Selenoprotein P regulation by the glucocorticoid receptor

Prolonged maternal exposure to glucocorticoids alters selenoprotein expression in the developing brain

Aberrant activation of the stress-response system in early life can alter neurodevelopment and cause long-term neurological changes. Activation of the hypothalamic-pituitary-adrenal axis releases glucocorticoids into the bloodstream, to help the organism adapt to the stressful stimulus. Elevated glucocorticoid levels can promote the accumulation of reactive oxygen species, and the brain is highly susceptible to oxidative stress. The essential trace element selenium is obtained through diet, is used to synthesize antioxidant selenoproteins, and can mitigate glucocorticoid-mediated oxidative damage. Glucocorticoids can impair antioxidant enzymes in the brain, and could potentially influence selenoprotein expression. We hypothesized that exposure to high levels of glucocorticoids would disrupt selenoprotein expression in the developing brain. C57 wild-type dams of recently birthed litters were fed either a moderate (0.25 ppm) or high (1 ppm) selenium diet and administered corticosterone (75 μg/ml) via drinking water during postnatal days 1 to 15, after which the brains of the offspring were collected for western blot analysis. Glutathione peroxidase 1 and 4 levels were increased by maternal corticosterone exposure within the prefrontal cortex, hippocampus, and hypothalamus of offspring. Additionally, levels of the glucocorticoid receptor were decreased in the hippocampus and selenoprotein W was elevated in the hypothalamus by corticosterone. Maternal consumption of a high selenium diet independently decreased glucocorticoid receptor levels in the hippocampus of offspring of both sexes, as well as in the prefrontal cortex of female offspring. This study demonstrates that early life exposure to excess glucocorticoid levels can alter selenoprotein levels in the developing brain.

Selenium Protects Mouse Hypothalamic Cells from Glucocorticoid-Induced Endoplasmic Reticulum Stress Vulnerability and Insulin Signaling Impairment

The use of glucocorticoid medications is known to cause metabolic side effects such as overeating, excess weight gain, and insulin resistance. The hypothalamus, a central regulator of feeding behavior and energy expenditure, is highly responsive to glucocorticoids, and it has been proposed that it plays a role in glucocorticoid-induced metabolic defects. Glucocorticoids can alter the expression and activity of antioxidant enzymes and promote the accumulation of reactive oxygen species. Recent evidence indicates that selenium can counter the effects of glucocorticoids, and selenium is critical for proper hypothalamic function. This study sought to determine whether selenium is capable of protecting hypothalamic cells from dysfunction caused by glucocorticoid exposure. We treated mHypoE-44 mouse hypothalamic cells with corticosterone to study the effects on cellular physiology and the involvement of selenium. We found that corticosterone administration rendered cells more vulnerable to endoplasmic reticulum stress and the subsequent impairment of insulin signaling. Supplementing the cell culture media with additional selenium alleviated endoplasmic reticulum stress and promoted insulin signaling. These findings implicate a protective role of selenium against chronic glucocorticoid-induced hypothalamic dysfunction.

Selenium in Bodily Homeostasis: Hypothalamus, Hormones, and Highways of Communication

The ability of the body to maintain homeostasis requires constant communication between the brain and peripheral tissues. Different organs produce signals, often in the form of hormones, which are detected by the hypothalamus. In response, the hypothalamus alters its regulation of bodily processes, which is achieved through its own pathways of hormonal communication. The generation and transmission of the molecules involved in these bi-directional axes can be affected by redox balance. The essential trace element selenium is known to influence numerous physiological processes, including energy homeostasis, through its various redox functions. Selenium must be obtained through the diet and is used to synthesize selenoproteins, a family of proteins with mainly antioxidant functions. Alterations in selenium status have been correlated with homeostatic disturbances in humans and studies with animal models of selenoprotein dysfunction indicate a strong influence on energy balance. The relationship between selenium and energy metabolism is complicated, however, as selenium has been shown to participate in multiple levels of homeostatic communication. This review discusses the role of selenium in the various pathways of communication between the body and the brain that are essential for maintaining homeostasis.

