Selenium Deficiency Induces Autophagy in Immune Organs of Chickens

Advances in selenium supplementation: From selenium-enriched yeast to potential selenium-enriched insects, and selenium nanoparticles

Selenium (Se) is an essential micronutrient that plays an important role in animal and human development and physiological homoeostasis. This review surveys the role of Se in the environment, plants and animal bodies, and discusses data on Se biofortification with different sources of supplementation, from inorganic to organic forms, with special focus on Se-enriched yeast (Se-yeast). Although Se-yeast remains one of the main sources of organic Se, other emerging and innovative sources are reviewed, such as Se-enriched insects and Se-nanoparticles and their potential use in animal nutrition. Se-enriched insects are discussed as an option for supplying Se in organic form to livestock diets. Se-nanoparticles are also discussed, as they represent a more biocompatible and less toxic source of inorganic Se for animal organisms, compared to selenite and selenate. We also provide up to date information on the legal framework in the EU, USA, and Canada of Se that is contained in feed additives. From the scientific evidence available in the literature, it can be concluded that among the inorganic forms, sodium selenite is still one of the main options, whereas Se-yeast remains the primary organic form. However, other potential sources such as Se-enriched insects and Se-nanoparticles are being investigated as they could potentially combine a high bioavailability and reduced Se emissions in the environment.

Effects of the Seleno-Chitosan on Daily Gain, Wool Yield, and Blood Parameter in the Chinese Merino Sheep

To study the effects of the seleno-chitosan on daily gain, wool yield, and blood parameters in the Chinese merino sheep in the selenium (Se)-deficient pastures. The samples of soils, forages, and tissues had been collected in the Southern Xinjiang of Northwest China. Our findings indicated that the Se contents in soils and forages from affected pastures were remarkably lower than those unaffected by the pastures (P < 0.01). The Se contents in the blood and the wool from affected Chinese merino sheep were extremely lower than those from healthy sheep. Meanwhile, the values of Hb, PCV, and PLT in affected sheep were significantly decreased (P < 0.01). The yield of wool and the growth rate in affected sheep were also remarkably reduced (P < 0.01). The affected Chinese merino sheep were orally treated by seleno-chitosan for 150 days; the Se contents in blood were remarkably increased and reached the healthy range on day 5. The blood parameters soon recovered to a healthy range on day 10. The growth rate of sheep in the treated group was remarkably higher than that in the control animals. The yield of the wool was also significantly increased in the treated group. Consequently, the Se-deprived environment caused a threat to daily gain, wool yield, and blood parameters in the Chinese merino sheep. The seleno-chitosan could not only markedly increase the Se contents blood contents, but also significantly increase the production performance (daily gain and wool yield), and release the symptoms of anemia in the Se-deprived animal.

Recent evidence for toxic effects of NH3 exposure on lung injury: Protective effects of L-selenomethionine

Ammonia (NH₃) is a common air pollutant, which poses a serious threat to farm animals. L-selenomethionine is organic selenium (Se), which can inhibit intracellular ROS generation, block ROS-dependent autophagy, promote mitochondrial energy metabolism, and enhance the body's immunity. Lung, as an important organ of the respiratory system, is highly susceptible to the toxic effects of NH₃. However, there were few studies on the mechanism of toxic effects of NH₃ on lung tissues. The aim of this study was to investigate the effect of NH₃ on the lungs in pigs and the alleviating effect of L-selenomethionine. Twenty-four Large White*Duroc*Min pigs were randomly assigned to 4 groups: control group, NH₃ group, Se group, and NH₃ +Se group. The results showed that exposure to NH₃ caused damage and inflammation in lung tissues and significantly increased blood NH₃ concentration. NH₃ induced changes of oxidative stress indexes (GSH, GSH-Px, SOD, MDA, Keap1, Nrf2, and HO-1) and expressions of energy metabolism related genes (HK1, HK2, PFK, PK, LDHA, and HIF-1α). Ultrastructure showed that mitochondrial damage and autophagosome increased significantly, and the expression levels of autophagy related genes (Beclin1, ATG5, ATG7, ATG10, and p62) changed. However, the addition of L-selenomethionine alleviated the above changes, but there was still a significant difference compared with the control group (P < 0.05). This finding can provide a new evidence for mitigation of NH₃ toxicity.

Effects of Se-Enriched Malt on the Immune and Antioxidant Function in the Se-Deprived Reclamation Merino Sheep in Southern Xinjiang

