Selenium induces a multi-targeted cell death process in addition to ROS formation

Exposure to Selenomethionine and Selenocystine Induces Redox-Mediated ER Stress in Normal Breast Epithelial MCF-10A Cells

Selenium is an essential trace element co-translationally incorporated into selenoproteins with important biological functions. Health benefits have long been associated with selenium supplementation. However, cytotoxicity is observed upon excessive selenium intake. The aim of this study is to investigate the metabolic pathways underlying the response to the selenium-containing amino acids selenomethionine and selenocysteine in a normal human breast epithelial cell model. We show that both selenomethionine and selenocystine inhibit the proliferation of non-cancerous MCF-10A cells in the same concentration range as cancerous MCF-7 and Hela cells, which results in apoptotic cell death. Selenocystine exposure in MCF-10A cells caused a severe depletion of free low molecular weight thiols, which might explain the observed upregulation of the expression of the oxidative stress pathway transcription factor NRF2. Both selenomethionine and selenocystine induced the expression of target genes of the unfolded protein response (GRP78, ATF4, CHOP). Using a redox-sensitive fluorescent probe targeted to the endoplasmic reticulum (ER), we show that both selenoamino acids shifted the ER redox balance towards an even more oxidizing environment. These results suggest that alteration of the redox state of the ER may disrupt protein folding and cause ER stress-induced apoptosis in MCF-10A cells exposed to selenoamino acids.

Comprehensive distribution and species of selenium in Se-enriched Pichia kudriavzevii 1845

This study is the first to demonstrate the yeast Pichia kudriavzevii can effectively deliver Se and investigate the distribution and species of Se in Se-enriched P. kudriavzevii. Results showed that P. kudriavzevii can accumulate Se and convert 84.883% of absorbed Se into organic forms, of which 78.338% was incorporated into protein, 1.978% combined with polysaccharides, and 0.456% bound to nucleic acid. Besides, water-soluble, salt-soluble, and alkali-soluble proteins account for 49.398%, 1.867%, and 20.628% of selenoprotein, respectively. The dominant Se species were SeCys2 and MeSeCys. Additionally, Se-enrichment enhanced nutritional value of P. kudriavzevii by increasing the levels of amino acids, iron, and zinc. The activity of key rate-limiting enzyme sephosphate synthetase involved in Se biotransformation was improved after Se enrichment. The extracellular pH results suggest that Se enrichment ability can be further enhanced by elevating pH. These results suggest P. kudriavzevii holds great promise as an effective vehicle for delivering Se.

Targeting paraptosis in cancer: opportunities and challenges

Cell death can be classified into two primary categories: accidental cell death and regulated cell death (RCD). Within RCD, there are distinct apoptotic and non-apoptotic cell death pathways. Among the various forms of non-apoptotic RCD, paraptosis stands out as a unique mechanism characterized by distinct morphological changes within cells. These alterations encompass cytoplasmic vacuolization, organelle swelling, notably in the endoplasmic reticulum and mitochondria, and the absence of typical apoptotic features, such as cell shrinkage and DNA fragmentation. Biochemically, paraptosis distinguishes itself by its independence from caspases, which are conventionally associated with apoptotic death. This intriguing cell death pathway can be initiated by various cellular stressors, including oxidative stress, protein misfolding, and specific chemical compounds. Dysregulated paraptosis plays a pivotal role in several critical cancer-related processes, such as autophagic degradation, drug resistance, and angiogenesis. This review provides a comprehensive overview of recent advancements in our understanding of the mechanisms and regulation of paraptosis. Additionally, it delves into the potential of paraptosis-related compounds for targeted cancer treatment, with the aim of enhancing treatment efficacy while minimizing harm to healthy cells.

Tumor Targeted Cuprous-Based Nanocomposite as Responsive Cascade Nanocatalyst for Efficient Tumor Synergistic Therapy

The single-functionality of traditional chemodynamic therapy (CDT) reagents usually limits the therapeutic efficacy of cancer treatment. Synergistic nanocomposites that involve cascade reaction provide a promising strategy to achieve satisfactory anticancer effects. Herein, a cuprous-based nanocomposite (CCS@GOx@HA) is fabricated, which owns the tumor targeting ability and can undergo tumor microenvironment responsive cascade reaction to enhance the tumor therapeutic efficiency significantly. Surface modification of nanocomposite with hyaluronic acid enables the targeted delivery of the nanocomposite to cancer cells. Acid-triggered decomposition of nanocomposite in cancer cell results in the release of Cu+ , Se2- and GOx. The Cu+ improves the Fenton-like reaction with endogenous H2 O2 to generate highly toxic • OH for CDT. While GOx can not only catalyze the in situ generation of endogenous H2 O2 , but also accelerate the consumption of intratumoral glucose to reduce nutrient supply in tumor site. In addition, Se2- further improves the therapeutic effects of CDT by upregulating the reactive oxygen species (ROS) in tumor cells. Meanwhile, the surface modification endows the nanocomposite the good water dispersibility and biocompatibility. Moreover, in vitro and in vivo experiments demonstrate satisfactory anti-cancer therapeutic performance by the synergistic cascade function of CCS@GOx@HA than CDT alone.

Selenium Compounds Affect Differently the Cytoplasmic Thiol/Disulfide State in Dermic Fibroblasts and Improve Cell Migration by Interacting with the Extracellular Matrix

Deficient wound healing is frequently observed in patients diagnosed with diabetes, a clinical complication that compromises mobility and leads to limb amputation, decreasing patient autonomy and family lifestyle. Fibroblasts are crucial for secreting the extracellular matrix (ECM) to pave the wound site for endothelial and keratinocyte regeneration. The biosynthetic pathways involved in collagen production and crosslinking are intimately related to fibroblast redox homeostasis. In this study, two sets of human dermic fibroblasts were cultured in normal (5 mM) and high (25 mM)-glucose conditions in the presence of 1 µM selenium, as sodium selenite (inorganic) and the two selenium amino acids (organic), Se-cysteine and Se-methionine, for ten days. We investigated the ultrastructural changes in the secreted ECM induced by these conditions using scanning electron microscopy (SEM). In addition, we evaluated the redox impact of these three compounds by measuring the basal state and real-time responses of the thiol-based HyPer biosensor expressed in the cytoplasm of these fibroblasts. Our results indicate that selenium compound supplementation pushed the redox equilibrium towards a more oxidative tone in both sets of fibroblasts, and this effect was independent of the type of selenium. The kinetic analysis of biosensor responses allowed us to identify Se-cysteine as the only compound that simultaneously improved the sensitivity to oxidative stimuli and augmented the disulfide bond reduction rate in high-glucose-cultured fibroblasts. The redox response profiles showed no clear association with the ultrastructural changes observed in matrix fibers secreted by selenium-treated fibroblasts. However, we found that selenium supplementation improved the ECM secreted by high-glucose-cultured fibroblasts according to endothelial migration assessed with a wound healing assay. Direct application of sodium selenite and Se-cysteine on purified collagen fibers subjected to glycation also improved cellular migration, suggesting that these selenium compounds avoid the undesired effect of glycation.

