两型TNF-α的细胞毒效应与靶细胞内Ca2+浓度变化的关系

目的 :比较分泌型TNF α(S TNF α)和跨膜型TNF α(TM TNF α)发挥细胞毒效应时 ,引起靶细胞内Ca2 浓度的变化。方法 :采用生物学活性检测法 ,观察两型TNF α对不同靶细胞的杀伤效应 ;用Fura 2检测细胞内Ca2 浓度的变化。结果 :TM TNF α可杀伤实验所用 6株靶细胞 ;而S TNF α则仅对其中两株有细胞毒效应。两型TNF α杀伤靶细胞时 ,均伴有明显的Ca2 浓度升高。用钙螯合剂EGTA(10mmol/L)预先处理靶细胞30min ,只能降低S TNF α作用的靶细胞内的Ca2 浓度 ,并使其细胞毒效应明显减弱 (P <0 .0 1) ;对TM TNF α无影响。结论 :两型TNF α发挥细胞毒效应时 ,均可引起靶细胞内钙离子的重分布 ,导致靶细胞内Ca2 浓度的升高 ,但S TNF α的作用还可能与促进胞外Ca2 内流有关

Relationship between cytotoxicity of two types of TNF-α and intracellular free calcium concentration in target cells

AIM: To compare the changes of free calcium concentration in target cells killed by transmembrane tumor necrosis factor-alpha(TM-TNF-alpha) and secretory TNF-alpha(S-TNF-alpha). METHODS: The cytotoxicity of two types of TNF-alpha was tested by bioassay. The intracellular Ca(2+) concentration was determined by Frua-2. RESULTS: TM-TNF-alpha had cytotoxic effect on all 6 kinds of target cells, whereas S-TNF-alpha could kill only two of them. The cytotoxic activity of both types of TNF-alpha was accompanied by a dramatically increase of intracellular free Ca(2+) concentration. The intracellular Ca(2+) concentration in the target cells treated with S-TNF-alpha was obviously reduced by pretreating target cells with 10 micromol/L calcium chelator EGTA for 30 minutes (P<0.01) and the cytotoxicity of S-TNF-alpha was significantly inhibited (P<0.01), while the pretreatment with EGTA had no effect on the intracellular Ca(2+) concentration in the target cells treated with TM-TNF-alpha and the cytotoxicity of TM-TNF-alpha. CONCLUSION: These results suggest that both types of TNF-alpha increase Ca(2+) concentration in target cells by promoting the redistribution of intracellular free calcium and only S-TNF-alpha seems to be able to accelerate the influx of extracellular calcium into the target cells.