Diphenyl diselenide modulates gene expression of antioxidant enzymes in the cerebral cortex, hippocampus and striatum of female hypothyroid rats

Effect of Prepartum Maternal Supplementation with Diphenyl Diselenide on Biochemical, Immunological, and Oxidative Parameters of the Offspring

This study aimed to assess the impact of prepartum maternal diphenyl diselenide (PhSe)2 supplementation on the development, biochemical, immune, and antioxidant parameters of calves. Eighteen Holstein breed calves were used, born to females who were or were not subjected to supplementation, at 42, 28, and 14 days prior to calving. The (PhSe)2 group (DDG) was administered 3 μmol/kg of (PhSe)2 in 4 mL of dimethyl sulfoxide (DMSO), while the DMSO and NaCl groups were administered 4 mL of DMSO and 0.9% NaCl, subcutaneously. The calves were evaluated based on their weight, withers height, body condition score 24 h post-birth (0), as well on days 14, 28, 42, 56, 70. Blood samples were also taken to determine serum variables. Calves on the DDG showed higher average levels of total protein, albumin, and globulins on day 0, and the immunoglobulin G level was significantly higher than the other groups on days 0, 14, 56, 70. Maternal supplementation showed immunomodulatory effect on calves, evidenced by the exceptional rates of passive immunity transfer, as well as the enhancement of humoral immunity. Our research offers fresh insights into the immunomodulatory potential of (PhSe)2, making it a viable alternative in facing this challenging phase, rearing dairy calves.

Beneficial Effect of Selenium Doped Carbon Quantum Dots Supplementation on the in vitro Development Competence of Ovine Oocytes

Background

After the synthesis of selenium doped carbon quantum dots (Se/CDs) via a step-by-step hydrothermal synthesis method with diphenyl diselenide (DPDSe) as precursor, the beneficial effects of Se/CDs’ supplementation on the in vitro development competence of ovine oocytes were firstly investigated in this study by the assay of maturation rate, cortical granules’ (CGs) dynamics, mitochondrial activity, reactive oxygen species (ROS) production, epigenetic modification, transcript profile, and embryonic development competence.

Results

The results showed that the Se/CDs’ supplementation during the in vitro maturation (IVM) process not only enhanced the maturation rate, CGs’ dynamics, mitochondrial activity and embryonic developmental competence of ovine oocytes, but remarkably decreased the ROS production level of ovine oocytes. In addition, the expression levels of H3K9me3 and H3K27me3 in the ovine oocytes were significantly up-regulated after the Se/CDs’ supplementation, in consistent with the expression levels of 5mC and 5hmC. Moreover, 2994 up-regulated differentially expressed genes (DEGs) and 846 repressed DEGs were found in the oocytes after the Se/CDs’ supplementation. According to the analyses of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG), these DEGs induced by the Se/CDs’ supplementation were positively related to the progesterone mediated oocyte maturation and mitochondrial functions. And these remarkably up-regulated expression levels of DEGs related to oocyte maturation, mitochondrial function, and epigenetic modification induced by the Se/CDs’ supplementation further confirmed the beneficial effect of Se/CDs’ supplementation on the in vitro development competence of ovine oocytes.

Conclusion

The Se/CDs prepared in our study significantly promoted the in vitro development competence of ovine oocytes, benefiting the extended research about the potential applications of Se/CDs in mammalian breeding technologies.

Modulation of redox and insulin signaling underlie the anti-hyperglycemic and antioxidant effects of diphenyl diselenide in zebrafish

The organic selenium compound diphenyl diselenide (DD) has been recognized as an antioxidant and neuroprotective agent, exerting an anti-hyperglycemic effect in experimental models of diabetes. However, the precise mechanisms involved in the protection are unclear. Using the zebrafish (Danio rerio) as a model organism, here we investigated biomarkers underlying the protective effects of DD against hyperglycemia, targeting in a transcriptional approach the redox and insulin-signaling pathway. Fish were fed on a diet containing DD (3 mg/kg) for 74 days. In the last 14 days, they were exposed to a 111 mM glucose solution to induce a hyperglycemic state. DD reduced blood glucose levels as well as normalized the brain mRNA transcription of four insulin receptors-coding genes (Insra1, Insra2, Insrb1, Insrb2), which were down-regulated by glucose. DD alone caused an up-regulation of relative mRNA transcription in both Insra receptors and glucose transporter 3 genes. DD counteracted hyperglycemia-induced lipid peroxidation, protein and thiol depletion. Along with the decreased activity of antioxidant enzymes SOD and GPx, the brain of hyperglycemic fish presented a reduction in mRNA transcription of FoxO3A, FoxO3B, Nrf2, GPx3A, SOD1, and SOD2 genes. Besides normalizing the transcriptional levels, DD caused an up-regulation of relative mRNAs that encode Nrf2, FoxO1A, FOXO3A, GPx4A, PTP1B, AKT and SelP. Collectively, our findings suggest that the antioxidant and anti-hyperglycemic actions of DD in a zebrafish diabetes model are likely associated with the regulation of the oxidative stress resistance and the insulin-signaling pathway and that could be related to the modulation at mRNA level of two important transcription factors, Nrf2 and FoxO.

