Selenium in the prevention of human cancers

Exploring the Anti-Inflammatory and Antioxidative Potential of Selenium Nanoparticles Biosynthesized by Lactobacillus casei 393 on an Inflamed Caco-2 Cell Line

Selenium (Se) plays a crucial role in modulating inflammation and oxidative stress within the human system. Biogenic selenium nanoparticles (SeNPs) synthesized by Lactobacillus casei (L. casei) exhibit anti-inflammatory and anti-oxidative properties, positioning them as a promising alternative to traditional supplements characterized by limited bioavailability. With this context in mind, this study investigates the impact of selenium and L. casei in ameliorating inflammation and oxidative stress using a cell line model. The study is centered on the biosynthesis of selenium nanoparticles (SeNPs) by L. casei 393 under anaerobic conditions using a solution of sodium selenite (Na2SeO3) in the bacterial culture medium. The generation of SeNPs ensued from the interaction of L. casei bacteria with selenium ions, a process characterized via transmission electron microscopy (TEM) to confirm the synthesis of SeNPs. To induce inflammation, the human colonic adenocarcinoma cell line, Caco-2 was subjected to interleukin-1 beta (IL-1β) at concentrations of 0.5 and 25 ng/ml. Subsequent analyses encompass the evaluation of SeNPs derived from L. casei, its supernatant, commercial selenium, and L. casei probiotic on Caco2 cell line. Finally, we assessed the inflammatory and oxidative stress markers. The assessment of inflammation involved the quantification of NF-κB and TGF-β gene expression levels, while oxidative stress was evaluated through the measurement of Nrf2, Keap1, NOX1, and SOD2 gene levels. L. casei successfully produced SeNPs, as confirmed by the color change in the culture medium and TEM analysis showing their uniform distribution within the bacteria. In the inflamed Caco-2 cell line, the NF-κB gene was upregulated, but treatment with L. casei-SeNPs and selenium increased TGF-β expression. Moreover, L. casei-SeNPs upregulated SOD2 and Nrf2 genes, while downregulating NOX1, Keap1, and NF-κB genes. These results demonstrated the potential of L. casei-SeNPs for reducing inflammation and managing oxidative stress in the Caco-2 cell line. The study underscores the ability of L. casei-SeNPs to reduce oxidative stress and inflammation in inflamed Caco-2 cell lines, emphasizing the effectiveness of L. casei as a source of selenium. These insights hold significant promise for the development of SeNPs derived from L. casei as potent anti-inflammatory and anti-cancer agents, paving the way for novel therapeutic applications in the field.

The interaction effect of dietary selenium intake and the IL10 rs1800871 polymorphism on the risk of colorectal cancer: a case-control study in Korea

The importance of Se in human health has received much attention due to its antioxidant properties when it is consumed at an appropriate level. However, the existing evidence is limited to obtain an effective conclusion for colorectal cancer (CRC). Notably, an adequate intake of Se was reported for Koreans. Furthermore, cytokine secretion and immune function may be affected by dietary Se. Our study aimed to explore whether Se potentially reduces CRC risk and whether the IL10 rs1800871 polymorphism has an effect on this association. We designed a case-control study with 1420 cases and 2840 controls. A semi-quantitative FFQ was used to obtain information on Se intake. We determined IL10 rs1800871 through genetic analysis. Different models were developed to explore Se intake related to CRC risk by calculating OR and 95 % CI using unconditional logistic regression. A reduced risk of CRC was found as Se intake increased, with an OR (95 % CI) of 0·44 (0·35, 0·55) (Pfor trend < 0·001). However, this association seems to be allele-specific and only present among risk variant allele carriers (GA/GG) with a significant interaction between dietary Se and IL10 rs1800871 (Pfor interaction = 0·043). We emphasised that a reduction in CRC risk is associated with appropriate Se intake. However, the IL10 rs1800871 polymorphism has an impact on this reduction, with a greater effect on variant allele carriers. These findings suggest the importance of considering an individual's genetic characteristics when developing nutritional strategies for CRC prevention.

Oxidative Stress and Male Infertility: The Protective Role of Antioxidants

Oxidative stress is a significant factor in male infertility, compromising sperm function and overall reproductive health. As male infertility garners increasing attention, effective therapeutic interventions become paramount. This review investigates the therapeutic role of antioxidants in addressing male infertility. A detailed examination was conducted on antioxidants such as vitamin C, E, B12, D, coenzyme Q10, zinc, folic acid, selenium, l-carnitine, l-arginine, inositols, and alpha-lipoic acid. This analysis examines the methodologies, outcomes, and constraints of current clinical studies. Antioxidants show notable potential in counteracting the negative effects of oxidative stress on sperm. Based on the evidence, these antioxidants, individually or synergistically, can enhance sperm health and reproductive outcomes. However, certain limitations in the studies call for careful interpretation. Antioxidants are integral in tackling male infertility attributed to oxidative stress. The current findings underscore their therapeutic value, yet there's a pressing need for deeper, comprehensive research. Future studies should focus on refining dosage guidelines, identifying potential side effects, and discerning the most efficacious antioxidant combinations for male infertility solutions.

