Selenoprotein P mRNA expression in human hepatic tissues

The Role of Selenium Nanoparticles in the Treatment of Liver Pathologies of Various Natures

The liver is the body's largest gland, and regulates a wide variety of physiological processes. The work of the liver can be disrupted in a variety of pathologies, the number of which is several hundred. It is extremely important to monitor the health of the liver and develop approaches to combat liver diseases. In recent decades, nanomedicine has become increasingly popular in the treatment of various liver pathologies, in which nanosized biomaterials, which are inorganic, polymeric, liposomal, albumin, and other nanoparticles, play an important role. Given the need to develop environmentally safe, inexpensive, simple, and high-performance biomedical agents for theragnostic purposes and showing few side effects, special attention is being paid to nanoparticles based on the important trace element selenium (Se). It is known that the metabolism of the microelement Se occurs in the liver, and its deficiency leads to the development of several serious diseases in this organ. In addition, the liver is the depot for most selenoproteins, which can reduce oxidative stress, inhibit tumor growth, and prevent other liver damage. This review is devoted to the description of the results of recent years, revealing the important role of selenium nanoparticles in the therapy and diagnosis of several liver pathologies, depending on the dose and physicochemical properties. The possibilities of selenium nanoparticles in the treatment of liver diseases, disclosed in the review, will not only reveal the advantages of their hepatoprotective properties but also significantly supplement the data on the role of the trace element selenium in the regulation of these diseases.

Supression Thioredoxin reductase 3 exacerbates the progression of liver cirrhosis via activation of ferroptosis pathway

AIMS

In the past decades, Txnrd3 as selenoprotein is considered to be highly expressed in testis and participate in sperm mature; however its role in liver diseases needs further study. Iron is essential for humans and animals, while its overload could damage to multiple organs. However, role of Txnrd3 and iron in cirrhosis is still unclear.

MATERIALS AND METHODS

Forty 8-week-old wild-type and forty Txnrd3-/- mice were selected to build liver cirrhosis model using Thiacetamide solution, deposition of iron in liver was observed via Prussian blue staining. Txnrd3 overexpression/knockdown model in vitro was constructed based on cell transfection techniques in AML12 cells, expression abundance of ferroptosis pathway genes within cells and tissues were determined by qRT-PCR and Western Blot.

KEY FINDINGS

Results showed that Txnrd3-/- mice developed more pronounced liver damage, accompanied by reduced GPX4 expression and iron deposition. A significant decrease in the expression abundance of GPX4 was also detected in Txnrd3 knock-down AML12 cells. In summary, Txnrd3 knockdown could result in iron overload and ferroptosis pathway activation within liver tissues and hepatocytes, ultimately lead to the occurrence of liver injury and cirrhosis.

SIGNIFICANCE

These results will provide biological markers for early diagnosis during cirrhosis and lay a theoretical basis for clinical therapy.

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.

Potential relationship between the selenoproteome and cancer

The role of the selenoproteome, which is the collection of all proteins containing selenium in an organism, in cancer development, growth and progression requires further investigation, due to the importance of selenium in both cancer and immune system function. Data about the selenoproteome, including its differential expression, single nucleotide variations, copy number variations, methylation, pathways and overall survival (OS) in five leading types of cancer are available from the GSCALite website. Subsequent to the analysis of these datasets, it was revealed that there was increased expression of GPX3 in stomach adenocarcinoma and lung squamous cell carcinoma, SELENOV in oesophageal carcinoma, GPX8 and GPX4 in colon adenocarcinoma, TXNRD1 and SEPHS1 in hepatocellular carcinoma and GPX8 in lung adenocarcinoma were associated with poor survival. Decreased gene expression of SELENOP was indicated in liver hepatocellular carcinoma and GPX3, and SELENOW, SELENOK, SELENBP1 and SECISBP2 in lung adenocarcinoma were associated with a poor prognosis. OS data suggested that hypermethylation of GPX4 in colon adenocarcinoma, GPX8 in lung squamous cell carcinoma, GPX1 in stomach adenocarcinoma and GPX3 in lung adenocarcinoma was associated with low survival, as is hypomethylation of GPX5 in lung adenocarcinoma. The selenoproteome is heterogeneous, especially in its effect on the OS of patients with cancer. The present study demonstrated that the roles of GPX4 in colon adenocarcinoma, SCLY and SELENOV in oesophageal carcinoma, SEPHS1 in liver hepatocellular carcinoma, SELENOK in lung cancer, as well as SELENOM and SELENOW in stomach adenocarcinoma requires further research. The present study may lead to the identification of novel biomarkers or potential therapeutic targets for use in the treatment of cancers, such as colon adenocarcinoma, oesophageal carcinoma, liver hepatocellular carcinoma, lung cancer and stomach adenocarcinoma.

