Selenium Concentration in Cerebrospinal Fluid Samples from a Paediatric Population

Blood-cerebrospinal fluid barrier permeability of metals/metalloids and its determinants in pediatric patients

Concerns regarding adverse effects of metal/metalloids exposure on brain development and neurological disorders among children are increasing. However, the transport patterns of metals/metalloids across the blood-cerebrospinal fluid barrier (BCSFB) need to be clarified in children. A total of 99 Chinese pediatric patients were enrolled from February 2020 to August 2021, with a median age of 6.76 months. We detected 16 metal/metalloid levels in matched serum and cerebrospinal fluid (CSF) samples using inductively coupled plasma mass spectrometry. The BCSFB permeability of metals/metalloids were estimated and the potential effects of biomedical parameters were explored. Most metals/metalloids were detectable among > 80.0% of CSF samples. Significant correlations were observed between strontium (Sr, r = 0.46), molybdenum (Mo, r = 0.50), and cadmium (Cd, r = 0.24) concentrations in serum and CSF (P < 0.05). Ratios of metal/metalloid levels in CSF to serum (Rmetal) ranged from 0.02 to 0.74, and hazardous metals/metalloids including arsenic (As), Cd, lead (Pb), thallium (Tl), and manganese (Mn) showed high transfer efficiencies across the BCSFB (Rmetals > 0.5). With the adjustment of age and sex, albumin, β2-microglobulin, and total protein levels in CSF were positively associated with copper (Cu) permeability (FDR-adjusted P < 0.05), while glucose in CSF was negatively correlated with calcium (Ca), Cu, Sr, and Mo BCSFB permeability (FDR-adjusted P < 0.05). Q-Alb promoted Cu permeability across the BCSFB (FDR-adjusted P < 0.001), while C-reactive protein levels in serum were positively associated with selenium (Se) permeability (FDR-adjusted P = 0.046). For the first time, our findings provided data for the BCSFB permeability of 16 metals/metalloids in children, and indicated that some biomedical parameters could influence the transformation of metals/metalloids from serum to CSF. Metals/metalloids with strong BCSFB permeability warrant attention for their potential neurotoxicity.

Review: Advances in the Accuracy and Traceability of Metalloprotein Measurements Using Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

Advances in inductively coupled plasma mass spectrometry and the methods used to prepare isotopically enriched standards, allow for the high accuracy measurement of metalloproteins by isotope dilution mass spectrometry. This technique has now reached a level of maturity whereby a step change in the accuracy, precision, and traceability of, in particular, clinical, and biomedical measurements is achievable. Current clinical measurements, which require low limits of detection in the presence of complex sample matrices, use indirect methods based on immunochemistry for the study of human disease. However, this approach suffers from poor traceability, requiring comparisons based on provision of matrix-based reference materials, used as analytical standards. This leads to difficulty when changes in the reference material are required, often resulting in a lack of interlaboratory and temporal comparability in clinical results and reference ranges. In this review, we focus on the most important metalloproteins for clinical studies, to illustrate how the attributes of chromatography coupled to inorganic mass spectrometry can be used for the direct measurement of metalloproteins such as hemoglobin, transferrin, and ceruloplasmin. By using this approach, we hope to demonstrate how isotope dilution analysis can be used as a reference method to improve traceability and underpin clinical, biomedical, and other biological measurements.

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.

Selenium at the eural arriers: eview

Selenium (Se) is known to contribute to several vital physiological functions in mammals: antioxidant defense, fertility, thyroid hormone metabolism, and immune response. Growing evidence indicates the crucial role of Se and Se-containing selenoproteins in the brain and brain function. As for the other essential trace elements, dietary Se needs to reach effective concentrations in the central nervous system (CNS) to exert its functions. To do so, Se-species have to cross the blood-brain barrier (BBB) and/or blood-cerebrospinal fluid barrier (BCB) of the choroid plexus. The main interface between the general circulation of the body and the CNS is the BBB. Endothelial cells of brain capillaries forming the so-called tight junctions are the primary anatomic units of the BBB, mainly responsible for barrier function. The current review focuses on Se transport to the brain, primarily including selenoprotein P/low-density lipoprotein receptor-related protein 8 (LRP8, also known as apolipoprotein E receptor-2) dependent pathway, and supplementary transport routes of Se into the brain via low molecular weight Se-species. Additionally, the potential role of Se and selenoproteins in the BBB, BCB, and neurovascular unit (NVU) is discussed. Finally, the perspectives regarding investigating the role of Se and selenoproteins in the gut-brain axis are outlined.

The Use of Trace and Essential Elements in Common Clinical Disorders: Roles in Assessment of Health and Oxidative Stress Status

During the early life, the diet of infants is mainly dominated by milk. Milk is a natural food rich in trace elements focus on essential elements. These elements are very necessary for human metabolism and since they cannot be synthesized by the body, the only source available for the humans to obtain them is by ingestion of natural food. This mini-review aims at updating the knowledge on trace elements, outlining their natural food sources, and their possible implications in common clinical disorders in early and adult life. However, it was found that consumption of food with micronutrients and trace elements may release intracellular compounds and offer oxidative protection or exacerbate oxidative damage to metabolically compromised cells.