Selenium supplementation may improve COVID-19 survival in sickle cell disease

Sickle cell disease is associated with lower selenium levels, and the serum selenium level is inversely associated with haemolysis in SCD. The SCD population is more vulnerable to adverse COVID-19 outcomes. SARS-CoV-2 infection lowers the serum selenium level and this is associated with severity of COVID-19. Selenium supplementation is proposed to improve COVID-19 outcomes in the sickle cell disease population.

Administration of Selenium Nanoparticles Reverses Streptozotocin-Induced Neurotoxicity in the male rats

Alzheimer's disease is the most common neurodegenerative disease associated with deposition of amyloid-beta and the increased oxidative stress. High free radical scavenging ability of selenium nanoparticles (SeNPs) has been acknowledged, so in the present study, the effects of treatment with SeNPs on Streptozotocin (STZ)-induced neurotoxicity were evaluated in the male rats. Learning and memory impairment was induced by intraventricular injection of STZ. Following induction of memory impairment, the rats received 0.4 mg/kg of SeNPs daily for one month. Memory function, antioxidant capacity, and deposition of Amyloid β (Aβ) were assessed using the shuttle box task, biochemical methods, and Congo red staining. Injection of STZ caused memory impairment, a decrease in the level of total thiol group (TTG), and an increase in the malondialdehyde (MDA) content and deposition of Aβ. Administration of SeNPs reversed the neurotoxicity induced by STZ. It seems that SeNPs likely had neuroprotective effects on the animal model of Alzheimer's disease through increasing antioxidants҆ capacity.

Stress and the Brain: An Emerging Role for Selenium

The stress response is an important tool in an organism’s ability to properly respond to adverse environmental conditions in order to survive. Intense acute or chronic elevation of glucocorticoids, a class of stress hormone, can have deleterious neurological effects, however, including memory impairments and emotional disturbances. In recent years, the protective role of the antioxidant micronutrient selenium against the negative impact of externally applied stress has begun to come to light. In this review, we will discuss the effects of stress on the brain, with a focus on glucocorticoid action in the hippocampus and cerebral cortex, and emerging evidence of an ability of selenium to normalize neurological function in the context of various stress and glucocorticoid exposure paradigms in rodent models.

Fabrication of Calcium Sulfate Coated Selenium Nanoparticles and Corresponding In-Vitro Cytotoxicity Effects Against 4T1 Breast Cancer Cell Line

BACKGROUND

The inhibitory effect of selenium nanoparticles (SeNPs) on cancer cells has been reported in many studies. In this study, the purpose was to compare the in vitro effects of SeNPs and calcium sulfate coated selenium nanoparticles (CaSO₄@SeNPs) on breast cancer cells.

METHODS

CaSO₄@SeNPs and SeNPs were chemically synthesized and characterized with Field Emission Scanning Electron Microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDX). By applying MTT assay, the cytotoxicity effect of both nanomaterials on the 4T1 cancer cells was investigated.

RESULTS

While LD₅₀ of SeNPs on 4T1 cancer cells was 80 μg, the LD₅₀ of CaSO₄@SeNPs was reported to be only 15 μg. The difference between the inhibition rates obtained for SeNPs and CaSO₄@SeNPs was statistically significant (p=0.05). In addition, at higher concentrations (50 μg) of CaSO₄@SeNPs, the cytotoxicity was 100% more than SeNPs alone.

CONCLUSION

According to the result of the present work, it can be concluded that decoration of SeNPs with calcium sulfate leads to an increase in potency by decreasing the effective dose. This effect can be attributed to activation of intrinsic apoptosis signaling and/or pH regulatory properties of CaSO₄@SeNPs. However, further studies are still needed to determine the exact corresponding mechanisms of this synergistic effect.

Benzeneselenol-modified gold nanoclusters for cancer therapy

We report that benzeneselenol-modified gold nanoclusters (Se_Au NCs) can induce autophagy and interfere with actin expressions in cancer cells.

