Role of tRNA selenocysteine 1 associated protein 1 in the proliferation and apoptosis of cardiomyocyte‑like H9c2 cells

Selenium Deficiency-Induced Damage and Altered Expression of Mitochondrial Biogenesis Markers in the Kidneys of Mice

Previous studies have raised concerns that kidney disease is often closely related to low serum Se levels in patients and that hyposelenemia may increase the vulnerability of patients to complications. However, few studies examining renal injury caused by Se deficiency have been conducted. To determine the effects of a selenium-deficient diet on renal function, a mouse model was fed a selenium-deficient diet (0.02 mg Se/kg) for 20 weeks. Meanwhile, mice in the control group (selenium-adequate) were fed a standard diet (0.18 mg Se/kg). The cellular models were established by lentiviral Trnau1ap-shRNA vectors transfected into mouse podocyte (MPC5) and mouse renal tubular epithelial (TCMK1) cell lines. Significant increases in serum creatinine levels and urinary protein/creatinine ratios were accompanied by increased MDA content in the Se-deficient group compared to the control group. The morphological observations of tissues showed widespread inflammation and ultrastructural changes in the Se-deficient group, such as swollen mitochondria and extensive podocyte fusion and renal tubular microvilli shedding. In addition, the expression of COXIV and cytochrome c was significantly downregulated in the Se-deficient group. Importantly, the mRNA levels of silent mating type information regulation 2 homolog 1 (SIRT1) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and the protein levels of SIRT1 were increased in the Se-deficient group compared with the normal control group. Our data indicate that Se deficiency induces renal injury in mice. The elevated oxidative stress caused by Se deficiency may result in mitochondrial damage, which might affect renal function. Moreover, the SIRT1/PGC1α axis likely plays an important role in the compensatory mechanism of mitochondrial dysfunction.

The many lives of Myc in the pancreatic β-cell

Diabetes results from insufficient numbers of functional pancreatic β-cells. Thus, increasing the number of available functional β-cells ex vivo for transplantation, or regenerating them in situ in diabetic patients, is a major focus of diabetes research. The transcription factor, Myc, discovered decades ago lies at the nexus of most, if not all, known proliferative pathways. Based on this, many studies in the 1990s and early 2000s explored the potential of harnessing Myc expression to expand β-cells for diabetes treatment. Nearly all these studies in β-cells used pathophysiological or supraphysiological levels of Myc and reported enhanced β-cell death, dedifferentiation, or the formation of insulinomas if cooverexpressed with Bcl-xL, an inhibitor of apoptosis. This obviously reduced the enthusiasm for Myc as a therapeutic target for β-cell regeneration. However, recent studies indicate that "gentle" induction of Myc expression enhances β-cell replication without induction of cell death or loss of insulin secretion, suggesting that appropriate levels of Myc could have therapeutic potential for β-cell regeneration. Furthermore, although it has been known for decades that Myc is induced by glucose in β-cells, very little is known about how this essential anabolic transcription factor perceives and responds to nutrients and increased insulin demand in vivo. Here we summarize the previous and recent knowledge of Myc in the β-cell, its potential for β-cell regeneration, and its physiological importance for neonatal and adaptive β-cell expansion.

Calcium inhibitor inhibits high glucose‑induced hypertrophy of H9C2 cells

The aim of the present study was to explore whether the hypertrophy of H9C2 cardiomyocytes was induced by high glucose, to investigate whether the calcium channel inhibitor (Norvasc) could inhibit this process and to clarify the possible signaling pathways. The morphology of H9C2 cells was observed under an optical microscope, and the cell surface area was measured by Image Pro Plus 6.1 software. Furthermore, fluorescence spectrophotometry was used to detect intracellular calcium concentration ([Ca²⁺]i). ELISA was performed to detect calcineurin (CaN) activity; reverse transcription-quantitative PCR and western blotting were performed to detect the mRNA and protein expression levels of CaN Aβ subunit (CnAβ), nuclear factor of activated T cells 3 (NFAT3) and β type myosin heavy chain (β-MHC). Cell size was increased with the increase in glucose concentration of culture medium at 48 and 72 h, respectively, and decreased with the addition of Norvasc compared with those without Norvasc (P<0.05). There was no significant difference in cell size with the addition of Norvasc compared with cells cultured with 5 mM glucose (P>0.05). The average [Ca²⁺]i activity of single cells in the 48- and 72-h culture groups treated with 50 mM glucose was significantly higher than cells treated with 5 mM glucose (P<0.05); and the fluorescent value of average [Ca²⁺]i activity of single cells was lower, following the addition of Norvasc than that without Norvasc (P<0.05). CaN activity in the 48- and 72-h culture group treated with 50 mM glucose was markedly higher than that treated with 5 mM glucose, and the activity of CaN notably decreased with the addition of Norvasc compared with those without Norvasc. The mRNA and protein expression levels of CnAβ, NFAT3 and β-MHC in the 48- and 72-h culture groups treated with 50 mM glucose were all significantly higher than those treated with 5 mM glucose (P<0.05). The mRNA and protein expression of CnAβ, NFAT3 and β-MHC cultured with 50 mM glucose were significantly decreased following the addition of Norvasc (P<0.05). Thus, the calcium channel inhibitor Norvasc may inhibit high glucose-induced hypertrophy of H9C2 cardiomyocytes by inhibiting the Ca²⁺-CaN-NFAT3 signaling pathway.

