Homozygous mutation in TXNRD1 is associated with genetic generalized epilepsy

New horizons for the role of selenium on cognitive function: advances and challenges

Cognitive deficits associated with oxidative stress and the dysfunction of the central nervous system are present in some neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. Selenium (Se), an essential microelement, exhibits cognition-associated functions through selenoproteins mainly owing to its antioxidant property. Due to the disproportionate distribution of Se in the soil, the amount of Se varies greatly in various foods, resulting in a large proportion of people with Se deficiency worldwide. Numerous cell and animal experiments demonstrate Se deficiency-induced cognitive deficits and Se supplementation-improved cognitive performances. However, human studies yield inconsistent results and the mechanism of Se in cognition still remains elusive, which hinder the further exploration of Se in human cognition. To address the urgent issue, the review summarizes Se-contained foods (plant-based foods, animal-based foods, and Se supplements), brain selenoproteins, mechanisms of Se in cognition (improvement of synaptic plasticity, regulation of Zn2+ level, inhibition of ferroptosis, modulation of autophagy and de novo synthesis of L-serine), and effects of Se on cognitive deficits, as well as consequently sheds light on great potentials of Se in the prevention and treatment of cognitive deficits.

Whole-Exome sequencing identifies GYS2 biallelic variants in individuals with suspected epilepsy

BACKGROUND

Adequate glucose supply is essential for brain function, therefore hypoglycemic states may lead to seizures. Since blood glucose supply for brain is buffered by liver glycogen, an impairment of liver glycogen synthesis by mutations in the liver glycogen synthase gene (GYS2) might result in a substantial neurological involvement. Here, we describe the phenotypes of affected siblings of two families harboring biallelic mutations in GYS2.

METHODS

Two suspected families - a multiplex Pakistani family (family A) with three affected siblings and a family of Moroccan origin (family B) with a single affected child who presented with seizures and reduced fasting blood glucose levels were genetically characterized. Whole exome sequencing (WES) was performed on the index patients, followed by Sanger sequencing-based segregation analyses on all available members of both families.

RESULTS

The variant prioritization of WES and later Sanger sequencing confirmed three mutations in the GYS2 gene (12p12.1) consistent with an autosomal recessive pattern of inheritance. A homozygous splice acceptor site variant (NM_021957.3, c. 1646 -2A>G) segregated in family A. Two novel compound heterozygous variants (NM_021957.3: c.343G>A; p.Val115Met and NM_021957.3: c.875A>T; p.Glu292Val) were detected in family B, suggesting glycogen storage disorder. A special diet designed to avoid hypoglycemia, in addition to change of the anti-seizure medication led to reduction in seizure frequency.

CONCLUSIONS

This study suggests that the seizures in patients initially diagnosed with epilepsy might be directly caused, or influenced by hypoglycemia due to pathogenic variants in the GYS2 gene.

Identification of hub genes and key signaling pathways by weighted gene co-expression network analysis for human aortic stenosis and insufficiency

Background

Human aortic valve stenosis (AS) and insufficiency (AI) are common diseases in aging population. Identifying the molecular regulatory networks of AS and AI is expected to offer novel perspectives for AS and AI treatment.

Methods

Highly correlated modules with the progression of AS and AI were identified by weighted genes co-expression network analysis (WGCNA). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed by the clusterProfiler program package. Differentially expressed genes (DEGs) were identified by the DESeqDataSetFromMatrix function of the DESeq2 program package. The protein-protein interaction (PPI) network analyses were implemented using the STRING online tool and visualized with Cytoscape software. The DEGs in AS and AI groups were overlapped with the top 30 genes with highest connectivity to screen out ten hub genes. The ten hub genes were verified by analyzing the data in high throughput RNA-sequencing dataset and real-time PCR assay using AS and AI aortic valve samples.

Results

By WGCNA algorithm, 302 highly correlated genes with the degree of AS, degree of AI, and heart failure were identified from highly correlated modules. GO analyses showed that highly correlated genes had close relationship with collagen fibril organization, extracellular matrix organization and extracellular structure organization. KEGG analyses also manifested that protein digestion and absorption, and glutathione metabolism were probably involved in AS and AI pathological courses. Moreover, DEGs were picked out for 302 highly correlated genes in AS and AI groups relative to the normal control group. The PPI network analyses indicated the connectivity among these highly correlated genes. Finally, ten hub genes (CD74, COL1A1, TXNRD1, CCND1, COL5A1, SERPINH1, BCL6, ITGA10, FOS, and JUNB) in AS and AI were found out and verified.

