Selenoprotein V Protects Against Oxidative Stress, Endoplasmic Reticulum Stress, and Apoptosis

Objectives Selenoprotein V (SELENOV) contains a thioredoxin-like fold and a conserved CxxU motif with a potential redox function. Three experiments were performed to assess its in vivo and in vitro roles and mechanisms in coping with different oxidant insults. Methods In Expt.1, SELENOV knockout (KO) and wildtype (WT) mice (male, 8-wk old) were given an IP injection of saline, diquat (DQ, 12.5 mg/kg), or acetaminophen (APAP, 300 mg/kg) (n = 10), and killed 5 h after the injection to collect liver and blood. In Expt. 2, primary hepatocytes were isolated from the 2 genotypes, cultured in complete Williams's medium E, and treated with DQ (0, 0.25 and 0.75 mM) and APAP (0, 1, 3, and 6 mM) for 12 h. In Expt. 3, 293 T cells were transfected with a control plasmid (GFP) or the plasmid containing Selenov gene (full length, OE) and treated with APAP (0, 1, 2, and 4 mM) for 24 h or H2O2 (0.1, 0.2, and 0.4 mM) for 12 h. Results In Expt. 1, the DQ and APAP injections caused greater (P < 0.05) rises in serum alanine aminotransferase activities, hepatic malondialdehyde (MDA) and carbonyl contents, endoplasmic reticulum (ER) stress-related proteins (BIP and CHOP), apoptosis-related proteins (FAK and caspase 9), and 3-nitrotyrosine, along with lower total anti-oxidizing-capability (T-AOC) and severer hepatocyte necrosis in the central lobular areas, in the KO than in the WT. In Expt. 2, the DQ and APAP treatments induced elevated (P < 0.05) cell death (20–40%), MDA contents (25–35%), and decreased (P < 0.05) T-AOC (50–65%) in the KO hepatocytes than in the WT cells. The KO hepatocytes treated with APAP displayed a sharp decline (P < 0.05) in cellular total respiration ability than the WT cells. In Expt. 3, the OE cells had greater viability and T-AOC and lower reactive oxygen species, MDA, and carbonyl contents after the APAP and H2O2 exposures (all at P < 0.05) than the controls. Moreover, the OE cells had greater (P < 0.05) redox enzyme activities (GPX, TrxR, and SOD), and lower (P < 0.05) expressions of ER stress-related genes (Atf4, Atf6, Bip, Xpp1t, Xbp1s, and Chop) and proteins (BIP, CHOP, FAK, caspase 9) than the controls after the treatment of H2O2 (0.4 mM). Conclusions Our data revealed the in vivo and in vitro roles and mechanisms of SELENOV in protecting against oxidative stress, ER stress, and apoptosis induced by pro-oxidants. Funding Sources This research is supported in part by an NSFC grant #31,320,103,920.

Knockout of Selenoprotein V Affects Regulation of Selenoprotein Expression by Dietary Selenium and Fat Intakes in Mice

ABSTRACT Background The metabolic function of selenoprotein V (SELENOV) remains unknown. Objectives Two experiments were conducted to determine effects of the Selenov knockout (KO) on selenium concentration and mRNA, protein, and/or activity of 4 major selenoproteins [glutathione peroxidase (GPX) 1, GPX4, thioredoxin reductase-1 (TXNRD1), and selenoprotein P (SELENOP)] in the serum, liver, testis, and/or white adipose tissue (WAT) of mice fed different dietary selenium and fat concentrations. Methods In Experiment (Expt) 1, 40 KO and 40 wild-type (WT) mice (males, 8 wk old) were fed (n = 10/genotype) a casein-sucrose basal diet plus 0, 0.3, 1, or 3 mg Se/kg (as sodium selenite) for 32 wk . In Expt 2, 20 KO and 20 WT mice (males, 8 wk old) were fed (n = 10/genotype) a normal-fat diet (NF; 10% calories from fat) or a high-fat diet (HF; 60% calories from fat) for 19 wk. Results In Expt 1, the KO caused consistent or substantial decreases (P < 0.05) of mRNA amounts of Gpx1, Txnrd1, and Selenop in the testis (≤52%), but selenium concentrations (19–29%) and GPX activities (≤ 50%) were decreased in the liver across different dietary selenium concentrations . Hepatic and testis GPX1 protein was elevated (≤31%) and decreased (≤45%) by the KO, respectively. In Expt 2, the genotype and dietary fat intake exerted interaction effects ( P < 0.05) on Gpx1 mRNA amounts in the WAT; Gpx1, Txnrd1, and Selenop mRNA amounts and TXNRD activities in the testis; and selenium concentrations in the serum and liver. However, these 2 treatments produced largely independent or additive effects (P < 0.05) on the GPX1 and SELENOP protein amounts in the liver and testis (up to ± 50% changes). Conclusions The KO-mediated changes in the tissue selenium concentrations and functional expression of 3 major selenoproteins implied potential for SELENOV in regulating body selenium metabolism in the mouse.

Loss of Selenoprotein V Predisposes Mice to Body Fat Accumulation (OR11-02-19)

Objectives Metabolic function of selenoprotein V (SELENOV) remains unknown, although we previously showed a strong correlation of its gene expression with the high-fat diet-induced obesity in pigs. This study was conducted to explore the role and mechanism of SELENOV in body fat metabolism. Methods We applied the CRISPR/Cas9 gene-targeting deletion to generate Selenovknockout (KO) mice (C57BL/6 J background). Male KO and their wild-type (WT) (8 weeks old, n = 10 per genotype by treatment group) were fed a normal diet (NF, 10% calories coming from fat) or a high-fat diet (HF, 60% calories coming from fat) for 27 weeks. At the end, body weights and composition of mice were recorded, and tissues were collected to assay for gene expression and protein production related to lipid metabolism. Results Body weights of the KO mice fed the NF or HF diet were 16–19% higher (P < 0.05) than those of the WT mice. Total fat mass of the KO mice was 54% higher (P < 0.05) than the WT mice fed either diet, whereas total lean mass of the KO mice was 5 and 35% lower (P < 0.05) than that of WT mice fed the NF and HF diets, respectively. Gene expression of key enzymes (Fasn, Acaca, Dgat1, and Lpl) involved in lipogenesis was elevated (P < 0.05) in the white adipose tissue of the KO mice compared with the WT mice. In contrast, differences in gene expression of enzymes related to lipolysis and fatty acid oxidation (Atgl, Hsl, Ces1d, and Cpt1a) between the two genotypes were exactly the opposite (P < 0.05). Consistently, levels of proteins related to lipid accumulation (pACC, ACC, FAS, and LPL) were upregulated (P < 0.05) and proteins related to lipolysis (ATGL, HSL, and pHSL) were down-regulated (P < 0.05) in the KO mice compared with the WT mice. Conclusions Knockout of Selenov predisposed the male mice to elevated lipogenesis and attenuated lipolyis, leading to the body fat accumulation. This illustrated role and mechanism of SELENOV helps explain our previously-reported correlation between its gene expression and the high-fat diet-induced obesity in pigs. Funding Sources This research was supported in part by a NSFC grant #31,320,103,920.