THE INVOLVEMENT OF OXIDANT AND ANTIOXIDANT SYSTEM IN FAS-MEDIATED APOPTOSIS OF ATL CELLS.

从氧化和抗氧化系统的角度研究了FSA(CD95)介导ATL细胞凋亡的机制。我们建立了几个对抗Fas-IgM单抗敏感或耐药的ATL细胞系，虽然抗Fas单抗的加入导致敏感细胞产生氧自由基，但耐药细胞不产生氧自由基。8-羟基脱氧鸟苷(8-OHdG)的形成与氧自由基的产生密切相关，表明氧自由基能引起DNA损伤。抗性细胞内抗氧化剂谷胱甘肽(GSH)和谷氨酰半胱氨酸合成酶(GCS)是GSH合成的关键酶，是敏感细胞的2~3倍。有趣的是，Fas耐药细胞对抗肿瘤药物表现出交叉耐药性。此外，ATL患者化疗后尿样中8-OHdG呈一过性升高，提示抗肿瘤药物也使用氧化剂进行细胞杀伤。但由于外源性GSH的加入并不能消除Fas诱导的细胞凋亡，因此提示除了抗氧化剂外，还有其他保护机制参与其中。通过对抗性细胞Fas基因的分子分析，我们发现其中一个细胞系存在死亡结构域基因的缺失。

The mechanism of Fsa (CD95)-mediated apoptosis of ATL cells was studied in the context of oxidant and antioxidant system. We established several ATL cell lines, which were sensitive or resistant to anti-Fas IgM monoclonal antibody.Although the addition of anti-Fas resulted in formation of oxygen radical species in the sensitive ce11s, no oxygen radical was produced from the resistant cells. The oxygen radical induced DNA damage as determined by formation of 8-hydroxydeoxyguanosine (8-OHdG), which showed a mutual relation with oxygen radical production. The resistant cells had two to three times higher amounts of intracellular glutathione (GSH) as antioxidant and gamma-glutamylcysteine synthetase (gamma-GCS) as the key enzyme for GSH synthesis than the sensitive cells. Interestingly, Fas-resistant cells showed cross resistance to antineoplastic drugs. Moreover, the urine samples from ATL patients showed transient increase of 8-OHdG after chemotherapy suggesting that antineoplastic agents also use oxidant for cell killing.However, since the addition of exogenous GSH did not abrogate the Fas-induced apoptosis, the involvement of protective machanism other than antioxidant was suggested. By the molecular analysis of Fas genes of resistant cells, we found that one of the cell line had a deletion of the gene for death domain.