Antimicrobial and anti-viral effects of selenium nanoparticles and selenoprotein based strategies: COVID-19 and beyond

Deficiency of selenium (Se) has been described in a significant number of COVID-19 patients having a higher incidence of mortality, which makes it a pertinent issue to be addressed clinically for effective management of the COVID-19 pandemic. Se nanoparticles (SeNPs) provide a unique option for managing the havoc caused by the COVID-19 pandemic. SeNPs possess promising anti-inflammatory and anti-fibrotic effects by virtue of their nuclear factor kappa-light-chain-stimulator of activated B cells (NFκB), mitogen-activated protein kinase (MAPKs), and transforming growth factor-beta (TGF-β) modulatory activity. In addition, SeNPs possess remarkable immunomodulatory effects, making them a suitable option for supplementation with a much lower risk of toxicity compared to their elemental counterpart. Further, SeNPs have been shown to curtail viral and microbial infections, thus, making it a novel means to halt viral growth. In addition, it can be administered in the form of aerosol spray, direct injection, or infused thin-film transdermal patches to reduce the spread of this highly contagious viral infection. Moreover, a considerable decrease in the expression of selenoprotein along with enhanced expression of IL-6 in COVID-19 suggests a potential association among selenoprotein expression and COVID-19. In this review, we highlight the unique antimicrobial and antiviral properties of SeNPs and the immunomodulatory potential of selenoproteins. We provide the rationale behind their potentially interesting properties and further exploration in the context of microbial and viral infections. Further, the importance of selenoproteins and their role in maintaining a successful immune response along with their association to Se status is summarized.

V. J, Pal S, Nair BG, Kar R, Mishra N. Paraptosis: a unique cell death mode for targeting cancer

Programmed cell death (PCD) is the universal process that maintains cellular homeostasis and regulates all living systems' development, health and disease. Out of all, apoptosis is one of the major PCDs that was found to play a crucial role in many disease conditions, including cancer. The cancer cells acquire the ability to escape apoptotic cell death, thereby increasing their resistance towards current therapies. This issue has led to the need to search for alternate forms of programmed cell death mechanisms. Paraptosis is an alternative cell death pathway characterized by vacuolation and damage to the endoplasmic reticulum and mitochondria. Many natural compounds and metallic complexes have been reported to induce paraptosis in cancer cell lines. Since the morphological and biochemical features of paraptosis are much different from apoptosis and other alternate PCDs, it is crucial to understand the different modulators governing it. In this review, we have highlighted the factors that trigger paraptosis and the role of specific modulators in mediating this alternative cell death pathway. Recent findings include the role of paraptosis in inducing anti-tumour T-cell immunity and other immunogenic responses against cancer. A significant role played by paraptosis in cancer has also scaled its importance in knowing its mechanism. The study of paraptosis in xenograft mice, zebrafish model, 3D cultures, and novel paraptosis-based prognostic model for low-grade glioma patients have led to the broad aspect and its potential involvement in the field of cancer therapy. The co-occurrence of different modes of cell death with photodynamic therapy and other combinatorial treatments in the tumour microenvironment are also summarized here. Finally, the growth, challenges, and future perspectives of paraptosis research in cancer are discussed in this review. Understanding this unique PCD pathway would help to develop potential therapy and combat chemo-resistance in various cancer.

Antiproliferative Effect of Inorganic and Organic Selenium Compounds in Breast Cell Lines

Triple-negative breast cancer (TNBC) is an aggressive, fast-growing tumor that is more likely to spread to distant organs. Among women diagnosed with breast cancer, the prevalence of TNBC is 20%, and treatment is currently limited to chemotherapy. Selenium (Se), an essential micronutrient, has been explored as an antiproliferative agent. Therefore, this study aimed to evaluate the effects of exposure to organic (selenomethionine, ebselen, and diphenyl diselenide) and inorganic (sodium selenate and sodium selenite) Se molecules in different breast cell lines. The compounds were tested at 1, 10, 50, and 100 μM for 48 h in the non-tumor breast cell line (MCF-10A) and TNBC derivatives cell lines (BT-549 and MDA-MB-231). The effects of Se on cell viability, apoptotic and necrotic processes, colony formation, and cell migration were analyzed. Exposure to selenomethionine and selenate did not alter the evaluated parameters. However, selenomethionine had the highest selectivity index (SI). The exposure to the highest doses of selenite, ebselen, and diphenyl diselenide resulted in antiproliferative and antimetastatic effects. Selenite had a high SI to the BT cell line; however, the SI of ebselen and diphenyl diselenide was low in both tumoral cell lines. In conclusion, the Se compounds had different effects on the breast cell lines, and additional tests are needed to reveal the antiproliferative effects of Se compounds.

Selenium nanoparticles modulate histone methylation via lysine methyltransferase activity and S-adenosylhomocysteine depletion

At physiological levels, the trace element selenium plays a key role in redox reactions through the incorporation of selenocysteine in antioxidant enzymes. Selenium has also been evaluated as a potential anti-cancer agent, where selenium nanoparticles have proven effective, and are well tolerated in vivo at doses that are toxic as soluble Se. The use of such nanoparticles, coated with either serum albumin or the naturally occurring alkaline polysaccharide chitosan, also serves to enhance biocompatibility and bioavailability. Here we demonstrate a novel role for selenium in regulating histone methylation in ovarian cancer cell models treated with inorganic selenium nanoparticles coated with serum albumin or chitosan. As well as inducing thioredoxin reductase expression, ROS activity and cancer cell cytotoxicity, coated nanoparticles caused significant increases in histone methylation. Specifically, selenium nanoparticles triggered an increase in the methylation of histone 3 at lysines K9 and K27, histone marks involved in both the activation and repression of gene expression, thus suggesting a fundamental role for selenium in these epigenetic processes. This direct function was confirmed using chemical inhibitors of the histone lysine methyltransferases EZH2 (H3K27) and G9a/EHMT2 (H3K9), both of which blocked the effect of selenium on histone methylation. This novel role for selenium supports a distinct function in histone methylation that occurs due to a decrease in S-adenosylhomocysteine, an endogenous inhibitor of lysine methyltransferases, the metabolic product of methyl-group transfer from S-adenosylmethionine in the one-carbon metabolism pathway. These observations provide important new insights into the action of selenium nanoparticles. It is now important to consider both the classic antioxidant and novel histone methylation effects of this key redox element in its development in cancer therapy and other applications.

Protective effect of spore oil-functionalized nano-selenium system on cisplatin-induced nephrotoxicity by regulating oxidative stress-mediated pathways and activating immune response

In clinical practice, cisplatin is the most commonly used chemotherapy drug to treat a range of malignancies. Severe ROS-regulated nephrotoxicity, however, restricts its applicability. Currently, the main mechanisms leading to cisplatin-induced nephrotoxicity in clinical settings involve hydration or diuresis. However, not all patients can be treated with massive hydration or diuretics. Therefore, it is crucial to develop a treatment modality that can effectively reduce nephrotoxicity through a foodborne route. Selenium has been reported to have strong antioxidant as well as anticancer effects when administered as spore oil. Herein, we established cellular and animal models of cisplatin-induced nephrotoxicity and synthesized spore oil-functionalized nano-selenium (GLSO@SeNPs). We found that GLSO@SeNPs inhibit the mitochondrial apoptotic pathway by maintaining oxidative homeostasis and regulating related signaling pathways (the MAPK, caspase, and AKT signaling pathways). In vivo, GLSO@SeNPs could effectively improve cisplatin-induced renal impairment, effectively maintaining oxidative homeostasis in renal tissues and thus inhibiting the process of renal injury. In addition, GLSO@SeNPs were converted into selenocysteine (SeCys2), which may exert protective effects. Furthermore, GLSO@SeNPs could effectively modulate the ratio of immune cells in kidneys and spleen, reducing the proportions of CD3⁺CD4⁺ T cells, CD3⁺CD8⁺ T cells, and M1 phenotype macrophages and increasing the proportion of anti-inflammatory regulatory T cells. In summary, in this study, we synthesized food-derived spore oil-functionalized nanomaterials, and we explored the mechanisms by which GLSO@SeNPs inhibit cisplatin-induced nephrotoxicity. Our study provides a basis and rationale for the inhibition of cisplatin-induced nephrotoxicity by food-derived nutrients.

