甲醛致DNA-蛋白质交联作用及其修复的研究

Study on the effects of DNA-protein crosslinks induced by formaldehyde and its repair process

为了探讨甲醛致生物机体DNA蛋白质交联作用及其修复能力,以昆明纯系小鼠和人肝癌细胞系HepG2为实验材料分别进行体内和体外实验,采用KClSDS沉淀法来检测甲醛染毒后小鼠肝细胞和HepG2细胞中DNA蛋白质交联的含量及其修复效果.体内实验结果表明,低浓度的气态甲醛(0.5mg·m-3)不能引起DNA蛋白质的交联,较高浓度的甲醛(1.0mg·m-3,3.0mg·m-3,p<0.01)可以产生明显的DNA蛋白质交联作用;由3.0mg·m-3浓度的气态甲醛产生的DNA蛋白质交联在12h内可以得到明显的修复,并在24h内恢复到空白对照水平.体外实验结果表明,经低浓度液态甲醛(25μmol·L-1和50μmol·L-1)处理后,HepG2细胞内的DPC系数虽然稍有变化,但是与空白对照组相比较无显著差异,而当甲醛浓度上升至75μmol·L-1及以上时,细胞中的DPC系数出现了极显著上升(p<0.01);采用75μmol·L-1甲醛染毒HepG2细胞,在染毒18h和24h后,细胞内的DPC水平较染毒结束时发生了极显著的下降(p<0.01),且与空白对照组相比无显著差异.以上结果显示,低浓度的甲醛不能引起DNA蛋白质的交联,较高浓度的甲醛可以引起明显的DNA蛋白质的交联作用,且甲醛所致的DNA蛋白质交联在体内修复比体外修复所需时间要短.

To explore the effects of formaldehyde induced DNA-protein crosslinks （ DPC ） and the repair process of DPC, purebred Kunming mice and HepG2 cell line were used as experimental materials in vivo and in vitro respectively, and KCI - SDS assay were applied to determine the amount of DPC and the repair process. The results in vivo showed that gaseous formaldehyde could cause DPC at high concentrations （l. 0 mg m^-3,3.0 mg· m^-3, p 〈0.01 ） , hut not happened the case at low eoneentrations （0.5 mg·m^-3 ）. DPC induced by gaseous formaldehyde at 3.0 mg·m^ -3 could be removed within 12 hours. Meanwhile, the results in vitro showed that liquid formaldehyde at low concentration （25 μmol· L^-1and 50 μmol· L^- 1 ） resulted in an insignificant increase in DPC content compared with control groups. When formaldehyde concentration was up to as high as 75 μmol· L^ - 1, DPC could be formed significantly, which could be removed significantly after 18 and 24 hours, but not happend the case after 6 and 12 hours. In combination, these results suggested that formaldehyde can induce DPC at relatively high concentration, and removing of DPC in vivo requires shorter time than that in vitro.