McConkey D J, Hartzell P, Nicotera P, Orrenius S
Department of Toxicology, Karolinska Institutet, Stockholm, Sweden.
FASEB J. 1989 May;3(7):1843-9. doi: 10.1096/fasebj.3.7.2497041.
Glucocorticoid hormones kill immature thymocytes by activating a self-destructive process that involves extensive DNA fragmentation. It has been demonstrated that thymocyte suicide is dependent on an early, sustained increase in cytosolic Ca2+ concentration, and new protein synthesis, but the biochemical lesion that leads to cell death has not been established. To determine whether endonuclease activation or activation of another Ca2+-dependent process could mediate cell killing, we treated thymocytes with the glucocorticoid methylprednisolone in the presence of inhibitors of various Ca2+-dependent degradative enzymes. The role of poly(ADP-ribose) polymerase, an enzyme known to be activated by DNA damage, was also assessed. Glucocorticoid-induced chromatin cleavage and cell killing were blocked by the endonuclease inhibitor aurintricarboxylic acid, whereas inhibitors of other Ca2+-dependent degradative processes or of poly(ADP-ribose) polymerase did not abrogate cell death. In addition, stimulation of thymocyte DNA fragmentation by the Ca2+ ionophore A23187 resulted in cell killing that could be blocked by the endonuclease inhibitor. Together, our results suggest that thymocyte suicide is caused by extensive Ca2+-stimulated DNA fragmentation.
糖皮质激素通过激活一个涉及广泛DNA片段化的自我毁灭过程来杀死未成熟的胸腺细胞。已经证明胸腺细胞自杀依赖于胞质Ca2+浓度的早期持续升高以及新的蛋白质合成，但导致细胞死亡的生化损伤尚未明确。为了确定核酸内切酶激活或另一个Ca2+依赖过程的激活是否能介导细胞杀伤，我们在各种Ca2+依赖降解酶的抑制剂存在下，用糖皮质激素甲泼尼龙处理胸腺细胞。还评估了聚（ADP - 核糖）聚合酶的作用，该酶已知可被DNA损伤激活。核酸内切酶抑制剂金精三羧酸可阻断糖皮质激素诱导的染色质裂解和细胞杀伤，而其他Ca2+依赖降解过程或聚（ADP - 核糖）聚合酶的抑制剂并不能消除细胞死亡。此外，Ca2+离子载体A23187刺激胸腺细胞DNA片段化会导致细胞杀伤，而这种杀伤可被核酸内切酶抑制剂阻断。总之，我们的结果表明胸腺细胞自杀是由广泛的Ca2+刺激的DNA片段化引起的。