Selenium-enriched plant foods: Selenium accumulation, speciation, and health functionality

Selenium (Se) is an essential element for maintaining human health. The biological effects and toxicity of Se compounds in humans are related to their chemical forms and consumption doses. In general, organic Se species, including selenoamino acids such as selenomethionine (SeMet), selenocystine (SeCys₂), and Se-methylselenocysteine (MSC), could provide greater bioactivities with less toxicity compared to those inorganics including selenite (Se IV) and selenate (Se VI). Plants are vital sources of organic Se because they can accumulate inorganic Se or metabolites and store them as organic Se forms. Therefore, Se-enriched plants could be applied as human food to reduce deficiency problems and deliver health benefits. This review describes the recent studies on the enrichment of Se-containing plants in particular Se accumulation and speciation, their functional properties related to human health, and future perspectives for developing Se-enriched foods. Generally, Se's concentration and chemical forms in plants are determined by the accumulation ability of plant species. Brassica family and cereal grains have excessive accumulation capacity and store major organic Se compounds in their cells compared to other plants. The biological properties of Se-enriched plants, including antioxidant, anti-diabetes, and anticancer activities, have significantly presented in both in vitro cell culture models and in vivo animal assays. Comparatively, fewer human clinical trials are available. Scientific investigations on the functional health properties of Se-enriched edible plants in humans are essential to achieve in-depth information supporting the value of Se-enriched food to humans.

Amelioration Strategies for Silver Diamine Fluoride: Moving from Black to White

Topical cariostatic agents have become a reasonable alternative for managing dental caries in young children. Silver diamine fluoride (SDF) is a practical topical approach to arrest caries and avoid extensive and risky dental treatment. However, the literature demonstrates a parental hesitation towards accepting SDF because of black unaesthetic tooth discolouration following application. The rapid oxidation of ionic silver darkens demineralised tooth structure permanently. In this regard, nano-metallic antimicrobials could augment or substitute for silver, and thereby enhance SDF aesthetic performance. Recently, biomedical research has drawn attention to selenium nanoparticles (SeNPs) due to their antimicrobial, antioxidant, and antiviral potencies. Various in vitro studies have examined the effect of SeNPs on the virulence of bacteria. This narrative review explores practical issues when using SDF and suggests future directions to develop it, focusing on antimicrobial metals. Several methods are described that could be followed to reduce the discolouration concern, including the use of nanoparticles of silver, of silver fluoride, or of selenium or other metals with antimicrobial actions. There could also be value in using remineralising agents other than fluoride, such as NPs of hydroxyapatite. There could be variations made to formulations in order to lower the levels of silver and fluoride in the SDF or even to replace one or both of the silver and fluoride components completely. Moreover, since oxidation processes appear central to the chemistry of the staining, adding SeNPs which have antioxidant actions could have an anti-staining benefit; SeNPs could be used for their antimicrobial actions as well. Future research should address the topic of selenium chemistry to optimise how SeNPs would be used with or in place of ionic silver. Incorporating other antimicrobial metals as nanoparticles should also be explored, taking into account the optimal physicochemical parameters for each of these.

Intravenous Infusion of High Dose Selenite in End-Stage Cancer Patients: Analysis of Systemic Exposure to Selenite and Seleno-Metabolites

Cancer is one of the main causes of human death globally and novel chemotherapeutics are desperately required. As a simple selenium oxide, selenite is a very promising chemotherapeutic because of pronounced its dose-dependent tumor-specific cytotoxicity. We previously published a first-in-man systematic phase I clinical trial in patients with cancer (from IV to end-stage) (the SECAR trial) showing that selenite is safe and tolerable with an unexpectable high maximum tolerated dose (MTD) and short half-life. In the present study, we analyzed the selenium species in plasma samples, from the patients participating in the SECAR trial and from various time points and dose cohorts using LC-ICP-MS. In conclusion, selenite, selenosugars, and 1-2 unidentified peaks that did not correspond to any standard, herein denoted ui-selenium, were detected in the plasma. However, trimethylated selenium (trimethylselenonoium) was not detected. The unidentified ui-selenium was eluting close to the selenium-containing amino acids (selenomethionine and selenocysteine) but was not part of a protein fraction. Our data demonstrate that the major metabolite detected was selenosugar. Furthermore, the identification of selenite even long after the administration is remarkable and unexpected. The kinetic analysis did not support that dosing per the body surface area would reduce interindividual variability of the systemic exposure in terms of trough concentrations.

Antitumor effect of selenium-rich Brazil nuts and selenomethionine dietary supplementation on pre-existing 4T1 mammary tumor growth in mice

Selenium (Se) is an essential micronutrient known to play an important role in the antioxidant system that can potentially influence tumor growth. We aimed to investigate the effects of dietary Se supplementation after detection of 4T1 mammary tumor growth in BALB/c mice. Thirty female mice received subcutaneous inoculation of 4T1 cells. After five days, all animals presenting palpable tumors were randomly assigned to three groups: a control group (Se-control) receiving a diet with adequate Se (0.15 mg/kg) and two other groups that received Se-supplemented diets (1.4 mg/kg of total Se) with either Brazilian nuts (Se-Nuts) or selenomethionine (SeMet). Data were assessed by either One or Two-way ANOVA followed by Tukey's HSD or Bonferroni's post hoc tests, respectively. Both Se-supplemented diets reduced tumor volume from the thirteenth day of feeding compared with the Se-adequate (control) diet (p < 0.05). The SeMet group presented a higher Se blood concentration (p < 0.05) than the Se-control group, with the Se-Nuts group presenting intermediate values. Selenoprotein P gene expression in the liver was higher in the Se-Nuts group than in the Se-control group (p < 0.05), while the SeMet group presented intermediate expression. Dietary Se supplementation, starting after detection of 4T1 palpable lesions, reduced tumor volume in mice.

Scientific opinion on the tolerable upper intake level for selenium

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the tolerable upper intake level (UL) for selenium. Systematic reviews of the literature were conducted to identify evidence regarding excess selenium intake and clinical effects and potential biomarkers of effect, risk of chronic diseases and impaired neuropsychological development in humans. Alopecia, as an early observable feature and a well-established adverse effect of excess selenium exposure, is selected as the critical endpoint on which to base a UL for selenium. A lowest-observed-adverse-effect-level (LOAEL) of 330 μg/day is identified from a large randomised controlled trial in humans (the Selenium and Vitamin E Cancer Prevention Trial (SELECT)), to which an uncertainty factor of 1.3 is applied. A UL of 255 μg/day is established for adult men and women (including pregnant and lactating women). ULs for children are derived from the UL for adults using allometric scaling (body weight0.75). Based on available intake data, adult consumers are unlikely to exceed the UL, except for regular users of food supplements containing high daily doses of selenium or regular consumers of Brazil nuts. No risk has been reported with the current levels of selenium intake in European countries from food (excluding food supplements) in toddlers and children, and selenium intake arising from the natural content of foods does not raise reasons for concern. Selenium-containing supplements in toddlers and children should be used with caution, based on individual needs.