Identification of Hub Genes in Duchenne Muscular Dystrophy: Evidence from Bioinformatic Analysis

The hub genes and signaling pathways associated with Duchenne muscular dystrophy (DMD) were predicted by bioinformatic methods to improve the therapeutic effect and quality of life of patients. Microarray data sets GSE465, GSE1004, and GSE1007 were downloaded from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) were identified by GEO2R, and function enrichment analyses were performed by DAVID. The protein-protein interaction (PPI) network was constructed and the module analysis was performed using STRING and Cytoscape. A total of 195 DEGs were identified. The enriched functions and pathways of the DEGs include extracellular exosome, focal adhesion, extracellular matrix (ECM), focal adhesion, PI3K-Akt signaling pathway, calcium signaling pathway, and ECM-receptor interaction. Fifteen hub genes were identified. DEGs and hub genes identified in the present study help us understand the molecular mechanisms underlying the pathogenesis and progression of DMD, and provide candidate targets for treatment of DMD.

Characterization of Folic Acid Surface-Coated Selenium Nanoparticles and Corresponding In Vitro and In Vivo Effects Against Breast Cancer

BACKGROUNDS AND AIMS

Selenium nanoparticles (SeNPs) have been reported to exhibit an inhibitory effect on cancer cells. In the present study, we aimed to compare the in vitro and in vivo effects of SeNPs and folic acid surface-coated selenium nanoparticles (FA@SeNPs) on breast cancer.

METHODS

FA@SeNPs and SeNPs were chemically synthesized and characterized with different instrumental techniques. The cytotoxicity of both nanomaterials was evaluated against 4T1 cells. In addition, the intravenous administration effect of these nanomaterials (300 μg/week) on the lifespan and tumor size of cancer-bearing mice was investigated.

RESULTS

Although the SeNPs showed an antiproliferative effect against the cell line, the cytotoxicity of the FA@SeNPs was higher than that of the SeNPs. A low concentration of FA@SeNPs (25 μg/mL corresponding to 8.75 μg/mL of elemental SeNPs) caused approximately 68% cell mortality. In the in vivo study, the nanomaterials decreased the tumor growth rate in cancerous mice in relation to the control group. FA@SeNPs were more effective than SeNPs.

CONCLUSIONS

The combination of SeNPs and FA has a potent antiproliferative effect against 4T1 cells, significantly increases the lifespan, and prevents tumor growth.

Stress-response pathways are altered in the hippocampus of chronic alcoholics

The chronic high-level alcohol consumption seen in alcoholism leads to dramatic effects on the hippocampus, including decreased white matter, loss of oligodendrocytes and other glial cells, and inhibition of neurogenesis. Examining gene expression in post mortem hippocampal tissue from 20 alcoholics and 19 controls allowed us to detect differentially expressed genes that may play a role in the risk for alcoholism or whose expression is modified by chronic consumption of alcohol. We identified 639 named genes whose expression significantly differed between alcoholics and controls at a False Discovery Rate (FDR) ≤ 0.20; 52% of these genes differed by at least 1.2-fold. Differentially expressed genes included the glucocorticoid receptor and the related gene FK506 binding protein 5 (FKBP5), UDP glycosyltransferase 8 (UGT8), urea transporter (SLC14A1), zinc transporter (SLC39A10), Interleukin 1 receptor type 1 (IL1R1), thioredoxin interacting protein (TXNIP), and many metallothioneins. Pathways related to inflammation, hypoxia, and stress showed activation, and pathways that play roles in neurogenesis and myelination showed decreases. The cortisol pathway dysregulation and increased inflammation identified here are seen in other stress-related conditions such as depression and post-traumatic stress disorder and most likely play a role in addiction. Many of the detrimental effects on the hippocampus appear to be mediated through NF-κB signaling. Twenty-four of the differentially regulated genes were previously identified by genome-wide association studies of alcohol use disorders; this raises the potential interest of genes not normally associated with alcoholism, such as suppression of tumorigenicity 18 (ST18), BCL2-associated athanogene 3 (BAG3), and von Willebrand factor (VWF).

