alpha-tocopherol increases the intracellular glutathione level in HaCaT keratinocytes.
alpha-Tocopherol is a lipophilic vitamin that exhibits an antioxidative activity. The purpose of this study was to clarify the roles of alpha-tocopherol in the regulation of intracellular glutathione (GSH) levels in HaCaT keratinocytes. When HaCaT keratinocytes were cultivated with alpha-tocopherol for 24 h, the intracellular GSH was increased at every concentration of alpha-tocopherol tested. Furthermore, the HaCaT keratinocytes cultured with alpha-tocopherol at 50 microM for 24 h exhibited resistance against H2O2. However, a short exposure of HaCaT keratinocytes to alpha-tocopherol for 1 h did not influence either the GSH level or the resistance to H2O2. These findings suggest that GSH, which is inductively synthesized by alpha-tocopherol, effectively reduces exogenous oxidative stress. To evaluate the effect of alpha-tocopherol on the GSH level, BSO, which is a typical inhibitor of gamma-glutamylcysteine synthetase (gamma-GCS), was used. When BSO was added to HaCaT keratinocytes, no action of alpha-tocopherol on the GSH level was observed. On the other hand, alpha-tocopherol resulted in the up-regulation of gamma-GCS-HS (heavy subunit) mRNA. In addition, water soluble alpha-tocopherol derivatives (alpha-tocopherol phosphate and trolox) caused no changes in GSH level. From these results, it was concluded that alpha-tocopherol increases the intracellular GSH level of HaCaT keratinocytes through the up-regulation of gamma-GCS-HS mRNA.
Masaki
Hitoshi
H
Kobe Research Laboratory, Noevir Co., Ltd, 13-1 Port Island, Naka-machi, 6-chome, Chuo-ku, Kobe 650-8521, Japan.
Okano
Yuri
Y
Ochiai
Yasunobu
Y
Obayashi
Kei
K
Akamatsu
Hirohiko
H
Sakurai
Hiromu
H
D000975:Antioxidants / Q000378:metabolism* / Q000494:pharmacology; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002478:Cells, Cultured; D002839:Chromans / Q000378:metabolism / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D005721:Glutamate-Cysteine Ligase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D015854:Up-Regulation; D024502:alpha-Tocopherol / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology
D000975:Antioxidants; D002839:Chromans; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; C012552:alpha-tocopherol phosphate; D019328:Buthionine Sulfoximine; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D024502:alpha-Tocopherol; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid