| Research Abstract |
Fas antigen is a member of the tumor necrosis receptor family and mediates lethal signal to the Fas-sensitive cells. We previously established the Fas-resistant variant cell lines LAC2D1R and JKT2D1R from the original Fas-sensitive cell lines, SUPT13 and Jurkat, respectively. Recently, we also isolated the Fas-resistant variant CEM2D1R from CCRF-CEM.All of the variants were Fas-positive but resistant to Fas-mediated apoptosis. Further biochemical analysis revealed that the intracellular glutathione (GSH) content of the Fas-resistant variants was higher than in the original cells. When the Fas-resistant variants were incubated with buthionine sulfoximine (BSO) or in GSH-free/cysteine-free medium to deplete GSH,Fas-resistance was reversed. Incubation of the cells with cycloheximide also decreased intracellular GSH and reversed the Fas-resistance. Furthermore, incubation of activated peripheral blood lymphocytes with BSO enhanced Fas-mediated apoptosis. When the Fas-sensitive cells were incubated with n-acetyl cysteine (NAC), intracellular GSH was increased and Fas-mediated apoptosis was blocked. In contrast, Fas-resistant variants, as well as Fas-sensitive cells pretreated with NAC,remained susceptible to allogenic lymphokine-activated killer cells, most likely due to perforin-dependent killing. The results suggest that Fas-mediated apoptosis, but not perforin-dependent killing, is modulated by the intracellular GSH in human T lymphocytes.
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