Conclusion

Our study may provide the underlying molecular targets for the mechanism research, diagnosis, and treatment of AS and AI in the future.

Selenium and Selenoproteins in Health

Selenium is a trace mineral that is essential for health. After being obtained from food and taken up by the liver, selenium performs various physiological functions in the body in the form of selenoproteins, which are best known for their redox activity and anti-inflammatory properties. Selenium stimulates the activation of immune cells and is important for the activation of the immune system. Selenium is also essential for the maintenance of brain function. Selenium supplements can regulate lipid metabolism, cell apoptosis, and autophagy, and have displayed significant alleviating effects in most cardiovascular diseases. However, the effect of increased selenium intake on the risk of cancer remains unclear. Elevated serum selenium levels are associated with an increased risk of type 2 diabetes, and this relationship is complex and nonlinear. Selenium supplementation seems beneficial to some extent; however, existing studies have not fully explained the influence of selenium on various diseases. Further, more intervention trials are needed to verify the beneficial or harmful effects of selenium supplementation in various diseases.

Cerebral Malaria Model Applying Human Brain Organoids

Neural injuries in cerebral malaria patients are a significant cause of morbidity and mortality. Nevertheless, a comprehensive research approach to study this issue is lacking, so herein we propose an in vitro system to study human cerebral malaria using cellular approaches. Our first goal was to establish a cellular system to identify the molecular alterations in human brain vasculature cells that resemble the blood-brain barrier (BBB) in cerebral malaria (CM). Through transcriptomic analysis, we characterized specific gene expression profiles in human brain microvascular endothelial cells (HBMEC) activated by the Plasmodium falciparum parasites. We also suggest potential new genes related to parasitic activation. Then, we studied its impact at brain level after Plasmodium falciparum endothelial activation to gain a deeper understanding of the physiological mechanisms underlying CM. For that, the impact of HBMEC-P. falciparum-activated secretomes was evaluated in human brain organoids. Our results support the reliability of in vitro cellular models developed to mimic CM in several aspects. These systems can be of extreme importance to investigate the factors (parasitological and host) influencing CM, contributing to a molecular understanding of pathogenesis, brain injury, and dysfunction.

Advances in the Functions of Thioredoxin System in Central Nervous System Diseases

Significance: The thioredoxin system comprises thioredoxin (Trx), thioredoxin reductase (TrxR), and nicotinamide adenine dinucleotide phosphate, besides an endogenous Trx inhibitor, the thioredoxin-interacting protein (TXNIP). The Trx system plays critical roles in maintaining the redox homeostasis in the central nervous system (CNS), in which oxidative stress damage is prone to occurrence due to its high-energy demand. Recent Advances: Increasing studies have demonstrated that the expression or activity of Trx/TrxR is usually decreased and that TXNIP expression is increased in patients with CNS diseases, including neurodegenerative diseases, cerebral ischemia, traumatic brain injury, and depression, as well as in their cellular and animal models. The compromise of Trx/TrxR enhances the susceptibility of neurons to related pathological state. Increased TXNIP not only enhances the inhibition of Trx activity, but also activates the NOD-like receptor protein 3 inflammasome, resulting in neuroinflammation in the brain. Critical Issues: In this review, we highlight the sources of oxidative stress in the CNS. The expression and function of the Trx system are summarized in different CNS diseases. This review also mentions that some inducers of Trx show neuroprotection in CNS diseases. Future Directions: Accumulating evidence has demonstrated the important roles of the Trx system in CNS diseases, suggesting that the Trx system may be a promising therapeutic target for CNS diseases. Further study should aim to develop the most effective inducers of Trx and specific inhibitors of TXNIP and to apply them in the clinical trials for the treatment of CNS diseases. Antioxid. Redox Signal. 38, 425-441.

Oxidative stress: a common imbalance in diabetes and epilepsy

The brain requires a large amount of energy. Its function can be altered when energy demand exceeds supply or during metabolic disturbances such as diabetes mellitus. Diabetes, a chronic disease with a high incidence worldwide, is characterized by high glucose levels (hyperglycemia); however, hypoglycemic states may also occur due to insulin treatment or poor control of the disease. These alterations in glucose levels affect the brain and could cause epileptic seizures and status epilepticus. In addition, it is known that oxidative stress states emerge as diabetes progresses, contributing to the development of diseases secondary to diabetes, including retinopathy, nephropathy, cardiovascular alterations, and alterations in the central nervous system, such as epileptic seizures. Seizures are a complex of transient signs and symptoms resulting from abnormal, simultaneous, and excessive activity of a population of neurons, and they can be both a cause and a consequence of oxidative stress. This review aims to outline studies linking diabetes mellitus and seizures to oxidative stress, a condition that may be relevant to the development of severe seizures in diabetes mellitus patients.

