.

CONCLUSION

Speciation analysis, therefore, is a powerful technique to investigate changes in a case-control study where ratios of different species play an important role.

Intake of arsenic and mercury from fish and seafood in a Northern Italy community

Regular consumption of fish is generally recommended by authorities because fish is an important source of essential nutrients. However, the presence of potentially toxic contaminants in fish has raised many concerns about the food's safety for human health. In the present study, we used a validated semi-quantitative food frequency questionnaire to assess the dietary habits of a representative sample of 719 individuals (319 males and 400 females) aged 18-87 years residing in Northern Italy. We estimated weekly dietary intakes of Arsenic (As) and Mercury (Hg), and we compared them with safety standards set by the European Food Safety Authority. In this population, fish was the main contributor to As and Hg intake. The highest levels of As were in sardine, sole/flounder and cephalopods, and of Hg in the biggest, predatory fish. About the other foods, cereals were the second contributor to the intake of these elements, especially rice for As and bread for Hg, and high levels of As and Hg were also found in mushrooms, coffee and wine. Average weekly intake of both contaminants was below recommended safety limits.