Mechanisms associated with oxidative stress in triggering cell cycle arrest in various cell lines

• Main Authors: Tzung-De, 林宗德
• Other Authors: 鄭鈞文
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/45824545509205655499

碩士 === 中山醫學大學 === 生化暨生物科技研究所 === 93 === Oxidative damage to DNA via reactive oxygen species（ROS）is considered to play a crucial role in cell aging, tumorigenesis and cancer. Under exposure to environment of high oxidative stress, cells are predisposed to DNA structure damage, cell senescence and tumorigenesis. To prevent oxidative damage, cells therefore, evolve mechanisms involving in the activation of tumor suppress proteins, cell cycle control and DNA damage repair for the maintenance of DNA integrity. However, there are few data discussed about the cellular response under exposure of transient oxidative stress. The aim of this study was to clarify the possible mechanisms against oxidative injuring in different cell lines. Various cell lines, including a kidney cell line HEK 293 and breast cancer cell lines MCF-7, HCC1937 and HCC1937 (BRCA1), were enrolled, and all of them were treated with different concentrations of H2O2. Several techniques, including Comet assay, Flow cytometry, DNA fragmentation, Western blotting and Enzyme activity assay were used to analysis the physiological alternations of these cell lines. After the H2O2 treatment, we found that HEK 293 cells is the most sensitive to oxidative stress, showing of the largest moment tail among these four cell lines. In addition, up-regulated expression of Chk 1, p53 and phosphorylated-p53 proteins will correlated with down-regulation of A- and B1- cyclins in HEK 293 cells, resulting in the cell cycle arrested in G2/M stage. On the other hand, either p53 positive or p53 negative, p21 were apparently expressed in MCF-7, HCC1937 and HCC1937 (BRCA1) cells. Interestingly, these breast tumor cell lines showed an increasing trend of accumulation of cells in SubG1 phase after to high dosage of H2O2 treatment. Catalase activity will be forced to enhance after exposure to environment of high oxidative stress among these cell lines. In this study, we established a cell model with the temporal oxidative stress for the mimic of real oxidative stress surrounding that cells met with. We were able to define a real physiological status of cells under exposure to oxidative substance. The susceptibilities to oxidative injury were also ascribed to different genetic profiles of tumor suppressor gene. Therefore, the molecular mechanisms of cell cycle arrest for the potential benefit in triggering oxidative DNA damage repair were dependent upon the tissue- and genetic specificities. In conclusion, these findings may reassure the mechanisms of tumor suppressor gene against oxidative damage but also provide the functional role of the scavengers and cell cycle regulation in the response of oxidative stress.