Biodegradable hollowed mesoporous SeO2 nanoplatform loaded with indocyanine green for simultaneous NIR II fluorescence imaging and synergistic breast carcinoma therapy

Contrast agents in the second window of the near-infrared region (NIR II, 1000–1700 nm) have several advantages and indocyanine green (ICG), which emits NIR II fluorescence, is clinically approved and its use has been widely investigated for in vivo imaging, specifically for delineating tumor outlines; however, insufficient tumor targeting and rapid physiological metabolism of free ICG has substantially impeded its further clinical application. Here, we constructed novel hollowed mesoporous selenium oxide nanocarriers for precise ICG delivery. After surface modification with the active tumor targeting amino acid motif, RGD (hmSeO2@ICG-RGD), the nanocarriers were preferentially targeted toward tumor cells and subsequently degraded for ICG and Se-based nanogranule release under tumor tissue extracellular pH conditions (pH 6.5). The released ICG acted as an NIR II contrast agent, highlighting tumor tissue, after intravenous administration of hmSeO2@ICG-RGD into mammary tumor-bearing mice. Importantly, the photothermal effect of ICG improved reactive oxygen species production from SeO2 nanogranules, inducing oxidative therapy. The synergistic therapeutic effects of hyperthermia and increased oxidative stress on 808 nm laser exposure induced significant tumor cell killing. Thus, our nanoplatform can generate a high-performance diagnostic and therapeutic nanoagent that facilitates in vivo tumor outline discrimination and tumor ablation.

Potential Role of Natural Antioxidant Products in Oncological Diseases

Nutrition has a significant effect and a crucial role in disease prevention. Low consumption of fruit and vegetables and a sedentary lifestyle are closely related with the onset and development of many types of cancer. Recently, nutraceuticals have gained much attention in cancer research due to their pleiotropic effects and relatively non-toxic behavior. In fact, although in the past there have been conflicting results on the role of some antioxidant compounds as allies against cancer, numerous recent clinical studies highlight the efficacy of dietary phytochemicals in the prevention and treatment of cancer. However, further investigation is necessary to gain a deeper understanding of the potential anticancer capacities of dietary phytochemicals as well as the mechanisms of their action. Therefore, this review examined the current literature on the key properties of the bioactive components present in the diet, such as carotenoids, polyphenols, and antioxidant compounds, as well as their use in cancer therapy. The review focused on potential chemopreventive properties, evaluating their synergistic effects with anticancer drugs and, consequently, the side effects associated with current cancer treatments.

Nuclear analytical techniques used to study the trace element content of Centaurium erythraea Rafn, a medicinal plant species from sites with different pollution loads in Lower Silesia (SW Poland)

Centaurium erythraea (Gentianaceae) is a medicinal plant species with therapeutic potential officially listed in the pharmacopoeias of many European, Asian and American countries. It has had many uses in natural medicine since ancient times and it is collected mostly from wild populations. The aim of this study is to investigate the trace element composition of C. erythraea using instrumental neutron activation analysis (INAA). The results of the performed investigations show that INAA has proved to be an efficient analytical technique for the determination of trace elements in medicinal plants. The studied plant contains elements important to the human diet and metabolism that are needed for growth, development and the prevention and curing of disease. A comparison with the reference levels of elements for plants shows that the concentrations of most elements in C. erythraea collected from all types of sites exceed those regarded as the reference. Compared to the values of the elements in C. erythraea from rural areas (LP), the concentrations of most of the investigated elements in C. erythraea collected from the lignite basin, urban areas and in the vicinity of the A4 highway (MP) were significantly higher. The results obtained can be used for control and monitoring in the production of pharmaceuticals based on natural medical plants.

Structure, stability, antioxidant activity, and controlled-release of selenium nanoparticles decorated with lichenan from Usnea longissima

Selenium nanoparticles (SeNPs) have attracted widespread attention, but the poor water dispersibility restricted their applications seriously. Herein, Usnea longissima lichenan decorated selenium nanoparticles (L-SeNPs) were constructed. The formation, morphology, particle size, stability, physicochemical characteristics, and stabilization mechanism of L-SeNPs were investigated via TEM, SEM, AFM, EDX, DLS, UV-Vis, FT-IR, XPS, and XRD. The results indicated that the L-SeNPs displayed orange-red, amorphous, zero-valent, and uniform spherical nanoparticles with an average diameter of 96 nm. Due to the formation of CO⋯Se bonds or the hydrogen bonding interaction (OH⋯Se) between SeNPs and lichenan, L-SeNPs exhibited better heating and storage stability, which kept stable for more than one month at 25 °C in an aqueous solution. The decoration of the SeNPs surface with lichenan endowed the L-SeNPs with superior antioxidant capability, and their free radicals scavenging ability exhibited in a dose-dependent manner. Furthermore, L-SeNPs showed excellent selenium controlled-release performance. In simulated gastric liquids, selenium release kinetics from L-SeNPs followed the Linear superimposition model, which was governed by the polymeric network retardation of macromolecular, while in simulated intestinal liquids, it was well fitted to the Korsmeyer-Peppas model and followed a Fickian mechanism controlled by diffusion.

Emergence of nutrigenomics and dietary components as a complementary therapy in cancer prevention

Cancer is an illness characterized by abnormal cell development and the capability to infiltrate or spread to rest of the body. A tumor is the term for this abnormal growth that develops in solid tissues like an organ, muscle, or bone and can spread to other parts of the body through the blood and lymphatic systems. Nutrition is a critical and immortal environmental component in the development of all living organisms encoding the relationship between a person's nutrition and their genes. Nutrients have the ability to modify gene expression and persuade alterations in DNA and protein molecules which is researched scientifically in nutrigenomics. These interactions have a significant impact on the pharmacokinetic properties of bioactive dietary components as well as their site of action/molecular targets. Nutrigenomics encompasses nutrigenetics, epigenetics, and transcriptomics as well as other "omic" disciplines like proteomics and metabolomics to explain the vast disparities in cancer risk among people with roughly similar life style. Clinical trials and researches have evidenced that alternation of dietary habits is potentially one of the key approaches for reducing cancer risk in an individual. In this article, we will target how nutrigenomics and functional food work as preventive therapy in reducing the risk of cancer.