Seizures, ataxia and parvalbumin-expressing interneurons respond to selenium supply in Selenop-deficient mice

Mice with constitutive disruption of the Selenop gene have been key to delineate the importance of selenoproteins in neurobiology. However, the phenotype of this mouse model is exquisitely dependent on selenium supply and timing of selenium supplementation. Combining biochemical, histological, and behavioral methods, we tested the hypothesis that parvalbumin-expressing interneurons in the primary somatosensory cortex and hippocampus depend on dietary selenium availability in Selenop-/- mice. Selenop-deficient mice kept on adequate selenium diet (0.15 mg/kg, i.e. the recommended dietary allowance, RDA) developed ataxia, tremor, and hyperexcitability between the age of 4-5 weeks. Video-electroencephalography demonstrated epileptic seizures in Selenop-/- mice fed the RDA diet, while Selenop± heterozygous mice behaved normally. Both neurological phenotypes, hyperexcitability/seizures and ataxia/dystonia were successfully prevented by selenium supplementation from birth or transgenic expression of human SELENOP under a hepatocyte-specific promoter. Selenium supplementation with 10 μM selenite in the drinking water on top of the RDA diet increased the activity of glutathione peroxidase in the brains of Selenop-/- mice to control levels. The effects of selenium supplementation on the neurological phenotypes were dose- and time-dependent. Selenium supplementation after weaning was apparently too late to prevent ataxia/dystonia, while selenium withdrawal from rescued Selenop-/- mice eventually resulted in ataxia. We conclude that SELENOP expression is essential for preserving interneuron survival under limiting Se supply, while SELENOP appears dispensable under sufficiently high Se status.

Selenoproteins in brain development and function

Expression of selenoproteins is widespread in neurons of the central nervous system. There is continuous evidence presented over decades that low levels of selenium or selenoproteins are linked to seizures and epilepsy indicating a failure of the inhibitory system. Many developmental processes in the brain depend on the thyroid hormone T3. T3 levels can be locally increased by the action of iodothyronine deiodinases on the prohormone T4. Since deiodinases are selenoproteins, it is expected that selenoprotein deficiency may affect development of the central nervous system. Studies in genetically modified mice or clinical observations of patients with rare diseases point to a role of selenoproteins in brain development and degeneration. In particular selenoprotein P is central to brain function by virtue of its selenium transport function into and within the brain. We summarize which selenoproteins are essential for the brain, which processes depend on selenoproteins, and what is known about genetic deficiencies of selenoproteins in humans. This review is not intended to cover the potential influence of selenium or selenoproteins on major neurodegenerative disorders in human.

A novel animal model of combined generalized and focal epilepsy

Thioredoxin, encoded by Txn1, is a critical antioxidant that protects against oxidative damage by regulating the dithiol/disulfide balance of interacting proteins. We recently discovered the Adem rat, an epileptic rat harboring the Txn1-F54L mutation, characterized by wild running and vacuolar degeneration in the midbrain. This study aimed to characterize the classification of epilepsy in Adem rats. We performed simultaneous video-EEG recordings, MRI, neurotransmitter measurements using gas chromatography-mass spectrometry (GC-MS), and immunohistochemistry. Adem rats exhibited absence, tonic, and focal seizures. The type of epilepsy was classified as combined generalized and focal epilepsy. Neurotransmitters in the midbrain and cortex were measured at three weeks of age when neuronal cell death occurs in the midbrain. The results of GC-MS ruled out the dominance of the excitatory system in the midbrain and cortex of Adem rats. Activation of astrocytes and microglia was more pronounced at five weeks of age, at which time epileptic seizures occurred frequently. The underlying pathology in Adem rats remains unknown. However, glial cell activation and inflammation may play a significant role in the occurrence of epilepsy.

