Repair of sulfur mustard-induced DNA damage in mammalian cells measured by a host cell reactivation assay
作者:Z. Matijasevic、M.L. Precopio、J.E. Snyder、D.B. Ludlum
DOI:10.1093/carcin/22.4.661
日期:2001.4
DNA damage is thought to be the initial event that causes sulfur mustard (SM) toxicity, while the ability of cells to repair this damage is thought to provide a degree of natural protection. To investigate the repair process, we have damaged plasmids containing the firefly luciferase gene with either SM or its monofunctional analog, 2-chloroethyl ethyl sulfide (CEES). Damaged plasmids were transfected into wild-type and nucleotide excision repair (NER) deficient Chinese hamster ovary cells; these cells were also transfected with a second reporter plasmid containing Renilla luciferase as an internal control on the efficiency of transfection. Transfected cells were incubated at 37°C for 27 h and then both firefly and Renilla luciferase intensities were measured on the same samples with the dual luciferase reporter assay. Bioluminescence in lysates from cells transfected with damaged plasmid, expressed as a percentage of the bioluminescence from cells transfected with undamaged plasmid, is increased by host cell repair activity. The results show that NER-competent cells have a higher reactivation capacity than NER-deficient cells for plasmids damaged by either SM or CEES. Significantly, NER-competent cells are also more resistant to the toxic effects of SM and CEES, indicating that NER is not only proficient in repairing DNA damage caused by either agent but also in decreasing their toxicity. This host cell repair assay can now be used to determine what other cellular mechanisms protect cells from mustard toxicity and under what conditions these mechanisms are most effective.
DNA损伤被认为是引起硫芥(SM)毒性的起始事件,而细胞修复这种损伤的能力则被认为提供了一定程度的自然保护。为了研究修复过程,我们使用SM或其单功能类似物2-氯乙基乙基硫化物(CEES)对含有萤火虫荧光素酶基因的质粒进行了损伤。损伤后的质粒被转染到野生型和核苷酸切除修复(NER)缺陷的中国仓鼠卵巢细胞中;这些细胞还转染了第二个报告质粒,其中包含海肾荧光素酶作为转染效率的内部对照。转染后的细胞在37°C下孵育27小时,然后用双荧光素酶报告分析法在同一样本上测量萤火虫和海肾荧光素酶的强度。细胞裂解液中转染了损伤质粒的生物发光,以转染了未损伤质粒的细胞的生物发光的百分比表示,随宿主细胞修复活性而增加。结果显示,对于被SM或CEES损伤的质粒,具有NER能力的细胞比NER缺陷的细胞具有更高的再激活容量。值得注意的是,具有NER能力的细胞对SM和CEES的毒性影响也更具抵抗力,表明NER不仅擅长修复这两种试剂引起的DNA损伤,还能降低它们的毒性。现在,这种宿主细胞修复分析可以用来确定其他哪些细胞机制保护细胞免受芥子气毒性影响及其在这些机制最有效时的条件。