ADULT T-CELL LEUKEMIA (ATL)-DERIVED FACTOR HUMAN THIOREDOXIN PREVENTSAPOPTOSIS OF LYMPHOID-CELLS INDUCED BY L-CYSTINE AND GLUTATHIONE DEPLETION - POSSIBLE INVOLVEMENT OF THIOL-MEDIATED REDOX REGULATION IN APOPTOSIS CAUSED BY PROOXIDANT STATE

Thiol compounds, such as L-cysteine and glutathione (GSH), play crucia l roles in the regulation of lymphocyte proliferation. In this study, we analyzed the effect of L-cystine and GSH depletion on lymphocyte su rvival and investigated the regulatory roles of adult T cell leukemia (ATL)-derived factor (ADF)/human thioredoxin (hTRX) in relation to the se low m.w. thiols, MT-1, MT-2, and Jurkat cells underwent apoptosis w hen cultured in the L-cystine- and GSH-free medium within 18 to 24 h. Dichlorofluorescin oxidation assay indicated that the apoptosis in MT- 1 and MT-2 cells was preceded by an increase in the level of intracell ular hydrogen peroxide (H2O2). The addition of catalase and recombinan t ADF/hTRX (rADF) partially blocked the apoptosis in a dose-dependent manner, rADF has been also shown to enhance the internalization of L-c ystine into MT-2 cells in a dose-dependent manner, whereas oxidized rA DF or mutated rADF that has no insulin-reducing activity failed to do so, Furthermore, culture in the L-cystine- and GSH-free medium lowered the cellular GSH content of PHA blasts, which was restored dose-depen dently by rADF, These data suggest that the inability to neutralize ox idative stress results in the apoptosis of lymphoid cells under L-cyst ine- and GSH-depleted conditions. The protective effects of rADF may b e explained by direct scavenging action on H2O2 (catalase-like activit y) or by indirect neutralizing effects on the pro-oxidant status throu gh enhancing the L-cystine internalization and elevating the intracell ular GSH content.