Missense mutation in selenocysteine synthase causes cardio-respiratory failure and perinatal death in mice which can be compensated by selenium-independent GPX4

Selenoproteins are a small family of proteins containing the trace element selenium in form of the rare amino acid selenocysteine (Sec), which is decoded by the UGA codon. In humans, a number of pathogenic variants in genes encoding distinct selenoproteins or selenoprotein biosynthesis factors have been identified. Pathogenic variants in selenocysteine synthase (SEPSECS), which catalyzes the last step in Sec-tRNA[Ser]Sec biosynthesis, were reported in children suffering from progressive cerebello-cerebral atrophy. To understand the pathomechanism associated with SEPSECS deficiency, we generated a novel mouse model recapitulating the respective human pathogenic p.Y334C variant in the murine Sepsecs gene (SepsecsY334C). Unlike in patients, pups homozygous for the p.Y334C variant died perinatally with signs of cardio-respiratory failure. Perinatal death is reminiscent of the Sedaghatian spondylometaphyseal dysplasia disorder in humans, which is caused by pathogenic variants in the gene encoding the selenoprotein and key ferroptosis regulator glutathione peroxidase 4 (GPX4). Protein expression levels of distinct selenoproteins in SepsecsY334C/Y334C mice were found to be generally reduced in brain and isolated cortical neurons, while transcriptomics analysis uncovered an upregulation of NRF2-regulated genes. Crossbreeding of SepsecsY334C/Y334C mice with mice harboring a targeted mutation of the catalytically active Sec to Cys in GPX4 rescued perinatal death of SepsecsY334C/Y334C mice, showing that the cardio-respiratory defects of SepsecsY334C/Y334C mice were caused by the lack of GPX4. Like in SepsecsY334C/Y334C mice, selenoprotein expression levels remained low and NRF2-regulated genes remained highly expressed in these compound mutant mice, indicating that selenium-independent GPX4, along with a sustained antioxidant response are sufficient to compensate for dysfunctional Sec-tRNA[Ser]Sec biosynthesis. Our findings imply that children with pathogenic variants in SEPSECS or GPX4 may even benefit from treatments that incompletely compensate for impaired GPX4 activity.

Pathogenic Variants in Selenoproteins and Selenocysteine Biosynthesis Machinery

Selenium is incorporated into selenoproteins as the 21st amino acid selenocysteine (Sec). There are 25 selenoproteins encoded in the human genome, and their synthesis requires a dedicated machinery. Most selenoproteins are oxidoreductases with important functions in human health. A number of disorders have been associated with deficiency of selenoproteins, caused by mutations in selenoprotein genes or Sec machinery genes. We discuss mutations that are known to cause disease in humans and report their allele frequencies in the general population. The occurrence of protein-truncating variants in the same genes is also presented. We provide an overview of pathogenic variants in selenoproteins genes from a population genomics perspective.

A Reliable Prognostic Model for HCC Using Histological Grades and the Expression Levels of Related Genes

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and is a leading cause of cancer-related death worldwide. This study aimed to establish a reliable prognostic model for HCC using histological grades and the expression levels of related genes. The histological grade of a tumor provides prognostic information. The expression data of HCC samples were downloaded from The Cancer Genome Atlas (TCGA) database. We employed the univariate and multivariate Cox regression analyses, as well as the least absolute shrinkage and selection operator (LASSO) regression to establish the prognostic model. After verification of the proposed model using data downloaded from the International Cancer Genome Consortium (ICGC) database, we found that the model was highly reliable, and it was revealed that the prognosis in the high-risk group was significantly worse than that in the low-risk group. Next, we explored the correlation of RiskScore with patients' clinicopathological characteristics, and we found that the RiskScore could be used as an independent prognostic factor, which further confirmed the reliability of our model. In summary, the proposed model could accurately predict the prognosis of HCC patients, assisting clinicians to study the roles of different histological grades of HCC.

Production and purification of homogenous recombinant human selenoproteins reveals a unique codon skipping event in E. coli and GPX4-specific affinity to bromosulfophthalein

Selenoproteins are translated via animal domain-specific elongation machineries that redefine dedicated UGA opal codons from termination of translation to selenocysteine (Sec) insertion, utilizing specific tRNA species and Sec-specific elongation factors. This has made recombinant production of mammalian selenoproteins in E. coli technically challenging but recently we developed a methodology that enables such production, using recoding of UAG for Sec in an RF1-deficient host strain. Here we used that approach for production of the human glutathione peroxidases 1, 2 and 4 (GPX1, GPX2 and GPX4), with all these three enzymes being important antioxidant selenoproteins. Among these, GPX4 is the sole embryonically essential enzyme, and is also known to be essential for spermatogenesis as well as protection from cell death through ferroptosis. Enzyme kinetics, ICP-MS and mass spectrometry analyses of the purified recombinant proteins were used to characterize selenoprotein characteristics and their Sec contents. This revealed a unique phenomenon of one-codon skipping, resulting in a lack of a single amino acid at the position corresponding to the selenocysteine (Sec) residue, in about 30% of the recombinant GPX isoenzyme products. We furthermore confirmed the previously described UAG suppression with Lys or Gln as well as a minor suppression with Tyr, together resulting in about 20% Sec contents in the full-length proteins. No additional frameshifts or translational errors were detected. We subsequently found that Sec-containing GPX4 could be further purified over a bromosulfophthalein-column, yielding purified recombinant GPX4 with close to complete Sec contents. This production method for homogenously purified GPX4 should help to further advance the studies of this important selenoprotein.

