Selenium attenuates expression of MnSOD and uncoupling protein 2 in J774.2 macrophages: molecular mechanism for its cell-death and antiinflammatory activity

Emerging role and the signaling pathways of uncoupling protein 2 in kidney diseases

OBJECTIVES

Uncoupling protein 2 (UCP2) was involved in the pathogenesis and development of kidney diseases. Many signaling pathways and factors regulate the expression of UCP2. We aimed to investigate the precise role of UCP2 and its signaling pathways in kidney diseases.

METHODS

We summarized the available evidence to yield a more detailed conclusion of the signal transduction pathways of UCP2 and its role in the development and progression of kidney diseases.

RESULTS

UCP2 could interact with 14.3.3 family proteins, mitochondrial phospholipase iPLA2γ, NMDAR, glucokinase, PPARγ2. There existed a signaling pathway between UCP2 and NMDAR, PPARγ. UCP2 can inhibit the ROS production, inflammatory response, and apoptosis, which may protect against renal injury, particularly AKI. Meanwhile UCP2 can decrease ATP production and inhibit the secretion of insulin, which may alleviate chronic renal damages, such as diabetic nephropathy and kidney fibrosis.

CONCLUSIONS

Homeostasis of UCP2 is helpful for kidney health. UCP2 may play different roles in different kinds of renal injury.

The protective effects of selenium on chronic ammonia toxicity in yellow catfish (Pelteobagrus fulvidraco)

Ammonia is toxic to most fish, and its negative effects can be eliminated by nutritional manipulation. In this study, triplicate groups of yellow catfish (0.58 ± 0.03 g) were fed diets supplemented with 0, 0.30 and 0.60 mg selenium (Se) kg^-1 diet for 56 days under three ammonia contents (0.00, 5.70 and 11.40 mg L^-1 total ammonia nitrogen). The results showed that ammonia toxicity could affects growth (weight gain, feed efficiency ratio, Se contents in muscle and whole body declined) and survival, leads to oxidative stress (total antioxidant capacity, superoxide dismutase, catalase and glutathione peroxidase activities declined and malondialdehyde accumulation), immunosuppression (lysozyme activity, 50% hemolytic complement, immunoglobulin M, respiratory burst and phagocytic index declined) and cytokines release (TNF, IL 1 and IL 8 elevated), induces up-regulation of antioxidant enzymes (Cu/Zn-SOD, Mn-SOD, CAT and GPx), cytokines (TNFα, IL 1 and IL 8) and pro-apoptotic genes (p53, Bax, Cytochrome c, Caspase 3 and Caspase 9) transcription, and down-regulation of anti-apoptotic gene Bcl2 transcription. The dietary Se supplementation could mitigate the adverse effect of ammonia poisoning on fish growth, oxidative damage, immunosuppression and apoptotic.

Supplemental dietary selenium enhances immune responses conferred by a vaccine against low pathogenicity avian influenza virus

Selenium is a trace mineral that has antioxidant activities and can influence the immune system. However, antiviral effects of selenium have not been well studies in chickens. Chickens were therefore fed diets supplemented with two levels of two different sources of selenium (organic: selenium enriched yeast; SEY or inorganic: sodium selenite; SS). Chickens in the control groups did not receive supplemental dietary selenium. At 14 and 21 days of age, chickens were vaccinated with an inactivated low pathogenicity avian influenza virus (AIV, subtype H9N2) vaccine and blood samples were collected to determine the level of antibodies using hemagglutination inhibition (HI) and ELISA. At 30 days of age, chickens were also challenged with the same virus and swab samples were collected to assess the amount of virus shedding. Antibody levels, as measured by HI, increased significantly in the chickens that received higher levels of SEY at 16 days post vaccination. ELISA titers for IgM and IgY were higher in selenium supplemented chickens. Comparing to challenged control, virus shedding was lower in organic as well as inorganic selenium treated groups. Therefore, it may be concluded that supplemental dietary selenium could enhance vaccine conferred immunity thereby impacting protection against viral challenge in chickens.

Micronutrients Selenomethionine and Selenocysteine Modulate the Redox Status of MCF-7 Breast Cancer Cells

Selenium is a micronutrient which is found in many foods, with redox status modulation activity. Our aim was to evaluate the effects of two chemical forms of selenoamino acids, Seleno-L-methionine and Seleno-L-cystine (a diselenide derived from selenocysteine), at different concentrations on cell viability, hydrogen peroxide production, antioxidant enzymes, UCP2 protein expression, as well as lipid and protein oxidative damage in MCF-7 breast cancer cells. Results showed that Seleno-L-methionine did not cause an increase in hydrogen peroxide production at relatively low concentrations, accompanied by a rise in the antioxidant enzymes catalase and MnSOD, and UCP2 protein expression levels. Furthermore, a decrease in protein and lipid oxidative damage was observed at 10 µM concentration. Otherwise, Seleno-L-cystine increased hydrogen peroxide production from relatively low concentrations (100 nM) to a large increase at high concentrations. Moreover, at 10 µM, Seleno-L-cystine decreased UCP2 and MnSOD protein expression. In conclusion, the chemical form of selenoamino acid and their incorporation to selenoproteins could affect the regulation of the breast cancer cell redox status. Taken together, the results obtained in this study imply that it is important to control the type of selenium-enriched nutrient consumption, taking into consideration their composition and concentration.