Purinoceptor Targeted Cytotoxicity of Adenosine Triphosphate-Conjugated Biogenic Selenium Nanoparticles in Human Colon Cancer Cells

The adenosine triphosphate (ATP)-conjugated biogenic selenium nanoparticles (SeNPs) for P2 (purinoceptors) receptor-targeted anti-colon cancer activity were developed in this study. First, the SeNPs were synthesized using Trichoderma extracts (TE) and then conjugated with ATP to enhance their anticancer activity. The developed SeNPs had an oval crystalline structure with an average diameter size of 26.45 ± 1.71 d. nm, while the ATP-SeNPs were 78.6 ± 2.91 d. nm. The SeNPs contain Se, and less persistence of P while the ATP-SeNPs have high level of P, and Se in the energy-dispersive spectroscopy (EDS). Further, both nanoparticles exhibited larger sizes in the dynamic light scattering (DLS) analysis than in the transmission electron microscopy (TEM) analysis. The DLS and Fourier transform infrared spectroscopy (FTIR) results provide evidence that the amine group (-NH2) of ATP might bind with the negatively charged SeNPs through covalent bonding. The IC50 concentration was 17.25 ± 1.16 µg/mL for ATP-SeNPs and 61.24 ± 2.08 µg/mL against the caco-2 cell line. The IC50 results evidenced the higher cytotoxicity of ATP-SeNPs in the caco-2 cell line than in HEK293 cells. ATP-SeNPs trigger the anticancer activity in the caco-2 cell line through the induction of mitochondrial membrane potential (MMP) loss and nucleus damage. The biocompatibility test of hemolysis and the egg CAM assay confirmed the non-toxicity of these nanoparticles. Overall, the results proved that the newly developed ATP-SeNPs exhibited higher cytotoxicity in the caco-2 cell line than SeNPs. However, further molecular and in vivo experiments are required to develop the ATP-SeNPs as a candidate drug for cancer-targeted therapeutics.

Selenium and protozoan parasitic infections: selenocompounds and selenoproteins potential

The current drug treatments against protozoan parasitic diseases including Chagas, malaria, leishmaniasis, and toxoplasmosis represent good examples of drug resistance mechanisms and have shown diverse side effects. Therefore, the identification of novel therapeutic strategies and drug compounds against such life-threatening diseases is urgent. According to the successful usage of selenium (Se) compounds-based therapy against some diseases, this therapeutic strategy has been recently further underlined against these parasitic diseases by targeting different parasite´s essential pathways. On the other hand, due to the important functions played by parasite selenoproteins in their biology (such as modulating the host immune response), they can be also considered as a novel therapeutic strategy by designing specific inhibitors against these important proteins. In addition, the immunomodulatory potentiality of these compounds to trigger T helper type 1 (Th1) cells and cytokine-mediated immune response for the substantial induction of proinflammatory cytokines, thus, Se, selenoproteins, and parasite selenoproteins could be further investigated to find possible vaccine antigens. Herein, we collect and present the results of some studies regarding Se-based therapy against protozoan parasitic diseases and highlight relevant information and some viewpoints that might be insightful to advance toward more effective studies in the future.

Selenofolate inhibits the proliferation of IGROV1 cancer cells independently from folate receptor alpha

Cancer is one of the main causes of human mortality worldwide and novel chemotherapeutics are required due to the limitations of conventional cancer therapies. For example, using redox selenium compounds as novel chemotherapeutics seem to be very promising. The objective of this study was to explore if folate could be used as a carrier to deliver a newly synthesised selenium derivative selenofolate into cancer cells. Particularly, the cytotoxic effects of this selenofolate compound were investigated in a variety of cancer cell types including lung, liver, and cervical cancers and specifically IGROV1 cells. Our results showed that selenofolate inhibits the growth of cancer cells in-vitro. However, despite the expectations, folate receptor alpha (FRα) was not involved in the transportation of selenofolate compound into the cells i.e. growth inhibition was independent of FRα, suggesting that multiple transporters (e.g. reduced folate carrier-1) are possibly involved in the delivery and internalisation of folate in IGROV1 cells. Additionally, selenofolate did not exert cell death through apoptosis. Instead, anti-proliferative activity showed to be the main cause of growth inhibition of selenolofate in the IGROV1 cell line. In conclusion, selenofolate inhibits the growth of cancer cells and thus, may be explored further as a potential chemotherapeutic agent.

Biogenic selenium nanoparticles produced by Lactobacillus casei ATCC 393 inhibit colon cancer cell growth in vitro and in vivo

Selenium compounds exhibit excellent anticancer properties but have a narrow therapeutic window. Selenium nanoparticles, however, are less toxic compared to other selenium forms, and their biogenic production leads to improved bioavailability. Herein, we used the probiotic strain Lactobacillus casei ATCC 393, previously shown to inhibit colon cancer cell growth, to synthesize biogenic selenium nanoparticles. We examined the anticancer activity of orally administered L. casei, L. casei-derived selenium nanoparticles and selenium nanoparticle-enriched L. casei, and investigated their antitumor potential in the CT26 syngeneic colorectal cancer model in BALB/c mice. Our results indicate that L. casei-derived selenium nanoparticles and selenium nanoparticle-enriched L. casei exert cancer-specific antiproliferative activity in vitro. Moreover, the nanoparticles were found to induce apoptosis and elevate reactive oxygen species levels in cancer cells. It is noteworthy that, when administered orally, selenium nanoparticle-enriched L. casei attenuated the growth of colon carcinoma in mice more effectively than the isolated nanoparticles or L. casei, suggesting a potential additive effect of the nanoparticles and the probiotic. To the best of our knowledge this is the first comparative study examining the anticancer effects of selenium nanoparticles synthesized by a microorganism, the selenium nanoparticle-enriched microorganism and the sole microorganism.