The Neurobiology of Selenium: Looking Back and to the Future

Eighteen years ago, unexpected epileptic seizures in Selenop-knockout mice pointed to a potentially novel, possibly underestimated, and previously difficult to study role of selenium (Se) in the mammalian brain. This mouse model was the key to open the field of molecular mechanisms, i.e., to delineate the roles of selenium and individual selenoproteins in the brain, and answer specific questions like: how does Se enter the brain; which processes and which cell types are dependent on selenoproteins; and, what are the individual roles of selenoproteins in the brain? Many of these questions have been answered and much progress is being made to fill remaining gaps. Mouse and human genetics have together boosted the field tremendously, in addition to traditional biochemistry and cell biology. As always, new questions have become apparent or more pressing with solving older questions. We will briefly summarize what we know about selenoproteins in the human brain, glance over to the mouse as a useful model, and then discuss new questions and directions the field might take in the next 18 years.

Novel KCNH1 Mutations Associated with Epilepsy: Broadening the Phenotypic Spectrum of KCNH1-Associated Diseases

Here, we describe four patients suffering from a rather broad spectrum of epilepsy-related disorders, ranging from developmental and epileptic encephalopathy with intellectual disability (DEE) to genetic generalized epilepsy (GGE), which all harbor novel KCNH1 mutations. In one family, we found a weak association of a novel nonsense mutation with epilepsy, suggesting reduced penetrance, and which shows, in agreement with previous findings, that gain-of-function effects rather than haploinsufficiency are important for the pathogenicity of mutations. De novo missense variants in the pore region of the channel result in severe phenotypes presenting usually with DEE with various malformations. The potential pathogenicity of a novel KCNH1 germline mutation located outside of the critical pore domain observed in a GGE patient with a milder phenotype is supported by the fact that the very same amino acid exchange was detected as a somatic mutation in the resected brain tissue of a patient suffering from a focal cortical dysplasia type IIb. Thus, our case series broadens the phenotypic spectrum of KCNH1-associated diseases.

Circ0120816 acts as an oncogene of esophageal squamous cell carcinoma by inhibiting miR-1305 and releasing TXNRD1

BACKGROUND

Circular RNAs (circRNAs) have been discovered to participate in the carcinogenesis of multiple cancers. However, the role of circRNAs in esophageal squamous cell carcinoma (ESCC) progression is yet to be properly understood. This research aimed to investigate and understand the mechanism used by circRNAs to regulate ESCC progression.

METHODS

Bioinformatics analysis was first performed to screen dysregulated circRNAs and differentially expressed genes in ESCC. The ESCC tissue samples and adjacent normal tissue samples utilized in this study were obtained from 36 ESCC patients. All the samples were subjected to qRT-PCR analysis to identify the expression of TXNRD1, circRNAs, and miR-1305. Luciferase reporter assay, RNA immunoprecipitation assay and RNA pull-down assay were later conducted to verify the existing relationship among circ0120816, miR-1305 and TXNRD1. CCK-8, BrdU, cell adhesion, cell cycle, western blot and caspase 3 activity assays were also employed to evaluate the regulation of these three biological molecules in ESCC carcinogenesis. To evaluate the effect of circ0120816 on ESCC tumor growth and metastasis, the xenograft mice model was constructed.

RESULTS

Experimental investigations revealed that circ0120816 was the highest upregulated circRNA in ESCC tissues and that this non-coding RNA acted as a miR-1305 sponge in enhancing cell viability, cell proliferation, and cell adhesion as well as repressing cell apoptosis in ESCC cell lines. Moreover, miR-1305 was observed to exert a tumor-suppressive effect in ESCC cells by directly targeting and repressing TXNRD1. It was also noticed that TXNRD1 could regulate cyclin, cell adhesion molecule, and apoptosis-related proteins. Furthermore, silencing circ0120816 was found to repress ESCC tumor growth and metastasis in vivo.