Impact of Selenium Deficiency on Inflammation, Oxidative Stress, and Phagocytosis in Mouse Macrophages

Although it has been reported that selenium (Se) deficiency can trigger inflammation, however, there are few reports on the effect of Se on the function of mouse peritoneal macrophages. Herein, we examined the expression of inflammatory factors, oxidative stress levels, and phagocytosis for primary-cultured peritoneal macrophages using control and Se-deficient groups. Our results revealed that Se deficiency induced the accumulation of oxygen free radicals and weakened antioxidant capacity. Se deficiency also significantly increased the expression of inflammation factors including iNOS, IL-1β, IL-12, IL-10, PTGe, and NF-κB. Meanwhile, Se suppression restrained macrophage production of TNF-α. The results of the phagocytosis assay demonstrated that Se deficiency inhibited the phagocytosis of macrophages. In conclusion, Se-deficient macrophages undergo severe inflammation through the NF-κB pathway due to the accumulation of oxygen free radicals and are hindered in their phagocytic capacity.

Early morphological changes in cardiac mitochondria after subcutaneous administration of trastuzumab in rabbits: possible prevention with oral selenium supplementation

Trastuzumab-mediated cardiotoxicity poses a significant challenge in the treatment of human epidermal growth factor receptor 2-positive breast cancer. To understand the underlying mechanisms, we conducted experiments to determine ultrastructural changes of rabbit cardiac tissue under different experimental conditions, including differing doses of trastuzumab and supplementation with oral sodium selenite, an antioxidant. Histopathology revealed lymphocyte and macrophage infiltration in myocardium of rabbits receiving four doses of trastuzumab. Transmission electron microscopy showed substantial changes with trastuzumab, including edema with separation of myofibril bundles and rupture of sarcomeres. Within mitochondria, edema resulted in disorganization of the cristae. Some mitochondria exhibited eccentric projections of their membranes with disruption of both inner and outer membranes. These changes were seen to a lesser extent in rabbits who received oral sodium selenite prior to trastuzumab. Selenium is integral to functioning of mitochondrial glutathione peroxidases, important antioxidants that also maintain membrane integrity. If mitochondria are disrupted as part of trastuzumab cardiac toxicity, selenium supplementation might be an important therapeutic or preventive consideration. Larger studies to explore this hypothesis are warranted.

Antioxidant Rescue of Selenomethionine-Induced Teratogenesis in Zebrafish Embryos

Selenium (Se) is an essential micronutrient that can be found at toxic concentrations in surface waters contaminated by runoff from agriculture and coal mining. Zebrafish (Danio rerio) embryos were exposed to aqueous Se in the form of selenate, selenite, and l-selenomethionine (SeMet) in an attempt to determine if oxidative stress plays a role in selenium embryo toxicity. Selenate and selenite exposure did not induce embryo deformities (lordosis and craniofacial malformation). l-selenomethionine, however, induced significantly higher deformity rates at 100 µg/L compared with controls. SeMet exposure induced a dose-dependent increase in the catalytic subunit of glutamate-cysteine ligase (gclc) and reached an 11.7-fold increase at 100 µg/L. SeMet exposure also reduced concentrations of TGSH, RGSH, and the TGSH:GSSG ratio. Pretreatment with 100 µM N-acetylcysteine significantly reduced deformities in the zebrafish embryos secondarily treated with 400 µg/L SeMet from approximately 50–10 % as well as rescued all three of the significant glutathione level differences seen with SeMet alone. Selenite exposure induced a 6.6-fold increase in expression of the glutathione-S-transferase pi class 2 (gstp2) gene, which is involved in xenobiotic transformation and possibly oxidative stress. These results suggest that aqueous exposure to SeMet can induce significant embryonic teratogenesis in zebrafish that are at least partially attributed to oxidative stress.

Role of nutrients in the development of neonatal immune response

Nutrients exert unique regulatory effects in the perinatal period that mold the developing immune system. The interactions of micronutrients and microbial and environmental antigens condition the post-birth maturation of the immune system, influencing reactions to allergens, fostering tolerance towards the emerging gastrointestinal flora and ingested antigens, and defining patterns of host defense against potential pathogens. The shared molecular structures that are present on microbes or certain plants, but not expressed by human cells, are recognized by neonatal innate immune receptors. Exposure to these activators in the environment through dietary intake in early life can modify the immune response to allergens and prime the adaptive immune response towards pathogens that express the corresponding molecular structures.