Organoselenotriazoles attenuate oxidative damage induced by mitochondrial dysfunction in mev-1 Caenorhabditis elegans mutants

Organic selenium compounds have several pharmacological activities already described, as anti-inflammatory and antitumor activities, which have been attributed to their antioxidant effects. Because they are promising in pharmacology, the synthesis of these compounds has increased significantly. As many new molecules are synthesized the use of a simple model like Caenorhabditis elegans is highly advantageous for initial evaluation of the toxicity and therapeutic potential of these molecules. The objective of this study was to evaluate the toxicity and antioxidant capacity of a series of selenotriazoles compounds in C. elegans. The animals were exposed to the compounds in liquid medium for only 30 min at the first larval stage (L1). The compounds had no toxic effects at the concentrations tested. Treatment with selenotriazoles (10 μM) partially reversed the stress induced by the pesticide paraquat (1 mM). Se-Tz Ia compound partially increased the survival of worms treated with H₂O₂ (0.5 mM). The compounds also increased the longevity of mev-1 mutants, which have a reduced life span by the production of excessive reactive oxygen species (ROS) in the mitochondria caused by a mutation in complex II of the electron transport chain. In addition, the compounds reduced the levels of ROS determined by the fluorescent probe DCF-DA as well as also reduced catalase enzyme activity in these animals. Based on the results found, it is possible to conclude that the compounds have antioxidant activity mainly in oxidative stress condition generated by a mitochondrial dysfunction in C. elegans.

Diphenyl diselenide protects neuronal cells against oxidative stress and mitochondrial dysfunction: Involvement of the glutathione-dependent antioxidant system

Oxidative stress and mitochondrial dysfunction are critical events in neurodegenerative diseases; therefore, molecules that increase cellular antioxidant defenses represent a future pharmacologic strategy to counteract such conditions. The aim of this study was to investigate the potential protective effect of (PhSe)2 on mouse hippocampal cell line (HT22) exposed to tert-BuOOH (in vitro model of oxidative stress), as well as to elucidate potential mechanisms underlying this protection. Our results showed that tert-BuOOH caused time- and concentration-dependent cytotoxicity, which was preceded by increased oxidants production and mitochondrial dysfunction. (PhSe)2 pre-incubation significantly prevented these cytotoxic events and the observed protective effects were paralleled by the upregulation of the cellular glutathione-dependent antioxidant system: (PhSe)2 increased GSH levels (> 60%), GPx activity (6.9-fold) and the mRNA expression of antioxidant enzymes Gpx1 (3.9-fold) and Gclc (2.3-fold). Of note, the cytoprotective effect of (PhSe)2 was significantly decreased when cells were treated with mercaptosuccinic acid, an inhibitor of GPx, indicating the involvement of GPx modulation in the observed protective effect. In summary, the present findings bring out a new action mechanism concerning the antioxidant properties of (PhSe)2. The observed upregulation of the glutathione-dependent antioxidant system represents a future pharmacologic possibility that goes beyond the well-known thiol-peroxidase activity of this compound.

Organoselenium compounds as mimics of selenoproteins and thiol modifier agents

Selenium is an essential trace element for animals and its role in the chemistry of life relies on a unique functional group: the selenol (-SeH) group. The selenol group participates in critical redox reactions. The antioxidant enzymes glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) exemplify important selenoproteins. The selenol group shares several chemical properties with the thiol group (-SH), but it is much more reactive than the sulfur analogue. The substitution of S by Se has been exploited in organic synthesis for a long time, but in the last 4 decades the re-discovery of ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) and the demonstration that it has antioxidant and therapeutic properties has renovated interest in the field. The ability of ebselen to mimic the reaction catalyzed by GPx has been viewed as the most important molecular mechanism of action of this class of compound. The term GPx-like or thiol peroxidase-like reaction was previously coined in the field and it is now accepted as the most important chemical attribute of organoselenium compounds. Here, we will critically review the literature on the capacity of organoselenium compounds to mimic selenoproteins (particularly GPx) and discuss some of the bottlenecks in the field. Although the GPx-like activity of organoselenium compounds contributes to their pharmacological effects, the superestimation of the GPx-like activity has to be questioned. The ability of these compounds to oxidize the thiol groups of proteins (the thiol modifier effects of organoselenium compounds) and to spare selenoproteins from inactivation by soft-electrophiles (MeHg⁺, Hg²⁺, Cd²⁺, etc.) might be more relevant for the explanation of their pharmacological effects than their GPx-like activity. In our view, the exploitation of the thiol modifier properties of organoselenium compounds can be harnessed more rationally than the use of low mass molecular structures to mimic the activity of high mass macromolecules that have been shaped by millions to billions of years of evolution.