Selenium supplementation protects against oxidative stress-induced cardiomyocyte cell cycle arrest through activation of PI3K/AKT

Oxidative stress significantly contributes to heart disease, and thus might be a promising target for ameliorating heart failure. Mounting evidence suggests that selenium has chemotherapeutic potential for treating heart disease due to its regulation of selenoproteins, which play antioxidant regulatory roles. Oxidative stress-induced cardiomyocyte cell cycle arrest contributes to the loss of cardiomyocytes during heart failure. The protective effects and mechanism of selenium against oxidative stress-induced cell cycle arrest in cardiomyocytes warrant further study. H9c2 rat cardiomyoblast cells were treated with hydrogen peroxide in the presence or absence of selenium supplementation. Na2SeO3 pretreatment alleviated H2O2-induced oxidative stress, increased thioredoxin reductase (TXNRD) activity and glutathione peroxidase (GPx) activity and counteracted the H2O2-induced cell cycle arrest at the S phase. These effects were accompanied by attenuation of the H2O2-induced strengthening of the G2/M-phase inhibitory system, including increased mRNA and protein levels of cyclin-dependent kinase 1 (CDK1) and decreased p21 mRNA levels. Notably, Na2SeO3 pretreatment activated the PI3K/AKT signaling pathway, and inhibition of PI3K counteracted the protective effects of selenium on H2O2-induced cell cycle arrest. We corroborated our findings in vivo by inducing oxidative stress in pig heart by feeding a selenium deficient diet, which decreased the TXNRD activity, inactivated PI3K/AKT signaling and strengthened the G2/M-phase inhibitory system. We concluded that the cardioprotective effects of selenium supplementation against oxidative stress-induced cell cycle arrest in cardiomyocytes might be mediated by the selenoprotein-associated (GPx and TXNRD) antioxidant capacity, thereby activating redox status-associated PI3K/AKT pathways, which promote cell cycle progression by targeting the G2/M phase inhibitory system. This study provides new insight into the underlying mechanisms of cardioprotection effects of selenium at the cellular level.

[Selenium compounds in redox regulation of inflammation and apoptosis]

Monocytes and macrophages play a key role in the development of inflammation: under the action of lipopolysaccharides (LPS), absorbed from the intestine, monocytes and macrophages form reactive oxygen species (ROS) and cytokines, this leads to the development of oxidative stress, inflammation and/or apoptosis in all types of tissues. In the cells LPS induce an "internal" TLR4-mediated MAP-kinase inflammatory signaling pathway and cytokines through the superfamily of tumor necrosis factor receptor (TNFR) and the "death domain" (DD) initiate an "external" caspase apoptosis cascade or necrosis activation that causes necroptosis. Many of the proteins involved in intracellular signaling cascades (MYD88, ASK1, IKKa/b, NF-kB, AP-1) are redox-sensitive and their activity is regulated by antioxidants thioredoxin, glutaredoxin, nitroredoxin, and glutathione. Oxidation of these signaling proteins induced by ROS enhances the development of inflammation and apoptosis, and their reduction with antioxidants, on the contrary, stabilizes the signaling cascades speed, preventing the vicious circle of oxidative stress, inflammation and apoptosis that follows it. Antioxidant (AO) enzymes thioredoxin reductase (TRXR), glutaredoxin reductase (GLRXR), glutathione reductase (GR) are required for reduction of non-enzymatic antioxidants (thioredoxin, glutaredoxin, nitroredoxin, glutathione), and AO enzymes (SOD, catalase, GPX) are required for ROS deactivation. The key AO enzymes (TRXR and GPX) are selenium-dependent; therefore selenium deficiency leads to a decrease in the body's antioxidant defense, the development of oxidative stress, inflammation, and/or apoptosis in various cell types. Nrf2-Keap1 signaling pathway activated by selenium deficiency and/or oxidative stress is necessary to restore redox homeostasis in the cell. In addition, expression of some genes is changed with selenium deficiency. Consequently, growth and proliferation of cells, their movement, development, death, and survival, as well as the interaction between cells, the redox regulation of intracellular signaling cascades of inflammation and apoptosis, depend on the selenium status of the body. Prophylactic administration of selenium-containing preparations (natural and synthetic (organic and inorganic)) is able to normalize the activity of AO enzymes and the general status of the body. Organic selenium compounds have a high bioavailability and, depending on their concentration, can act both as selenium donors to prevent selenium deficiency and as antitumor drugs due to their toxicity and participation in the regulation of signaling pathways of apoptosis. Known selenorganic compounds diphenyldiselenide and ethaselen share similarity with the Russian organo selenium compound, diacetophenonylselenide (DAPS-25), which serves as a source of bioavailable selenium, exhibits a wide range of biological activity, including antioxidant activity, that governs cell redox balance, inflammation and apoptosis regulation.