1Alpha,25-dihydroxyvitamin D3 attenuates cyanide-induced neurotoxicity by inhibiting uncoupling protein-2 up-regulation

1Alpha,25-dihydroxyvitamin D(3) (VD(3)) is a neuroprotectant that can reduce cytotoxicity produced by a variety of toxicants. The mechanism of the neuroprotection was studied in rat primary cortical cells in which Wy14,643, an agonist of peroxisome proliferator activated receptor-alpha (PPARalpha), enhances cyanide (KCN) neurotoxicity. In this cell model, Wy14,643 pretreatment enhanced cyanide-induced cell death, and the increased cell death was linked to up-regulation of uncoupling protein-2 (UCP-2). VD(3) reversed cyanide-induced mitochondrial dysfunction in cells pretreated with Wy14,643, as reflected by restoration of cellular ATP and mitochondrial membrane potential (DeltaPsi(m)). Analysis of cellular state 4 oxygen consumption showed increased mitochondrial uncoupling accompanied by up-regulation of UPC-2. The uncoupling was attenuated by prior treatment with VD(3). The interaction of VD(3) with UCP-2 was attributed to increased expression of IkappaB, an inhibitor of NF-kappaB (transcription factor that regulates UCP-2 expression). The increased IkappaB levels lead to reduced nuclear translocation and DNA binding of nuclear factor-kappaB. The role of oxidative stress in the response was then evaluated. Cotreatment with Wy14,643 and cyanide markedly increased reactive oxygen species generation and decreased reduced glutathione levels. The oxidative stress was blocked by VD(3) pretreatment. It was concluded that VD(3) blocks Wy14,643 enhancement of cyanide neurotoxicity by suppressing the redox-mediated transcriptional up-regulation of UCP-2, resulting in reduced mitochondrial proton leak and stabilization of mitochondrial function.

Selenium supplementation increases liver MnSOD expression: molecular mechanism for hepato-protection

Selenium is recognized as essential in animal and human nutrition. Several hypotheses have been advanced for its biological activity. The aim of this study was to investigate the in vivo effect of selenium on rat liver manganese superoxide dismutase (MnSOD), a key antioxidant enzyme, under naïve and inflammatory conditions. Rats received sodium selenite supplementation and LPS injection. Whole-liver samples, isolated hepatocytes, Kupffer cells and blood samples were subjected to protein, RNA and biochemical analysis. Liver enrichment with selenium increased whole-liver MnSOD levels due to an increase in MnSOD transcription in hepatocytes. This was due to an increase in the ratio of specificity protein 1 to activating enhancer binding protein 2 DNA-binding activity. The inflammatory stimulus further elevated MnSOD levels in the whole-liver that was abrogated in sodium selenite supplementation due to reduced transcription of MnSOD in Kupffer cells. Moreover, selenium enrichment decreased Kupffer cells IL-6 transcription in LPS-injected animals. Anti-inflammatory activity of selenium was demonstrated by normalized blood levels of ALT and IL-6 in LPS-injected animals. In conclusion, selenium up-regulates hepatocytes MnSOD expression, probably improving their anti-oxidant defense, while decreasing MnSOD and IL-6 transcription in Kupffer cells in the presence of inflammatory stimuli, attenuating their inflammatory response. This selective mechanism may explain the anti-inflammatory and hepato-protective effect of selenium.

High Selenium Reduces NF-κB-Regulated Gene Expression in Uninduced Human Prostate Cancer Cells

Nuclear factor kappa B (NF-kappaB) induces expression of antiapoptotic and pro-inflammatory genes and is constitutively activated in prostate cancer. We tested the hypothesis that a biologically and physiologically relevant form and concentration of selenium (Se) may alter NF-kappa B activation in early prostate cancer cells in the absence of exogenously added inducers of the NF-kappaB pathway. LNCaP cells were cultured in medium without added tumor necrosis factor alpha or lipopolysaccharide but with methylseleninic acid added to provide final concentrations of Se of 30 nM-7.6 microM. Compared to 50 nM Se, treatment with 7.6 microM Se virtually eliminated NF-kappaB binding to its DNA response element and reduced transcription rates and mRNA levels by half for NF-kappaB-regulated genes. There were no differences due to Se in tyrosine phosphorylation, inhibitor of kappa B alpha (I kappa B alpha) levels, or NF-kappaB translocation from cytosol to nucleus. The observation in these basal, unstimulated cells of altered NF-kappaB binding to DNA in the absence of effects on the NF-kappaB activation pathway suggests an interaction of Se with the NF-kappaB protein or an effect on recruitment of NF-kappaB coactivators or corepressors. Inhibition of transcription factor binding and anti-apoptotic gene expression may be one mechanism for the chemopreventive effects of Se against prostate cancer.