Selenocompounds and Sepsis-Redox Bypass Hypothesis: Part B-Selenocompounds in the Management of Early Sepsis

Significance: Endothelial barrier damage, which is in part caused by excess production of reactive oxygen, halogen and nitrogen species (ROHNS), especially peroxynitrite (ONOO^-), is a major event in early sepsis and, with leukocyte hyperactivation, part of the generalized dysregulated immune response to infection, which may even become a complex maladaptive state. Selenoenzymes have major antioxidant functions. Their synthesis is related to the need to limit deleterious oxidant redox cycling by small selenocompounds, which may be of therapeutic cytotoxic interest. Plasma selenoprotein-P is crucial for selenium transport from the liver to the tissues and for antioxidant endothelial protection, especially against ONOO^-. Above micromolar concentrations, sodium selenite (Na₂SeO₃) becomes cytotoxic, with a lower cytotoxicity threshold in activated cells, which has led to cancer research. Recent Advances: Plasma selenium (<2% of total body selenium) is mainly contained in selenoprotein-P, and concentrations decrease rapidly in the early phase of sepsis, because of increased selenoprotein-P binding and downregulation of hepatic synthesis and excretion. At low concentrations, Na₂SeO₃ acts as a selenium donor, favoring selenoprotein-P synthesis in physiology, but probably not in the acute phase of sepsis. Critical Issues: The cytotoxic effects of Na₂SeO₃ against hyperactivated leukocytes, especially the most immature forms that liberate ROHNS, may be beneficial, but they may also be harmful for activated endothelial cells. Endothelial protection against ROHNS by selenoprotein-P may reduce Na₂SeO₃ toxicity, which is increased in sepsis. Future Direction: The combination of selenoprotein-P for endothelial protection and the cytotoxic effects of Na₂SeO₃ against hyperactivated leukocytes may be a promising intervention for early sepsis. Antioxid. Redox Signal. 37, 998-1029.

Sodium selenite inhibits cervical cancer growth via ROS mediated AMPK/FOXO3a /GADD45a axis

Selenium is a trace element that has been shown to inhibit the growth of various cancer cell types. However, its role in cervical cancer and its underlying mechanisms remains largely unknown. Herein, we explored the anti-cervical cancer effect of selenium and its potential mechanisms through xenograft and in vitro experiments. HeLa cell xenografts in female nude mice showed tumor growth retardation, with no obvious liver and kidney toxicity, after being intraperitoneally injected with 3 mg/kg sodium selenite (SS) for 14 days. Compared to the control group, selenium levels in the tumor tissue increased significantly after SS treatment. In vitro experiments, SS inhibited the viability of HeLa and SiHa cells, blocked the cell cycle at the S phase, and enhanced apoptosis. RNA-sequencing, Kyoto encyclopedia of genes and genomes pathway analysis showed that forkhead box protein O (FOXO) was a key regulatory signaling pathway for SS to exhibit anticancer effects. Gene Ontology analysis filtered multiple terms associated with apoptosis, anti-proliferation, and cell cycle arrest. Further research revealed that SS increased intracellular reactive oxygen species (ROS) and impaired mitochondrial function, which activated adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) via phosphorylation at Thr172, resulting in activation of FOXO3a and its downstream growth arrest and DNA damage-inducible alpha (GADD45a). In summary, SS exhibited anti-cervical cancer effects, and their mechanisms may be that SS is involved in inducing cell cycle arrest and potentiating cell apoptosis caused by ROS-dependent activation of the AMPK/FOXO3a/GADD45a axis.

Voyage of selenium from environment to life: Beneficial or toxic?

Selenium (Se), a naturally occurring metalloid, is an essential micronutrient for life as it is incorporated as selenocysteine in proteins. Although beneficial at low doses, Se is hazardous at high concentrations and poses a serious threat to various ecosystems. Due to this contrasting 'dual' nature, Se has garnered the attention of researchers wishing to unravel its puzzling properties. In this review, we describe the impact of selenium's journey from environment to diverse biological systems, with an emphasis on its chemical advantage. We describe the uneven distribution of Se and how this affects the bioavailability of this element, which, in turn, profoundly affects the habitat of a region. Once taken up, the subsequent incorporation of Se into proteins as selenocysteine and its antioxidant functions are detailed here. The causes of improved protein function due to the incorporation of redox-active Se atom (instead of S) are examined. Subsequently, the reasons for the deleterious effects of Se, which depend on its chemical form (organo-selenium or the inorganic forms) in different organisms are elaborated. Although Se is vital for the function of many antioxidant enzymes, how the pro-oxidant nature of Se can be potentially exploited in different therapies is highlighted. Furthermore, we succinctly explain how the presence of Se in biological systems offsets the toxic effects of heavy metal mercury. Finally, the different avenues of research that are fundamental to expand our understanding of selenium biology are suggested.

Therapeutic Benefits of Selenium in Hematological Malignancies

Supplementing chemotherapy and radiotherapy with selenium has been shown to have benefits against various cancers. This approach has also been shown to alleviate the side effects associated with standard cancer therapies and improve the quality of life in patients. In addition, selenium levels in patients have been correlated with various cancers and have served as a diagnostic marker to track the efficiency of treatments or to determine whether these selenium levels cause or are a result of the disease. This concise review presents a survey of the selenium-based literature, with a focus on hematological malignancies, to demonstrate the significant impact of selenium in different cancers. The anti-cancer mechanisms and signaling pathways regulated by selenium, which impart its efficacious properties, are discussed. An outlook into the relationship between selenium and cancer is highlighted to guide future cancer therapy development.

Ferroptosis and Apoptosis Are Involved in the Formation of L-Selenomethionine-Induced Ocular Defects in Zebrafish Embryos

Selenium is an essential trace element for humans and other vertebrates, playing an important role in antioxidant defense, neurobiology and reproduction. However, the toxicity of excessive selenium has not been thoroughly evaluated, especially for the visual system of vertebrates. In this study, fertilized zebrafish embryos were treated with 0.5 µM L-selenomethionine to investigate how excessive selenium alters zebrafish eye development. Selenium-stressed zebrafish embryos showed microphthalmia and altered expression of genes required for retinal neurogenesis. Moreover, ectopic proliferation, disrupted mitochondrial morphology, elevated ROS-induced oxidative stress, apoptosis and ferroptosis were observed in selenium-stressed embryos. Two antioxidants—reduced glutathione (GSH) and N-acetylcysteine (NAC)—and the ferroptosis inhibitor ferrostatin (Fer-1) were unable to rescue selenium-induced eye defects, but the ferroptosis and apoptosis activator cisplatin (CDDP) was able to improve microphthalmia and the expression of retina-specific genes in selenium-stressed embryos. In summary, our results reveal that ferroptosis and apoptosis might play a key role in selenium-induced defects of embryonic eye development. The findings not only provide new insights into selenium-induced cellular damage and death, but also important implications for studying the association between excessive selenium and ocular diseases in the future.

Novel microtubule inhibitor SQ overcomes multidrug resistance in MCF-7/ADR cells by inhibiting BCRP function and mediating apoptosis

The occurrence of multidrug resistance (MDR) is one of the impediments in the clinical treatment of breast cancer, and MDR breast cancer has abnormally high breast cancer resistance protein (BCRP/ABCG2) expression. However, there are currently no clinical drugs that inhibit this target. Our previous study found that 2-Methoxy-5((3,4,5-trimethosyphenyl)seleninyl) phenol (SQ0814061/SQ), a small molecule drug with low toxicity to normal tissues, could target microtubules, inhibit the proliferation of breast cancer, and reduce its migration and invasion abilities. However, the effect and the underlying mechanism of SQ on MDR breast cancers are still unknown. Therefore, in this study, we investigated the effect of SQ on adriamycin-resistant MCF-7 (MCF-7/ADR) cells and explored the underlying mechanism. The MTT assay showed that SQ had potent cytotoxicity to MCF-7/ADR cells. In particular, the results of western blot and flow cytometry proved that SQ could effectively inhibit the expression of BCRP in MCF-7/ADR cells to decrease its drug delivery activity. In addition, SQ could block the cell cycle at G2/M phase in parental and MCF-7/ADR cells, thereby mediating cell apoptosis, which was related with the inhibition of PI3K-Akt-MDM2 pathway. Taken together, our findings indicate that SQ overcomes multidrug resistance in MCF-7/ADR cells by inhibiting BCRP function and mediating apoptosis through PI3K-Akt-MDM2 pathway inhibition.