Inhibition of acrolein-induced apoptosis by the antioxidant selenium

In this study, the effects of a potent antioxidant, selenium, on apoptosis induced by acrolein, a cytotoxic and genotoxic environmental pollutant, were investigated by immunohistochemical and electron microscopic methods. One hundred adult male Wistar albino rats were used in the study. The rats were divided into four main groups: control, acrolein, selenium, and acrolein + selenium. The animals in the experimental groups were given 1 mg/kg/day selenium and 4 mg/kg/day acrolein daily for 7 days by gavage. After drug administration, each group was divided into subgroups according to the time they were to be euthanized: 12th hour, 1st, 2nd, 3rd, and 5th day. The rats in each group at the determined time were euthanized and their livers were removed. Routine histological procedures were performed for light and electron microscopy examinations. After applying the Terminal Deoxynucleotidyl Transferase dUTP nick end labeling assay on the liver sections, apoptotic index values were calculated. Comparing the liver sections of the rats in the acrolein group and the control group, acrolein was found to cause a significant increase in the apoptotic index. The apoptotic index values of the acrolein + selenium group decreased compared to the acrolein group. In the electron microscopic examinations, apoptotic findings were observed in the liver tissues of the rats given acrolein, such as chromatin condensation in the nucleus of hepatocytes, dilatations in the perinuclear space, and cytoplasmic vacuolization. These apoptotic findings were not observed in the acrolein + selenium group after the 12th hour. These findings show that selenium may potentially be useful as a protective agent for people exposed to acrolein.

Absolute quantification of selenoproteins and selenometabolites in lung cancer human serum by column switching coupled to triple quadrupole inductively coupled plasma mass spectrometry

One of the most important causes of the high mortality rate and low life expectancy of lung cancer is the detection at advanced stages. Thus, there is an urgent need for early diagnosis and the search of new selective biomarkers. Selenium is an important constituent of selenoproteins and a powerful antioxidant able to protect against cancer. In this work, the absolute quantification of selenium in selenoproteins and the total content in selenometabolites has been performed for the first time in serum from lung cancer patients (LC) and healthy controls (HC). To this end, a method for the simultaneous speciation of selenoproteins using size exclusion chromatography (SEC) and affinity chromatography (AF) with detection by ICP-QQQ-MS, and quantification by isotopic dilution (IDA) (SEC-AF-HPLC-SUID-ICP-QQQ-MS) was developed to determine the selenium concentration in eGPx, SEPP1 and SeAlb, as well as total selenometabolites, to find alterations that may serve as biomarkers of this disease. In the same way, a method based on anion-exchange chromatography coupled to ICP-QQQ-MS was developed to quantify selenometabolites (SeCys2, SeMeSeCys, SeMet, selenite and selenate) in the same LC and HC serum samples. The results showed that the averaged concentrations of selenium in eGPx, SeAlb and selenite were significantly higher in LC patients (LC (eGPx: 21.24 ± 0.77 ng g^-1; SeAlb: 49.56 ± 3.16 ng g^-1 and Se(IV): 6.20 ± 1.22 ng g^-1) than in HC group (eGPx: 16.96 ± 0.53 ng g^-1; SeAlb: 38.33 ± 2.66 ng g^-1 and Se(IV): 3.56 ± 0.55 ng g^-1). In addition, the ratios between selenoproteins and selenometabolites have been calculated for the first to study their potential use as LC biomarkers. The rates eGPx/SEPP1, SEPP1/SeAlb, eGPx/Se(IV) and SEPP1/Se(IV) were significantly different between LC and HC groups.

Selenium Anticancer Properties and Impact on Cellular Redox Status

(1) Background: In this review, we provide information published in recent years on the chemical forms, main biological functions and especially on antioxidant and prooxidant activities of selenium. The main focus is put on the impact of selenoproteins on maintaining cellular redox balance and anticancerogenic function. Moreover, we summarize data on chemotherapeutic application of redox active selenium compounds. (2) Methods: In the first section, main aspects of metabolism and redox activity of selenium compounds is reviewed. The second outlines multiple biological functions, asserted when selenium is incorporated into the structure of selenoproteins. The final section focuses on anticancer activity of selenium and chemotherapeutic application of redox active selenium compounds as well. (3) Results: optimal dietary level of selenium ensures its proper antioxidant and anticancer activity. We pay special attention to antioxidant activities of selenium compounds, especially selenoproteins, and their importance in antioxidant defence. It is worth noting, that data on selenium anticancer properties is still contraversive. Moreover, selenium compounds as chemotherapeutic agents usually are used at supranutritional doses. (4) Conclusions: Selenium play a vital role for many organism systems due to its incorporation into selenoproteins structure. Selenium possesses antioxidant activity at optimal doses, while at supranutritional doses, it displays prooxidant activity. Redox active selenium compounds can be used for cancer treatment; recently special attention is put to selenium containing nanoparticles.

Seeds

A wide variety of plant species provide edible seeds. Seeds are the dominant source of human calories and protein. The most important and popular seed food sources are cereals, followed by legumes and nuts. Their nutritional content of fiber, protein, and monounsaturated/polyunsaturated fats make them extremely nutritious. They are important additions to our daily food consumption. When consumed as part of a healthy diet, seeds can help reduce blood sugar, cholesterol, and blood pressure.