We have found that the Reclamation merino sheep in Southern Xinjiang, China, showed emaciation, stiff limbs, instability, and sudden death, which is related to the impairment of immune function and antioxidant capacity caused by selenium (Se) deficiency. The experiments were to study the effects of Se-enriched malt on the immune and antioxidant function in Se-deprived Reclamation merino sheep in Southern Xinjiang, China. The samples of soil and forage had been collected from tested pastures, and animal tissues were also collected in tested animals. The mineral content of soil, forage, and animal tissues was measured in the collected samples. Hematological indexes and biochemical values were also examined. The findings showed that the Se contents were extremely lower in affected soil and forage than those from healthy soil and forage (P < 0.01). The Se contents in affected blood and wool were also extremely lower than those from healthy blood and wool (P < 0.01). The values in glutathione peroxidase and total antioxidant capacity in affected serum samples were also extremely lower than those from healthy serum samples, and levels of malondialdehyde, total nitric oxide synthase, and lipid peroxide were extremely higher in affected serum samples than those from healthy serum samples (P < 0.01). Meanwhile, the values of hemoglobin, packed cell volume, and platelet count from affected blood were extremely lower than those from healthy blood (P < 0.01). The levels of interleukin (IL)-1β, IL-2, tumor necrosis factor-alpha, immunoglobulin A, and immunoglobulin G in serum were extremely decreased in the affected Reclamation merino sheep (P < 0.01). The levels of IL-6 and immunoglobulin M in serum were extremely reduced in the affected Reclamation merino sheep compared to healthy animals (P < 0.01). The animals in affected pastures were orally treated with Se-enriched malt, and the Se contents in blood were extremely increased (P < 0.01). The immune function and antioxidant indicator returned to within the healthy range. Consequently, our findings were indicated that the disorder of the Reclamation merino sheep was mainly caused by the Se deficiency in soil and forage. The Se-enriched malt could not only markedly increase the Se content in blood but also much improve the immune function and the antioxidant capacity in the Se-deprived Reclamation merino sheep.

Selenium Deficiency Induces Autophagy in Chicken Bursa of Fabricius Through ChTLR4/MyD88/NF-κB Pathway

To explore the role of ChTLR4/MyD88/NF-κB signaling pathway on autophagy induced by selenium (Se) deficiency in the chicken bursa of Fabricius, autophagosome formation in the bursa of Fabricius was observed by transmission electron microscopy. Quantitative real-time PCR (qRT-PCR) and Western blot were used to detect the expression of ChTLR4 and its signaling pathway molecules (MyD88, TRIF, and NF-κB), inflammatory factors (IL-1β, IL-8, and TNF-α), and autophagy-related factors (ATG5, Beclin1, and LC3-II) in the Se-deficient chicken bursa of Fabricius at different ages. The results showed that ChTLR4/MyD88/NF-κB signaling pathway was activated in the chicken bursa of Fabricius and autophagy was induced at the same time by Se deficiency. In order to verify the relationship between the autophagy and ChTLR4/MyD88/NF-κB signaling pathway, HD11 cells were used to establish the normal C group, low Se group, and low Se + TLR4 inhibitor (TAK242) group. The results demonstrated that autophagy could be hindered when the TLR4 signaling pathway was inhibited under Se deficiency. Furthermore, autophagy double-labeled adenovirus was utilized to verify the integrity of autophagy flow induced by Se deficiency in HD11 cells. The results showed that it appeared to form a complete autophagy flow under the condition of Se deficiency and could be blocked by TAK242. In summary, we found that Se deficiency was involved in the chicken bursa of Fabricius autophagy occurring by activating the ChTLR4/MyD88/NF-κB pathway.

The health benefits of selenium in food animals: a review

Selenium is an essential trace mineral important for the maintenance of homeostasis in animals and humans. It evinces a strong antioxidant, anti-inflammatory and potential antimicrobial capacity. Selenium biological function is primarily achieved by its presence in selenoproteins as a form of selenocysteine. Selenium deficiency may result in an array of health disorders, affecting many organs and systems; to prevent this, dietary supplementation, mainly in the forms of organic (i.e., selenomethionine and selenocysteine) inorganic (i.e., selenate and selenite) sources is used. In pigs as well as other food animals, dietary selenium supplementation has been used for improving growth performance, immune function, and meat quality. A substantial body of knowledge demonstrates that dietary selenium supplementation is positively associated with overall animal health especially due to its immunomodulatory activity and protection from oxidative damage. Selenium also possesses potential antiviral activity and this is achieved by protecting immune cells against oxidative damage and decreasing viral replication. In this review we endeavor to combine established and novel knowledge on the beneficial effects of dietary selenium supplementation, its antioxidant and immunomodulatory actions, and the putative antimicrobial effect thereof. Furthermore, our review demonstrates the gaps in knowledge pertaining to the use of selenium as an antiviral, underscoring the need for further in vivo and in vitro studies, particularly in pigs.

Effects of Dietary Selenium Sources on Physiological Status of Laying Hens and Production of Selenium-Enriched Eggs

