Se-(Methyl)-selenocysteine ameliorates blood-brain barrier disruption of focal cerebral ischemia mice via ferroptosis inhibition and tight junction upregulation in an Akt/GSK3ß-dependent manner.

BACKGROUND: Ischemic stroke still ranks as the most fatal disease worldwide. Blood-brain barrier (BBB) is a promising therapeutic target for protection. Brain microvascular endothelial cell is a core component of BBB, the barrier function maintenance of which can ameliorate ischemic injury and improve neurological deficit. Se-methyl L-selenocysteine (SeMC) has been shown to exert cardiovascular protection. However, the protection of SeMC against ischemic stroke remains to be elucidated. This research was designed to explore the protection of SeMC from the perspective of BBB protection. METHODS: To simulate cerebral ischemic injury, C57BL/6J mice were subjected to middle cerebral artery occlusion/reperfusion (MCAO/R), and bEnd.3 was exposed to oxygen-glucose deprivation/reoxygenation (OGD/R). After the intervention of SeMC, the barrier function and the expression of tight junction and ferroptosis-associated proteins were determined. For mechanism exploration, LY294002 (Akt inhibitor) was introduced both in vivo and in vitro. RESULTS: SeMC lessened the brain infarct volume and attenuated the leakage of BBB in mice. In vitro, SeMC improved cell viability and maintained the barrier function of bEnd.3 cells. The protection of SeMC was accompanied with ferroptosis inhibition and tight junction protein upregulation. Mechanism studies revealed that the effect of SeMC was reversed by LY294002, indicating that the protection of SeMC against ischemic stroke was mediated by the Akt signal pathway. CONCLUSION: These results suggested that SeMC exerted protection against ischemic stroke, which might be attributed to activating the Akt/GSK3ß signaling pathway and increasing the nuclear translocation of Nrf2 and ß-catenin, subsequently maintaining the integrity of BBB.

LRP8-mediated selenocysteine uptake is a targetable vulnerability in MYCN-amplified neuroblastoma.

Ferroptosis has emerged as an attractive strategy in cancer therapy. Understanding the operational networks regulating ferroptosis may unravel vulnerabilities that could be harnessed for therapeutic benefit. Using CRISPR-activation screens in ferroptosis hypersensitive cells, we identify the selenoprotein P (SELENOP) receptor, LRP8, as a key determinant protecting MYCN-amplified neuroblastoma cells from ferroptosis. Genetic deletion of LRP8 leads to ferroptosis as a result of an insufficient supply of selenocysteine, which is required for the translation of the antiferroptotic selenoprotein GPX4. This dependency is caused by low expression of alternative selenium uptake pathways such as system Xc- . The identification of LRP8 as a specific vulnerability of MYCN-amplified neuroblastoma cells was confirmed in constitutive and inducible LRP8 knockout orthotopic xenografts. These findings disclose a yet-unaccounted mechanism of selective ferroptosis induction that might be explored as a therapeutic strategy for high-risk neuroblastoma and potentially other MYCN-amplified entities.

L-Selenocysteine induced HepG-2 cells apoptosis through reactive oxygen species-mediated signaling pathway.

BACKGROUND: Currently, Liver cancer is the fifth most common tumor and the second most important reason for cancer-related death in the world. However, there are still many limitations of the clinical treatment of liver cancer, and new treatment options are clearly needed. Fortunately, studies have shown that L-Selenocysteine has a certain effect on cancer. This study was to investigate the effects of L-Selenocysteine on the inhibition of cell proliferation and the promotion of apoptosis of HepG-2 cells through ROS mediated fine signaling pathway. MATERIALS AND METHODS: CCK-8 assay was applied to evaluating the cytotoxic effect of L-Selenocysteine on HepG-2 cells. Electron microscopy, flow cytometry and Western Blot was utilization in further researching cells signaling pathways. RESULTS: The growth of HepG-2 cells was inhibited by L-selenocysteine ​​treatment in a dose-dependent manner. The cell viability decreased to 52.20%, 43.20% and 30.83% under the treatment of 4, 8, 16 µM L-selenocysteine, respectively. L-Selenocysteine had higher cytotoxicity towards HepG-2 cells than normal cells. L-Selenocysteine can induce the apoptosis of HepG-2 cells by increasing the DNA fragmentation, and activating the Caspase-3. In addition, it was found that the mechanism of the induction to HepG-2 cell apoptosis by L-Selenocysteine was closely related to the overproduction of ROS and promoted apoptosis through the Bcl-2 signaling pathway. CONCLUSIONS: Our data suggest that L-selenocysteine ​​may cause mitochondrial damage and subsequently stimulate ROS production. ROS can damage cellular DNA and mediate the production of Casapase-8, Bid, Bcl-2 and other proteins, affecting downstream signaling pathways, and ultimately induced apoptosis.

In vitro cytotoxic data on Se-methylselenocysteine conjugated to dendritic poly(glycerol) against human squamous carcinoma cells.

