Selenium spares ascorbate and alpha-tocopherol in cultured liver cell lines under oxidant stress.
The selenoenzyme thioredoxin reductase (TR) can recycle ascorbic acid, which in turn can recycle alpha-tocopherol. Therefore, we evaluated the role of selenium in ascorbic acid recycling and in protection against oxidant-induced loss of alpha-tocopherol in cultured liver cells. Treatment of HepG2 or H4IIE cultured liver cells for 48 h with sodium selenite (0-116 nmol/l) tripled the activity of the selenoenzyme TR, measured as aurothioglucose-sensitive dehydroascorbic acid (DHA) reduction. However, selenium did not increase the ability of H4IIE cells to take up and reduce 2 mM DHA, despite a 25% increase in ascorbate-dependent ferricyanide reduction (which reflects cellular ascorbate recycling). Nonetheless, selenium supplements both spared ascorbate in overnight cultures of H4IIE cells, and prevented loss of cellular alpha-tocopherol in response to an oxidant stress induced by either ferricyanide or diazobenzene sulfonate. Whereas TR contributes little to ascorbate recycling in H4IIE cells, selenium spares ascorbate in culture and alpha-tocopherol in response to an oxidant stress.
Li
X
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Department of Medicine, 715 Medical Research Building II, Vanderbilt University School of Medicine, Nashville, TN 37232-6303, USA.
Hill
K E
KE
Burk
R F
RF
May
J M
JM
D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism*; D003470:Culture Media; D003683:Dehydroascorbic Acid / Q000378:metabolism; D003979:Diazonium Compounds / Q000494:pharmacology; D005292:Ferricyanides / Q000378:metabolism / Q000494:pharmacology; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism; D051381:Rats; D017279:Selenocysteine / Q000494:pharmacology; D018038:Sodium Selenite / Q000494:pharmacology*; D013425:Sulfanilic Acids / Q000494:pharmacology; D013880:Thioredoxin-Disulfide Reductase / Q000378:metabolism*; D013879:Thioredoxins / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D024502:alpha-Tocopherol / Q000378:metabolism*
D003470:Culture Media; D003979:Diazonium Compounds; D005292:Ferricyanides; D013425:Sulfanilic Acids; D017279:Selenocysteine; C007931:hexacyanoferrate III; D013879:Thioredoxins; D010088:Oxidoreductases; D013880:Thioredoxin-Disulfide Reductase; C020666:glutathione dehydrogenase (ascorbate); D024502:alpha-Tocopherol; D018038:Sodium Selenite; D001205:Ascorbic Acid; D003683:Dehydroascorbic Acid; C000469:diazobenzenesulfonic acid