Developing new sources of organic selenium (Se) has potential benefits for animal production and human nutrition via animal-based foods enriched with Se. The objective of this study was to evaluate the effects of Se-enriched insect protein (SEIP) in comparison with other sources, such as sodium selenite (SS) and selenium-enriched yeast (SEY), on performance, egg quality, selenium concentration in eggs, serum biochemical indices, immune capacity, and intestinal morphology of laying hens. Four hundred and fifty 24-week-old Hy-Line Brown laying hens with 94.0 ± 1.5% laying rate were randomly allocated to five groups with six replicates of 15 hens each. The control diet was prepared without adding exogenous selenium (calculated basal Se content of 0.08 mg/kg). The normal group was fed basal diets supplemented with 0.3 mg/kg of Se provided by sodium selenite. Three treatment groups (SS, SEY, and SEIP, respectively) were fed basal diets supplemented with 2 mg/kg of Se provided by sodium selenite, Se-enriched yeast, and SEIP, respectively. The feeding trial lasted for 12 weeks. Results revealed that dietary supplementation of 2 mg/kg of Se increased egg weight, decreased feed conversion ratio, and enhanced the antioxidant capacity of eggs in laying hens relative to the control group, whereas no significant differences were observed among SS, SEY, and SEIP treatment groups for the same. The organic source of Se provided by SEY or SEIP showed higher bio efficiency, as indicated by higher selenium content in eggs of SEY and SEIP compared with SS, although higher content was observed in SEY compared with SEIP. Also, the organic Se source significantly improved antioxidant capacity and immune functions of laying hens than the inorganic Se source. Diets supplemented with SEIP and SS significantly improved jejunal morphology of the laying hens compared with SEY, whereas SEIP was more effective than SEY to improve the oviduct health of laying hens. The results of this work evidently points the additive effect and nontoxicity of SEIP. Thus, SEIP could be used as another organic source of Se in the diet of laying hens and production of selenium-enriched eggs for humans.

MiR-144-3p targets STC1 to activate PI3K/AKT pathway to induce cell apoptosis and cell cycle arrest in selenium deficiency broilers

Selenium (Se) is an indispensable trace element in vertebrate. Se deficiency can damage the immune system. Studies have shown that Se deficiency can cause immune organ damage by regulating the expression of microRNA. Bursa of Fabricius is a special immune organ in poultry. In order to explore the mechanism of bursa of Fabricius injury caused by Se deficiency and the role of miRNA in this process. Firstly, we established the Se deficient model of broilers in vivo and found that Se deficiency could induce apoptosis and cell cycle arrest of bursa of Fabricius cells through Phosphoinositide 3-kinase (PI3K)/Protein Kinase B (AKT) pathway. Secondly, we inferred miRNA (miR-144-3p) and target gene Stanniocalcin 1 (STC1) that may regulate PI3K/AKT pathway through biological analysis system, and further predicted and determined the targeting relationship between them through dual luciferase, it was found that miR-144-3p was highly expressed in the process of cell apoptosis and cell cycle arrest induced by Se deficiency. Finally, in order to further understand whether miR-144-3p/STC1 axis is involved in the process, miR-144-3p knockdown and overexpression experiments were carried out, it was found that miR-144-3p inhibitor can reduce the occurrence of cell apoptosis and cell cycle arrest. In conclusion, Se deficiency can induce apoptosis and cell cycle arrest of bursa of Fabricius in Broilers by up regulating miR-144-3p targeting STC1 and activating PI3K/AKT pathway, leading to injury of bursa of Fabricius in broilers.

Maternal selenium deficiency suppresses proliferation, induces autophagy dysfunction and apoptosis in the placenta of mice

Selenium deficiency is thought to be associated with the occurrence of gestational complications. However, the underlying mechanism of selenium deficiency impairs placental function remains unclear. In this study, female mice were separately supplemented with a Se-deficient (0.02 mg/kg Se) or control diet (0.2 mg/kg Se) for 12 weeks before mating and throughout gestation. Maternal liver and placentas were collected at embryonic day 15.5 and analyzed for Se content. Oxidative stress status, proliferation capability, autophagy, and apoptosis of the placenta were determined. We found that maternal selenium deficiency decreased placental Se concentration and some antioxidant selenoproteins expressions. The concentrations of catalase and glutathione in selenium-deficient placentas were reduced, along with an increase in hydrogen peroxide (H2O2) content. Selenium deficiency inhibited the expression of proliferating cell nuclear antigen. Autophagosomes, autophagolysosomes, and upregulation of autophagy-related protein microtubule-associated protein 1 light chain 3 alpha II (LC3B), Beclin1, PTEN-induced putative kinase 1 (PINK1), and Parkin were found in the selenium-deficient trophoblasts. Autophagic substrate p62/sequestosome 1 was surprisingly increased, indicating autophagy flux dysfunction. Selenium deficiency increased expressions of B cell leukemia/lymphoma 2 associated X protein (Bax), cleaved caspase-9/-3, and decreased the B cell leukemia/lymphoma 2 (Bcl2) level. Moreover, typical apoptotic ultrastructure and apoptosis-positive cells were observed in the selenium-deficient placenta. Our results suggested that maternal selenium deficiency impaired placental proliferation, induced autophagy dysfunction and apoptosis via increasing oxidative stress, and the Akt/mechanistic target of rapamycin (mTOR) pathway involved in this process. This study revealed a novel mechanism by which maternal selenium deficiency caused impairment of the placenta.