CONCLUSIONS

This research confirmed that circ0120816 played an active role in promoting ESCC development by targeting miR-1305 and upregulating oncogene TXNRD1.

Metabolism-based drug discovery in zebrafish: An emerging strategy to uncover new anti-seizure therapies

As one of the most common neurological disorders, epilepsy can occur throughout the lifespan and from a multiplicity of causes, including genetic mutations, inflammation, neurotrauma, or brain malformations. Although pharmacological agents are the mainstay of treatment for seizure control, an unyielding 30-40% of patients remain refractory to these medications and continue to experience spontaneous recurrent seizures with attendant life-long cognitive, behavioural, and mental health issues, as well as an increased risk for sudden unexpected death. Despite over eight decades of antiseizure drug (ASD) discovery and the approval of dozens of new medications, the percentage of this refractory population remains virtually unchanged, suggesting that drugs with new and unexpected mechanisms of action are needed. In this brief review, we discuss the need for new animal models of epilepsy, with a particular focus on the advantages and disadvantages of zebrafish. We also outline the evidence that epilepsy is characterized by derangements in mitochondrial function and introduce the rationale and promise of bioenergetics as a functional readout assay to uncover novel ASDs. We also consider limitations of a zebrafish metabolism-based drug screening approach. Our goal is to discuss the opportunities and challenges of further development of mitochondrial screening strategies for the development of novel ASDs. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Functional Nutrients for Epilepsy

Epilepsy is a common neurological disorder of which seizures are a core symptom. Approximately one third of epileptic patients are resistant to antiepileptic drugs and therefore require alternative therapeutic options. Dietary and nutritional supplements can in some cases replace drugs, but with the exception of ketogenic diets, there are no officially recommended dietary considerations for patients with epilepsy. In this review we summarize a selection of nutritional suggestions that have proved beneficial in treating different types of epilepsy. We describe the types of seizures and epilepsy and follow this with an introduction to basic molecular mechanisms. We then examine several functional nutrients for which there is clinical evidence of therapeutic efficacy in reducing seizures or epilepsy-associated sudden death. We also discuss experimental results that demonstrate possible molecular mechanisms elicited by the administration of various nutrients. The availability of multiple dietary and nutritional candidates that show favorable outcomes in animals implies that assessing the clinical potential of these substances will improve translational medicine, ultimately benefitting epilepsy patients.

Cell-Type Specific Analysis of Selenium-Related Genes in Brain

Selenoproteins are a unique class of proteins that play key roles in redox signaling in the brain. This unique organ is comprised of a wide variety of cell types that includes excitatory neurons, inhibitory neurons, astrocytes, microglia, and oligodendrocytes. Whereas selenoproteins are known to be required for neural development and function, the cell-type specific expression of selenoproteins and selenium-related machinery has yet to be systematically investigated. Due to advances in sequencing technology and investment from the National Institutes of Health (NIH)-sponsored BRAIN initiative, RNA sequencing (RNAseq) data from thousands of cortical neurons can now be freely accessed and searched using the online RNAseq data navigator at the Allen Brain Atlas. Hence, we utilized this newly developed tool to perform a comprehensive analysis of the cell-type specific expression of selenium-related genes in brain. Select proteins of interest were further verified by means of multi-label immunofluorescent labeling of mouse brain sections. Of potential significance to neural selenium homeostasis, we report co-expression of selenoprotein P (SELENOP) and selenium binding protein 1 (SELENBP1) within astrocytes. These findings raise the intriguing possibility that SELENBP1 may negatively regulate astrocytic SELENOP synthesis and thereby limit downstream Se supply to neurons.

Prioritized brain selenium retention and selenoprotein expression: Nutritional insights into Parkinson's disease

Selenium (Se), an essential trace mineral, confers its physiological functions mainly through selenoproteins, most of which are oxidoreductases. Results from animal, epidemiological, and human genetic studies link Parkinson's disease to Se and certain selenoproteins. Parkinson's disease is characterized by multiple motor and non-motor symptoms that are difficult to diagnose at early stages of the pathogenesis. While irreversible, degenerative and age-related, the onset of Parkinson's disease may be delayed through proper dietary and environmental controls. One particular attribute of Se biology is that brain has the highest priority to receive and retain this nutrient even in Se deficiency. Thus, brain Se deficiency is rare; however, a strong body of recent evidence implicates selenoprotein dysfunction in Parkinson's disease. Direct and indirect evidence from mouse models implicate selenoprotein T, glutathione peroxidase 1, selenoprotein P and glutathione peroxidase 4 in counteracting Parkinson's disease through Se transportation to the brain and reduced oxidative stress. It is of future interest to further characterize the full selenoproteomes in various types of brain cells and elucidate the mechanism of their actions in Parkinson's disease.

