Wu Qiangen, Beland Frederick A, Chang Ching-Wei, Fang Jia-Long
Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, USA; ; Department of Environmental Health, Indiana University, Bloomington, IN 47405, USA.
Int J Biomed Sci. 2013 Mar;9(1):18-25.
The nucleoside reverse transcriptase inhibitor zidovudine (3'-azido-3'-dexoythymidine, AZT) can be incorporated into DNA and cause DNA damage. Previously, we determined that the human hepatocellular carcinoma HepG2 cells are more susceptible to AZT-induced toxicities than the immortalized normal human liver THLE2 cells and the nucleotide excision repair (NER) pathway plays an essential role in the response to AZT-induced DNA damage. We have now investigated if the effects of AZT treatment on the expression levels of genes related to DNA damage and repair pathways contribute to the differences in sensitivity to AZT treatment between HepG2 cells and THLE2 cells. Of total 84 genes related to DNA damage and repair, two, five, and six genes were up-regulated more than 1.5-fold at 50, 500, and 2,500 µM AZT groups compared with that of control THLE2 cells. Seven genes showed a decreased expression of more than 1.5-fold following the 2,500 µM AZT treatment. Two-sided multivariate analysis of variance indicated that the change in expression of genes involved in apoptosis, cell cycle, and DNA repair pathways was significant only at 2,500 µM AZT. Statistically significant dose-related increases were identified in XPC gene expression and GTF2H1 protein level after the AZT treatments, which implicated the NER pathway in response to the DNA damage induced by AZT. In contrast, AZT treatment did not alter significantly the expression of the APE1 gene or the levels of APE1 protein. These results indicate that the NER repair pathway is involved in AZT-induced DNA damage response in immortalized human hepatic THLE2 cells.
核苷类逆转录酶抑制剂齐多夫定（3'-叠氮-3'-脱氧胸苷，AZT）可掺入DNA并导致DNA损伤。此前，我们确定人肝癌HepG2细胞比永生化正常人肝脏THLE2细胞对AZT诱导的毒性更敏感，并且核苷酸切除修复（NER）途径在对AZT诱导的DNA损伤的反应中起重要作用。我们现在研究了AZT处理对与DNA损伤和修复途径相关基因表达水平的影响是否导致HepG2细胞和THLE2细胞对AZT处理的敏感性差异。在总共84个与DNA损伤和修复相关的基因中，与对照THLE2细胞相比，在50、500和2500μM AZT组中分别有2个、5个和6个基因上调超过1.5倍。在2500μM AZT处理后，有7个基因的表达下降超过1.5倍。双向多变量方差分析表明，参与凋亡、细胞周期和DNA修复途径的基因表达变化仅在2500μM AZT时显著。AZT处理后，XPC基因表达和GTF2H1蛋白水平出现统计学上显著的剂量相关增加，这表明NER途径参与了对AZT诱导的DNA损伤的反应。相比之下，AZT处理并未显著改变APE1基因的表达或APE1蛋白的水平。这些结果表明，NER修复途径参与了永生化人肝脏THLE2细胞中AZT诱导的DNA损伤反应。