Calcium overload and reactive oxygen species accumulation induced by selenium deficiency promote autophagy in swine small intestine

Selenium (Se) deficiency can seriously affect the small intestine of swine, and cause diarrhea in swine. However, the specific mechanism of Se deficiency-induced swine diarrhea has rarely been reported. Here, to explore the damage of Se deficiency on the calcium homeostasis and autophagy mechanism of swine, in vivo and in vitro models of swine intestinal Se deficiency were established. Twenty-four pure line castrated male Yorkshire pigs (45 d old, 12.50 ± 1.32 kg, 12 full-sibling pairs) were divided into 2 equal groups and fed Se-deficient diet (0.007 mg Se/kg) as the Se-deficiency group, or fed Se-adequate diet (0.3 mg Se/kg) as the control group for 16 weeks. The intestinal porcine enterocyte cell line (IPEC-J2) was divided into 2 groups, and cultured by Se-deficient medium as the Se-deficient group, or cultured by normal medium as the control group. Morphological observations showed that compared with the control group, intestinal cells in the Se-deficiency group were significantly damaged, and autophagosomes increased. Autophagy staining and cytoplasmic calcium staining results showed that in the Se-deficiency group, autophagy increased and calcium homeostasis was destroyed. According to the reactive oxygen species (ROS) staining results, the percentage of ROS in the Se-deficiency group was higher than that in the control group in the in vitro model. Compared with the control group, the protein and mRNA expressions of autophagy-calcium-related genes including Beclin 1, microtubule-associated proteins 1A (LC3-1), microtubule-associated proteins 1B (LC3-2), autophagy-related protein 5 (ATG5), autophagy-related protein 12 (ATG12), autophagy-related protein 16 (ATG16), mammalian target of rapamycin (mTOR), calmodulin-dependent protein kinase kinase β (CAMKK-β), adenosine 5′-monophosphate-activated protein kinase (AMPK), sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA), and calpain in the Se-deficiency group were significantly increased which was consistent in vivo and in vitro (P < 0.05). Altogether, our results indicated that Se deficiency could destroy the calcium homeostasis of the swine small intestine to trigger cell autophagy and oxidative stress, which was helpful to explain the mechanism of Se deficiency-induced diarrhea in swine.

Selenium deficiency induced apoptosis via mitochondrial pathway caused by Oxidative Stress in porcine gastric tissues

Selenium (Se) is an essential nutrient for the body, which can ensure GSH-Px activity and has antioxidant effect. Se deficiency may lead to apoptosis in various tissues and organs in animals. Pigs as major livestock in the farming industry, Se deficiency can cause various types of diseases such as white muscle disease, and mulberry heart disease.The aim of this experiment was to investigate the effect and mechanism of Se deficiency on apoptosis in porcine gastric tissue. Forty weaned piglets were randomly divided into Se deficiency group and control group, and fed with low Se diet and normal diet for six weeks respectively. The histochemical characteristics, antioxidant indexes, apoptotic genes and apoptotic protein expression of gastric cells in Se-deficient piglets were detected. The results of antioxidant index, TUNEL, RT-PCR and Western blot showed that Se deficiency decreased the activities of CAT, SOD and GSH-Px, increased the apoptotic rate of porcine gastric tissue, increased the expression of Bax and Caspase-3, and decreased the expression of Bcl-2. The results demonstrated that Se deficiency could induce apoptosis in porcine gastric tissue cells through oxidative stress-induced mitochondrial pathway. The stomach was a key target of Se deficiency and may play a key role in the response to Se deficiency. Our study may provide new ideas for the prevention and treatment of swine gastric diseases caused by Se deficiency and is beneficial to the development of pig farming industry.

Macrophage Selenoproteins Restrict Intracellular Replication of Francisella tularensis and Are Essential for Host Immunity

The essential micronutrient Selenium (Se) is co-translationally incorporated as selenocysteine into proteins. Selenoproteins contain one or more selenocysteines and are vital for optimum immunity. Interestingly, many pathogenic bacteria utilize Se for various biological processes suggesting that Se may play a role in bacterial pathogenesis. A previous study had speculated that Francisella tularensis, a facultative intracellular bacterium and the causative agent of tularemia, sequesters Se by upregulating Se-metabolism genes in type II alveolar epithelial cells. Therefore, we investigated the contribution of host vs. pathogen-associated selenoproteins in bacterial disease using F. tularensis as a model organism. We found that F. tularensis was devoid of any Se utilization traits, neither incorporated elemental Se, nor exhibited Se-dependent growth. However, 100% of Se-deficient mice (0.01 ppm Se), which express low levels of selenoproteins, succumbed to F. tularensis-live vaccine strain pulmonary challenge, whereas 50% of mice on Se-supplemented (0.4 ppm Se) and 25% of mice on Se-adequate (0.1 ppm Se) diet succumbed to infection. Median survival time for Se-deficient mice was 8 days post-infection while Se-supplemented and -adequate mice was 11.5 and >14 days post-infection, respectively. Se-deficient macrophages permitted significantly higher intracellular bacterial replication than Se-supplemented macrophages ex vivo, corroborating in vivo observations. Since Francisella replicates in alveolar macrophages during the acute phase of pneumonic infection, we hypothesized that macrophage-specific host selenoproteins may restrict replication and systemic spread of bacteria. F. tularensis infection led to an increased expression of several macrophage selenoproteins, suggesting their key role in limiting bacterial replication. Upon challenge with F. tularensis, mice lacking selenoproteins in macrophages (TrspM) displayed lower survival and increased bacterial burden in the lung and systemic tissues in comparison to WT littermate controls. Furthermore, macrophages from TrspM mice were unable to restrict bacterial replication ex vivo in comparison to macrophages from littermate controls. We herein describe a novel function of host macrophage-specific selenoproteins in restriction of intracellular bacterial replication. These data suggest that host selenoproteins may be considered as novel targets for modulating immune response to control a bacterial infection.