Antitumor Effects of Selenium

Functions of selenium are diverse as antioxidant, anti-inflammation, increased immunity, reduced cancer incidence, blocking tumor invasion and metastasis, and further clinical application as treatment with radiation and chemotherapy. These functions of selenium are mostly related to oxidation and reduction mechanisms of selenium metabolites. Hydrogen selenide from selenite, and methylselenol (MSeH) from Se-methylselenocyteine (MSeC) and methylseleninicacid (MSeA) are the most reactive metabolites produced reactive oxygen species (ROS); furthermore, these metabolites may involve in oxidizing sulfhydryl groups, including glutathione. Selenite also reacted with glutathione and produces hydrogen selenide via selenodiglutathione (SeDG), which induces cytotoxicity as cell apoptosis, ROS production, DNA damage, and adenosine-methionine methylation in the cellular nucleus. However, a more pronounced effect was shown in the subsequent treatment of sodium selenite with chemotherapy and radiation therapy. High doses of sodium selenite were effective to increase radiation therapy and chemotherapy, and further to reduce radiation side effects and drug resistance. In our study, advanced cancer patients can tolerate until 5000 μg of sodium selenite in combination with radiation and chemotherapy since the half-life of sodium selenite may be relatively short, and, further, selenium may accumulates more in cancer cells than that of normal cells, which may be toxic to the cancer cells. Further clinical studies of high amount sodium selenite are required to treat advanced cancer patients.

Hepatoprotective, antioxidant and anti-inflammatory potentials of Vit-E/C@SeNPs in rats: Synthesis, characterization, biochemical, radio-biodistribution, molecular and histopathological studies

This study aimed to synthesize a nano-structure between selenium, Vit. C, and Vit. E (Vit-E/C@SeNPs) as a promising protective and therapeutic agent for hepatocellular carcinoma. Vit-E/C@SeNPs were characterized using TEM and DLS and its zetapotential was measured to evaluate its stability. DPPH assay and SRB test were performed to estimate its antioxidant capacity and cytotoxicity, respectively. A radiosynthesis of ^99mTc-Vit-E/C@SeNPs was done for further in-vivo pharmacokinetic studies on normal and solid tumor induced mice. Further, in-vivo studies were conducted to investigate Vit-E/C@SeNPs efficacy against hepatocellular damage in Wistar albino rats induced by diethylnitrosamine (DEN) / Carbon Tetra chloride (CCl₄). The synthesis results showed spherical Vit-E/C@SeNPs with core size of 50 nm, radical scavenging activity (%RSC) of 75.9%, and IC₅₀ of 27.9 µg/ml. The biochemical analysis results showed that the lower liver function biomarker values (ALT, AST, ALP, total bilirubin and GGT) has gone for the Vit-E/C@SeNPs prevention and treated group, which also showed significant depletion of liver tissue l-MDA, and obvious increase in GSH concentration and CAT activity and marked improvement in the histological feature of liver tissue. Additionally, a significant up-regulation of mRNA gene expression levels of inflammatory gene (TGFβ1, NFκB, iNOS, PPAR-γ and TNFα) and Apoptotic gene (P53) were determined by using Quantitative real-time PCR (qPCR). The values down regulate and tend to normal in prevention and control group. All of these introduce Vit-E/C@SeNPs as a promising agent as protective and therapeutic agent against DEN/ CCl₄-induced hepatocellular damage (Hepatocellular carcinoma).

Drug delivery carriers with therapeutic functions

Design of micro- or nanocarriers for drug delivery has primarily been focused on properties such as hydrophobicity, biodegradability, size, shape, surface charge, and toxicity, so that they can achieve optimal delivery with respect to drug loading, release kinetics, biodistribution, cellular uptake, and biocompatibility. Incorporation of stimulus-sensitive moieties into the carriers would lead to "smart" delivery systems. A further evolution would be to endow the carrier with a therapeutic function such that it no longer serves as a mere passive entity to release the drug at the target tissue but can be viewed as a therapeutic agent in itself. In this review, we will discuss recent and ongoing efforts over the past decade to design therapeutic drug carriers that confer a biological benefit, including ROS scavenging or generating, pro- or anti-inflammatory, and immuno-evasive properties, to enhance the overall therapeutic efficacy of the delivery systems.

A U-Shaped Relationship Between Selenium Concentrations and All-Cause or Cardiovascular Mortality in Patients With Hypertension

Background: Given the antioxidant activity of selenium, it has been reported benefits for blood pressure control and hypertension prevention, but few studies have investigated the association between serum selenium with mortality in hypertensive population. Methods: All participants with hypertension aged ≥18 years at baseline were recruited from the National Health and Nutritional Examination Surveys (NHANES) 2003-2004, and followed for mortality through December 31, 2015. Subjects were categorized by quartiles of serum selenium (Q1: ≤124 μg/L, Q2: 125-135 μg/L, Q3: 136-147 μg/L, Q4: ≥148 μg/L). Multivariate Cox regression were implemented to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Restricted cubic spline analysis and two-piecewise linear regression were used to evaluate the relationship of serum selenium with mortality. Survival curves were used to depict cause-specific mortalities. Results: A total of 929 participants (52.53% were male) were eligible for the current study with the average age of 63.10 ± 12.59 years. There were 307 deaths occurred including 56 cardiovascular death events during the mean follow-up time of 121.05 ± 40.85 months. A U-shaped association was observed between serum selenium and all-cause or cardiovascular mortality. In fully adjusted model, comparisons among quartiles revealed that risks of all-cause [HR (95%CI), 0.57 (0.39-0.81)] and cardiovascular death [HR (95%CI), 0.33 (0.13-0.86)] were lower in Q3. The nadir mortality of all-cause and cardiovascular was occurred at the serum selenium level of 136 μg/L and 130 μg/L, respectively. Conclusion: Serum selenium concentration showed a U-shaped association with all-cause and cardiovascular mortality.

Selenomethionine alleviates LPS-induced JNK/NLRP3 inflammasome-dependent necroptosis by modulating miR-15a and oxidative stress in chicken lungs

Selenium (Se) was involved in many physiological processes in humans and animals. microRNAs (miRNAs) also played important roles in lung diseases. However, the regulatory mechanism of miRNA in chicken lungs and the mechanism of lipopolysaccharide (LPS)-induced pneumonia remained unclear. To further study these mechanisms, we established a supplement of selenomethionine (SeMet) and/or LPS-treated chicken model and a cell model of LPS and/or high and low expression of miR-15a in chicken hepatocellular carcinoma (LMH) cells. We detected the expression of some selenoproteins, p-c-Jun N-terminal kinase (JNK), nod-like receptor protein 3 (NLRP3), caspase1, receptor-interacting serine-threonine kinase 1 (RIPK1), receptor-interacting serine-threonine kinase 3 (RIPK3), mixed lineage kinase domain-like pseudokinase (MLKL), miR-15a and oxidative stress kits. Additionally, we observed the morphology of lungs by H.E. staining in vitro. The results indicated that necroptosis occurred in LPS-treated chicken and LMH cells. Moreover, LPS stimulation inhibited miR-15a, and increased the expression of JNK, NLRP3, caspase1, RIPK1, RIPK3, MLKL. We also found that LPS treatment not only increased the content of H2O2 and MDA in the lungs but also increased the activities of iNOS and CAT and the content of GSH decreased. Conclusion: SeMet could reduce the oxidative damage and activate NLRP3 inflammasome reaction by stimulating miR-15a/JNK, thus reduced the pulmonary necroptosis induced by LPS.