Polymeric nanoparticles acting as sources of selenium (Se) are currently an interesting topic in cancer chemotherapy. In this study, polyglycerol dendrimer (DPGLy) was functionalized with seleno-methyl-selenocysteine (SeMeCys) by means of Steglich esterification with 4-dimethylaminopyridine/(l-ethyl-3-(3-dimethylaminopropyl)carbodiimide) (EDC/DMAP) and cerium chloride as cocatalyst in acetonitrile at quantitative yields of 98 ± 1%. The SeMeCys coupling DPGLy efficiency vs. time were determined by Fourier Transform infrared spectroscopy (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy. The cytotoxic effects of SeMeCys-DPGLy on the Chinese Hamster ovary cell line (CHO-K1) and head and neck squamous cell carcinoma (HNSCC) cells line were assessed by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. No signs of general toxicity of SeMeCys-DPGLy against CHO-K1 cells were detectable at which cell viability was greater than 98%. MTS assays revealed that SeMeCys-DPGLy reduced HNSCC cell viability and proliferation at higher doses and long incubation times.

L-Se-methylselenocysteine sensitizes lung carcinoma to chemotherapy.

OBJECTIVES: Organic Selenium (Se) compounds such as L-Se-methylselenocysteine (L-SeMC/SeMC) have been employed as a class of anti-oxidant to protect normal tissues and organs from chemotherapy-induced systemic toxicity. However, their comprehensive effects on cancer cell proliferation and tumour progression remain elusive. MATERIALS AND METHODS: CCK-8 assays were conducted to determine the viabilities of cancer cells after exposure to SeMC, chemotherapeutics or combined treatment. Intracellular reactive oxygen species (ROS) levels and lipid peroxidation levels were assessed via fluorescence staining. The efficacy of free drugs or drug-loaded hydrogel against tumour growth was evaluated in a xenograft mouse model. RESULTS: Among tested cancer cells and normal cells, the A549 lung adenocarcinoma cells showed higher sensitivity to SeMC exposure. In addition, combined treatments with several types of chemotherapeutics induced synergistic lethality. SeMC promoted lipid peroxidation in A549 cells and thereby increased ROS generation. Significantly, the in vivo efficacy of combination therapy was largely potentiated by hydrogel-mediate drug delivery. CONCLUSIONS: Our study reveals the selectivity of SeMC in the inhibition of cancer cell proliferation and develops an efficient strategy for local combination therapy.

A disease-modifying treatment for Alzheimer's disease: focus on the trans-sulfuration pathway.

High homocysteine levels in Alzheimer's disease (AD) result from low activity of the trans-sulfuration pathway. Glutathione levels are also low in AD. L-cysteine is required for the synthesis of glutathione. The synthesis of coenzyme A (CoA) requires L-cysteine, which is synthesized via the trans-sulfuration pathway. CoA is required for the synthesis of acetylcholine and appropriate cholinergic neurotransmission. L-cysteine is required for the synthesis of molybdenum-containing proteins. Sulfite oxidase (SUOX), which is a molybdenum-containing protein, could be dysregulated in AD. SUOX detoxifies the sulfites. Glutaminergic neurotransmission could be dysregulated in AD due to low levels of SUOX and high levels of sulfites. L-cysteine provides sulfur for iron-sulfur clusters. Oxidative phosphorylation (OXPHOS) is heavily dependent on iron-sulfur proteins. The decrease in OXPHOS seen in AD could be due to dysregulations of the trans-sulfuration pathway. There is a decrease in aconitase 1 (ACO1) in AD. ACO1 is an iron-sulfur enzyme in the citric acid cycle that upon loss of an iron-sulfur cluster converts to iron regulatory protein 1 (IRP1). With the dysregulation of iron-sulfur cluster formation ACO1 will convert to IRP1 which will decrease the 2-oxglutarate synthesis dysregulating the citric acid cycle and also dysregulating iron metabolism. Selenomethionine is also metabolized by the trans-sulfuration pathway. With the low activity of the trans-sulfuration pathway in AD selenoproteins will be dysregulated in AD. Dysregulation of selenoproteins could lead to oxidant stress in AD. In this article, we propose a novel treatment for AD that addresses dysregulations resulting from low activity of the trans-sulfuration pathway and low L-cysteine.

Non-Coding Micro RNAs and Hypoxia-Inducible Factors Are Selenium Targets for Development of a Mechanism-Based Combination Strategy in Clear-Cell Renal Cell Carcinoma-Bench-to-Bedside Therapy.