Targeting Glutathione and Cystathionine β-Synthase in Ovarian Cancer Treatment by Selenium-Chrysin Polyurea Dendrimer Nanoformulation

Ovarian cancer is the main cause of death from gynecological cancer, with its poor prognosis mainly related to late diagnosis and chemoresistance (acquired or intrinsic) to conventional alkylating and reactive oxygen species (ROS)-generating drugs. We and others reported that the availability of cysteine and glutathione (GSH) impacts the mechanisms of resistance to carboplatin in ovarian cancer. Different players in cysteine metabolism can be crucial in chemoresistance, such as the cystine/glutamate antiporter system Xc (xCT) and the H2S-synthesizing enzyme cystathionine β-synthase (CBS) in the pathway of cysteine catabolism. We hypothesized that, by disrupting cysteine metabolic flux, chemoresistance would be reverted. Since the xCT transporter is also able to take up selenium, we used selenium-containing chrysin (SeChry) as a plausible competitive inhibitor of xCT. For that, we tested the effects of SeChry on three different ovarian cancer cell lines (ES2, OVCAR3, and OVCAR8) and in two non-malignant cell lines (HaCaT and HK2). Results showed that, in addition to being highly cytotoxic, SeChry does not affect the uptake of cysteine, although it increases GSH depletion, indicating that SeChry might induce oxidative stress. However, enzymatic assays revealed an inhibitory effect of SeChry toward CBS, thus preventing production of the antioxidant H2S. Notably, our data showed that SeChry and folate-targeted polyurea dendrimer generation four (SeChry@PUREG4-FA) nanoparticles increased the specificity for SeChry delivery to ovarian cancer cells, reducing significantly the toxicity against non-malignant cells. Collectively, our data support SeChry@PUREG4-FA nanoparticles as a targeted strategy to improve ovarian cancer treatment, where GSH depletion and CBS inhibition underlie SeChry cytotoxicity.

Insights into cancer and neurodegenerative diseases through selenoproteins and the connection with gut microbiota - current analytical methodologies

Introduction: Selenium plays many key roles in health especially in connection with cancer and neurodegenerative diseases. However, it needs to be appreciated that the essentiality/toxicity of selenium depends on both, a narrow range of concentration and the chemical specie involved. In this context, selenoproteins are essential biomolecules against these disorders, mainly due to its antioxidant action. To this end, analytical methodologies may allow identifying and quantifying individual selenospecies in human biofluids and tissues. Areas covered: This review focus on the role of selenoproteins in medicine, with special emphasis in cancer and neurodegenerative diseases, considering the possible link with gut microbiota. In particular, this article reviews the analytical techniques and procedures recently developed for the absolute quantification of selenoproteins and selenometabolites in human biofluids and tissues. Expert commentary: The beneficial role of selenium in human health has been extensively studied and reviewed. However, several challenges remain unsolved as discussed in this article: (i) speciation of selenium (especially selenoproteins) in cancer and neurodegenerative disease patients; (ii) supplementation of selenium in humans using functional foods and nutraceuticals; (iii) the link between selenium and selenoproteins expression and the gut microbiota and (iv) analytical methods and pitfalls for the absolute quantification of selenoproteins and selenometabolites.

The Metallome of Lung Cancer and its Potential Use as Biomarker

Carcinogenesis is a very complex process in which metals have been found to be critically involved. In this sense, a disturbed redox status and metal dyshomeostasis take place during the onset and progression of cancer, and it is well-known that trace elements participate in the activation or inhibition of enzymatic reactions and metalloproteins, in which they usually participate as cofactors. Until now, the role of metals in cancer have been studied as an effect, establishing that cancer onset and progression affects the disturbance of the natural chemical form of the essential elements in the metabolism. However, it has also been studied as a cause, giving insights related to the high exposure of metals giving a place to the carcinogenic process. On the other hand, the chemical species of the metal or metallobiomolecule is very important, since it finally affects the biological activity or the toxicological potential of the element and their mobility across different biological compartments. Moreover, the importance of metal homeostasis and metals interactions in biology has also been demonstrated, and the ratios between some elements were found to be different in cancer patients; however, the interplay of elements is rarely reported. This review focuses on the critical role of metals in lung cancer, which is one of the most insidious forms of cancer, with special attention to the analytical approaches and pitfalls to extract metals and their species from tissues and biofluids, determining the ratios of metals, obtaining classification profiles, and finally defining the metallome of lung cancer.

Recent advances in the mechanism of selenoamino acids toxicity in eukaryotic cells

Selenium is an essential trace element due to its incorporation into selenoproteins with important biological functions. However, at high doses it is toxic. Selenium toxicity is generally attributed to the induction of oxidative stress. However, it has become apparent that the mode of action of seleno-compounds varies, depending on its chemical form and speciation. Recent studies in various eukaryotic systems, in particular the model organism Saccharomyces cerevisiae, provide new insights on the cytotoxic mechanisms of selenomethionine and selenocysteine. This review first summarizes current knowledge on reactive oxygen species (ROS)-induced genotoxicity of inorganic selenium species. Then, we discuss recent advances on our understanding of the molecular mechanisms of selenocysteine and selenomethionine cytotoxicity. We present evidences indicating that both oxidative stress and ROS-independent mechanisms contribute to selenoamino acids cytotoxicity. These latter mechanisms include disruption of protein homeostasis by selenocysteine misincorporation in proteins and/or reaction of selenols with protein thiols.