Small molecule selenium-containing compounds: Recent development and therapeutic applications

Selenium (Se) is an essential micronutrient of organism and has important function. It participates in the functions of selenoprotein in several manners. In recent years, Se has attracted much attention because of its therapeutic potential against several diseases. Many natural and synthetic organic Se-containing compounds were studied and explored for the treatment of cancer and other diseases. Studies have showed that incorporation of Se atom into small molecules significantly enhanced their bioactivities. In this paper, according to different applications and structural characteristics, the research progress and therapeutic application of Se-containing compounds are reviewed, and more than 110 Se-containing compounds were selected as representatives which showed potent activities such as anticancer, antioxidant, antifibrolytic, antiparasitic, antibacterial, antiviral, antifungal and central nervous system related effects. This review is expected to provide a basis for further study of new promising Se-containing compounds.

Utilization of redox modulating small molecules that selectively act as pro-oxidants in cancer cells to open a therapeutic window for improving cancer therapy

There is a rapidly growing body of literature supporting the notion that differential oxidative metabolism in cancer versus normal cells represents a metabolic frailty that can be exploited to open a therapeutic window into cancer therapy. These cancer cell-specific metabolic frailties may be amenable to manipulation with non-toxic small molecule redox active compounds traditionally thought to be antioxidants. In this review we describe the potential mechanisms and clinical applicability in cancer therapy of four small molecule redox active agents: melatonin, vitamin E, selenium, and vitamin C. Each has shown the potential to have pro-oxidant effects in cancer cells while retaining antioxidant activity in normal cells. This dichotomy can be exploited to improve responses to radiation and chemotherapy by opening a therapeutic window based on a testable biochemical rationale amenable to confirmation with biomarker studies during clinical trials. Thus, the unique pro-oxidant/antioxidant properties of melatonin, vitamin E, selenium, and vitamin C have the potential to act as effective adjuvants to traditional cancer therapies, thereby improving cancer patient outcomes.

Hepatocellular-Targeted mRNA Delivery Using Functionalized Selenium Nanoparticles In Vitro

Selenium's (Se) chemopreventative and therapeutic properties have attracted attention in nanomedicine. Se nanoparticles (SeNPs) retain these properties of Se while possessing lower toxicity and higher bioavailability, potentiating their use in gene delivery. This study aimed to formulate SeNPs for efficient binding and targeted delivery of FLuc-mRNA to hepatocellular carcinoma cells (HepG2) in vitro. The colorectal adenocarcinoma (Caco-2) and normal human embryonic kidney (HEK293) cells that do not have the asialoorosomucoid receptor (ASGPR) were utilized for comparison. SeNPs were functionalized with chitosan (CS), polyethylene glycol (PEG), and lactobionic acid (LA) for ASGPR targeting on HepG2 cells. Nanoparticles (NPs) and their mRNA-nanocomplexes were characterized by Fourier transform infra-red (FTIR) and UV-vis spectroscopy, transmission electron microscopy (TEM), and nanoparticle tracking analysis (NTA). Gel and fluorescence-based assays assessed the NP's ability to bind and protect FLuc-mRNA. Cytotoxicity was determined using the -(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, while transgene expression was evaluated using the luciferase reporter gene assay. All NPs appeared spherical with sizes ranging 57.2-130.0 nm and zeta potentials 14.9-31.4 mV. NPs bound, compacted, and protected the mRNA from nuclease digestion and showed negligible cytotoxicity in vitro. Targeted gene expression was highest in the HepG2 cells using the LA targeted NPs. These NPs portend to be efficient nanocarriers of nucleic acids and warrant further investigation.

The solvent and treatment regimen of sodium selenite cause its effects to vary on the radiation response of human bronchial cells from tumour and normal tissues

Sodium selenite is often given to moderate the side effects of cancer therapy to enhance the cellular defence of non-cancerous cells. To determine whether sodium selenite during radiotherapy protects not only normal cells but also cancer cells, which would imply a reduction of the desired effect of irradiation on tumour during radiotherapy, the effect of the combined treatment of irradiation and sodium selenite was investigated. Human bronchial cells from carcinoma (A549) and normal tissue (BEAS-2B) were treated with sodium selenite and effects on growth and in combination with radiation on metabolic activity and cell cycle distribution were studied. The influence on radiosensitivity was determined via colony forming assays using different solvents of sodium selenite and treatment schedules. It was shown that sodium selenite inhibits growth and influences cell cycle distribution of both normal and tumour cells. Metabolic activity of normal cells decreased more rapidly compared to that of cancer cells. The influence of sodium selenite on radiation response depended on the different treatment schedules and was strongly affected by the solvent of the agent. It could be shown that the effect of sodium selenite on radiation response is strongly dependent on the respective experimental in vitro conditions and ranges from lead to an initially suspected but ultimately no real radioprotection to radiosensitizing up to no effect in one and the same cell line. This might be a reason for controversially described cell responses to radiation under the influence of sodium selenite in studies so far.

Apoptosis oxidative damage-mediated and antiproliferative effect of selenylated imidazo[1,2-a]pyridines on hepatocellular carcinoma HepG2 cells and in vivo

Imidazo[1,2-a]pyridines (IP) and organoselenium compounds have been widely exploited in medicinal chemistry due to their pharmacological activities. Hepatocellular carcinoma (HCC) has few treatment options, and unfortunately, the prognosis is poor. Thus, the development of novel therapeutic drugs is urgent. The present study aimed at evaluating the antitumor mechanism of selenylated IP against HepG2 cells and in vivo. The selenylated IP named IP-Se-06 (3-((2-methoxyphenyl)selanyl)-7-methyl-2-phenylimidazol[1,2-a]pyridine) showed high cytotoxicity against HepG2 cells (half-maximal inhibitory concentration [IC₅₀ ] = 0.03 µM) and selectivity for this tumor cell line. At nontoxic concentration, IP-Se-06 decreased the protein levels of Bcl-xL and increased the levels of p53, leading to inhibition of cell proliferation and apoptosis. This compound decreased the level of extracellular signal-regulated kinase 1/2 protein and changed the levels of proteins involved in the drive of the cell cycle, tumor growth, and survival (cyclin B1, cyclin-dependent kinase 2). In addition, IP-Se-06 decreased the number of cells in the S phase. In addition, IP-Se-06 led to increased generation of reactive oxygen species, changed antioxidant defenses, and caused DNA fragmentation. Finally, IP-Se-06 significantly inhibited the growth of Ehrlich ascites tumors in mice, increased survival time, and inhibited angiogenesis. Therefore, IP-Se-06 may be an important compound regarding the development of a therapeutic drug for HCC treatment.

Small molecules regulating reactive oxygen species homeostasis for cancer therapy

Elevated intracellular reactive oxygen species (ROS) and antioxidant defense systems have been recognized as one of the hallmarks of cancer cells. Compared with normal cells, cancer cells exhibit increased ROS to maintain their malignant phenotypes and are more dependent on the "redox adaptation" mechanism. Thus, there are two apparently contradictory but virtually complementary therapeutic strategies for the regulation of ROS to prevent or treat cancer. The first strategy, that is, chemoprevention, is to prevent or reduce intracellular ROS either by suppressing ROS production pathways or by employing antioxidants to enhance ROS clearance, which protects normal cells from malignant transformation and inhibits the early stage of tumorigenesis. The second strategy is the ROS-mediated anticancer therapy, which stimulates intracellular ROS to a toxicity threshold to activate ROS-induced cell death pathways. Therefore, targeting the regulation of intracellular ROS-related pathways by small-molecule candidates is considered to be a promising treatment for tumors. We herein first briefly introduce the source and regulation of ROS, and then focus on small molecules that regulate ROS-related pathways and show efficacy in cancer therapy from the perspective of pharmacophores. Finally, we discuss several challenges in developing cancer therapeutic agents based on ROS regulation and propose the direction of future development.

