Li Yan, Guo Jianru, Zhang Huixia, Lam Christopher Wai Kei, Luo Wendi, Zhou Hua, Zhang Wei
State Key Laboratory of Quality Research in Chinese Medicine and Faculty of Chinese Medicine, Macau University of Science and Technology, Taipa 999078, Macau, China.
ACS Omega. 2020 Aug 19;5(34):21796-21804. doi: 10.1021/acsomega.0c02843. eCollection 2020 Sep 1.
Intracellular ribonucleotide (RN) and deoxyribonucleotide (dRN) pool sizes are critical for the fidelity of DNA synthesis. They are likely to be severely perturbed by many factors which disrupt the integrity and stability of DNA, leading to DNA damage. Exogenously supplied nucleosides are able to increase the deoxynucleoside triphosphate pools, then reverse the DNA damage, and decrease the oncogene-induced transformation dramatically. In this study, the impact of thymidine on the hydrogen peroxide (HO)-induced DNA damage was investigated in HepG2 liver cancer cells. From the result of the comet assay, the tail length of cells in the thymidine 600 μM + HO 1.0 mM group was dramatically decreased from 42.1 ± 10.8 to 21.9 ± 2.4 μm compared to that exposed with 1.0 mM HO ( < 0.05), suggesting that pretreatment of thymidine reduced the DNA damage of HepG2 cells. Although the RN and dRN contents decreased in the damage group, most of them presented increasing tendency when pretreated with thymidine, especially the key metabolites dCTP, which was mainly related with the decline in the rate of DNA synthesis. The restoration also showed a significant G0/G1 phase arrest of cell cycle progression from 44.6 ± 2.2 to 56.6 ± 0.4% after pretreated with thymidine ( < 0.05). In conclusion, our data demonstrated that the pretreatment with thymidine had a potential protective ability against oxidative damage for DNA in HepG2 cells through the perturbation of RN and dRN pools as well as cell cycle arrest, which should provide new insights into the molecular basis of preventing HO-induced oxidative DNA damage in mammalian cells.
细胞内核糖核苷酸（RN）和脱氧核糖核苷酸（dRN）库的大小对于DNA合成的保真度至关重要。它们很可能会受到许多破坏DNA完整性和稳定性的因素的严重干扰，从而导致DNA损伤。外源供应的核苷能够增加脱氧核苷三磷酸库，进而逆转DNA损伤，并显著降低癌基因诱导的转化。在本研究中，在人肝癌细胞系HepG2中研究了胸腺嘧啶核苷对过氧化氢（HO）诱导的DNA损伤的影响。从彗星实验结果来看，与暴露于1.0 mM HO的细胞相比，胸腺嘧啶核苷600 μM + HO 1.0 mM组细胞的尾长从42.1±10.8显著降低至21.9±2.4 μm（P<0.05），这表明胸腺嘧啶核苷预处理减少了HepG2细胞的DNA损伤。尽管损伤组中RN和dRN含量降低，但用胸腺嘧啶核苷预处理后，它们中的大多数呈现增加趋势，尤其是关键代谢产物dCTP，这主要与DNA合成速率的下降有关。用胸腺嘧啶核苷预处理后，细胞周期进程的G0/G1期阻滞也从44.6±2.2%显著恢复至56.6±0.4%（P<0.05）。总之，我们的数据表明，胸腺嘧啶核苷预处理通过干扰RN和dRN库以及细胞周期阻滞，对HepG2细胞中的DNA氧化损伤具有潜在的保护能力，这应为预防哺乳动物细胞中HO诱导的氧化性DNA损伤的分子基础提供新的见解。