Induction of reactive oxygen species by diphenyl diselenide is preceded by changes in cell morphology and permeability in Saccharomyces cerevisiae

Organoselenium compounds, such as diphenyl diselenide (PhSe)₂ and phenylselenium zinc chloride (PhSeZnCl), show protective activities related to their thiol peroxidase activity. However, depending on experimental conditions, organoselenium compounds can cause toxicity by oxidising thiol groups of proteins and induce the production of reactive oxygen species (ROS). Here, we analysed the toxicity of (PhSe)₂ and PhSeZnCl in yeast Saccharomyces cerevisiae. Cell growth of S. cerevisiae after 1, 2, 3, 4, 6, and 16 h of treatment with 2, 4, 6, and 10 μM of (PhSe)₂ was evaluated. For comparative purpose, PhSeZnCl was analysed only at 16 h of incubation at equivalent concentrations of selenium (i.e. 4, 8, 12, and 20 μM). ROS production (DCFH-DA), size, granularity, and cell membrane permeability (propidium iodide) were determined by flow cytometry. (PhSe)₂ inhibited cell growth at 2 h (10 μM) of incubation, followed by increase in cell size. The increase of cell membrane permeability and granularity (10 μM) was observed after 3 h of incubation, however, ROS production occurs only at 16 h of incubation (10 μM) with (PhSe)₂, indicating that ROS overproduction is a more likely consequence of (PhSe)₂ toxicity and not its determinant. All tested parameters showed that only concentration of 20 μM induced toxicity in samples incubated with PhSeZnCl. In summary, the results suggest that (PhSe)₂ toxicity in S. cerevisiae is time and concentration dependent, presenting more toxicity when compared with PhSeZnCl.

Chronic Oxidative Stress, Mitochondrial Dysfunction, Nrf2 Activation and Inflammation in the Hippocampus Accompany Heightened Systemic Inflammation and Oxidative Stress in an Animal Model of Gulf War Illness

Memory and mood dysfunction are the key symptoms of Gulf war illness (GWI), a lingering multi-symptom ailment afflicting >200,000 veterans who served in the Persian Gulf War-1. Research probing the source of the disease has demonstrated that concomitant exposures to anti-nerve gas agent pyridostigmine bromide (PB), pesticides, and war-related stress are among the chief causes of GWI. Indeed, exposures to GWI-related chemicals (GWIR-Cs) and mild stress in animal models cause memory and mood impairments alongside reduced neurogenesis and chronic low-level inflammation in the hippocampus. In the current study, we examined whether exposure to GWIR-Cs and stress causes chronic changes in the expression of genes related to increased oxidative stress, mitochondrial dysfunction, and inflammation in the hippocampus. We also investigated whether GWI is linked with chronically increased activation of Nrf2 (a master regulator of antioxidant response) in the hippocampus, and inflammation and enhanced oxidative stress at the systemic level. Adult male rats were exposed daily to low-doses of PB and pesticides (DEET and permethrin), in combination with 5 min of restraint stress for 4 weeks. Analysis of the hippocampus performed 6 months after the exposure revealed increased expression of many genes related to oxidative stress response and/or antioxidant activity (Hmox1, Sepp1, and Srxn1), reactive oxygen species metabolism (Fmo2, Sod2, and Ucp2) and oxygen transport (Ift172 and Slc38a1). Furthermore, multiple genes relevant to mitochondrial respiration (Atp6a1, Cox6a1, Cox7a2L, Ndufs7, Ndufv1, Lhpp, Slc25a10, and Ucp1) and neuroinflammation (Nfkb1, Bcl6, Csf2, IL6, Mapk1, Mapk3, Ngf, N-pac, and Prkaca) were up-regulated, alongside 73–88% reduction in the expression of anti-inflammatory genes IL4 and IL10, and nuclear translocation and increased expression of Nrf2 protein. These hippocampal changes were associated with elevated levels of pro-inflammatory cytokines and chemokines (Tnfa, IL1b, IL1a, Tgfb, and Fgf2) and lipid peroxidation byproduct malondialdehyde in the serum, suggesting the presence of an incessant systemic inflammation and elevated oxidative stress. These results imply that chronic oxidative stress, inflammation, and mitochondrial dysfunction in the hippocampus, and heightened systemic inflammation and oxidative stress likely underlie the persistent memory and mood dysfunction observed in GWI.

Selenium, selenoproteins and neurodegenerative diseases

A review of selenium's essential role in normal brain function and its potential involvement in neurodegenerative diseases.