Oxidative stress and inflammation in a spectrum of epileptogenic cortical malformations: molecular insights into their interdependence

Oxidative stress (OS) occurs in brains of patients with epilepsy and coincides with brain inflammation, and both phenomena contribute to seizure generation in animal models. We investigated whether expression of OS and brain inflammation markers co-occurred also in resected brain tissue of patients with epileptogenic cortical malformations: hemimegalencephaly (HME), focal cortical dysplasia (FCD) and cortical tubers in tuberous sclerosis complex (TSC). Moreover, we studied molecular mechanisms linking OS and inflammation in an in vitro model of neuronal function. Untangling interdependency and underlying molecular mechanisms might pose new therapeutic strategies for treating patients with drug-resistant epilepsy of different etiologies. Immunohistochemistry was performed for specific OS markers xCT and iNOS and brain inflammation markers TLR4, COX-2 and NF-κB in cortical tissue derived from patients with HME, FCD IIa, IIb and TSC. Additionally, we studied gene expression of these markers using the human neuronal cell line SH-SY5Y in which OS was induced using H₂ O₂ . OS markers were higher in dysmorphic neurons and balloon/giant cells in cortex of patients with FCD IIb or TSC. Expression of OS markers was positively correlated to expression of brain inflammation markers. In vitro, 100 µM, but not 50 µM, of H₂ O₂ increased expression of TLR4, IL-1β and COX-2. We found that NF-κB signaling was activated only upon stimulation with 100 µM H₂ O₂ leading to upregulation of TLR4 signaling and IL-1β. The NF-κB inhibitor TPCA-1 completely reversed this effect. Our results show that OS positively correlates with neuroinflammation and is particularly evident in brain tissue of patients with FCD IIb and TSC. In vitro, NF-κB is involved in the switch to an inflammatory state after OS. We propose that the extent of OS can predict the neuroinflammatory state of the brain. Additionally, antioxidant treatments may prevent the switch to inflammation in neurons thus targeting multiple epileptogenic processes at once.

Selenium and GPX4, a vital symbiosis

Selenium has transitioned from an environmental poison and carcinogen to an essential micronutrient associated with a broad array of health promoting effects. These beneficial effects are now accepted to be linked to its incorporation into selenoproteins, a family of rare proteins utilizing a specialized translation machinery to integrate selenium in the form of selenocysteine. Despite this recognized role, much less is known regarding the actual role of selenium in these proteins. Here, we will provide the reader with an overview of the essential role of specific selenoproteins and their link to pathology based on mouse studies and relevant mutations discovered in humans. Additionally, we will cover recent insights linking a non-interchangeable role for selenium in glutathione peroxidase 4 and its function in suppressing ferroptosis. This critical dependency ultimately generates a strong reliance on metabolic pathways that regulate selenium metabolism and its incorporation into proteins, such as the mevalonate pathway.

Consequences of mutations and inborn errors of selenoprotein biosynthesis and functions

In its 200 years of history, selenium has been defined first as a toxic element and finally as a micronutrient. Selenium is incorporated into selenoproteins as selenocysteine (Sec), the 21st proteinogenic amino acid codified by a stop codon. Specific biosynthetic factors recode UGA stop codon as Sec. The significance of selenoproteins in human health is manifested through the identification of patients with inborn errors in selenoproteins or their biosynthetic factors. Selenoprotein N-related myopathy was the first disease identified due to mutations in a selenoprotein gene. Mutations in GPX4 were linked to Sedaghatian disease, characterized by bone and brain anomalies and cardiorespiratory failure. Mutations in TXNRD2 produced familial glucocorticoid deficiency (FGD) and dilated cardiomyopathy (DCM). Genetic generalized epilepsy was associated with mutations in TXNRD1 gene. Mutations in biosynthetic factors as SEPSECS, SECISBP2 and even tRNA^[Ser]Sec, have been also related to diseases. Thus, SEPSECS mutations produce a neurodegenerative disease called now pontocerebellar hypoplasia type 2D (PCH2D). SECISBP2 syndrome, caused by SECISBP2 mutations, is a multifactorial disease affecting mainly thyroid metabolism, bone, inner ear and muscle. Similar symptoms were reproduced in a patient carrying a mutation in tRNA^[Ser]Sec gene, TRU-TCA1-1. This review describes human genetic disorders caused by selenoprotein deficiency. Human phenotypes will be compared with mouse models to explain the pathologic mechanisms of lack of selenoproteins.