Seleno-l-methionine suppresses copper-enhanced zinc-induced neuronal cell death via induction of glutathione peroxidase

Excessive zinc ion (Zn²⁺) release is induced in pathological situations and causes neuronal cell death. Previously, we have reported that copper ions (Cu²⁺) markedly exacerbated Zn²⁺-induced neuronal cell death by potentiating oxidative stress, the endoplasmic reticulum (ER) stress response, and the activation of the c-Jun amino-terminal kinase (JNK) signaling pathway. In contrast, selenium (Se), an essential trace element, and amino acids containing selenium (such as seleno-l-methionine) have been reported to inhibit stress-induced neuronal cell death and oxidative stress. Thus, we investigated the effect of seleno-l-methionine on Cu²⁺/Zn²⁺-induced neuronal cell death in GT1-7 cells. Seleno-l-methionine treatment clearly restored the Cu²⁺/Zn²⁺-induced decrease in the viable cell number and attenuated the Cu²⁺/Zn²⁺-induced cytotoxicity. Accordingly, the levels of ER stress-related factors (especially, CHOP and GADD34) and of phosphorylated JNK increased upon CuCl₂ and ZnCl₂ co-treatment, whereas pre-treatment with seleno-l-methionine significantly suppressed these upregulations. Analysis of reactive oxygen species (ROS) as upstream factors of these pathways revealed that Cu²⁺/Zn²⁺-induced ROS production was clearly suppressed by seleno-l-methionine treatment. Finally, we found that seleno-l-methionine induced the antioxidative protein, glutathione peroxidase. Taken together, our findings suggest that seleno-l-methionine suppresses Cu²⁺/Zn²⁺-induced neuronal cell death and oxidative stress via induction of glutathione peroxidase. Thus, we think that seleno-l-methionine may help prevent refractory neurological diseases.

Suppression of CXCL-1 Could Restore Necroptotic Pathway in Chronic Lymphocytic Leukemia

Purpose

To clarify the role of different cytokines and selenite in the defective necroptotic pathway of chronic lymphocytic leukemia (CLL).

Patients and Methods

We randomly collected the peripheral blood samples of 11 untreated CLL patients and 10 healthy volunteers, and then separated B lymphocytes from peripheral blood. Then, real-time polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA) and Western Blot were performed to detect the expression of different cytokines, including CXC-motif chemokine ligand 1 (CXCL-1). Finally, we used flow cytometry to analyze the percentage of surviving cells to figure out whether CLL cells or normal B lymphocytes underwent necroptosis.

Results

1) The high expression of CXCL-1 was seen in CLL cells compared with normal B lymphocytes (p = 0.0001, adjusted p =0.0012); 2) The downregulation of CXCL-1 was shown in normal B lymphocytes after induction by TNF-α and z-VAD; 3) CLL cells could restore necroptosis induced by TNF-α and z-VAD after knockdown of CXCL-1; 4) The transcriptional and translational expression of LEF-1 were downregulated after the knockdown of CXCL-1 in CLL cells; 5. 3.2μM selenite could help CLL cells restore necroptosis (p = 0.0102) and inhibit the transcriptional and translational expression of CXCL-1.

Conclusion

CXCL-1 played an important role in the defective necroptosis of CLL cells and regulated the expression of LEF-1. Selenite could inhibit the expression of CXCL-1 and help CLL cells restore necroptosis together with TNF-α and z-VAD. Selenite might be the potential medication of CLL in the future.

Selenium Nanoparticles Synthesized Using Pseudomonas stutzeri (MH191156) Show Antiproliferative and Anti-angiogenic Activity Against Cervical Cancer Cells

Purpose

Selenium nanoparticles (SeNP) have several applications in the field of biotechnology, including their use as anti-cancer drugs. The purpose of the present study is to analyze the efficacy of green synthesis on the preparation of SeNP and its effect on their anti-cancer properties.

Methods

A bacterial strain isolated from a freshwater source was shown to efficiently synthesize SeNP with potential therapeutic properties. The quality and stability of the NP were studied by scanning electron microscopy, X-ray diffraction, zeta-potential and FTIR analysis. A cost-effective medium formulation from biowaste having 6% banana peel extract enriched with 0.25 mM tryptophan was used to synthesize the NP. The NP after optimization was used to analyze their anti-tumor and anti-angiogenic activity. For this purpose, first, the cytotoxicity of the NP against cancer cells was analyzed by MTT assay and then chorioallantoic membrane assay was performed to assess anti-angiogenic activity. Further, cell migration assay and clonogenic inhibition assay were performed to test the anti-tumor properties of SeNP. To assess the cytotoxicity of SeNP on healthy RBC, hemolysis assay was performed.

Results

The strain identified as Pseudomonas stutzeri (MH191156) produced phenazine carboxylic acid, which aids the conversion of Se oxyanions to reduced NP state, resulting in particles in the size range of 75 nm to 200 nm with improved stability and quality of SeNP, as observed by zeta (ξ) potential of the particles which was found to be −46.2 mV. Cytotoxicity of the SeNP was observed even at low concentrations such as 5 µg/mL against cervical cancer cell line, ie, HeLa cells. Further, neovascularization was inhibited by upto 30 % in CAMs of eggs coinoculated with SeNp when compared with untreated controls, indicating significant anti-angiogenic activity of SeNP. The NP also inhibited the invasiveness of HeLa cells as observed by decreased cell migration and clonogenic proliferation. These observations indicate significant anti-tumor and anti-angiogenic activity of the SeNP in cervical cancer cells.

Conclusion

P. stutzeri (MH191156) is an efficient source of Se NP production with potential anti-angiogenic and anti-tumor properties, particularly against cervical cancer cells.

Poly(selenoviologen)-Assembled Upconversion Nanoparticles for Low-Power Single-NIR Light-Triggered Synergistic Photodynamic and Photothermal Antibacterial Therapy

The development of a highly effective photosensitizer (PS) that can be activated with a low-power single light is a pressing issue. Herein, we report a PS for synergistic photodynamic and photothermal therapy constructed through self-assembly of poly(selenoviologen) on the surface of core-shell NaYF₄:Yb/Tm@NaYF₄ upconversion nanoparticles. The hybrid UCNPs/PSeV PS showed strong ROS generation ability and high photothermal conversion efficiency (∼52.5%) under the mildest reported-to-date irradiation conditions (λ = 980 nm, 150 mW/cm², 4 min), leading to a high efficiency in killing methicillin-resistant Staphylococcus aureus (MRSA) both in vitro and in vivo. Remarkably, after intravenous injection, the reported PS accumulated preferentially in deep MRSA-infected tissues and achieved an excellent therapeutic index. This PS design realizes a low-power single-NIR light-triggered synergistic phototherapy and provides a simple and versatile strategy to develop safe clinically translatable agents for efficient treatment of deep tissue bacterial inflammations.

