Caspase cascades which activated by ionizing irradiation

1. 人正常和肿瘤细胞系的辐射抗性。测定了10Gy辐照后人正常细胞（MRC5）和肿瘤细胞（HL60、MGF7）中caspase-8、caspase-9的酶活性。HL60表达了大量的活化caspase，而MRC5仅表达了少量的活化caspase-9（未检测到活性caspase-8）。结果表明，抗辐射能力与半胱天冬酶活性呈正相关。MRC5辐照后的条件培养基中含有大量的化学引诱剂。我们发现辐照后的MRC5衍生条件培养基含有更多的化学引诱剂。Northern印迹和抗hgf抗体的竞争活性表明，hgf - 3是这些化学引诱剂之一。电离辐射诱导基因表达（DNA阵列分析）我们对辐照后的MRC5进行了DNA分析。bcl-2相关基因无明显变化。我们发现caspase-2、-6和10的表达上调。我们还发现凋亡抑制基因的上调。我们认为这些抗凋亡蛋白的上调可能解释了正常结缔组织的抗辐射能力。

1. Radiation resistance of human normal and tumor cell lines.An enzymatic activities of caspase-8 and caspase-9 of human normal (MRC5) and tumor (HL60, MGF7) were analyzed after 10Gy gamma-irradiation. HL60 expressed a significant amount of activated caspases, whereas MRC5 showed only a few amount of active caspase-9 (no active caspase-8 was detected). We concluded that radiation resistance and an amount of active caspase were well corresponding.2. A conditioned medium from irradiated MRC5 contained elevated amount of chemoattractants.We found that irradiated MRC5 derived conditioned medium contained increased amount of chemoattractants. Northern blotting and competitive activity of anti-HGF antibodies indicate that one of these chemoattractants is HGF.3. Ionizing radiation induced gene expression (DNA array analysis)We performed DNA analysis for irradiated MRC5. There were no significant changes in bcl-2 related genes. We found the up-regulation of caspase-2,-6 and 10. We also found the up-regulation of apoptosis suppressing genes. We concluded that these up-regulation of anti-apoptotic proteins may explain the radiation resistance of normal connective tissue.