Application of Sodium Selenite in the Prevention and Treatment of Cancers

Selenium is an essential trace element that occurs in nature, in both inorganic and organic forms. This element participates in numerous biochemical processes, including antioxidant potential, but the mechanism of its anti-cancer action is still not well known. It should be noted that the anti-cancer properties of selenium depends on its chemical form, therapeutic doses, and the tumor type. Higher nutritional doses of selenium can stimulate human immune system. There are several hypotheses concerning the anticancer activity of selenium, including oxidation of sulfhydryl groups in proteins causing their conformational alterations. Conformational changes in proteins have the ability to weaken the activity of enzymes involved in the metabolism of cancer cells. In case of human fibrinogen sodium selenite, but not selenate, it inhibits protein disulfide exchange reactions, thus preventing formation of a hydrophobic polymer termed parafibrin, circulatory accumulation, of which is associated with numerous degenerative diseases. Parafibrin can specifically form a protein coat around tumor cells that is completely resistant to degradation induced with lymphocyte protease. In this way, cancer cells become protected against destruction by the organism's immune system. Other possible mechanisms of anticancer action of selenium are being still investigated.

Serum selenium levels and prostate cancer risk: A MOOSE-compliant meta-analysis

Some observational studies have shown that elevated serum selenium levels are associated with reduced prostate cancer risk; however, not all published studies support these results. A literature search of PubMed, Embase, Medline, and the Cochrane Library up until September 2016 identified 17 studies suitable for further investigation. A meta-analysis was conducted on these studies to investigate the association between serum selenium levels and subsequent prostate cancer risk. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the overall OR of prostate cancer for the highest versus the lowest levels of serum selenium. We found a pooled OR (95% CI) of 0.76 (0.64, 0.91; P < 0.05). In subgroup analysis, an inverse association between serum selenium levels and prostate cancer risk was found in each of case-control studies, current and former smokers, high-grade cancer cases, advanced cancer cases, and different populations. Such correlations were not found for subgroups containing each of cohort studies, nonsmokers, low-grade cancer cases, and early stage cancer cases. In conclusion, our study suggests an inverse relationship between serum selenium levels and prostate cancer risk. However, further cohort studies and randomized control trials based on non-Western populations are required.

Time for paradigm change in management of hepatocellular carcinoma: is a personalized approach on the horizon?

Hepatocellular carcinoma (HCC) is the fifth most frequent cancer form but the second leading cause of all cancer-related deaths. There are several reasons for high mortality in the HCC cohort: lack of effective screening programs and consequently late diagnosis, multifactorial origin with cumulative risk factors, complex carcinogenesis, tumor heterogeneity, unpredictable impacts of individual microenvironment on tumor development and progression, and, as the consequence, frequently untargeted therapy and cancer resistance toward currently applied treatment approaches. The currently applied 'treat and wait' approach is inappropriate in the overall HCC management. Urgent need in paradigm change toward predictive, preventive and personalized medicine is discussed in this review article. Innovative strategies for an advanced predictive, preventive and personalized medicine approach in the overall HCC management benefiting the patient are presented.

Quantification of low molecular weight selenium metabolites in human plasma after treatment with selenite in pharmacological doses by LC-ICP-MS

The paper presents an analytical method for quantification of low molecular weight (LMW) selenium compounds in human plasma based on liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS) and post column isotope dilution-based quantification. Prior to analysis, samples were ultrafiltrated using a cut-off value of 3000 Da. The method was validated in aqueous solution as well as plasma using standards of selenomethionine (SeMet), Se-methylselenocysteine (MeSeCys), selenite, and the selenosugar Se-methylseleno-N-acetylgalactosamine (SeGal) for linearity, precision, recoveries, and limits of detection and quantitation with satisfactory results. The method was applied for analysis of a set of plasma samples from cancer patients receiving selenite treatment in a clinical trial. Three LMW selenium compounds were observed. The main compounds, SeGal and selenite were tentatively identified by retention time matching with standards in different chromatographic systems, while the third minor compound was not identified. The identity of the selenosugar was verified by ESI-MS-MS product ion scanning, while selenite was identified indirectly as the glutathione (GSH) reaction product, GS-Se-SG.

L-selenomethionine reduces platinum(IV) anticancer model compounds at strikingly faster rates than L-methionine

L-Selenomethionine (SeMet), the predominant form of selenium acquired from the diet by humans, has been used as a supplement, and exhibit some important functions like cancer prevention and antioxidative defense. Its interactions with Pt(II) anticancer drugs have been characterized, but its redox reactions with platinum(IV) anticancer prodrugs have not been exploited. In this work, the oxidation of SeMet by Pt(IV) anticancer model compounds trans-[PtX2(CN)4](2-) (X = Cl, Br) was characterized. A stopped-flow spectrometer was used to record the rapid scan spectra and to follow the reaction kinetics over a wide pH range. An overall second-order rate law was derived: -d[Pt(IV)]/dt = k'[Pt(IV)][SeMet], where k' pertains to the observed second-order rate constants. The k'-pH profiles showed that k' increased only about 6 times even though the solution pH was varied from 0.25 to 10.5. The redox stoichiometry was determined as Δ[Pt(IV)]/Δ[SeMet] = 1 : (1.07 ± 0.07), suggesting that SeMet was oxidized to selenomethionine selenoxide. The selenoxide together with its hydrated form was identified explicitly by high resolution mass spectral analysis. A reaction mechanism was proposed which encompassed three parallel rate-determining steps relying on the protolytic species of SeMet. Rate constants of the rate-determining steps were obtained from the simulations of the k'-pH profiles. Activation parameters were determined for the reactions of the zwitterionic form of SeMet with the Pt(IV) complexes. A bridged electron transfer process is delineated in the rate-determining steps and several lines of evidence support the bridged electron transfer mode. Strikingly, reduction of [PtX2(CN)4](2-) by SeMet is 3.7 × 10(3)-5.7 × 10(4) times faster than that by L-methionine. Some potential biological consequences resulting from the strikingly fast reduction are discussed.