Autophagy in farm animals: current knowledge and future challenges

Autophagy (a process of cellular self-eating) is a conserved cellular degradative process that plays important roles in maintaining homeostasis and preventing nutritional, metabolic, and infection-mediated stresses. Surprisingly, little attention has been paid to the role of this cellular function in species of agronomical interest, and the details of how autophagy functions in the development of phenotypes of agricultural interest remain largely unexplored. Here, we first provide a brief description of the main mechanisms involved in autophagy, then review our current knowledge regarding autophagy in species of agronomical interest, with particular attention to physiological functions supporting livestock animal production, and finally assess the potential of translating the acquired knowledge to improve animal development, growth and health in the context of growing social, economic and environmental challenges for agriculture.Abbreviations: AKT: AKT serine/threonine kinase; AMPK: AMP-activated protein kinase; ASC: adipose-derived stem cells; ATG: autophagy-related; BECN1: beclin 1; BNIP3: BCL2 interacting protein 3; BVDV: bovine viral diarrhea virus; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CMA: chaperone-mediated autophagy; CTSB: cathepsin B; CTSD: cathepsin D; DAP: Death-Associated Protein; ER: endoplasmic reticulum; GFP: green fluorescent protein; Gln: Glutamine; HSPA8/HSC70: heat shock protein family A (Hsp70) member 8; IF: immunofluorescence; IVP: in vitro produced; LAMP2A: lysosomal associated membrane protein 2A; LMS: lysosomal membrane stability; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MDBK: Madin-Darby bovine kidney; MSC: mesenchymal stem cells; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; NBR1: NBR1 autophagy cargo receptor; NDV: Newcastle disease virus; NECTIN4: nectin cell adhesion molecule 4; NOD1: nucleotide-binding oligomerization domain 1; OCD: osteochondritis dissecans; OEC: oviduct epithelial cells; OPTN: optineurin; PI3K: phosphoinositide-3-kinase; PPRV: peste des petits ruminants virus; RHDV: rabbit hemorrhagic disease virus; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy.

Application of Selenium Conjugated to Animal Protein in Laying Hens' Diet for the Production of Selenium-Enriched Eggs

The current experiment was conducted to investigate the application effects of selenium conjugated to insect protein (SCIP) in the production of selenium-enriched eggs. A total of 450 laying hens were randomly assigned to five dietary groups, each group consisting of six replicates. Hens in the control group received a diet without selenium supplementation, whereas hens in the other four groups received diets supplemented with either 1, 2, 5, or 10 mg/kg of selenium from SCIP. The productive performance, egg quality, antioxidant and immune capacity, biochemical indices, intestinal morphology, and oviduct health of laying hens were evaluated. The results showed that the supplementation of organic selenium provided by SCIP in the diets of laying hens enhanced performance and egg quality without any toxicity effect, even at the 10 mg/kg inclusion level. A level of 2 mg/kg of selenium provided by SCIP in diets tentatively improved the serum antioxidant and immune capacity, intestinal development, and oviduct health of laying hens in a conspicuous manner. Hence, the biosafety and positive effects of SCIP as a feed additive supplement in laying hens' diet have been demonstrated with the enhanced production of safe and selenium-enriched eggs.

Selenium relieves oxidative stress, inflammation, and apoptosis within spleen of chicken exposed to mercuric chloride

Mercuric chloride (HgCl₂) is a widely distributed environmental pollutant with multiorgan toxicity including immune organs such as spleen. Selenium (Se) is an essential trace element in animal nutrition and exerts biological activity to antagonize organ toxicity caused by heavy metals. The objective of this study was to explore the underlying mechanism of the protective effects of Se against spleen damage caused by HgCl₂ in chicken. Ninety male Hyline brown chicken were randomly divided into 3 groups namely Cont, HgCl₂, and HgCl₂+Se group. Chicken were provided with the standard diet and nontreated water, standard diet and HgCl₂-treated water (250 ppm), and sodium selenite-treated diet (10 ppm) plus HgCl₂-treated water (250 ppm), respectively. After being fed for 7 wk, the spleen tissues were collected, and spleen index, the microstructure of the spleen, and the indicators of oxidative stress, inflammation, apoptosis as well as heat shock proteins (HSP) were detected. First, the results of spleen index and pathological examination confirmed that Se exerted an antagonistic effect on the spleen injury induced by HgCl₂. Second, Se ameliorated HgCl₂-induced oxidative stress by decreasing the level of malondialdehyde and increasing the levels of glutathione, glutathione peroxidase, and total antioxidant capacity. Third, Se attenuated HgCl₂-induced inflammation by decreasing the protein expression of nuclear factor kappa-B, inducible nitric oxide synthase, and cyclooxygenase-2, and the gene expression of interleukin (IL)-1β, IL-6, IL-8, IL-12β, IL-18 as well as tumor necrosis factor-α. Fourth, Se inhibited HgCl₂-induced apoptosis by downregulating the protein expression of BCL2 antagonist/killer 1 and upregulating the protein expression of B-cell lymphoma-2. Finally, Se reversed HgCl₂-triggered activation of HSP 60, 70, and 90. In conclusion, Se antagonized HgCl₂-induced spleen damage in chicken, partially through the regulation of oxidative stress, inflammatory, and apoptotic signaling.