A Metabolic Paradigm for Epilepsy

There is a resurgence of interest in the role of metabolism in epilepsy. Long considered ancillary and acknowledged only in the context of clinical application of ketogenic diets, metabolic control of epilepsy is gaining momentum and mainstream interest among researchers. A metabolic paradigm for epilepsy rests upon known perturbations in three major interconnected metabolic nodes and therapeutic targets therefrom (i.e., glycolysis, mitochondria, and redox balance).

Synthesis of varisized chitosan-selenium nanocomposites through heating treatment and evaluation of their antioxidant properties

Varisized chitosan-selenium (CS-Se) nanocomposites were synthesized through an innovative method. It is the first time to use CS both as reductant and stabilizer to synthesize selenium nanoparticles (SeNPs). By manipulating the temperature, the well-dispersed CS-Se nanocomposites were synthesized via a simple one pot reaction with the size ranging from 83 to 208nm before being characterized by TEM, DLS, UV-vis, FTIR, XRD and TG analyses. The results showed that SeO₃^2- was reduced to a stable SeNPs colloid at a comparatively high temperature, the amino group and hydroxyl group of CS were conjugated to the surface of SeNPs. Besides, the antioxidant activities of CS-Se nanocomposites were investigated by DPPH, ABTS⁺, hydroxyl radical, metal ion chelating and reducing power assays, which proved to be concentration-dependent, size-dependent and exhibited good antioxidant activities. The results suggested that CS-Se nanocomposites might be considered as a more appropriate selenium-adding form to achieve antioxidative goals in food.

The A to Z of modulated cell patterning by mammalian thioredoxin reductases

Mammalian thioredoxin reductases (TrxRs) are selenocysteine-containing proteins (selenoproteins) that propel a large number of functions through reduction of several substrates including the active site disulfide of thioredoxins (Trxs). Well-known enzymatic systems that in turn are supported by Trxs and TrxRs include deoxyribonucleotide synthesis through ribonucleotide reductase, antioxidant defense through peroxiredoxins and methionine sulfoxide reductases, and redox modulation of a number of transcription factors. Although these functions may be essential for cells due to crucial roles in maintenance of cell viability and proliferation, findings during the last decade reveal that mammals have major redundancy in their cellular reductive systems. The synthesis of glutathione (GSH) and reductive functions of GSH-dependent pathways typically act in parallel with Trx-dependent pathways, with only one of these systems often being sufficient to support viability. Importantly, this does not imply that a modulation of the Trx system will remain without consequences, even when GSH-dependent pathways remain functional. As suggested by several recent findings, the Trx system in general and the TrxRs in particular, function as key regulators of signaling pathways. In this review article we will discuss findings that collectively suggest that modulation in mammalian systems of cytosolic TrxR1 (TXNRD1) or mitochondrial TrxR2 (TXNRD2) influence cell patterning and cellular stress responses. Effects of lower activities include increased adipogenesis, insulin responsiveness, glycogen accumulation, hyperproliferation, and distorted embryonic development, while increased activities correlate with decreased proliferation and extended lifespan, as well as worse cancer prognosis. The molecular mechanisms that underlie these diverse effects, involving regulation of protein phosphorylation cascades and of key transcription factors that guide cellular differentiation pathways, will be discussed. We conclude that the selenium-dependent oxidoreductases TrxR1 and TrxR2 should be considered as key components of signaling pathways that control cell differentiation and cellular stress responses.

Metabolic Dysfunction and Oxidative Stress in Epilepsy

The epilepsies are a heterogeneous group of disorders characterized by the propensity to experience spontaneous recurrent seizures. Epilepsies can be genetic or acquired, and the underlying mechanisms of seizure initiation, seizure propagation, and comorbid conditions are incompletely understood. Metabolic changes including the production of reactive species are known to result from prolonged seizures and may also contribute to epilepsy development. In this review, we focus on the evidence that metabolic and redox disruption is both cause and consequence of epileptic seizures. Additionally, we discuss the promise of targeting redox processes as a therapeutic option in epilepsy.