Sex-specific transcriptional responses of the zebrafish (Danio rerio) brain selenoproteome to acute sodium selenite supplementation

The potential benefits of selenium (Se) supplementation are currently under investigation for prevention of certain cancers and treatment of neurological disorders. However, little is known concerning the response of the brain to increased dietary Se under conditions of Se sufficiency, despite the majority of Se supplementation trials occurring in healthy, Se sufficient subjects. We evaluated the transcriptional response of Se-dependent genes, selenoproteins and the genes necessary for their synthesis (the selenoproteome), in the zebrafish (Danio rerio) brain to supplementation with nutritionally relevant levels of dietary Se (sodium selenite) during conditions of assumed Se sufficiency. We first used a microarray approach to analyze the response of the brain selenoproteome to dietary Se supplementation for 14 days and then assessed the immediacy and time-scale transcriptional response of the brain selenoproteome to 1, 7, and 14 days of Se supplementation by quantitative real-time PCR (qRT-PCR). The microarray approach did not indicate large-scale influences of Se on the brain transcriptome as a whole or the selenoproteome specifically; only one nonselenoproteome gene (si:ch73-44m9.2) was significantly differentially expressed. Our qRT-PCR results, however, indicate that increases of dietary Se cause small, but significant transcriptional changes within the brain selenoproteome, even after only 1 day of supplementation. These responses were dynamic over a short period of supplementation in a manner highly dependent on sex and the duration of Se supplementation. In nutritional intervention studies, it may be necessary to utilize methods such as qRT-PCR, which allow larger sample sizes, for detecting subtle transcriptional changes in the brain.

Pathway of cytotoxicity induced by folic acid modified selenium nanoparticles in MCF-7 cells

Selenium nanoparticles (Se NPs) have been recognized as promising materials for biomedical applications. To prepare Se NPs which contained cancer targeting methods and to clarify the cellular localization and cytotoxicity mechanisms of these Se NPs against cancer cells, folic acid protected/modified selenium nanoparticles (FA-Se NPs) were first prepared by a one-step method. Some morphologic and spectroscopic methods were obtained to prove the successfully formation of FA-Se NPs while free folate competitive inhibition assay, microscope, and several biological methods were used to determine the in vitro uptake, subcellular localization, and cytotoxicity mechanism of FA-Se NPs in MCF-7 cells. The results indicated that the 70-nm FA-Se NPs were internalized by MCF-7 cells through folate receptor-mediated endocytosis and targeted to mitochondria located regions through endocytic vesicles transporting. Then, the FA-Se NPs entered into mitochondria; triggered the mitochondria-dependent apoptosis of MCF-7 cells which involved oxidative stress, Ca(2)+ stress changes, and mitochondrial dysfunction; and finally caused the damage of mitochondria. FA-Se NPs released from broken mitochondria were transported into nucleus and further into nucleolus which then induced MCF-7 cell cycle arrest. In addition, FA-Se NPs could induce cytoskeleton disorganization and induce MCF-7 cell membrane morphology alterations. These results collectively suggested that FA-Se NPs could be served as potential therapeutic agents and organelle-targeted drug carriers in cancer therapy.

S-adenosylmethionine-dependent protein methylation is required for expression of selenoprotein P and gluconeogenic enzymes in HepG2 human hepatocytes

Cellular methylation processes enable expression of gluconeogenic enzymes and metabolism of the nutrient selenium. Selenium status has been proposed to relate to type II diabetes risk, and plasma levels of selenoprotein P (SEPP1) have been positively correlated with insulin resistance. Increased expression of gluconeogenic enzymes glucose-6-phosphatase (G6PC) and phosphoenolpyruvate carboxykinase 1 (PCK1) has negative consequences for blood glucose management in type II diabetics. Transcriptional regulation of SEPP1 is directed by the same transcription factors that control the expression of G6PC and PCK1, and these factors are activated by methylation of arginine residues. We sought to determine whether expression of SEPP1 and the aforementioned glucoconeogenic enzymes are regulated by protein methylation, the levels of which are reliant upon adequate S-adenosylmethionine (SAM) and inhibited by S-adenosylhomocysteine (SAH). We treated a human hepatocyte cell line, HepG2, with inhibitors of adenosylhomocysteine hydrolase (AHCY) known to increase concentration of SAH before analysis of G6PC, PCK1, and SEPP1 expression. Increasing SAH decreased 1) the SAM/SAH ratio, 2) protein-arginine methylation, and 3) expression of SEPP1, G6PC, and PCK1 transcripts. Furthermore, hormone-dependent induction of gluconeogenic enzymes was reduced by inhibition of protein methylation. When protein-arginine methyltransferase 1 expression was reduced by siRNA treatment, G6PC expression was inhibited. These findings demonstrate that hepatocellular SAM-dependent protein methylation is required for both SEPP1 and gluconeogenic enzyme expression and that inhibition of protein arginine methylation might provide a route to therapeutic interventions in type II diabetes.