Selenoprotein P inhibits cell proliferation and ROX production in HCC cells

Selenoprotein P (SEPP1) is a kind of secretory glycoproteins with an antioxidant effect during the development of some diseases. In this study, we attempted to observe the expression of SEPP1 in livers from the patients with hepatocellular carcinoma (HCC) and explore its effect on HCC cells. All the tissues from patients with HCC were obtained from Affiliated Hospital of Nantong University. Western blot and immunohistochemical results showed that SEPP1 was reduced in HCC liver tissues. Its expression was negatively correlated with Ki67 expression in tissues. The expression of SEPP1 in normal liver cell line was significantly higher than those in the liver cancer cell lines. Serum starvation and release experiment demonstrated that SEPP1 expression was reduced and PCNA expression was increased, when the serum was re-added into cell culture system and the cells were on a proliferation state. After SEPP1 over-expression plasmid was transfected into HepG2 cells, cell proliferation of HepG2 cells and PCNA expression level were all inhibited by SEPP1. Results obtained via 8-isoprostane ELISA further indicated that inhibited ROS level was found in HepG2 cells transfected with SEPP1 over-expression plasmid. In addition, RT-qPCR results demonstrated that GPX1 expression levels increased in HepG2 cells transfected with SEPP1 over-expression plasmid. In conclusion, SEPP1 may inhibit the proliferation of HCC cells, accompanied by the reduction of ROS production and the increasing of GPX1 expression.

Selenium and selenoprotein P in nonalcoholic fatty liver disease

Conflicting data link nonalcoholic fatty liver disease (NAFLD), a disease with no currently approved treatment, with selenium (Se) and selenoprotein P (SELENOP), a glycoprotein synthesized and primarily secreted by the hepatocytes, functioning as a Se transporter from the liver to other tissues. This review aims to summarize the evidence between Se, SELENOP, and NAFLD, which may hopefully clarify whether current data on Se and SELENOP in NAFLD warrant further investigation for their diagnostic and therapeutic potential. Most, albeit not all, experimental data show a favorable effect of Se on hepatic steatosis, inflammation, and fibrosis. It seems that Se may exert an antioxidant effect on the liver, at least partly via increasing the activity of glutathione peroxidase, whose depletion contributes to the pathogenesis of hepatic inflammation and fibrosis. Se may also affect metalloproteinases, cytokines, and growth factors participating in the pathogenesis of NAFLD and, most importantly, may induce the apoptosis of hepatic stellate cells, the key players in hepatic fibrosis. However, the association between Se or SELENOP and insulin resistance, which is a principal pathogenetic factor of NAFLD, remains inconclusive. Clinical studies on Se or SELENOP in NAFLD are conflicting, apart from those in advanced liver disease (cirrhosis or hepatocellular carcinoma), in which lower circulating Se and SELENOP are constant findings. Existing data warrant further mechanistic studies in valid animal models of human NAFLD. Prospective cohort studies and possibly randomized controlled trials are also needed to elucidate the diagnostic and therapeutic potential of Se supplementation in selected NAFLD individuals with Se deficiency.

Role of microRNA-7 and selenoprotein P in hepatocellular carcinoma

There is an obvious need to diagnose hepatocellular carcinoma using novel non-invasive and sensitive biomarkers. In this regard, the aim of this study was to evaluate and correlate both relative quantification of microRNA-7 using quantitative real time polymerase chain reaction and quantitative analysis of selenoprotein P using enzyme-linked immunosorbent assay in sera of hepatocellular carcinoma patients, chronic liver disease patients, as well as normal healthy subjects in order to establish a new diagnostic biomarker with a valid non-invasive technique. In addition, this study aimed to investigate whether changes in selenium supply affect microRNA-7 expression and selenoprotein P levels in human hepatocarcinoma cell line (HepG2). The results showed a highly significant decrease in serum microRNA-7 relative quantification values and selenoprotein P levels in malignant group in comparison with benign and control groups. The best cutoff for serum microRNA-7 and selenoprotein P to discriminate hepatocellular carcinoma group from benign and control groups was 0.06 and 4.30 mg/L, respectively. Furthermore, this study showed that changes in selenium supply to HepG2 cell line can alter the microRNA-7 profile and are paralleled by changes in the concentration of its target protein (selenoprotein P). Hence, serum microRNA-7 and selenoprotein P appear to be potential non-invasive diagnostic markers for hepatocellular carcinoma. Moreover, the results suggest that selenium could be used as an anticancer therapy for hepatocellular carcinoma by affecting both microRNA-7 and selenoprotein P.