Transcriptomic Analysis of Spleen Revealed Mechanism of Dexamethasone-Induced Immune Suppression in Chicks

Stress-induced immunosuppression is a common problem in the poultry industry, but the specific mechanism of its effect on the immune function of chicken has not been clarified. In this study, 7-day-old Gushi cocks were selected as subjects, and a stress-induced immunosuppression model was successfully established via daily injection of 2.0 mg/kg (body weight) dexamethasone. We characterized the spleen transcriptome in the control (B_S) and model (D_S) groups, and 515 significant differentially expressed genes (SDEGs) (Fragments Per Kilobase of transcript sequence per Millions base pairs sequenced (FPKM) > 1, adjusted p-value (padj) < 0.05 and Fold change (|FC|) ≥ 2) were identified. The cytokine-cytokine receptor interaction signaling pathway was identified as being highly activated during stress-induced immunosuppression, including the following SDEGs-CXCL13L2, CSF3R, CSF2RB, CCR9, CCR10, IL1R1, IL8L1, IL8L2, GHR, KIT, OSMR, TNFRSF13B, TNFSF13B, and TGFBR2L. At the same time, immune-related SDEGs including CCR9, CCR10, DMB1, TNFRSF13B, TNFRSF13C and TNFSF13B were significantly enriched in the intestinal immune network for the IgA production signaling pathway. The SDEG protein-protein interaction module analysis showed that CXCR5, CCR8L, CCR9, CCR10, IL8L2, IL8L1, TNFSF13B, TNFRSF13B and TNFRSF13C may play an important role in stress-induced immunosuppression. These findings provide a background for further research on stress-induced immunosuppression. Thus, we can better understand the molecular genetic mechanism of chicken stress-induced immunosuppression.

Selenoprotein-U (SelU) knockdown triggers autophagy through PI3K-Akt-mTOR pathway inhibition in rooster Sertoli cells

Selenium (Se) is a major component of male reproduction which exerts its effects via selenoproteins. Selenoprotein U (SelU), a newly identified protein, is expressed highly in eukaryotes and possesses a conserved motif similar to that existing in other thiol-dependent redox regulating selenoproteins; however its function is unknown. To investigate the role of SelU in testis autophagic and/or apoptosis cell death mechanisms, we established a Sertoli cell (SC) model isolated from 45 day old layer roosters. Small interfering RNA (siRNA) technology was used to develop SelU-knockdown (SelU-KD) and normal (N) SC models. Consequent to transfection, electron microscopy, qPCR, and western blot were performed. The results show that the mRNA and proteins of autophagy and anti-apoptosis genes increased while that of anti-autophagic mammalian target of rapamycin (mTOR) and pro-apoptosis genes decreased significantly in SelU-KD in contrast to N cells. Simultaneously, in contrast to N cells the expression of phosphoinositide-3-kinase (PI3K) and protein kinase B (PKB/Akt) both at the mRNA and protein levels decreased significantly in SelU-KD cells. In-addition, SelU depletion altered the expression of regulatory factors and increased the mRNA of TSC (tuberous sclerosis complex) genes as compared to N cells. Extensive autophagosome formation and lysosome degradation with an intact cytoskeleton were observed in SelU-KD cells. Our data indicate that SelU deprivation elicits autophagy and reduces the expression of important growth factors in SCs by disrupting the PI3K-Akt-mTOR signaling pathway. However SelU attenuation did not induce apoptosis in rooster SCs. Taken together, we conclude that SelU is essential for the survival and normal functioning of SCs.

Arsenic trioxide and/or copper sulfate induced apoptosis and autophagy associated with oxidative stress and perturbation of mitochondrial dynamics in the thymus of Gallus gallus

Arsenic (As) and copper (Cu) are ubiquitous environmental contaminants that are hazardous to the immune system. Our objective was to investigate the toxicity and potential mechanisms of thymus exposure to As and/or Cu. A chicken model was established by adding arsenic trioxide (As₂O₃; 30 mg/kg), copper sulfate (CuSO₄; 300 mg/kg), and simultaneously both elements in the basal diet. After the chickens were fed for 12 weeks, a significant reduction in antioxidant enzyme levels or production of malondialdehyde (MDA) emphasized the occurrence of oxidative stress. Furthermore, an imbalance in mitochondrial dynamics along with its abnormal structure certified mitochondrial dysfunction. Additionally, elevated levels of pro-apoptotic and autophagy genes and decreased levels of antiapoptotic genes were found in treated groups. Karyopyknosis and chromatin peripheral condensation were accompanied by an increased apoptosis ratio, as well as accumulation of autophagosomes, thus indicating that apoptosis and autophagy are involved in immune cell death. All of the above thymus lesions and index abnormalities occurred in a time-dependent manner, and the Cu and As co-administered groups showed more deteriorating effects than the Cu and As groups alone. Moreover, in the As or Cu group, the thymus tissue suffered different susceptibilities in oxidative toxicity, which needs further study. Collectively, our results manifested that co-exposure to As and Cu increased the oxidative burden and exacerbated mitochondrial dysfunction on the thymus. Additionally, apoptosis and autophagy may act as partners in inducing cell death in a cooperative manner in chicken thymus after As and/or Cu exposure.