Durable response, inherent or acquired resistance, and dose-limiting toxicities continue to represent major barriers in the treatment of patients with advanced clear-cell renal cell carcinoma (ccRCC). The majority of ccRCC tumors are characterized by the loss of Von Hippel⁻Lindau tumor suppressor gene function, a stable expression of hypoxia-inducible factors 1α and 2α (HIFs), an altered expression of tumor-specific oncogenic microRNAs (miRNAs), a clear cytoplasm with dense lipid content, and overexpression of thymidine phosphorylase. The aim of this manuscript was to confirm that the downregulation of specific drug-resistant biomarkers deregulated in tumor cells by a defined dose and schedule of methylselenocysteine (MSC) or seleno-l-methionine (SLM) sensitizes tumor cells to mechanism-based drug combination. The inhibition of HIFs by selenium was necessary for optimal therapeutic benefit. Durable responses were achieved only when MSC was combined with sunitinib (a vascular endothelial growth factor receptor (VEGFR)-targeted biologic), topotecan (a topoisomerase 1 poison and HIF synthesis inhibitor), and S-1 (a 5-fluorouracil prodrug). The documented synergy was selenium dose- and schedule-dependent and associated with enhanced prolyl hydroxylase-dependent HIF degradation, stabilization of tumor vasculature, downregulation of 28 oncogenic miRNAs, as well as the upregulation of 12 tumor suppressor miRNAs. The preclinical results generated provided the rationale for the development of phase 1/2 clinical trials of SLM in sequential combination with axitinib in ccRCC patients refractory to standard therapies.

Selenocysteine inhibits human osteosarcoma cells growth through triggering mitochondrial dysfunction and ROS-mediated p53 phosphorylation.

Osteosarcoma represents the most common primary malignant bone tumor in children and adolescents, which shows severe resistance toward standard chemotherapy because of high invasive capacity and growing incidence. Selenocysteine (SeC) is a naturally available Se-containing amino acid that displays splendid anticancer activities against several human tumors. However, little information about SeC-induced growth inhibition against human osteosarcoma is available. Herein, the anticancer efficiency and underlying mechanism of SeC against human osteosarcoma were evaluated in vitro and in vivo. The results revealed that SeC significantly inhibited MG-63 human osteosarcoma cells growth in vitro through induction of S-phase arrest and apoptosis, as reflected by the decrease of cyclin A and CDK-2, PARP cleavage, and caspases activation. SeC treatment also resulted in mitochondrial dysfunction through affecting Bcl-2 family expression. Moreover, SeC triggered p53 phosphorylation by inducing reactive oxygen species (ROS) overproduction. ROS inhibition effectively blocked SeC-induced cytotoxicity and p53 phosphorylation. Importantly, MG-63 human osteosarcoma xenograft growth in nude mice was significantly suppressed in vivo through triggering apoptosis and p53 phosphorylation. These results indicated that SeC had the potential to inhibit human osteosarcoma cells growth in vitro and in vivo through triggering mitochondrial dysfunction and ROS-mediated p53 phosphorylation, which validated the potential application of Se-containing compounds in treatment of human osteosarcoma.

Which form is that? The importance of selenium speciation and metabolism in the prevention and treatment of disease.

The biological activity of selenium is dependent upon its speciation. We aim to integrate selenium speciation and metabolism into a discussion of the mechanisms by which selenium exerts its biological activity. First, we present the current status of selenium in the prevention of cancer, cardiovascular and neurodegenerative diseases with particular attention paid to the results of major chemoprevention trials involving selenium supplementation. A comprehensive review of the current understanding of the metabolism of common dietary selenium compounds - selenite, selenomethionine, methylselenocysteine and selenocystine - is presented, with discussion of the evidence for the various metabolic pathways and their products. The antioxidant, prooxidant and other mechanisms of the dietary selenium compounds have been linked to their disease prevention and treatment properties. The evidence for these various mechanisms -in vitro, in cells and in vivo- is evaluated with emphasis on the selenium metabolites involved. We conclude that dietary selenium compounds should be considered prodrugs, whose biological activity will depend on the activity of the various metabolic pathways in, and the redox status of, cells and tissues. These factors should be considered in future laboratory research and in selecting selenium compounds for trials of disease prevention and treatment by selenium supplementation.

Organic and inorganic selenium compounds inhibit mouse mammary cell growth in vitro by different cellular pathways.

Selenium, both organic and inorganic forms, inhibit mammary tumorigenesis in vivo and mammary cell growth in vitro. In the present study, sodium selenite was compared to methylselenocysteine (MSC) for their individual effects on cell growth, cdc2/cdk2 kinase activities and the levels of cyclins D1, E and A bound to cdk2 in a mouse mammary epithelial cell culture model. Selenite arrested the growth of cells in S-G2-M phase in contrast to MSC which arrested or delayed the cells in G1. In MSC-treated cells there was a 57% drop in the cdk2 kinase activity accompanied by a 73.5% decrease in cyclin E-cdk2 content as compared to the control cells. Selenite treatment increased the cdk2 kinase activity by 30% without any appreciable change in either of the cyclins D1, E or A bound to cdk2 when compared to the control cells. These data support the hypothesis that selenite and MSC have distinct modes of action in the inhibition of cell growth in vitro. Selenite has a strong genotoxic effect on the tumor cells; in contrast, MSC appears to inhibit cell growth via specific inhibition of cell cycle regulatory proteins.