title: Synergy between sulforaphane and selenium in the up-regulation of thioredoxin reductase and protection against hydrogen peroxide-induced cell death in human hepatocytes.
abstract: Dietary isothiocyanates and selenium are chemopreventive agents and potent inducers of antioxidant enzymes. It has been previously shown that sulforaphane and selenium have a synergistic effect on the upregulation of thioredoxin reductase-1 (TrxR-1) in human hepatoma HepG2 cells. In this paper, further evidence is presented to show that sulforaphane and selenium synergistically induce TrxR-1 expression in immortalised human hepatocytes. Sulforaphane was found to be more toxic toward hepatocytes than HepG2 cells with IC50=25.1 and 56.4 μM, respectively. Sulforaphane can protect against hydrogen peroxide-induced cell death and this protection was enhanced by co-treatment with selenium. Using siRNA to knock down TrxR-1 or Nrf2, sulforaphane (5 μM)-protected cell viability was reduced from 73% to 46% and 34%, respectively, suggesting that TrxR-1 is an important enzyme in protection against hydrogen peroxide-induced cell death. Sulforaphane-induced TrxR-1 expression was positively associated with significant levels of Nrf2 translocation into the nucleus, but co-treatment with selenium showed no significant increase in Nrf2 translocation. Moreover, MAPK (ERK, JNK and p38) and PI3K/Akt signalling pathways were found to play no significant role in sulforaphane-induced Nrf2 translocation into the nucleus. However, blocking ERK and JNK signalling pathways decreased sulforaphane-induced TrxR-1 mRNA by about 20%; whereas blocking p38 and PI3K/AKT increased TrxR-1 transcription. In summary, a combination of sulforaphane and selenium resulted in a synergistic upregulation of TrxR-1 that contributed to the enhanced protection against free radical-mediated oxidative damage in human hepatocytes.
authors: Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, Harbin 150081, China.
authors: Dan
authors: D
authors: Li
authors: Department of Nutrition, Norwich Medical School, University of East Anglia, Norwich NR4 7TJ, UK.
authors: Wei
authors: W
authors: Wang
authors: Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, Harbin 150081, China.
authors: Yujuan
authors: Y
authors: Shan
authors: Department of Nutrition, Norwich Medical School, University of East Anglia, Norwich NR4 7TJ, UK.
authors: Lawrence N
authors: LN
authors: Barrera
authors: University of Edinburgh, Division of Reproduction and Development Sciences, Edinburgh EH16 4SB, UK.
authors: Alexander F
authors: AF
authors: Howie
authors: University of Edinburgh, Division of Reproduction and Development Sciences, Edinburgh EH16 4SB, UK.
authors: Geoffrey J
authors: GJ
authors: Beckett
authors: Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, Harbin 150081, China. Electronic address: wukun_15000@126.com.
authors: Kun
authors: K
authors: Wu
authors: Department of Nutrition, Norwich Medical School, University of East Anglia, Norwich NR4 7TJ, UK. Electronic address: y.bao@uea.ac.uk.
authors: Yongping
authors: Y
authors: Bao
mesh_terms: D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D004357:Drug Synergism; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity; D017879:Isothiocyanates / Q000378:metabolism / Q000494:pharmacology*; D012643:Selenium / Q000494:pharmacology*; D013454:Sulfoxides; D013880:Thioredoxin-Disulfide Reductase / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D017879:Isothiocyanates; D013454:Sulfoxides; C037152:isothiocyanic acid; D006861:Hydrogen Peroxide; D013880:Thioredoxin-Disulfide Reductase; C016766:sulforaphane; D012643:Selenium
keywords: Cruciferous vegetable; Dietary supplement; Hepatocytes; Selenium; Sulforaphane; Thioredoxin reductase