Understanding the Redox Biology of Selenium in the Search of Targeted Cancer Therapies

Selenium (Se) is an essential trace nutrient required for optimal human health. It has long been suggested that selenium has anti-cancer properties. However, clinical trials have shown inconclusive results on the potential of Se to prevent cancer. The suggested role of Se in the prevention of cancer is centered around its role as an antioxidant. Recently, the potential of selenium as a drug rather than a supplement has been uncovered. Selenium compounds can generate reactive oxygen species that could enhance the treatment of cancer. Transformed cells have high oxidative distress. As normal cells have a greater capacity to meet oxidative challenges than tumor cells, increasing the flux of oxidants with high dose selenium treatment could result in cancer-specific cell killing. If the availability of Se is limited, supplementation of Se can increase the expression and activities of Se-dependent proteins and enzymes. In cell culture, selenium deficiency is often overlooked. We review the importance of achieving normal selenium biology and how Se deficiency can lead to adverse effects. We examine the vital role of selenium in the prevention and treatment of cancer. Finally, we examine the properties of Se-compounds to better understand how each can be used to address different research questions.

Selenium and selenoproteins: it's role in regulation of inflammation

Abstract

Selenium is an essential immunonutrient which holds the human’s metabolic activity with its chemical bonds. The organic forms of selenium naturally present in human body are selenocysteine and selenoproteins. These forms have a unique way of synthesis and translational coding. Selenoproteins act as antioxidant warriors for thyroid regulation, male-fertility enhancement, and anti-inflammatory actions. They also participate indirectly in the mechanism of wound healing as oxidative stress reducers. Glutathione peroxidase (GPX) is the major selenoprotein present in the human body, which assists in the control of excessive production of free radical at the site of inflammation. Other than GPX, other selenoproteins include selenoprotein-S that regulates the inflammatory cytokines and selenoprotein-P that serves as an inducer of homeostasis. Previously, reports were mainly focused on the cellular and molecular mechanism of wound healing with reference to various animal models and cell lines. In this review, the role of selenium and its possible routes in translational decoding of selenocysteine, synthesis of selenoproteins, systemic action of selenoproteins and their indirect assimilation in the process of wound healing are explained in detail. Some of the selenium containing compounds which can acts as cancer preventive and therapeutics are also discussed. These compounds directly or indirectly exhibit antioxidant properties which can sustain the intracellular redox status and these activities protect the healthy cells from reactive oxygen species induced oxidative damage. Although the review covers the importance of selenium/selenoproteins in wound healing process, still some unresolved mystery persists which may be resolved in near future.

Graphic abstract

The emerging role of paraptosis in tumor cell biology: Perspectives for cancer prevention and therapy with natural compounds

Standard anti-cancer therapies promote tumor growth suppression mainly via induction of apoptosis. However, in most cases cancer cells acquire the ability to escape apoptotic cell death, thus becoming resistant to current treatments. In this setting, the interest in alternative cell death modes has recently increased. Paraptosis is a new form of programmed cell death displaying endoplasmic reticulum (ER) and/or mitochondria dilation, generally due to proteostasis disruption or redox and ion homeostasis alteration. Recent studies have highlighted that several natural compounds can trigger paraptosis in different tumor cell lines. Here, we review the molecular mechanisms underlying paraptotic cell death, as well as the natural products inducing this kind of cell death program. A better understanding of paraptosis should facilitate the development of new therapeutic strategies for cancer prevention and treatment.

Small-molecule compounds target paraptosis to improve cancer therapy

According to its different occurrence mechanism, programmed cell death (PCD) is divided into apoptosis, autophagy, necrosis, paraptosis and so on. Paraptosis is morphologically different from apoptosis and autophagy, which exhibit cytoplasmic vacuolation derived from the ER, independent of caspase, absence of apoptotic morphology. Recent researches have implied that a variety of small molecule compounds, such as celastrol, curcumin, can induce paraptosis-associated cell death as the reagent to enhance anti-cancer activity. A better understanding of paraptosis will lay the foundation to develop new therapeutic strategies to treat human cancers that make full use of small-molecule compounds.

Selenium cytotoxicity in Tetrahymena thermophila: New clues about its biological effects and cellular resistance mechanisms

Selenium is an essential micronutrient but at high concentrations can produce severe cytotoxicity and genomic damage. We have evaluated the cytotoxicity, ultrastructural and mitochondrial alterations of the two main selenium inorganic species; selenite and selenate, in the eukaryotic microorganism Tetrahymena thermophila. In this ciliate, selenite is more toxic than selenate. Their LC₅₀ values were calculated as 27.65 μM for Se(IV) and 56.88 mM for Se(VI). Significant levels of peroxides/hydroperoxides are induced under low-moderate selenite or selenate concentrations. Se(VI) exposures induce an immediate mitochondrial membrane depolarization. Selenium treated cells show an intense vacuolization and some of them present numerous discrete and small electrondense particles, probably selenium deposits. Mitochondrial fusion, an intense swelling in peripheral mitochondria and mitophagy are detected in selenium treated cells, especially in those exposed to Se (IV). qRT-PCR analysis of diverse genes, encoding relevant antioxidant enzymes or other proteins, like metallothioneins, involved in an environmental general stress response, have shown that they may be crucial against Se(IV) and/or Se (VI) cytotoxicity.

Redox biology of regulated cell death in cancer: A focus on necroptosis and ferroptosis

Redox changes and generation of reactive oxygen species (ROS) are part of normal cell metabolism. While low ROS levels are implicated in cellular signaling pathways necessary for survival, higher levels play major roles in cancer development as well as cell death signaling and execution. A role for redox changes in apoptosis has been long established; however, several new modalities of regulated cell death have been brought to light, for which the importance of ROS production as well as ROS source and targets are being actively investigated. In this review, we summarize recent findings on the role of ROS and redox changes in the activation and execution of two major forms of regulated cell death, necroptosis and ferroptosis. We also discuss the potential of using modulators of these two forms of cell death to exacerbate ROS as a promising anticancer therapy.

Suppression of proliferation and activation of cell death by sodium selenite involves mitochondria and lysosomes in chemoresistant bladder cancer cells

The specific effects of sodium selenite (selenite) on a chemoresistant human bladder cancer cell line RT-112/D21 were investigated during 72 h. Selenite at low concentration of 2.5 μmol (otherwise tolerated in normal urothelial cells UROtsa) suppressed growth and proliferation of the tested cancer cells via induced oxidative stress. Selenite further altered mitochondrial functions (i.e. decreased mitochondrial membrane potential, increased production of superoxide and reduced ATP synthesis), disrupted lysosomal membranes and activated autophagy. These changes in selenite-exposed cells ultimately resulted in their demise via necrosis and other cell death modality displaying heterotypic apoptotic and autophagic features.

Strategies for the development of selenium-based anticancer drugs

Many experimental models demonstrated that inorganic and organic selenium (Se) compounds may have an anticancer activity. However, large clinical studies failed to demonstrate that Se supplementations may prevent the outcome of cancers. Moreover, there are few randomized trials in cancer patients and there is not yet any Se compound recognized as anticancer drug. There is still a need to develop new Se compounds with new strategies. For that, it may be necessary to consider that Se compounds may have a dual role, either as anti-oxidant or as pro-oxidant. Experimental studies demonstrated that it is as pro-oxidant that Se compounds have anticancer effects, even though cancer cells have a pro-oxidant status. The oxidative status differs according to the type of cancer, the stage of the disease and to other parameters. We propose to adapt the doses of the Se compounds to markers of the oxidative stress, but also to markers of angiogenesis, which is strongly related with the oxidative status. A dual role of Se on angiogenesis has also been noted, either as pro-angiogenesis or as anti-angiogenesis. The objective for the development of new Se compounds, having a great selectivity on cancer cells, could be to try to normalize these oxidative and angiogenic markers in cancer patients, with an individual adaptation of doses.