Dietary selenium affects host selenoproteome expression by influencing the gut microbiota

Colonization of the gastrointestinal tract and composition of the microbiota may be influenced by components of the diet, including trace elements. To understand how selenium regulates the intestinal microflora, we used high-throughput sequencing to examine the composition of gut microbiota of mice maintained on selenium-deficient, selenium-sufficient, and selenium-enriched diets. The microbiota diversity increased as a result of selenium in the diet. Specific phylotypes showed differential effects of selenium, even within a genus, implying that selenium had unique effects across microbial taxa. Conventionalized germ-free mice subjected to selenium diets gave similar results and showed an increased diversity of the bacterial population in animals fed with higher levels of selenium. Germ-free mice fed selenium diets modified their selenoproteome expression similar to control mice but showed higher levels and activity of glutathione peroxidase 1 and methionine-R-sulfoxide reductase 1 in the liver, suggesting partial sequestration of selenium by the gut microorganisms, limiting its availability for the host. These changes in the selenium status were independent of the levels of other trace elements. The data show that dietary selenium affects both composition of the intestinal microflora and colonization of the gastrointestinal tract, which, in turn, influence the host selenium status and selenoproteome expression.

Selenoprotein P protects cells from lipid hydroperoxides generated by 15-LOX-1

Reactive lipid hydroperoxides formed by lipoxygenases and cyclooxygenases can contribute to disease through cellular oxidative damage. Several selenoproteins have lipid hydroperoxidase activity, including glutathione peroxidase 4, thioredoxin reductase, and selenoprotein P (SelP). SelP is an extracellular glycoprotein that functions both in selenium distribution and has an antioxidant activity. The major objective of this study was to determine if an SelP, at physiological concentrations and in selenium replete media, possessed hydroperoxidase activity directed at lipid hydroperoxides generated from the metabolism of arachidonic acid by 15-lipoxygenase-1 (15-LOX-1). An SelP displayed in vitro lipid hydroperoxidase activity of 15-hydroperoxyeicosatetraenoic acid (15-HpETE), attenuated 15-HpETE oxidation in cellular assays, and in transcellular assay when 15-LOX-1 is metabolically active. These results suggest that an SelP can function as an antioxidant enzyme against reactive lipid intermediates formed during inflammation, but an SelP has modest activity. Nevertheless, this effect may help protect cells against the oxidative damage induced by these lipid metabolites.

Intrauterine growth restriction modifies the developmental pattern of intestinal structure, transcriptomic profile, and bacterial colonization in neonatal pigs

Neonates with intrauterine growth restriction (IUGR) are prone to suffer from digestive diseases. Using neonatal pigs with IUGR, we tested the hypothesis that IUGR may induce alterations in the developmental pattern of intestinal barrier and thereby may be responsible for IUGR-associated increased morbidity. Piglets with a birth weight near the mean birth weight (+/-0.5 SD) were identified as normal birth weight (control) and piglets with a mean -2 SD lower birth weight (-30%) were defined as piglets with IUGR. The developmental pattern of intestinal structure, transcriptomic profile, and bacterial colonization was investigated from birth to d 5 postnatal. At birth, intestinal weight and length, ileal and colonic weight per unit of length, and villous sizes were lower (P < 0.05) in piglets with IUGR than in same-age control piglets. These IUGR-induced intestinal alterations further persisted, although they were less marked at d 5. Counts of adherent bacteria to ileal and colonic mucosa were greater (P < 0.05) in 2-d-old piglets with IUGR than in same-age control piglets. Dynamic analyses of the transcriptomic profile of the intestine revealed molecular evidence of IUGR-induced intestinal growth impairment that may result from a change in the cell proliferation-apoptosis balance during the first days of life, while a protective process would occur later on. In addition, changes in the expression of several genes suggest a pivotal role of both glucocorticoids and microbiota in driving IUGR intestinal development during the neonatal period.