Molecular network pathways and functional analysis of tumor signatures associated with development of resistance to viral gene therapy

Replication-competent attenuated herpes simplex viruses have proven effective in killing many cancer cell lines. However, determinants of resistance to oncolytic therapy are mostly unknown. We developed viral therapy-resistant cells and examined changes in gene-expression pattern compared with therapy-sensitive parental cells. Colon cancer cell line HT29 and hepatoma cell line PLC5 were exposed to increasing concentrations of virus G207. Therapy-resistant cells were isolated and grown in vitro. Tumorigenicity was confirmed by ability of cell lines to form tumors in mice. Human Genome U133A complementary DNA microarray chips were used to determine gene-expression patterns, which were analyzed in the context of molecular network interactions, pathways and gene ontology. In parental cell lines, 90-100% of cells were killed by day 7 at 1.0 multiplicity of infection. In resistant cell lines, cytotoxicity assay confirmed 200- to 400-fold resistance. Microarray analysis confirmed changes in gene expressions associated with resistance: cell surface proteins affecting viral attachment and entry, cellular proteins affecting nucleotide pools and proteins altering apoptotic pathways. These changes would decrease viral infection and replication. Our study identifies gene-expression signatures associated with resistance to oncolytic viral therapy. These data provide potential targets to overcome resistance, and suggest that molecular assays may be useful in selecting patients for trial with this novel treatment.

Relevance of selenoprotein transcripts for selenium status in humans

The most commonly used methods for assessing the selenium (Se) status in humans involve analysis of Se concentration, selenoprotein activity, and concentration in the blood and its compartments. Recently, it has been suggested that the expression of selenoprotein mRNA in circulating blood leukocytes could differently reflect Se status, due to prioritization of specific selenoprotein synthesis in response to dietary Se supply. Whereas the Se levels required for optimization of selenoprotein P level and plasma glutathione peroxidise activity are well known, estimation of Se level that is required for maximal mRNA expression of selenoprotein in humans is the subject of current investigations. Studies on rats suggest that whole blood selenoprotein mRNA level can be used as the relevant molecular biomarker for assessing Se status, and suboptimal Se intake may be sufficient to achieve effective expression. Human studies, however, did not confirm this hypothesis. According to studies on rodents and humans discussed in this review, it appears that suboptimal Se intake may be sufficient to satisfy molecular requirements of Se and it is lower than current recommended dietary intake in humans. The use of selenoprotein transcripts as a molecular biomarker of Se status requires further studies on a large group of healthy individuals with different baseline Se, including data regarding genetic polymorphism of selenoproteins and data regarding potential modifiers of Se metabolism.

Expression of selenoprotein-coding genes SEPP1, SEP15 and hGPX1 in non-small cell lung cancer

Aim of the study was to investigate the mRNA expression level of selenoprotein P (SEPP1), 15-kDa selenoprotein (SEP15) and glutathione peroxidase 1 (hGPX1) in paired malignant and non-malignant tissue. To achieve this goal, the quantitative real-time PCR technique was utilized in paired tissue samples from 33 non-small cell lung cancer (NSCLC) patients. Simultaneously, the activity of glutathione peroxidases (GPX) and the level of thiobarbituric acid-reactive species (TBARS) in paired tissue specimens and the blood plasma selenium level was measured. We found significant down-regulation of SEPP1 expression level in tumorous lung tissue (2.732-fold; p<0.001). The expression of hGPX1 and SEP15 in tumorous tissue remained unchanged compared to healthy tissue. The level of TBARS in malignant tissue was significantly increased (p<0.005) and negatively correlated with SEPP1 expression level (R(S)=-0.3238; p<0.05). The activity of GPX in malignant tissue was significantly increased compared to the non-malignant one (p<0.005) and negatively correlated with the expression level of SEPP1. It seems possible, that the down-regulation of SEPP1 expression may lead to an increased oxidative stress possibly resulting in lung carcinogenesis. Increased activity of GPX in tumorous lung tissue seems to be a feedback mechanism.

Tissue Microarray Assessment of Selenoprotein P Expression in Gastric Adenocarcinoma

This study investigated selenoprotein P expression, using immunohistochemistry, in gastric adenocarcinoma tissue microarrays constructed from 30 gastric adenocarcinoma specimens and 30 normal gastric tissues (controls). Selenoprotein P expression scores were significantly lower in gastric adenocarcinoma (17/30, 56.7%) than in control tissues (25/30, 83.3%). Selenoprotein P was significantly more likely to be expressed in well-to-moderately differentiated cases (13/17, 76.5%) than in cases with low differentiation (4/13, 30.8%) and there was no significant difference in selenoprotein P expression between tumour node metastasis (TNM) stage I – II (11/19, 57.9%) and TNM stage III (6/11, 54.5%). In conclusion, selenoprotein P expression was low in gastric adenocarcinoma tissues compared with control tissues and was related to the degree of gastric adenocarcinoma differentiation but not to TNM stage.