Accumulation of intracellular ascorbate from dehydroascorbic acid by astrocytes is decreased after oxidative stress and restored by propofol.
Primary rat astrocyte cultures absorbed dehydroascorbic acid from the medium and reduced it to intracellular ascorbate. Uptake of dehydroascorbic acid (5-200 microM) was inhibited only partially by glucose (10 mM). The remaining glucose-insensitive component of dehydroascorbic acid uptake was inhibited reversibly by sulfinpyrazone (IC(50) = 80 microM). Dehydroascorbic acid uptake was not mediated by Na(+)-ascorbate cotransporters or volume-sensitive anion channels because it was neither Na(+)-dependent nor blocked by the channel antagonist, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid. Oxidative stress, induced in astrocytes by the lipophilic radical generator tert-butyl hydroperoxide, decreased intracellular glutathione concentration and inhibited accumulation of intracellular ascorbate from dehydroascorbic acid. Subsequent administration of either the native antioxidant alpha-tocopherol (200 microM) or anesthetic concentrations of the antioxidant sedative propofol (1-8 microM, administered 30 min after tert-butyl hydroperoxide), did not change glutathione concentration but restored the ability of astrocytes to accumulate intracellular ascorbate from dehydroascorbic acid. These results are consistent with a novel mechanism of astrocytic ascorbate accumulation that is inhibited by lipophilic radicals and protected by lipophilic antioxidants such as propofol.
Daskalopoulos
Rina
R
Department of Physiology, Faculty of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.
Korcok
Jasminka
J
Tao
Lei
L
Wilson
John X
JX
D000818:Animals; D000831:Animals, Newborn; D001205:Ascorbic Acid / Q000096:biosynthesis*; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D002545:Brain Ischemia / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology; D002478:Cells, Cultured; D003683:Dehydroascorbic Acid / Q000378:metabolism* / Q000494:pharmacology; D003847:Deoxyglucose / Q000378:metabolism / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D016166:Free Radical Scavengers / Q000494:pharmacology*; D005632:Fructose / Q000378:metabolism / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D010693:Phloretin / Q000494:pharmacology; D015742:Propofol / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000172:deficiency; D013442:Sulfinpyrazone / Q000494:pharmacology; D014528:Uricosuric Agents / Q000494:pharmacology
D016166:Free Radical Scavengers; D014528:Uricosuric Agents; D005632:Fructose; D003847:Deoxyglucose; D012964:Sodium; D005947:Glucose; D001205:Ascorbic Acid; D010693:Phloretin; D013442:Sulfinpyrazone; D003683:Dehydroascorbic Acid; D015742:Propofol