Selenitetriglycerides-Redox-active agents

BACKGROUND

Human prostate cancer (hPCa) is the most commonly diagnosed cancer in elderly men and is the second leading cause of male cancer death. Data from epidemiological, eco-environmental, nutritional prevention and clinical trials suggest that selenium Se(IV) can prevent prostate cancer. Selol, a new organic semisynthetic derivative of Se(IV), is a mixture of selenitetriglycerides. This mixture is non-toxic and non-mutagenic, and after po treatment - 56-times less toxic (in mice) than sodium selenite. It exhibits strong anti-cancer activity in vitro in many cancer cell lines and can overcome the cell resistance to doxorubicin. Selol seems a promising compound for prostate cancer therapy.

MATERIALS AND METHODS

The aim of the present study is the evaluation of Selol's influence on intracellular redox state (Eh) of prostatic tumors and the liver in androgen-dependent hPCa-bearing mice, and extracellular redox state in serum of these mice.

RESULTS AND CONCLUSIONS

The anticancer activity of Selol involves perturbation of the redox regulation in the androgen dependent hPCa (LNCaP) cells, but not in healthy cells. After Selol treatment, intracellular Eh has increased in tumors from -223 mV to -175 mV, while in serum it has decreased (-82 mV vs -113 mV). It shows significant changes Eh in the extra- and intracellular environment. The difference decreases from 141 mV to 62 mV. The changes suggest that a tumor cell was probably directed toward apoptosis. This is exemplified in a significant decrease in cancer tumor mass by approx. 17% after the three weeks of Selol administration.

Toxic-selenium and low-selenium transcriptomes in Caenorhabditis elegans: toxic selenium up-regulates oxidoreductase and down-regulates cuticle-associated genes

Selenium (Se) is an element that in trace quantities is both essential in mammals but also toxic to bacteria, yeast, plants and animals, including C. elegans. Our previous studies showed that selenite was four times as toxic as selenate to C. elegans, but that deletion of thioredoxin reductase did not modulate Se toxicity. To characterize Se regulation of the full transcriptome, we conducted a microarray study in C. elegans cultured in axenic media supplemented with 0, 0.05, 0.1, 0.2, and 0.4 mM Se as selenite. C. elegans cultured in 0.2 and 0.4 mM Se displayed a significant delay in growth as compared to 0, 0.05, or 0.1 mM Se, indicating Se-induced toxicity, so worms were staged to mid-L4 larval stage for these studies. Relative to 0.1 mM Se treatment, culturing C. elegans at these Se concentrations resulted in 1.9, 9.7, 5.5, and 2.3%, respectively, of the transcriptome being altered by at least 2-fold. This toxicity altered the expression of 295 overlapping transcripts, which when filtered against gene sets for sulfur and cadmium toxicity, identified a dataset of 182 toxic-Se specific genes that were significantly enriched in functions related to oxidoreductase activity, and significantly depleted in genes related to structural components of collagen and the cuticle. Worms cultured in low Se (0 mM Se) exhibited no signs of deficiency, but low Se was accompanied by a transcriptional response of 59 genes changed ≥2-fold when compared to all other Se concentrations, perhaps due to decreases in Se-dependent TRXR-1 activity. Overall, these results suggest that Se toxicity in C. elegans causes an increase in ROS and stress responses, marked by increased expression of oxidoreductases and reduced expression of cuticle-associated genes, which together underlie the impaired growth observed in these studies.

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

Selenium compounds inhibit neoplastic growth. Redox active selenium compounds are evolving as promising chemotherapeutic agents through tumour selectivity and multi-target response, which are of great benefit in preventing development of drug resistance. Generation of reactive oxygen species is implicated in selenium-mediated cytotoxic effects on cancer cells. Recent findings indicate that activation of diverse intracellular signalling leading to cell death depends on the chemical form of selenium applied and/or cell line investigated. In the present study, we aimed at deciphering different modes of cell death in a single cell line (HeLa) upon treatment with three redox active selenium compounds (selenite, selenodiglutathione and seleno-DL-cystine). Both selenite and selenodiglutathione exhibited equipotent toxicity (IC₅₀ 5 μM) in these cells with striking differences in toxicity mechanisms. Morphological and molecular alterations provided evidence of necroptosis-like cell death in selenite treatment, whereas selenodiglutathione induced apoptosis-like cell death. We demonstrate that selenodiglutathione efficiently glutathionylated free protein thiols, which might explain the early differences in cytotoxic effects induced by selenite and selenodiglutathione. In contrast, seleno-DL-cystine treatment at an IC₅₀ concentration of 100 μM induced morphologically two distinct different types of cell death, one with apoptosis-like phenotype, while the other was reminiscent of paraptosis-like cell death, characterized by induction of unfolded protein response, ER-stress and occurrence of large cytoplasmic vacuoles. Collectively, the current results underline the diverse cytotoxic effects and variable potential of redox active selenium compounds on the survival of HeLa cells and thereby substantiate the potential of chemical species-specific usage of selenium in the treatment of cancers.