Reuniting overnutrition and undernutrition, macronutrients, and micronutrients

Over-nutrition and its late consequences are a dominant theme in medicine today. In addition to the health hazards brought on by over-nutrition, the medical community has recently accumulated a roster of health benefits with obesity, grouped under "obesity paradox." Throughout the world and throughout history until the 20^th century, under-nutrition was a dominant evolutionary force. Under-nutrition brings with it a mix of benefits and detriments that are opposite to and continuous with those of over-nutrition. This continuum yields J-shaped or U-shaped curves relating body mass index to mortality. The overweight have an elevated risk of dying in middle age of degenerative diseases while the underweight are at increased risk of premature death from infectious conditions. Micronutrient deficiencies, major concerns of nutritional science in the 20^th century, are being neglected. This "hidden hunger" is now surprisingly prevalent in all weight groups, even among the overweight. Because micronutrient replacement is safe, inexpensive, and predictably effective, it is now an exceptionally attractive target for therapy across the spectrum of weight and age. Nutrition-related conditions worthy of special attention from caregivers include excess vitamin A, excess vitamin D, and deficiency of magnesium.

Prenatal nicotine exposure induces thymic hypoplasia in mice offspring from neonatal to adulthood

Clinical study showed that smoking during pregnancy deceased the thymus size in newborns. However, the long-term effect remains unclear. This study was aimed to observe the effects of prenatal nicotine exposure (PNE) on the development of thymus and the T-lymphocyte subpopulation in mice offspring from the neonatal to adulthood. Both the thymus weight and cytometry data indicated that PNE caused persistent thymic hypoplasia in male offspring from neonatal to adult period and transient changes in female offspring from neonatal to prepuberal period. Flow cytometry analysis disclosed a permanent decreased proportion and number of mature CD4 single-positive (SP) T cells in thymus of both sex. In addition, the PNE male offspring showed a more serious thymus atrophy in the ovalbumin (OVA)-sensitized model. Moreover, increased autophagic vacuole and elevated mRNA expression of Beclin 1 were noted in PNE fetal thymus. In conclusion, PNE offspring showed thymus atrophy and CD 4 SP T cell reduction at different life stages. Mechanically, PNE induced excessive autophagy in fetal thymocytes might be involved in these changes. All the results provided evidence for elucidating the PNE-induced programmed immune diseases.

Characteristics of Time-Dependent Selenium Biofortification of Rice ( Oryza sativa L.)

The application of selenite to soil has increasingly been used to produce Se-enriched food. This study investigated the biofortification characteristics of Se in rice after application of selenite to soil at different growth stages. The results showed that the application of Se during booting stage resulted in the highest concentration of Se in brown rice due to the highest upward translocation of Se. More than 90% of Se in the brown rice was organic species, with selenomethionine predominated. The proportion of selenomethionine in the brown rice decreased with the delay in application time. The rice grown in the acidic soil had higher Se concentrations than in the neutral soil. With increasing soil Cd level, Se accumulation and the proportion of Se-methylselenocysteine in the brown rice were reduced. This study provides a theoretical basis for the production of Se-enriched rice in clean soil or slightly to moderately Cd-contaminated soil.

Selenium (Na2SeO3) Upregulates Expression of Immune Genes and Blood-Testis Barrier Constituent Proteins of Bovine Sertoli Cell In Vitro

Sertoli cells were isolated from newborn calves and cultured in a medium supplemented with 0, 0.25, 0.50, 0.75, and 1.00 mg/L of sodium selenite to study their immune stimulatory effect, influence on cell's viability, and expression of blood-testis barrier proteins (occludin, connexin-43, zonula occluden, E-cadherin) using quantitative PCR and western blot analyses. Results showed that medium supplemented with 0.50 mg/L of selenium significantly (P < 0.05) promoted cell viability, upregulated toll-like receptor gene (TLR4), anti-inflammatory cytokines (IL-4, IL-10, TGFβ1), and expressions of blood-testis barrier proteins, and modulated expressions of pro-inflammatory cytokines (TNF-α, IL-1β, IFN-γ). Sertoli cells grown in culture medium supplemented with 0.25 mg/L of selenium significantly upregulated TLR4, IL-4, IL-10, TGFβ1, and blood-testis barrier proteins compared to the control group. Sodium selenite supplementation at 0.75 and 1.00 mg/L levels was cytotoxic and temporarily downregulated the expression of blood-testis barrier protein within 24 h after culture; however, commencing from 72 h post culture, increased cell viability and upregulation of expression of blood-testis barrier proteins were observed. In conclusion, the results of this study showed that selenium supplementation in the culture medium up to 0.50 mg/L concentration upregulates immune genes and blood-testis barrier constituent proteins of bovine Sertoli cells.