Manganese and selenium concentrations in cerebrospinal fluid of seriously ill children

BACKGROUND

The homeostasis of essential trace elements such as selenium and manganese may be altered in patients with severe diseases of various etiologies (trauma brain injuries, tumors, leukemias, lymphomas, neurological diseases).

METHODS

Concentration of manganese and selenium were determined in cerebrospinal fluid by electrothermal atomic absorption spectrometry in 50 hospitalized children with various clinical ethiologies including oncological, neurological, and brain related diseases.

RESULTS

The concentrations of manganese in cerebrospinal fluid of children were 0.97±0.67 μg/L. The concentrations of selenium were 13.3±3.5 μg/L. The concentrations were similar as published in adults. The values did not correlated with the age, gender and severity of the disease.

CONCLUSION

We evaluated values of selenium and manganese in cerebrospinal fluid of seriously diseased children.

Selenium speciation in paired serum and cerebrospinal fluid samples of sheep

This study was performed to characterise selenium (Se) and Se species in cerebrospinal fluid (CSF) of sheep and its relation to the respective Se concentrations in serum. Paired samples from 10 adult sheep were used for the study. Five sheep were fed a diet with a marginal Se concentration of <0.05mg Se/kg diet dry weight (dw, Se(-)), and five animals were fed the same diet supplemented with sodium selenite revealing a concentration of 0.2mg Se/kg diet dw (Se(+)). The feeding strategy was conducted for two years; The results on metabolic effects were published previously. At the end of the feeding period, paired samples of serum and CSF were collected and analysed using ion exchange chromatography inductively coupled plasma-dynamic reaction cell-mass spectrometry (IEC-ICP-DRC-MS) technique for total Se concentration and concentrations of Se species. Albumin concentrations were analysed additionally. The feeding strategy caused significant differences (p<0.01) in serum Se concentrations with 33.1±5.11μg Se/l in the Se(-) group and 96.5±18.3μg Se/l in the Se(+) group, respectively. The corresponding total Se concentrations in CSF were 4.38±1.02μg Se/l and 6.13±1.64μg Se/l in the Se(-) and the Se(+) group, respectively, missing statistical significance (p=0.077). IEC-ICP-DRC-MS technique was able to differentiate the Se species selenoprotein P-bound Se (SePP), selenomethionine, glutathione peroxidase-bound Se (Se-GPx), selenocystine, thioredoxin reductase-bound Se, ovine serum albumin-bound Se (Se-OSA), SeIV and SeVI in ovine serum and CSF. Quantitatively, SePP is the main selenoprotein in ovine serum followed by Se-GPx. The CSF/blood ratio of albumin (QAlbumin) reflected a physiological function of the blood-CSF barrier in all sheep. QSe-species were higher than QAlbumin both feeding groups, supporting the hypothesis of local production of Se species in the brain. Significant positive regression lines for CSF vs. serum were found for albumin and Se-OSA only, suggesting a role of albumin to convey Se across the blood-CSF barrier. The ovine model, together with the IEC-ICP-DRC-MS technique to characterise the Se species, might be a worthwhile model for further studies as repeated sample collection as well as modification of the nutritional status is feasible and effective.

Importance of selenium and selenoprotein for brain function: From antioxidant protection to neuronal signalling

Multiple biological functions of selenium manifest themselves mainly via 25 selenoproteins that have selenocysteine at their active centre. Selenium is vital for the brain and seems to participate in the pathology of disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and epilepsy. Since selenium was shown to be involved in diverse functions of the central nervous system, such as motor performance, coordination, memory and cognition, a possible role of selenium and selenoproteins in brain signalling pathways may be assumed. The aim of the present review is to analyse possible relations between selenium and neurotransmission. Selenoproteins seem to be of special importance in the development and functioning of GABAergic (GABA, γ-aminobutyric acid) parvalbumin positive interneurons of the cerebral cortex and hippocampus. Dopamine pathway might be also selenium dependent as selenium shows neuroprotection in the nigrostriatal pathway and also exerts toxicity towards dopaminergic neurons under higher concentrations. Recent findings also point to acetylcholine neurotransmission involvement. The role of selenium and selenoproteins in neurotransmission might not only be limited to their antioxidant properties but also to inflammation, influencing protein phosphorylation and ion channels, alteration of calcium homeostasis and brain cholesterol metabolism. Moreover, a direct signalling function was proposed for selenoprotein P through interaction with post-synaptic apoliprotein E receptors 2 (ApoER2).

Biochemical parameters to assess choroid plexus dysfunction in Kearns-Sayre syndrome patients

Our aim was to assess biochemical parameters to detect choroid plexus dysfunction in Kearns-Sayre syndrome (KSS) patients. We studied CSF from 7 patients with KSS including total proteins, 5-methyltetrahydrofolate, homovanillic acid (HVA) and Selenium (Se) concentrations. High Se values, increased HVA and total protein concentrations and decreased 5-MTHF values were observed in all cases. This pattern seems very specific to KSS since it was only detected in 7 patients out of 1850 CSF samples analysed, and may represent a good biochemical model for evaluating choroid plexus dysfunction. The accumulated Se in CSF might have deleterious consequences such as toxicity effects.