Glyphosate, pathways to modern diseases II: Celiac sprue and gluten intolerance

Celiac disease, and, more generally, gluten intolerance, is a growing problem worldwide, but especially in North America and Europe, where an estimated 5% of the population now suffers from it. Symptoms include nausea, diarrhea, skin rashes, macrocytic anemia and depression. It is a multifactorial disease associated with numerous nutritional deficiencies as well as reproductive issues and increased risk to thyroid disease, kidney failure and cancer. Here, we propose that glyphosate, the active ingredient in the herbicide, Roundup(®), is the most important causal factor in this epidemic. Fish exposed to glyphosate develop digestive problems that are reminiscent of celiac disease. Celiac disease is associated with imbalances in gut bacteria that can be fully explained by the known effects of glyphosate on gut bacteria. Characteristics of celiac disease point to impairment in many cytochrome P450 enzymes, which are involved with detoxifying environmental toxins, activating vitamin D3, catabolizing vitamin A, and maintaining bile acid production and sulfate supplies to the gut. Glyphosate is known to inhibit cytochrome P450 enzymes. Deficiencies in iron, cobalt, molybdenum, copper and other rare metals associated with celiac disease can be attributed to glyphosate's strong ability to chelate these elements. Deficiencies in tryptophan, tyrosine, methionine and selenomethionine associated with celiac disease match glyphosate's known depletion of these amino acids. Celiac disease patients have an increased risk to non-Hodgkin's lymphoma, which has also been implicated in glyphosate exposure. Reproductive issues associated with celiac disease, such as infertility, miscarriages, and birth defects, can also be explained by glyphosate. Glyphosate residues in wheat and other crops are likely increasing recently due to the growing practice of crop desiccation just prior to the harvest. We argue that the practice of "ripening" sugar cane with glyphosate may explain the recent surge in kidney failure among agricultural workers in Central America. We conclude with a plea to governments to reconsider policies regarding the safety of glyphosate residues in foods.

Deletion of thioredoxin reductase and effects of selenite and selenate toxicity in Caenorhabditis elegans

Thioredoxin reductase-1 (TRXR-1) is the sole selenoprotein in C. elegans, and selenite is a substrate for thioredoxin reductase, so TRXR-1 may play a role in metabolism of selenium (Se) to toxic forms. To study the role of TRXR in Se toxicity, we cultured C. elegans with deletions of trxr-1, trxr-2, and both in axenic media with increasing concentrations of inorganic Se. Wild-type C. elegans cultured for 12 days in Se-deficient axenic media grow and reproduce equivalent to Se-supplemented media. Supplementation with 0-2 mM Se as selenite results in inverse, sigmoidal response curves with an LC50 of 0.20 mM Se, due to impaired growth rather than reproduction. Deletion of trxr-1, trxr-2 or both does not modulate growth or Se toxicity in C. elegans grown axenically, and (75)Se labeling showed that TRXR-1 arises from the trxr-1 gene and not from bacterial genes. Se response curves for selenide (LC50 0.23 mM Se) were identical to selenite, but selenate was 1/4(th) as toxic (LC50 0.95 mM Se) as selenite and not modulated by TRXR deletion. These nutritional and genetic studies in axenic media show that Se and TRXR are not essential for C. elegans, and that TRXR alone is not essential for metabolism of inorganic Se to toxic species.

Methylselenol formed by spontaneous methylation of selenide is a superior selenium substrate to the thioredoxin and glutaredoxin systems

Naturally occurring selenium compounds like selenite and selenodiglutathione are metabolized to selenide in plants and animals. This highly reactive form of selenium can undergo methylation and form monomethylated and multimethylated species. These redox active selenium metabolites are of particular biological and pharmacological interest since they are potent inducers of apoptosis in cancer cells. The mammalian thioredoxin and glutaredoxin systems efficiently reduce selenite and selenodiglutathione to selenide. The reactions are non-stoichiometric aerobically due to redox cycling of selenide with oxygen and thiols. Using LDI-MS, we identified that the addition of S-adenosylmethionine (SAM) to the reactions formed methylselenol. This metabolite was a superior substrate to both the thioredoxin and glutaredoxin systems increasing the velocities of the nonstoichiometric redox cycles three-fold. In vitro cell experiments demonstrated that the presence of SAM increased the cytotoxicity of selenite and selenodiglutathione, which could neither be explained by altered selenium uptake nor impaired extra-cellular redox environment, previously shown to be highly important to selenite uptake and cytotoxicity. Our data suggest that selenide and SAM react spontaneously forming methylselenol, a highly nucleophilic and cytotoxic agent, with important physiological and pharmacological implications for the highly interesting anticancer effects of selenium.

Effects of lead and/or cadmium on the distribution patterns of some essential trace elements in immature female rats

Lead acetate (300 mg/L) and/or cadmium chloride (50 mg/L) were administered as drinking water to Sprague-Dawley rats for 9 weeks to investigate the effects of concurrent exposure to lead and cadmium on the distribution patterns of five essential trace elements. Inductively coupled plasma mass spectrometry was used to determine the concentrations of zinc, copper, manganese, selenium and iron in the urine at different exposure times, as well as their levels in the renal cortex and serum at the end of treatment. Compared with the control group, exposure to lead and/or cadmium resulted in a significant increase in the urinary excretion of these five elements during the experiment, whereas significant decreased levels of these elements were found in kidney and serum. In conclusion, increased urinary loss of antioxidant trace elements due to lead and/or cadmium exposure induced the deficiency of antioxidants in the body, which could result in further oxidative damage. Moreover, there was an obvious synergistic effect of lead combined with cadmium on the distribution patterns of these essential trace elements, which may be related to the severity of co-exposure to these two metals.