Lower Selenoprotein T Expression and Immune Response in the Immune Organs of Broilers with Exudative Diathesis Due to Selenium Deficiency

The objective of the present study was to investigate whether dietary selenium (Se) deficiency would affect the expression of selenoprotein T (SelT) and immune response in the immune organs of broilers. Changes in expression of inflammatory cytokines and oxidative stress response caused by Se deficiency can lead to organism damage, which in turn leads to immune response. Sixty (1-day-old) broilers were divided into the control group and Se-deficiency group. Animal models with exudative diathesis were duplicated in the broilers by feeding them Se-deficient diet for 20 days. After the Se-deficient group exhibited symptoms of exudative diathesis, all the broilers were euthanized, and their immune organs were taken for analysis. The tissues including spleen, bursa of Fabricius, and thymus were treated to determine the pathological changes (including microscopic and ultramicroscopic), the messenger RNA (mRNA) expression levels of SelT and its synthetase (SecS and SPS1), cytokine mRNA expression levels, and antioxidant status. The microscopic and ultramicroscopic analyses showed that immune tissues were obviously injured in the Se-deficient group. The mRNA expression of SelT was decreased compared with that in the control group. Meanwhile, the mRNA expression levels of SecS and SPS1 were downregulated. In the Se-deficient group, the mRNA expression levels of IL-1R and IL-1β were higher than those of three control organs. Additionally, the IL-2 and INF-γ mRNA expression levels were lower than those of the control group. The activity of CAT was decreased, and the contents of H₂O₂ and •OH were increased due to Se deficiency. Pearson method analysis showed that the expression of SelT had a positive correlation with IL-2, INF-γ, SecS, and SPS1 and a negative correlation with IL-1R and IL-1β. In summary, these data indicated that Se-deficient diet decreased the SelT expression and its regulation of oxidative stress, and it inhibited a pleiotropic mechanism of the immune response.

Antagonistic effects of selenium on lead-induced autophagy by influencing mitochondrial dynamics in the spleen of chickens

Lead (Pb) may damage the immune function in human and animal. Selenium (Se) has antagonistic effects on Pb. In our study, brown layer chickens were randomly allocated to control group, Se group (1 mg/kg Se), Se+Pb group (1 mg/kg Se and 350 mg/kg Pb), and Pb group (350 mg/kg Pb). The chickens were sacrificed on the 90^th day; spleen tissues were subjected to observation of ultrastructure and detection of spleen-related indexes. The results revealed that in the Pb group, expression levels of the cytokines IL-1 and TNF-α significantly increased, and expression levels of IL-2 and INF-γ significantly decreased; activities of antioxidant enzyme GPX, SOD and CAT significantly decreased, and expression level of malondialdehyde (MDA) significantly increased; expression levels of mitochondrial fission-related genes (Mff and Drp1) significantly increased, and expression levels of mitochondrial fusion-related genes (Opa1, Mfn1 and Mfn2) significantly decreased; expression of autophagy-related genes (Beclin 1, Dynein, Atg 5, LC3-I and LC-II) was upregulated, while expression of mammalian target of rapamycin (mTOR) was downregulated. The results of transmission electron microscopy indicated that Pb induced mitochondrial fragmentation, and triggered autophagy in the spleen of chickens. The Se and Pb co-treatment remarkably alleviated these injuries induced by Pb in the spleen of chickens. In conclusion, Pb can induce the oxidative stress to influence the mitochondrial dynamics balance and lead to autophagy, which triggers the immune dysfunction in the spleen of chickens; the Se exhibits the antagonistic effects on lead-induced autophagy by influencing mitochondrial dynamics in the spleen of chickens.

Assessment of toxicity of selenium and cadmium selenium quantum dots: A review

This paper reviews the current understanding of the toxicity of selenium (Se) to terrestrial mammalian and aquatic organisms. Adverse biological effects occur in the case of Se deficiencies, associated with this element having essential biological functions and a narrow window between essentiality and toxicity. Several inorganic species of Se (-2, 0, +4, and +6) and organic species (monomethylated and dimethylated) have been reported in aquatic systems. The toxicity of Se in any given sample depends not only on its speciation and concentration, but also on the concomitant presence of other compounds that may have synergistic or antagonistic effects, affecting the target organism as well, usually spanning 2 or 3 orders of magnitude for inorganic Se species. In aquatic ecosystems, indirect toxic effects, linked to the trophic transfer of excess Se, are usually of much more concern than direct Se toxicity. Studies on the toxicity of selenium nanoparticles indicate the greater toxicity of chemically generated selenium nanoparticles relative to selenium oxyanions for fish and fish embryos while oxyanions of selenium have been found to be more highly toxic to rats as compared to nano-Se. Studies on polymer coated Cd/Se quantum dots suggest significant differences in toxicity of weathered vs. non-weathered QD's as well as a significant role for cadmium with respect to toxicity.